PubMed Health⌕ Search

Biomedical subjects

C R Dean

Publications and source records attributed to C R Dean.

At least 19 recordsLinked to original sources
PubMed2000

The wbpM gene in Pseudomonas aeruginosa serogroup O17 resides on a cryptic copy of the serogroup O11 O antigen gene locus.

The Pseudomonas aeruginosa serogroup O11 strain PA103 O antigen gene locus consists of 11 genes designated wzz, wzx, wbjA, wzy, wbjB-F, wbpL, and wbpM. The distribution of each of these genes amongst the 20 P. aeruginosa international antigenic typing system (IATS) serogroups was analyzed by Southern blot. As shown previously, wbpM was present in all 20 serogroups. The remaining O11 O antigen genes, with the exception of wzy, were present in the serogroup O17 strain IATSO17, despite the structural unrelatedness of the O11 and O17 O antigens. Sequencing revealed the presence of a cryptic serogroup O11 locus in the IATSO17 interrupted by two copies of a 1.1-kb insertion element. Introduction of plasmid pLPS2, containing the complete O11 O antigen locus from strain PA103, into IATSO17 resulted in production of both the O11 and O17 O antigens. The results of insertional inactivation of wbpM in IATSO17 are discussed.

Base Sequence↗
PubMed1999

Characterization of the serogroup O11 O-antigen locus of Pseudomonas aeruginosa PA103.

We previously cloned a genomic DNA fragment from the serogroup O11 Pseudomonas aeruginosa strain PA103 that contained all genes necessary for O-antigen synthesis and directed the expression of serogroup O11 antigen on recombinant Escherichia coli and Salmonella. To elucidate the pathway of serogroup O11 antigen synthesis, the nucleotide sequence of the biosynthetic genes was determined. Eleven open reading frames likely to be involved in serogroup O11 O-antigen biosynthesis were identified and are designated in order as wzzPaO111 (wzz from P. aeruginosa serogroup O11), wzxPaO11, wbjA, wzyPaO11, wbjB to wbjF, wbpLO11 and wbpMO11 (wbpL and wbpM from serogroup O11). Consistent with previous descriptions of O-antigen biosynthetic gene loci, the entire region with the exception of wbpMO11 has a markedly reduced G+C content relative to the chromosomal average. WzyPaO11 shows no significant similarity at the protein or DNA sequence level to any database sequence and is very hydrophobic, with 10 to 12 putative transmembrane domains, both typical characteristics of O-antigen polymerases. A nonpolar chromosomal insertion mutation in wzyPaO11 in P. aeruginosa PA103 confirmed the identity of this gene. There is striking similarity between WbjBCDE and Cap(5/8)EFGL, involved in type 5 and type 8 capsule biosynthesis in Staphylococcus aureus. There is nearly total identity between wbpMO11 and wbpMO5, previously shown by others to be present in all 20 P. aeruginosa serogroups. Using similarity searches, we have assigned functions to the proteins encoded by the PA103 O-antigen locus and present the potential steps in the pathway for the biosynthesis of P. aeruginosa serogroup O11 O antigen.

Bacterial Proteins↗
PubMed1996

PfeR, an enterobactin-responsive activator of ferric enterobactin receptor gene expression in Pseudomonas aeruginosa.

PfeR (Regulator) and PfeS (Sensor), members of the superfamily of so-called two-component regulatory protein pairs, are required for the enterobactin-inducible production of the ferric enterobactin receptor (PfeA) in Pseudomonas aeruginosa. A pfeR knockout mutant failed to demonstrate enterobactin-inducible expression of a pfeA-lacZ fusion, indicating that PfeR acts at the level of pfeA gene expression. Consistent with this, PfeR overexpressed in P. aeruginosa bound, in bandshift assays, the promoter region of pfeA. Such binding was enhanced when PfeR-containing extracts were prepared from cells cultured in the presence of enterobactin, consistent with a model of PfeR as an enterobactin-responsive activator of pfeA expression. A region showing homology to the consensus binding sequence for the global iron repressor Fur was identified upstream of pfeR, suggesting that the pfeRS operon is iron regulated. As expected, expression of a pfeR-lacZ fusion in P. aeruginosa was increased under conditions of iron limitation. Enterobactin failed, however, to provide any enhancement of pfeR-lacZ expression under iron-limiting conditions, indicating that PfeR does not positively regulate pfeRS expression. A pfeA knockout mutant demonstrated enterobactin-inducible expression of a pfeA-lacZ fusion, indicating that the receptor is not required for the enterobactin inducibility of pfeA gene expression. Such mutants show growth, albeit reduced, in enterobactin-supplemented iron-limiting minimal medium, indicating that a second route of uptake across the outer membrane exists for ferric enterobactin in P. aeruginosa and may be important for the initial induction of pfeA in response to enterobactin.

Bacterial Outer Membrane Proteins↗
PubMed1994

Gay marriage: a civil right.

This article describes the author's efforts to secure marriage rights for same-sex couples in the District of Columbia. The importance of such rights are described in terms of their benefits to partners in areas such as inheritance, taxation, and benefit to society. It is argued that refusal to recognize same-sex marriages is not justified by statute and that discrimination on the basis of sex violates the District's Human Rights Act. Certain prior court cases, moreover, affirm the moral logic for extending marriage rights to same-sex couples.

Civil Rights↗
PubMed1993

Expression of the ferric enterobactin receptor (PfeA) of Pseudomonas aeruginosa: involvement of a two-component regulatory system.

Expression of the ferric enterobactin receptor in Pseudomonas aeruginosa is inducible by enterobactin and requires sequences upstream of the structural gene (pfeA). Nucleotide sequencing of a 2.5 kilobase pair (kb) region of DNA immediately upstream of pfeA revealed two open reading frames (ORFs), pfeR and pfeS, which appeared to comprise an operon. The predicted products of pfeR and pfeS (molecular weight 26,796 and 50,597, respectively) exhibited a high degree of homology to response-regulator and sensor components, respectively, of the superfamily of prokaryotic environmentally responsive protein pairs. Consistent with an apparent role in regulating expression of pfeA in response to enterobactin, introduction of pfeR/pfeS into P. aeruginosa on a high-copy-number vector enhanced enterobactin-dependent expression of pfeA. Furthermore, a pfeR mutant obtained by in vitro mutagenesis and gene replacement failed to express PfeA despite the presence of enterobactin in the culture medium. Analysis of the hydropathy profiles of PfeR and PfeS supported a cytoplasmic location for PfeR and a cytoplasmic membrane location for PfeS.

Amino Acid Sequence↗
PubMed1993

Cloning and characterization of the ferric enterobactin receptor gene (pfeA) of Pseudomonas aeruginosa.

Pseudomonas aeruginosa K407, a mutant lacking a high-affinity 80,000-molecular-weight ferric enterobactin receptor protein (80K protein), exhibited poor growth (small colonies) on iron-deficient succinate minimal medium containing ethylenediamine-di(o-hydroxyphenylacetic acid) (EDDHA) and enterobactin. The gene encoding the ferric enterobactin receptor was cloned by complementation of this growth defect. The complementing DNA was subsequently localized to a 7.1-kilobase-pair (kb) SstI-HindIII fragment which was able to restore synthesis of the 80K protein in strain K407 and also to direct the synthesis of high levels of a protein of the same molecular weight in the outer membranes of Escherichia coli fepA strains MT912 and IR20. Moreover, the fragment complemented the fepA mutation in MT912, restoring both growth in EDDHA-containing medium and enterobactin-dependent uptake of 55Fe3+. Expression of the P. aeruginosa receptor in E. coli IR20 was shown to be regulated by both iron and enterobactin. The complementing DNA was further localized to a 5.3-kb SphI-SstI fragment which was then subjected to deletion analysis to obtain the smallest fragment capable of directing the synthesis of the 80K protein in the outer membrane of strain K407. A 3.2-kb DNA fragment that restored production of the receptor in strain K407 was subsequently isolated. The fragment also directed synthesis of the protein in E. coli MT912 but at levels much lower than those previously observed. Nucleotide sequencing of the fragment revealed an open reading frame (designated pfeA for Pseudomonas ferric enterobactin) of 2,241 bp capable of encoding a 746-amino-acid protein with a molecular weight of 80,967. The PfeA protein showed more than 60% homology to the E. coli FepA protein. Consistent with this, the two proteins showed significant immunological cross-reactivity.

Amino Acid Sequence↗
PubMed1991

Nature of Escherichia coli cell lysis by culture supernatants of Bacillus species.

Escherichia coli cells were found to be sensitive to lysis by the supernatants of a variety of protease-positive Bacillus species when treated at 45 degrees C but not when treated at 37 degrees C. Different E. coli strains manifested different lysis sensitivities when treated at 45 degrees C. When the lysis rates of E. coli cells at various stages of growth were investigated, post-exponential-phase cells were shown to be most sensitive to lysis. The lysis rate was inversely related to cell viability, and susceptibility appeared to be at least partly due to lysis of dead E. coli cells. A close relation was observed between levels of lysis activity and proteolytic activity. A Bacillus subtilis mutant lacking alkaline and neutral protease activity failed to lyse E. coli cells. It was concluded that Bacillus proteases played a major role in the observed E. coli lysis.

Bacillus↗
PubMed1985

Rapid measurement of creatine kinase activity in a coronary care unit using a portable benchtop reflectance photometer.

Rapid measurements of plasma creatine kinase activity using an inexpensive benchtop reflectance photometer (Ames Seralyzer) and disposable reagent strips were evaluated in the laboratory and coronary care unit. The system proved simple to use and capable of yielding rapid (four minutes per analysis), precise (coefficient of variation less than 9%), and accurate results (correlation with routine method 0.995) when used by medical staff. Creatine kinase values were available 6.5-102 hours earlier than routine laboratory data, depending on the time and day of sampling, thereby facilitating appropriate and economic patient management. This instrument might be used to supplement the routine enzyme service for selected admissions, resulting in greatly improved availability of results and hence contributing to the early discharge of patients from intensive care facilities.

Clinical Enzyme Tests↗
PubMed1980

Effect of propranolol on plasma norepinephrine during sodium nitroprusside-induced hypotension.

The possibility of an action of propranolol which reduces traffic in the sympathetic nervous system and/or reduces release of norepinephrine at sympathetic nerve endings has been investigated in normal subjects. Plasma norephinephrine was measured in resting supine subjects before and during infusions of sodium nitroprusside which reduced the systolic blood pressure by approximately 10 and later by 20 mm Hg. In 5 subjects these observations were repeated 2 hr after a single 200-mg oral dose of propranolol and in 3 they were repeated after 2 to 8 wk of propranolol 320 mg twice daily. In the control experiments, plasma norepinephrine increased from 0.22 up to 0.74 ng/ml when the blood pressure was reduced by 17/15 mm Hg. Corresponding figures 2 hr after 200 mg propranolol were an increase of plasma norepinephrine from 0.30 or 0.79 ng/ml with a reduction of blood pressure of 19/15 mm Hg. After long-term treatment with 640 mg propranolol daily, a similar reduction of pressure with sodium nitroprusside increased plasma norepinephrine from 0.24 to 0.68 ng/ml. There was no significant alteration in the elevation of plasma norepinephrine following blood pressure reduction with nitroprusside after either short- or long-term treatment with propranolol. These experiments do not suggest a significant role for a nervous system effect of propranolol in modifying sympathetic activity.

Adult↗
PubMed1979

The effects of desmethylimipramine on the pharmacological actions of alpha methyldopa in man.

The effect of pretreatment with the tricyclic antidepressant desmethylimipramine (DMI) 75 mg daily for 3 days on the action of oral methyldopa 750 mg was investigated in a double blind crossover design in volunteers. DMI pretreatment caused a small but not significant increase in supine systolic and diastolic blood pressure and heart rate. However, the effects of methyldopa on lying and standing blood pressure and heart rate were not markedly altered by pretreatment. In particular, the fall in standing blood pressure after methyldopa was present with and without DMI and the sedative action of methyldopa was similar. DMI alone reduced saliva production. No evidence was found that tricyclic antidepressant drugs significantly modify the hypotensive effect of methyldopa in man.

Adult↗
PubMed1979

Atenolol and chlorthalidone in combination for hypertension.

1 The hypotensive effect of single daily dosing with atenolol 100 mg and chlorthalidone 25 mg given alone or in combination has been assessed in a double-blind, crossover, placebo controlled trial in fifteen hypertensive patients. 2 Average lying blood pressures were: Placebo 155.4/103.9 mm Hg, atenolol 134.6/85.8 mm Hg, chlorthalidone 139.5/90.1 mm Hg, combination 127.7/82.5 mm Hg. 3 The effect of the combination therapy in reducing lying diastolic pressure compared with placebo (a fall of 21.4 mm Hg) was significantly less than the 31.9 mm Hg fall predicted from the sum of the individual effects (P = 0.01). 4 Observations on blood pressure at rest and under mental, isometric and bicycle ergometer stress were made pre-dose and post-dose for a 12 h period at the end of the last treatment period. 5 Lying blood pressure declined from the zero hour (pre-dose) reading on all treatments to a low at 15.00--18.00 h and then rose again. 6 The rise in systolic blood pressure after isometric exercise and mental stress was of a similar magnitude with all four treatment regimes. 7 Atenolol, alone and in combination with chlorthalidone, reduced the blood pressure and the pulse rate increase on exercise 2 h post-dose when compared with readings 24 h post-dose. 8 Once daily dosing with a combination of atenolol and chlorthalidone produced a fall in supine blood pressure over a 24 h period but the effect on exercise induced changes was not uniform over this period.

Adolescent↗
PubMed1977

Functional modification of indole binding site with indomethacin congeners.

Indomethacin and four congeners were shown by equilibrium dialysis to interfere with the binding of L-tryptophan at the primary indole binding site on defatted human serum albumin. Incubation of albumin with 1-(p-bromoacetamidobenzovl)- and 1-(m-bromoacetamidobenzoyl)-5-methoxy-2-methyl-3-indolylacetic acid functionally modified this site, decreasing the availability of the site for the binding of L-tryptophan. Incubation in the presence of a large excess of L-tryptophan resulted in the partial protection of the site from modification by 1-(m-bromoacetamidobenzoyl)-5-methoxy-2-methyl-3-indolylacetic acid.

Alkylation↗
PubMed1976

Clinical pharmacology and pharmacokinetics of clonidine.

A 300-mug oral dose of clonidine was administered to 5 normal volunteers and measurements of plasma concentration and effects upon blood pressure, heart rate, circulatory reflexes, sedation, and dry mouth were made for the following 8 hr. The plasma concentration rose to a peak of 1.02 +/- 0.52 ng/ml (SD) at 90 min and fell with a mean half-life of 12.7 hr. Blood pressure of the group fell from 111.0/77.0 to 87.2/60.4 after 3 hr and was 95.2/62.2 mm Hg at 8 hr. Heart rate in recumbency was slowed. Marked sedation and a fall in salivary flow followed the same time-course as the plasma concentration. The cold pressor response was reduced but the Valsalva overshoot was little affected.

Adult↗
PubMed1968

The isolation of neurophysin-I and-II from bovine pituitary neurosecretory granules separated on a large scale from other subcellular organelles. Demonstration of slow equilibration of neurosecretory granules during centrifugation in a sucrose density gradient.

1. An improved procedure for the isolation of neurosecretory granules from the posterior lobe of the bovine pituitary gland is described. 2. Of the total oxytocic and pressor activities present in the original tissue 80% was sedimentable. 3. The granules were separated from mitochondria by prolonged centrifugation in a sucrose density gradient. During a sedimentation period of 5hr. the granules moved progressively into denser regions of the gradient and the mitochondria remained at the top. 4. The biological activities of the granules were measured: the oxytocic activity was 11.56+/-1.63 and the pressor activity was 15.60+/-3.91 units/mg. of protein. 5. A protein was isolated from a lysate of granules prepared from 40 pituitary glands. Amino acid analysis showed that it consisted of a mixture of neurophysin-I and neurophysin-II in equal proportions. It accounted for 60% of the soluble granule protein and for 50% of the total granule protein. 6. The neurophysins present in the granules are associated with 19.1 units of oxytocic and 21.1 units of pressor activity/mg. of protein. 7. Starch-gel electrophoresis revealed the presence of both neurophysins in extracts of 15 pituitary glands studied individually. 8. We conclude that the polypeptide hormones, oxytocin and [8-arginine]-vasopressin, are normally closely associated with the two neurophysins within neurosecretory granules of the pituitary gland.

Acid Phosphatase↗