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.
R. Jones and T. Mann
R. Jones and T. Mann
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.
Keith T Jones
Mammalian eggs arrest at metaphase of the second meiotic division (MetII). Sperm break this arrest by inducing a series of Ca2+ spikes that last for several hours. During this time cell cycle resumption is induced, sister chromatids undergo anaphase and the second polar body is extruded. This is followed by decondensation of the chromatin and the formation of pronuclei. Ca2+ spiking is both the necessary and solely sufficient sperm signal to induce full egg activation. How MetII arrest is established, how the Ca2+ spiking is induced and how the signal is transduced into cell cycle resumption are the topics of this review. Although the roles of most components of the signal transduction pathway remain to be fully investigated, here I present a model in which a sperm-specific phospholipase C (PLCζ) generates Ca2+ spikes to activate calmodulin-dependent protein kinase II and so switch on the Anaphase-Promoting Complex/Cyclosome (APC/C). APC/C activation leads to securin and cyclin B1 degradation and in so doing allows sister chromatids to be segregated and to decondense.
C. T. Jones
The Nuffield Institute for Medical Research, University of Oxford, Oxford, OX3 9DS, U.K.
Although a great deal is known about the metabolism of fetal tissues (Roux & Yoshioka, 1970; Jost & Picon, 1970; Stave, 1970; Greengard, 1971) there is no direct information about the influence the fetal metabolism exerts in the control of fetal growth. The assessment of any interrelationships has to be inferential, largely through an analysis of differences in fetal metabolism associated with variations in the fetal growth rate. There appear to be three major factors regulating fetal growth. The first is the maternal organism, by means of its control over the supply of nutrients and hormones to the fetus through its own metabolic activities and by its influence on the placental blood supply. The second is the placenta which may affect fetal growth through the production and transport of substances to the fetus. The third is fetal
R. JONES and T. D. GLOVER
A technique is described for collection of the epididymal contents from the cauda epididymidis of anaesthetized rabbits. The technique avoids undue contamination of the epididymal contents with blood or tissue fluid and overcomes the difficulty of post-mortem change.
The effects of high-speed centrifugation and cold shock on the composition of epididymal plasma have also been investigated, and it has been shown that lactic dehydrogenase and glutamic-oxaloacetic transaminase are largely intracellular constituents, whilst sodium, potassium, acid phosphatase, alkaline phosphatase and β-N-acetylglucosaminidase are extracellular. Finally, some results are presented on the overall composition of epididymal plasma in the rabbit.
R. JONES and T. D. GLOVER
The composition of luminal plasma from the cauda epididymidis of rabbits has been investigated after prolonged retention of spermatozoa in the cauda epididymidis of entire animals, and of castrated animals both with and without hormone replacement. The morphology of the contained spermatozoa and the epididymal cells has also been examined.
In the presence of androgen, spermatozoa survived for 4 to 5 weeks before degenerative changes became apparent and the composition of the epididymal plasma and the histological characteristics of the lining cells were not seriously affected during this period. The only change in the plasma which could be due to sperm death was an increase in the lactic dehydrogenase (LDH) activity. After androgen withdrawal, spermatozoa degenerated rapidly and there were considerable changes in the composition of the luminal plasma. There was a rapid increase in the level of sodium ions and pH, and a decrease in the concentrations of glycerylphosphorylcholine (GPC) and protein. The activity of acid phosphatase and LDH also decreased. Initially, the concentration of inorganic phosphate and potassium increased but this was soon followed by a decrease. Five weeks after castration, all the spermatozoa disappeared from the epididymis and the epididymal cells had regressed. If testosterone replacement was given at this stage, the level of sodium ions in the plasma decreased and the concentration of GPC increased. The epididymal cells were also restored to their normal histological appearance.
These results provide evidence that, in the presence of androgen, the epididymal cells in the cauda epididymidis actively maintain a constant milieu in the lumen of the duct by their capacity for absorption and secretion. If androgen is withdrawn, these functions cease and considerable changes take place in the lumen.
Janet T. Jones and Sandra J. Andrews
Summary. The activity of G6PD was examined by spectrophotometric and electrophoretic assays in cell fractions from the testes of mice at different ages (5–62 days). (1) The G6PD activity of the cells of the seminiferous tubule was as high or higher than that of the interstitial tissue. (2) The high G6PD activity of the testis of the immature mouse was mainly due to a high specific activity of the Sertoli cells which declined with age. (3) The G6PD activity was more easily lost during culture from the germinal cells than from the interstitial or Sertoli cells. (4) All the cell types of the testis contained G6PD and hexose-6-phosphate dehydrogenase. The functional significance of the high G6PD activity in the Sertoli cells of immature mice is not at present understood.
S. J. Arkinstall and C. T. Jones
Summary. High-pressure liquid chromatography with electrochemical detection was used to identify and measure catecholamines in rat, rabbit, sheep, guinea-pig and human uteri and follow changes with pregnancy. Noradrenaline was consistently the major catecholamine and pregnancy caused a regionally specific fall in its concentration which, in rat, rabbit and guinea-pig, was associated with a decline in total content. Adrenaline was undetectable (<10 pmol/g myometrium) in all species and at all gestational ages studied. Dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were detected at high concentrations in guinea-pig and particularly sheep uterus. In guinea-pig uterus the dopamine/DOPAC ratio fell dramatically with pregnancy, suggesting that increased quantities of dopamine were released and catabolized. The dopamine/noradrenaline ratios suggested that dopamine is stored with noradrenaline in adrenergic neurones in guinea-pig myometrium and within an additional neuronal or cellular store(s) in sheep uterus.
Josie K Collins and Keith T Jones
DNA damage acquired during meiosis can lead to infertility and miscarriage. Hence, it should be important for an oocyte to be able to detect and respond to such events in order to make a healthy egg. Here, the strategies taken by oocytes during their stages of growth to respond to DNA damaging events are reviewed. In particular, recent evidence of a novel pathway in fully grown oocytes helps prevent the formation of mature eggs with DNA damage. It has been found that fully grown germinal vesicle stage oocytes that have been DNA damaged do not arrest at this point in meiosis, but instead undergo meiotic resumption and stall during the first meiotic division. The Spindle Assembly Checkpoint, which is a well-known mitotic pathway employed by somatic cells to monitor chromosome attachment to spindle microtubules, appears to be utilised by oocytes also to respond to DNA damage. As such maturing oocytes are arrested at metaphase I due to an active Spindle Assembly Checkpoint. This is surprising given this checkpoint has been previously studied in oocytes and considered to be weak and ineffectual because of its poor ability to be activated in response to microtubule attachment errors. Therefore, the involvement of the Spindle Assembly Checkpoint in DNA damage responses of mature oocytes during meiosis I uncovers a novel second function for this ubiquitous cellular checkpoint.
M. D. KAYE, W. R. JONES and D. T. ANDERSON
The delayed rejection of allografted tissue in the presence of specific antibodies (Kaliss, 1958, 1962) has been considered as a possible mechanism for the maintenance of the fetal-maternal relationship in mammalian reproduction. Experiments which demonstrate the abrogation of cellular immunity to mouse embryonic cells by serum from pregnant or multiparous female strain animals have been taken to indicate that specific 'blocking' antibodies might prevent the cytotoxic action of maternal lymphocytes on embryonic cells (Hellstrom, Hellstrom & Braun, 1969). In turn, it has been suggested (Hellstrom & Hellstrom, 1970) that this might be the mechanism underlying the paradoxical survival of the mammalian conceptus as an allograft.
The existence of immunological enhancement, as this phenomenon is called, depends on the simultaneous presence in a particular system of