Physical activity and the initiation of high-risk health behaviors in adolescents

The association of physical activity to the initiation of health risk behaviors was examined in a 3-yr prospective study of a population-based cohort of 1245 adolescents aged 12-16 yr. Four hundred thirty-seven students (35% of the cohort) were identified at baseline via self-report survey as never having smoked cigarettes, consumed alcohol, used marijuana, or carried a weapon. Three measures of physical activity were obtained at baseline: leisure-time physical activity (LTPA), level of aerobic fitness (AF), and participation in competitive athletics. Significant associations, with notable gender differences, were observed between physical activity and the initiation of cigarette smoking and alcohol use. The cumulative proportion of male students initiating alcohol use was 48%, 42%, and 24% for high, moderate, and low LTPA, respectively (P < 0.01). Males who participated in competitive athletics were significantly more likely than nonathletes to initiate alcohol use (44% vs 17%, P < 0.01). The cumulative proportion of female students initiating cigarette use was 10%, 23%, and 22% for high, moderate, and low LTPA, respectively (P < 0.05) and 7%, 28%, and 16% for high, moderate, and low AF, respectively (P < 0.05). No association was found between physical activity and weapon carrying. These results indicate that in this cohort of adolescents, the most active or most fit females were less likely to initiate cigarette smoking. In contrast, the most active males or males who participated in competitive athletics appeared more at-risk for initiating alcohol consumption than their less active counterparts.

Measurement of anti-acetylcholine receptor auto-antibodies in myasthenia gravis

Two different acetylcholine receptor (AChR) preparations derived from amputated human muscle (AChRAMP) and from the human rhabdomyosarcoma cell line TE671 (AChRTE671) were compared in radio-immunoprecipitation assays for the detection of AChR auto-antibodies in serum specimens from 20 patients with proven myasthenia gravis. Tests performed with the AChRTE671 and AChRAMP antigen preparations were positive in all the patients and in 19/20 respectively. A high degree of correlation (r = 0.94) was evident between the two auto-antigen preparations. Assays based on the use of TE671-derived antigen represent a useful alternative to the conventional assay using AChRAMP for the detection of AChR auto-antibodies.

The politics of delegation

The American Nurses Association has stated that every patient needs a nurse, and they are right. But what do patients need a nurse to do? Politics has arisen around this issue in two ways: the development of new patient care delivery system models that use unlicensed assistive personnel to help professional staff, and a decrease in inpatient census has been seen throughout the country, resulting in changes in jobs and job locations. We argue that the best way to deal with these two factors is for nurses to redefine their functions, to focus on the professional aspects of care that only they can deliver and to keep open minds about where the delivery of services may take place. In the long run, this approach will take the profession much farther than blind adherence to outdated tradition.

Alanine as an end product during fermentation of monosaccharides by Clostridium strain P2

The thermophilic Clostridium P2 was isolated from a semi-continuously fed reactor with high ammonium concentration. This bacterium formed substantial amounts of L-alanine as a major fermentation product from glucose, fructose and mannose. Low amounts of acetate, butyrate, carbon dioxide and hydrogen were also formed. A high partial pressure of hydrogen inhibited the degradation of the monosaccharides, whereas hydrogen removal, in the form of methanogenesis was found to be stimulatory. However, the amount of alanine produced per mole of hexose degraded did not change. Hexose degradation and alanine production were favoured by high ammonium concentrations. Nuclear magnetic resonance spectroscopy studies provided strong evidence that an active Embden-Meyerhof-Parnas pathway existed and that alanine was produced via an amination of pyruvate.

Antibody-enhanced binding of dengue-2 virus to human platelets

The mechanisms underlying severe thrombocytopenia in dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) are not completely understood. We present here the first evidence that dengue type 2 virus binds to human platelets only in the presence of virus-specific antibody, supporting a role for immune-mediated clearance of platelets in the pathogenesis of thrombocytopenia in DHF/DSS. Antibody-enhanced binding of virus of platelets was also demonstrated with a panel of eight murine monoclonal antibodies specific for the dengue E protein. The degree of binding was dependent on the antibody used but not on the antibody IgG subclass, indicating that factors other than the platelet Fc receptor are involved in binding of virus-antibody complexes to the platelet surface. Confirmation that antibody-dependent virus binding to platelets is not primarily mediated by the platelet Fc receptor was obtained by demonstrating good binding even when platelets were pretreated with the Fc gamma RII-specific antibody IV.3.

Population pharmacokinetics of stavudine (d4T) in patients with AIDS or advanced AIDS-related complex

The population pharmacokinetics and bioavailability of oral stavudine (d4T; 2',3'-dideoxy-3'-deoxythymidine) was determined in 81 patients with AIDS or AIDS-related complex (ARC) enrolled in phase I and phase I/II dose-ranging trials. Each patient underwent inpatient pharmacokinetic studies following administration of the first oral stavudine dose; 59 patients were restudied after chronic therapy for an average of 19 days. Thirty-three of these patients also received a single intravenous stavudine dose prior to starting an oral regimen. A two-compartment model with first-order absorption and elimination was used as the structural pharmacokinetic model. A basic model provided the following population parameter estimates (interpatient variability expressed in parentheses as percent coefficient of variation): clearance/bioavailability = 30.9 (24.5%) liters/h; volume of distribution/bioavailability = 8.42 (not modeled) liters; volume of distribution at steady state/bioavailability = 68.9 (105%) liters; intercompartmental clearance/bioavailability = 12.4 (26%) liters/h; and first-order absorption rate constant = 1.32 (78.9%) liters/h. In the subset of 33 patients receiving both intravenous and oral doses, the bioavailability of stavudine was estimated to be 99.1% (18.5%). Total body weight, stage of disease (AIDS versus ARC), and an oral stavudine dose of > or = 200 mg were found to have a statistically significant but a clinically marginal effect on the estimate of the oral clearance of stavudine. This analysis shows the high degree of bioavailability of stavudine in patients with AIDS and ARC and the relatively low degree of interpatient variability in oral drug clearance compared with those of other nucleosides. Population pharmacokinetic analysis is a useful tool for assessing the combined effects of several patient variables on the pharmacokinetic properties of drugs in human immunodeficiency virus-infected patients.

The pro-oxidative riminophenazine B669 neutralizes the inhibitory effects of Mycobacterium tuberculosis on phagocyte antimicrobial activity

The effects of clofazimine, a riminophenazine antimicrobial agent, and its analogue B669 on phagocyte functions have been investigated. Clofazimine, at concentrations attainable in vivo, and B669, in particular, increased the intracellular killing ability of phagocytes following appropriate cell stimulation. Similarly, nitro blue tetrazolium reduction, hydrogen peroxide production, lysosyme release and hexose monophosphate shunt activity were all increased by treating phagocytes with the riminophenazines. It has previously been shown that a 25 kDa glycolipoprotein derived from Mycobacterium tuberculosis inhibits phagocyte functions associated with phagocyte antimicrobial activity. The present study confirms these observations. A further aspect of the study examined the ability of riminophenazines to reverse the inhibition of phagocyte functions by the 25 kDa mycobacterial fraction. Whilst both riminophenazines were capable of partially but significantly reversing the inhibition due to the mycobacterial fraction, the restorative capacity of B669 was greater than that of clofazimine.

Chronic inhalation studies of man-made vitreous fibres: characterization of fibres in the exposure aerosol and lungs

Inhalation studies were conducted to determine the chronic biological effects in rodents of respirable fractions of different man-made vitreous fibres (MMVFs), including refractory ceramic fibre (RCF), fibrous glass, rock (stone) wool and slag wool. Animals were exposed nose-only, 6 h per day, 5 days per week, for 18 months (hamsters) or 24 months (rats). Exposure to 10 mg m-3 of crocidolite or chrysotile asbestos induced pulmonary fibrosis, lung tumours and mesothelioma in rats, thus validating the inhalation model with known human carcinogenic fibres. Exposure of rats to 30 mg m-3 of refractory ceramic fibres (RCF) also resulted in pulmonary fibrosis as well as significant increases in lung tumours and mesothelioma. In hamsters, 30 mg m-3 of RCF induced a 41% incidence of mesotheliomas. Exposure of rats to 30 mg m-3 of fibre glasses (MMVF 10 or 11) or of slag wool (MMVF 22) was associated with an inflammatory response, but no mesotheliomas or significant increase in the lung tumours were observed. Rock wool (stone wool: MMVF 21) at the same exposure level resulted in minimal lung fibrosis, but no mesotheliomas or significant increase in the lung tumours were observed. Fibre numbers (WHO fibres) and dimensions in the aerosols and lungs of exposed animals were comparable in this series of inhalation studies. Differences in lung fibre burdens and lung clearance rates could not explain the differences observed in the toxicologic effects of the MMVFs. These findings indicate that dose, dimension and durability may not be the only determinants of fibre toxicity. Chemical composition and the surface physico-chemical properties of the fibres may also play an important role.

Role of social class in excess black stroke mortality

BACKGROUND AND PURPOSE

It has been suggested that a substantial proportion of the excess stroke mortality among black Americans may be attributable to relatively lower socioeconomic status (SES) in this group. In this report we provide the first quantitative estimates of the proportion of excess black stroke mortality attributable to SES for a large population-based cohort.

METHODS

We used data from the National Longitudinal Mortality Study for persons 45 years and older (73,400 white men, 87,528 white women, 6522 black men, and 8816 black women). Sex-specific proportional hazards model were used to estimate excess black stroke mortality with and without adjustment for education and income (measures of SES). The contribution of SES to the excess black stroke risk was estimated from the difference in regression coefficients for race in these models.

RESULTS

In men, low SES was associated with increased stroke mortality (P < or = .0001) and accounted for 14% to 46% of the excess black stroke risk (P < .05). However, we could find no association between SES and stroke mortality in women, and SES did not account for a significant proportion of the excess stroke mortality in black women.

CONCLUSIONS

Although SES proved to account for a statistically significant proportion of excess male black stroke mortality, overall SES explained less than one quarter of the observed excess between ages 45 and 65. In women, SES did not significantly reduce the estimated excess black stroke mortality. Although SES may be playing a role in excess black stroke mortality, a substantial proportion of the excess appears attributable to other sources, including cerebrovascular risk factors that are unrelated to SES, unmeasured lifestyle influences, social resources, and genetic factors.

Evaluation of the oncogenic potential of man-made vitreous fibres: the inhalation model

A rodent inhalation model has been developed for the evaluation of the eoncogenic potential of man-made vitreous fibres. It is successful in delivering a quantified dose of well-characterized fibres to the lungs of rodents, and with it sufficiently high fibre aerosol concentrations were lofted to enable a maximum tolerated dose to be achieved. Fischer 344 male rats were exposed to a well-defined rat-respirable aerosol at concentrations for MMVF of 30, 16 or 3 mg m-3, 6 h per day, 5 days per week for 104 weeks with final sacrifice at 20% survival. A control group was exposed to filtered air. The high dose was chosen based upon a 28-day maximum tolerated dose study with refractory ceramic fibres (RCF). The fibre aerosol generation system lofted fibres without breaking, grinding or contaminating the bulk material. Exposure was by flow-past nose-only systems which provided fresh fibre in a laminar stream to each animal individually. The study was performed according to the Good Laboratory Practice regulations. Fibre count, fibre diameter and length distribution, aerosol mass and chemical composition were determined throughout the study. Interim sacrifices were performed at 3 or 6 month intervals for 24 months. At each sacrifice, full necropsy was performed, the accessory lobe removed for subsequent digestion to determine the fibre lung burden and the remaining lobes inflated with fixative for histopathological evaluation. The lungs were evaluated by a pathologist and graded for the degree of macrophage infiltration, bronchiolization, fibrosis and pleural thickening, and were also scored according to the Wagner scale. Lesions were evaluated according to the number of adenomas, carcinomas and mesotheliomas. The accessory lobe was digested by low-temperature plasma ashing and the number, size distribution and chemical composition of the fibres determined. This model provides a sensitive and reproducible method for evaluating existing and new fibres. A variety of different of ceramic, glass, rockwool and slagwood fibres have been evaluated with this model.

Augmentative inhibition of lymphocyte proliferation by cyclosporin A combined with the riminophenazine compounds clofazimine and B669

We have investigated the effects of cyclosporin A (CsA, 3-50 ng/ml) in combination with the riminophenazine agents clofazimine and B669 (60-500 ng/ml) on the mitogen- and alloantigen-activated proliferative responses of human mononuclear leukocytes (MNL), as well as on the phospholipase A2 and Na+, K+- adenosine triphosphatase activities of these cells. When used in combination these agents caused inhibition of the proliferative responses of both mitogen- and alloantigen-activated MNL which was at least additive. Combinations of CsA with the riminophenazines also caused augmentative activation of PLA2 and inhibition of Na+, K+-ATPase. The inhibitory effects of these agents, both individually and in combination, on the Na+, K+-ATPase and proliferative responses of MNL were neutralized by the membrane-stabilizing, lysophospholipid complex-forming agent alpha-tocopherol (vitamin E, 20 microgram/ml). These observations suggest that combinations of CsA with riminophenazines cause interactive enhancement of the activity of PLA2 in MNL leading to lysophospholipid-mediated inactivation of Na+, K+-ATPase and consequent inhibition of the proliferative responses of these cells. In the therapeutic setting combinations of these agents may enable reduction in the dose of CsA required to achieve meaningful immunosuppression with a consequent decrease in the risk of chemotherapy-related organ toxicity.

The bidirectional interaction between ventral tegmental rewarding and hindbrain aversive stimulation effects in the rat

We used the curve-shift procedure in self-stimulating rats to examine the interaction of aversive and rewarding electrical stimuli in terms of duration and direction. The subjects were implanted with two moveable electrodes, one in a region supporting self-stimulation (the ventral tegmental area, VTA) and another in a region supporting escape (the nucleus reticularis gigantocellularis, Gi). The function relating self-stimulation rate to pulse frequency (RF function) was first obtained and then replicated in a condition where each VTA pulse was followed 0.2 or 2.0 ms later by a Gi pulse. The intensity of Gi pulses was set at a value previously found to elicit escape within less than 5 sec. The following observations were made: (1) rats self-stimulated consistently, despite the presence of Gi pulses, (2) the presence of Gi pulses shifted the RF function rightward (decreased the rewarding efficacy of VTA stimulation), with little effect on the maximum rate, (3) after 2 to 5 VTA-Gi self-stimulation sessions, the Gi pulses progressively lost their ability to shift the RF function, and (4) at the end of testing, escape was no longer detectable using Gi pulses alone. It was concluded that (1) the interaction between rewarding VTA and aversive Gi stimulation effects is bidirectional, thus suggesting the presence of algebraic summation; (2) the effect of Gi on VTA reward is transient whereas that of VTA on Gi aversion cumulates and eventually results in total abolition of Gi aversion. The present study represents the first account of cumulative and long-lasting suppression of aversion following brain stimulation in the rat.

Plasma levels of beta-carotene are inversely correlated with circulating neutrophil counts in young male cigarette smokers

Relationships between plasma levels of beta-carotene (BC) and the numbers and oxidant-generating activities of circulating neutrophils have been investigated in a group of asymptomatic young male cigarette smokers (N = 40) and in a group of nonsmoking control subjects. Plasma BC levels were measured using HPLC, while oxidant generation was measured using a phorbol myristate acetate (PMA) activated whole blood luminol-enhanced chemiluminescence (LECL) method. Relative to nonsmokers, the numbers of circulating neutrophils, as well as the LECL responses of these cells, were increased by 41% (p = 0.0001) and 47% (p = 0.004), respectively, while plasma BC levels were decreased by 24% (p = 0.01). In cigarette smokers, but not in nonsmokers, the numbers of circulating neutrophils, as well as the LECL responses of these cells, were significantly and inversely correlated with plasma BC levels (r = -0.36, p = 0.02; and r = -0.33, P = 0.04 respectively). Diminished plasma levels of BC in cigarette smokers probably reflect the increased numbers and prooxidative activities of circulating neutrophils. Intake of this antioxidant nutrient may be a determinant of susceptibility to smoking-related pulmonary dysfunction mediated by oxidants derived from smoke-activated phagocytes.

Anterior tibial tendon rupture

Twelve patients with rupture of the anterior tibial tendon are presented. Nine patients were aware of an acute event prior to their symptom onset and three were not aware of any acute event. Complete rupture of the tendon was noted in 10 patients and incomplete rupture was seen in two patients. Treatment was individualized based on age, etiology, preinjury function, patient health, and personal considerations. Five patients were treated without surgery. Three preferred no orthotic devices, and two believed their function was improved with an ankle-foot orthosis. Seven patients were treated operatively using a variety of individualized reconstructive techniques. All operatively treated patients demonstrated increased function and strength. Based on our findings, operative reconstruction is recommended in appropriate patients.

Contribution of visceral fat mass to the insulin resistance of aging

Recent studies have shown that central obesity (increased waist to hip ratio [WHR]) is related to insulin resistance and aging. Furthermore, in central-obesity states, the intraabdominal fat (IAF) depot has been postulated to contribute most to the development of insulin resistance. Therefore, the observed insulin resistance of aging may be related more to changes in body composition than to aging per se. The purpose of this study was to explore the association of IAF with age and insulin sensitivity (SI) after controlling for obesity. We examined 60 healthy nondiabetic subjects (normal 75-g oral glucose tolerance test, aged 23 to 83, 15 men and 45 women). We chose subjects so that those < or = 125% and greater than 125% of ideal body weight were equally represented in each age decade. We quantified total and subcutaneous abdominal fat and IAF at the umbilicus using a validated magnetic resonance imaging (MRI) scanning technique and determined SI using a modified minimal model. IAF correlated significantly with age (r = .49, P = .0001) in the group as a whole, as well as in men (r = .58, P = .022) and women (r = .48, P = .0008) separately. In all subjects, SI was significantly related to IAF (r = -.50, P < .0001) but was not related to age (r = .00, P = .98). In multivariate analysis for various combinations of age, sex, and measures of fat distribution, WHR accounted for 28% and IAF for 51% of the variance in SI, whereas age, sex, and interactions of age and sex accounted for only 1%.(ABSTRACT TRUNCATED AT 250 WORDS)

An in vitro investigation of the bioactivities of ciprofloxacin and the new fluoroquinolone agents clinafloxacin (CI-960) and PD 131628 against Mycobacterium tuberculosis in human macrophages

In this study the intracellular bioactivity of ciprofloxacin and the new fluoroquinolone agents clinafloxacin (CI-960) and PD 131628 against Mycobacterium tuberculosis (H37Rv) was compared with rifampicin using human macrophages. Monocyte-derived macrophages were infected with M. tuberculosis in the presence of 10% autologous serum and treated with the antibiotics for 2 days, either immediately after infection or 3 days post-infection. The survival of the intracellular microorganisms was determined using the BACTEC tuberculosis system. Clinafloxacin, although not as active, compared favourably with rifampicin at concentrations ranging from 0.1 to 5 micrograms/ml in both systems, whereas PD 131628 performed reasonably well only when added directly after infection. However, ciprofloxacin was relatively unimpressive with intracellular bioactivity detected only with the highest concentration used (5 micrograms/ml). The ability of clinafloxacin, but not PD 131628, to inhibit mycobacteria after most of the organisms have escaped from the fused phagosomes emphasizes the importance of using a prolonged incubation time after infection when screening new antituberculosis drugs for intracellular bioactivity.

On the mechanism of skin wound "contraction": a granulation tissue "knockout" with a normal phenotype

This report explores the mechanism of spontaneous closure of full-thickness skin wounds. The domestic pig, often used as a human analogue for skin wound repair studies, closes these wounds with kinetics similar to those in the guinea pig (mobile skin), even though the porcine dermis on the back is thick and nearly immobile. In the domestic pig, as in the guinea pig, daily full-thickness excisions of the central granulation tissue up to but not including the wound edges in both back and flank wounds do not alter the rate or completeness of wound closure or the final pattern of the scar. A purse-string mechanism of closure was precluded by showing that surgical interruption of wound edge continuity does not alter closure kinetics or wound shape. We conclude that "tightness" of skin is not a key factor nor is the central granulation tissue required for normal wound closure. These data imply that in vitro models such as contraction of isolated granulation tissue or of the cell-populated collagen lattice may not be relevant for understanding the cell biology of in vivo wound closure. Implications for the mechanism for wound closure are discussed.