Biomedical subjects

R A Cox

Publications and source records attributed to R A Cox.

At least 55 records · Page 3Linked to original sources

PubMed1995

A major outbreak of methicillin-resistant Staphylococcus aureus caused by a new phage-type (EMRSA-16)

An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) infection caused by a novel phage-type (now designated EMRSA-16) occurred in three hospitals in East Northamptonshire over a 21-month period (April 1991--December 1992). Four hundred patients were colonized or infected. Seven patients died as a direct result of infection. Chest infections were significantly associated with the outbreak strain when compared with methicillin-sensitive S. aureus. Twenty-seven staff and two relatives who cared for patients were also colonized. A 'search and destroy' strategy, as advocated in the current UK guidelines for control of epidemic MRSA was implemented after detection of the first case. Despite extensive screening of staff and patients and isolation of colonized and infected patients, the outbreak strain spread to all wards of the three hospitals except paediatrics and maternity. A high incidence of throat colonization (51%) was observed. Failure to recognize the importance of this until late in the outbreak contributed to the delay in containing its spread. Key parts of the strategy which eventually contained the local outbreak were the establishment of isolation wards in two hospitals, treatment of all colonized patients and staff to eradicate carriage and screening of all patients upon discharge from wards where MRSA had ever been detected. EMRSA-16 spread to neighbouring hospitals by early 1992 and to London and the South of England by 1993. It is distinguished from other epidemic strains by its characteristic phage-type, antibiogram (susceptibility to tetracycline and resistance to ciprofloxacin), and in the pattern given on pulse field electrophoresis.

Adolescent↗

PubMed1995

Epidemic methicillin-resistant Staphylococcus aureus: controlling the spread outside hospital.

Over a 21-month period an outbreak of methicillin-resistant Staphylococcus aureus infection occurred in east Northamptonshire. The outbreak was caused by a novel phage-type (EMRSA-16) and affected 400 patients. It was centred on three hospitals but spread was also detected in the community, particularly among clients of nursing and residential homes. Three hundred and fifty residents in 15 care homes were screened for MRSA. Cross-infection of MRSA was demonstrated in 14 patients in six different homes. A key aspect of the overall containment of the outbreak was the implementation of infection control measures in the community, together with treatment and screening of known positive patients following their discharge from hospital.

Community-Acquired Infections↗

PubMed1995

Production of tumor necrosis factor alpha, interleukin-1 alpha, and interleukin-6 during murine coccidioidomycosis.

The proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), and interleukin-6 (IL-6) were induced in mice infected with Coccidioides immitis. Analyses of the cytokine profiles of two inbred mouse strains which differ in their susceptibility to pulmonary challenge with C. immitis revealed higher levels of IL-6 in lungs from DBA/2 mice (resistant strain) than in those from BALB/c mice (susceptible strain) beginning at day 6 and continuing through day 15 postinfection. Spleen cells from both mouse strains secreted TNF-alpha, IL-1 alpha, and IL-6 in vitro in response to stimulation with killed spherules but differed in that spleen cells from the resistant strain produced increased levels of these cytokines earlier after pulmonary challenge and at increased levels throughout the course of the disease.

Animals↗

PubMed1995

Roles of gamma interferon and interleukin-4 in genetically determined resistance to Coccidioides immitis.

The profiles of gamma interferon (IFN-gamma) and interleukin-4 (IL-4) production were evaluated during the course of coccidioidomycosis in two inbred mouse strains which differ in their susceptibility to Coccidioides immitis. Cytokine responses, measured at the molecular and protein levels, showed increased levels of IFN-gamma in lung extracts from mice of the resistant DBA/2 strain after a pulmonary challenge, whereas the susceptible BALB/c strain manifested a predominant IL-4 response. The importance of these cytokines in host defense against C. immitis was established by treating the mice with recombinant cytokines or neutralizing anticytokine monoclonal antibodies. Treatment of the susceptible BALB/c mice with recombinant murine IFN-gamma significantly protected mice against systemic challenge, and in the reciprocal experiment, the administration of an anti-IFN-gamma monoclonal antibody to the resistant DBA/2 mice significantly decreased their capacity to control disease. Although the treatment of DBA/2 mice with recombinant IL-4 did not alter the disease, neutralization of endogenous IL-4 in infected BALB/c mice by administration of a neutralizing anti-IL-4 antibody led to a significant reduction in the fungal load in their tissues. These results, taken together, establish that IFN-gamma plays a pivotal role in resistance to C. immitis, whereas IL-4 down-regulates protective immunity against C. immitis.

Animals↗

PubMed1995

Acute, subacute and chronic oral toxicity studies of the new serotonin (5-HT)3-receptor antagonist ramosetron in beagle dogs.

The oral toxicity of ramosetron ((R)-5-[(1-methyl-3-indolyl) carbonyl]-4,5,6,7-tetrahydro-1H-benzimidazole hydrochloride, CAS 132907-72-3, YM060), a new compound having serotonin (5-HT)3 receptor antagonist activity was investigated in beagle dogs. To evaluate the acute toxicity, two groups of beagle dogs, each comprised of one male and one female, were given YM060 bulk powder in gelatin capsules at dose of 0, 3 mg/kg or 0, 30 and 60 mg/kg in ascending order in at least 7-day intervals. After the final dose, animals were observed for 2 weeks. No deaths were observed at any dose. At 60 mg/kg, the male exhibited frequent vomiting, salivation and prone position 1-3 h after administration, when the plasma concentration of the unchanged drug reached Cmax or was close to Cmax. The female exhibited no changes except vomiting. No effects on either the male or the female were detected in body weight, food consumption, electrocardiography, hematology, plasma biochemistry or urinalysis. To evaluate the subacute toxicity of YM060, three male and 3 female beagle dogs per group received doses of 0, 1, 3, 10 and 20 mg/kg/d for 13 weeks. YM060 was triturated 10-fold using lactose and filled in gelatin capsules before use. The plasma concentration of unchanged drug increased almost dose-dependently, peaked about 2 h post-dosing and subsequently decreased with time. The plasma concentration-time profile after the final dose at week 13 was not different from that after the initial dose. No treatment-related changes were observed up to 3 mg/kg/d.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1995

Dilated cardiomyopathy: a clinical review of patients evaluated at a tertiary care center in Puerto Rico.

OBJECTIVES: The purpose of this study was to determine the causes, epidemiologic baseline data and clinical characteristics of a group of patients referred to a tertiary care center in Puerto Rico with the diagnosis of dilated cardiomyopathy. METHODS: The medical records of 91 new patients with the diagnosis of dilated cardiomyopathy were analyzed. Data was recopilated regarding initial medical history and physical examination, basic blood chemistry, electrocardiograms, chest films and other cardiac studies including echocardiogram, radionuclear ventriculography, cardiac catheterization, contrast ventriculography and coronary angiography. After reviewing the records the etiology for dilated cardiomyopathy was identified in each patient following the World Health Organization Task Force criteria. RESULTS: Ischemic cardiomyopathy was identified as the most common cause of dilated cardiomyopathy, representing 37% of the reviewed patient population; an idiopathic etiology was found in 22% of the patients and valvular heart disease in 14%. DISCUSSION: A comparison with previously described series in the medical literature regarding this subject is presented, along with the most prominent clinical characteristics of the studied population. It is felt that the findings presented will require further study of the underlying causes and clinical course of this condition in a larger patient sample and a longer follow-up period.

Academic Medical Centers↗

PubMed1994

The ribosomal RNA (rrn) operons of fast-growing mycobacteria: primary and secondary structures and their relation to rrn operons of pathogenic slow-growers.

The two ribosomal RNA (rrn) operons (rrnA and rrnB) of Mycobacterium smegmatis were investigated. The leader regions, part of the 16S rRNA genes, the spacer-1 regions, part of the 23S rRNA genes, and the spacer-2 regions were amplified by PCR or by inverse PCR and the products were cloned and sequenced. No differences in the sequences of the two operons were detected downstream from the Box A antitermination element of the leader region. Upstream from Box A a slow-grower-like Box B antitermination element was found in rrnA but not in rrnB. Primer extension experiments revealed that the start of transcription lies at least 370 nucleotides upstream from the 5'-end of the 16S rRNA gene and an RNase processing site near to the Box A element. Secondary structures were deduced for pre-16S rRNA and pre-23S rRNA which are distinct from, but closely related to, the corresponding structures of slow-growing mycobacteria. On the basis of these results it is proposed that the emergence of the slow-growers from the main mycobacterial line was coincident with the deletion of a segment of DNA spanning an rrnB-like operon, leaving an rrnA-like operon as the sole source of rRNA. An explanation is also proposed for the need for two Box A motifs in the transcription of an rrn operon based on competition between the polymerase and the nascent 30S subunit for either protein S10 and/or Box A sequences.

Base Sequence↗

PubMed1994

Nucleotide sequence and secondary structures of precursor 16S rRNA of slow-growing mycobacteria.

Slow-growing mycobacteria have a single ribosomal RNA (rrn) operon, with the genes for 16S, 23S and 5s rRNA being present in that order. The transcription start site of the rrn operon of Mycobacterium tuberculosis was identified in Escherichia coli. PCR methodology was used to amplify parts of the rrn operon, namely the leader region and the spacer-1 region separating the 16S rRNA and 23S rRNA genes of Mycobacterium avium, Mycobacterium paratuberculosis, Mycobacterium intracellulare, 'Mycobacterium lufu', Mycobacterium simiae and Mycobacterium marinum. The amplified DNA was sequenced. The sequence data, together with those obtained previously for Mycobacterium leprae and M. tuberculosis, were used to identify putative antitermination signals and RNase III processing sites within the leader region. Notable features include a highly conserved Box B element and a sequence of 31 nucleotides which is common to all eight slow-growers which were scrutinized. A secondary structure for mycobacterial precursor-16S rRNA was devised, based on sequence homologies and homologous nucleotide substitutions. The 18 nucleotides at the 5'-end of spacer-1 have the capacity of binding sequences close to the 5'- and 3'-ends of mature 16S rRNA, suggesting that secondary structure is important to the maturation process. All the slow-growers, including M. leprae, conform to the same scheme of secondary structure. The scheme proposed for M. tuberculosis is a variant of the main theme. The leader and spacer sequences may prove a useful supplement to 16S rRNA sequences in establishing phylogenetic relationships between very closely related species. 'M. lufu' appears to be a close relative of M. intracellulare.

Base Sequence↗

PubMed1994

Nucleotide sequences of the spacer-1, spacer-2 and trailer regions of the rrn operons and secondary structures of precursor 23S rRNAs and precursor 5S rRNAs of slow-growing mycobacteria.

The single ribosomal RNA (rrn) operons of slow-growing mycobacteria comprise the genes for 16S, 23S and 5S rRNA, in that order. PCR methodology was used to amplify parts of the rrn operons, namely the spacer-1 region separating the 16S rRNA and 23S rRNA genes and the spacer-2 region separating the 23S rRNA and 5S rRNA genes of Mycobacterium avium, Mycobacterium intracellulare, 'Mycobacterium lufu' and Mycobacterium simiae. The amplified DNA was sequenced. The spacer-2 region, the 5S rRNA gene, the trailer region and the downstream region of the rrn operon of Mycobacterium tuberculosis were cloned and sequenced. These data, together with those obtained previously for Mycobacterium leprae, were used to identify putative antitermination signals and RNase III processing sites within the spacer-1 region. Notable features include two adjacent potential Box B elements and a Box A element. The latter is located within a sequence of 46 nucleotides which is very highly conserved among the slow-growers which were examined. The conserved sequence has the capacity to interact through base-pairing with part of the spacer-2 region. Secondary structures for mycobacterial precursor 23S rRNA and for precursor 5S rRNA were devised, based on sequence homologies and homologous nucleotide substitutions. All the slow-growers, including M. leprae, conform to the same scheme of secondary structure. A putative motif for the intrinsic termination of transcription was identified approximately 33 bp downstream from the 3'-end of the 5S rRNA gene. The spacer-1 and spacer-2 sequences may prove a useful supplement to 16S rRNA sequences in establishing phylogenetic relationships between very closely related species.

Base Composition↗

PubMed1994

Cytokine induction in human coccidioidomycosis.

To investigate the immune response to human infection with the fungus Coccidioides immitis, we measured cytokine production from peripheral blood mononuclear cells (PBMC) and plastic-adherent monocytes/macrophages (Mphi) isolated from healthy subjects who were skin test positive to spherulin, healthy subjects who were skin test negative, and patients with active coccidioidomycosis. PBMC and Mphi from all these donor groups secreted increased levels of tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 in response to stimulation with formalin-killed spherules (FKS), as measured by enzyme-linked immunosorbent assays. Viable C. immitis spherules also stimulated PBMC and Mphi from healthy subjects and patients to secrete tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6, although at levels lower than those induced by FKS. The production of these acute inflammatory cytokines may contribute to the immunopathogenesis of active coccidioidomycosis and could account for the toxicity of the FKS vaccine in humans.

Coccidioidomycosis↗

PubMed1994

Pulmonary inflammatory cell response to sustained endotoxin administration.

We have developed a model of human sepsis in sheep. Twenty-four hours after continuous infusion of Escherichia coli endotoxin (lipopolysaccharide) (10 ng.kg-1.min-1) was begun, pulmonary transvascular fluid flux was almost five times the baseline values, cardiac output was nearly doubled, and mean arterial pressure was reduced by approximately 20 mmHg. At this time, the animals were killed and their lungs were fixed by endotracheal installation of 2.5% glutaraldehyde at 25 cmH2O pressure. Morphometry was performed by point counting, and data were expressed as relative volume density. Pulmonary edema and congestion were observed in sheep receiving lipopolysaccharide, whereas sham controls appeared normal. There was an increase in interstitial volume density. There was a significant increase (P < 0.01) in volume density of the pulmonary intravasculature (180%), interstitial macrophages (270%), and mast cells (240%). The volume densities of intravascular and interstitial polymorphonuclear neutrophils also showed a small insignificant increase.

Animals↗

PubMed1994

Efficacy of cefazolin in promoting ovine tracheal epithelial repair.

Inhalation of toxic materials has been shown injurious to the upper airways. Because secondary infection can slow the repair process, we undertook this study to determine the efficacy of antibiotic therapy in promoting the healing process of acute tracheal wounds. In 18 anesthetized sheep, a portion of the cervical trachea was exposed to smoke from smoldering cotton cooled to 38 degrees C. Nine received the broad-spectrum antibiotic, cefazolin, while none received saline placebo. At 13 days after injury, nonciliated and ciliated cell counts were 75% and 33% respectively of noninjured trachea receiving placebo, while in those receiving cefazolin, nonciliated and ciliated cell counts increased to 93% and 114% of paired noninjured trachea, respectively. We suggest that cefazolin therapy allows cell proliferation and differentiation to proceed more rapidly than observed with placebo therapy and thus may be a helpful augmentor to the healing of an acute airway injury.

Animals↗

PubMed1993

Organization of cytokeratin intermediate filaments in basal cells of growing rat trachea.

The basal cell in airway epithelium plays a major role in attachment of ciliated and nonciliated columnar cells to the basal lamina. As the airway grows in diameter and the columnar epithelium in height, the number of basal cells and the amount of tonofilaments (cytokeratin filaments) and anchoring junctions increase. In this way they maintain a constant attachment strength between the increased volume of the epithelium and the basal lamina. The purpose of this study was to determine which cytokeratins (CKs) are expressed in growing basal cells of the rat and demonstrate where they are localized in the cytoskeleton. Sprague Dawley rats 10, 30 and 90 days of age were used in this study. For light microscopy, tracheal samples were fixed in 95% alcohol or 4% formalin for 2 hr and then embedded in paraffin. For electron microscopy, the tracheal samples were placed in 20 mM EDTA in HBSS media minus Ca++ and Mg++ at pH 7.4 for 60 min to permeabilize the cells and expose the intracellular structures. Antibodies to cytokeratins 7, 8, 10, 13 and 18 did not react to basal cells at any age studied. Antibodies to CKs 5 + 8, 14, 16 + 13, and 19 gave a positive reaction with basal cells at each age studied. Immunogold particles representing antibodies to CK 14 were heavily distributed over intermediate filaments making up the cytoskeleton. Both CK 16 + 13 and 19 were also over intermediate filaments but at a much lower density.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

In situ preparation of rat tracheal basal cells.

The primary function of basal cells is to attach columnar epithelium to the basal lamina. They may also have limited stem cell potential, but very little is known of other biological functions. Basal cells lie on the basal lamina beneath the ciliated and secretory cells and do not reach the surface of the epithelium. The position of the cell beneath the ciliated and secretory cell epithelium makes their in situ study difficult. In order to further aid in the study of basal cells, we have developed an in situ preparation technique in which ciliated and secretory cells are removed. Treatment of rat tracheas with a 20 mM Na2 EDTA solution, pH 7.4, results in partial removal of columnar epithelium from the basal lamina. The percent of denuded columnar epithelial cells per mm of basal lamina is 43.9 +/- 7.8% at 60 min, 47.6 +/- 8.4% at 90 min, and 52.6 +/- 2.7% at 120 min. The viability of the exposed basal cells was the same at both 60 and 90 min of treatment (79.4 +/- 7.8 and 78.0 +/- 8.5, respectively). Morphologically, the exposed basal cells are attached to the basal lamina by hemidesmosomes and are similar to those in the intact animal.

Animals↗

PubMed1993

Production of a murine monoclonal antibody that recognizes an epitope specific to Coccidioides immitis antigen 2.

Antigen 2 (Ag2) has been implicated as a T-cell-reactive component of the pathogenic fungus Coccidioides immitis. We report the production of a murine monoclonal antibody (MAb) of the immunoglobulin G2a isotype that recognizes an epitope specific to C. immitis Ag2. This specificity was evidenced by the finding that the MAb did not recognize other antigens present in coccidioidin or spherulin and did not show reactivity with antigenic extracts from Histoplasma capsulatum or Blastomyces dermatitidis. The epitope was labile to enzymatic digestion with pronase but resistant to treatment with glycolytic enzymes and to periodate oxidation. This peptide epitope appears to require conformational structure on the basis that it was not recognized by the MAb in immunoblots of antigen that had been electrophoresed in polyacrylamide gels under denaturing, reducing conditions. Immunoaffinity chromatography of spherulin on columns containing the MAb established that the MAb was effective as a ligand for isolating Ag2 from heterogeneous extracts. The production of a MAb which recognizes an Ag2-specific epitope and its utility as a ligand for isolating Ag2 will provide a valuable reagent for studies of this immunologically important antigen.

Animals↗

PubMed1993

Attenuated fibroblast sheath around the basement membrane zone in the trachea.

In the connective tissue underlying the epithelium of the airways, there are thin attenuated cells that appear to be fibroblasts. These cells are close to the basal lamina and delineate an area equivalent to the basement membrane zone (BMZ). Using the mean data from transversely and longitudinally sectioned attenuated fibroblasts, we estimate that the diameter of the attenuated fibroblast is approximately 28.0 microns and its thickness 0.55 microns. Serial sections indicate there are pores of various sizes in the attenuated fibroblast. Also, the presence of cell segments less than 5 microns in length suggests there are processes from the edge of the cell which would give it a stellate appearance. These large flat cells form a sheath covering 66 to 70% of the BMZ at an average distance of 1.9 microns from the basal lamina. In addition, they make contact with the basal lamina approximately 7,000 times per mm2 of basal lamina. The majority of the contacts with the basal lamina are beneath basal cells. Cells of the attenuated fibroblast sheath are probably associated with lung morphogenesis, wound healing, and development of the BMZ. Their existence as a sheath demonstrates an anatomical unit associated with fibroblast-epithelial cell interactions in airway epithelium.

Animals↗

PubMed1992

Cellular sequence of tracheal repair in sheep after smoke inhalation injury.

The cellular repair process of injured tracheal epithelium is described for sheep after exposure to toxic smoke containing high concentrations of acrolein. Fourteen fasted 3-4-year-old ewes had a portion of their cervical trachea exposed to cotton smoke for 20 min and then were sacrificed at various time intervals ranging from 1 to 22 days after exposure. Within 1 day of injury, columnar epithelium sloughed intact from the trachea with a concomitant reduction of nearly 35% in the basal cell population. At 2 days of recovery, the cellularity of the epithelium had increased and mitotic figures were observed in some tracheal epithelial and gland cells. By 8 days, undifferentiated hyperplastic cells increased to 30/100 microns, differentiated nonciliated columnar cells first appeared, and the basal cell population returned to a normal count of 13 cells/100 microns. Thirteen days after exposure, the undifferentiated hyperplastic cell population had declined to 7 cells/100 microns, nonciliated columnar cells were at control values, and some ciliated cells were identified. At 18 and 22 days, epithelium was normal in appearance and the count was 13 cells/100 microns. Data suggest that because the columnar epithelium sloughs intact with the cilia remaining active, toxic smoke may affect their attachment to the basal lamina. Furthermore, the regeneration process involves differentiation of hyperplastic cells in which they elongate down to the basal lamina, thus re-establishing the integrity of tall epithelium in the sheep trachea.

Animals↗

PubMed1992

Epstein-Barr virus serology in the chronic fatigue syndrome.

The antibody profiles against Epstein-Barr virus were studied in 136 patients presenting with chronic fatigue syndromes. These profiles were compared with a panel of sera from blood donors. The patients exhibited higher titres in a combined assay for antibodies to the Restricted (R) and Diffuse (D) components of the Early Antigen complex than controls (P less than 0.001) but titres against these antigens were not useful on an individual patient basis. The patients who displayed elevated titres of antibodies to Early Antigens did not differ clinically from those displaying titres in the control range. Four of nine patients who had increased antibodies to Early Antigens also had evidence of active enterovirus infection.

Adult↗