Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Snakes”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61Linked to original sources
PubMed1983

Parathyroid gland of the freshwater snake Natrix piscator Schneider.

The structure and function of the parathyroid glands of freshwater snake, Natrix piscator, were studied. N. piscator has two pairs of parathyroid glands which are composed of cell cords of typical endocrine appearance, and follicles are absent. Parathyroidectomy was followed by significant (P less than 0.001) hypocalcemia and hyperphosphatemia throughout the 5th week of experimental period. Following parathyroidectomy, calcium and phosphate concentrations in bone were significantly (P less than 0.05) increased after 5 weeks; however, these values in muscle were not significantly changed. Tetany was also observed in parathyroidectomized snakes. Histological structure and function of the glands do not appear to vary seasonally. Administration of parathyroid gland extract of this ophidian reptile into rats caused significant (P less than 0.05) elevation of serum calcium.

Animals↗
PubMed1984

The vasopressor action of the renin-angiotensin system in the rat snake, Ptyas korros.

The pressor actions of homologous kidney extract and human angiotensins I and II were studied in the conscious rat snake, Ptyas korros. A converting enzyme inhibitor (captopril), an angiotensin II analogue [( Sar1,Ala8]ANG II), an alpha-adrenergic receptor antagonist (phentolamine), and a catecholamine releaser (reserpine) were used to elucidate their actions. It was found that captopril attenuated the pressor effects of the kidney extract and angiotensin I but not that of angiotensin II. [Sar1,Ala8]ANG II and phentolamine both significantly attenuated, but did not completely inhibit the vasopressor actions of the kidney extract and angiotensins I and II. However, reserpine administration did not reduce the action of angiotensin II. These findings suggest that the renin-angiotensin system in snakes is similar to those present in mammals and other nonmammalian species, except for the mechanism of angiotensin II action. In the present study, angiotensin II was found to act partly through the alpha-adrenergic receptor which is not as specific as that in mammals and thus may respond to an agonist other than its usual ones, and partly through the vascular angiotensin II receptor.

Angiotensin I↗
PubMed1984

Erythropoietin, testosterone, and thyroxine in the erythropoietic response of the snake, Xenochrophis piscator.

The erythropoietic response of snakes was examined after injecting human urinary erythropoietin (Ep), testosterone propionate (TP), and L-thyroxine (T4), separately and in combinations, into starved ophids. The effect of starvation was reflected by a decrease in the number of erythrocytes, a fall in hemoglobin concentration, and a decline in hematocrit. Statistically significant elevation of erythrocyte number, hemoglobin concentration, and hematocrit was observed at 24 hr following the administration of Ep + T4, and Ep + TP + T4 into starved ophids. The erythrocyte number was also increased by T4 treatment at 24 hr. Furthermore, while T4 and Ep individually increased the red blood cell number at 168 hr, T4, TP + T4, and Ep + TP + T4 elevated the hemoglobin concentration and Ep + T4 and Ep + TP + T4 increased the hematocrit value. It is suggested that the influence of any one of the hormones utilized in the present study on blood morphology of fasted snakes depends to a greater extent on the presence or absence of the other hormone(s).

Animals↗
PubMed1986

Ovarian development in red-sided garter snakes, Thamnophis sirtalis parietalis: relationship to mating.

Female red-sided garter snakes (Thamnophis sirtalis parietalis) exhibit a complex array of behavioral patterns. Females may mate once, more than once, or not at all in the spring of the year, and a high percentage of females may mate in late summer before returning to winter hibernacula. The role of mating in the induction of ovarian growth in this species is complicated by this pattern of spring and late summer mating. Females hibernated in the laboratory that mate on emergence in the spring exhibit higher frequencies of ovarian recrudescence than females that do not mate when exposed to males. Yet neither male courtship nor mating in the spring is required for ovarian development. However, mated and unmated females collected in the field in the spring of the year do not differ in frequencies of ovarian recrudescence. Ovarian growth in unmated females collected in the spring parallels the incidence of mating in the previous late summer. Thus, mating may influence the initiation of ovarian growth, but the effect can occur immediately (from spring mating) or be stored over winter (from late summer mating). Large year-to-year variation in reproductive rates of female red-sided garter snakes suggests that other factors such as nutrition and stored energy reserves may modify the effects of mating on ovarian growth.

Animals↗
PubMed1987

Plasma steroid hormone levels of female red-sided garter snakes, Thamnophis sirtalis parietalis: relationship to mating and gestation.

Plasma levels of progesterone (P), testosterone (T), estradiol (E2), and corticosterone (B) of female red-sided garter snakes were measured during the period of ovarian development. Differences in hormone levels were analyzed with respect to three factors: whether the female mated in the spring, ovarian condition, and time after emergence from hibernation. The influence of these three factors on steroid hormone levels of two groups of females were then compared. In experiment I, females were obtained in the fall, subjected to an artificial dormancy period, and placed on warm, summer-like conditions in the laboratory. In experiment II, females were collected in the spring and sampled in the field. They were held in the field on fluctuating conditions for several weeks and then returned to the laboratory for sampling during early vitellogenesis. Females in experiment I had a shortened but otherwise normal ovarian and gestational cycle, whereas females in experiment II had an ovarian and gestational cycle typical of females in the field. In spite of these differences, the steroid hormone levels in relation to the ovarian cycle were remarkably similar for the two groups of females. We confirmed that mating in the spring induces a surge in E2; E2 also was elevated in a single sample obtained from animals collected in the fall. This elevation in plasma levels of E2 in the fall occurs at a time when the majority of females have recently deposited sperm in their oviducts. Plasma levels of T, P, and B were not significantly influenced by mating. Unlike previous reports of other viviparous snakes, plasma levels of P were low and mostly nondetectable, even during late gestation. Plasma T was significantly elevated around the time of late vitellogenesis and ovulation, and there was a tendency for E2 levels to be elevated at this time. In the field, plasma B levels were initially high immediately after capture and declined with time. Plasma B was significantly elevated in all females several weeks after emergence, suggesting that levels of B may vary with other annual cycles.

Animals↗
PubMed1985

Behavioral and physiological control of yolk synthesis and deposition in the female red-sided garter snake (Thamnophis sirtalis parietalis).

Ovarian recrudescence in female garter snakes, Thamnophis sirtalis parietalis, follows spring emergence from hibernation and mating. In the laboratory, courtship and mating stimuli significantly increased the proportion of female garter snakes becoming pregnant, although some noncourted nonmated controls also became pregnant. Females given artificial mating stimuli under anesthetic, without courtship stimuli, were no more likely than either noncourted, nonmated or anesthetized controls to become pregnant. Hormonal changes and yolk synthesis rapidly followed mating in both laboratory and field females; serum estradiol increased more than 10-fold in 2 days and serum calcium, a measure of yolk precursor lipoprotein (vitellogenin) concentration, increased more than two times in 10 days. Administration of exogenous estradiol stimulated yolk synthesis, but did not result in yolk deposition into ovarian follicles. However, administration of ovine follicle-stimulating hormone induced both hepatic yolk synthesis and yolk deposition. Our results are consistent with the hypotheses that courtship and copulation are facilitatory to ovarian recrudescence but neither alone nor in combination is necessary nor sufficient, and in this species yolk synthesis and yolk deposition are separately regulated.

Animals↗
PubMed1992

Inhibition of Sendai virus by various snake venom.

Viperid, elapid and crotalid snake venoms were screened in vitro for antiviral activity against Sendai virus. The hemolysis of 10(8) human erythrocytes in 1 ml, caused by 70 HAU of Sendai virus, was abolished when the virions were pretreated with 10 ug of the viperid venom of Echis coloratus, and was considerably diminished when pretreated with 10 ug of the venom of Echis carinatus sochureki, the cobra venoms of Naja atra and Naja nigricollis nigricollis. These venoms did not affect the erythrocytes but inhibited the virions themselves irreversibly. All other examined snake venoms had low or no antiviral activity. There was no correlation between the proteolytic and the antiviral activity of the venoms.

Animals↗
PubMed1994

Food consumption in relation to bodyweight in captive snakes.

The weekly food consumption of 25 captive snakes of nine species fed on freshly killed laboratory mice was measured for periods of three to eight weeks. Their ad libitum intake was found to vary in proportion to their initial body weight (w) raised to an exponent close to and not significantly different from 0.75 (mean [SE] 0.79 [0.064]. However, the food consumption in relation to w varied between animals, and the rates of change in bodyweight relative to w0.75 during the measurement period were highly correlated with food consumption (r = 0.801, P < 0.001). From the regression describing the relationship between these variables, the mean food requirement for maintenance was estimated at 4.2 g day-1 kg-0.75 and the mean rate of weight loss when fasting was estimated at 2.0 g day-1 kg-0.75. The mean weight gain for each gram of food eaten above maintenance level was estimated to be 0.46 g. The limits, in relation to w, within which the ad libitum food consumption of snakes can be predicted from these results with 95 per cent probability are estimated.

Animals↗
PubMed1982

Ventilation, gas exchange and blood gases in the snake, Pituophis melanoleucus.

Oxygen consumption of Pituophis melanoleucus was about 30-50% of values predicted for snakes of similar body mass. Following a rise in body temperature there were transient increases in CO2 elimination and the respiratory exchange ratio for about 6 hours. Lowering body temperature produced transient decreases in CO2 elimination and the respiratory exchange ratio for about 24 hours. Respiratory exchange ratios measured up to 6 days following these transients were found to be significantly higher at higher temperatures. From 20 to 30 degrees C arterial pH declined 0.157 unit, and there was a significant decline in blood CO2 of 1.3 mM which is consistent with the direction of the transients in CO2 elimination. This fall in CO2 at higher temperatures probably results from increased levels of plasma fixed acid (e.g., lactate). Minute ventilation and breathing frequency increased with body temperature while tidal volume remained nearly constant at 29 ml/kg. Breathing was regular, with each breath followed by an inspiratory pause. Air convection requirement declined from about 61 ml air/ml O2 at 15 degrees C to 36 ml air/ml O2 at 30 degrees C. Blood convection requirement remained constant at about 44.6 ml blood/ml O2 at 20 degrees C and 30 degrees C with the result that ventilation/perfusion declined from approximately 1.13 to 0.76. In Pituophis, mechanisms of acid-base regulation and adjustments in gas transfer with temperature do not differ fundamentally from those of other air-breathing ectotherms. However, snakes utilize tidal volumes which are 2 to 2.5 times larger than other reptiles and have air convection requirements which exceed other reptiles by about 50%.

Acid-Base Equilibrium↗
PubMed1983

Effects of hypoxia on lung volume in the garter snake.

Ventilation and lung volume were measured in unanesthetized garter snakes using a headout body plethysmograph. The breathing cycle consisted of expiration, inspiration and a prolonged post-inspiratory breath-holding period, which lasted until the onset of the next expiration. Hypoxia induced increases in VT and in the volume at which the breath was held between cycles. Hypercapnia usually elicited hyperpnea after an initial, transient inhibition of breathing movements, but was accompanied by little or no increase in breath-holding lung volume. Snakes with T-tube tracheostomies failed to maintain the normal positive intrapulmonary pressure during the breath-holding period and failed to increase breath-holding lung volume in hypoxia, despite increased inspiratory excursions. These studies demonstrate a pronounced increase in lung volume during hypoxia and indicate that this response requires an intact upper airway. These findings in a reptile may be related in evolutionary terms to the increase in lung volume and post-inspiratory laryngeal narrowing that occur in mammals during hypoxia.

Animals↗
PubMed1988

Intrapulmonary receptors in the garter snake (Thamnophis sirtalis).

Receptors in the respiratory system of anesthetized, unidirectionally ventilated garter snakes were analyzed from single-unit vagal recordings. Three types of receptors were found: rapidly adapting mechanoreceptors (RARs), slowly adapting pulmonary stretch receptors (SARs) and intrapulmonary chemoreceptors (IPCs). RARs gave a burst of activity when the lung was inflated or deflated. Discharge frequency of SARs increased during a sustained elevation of intrapulmonary pressure (PIP); a step increase in PIP usually caused an overshoot in receptor activity that slowly adapted to a new tonic level during the sustained inflation. The activity of intrapulmonary chemoreceptors (IPCs) decreased when airway CO2 was raised. A sudden removal of CO2 caused a striking overshoot in activity which slowly adapted. Receptor discharge of SARs and IPCs was studied at 20, 25 and 30 degrees C. Discharge frequency increased with increasing temperature. The Q10 of discharge frequency averaged 3.0 for IPCs and 1.5 for SARs. Temperature clearly had a profound effect on pulmonary receptor activity; however, the relative change of activity of IPCs or SARs to a given stimulus was similar regardless of body temperature, and since the body temperature of snakes varies considerably, this may have important implications regarding the control of breathing in these animals.

Animals↗
PubMed1983

Local necrotizing effect of snake venoms on skin and muscle: relationship to serum creatine kinase.

Twenty-five snake venoms were tested for their ability to induce an increase of serum creatine kinase (CK) level after i.m. injection (0.125-1.0 mg/kg) into rates. Of six Australian elapid venoms only those from Pseudechis colletti guttatus and P. australis produced a steep rise of CK-activity (30-70 times the normal value) 4 and 16 hr after injection (0.5 mg/kg). Viperid and crotalid venoms had only slight effects (2-5 times the normal value) even in doses of 1.0 mg/kg except for a sample of Crotalus adamanteus venom which caused a 20 fold increase in CK-level. From this venom a toxin of 5800 mol. wt. consisting of 50 amino acid residues was isolated. This toxin exhibited similarities in amino acid composition and in lethality to crotamine from Crotalus durissus terrificus and to a toxin from C. horridus horridus. The toxin from C. adamanteus induced some increase of CK-level in rats, but this does not account entirely for the activity of the crude venom, whereas crotamine and the toxin from C. horridus horridus were ineffective. Phospholipase A2 (fraction II) from Pseudechis colletti guttatus venom caused a dose-dependent increase of CK-level and myoglobinuria. Intradermal injection of snake venoms into mice is useful for testing hemorrhagic activity, but is too insensitive to measure necrotizing effects. Venom induced myonecrosis can be evaluated by assaying the CK-serum level and by histological examination.

Animals↗
PubMed1984

Lethal potency in mice of toxins from scorpion, sea anemone, snake and bee venoms following intraperitoneal and intracisternal injection.

The lethal potency of 29 toxins from scorpion, sea anemone, snake and bee venoms was studied. Lethality following intracisternal injection of these toxins is considerably higher than following i.p. injection (except for the snake neurotoxins). This is of practical interest in the determination of the concentration of active toxins in a solution when only small amounts are available, as in the case of radiolabelled toxins.

Animals↗
PubMed1984

Quantification of myonecrosis and comparison of necrotic activity of snake venoms by determination of creatine phosphokinase activity in mice sera.

Serum creatine phosphokinase (CK) values were measured in venom-injected mice. The increase of CK levels was proportional to both the amount of venom injected and the myonecrotic actions determined microscopically. The CK isoenzymes were regarded as due to the predominant increase of CK-MM, which was considered to be of skeletal muscle origin in the venom-injected area. No CK isozyme variants were found by electrophoretic examination. For a comparative study on necrotic intensity, nine snake venoms were examined. The elapid venoms induced higher values of serum CK with a stronger necrotic effect than the crotalid venoms, and the data agreed with the histological findings. On application of the antivenom, an initially elevated CK value was significantly decreased and no severe damage was observed under light microscopy. Since the changes of serum CK activities paralleled necrotic intensity, the CK value is useful as an indicator of myonecrosis due to snake venom.

Animals↗
PubMed1985

Renal cortical necrosis following Bothrops jararaca and B. jararacussu snake bite.

Out of 22 patients admitted to the Intensive Care Unit of the Hospital das Clínicas, Federal University of Minas Gerais, with acute renal failure following Bothrops snake bite, 7 had renal cortical necrosis. This complication was suspected when the oligoanuric phase ranged from 21 to 28 days or when the patient, in spite of having a polyuric phase, maintained elevated blood levels of urea and creatinine after the interruption of the dialysis program, and was confirmed by a kidney biopsy. Three patients died and in two of them renal cortical necrosis was found at necropsy. Four patients were discharged from the hospital and follow-up was possible in two of them who showed recovery of renal function. Vasospasm, direct nephrotoxicity of Bothrops venom and/or disseminated intravascular coagulation leading to vascular occlusion and renal ischemia are the proposed pathogenetic mechanisms to explain renal cortical necrosis following Bothrops snake bite.

Acute Kidney Injury↗
PubMed1986

Comparison of two methods for proteolytic enzyme detection in snake venom.

An acrylamide gel system containing fibrinogen was used to detect proteolytic enzymes in snake venoms. Proteolytic activity was observed as a clear area on a blue background after electrophoresis and overnight incubation in Tris buffer, prior to staining with Coomassie blue. Venoms from eastern and western diamondback and west coast Mexican rattlesnakes, Crotalus adamanteus, C. atrox and C. basiliscus basiliscus, respectively, and southern copperhead, Agkistrodon contortrix contortrix, were analyzed at the level of 1 mg of venom. The effect of the serine proteinase inhibitor diisopropylfluorophosphate (DFP) and the metalloproteinase inhibitors tetraethylenepentamine (TEP) or EDTA on fibrinogen and normal gel profiles were evaluated. Normal gels (without fibrinogen) were Coomassie stained to visualize migration of 250 micrograms of venom proteins on the gels. Several proteolytic enzymes detected in C. atrox and C. b. basiliscus venoms were inhibited by TEP, whereas DFP had no effect on activity. The fibrinogen gels detected no protease activity in C. adamanteus venom, although it is known from other studies that there are several proteolytic enzymes in this venom. Several proteases were detected in A. c. contortrix venom, one of which was inhibited by TEP. By comparison, proteolytic activity in 5-10 micrograms of all venoms was readily detected using the mammalian plasma kallikrein specific chromogenic substrate, S2302 (H-D-Pro-Phe-Arg-p-nitroanilide). The fibrinogen gel method does not appear to have the specificity nor the sensitivity of the recently developed chromogenic substrates for detection of proteolytic enzymes in snake venom.

Animals↗
PubMed1990

Effects of snake venom proteins on blood platelets.

Snake venoms are complex mixtures which contain pharmacologically active polypeptides and proteins. Several snake venom constituents interfere in platelet aggregation, an important cellular process in thrombosis and hemostasis. These components range in size from small molecular weight polypeptides to high molecular weight proteins. Some of the proteins are enzymes, such as phospholipase A2, proteinases, nucleotidases, or L-amino acid oxidase, while others do not exhibit enzymatic activity. These components may initiate and/or inhibit platelet aggregation. Some venom factors induce platelet agglutination. This review deals with the physical characteristics of these venom factors, the mechanisms of their platelet effects, structure-function relationships, and their physiological significance.

Amino Acid Sequence↗
PubMed1990

Snake bite in Kelantanese children: a five year experience.

The records associated with 83 children from 16 months to 12 years of age who were admitted with snake bite to Kota Bharu General Hospital and University Hospital, Universiti Sains Malaysia over a 5 year period were reviewed. Elapid bites were more common than viper bites while sea-snake bites were not recorded. Symptoms were relatively mild, the common clinical features being pain and local swelling. Antivenom therapy was required in 11 children. Only three of the 11 children developed minor adverse reactions to antivenom. Four of the 83 required ventilatory support for respiratory failure and two children died.

Antivenins↗