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Biomedical subjects

J Heinonen

Publications and source records attributed to J Heinonen.

At least 91 records · Page 5Linked to original sources
PubMed1976

Thymectomy for myasthenia gravis.

Thymectomy was performed on 31 patients with myasthenia gravis. Four of them had thymoma, 17 hyperplasia and 9 had normal thymic histology on microscopy. Discontinuation of anticholinergic medication together with tracheostomy, artificial ventilation and intensive observation were essential in the postoperative management. All the patients survived operation and were discharged from hospital. Sixty-eight per cent of the patients were in remission or improved after an average follow-up of 2.5 years. If the patients with thymoma were excluded, 74% were improved and, if only the patients with thymic hyperplasia were included in the series, 89% were improved after thymectomy. The severity of disease and duration of symptoms pre-operatively seemed to be of minor importance for the results of operation, since good results were obtained also in patients with a long history and in clinical classes III and IV. Two patients developed tracheal stenosis as a complication of intubation with a tracheostomy tube. Tracheal resection was performed in one of them and endobronchial removal of granulation tissue producing the stenosis in the other. Both recovered uneventfully. One patient, who was asymptomatic and without medication for myasthenia, died suddenly of acute cerebral bleeding 3 years after thymectomy.

Adolescent↗
PubMed1975

The mechanism of aminoacylation of transfer ribonucleic acid. Reactivity of enzyme-bound isoleucyl adenylate.

Isoleucyl adenylate bound to isoleucine:tRNA ligase of Escherichia coli (EC 6.1.1.5; isoleucyl-tRNA synthetase) transfers the isoleucine moiety to tRNA-Ile-E. coli with a half-time of about 35 s at 0 degrees and pH 7.6 in the presence of spermine or Mg2+. If a limited amount of tRNA-Ile is supplied to a mixture of free enzyme and enzyme-bound [14c]isoleucyl adenylate in a medium containing spermine, ATP, and [3H]isoleucine, almost none of the resultant isoleucyl tRNA is derived from preformed enzyme-bound [14C]isoleucyl adenylate. Almost all of the isoleucyl tRNA formed results directly from reaction of free enzyme, ATP, and isoleucine with tRNA. Similar but less clearcut results are obtained when Mg2+ is substituted for spermine. We conclude that isoleucyl adenylate bound to isoleucine:tRNA ligase is not a significant intermediate in the synthesis of isoleucyl tRNA under these conditions.

Adenosine Monophosphate↗
PubMed1975

Cardiorespiratory function during thoracic anaesthesia: a comparison of two-lung ventilation and one-lung ventilation with and without PEEP5.

Previous studies have shown that, in patients undergoing thoracic surgery, a relatively high positive end-expiratory pressure (PEEP of 10 cmH2O = PEEP10) has no beneficial effect on oxygenation during one-lung ventilation (OLV). In the present investigation, cardiorespiratory function was examined in 11 patients intubated endobronchially and undergoing thoracotomy. Comparison was made between two-lung ventilation (TLV) and OLV and between zero end-expiratory pressure and PEEP5 during OLV. Cardiac output was determined to obtain information of the total oxygen delivery (cardiac output times arterial O2 content. The change from TLV to OLV was accompanied by a marked fall in PaO2 and a marked rise in shunt, whereas no significant change was observed in mean cardiac output. Oxygen delivery also remained unchanged due to relatively small decrease in SaO2 (arterial oxygen saturation) and maintenance of cardiac output. The application of PEEP5 during OLV produced no significant changes in these parameters. The findings in individual patients demonstrated the relative importance of cardiac output in determining oxygen delivery during OLV. A significant negative correlation was found between inspiratory airway pressure and cardiac index during OLV.

Adult↗
PubMed1972

Regulation of the tyrosine biosynthetic enzymes in Salmonella typhimurium: analysis of the involvement of tyrosyl-transfer ribonucleic acid and tyrosyl-transfer ribonucleic acid synthetase.

Mutants of Salmonella typhimurium were isolated that require tyrosine for growth because of an altered tyrosyl-transfer ribonucleic acid (tRNA) synthetase. Extracts of one strain (JK10) contain a labile enzyme with decreased ability to transfer tyrosine to tRNA(Tyr) and a higher K(m) for tyrosine than the wild-type enzyme. Strain JK10 maintains repressed levels of the tyrosine biosynthetic enzymes when the growth rate is restricted due to limitation of charged tRNA(Tyr). Several second-site revertants of strain JK10 exhibit temperature-sensitive growth due to partially repaired, heat-labile tyrosyl-tRNA synthetase. The tyrosine biosynthetic enzymes are not derepressed in thermosensitive strains grown at the restrictive temperature. A class of tyrosine regulatory mutants, designated tyrR, contains normal levels of tyrosyl-tRNA synthetase and tRNA(Tyr). These results suggest that charging of tRNA(Tyr) is not necessary for repression. This conclusion is substantiated by the finding that 4-aminophenylalanine, a tyrosine analogue which causes repression of the tyrosine biosynthetic enzymes, is not attached to tRNA(Tyr) in vivo, nor does it inhibit the attachment reaction in vitro. A combined regulatory effect due to the simultaneous presence of tyrS and tyrR mutations in the same strain was detected. The possibility of direct participation of tyrosyl-tRNA synthetase in tyrosine regulation is discussed.

Aldehyde-Lyases↗