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Biomedical subjects

H K Robinson

Publications and source records attributed to H K Robinson.

14 recordsLinked to original sources
PubMed2006

Blunt cervical spine trauma as a cause of spinal cord injury and delayed cortical blindness.

STUDY DESIGN: Case report. OBJECTIVE: To present and discuss the case of a patient who sustained a significant flexion compression injury of the cervical spine with resulting tetraplegia and development of cortical blindness. SETTING: National Spinal Injuries Unit and Institute of Neurological Sciences, Southern General Hospital, Glasgow, Scotland, UK. METHODS: Clinical and radiological follow-up of the patient. RESULTS: Cortical blindness resulted from vertebral artery dissection associated with blunt cervical spine trauma. The patient is registered blind and is ventilator dependent. CONCLUSION: The potential complications of blunt vertebral artery injury remain poorly recognised. Screening is routinely not performed. Advances in noninvasive radiological techniques may result in recognition of asymptomatic disease and the potential for therapeutic intervention.

Adult↗
PubMed1990

The metabolism of the carcinogen dibenz[a,j]acridine in isolated rat hepatocytes and in vivo in rats.

1. 3H-Dibenz[a,j]acridine (DBAJAC) metabolism occurred readily in vitro in incubations with hepatocytes from phenobarbital-pretreated, 3-methylcholanthrene-pretreated and untreated rats, with the formation of water-soluble conjugates and unconjugated metabolites. 2. For incubations of 3H-DBAJAC with hepatocytes the major organic solvent-soluble metabolites found with and without beta-glucuronidase/arylsulphatase hydrolysis were the phenols, 3-hydroxy-DBAJAC, and 4-hydroxy-DBAJAC, and the proposed proximate carcinogen, trans-3,4-dihydroxy-3,4-dihydro-DBAJAC. The latter comprised 34-66% of the total organic solvent-soluble metabolites. 3. In contrast to results previously reported for rat hepatic microsomes, the K-region 5,6-oxide, and its dihydrodiol were minor metabolites detected after hepatocyte incubations. 4. Faecal excretion accounted for the bulk of radioactivity after i.p. doses of 3H-DBAJAC (0.5 mg/kg), and i.v. doses (0.5 mg/kg) were rapidly excreted into the 6 h bile. The organic solvent-soluble fraction obtained after enzymic hydrolysis of bile (approximately 25% of excreted radioactivity) was subjected to h.p.l.c. It contained polar secondary oxidation products and virtually no 3,4-dihydrodiol. 5. Experiments conducted with greater hepatocyte densities (10(7) cells/ml) and longer incubation times showed increased extents of metabolism, DNA and protein binding of radioactivity which paralleled the extent of metabolism. Very considerable metabolism of the 3,4-dihydrodiol occurred by the end of the incubation period.

Acridines↗
PubMed1985

Metabolism of the carcinogen 7-methylbenz[c]-acridine in the rat.

The biliary excretion of radioactivity by adult Wistar rats given i.v. 7-methyl-[7-14C]benz[c]acridine(14C-7-MBAC) and [methyl-3H]-7-methylbenz[c]acridine (3H-7-MBAC) (2 mg/kg) was 61% and 48%, respectively, in males in six hours. Females excreted 33% of a 2 mg/kg dose of 3H-7-MBAC in the same time-period. For male rats, the urinary and faecal excretions were about 10% and 61% of the dose of 14C-7-MBAC, respectively, in seven days. No enterohepatic circulation could be demonstrated in control male rats. The biliary excretion of radioactivity by phenobarbital- and 3-methylcholanthrene-induced male rats given 14C-7-MBAC was similar to or greater than that of control male rats. The organo-soluble biliary metabolites after beta-glucuronidase/arylsulphatase hydrolysis were separated by h.p.l.c., and quantitative metabolite distributions were obtained for induced and control rats by comparison with metabolite standards. The mutagenicity of bile from carcinogen-dosed control rats was greater than that of equivalent bile from carcinogen-dosed 3-methylcholanthrene-pretreated animals.

Acridines↗
PubMed1974

A new systematic strategy for the isolation of proteins, illustrated by the purification of a mammalian exo-beta-N-acetyl-D-glucosaminidase.

The ;B' form of the exo-beta-N-acetyl-d-glucosaminidase from pig epididymis was purified by a new systematic strategy to yield a preparation with a specific activity at least equal to that obtainable by an existing empirically derived procedure. The new strategy is essentially a sequence of three carefully chosen steps consisting of an initial fractionation of the constituent proteins according to molecular size, followed by an ion-exchange step designed to select out proteins with closely similar electric-charge properties to those of the protein of interest, and a final high-resolution step dependent on the isoelectric points of the residual proteins. Gel isoelectric focusing itself, or as an element in the technique described by Leaback & Robinson (1974) for the separate display of the molecular size and electric-charge characteristics of proteins, played an important part in the choice of the experimental conditions used in the new strategy, and also in monitoring the progress of the purification.

Animals↗
PubMed1968

The preparation of ribosomal ribonucleic acid from whole bacteria.

1. A simple method for the preparation of ribonuclease-free ribosomal RNA is described in which ribonuclease-deficient bacteria are treated with acetone and the RNA is extracted with phenol and purified by precipitating it with potassium acetate. The treatment with acetone appears to render the cell wall permeable to RNA but not to DNA during the extraction with phenol. The method thus avoids the need to disrupt the bacteria and greatly simplifies the subsequent purification. 2. The method has been used successfully with ribonuclease-deficient strains of Escherichia coli, Pseudomonas fluorescens and Staphylococcus epidermidis. The recovered purified RNA accounts for about 70% of the total ribosomal RNA and shows the normal sedimentation pattern of the 16s and 23s components in the analytical centrifuge.

Acetates↗
PubMed1966

Magnesium ion-independent ribonucleic acid depolymerases in bacteria.

The distribution of ribonucleases among bacteria has been determined from the examination of a wide variety of species. Bacteria that had been growing rapidly on a solid medium were harvested, treated with acetone and incubated in the presence of EDTA between pH4 and pH9. The ribonuclease activity was determined from the rate at which acid-soluble nucleotides were released. Out of nearly 200 strains examined, about 30 did not contain a detectable ribonuclease. The pH optima of ribonucleases in the remainder were sufficiently distinctive to suggest a use in taxonomy. Escherichia coli B was examined in more detail to determine the factors responsible for variations in the ribonuclease content of this bacterium. Growth rate had little influence on ribonuclease content when a complex medium containing no readily assimilable carbohydrate was used; the addition of glucose resulted in a marked increase in ribonuclease and a dependence of enzyme content on growth rate. An increase in the concentration of sodium chloride in the medium decreased the ribonuclease content of bacteria growing on it.

Arthrobacter↗
PubMed1965

The distribution of ribosomal ribonucleic acids among subcellular fractions from bacteria and the adverse effect of the membrane fraction on the stability of ribosomes.

1. The distributions of nucleic acids and protein among fractions obtained by differential centrifugation from species of Pseudomonas, Aerobacter, Escherichia, Proteus and Bacillus have been studied. 2. The DNA in a cell wall-membrane fraction obtained by low-speed centrifugation from the Gram-negative species could be removed by homogenizing and subsequent washing. About 7-14% of the total RNA remained firmly attached and resembled ribosomal RNA in base composition. A similar fraction from the Gram-positive B. subtilis contained about one-half of the total bacterial DNA and only 60% of this could be removed by homogenizing and subsequent washing. 3. A deposit obtained by high-speed centrifugation could be separated into a heavy ribosome layer and a light turbid layer. In E. coli B the latter contained about equal concentrations of RNA and DNA and accounted for about one-half of the total bacterial NADP-activated 6-phosphogluconate dehydrogenase. 4. The washed cell wall-membrane fraction from most species accelerated the degradation of ribosomes. In Pr. vulgaris the activity of this fraction was exceptionally high and resulted in the progressive degradation of ribosomes during their isolation from this species. 5. A possible connexion between ribosome degradation and the synthesis of flagella is discussed in the light of these results.

Bacillus subtilis↗
PubMed1965

The inhibition of ribosomal ribonuclease by bacterial ribosomes.

1. A comparison has been made between the ribonuclease activities of untreated ribosomes from Escherichia coli B and Pseudomonas fluorescens and the activities of ribosomes on to which ribosomal ribonuclease from E. coli B has been adsorbed. 2. The normal ribosomes from both species were stable in 5-10mm-Mg(2+) (I0.16) at pH6. The RNA in ribosomes from Ps. fluorescens was attacked by the adsorbed ribonuclease under these conditions, whereas the ribosomes from E. coli B were able to adsorb and inhibit this enzyme. 3. Inhibition was also observed with ribosomes from Aerobacter aerogenes, Proteus vulgaris and two other strains of E. coli. It was not observed in ribosomes from three species of Pseudomonas. 4. The inhibition depended on the integrity of the ribosomes and was not observed under conditions of low Mg(2+) concentration that cause irreversible degradation into more slowly sedimenting particles.

Enterobacter↗