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Biomedical subjects

A Lernmark

Publications and source records attributed to A Lernmark.

At least 271 records · Page 15Linked to original sources
PubMed1983

Glucose stimulates the biosynthesis of a human pancreatic islet cell protein detected by an antiserum against the human erythrocyte glucose transporter.

An antiserum raised against the purified human erythrocyte glucose transporter specifically immunoprecipitated a major protein of Mr36000 and a minor protein of Mr58000 from human pancreatic islets. The biosynthetic incorporation of [35S]methionine into the 36-kDa protein increased 2-3-fold in 16 mM D-glucose with 0.1 mM IBMX as compared to islets incubated in 3 mM D-glucose either with or without IBMX. D-Glucose tested without or with IBMX had no effect on the biosynthesis of the 58-kDa protein. The 36-kDa protein was also detected in rat islets and rat islet tumor cells. It is suggested that this protein may represent a D-glucose and cAMP sensitive component of a glucose transport or glucose binding protein in the pancreatic beta-cell.

1-Methyl-3-isobutylxanthine↗
PubMed1983

HLA-D region beta-chain DNA endonuclease fragments differ between HLA-DR identical healthy and insulin-dependent diabetic individuals.

The human HLA-D histocompatibility region encodes class II antigens each of which consists of two polypeptide chains (alpha and beta) inserted in the plasma membrane. These molecules are implicated in the regulation of the immune response but several human diseases are also found to be associated with certain HLA-DR antigens. The occurrence of insulin-dependent (type I) diabetes (IDDM) is strongly associated with HLA-DR3 and/or 4 (ref. 5). The class II antigens, however, show a marked genetic polymorphism associated with the beta-chains which seem, from hybridization studies, to be encoded by several genes. We have therefore used the beta-chain cDNA probe, pDR-beta-1 (refs 8, 10) to test whether there are differences in hybridization pattern between DNA from healthy individuals and diabetic patients, after digestion with restriction endonucleases. Among the HLA-DR 4 and 3/4 individuals, the IDDM patients showed an increased frequency of a PstI 18 kilobase (kb) fragment. A BamHI 3.7 kb fragment, frequent among controls (30-40%), was rarely detected in the IDDM patients (0-2%). These differences may be related to susceptibility to develop the disease.

DNA Restriction Enzymes↗
PubMed1983

Plasmapheresis in the initial treatment of insulin-dependent diabetes mellitus in children.

Several factors indicate that autoimmune mechanisms may play a part in the aetiology of insulin-dependent diabetes mellitus. At the onset of the disease in 10 children (aged 11-16 years) plasmapheresis was performed four times over one to two weeks. Seventeen age-matched children with the same clinical features served as controls. The C-peptide concentrations at onset were the same in the two groups, but after one month the children treated with plasmapheresis had significantly higher values. This difference became even more pronounced after three, nine, and 18 months, both during fasting and at the maximum response to a standardised meal. The study group also had a significantly more stable metabolism, longer partial remission, and no higher insulin requirement. Of the 10 treated children islet-cell cytoplasmic antibodies were present in seven before plasmapheresis and in nine during treatment. The antibodies remained detectable in five and six out of nine patients at one and six months respectively after plasmapheresis. Although the mechanisms are obscure, plasmapheresis performed at the onset of insulin-dependent diabetes mellitus may help to preserve beta-cell function.

Adolescent↗
PubMed1983

Human class II major histocompatibility antigen beta-chains are derived from at least three loci.

Class II antigens of the major histocompatibility complex (MHC) consist of two glycosylated, membrane-integrated polypeptide chains. These cell surface-expressed molecules are involved in several immunobiological events involving cell-cell interactions, most of which seem to require that genetically identical class II antigens, or other molecules controlled by the same region of the MHC, are expressed on the interacting cells. The extensive genetic polymorphism of the class II antigens has rendered analyses in the human system of the number of non-allelic species of class II antigens difficult, although several laboratories have reported the existence of at least two types of human class II antigens. Here we present the results of experiments using restriction enzyme digestions and separation of DNA from individuals homozygous for the MHC followed by hybridization to human class II antigen alpha- and beta-chain cDNA probes. While the alpha-chain probe gave only a single hybridization band, the various beta-chain probes revealed a more complex pattern that is consistent with the existence of at least three separate beta-chain genes or pseudogenes in the human MHC.

Bacterial Proteins↗
PubMed1983

Analysis of islet cell antibodies on frozen sections of human pancreas.

The sensitivity and specificity of the assay for islet cell cytoplasmic antibodies in human serum were examined using cryostat sections from fresh frozen pancreas. The specificity of the assay was close to 100% while the sensitivity was 40%-98% depending on the pancreas used. Inter-observer variation was 12-27%. End-point titres of islet cell antibodies varied with the sensitivity of each pancreas. End-point titration of the antibodies in two different laboratories using the same pancreas was significantly correlated (Spearman test p less than 0.001). We conclude that a reliable determination of islet cell antibody titres in human serum requires careful characterization of the sensitivity and specificity of each pancreas used as a source of frozen sections, in the indirect immunofluorescence assay.

Adolescent↗
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

Detection of HLA-D/DR-related DNA polymorphism in HLA-D homozygous typing cells.

Sequences of different sizes are generated when DNA from homozygous HLA-Dw/DR typing cells are digested with restriction endonuclease and analyzed by hybridization with a HLA-D region class II antigen beta-chain cDNA probe. The patterns of hybridization were highly polymorphic but one endonuclease, BamHI, defined sequences unique to all HLA-Dw/DR specificities 1-8 except HLA-Dw/DR 2 and 6; however, these two specificities were resolved with the enzyme EcoRI. Digestion with other endonucleases such as Pst I results in patterns of restriction fragments that differ between homozygous typing cells of the same HLA-Dw/DR specificity. HLA-D region beta-chain probes permit HLA-D region genotyping at the DNA level and may allow detection of genes controlling the association of HLA specificities with a wide variety of diseases.

DNA↗
PubMed1983

B-cell function and islet cell and other organ-specific autoantibodies in relatives to insulin-dependent diabetic patients.

The pancreatic B-cell function (glucose tolerance, C-peptide release) and organ-specific autoantibodies, including islet cell cytoplasmic and cell surface (mouse), were studied in 45 first-degree relatives of patients with insulin-dependent diabetes mellitus diagnosed before the age of 30 years. Compared to 107 healthy persons without any family history of either insulin-dependent or non-insulin-dependent diabetes mellitus, the prevalence of autoantibodies was increased among the relatives. The prevalence of islet cell antibodies did not differ between relatives and controls and none of the individuals had complement-fixing islet cell antibodies. There was no difference in glucose tolerance or C-peptide release between relatives and controls, whether they had autoantibodies or not. At a three-year follow-up, none of the individuals had developed insulin-dependent diabetes.

Adult↗
PubMed1983

L-leucine methyl ester stimulates insulin secretion and islet glutamate dehydrogenase.

Column perifusion of collagenase-isolated mouse pancreatic islets was used to study the dynamics of insulin release in experiments lasting for several hours. The methyl esters of L-leucine and L-arginine were synthesized. Whereas L-arginine methyl ester (L-arginine OMe) had no effect, L-leucine OMe stimulated the release of insulin. The effect of L-leucine OMe was maximal at 5 mmol/liter. Whereas the Km for glucose-stimulated insulin release was unaffected by 1 mmol/liter L-leucine OMe, the maximal release of D-glucose was increased by the amino acid derivative that appeared more effective than L-leucine. L-Leucine OMe was also a potent stimulus of insulin release from the perfused mouse pancreas. In the presence of 10 mmol/liter L-glutamine, 1 mmol/liter L-leucine OMe induced a 50- to 75-fold increase in insulin release. A similar stimulatory effect was also observed in column-perifused RIN 5F cells, a cloned rat islet tumor cell line. A twofold increase in islet glutamate dehydrogenase activity was induced by 5 mmol/liter L-leucine OMe, a larger effect than that of L-leucine (P less than 0.02), whereas L-arginine OMe had a small inhibitory effect. We conclude that L-leucine OMe is a potent stimulus of insulin secretion and that its effect on the beta-cells may be exerted by activating islet glutamate dehydrogenase.

1-Methyl-3-isobutylxanthine↗
PubMed1983

beta-Cell function relative to islet volume and hormone content in the isolated perfused mouse pancreas.

The beta-cell function, total islet volume, and number were studied in 1- to 18-month-old mice, together with the extractable pancreatic insulin and glucagon. The beta-cell function, determined as the total amount of insulin released in response to glucose from the in vitro perfused pancreas showed an age-related increase, without any differences in the kinetics of insulin secretion between young and old mice. The total islet number and area in each individual pancreas was determined planimetrically after selective staining of the islets by perfusing the pancreas with dithizone. The islet area increased from 5.4 +/- 1.7 mm2 at 1 month to 16.3 +/- 2.1 mm2 at 18 months, whereas the number of islets remained virtually unchanged (1072 +/- 51). Pancreatic insulin increased with age by nearly 500%, in contrast to a 35% reduction in pancreatic glucagon. There was a strong relationship between body weight and total pancreatic DNA (P = 4.7 X 10(-8)), islet area (P = 3.2 X 10(-7)), insulin secretory capacity (P = 7 X 10(-4)), and total pancreatic insulin (P = 1.9 X 10(-5)), but no relationship between body weight and islet number. The insulin secretory capacity increased proportionally to the increase in islet area (P = 9.9 X 10(-3)). The islet area and total pancreatic insulin were closely related (P = 2.8 X 10(-12)), as were pancreatic insulin and the insulin secretory capacity (P = 3.3 X 10(-11)). There was a negative relationship between pancreatic glucagon and islet area (P = 0.005) and between pancreatic glucagon and insulin (P = 0.01). The close relationship between pancreatic insulin and islet area, shown to be an expression of islet volume, makes it possible to estimate the volume of the endocrine pancreas after standard RIA of pancreatic insulin. The combined morphometric and physiological analysis is unique in studying islet cell function relative to the volume of the endocrine pancreas.

Aging↗
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↗
PubMed1983

Quantitative determination of islet cell surface antibodies using 125I-protein A.

A quantitative method to measure islet cell surface antibodies in human patients has been developed using 125I-protein A. Isolated, dispersed, viable rat islet cells prepared by collagenase digestion were fixed in 4% paraformaldehyde to allow storage for up to 7 wk at 4 degrees C. Human sera, heat inactivated and adsorbed with rat liver and kidney powder (100 mg/ml), were incubated with the fixed cells (50 x 10(3)) for 60 min at 37 degrees C. Thereafter the cells were washed and exposed to 5 x 10(5) cpm 125I-protein A, which binds to IgG attached to the cell surface. Assay precision (14%) and reproducibility (16%) were established by repeated analysis of pooled sera from healthy individuals and IDDM patients using pooled batches of islet cells. Using this method, islet cell surface antibodies were detected in 35% of insulin-dependent diabetic patients.

Adult↗
PubMed1983

Immunoglobulin from insulin-dependent diabetic children inhibits glucose-induced insulin release.

Immunoglobulin was separated from islet cell antibody positive plasma of six children with newly diagnosed insulin-dependent (type I) diabetes mellitus. The dynamics of insulin release in response to glucose and partially purified antibodies were determined in dispersed rat islet cells perifused on small columns of Biogel P-2 beads. After perifusion at 5.5 mmol/L D-glucose in the presence of healthy control immunoglobulin, the rate of insulin release increased in a biphasic manner after stimulation with 30 mmol/L D-glucose. In cells exposed to diabetic immunoglobulin, 30 mmol/L D-glucose had little, if any, effect on insulin release. These results suggest that islet cell antibodies in insulin-dependent diabetes may interfere with the insulin release mechanisms in the pancreatic B-cells.

Adolescent↗
PubMed1982

Flow sorting of mouse pancreatic B cells by forward and orthogonal light scattering.

Mouse islet cell suspensions were separated into subpopulations based on forward low angle and orthogonal scattered light. Separation fractions were analyzed for hormone content by radioimmunoassays. The pancreatic B-cells had the highest orthogonal light scattering, while they overlapped in forward low angle light scattering with other endocrine (glucagon, pancreatic polypeptide and somatostatin containing cells) and nonendocrine cells. Living and paraformaldehyde fixed islet cell suspensions showed similar distributions of combined light scattering.

Animals↗
PubMed1982

New approaches to therapy and diagnosis of diabetes.

Recent progress within the field of molecular biology has resulted in the development of a new technology known as 'recombinant DNA'. This technology deals with a number of biochemical techniques for handling DNA which include: (1) cutting DNA at specific sites, (2) inserting DNA into bacteria or mammalian cells so that the cell will replicate the DNA and (3) manipulation of cloned DNA so that the host cell makes the protein for which the DNA codes [1-3]. Already a number of hormones including somatostatin, human growth hormone and human insulin [4] have been produced by these new methods. However, there are certain criteria which should be considered before new sources of hormones are generally accepted for treatment of human diseases. We shall review some of the problems which may arise in the case of insulin, by comparing the chemical and immunological properties of insulin from various sources. Recombinant DNA methods have, in addition, made it possible to study islet cell structure and function at the gene level. These studies include analysis of gene structure and of how they are transcribed and translated. Structural analyses which seem to be significant in the differential diagnosis of diabetes will be reviewed.

Animals↗