Objective-To determine whether the quality of semen has changed in a group of over 500 Scottish men born between 1951 and 1973. Design-Retrospective review of data on semen quality collected in a single laboratory over 11 years and according to World Health Organisation guidelines.Setting-Programme of gamete biology research funded by Medical Research Council.Subjects-577 volunteer semen donors. Of these, 171 were born before 1959, 120 were born in 1960-4, 171 in 1965-9, and 115 in 1970-4. Main outcome measures-Conventional criteria of semen quality including semen volume (ml), sperm concentration (106/ml), overall motility (0/% motile), total number ofsperm in the ejaculate (106), and total number ofmotile sperm in the ejaculate (10').

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Summary. Cells isolated from the ejaculates of a high proportion of patients exhibiting oligozoospermia are characterized by generation rates of reactive oxygen species that considerably exceed those obtained for the normal fertile population. The purpose of this study was to resolve the cellular source of this enhanced activity. Semen samples from a cohort of oligozoospermic patients and a group of fertile controls were fractionated on discontinuous Percoll gradients to generate three cell populations (0, 50 and 100%) of differing density. For each fraction, both the steady-state and the phorbolester-induced chemiluminescent signals were significantly (P < 0\m=.\001)greater for the oligozoospermic samples than for the fertile controls. In the fertile donors, leucocytes comprised the major source of reactive oxygen species, particularly in the low-density Percoll fractions; in oligozoospermic patients, however, spermatozoa were identified as a second major source of reactive oxygen species. Particularly striking was an intense phorbol-ester-induced chemiluminescent signal generated by oligozoospermic spermatozoa, purified by passage through isotonic Percoll and free of leucocyte contamination, which was 167 times greater than the median signal generated by the corresponding fraction from the fertile controls (P < 0\m=.\001). These results emphasize the importance of spermatozoa as a major source of reactive oxygen species in oligozoospermia and have implications for the diagnosis and treatment of this condition, as well as for the design of appropriate diagnostic strategies.

The onset of production of spermatozoa (spermarche) is the basis for achievement of reproductive capacity in men. We collected 24-h urine samples every 3 months in a 7-yr longitudinal study of 40 normal boys initially aged 8.6-11.7 yr. After centrifugation, the urine was analyzed for the presence of spermatozoa by microscopic examination, and spermarche was estimated on the basis of age at first observed spermaturia. The results were corrected for the intermittent occurrence of spermatozoa in the urine after first observed spermaturia and the fact that the urine samples were collected quarterly. In addition, physical examination, including determination of testicular size by orchidometer measurement, pubic hair distribution (Tanner stage), and height, was carried out every 6 months. Spermarche occurred at a median age of 13.4 yr (range, 11.7-15.3 yr), at a time when testicular size was 4.7-19.6 ml (median, 11.5 ml), and pubic hair distribution was 1-5 (median, 2.5). In most boys, spermarche preceded the age of peak height velocity (median, 13.8 yr; range, 12.2-15.2 yr); at the time of spermarche, median peak height growth velocity was 9.9 cm/yr (range, 7.5-13.4 cm/yr), and median height was 160.4 cm (range, 151.7-175.9 cm). We conclude that spermarche is an early pubertal event and that a wide variation in testicular size and secondary sex characteristics is found at that time. In particular, spermarche may occur when little or no pubic hair has developed, and the testes have grown only slightly.

In a group of normospermic donors exhibiting hamster oocyte penetration scores of 0-100%, multiple regression analysis indicated that only 20% of the variation in fertilizing potential could be explained by differences in the movement characteristics of the spermatozoa following incubation in vitro. When the movement characteristics of the spermatozoa in semen were considered this figure was reduced to 6.8% as a result of significant differences in the motility patterns exhibited by the seminal and post-incubation sperm populations. A much closer relationship was observed between the movement characteristics of human spermatozoa in semen and their ability to penetrate cervical mucus. When differences in motile sperm densities were taken into account, 76% of the variation in cervical mucus penetration could be accounted for by the existence of linear correlations with certain aspects of sperm movement (multiple R = 0.874). Of the various attributes of sperm motility measured (linear velocity of progression, frequency of rotation, amplitude of sperm head displacement, % rolling and % yawing), a failure to exhibit an adequate amplitude of lateral sperm head displacement was consistently found to be the most significant factor determining the success of sperm-cervical mucus interaction (R2 = 0.53).

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The pH and the carbon dioxide tension of the blood flowing through a tissue are commonly thought to be major factors in the local control of regional blood flow, for instance in the vasodilation in exercising muscle (1). They also are of recognized importance in the control of general circulatory homeostasis; for example, systemic hypertension accompanies acutely induced hypercapnia (2, 3), and hypotension the hypocapnia of hyperventilation (4). Furthermore, disorders of acid-base equilibrium occur in pathologic states with sufficient frequency to merit consideration of the role of blood pH and CO2 tension in control of the circulation burdened by disease such as the acidosis of uremia and diabetic coma or the alkalosis of vomiting.With these considerations in mind, the present studies were undertaken in healthy humans to determine the effects of variation in blood pH and CO2 tension (Pco2) on cardiac output and on the flow of blood through extremity musculature. In an attempt to separate direct effects of change in pH or Pco0 on blood vessels themselves from those mediated by the nervous system, sympathetic impulses to the extremity were blocked with phenoxybenzamine (Dibenzyline 1) administered intraarterially to the extremity under study. METHODSThe subjects studied were healthy male volunteers and one male with essential hypertension. Their ages ranged from 22 to 46 years. Most had participated repeatedly in similar studies in the same laboratory and were, therefore, relaxed and at ease.Acidemia was induced by intravenous infusion of 500 to 800 ml of 0.2 M lactic acid or 0.17 M ammonium chlo-*

Summary. In 17 healthy men, beta-adrenergic blockade reduced significantly the tachycardia and the elevation of cardiac output associated with inhalation of 7.5% oxygen for 7 to 10 minutes.Hypoxia did not increase plasma concentrations of epinephrine or norepinephrine in six subjects. Furthermore, blockade of alpha and beta receptors in the forearm did not modify the vasodilation in the forearm induced by hypoxia, providing pharmacologic evidence that hypoxia of the degree and duration used was not associated with an increase in the concentrations of circulating catecholamines in man.Part of the increase in cardiac output and heart rate during acute hypoxia in man is produced by stimulation of beta-adrenergic receptors, probably by cardiac sympathetic nerves. The mechanism of the vasodilation in the forearm during hypoxia remains uncertain.