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Biomedical subjects

S H Yeo

Publications and source records attributed to S H Yeo.

18 recordsLinked to original sources
PubMed2004

Rapid biocompatible micro device fabrication by micro electro-discharge machining.

Fabrication of a biocompatible micro device is predominantly done by silicon micromachining techniques. The lithographic and etching techniques require preparation and the use of masks which are time consuming and costly. Since bio research involves highly complex mechanisms, the modeling and simulation is difficult and experimental study is inevitable. To incorporate frequent design changes and to realize the hardware quickly, fabrication processes, complementary to the silicon micromachining techniques are required. In the present work the feasibility of using micro electro-discharge machining (EDM) for the fabrication of biocompatible microdevice has been studied. Micro channels with feature size as small as 25 microm are realized. The process is further improved by the introduction of ultrasonic vibration of the workpiece and the total time taken for the hardware realization is about 4 hours. The effects of ultrasonic vibration on the roughness of the spark eroded surface has been studied and reported. The potential of using micro EDM for making biocompatible devices for bio experiments is demonstrated and the surface finish achieved is well within the recommended Rz and Ra values of 3.4 and 0.4 microm respectively for biological studies like implant abutment.

Biocompatible Materials↗
PubMed2001

Morphologic evaluation and integrin expression profile of renal tubular cells cultured from percutaneous renal biopsy specimen.

Kidney biopsy is an indispensible procedure for making a pathologic diagnosis of renal diseases by fixing and staining the biopsy specimen. However, it is not a routine procedure to culture the cells from a renal biopsy specimen directly, or to utilize the cultured cells for any kind of diagnostic or functional evaluation. In this study, primary culture of the renal tubular epithelial cells was tried from a piece of percutaneous kidney biopsy specimen. Successive passages of the cells were possible until fourth passage. With these cells, morphologic characteristics of the cultured cells and integrin expression profiles were investigated. On light and electron microscopy, these cells were characterized by the cobblestone-like growth, presence of microvilli and tight junction, and the preservation of polarity. Immunohistochemical studies demonstrated the epithelial nature of these cells and particularly their differentiation from renal tubular epithelial cells, of either proximal or distal nephronic segment. The integrin profile confirms the epithelial nature of the cell. We hope that our results facilitate the understanding of pathophysiology of renal tubular cells from the patient directly.

Biopsy↗
PubMed2000

Involvement of p27(kip1) in ceramide-mediated apoptosis in HL-60 cells.

Ceramide acts as a mediator of apoptosis in various cell lines, but little is known regarding the molecular mechanism linked to the cell cycle. In the present study, we examined the expression of p27(kip1) and its relationship to apoptosis induced by ceramide. We demonstrated that treatment of HL-60 cells with C6-ceramide resulted in G1 phase elevation followed by apoptotic cleavage associated with increase in the level of cdk inhibitor p27(kip1). Ceramide inhibited the kinase activities of cdk2 and cdk4 within 24 h of treatment. Ceramide-induced inhibition of cdk2 and cdk4 kinase activities was accompanied by increase of p27(kip1) in the cdks complexes. In addition, we have shown that both the cell death and expression of p27(kip1) protein induced by ceramide were significantly decreased in HL-60 cells overexpressing bcl-2. Furthermore, ceramide induced a significant increase in Bax protein expression coincided with increase in p27(kip1) protein level. These findings indicate that p27(kip1) may play important roles in mediating ceramide-induced apoptosis and its expression can be regulated by Bax and Bcl-2.

Apoptosis↗
PubMed2000

Abdominal pregnancy: a case report and literature review.

We report a rare and unusual case of an Abdominal pregnancy that was delivered successfully at term. It is the first documented case in the local literature in almost 30 years. What makes it even more exceptional is that despite the high mortality associated with the condition, both mother and baby survived the ordeal. She subsequently delivered another child, 2 years later by an elective lower segment caesarean section and had a tubal ligation performed concomitantly. A review of the topic and its management is also presented.

Adult↗
PubMed1998

Purification and characterization of tert-butyl ester-hydrolyzing lipase from Burkholderia sp. YY62.

An intracellular novel lipase which can hydrolyze t-butyl octanoate (TBO) was purified to homogeneity from crude cell-free extracts of Burkholderia (formerly Pseudomonas) sp. YY62 with 9% overall yield. Seventy-four-fold purification was achieved by ammonium-sulfate precipitation, three consecutive open-column chromatographies (DEAE anion-exchange, Sepharose CL-6B gel-filtration, and the second DEAE anion-exchange columns), and two HPLCs (TSK G2000SWXL gel-filtration and phenyl 5PW hydrophobic interaction columns). Enzymes hydrolyzing p-nitrophenyl acetate were separated into two peaks (peak I and II) on the hydrophobic HPLC, and only peak II was found to have TBO-hydrolyzing activity. The peak preparation showed a single band of 40 kDa on SDS-PAGE and a molecular mass of 39 kDa on gel-filtration under non-denatured conditions, indicating the monomeric nature of the TBO-hydrolyzing lipase. The lipase showed maximum activity at pH 7.0 and 28 degrees C. The N-terminal 15 amino acid residues were determined as Met-Asp-Phe-Tyr-Asp-Ala-Asn-Glu-Thr-Arg-His-Pro-Glu-Gln-Arg, which showed no homology to known proteins, suggesting that the purified enzyme may belong to a novel class of hydrolase.

Amino Acid Sequence↗
PubMed1996

Is postnatal oral glucose tolerance testing necessary in all women with gestational diabetes.

Currently, women with gestational diabetes mellitus have a repeat oral glucose tolerance test 6 weeks after delivery to identify those with persistent glucose intolerance. In this study, 298 women with gestational diabetes had a postnatal oral glucose tolerance test and of these, 23.2% had persistent glucose intolerance after delivery. The aim of this study was to determine if the antenatal oral glucose tolerance test results could be used to predict which patients would have persistent glucose intolerance after delivery. If only those with severely abnormal antenatal results had persistent disease, then those with only mildly abnormal antenatal results could be spared the postnatal oral glucose tolerance test. Using receiver operator characteristic curves, this study showed that the antenatal oral glucose tolerance test results could not be used to predict reliably which patients would continue to have abnormal glucose tolerance postnatally. Hence, postnatal oral glucose tolerance testing of all patients with gestational diabetes is still necessary as the detection of persistent glucose intolerance is important for the control of the diabetic condition so as to minimise long-term complications.

Adult↗
PubMed1995

Reproducibility of the amniotic fluid index: its effect on clinical practice.

Two methods of measuring the amniotic fluid index (AFI) were subjected to tests of intra- and interobserver reproducibility. In the first method, amniotic fluid in each quadrant was measured by using the deepest pool perpendicular to the floor; in the second method, amniotic fluid in each quadrant was measured by using the deepest pool perpendicular to the uterine contour. Intraobserver and interobserver variability were assessed by using one-way analysis of variance and limits of agreement, respectively. Intraobserver standard deviations were all < 9 mm. When the AFI was measured using the first method, there was an inverse relationship between the interobserver difference and mean values of AFI. Plots of the differences between observers against their means showed that the lower the AFI, the greater the interobserver variability. No such correlation was noted when the AFI was measured by the second method. The limits of agreement (within which 95% of interobserver differences lie) were comparable for the two methods [(-42 mm to 29.4 mm) and (-46.4 mm to 41.6 mm), respectively]. The results suggest that the amniotic fluid index measured by the second method is more reproducible, especially in the presence of reduced amniotic fluid.

Amniotic Fluid↗
PubMed1995

Pericentric inversion 9--incidence and clinical significance.

Pericentric inversion of the chromosome 9, inv(9)(p11q13), is such a common occurrence that some cytogeneticists would consider them as normal variants. The incidence is said to be about 1% to 1.65% in the general population. Despite being categorised as a minor chromosomal rearrangement which does not correlate with abnormal phenotypes, many reports in the literature raised conflicting views regarding the association with subfertility and recurrent abortions, abnormal clinical conditions, as well as chromosomal abnormalities arising as a result of having this inversion. We studied the incidence and clinical significance of inv(9)(p11q13) patients retrospectively from 2448 antenatal cytogenetic analysis and 1058 peripheral blood karyotype collected over a 3-year period. Thirty cases of inv(9)(p11q13) from 29 families were found from the antenatal group, which gave an incidence of 1.2% and 6 cases from the peripheral blood karyotype analysis (incidence of 0.6%). The parental origin of the inv(9)(p11q13) in the antenatal group was of equal proportion and there was also no sex predilection for the fetuses carrying the inversion. The babies with the inversion were born with no phenotypic abnormalities. The 6 cases picked up from the peripheral blood karyotype analysis were 2 cases of paediatric patients with associated chromosomal abnormalities (one Trisomy 21 and the other del 13(q22q32)) and 4 adult patients with obstetric and fertility problems. The incidence of subfertility (36%) appeared to be high amongst the adult patients with inv(9)(p11q13). This may represent a true reflection of subfertility in inv(9)(p11q13) patients or a selective bias towards the older subfertile women who conceive at a later age and thus utilising the antenatal diagnostic setup.

Abortion, Habitual↗
PubMed1993

Non-puerperal uterine inversion--a case report.

A rare case of non-puerperal uterine inversion caused by a large fundal leiomyoma in a 36-year-virgo intacta resulting in intractable haemorrhage was reported. After a myomectomy, attempts to reduce the inversion vaginally by transecting the anterior and posterior cervix was unsuccessful and a laparotomy was performed. The inversion was successfully corrected with return of normal function of the uterus.

Adult↗
PubMed1992

Placental chorioangioma: a case report and review.

Placental Chorioangioma occurs in 1% of pregnancies and are generally asymptomatic. However, they are known to cause a number of complications which are detrimental to the mother, fetus or the neonate. A typical case where acute polyhydramnios precipitated premature labour and delivery of the fetus as a result of a large placental chorioangioma is presented. A brief review of the other possible complications are also included.

Adult↗
PubMed1991

Local norms of maternal serum alpha-fetoprotein values in early second trimester: a prelude to a Down's syndrome screening programme incorporating maternal serum alpha-fetoprotein values.

Maternal alpha-fetoprotein in (MSAFP) has recently been proposed for screening of Down's syndrome. This is based on the association of a lowered MSAFP level at a given gestational age in Down's syndrome (DS) pregnancies. Most conventional 'screening' programmes in DS are based on the maternal age alone, selecting older mothers, who are at greater risk of having a DS infant born, for antenatal karyotyping. However, as 75% of DS infants are born to mothers less than 35 years old, a combination of blood tests including MSAFP and maternal age as independent risk factors would screen the younger mothers as a good cost-benefit ratio in selecting the 'at-risk' mothers for karyotyping. In this study, the gestational age was calculated from the first day of the last menstrual period (LMP) as well as from ultrasound cephalometry. The local MSAFP levels follow the same trend at a slightly higher level as those based on clinical evaluation of the Abbot AFP-EIA Monoclonal kits.

Down Syndrome↗
PubMed1990

Cation transport across lymphocyte plasma membranes in euthyroid and thyrotoxic men with and without hypokalaemic periodic paralysis.

1. To study potassium transport in hypokalaemic periodic paralysis in a model of striated muscle cells, we measured specific [3H]ouabain binding (the number of sodium-potassium pumps), sodium-potassium-pump-mediated (ouabain-sensitive) 86Rb+ influx and sodium-potassium-pump-independent (ouabain-resistant) 86Rb+ influx in lymphocytes in vitro. 2. The subjects comprised euthyroid and thyrotoxic men with hypokalaemic periodic paralysis between attacks, men with uncomplicated thyrotoxicosis, and healthy men matched for age and weight. 3. Thyrotoxic patients, both with and without periodic paralysis, had significantly more lymphocyte sodium-potassium pumps than normal, and a significantly greater sodium-potassium-pump-mediated 86Rb+ influx. Anti-thyroid treatment corrected this defect in patients with thyrotoxic periodic paralysis. Euthyroid patients with cryptogenic periodic paralysis had significantly increased sodium-potassium-pump-mediated 86Rb+ influx, but a normal number of sodium-potassium pumps. 4. Only untreated thyrotoxic and euthyroid patients with periodic paralysis showed a significant increase in sodium-potassium-pump-independent 86Rb+ influx (5.2 +/- 2.8 and 4.5 +/- 1.8 respectively, vs control 2.8 +/- 1.0 pmol h-1 10(-6) cells; mean +/- SD; P less than 0.001, P less than 0.005). 5. We conclude that thyrotoxicosis increases the number and activity of sodium-potassium pumps and facilitates, but is probably not necessary for, periodic paralysis. Hypokalaemic periodic paralysis is associated with an increase in sodium-potassium-pump-independent potassium influx.

Adult↗
PubMed1989

Correlation of contraceptive activity of norethisterone and levonorgestrel esters with VR(w) values and hydrolysis rates.

The relationships between contraceptive activity, hydrophobic character and alkaline hydrolysis rates were studied in three homologous series of norethisterone and levonorgestrel esters. Hydrophobic character was expressed by the high-performance liquid chromatographic retention term, VR(w) or retention volume at 100% aqueous mobile phase. A parabolic and bilinear relationship was shown between log VR(w) and log biological response. No correlation between second-order alkaline hydrolysis rates, k2, measured in 70% (v/v) aqueous dioxan and contraceptive activity was established.

Acetic Anhydrides↗
PubMed1989

An open clinical trial with the long-acting neuroleptics flupenthixol decanoate and fluphenazine decanoate in the maintenance treatment of schizophrenia.

An open clinical trial was carried out in 21 chronic schizophrenics to assess the effectiveness and side-effects of treatment with depot neuroleptics. All patients had been stabilized on fluphenazine decanoate for at least 6 months and on entry to the study were given the choice of continuing with this treatment or changing over to flupenthixol decanoate. Sixteen patients chose to receive flupenthixol decanoate (40 mg) and the other 5 fluphenazine decanoate (25 mg). Doses were given every 4 weeks during the 12-week study period. Clinical assessments were carried out every 4 weeks (Weeks 0, 4, 8 and 12) using the Brief Psychiatric Rating Scale and a side-effects checklist, and the Hamilton Rating Scale for Depression, the Schedule for Affected Disorders and Schizophrenia--Change Version, and the Global Assessment Scale were completed on entry (Week 0) and at the end of the study (Week 12). The results indicated that symptoms of depression, withdrawal, worrying, and psychomotor retardation were improved significantly (p less than 0.05) more with flupenthixol than with fluphenazine. The frequency of side-effects decreased during treatment with flupenthixol and there was a tendency towards fewer side-effects in the flupenthixol group than in the fluphenazine group after 8 weeks of treatment. It is concluded that a group of schizophrenic patients characterized by depressive symptoms or side-effects attributable to a prescribed neuroleptic might benefit from a switch to flupenthixol treatment.

Clinical Trials as Topic↗