Sensitivity of In-line Rheometry for Extrusion of Mg(OH)2 filled LDPE Compounds

In-process and off-line rheometry studies are reported for compounds based on Mg(OH)2 filled low density polyethylene, some of which were first subjected to a range of strain histories in typical compounding operations. In the study reported here, the compounds were processed using an instrumented, computer monitored single screw extruder in the IRC laboratories, fitted with in line rheometers (ILR). In initial experiments a four sensor ILR slit die was used for the in-process shear rheometry, and a Rosand RH7 twin bore capillary rheometer for off-line shear and entry pressure measurements. Off line and in-line results are compared, showing good agreement for shear. Estimates have been obtained for the sensitivity to filler loading of the off line rheometer (shear flow and entry pressure measurements), and the 4 sensor ILR (shear flow measurements), which indicate that the ILR offers similar resolution of filler level to the off line rheometer at the higher loadings, although the ILR appears to have much lower sensitivity at higher shear rates at lower loadings, an effect which appears to be related to processing effects on the rheology of the compound rather than the measurement ability of the ILR. The ILR was also able to discriminate between samples with differing processing histories. Results from a six-sensor ILR die have shown good agreement in shear flow measurements, and have added the ability to measure entry pressures, which are compared with off-line measurements.

Food concentration affects the life history response of Ceriodaphnia cf. dubia to chemicals with different mechanisms of action

The effect of three chemicals with different mechanisms of action (3,4-dichloroaniline, fenoxycarb, and chlorpyrifos) on the life history response of the cladoceran Ceriodaphnia cf. dubia was examined under both limited (3 x 10(4) cells/mL) and abundant (15 x 10(4) cells/mL) food conditions. Toxicity tests were conducted at both food concentrations simultaneously for each chemical, and cladocerans were examined daily from less than 24 h old until their death. A range of life history parameters were calculated, including mean brood sizes, survival, net reproductive rate, and population growth rate. The toxicity of 3,4-dichloroaniline was not significantly affected by food concentration. However, limited food significantly decreased the toxicity of fenoxycarb, and significantly increased the toxicity of chlorpyrifos. The effect of food concentration on toxicity appears to depend on the mechanism by which the chemical exerts its toxicity and on food--chemical interactions. Possible mechanisms for the different effects of food concentration on toxicity are discussed.

The presence of chemicals exuded by fish affects the life-history response of Ceriodaphnia cf. dubia to chemicals with different mechanisms of action

The toxicity of chemicals with different mechanisms of action (3,4-dichloroaniline, fenoxycarb, and chlorpyrifos) to the cladoceran Ceriodaphnia cf. dubia was examined in the presence and absence of chemicals exuded by fish, termed fish kairomones. A range of life-history traits were examined, including mean brood sizes, survival, net reproductive rate (Ro) and population growth rate (r). Cladocerans exposed to 3,4-dichloroaniline showed similar sensitivities in the presence and absence of fish kairomones with respect to all of the life-history traits examined. The presence of fish kairomones reduced the sensitivity of cladocerans to fenoxycarb with respect to mean brood sizes and r but increased their sensitivity in terms of Ro. The presence of fish kairomones increased the sensitivity of cladocerans to chlorpyrifos with respect to survival, r, Ro, and mean brood sizes. The general trends observed were similar to those shown when C. cf. dubia was exposed to these chemicals under low food conditions, and it is suggested that the effects of fish kairomones on toxicity may be attributed to the reduction in feeding rates observed when C. cf. dubia is exposed to fish kairomones.

Depression and work productivity: the comparative costs of treatment versus nontreatment

This article discusses the impact of depression on work productivity and the potential for improved work performance associated with effective treatment. We undertook a review of the literature by means of a computer search using the following key terms: cost of illness, work loss, sickness absence, productivity, performance, and disability. Published works were considered in four categories: (1) naturalistic cross-sectional studies that found greater self-reported work impairment among depressed workers; (2) naturalistic longitudinal studies that found a synchrony of change between depression and work impairment; (3) uncontrolled treatment studies that found reduced work impairment with successful treatment; and (4) controlled trials that usually, but not always, found greater reduction in work impairment among treated patients. Observational data suggest that productivity gains following effective depression treatment could far exceed direct treatment costs. Randomized effectiveness trials are needed before we can conclude definitively that depression treatment results in productivity improvements sufficient to offset direct treatment costs.

Alveolar macrophages from human immunodeficiency virus-infected persons demonstrate impaired oxidative burst response to Pneumocystis carinii in vitro

The alveolar macrophage (AM) oxidative burst response is an important component of microbicidal effector cell function against a variety of potential pathogens in the lungs, although the role against Pneumocystis carinii has not been fully investigated. The goals of this study were to characterize the P. carinii-mediated oxidative burst of AMs from healthy individuals, and to examine the oxidative burst of AMs from human immunodeficiency virus (HIV)-infected persons. For healthy individuals, the AM oxidative burst (measured as hydrogen peroxide [H(2)O(2)] production) increased in a time- and concentration-dependent manner in response to P. carinii or to the major surface glycoprotein of P. carinii, gp-A (0.01 to 10 microg/ml), required physical contact of P. carinii with AMs, and was not dependent on organism viability. Enzymatic removal of the surface-associated molecules of P. carinii reduced the oxidative burst to 43% of control (P = 0.01). Blocking the AM mannose receptor reduced the P. carinii-mediated oxidative burst response to 37% of control (P = 0.01). Compared with AMs from healthy individuals, P. carinii-mediated H(2)O(2) production was significantly reduced in AMs from asymptomatic HIV-positive (HIV+) persons with CD4+ counts < 200 cells/mm(3) (249+/-43 relative fluorescence units [RFU] versus 130+/-44 RFU; mean +/- standard error of the mean, P = 0.038) and HIV+ persons with active P. carinii pneumonia (78+/-40 RFU; P = 0.014), but preserved for HIV+ persons with CD4+ counts > 200 cells/mm(3). Importantly, H2O2 production in response to phorbol myristate acetate or serum-opsonized zymosan particles was preserved in all groups studied. Thus, AM oxidative burst, mediated in part via P. carinii gp-A and AM mannose receptor may represent an important host response to P. carinii. A specific impairment of P. carinii-mediated AM oxidative burst in persons with advanced HIV infection may contribute to the pathogenesis of P. carinii pneumonia.

Randomized, placebo-controlled pilot study of divalproex sodium in the treatment of acute exacerbations of chronic schizophrenia

Experimental and clinical data suggest that GABA-ergic drugs such as valproate may have a potential role in the treatment of schizophrenia. The authors designed a 21-day prospective, double-blind, randomized, placebo-controlled pilot study of divalproex sodium as add-on treatment to haloperidol in 12 hospitalized patients with acute exacerbations of chronic schizophrenia. All patients received haloperidol 10 mg/day for 3 days and 15 mg/day for the remaining 18 days. In addition, five patients were randomly assigned to receive divalproex augmentation and seven to receive placebo. The divalproex dose was adjusted to a target serum concentration of 75 microg/mL for 2 weeks; placebo replaced divalproex during the third and last weeks to determine any carryover effect. Psychiatric rating scales were administered at baseline and on days 7, 14, and 21. Although the placebo group improved with haloperidol treatment, the divalproex group demonstrated greater improvement. On day 21, the divalproex group had greater improvement from baseline on the Clinical Global Impression Scale (p < or = 0.04), Brief Psychiatric Rating Scale (p < or = 0.13), and Schedule for Assessment of Negative Symptoms scores (p < or = 0.007). After divalproex withdrawal on day 15, a carryover effect was observed during week 3. The authors concluded that the addition of divalproex sodium to standard antipsychotic drugs may prove effective in relieving the symptoms of acute schizophrenia. Future studies may benefit from the design of this pilot study. However, it is premature to apply this augmentation strategy in the clinical setting just yet because of the small sample size and the likely heterogeneity of the disorder.

Depression in the workplace: effects on short-term disability

We analyzed data from two national surveys to estimate the short-term work disability associated with thirty-day major depression. Depressed workers were found to have between 1.5 and 3.2 more short-term work-disability days in a thirty-day period than other workers had, with a salary-equivalent productivity loss averaging between $182 and $395. These workplace costs are nearly as large as the direct costs of successful depression treatment, which suggests that encouraging depressed workers to obtain treatment might be cost-effective for some employers.

Critical review of GABA-ergic drugs in the treatment of schizophrenia

GABA-ergic medications may have a potential role in the treatment of schizophrenia. Laboratory evidence has generally supported the ability of gamma-aminobutyric acid (GABA) to reduce dopaminergic activity and has suggested that GABA may be effective in combating hypofrontality by acting on mesoprefrontocortical tracts in patients resistant to treatment with antipsychotic drugs. Although the results of clinical trials of several GABA-ergic compounds have been inconclusive because of methodologic limitations and drug toxicity, benzodiazepines and valproate seem to be associated with favorable treatment outcomes, especially when combined with typical antipsychotic agents. This study concludes that further investigation of the use of GABA in schizophrenia is likely to improve the understanding of the psychopathology of this illness and to expand our treatment alternatives. Also provided are suggestions to enhance the design of future studies, improve the potential for favorable treatment outcomes, and assist in predicting patients' responses to GABA-ergic medications.

Reduced binding and phagocytosis of Pneumocystis carinii by alveolar macrophages from persons infected with HIV-1 correlates with mannose receptor downregulation

The macrophage mannose receptor, a pattern recognition molecule and component of innate immunity, mediates binding and phagocytosis of Pneumocystis carinii and likely represents an important clearance mechanism in the lungs of immunocompetent hosts. The purpose of this study was to examine the ability of alveolar macrophages from HIV-infected individuals to bind and phagocytose P. carinii, and to investigate the role of the macrophage mannose receptor in mediating this interaction. Compared with healthy individuals, alveolar macrophage phagocytosis of P. carinii from HIV+ persons was reduced up to 74% (P = 0.02), primarily reflecting a reduction in the number of organisms associated with each macrophage (P = 0.019). Furthermore, macrophages from HIV+ individuals demonstrated up to an 80% (P < 0.05) reduction in mannose receptor surface expression and endocytosis. Mannose receptor affinity was unaltered, and mRNA levels were modestly reduced (P < 0.05). Cells from HIV+ individuals with CD4(+) counts < 200 cells/mm3 (representing individuals at high clinical risk for P. carinii pneumonia) demonstrated the lowest levels of P. carinii phagocytosis and mannose receptor endocytosis. In vitro HIV infection of alveolar macrophages from healthy individuals reduced mannose receptor endocytosis to 53.2% (P < 0.05) and P. carinii binding and phagocytosis to 67.4% (P < 0.05) of control. Our studies suggest that HIV infection may alter innate immunity in the lungs, and that impaired alveolar macrophage mannose receptor-mediated binding and phagocytosis of P. carinii may contribute to the susceptibility of HIV-infected individuals to this opportunistic pulmonary pathogen.

Surfactant protein-A reduces binding and phagocytosis of pneumocystis carinii by human alveolar macrophages in vitro

Surfactant protein-A (SP-A) levels are increased in Pneumocystis carinii pneumonia, but the role of SP-A in the pathogenesis of P. carinii pneumonia is not completely understood. This study investigated the effect of SP-A on the in vitro binding and phagocytosis of P. carinii by normal human alveolar macrophages (AM). Determination of binding and phagocytosis was done with a fluorescence-based assay, utilizing fluorescein isothiocyanate (FITC)-labeled P. carinii. Binding and phagocytosis of P. carinii to AM correlated inversely with the levels of SP-A present on the surface of the organisms (r = -0.6323, P = 0.0086; and r = -0.9827, P < 0.0001, respectively). The addition of exogenous SP-A to organisms with low surface-associated SP-A reduced P. carinii binding by 30% (P < 0.05) and reduced phagocytosis by 20% (P < 0.05), whereas this effect was reversed with ethylenediamine tetraacetic acid (EDTA) or anti-SP-A antibody. Furthermore, binding and phagocytosis were enhanced after enzymatic removal of P. carinii surface-associated SP-A, and this effect was reversed with the addition of exogenous SP-A. The observed inhibitory effect of SP-A on P. carinii binding and phagocytosis reflected binding of SP-A to the organisms rather than a direct effect of SP-A on the macrophages. These data suggest that increased levels of SP-A may contribute to the pathogenesis of P. carinii pneumonia through binding to the surface of the organism and interfering with AM recognition of this opportunistic pulmonary pathogen.

Quantitative structure-activity relationships and volume fraction analysis for nonpolar narcotic chemicals to the australian cladoceran ceriodaphnia cf. dubia

The toxicity of eleven nonpolar narcotic chemicals to the cladoceran Ceriodaphnia cf. dubia was determined. C. cf. dubia was found to be approximately four times more sensitive to these narcotic chemicals than Daphnia magna tested under virtually identical conditions. The toxicity data were also used to develop and validate quantitative structure-activity relationships (QSARs) using a range of physicochemical properties of the chemicals. The three best QSARs, based on octanol-water partition coefficients and two lipid-water partition coefficients, were able to explain 98% of the variation in toxicity. The mean absolute percentage errors between the predicted and experimental EC50 values for these three QSARs were 17.3%, 20.6%, 24.6%. Neither the critical concentration (CC) nor the critical volume (CV) hypotheses validly modeled the toxicity data when octanol-water and triolein-water partition coefficients were used although the CV hypothesis was the better of the two. When a phospholipid-water partition coefficient was used the CV hypothesis was valid. The mean toxic membrane volume fraction of 0.48 x 10(-2) m3/m3 derived in this study agreed with published values for nonpolar narcotics and supports the use of this property to determine the mode of action of chemicals.

Fatigue strength of polyethylene after sterilization by gamma irradiation or ethylene oxide

The oxidation level of ultrahigh molecular weight polyethylene specimens sterilized by gamma irradiation in either air or Ar gas was compared with that of unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene. The fatigue strength of ultrahigh molecular weight polyethylene specimens sterilized by gamma irradiation in air was compared with that of unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene. At the specimen surface, oxidation was highest for ultrahigh molecular weight polyethylene gamma irradiated in air, lower for ultrahigh molecular weight polyethylene gamma irradiated in Ar gas, and absent in unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene. At a depth of 3.5 mm below the specimen surface, oxidation levels were equivalent for ultrahigh molecular weight polyethylene gamma irradiated in either air or Ar gas whereas unsterilized and ethylene oxide sterilized specimens were again unoxidized. Thus, even in an inert atmosphere, oxidative degradation of gamma irradiated ultrahigh molecular weight polyethylene occurs. The 10 million cycle fatigue strength was similar for unsterilized and ethylene oxide sterilized ultrahigh molecular weight polyethylene whereas the fatigue strength of gamma irradiated in air ultrahigh molecular weight polyethylene was lower. Results of this study show that ethylene oxide gas does not degrade ultrahigh molecular weight polyethylene whereas gamma radiation in air causes changes in the polymer that adversely affect its mechanical properties. Ethylene oxide gas is a viable alternative to gamma radiation in air that avoids oxidation and fatigue strength degradation known to accompany irradiation of ultrahigh molecular weight polyethylene polymer bearing surfaces in total joint implants.

Elevated selectin levels after severe trauma: a marker for sepsis and organ failure and a potential target for immunomodulatory therapy

Severe injury is frequently complicated by sepsis and organ failure. Activated neutrophils adherent to inflamed endothelia have been implicated in the pathogenesis of these complications. Identification of high-risk patients to target immunomodulatory therapy, however, remains an elusive goal. We postulated that (1) patients at risk for sepsis and organ failure could be identified by measuring shed selectin adhesions molecules as a marker of endothelial activation after injury and reperfusion, and (2) these elevated selectin levels would correlate with injury severity, shock, major complications, and mortality.

METHODS

Blood samples were drawn from 50 patients with multiple trauma every 2 hours after admission for the first 24 hours, and every 6 hours for the subsequent 24 hours, and assayed for levels of shed E- and P-selectin. Patients were then stratified according to Injury Severity Score (ISS), presence or absence of shock, presence or absence of organ failure and/or infectious complications, and finally, death versus survival.

RESULTS

Trauma patients who had ISS < 30, who did not develop shock, sepsis, or organ dysfunction, had minimal increase in circulating E- and P-selectin over admission levels. In patients who subsequently developed infectious complications, organ dysfunction, or both, or subsequently went on to die, elevated levels of E-selectin levels were evident by 36 hours, and in some cases, earlier. Differences between nonsurvivors and survivors was statistically significant. There was also a trend toward increased levels of P-selectin in the same group of patients, although these differences were not significant. There was no differentiation in either of the two selections when patients were stratified according to ISS or presence of shock.

CONCLUSION

A subset of major trauma patients manifest increased levels of circulating E-selectin adhesion molecules after resuscitation. These patients seem to be at increased risk of death and possibly at risk for infections complications and organ failure. Selectin blockade is a potential new immunomodulatory strategy in this subgroup of patients.

Surfactant protein-A levels increase during Pneumocystis carinii pneumonia in the rat

In bronchoalveolar lavage (BAL) of human immunodeficiency virus (HIV)-infected patients with Pneumocystis carinii pneumonia and in lungs of glucocorticoid-immunosuppressed rats infected with P. carinii, surfactant phospholipid levels are reduced. However, levels of the surfactant-associated protein-A (SP-A) in BAL are 4-5 times higher than normal in patients with P. carinii pneumonia. In this study, we examined the effects of glucocorticoid immunosuppression and P. carinii infection on SP-A messenger ribonucleic acid (mRNA) and protein levels in rat lungs. Rats were immunosuppressed by adding dexamethasone to their drinking water and were infected with P. carinii by intratracheal instillation of the organism. SP-A was measured by enzyme-linked immunosorbent assay (ELISA) and SP-A mRNA by hybridization of Northern blots with an SP-A complementary deoxyribonucleic acid (cDNA) probe. There was a severalfold increase in SP-A protein and mRNA levels in uninfected glucocorticoid-treated rats. However, contrary to what has been reported with the surfactant-associated lipids, SP-A mRNA and protein levels in P. carinii-infected animals were significantly higher than those found in the uninfected, immunosuppressed animals. Our results demonstrate that SP-A increases, probably as a result of elevated mRNA levels, in immunosuppressed rats with P. carinii infection and are consistent with our findings in HIV-positive patients with P. carinii pneumonia.

Administration of an antibody to E-selectin in patients with septic shock

OBJECTIVES

To determine the safety and pharmacokinetics of a murine monoclonal antibody to E-selectin in patients with newly developed septic shock.

DESIGN

Open-label, prospective, phase II pilot study with escalating doses of the antibody.

SETTING

Intensive care unit of a 900-bed university hospital.

PATIENTS

Nine patients who survived the first 24 hrs of septic shock.

INTERVENTIONS

In addition to standard therapy, an intravenous bolus of a murine monoclonal antibody to E-selectin, CY1787, was given at doses of 0.1 mg/kg (n = 3), 0.33 mg/kg (n = 3), and 1.0 mg/kg (n = 3).

MEASUREMENTS AND MAIN RESULTS

CY1787 was well tolerated in all patients. Signs of shock resolved in all patients, and organ failure entirely reversed in eight patients. All patients survived the 28-day follow-up. Administration of CY1787 was associated with an early and brisk increase in PaO2/FIO2 ratio (p < .001), from 146 +/- 38 mm Hg (19.5 +/- 5.1 kPa) to 205 +/- 45 mm Hg (27.3 +/- 6.0 kPa) after 2 hrs, and 250 +/- 58 mm Hg (33.3 +/- 7.7 kPa) after 12 hrs. A dose-related effect of CY1787 was suggested by an earlier weaning from catecholamine therapy and a faster resolution of organ failure in the high-dose group. Development of antimouse antibodies was documented in eight patients.

CONCLUSIONS

This pilot study indicates that this antibody to E-selectin appears to be safe and may represent a promising form of therapy in septic shock.

Quantitative culture of HIV-1 from bronchoalveolar lavage cells

Determination of the infectious virus burden at the organ level is critical for understanding the pathophysiology of human immunodeficiency virus type 1 (HIV-1) infection. To evaluate the burden of HIV-1 in the lung, quantitative cultures were performed on bronchoalveolar lavage (BAL) cells from 11 HIV-1 seropositive subjects without respiratory infections and compared with peripheral blood mononuclear cells (PBMC) obtained from the same subjects. Fifty percent (50%) of subjects had positive BAL cell cultures while 82% had positive PBMC cultures. There was much less virus cultured from BAL cells than from PBMCs, whether using phytohemagglutinin (PHA)-stimulated peripheral blood lymphocyte (PBL) targets (p < 0.05) or adherent monocyte targets (p < 0.02). There was no significant difference between the HIV-1 titers obtained for BAL cells whether using PHA-stimulated PBL or adherent monocyte targets (p = 0.13). These studies demonstrate that BAL cell cultures for HIV-1 in subjects without respiratory infections are less frequently positive than PBMC cultures, that less virus can be recovered from BAL cells than from PBMC, and that HIV-1 isolates from BAL cells replicate in both PHA-stimulated PBL targets and adherent monocyte targets. Quantitative assessment of virus burden in the lung is important for future studies of HIV-1 pathogenesis and for evaluating potential antiretroviral therapies aimed at altering the natural history of organ dysfunction associated with retroviral replication.

Use of personal characteristics in the selection of astronauts

Which personal characteristics are used in selecting astronauts? We decided to examine this question using National Aeronautics and Space Administration (NASA) archival data collected on 2288 applicants. Undergraduate grade point average, graduate grade point average, and several facets of aviation experience were the best predictors of who was interviewed and then selected to be an astronaut. Adjustments were made to insure that a sufficient number of women and minority group members were selected, while still maintaining high selection standards. The selection process seems well-designed, and follows explicit NASA guidelines. We suggest simplifying the selection process by using a single discriminant function as an interview and/or selection criterion.

Phytosterols are present in Pneumocystis carinii

Although originally classified as a protozoan, Pneumocystis carinii is now considered to have fungal characteristics. Drugs typically used for the treatment of fungal infections target ergosterol. Because P. carinii is an important pathogen in AIDS and other immunocompromised patients, knowledge of the sterol content of this organism may be useful as a basis for developing new treatment strategies or for improving diagnosis. P. carinii organisms were harvested from infected rat lungs and were purified by filtration. Control preparations from uninfected animals were identically prepared. Lipids were extracted from the organisms and control preparations and were separated into neutral lipid, glycolipid, and phospholipid fractions by silicic acid chromatography. The neutral lipid fraction was further treated by alkaline hydrolysis and was analyzed by reversed-phase high-pressure liquid chromatography (HPLC), gas chromatography (GC), and GC-mass spectrometry (GC-MS). As shown by HPLC, the neutral lipid fraction from infected rats contained a minimum of six peaks, while in control preparations a single peak with a retention time identical to that of cholesterol was observed. The predominant sterol in these preparations was positively identified by GC-MS as cholesterol and constituted 80 to 90% of the total. The remaining peaks had relative retention times similar to those of phytosterols by both HPLC and GC, and the similarity of these sterols to those derived from plants and fungi was confirmed by MS. Ergosterol, however, was not present. These results provide further evidence for a close phylogenetic relationship between P. carinii and fungi and suggest that these sterols could be used as targets for drug development and for improving diagnosis.

Resonance in a model of a mammalian neuron

In this paper we show that for a small range of voltages the model described in the previous paper (Hindmarsh & Rose Phil. Trans. R. Soc. Lond. B 346, 129-150 (1994a)) will generate damped oscillations in response to a negative current pulse. As a consequence the cell has the property that it can be driven into bursting by periodic sinusoidal inputs close to the resonant frequency. The main objective of this paper is to analyse this resonant behaviour using the model of the model introduced in the previous paper. We derive analytical expressions which closely approximate the nonlinear resonance observed in the physiological model driven by a periodic sinusoidal input. This leads to the conclusion that resonance could play a role in synaptic transmission at relay nuclei in the mammalian brain.

A model for rebound bursting in mammalian neurons

In this paper we begin by simplifying our previous model of a thalamic neuron (Rose & Hindmarsh Proc. R. Soc. Lond. B 237, 289-312 (1989b)) by removal of the A current. A Ca(2+)-activated K+ current, with Ca2+ entering through T channels, is then added to give a model for a class of mammalian neurons in which the membrane potential oscillates in the subthreshold region following a hyperpolarizing current step. The properties of the model are represented using an experimentally observable bifurcation diagram. In the subthreshold region only three variables are required to explain the essential dynamic properties of the cell. In this three-dimensional space the solutions tend to lie on a surface which resembles a paraboloid. We use a simplified model of this model to explain both the dynamics of the solutions on this surface and the form of the bifurcation diagram.

A model of intrinsic and driven spindling in thalamocortical neurons

We add a slow hyperpolarization-activated inward current IH = gHmH (v-vH) to our previous model of rebound bursting (Hindmarsh & Rose Phil. Trans. R. Soc. Lond. B 346, 129-150 (1994a)) to give a four-dimensional physiological model, and a corresponding four-dimensional model of the model. The physiological model generates periodic 'bursts of bursts' or 'spindles' resembling those recorded experimentally in thalamocortical (TC) neurons. The model of the model is simplified to a two-dimensional system having a limit cycle which corresponds to the slow spindle oscillation of the physiological model. Analysis of the stability of this two-dimensional model allows us to divide the parameter space of the slope (gamma mH) and shift (theta mH) parameters of mH infinity (v) into regions in which the model generates spindles or continuous bursting. This enables us to determine the parameter values required for spindling in the physiological model and to explain the experimentally observed effects of noradrenaline. Next we examine whether a cell at a stable equilibrium point can be driven into spindling by applying a sinusoidal input at the resonant frequency. This is done by averaging the equations for the driven model of the model. Analysis of the stability of these averaged equations shows how the regions of the (theta mH, gamma mH) parameter space change when the system is driven by a sinusoidal input. This enables us to choose parameter values for a physiological model of a driven spindle. We show that if the physiological model is modified to include a voltage-dependent time constant for mH, spindles, similar to those of TC cells, can be obtained with a small Ca(2+)-activated K+ current. Finally our knowledge of the form of the bifurcation diagram and the conditions for resonance leads to a new suggestion for the roles of GABAA and GABAB inhibitory postsynaptic potentials when TC cells are driven into spindling by neurons of the nucleus reticularis thalami.

Predicting astronaut effectiveness: a multivariate approach

In this study, measures of astronaut effectiveness were administered to volunteers from the astronaut corps in order to validate psychological "select-in" criteria for long-duration space missions. Using a peer nomination format, astronauts rated their peers with whom they had either flown or trained. Factor analysis revealed two latent performance dimensions: job competence and group living. The job competence dimension measured the instrumental aspects relating to job knowledge and job performance. The group living dimension measured the interpersonal aspects relating to teamwork and desirability as a colleague on Space Station. Analyses revealed that the personality variables could explain a significant proportion of the variance in the group living performance dimension, but not the job competence performance dimension. The findings are not surprising since astronauts are highly screened on the basis of past attainment, but are not as highly screened on aspects relating to teamwork and interpersonal concerns.

Psychological predictors of astronaut effectiveness

Are the personality characteristics of astronauts related to their professional effectiveness? In order to answer this question, effectiveness and personality data were collected from 65 NASA astronauts. Several findings emerged from these data. Five personality subscales were related to effectiveness in one form or another. They were: high Negative Expressivity and Negative Communion (subordinate and gullible), low Impatience and Irritability, low Openness (to new ideas and experiences), low Negative Instrumentality (egoism) and high Agreeableness. Examining the graphs of these relationships indicated that they were not linear. This examination indicated that high levels on these undesirable personality characteristics (e.g., Impatience/Irritability) were distributed across all levels of effectiveness. Low levels of the undesirable personality characteristics were found only among the most effective astronauts. We concluded that these other-directed personality qualities will assume increasing importance in long-term spaceflight, and consequently, should be the focus of greater attention in future astronaut selection and training.

Abnormal lipid composition of bronchoalveolar lavage fluid obtained from individuals with AIDS-related lung disease

Surfactant lipids are not only important to the physiologic function of the lungs, but may also influence disease processes like Pneumocystis pneumonia, in which the interaction of host-defense cells with pathogen occurs within the confines of the surfactant-rich alveolar hypophase. In the present studies the lipid profile of bronchoalveolar lavage fluid (BALF) was characterized in subjects with AIDS-related lung diseases including Pneumocystis pneumonia. BALF lipid and total protein measurements were made in 43 subjects with acquired immune deficiency syndrome (AIDS)-related lung disease and compared with those made in 50 normal human immunodeficiency virus (HIV)-seronegative controls. The AIDS patient samples contained significantly greater amounts of total cholesterol, phosphatidylglycerol (PG), and protein than the control samples; in contrast to previous observations in rodent P. carinii infection, no differences were seen in total phospholipid (PL) or phosphatidylcholine (PC) in the two groups. The proportions of several of these lipids were deranged in BALF obtained from the patient group: PG/PL and PC/cholesterol differed significantly from normal samples. In the subset of patients with AIDS-related Pneumocystis pneumonia, no correlation was apparent between discrete BALF lipids and clinical indices reflective of disease severity. Using these measurements to approximate the lipid composition of the alveolar microenvironment in AIDS-related lung disease, we performed experiments in which normal human alveolar macrophages were exposed to exogenous liposomal lipids and then challenged with P. carinii. The ingestion but not binding of P. carinii by macrophages was diminished as a result of lipid exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Human immunodeficiency virus type 1 infection of human macrophages modulates the cytokine response to Pneumocystis carinii

The present studies examined production of the cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and IL-6 by human monocyte-derived macrophages exposed to Pneumocystis carinii in vitro and the impact of concurrent macrophage infection with human immunodeficiency virus type 1 (HIV-1) on these cytokine responses. Macrophages were infected with the HIV-1 BaL monocytotropic strain for 10 to 14 days and then exposed to P. carinii. At various times following P. carinii treatment, culture supernatants were harvested to assess the cytokine profile. Addition of P. carinii to HIV-uninfected macrophages resulted in augmented production of IL-6, TNF-alpha, and IL-1 beta protein. By contrast, in HIV-infected macrophages exposed to P. carinii, only the release of IL-6 was increased compared with that for HIV-uninfected macrophages, while the levels of TNF-alpha and IL-1 beta decreased. This altered response was confirmed at the molecular level for TNF-alpha mRNA. Preventing physical contact between P. carinii and macrophages by a membrane filter inhibited all cytokine release. Substituting P. carinii with a preparation of P. carinii 95- to 115-kDa major membrane glycoprotein A yielded a response similar to that obtained by addition of intact P. carinii. These results suggest that HIV-1 infection of human macrophages modulates cytokine responses to P. carinii.

Long-term performance and wear of ultrahigh-molecular-weight polyethylene in total joint replacement prostheses: a brief overview and perspective

Ultrahigh-molecular-weight polyethylene (UHMWPE) is used extensively in total joint replacements, particularly in hip and knee joints. At present, there is extensive concern with the long-term consequences of wear of this material, specifically osteolytic reactions to wear debris. The relationship of wear behavior to polymer morphology is almost completely unknown. Information on the effects of radiation sterilization on crystallinity is available, but gross conflicts exist. A central problem is the release, over long time periods, of huge numbers of submicron particles by wear. It has not been generally recognized that short-term, severe wear and long-term wear of UHMWPE in total joint replacements are very different in character and results. When the long-term wear regime is correctly defined, it is clear that knowledge of the influence of structure and properties on this specific phenomenon is almost completely absent.

Assessments of astronaut effectiveness

This study examined the reliability and convergent validity of three methods of peer and supervisory ratings of the effectiveness of individual NASA astronauts and their relationships with flight assignments. These two techniques were found to be reliable and relatively convergent. Seniority and a peer-rated Performance and Competence factor proved to be most closely associated with flight assignments, while supervisor ratings and a peer-rated Group Living and Personality factor were found to be unrelated. Results have implications for the selection and training of astronauts.

Concurrent infection of human macrophages with HIV-1 and Mycobacterium avium results in decreased cell viability, increased M. avium multiplication and altered cytokine production

The effects of a concurrent HIV-1 and Mycobacterium avium infection in vitro were assessed in human peripheral blood-derived macrophages (M phi). M phi were infected with HIV-1Ba-L strain for 14 days then infected with M. avium (HIV/M. avium) or treated with LPS (HIV/LPS). At various times after M. avium or LPS treatment, Mo phi cultures were harvested for quantitation of HIV and M. avium replication, as well as M phi cellular viability. In addition, mRNA and supernatants were collected for assessment of induction of the cytokines TNF-alpha, IL-1 beta and IL-6. M. avium multiplication was greater in HIV-infected M phi, whereas no difference in virus production, based on p24 and RT values, was observed between HIV-infected cells and HIV/M. avium or HIV/LPS M phi. M. avium infection of HIV-1-infected M phi also caused a decrease in viability of the M phi. HIV-1/M. avium-infected M phi had a 24 h delay in induction of TNF-alpha steady state mRNA when compared with HIV/LPS or M. avium only or LPS-only treated M phi. HIV infection also increased the amount and the length of induction of IL-1 beta and IL-6 steady state mRNA stimulated by either M. avium or LPS. In addition, prolonged and increased protein production of TNF-alpha, IL-6, and IL-1 beta was observed in HIV/M. avium-infected cells when compared with the other treatments. In direct contrast to M. avium infection, no significant differences in LPS-induced protein production of the three cytokines was observed between HIV-1-infected and -noninfected M phi. Treatment of HIV/M. avium-infected cells with human rGM-CSF did not increase either the time or quantity of induction of TNF-alpha mRNA or protein production in HIV/M. avium-infected M phi. The increase in M. avium numbers, dysregulation of cytokine production, and subsequent cell death seen in vitro in HIV/M. avium-infected human M phi may reflect part of the underlying cause of the highly disseminated M. avium disease pattern observed in AIDS patients.

Concurrent infection of human macrophages with HIV-1 and Mycobacterium avium results in decreased cell viability, increased M. avium multiplication and altered cytokine production

The effects of a concurrent HIV-1 and Mycobacterium avium infection in vitro were assessed in human peripheral blood-derived macrophages (M phi). M phi were infected with HIV-1Ba-L strain for 14 days then infected with M. avium (HIV/M. avium) or treated with LPS (HIV/LPS). At various times after M. avium or LPS treatment, Mo phi cultures were harvested for quantitation of HIV and M. avium replication, as well as M phi cellular viability. In addition, mRNA and supernatants were collected for assessment of induction of the cytokines TNF-alpha, IL-1 beta and IL-6. M. avium multiplication was greater in HIV-infected M phi, whereas no difference in virus production, based on p24 and RT values, was observed between HIV-infected cells and HIV/M. avium or HIV/LPS M phi. M. avium infection of HIV-1-infected M phi also caused a decrease in viability of the M phi. HIV-1/M. avium-infected M phi had a 24 h delay in induction of TNF-alpha steady state mRNA when compared with HIV/LPS or M. avium only or LPS-only treated M phi. HIV infection also increased the amount and the length of induction of IL-1 beta and IL-6 steady state mRNA stimulated by either M. avium or LPS. In addition, prolonged and increased protein production of TNF-alpha, IL-6, and IL-1 beta was observed in HIV/M. avium-infected cells when compared with the other treatments. In direct contrast to M. avium infection, no significant differences in LPS-induced protein production of the three cytokines was observed between HIV-1-infected and -noninfected M phi. Treatment of HIV/M. avium-infected cells with human rGM-CSF did not increase either the time or quantity of induction of TNF-alpha mRNA or protein production in HIV/M. avium-infected M phi. The increase in M. avium numbers, dysregulation of cytokine production, and subsequent cell death seen in vitro in HIV/M. avium-infected human M phi may reflect part of the underlying cause of the highly disseminated M. avium disease pattern observed in AIDS patients.

Definition of a responder: analysis of behavioral, cardiovascular, and endocrine responses to varied workload in air traffic controllers

Individual differences in behavioral, cardiovascular, and endocrine responses to varying workload among 381 air traffic controllers were assessed using random regression modeling. Although most men showed significant increases in behavioral arousal associated with increasing planes, there were major individual differences in response in systolic and diastolic blood pressure, heart rate, and cortisol. Approximately 20% to 25% of those studied had large increases in each of these domains, along with a smaller group showing inverse responses in heart rate and cortisol. There was also evidence of a smaller number of enhanced responders within the highest groups, who tended to have more missing values at higher levels of workload. There was convergence in the definition of responders using three statistical strategies: random regression, correlational analyses, and ANOVA. Response in one physiological/behavioral domain was essentially independent of response in another, supporting the conclusion of specificity, rather than a global tendency to respond to increasing work load.

Results of a structured psychiatric interview to evaluate NASA astronaut candidates

One hundred six astronaut applicants who had passed initial screening were evaluated for Axis I and Axis II DSM-III-R diagnoses using a structured psychiatric interview. Nine of 106 candidates (8.5%) met diagnostic criteria for six Axis I (including V-code), or Axis II disorders. The use of the NASA structured interview was effective in identifying past and present psychopathology in a group of highly motivated and healthy astronaut applicants. This was the first time that a structured interview had been used in such a setting for this purpose. The methodology described is applicable to any situation where the presence or history of psychopathology requires evaluation for job selection (e.g. pilot selection).

The effect of aerosolized recombinant human granulocyte macrophage colony-stimulating factor on lung leukocytes in nonhuman primates

The number and function of myeloid cells in the lungs are critical determinants of health and disease. To examine whether these cells can be modulated in vivo by a colony-stimulating factor (CSF), recombinant human granulocyte macrophage-CSF (GM-CSF) was given to cynomolgus monkeys by either continuous intravenous infusion (7,200 U/kg/day) for 2 wk or by aerosol exposure to 10(7) U on 1 or 2 consecutive days. At intervals after the initiation of GM-CSF administration, animals underwent bronchoalveolar lavage (BAL) and had peripheral blood sampled to characterize changes in lung and circulating phagocytic cells. Compared with animals exposed to bovine serum albumin, there was an increase in the total number of BAL cells retrieved. This increase was greatest in animals receiving aerosolized GM-CSF, and it was the result of more macrophages and neutrophils. Both lung macrophages and blood neutrophils from animals exposed to aerosolized GM-CSF exhibited an augmented respiratory burst in response to phorbol myristate acetate. Lung macrophages from GM-CSF-exposed animals exhibited increased capacity to bind and/or ingest opsonized and unopsonized Staphylococcus aureus. Despite functional activation of lung phagocytic cells, biochemical analyses of BAL fluid for markers of lung injury revealed an increase in only some parameters in the GM-CSF group. Intravenous administration of GM-CSF had the expected effect on augmenting the number of myeloid cells in the bloodstream. Aerosolized GM-CSF produced a transient effect on circulating myeloid cell number between 3 and 5 days after exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of colony stimulating factor activity in the human respiratory tract. Comparison of healthy smokers and nonsmokers

The number and function of pulmonary macrophages are critical to lung homeostasis. To characterize factors normally present in the human respiratory tract that can influence these parameters, bronchoalveolar lavage (BAL) fluid obtained from healthy smokers and nonsmokers was assayed for the presence of colony-stimulating factor (CSF) activity. Concentrated BAL fluid from both populations was capable of inducing incorporation of [3H]thymidine by murine macrophages. The mean increase (+/- SEM) in incorporation over control cultures not exposed to BAL fluid was 0.98 +/- 0.22 for nonsmokers and 2.25 +/- 1.19 for smokers (p less than 0.001). This CSF bioactivity was characterized as macrophage-CSF (M-CSF) by virtue of its action on murine macrophages, the detection of M-CSF protein by a specific ELISA assay, and the inability to detect other macrophage-active CSFs, granulocyte macrophage-CSF (GM-CSF) and interleukin-3 (IL-3), in a proliferation assay employing the MO7E cell line. There was a significant correlation between macrophage number in BAL samples and measureable bioactivity among both smokers and nonsmokers (r = 0.763; p less than 0.001). This suggested that macrophages themselves are a source of the M-CSF detected in BAL fluid. To examine this possibility, slot-blot analysis of macrophage RNA was performed. Constitutive expression of comparable amounts of M-CSF mRNA and protein was found in cells from both smokers and nonsmokers. However, macrophages obtained from a randomly selected subset of four smokers but none of five nonsmokers exhibited increased production of M-CSF in response to an inflammatory stimulus, lipopolysaccharide (LPS; 5 ng/ml). M-CSF added to macrophage cultures was degraded by nonsmokers' cells as expected over 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipid content of alveolar lining material collected by bronchoalveolar lavage. Improved methods for measuring the major lipid classes

Current methods for measuring lung lipids obtained by bronchoalveolar lavage are time consuming and require sample extraction with organic solvents. Here we utilized enzymatic methods for measuring the major phospholipid classes found in human bronchoalveolar lavage fluid (BALF), namely phosphatidylcholine and phosphatidylglycerol, as well as the neutral lipid cholesterol. These assays can be carried out on as little as 200 microliters lavage fluid in 96-well microtiter plates without the need for organic solvents. Results were verified by comparison with HPLC and chemical methods. The measured values by all three methods were in agreement with previous studies in which lipid analysis was performed by thin-layer chromatography. By contrast to thin-layer chromatography, however, the methods described here can be efficiently performed with small quantities of material without sacrificing accuracy. This methodology can facilitate the characterization of the major surfactant-associated lipids in BALF and foster improved understanding of the role of these lipids in human lung disease.

Glucocorticoid receptor binding in three different cell types in major depressive disorder: lack of evidence of receptor binding defect

1. In order to further understand the apparent glucocorticoid resistance in major depressive disorder, circadian variation in cortisol concentration, dexamethasone suppression and glucocorticoid receptor binding in mononuclear leukocytes, polymorphonuclear leukocytes and cultured skin fibroblasts were measured in rigidly defined major depressive disorder patients and non-depressed psychiatric controls. 2. Mononuclear leukocytes binding to glucocorticoid correlated significantly with polymorphonuclear leukocytes binding to glucocorticoid, but both determinations failed to differentiate major depressive disorder and control subjects. 3. Initial and post-dexamethasone in vitro fibroblast binding to glucocorticoid was not different between major depressive disorder and non-depressed control subjects. 4. The phenomenon of glucocorticoid resistance in major depressive disorder remains unexplained.

New rapid method for the study of Pneumocystis carinii interaction with alveolar macrophages

Understanding the pathophysiology of Pneumocystis carinii infection has been limited by the availability of methods for precisely measuring the interaction of P. carinii with host cells. Here we describe a new method which allows for the rapid assessment of P. carinii binding to, and internalization by, adherent alveolar macrophages. The method is based on the detection of fluorescein-labelled P. carinii by an automated fluorescence measurement system.

Indicators of Pneumocystis carinii viability in short-term cell culture

Growth of P. carinii in culture has been difficult to document in the absence of reliable methods for distinguishing live from dead organisms. We studied three markers of cell function in P. carinii during the course of short-term cell culture, and correlated these with the number of P. carinii present in culture supernatants. The markers were glucan synthase activity, esterase activity and cell membrane integrity. The last two were assessed by double staining with fluorescein diacetate and propidium iodide followed by analysis of fluorescence using flow cytometry. The rise in P. carinii number after 5 to 7 days in culture was associated with increased glucan synthase activity. Flow cytometry analysis of day-6 P. carinii cultures confirmed that over 80% of the organisms catalyzed the conversion of fluorescein diacetate to fluorescein and excluded propidium iodide. The demonstration of three indices of metabolic activity in an expanding P. carinii population has confirmed the efficacy of a culture system as a means of sustaining the continued activity, albeit short-lived, of viable P. carinii.

The effects of extracellular matrix (ECM) proteins on the attachment of Pneumocystis carinii to lung cell lines in vitro

Pneumocystis carinii cells labeled with fluorescein isothiocyanate were co-cultured with tissue culture cells. Measurements of attachment was determined by the tissue culture cell fluorescence after washing out the P. carinii organisms. The effects of the extracellular matrix proteins, laminin and fibronectin, on the binding of P. carinii onto the monolayer of cultured cells were investigated for better understanding of organism-cell interactions. The internalization of P. carinii by MRC5 cells was observed.

Uptake of Pneumocystis carinii mediated by the macrophage mannose receptor

Human exposure to Pneumocystis carinii is common but, in the absence of acquired or genetic dysfunction of either cellular or humoral immunity, exposure rarely leads to illness. Although alveolar macrophages can degrade P. carinii, macrophage receptors involved in P. carinii recognition have not been clearly defined. Characterization of a predominant surface glycoprotein of the high mannose type led us to investigate the role of the macrophage mannose receptor in this process. We report here that binding and uptake of cultured rat P. carinii by human and rat alveolar macrophages is reduced by 90% in the presence of competitive inhibitors of mannose receptor activity and by adherence of alveolar macrophages to mannan-coated surfaces. Further, only those COS cells transfected with the human macrophage mannose receptor complementary DNA that express surface mannose receptors bind and ingest P. carinii. These studies establish that the macrophage mannose receptor is sufficient for uptake of P. carinii and emphasize the role of the alveolar macrophage in first-line host defence against P. carinii.

Increased recovery of surfactant protein A in AIDS-related pneumonia

Respiratory infection with Pneumocystis carinii (PC) is the most frequent serious opportunistic infection in the clinical setting of acquired immunodeficiency syndrome (AIDS). The factors responsible for the predisposition of human immunodeficiency virus (HIV)-infected patients for PC infection are not fully understood. We postulated that changes in the alveolar lining material (ALM) could play a role in the pathogenesis of PC infection in AIDS. We have compared constituents of ALM in bronchoalveolar lavage fluid from normal, nonsmoking volunteers with that of HIV-infected patients with pneumonia. Using an ELISA, we found that surfactant protein A (SP-A) was markedly elevated in the pneumonia patients. Mean SP-A values for the normal nonsmoking individuals (n = 21) were 1.50 +/- 0.25 micrograms/ml (mean +/- SEM). SP-A levels in the HIV-infected patients (n = 22) were significantly elevated (p less than 0.01) with a mean of 5.23 +/- 0.54 micrograms/ml. This increase was greatest in the patients with more clinically severe pneumonia. The increase in SP-A did not appear to be pathogen-specific as it was also observed in cases of non-PC pneumonia. We also found that total protein levels were nearly five times higher in the HIV-infected pneumonia patients. These studies indicate that the protein component of the ALM is markedly different from normal in cases of HIV-associated PC and non-PC infection. Further investigation is needed to determine the mechanism of these alterations and their role, if any, in AIDS-related pneumonia.

Frequent identification of HIV-1 DNA in bronchoalveolar lavage cells obtained from individuals with the acquired immunodeficiency syndrome

Tissue macrophages are recognized as a cellular target for infection with the human immunodeficiency virus type 1 (HIV-1). To characterize the nature of this cell-retrovirus interaction within the lower respiratory tract we analyzed fluid and cells obtained by bronchoalveolar lavage (BAL) of eight individuals with acquired immunodeficiency syndrome (AIDS) who were undergoing diagnostic fiberoptic bronchoscopy. Of these eight individuals, seven had active infection with Pneumocystis carinii; one had suspected cytomegalovirus pneumonitis. At the time of study two were receiving the antiretroviral drug zidovudine (azidothymidine [AZT]). HIV-1 could not be isolated from any of the eight samples of BAL fluid concentrated by ultracentrifugation through 20% sucrose. HIV-1 antigen (p24) was detected in one of eight samples of concentrated BAL fluid but could not be found in eight samples of media conditioned by overnight incubation with adherent BAL cells. Despite the infrequent detection of HIV-1 antigen it was possible to identify HIV-1 genomic sequences by the use of a DNA amplification technique, the polymerase chain reaction, in all eight BAL cell preparations. In BAL cells adherent for up to 5 days in culture this method detected retroviral DNA that hybridized to a complementary pair of primers located in the env and gag gene regions of HIV-1. These studies demonstrate the uniform presence of HIV-1 harboring cells within the airways of the lung in individuals with AIDS and active respiratory infection and may have implications for local organ defense.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth inhibition of Mycobacterium avium complex in human alveolar macrophages by the combination of recombinant macrophage colony-stimulating factor and interferon-gamma

The reservoir of Mycobacterium avium complex (MAC) during human infection is the mononuclear phagocyte. In these studies, the ability of certain macrophage-active cytokines to affect MAC growth in human alveolar macrophages was evaluated. Neither recombinant interferon-gamma (2 x 10(2) to 10(3) U/well of 5 x 10(5) cells) nor recombinant macrophage colony-stimulating factor (20 to 50 ng/well), when tested alone, exhibited a consistent ability to induce macrophage targets to inhibit the growth of a clinical strain of MAC serovar 4. However, the combination of these cytokines (1 to 50 ng macrophage colony-stimulating factor + 10(3) U interferon per well) was remarkably effective in diminishing replication of MAC in all experiments. These cytokines were also able to induce alveolar macrophages to restrict MAC growth even though cells were obtained from several individuals with acquired immunodeficiency syndrome (AIDS) or from normal donors and infected in vitro with the human immunodeficiency virus type 1. The effect of this cytokine combination was not abrogated by 10(4) neutralizing U/ml of anti-tumor necrosis factor-alpha antibody. Rather, the combination of interferon-gamma and macrophage colony-stimulating factor appeared to activate intrinsic macrophage mechanisms for restricting MAC growth and deserves further study to determine the potential value of this cytokine combination in the treatment of human infection.

Immunology of the lung in HIV infection: the pathophysiologic basis for the development of tuberculosis in the AIDS setting

Active tuberculosis is now recognized as a frequent and serious complication of infection with the human immunodeficiency virus (HIV), the causative agent of AIDS. HIV mediated alteration in host defenses against mycobacteria contribute to the magnitude and severity of this problem. HIV can affect a variety of cellular mechanisms important in the restriction of mycobacterial growth. Qualitative and quantitative defects in T lymphocyte function result from direct HIV infection of cells expressing the CD4 epitope, and can severely limit the production of macrophage activating cytokines capable of inducing an anti-mycobacterial state in cells of monocyte lineage. In addition, macrophages themselves are susceptible to HIV infection, and have been shown to be defective with respect to a variety of host defense functions. Both T4 lymphopenia and HIV infected macrophages are present in the lower respiratory tract of HIV infected individuals, a circumstance which likely underlies the unique susceptibility of HIV infected to tuberculosis.