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Biomedical subjects

L L Lin

Publications and source records attributed to L L Lin.

At least 91 records · Page 5Linked to original sources
PubMed1988

Correlation of optical components with ocular refraction among teen-agers in Taipei.

From 2 senior-high and 2 vocational schools in Taipei, 3251 children with age 16-19 were randomly selected to study the relationship between ocular refraction and its main optical components, corneal curvature and axial length. While the corneal curvature was found to play only a minor role in the determination of ocular refraction, the measurements of axial length parallelled the degree of myopia (r = 0.74). A two-years' longitudinal study of additional 411 children from one junior-high school (age 13 through 15) further pointed to the importance of axial length in the production and progression of myopia.

Adolescent↗
PubMed1988

Isolation and characterization of noncleavable (Ind-) mutants of the LexA repressor of Escherichia coli K-12.

The LexA repressor of Escherichia coli represses a set of genes that are expressed in the response to DNA damage. After inducing treatments, the repressor is inactivated in vivo by a specific cleavage reaction which requires an activated form of RecA protein. In vitro, specific cleavage requires activated RecA at neutral pH and proceeds spontaneously at alkaline pH. We have isolated and characterized a set of lexA mutants that are deficient in in vivo RecA-mediated cleavage but retain significant repressor function. Forty-six independent mutants, generated by hydroxylamine and formic acid mutagenesis, were isolated by a screen involving the use of operon fusions. DNA sequence analysis identified 20 different mutations. In a recA mutant, all but four of the mutant proteins functioned as repressor as well as wild-type LexA. In a strain carrying a constitutively active recA allele, recA730, all the mutant proteins repressed a sulA::lacZ fusion more efficiently than the wild-type repressor, presumably because they were cleaved poorly or not at all by the activated RecA protein. These 20 mutations resulted in amino acid substitutions in 12 positions, most of which are conserved between LexA and four other cleavable proteins. All the mutations were located in the hinge region or C-terminal domain of the protein, portions of LexA previously implicated in the specific cleavage reactions. Furthermore, these mutations were clustered in three regions, around the cleavage site (Ala-84-Gly-85) and in blocks of conserved amino acids around two residues, Ser-119 and Lys-156, which are believed essential for the cleavage reactions. These three regions of the protein thus appear to play important roles in the cleavage reaction.

Amino Acid Sequence↗
PubMed1987

Twin study on myopia.

In order to reassess the relative importance of genetic and environmental factors in the development of myopia in Chinese schoolchildren, 90 pairs of MZ and 36 pairs of like-sex DZ twins were enrolled for detailed ophthalmological examination about their ocular refractions. Corneal curvatures and axial lengths were also measured. With equivalent settings of the range for concordance, corneal curvatures showed higher concordance rate (84%) than ocular refractions (65%) and axial lengths (59%) in MZ twins. F-test on the intrapair variances between MZ and DZ twins revealed a significant hereditary role in determining the ocular refraction and its optical components. The degree of genetic determination was expressed by heritability indices, which were derived from intraclass correlation coefficients. The diversity of sample ages and refractions, while making the obtained data difficult to further explore the gene-environment interaction, led to the observation of more intrapair differences with age and myopic progression in MZ twins.

Adolescent↗
PubMed1985

Antitumor lectin-trypsin inhibitor conjugate.

Concanavalin A (Con A) and trypsin inhibitor isolated from Acacia confusa were covalently linked with N-succinimidyl-3-(2-pyridyldithio)propionate. Con A-A. confusa trypsin inhibitor (ACTI) conjugate covalently bound (Con A-ACTI) retained about 42% of the trypsin inhibitory activity present in the native ACTI and had a higher hemagglutinating activity than did the native Con A. Con A-ACTI had a greater resistance to tryptic digestion than did the mixture of Con A and ACTI. The conjugate entered sarcoma 180 tumor cells, whereas the free ACTI did not. A single dose of the conjugate injected ip into noninbred N:NIH(S) white mice bearing sarcoma 180 had a remarkable effect of increasing the survival of tumor-bearing mice, while the mixture of an equivalent dose of free Con A and ACTI was not effective.

Animals↗
PubMed1982

Magnesium reduces affinities of antagonists at rat cortex alpha 2-adrenergic receptors labeled with 3H-clonidine: evidence for heterogeneity of alpha 2-receptor conformations with respect to antagonists.

3H-clonidine labeled two binding sites in rat cortex membranes with apparent KD values of about 1.0 and 5.9 nM. These sites appeared analogous to "super-high" (SH) and "high" (H) affinity states of the alpha 2-receptor described in human platelets. 10 mM magnesium increased the number of SH receptors by 30% whereas 100 microM GTP reduced SH receptor number by 45% with no significant change in the KD of 3H-clonidine at alpha 2 (SH) sites. IN drug competition studies using 1.0 nM 3H-clonidine, 100 microM GTP reduced the affinity of clonidine and increased the affinity of yohimbine, whereas 10 mM magnesium increased the affinity of clonidine and reduced the affinity of yohimbine. The effect of magnesium on the affinity of several antagonists at cortex 3H-clonidine sites ranged from none (phentolamine) to a 6-fold reduction (piperoxan). These data indicate that different states of the alpha 2-receptor exhibit different affinities for some antagonists.

Animals↗
PubMed1979

Time analysis of corneal endothelial cell density after cataract extraction.

Serial endothelial photographs were taken preoperatively and postoperatively in 200 eyes; 111 eyes contained a Rayner iris clip lens, 54 eyes contained a Fyodorov Sputnik lens, and 35 eyes had no lens. Central endothelial cell density was changed in all instances, with counts in implanted eyes declining 25 to 30%, and in nonimplanted eyes 10 to 15%. In both instances, the decline essentially ceased at about three months. The cause of the greater decline in implanted eyes appeared to be mechanical and subsequent cell loss after the 90-day period was virtually equal for the two groups. Methods that may be used to alter the difference in cell density occurring with implantation are best analyzed by using the 90-day period data for comparison.

Animals↗