PubMed Health⌕ Search

Biomedical subjects

I G White

Publications and source records attributed to I G White.

At least 19 recordsLinked to original sources
PubMed1992

Frequent semen collection and sperm reserves of the male Angora goat (Capra hircus).

Semen was collected from six mature and sexually rested Angora bucks at one-hour intervals five times a day on each of 5 consecutive days in the breeding season. There was a marked decline in semen volume (P less than 0.001), sperm concentration (P less than 0.05) and number of spermatozoa (P less than 0.001) on consecutive days. Successive ejaculates within days differed only in number of spermatozoa (P less than 0.001). The following year at the beginning of the breeding season, the weights of testes and epididymides and the reserves of spermatozoa in these parts were examined after slaughter of the six bucks. The mean number of spermatozoa in the paired testes, capita, corpora and caudae of the epididymides were (22.8 +/- 1.24) x 10(9), (9.4 +/- 1.19) x 10(9), (3.4 +/- 0.22) x 10(9) and (35.0 +/- 2.21) x 10(9), respectively. Epididymal reserves of spermatozoa were correlated with testicular weight (r = 0.50, P = 0.01) and number of spermatozoa in the testes (r = 0.42, P = 0.07), but not with epididymal weight. The daily production of spermatozoa per animal in the breeding season was estimated to be 4.0-6.4 x 10(9).

Animals↗
PubMed1990

Electron microscopic observations on the effect of gossypol on rat cauda epididymis.

Gossypol administered orally to male rats at a daily dose of 20 mg/kg body weight for 63 days caused hypertrophy of the cauda epididymal epithelium, with more than fourfold increase in height of the cells. The principal cells lost most of their microvilli and formed apical blebs which appeared to produce the dense secretory material which was found in the lumen. Less dramatic but similar changes also occurred after 9 days on the same regimen, with the height of the epithelium doubling. However after 19 days on this regimen, with the height of the epithelium doubling. However after 19 days on this regimen, the epithelium looked fairly normal apart from a maintained hypertrophy. As reported in other studies, the cauda epididymal sperm were severely damaged and immotile; many were decapitated and the oxygen uptake was low. Ultrastructural defects were abnormal or absent mitochondria, absence of plasma membranes and axonemal components and accessory fibres.

Animals↗
PubMed1988

Studies of the mechanism of action of gossypol as a male antifertility agent.

Gossypol administered orally to male rats at a daily dose of 20 mg/kg body weight for 62 days caused infertility. There were changes in the epididymal epithelium and the sperm were severely damaged and immotile. The sperm head was often detached; other defects were abnormal mitochondria, absence of plasma membranes and axonemal and accessory fibres and a lower oxygen uptake. To study the effect of gossypol on the motor apparatus of sperm, ram sperm were demembranated with the detergent, Triton-X-100. Such sperm models can normally be reactivated with ATP but gossypol (2.5-12.5 microM) decreased reactivation and must have a direct effect on the axoneme. Gossypol also inhibited ram sperm adenyl cyclase which is essential for maintaining high levels of cAMP in sperm and, in turn, motility. Ram sperm adenyl cyclase required Mn2+ for activity and high Mn2+ concentrations protected the enzyme from gossypol inhibition. Electron spin resonance studies proved that gossypol chelated Mn2+ with the formation of a 2:1 complex.

Adenosine Triphosphate↗
PubMed1985

Effects of malonic, maleic, citric and caffeic acids on the motility of human sperm and penetration of cervical mucus.

The spermicidal effect of four organic acids (malonic, maleic, citric and caffeic acids) was evaluated by adding the acids to sperm, and by observing sperm survival and penetration following addition of these acids to human cervical mucus. Direct addition of 0.1% malonic, maleic and citric acid rendered the sperm immotile by a reduction of pH. In capillaries filled with cervical mucus, the incorporation of 0.01% maleic, malonic and citric acids was sufficient to reduce sperm penetration, and at 0.1%, penetration was completely abolished. Thus, malonic, and maleic and citric acids show promise as cervical or vaginal contraceptives. Caffeic acid was found to be unsuitable owing to its insolubility in aqueous media. Electron microscopy indicated that human sperm do not undergo the acrosome reaction while penetrating cervical mucus in vitro.

Caffeic Acids↗
PubMed1979

The antifertility activity and toxicity of alpha-chlorohydrin derivatives in male rats.

The antifertility activity and toxicity of alpha-chlorohydrin, six derivatives and glycidol were investigated in male rats. At a dose of 5 mg/kg injected intraperitoneally each day for 14 days, only alpha-chlorohydrin produced complete infertility. When rats were injected with the derivatives at a dose equivalent to 5 mg/kg of alpha-chlorohydrin on a molar basis, the phosphorylated and amino acid derivatives produced complete infertility within 7 days; however, there were some signs of toxicity. Compound II also produced complete infertility and appeared less toxic. AY - 22,352, compounds III and IV and glycidol had no antifertility activity, although spermatozoan motility was reduced by injection of glycidol.

Adrenal Glands↗
PubMed1978

Mode of action of alpha-chlorohydrin as a male anti-fertility agent. Inhibition of the metabolism of ram spermatozoa by alpha-chlorohydrin and location of block in glycolysis.

1. The effect of alpha-chlorohydrin on the metabolism of glycolytic and tricarboxylate-cycle substrates by ram spermatozoa was investigated. The utilization and oxidation of fructose and triose phosphate were much more sensitive to inhibition by alpha-chlorohydrin (0.1-1.0mm) than lactate or pyruvate. Inhibition of glycolysis by alpha-chlorohydrin is concluded to be between triose phosphate and pyruvate formation. Oxidation of glycerol was not as severely inhibited as that of the triose phosphate. This unexpected finding can be explained in terms of competition between glycerol and alpha-chlorohydrin. A second, much less sensitive site, of alpha-chlorohydrin inhibition appears to be associated with production of acetyl-CoA from exogenous and endogenous fatty acids. 2. Measurement of the glycolytic intermediates after incubation of spermatozoal suspensions with 15mm-fructose in the presence of 3mm-alpha-chlorohydrin showed a ;block' in the conversion of glyceraldehyde 3-phosphate into 3-phosphoglycerate. alpha-Chlorohydrin also caused conversion of most of the ATP in spermatozoa into AMP. After incubation with 3mm-alpha-chlorohydrin, glyceraldehyde 3-phosphate dehydrogenase and triose phosphate isomerase activities were decreased by approx. 90% and 80% respectively, and in some experiments aldolase was also inhibited. Other glycolytic enzymes were not affected by a low concentration (0.3mm) of alpha-chlorohydrin. Loss of motility of spermatozoa paralleled the decrease in glyceraldehyde 3-phosphate dehydrogenase activity. alpha-Chlorohydrin, however, did not inhibit glyceraldehyde 3-phosphate dehydrogenase or triose phosphate isomerase in sonicated enzyme preparations when added to the assay cuvette. 3. Measurement of intermediates and glycolytic enzymes in ejaculated spermatozoa before, during and after injection of rams with alpha-chlorohydrin (25mg/kg body wt.) confirmed a severe block in glycolysis in vivo at the site of triose phosphate conversion into 3-phosphoglycerate within 24h of the first injection. Glyceraldehyde 3-phosphate dehydrogenase activity was no longer detectable and both aldolase and triose phosphate isomerase were severely inhibited. Spermatozoal ATP decreased by 92% at this time, being quantitatively converted into AMP. At 1 month after injection of alpha-chlorohydrin glycolytic intermediate concentrations returned to normal in the spermatozoa but ATP was still only 38% of the pre-injection concentration. Motility of spermatozoa was, however, as good as during the pre-injection period. The activity of the inhibited enzymes also returned to normal during the recovery period and 26 days after injection were close to pre-injection values. 4. An unknown metabolic product of alpha-chlorohydrin is suggested to inhibit glyceraldehyde 3-phosphate dehydrogenase and triose phosphate isomerase of spermatozoa. This results in a lower ATP content, motility and fertility of the spermatozoa. Glycidol was shown not to be an active intermediate of alpha-chlorohydrin in vitro.

Animals↗
PubMed1978

Effect of alpha-chlorohydrin and vasoligation on epididymal and testicular blood flow in the rat and on sperm parameters.

Rats were injected subcutaneously with the male antifertility agent, alpha-chlorohydrin (90 mg/kg), and the animals killed 4/24, 2, 5, 10 and 20 days after the injection. Rats in a second series were killed at the same time intervals following bilateral ligation of the vasa efferentia to mimic the effect of the high dose of alpha-chlorohydrin in blocking the initial segment of the epididymis. The epididymides were cut into segments for relative blood flow estimations. There was little change in the pattern of blood flow in the epididymal segments of rats injected with alpha-chlorohydrin, and it appears that interference with the epididymal vasculature is not an important factor in the mode of action of alpha-chlorohydrin. Bilateral ligation of the vasa efferentia produced a marked effect on blood flow through the epididymis. The results suggest that this dose of alpha-chlorohydrin disrupts the motility and morphology of sperm in the epididymis.

Animals↗
PubMed1977

Phospholipids and phospholipid-bound fatty acids and aldehydes of spermatozoa and seminal plasma of rhesus monkeys.

The major components of the phospholipids of rhesus monkey spermatozoa are phosphatidyl choline (33%), phosphatidyl ethanolamine (25%), ethanolamine plasmalogen (16-1%), sphingomyelin (8-1%), choline plasmalogen (6-9%) and cardiolipin (4-5%). The major phospholipid-bound fatty acids are 16:0, 18:0, 18:1 and 22:6; the major fatty aldehydes are 15:0, 16:0 and 18:2. The same phospholipids are also present in the seminal plasma.

Aldehydes↗
PubMed1977

Characteristics of semen collected from the cauda epididymis of conscious rams.

A technique which permits collection of the total output of spermatozoa and fluid from the cauda epididymidis of conscious rams is described. The volume of epididymal semen collected varied in an approximately inverse proportions with the frequency of collection, but there was little variation in the concentration of spermatozoa. Chemical analyses showed that cell-free cauda epididymidis fluid contained lactic acid at various concentrations, only traces of glucose but relatively high amounts of phospholipid, pregenenolone, androgen-binding protein and 5alpha-dihydrotestosterone (5alpha-DHT). Testicular spermatozoa maintained their metabolic activity and cellular integrity when stored in cauda epididymidis fluid in vitro at low temperature. After exposure to cauda epididymidis fluid for 14 days, testicular spermatozoa were predominantly glycolytic in their mode of glucose dissimilation and in this respect they resembled ejaculated spermatozoa.

Animals↗
PubMed1976

Disruption of the metabolism, motility and morphology of spermatozoa by injection of alpha-chlorohydrin into rams.

Ejaculated spermatozoa from rams given intramuscular injections of alpha-chlorohydrin (25 mg/kg, daily for 5 days) were studied. Respiratory and glycolytic activity of the spermatozoa was almost entirely suppressed within 1 day and motility had decreased within 4 days of the first injection. Morphologically abnormal spermatozoa appeared in ejaculates after 2 weeks. The most common abnormality was an increase in the number of spermatozoa with looped or bent tails. There was little change in the fructose or amino acid concentration of the seminal plasma. All effects of alpha-chlorohydrin were fully reversible. It is suggested that the initial primary mode of action of alpha-chlorohydrin is to disrupt the metabolism of spermatozoa in the cauda epididymis.

Animals↗
PubMed1976

The fatty acid composition of the major phosphoglycerides of ram and human spermatozoa.

The major individual phosphoglycerides of ram spermatozoa have specific fatty acid compositions, whereas human spermatozoan phosphoglycerides contain a similar pattern of fatty acids. The difference in the polyunsaturated:saturated fatty acid ratio of the spermatozoan phosphoglycerides between the two species were associated with the very high polyunsaturated fatty acid content of ram spermatozoan plasmalogens. The major unsaturated fatty acid of ram spermatozoa phospholipids, docosahexaenoic acid, was concentrated in the choline phosphoglycerides, whereas the chief saturates of ram and human spermatozoa, and docosahexaenoic acid in the latter, were largely located in the choline and ethanolamine diacylphosphoglycerides.

Animals↗