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Biomedical subjects

L Jin

Publications and source records attributed to L Jin.

At least 379 records · Page 21Linked to original sources
PubMed1994

Regulation of scatter factor production via a soluble inducing factor.

Scatter factor (SF) (also known as hepatocyte growth factor [HGF]) is a fibroblast-derived cytokine that stimulates motility, proliferation, and morphogenesis of epithelia. SF may play major roles in development, repair, and carcinogenesis. However, the physiologic signals that regulate its production are not well delineated. We found that various human tumor cell lines that do not produce SF secrete factors that stimulate SF production by fibroblasts, suggesting a paracrine mechanism for regulation of SF production. Conditioned medium from these cell lines contained two distinct scatter factor-inducing factor SF-IF activities: a high molecular weight (> 30 kD), heat sensitive activity and a low molecular weight (< 30 kD) heat stable activity. Further studies revealed that SF-producing fibroblasts also secrete factors that stimulate their own SF production. We characterized the < 30-kD SF-IF activity from ras-3T3 (clone D4), a mouse cell line that overproduces both SF and SF-IF. The < 30-kD filtrate from ras-3T3 conditioned medium induced four- to sixfold increases in expression of SF biologic activity, immunoreactive protein, and mRNA by multiple SF-producing fibroblast lines. Ras-3T3 SF-IF activity was stable to boiling, extremes of pH, and reductive alkylation, but was destroyed by proteases. We purified ras-3T3 SF-IF about 10,000-fold from serum-free conditioned medium by a combination of ultrafiltration, cation exchange chromatography, and reverse phase chromatography. The purified protein exhibited electrophoretic mobility of about 12 kD (reduced) and 14 kD (nonreduced) by SDS-PAGE. The identity of the protein was verified by elution of biologic activity from gel slices. Purified SF-IF stimulated SF production in a physiologic concentration range (about 20-400 pM). Its properties and activities were distinct from those of IL-1 and TNF, two known inducers of SF production. We suggest that SF-IF is a physiologic regulator of SF production.

3T3 Cells↗
PubMed1994

Estimation of genetic distance and coefficient of gene diversity from single-probe multilocus DNA fingerprinting data.

DNA fingerprinting exhibits multilocus genotypes of individuals, detected by the use of a single multilocus probe. Consequently, population data on DNA fingerprinting do not provide a complete characterization of the genetic variation in terms of allele-frequency distributions, since neither the number of loci nor the locus affiliation of alleles is directly observable. Yet DNA fingerprinting has been proved to be a cost-effective method of detecting hypervariable polymorphisms in several organisms, where the traditional loci fail to detect enough variation for microevolutionary studies. In the present paper we demonstrate that the above-mentioned features of DNA fingerprinting data do not cause any serious problem when they are used in evolutionary studies. Bias-corrected estimators of Nei's standard and minimum genetic distances are derived, and, by an application of this theory to data on seven short tandem repeat loci in three major human populations, it is shown that these modified measures of genetic distances based on DNA fingerprint patterns are quite close to Nei's distances based on locus-specific allele frequencies. Empirical as well as theoretical support of the adequacy of such genetic distances from DNA fingerprinting data is also discussed, and it indicates that the technical limitations of DNA fingerprinting should not deter the use of the method for short-term evolutionary studies.

Alleles↗
PubMed1994

Analysis of chromogranin/secretogranin messenger RNAs in human pituitary adenomas.

Twenty-five pituitary adenomas were analyzed for expression of various chromogranin/secretogranin (Cg/Sg) messenger RNA (mRNA) transcripts by in situ hybridization (ISH). An additional five adenomas were also analyzed by Northern hybridization. Immunohistochemical staining for CgA and for SgIV (with monoclonal antibody HISL-19) was also performed. Most prolactin and adrenocorticotropin adenomas did not express CgA mRNA or protein, whereas growth hormone (GH) tumors had low to moderate amounts of CgA mRNA by Northern and in situ hybridization analyses and were focally positive for CgA protein. CgB, SgII, SgIII, and SgV mRNA transcripts were present in most adenomas, and SgIV protein was detected in all groups of tumors. A GH and a null cell adenoma cultured for 7 days also expressed CgA/Sg mRNA transcripts and protein. Paraffin sections of some adenomas that were negative for CgA protein had detectable CgA mRNA by in situ hybridization analysis. These results indicate that CgA mRNA and protein are more commonly expressed in glycoprotein hormone-producing tumors compared with other types of pituitary adenomas and that ISH for CgA may detect the mRNA transcripts for CgA even when CgA protein is not detected by immunohistochemistry.

Adenoma↗
PubMed1994

Phylogeny of mitochondrial DNA clones in tassel-eared squirrels Sciurus aberti.

The tassel-eared squirrel, Sciurus aberti, includes six subspecies which occupy restrictive and apparently identical habitats in Ponderosa pine forests in the south-western United States and Mexico; the strict habitat requirement of this species is based on dietary requirements which are only fulfilled in these forests. To examine evolutionary relationships among certain subspecies of S. aberti, we obtained estimates of nucleotide diversity within subspecies as well as nucleotide divergence between subspecies using mitochondrial DNA (mtDNA) analysis. Restriction site polymorphisms were identified in samples of the four US subspecies: S. a. aberti (Abert), S. a. kaibabensis (Kaibab), S. a. ferreus (Ferreus), and S. a. chuscensis (Chuska) Fourteen mtDNA clones were resolved that were, with one exception, uniquely subspecific. Dendrograms constructed by neighbour-joining and maximum parsimony methods revealed two major assemblages: (1) an Abert/Kaibab group; and (2) a Ferreus/Chuska group. The Abert vs. Ferreus clones exhibited the greatest net nucleotide divergence, with a lineage separation estimate approximating 572,000 years ago assuming a nucleotide substitution rate of 7.15 x 10(-9)/year/site. Five out of ten Chuska squirrels shared a clone with one Abert sample; the relative sizes of these two populations and their respective ranges as well as their close proximity support the proposal for relatively recent intermixing of Abert and Chuska populations resulting in what appears to be Abert-->Chuska migration. Nucleotide diversity within subspecies ranked as Kaibab < Ferreus < Abert < Chuska; the relatively high diversity for the Chuska sample is based on the apparent introgression of Abert mtDNA. The relative diversity exhibited by Kaibab, Ferreus and Aberti samples corresponds to the range size of the respective subspecies.

Animals↗
PubMed1994

The effects of zinc oxide and diethyldithiocarbamate on the mitotic index of epidermal basal cells of mouse skin.

The purpose of this study was to investigate the effects of topical treatment with zinc oxide (2.5%, 10%, 25% and 50%) and intraperitoneal treatment with diethyldithiocarbamate (DEDTC) (50 mg/kg, 500 mg/kg and 1,000 mg/kg) on the mitotic index of epidermal basal cells in incised and non-incised mouse skin. The present results showed that topical application of zinc oxide (25% and 50%) increased the mitotic index of epidermal basal cells in incised skin and non-incised skin. Conversely, intraperitoneal administration of DEDTC (500 mg/kg and 1,000 mg/kg) decreased the mitotic index, but only in the incised skin. These results suggest that mitosis of epidermal basal cells may be stimulated by the topical application of zinc oxide both in incised and non-incised mouse skin, and that it also may be inhibited by the intraperitoneal administration of DEDTC in incised mouse skin.

Animals↗
PubMed1994

Effects of dietary fiber on intestinal growth, cell proliferation, and morphology in growing pigs.

Growing pigs (initial BW 14.3 +/- 1.2 kg) were fed isocaloric (3.26 Mcal of ME/kg) and isonitrogenous (16% CP) diets containing either 0 (low fiber, LF; n = 4) or 10% (high fiber, HF; n = 4) wheat straw for ad libitum intake for 14 d. On d 14, each pig was injected i.v. with bromodeoxyuridine (BrdU, a thymidine analog; 5 mg/kg) and was slaughtered 1 h later. Visceral organs (liver, pancreas, and intestines) were weighed, and tissue samples were obtained. Feed consumption, daily gain, gain: feed, and final BW did not differ between treatments. Neither visceral weights nor visceral weights per unit of eviscerated BW were affected by diets. Tissue concentrations of DNA (milligrams/gram of tissue) were lower (P < .03) in HF than in LF only for jejunum, ileum, and liver. Contents of DNA and protein (milligrams) did not differ between LF and HF for intestinal segments or liver. Content of RNA (milligrams) was greater (P < .04) in HF than in LF only for colon. The number of crypt cell nuclei that were labeled with BrdU (indicating DNA synthesis and thus cell proliferation) was increased (P < .03) in HF relative to LF for jejunum and colon. The number of epithelial cells exhibiting DNA fragmentation (indicating programmed cell death) was greater (P < .07) in the HF than in the LF group for jejunum and ileum. Width of intestinal villi was increased (P < .10) in HF vs LF for jejunum and ileum. Depth of intestinal crypts was increased (P < .08) in HF vs LF for jejunum, ileum, and colon.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[Changes in the clinical features of infective endocarditis in recent decade].

In order to know whether there are changes of the clinical features of infective endocarditis (IE) in recent decades, 66 cases of IE diagnosed from 1983 to 1992 were included in this study and compared with the IE patients of Beijing area from 1948 to 1963. The results showed the following changes in the recent decade: 1. Rheumatic heart diseases accounted for less and congenital heart diseases more of the proportion of IE cases when compared with materials of previous decades. Idiopathic mitral valve prolapse and valvular degeneration were found in some of the patients. 2. Cardiac operation and catheterization induced IE became more common, whereas oral infection incited IE less. 3. Skin lesion got much less so that the clinical manifestations of IE were atypical. 4. Hospital mortality decreased markedly.

Adolescent↗
PubMed1994

Effects of estrogen and dexamethasone on a transgenic pituitary cell line. Regulation of hormone and chromogranin/secretogranin expression.

BACKGROUND: Recent studies with the growth hormone releasing hormone (GHRH) transgenic mouse model have shown that growth hormone (GH) and prolactin (PRL) cell hyperplasia and adenomas develop in a time-dependent manner after chronic stimulation by GHRH. However, the adenomatous foci have not been shown to be neoplastic with the ability to proliferate in vitro in the absence of GHRH stimulation. EXPERIMENTAL DESIGN: A cell line was established from an enlarged pituitary from a GHRH transgenic mouse. The cells proliferated readily in culture and were characterized with respect to PRL and GH production and response to estradiol and dexamethasone. The production of chromogranin/secretogranin (Cg/Sg) mRNA transcripts and the regulation of Cg/Sg expression was also analyzed in the newly established cell line to analyze the relationship between PRL, GH, and Cg/Sg production by this cell line. RESULTS: The tumor cells responded to 10(-7) M 17 beta-estradiol (estradiol) by increasing the percentage of immunoreactive PRL-positive cells, and to dexamethasone by decreasing the percentage of PRL-positive cells and mRNA levels. Dexamethasone (10(-7) M) treatment resulted in a 3-fold reduction in PRL mRNA and CgB mRNA, whereas GH and Sg II mRNAs were both increased after dexamethasone treatment. CgA mRNA level was not changed significantly by estradiol or dexamethasone in this cell line. CONCLUSIONS: This stable transgenic cell line is regulated by estradiol and dexamethasone with changes in PRL, GH, and Cg/Sg mRNA transcript levels. There is concordant regulation of PRL and CgB mRNAs as well as GH and SgII mRNAs. These findings indicate that this cell line can be used to study the regulation and possible functions of Cg/Sg in vitro.

Animals↗
PubMed1994

Evaluation of 13 short tandem repeat loci for use in personal identification applications.

Personal identification by using DNA typing methodologies has been an issue in the popular and scientific press for several years. We present a PCR-based DNA-typing method using 13 unlinked short tandem repeat (STR) loci. Validation of the loci and methodology has been performed to meet standards set by the forensic community and the accrediting organization for parentage testing. Extensive statistical analysis has addressed the issues surrounding the presentation of "match" statistics. We have found STR loci to provide a rapid, sensitive, and reliable method of DNA typing for parentage testing, forensic identification, and medical diagnostics. Valid statistical analysis is generally simpler than similar analysis of RFLP-VNTR results and provides powerful statistical evidence of the low frequency of random multilocus genotype matching.

Alleles↗
PubMed1994

Nondetectability of restriction fragments and independence of DNA fragment sizes within and between loci in RFLP typing of DNA.

We provide experimental evidence showing that, during the restriction-enzyme digestion of DNA samples, some of the HaeIII-digested DNA fragments are small enough to prevent their reliable sizing on a Southern gel. As a result of such nondetectability of DNA fragments, individuals who show a single-band DNA profile at a VNTR locus may not necessarily be true homozygotes. In a population database, when the presence of such nondetectable alleles is ignored, we show that a pseudodependence of alleles within as well as across loci may occur. Using a known statistical method, under the hypothesis of independence of alleles within loci, we derive an efficient estimate of null allele frequency, which may be subsequently used for testing allelic independence within and across loci. The estimates of null allele frequencies, thus derived, are shown to agree with direct experimental data on the frequencies of HaeIII-null alleles. Incorporation of null alleles into the analysis of the forensic VNTR database suggests that the assumptions of allelic independence within and between loci are appropriate. In contrast, a failure to incorporate the occurrence of null alleles would provide a wrong inference regarding the independence of alleles within and between loci.

Alleles↗
PubMed1994

[The evaluation of thrombolytic effect of snake venom antithrombus enzyme in treatment of acute myocardial infarction].

To evaluate the thrombolytic effect of Snake Venom Antithrombus Enzyme (SVATE) in the treatment of early acute myocardial infarction (AMI), 52 cases with AMI were randomly allocated to three groups, control (22 cases), SVATE (15 cases), and Urokinase (15 cases). The results show that SVATE can inhibit platelet aggregation, activate slightly fibrinolytic system and decrease markedly plasma fibrinogen level. However, the thrombolytic effect of SVATE in early treatment of AMI is not ideal, it can be used in combination with effective thrombolytic drugs to prevent reocclusion and reinfarction in AMI.

Ancrod↗
PubMed1994

Genetic characterization of American and Western Samoans.

The Samoan islands were politically separated into American Samoa and Western Samoa in the early 1900s. Economic modernization is far more extensive in American Samoa. However, the Samoan archipelago has maintained a remarkable degree of sociocultural homogeneity, including intermarriage. The sociocultural exchanges presumably led to genetic homogeneity between the two Samoas. Detailed genetic comparisons and characterizations of Samoans are scanty, however. As part of a multidisciplinary study of modernization and cardiovascular risk factors in adults, we analyzed nine hypervariable nuclear DNA (HVR) and four serum protein polymorphisms in the two Samoan groups. The average heterozygosities at both DNA and serum protein loci are comparable in the two groups. As expected, the HVR loci reveal a high degree of variability (heterozygosity 30-87%) compared with the serum protein loci (heterozygosity 1-52%). A large proportion of alleles at the HVR loci, ranging from 50% to 100%, are shared between American and Western Samoa. With the exceptions of the D1S80 locus in American Samoa and the D13S118 locus in Western Samoa, the genotype distributions at all loci conform to their respective Hardy-Weinberg expectations. Sporadic occurrence of the F13B*2 allele at the F13B locus in Samoans indicates a low level of European admixture because this allele is unique to Europeans. The calculated zero values of kinship coefficients and standard genetic distances indicate minimal population differentiation between the two Samoan groups.

Alleles↗
PubMed1993

Nerve growth factor effects on human and mouse melanoma cell invasion and heparanase production.

The role of growth factor networks in regulating the progression of human melanocytes towards tumorigenicity and ultimately the malignant phenotype is poorly understood. In particular, the autocrine and paracrine influences that modulate cellular invasion and extracellular matrix degradative enzymes of melanoma cells remain undefined at the molecular level. We report here that nerve growth factor (NGF) can modify some metastasis-associated cellular properties of human and mouse melanoma cells. Treatment of early-passage human metastatic melanoma cells (MeWo) or their variants (3S5, 70W) with biologically active 2.5S NGF resulted in (a) delayed density-dependent inhibition of melanoma cell growth; (b) increased in vitro invasion through a reconstituted basement membrane; and (c) time- and dose-dependent induction of heparanase, a heparan-sulfate-specific endo-beta-D-glucuronidase associated with human melanoma metastasis. These effects of NGF were most marked in the 70W brain-colonizing cells (70W > MeWo > 3S5). The NGF enhancement of heparanase secretion was not species-specific, since it was also observed in murine B16 melanoma cells; the highest NGF stimulation of heparanase was found in brain-colonizing murine B16-B15b variant (B16-B15b > B16-BL6, B16-F10, B16-F1). NGF also increased the invasive capacity of the human 70W and murine B16-B15b sublines in a chemoinvasion assay performed with filters coated with purified heparan sulfate proteoglycan (HSPG). The enhancement of chemotactic response and heparanase production was detected at NGF concentrations sufficient to fully saturate both low- and high-affinity NGF receptors (NGFR), the neurotrophin receptor (p75) and the trkA gene product, respectively. The results suggest that, in addition to the effects of NGF on cellular development and differentiation within the peripheral and central nervous systems, NGF can exert changes in the invasive properties of neuroectoderm-derived melanoma cells.

Animals↗
PubMed1993

Thermodynamics of ligand binding to trp repressor.

The thermodynamics of L-tryptophan and operator DNA binding to the tryptophan repressor of Escherichia coli were analyzed by titration microcalorimetry and van't Hoff analysis of footprinting titrations, respectively. At 25 degrees C in 10 mM sodium phosphate, pH 7.6, and 0.1 M NaCl, the binding of L-tryptophan to the repressor is characterized by values of delta G degrees = -6.04, delta H degree = -14.7, and T delta S degree = -8.67 kcal/mol. The temperature dependence of delta H degree yields delta Cp degree = -0.46 +/- 0.08 kcal/(mol.K) per dimer. The binding is noncooperative at all temperatures studied. At 23 degrees C in 2.5 mM sodium phosphate, pH 7.6, and 25 mM NaCl, the binding of operator DNA to the repressor is characterized by values of delta G degree = -13.3 kcal/mol, delta H degree = -1.55 kcal/mol, T delta S degree = 11.8 kcal/mol, and delta Cp degree = -0.54 +/- 0.10 kcal/(mol.K). Changes in water-accessible surface areas upon binding of L-tryptophan or DNA were calculated from X-ray crystal structures. The experimentally observed delta Cp degree values were compared with delta Cp degree values calculated according to several methods based on various proposed relationships between surface area changes and heat capacity changes. Regardless of which method is used, we find poor agreement between the calorimetric results for L-tryptophan binding and the surface areas calculated from X-ray data; the direction of the discrepancy is that the X-ray data underestimate the value of delta Cp degree.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Proteins↗
PubMed1993

Chronic inhibition of glutamate uptake produces a model of slow neurotoxicity.

Defects in neurotransmitter glutamate transport may be an important component of chronic neurotoxicity in diseases such as amyotrophic lateral sclerosis. There are no reliable models of slow glutamate neurotoxicity. Most previous in vitro systems have studied the rapid neurotoxic effects of direct-acting glutamate agonists. Therefore, we developed a model of slow toxicity in cultured organotypic spinal cord slices. The model was based on selective inhibition of glutamate transport, which continuously raised the concentration of glutamate in the culture medium. This resulted in the slow degeneration of motor neurons over several weeks. Motor neuron toxicity was selectively prevented by non-N-methyl-D-aspartate glutamate receptor antagonists and glutamate synthesis or release inhibitors but not by N-methyl-D-aspartate receptor antagonists. Thus, selective inhibition of glutamate transport produces a model of clinically relevant slow neurotoxicity and appears to be mediated by the action of non-N-methyl-D-aspartate receptors. This data supports the hypothesis that the slow loss of motor neurons in amyotrophic lateral sclerosis could be due, in part, to defective glutamate transport.

Amyotrophic Lateral Sclerosis↗
PubMed1993

BK virus antigenic variants: sequence analysis within the capsid VP1 epitope.

DNA sequences for the VP1 gene which codes for the major capsid protein of BK virus (BKV) and may be responsible for antigenic variability were determined for seven BKV isolates. The observed sequence differences and those previously reported correlate with the typing of isolates into four groups by haemagglutination inhibition. Amino acid coding alterations were found to be clustered within residues 61 to 83. Each antigenic group was found to have a characteristic amino acid sequence between residues 61 and 83. Several clones originating from a single isolate, although differing slightly in restriction enzyme digestion patterns, were found to be identical in this region. The VP1 sequences of three of the four groups were analysed by hydropathy plots and two hydrophilic areas of high antigenicity were identified. One of these corresponds to residues 61 to 83 and it is postulated that this region is the epitope responsible for serotypic differences between BK isolates.

Amino Acid Sequence↗