Distribution of Fusarium wilt of Bambara nut (Vigna subterranea (L.) Verdc.) in farmers’ fields’ of Busia County in Western Kenya and its management using farmyard manure

A study was carried out to determine Fusarium wilt distribution in Bambara nut farmers’ fields and its management using farm yard manure (FYM). Four villages in Busia County were purposively sampled for the study. The data generated were subjected to analysis of variance and treatment means separated by least significant difference test. Fusarium wilt incidence in the fields ranged from 14.63 to 43.56%. In the greenhouse, FYM reduced the disease incidence by 10.2% and severity by 9.5% on the black landrace and 1.9 and 12.8%, respectively, on the red landrace. In the field, FYM reduced disease incidence by 9.1% and severity by 6.9% on the black landrace and 10.4 and 10.4%, respectively, on the red landrace. Farm yard manure had the lowest area under disease progress curve irrespective of the landrace. The study confirmed the presence of the pathogen in the fields and the ability to manage the disease using FYM.     

The biometry of gills of 0-group European flounder

The gill surface area of 0-group, post-metamorphic Pleuronectes flesus L. was examined using digital image analysis software and expressed in relation to body mass according to the equation log Y=loga+c logW ( a =239·02; c =0·723). The components that constitute gill area, total filament length, interlamellar space and unilateral lamellar area were measured. The measurement of the length of every filament on all eight arches showed that commonly used methods of calculation can lead to an under-estimation of up to 24% of total filament length. Direct measurements of unilateral lamellar area with digital image analysis showed that previously reported gill area data for the same species was over-estimated by as much as 58%. In addition, in this species the neglect of gill pouch asymmetry after metamorphosis, can bring about a 14% over-estimation of total gill area.     

Multiple metabolic pools of phosphoinositides and phosphatidate in human erythrocytes incubated in a medium that permits rapid transmembrane exchange of phosphate.

1. A Hepes-based medium has been devised which allows rapid Pi exchange across the plasma membrane of the human erythrocyte. This allows the metabolically labile phosphate pools of human erythrocytes to come to equilibrium with [32P]Pi in the medium after only 5 h in vitro. 2. After 5-7 h incubation with [32P]Pi in this medium, only three phospholipids, phosphatidic acid (PtdOH), phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 4,5-bisphosphate (PtdIns4,5P2) are radioactively labelled. The concentrations of PtdIns4P and PtdIns4,5P2 remain constant throughout the incubation, so this labelling process is a reflection of the steady-state turnover of their monoester phosphate groups. 3. During such incubations, the specific radioactivities of the monoesterified phosphates of PtdIns4, PtdIns4,5P2 and PtdOH come to a steady value after 5 h that is only 25-30% of the specific radioactivity of the gamma-phosphate of ATP at that time. We suggest that this is a consequence of metabolic heterogeneity. This heterogeneity is not a result of the heterogeneous age distribution of the erythrocytes in human blood. Thus it appears that there is metabolic compartmentation of these lipids within cells, such that within a time-scale of a few hours only 25-30% of these three lipids are actively metabolized. 4. The phosphoinositidase C of intact human erythrocytes, when activated by Ca2+-ionophore treatment, only hydrolyses 50% of the total PtdIns4,5P2 and 50% of 32P-labelled PtdIns4,5P2 present in the cells: this enzyme does not discriminate between the metabolically active and inactive compartments of lipids in the erythrocyte membrane. Hence at least four metabolic pools of PtdIns4P and PtdIns4,5P2 are distinguishable in the human erythrocyte plasma membrane. 5. The mechanisms by which multiple non-mixing metabolic pools of PtdOH, PtdIns4P and PtdIns4,5P2 are sustained over many hours in the plasma membranes of intact erythrocytes are unknown, although some possible explanations are considered.     

Turkey erythrocyte membranes as a model for regulation of phospholipase C by guanine nucleotides

Phosphoinositides of human, rabbit, rat, and turkey erythrocytes were radiolabeled by incubation of intact cells with [32P]Pi. Guanosine 5'-O-(thiotriphosphate) (GTP gamma S) and NaF, which are known activators of guanine nucleotide regulatory proteins, caused a large increase in [32P]inositol phosphate release from plasma membranes derived from turkey erythrocytes, but had no effect on inositol phosphate formation by plasma membranes prepared from the mammalian erythrocytes. High performance liquid chromatography analysis indicated that inositol bisphosphate, inositol 1,3,4-trisphosphate, inositol 1,4,5-trisphosphate, and inositol 1,3,4,5-tetrakisphosphate all increased by 20-30-fold during a 10-min incubation of turkey erythrocyte membranes with GTP gamma S. The increase in inositol phosphate formation was accompanied by a similar decrease in radioactivity in phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2). GTP gamma S increased inositol phosphate formation with a K0.5 of 600 nM; guanosine 5'-(beta, gamma-imido)trisphosphate was 50-75% as efficacious as GTP gamma S and expressed a K0.5 of 36 microM. Although GTP alone had little effect on inositol phosphate formation, it blocked GTP gamma S-stimulated inositol phosphate formation, as did guanosine 5'-O-(2-thiodiphosphate). Turkey erythrocytes were also shown to express phosphatidylinositol synthetase activity in that incubation of cells with [3H] inositol resulted in incorporation of radiolabel into phosphatidylinositol, PIP, and PIP2. Incubation of membranes derived from [3H]inositol-labeled erythrocytes with GTP gamma S resulted in large increases in [3H] inositol phosphate formation and corresponding decreases in radiolabel in PIP and PIP2. The data suggest that, in contrast to mammalian erythrocytes, the turkey erythrocyte expresses a guanine nucleotide-binding protein that regulates phospholipase C, and as such, should provide a useful model system for furthering our understanding of hormonal regulation of this enzyme.     

Mechanism of biosynthesis of 11R-and 12R-hydroxyeicosatetraenoic acids by eggs of the sea urchin Strongylocentrotus purpuratus

11(R)-Hydroxyeicosatetraenoic acid [11(R)-HETE] and 12(R)-HETE are biosynthesized by eggs of the sea urchin S. purpuratus. We report here the isolation of the 11(4)- and 12(R)-hydroperoxy-eicosanoids from incubations of the desalted 30-50%(NH4)2SO4 fraction of the egg homogenate; biosynthesis required the addition of calcium but not NADPH. Egg 11- and 12-HETE were formed from octadeuterated arachidonic acid without loss of geminal 2H from C11 or C12, thus revealing that 11- or 12-keto intermediates are not involved in the biosynthesis. The results support the conclusion that egg 11(R)- and 12(R)-HETE are synthesized by a lipoxygenase and not by an NADPH-dependent cytochrome P450 monooxygenase mechanism.     

Lipoxygenase metabolism of polyunsaturated fatty acids in oocytes of the frog Xenopus laevis

Recently, oocytes or eggs of two marine invertebrates have been found to metabolize arachidonic acid to specific monohydroxy products. These studies have prompted our examination of the oocytes of higher organisms. In the present study, oocytes of an amphibian, Xenopus laevis, were examined for their capacity to biosynthesize hydroxyeicosatetraenoic acids (HETEs) and related hydroxy fatty acids. Two hydroxyeicosanoids were formed during incubations of oocyte homogenates with [14C]arachidonic acid; their structures and stereochemistry were determined by high-pressure liquid chromatography, uv spectroscopy, and gas chromatography-mass spectrometry. The compounds were identified as 15(S)- and 12(S)-hydroxyeicosatetraenoic acids. The synthesis of the two HETEs was not blocked by a cyclooxygenase inhibitor, indomethacin (10 microM), or by prior exposure of the oocyte homogenates to carbon monoxide, an inhibitor of cytochrome P450. Furthermore, 12(S)- and 15(S)-hydroperoxyeicosatetraenoic acids were isolated from brief incubations of gel-filtered ammonium sulfate fraction of frog oocyte homogenates; isolation of the hydroperoxide is further support for the existence of 12(S)- and 15(S)-lipoxygenase activities in the oocytes of X. laevis. Other polyunsaturated acids, including C18.2, C18.3, C20.3, C20.5, and C22.6 were also substrates for the lipoxygenase, and in each case the major product was formed by omega 6 oxygenation.