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Biomedical subjects

Y M Chan

Publications and source records attributed to Y M Chan.

85 records · Page 5Linked to original sources
PubMed1988

Comparative study of combined GIFT and IVF-ET with GIFT alone.

Twenty-eight couples with unexplained infertility, or with suboptimal spermatozoa were divided into two groups. One group underwent gamete intra-Fallopian transfer (GIFT), and the other had combined GIFT and in-vitro fertilization--embryo transfer (IVF-ET) (GET). There was a marked difference in pregnancy rates between the two groups, with the pregnancy rate surprisingly being less in the combined GET group; 10% for GET, as compared with 39% for GIFT alone. The results suggest that GIFT and IVF-ET are incompatible. Differences in the pregnancy rates may be explained by limitations in implantation, whereby the embryo-endometrium interaction that allows for implantation and continued embryonic development has a 'single event capacity', and once this interaction is initiated, the 'implantation window' is closed to other embryos that may arrive later in the uterus.

Adult↗
PubMed1987

Intravenous regional analgesia with a forearm tourniquet.

Lidocaine 0.5 per cent in a dose of 2 mg X kg-1 was used for intravenous regional analgesia with the tourniquet cuff placed over the forearm. The level of tourniquet cuff pressure employed was the arterial "occlusion pressure" plus 50 mmHg. In 48 normotensive patients successful analgesia was achieved; in seven hypertensive patients, four were pain-free, but the other three required more lidocaine to achieve adequate analgesia. No toxic symptoms and signs were observed. Measurement of serum lidocaine concentrations in 12 patients confirmed the safety of the technique, although small leakage of lidocaine past the inflated forearm tourniquet was detected in some patients.

Adolescent↗
PubMed1987

Studies of lymphocyte subpopulations and immunoglobulin production in IgA nephropathy.

This work was undertaken to examine the immunoregulation of T lymphocytes in patients with IgA nephropathy. Fifty patients and thirty-seven control subjects were studied in an infection-free interval. T lymphocyte subpopulations were determined using OKT monoclonal antibodies against helper (OKT4) and suppressor (OKT8) T cell subsets. The proportions of T lymphocyte subpopulations did not differ between patients and controls. Patients with significant renal impairment demonstrated a reduced OKT4/T8 ratio (p less than 0.001) due to an absolute reduction of T helper cells (p less than 0.02) and an increase of T suppressor cells (p less than 0.001). Longitudinal studies performed in 13 patients revealed consistent findings during clinical quiescence. However, synpharyngitic macroscopic haematuria was associated with a rise in T4 positive cells and a simultaneous reduction of T8 positive cells; these changes reverted to pre-infection values when the infection subsided. Functional studies assessing T lymphocyte activities including in vitro immunoglobulin synthesis by cultured peripheral blood mononuclear cells, thymidine uptake by cultured lymphocytes and T lymphocytes activation with expression of interleukin-2 receptors were measured in unstimulated and mitogen stimulated cultures. No significant difference between patients with IgA nephropathy in clinical quiescence and the control subjects was demonstrated. Our results failed to support a shift in the immuno-regulatory T lymphocyte subpopulations during clinical quiescence but a more profound defect in immunoregulation may probably occur during clinical exacerbation.

Fluorescent Antibody Technique↗
PubMed1980

Gas chromatographic/mass spectrometric analysis of methylphenidate (ritalin) in serum.

A gas chromatographic/mass spectrometric (GG/MS) procedure for the determination of methylphenidate in 1 mL of serum or plasma is reported employing ethylphenidate as internal standard. A 50/50 (V/V) mixture of benzene and hexane is used to extract the methylphenidate and ethylphenidate from plasma. After evaporation of solvent the residue is redissolved in 50 microL hexane. Methyl- and ethylphenidate are then derivatized by the addition of 50 ML of trifluoroacetic anhydride and the TFA derivatives are injected into a quadrupole GC/MS for analysis. This method has a lower limit of sensitivity for methylphenidate of 2.0 micrograms/L. The between-day precision study yielded coefficients of variation of 10.4% and 14.8% at methylphenidate concentrations of 25.6 and 5.2 micrograms/L respectively. The assay has been used to investigate the pharmacokinetics of methylphenidate administered to 6 children for treatment of hyperkinesis. The study yielded ranges for volume of distribution, elimination half-life, and total body clearance of 5.0-6.8 L/kg, 1.6-2.7 hours, and 1.4-2.9 L/kg-hr respectively.

Adolescent↗
PubMed1978

Isolation and characterization of the sesquiterpene lactones costunolide, parthenolide, costunolide diepoxide, santamarine, and reynosin from Magnolia grandiflora L.

The germacranolide sesquiterpene lactones costunolide, parthenolide, and costunolide diepoxide were isolated from the leaves of Magnolia grandiflora L. Costunolide diepoxide might be, at least in part, an artifact derived from air oxidation of parthenolide. The root bark yielded only costunolide together with the two eudesmanolides, santamarine and reynosin. In an attempt to synthesize costunolide diepoxide, the action of m-chloroperbenzoic acid on parthenolide and on costunolide was studied. The products were costunolide diepoxide from parthenolide and the two cyclized derivatives, santamarine and reynosin, from costunolide. The elusive 1,10-epoxide was obtained by epoxidizing costunolide using a biphasic system containing sodium bicarbonate. Under these conditions, epoxidation of costunolide took place without cyclization.

Cyclization↗
PubMedDate not supplied

The diagnostic value of seminal adenosine triphosphate (ATP) in an in vitro fertilization (IVF) program.

The level of adenosine triphosphate (ATP) was quantitated in semen samples used for in vitro fertilization of human oocytes. Seminal ATP level correlated with the concentration and percentage motility of spermatozoa but not with the in vitro fertilization rate of human oocytes. Seminal ATP measurement appears to have little diagnostic value in predicting the fertilizing capacity of spermatozoa as evaluated by the multivariate stepwise discriminant analysis.

Adenosine Triphosphate↗
PubMedDate not supplied

Comparison of characteristics of human spermatozoa selected by the multiple-tube swim-up and simple discontinuous Percoll gradient centrifugation.

The multiple-tube swim-up (MT-SU) and simple, discontinuous Percoll gradient centrifugation are two recent methods for the processing of human spermatozoa for assisted reproductive technologies. The present study was undertaken to compare the effects of these two methods on various parameters of spermatozoal qualities of normospermic semen samples. Both methods were found to select spermatozoa of better percentage motility, percentage normal morphology, viability, functional integrity of plasma membrane, movement characteristics including the curvilinear velocity, linearity of movement and head beat frequency, and in vitro fertilizing capacity with comparable degree of efficacy. It is concluded that both methods are effective for the separation of spermatozoa from normospermic semen samples for use in infertility treatment.

Acrosome↗
PubMedDate not supplied

Ethnicity is a factor to be considered before dose planning in ovarian cancer patients to be treated with topotecan.

The objective of this study was to determine the efficacy and toxicity of topotecan in Chinese patients with ovarian cancer. A retrospective analysis on recurrent ovarian cancer patients receiving topotecan 1.25 mg/m(2) daily for 5 consecutive days on a 21-day cycle from 1997 to 2002 was conducted. The patients included were all treated with at least two cycles of topotecan. The patient characteristics were compared in relation to their toxicity profile and their response to treatment. Response was evaluated by physical findings, imaging techniques, and serum CA125 level. A total of 60 patients were included in the study. All patients were evaluable for response and toxicities. A total of 361 cycles were given (median, 5 per patient; range 2-15). The major toxicity was neutropenia, which was grade 4 in 45.0% of the patients and 10.2% of the cycles. Age was the only covariate predicting the occurrence of grade 4 neutropenia (logistic regression P= 0.046, CI 1.01-1.12). Neutropenic fever occurred in 8.3% of the patients. Eighteen (30%) patients were required to delay their chemotherapy and 11 (18.3%) required dose reduction. Nonhematologic toxicities were mild. The overall response rate was 21.6%, with eight (13.3%) complete responses and five (8.3%) partial responses. The median duration of response and median time to progression were 11 and 5 months, respectively. The median survival was 14 months. Topotecan 1.25 mg/m(2) in a five-times-daily schedule was well tolerated in a cohort of Chinese patients. Myelotoxicity was the most important side effect in our study, but the incidence is much lower than that reported in other studies. Age was an independent factor predicting the occurrence of grade 4 neutropenia.

Adult↗
PubMedDate not supplied

If a well-stabilized epileptic patient has a subtherapeutic antiepileptic drug level, should the dose be increased? A randomized prospective study.

In an attempt to determine whether the dose of an antiepileptic drug should be increased in epileptic patients who were seizure-free and had subtherapeutic serum levels, 79 patients with idiopathic generalized tonic-clonic seizures treated with monotherapy [phenytoin (PHT) or phenobarbital (PB)] and with a subtherapeutic serum level were prospectively studied. Their last seizure was at least 3 months prior to entry, and no patient had any clinical evidence of toxicity. They were randomized to study arm A (keeping the level in the subtherapeutic range) or study arm B (increasing the dose until the level reached and stayed at the therapeutic range). Over a mean follow-up period of 24 months, there was no significant difference between the two study arms in the occurrence of seizures, but arm B patients had an increased incidence of neurotoxic side effects from the dose increment. These results confirm the clinical impression that it is unnecessary to increase the dose of the antiepileptic drug despite a subtherapeutic serum concentration in a relatively well-stabilized patient, thus minimizing the frequency of dose adjustment and the need for expensive therapeutic drug monitoring.

Adult↗
PubMedDate not supplied

Routine intrauterine insemination and the effect of spermatozoal washing as assessed by computer-assisted semen analyzer.

We present the results from 283 cycles of intrauterine insemination (IUI) performed on 237 patients. Their indications for treatment included cervical factor infertility, spermatozoal antibodies, idiopathy, poor postcoital test, and oligozoospermia. Pregnancies arose in all groups, with 28 pregnancies from natural cycles, and 17 from clomiphene citrate-supplemented cycles. A live birth rate per cycle of 12.7% (36/283) was achieved following nine miscarriages. A further 133 patients, with only cervical factor or idiopathic infertility, underwent 144 cycles of IUI in natural cycles; this more homogeneous group had their spermatozoal performance monitored by a computer-assisted semen analyzer (CASA) before and after spermatozoal washing for IUI. All factors in the spermatozoal profile changed significantly after washing. Twelve clinical pregnancies resulted from these 144 cycles of IUI, and a comparison was made between the spermatozoal profiles, as assessed by CASA, of conceptual and nonconceptual cycles. Post-wash spermatozoal concentration was slightly greater (P less than .1) in the conceptual cycles, whilst spermatozoal velocity was significantly less (P less than .005). The relevance of these findings to the definition of a "hyperactivational" state for human spermatozoa is discussed, and the general applicability of IUI as a "frontline" treatment for nontubal infertility is proposed.

Adult↗