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Biomedical subjects

A T Tu

Publications and source records attributed to A T Tu.

At least 109 records · Page 6Linked to original sources
PubMed1976

Nephrotoxic action of rattlesnake and sea snake venoms: an electron-microscopic study.

The fine structure of renal corpuscles and proximal convoluted tubules of the right kidneys of Suiss mice were studied 9 hr after the injection of the venom of Crotalus atrox (Western diamond-back rattlesnake) or the venom of Laticauda semifasciata (broad-banded blue sea snake). Rattlesnake envenomation resulted in several ultrastructural changes in the renal corpuscles and proximal convoluted tubules. Visceral epithelial changes included intracellular oedema, blebbing, vesiculations, the formation of microvillus projections and dilatation of the endoplasmic reticulum and mitochondria. Changes in the parietal epithelium were similar except that no microvillus projections were noted. Mesangiolysis was a consistent finding. Collagenous fibrils were very prominent in the lysed areas of the mesangial cells. Increased numbers of lysosome-related structures were noted in the proximal convoluted tubule cells. Most of the nuclear cisternae of the cells of the renal corpuscles and proximal convoluted tubules were greatly dilated. Sea snake envenomation resulted in focal organellar swelling and focal intracellular oedema of the visceral epithelium. This venom did not affect the cells of the proximal convoluted tubule. The presence of light and dark visceral epithelial cells has been a consistent finding for both the control and the environmated groups.

Animals↗
PubMed1976

Laser Raman spectroscopy of snake venom neurotoxins: conformation.

Laser Raman spectra of neurotoxins of Pelamis platurus (yellow-bellied sea snake) and Laticauda semifasciata (broad-banded blue sea snake) were investigated. The amide I band appeared at 1672 cm-1 for both toxins, which presents an indication of anti-parallel beta structure. Since this agrees well with the result from the CD-ORD studies of snake neurotoxin, it was concluded that snake neurotoxins mainly consist of beta structure. The amide III band appeared at 1245 cm-1 for P. platurus toxin and 1248 cm-1 for L. semifasciata toxin. The four disulfide bonds present in the toxin have a very similar geometry. After vigorous heat treatment, the backbone configuration of the toxin molecule basically remained the same although it was partially denatured. The major peak at 512 cm-1 was not altered by the heat treatment but a new shoulder appeared at 546 cm-1. This suggests that a new type of S-S stretching vibration (trans-gauche-trans) was produced as a result of heat treatment. However, the majority of the S-S vibrations remained in the gauche-gauche-gauche orientation. A substantial change in the interactions between a tyrosine aromatic ring and neighboring residues was apparently the alteration caused by the heat treatment.

Amino Acids↗
PubMed1976

Some pharmacological properties of the venom, venom fractions and pure toxin of the yellow-bellied sea snake Pelamis platurus.

The effects of the crude venom, four partially purified venom fractions and pure toxin (Pelamis toxin alpha) from yellow-bellied sea snake, Pelamis platurus, on respiration, blood pressure, heart and skeletal muscle of rabbits have been examined. Results indicated that crude venom, a partially purified toxic fraction and Pelamis toxin alpha caused initial respiratory stimulant effects followed by respiratory paralysis. In most cases, respiratory paralysis occurred before a profound fall in arterial pressure. Depression of the twitch response to nerve stimulation was observed in the tibialis anterior muscle. No significant change in the electrocardiogram was seen. Three partially purified non-toxic fractions of the crude venom induced transient respiratory stimulant effects. It was concluded that the crude venom and Pelamis toxin alpha had an identical mode of action and that they caused respiratory paralysis in rabbits.

Animals↗
PubMed1976

Variations in kidney ultrastructure with a variety of paraformaldehyde fixation techniques.

Variations in fine structure of glomeruli and proximal tubules were studied to determine the results of several fixation techniques with paraformaldehyde. Immersion fixation techniques generally resulted in poor fixation, while the quality of fixation by perfusion was directly related to the concentration of the paraformaldehyde. The best technique was fixation by perfusion and immersion in 3% paraformaldehyde for 2 h followed by a post-fixation in 1% OsO4 for 1 h. Intracellular edema was noted in all epithelial, mesangial and proximal tubular cells that were from poorly fixed kidneys. Swollen mitochondria and the dilated endoplasmic reticulum were common in many of those cells. Mesangial and proximal tubular cells were the first to swell. Poor fixation produced the early stages of autolysis. The criteria for good paraformaldehyde fixation are discussed.

Animals↗
PubMed1976

Isolation of myotoxic component from rattlesnake (Crotalus viridis viridis) venom. Electron microscopic analysis of muscle damage.

The pathogenesis of myonecrosis induced by a purified component of rattlesnake (Crotalus viridis viridis) venom was studied at the light and electron microscopic levels. Crude venom was fractionated by gel filtration (Sephadex G-50) followed by cation exchange chromatography (Sephadex C-25). Electrophoretic homogeneity of the isolated myotoxin (Fraction II from C-25 column) was demonstrated in isoelectric focusing and disc gel polyacrylamide gel electrophoresis. White mice were injected intramuscularly with 1.5 mug/g of the purified protein in 0.1 ml of physiologic saline. Light microscopic examination of injected muscle revealed a series of degenerative events including partial vacuolation of muscle cells at 6, 12, and 24 hours and complete vacuolation and loss of striations at 48 and 72 hours. Hemorrhage was not observed. At the electron microscopic level the perinuclear space and sarcoplasmic reticulum were dilated in all samples. By 48 and 72 hours the myofibrils lacked striations and the sarcomeres were disorganized. Plasma membranes and T tubules remained intact in all samples. These results correlated well with the myonecrosis induced by crude Crotalus viridis viridis venom except for several important aspects. The pure component altered skeletal muscle cells specifically, with the sarcoplasmic reticulum being the primary site of action.

Animals↗
PubMed1975

Purification and chemical characterization of the major neurotoxin from the venom of Pelamis plautrus.

A major toxin was isolated from the venom of the sea snake Pelamis platurus (yellow-bellied sea snake) by Sephadex G-50 and carboxymethylcellulose column chromatography. The LD50 of the pure toxin (Pelamis toxin a) was 0.044 mug/g in mice representing a tenfold increase in toxicity after purification. The toxin was homogeneous in acrylamide disc gel electrophoresis and eluted as a single peak after isoelectric focusing in a sucrose density gradient column. The isoelectric point was 9.69; thus it is a highly basic protein. The toxin contained 55 amino acid residues with four disulfide linkages. When all disulfide linkages were reduced and alkylated, the toxic action of the pure toxin disappeared leading to the conclusion that the disulfide bonds of the neurotoxin were essential for toxic action.

Amino Acids↗
PubMed1975

Studies of an acidic cardiotoxin isolated from the venom of Mojave rattlesnake (Crotalus scutulatus).

A major lethal protein was isolated from the venom of Mojave rattlesnake (Crotalus scutulatus) by successive purification in DEAE column chromatography and isoelectric focusing. This homogeneous and monomeric form of toxin is designated as "Mojave toxin". Unlike basic neurotoxins or cytotoxins isolated from venoms of cobras, kraits and sea snakes, the Mojave toxin is an acidic protein with an isoelectric point of 4.7. The toxin is also different from crotoxin (from Crotalus durissus terrificus) which consists of both acidic and basic components. The molecular weight determined by Sephadex G-75 column chromatography resulted in a value of about 22 000. A singel protein band with a molecular weight of about 12 000, was observed after sodium dodecyl sulfate gel electrophoresis of the reduced Mojave toxin. Isoelectric focusing gel in the presence of 8 M urea also showed a single protein band, suggesting that the toxin is composed of subunits. Unlike the neurotoxic nature of the basic proteins from the venoms of Elapidae and sea snakes (Hydrophiidae) and crotoxin, Mojave toxin is cardiotoxic rather than neurotoxic. It is very likely that venoms of all rattlesnakes from North and Central America contain Mojave toxin as the common toxin.

Amino Acids↗
PubMed1975

Laser Raman scattering of neurotoxins isolated from the venoms of sea snakes Lapemis hardwickii and Enhydrina schistosa.

The venoms of sea snakes (family: Hydrophiidae) contain potent neurotoxins which bind to the acetylcholine receptor in the neuromuscular junction. A major toxin was isolated from the venoms of the sea snakes Lapemis hardwickii and Enhydrina schistosa according to previously published methods. These pure toxins were studied by laser Raman spectroscopy to elucidate further the structure-function relationship to the neurotoxin. Spectra were obtained from the powder, aqueous solution, and deuterated derivatives of each toxin. The peptide backbone conformation of these neurotoxins was found to be of "anti-parallel beta configuration," as distinct amide I and III bands appeared at 1672 and 1240 cm-1, respectively. No indication of alpha helical structure in the neurotoxins was observed from amide I and III bands. This was further confirmed by the spectra of the neurotoxins after deuterium exchange. The peaks due to a single tyrosine residue appeared at 644, 834, and 846 cm-1. The intensity ratios of the toxin from L. hardwickii venom were 0.92, 1.0, and 0.84 at 644, 834, and 846 cm-1. It is concluded that the tyrosine residue is involved in some unusual intramolecular interactions and not readily accessible to water molecules. Similar results were obtained for the toxin of Enhydrina schistosa (common sea snake). The fact that only 50% of the tyrosine molecule is modified by nitration is in complete agreement with laser Raman result. The lack of a sharp Raman line at 1361 cm-1 suggested that the single tryptophan residue may be "exposed." The previous demonstration that the tryptophan residue can be modified readily with different reagents confirms these results. A relatively symmetrical disulfide peak at 512 cm-1 indicates that the geometry of the C-C-S-S-C-C linkage is nearly identical for all four disulfide bonds in the molecule. The absence of phenylalanine was established by the lack of a phenylalanine peak in the laser Raman spectra and by amino acid analysis.

Amino Acids↗
PubMed1974

Pathogenesis of hemorrhage induced by rattlesnake venom. An electron microscopic study.

The pathogenesis of hemorrhage induced by rattlesnake (Crotalus atrox) venom was investigated at the electron microscopic level. Swiss-Webster white mice were injected intramuscularly with one-fifth the LD(50) dose of whole venom. Muscle samples were obtained by biopsy 2 minutes, 30 minutes and 3 hours after venom injection. Capillaries in the endomysium were in various stages of degeneration. Endothelial cells of damaged capillaries contained dilatated endoplasmic reticulum and perinuclear space, and, in many cases, swollen cytoplasm. Blebbing of endothelial cytoplasm of swollen and nonswollen cells was observed. These changes were followed by rupture of the plasma membrane which resulted in the subsequent extravasation of blood. Platelet aggregations plugged gaps in vessel walls and often completely occluded the lumina of capillaries. The experimental injection of rattlesnake venom induced hemorrhage by rhexis. The same or a similar pathogenesis is probably responsible for hemorrhage which occurs in actual snakebite cases.

Animals↗