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Biomedical subjects

M S Lin

Publications and source records attributed to M S Lin.

At least 109 records · Page 6Linked to original sources
PubMed1985

Reduction of fragile X expression in blood after cryopreservation.

Frequency of fragile X expression was investigated before and after cryopreservation (-196 degrees C) in the blood of 4 affected males, 3 fragile X carriers and in a fibroblast cell strain from a fragile X male fetus. The results indicate that there is a significant decrease (p less than 0.05) in the frequency of the fragile X expression in lymphocytes after cryopreservation, as compared to the fresh blood, but not in fibroblasts. This suggests that cryopreserved blood specimens may not be suitable for fragile X analysis.

Female↗
PubMed1985

Trisomy 14 mosaicism with t(14;15)(q11;p11) in offspring of a balanced translocation carrier mother.

A 2-year-old girl with growth and developmental retardation, minor facial anomalies, asymmetry of face and body, tetralogy of Fallot, and reticular hyperpigmentation of the skin was found to have mosaic trisomy 14 involving a t(14;15)(q11;p11). The patient showed mosaicism for 46,XX cell line, apparently resulting from a break of the translocation chromosome and a subsequent loss of 14q. The mother has a balanced translocation t(14;15)(q11;p11). Inherited trisomy 14 has not been reported previously.

Abnormalities, Multiple↗
PubMed1985

Interpolative computation of spin-lattice relaxation times from signal ratios.

An iterative linear interpolation is described for computing T1 estimates from image-signal ratios that are monotonous functions of T1. Whether the function decreases or increases with T1, the same algorithm described applies. The iterative process converges readily. Narrowing the whereabouts of T1 sought in lookup tables to T1 regions just small enough to require only a few subsequent interpolations tends to shorten overall T1 image computing time. Used with imaging methods for which the function is readily evaluated, the iterative interpolation allows a rapid and precise T1 computation compatible with variable choice of pulse-sequence parameters. The flexibility is suitable to stochastic analysis of T1 measurement from signal ratios. Examples of applications to computing the stochastic uncertainty represented either by crude indicators or by standard statistical quantities are given. A method of stochastic simulation yielding the statistical quantities is described.

Magnetic Resonance Spectroscopy↗
PubMed1985

Accuracy of proton T1 calculated by approximations from image signals.

In proton magnetic resonance imaging, T1 calculation from two measurements is simplified by using an approximation algorithm that assumes equilibrium recovery of longitudinal magnetizations or one that ignores refocusing 180 degrees pulses used. Errors in calculated T1 arising from either approximation are evaluated using signal expressions that presume neither approximation. The approximation error depends on T1, sequence parameters, and the simplifying algorithm. The computed relation can be used to correct for the approximation error. The correction reduces calculated-T1 errors, but does not eliminate them, since other significant or potentially significant sources of the error are unaccounted for. These sources relate to ever-present stochastic noises, proper signal expressions, various instrumental factors, exponential compared with nonexponential nature of tissue proton relaxations, and tissue movements. The problem of quantitative T1 measurement from image signals is briefly discussed.

Humans↗
PubMed1984

Measurement of spin-lattice relaxation times in double spin-echo imaging.

Calculation of tissue T1 in double spin-echo imaging (90 degrees-T-180 degrees-2T-180 degrees) using two repetition times (b1 and b2) has entailed an approximation that ignores the two 180 degrees pulses. The theoretical consequence of the simplification is to overestimate T1 with a fractional error that increases with increasing T1 faster than linearly in a manner dependent on the sequence parameters. With b1, b2, and T as parameters, the theory gives a family of curves relating T1 to the predicted ratio of signals acquired at b2 versus b1 intervals. Tissue T1 can be determined from the observed signal ratio with no approximation. Consideration of noise effect on the precision of T1 so determined favors the use, within limits, of higher b2/b1 ratio for the same b1 + b2 time. At constant b2/b1, using longer b1 + b2 permits wider range of T1 to be measurable with a specified minimum precision.

Magnetic Resonance Spectroscopy↗
PubMed1984

Comparison of expression of the fragile site at Xq27 in T and B lymphocytes.

We compared the fragile X (fraX) expression in T and B lymphocytes from four hemizygous males with fraX. Blood cultures were stimulated with a T cell mitogen (phytohemagglutinin:PHA) and with a B cell mitogen (pokeweed mitogen:PWM). A significant decrease in fraX expression was observed in cultures stimulated with PWM when compared to PHA-stimulated ones.

Adolescent↗
PubMed1984

Ultraviolet light and mitomycin C induced sister-chromatid exchanges in fibroblasts from patients with retinoblastoma.

Ultraviolet light and mitomycin C (MMC) induced sister-chromatid exchanges (SCEs) were investigated in 6 diploid fibroblast strains derived from 3 patients with deletion 13 and retinoblastoma, one patient with a hereditary form of retinoblastoma, one patient with trisomy 13, and one normal control. Two fibroblast strains with del(13)(q14q22) showed a significant increase in SCEs compared to the control after UV and MMC treatments. In contrast, cell strains with del(13)(q12q14) and trisomy 13 did not show increased SCEs. The frequency of SCEs in fibroblasts from a patient with autosomal dominant retinoblastomas (no deletions) was significantly increased by UV, but not by MMC. The results suggest that cell strains with different deletions of chromosome 13 have different SCE responses to UV and MMC inductions. The cells with del(13)(q14q22) may have a DNA-repair defect.

Chromosome Deletion↗
PubMed1984

Effect of oral dose size on hydralazine kinetics and vasodepressor response.

Levels of hydralazine in blood are log-linearly related to its vasodepressor effect. We examined the effect of oral dose size on the proportion of hydralazine that reaches systemic circulation. Nine subjects with hypertension were given hydralazine in oral doses in the therapeutic range. Blood hydralazine levels, effective liver blood flow, blood pressure, and heart rate were measured. As the hydralazine dose increased, the ratios of the AUC of hydralazine to hydralazine dose and of peak blood hydralazine concentration to hydralazine dose increased, indicating an increase in the proportion of the dose in blood. Liver blood flow tended to increase (maximum 40%) as dose increased above 0.5 mg/kg. Vasodepressor response and degree of tachycardia increased disproportionately with increasing hydralazine dose. There were strong log-linear relationships between peak hydralazine levels and both vasodepressor response and tachycardia that did not change with increasing hydralazine dose. Thus blood hydralazine and vasodepressor response increase disproportionately with increasing hydralazine doses in hypertension.

Acetylation↗
PubMed1984

An in vitro and in vivo study of a BrdU-sensitive fragile site in the Chinese hamster.

The frequencies of chromosome aberrations and development of the bromodeoxyuridine (BrdU)-sensitive fragile site were studied in vitro in Chinese hamster kidney and bone marrow cells and in vivo in Chinese hamster bone marrow cells. Chromosome aberrations in these cell systems were measured in response to different concentrations of BrdU, fluorodeoxyuridine, or both. The fragile site was found in both homologues of chromosome 1 at 1q22. Treatment with BrdU in vitro but not in vivo produces significant chromosome aberrations. About 50% of chromosome aberrations found after treatment in vitro were at the BrdU-sensitive fragile site compared with 12.5% after treatment in vivo. These results show that BrdU is much more potent in vitro than in vivo in inducing both chromosome aberrations and the expression of the BrdU-sensitive site.

Animals↗
PubMed1983

Ullrich-Turner syndrome associated with interstitial deletion of Xp11.4 leads to p22.31.

The full phenotype of the Ullrich-Turner syndrome (UTS) is thought to be due to loss of the short arm of X. We report a 16-year-old girl with lack of secondary sexual development, amenorrhea, and short stature. She had thyroiditis and numerous other UTS manifestations and was found to have a non-mosaic 46,X,del(Xp) chromosome abnormality. Breakpoints occurred at p11.4 and p22.31, with a loss of the intervening segment.

Adolescent↗
PubMed1983

Sister chromatid exchanges and chromosome aberrations in fibroblasts from patients with retinoblastoma.

The frequencies of sister chromatid exchanges (SCEs) and chromosome breaks were investigated in five diploid fibroblast strains derived from three patients with deletion 13 [del(13)] retinoblastoma, one patient with a hereditary form of retinoblastoma, and one trisomy 13. The fibroblasts with del(13)(q14q22) showed slightly increased SCEs (at a P level of 5-10%), but the others, including del(13)(q12q14), the hereditary form of retinoblastoma, and trisomy 13, did not have increased SCEs as compared to normal controls. No increase in chromosome breaks was found in these fibroblasts. The results suggest that retinoblastoma is not associated with spontaneous increased chromosomal instability.

Chromosome Aberrations↗
PubMed1983

The sequence of DNA replication in an iso-dicentric X-chromosome in peripheral blood lymphocytes and skin fibroblasts from the same individual.

A comparison of the sequence of DNA replication in an isodicentric (idic) X chromosome was made between peripheral blood lymphocytes and skin fibroblasts from a 33-year-old female with primary amenorrhea, somatic stigmata of Turner syndrome, and normal stature and intelligence. The patient had a karyotype 45,X/46,X,idic(X)(q27.1) to lymphocytes and 46,X,idic(X)(q27.1) in skin fibroblasts. Both centromeric regions of the idic X showed C-staining but only one primary constriction. BrdU-33258 Hoechst-Giemsa techniques were used to analyze regional DNA replication patterns. The idic X chromosome was always late replicating in lymphocytes and skin fibroblasts, except that about 1-2% of cells completed replication simultaneously in both normal and idic X chromosomes. Fifty-six percent of the asymmetric patterns in lymphocytes showed an equal proportion of early and late functional and non-functional centromere halves. In skin fibroblasts, 60.8% of cells were asymmetric: the functional half tended to replicate later than the non-functional half. Some differences were observed between these two cell types. As examples, band q23 was late replicating in lymphocytes, but early replicating in fibroblasts; q25 was intermediate to late replicating in lymphocytes, but one of the last bands to complete replication in fibroblasts. Thus, different cell typed influenced the replication kinetics of the idic(X). Furthermore, several variants of the replication sequence were found in both cell types. The findings support the hypothesis that the control of DNA replication in the inactive X chromosome is multifocal, and suggest that the active idic X chromosome replication may reflect a relative lack of self-control or heterogeneity of cell population.

Adult↗
PubMed1983

Effect of intravenous dose on hydralazine kinetics after administration.

Six male hypertensive patients, three rapid and three slow acetylators, each received four different intravenous hydralazine doses by constant infusion over 100 sec. Two to four days elapsed between doses. Plasma or whole-blood hydralazine concentrations were measured by HPLC after each dose. There was no influence of acetylator phenotype on hydralazine kinetics after intravenous dosing. There also was no consistent effect of dose size on hydralazine clearance or volume of distribution at doses up to 0.45 mg (2.3 mumol/kg). One subject, who received doses up to 0.6 mg/kg (3.05 mumol), had an apparent decrease in clearance at the higher doses. These findings are consistent with the fact that hydralazine is converted intravascularly to hydralazine pyruvic acid hydrazone and the fact that potentially saturable hepatic metabolic pathways play only a modest role in systemic clearance.

Dose-Response Relationship, Drug↗
PubMed1983

The response of plasma catecholamines to intravenous labetalol: a comparison with sodium nitroprusside.

Changes in mean arterial pressure (MAP), heart rate (HR), and plasma concentrations of norepinephrine (NE) and epinephrine were measured in eight hypertensive patients in a supine position after stepwise infusion of incremental sodium nitroprusside doses and intravenous injection of cumulative labetalol doses. Both drugs induced rises in plasma NE concentration that were linearly related to reductions in MAP. For any reduction in blood pressure (BP), however, the rise in plasma NE concentration induced by labetalol was approximately four times that induced by sodium nitroprusside. The difference can be explained by two effects of labetalol: impairment of neuronal NE uptake and beta-adrenergic-receptor blockade, which are known to reduce NE clearance from plasma. After both drugs there was a correlation between changes in HR and changes in BP and a correlation between changes in HR and changes in plasma NE concentration. Slopes of the regression lines for both relationships were less after labetalol than after sodium nitroprusside, presumably because of the beta-adrenergic-blocking properties of labetalol. Multiple-regression analysis indicated that the plasma NE rise was an important determinant of the vasodepressor response to each drug. The greater plasma NE elevation after labetalol may limit its antihypertensive effect.

Adult↗
PubMed1983

Effects of hydralazine and sodium nitroprusside on plasma catecholamines and heart rate.

Hydralazine and sodium nitroprusside induce different effects on systemic hemodynamics, but their effects on sympathetic neuronal activity have not been compared. Five hypertensive subjects receiving only hydrochlorothiazide were studied during two sessions. During one session, four doses of hydralazine, 0.1 to 0.6 mg/kg, were given intravenously at least 3 days apart, and during the other session, sodium nitroprusside was infused in stepwise doses, 0.05 to 4.8 micrograms/kg/min for 10 min per dose. Mean arterial pressure (MAP), heart rate (HR), and plasma norepinephrine (NE) and epinephrine concentrations were determined before and after dosing. The following correlated linearly for hydralazine and sodium nitroprusside: delta HR/delta MAP, delta NE/delta MAP, and delta HR/delta NE. Comparison of these relationships, however, indicated significant differences between the sympathetic neuronal and hemodynamic responses to hydralazine and sodium nitroprusside. Increase in HR relative to decrease in MAP was greater for hydralazine than for sodium nitroprusside. There were greater increases in plasma NE concentration relative to falls in MAP with sodium nitroprusside than with hydralazine, but increases in HR relative to increases in plasma NE concentration were smaller for sodium nitroprusside than for hydralazine. Such responses may reflect differential effects of hydralazine and sodium nitroprusside on the systemic clearance of NE or of the activity of cardiopulmonary baroreceptors.

Adult↗