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At least 1,081 records · Page 60Linked to original sources
PubMed1981

Behaviour of the ZW sex bivalent in the snake Bothrops jararaca.

The behavior of the ZW sex bivalent was investigated in female meiosis of the poisonous snake Bothrops jararaca. The Z is euchromatic and synapses end to end with the W. The W chromosome shows a heterochromatic segment distally in the short arm. Pairing occurs between the long arm of the W and the slightly longer arm of the mediocentric Z. A sex vesicle, similar to the one found in the XY placental mammals, does not occur in snakes. The Z and W chromosomes segregate reductionally in the first meiotic division and equationally in the second.

Animals↗
PubMed1979

Behaviour of sex chromosome associated satellite DNAs in somatic and germ cells in snakes.

Sex chromosome associated satellite DNAs is isolated from the snakes Elaphe radiata (sat III) (Singh et al., 1976) and Bungarus fasciatus (Elapidae) (minor satellite) are evolutionarily conserved throughout the suborder Ophidia. An autosome limited satellite DNA (B. fasciatus major satellite) is not similarly conserved. Both types of satellites have been studied by in situ hybridisation in various somatic tissues and germ cells where it has been observed that the W sex chromosome remains condensed in interphase nuclei. In growing oocytes however, the W chromosome satellite rich heterochromatin decondenses completely whilst the autosomal satellite rich regions remain condensed. Later, the cycle is reversed and the W chromosome condenses whilst the autosomal satellite regions decondense. In a primitive snake (Eryx johni johni) where the sex chromosomes are not differentiated and where there is no satellite DNA specific to them, these phenomena are absent. - The differential behaviour of autosomal and sex chromosome associated satellite DNAs is discussed in the light of gene regulation.

Animals↗
PubMed1991

Tetraethylammonium transport by snake renal brush-border membrane vesicles.

Transport of tetraethylammonium (TEA) by snake (Thamnophis spp.) renal brush-border membrane vesicles (BBMV) was studied. An outwardly directed proton gradient (pH 6.0 in, pH 7.5 out) stimulated uptake of TEA into BBMV and supported concentrative accumulation. Uptake of radioactively labeled TEA was also stimulated by outwardly directed gradients of unlabeled TEA and choline. The initial rate of TEA uptake was a saturable process that was adequately described by Michaelis-Menten kinetics. TEA uptake was not influenced by changes in the electrical potential difference across the membranes. Although uptake of TEA was stimulated by an outwardly directed Na+ gradient and inhibited by an inwardly directed Na+ gradient, these effects were probably secondary to the generation of proton gradients via a Na+/H+ exchanger demonstrated in these same BBMV. In agreement with previous studies with intact snake renal tubules, the present results indicate that TEA transport across the brush-border membrane involves electroneutral countertransport for protons or organic cations.

Animals↗
PubMed1981

Comments on snake symbolism and mind-body relations.

In summary, the symbolic use of an object in part depends on which of its functional-structural qualities is emphasized in a given moment. For example, the snake may take on different symbolic meanings when emphasis is given to its eyes, tongue, fangs, anatomical form, or movement. Its various aspects constitute a complex system of references to unconscious (and conscious) mental and body self-configurations. These references frequently undergo transformations which make use of structurally related symbols. In the present paper, various aspects of the snake symbol were related to one another and to other symbolic transformations, including the elevator and flying. The structural principles underlying these analyses may be found to organize a wide range of phenomena and were here applied to Tausk's "influencing machine."

Animals↗
PubMed1987

The muscle-tendon junctions of fast and slow fibres in the garter snake: ultrastructural and stereological analysis and comparison with other species.

The muscle-tendon junctions of fast and slow muscle fibres from the costocutaneous muscles of garter snakes have been analyzed by scanning and transmission electron microscopy and by a stereological protocol. The junctions of the two fibre types are morphologically similar, and consist of anastomosing processes which increase the surface area of the muscle-tendon interface and significantly reduce the stress at the junction when the fibres contract. The muscle-tendon junctions of these fibres are analogous to adhesive joints between stiff adherends and fibre-reinforced composite materials. Stereological estimates of the area of surface membrane devoted to force transmission, relative to the cross-sectional area of myofilaments (the 'interfacial ratio'), have produced values of about 14 for the fast fibres and about 16 for the slow fibres. This difference is small but statistically significant. Interfacial ratios of about 14 and 10 were previously determined for fast and slow fibres, respectively, of both chickens and mice. Thus the slower fibres of the snake differ from those of the mouse and chicken, in that their interfacial ratio is greater than that of fast fibres.

Animals↗
PubMed1977

Molecular evolution of snake venom toxins.

Phylogenetic trees were constructed for 62 venom toxins of snakes of Proteroglyphae suborder using matrix method. The resulting tree from Minimum Spanning Tree-Cluster Analysis technique had the lowest "percent deviation" (8.55). The taxonomic relationship of these toxins agrees very well with zoological opinions. However, the appearance of the tree did not directly provide a plausible evolutionary model for the toxins. A model was derived from nodal ancestral sequence calculations, comparisons between intra- and intergenerical rates of amino acid change, and generally held ideas about protein evolution. According to the model, short neurotoxin is the ancient form of snake venom toxins. The courses of evolution leading to the present intraspecific homologous toxins are explained by gene duplication and allelomorphism.

Amino Acid Sequence↗
PubMed1995

Screening of Bothrops snake venoms for L-amino acid oxidase activity.

Toxins, enzymes, and biologically active peptides are the main components of snake venoms from the genus Bothrops. Following the venom inoculation, the local effects are hemorrhage, edema, and myonecrosis. Nineteen different species of Brazilian Bothrops were screened for protein content and L-amino acid oxidase activity. B. cotiara, formerly found in the South of Brazil, is now threatened with extinction. Its venom contains a highly hemorrhagic fraction and, as expected from the deep yellow color of the corresponding lyophilized powder, a high L-amino acid oxidase (LAO) activity was also characterized. Flavin adenine dinucleotide (FAD) is its associate coenzyme. B. cotiara venom LAO catalyzed the oxidative deamination of several L-amino acids, and the best substrates were methionine, leucine, tryptophan, and phenylalanine, hence, its potential application for the use of biosensors for aspartame determination and for the removal of amino acids from plasma. High levels for LAO were also found in other species than B. cotiara. In addition, the technique of isoelectric focusing (IEF) was employed as a powerful tool to study the iso- or multi-enzyme distribution for LAO activity in the B. cotiara snake venom.

Amino Acid Oxidoreductases↗
PubMedDate not supplied

Hemoperitoneum complicating snake bite: rare CT features.

Russels's viper bite victims with systemic poisoning may present with hemorrhagic manifestations, including spontaneous bleeding and incoagulable blood associated with disseminated intravascular coagulation and primary fibrinolysis, two of the most prominent manifestations of the systemic envenoming by this species. Various vascular complications of viperine snake bite have been reported in the literature. We report the computed tomographic findings in a case of snake bite resulting in hemoperitoneum, which, to the best of our knowledge, has not been reported in the literature.

Adult↗
PubMed1997

The photoreceptors and visual pigments of the garter snake (Thamnophis sirtalis): a microspectrophotometric, scanning electron microscopic and immunocytochemical study.

Scanning electron microscopy, immunocytochemistry, and single cell microspectrophotometry were employed to characterize the photoreceptors and visual pigments in the retina of the garter snake, Thamnophis sirtalis. The photoreceptor population was found to be comprised entirely of cones, of which four distinct types were identified. About 45.5% of the photoreceptors are double cones consisting of a large principal member joined near the outer segment with a much smaller accessory member. About 40% of the photoreceptors are large single cones, and about 14.5% are small single cones forming two subtypes. The outer segments of the large single cones and both the principal and accessory members of the doubles contain the same visual pigment, one with peak absorbance near 554 nm. The small single cones contain either a visual pigment with peak absorbance near 482 nm or one with peak absorbance near 360 nm. Two classes of small single cones could be distinguished also by immunocytochemistry and scanning electron microscopy. The small single cones with the 360-nm pigment provide the garter snake with selective sensitivity to light in the near ultraviolet region of the spectrum. This ultraviolet sensitivity might be important in localization of pheromone trails.

Animals↗
PubMed1997

Gravitational gradients and blood flow patterns in specialized arboreal (Ahaetulla nasuta) and terrestrial (Crotalus adamanteus) snakes.

Blood pressure and blood flow patterns were recorded from the carotid artery and aortae of a thick-bodied terrestrial snake (Crotalus adamanteus) and a thin-bodied arboreal species (Ahaetulla nasuta) anesthetized with ketamine hydrochloride. Hemodynamic stress induced by rotation resulted in pronounced changes in the blood flow patterns and pressure in C. adamanteus: rotation of A. nasuta produced changes of a similar type, but of a much lower magnitude. The markedly different responses of these two species, the baroreceptor reflexes of which were disrupted, suggest that morphological factors--such as differential gross cardiac displacement, or variation in the interaortic foramen--in addition to physiological factors, are important in determining a snake's ability to withstand hemodynamic stress.

Adaptation, Physiological↗
PubMed2002

Haematopoiesis and a new mechanism for the release of mature blood cells from the bone marrow into the circulation in snakes (Ophidia).

This is the first description of haematopoiesis in snakes. Studies were carried out on the following species belonging to Ophidia: Bothrops jararaca, Bothrops jararacusu, Waglerophis merremii, Elaphe taeniura taeniura, Boa constrictor,and Python reticulatus. Smears of the peripheral blood and histological preparations from the vertebrae, ribs, liver, and spleen were studied under a light and electron microscope. Myeloid cells were present in the following locations in the vertebrae: the neural spine, zygoapophysial processes, floor of the neural canal, lacunae in the bodies of vertebrae and also inside the ribs. Although the vascular system was well developed, especially around the ribs, vessels inside the marrow cavities were scarce, both in the ribs and elsewhere where haematopoiesis was found. Venous sinuses were well developed in the vertebrae and in the rib regions from their costal head towards the middle area. They consisted of one layer of fine endothelial cells. Mature cells in the process of migration into the general circulation were only sporadically encountered when venous sinuses were studied on perfusion-fixed specimens. In contrast, almost every sinus venosus contained protrusions directed towards the lumen, filled mostly with mature and immature blood cells. Various stages of their formation were seen in the cross sections of venous sinuses ranging from small, newly formed to large, elongated ones, filled with many fully developed and some maturing blood cells. In many cases the apices of the protrusions were ruptured, and mature blood cells, as well as a few immature ones, were seen in their vicinity. This observation led us to a new hypothesis that blood cells are released from the extravascular space into the lumen of venous sinuses. In snakes, these cells are released into the systemic circulation mainly via the rupture of protrusions filled with mature blood cells and, to a lesser degree, by transcytosis as known in mammals. In the spleens from young specimens, 1-2 foci of haematopoiesis were encountered where lymphopoiesis predominated. Haematopoiesis was not detected in the liver.

Animals↗
PubMed1988

Isolation from earthworms of a proteinaceous chemoattractant to garter snakes.

We have isolated a potent proteinaceous chemoattractant from aqueous washes of earthworm (Lumbricus terrestris) for garter snakes (Thamnophis sirtalis) by means of a covalent chromatography. It contained free sulfhydryl groups and showed an apparent mass of 20 kDa. The chemoattractive activity of this protein could be destroyed by heating as well as by proteolysis. Its activity could also be reversibly blocked by mixed disulfide formation with dithiodipyridine, suggesting that the free sulfhydryl(s) was essential for its function as a chemoattractant. This bioactive material had a tendency to form intermolecular crosslinked aggregates during isolation, if reducing agents were not included. Some of the high-molecular-weight aggregates cochromatographed with earthworm cuticle collagen on Ultragel AcA 34 or 44 columns. In contrast to an earlier report by D. M. Kirschenbaum, N. Schulman, and M. Halpern [1986) Proc. Natl. Acad. Sci. USA 83, 1213-1216) the purified earthworm collagen showed no chemoattractive activity to garter snakes.

Animals↗
PubMed1982

The effects of viewing distance on fear of snakes.

Phobic subjects made magnitude estimations of the intensity of fear felt when viewing a snake at distances from 2.5 to 15.0 ft. Heart rate, skin conductance, and respiration were also measured throughout each 20 sec viewing period. A control group of nonphobic subjects made magnitude estimates of perceived nearness for the empty Plexiglas snake box at the same test distances. Judged fear was inversely proportional to distance. Thus, the fear-distance relation obeys Stevens' psychophysical power law with an exponent of -1.0. Examination of previous studies reporting such a finding revealed systematic departures from a power relation similar in form to the results of the perceived nearness control group, and to the expected outcome when category judgements of fear are made instead of magnitude estimates. The physiological measures varied in outcome. Measures of respiration showed no reliable effects. But heart rate and skin conductance decreased significantly for phobics as viewing distance increased.

Adolescent↗
PubMed1990

Effects of diazepam on approach, self-reported fear and psychophysiological responses in snake phobics.

The effects of diazepam was assessed on a number of measures of phobic anxiety. Snake-phobic subjects underwent two sessions on either diazepam or placebo in a crossover design. In addition to a habituation series, a slide with the phobic object was displayed as well as a live snake which subjects were asked to approach. The anxiolytic effect of diazepam was manifest in only one measure of fear, namely self-rated fear at the point of closest approach when it also attained the highest level. The result would indicate that diazepam has an anxiolytic only on high levels of subjective anxiety. The magnitude of the phasic cardiac reaction to the slide was highly and positively correlated with self-rated fear of the slide.

Adolescent↗
PubMed1983

Dissociation of pharmacological and enzymatic activities of snake venom phospholipases A2 by modification of carboxylate groups.

The carboxylate groups in an acidic and in a basic phospholipase A2 (PLA2) enzyme, purified, respectively, from Naja naja atra and Naja nigricollis snake venoms, were modified with carbodiimide and semicarbazide. The derivatives modified at pH 3.5 and pH 5.5 had less than 1% (N. nigricollis) or 2% (N. n. atra) residual enzymatic activity, whereas 12-16% enzymatic activity remained following modification at pH 5.5 in the presence of Ca2+. In marked contrast, these derivatives retained variable, but significantly greater, levels of lethal potency, hemolytic and anticoagulant activities, and abilities to block indirectly and directly induced contractions of the diaphragm. By this modification of aspartic and glutamic acid residues we have, for the first time, obtained derivatives of PLA2 which selectively retain greater pharmacological activity relative to enzymatic activity. Previously, we had found that modification of lysine and arginine residues produced derivatives which retain enzymatic activity but show a loss of pharmacological properties. These findings suggest that some pharmacological effects of snake venom PLA2 enzymes are due to a non-enzymatic action, suggesting two distinct but perhaps overlapping active sites.

Animals↗
PubMed1985

The nucleus dorsalis myelencephali of snakes: relay nucleus between the spinal cord and the posterior colliculus (paratorus).

Nucleus dorsalis myelencephali is in the dorsolateral area of the caudal medulla in snakes. The parvocellular area projects bilaterally to the paratorus and receives ipsilateral projections from the spinal cord. The magnocellular area projects bilaterally to the spinal cord. This nucleus has been only briefly described in snakes but not in any other reptilian group.

Animals↗
PubMed1996

Distribution of NADPH-diaphorase in the central nervous system of an infrared-sensitive snake, Trimeresurus flavoviridis.

The distribution of NADPH-diaphorase (NADPH-d) activity was studied in the central nervous system of an infrared sensitive snake. An inhibitor of nitric oxide synthase, dichloroindophenol (DPIP), was used to distinguish the characteristics of NADPH-d activity. Intensely and weakly NADPH-d-stained neurons and fibers were found in discrete regions throughout the snake brain and cervical spinal cord, such as the olfactory bulb, subcommissural organ, stratum griseum periventriculare, locus coeruleus, dorsal root, dorsal horn, and area X. It was particularly noticed that the trigeminal descending nuclei and reticular formation of the medulla oblongata contained many positive neurons and fibers, but the lateral descending nucleus and nucleus reticularis caloris (infrared sensory nuclei) certainly did not. The positive neurons and fibers were also observed in supraspinal sensory ganglia. DPIP inhibited NADPH-d activity in all regions except for the olfactory/vomeronasal nerve and glomeruli. The results prove for the first time the presence of NADPH-d activity in the ophidian brain and suggest that nitric oxide may be involved in many neural functions, but not in infrared sensory processing.

Animals↗
PubMed1988

Fast functional assay of protein C in whole plasma using a snake venom activator: evaluation in patients with congenital and acquired protein C deficiencies.

Both anticoagulant and amidolytic activities of protein C (PC) were measured using a snake venom activator in 4 patients with hereditary PC deficiency, 37 with disseminated intravascular coagulation (DIC), and 30 under stabilized warfarin therapy. The results were compared with those obtained by an immunological assay (ELISA). PC levels measured by different functional and immunological assays were very close in patients with hereditary PC deficiency and DIC. In patients under stable oral anticoagulant therapy, there was no detectable difference between amidolytic activity and antigen levels of PC in each patient plasma, whereas a decrease in anticoagulant activity was much more pronounced. These results indicate that the present activity assays measure PC specifically, and that the snake venom activator is capable of activating both carboxylated and hypocarboxylated forms of PC, but only anticoagulant assay can evaluate the physiological PC function in vitamin K-deficient states.

Biological Assay↗