Tissue Anoxia Research Articles

Sodium Nitroprusside

Sodium Nitroprusside

Anoxic disturbance of the isolated respiratory network of neonatal rats.

Tissue oxygen (PO2), K+ (aKe), pH (pHe) and Ca2+ ([Ca2+]e) were measured in the region of the ventral respiratory group (VRG) in the in vitro brainstem-spinal cord preparation of neonatal rats. During tissue anoxia, elicited by superfusion of N2-gassed solutions, an initial increase in the frequency of respiratory activity, lasting between 2 and 12 min, turned into a frequency depression. During anoxia periods of up to 60 min, respiratory activity persisted in solutions containing CO2/bicarbonate, whereas a complete blockade was observed after 15-25 min in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid- (Hepes)-buffered salines. After such anoxic apnea, respiratory rhythmicity could be reactivated by superfusion of hypoxic, CO2/bicarbonate-buffered solutions. In both types of hypoxic solutions, aKe increased by maximally 1.5 mM, whereas an initial increase of pHe by up to 0.05 pH units turned, after 2-4 min, into an acidification which could exceed 0.5 pH units. In contrast, [Ca2+]e remained unaffected by anoxia. Addition of 2-5 mM cyanide (CN-) to oxygenated Hepes-buffered saline evoked an increase in PO2 in the VRG from 100 to more than 300 mmHg. The effects of CN- on respiratory activity, aKe and pHe were almost identical to those during anoxia. In oxygenated, CO2/bicarbonate-free solutions of different pH, however, an increase in pHe in the VRG led to a decrease in respiratory frequency, whereas a fall of pHe produced a frequency acceleration. A rise of aKe in the VRG by more than 2 mM as induced by superfusion of a 7 mM K+ solution led to a sustained increase of respiratory frequency. The results indicate that blockade of aerobic metabolism does not severely perturb K+ and Ca2+ homeostasis and that the biphasic response to anoxia is not directly related to the observed changes in PO2, aKe, pHe, or [Ca2+]e. In the respiratory network of neonatal mammals, CO2 might provide a stimulus for long-term maintenance of respiratory activity under oxygen depletion.

Oxygen supply and ion homeostasis of the respiratory network in the in vitro perfused brainstem of adult rats.

An in vitro arterially perfused medulla preparation of 3- to 8-week-old rats is described in which synchronous rhythmic activity (frequency 4.5 +/- 1.7 cycles/min, burst duration 3.1 +/- 1.1 s, n = 40) was recorded from hypoglossal (XII), vagal (X), or spinal (C1-2) nerves and from different classes of neurons in the region of the ventral respiratory group (VRG). Stimulation of dorsal X nerve rootlets produced a reversible blockade of rhythmic activity. Under steady-state conditions, tissue oxygen (pO2) in the VRG (depth of 600-1600 microns below the ventral surface) fell from 180 to 40 mmHg. Extracellular K+ activity (aKe) in the VRG was about 0.3 mM higher, calcium concentration ([Ca]e) did not differ, and pH (pHe) was about 0.27 units lower than in the perfusion or superfusion solution (with an aKe of 2.2 mM, a [Ca]e of 1.5 mM and a pHe of 7.4). During inspiratory XII nerve discharges, rhythmic increases of aKe by up to 0.8 mM were detected in the VRG. Perfusion of N2-gassed hypoxic solutions (5-10 min) resulted in a tissue anoxia of the VRG and a reversible cessation of rhythmic activity after 2-7 min. Such anoxia was accompanied by a rise of aKe by up to 35 mM, whereas pHe and [Ca]e fell (from mean levels of 7.17 and of 1.5 mM, respectively) by more than 0.2 pH units and 1 mM. Similar observations were made during a 2- to 5-min arrest of the perfusion pump to simulate ischaemia, whereas significantly larger changes in aKe, pHe and [Ca]e were revealed during an "ischaemia" period of 10 min. The results indicate that the rhythmic activity is generated by the functionally intact respiratory network of the VRG in which neurons are under aerobic conditions and ion homeostasis is not impaired. We conclude that the preparation is an appropriate in vitro model for the analysis of the cellular mechanisms for generation of respiratory rhythm and of metabolic perturbations like anoxia and ischaemia in the mature respiratory network.

Anoxia induced functional inactivation of neonatal respiratory neurones in vitro.

In the isolated brain stem-spinal cord preparation of neonatal rats, respiratory (C4) activity persisted at reduced frequency during tissue anoxia. In seven biphasic expiratory (Bi-E) and in 12 of 22 inspiratory (Insp) neurones, recorded with the 'blind' patch-clamp technique, anoxia evoked a persistent hyperpolarization by up to 16 mV whereas membrane potential of the remaining Insp neurones depolarized slightly or remained unaffected. Respiration-related synaptic potentials and action potential discharges were blocked in all Bi-E and in about 50% of the Insp neurones, whereas rhythmic activity persisted in the other cells. The results indicate that a major population of neonatal respiratory neurones is functionally inactivated during anoxia. This mechanism might contribute to the anoxia tolerance of the immature brain.

NMDA antagonists increase recovery of evoked potentials from slices of rat olfactory cortex after anoxia.

1. The role of glutamate in producing tissue damage during cerebral anoxia was investigated in brain slices using antagonists to the NMDA and AMPA receptor types. 2. Tissue function was assessed by field recordings of the synaptically evoked potentials elicited by stimulating the main afferent input to the olfactory cortex, the lateral olfactory tract. Anoxia was produced by bathing the slice in glucose-free solution equilibrated with 95% N2/5% CO2. 3. The amount of recovery of the evoked potential was inversely dependent on the period of anoxia and temperature: at 24 degrees C, 15 min of anoxia followed by reoxygenation produced a 14.6 +/- 4.1% recovery whereas there was no recovery at 35 degrees C. 4. Dizocilpine and ketamine had no effect on synaptic transmission in oxygenated media but following anoxia they produced an increased recovery of the responses: from 14.6 +/- 4.1% to 48.3 +/- 7.8% for dizocilpine (10 microM) and 21.6 +/- 7.7% to 87.2 +/- 7.1% for ketamine (200 microM); the tissue endurance to anoxia was increased by around 5 min. 5. Blockade of the AMPA receptors did not influence recovery in spite of the depressed synaptic transmission. A similar synaptic attenuation produced by lignocaine provided some increase in post-anoxic recovery. 6. The NMDA receptor antagonist, AP5, antagonized NMDA at 50 microM by 3.7 fold and at 200 microM by 15 fold but only 200 microM increased post-anoxic recovery. This suggests that a substantial degree of NMDA antagonist is required before anoxic tissue damage due to NMDA receptor activation can be nullified. The antagonist to the glycine binding site, 7-chlorokynurenic acid also increased recovery. 7. These in vitro experiments confirm the idea that NMDA receptor activation makes a substantial contribution to cerebral tissue damage and that this can be reduced by a substantial blockade of these receptors.

Sulfide and cyanide induced mortality and anaerobic metabolism in the arcid blood clam Scapharca inaequiv alvis

1. The survival and metabolic adjustments of the blood clam S. inaequivalvis have been determined at environmental anoxia and tissue anoxia induced by sulfide and cyanide. 2. Times to 50% mortality were established in clams placed in oxygenated seawater with and without dissolved sulfide or free cyanide or deoxygenated seawater with and without dissolved sulfide. 3. Anaerobic metabolism was studied in live animals and in red blood cells incubated in vitro. Tissue anoxia due to sulfide and cyanide caused greater changes in the levels of aspartate and the pyruvate derivatives, compared to environmental anoxia.

Host factors predisposing to anaerobic infections

Factors that predispose to infection in general, of course, may predispose to infection with anaerobes. Included in this category are diabetes mellitus, neutropenia, hypogammaglobulinaemia, malignancy, splenectomy, collagen vascular disease, cytotoxic drug therapy, corticosteroid therapy and other immunosuppression. However, even with these situations there may be certain, more specific, associations: anaerobic cholecystitis and anaerobic osteomyelitis in diabetics, neutropenic colitis, and the increased incidence of local anaerobic infections associated with carcinoma of the lung, colon and uterus. Conditions that lead to decreased redox potential more specifically predispose to infection with anaerobes. Included in this category are obstruction and stasis, tissue anoxia, tissue destruction, vascular insufficiency, prior aerobic infection, burns, foreign body implantation, and calcium salts in a wound (in association with fractures). Other specific clinical situations that predispose to anaerobic infections include leukaemia; oral, gastrointestinal, and female pelvic surgery; trauma at other sites; childbirth; aspiration pneumonia; human and animal bites; and therapy with agents with poor activity against anaerobes (e.g. aminoglycosides, quinolones). AIDS patients appear to be predisposed to severe periodontal disease and its complications.

Host factors predisposing to anaerobic infections

Factors that predispose to infection in general, of course, may predispose to infection with anaerobes. Included in this category are diabetes mellitus, neutropenia, hypogammaglobulinaemia, malignancy, splenectomy, collagen vascular disease, cytotoxic drug therapy, corticosteroid therapy and other immunosuppression. However, even with these situations there may be certain, more specific, associations: anaerobic cholecystitis and anaerobic osteomyelitis in diabetics, neutropenic colitis, and the increased incidence of local anaerobic infections associated with carcinoma of the lung, colon and uterus. Conditions that lead to decreased redox potential more specifically predispose to infection with anaerobes. Included in this category are obstruction and stasis, tissue anoxia, tissue destruction, vascular insufficiency, prior aerobic infection, burns, foreign body implantation, and calcium salts in a wound (in association with fractures). Other specific clinical situations that predispose to anaerobic infections include leukaemia; oral, gastrointestinal, and female pelvic surgery; trauma at other sites; childbirth; aspiration pneumonia; human and animal bites; and therapy with agents with poor activity against anaerobes (e.g. aminoglycosides, quinolones). AIDS patients appear to be predisposed to severe periodontal disease and its complications.

Resuscitation from Severe Acute Hypercapnia: Determinants of Tolerance and Survival

A 46-year-old man underwent cosmetic facial surgery under general anesthesia. He was ventilated by mask with an oxygen-enriched gas mixture for 4 to 6 h and monitored by pulse oximetry. Despite adequate arterial saturation (SaO2 > 90 percent) throughout the procedure, he remained in a deep coma after termination of anesthesia. Initial arterial blood gas analysis revealed a pH of 6.60 and a PaCO2 of 375 mm Hg. The patient was intubated and placed on mechanical ventilation. As his respiratory acidosis resolved, he regained consciousness quickly and recovered without any neurologic deficits. This case of record extreme hypercapnia and review of the literature demonstrates that survival is possible in acute severe respiratory acidosis as long as tissue anoxia and ischemia are prevented. We discuss the tissue effects of acute hypercapnia and newer aspects of the nature of intracellular pH regulation in critical tissues that afford considerable tolerance to acidosis. The dependence of these mechanisms upon active ion transport underscores the importance of adequate tissue oxygenation and perfusion.

Oxygenation of mammary tumors: from isotransplanted rodent tumors to primary malignancies in patients.

As a result of a compromised and anisotropic microcirculation, isotransplanted mammary tumors in mice exhibit hypoxic and anoxic tissue areas which are heterogeneously distributed within the tumor mass. Similarly, in poorly perfused human breast cancer xenografts, hypoxia develops at early growth stages and expands with tumor growth. In contrast, breast cancer xenografts with high perfusion rates exhibit an oxygenation status comparable to that of most normal organs. There is clear experimental evidence that the efficiency of tumor blood flow in isotransplanted tumors and in xenografted human breast cancers is the principal modulator of tissue oxygenation. The pO2 distribution found in primary lesions in patients ranged from the pO2 histograms obtained in "low-flow" isotransplants and xenografts to those measured in "high-flow" breast cancer xenografts or normal tissues. From our extended and systematic clinical studies there is clear indication that the oxygenation status of human breast cancers in situ does not correlate with the clinical stage and/or histological grade of an individual tumor.

1,2-Diacylglycerol and ceramide levels in rat liver and skeletal muscle in vivo

1,2-Diacylglycerol and ceramide levels were measured in liver and skeletal muscle of rats under the following four experimental conditions: 1) during rapid fetal growth in the second half of gestation and during postnatal aging, 2) during tissue anoxia lasting up to 10 min, 3) during fasting for up to 6 days, and 4) during stress induced by injection of endotoxin (lipopolysaccharide from Salmonella enteritidis). 1,2-Diacylglycerol and ceramide levels in fetal liver were 77 and 58% lower, respectively, than those of young rats after weaning. 1,2-Diacylglycerol and ceramide concentrations in liver of postnatal rats were not influenced by aging. Anoxia produced a 41-64% increase in liver 1,2-diacylglycerol levels and a 9-21% increase in liver ceramides. Fasting of adult rats for up to 6 days had no effect on 1,2-diacylglycerol and ceramide levels in liver. However, fasting increased skeletal muscle concentrations of 1,2-diacylglycerol and ceramides 88 and 44%, respectively. Injection of endotoxin had a biphasic effect on liver 1,2-diacylglycerol levels, causing a transient 52% increase at 1 h, followed by a 24-38% decrease below the control level at 17 h after endotoxin administration. Liver ceramide levels were increased 66, 52, and 27% at 1, 3, and 5 h after endotoxin, respectively, but did not differ from control at 17 h after injection. Endotoxin had no effect on muscle 1,2-diacylglycerol and ceramide concentrations at any interval.

Osteomyelitis of the mandible as a result of sickle cell disease: Report and literature review

Only five cases of osteomyelitis of the mandible as a result of sickle disease have been published. We report another case, which uniquely affected not only the osseous portion of the mandible, including the condyle, but also the adjacent musculature. Radical resection of the involved hard and soft tissue was necessary to cure the patient. Two possible etiologies are discussed. The first states that the sickle cell crisis caused a tissue anoxia in which this tissue became secondarily infected; the second states that the preexisting infection triggered or augmented the sickling phenomena.

Tumor tissue oxygenation as evaluated by computerized-po 2-histography

A computerized pO 2 measurement system with a novel electrode motion pattern (Sigma-pO 2-histography) was evaluated in vitro and in vivo. The system was found to be reliable in 0.9% saline and 10% hydroxyethylene starch solution and in fresh donor blood. Marked deviations were found in lipid and hemoglobin solutions and in fluorocarbon emulsions. Histograms obtained in rat liver, mouse muscle, and subcutis were similar to previously reported distributions. Direct comparison between Sigma-Eppendorf and self-constructed Whalen-type electrodes in hypoxic tumors gave similar results. A large series of measurements indicated that hypoxic and anoxic tissue areas were frequently found both in isografted rodent and in xenografted human tumors. The extent of oxygen deprivation depended on the cell line studied, tumor size, implantation site, the vascularity, and the actual tissue perfusion. Pentobarbital anesthesia redistributed the tumor oxygenation without affecting the median pO 2 value. Tumors growing in a pre-irradiated bed were less oxygenated than those at untreated sites. Hyperthermia at therapeutically relevant temperatures reduced pO 2 levels in adequately oxygenated tumors whereas little change was detected in poorly oxygenated tumors. First measurements in tumors in patients revealed marked inter- and intratumor heterogeneity. It is concluded that this novel technique is suitable for routine measurements of tissue oxygenation of solid tumors in situ.

Circadian Influence in Cardiovascular Disease (Part 1)

This department will offer stylized clinical presentations of current cardiovascular issues. Questions raised as a case history evolves highlight key elements that are elaborated upon in the discussions which follow.

Etiology of childhood leukemia: A possible alternative to the Greaves hypothesis

Whenever a country has experienced a significant decrease in infant mortality there has always been a concomitant increase in childhood cases of acute lymphoblastic leukemia (ALL). According to Greaves, this increase is the result of a new type of leukemia, which was first seen in Britain between 1920 and 1940. An alternative hypothesis is proposed which assumes that, for childhood cases of ALL, infections are competing causes of death and for juvenile myeloid leukemia (JML) the principal competitor is the sudden infant death syndrome (SIDS). The SIDS association is the result of JML originating in undifferentiated (erythro-myeloid) stem cells and having faulty erythropoiesis as a side effect. With this congenital anomaly as part of the disease process, the low oxygen pressures of deep sleep may be sufficient to cause sudden death from tissue anoxia.

Aspartate activation of pyruvate kinase from the kidney of Concholepas concholepas (gastropoda: muricidae)

1. 1. Kinetics of Concholepas concholepas kidney pyruvate kinase (EC 2.7.1.40) was sigmoidal with regard to phosphoenolpyruvate ( S 0.5 = 0.28 mM; n H = 1.92 ) and hyperbolic with respect to ADP ( m = 0.29 mM ). 2. 2. The enzyme was activated by aspartate ( a = 0.89 mM ) and fructose 1k,6-diphosphate ( K a = 9.8 μM ). Saturation with activators was hyperbolic. 3. 3. Co-operativity was observed with regard to the negative effector alanine ( I 0.5 = 0.23 mM; n H = 1.25 ). In the presence of 0.1 mM fructose 1,6-diphosphate, I 0.5 = 3.89 mM and n H = 2.16 . In the presence of 3 mM aspartate, I 0.5 = 0.56 mM and n H = 1.21 . Alanine inhibition was only partially reversed by the activators. 4. 4. Pyruvate kinase activity decreased from 3.45 ± 0.15 units/g wet wt in the aerobic kidney to 1.1 ± 0.10 units/g wet wt in the anoxic tissue. Kinetic parameters for substrates and allosteric effectors of the enzyme were not altered by anoxic stress. 5. 5. The results are discussed in connection with the adaptation to anoxia of the kidney of C. concholepas.

Enhanced lipolysis of myocardial triglycerides during low-flow ischemia and anoxia in the isolated rat heart.

We studied lipolysis in the isolated rat heart, measured as glycerol release during anoxia, low-flow ischemia and subsequent reperfusion. It was found that the rate of lipolysis was enhanced during ischemia/anoxia while the lipase activities in tissue extracts involved in the myocardial lipolysis and the amount of triglycerides were not affected. This indicates the dominant occurrence of a lipolysis-reesterification principle in ischemic and anoxic tissue. A common observation of ischemia/anoxia is an increase in the tissue NADH/NAD+ ratio. Therefore we investigated the effect of lactate and malate, both of which enhance the tissue redox state on myocardial lipolysis. Perfusion in the presence of lactate (10 mM) and malate (10 mM) both stimulated myocardial lipolysis by about five times. This suggests that the rate of reesterification of product fatty acids to triglycerides, which is determined by the NADH/NAD+ ratio, because of the increased formation of glycerol 3-phosphate from dihydroxy acetone phosphate, plays an important role in the regulation of lipolysis. The existence of triglyceride-fatty acid-triglyceride cycle is discussed.

Degradation of phospholipids and triacylglycerol, and accumulation of fatty acids in anoxic myocardial tissue, disrupted by freeze-thawing.

The degradation of lipids by endogenous hydrolytic activity has been studied in rat cardiac tissue deliberately damaged by freezing and thawing prior to storage under anoxic conditions. Aliquots of the freeze-thawed material were kept at 37 degrees C under an atmosphere of N2 up to 120 minutes. Triacylglycerol was hydrolyzed at a rate of 0.14 mumol fatty acids per minute per gram dry weight of tissue. Hydrolysis of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was associated with proportional production of lyso PC and lyso PE, respectively. This finding indicates that the activity of lysophospholipase is negligible in autolyzing cardiac tissue. The rate of hydrolysis of PC and PE was found to be 0.10 and 0.06 mumol per minute per gram dry weight of tissue. The observation that lyso PC and lyso PE mainly contained saturated and mono-unsaturated fatty acids indicates that phospholipase A2 rather than A1 is active in autolyzing cardiac tissue. The accumulation of fatty acids corresponded with the loss of triacylglycerol and phospholipids from the tissue during 120 minutes of autolysis.

Age and immunity to respiratory tract infections

Immunological reactions that occur in the respiratory tract in response to infectious agents have recently gained distinct attention. Humoral (1–20) and cellular immune reactions (16, 21–34) have been identified in the lungs of a number of animal species and of man. Respiratory tract infections occur frequently among the elderly and constitute one of the leading causes of death. Aged humans have a greater mortality from pneumonia (35), influenza (36), tuberculosis (37), infective endocarditis (38), urinary tract (39) and intraabdominal (40) infections. Perla and Marmorston reviewed the effects of aging on natural resistance to infection (41–42), and focused on four factors as major determinants of resistance in old age: (a) changes in structure and function of vital organs, especially endocrine glands and the splenic lymphatic apparatus; (b) underlying pathological conditions facilitating microbial invasion; (c) alterations in circulatory and nervous systems which lead to trophic changes and tissue anoxia; and (d) prolonged subclinical vitamin and mineral deficiencies. Some investigators have postulated that the predisposition of the aged to infections is not due to a declining immune response (42–43), rather than to other physiologic changes of aging. Many studies of animals and man have linked the increase of infectious disease in the aged to reduced immunological vigor (44–47), in particular, deficiency of T-cell dependent immune responses (reviewed in 48–51). These studies which focused on the circulating immune system (peripheral blood, spleen, and peripheral lymph nodes) while clearly important, have not included information on age-related changes in the mucosal immune system. Studies on mucosal immunity are obviously relevant for elucidating the mechanisms of infectious diseases in the elderly. The importance of such information is emphasized by accumulating evidence that microorganisms entering the host encounter a functionally compartmentalized and distinct lymphoid area underlying the mucosal surfaces of the lung, genital tract, and intestine. These distinct lymphoid areas are characterized by unique immune cell populations, cell trafficking and homing patterns, and immune responsiveness (reviewed in 48, 52–54).

Blood flow and tissue reaction at skin wound closures.

AbstractThe purpose of this study was to compare blood flow and tissue reaction in rats following wound closure with either staples or interrupted sutures using nylon pr silk. Microblood flow over a period of 6 days was measured in each layer of normal skin and at the incision site, Macroscopic changes in skin incisions were evaluated 2 hours after closure and 6 days after closure for histologic examination. Measurements of blood flow in normal skin showed the greatest amount of the stratum papillare of the corium. Blood flow in wound tissue closed with staples increased from baseline after 1 hour and continued over the 6‐day period, suggesting active regeneration of new capillaries. Blood flow in rats sutured with nylon decreased markedly to below baseline value, but increased after 3 days and 6 days. A similar trend occurred in wounds closed with silk although the decrease was greater and blood flow did not increase above the baseline at 6 days. Wound healing was complete 6 days after closure with staples, skin color normal, the incision hardly discernible. The wound sutured with nylon showed anoxia of tissue after 2 hours, but at 6 days, appeared similar to the stapled wound. Six days after closure, the silk suture site was swollen, dark in color, and tight. Histologic findings revealed no hypertrophy of the regenerated epidermis at the stapled suture site. The nylon group showed slight hypertrophy of the epidermis, inflamed cells in the subcutaneous tissues, and slight edema at the wound site. It is my conclusion that blood flow and wound healing are most satisfactory when staples are used for wound closure.