Role of the kidney in regulating plasma immunoreactive beta-melanocyte-stimulating hormone

An analysis of the factors that influence the increase in plasma immunoreactive beta-melanocyte-stimulating hormone (beta-MSH) concentration in chronic renal failure showed that: (a) the increase correlated with the increase in serum creatinine concentrations; (b) beta-MSH was not cleared from the plasma by haemodialysis; (c) beta-MSH concentrations increased with length of time on dialysis and increased further after bilateral nephrectomy but there was no further increase with time; (d) beta-MSH levels decreased to normal after renal transplantation; and (e) beta-MSH was excreted in urine only when plasma levels rose to well above those of chronic renal failure (in Nelson's syndrome). These findings suggest that the kidney regulated plasma beta-MSH by a non-excretory mechanism and is the major site of beta-MSH metabolism.     

Serum cortisol (hydrocortisone) values in normal dogs as determined by radioimmunoassay

A radioimmunoassay method was utilized to determine serum cortisol (hydrocortisone) concentrations in normal dogs. The mean value was 2.32 mug/dl (minimum, 0.94; maximum, 3.70; with a coefficient of variation of 29.7%). Samples had been collected in the morning of the diurnal cycle. The cortisol antibody used was highly specific for cortisol and showed little cross reaction with other common physiologic corticosteroids, when they were assayed, using the radioimmunoassay procedure described.     

Augmented water binding and low cellular water content in erythrocytes of camel and camelids

We investigated a link between hemoglobin primary structure, hemoglobin hydrophobicity-hydrophilicity, and erythrocyte water content in various mammalian species. Some hemoglobin molecules, particularly those of the camel and camelids, contain more charged amino acid residues and are more hydrophilic than the hemoglobins of human and a number of other mammalian species. To test the in vivo significance of these alterations of hemoglobin primary structure, we determined the osmotically unresponsive erythrocyte water fractions in mannit solutions of various osmolarities at 4 degreesC. Among the species investigated, the size of the osmotically unresponsive erythrocyte water fraction relates in a positive linear way to hemoglobin hydrophilicity. The extreme low total erythrocyte water content of camel erythrocytes (1.1-1.3 g water/g dry mass) may be explained by a comparatively high osmotically unresponsive erythrocyte water fraction. It is proposed that alterations of hemoglobin sequences of camel and camelids may be the part of a natural selection process aimed at protecting these animals against osmotic dehydration in arid environments.     

Formation of nanoparticle aggregates and agglomerates in polymer nanocomposites and their distinct impacts on the mechanical properties

In this study, the different effects of nanoparticle aggregates and agglomerates on the mechanical properties of polymer nanocomposites are comprehensively investigated. To this end, a specific strategy, based on the equilibrium between the dispersion and cohesion energies in the mixing stage, is proposed using which the content and size of aggregates/agglomerates can be defined. The aggregated/agglomerated networks are considered to place in constrained volumes (CVs), having co-continuous morphology. An equivalent box model (EBM), corresponding to the system, is used to predict the tensile modulus of the nanocomposite. Different test results of HDPE nanocomposite samples, containing 1–3 wt.% of surface-modified silica nanoparticles, prepared by a semi-industrial single screw extruder, are applied to validate the model. Moreover, other data from the literature are also used to further evaluate the accuracy and capability of the proposed analytical method.