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Biomedical subjects

M F Chen

Publications and source records attributed to M F Chen.

At least 379 records · Page 21Linked to original sources
PubMed1979

A radiometric microbiologic assay for the biologically active forms at niacin.

A radiometric microbiologic assay has been developed for the determination of niacin in biologic fluids. Lactobacillus plantarum produced 14CO2 from L-[U-14C] hr malic acid in quantities proportional to the amount of niacin present. The assay is specific for the biologically active forms of niacin in humans. Thirty normal hemolysates were analyzed and the values ranged from 13.0 to 17.8 micrograms niacin/ml RBC (mean = 15.27 +/- 1.33 s.d.). Good recovery and reproducibility studies were obtained with this assay. On thirty blood samples, correlation was excellent between the radiometric and the conventional turbidimetric assays.

Animals↗
PubMed1978

Rapid radiometric susceptibility testing of Mycobacterium tuberculosis.

A 48-hour radiometric test for determining the drug susceptibility of Mycobacterium tuberculosis has been developed. The test is based on the measurement of 14CO2 produced by the oxidation of formate labeled with carbon-14. The test system uses 5 X 10(7) organisms in 1 ml of Middlebrook 7H9 medium plus albumin-dextrose-catalase enrichment and 1 muCi of [14C]formate. The 14CO2 produced is measured in an ionization chamber at 24-, 48-, and 72-hour intervals, with and without the addition of antituberculous drugs. Isoniazid, streptomycin, rifampin, and ethambutol were each tested at 3 concentrations by the radiometric method and the reference (agar dilution) method. Six standard strains and 21 patient isolates were compared by both methods. Production of 14CO2 was quantitatively decreased in the presence of drugs that inhibit the organism. The radiometric method requires 2 days; the agar dilution, 14 to 21 days.

Antitubercular Agents↗
PubMed1978

Measurement of folates in human plasma and erythrocytes by a radiometric microbiologic method.

A radiometric microbiologic assay for the determination of folic acid in human plasma and red blood cells is described. The assay is based upon the measurement of 14CO2 produced from the metabolism of [1-14C] gluconate by Lactobacillus casei. The 14CO2 evolved was shown to be proportional to the amount of added DL-N-5-methyltetrahydrofolage (DL-N-5-methyl FH4). A total of 26 normal plasma and 57 blood hemolysates were assayed in parallel by this radiometric and the standard (turbidimetric) microbiologic assay. The correlation coefficients for the two assays were r = 0.96 for plasma and r = 0.98 for red-cell folate. Lyophilization of L. casei was found to simplify this radiometric assay by eliminating routine maintenance and culture of this microorganism.

Biological Assay↗
PubMed1977

A radiometric microbiologic method for vitamin B12 assay.

A radiometric microbiologic method was developed for assaying vitamin B12 in human serum. In the presence of 14C-arginine and cyanocobalamin, Lactobacillus leichmannii produced significant amounts of 14CO2 within 16-20 hr. The amount of 14CO2 evolved was optimized with the use of guanido-labeled arginine and is proportional to the amount of cyanoco-balamin added. The method gave satisfactory recovery of added vitamin B12 to sera, and it gave values comparable to the standard microbiologic (turbidimetric) method using L. leichmannii. The radiometric microbiologic method allowed elimination of several steps considered essential in the standard microbiologic methods: (A) Extraction of vitamin B12 bound to serum proteins could be accomplished in one autoclaving step with the assay medium at 15 psi for 3-5 min; (B) The precipitated serum proteins did not need to be separated, since they do not interfere with this assay,

Arginine↗
PubMed1975

Inhibitors of nucleoside transport. A structure-activity study using human erythrocytes.

The passage of nucleosides across the plasma membrane of erythrocytes is a membrane-mediated process which is strongly inhibited by derivatives of 9-beta-D-ribofuranosylpurine (1) with S, O, or N atoms at the purine 6 position bearing variously substituted arylalkyl groups. In this structure-activity study, nucleoside derivatives were compared in respect to their ability to inhibit a transport-dependent aspect of nucleoside metabolism in erythrocytes, the synthesis of inosine from external guanosine and hypoxanthine. 6-Benzylthio, 6-benzylamino, and 6-benzyloxy derivatives of 1 were inhibitory at 10(-5)-10(-6) M and the similarity of their activities suggested that alkylation of the transporter as the mechanism of transport inhibition was unlikely. The hydrophobicity of the 6-position substituents appeared to contribute importantly to inhibitory activity. Although replacement of the ribofuranose moiety by other sugars reduced inhibitory activity, compounds with 9-butyl groups were inhibitory. 6-[(2-Hydroxy-5-nitrobenzyl)thio] derivatives of 1 were the most potent of the inhibitors tested, being active at about 10(-7) M.

Adenosine↗
PubMedDate not supplied

Nicotine-induced neuroepithelial cell changes in young rabbits: a preliminary communication.

Nicotine, 1 mg/kg body weight/day, was injected subcutaneously in 3 female rabbits during gestational and lactating periods, and the lungs of the offspring were studied by scanning and transmission electron microscopy (SEM and TEM) on days 5, 10, and 25 postpartum. Three other female rabbits served as controls. The size and number of neuroepithelial bodies (NEB) as estimated by SEM were larger in the experimental group than in the control group, especially on days 5 and 25. Moreover, the NEB in the nicotine-exposed groups showed loss of normal boundaries and derangement of cells and granules by TEM. Neural components also became prominent. These findings suggest that chronic maternal exposure to nicotine may directly, or, through the neural route, indirectly induce hyperplasia and dysplasia of the NEB in the offspring of rabbits. Because NEB are suspected to regulate regional bronchial and vascular smooth muscle cells, such alterations may be similar to respiratory functional impairments found in infants of mothers who smoke.

Animals↗
PubMedDate not supplied

Human fetal lung changes associated with maternal smoking during pregnancy.

Pulmonary impairment in the offspring of smoking mothers is well documented by epidemiologic studies. The morphologic bases for the functional impairment are largely unexplored. We studied 17 infant lungs obtained at autopsy, ten from smoking (group 1) and seven from nonsmoking (group 2) mothers, by light (LM), transmission (TEM), and scanning electron microscopy (SEM). By LM, the alveolar mean linear intercept was similar in both groups; the total lung volume and alveolar surface area increased with the increase in gestational age in all lungs studied. By SEM, the sizes of the neuroepithelial bodies (NEB) were larger in group 1 than in group 2. By SEM and TEM, ciliated cells were increased, but the amount of dense core granules was decreased, in the NEB of the smoking group. Maternal smoking during pregnancy appears to alter the size and cellular composition of fetal NEB. The detailed mechanisms of the alteration in NEB and their implications are unclear from this study and needed further clarification.

Female↗
PubMedDate not supplied

Effects of highly selective vagotomy and additional procedures on gastric emptying in patients with obstructing duodenal ulcer.

A solid gastric emptying study was conducted on 46 patients more than 1 year after highly selective vagotomy (HSV) and additional procedures for obstructing duodenal ulcer and on 21 patients after HSV alone for uncomplicated duodenal ulcer. The additional procedures included dilatation (n = 14; HSV + D group), Holle pyloroplasty (n = 14; HSV + P group), and Jaboulay gastroduodenostomy (n = 18; HSV + GD group). The test meal consisted of two eggs labeled with 99mTc sulfur colloid, two slices of white bread toast, and 300 ml of orange juice (total 322 kcal). Gastric emptying curves and emptying parameters (t1/2, half emptying time; lag phase, TLAG; emptying rate, k; and beta value) were compared with those of 17 healthy volunteers, the normal control group. The patients after HSV alone had an almost normal gastric emptying. The HSV + D group showed a significant delay from minute 45 to the end of the emptying curve, corresponding to a longer t1/2 (p = 0.02), and a slower emptying rate (p = 0.029). The HSV + P group approached a nearly normal emptying curve, corresponding to an insignificant difference in emptying parameters. The HSV + GD group had significantly faster emptying from minute 15 to the end of the emptying curve, corresponding to a faster t1/2 (p = 0.0005), a shorter lag phase (p = 0.027), and a faster emptying rate (p = 0.021). Recurrent ulcerations were noted in one patient (4.8%) of the HSV alone group, five (35.7%) of the HSV + D group, one (7.1%) of the HSV + P group, and one (5.6%) of the HSV + GD group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Change of gastric liquid emptying after highly selective vagotomy and pyloric dilatation for patients with obstructing duodenal ulcer.

Gastric liquid emptying was studied in duodenal ulcer patients with and without stenosis before highly selective vagotomy (HSV) and 1 week, 3 months, and 1 year after. The test meal consisted of 1 mCi of 99m Technetium-diethylene penta-acetic acid (DTPA) in 500 ml of isotonic saline. The patients were divided into 2 groups: group 1 (16 cases) without clinical stenosis, who underwent HSV alone, served as control; group 2 (14 cases) with mild to moderate stenosis, who underwent HSV and transgastric dilatation to 20 mm in diameter. Before HSV, the stenotic group showed a significantly slower liquid emptying than the nonstenotic. Most of the stenotic group could resume a normal diet quickly after operation, but they still had prolonged liquid emptying. At 3 months, the emptying curve of the stenotic patients had approached that of the preoperative controls without a significant difference, while the nonstenotic patients showed an accelerated initial emptying. Although there was a significant improvement with the appearance of accelerated initial emptying at 1 year, the stenotic group still demonstrated slightly slower emptying than the nonstenotic group. A temporary state of preexistent gastric atony due to chronic outlet obstruction may explain the delayed emptying in the early postoperative period; however, minor residual resistance in the fibrotic, scarred tissue was postulated to be persistent despite dilatation, and responsible for the slower emptying of the stenotic than the nonstenotic group at 1 year.

Adult↗