Biomedical subjects

J M Chen

Publications and source records attributed to J M Chen.

At least 163 records · Page 9Linked to original sources

PubMed1996

Topical gentamicin-induced hearing loss: a mitochondrial ribosomal RNA study of genetic susceptibility.

Mitochondrial ribosomal RNA mutation has been shown to predispose affected individuals to aminoglycoside-induced hearing loss (AIHL). An A-to-G nucleotide substitution at the 1555 position within the 12S ribosomal RNA gene has been identified with a maternally inherited pattern in affected Asian pedigrees. The aim of this study was to identify the frequency of this DNA polymorphism in subjects who appear to show hypersensitivity to topical (middle ear) application of aminoglycoside. In this pilot study, 10 subjects with AIHL were recruited. Eight underwent vestibular ablative therapy with middle ear instillation of gentamicin for disabling vertigo, and two were treated with topical antibiotic drops for otitis media in the presence of a tympanic perforation. DNA samples were extracted, and polymerase chain reaction (PCR) technique was used for gene amplification and purification, searching for 1555 A-to-G substitution in the 12S ribosomal RNA gene. None of the subjects demonstrated this specific mutation.

Adult↗

PubMed1996

Two decades of cardiac transplantation at the Columbia-Presbyterian Medical Center: 1977-1997.

Since its inception in 1977, the Cardiac Transplantation Service at Columbia-Presbyterian Medical Center has performed more than 900 heart transplant procedures, with a one-year survival rate of approximately 80%, and a 5-year survival rate of approximately 60%. Throughout our 20-year experience, the criteria for eligibility both donors and recipients has widened to include older and "reanimated" donors for selected recipients, as well as an extensive experience with recipients bridged to transplantation with mechanical assist devices. Of particular interest in recent years has been the need for additional therapy for the highly sensitized transplant candidate and ultimate transplant recipient, whose immunosuppressive regimen must be continuously monitored and modified to ensure graft survival. In light of the persistent donor organ crisis, continued efforts are being developed to more accurately characterize the transplant candidate waiting list in order to identify those patients who may be better served by either medical management or an alternative surgical procedure to transplantation, including high-risk coronary revascularization and mechanical or biological assistance. Current research interests at CPMC include left ventricular assist devices, xenotransplantation, and management of both transplant coronary artery disease and immunologic sensitization. Ongoing investigations in these and other areas of transplantation have been established to encourage continued growth both within the field and at CPMC through the 21st century.

Adult↗

PubMed1996

[Nuclear matrix-lamina-intermediate filament system in PtK 2 cells].

Selective extraction, whole mount cell preparation and DGD embeddment-free section were involved in visualizing the nuclear matrix-lamina-intermediate filament system in PtK 2 cells. After extraction the anaphase chromosome residues adjoined to the cytoplasmic intermediate filament in some areas. Immunofluorescent staining showed us that the intermediate filament reacted with AE 1 and AE 3; McAb 223 could be localized specifically on the lamina while McAb C 23 could crossreact with cytoplasmic intermediate filament beside the lamina location, monoclonal antibody against lamin A (C) could also bind to chromosome residues. Antibody to 280 kD nuclear matrix protein which were positive stained in HeLa cells could not react with the nuclear matrix components of PtK 2 cells. 2-D electrophoresis demonstrated that there were some differences in the composition of the nuclear matrix-lamina-intermediate filament system of HeLa and PtK 2 cells. TdR treatment could lead to alteration of nuclear matrix proteins.

Animals↗

PubMed1995

Reversal of chronic ventricular dilation in patients with end-stage cardiomyopathy by prolonged mechanical unloading.

BACKGROUND: Ventricular dilation, indexed by marked shifts toward larger volumes of the end-diastolic pressure-volume relation (EDPVR), has been considered to represent an irreversible aspect of ventricular remodeling in end-stage heart failure. However, we hypothesized that such dilation could be reversed with sufficient hemodynamic unloading, such as can be provided by a left ventricular assist device (LVAD). METHODS AND RESULTS: The EDPVRs of hearts from seven patients with end-stage idiopathic cardiomyopathy and comparable baseline hemodynamics were measured ex vivo at the time of cardiac transplantation; these were compared with EDPVRs from three normal human hearts that were technically unsuitable for transplantation. Four of the patients received optimal medical therapy; three of the patients, who deteriorated on optimal therapy, underwent LVAD support for approximately 4 months. Compared with the normal hearts, EDPVRs of hearts from medically treated patients were shifted toward markedly larger volumes. In contrast, EDPVRs of hearts from LVAD patients were similar to those of normal hearts. CONCLUSIONS: Chronic hemodynamic unloading of sufficient magnitude and duration can result in reversal of chamber enlargement and normalization of cardiac structure as indexed by the EDPVR, both important aspects of remodeling, even in the most advanced stages of heart failure.

Adult↗

PubMed1995

Newborn baboon serum lacks natural anti-pig xenoantibody.

Discordant xenotransplantation represents an attractive alternative to allotransplantation in light of the shortage of donor organs currently available for cardiac allotransplantation. Unfortunately, discordant xenotransplantation is still limited by hyper-acute rejection, a process thought to be mediated by natural anti-xenodonor antibody. Based on data that cytotoxic natural xenoantibodies are IgM in nature, we postulated that natural xenoantibodies may be absent from newborn serum. Baboon sera were collected from infant baboons. Pooled adult baboon sera were used as controls. A whole cell ELISA was performed to determine the binding of xenoantibodies to pig aortic endothelial cells and pig lymphocytes. The cytotoxicity of both adult and newborn baboon sera to pig aortic endothelial cells was measured by a MTT (3-(4,5-dimethyl-thiazoyl-2-y) 2,5 diphenyl-tetrazolium bromide) assay. Newborn baboon sera demonstrated very low levels of binding of natural IgM xenoantibodies to pig endothelial cells and lymphocytes, whereas natural IgM xenoantibodies from adult baboon sera bound significantly to both pig aortic endothelial cells and lymphocytes. IgG natural antibodies in both adult and newborn sera bound to pig endothelial cells and pig lymphocytes. The MTT assay demonstrated high levels of cytotoxicity to pig endothelial cells from adult baboon sera and very low levels of cytotoxicity from newborn baboon sera. In this study, newborn baboon sera were demonstrated to be free of natural IgM xenoantibodies to pig endothelial cells and lymphocytes. Although natural anti-pig IgG antibodies were present in newborn sera, newborn baboon sera lack cytotoxicity to pig target cells. These findings suggest that IgM is the more important xenoantibody and that hyperacute rejection of discordant cardiac xenografts may be avoidable in the newborn.

Aging↗

PubMed1995

Immunolocalization of thimet oligopeptidase in chicken embryonic fibroblasts.

An antiserum was raised against chicken thimet oligopeptidase (TOP), and specific antibodies were isolated by immunoadsorption. The specificity of the antibodies was confirmed by immunoblot analysis with the cell extract of cultured chicken fibroblasts. Subcellular localization of TOP in normal and Rous sarcoma virus-transformed chicken embryonic fibroblasts was investigated by indirect immunofluorescence staining with affinity-purified, monospecific anti-TOP antibodies. In addition to the diffuse reaction expected for a cytosolic enzyme, a punctate, cytoplasmic localization was observed. The appearance of the organelles containing TOP did not correspond to that expected for secondary lysosomes, mitochondria, endoplasmic reticulum, or Golgi apparatus, but did resemble that of endosomes. When cells were allowed to internalize Lucifer yellow before fixation, some of the organelles containing TOP were observed to contain Lucifer yellow. Moreover, those organelles containing TOP were positively immunolabeled with the anti-transferrin receptor antibody. We conclude that part of the TOP in chicken embryonic fibroblasts is located in endosomes and discuss the implications of this.

Animals↗

PubMed1995

Structural effects of the binding of GTP to the wild-type and oncogenic forms of the ras-gene-encoded p21 proteins.

Molecular dynamics calculations have been performed to determine the average structures of ras-gene-encoded p21 proteins bound to GTP, i.e., the normal (wild-type) protein and two oncogenic forms of this protein, the Val 12- and Leu 61-p21 proteins. We find that the average structures for all of these proteins exhibit low coordinate fluctuations (which are highest for the normal protein), indicating convergence to specific structures. From previous dynamics calculations of the average structures of these proteins bound to GDP, major regional differences were found among these proteins [Monaco et al. (1995), J. Protein Chem., in press]. We now find that the average structures of the oncogenic proteins are more similar to one another when the proteins are bound to GTP than when they are bound to GDP [Monaco et al. (1995), J. Protein Chem., in press]. However, they still differ in structure at specific amino acid residues rather than in whole regions, in contradistinction to the results found for the p21-GDP complexes. Two exceptions are the regions 25-32, in an alpha-helical region, and 97-110. The two oncogenic (Val 12- and Leu 61-) proteins have similar structures which differ significantly in the region of residues 97-110. This region has recently been identified as being critical in the interaction of p21 with kinase target proteins. The differences in structure between the oncogenic proteins suggest the existence of more than one oncogenic form of the p21 protein that can activate different signaling pathways.

Binding Sites↗

PubMed1995

Comparison of the computed three-dimensional structures of oncogenic forms (bound to GDP) of the ras-gene-encoded p21 protein with the structure of the normal (non-transforming) wild-type protein.

The ras-oncogene-encoded p21 protein becomes oncogenic if amino acid substitutions occur at critical positions in the polypeptide chain. The most commonly found oncogenic forms contain Val in place of Gly 12 or Leu in place of Gln 61. To determine the effects of these substitutions on the three-dimensional structure of the whole p21 protein, we have performed molecular dynamics calculations on each of these three proteins bound to GDP and magnesium ion to compute the average structures of each of the three forms. Comparisons of the computed average structures shows that both oncogenic forms with Val 12 and Leu 61 differ substantially in structure from that of the wild type (containing Gly 12 and Gln 61) in discrete regions: residues 10-16, 32-47, 55-74, 85-89, 100-110, and 119-134. All of these regions occur in exposed loops, and several of them have already been found to be involved in the cellular functioning of the p21 protein. These regions have also previously been identified as the most flexible domains of the wild-type protein and have been bound to be the same ones that differ in conformation between transforming and nontransforming p21 mutant proteins neither of which binds nucleotide. The two oncogenic forms have similar conformations in their carboxyl-terminal domains, but differ in conformation at residues 32-47 and 55-74. The former region is known to be involved in the interaction with at least three downstream effector target proteins. Thus, differences in structure between the two oncogenic proteins may reflect different relative affinities of each oncogenic protein for each of these effector targets. The latter region, 55-74, is known to be a highly mobile segment of the protein. The results strongly suggest that critical oncogenic amino acid substitutions in the p21 protein cause changes in the structures of vital domains of this protein.

Cell Transformation, Neoplastic↗

PubMed1995

Use of aprotinin in LVAD recipients reduces blood loss, blood use, and perioperative mortality.

Aprotinin, a bovine protease inhibitor, has been used extensively in patients undergoing cardiac surgical procedures in an effort to minimize blood loss and prevent the complications associated with blood replacement. We sought to evaluate the effect of aprotinin on postoperative blood loss, renal function, and the incidence of right ventricular failure in patients undergoing placement of a TCI Heartmate left ventricular assist device as a bridge to cardiac transplantation. Retrospective data analysis in 142 patients (42 receiving aprotinin and 100 untreated) demonstrated that the use of aprotinin was associated with a significant decrease in postoperative blood loss (p = 0.019) and in the intraoperative packed red blood cell transfusion (p = 0.019) and total blood product (p = 0.016) requirements. A transient, yet significant, increase in the postoperative creatinine level in the aprotinin group (p = 0.0006), but not in blood urea nitrogen level (p = 0.22), was noted. Interestingly, we noted an association between blood loss and the subsequent development of right ventricular failure; patients who required a right ventricular assist device bled significantly more than did those who did not suffer right ventricular failure (p = 0.02). Additionally, aprotinin recipients benefited by a reduction of nearly one half in the incidence of the need for a right ventricular assist device. The incidence of perioperative mortality was reduced in those receiving aprotinin compared with that in untreated patients, (p = 0.05). We conclude that aprotinin is safe and effective in decreasing postoperative blood loss and intraoperative blood product requirements, and in reducing perioperative mortality in patients undergoing left ventricular assist device placement as a bridge to cardiac transplantation.

Adult↗

PubMed1995

A follow-up study of combined vaccination with plasma-derived and recombinant hepatitis B vaccines in infants.

This study was aimed to evaluate the efficacy and immunogenicity of combined hepatitis B vaccination with plasma-derived vaccine (PDV) and recombinant vaccine (RV). A total of 329 infants was recruited, including 224 high-risk infants born to hepatitis B e antigen-positive mothers and 105 low-risk infants born to hepatitis B e antigen-negative mothers. The high-risk infants received four doses of hepatitis B vaccine at 0, 1, 2 and 12 months of age with five different schedules. Group A1 and A2 infants were vaccinated with PDV as the first dose and RV (SB vaccine for group A1, MSD vaccine for group A2) as the remaining three doses. Group B1 and group B2 infants were vaccinated with PDV as the first two doses and RV (SB vaccine for group B1, MSD vaccine for group B2) as the remaining two doses. Group C infants received four doses of PDV. Low-risk infants were vaccinated with PDV at birth, and RV at 1 and 6 months of age (group D1, using SB vaccine; group D2, using MSD vaccine). At completion of vaccination schedules, 20 of 224 high-risk infants (9%) were positive for hepatitis B surface antigen. The overall protective efficacy was 90%. Hepatitis B surface antibody (anti-HBs)-positive rate ranged between 94 and 100% among the remaining infants. The protective efficacy and immunogenicity were similar among groups except that the mean level of anti-HBs in group C, D1 and D2 infants tended to be lower than that of the other four groups. To ensure an optimal immune response, four doses of vaccine are recommended in high-risk infants when two types of vaccine are to be used in combination.

Child, Preschool↗

PubMed1995

Use of explanted human hearts as a model for the study of cardiac pathophysiologic conditions.

The purpose of this paper is to describe an isolated heart model that uses human hearts to study cardiomyopathy. Techniques of organ preparation and perfusion are described that result in successful restoration of explanted human hearts to a beating condition. Native hearts of transplant recipients were placed on an isolated perfusion circuit immediately after explant. After appropriate organ and circuit preparation these hearts were restored to a functional state. Studies were done to assess the stability over time and response to inotropic stimulation. Six of seven hearts were returned to a functional condition. Left ventricular pressure generation ranged from 56 to 118 mm Hg (mean 84.8 +/- 34.11) at physiologic loading conditions. Hearts remained functional from 67 to 271 minutes (mean 152 +/- 71.7) and retained up to 70% of functional capacity after 120 minutes. Hearts performed in isovolumic and ejecting modes. Hearts had a marked response to inotrope administration not previously described. We conclude that human hearts can be reproducibly restored to a functional condition after explant from transplant recipients and can be maintained in a beating state with reasonably stable pressure generation for an extended period of time, which makes this a useful model with which to study cardiac pathophysiologic conditions. These hearts demonstrate an appropriate response to inotropes not previously observed, most likely because of improved myocardial preservation and stringent control of perfusate chemical make-up.

Adult↗

PubMed1995

Age-related development of human anti-pig xenoantibody.

Human cytotoxic natural xenoantibodies are believed to be of the immunoglobulin M class in nature. However, a thorough understanding of the development of these natural antixenodonor xenoantibodies remains incomplete. In this study, serum samples were obtained from newborn, infant, and adult human beings. An enzyme-linked immunosorbent assay was used to determine the binding of human natural immunoglobulin M xenoantibodies to pig aortic endothelial cells and pig lymphocytes. A complement-mediated cytotoxicity assay was used to measure the cytotoxicity of newborn, infant, and adult serum to cultured pig aortic endothelial cells and pig lymphocytes. Adult human serum contained both natural immunoglobulin M and immunoglobulin G xenoantibodies to pig endothelial cells and lymphocytes, whereas newborn infant serum contained only immunoglobulin G xenoantibodies. Only adult human serum was cytotoxic to pig endothelial cells and lymphocytes. Human immunoglobulin M xenoantibodies became detectable by age 1 month. By age 2 months these natural anti-pig xenoantibodies reached serum levels equivalent to those in the human adult and resulted in similar cytotoxicity to that of adult human serum. These findings indicate that (1) natural anti-pig immunoglobulin M xenoantibodies are absent from newborn infant human serum, (2) newborn human serum is not cytotoxic to pig endothelial cells and lymphocytes despite the presence of immunoglobulin G xenoantibodies that bind to pig endothelial cells and lymphocytes, and (3) natural anti-pig immunoglobulin M xenoantibodies begin to develop as early as age 1 month and by age 2 months attain a circulating level comparable to that found in the adult.

Adult↗

PubMed1995

Establishment of human IgE system in severe combined immunodeficient mice with peripheral blood mononuclear cells from asthmatic children.

The frequency of allergic diseases, such as asthma, has increased rapidly during the past decade; however, the exact mechanisms have not been established. In this study we tried to establish an in vivo system to investigate immune regulation of allergic diseases by using severe combined immunodeficient (SCID) mice. Peripheral blood mononuclear cells isolated from asthmatic children or normal adults were injected into peritoneal cavities of SCID mice. Human IgG, IgA, IgM, and IgE could be detected in SCID mice reconstituted with human PBMCs (SCID-PBL-hu mice) 3 weeks later. Moreover, the mice injected with peripheral blood mononuclear cells from asthmatic children had much higher IgE levels than mice reconstituted with cells from normal adults. Phenotypic analysis of spleen cells and peritoneal exudate cells from SCID-PBL-hu mice demonstrated that human lymphocytes could survive in the peritoneal cavity and spleen for several months. After intraperitoneal immunization, mite-specific IgE antibodies could also be detected in SCID-PBL-hu mice. This study indicates that the human IgE system can be established in SCID mice and that this model can be used to study the regulation of IgE production and the immunopathogenesis of human allergic disease.

Animals↗

PubMed1995

Three-dimensional energy-minimized model of human type II "Smith" collagen microfibril.

A procedure is described for constructing a three-dimensional model of fibril-forming human type II collagen based on the "Smith" microfibril model. This model is a complex of five individual collagen triple-helical molecules, and is based on known structural parameters for collagen. Both experimental and theoretical data were used as constraints to guide the modeling. The resulting fibril model for type II collagen is in agreement with both physical and chemical characteristics produced by experimental staining patterns of type II fibrils. Some advantages of the type II model are that the stereochemistry of all the sidechain groups is accounted for, and specific atomic interactions can now be studied. This model is useful for: development of therapeutics for collagen related diseases; development of synthetic collagen tissues; design of chemical reagents (i.e., tanning agents) to treat collagen-related products; and study of the structural and functional aspects of type II collagen. Described is the procedure by which the Smith microfibril of type II collagen was developed using molecular modeling tools, validation of the model by comparison to electron-microscopic images of fibril staining patterns, and some applications of this microfibril model.

Amino Acid Sequence↗

PubMed1995

Transfer and expression of human O6-methylguanine-DNA methyltransferase cDNA confers resistance of Mer- HeLa MR cells to 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosoure a.

Previous studies have demonstrated that O6-methylguanine-DNA methyltransferase (MGMT) is a major contributor to tumor cellular resistance toward chloroethylnitrosoureas. To further clarify the effect of MGMT gene expression on cellular chemosensitivity to 1-(4-amino-2-methyl-5-pyrimidinyl)-3-(2-chloroethyl)-3-nitrosourea (ACNU) in human cells, a repair-deficient human tumor cell line (HeLa MR) was transfected with a human MGMT expression vector (pSV2MGMT-neo). Multiple unique transfectants were isolated which exhibited variable levels of MGMT mRNA by Northern hybridization analysis. Vector-transfected controls were generated simultaneously. Transfectants expressing high levels of MGMT activity showed an increased resistance to ACNU-induced cytotoxicity. Furthermore, the levels of the protective effect against ACNU correlated generally with the levels of introduced MGMT expression. This study further provided direct evidence of MGMT contribution to ACNU resistance in human tumor cells. Based on the results presented here, we also discussed the perspective of the clinical utility of MGMT cDNA transfer and expression.

Antineoplastic Agents↗

PubMed1995

Local massage after vaccination enhances the immunogenicity of diphtheria-tetanus-pertussis vaccine.

The effect of local massage on adverse reactions and immunogenicity of diphtheria-tetanus-pertussis vaccine was investigated. After diphtheria-tetanus-pertussis vaccination 327 infants were either massaged or not, and adverse reactions were evaluated. Local pain and fever were more frequent in the massage group. The extra febrile episodes from massage were mild (38-39 degrees C). For evaluation of the antibody responses, 124 infants were recruited into massage or nonmassage cohorts and antibody production was measured at 2, 6, 7, 18 and 19 months of age, respectively. Subjects in the massage group developed significantly higher antibodies against filamentous hemagglutinin at 6 and 7 months of age, pertussis toxin at 6, 7, 18 and 19 months of age, pertussis agglutinogen at 18 and 19 months of age and those in the nonmassage group. Local massage after diphtheria-tetanus-pertussis vaccination was associated with better immunogenicity and more adverse reactions, including low grade fever and local pain, which were mild and not particularly disturbing.

Antibodies, Bacterial↗

PubMed1995

[A prospective epidemiological investigation on the effect of China-mode attenuated live vaccine against hepatitis A in the population of Liu Zhou].

An 24-month prospective epidemiological investigation on the results of China-mode Hepatitis A attenuated live vaccine against hepatitis A by random group sampling was carried out. The incidence of case group was 15.91/10(5) (5/31421), the incidence of control group was 95.92/10(5) (30/ 31277) which showed a significant difference. In case group 2081 persons who missed vaccination, there was one person developed hepatitis A, making the incidence 48.05/10(5). In control group 760 persons were vaccinated by mistake and there was no case developed in this sub-population. There were 644 cases of hepatitis A in the external control group, the incidence was 90.14/10(5). Data showed that there was no significant difference among external control group, control group and persons from case group who missed vaccination. Comparing the data from case group and from the above 3 groups, the protective rates were 82.35%, 83.41% and 66.89%. respectively. When conparing the data from persons who had been mistakenly vaccinated in control group, there was no significant difference being noticed.

Adolescent↗

PubMed1995

[Protective effects of bepridil in combination with anisodamine on myocardial ischemia and reperfusion injury in rats].

The effects of bepridil (Bep) in combination with anisodamine (Ani) on myocardial ischemia and reperfusion injury induced by ligating the left coronary artery were studied in rats. Administration of a combination of Bep and Ani was found to decrease the incidence of arrhythmia induced by myocardial ischemia and reperfusion, increase the myocardial superoxide dismutase (SOD) activities and reduce the myocardial ultrastructural injury in rats. The effect of combination of Bep and Ani was shown to be better than either Bep or Ani alone.

Animals↗