I. G. White

Influence of the cholesterol content of mammalian spermatozoa on susceptibility to cold-shock.

The cholesterol content of spermatozoa with highly unsaturated phospholipids, i.e., ram and bull, which are very susceptible to cold-shock was compared with that of rabbit and human spermatozoa which have more saturated phospholipids and a greater resistance to cold-shock. The level of cholesterol in the seminal plasma was also estimated. Cholesterol was present in ram and bull spermatozoa in comparable amounts (280–346 μg) and at approximately half the level (in micrograms per 109 spermatozoa) in rabbit and human spermatozoa (545–556 μg). The molar ratio of cholesterol: phospholipid in rabbit and human spermatozoa was 0.88 and 0.99, respectively, which is similar to the ratio of these lipids in erythrocytes and higher than the ratio of 0.38 and 0.45 for ram and bull spermatozoa, respectively. This ratio is of some importance in determining the nature and degree of packing in the spermatozoan membrane; higher levels of cholesterol result in a more cohesive, rigid, and impermeable structure. A definite relationship is apparent between the ratio of cholesterol: phospholipid, the ratio of polyunsaturated: saturated phospholipid-bound fatty acids, and the susceptibility of the spermatozoa to cold-shock.

The phospholipid-bound fatty acids and aldehydes of mammalian spermatozoa

Abstract 1. 1. The phospholipid-bound fatty acids of ram, bull, boar, rabbit and human spermatozoa contained high levels of polyunsaturated fatty acids. Values ranged from 70 per cent by weight of the total fatty acid fraction in the boar to approximately 40 per cent in both human and rabbit. 2. 2. Docosahexaenoic acid (22:6) was quantitatively the most important fatty acid found in all species except the rabbit. 3. 3. The major saturated fatty acid found in mammalian spermatozoa was palmitic acid. 4. 4. The predominant fatty aldehyde was palmitaldehyde (16:0) and values ranged from 91·2 per cent in ram to 51·1 per cent in human spermatozoa.

Heavy metals and human spermatozoa. III. The toxicity of copper ions for spermatozoa

The dissolution of copper ions from copper metal into a saline medium in vitro was quantified using a colourimetric assay. The presence of spermatozoa enhanced this dissolution and increasing the protein content of the medium further increased the rate of dissolution. Approximately 17% of the copper released was either tightly bound to the spermatozoa or was within the cell and could not be removed by repeated washing. Once spermatozoa were immobilized, they could not be revived by washing and repeated changes of medium, by addition of copper specific-chelating agent or by extensive dialysis. When the toxicity to spermatozoa of cuprous and cupric ions was compared with copper metal, it could be shown that the quantity of cupric ions required (0.2-0.4 mg/ml) was in excess of the total quantity of copper released into solution. The quantity of cuprous ion required (0.08-0.16 mg/ml) to exert similar toxic effects to copper, was within the range of copper released from the metal. Under the conditions of this study, it is possible that cuprous ion would be oxidised to the cupric form generating free radicals in the process. It is not known whether the toxic effect is due to the cuprous ion, per se, or to radicals generated in its oxidation. Increasing the protein content of the medium to levels similar to low (8 mg/ml) and high (64 mg/ml) values reported in human uterine fluid increased the dissolution rate of copper but also offered some protection against the toxic effects of copper metal and cuprous and cupric ions.

Heavy Metals and Spermatozoa. 1. Inhibition of the Motility and Metabolism of Spermatozoa by Metals Related to Copper

The toxicity to human spermatozoa of seven metals (nickel, palladium, platinum, silver, gold, zinc, and cadmium) and one alloy (brass: 80% copper, 20% zinc) related to copper was assessed in vitro. Only brass and cadmium significantly reduced the percentage of motile unwashed spermatozoa; however, washing the spermatozoa increased the spermicidal effectiveness of both brass and cadmium and also resulted in a significant reduction in motility caused by zinc and silver. Oxygen consumption by once-washed spermatozoa was apparently increased by zinc and brass, but the high rate of oxidation of these metals confounds interpretation of their effect. Silver caused a decline in the oxygen uptake of spermatozoa. Silver, zinc, brass, and, to a lesser extent, cadmium decreased the quantity of glucose utilized by spermatozoa and also decreased the glucose oxidized. Accumulation of lactate by washed spermatozoa was impaired severely by zinc and less severely by brass and cadmium.

Origin of Glycerylphosphorylcholine, Inositol, N-Acetylaminosugar, and Prostaglandins in Human Seminal Plasma and Their Effects on Sperm Metabolism

The origin of glycerylphosphorylcholine (GPC), N-acetylaminosugar, inositol, and prostaglandins in human seminal plasma was investigated by correlating the concentration of these components in split ejaculates with known marker constituents. Fructose and acid phosphatase were selected as markers of the secretory activity of the seminal vesicles and prostate gland, respectively, and spermatozoa indicated epididymal origin. The concentration of fructose was lowest in the first fraction of the semen and increased to a maximum in the final portion. Prostaglandins E and F and N-acetylaminosugar values closely followed this pattern, indicating that these components originate in the seminal vesicles. The concentration of spermatozoa was high in the first two fractions, decreasing to a minimum in the final fraction. The distribution of GPC was similar to that of the spermatozoa, indicating that the epididymis secretes this compound. Inositol levels were similar in all fractions, indicating that it is probably present in epididymal, vesicular, and prostatic fluid. Human spermatozoa were unable to utilize N-acetylglucosamine or inositol. High concentrations of some prostaglandins (100 micrograms/ml of PGF1 alpha, 15S 15 met. F2 alpha, PGA1, and PGA2) depressed the endogenous oxygen uptake of human spermatozoa.

Effect of α-chlorohydrin on cauda epididymis and spermatozoa of the rat and general physiological status

A study was undertaken to determine whether alpha-chlorohydrin affects the metabolism of spermatozoa directly or through disruption of the metabolism of the eipdidymal tissue in the caudal region of the duct after a single high-dose injection in mature rats. A number of physiological studies were also conducted to determine whether damage was localized to the reproductive tract or of a more general nature. Oxygen uptake, glucose utilization, and lactic acid accumulation were reduced in the spermatozoa obtained from the cauda epididymis 48 and 240 hours after alpha-chlorohydrin injection (90 mg/kg). Motility of the spermatozoa was also significantly decreased. The results indicated that alpha-chlorohydrin had very little effect on the respiratory activity of the flushed epididymal tubule, liver, or kindey tissue, but it did stimulate glycolysis in the kidney. It appeared that the metabolic effects of alpha-chlorohydrin were fairly specifically confined to the spermatozoa in the epididymis. The drug at the high dosage did cause a loss of body weight, hypertrophy of the adrenal glands, and an increase in the total leukocyte count.

The Fatty Acid Composition of the Major Phosphoglycerides of Ram and Human Spermatozoa

Die Fettsäurenzusammensetzung der wichtigsten Phosphoglyceride von Widder‐ und Menschen‐Spermatozoen

Studies of chemical components of Angora goat seminal plasma.

Ejaculates were collected by artificial vagina from 11 Angora goats, once or twice weekly, between April and July in two successive years. The mean +/- SEM ejaculate volumes each year were 0.8 +/- 0.30 and 0.98 +/- 0.52 ml; the sperm concentrations were 3.33 +/- 0.49 and 2.94 +/- 0.45 x 10(9)/ml, and the pH values were 7.01 +/- 0.34 and 7.20 +/- 0.17. The concentrations (mg/100ml) of fructose (875 +/- 97) and lactic acid (73 +/- 17) in goat seminal plasma were sufficiently high to be important substrates for maintenance of sperm motility. Only trace amounts of glucose were present in seminal plasma. The glycerylphosphorylcholine (GPC) concentration of seminal plasma (809 +/- 154 mg 100 ml ) was correlated with whole semen sperm concentration (P < 0.001), indicating that GPC is of epididymal origin. Goat sperm are not likely to utilize GPC as a substrate and its metabolizable derivatives, glycerophosphate (3.3 +/- 1.1 mg 100 ml ) and glycerol (1.8 +/- 1.0 mg 100 ml ), were not present in sufficiently high concentrations to be significant as energy sources for the sperm. The mean concentration of citric acid was 331 mg 100 ml seminal plasma. Colored semen was consistently produced by eight bucks, and in yellow, light yellow and white ejaculates, the seminal plasma riboflavin (mug/ml) concentrations were 5.38 +/- 2.89, 3.09 +/- 0.85 and 1.73 +/- 0.88, respectively. This suggests that the color is due to riboflavin, which is probably produced by the vesicular glands since the concentration of riboflavin in the seminal plasma was correlated with fructose and citric acid levels.

Calcium ionophore A23187 as a probe for freeze-fracture studies of membrane changes in the head of human spermatozoa.

The membranes of the head of human spermatozoa were examined after incubating the sperm with and without inophore A23187 and calcium ions, using freeze-fracture electron microscopy. After exposure to ionophore and calcium there was a remarkable rearrangement of the intramembraneous particles, especially in the plasma membrane. Buckling of the plasma membrane occurred prior to breaking away from the outer region of the sperm head. The outer acrosomal membrane bubbled and broke down to form vesicles, and blebbing of the inner acrosome membrane also occurred. The nuclear envelope degenerated and often displayed an undulating topography.

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.