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Biomedical subjects

S Chen

Publications and source records attributed to S Chen.

At least 1,423 records · Page 79Linked to original sources
PubMed1988

Human monoamine oxidase gene (MAOA): chromosome position (Xp21-p11) and DNA polymorphism.

An essentially full-length cDNA clone for the human enzyme monoamine oxidase type A (MAO-A) has been used to determine the chromosomal location of a gene encoding it. This enzyme is important in the degradative metabolism of biogenic amines throughout the body and is located in the outer mitochondrial membrane of many cell types. Southern blot analysis of PstI-digested human DNA revealed multiple fragments that hybridized to this probe. Using rodent-human somatic cell hybrids containing all or part of the human X chromosome, we have mapped these fragments to the region Xp21-p11. A restriction fragment length polymorphism (RFLP) for this MAOA gene was identified and used to evaluate linkage distances between this locus and several other loci on Xp. The MAOA locus lies between DXS14 and OTC, about 29 cM from the former.

Alleles↗
PubMed1988

Basal joint reconstruction in a punch injury of the hand.

Severe hand trauma caused by an industrial accident resulted in composite tissue loss in the basal joint area of the right hand. The crushed metacarpal bone was replaced, and ligamentous and capsular reconstruction was performed with flexor carpi radialis tendon and additional tendon graft. We present our experience, with a follow-up of one year and eight months.

Accidents, Occupational↗
PubMed1988

Human placental acetylcholine content and release at parturition.

1. Measurements were made of human placental acetylcholine (ACh) content and release into maternal and fetal circulations from placenta obtained before, during and after labours of both spontaneous and induced onsets. ACh content was determined in ex vivo placental biopsies using a radio-enzymatic assay. ACh release was determined by bioassay of the effluent from placental lobules perfused with amniotic fluid-like Kreb's containing physostigmine (2.4 mumol/l). 2. ACh content of placentae obtained after labour (spontaneous onset of labour, normal vaginal delivery) and during labour (spontaneous onset of labour, Caesarean section delivery) was significantly less than before labour (no labour onset, Caesarean section delivery). 3. Mean ACh output into maternal vessels 1.5-4.0 h after commencement of perfusion of placentae obtained after labour (spontaneous onset of labour, normal vaginal delivery) was significantly less than from those obtained before labour (no labour onset, Caesarean section delivery). No differences were found in ACh output into fetal vessels of placentae obtained before, during or after labour. 4. These results suggest a role for placental ACh in the events of human labour. The decrease in ACh content and maternal vascular release in placenta obtained after labour is consistent with a depletion of placental ACh during labour which may indicate ACh release at this time. The lack of any significant change in fetal vascular release of ACh in placenta obtained before, during or after labour, raises the possibility of different roles for ACh released into fetal and maternal vasculature.

Acetone↗
PubMed1988

Structural features of human monoamine oxidase A elucidated from cDNA and peptide sequences.

Monoamine oxidase (MAO), an important enzyme for the degradation of amine neurotransmitters, has been implicated in neuropsychiatric illness. The amino acid sequence for one form of the enzyme, MAO-A, has been deduced from human cDNA clones and verified against proteolytic peptides. The covalent binding site for the flavin adenine dinucleotide (FAD) cofactor is near the C-terminal region. The presence of features characteristic of the ADP-binding fold suggests that the N-terminal region is also involved in the binding of FAD. These cDNAs should facilitate the study of the structure, function, and intracellular targeting of MAO, as well as the analysis of its expression in normal and pathological states.

Adenosine Diphosphate↗
PubMed1988

Multiple insertions and tandem repeats of origin-minus simian virus 40 DNA in transformed rat and mouse cells.

Stable simian virus 40 (SV40) transformation requires integration and expression of the early region of the SV40 genome. We have examined the amount and state of integrated viral DNA of SV40-transformed NIH 3T3 mouse and F2408 rat fibroblast lines generated by transfection with either wild-type or origin-defective SV40 DNA. A functional SV40 replication origin was not required for multiple inserts and partial-repeat structures to form in NIH 3T3 mouse transformants. In contrast, partial repeats in F2408 rat transformants were rare when the SV40 replication origin was intact and not detected at all when it was defective.

Animals↗
PubMed1987

Determination of 6-(2'-chlorophenyl)-4-hydroxy-4H-imidazo[1,5-a] [1,4]benzodiazepine-3-carboxamide, a mixed agonist-antagonist anxiolytic agent, in human plasma and urine by gas chromatography-negative-ion chemical-ionization mass spectrometry.

A simple, sensitive and specific assay was developed for the determination in plasma and urine of 6-(2'-chlorophenyl)-4-hydroxy-4H-imidazo[1,5-alpha] [1,4]benzodiazepine- 3-carboxamide, compound I, a mixed agonist-antagonist anxiolytic agent. A hexadeuterated analogue of the compound was added to plasma or urine as the reference standard. The titled compound was extracted with benzene at pH 11. Following evaporation of the solvent, the residue was reacted with pentafluoropropionic anhydride in the presence of triethylamine. The derivatizing reagents were evaporated, and the carbonitrile derivative of the analyte was extracted into ethyl acetate at pH 11. The residue remaining after removal of the ethyl acetate was silylated with bis(trimethylsilyl)trifluoroacetamide, and a portion of this solution was analyzed by gas chromatography-negative-ion chemical-ionization mass spectrometry. The mass spectrometer was set to monitor, in the gas chromatographic effluent, the M-. ion of the titled compound and its hexadeuterated reference standard. The ratio of these two ions was calculated and converted to a concentration of analyte using a calibration curve that was generated from the analyses of control plasma fortified with various amounts of analyte and a fixed amount of the hexadeuterated reference standard. The limit of quantitation of the assay was 1 ng/ml for plasma and urine.

Anti-Anxiety Agents↗
PubMed1987

A lymphoproliferative abnormality associated with inappropriate expression of the Thy-1 antigen in transgenic mice.

The Thy-1 antigen is a cell-surface glycoprotein of unknown function expressed on mouse T lymphocytes, neurons, and hematopoietic stem cells. To alter the normal pattern of Thy-1 expression during hematopoietic differentiation, we created transgenic mice using a hybrid Thy-1 gene containing a transcriptional enhancer of the mouse immunoglobulin heavy chain gene (E mu). Strains of mice bearing the Thy-1.2/E mu gene express the Thy-1.2 antigen on mature B lymphocytes and their progenitors, and develop a heritable lymphoid hyperplasia characterized by massive expression of the Thy-1.2 antigen in the bone marrow and lymph nodes. The phenotype associated with inappropriate developmental regulation of the Thy-1 gene suggests that the Thy-1 antigen may play a role in inducing activation or differentiation events on early lymphocyte progenitor cells.

Animals↗
PubMed1987

Determination of (E)-1,2,3,4-tetrahydro-1,1,4,4-tetramethyl-6-(1-methyl-2- phenylethenyl) naphthalene, an antiacne agent, and its phenolic metabolite in plasma by reversed-phase high-performance liquid chromatography.

A rapid, sensitive and selective high-performance liquid chromatographic (HPLC) assay was developed for the determination of (E)-1,2,3,4-tetrahydro-1,1,4,4-tetramethyl-6-(1-methyl-2- phenylethenyl)naphthalene (I) and its phenolic metabolite, (E)-4-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-2- methylethenyl]phenol (II) in plasma. The assay for both compounds involves precipitation of the plasma proteins with acetonitrile, followed by extraction of the entire mixture into methyl tert.-butyl ether and subsequent analysis by reversed-phase HPLC. The overall recovery of I and II was 96.9 +/- 5.3 and 96.2 +/- 5.8% for dog plasma, 80.0 +/- 4.0 and 93.5 +/- 5.0% for human plasma and 97.4 +/- 2.9 and 97.6 +/- 9.6% for rat plasma, respectively. The sensitivity limit is 20 ng/ml of plasma for both compounds I and II using UV detection at 280 nm. The HPLC assay was used in studies in the dog and in the rat.

Acne Vulgaris↗
PubMed1987

Complications of chronic indwelling urinary catheters among male nursing home patients: a prospective study.

We studied prospectively the incidence of symptomatic infections of presumed urinary tract origin requiring antimicrobial therapy among 54 male nursing home patients with chronic indwelling bladder catheters. During 514 patient-months at risk there were 106 episodes of symptomatic infection, for an incidence of 0.21 per patient-month at risk. Of the patients 80 per cent had at least 1 episode and 48 per cent had 2 or more. None of the clinical factors we examined, including age, nutritional status, stool incontinence, diabetes mellitus, episodes of catheter blockage and the use of chronic suppressant antimicrobial therapy, was associated with the development of symptomatic infection. Further research on host and pathogen-related factors that increase the risk for symptomatic infection, and improvements in infection control and catheter care protocols are necessary to decrease catheter-associated morbidity among male nursing home patients who must be managed by chronic indwelling catheterization.

Catheters, Indwelling↗
PubMed1987

Protein, lactose and fat concentration of breast milk of mothers of term and premature neonates.

The protein, lactose and fat concentrations in the milk of seven mothers giving birth at term and six mothers giving birth prematurely were determined. Samples were obtained during the first 31 days of lactation. The protein, lactose and fat concentrations of preterm milk were found to be similar to those of fullterm milk over this period. For both term and preterm groups, protein concentration decreased with increasing age, while lactose concentration increased. Fat concentration did not show a consistent pattern of change in the preterm group, but tended to increase with advancing age in the term group.

Adult↗
PubMed1987

External catheter use and urinary tract infections among incontinent male nursing home patients.

In order to examine the relative frequency of urinary tract infection (UTI) and bacteriuria among male nursing home patients managed with and without external catheters (EC), we prospectively followed four cohorts of patients (EC worn continuously, N = 30; EC worn at night only, N = 19; incontinent without catheter, N = 13; and continent, N = 30) for a total of 497 patient months at risk. The proportion of patients with EC worn continuously who had at least one episode of bacteriuria (87%) and at least one UTI (40%), and the incidence of UTI (0.08 episodes per patient-month at risk) was significantly higher than among continent or incontinent patients without EC. Patients with EC at night only had an intermediate frequency of these findings. Differences in clinical and functional status characteristics among the four cohorts, in addition to the use of EC, could have contributed to the higher frequencies of bacteriuria and UTI. None of the clinical characteristics we examined were associated with the development of UTI among patients with EC. Further studies are necessary to identify factors associated with UTI among patients who are managed by EC so that effective preventive strategies can be developed and targeted to patients at high risk.

Aged↗
PubMed1987

Transformation of precrisis human cells by the simian virus 40 cytoplasmic-localization mutant pSVCT3 is accompanied by nuclear T antigen.

pSVCT3 is a cytoplasmic-localization mutant of simian virus 40 (SV40) isolated from the SV40 adenovirus 7 hybrid virus (PARA) and cloned into plasmid PBR. The large T antigen of pSVCT3 accumulates in the cytoplasm of infected monkey cells instead of being transported to the nucleus. The sole change in CT3 large T antigen is amino acid residue 128 (Lys----Asn). Transformation of precrisis rodent cells by pSVCT3 is negligible, whereas the frequency of transformation of established rodent cell lines by pSVCT3 is comparable to that of wild-type SV40. According to the model, in which transformation of precrisis cells involves the combined oncogenic action of both nuclear and cytoplasmic gene products, we predicted that pSVCT3 would localize in the cytoplasm of human cells and would therefore at most only partially and rarely transform precrisis human cells. We have found that pSVCT3 is able to transform precrisis human cells at high frequency. Furthermore, pSVCT3-transformed human precrisis cells relocalized T antigen to their nuclei. The relocalization of large T antigen was not dependent on cell growth. Wild-type and pSVCT3-transformed human cell lines both have about five copies of integrated SV40 DNA. SV40 virus-specific proteins, including the 100,000-molecular-weight super large T antigen, were expressed in pSVCT3-transformed human cells. Our results suggest that molecules in precrisis human cells, but not cells of other species, are able to complement the cytoplasmic-localization defect of the CT3 mutant large T antigen.

Animals↗