The first original Russian class-III antiarrhythmic nibentan

The paper presents experimental and clinical findings of the new antiarrhythmic drug nibentan. The agent was found to be a class-III antiarrhythmic agent in terms of its electrophysiological effects and an inhibitor of the delayed rectifier potassium current in terms of its effects on the ionic channels of cardiomyocytes. The clinical trial of nibentan shows that the drug is highly effective (in 70-100% of cases) in patients with atrial flutter and fibrillation and in those with supraventricular tachycardia and it is less effective in suppressing ventricular premature contractions and tachycardia. The rate of arrhythmogenic effects produced by the drug was inversely related to its antiarrhythmic action. Nibentan has been approved for clinical use.     

Spinal motion in lumbar degenerative disc disease

We have measured the dynamic movement of the lumbar spine in 57 patients with degenerative lumbar disc disease. Each completed a questionnaire which recorded pain and subjective signs and symptoms. From plain lateral radiographs, the subjects were graded using the criteria of Kellgren and Lawrence and those of Lane et al, which are both based on the severity of degenerative changes. Measurements of the height of the disc space and the vertebral height were obtained and expressed as a ratio. We found no relationship between the characteristics of spinal movement and the overall grading of degenerative disc disease with either system. Both were influenced (p < 0.01) by age, walking distance, severity of symptoms, drug intake and frequency of pain. The present systems for grading degenerative disc disease from plain lateral radiographs have limited application.     

Determinants of cholesterol screening and treatment patterns. Insights for decision-makers

We isolated rat UCP2 cDNA, which has been proposed to play an important role in mammalian thermogenesis and body weight regulation. The nucleotide sequence of the cDNA revealed that the rat UCP2 protein is composed of 309 amino acid residues, and is 99% and 95% identical to the mouse and human proteins, respectively. The molecular weight of rat UCP2, calculated from the predicted amino acid sequence, was 33,369, and the UCP2 protein of this size was detected when the cDNA was expressed in vitro. Northern blot analysis revealed that the corresponding mRNA is approximately 1.7 kb in size, and is expressed in a variety of rat organs, with predominant expression in the heart, lung and spleen. UCP2 mRNA levels in the heart, liver, muscle and epididymal adipose tissue of Zucker fatty (fa/fa) rats were comparable to those in the lean littermates, while ob mRNA level markedly increased in the epididymal adipose tissue of Zucker (fa/fa) rats.     

Na(+)-Ca2+ exchange currents in cortical neurons: concomitant forward and reverse operation and effect of glutamate

Na(+)-Ca2+ exchanger-associated membrane currents were studied in cultured murine neocortical neurons, using whole-cell recording combined with intracellular perfusion. A net inward current specifically associated with forward (Na+(o)-Ca2+(i)) exchange was evoked at -40 mV by switching external 140 mM Li+ to 140 mM Na+. The voltage dependence of this current was consistent with that predicted for 3Na+:1Ca2+ exchange. As expected, the current depended on internal Ca2+, and could be blocked by intracellular application of the exchanger inhibitory peptide, XIP. Raising internal Na+ from 3 to 20 mM or switching the external solution from 140 mM Li+ to 30 mM Na+ activated outward currents, consistent with reverse (Na+(i)-Ca2+(o)) exchange. An external Ca2(+)-sensitive current was also identified as associated with reverse Na(+)-Ca2+ exchange based on its internal Na+ dependence and sensitivity to XIP. Combined application of external Na+ and Ca2+ in the absence of internal Na+ triggered a 3.3-fold larger inward current than the current activated in the presence of 3 mM internal Na+, raising the intriguing possibility that Na(+)-Ca2+ exchangers might concurrently operate in both the forward and the reverse direction, perhaps in different subcellular locations. With this idea in mind, we examined the effect of excitotoxic glutamate receptor activation on exchanger operation. After 3-5 min of exposure to 100-200 microM glutamate, the forward exchanger current was significantly increased even when external Na+ was reduced to 100 mM, and the external Ca2(+)-activated reverse exchanger current was eliminated.     

Neuroprotective actions of FK506 in experimental stroke: in vivo evidence against an antiexcitotoxic mechanism

The cellular mechanisms underlying the neuroprotective action of the immunosuppressant FK506 in experimental stroke remain uncertain, although in vitro studies have implicated an antiexcitotoxic action involving nitric oxide and calcineurin. The present in vivo study demonstrates that intraperitoneal pretreatment with 1 and 10 mg/kg FK506, doses that reduced the volume of ischemic cortical damage by 56-58%, did not decrease excitotoxic damage induced by quinolinate, NMDA, and AMPA. Similarly, intravenous FK506 did not reduce the volume of striatal quinolinate lesions at a dose (1 mg/kg) that decreased ischemic cortical damage by 63%. The temporal window for FK506 neuroprotection was defined in studies demonstrating efficacy using intravenous administration at 120 min, but not 180 min, after middle cerebral artery occlusion. The noncompetitive NMDA receptor antagonist MK801 reduced both ischemic and excitotoxic damage. Histopathological data concerning striatal quinolinate lesions were replicated in neurochemical experiments. MK801, but not FK506, attenuated the loss of glutamate decarboxylase and choline acetyltransferase activity induced by intrastriatal injection of quinolinate. The contrasting efficacy of FK506 in ischemic and excitotoxic lesion models cannot be explained by drug pharmacokinetics, because brain FK506 content rose rapidly using both treatment protocols and was sustained at a neuroprotective level for 3 d. Although these data indicate that an antiexcitotoxic mechanism is unlikely to mediate the neuroprotective action of FK506 in focal cerebral ischemia, the finding that intravenous cyclosporin A (20 mg/kg) reduced ischemic cortical damage is consistent with the proposed role of calcineurin.     

Qualitative and quantitative effects of CD28/B7-mediated costimulation on naive T cells in vitro

The CD28/B7 system provides costimulatory signals necessary for optimal T cell activation. We have examined the effects of blocking B7.1 and/or B7.2 in an in vitro system using TCR transgenic T cells specific for myelin basic protein. Activation of naive T cells was found to be B7.2 dependent and not dependent on the presence of B7.1 molecules. However, increasing the strength of signal through the TCR using peptide analogues with higher affinity for MHC compensated for blockade of B7.2 molecules, suggesting that signal 1 alone can be sufficient for the activation of naive T cells. The role of B7 molecules in the differentiation of T cells was further investigated by restimulating T cells with fresh APC and peptide in B7-sufficient conditions. A down-regulation of IL-2 and IFN-gamma production by T cells primed in the presence of anti-B7.2 mAb was partially overcome when high affinity peptide analogues were used to restimulate T cells. In contrast, a significant down-regulation of the differentiation of cells producing Th-2 cytokines was observed in the presence of anti-B7 Abs. Differentiation of IL-4-secreting cells was influenced by both B7.1 and B7.2, while IL-5 secretion was totally dependent on B7.2. These results suggest that B7-mediated costimulation is essential for the development of Th-2-associated cytokines, the absence of which cannot be overcome by increasing the strength of the signal through the TCR.     

Turnover of amyloid beta-protein in mouse brain and acute reduction of its level by phorbol ester

Fibrillar amyloid deposits are defining pathological lesions in Alzheimer's disease brain and are thought to mediate neuronal death. Amyloid is composed primarily of a 39-42 amino acid protein fragment of the amyloid precursor protein (APP), called amyloid beta-protein (Abeta). Because deposition of fibrillar amyloid in vitro has been shown to be highly dependent on Abeta concentration, reducing the proteolytic release of Abeta is an attractive, potentially therapeutic target. Here, the turnover rate of brain Abeta has been determined to define treatment intervals over which a change in steady-state concentration of Abeta could be measured. Mice producing elevated levels of human Abeta were used to determine approximate turnover rates for Abeta and two of its precursors, C99 and APP. The t1/2 for brain Abeta was between 1.0 and 2.5 hr, whereas for C99, immature, and fully glycosylated forms of APP695 the approximate t1/2 values were 3, 3, and 7 hr, respectively. Given the rapid Abeta turnover rate, acute studies were designed using phorbol 12-myristate 13-acetate (PMA), which had been demonstrated previously to reduce Abeta secretion from cells in vitro via induction of protein kinase C (PKC) activity. Six hours after intracortical injection of PMA, Abeta levels were significantly reduced, as measured by both Abeta40- and Abeta42-selective ELISAs, returning to normal by 12 hr. An inactive structural analog of PMA, 4alpha-PMA, had no effect on brain Abeta levels. Among the secreted N-terminal APP fragments, APPbeta levels were significantly reduced by PMA treatment, whereas APPalpha levels were unchanged, in contrast to most cell culture studies. These results indicate that Abeta is rapidly turned over under normal conditions and support the therapeutic potential of elevating PKC activity for reduction of brain Abeta.     

Use of full cortical allograft to repair a metatarsal fracture in a foal

A 4-month-old Quarter Horse colt was admitted for repair of an open, comminuted fracture of the proximal portions of the diaphyses of the left second, third, and fourth metatarsal bones. Initial repair included internal fixation and cancellous bone graft. However, the third metatarsal bone became infected and failed to heal. After removal of infected portions of the bone, a 5-cm, fullthickness cortical allograft was placed in the defect. Rigid internal fixation provided stability for the allograft and remaining fracture fragments so that the horse was able to bear weight on the second and fourth metatarsal bones. The allograft was ultimately resorbed; however, appositional bone growth permitted a massive, functional metatarsal bone to form that incorporated the second, third, and fourth metatarsal bones. The colt went on to compete successfully, long term, as a show horse.     

cis-Acting signals involved in termination of vesicular stomatitis virus mRNA synthesis include the conserved AUAC and the U7 signal for polyadenylation

We investigated the cis-acting sequences involved in termination of vesicular stomatis virus mRNA synthesis by using bicistronic genomic analogs. All of the cis-acting signals necessary for termination reside within the first 13 nucleotides of the 23-nucleotide conserved gene junction. This 13-nucleotide termination sequence at the end of the upstream gene comprises the tetranucleotide AUAC, the tract containing seven uridines (U7 tract), and the intergenic dinucleotide (GA), but it does not include the downstream gene start sequence. Data presented here show that upstream mRNA termination is independent of downstream mRNA initiation. Alteration of any nucleotide in the 13-nucleotide sequence decreased the termination activity of the gene junction and resulted in increased synthesis of a bicistronic readthrough RNA. This finding indicated that the wild-type gene junction has evolved to achieve the maximum termination efficiency. The most critical position of the AUAC sequence was the C, which could not be altered without complete loss of mRNA termination. Reducing the length of the wild-type U7 tract to zero, five, or six U residues also totally abolished mRNA termination, resulting in exclusive synthesis of the bicistronic readthrough mRNA. Shortening the wild-type U7 tract to either five or six U residues abolished VSV polymerase slippage during readthrough RNA synthesis. Since neither the U5 nor U6 template was able to direct mRNA termination, these data imply that polymerase slippage is a prerequisite for termination. Evidence is also presented to show that in addition to causing polymerase slippage, the U7 tract itself or its poly(A) product constitutes an essential signal for mRNA termination.