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Biomedical subjects

D W Hamilton

Publications and source records attributed to D W Hamilton.

At least 73 records · Page 4Linked to original sources
PubMed1976

Testosterone metabolism in male rat epiphysis.

Using radioactive substrate, thin-layer chromatography and recrystallization methods as well as differential centrifugation, gel filtration and electrophoresis, testosterone metabolism was investigated in male rat epiphyseal growth plate. 5alpha-androstane 3alpha-17beta-diol was found to be a major metabolite in vitro; lesser amounts of androstenedione and androstanedione, and a very small amount of 5alpha-dihydrotestosterone were also identified. Radioactivity was recovered in epiphyseal subcellular fractions 30 minutes following in vivo administration of tritiated 5alpha-dihydrotestosterone; within 2 hours radioactivity had fallen to essentially background level in all fractions but the cytosol. A testosterone binding protein could not be identified within epiphyseal cytosol.

Androstane-3,17-diol↗
PubMed1976

Morphological changes in the midpiece of wooly opossum spermatozoa during epididymal transit.

Several ultrastructural changes were found to occur in the midpiece region of wooly opossum spermatozoa during epididymal maturation. The changes include alterations in mitochondrial morphology, development of structural specializations of the plasma membrane, and acquisition of a prominent extracellular coating. The lamellar membrane network which is wound about the periphery of the mitochondria becomes more densely packed during sperm development and the reticular network of membranes noted in the center of the mitochondria of immature sperm disappears leaving a homogeneous electron dense central zone. During epididymal transit the plasma membrane over the sperm midpiece region shows extensive structural modification. In cross sections of paired spermatozoa the plasma membrane of the midpiece regions shows a very regular, repetitive scalloping. In longitudinal sections the scalloping is observed as continuous parallel ridges which extend slightly obliquely to the flagellar long axis. Each ridge appears to be greater in density than the interridge areas. In the epididymis a prominent extracellular coating of dense material is deposited over the midpiece surface; this material is similar in appearance to dense material seen in restricted areas of the epididymal lumen. At the proximal and distal ends of the midpiece the plasma membrane comes into intimate contact with underlying structural specializations and it is suggested that these zones of fusion may serve to preserve regional differences in membrane composition.

Animals↗
PubMed1976

Isolation and characterization of the perforatorium of rat spermatozoa.

The perforatorium of rat spermatozoa was isolated and its protein composition determined. SDS-polyacrylamide gel electrophoresis showed that the organelle is composed of a single polypeptide component with a molecular weight of 13,000. The perforatorium becomes more resistant to solubilization during epididymal transit due to an apparent increase in disulphide bond content. Amino acid analysis of the perforatorium polypeptide revealed a content of 6-5% cysteine.

Amino Acids↗
PubMed1975

Phagocytosis of spermatozoa by the epithelial cells of the ductuli efferentes after epididymal obstruction in the rat.

The effects of ligation of an isolated loop of the ductus epididymidis in the region of the caput were compared with those of the exfoliative lesion of the epididymis that follows administration of alpha-chlorhydrin to rats. Electron micrographs of the ductuli efferentes in both cases revealed early phagocytosis of apparently normal spermatozoa by the epithelial cells, followed at later intervals by invasion of macrophages and intraluminal phagocytosis. It is concluded that epithelial spermiophagy is a consequence of obstruction, whether mechanically or chemically induced.

Animals↗
PubMed1975

Origin and histogenesis of equine endometrial cups.

Biochemical and morphological studies were carried out to determine the origin and histogenesis of endometrial cups in mares. A wide range of fetal and maternal tissues were cultured in vitro and their ability to secrete gonadotrophin (PMSG) was monitored. High levels of PMSG were produced in culture only by cells from the restricted area of the equine trophoblast known as the chorionic girdle which is an annular band of highly specialized cells at the junction of the allantois and the regressing yolk sac. The morphological appearance of girdle cells after cultivation in vitro and after allogeneic grafting to the uterus or testis was identical to that of endometrial cup cells. Firm attachment between the cells of the chorionic girdle and the adjacent endometrium occurs on Day 36. Girdle cells then rapidly invade and phagocytose the endometrial epithelium, and migrate into the endometrial glands and the uterine stroma where they differentiate into large, sessile endometrial cup cells.

Animals↗