Biomedical subjects

C Lin

Publications and source records attributed to C Lin.

At least 19 recordsLinked to original sources

PubMed1992

A cold-regulated Arabidopsis gene encodes a polypeptide having potent cryoprotective activity.

We previously showed that cor15, a cold-regulated gene from Arabidopsis thaliana, encodes a 15 kDa polypeptide designated COR15. Here we report that COR15 has potent cryoprotective activity in an in vitro cryoprotection assay. Specifically, COR15 was very effective in protecting the cold-labile enzyme lactate dehydrogenase against freeze-inactivation; on a concentration basis, it was about 10(6) times more effective than sucrose and 10(2)-10(3) times more effective than other proteins including bovine serum albumin. The possible role of cor15 in cold acclimation is discussed.

Cloning, Molecular↗

PubMed1992

Effect of human mammary MX-1 tumor on plasma free fatty acids in fasted and fasted-refed nude mice.

We hypothesized that tumor-bearing (TB) nude mice, because they are reported to have no detectable, circulating tumor necrosis factor (TNF)/cachectin, would regulate their plasma free fatty acid (FFA) levels normally when fasted and refed. We compared levels of individual plasma FFA in response to fasting (24 hr) and to refeeding (for 20 hr after fasting) a fat-free, 65% sucrose diet in control, nude mice and in mice bearing 1.3 +/- 0.4 g MX-1 tumors. Total plasma FFA levels were typically high in 24-hr fasted mice [mean concentrations in microM +/- SE (n); controls 515 +/- 63 (6); TB, 625 +/- 63 (6)]. FFA levels were reduced by 65% in each group in response to refeeding. Each major plasma FFA species fell in response to refeeding, except arachidonate, which did not change significantly (fasted vs. fasted-refed concentrations) in either controls or TB mice. In refed mice, the molar FFA ratio of oleate to linoleate rose; however, that of oleate to arachidonate fell markedly. TB nude mice had normal appetites. We conclude that all species of FFA were mobilized from adipose tissue in a normal manner in TB nude mice; therefore, regulation of adipose triacylglycerol fatty acid mobilization (as plasma FFA) by dietary sugar is probably not affected by MX-1 tumor growth in these mice. Our findings are consistent with the hypothesis that nude mice may be unable to secrete TNF/cachectin in response to tumor growth, but they do not establish whether or not endogenous, circulating TNF/cachectin increases FFA mobilization in any TB animal.

Adipose Tissue↗

PubMed1992

Temporal and regional production of 12(S)hydroxyeicosatetraenoic acid [12(S)-HETE] in rat lens.

Enzymatic production of 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] from exogenous arachidonic acid (AA) was studied in the 9000 g supernatant fraction of either whole rat lens or the capsule-epithelium and cortex-nucleus regions with age (4-180 days). Whole rat lens 12(S)-HETE synthetic capacity measured either by RIA or HPLC was significantly decreased with lens growth. 12(S)-HETE production was highest in the 4-day-old rat lens, the earliest time point measured, and declined to background levels by 6 months of age. Regional studies demonstrated that the capsule-epithelium possessed a higher specific activity in comparison to the cortex-nucleus. However, lipoxygenase activity decreased significantly faster in the capsule-epithelium compared to the cortex-nucleus. The bulk of the 12-lipoxygenase activity was located in the cortex-nucleus due to the higher amount of tissue in the region. The elevated lipoxygenase activity in the neonate and its rapid decline with growth suggests that the enzyme may contribute in transforming the epithelial cells to fiber cells.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1992

The Huntington's disease candidate region exhibits many different haplotypes.

Analysis of 78 Huntington's disease (HD) chromosomes with multi-allele markers revealed 26 different haplotypes, suggesting a variety of independent HD mutations. The most frequent haplotype, accounting for about one third of disease chromosomes, suggests that the disease gene is between D4S182 and D4S180. However, the paucity of an expected class of chromosomes that can be related to this major haplotype by assuming single crossovers may reflect the operation of other mechanisms in creating haplotype diversity. Some of these mechanisms sustain alternative scenarios that do not require a multiple mutational origin for HD and/or its positioning between D4S182 and D4S180.

Alleles↗

PubMed1992

A novel G protein-coupled receptor kinase gene cloned from 4p16.3.

Within the Huntington's disease (HD) candidate region of 4p16.3, the D4S127 locus displays strong linkage disequilibrium with the defect and anchors a conserved haplotype found on many HD chromosomes. To isolate genes from this region we have applied the exon amplification technique to overlapping cosmids spanning D4S127. Here, we report the discovery of a new gene encoding a novel member of a family of protein kinases that specifically phosphorylate the activated forms of G protein-coupled receptors. Such kinases are thought to participate in desensitization of specific receptors, thereby blocking further signal transduction. This gene must now be carefully scrutinized to determine whether it might be involved in HD.

Amino Acid Sequence↗

PubMed1992

Ultrasonic attenuation estimation in-vivo using the difference ratio correction method.

In recent years, B scanners have been widely used clinically. Obviously, it is of particular importance to use the commercial B scanners to characterize tissue by estimating its ultrasonic attenuation in vivo. However, there are a lot of difficulties in doing so because the output of a B scanner is affected by many unknown factors. In this paper, a time domain method named the difference ratio correction (DRC) method is proposed to estimate the ultrasonic attenuation of tissue in vivo. In this method, three tissue-mimicking phantoms with known acoustical properties were employed to eliminate the instrumentation errors of the B scanner and the measuring system and to correct beam diffraction for correct attenuation estimation. Other advantages of this method are that it is very convenient to apply this method clinically and there is no need to change the inner construction of the B scanner because this method only utilizes the video output. Experimental and clinical results have proved the validity of this method.

Biophysical Phenomena↗

PubMed1992

Epiphytic microflora on alfalfa and whole-plant corn.

Epiphytic microflora were identified and counted on four cuttings of alfalfa, each harvested at three stages of maturity, and on three whole-plant corn hybrids. Enterobacteriaceae were predominant on both crops. Yeasts and molds also were major epiphytic microorganisms on whole-plant corn. The group--including lactobacilli, pediococci, and leuconostocs, which are genera that produce lactic acid and thus are instrumental in silage preservation--constituted only a small proportion of the total population (less than .5%) on both crops. Lactate-fermenting clostridial spores were not detected on standing alfalfa, and occurrences of these spores on standing corn plants were due to soil contamination from rainfall prior to harvest. The numbers of epiphytic microorganisms, except for the lactobacilli, pediococci, and leuconostocs group, were higher on standing corn than on alfalfa. The epiphytic microflora on alfalfa increased with increasing temperature during the growing season. However, neither cutting number nor maturity affected the epiphytic microflora on standing alfalfa, and wilting following mowing had little effect on most populations. Higher temperatures during wilting increased yeast and mold counts but had no effect on other microbial counts. The chopping process tended to increase the epiphytic microflora populations compared with those on the standing crops, and the group containing lactobacilli, pediococci, and leuconostocs was most enhanced. Only yeast and mold counts on the chopped alfalfa increased with greater DM content and buffering capacity.

Animal Feed↗

PubMed1992

[Purification and characterization of hec toxin produced by Aeromonas hydrophila].

An extracellular toxin produced by Aeromonas hydrophila from cultured crucian carp with septicemia was detected. The toxin was purified by ammonium sulfate precipitation, DEAE-cellulose chromatography and Sephadex G-100 gel filtration. The factor was a single polypeptide with a molecular weight of 52.5kd determined by SDS-PAGE. The heat-stable toxin possesses hemolytic, enterotoxic and cytolytic activities. The hemolytic activity on human erythrocytes was 3.81 x 10(3) HU/mg, CD50 for Vero cell was 0.26 microgram. The LD50 for crucian carp and mice was 4.44 micrograms and 3.58 micrograms respectively. The toxin was neutralized py homologous antibodies. The toxin shows unique characteristics as compared with other known bacterial toxins therefore the authors propose to name the toxin "hec" toxin.

Aeromonas hydrophila↗

PubMed1991

Bivalent ACTH antagonists: influence of peptide and spacer components on potency enhancement.

The antagonist potency of a series of bivalent adrenocorticotropic hormone (ACTH) peptides was examined using suspensions of inner zone rat adrenocortical cells. Bivalent antagonists were prepared by bis(maleimide) covalent cross-linking of carboxyl terminal cysteine sulfhydryl groups of synthetic ACTH peptides, Cys25 ACTH(7-25) and Cys39 ACTH(7-39). Antagonist potency enhancement was defined by shifts in ACTH(1-39) concentration-steroidogenic response curves relative to monovalent antagonist analogs. The EC50 values measured in the presence of 0.5 microM monovalent antagonist were 110 +/- 28 pM for Cys25 ACTH(7-25)-S-N-ethylsuccinimide and 44 +/- 9 pM for Cys39 ACTH(7-39)-S-N-ethylsuccinimide. Some bivalent ACTH antagonists displayed much greater antagonist potency than their monovalent analogs, which supports the findings of Stolz and Fauchere (Helv Chim Acta 71: 1421-1428, 1988). The level of potency enhancement, however, was found to be dependent upon the spacer used to link receptor binding domains and the length of the ACTH peptide used in bivalent antagonist synthesis. The most potent inhibitor, bis(Cys25 ACTH(7-25)-S-succinimidopropionyl)2-hydroxy-1,3-propanediamine, was 28 times more potent than its monovalent analog, Cys25 ACTH(7-25)-S-N-ethylsuccinimide. However, a bivalent Cys25 ACTH(7-25) peptide containing two bis(succinimidopropionyl)2-hydroxy-1,3-propanediamine spacers that had been linked end-to-end via dithioerythritol showed no potency enhancement. Cys25 ACTH(7-25) based peptides containing one receptor binding domain and having the structure peptide-spacer-cysteine displayed no enhancement in antagonist potency. Bivalent Cys39 ACTH(7-39) linked by bis(succinimidopropionyl)2-hydroxy-1,3-propanediamine spacer exhibited only 4-fold enhancement in antagonist potency relative to Cys39 ACTH(7-39)-S-N-ethylsuccinimide. We therefore conclude that the potency enhancement observed with bivalent ACTH peptides: (1) is optimal with spacers less than approximately 40 A in length, (2) is not due to direct interactions between the spacer and cell surface, and (3) is dependent on the length of the ACTH peptide component. In addition, these results indicate that electrostatic interaction between bivalent ACTH peptides and plasma membrane lipids does not adequately account for the potency enhancements observed.

Adrenal Cortex↗

PubMed1991

Diffusion of water in tissues and MRI.

The purpose of this paper is to present an overview of the diffusive behavior of water in biological tissues. The analysis shows that obstructive barriers would have to occupy very large volume fractions in order to account for the reduction in the diffusion coefficient (D) observed in biological systems. Generally, most models lead to the supposition that a substantial fraction (20-40%) of the cell water is hydration water, or that the diffusion coefficient of the cytoplasmic water is reduced substantially from the free water value. Thus, the conclusion that a substantial fraction of cell water has diffusive properties that are altered by the macromolecules of the cytoplasm seems inescapable. The impact of these findings on MRI remain to be determined.

Body Water↗

PubMed1991

Mapping of cosmid clones in Huntington's disease region of chromosome 4.

Huntington's disease (HD) is tightly linked to genetic markers in 4p16.3. We have used a regional somatic cell hybrid mapping panel to isolate and map 25 cosmids to the proximal portion of 4p16.3 and 17 cosmids to the distal portion. The latter were positioned by long-range restriction mapping relative to previously mapped markers. One cosmid, L6 (D4S166), spans the critical breakpoint in the mapping panel that distinguishes proximal and distal 4p16.3. Four of the cosmids mapped distal to D4S90, the previous terminal marker on 4p, and stretched to within 75 kb of the telomere. Several of the cosmids that mapped between L6 and D4S90 were clustered near a number of previously isolated clones in a region with many NotI sites. Cosmid E4 (D4S168) was localized immediately proximal to the one remaining gap in the long-range restriction map of distal 4p16.3. Although pulsed field gel mapping with E4 failed to link the two segments of the map, the intervening gap was excluded as a potential site for the HD gene by genetic analysis.

Chromosome Mapping↗

PubMed1991

Classification of supratentorial arteriovenous malformations. A score system for evaluation of operability and surgical strategy based on an analysis of 66 cases.

A classification of arteriovenous malformations (AVM) is proposed, which is based on a retrospective analysis of the records and results of radical operation in 57 patients between 1983 and 1990. It represents the new developments and more recent technical facilities which influence operability of supratentorial AVMs. Predictability of outcome has been settled upon three groups of factors: anatomical, haemodynamical, and clinical. Anatomical factors are localisation and sectorisation of AVM, determination, caliber and straightening of feeding arteries. Haemodynamical factors are volume of AVM and vascular autoregulation, circulatory velocity of red blood cells in the main arteries of the neck and brain tissue cellular steal. Clinical factors are age, previous rupture of AVM, associated diseases and malformations of vital organs. Each of these factor groups has been divided into parameters to which a code number from 0 to 5 according to the severity of the considered parameter has been attributed. When a contraindication for radical surgery was clearly obvious, as, for example, an AVM with extension to the upper brain stem, number 10 was given. This grading has been done by a team of four persons (3 neurosurgeons including the senior author, and one biophysicist). By adding up all code numbers an Operability Score for a given patient is defined by the number of points, with a minimum of 3 and a maximum of 69. In cases with a score higher than 30 surgery is not advisable. A score between 21 and 30 indicates that always several staged operations are required, whilst only some of the patients with a score between 11 and 20 may require two stage operative treatment. The AVM in patients with a score under 10 can always be radically excised in a single stage operation. We have been able to demonstrate that the Operability Score allows a reliable prediction of outcome, thus giving indications and contraindications for surgery, and also for the surgical strategy. Moreover, we have explained why surgery had been refused in 9 additional cases during the same period. The causes of 8 fatalities out of 57 surgical cases are analyzed. These 57 cases represent a systematically explored series of the senior author; his experience is based upon 295 personal AVM cases (1958-1990).

Adult↗

PubMed1991

Evidence of extensive phospholipid fatty acid methylation during the assumed selective methylation of plasma free fatty acids by diazomethane.

We compared a conventional method (Method I) for measuring plasma free fatty acid (FFA) concentrations with two more rapid procedures (Method II and Method III). Method I required total lipid extraction, separation of FFA by thin-layer chromatography, methylation, and gas-liquid chromatographic analysis of the fatty acid (FA) methyl esters. Method II was a colorimetric procedure. Method III relied upon diazomethane's presumed ability to selectively methylate FFA even in the presence of FA esters. The three methods were compared using plasma from fasted and from fed nude mice, tumor-bearing mice (MX-1 and ZR-75-1 human mammary carcinomas), and controls. Method II, was less reliable than Method I, but both gave similar mean values for plasma FFA levels in fasted mice. Both Methods I and II also showed similar lowering of plasma FFA levels after feeding previously fasted mice. Method III consistently gave values that were far greater than those obtained using Methods I and II. Moreover, highly significant differences between fasted and fed mice were obscured by direct methylation of plasma FFA with diazomethane (Method III). The excess FA methyl esters formed in Method III were derived from plasma phospholipids, but not from plasma triacylglycerols. After feeding fasted mice, plasma free palmitic acid and oleic acid levels fell (Method I); by contrast, the excess "FFA" formed by methylation of plasma phospholipid FA increased two-fold and fourteen-fold, respectively. Caution is therefore advised in the use of direct methylating agents when measuring total and individual plasma FFA levels.

Animals↗

PubMed1991

Synthesis and properties of sulfhydryl-group-specific reagents containing 125I.

125I-containing compounds that react specifically with sulfhydryl groups were prepared in yields of 30 to 40% on the basis of starting 125I quantity. The synthetic precursors were commercially available heterobifunctional crosslinkers and the peptide L-arginyl-L-tyrosine. Two types of sulfhydryl specific reagents were prepared: 3-(2-pyridyldithio)propionylarginyl-[125I]-monoiodotyrosine, which permits reversible incorporation of 125I at sulfhydryl sites, and 3-maleimidopropionylarginyl- [125I]monoiodotyrosine, an irreversible labeling reagent. These products were isolated in a highly radiochemically pure form by C18 HPLC. The second-order rate constants for the reaction of 3-(2-pyridyldithio)propionylarginylmonoiodotyrosine and 3-maleimidopropionylarginylmonoiodotyrosine with N-acetylcysteine were 28 +/- 3 M-1 s-1 and 154 +/- 4 M-1 s-1, respectively, at pH 7.3. Storage of carrier-free 3-(2-pyridyldithio)propionylarginyl-[125I]monoiodotyrosine and 3-maleimidopropionylarginyl-[125I]monoiodotyrosine at -80 degrees C at a radioactive concentration of 0.4 mCi/ml resulted in conversion of 125I to species that did not react covalently with sulfhydryl groups. This process occurred with first-order kinetics and a t1/2 of 5.7 days for the pyridyldithio compound and 7.5 days for the maleimido compound. No conversion was observed during storage at -80 degrees C at radioactive concentrations of 0.02 mCi/ml or less. The labeling properties of these compounds were examined using red blood cell proteins as a test system. 3-(2-Pyridyldithio)propionylarginyl- [125I]monoiodotyrosine and maleimidopropionylarginyl-[125I]monoiodotyrosine reacted preferentially with membrane - associated sulfhydryl groups when incubated with intact red blood cells.

Blood Proteins↗

PubMed1991

Identification of 12(S)-hydroxyeicosatetraenoic acid in the young rat lens.

Evidence is presented indicating that young rat lens has the capacity to synthesize 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) from exogenous arachidonic acid (AA). A 9,000 xg supernatant prepared from 15 day old rat lenses, when incubated with calcium and U-[14C]-AA, generated a radiolabelled product with a retention time identical to authentic unlabelled 12-HETE in two different HPLC solvent systems. Mass spectral analysis provided evidence that the metabolite was 12-HETE while chiral studies demonstrated the exclusive presence of the 12(S) isomer. Radiolabelled 12-HETE synthesis was inhibited by preincubating the 15 day old rat lens supernatant with 0.2 Mm curcumin, a mixed cyclooxygenase/lipoxygenase inhibitor. Radiolabelled 12(S)-HETE synthetic capacity was highest in the 4 day old rat lens, the earliest time period measured, and rapidly declined with age reaching negligible levels at about 4 months. These results suggest that the young rat lens possess the biosynthetic capacity to generate radiolabelled 12(S)-HETE from U-[14]C-AA. The profile of 12-HETE synthetic activity suggests a possible regulatory function of the hydroxylated AA metabolite in the developing lens.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1991

Complex patterns of linkage disequilibrium in the Huntington disease region.

The genetic defect causing Huntington disease (HD) has been mapped to 4p16.3 by linkage analysis using DNA markers. Two apparently contradictory classes of recombination events in HD kindreds preclude precise targeting of efforts to clone the disease gene. Here, we report a new recombination event that increases support for an internal candidate region of 2.5 Mb between D4S10 and D4S168. Analysis of 23 DNA polymorphisms in 4p16.3 revealed a complex pattern of association with the disease gene that failed to narrow the size of the candidate region. The degree of linkage disequilibrium did not show a continuous increase across the physical map, nor was a region of extreme disequilibrium identified. Markers displaying no association with the disorder were interspersed with and, in many cases, close to markers displaying significant disequilibrium. Comparison of closely spaced marker pairs on normal and HD chromosomes, as well as analysis of haplotypes across the HD region, suggest that simple recombination subsequent to a single original HD mutation cannot easily explain the pool of HD chromosomes seen today. A number of different mechanisms could contribute to the diversity of haplotypes observed on HD chromosomes, but it is likely that there has been more than one and possibly several independent origins of the HD mutation.

Alleles↗

PubMed1991

The thermal response and development of thermotolerance of the bone marrow stromal progenitor CFU-F.

The effect of hyperthermia on the murine bone marrow stromal progenitor (fibroblast colony-forming unit, CFU-F) was evaluated and its ability to develop thermotolerance demonstrated. CFU-F were obtained from nucleated marrow of Balb/c mice and heated in vitro in alpha minimum essential medium plus 15% fetal bovine serum. Thermotolerance development was tested two ways. 1) The development of thermotolerance during prolonged hyperthermia was observed with a "step-up" heating protocol (i.e., cells were incubated at 41 degrees C and at regular intervals challenged with 15 min at 44 degrees C). 2) The development of thermotolerance at 37 degrees C after a short exposure to a high temperature (greater than or equal to 43 degrees C) was observed with a split treatment protocol that consisted of two 15-min treatments of 44 degrees C separated with time at 37 degrees C. The inverse of the slopes of the hyperthermia dose-response relationships (Do +/- SE) for CFU-F were 118 +/- 14, 53 +/- 7, 23 +/- 0.6, 11 +/- 0.3, 7 +/- 0.3, and 5 +/- 0.5 min for exposures of 41.5 degrees, 42 degrees, 42.5 degrees, 43 degrees, 43.5 degrees, and 44 degrees C, respectively. The plot of the slopes of the heat "dose-response" relationships versus the inverse of the absolute temperature (Arrhenius plot) yields a change in slope at approximately 43 degrees C, and the inactivation enthalpies (slopes above and below the inflection point at 43 degrees C) were 606 +/- 100 kJ/mol (145 +/- 24 kcal/mol) and 1372 +/- 29 kJ/mol (328 +/- 7 kcal/mol) above and below 43 degrees C, respectively. The maximum thermotolerance ratio (TTR, surviving fraction after maximum thermotolerance development to surviving fraction of normotolerant CFU-F) at 37 degrees C after an acute thermal exposure to 15 min at 44 degrees C occurred after 12 h, with a half time of 60 min and a TTR of 41. The maximum TTR during prolonged hyperthermia at 41 degrees C was 2.4 by approximately 50 min. These results show that CFU-F are as sensitive as committed hematopoietic precursors (e.g., granulocyte-macrophage colony-forming units, CFU-GM) to hyperthermia over a wide range of thermal exposures and are capable of thermotolerance development during prolonged hyperthermic exposures and at 37 degrees C after short exposures. We conclude that at least one of the stromal elements of normal marrow may be compromised during whole-body or regional clinical hyperthermia protocols.

Animals↗

PubMed1991

[Effects of l-stepholidine on isolated rabbit basilar artery, mesenteric artery, and thoracic aorta].

l-Stepholidine (SPD) has been shown to be effective in treating migraine, but its mechanism is not clear. So the effects of SPD on isolated rabbit basilar artery (BA), mesenteric artery (MA) and thoracic aorta (TA) were studied. The contractions of BA and MA were induced by KCl (10-160 mmol.L-1) and the contraction of TA was caused by 5-HT (0.1-100 mumol.L-1). Ketanserin was used as reference. SPD (0.1-0.2 mmol.L-1) relaxed the contractions of BA and MA induced by KCl in a noncompetitive manner with pD'2 3.4 +/- 0.3 and 4.0 +/- 0.3, respectively. SPD had no selectivity in BA and MA. SPD also inhibited the contraction of TA induced by 5-HT with pA2 9.7 +/- 2.0 and pD'2 5.4 +/- 0.6, which showed a dual of both competitive and noncompetitive antagonisms. These results suggested that SPD had a blockade effect on the calcium channel and 5-HT2 receptors.

Animals↗