Antigenic and virulence properties of Pasteurella haemolytica leukotoxin mutants.

Antigenic properties of two mutants of Pasteurella haemolytica, strains 59B0071 and 59B0072, that do not produce detectable leukotoxin were investigated. Western blot (immunoblot) analysis with a number of polyclonal sera from animals recovering from pasteurellosis revealed that both mutants secreted a variety of antigens that were also present in cultures of several wild-type strains. These antigens ranged from about 100 to 15 kDa. Mutant strain 59B0071 was found to be totally deficient in leukotoxin, as judged not only by Western blotting but also by cytotoxicity assays with bovine lymphoma (BL-3) cells or bovine polymorphonuclear cells as targets. The mutant strain 59B0071 had normal levels of a secreted sialylglycoprotease, however. When strains were tested for virulence in goat and cattle challenge experiments, a reduction in mortality and lung lesions was observed with the mutant 59B0071 in comparison with results obtained with wild-type strains. These results are consistent with an important role for leukotoxin in P. haemolytica virulence and suggest that leukotoxin-negative mutants may be useful tools in the investigation of other virulence properties involved in P. haemolytica infections.     

Relationship between baroreflex sensitivity, renin suppression and natriuresis in salt-sensitive rabbits.

This study determined the influence of baroreflex sensitivity (BRS) on the rate of urinary sodium excretion and plasma renin activity (PRA) in response to a saline infusion in conscious male rabbits specifically bred for high (Group I; n = 7) and low (Group II; n = 10) BRS and in seven control animals. Only Group II showed significant increases in blood pressure on a chronic high-salt intake. After ensuring that each animal was in sodium balance, a (0.7-0.9%) saline infusion of 3-4 ml/kg per h for 90 min (25% daily sodium intake for each rabbit) was given and urine collected at 15-min intervals via a bladder catheter. No differences were found in control urine volumes, urinary sodium or PRA. Group I excreted over 50% of the sodium load and Group II less than 20% within 90 min. PRA fell by more than 30% within 30 min in six Group I rabbits but decreased by less than 30% or increased in Group II. In the control animals, sodium excretion rates and PRA suppression were also much greater in those with high BRS. A highly significant correlation (r = 0.808, P less than 0.01) was found between the per cent of the sodium load excreted and BRS. It is suggested that the delayed sodium excretion and blood pressure elevation in salt-sensitive subjects may be due to a genetic impairment in baroreflex control of renal sympathetic nerve activity.     

Effects of the antimigraine compound zolmitriptan ('Zomig') on psychomotor performance alone and in combination with diazepam in healthy volunteers

Zolmitriptan (Zomig^TM) is a 5HT_1B/1D agonist which has the ability to cross the intact blood-brain barrier to access central as well as peripheral receptors. Because of the potential for central nervous system side effects, this randomized, double-blind, placebo-controlled, 6-period crossover study evaluated the effects of 2.5 and 5 mg doses of zolmitriptan on psychomotor performance and investigated any pharmacodynamic or pharmacokinetic interaction with diazepam. Twelve healthy volunteers received the following "treatments" as single doses: zolmitriptan 2.5 mg, zolmitriptan 5 mg, diazepam 10 mg, zolmitriptan 2.5 mg+diazepam 10 mg, zolmitriptan 5 mg+diazepam 10 mg and placebo. Pre-dose and at 1, 4, 8, and 24 h post-dose, the following validated battery of psychomotor tests was performed: Bond-Lader visual analogue scales (calmness, contentedness, and alertness factors), critical flicker fusion test, choice reaction time (recognition, motor, and total reaction times), finger-tapping test, number cancellation test and digit symbol substitution test. Plasma concentrations of zolmitriptan, its active metabolite, and diazepam and its active metabolites were measured at the same timepoints. Zolmitriptan 2.5 and 5 mg had no effect on psychomotor function when given alone. In contrast, diazepam 10 mg had profound effects, consistent with its sedative properties, but there was no synergism on concomitant administration of either dose of zolmitriptan. Plasma concentrations of zolmitriptan, diazepam, and their respective active metabolites were similar when the two drugs were given alone or in combination.     

Indapamide inhibits endothelium-dependent contractions in the aorta of the spontaneously hypertensive rat

Summary— Experiments were designed to determine whether or not indapamide, an antihypertensive agent with vasodilator properties, inhibits endothelium-dependent contractions. Rings of aortae with and without endothelium from spontaneously hypertensive rats (SHR) were suspended in conventional organ chambers for the measurement of isometric force. Acetylcholine and adenosine diphosphate-β-S in the presence of a nitric oxide synthase inhibitor, caused endothelium-dependent contractions, which were inhibited by indapamide. The compound (10⁻⁴M) also slightly reduced the contractions of rings without endothelium evoked by U-46,619, which activates thromboxane-endoperoxide receptors. These results demonstrate that indapamide inhibits endothelium-dependent contractions in the SHR aorta, and suggest that the inhibition is due, at least in part, to the action of the drug on the hypertensive vascular smooth muscle.     

HIV seroincidence among patients at clinics for sexually transmitted diseases in nine cities in the United States

Although the numbers of newly reported diagnoses of AIDS decreased in the 1990s, it is not clear whether they reflect a decreasing number of new HIV infections. Direct measurement of HIV incidence through follow-up cohort studies is difficult and costly. We estimated HIV incidence and trends in incidence among men who have sex with men (MSM) and heterosexual men and women at clinics for sexually transmitted diseases (STDs) by using a recently developed serologic testing algorithm that requires only a single blood specimen. Cross-sectional anonymous serosurveys were conducted at 13 STD clinics in nine cities in the United States from 1991 through 1997. Before anonymous HIV testing, demographic and clinical information was abstracted. Of 129,774 specimens tested, 362 (0.28%) were from persons estimated to be recently infected. Incidence among MSM was 7.1% (95% confidence interval (CI): 4.8-10.3), 14 times higher than that among heterosexuals, which was 0.5% (CI: 0.4- 0.7). Incidence among MSM and heterosexuals remained unchanged during the time studied. Decreasing rates of new AIDS diagnoses in the 1990s do not reflect stable rates of new HIV infections among MSM and heterosexual patients attending these clinics.     

Effect of hemoglobin concentration variation on the accuracy and precision of glucose analysis using tissue modulated, noninvasive, in vivo Raman spectroscopy of human blood: a small clinical study

Tissue modulated Raman spectroscopy was used noninvasively to measure blood glucose concentration in people with type I and type II diabetes with HemoCue fingerstick measurements being used as reference. Including all of the 49 measurements, a Clarke error grid analysis of the noninvasive measurements showed that 72% were A range, i.e., clinically accurate, 20% were B range, i.e., clinically benign, with the remaining 8% of measurements being essentially erroneous, i.e., C, D, or E range. Rejection of 11 outliers gave a correlation coefficient of 0.80, a standard deviation of 22 mg/dL with p<0.0001 for N=38 and places all but one of the measurements in the A and B ranges. The distribution of deviations of the noninvasive glucose measurements from the fingerstick glucose measurements is consistent with the suggestion that there are at least two systematic components in addition to the random noise associated with shot noise, charge coupled device spiking, and human factors. One component is consistent with the known variation of fingerstick glucose concentration measurements from laboratory reference measurements made using plasma or whole blood. A weak but significant correlation between the deviations of noninvasive measurements from fingerstick glucose measurements and the test subject's hemoglobin concentration was also observed.     

Heligmosomoides polygyrus inhibits established colitis in IL-10-deficient mice

Inflammatory bowel disease (IBD) is prevalent in industrialized countries, but rare in less-developed countries. Helminths, common in less-developed countries, may induce immunoregulatory circuits protective against IBD. IL-10(-/-) mice given piroxicam develop severe and persistent colitis. Lamina propria mononuclear cells from colitic IL-10(-/-) mice released IFN-gamma and IL-12. The ongoing piroxicam-induced colitis could be partially blocked with anti-IL-12 monoclonal antibody suggesting that the inflammation was at least partly IL-12 dependent. Colonization of piroxicam-treated colitic IL-10(-/-) mice with Heligmosomoides polygyrus (an intestinal helminth) suppressed established inflammation and inhibited mucosal IL-12 and IFN-gamma production. H. polygyrus augmented mucosal IL-13, but not IL-4 or IL-5 production. Transfer of mesenteric lymph node (MLN) T cells from IL-10(-/-) animals harboring H. polygyrus into colitic IL-10(-/-) recipients inhibited colitis. MLN T cells from worm-free mice did not. Foxp3 (scurfin) drives regulatory T cell function. H. polygyrus enhanced Foxp3 mRNA expression in MLN T cells that had regulatory activity. This suggests that H. polygyrus inhibits ongoing IL-10(-/-) colitis in part through blocking mucosal Th1 cytokine production. Resolution of inflammation is associated with increased IL-13 production and can be adoptively transferred by MLN T cells.     

Diversity of ace, a gene encoding a microbial surface component recognizing adhesive matrix molecules, from different strains of Enterococcus faecalis and evidence for production of ace during human infections

Our previous work reported that most Enterococcus faecalis strains adhered to the extracellular matrix proteins collagen types I and IV and laminin after growth at 46 degrees C, but not 37 degrees C, and we subsequently identified an E. faecalis sequence, ace, that encodes a bacterial adhesin similar to the collagen binding protein Cna of Staphylococcus aureus. In this study, we examined the diversity of E. faecalis-specific ace gene sequences among different isolates obtained from various geographic regions as well as from various clinical sources. A comparison of nucleotide and deduced amino acid sequences of Ace from nine E. faecalis strains identified a highly conserved N-terminal A domain, followed by a variable B domain which contains two to five repeats of 47 amino acids in tandem array, preceded by a 20-amino-acid partial repeat. Using 17 other strains collected worldwide, the 5' region of ace that encodes the A domain was sequenced, and these sequences showed > or =97.5% identity. Among the previously reported five amino acids critical for collagen binding by Cna of S. aureus, four were found to be identical in Ace from all strains tested. Polyclonal immune rabbit serum prepared against recombinant Ace A derived from E. faecalis strain OG1RF detected Ace in mutanolysin extracts of seven of nine E. faecalis strains after growth at 46 degrees C; Ace was detected in four different molecular sizes that correspond to the variation in the B repeat region. To determine if there was any evidence to indicate that Ace might be produced under physiological conditions, we quantitatively assayed sera collected from patients with enterococcal infections for the presence of anti-Ace A antibodies. Ninety percent of sera (19 of 21) from patients with E. faecalis endocarditis showed reactivity with titers from 1:32 to >1:1,024; the only 2 sera which lacked antibodies to Ace A had considerably lower titers of antibodies to other E. faecalis antigens as well. Human-derived, anti-Ace A immunoglobulins G purified from an E. faecalis endocarditis patient serum inhibited adherence of 46 degrees C-grown E. faecalis OG1RF to collagen types I and IV and laminin. In conclusion, these results show that ace is highly conserved among isolates of E. faecalis, with at least four variants related to the differences in the B domain, is expressed by different strains during infection in humans, and human-derived antibodies can block adherence to these extracellular matrix proteins.