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Biomedical subjects

J W Yoon

Publications and source records attributed to J W Yoon.

At least 109 records · Page 6Linked to original sources
PubMed1989

An efficient and site-specific gene trimming method.

Trimming a DNA strand into a precisely determined fragment can be carried out efficiently by an improved method involving a site-specific trim-primer and a single-stranded DNA template which is generated from a multifunctional vector, pTZ18R, and linearized by using an Eco RI-pTZ18R splinter. A complementary DNA strand is synthesized by DNA polymerase I (Klenow), and the 3'-end of the template upstream from the annealed primer is trimmed by subsequent T4 DNA polymerase reaction. An ATG translation initiator codon or a termination codon can be incorporated into the trim-primer, providing versatility to this single-stranded DNA-initiated gene trimming method that can be applied to subcloning and expression of any DNA fragment with known terminal sequences.

Biotechnology↗
PubMed1989

Genetic conditions among Canadian Mennonites: evidence for a founder effect among the old colony (Chortitza) Mennonites.

Distinctive disease patterns exist among Canadian Old Colony (Chortitza) Mennonites. This religious and genetic isolate is of 16th century Dutch/German ancestry. The group originated in the Netherlands, then settled in the Vistula delta area of western Prussia for 200 years. A small number of founding families later migrated to Chortitza, the "Old Colony", in the Ukraine in the late 18th/early 19th century, where they remained a distinct genetic isolate. This group has come to Canada over the past 100 years. The more conservative Canadian Mennonites of Chortitza descent practice strict endogamy, have a large family size and live predominantly in rural public health subdistricts in the four western provinces, and in southern Ontario. The world's largest reported familial aggregations of insulin-dependent diabetes mellitus, of autoimmune diseases and of Tourette syndrome were initially ascertained in a small northern Alberta public health subdistrict. Clusterings of malformations, inborn errors of metabolism, and other conditions were also found in the subdistrict, and in group descendents living in other provinces. A founder effect, or genetic drift, accounts for the familial aggregations of autosomal recessive and dominant conditions, some diseases of multifactorial determination, and other inherited conditions in Canadian kinships descending from this ancestral group. The medical literature on genetic conditions among Canadian Mennonites is reviewed and re-evaluated in the light of this information. There is biochemical, serologic, and molecular biologic evidence in favour of genetic homogeneity amongst patients with certain inherited conditions in this special population group. This genetic isolate offers potential for the study of the genetic epidemiology and molecular biology of inherited diseases. A computerized genealogic data base on about 1400 group members, as well as a cryopreserved lymphocyte/DNA bank on over 100 individuals with genetic conditions has been established in this special population group.

Alberta↗
PubMed1988

Association of cytomegalovirus infection with autoimmune type 1 diabetes.

The lymphocytes from 59 newly diagnosed type 1 diabetic patients and 38 normal control subjects were examined for the presence of human cytomegalovirus (CMV) genome by molecular hybridizations with human CMV specific probe. The CMV specific viral genome was found in 13 (22%) of 59 diabetic patients, but in 1 (2.6%) of 38 control subjects. Of the patients, 39% had islet cell antibody (ICA) and 41% had cytotoxic beta cell surface antibody (CBSA) in their serum; of the controls the corresponding rates were 2.6% and 2.6%. 62% and 69% of CMV genome-positive patients had ICA and CBSA, respectively, compared with 33% and 33% of CMV genome-negative patients. The single CMV genome-positive control subject did not have either ICA or CBSA whereas only 1 of the 37 CMV genome-negative control subjects had ICA. The strong correlation between CMV genome and islet cell autoantibodies detected in diabetic patients suggests that persistent CMV infections may be relevant to pathogenesis in some cases of type 1 diabetes.

Adolescent↗
PubMed1988

Unusual clustering of diseases in a Canadian Old Colony (Chortitza) Mennonite kindred and community.

We investigated a large Old Colony (Chortitza) Mennonite kindred with branches across Canada. Six generations of the kindred were traced. There was intermarriage among numerous family members. Insulin-dependent diabetes mellitus (IDDM) was identified in 10 members; all 7 living patients were found to carry the immunogenetic marker HLA-DR4. Nine other close relatives had disorders of carbohydrate metabolism, including gestational diabetes mellitus and non-insulin-dependent diabetes mellitus progressing to insulin use. Ten other relatives had autoimmune diseases, including rheumatoid arthritis, hyperthyroidism, hypothyroidism and multiple sclerosis. Cases of Alport's syndrome, congenital malformations, inborn errors of metabolism and unusual malignant diseases were also found in the kindred. In the small Alberta community in which the kindred was ascertained there were people of Old Colony Mennonite descent with genetic conditions such as Gilles de la Tourette's syndrome and congenital malformations, including congenital heart disease. This kindred represents the largest reported familial aggregation of IDDM. This disease and other disorders of carbohydrate metabolism occur in the context of a strong familial predisposition to autoimmune disease. Study of this family may permit empiric testing of proposed models of inheritance of diseases of complex origin such as IDDM. We report this Old Colony (Chortitza) Mennonite community because it is one of the settlements populated by this religious and genetic isolate, which extends across Canada and Central and South America and affords opportunities for the study of both common and rare inherited diseases.

Adolescent↗
PubMed1988

Relationship of islet cell and islet cell surface antibodies to the presentation and early course of IDDM in childhood.

Islet cell (ICA) and islet cell surface (ICSA) antibodies were measured in 30 children (aged 6-17.7 years) with newly diagnosed insulin-dependent diabetes mellitus (IDDM) to determine the relationship of antibody positivity/negativity to a variety of factors both at presentation (e.g., age, severity of onset, residual insulin secretion, insulin autoantibodies) and during the first year thereafter (HbA1c, insulin antibody binding, residual insulin secretion). At diagnosis, 10 of 30 were ICA (+) and 13 ICSA (+): no differences were found between ICA (+) and (-) subjects at onset; however ICSA (+) children had a lower bicarbonate concentration than those (-) for ICSA (P less than 0.01). During the first year after diagnosis the only significant finding was that in ICA (+) patients insulin dose (units/kg) was lower at both 6 and 12 months (mean +/- SD 0.55 +/- 0.14 and 0.67 +/- 0.12 U/kg, respectively) than ICA (-)'s (0.70 +/- 0.22 and 0.96 +/- 0.38, respectively, both P less than 0.05). Those children positive for both ICA and ICSA did not differ in any way at onset or during the subsequent 12 months from those negative for both antibodies. These results suggest that, except for minor differences, the presentation and course during the first year after diagnosis of IDDM do not differ in those children positive or negative for either or both ICA and ICSA.

Adolescent↗
PubMed1988

Prevention of lymphocytic thyroiditis and insulitis in diabetes-prone BB rats by the depletion of macrophages.

Diabetes-prone biobreeding (BB) rats often develop lymphocytic thyroiditis. Intraperitoneal administration of silica to young BB rats (40-days-old) nearly completely prevented the development of lymphocytic thyroiditis as well as insulitis. Since silica is known to be toxic to macrophages, these data suggest that the presentation of autoantigen(s) on the specific target cells such as thyroid and pancreatic B cells by antigen-presenting cells (e.g., macrophages) would be the initial step in the development of organ-specific autoimmune diseases in diabetes-prone BB rats.

Animals↗
PubMed1988

Amino acid differences in capsid protein, VP1, between diabetogenic and nondiabetogenic variants of encephalomyocarditis virus.

The genes for the major capsid protein, VP1(1D), of both diabetogenic D variant (EMC-D) and nondiabetogenic B variant (EMC-B) of encephalomyocarditis virus were cloned by using two synthetic primers which are common to both EMC-D and EMC-B. The cloned genes were mapped for major restriction enzyme sites including AccI, BamHI, EcoRI, HincII, KpnI, PvuII, SstI, TaqI, and XbaI. Among those nine restriction enzyme sites, only the TaqI site distinguished EMC-D genome from the counterpart of EMC-B genome. The complete nucleotide sequences (831 bases) of the VP1 genes revealed five amino acid differences between the two variants. Three of the changes, at positions 41, 58, and 152, were Thr (EMC-B) to Ala (EMC-D). The additional two changes occurred at positions 63 [Gln (EMC-B) to Glu (EMC-D)] and 181 [Thr (EMC-B) to Ser (EMC-D)]. All of these amino acid changes were due to point mutations at the first base of each codon.

Amino Acid Sequence↗
PubMed1988

Identification of antigenic differences between the diabetogenic and non-diabetogenic variants of encephalomyocarditis virus using monoclonal antibodies.

The M variant of encephalomyocarditis (EMC) virus consists of two biologically distinct variants: one, diabetogenic D variant (EMC-D) and the other, non-diabetogenic B variant (EMC-B). These two variants cannot be distinguished by hyperimmune sera. Monoclonal antibodies were generated against EMC-D or EMC-B to identify antigenic differences between these two variants. Fourteen independent hybrid cell lines, selected from seven separate fusions of mouse myeloma cells to spleen cells isolated from mice immunized with EMC-D, consisted of 12 hybrids which produced monoclonal antibodies that neutralized both EMC-D and EMC-B, and two hybrids (ED-HJ-23 and ED-HJ-31) which produced monoclonal antibodies that neutralized EMC-D but not EMC-B. Similarly, 16 independent hybrid cell lines, selected from eight separate fusions using spleen cells prepared from mice immunized with EMC-B, consisted of 15 hybrids which produced monoclonal antibodies neutralizing both EMC-D and EMC-B, and one hybrid (EB-48A-F1) which produced antibody that neutralized EMC-B, but not EMC-D. The specificities of these monoclonal antibodies (ED-HJ-23, ED-HJ-31, EB-48A-F1) were further confirmed using an immunofluorescent technique. The D variant-specific monoclonal antibodies reacted with cells infected with EMC-D but not EMC-B. In contrast, the B variant-specific monoclonal antibody reacted with the cells infected with EMC-B but not EMC-D. It is concluded that the EMC-D- and EMC-B-specific monoclonal antibodies are able to identify antigenic differences between diabetogenic and non-diabetogenic variants of EMC virus which cannot be distinguished by hyperimmune sera.

Animals↗
PubMed1988

An apparent deletion of an oligonucleotide detected by RNA fingerprint in the nondiabetogenic B variant of encephalomyocarditis virus is caused by a point mutation.

The diabetogenic D variant of encephalomyocarditis virus (EMC-D) was previously shown to be different from the nondiabetogenic B variant of encephalomyocarditis virus (EMC-B) by a single spot in an oligonucleotide fingerprint after RNase T1 digestion of their genomic RNAs. An oligoribonucleotide was missing from EMC-B but was present in EMC-D. The oligoribonucleotide specific to EMC-D was isolated from a two-dimensional polyacrylamide gel and sequenced as 5'-ACAAUCUCACUUUUCCAACAACAG-3'. Molecular hybridizations of EMC-D and EMC-B genomic RNAs with a DNA primer complementary to the EMC-D-specific oligoribonucleotide revealed that the absence of a corresponding spot in EMC-B was due to a point mutation rather than a deletion. By sequencing a cloned cDNA of EMC-B corresponding to the EMC-D-specific oligoribonucleotide, the point mutation was identified as a G for EMC-B and an A for EMC-D transversion at base 9 of the oligonucleotide. Comparative sequence analysis of eight randomly picked RNA segments around the EMC-D-specific oligoribonucleotide revealed that there were no base changes between EMC-D and EMC-B. It is concluded that the diabetogenic EMC-D viral genome differs from the nondiabetogenic EMC-B viral genome by at least a point mutation.

Animals↗
PubMed1988

Association of beta-cell-specific expression of endogenous retrovirus with development of insulitis and diabetes in NOD mouse.

The administration of cyclophosphamide to nonobese diabetic (NOD) male mice produces a rapid progression to overt diabetes (greater than 70%) with severe insulitis in 2-3 wk, whereas none of the untreated control NOD male mice became diabetic. When the thin sections of islets from the NOD male mice, which received silica for the preservation of islets and subsequently cyclophosphamide, were examined under the electron microscope, clusters of endogenous retrovirus-like particles (type A) were frequently found in the beta-cells. In contrast, retrovirus-like particles were rarely found in the beta-cells from NOD male mice that received only silica. Other endocrine cells, including alpha-, delta-, pancreatic polypeptide-producing, and exocrine acinar cells, did not contain such viruslike particles. These viruslike particles were also not found in spleen, liver, or kidney in either cyclophosphamide-treated or untreated NOD male mice. There was a clear correlation between the presence of retrovirus-like particles in the beta-cells and insulitis lesions in the cyclophosphamide-treated mice. On the basis of these observations, we conclude that the beta-cell-specific expression of endogenous retrovirus (like particles) is associated with the development of insulitis and diabetes in NOD mice.

Animals↗
PubMed1988

Evidence for initial involvement of macrophage in development of insulitis in NOD mice.

Macrophages have been shown to be the major population of infiltrated immunocytes at the early stage of insulitis in diabetes-prone BB rats. This study was undertaken to investigate the role of macrophages in the development of insulitis in nonobese diabetic (NOD) mice. Administration of cyclophosphamide to NOD mice resulted in a significant increase in the incidence of overt diabetes and severity of insulitis compared with that in untreated NOD mice. Intraperitoneal injections of silica completely prevented the development of diabetes and insulitis in both cyclophosphamide-treated and untreated animals. Because silica is selectively toxic to macrophages, the results suggest that macrophages play an important role in the initiation of insulitis in NOD mice.

Animals↗
PubMed1988

Preferential infiltration of macrophages during early stages of insulitis in diabetes-prone BB rats.

The subpopulation of lymphoid cells at the different stages of insulitis in BB rats was determined by immunohistochemical techniques with various monoclonal antibodies, including the recently developed OX41, which distinguishes macrophages from T-lymphocytes, OX19 for pan-T-lymphocytes, W3/25 for both helper T-lymphocytes and macrophages, OX8 for cytotoxic T-lymphocytes and natural killer cells, and OX12 for B-lymphocytes. The major population of infiltrated cells found during the early stages of insulitis appeared to be macrophages. This preceded invasion by a mixed population of cells, including both T- and B-lymphocytes and/or natural killer cells. The preferential infiltration of macrophages during the early stages of insulitis strongly suggested that there might be an initial change in the target beta-cells that precedes their immune destruction, although the amplification of immune response by activated T-lymphocytes and natural killer cells at a later stage seemed to be required for the clinical expression of the disease.

Animals↗
PubMed1988

Genetic control of organ-reactive autoantibody production in mice by obesity (ob) diabetes (db) genes.

Inbred strains of mice exhibited genetic and sex-dependent differences in spontaneous production of organ-reactive autoantibodies detected by indirect immunofluorescence. Antitestis autoreactivity was found primarily in sera from C57BL/6J (B6) mice, whereas antigastric autoreactivity was common to both CBA/J and 129/J strains. Autoantibodies against islet cell cytoplasmic antigens (ICAs) were uniquely expressed by C57BL/KsJ (BKs) males. Introduction of the diabetes (db) mutation into these various inbred-strain backgrounds induced expression of ICA, with stronger induction observed in males. The stress imposed by the db or obesity (ob) mutation induced ICA in BKs mice at a higher frequency than in B6 mice; this differential sensitivity was somehow related to a gene linked to the H-2 complex because BKs.B6 H-2b congenic mice resembled B6 mice. The db3J mutation increased the expression of these autoantibodies in 129/J mice, which, like B6, were H-2b and therefore presumably possessed the same H-2-linked inducibility allele as BKs. Cytotoxic autoantibodies against islet cell surface antigens were only observed in C3HeB/FeJ db/db males, and their presence was correlated with beta-cell necrosis. It is concluded that db and/or ob genes appear to play an important role in the production of autoantibodies to islet cells, and sex-linked factor(s) may modify the phenotypic expression of the autoantibodies.

Animals↗
PubMed1988

Studies on the correlation between the presence of cytotoxic islet cell surface antibody and the incidence of overt diabetes in BB rats.

Antibodies directed to the surface of islet cells are often present in the sera of both humans with insulin-dependent diabetes and the BioBreeding (BB) rat. These autoantibodies have been implicated in the disease process although the correlation between the presence of islet cell surface antibodies (ICSA) and diabetes is controversial. In this study the presence of cytotoxic islet cell surface antibody (ICSA) was examined in 65 BB rats from 60-150 days of age. Blood was collected every 7-10 days and sera were assayed by a 51Cr-release assay using rat insulinoma cells (RINm5F) as target cells. Onset of diabetes was determined by bi-weekly urinalysis. The incidence of diabetes was 51%. While 29% of the rats exhibited cytotoxic ICSA and diabetes, 22% were overtly diabetic without showing any measurable ICSA. An additional 22% showed ICSA but did not become diabetic in the time period studied. These results suggest no correlation between cytotoxic ICSA and diabetes in our BB rat colony.

Animals↗
PubMed1988

Excessive growth of cultured beta cells from an adult patient with beta cell hyperplasia.

We have studied a 25-year-old female with frequent, severe hypoglycemic episodes. Concurrent with low serum glucose levels, the concentrations of C-peptide and insulin were markedly elevated. Tests for sulfonylurea hypoglycemic agents were negative. Special tests did not disclose any neoplasm. Biopsy of the pancreatic tail revealed islet cell hyperplasia and adenomatosis. About two-thirds of the pancreas was resected, resulting in correction of all metabolic abnormalities. Specific fluorescein-labeled anti-insulin antibodies revealed staining in 60-80% of the cultured cells isolated from the patient's pancreas, while electron microscopy disclosed insulin storage granules in about 80%. By comparison, for each of these findings, the range for cells from normal pancreases was 30-50%. In contrast to these control cells, cells from the patient grew about 2 and 2.6 times more rapidly during the first two cell cycles, and the growth persisted through four cycles. The greater and more enduring growth of the patient's cells in culture must have been at least partly independent of circulating factors. Paracrine/autocrine principles from the beta cells or other islet cells may have been responsible.

Adult↗
PubMed1987

Role of cyclosporin A in macromolecular synthesis of beta-cells.

Wistar rats developed hypoinsulinemia and hyperglycemia within 7 days when treated daily with 40 mg/kg body wt of cyclosporin A (CsA) and recovered from the metabolic alteration within 1 wk when CsA treatment was terminated. By light microscopy, there was no lymphocytic infiltration, but cytoplasmic vacuolization in the islets of Langerhans from the CsA-treated rats was seen. By electron microscopy, severe degranulation, cytoplasmic vacuolization, and dilation of endoplasmic reticulum were clearly seen in the pancreatic beta-cells. Islet cells isolated from the CsA-treated rats showed greater than 50% reduction in mRNA synthesis. A similar inhibitory pattern of mRNA synthesis was observed in in vitro CsA-treated (10 micrograms/ml) human pancreatic islet cells from one biopsy sample and in similarly treated rat insulinoma cells (RINm5F). The inhibitory effect of CsA on mRNA synthesis in RINm5F cells was dose dependent, with a 50%-inhibiting dose of 5 micrograms/ml. In addition to the inhibition of mRNA synthesis, CsA also inhibited protein and DNA syntheses, although the inhibitory effect on these macromolecular syntheses was significantly less than that on mRNA synthesis. However, there was only a minor effect of CsA on in vitro transcription and translation compared with that on RINm5F and islet cells. It is concluded that CsA-induced degranulation of the beta-cells in Wistar rats, accompanied by hypoinsulinemia and hyperglycemia, may be due to indirect, reversible interference of the cellular function primarily involved in mRNA synthesis.

Animals↗
PubMed1987

Possible mechanisms in the pathogenesis of virus-induced diabetes mellitus.

Insulin-dependent diabetes mellitus results from destruction of pancreatic beta cells. Viruses and autoimmunity have been implicated as possible causes of beta cell destruction in genetically predisposed individuals. The evidence for viruses comes largely from experiments in animals, but several studies in humans point to viruses as triggers in the pathogenesis of diabetes in some cases. In animal models, at least 4 different possible mechanisms for virus-induced diabetes have been proposed. The first mechanism is direct cytolytic infection of pancreatic beta cells. One group of viruses, including encephalomyocarditis virus, Mengovirus 2T, and Coxsackie B viruses, can directly infect and destroy pancreatic beta cells independent of autoimmune processes. The second mechanism is triggering of autoimmune responses. In contrast to the encephalomyocarditis virus-induced diabetes, reovirus type 1 and rubella virus seem to be somehow associated with autoimmunity in the genesis of a diabetes-like syndrome in a certain strain of suckling mice and hamsters, respectively. The third mechanism is cumulative environmental insults. The cumulative environmental insults with viruses and beta cell toxic chemicals can result in diabetes in genetically predisposed non-human primates and certain inbred strains of mice. The fourth mechanism is persistent infection. A certain virus, such as lymphocytic choriomeningitis virus, persistently infects murine pancreatic beta cells and produces hyperglycemia. The evidence that viruses cause diabetes in humans is more circumstantial.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗