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Biomedical subjects

J H Robertson

Publications and source records attributed to J H Robertson.

At least 73 records · Page 4Linked to original sources
PubMed1980

Marrow hypoplasia with splenomegaly in adolescence.

Four adolescents presented with leucopenia, thrombocytopenia, and splenomegaly; three had associated congenital abnormalities and two had a cirrhosis. They provide further evidence of an association between hepatic disease and bone marrow dysfunction. It is considered that these patients suffer from a genetic or constitutional disorder which may result in a susceptibility of their bone marrow to hypoplasia following viral hepatitis or other infections.

Adolescent↗
PubMed1979

Pools and protein synthesis in mammalian cells.

From the kinetics of incorporation into protein shown by four amino acids and one amino acid analogue in suspension cultured HeLa S-3 cells, two distinctly different patterns were observed under the same experimental conditions. An initial slow exponential incorporation followed by linear kinetics was characteristic of the two non-essential amino acids, glycine and proline, whereas the two essential amino acids studied, phenylalanine and leucine, showed linear kinetics of incorporation with no detectable delay. The analogue amino acid, p-fluorophenylalanine also showed immediate linear kinetics of incorporation. There was a poor correlation between the rate of formation of acid-soluble pools and incorporation kinetics. However, the rate of formation of the freely diffusible pool of amino acids correlated more closely with incorporation kinetics. The lack of direct involvement of the acid-soluble pool in protein synthesis was also demonstrated by pre-loading of pools before treatment of cells with labelled amino acids. The results partially support the hypothesis that precursor amino acids for protein synthesis come from the external medium rather than the acid-soluble pool, but suggest that the amino acid which freely diffuses into the cell from the external medium could also be the source.

Amino Acids↗
PubMed1979

Malignant lymphoma with a high content of epithelioid histiocytes.

A series of 12 patients with a rare malignant lymphoma containing numerous epithelioid histiocytes (MLEH), originally believed to be an atypical variant of Hodgkin's disease, is described. Clinicopathological studies suggest MLEH is a distinct entity among the non-Hodgkin's lymphomas which is generally resistant to therapy and has an unfavourable prognosis. Differentiation of the disease from angioimmunoblastic lymphadenopathy and Hodgkin's disease is discussed. In the necropsy case MLEH had transformed into a malignant lymphoma of histiocytic type.

Aged↗
PubMed1979

Amino acid analogues: uptake, pool formation and incorporation of phenylalanine and two halogenated derivatives in cultured mammalian cells.

HeLa cells take up Phe and two of its ring halogenated derivatives (pFPhe and pClPhe) with rpaidity, concentrating them against the external medium both at 4 and 37 degrees C. The majority of amino acid (greater than 90%) is accumulated without energy expenditures at 4 degrees C, and can be quickly discharged by normal cell washing procedures in saline. At 37 degrees C the freely-diffusible (FDP) pool is accompanied by another which develops more slowly and cannot diffuse out freely during washings with saline but is extractable with trichloracetic acid (the slowly-diffusible pool, SDP, or more conventionally, the acid-soluble pool). Both of the analogues produced larger pools of the latter type than Phe itself from external concentrations ranging from 10(-5) to 10(-3) M. The incorporation of pFPhe into proteins over these same concentrations ranged from 30 to 90--95% of Phe incorporation, whereas pClPhe showed negligible incorporation. From these and similar analyses it can be concluded that amino acid pools form largely independently of protein synthesis, but bear a close relationship with the external amino acid concentration. The fraction of total uptake into cellular pools entering the SDP was relatively constant over a wide range of external concentrations. pFPhe incorporation into cellular proteins produced the same labelling distribution of Phe. It appears to ener all proteins, the vast majority of which have similar half-lives and turnover rates to Phe proteins. In competition, little or no interference was experienced between the analogue and Phe in uptake and pool formation until excessive amounts of one or the other were present (50--100x). By contrast, incorporation of pFPhe into protein was markedly reduced by the presence of Phe. However, the development of normal or large pools of pFPhe or Phe in cells prior to 3H-Phe incorporation did not affect the linear incorporation pattern of the radioisotope into protein. The relationship of pools to protein synthesis is discussed, and it is concluded that, although the SDP could contain potential precursor molecules for protein synthesis, it does not usually act as the direct supplier of amino acid for protein synthesis. Alternative explanations for precursor supply are discussed.

Biological Transport↗
PubMed1978

Dry-heat destruction of lipopolysaccharide: design and construction of dry-heat destruction apparatus.

A dry-heat oven with automatic, multiple-sample introduction and withdrawal has been constructed to achieve instantaneous heating and cooling of samples. The oven temperature fluctuation at set points of 170 to 250 degrees C was +/- 0.1 degrees C, with temperature variation between the replicate samples of +/- 0.2 degrees C. Correction required for a sample come-up time was minimal, i.e., less than 0.25 min of the dry-heat destruction time.

Hot Temperature↗
PubMed1978

The relationship between suture number and quality of anastomoses in microvascular procedures.

Microvascular end-to-side arterial anastomoses of vessels 1 to 2 mm in diameter were performed in 30 Sprague-Dawley rats. The animals studied differed in only one aspect, variance of suture number to complete the anastomosis. Angiographic and gross pathological evaluation of each animal demonstrated a direct correlation between quality of patency and number of sutures used to complete the anastomoses. A significant observation was made regarding unrecognized pathology in angiographically patent anastomosis.

Animals↗
PubMed1977

Embolism to the central nervous system from cardiac myxoma. Report of two cases.

Two cases of left atrial myxoma are reviewed, both presenting as embolic phenomena. Neither patient gave a history compatible with pre-existent cardiac dysfunction. Sudden collapse and subsequent right hemiplegia resulted in one patient when an embolus lodged in the left middle cerebral artery. The second patient presented with headache and transient visual obscuration in the left eye. She showed evidence of embolism to the central retinal artery, and particulate matter could be seen within the retinal arterioles. Attention is drown to the fact that echocardiography now constitutes a simple, noninvasive, and highly reliable method of making this diagnosis. The propensity for embolic tumor fragments to grow and invade cerebral arterial walls is discussed along with its possible neurosurgical significance.

Adolescent↗
PubMed1976

Analysis of tetracycline in pharmaceutical preparations by improved high-performance liquid chromatographic method.

The analysis of tetracycline in pharmaceutical preparations by an improved high-performance liquid chromatographic (HPLC) method is described. The improved method uses a 30-cm long stainless steel column packed with octadecylsilane bonded on 10-mum silica gel, with a linear gradient from 10 to 60% acetonitrile in pH 2.5, 0.02 M phosphate buffer in 11 min at a flow rate of 1.0 ml/min (68 atm). The resolution functions obtained between 4-epitetracycline and tetracycline and between 4-epianhydrotetracycline and anhydrotetracycline were improved 150 and 250%, respectively. The analysis of a tetracycline sample takes approximately 16 min; the original method required more tan 25 min. The relative standard deviation for the analysis of tetracycline powder was 0.66%, and the recovery of 4-epianhydrotetracycline added in tetracycline was linear over the 0.3-100% range. Recovery of tetracycline from products was better than 99.6% at label concentration. The drug content of products as calculated from the HPLC data agreed well with those of the microbiological assay methods.

Biological Assay↗
PubMed1975

Improved high-performance liquid chromatographic method for polypeptide antibiotics and its application to study the effects of treatments to reduce microbial levels in bacitracin powder.

Improvements were made in the high-performance liquid chromatographic (HPLC) method to obtain baseline separation of chromatographic peaks of structurally similar polypeptide components in bacitracin. The improved method uses a 30-cm-long stainless-stell column packed with muBondapak C18. The theoretical plates of the column are approximately 140,000 per meter for the bacitracin A peak. The resolution function between bacitracins B1 and B2 and that between bacitracins A and B2 have been improved 418 and 225%, respectively. The components of bacitracin, bacitracins A, B, C, D, E, F, and G, were fractionated by the countercurrent distribution technique. These components, together with Compound X, a compound separated on a carboxymethylcellulose column, and bacitracin F, obtained by degrading bacitracin A sample at neutral pH, were used to identify peaks in the HPLC chromatogram. Effects of processing methods used to reduce microbial contamination levels in bacitracin powders were evaluated. Heat treatment caused a significant loss of antimicrobial activity (35% reduction), bacitracins A, B1, and B2 were reduced by 37, 22, and 21%, respectively. A significant increase (2.8 times) of bacitracin F, an oxidative degradation compound, was show. Irradiation by 60Co at 1.8 Mrad caused no loss of potency nor change in any of the bacitracin components. Ethylene oxide treatment, on the other hand, caused considerable (46%) reduction of potency. Substantial reduction of areas under the peak of bacitracins A, B1, and B2 (50, 24 and 37%, respectively) were noted. The chromatograms showed numerous unresolved peaks around bacitracins A, B1 and B2,; however, no significant increase in the bacitracin F peak, nor appearance of non-UV absorbing peaks were observed. Peptide antibiotics of the polymyxin group, circulin, colistin, and polymyxin, were also analyzed using the muBondapak C18 column with a linear-gradient elution. A UV monitor was used for polymyxin. A moving-wire flame ionization detector was used to monitor circulin and colistin. A sample of polymyxin, circulin, and colistin may be analyzed in less than 20 min of chromatographic time.

Anti-Bacterial Agents↗
PubMed1975

High-performance liquid chromatographic analysis of ampicillin.

A high-pressure liquid chromatographic method for the analysis of ampicillin is described. The method uses a 1-m long stainless steel column packed with anionic exchange resin, with a mobile phase of 0.02 M NaNO3 in 0.01 M pH 9.15 borate buffer at a flow rate of 0.45 ml/min. The degradation products of ampicillin, penicillenic and penicilloic acids of ampicillin, can be separated and quantitated in less than 12 min of chromatographic time. The relative standard deviation for the analysis of ampicillin is less than 1%, and the method is sensitive to approximately 20 ng of ampicillin/sample injected. The method was applied to the analysis of various pharmaceutical preparations of ampicillin. It is also applicable, with a slight modification, for the analysis of penicillins G and V.

Ampicillin↗