Demonstration of a COOH-terminal extension on equine lutropin by means of a common acid-labile bond in equine lutropin and equine chorionic gonadotropin

The beta subunits of equine lutropin and equine chorionic gonadotropin were incubated in 0.013 N HCl for 30 min at 110 degrees C and separated into two fragments by reverse-phase high performance liquid chromatography. The amino acid and carbohydrate compositions of both fragments from each subunit were analyzed. The results demonstrated that equine lutropin-beta has a glycosylated COOH-terminal extension that differs only in carbohydrate composition from the COOH-terminal portion of equine chorionic gonadotropin-beta. This is the first demonstration of a glycosylated COOH-terminal extension in a pituitary glycoprotein hormone.     

Data-Limited Population-Status Evaluation of Two Coastal Fishes in Southern Angola Using Recreational Catch Length-Frequency Data

Excessive truncation of a population’s size structure is often identified as an important deleterious effect of exploitation, yet the effect on population persistence of size-structure truncation caused by exploitation is often not quantified due to data limitations. In this study, we estimate changes in eggs per recruit (EPR) using annual length-frequency samples over a 9 year period to assess persistence of the two most important recreational fishes in southern Angola: west coast dusky kob (Argyrosomus coronus) and leerfish (Lichia amia). Using a length- and age-structured model, we improve on an existing method to fit this type of model to length-frequency data and estimate EPR. The objectives of the methodological changes are to add flexibility and robustness to the approach for assessing population status in data-limited situations. Results indicate that dusky kob presents very low levels of EPR (5%-10% of the per recruit reproductive capacity in the absence of fishing) in 2013, whereas large inter-annual variability in leerfish estimates suggest caution must be applied when drawing conclusions about its exploitation status. Using simulated length frequency data with known parameter values, we demonstrate that recruitment decline due to overexploitation leads to overestimation of EPR values. Considering the low levels of EPR estimated for the study species, recruitment limitation is not impossible and true EPR values may be even lower than our estimates. It is, therefore, likely that management action, such as the creation of Marine Protected Areas, is needed to reconstitute the west coast dusky kob population.     

A simple procedure to obtain one-micrometer sections of routinely embedded paraffin material

By freezing blocks of paraffin-embedded tissues to a convenient temperature it is possible to obtain routinely 1 micron sections that can be further processed as normal thicker sections. Normal and disposable steel knives can be used and the staining time should be increased in most procedures. Gradual freezing of blocks to the temperature of dry ice is the simplest and safest way to obtain an adequate temperature. The best results were obtained using as fixative 4% paraformaldehyde in phosphate buffered saline solution.     

Altered chromatin structure of cerebral nuclei in experimental diabetes mellitus.

To determine whether diabetes alters chromatin structure in vivo, micrococcal nuclease digestion kinetics were analyzed in cerebral cortical and hepatic nuclei of streptozotocin-induced diabetic rats. Cerebral nuclei of diabetic rats maintained for 6 weeks were less susceptible to micrococcal nuclease digestion compared with control rats. Insulin treatment reversed diabetes-related changes in nuclease digestion kinetics. There were no changes in the kinetics of digestion in hepatic nuclei. The reduced digestibility of cerebral DNA in diabetes could not be attributed to altered DNA fluorescence spectra, or altered distribution of most abundant chromatin proteins that were either solubilized or that remained insoluble immediately following nuclease digestion. It is concluded that chronic, uncontrolled hyperglycemia can alter chromatin structure of some tissues in vivo, and this change is probably related to subtle alterations in DNA-protein interactions.