An essential role for interferon gamma in resistance to Mycobacterium tuberculosis infection

Tuberculosis, a major health problem in developing countries, has reemerged in recent years in many industrialized countries. The increased susceptibility of immunocompromised individuals to tuberculosis, and many experimental studies indicate that T cell-mediated immunity plays an important role in resistance. The lymphokine interferon gamma (IFN-gamma) is thought to be a principal mediator of macrophage activation and resistance to intracellular pathogens. Mice have been developed which fail to produce IFN-gamma (gko), because of a targeted disruption of the gene for IFN-gamma. Upon infection with Mycobacterium tuberculosis, although they develop granulomas, gko mice fail to produce reactive nitrogen intermediates and are unable to restrict the growth of the bacilli. In contrast to control mice, gko mice exhibit heightened tissue necrosis and succumb to a rapid and fatal course of tuberculosis that could be delayed, but not prevented, by treatment with exogenous recombinant IFN-gamma.

Immunology of tuberculosis

The resurgence of tuberculosis worldwide has intensified research efforts directed at examining the host defense and pathogenic mechanisms operative in Mycobacterium tuberculosis infection. This review summarizes our current understanding of the host immune response, with emphasis on the roles of macrophages, T cells, and the cytokine/chemokine network in engendering protective immunity. Specifically, we summarize studies addressing the ability of the organism to survive within macrophages by controlling phagolysosome fusion. The recent studies on Toll-like receptors and the impact on the innate response to M. tuberculosis are discussed. We also focus on the induction, specificity, and effector functions of CD4(+) and CD8(+) T cells, and the roles of cytokines and chemokines in the induction and effector functions of the immune response. Presentation of mycobacterial antigens by MHC class I, class II, and CD1 as well as the implications of these molecules sampling various compartments of the cell for presentation to T cells are discussed. Increased attention to this disease and the integration of animal models and human studies have afforded us a greater understanding of tuberculosis and the steps necessary to combat this infection. The pace of this research must be maintained if we are to realize an effective vaccine in the next decades.

Stimulation of bone formation in vitro and in rodents by statins

Osteoporosis and other diseases of bone loss are a major public health problem. Here it is shown that the statins, drugs widely used for lowering serum cholesterol, also enhance new bone formation in vitro and in rodents. This effect was associated with increased expression of the bone morphogenetic protein-2 (BMP-2) gene in bone cells. Lovastatin and simvastatin increased bone formation when injected subcutaneously over the calvaria of mice and increased cancellous bone volume when orally administered to rats. Thus, in appropriate doses, statins may have therapeutic applications for the treatment of osteoporosis.

Tumor necrosis factor-alpha is required in the protective immune response against Mycobacterium tuberculosis in mice

Understanding the immunological mechanisms of protection and pathogenesis in tuberculosis remains problematic. We have examined the extent to which tumor necrosis factor-alpha (TNF alpha) contributes to this disease using murine models in which the action of TNF alpha is inhibited. TNF alpha was neutralized in vivo by monoclonal antibody; in addition, a mouse strain with a disruption in the gene for the 55 kDa TNF receptor was used. The data from both models established that TNF alpha and the 55 kDa TNF receptor are essential for protection against tuberculosis in mice, and for reactive nitrogen production by macrophages early in infection. Granulomas were formed in equal numbers in control and experimental mice, but necrosis was observed only in mice deficient in TNF alpha or TNF receptor. TNF alpha and the 55 kDa TNF receptor are necessary conditions for protection against murine M. tuberculosis infection, but are not solely responsible for the tissue damage observed.

Killing of virulent Mycobacterium tuberculosis by reactive nitrogen intermediates produced by activated murine macrophages

Tuberculosis remains one of the major infectious causes of morbidity and mortality in the world, yet the mechanisms by which macrophages defend against Mycobacterium tuberculosis have remained obscure. Results from this study show that murine macrophages, activated by interferon gamma, and lipopolysaccharide or tumor necrosis factor alpha, both growth inhibit and kill M. tuberculosis. This antimycobacterial effect, demonstrable both in murine macrophage cell lines and in peritoneal macrophages of BALB/c mice, is independent of the macrophage capacity to generate reactive oxygen intermediates (ROI). Both the ROI-deficient murine macrophage cell line D9, and its ROI-generating, parental line J774.16, expressed comparable antimycobacterial activity upon activation. In addition, the oxygen radical scavengers superoxide dismutase (SOD), catalase, mannitol, and diazabicyclooctane had no effect on the antimycobacterial activity of macrophages. These findings, together with the results showing the relative resistance of M. tuberculosis to enzymatically generated H2O2, suggest that ROI are unlikely to be significantly involved in killing M. tuberculosis. In contrast, the antimycobacterial activity of these macrophages strongly correlates with the induction of the L-arginine-dependent generation of reactive nitrogen intermediates (RNI). The effector molecule(s) that could participate in mediating this antimycobacterial function are toxic RNI, including NO, NO2, and HNO2, as demonstrated by the mycobacteriocidal effect of acidified NO2. The oxygen radical scavenger SOD adventitiously perturbs RNI production, and cannot be used to discriminate between cytocidal mechanisms involving ROI and RNI. Overall, our results provide support for the view that the L-arginine-dependent production of RNI is the principal effector mechanism in activated murine macrophages responsible for killing and growth inhibiting virulent M. tuberculosis.

Sonic hedgehog--regulated oligodendrocyte lineage genes encoding bHLH proteins in the mammalian central nervous system

During development, basic helix-loop-helix (bHLH) proteins regulate formation of neurons from multipotent progenitor cells. However, bHLH factors linked to gliogenesis have not been described. We have isolated a pair of oligodendrocyte lineage genes (Olg-1 and Olg-2) that encode bHLH proteins and are tightly associated with development of oligodendrocytes in the vertebrate central nervous system (CNS). Ectopic expression of Olg-1 in rat cortical progenitor cell cultures promotes formation of oligodendrocyte precursors. In developing mouse embryos, Olg gene expression overlaps but precedes the earliest known markers of the oligodendrocyte lineage. Olg genes are expressed at the telencephalon-diencephalon border and adjacent to the floor plate, a source of the secreted signaling molecule Sonic hedgehog (Shh). Gain- and loss-of-function analyses in transgenic mice demonstrate that Shh is both necessary and sufficient for Olg gene expression in vivo.

Body mass index, waist circumference and waist:hip ratio as predictors of cardiovascular risk--a review of the literature

Overweight and obesity have become a major public health problem in both developing and developed countries as they are causally related to a wide spectrum of chronic diseases including type II diabetes, cardiovascular diseases and cancer. However, uncertainty regarding the most appropriate means by which to define excess body weight remains. Traditionally, body mass index (BMI) has been the most widely used method by which to determine the prevalence of overweight in, and across, populations as well as an individual's level of risk. However, in recent years, measures of central obesity, principally waist circumference and the waist:hip ratio and to a lesser extent the waist:height ratio, which more accurately describe the distribution of body fat compared with BMI, have been suggested to be more closely associated with subsequent morbidity and mortality. There is also uncertainty about how these measures perform across diverse ethnic groups; earlier, most of the evidence regarding the relationships between excess weight and risk has been derived chiefly from Caucasian populations, and hence, it remains unclear whether the relationships are consistent in non-Caucasian populations. The purpose of this review, therefore, is to provide an overview of the current evidence-base focusing predominantly on three main questions: (1) Which, if any, of the commonly used anthropometric measures to define excess weight is more strongly associated with cardiovascular risk? (2) Which of the anthropometric measures is a better discriminator of risk? and (3) Are there any notable differences in the strength and nature of these associations across diverse ethnic groups?

Optimization of differential immunogold-silver and peroxidase labeling with maintenance of ultrastructure in brain sections before plastic embedding

The limited success of immunogold labeling for pre-embedding immunocytochemistry of neuronal antigens is largely attributed to poor penetration of large (5-20 nm) colloidal gold particles. We examined the applicability of using silver intensification of 1 nm colloidal gold particles non-covalently bound to goat anti-rabbit immunoglobulin (1) for single labeling of a rabbit antiserum against the catecholamine synthesizing enzyme, tyrosine hydroxylase (TH), and (2) for immunogold localization of rabbit anti-TH simultaneously with immunoperoxidase labeling of a mouse monoclonal antibody against the opiate peptide, leucine-enkephalin (LE). Vibratome sections were collected from acrolein fixed brains of adult rats. These sections were immunolabeled without use of freeze-thawing or other methods that enhance penetration, but damage ultrastructure. By light microscopy, incubations in the silver intensifier (Intense M, Janssen) for less than 10 min at room temperature resulted in a brownish-red reaction product for TH. This product was virtually indistinguishable from that seen using diaminobenzidine reaction for detection of peroxidase immunoreactivity. Longer incubations produced intense black silver deposits that were more clearly distinguishable from the brown immunoperoxidase labeling. However, by light microscopy, the gold particles seen by electron microscopy were most readily distinguished from peroxidase reaction product with shorter silver intensification periods. The smaller size of gold particles with shorter periods of silver intensification also facilitated evaluation of labeling with respect to subcellular organelles. Detection of the silver product did not appear to be appreciably changed by duration of post-fixation in osmium tetroxide. In dual-labeled sections, perikarya and terminals exhibiting immunogold-silver labeling for TH were distinct from those containing immunoperoxidase labeling for LE. These results (1) define the conditions needed for optimal immunogold-silver labeling of antigens while maintaining the ultrastructural morphology in brain, and (2) establish the necessity for controlled silver intensification for light or electron microscopic differentiation of immunogold-silver and peroxidase reaction products and for optimal subcellular resolution.

Prospective study of cigarette smoking, alcohol use, and the risk of diabetes in men

OBJECTIVE

To examine the association between smoking, alcohol consumption, and the incidence of non-insulin dependent diabetes mellitus in men of middle years and older.

DESIGN

Cohort questionnaire study of men followed up for six years from 1986.

SETTING

The health professionals' follow up study being conducted across the United States.

SUBJECTS

41,810 male health professionals aged 40-75 years and free of diabetes, cardiovascular disease, and cancer in 1986 and followed up for six years.

MAIN OUTCOME MEASURE

Incidence of non-insulin dependent diabetes mellitus diagnosed in the six years.

RESULTS

During 230,769 person years of follow up 509 men were newly diagnosed with diabetes. After controlling for known risk factors men who smoked 25 or more cigarettes daily had a relative risk of diabetes of 1.94 (95% confidence interval 1.25 to 3.03) compared with non-smokers. Men who consumed higher amounts of alcohol had a reduced risk of diabetes (P for trend < 0.001). Compared with abstainers men who drank 30.0-49.9 g of alcohol daily had a relative risk of diabetes of 0.61 (95% confidence interval 0.44 to 0.91).

CONCLUSIONS

Cigarette smoking may be an independent, modifiable risk factor for non-insulin dependent diabetes mellitus. Moderate alcohol consumption among healthy people may be associated with increased insulin sensitivity and a reduced risk of diabetes.

Effects of tumor necrosis factor alpha on host immune response in chronic persistent tuberculosis: possible role for limiting pathology

Reactivation of latent tuberculosis contributes significantly to the incidence of disease caused by Mycobacterium tuberculosis. The mechanisms involved in the containment of latent tuberculosis are poorly understood. Using the low-dose model of persistent murine tuberculosis in conjunction with MP6-XT22, a monoclonal antibody that functionally neutralizes tumor necrosis factor alpha (TNF-alpha), we examined the effects of TNF-alpha on the immunological response of the host in both persistent and reactivated tuberculous infections. The results confirm an essential role for TNF-alpha in the containment of persistent tuberculosis. TNF-alpha neutralization resulted in fatal reactivation of persistent tuberculosis characterized by a moderately increased tissue bacillary burden and severe pulmonic histopathological deterioration that was associated with changes indicative of squamous metaplasia and fluid accumulation in the alveolar space. Analysis of pulmonic gene and protein expression of mice in the low-dose model revealed that nitric oxide synthase was attenuated during MP6-XT22-induced reactivation, but was not totally suppressed. Interleukin-12p40 and gamma interferon gene expression in TNF-alpha-neutralized mice was similar to that in control mice. In contrast, interleukin-10 expression was augmented in the TNF-alpha-neutralized mice. In summary, results of this study suggest that TNF-alpha plays an essential role in preventing reactivation of persistent tuberculosis, modulates the pulmonic expression of specific immunologic factors, and limits the pathological response of the host.

Effects of nitric oxide synthase inhibitors on murine infection with Mycobacterium tuberculosis

We have recently demonstrated that the macrophage L-arginine-dependent cytotoxic pathway effectively kills the virulent Erdman strain of Mycobacterium tuberculosis in vitro via the generation of toxic reactive nitrogen intermediates by the enzyme nitric oxide synthase. This report demonstrates that two distinct inhibitors of nitric oxide synthase (aminoguanidine and NG-monomethyl-L-arginine) render similar deleterious effects on tuberculous infection in mice, as assessed by mortality, bacterial burden, and pathological tissue damage, thus confirming the importance of reactive nitrogen intermediates in resistance against M. tuberculosis.

Rapid assessment of drug susceptibilities of Mycobacterium tuberculosis by means of luciferase reporter phages

Effective chemotherapy of tuberculosis requires rapid assessment of drug sensitivity because of the emergence of multidrug-resistant Mycobacterium tuberculosis. Drug susceptibility was assessed by a simple method based on the efficient production of photons by viable mycobacteria infected with specific reporter phages expressing the firefly luciferase gene. Light production was dependent on phage infection, expression of the luciferase gene, and the level of cellular adenosine triphosphate. Signals could be detected within minutes after infection of virulent M. tuberculosis with reporter phages. Culture of conventional strains with antituberculosis drugs, including isoniazid or rifampicin, resulted in extinction of light production. In contrast, light signals after luciferase reporter phage infection of drug-resistant strains continued to be produced. Luciferase reporter phages may help to reduce the time required for establishing antibiotic sensitivity of M. tuberculosis strains from weeks to days and to accelerate screening for new antituberculosis drugs.

Survival of reproductive behaviors in estrogen receptor beta gene-deficient (betaERKO) male and female mice

Previously, it was shown that the lack of a functional estrogen receptor (ER) alpha gene (ERalpha) greatly affects reproduction-related behaviors in both female and male mice. However, widespread expression of a novel second ER gene, ERbeta, demanded that we examine the possible participation of ERbeta in regulation of these behaviors. In dramatic contrast to our results with ERalpha knockout (alphaERKO) males, betaERKO males performed at least as well as wild-type controls in sexual behavior tests. Moreover, not only did betaERKO males exhibit normal male-typical aggressive behavior, including offensive attacks, but they also showed higher levels of aggression than wild-type mice under certain conditions of social experience. These data revealed a significant interaction between genotype and social experience with respect to aggressive behavior. Finally, females lacking a functional beta isoform of the ER gene showed normal lordosis and courtship behaviors, extending in some cases beyond the day of behavioral estrus. These results highlight the importance of ERalpha for the normal expression of natural reproductive behaviors in both sexes and also provide a background for future studies evaluating ERbeta gene contributions to other, nonreproductive behaviors.

Delays in the administration of antibiotics are associated with mortality from adult acute bacterial meningitis

BACKGROUND

Bacterial meningitis continues to cause high mortality. Few studies address the possible association between this mortality and antibiotic administration delays.

AIM

To determine whether delays in antibiotic administration are associated with mortality from bacterial meningitis, and to identify inappropriate diagnostic-treatment sequences leading to such delays.

DESIGN

Retrospective case record study.

METHODS

We reviewed 123 cases of adult acute bacterial meningitis in 119 patients aged >/=16 years admitted to hospital from January 1990 to March 2002, using multivariate regression analysis to assess the association between meningitis mortality and door-to-antibiotic time (the time elapsed between emergency room presentation and antibiotics administration).

RESULTS

The case fatality rate was 13% (16/123). Adjusted odds ratios (OR) for mortality were: 8.4 (95%CI 1.7-40.9) for door-to-antibiotic time >6 h; 39.4 (95%CI 4.3-358.1) for afebrility at presentation; and 12.6 (95%CI 2.2-72.0) for severely impaired mental status at presentation. Factors associated with a door-to-antibiotic time of >6 h were: (i) failure to administer antibiotics prior to transfer from another institution (OR 21.8); (ii) the diagnostic-treatment sequence: head CT then lumbar puncture, then antibiotics (OR 5.6); and (iii) the absence of the classic meningitis triad (OR 4.9).

DISCUSSION

There is an independent incremental association between delays in administrating antibiotics and mortality from adult acute bacterial meningitis. Inappropriate diagnostic-treatment sequences were significant predictors of such treatment delays.

Lipoarabinomannan, a possible virulence factor involved in persistence of Mycobacterium tuberculosis within macrophages

Mycobacterium tuberculosis and Mycobacterium leprae, the causative agents of tuberculosis and leprosy, respectively, produce large quantities of lipoarabinomannan (LAM), a highly immunogenic, cell wall-associated glycolipid. This molecule has been previously reported to be a potent inhibitor of gamma interferon-mediated activation of murine macrophages. Studies of the mechanism by which this mycobacterial glycolipid down-regulates macrophage effector functions provide evidence that LAM acts at several levels and that it can (i) scavenge potentially cytotoxic oxygen free radicals, (ii) inhibit protein kinase C activity, and (iii) block the transcriptional activation of gamma interferon-inducible genes in human macrophage-like cell lines. These results suggest that LAM can inhibit macrophage activation and triggering and cytocidal activity and that it may represent a chemically defined virulence factor contributing to the persistence of mycobacteria within mononuclear phagocytes.

Idiopathic cervical dystonia: clinical characteristics

We reviewed detailed clinical features of 266 patients with idiopathic cervical dystonia, commonly called spasmodic torticollis. Mean age at onset (41 years), female-to-male ratio (1.9:1), clustering of onset between ages 30 and 59 (70%), familial history of dystonia (12%), and remissions (9.8%) were similar to those found in previous studies. In contrast to the single prior large clinical study of this disorder, no predominance of right-handers or significant thyroid disease was found. Pain, which occurred in 75% of patients and contributed to disability score (p less than 0.01), distinguishes this syndrome from all other focal dystonias. Pain was also strongly associated with constant (vs. intermittent) head turning, severity of head turning, and presence of spasm. Eighty-three percent of patients had deviation of the head of greater than 75% of the time when sitting with the head unsupported (constant head deviation at rest). Of the 97% who had head turning, 81% also had head tilting in various combinations. The 23% with hand tremor had an older age at onset (mean, 46 vs. 41 years; p less than 0.05). An earlier age at onset (p less than 0.05) was seen in patients with a family history of dystonia (mean, 36 years), with trauma shortly preceding symptoms (mean, 36 years), with a change in the direction of head turning (mean, 30 years), and with remissions (mean, 33 years). Jerky movements or forced transient spasms of the head occurred in 62% of the patients, and these patients would be the ones for whom the designation "spasmodic torticollis" could logically apply.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxygenated mycolic acids are necessary for virulence of Mycobacterium tuberculosis in mice

Members of the Mycobacterium tuberculosis group synthesize a family of long-chain fatty acids, mycolic acids, which are located in the cell envelope. These include the non-oxygenated alpha-mycolic acid and the oxygenated keto- and methoxymycolic acids. The function in bacterial virulence, if any, of these various types of mycolic acids is unknown. We have constructed a mutant strain of M. tuberculosis with an inactivated hma (cmaA, mma4) gene; this mutant strain no longer synthesizes oxygenated mycolic acids, has profound alterations in its envelope permeability and is attenuated in mice.

Attenuation of and protection induced by a leucine auxotroph of Mycobacterium tuberculosis

Attenuated mutants of Mycobacterium tuberculosis represent potential vaccine candidates for the prevention of tuberculosis. It is known that auxotrophs of a variety of bacteria are attenuated in vivo and yet provide protection against challenge with wild-type organisms. A leucine auxotroph of M. tuberculosis was created by allelic exchange, replacing wild-type leuD (Rv2987c), encoding isopropyl malate isomerase, with a mutant copy of the gene in which 359 bp had been deleted, creating a strain requiring exogenous leucine supplementation for growth in vitro. The frequency of reversion to prototrophy was <10(-11). In contrast to wild-type M. tuberculosis, the DeltaleuD mutant was unable to replicate in macrophages in vitro. Its attenuation in vivo and safety as a vaccine were established by the fact that it caused no deaths in immunodeficient SCID mice. Complementation of the mutant with wild-type leuD abolished the requirement for leucine supplementation and restored the ability of the strain to grow both in macrophages and in SCID mice, thus confirming that the attenuated phenotype was due to the DeltaleuD mutation. As a test of the vaccine potential of the leucine auxotroph, immunocompetent BALB/c mice, susceptible to fatal infection with wild-type M. tuberculosis, were immunized with the DeltaleuD mutant and subsequently challenged with virulent M. tuberculosis by both the intravenous and aerosol routes. A comparison group of mice was immunized with conventional Mycobacterium bovis BCG vaccine. Whereas all unvaccinated mice succumbed to intravenous infection within 15 weeks, mice immunized with either BCG or the DeltaleuD mutant of M. tuberculosis exhibited enhanced and statistically equivalent survival curves. However, the leuD auxotroph was less effective than live BCG in reducing organ burdens and tissue pathology of mice challenged by either route. We conclude that attenuation and protection against M. tuberculosis challenge can be achieved with a leucine auxotroph and suggest that to induce optimal protection, attenuated strains of M. tuberculosis should persist long enough and be sufficiently metabolically active to synthesize relevant antigens for an extended period of time.

Cognitive function in depression: a distinct pattern of frontal impairment in melancholia?

BACKGROUND

Although depressed patients demonstrate impaired performance on a range of neuropsychological tests, there is little research that examines either frontal cognitive deficits or possible differences in test performance between melancholic and non-melancholic subtypes.

METHODS

Depressed subjects were administered a broad neuropsychological battery. In an overall analysis, 77 depressed subjects were compared with 28 controls. In a second set of analyses, the depressed sample was divided into melancholic and non-melancholic subsets according to DSM-III-R, the CORE system and the Newcastle scale. These depressed subsets were contrasted to controls and with each other using ANCOVA controlling for age, IQ, simple reaction time and Hamilton Depression scores where appropriate.

RESULTS

The total depressed sample was impaired on most mnemonic tasks, simple reaction time and Trails B. Similar findings applied to DSM-III-R melancholic and non-melancholic subjects. When defined by the CORE and Newcastle (narrower definitions of melancholia), melancholic patients were additionally impaired on WCST (perseverative response) and (for Newcastle) digit symbol substitution. In contrast, the cognitive performance of the CORE and Newcastle-defined non-melancholic patients was largely unimpaired.

CONCLUSIONS

Using narrower definitions of melancholia, i.e. CORE and (in particular) Newcastle, melancholic patients were impaired on mnemonic tasks and tasks of selective attention, and set-shifting while non-melancholic subjects were largely unimpaired in their cognitive performance. These differences may be due to impairment of specific neuroanatomical regions in narrowly defined melancholic patients, in particular the anterior cingulate.

Mechanism of STAT3 activation by insulin-like growth factor I receptor

Recent evidence indicates that STAT proteins can be activated by a variety of receptor and non-receptor protein-tyrosine kinases. Unlike cytokine-induced activation of STATs, where JAKs are known to play a pivotal role in phosphorylating STATs, the mechanism for receptor protein-tyrosine kinase-mediated activation of STATs remains elusive. In this study, we investigated the activation of STAT proteins by the insulin-like growth factor I receptor (IGF-IR) in vitro and in vivo and assessed the role of JAKs in the process of activation. We found that STAT3, but not STAT5, was activated in response to IGF-I in 293T cells cotransfected with IGF-IR and STAT expression vectors. Moreover, tyrosine phosphorylation of STAT3, JAK1, and JAK2 was increased upon IGF-I stimulation of endogenous IGF-IR in 293T cells transfected with the respective STAT or JAK expression vector. Supporting the observation in 293T cells, endogenous STAT3 was tyrosine-phosphorylated upon IGF-I stimulation in the muscle cell line C2C12 as well as in various embryonic and adult mouse organs during different stages of development. Dominant-negative JAK1 or JAK2 was able to block the IGF-IR-mediated tyrosine phosphorylation of STAT3 in 293T cells. A newly identified family of proteins called SOCS (suppressor of cytokine signaling), including SOCS1, SOCS2, SOCS3 and CIS, was able to inhibit the IGF-I-induced STAT3 activation as well with varying degrees of potency, in which SOCS1 and SOCS3 appeared to have the higher inhibitory ability. Inhibition of STAT3 activation by SOCS could be overcome by overexpression of native JAK1 and JAK2. We conclude that IGF-I/IGF-IR is able to mediate activation of STAT3 in vitro and in vivo and that JAKs are essential for the process of activation.

What is the role of nitric oxide in murine and human host defense against tuberculosis?Current knowledge

The production of reactive oxygen intermediates and reactive nitrogen intermediates by innate immune cells is considered to be an effective host-defense mechanism against microbial pathogens. In the murine model of tuberculosis (TB), nitric oxide (NO) plays an essential role in the killing of Mycobacterium tuberculosis by mononuclear phagocytes. For example, in the mouse strain with a genetic disruption for inducible NO synthase (iNOS-/-), infection with M. tuberculosis is associated with a significantly higher risk of dissemination and mortality. Although more controversial in humans, there is a growing body of evidence that NO produced by TB-infected macrophages and by epithelial cells also has antimycobacterial effects against M. tuberculosis. The precise mechanism(s) by which NO and other reactive nitrogen species antagonize M. tuberculosis is not known, but may involve disruption of bacterial DNA, proteins, signaling, and/or induction of apoptosis of macrophages that harbor mycobacteria. In addition to cytokines such as tumor necrosis factor-alpha and interleukin 1-beta, mycobacterial cell wall components such as lipoarabinomannan and 19 kD lipoprotein, along with the T-cell-derived interferon-gamma, may also induce NO expression. In a Darwinian fashion, it also appears that certain strains of M. tuberculosis have evolved strategies to combat the toxic effects of NO.

The influence of the composition of the nursing staff on primary bloodstream infection rates in a surgical intensive care unit

OBJECTIVES

To determine the risk factors for acquisition of nosocomial primary bloodstream infections (BSIs), including the effect of nursing-staff levels, in surgical intensive care unit (SICU) patients.

DESIGN

A nested case-control study.

SETTING

A 20-bed SICU in a 1,000-bed inner-city public hospital.

PATIENTS

28 patients with BSI (case-patients) were compared to 99 randomly selected patients (controls) hospitalized > or =3 days in the same unit.

RESULTS

Case- and control-patients were similar in age, severity of illness, and type of central venous catheter (CVC) used. Case-patients were significantly more likely than controls to be hospitalized during a 5-month period that had lower regular-nurse-to-patient and higher pool-nurse-to-patient ratios than during an 8-month reference period; to be in the SICU for a longer period of time; to be mechanically ventilated longer; to receive more antimicrobials and total parenteral nutrition; to have more CVC days; or to die. Case-patients had significantly lower regular-nurse-to-patient and higher pool-nurse-to-patient ratios for the 3 days before BSI than controls. In multivariate analyses, admission during a period of higher pool-nurse-to-patient ratio (odds ratio [OR]=3.8), total parenteral nutrition (OR=1.3), and CVC days (OR=1.1) remained independent BSI risk factors.

CONCLUSIONS

Our data suggest that, in addition to other factors, nurse staffing composition (ie, pool-nurse-to-patient ratio) may be related to primary BSI risk. Patterns in intensive care unit nurse staffing should be monitored to assess their impact on nosocomial infection rates. This may be particularly important in an era of cost containment and healthcare reform.

The role of diabetes mellitus in the aetiology of renal cell cancer

To investigate the relation between diabetes mellitus and the risk of renal cell cancer we carried out a population-based retrospective cohort study. Patients identified in the Swedish Inpatient Register who were discharged from hospitals with a diagnosis of diabetes mellitus between 1965 and 1983 formed a cohort of 153852 patients (80005 women and 73847 men). The cohort members were followed up to 1989 by record linkage to three nation-wide registries. Standardized incidence ratios (SIRs) and standardized mortality ratios (SMRs) were computed using age-specific sex-specific and period-specific incidence and mortality rates derived from the entire Swedish population. After exclusion of the first year of observation, a total of 267 incidences of renal cell cancer (ICD-7:180.0) occurred in diabetic patients compared with the 182.4 that had been expected. Increased risks were observed in both women (SIR = 1.7, 95% confidence interval, CI = 1.4-2.0) and men (SIR = 1.3; 95 % CI = 1.1-1.6) throughout the duration of follow-up (1-25 years). A higher risk was seen for kidney cancer (ICD-7:180) mortality (SMR = 1.9; 95% CI = 1.7-2.2, women; SMR 1.7, 95% CI = 1.4-1.9, men). In comparison with the general population, patients with diabetes mellitus have an increased risk of renal cell cancer.