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Biomedical subjects

B Lee

Publications and source records attributed to B Lee.

At least 343 records · Page 19Linked to original sources
PubMed1991

Mutations in the small subunit of cyanobacterial ribulose-bisphosphate carboxylase/oxygenase that modulate interactions with large subunits.

In the cyanobacterium Anacystis nidulans (Synechococcus PCC6301), ribulose 1,5-bisphosphate carboxylase/oxygenase (Rbu-P2 carboxylase) is composed of eight large subunits and eight small subunits. There are three regions of the small subunit that contain amino acids that are conserved throughout evolution, from bacteria to higher plants. Since the function of the small subunit is not fully understood, site-directed mutagenesis was performed on highly conserved residues in the first and second conserved regions. Ser-16, Pro-19, Leu-21, and Tyr-54 were replaced by Asp-16, His-19, Glu-21, and Ser-54, respectively. Crude extracts containing the recombinant His-19 mutant enzyme indicated that there was little effect on either Rbu-P2 carboxylase activity or interactions between large and small subunits. However, the Asp-16, Glu-21, and Ser-54 mutations showed effects on Rbu-P2 carboxylase activity and the interaction between large and small subunits. The large and small subunits of the Asp-16, Glu-21, and Ser-54 enzymes were found to dissociate during nondenaturing gel electrophoresis or sucrose density gradient centrifugation. However, the dissociated small subunits remained functional and were capable of reconstituting Rbu-P2 carboxylase activity when added to large subunits. These results indicated that Ser-16, Leu-21, and Tyr-54 might play an important role in interactions between large and small subunits of the A. nidulans enzyme.

Amino Acid Sequence↗
PubMed1991

G to T transversion at position +5 of a splice donor site causes skipping of the preceding exon in the type III procollagen transcripts of a patient with Ehlers-Danlos syndrome type IV.

We identified a splicing mutation in a patient with Ehlers-Danlos syndrome type IV, a heritable connective tissue disorder associated with dysfunctions of type III collagen. The mutation was first localized in the patient's type III procollagen mRNA by amplifying the reverse transcribed product in several overlapping fragments using the polymerase chain reaction. Amplified products spanning exon 24-26 sequences displayed two distinct fragments, one of normal size and the other lacking the 99 base pairs of exon 25. Sequencing of amplified genomic products identified a G to T transversion at position +5 of the splice donor site of intron 25 in one of the patient's procollagen III genes. Expression of allelic minigene constructs correlated the T for G substitution with skipping of exon 25 sequences. Like previously characterized splicing mutations in other collagen genes, lowering the temperature at which the patient's fibroblasts were incubated nearly abolished exon skipping. As a part of this study, we also identified a highly polymorphic, intronic DNA sequence whose different allelic forms can be detected easily by the polymerase chain reaction technique.

Alleles↗
PubMed1991

Multiexon deletion in the procollagen III gene is associated with mild Ehlers-Danlos syndrome type IV.

We have characterized a deletion of approximately 9 kilobases which spans from intron 33 to exon 48 of one pro-alpha 1 (III) collagen allele in a patient with Ehlers-Danlos syndrome type IV. The mutation results in the production of an in-frame species of mRNA which lacks the sequences corresponding to residues 595-1,008 of the triple-helical domain. Thus, half of the pro-alpha 1 (III) chains synthesized by the patient's fibroblasts are nearly 30% shorter than normal. The procollagen III molecules composed of either three normal length or three shortened chains are thermally stable and efficiently secreted. In contrast, the procollagen III molecules that contain one or two shortened chains are unstable and are not secreted. Failure to secrete unstable molecules and a residual functional role of the shortened but stable homotrimers may explain the somewhat milder phenotype of this individual compared with that of another Ehlers-Danlos type IV patient bearing a deletion of similar size in the amino-terminal portion of the alpha 1 (III) collagen chain.

Chromosome Deletion↗
PubMed1991

Solvent reorganization contribution to the transfer thermodynamics of small nonpolar molecules.

The experimental thermodynamic data for the dissolution of five simple hydrocarbon molecules in water were combined with the solute-solvent interaction energy from a computer simulation study to yield data on the enthalpy change of solvent reorganization. Similar data were generated for dissolving these same solute molecules in their respective neat solvents using the equilibrium vapor pressure and the heat of vaporization data for the pure liquid. The enthalpy and the free energy changes upon cavity formation were also estimated using the temperature dependence of the solute-solvent interaction energy. Both the enthalpy and T delta S for cavity formation rapidly increase with temperature in both solvent types, and the free energy of cavity formation can be reproduced accurately by the scaled particle theory over the entire temperature range in all cases. These results indicate that the characteristic structure formation around an inert solute molecule in water produces compensating changes in enthalpy and entropy, and that the hydrophobicity arises mainly from the difference in the excluded volume effect.

Computer Simulation↗
PubMed1991

The Kilkenny Health Project: a community research and demonstration cardiovascular health programme.

Ireland has one of the highest death rates in the world from coronary heart disease (CHD) and has not shared in the rapid decline in mortality which has occurred in other countries. The Kilkenny Health Project was established as a community-based research and demonstration programme for cardiovascular disease prevention in County Kilkenny and as a pilot project for future national initiatives. The first phase of the health promotion programme in Kilkenny is being carried out between 1985 and 1990. Changes in behaviour and in factors associated with CHD will be estimated by the difference in changes over time between Kilkenny and the reference area, as measured by independent random sample surveys of men and women aged 35 to 64 years. CHD and stroke events, fatal and non-fatal, will be registered in both areas from 1987-1992. The Project has studied attitudes to CHD and its prevention. Health behaviours have been studied in adults and in post-primary school pupils. Risk factors for CHD have been measured in adults in accordance with the methods of the international MONICA Project. It has been demonstrated that health and education professionals can incorporate preventive activities and health education into everyday practice.

Adult↗
PubMed1991

A heart health assessment programme in general practice in County Kilkenny, Ireland.

The Kilkenny Faculty of the Irish College of General Practitioners and the Kilkenny Health Project have established a Health Assessment Programme (HAP) to standardise the examination and recording of coronary heart disease (CHD) risk factors in general practice. Criteria were agreed for classification and coding of demographic data, relevant medical history and risk behaviours. Height, weight and blood pressure are measured and venous blood sample is taken for total cholesterol estimation. The assessment is followed by appropriate counselling. The HAP was first targetted at men and women aged 40 to 49 years. During the first 16 months of the programme, 2102 assessments were carried out by 41 general practitioners, which represents 29% of the target group. Those taking part had a lower social class distribution when compared with participants in the KHP baseline survey in 1985. There were no significant differences between the two groups in smoking prevalence or in the distribution of body mass index. Median cholesterol was 5% lower in the HAP group than at the baseline survey. 16% of the HAP clients had diastolic blood pressures of 90 mm Hg or more. The HAP has demonstrated that it is feasible to measure CHD risk factors in a variety of general practice settings. The format facilitates a preventive orientation and has proved acceptable to patients.

Adult↗
PubMed1991

A modified minimal model analysis of insulin sensitivity and glucose-mediated glucose disposal in insulin-dependent diabetes.

Although glucose utilization is impaired in insulin-dependent diabetes mellitus (IDDM), it is unclear whether this is due to reductions in insulin sensitivity (Si) and/or glucose-mediated glucose disposal (SG). The minimal model of Bergman et al can be applied to a frequently sampled intravenous glucose tolerance test (FSIGT) to simultaneously estimate Sl and SG, but cannot accommodate data from diabetics. Exogenous insulin approximating the normal pattern of insulin secretion was infused during FSIGTs in eight young non-obese C-peptide-negative IDDM subjects, but with the total dose modified to achieve sufficient glucose disappearance rates (KG) to allow analysis of data. The minimal model was modified to model the effects of the exogenous insulin on glucose kinetics to estimate SI and SG. Despite deliberately achieving supranormal plasma-free insulin levels during the FSIGT ("first-phase insulin" = 62 +/- 9 SE mU/L; "second phase insulin" = 34 +/- 9 mU/L), the diabetics showed low-normal KG values (1.3 +/- 0.29 min-1 X 10(2). Using the model, good parameter resolution (fractional SD [FSD] less than .5) was achieved (IDDM v controls: SI = 2.5 +/- 0.6 v 8.3 +/- 1.5 min-1.mU-1.L-1 X 10(4); SG = 1.6 +/- 0.5 v 2.6 +/- 0.2 min-1 X 10(2); P less than .05). This reduction in SG was confirmed in the same IDDM subjects by FSIGT during basal insulin infusion only (SG = 1.0 +/- 0.3 min-1 X 10(2)).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Biodegradation of degradable plastic polyethylene by phanerochaete and streptomyces species.

The ability of lignin-degrading microorganisms to attack degradable plastics was investigated in pure shake flask culture studies. The degradable plastic used in this study was produced commercially by using the Archer-Daniels-Midland POLYCLEAN masterbatch and contained pro-oxidant and 6% starch. The known lignin-degrading bacteria Streptomyces viridosporus T7A, S. badius 252, and S. setonii 75Vi2 and fungus Phanerochaete chrysosporium were used. Pro-oxidant activity was accelerated by placing a sheet of plastic into a drying oven at 70 degrees C under atmospheric pressure and air for 0, 4, 8, 12, 16, or 20 days. The effect of 2-, 4-, and 8-week longwave UV irradiation at 365 nm on plastic biodegradability was also investigated. For shake flask cultures, plastics were chemically disinfected and incubated-shaken at 125 rpm at 37 degrees C in 0.6% yeast extract medium (pH 7.1) for Streptomyces spp. and at 30 degrees C for the fungus in 3% malt extract medium (pH 4.5) for 4 weeks along with an uninoculated control for each treatment. Weight loss data were inconclusive because of cell mass accumulation. For almost every 70 degrees C heat-treated film, the Streptomyces spp. demonstrated a further reduction in percent elongation and polyethylene molecular weight average when compared with the corresponding uninoculated control. Significant (P < 0.05) reductions were demonstrated for the 4- and 8-day heat-treated films by all three bacteria. Heat-treated films incubated with P. chrysosporium consistently demonstrated higher percent elongation and molecular weight average than the corresponding uninoculated controls, but were lower than the corresponding zero controls (heat-treated films without 4-week incubation). The 2- and 4-week UV-treated films showed the greatest biodegradation by all three bacteria. Virtually no degradation by the fungus was observed. To our knowledge, this is the first report demonstrating bacterial degradation of these oxidized polyethylenes in pure culture.

Journal Article↗
PubMed1991

Characteristics of blood flow velocity patterns of central systemic veins in healthy adults assessed by Doppler echocardiography.

To evaluate the differences in shape and phase lag of the flow velocity curves in the superior (SVC) and inferior (IVC) venae cavae and the hepatic vein (HV), Doppler echocardiographic examination was performed in 40 healthy adults (aged 20 to 67 years, mean +/- SD: 39 +/- 12 years). Flow velocity patterns in each vein were characterized by 4 major deflections: S wave, a systolic forward flow; D wave, a diastolic forward flow; A wave, a small backward flow or reduction of diastolic forward flow due to atrial contraction; and O wave, a small backward flow or reduction of forward flow after the second heart sound. Except for a reduced phasic flow in a collapsed IVC, the venous flow velocity recordings in each vein demonstrated very similar pulsatile patterns and small differences in mean time lags of less than 50 msec. In general, the lowest values of peak A/peak S, peak O/peak S and peak D/peak S were observed in HV flow and the highest in IVC flow. Backflows of A and O waves were prominent in HV flow, but small and least frequent in IVC flow. These data suggest that the baseline of the central venous flow recordings might shift downward in HV flow and upward in IVC flow. However, even if both the baseline shift and amplitude of the flow curve were normalized in each venous flow velocity curve, apparent differences in shape of the flow velocity curves would remain. We concluded that the characteristics and differences of each central venous flow velocity pattern should be noted in studies of these areas.

Adult↗
PubMed1991

Modifications in the organization and expression of collagen genes associated with skeletal disorders.

Fibril-forming collagens represent an evolutionary related group of structurally similar molecules within the larger family of collagen proteins. Characterization of naturally occurring mutations has provided a model whereby clinically distinct phenotypes are predicted on the basis of how specific mutations alter normal fibrillogenesis. This model, originally derived from studies of type I collagen defects in osteogenesis imperfecta and Ehlers Danlos syndrome type VII, has been modified and extended by recent correlations of type II collagen defects with several chondrodysplasias and of type III collagen defects with Ehlers Danlos syndrome type IV. From analysis of the skeletal dysplasias, the pathogenic role of fibrillar collagen defects in more common clinical entities has been suggested and awaits rigorous proof. Although informative, these collective studies have revealed important exceptions to predictions of the original pathobiochemical paradigm, and, thus, they have initiated a more rigorous reconsideration of the deductive model. As an alternative, investigations are currently underway to generate transgenic mouse models of human collagenopathies. This task will not only clarify the complexity of collagen pathophysiology, but it will also permit the development of therapeutic strategies.

Animals↗
PubMed1991

Characterization of a large deletion associated with a polymorphic block of repeated dinucleotides in the type III procollagen gene (COL3A1) of a patient with Ehlers-Danlos syndrome type IV.

Ehlers-Danlos syndrome type IV (EDS IV) is an autosomal dominant condition characterized by extreme fragility of skin, blood vessels, intestine, gravid uterus, and lungs. The phenotype is accounted for by mutations affecting the integrity and/or synthesis of the precursor procollagen molecules of type III collagen. In this article, we report the elucidation of the molecular defect in an EDS IV patient whose type III collagen was previously found to be structurally abnormal. We utilized PCR in a two-step process involving first the localization of the mutation in the mRNA and then the characterization of the defect in the gene. The results established the patient's heterozygosity for a genomic deletion of about 7.5 kb which eliminates 1,026 nucleotides of coding sequences in the message. The mutation arose as a result of an exon-to-intron recombination. The deleted segment extends from the 13th nucleotide of exon 9 to within a DNA sequence of intron 24, which is composed of a series of dinucleotide repeats. Using PCR, we tested the polymorphic nature of this DNA element on several unrelated individuals. Analysis of amplified genomic products of 45 chromosomes recognized at least four distinct allelic forms that display frequencies ranging from 5% to 61%. Mendelian segregation of three of the four alleles was established by the same method in a 3-generation family.

Alleles↗
PubMed1990

Purification of recombinant ribulose-1,5-bisphosphate carboxylase/oxygenase large subunits suitable for reconstitution and assembly of active L8S8 enzyme.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) from Anacystis nidulans was reconstituted in vitro from extracts of Escherichia coli strains that separately express large and small subunits. This reconstitution system was shown to be useful for monitoring the appearance of dissociated or fractionated subunit preparations. Recombinant large subunits were purified to a state of homogeneity and retained reconstitution capacity in the presence of added small subunits. The purified large subunits appeared to be in the form of an octamer, probably an L8 structure, and showed 0.15% of the carboxylase activity of the purified L8S8 enzyme. Purified large subunit octamers are disrupted by nondenaturing PAGE; however, the octamer is stable to electrophoresis in the presence of exogenous protein.

Cyanobacteria↗
PubMed1990

Oral therapy for Pneumocystis carinii pneumonia in the acquired immunodeficiency syndrome. A controlled trial of trimethoprim-sulfamethoxazole versus trimethoprim-dapsone.

BACKGROUND: Antimicrobial drugs that can be taken orally are needed for the treatment of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome (AIDS). Preliminary data indicate that dapsone with trimethoprim may be an effective alternative to trimethoprim-sulfamethoxazole, which is frequently toxic. METHODS: In a double-blind trial, 60 patients with AIDS and mild-to-moderately-severe first episodes of P. carinii pneumonia (partial pressure of oxygen in arterial blood, greater than 60 mm Hg while breathing room air) were randomly assigned to 21 days of treatment with either trimethoprim-sulfamethoxazole (20 and 100 mg per kilogram of body weight per day, respectively) or trimethoprim-dapsone (20 mg per kilogram per day and 100 mg per day). RESULTS: The orally administered treatment failed because of progressive pneumonitis in 3 of the 30 patients assigned to trimethoprim-sulfamethoxazole and in 2 of the 30 assigned to trimethoprim-dapsone (P greater than 0.3). Major toxic effects required a switch to intravenous pentamidine for 17 patients (57 percent) in the trimethoprim-sulfamethoxazole group, as compared with 9 (30 percent) in the trimethoprim-dapsone group (P less than 0.025). With trimethoprim-sulfamethoxazole, there were more instances of severe chemical hepatitis (six, as compared with one in the trimethoprim-dapsone group) and marked neutropenia (five vs. one). Intolerable rash (three in each treatment group) and severe nausea and vomiting (two in each group) occurred with equal frequency with both drug combinations. Methemoglobinemia occurred in most of the patients treated with trimethoprim-dapsone, but it was asymptomatic and the level exceeded 20 percent in only one patient. Mild hyperkalemia (serum potassium level, 5.1 to 6.1 mmol per liter) also occurred in 53 percent of the patients treated with trimethoprim-dapsone. CONCLUSIONS: In patients with AIDS, oral therapy with trimethoprim-sulfamethoxazole and with trimethoprim-dapsone are equally effective for mild-to-moderate first episodes of P. carinii pneumonia, but with trimethoprim-dapsone there are fewer serious adverse reactions than with trimethoprim-sulfamethoxazole.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Probe angioplasty of total coronary occlusion using the Probing Catheter technique.

Coronary angioplasty (PTCA) of total coronary occlusion is limited by the inability of guidewires and conventional dilating catheters to cross all such lesions. A new technique was therefore prospectively evaluated for PTCA of these lesions using the ultra-low-profile Probe "balloon on a wire" device. An intracoronary Probing Catheter was used to facilitate crossing the stenosis with a guidewire and then to deliver a Probe into the obstruction for balloon dilatation. This technique was utilized in 64 consecutive patients with "absolute" coronary occlusions demonstrating no angiographically detectable antegrade coronary flow. Successful dilatation was achieved in 47 (73%). Among 33 occlusions of less than 3 mo duration 31 (94%) were successfully dilated whereas only 16 of 31 more chronic occlusions were dilated (P less than .01). Chronic occlusions with a tapered morphology and those located more than 1 cm from a branch point were more frequently dilatable. There were no serious complications including no vessel perforations with this technique. The Probing Catheter technique offers a safe and effective method for the dilatation of recent coronary occlusions by using balloon on a wire technology.

Angioplasty, Balloon, Coronary↗
PubMed1990

Effects of cytochalasin D on actin and vinculin in cultured corneal epithelial cells.

Migrating corneal epithelial cells in culture elaborate lush arrays of actin filament bundles (stress fibers) which terminate peripherally at discrete cell-to-substratum adhesion complexes. These complexes contain several specific adhesion plaque proteins, of which vinculin is one. Vinculin, a 130 kD protein, putatively links the intracellular actin bundles in a transmembrane fashion (via integrin, a specific plasmalemmal junction protein) to focal attachment sites onto the underlying extracellular matrix substratum. Migrating rat corneal epithelial cells in tissue culture are treated with 0.1-1.0 microgram/ml cytochalasin D, an inhibitor of actin polymerization. This resulted in a generalized disruption of stress fibers, causing actin to the diffusely redistributed into discrete, round patches. Most, but not all, of these patches of actin appeared to colocalize with foci of vinculin. The focal patches of vinculin appeared to be larger and more diffuse in the cytochalasin-treated cells compared to the drug-free cells. These cytochalasin-induced cytoskeletal changes were associated with total cessation of cell migration and increased cellular detachment from the substratum.

Actins↗