Gabaculine Inhibition of Chlorophyll Biosynthesis and Nodulation in Phaseolus lunatus L

Gabaculine (3-amino-2,3-dihydrobenzoic acid) was an inhibitor of in vivo chlorophyll biosynthesis in lima bean (Phaseolus lunatus L. cv Henderson). When applied to roots of 9-day-old plants, 10 micromolar gabaculine was sufficient to terminate biosynthesis of new chlorophyll. The trifoliolate leaves which emerged after gabaculine treatment were yellow. Gabaculine-treated plants had slightly lower dry weights; yet, overall plant size showed very little change. Chlorophyll fluorescence induction kinetics and CO₂ exchange measurements were used to monitor both immediate and long-term effects of gabaculine on photosynthesis. A lowered rate of the decline from the maximum level of fluorescence was observed after 10 hours for nitrate-supplemented plants, and all treated plants showed a slightly increased level of original fluorescence after 6 days. No change was observed in the rate of photosynthesis by unifoliolate leaves. The trifoliolate leaves, though not able to photosynthesize, were able to continue respiration. This suggested that heme biosynthesis for mitochondrial cytochromes was not abolished. In untreated lima bean, root nodules were induced by Rhizobium sp. 127E15. Following gabaculine treatment, root nodules formed, but were largely ineffective in nitrogen fixation. Nodule dry weight, nitrogen fixation activity, and leghemoglobin content were decreased by gabaculine.     

Effect of incubation temperature on the hatching of rotifer resting eggs collected from sediments

Sediment samples from Loch Leven, Scotland, were incubated at 5°C, 10°C and 15°C to induce hatching of rotifer resting eggs. The emergent animals were identified and counted. The temperature which induced hatching varied among the nine species studied. These results are discussed in relation to seasonality and temperature preferences previously recorded for the most abundant species. Resting egg densities of 2.2–13.9 eggs cm^–3 were recorded in the upper 5 cm of sediment.     

Labeling of human erythrocyte band 3 with maltosylisothiocyanate. Interaction with the anion transporter

Maltosylisothiocyanate (MITC), synthesized as an affinity label for the hexose carrier, has been reported to label a Band 3 or Mr = 100,000 protein in human erythrocytes, in contradistinction to many studies showing the carrier as a Band 4.5 or Mr = 45,000-66,000 protein on gel electrophoresis. In this work the possibility that MITC interacts with the Band 3 anion transporter was studied. In intact human erythrocytes, MITC labeling was largely confined to Band 3 and was decreased by several competitive inhibitors of hexose transport. However, MITC also appeared to react with the anion transport protein, since MITC labeling of Band 3 was irreversibly decreased by the anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) and since MITC also irreversibly inhibited both tritiated dihydro-DIDS labeling of Band 3 and sulfate uptake in intact cells. Although 20 microM DIDS had little effect on hexose transport, the labeling of erythrocyte Band 3 by the dihydro analog was significantly diminished by competitive inhibitors of hexose transport. These data suggest that MITC labels in part the anion transporter as well as other DIDS-reactive sites on Band 3 which appear to be sensitive to competitive inhibitors of hexose transport.     

Subcellular Location and Neuronal Release of Diazepam Binding Inhibitor

Diazepam binding inhibitor (DBI), a peptide located in CNS neurons, blocks the binding of benzodiazepines and beta-carbolines to the allosteric modulatory sites of gamma-aminobutyric acid (GABAA) receptors. Subcellular fractionation studies of rat brain indicate that DBI is compartmentalized. DBI-like immunoreactivity is highly enriched in synaptosomes obtained by differential centrifugation in isotonic sucrose followed by a Percoll gradient. In synaptosomal lysate, DBI-like immunoreactivity is primarily associated with synaptic vesicles partially purified by differential centrifugation and continuous sucrose gradient. Depolarization induced by high K+ levels (50 mM) or veratridine (50 microM) released DBI stored in neurons of superfused slices of hypothalamus, hippocampus, striatum, and cerebral cortex. The high K+ level-induced release is Ca2+ dependent, and the release induced by veratridine is blocked by 1.7 microM tetrodotoxin. Depolarization released GABA and Met5-enkephalin-Arg6-Phe7 together with DBI. DBI is also released by veratridine depolarization, in a tetrodotoxin-sensitive fashion, from primary cultures of cerebral cortical neurons, but not from cortical astrocytes. Depolarization fails to release DBI from slices of liver and other peripheral organs. These data support the view that DBI may be released as a putative neuromodulatory substance from rat brain neurons.     

Repeated floristical observations on islets in the Aegean

Repeated observations are made on species and numbers of individuals in some islets. The changes after 14 years are reported for 11 islets. They include several extinctions and invasions. Great changes in numbers of individuals were found, especially for many of the annuals, in some of them as great as between 0–10 and over 10 000 individuals. The greatest constancy was found in a few dominant and subdominant perennials.Dedicated to Prof.K. H. Rechinger on the occasion of his 80th birthday.     

Linkage Relationships Reflecting Ancestral Tetraploidy in Salmonid Fish

Fifteen classical linkage groups were identified in two salmonid species (Salmo trutta and Salmo gairdneri) and three fertile, interspecific hybrids (S. gairdneri X Salmo clarki, Salvelinus fontinalis X Salvelinus namaycush and S. fontinalis X Salvelinus alpinus) by backcrossing multiply heterozygous individuals. These linkage relationships of electrophoretically detected, protein coding loci were highly conserved among species. The loci encoding the enzymes appeared to be randomly distributed among the salmonid chromosomes. Recombination frequencies were generally greater in females than in males. In males, certain linkage groups were pseudolinked with other linkage groups, presumably because of facultative multivalent pairing and directed disjunction of chromosomes. Five such pseudolinkage groups were identified and they also appeared to be common among species and hybrids. Duplicate loci were never classically linked with each other, although some exhibited pseudolinkage and some showed evidence of exchanging alleles. Gene-centromere recombination frequencies estimated from genotypic distributions of gynogenetic offspring were consistent with map locations inferred from female intergenic recombination frequencies. These linkage relationships support the contention that all extant salmonids arose from a common tetraploid progenitor and that this progenitor may have been a segmental allotetraploid.     

Genetic diversity in Cucumis sativus L. assessed by variation at 18 allozyme coding loci

Summary The genetic diversity of the U.S. Cucumis sativus L. germplasm collection [757 plant introductions (PI) representing 45 countries] was assessed using 40 enzymes which represented 74 biochemical loci. Polymorphisms were observed at 18 loci (G2dh-1, Gpi-1, Gpi-2, Gr-1, Gr-2, Idh, Mdh-1, Mdh-2, Mdh-3, Mpi-2, Pepla-2, Peppap-2, Per-4, Pgd-1, Pgd-2, Pgm-1, Pgm-3, and Skdh). Two PIs (285606 and 215589) contained alleles [G2dh-1(1) and Per-4(2), respectively] which did not occur in any other PI. Other alleles which occurred in low frequencies (in < 1% of the PIs) included Gpi-1(3), Gpi-2(3), Gr-1(3), Gr-2(1), Idh(1), Mdh-1(2), Mdh-2(1), Peppap-2(1), and Pgd-1(1). Individual loci containing more than one allele in greater than 20% of the PIs included Mpi-2, Pepla-2, Pgd-2, and Pgm-1. Multivariate analyses aided in the reduction of data (principle components), depicted relationships among PIs (cluster), and identified the most discriminating enzyme loci (Pgm-1, Pepla-2, Gr-1, Pgd-2, Mpi-2, and Skdh) (classification and regression tree).Research partially supported by Asgrow, DeRuiter, Nickerson-Zwaan, Nunhems, and Sun Seed Companies; and the Graduate School, University of Wisconsin, Madison