The curli regulator CsgD mediates stationary phase counter-silencing of csgBA in Salmonella Typhimurium.

Integration of horizontally acquired genes into transcriptional networks is essential for the regulated expression of virulence in bacterial pathogens. In Salmonella enterica, expression of such genes is repressed by the nucleoid-associated protein H-NS, which recognizes and binds to AT-rich DNA. H-NS-mediated silencing must be countered by other DNA-binding proteins to allow expression under appropriate conditions. Some genes that can be transcribed by RNA polymerase (RNAP) associated with the alternative sigma factor σS or the housekeeping sigma factor σ70 in vitro appear to be preferentially transcribed by σS in the presence of H-NS, suggesting that σS may act as a counter-silencer. To determine whether σS directly counters H-NS-mediated silencing and whether co-regulation by H-NS accounts for the σS selectivity of certain promoters, we examined the csgBA operon, which is required for curli fimbriae expression and is known to be regulated by both H-NS and σS . Using genetics and in vitro biochemical analyses, we found that σS is not directly required for csgBA transcription, but rather up-regulates csgBA via an indirect upstream mechanism. Instead, the biofilm master regulator CsgD directly counter-silences the csgBA promoter by altering the DNA-protein complex structure to disrupt H-NS-mediated silencing in addition to directing the binding of RNAP.

Deposition of C3b and iC3b onto particulate activators of the human complement system. Quantitation with monoclonal antibodies to human C3.

Monoclonal antibodies were used to determine the number and molecular form of C3 bound to particulate activators of the complement (C) system by human serum. Sheep erythrocytes (E) coated with IgM (EIgM) and IgG (EIgG) were used to study activation of the classical pathway (CP). Yeast (Y), rabbit erythrocytes (ER), and five species of bacteria (Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae type 3, Streptococcus pyogenes, and Hemophilus influenzae type b) were used to study activation of the alternative pathway (AP). The deposition of C3b onto EIgM and EIgG incubated in C7-deficient human serum was dependent on the serum concentration. At all serum concentrations tested, there was complete conversion of C3b to iC3b. Kinetic analysis of C3b deposition and conversion to iC3b indicated that these events occurred almost simultaneously; the reaction was completed by 15 min. The deposition of C3 onto the AP activators ER and Y was also dependent on serum concentration, and ER, but not Y, required the presence of Mg-EGTA and thus the activation of only the AP. C3b deposition and conversion to iC3b on Y was complete in 15 min, with 82% of bound C3 converted to iC3b. For ER, maximum C3 deposition required 30 min in both the presence and absence of Mg-EGTA. However, after 1 h of incubation, 74% of bound C2 was iC3b in the absence of Mg-EGTA, compared with only 52% in the presence of Mg-EGTA. Thus, even on AP activators, a large portion of C3b may be converted to iC3b, and this conversion is probably controlled by elements on the particle's surface. Studies with the five species of bacteria yielded similar results. Approximately 3-5 X 10(4) molecules of C3 were bound per microorganism, with opsonization being completed in 30 min. Remarkably, only 16-28% of bound C3 was in the form of iC3b, even after 2 h of incubation. The presence or absence of Mg-EGTA, or the addition of purified CR1 to the reaction mixture, did not significantly effect the ratio of C3b to iC3b. Finally, SDS-PAGE and autoradiography of particle-bound 125I-C3 fragments confirmed that there was no conversion of iC3b to C3d,g or C3d. The data obtained about the opsonization of bacteria suggest that the predominant form of C3 that is encountered by inflammatory phagocytes may be C3b.

Phagocytosis of senescent neutrophils by human monocyte-derived macrophages and rabbit inflammatory macrophages.

An in vitro system to investigate the ability of macrophages to recognize and ingest senescent polymorphonuclear neutrophils has been used that uses chromium-labeled neutrophils and staining for myeloperoxidase (MPO). Human monocyte-derived macrophages obtained from in vitro cultures were able to recognize "aged" but not freshly isolated 51Cr-labeled human neutrophils and ingest them. Freshly isolated monocytes did not exhibit this property. Because the aged neutrophils were greater than 95% viable, death did not appear to be a prerequisite for recognition and ingestion. Serum was not required for the aging of the neutrophils, and when serum was used, different concentrations did not appear to effect the aging process; that is, neutrophils aged in different concentrations of serum were ingested equally. Phagocytosis of senescent neutrophils by macrophages occurred in a time-dependent manner and was also dependent on the number of neutrophils added. Monocyte-derived macrophages first exhibited the ability to phagocytose senescent neutrophils on the 3rd d of culture, with the percentage of active macrophages increasing through day 7. In experiments with rabbit mononuclear phagocytes, immune complex-induced inflammatory macrophages from the lung but not resident bronchoalveolar macrophages or peripheral blood monocytes were found to be capable of recognition and ingestion of senescent rabbit neutrophils. These data suggest that the monocyte maturation process, akin to that seen during inflammation, is necessary in vitro before macrophages recognize and remove senescent neutrophils.

Generation of three different fragments of bound C3 with purified factor I or serum. II. Location of binding sites in the C3 fragments for factors B and H, complement receptors, and bovine conglutinin.

The many different recognized functions of C3 are dependent upon the ability of the activated C3 molecule both to bind covalently to protein and carbohydrate surfaces and to provide binding sites for as many as eleven different proteins. The location of the binding sites for six of these different proteins (factors B and H, complement receptors CR(1), CR(2) and CR(3) and conglutinin) was examined in the naturally occurring C3-fragments generated by C3 activation (C3b) and degradation by Factor I (iC3b, C3c, C3d,g) and trypsin (C3d). Evidence was obtained for at least four distinct binding sites in C3 for these six different C3 ligands. One binding site for B was detectable only in C3b, whereas a second binding site for H and CR(1) was detectable in both C3b and iC3b. The affinity of the binding site for H and CR(1) was charge dependent and considerably reduced in iC3b as compared to C3b. H binding to iC3b-coated sheep erythrocytes (EC3bi) was measurable only in low ionic strength buffer (4 mS). The finding that C3c-coated microspheres bound to CR(1), indicated that this second binding site was still intact in the C3c fragment. However, H binding to C3c was not examined. A third binding site in C3 for CR(2) was exposed in the d region by factor I cleavage of C3b into iC3b, and the activity of this site was unaffected by the further I cleavage of iC3b into C3d,g. Removal of the 8,000-dalton C3g fragment from C3d,g with trypsin forming C3d, resulted in reduced CR2 activity. However, because saturating amounts of monoclonal anti-C3g did not block the CR(2)-binding activity of EC3d,g, it appears unlikely that the g region of C3d,g or iC3b forms a part of the CR(2)-binding site. In addition, detergent-solubilized EC3d (C3d-OR) inhibited the CR(2)-binding activity of EC3d,g. Monocytes and neutrophils, that had been previously thought to lack CR(2) because of their inability to form EC3d rosettes, did bind EC3d,g containing greater than 5 x 10(4) C3d,g molecules per E. The finding that monocyte and neutrophil rosettes with EC3d,g were inhibited by C3d-OR, suggested that these phagocytic cells might indeed express very low numbers of CR(2), and that these CR(2) were detectable with EC3d,g and not with EC3d because C3d,g had a higher affinity for CR2 than did C3d. A fourth C3 binding site for CR(3) and conglutinin (K) was restricted to the iC3b fragment. Because of simultaneous attachment of iC3b to phagocyte CR3 and CR(3), the characteristics of iC3b binding to CR3 could only be examined with phagocytes on which the CR(1) had been blocked with anti-CR(1). Inhibition studies with EDTA and N-acetyl-D-glucosamine demonstrated a requirement for both calcium cations and carbohydrate in the binding of EC3bi to CR3 and to K. However, CR(3) differed from K in that magnesium cations were required in addition to calcium for maximum CR(3) binding activity, and NADG produced less inhibition of CR(3) activity than of K activity.

Modulation of the effector function of human macrophages for Histoplasma capsulatum by HIV-1. Role of the envelope glycoprotein gp120.

We have demonstrated that monocyte-derived macrophages (Mphi) from HIV+ individuals are deficient in their capacity to phagocytose Histoplasma capsulatum (Hc) yeasts, and are more permissive for the intracellular growth of Hc. To determine whether these defects in Mphi function were caused by HIV infection of the Mphi and/or by pathological events associated with HIV infection, cultured normal human Mphi were infected with the HIV-1BaL strain. Virus production, quantified by reverse transcriptase activity and p24 antigen, was evident on day 8 after infection and peaked on day 16. On days 12, 16, and 20 after infection, HIV-1-infected Mphi were deficient in their capacity to recognize and bind Hc yeasts compared with control Mphi, and also were more permissive for the intracellular growth of Hc. Culture of normal Mphi with the envelope glycoprotein gp120 inhibited phagocytosis of Hc yeasts by Mphi in a concentration-dependent manner, but did not cause more rapid intracellular growth of Hc. Normal Mphi cultured in the serum of HIV+ individuals with impaired Mphi function subsequently were deficient in their capacity to phagocytose Hc yeasts, and were more permissive for the intracellular growth of yeasts compared with Mphi cultured in normal serum. Conversely, culture of normal Mphi in the serum of HIV+ patients with normal Mphi function did not affect the interaction of Hc yeasts with Mphi. Moreover, when Mphi from HIV+ individuals that were initially defective in host defense against Hc were cultured in normal HIV- serum, normal Mphi function was demonstrated. Adsorption of gp120 from the serum of two HIV+ patients removed the capacity of the serum to cause a Mphi defect in phagocytosis of Hc, but had no effect on the capacity of the serum to cause accelerated intracellular growth. These data demonstrate that observed defects in Mphi interaction with Hc yeasts may be caused by gp120 and other, as yet unknown serum component(s) probably released into serum by HIV-infected cells.

Regulation of human monocyte/macrophage function by extracellular matrix. Adherence of monocytes to collagen matrices enhances phagocytosis of opsonized bacteria by activation of complement receptors and enhancement of Fc receptor function.

In inflammation monocytes emigrate from the peripheral circulation into an extravascular area rich in extracellular matrix proteins. In this milieu, phagocytes ingest and kill invading pathogens. In the present studies, we found that monocytes adhered to type I collagen gels phagocytized 2.5-12-fold more opsonized Escherichia coli, Staphylococcus aureus, Streptococcus pyogenes, and Streptococcus pneumoniae than plastic-adherent monocytes. The rate of phagocytosis and the number of bacteria ingested by collagen-adherent monocytes was equal to, or greater than, the number of bacteria ingested by 7-d cultured macrophages (M phi). Although both collagen- and plastic-adherent monocytes were bactericidal for E. coli and S. aureus, more bacteria were killed by collagen-adherent monocytes by virtue of their enhanced phagocytic capacity. Cultured M phi only were bacteriostatic. Adherence of monocytes to collagen gels activated C receptors (CR) types 1 and 3 for phagocytosis, and enhanced Fc receptor (FcR)-mediated phagocytosis. Collagen- and plastic-adherent monocytes produced equivalent amounts of superoxide anion in response to phorbol myristate acetate and opsonized zymosan. Thus, the enhanced phagocytosis and killing of opsonized bacteria by collagen-adherent monocytes appear to be by regulation of the function of membrane CR and FcR, without apparent enhancement of the respiratory burst. These data suggest that adherence of monocytes to the extracellular matrix during inflammation may rapidly activate these cells for enhanced phagocytic bactericidal activity.

Human neutrophil-mediated fungistasis against Histoplasma capsulatum. Localization of fungistatic activity to the azurophil granules.

Human neutrophils (PMN) demonstrated potent fungistatic activity against Histoplasma capsulatum (Hc) yeasts in a sensitive microassay that quantifies the growth of yeasts by the incorporation of [3H]leucine. At a PMN:yeast ratio of 1:2, PMN inhibited the growth of yeasts by 37%. Maximum inhibition of 85% to 95% was achieved at a PMN/yeast ratio of 10:1 to 50:1. Opsonization of the yeasts in fresh or heat-inactivated serum was required for PMN-mediated fungistasis, but ingestion of the yeasts was not required. Recognition and phagocytosis of opsonized yeasts was via PMN complement receptor (CR) type 1 (CR1), CR3, and FcRIII (CD16). PMN fungistatic activity was evident by 2 h, was maximum at 24 h, and persisted up to 5 d. In contrast, yeasts multiplied within monocytes to a greater extent than in culture medium alone. PMN from three patients with chronic granulomatous disease (CGD) inhibited the growth of Hc yeasts by an average of 97%, compared with 86% in three normal controls. Furthermore, preincubation of PMN with the lysosomotropic agent NH4Cl inhibited fungistatic activity in a concentration-dependent manner. Finally, experiments with subcellular fractions of PMN demonstrated that the principal component of the fungistatic activity of PMN was localized in the azurophil granules. These data demonstrate that human PMN possess potent fungistatic activity against Hc yeasts and further show that fungistasis is mediated by antimicrobial agents contained in the azurophil granules.

Phagocytosis of Histoplasma capsulatum yeasts and microconidia by human cultured macrophages and alveolar macrophages. Cellular cytoskeleton requirement for attachment and ingestion.

Phagocytosis of Histoplasma capsulatum (Hc) yeasts and microconidia by human macrophages (M phi) was quantified by a fluorescence quenching technique. Phagocytosis of unopsonized Hc yeasts by monocyte-derived M phi and human alveolar M phi (AM) was rapid. After 60 min, 79% of cultured M phi and 59% of AM had ingested an average of 9.8 and 11 yeasts/M phi, respectively. In contrast, only 26% of monocytes ingested 4.5 yeasts/cell after 60 min. Phagocytosis of unopsonized microconidia by cultured M phi and by AM was equivalent. Monoclonal antibodies specific for the alpha-chains and beta-chain of the CD18 family of adhesion receptors inhibited the binding of Hc yeasts and microconidia to cultured M phi and AM. Thus, the M phi CD18 complex mediates recognition of both phases of this dimorphic fungus. Disruption of actin microfilaments with cytochalasin D inhibited both attachment and ingestion of yeasts by M phi. In contrast, nocodazole, which prevents polymerization of microtubules, did not inhibit binding or ingestion. Both drugs inhibited ingestion, but neither drug inhibited binding of C3b- and C3bi-coated sheep erythrocytes to complement receptors type one (CR1) or type three (CR3), respectively. Therefore, different signal transducing mechanisms for phagocytosis appear to be triggered by the binding of Hc yeasts to CD18, and by the binding of EC3bi to CD11b/CD18, respectively.

Chloroquine induces human macrophage killing of Histoplasma capsulatum by limiting the availability of intracellular iron and is therapeutic in a murine model of histoplasmosis.

We investigated the role of intracellular iron on the capacity of Histoplasma capsulatum (Hc) yeasts to multiply within human macrophages (Mphi). Coculture of Hc-infected Mphi with the iron chelator deferoxamine suppressed the growth of yeasts in a concentration-dependent manner. The effect of deferoxamine was reversed by iron-saturated transferrin (holotransferrin) but not by iron-free transferrin (apotransferrin). Chloroquine, which prevents release of iron from transferrin by raising endocytic and lysosomal pH, induced human Mphi to kill Hc. The effect of chloroquine was reversed by iron nitriloacetate, an iron compound that is soluble at neutral to alkaline pH, but not by holotransferrin, which releases iron only in an acidic environment. Chloroquine (40-120 mg/kg) given intraperitoneally for 6 d to Hc-infected C57BL/6 mice significantly reduced the growth of Hc in a dose-dependent manner. At 120 mg/kg there was a 17- and 15-fold reduction (P < 0.01) in CFU in spleens and livers, respectively. The therapeutic effect of chloroquine also correlated with the length of treatment. As little as 2 d of chloroquine therapy (120 mg/kg), when started at day 5 after infection, reduced CFU in the spleen by 50%. Treatment with chloroquine for 10 d after a lethal inoculum of Hc protected six of nine mice; all control mice were dead by day 11 (P = 0.009). This study demonstrates that: (a) iron is of critical importance to the survival and multiplication of Hc yeasts in human Mphi; (b) in vitro, chloroquine induces Mphi killing of Hc yeasts by restricting the availability of intracellular iron; and (c) in vivo, chloroquine significantly reduces the number of organisms in the spleens and livers of Hc-infected mice and can protect mice from a lethal inoculum of Hc yeasts. Thus, chloroquine may be effective in the treatment of active histoplasmosis and also may be useful in preventing relapse of histoplasmosis in patients with acquired immunodeficiency syndromes.

Dedicated Followers of Fashion? Bioarchaeological Perspectives on Socio-Economic Status, Inequality, and Health in Urban Children from the Industrial Revolution (18th-19th C), England.

The 18th and 19th centuries in England were characterised by a period of increasing industrialisation of its urban centres. It was also one of widening social and health inequalities between the rich and the poor. Childhood is well-documented as being a stage in the life course during which the body is particularly sensitive to adverse socio-economic environments. This study therefore aims to examine the relationship between health and wealth through a comprehensive skeletal analysis of a sample of 403 children (0-17 years), of varying socio-economic status, from four cemetery sites in London (c.1712-1854). Measurements of long bone diaphyseal length, cortical thickness, vertebral neural canal size, and the prevalence of a range of pathological indicators of health stress were recorded from the Chelsea Old Church (high status), St Benet Sherehog (middle status), Bow Baptist (middle status), and Cross Bones (low status) skeletal collections. Children from the low status Cross Bones site demonstrated deficient growth values, as expected. However, those from the high status site of Chelsea Old Church also demonstrated poor growth values during infancy. Fashionable child-care practices (e.g. the use of artificial infant feeds and keeping children indoors) may have contributed to poor infant health amongst high status groups. However, differing health risks in the lower status group revealed the existence of substantial health inequality in London at this time.

Lymphokine-induced monocytic differentiation as a possible mechanism for hypercalcemia associated with adult T-cell lymphoma.

Patients with adult T-cell lymphoma frequently have hypercalcemia. Bone biopsies from these patients show increased numbers of osteoclasts. We hypothesized that substances produced by the malignant T-cell caused these phenomena by increasing the formation and/or activity of osteoclasts. To test this hypothesis, we cultured U937 cells in conditioned media from a clonal T-cell line derived from a patient with adult T-cell lymphoma and hypercalcemia. This conditioned media produced maturational changes in the U937 cells as evidenced by decreased proliferation, increased adherence, increased expression of complement receptors, and formation of multinucleated giant cells. These changes were synergistically enhanced by the addition of 1 alpha, 25-dihydroxyvitamin D3 which is known to promote monocyte differentiation. We also tested interleukin 2 and gamma- and alpha-interferon to see if they were responsible for the maturational changes. Although some effects were seen, these lymphokines could not account for all the changes induced by the T-cell conditioned media. These findings support the above hypothesis and suggest that other unidentified factors may promote the differentiation of osteoclast precursors and be involved in the pathogenesis of the hypercalcemia.

Macrophages in host defense against Histoplasma capsulatum.

Macrophages function in both innate and cell-mediated immunity in host defense against pathogenic fungi. They initially serve as a protected environment in which the primary fungal pathogen Histoplasma capsulatum multiplies and disseminates from the lung to other organs. Upon induction of cell-mediated immunity, cytokines activate macrophages to destroy the yeasts and thus remove them from the host.

Role of cell-surface molecules of Blastomyces dermatitidis in host-pathogen interactions.

The fungal pathogen Blastomyces dermatitidis produces an adhesin (WI-1) in yeast stages, which contains repetitive regions that bind host-cell receptors. Adhesin and glucan may modulate fungal interactions with macrophages; their level of expression is altered in hypovirulent mutants. Adhesin is also involved in immune responses, and may be important in eliciting the clearance of the fungus.

Phagocytosis by receptors for C3b (CR1), iC3b (CR3), and IgG (Fc) on human peritoneal macrophages.

Human peritoneal macrophages (HPM) obtained via laparoscopy were examined for the presence and functional capacity of complement and Fc receptors. Between 5 and 20 ml of peritoneal fluid containing 1-2 X 10(6) macrophages/ml was available for each study. Macrophages made up 80-95% of the cells in the fluid. Fc and C3 receptors on HPM were characterized by rosette formation with, and phagocytosis of, IgG- and C3-coated sheep erythrocytes (E). ElgG were bound by 82% and ingested by 63% of HPM, with 4-15 E ingested/HPM. The HPM formed rosettes with EC3b (56%) and EC3bi (71%) but not EC3d,g or EC3d. Antibodies to complement receptors type 1 (CR1) and type 3 (CR3) inhibited rosette formation with EC3b and EC3bi, respectively, indicating that HPM possessed separate and distinct receptors for the C3b and iC3b ligands. In 60% of the samples studied, HPM demonstrated the ability to ingest both EC3b and EC3bi, as well as ElgG. Because of the heterogeneous nature of the cells obtained in peritoneal fluid, due to their progressive change from monocytelike cells into mature macrophages, HPM were separated by 1 g velocity sedimentation into fractions of increasing maturity. They were then examined for phagocytosis via Fc and complement receptors. Fc receptor mediated phagocytosis occurred throughout the monocyte-to-macrophage maturation sequence, while the ability of HPM to ingest via CR1 and CR3 was maturation dependent, with ingestion via CR3 occurring before CR1, in a manner analogous to in vitro differentiation of monocyte-derived macrophages.

Recurrent meningococcal meningitis with absence of the sixth component of complement: an evaluation of underlying immunologic mechanisms.

A 51/2-year-old black girl with recurrent meningococcal meningitis and absence of the sixth component of complement (C6) is reported. To explore the pathogenesis of recurrent neisserial infections in C6 deficiency, a detailed analysis of her immune competence was conducted. Her serum had normal chemotactic, opsonic, alternative complement pathway, and specific antibody activity, but lacked complement-mediated bacteriolytic activity. In addition, her C6-deficient serum was indistinguishable from normal serum in a complement-dependent assay of phagocyte bactericidal activity. Absent bacteriolysis remains the only consistent defect associated with recurrent neisserial infections and absence of one of the late-acting complement components.

Evidence for hypertyraminemia in Reye's syndrome.

Utilizing a specific and sensitive radioimmunoassay, palsma and urine tyramine were measured in 14 consecutive patients with liver biopsy-proven Reye's syndrome. Plasma tyrosine was measured in 11 of these patients. The results revealed significant (P less than .003) elevation in plasma (3.4 +/- .52 ng/ml) (mean +/- SEM) and urine (1.00 +/- .26 mg/24 hr) tyramine as well as plasma tyrosine (204 +/- 52.5 mumole/liter) at the onset of the disease when compared to the levels of tyramine and tyrosine in a group of hospitalized patients without hepatic disorders. Furthermore, there was a positive correlation between plasma tyramine and days in coma (r = .86; P less than .001), and between plasma tyramine and tyrosine (r = 0.80; P less than .001). These data suggest that there is s substantial disturbance of tyrosine metabolism in Reye's syndrome and that the accumulation of this amino acid and its metabolite, tyramine, may contribute to the encephalopathy of this disease.

Hypercatecholaminemia in Reye's syndrome.

To evaluate the role of catecholamines in Reye's syndrome, a specific and sensitive radioenzymatic assay was used to study plasma and CSF concentration of dopamine, norepinephrine, and epinephrine in 14 patients with liver-biopsy-proven Reye's syndrome. The results (median and range) revealed significant (P less than .04, P less than .0024, and P less than .030, respectively) elevation in plasma dopamine (131, 0 to 1,193 pg/mL), norepinephrine (1,455, 20 to 5,271 pg/mL), and epinephrine (345, 7.6 to 2,504 pg/mL) at the onset of the disease when compared with the level of these neurotransmitters in a group of hospitalized patients without hepatic disorders. There was a positive correlation between plasma catecholamines and stage of coma on admission (r = .54 to .86; P less than .001 to .024). Furthermore, the concentration of dopamine, norepinephrine, and epinephrine in the CSF increased significantly during the development of cerebral edema in all patients with Reye's syndrome as compared with concentrations in a control population. Hypercatecholaminemia may contribute to the encephalopathy of Reye's syndrome.

Assignment of the rhodopsin gene to human chromosome 3.

The human rhodopsin gene has been assigned to human chromosome 3 through the use of a mouse DNA probe and human/mouse somatic cell hybrids.

Identification of the cyanopregnenolone-inducible form of hepatic cytochrome P-450 as a catalyst of aldrin epoxidation.

In light of recent suggestions that hepatic microsomal aldrin expoxidation activity selectively reflects the phenobarbital (PB)-inducible form(s) of cytochrome P-450 (P-450PB), we tested the effect of pregnenolone-16 alpha-carbonitrile (PCN), a synthetic steroid that induces P-450PCN, a form of the cytochrome biochemically and immunochemically distinguishable from P-450PB. In hepatic microsomes prepared from rats receiving PB, 3-methylcholanthrene (3-MC), or PCN, the latter compound produced a greater increase in aldrin epoxidation activity relative to control than did PB, whereas 3-MC decreased enzyme activity. Moreover, the aldrin epoxidation activity in microsomes prepared from PCN- or PB-pretreated rats was selectively inhibited by form-specific antibodies directed against P-450PCN or P-450PB, respectively, whereas anti-P-450MC antibodies gave no inhibition with microsomes prepared from induced or control animals. We conclude that P-450PCN, P-450PB, and probably other cytochromes P-450 catalyze aldrin epoxidation, precluding use of this enzyme as a specific marker of a single form of the cytochrome.

Negative pressure ventilation. Effects on ventilation during sleep in normal subjects.

Negative pressure ventilation (NPV) is used for ventilatory support of patients with respiratory failure due to neuromuscular disorders and thoracic deformities, and to provide ventilatory muscle rest for patients with severe chronic airflow limitation. To determine whether NPV would result in episodes of upper airway obstruction during sleep, we studied five normal subjects on two consecutive nights with the first night serving as a control and NPV being administered on the second night. Ventilators were adjusted so as to reduce the peak phasic diaphragm electromyogram signal by at least 50 percent. All subjects demonstrated an increase in the total number of apneas + hypopneas per hour on NPV control nights. Although differences were not significant, there was a tendency to develop decreased sleep efficiency, sleep fragmentation and altered sleep architecture with NPV. We conclude that nocturnal NPV can induce sleep apneas and impair sleep quality in normal subjects.