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Biomedical subjects

R M Gibson

Publications and source records attributed to R M Gibson.

At least 19 recordsLinked to original sources
PubMed1992

A novel Bacillus subtilis expression vector based on bacteriophage phi 105.

We have developed a novel expression vector based on the bacteriophage phi 105, and employed it for the production of mutant beta-lactamases in Bacillus subtilis. Expression of the beta-lactamase-encoding gene was low when cloned into the prophage under the control of its own promoter. However, expression was considerably elevated when the gene was inserted into the phage genome in the same orientation as phage transcription. A defective phi 105 vector was constructed with a deletion removing a region needed for cell lysis, and with a mutation in the immunity repressor, rendering it temperature sensitive. Production of beta-lactamase could then be induced by a shift in temperature and without concomitant cell lysis, facilitating purification of the protein from the culture supernatant. This phage has considerable potential for development as a vector for controllable production of heterologous proteins in B. subtilis.

Bacillus subtilis↗
PubMed1992

P-selectin and E-selectin. Distinct but overlapping leukocyte ligand specificities.

P-selectin on platelets and endothelial cells and E-selectin on endothelial cells are leukocyte receptors that recognize lineage-specific carbohydrates on neutrophils and monocytes. The proposed ligands for these receptors contain the Le(x) core and sialic acid. Since other investigators have shown that both E-selectin and P-selectin bind to sialylated Le(x), we evaluated whether E-selectin and P-selectin recognize the same counter-receptor on leukocytes. The interaction of HL60 cells with Chinese hamster ovary (CHO) cells expressing P-selectin or E-selectin was studied. To determine whether a protein component is required in addition to sialyl Le(x) for either P-selectin or E-selectin recognition, HL60 cells or neutrophils were digested with proteases, including chymotrypsin, elastase, proteinase Glu-C, ficin, papain, or thermolysin. Cells treated with these proteases bound E-selectin but not P-selectin. Fucosidase or neuraminidase treatment of HL60 cells markedly decreased binding to both E-selectin- and P-selectin-expressing CHO cells. Growth of HL60 cells in tunicamycin inhibited the ability of these cells to support P-selectin-mediated binding and, to a lesser extent, E-selectin-mediated binding. Purified P-selectin inhibited CHO:P-selectin binding to HL60 cells, but incompletely inhibited CHO:E-selectin binding to HL60 cells. However, purified soluble E-selectin inhibited CHO:P-selectin and CHO:E-selectin binding to HL60 cells equivalently and completely. COS cells, unable to bind to E-selectin or P-selectin, bound E-selectin but not P-selectin upon transfection with alpha-1,3-fucosyltransferase or alpha-1,3/1,4-fucosyltransferase. Similarly, LEC 11 cells expressing sialyl Le(x) bound E-selectin- but not P-selectin-expressing CHO cells. Sambucus nigra lectin, specific for the sialyl-2,6 beta Gal/GalNAc linkage, inhibited P-selectin but not E-selectin binding to HL60 cells. Although sialic acid and Le(x) are components of the P-selectin ligand and the E-selectin ligand, these results indicate that the ligands are related, having overlapping specificities, but are structurally distinct. A protein component containing sialyl Le(x) in proximity to sialyl-2,6 beta Gal structures on the P-selectin ligand may contribute to its specificity for P-selectin.

Animals↗
PubMed1990

Site-directed mutagenesis of beta-lactamase I. Single and double mutants of Glu-166 and Lys-73.

Two single mutants and the corresponding double mutant of beta-lactamase I from Bacillus cereus 569/H were constructed and their kinetics investigated. The mutants have Lys-73 replaced by arginine (K73R), or Glu-166 replaced by aspartic acid (E166D), or both (K73R + E166D). All four rate constants in the acyl-enzyme mechanism were determined for the E166D mutant by the methods described by Christensen, Martin & Waley [(1990) Biochem. J. 266, 853-861]. Both the rate constants for acylation and deacylation for the hydrolysis of benzylpenicillin were decreased about 2000-fold in this mutant. In the K73R mutant, and in the double mutant, the rate constants for acylation were decreased about 100-fold and 10,000-fold respectively. All three mutants also had lowered values for the rate constants for the formation and dissociation of the non-covalent enzyme-substrate complex. The specificities of the mutants did not differ greatly from those of wild-type beta-lactamase, but the hydrolysis of cephalosporin C by the K73R mutant gave 'burst' kinetics.

Bacillus cereus↗
PubMed1990

Impact of L-phenylalanine supplementation on the performance of three-week-old broilers fed diets containing ochratoxin A. 1. Effects on body weight, feed conversion, relative organ weight, and mortality.

An experiment with a completely randomized 2-by-3 factorial design was used to study the effects of ochratoxin A (OA; 0 and 4 mg of OA per kg) and supplemental L-phenylalanine (Phe; .0%, .8%, and 2.4% of Phe) in the diets of 3-wk-old broilers. Diets based on ground yellow corn and dehulled soybean meal were fed from Day 1 to 3 wk of age. A total of 240 male Hubbard-by-Hubbard broilers were randomly placed in battery brooders with 10 birds per pen. Each treatment was replicated 4 times. The parameters measured included mortality, BW, feed conversion, and relative organ weight. Broilers receiving OA weighed less and had poorer feed conversions than birds not receiving OA. For broilers receiving OA, the relative weights (grams of organ weight per 100 g of BW) of the liver, proventriculus, gizzard, and heart increased, while the relative weight of the bursa decreased. Supplemental Phe decreased the relative weight of the liver and increased the relative weight of the gizzard and heart. The regression slopes for Phe at 4 mg of OA per kg of diet were significantly different from 0 for BW, the relative weights of the kidney, spleen, and pancreas and approached significance for mortality (P = .065). In the absence of supplemental Phe, 42.5% of the birds died during the study when the dose level was 4 mg of OA per kg of diet. However, when Phe was supplemented at .8 and 2.4%, only 12.5 and 15.0% of the birds died, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Impact of L-phenylalanine supplementation on the performance of three-week-old broilers fed diets containing ochratoxin A. 2. Effects on hematology and clinical chemistry.

Phenylalanine was evaluated for its ability to protect broiler chickens from the toxic effects of ochratoxin A (OA). A completely randomized 2-by-3 factorial design was utilized consisting of 0, .8, and 2.4% supplemental L-phenylalanine (Phe) and of 0 and 4 mg of OA per kg of diet. The basal diet contained 14% protein. Broilers were raised in battery brooders to 3 wk of age, when blood was collected and various hematological parameters were determined. The health status of the broilers was evaluated by assaying serum for various enzyme activities and metabolites using an automated, clinical chemistry analyzer. Adding OA to the broiler diets resulted in an increased concentration of serum hemoglobin as well as increased activity for cholinesterase and gamma glutamyl transferase but in decreased activity for aspartate amino transferase, lactate dehydrogenase, and alkaline-phosphatase activity as well as decreased concentrations of total triglyceride and of inorganic phosphorus. Supplemental Phe decreased the concentrations of hemoglobin and serum glucose. The regression slopes for Phe at 4 mg of OA per kg of diet were significant for uric acid, creatinine, total protein, albumin, and cholesterol suggesting that supplemental Phe improved the health status of the broilers fed diets containing OA with respect to these parameters.

Alkaline Phosphatase↗
PubMed1989

Aggressive management of severe closed head trauma: time for reappraisal.

The records of 187 patients (age 6 months to 82 years) who sustained severe closed head injuries and were admitted to a neurosurgical unit between 1983 and 1987 were retrospectively reviewed. The aim was to develop a scale for selecting patients whose death could be predicted with certainty at an early stage and who should therefore not receive prolonged intensive care. The scale was prospectively tested on 52 comparable patients admitted during 1988 and was found to be accurate with no falsely pessimistic predictions. The score is based mainly on clinical observations within 12 h of presentation.

Adolescent↗
PubMed1989

Acute spontaneous subdural haematoma of arterial origin.

Spontaneous arterial subdural haematoma is arguably a rare condition. We report on three patients who presented with progressive neurological deficit or coma and who had been initially diagnosed as strokes. Explanations for the development of this condition are reviewed and it is suggested that it is not as rare as previously thought.

Aged↗
PubMed1989

Ochratoxin A and dietary protein. 1. Effects on body weight, feed conversion, relative organ weight, and mortality in three-week-old broilers.

An experiment with a completely randomized 3 x 4 factorial design was used to study the effects of ochratoxin A (0, 2, and 4 mg/kg) and protein (14, 18, 22, and 26%) in three-wk-old broilers. The diets were based on ground yellow corn and dehulled soybean meal. Four hundred and eighty Hubbard x Hubbard broilers were randomly placed in battery brooders, with 10 birds per pen. Each treatment was replicated four times. Body weight increased with rising levels of protein, and decreased with rising levels of ochratoxin A (OA). The efficiency of feed utilization was improved in broilers fed 22 and 26% protein, compared with broilers fed 14 and 18% protein. The efficiency of feed utilization was lower for the birds fed 4 mg/kg of OA, compared with broilers fed 0 and 2 mg/kg of OA, respectively. Using OA increased the relative weight of the liver, kidney, spleen, pancreas, proventriculus, gizzard, and heart and also significantly decreased the relative weight of the bursa of fabricius. A significant interaction between OA and protein was seen in terms of the relative weight of the liver, pancreas, and gizzard, indicating that the rising protein levels spared the OA effect on those organs. Mortality was highest among the broilers fed 4 mg/kg of OA. Protein regression coefficients (beta's) were positive with respect to 21-day body weight and were negative for the feed:gain ratio and mortality, suggesting that protein provided beneficial effects.

Animal Feed↗
PubMed1989

Ochratoxin A and dietary protein. 2. Effects on hematology and various clinical chemistry measurements.

The health status of broilers fed diets with varying protein contents in the presence of ochratoxin A (OA) were evaluated using clinical-chemistry techniques for blood analysis. A completely randomized, 3 x 4 factorial design was utilized: 14, 18, 22, and 26% of dietary protein and 0, 2, and 4 mg/kg of OA. The broilers were raised to 3 wk of age, at which time blood was collected and various hematological parameters were evaluated. The serum was analyzed for various enzyme activities and for concentrations of metabolites and minerals using an automated, clinical-chemistry analyzer and an atomic-absorption spectrophotometer. Adding OA to the diets of broilers decreased the hemoglobin concentration, corpuscular volume, and the activity of serum alkaline and phosphatase but increased the activity of gamma-glutamyl transferase. Adding protein to the diet increased the activity of the serum aspartate aminotransferase, creatine kinase, and alkaline phosphatase. Adding OA to the diet of broilers decreased the concentrations of serum total protein, as well as the concentrations of albumen and cholesterol and increased the concentrations of serum creatinine and uric acid. The concentrations of serum total protein, albumin, urea nitrogen, and triglyceride were increased by adding protein to the diet. The concentrations of calcium, potassium, and inorganic phosphorus in the serum decreased when OA was added to the diet; but the concentrations of calcium and potassium content in the serum increased along with dietary protein. A regression analysis suggested that dietary protein was synergistic toward OA with regard to the blood levels of cholinesterase, lactate dehydrogenase, and glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1989

Smiling and facial exercise.

The exercise program presented uses exercises to quickly build up the patient's facial muscles and confidence. It is an active process, and the patient must be encouraged to do the exercise to get the full and satisfactory effect. The dental office staff should be encouraged to follow this program too. The results will be noticed, and they can support the patients in doing these exercises. Smiles do much to improve the environment we work and live in.

Exercise Therapy↗
PubMed1988

Paraplegia caused by spinal epidural abscess.

Two patients with spinal epidural abscess, but with different neurological outcomes, are presented. The pathogenesis, clinical features and current treatment are reviewed. The need for early diagnosis is once again stressed.

Abscess↗
PubMed1987

Crystallization of barley malt alpha-amylases and preliminary x-ray diffraction studies of the high pI isozyme, alpha-amylase 2.

alpha-Amylase isozymes 1 and 2 isolated from germinated barley seeds have been crystallized by the hanging- or sitting-drop vapor diffusion technique. Crystals of alpha-amylase 2 suitable for x-ray diffraction analysis were grown at pH 6.7 and 22 degrees C from a solution of 1 mM calcium chloride, 10 mM MES, and 16% saturated ammonium sulfate. The space group is trigonal P3121 (or P3221) with unit cell dimensions a = b = 135.20 A, c = 79.63 A, and probably two molecules per asymmetric unit.

Crystallization↗
PubMed1986

Effect of high-dose dexamethasone on outcome from severe head injury.

The conflicting evidence concerning the influence of high-dose steroids on intracranial pressure (ICP) and outcome following severe head injury has led to the institution of the prospective double-blind controlled trial reported here. Severely head-injured patients admitted to intensive care during a 3-year period were randomly allocated to a dexamethasone- or placebo-treated group. Adults in the steroid group received dexamethasone, 50 mg intravenously, as a bolus on admission to the neurosurgical unit, then 100 mg on Days 1, 2, and 3, 50 mg on Day 4, and 25 mg on Day 5 on continuous intravenous infusion. Children received proportionate intravenous dosages calculated on a weight basis. Severity of head injury was assessed from admission Glasgow Coma Scale (GCS) scores and the appearance of the admission computerized tomography scan. Intracranial pressure (ICP) was monitored in all patients from the surface subarachnoid space. Outcome at 6 months was assessed using the Glasgow Outcome Scale. Steroid and placebo groups were similar in terms of admission GCS score, intracranial pathology, incidence of associated injuries, and time interval from injury to admission to intensive care. The ICP generally increased during the first 48 hours of intensive therapy; there was no difference in this trend between the steroid and placebo groups. A poorer outcome was observed in patients with elevated ICP who received steroids. No increase in the incidence of pulmonary, gastrointestinal, or other extracranial complications was seen in the steroid group. The 6-month outcome did not differ between the steroid and placebo groups. No advantage of high-dose dexamethasone on ICP trends or clinical outcome in the treatment of severe head injury has emerged from this study.

Adolescent↗
PubMed1984

Assessment of Leeds device for monitoring intracranial pressure.

In Leeds a screw device is used to monitor surface subarachnoid pressure following severe head injury. The possibility that such measurements may under-read true intracranial pressure (ICP) has led to the development of an infusion test to confirm free communication with the surface subarachnoid space. The results of 69 infusion tests using 18 devices reveal that the device was reading accurately on 33 of 69 occasions. In 31 of the remaining 36, correction of the problem was possible. Particularly at ICP values exceeding 20 mm Hg the Leeds device may under-read, and possible causes for this are discussed. Reliable readings can usually be obtained using the infusion sequence described.

Brain Injuries↗
PubMed1983

Intensive management of severe head injuries. A scheme of intensive management of severe head injuries.

Seventy-six severely head-injured patients, 67% of whom had Glasgow Coma scores of five or less on admission, were managed according to an intensive treatment regime which included controlled hyperventilation (under full muscular paralysis), high-dose steroids, dehydrating agents, diuretics and hypnotics (Althesin and thiopentone). Intracranial pressure (ICP) was measured throughout the period of controlled ventilation. Treatment was directed to keeping the mean ICP below 25-30 mmHg and to the prevention of increases in ICP during chest physiotherapy and other noxious stimulation. Six months after injury 46% of patients had died and 4% were vegetative survivors, whilst 43% had made a good recovery or were only moderately disabled. Features associated with worse than average prognosis were: low coma score, pupillary abnormalities, respiratory dysrhythmia and ICP greater than 30 mmHg. Spontaneous hyperventilation was a relatively good initial feature. These results support the employment of intensive care in severely head-injured patients, particularly those with diffuse brain injury.

Adolescent↗