Regulation of B Cell:T Cell Interactions: Potential Involvement of an Endogenous B Cell Sialidase

In light of the ability of B cells treated with neuraminidase to interact more effectively with T cells, the increased capacity of activated, but not small resting B cells, to interact with T cells could be associated with the level of sialylation on certain B cell surface molecules which influences the effectiveness of the physical interaction between B and T cells. The purpose of this study was to determine if activation of B cells altered sialylation via an endogenous sialidase which affected both the initial interaction between T and B cells and subsequent B cell-induced T cell proliferation. The competitive neuraminidase inhibitor, 2-deoxy-2,3-dehydro-N-acetylneuraminic acid (NeuAc2en), inhibited LPS-mediated enhancement of B cell conjugate formation with Ia-specific T cell clones as well as enhancement of their capacity to stimulate a mixed lymphocyte reaction. The addition of NeuAc2en during LPS stimulation did not affect the surface expression of Ia, LFA-1, ICAM-1 or mB7, suggesting that inhibition of LPS-mediated enhancement by the sialidase inhibitor was not due to changes in the level of expression of the major B cell adhesion or co-stimulatory molecules. Short term stimulation with phorbol myristate acetate (PMA) and ionomycin also enhanced the ability of resting B cells to form antigen specific T:B conjugates. However, activation of B cells with PMA and ionomycin or with LPS did not change the capacity of a sialic acid specific lectin to bind to the B cells, suggesting that activation was not associated with global changes in surface sialic acid content. B cell stimulation did not appear to increase the activity of the most prevalent B cell sialidase activity as measured in an in vitro assay system, suggesting that the major B cell sialidase may not be responsible for the alteration of B cell sialylation levels or the ability of activated B cells to interact more effectively with T cells. The possibility of intracellular compartmentalization of sialidase activity or that a minor B cell sialidase may play a role in the regulation of a B cells ability to interact with T cells are discussed.     

Effects of induced hypotension during experimental vasospasm: a neurological, electrophysiological, and pathological analysis

Vasospasm of the vertebrobasilar system was induced in seven dogs by the intracisternal injection of autologous blood. Somatosensory and brain stem auditory evoked potentials were recorded before and after the induction of angiographically confirmed vasospasm. Additionally, somatosensory evoked potentials were monitored during graded hypotension to 40 mm Hg. There was no significant alteration in the evoked potentials by vasospasm or hypotension. Detailed clinical examination and postmortem histopathological studies did not demonstrate any focal neurological deficit or infarction attributable to vasospasm. Previous studies have noted close correlations between decreased cerebral blood flow and evoked potential alterations. Induced hypotension to a mean arterial pressure of 40 mm Hg in the presence of documented vasospasm was not sufficient to cause evoked potential changes, focal neurological deficit, or pathological evidence of infarction in the canine model.     

Axial diffusion of retinol in isolated frog rod outer segments following substantial bleaches of visual pigment

Partial bleaches of rhodopsin were made in either the proximal or distal halves of isolated Rana pipiens rod outer segments. The fluorescence of all-trans retinol was recorded 15, 60 and 120 min following 17% and 63% bleaches. Some of the retinol that formed remained immobilized in the bleached halves of the outer segments, while another portion was slowly mobilized and diffused along the cell axis.     

Substance abuse and schizophrenia: effect on symptoms but not on neurocognitive function.

The authors compare symptoms and neuropsychological test performance in DSM-III schizophrenic patients who reported prior substance abuse (N = 38) with those in patients who reported no such abuse (N = 25) to determine the impact of substance abuse on the psychopathology of schizophrenia. Positive and negative symptom scores were derived from the Schedule for Affective Disorders and Schizophrenia. Sixty neuropsychological measures drawn from commonly used tests of intelligence, memory, learning, fluency, and problem solving were calculated. Separate analyses were performed on patients in a psychotic episode who were free of neuroleptics (N = 27) and on those taking maintenance neuroleptics (N = 36). Among unmedicated patients, those who reported prior substance abuse had significantly higher thought disorder scores. Among neuroleptic-medicated patients, hallucination and delusion scores were significantly higher in the patients who reported prior substance abuse. The substance abuse followed withdrawal from social relations and preceded the onset of positive symptoms. None of the neuropsychological tests discriminated between abusers and nonabusers.     

Frequent attendance at religious services and mortality over 28 years.

OBJECTIVES: This study analyzed the long-term association between religious attendance and mortality to determine whether the association is explained by improvements in health practices and social connections for frequent attenders. METHODS: The association between frequent attendance and mortality over 28 years for 5286 Alameda Country Study respondents was examined. Logistic regression models analyzed associations between attendance and subsequent improvements in health practices and social connections. RESULTS: Frequent attenders had lower mortality rates than infrequent attenders (relative hazard [RH] = 0.64;95% confidence interval [CI] = 0.53,0.77). Results were stronger for females. Health adjustments had little impact, but adjustments for social connections and health practices reduced the relationship (RH = 0.77; 95% CI = 0.64, 0.93). During follow-up, frequent attenders were more likely to stop smoking, increase exercising, increase social contacts, and stay married. CONCLUSIONS: Lower mortality rates for frequent religious attenders are partly explained by improved health practices, increased social contacts, and more stable marriages occurring in conjunction with attendance. The mechanisms by which these changes occur have broad intervention implications.     

Test-retest reliability of audio-taped phallometric stimuli with adolescent sexual offenders

Twenty adolescent male sexual offenders were evaluated by penile plethysmography on two separate occasions. Stimuli consisted of 19, two-minute audiotaped cues. Test-retest reliability was demonstrated for 15 of the 19 audiotaped vignettes. The highest correlations were found for those sexual behaviors in which the adolescents had engaged.     

The role of morphogens in endochondral ossification

Summary The formation of bone occurs normally by one of two developmental processes: intramembranous or endochondral ossification. Endochondral ossification occurs in the morphogenesis of the limb buds and growth plates, and in the regeneration of bone following injury (fracture callus). Two classes of diffusible morphogen-like molecules (MLMs) involved in limb development are the bone morphogenetic proteins (BMPs) and retinoic acid (RA). These MLMs are associated, respectively, with the apical ectodermal ridge (AER) and the zone of polarizing activity (ZPA) of the primitive limb bud. They function as potent regulators of pattern formation and are involved in tissue proliferation and differentiation. The presence of endochondral ossification in fracture callus suggests a role for MLMs in that process as well. To date, virtually nothing is known about the role of morphogens in the regeneration of bone (fracture healing). In this article, we review the current knowledge of MLMs in bone formation and propose a theory on their role in fracture healing. We hypothesize that MLMs involved in fracture healing may also express spatial and temporal information. A more complete understanding of the role of morphogens in both limb development and fracture healing is of major importance to practicing orthopedists and their patients.