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C Betsholtz

Publications and source records attributed to C Betsholtz.

At least 55 records · Page 3Linked to original sources
PubMed1996

PDGF-A signaling is a critical event in lung alveolar myofibroblast development and alveogenesis.

A mouse platelet-derived growth factor A chain (PDGF-A) null allele is shown to be homozygous lethal, with two distinct restriction points, one prenatally before E10 and one postnatally. Postnatally surviving PDGF-A-deficient mice develop lung emphysema secondary to the failure of alveolar septation. This is apparently caused by the loss of alveolar myofibroblasts and associated elastin fiber deposits. PDGF alpha receptor-positive cells in the lung having the location of putative alveolar myofibroblast progenitors were specifically absent in PDGF-A null mutants. We conclude that PDGF-A is crucial for alveolar myofibroblast ontogeny. We have previously shown that PDGF-B is required in the ontogeny of kidney mesangial cells. The PDGFs therefore appear to regulate the generation of specific populations of myofibroblasts during mammalian development. The two PDGF null phenotypes also reveal analogous morphogenetic functions for myofibroblast-type cells in lung and kidney organogenesis.

Actins↗
PubMed1996

The cDNA sequence of proton-pumping nicotinamide nucleotide transhydrogenase from man and mouse.

cDNA clones for the human and mouse nicotinamide nucleotide transhydrogenases have been isolated and their sequences have been determined. Multiple alignments show that the functional proteins are encoded by single mRNAs. The deduced amino acid sequences are approximately 95% identical for the previously known bovine, and the human and mouse proteins. The major variable region is located in the presequence. It is proposed that all mammalian transhydrogenases have a similar structure.

Amino Acid Sequence↗
PubMed1996

Scrapie in mice deficient in apolipoprotein E or glial fibrillary acidic protein.

In the prion diseases, extensive reactive gliosis is often found to be out of proportion to the degree of apparent neuronal damage. To evaluate the role of astrocytic gliosis in experimental scrapie of the mouse, we inoculated mice deficient in apolipoprotein E (apoE) or the glial fibrillary acidic protein (GFAP) with mouse prions. The expression of both apoE and GFAP in astrocytes increases as part of the reactive gliosis that accompanies scrapie. Null mice deficient in either apoE or GFAP inoculated with prions exhibited incubation times indistinguishable from untargeted control mice. The level of PrPSc and its regional deposition in the brains of ill mice deficient in either protein were also similar to control mice. Our findings demonstrate that neither apoE nor GFAP participates in the pathogenesis of the disease or in the production of PrPSc.

Animals↗
PubMed1995

Mice lacking glial fibrillary acidic protein display astrocytes devoid of intermediate filaments but develop and reproduce normally.

Glial fibrillary acidic protein (GFAP) is the main component of the intermediate filaments in cells of astroglial lineage, including astrocytes in the CNS, nonmyelin forming Schwann cells and enteric glia. To address the function of GFAP in vivo, we have disrupted the GFAP gene in mice via targeted mutation in embryonic stem cells. Mice lacking GFAP developed normally, reached adulthood and reproduced. We did not find any abnormalities in the histological architecture of the CNS, in their behavior, motility, memory, blood-brain barrier function, myenteric plexi histology or intestinal peristaltic movement. Comparisons between GFAP and S-100 immunohistochemical staining patterns in the hippocampus of wild-type and mutant mice suggested a normal abundance of astrocytes in GFAP-negative mice, however, in contrast to wild-types, GFAP-negative astrocytes of the hippocampus and in the white matter of the spinal cord were completely lacking intermediate filaments. This shows that the loss of GFAP intermediate filaments is not compensated for by the up-regulation of other intermediate filament proteins, such as vimentin. The GFAP-negative mice displayed post-traumatic reactive gliosis, which suggests that GFAP up-regulation, a hallmark of reactive gliosis, is not an obligatory requirement for this process.

Animals↗
PubMed1995

Characterization of human buccal epithelial cells transfected with the simian virus 40 T-antigen gene.

Serum-free cultures of normal human buccal epithelial cells were transfected with a plasmid containing the SV40 T-antigen (SV40T) gene. Two major lines developed that showed extended lifespans (between 30 and 40 weeks) as compared with the controls (approximately 6 weeks). Continued growth through one or two crises generated several sublines. They expressed the epithelial marker keratin and also exhibited nuclear expression of SV40T. The lines showed abnormal karyotypes with both numerical and structural aberrations and variably responded to agents that normally inhibit growth and/or induce terminal differentiation, i.e. transforming growth factor-beta 1 and fetal bovine serum. One of the lines, termed SVpgC2a, developed into an apparently immortal line, since it had undergone more than 700 population doublings from over 2 years in culture. Further characterization of this line demonstrated its clonal origin, with integration of two copies of SV40T at the same site and the presence of both normal retinoblastoma and wild-type p53 proteins. This line showed high resistance to growth inhibition by transforming growth factor-beta 1 and serum similar to that shown by buccal carcinoma cell line SqCC/Y1. Neither SVpgC2a nor its parental lines were tumorigenic when injected into athymic nude mice, whereas the SqCC/Y1 cells induced tumors. The various lines with extended but finite lifespans, complemented by one immortalized line, which retained non-malignant properties upon extended culture, provide a battery of model systems that will be useful for studying mechanisms of human oral carcinogenesis.

Animals↗
PubMed1995

Role of platelet-derived growth factors in mouse development.

The current understanding of platelet-derived growth factor (PDGF) physiological functions in vivo is discussed in the context of mouse development. In particular, the review focuses on recent experiments in which genetic approaches have been applied in order to mutate the PDGF and PDGF receptor genes in the mouse. Thus, the PDGF-B and PDGF beta receptor (PDGFRb) genes were recently inactivated by homologous recombination in embryonic stem cells. Their phenotypes are highly similar, displaying cardiovascular, hematological and renal defects. The latter is particularly interesting since it consists of a specific cellular defect: the complete loss of kidnety glomerular mesangial cells. As such, the phenotype not only sheds light on the developmental importance of PDGF-B-PDGFRb interactions, but also reveals information about the function of mesangial cells. Based on detailed morphological studies of mutant glomeruli and the absence of urine collection in the urinary bladder, I propose that the mesangial cells function as interior "filter holders", the "filter" consisting of the glomerular basement membrane and associated cell types. The filter holder model would predict that glomerular filtration is critically dependent on an interior structural support of the filter, which is normally provided by the mesangial cells and the mesangial matrix. In addition to the mutants generated by gene targeting, the mouse patch mutation is discussed. This deletion encompasses the PDGFRa locus. The last part of the review focuses on the problems encountered when interpreting gene knockout phenotypes in the physiological functions of gene products.

Aging↗
PubMed1994

Islet amyloid polypeptide stimulates cyclic AMP accumulation via the porcine calcitonin receptor.

CHO-cells stably transfected with an expression vector for the porcine calcitonin receptor were exposed to various concentrations of IAPP, CGRP or calcitonin from different species. In these, but not in untransfected cells, rat IAPP mediated cAMP accumulation at concentrations above 25 nM. This potency was three orders of magnitude lower than that of porcine calcitonin and two and four orders of magnitude lower than those of human and salmon calcitonin, respectively. Human beta-CGRP had an effect similar to rat IAPP whereas human alpha-CGRP was at least one order of magnitude less potent than rat IAPP. COS cells expressing recombinant porcine calcitonin receptors transiently or stably showed a different pattern of responses to calcitonin, IAPP and the CGRPs. In these cells, rat IAPP was as potent an inducer of cAMP as was salmon or porcine calcitonin and more potent than human calcitonin or the CGRPs. The dissociation constants for salmon calcitonin binding to the porcine calcitonin receptors on CHO and COS cells were 0.2 nM and 2.0 nM and the corresponding number of binding sites per cell were approximately 7 x 10(4) and 2 x 10(6), respectively. These results demonstrate that IAPP and CGRP can mediate signal transduction via the porcine calcitonin receptor and provide a possible explanation for the calcitonin-like effects of pharmacological levels of IAPP and CGRP administrated in vivo. The difference between CHO and COS cells in their relative response to the various ligands may relate to the difference in receptor number, post-transcriptional processing, or to dissimilarities in the signal transduction pathways between the two cell types.

Amino Acid Sequence↗
PubMed1994

Mice deficient for PDGF B show renal, cardiovascular, and hematological abnormalities.

Platelet-derived growth factor (PDGF) affects the growth, migration, and function in vitro of mesenchymal cells, but little is known about its normal physiological functions in vivo. We show here that mice deficient for PDGF B die perinatally and display several anatomical and histological abnormalities. Kidney glomerular tufts do not form, apparently because of absence of mesangial cells. Instead, a single or a few distended capillary loops fill the glomerular space. The heart and some large arteries dilate in late-stage embryos. Most PDGF B mutant embryos develop fatal hemorrhages just prior to birth. Their hematological status includes erythroblastosis, macrocytic anemia, and thrombocytopenia. On the basis of these findings, we conclude that PDGF B has crucial roles in vivo in establishing certain renal and circulatory functions.

Anemia↗
PubMed1993

Negative trans-acting mechanisms controlling expression of platelet-derived growth factor A and B MRNA in somatic cell hybrids.

We have studied a human malignant melanoma cell line (WM115) which expresses high levels of PDGFA and PDGFB mRNAs, a hamster fibroblast cell line (Wq3H) which lacks PDGFB and has a very low expression of PDGFA mRNA, and hybrids between these cell lines. The PDGFA and PDGFB mRNA expression in the hybrid cells was markedly suppressed, indicating that the melanoma PDGF genes are controlled in the hybrid cells by negative factors/mechanisms contributed by the fibroblast genome. The melanoma but not the fibroblast PDGFB mRNA was induced by cycloheximide in the hybrid cells, indicating that the fibroblast and the melanoma PDGFB genes are regulated differently despite their presence in the same intracellular environment.

Animals↗
PubMed1993

Islet amyloid polypeptide in the rabbit and European hare: studies on its relationship to amyloidogenesis.

In this study, we determined the cDNA-predicted amino acid sequence of positions 9-31 of islet amyloid polypeptide from the rabbit and European hare. A synthetic rabbit/hare islet amyloid polypeptide 20-29 peptide was subsequently shown to be strongly fibrillogenic in vitro even though the putative amyloidogenic AILS sequence at positions 25-28 of human and cat islet amyloid polypeptide is modified in the rabbit and hare by a substitution of phenylalanine for leucine at position 27 (i.e. AIFS). Although islet amyloid polypeptide of both the rabbit and hare has an amyloidogenic sequence and is in fact amyloidogenic in vitro, the apparent lack of in vivo islet amyloidosis in rabbits and hares may be related to relatively low levels of islet amyloid polypeptide production by the islet beta cells in these species. This was supported by our findings that there is no substantial immunoreactivity in either rabbit or hare islets, and no measurable amount either in extracts of rabbit pancreases, or in rabbit plasma. This study supports the need for at least two prerequisites for the development of islet amyloidosis in vivo: an inherent fibrillogenic sequence within the islet amyloid polypeptide molecule and an adequate local concentration of islet amyloid polypeptide to promote self aggregation and formation of islet amyloid.

Amino Acid Sequence↗
PubMed1993

Islet amyloid polypeptide: demonstration of mRNA in human pancreatic islets by in situ hybridization in islets with and without amyloid deposits.

Islet amyloid polypeptide which is normally coexpressed with insulin in beta cells, forms amyloid deposits especially in islets of Type 2 (non-insulin-dependent) diabetic subjects. Occurrence of islet amyloid is paradoxically associated with loss of islet amyloid polypeptide immunoreactivity in beta cells. The present study was undertaken to examine whether the islet amyloid polypeptide gene is expressed in islets with decreased islet amyloid polypeptide immunoreactivity. Pancreatic tissue from 14 patients, 7 with Type 2 diabetes and 7 non-diabetic, were obtained at autopsy or surgery and studied for islet amyloid polypeptide expression by in situ hybridization and for presence of insulin and islet amyloid polypeptide by immunohistochemistry. Six of the specimens from the diabetic and three of those from the non-diabetic patients had varying degrees of islet amyloid polypeptide-derived islet amyloid. Amyloid deposits were associated with decreased numbers of beta cells with islet amyloid polypeptide immunoreactivity despite an apparent normal frequency of insulin-containing cells. This discrepancy might reflect an alteration in islet amyloid polypeptide production or processing at a transcriptional or post-transcriptional level. In contrast to the varying immunohistochemical patterns, islets of all categories showed strong labelling using an islet amyloid polypeptide probe for in situ hybridization. It is concluded that islet amyloid polypeptide production is not altered at the transcriptional level. The following possibilities remain: (1) islet amyloid polypeptide production may be altered at a post-transcriptional level or (2) that islet amyloid polypeptide production is normal but the reduced immunoreactivity of the cells reflects a reduced storage of IAPP in secretory granules.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Demonstration of GAD-65 as the main immunogenic isoform of glutamate decarboxylase in type 1 diabetes and determination of autoantibodies using a radioligand produced by eukaryotic expression.

Plasmids containing cDNA for the rat 67- and 65-kD isoforms of glutamate decarboxylase (GAD-67 and GAD-65) were expressed in COS-cells, and lysates of [35S]methionine-labeled cells were used for immunoprecipitations. Sera from 38 patients with type 1 (insulin-dependent) diabetes mellitus, which precipitated a 64-kD antigen from rat islets, reacted with recombinant GAD-65 in relation to their anti-64-kD titers. The eight strongest sera also precipitated recombinant GAD-67, suggesting that certain epitopes are common to both isoforms. Subsequently, [35S]methionine-labeled GAD-65 was purified from COS cell lysates and employed in a binding assay with 50 sera of patients with recent onset of type 1 diabetes mellitus. 38 sera (76%) precipitated labeled GAD-65 with titers that correlated with islet cell antibodies (ICA), determined in a standard immunofluorescence assay. 2 sera were GAD positive but ICA negative, 4 were positive only for ICA, and 6 were negative for both GAD and ICA, as were the sera of 20 controls. The data illustrate that antibodies against GAD-65 are present in a majority of patients with type 1 diabetes mellitus and that autoantibodies against other islet cell antigens also exist. The radioligand-binding assay, which is convenient and sensitive for detecting GAD antibodies, will facilitate the screening of individuals with autoimmune islet cell disease.

Adolescent↗
PubMed1993

Islet amyloid polypeptide--hen or egg in type 2 diabetes pathogenesis?

Islet amyloid polypeptide (IAPP or amylin) was first identified as the major peptide constituent of amyloid deposited in the islets of Langerhans in patients with type-2 diabetes mellitus or in insulinomas. It was subsequently shown that IAPP is produced by the pancreatic beta-cells, co-stored and co-released with insulin. IAPP is homologous with the neuropeptide calcitonin gene-related peptide (CGRP) and has therefore been assumed to have a function as an endocrine, paracrine or autocrine hormone. This has prompted the search for its physiological function as well as a putative pathogenic role in type 2 diabetes mellitus.

Amyloid↗
PubMed1992

Human islet amyloid polypeptide at pharmacological levels inhibits insulin and phorbol ester-stimulated glucose transport in in vitro incubated human muscle strips.

Human islet amyloid polypeptide, at concentrations of 1-100 nmol/l, has been demonstrated to inhibit the insulin-stimulated increase in rat muscle glycogen content. However, at physiological concentrations (1-10 pmol/l) of islet amyloid polypeptide, no effects have been reported. We tested the effect of a wide range of concentrations of human islet amyloid polypeptide on insulin- and phorbol ester-stimulated 3-0-methylglucose transport in in vitro incubated human skeletal muscle. Muscle specimens from the quadriceps femoris muscle were obtained from 23 healthy subjects with the use of a newly-developed open muscle biopsy technique. Human islet amyloid polypeptide at a concentration of 100 nmol/l had no effect on basal glucose transport, but inhibited the stimulatory effect of a maximal insulin concentration (1000 microU/ml) by 69% (p less than 0.001). The presence of human islet amyloid polypeptide at 1, 10 and 100 nmol/l decreased the effect of 100 microU/ml of insulin on glucose transport by 61% (p less than 0.05), 78% (p less than 0.05) and 76% (p less than 0.05), respectively. Similarly, human islet amyloid polypeptide at a concentration of 10 nmol/l inhibited phorbol ester-stimulated glucose transport by 100% (p less than 0.05). The inhibitory effects of human islet amyloid polypeptide on glucose transport were present in the muscle strips despite no net changes in glycogen content. Human islet amyloid polypeptide at 10 and 100 pmol/l had no effect on the rate of insulin-stimulated glucose transport.(ABSTRACT TRUNCATED AT 250 WORDS)

3-O-Methylglucose↗
PubMed1992

Characterization of the mouse PDGF A-chain gene. Evolutionary conservation of gene structure, nucleotide sequence and alternative splicing.

The mouse platelet-derived growth factor (PDGF) A-chain gene has been structurally characterized and compared with its human counterpart. The organization of the two genes is similar. Both consist of 7 exons spaced by 6 introns of corresponding sizes. As in the human gene, exon 6 encodes a sequence which is alternatively spliced. When present, it codes for an alternative C-terminus of the A-chain. In intron 5, conserved stretches of nucleotides, potentially involved in the regulation of the alternative splicing, are identified. The untranslated sequences show a high degree of nucleotide sequence identity and several conserved consensus binding sites for transcription factors are identified within the 5' untranslated as well as in the 5' flanking region.

Alternative Splicing↗
PubMed1992

Platelet-derived growth factor (PDGF) A-chain mRNA heterogeneity generated by the use of alternative promoters and alternative polyadenylation sites.

Expression of the platelet-derived growth factor (PDGF) A-chain gene is known to give rise to multiple transcripts of different sizes. Northern blot analysis, using a set of DNA probes corresponding to various parts of the human PDGF A-chain gene, indicated heterogeneity in both the 5' and 3' end of the transcripts. The 3' heterogeneity was shown to be the result of differential use of three polyadenylation signals. S1-nuclease protection- and chloramphenicol acetyltransferase (CAT)-assays, revealed the 5' heterogeneity to be the consequence of two alternative promoters. Whereas the upstream promoter contained typical TATA- and CAAT-boxes, the downstream promoter lacked a TATA-box but seemed to be composed of several GC-boxes.

Alternative Splicing↗