Thapsigargin inhibits contraction and Ca2+ transient in cardiac cells by specific inhibition of the sarcoplasmic reticulum Ca2+ pump.

Regulation of the level of ionized calcium, [Ca2+]i, is critical for its use as an important intracellular signal. In cardiac and skeletal muscle the control of fluctuations of [Ca2+]i depend on sarcolemmal and sarcoplasmic reticulum ion channels and transporters. We have investigated the sesquiterpine lactone, thapsigargin (TG), because of its reported action to alter cellular calcium regulation in diverse cell types, including striated muscle cells. We have combined biochemical and physiological methods at the cellular level to determine the site of action of this agent, its specificity, and its cellular effects. Using a patch-clamp method in whole cell configuration while measuring [Ca2+]i with Indo-1 salt, we find that TG (100 nM) largely blocks the contraction and the [Ca2+]i transient in rat ventricular myocytes. Analysis of these data indicate that no sarcolemmal current or transport system is directly altered by TG, although indirect [Ca2+]i-dependent processes are affected. In permeabilized myocytes, TG blocked oxalate-stimulated calcium uptake (half-maximal effect at 10 nM) into the SR. However, TG (100 microM) had no effect on Ca(2+)-induced Ca(2+)-release in purified muscle (ryanodine-receptor enriched) vesicles while clearly blocking Ca(2+)-ATPase activity in purified (longitudinal SR) vesicles. We conclude that in striated muscle TG markedly alters calcium metabolism and thus alters contractile function only by its direct action on the Ca(2+)-ATPase.     

Disruptive medical patients. Forensically informed decision making.

Patients who disrupt medical care create problems for physicians. The risks are not entirely clinical. Although these patients may compromise sound clinical judgment, some are also litigious and express their dissatisfaction in legal or other forums. It then becomes necessary for treating physicians to be aware of the legal and ethical boundaries of their patient care responsibilities. Some disruptive patients are treated by setting limits, which is usually affirmed by health care agreements. A hospital review board may advise clinicians on these agreements and on the management of disruptive patients. If termination of the physician-patient relationship is considered, physicians must follow proper protocol. We examine these forensic considerations and place them in the context of malpractice. Communication, consultation, and documentation are the key elements in reducing liability.     

An epidemiologic study of sacroiliac fusion in some human skeletal remains

A case-control study was undertaken to generate some hypotheses concerning the etiology of sacroiliac fusion in a group of skeletons dating from the 18th and 19th centuries. Forty-one skeletons with fusion of the sacroiliac joint were compared with eighty-two adult skeletons without the condition. The sacroiliac joints were most frequently fused with bridging osteophytes and no preference for site or side of fusion could be detected. Except where there were other features in the skeleton suggestive of a sero-negative arthropathy, radiography demonstrated that there was no intra-articular ankylosis. We were able to confirm earlier observations that the condition is more prevalent in males and in older age-groups. The study also showed a significant association between sacroiliac fusion and the presence of diffuse idiopathic skeletal hyperostosis (DISH) and osteoarthritis of the spine but not for osteoarthritis at any other site. There was a highly significant association between sacroiliac fusion and the phenomenon that we refer to as "bone forming." We devised a series of bone-former scores and were able to show a significant excess of cases with high scores compared with the controls. This association persisted when allowance had been made for potential confounding factors such as DISH, osteoarthritis of the spine, and age.     

Production of 6-oxo-prostaglandin F1 alpha and prostaglandin E2 by isolated glomeruli from normal and diabetic rats.

Production of 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha) and prostaglandin E2 (PGE2) was measured by radioimmunoassay in supernatants of isolated glomeruli from rats with streptozocin-induced diabetes and non-diabetic rats. Production of 6-oxo-PGF1 alpha by discs of aortas from these rats was measured at the same time. As shown before, aortic discs from diabetic rats produced significantly less 6-oxo-PGF1 alpha than aortic discs from non-diabetic rats (diabetic 1.99 +/- SEM 0.27 ng v non-diabetic 2.92 +/- 0.46 ng/mg net weight aorta; p less than 0.05). In contrast production of 6-oxo-PGF1 alpha by isolated glomeruli was not reduced in the diabetic rats (diabetic 77 +/- 7 pg v non-diabetic 70 +/- 8 pg/micrograms glomerular DNA). Similarly production of PGE2 was not diminished in the diabetic glomeruli (diabetic 1.20 +/- 0.15 ng v non-diabetic 0.91 +/- 0.12 ng/microgram glomerular DNA). It is concluded that regional differences in production of prostacyclin and 6-oxo-PGF1 alpha occur in experimental diabetes. Diminished prostacyclin production may contribute to the increased susceptibility of diabetic patients to atherosclerosis but is less likely to have a role in the pathogenesis of microangiopathy.     

Antibacterial effect of the scandium and indium complexes of enterochelin on Escherichia coli

Enterochelin, the iron chelator produced by a number of pathogenic enterobacteria, appears to be an essential metabolite for multiplication within the host, where it transports iron from the host iron-binding proteins to the bacteria. Previous work showed that complexes of enterochelin containing either scandium (Sc3+) or indium (In3+) exerted a bacteriostatic effect on Klebsiella pneumoniae in serum, whilst the Sc3+ complex exerted a significant therapeutic effect on mice infected with K. pneumoniae. These observations have now been extended to a number of pathogenic serotypes of Escherichia coli including those carrying either the K1 antigen or the ColV plasmid. The Sc3+ and In3+ complexes each exert a bacteriostatic effect on these organisms growing in either whole serum or media containing an iron-binding protein. Evidence is presented that the Sc3+ complex may act as a competitive inhibitor of the Fe3+ complex. In contrast to their effects on K. pneumoniae, sideramines other than enterochelin fail to reverse the bacteriostatic effect of the Sc3+ complex of enterochelin in E. coli, suggesting that the complex produces a more profound derangement of metabolism in this organism. The Sc3+ complex exerts a significant therapeutic effect on E. coli infections in mice although the In3+ complex is less active.     

Comparative properties of ferredoxins from a marine and freshwater species of Porphyridium

Ferredoxins were isolated from the freshwater red alga Porphyridium aerugineut, and from Porphyridium cruentum, a related marine species. A sin     

The purification of murine histocompatibility antigens (H-2b) from RBL-5 tumor cells using detergents.

A detergent-solubilized form of H-2b (dH-2b) has been purified 1500-fold from RBL-5 tumor cells. The purification was accomplished by deoxycholate solubilization of purified plasma membranes, gel filtration, Lens culinaris lectin affinity chromatography, and affinity chromatography on a sheep anti-dH-2b immunoadsorbent. Both alloantigen and beta 2-microglobulin were monitored by radioimmunoassay during purification. The final product was judged to be greater than 90% pure by the following criteria: 1) sodium dodecyl sulfate-polyacrylamide electrophoresis which showed the expected 2-component structure of histocompatibility antigens, i.e. a heavy chain and beta 2-microglobulin; 2) amino acid composition which was comparable to the known compositions of other H-2 and HLA molecules; 3) NH2-terminal sequencing which gave a unique sequence for the heavy chain, and the reported sequence for beta 2-microglobulin; and 4) immunoprecipitation of the bulk of the preparation by appropriate alloantisera.     

The terminal structures of feather keratin mRNA

Terminal labeling of embryonic feather keratin mRNA with [³H]KBH₄ followed by digestion with ribonuclease T₁ and T₂, alkaline phosphatase, snake venom phosphodiesterase, and nucleotide pyrophosphatase and analysis of the products by high voltage paper electrophoresis, indicated the presence of the sequence m⁷G(5)ppp(5)N at the 5-end of the mRNA. Ribonuclease T₁ and A digests of the terminally labeled, and also of unlabeled mRNA followed by fractionation on denaturing polyacrylamide gels indicated the presence of polyadenylate tracts ranging in size from 45 to 165 nucleotides at the 3-end of the mRNA.     

Kinetic analysis of batch and continuous culture of Streptococcus cremoris HP1.

The growth of Streptococcus cremoris on a semidefined medium was studied at initial lactose concentrations of 0.2-5.0% in batch culture, and in lactose-limited chemostat cultures at 0.5% lactose. Kinetic analysis of the batch data, using statisitcal techniques, indicated the importance of lactose limitation and lactic acid inhibition of the growth of S. cremoris. A model for the biomass production, lactose utilization, and lactic acid production in batch culture was proposed. In continuous culture, it was found that steady state populations were maintained at higher dilution rates (D = 0.6-0.7 h-1) than the maximum predicted by batch culture (0.56h-1). No evidence for a selection of fast growing mutants was obtained. Copious growth adhering to the walls of the fermentor (i.e. wall growth) occurred very rapidly at higher dilution rates and this undoubtedly affected steady-state growth and wash-out and, as a consequence, the apparent maximum dilution rate.