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Biomedical subjects

J M Rossi

Publications and source records attributed to J M Rossi.

12 recordsLinked to original sources
PubMed2001

Distinct mesodermal signals, including BMPs from the septum transversum mesenchyme, are required in combination for hepatogenesis from the endoderm.

Mesodermal signaling is critical for patterning the embryonic endoderm into different tissue domains. Classical tissue transplant experiments in the chick and recent studies in the mouse indicated that interactions with the cardiogenic mesoderm are necessary and sufficient to induce the liver in the ventral foregut endoderm. Using molecular markers and functional assays, we now show that septum transversum mesenchyme cells, a distinct mesoderm cell type, are closely apposed to the ventral endoderm and contribute to hepatic induction. Specifically, using a mouse Bmp4 null mutation and an inhibitor of BMPs, we find that BMP signaling from the septum transversum mesenchyme is necessary to induce liver genes in the endoderm and to exclude a pancreatic fate. BMPs apparently function, in part, by affecting the levels of the GATA4 transcription factor, and work in parallel to FGF signaling from the cardiac mesoderm. BMP signaling also appears critical for morphogenetic growth of the hepatic endoderm into a liver bud. Thus, the endodermal domain for the liver is specified by simultaneous signaling from distinct mesodermal sources.

Animals↗
PubMed1995

Phenotypic and molecular analysis of a transgenic insertional allele of the mouse Fused locus.

Spontaneous mutations at the mouse Fused (Fu) locus cause dominant skeletal and neurological defects and recessive lethal embryonic defects including neuroectodermal abnormalities and axial duplications. Here, we describe a new allele at the Fu locus caused by a transgenic insertional mutation, H epsilon 46. Embryos homozygous for the H epsilon 46 insertion die at day 9-10 post coitum and display phenotypic defects similar to those associated with Fu alleles. The H epsilon 46 locus was cloned and shown to contain a 20-kb deletion at the site of transgene insertion with no other detectable rearrangements. Genomic probes from the H epsilon 46 locus were mapped to a genetic locus closely linked to Fu on chromosome 17 and were hybridized to a YAC contig covering the FuKi critical region. Compound heterozygotes between H epsilon 46 and FuKi were inviable and displayed abnormalities at the same stage of embryogenesis as do homozygotes for either of the two mutations, demonstrating that these two recessive lethal mutations belong to the same complementation group. A genomic probe from the wild-type H epsilon 46 locus detected a transcript that is disrupted by the transgenic insertion, representing a candidate for the wild-type allele of Fused.

Alleles↗
PubMed1994

Genetic map of the fused locus on mouse chromosome 17.

Fused (Fu) is a dominant mutation in mice resulting in the asymmetry and fusion of tail vertebrae in heterozygotes. Fu/Fu homozygotes are often viable and can exhibit a duplication of the terminal tail vertebrae resulting in bifurcated tails. There are two more severe alleles at Fu, Kinky (FuKi) and Knobbly (FuKb), which die between 9 and 10 days of gestation as homozygotes, exhibiting a duplication of the embryonic axis, leading to incomplete or complete twinning. To define the precise map position of the FuKi mutation on mouse Chromosome 17, a 983-animal (FuKi tf x Mus spretus)F1 x +tf/+tf interspecific backcross was generated and scored for FuKi, another tightly linked visible marker tufted (tf), and five linked molecular loci, D17MIT18, D17Leh54, D17Aus57, Hba-ps4, and Pim1. The order and genetic distances between the markers were determined to be centromere-D17MIT18-5.79 cM-D17Leh54-0.85 cM-D17Pri6-0.12 cM-D17Pri7-0.12 cM-Hba-ps4-1.20 cM-D17Pri8-0.48 cM-tf-2.05 cM-Pim1. The FuKi gene could not be genetically separated from three molecular markers, D17Pri6, D17Pri7, and Hba-ps4. Yeast artificial chromosome clones that contain these tightly linked markers have been isolated to form a contig that contains FuKi. Recombination breakpoints generated through the interspecies backcross were mapped onto the contig and demonstrate that recombination in this region is not random.

Animals↗
PubMed1992

Neurotrophic factor-like activity in Drosophila.

The NGF-family of neurotrophic factors are structurally similar peptides with related functional properties. So far, this family of neurotrophic factors has only been identified in the vertebrate nervous system. We have determined that cultured Drosophila embryonic cells produce and secrete into medium, an activity which stimulates neurite outgrowth of embryonic chick sensory ganglia. This Drosophila activity can be blocked by antibodies to mouse NGF, indicating an immunological relationship between the Drosophila factor, mouse NGF and possibly other vertebrate neurotrophic factors. Addition of mouse NGF to Drosophila embryonic cells in culture results in increased cell number and enrichment of the neuronal phenotype, indicating that Drosophila cells have the ability to respond to the vertebrate factor. In addition, poly(A)+RNA extracted from Drosophila contains a single 1.4 Kb band which cross-hybridizes with a mouse NGF cRNA probe. These results indicate that vertebrate neurotrophic factor-like functions may operate in a genetically defined invertebrate species.

Animals↗
PubMed1992

Genomic analysis using a yeast artificial chromosome library with mouse DNA inserts.

A yeast artificial chromosome library with mouse genomic DNA inserts has been constructed. The library encompasses a 2.5-fold coverage of the mouse genome, with an average insert size of 250 kilobases. The screening strategy uses the polymerase chain reaction on pooled DNAs prepared from individually stored clones. The usefulness of the library for chromosome walking was illustrated by constructing a 600-kilobase-long contig of DNA surrounding Hba-ps4, a DNA marker that is tightly linked to the fused (Fu) locus on chromosome 17.

Animals↗
PubMed1992

The consequences of expressing hsp70 in Drosophila cells at normal temperatures.

In Drosophila cells, regulatory mechanisms not only act to provide rapid induction of hsp70 during heat shock but also to prevent expression at normal temperatures. To determine whether expression of hsp70 is detrimental to cells growing at normal temperatures, we used heterologous promoters to force expression of the protein in tissue culture cells and in larval salivary glands. Initially, constitutive expression of hsp70 substantially reduces the rate of cell growth. With continued expression, however, growth rates recover. At the same time, the intracellular distribution of hsp70 changes. Immediately after induction, the protein is diffusely distributed throughout the cell, but as growth resumes it coalesces into discrete points of high concentration, which we term hsp70 granules. hsp70 granules are also observed both in wild-type Drosophila tissue culture cells and in salivary glands after extended periods of recovery from heat shock. The protein in these granules appears to be irreversibly inactivated. It cannot be dispersed with a second heat shock, and cells containing these granules do not show thermotolerance. Only partial overlap between hsp70 granules and lysosomes indicates that the granules form independently of lysosomes. We conclude that expression of hsp70 is detrimental to growth at normal temperatures. We suggest that the change in hsp70 distribution, from diffuse to granular, represents a mechanism for controlling the protein's activity by sequestration.

Animals↗
PubMed1991

Changes in hsp70 alter thermotolerance and heat-shock regulation in Drosophila.

To test the role of the heat shock protein hsp70 in induced thermotolerance and in the regulation of the heat-shock response, we established cell lines with altered expression of the Hsp70 gene. Underexpressing cells were created by transformation with antisense Hsp70 genes, and overexpressing cells by transformation with extra copies of the wild-type gene. Expression at normal temperatures was achieved by placing Hsp70 coding sequences under the control of the metallothionein promoter. Cells that expressed mutant hsp70s were created by transforming cells with deletion and frameshift mutations. The results indicate that hsp70 plays a major role in both thermotolerance and regulation. Surprisingly, they also indicate that these functions can be separated. Overexpression affected thermotolerance more than regulation; underexpression affected regulation more than thermotolerance. A carboxyl-terminal deletion of Hsp70 had a severe dominant-negative effect on thermotolerance but only a minor effect on regulation; an amino-terminal deletion strongly affected regulation but not thermotolerance. A model that explains these observations is presented.

Animals↗
PubMed1989

The intracellular location of yeast heat-shock protein 26 varies with metabolism.

An antibody highly specific for heat-shock protein (hsp)26, the unique small hsp of yeast, and mutants carrying a deletion of the HSP26 gene were used to examine the physical properties of the protein and to determine its intracellular distribution. The protein was found in complexes with a molecular mass of greater than 500 kD. Thus, it has all of the characteristics, including sequence homology and induction patterns, of small hsps from other organisms. When log-phase cells growing in glucose were heat shocked, hsp26 concentrated in nuclei and continued to concentrate in nuclei when these cells were returned to normal temperatures for recovery. However, hsp26 did not concentrate in nuclei under a variety of other conditions. For example, in early stationary-phase cells hsp26 is induced at normal growth temperatures. This protein was generally distributed throughout the cells, even after heat shock. Similarly, in cells genetically engineered to synthesize hsp26 in the presence of galactose, hsp26 did not concentrate in nuclei, with or without a heat shock. To determine if the failure of hsp26 to concentrate in the nucleus of these cells was due to the fact that the protein had been produced at 25 degrees C or to a difference in the physiological state of the cell, we investigated the distribution of the heat-induced protein in cells grown under several different conditions. In wild-type cells grown in galactose or acetate and in mitochondrial mutants grown in glucose or galactose, hsp26 also failed to concentrate in nuclei with a heat shock. We conclude that the intracellular location of hsp26 in yeast depends upon the physiological state of the cell and not simply upon the presence or absence of heat stress. Our findings may explain why previous investigations of the intracellular localization of small hsps in a variety of organisms have yielded seemingly contradictory results.

Acetates↗
PubMed1989

[Intermittent mechanical ventilation as home care].

Nocturnal mechanical ventilation (NMV) is a promising technique increasing survival and improving the quality of life of myopathic and kyphoscoliotic patients. The indications for NMV must be careful and the patients strictly selected. NMV is rarely useful in patients with pulmonary diseases, like COPD or restrictive disorders. When a professional medical and paramedical support is locally available, NMV can be undertaken at home. Negative and positive pressure ventilation can be used for NMV. Actually, tracheostomy can be replaced very often by a new type of positive pressure ventilation via a nasal face mask. We present here our series of 11 patients submitted to NMV and describe carefully the problems and the results of a 5-years experience with NMV in Geneva.

Adolescent↗
PubMed1984

[Automatization of heparin determination using chronometric evaluation of anti-Xa activity of the AT III-heparin complex].

The authors describe an adaptation on a semi- automatique coagulometer KC 10 of a manual assay of anti-Xa activity of the Heparin-Antithrombin III Complex close to the technique described by Yin and al. ( Hepaclot - Stago ). The results show a good linearity and a good reproducibility, with a better sensitivity than the manuel method. Freezing has no influence. Significant differences were observed between our assay and the manuel anti-IIa assay. These last results neither depend on the administration route nor on the heparin batches.

Antithrombin III↗