Inherited nuclear pore substructures template post-mitotic pore assembly

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Decreased sodium-potassium pump activity in isolated hypertrophied feline ventricular myocytes

The activity of the Na-K pump was assessed in normal and hypertrophied isolated feline myocytes by measuring ouabain-sensitive 42-K uptake. Right ventricular hypertrophy was produced in feline myocardium by placing a constricting band around the pulmonary artery of adult cats. High yields of calcium tolerant myocytes were isolated from the right and left ventricle of banded and sham operated animals. Intracellular sodium (Na) and potassium (K) concentrations (mM) were not significantly different (P greater than 0.5) in normal (Na: 13.2; K: 133.4) and hypertrophied (Na: 12.3; K: 127.5) myocytes. Morphometric analysis demonstrated a 26% increase in width and a 42% increase in volume of hypertrophied myocytes, however, the sarcomere length (1.9 mu) was not different in both cell types. The rate constant (k, min-1) describing 42-K uptake and the calculated total K influx (I, pmol/cm2/sec) were not significantly different (P greater than 0.5) in normal (k = 0.059; I = 15.9) and hypertrophied (k = 0.062; I = 15.3) cells. Ouabain-sensitive (active) K influx, a measure of Na-K pump activity, was maximally inhibited at 10(-4)M ouabain in both cell types. At this concentration, ouabain-sensitive K uptake was decreased 23.5% in hypertrophied myocytes compared to control. The decrease in active K influx may be due to a decrease in the activity of the Na-K ATPase and/or to a reduction in the passive movement of sodium and potassium down their electrochemical gradients.     

Regulation of the hepatic response to glucagon: role of insulin, growth hormone and cortisol

The hepatic response to glucagon was investigated in five groups of animals: (1) controls; (2) excess growth hormone (GH; tumor-bearing); (3) streptozotocin-induced diabetic; (4) cortisol-treated, and (5) insulin-treated animals. Blood samples were collected from the animal models and hepatocytes were prepared and used for glucagon-binding studies and studies of total glucose production, gluconeogenesis and glycogen determinations. Glucagon binding was elevated in GH-tumor-bearing and cortisol-treated hepatocytes but lower in hepatocytes from diabetic animals. Basal total glucose production wash higher in hepatocytes from diabetic rats but not changed in hepatocytes from GH-tumor-bearing, insulin-treated or cortisol-treated animals. Glucagon significantly stimulated total glucose production in hepatocytes from control, insulin-treated and cortisol-treated but not diabetic and GH tumor models. Gluconeogenesis as evaluated by alanine conversion to glucose was significantly increased in hepatocytes from diabetic and cortisol-treated animals and was significantly lower in hepatocytes from GH-tumor-bearing animals. Glucagon failed to significantly stimulate gluconeogenesis in hepatocytes from diabetic and tumor-bearing animals. Hepatic glycogen content was significantly decreased in diabetic and GH-tumor-bearing animals but not changed in insulin-treated and cortisol-treated animals. We conclude that increased glucagon binding was not always correlated with an increase in glucagon-stimulated glycogenolysis, gluconeogenesis or increased sensitivity to glucagon. Persistent hyperinsulinism may effectively suppress glucagon- or cortisol-stimulated pathways.     

Correlation between percentage of palmitic acid in adipose tissue and serum cholesterol level in patients with multiple sclerosis

To investigate mechanisms controlling the concentration of serum cholesterol we studied its relationship to the proportions of fatty acids in the lipids of adipose tissue of patients with multiple sclerosis. In 26 men the serum cholesterol concentration had a significant multiple linear regression on the proportion of palmitic, palmitoleic, and grouped longer-chain acids in adipose tissues. In 29 women the serum cholesterol had a significant regression on the proportion of palmitic acid and age. Whether these observations would hold for normal people must be determined in future studies.     

Specific RNA binding by amino-terminal peptides of alfalfa mosaic virus coat protein.

Specific RNA-protein interactions and ribonucleoprotein complexes are essential for many biological processes, but our understanding of how ribonucleoprotein particles form and accomplish their biological functions is rudimentary. This paper describes the interaction of alfalfa mosaic virus (A1MV) coat protein or peptides with viral RNA. A1MV coat protein is necessary both for virus particle formation and for the initiation of replication of the three genomic RNAs. We have examined protein determinants required for specific RNA binding and analyzed potential structural changes elicited by complex formation. The results indicate that the amino-terminus of the viral coat protein, which lacks primary sequence homology with recognized RNA binding motifs, is both necessary and sufficient for binding to RNA. Circular dichroism spectra and electrophoretic mobility shift experiments suggest that the RNA conformation is altered when amino-terminal coat protein peptides bind to the viral RNA. The peptide--RNA interaction is functionally significant because the peptides will substitute for A1MV coat protein in initiating RNA replication. The apparent conformational change that accompanies RNA--peptide complex formation may generate a structure which, unlike the viral RNA alone, can be recognized by the viral replicase.     

Evaluating Alternative Explanations in Ecosystem Experiments

Unreplicated ecosystem experiments can be analyzed by diverse statistical methods. Most of these methods focus on the null hypothesis that there is no response of a given ecosystem to a manipulation. We suggest that it is often more productive to compare diverse alternative explanations (models) for the observations. An example is presented using whole-lake experiments. When a single experimental lake was examined, we could not detect effects of phosphorus (P) input rate, dissolved organic carbon (DOC), and grazing on chlorophyll. When three experimental lakes with contrasting DOC and food webs were subjected to the same schedule of P input manipulations, all three impacts and their interactions were measurable. Focus on multiple alternatives has important implications for design of ecosystem experiments. If a limited number of experimental ecosystems are available, it may be more informative to manipulate each ecosystem differently to test alternatives, rather than attempt to replicate the experiment.     

Use of serum C-reactive protein as an early marker of inflammatory activity in canine type II immune-mediated polyarthritis: case report

Background  

Monitoring systemic inflammatory activity during steroid therapy of canine immune-mediated polyarthritis (IMPA) is difficult and mainly relies on clinical signs.