Hereditary retinoblastoma: can balanced insertion entirely explain the differences of expressivity among families?

Summary Although the retinoblastoma gene has been isolated and sequenced, the difference in penetrance and expressivity among families has not yet been fully explained. Balanced chromosomal insertion involving the 13q14 regions has been shown to account for some families with several unaffected carriers. Since there could be cases with karyotypically undetectable insertions, we tested whether this mechanism was general enough to explain the whole difference in expressivity among families. Using 166 pedigrees, reported in nine series available in the literature (including our own), we conclude that balanced insertion cannot entirely explain the familial data, even if we allow for a reduced viability of unbalanced gametes. Other mechanisms are proposed and discussed in this paper.     

Streptokinase in the management of limb arterial thrombosis following free-flap surgery

Intraarterial streptokinase was used in the treatment of leg vessel thrombosis following free-flap closure of a large, open wound. Attention is focused on the coagulation anomalies present in such cases and the successful use of local thrombolytic therapy to salvage the limb.     

Intermediates on the reassociation pathway of phosphofructokinase I from Escherichia coli

The folding and association pathway of the allosteric phosphofructokinase from Escherichia coli has been investigated after complete denaturation of the protein in guanidine hydrochloride by spectroscopical methods, fluorescence and circular dichroism. Three successive processes can be observed during the renaturation of this protein. First, a fast reaction, detected by fluorescence, results in the formation of a (partially) structured monomer. Second, two monomers associate into a dimeric species. This step involves the shielding of the unique tryptophan residue, Trp 311, from the aqueous solvent, and it corresponds to the formation of the interface containing the effector binding site. The presence of ATP during renaturation increases the rate of formation of this dimeric species. The other ligands of the enzyme have no effect on this reaction as well as on the whole reactivation. Finally, the enzymatic activity is regained during the third slowest step. This last reaction is due to the association of two dimers into the native tetrameric structure. The presence of fructose 6-phosphate does not increase the rate of reactivation, even though this ligand strongly stabilizes the native enzyme against denaturation by bridging the interface corresponding to the active site. The self-assembly of phosphofructokinase from E. coli from its unfolded and separated chains follows a specific order in the formation of the interactions between subunits and involves a dimeric intermediate with a defined geometry.     

Differential regulation by dexamethasone of glucocorticoid receptor messenger RNA concentrations in neuronal cultures derived from fetal rat hypothalamus and cerebral cortex

1. Differential regulation, by dexamethasone, of glucocorticoid receptor gene expression was studied in three different neuronal cultures derived from hypothalamus amygdala, and cerebral cortex. 2. Cellular glucocorticoid receptor (GR) mRNA concentration was measured by hybridization using a 32P-labeled RNA probe complementary to a 2.2-kb fragment of the glucocorticoid receptor mRNA. Changes in the amount of GR mRNA were evaluated in relation to the content of beta-actin mRNA. 3. In cells derived from either hypothalamus or cerebral cortex, we observed a complex pattern of GR mRNA concentrations which were characterized by cyclic variations of GR mRNA content during continuous treatment with dexamethasone for up to 72 hr. 4. In contrast to cells derived from the hypothalamus where a persistent 30-40% reduction in GR mRNA levels was seen for up to a least 72 hr, we observed, in cells derived from the cerebral cortex, a sustained increased (1.4-fold) of the GR mRNA at this same time interval.     

Human bisphosphoglycerate mutase expressed in E coli: purification, characterization and structure studies

Bisphosphoglycerate mutase (EC 5.4.2.4.) is an erythrocyte-specific enzyme whose main function is to synthesize 2,3-diphosphoglycerate (glycerate-2,3-P2) an effector of the delivery of O2 in the tissues. In addition to its main synthase activity the enzyme displays phosphatase and mutase activities both involving 2,3-diphosphoglycerate in their reaction. Using a prokaryotic expression system, we have developed a recombinant system producing human bisphosphoglycerate mutase in E coli. The expressed enzyme has been extracted and purified to homogeneity by 2 chromatographic steps. Purity of this enzyme was checked with sodium dodecyl sulfate polyacrylamide gel and Cellogel electrophoresis and structural studies. The bisphosphoglycerate mutase expressed in E coli was found to be very similar to that of human erythrocytes and showed identical trifunctionality, thermostability, immunological and kinetics' properties. However, the absence of a blocking agent on the N-terminus results in a slight difference of the electrophoretic mobility of the enzyme expressed in E coli compared to that of the erythrocyte.     

Alport syndrome: a genetic study of 31 families

Thirty one families with Alport syndrome including 3 families with associated syndromes were studied. The location of the COL4A5 gene, responsible for the Alport syndrome, was determined by linkage analysis with eight probes of the Xq arm and by a radiation hybrid panel. Concordant data indicated the localization of the Alport gene between DXS17 and DXS11. Four deletions and one single base mutation of the COL4A5 gene were detected. Homogeneity tests failed to show any evidence of genetic heterogeneity superimposed on clinical heterogeneity for ophthalmic signs and end-stage renal disease age.     

Assignment by in situ hybridization of a fibroblast growth factor receptor gene to human chromosome band 10q26

Summary A 2.3-kb cDNA probe for the human bek fibroblast growth factor receptor was used to determine the chromosomal localization of the corresponding gene by in situ hybridization. The results show that this gene, a form of which is amplified in some poorly differentiated stomach cancers, is localized on chromosome region 10q26. The two previously identified fibroblast growth factor receptor genes are thus not on the same chromosome, as the related fig (fms-like gene) fibrovblast growth factor receptor gene has previously been mapped to human chromosome region 8p12.     

Effects of cold exposure on calcitonin secretion in the young rat

The effects of cold exposure on calcitonin (CT) secretion were evaluated in young rats. Acute cold exposure (5 h to 5 degrees C) induced a rise in plasma CT concentrations and a decrease in thyroidal CT stores without change in total and ionized plasma calcium levels. The cold activation of sympathico-adrenomedullary axis and the inhibition of CT response to cold after beta-antagonist treatment might suggest that endogenous catecholamines can enhance CT secretion in young rats. Cold adaptation (3 weeks to 5 degrees C) induced a fall in plasma calcium concentration and a rise in thyroidal CT stores without change in plasma CT levels. The high plasma glucocorticoid levels which are known to occur during chronic cold exposure could be involved in the rise of thyroidal CT content in cold adapted rats.     

An immunological study of the uncoupling protein of brown adipose tissue mitochondria

1. Ewes were injected with purified 32,000-Mr uncoupling protein from mitochondria of brown adipose tissue of cold-adapted rats in order to raise antibodies. 2. The existence of antibodies in the plasma of ewes and the cross-reactivity of plasmas were demonstrated and studied by 125I-labelled antigen-antibody reaction, double immunodiffusion, the inhibition of GDP binding to the 32,000 Mr protein and by immunohistochemistry. 3. The antibodies raised against the homogeneous protein yielded a single immunoprecipitation band with detergent-solubilized mitochondrial membranes of brown adipose tissue from rat, hamster, guinea-pig, rabbit and with the purified uncoupling protein of these animals. No immunoprecipitation was obtained with the protein purified from brown adipose tissue of term lamb foetus. 4. The GDP-binding activity of the uncoupling protein (isolated or in solubilized membranes) was largely inhibited by the antiserum. 5. The anti-(rat uncoupling protein) could not cross-react with solubilized membranes from liver or muscle, nor with the purified beef heart or rat liver ADP/ATP translocator.