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Biomedical subjects

J R McCormick

Publications and source records attributed to J R McCormick.

At least 19 recordsLinked to original sources
PubMed2004

SCP1, a 356,023 bp linear plasmid adapted to the ecology and developmental biology of its host, Streptomyces coelicolor A3(2).

The sequencing of the entire genetic complement of Streptomyces coelicolor A3(2) has been completed with the determination of the 365,023 bp sequence of the linear plasmid SCP1. Remarkably, the functional distribution of SCP1 genes somewhat resembles that of the chromosome: predicted gene products/functions include ECF sigma factors, antibiotic biosynthesis, a gamma-butyrolactone signalling system, members of the actinomycete-specific Wbl class of regulatory proteins and 14 secreted proteins. Some of these genes are among the 18 that contain a TTA codon, making them targets for the developmentally important tRNA encoded by the bldA gene. RNA analysis and gene fusions showed that one of the TTA-containing genes is part of a large bldA-dependent operon, the gene products of which include three proteins isolated from the spore surface by detergent washing (SapC, D and E), and several probable metabolic enzymes. SCP1 shows much evidence of recombinational interactions with other replicons and transposable elements during its history. For example, it has two sets of partitioning genes (which may explain why an integrated copy of SCP1 partially suppressed the defective partitioning of a parAB-deleted chromosome during sporulation). SCP1 carries a cluster of probable transfer determinants and genes encoding likely DNA polymerase III subunits, but it lacks an obvious candidate gene for the terminal protein associated with its ends. This may be related to atypical features of its end sequences.

Amino Acid Sequence↗
PubMed2001

Two new loci affecting cell division identified as suppressors of an ftsQ-null mutation in Streptomyces coelicolor A3(2).

Mutations in fts genes partially or completely block both vegetative cell division and sporulation septation in the filamentous bacterium Streptomyces coelicolor A3(2). Using a novel screen, we independently isolated two double-mutant strains, each containing a spontaneous suppressor mutation, which partially restores division to an ftsQ-null mutant. Genetic complementation experiments revealed that the suppressor mutations alone confer no observable defect in sporulation. The suppressor mutations were genetically mapped to regions of the chromosome, distinct from each other and the division and cell wall cluster containing ftsQ. Therefore, the genes identified by the suppressor mutations were named sqnA and sqnB (suppressor of ftsQ-null) and may be representatives of a novel class of genes involved in cell division or the regulation of cell division in this mycelial organism.

Bacterial Proteins↗
PubMed1998

Use of 3.5-mm acetabular reconstruction plates for internal fixation of flail chest injuries.

The technique of using 3.5-mm acetabular reconstruction plates for multiple rib fractures with cerclage wires has been successful. We modified it by securing the reconstruction plates to the fractured ribs with cortical screws using the standard AO-ASIF (Arbeitsgemeindschaft fur Osteosynthesefragen [Association for the Study of Internal Fixation]) group technique. Our method for the internal fixation of the unstable chest wall is described. It is relatively simple and provides uniform results.

Bone Plates↗
PubMed1998

The role of lung biopsy in children with perinatally acquired AIDS.

There is a need for a rapid and efficacious method of diagnosis of pulmonary infiltrates in perinatal HIV infection. However, controversy still exists about which method--open lung biopsy (OLB) versus bronchoscopic techniques--is the best for this population. We present our results with OLB in 24 children with HIV-related lung disease. Over a 6-year period, 27 OLBs were performed on 24 children with diagnosis of HIV infection. The procedures were performed under general anesthesia using a limited anterolateral thoracotomy. Suspicious areas were removed with the autostapler. The specimens were studied for the presence of non-infectious as well as bacterial, viral, fungal, and mycobacterial diseases. There were no operative deaths related to the procedure. Morbidity was limited to prolonged but self-resolving air leaks in two patients (8.3%). Five hospital deaths occurred between 3 and 12 weeks postoperatively and 11 late deaths between 3 months and 6.5 years. All deaths were related to AIDS. Eight patients (33.3%) are still alive 2 to 8 years postoperatively. A total of 43 pathologies were found in 27 specimens. A positive pathologic finding was obtained in all patients, with two patients having nonspecific minimal changes. This resulted in a change of therapy in all but one case. The technique of OLB in children with AIDS is safe and simple. It should be performed early in the course of the disease and, a careful selection of candidates can minimize the incidence of complications.

AIDS-Related Opportunistic Infections↗
PubMed1997

Assembly of the cell division protein FtsZ into ladder-like structures in the aerial hyphae of Streptomyces coelicolor.

In the filamentous bacterium Streptomyces coelicolor, the cell division protein FtsZ is required for the conversion of multinucleoidal aerial hyphae into chains of uninucleoidal spores, although it is not essential for viability. Using immunofluorescence microscopy, we have shown that FtsZ assembles into long, regularly spaced, ladder-like arrays in developing aerial hyphae, with an average spacing of about 1.3 microm. Within individual hyphae, ladder formation was relatively synchronous and extended for distances over 100 microm. These ladders were present only transiently, decreasing in intensity as chromosomes separated into distinct nucleoids and disappearing upon the completion of septum formation. Evidence from the overall intensity of immunofluorescence staining suggested that ladder formation was regulated in part at the level of the accumulation and degradation of FtsZ within individual aerial hyphae. Finally, FtsZ ladder formation was under developmental control in that long arrays of FtsZ rings could not be detected in certain so-called white mutants (whiG, whiH and whiB), which are blocked in spore formation. The assembly of FtsZ into ladders represents the earliest known molecular manifestation of the process of spore formation, and its discovery provides insight into the role of whi genes in the conversion of aerial hyphae into chains of spores. We have also described a novel use of a cell wall-staining technique to visualize apical tip growth in vegetatively growing hyphae.

Antibodies, Bacterial↗
PubMed1996

Venous cannula obstruction by Swan-Ganz catheter during cardiopulmonary bypass.

During a routine coronary revascularization procedure in a 51-year-old man, venous return was suddenly interrupted. The venous cannula was rapidly removed, revealing the pulmonary artery catheter wrapped around it. The catheter also had entered the lumen of the cannula, and the inflated balloon completely obstructed the venous return. The prompt removal and reinsertion of the venous cannula resulted in uneventful recovery of the patient.

Cardiopulmonary Bypass↗
PubMed1996

Calcification of bovine pericardium: glutaraldehyde versus No-React biomodification.

BACKGROUND: Calcific degeneration is the most frequent cause of clinical dysfunction of glutaraldehyde (GA)-pretreated bioprosthetic heart valves. The No-React (NR) process has been shown to be a promising anticalcification treatment. In this comparative study, our objective was to delineate the advantages of the NR treatment over GA. METHODS: Bovine pericardial strips pretreated with GA and NR were individually incubated in calcium phosphate solution for 21 days at 37 degrees C. The pretreated bovine pericardium then was implanted subcutaneously in rats and retrieved at 14, 21, and 35 days after-implantation. Mineral and morphologic analyses were performed on each specimen. RESULTS: The NR-treated pericardium revealed significantly reduced in vitro calcification compared with the GA-treated tissue (mean tissue calcium content 1.3 +/- 0.2 versus 5.9 +/- 0.7 micrograms/mg; p < 0.001). Mineral analysis showed progressive calcification of the GA-pretreated pericardium over the period of implantation (calcium content increasing from 49.6 +/- 9.6 micrograms/mg after 2 weeks to 134.3 +/- 9.1 micrograms/mg at 5 weeks after-implantation). The NR-treated implants had calcified significantly less (p < 0.05) at each corresponding interval. Moreover, morphologic examinations demonstrated a protracted inflammatory response in the form of giant cell and mononuclear cell infiltration associated with intrinsic collagen disruption in the GA-treated tissue; the NR-treated pericardium maintained morphologic integrity with a mild inflammatory response. CONCLUSIONS: The NR biochemical process appears not only to attenuate pericardial calcification, but also to abort the host's destructive inflammatory response to the xenograft.

Animals↗
PubMed1996

No-react detoxification process: a superior anticalcification method for bioprostheses.

BACKGROUND: Glutaraldehyde pretreatment of bioprosthetic heart valves is the major pathogenic factor in their calcific degeneration. This comparative study investigates the merit of the No-React aldehyde detoxification process as an alternative modifier of xenograft tissues. METHODS: Glutaraldehyde- and No-React-pretreated porcine aortic valve cusps were implanted subcutaneously in 6-week-old rats (n = 20). At 3, 6, and 14 weeks, randomly selected animals were sacrificed and the explants underwent mineral and morphologic analyses. Glutaraldehyde- and No-React-treated bovine pericardium and porcine aortic valve cusp were incubated in fibroblast cell culture plates. Cell viability was observed under reversed microscope at 6, 24, 48, and 96 hours. Erythrosin B dye exclusion test was used to validate percent cell death. RESULTS: Pretreatment with No-React significantly inhibited calcification of aortic cusp subcutaneous implants throughout the 14-week period (mean tissue Ca2+ content = 1.3 +/- 0.7 micrograms/mg at 14 weeks.) Glutaraldehyde-treated cusps underwent protracted calcification (Ca2+ content = 190.6 +/- 89.5 micrograms/mg; p < 0.01). Morphologic findings correlated with mineral analyses. One-hundred percent of fibroblast cells survived in the presence of No-React-treated tissue, with a growth pattern indistinguishable from control cell culture (ie, in the presence of no tissue). The cells incubated with glutaraldehyde-treated tissue showed signs of nonviability by 6 hours, with 100% cell death by 48 hours. Dye exclusion tests validated these findings. CONCLUSIONS: The No-React detoxification process completely abolishes the cytotoxicity of the xenograft tissue and inhibits calcific degeneration.

Animals↗
PubMed1996

Cell division gene ftsQ is required for efficient sporulation but not growth and viability in Streptomyces coelicolor A3(2).

We show that the cell division gene ftsQ of Streptomyces coelicolor A3(2) is dispensable for growth and viability but is needed during development for the efficient conversion of aerial filaments into spores. Combined with our previous demonstration that ftsZ of S. coelicolor is not needed for viability, these findings suggest that cell division has been largely co-opted for development in this filamentous bacterium. This makes S. coelicolor an advantageous system for the study of cell division genes.

Amino Acid Sequence↗
PubMed1994

Correlation of translation efficiency with the decay of lacZ mRNA in Escherichia coli.

We isolated mutations in the leader of a ribosomal protein (r-protein)/lacZ fusion gene in Escherichia coli that caused the mRNA to be translated at efficiencies between < 1% and 62% of the rate of wild-type message. Using a subset of these mutants with translation efficiencies between 5% and 62%, we studied both physical and functional decay of the mRNA after rifampicin inhibition of transcription initiation. The decay of physically intact transcript was analyzed by gel electrophoresis of hybrid-selected messenger RNA segments. The output from the message was analyzed by measuring the synthesis rate of r-protein/lacZ fusion protein. Decay of physically intact message after rifampicin addition correlated with the translation efficiency, with the more active messengers being more stable. Different segments of the r-protein/lacZ fusion mRNA decayed with the same rate, indicating that there is no hyper-labile region in the transcript. The decay rate was also independent of the length of the segment probed, suggesting that the mRNA is not degraded by random attacks along the entire length of the molecule. Our results are consistent with an overall 5' to 3' degradation pathway. Surprisingly, the rate of fusion protein synthesis did not decrease immediately after rifampicin addition. Rather, a lag preceded the exponential decay phase; the length of this delay correlated with the translation efficiency, such that the lag increased with increasing efficiency of translation. We suggest that these lags indicate that mRNAs are normally competing for ribosomes during exponential growth and, after rifampicin addition, RNA molecules with longer physical half-lives are translated by ribosomes released from fast decaying messengers.

Base Sequence↗
PubMed1994

Growth and viability of Streptomyces coelicolor mutant for the cell division gene ftsZ.

A homologue of the bacterial cell division gene ftsZ was cloned from the filamentous bacterium Streptomyces coelicolor. The gene was located on the physical map of the chromosome at about '11 o'clock' (in the vicinity of glkA, hisA and trpB). Surprisingly, a null mutant in which the 399-codon ftsZ open reading frame was largely deleted was viable, even though the mutant was blocked in septum formation. This indicates that cell division may not be essential for the growth and viability of S. coelicolor. The ftsZ mutant was able to produce aerial hyphae but was unable to produce spores, a finding consistent with the idea that ftsZ is required in order for aerial hyphae to undergo septation into the uninucleoid cells that differentiate into spores.

Amino Acid Sequence↗
PubMed1992

PMA-activated neutrophils decrease ectoenzyme activities in rabbit aortic endothelial cells in culture.

We have studied the effects of phorbol 12-myristate 13-acetate (PMA)-activated neutrophils [polymorphonuclear leukocytes (PMN)] on endothelial ectoenzyme [angiotensin-converting enzyme (ACE) and 5'-nucleotidase (NCT)] activities in cultured rabbit aortic endothelial cells (EC) with the use of [3H]benzoyl-Phe-Ala-Pro and 14C-labeled AMP as substrates, respectively, under first-order reaction conditions. PMA (1-1,000 ng/ml) or PMN alone had no effect on ACE activity. When PMA was incubated together with PMN (PMN/EC = 1.25:1 or 2.5 x 10(5) neutrophils/ml) for 4 h in Earle's salts, a PMA dose-dependent decrease in ACE activity was observed. Threshold PMA concentration was 2 ng/ml. At 8 ng PMA/ml, ACE activity was totally abolished, without any evidence of cytotoxicity, as inferred from release of 51Cr from prelabeled EC. The decrease in ACE activity was also dependent on PMN concentration and was detectable at PMN/EC values as low as 1.25:10 (0.25 x 10(5) PMN/ml). Inhibition of ACE occurred as early as 1 h after incubation (PMA 10 ng/ml, PMN/EC = 1.25:1). PMA alone caused a small but significant increase in NCT activity, whereas PMA coincubation with PMN produced a significant decrease in NCT activity (20-29%), which was PMA and PMN concentration independent. PMA increased PMN adherence to endothelial monolayers in a concentration-dependent manner. Pretreating PMN with monoclonal antibody 60.3 (raised against the adhesion glycoprotein CD18) or placing a 2-microns filter between PMN and EC, protected the decrease in ACE activity.(ABSTRACT TRUNCATED AT 250 WORDS)

5'-Nucleotidase↗
PubMed1991

Intermediates in the degradation of mRNA from the lactose operon of Escherichia coli.

We have analyzed the processing of mRNA from the lac operon in an Escherichia coli strain carrying the lac on a multicopy plasmid. Messenger RNA was analyzed by hybridization and nuclease protection of pulse-labeled RNA and precursor-product relationships were determined by quantitating radioactivity in primary and processed transcripts at various times after induction of the lac promoter or inhibition of transcription with rifampicin. Our results support the existence of two types of processed transcripts with endpoints in the lacZ-lacY intercistronic region. One of these carries lacZ sequences and has a 3' endpoint about 30 bases downstream of this gene. The other carries lacY sequences and has a 5' end in the translation termination region of the lacZ gene. Finally, we have found evidence that transcription is continued at least 268 bases beyond the last gene (lacA) and that this 3' non-translated region is shortened by post-transcriptional processing.

Base Sequence↗
PubMed1989

Translational coupling of the two proximal genes in the S10 ribosomal protein operon of Escherichia coli.

We have examined the translational coupling between the first two genes in the S10 ribosomal protein operon. We isolated mutations blocking the translation of the first gene of the operon, coding for S10, and monitored their effects on translation of the downstream gene, coding for L3. All of the mutations inhibiting S10 synthesis also affected the synthesis of L3. However, these experiments were complicated by decreased mRNA synthesis resulting from transcription polarity, which we could only partially eliminate by using a rho-100 strain. To completely eliminate the problem of transcription polarity and obtain a more accurate measurement of the coupling, we replaced the natural S10 promoter with a promoter used by the bacteriophage T7 RNA polymerase. As expected, the T7 RNA polymerase was not subject to transcription polarity. Using this system, we were able to show that a complete abolishment of S10 translation resulted in an 80% inhibition of L3 synthesis. Other experiments show that the synthesis of L3 goes up as a function of increasing S10 synthesis, but the translational coupling does not assure strictly proportional output from the two genes.

DNA Mutational Analysis↗
PubMed1987

Early pulmonary endothelial enzyme dysfunction after phorbol ester in conscious rabbits.

We investigated changes in angiotensin converting-enzyme (ACE) activity before and at 5, 15, 60, and 240 min after 20 micrograms phorbol myristate acetate/kg body wt iv in conscious rabbits. ACE activity was estimated in vivo from the single-pass transpulmonary metabolism of the synthetic substrate [3H]benzoyl-Phe-Ala-Pro [( 3H]BPAP) under first-order reaction conditions. Within 5 min after PMA administration, all animals developed profound granulocytopenia (15% of control) and moderate thrombocytopenia (57% of control), both lasting for the duration of the experiment. Concomitantly, there was a significant decrease in the transpulmonary metabolism of [3H]BPAP and the calculated apparent first-order reaction constant Amax/Km of ACE for [3H]BPAP. No histological evidence of lung injury was observed at these times. Since a concomitant fall in the permeability surface area product for urea was also observed, we considered that the apparent decline in ACE activity might have resulted from a reduction in perfused endothelial surface area. To resolve this, we studied the effect of PMA on the Km (a measure of enzyme affinity for its substrate) and Amax (a derivative of Vmax that is dependent upon total enzyme present and thus capillary surface area) of ACE and 5'-nucleotidase for [3H]BPAP and [14C]AMP, respectively. A significant increase in Km for both enzymes was observed at 1 h after PMA, whereas Amax was unaffected, suggesting that low-dose PMA may indeed produce endothelial cell enzyme dysfunction independent of its effect on capillary surface area. These results provide evidence of pulmonary capillary functional injury before or in the absence of structural endothelial damage.

Adenosine Monophosphate↗