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Biomedical subjects

J D Gitlin

Publications and source records attributed to J D Gitlin.

72 records · Page 4Linked to original sources
PubMed1991

Rat hemopexin. Molecular cloning, primary structural characterization, and analysis of gene expression.

A full-length hemopexin cDNA was isolated from a rat liver cDNA library and the derived amino acid sequence was obtained. Rat hemopexin shows a 76% amino acid homology with human hemopexin. The amino-terminal domain of rat hemopexin contains two histidine residues that are conserved in the human and rat sequences and are the most likely heme axial ligands. Analogous to human hemopexin, the rat hemopexin consists of 10 internal repeating peptide motifs characteristic of the pexin gene family. A complete conservation of cysteine residues is seen between the human and rat sequences suggesting an identical disulfide bridge structure in both proteins. Our analysis of the primary structure of rat hemopexin reveals characteristics typical for members of the pexin gene family and suggests a conserved evolutionary role for the C-terminal (non-heme-binding) domain of this protein. The full-length rat hemopexin cDNA was used to analyze changes in hemopexin gene expression during development and experimental inflammation. RNA blot analysis showed a single 2.0-kb hemopexin mRNA present in fetal liver at day 14. Hemopexin-specific mRNA was not detected in embryonic or fetal tissues at earlier stages of development and was confined to the liver throughout fetal, newborn, and adult life. The abundance of hemopexin mRNA was found to increase throughout gestation, with a sharp increase in the first postnatal weeks, reaching maximum levels in adult animals. Endotoxin-induced inflammation resulted in a 5-fold increase in hepatic hemopexin mRNA content within 48 h without associated changes in hemopexin transcript size. Adult animals exposed to hyperoxia (95% oxygen) showed a 3-fold increase in hepatic hemopexin mRNA content.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Molecular cloning of a rat uterine gap junction protein and analysis of gene expression during gestation.

To study the molecular mechanisms controlling the rapid increase in myometrial gap junctions observed in the parturient uterus, we have isolated a full-length cDNA clone corresponding to a rat uterine gap junction protein. Nucleotide sequence analysis of the cDNA clone reveals complete identity of the coding region with that of a previously reported heart gap junction protein (connexin43). Southern blot analysis suggests that the gene encoding this gap junction protein exists as a single copy in the rat haploid genome and contains no introns within the coding region. RNA blot analysis with this gap junction cDNA reveals a single 3.0-kb mRNA in uterine tissue without changes in transcript size throughout gestation. When normalized to the amount of 28S rRNA, the relative abundance of the connexin43 transcript in uterine tissue is quite constant between the nonpregnant state, during gestation, intrapartum, and postpartum. Similar size transcripts are shown by RNA blot analysis to be present in heart, lung, liver, brain, and skeletal muscle, and these transcripts are identified by the same 3'-nontranslated sequence probe. The results of these studies suggest that rat connexin43 is encoded by a single gene that is transcribed to identical transcripts in heart, uterus, and other tissues. They further suggest that changes in the abundance of connexin43 transcript are unlikely to be responsible for the abrupt increase in connexin43-containing myometrial gap junctions at term.

Amino Acid Sequence↗
PubMed1991

Induction of ceruloplasmin gene expression in rat lung during inflammation and hyperoxia.

To determine the effect of inflammation on extrahepatic ceruloplasmin gene expression we examined the ceruloplasmin mRNA content of adult rat tissues after endotoxin injection. Within 8 h of a dose of endotoxin ceruloplasmin mRNA content increased in the liver as expected and was also detectable in the lung. The effect of endotoxin was tissue specific because ceruloplasmin mRNA was not consistently detected in other extrahepatic tissues. The kinetics of ceruloplasmin mRNA accumulation in lung and liver tissue were similar with a maximum seven- to ninefold increase in ceruloplasmin mRNA content in each tissue within 24 h. The relative rate of ceruloplasmin gene transcription was increased in both tissues within 3 h of endotoxin, suggesting similar mechanisms of regulation of ceruloplasmin gene expression during inflammation. One cellular site of ceruloplasmin production in the inflamed lung was found to be the alveolar macrophage, which expressed the ceruloplasmin gene and synthesized ceruloplasmin protein in response to endotoxin in vitro. Because of these findings we also examined the effects of hyperoxia on ceruloplasmin gene expression. Exposure of adult rats to 95% O2 resulted in a five- to sixfold induction of ceruloplasmin mRNA in lung tissue within 46 h, and this response was time dependent, reaching maximum values at 86 h. Hyperoxic induction of ceruloplasmin mRNA was specific to the lung and not the result of systemic inflammation because hepatic ceruloplasmin mRNA content remained constant. These data indicate that the lung is a prominent site of ceruloplasmin gene expression during inflammation and hyperoxia and suggest that this protein may play a previously unappreciated role in pulmonary injury or repair.

Animals↗
PubMed1990

Primary structure of rat ceruloplasmin and analysis of tissue-specific gene expression during development.

cDNA clones corresponding to rat ceruloplasmin were isolated from newborn rat lung and liver cDNA libraries and the nucleotide sequence was obtained. The derived amino acid sequence of rat ceruloplasmin is 93% homologous to the corresponding human sequence and contains a 19-amino acid leader peptide plus 1040 amino acids of mature protein. Southern blot analysis indicates that the ceruloplasmin gene exists as a single copy in the rat haploid genome. Using these cDNA clones in RNA blot analysis, a single 3.7-kilobase ceruloplasmin-specific transcript is detected in fetal rat liver and lung by day 15 of gestation. During fetal development the abundance of this transcript increases selectively in these two tissues and at birth is 60% of that found in the adult liver. Postnatally the temporal pattern of ceruloplasmin gene expression in lung and liver differs. Within the first 3 weeks postpartum ceruloplasmin mRNA content decreases in lung to undetectable levels, while that in the liver reaches adult levels. Primer extension reveals a single identical start site of ceruloplasmin gene transcription in lung and liver and biosynthetic studies indicate that each tissue synthesizes a ceruloplasmin protein which is qualitatively similar to that synthesized by adult liver. Ceruloplasmin mRNA is also detected in human fetal lung explant and a human lung adenocarcinoma cell line suggesting that a similar pattern of expression occurs in the developing human lung. These data indicate that lung is the predominant extrahepatic site of ceruloplasmin gene expression during fetal development and suggest that this protein may play a previously unappreciated role in lung development or pulmonary antioxidant defense.

Aging↗
PubMed1989

Regulation of human and murine complement: comparison of 5' structural and functional elements regulating human and murine complement factor B gene expression.

The serine protease complement factor B (Bf), an acute phase plasma protein, is a component of the alternative pathway of complement activation. Previous studies revealed that several cytokines including IFN-gamma and IL-1 are involved in mediating acute phase Bf expression. To determine the molecular details of Bf expression we isolated, sequenced and characterized the 5' flanking regions of the human and murine Bf genes. In both species the Bf transcriptional start site in liver was located less than 400 bp 3' to the polyadenylation site of the upstream C2 gene. This upstream intergenic region contained greater than 65% nucleotide homology between species. Within this region, an IRS and three heat shock consensus elements were found in the murine sequence in an identical position to that of the human. To examine the functional details of Bf expression, a series of mouse and human Bf promoter-chloramphenicol acetyltransferase (CAT) chimeric gene constructs were transfected into mouse L or human HepG2 cells. Analysis of expression of these fusion gene constructs revealed that 1) cis-acting DNA sequences identified, at least in part, in the 3' untranslated region of the C2 gene (within the 400 bp upstream of the Bf cap site) mediate responsiveness to IL-1 and IFN-gamma, 2) the responsiveness to each mediator appears to be conferred by separate upstream regions similar in position and homologous in man and mouse, and 3) the IL-1 responsive region in both species appears to have the characteristics of an enhancer element. The results of this analysis suggest a selective pressure to conserve the intergenic sequence between C2 and Bf genes and that further studies of these sequences will be useful in elucidating mechanisms controlling the acute phase response.

Animals↗
PubMed1988

Transcriptional regulation of ceruloplasmin gene expression during inflammation.

Mixed sequence oligonucleotides were used to isolate a series of acute-phase human liver cDNA clones corresponding to the serum alpha 2-globulin ceruloplasmin. These clones were characterized, sequenced, and used to analyze changes in hepatic ceruloplasmin mRNA content during inflammation. In all species examined, hepatic ceruloplasmin mRNA content increased approximately 6-10-fold over control values within 24 h following the induction of inflammation. The mechanisms leading to this increase in hepatic ceruloplasmin mRNA content were studied following turpentine-induced inflammation in Syrian hamsters. Nuclear run-on assays demonstrated an increase in the relative rate of transcription of the ceruloplasmin gene within 3 h following induction, reaching maximum values by 18 h. Hepatic ceruloplasmin mRNA content increased 2-fold within 12 h following induction, reached maximum values by 24 h, and returned to control within 72 h. In contrast, serum ceruloplasmin concentration did not increase until 36 h, reached maximal levels by 120 h, and remained elevated for the course of the study. These data indicate that inflammation leads to a rapid increase in hepatic ceruloplasmin mRNA content. This increase is largely the result of increased ceruloplasmin gene transcription, but comparison of the relative rate of transcription and mRNA accumulation suggests that changes in ceruloplasmin mRNA turnover are also involved. In addition, translational and/or post-translational mechanisms must account for the observed changes in serum ceruloplasmin concentration seen during inflammation.

Animals↗
PubMed1987

Randomized controlled trial of exogenous surfactant for the treatment of hyaline membrane disease.

We conducted a prospective, randomized, unblinded, controlled trial of exogenous bovine surfactant (surfactant TA) in premature infants requiring ventilator support for the treatment of severe hyaline membrane disease. Forty-one low birth weight infants with severe hyaline membrane disease were randomly assigned to saline or surfactant therapy and treated within eight hours of birth. Significant improvements in oxygenation (increased arterial/alveolar PO2) and respiratory support (decreased mean airway pressure) were seen in the group receiving surfactant within four hours after treatment. These improvements were maintained in the surfactant-treated infants, who also had fewer pneumothoraces and fewer number of days in environments of fractional inspiratory oxygen greater than 0.4 mm Hg. No problems were associated with administration of surfactant, and no acute side effects were detected. We conclude that exogenous surfactant, administered early in the course of severe hyaline membrane disease, is an effective therapy that can diminish the amount of respiratory support required during the first 48 hours of life.

Animals↗
PubMed1984

Exogenous surfactant therapy in hyaline membrane disease.

Exogenous surfactant therapy appears to offer promise in the treatment and possible prevention of HMD. Laboratory investigations have begun to reveal the molecular basis for surfactant metabolism and the relationship of this complex process to alveolar stability and pulmonary function. There is every reason to encourage clinical investigation with surfactant therapy in parallel with further basic research. Nevertheless, pediatricians must proceed in small steps with carefully designed studies to address specific questions regarding both efficacy and toxicity. Results from various studies must be shared and discussed and every attempt must be made to eventually provide standardized, readily available preparations of known efficacy and toxicity. Efforts by many investigators make it seem probable that this goal will be achieved in the near future.

Animals↗
PubMed1983

Culture of retinal capillary cells using selective growth media.

Capillary fragments are isolated from the microvasculature of the bovine retina using limited collagenase digestion and sieving. The endothelial cells obtained from these capillary fragments are cultured in media containing platelet-poor plasma supplemented with retinal extract, which contains an endothelial cell mitogen. These cells form typical monolayers in vitro, contain Factor VIII antigen, and can be passaged serially. The pericytes obtained from these capillary fragments are cultured in media containing calf serum. These cells can also be passaged serially, are not contact-inhibited, and do not stain for Factor VIII antigen. Cultures of capillary cells such as these will allow the study of the individual cells from specific microvascular beds involved in various normal and pathological processes.

Animals↗
PubMed1976

Selective transfer of plasma proteins across mammary gland in lactating mouse.

Specific plasma proteins were labeled with 131I, and their half-lives in lactating and nonlactating mice were determined. The proteins included mouse IgF and IgM, mouse, bovine, rabbit, and human IgG, human serum and salivary IgA, human transferrin and albumin, and mouse and human immunoglobin light chains. The rates at which these proteins are transferred across the mammary gland in mice suckling their young were calculated: transmammary protein transfer was found to be highly selective. The G-class immunoglobulins readily traversed the mammary gland, the rate being dependent on the IgG load presented to the transport system. Immunoglobulin lambda-chains and human serum IgA crossed the mammary gland even more rapidly than did the G immunoglobulins. Human IgA without secretory piece was transported into milk more rapidly than IgA with secretory piece attached. Protein transport across the mouse mammary gland was found to be similar to and yet different from protein transport across either the suckling mouse intestine or the mouse placenta as to which proteins crossed and at what relative rates.

Animals↗
PubMed1975

The opsonic fragment of the third component of human complement (C3).

Human peripheral blood phagocytes ingest Escherichia coli 026:B6 lipopolysaccharide (LPS)-coated paraffin oil droplets containing Oil red O only if fresh serum deposits C3 on the surfaces of the particles (opsonizes them), by reactions involving the properdin system. The rate of binding of purified [125-I]C3 in serum to LPS-coated particles correlated precisely with the rate of acquisition of ingestibility assayed spectrophotometrically. Once opsonized, LPS-coated particles remained fully ingestible and retained fixed [125-I]C3 radioactivity even after exposure to extremes of temperature, pH, ionic strength, phospholipases, urea or guanidine, some nonionic and ionic detergents, and organic solvents. Trypsin, human conglutinogen-activating factor, another heat-stable activity found in human serum, and sodium dodecyl sulfate removed radioactivity and diminished ingestibility of the opsonized particles. Alkylation, reduction plus alkylation and F(ab')2 from anti-C3 blocked ingestibility but did not alter particle-bound radioactivitymelectrophoretic and tryptic peptide autoradiographic analysis of dodecyl sulfate eluates of opsonized particles, cleansed of many contaminating proteins by boiling with 2 M NaCl (yet still opsonized), revealed that the polypeptide with C3-derived radioactivity had a mol wt of approximately 140,000 and was composed of 70,000 mol wt subunits linked by disulfide bonds. Immunochemical analysis and comparison of the peptide structure of the eluate with that of C3 indicated that the opsonic fragment is not the fragment defined as C3b but a smaller derivative of C3.

Chemical Phenomena↗
PubMed1975

The mechanism of action of the C3b inactivator (conglutinogen-activating factor) on its naturally occurring substrate, the major fragment of the third component of complement (C3b).

The fixation of the third component of complement (C3) results in many important biological phenomenon, among which are (a) immune adherence (1), (b) enhancement of phagocytosis (2,3), (c) the release of an anaphylatoxin which is a potent releaser of histamine (4), and (d) the feedback activation of the alternative pathway (5,6). The physiological mechanisms involving C3 fixation require the generation of a C3 convertase which may occur by two separate pathways. C3 convertase can be generated, in the form of C42, by the so-called classical pathway of activation or in the form C3b,B by the alternative or properdin pathway (7). In both cases, C3 is converted to C3b by cleavage of a small peptide, C3a. Normal human serum contains an inactivator of activated C3b. This C2b inactivator or conglutinogen-activating factor (KAF) has been shown to inhibit both immune hemolysis and the immune adherence properties of C3b and to cause cleavage of C3b in the fixed and fluid- phase stages (8-11). Although it is known that the C3b inactivator is not depleted during its reaction with C3b and that C3b treated with the C3b inactivator becomes extremely sensitive to proteolytic digestion by trypsin and "trypsin-like" enzymes (9), the exact molecular nature of the action of the C3b inactivator on C3b has not been studied. In an effort to delineate the products of this interaction, purified C3b and C3b inactivator were allowed to react for various specific lengths of time and the products of these reactions were then analyzed.

Animals↗
PubMed1974

Protein binding by specific receptors on human placenta, murine placenta, and suckling murine intestine in relation to protein transport across these tissues.

Human, rat, and mouse placentas and rat and mouse intestines were homogenized in buffered saline, and fraction consisting primarily of cell membranes was separated from each of the homogenates by differential centrifugation. Human, bovine, and guinea pig IgG, and human IgE, Bence-Jones protein, serum albumin, insulin, and growth hormone were labeled with (131)I or (125)I, and the binding of these proteins by the cell membrane fractions was investigated. Rat and mouse sucklings were given labeled proteins intragastrically, and the amount of each protein absorbed after a given interval of time was determined. It was found that the degree and specificity of protein binding by the cell membrane fractions from human and murine placentas strikingly paralleled the relative rate and specificity of protein transport from mother to fetus in the respective species at or near term. Similarly, the degree and specificity of protein binding by the cell membrane fractions from suckling rat and mouse intestines tended to parallel the rate and specificity of protein absorption from the gastrointestinal tract in these animals. However, some discordance between protein binding and protein transport was also observed. The data suggest that: (a) the binding of a protein by specific receptors on cell membranes may be a necessary first step in the transcellular transport of the protein; (b) specific protein binding by cell receptors does not ensure the transport of that protein across the tissue barrier; and (c) specific transport mechanisms other than or in addition to specific cell membrane receptors are involved in the active transport of proteins across the human or murine placenta or the suckling murine intestine.

Animals↗
PubMedDate not supplied

Localizing of C-reactive protein in synovium of patients with rheumatoid arthritis.

Synovial biopsies from 8 patients with rheumatoid arthritis, 2 patients with degenerative osteoarthritis, and 4 patients with nonarthritic disease were studied for localization of C-reactive protein (CRP) using immunofluorescence microscopy. The nuclei of many synoviocytes and histiocytes in rheumatoid synovial membrane were found to bind CRP. Cultures of rheumatoid synovium in 14C-labeled amino acids produced radioactive IgG, IgM, IgA, and C3; but not CRP, indicating the synovial-bound CRP was not of local origin. A few CRP-binding nuclei were present in one osteoarthritis synovium, but none was found in the other and none in synovium from the 4 nonarthritis patients. The nature of the nuclear CRP ligand in rheumatoid synovium was not determined.

Adult↗
PubMedDate not supplied

Lymphocytes recognize human vascular endothelial and dermal fibroblast Ia antigens induced by recombinant immune interferon.

T-lymphocyte-mediated responses to the cellular components of blood vessels are important in rejection of allografts. The induction of cytolytic T lymphocytes (CTLs) depends on recognition of foreign class II major histocompatibility complex antigens (human HLA-DR, DC/DS, SB and others, collectively referred to as Ia) on the target cells whereas killing by CTLs usually depends on recognition of foreign class I antigens (HLA-A, B), although some alloreactive CTLs recognize foreign Ia instead of HLA-A, B (refs 5-8). The expression of Ia antigens has traditionally been regarded as restricted to immunological cell types, and the presence of class II antigen-bearing 'passenger' leukocytes in rodent organ grafts appears necessary for graft rejection. Recently, Ia antigens have been observed by immunofluorescence microscopy on human renal and dermal capillary endothelium. We have previously shown that human umbilical vein endothelial (HUVE) cells in standard culture conditions do not bear Ia antigens, but may be induced to do so by products of lectin- or alloantigen-activated T lymphocytes. Furthermore, we found that recombinant immune interferon (IFN-gamma), free of other lymphokines, is a potent inducer of Ia expression in HUVE cells. Here we report that IFN-gamma also induces Ia expression on human foreskin capillary endothelial (HFCE) cells, HUVE cells transformed by Simian virus 40 viral DNA (SV-HUVE cells) and human dermal fibroblast (HDF) cells in culture. Further, we present evidence that Ia present on HUVE cells and HDF cells can be functionally recognized by human T cells, resulting in a two-way interaction between T cells and mesenchymal cells that may be important in allograft rejection.

Cells, Cultured↗