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The secretory activity of male accessory organs of reproduction such as the prostate, seminal vesicle, Cowper's gland and similar organs, differs in many ways from that of other secretory organs in the animal body.

Summary. The toxicity of unsaturated fatty acids towards spermatozoa was shown to be directly related to their degree of peroxidation. The toxicity was manifested by an immediate arrest of motility and irreversible loss of respiratory and fructolytic activity. Repeated washing of spermatozoa, or the addition of fructose, lactate, or ATP, failed to restore these functions. The structural damage incurred as a result of the fatty acid peroxides was particularly evident in the acrosomal region. Partial protection from the adverse effects of these peroxides was provided by prior treatment of spermatozoa with dialysed egg yolk or milk, but tocopherol, albumin and mercaptoethanol were ineffective. It is suggested that lipid peroxides or their degradation products, whether introduced exogenously or derived from the peroxidation of endogenous phospholipids in semen, constitute a potential hazard to the functional integrity of spermatozoa.

Summary. We examined the damaging effects on spermatozoa of endogenous phospholipid peroxidation brought about by aerobic incubation at 37°C in the presence of 0·5 mM-ascorbic acid and 0·5 mM-FeSO₄. As well as becoming immotile, such peroxidized spermatozoa also lost, through leakage, certain intracellular enzymes into the surrounding medium, on a scale resembling that produced by cold shocking nonperoxidized spermatozoa. Morphological observations revealed that peroxidation damaged the plasma membrane, particularly in the region of the acrosome. Further experiments showed that lipid peroxidation irreversibly abolished the fructolytic and respiratory activity of spermatozoa. The susceptibility of spermatozoa to peroxidation was greater when the cells were damaged before incubation with ascorbic acid and FeSO₄. To some extent, peroxidation could be prevented, but not reversed, by the addition to sperm suspensions of dialysed egg yolk or dialysed bull seminal plasma. However, dialysed seminal plasma from ram, stallion or man had no protective effect.

The purpose of the preliminary experiments described below was to label mammalian spermatozoa with ³² P to such a degree that they could afterwards be used for a quantitative follow-up of the so-called leakage of intracellular sperm compounds, such as is known to accompany sperm 'ageing' or 'senescence' (Mann, 1964). The approach was twofold, by means of labelling in vivo and in vitro.

The in-vivo study, in which four buck rabbits were injected subcutaneously with inorganic [³² p]phosphate (1 mc/animal), included radio-activity assays by liquid scintillation counting of urine, blood plasma, blood corpuscles, seminal plasma and spermatozoa. In the urine and blood plasma, specific radio-activity, high at first, declined rapidly, reaching a very low level by the end of the first month. In the blood corpuscles, there was first a decline in radio-activity which, however,

Summary.

We have studied the antlers and male reproductive organs of thirteen roebucks, shot at approximately monthly intervals throughout the year. The roebuck is a seasonally breeding mammal that is in rut from mid-July to mid-August. Antlers `in velvet' begin to develop in January, and the velvet is shed in March or April. The animal then remains in `hard horn' until November or December, when the antlers are cast.

The testes are at their most inactive state in January, when there is no spermatogenic activity and a very low content of testosterone. By mid-February, the testicular testosterone content has risen considerably, and primary spermatocytes are to be seen in the enlarging seminiferous tubules. The testosterone content of the testis remains high until the beginning of the rut, but falls precipitously towards the end. Spermatogenesis is not finally completed until April or May, and, although it continues for several weeks after the end of the rut, there is a highly significant decline in testis tubular diameter that coincides with the fall in testosterone content. Thus spermatogenesis and androgenesis are closely related at the beginning and end of the sexual cycle, suggesting that fsh and lh secretion by the pituitary gland normally go hand-in-hand.

The seminal vesicles secrete fructose, sorbitol, inositol and citric acid. Although there is a significant correlation between testicular testosterone and vesicular fructose and citric acid, the correlation coefficients are not high. This is probably because the seminal vesicles do not respond until some weeks after the onset of testosterone production in the spring, and their secretion declines less rapidly than testicular testosterone after the end of the rut.

These endocrine changes are in accord with the seasonal changes in antler growth, which are known to be under endocrine control. Shedding of the velvet occurs soon after the testicular testosterone levels have risen in the spring, and casting of the antlers in late autumn coincides with extremely low testicular testosterone levels.

Summary.

Boar spermatozoa utilize pyruvate efficiently both anaerobically and aerobically. Pyruvate metabolism, in marked contrast to fructolysis, continues in spermatozoa immobilized by cold shock. Sperm cytoplasmic droplets alone do not metabolize pyruvate. Carbon dioxide, lactate, acetate, succinate and acetoacetate were identified as anaerobic products of pyruvate metabolism; the ratio between pyruvate utilized and lactate and acetate formed did not fit into the stoichiometry of a simple dismutation. Carbon dioxide and lactate were formed from pyruvate aerobically. The rate of pyruvate disappearance, as well as the percentage of pyruvate converted to lactate, were higher aerobically than anaerobically. Very little acetoacetate was utilized by boar spermatozoa aerobically. Lactate was oxidized but at a much lower rate than pyruvate. Acetate (0·18 μmol/10⁹ cells) was extracted from exhaustively washed spermatozoa; this acetate is assumed to be derived from acetyl compounds of the sperm cells.

Summary.

When semen is collected from boars 30 min after a single injection of 25 to 50 mg atropine sulphate, the volume of the ejaculate is reduced to about one-fourth, and hardly any gel is present. The ejaculate from an atropine-treated boar has less chloride, but a higher concentration of spermatozoa, organically-bound acid-soluble phosphate, fructose, ergothioneine, and citric acid, than normal semen. These changes are thought to be due to the inhibiting action of atropine on the parasympathetic stimuli which normally reach the urethral and bulbo-urethral glands at the time of ejaculation. In consequence, the urethral glands no longer contribute the watery, chloride-rich fluid, and the bulbo-urethral glands fail to provide the gel. Atropine does not interfere either with epididymal function, in so far as the output of spermatozoa and acid-soluble phosphate (mainly glycerylphosphorylcholine) is concerned, or with the secretory output of fructose, ergothioneine and citric acid, by the seminal vesicles. Thus, being made up to a large extent by the epididymal and vesicular contributions, the semen voided by the atropine-treated animal resembles the so-called spermrich or middle portion of a normal ejaculate.

Summary.

Stallion and jackass semen have several chemical characteristics in common, such as ergothioneine, which originates chiefly in the ampullae, and citric acid, which is derived from the seminal vesicles; the vesicular secretion also contains an extraordinarily high concentration of lactic acid. In both species the semen is ejaculated in the form of a 'pre-sperm', 'sperm-rich' and 'post-sperm' fraction, represented by the urethral, ampullar and vesicular contributions, respectively. Stallion and jackass semen are practically free from fructose, but the spermatozoa are able to metabolize added fructose anaerobically and aerobically. In the absence of oxygen, the rate of fructose conversion to lactic acid as well as sperm motility are very low; in the presence of oxygen, the rate of fructose disappearance, as well as motility, are much higher. In this and other respects, stallion and jackass spermatozoa resemble those of the boar, but differ from human, ram and bull spermatozoa. An easily oxidizable substance occurs in the seminal plasma of both the jackass and stallion, like in the boar; this substance is responsible for the plasma's own oxygen uptake.

Stallion and jackass semen differ from each other with respect to the rate of aerobic metabolism, and sperm survival in vitro. Exogenous substrates increase the oxygen uptake of jackass spermatozoa more than that of the stallion spermatozoa. The motility and respiratory activity in jackass semen diluted with an egg-yolk medium are maintained at 5° C much longer than in stallion semen.

Summary.

The metabolism of boar semen differs in several respects from that of bull and ram. Anaerobically, boar spermatozoa convert fructose to lactic acid at a much lower rate than ram or bull spermatozoa, and under these conditions their motility is also characteristically small. Aerobically, boar spermatozoa convert fructose to lactic acid at the same or even lower rate, yet their motility is very high. This is due to the ability of boar spermatozoa to oxidize lactic acid with an efficiency as high as that encountered in ram or bull semen. Apart from lactic acid, boar spermatozoa are capable of utilizing aerobically a number of other substrates, including glycerol, pyruvic acid and acetic acid, but unlike ram spermatozoa, they lack the ability to oxidize sorbitol. Two other unusual features of the aerobic metabolism of boar semen are (i) an increase in oxygen uptake, which occurs after the semen has been stored in vitro, and (ii) the occurrence in the boar seminal plasma of an easily oxidizable substance which is responsible for the plasma's own oxygen uptake.