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Biomedical subjects

C Larsson

Publications and source records attributed to C Larsson.

At least 235 records · Page 13Linked to original sources
PubMed1995

Calmidazolium inhibits muscarinic receptor-mediated PLC activation in SH-SY5Y cells.

The aim of this study was to investigate the effect of a calmodulin antagonist, calmidazolium, on the muscarinic receptor-mediated increase in inositol 1,4,5-trisphosphate [I(1,4,5)P3] in SH-SY5Y cells. Exposure to 10 microM calmidazolium suppressed the initial I(1,4,5)P3 peak increase (IC50 1 microM) whereas the steady-state was less affected. Furthermore, calmidazolium displayed non-competitive antagonistic properties of [3H]quinuclidinyl benzylate binding to intact SH-SY5Y cells and to membranes from these cells. These effects were also obtained with another calmodulin inhibitor, trifluoperazine (10 microM). These results demonstrate that novel finding that the calmodulin inhibitors calmidazolium and trifluoperazine act as non-competitive muscarinic antagonists in SH-SY5Y cells and inhibit muscarinic receptor-stimulated phospholipase C activation in these cells.

Animals↗
PubMed1995

Tumor suppressor activity of the gene encoding mammary-derived growth inhibitor.

The gene encoding mammary-derived growth inhibitor (MDGI), a protein previously purified from bovine mammary gland and shown to have modest antiproliferative activity for human breast cancer cells in vitro, is demonstrated to function as a potent tumor suppressor gene. Human breast cancer cells transfected with a MDGI expression construct exhibited differentiated morphology, reduced proliferation rate, reduced clonogenicity in soft agar, and reduced tumorgenicity in nude mice relative to mock-transfected or untransfected controls. We mapped the human homologue of this gene to chromosome 1p33-35, a locus previously shown to exhibit frequent loss of heterozygosity in human breast cancer. MDGI immunoreactivity was detected in epithelial cells of human breast tissue, but not on ductal carcinoma cells on the same sections. Our results suggest that MDGI is a strong candidate for the distal 1p breast tumor suppressor gene. Furthermore, as prior reports have demonstrated that MDGI is hormonally regulated in breast epithelial cells and maximally expressed at the time of maximal differentiated function (just prior to lactation), MDGI is a candidate mediator of the differentiating effect of pregnancy on breast epithelial cells, which may be involved in the protective effect of early parity on subsequent breast cancer incidence.

Animals↗
PubMed1995

Genomic organization and complete cDNA sequence of the human phosphoinositide-specific phospholipase C beta 3 gene (PLCB3).

We have characterized the complete cDNA sequence, genomic structure, and expression of the human phosphoinositide-specific phospholipase C beta 3 (PLC beta 3) gene (gene symbol PLCB3). PLC beta 3 plays an important role in initiating receptor-mediated signal transduction. Activation of PLC takes place in many cells as a response to stimulation by hormones, growth factors, neurotransmitters, and other ligands. The partial cDNA sequence of PLC beta 3, previously published, was extended with 876 bp in the 5' direction, giving a transcript of 4400 bp and a total open reading frame of 1234 amino acids. This was in accordance with expression analysis by Northern blotting that revealed a single 4.4-kb transcript in all tissues tested. Genomic data were obtained by sequencing plasmid subclones of a cosmid that contained the whole gene. The size of the complete transcription unit was estimated to be on the order of 15 kb. The gene contains 31 exons, with all splice donor and acceptor sites conforming to the GT/AG rule. No exon exceeds 571 bp in length, and the shortest exon spans only 36 bp. More than half of the introns are smaller than 200 bp, with the smallest being only 79 bp long. The transcription initiation site was determined to be within an 8-bp cluster 328-321 bp upstream of the translation initiation site. The 5'flanking region is highly GC rich, with multiple CpG doublets, and contains multiple binding sites for Sp1. Lacking typical transcriptional regulatory sequences such as TATA and CAAT boxes, the putative promoter region conforms to the group of housekeeping promoters.

Amino Acid Sequence↗
PubMed1995

Molecular cloning, characterization, and chromosomal localization of a human lymphoid tyrosine kinase related to murine Blk.

Triggering of Ag receptors on lymphocytes induces rapid phosphorylation of several receptor-associated protein tyrosine kinases (PTKs), implicating their role in controlling cellular growth and differentiation. In this study, we report the cloning of a human cDNA encoding a nonreceptor PTK with a calculated M(r) of about 58 kDa. The kinase has an overall amino acid identity of approximately 87% with the murine Blk. However, in the unique domain there is only 58% homology and an insertion of six amino acids in the N-terminal region. The nature of this insertion suggests a functional role in membrane attachment. Northern blot analysis showed expression in all stages of B cell development and in T cell lines. The message was not observed in the nonlymphoid tissues examined. In contrast, expression of murine blk in plasma cells and T lymphocytes has not been reported. Importantly, transcripts were seen in human embryonic liver as early as 7.5 wk of gestation before the rearrangement of Ig H chain locus. Furthermore, transcripts were detected in human thymocytes and not in mature T cells. Southern blot analysis revealed polymorphism of this gene in a Caucasian population but not in a Gambian population, indicating a recent origin of this polymorphism. The gene was localized to chromosome 8p22-23. The homology at the protein level suggests that this kinase may be the human homologue of murine Blk. Expression of BLK in immature T cells suggests that BLK may play an important role in thymopoiesis.

Amino Acid Sequence↗
PubMed1995

Exclusion of the 13-kDa rapamycin binding protein gene (FKBP2) as a candidate gene for multiple endocrine neoplasia type 1.

The MEN1 gene is considered to be a tumour suppressor gene and has been localised to a 1-Mb region of 11q13.1. In this study, we report the physical localisation of the 13-kDa FK506 and rapamycin binding protein gene (FKBP2) to the cosmid marker D11S750, which is located inside the MEN1 region of non-recombination. The product of this gene is involved in signal transduction and is thus a candidate cell growth regulator or tumour suppressor gene. Northern studies have revealed that FKBP2 is expressed in those tissues predisposed to hyperplasia in MEN1; however, single-strand conformation polymorphism analysis and direct sequencing of DNAs from affected members of MEN1 kindreds and sporadic tumour DNAs have been performed and no mutations have been found. These studies exclude FKBP2 as a candidate gene for MEN1.

Base Sequence↗
PubMed1995

Allelotyping of follicular thyroid tumors.

To elucidate further the genetic mechanisms for follicular thyroid tumor development and progression, we allelotyped follicular thyroid tumors and other thyroid lesions from 92 patients. In general, a low frequency of loss of heterozygosity (LOH) was found, the highest being for chromosomes 3q, 10q, 11p, 11q, 13q, and 22q (10%-15%). However, detailed study of LOH of these chromosome arms with regard to the different histopathological diagnoses indicates that a locus on chromosome 10q may be involved in follicular thyroid tumor progression. In addition, the majority of Hürthle cell adenomas showed LOH on either chromosome 3q or 18q, in contrast to the other tumor types. This discrepancy in genetic alterations may contribute to the divergent clinical features occurring in these tumors.

Adenocarcinoma, Follicular↗
PubMed1995

Localization of the human soluble epoxide hydrolase gene (EPHX2) to chromosomal region 8p21-p12.

Epoxide hydrolases have an important function in organisms in that they catalyze the transformation of potentially toxic or carcinogenic epoxides into the corresponding diols. In this study, the chromosomal localization was determined for the human gene encoding soluble epoxide hydrolase. A polymerase chain reaction fragment corresponding to the C-terminal region of the mouse protein was used to isolate a cosmid clone from a human genomic library. By fluorescence in situ hybridization to metaphase chromosomes, the soluble epoxide hydrolase gene was then localized to chromosomal region 8p21-p12.

Animals↗
PubMed1995

Hyperparathyroidism of multiple endocrine neoplasia type 1: candidate gene and parathyroid calcium sensing protein expression.

BACKGROUND: Hyperparathyroidism affects most patients with multiple endocrine neoplasia type 1 (MEN 1). This study investigates expression of the candidate MEN1 gene phospholipase C beta 3 (PLC beta 3) and expression and function of a putative calcium sensing protein (CAS) in hyperparathyroidism of MEN 1. METHODS: In 31 parathyroid glands from 17 patients with MEN 1, CAS distribution was studied immunohistochemically and parallel sections were explored for PLC beta 3 mRNA expression by in situ hybridization. Enzymatically dispersed parathyroid cells were analyzed for cytoplasmic calcium concentrations [Ca2+]i and parathyroid hormone (PTH) release. RESULTS: All glands exhibited a heterogeneously reduced CAS immunoreactivity, especially meager in nodularly assembled parathyroid cells. Calcium regulated [Ca2+]i and PTH release tended to be more deranged in the glands possessing the lowest immunostaining. Parathyroid PLC beta 3 invariably was homogeneously expressed, and this included even MEN 1 patients with reduced PLC beta 3 expression in endocrine pancreatic tumors. CONCLUSIONS: The findings support variable calcium insensitivity of [Ca2+]i and PTH release in hyperparathyroidism of MEN 1, apparently coupled to heterogeneously reduced CAS expression. For clarification of the role of PLC beta 3 in MEN 1 parathyroid tumorigenesis further study of this protein is required.

Adult↗
PubMed1995

Adrenal lesion in multiple endocrine neoplasia type 1.

BACKGROUND: Multiple endocrine neoplasia (MEN) type 1 is accompanied by adrenal involvement, but characteristics and clinical handling of this lesion have been insufficiently explored. METHODS: Patients with MEN 1 (n = 43) were monitored (mean, 6.3 years) with annual biochemical and radiologic adrenal evaluation. Adrenal specimens were examined by in situ RNA-RNA hybridization for expression of the MEN1 candidate gene phospholipase C beta 3 (PLC beta 3) and immunostaining for insulin-like growth factor-1 receptor. RESULTS: Altogether 17 patients (40%) displayed adrenal enlargement, which was limited to the adrenal cortex and showed signs of progression, marked atypia, and cancer development in three of them. Only the carcinoma exhibited adrenocortical hormone excess. PLC beta 3 was expressed in the hyperplastic and adenomatous proliferation but not the carcinoma. Pancreatic endocrine tumors with insulin-proinsulin excess were overrepresented in the patients with adrenocortical involvement, but significant insulin-like growth factor-1 receptor immunoreactivity was restricted to the carcinoma. CONCLUSIONS: The prevalent adrenocortical lesion associated with MEN 1 requires regular attention because of malignant potential. It was unrelated to loss of constitution heterozygosity for the MEN1 locus (11q13) and PLC beta 3 expression, except for the cortical carcinoma exhibiting allelic losses involving also the Wiedemann-Beckwith gene at 11p15. Mechanisms for mitogenic relationships between the pancreatic and adrenal lesions of MEN 1 demand further clarification.

Adrenal Gland Diseases↗
PubMed1995

Solution structure of a mammalian PCB-binding protein in complex with a PCB.

Metabolites of polychlorinated biphenyls (PCBs) bind with high affinity to uteroglobin, a small homodimeric protein that also binds progesterone. We present the solution structure of the reduced form of rat uteroglobin in complex with a PCB methylsulphone, (MeSO2)2-TCB. The structure reveals the molecular basis for the accumulation of (MeSO2)2-TCB by uteroglobin. The structure also shows how ligand binding and release might be controlled by reduction/oxidation of two intermolecular disulphide bonds. Breakage of these bonds induces a local unfolding of the N- and C-termini and a separation of helices creating a channel into the binding site. These effects make the ligand binding cavity readily accessible to entry of the ligand.

Amino Acid Sequence↗
PubMed1995

Brij 58, a polyoxyethylene acyl ether, creates membrane vesicles of uniform sidedness. A new tool to obtain inside-out (cytoplasmic side-out) plasma membrane vesicles.

Most of the plasma membrane vesicles formed upon homogenization of plant tissue have a right-side-out (cytoplasmic side-in) orientation. Subsequent purification of plasma membrane vesicles using aqueous two-phase partitioning leads to a further enrichment in right-side-out vesicles resulting in preparations with 80-90% of the vesicles in this orientation. Thus, to be able to assay, e.g. the ion-pumping activities of the H(+)-ATPase and the Ca(2+)-ATPase, which expose their active sites towards the cytoplasm, the vesicles have to be inverted. This is very efficiently achieved by including 0.05% of the detergent Brij 58 (C16E20) in the assay medium, which produces 100% sealed, inside-out (cytoplasmic side-out) vesicles from preparations of 80-90% right-side-out vesicles. This was shown by assaying ATP-dependent H+ pumping using the delta pH probe acridine orange and dissipating the H+ gradient with nigericin, and by assaying ATP-dependent Ca2+ transport using 45Ca2+ and dissipating the Ca2+ gradient with the ionophore A23187. The presence of intact vesicles was confirmed by electronmicroscopy. The detergent Brij 58 is a polyoxyethylene acyl ether and a survey among some other members of this series revealed that those with a head group of relatively large size (E20-23) showed this 'non-detergent behavior', whereas those with smaller head groups (E8-10) behaved as normal detergents and permeabilized the membranes. Thus, a very convenient system for studies on ion-pumping activities and other vectorial properties of the plasma membrane is obtained by simply including the detergent Brij 58 in the assay medium.

Cell Membrane↗
PubMed1995

Molecular tools for presymptomatic testing in multiple endocrine neoplasia type 1.

The aim of this workshop session was to define a set of molecular tools for pre-clinical diagnosis in affected families, and to assess presence or absence of linkage to 11q13 in families with classical MEN1 as well as with MEN1-related clinical features. A consensus linkage map of first- and second-choice markers based on PCR as well as Southern blotting was established at the workshop. Based on the results from linkage analysis in 87 families with classical MEN1, presymptomatic testing using the suggested panel of markers, can now be performed with great accuracy.

Acromegaly↗
PubMed1995

Candidate genes for multiple endocrine neoplasia type 1.

The aim of this study was to isolate and characterize candidates for the multiple endocrine neoplasia type 1 (MEN1) gene. The development of tumours related to MEN1 is associated with somatic deletions involving the MEN1 locus, suggesting inactivation of a tumour-suppressor gene in this region. We have isolated five cDNA candidates located within the 900 kb remaining for the MEN1 gene, determined their sequence, and characterized their expression in normal tissues and several endocrine tumours. One of the candidates, encoding for phospholipase C-beta 3, showed properties consistent with the idea of a tumour-suppressor gene.

Blotting, Northern↗
PubMed1995

Genetic mapping of the multiple endocrine neoplasia type 1 locus at 11q13.

Oncogenesis of tumours related to multiple endocrine neoplasia type 1 (MEN1) is associated with somatic deletions involving the MEN1 locus at chromosomal region 11q13, suggesting inactivation of a tumour-suppressor gene in this region. Here we describe the localization of the MEN1 gene to a 900-kb region, based on linkage analysis in affected families and deletion mapping of MEN1-associated tumours. In addition, a set of microsatellite markers mapped to the 11q11-13 region were used for linkage analysis in a large Tasmanian MEN1 pedigree, demonstrating the usefulness of these markers for presymptomatic testing in affected families.

Adult↗
PubMed1995

Assignment of the mouse homologue of a human MEN1 candidate gene, phospholipase C-beta 3 (Plcb3), to chromosome region 19B by FISH.

A recent study using comparative mapping analysis suggests that the proximal segment of mouse chromosome 19 contains the mouse homologs of the human multiple endocrine neoplasia type 1 (MEN1) flanking markers proximal to the locus. We have recently shown that phospholipase C-beta 3 (PLCB3) is a candidate gene for the MEN1 syndrome. In the present investigation we used fluorescence in situ hybridization with a genomic DNA clone for mouse Plcb3, and mapped the locus to chromosome region 19B. This is in agreement with the comparative mapping of the MEN1 flanking markers in mouse.

Animals↗