Presence and binding characteristics of calcitriol receptors in human fetal gut

In the present study, we show for the first time the presence of calcitriol-specific binding sites in hypertonic extracts of cells isolated from human fetal small intestine and colon from 13-21 weeks of gestation. Woolf plot analysis of the binding characteristics revealed the presence of a single class of high affinity receptors. The presence of specific receptors for calcitriol in fetal intestine and colon opens interesting possibilities as to the role of this hormone in human gut development.     

Enzyme polymorphism and clinical variability of diseases: study of acid phosphatase locus 1 (ACP1) in obese subjects

The ACP1*A allele of erythrocyte acid phosphatase (ACP1) has a lower enzymatic activity when compared to other ACP1 alleles and is associated with maximal rate of body growth during intrauterine life. In three different samples of obese subjects (total number = 218). ACP1*A was associated with extreme body mass deviations. No difference in ACP1 allele distribution was observed between obese and nonobese subjects. These data suggest that a genetically determined variability of ACP1 influences the degree of obesity, but only when obesity itself has been triggered by some other factors.     

Differential accessibility of the tail domain of nuclear lamin A in interphase and mitotic cells

Human autoantibodies reactive against the tail domain exclusive to lamin A and absent from lamin C have been used for immunofluorescence studies on human fibroblast and epithelial cells. These autoantibodies were seen to react on mitotic cells where lamin A is present in a soluble depolymerized form and to react against lamin A in assembled interphase nuclear lamina after in situ extraction of chromatin. Taken together, these results support the suggestion that the tail domain of lamin A may be involved in the putative interaction of lamin A with chromatin.     

Mycobacteria glycolipids as potential pathogenicity effectors: alteration of model and natural membranes

Four mycobacterial wall glycolipids were tested for their effects on phospholipidic liposome organization and passive permeability and on oxidative phosphorylation of isolated mitochondria. From fluorescence polarization of diphenylhexatriene performed on liposomes it was concluded that the two trehalose derivatives (dimycoloyltrehalose and polyphthienoyltrehalose) rigidified the fluid state of liposomes, the triglycosyl phenolphthiocerol slightly fluidized the gel state, while the peptidoglycolipid ("apolar" mycoside C) just shifted the phase transition temperature upward. Dimycoloyltrehalose was without effect on liposome passive permeability, as estimated from dicarboxyfluorescein leak rates, and polyphthienoyltrehalose and triglycosyl phenolphthiocerol slightly decreased leaks, while mycoside C dramatically increased leaks. Activity of these lipids on mitochondrial oxidative phosphorylation was examined. The two trehalose derivatives have been tested previously: both had the same type of inhibitory activity, dimycoloyltrehalose being the most active. Triglycosyl phenolphthiocerol was inactive. Mycoside C was very active, with effects resembling those of classical uncouplers: this suggested that its activity on mitochondria was related to its effect on permeability. All these membrane alterations were called nonspecific because it is likely that they result from nonspecific lipid-lipid interactions, and not from recognition between specific molecular structures. Such nonspecific interactions could be at the origin of some of the effects of mycobacteria glycolipids on cells of the immune system observed in the last few years.     

Control of electric field induced cell membrane permeabilization by membrane order

Cells can be made temporarily permeable if pulsed by high-intensity short-duration electric fields. The molecular mechanisms underlying this electropermeabilization are still unknown. The kinetic events may be described by four successive steps: induction, expansion, stabilization, and resealing. On one hand, cell electropermeabilization is detected only under more stringent conditions when cells have been treated by ethanol. On the other hand, lysolecithin is observed to facilitate cell electropermeabilization. More precisely, these molecules that modify membrane order, when used in concentrations compatible with cell viability, are shown to affect only the expansion and resealing steps. Electropermeabilization is inducing a transition in the membrane organization. Membrane order is modulating the energy barrier needed to evoke this membrane transition which occurs when cells are submitted to a field larger than a characteristic threshold (expansion step). Less order would increase the magnitude of this energy barrier; more order would decrease it.     

In vivo and in vitro analysis of structure-function relationships in ribosomal protein L25 from Saccharomyces cerevisiae

We have developed a combination of in vivo and in vitro methods which allows us to determine the effect of practically every structural change, deletions as well as point mutations, on various biological functions of a ribosomal protein (r-protein). We have used this approach to delineate the functional domains of r-protein L25 from Saccharomyces cerevisiae. By analysis of the intracellular distribution of fusion proteins carrying various portions of L25 linked to Escherichia coli beta-galactosidase we traced the nuclear localization signal(s) of L25 to the region encompassing the N-terminal 61 amino acids of the protein. On the other hand, using in vitro prepared fragments of L25 we located the domain responsible for its specific binding to 26S rRNA to the region between amino acids 61 and 135. In order to be able to analyze the effect of mutations in L25 on ribosome biogenesis and function in vivo we constructed a mutant yeast strain in which the chromosomal L25 gene is placed under control of the inducible yeast GAL promoter. Since this strain is unable to grow on glucose as a carbon source the L25 gene must be essential for cell viability. Growth on glucose can be restored by introduction of a wild-type L25 gene on a plasmid, demonstrating that under these conditions the cells are dependent upon an extrachromosomally supplied copy of the gene.     

Adenylate cyclase activity in cyanobacteria: activation by Ca(2+)-calmodulin and a calmodulin-like activity

An adenylate cyclase activity was partially characterized in the cyanobacterium Anabaena sp. The enzyme activity is found in soluble cell fractions and shows an apparent molecular weight of about 183,400. This adenylate cyclase is activated by Ca2+ and bovine brain or spinach calmodulin and it is inhibited by EGTA and some phenothiazine derivatives. Furthermore, Anabaena sp. extracts contain a calmodulin-like activity which stimulates bovine brain cyclic AMP phosphodiesterase and the Anabaena adenylate cyclase. EGTA and phenothiazine derivatives block the cyanobacterial modulator effect.     

Studies on the N-acetyl-beta-D-hexosaminidase B from germinating Lupinus luteus L. seeds. II. Mechanism and inhibition with some 2-acetamido-2-deoxyaldono(1----4)lactones

The N-acetyl-beta-D-hexosaminidase B of germinating yellow lupin seeds catalyzed the hydrolysis of both p-nitrophenyl-N-acetyl-beta-D-glucosaminide and -galactosaminide substrates. The investigation of the pH dependence of the kinetic parameters (Vmax and Vmax/Km) demonstrated that two common ionizable groups (probably two carboxyl groups) play an essential role in the catalysis. That is, the enzyme has a lysozyme-like splitting mechanism, and the possibility of an anchimeric assistance provided by the acetamido group seems to be negligible. The presence of a deprotonated carboxyl group near the glycosidic linkage was also supported by inhibition with 1-thio substrate analogues. On the other hand, some 2-acetamido-2-deoxyaldono(1----4)lactones proved to be effective inhibitors of the hexosaminidase with the exception of the D-arabinose derivative, which can be explained by high stereospecificity in the binding.     

r14 syndrome without major dysmorphism

An 8-year-old boy, mentally retarded and epileptic since the age of six months, was found carrier of ring 14 chromosome. A dystrophy of the eye fundi was observed (whitish puncta of the macula); except for the "almond shaped eyes", there was no obvious dismorphism.     

Duplication 16q12----qter arising from 3:1 segregation in a 46,XX,t(13;16) (q12;q12) mother

A congenitally abnormal female baby was found to have the karyotype 46, XX, +der (16) t (13; 16) (q12;q12) mat. GTG, QFQ, CBG, THA and Ag-NOR banding techniques allowed the identification of the abnormal chromosomes in the proposita and in the translocation carriers through three generations. Duplication 16q resulted from 3:1 segregation in the carrier mother. The hypothesis of a specific meiotic segregation for this translocation is discussed. The phenotypic effects of proximal 16q duplications are analysed together with other four reported cases, which have similar duplicated segment and no other relevant chromosomal abnormality.