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Biomedical subjects

W G Breed

Publications and source records attributed to W G Breed.

At least 73 records · Page 4Linked to original sources
PubMed1989

Light microscopical structure of the excurrent ducts and distribution of spermatozoa in the Australian rodents Pseudomys australis and Notomys alexis.

The light microscopical structure of the male excurrent ducts and the distribution of spermatozoa were examined in two species of Australian rodents, the plains rat, Pseudomys australis, and the hopping mouse, Notomys alexis. In plains rats the microstructure of the ductus epididymidis and ductus deferens was similar to that of the common laboratory rodents, with the majority of the spermatozoa being found in the cauda epididymides. By contrast, in the hopping mouse, the structure of the cauda epididymidis differed significantly as the height of the epithelium and stereocilia did not decrease from the distal caput to the cauda region, and luminal diameter did not increase markedly along its length. In addition, few spermatozoa were stored in the cauda region of the tract, and as many as 60% were located in the ductus deferens, the distal portion of which displayed a highly infolded epithelium and underlying lamina propria. These differences in histological structure of the hopping mouse excurrent ducts presumably reflect divergence in function of the various regions of the tract. Although the functional implications of the present findings remain to be determined, this study demonstrates the considerable plasticity in the male excurrent ducts amongst the hydromyine rodents of Australia.

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PubMed1988

Morphological observations on sperm-egg interactions during in vivo fertilization in the dasyurid marsupial Sminthopsis crassicaudata.

The aim of the present study was to determine the morphological changes that take place in the male and female gametes during in vivo fertilization in the Australian marsupial, the fat-tailed dunnart, Sminthopsis crassicaudata. Plastic sections were cut of sperm and eggs recovered from the oviducts of recently mated individuals, and light microscopy of thick, and transmission EM of thin, sections was carried out. It was found that, before penetration of the zona, the spermatozoon came to lie along the outer surface with its rostral tip forming a depression in the zona substance. During penetration, zona material was packed tightly around the spermatozoon, and no large hole was formed. A spermatozoon within the perivitelline space had made contact with the oolemma by way of its apical tip. In a spermatozoon partly incorporated into the ooplasm, fusion appeared to have taken place between its plasma membrane and that of the oolemma. Mucoid coat material became deposited outside the zona at this time; its existence and/or the release of cortical granule content probably prevented polyspermy. Once inside the egg cytoplasm, the sperm head sometimes travelled a considerable distance before chromatin decondensation occurred. In addition, it appeared to rotate somewhat on its axis at this time. Finally, some membranous structures were found around two condensed sperm heads in the ooplasm, which may have been part of the pronuclear envelope. Thus this study on in vivo fertilization in the dunnart documents, for the first time, some aspects of fertilization in an Australian marsupial as seen with the transmission electron microscope; it indicates a few differences from those previously found for the American opossum.

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PubMed1988

Sperm head structure of a murid rodent from southern Africa: the red veld rat Aethomys chrysophilus.

The morphology of spermatozoa from the red veld rat, Aethomys chrysophilus, of Southern Africa is described; two very different types were found, which came from animals from two separate, as-yet-undescribed, species. In individuals from South Africa the sperm head had a somewhat disc-shaped nucleus and a large acrosome with a huge apical segment that, during epididymal transit, changed in form from initially projecting anteriorly to a highly complex structure that was flexed caudad and lay alongside part of the rest of the sperm head. In addition, the chromatin generally appeared to be not fully condensed. Spermatozoa from animals collected in Malawi were very different in morphology and had a head with a typical apical hook, a perforatorium, fully condensed chromatin, and a 4-micron-long ventral spur. Its sperm tail was also significantly longer. The time of divergence of these two groups of animals from a common ancestor is not known, but the present results show that a considerable morphological change in the sperm nucleus, acrosome, and subacrosomal space can evolve even between two, presumably closely related, species.

Acrosome↗
PubMed1988

Ultrastructural features of the ventral prostate epithelial cells in the Australian plains rat, Pseudomys australis.

The fine structure of epithelial cells of the small ventral prostate of Pseudomys australis males was studied. The cells were sometimes binucleated, exhibited relatively little granular endoplasmic reticulum, generally few secretory granules (probably reflecting a low proteinaceous secretory activity), but had abundant agranular endoplasmic reticulum (AER), similar to that in steroidogenic cells. Some of the mitochondria also showed tubular cristae. Furthermore, most cells had some irregular dense bodies in the cytoplasm which may have developed, by a gradual transformation process, from the membranes of AER, mitochondria and other organelles; they could be the product of degenerative changes in these organelles. These findings indicate a significant difference in the structure of these cells from those present in the ventral prostate of the hopping mouse, Notomys alexis. It is speculated that this gland secretes relatively little protein but perhaps more lipid or cholesterol-derived substance.

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PubMed1988

Variation in intramembranous particle distribution in the cell membrane of the sperm head of the plains rat and western chestnut mouse (Pseudomys Spp.).

Freeze-fracture studies were used to investigate the size, density, and distribution of intramembranous particles (IMPs) in the plasma membrane of the sperm head of two species of Australian hydromyine rodents Pseudomys australis and P. nanus both of which are characterized by having, in addition to a dorsal hook, two long ventral hooks that extend from the antero-concave surface. It was found that on the P face of the plasma membrane over the dorsal hook of caput and upper corpus spermatozoa a paracrystalline arrangement of small, approximately 7nm, IMPs were interspersed with a few large, 9 to 12 nm, IMPs. In the cauda epididymidis the small particles became randomly arranged. On the P face of the plasma membrane over the ventral hooks of caput sperm, and in the postacrosomal region, a much higher density of large, 9 to 12 nm, IMPs was present. In the ventral hooks of cauda sperm the IMPs were increased even further and were arranged in short, variably orientated, ridges; this did not appear to be evident in the plasma membrane over the postacrosomal region. It suggests a change in distribution of the IMPs in the cell membrane over the ventral hooks, but not over the postacrosomal region, during epididymal transit of the spermatozoa. This may indicate that the plasma membrane of these two regions of the head of ejaculated spermatozoa has intrinsic differences in its structure and function.

Animals↗
PubMed1987

Formation of the ventral hooks on the sperm head of the plains mouse, Pseudomys australis.

The sperm head of the plains mouse, Pseudomys australis, has three curved hooks projecting from its anterior margin. The two ventral hooks have previously been shown to consist largely of an extension of the subacrosomal material. To characterize further the structure and composition of the ventral hooks, we have examined their formation during spermiogenesis using transmission electron microscopy, silver staining, and actin localization with NBD-phallacidin. The ventral hooks develop as an extension of the perinuclear space and postacrosomal dense lamina on the anteroventral margin of the sperm head. Bundles of 6-nm-thick filaments appear in the core of each hook; these are probably actin filaments based on staining of the hooks with NBD-phallacidin. Just prior to spermiation, electron-dense material condenses in the core of the ventral hooks and concurrently in the perinuclear space in the remainder of the sperm head. The two ventral hooks thus appear to consist of a core of perinuclear material and actin filaments, which is enclosed by a continuation of the postacrosomal dense lamina.

Actins↗
PubMed1987

Cytological organization of the seminiferous epithelium in the Australian rodents Pseudomys australis and Notomys alexis.

Absolute and relative testis mass of two species of conilurine rodents, the plains rat (Pseudomys australis) and the hopping mouse (Notomys alexis), were markedly different. In plains rats the testis comprised approximately 3% of body mass while in hopping mice they rarely accounted for more than 0.2%. In both species, 8 cellular associations, or cycle stages, were recognized in the seminiferous epithelium. The relative frequencies, and hence durations, of Stages I to VIII were 5.1, 7.0, 12.5, 10.5, 5.4, 25.9, 4.4 and 29.0% of one cycle for plains rats (N = 14), and 20.4, 10.9, 9.6, 8.1, 5.1, 20.4, 14.7 and 10.8% for laboratory-bred hopping mice (N = 35). Generally, the relative durations of the cycle stages were very similar between plains rat individuals, but were variable between hopping mice. Also, organization of the seminiferous epithelium was less rigid in hopping mouse testes, and several anomalies were observed. These included: the occurrence of 2-4 cellular associations in about 20% (range 11.3-33.9%) of tubular cross-sections, deviations in cellular composition in certain cycle stages from that usually observed, and an increased incidence of degenerating cells, together with the presence of multinucleated "giant' cells, within the seminiferous epithelium.

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PubMed1985

Ultrastructure of the epithelial cells of the ventral prostate from the hopping mouse Notomys alexis.

The large ventral prostate of the hopping mouse has abundant secretory units whose epithelial cells vary in height and which often have nuclei in the apical region of the cell. TEM observations indicated two epithelial cell types in which some unusual features occurred. Type A cells had granular endoplasmetic reticulum (GER) whose membranes often formed intracytoplasmic confronting cisternae. Type B cells had more fragmented and vesiculated GER with sparse ribosomes and less frequently also intracytoplasmic confronting confronting cisternae. In the latter cells, two types of granules were found, one of which was derived from the Golgi and the other possibly directly from the GER. Type A cells only had one type of granule present. A highly convoluted membrane was also found at the basal region in many of the cells. The significance of these unusual ultrastructural features has yet to be ascertained.

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PubMed1985

Morphological variation in the female reproductive tract of Australian rodents in the genera Pseudomys and Notomys.

Morphological studies of the vagina and cervix from females of several species of Pseudomys (pseudo-mice) and Notomys (hopping-mice) have shown marked interspecific differences. In females of all four species of Pseudomys and in N. cervinus there was a relatively thin walled, dorsoventrally flattened, vagina with a large lumen, longitudinal epithelial folds, and conspicuous fornices. By contrast, in females of N. alexis and N. mitchelli the vagina had a much smaller lumen, few or no folds, minute fornices, but a well developed muscle coat. The cervix of the Pseudomys females was a conspicuous fibrous structure, rich in collagen, with two canals throughout its length. In N. cervinus females it was smaller and the two canals, although separated by a median septum for much of their lengths, joined just before the external os. In N. alexis and N. mitchelli females the cervix was much less extensive, its boundaries could not be discerned externally, and, histologically, it was more cellular and less fibrous. This variation in morphology of the female reproductive tract appears to complement that of the excurrent ducts, accessory sex glands and external genitalia of males of these species of Australian murid rodents.

Animals↗
PubMed1985

The Harderian gland, its secretory duct and porphyrin content in the Plains mouse (Pseudomys australis).

The Harderian gland of the Australian Plains mouse (Pseudomys australis) consists of tubules lined by a single layer of epithelial cells with a surrounding meshwork of myoepithelial cells. The epithelium contains three types of cell. Type I cells, characterised by their many large apical lipid vacuoles, are comparable with cells reported in other rodents. Secretion is exocytotic and, to a lesser extent, apocrine. Type II cells are highly distinctive with extremely large mitochondria arranged in stacks and whorls. Unusually for Harderian glands, these cells possess prominent conventional Golgi complexes and lysosomes. Cytoplasmic 'slashes', possible vacuole-precursors, are also present. Type III cells have few distinguishing features and may be resting cells. They are occasionally binucleate and mitotic figures occur. The gland contains stored porphyrins, chiefly protoporphyrin, in the form of solid intraluminal accretions. There is a marked sex difference, with females having higher levels of porphyrin than males. Among the components of the interstitial tissue are mast cells, plasma cells and porphyrin-containing macrophages. The secretory duct contains large quantities of cell debris, including nuclei, and is lined by columnar cells with single large apical vacuoles. The outer opening of the duct is lined by mucus-secreting cells and stratified squamous epithelium.

Animals↗
PubMed1984

Why so many mammalian spermatozoa--a clue from marsupials?

Mammals generally ejaculate many more spermatozoa than seem to be needed for fertilization. This apparent profligacy has not been explained, but observations made in marsupials may shed light on it. The Virginia opossum, Didelphis virginiana, inseminates only about three million spermatozoa, a very low number. As a corollary, relatively few (ca. 13 X 10(6] are stored in each cauda epididymidis. However, some 5% of the spermatozoa that the opossum ejaculates populate the oviduct about 12 h later when ovulation can be anticipated--a success rate in the female orders of magnitude greater than in eutherian mammals. It is not certain what determines the unusually efficient transport to and the high survival rate of spermatozoa in the oviduct of Didelphis, but two unusual features suggest themselves as possible contributors. Didelphis (and all other American marsupial) spermatozoa undergo a head-to-head pairing in the epididymis by the acrosomal face; this serves to isolate the acrosome of ejaculated spermatozoa from the female milieu until the pairs separate in the oviduct. Secondly, spermatozoa are housed in special crypts in the isthmus of the oviduct. Australian marsupials, which usually lack such features, store spermatozoa in the epididymis in numbers more close to those in comparably sized eutheriam mammals. Exceptions which store very low sperm numbers there can be seen in one Australian Family, the Dasyuridae . The spermatozoa of dasyurids are not paired, but the species examined possess distinctive sperm storage crypts in the oviducal isthmus similar to those in the opossum. The present findings suggest that where mechanisms exist that could protect the acrosome and, or, the whole spermatozoon in the female tract, a much lower level of sperm production can be maintained without compromising fertility. While the number ejaculated typically by any one species is probably determined ultimately by several interacting factors, it therefore seems likely that a most important one in this respect relates to conditions spermatozoa face in the female tract.

Animals↗
PubMed1983

Localization of actin in the sperm head of the plains mouse, Pseudomys australis.

Actin was localized in the sperm head of the plains mouse, Pseudomys australis, using NBD-phallacidin, a fluorescent-labeled phallotoxin. It was found to be present in the two ventral hooks in sperm from the testis, epididymis, and vas deferens. Faint fluorescence was observed in other regions of the sperm head, whereas autofluorescence occurred in the midpiece of the tail in some preparations. The material in the ventral hooks was also found to be birefringent, which is consistent with it showing preferential orientation.

Actins↗
PubMed1983

Variation in sperm morphology in the Australian rodent genus, Pseudomys (Muridae).

Sperm morphology among the various members of the genus Pseudomys showed great interspecific variation. In P. apodemoides, P. desertor, P. fumeus, P. gracilicaudatus, P. hermannsburgensis, P. higginsi and P. nanus the sperm head was bilaterally flattened and possessed three hooks, the length of which varied somewhat between species. The top hook contained nuclear, subacrosomal and acrosomal material, whereas the two lower ventral hooks displayed largely only an extension of the subacrosomal material. Four other species of Pseudomys had no ventral hooks in their sperm head. In P. novaehollandiae there was a single long top hook, whereas in P. pilligaensis it was almost nonexistent. Neither the sperm head of P. delicatulus, nor that of P. shortridgei possessed any hooks; the former became narrower towards the tip, whereas the latter was spatulate in shape. The acrosome covered about two thirds of the nucleus and varied considerably in shape between species. Insertion of the connecting piece of the tail occurred on the lower ventral side of the sperm head in all species with a long top hook but was nearly basal in P. delicatulus and midbasal in P. shortridgei. The ultrastructure of mid and principal pieces was similar among species, but the number of gyres of mitochondria ranged from about 64 to 100.

Animals↗
PubMed1982

Morphological variation in the testes and accessory sex organs of Australian rodents in the genera Pseudomys and Notomys.

The relative size and histology of the testes of sexually active adult Pseudomys and Notomys differed markedly between species. Average weight of testes (as % of body wt) ranged from about 3% in P. australis and P. nanus to about 0.15% in most Notomys. In the testes of most species, interstitial tissue was relatively sparse, but in P. apodemoides, P. delicatulus and P. hermannsburgensis it was abundant and consisted of a mass of lipid-rich epithelioid Leydig cells. Seminiferous tubule diameters were similar in all species, but epididymides ranged from about 500 mg in weight (about 1% body wt) in P. australis to about 20 mg (about 0.05% body wt) in most Notomys. Likewise numbers of spermatozoa in the paired cauda epididymidis ranged from about 500 x 10(6) in P. australis and P. nanus to about 2 x 10(6) in 3 of 4 Notomys species.

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PubMed1981

Sperm head morphology of the plains mouse Pseudomys australis.

Spermatozoa of plains mice were studied by transmission and scanning electron microscopy. The occurrence of a distinct dorsal hook and 2 ventral hooks joined at the base was confirmed. Acrosomal material covered the dorsal hook and appeared to constitute most of the 2 ventral hooks which contained nuclear material only at the base. Incubation in sodium dodecyl sulphate resulted in loss of all the material presumed to be acrosomal.

Animals↗
PubMed1981

Biochemistry of male accessory organs of conilurine rodents.

The plains mouse has large seminal vesicles, coagulating glands, and dorsal and ventral prostates, whereas in the hopping mouse the only large accessory sex gland is the ventral prostate. Fructose concentration was found to be high in the coagulating glands and dorsal prostate of the plains mouse, but low in all other glands of both species; low concentrations of glucose were found in all glands. Citric acid concentration was high in the dorsal prostate of the plains mouse and ventral prostate of the hopping mouse. Acid and alkaline phosphatase activities were low in all glands of both species. In castrated hopping mice, enlargement of vestigial glands could not be induced with high doses of exogenous testosterone, although there was increased secretory activity of the seminal vesicle epithelial cells.

Acid Phosphatase↗
PubMed1981

Histology of accessory sex organs and extragonadal sperm reserves in the male hopping mouse Notomys alexis.

In the hopping mouse, Notomys alexis, there are very small testes and relatively low numbers of spermatozoa in the extragonadal ducts. Large ventral prostates are present, but the seminal vesicles, coagulating glands, ampullaries, and dorsal prostates are all extremely small, although their histological structure and secretory activity is similar to that of the laboratory murids. Bulbourethrals are typical, but the preputials are very small and composed of sebaceous secretory units and an associated hair follicle. The possible functional significance of these findings is briefly discussed.

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