Early onset neonatal group B streptococcal infection in Hong Kong.
Explore the source record for details and available documents.
Adult↗
Biomedical subjects
S H Chan
Publications and source records attributed to S H Chan.
Perinatal colonization of group B streptococcus--an epidemiological study in a Chinese population.
An epidemiological study of perinatal colonization of group B streptococcus (GBS) was carried out prospectively in a Chinese population. One hundred and sixty-eight mother-infant pairs were studied. Maternal carriage rate from multiple sites was 19.0%, with an overall neonatal colonization rate of 19.6%. There was no neonatal sepsis due to GBS. No obstetrical risk factors that could influence material carriage could be identified. Neonatal colonization was associated with premature/prolonged rupture of membranes, increased duration of rupture of membranes and intrapartum pyrexia. The number of infected sites and the density of organism in each site in the infant were directly proportional to the number and density of organisms in the culture-positive sites in the mother. Serotypical study showed a complete absence of type II GBS in this population. Since the vertical transmission rate was only 37.5%, it is postulated that nosocomial spread of the organism contributed significantly towards colonization of the infants in our study population.
Carrier State↗
Estradiol binding capacity of breast cancer cell line in correlation with cell cycle.
The specific estrogen binding capacity of the MCF-7 cells has been studied throughout the cell cycle. Two days after plating 1-4 X 10(5) cells per well, we observed that cell number, protein concentration and DNA level began to rise but the estrogen binding capacity was lowered. At logarithmic phase the binding increased gradually then sharply to just before confluency. When the cells reached the quiescent phase the estrogen binding capacity fell rapidly. Since estrogen binding capacity of the intact MCF-7 cells varies with different phases in the cell cycle as well as the incubation temperature and time and the plating density, all these factors should be taken into consideration when this cell line is used for hormone studies.
Breast↗
Quality control of estrogen and progesterone receptor assays.
The intra-laboratory QC materials for estrogen and progesterone receptor assays were prepared using different methods. The most convenient and economical method was found to be the use of lyophilized rat uterine cytosol. The level of receptors remained stable for 12 months when stored at -70 degrees C with the inclusion of 10 mM phenylmethyl sulfonyl-fluoride in the cytosol extraction buffer. For inter-laboratory comparison, we received QC materials from Dr E D Ryan (McMaster University, Canada) monthly and our results fell within +/- 1SD of the mean value of 15 centres from North America and Europe participating in this program.
Animals↗
Pulmonary edema as a cause for fulminant death following microinjection of kainic acid into the rat medulla oblongata.
The present study confirmed histopathologically the suggestion that pulmonary edema may underlie the fulminant death following microinjection of kainic acid into many medullary sites in rats anesthetized with pentobarbital sodium. We also observed a sustained elevation in systemic arterial pressure, cardiac contractility and heart rate before the animal succumbed to kainate neurotoxicity. It is suggested that the increased systemic hydrostatic pressure may retrogradely promote pulmonary hypertension that precipitates pulmonary edema.
Animals↗
Correlation of steroid receptors with histologic differentiation in mammary carcinoma. A Singapore experience.
Cancer of the breast is the most common tumor in females in Singapore, with the rate of 20.7 per 100,000 per year (1977 estimate), which is predicted to increase to 29.8 per 100,000 women per year by 1995. A detailed histopathologic review of 50 primary breast cancer tumors analyzed for estrogen receptor (ER) level was carried out and a variety of morphologic features correlated with ER results to identify any factors that will improve the management and prognosis for breast cancer. Cytosol was incubated with 3H-estradiol in the presence and absence of cold diethylstilbestrol, and bound and free hormone were separated by Dextran-coated charcoal method. Tumors binding more than 5 fmol/mg cytosol protein were classified as ER-positive. Progesterone receptor (PR) level was analyzed in some specimens with the use of a similar method. Most of the patients were Chinese (90%). Three patients were Malays, one was Indian, and one was European in this series. Results indicated that there was strong correlation between ER level, age, and histologic grade of the tumors. No correlation existed between absence or presence of lymph node metastases and ER. Although there was a trend for ER-positive tumors to have a low-grade lymphocytic infiltration, the difference was not statistically significant.
Adult↗
Participation of nucleus reticularis gigantocellularis in guanabenz-promoted hypotension, decrease in cardiac contractility and bradycardia in rats.
The possible participation of the nucleus reticularis gigantocellularis in the hypotension, decrease in cardiac contractility and bradycardia induced by guanabenz was examined in rats that were anesthetized with pentobarbital sodium (40 mg/kg, i.p.). Guanabenz (10 micrograms/kg, i.v.) elicited an initial, transient hypertension, accompanied by an increase in cardiac contractility, followed by a significant and sustained hypotension, as well as decrease in the force and rate of cardiac contraction. In rats receiving bilateral focal electrolytic lesions of the nucleus reticularis gigantocellularis, the same injection produced only the initial transient responses, without the subsequent depressant effects. Microinjection of guanabenz directly into the ventro-medial portion of the nucleus reticularis gigantocellularis, at an ineffective systemic concentration (500 ng), produced significant and prolonged reduction in arterial pressure, cardiac contractility and heart rhythm. On the other hand, local application of the same concentration (500 ng) of guanabenz into the lateral portion of the same nucleus produced only minor hypotension and bradycardia, with no decrease in cardiac contractility. It is concluded that the nucleus reticularis gigantocellularis is at least one of the central sites through which guanabenz may produce its cardiovascular suppressant effects.
Animals↗
Arterial pressure- and cardiac rhythm-related single-neuron activities in the nucleus reticularis gigantocellularis of the rat.
This communication presents an analysis of 531 extracellularly recorded spontaneously active nucleus reticularis gigantocellularis (NRGC) single-neurons in pentobarbital anesthetized rats, with particular reference to their cardiovascular-related activities. Fifty-nine percent of the gigantocellular neurons evaluated had temporal relationship with induced or spontaneous arterial pressure fluctuations. Twenty-eight percent of the NRGC neurons manifested definite discharge patterns and periodicity with reference to the cardiac cycle. It is discussed that these gigantocellular neurons may serve as a primary component of the cardiovascular regulatory mechanism. Alternatively, they may coordinate the necessary circulatory support for activities varying from respiration to somatomotor functions or sleep-wakefulness.
Animals↗
HLA and nasopharyngeal carcinoma in Malays.
HLA associations were observed in unrelated Malay patients with nasopharyngeal carcinoma (NPC). HLA-B18 was observed in 18/45 (40%) Malay NPC patients compared to 22/167 (13%) Malay normals (P = 0.0001; Pc = 0.0027, RR = 4.4). The frequency of HLA-B17, one of the antigens associated with Chinese NPC, was also increased among Malay NPC (13/45 29%) compared to controls (18/167 11%; P = 0.003, Pc = 0.07 RR = 3.4). Similar to the findings among Chinese NPC, the frequency of B17 was higher in early onset (less than or equal to 30 years) Malay NPC resulting in a higher relative risk (RR = 5.0).
Adult↗
Maternal-child hepatitis B virus transmission in Singapore.
A study of maternal-infant transmission of hepatitis B virus (HBV) was conducted in Singapore between June 1980 and June 1982. HBsAg carrier rate was highest among Chinese (6.2%) followed by Malay (2.3%) and Indian (0.6%) mothers. The presence of HBeAg in maternal sera correlated well with high titre HBsAg (p = 7.34 X 10(-5)). Overall HBV transmission occurred in 27/56 (48.2%) infants from carrier mothers. The majority of the transmission was perinatal. There was a very strong correlation between transmission and HBeAg status of the mother (p = 1.85 X 10(-9); odds ratio = 68.44) and to a lesser extent with high titre HBsAg (p = 0.002; odds ratio = 6.38). A strong negative correlation was seen between transmission and anti-HBeAg (p = 8.19 X 10(-7); odds ratio = 0.04). At one year 19 (70.4%) infants were still HBsAg positive while seven (25.9%) lost the antigenemia and acquired anti-HBsAg and one developed HBsAg after one year. It could be calculated that perinatal HBV transmission contributed about 18% to the total pool of HBsAg positive infants of one year of age.
Carrier State↗
Hepatitis B virus markers in prostitutes in Singapore.
The prevalence of hepatitis B virus markers in 121 men and 239 women prostitutes was studied. Of 33 (9.7%) with hepatitis B surface antigen (HBsAg), nine (27.3%) also had hepatitis Be antigen, which was more prevalent in men than women. Antibodies to HBsAg (anti-HBs) and to hepatitis B core antigen (anti-HBc) were found in about 71% of men and women prostitutes. Hepatitis B virus markers were more prevalent in men than in women prostitutes. Compared with other people, prostitutes had a significantly greater prevalence of hepatitis B virus markers. This study strongly suggested the importance of sexual transmission of infection with hepatitis B virus in a country where infection is endemic.
Antibodies, Viral↗
Physiologic and pharmacologic characterization of a novel group of substantia nigra zona reticulata neurons involved in striatal dopamine regulation.
The physiologic and pharmacologic characteristics of a novel group of substantia nigra zona reticulata (SNR) neurons were studied using standard electrophysiologic techniques in lightly pentobarbital anesthetized rats. Microinjection of dopamine (DA) into the caudate nucleus (CN) (25-40 micrograms) sufficiently activated these SNR cells. Application of the inhibitory amino acid, glycine (7 micrograms), into the substantia nigra zona compacta (SNC) simultaneously suppressed compacta neuronal discharges and enhanced CN activities. Direct nigral injection of the glycine-antagonist, strychnine (5 micrograms), on the other hand, resulted in a parallel decrease in CN activities and an increase in SNC discharges. The glycine/strychnine effects on CN were blocked by haloperidol (100 micrograms/kg, i.p.) pretreatment. These observations suggested that this novel group of SNR cells may participate in the striatonigral feedback regulation of caudate DA contents. Furthermore, these reticulata neurons may exert a tonic inhibition on the compacta cells, possibly using glycine as the putative neurotransmitter. Pharmacologically, morphine (5 mg/kg, i.v.) may promote a suppression of spontaneous CN activities by simultaneously exciting the DA-containing SNC nigrostriatal neurons and inhibiting these novel SNR neurons, in a process that was reversed by naloxone (1 mg/kg, i.v.).
Animals↗
Suppressor cell function in renal failure and transplant patients.
Suppressor cell function was assessed in 13 patients with chronic renal failure not on dialysis, 10 patients on regular hemodialysis and 11 renal transplant patients by means of the Concanavalin A inducible Suppressor Cell Assay. The mean Suppression Index (S.I.) in the undialysed patients (0.76 +/- 0.39) and those of the dialysed patients (0.72 +/- 0.18) were not significantly different from the 25 healthy controls (0.68 +/- 0.22). However the S.I. in the renal transplant patients (1.11 +/- 0.41) was significantly different from the normal controls as well as the undialysed and dialysed patients. Although there was no correlation between S.I. and age, post transplant follow up period, serum creatinine concentration, prednisolone or azathioprine dosage it is likely that the cause of the impaired suppressor cell function was due to the immunosuppressive agents used.
Adult↗
HLA and insulin dependent diabetes mellitus in Singaporean Chinese.
Singaporean Chinese IDDM was significantly associated with AW33, BW58, DR3 and DR4. AW33, BW58 and DR3 being in strong linkage disequilibrium among the Chinese, were associated most strongly with IDDM whose onset was less than or equal to 10 years. The strength of this association showed a significant inverse relationship with age of onset. The frequency of DR4 was significantly elevated on in the 11-20 year IDDM group. The importance of DR3 in Chinese IDDM was also reflected in the observations of joint occurrences of DR antigens. In the less than or equal to 10 years subgroup, the significant association were either DR3/DRW9, DR3/DR4 or DR3/BLANK. In the 11-20 years subgroup, DR4 appeared to be more important and DR4/DR3 and DR4/BLANK were strongly associated with IDDM in this subgroup.
Adolescent↗
HLA and Chinese patients with juvenile onset diabetes mellitus.
The HLA profile of 147 Chinese patients with juvenile onset diabetes mellitus was studied. There were HLA associations related to different age of onset of the disease. The patients who presented during the first decade of life had strong linkages with AW 33, B 17 and BW 22 (BW 54/55) but a weak association with DR 4. In contrast, patients whose age of onset ranged from 31 to 39 years had increased frequency of BW 46. Patients with diabetic complications (retinopathy, nephropathy, neuropathy and peripheral vascular disease) which were present singly or in combination were associated with HLA AW 33 and B 17. It would appear that genetic factor may be related to both the age of onset of diabetes as well as to the development of complications.
Adolescent↗
HLA-DR antigens in Chinese children with insulin-dependent diabetes mellitus.
We studied the distribution of HLA-DR and MT1, MT2, MT3 genotypes in 23 Chinese children with insulin-dependent diabetes mellitus (IDDM). The frequency of DR3 was 48% in IDDM children compared to 14% of normal controls (corrected p = 0.0098, RR = 5.70). The frequency of DR4 was not increased. These differences when compared with the results of Western populations may contribute to the relative rarity of IDDM among Chinese children.
Adolescent↗
Multiple roles of nucleus reticularis gigantocellularis in physiologic and pharmacologic regulation of cardiovascular functions.
This communication summarizes results from our laboratory during the past few years indicating that the nucleus reticularis gigantocellularis (NRGC) in the medulla oblongata plays an active role in the physiologic and pharmacologic regulation of cardiovascular functions. Apart from directly eliciting hypotension and cardioinhibition, the NRGC also assumes a modulatory role on the baroreceptor reflexes. Some gigantocellular reticular neurons exhibit electrophysiologic properties of cardiovascular neurons (neurons that alter their discharge frequencies in response to arterial pressure fluctuations), while others manifest cardiac rhythm-related activities. Pharmacologically, this reticular nucleus may be engaged by the centrally-acting antihypertensive agent, clonidine (Catapres, Boehringer Ingelheim), to produce hypotension and bradycardia. It may also participate in the cardiovascular suppressive effects of morphine and endogenous opioid peptides.
Animals↗
Some experimental pain indices and their applications in the study of analgesic mechanisms.
This communication presents some insights into the controversies and complications in experimental pain research using laboratory animals. In particular, I have singled out two experimental pain indices that are used in my laboratory for a decade, viz, dental pain model and hot-plate algesiometric assay for discussion. Using these two models, my colleagues and I have identified that morphine may promote analgesia by enlisting synergistic actions from the central cholinergic and dopaminergic systems, in a process that involves shifting of balance between various neurotransmitter systems. We confirmed the medullary nucleus reticularis gigantocellularis as a site for clonidine- and morphine-induced and stimulation-produced antinociception. Finally, a progressive increase in pain sensitivity and a gradual reduction in the analgesic potency of morphine and clonidine are unveiled in aging rats.
Analgesia↗