Engraftment of isolated islets after syngeneic transplantation into normal and diabetic mice.
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Animals↗
Biomedical subjects
A Andersson
Publications and source records attributed to A Andersson.
Homocysteine export from erythrocytes and its implication for plasma sampling.
The concentration of free and total homocysteine in plasma increases in time if blood is stored uncentrifuged after sampling. The increase is temperature dependent and the maximal increase in total plasma homocysteine at 37 degrees C was 3.0 mumol.L-1.h-1. Even at 4 degrees C there is a substantial increase, particularly of free plasma homocysteine. Plasma glutathione, cysteinylglycine, and gamma-glutamylcysteine also show an increase in time if whole blood is stored, whereas cysteine decreases. We show that the erythrocytes are responsible for most of the increase in plasma homocysteine and suggest that homocysteine is derived from adenosylmethionine-dependent protein carboxymethylations in the cells. We conclude that strict sampling conditions are necessary when plasma homocysteine and especially its free fraction are assayed.
Adult↗
Population dynamics of natural antibodies in normal and autoimmune individuals.
We have measured the quantities of naturally occurring autoantibodies in the serum of normal, unmanipulated individuals. These changes over time following broad-band complex dynamical patterns that are similar in mouse and man. The patterns more likely reflect the network architecture of the natural antibody repertoire, regulating the activation and decay of individual clones. The temporal changes of both disease-specific and nonspecific autoantibodies are consistently modified in autoimmune individuals.
Animals↗
Binding of epidermal growth factor-dextran conjugates to cultured glioma cells.
Some gliomas, melanomas and squamous carcinomas have large numbers of EGF receptors which could, in these cases, be used for targeting with toxic agents. We investigated whether EGF could be conjugated to dextran, which is a suitable carrier for toxic agents, without losing its ability to bind to the receptor. Dextran of 20 kDa molecular weight was activated with I-cyano-4-dimethylamino pyridinium tetrafluoroborate (CDAP) yielding highly active pyridinium-isourea derivatives. EGF was coupled to the activated dextran through the amino terminus and glycine was added to block residual activity. The EGF-dextran conjugate was, after purification on Sephadex G25 and Sephacryl 200 columns, tested for its receptor binding properties on human malignant glioma, U343MGaC12:6, cells. The conjugate inhibited binding of 125I-EGF in a competitive assay, showing that the binding was receptor-specific. Dextran conjugated with glycine, without EGF, had no inhibitory effect. The conjugate was radio-labelled either on the EGF part with 125I or on the dextran part with 3H-glycine, and the internalization patterns were compared to the internalization of 125I-EGF. The radioactivity of the conjugates remained cell-associated for more than 20 hr, regardless of whether the radioactivity was on the EGF or on the dextran part, while the radioactivity of unconjugated EGF rapidly disappeared from the cells. Most of the cell-associated radioactivity was, at all analysed time intervals, located intracellularly. Thus, it seems promising to use dextran, conjugated with EGF, as a carrier of, for example, toxic radioactive nuclides.
Dextrans↗
Germ-line origin of functional idiotypic interactions: identification of two idiotypically connected, natural antibodies that are encoded by germ-line gene elements.
Two monoclonal, natural IgM antibodies derived from normal BALB/c mice were selected on the basis of being idiotypically complementary and functionally connected. Nucleotide sequence analysis of their respective heavy and light chain V regions showed that both of the clones expressed VH, D, JH, VL and JL gene segments of germ-line origin. Furthermore, none of the clones displayed N-sequence additions. These data suggest a germ-line origin of a functional idiotypic network and confirm a minimized contribution of somatic diversification through template-independent addition of N-nucleotides in neonatal B cell repertoires.
Animals↗
Functional and morphological differentiation of fetal porcine islet-like cell clusters after transplantation into nude mice.
By using a previously described culture technique for the midgestational fetal porcine pancreas, islet-like cell clusters with a Beta-cell frequency of approximately 5% have been produced in large numbers. These islet-like cell clusters were transplanted beneath the kidney capsule to either normoglycaemic or alloxan-treated nude mice. The grafts consistently failed to cure the alloxan-treated mice immediately after implantation, however, normoglycaemia was restored in a majority of the mice within 2 months after transplantation and in all animals after 4 and 6 months. Indeed, the insulin released from the transplanted fetal Beta cells was able to normalize the serum glucose concentration at porcine levels (4-5 mmol/l) rather than at the level maintained in mice (8-10 mmol/l). In the cured mice there was a normal secretory response to glucose in the grafts as evidenced by normal glucose profiles during intravenous glucose tolerance test and a biphasic insulin response to high glucose when perfusing the graft bearing kidney. On the other hand, in the normoglycaemic animals the second phase faded before the glucose stimulus had been withdrawn. Two months after transplantation the endocrine cells were arranged so that the endocrine non-Beta cells were randomly scattered among a majority of Beta cells. The cell replication of the Beta cells, measured by 3H-thymidine incorporation, was within the lower range of that seen in the native islets of adult mice. No major differences between the controls and the alloxan-treated animals were observed in this respect. Cultured islet-like cell clusters had high rates of glucose utilization, paralleled by low rates of glucose oxidation, compared with adult mouse islets.(ABSTRACT TRUNCATED AT 250 WORDS)
Alloxan↗
Influence of hydrolysis on plasma homocysteine determination in healthy subjects and patients with myocardial infarction.
After acid hydrolysis, mean plasma homocysteine concentrations, measured as homocysteine disulphides, of about 1000 and 40 mumol/l have recently been reported in 26 survivors of myocardial infarction and 26 matched control subjects, respectively. This finding contrasts sharply with those more than 50 times lower total homocysteine concentrations found by other research groups in non-hydrolysed plasma from survivors of myocardial infarction. Using the same hydrolysis conditions, we could not detect any homocysteine disulphides in plasma hydrolysates from 9 survivors of myocardial infarction and 10 healthy subjects, who had mean total homocysteine concentrations in non-hydrolysed plasma of 16.9 +/- 6.5 and 15.8 +/- 10.3 mumol/l, respectively. The chromatograms contained several peaks, probably representing peptides, which disappeared with more complete hydrolysis and which might have been misinterpreted as homocysteine disulphides in the reported study. Only after reduction of disulphides and by using a sulphydryl-selective extraction procedure were we able to determine mean homocysteine concentrations in hydrolysed plasma to be 26.2 +/- 7.9 mumol/l in the survivors of myocardial infarction and 24.5 +/- 12.2 mumol/l in the healthy reference subjects. Thus, we could not confirm that survivors of myocardial infarction have homocysteine concentrations that are many times higher than found in healthy subjects.
Adult↗
Lysosomes and pancreatic islet function: adaptation of beta-cell lysosomes to various metabolic demands.
The effect of various functional demands on the lysosomes of pancreatic islet beta cells was studied in vivo. To expose pancreatic islets to different metabolic situations, normal syngeneic mouse islets were transplanted to either lean mice, alloxan-diabetic mice, or obese hyperglycemic mice. Two weeks after transplantation, primary and secondary beta-cell lysosomes of the islet grafts were analyzed by morphometry. The beta-cell lysosomes and secretory granules of the endogenous islets of lean and obese hyperglycemic mice were also measured. The beta cells of the islets transplanted to lean normoglycemic mice showed only a moderately developed synthetic apparatus and a great number of secretory granules. They had mainly secondary lysosomes, frequently containing secretory granule material, indicating a high crinophagic activity. The islet beta cells exposed to the high serum glucose concentration of alloxan-diabetic and obese hyperglycemic mice had an extensive synthetic apparatus, but a very small content of secretory granules. In these beta cells, there was a predominance of small primary lysosomes, indicating a low crinophagic activity. It is concluded that crinophagy may provide a mechanism for the pancreatic beta cell to moderate its content of insulin. When its secretory granule stores are diminished due to increased demands on insulin secretion, the beta cell seems able to drastically decrease the crinophagic activity. The detailed morphometric analysis of the endogenous islets of the lean and obese hyperglycemic mice showed that the beta cells of the obese hyperglycemic mice had a smaller number and size of the secretory granules.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Monoclonal, natural antibodies prevent development of diabetes in the non-obese diabetic (NOD) mouse.
The development of diabetes in the non-obese diabetic (NOD) mouse is mediated by T cells of both the CD4+CD8- and CD4-CD8+ phenotypes, while B cells are not involved in the effector stage of the disease. We have recently found, however, that treatments with heterologous, polyclonal immunoglobulin (Ig) preparations, as well as suppressing the developing B cell repertoire for the first 4 weeks of life dramatically reduce the incidence of disease and the severity of insulitis, in treated mice. We have further investigated the influence of Igs on the development of autoimmunity by testing the effect of polyclonal mouse-Ig or monoclonal, natural antibodies derived from normal, neonatal BALB/c mice. We found that repeated administration of high doses of polyclonal Ig (of xenogenic or isogenic origin), given at birth, inhibits the development of insulitis, as well as diabetes. Furthermore, single injections of moderate doses of isogenic, natural monoclonal antibodies (mAb) administered at the same age, while failing to significantly alter the degree of insulitis, efficiently prevent the development of disease. The effect of mAbs was found to be related to V-region specificity, as only some mAbs of a given isotype and origin had the observed effect.
Animals↗
Immunoglobulin-mediated prevention of autoimmune diabetes in the non-obese diabetic (NOD) mouse.
We investigated whether the development of spontaneous T-cell-mediated type I diabetes in NOD mice is influenced by B cells and immunoglobulin (Ig). During the first 4 weeks of life, B-cell development was suppressed by repeated administration of rabbit anti-mouse IgM (RaIgM), while controls received polyclonal rabbit Ig (NRIg). A reduction in the incidence of diabetes, as well as in development of insulitis, was observed after either of these treatments. However, the effect on insulitis was more pronounced in mice treated with RaIgM compared with those treated with NRIg. Furthermore, while the optimal effect of NRIg was obtained after a single injection at birth, the additional effect of RaIgM on development of insulitis was observed only after continued treatment for the first 4 weeks of life. Taken together these data suggest a possible role of Ig/B cells in the development of autoimmunity in the NOD mouse. The additional effect observed after continued suppression of the neonatal B-cell development suggests that this population may contribute significantly to the establishment of an auto-aggressive lymphocyte repertoire in the NOD mouse.
Animals↗
Organization and chromosomal localization of the human platelet-derived endothelial cell growth factor gene.
Human platelet-derived endothelial cell growth factor (hPD-ECGF) is a novel angiogenic factor which stimulates endothelial cell growth in vitro and promotes angiogenesis in vivo. We report here the cloning and sequencing of the gene for hPD-ECGF and its flanking regions. This gene is composed of 10 exons dispersed over a 4.3-kb region. Its promoter lacks a TATA box and a CCAAT box, structures characteristic of eukaryotic promoters. Instead, six copies of potential Sp1-binding sites (GGGCGG or CCGCCC) were clustered just upstream of the transcription start sites. Southern blot analysis using genomic DNAs from several vertebrates suggested that the gene for PD-ECGF is conserved phylogenetically among vertebrates. The gene for hPD-ECGF was localized to chromosome 22 by analysis of a panel of human-rodent somatic cell hybrid lines.
Animals↗
Increased levels of plasma homocysteine are associated with nephropathy, but not severe retinopathy in type 1 diabetes mellitus.
The reactive vascular-injuring amino acid homocysteine was measured in plasma samples from 79 well-characterized type 1 diabetic patients and 46 control subjects. Patients with proliferative retinopathy had higher homocysteine levels (15.0 +/- 6.3 mumols l-1; mean +/- SD, p less than 0.001; n = 42) than those with progressive retinopathy during a two-year period (10.4 +/- 1.6 mumols l-1; n = 12), no or minimal retinopathy (10.7 +/- 4.3 mumols l-1; n = 25), and the control subjects (11.0 +/- 3.4 mumols l-1). Within the group of patients with proliferative retinopathy increased homocysteine levels were confined to those patients that had serum creatinine levels greater than 115 mumols l-1 and/or an albumin:creatinine clearance ratio greater than or equal to 0.02 x 10(-3) (17.0 +/- 5.9 mumols l-1; n = 23), whereas those with no or only minimal nephropathy had levels (12.1 +/- 5.5 mumols l-1; n = 18) that were not different from the control group. We conclude that neither type 1 diabetes mellitus nor diabetic retinopathy per se is associated with increased plasma homocysteine levels. In contrast, homocysteine accumulates, probably owing to reduced glomerular filtration, in diabetic patients with advanced nephropathy. This suggests that homocysteine might contribute to the accelerated development of macroangiopathy seen especially in this subgroup of diabetic patients.
Adult↗
New perspectives on the structure and function of the normal and diabetic beta-cell.
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Diabetes Mellitus, Type 1↗
Reinnervation of transplanted mouse pancreatic islets.
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Acetylcholinesterase↗
The effect of excess daily methionine intake on plasma homocysteine after a methionine loading test in humans.
Impaired homocysteine metabolism might be a risk factor for vascular disease. Peroral methionine loading and post-load determination of methionine and homocysteine in plasma has frequently been used for identifying subjects with genetically impaired homocysteine metabolism. However, a methionine-rich diet induces a more efficient homocysteine catabolism in the rat, which suggests that humans on diets with differing methionine content might respond differently to the methionine loading test. To study this we performed methionine loading in six healthy subjects before and after 2 wk of excessive daily methionine intake (300% of normal). On each occasion plasma homocysteine and methionine were measured at several intervals post-load. However, neither the methionine clearance nor the post-load homocysteine concentrations were affected by excess methionine. We conclude that variations in the daily methionine intake will not influence the methionine loading test.
Adult↗
Genes for C4b-binding protein alpha- and beta-chains (C4BPA and C4BPB) are located on chromosome 1, band 1q32, in humans and on chromosome 13 in rats.
C4b-binding protein is involved in the regulation of the complement system. It is a multimeric protein composed of seven identical alpha-chains and a single copy of a unique beta-chain. The latter was identified only recently and its structure determined by cDNA cloning. Both subunits in C4b-binding protein belong to the same superfamily of proteins composed predominantly of tandemly arranged short consensus repeats (SCR) approximately 60 amino acid residues in length. The gene for the human alpha-chain is known to be located in a gene cluster on chromosome 1, band 1q32, which is called the regulators of complement activation (RCA) gene cluster. We have used cDNA probes for both alpha- and beta-chains of human C4b-binding protein to localize their genes with an in situ hybridization technique. We find the genes for both chains to be located on chromosome 1, band 1q32, in the human. This suggests that the beta-chain gene is also a member of the RCA gene cluster and that the alpha- and beta-chain genes are located close to each other. The cDNA probes for the alpha- and beta-chains also were used to screen mouse-rat somatic cell hybrids using Southern blotting to localize their genes in the rat. Both the alpha- and beta-chain genes were shown to be located on chromosome 13 in the rat. These are the second and third genes to be located on rat chromosome 13, and the results suggest that the genes for the alpha- and beta-chains together with the gene for coagulation factor V represent a conserved chromosomal region in rat and man.
Animals↗
On factors that regulate growth of transplanted islets.
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Animals↗
DNA replication in mouse pancreatic islets transplanted subcapsularly into the kidney or intraportally into the liver. Influence of unilateral nephrectomy or partial hepatectomy.
3H-thymidine incorporation into DNA (estimated as the autoradiographic labeling index [LI]) was used as an index of DNA replication in syngeneic mouse islets grafted into the kidney or liver 4 weeks before unilateral nephrectomy (UN) or partial hepatectomy (PH). Removal of one kidney resulted in a significantly increased growth of the remaining islet-bearing kidney initiated during the first week after surgery. Seven days after 40% hepatectomy the remaining liver mass corresponded to 91% of that of sham-operated (SO) mice. The induced kidney and liver growth in mice subjected to UN or PH was correlated with an increased LI, which was similar in both organs (3.5 times the LI in kidneys and livers of SO-controls). Pancreatic islets implanted into the organs undergoing compensatory growth also had higher LI values that were less pronounced as compared with the LI measured in the parenchymal cells of the kidney or the liver after UN or PH, respectively. In contrast to the grafted islets, no changes in the LI of the endogenous pancreatic islets were found. To evaluate possible systemic effects of the induced growth stimulation, the livers of UN-mice and the kidneys of PH-mice were investigated. No change in the LI of the liver tissue was observed 3 and 6 days after UN, whereas the kidney cortex showed a significantly increased LI7 days after PH. It is concluded that when exposed to a local, non-specific growth stimulation in vivo pancreatic islets prepared from adult donors are able to respond with an enhanced replicatory activity. The effect is, however, only present when the islets are located in the organs in which growth has been induced.
Animals↗