The cycle of the seminiferous epithelium of the dog was divided into eight stages, using as criteria the shape of the spermatid nucleus, the location of spermatids and spermatozoa in regard to the basement membrane, the presence of meiotic figures and the release of spermatozoa from the lumen of the tubule. Based upon these criteria, a modification of the eight-stage system of classification of the cycle of the seminiferous epithelium was developed. Cell populations making up each stage are described. The relative frequencies of stages 1 through 8 were 21.9, 12.7, 2.8, 11.5, 8.3, 15.4, 13.3 and 14.0%, respectively. The duration of one cycle of the seminiferous epithelium was 13.6 days (SE -t. 0.7), as determined from cells labeled by tritiated thymidine. The absolute durations of stages 1 through 8 were 3.0, 1.7, 0.4, 1.6, 1 .l, 2.1, 1.8 and 1.9 days, respectively. The life span of primary spermatocytes was 20.9 days, of secondary spermatocytes 0.5 days, spermatids with round nuclei 10.5 days, spermatids with elongated nuclei up to the time they are released into the lumen, 10.6 days. Counts of the different types of spermatogenic cells in tubular cross sections revealed little or no germ cell degeneration during the two maturation divisions.The mitotic and meiotic divisions and associated processes by which spermatogonia are transformed into spermatids and by spermiogenesis into spermatozoa occur in an organized manner in mammals. Several germ cell generations develop simultaneously, and this leads to fixed cellular associations in the sexually mature male. 14s a result, at any given point of seminiferous epithelium a series of cellular associations or stages follow one another with passage of time. A complete series of stages up to the reappearance of the first one at a given point constitute the cycle of the seminiferous epithelium '50; Leblond and Clermont, '52; Ortavant, Courot and :Hochereau, '69).Despite intensive use of the dog for research, including studies pertaining to :reproduction, there seems to be little detailed quantitative information on spermatogenesis in this species. Bascom and Osterud ('25) studied the size and proportion of the seminiferous tubules. Malone ('18) and Minouchi ('28) described nuclear cytology and chromosomal behavior ANAT. REC., 173: 341-352.

Alzheimer's disease (AD), the most common form of dementia, is a chronic, progressive neurodegenerative disease that manifests clinically as a slow global decline in cognitive function, including deterioration of memory, reasoning, abstraction, language and emotional stability, culminating in a patient with end-stage disease, totally dependent on custodial care. With a global ageing population, it is predicted that there will be a marked increase in the number of people diagnosed with AD in the coming decades, making this a significant challenge to socio-economic policy and aged care. Global estimates put a direct cost for treating and caring for people with dementia at $US604 billion, an estimate that is expected to increase markedly. According to recent global statistics, there are 35·6 million dementia sufferers, the number of which is predicted to double every 20 years, unless strategies are implemented to reduce this burden. Currently, there is no cure for AD; while current therapies may temporarily ameliorate symptoms, death usually occurs approximately 8 years after diagnosis. A greater understanding of AD pathophysiology is paramount, and attention is now being directed to the discovery of biomarkers that may not only facilitate pre-symptomatic diagnosis, but also provide an insight into aberrant biochemical pathways that may reveal potential therapeutic targets, including nutritional ones. AD pathogenesis develops over many years before clinical symptoms appear, providing the opportunity to develop therapy that could slow or stop disease progression well before any clinical manifestation develops.

Repeated superovulation and in-vivo collection of ova were carried out with thirty does divided into three groups of ten does each. One group received fsh\p=m-\lh, a second group received pmsg\p=m-\hcg and the controls received only lh. Injections of fsh\p=m-\lh at three 16-week intervals followed by one 8-week interval resulted in 46\m=.\5,35\m=.\4,25\m=.\2 and 18\m=.\0ovulation points/doe. This decrease with time was significant (P<0\m=.\05).Corresponding values for the pmsg\p=m-\hcg group which, however, received fsh\p=m-\lhfor the final superovulation were 13\m=.\6,5\m=.\7, 6\m=.\2and 20\m=.\3.The lh controls averaged 7\m=.\8,7\m=.\0,5\m=.\1 and 5\m=.\6ovulation points. Overall treatment differences were highly significant (P<0\m=.\005). From the 1920 ovulation points 1593 ova (83%) were recovered, of which 83\m=.\1% were cleaved. Young born from unrecovered ova accounted for 3\m=.\1%.Control kindlings by the same does at regular periods resulted in normal litter size but in fewer does kindling as the experiment progressed. Results of two bio-assays for antihormones suggested that this decrease was due to hormonal refractoriness which was most pronounced in the pmsg\p=m-\hcg group.

The ability of transferred ova to develop normally during the pre-natal and early post-natal periods has received only limited attention in the rabbit (Venge, 1950(Venge, , 1953. This investigation was undertaken: (1) to determine the pre-natal survival of transferred ova obtained from superovulated and normally ovulated does, and (2) to compare early post-natal development of young rabbits resulting from transferred and non-transferred ova. Superovulated ova obtained from ten does receiving follicle stimulating hormone and luteinizing hormone (fsh\p=m-\lhtreatment) and from ten does receiving pregnant mares serum and human chorionic gonadotrophin (pmsg\p=m-\ hcg treatment) were compared with ova recovered from ten does receiving only lh (Maurer, Hunt & Foote, 1968). Ova were collected in vivo from anaesthetized does 26 to 32 hr after the injection of lh or hcg and transferred to the recipients within 30 min of collection. The recipients consisted of thirty-two nulliparous does averaging 25 weeks of age and thirty-four parous does averaging 73 weeks of age. All animals were kept in individual cages at 21\s=deg\C with 12 hr of artificial light daily.The recipient and donor does were injected simultaneously with the same ovulating hormones (2\m=.\5mg lh, or 50 i.u. hcg). Each recipient doe was anaesthetized and a flank incision was made. The ova in a small volume of serum were deposited 2 to 3 cm into the fimbriated end of the oviduct. Normally five ova were transferred to each oviduct of the recipient. Where no more than five ova were available, the ova were deposited in one oviduct and never less than two ova were transferred.Shortly after the recipient does kindled, the young were counted, earnotched for identification, sexed and weighed. Each recipient doe had her litter size adjusted to six young. The six young consisted of three young from the litter which the recipient doe delivered (young from transferred ova) and three foster young from does bearing their own young following injection of the same ovulating hormone given to the donor of the transferred ova. The fostered young were readily accepted by the foster mothers. Each doe was allowed to raise the young for 2 or 4 weeks, depending upon the available space. Forty-one of the fifty-six litters resulting from transferred ova were * Present address :

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