Hyperprolactinemia and estrogen-induced rhythms in LH and prolactin release in the ovariectomized rat

Short-term (9 days) hyperprolactinemia induced by pituitary grafts reduced basal plasma LH levels in ovariectomized rats whereas long-term (31 days) grafts increased basal LH levels. Although long-term grafts inhibited estradiol-induced prolactin surges, hyperprolactinemia had no effect on the LH surge. It is concluded that the estrogen-treated ovariectomized rat is not suitable for studying the effects of hyperprolactinemia on LH release.     

Juvenile hormone titre and regulation in the cockroach Diploptera punctata

Titres of juvenile hormone (JH) have been determined in both hemolymph and whole body extracts of female Diploptera punctata during the first gonotrophic cycle using a method employing gas chromatography/mass spectrometry for qualitative and quantitative analysis. JH III is the sole JH found in both adult and last instar D. punctata. Maximum values of approximately 1500 ng/ml (approximately 6 microM) were observed at the middle of the gonotrophic cycle, when basal oocyte growth rate was greatest. Changes in rates of JH release in vitro by corpora allata paralleled closely the changes in JH titre, suggesting that biosynthesis is a major regulator of titre. JH levels per animal were calculated from observed JH titres, and at certain time points in the gonotrophic cycle JH obtained from analysis of whole bodies were significantly greater than those predicted from hemolymph titres. These results suggest the existence of a nonhemolymph JH pool in D. punctata. Decay in JH titre after allatectomy of 5 day females has also been studied. Following a rapid initial decline, the rate of decay slowed appreciably 4 h post-operation. Thus, use of a first-order rate constant to estimate half-life of JH significantly underestimated the longevity of the hormone. The apparent persistence of JH following allatectomy may be due to the existence of a nonhemolymph JH pool.     

The largest known chromosome number for a mammal,in a South American desert rodent

Summary Tympanoctomys barrerae, a desert specialist member of the family Octodontidae, until now thought to be conservative, and ancestral to South American hystricognath rodents, presents the highest diploid chromosome number (2n=102) known in a mammal. Unexpectedly, its karyotype was found to be composed mainly of metacentric to sub-metacentric chromosomes. Mechanisms by which such a karyotype may have been derived are discussed.     

The effects of vitamin A nutritional status on glutathione levels and microsomal lipid peroxidation in rat lung

Summary In vitamin A-deficient rats, the glutathione level in lung was diminished and microsomal lipid peroxidation much increased. In vitamin A-loaded animals, however, both were depressed below control. Thus vitamin A protection against lipid peroxidation is independent of glutathione.Acknowledgments. We thank Dr L. Y. Y. Fong and Mr David Y. H. Woo for preparing the animals used in this research, for retinol determinations and for valuable discussions, and also the China Medical Board of New York and the University of Hong Kong for the award of a Fellowship to V.P.     

Loss of the SKI proto-oncogene in individuals affected with 1p36 deletion syndrome is predicted by strain-dependent defects in Ski-/- mice.

Experiments involving overexpression of Ski have suggested that this gene is involved in neural tube development and muscle differentiation. In agreement with these findings, Ski-/- mice display a cranial neural tube defect that results in exencephaly and a marked reduction in skeletal muscle mass. Here we show that the penetrance and expressivity of the phenotype changes when the null mutation is backcrossed into the C57BL6/J background, with the principal change involving a switch from a neural tube defect to midline facial clefting. Other defects, including depressed nasal bridge, eye abnormalities, skeletal muscle defects and digit abnormalities, show increased penetrance in the C57BL6/J background. These phenotypes are interesting because they resemble some of the features observed in individuals diagnosed with 1p36 deletion syndrome, a disorder caused by monosomy of the short arm of human chromosome 1p (refs. 6-9). These similarities prompted us to re-examine the chromosomal location of human SKI and to determine whether SKI is included in the deletions of 1p36. We found that human SKI is located at distal 1p36.3 and is deleted in all of the individuals tested so far who have this syndrome. Thus, SKI may contribute to some of the phenotypes common in 1p36 deletion syndrome, and particularly to facial clefting.     

Altered brain cholinergic enzymes activity in the genetically obese rat

Genetically obese male Zucker rats (fa/fa) and their lean littermates (Fa/-) were used in this experiment. Fourteen-week-old obese and lean littermates were sacrificed and choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) enzymes were assayed in specific brain regions. The assays of these enzymes indicate that obese animals had a significantly lower ChAT activity in the cerebellum, pons, and cerebral cortex and a significant increase in ChAT activity in the thalamus and hypothalamus. Meanwhile, the cerebral cortex, cerebellum, midbrain, thalamus and hypothalamus of the obese animals showed significantly higher AChE activity than their lean littermates. It was concluded from this study that obesity may be associated with changes in the enzymes of the brain cholinergic system.     

System identification and validation for output prediction of a dynamic hydrologic process

The paper presents an identification procedure for a dynamic model of am hydrologic process. The process involves solute transport in streams subject to aquifer interaction and unsteady flows and the intended use of the model is prediction. Detailed assumptions and results are provided to illustrate the level of comprehensive analysis required to assess model adequacy. The assessment procedure easily generalizes to any dynamic model which is linear-in-the-parameters. As a fundamental tool, instrumental variable algorithms can be adopted which have a number of attractive features. These algorithms make both model-order identification and specification among alternatives a straightforward task. They are known to be consistent estimators in the presence of a wide class of errors. It is seen that they can be made stable and robust in the presence of data outliers. Instrumental variable algorithms can also be used which are asymptotically efficient and provide a covariance matrix of parameter estimates. The paper shows how they aid the quantification of predictive uncertainty and investigates the validity of the underlying assumptions. Further, it illustrates that, when instrumental variable algorithms are used in recursive mode, they can be used not only as an additional tool to access model inadequacy but also as an aid to model improvements.     

Neutrophil influx into an inflammatory site inhibited by a soluble homing receptor-IgG chimaera

Neutrophil-mediated inflammation is involved in a number of human clinical manifestations, including the adult respiratory distress syndrome, multi-organ failure and reperfusion injury. One way of inhibiting this type of inflammatory response would be to block competitively the adhesive interactions between neutrophils and the endothelium adjacent to the inflamed region. The lectin-containing murine adhesion molecule gp90MEL, the homing receptor, is found on all leukocytic cells, including neutrophils. MEL 14, a monoclonal antibody directed against this adhesion molecule, blocks lymphocyte traffic to lymph nodes and extravasation of neutrophils from blood to inflammatory sites. Here we show that administration to mice of a soluble immunoglobulin chimaera containing the murine homing receptor extracellular domain significantly decreases the number of neutrophils that migrate to the peritoneum in response to the inflammatory irritant thioglycollate. These results indicate that soluble forms of a single type of adhesion molecule, the homing receptor, could be clinically effective compounds for the inhibition of neutrophil-mediated inflammation.