Postnatal Development of a Granule Cell-Enriched, Neurone-Specific Glycoprotein, gp50, in Normal and Thyroid-Deficient Rats

Glycoprotein gp50 is a neurone-specific, granule cell-enriched glycoprotein that is also a major component of isolated synaptic membranes. Here, we describe the use of a monoclonal antibody, mab SM gp50, to study the postnatal development of gp50 in the brain of normal and thyroid-deficient rats. Radioimmunoassay, enzyme-linked immunosorbent assay, and Western blotting show that gp50 is not detectable in brain until postnatal day 4 (P4) in both forebrain and cerebellum. In forebrain, the rate of increase of gp50 levels is maximal between P12 and P20. It is somewhat later in cerebellum, where peak levels are attained between P30 and P35. Immunocytochemical studies show little detectable gp50-like immunoreactivity before P16, and the staining is still weak, relative to adult tissue, at P25. The intense staining of the granule cell layer characteristic of adult cerebellum predominantly appears after P25. Development of gp50 is severely retarded in the cerebellum of thyroid-deficient rats, particularly during the second and third postnatal weeks. However, by the fourth postnatal week, gp50 levels in normal and hypothyroid animals are comparable. The results indicate that significant alterations in the pattern of gp50 expression continue to occur at a late stage of cerebellar development. In particular, the increase in immunocytochemical staining of the granule cells after P25 is striking in that by this time most major events associated with cerebellar development are essentially complete.     

Characterization of inositol 1,4,5-trisphosphate-sensitive (IsCaP) and-insensitive (IisCaP) nonmitochondrial Ca2+ pools in rat pancreatic acinar cells

Summary We have measured Ca²⁺ uptake and Ca²⁺ release in isolated permeabilized pancreatic acinar cells and in isolated membrane vesicles of endoplasmic reticulum prepared from these cells. Ca²⁺ uptake into cells was monitored with a Ca²⁺ electrode, whereas Ca²⁺ uptake into membrane vesicles was measured with⁴⁵Ca²⁺. Using inhibitors of known action, such as the H⁺ ATPase inhibitors NBD-Cl and NEM, the Ca²⁺ ATPase inhibitor vanadate as well as the second messenger inositol 1,4,5-trisphosphate (IP₃) and its analog inositol 1,4,5-trisphosphorothioate (IPS₃), we could functionally differentiate two non-mitochondrial Ca²⁺ pools. Ca²⁺ uptake into the IP₃-sensitive Ca²⁺ pool (IsCaP) occurs by a MgATP-dependent Ca²⁺ uptake mechanism that exchanges Ca²⁺ for H⁺ ions. In the absence of ATP Ca²⁺ uptake can occur to some extent at the expense of an H⁺ gradient that is established by a vacuolar-type MgATP-dependent H⁺ pump present in the same organelle. The other Ca²⁺ pool takes up Ca²⁺ by a vanadate-sensitive Ca²⁺ ATPase and is insensitive to IP₃ (IisCaP). The IsCaP is filled at higher Ca²⁺ concentrations (10^–6 mol/liter) which may occur during stimulation. The low steady-state [Ca²⁺] of 10^–7 mol/liter is adjusted by the IisCaP.It is speculated that both Ca²⁺ pools can communicate with each other, the possible mechanism of which, however, is at present unknown.     

Chilling,oxidative stress and antioxidant responses inArabidopsis thaliana callus

Chilling ofArabidopsis thaliana (L.) Heynh. callus tissue to 4 °C led to conditions of oxidative stress, as indicated by increased levels of the products of peroxidative damage to cell membranes. Cellular H₂O₂ was also observed to increase initially upon chilling but by day 8 cellular levels had declined to below control levels. Although levels of catalase activity remained similar to those in unchilled tissue, activity of ascorbate peroxidase increased between days 4 and 8 of chilling to 4 °C. In callus held at 23 °C, levels of reduced glutathione remained static whereas they rose in callus held at 4 °C. Levels of oxidised glutathione were initially low but increased significantly by day 4 in the chilled callus. At 23 °C, however, levels of oxidised glutathione remained low. Between days 1 and 3 at 4 °C, levels of glutathione reductase activity increased but by day 8 glutathione reductase activity was similar to that in cells held at 23 °C. Exposure of callus to abscisic acid at 23 °C also led to increased activities of ascorbate peroxidase and glutathione reductase.Abbreviations ABA abscisic acid - GSH reduced glutathione - GSSG oxidised glutathione - TTC 2,35-triphenyltetrazolium chloride This work is supported by a grant from the Biotechnology and Biological Sciences Research Council.     

A Second Gene for Cerulean Cataracts Maps to the β Crystallin Region on Chromosome 22

Congenital cataracts are one of the most common major eye abnormalities and often lead to blindness in infants. At least a third of all cases are familial. Within this group, highly penetrant, autosomal dominant forms of congenital cataracts (ADCC) are most common. ADCC is a genetically heterogeneous group of disorders, in which at least eight different loci have been identified for nine clinically distinct forms. Among these, Armitageet al.(Nature Genet.9: 37–40, 1995) mapped a gene for cerulean blue cataracts to chromosome 17q24. Bodkeret al.(Am. J. Med. Genet.37: 54–59, 1990) described a large family with cerulean blue cataracts, in which the affected daughter of affected first cousins was presumed to be homozygous for the purported gene. We report linkage in this family to the region on chromosome 22q that includes two β crystallin genes (CRYBB2, CRYBB3) and one pseudogene (CRYBB2P1). The affected female in question is homozygous at all markers.     

A Gene for Autosomal Dominant Congenital Nystagmus Localizes to 6p12

Congenital nystagmus is an idiopathic disorder characterized by bilateral ocular oscillations usually manifest during infancy. Vision is typically decreased due to slippage of images across the fovea. As such, visual acuity correlates with nystagmus intensity, which is the amplitude and frequency of eye movements at a given position of gaze. X-linked, autosomal dominant, and autosomal recessive pedigrees have been described, but no mapping studies have been published. We recently described a large pedigree with autosomal dominant congenital nystagmus. A genome-wide search resulted in six markers on 6p linked by two-point analysis at θ = 0 (D6S459, D6S452, D6S465, FTHP1, D6S257, D6S430). Haplotype analysis localizes the gene for autosomal dominant congenital motor nystagmus to an 18-cM region between D6S271 and D6S455.     

Advantages and limitations in the use of hairy root cultures for the production of tropane alkaloids: Use of anti-auxins in the maintenance of normal root morphology

Summary Brugmansia candida hairy roots, obtained by infection withAgrobacterium rhizogenes LBA 9402, exhibit, after subculturing in liquid media, a tendency towards dedifferentiation. It has been found that the following strategies can be applied to inhibit this dedifferentiation and preserve normal root morphology: (a) lowering both the mineral and sucrose concentration in the media employed so as to diminish osmotic stress (a condition to which these roots appear to be particularly susceptible); (b) employing antiauxins in appropriate concentrations; and (c) maintaining the hairy roots on solid media prior to use in production processes in liquid media. The first strategy suggested does not favor alkaloid productivity, but in this case a two-step method could be attempted: biomass with normal root morphology could be obtained in a first stage using low sucrose concentrations, and in a second stage, sucrose could be increased in order to achieve higher productivity. In all the clones ofB. candida obtained, alkaloid production was biased towards scopolamine.     

Specific DNA probes for the identification of the fish pathogen,Renibacterium salmoninarum

To obtain specific DNA probes for the identification of the fish pathogen, Renibacterium salmoninarum, a discriminatory recombinant DNA library was constructed using selective fragments of the bacterial genome. Three renibacterial clones, pMAM29, pMAM46 and pMAM77, containing 149, 73, and 154 bp respectively, were isolated and characterized. The specificity of the probes was confirmed by dot-blot and Southern hybridization analyses. Bacterial hybridization experiments revealed that pMAM29 discriminates the R. salmoninarum genome from that of other fish pathogens such as Aeromonas salmonicida, Yersinia ruckeri, Flexibacter columnaris, Lactobacillus piscicola, Vibrio ordalii, Vibrio anguillarum and Aeromonas hydrophila. Thus, this probe may provide a new means to diagnose bacterial kidney disease in asymptomatic fish and ova.The authors are with the instituto de Bioquímica, Universidad Austral de Chile, P.O. Box 567, Valdivia, Chile     

Phytoplankton composition in the Weddell-Scotia Confluence area during austral spring in relation to hydrography

During the EPOS leg 2 cruise of the RV Polarstern, carried out in late austral spring of 1988–1989, the composition of phytoplankton in relation to the distribution of hydrographic parameters was studied in four successive transects carried out along 49°W and 47°W, across the Weddell-Scotia Confluence (WSC) and the marginal ice zone (which overlapped in part). In all transects, a maximum of phytoplankton biomass was found in the WSC, in surface waters stabilized by ice melting. Different phytoplankton assemblages could be distinguished. North of the Scotia Front (the northern limit of the WSC) diatoms with Chaetoceros neglectus, Nitzschia spp. and (Thalassiosira gravida) dominated the phytoplankton community. This assemblage appeared to have seeded a biomass maximum which occupied, during the first transect, an area of the WSC, south of the Scotia Front. The southernmost stations of the first transect and all the stations to the south of the Scotia Front in the other transects were populated by a flagellate assemblage (with a cryptomonad, Pyramimonas spp. and Phaeocystis sp.) and an assemblage of diatoms (Corethron criophilum and Tropidoneis vanheurkii among others) associated to the presence of ice. During the last three transects, the flagellate assemblage formed a bloom in the low salinity surface layers of the WSC zone. The bulk of the biomass maximum was formed by the cryptomonad which reached concentrations up to 4×10⁶ cells l^–1 towards the end of the cruise. Multivariate analysis is used to summarize phytoplankton composition variation. The relationships between the distribution of the different assemblages and the hydrographic conditions indicate that the change of dominance from diatoms to flagellates in the WSC zone was related to the presence of water masses from different origin.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation