Variations In Liver Research Articles

Time course for cryoprotectant synthesis in the freeze-tolerant chorus frog, Pseudacris triseriata

Increases in liver glycogen phosphorylase activity, along with inhibition of glycogen synthetase and phosphofructokinase-1, are associated with elevated cryoprotectant (glucose) levels during freezing in some freeze-tolerant anurans. In contrast, freeze-tolerant chorus frogs, Pseudacris triseriata, accumulate glucose during freezing but exhibit no increase in phosphorylase activity following 24-h freezing bouts. In the present study, chorus frogs were frozen for 5- and 30-min and 2- and 24-h durations. After freezing, glucose, glycogen, and glycogen phosphorylase and synthetase activities were measured in leg muscle and liver to determine if enzyme activities varied over shorter freezing durations, along with glucose accumulation. Liver and muscle glucose levels rose significantly (5–12-fold) during freezing. Glycogen showed no significant temporal variation in liver, but in muscle, glycogen was significantly elevated after 24 h of freezing relative to 5 and 30 min-frozen treatments. Hepatic phosphorylase a and total phosphorylase activities, as well as the percent of the enzyme in the active form, showed no significant temporal variation following freezing. Muscle phosphorylase a activity and percent active form increased significantly after 24 h of freezing, suggesting some enhancement of enzyme function following freezing in muscle. However, the significance of this enhanced activity is uncertain because of the concurrent increase in muscle glycogen with freezing. Neither glucose 6-phosphate independent (I) nor total glycogen synthetase activities were reduced in liver or muscle during freezing. Thus, chorus frogs displayed typical cryoprotectant accumulation compared with other freeze-tolerant anurans, but freezing did not significantly alter activities of hepatic enzymes associated with glycogen metabolism.

Variation in condition of coastal Newfoundland 0-group Atlantic cod ( Gadus morhua ): field and laboratory studies using simple condition indices

Demersal 0-group Atlantic cod (Gadus morhua L.) were collected in Trinity Bay, Newfoundland, Canada, between August 1993 and January 1994. Diet composition and simple indices of condition (hepato-somatic index, condition factors and body ash content) were determined. Laboratory experiments were also conducted to determine whether simple indices of condition reflect differences in energy intake (ration level) and to determine minimum index of condition values, assessed from 0-group cod that died due to exhaustion of their energy reserves. Determination of lower critical indices of condition provided a meaningful interpretation of field data on feeding, condition and survival of 0-group cod. In the wild, indices of condition reflecting variation in liver and muscle energy reserves of cod increased rapidly with the consumption of Calanus finmarchicus, which exhibited a high incidence of oil sacs, and declined abruptly when this lipid-rich prey was no longer consumed. Liver and muscle condition of 0-group cod from the field varied seasonally, but their condition was consistently above that of cod that died in the laboratory. Laboratory studies, using three ration levels, revealed that condition indices differed over time and among ration levels. Indices of condition representing variation in muscle energy reserves exhibited a steady decline once the hepato-somatic index fell below about 2.0. We interpret this as evidence for depletion of lipids first and then proteins, a pattern similar to that of larger juveniles and adults. We conclude that as long as 0-group cod are above a “safe” level of condition their body length can still increase even when condition is declining.

Liver and kidney kynurenine aminotransferase activity in different strains of rats.

Variations in liver and kidney kynurenine aminotransferase (KAT) activity in Pittsburg-Yoshida, Brown-Norway, albino Wistar, Sprague-Dawley, Long Evans and heterozygous Gunn rats were studied. In liver, values of KAT specific activity, expressed as mumoles of kynurenic acid formed per hour per mg of protein, were different in the groups of Brown-Norway and Pittsburg-Yoshida rats versus Long Evans and Sprague-Dawley rats. The activity expressed as mumoles of kynurenic acid per g of fresh liver showed other differences, being significantly higher in Gunn with respect to other strains of rats and lower in Pittsburg-Yoshida and Brown-Norway rats. In addition, KAT activity was significantly lower in Pittsburg-Yoshida than in Brown-Norway rats. In kidney, the specific activity of kynurenine aminotransferase showed significant differences in the values of Sprague-Dawley and Long Evans rats versus the other strains. The activity expressed per g of fresh tissue was significantly higher in Wistar, Sprague-Dawley, Long Evans and Gunn than in Pittsburg-Yoshida and Brown-Norway rats. No significant differences were found in values between hyperlipidemic Pittsburg-Yoshida and their control Brown-Norway rats. These results high-light the importance of considering various rat strains when inbred animal experimental models are used.

What does carcinogenicity mean and how should we test for it?

Chloral hydrate, which is used as a sedative in pediatric medicine and is a by-product of water chlorination, is hepatocarcinogenic in B6C3F1 mice, a strain that can exhibit high rates of background liver tumor incidence, which are associated with increased body weight. In this study, dietary control was used to manipulate body growth in male B6C3F1 mice in a 2-year bioassay of chloral hydrate. Male B6C3F1 mice were treated with water or 25, 50, or 100 mg/kg chloral hydrate by gavage. The study compared ad libitum-fed mice with dietary controlled mice. The latter received variably restricted feed allocations to maintain their body weights on a predetermined “idealized” weight curve predictive of a terminal background liver tumor incidence of 15–20%. These mice exhibited less individual body weight variation than did their ad libitum-fed counterparts. This was associated with a decreased variation in liver to body weight ratios, which allowed the demonstration of a statistically significant dose response to chloral hydrate in the dietary controlled, but not the ad libitum-fed, test groups. Chloral hydrate increased terminally adjusted liver tumor incidence in both dietary controlled (23.4, 23.9, 29.7, and 38.6% for the four dose groups, respectively) and ad libitum-fed mice (33.4, 52.6, 50.6, and 46.2%), but a statistically significant dose response was observed only in the dietary controlled mice. This dose response positively correlated with markers of peroxisomal proliferation in the dietary controlled mice only. The study suggests that dietary control not only improves terminal survival and decreases interassay variation, but also can increase assay sensitivity by decreasing intra-assay variation.

Reproductive cycle and heavy metals in the organs of red mullet, Mullus barbatus (L.), from the northwestern Mediterranean

Concentrations of the heavy metals Cd, Cu, Fe Mn, V and Zn have been measured in the principal tissues of the red mullet, Mullus barbatus (L.), during a complete sexual cycle. By comparison of metal levels during the reproductive and non-reproductive periods, it was found that concentrations as well as total amounts of Cu, Mn and Zn in liver and gonads of male and female mullets were dependent upon the stage of the sexual cycle. No relationship with the sexual cycle was noted for these metals measured in muscle, kidney, spleen or pyloric caecum. Because of the observed variation in liver and gonad metal concentrations, these tissues appear to be poor indicators of ambient levels of metals in the surrounding waters. However, muscle may prove useful as an indicator tissue owing to its apparent independence of effects of the sexual cycle.

Intestinal phase II detoxification systems: effect of low-protein diet in weanling rats

The effect of a low-protein diet (6% protein, LPD) in vivo on the in vitro activities of cytosolic and microsomal gluthatione S-transferase (GST-c, GST-m) and microsomal UDP-glucuronyltransferase (UDP-GT) was studied in small intestine and liver of weanling male Wistar rats. LPD interrupted the normal curve of growth of the animals, which returned to control values after refeeding with a normal diet (11% protein, ND). Hepatic and intestinal GST-c increased in control rats in parallel with the growth curve. The microsomal enzymes did not show growth variations, except for intestinal UDP-GT activity which began to increase from the second day of ND. After 7 days of LPD there was an increase in GST-c (liver 35ft, P < 0.05; intestine 152%, P < 0.01) and of UDP-GT (liver 58%, intestine 178%, P < 0.05) which returned to control values after 2 days of refeeding with ND. GST-m did not show any variations in liver or intestine. The increase in GST-c, but not in GST-m, with nutritional stress suggests preferential induction of cytosolic enzymes in those enzymatic systems which are located in both positions. The increase in such enzymes after protein malnutrition could indicate an adaptive response by detoxification mechanisms, enhancing intestinal over hepatic capacity, perhaps because the intestine is the primary route of access for orally ingested xenobiotics.

Hypoxia and deposition of iron in liver and spleen of mice given iron supplement

Iron-related changes in peripheral blood and variations in liver and spleen iron concentrations during alternating periods of hypoxia and normoxia have been investigated in iron-supplemented mice by chemical and histological methods. During hypoxia, packed cell volume increased from 40 to 70%. The iron content of the liver increased during the first hypoxic and the following normoxic period, while an increase in spleen iron started after the first hypoxic period. Transferrin saturation fell from about 60 to about 20% during hypoxia and normalized during normoxia. Hypoxia together with iron supplementation led to increased erythropoiesis and parenchymal iron deposition in liver. The reduction in transferrin saturation may be attributed to the effective uptake of iron by hepatocytes simultaneously with the erythropoiesis. The spleen seemed to participate in the production of red cells during hypoxia. The increase in spleen iron during normoxia can be explained by the role of the spleen in the catabolism of excess erythrocytes.

Aspects of the moult, morphology and anatomy of rock pigeons

Aspects of the morphology and anatomy of rock pigeons (Columba guinea) were investigated. Moulting apparently takes place throughout the year at a relatively low intensity. Marked peaks in moulting could only be distinguished for the primaries, secondaries and tail feathers of males. The renewal process for females takes place more irregularly. Apart from the bill dimensions, all standard body measurements of adult males are significantly larger than those of females. The opposite tendency occurs in immatures. Seasonal variation in liver and body mass as well as visible fat content of adult individuals can probably be related to breeding activities and the availability of seasonally abundant food sources. In comparison to the other populations sampled, considerable differences in body mass and fat content were noted for the pigeons from South West Africa.

Diurnal Variation in Liver and Muscle Glutathione Pools of Molting and Nonmolting White-Crowned Sparrows

To test the hypothesis that the tripeptide glutathione (γ-glutamylcysteinylglycine) might function as a free-cysteine buffer in adequately nourished birds, we measured liver and muscle glutathione concentrations early and late in the 8-h overnight fast of molting and nonmolting white-crowned sparrows. During molt-when the overnight requirement for cysteine in keratin synthesis is greatest-liver glutathione concentration early in the overnight fast was greater than that during the pre- or postmolt stages, and the overnight loss of glutathione was greater than that in the postmolt stage. Liver glutathione concentration remained constant overnight or increased slightly during the premolt stage. Variation in muscle glutathione paralleled liver glutathione except that concentrations in muscle were greatest during the postmolt stage. These results suggest that glutathione pools in the liver and muscle of adequately nourished birds (1) could serve as a buffer that accepts or donates cysteine as required by the exigencies of supply (feeding bouts) and demand (intervals between feeding bouts) and (2) may have a homeostatic role in protein synthesis.

Ultrasound attenuation measurements of the liver in vivo using a commercial sector scanner.

Attenuation measurements of various tissue mimicking phantoms and three different groups of patients were obtained using a modified commercial sector scanner. Estimates of attenuation were made using the spectral shift method with mean frequencies at different depths of a region of interest being obtained by both zero crossing and fast Fourier transform techniques. The accuracy and precision of both techniques was compared in phantoms and it was found that the FFT technique yielded less day-to-day variation (SD=3 percent) than the zero crossing technique (5 percent). For larger regions of interest, the range of variation in both techniques was more similar. Day-to-day variation in livers of normal patients was much larger than that seen in phantoms (10 to 15 percent) suggesting that in vivo measurements may be less precise due to actual daily changes in patients' livers. Attenuation estimates of phantoms were high by approximately 0.16 dB/MHz/cm compared to values obtained by transmission techniques. The attenuation values of livers in a group of 31 normal patients ranged from 0.214 dB/cm/MHz to 0.849 dB/cm/MHz with a mean of 0.627 +/- 0.126 dB/cm/MHz for the zero crossing technique while the mean value using the FFT technique was 0.86 +/- 0.168 dB/cm/MHz. A group of 26 Gauchers disease patients also showed wide variation with a mean attenuation value of 0.768 +/- 0.21 dB/cm/MHz using the FFT technique. This was significantly different than that of the normal group (p less than .05). Also, a group of 22 chronic B hepatitis patients was examined, having a mean attenuation value of 0.823 +/- 0.21 dB/cm/MHz, not significantly different from those of normal patients. Highly significant differences were found between the three groups when the power spectrum bandwidths of signals received were compared. These differences may be due to differences in the dependence of attenuation as a function of frequency between the groups and may represent a useful tissue characterization parameter.

Variation in liver and plasma copper concentrations of sheep in relation to breed and haemoglobin type

Copper levels were determined in the liver DM and plasma of 193 entire male lambs aged approximately 24 weeks old when killed and drawn from a flock of grazing sheep comprising 3 breeds and their crosses. Breed contributed significantly to the variation in both liver and plasma copper concentration but whilst for liver the average of the crossbred values was almost the same as the average of the purebred values, for plasma the crossbred values considerably exceeded those of the pure breeds. Haemoglobin type of lamb came close to statistical significance as a source of variation for liver copper concentration ( P < 0·08), but not for plasma copper. However, the differences were in agreement with earlier studies, showing Hb B sheep to have the highest and Hb A sheep the lowest Cu concentrations. Age of dam, age of lamb when killed, birth type and rearing (by virtue of very high values in bottlefed and fostered lambs) and inbreeding of dam also contributed significantly to variation in liver, but not in plasma, copper concentration. The relationship between liver and plasma copper levels was curvilinear, but the residual correlation between logarithmically transformed liver values and the plasma values was low (0·18). Plasma Cu levels were a poor indicator of liver Cu levels and even low levels in liver ( <20 parts 10 6 ) were associated with plasma levels in the range 40 to 160 μg. 100 ml. and mostly above 80 μg. 100 ml.

Effects of hormones and drugs on phosphoribosyl pyrophosphate concentrations in mouse liver.

Concentrations of phosphoribosyl pyrophosphate (PP-ribose-P) in mouse liver were studied as a function of time of day and following injection of a number of metabolites and drugs. A twofold diurnal variation in liver PP-ribose-P concentration was observed. Liver PP-ribose-P concentrations were elevated following injection of glucagon, insulin, epinephrine, and ethylaminothiasiazole.

Phagocytosis of Colloidal Carbon by the Fixed Tissue and Peritoneal Macrophages of New Zealand Mice

The peritoneal cellular response to colloidal carbon has been studied in NZB, NZW, BWF1, BALB/c, CBA and C3Hf mice aged 8 to 10 weeks. The overall patterns of total and differential peritoneal cell counts was similar in all 6 strains of mice. No inter-strain differences were noted in either the removal of carbon from the peritoneal cavity or the distribution of carbon in the fixed tissue macrophages. The results show that phagocytosis of colloidal carbon, an inert particle, is normal in New Zealand mice. Intravenous carbon clearance studies performed on NZB, BALB/c and CBA mice showed that phagocytosis of carbon was identical in each strain when correction was made for variations in liver and spleen weight.

Evidence for a Linear Correlation between the Level of Dietary Tryptophan and Hepatic NAD Concentration and for a Systematic Variation in Tissue NAD Concentration in the Mouse and the Rat

The purpose of the study was to determine the relationship of tryptophan intake (substrate availability) and tryptophan oxygenase (TO) activity to formation of nicotinamide adenine dinucleotide (NAD). Mice, both normal and adrenalectomized, and young rats were maintained on a 6 AM to 6 PM light, 6 PM to 6 AM dark schedule and fed ad libitum a synthetic amino acid diet containing various amounts of tryptophan, from zero to about three times the normal requirement for growth. Tissue free tryptophan, TO activity, and tissue NAD were measured. The animals displayed a positive linear correlation between level of dietary tryptophan and hepatic NAD concentration which was most evident during the dark period. There was some indication of a direct relationship between NAD values and tryptophan oxygenase activity at night. These results suggest that increases in enzyme activity may be necessary at the time of feeding in order to achieve the elevated levels of NAD occasioned by intakes of dietary tryptophan which are in excess of that needed for growth. Additional findings indicate the existence of a systematic variation in liver, heart and spleen NAD concentration and in hepatic NAD/NADH ratio.