Early differentiation of the gonads in the gray short-tailed opossum (Monodelphis domestica).

The time course for gonadal development in gray short-tailed opossums was examined in this study. It was found that the gonads were not differentiated on day 1 of postnatal life (the day of birth). While testis development was seen by postnatal day 4, ovarian development did not occur until after postnatal day 16. In both sexes, primordial germ cells were not identified until after postnatal day 1. These findings are discussed with respect to gonadal differentiation in other marsupial species.

Inhibition of testicular development and feminization of the male genitalia by neonatal estrogen treatment in a marsupial.

Differentiation of the mammalian gonad is thought to be constitutive, occurring independently of and not significantly altered by gonadal hormones. In this study, estradiol benzoate (EB) and testosterone propionate (TP) were administered to newborn gray opossums (Monodelphis domestica) during the first week after birth. It was found that males and females treated with TP and females treated with EB developed normally. In males treated with EB on both Day 1 and Day 3 of postnatal life, gonads did not differentiate and internal and external genitalia were feminine. These findings are discussed with respect to current theories of mammalian sexual differentiation.

Light and electron microscopic studies of an antibiotic bonded vascular graft.

Polytetrafluoroethylene grafts were bonded to oxacillin with the cationic surfactant, benzalkonium chloride. Grafts were placed in the canine aorta and harvested six and twelve weeks after implantation. Light and scanning and transmission electron microscopy were performed in all specimens. No histological differences could be demonstrated between control and antibiotic bonded grafts. Significant antibacterial activity was demonstrated at the time of graft implantation. However, none remained six and twelve weeks later.

Noncovalent bonding of penicillin and cefazolin to dacron.

Dacron grafts treated with the surfactant, benzalkonium chloride or TDMAC bind significant quantities of penicillin-14C or cefazolin-14C. The treated grafts showed strong antibacterial activity which indicated that bound radioactivity corresponds to the reversible adsorption of biologically active molecules. Bound penicillin-14C or cefazolin-14C slowly dissociates when the grafts are placed in a surgically prepared muscle pouch in the rat. This slow release of antibiotic produces therapeutic levels of antibiotic in the adjacent tissue. Binding can also be achieved by in situ irrigation of surfactant treated grafts with antibiotic or by injection of the antibiotic.

Alterations of renal cortex and medullary glycosaminoglycans in aging dog kidney.

Age-related changes in renal function have been attributed to alterations in the chemical composition of the kidney tissues. Hence, the glycosaminoglycan composition of the renal cortex and medulla at varying age intervals was investigated. Glycosaminoglycans were isolated from the tissues by means of digestion with collagenase and pronase and purified by ethanol precipitation. Subsequent separation of various polyanions was accomplished by ion exchange chromatography on a Dowex 1-X2 column, using sodium chloride buffers of increasing ionic strengths. The glycosaminoglycans in each fraction were identified and quantitated by digestion with specific enzymes, including hyaluronidase, chondroitinase AC and ABC. The enzyme resistant material was separated and further digested with nitrous acid to quantitate the proportion of heparon sulfate. The results indicate that the glycosaminoglycan content of the renal medulla was much higher than the cortex at all the age intervals studied, and age-induced reduction was mainly cortical. There was a significant reduction in the heparan sulfate content of the cortex in aging. Interestingly, the major glycosaminoglycan content of the medulla was hyaluronic acid, which showed a sharp increase during aging, whereas heparan sulfate declined. Chondroitin sulfate was not altered due to age in either tissue. The molecular weight of hyaluronic acid was determined by column chromatography. Results indicate that the size of hyaluronate in the cortex was small and did not vary with age. In the medulla of the younger age group, a considerable amount of large size hyaluronate was observed. As age increased, the size decreased. The results strongly suggest that alteration in the renal glycosaminoglycans may be partly responsible for the age related protinuria and ionic imbalance.

Prevention of vascular prosthetic infection by a benzalkonium-oxacillin bonded polytetrafluoroethylene graft.

Polytetrafluoroethylene grafts were bonded to oxacillin using benzalkonium chloride. Grafts were then placed in the infrarenal aorta of dogs and contaminated with Staphylococcus aureus. At death or sacrifice, bonded grafts were significantly superior to that for controls in the absence of bacteria histologically, negative cultures, patency and survival. Histologic evaluation of grafts by light and electron microscopy demonstrated normal healing and neointima formation of bonded grafts. The future role of antibiotic bonding in the prevention of vascular prosthetic infections is discussed.

Early ultrastructural changes of developing oocytes in the dog.

Many aspects of the developmental stages of the oocytes of the dog resemble those of other mammalian species. The oocytes of the dog, however, contains large amounts of lipid yolk material. A study of the ultrastructural morphology of early growth and maturation of dog oocytes was undertaken to clarify the nature and appearance of this yolk material. The lipid yolk first appears in early primary oocytes as aggregated dense bodies that gradually fill the ooplasm as the oocyte matures. The site of the yolk's initial appearance is consistently related to a single centriole and often to the lamellae of smooth endoplasmic reticulum that surrounds groups of forming lipid yolk bodies. Dense cortical granule-like vesicles are found to lie deep within the maturing oocyte and often are enclosed within the lamellar yolk space. Granules within this space undergo changes in size, matrix configuration, and vacuolization. These changes suggest a mechanism whereby material is added to the lipid yolk bodies. Light microscope histochemistry for lipid and polysaccharide material is described.

The distribution and fate of 3H-glucose and 3H-galactose in oocytes of Oryzias latipes: Formation of the cortical alevoli.

The distribution and fate of 3H-glucose and 3H-galactose and the formation of the cortical alveoli in the oocytes of the teleost Oryzias latipes were investigated. Fish were given intraperitoneal injections of either labeled hexose, and the relative amounts of each were measured in autoradiographs prepared for light and electron microscopy. There were significant differences in the amounts of each hexose in the oocytes at all time intervals studied. During the earlier time periods, the oocyte incorporates more 3H-glucose than 3H-galactose in both the cytoplasmic and cortical alveoli compartments; however, the overall rate of formation of the cortical alevoli appears to be similar for the two tracers. Electron microscopic autoradiographs reveal the participation of cytoplasmic elements, e.g., endoplasmic reticulum and Golgi apparatus, in the formation of the cortical alveoli. The chorion does not incorporate significant amounts of either tracer, while the yolk granules contain small but significant amounts.

Formation of the chorion (zona pellucida) in the teleost, Oryzias latipes. II. Polysaccharide cytochemistry of early oogenesis.

It has been proposed that the mechanism of formation of the chorion of Oryzias latipes involves the transfer of precursor material from the Golgi bodies of the oocyte to the chorion by means of a population of dense cored vesicles. Thin sectioned ovarian material was investigated by means of several techniques available for the resolution of periodate reactive material at the ultrastructural level. The techniques employed were modifications of the thiocarbohydrazide, thiosemicarbazide, alkaline bismuth subnitrate and silver methenamine reactions. These all demonstrated a positive reaction in the material of the chorion and that of the dense cored vesicles. This finding is in accord with the hypothesis that the dense cored vesicles are transporting material from the Golgi to the growing chorion.