Search PubMed⌕ Search

Biomedical subjects

E Kochva

Publications and source records attributed to E Kochva.

54 records · Page 3Linked to original sources
PubMed1984

Cardiotoxic effects of the venom of the burrowing asp, Atractaspis engaddensis (Atractaspididae, Ophidia).

The venom from the snake Atractaspis engaddensis has a very high lethal potency, with an i.v. LD50 of 0.06-0.075 micrograms per g body weight in mice. The action of the venom is rapid and death results from seemingly neurotoxic effects. However, even at high concentrations, the venom does not block contractions of skeletal muscles that are directly or indirectly stimulated. The most prominent action of the venom is seen in the function of the heart in anesthetized mice, with or without artificial respiration. The changes observed in the ECG are similar to those recorded in human victims and are the result of an A-V block that is caused by an apparent direct action of the venom on the heart.

Animals↗
PubMed1982

A new type of toxin in the venom of snakes of the genus Atractaspis (Atractaspidinae).

The venom of Atractaspis is unique in having a large percentage of both high and low molecular weight components. Its Sephadex G-50 S5 fraction appears to represent a new type of toxin that contains 17-18 Asx, 13-14 Cys and 10-11 Glx out of a total of 72-78 amino acids. The N-terminal of this toxin does not seem to resemble any of the known toxins. The overall lethal potency of the venom is very high; i.v. injections of 5 microgram of venom or 1 microgram of fractions S5 or S6 per mouse causes death within minutes. The results of the present study corroborate previous findings that suggested a separate grouping of the snakes genus Atractaspis at the subfamilial or familial level.

Amino Acids↗
PubMed1982

Biosynthesis, secretion and in vivo isotopic labelling of venom of the Egyptian cobra, Naja haje annulifera.

The venom glands of Elapidae differ from those of the Viperidae by lacking an expanded central lumen; the venom is stored in the tubular lumina as well as inside the cells in densely packed secretion granules. Using isotope tracer techniques, it was found that in the Egyptian cobra (Naja haje annulifera) venom is secreted both from pre-existing and from newly-formed granules. The rate of protein biosynthesis peaks at 4-9 days after venom was extracted (milked) from the glands. Highly labelled toxins (1-10 mCi/mmole protein) were isolated in good yield from the venom of snakes chronically intubated and infused i.p. with (3H)-amino acids. Repeated Fluothane (Halothane) anaesthesias and venom collections had no ill effect on venom yield. The radioactive venom and its component toxins retained full biological potency.

Amino Acids↗
PubMed1977

The neutralization mechanism of Vipera palaestinae neurotoxin by a purified factor from homologous serum.

The serum of Vipera palaestinae contains two separate factors which neutralize the hemorrhagic and the neurotoxic activities of its venom. The purified antineurotoxic factor shows one major band in disc electrophoresis and an 800-fold increase in specific activity. Its molecular weight is approximately 56 000 and the isoelectric point is 4.0. These data, together with the failure to form precipitin lines in immuno-diffusion tests, suggest that the antineurotoxic factor of Vipera palaestinae serum is probably an albumin-like or alpha-globulin fraction rather than an immunoglobulin fraction. In vivo experiments show that the neutralizing protein does not protect or block the neurotoxin target sites. When the neurotoxic fraction is injected into mice intravenously at different intervals following injection of the snake serum, the neutralizing activity decreases with time. Experiments carried out in vitro show that the antineurotoxic factor is inactivated upon heating at 95 degrees C for 10 min but resists boiling when mixed with the neurotoxic component, suggesting the formation of a thermostable complex between the two components. This assumed complex dissociates at pH 2.5 and the neurotoxic activity reappears. Further investigation of the reaction with 131I-labeled neurotoxin and neurotoxin components shows that a stable complex is formed between the neutralizing protein and one of the synergistic components of the neurotoxic fraction.

Animals↗
PubMed1975

Accumulation of some secretory enzymes in venom glands of Vipera palaestinae.

Secretion of venom in the venom glands of Vipera palaestinae was studied by measuring the protein content and enzymatic activities of L-amino acid oxidase (LAO), phosphodiesterase (PDE), and benzoylarginine ethyl esterase (BAEE). These were tested in the accumulating venom and gland homogenates at 0, 2, 3, 4,6, and 15 days after an intitial emptying of the venom glands by milking. Changes in the total activities of the enzymes and in the protein concentration were found in the venom samples, but not in the homogenates, at the different intervals after milking. In the venom the total activities of LAO, PDE, and BAEE were higher the longer the time intervals from the initial milking. When the data were fit by a straight line, the fluctuations from the line were of opposite signs for LAO and PDE at the 3- and the 4-day intervals. There were no significant correlations between the specific activities or between the changes in the specific activities of any two of the enzymes at any time interval. It is concluded that each of the enzymes is secreted at a rate independent of the other two; this pattern of secretion can best be described as nonparallel.

Amino Acid Oxidoreductases↗
PubMed1971

Studies on ribonucleic acid synthesis in the venom glands of Vipera palaestinae (Ophidia, Reptilia).

RNA metabolism in the venom glands of Vipera palaestinae was studied at different stages after manual extraction of the venom (milking). The rate of (32)P incorporation into gland RNA was found to be maximal at 1-4 days after milking in correlation with the height of the secretory epithelium. Venom production attained a maximum only after 8-16 days, in parallel with the accumulation of stable species of cellular RNA.

Animals↗
PubMedDate not supplied

Inhibition of the proteolytic activity of hemorrhagin-e from Crotalus atrox venom by antihemorrhagins from homologous serum.

Antihemorrhagic proteins from Crotalus atrox serum were tested for their ability to inhibit the proteolytic activity of the hemorrhagic toxin-e from Crotalus atrox venom and of several other proteolytic enzymes: trypsin, collagenase and thermolysin. The antihemorrhagic proteins inhibited the proteolytic activity of hemorrhagin-e when tested on gelatin type I and collagen type IV, the proteolytic activity of trypsin on photofilm gelatin and the proteolytic activity of whole venom when tested on azocollagen and photofilm gelatin. The antihemorrhagins failed to inhibit the proteolytic activity of trypsin when tested on the specific synthetic substrate N-acetyl-DL-phenylalanine-beta-naphthyl ester (APNE), the activity of microbial collagenase on N-(3-[2-furyl]acryloyl)-Leu-Gly-Pro-Ala (FALGPA) or on azocollagen and the activity of thermolysin on N-(3-[2-furyl]acryloyl)-Gly-Leu amide (FAGLA). It is tentatively suggested that the antihemorrhagins from snake blood serum are proteinase inhibitors that underwent specialization towards the neutralization of the proteolytic activity of hemorrhagic toxins.

Amino Acid Sequence↗
PubMedDate not supplied

Endothelins and sarafotoxins: effects on motility, binding properties and phosphoinositide hydrolysis during the estrous cycle of the rat uterus.

The effects of four peptides of the endothelin/sarafotoxin (ET/SRTX) family on the motility of the rat uterus were examined during the different stages of the estrous cycle. ET-1, ET-3, SRTX-b and SRTX-c showed similar effects on the contraction of the uterus: a slight increase in the maximum tension of the spontaneous rhythmic contractions, a suppression of the relaxation phase of these contractions and an increase in their rate. All three effects were concentration dependent. Of the four peptides, ET-1 and SRTX-b showed the highest potency and efficacy, suggesting that among the various peptides of this family so far studied, ET-1 and SRTX-b are the two full agonists. The rank order of susceptibility of the different stages was, in most cases: proestrus greater than estrus greater than metestrus. Freshly excised diestrus uteri showed no spontaneous contractions and did not respond to any of the peptides. The binding potency of ET-1 and SRTX-b to uterine membranes was similar at the various estrous stages, but their maximal binding decreased gradually from proestrus to diestrus. All four peptides induced phosphoinositide (PI) hydrolysis in uterine slices at all four different stages, with ET-1 and SRTX-b again being more potent than ET-3 or SRTX-c. The maximal PI hydrolysis correlated with the increased rate of the rhythmic contractions. It is suggested that the reaction of the rat uterus to the ET/SRTX peptides depends on its hormonal status and that ET may act in concert with steroid hormones in the modulation of the estrous cycle.

Animals↗