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Biomedical subjects

S M Chen

Publications and source records attributed to S M Chen.

At least 163 records · Page 9Linked to original sources
PubMed1975

Changes in brain hydrolytic enzyme activities in rats treated with cholesterol biosynthesis inhibitor, AY9944.

Intraperitoneal administration of AY9944 causes accumulation of 7-dehydrocholesterol, appearance of abnormal neuronal cytoplasmic lamellar inclusions containing acid phosphatase activities, and degeneration of oligodendroglial cells. In the present study, we attempted to correlate appearance and disappearance of abnormal inclusions, oligodendroglial degeneration, activities of lysosomal enzymes, and accumulation of 7-dehydrocholesterol. One group of 5-day-old rats received daily injection of AY9944, 30 mg/kg, for 30 days. Other groups received the same daily dosage but only in 10 consecutive days, starting from 5, 15, 25, and 35 days, respectively. Activities of 13 brain hydrolytic enzymes were determined. In the first group, activities of most enzymes increased over the controls, reaching the peak between the 15th and 25th day, corresponding to the maximum appearance of the neuronal inclusions and degenerating oligodendroglia. Despite the continued administration of AY9944 and the high tissue concentration of 7-dehydrocholesterol, activities of most enzymes declined after 25 days to relatively steady levels somewhat higher than controls. In the group which received 10-day injections, enzyme activities reached the peak at the end of the injections and then rapidly returned to normal within 10 days thereafter, corresponding to the appearance and disappearance of the abnormal inclusions. However, 7-dehydrocholesterol continued to increase for 10 days after the drug administration was discontinued. AY9944 had no direct effect on any of the enzymes in vitro. There appears to be generalized lysosomal activation concomitant with formation of abnormal neuronal inclusions in the experimental conditions.

Animals↗
PubMed1975

Effect of hypocholesterolemic drug AY9944 on cultured nervous tissue: morphologic and biochemical studies.

The effects of different concentrations of the hypocholesterolemic drug AY9944, an inhibitor of delta7-reductase, on organotypic cultures of fetal mouse spinal cord, were studied by light and electron microscopy. Exposure to 10(-6)M produced no observable changes. After 6 hours exposure to 10(-4)M, dense membrane-bound inclusions were occasionally observed in neurons. After 24 hours exposure to 10(-4)M, numerous cytoplasmic inclusions occurred in neurons, glia and macrophages. The form of these inclusions varied but were predominantly of two types; concentric, loosely-packed lamellae resembling membranous cytoplasmic bodies (MCB) of Tay-Sachs disease and irregular dense bodies. They were identical to those observed in our previous in vivo study. Prolonged exposure to the drug at 10(-4)M caused an increased number of inclusions in all cell types. Eventually the cultures degenerated. The number of inclusions increased for at least 38 days following a 2-5 day exposure to AY9944 at 10(-4)M. However, by 70 days, although inclusions persisted, the cultures were mostly astrocytic. In long-term cultures, in addition to these inclusions, curved or straight electron-dense paired profiles were seen in some cells, presumably macrophages. Biochemical analysis of cultures exposed to 10(-4)M revealed the continuous presence of delta7, 24-cholesta-diene-3beta-ol and 7-dehydrocholesterol even after the drug wa removed from the cultures. In our previous animal experiments, intracytoplasmic inclusions and abnormal sterols with a double bond at the 7 position disappeared quickly after discontinuation of the drug. Therefore, the results obtained in our present in vitro experiments are different in this regard from the in vivo studies of AY9944.

Cholestadienols↗
PubMedDate not supplied

Second trimester maternal serum hCG level in an Asian population: normal reference values by ultrasound dating.

OBJECTIVE: To establish normative data of maternal serum chorionic gonadotropin (hCG) during the second trimester in an Asian population. METHODS: We measured the maternal serum hCG levels in 17,955 normal singleton pregnancies between 15 and 21 weeks of gestation. The gestation age was estimated by measurement of fetal biparietal distance (BPD) in all cases. Median values of hCG at various gestational weeks were calculated and the values of hCG were converted to multiple of median (MoM). The incidences of low MoM value and high MoM value were also calculated. RESULTS: The mean and median values of hCG were 57,153 mIU/ml and 50,120 mIU/ml, respectively, at 15 weeks of gestation and then decreased to 30,898 mIU/ml and 26,226 mIU/ml, respectively, at 21 weeks. We found 8.6% and 9.4% of normal singleton pregnancies have hCG MoM values >2.0 MoM and <0.5 MoM, respectively. CONCLUSIONS: Our report provides a normal reference data of second trimester maternal hCG levels by ultrasound dating in an Asian population.

Chorionic Gonadotropin↗
PubMedDate not supplied

An improved vector for the expression of proteins in all three translational reading frames.

We have constructed a novel vector (pN-7) that is capable of producing large amounts of recombinant proteins in E. coli and requires minimal manipulation for the construction of recombinant expression vectors. This expression vector (pN-7) contains the tightly regulated lambda pL promoter, cII ribosome binding site, and initiator condon ATG. The pN-7 vector also contains cleavage sites for the restriction enzymes SmaI, EcoRV, and HpaI that provide blunt ends in all three reading frames. Thus after cleavage with the appropriate restriction enzyme, this novel vector can be directly ligated to the DNA fragment that contains the open reading frame without further manipulation.

Base Sequence↗
PubMedDate not supplied

Computed tomography of an exophytic gastric hemangioma with torsion and intratumoral hemorrhage.

A case of exophytic gastric hemangioma with intratumoral bleeding due to torsion of the tumor pedicle is reported. A radiograph showed a mass without phleboliths. Computed tomography (CT) demonstrated a 14-cm mass with high densities due to hemorrhage, which was contiguous to the stomach and extended to the pelvis. The tumor showed no remarkable enhancement on post-enhanced CT due to torsion of the tumor pedicle.

Aged↗
PubMedDate not supplied

Ability of chronic wound fluids to degrade peptide growth factors is associated with increased levels of elastase activity and diminished levels of proteinase inhibitors.

The stability of peptide growth factors exposed to fluids from healing surgical wounds and from nonhealing chronic wounds was examined in vitro. (125)I-Labeled transforming growth factor-beta1 or platelet-derived growth factor-BB was incubated with fluids from healing surgical wounds and fluids from venous stasis or pressure ulcers. Fluids from healing surgical wounds had no appreciable effect on the level of (125)I corresponding to intact growth factor. In contrast, incubation with fluids from several venous stasis or pressure ulcers resulted in significant degradation of these growth factors. Degradation was blocked by broad-spectrum serine proteinase inhibitors and by specific inhibitors of neutrophil elastase. Levels of elastase activity in wound fluids correlated with the ability to degrade peptide growth factors. Further comparisons showed qualitative and quantitative differences in the endogenous proteinase inhibitors, alpha2-macroglobulin and alpha1-antiproteinase. These results could explain, in part, the variable growth factor levels which have been found in chronic wounds. More importantly, the ability of some chronic nonhealing wounds to rapidly degrade exogenously added growth factors has important implications with regard to past and future clinical attempts to use peptide growth factors to treat these types of problem wounds.

Journal Article↗
PubMedDate not supplied

Maternal serum screening for down syndrome by using alpha-fetoprotein and human chorionic gonadotropin in an asian population. a prospective study.

The purpose of the present study is to evaluate the efficacy of second-trimester maternal serum screening program by using alpha-fetoprotein (AFP) and total human chorionic gonadotropin (hCG) in an Asian population. During June 1994 to July 1998, we conducted a prospective study of serum screening protocol for Down syndrome. The cut-off point for a positive result in this analysis was a risk of >/=1/270. A total of 17,742 pregnant women with singleton pregnancy were screened, and 1,153 (6.5%) had positive result. Sixteen of the 17,742 pregnancies had Down syndrome, and 10 of them had positive result. The positive rate and detective rate for Down syndrome were 6.5 and 62.5%, respectively. However, the detective rate will reduce to 47.6% after being adjusted by age-specific risk. It is indicated that the double-marker test using AFP and total hCG is an effective screen strategy for second-trimester detection of Down syndrome in Asian women.

Adult↗
PubMedDate not supplied

An experimental study of the antitumour effect of bleomycin hydrochloride microcapsules.

The controlled release behaviour of bleomycin hydrochloride microcapsules was investigated by an in vitro dissolution method and an in vivo antitumour test. Bleomycin hydrochloride microcapsules prepared using the highest cooling rate exhibited sustained release characteristics and its release rate obeyed a nearly zero order release kinetics. Microcapsules containing bleomycin hydrochloride were locally injected into the solid tumour of uterine cervix carcinoma bearing nude mice. Tumour growth was markedly inhibited by treatment using bleomycin hydrochloride microcapsules compared to the control group and the group receiving direct local administration of bleomycin hydrochloride. No significant differences in the changes of body weight after treatment were found between the control group and the treated group. These results suggest that controlled release microcapsules may be applicable as a drug carrier for delivery of antitumour agents in cancer chemotherapy.

Animals↗
PubMedDate not supplied

Dual infection with Ehrlichia chaffeensis and a spotted fever group rickettsia: a case report.

Well-documented cases of simultaneous human infection with more than one tick-borne pathogen are rare. To our knowledge only two dual infections have been reported: simultaneous human infection with the agent of human granulocytic ehrlichiosis and Borrelia burgdorferi and simultaneous human infection with B. burgdorferi and Babesia microti (1-2). Rocky Mountain spotted fever has long been known to be endemic in North Carolina; cases of human ehrlichial infection were recognized there soon after Ehrlichia chaffeensis was recognized as an important cause of tick-borne disease in the southeastern United States. Because both Rocky Mountain spotted fever and ehrlichiosis are prevalent in North Carolina, occasional cases of simultaneous human infection by rickettsial and ehrlichial agents would not be surprising; however, no such cases seem to have been reported.

Adult↗
PubMedDate not supplied

Type I primary hyperoxaluria associated with type I renal tubular acidosis.

An 8-year-old boy who had suffered from recurrent stone formation since the age of 4 years, was admitted as an emergency due to anuria for a half day on November 20, 1986. Kidney-ureter-bladder film showed that the urethra was obstructed by a stone, and emergent cystoscopy was performed to remove it. He is the product of consanguinous marriage, his parents being first cousins. There was no family history of renal stone. Laboratory investigations showed hypokalemic, hyperchloremic metabolic acidosis. The ammonium chloride loading test revealed inability to acidify the urine and a markedly decreased excretion of titrable hydrogen ion and ammonium ion in the urine. These results indicate that this is a case of Type I renal tubular acidosis. His 24-hour urinary excretion of oxalate and glyoxylate were also markedly increased. There were no underlying causes leading to the development of secondary hyperoxaluria. These results also establish the diagnosis of Type I primary hyperoxaluria. The patient then received regimens of Polycitra 1ml/kg/day and Vitamin B6 50mg/day for 4 months. However, urinary stone developed again in this patient 4 months later. To our knowledge, Type I primary hyperoxaluria in association with Type I renal tubular acidosis has not been previously reported.

Acidosis, Renal Tubular↗