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Biomedical subjects

S C Ling

Publications and source records attributed to S C Ling.

27 records · Page 2Linked to original sources
PubMed1991

Comparison of nonabsorbable markers Poly R-478 and [14C]PEG-4,000 for use in developmental absorption studies.

To determine the utility of Poly R-478, a stable, polymeric dye (MW, 40,000), as a nonabsorbable marker for studies in the developing small intestine, it was validated by comparison to carbon 14-labeled polyethylene glycol, MW 4,000 [( 14C]PEG-4,000) in rats from 14 to 40 days of age. The recovery and quantification of Poly R-478 from biological samples is simple and rapid compared to other nonradioactive nonabsorbable markers. In 40-day-old rats simultaneously given Poly R-478 and [14C]PEG, total recoveries were similar, the percentages of the Poly R-478 dose and the [14C]PEG dose recovered per segment were identical, and taurocholate absorption rates calculated using each marker were comparable. Recovery of Poly R-478 from flushed intestinal segments, determined by a one-step extraction, was equivalent to that of [14C]PEG in 40-day-old rats (96.5 +/- 3.7% versus 102.7 +/- 10.1%; NS) but was superior to that of [14C]PEG in 21-day-old rats (98.0 +/- 6.2% versus 63.4 +/- 5.5%; p less than 0.001) and 14-day-old rats (97.8 +/- 6.7% versus 56.7 +/- 12.6%; p less than 0.001). Within each age group, the distribution of Poly R-478 within the intestine was similar to that of [14C]PEG. In addition, total taurocholate absorption in the presence of Poly R-478 was comparable to that in the presence of [14C]PEG. Complete recovery of Poly R-478 from a suspension of liver particles and from mixtures with two commercial infant formulas was demonstrated in vitro, suggesting that Poly R-478 may be used when foods are present in the intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1990

A study on the vascular supply of the supraspinatus tendon.

The vascular supply of the rotator cuff in 22 adult shoulders was studied by way of mixture infusion of gelatin and India ink and vascular cast, in combination with Scanning Electronic Microscopy of the vascular pattern in the supraspinatus tendon. It was found that the vessels of the supraspinatus tendon mainly derive from the anterior circumflex humeral and suprascapular arteries. Macroscopically, an avascular zone or critical zone could be seen on the surface of supraspinatus, and the mean distance of the external edge from the osteo-tendinous attachment was 7.8 mm. The area of the avascular zone increased with age.

Arteries↗
PubMed1990

Taurocholate transport by brush-border membrane vesicles from the developing rabbit ileum: structure/function relationships.

To examine the ontogenesis of bile acid transport in the rabbit ileum, brush-border membrane vesicles (12- to 20-fold purified) were prepared from 14- to 49-day-old animals. Taurocholate uptake was characterized by the emergence of secondary active, Na(+)-dependent transport at the start of weaning (21 days). Transient intravesicular accumulation (overshoot) of taurocholate occurred at 5-10 s of incubation, and the overshoot maximum increased significantly from 21 days (349.2 +/- 22.4 nmol/mg protein) to 35 days (569.0 +/- 84.3 nmol/mg protein; p less than 0.001), without further increase at maturity (49 days, not equal to 607.6 +/- 136.7 nmol/mg protein). No significant taurocholate active uptake component was noted at 14 days; however, ileal vesicles from sucklings showed carrier-mediated, Na+ D-glucose cotransport. In greater than or equal to 35-day-old rabbits, osmolarity studies at 20 s of incubation showed that only approximately 12% of [14C]taurocholate uptake was secondary to bile acid-to-membrane binding. Conversely, at 20 min, greater than 95% of radiolabel incorporation represented solute bound to the external and/or internal membrane surface. Arrhenius plots establish brush-border membrane taurocholate uptake as an intrinsic, lipid-dependent process, with a slope discontinuity between 24 and 28 degrees C, similar to the membrane lipid thermotropic transition region. Steady-state fluorescence polarization studies (1,6-diphenyl-1,3,5-hexatriene) demonstrate a temporal association between the maturation of taurocholate uptake and age-related decreases in ileal brush-border membrane fluidity. These data indicate that maturation of bile acid secondary active transport in the rabbit ileum may be regulated, at least in part, by changes in brush-border membrane lipid dynamics.

Age Factors↗
PubMed1986

Effects of ethinyl estradiol on intestinal membrane structure and function in the rabbit.

Structural and functional properties of the small intestinal microvillus membrane were evaluated in the rabbit after administration of ethinyl estradiol, a synthetic estrogen with a demonstrated propensity to alter hepatic membrane lipid fluidity, and promote cholestasis. In the jejunum, no estrogen-induced changes in microvillus membrane total lipid, cholesterol or phospholipid content were observed. However, the ileal microvillus membrane in estradiol-treated animals demonstrates significant reductions vs. controls (per mg protein) in total lipid (0.55 milligrams vs. 0.89 milligrams) [corrected] and phospholipid (206.7 micrograms vs. 304.91 micrograms) (p less than 0.001) content, as well as modifications in specific phospholipid species. The increase in the ileal microvillus membrane cholesterol: phospholipid molar ratio (0.65 vs. 0.51, p less than 0.05) was associated with a significant decrease in membrane lipid fluidity reflected by an increase in fluorescence anisotropy measurements utilizing diphenyl hexatriene as the fluorophore (r at 25 degrees C = 0.306 vs. 0.282, p less than 0.05). Thermotropic lipid phase transitions, assessed by Arrhenius plots of both fluorescence data and ileal microvillus membrane p-nitrophenylphosphatase activity demonstrate that phase changes occur between and 24 and 28 degrees C in both treated and untreated groups. Within the temperature range studied (40-10 degrees C) no differences from control were observed in microvillus membrane alkaline phosphatase activity following estrogen treatment. These data therefore indicate that ethinyl estradiol-induced effects on microvillus membrane lipid composition and physical properties occur predominantly in the ileum and appear to be related, in part, to specific alterations in the availability of phospholipid following estrogen treatment.

4-Nitrophenylphosphatase↗
PubMed1975

Analysis of coronary flow fields in thoracotomized dogs.

A nonlinear theory of pulsatile flow was used to investigate the detailed flow field in the left circumflex coronary artery of anesthetized open-chest dogs. Studies were carried out under a wide range of blood pressures and flow rates induced by intravenous infusions of dipyridamole. The results indicated that (1) the flow profiles, although less blunt than those in the descending aorta, are still nonparabolic, (2) the wall shear in the coronary arteries maintains a high value through diastole, and (3) during intravenous infusions of dipyridamole both coronary flow and wall shear increase. The peak value of the shear stress during these infusions, which reached 360 dynes/cm2, can approach the yield stress value of 400 dynes/cm2 reported by Fry for endothelial cells.

Animals↗