Physiological and enzymatic activity of pepper seeds (Capsicum annuum) during priming

Pepper ( Capsicum annuum L. cv. Keystone Resistance Giant 3) seeds were monitored during priming to determine if seed treatments which accelerate the rate of germination could be correlated with specific physiological changes within the seeds. Pepper seeds primed with −0.90 and −1.35 MPa NaCl solutions at 23°C for 18 days did not completely equilibrate with the osmotic potential of the priming solution. Seed respiratory rates indicated that priming extends the lag phase of germination following imbibition. Soluble protein levels increased 115% in primed seeds, and the uptake and incorporation of [¹⁴C(U)] labelled amino acids into the acid insoluble fraction increased throughout the priming treatments. Alcohol dehydrogenase (EC 1.1.1.1, anaerobic metabolism), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (EC 1.1.1.44, pentose phosphate pathway) activities remained stable throughout the priming treatment, but were higher after 6 days. than the water-imbibed controls. Aldolase (EC 4.2.1.1. glycolysis) and isocitrate lyase (EC 4.1.3.1, glyoxylate cycle) activities increased with imbibition and were 61 and 56% (respectively) higher in primed seeds as compared to the water-imbibed controls after 12 days. Treatment with the −0.90 MPa NaCl solution was more effective than the −1.35 MPa solution in improving the rate of germination, yet there were no significant differences between the protein concentrations or enzyme activities of the two priming treatments. However, the incorporation of labelled amino acids into pepper seeds was significantly higher in the −0.90 MPa priming treatment.     

Aluminium,boron and molybdenum availability and uptake by rice in acid sulfate soils

Although Al toxicity is believed to be a problem in acid sulfate soils cropped to rice (Oryza, sativa L.), little is known about the behavior of other trace metals such as B and Mo in these soils. The objectives of this study were to measure the availability of Al, B, and Mo in these soils, to determine what governs the availability of these metals and to investigate the relationships between metal availability and uptake by rice. Metal availability and uptake by rice were evaluated in 134 flooded acid sulfate soils in the Central Plains region of Thailand and in a growth chamber study using 50 of the same soils. Soil and plant metal analyses were conducted at the panicle differentiation stage of growth in both studies and in the soil prior to transplanting in the growth chamber study. Metal activities were determined with GEOCHEM. The mineral phases believed to be governing Al³⁺ activities were jurbanite under low pH conditions and amorphous Al(OH)₃ at high pH. The Al chemistry is believed to be intimately linked to the redox-pH cycle, which is driven by the monsoonal climate. Mortality of rice associated with Al toxicity was observed under field and growth chamber conditions. Interference in P uptake and/or assimilation was believed to be the mechanism of Al toxicity. Activities of B(OH) ₄ ^– and B(OH) ₃ ⁰ were found to be highly correlated to pH and ionic strength, respectively, with the latter being the dominant B ion found in these soils. Activities of MoO ₄ ^2– were positively correlated to pH and appeared to be controlled by wulfenite. Leaf Mo contents were found to be positively correlated with MoO ₄ ^2– activity.     

Outer membranes of Gram-negative bacteria are permeable to steroid probes

The permeability of bacterial outer membranes was assayed by coupling the influx of highly hydrophobic probes, 3-oxosteroids, with their subsequent oxidation catalysed by 3-oxosteroid delta 1-dehydrogenase, expressed from a gene cloned from Pseudomonas testosteroni. In Salmonella typhimurium producing wild-type lipopolysaccharide, the permeability coefficients for uncharged steroids were 0.45 to 1 x 10(-5) cm s-1, and the diffusion appeared to occur mainly through the lipid bilayer domains of the outer membrane. These rates are one or two magnitudes lower than that expected for their diffusion through the usual biological membranes. The permeation rates were markedly increased (up to 100 times) when the lipopolysaccharide leaflet was perturbed either by adding deacylpolymyxin or by introducing mutations leading to the production of deep rough lipopolysaccharides. An amphiphilic, negatively charged probe, testosterone hemisuccinate, penetrated much more slowly than the uncharged steroids. Study of various Gram-negative species revealed that P. testosteroni, Pseudomonas acidovorans, and Acinetobacter calcoaceticus showed higher outer membrane permeability to steroid probes and higher susceptibility to hydrophobic agents such as fusidic acid, novobiocin and crystal violet relative to S. typhimurium and Escherichia coli.     

Extended investigation of the substrate specificity of dipeptidyl peptidase IV from pig kidney.

The substrate specificity of dipeptidyl peptidase IV (dipeptidyl peptide hydrolase, EC 3.4.14.5) from pig kidney was investigated, using a series of substrates, in which the amino-acid residue in position P1, a structural derivative of proline, was altered with respect to ring size and substituents. It was demonstrated that dipeptidyl peptidase IV hydrolyses substrates of the type Ala-X-pNA, where X is proline (Pro), (R)-thiazolidine-4-carboxylic acid (Thz), (S)-pipecolic acid (Pip), (S)-oxazolidine-4-carboxylic acid (Oxa), or (S)-azetidine-2-carboxylic acid (Aze). The ring size and ring structure of the residue in the P1 position influence the rate of enzyme-catalysed hydrolysis of the substrate. The highest kcat value (814 s-1) was found for Ala-Aze-pNA. In contrast, the kcat value for Ala-Pro-pNA is nearly 55 s-1. With all substrates of this series, the rate-limiting step of the hydrolysis by dipeptidyl peptidase IV is the deacylation reaction. Compounds of substrate-like structure, in which the P2 residue has an R-configuration, are not hydrolysed by dipeptidyl peptidase IV.     

Structure-activity relationships of cyclic β-casomorphin-5 analogues

Cyclic analogues of the β-casein-derived opioid peptide β-casomorphin-5 (H-Tyr-Pro-Phe-Pro-Gly-OH) were prepared through substitution of the Pro² residue with various ,ω-diamino acid residues (lysine, ornithine, 2,4-diaminobutyric acid) and cyclization of the ω-amino group to the C-terminal carboxyl function. Compounds of this type, with D-configuration at the 2-position residue, showed high opioid receptor affinity with some preference for μ receptors over δ receptors, high potency in the guinea pig ileum assay and considerable activity in the mouse vas deferens assay. Configurational inversion at the 4-position in these cyclic analogues resulted in enhanced affinity for both μ and δ receptors, whereas N-methylation of the Phe³ residue produced a potency decrease.     

Isolation and regional localization of a large collection (2,000) of single-copy DNA fragments on human chromosome 3 for mapping and cloning tumor suppressor genes

Summary A collection of 2,000 lambda phage-carrying human single-copy inserts (> 700 bp) were isolated from two chromosome-3 flow-sorted libraries. The single-copy DNA fragments were first sorted into 3p and 3q locations and about 700 3p fragments were regionally mapped using a deletion mapping panel comprised of two humanhamster and two-human-mouse cell hybrids, each containing a chromosome 3 with different deletions in the short arm. The hybrids were extensively mapped with a set of standard 3p markers physically localized or ordered by linkage. The deletion mapping panel divided the short arm into five distinct subregions (A-E). The 3p fragments were distributed on 3p regions as follows: region A, 26%; B, 31%; C, 4%; D, 4% and E, 35%. We screened 300 single-copy DNA fragments from the distal part of 3p (regions A and B) with ten restriction endonucleases for their ability to detect restriction fragment length polymorphisms (RFLPs). Of these fragments 110 (36%) were found to detect useful RFLPs: 35% detected polymorphisms with frequency of heterozygosity of 40% or higher, and 25% with frequency of 30% or higher. All polymorphisms originated from single loci and most of them were of the base pair substitution type. These RFLP markers make it possible to construct a fine linkage map that will span the distal part of chromosome 3p and encompasses the von Hippel-Lindau disease locus. The large number of single-copy fragments (2,000) spaced every 100–150 kb on chromosome 3 will make a significant contribution to mapping and sequencing the entire chromosome 3. The 300 conserved chromosome 3 probes will increase the existing knowledge of man-mouse homologies.     

Spawning behaviour ofCheimerius nufar in captivity

Synopsis The santerCheimerius nufar is widespread in tropical and subtropical waters of the western Indian Ocean and forms an important component of linefish catches along the east coast of southern Africa. Observations of spawning behaviour in captivity have revealed that spawning occurs during spring over a period of four months. Mating takes place at sunrise and may continue for up to 105 min (mean duration = 60 min). During spawning males become dark with prominent white markings. They become very aggressive and set up territories. Females remain a uniform silvery-pink. Mating occurs between males and females of similar sizes, culminating in egg and sperm release near the surface. Individual fish spawned up to 14 times during a morning. Streaking occurred throughout the season, with a second male joining a spawning pair and releasing gametes simultaneously. Slinger,Chrysoblephus puniceus, a dominant fish on offshore reefs in the same region, interfered with spawning throughout the season and were observed to eat eggs when they were released. The spawning strategy ofC. nufar is similar to protogynous species in several respects, indicating that this functional gonochorist may not conform to current theoretical predictions.     

Enhancement of Butanol Formation by Clostridium acetobutylicum in the Presence of Decanol-Oleyl Alcohol Mixed Extractants

Extractive fermentation has been proposed to enhance the productivity of fermentations that are end product inhibited. Unfortunately, good extractants for butanol, such as decanol, are toxic to Clostridium acetobutylicum. The use of mixed extractants, namely, mixtures of toxic and nontoxic coextractants, was proposed to circumvent this toxicity. Decanol appeared to inhibit butanol formation by C. acetobutylicum when present in a mixed extractant that also contained oleyl alcohol. However, maintenance of the pH at 4.5 alleviated the inhibition of butanol production and the consumption of butyrate during solventogenesis. A mixed extractant that contained 20% decanol in oleyl alcohol enhanced butanol formation by 72% under pH-controlled conditions. The production of acetone and acetoin was also increased, even though these two products were not extractable. The enhancement of butanol formation was not limited by the toxicity of decanol. Supplementation of glucose and butyrate in the extractive fermentation yielded a 47% increase in butanol. The enhancement of butanol formation appeared to be dependent on the presence of dissolved decanol in the broth but was not observed unless an organic phase was present to extract butanol. A mechanism for the effects of decanol on product formation is proposed.     

Secondary production of an intertidal mussel (Mytilus edulis L.) population in the Eastern Scheldt (S.W. Netherlands)

We monitored an intertidal mussel (Mytilus edulis L.) population between June 1981 and June 1982 in the Eastern Scheldt estuary (S.W. Netherlands). Density and biomass of the population remained relatively constant over the study period. The shell length growth was described by a Gompertz growth curve. The parameters of this equation were estimated from a log-log-modified Ford-Walford plot of the growth-ring data. The slope of the relationship between animal weight and shell length is season-dependent, mainly due to the spawning cycle in larger mussels.Secondary production is estimated with the growth rate method. In the calculated growth rates the change in slope of the length-weight relationship is incorporated, as well as differences in length growth rates between summer and winter. Secondary production amounts to 156 g AFDW m^–2a ^–1 (expressed per m² of mussel bank). P:B is 0.50 a^–1. The mussel productivity is probably a limiting factor for the density of overwintering Oystercatchers (Haematopus ostralegus).