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Biomedical subjects

S H Lim

Publications and source records attributed to S H Lim.

At least 109 records · Page 6Linked to original sources
PubMed1997

Molecular analysis of T cell receptor beta variability in a patient with orofacial granulomatosis.

BACKGROUND: Orofacial granulomatosis (OFG) is a rare chronic inflammatory disorder of unknown causation and is characterised histologically by non-caseating granulomas and aggregates of small lymphocytes. The molecular nature of these T cells is, however, unclear. AIMS: To determine the T cell receptor (TCR) V beta gene usage of the T cell infiltrate associated with the primary lesions in a patient with OFG. METHODS: A molecular method involving reverse transcriptase (RT)-polymerase chain reaction (PCR), DNA cloning, single strand conformation polymorphism (SSCP), length analysis, and nucleotide sequencing was used. RESULTS: Compared with peripheral blood lymphocytes from the same patient, notably restricted TCRV beta gene usage was observed in the T cell infiltrate. Only three of the 24 major TCRV beta gene families were represented in the repertoire. There was preferential usage of the V beta 6 gene. In addition, more than 20% of the V beta 6 TCR transcripts exhibited an identical unique V-D-J junctional sequence, suggesting a local antigen driven V beta 6 T cell clonal expansion in vivo, a phenomenon not observed in normal oral mucosa. CONCLUSIONS: The TCRV beta repertoire of T cells associated with OFG is restricted. It is also associated with a local T cell clonal expansion. The results, therefore, provide a new perspective on the immunopathology of OFG.

Amino Acid Sequence↗
PubMed1997

Post-caesarean septicaemia in Kandang Kerbau Hospital, Singapore, 1993-1995.

We reviewed all documented cases of septicaemia following caesarean deliveries in Kandang Kerbau Hospital between 1st January 1993 to 31st December 1995. There were 22 cases of septicaemia among 8201 caesarean births, and hence the incidence is 2.7:1000. There were 45,412 deliveries, and the overall caesarean section rate was 18.1%. Among the 22 documented cases of septicaemia which came under this study, the most common clinical conditions found were endomyometritis (7 cases), urinary tract infection (6 cases), and wound infection (3 cases). One of the three cases with wound infection also had pneumonia. There was one patient who had mild transient myocarditis. We could not determine with certainty any site of infection in five patients. The most common bloodstream bacterial isolates was Staphylococcus aureus (16), while the uncommon ones were Acinetobacter baumanii (2), Escherichia coli (1), Klebsiella sp. (1), Staphylococcus epidermidis (1), Streptococcus Group F (1), Peptostreptococcus species and Veillonella species (1). There was no mortality and prompt, vigorous treatment had led to uneventful recovery in all the cases.

Adolescent↗
PubMed1996

T cell receptor Vbeta repertoire of tumour-infiltrating lymphocytes in oral squamous-cell carcinoma.

Oral squamous cell carcinoma (OSCC) are frequently infiltrated by tumour infiltrating lymphocytes (TILs) which may demonstrate specific anti-tumour cytotoxicity. We have used a panel of family-specific primers in reverse-transcriptase (RT)-polymerase chain reactions (PCR) to determine the TCR Vbeta repertoire of TILs in the primary and metastatic tumours in patients with OSCC. We observed a diverse and heterogenous usage of TCR Vbeta genes by TILs in the primary tumours, a scenario not unlike normal oral mucosal lymphocytes. In one patient with a longstanding history of OSCC, the repertoire was restricted. Restricted TCR Vbeta gene usage also occurred in TILs of metastatic tumours. Within individual patients, discrepancies of TCR Vbeta gene usage were also observed between TILs in the primary OSCC and those in metastatic lymph nodes. Work is ongoing to determine the clonality and functional significance of these TILs.

Biopsy↗
PubMed1996

Molecular evidence for a common leukaemic progenitor in acute mixed lymphoid and myeloid leukaemia.

De novo acute leukaemia presenting with a mixed lymphoid and myeloid leukaemic population has rarely been described. We have used the consensus Ig heavy chain primers and DNA isolated from these two distinct populations of cells in polymerase chain reactions. We demonstrated that both populations of cells exhibited Ig heavy chain gene rearrangements. Cloning and subsequent DNA sequencing of the amplified products showed a common V-D-J junctional nucleotide sequence. This work therefore provides the first evidence that the leukaemic cells in de novo acute leukaemia with a mixed lymphoid and myeloid population are derived from a common progenitor clone and may offer an explanation for the poor prognosis in these patients.

Adult↗
PubMed1996

Parents' perceptions towards their child's use of inhaled medications for asthma therapy.

OBJECTIVE: Understanding patients' and their parents' perceptions towards asthma medication is important in developing strategies to ensure patient compliance. In this study, parents' perceptions towards their children's use of inhaled medication for asthma treatment were evaluated. METHODOLOGY: A questionnaire was administered by interviewing parents of 210 asthmatic children attending the Department of Paediatrics, National University Hospital. RESULTS: Our results showed that 76/210 (36%) of parents either felt opposed to inhaler therapy and/or preferred oral medications. The main reasons for their reluctance to use inhalers were related to fear of dependence, side effects and overdosage, and the child's dislike for inhalers. A third of these parents felt that inhalers were only indicated for very severe asthma. CONCLUSIONS: We conclude that a significant proportion of parents have reservations regarding the use of inhalers for the treatment of asthma. These factors should be taken into consideration when planning an effective asthma education programme.

Administration, Inhalation↗
PubMed1996

Latchkey children.

Children who are regularly left without adult supervision during a significant portion of the day, referred to as 'latchkey children', are a growing social phenomenon. The main reason for the rising prevalence of latchkey children is the increase in dual income and single parent families. Studies on the effects of the latchkey phenomenon report conflicting results. The potential positive consequences include learning to be independent and responsible. The potential negative consequences include loneliness, boredom, fear, academic under-achievement, drug and alcohol abuse, accidental injury, and impairment of the parent-child relationship. Such wide variations in reported consequences in latchkey children might reflect differences in the maturity of the children and in the parent-child relationships prior to entering the latchkey arrangement. Counselling parents about the problems associated with a latchkey arrangement, referring children to an after-school programme, and teaching children self-help skills might minimise the possibility of negative consequences.

Adolescent↗
PubMed1996

Pleomorphic adenoma of the trachea--a case report.

An unusual tracheal tumor was found in a 50 year old male who was admitted due to mild dyspnea on exertion. Simple chest X-ray showed an abnormal mass shadow in the trachea and computerized chest tomogram revealed a tumor in the mid 1/3 of the trachea obstructing 80% of the lumen. Through a right thoracotomy incision, resection of a 2.5 cm segment of the trachea with end-to-end anastomosis was done and microscopic findings showed many cystic spaces with myxomatous hyalinous stroma. It was diagnosed as a pleomorphic adenoma of the trachea.

Adenoma, Pleomorphic↗
PubMed1996

Autologous MHC-dependent leukaemia-reactive T lymphocytes in a patient with chronic myeloid leukaemia.

We have investigated the presence of T cells capable of recognizing autologous leukaemia cells in a patient with CML. We demonstrated that these cells were anergic to the leukaemia cells. They were estimated to be present at a frequency of 1:4000 T cells in the peripheral blood. However, following incubation with high dose rIL-2, these effector cells were able to proliferate, secrete TH1 cytokines and lyse target cells upon challenging with fresh autologous leukaemia cells. Both CD4 and CD8 T cells were involved in the proliferative responses. Moreover, the immune response was blocked by monomorphic anti-HLA antibodies, suggesting that the MHC molecules are needed by the T cells for leukaemia cell/antigen recognition. This work therefore indicates a potential reservoir of effector cells in CML patients which may be exploited for the modulation of leukaemia cell growth. It also provides evidence for a distinct T cell population capable of mediating GVL responses.

Autoimmunity↗
PubMed1995

Abnormal TCR V beta repertoire in patients with chronic myeloid leukaemia.

We have used 25 sets of oligonucleotide primers specific for the 24 known major human T-cell receptor (TCR) V beta families in polymerase chain reactions to analyse the T-cell repertoire of the peripheral blood in seven patients with chronic myeloid leukaemia (CML). In contrast to normal healthy individuals, all seven patients exhibited variable degrees of TCR V beta-specific T-cell deletion, ranging from two to eight of the 24 major families. T cells bearing V beta 17 and 8 were most commonly deleted. These results suggest a superantigen effect associated with CML. The patterns of deletion did not appear to correlate with either of the two bcr-abl transcripts. The reason and aetiological agent responsible for the T-cell deletion remain speculative. Further work is ongoing to characterize this phenomenon in animal models and patients with CML.

Base Sequence↗
PubMed1995

Does routine gowning reduce nosocomial infection and mortality rates in a neonatal nursery? A Singapore experience.

A 1 year prospective study on routine gowning before entering a neonatal unit was conducted in a maternity hospital in Singapore. This study was done based on previous work by Donowitz, Haque and Chagla and Agbayani et al., as there have been no known studies done in Singapore. The aim of the study was to test the hypothesis that routine gowning before entering a neonatal nursery does not reduce nosocomial infection and mortality rate. A total of 212 neonates from the neonatal intensive care unit (NICU) and 1694 neonates from the neonatal special care unit (NSCU) were studied. Neonates admitted during the 1 year study were assigned to the gowning (control) and no routine gowning (trial) group on every alternate 2 months. The hospital infection control nurse provided data on nosocomial infection. The overall nosocomial infection rate in the NICU was 24% (25 of 104 admissions) during gowning periods compared to 16.6% (18 of 108 admissions) when plastic aprons were not worn before entry. In the NSCU, the overall infection rate was 1.5% (12 of 800 admissions) during gowning periods compared to 2.1% (19 of 894 admissions) when no gown was worn before entry. Results of the study found no significant differences in the incidences of nosocomial infection and mortality in the neonates. The cost of gowns used during the no routine gowning periods was S$2012.8 compared to S$3708 used during the routine gowning procedure. The investigators recommend that routine gowning before entering a neonatal unit is not essential and cost effective for the purpose of reducing infection. Rather the focus should be on adequate handwashing by all hospital personnel and visitors before handling neonates.

Cross Infection↗
PubMed1995

Allergens of Bipolaris species.

Skin prick tests done previously revealed a significantly higher percentage of sensitization to an extract of Bipolaris sp. among atopic individuals (34/147, 23.1%) compared to non-atopic individuals. Bipolaris-specific IgE levels were quantified in sera from a representative group of 38 individuals using the Fluorescence Allergosorbent Test (FAST). Result obtained by FAST were found to be comparable to the skin prick test results (r2 = 0.60, p < 0.001 for IgE levels vs wheal sizes; r2 = 0.44, p < 0.001 for IgE levels vs erythema sizes). Characterisation of the extract's allergenic component by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed 28 protein bands with molecular weights (MW) ranging from 11 kDa to above 100 kDa. Immunoblotting with sera of 10 Bipolaris-sensitive (skin prick test, 3 +) individuals showed that Bipolaris spore extract contained at least 4 IgE binding proteins (MW 11-13 kDa, 16-17 kDa, 20-22 kDa and 36 kDa). All 10 sera reacted to the protein at MW 20-22 kDa, 2 sera with MW 11-13 kDa, 3 sera with 16-17 kDa and 6 sera with 36 kDa. This study has thus demonstrated that spores of Bipolaris sp. contain allergenic components which may elicit IgE-mediated reactions.

Allergens↗
PubMed1994

Attention-deficit hyperactivity disorder. Getting control of impulsive behavior.

A sizable number of school-aged children, more often boys, may have attention-deficit hyperactivity disorder (ADHD). Its cause is unknown. Some investigators implicate food additives or lead poisoning. These theories are not supported by study results, however. Physicians are dependent on reports of parents and teachers to diagnose ADHD, since the children may not show signs at an office visit. The presence of criteria listed in the Diagnostic and Statistical Manual of Mental Disorders, third revised edition, and descriptions by parents and teachers of significant and pervasive impairment at home or school are diagnostic. Treatment is essential to minimize the academic failure, rejection, and loss of self-esteem that can result from the behaviors that typify ADHD. Use of stimulant medication is the most effective intervention and should be continued as long as it provides benefits without adverse effects. Concomitant behavioral therapy may be useful, and the entire family may benefit from psychotherapy.

Attention Deficit Disorder with Hyperactivity↗
PubMed1994

Porphobilinogen deaminase is encoded by a single gene in Arabidopsis thaliana and is targeted to the chloroplasts.

Porphobilinogen deaminase (PBG deaminase) is an early enzyme of the pathway for chlorophyll and heme synthesis. Using degenerate oligonucleotide primers, based on amino acid sequence data for purified PBG deaminase from pea, a fragment was amplified from Arabidopsis genomic DNA by PCR, and then used to isolate both a cDNA and a genomic clone for PBG deaminase from Arabidopsis. The cDNA, shown to be full-length by primer extension, encodes a precursor protein of 382 residues, which can be imported into isolated chloroplasts and processed to the mature size. The genomic clone encodes an identical sequence to the cDNA, except for the presence of four introns within the coding region of the mature protein, and 1.7 kb of upstream sequence. There is no obvious TATA box within 50 bp of the transcription start. Southern blot analysis suggests that PBG deaminase is encoded by a single gene in the Arabidopsis genome, and RNase protection experiments demonstrated that this gene is expressed in both leaves and roots. These results support the conclusion that there is only one form of PBG deaminase in all plant cells, which is located in the plastid.

Arabidopsis↗
PubMed1994

Functional anatomy of the human supplementary sensorimotor area: results of extraoperative electrical stimulation.

Electrical stimulation studies have demonstrated that a "supplementary motor area" (SMA) exists in humans. However, its precise functional organization has not been well defined. We reviewed the extraoperative electrical stimulation studies of 15 patients with intractable epilepsy who were evaluated with chronically implanted interhemispheric subdural electrodes. SMA-type positive motor responses were elicited not only from the mesial portion of the superior frontal gyrus but also from its dorsal convexity, and from the paracentral lobule, cingulate gyrus, and precuneus. Sensory symptoms, that could not be attributed to stimulation of the primary sensory area, were elicited from the superior frontal and cingulate gyri in addition to the precuneus. Therefore, human SMA, as defined by electrical stimulation, is not always confined to the mesial portion of the superior frontal gyrus as described previously. It is also not strictly "motor" but "sensorimotor" in representation. We propose referring to this region as the "supplementary sensorimotor area" (SSMA). We observed a somatotopic organization within the SSMA with an order of lower extremity, upper extremity, and head from posterior to anterior. Sensory representation in an individual was either anterior or posterior to the positive motor representation but never both. There was a supplementary eye field within the head representation. A supplementary negative motor area was noted at the anterior aspect of the SSMA. No language area was demonstrated within the SSMA. The physiologic significance of the SSMA and functional consequences of its resection must be addressed in further studies.

Adolescent↗