PubMed Health⌕ Search

Biomedical subjects

M Lim

Publications and source records attributed to M Lim.

At least 91 records · Page 5Linked to original sources
PubMed1992

High frequency jet ventilation: use of the Bain system for entrainment.

The use of a Bain system to convey anaesthetic gases for entrainment during high frequency jet ventilation (HFJV) was evaluated by examining the effect of varying the fresh gas flow (Vf) on the end-tidal carbon dioxide (PECO2) in 46 ASA physical status I and II patients undergoing extracorporeal shock-wave lithotripsy (ESWL). Anaesthesia was induced with methohexitone (1-2 mg.kg-1), fentanyl (1-1.5 micrograms.kg-1) and vecuronium (0.1 mg.kg-1). After endotracheal intubation with a Mallinckrodt Hi-Lo Jet cuffed endotracheal tube, the patient was immersed in a water bath and HFJV at 150 breaths per minute was instituted with an Acutronic AMS 1000 jet ventilator attached to the side channel of the Hi-Lo tube. A Bain system was attached to the proximal end of the endotracheal tube to provide gases for entrainment. Anaesthesia was maintained with an intravenous infusion of methohexitone (5 mg.kg-1.h-1) and 50% nitrous oxide in oxygen for both the jetted and entrained gases. PECO2 was determined at 5-min intervals by a single-breath technique using a calibrated Engstrom Eliza capnograph. Thirty patients were randomly allocated to receive Vf's of 50 (Group 1), 75 (Group 2) and 100 (Group 3) ml.kg-1.min-1, respectively. A further eight patients (Group 4) received a Vf of 100 ml.kg-1.min-1 for 15 min, 75 ml.kg-1.min-1 for the next 15 min and 50 ml.kg-1.min-1 thereafter. In a further group of eight patients (Group 5), Vf was initially 25 ml.kg-1.min-1 for 10 min and was then switched off for the remainder of the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Postspinal headache. A comparison of the 24G Sprotte syringe and a 29G Quincke needle].

PATIENTS AND METHODS: A randomised study was performed to compare the frequency of postdural puncture headache in 56 patients who underwent spinal anaesthesia for extra-corporeal shockwave lithotripsy using either a Sprotte 24 G (n = 28) or Vygon 29 G or Quincke type needle (n = 28). Frequency of headache was recorded in a similar group of 28 patients who received general anaesthesia. RESULTS: Dural puncture was easier with the Sprotte 24 G cannula than with the less stable Quincke needle, as documented by a significantly shortened time for insertion of the cannula (4.6 +/- 2.6 vs 8.6 +/- 6.3 min, P less than 0.005). The total frequency of post-operative headache was 57% in the Vygon 29 G group and 25% in the Sprotte 24 G group; 21% of patients in the general anaesthesia group complained of headache. Frequency of postdural puncture headache, classified as being posture-related, was 25% in the 29 G Vygon group, compared with 11% in the 24 G Sprotte group (P = 0.148). When only moderate and severe postdural puncture headache was considered, there was a significant difference (25% vs. 4%; P = 0.026) in favour of the Sprotte cannula. DISCUSSION AND CONCLUSIONS: Thus, the 24 G Sprotte needle was at least as effective as the 29 G Vygon needle, and there is a suggestion that the former is more effective in minimising the incidence of moderate or severe postdural puncture headache.

Adolescent↗
PubMed1992

A review of patients with a 'normal' coronary angiogram over a 3-year period.

Over a period of 36 months, we detected 54 patients with normal coronary arteries or non-critical coronary artery stenosis within our study series of coronary angiography. We studied these patients to determine their clinical, electrocardiographic, stress testing and angiocardiographic characteristics. We detected among them a preponderance of female sex and a higher incidence of ethnic Indians. The majority of the patients studied had one or more coronary risk factors. 52% had a normal resting ECG. In those with a positive stress test and reports available for review, there is a near equal distribution of horizontal and J-type ST depression. Those patients with a positive treadmill tend to have a higher left ventricular end diastolic pressure (LVEDP) at cardiac catheterization. We also noted in this group of patients a higher proportion with a small distal left anterior descending artery. These patients also tend to have higher LVEDP even in the presence of normal left ventriculogram. Our current series suggests the possibility of raised left ventricular end-diastolic pressure and the presence of a "small distal left anterior descending artery" syndrome in association with patients with a 'false positive' treadmill test.

Adult↗
PubMed1991

Chemical synthesis of 10 kDa chaperonin. Biological activity suggests chaperonins do not require other molecular chaperones.

Molecular chaperones are required for the correct folding and assembly of certain other polypeptides. It is not known whether molecular chaperones themselves require other chaperones to become functional. A 97-amino acid chaperone, the chaperonin 10 protein was chemically synthesised so that during synthesis and purification there was no contact of the chaperone with any other protein. The purified, synthetic chaperonin 10 protein formed oligomeric structures spontaneously and was biologically active as a chaperonin. This is the first description of a chemically synthesised chaperonin, and suggests that no other chaperones are required for correct folding, polymerisation and biological activity of this chaperone.

Bacterial Proteins↗
PubMed1990

Atropine-induced heart rate changes: a comparison between midazolam-fentanyl-propofol-N2O and midazolam-fentanyl-thiopentone-enflurane-N2O anaesthesia.

Atropine-induced heart rate (HR) changes were studied in 19 patients (ASA physical status I) during anaesthesia-maintained predominantly with propofol-N2O or thiopentone-enflurane-N2O. Ten patients (Group A) received midazolam (0.07 mg.kg-1), fentanyl (1 microgram.kg-1), propofol (2 mg.kg-1) and succinylcholine (1 mg.kg-1). Following tracheal intubation, anaesthesia was maintained with propofol (6 mg.kg-1.hr-1), N2O (67 per cent) and O2 (33 per cent). In nine patients (Group B) thiopentone (4 mg.kg-1) was substituted for propofol and anaesthesia maintained with N2O (67 per cent) O2 (33 per cent), and enflurane (0.5 per cent inspired concentration). The study was non-randomised because Group B patients were only included if HR before administration of atropine less than 90 beats.min-1. IPPV was performed in all patients using a Manley ventilator (minute vol. 85 ml.kg-1; tidal vol. 7 ml.kg-1). Ten minutes after tracheal intubation, incremental doses of atropine (equivalent cumulative doses: 1.8, 3.6, 7.2, 14.4, 28.8 micrograms.kg-1) were administered at two-minute intervals and HR responses calculated during the last 45 sec of each intervening period. No differences were observed between the groups following 1.8 and 3.6 micrograms.kg-1 atropine, but propofol-N2O anaesthesia was associated with reduced responses (P less than 0.01) following 7.2, 14.4 and 28.8 micrograms.kg-1 atropine. These results suggest that there is a predominance of parasympathetic influences during propofol-N2O anaesthesia compared with thiopentone-enflurane-N2O anaesthesia.

Adult↗
PubMed1990

HPV DNA typing of adult-onset respiratory papillomatosis.

Respiratory papillomatosis is a recalcitrant, human papillomavirus-induced disorder of the upper airways. Using in situ hybridization and biotinylated deoxyribonucleic acid (DNA) probes, the type of human papillomavirus (HPV) in nine adults was determined both at presentation and during subsequent recurrences. Fifty-three biopsies obtained from seven men and two women over a 10-year period were examined for HPV 6, 11, 16 and 18. All patients had either type 6 or 11. One dual infection was found. Despite intensive therapy with lasers with or without alpha interferon, no elimination or change in viral type occurred. Despite identical histologies, the amount of HPV DNA present in a given patient's papillomata varied markedly. The results suggest that adult-onset respiratory papillomatosis is due to HPV 6 and/or HPV 11, and that its recurrent nature, despite therapy, is due to persistence of a viral reservoir.

Adult↗
PubMed1990

Ascorbic acid potentiates the inhibitory effect of dopamine on prolactin release: a putative supplementary agent for PIF.

Dopamine has a catechol group which can be easily oxidized by mild oxidizing agents. Ascorbic acid has been routinely added to a dopamine solution in order to protect it from oxidation. We have examined the effect of ascorbic acid on dopaminergic inhibition of prolactin release. Male rat pituitary cells were dispersed using trypsin and cultured for 5-7 days before experiments. Ascorbic acid did not stimulate nor inhibit prolactin release in both static monolayer culture and dynamic perifusion systems, but potentiated by approximately 100 times the inhibitory effect of dopamine on prolactin release. In order to differentiate chemical protection from potentiation, we tested the potentiation effect of isoascorbic acid which is an epimer of biologically active L-ascorbic acid but is biologically less active. Our results indicated that isoascorbic acid caused less potentiation of the dopaminergic effect on prolactin release than did ascorbic acid. In a perifusion system, a high concentration of dopamine (100 nmol/l) was unable to inhibit prolactin release for a 1 h experimental period, but a low concentration of dopamine (10 nmol/l) plus ascorbic acid (10 mumol/l) inhibited prolactin release for the entire 1 h perifusion period. There is a strong possibility that ascorbic acid may be a physiological supplementary agent for the prolactin-release inhibiting factor (PIF) since the blood concentration of ascorbic acid is rather high (23-85 mumol/l).

Animals↗
PubMed1989

Multiple T and B cell epitopes in the S1 subunit ("A"-monomer) of the pertussis toxin molecule.

The immunogenicity and reactogenicity of Bordetella pertussis vaccine are mediated in part by the S1 subunit of pertussis toxin (PT). To identify the immune epitopes in the S1 subunit of PT, synthetic peptides were prepared and tested for their capacity to induce antibodies in mice with different MHC genotypes. In BALB/c mice, peptides corresponding to sequences 1-17, 70-82 and 189-199 generate T cell proliferative responses, induce the production of antibodies capable of neutralization of the toxin in the Chinese hamster ovary-cell assay, and protect mice from a shock-like syndrome caused by alternate injections of BSA and PT. Protection and neutralization correlated with the ability of these peptides to elicit high anti-PT titers. Different B cell epitopes were detected in other inbred mouse strains. The antibody reactivity against synthetic peptides from two infants vaccinated with pertussis vaccine was tested. These infants had antibodies reactive to a variety of epitopes in the S1 subunit, including peptides 1-17, 70-82, 99-112, 135-145, and 189-199. Thus, it appears that there are multiple T and B cell epitopes in the S1 subunit of PT.

Algorithms↗
PubMed1989

Prevention of postdural puncture headache after spinal anaesthesia for extracorporeal shockwave lithotripsy. An assessment of prophylactic epidural blood patching.

The prevention of postdural puncture headache after spinal anaesthesia for extracorporeal shockwave lithotripsy was investigated by a controlled clinical trial which compared epidural injection of 10 ml of autologous blood with 10 ml of normal saline immediately after intrathecal injection of local anaesthetic. The incidence of postdural puncture headache was 8.3% in the group that received blood compared with 45% in the group that received saline, a significant reduction (p less than 0.01). The incidences of backache and lower limb paraesthesiae were similar in both groups. No serious complications were reported.

Adult↗
PubMed1989

Effect of vecuronium on atropine-induced changes in heart rate.

The effect of vecuronium on the heart rate response to atropine has been studied by comparing dose-response relationships in two groups of patients who underwent extracorporeal shock wave lithotripsy. One group received vecuronium (0.1 mg/kg) and the other acted as control. Incremental doses of atropine (1.8, 1.8, 3.6, 7.2 and 14.4 micrograms/kg) were administered and changes in heart rate recorded. No significant differences were observed between the two groups following each incremental dose of atropine.

Adult↗
PubMed1988

MHC-restricted recognition of immunogenic T cell epitopes of pertussis toxin reveals determinants in man distinct from the ADP-ribosylase active site.

The S1 subunit of Pertussis toxin (PT) is responsible for the reactogenicity and in part the immunogenicity of Bordetella pertussis vaccine. The critical residues associated with the immunomodulatory effects of PT were located around Glu140 in the S1 subunit. In man, T cell responses to PT are directed at S1 peptides distinct from Glu140. Two such epitopes, p64-75 and p151-161, are immunogenic in a panel of individuals covering a wide range of HLA genotypes. The response to PT peptides is HLA class II restricted. The response to p64-75 is blocked by an anti-HLA-DQ mAb, while that to p151-161 is blocked by an anti-HLA-DR mAb. These findings may allow for the development of a B. pertussis vaccine free from reactogenicity.

Amino Acid Sequence↗
PubMed1988

ADP-ribosyltransferase activity of pertussis toxin and immunomodulation by Bordetella pertussis.

Pertussis toxin is produced by the causative agent of whooping cough, Bordetella pertussis, and is an adenosine diphosphate (ADP)-ribosyltransferase capable of covalently modifying and thereby inactivating many eukaryotic G proteins involved in cellular metabolism. The toxin is a principal determinant of virulence in whooping cough and is a primary candidate for an acellular pertussis vaccine, yet it is unclear whether the ADP-ribosyltransferase activity is required for both pathogenic and immunoprotective activities. A B. pertussis strain that produced an assembled pertussis holotoxin with only 1 percent of the ADP-ribosyltransferase activity of the native toxin was constructed and was found to be deficient in pathogenic activities associated with B. pertussis including induction of leukocytosis, potentiation of anaphylaxis, and stimulation of histamine sensitivity. Moreover, this mutant strain failed to function as an adjuvant and was less effective in protecting mice from intracerebral challenge infection. These data suggest that the ADP-ribosyltransferase activity is necessary for both pathogenicity and optimum immunoprotection. These findings bear directly on the design of a nontoxic pertussis vaccine.

ADP Ribose Transferases↗