Effect of clozapine on motor function in schizophrenic patients

It is well established that clozapine is less likely than typical antipsychotic drugs to cause clinically discernible extrapyramidal side-effects. There is a paucity of data, however, on clozapine's motor effects. In this report we compare normal controls to groups of chronic schizophrenic patients treated with either typical antipsychotic drugs or with clozapine. Motor function was measured with a target-matching task, a test relying on submaximal sustained force control. Results indicated that patients on clozapine performed with significantly lower accuracy (greater variability) of force control. Even though the clozapine patients were treatment resistant to typical antipsychotic drugs, and many had a history of tardive dyskinesia, we postulate that the observed deficit is likely due to clozapine treatment rather than to earlier treatments or other factors. The observed force control deficit may be the result of an increase in myoclonus and a generally lower level of overall motor activity.     

CD4-mediated and CD8-mediated cytotoxic and proliferative immune responses to Toxoplasma gondii in seropositive humans

Both CD4+ and CD8+ cytotoxic T lymphocytes (CTL) are part of the human immune response to Toxoplasma gondii infection. To further our understanding of Toxoplasma immunity, we investigated factors influencing stimulation of CD4+ or CD8+ human T. gondii-specific immune cells. Both antigen-pulsed and Toxoplasma-infected antigen-presenting cells (APC) induced cell proliferation. Toxoplasma-infected APC elicited strong proliferation of CD4+ cells, but little or no proliferation of CD8+ cells, unless high antigen loads were used. Toxoplasma-infected APC stimulated specific cytotoxicity poorly or not at all, owing to death of stimulated cultures, whereas antigen-pulsed APC strongly elicited specific cytotoxicity. Cytotoxicity elicited by either type of APC resided exclusively in CD4+ T cells in polyclonal cultures. Thus, Toxoplasma-infected APC elicited stronger CD4-mediated than CD8-mediated cell proliferation and generated CD4+ CTL more readily than CD8+ CTL. Nonetheless, specific CD8+ memory cells were demonstrated, and rare CD8+ Toxoplasma-specific CTL were subcloned. Fixed Toxoplasma-infected APC (which induce CD8+ CTL) also elicited cell proliferation, but polyclonal cultures stimulated with these infected APC did not die. Unfixed Toxoplasma-infected APC strongly inhibited phytohemagglutinin-induced cell proliferation, whereas fixed APC did not. These data suggested that infected APC were inhibitory or lethal to some immune cells. Further investigations into interactions between immune cells and Toxoplasma-infected cells likely will help elucidate factors involved in the immunopathogenesis of Toxoplasma infection. As other intracellular parasites, including Plasmodium spp. and Leishmania spp., also elicit CD4+ CTL, such work may help establish paradigms governing immunity to intracellular parasites.     

Interleukin-6-type cytokines in vivo: regulated bioavailability

Investigators have traditionally thought of the class of inflammation- and injury-associated cytokines in large part as "free" entities in the peripheral circulation. In the case of interleukin-6 (IL-6), the cytokine can be found in blood in complexes of molecular mass 400-500, 150-200, and 25-35 kDa in association with binding proteins that can include soluble IL-6 receptor (sIL-6R), anti-IL-6, and anti-sIL-6R IgG, and others. Sustained high levels of different particular IL-6 complexes are observed in the human circulation in cancer patients subjected to particular active anticancer immunotherapy regimens. In the "chaperoned" state, circulating IL-6 complexes display differential immunoreactivity in different ELISAs and possess differential biological activity as assayed ex vivo. The discovery of "chaperoned" circulating IL-6 in humans points to a new level of modulation of cytokine function, that of regulated bioavailability of IL-6 in vivo.     

Centrally infused galanin-(1-15) but not galanin-(1-29) reduces the baroreceptor reflex sensitivity in the rat

It has been demonstrated previously that central administration of the N-terminal galanin fragment (1-15) elicits hypertension and tachycardia and antagonizes the hypotensive effect of the parent molecule galanin-(1-29). In order to further clarify the role of galanin in central cardiovascular control, the possible modulation of the baroreceptor reflex by both galanin molecules has been studied. Different groups of rats were injected in the lateral ventricle with subthreshold doses of galanin-(1-15) (0.1 nmol/rat, or 0.3 nmol/rat), with subthreshold doses of galanin-(1-29) (0.1 nmol/rat, and 0.3 nmol/rat) or with an effective dose of galanin-(1-29) (3.0 nmol/rat). The baroreceptor reflex was elicited by intravenous injections of different doses of L-phenylephrine before and after the intraventricular administration of galanin peptides. The changes of the bradycardic responses after galanin peptide injections as well as the modifications of the baroreceptor reflex sensitivity were evaluated. Intraventricular injections of galanin-(1-15) significantly inhibited the reflex bradycardia elicited by intravenous L-phenylephrine and thus decreased the baroreceptor sensitivity. However, neither subthreshold doses of galanin-(1-29) nor its effective dose were able to modulate these cardiovascular responses. From these data it may be suggested that the galanin fragment (1-15) plays a more important role in central cardiovascular regulation than galanin-(1-29), possibly acting on a specific receptor subtype which exclusively recognizes N-terminal fragments of galanin, and exists on cardiovascular areas of the central nervous system.     

Pasteurella multocida toxin is a mitogen for bone cells in primary culture

The effect of recombinant Pasteurella multocida toxin (PMT) on primary cultures of embryonic chick bone-derived osteoblastic cells was investigated. It was found that PMT was a potent mitogen for primary derived chicken osteoblasts. The toxin stimulated DNA synthesis and cell proliferation in quiescent osteoblasts at the first passage and accelerated cell growth in subconfluent cultures. Cell viability was not affected by PMT, even at relatively high concentrations. Osteoblast numbers increased in a dose-dependent manner in response to PMT. Intracellular inositol phosphates were elevated in response to PMT, but no elevation in cyclic AMP (cAMP) levels was evident. Indeed, PMT inhibited cAMP elevation in osteoblasts in response to cholera toxin at a stage before other PMT-mediated events take place. In addition to increased cell turnover, PMT down-regulated the expression of several markers of osteoblast differentiation. Both alkaline phosphatase and type I collagen were reduced, but osteonectin was not affected. The in vitro deposition of mineral in cultures of primary osteoblasts and osteoblast-like osteosarcoma cells was also inhibited by the presence of PMT. This suggests that PMT interferes with differentiation at a preosteoblastic stage.     

Crystal structure at 2.4 angstroms resolution of the complex of transducin betagamma and its regulator, phosducin

The crystal structure of transducin's betagamma subunits complexed with phosducin, which regulates Gtbetagamma activity, has been solved to 2.4 angstroms resolution. Phosducin has two domains that wrap around Gtbetagamma to form an extensive interface. The N-terminal domain binds loops on the "top" Gtbeta surface, overlapping the Gtalpha binding surface, explaining how phosducin blocks Gtbetagamma's interaction with Gtalpha. The C-terminal domain shows structural homology to thioredoxin and binds the outer strands of Gtbeta's seventh and first blades in a manner likely to disrupt Gtbetagamma's normal orientation relative to the membrane and receptor. Phosducin's Ser-73, which when phosphorylated inhibits phosducin's function, points away from Gtbetagamma, toward a large flexible loop. Thus phosphorylation is not likely to affect the interface directly, but rather indirectly through an induced conformational change.     

A cytosolic granzyme B inhibitor related to the viral apoptotic regulator cytokine response modifier A is present in cytotoxic lymphocytes

Using a polymerase chain reaction strategy we identified a serine proteinase inhibitor (serpin) in human bone marrow that is related to the cellular serpin proteinase inhibitor 6 (PI-6) and the viral serpin cytokine response modifier A (CrmA). This serpin, proteinase inhibitor 9 (PI-9), has an unusual reactive center P1(Glu)-P1'(Cys), which suggests that it inhibits serine proteinases that cleave after acidic residues. The only known serine proteinase with this specificity is granzyme B, a granule cytotoxin produced by cytotoxic lymphocytes. To test the interaction of PI-9 with granzyme B we prepared recombinant hexa-histidine tagged PI-9 in a yeast expression system. Addition of the recombinant protein to native granzyme B resulted in an SDS-resistant complex typical of serpin-serine proteinase interactions. Further analysis showed that complex formation followed bimolecular kinetics with a second order rate constant of 1.7 +/- 0.3 x 10(6) M-1 s-1, which is in the range for a physiologically significant serpin-proteinase interaction. Recombinant PI-9 also completely abrogated granzyme B and perforin-mediated cytotoxicity in vitro. Examination of PI-9 mRNA distribution demonstrated that it is expressed in immune tissue, primarily in lymphocytes. The highest levels of PI-9 mRNA and protein were observed in natural killer cell leukemia cell lines and in interleukin-2 stimulated peripheral blood mononuclear cells, which also produce granzyme B. Like PI-6, PI-9 was shown to be a cytosolic protein that is not secreted. Fractionation of natural killer cells and stimulated peripheral blood mononuclear cells demonstrated that PI-9 is in a separate subcellular compartment to granzyme B. These results suggest that PI-9 serves to inactivate misdirected granzyme B following cytotoxic cell degranulation. This may explain why cytotoxic cells are not damaged by their own granzyme B during destruction of abnormal cells.     

Outbreak of serogroup C meningococcal disease associated with campus bar patronage

Between February 1991 and April 1992, eight undergraduates at a US residential university and one at a nearby 2-year college contracted serogroup C meningococcal disease. A case-control investigation with 20 controls per case, oropharyngeal carriage surveys, and multilocus enzyme electrophoresis (MEE) of serogroup C isolates were used to identify factors contributing to the outbreak. All eight sterile-site isolates from cases were closely related by MEE and were similar (though not identical) to the strain associated with the 1991-1992 epidemic of meningococcal disease in eastern Canada. Disease was associated with cigarette smoking (p = 0.012), recent patronage of campus-area bars (p = 0.034), estimated amount of time spent in campus-area bars (p = 0.0003), and, especially, recent patronage of one specific bar, bar A (p = 0.0006; odds ratio = 23.1, 95% confidence interval 3.0-571.5). In carriage surveys, 1,528 throat cultures taken from (primarily student) noncases yielded only five (0.3%) strains that were identical by MEE to those from cases. Two of these were found among 22 cultures obtained from bar A employees in spring 1992. Some cases in this outbreak may have followed transmission of the epidemic strain in bar A. Campus bar environments may facilitate the spread of meningococcal disease among teenagers and young adults.