Biomedical subjects

L Jin

Publications and source records attributed to L Jin.

At least 415 records · Page 23Linked to original sources

PubMed1992

High resolution functional analysis of antibody-antigen interactions.

A comprehensive mutational analysis was used to analyze the side-chains on human growth hormone (hGH) important for binding 21 different anti-hGH mouse monoclonal antibodies (MAbs) whose equivalent concentrations for 50% binding (EC50) ranged from approximately 10(7) to 3 x 10(10) M-1. A combination of homolog- and alanine-scanning mutagenesis coupled with a robot-aided enzyme-linked immunosorbent assay were used to create high resolution "functional epitopes" for each MAb. Every functional epitope mapped to at least two polypeptide segments of hGH that were close together in the folded protein to form a patch. Although these patches sometimes overlapped, each was different indicating no two MAbs bound identically to hGH. The MAbs bound to determinants in loops and helices that were generally most accessible to a 9 A radius probe. Only a few side-chains dominated each functional epitope and these tended to be Arg greater than Pro greater than Glu approximately Asp approximately Phe approximately Ile (Ala, Cys and Trp were not tested). Our studies indicate that most of the accessible surface of hGH is potentially antigenic in the mouse and suggest that functional epitopes are dominated by fewer side-chains than may be in the contact epitope.

Alanine↗

PubMed1992

Heterozygote deficiency, population substructure and their implications in DNA fingerprinting.

Substructured populations exhibit an overall deficiency of heterozygosity whose proportional magnitude depends on the nature of substructuring, i.e., the number of subpopulations (s), their time of divergence (t) from the ancestral population, and the rate of gene flow amongst them (m). Since apparent heterozygote deficiency could be caused by many factors other than population substructuring, one must examine the nature of substructuring that could produce the observed extent of heterozygote deficiency, in order to infer the substructuring from an observed heterozygote deficiency. Using the equivalence of proportional heterozygote deficiency and the coefficient of gene differentiation (GST), we can generate isolines of GST as functions of s, t (in units of 2Ne generations, Ne being the effective population size) and m. Analytical results suggest that large GST values cannot be reached by substructuring alone, unless the number of subpopulations are large and they remain isolated over a long period of time. Application of the theory to population data on six variable number of tandem repeats (VNTR) loci in US Caucasians and US Blacks demonstrates that the observed heterozygote deficiencies at these loci cannot be explained by substructuring within these populations alone. This is so because such large values of GST (3%-10%) would require an absence of gene exchange between the subpopulations and a divergence time from each other of at least 25,000 years ago, neither of which is compatible with the demography and ethnohistory of US Caucasians and Blacks. In contrast, the inability to detect extreme-sized alleles and/or incomplete resolution of nearly similar-sized alleles following Southern gel electrophoresis could easily explain the observed heterozygote deficiencies. The implications of these results are discussed in the context of the forensic use of DNA-typing data, and justify the employment of population genetic principles in forensic genetics.

Black People↗

PubMed1992

Pituitary lactotrophs and somatotrophs in pregnancy: a correlative in situ hybridization and immunocytochemical study.

Lactotroph hyperplasia is a prominent finding in the adenohypophyses of pregnant women. In order to elucidate the morphogenesis of this change, pituitaries from 16 women in various phases of pregnancy were collected at autopsy and studied by histology, immunocytochemistry and in situ hybridization. The results showed that the increase in the amount of prolactin (PRL) mRNA paralleled the progressive lactotroph hyperplasia. The presence of mitoses in PRL-immunoreactive cells provided evidence that proliferation of preexisting lactotrophs contribute to lactotroph accumulation. Growth hormone (GH) immunoreactive cells showed a marked reduction in GH mRNA indicating that GH synthesis was inhibited. In many GH-immunoreactive cells, PRL mRNA became apparent. These findings demonstrate that GH is stored following discontinuation of GH synthesis. It appears that, when PRL is secreted in excess during pregnancy, somatotrophs are recruited to produce PRL. These somatotrophs begin to express PRL mRNA, transform to bihormonal mammosomatotrophs and possibly later to lactotrophs, contributing to PRL production. Mature somatotrophs may be regarded as reserve cells in the adenohypophysis, having the potential to switch hormone synthesis and to convert to mammosomatotrophs and possibly lactotrophs.

Adolescent↗

PubMed1992

Differential polymerase chain reaction for detection of wild-type and a vaccine strain of Aujeszky's disease (pseudorabies) virus.

A polymerase chain reaction (PCR) strategy for differentiating between a vaccine mutant strain and wild-type (WT) strains of Aujesky's disease (pseudorabies) virus (ADV) was evaluated. With this approach, a single virus or a concurrent WT and vaccine virus infection could be distinguished by targeting the genomic alteration within the vaccine strain. PCR primers were designed for a recombinant vaccine virus that has almost all of the WT gX gene replaced by the lacZ gene. One primer, corresponding to a conserved sequence upstream of the altered region, was selected for common use. The differentiating primers were chosen from the unique WT gX and vaccine lacZ gene sequences. The sensitivity of the differential PCR was analyzed using extracted viral DNA and in vitro infected cell lysates. Approximately 10 and between 10 to 100 molecules of WT and vaccine viral DNAs, respectively, could be detected, regardless of the presence or absence of uninfected cell lysates. Detection of viral DNA from in vitro infected cell cultures approximated this level of sensitivity. The specificity of the amplifications was verified by restriction endonuclease analysis and Southern hybridization. Although the vaccine primer pair target was amplified to a lesser degree as compared to the WT primer pair product, utility of the differential PCR was demonstrated using trigeminal nerve ganglia from swine infected with vaccine virus and WT virus. Both viral targets were detected only by their specific primer pair, in either the single or dual infection.

Animals↗

PubMed1992

Genetic variation at five trimeric and tetrameric tandem repeat loci in four human population groups.

Trimeric and tetrameric short tandem repeats (STRs) represent a rich source of highly polymorphic markers in the human genome that may be studied with the polymerase chain reaction (PCR). We report the analysis of a multilocus genotype survey of 97-380 chromosomes in U.S. Black, White, Mexican-American, and Asian populations at five STR loci located on chromosomes 1, 4, 11, and X. The heterozygote frequencies of the loci ranged from 0.36 to 0.91 and the number of alleles from 6 to 20 for the 20 population and locus combinations. Relative allele frequencies exhibited differences between populations and unimodal, bimodal, and complex distributions. Although deviations were noted at some locus-population test combinations, genotype data from the loci were consistent overall with Hardy-Weinberg equilibrium by three tests. Population subheterogeneity within each ethnic group was not detected by two additional tests. No mutations were detected in a total of 860 meioses for two loci studied in the CEPH kindreds and five loci studied in other families. An indirect estimate of the mutation rates gave values from 2.3 x 10(-5) to 15.9 x 10(-5) for the five loci. Higher mutation rates appear to be associated with greater numbers of tandem repeats in the core motif. The most frequent genotype for all five loci combined appears to have a frequency of 7.59 x 10(-4). Together, these results suggest that trimeric and tetrameric STR loci are useful markers for the study of new mutations and genetic linkage analysis and for application to personal identification in the medical and forensic sciences.

Alleles↗

PubMed1992

Molecular approaches for the analysis of chromogranins and secretogranins.

Recent molecular analyses have contributed to our knowledge about the chromogranin/secretogranin (Cg/Sg) family and their utility in diagnostic pathology. The genes for five of these proteins have been cloned, and the deduced amino acid sequences have provided insights into the structure and possible functions of the Cgs/Sgs, including their role as prohormones. Northern hybridization and in situ hybridization histochemistry have provided a great deal of information about the tissue distribution of the Cg/Sg gene products. Some neoplasms such as small cell lung carcinomas, which have little stored Cg/Sg protein, have abundant cytoplasmic mRNAs that can be readily detected by hybridization studies. Some other neoplasms such as neuroblastomas have decreased CgA and increased SgII mRNAs during maturation to ganglioneuromas. There is also a differential expression of Cgs/Sgs in some endocrine neoplasms such as parathyroid adenomas, which express abundant CgA mRNA and little CgB mRNA, and in pituitary prolactinomas, which express CgB mRNA but not CgA mRNA. The mRNA for CgA has been found unexpectedly in some neoplasms such as 15% of colonic adenocarcinomas. Thus, molecular approaches in the analysis of Cgs/Sgs should contribute to the diagnosis of endocrine neoplasms and may provide support for a molecular classification of neoplasms in diagnostic pathology.

Animals↗

PubMed1992

Analysis of gastrinomas by immunohistochemistry and in situ hybridization histochemistry.

Gastrinomas from 25 patients were examined by immunohistochemistry (IHC) and in situ hybridization histochemistry (ISH). Most patients (84%) presented with the Zollinger-Ellison syndrome. Six had multiple endocrine neoplasia type I (MEN-I). Twelve patients (48%) had duodenal primaries and 11 of 12 of these had metastases to regional lymph nodes and/or liver in spite of the small sizes of the primary tumors (mean size of 0.9 cm). Five patients had pancreatic gastrinomas and eight patients had metastatic tumor in regional lymph nodes or liver at surgery but a primary was not found. IHC and ISH analyses showed that all cases were positive for gastrin protein and 24 of 25 (96%) expressed gastrin mRNA that was easily detected in formalin-fixed, paraffin-embedded tissue sections. Both benign and malignant tumors expressed alpha subunit of human chorionic gonadotropin protein (alpha-HCG). However, only malignant gastrinomas (29%) expressed adrenocorticotropic hormone protein or proopiomelanocortin (POMC) mRNA. ISH and Northern hybridization analysis revealed that chromogranin A mRNA was the most common member of the chromogranin/secretogranin (Cg/Sg) family which was expressed in both benign and malignant gastrinomas. These results indicate that duodenal gastrinomas are common in both sporadic and MEN-1-associated cases, and small duodenal primaries may be associated with extensive regional lymph node and liver metastases. Expression of ACTH/POMC protein and mRNA was consistently associated only with malignant gastrinomas while gastrin protein, gastrin mRNA and Cgs/Sgs mRNAs were readily detected in both benign and malignant gastrinomas.

Adrenocorticotropic Hormone↗

PubMed1992

Effects of atrial natriuretic factor on patients with renovascular hypertension.

Previous studies have shown the effects of atrial natriuretic factor (ANF) on rats with renovascular hypertension (RVH). In the present study low dose alpha-hANF (0.025 microgram/kg/min) was administered intravenously for 60 minutes to seven RVH patients. Results demonstrated an inhibition of renin-angiotensin-aldosterone system (RAAS), reduction of plasma catecholamine and arginine vasopressin(AVP), diuresis and natriuresis, increase of hematocrit and creatinine clearance, and slight decrease of blood pressure. These results showed that most factors involved in the establishment and maintenance of RVH are affected by ANF infusion.

Adult↗

PubMed1992

Chromogranin A, chromogranin B and secretogranin II mRNAs in the pituitary and adrenal glands of various mammals. Regulation of chromogranin A, chromogranin B and secretogranin II mRNA levels by estrogen.

BACKGROUND: The chromogranin/secretogranin (Cg/Sg) acidic proteins are widely distributed in vertebrate species. They are thought to play a role in hormone packaging within secretory granules, in hormone secretion, and serve as prohormones for various proteolytic cleavage products. The genes for most members of the Cg/Sg family have been cloned, so hybridization analysis can be used to analyze the distribution and regulation of Cg/Sg mRNAs in various vertebrate species. EXPERIMENTAL DESIGN: The method of in situ hybridization was used to localize chromogranin A, chromogranin B, and secretogranin II in adrenal and pituitary tissues from laboratory animals and from humans in order to analyze the distribution of various Cg/Sg mRNAs in these tissues. To gain some insight into the regulation and possible functions of specific Cg/Sg members, female rats were ovariectomized for different periods with and without estrogen replacement and the pituitaries were subsequently analyzed by in situ hybridization and Northern hybridization analyses. Combined ISH and immunohistochemistry were used to localize the specific cell types in normal rat pituitary that expressed the mRNA for chromogranin A, chromogranin B, and secretogranin II. RESULTS: All three Cg/Sg mRNAs were detected in pituitary and adrenal tissues of rats, mice, dogs, monkeys, and humans. Combined in situ hybridization and immunohistochemistry using rat pituitary revealed that the glycoprotein hormone-secreting cells expressed all three Cg/Sg mRNAs in approximately equal amounts. Ovariectomy followed by estrogen replacement resulted in decreased levels of CgA and SgII mRNAs. In contrast, the level of CgB mRNA, that was not changed by ovariectomy, was increased after estrogen treatment, probably secondary to prolactin cell hyperplasia. CONCLUSIONS: The three principal Cg/Sg mRNAs are present in the adrenal and pituitary of various vertebrates. Estrogen plays a significant role in regulating the mRNA levels of different Cgs/Sgs suggesting functional and regulatory differences in Cg/Sg proteins.

Adrenal Glands↗

PubMed1992

Morphologic effects of hGRH gene expression on the pituitary, liver, and pancreas of MT-hGRH transgenic mice. An in situ hybridization analysis.

Morphologic changes in the pituitary, liver, and pancreas of mice with the metallothionein-human growth hormone--releasing hormone (MT-hGRH) transgene were analyzed by in situ hybridization histochemistry (ISH). There was progression from somatotroph hyperplasia to neoplasia in pituitaries of transgenic mice. Pituitary neoplasms were present between 9 to 12 months of age in some mice. Magnetic resonance imaging (MRI) readily identified enlarged pituitaries in MT-hGRH transgenic mice. Serum mouse GH and hGRH levels were marked elevated in MT-hGRH transgenic mice. In situ hybridization histochemistry showed mRNA for hGRH in liver, pituitary, pancreas, spleen, and in most other tissues examined. Combined ISH and immunohistochemistry in the pituitary gland showed that some of the GH cells also produced hGRH, and ultrastructural immunohistochemical analysis of pituitaries showed that GH and hGRH were localized in the same cell and within the same secretory granules. Liver cells of MT-hGRH transgenic mice showed evidence of hypertrophy, and the pancreatic islets were hyperplastic with significant increases in the islet cell areas. The morphologic changes in the liver were distinctive enough to separate control littermates from MT-hGRH transgenic mice in all cases. The enlarged pancreatic islets had increased numbers of insulin-producing cells. Immunoreactive hGRH and hGRH mRNA were both localized in islet cells, and an intense hybridization signal of hGRH mRNA, but only weak staining for hGRH protein, were detected in the liver of transgenic mice. These results indicate that excessive hGRH production leads to distinct morphologic changes in various organs in MT-hGRH transgenic mice and that there is temporal progression from hyperplasia to adenomatous somatotrophs in pituitaries with chronic stimulation by hGRH that involves paracrine, endocrine, and autocrine mechanisms.

Adenoma↗

PubMed1992

Cloning and expression of midecamycin 4"-acylase gene in spiramycin producing strains.

A recombinant plasmid p66B containing the midecamycin 4"-acylase gene was obtained by cloning this gene into plasmid vetor pIJ680 from the primary clone pCN6C5, presumably harboring the midecamycin biosynthetic gene. The expression of the midecamycin 4"-acylase gene (p66B) in spiramycin producing strains resulted mainly in the production of 4"-isovalerylspiramycin. Another positive clone pCN10F5 was discovered from the genomic library of S. mycarofacians 1748 by probing with p66B DNA BamHI-BamHI 2.3kb fragment. A BamHI-BamHI 8.0kb homologous region on pCN10F5 was determined by Southern hybridization and was subcloned into plasmids pWHM3 and pIJ680. Recombinant plasmids pWF5 and p6F5 with molecular size about 15.2kb and 13.3kb, respectively, were obtained. Transformation of spiramycin producing strains with these plasmids resulted in the production of two major components. Based on their physicochemical properties and spectral evidences, component I was identified as 4"-propionylspiramycin III, and component II as 4"-propionylspiramycin II. Southern hybridization confirmed that the BamHI-BamHI 8.0kb fragment was cloned in the spiramycin producing strain. Only pCN10F5 clone was identified from the genomic library of S. mycarofaciens 1748 when the 4"-isovaleryltransferase gene of carbomycin producing strain S. thermotolerans was used as a probe in colony hybridization. It suggests that there is a difference between the 4"-acyltransferase genes in the pCN6C5 and pCN10F5 clones.

Acyltransferases↗

PubMed1992

Clinical manifestations and prevalence of different types of supraventricular tachycardia among Chinese.

Sixty-nine cases of paroxysmal supraventricular tachycardia (PSVT) were submitted to electrophysiological studies. The prevalence of different types of PSVT is as follows: 49% of the cases had atrioventricular reentry tachycardia (AV-RT), 14.5% atrioventricular nodal reentry tachycardia (AVN-RT), 28% AV + AVN - RT, and 8.5% other types. Altogether 77% in this group had atrioventricular accessory pathway, of which half are concealed pathway. Electrocardiographic characteristics during tachycardia give hints to diagnosis: (1) AV - RT has the fastest heart rate, with 62% 200 BPM or more, and 82% more than 188 BPM; (2) retrograde P waves can be detected in 64% of cases with AV bypass; (3) 50% of AV - RT shows QRS of bundle branch block pattern. Since accessory pathways are present in the majority of PSVT patients in China, the importance of treatment is stressed.

China↗

PubMed1991

Cytogenetic studies of gastric adenocarcinoma.

Cytogenetic analyses were performed on a short-term culture of a primary tumor and an established cell line of gastric adenocarcinoma (SC-M1). The former case was near-diploid, and the latter was near-triploid. No common numerical and structural change or breakpoint was found in these cells. Review of the 13 cases of gastric carcinomas so far reported showed that only trisomies 8 and 9 were consistent findings. The Y chromosome, although lost in all the near-triploid cases, was preserved in all of the near-diploid cases. No consistent structural abnormality and breakpoint were identified in this and other studies.

Adenocarcinoma↗

PubMed1991

In situ hybridization in the study of pituitary tissues.

This presentation summarizes the use of in situ hybridization in the study of pituitary abnormalities. The basic techniques, technical problems and pitfalls in in interpretation and the application of in situ hybridization are discussed.

Adenoma↗

PubMed1991

Effects of estrogens on pituitary cell and pituitary tumor growth.

Estrogens have been known to induce PRL cell hyperplasia in the anterior pituitary of some species for many decades. Recent studies have shown variable susceptibility to estrogen-induced hyperplasia in different strains of rats. The distinction between hyperplastic pituitaries and adenomas is usually not made by most investigators in this field, although true neoplasms can usually be propagated by serial transplantation. The growth of transplantable tumors is usually inhibited by estrogen in vivo. Estrogens have a biphasic effect on pituitary cell proliferation in vitro with higher concentrations of estradiol inhibit cell growth, and lower concentrations stimulating PRL secretion. Estrogens can regulate PRL gene methylation in vivo thus affecting PRL mRNA expression. Recent studies have suggested that estrogen regulates signal transduction by stimulating protein kinase C. Estrogens also regulate specific proto-oncogenes such as c-myc and c-fos. These observations may help to explain some of the regulatory effects of estrogens on cell proliferation and tumor development.

Animals↗

PubMed1991

Detection of estrogen receptor in paraffin-embedded sections of breast carcinoma by immunohistochemistry and in situ hybridization.

Biopsy specimens of small breast carcinomas are often insufficient for both diagnosis and the biochemical determination of estrogen receptor (ER) protein. Recent reports from various laboratories have shown the utility of immunohistochemical detection of ER protein in paraffin-embedded tissue sections. We used immunohistochemical (IHC) staining with the Abbott ER antibody (H222) and in situ hybridization (ISH) analysis with a 35S-labeled and a biotinylated oligonucleotide probe to detect ER protein and messenger RNA (mRNA) in tissue sections of 53 breast carcinomas. The dextran-coated charcoal (DCC) assay of these same cases revealed positive receptor levels in 31 of 53 cases, whereas the IHC method was positive in 33 of 53 cases. ISH for detection of ER mRNA was more sensitive than IHC or the biochemical assay for estrogen binding proteins, as the isotopic probe detected ER mRNA in 47 of 53 cases, whereas the biotinylated probe detected ER mRNA in 46 of 53 cases. These results indicate that ER protein can be readily detected in enzyme-treated paraffin tissue sections and that the IHC detection of ER protein correlates highly with the DCC assay. ISH with isotopic and biotinylated probes detects ER mRNA in most cases found to be positive for ER protein and also in many cases without detectable ER protein. Although detection of ER protein in paraffin sections correlates highly with the biochemical assay in this report and in other reported studies, the clinical significance of increased sensitivity by ISH is unknown and must await clinical correlative follow-up studies.

Breast Neoplasms↗

PubMed1991

Sensitivity of the standardized pseudorabies virus neutralization test varies with the test strain used.

The effect of altering the strain of the test virus used in the standardized pseudorabies virus neutralization (VN) test on the sensitivity of the assay was evaluated. Comparative VN tests were performed using 4 different strains: the avirulent Bartha parental, the avirulent recombinant Bartha gIIIKa, the moderately virulent Shope (currently used for the VN test at the National Veterinary Services Laboratory, Ames, IA), and the highly virulent P2208 (Funkhauser). A radioimmunoassay and a Western immunoblotting technique were employed to verify the presence of anti-pseudorabies virus (PrV) antibodies in sera. Statistical analysis indicated that replacement of the Shope strain by the Bartha gIIIKa or the P2208 strain resulted in VN titers that were 4.23- and 2.00-fold higher, respectively. Despite these differences, specificity with regard to PrV diagnosis was unaltered. This apparent enhancement of the sensitivity of the PrV VN test would be beneficial for the serologic identification of PrV-infected animals during an eradication effort.

Animals↗

PubMed1991

Targeted ablation of pituitary gonadotropes in transgenic mice.

LH, FSH, and TSH are heterodimeric glycoprotein hormones composed of a common alpha-subunit and unique beta-subunits. The alpha-subunit is produced in two distinct specialized cell types of the pituitary gland: gonadotropes, which synthesize LH and FSH, and thyrotropes, which synthesize TSH. We have demonstrated that 313 base pairs of the bovine-alpha subunit promoter direct expression of diphtheria toxin A chain specifically to the gonadotropes in transgenic mice. Animals carrying this transgene generally exhibit reproductive failure and lack of gonadal differentiation, consistent with gonadotrope ablation. Lack of gonadotrope activity was verified by RIA and immunohistochemical staining for LH. The phenotype of these transgenic mice is nearly identical to mice homozygous for the spontaneous mutation, hpg, which is due to a deletion in the gene encoding GnRH. Thyrotrope function was judged normal based on overall growth of the animals, appearance of their thyroids, T4 levels measured by RIA, and immunohistochemical staining for TSH. The ablation of gonadotropes but not thyrotropes suggests that separate cis-acting elements are necessary for expression of the alpha-subunit gene in these two cell types. Pituitary content of ACTH and GH was apparently normal, while PRL synthesis and storage were reduced. Thus, in a pituitary almost completely devoid of gonadotropes, most other pituitary functions were normal. This suggests that most pituitary cells are able to differentiate independently of terminal gonadotrope differentiation and can function in the absence of paracrine signaling provided by gonadotropes.

Adrenocorticotropic Hormone↗