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At least 451 records · Page 25Linked to original sources
PubMed1983

Organogenesis of the pituitary, adrenal, and lung at birth in the wallaby, Macropus rufogriseus.

The ultrastructure of the pituitary, the adrenal, and the lung was examined in the newborn wallaby, Macropus rufogriseus. Tissue from six wallaby neonates (less than 8 hr of age), two near-term fetuses (26 days after removal of suckling pouch young [RPY]), and a two-day-old pouch young was examined; and tissue levels of cortisol in the adrenal glands of five neonates and a near-term fetus (26 days) were measured by radioimmunoassay. At birth the adenohypophysis comprised the bulk of the pituitary gland. The pars distalis was well vascularized and many cells contained electron-dense, membrane-bound granules. The adrenal glands lacked specific zones but comprised two distinct populations of cells. The cytoplasm of one cell type contained electron-dense, membrane-bound granules, similar to those observed inside catecholamine-secreting cells of the adrenal medulla; the other cell type possessed large amounts of smooth endoplasmic reticulum and mitochondria with tubulo-vesicular cristae. These features are characteristic of cells which are actively synthesizing steroid hormones. The concentration of cortisol was 0.58 ng/adrenal in the wallaby at birth. The fetal lungs near term were at the glandular stage of development, and epithelial differentiation of type I and type II pneumocytes was imminent although attenuation was not evident. The canalicular neonatal lung did not contain true alveoli, but type II pneumocytes contained osmiophilic lamellar inclusions of surfactant. The fetal pituitary and adrenal are functional at birth and are thus capable of initiating parturition and of influencing lung maturation in the fetus.

Adrenal Glands↗
PubMed1987

Brain sizes, surfaces, and neuronal sizes of the cortex cerebri: a stereological investigation of man and his variability and a comparison with some mammals (primates, whales, marsupials, insectivores, and one elephant).

This study deals with the stereological estimation of macroscopic sizes of brain and cortex, i.e., volume, surface, and folding, and of microscopic neuronal sizes, i.e., density, mean size, size distribution, and number of neurons. The results show that the degree of variability in man amounts to about 15%. A decrease in volume of the different gray structures can be observed in man after the age of 65 years. The surface, folding index, and length of convolution do not alter with aging. The comparison with mammals of various sizes allows the conclusion that there is a high correlation to brain size for nearly all macroscopic values. Man and elephant, however, have a cortical surface which is, in comparison with whales, relatively small. In contrast, whales have very small cortices compared with man. At the cytoarchitectonic level, the neuronal density has a correlation to brain size. Contrary to other mammals, the primates and man have a high fraction of small granular neurons, especially in layer 4. The assumption that the number of cortical neurons beneath a given surface area of cortex is the same in all mammals cannot be verified, especially in those with large brains. The allometric connection between brain size and parameters is not valid for all measurements (e.g., thickness of cortex, mean size of neurons, perikaryal size distribution, and glial density). Yet some other measurements are well correlated.

Animals↗
PubMed1994

Penoscrotal transposition: a case report and review.

We report on a boy born with complete penoscrotal transposition, normal scrotum, twisted penile shaft with hypoplastic penile urethra, meatal stenosis, normal bladder, and bilateral cystic dysplastic kidneys. The patient died of renal failure at 2.5 months. This is the 13th reported case of complete penoscrotal transposition with normal scrotum. The possible pathogenesis is discussed and the literature is reviewed.

Abnormalities, Multiple↗
PubMed1995

Limb joint surface areas and their ratios in Malagasy lemurs and other mammals.

Surface areas of humeral and femoral heads scale largely as a function of body size. However, differences in the relative sizes of these articular surfaces are correlated with differential joint mobility and force transmission through fore- and hindlimbs. They can therefore assist interpretation of the positional behavior of extinct species. In this paper, we document variation in ratios of humeral head surface area to femoral head surface area among extant primates and other mammals. We then examine a group of extinct primates: the subfossil lemurs of Madagascar. Many Malagasy lemurs, including some giant extinct species with very long forelimbs and short hindlimbs, have relatively small humeral heads and large femoral heads. We explore the adaptive implications of this pattern.

Animals↗
PubMed1995

Structural adaptations for gliding in mammals with implications for locomotor behavior in paromomyids.

The gliding abilities of paromomyid plesiadapiforms are evaluated through a functional analysis of long bone morphology in a comparative sample of modern gliders and related nongliders. Relationships between body mass, long bone lengths, and long bone midshaft cross-sectional areas are explored. Theory suggests that gliders should have long humeri and femora to improve aspect ratio, and that larger gliders should have relatively longer limb bones than smaller gliders to minimize drag and patagial loading at greater body masses. Comparisons between extant taxa support these predictions: gliders have relatively longer humeri and femora than those of nongliders, and glider long bone lengths scale with positive allometry, while the scaling of nonglider long bones does not differ from isometry. Preliminary analysis of distal to proximal limb segment proportions further suggests that bone lengthening is, to some extent, related to patagial attachment site, although humeri and femora are relatively long in all of the gliders, regardless of attachment site. The proportions of paromomyids relative to those of extant mammals do not support a gliding interpretation for these fossils.

Adaptation, Biological↗
PubMed2002

Bony orbital anatomy of the koala (Phascolarctos cinereus).

This is the first documented study of the anatomical details of the normal koala orbit. Baseline data are established which are necessary for understanding and treating ocular disease in the koala (Phascolarctos cinereus). The bony anatomy of the orbit of the koala was examined and described from animals that presented dead or had been euthanized for humane reasons. Dissections of the orbital cavity were performed under magnification, and descriptions of the orbital bones were from macerated skulls that had been boiled and cleaned. In general, the orbital bones of the koala, and their respective foramina, are consistent with those of other carnivorous polyprotodont and herbivorous diprotodont marsupials.

Animals↗
PubMed2002

Intraorbital anatomy of the koala (Phascolarctos cinereus).

This is the first documented study of the anatomical details of the contents of the normal koala orbit, excluding the bulbus oculi. Baseline data were established which are necessary for understanding and treating ocular disease in the koala (Phascolarctos cinereus). The anatomy of the orbital contents of the koala were examined and described from animals that presented dead or were euthanized for humane reasons. Dissections of the orbital cavity were performed under magnification. Polymethyl methacrylate (PMMA) casts of the nasolacrimal system and the vascular supply of the orbit were also made in order to study these systems. The superficial lymphatic drainage of the conjunctival tissues was studied by subcutaneous injection of Evan's Blue into the palpebral conjunctiva of a freshly deceased animal, and by Microfil casts of the efferent lymphatics. In general, the orbital contents of the koala are consistent with those of other carnivorous polyprotodont and herbivorous diprotodont marsupials.

Animals↗
PubMed1976

The growth of the oocyte and follicle in the ovaries of monotremes and marsupials.

Oocyte growth in relation to follicular growth in marsupials conforms to the uniform biphasic pattern characteristic of eutherian mammals. However, the oocyte of the marsupial is larger and completes growth in a correspondingly larger follicle. At the completion of oocyte growth the follicle, like that of eutherians, shows no appreciable accumulation of follicular fluid. The ratio of oocyte/follicular diameter in marsupials at this stage is 0.59, a value close to that of 0.55 for eutherian mammals. The oocyte nucleus of the marsupial is also significantly larger than that of the eutherian, but the oocyte nucleolus is approximately the same diameter. By contrast, the growth of the oocyte in relation to the follicle in monotremes in linear throughout the whole period of follicular growth. However, like eutherians and marsupials oocyte nuclear and oocyte nucleolar growth are arrested in the early stages of follicular growth. The diameters of the oocyte nucleus and nucleolus at the completion of growth are approximately twice those found in marsupials. It is concluded that the growth patterns of the oocyte nucleus and nucleolus are common to all mammals but that the biphasic pattern of oocyte and follicular growth which is characteristic of eutherian and marsupial ovaries is not found in the monotremes.

Animals↗
PubMed1982

Aspects of renal vascular organization and early vascular tubular relations of the marsupial Isoodon obesulus.

Renal vascular tubular relationships were studied in the marsupial Isoodon obesulus (the common brown bandicoot). The microcirculation was filled with colored silicone rubber by intra-arterial injection of the intact kidney. Nephrons were defined by the injection of silicone rubber of a contrasting color into the space of Bowman's capsule in thick, cleared slices of renal tissue. The details of the vascular tubular relationship in this marsupial are strikingly similar to relationships previously described in true mammalian kidneys. An unusual feature is a wide (600mu) glomerulus-free zone at the outer cortex. This zone contains the proximal and distal convoluted tubules of the most superficial cortical nephrons and is perfused by efferent vessels from glomeruli in superficial strata of the cortex.

Animals↗
PubMed1982

Ultrastructural evidence for steroid-hormone production in the adrenal of the marsupial Isoodon macrourus, at birth.

To determine whether the adrenal gland of the bandicoot is actively producing steroid hormones at birth, the cellular structure was examined by electron microscopy, and the concentration of cortisol in the gland was determined by radioimmunoassay. Two distinct cell populations were seen in the adrenal gland. One group of cells possessed dark staining granules, normally observed in catecholamine-secreting cells, and the second group contained large amounts of smooth endoplasmic reticulum and mitochondria with tubulo-vesicular cristae. Both features are characteristic of steroid-secreting cells. A concentration of 0.094 ng of cortisol per adrenal was determined by pooling glands from nine individual newborn bandicoots. This evidence of cortisol secretion from the bandicoot adrenal at birth indicates that, as in many eutherians, the marsupial adrenal may play an important role in determining the length of gestation.

Adrenal Glands↗