Marsupial fertilization: some further ultrastructural observations on the dasyurid Sminthopsis crassicaudata.

Various morphological aspects of in vivo egg maturation and sperm-egg interaction were investigated in the Australian marsupial Sminthopsis crassicaudata with the transmission and scanning electron microscopes. Cortical granules invariably occurred in primary oocytes, with the number increasing after resumption of the first meiotic division. They generally occurred close to the oolemma, including the region near the oocyte nucleus. After mating, spermatozoa with intact acrosomes, which had a homogeneous electron-dense matrix, were found on the outer zona surface, but loss of acrosomal contents had occurred by the time of zona penetration. Sperm incorporation into the egg took place at the metaphase II stage of meiosis, and, at this time, cortical granules disappeared from the egg cortex. Sperm heads with condensed chromatin in the egg cytoplasm had an electron-dense layer of subacrosomal material over part of the dorsal nuclear surface, but no membranes were present around these incorporated spermatozoa. Sperm chromatin decondensation resulted in an elevation of egg cytoplasm, and the cell membrane over this area lacked microvilli. The pronuclear envelope was not laid down until after chromatin decondensation had occurred. By this time the fertilized egg had reached the uterus, and a smooth, electron-dense, shell membrane had been deposited. These observations, together with our previous findings, indicate that some of the processes of sperm-egg interaction are similar to those in eutherian mammals, whereas others appear highly divergent.     

Sexual dimorphism in the baboon facial skeleton

Baboons exhibit marked sexual dimorphism in many aspects of their morphology. Dimorphism is especially pronounced in the face. We use finite-element analysis to investigate the ontogeny of sexual dimorphism in a cross-sectional sample of baboon (Papio sp.) faces. This method provides detailed quantitative information about size and shape changes at anatomical landmarks in the face during growth. Allometric results suggest that sexual dimorphism in facial size and shape is produced by ontogenetic scaling: males and females share a common ontogenetic trajectory. Analyses of growth in time, which complement allometric analyses, show that female growth slows much earlier than male growth, accounting for the differences between sexes. Local size and local shape follow similar patterns of growth, but changes in these variables are slower in females. Local and global facial size are much more dimorphic than local and global facial shape.     

Plasma B-cell tropin (ACTH22-39) concentration in lean and obese (ob/ob) mice and lean and obese (fa/fa) Zucker rats

A method has been developed for the measurement of plasma concentrations of Beta-cell tropin (BCT), which is a potent insulinotropic and lipogenic peptide secreted by the pituitary. The method was employed to compare plasma Beta-cell tropin concentrations between lean and genetically obese (ob/ob) mice and between lean and genetically obese (fa/fa) Zucker rats. The plasma concentration in lean mice was 0.17 +/- 0.02 (5)nmole/l (mean +/- SEM, n = 5), while that in obese (ob/ob) mice was significantly higher, being 2.88 +/- 1.13 (5)nmole/l. The plasma BCT concentration in Zucker rats was 0.14 +/- 0.02 (15)nmole/l, while that in obese Zucker (fa/fa) rats was significantly higher, being 1.69 +/- 0.72 (16)nmole/l. These results explain previously observed differences in the Beta-cell tropin-like biological activity in plasma from lean and obese animals, and support the hypothesis that the peptide has a role in the development of hyperinsulinaemia and obesity.     

Management of selected patients with hyperprolactinaemia by partial hypophysectomy.

Results are reported in 35 patients with prolactinomas who underwent pituitary surgery within the past five years. After surgery prolactin concentrations became normal in 26 patients and symptoms were alleviated, and nine normal pregnancies were achieved in seven women, including all those who had complained of infertility. Normal prolactin concentrations were restored in 16 of 17 patients with tumours 5-19 mm in diameter but in only six of 11 with tumours less than or equal to 4 mm and four of seven with tumours greater than or equal to 20 mm. Normal prolactin concentrations were restored in all those with preoperative concentrations below 1000 mU/l but in none of those with concentrations above 10 000 mU/l. Although not all of the patients were followed up for five years, hyperprolactinaemia did not recur in any patient whose prolactin concentration had returned to normal six weeks after surgery. This included 16 patients with macroprolactinomas (greater than 10 mm in diameter), who were followed up for from two to five years. These data contrast strikingly with those reported by others at similar stages of follow up and show clearly that partial hypophysectomy offers an acceptable alternative treatment for selected patients with prolactinomas.     

The population dynamics, reproductive strategy and life history tactics of Musculium lacusfre (Bivalvia: Pisidiidae) in Hong Kong

Hitherto uninvestigated in Hong Kong are the population dynamics, reproductive strategies and life history tactics of the Pisidiidae of which three species are known to occur locally. This study is of Musculium lacustre inhabiting a drainage ditch of the Lam Tsuen River in the New Territories of Hong Kong and extended over 15 months during 1983–84.
In Hong Kong, M. lacustre is a protandric, simultaneous hermaphrodite that matures at a length of 2 mm; the majority of each generation is, however, not mature until a length of between 4–6 mm is attained. Fertilized eggs are brooded in the inner demibranchs until they reach a length of 1.5 mm when they are released as post-foetal larvae. Musculium lacustre is univoltine. Reproduction occurs twice a year but, since M. lacustve is semelparous, the population contains, at any one time, two overstepping generations. Thus, a spring generation is recruited and grows rapidly to generate a second, smaller, autumn generation. This in turn grows rapidly and matures to produce the spring generation of the succeeding year. Adult mortality occurs in late summer and winter. A few of the late-born spring generation may overwinter to contribute to the spring generation of the succeeding year. This is not so with the autumn generation.
Such sexual and life history tactics can be related to the climate and hydrology of Hong Kong and its freshwater habitats. Reproduction takes place in spring and autumn when temperatures are moderate. Mortality is high in summer and winter when the habitat is either, respectively, hot and flushed out by summer rains or cold and dry. As M. larustre is able to overwinter but not aestivate at these latitudes (22° N), it is postulated that this holarctic species is approaching the southern limit of its asiatic range. Musculium larustre is compared with the other bivalves inhabiting fresh and brackish-water habitats in southern China.     

Fiber‐based fluorescence lifetime imaging of recellularization processes on vascular tissue constructs

New techniques able to monitor the maturation of tissue engineered constructs over time are needed for a more efficient control of developmental parameters. Here, a label‐free fluorescence lifetime imaging (FLIm) approach implemented through a single fiber‐optic interface is reported for nondestructive in situ assessment of vascular biomaterials. Recellularization processes of antigen removed bovine pericardium scaffolds with endothelial cells and mesenchymal stem cells were evaluated on the serous and the fibrous sides of the scaffolds, 2 distinct extracellular matrix niches, over the course of a 7 day culture period. Results indicated that fluorescence lifetime successfully report cell presence resolved from extracellular matrix fluorescence. The recellularization process was more rapid on the serous side than on the fibrous side for both cell types, and endothelial cells expanded faster than mesenchymal stem cells on antigen‐removed bovine pericardium. Fiber‐based FLIm has the potential to become a nondestructive tool for the assessment of tissue maturation by allowing in situ imaging of intraluminal vascular biomaterials.