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Biomedical subjects

J Chan

Publications and source records attributed to J Chan.

At least 307 records · Page 17Linked to original sources
PubMed1978

Continuity of electron histochemically demonstrable substances in the basal lamina, the ground substance of the connective tissue and the intercellular spaces of eptihelial cells of rat gingiva.

Rat gingiva was examined in the electron microscope for substances reactive to ruthenium red and lanthanum nitrate. Both reagents produced an electron-dense band in the basal lamina where the lamina lucida could not be distinguished from the lamina densa. There was continuity between this electron-dense material and that in the ground substance of the adjacent connective tissue and the intercellular spaces of the adjacent epithelial cells. It was concluded that the lamina lucida is not a simple fluid space but is occupied by histchemically demonstrable substances, probably proteoglycans, and that there is a continuum of histochemically demonstrable proteoglycan through which metabolites pass between the blood vessels of the connective tissue and the epithelial cells.

Animals↗
PubMed1975

Effect of uridine diphospho-N-acetylglucosamine and sodium salicylate on L-glutamine-D-fructose-6-phosphate aminotransferase activity from rat gastric mucosa.

Mechanisms of inhibitory action of sodium salicylate on L-glutamine-D-fructose-6-phosphate aminotransferase, prepared from rat gastric mucosa, were studied. Sodium salicylate at lower concentrations (10-20 mM) inhibited reversibly aminotransferase activity by competing with fructose-6-phosphate. At higher concentrations, sodium salicylate inactivated the enzyme irreversibly, with an inactivation rate following first-order kinetics with respect to the enzyme concentration. Uridine-5'-diphospho-N-acetylglucosamine is an endogenous feedback inhibitor. It inhibited the aminotransferase-catalyzed reaction also by competing with fructose-6-phosphate but with an inhibiting activity 1000 times that of sodium salicylate. Uridine-5'-diphospho-N-acetylglucosamine reduced the salicylate inhibition of the enzymic reaction and protected the enzyme from salicylate-induced irreversible inactivation. At a fixed concentration of uridine-5'-diphospho-N-acetylglucosamine (7x10(-6)M), an increase of salicylate concentration produced an increase in enzyme activity as compared with the control.

Animals↗
PubMed1975

Intraoperative bacterial transmission.

A clinical evaluation of bacterial penetration through operating room gowns was made during 100 general surgical procedures. A comparison of the degree of penetration through the standard cloth and a commercially available disposible gown was carried out. Cloth gowns, even in the dry state, were shown to be ineffective bacterial barriers. In addition, routine laundering of scrub suits failed to eliminate pathogenic bacteria.

Alkenes↗
PubMedDate not supplied

Mycoplasma hominis septic thrombophlebitis in a patient with multiple trauma: a case report and literature review.

Mycoplasma hominis was recovered from the site of a septic thrombophlebitis on the left cephalic veins of a patient with pelvic and other multiple trauma. The organisms were initially isolated from routine cultures in conventional blood agar media incubated anaerobically. The absence of other demonstrable pathogens and the patient's serologic response to the isolate support the role of the organism as the cause of this previously unreported mycoplasmal infection. M. hominis should be considered a possible cause of sepsis in selected cases of infections following pelvic trauma or manipulations of the genitourinary tract.

Adult↗
PubMedDate not supplied

Myocardial expression of endothelin-1 in murine Trypanosoma cruzi infection.

Chagas' disease, caused by Trypanosoma cruzi, is an important cause of myocarditis and chronic cardiomyopathy and is accompanied by microvascular spasm and myocardial ischemia. We reported previously that infection of cultured endothelial cells with T. cruzi increased the synthesis of biologically active endothlein-1 (ET-1). In the present study, we examined the role of ET-1 in the cardiovascular system of CD1 mice infected with the Brazil strain of T. cruzi and C57BL/6 mice infected with the Tulahuen strain during acute infection. In the myocardium of infected mice myonecrosis and multiple pseudocysts were observed. There was also an intense vasculitis of the aorta, coronary artery, smaller myocardial vessels and the endocardial endothelium. Immunohistochemistry studies employing anti-ET-1 antibody revealed increased expression of ET-1 that was most intense in the endocardial and vascular endothelium. Elevated levels of mRNA for preproET-1, endothelin converting enzyme and ET-1 were observed in the same myocardial samples. Plasma ET-1 levels were significantly elevated in infected CD1 mice 10-15 days post infection. These observations suggest that increased levels of ET-1 are a consequence of the initial invasion of the cardiovascular system and provide a mechanism for infection-associated myocardial dysfunction.

Animals↗
PubMedDate not supplied

Adductor release in nonambulant children with cerebral palsy.

Historically, nonambulatory children with cerebral palsy represent a "group at risk" for spastic hip dislocation. We reviewed the effectiveness of adductor release and anterior obturator neurectomy in treating 86 hips at risk in 50 nonambulatory children. Results were judged by comparing the migration percentages measured on the preoperative, early postoperative, and final postoperative radiographs. Adductor release succeeded in preventing hip dislocation and obviating the need for further surgery in 80% of cases. Patients with preoperative uncoverage exceeding 50% were found to be at greater risk for deterioration of femoral head coverage despite adductor release. Unilateral adductor release had a negative effect on the nonoperated hip.

Cerebral Palsy↗
PubMedDate not supplied

Discrepancy between cytogenetic and FISH results on an amniotic fluid sample of 45,X/46,X,idic(Y)(p11).

The presence of abnormal ultrasound markers showing a thick nuchal fold with short middle phalanx of the fifth finger in an otherwise normal-appearing female fetus led to the sampling of amniotic fluid at 16 weeks gestation. Cytogenetic analysis with routine G-banding showed a 45,X karyotype in all 20 cells analysed from two flasks. However, fluorescent in situ hybridization on uncultured cells showed presence of a Y signal in 9 cells, 11 cells showing a single signal for the X. A cytogenetic analysis of the fetal blood at 23 weeks confirmed the presence of two cell lines, 45,X and 46,X, idic(Y)(p11). The couple opted to have the pregnancy terminated. However, the fetus was not available to carry out confirmatory tests.

Amniotic Fluid↗
PubMedDate not supplied

Effects of elbow flexion on radial nerve motor conduction velocity.

The position of the elbow while conducting motor studies of the radial nerve is generally extended (15) or slightly flexed (10), but little is known about the effects of elbow flexion on the radial motor conduction velocity. We attempted to measure the effects of the elbow position on the radial motor conduction velocity, as well as directly measure the change in the length of the nerve at different elbow positions in the cadaver. In addition, we established normal values for the radial F-wave with the recording electrode on the extensor indicis proprius muscle. Radial motor nerve conduction was studied in 25 normal subjects to evaluate the effect of 3 different elbow positions (0 degree, 45 degrees, and 90 degrees) on motor conduction velocity (MCV) across the elbow. Direct (in situ) radial nerve measurements were performed on four cadaver specimens to compare changes in nerve length during elbow flexion. Normal values for radial F-wave latencies recording from the extensor indicis proprius muscle were also determined in 23 subjects. The radial MCV decreased significantly as the elbow flexed from 0 degree to 90 degrees. The normal range of values for radial motor nerve conduction at 0 degree of elbow flexion was 71.7 +/- 4.7 m/s, 68.9 +/- 4.9 at 45 degrees of elbow flexion, and 62.0 +/- 6.4 m/s at 90 degrees elbow flexion. Actual (in situ) radial nerve measurements were also found to decrease in length as the elbow flexed. The minimal radial F-wave latency was 19.8 +/- 3.7 milliseconds. For routine determination of motor nerve conduction velocity across the elbow, we recommend that the elbow be fully extended, as the distance measurement most accurately reflects the maximum anatomic length of the nerve. We also feel that the radial nerve F-wave latency is readily obtainable from the extensor indicis proprius muscle.

Adult↗
PubMedDate not supplied

Diagnostic accuracy of preoperative CT scanning of pituitary prolactinomas.

Between 1980 and 1985, 102 patients (84 women and 18 men) who had coronal CT scans of the sella turcica for suspected prolactin adenoma underwent transsphenoidal exploration. The CT examinations were performed with a fourth-generation EMI scanner (CT 7070), and reports of the preoperative CT examinations were compared with the findings at transsphenoidal exploration. The same neurosurgeon performed all the operations. In 97 patients distinct adenomas were found at surgery, among which were 36 macroadenomas (diameter larger than 10 mm) and 62 microadenomas (one patient had two coexisting microadenomas). All macroadenomas were identified correctly on the preoperative CT scans. Preoperative CT scans correctly localized 58 microadenomas in 57 of 62 patients, for a sensitivity rate of 91.9%; this included correct localization in four patients with recurrent microprolactinomas and in the one patient with two coexisting adenomas. Three patients in whom the adenomas were found in a location other than that reported on the preoperative CT scan were considered to have false-negative scans for the purpose of statistical calculations; two other false negatives occurred in patients whose scans had been interpreted as entirely normal and who were subsequently found to have adenomas at operation. Four patients had negative surgical explorations and the preoperative CT scan was correct in one, for a specificity of 25%. The overall accuracy rate was 92.1% for the entire group of patients and 87.7% for the subgroup of microadenomas. In our experience, coronal CT scanning has high diagnostic accuracy in patients with pituitary prolactinomas.

Adenoma↗