Sulfoglucuronyl Neolactoglycolipids in Adult Cerebellum: Specific Absence in Murine Mutants with Purkinje Cell Abnormality

It is shown here that glycolipids of the sulfoglucuronyl neolacto series (SGGLs) are present in the adult rodent cerebellum. SGGLs were not detected in the cerebellar murine mutants lurcher, Purkinje cell degeneration, and staggerer, in which Purkinje cell loss is the primary defect. SGGLs were present, however, in normal amounts in weaver and reeler mutants, in which there is a major and relatively specific loss of granule cells without obvious deficiency in Purkinje cells. In the myelin-deficient quaking mutant, the expression of SGGLs also was nearly normal. The loss of SGGLs in Purkinje cell-deficient mutants was specific, since most of the major lipids were not affected significantly and only the percentage composition of other lipids, such as sulfatides and gangliosides, was altered in the mutants. These and other results strongly suggest that SGGLs and other glycolipids of the paragloboside family are localized specifically in Purkinje cells and their arbors in the adult cerebellum. This is the first demonstration of the localization of a specific glycolipid and its analogs in a specific cell type in the nervous system.     

Constitutive and transport-related endocytotic pathways in turtle bladder epithelium

Summary Proton secretion in the urinary bladder of the fresh-water turtle is mediated by a proton pump located in the apical membrane of a population of cells characteristically rich in carbonic anhydrase. Earlier studies have demonstrated that these cells exhibit apical-membrane endocytotic and exocytotic processes which are thought to be involved in the regulation of the rate of proton transport via alterations in the number of pumps within the apical membrane. In this study, we sought to characterize these processes using two different methods. Analysis of transepithelial impedance yielded estimates of membrane capacitance which could be related to membrane area, thereby allowing one to monitor net changes in apical-membrane area resulting from changes in the net rates of endo-and exocytosis. Uptake of the fluid-phase marker FITC-dextran provided a measure of net extracellular volume uptake which was related to net rates of endocytosis. Our major conclusions are summarized as follows. The bladder cells exhibit a high baseline rate of endocytosis which appears to be a constitutive process similar to pinocytosis. This process is completely inhibited when ambient temperature is reduced to 15°C. In addition, serosal application of 0.5mm acetazolamide causes a transient increase in the rate of endocytosis, concomitant with a decrease in the rate of transport. Reduction of ambient temperature to 15°C reduces the rate of acetazolamide-induced endocytosis, but does not abolish it. Addition of 1mm serosal azide not only prevents the acetazolamide-induced increase in endocytosis, but also prevents the decrease in transport caused by acetazolamide. Azide has no effect on the baseline rate of endocytosis, nor does it prevent inhibition of carbonic anhydrase by acetazolamide. The specificity of azide, coupled with the different temperature sensitivities, demonstrate that the constitutive and transport-dependent endocytotic pathways are distinct processes. The observation that azide prevents both the acetazolamide-induced increase in endocytosis and the decrease in transport strongly supports the notion that endocytosis of proton-pump-containing membrane is requisite for the inhibition of transport by acetazolamide. Finally, the results also demonstrate that acetazolamide does not inhibit proton secretion simply by inhibiting carbonic anhydrase.     

Interactions between the roach,Rutilus rutilus,and waterfowl populations of Lough Neagh,Northern Ireland

Synopsis Following the introduction of roach, Rutilus rutilus, to a large eutrophic lake in ca. 1973, a subsequent increase in the abundance of this cyprinid through the 1970s was accompanied by a decline in the numbers of one of the lake&s most abundant overwintering waterfowl, the tufted duck, Aythya fuligula, and an increase in overwintering piscivorous great crested grebes, Podiceps cristatus. We suggest that these contrasting trends are causally related and that competition for benthos and increased prey availability are the mechanisms responsible for the changes in the tufted duck and grebe populations respectively. In agreement with these hypotheses, a reduction in the roach population during the mid 1980s was accompanied by a recovery of tufted ducks and a decline of grebes.     

The regulatory status of the fixL- and fixJ-like genes in Bradyrhizobium japonicum may be different from that in Rhizobium meliloti

Summary The cloning, sequencing and mutational analysis of the Bradyrhizobium japonicum symbiotic nitrogen fixation genes fixL and fixJ are reported here. The two genes were adjacent and probably formed an operon, fixLJ. The predicted FixL and FixJ proteins, members of the two-component sensor/regulator family, were homologous over almost their entire lengths to the corresponding Rhizobium meliloti proteins (approx. 50% identity). Downstream of the B. japonicum fixJ gene was found an open reading frame with 138 codons (ORF138) whose product shared 36% homology with the N-terminal part of FixJ. Deletion and insertion mutations within fixL and fixJ led to a loss of approximately 90% wildtype symbiotic nitrogen fixation (Fix) activity, whereas an ORF138 mutant was Fix⁺. In fixL, fixJ and ORF138 mutant backgrounds, the aerobic expression of the fixR-nifA operon was not affected. NifA itself did not regulate the expression of the fixJ gene. Thus, the B. japonicum FixL and FixJ proteins were neither involved in the regulation of aerobic nifA gene expression nor in the anaerobic NifA-dependent autoregulation of the fixRnifA operon; rather they appeared to control symbiotically important genes other than those whose expression was dependent on the NifA protein. The fixL and fixJ mutant strains were unable to grow anaerobically with nitrate as the terminal electron acceptor. Therefore, some of the FixJ-dependent genes in B. japonicum may be concerned with anaerobic respiration.     

Liver transplantation in 100 children: Cambridge and King's College Hospital series.

To review the results of the Addenbrooke''s and King''s College Hospital children''s liver transplantation programme.Retrospective analysis of the first 100 children to receive liver grafts at Addenbrooke''s Hospital, Cambridge, from December 1983 to March 1990.Addenbrooke''s Hospital, Cambridge, and King''s College Hospital, London.153 children assessed for liver transplantation, of whom 22 died before a donor became available and 31 were considered unsuitable. 100 children received grafts, of whom 27 had second grafts.One year actuarial patient survival was 71%, with 57% one year graft survival. In the last two years survival rates had improved considerably, with 86% of patients and 63% of grafts surviving for at least one year. Sixty five children were alive 12 to 86 months after transplantation; 63 were well and leading normal active lives and 56 had entirely normal liver function. Children''s growth and development were essentially normal, with many showing remarkable catch up growth.Liver transplantation offers children with terminal liver disease a high chance of a return to full quality life and normal development. Improved surgical and medical care have progressively improved survival. The timing of transplantation is critical but has been constrained particularly by the availability of donors and resources.     

The biogeography of three Boeckella species (Copepoda: Calanoida) in New Zealand

The New Zealand distributions of three species of Boeckella (Copepoda, Calanoida), B. triarticulata, B. dilatata and B. hamata are mapped. B. triarticulata is primarily a pond dweller but is also found in reservoirs and shallow lakes. B. dilatata is mainly found in the deeper glacial lakes and ponds in the central region of the South Island and B. hamata has a more widespread distribution in lakes and ponds in the South Island and lower half of the North Island. Differences in temperature optima, food requirements and dispersal ability among the three Boeckella species are related to vicariant events to explain their distribution in New Zealand.     

Activation of platelets by alpha-thrombin is a receptor-mediated event. D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone-thrombin, but not N alpha-tosyl-L-lysine chloromethyl ketone-thrombin, binds to the high affinity thrombin receptor

Competition binding studies have been carried out to evaluate the antagonism of TLCK-thrombin (N alpha-tosyl-L-lysine chloromethyl ketone-treated thrombin) and PPACK-thrombin (D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone-treated thrombin) with alpha-thrombin using computer-assisted analysis of the binding isotherms (LIGAND). alpha-Thrombin bound to high, moderate, and low affinity sites as previously described (Harmon, J. T., and Jamieson, G. A. (1985) Biochemistry 24, 58-64). PPACK-thrombin bound to all three sites accessible to alpha-thrombin (K1, 7 nM; R1, 20 sites/platelet; K2, 3 nM; R2, 1800 sites/platelet; K3, 510 nM; R3, 84,000 sites/platelet) as well as to a separate fourth site (Kx, 0.4 nM; Rx, 20 sites/platelet) for PPACK-thrombin that was not accessible to alpha-thrombin. In contrast, TLCK-thrombin did not bind to the high affinity site for alpha-thrombin but bound to the moderate and low affinity sites for alpha-thrombin with similar affinity (K2, 2 nM; R2, 890 sites/platelet; K3, 900 nM; R3, 100,000 sites/platelet) and to another site (Ky, 0.03 nM; Ry, 10 sites/platelet) which was not accessible to alpha-thrombin. As predicted from these binding studies, TLCK-thrombin did not compete with alpha-thrombin for platelet activation at concentrations as high as 1000 nM (500-fold excess). In contrast a 300-fold excess of PPACK-thrombin (670 nM) totally inhibited platelet activation by 2 nM thrombin. These results demonstrate that the high affinity binding site for thrombin on human platelets is a classical receptor, occupancy of which is necessary for platelet activation by low concentrations of thrombin; that TLCK-thrombin does not occupy this high affinity site and hence cannot inhibit platelet activation by alpha-thrombin; and that PPACK-thrombin does compete with alpha-thrombin at the high affinity site and is an antagonist of alpha-thrombin induced activation.