PubMed Health⌕ Search

Biomedical subjects

M Koenig

Publications and source records attributed to M Koenig.

At least 109 records · Page 6Linked to original sources
PubMed1992

Gastrin-releasing peptide: in vivo and in vitro growth effects on an acinar pancreatic carcinoma.

The mammalian gastrin-releasing-peptide (GRP) and its structural amphibian analogue, bombesin, are known to be trophic factors for the normal exocrine pancreas. This work investigates the possible role of GRP in the growth of an acinar pancreatic cancer transplanted to the rat and in primary tumor cell cultures. Moreover, this adenocarcinoma was tested for its content of specific bombesin/GRP receptors by using autoradiographic technics and in vitro binding assays with tumor cells. In Lewis rats bearing the pancreatic carcinoma transplanted s.c. in the scapular region, chronic administration of GRP at the dose 30 micrograms/kg/day for 15 successive days significantly increased the tumor volume, the final tumor weight, and amylase, protein, RNA and DNA contents. Autoradiographic studies showed that tumor tissue was GRP receptor positive with a high density. The biochemical characterization indicated that receptor positive tumor tissue had saturable and high affinity receptors with pharmacological specificity for GRP and its bioactive analogues. In primary tumor cell cultures, GRP increased the incorporation of [3H] thymidine in DNA in a dose- and time-dependent manner. There was a good correlation between the ability of GRP and its COOH terminal analogues to elicit DNA synthesis and their affinity for 125I-GRP binding sites. These results from in vivo and in vitro experiments demonstrated that GRP induces growth of pancreatic carcinoma by acting directly on specific membrane receptors present on the tumor cells.

Adenocarcinoma↗
PubMed1992

A 530kb YAC contig tightly linked to the Friedreich ataxia locus contains five CpG clusters and a new highly polymorphic microsatellite.

Friedreich ataxia (FA) is a severe autosomal recessive neurodegenerative disease. The defective gene has been previously assigned to chromosome 9q13-q21 by demonstration of tight linkage to the two independent loci D9S15 and D9S5. Linkage data indicate that FRDA is at less than 1 cM from both markers. Previous physical mapping has shown that probes defining D9S15 (MCT112) and D9S5 (26P) are less than 260 kb apart and are surrounded by at least six CpG clusters within 450 kb, which might indicate the presence of "candidate" genes for FA. We isolated and characterized a 530 kb YAC (yeast artificial chromosome) contig that contains five of the CpG clusters. The YACs were used to search for new polymorphic markers needed to map FRDA precisely with respect to the cloned segment. In particular, we found a (CA)n microsatellite polymorphism, GS4, that detects 13 alleles with a PIC value of 0.83 and allows the definition of haplotypes extending over 310 kb when used in combination with polymorphic markers at D9S5 and D9S15.

Base Sequence↗
PubMed1992

Friedreich ataxia in Louisiana Acadians: demonstration of a founder effect by analysis of microsatellite-generated extended haplotypes.

Eleven Acadian families with Friedreich ataxia (FA) who were from southwest Louisiana were studied with a series of polymorphic markers spanning 310 kb in the D9S5-D9S15 region previously shown to be tightly linked to the disease locus. In particular, three very informative microsatellites were tested. Evidence for a strong founder effect was found, since a specific extended haplotype spanning 230 kb from 26P (D9S5) to MCT112 (D9S15) was present on 70% of independent FA chromosomes and only once (6%) on the normal ones. There was no evident correlation between haplotypes and clinical expression. The typing of an additional microsatellite (GS4) located 80 kb from MCT112 created a divergence of the main FA-linked haplotype, generating four minor and one major haplotype. A similar split was observed with GS4 in a patient homozygous for a rare 26P-to-MCT112 haplotype. These results suggest that GS4 is flanking marker for the disease locus, although other interpretations are possible.

Adolescent↗
PubMed1992

Study of large inbred Friedreich ataxia families reveals a recombination between D9S15 and the disease locus.

Friedreich ataxia is a neurodegenerative disorder with autosomal recessive inheritance. Precise linkage mapping of the Friedreich ataxia locus (FRDA) in 9q13-q21 should lead to the isolation of the defective gene by positional cloning. The two closest DNA markers, D9S5 and D9S15, show very tight linkage to FRDA, making difficult the ordering of the three loci. We present a linkage study of three large Friedreich ataxia families of Tunisian origin, with several multiallelic markers around D9S5 and D9S15. Haplotype data were used to investigate genetic homogeneity of the disease in these geographically related families. A meiotic recombination was found in a nonaffected individual, which excludes a 150-kb segment, including D9S15, as a possible location for the Friedreich ataxia gene and which should orient the search in the D9S5 region.

Adolescent↗
PubMed1991

Physical mapping of two loci (D9S5 and D9S15) tightly linked to Friedreich ataxia locus (FRDA) and identification of nearby CpG islands by pulse-field gel electrophoresis.

The Friedreich's ataxia locus (FRDA) has recently been mapped to 9q13-q21 by tight linkage to D9S15 and D9S5 loci. The present lack of recombination between these loci precludes further genetic mapping and suggests that the distances involved are in the megabase range. We have established a 1-Mb map around loci D9S15 (defined by probe MCT112) and D9S5 (defined by probe DR47) and found that they are at most 260 apart. Six rare cutting site clusters were found in a 450-kb segment containing both loci. Three clusters were completely unmethylated in two cell lines tested and might correspond to CpG islands flanking transcribed sequences. Cosmid mapping of a 52-kb region around D9S5 and pulse-field gel electrophoresis analysis showed the presence of three other CpG clusters that were partially or completely methylated. Two of them were present in the cosmid clones available and were associated with sequences conserved in other vertebrate species. The CpG islands and conserved sequences presented here can be used to search for genes defective in Friedreich's ataxia.

Animals↗
PubMed1991

[Intestinal absorption of insulin with a new telemetric shuttle in dogs].

Telemetric shuttles for the in vivo investigation of the gastrointestinal tract have been available for sometime. We describe herein the use of a new shuttle model whose original features include: a) continuous, real time transmission of its location in the small bowel and accurate measurement of the gut length, b) controlled release of 1 ml of a given substance at any chosen site, allowing detailed investigation of intestinal absorption at different levels of the small bowel under physiological conditions. Small bowel length was measured in dogs using the shuttle and was later compared to the actual small gut length measured in the same animals at laparotomy. The telemetric measurements appeared to closely match the direct operative measurements. Insulin absorption from the canine small bowel was then investigated releasing different dosages of insulin together with the pancreatic enzyme inhibitors Soybean and Aprotinine and a surfactant (5-methoxysalicylate). By adjusting the dose of insulin released, the type of adjuvant substance delivered with it and the site of release in the small bowel, we have been able to precisely define the conditions of insulin absorption. Insulin as such is exclusively absorbed in the ileum when released in doses of 500 IU or higher and mixed with aprotinine. For absorption to take place the solution delivered by the shuttle needs to have the correct pH and natremic concentration.

Animals↗
PubMed1991

Primary acquired melanosis of the conjunctiva is melanoma in situ.

This essay places the concept of "primary acquired melanosis" of the conjunctiva in historical perspective and shows that it and its analogs, namely, lentigo-melanosis (Hutchinson), melanotic freckle (Hutchinson), melanose circonscrite precancereuse (Dubrueilh), melanotische precancerose (Miescher), lentigo maligna (Clark), precancerous melanosis (Reese), benign, precancerous, and cancerous melanosis (Zimmerman), atypical melanocytic hyperplasia (Silver et al.), and benign acquired melanosis (Zimmerman), are synonyms for melanoma in situ. The issue is not merely semantic or philosophical; it is urgently practical. If a clinician takes literally the meaning of a lesion designated "benign melanosis" and considers it to be benign, rather than the malignant melanoma that it actually is, a patient who bears that flat pigmented lesion may one day die of metastasis from an elevated sequella of it. The same is true of "primary acquired melanosis," which is not simply a condition of blackening by melanin, but a flat melanoma that, if not removed completely, may give rise one day to metastases that cause death. To avoid such misconstructions, we advocate naming melanomas in all organs "melanoma" and those that are confined to epithelial structures "melanoma in situ." Euphemisms like lentigo maligna and primary acquired melanosis are evasions of the diagnosis of melanoma, and use of them may be harmful. For that reason, they should be eschewed.

Conjunctival Neoplasms↗
PubMed1990

Effect of dystrophin gene deletions on mRNA levels and processing in Duchenne and Becker muscular dystrophies.

Muscle dystrophin mRNAs from Duchenne (DMD) and Becker (BMD) patients with internal deletion of the DMD gene were quantitated and sequenced. In all cases (eight DMD and three BMD), truncated mature transcripts were found, and their amount was correlated to the clinical phenotype and to the reading frame. We focused on four cases that were apparently not in agreement with the reading frame rule. In two DMD cases, slightly reduced amounts of in-frame truncated mRNA are present but no dystrophin is detected, suggesting impaired translation and/or instability of the protein. In two BMD patients with out-of-frame deletions, the presence of minor in-frame alternatively spliced mRNA species is congruent with the observed truncated dystrophin and the mild phenotype.

Base Sequence↗
PubMed1990

Detailed analysis of the repeat domain of dystrophin reveals four potential hinge segments that may confer flexibility.

Most of dystrophin, the protein product of the Duchenne muscular dystrophy locus, is composed of spectrin-like repeats, suggesting that dystrophin is an elongated cytoskeletal molecule (Davison, M. D., and Critchley, D. R. (1988) Cell 52, 159-160; Koenig, M., Monaco, A. P., and Kunkel, L. M. (1988) Cell 53, 219-228). We present here a detailed analysis of the repeat domain of human dystrophin and propose that it is composed of 24 rather than 26 repeat units as previously suggested. Moreover, spacer sequences which do not align with the repeat consensus are present at the beginning and at the end of the repeat domain. Two other non-repeat spacers are found between repeat elements 3 and 4 and 19 and 20. The high proline content of each spacer suggests that it might represent a hinge. Using five new anti-dystrophin antisera and two previously described antisera (Hoffman, E. P., Brown, R. H., Jr., and Kunkel, L. M. (1987a) Cell 51, 919-928) to detect different dystrophin peptides after proteolytic cleavage, we show that the four hinge segments are sensitive sites for proteolysis. We present a model for a membrane-associated network of dystrophin in which the hinges play a key role by conferring flexibility to the network and thus resilience to the membrane.

Actinin↗
PubMed1990

Detection of 98% of DMD/BMD gene deletions by polymerase chain reaction.

We describe oligonucleotide primer sequences that can be used to amplify eight exons plus the muscle promoter of the dystrophin gene in a single multiplex polymerase chain reaction (PCR). When used in conjunction with an existing primer set, these two multiplex reactions detect about 98% of deletions in patients with Duchenne or Becker muscular dystrophy (DMD, BMD). Furthermore, these primers amplify most of the exons in the deletion prone "hot spot" region around exons 44 to 53, allowing determination of deletion endpoints and prediction of mutational effects on the translational reading frame. Thus, use of these PCR-based assays will allow deletion detection and prenatal diagnosis for most DMD/BMD patients in a fraction of the time required for Southern blot analysis.

Base Sequence↗
PubMed1989

Alternative splicing of human dystrophin mRNA generates isoforms at the carboxy terminus.

Dystrophin is the protein product of the Duchenne/Becker muscular dystrophy locus. It has a relative molecular mass of 427,000 and is encoded by a large RNA transcript processed from more than 65 exons spread over two million base pairs of the human X chromosome. We have used the polymerase chain reaction to see whether any of these exons are used alternatively in the different tissues that express dystrophin. As reported for rat dystrophin, we find that the first exons of the human dystrophin transcript is different in brain and muscle, indicating that dystrophin expression could be differentially regulated in these tissues by usage of distinct promoters. The 3' end of the dystrophin transcript can be alternatively spliced to create numerous isoforms differing at their carboxyl domains; this is the only domain of dystrophin that does not share any similarity with the related cytoskeletal alpha-actinins. These alternative transcripts yield dystrophin molecules which may interact with different proteins of the tissues expressing dystrophin.

Base Sequence↗
PubMed1989

Molecular deletion patterns in Duchenne and Becker type muscular dystrophy.

DNA from 80 Duchenne (DMD) and 15 Becker (BMD) index patients was analyzed with 12 genomic probes and the total cDNA. Deletions were detected in 24 DMD (30%) and 10 BMD patients (67%) by genomic probes alone, mostly p20, pXJ, and/or pERT87. All deletions were confirmed by cDNA probes, and an additional 29 DMD deletions were detected, resulting in a total of 63/95 deletions (66%). The majority of the deletions are localized between kb 6.7 and 9.7 of the cDNA; a smaller group, between kb 0.5 and 3.5. Of the deletions, 90% are detected by the three cDNA probes 1-2a, 7, and 8. This can be applied to strategies for carrier detection and prenatal diagnosis. The order of 13 exon-containing HindIII fragments in the region between probes 7 and 9-10, where most of the deletions are found, could be defined. The deletion patterns in DMD and BMD patients are different and well in accordance with the "reading frame theory" of Monaco and coworkers. Thus our findings indicate that a DMD or BMD phenotype may be predicted according to the breakpoint position and the number of deleted exons.

Chromosome Deletion↗
PubMed1989

Complementary DNA probes for the Duchenne muscular dystrophy locus demonstrate a previously undetectable deletion in a patient with dystrophic myopathy, glycerol kinase deficiency, and congenital adrenal hypoplasia.

Genomic DNA from a patient with dystrophic myopathy, glycerol kinase deficiency, and congenital adrenal hypoplasia was investigated using cDNA probes for the Duchenne muscular dystrophy (DMD) locus. Genomic probes had not detected a deletion in this patient. Southern analysis of Hind III-digested genomic DNA from this patient identified a deletion when the three distal Hinc II DMD cDNA fragments were used as probes. The deletion began in the genomic region corresponding to the 1.05-kb Hinc II cDNA fragment and extended through the 3' end of the DMD gene. This represents a centromeric breakpoint that corresponds to a position approximately 10.2-10.6 kb from the 5' end of the 14-kb DMD cDNA. These investigations demonstrate the value of the DMD cDNA probes for improved diagnoses in patients with molecular lesions involving the DMD locus. Furthermore, this novel deletion involving the coding portion of the 3' end of the DMD gene assists in the ordering of exons in this region and will provide insight into the functional role of the carboxy terminus of the DMD gene product, dystrophin.

Adrenal Insufficiency↗
PubMed1989

The molecular basis for Duchenne versus Becker muscular dystrophy: correlation of severity with type of deletion.

About 60% of both Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) is due to deletions of the dystrophin gene. For cases with a deletion mutation, the "reading frame" hypothesis predicts that BMD patients produce a semifunctional, internally deleted dystrophin protein, whereas DMD patients produce a severely truncated protein that would be unstable. To test the validity of this theory, we analyzed 258 independent deletions at the DMD/BMD locus. The correlation between phenotype and type of deletion mutation is in agreement with the "reading frame" theory in 92% of cases and is of diagnostic and prognostic significance. The distribution and frequency of deletions spanning the entire locus suggests that many "in-frame" deletions of the dystrophin gene are not detected because the individuals bearing them are either asymptomatic or exhibit non-DMD/non-BMD clinical features.

Adolescent↗