Arterial Glucose Concentration Research Articles

Effects of Exogenous Bovine Somatotropin on Mammary Function of Late Lactating Crossbred Holstein Cows

The objective of the present study was to determine the effect of exogenous bovine somatotropin on the mammary function in late lactating crossbred Holstein cows. Twelve 87.5% late lactating Holstein cows, approximately 30 weeks postpartum, were divided into two groups of 6 animals each. Animals in the control group were given sodium bicarbonate buffer by subcutaneous injection, while animals in the treated group were given recombinant bovine somatotropin (bST) by subcutaneous injection with 500 mg of bST (14 day prolonged-release bST). After bST injection, milk yield significantly increased from the control level on day 8 to day 20 (p<0.05) with a concomitant increase in mammary blood flow (p<0.01). An increase in mammary blood flow in response to bST treatment was greater than an increase in milk production. An increased plasma concentration of IGF-I coincided with an increase in mammary blood flow in animals treated with bST. There were no significant changes in the concentration of arterial plasma glucose concentration, the arteriovenous concentration difference (A-V difference) and mammary extraction ratio while the mammary glucose uptake increased when compared to the control group. The concentration of arterial plasma triglyceride decreased throughout the experimental period in animals give bST. The plasma concentration of acetate, and the mammary uptake for acetate significantly increased (p<0.05) after bST treatment. The action of bST did not affect the plasma concentration, A-V difference and extraction ratio across the mammary gland for β-hydroxybutyrate. The concentrations of milk fat and lactose tended to increase during bST treatment. Milk protein concentration initially increased in the first few days and decreased after bST injection when compared to the pretreated period. The present results indicated that bST could affect the mammary function in late lactating cows by increase in milk yield involving changes in both extra-mammary and intra-mammary mechanisms. The exogenous bST exerted its galactopoietic action through an increase in circulating IGF-I of the late lactating Crossbred Holstein cattle. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 1 : 88-95)

Impact of chronic fructose infusion on hepatic metabolism during TPN administration.

During chronic total parenteral nutrition (TPN), net hepatic glucose uptake (NHGU) is markedly elevated. However, NHGU is reduced by the presence of an infection. We recently demonstrated that a small, acute (3-h) intraportal fructose infusion can correct the infection-induced impairment in NHGU. The aim of this study was to determine whether the addition of fructose to the TPN persistently enhances NHGU in the presence of an infection. TPN was infused continuously into the inferior vena cava of chronically catheterized dogs for 5 days. On day 3, a bacterial clot was implanted in the peritoneal cavity, and either saline (CON, n = 5) or fructose (+FRUC, 1.0 mg. kg(-1). min(-1), n = 6) infusion was included with the TPN. Forty-two hours after the infection was induced, hepatic glucose metabolism was assessed in conscious dogs with arteriovenous and tracer methods. Arterial plasma glucose concentration was lower with chronic fructose infusion (120 +/- 4 vs. 131 +/- 3 mg/dl, +FRUC vs. CON, P < 0.05); however, NHGU was not enhanced (2.2 +/- 0.5 vs. 2.8 +/- 0.4 mg. kg(-1). min(-1)). Acute removal of the fructose infusion dramatically decreased NHGU (2.2 +/- 0.5 to -0.2 +/- 0.5 mg. kg(-1). min(-1)), and net hepatic lactate release also fell (1.6 +/- 0.3 to 0.5 +/- 0.3 mg. kg(-1). min(-1)). This led to an increase in the arterial plasma glucose (Delta13 +/- 3 mg/dl, P < 0.05) and insulin (Delta5 +/- 2 micro U/ml) concentrations and to a decrease in glucagon (Delta-11 +/- 3 pg/ml) concentration. In conclusion, the addition of chronic fructose infusion to TPN during infection does not lead to a persistent augmentation of NHGU.

Muscle glucose uptake does not increase when only local arterial glucose concentration is increased.

Published models of mammalian whole-body glucose metabolism generally assume that glucose uptake is proportional to circulating glucose concentration at constant insulin concentration. One widely used model labels the increased whole-body glucose uptake seen with increased venous glucose concentration as "glucose effectiveness." In 1956 and 1957, we found on average no change in forearm glucose uptake when we doubled, or more than doubled, local forearm arterial glucose concentration by close arterial infusion so that pancreatic arterial glucose concentration did not change. These experiments are being reported in extenso for the first time. Since that time, two other groups have found in glucose/insulin clamp experiments that whole-body glucose uptake was not proportional to hyperglycemic concentrations, although uptake did increase. It was hypothesized that perhaps some organs and tissues do increase uptake proportionally and other tissues not at all. Our results show that skeletal muscle is a tissue in which glucose uptake, at constant insulin, is not changed acutely by hyperglycemia; there is no forearm glucose effectiveness. We suppose that this constancy occurs because there are so few GLUTs on the sarcolemma surface in the basal state and that they are saturated even at euglycemia. We also report earlier experiments from 1954 to 1955 in which comparable hyperglycemia was reached by a large oral dose of glucose, with a 10-fold increase in glucose uptake. The arterial glucose time curve during hyperglycemia was 20-30 mg/dl higher than the forearm venous curve.

Placental glucose transport in growth-restricted pregnancies induced by overnourishing adolescent sheep.

Glucose clamp procedures were used to determine whether the slowing of fetal growth during the final third of gestation in overnourished adolescent ewes is due to a reduction in placental glucose transport capacity. Singleton pregnancies to a single sire were established by embryo transfer and thereafter adolescent dams were offered a high (n = 11) or moderate (n = 7) nutrient intake. Studies were conducted at 130 +/- 0.5 days gestation. Uterine and umbilical blood flows were studied by the steady-state transplacental diffusion technique and glucose fluxes quantified by the Fick principle. To determine the relationship between the transplacental glucose gradient and umbilical (fetal) glucose uptake, studies were conducted with maternal arterial glucose clamped at 5 micromol ml(-1) and fetal glucose at spontaneously occurring and two additional higher levels. Maternal body weight gain during gestation averaged 282 and 57 g day(-1) for high- and moderate-intake dams, respectively. Total placentome weight (209 +/- 23 vs. 386 +/- 34 g) and fetal weight (3072 +/- 266 vs. 4670 +/- 196 g) were lower (P < 0.001) in high- than in moderate-intake groups. The growth-restricted pregnancies in the high-intake dams were associated with reduced uterine (P < 0.05) and umbilical (P < 0.02) blood flows and, in the non-perturbed state, the fetuses were relatively hypoxic (2.1 vs. 3.0 micromol ml(-1), P < 0.05) and hypoglycaemic (0.90 vs. 1.31 micromol ml(-1), P < 0.002). Linear regression analysis of umbilical glucose uptake at three steady-state uterine-umbilical arterial transplacental plasma glucose concentration gradients revealed that absolute placental glucose transport capacity was lower in high- than in moderate-intake dams (mean slope, 0.8 vs. 1.5 dl min(-1), P < 0.05; and mean intercept, 1.84 vs. 3.40 micromol ml(-1)). However, glucose transfer capacity was not different between the two groups when expressed on a placental weight-specific basis. This confirms that the small size of the placenta per se is the major limitation to placental glucose transfer in the overnourished adolescent pregnant sheep.

Accidental injection of intravenous bupivacaine

EDITOR: Toxic reactions to local anaesthetics usually occur as a result of accidental overdosage or inadvertent intravenous (i.v.) injections. We report such a case; the reasons for this occurrence and suggestions for prevention are discussed. A 53-yr-old, 60 kg, ASA I female patient was scheduled for elective total knee replacement. There was nothing of note in her medical history. After institution of monitoring and establishment of venous access, the patient was premedicated with midazolam 3 mg. The baseline heart rate was 78 beats min−1 and blood pressure was 140/80 mmHg. An epidural catheter was inserted at the L3-4 interspace. Lidocaine 2% 3 mL was injected through the epidural catheter as a test dose. After 5 min, as the patient did not feel any change in her legs, a bolus of bupivacaine 0.5% 12 mL was injected slowly. Heart rate was 74 beats min−1 and blood pressure was 110/65 mmHg. The level of the regional blockade was T10. General anaesthesia was then induced with fentanyl 0.05 mg, propofol 2 mg kg−1 and atracurium 0.5 mg kg−1 and maintained with sevoflurane 1% in a mixture of oxygen and air. The operation was uneventful and lasted 110 min. The patient was extubated at the end of the operation and remained for 15 min in the recovery room before she was transferred to her bed. Postoperative analgesia was planned with bolus injections of a mixture of bupivacaine 0.25% and morphine 2 mg in 6 mL solution, via the epidural catheter. Two hours later, the patient requested epidural analgesia and a nurse injected the solution through the catheter. Six hours later another injection of same dose of bupivacaine was given i.v. by mistake by the same nurse. The patient was in some distress and complained of ringing in her ears, palpitations and dizziness. She could co-operate for examination of muscle tone and strength, which were normal as were the deep tendon reflexes. There were no lateralizing findings. The patient was afebrile. The i.v. bupivacaine produced a tachycardia of 120 beats min−1 but in sinus rhythm. The tachycardia reduced slightly over the next 20 min and normal blood pressure was always sustained. Investigations performed were arterial blood gases, serum glucose and electrolyte concentrations: all were normal other than PaCO2 4.0 kPa, and serum glucose 9.6 mmol L−1. The patient was immediately transferred to the intensive care unit where, fortunately, she passed the night uneventfully and no treatment was required. She was discharged from the hospital on the seventh postoperative day. Our normal practice for total knee replacement surgery is to site an epidural catheter and administer intermittent boluses of local anaesthetic combined with opioid at intervals of 6-8 h postoperatively. This epidural catheter had been sited uneventfully and had been used to give one bolus dose of bupivacaine. The second dose was an explicit i.v. injection despite clear written orders that it was to be given through the epidural catheter. Complications arise from the use of drugs and equipment, and from human error [1]. Local anaesthetics and opioids are commonly used for epidural analgesia in the postoperative period. There are reports of accidental injections of drugs with consequences ranging from no clinical effect to irreversible damage [2,3]. In our patient, we believe that the low concentration and volume of the bupivacaine protected the patient from an untoward reaction. Eldor and Frankel [4] reported a case of inadvertent i.v. injection using bupivacaine 0.5% where tinnitus was an early sign; indeed, our patient's first complaint was of tinnitus. Dysrrhythmias may occur with i.v. injection of bupivacaine. The striking feature of accidental i.v. bupivacaine is the great difficulty in resuscitating the patient [5]. In convulsant dosages, local anaesthetics cause increases in blood pressure, heart rate and cardiac output by stimulating the autonomic control centres in the brainstem [6]; however, in our patient, the low concentration of the bupivacaine produced only a sinus tachycardia. Because the nurses take part in postoperative analgesia management rather than the anaesthesiologists, they need to be trained and regulated. This case history demonstrates an inherent safety advantage of the 'bolus top-up' system over the 'continuous infusion' analgesia method when patients are cared for by a busy nursing team. Our nurse was still with the patient when the adverse symptoms and signs developed. Therefore, the effects of the inadvertent i.v. administration were observed and the nurse was able to call the anaesthesiologist immediately. If an intended epidural infusion had been connected, incorrectly, to an i.v. line, the nurse would have been occupied elsewhere by the time that toxic effects began to occur and a dangerous delay in diagnosis and management could have ensued. S. Karaca E. Ö. Ünlüsoy Department of Anesthesiology; Faculty of Medicine Cerrahpasa; University of Istanbul; Istanbul, Turkey

Effects of Abomasal Vegetable Oil Infusion on Splanchnic Nutrient Metabolism in Lactating Dairy Cows

Changes in the metabolism of nutrients by the portal-drained viscera (PDV) and liver may contribute to the reduction in dry matter intake (DMI) and other production responses generally observed in lactating dairy cows fed supplemental long-chain fatty acids (LCFA). In the present study, effects of a 7-d abomasal infusion of vegetable oil on arterial concentration and splanchnic (PDV and liver) metabolism of nutrients were measured in six cows at 55 (early lactation [ELAC]) and 111 (midlactation [MLAC]) d postpartum. Cows were fed for ad libitum DMI at 8-h intervals, and blood samples for measurement of splanchnic metabolism were obtained over 8h beginning 2h before feeding at 0830h. Blood flow for the PDV and liver was increased by oil infusion and was greater in ELAC, despite similar-feed DMI during blood sampling. Increased blood flow in ELAC was associated with greater liver oxygen removal and glucose release that accompanied greater milk yield. In contrast, oil infusion had no effect on splanchnic oxygen use. Greater blood flow during oil infusion may have been due to specific effects of intestinal LCFA supply on PDV blood flow. Net PDV release and liver removal of branched-chain volatile fatty acids (VFA) and ammonia were increased by oil infusion. Net PDV release of longer-chain (4 and 5C) VFA and NEFA was greater in ELAC, but net PDV flux of other nutrients was not affected by lactation stage, possibly due to the similarity of feed DMI. Oil infusion increased arterial concentration and net PDV release and liver removal of NEFA, and it decreased net liver release and arterial concentration of glucose. Effects of oil infusion on liver glucose release were associated with decreased daily DMI. In ELAC, arterial concentration and net liver removal of NEFA were also increased, but liver release of glucose was greater than in MLAC. Oil infusion and ELAC both increased net liver removal of l-lactate. The resulting decrease in net total splanchnic release of l-lactate in ELAC reflects decreased tissue energy balance of the cows. Generally, stage of lactation and relative milk yield had greater effects on metabolism of the liver than the PDV, in which metabolism was largely dictated by DMI. In the present study, there was little evidence to suggest an effect of stage of lactation on the metabolic response of the PDV and liver to postruminal LCFA supply.

Coronary blood flow control is impaired at rest and during exercise in conscious diabetic dogs.

This study tested whether diabetes mellitus impairs coronary blood flow control sufficiently to alter the balance between myocardial oxygen delivery and metabolism. Dogs (n = 7) were instrumented with catheters in the aorta and coronary sinus, and with a flow transducer on the circumflex coronary artery. Coronary blood flow, myocardial oxygen consumption (MVO2), heart rate and aortic pressure were measured at rest and during treadmill exercise before and after induction of diabetes with alloxan monohydrate (40 - 60 mg/kg). Arterial plasma glucose concentration increased from 4.6+/-0.2 mM in non-diabetic, control dogs to 20.2+/-2.3 mM one week after alloxan injection. In non-diabetic control dogs, exercise increased MVO2 3.1-fold, coronary blood flow 2.7-fold, and heart rate 2.4-fold. Coronary venous PO2 decreased from 19.4+/-0.6 mmHg at rest to 14.7+/-0.7 mmHg during exercise. Diabetes significantly attenuated exercise coronary hyperemia and reduced coronary venous PO2 at rest (15.6+/-0.5 mmHg) and during exercise (12.6+/-0.8 mmHg). Diabetes also significantly reduced myocardial oxygen delivery at each level of exercise. Acute hyperglycemia alone did not alter exercise-induced coronary vasodilation or reduce coronary venous PO2. These findings demonstrate that experimental diabetes attenuates functional coronary hyperemia and impairs the balance between coronary blood flow and myocardial metabolism. However, this deleterious effect is not related to acute hyperglycemia but to the chronic disease process of diabetes mellitus.

Eliminating discard volumes in neonatal and pediatric blood sampling from arterial catheters: A comparison of three simple blood-conserving aspiration techniques.

OBJECTIVE: To compare different blood aspiration techniques to eliminate discarding of blood in arterial blood sampling from critically ill neonates and children. DESIGN: Prospective, randomized controlled trial. SETTING: A 19-bed tertiary neonatal and pediatric intensive care unit. PATIENTS: Critically ill neonates and children with existing arterial and central venous access. INTERVENTIONS: Paired blood samples were obtained by using conventional blood discarding techniques and one of the following blood-conserving aspiration techniques: passive extracorporeal arteriovenous backflow, free passive backflow to ambient pressure, and active aspiration backflow to a distance of 10 or 20 cm proximal to the sampling port of the arterial pressure catheter. Repetitive conventional sampling served as a control and as the standard. The order of sampling was randomly allocated. We determined arterial blood gases, electrolytes, blood glucose, and hemoglobin concentration. Measurement and RESULTS: Bland-Altman bias analysis of the variability among the techniques revealed that the passive backflow and the active aspiration backflow technique with a backflow distance of 20 cm yielded identical results to repetitive conventional sampling with a standardized discard volume of 0.6 mL. In contrast, the extracorporal arteriovenous backflow technique carried the risk of overestimating blood glucose levels (mean bias, 0.96 mmol/L.). A backflow distance of 10 cm (active aspiration) proved insufficient to eliminate contamination by the catheters' flushing solution. CONCLUSIONS: At a backflow distance of 20 cm, the passive backflow and the active aspiration backflow techniques produce, with the used monitoring set, reliable and precise results in critically ill newborns and children and eliminate discard volumes.

ATP-dependent K(+) channels contribute to local metabolic coronary vasodilation in experimental diabetes.

This study tested whether ATP-dependent K(+) channels (K(ATP) channels) are an important mechanism of functional coronary hyperemia in conscious, instrument-implanted diabetic dogs. Data were collected at rest and during exercise before and after induction of diabetes with alloxan monohydrate (40-60 mg/kg intravenously). K(ATP) channels were inhibited with glibenclamide (1 mg/kg intravenously). In nondiabetic dogs, arterial plasma glucose concentration increased from 4.8 +/- 0.3 to 21.5 +/- 2.2 mmol/l 1 week after alloxan injection. In nondiabetic dogs, exercise increased myocardial oxygen consumption (MVO(2)) 3.4-fold, myocardial O(2) delivery 3.0-fold, and heart rate 2.4-fold. Coronary venous PO(2) decreased from 19.9 +/- 0.8 mmHg at rest to 14.8 +/- 0.8 mmHg during exercise. Diabetes significantly reduced myocardial O(2) delivery and lowered coronary venous PO(2) from 16.3 +/- 0.6 mmHg at rest to 13.1 +/- 0.9 mmHg during exercise. Glibenclamide did not alter the slope of the coronary venous PO(2) versus MVO(2) relationship in nondiabetic dogs. In diabetic dogs, however, glibenclamide further reduced myocardial O(2) delivery; coronary venous PO(2) fell to 9.0 +/- 1.0 mmHg during exercise, and the slope of the coronary venous PO(2) versus MVO(2) relationship steepened. These findings indicate that K(ATP) channels contribute to local metabolic coronary vasodilation in alloxan-induced diabetic dogs.

Milk Synthetic Response of the Bovine Mammary Gland to an Increase in the Local Concentration of Arterial Glucose

Concentrations of glucose in the external iliac artery feeding one udder half of 14 midlactation Holstein cows were increased by infusion to test the following three hypotheses of mammary function: 1) that mammary glands control their blood supply to maintain intracellular energy balance, 2) that milk precursors are taken out of capillary blood according to mass action kinetics, and 3) that the rate of milk component synthesis is dependent on its precursor's uptake from blood. The first seven cows received 20g/h glucose during 10h of infusion. Arterial concentrations of glucose were locally increased by only 10%, and the iliac plasma flow was not affected by glucose infusion, so the next seven cows were given 90g/h glucose. Quantitative predictions resulting from the hypotheses were that arterial plasma flow would decrease by 32% with 90g/h glucose infusion, glucose uptakes would increase and acetate, fatty acid, and amino acid uptakes decrease, and milk protein and fat yields and percentages would decrease. Iliac plasma flow decreased 16%, half of what was predicted, which suggests that other regulatory processes besides blood flow control took part in the response. Acetate and fatty acid uptakes by the mammary glands were reduced as predicted because of the lower blood flow, but an unexpected depression in extraction of plasma triacylglycerol also contributed to the reduced fatty acid uptake. Milk fat and protein yields were not affected by the exogenous glucose, falsifying the third hypothesis that milk component secretion is a function of uptake of its precursor. Milk fat and protein percentages declined with glucose infusion because of increased lactose synthesis and secretion of water into milk.

Duodenal Glucose Increases Glucose Fluxes and Lactose Synthesis in Grass Silage-Fed Dairy Cows

The effect of intestinal glucose supply on whole body rate of glucose appearance (WBGRa) and mammary utilization of glucose was studied in four lactating dairy cows. Glucose (0, 443, 963 and 2398 g/d) was continuously infused in the duodenum over 14-d periods using a Latin square design. A grass silage-based diet was formulated so that treatments were isoenergetic and isonitrogenous and contained 100 and 110% of energy and protein requirements according to INRA (1989). The WBGRa was measured by the [6,6-2 H2]glucose dilution technique, and mammary glucose balance by arteriovenous differences and blood flow measurements. Duodenal glucose infusion increased arterial glucose concentrations linearly, whereas arterial concentrations of insulin, growth hormone, and glucagon were not changed. The WBGRa increased linearly with increasing glucose loads. The increase represented 42% of the intestinal glucose supplement. Mammary blood flow dramatically increased (up to 45%) and was associated with a significant increase of arterial insulin-like growth factor-1 concentrations. Mammary gland rate of glucose disappearance ([6,6-2H2]glucose measurement) increased linearly, whereas net mammary balance of glucose, lactose, and milk yields increased quadratically. Net mammary balance of glucose accounted for 60% of WBGRa, except for the greatest dose (47.6%). The decrease in milk yield with 2398 g/d of glucose may be explained by an imbalance in intracellular intermediate concentrations. The milk ratio of glucose-1-phosphate to glucose-6-phosphate decreased significantly at the greatest infusion of glucose. In conclusion, exogenous glucose supply to a grass silage-based diet increased WBGRa, mammary utilization of glucose and milk synthesis.

Is reduced first-phase insulin release the earliest detectable abnormality in individuals destined to develop type 2 diabetes?

Insulin is released from the pancreas in a biphasic manner in response to a square-wave increase in arterial glucose concentration. The first phase consists of a brief spike lasting approximately 10 min followed by the second phase, which reaches a plateau at 2-3 h. It is widely thought that diminution of first-phase insulin release is the earliest detectable defect of beta-cell function in individuals destined to develop type 2 diabetes and that this defect largely represents beta-cell exhaustion after years of compensation for antecedent insulin resistance. In this article, the origins of these concepts are reviewed and recent evidence is presented suggesting that reductions in both phases of insulin release are equally early, that they precede insulin resistance other than that simply due to obesity, and that they therefore may represent the primary genetic risk factor predisposing individuals to type 2 diabetes.

Studies on the Mode of Uptake of Plasma Glucose, Acetate, β-hydroxybutyrate Triglyceride Fatty Acids and Glycerol by the Mammary Gland of Crossbred Holstein Cattle Feeding on Different Types of Roughage

The present experiment was carried out to study the utilization of substrates in the mammary gland of crossbred Holstein Friesian during feeding on different types of roughage. Sixteen pregnant crossbred Holstein heifers consisted of two breed types of eight animals each; Holstein Friesian×Red Sindhi (50:50=50%HF) and Holstein Friesian×Red Sindhi (87.5:12.5=87.5%HF). Animals were divided into four groups of the same breed type in each group which were fed with either rice straw treated with 5% urea or pangola hay (Digitaria decumbens) as the source of roughage throughout the experiments. Four consecutive experimental periods were carried out in late pregnancy (20-23 days before parturition), early lactation (30 days postpartum), mid-lactation (120 days postpartum) and late lactation (210 days postpartum). Measurement of mammary blood flow in combining with measurement of AV difference was performed for the mammary uptake of substrates. In the period of lactation, udder blood flow was nearly three times higher than that of late pregnant period (p<0.05) in both 50%HF and 87.5%HF feeding on either hay or urea treated rice straw. During mid- and late lactation of both groups of 87.5%HF animals, mammary blood flow and milk yield showed decrease when compared to those during the early lactating period while the trends for persistency were apparent in both groups of 50%HF animals throughout experimental periods. The mean arterial plasma concentrations of glucose, acetate, β-hydroxybutyrate and free glycerol in each group remained constant throughout experimental periods. During late pregnancy in all groups, the AV difference and extraction ratio of glucose, β-hydroxybutyrate and triacylglycerol across the mammary gland markedly lowered (p<0.05), which coincided with a lower net uptake by the mammary gland in comparison to the early lactating period. The mean arterial plasma concentration, AV difference and extraction ratio for acetate showed no significant differences between late pregnancy and the early lactating period. The AV difference of free glycerol showed apparent release from mammary tissue during late pregnancy in all groups. In mid- and late lactation, the mammary uptake for glucose, acetate and β-hydroxybutyrate in both groups of 87.5%HF animals showed apparent decrease as compared to that in the early lactating period, whereas no appearances were observed in 50%HF animals feeding either hay or urea treated rice straw. The mean arterial plasma concentrations for free fatty acid (FFA) and triacylglycerol (C16 to C18) were higher in late pregnancy than in early lactation in both types of crossbred animals. The values of AV difference and the net uptake by the mammary gland for FFA were variable during late pregnancy and lactating periods in all groups. There were no significant differences for AV difference, extraction ratio and net uptake of triacylglycerol during lactation advance in both groups of 50%HF and 87.5%HF animals feeding either hay or urea treated rice straw. These results suggest that the adaptations to either hay or urea treated rice straw by the mammary gland of crossbred HF animals allow for an adequate nutrient supply during pregnancy and lactation. There is no difference in the mode of mammary uptake of substrates in the same crossbred animals in response to feeding hay or urea treated rice straw. The differences in utilizing nutrients by the mammary gland for milk production between 87.5%HF and 50%HF animals would be dependent on changes in both intra-mammary factors and extra-mammary factors. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 10 : 1445-1452)

Effects of cyclosporine A and prednisone treatment on mixed meal disposition in dogs with hepatic denervation

Compared with untreated dogs, normal dogs treated for 7 days with cyclosporine A and prednisone exhibited a 25% reduction in the absorption of glucose from a mixed meal and a 4- to 5-fold increase in net hepatic glucose uptake, without reduction of postprandial glycemia. The hepatic nerves are also involved in directing postprandial glucose disposition. Therefore, we hypothesized that the combination of immunosuppressive therapy and hepatic denervation would create additional alterations in the disposition of glucose from a mixed meal. Six 24-hour-fasted conscious dogs that had undergone surgical hepatic denervation (DN) and received cyclosporine A 15 mg/kg daily and prednisone 5 mg twice daily for 7 consecutive days before study (DN + CyP group) received an intragastric mixed-meal feeding over 30 minutes. The results were compared with those from a group of 8 normally innervated dogs receiving the same immunosuppressives (CyP group). Arterial blood glucose concentrations remained elevated over basal in both groups at the end of the 480 minutes postprandial period. The arterial plasma insulin response was no different in the 2 groups (area under the curve 119+/-25 and 100+/-40 nmol/L in DN + CyP and CyP, respectively). In both groups, net gut glucose output was equivalent to approximately 45% of the glucose in the meal, and net hepatic glucose uptake accounted for approximately 54% to 66% of the absorbed glucose. Arterial blood lactate concentrations and net hepatic lactate output were not different between groups at any time. Immunosuppressive therapy is responsible for most of the alterations in postprandial carbohydrate metabolism observed in this model; the lack of hepatic nerves has little additional impact.

Blood Glucose Concentration Measured Using a Glucose Oxidase Method is more Accurate in Venous Blood than Oxygenated Arterial Blood

Background: Portable glucometers are often utilized at the patient's bedside in the ICU or operating room for frequent measurements of the blood glucose concentration. Many of these devices are based on a glucose oxidase method that may be influenced by . The aim of this study was to evaluate the influence of a high of arterial blood on measured glucose values compared with venous blood. Methods: Forty adult patients who underwent surgery with general anesthesia were included in this study. Each patient had a cannula inserted into the radial artery and a central venous catheter through the right internal jugular vein. Two hours after the induction of anesthesia, we drew arterial and venous blood and measured the blood glucose concentration using both a bedside glucometer based on a glucose oxidase method and a laboratory glucometer based on a hexokinase method. We also measured blood gas, electrolyte, and hematocrit values. Statistical analyses were performed with repeated measure ANOVA, multiple linear regression, and Bland-Altman's analysis. Data is expressed as mean . SD. Results: The arterial blood glucose concentration measured by the glucose oxidase method (119.5 25.0 mg/dl) was significantly lower than the venous blood (133.5 24.8 mg/dl) and hexokinase method (134.2 27.1 mg/dl). There was no significant difference between the venous blood glucose concentration by the glucose oxidase method and hexokinase method. When we used the correction formula: corrected glucose value = arterial glucose value by glucose oxidase method + 0.1053 - 5.414, the bias improved from - 14.6 mg/dl to 1.0 mg/dl. Conclusions: The blood glucose concentration measured by the glucose oxidase method is more accurate in venous blood than oxygenated arterial blood. When we measure the blood glucose level using the glucose oxidase method, we should consider the influence of high oxygen tension.

Propofol anaesthesia for surgery in late gestation pony mares

ObjectiveTo characterize propofol anaesthesia in pregnant ponies. AnimalsFourteen pony mares, at 256 ± 49 days gestation, undergoing abdominal surgery to implant fetal and maternal vascular catheters. Materials and methodsPre-anaesthetic medication with intravenous (IV) acepromazine (20 µg kg−1), butorphanol (20 µg kg−1) and detomidine (10 µg kg−1) was given 30 minutes before induction of anaesthesia with detomidine (10 µg kg−1) and ketamine (2 mg kg−1) IV Maternal arterial blood pressure was recorded (facial artery) throughout anaesthesia. Arterial blood gas values and plasma concentrations of glucose, lactate, cortisol and propofol were measured at 20-minute intervals. Anaesthesia was maintained with propofol infused initially at 200 µg kg−1 minute−1, and at 130–180 µg kg−1 minute−1 after 60 minutes, ventilation was controlled with oxygen and nitrous oxide to maintain PaCO2 between 5.0 and 6.0 kPa (37.6 and 45.1 mm Hg) and PaO2 between 13.3 and 20.0 kPa (100 and 150.4 mm Hg). During anaesthesia flunixin (1 mg kg−1), procaine penicillin (6 IU) and butorphanol 80 µg kg−1 were given. Lactated Ringer's solution was infused at 10 mL kg−1 hour−1. Simultaneous fetal and maternal blood samples were withdrawn at 85–95 minutes. Recovery from anaesthesia was assisted. ResultsArterial blood gas values remained within intended limits. Plasma propofol levels stabilized after 20 minutes (range 3.5–9.1 µg kg−1); disposition estimates were clearance 6.13 ± 1.51 L minute−1 (mean ± SD) and volume of distribution 117.1 ± 38.9 L (mean ± SD). Plasma cortisol increased from 193 ± 43 nmol L−1 before anaesthesia to 421 ± 96 nmol L−1 60 minutes after anaesthesia. Surgical conditions were excellent. Fetal umbilical venous pH, PO2 and PCO2 were 7.35 ± 0.04, 6.5 ± 0.5 kPa (49 ± 4 mm Hg) and 6.9 ± 0.5 kPa (52 ± 4 mm Hg); fetal arterial pH, PO2 and PCO2 were 7.29 ± 0.06, 3.3 ± 0.8 kPa (25 ± 6 mm Hg) and 8.7 ± 0.9 kPa (65 ± 7 mm Hg), respectively. Recovery to standing occurred at 46 ± 17 minutes, and was generally smooth. Ponies regained normal behaviour patterns immediately. Conclusions and clinical relevancePropofol anaesthesia was smooth with satisfactory cardiovascular function in both mare and fetus; we believe this to be a suitable anaesthetic technique for pregnant ponies.

Regulation of mammary glucose uptake in goats: role of mammary gland supply, insulin, IGF-1 and synthetic capacity

Variations in mammary glucose uptake were measured during the normal pregnancy-lactation cycle in dairy goats. In addition mammary glucose uptake was studied in response to somatotropin (ST) treatment in mid-lactation and acute increases in glucose concentration induced by sodium-propionate challenge in early lactation. Mammary glucose uptake was independent of arterial glucose, insulin and Insulin-like Growth Factor-1 (IGF-1) concentrations during lactation and during acute increases in arterial glucose concentration. Glucose uptake in the lactating mammary gland of the goat must therefore be carried out by an insulin-independent carrier, possible GLUT1, and glucose supply is not a limiting factor for uptake under in vivo conditions. Extraction of glucose uptake changed markedly during the normal course of lactation, following the overall changes in milk yield. Concentrations of glucose in skimmed milk, believed to reflect intracellular glucose concentration, changed in opposite directions, resulting in decreasing ratios of arterial: skimmed milk glucose concentration with progressing lactation. Thus, mammary synthetic capacity also involves a capacity for glucose uptake, which may be influenced by variations in glucose carrier numbers, as well as mammary metabolic activity (intracellular glucose concentration). In contrast to the situation during the normal course of lactation, ST stimulated milk yield, despite less efficient glucose extraction.

Effects of dexmedetomidine on adrenocortical function, and the cardiovascular, endocrine and inflammatory responses in post-operative patients needing sedation in the intensive care unit

We have compared the effects of dexmedetomidine and propofol on endocrine, metabolic, inflammatory and cardiovascular responses in patients in the intensive care unit (ICU) after major surgery. Twenty patients who were expected to require 8 h of post-operative sedation and ventilation were allocated randomly to receive either an infusion of dexmedetomidine 0.2-2.5 microg kg(-1) h(-1) or propofol 1-3 mg kg(-1) h(-1). Arterial pressure, heart rate and sequential concentrations of circulating cortisol, adrenocorticotrophic hormone (ACTH), growth hormone, prolactin, insulin, glucose and interleukin 6 were measured. An ACTH stimulation test was performed in all patients who received dexmedetomidine. Heart rate was significantly lower in the dexmedetomidine patients. There were no differences in arterial pressure, cortisol, ACTH, prolactin and glucose concentrations between the two groups. A positive response to the ACTH stimulation test varied depending on the diagnostic criteria used. The insulin concentration was significantly lower in the dexmedetomidine group at 2 h (P=0.021), although this did not affect blood glucose concentrations. Growth hormone concentrations were significantly higher in dexmedetomidine-treated patients overall (P=0.036), but circulating concentrations remained in the physiological range. Interleukin 6 decreased in the dexmedetomidine group. We conclude that dexmedetomidine infusion does not inhibit adrenal steroidogenesis when used for short-term sedation after surgery.

BLOOD FLOW EFFECTS ON GLUCOSE UPTAKE FOLLOWING RESISTANCE EXERCISE

Although the effects of blood flow on insulin-stimulated glucose uptake have been extensively investigated, the relative importance of blood flow per se on glucose uptake remains unclear. The purpose of this study was to determine if elevated muscle blood flow following exercise affects muscle glucose uptake. Six subjects (three males, three females) were studied before and after a strenuous bout of lower-body resistance exercise. Following exercise, blood flow was selectively reduced in one leg to approximately the resting rate by inflation of an arterial balloon catheter. Femoral artery blood flow was determined using doppler ultrasound and femoral arterial and venous blood glucose concentrations were measured with a glucose analyzer. Post-exercise femoral artery blood flow was significantly reduced by balloon inflation (855 ± 93 ml/min in the control leg, 440 ± 106 ml/min in the decreased flow leg). Reduction of post-exercise blood flow resulted in a significant (p < 0.05) reduction in glucose uptake (0.196 ± 0.043 mmolòmin-1òleg-1 vs. 0.109 ± 0.038 mmolòmin-1òleg-1) when only femoral flow was considered. When collateral flow was considered, a trend toward a reduction in glucose uptake persisted (0.154 ± 0.045 mmolòmin-1òleg-1; P = 0.10). We conclude that the rate of blood flow is a determinant of muscle glucose uptake in humans following resistance exercise.

Role of fatty acids in the recovery of cardiac function during resuscitation from hemorrhagic shock.

This study tested the hypothesis that removal of fatty acids as a fuel source would improve cardiac efficiency at the expense of reduced cardiac contractile function in the isolated working heart after hemorrhage-retransfusion. Non-heparinized male Sprague-Dawley rats were anesthetized with ketamine-xylazine and were hemorrhaged to a mean arterial blood pressure of 40 mmHg for 1 h. Two-thirds volume of shed blood was reinfused together with 0.9% NaCl in a volume equal to 2.3 times the shed blood volume, followed by continuous infusion of 0.9% NaCl at 10 mL/kg per h for 3 h. Hearts were removed and perfused in closed, recirculating working mode for 60 min to measure hydraulic work and cardiac efficiency. Rates of glycolysis and glucose oxidation were assessed with [5-3H/U-14C] glucose (11 mM) in the absence or presence of 0.4 mM palmitate. Compared to baseline measurements, hemorrhage-retransfusion significantly reduced arterial blood glucose (228+/-7 versus 118+/-12 mg/dL) and non-esterified fatty acid concentrations (0.36+/-0.01 versus 0.30+/-0.02 mM), while elevating blood lactate (0.8+/-0.1 versus 2.5+/-0.4 mM). Perfusion of sham hearts with glucose-only did not alter cardiac work compared to shams perfused with glucose plus palmitate. However, shocked hearts perfused with glucose-only demonstrated a significant reduction in cardiac work compared to shocked hearts perfused with glucose plus palmitate and compared to sham hearts perfused with glucose only (P < 0.05, repeated measures ANOVA). Shocked hearts perfused with glucose plus palmitate showed no reduction in cardiac work compared to shams. Shocked hearts perfused with glucose-only had increased glucose oxidation rates compared to shams perfused with glucose plus palmitate. In sham hearts perfused with glucose-only, myocardial glycogen and triacylglycerol contents were significantly reduced compared to hearts freeze-clamped in situ. These endogenous fuels were not decreased in shocked hearts. These data indicate that hemorrhagic shock renders the heart unable to mobilize endogenous fuels, and suggest that withdrawal of fatty acid oxidation will impair myocardial energy metabolism during resuscitation.