Information transfer and sperm uptake by mammalian somatic cells

Interaction of gametes with exogenous genes: possible opportunities for incorporation into embryonic genome

The mechanism of incorporation of foreign DNA into newly fertilized eggs is poorly understood. It is not known with certainty if S phase DNA replication is required or if integration could occur at other times of the cell cycle that involve DNA strand breaks, such as chromatin rearrangements. We have investigated DNA strand breaks in mouse eggs and zygotes with a sensitive terminal uridine nucleotide end labeling (TUNEL) assay. Greater than 90% of all polar bodies and metaphase II chromosomes in freshly ovulated mouse eggs are TUNEL-assay positive. Approximately one-third of zygotes assayed 6 hr after fertilization contain at least one TUNEL assay positive pro-nucleus and/or decondensing sperm head. These results indicate that early embryonic DNA contains multiple transient DNA breaks that could play a role in the incorporation of foreign DNA.

Sexual behaviour and increased anal cancer

An increase in epidermoid anal cancer has been observed in the past 30 years (1959-89). This increase in anal cancer has been noted to be more pronounced in women than men. The absence of a significant interactive effect of the HIV and human papillomaviruses and the incidence of anal cancer has been noted in some studies. These observations provide the rationale for consideration of other aetiologic agents that may contribute to the increase of anal cancer in men and women. Within the context of their ability to serve as cancer initiating and promoting factors, spermatozoa and seminal plasma are suggested as aetiologic agents and/or cofactors which are common to men and women practising anal intercourse in whom an increase in anal cancer has been observed. It is further suggested that sexual behaviour, that is, anal intercourse, not sexual preference, is one of the primary factors in the development of anal cancer.

Intraprostatic spermatozoa

Spermatozoa have not previously been described within the prostate gland. Nine of one hundred prostates of nonhospitalized males obtained from autopsy during the course of medicolegal death investigation were found to contain spermatozoa. The potential role of spermatozoa in the pathogenesis of corpora amylacea/calculi formation, granulomatous inflammation, local antigenic stimulation, and carcinogenesis is considered.

Intraprostatic spermatozoa in the squirrel monkey

The recent observation of spermatozoa within the human prostate prompted this study to determine if spermatozoa were present in prostates of nonhuman primates. Six of 32 squirrel monkey prostates contained intraglandular spermatozoa. No associated pathologic lesions were found. Spermiophages were seen in one case. Although intraprostatic spermatozoa have been postulated to play a role in various prostatic diseases, a normal physiologic phenomenon cannot be excluded.

The metaphase-arrest technique applied to human cervical epithelium. I. Technique and dose-response studies

In order to study cell proliferation in intact human cervical epithelium, a technique involving metaphase arrest has been utilized. Metaphase accumulation is observed following intraepithelial administration of vincristine sulphate, at a predetermined optimum dose of 50 micrograms/ml. A significant delay before the onset of stathmokinetic activity is demonstrated; thereafter linearity of accumulation is apparent over a 4-hr period following injection. The technique appears applicable to the estimation and comparison of cell production rates in vivo of normal cervical epithelium, cervical intraepithelial neoplasia, wart-affected cervical epithelium and early invasive carcinoma. However, individual values are likely to be imprecise in isolation, indicating the need to study relatively large numbers of subjects in each group. Some practical difficulties are discussed.

Is a bi-clonal interaction, analogous to that underlying embryogenesis the origin of the earliest malignant phenotype?

We propose a theoretical model of carcinogenesis which parallels embryonic induction. It is based on the interaction between two clones of cells. One of them is of germ cell ancestry and is the source of transforming effector cells. The second clone is the potential target of such travelling "lymphocytoid" cells and emerges in tissues exhibiting the precancerous picture of dysplasia. In atypical fields each endopolyploid cell, arrested in G2 and involved in genomic changes, is the stem of a clonal growth. This emerging new phenotype is subjected to policing control by wandering effector cells. This situation establishes the probability of a random collision between two cells pertaining to different lineages, with two possible antithetical results, cytolysis or cell fusion comparable to fertilization. The latter event is suggested to determine malignancy.

Extraction and biochemical characterization of a nuclear deoxyribonucleic acid polymerase activity in bull spermatozoa

Bull spermatozoa heads were separated from cytoplasmic contaminants, especially mitochondria-rich middle pieces, by centrifugation through 2.4M-sucrose. DNA polymerase activity was demonstrated by incubating nuclear heads for 1 h at 37 degrees C or for 20 h at room temperature in a medium containing detergent and dithiothreitol or 2-mercaptoethanol. Optimal DNA polymerase activity was detected after extraction in a medium containing 50 mM-borate, pH9, 1 mg of soya-bean trypsin inhibitor/ml and supplemented with either 20 mM-dithiothreitol and 4% Tween 80 or 100mM-2-mercaptoethanol and 10% Tween 80. The DNA polymerase reaction was Mg2+-dependent; Mn2+ or Ca2+ could not replace Mg2+ and all four deoxynucleoside triphosphates were required for optimal activity. The polymerase activity was pH-dependent (optimum between 8.2 and 10.5) and was a function of buffer composition and also of pH values. Optimal activity was obtained with 50 mM-Na+ or 150mM-K+ and was partially lowered by N-ethylmaleimide; it was inhibited by spermidine and by salmon protamines, but was greatly stimulated by calf thymus histones. It was also resistant to actinomycin D, netropsin and ethidium bromide. The present results suggest that bull spermatozoa heads contain a beta-type DNA polymerase activity.

Presence of two deoxyribonucleic acid polymerases in bull spermatozoa

A DNA polymerase-endogenous template complex was isolated from nuclear heads of bull spermatozoa. The buoyant density of the complex was 1.15 g/cm 3. The sedimentation coefficient of the nuclear DNA polymerase isolated from the complex was higher at low ionic strength, but approached 3.4S when centrifuged in a medium containing 2M-KCl. Activated exogenous DNA increased polymerase activity. Only very low activities were detected with synthetic templates such as poly(A).(dT)12-18 and poly(dT).poly(A). The nuclear reaction was stimulated by 150mM-KCl and was slightly inhibited by N-ethylmaleimide; it was resistant to actinomycin D, netropsin and ethidium bromide. Another DNA polymerase, highly sensitive to ethidium bromide, was extracted from the mitochondira-rich middle-piece fraction. Its sedimentation coefficient was close to 9S, but fell to approx. 4S in high-ionic-strength medium.

The problem of sea urchin egg fertilization and its implications for biological studies

The analysis of sea urchin egg fertilization shows that several phenomena common to other biological systems are involved: cell recognition, cell fusion, exocytosis and initiation of mitotic activity. Both the role of calcium ions in cell fusion and exocytosis and the function of the cell surface in the initiation of mitotic activity appear to have general applicability. The study of fertilization can contribute to the elucidation of these processes and, reciprocally, progress in this field can help to advance our understanding of the mechanisms of fertilization in sea urchins and other organisms.