Ectopic Expression of the Tetratricopeptide Repeat Domain of SPINDLY Causes Defects in Gibberellin Response

The SPINDLY (SPY) protein of Arabidopsis is a negative regulator of gibberellin (GA) response. The SPY protein has 10 copies of the tetratricopeptide repeat (TPR) at the N terminus. TPR motifs function as protein-protein interaction domains. Several spy alleles are affected only in the TPR region suggesting that protein-protein interactions mediated by this domain are important for proper GA signaling. We have used a reverse genetics approach to further investigate the role of the TPR domain. The TPR domain of SPY was overexpressed in wild-type, gai, and spy plants. Expression of the TPR domain alone is not sufficient to rescue spy mutants. Expression of the TPR domain in a wild-type background produces phenotypes similar to those caused by loss-of-function spy mutants including resistance to GA biosynthesis inhibitors, short hypocotyl length, and early flowering. The dwarfing of the floral shoot internodes caused by the gai mutation was suppressed by expression of the TRP domain. Expression of the TPR domain had no effect on the abundance of endogenous SPY mRNA. The TPR domain was found to interact with SPY both in vitro and in yeast two-hybrid assays. These data indicate that the TPR domain of SPY can participate in protein-protein interactions and that these interactions are important for the proper functioning of SPY.     

Analysis of the distribution and structure of integrated Banana streak virus DNA in a range of Musa cultivars

Banana streak virus strain OL (BSV-OL) commonly infects new Musa hybrids, and this infection is thought to arise de novo from integrated virus sequences present in the nuclear genome of the plant. Integrated DNA (Musa6+8 sequence) containing the whole genome of the virus has previously been cloned from cv. Obino l’Ewai (Musa AAB group), a parent of many of the hybrids. Using a Southern blot hybridization assay, we have examined the distribution and structure of integrated BSV-OL sequences in a range of Musa cultivars. For cv. Obino l’Ewai, almost every restriction fragment hybridizing to BSV-OL was predicted from the Musa6+8 sequence, suggesting that this is the predominant type of BSV-OL integrant in the genome. Furthermore, since only two junction fragments of Musa/BSV sequence were detected, and the Musa6+8 sequence is believed to be integrated as multiple copies in a tandem array, then the internal Musa spacer sequences must be highly conserved. Similarly sized restriction fragments were detected in four BB group cultivars, but not in six AA or AAA group cultivars, suggesting that the BSV-OL sequences are linked to the B-genome of Musa. We also provide evidence that cv. Williams (Musa AAA group) contains a distinct badnavirus integrant that is closely related to the ‘dead’ virus integrant previously characterized from Calcutta 4 (Musa acuminata ssp. burmannicoides). Our results suggest that the virus integrant from cv. Williams is linked to the A-genome, and the complexity of the hybridization patterns suggest multiple sites of integration and/or variation in sequence and structure of the integrants.     

Species-specific algal responses to zooplankton: experimental and field observations in three nutrient-limited lakes

A series of 4-day manipulations of zooplankton biomass and nutrientavailability was performed in enclosures in three lakes to determinespecies-specific algal responses to herbivory and nutrient enrichment.Algal performance in enclosures was compared to the relationshipsbetween weekly algal growth rates and the zooplankton in situ.When in situ growth rates were significant functions of zooplanktonbiomass, the responses were generally consistent with responsesin the enclosure experiments. The importance of both nutrientsand zooplankton in mediating algal growth was demonstrated bynumerous observations: strong algal community response to enrichment,unimodal or positive responses of certain algal taxa to zooplanktonbiomass, differences in degree of nutrient limitation amongthe algal response types, lack of nutrient limitation of non-grazedalgal taxa and a preponderance of taxa with no net responseto increasing zooplankton biomass. Variation in the zooplanktoncommunity may be the largest source of variability in nutrientsupply rate during summer in stratified lakes, and causes substationalvariability in the algae. Algae responded more strongly to changesin zooplankton composition than to changes in zooplankton biomass.We conclude that, due to the close coupling of phytoplanktonand zooplankton communities in these nutrient-limited lakes,major compositional changes in the zooplankton have greatereffects on the algae than do changes in biomass of grazers alreadypresent. ¹Present address: Division of Environmental Studies, Universityof California, Davis, CA 95616, USA ²Present address: Division of Biological Sciences, Universityof California, Davis, CA 95616, USA     

Altered Mitochondrial Respiration in Selectively Vulnerable Brain Subregions Following Transient Forebrain Ischemia in the Rat

Mitochondrial respiratory function, assessed from the rate of oxygen uptake by homogenates of rat brain subregions, was examined after 30 min of forebrain ischemia and at recirculation periods of up to 48 h. Ischemia-sensitive regions which develop extensive neuronal loss during the recirculation period (dorsal-lateral striatum, CA1 hippocampus) were compared with ischemia-resistant areas (paramedian neocortex, CA3 plus CA4 hippocampus). All areas showed reductions (to 53-69% of control) during ischemia for oxygen uptake rates determined in the presence of ADP or an uncoupling agent, which then recovered within 1 h of cerebral recirculation. In the ischemia-resistant regions, oxygen uptake rates remained similar to control values for at least 48 h of recirculation. After 3 h of recirculation, a significant decrease in respiratory activity (measured in the presence of ADP or uncoupling agent) was observed in the dorsal-lateral striatum which progressed to reductions of greater than 65% of the initial activity by 24 h. In the CA1 hippocampus, oxygen uptake rates were unchanged for 24 h, but were significantly reduced (by 30% in the presence of uncoupling agent) at 48 h. These alterations parallel the development of histological evidence of ischemic cell change determined previously and apparently precede the appearance of differential changes between sensitive and resistant regions in the content of high-energy phosphate compounds. These results suggest that alterations of mitochondrial activity are a relatively early change in the development of ischemic cell death and provide a sensitive biochemical marker for this process.     

Variations in Membrane Sensitivity of Brain Region Synaptosomes to the Effects of Ethanol In Vitro and Chronic In Vivo Treatment

The effects of chronic ethanol treatment on the membrane order of synaptosomes from the cerebral cortex, striatum, cerebellum, brainstem, and hippocampus of rats were determined by measuring the fluorescence polarization of diphenylhexatriene (DPH) that had been incorporated into the synaptosomal membranes. Fischer-344 rats either were fed a nutritionally complete ethanol-containing liquid diet for 5 months or pair-fed with a diet that contained sucrose substituted isocalorically for ethanol. Polarization values for synaptosomes from all the brain regions studied were similar except for those from cerebral cortical synaptosomal membranes, which were significantly less ordered. Ethanol in vitro (30-500 mM) decreased the polarization values in synaptosomes from sucrose-control rats for all brain regions, although the sensitivity of cerebellar synaptosomes to the membrane disordering effects of ethanol in vitro was significantly greater that of synaptosomes from other brain regions. Chronic ethanol treatment did not alter baseline polarization for any brain region. Cerebellar and brainstem synaptosomes from the ethanol-fed rats were significantly less susceptible to the membrane disordering effects of ethanol in vitro compared to their sucrose controls, suggesting that chronic ethanol administration results in tolerance to ethanol's membrane effects. Striatal synaptosomes exhibited intermediate tolerance, whereas the sensitivities of cortical and hippocampal synaptosomes to membrane disordering by ethanol in vitro were not significantly affected by the chronic ethanol treatment. These results suggest that synaptosomal membranes have different membrane order requirements depending on the brain region from which they are prepared. Variations in brain regional neuronal membrane sensitivity to ethanol and differential tolerance development may contribute to some of the acute and chronic behavioral effects of ethanol.     

Clostridium acetobutylicum Mutants That Produce Butyraldehyde and Altered Quantities of Solvents

Spontaneous mutants of Clostridium acetobutylicum NRRL B643 that were resistant to allyl alcohol (AA) were selected and characterized. These mutants contained 10- to 100-fold reduced activities of butanol and ethanol alcohol dehydrogenase. The AA mutants formed two groups and produced no ethanol. Type 1 AA mutants produced significant amounts of a new solvent, butyraldehyde, and contained normal levels of the coenzyme A-dependent butyraldehyde dehydrogenase (BAD). Type 2 AA mutants produced no significant butyraldehyde and lower levels of all solvents, and they contained 45- to 100-fold lower activity levels of BAD. Following ethyl methanesulfonate mutagenesis, low-acid-producing (Acid⁻) mutants were selected and characterized as superinduced solvent producers, yielding more than 99% of theoretical glucose carbon as solvents and only small amounts of acetate and butyrate. Following ethyl methanesulfonate mutagenesis, 13 sporulation-negative (Spo⁻) mutants were characterized; and 3 were found to produce only butyrate and acetate, a minor amount of acetone, and no alcohols. These Spo⁻ mutants contained reduced butanol dehydrogenase activity and no BAD enzyme activity. The data support the view that the type 2 AA, the Acid⁻, and the Spo⁻ mutants somehow alter normal regulated expression of the solvent pathway in C. acetobutylicum.     

Immunological detection of low-density lipoproteins modified by malondialdehyde in vitro or in vivo

We describe an ELISA technique able to recognize malondialdehyde-modified low-density lipoproteins (LDL). For this purpose we produced antibodies to malondialdehyde-LDL, specific for the malondialdehyde modification of LDL; these antibodies recognized essentially malondialdehyde-LDL. Coating ELISA plates with the antibodies to malondialdehyde-LDL and using peroxidase-labelled antibodies to LDL, which reveal only apolipoprotein B, we obtained an accurate method of detecting malondialdehyde-modified apolipoprotein B. Preliminary studies demonstrated that this method allows the detection of lipoproteins containing malondialdehyde-modified apolipoprotein B in the serum of patients with cardiovascular diseases.     

Radioactive labeling techniques for the identification of G antigen in the human Rh blood group system

The G antigen is one of the erythrocyte membrane Rh antigens. The amount of Rh antigen present on the red blood cell is about 10(-15) g and radioactive labeling of membrane proteins is a useful method for its identification and characterization. In this paper, we compare 4 labeling techniques. Using a human monoclonal anti-Rh(G) antibody and an immunofixation technique, we located the G antigen on a polypeptide of an average molecular weight of 28,000 Da.     

Mortality among male anaesthetists in the United Kingdom, 1957-83.

A cohort of 3769 male anaesthetists resident in the United Kingdom between 1957 and 1983 was followed up for a total of 51,431 person years of observation. All subjects were fellows of the Faculty of Anaesthetists and held full registration with the General Medical Council. With all men in social class I being taken as the standard, the standardised mortality ratio among anaesthetists for all causes of death was 68 (95% confidence interval 59 to 77) and the standardised mortality ratio for all cancers was 50 (95% confidence interval 36 to 67). There was no significant excess mortality from lymphomas or leukaemias, but 16 of the 221 deaths in anaesthetists were due to suicide, giving a standardised mortality ratio of 202 (95% confidence interval 115 to 328). When anaesthetists were compared with all doctors the standardised mortality ratio for suicide was only 114, a nonsignificant excess. These findings confirm that the risk of suicide among anaesthetists is twice as high as among other men in social class I but suggest that the risk does not differ significantly from that among doctors as a whole. There was no evidence of a significant excess risk of cancer, and, in particular, the small excess of cancer of the pancreas reported previously could not be confirmed.