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Biomedical subjects

S T Lim

Publications and source records attributed to S T Lim.

At least 91 records · Page 5Linked to original sources
PubMed1979

The biosynthesis of nitrogenase MoFe protein polypeptides in free-living cultures of Rhizobium japonicum.

The biosynthesis of the constituent polypeptides of nitrogenase component I (Rj 1) in free-living cultures of Rhizobium japonicum (strain 110) was investigated under different growth conditions. Cells were pulse-labelled and the proteins analysed by one and two-dimensional gel electrophoresis. The positions of the constituent Rj 1 polypeptides were identified by co-electrophoresis with purified Rj 1 isolated from bacteroids of soybean nodules, and by comparison with an immunoprecipitate from a culture induced for nitrogenase. The synthesis of the proteins preceded any detectable enzyme activity and increased with time, reaching a maximum after 3 days. At this time, between 6 and 8% of the total sodium dodecyl sulfate-soluble protein synthesized was Rj 1. Exposure to air led to a dramatic decrease in the rate of Rj 1 synthesis, with almost complete regression after 20 min. In the presence of KNO3, there was no nitrogenase activity, but the proteins were present in similar amounts (7%) as the control culture. When mannitol and glycerol were used as the sole carbon sources, the amount of Rj 1 synthesized was extremely low.

Gluconates↗
PubMed1979

Regulation of hydrogen utilisation in Rhizobium japonicum by cyclic AMP.

Utilisation (uptake) of hydrogen gas by whole cells of Rhizobium japonicum was found to be influenced by the carbon source(s) present in the growth medium, with activity being highest in a medium containing sugars. Tricarboxylic acid cycle intermediates, such as malate, significantly reduced H2 utilisation. No reduction in the hydrogenase activity is observed when the enzyme is assayed directly by the tritium exchange method, indicating that the decrease in hydrogen uptake activity is not due to repression of hydrogenase biosynthesis. Cyclic AMP was found to alleviate the inhibition of H2 uptake by malate, and this requires new protein synthesis. Addition of chloramphenicol or rifampicin simultaneously with cyclic AMP eliminated the stimulation of H2 uptake in the malate medium. These results show that in R. japonicum cyclic AMP plays a major role in the regulation of H2 metabolism.

Carbohydrate Metabolism↗
PubMed1979

Chylothorax following resection of the oesophagus.

Chylothorax complicating operations on the oesophagus has been reported infrequently; it carries a mortality rate of about 50 per cent. A search of the literature has yielded only 10 cases. This paper reports 4 further cases which occurred among 685 resections of the oesophagus, giving an incidence of 0.6 per cent. The diagnosis should be confirmed with lymphangiography. Treatment should be early exploration and ligation in patients in whom the thoracic duct has been divided at operation. If the duct has been injured during blind dissection a period of conservative treatment is advisable. Parenteral nutrition is a useful adjunctive treatment.

Chylothorax↗
PubMed1979

Salvage operations for malignant obstruction of the oesophagus.

Two patients with locally advanced carcinoma of the oesophagus, who did not obtain palliation with radiotherapy, underwent salvage operations to restore their ability to swallow. One patient was subjected to pharyngolaryngo-oesophagectomy together with excision of the involved posterior tracheal wall. Reconstruction was by pharyngoglossogastrostomy, with a deltopectoral flap used to replace the tracheal defect. The second patient, who had cervical metastases and severe pulmonary complications, underwent a jejunal loop bypass operation. Both patients were able to eat normally before dying many months later from metastatic disease. Salvage operation should be considered for patients with primary tumours which appear to be slow-growing, even though locally advanced and free of widespread disease. Worthwhile palliation is obtained when the operation, either resection or bypass, has been successful.

Deglutition Disorders↗
PubMed1979

Acute suppurative cholecystitis: a retrospective study of 173 cases.

Over a 14-year period we treated 2,290 cases of non-malignant biliary tract conditions, and among them were 173 cases of acute suppurative cholecystitis, an incidence of 7.6%. A correct preoperative diagnosis of acute suppurative cholecystitis was made in only about half the cases because features of recurrent pyogenic cholangitis dominated the clinical picture on many occasions. The diagnosis was confirmed in all cases at operation. Cholecystectomy (88%) was performed whenever this was found to be safe, and cholecystostomy (12%) was carried out only in poor-risk patients or when operative difficulties were encountered. The overall mortality of operation was 5.8%. Old age, preoperative shock, delay of operation and the presence of free perforation affected the prognosis adversely.

Acute Disease↗
PubMed1979

The effects of experimental division of the vascular pedicle of a transposed subcutaneous ileal loop.

The effects of immediate division of the neurovascular pedicles of ileal loops implanted in the subcutaneous tissues for four weeks were studied in eight mongrel dogs. The structural and functional changes were studied by examining sections under light and electron microscopy and by comparing D-xylose absorption and motility patterns. Arteriograms were done to show the new subcutaneous collaterals supplying the loops. Of the eight dogs, four had loops showing normal histological appearances and D-xylose absorptive functions after division of the pedicles. In the remaining four dogs, the loops showed evidence of pseudomembranous changes in some areas, resulting in patching necrosis possibly due to inadequate collaterals. The absorption of D-xylose was impaired in these dogs. Perhaps a longer period of transposition and a gradual division of the vascular pedicle would improve the results. The motility pattern did not change after division of the pedicle, though the response to intravenous carbachol was significantly delayed.

Animals↗
PubMed1979

Primary sarcomas of the jaw.

Nine cases of primary sarcoma of the jaw seen over a period of 14 years are presented. They consisted of four osteosarcomas, three fibrosarcomas, one myxosarcoma and one Ewing's sarcoma. The treatment of choice for osteosarcomas of the mandible is hemimandibulectomy with disarticulation at the temporomandibular joint. Bone graft reconstruction from the iliac crest should be done at a second stage. Palliative maxillectomy for extensive fibrosarcoma of the maxilla served to relieve one patient of local symptoms for more than a year. Myxosarcoma, a variant of fibrosarcoma, and Ewing's sarcoma of the jaw, are very rare conditions, and since these lesions are usually very extensive radiotherapy is the treatment of choice.

Adolescent↗
PubMed1979

Effect of cyclic guanosine 3',5'-monophosphate on nitrogen fixation in Rhizobium japonicum.

The addition of exogenous cyclic guanosine 3',5'-monophosphate (cGMP) at a concentration of 0.1 mM to a free-living culture of Rhizobium japonicum 3I1b110 was found to completely inhibit the expression of nitrogenase activity and markedly inhibit the expression of hydrogenase and nitrate reductase activities. The effect was specific for cGMP. Experiments on the in vivo incorporation of radioactive methionine and subsequent analysis of the labeled proteins on polyacrylamide gels showed that the biosynthesis of nitrogenase polypeptides was inhibited. It appears that the time of addition of cGMP is important since the effect was only seen during the early stages of nif gene expression. The intracellular level of cGMP was found to respond to physiological changes in the cell, and there was a fall in cGMP concentrations when nitrogenase was induced. Microaerophilic-aerobic shift experiments showed that intracellular levels increased from 0.25 pmol/mg of cell protein under microaerophilic conditions to 2.6 pmol/mg of cell protein under aerobic conditions, suggesting that the cellular pool size of cGMP may be under redox control.

Cyclic GMP↗
PubMed1979

Gastric histology and function in patients with intrathoracic stomach replacement after esophagectomy.

The histological changes and gastric function alterations in 19 patients who had intrathoracic stomach replacement following esophagectomy were studied. Atrophic gastritis was noted in 13 of the 19 patients. The mechanical response of the stomach to distention by food was largely retained. The basal and maximal acid output was reduced markedly, and the serum gastrin was elevated. An association between the degree of gastritis, the percentage of gastric motility at rest, and acid secretion is demonstrated. These changes are consistent with patients with duodenal ulcer following vagotomy and dyloroplasty. Postprandial elevation in serum gastrin was noted in patients with or without vagotomy. The lack of significant difference in integrated gastrin response suggests that the vagus may not be important in the control of postprandial gastrin release.

Adult↗
PubMed1978

Determination of Hydrogenase in Free-living Cultures of Rhizobium japonicum and Energy Efficiency of Soybean Nodules.

A sensitive tritium exchange assay was applied to the Rhizobium system for measuring the expression of uptake hydrogenase in free-living cultures of Rhizobium japonicum. Hydrogenase was detected about 45 hours after inoculation of cultures maintained under microaerophilic conditions (about 0.1% O(2)). The tritium exchange assay was used to screen a variety of different strains of R. japonicum (including major production strains) with the findings that about 30% of the strains expressed hydrogenase activity with identical results being observed using an alternative assay based on uptake of H(2). The relative efficiency of intact soybean nodules inoculated with 10 different rhizobial strains gave results identical to those obtained using free-living cultures. The tritium exchange assay provides an easy, quick, and accurate assessment of H(2) uptake efficiency of intact nodules.

Journal Article↗
PubMed1978

Unresectable malignant obstruction of the bile ducts.

Over a 13-year period we encountered 135 patients with malignant obstruction of the bile ducts, and in 81 of these patients only palliative surgery was possible. The type of operation was largely determined by the site and nature of the obstruction and the condition of the patient. The operative mortality of palliative operation was 37%. Relief of jaundice or pruritus was obtained in 68%, and this figure included a number of patients who died in the first 30 days. The majority of survivors lived for between three and four months after operation, although occasional patients have lived for more than one year.

Adenocarcinoma↗
PubMed1977

Gene duplication in salmonid fishes: evidence for duplicated but catalytically equivalent A4 lactate dehydrogenases.

Skeletal muscle tissues from many species of salmonid fish are known to exhibit a set of three of five isozymes for A4-type lactate dehydrogenase (L-lactate: NAD oxidoreductase, E.C. 1.1.1.27), but the genetic basis for this isozyme system has not previously been assessed. This isozyme system was purified to homogeneity from salmon (Oncorhynchus tshawytscha) and shown to be composed of two polypeptides. Aalpha and Abeta, in binomial tetrameric combinations. Amino acid analysis revealed that Aalpha and Abeta are closely related but genetically distinct proteins, and thus are coded for the recently duplicated structural loci. Catalytic studies on the purified intact salmon isozyme system and on the isozymically pure Aalpha4 and Abeta4 homotetramers from brown trout (Salmo trutta) revealed no significant differences in catalytic properties among these enzymes, suggesting equivalent catalytic function of Aalpha and Abeta. These results, in combination with studies on polypeptide and isozyme ratios, suggest that one of the duplicated loci in salmon may be drifting toward a nonfunctional state by accumulation of mutations in regulatory DNA rather than in the structural gene itself.

Amino Acid Sequence↗
PubMed1977

Detection of subarachnoid blood clot and other thin, flat structures by computed tomography.

Eight cases of subarachnoid hemorrhages are reported to illustrate the ability of CT to demonstrate thin, flat collections of subarachnoid blood clots and the importance of CT in localization of the bleeding site, especially in cases of multiple aneurysms. The major factors in the detection of these lesions are discussed on the basis of partial volume phenomenon.

Adolescent↗