Enzyme-linked immunosorbent assay, using staphylococcal protein A for detecting virus antibodies

A modification of the indirect enzyme-linked immunosorbent assay (ELISA) was developed which used staphylococcal protein A linked to horseradish peroxidase. Virus antibodies in equine, bovine, porcine, feline, canine, lagomorphic (rabbit), and human sera were detected, using the indirect ELISA in which the antiglobulin enzyme conjugate was replaced by protein A linked to horseradish peroxidase. Results of the ELISA were compared with the results of the serum-virus neutralization test. The application of the test in laboratories performing serologic assays with sera from diverse animal species is discussed.     

Plaque herniation through an intracoronary stent

We present a case where a Wiktor intracoronary stent was inserted for 'poor angiographic result' following balloon angioplasty. Despite appropriate positioning and repeated dilation of the stent a suboptimal result was achieved because of plaque herniation through the stent. The case emphasizes that the choice of stent used is important and will become more so as the number of choices available increases.     

Conditioned defensive reflex in the edible snail (molecular-genetic aspects)

The proliferation of glioma cells requires cholesterol, which could be provided by synthesis within the cells or by uptake of cholesterol esters in particles of Low Density Lipoprotein (LDL). Cholesterol esters and cholesterol were therefore analysed in human glioma tissue, its surrounding areas and serum from 40 patients. The analyses revealed an increased concentration of cholesterol esters up to 100 times (0.1-10 mumol/g) in both tumour-tissue and surrounding areas compared with control material (< 0.1 mumol/g). The analyses also demonstrated that cholesterol esters in tumour tissue eminated mainly from serum. The cholesterol concentrations were significantly lower in tumour tissue compared with surrounding areas as expected. These results indicate that tumour cell proliferation utilises serum derived cholesterol esters presumably carried by LDL particles.     

The electrophysiological characteristics of the plasma membrane of rat macrophages at rest and under exposure to ATP]

The application of ATP in micromolar concentrations to the macrophages results in a biphasic response in the form of the short-time depolarization followed by a rather long hyperpolarization, the corresponding inward and outward macroscopic currents being observed. The ATP-induced hyperpolarization is accompanied by changes in current kinetics, I/V-curves pattern and shifting in the reversal potential. Such changes may be explained by a supposition that ATP activates an additional fraction of potassium channels with characteristics other than those in cells with initially low value of membrane potential. The data available are suggestive that in resting cells the inward rectification potassium conductance may dominate, whereas during ATP-induced hyperpolarization a certain type of Ca(2+)-dependent potassium conductance prevails. A rather high membrane potential in some part of macrophages, not treated with ATP, may be attributed to the latter type of conductance.     

Effects of calcitonin and parathyroid hormone on calcification of primary cultures of chicken growth plate chondrocytes

Few studies have been directed toward elucidating the action of calcitonin (CT) and parathyroid hormone (PTH) on growth plate chondrocytes, cells directly involved in longitudinal bone growth and provisional calcification. In this study, primary cultures of avian growth plate chondrocytes that calcify without the supplement of beta-glycerophosphate were used to investigate the effects of synthetic human CT and 1-34 bovine PTH on (1) cell division and growth; (2) the deposition of Ca2+ and inorganic phosphate (Pi); (3) the activity of alkaline phosphatase (AP), an enzyme long associated with the mineralization process; (4) the levels of proteoglycans; and (5) the synthesis of collagens. Added continually to preconfluent cultures from day 6 until harvest, CT (1-30 nM) and PTH (0.1-1.0 nM) increased mineral deposition; the maximal increase was seen between days 18-21 at 10 nM CT (175-260%) and 0.5 nM PTH (approximately 170-280%), both p < 0.001. CT had no significant effect on cellular protein, or AP-specific activity, whereas PTH increased cellular protein, DNA, proteoglycan, and collagen content of the cultures in a dosage-dependent manner. AP activity and levels of Type II and X collagens and fibronectin in the culture medium showed a biphasic response to PTH; maximal increases were seen at 0.5 nM between days 15-18. Longer exposure (days 21-27) to PTH at higher levels (5-10 nM) caused a marked decreased in AP activity but a lesser decrease in the collagens. These results indicate that CT and PTH can act directly on chondrocytes to stimulate mineralization, but that PTH specifically stimulated cell division and synthesis of cellular and extracellular proteins by growth plate chondrocytes. The implications of these findings with regard to Ca2+ homeostasis and bone formation are discussed.