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Biomedical subjects

T Dyrberg

Publications and source records attributed to T Dyrberg.

At least 73 records · Page 4Linked to original sources
PubMed1987

Spontaneously diabetic BB rats have age-dependent islet beta-cell-specific surface antibodies at clinical onset.

Diabetes-prone BB rats were examined before, during, and after clinical onset of diabetes for the occurrence of circulating islet cell surface antibodies (ICSAs) with a specific binding to islet beta-cells. The presence of ICSA was assessed by incubating serum immunoglobulin fractions with normal Wistar rat islet cells and identifying cell-bound immunoglobulins by indirect immunofluorescence and by a complement-induced cell toxicity reaction. Under the selected experimental conditions, none of the diabetes-resistant rats were ICSA positive over the entire study period (45-120 days of age). In two diabetes-prone BB rat strains, 19 animals developed diabetes with onset between 50 and 120 days. At day 45, none of these animals was positive for ICSA. In rats developing diabetes between 50 and 85 days of age, 7 of 9 animals presented ICSA at clinical onset, determined by either the immunofluorescence or cytotoxicity test. The antibodies bound to insulin-containing beta-cells but not to other islet cell types, and binding was not eliminated by absorption with liver powder. In animals developing diabetes between 85 and 120 days, only 1 of 10 was positive for beta-cell-specific surface antibodies at onset of the disease. After 30 days of insulin treatment, beta-cell-specific antibodies were detectable in 3 of 4 animals of age 50-85 days, whereas only 3 of 12 older rats presented ICSAs that were, in addition, of low titer or affinity. Our data confirm that ICSAs develop in diabetic BB rats and indicate that these antibodies can bind specifically to islet beta-cells compared with other islet cell types.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1986

Peptides as antigens. Importance of orientation.

Factors known to be important in producing protein-reactive peptide antibodies include the accessibility of the region from which the peptide sequence is derived, the hydrophilic-phobic character of the sequence, and the length of the peptide. The data presented here indicate that the orientation of the peptide coupled to a carrier protein also influences the binding pattern of peptide antibodies. An octapeptide, representing a sequence from the alpha chain of the human acetylcholine receptor, was coupled either through an N- or C-terminal cysteine-glycine-glycine linker to a carrier protein and used to immunize rabbits. The resulting antisera reacted at comparable titers to the uncoupled immunizing peptides, but did not crossreact with the identical but opposite-linked peptide. Characterization of the binding to other homologous peptides showed that immunization with the N-terminal-linked peptide induced antibodies reactive specifically with the C-terminal amino acid(s). Immunization with the C-linked peptide resulted in antibodies reactive with a site of the peptide near the C-terminus.

Amino Acid Sequence↗
PubMed1986

Genetic heterogeneity in the major histocompatibility complex of various BB rat sublines.

Fragments of cloned rat class I transplantation antigen genes were used to define the polymorphism detected between two lines of closely related BB rats. One line, BB-Hagedorn (BB/H), is prone to diabetes, and the other (BB control) is resistant. A cDNA probe representing part of the second extracellular domain of a class I antigen detected several DNA fragments and revealed a 2kb fragment present in resistant, but absent in diabetes-prone, BB/H rat DNA following digestion with BamH1. A 40 bp cDNA probe from the same domain showed a further simplified pattern in the DNA hybridization analysis. Only two fragments, 15 kb and 7 kb, were present in the resistant rats; the diabetes-prone BB/H rats lacked the 7 kb fragment. Several lines of evidence suggest that the gene contained in this 7 kb fragment may be deleted. Analysis of other diabetic BB rats and in the F2 generation of intercross offspring of F1 hybrid parents following crossbreeding between the resistant (BB-control) and diabetes-prone (BB/H) line demonstrate that the class I polymorphism was not linked directly to diabetes. Examination of various other BB lines and sublines indicate that these polymorphisms can be traced back to at least one other subline (Worcester) in the parent colony.

Animals↗
PubMed1986

A deletion in a rat major histocompatibility complex class I gene is linked to the absence of beta 2-microglobulin-containing serum molecules.

Class I major histocompatibility antigens are composed of a heavy chain that is noncovalently associated with beta 2-microglobulin (beta 2m). Most class I molecules are membrane bound, but mouse and rat cDNA clones and genes without a functional code for the transmembrane amino acids have been identified. The membrane-associated class I molecules are important in the control of cell-mediated cytotoxicity, while the function of the soluble molecules remains unclear. Previous studies have shown that beta 2m circulates in rat serum in three different molecular weight classes. The first is free beta 2m (Mr, 12,000), the second is about Mr 70,000, and the third is roughly Mr 200,000. In an inbred subline of immunodeficient, diabetes-prone BioBreeding rats (BioBreeding/Hagedorn), previous work detected two restriction fragment polymorphisms in class I major histocompatibility complex genes, one of them a gene deletion on a 7-kilobase BamHI fragment and the other on a 2-kilobase BamHI fragment. In these rats we have found that the third serum beta 2m-binding size class is absent. Analysis of F1 and F2 individuals following cross-breeding between BioBreeding/Hagedorn rats and genetically related (nondiabetic) control BioBreeding w-subline rats demonstrated that the large-size serum peak of beta 2m was associated with the presence of the class I restriction fragments.

Animals↗
PubMed1986

Insulin release and pancreatic insulin is reduced in young prediabetic BB rats.

The pancreases of approximately 50 days old diabetes-prone BB/Hagedorn (BB/H) and of the genetically closely related, but non-diabetic BB w-subline (control BB) rats were perfused to determine the capacity of D-glucose to release insulin before the expected development of diabetes. The BB/H rats were from a colony with 82-84% incidence of insulin-dependent diabetes mellitus (IDDM) by 140 days of age. The total amount of insulin released from the BB/H rat pancreas during stimulation with 20 mmol/1 mmol/ D-glucose was reduced by nearly 50% (P less than 0.01). The initial peak of insulin release was similar between the two groups of animals, whereas the amount of insulin released during the second peak accounted for the diminished release (P less than 0.01). The extractable pancreatic insulin was 30% (P less than 0.05) less in the BB/H rats. Total insulin release expressed relative to the pancreatic insulin content, was therefore not different between the two groups. It is concluded that about 20-40 days before the mean age of clinical onset of IDDM in BB/H rats, the capacity to release insulin in response to D-glucose is reduced along with a diminished pancreatic insulin content. This abnormality seems to be preceded only by islet cell surface antibodies but not by insulitis.

Animals↗
PubMed1986

Humoral autoimmunity in the pathogenesis of insulin-dependent diabetes mellitus. Studies in the spontaneously diabetic BB rat.

The present review describes the autoimmune aspects of the pathogenesis of insulin-dependent diabetes mellitus (IDDM) in man and in the BB rat, and the requirements for effective prevention. Using a xenotypic mouse islet cell antiserum, we demonstrated the presence of antibodies reacting specifically with the pancreatic beta cells and recognizing a Mr 40,000 plasma membrane glycoprotein. The existence of beta cell-specific surface antigens, which hypothetically could act as targets in an autoimmune response, might explain the selective disappearance of the beta cells in IDDM. The BB rat spontaneously develops an insulin-dependent diabetes much like IDDM in man. Diabetes in BB rats, as in IDDM of humans, is associated with a high incidence of islet cell surface antibodies. These antibodies precipitate a Mr 64,000 protein from lysates of islets of Langerhans isolated from normal rats. In the BB rat, islet cell antibodies precede the appearance of insulitis and the clinical onset of diabetes. We investigated the beneficial effects of early treatment with low doses of cortisone on diabetes in the BB rat, because comparable experiments in children with newly diagnosed IDDM have given inconclusive results. In the BB rat there was no effect on the incidence or severity of diabetes or on the diabetes-related, islet cell-directed autoimmune phenomena. However, immunologic intervention that prevents IDDM from developing in potentially susceptible individuals is a promising area for research on this disease.

Animals↗
PubMed1985

Cortisone fails to affect levels of islet cell surface antibodies and incidence of diabetes in the BB rat.

Cortisone acetate (250 micrograms/kg X day) was given by im injections to 40 21-day-old diabetes-prone BB rats. The animals were followed longitudinally to determine islet cell surface antibodies (ICSA), as an expression of an abnormal immune reaction against the pancreatic islet cells and plasma glucose to estimate the degree of metabolic control. ICSA were detected 10-150 days before the diagnosis of diabetes. In the cortisone-treated group the diabetic rats showed significantly higher ICSA values compared to the nondiabetic ones, both in frequency of positive tests (P less than 0.05) and in mean binding values (P less than 0.02). In the control group, no difference in ICSA levels were seen between diabetic and nondiabetic rats. The cortisone regimen also failed to influence the degree of insulitis, commonly associated with diabetes in these rats. These experiments in well defined animals which spontaneously develop diabetes do not support the use of low dose cortisone treatment in attempts to improve or prevent insulin-dependent diabetes in human subjects.

Animals↗
PubMed1984

Preparation of 125I-protein A usable for up to 10 months in immunoassays.

Chloramine-T iodination of protein A from Staphylococcus aureus and gel electrophoretic purification of the iodination mixture results in a stable tracer of high specific and functional activity. Following repeated gel electrophoresis of the tracer only a single component was observed. The specific activity of the 125I-protein A was between 30 and 55 muCi/micrograms. The binding of 125I-protein A to rabbit immunoglobulin exceeded 90% and the tracer competed effectively with unlabelled protein A in binding to cells incubated with sera containing surface antibodies. Storage of the tracer for up to 46 weeks resulted in a moderate decrease in maximal binding to immunoglobulin (from 91% to 64%), in TCA precipitable radioactivity (from 97% to 80%) and an approx. 30% decrease in the ability to detect cell bound immunoglobulin. It is concluded that gel electrophoretic purification of 125I-protein A produces a tracer with a very long shelf life.

Chloramines↗
PubMed1984

Autoantibodies to a 64-kilodalton islet cell protein precede the onset of spontaneous diabetes in the BB rat.

Spontaneous insulin-dependent diabetes mellitus (IDDM) in the BB rat is associated with the presence of antibodies to a 64-kilodalton rat islet cell protein. These protein antibodies appeared in young animals and remained for as long as 8 weeks before the clinical onset of IDDM. Antibodies to a 64-kilodalton human islet cell protein were found to be associated with human IDDM. Detection of the antibodies may therefore be used to predict an early immune reaction against pancreatic B cells.

Animals↗
PubMed1984

Islet cell surface and lymphocyte antibodies often precede the spontaneous diabetes in the BB rat.

The diabetic syndrome of the BB rat shows many homologies with that of human insulin-dependent diabetes and evidence that the onset of the disease is associated with the presence of autoantibodies, including islet cell surface antibodies. In this study, sera were sampled serially from weaning to 157 days of age from 26 BB rats in two low-incidence litters, and 22 rats of three high-incidence litters. Clinical and metabolic variables were monitored concurrently with blood lymphocyte counts. Islet morphology was correlated at sacrifice. In the high-incidence litters, eight rats developed insulin-dependent diabetes, five impaired glucose tolerance, and the remaining nine all showed insulitis. In the low-incidence litters, only one animal showed impaired glucose tolerance and another insulitis. In the high-incidence litters 16 rats (73%) had islet cell surface antibodies compared with 4 out of 26 (15%) low-incidence controls (p less than 0.002). Antibodies reactive with Wistar rat spleen lymphocytes were present in all high-incidence rats compared with 19% (5 out of 26) among the control litters (p less than 0.002). Time courses of islet cell surface and lymphocyte antibody appearance and their peak values varied, but already at weaning the levels of both antibodies were increased among the high-incidence litter rats (p less than 0.001). Islet cell surface and/or lymphocyte antibodies were therefore present in the majority of animals at an age where neither morphological nor metabolic evidence of the diabetic syndrome were yet detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Restriction fragment polymorphisms in the major histocompatibility complex of diabetic BB rats.

DNA isolated from diabetic BB (BB/Hagedorn) rats was examined for restriction fragment length differences within the major histocompatibility complex (MHC) as compared with nondiabetic (W-subline) BB rats. Polymorphisms were detected using a mouse class I MHC gene as probe. Specifically, a 2-kb BamHI fragment was present in all the nondiabetic rats examined, but absent in the diabetic rats. Similar polymorphisms were observed with various other restriction enzymes, particularly XbaI, HindII, and SacI. There were no polymorphisms detected using either a human DR-alpha (class II antigen heavy chain) or a human DC-beta (class II antigen light chain) gene as probes. These results indicate that the BB rat diabetic syndrome may be linked to differences in class I MHC genes.

Animals↗
PubMed1983

Humoral immunity in the spontaneously diabetic BB rat.

Litters of BB rats with an expected high and low incidence of insulin-dependent diabetes were followed from weaning until the age of about 140 days. Islet cell surface antibodies (ICSA) and lymphocyte antibodies (LA) were determined in a radioligand assay with fixed rat insulinoma (RIN 5F) cells, an insulin-secreting cell line, or spleen lymphocytes. In the low-incidence litter, 2 out of 14 rats had ICSA and LA; one showed insulitis at the end of the study. In the high-incidence litter, 3 out of 7 developed diabetes; all 3 showed ICSA at weaning. The remaining 4 showed insulitis. All 7 diabetes-susceptible rats had ICSA and LA at some time during the study. It is concluded that there is a high incidence of circulating ICSA and LA in the spontaneously diabetic BB rat. The antibodies can often be detected before the onset of diabetes, and may be implicated in the beta-cell destructive process and in the lymphocytopenia characteristic of the syndrome.

Animals↗
PubMed1983

Inhibition of insulin release after passive transfer of immunoglobulin from insulin-dependent diabetic children to mice.

We used the mouse passive transfer model to test whether islet cell antibodies affect beta-cell function. The immunoglobulin (Ig) fraction of plasma from 5 islet cell surface antibody-positive, newly diagnosed insulin-dependent diabetic children or of a pool of plasma from 12 normal subjects was injected daily (7-16 mg IgG/day) for 14 days into normal immunosuppressed BALB/c mice. Insulin secretory responses in the Ig-injected mice were then examined by perfusing the rodent pancreata in vitro. Insulin release induced by 20 mmol/liter D-glucose during 30 min of stimulation decreased from 900 ng insulin (median; range, 814-1138) from pancreata of mice injected with control Ig to 511 ng (range, 130-786) from pancreata of mice injected with diabetic Ig (P less than 0.003). Both the initial peak and the sustained second phase of glucose-stimulated insulin release were depressed in 4 of the 5 pancreata from mice injected with diabetic Ig. These results indicate that circulating antibodies in diabetic children may alter beta-cell function and possibly contribute to the pathogenesis of insulin-dependent diabetes.

Adolescent↗
PubMed1982

Specific pancreatic beta-cell surface antigens recognized by a xenogenic antiserum.

An antiserum (R4) from a rabbit immunized with suspensions of C57BL/61 ob/ob mouse islet cells contains antibodies which in a 125I-protein A radioligand assay can be demonstrated to bind to single cell suspensions of normal Naval Medical Research Institute (NMRI) mouse islet cells. The binding of 125I-protein A to islet cells was about four times that of normal rabbit serum (NRS) after incubation at a 1/600 dilution of R4 antiserum quantitatively absorbed to mouse spleen lymphocytes (R4A antiserum) and hepatocytes. Subsequent absorption of the R4A antiserum to islet cells significantly reduced the binding of 125I-protein A to islet cells incubated with the doubly absorbed serum. Immunoprecipitation of radiolabeled islet cell lysates followed by SDS polyacrylamide gel electrophoresis and autoradiography suggested that the R4A antiserum recognized a Mr 40,000 glycoprotein. This glycoprotein was not detected in spleen lymphocytes. Electron microscope detection of gold-protein A complexes suggested that the binding of islet cell surface antibodies was cell specific. islet cell suspensions incubated with R4A antiserum and gold-protein A showed that 86 +/- 3 gold particles were bound per 100 beta-cells (mean +/- SE for six experiments). In contrast, the number of gold particles per 100 endocrine non-beta-cells was 8 +/- 1 which was similar to the number achieved with NRS (3 +/- 1) on all endocrine islet cells. Our observations suggest that the pancreatic islet cells, in particular the beta-cells, express a specific antigen.

Animals↗
PubMed1982

Islet cell surface antibodies and lymphocyte antibodies in the spontaneously diabetic BB Wistar rat.

Plasma from 14 diabetic and 6 nondiabetic BB Wistar rats along with plasma from 6 non-BB Wistar rats was evaluated for the presence of islet cells surface antibodies (ICSA) and antibodies to spleen lymphocytes by the protein-A radioligand assay. Dispersed Wistar rat islet cells incubated with plasma from diabetic rats bound 4255 +/- 2208 cpm 125I-protein A/5 x 10(4) islet cells (mean +/- SD) compared with 984 +/- 454 cpm/5 x 10(4) islet cells in islet cells incubated with plasma from nondiabetic BB rats (P less than 0.005). Twelve of the 14 diabetic rats with a duration of diabetes for 3-11 days bound radioactivity above the mean and 2 x SC of controls. The binding of 125I-protein A did not differ between nondiabetic BB rats and non-BB Wistar rats. Wistar rat spleen lymphocytes incubated in diabetic plasma bound 20,249 +/- 10,783 cpm/2 x 10(6) spleen lymphocytes compared with 3460 +/- 1809 in the controls (P less than 0.005). Animals positive for ICSA correlated with those positive for spleen lymphocyte antibodies. It is concluded that ICSA and splenic lymphocyte antibodies are present in diabetic BB rats.

Animals↗