Seasonality and vertical structure of light-attracted insect communities in a dipterocarp forest in Sarawak

Nocturnal flying insects were collected monthly for 13 months using ultra violet light-traps set at various vertical levels in a weakly-seasonal, tropical lowland dipterocarp forest in Sarawak, Malaysia. Abundance, faunal composition, size distribution and guild structure of these samples were analyzed with respect to temperal and vertical distributions. The nocturnal flying insect community in the canopy level was highly dominated by fig wasps (84%) in individual number, and by scarabaeid beetles (28%) in weight. A principal component analysis on monthly catches detected non-random, seasonal trends of insect abundance. The first two principal trends were an alternation of wetter (September to January) and less wet seasons (February to August) and an alternation between the least wet (January to March) and the other seasons. Many insect groups were less abundant in the least wet season than the other seasons, whilst inverse patterns were found in Scarabaeidae and Tenebrionidae. Significantly positive and negative correlations between monthly catch and rainfall were detected only in ovule-feeders and in phloem-feeders, respectively. Delayed, significant negative correlations between monthly catch and 1–3 month preceding rainfall were more frequently detected in phytophages, phloem-feeders, seed-feeders, wood-borers and scavengers. The peak in abundance along vertical levels were found at the canopy level (35 m) for phloem-, ovule-, seed-, root-, fungal-feeders and nectar collectors, at an upper subcanopy level (25 m) for scavengers and aquatic predators, and at a middle subcanopy level (17 m) for ants. Catches at the emergent level (45 m) did not exceed those at the canopy level.     

The X-ray structure analysis of bis-2,2′,N,N′-bipyridyl ketone cobalt(III) nitrate dihydrate

An X-ray structural analysis of bis-2,2′,N,N′-bipyridyl ketone cobalt(III) nitrate dihydrate, CoC₂₂H₂₀N₄O₄⁺· NO₃⁻·2H₂O,M_r=559.38 g/mol, P , a=8.862(2), b=16.195(3), c=8.772(2) Å, α=103.54(2), β=95.74(3), γ=105.07°, V=1164.4(4) ų, Z=2, D_x=1.595 g/cm³, Mo Kα radiation (λ=0.71073 Å), μ=7.8 cm⁻¹ and R=0.079, revealed a Co(III) cation in a slightly distorted octahedral environment. The structure reveals that the ligand di-2-pyridyl ketone (dpk) has undergone a hydration reaction across the ketone double bond and one of the hydrate oxygen atoms coordinated to the metal forming a tridentate chelate. This new Co(dpk-hydrate)₂⁺ complex displays the least distorted geometry yet reported for either 1:1 or 1:2 (metal:ligand) complexes. A geometry optimization using the INDO model Hamiltonian as implemented in the program ZINDO was performed on the title complex with the Co³⁺ modeled as a singlet. The result of the computation corroborates the geometry of the title complex as that expected for Co³⁺.     

An In Vitro Test for Temperature Sensitivity and Resistance to Meloidogyne incognita in Tomato

An in vitro root explant tissue culture technique is described for determining susceptibility of tomato (Lycopersicon esculentum Mill.) breeding lines and cultivars to the root-knot nematode Meloidogyne incognita. Root explants were taken from 2-day-old seedlings cultured for 30 days at 28 C on Gamborg''s B-5 medium with or without nematode inoculum. The remaining portion of the root and stem from the excised root explants was transferred to soil in pots and grown to maturity in the greenhouse. In vitro root explants were evaluated for growth and occurrence of juveniles, adults, and egg masses. The regenerated plants were used to produce more seed, The proposed technique is simple, reliable, and adapted to routine screening of large numbers of F₁ and F₂ samples, and it utilizes less space than tests performed on intact plants in the greenhouse or growth chamber. Evidence is presented also on the breakdown of resistance to M. incognita under high temperature stress using this in vitro root explant technique.     

Aluminum Toxicity: A Case Study on Tobacco (<i>Nicotiana tabacum</i> L.)

Aluminum is an abundant metal in the earth’s crust that turns out to be toxic in acidic environments. Many plants are affected by the presence of aluminum at the whole plant level, at the organ level, and at the cellular level. Tobacco as a cash crop (Nicotiana tabacum L.) is a widely cultivated plant worldwide and is also a good model organism for research. Although there are many articles on Al-phytotoxicity in the literature, reviews on a single species that are economically and scientifically important are limited. In this article, we not only provide the biology associated with tobacco Al-toxicity, but also some essential information regarding the effects of this metal on other plant species (even animals). This review provides information on aluminum localization and uptake process by different staining techniques, as well as the effects of its toxicity at different compartment levels and the physiological consequences derived from them. In addition, molecular studies in recent years have reported specific responses to Al toxicity, such as overexpression of various protective proteins. Besides, this review discusses data on various organelle-based responses, cell death, and other mechanisms, data on tobacco plants and other kingdoms relevant to these studies.     

Toxin A secretion in Pseudomonas aeruginosa: the role of the first 30 amino acids of the mature toxin

Toxin A, one of several virulence factors secreted by the gram-negative bacterium Pseudomonas aeruginosa, is synthesized as a 71 kDa precursor with a typical prokaryotic leader peptide (LP), and is secreted as a 68 kDa mature protein. Evidence from a previous study suggested that a signal required for toxin A secretion in P. aeruginosa may reside within the region defined by the toxin A LP and the first 30 amino acids (aa) of mature toxin A. In the present study, we have used exonuclease Ba131 deletion analysis to examine the specific role of the first 30 as in toxin A secretion. Four toxA subclones, which encode products containing the toxin A LP and different segments of the 30-residue region fused to a toxin A carboxy-terminal region, were identified. In addition, a gene fusion encoding a hybrid protein consisting of the LP of P. aeruginosa elastase and the final 305 residues of toxin A, was generated. The cellular location of the toxA subclone products in P. aeruginosa was determined by immunoblotting analysis. Toxin A CRMs (cross-reacting material) encoded by different subclones were detected in different fractions of P. aeruginosa including the periplasm and the supernatant. Results from these studies suggest that (1) mature toxin A contains two separate secretion signals one within the N-terminal region and one within the C-terminal region; and (2) the first 30 residues of the mature toxin A form part of the N-terminal secretion signal.     

Native Enzyme Mobility Shift Assay (NEMSA): a new method for monitoring carboxyl group modification of carboxymethylcellulase from Aspergillus niger

A simple, sensitive, accurate and more informative assay for determining the number of modified groups during the course of carboxyl group modification is described. Monomeric carboxymethylcellulase (CMCase) from Aspergillus niger was modified by 1-ethyl-3(3-dimethylaminopropyl)carbodiimide (EDC) in the presence of glycinamide. The different time-course aliquots were subjected to non-denaturing PAGE and the gel stained for CMCase activity. The number of carboxyl groups modified are directly read from the ladder of the enzyme bands developed at given time. This method showed that after 75 min of modification reaction there were five major species of modified CMCases in which 6 to 10 carboxyls were modified.     

Variation in the free amino acid content of skeletal muscle of Ophicephalus punctatus (Bloch)

The skeletal muscle of Ophicephalus punctatus contains nine essential free amino acids, arginine, histidine, isoleucine, leucine, methionine, phenylalanine, threonine, valine and lysine, and eight non-essential amino acids, alanine, aspartic acid, cystine, glutamic acid, glycine, tyrosine, proline and serine. Histidine and lysine dominated the free amino acids pool. Seasonal variation was detected in the levels of histidine, arginine, leucine, phenylalanine, glycine, cystine and serine with highest values occurring in April and again in November. Changes were also detected in the concentrations of certain amino acids as the fish grew in size. Levels of free amino acids did not significantly differ between sexes. Factors effecting variation are discussed.     

Reproductive biology, length-weight relationship and relative condition of Tilapia leucosticta (Trewavas) in Lake Naivasha, Kenya

In Lake Naivasha Tilapia leucosticta (Trewavas) spawns throughout the year. Males attain maturity at 180 mm and females at 160 mm total length. Males predominate over females in the catches (sex ratio 1-00 : 0-51). Fecundity ranged from 320 to 1328 eggs with an average of 751. The relationship between fecundity (F) and total length (L), body weight (W) and gonad weight (GW) is:
The length-weight regression coefficient is near to the cube. There is little seasonal fluctuation in relative condition of the fishes.