Flow-by induced hypoventilation in high spinal cord lesions--report of two cases.

Flow triggering in ventilators is an alternative to pressure triggering. Differences between these two trigger mechanisms may not be clinically significant in most patients. We report two patients with high spinal cord lesions in whom the use of flow triggering was unsuccessful. Severe muscle weakness in these patients made them sensitive to small changes in ventilator trigger characteristics.

Suppression of lymphocyte mitogenesis in different rat strains exposed to footshock during early diurnal and nocturnal time periods.

The present study examined stressor interactions with genotype and light/dark cycle. Male Brown Norway (BN), Fischer 344 (F344), Lewis (from two different vendors: Lew/CR and Lew/H) and Sprague Dawley (SD) rats were exposed to footshock either in the early light or early dark circadian phase. Immediately after footshock, the spleen and whole blood proliferation to PHA and Con A was assessed. To provide endocrine indices of stress, serum was measured for corticosterone and interleukin-6 (IL-6). All rats showed significant increases in serum corticosterone and IL-6 following footshock either in the light or the dark. Rat strain differences were noted in the IL-6 response, while the corticosterone response was strong for all strains. The criterion for 'suppression' of lymphocyte proliferation was p < .05 (as determined by ANOVA) compared to non-shocked controls. Spleen: with the exception of BN rats, the other strains showed suppressed spleen cell proliferation to PHA and Con A both in the light and the dark. BN rats failed to show suppression of mitogenic activity to PHA when footshock was given in the light. Peripheral blood lymphocytes: suppression in Lew rats from either vendor, and in F344 and BN rats, did not vary with time of day nor with the type of mitogen tested. SD rats did not show suppression to PHA if shocked in the light. These results highlight the generality of stressor-induced mitogenic lymphocyte proliferation during the early diurnal and nocturnal periods of the day.

Stress-induced alterations in interferon production and class II histocompatibility antigen expression.

Mild electric foot-shock has been shown to be a stressor that can alter immune responses. Male Lewis rats were exposed to one session of 16 5.0-s 1.6-mA foot-shocks. Production of interferon-gamma by splenocytes in response to concanavalin-A was decreased in spleens from the shocked rats compared to control spleens. Spleen cells from rats treated with nadolol, a peripherally acting beta-adrenergic receptor antagonist, and then shocked, showed dose-dependent attenuation of the suppression of interferon-gamma production. This suggests that catecholamines mediate shock-induced suppression of interferon-gamma production. The percentage of splenic mononuclear cells expressing class II histocompatibility (Ia) antigens on their surfaces from spleens of shocked rats was determined by flow cytometry. Significantly decreased class II positive mononuclear cells were present in the spleens of shocked rats in comparison to the spleens of control rats. This may reflect an alteration of cell trafficking or decreased production of class II antigens.

Stressor-induced changes in mitogenic activity are not associated with decreased interleukin 2 production or changes in lymphocyte subsets.

Splenic lymphocytes from Lewis rats that received presentations of physically aversive electric shock demonstrated a marked reduction in responsiveness to T-cell mitogens such as concanavalin A. This study examined cellular mechanisms which may be responsible for this functional alteration. There was no difference in distribution of T-cell subsets from shocked and nonshocked rats. There was no difference in the production of interleukin 2 (IL-2) nor was there a difference in the percentage of IL-2 receptor positive T cells or T-cell subsets after culture for 24 hr. However, there was a marked lack of mitogenic stimulation in splenocytes from shocked rats when stimulated with the calcium ionophore A23187. This indicates a defect in the biochemical pathways necessary to activate T-cell mitogenesis.

Shock-induced modulation of lymphocyte responsiveness and natural killer activity: differential mechanisms of induction.

The present study was designed to determine the influence of signaled shock on splenic natural killer (NK) activity and nonspecific T-lymphocyte mitogenic responsiveness. Furthermore, experiments were conducted to examine possible mechanisms mediating this suppression. The results demonstrate that a single session of signaled shock induces suppression of splenic NK activity and T-cell response to the mitogens concanavalin A (Con A) and phytohemagglutinin (PHA). However, the suppression of mitogenic responsiveness was attenuated after five daily sessions of shock, while NK activity remained suppressed. The suppression of NK function was prevented by administration of naltrexone prior to the shock session indicating mediation by opiate receptors. However, naltrexone did not prevent the shock induced suppression of mitogenic responsiveness to Con A or PHA. Diazepam was not effective in preventing the shock-induced suppression of mitogenic responses or NK activity. Collectively, these results demonstrate that mononuclear cell populations in the spleen are differentially affected by the same stressor and that the immune alterations are mediated via different pathways.

Practical procedure for demonstrating bacterial flagella.

We developed a simple, rapid method for demonstrating bacterial flagella with Ryu staining solution that gave satisfactory results for numerous motile and nonmotile bacteria. Two major advantages of this method are that the staining solution, ready for use, is stable at ambient temperature indefinitely and that microscopic examination of bacteria in the stained drop preparations can be performed rapidly.

Differentiation of Peptococcus and Peptostreptococcus by gas-liquid chromatography of cellular fatty acids and metabolic products.

Gas-liquid chromatographic (GLC) profiles of cellular fatty acids and metabolic products were useful in identifying strains of Peptococcus saccharolyticus, Peptococcus asaccharolyticus, Peptostreptococcus anaerobius, Peptostreptococcus micros, and Streptococcus intermedius. The GLC results supported the recent taxonomic decision to transfer aerotolerant Peptostreptococcus species to the genus Streptococcus. Because inconsistencies in the results prevented our differentiating Peptococcus prevotii. Peptococcus magnus, and Peptococcus variabilis by GLC, additional strains will have to been examined. These GLC techniques are amenable to routine use; however, for interlaboratory results to be meaningful, the classification and nomenclature of the anaerobic gram-positive cocci should be standardized.

Evaluation of Port-A-Cul transport system for protection of anaerobic bacteria.

The protection of anaerobes in Port-A-Cul (PAC) transport system (Bioquest, Div. of Becton, Dickinson &Co., Cockeysville, Md.) tubes and vials was studied. Ten species of obligately anaerobic bacteria commonly isolated from clinical specimens were used to prepare simulated swab and fluid specimens in high and low concentrations. Samples in PAC tubes and vials were held for 2, 24, and 48 h at ambient temperature and in a refrigerator. In addition, samples of the simulated specimens were exposed to controlled anaerobic and aerobic conditions in vented tubes and vials, with and without PAC medium, at ambient and refrigerator temperatures. Viable bacterial colony counts from specimens in PAC tubes and vials used as recommended by the manufacturer were consistently greater than those from specimens exposed to the different controlled conditions. The protection in PAC was about equal for specimens with either high or low concentrations of bacteria. Protection of the anaerobes in PAC was more obvious with swab than with fluid specimens. Quantitative recovery of anaerobes from refrigerated PAC samples, with few exceptions, was comparable to that from PAC samples held at ambient temperature.

Susceptibility of Clostridium ramosum to antimicrobial agents.

The susceptibility of 49 strains of Clostridium ramosum to 10 antibiotics was determined by agar dilution and disk diffusion tests. Results showed that, among the anaerobes, C. ramosum is second only to Bacteroides fragilis in its resistance to antimicrobial agents. All strains were susceptible to penicillin, carbenicillin, chloramphenicol, vancomycin, and metronidazole at readily achievable blood levels. Most strains (83%) were susceptible to erythromycin. There was a high level of resistance to clindamycin in 16% of the strains. All isolates were resistant to rifampin and gentamicin, and most were resistant to lincomycin. Assessment of susceptibility by measurement of inhibition zone diameters with disk diffusion tests was not satisfactory.