Recruitment of a foreign quinone into the A(1) site of photosystem I. I. Genetic and physiological characterization of phylloquinone biosynthetic pathway mutants in Synechocystis sp. pcc 6803

Genes encoding enzymes of the biosynthetic pathway leading to phylloquinone, the secondary electron acceptor of photosystem (PS) I, were identified in Synechocystis sp. PCC 6803 by comparison with genes encoding enzymes of the menaquinone biosynthetic pathway in Escherichia coli. Targeted inactivation of the menA and menB genes, which code for phytyl transferase and 1,4-dihydroxy-2-naphthoate synthase, respectively, prevented the synthesis of phylloquinone, thereby confirming the participation of these two gene products in the biosynthetic pathway. The menA and menB mutants grow photoautotrophically under low light conditions (20 microE m(-2) s(-1)), with doubling times twice that of the wild type, but they are unable to grow under high light conditions (120 microE m(-2) s(-1)). The menA and menB mutants grow photoheterotrophically on media supplemented with glucose under low light conditions, with doubling times similar to that of the wild type, but they are unable to grow under high light conditions unless atrazine is present to inhibit PS II activity. The level of active PS II per cell in the menA and menB mutant strains is identical to that of the wild type, but the level of active PS I is about 50-60% that of the wild type as assayed by low temperature fluorescence, P700 photoactivity, and electron transfer rates. PS I complexes isolated from the menA and menB mutant strains contain the full complement of polypeptides, show photoreduction of F(A) and F(B) at 15 K, and support 82-84% of the wild type rate of electron transfer from cytochrome c(6) to flavodoxin. HPLC analyses show high levels of plastoquinone-9 in PS I complexes from the menA and menB mutants but not from the wild type. We propose that in the absence of phylloquinone, PS I recruits plastoquinone-9 into the A(1) site, where it functions as an efficient cofactor in electron transfer from A(0) to the iron-sulfur clusters.

TGF-beta1 stimulation of fibronectin transcription in cultured human lung fibroblasts requires active geranylgeranyl transferase I, phosphatidylcholine-specific phospholipase C, protein kinase C-delta, and p38, but not erk1/erk2

The cytokine transforming growth factor-beta (TGF-beta) has multiple effects on a variety of cell types, modulating cell growth and differentiation as well as extracellular matrix deposition and degradation. In the present work, we demonstrate that TGF-beta1 produces a fourfold increase in transcription of the fibronectin gene in cultured human fetal lung fibroblasts with only a small increase in mRNA stability resulting in a significant increase in fibronectin mRNA steady state level. A corresponding increase in production of fibronectin protein accompanied the increase in mRNA. Through the use of specific inhibitors, we demonstrate that geranylgeranylated, but not farnesylated or acylated protein(s), protein kinase C-delta, phosphatidylcholine-specific phospholipse C, tyrosine kinase activity, and stress-activated protein kinase p38 are required for this TGF-beta1 effect. Trimeric G proteins and mitogen-activated protein kinases erk1 and erk2 do not appear to be involved. While these results emphasize the complexities involved in the control of extracellular matrix synthesis by TGF-beta, they also identify reaction sites that may be amenable to pharmacologic modulation. Such modulation could be of great advantage in the treatment of a wide variety of undesirable fibrotic reactions.

The change of interleukin-6 and tumor necrosis factor in patients with obstructive sleep apnea syndrome

The levels of lipopolysaccharide (LPS)-induced interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) expression in culture of peripheral blood mononuclear cells (PBMC) and the plasma levels of IL-6 and TNF-alpha in the patients with obstructive sleep apnea syndrome (OSAS) were measured and the relationship between OSAS and IL-6 or TNF-alpha expression studied. Both IL-6 and TNF-alpha were detected by using ELISA in 22 patients with OSAS and 16 normal controls. The levels of LPS-induced IL-6 (787.82 +/- 151.97 pg/ml) and TNF-alpha (4165.45 +/- 1501.43 pg/ml) expression in the supernatant of the culture of PBMC and plasma level of IL-6 (50.67 +/- 4.70 pg/ml) and TNF-alpha (299.09 +/- 43.57 pg/ml) in the patients with OSAS were significantly higher than those in the normal controls (in the supernatant of the culture of PBMC: 562.69 +/- 197.54 pg/ml and 1596.25 +/- 403.08 pg/ml respectively; in the plasma; 12.69 +/- 2.75 pg/ml and 101.88 +/- 21.27 pg/ml respectively). There were significantly positive correlation between the levels of IL-6 and TNF-alpha and the percentage of time of apnea and hyponea, as well as the percentage of time spending at SaO2 below 90% in the total sleep time. It was concluded that LPS-induced IL-6 and TNF-alpha levels as well as plasma IL-6 and TNF-alpha levels in the patients with OSAS were up-regulated, which may be associated with the pathogenesis of OSAS.

Construction and analysis of three-dimensional graphic model of single-chain Fv derived from an anti-human placental acidic isoferritin monoclonal antibody by computer

A three-dimensional (3D) graphic model of a single-chain Fv (scFv) which was derived from an anti-human placental acidic isoferritin (PAF) monoclonal antibody (MAb) was constructed by a homologous protein-predicting computer algorithm on Silicon graphic computer station. The structure, surface static electricity and hydrophobicity of scFv were investigated. Computer graphic modelling indicated that all regions of scFv including the inker, variable regions of the heavy (VH) and light (VL) chains were suitable. The VH region and the VL region were involved in composing the "hydrophobic pocket". The linker was drifted away VH and VL regions. The complementarity determining regions (CDRs) of VH and VL regions surrounded the "hydrophobic pocket". This study provides a theory basis for improving antibody affinity, investigating antibody structure and analyzing the functions of VH and VL regions in antibody activity.

[Management of micrognathia deformity associated with obstructive sleep apnea syndrome by distraction osteogenesis]

OBJECTIVE

To review the early results of lengthening of the mandible by distraction osteogenesis for the correction of micrognathia deformity and treatment of the obstructive sleep apnea syndrome (OSAS) simultaneously.

METHODS

5 cases with micrognathia deformity associated with OSAS resulted from unilateral/bilateral temporomandibular joint ankylosis had undergone mandibular distraction osteogenesis. In all of the patients intraoral device was employed. Cephalometric radiographs and polysomnograms were obtained preoperatively and postoperatively.

RESULTS

The average distraction distance was 15.28 mm (range 8.5 mm to 24.4 mm). The micrognathia deformity was corrected effectively, at the mean time the incapacious pharyngeal airway was ameliorated. The patients' Apnea Index (AI) had been decreasing, SaO(2) during sleep had got to rise.

CONCLUSIONS

Compared with the traditional surgery for the micrognathia associated with OSAS, the technique of mandibular distraction osteogenesis has the advantages of avoiding bone grafting and donor side morbidity, expanding the surrounding soft tissue concurrently, reducing the extent of operation and stability of the treatment effects.

CD4+ T cell apoptosis induced by anti-CD4 antibodies

To explore the inhibitory effects of anti-CD4 human/murine chimeric antibodies on lymphocyte proliferation, CD4+ T cell apoptosis induced by anti-CD4 antibodies was examined. Annexin-V-FITC and PI double stain method was employed to qualitatively and quantitatively determined CD4+ T cell apoptosis induced by anti-CD4 antibodies. Our results showed that anti-CD4 chimeric antibodies could specifically induce CD4+ T cell apoptosis. The ability of anti-CD4 chimeric antibodies to induce CD4+ T cell apoptosis was related with the presence of monocytes. It is concluded that the further cross-linking of anti-CD4 antibodies is important for inducing CD4+ T cell apoptosis.

Complex transcriptional initiation pattern of the thymidylate synthase promoter in mouse tissues

Thymidylate synthase (TS) is an essential enzyme that must be expressed in all proliferating cells. The mouse TS promoter lacks a TATA box and an initiator element and initiates transcription over a broad region in cultured fibroblasts. The goal of this study was to determine if expression of the TS gene in a variety of cells and tissues involves the use of alternative promoters or different patterns of transcriptional initiation sites. The amount of TS mRNA and the pattern of initiation sites were determined using S1 nuclease protection assays. We found that even though the amount of TS mRNA varied over a wide range, reflecting differences in cell proliferation rates, the pattern of initiation sites was nearly identical in all of the cell lines and tissues that were examined. Therefore transcription of the TS gene is directed by a single promoter that is capable of being expressed in a wide variety of cellular environments.

The solution structure of photosystem I accessory protein E from the cyanobacterium Nostoc sp. strain PCC 8009

PsaE is a small basic subunit located on the stromal (cytoplasmic) side of photosystem I. In cyanobacteria, this subunit participates in cyclic electron transport and modulates the interactions of the complex with soluble ferredoxin. The PsaE protein isolated from the cyanobacterium Synechococcus sp. strain PCC 7002 adopts the beta topology of an SH3 domain, with five beta strands (betaA through betaE) and a turn of 3(10) helix between strands betaD and betaE [Falzone, C. J., Kao, Y.-H., Zhao, J., Bryant, D. A., and Lecomte, J. T. J. (1994) Biochemistry 33, 6052-6062]. The primary structure of the PsaE protein is strongly conserved across all oxygen-evolving photosynthetic organisms. However, variability in loop lengths, as well as N- or C-terminal extensions, suggests that the structure of a second representative PsaE subunit would be useful to characterize the interactions among photosystem I polypeptides. In this work, the solution structure of PsaE from the cyanobacterium Nostoc sp. strain PCC 8009 was determined by NMR methods. Compared to PsaE from Synechococcus sp. strain PCC 7002, this PsaE has a seven-residue deletion in the loop connecting strands betaC and betaD, and an eight-residue C-terminal extension. Angular and distance restraints derived from homonuclear and heteronuclear NMR experiments were used to calculate structures by a distance-geometry/simulated-annealing protocol. A family of 20 structures (rmsd of 0.24 A in the regular secondary structure) is presented. Differences between the two cyanobacterial proteins are mostly confined to the CD loop region; the C-terminal extension is disordered. The thermodynamic stability of Nostoc sp. strain PCC 8009 PsaE toward urea denaturation was measured by circular dichroism and fluorescence spectroscopy, and thermal denaturation was monitored by UV absorption spectroscopy. Chemical and thermal denaturation curves are modeled satisfactorily with two-state processes. The DeltaG degrees of unfolding at room temperature is 12.4 +/- 0.3 kJ mol(-1) (pH 5), and the thermal transition midpoint is 59 +/- 1 degrees C (pH 7). Interactions with other proteins in the photosystem I complex may aid in maintaining PsaE in its native state under physiological conditions.

Glutamine synthetase in cerebrospinal fluid, serum, and brain: a diagnostic marker for Alzheimer disease?

OBJECTIVES

To determine whether the glutamine synthetase (GS) level in cerebrospinal fluid (CSF) is a useful biochemical marker in the diagnosis of Alzheimer disease (AD), and to assess the source of GS (brain vs. blood derived) in CSF.

METHODS

Sandwich enzyme immunoassay and immunoblotting were applied to detect GS in CSF and in serum from neurologically healthy control subjects and patients with neurodegenerative diseases, including AD. The origin of GS was estimated by the concentration gradients of CSF to serum and ventricular to lumbar CSF. In addition, postmortem brain tissue from controls and patients with AD was analyzed using immunohistochemistry for expression of GS.

RESULTS

Levels of GS were significantly increased in lumbar CSF from patients with AD (20+/-12 pg/mL; P = .01) and to a lesser extent in patients with vascular dementia and amyotrophic lateral sclerosis. In CSF of controls, GS levels were 4+/-3 pg/mL. The GS concentration gradients were less than 1:10 for CSF to serum and 2:1 for ventricular to lumbar CSF. Immunoreactivity of GS was most prominent in astrocytes from temporal neocortex of patients with AD, suggesting a relationship between astrocyte reactions and increased GS levels in CSF.

CONCLUSIONS

Level of GS in lumbar CSF of patients with AD is increased significantly but nonspecifically, probably related to the strong astrogliosis in brain. Glutamine synthetase in lumbar CSF is mainly brain derived.

[Observation of special stain and ultrastructure of lattice, granular and macular corneal dystrophy]

OBJECTIVE

To investigate the histopathological changes of lattice, granular and macular corneal dystrophy.

METHODS

Corneal buttons were obtained from penetrating keratoplasty due to severe corneal dystrophy, and their sections and ultrathin sections with several special stains were observed under a light microscope (LM) and electron microscope (EM).

RESULTS

In cases with lattice dystrophy, the stromal fusiform deposits seen under LM were confirmed to be amorphous materiel with filaments by EM and stained positively for Masson trichrome, PAS and Congo red. In cases with granular dystrophy, the granular or bread debris deposits found between laminae under LM were extracellular material observed by EM and they were stained positively for Masson trichrome and alcian blue. In cases with macular dystrophy, the stromal spheroid or macular deposits were seen under LM, and there were numerous vacuoles containing fibrils and granules in the cytoplasm of keratocytes and accumulative amorphous material in the stroma under EM; the deposits were positive for colloidal iron and alcian blue stain.

CONCLUSION

In corneal lattice dystrophy, there are amyloid deposits; in granular dystrophy, there are extracellular material deposits; and in macular dystrophy, there is mucopolysaccharide accumulation.

[Quantitative evaluation of new bone formation in the posterior zone of the glenoid fossa in response to the mandibular advancement in rats]

OBJECTIVE

To quantify the new bone formation in the glenoid fossa of the temporal bone in response to the mandibular advancement.

METHODS

A bitejumping appliance with guide slope was fit on the upper jaw of each rat in the experimental groups, resulting in a downward and forward displacement of condyle and continuous mandibular advancement. Sections were cut through the glenoid fossa at the sagittal plane and stained with PAS under the same condition. The new bone formation at the posterior zone of the glenoid fossa was detected by quantitative measurement through computer-assisted image analyzing system (Q550IW, Leica) with the advanced software (Leica Qwin Pro, Version 2.2). Statistical analysis was performed with GraphPad 3.0.

RESULTS

1. a comparison among experimental groups revealed a peak of new bone deposition at the 21-day group, significantly greater than other groups (P < 0.001); 2. a comparison among control groups showed a gradual decrease of new bone deposition characterized by a peak of at the 3-day group and a bottom at the 30-day group (P < 0.001); 3. a comparison between experimental and control groups showed no significant difference statistically at the 3-day groups (P > 0.05), whereas a significant difference of new bone deposition starting from 7-day groups, with a peak at 21-day groups and a decrease towards 30-day groups (P < 0.001).

CONCLUSION

The advancement of mandible leads to the remodeling of the glenoid fossa indicated by the new bone deposition in growing rat.

[Image analysis of condylar cartilaginous adaptation to mandibular protrusion in rats]

OBJECTIVE

To quantify chondrogenesis in condylar cartilage in response to active forward positioning of mandible.

METHODS

Identical bite-jumping appliances were fixed to upper incisors of animals in experimental groups, causing a continuous mandibular forward positioning. Histological sections were performed through mandibular condyle and were stained with HE under the same condition. Chondrogenesis was quantified by measuring the area of cells in resting, proliferative, hypertrophic and erosive zones in the superioposterior region, through computer-assisted image analyzing system (Q550IW, Leica) with the advanced software (Leica Qwin Pro, V2.2). Statistical analysis was performed with GraphPad 3.0.

RESULTS

1. comparison among experimental groups revealed a fluctuation in proliferative zone, with 21-day group being the greatest (0.058 +/- 0.004 mm2) and 14-day the least (0.012 +/- 0.001 mm2). A change in erosive zone was also depicted by a peak of 0.112 +/- 0.001 mm2 in 7-day group and a bottom of 0.018 +/- 0.002 mm2 in 14-day group (P < 0.001). 2. comparison among the control groups manifested stable zonation, except for a slump of proliferative zone descending from 0.069 +/- 0.005 mm2 in 3-day group to 0.009 +/- 0.001 mm2 in 21-day group (P < 0.001). 3. comparison between experimental and control groups demonstrated significant discrepancy in proliferative zone, hypertrophic zone and erosive zone (P < 0.001).

CONCLUSION

Mandibular forward positioning stimulates and accelerates cartilaginous remodeling in mandibular condyle.

[The designing of a software for an automated biochemistry analyzer]

The structure, functions, user's interface, data storage and administration of a software system for an automated biochemistry analyzer are described. The methods to display the Chinese character menus and on-line help information are discussed in detail.

Meter-dosed, inhaled beclomethasone attenuates bronchoalveolar oxyradical inflammation in premature infants at risk for bronchopulmonary dysplasia

The object of this study was to examine the hypothesis that meter-dosed, inhaled beclomethasone administered to premature infants beginning at birth in a tapering dosage schedule over the first 12 days of life attenuates bronchoalveolar lining fluid oxyradical inflammation concomitant with modulation of bronchopulmonary dysplasia. The design of this study was an unblinded, uncontrolled phase I, pilot investigation of inhaled beclomethasone primarily examining safety and administration. The setting was a tertiary care neonatal intensive care unit. Intubated, premature infants were studied longitudinally to 36 weeks corrected gestational age. Meter-dosed, inhaled beclomethasone was administered in a tapering dosage schedule over the first 12 days of life. Endotracheal tube aspirates were collected on Days 2, 4, and 6 of life and assayed for various markers of bronchoalveolar lining fluid oxyradical stress. Infants were also assessed with regards to a number of relevant clinical variables and presence or absence of bronchopulmonary dysplasia at 36 weeks corrected gestational age. Although no differences in clinical outcome were apparent in comparing nine control infants with nine beclomethasone-treated infants, bronchoalveolar lining fluid from control infants exhibited evidence of apparent phospholipid peroxidation (enhanced polyunsaturated fatty acid consumption) on Day 2 of life compared to beclomethasone-treated infants. Significant differences were noted for percent arachidonic acid, total polyunsaturated fatty acids and ratio of polyunsaturated fatty acids, to saturated fatty acids. The ratio of monohydroxyl linolenic acid to native linoleic acid (a more specific marker of lipid peroxidation) as well as myeloperoxidase activity (a marker of neutrophil oxyradical stress) tended to be higher in the control group but did not achieve statistical significance for this small subject number study. No adverse reactions related to meter-dosed, inhaled beclomethasone were noted in the treatment group; most specifically no evidence of hypothalamic-pituitary-adrenal axis suppression was noted in either control or beclomethasone-treated infants. Meter-dosed, inhaled beclomethasone in the dosage schedule utilized was safe and appeared to moderate bronchoalveolar lining fluid phospholipid peroxidation. Small numbers of infants entered into the present investigation preclude comments on clinical efficacy because of the likelihood of a statistical type 2 error. However, additional investigations of inhaled beclomethasone initiated at birth in premature infants at risk for bronchopulmonary dysplasia, enrolling larger number of subjects and perhaps a higher dosage of beclomethasone, are warranted.

Preparation and characterization for bispecific antibodies of anti-CD3 x anti-idiotype to B cell lymphocytic leukemia

Bispecific antibodies (BsAbs) of anti-CD3 x anti-idiotype (Id) to B-cell lymphocytic leukemia (CLL) were prepared by chemical conjugation and direct hybridization technique of hybridoma and hybridoma without screening markers. The specificity of BsAbs from culture supernatants or ascites was assayed by indirect ELISA and indirect immunoflourescence (IF). The results showed that BsAbs could specifically react with homologous serum IgM from patients with B-CLL and cells carrying CD3 marker respectively. Cell combination test and LDH assay demonstrated that BsAb significantly increased the conjugate formation between lymphocyte activated kill (LAK) cells and Daudi cells, and enhanced the cytotoxic activity of LAK cells against Daudi cells.

Requirement for geranylgeranyl transferase I and acyl transferase in the TGF-beta-stimulated pathway leading to elastin mRNA stabilization

The TGF-betas are multipotent in their biological activity, modulating cell growth and differentiation as well as extracellular matrix deposition and degradation. Most of these activities involve modulation of gene transcription. However, TGF-beta1 has been shown previously to substantially increase the expression of elastin by stabilization of tropoelastin mRNA through a signaling pathway which involves a phosphatidylcholine-specific phospholipase and a protein kinase C. The present results, through the use of specific inhibitors of geranylgeranyl transferase I, farnesyl transferase, and acyl transferase, demonstrate that geranylgeranylated and acylated, but not farnesyslated protein(s) is required for this TGF-beta1 effect. In addition, the general tyrosine kinase inhibitor genistein completely blocked this TGF-beta1 effect. The results suggest that the TGF-beta1 signaling pathway requires not only receptor ser/thr kinase activity, but also tyrosine kinase and small GTPase activities.

Helium-oxygen improves Clinical Asthma Scores in children with acute bronchiolitis

OBJECTIVE

To determine the efficacy of a helium-oxygen mixture in children admitted to the pediatric intensive care unit with acute respiratory syncytial virus (RSV) bronchiolitis.

DESIGN

Randomized, double-blind, controlled, crossover study and nonrandomized, prospective study.

SETTING

A pediatric intensive care unit in a university hospital.

PATIENTS

Nonintubated children with signs of acute lower respiratory tract infection and a positive rapid immunoassay for RSV admitted to the pediatric intensive care unit.

INTERVENTIONS

Treatment with either helium-oxygen or air-oxygen was administered in random order for 20 mins. Nonrandomized patients received helium-oxygen as initial therapy.

MEASUREMENTS AND MAIN RESULTS

Clinical Asthma Score, respiratory rate, heart rate, and pulse oximetry oxygen saturation values were recorded at baseline (before randomization) and at the end of each 20-min treatment period (helium-oxygen or air-oxygen). Nonrandomized patients were studied 20 mins into helium-oxygen delivery. Eighteen patients were studied, 13 of whom were randomized. Five children with severe bronchiolitis (Clinical Asthma Score of > or =6) were initially given helium-oxygen and scored at 20 mins. Mean Clinical Asthma Score was 3.04 (range 1 to 7.5) in the 13 randomized patients and 4.25 (range 1 to 9) in the 18 patients overall. Clinical Asthma Score decreased in the 13 randomized patients (mean 0.46, p < .05) and in the 18 patients overall (mean 1.23, p < .01) during helium-oxygen delivery. In randomized patients with Clinical Asthma Scores of <6 (n = 12), a positive correlation (rs = .72) was observed between the Clinical Asthma Score at baseline and the change in Clinical Asthma Score during helium-oxygen administration (p = .009). Respiratory rate and heart rate decreased during helium-oxygen treatment but were not statistically significant. No complications occurred during helium-oxygen delivery.

CONCLUSIONS

Inhaled helium-oxygen improves the overall respiratory status of children with acute RSV lower respiratory tract infection. In patients with mild-to-moderate bronchiolitis (Clinical Asthma Scores of <6), the beneficial effects of helium-oxygen were most pronounced in children with the greatest degree of respiratory compromise.

FEMORAL STEM FIXATION

The excellent long-term results for the first-generation Charnley stem may not apply to later versions with flanges. It seems possible that the early design functioned as a taper-slip system, as accepted in the Exeter prosthesis.

Comparison with the requirements for the alternative composite-beam system for the femoral component shows considerable differences that have important implications. These include design, surface finish, cementing technique and the interpretation of radiological signs of loosening.

A distinction should be made between the requirements for the successful use of the two different engineering systems.s

Femoral stem fixation. An engineering interpretation of the long-term outcome of Charnley and Exeter stems

The excellent long-term results for the first-generation Charnley stem may not apply to later versions with flanges. It seems possible that the early design functioned as a taper-slip system, as accepted in the Exeter prosthesis. Comparison with the requirements for the alternative composite-beam system for the femoral component shows considerable differences that have important implications. These include design, surface finish, cementing technique and the interpretation of radiological signs of loosening. A distinction should be made between the requirements for the successful use of the two different engineering systems.

[Study on the relationship among ossification of finger's bone, maxillary and mandibular lengths and body height for Shanghai adolescents aged between 11-15 years old]

OBJECTIVE:To research the intrinsic relationship in the growth and development progress of adolescents and to provide scientific basis for orthodontic diagnosis and treatment.METHODS:Sample included 125 Shanghai adolescents between 11-15 years old, and the relationship among maxillary length, mandibular length, ossification of finger's bone, body height and the age of first coming of menstruation on female was studied.RESULTS:The ossification of finger's bone, the increase of maxilla and mandibular lengths and the body height of Shanghai adolescents between 11-15 years old keep the same pace tendency. Female goes into the young quick growing period 2 years earlier than male, but from about 13 years old the growing speed of male is apparently more quick than that of female. When the ossification of finger's bone is nearly 100%, the body height and the mandibular length of male still possesses great growing capacity. The age of sesamoid bone appearance for both male and female and the age of first coming menstruation for female are getting earlier when comparing with others regions.CONCLUSION: There is a close relationship among ossification of finger's bone, maxilla and mandibular lengths and body height of adolescents. Understanding the intrinsic rule correctly has the guiding significance to early diagnosis and treatment in clinical orthodontics.

Comprehensive analysis of risk factors for acquisition of Pseudomonas aeruginosa in young children with cystic fibrosis

The objective of this study was to identify risk factors of significance for acquisition of Pseudomonas aeruginosa by children with cystic fibrosis (CF). Our working hypothesis is that exposure of infants and young children with CF to older, infected patients increases their risk for acquiring this organism. A special opportunity arose to study this question in detail, as we have been performing a randomized clinical trial of neonatal screening for CF throughout the state of Wisconsin during the period of 1985-1994. Patients were selected for this study based on either early identification through screening or diagnosis by standard methods. A longitudinal protocol employed at Wisconsin's two CF Centers includes routine cultures of respiratory secretions and collection of clinical, demographic, and activity information on patients and their families. Previous observations in our trial revealed that one center at an old hospital in an urban location showed a significantly shorter time to acquisition of P. aeruginosa for CF patients followed there. To study the center effect further, we performed statistical analyses using survival curves and stepwise regression analysis of all life history covariates available. The results of these analyses showed that the statistically significant correlations involve the following risk factors: 1) center and old hospital (r=0.42); 2) center and original physician (r=0.61); 3) center and exposure to pseudomonas-positive patients (r=0.29); and 4) population density and urban location (r=0.49). The final statistical model demonstrated that increased risk due to aerosol use (odds ratio=3.45, P=0.014) and a protective effect associated with education of the mother (odds ratio=0.81, P=0.024) were the most significant factors for acquisition of P. aeruginosa. The previously observed center effect was confined to the 1985-1990 interval at the old hospital (odds ratio=4.43, P < 0.001). We conclude that multiple factors are involved in increasing the risk of young children with CF to acquire P. aeruginosa, and that the observed center effect can best be explained by a combination of factors. These results suggest that facilities and methods used to care for young children with CF can significantly influence their likelihood of acquiring pseudomonas in the respiratory tract.

Insertional inactivation studies of the csmA and csmC genes of the green sulfur bacterium Chlorobium vibrioforme 8327: the chlorosome protein CsmA is required for viability but CsmC is dispensable

Targeted mutagenesis was used to investigate the roles of the CsmA and CsmC proteins of the chlorosomes of the green bacteria Chlorobium tepidum and Chlorobium vibrioforme 8327. Under the photoautotrophic growth conditions employed, CsmA is required for the viability of the cells but CsmC is dispensable. The absence of CsmC caused a small red shift in the near-infrared absorption maximum of bacteriochlorophyll d in whole cells and chlorosomes, but chlorosomes were assembled in and could be isolated from the csmC mutant. The doubling time of the csmC mutant was approximately twice that of the wild-type strain. Fluorescence emission measurements suggested that energy transfer from the bulk bacteriochlorophyll d to another pigment, perhaps bacteriochlorophyll a, emitting at 800-804 nm, was less efficient in the csmC mutant cells than in wild-type cells. These studies establish that transformation and homologous recombination can be employed in targeted mutagenesis of Chlorobium sp. and further demonstrate that chlorosome proteins play important roles in the structure and function of these light-harvesting organelles.