Immunological studies on lysosomal sphingomyelinase: Identification of a 28 000-Da component deficient in urine from patients with Niemann-Pick disease types A and B

The immunoblotting technique was used to identify sphingomyeJinase protein in samples of tissue and urine after subjection to poIyacrylamide-gel etectrophoresis in the presence of sodium dodecyl sulphate. In a sphingomyelinase preparation purified from control urine a prominent band was seen with an M_r of 28 000 Da. Glycoprotein fractions from urine and placenta, a membrane extract from spleen, and a partially purified sphingomyelinase preparation from placenta contained the 28 000-Da band plus additional, higher-M_r bands. The 28 000-Da band was detectable in urine from a patient with Niemann-Pick disease type C, but not in urine from patients with Niemann-Pick disease types A and B. It is concluded t h a t sphingomyeJinase is composed of at least one polypeptide with an M_r of 28 000 Da and that this polypeptide is deficient in the urine of patients with Niemann-Pick disease types A and B.     

Changes in cytoplasmic and lysosomal enzyme activities in cultured rat heart cells: The relationship to cell differentiation and cell population in culture

Summary Postnatal rat heart cells in culture enriched with respect to muscle cells were obtained by either high density seeding or by the replating technique. [³H]Thymidine incorporation to DNA and the enzymatic pattern of cytoplasmic and lysosomal enzymes have been studied as a function of the culture’s age, of seeding density, and replating. It was shown that (a) replating maintains predominance of myocyte population for at least 2 wk in culture; (b) heavy seeding density allows homogeneous myocyte population for the 1st wk in culture; and (c) the enzyme profile of the culture may serve as an indicator for the type of cell population in culture and its state of differentiation. This study was done as partial fulfilment of the M.Sc. thesis in Biochemistry (SY). Supported by grants from The Chief Scientist, Ministry of Health, State of Israel; The Ministry of Education and Sciences, State of Niedersachssen (FRG); and The Foundation for Heart Research from Mr. and Mrs. D. Vidal-Madjar, Paris, France.     

Zeta potential of protoplasts from gravireacting maize roots

Protoplasts were isolated from cortical cells of the elongating zone of maize (Zea mays L. cv. LG 11) roots and submitted to microelectrophoresis. Significant and transient differences in zeta potential between protoplasts from upper and lower root sides were compared with the gravireaction and the differential elongation of these roots. The maximum difference in the zeta potential was obtained between protoplasts from the upper and lower cortical cells after 90 min, exactly the time of gravipresentation for which the maximum rate of gravireaction was observed. In addition, this almost corresponded to the time for which the difference between the elongation rates of upper and lower sides of the extending zone began to increase. Consequently, the changes in the charges of the plasmalemma of the cortical cells from the growing part of roots could be more or less directly related to the root graviresponse.     

Epidermal growth factor: structure, location, phosphorylation and regulation of its receptor

Epidermal growth factor (EGF) is a Mr 6045 polypeptide first characterized for its ability to stimulate mitogenesis in epidermal and epithelial cells. The first step in the action of the growth factor is its binding to specific, high affinity membrane receptors. These receptors have been studied in a number of tissues and cell culture lines. The level of EGF receptors is modulated by many agents. EGF down-regulates its receptor. In addition, the number of EGF receptors is decreased by other growth factors (platelet-derived growth factor; transforming growth factor), by many tumor promoters and by viral transformation. Several hormones also can regulate EGF binding in its target tissues.     

Allozyme variability and phylogenetic relationships in the cultivated potato (Solanum tuberosum) and related species

Gene frequencies at 13 isozyme loci were determined in three South American taxa of cultivated potatoes [the diploid group (gp.) Stenotomum, the diploid subgroups (subgp.) Goniocalyx, and the tetraploid gp. Andigena ofS. tuberosum], in the diploid weed speciesS. sparsipilum, and in most of the main cultivars now raised in the Northern Hemisphere (the tetraploid gp. Tuberosum ofS. tuberosum). High levels of genetic variability (mean number of alleles per locus, percentage of polymorphic loci, and mean heterozygosity) were detected, being higher in tetraploid potatoes. An equilibrium among the evolutionary factors which increase genetic variability and artificial selection for maximum yield would explain the high uniformity of heterozygosity values we observed in both Andigena (0.36 ± 0.02) and Tuberosum (0.38 ± 0.01) cultivars.—The low value of genetic distance (D = 0.044) between Stenotomum and Goniocalyx does not support the status of species forS. goniocalyx.—In most isozyme loci, the electromorphs of gp. Andigena were a combination of those found in both gp. Stenotomum andS. sparsipilum, suggesting an amphidiploid origin of gp. Andigena from that two diploid taxa. The presence in Andigena of unique electromorphs, which were lacking in both gp. Stenotomum andS. sparsipilum, suggests that other diploid species could be also implied in the origin of tetraploid Andean potatoes. Furthermore, since Andigena were more related to Stenotomum (D = 0.052) than toS. sparsipilum (D = 0.241), the autopolyploidization of Stenotomum individuals and the subsequent hybridization with gp. Andigena may also have occurred. Thus, our study suggests a multiple origin (amphidiploidy, autoploidy, and hybridization at tetraploid level) of gp. Andigena.—Most of the electromorphs of gp. Tuberosum were also found in gp. Andigena; both the direct derivation of that group from the Andean tetraploid potatoes and the repeated introgression provided by breeding programmes could explain this result. However, the allele c of Pgm-B, present in 30 out of 76 Tuberosum cultivars from Northern Hemisphere as well as in 3 Chilean Tuberosum cultivars, lacks in the 258 Andigena genotypes sampled, suggesting that Chilean germplasm could have taken part in the origin of at least the 39% of the potato cultivars from Europe and North America analyzed here.—The distanceWagner procedure provides an estimate of a 30% of heterogeneity in the evolutionary divergence shown by different groups of cultivated potatoes. Diploid groups show a higher (22.5%) evolutionary rate than tetraploids, which can be attributed to both tetrasomic inheritance and facultative autofecundation that exists in Andigena and Tuberosum groups. Thus, artificial selection acting since 10000 years has not resulted in a higher rate of molecular evolution at the isozyme level in the tetraploids.     

B-cells of the synovial membrane. II. Differentiation during development of the synovial cavity in the mouse

Summary Study of pre- and postnatal development of the metatarsophalangeal joint of the mouse shows that the synovial cavity (SC) forms before any differentiation of the synovial mesenchyme. The primitive cleft results from degradation of a thin vascular mesenchymal layer in direct contact with the chondrogenic layers. Differentiation of the synovial membrane coincides with clarification of the SC (3rd to 6th day of postnatal life). When dilatation of the SC occurs (6th to 8th day), the two intimal cells types (A- and B-cells) are well identified. The B-cells already show typical features at day 6; their content of typical dense secretory vesicles is comparable to that of the adult B-cells at day 13. The specific secretory function of B-cells could be correlated with the particular structure of the intimal interstitial tissue and could account for the origin of some protein(s) of the synovial fluid.ERA 178 (Neuroendocrinologie Comparée) du CNRS et INSERM     

Partial deletion of 4p16 band in a ring chromosome and wolf syndrome

Summary A new case of ring chromosome 4 in a 2-day-old female child with multiple malformations is described. By means of the GTG-banding technique, a karyotype 46,XX,r(4), (p16q35) was determined. The characteristics of the child's karyotype and the relationship with the structure of the chromosome, especially the location of the deletion that produces the syndrome, are compared with previous reports.     

Computer simulation and interpretation of45Ca efflux profile patterns

Summary Stimulations or inhibitions by various agents of⁴⁵Ca efflux from prelabeled cells or tissues display distinct and reproducible profile patterns when the results are plotted against time as fractional efflux ratios (FER). FER is the fractional efflux of⁴⁵Ca from stimulated cells divided by the fractional efflux from a control unstimulated group. These profile patterns fall into three categories: peak patterns, exponential patterns, and mixed patterns. Each category can be positive (stimulation) or negative (inhibition). The interpretation of these profiles is difficult because⁴⁵Ca efflux depends on three variables: the rate of calcium transport out of the cell, the specific activity of the cell compartment from which the calcium originates, and the concentration of free calcium in this compartment. A computer model based on data obtained by kinetic analyses of⁴⁵Ca desaturation curves and consisting of two distinct intracellular pools was designed to follow the concentration of the traced substance (⁴⁰Ca), the tracer (⁴⁵Ca), and the specific activity of each compartment before, during, and after the stimulation or the inhibition of calcium fluxes at various pool boundaries. The computer model can reproduce all the FER profiles obtained experimentally and bring information which may be helpful to the interpretation of this type of data. Some predictions of the model were tested experimentally, and the results support the views that a peak pattern may reflect a sustained change in calcium transport across the plasma membrane, that an exponential pattern arises from calcium mobilization from an internal subcellular pool, and that a mixed pattern may be caused by a simultaneous change in calcium fluxes at both compartment boundaries.