Environmental effects on the oxygen consumption rate in juvenile Epinephelus fuscoguttatus (Forsskal, 1775)

This study was designed to optimize the culture conditions of juvenile Epinephelus fuscoguttatus (Forsskål, 1775) under laboratory conditions. To this effect, the rate of oxygen consumption was monitored as an index of stress under different temperature, salinity, pH, photoperiod, and urea concentrations. The result obtained after 12 h of exposure suggests the preference of the juvenile E. fuscoguttatus to a temperature range of 15-25 °C and salinity of 30 ppt. Based on this study, temperature was found to be the most lethal as 100% mortality was observed after 6 h in fish exposure to temperatures above the optimal (≥ 30 °C). However, the oxygen consumption rate was similar under the different pH, photoperiod, and urea concentration tested. It was concluded that water temperature was most critical in terms of respiration physiology of the juvenile E. fuscoguttatus given the range and levels of environmental factors tested in this study.

Colour preference and light sensitivity in trilobite larvae of mangrove horseshoe crab, Carcinoscopius rotundicauda (Latreille, 1802)

The trilobite larvae of C. rotundicauda were tested to determine their colour preference and light sensitivity until their first moulting (25 days post hatching) under laboratory conditions. Maximum congregation size of the trilobite larvae was found in the white zone respectively where (n = 12) followed by yellow (n = 8) and orange (n = 8), which showed the larval preference for lighter zones. Morisita's index calculation showed a clumped/aggregated distribution (yellow, blue, orange and white) and uniform/hyper dispersed distribution (green, red and black) for various colours tested. Trilobite larvae showed least preference for brighter regions while tested in the experiment [black; (n = 4) and red; (n = 5)]. Experiments done to determine the light sensitivity of trilobite larvae showed that the larvae had more preference towards ultraviolet lights. The maximum congregation size of 38.8 and 40.7% of the larvae was encountered under ultraviolet light, when the light sources were kept horizontal and vertical, respectively. Overall, results suggested that the trilobite larvae of C. rotundicauda, preferred light source of shorter wavelengths (UV light) and colours of lighter zone (white, yellow, orange), which might be due to their adaptation to their natural habitat for predator avoidance, prey selection and water quality.

An unusual cause of pericardial tamponade

Pericardial effusion in hypothyroidism is common. But an effusion which causes cardiac tamponade is a rarity. Reported below is a case with myxedema and cardiac tamponade due to pericardial effusion.

Nonlinear effects in charge stabilized colloidal suspensions

Molecular-dynamics simulations are used to study the effective interactions in charged stabilized colloidal suspensions. We focus on highly charged macroions in the limit of low salt concentrations. Within this regime, nonlinear corrections to Debye-Hückel (DH) theory have to be considered. For non-bulk-like systems, such as isolated pairs or triples of macroions, we show that nonlinear effects can become relevant, which cannot be described by the charge renormalization concept [S. Alexander, J. Chem. Phys. 80, 5776 (1984)]. For an isolated pair of macroions, we find an almost perfect qualitative agreement between our simulation data and DH theory. However, on a quantitative level, neither DH theory nor the charge renormalization concept can be confirmed in detail. This seems mainly to be related to the fact that for small ion concentrations, microionic layers can strongly overlap, whereas, simultaneously, excluded volume effects are less important. In the case of isolated triples, where we compare between coaxial and triangular geometries, we find attractive corrections to pairwise additivity in the limit of small macroion separations and salt concentrations. These triplet interactions arise if all three microionic layers around the macroions exhibit a significant overlap. In contrast to the case of two isolated colloids, the charge distribution around a macroion in a triple is found to be anisotropic.

Cowpea mosaic virus: from the presentation of antigenic peptides to the display of active biomaterials

The potential of cowpea mosaic virus (CPMV), a plant icosahedral virus, for the presentation of foreign peptides and proteins is reported. The most prominent feature at the virus surface is a region of the smaller of the two coat proteins (S) which has been extensively used for the insertion of foreign peptides. Given the availability of the three-dimensional structure of the native virus and the amenability of foreign peptide-expressing CPMV chimeras to crystallisation, immunological data can be correlated with the conformational state of the foreign insert. The latter is influenced by proteolysis which occurs within the foreign inserts. In an effort to offer an alternative context for peptide expression, extensive exploration of a second region of the S protein is reported with respect to tolerance to small insertions. Moreover, to make CPMV suitable for a wider spectrum of presentation, a technique was developed to allow surface coupling of a peptide which can serve as the anchoring point for a range of proteins. This new approach is also widely applicable for the direct chemical cross-linking of peptides and full-length protein domains to the viral capsid.

Expression of the oligomerization domain of the replication-associated protein (Rep) of Tomato leaf curl New Delhi virus interferes with DNA accumulation of heterologous geminiviruses

The minimal DNA binding domain of the replication-associated protein (Rep) of Tomato leaf curl New Delhi virus was determined by electrophoretic mobility gel shift analysis and co-purification assays. DNA binding activity maps to amino acids 1-160 (Rep-(1-160)) of the Rep protein and overlaps with the protein oligomerization domain. Transient expression of Rep protein (Rep-(1-160)) was found to inhibit homologous viral DNA accumulation by 70-86% in tobacco protoplasts and in Nicotiana benthamiana plants. The results obtained showed that expression of N-terminal sequences of Rep protein could efficiently interfere with DNA binding and oligomerization activities during virus infection. Surprisingly, this protein reduced accumulation of the African cassava mosaic virus, Pepper huasteco yellow vein virus and Potato yellow mosaic virus by 22-48%. electrophoretic mobility shift assays and co-purification studies showed that Rep-(1-160) did not bind with high affinity in vitro to the corresponding common region sequences of heterologous geminiviruses. However, Rep-(1-160) formed oligomers with the Rep proteins of the other geminiviruses. These data suggest that the regulation of virus accumulation may involve binding of the Rep to target DNA sequences and to the other Rep molecules during virus replication.

Sequence parameters that determine specificity of binding of the replication-associated protein to its cognate site in two strains of tomato leaf curl virus-New Delhi

The DNA binding sites for the replication-associated protein (Rep) of two strains of tomato leaf curl virus from New Delhi (ToLCV-Nde) were identified using electrophoretic mobility shift assays (EMSAs). The Rep proteins of the two strains were found to exhibit sequence specificity in recognition of their cognate repeat motifs (iterons) in the origin, despite the fact that they share 91% sequence identity. Using a series of synthetic oligonucleotides as probes in EMSAs, the interaction of Rep protein with its binding site was found to be dependent on number, size, and sequence of the two iterons. Mutations in the sequence of the repeat motifs or alteration in the arrangement of the motifs compromised the ability of Rep protein to bind the DNA sequence and reduced accumulation of viral DNA in protoplasts, suggesting that binding of Rep protein to its cognate iterons is an essential step in virus replication. In addition, a difference in sequence of two base pairs in the binding site of two ToLCV-Nde strains was found to affect DNA binding by the corresponding Rep protein and replication of the virus DNA in protoplasts.

Identification of replication specificity determinants in two strains of tomato leaf curl virus from New Delhi

We used two strains of tomato leaf curl virus from New Delhi to investigate specificity in replication of their cognate genomes. The strains share 94% sequence identity and are referred to as severe and mild on the basis of symptoms on tomato and tobacco. Replication assays in tobacco protoplasts and plants showed that a single amino acid change, Asn10 to Asp in the N terminus of Rep protein, determines specificity for replication of the two strains based upon its interaction with the origin of replication (ori) sequences. The change of Asp10 to Asn in Rep protein of the mild strain coupled with point mutations at the 3rd and 10th nucleotides of the 13-mer binding site altered its replication ability, resulting in increased levels of virus accumulation. Similarly, changing Asn10 to Asp in Rep protein of the severe strain impaired replication of the virus and altered its severe phenotype in plants. Site-directed mutations made in ori and Asn10 of Rep protein suggested that Asn10 recognizes the third base pair of the putative binding site sequence GGTGTCGGAGTC in the severe strain.

Immunohistochemical co-expression of human papillomavirus type 16/18 transforming (E6) oncoprotein and p53 tumour suppressor gene proteins in oesophageal cancer

Human papillomaviruses have been widely implicated as important etiologic agents in various squamous cell carcinomas including oesophageal carcinoma. p53 mutant oncoprotein has also been implicated in various tumours. Immunohistochemical analysis was employed to detect the co-expression of HPV and p53 mutant protein in biopsy specimens of patients of cancer oesophagus as well as controls. This analysis revealed a significantly higher immunopositivity (63%) of E6 oncoprotein of HPV 16/18 in carcinoma of the oesophagus. Immunoexpression of E6 oncoprotein of HPV did not alter significantly the degree of differentiation of the tumour. Seventy-seven percent of cases of oesophageal carcinoma showed strong immuno-staining for mutant p53 protein. A higher percentage (89%) of tissues showed immunoexpression of mutant p53 protein in conjunction with E6 oncoprotein of HPV 16/18 indicating a selective degradation of key cellular protein of p53 having regulatory properties which in turn leads to uncontrolled cellular proliferation. Therefore, coexpression of oncoprotein E6 of HPV 16/18 and mutant p53 protein may be considered as a "high risk" factor for progression to oesophageal malignancy.

Triploidy induction in Nile tilapia, Oreochromis niloticus L. using pressure, heat and cold shocks

The results of a study aimed at the identification of treatment optima for triploidy induction in recently fertilised Oreochromis niloticus L. eggs by altering the intensity, duration and timing of application of pressure, heat and cold shocks are reported. Preliminary, but not directly comparable, trials suggested the following treatments to be close to the individual agent optima. Pressure: 8,000 psi 2-min duration applied 9 min after fertilisation (a.f.); heat: 41 °C, 3.5-min duration applied 5 min a.f., cold: 9°C, 30-min duration applied 7 min a.f. In a directly comparable trial in which the eggs of eight different females were separately exposed to the optimum shocks listed above, individual triploid yields were more variable following cold shocks and mean triploid yields were, therefore, higher following pressure and heat shock. These and other results obtained are presented and the light they shed on the timing of the second meiotic division in this species is discussed.

Effect of extracellular pH and DNFB treatment on the mechanical performance of frog skeletal muscle

isometric tension and maximum velocity of shortening of frog sartorious and biceps muscles were measured at varying pH and compared with the values obtained for muscles treated with DNFB. Both To and Vmax exhibited increase with increase in pH above neutral pH upto pH 9, and decreased as the pH was decreased up to 5. Muscle treated with DNFB at pH 7 showed about 30% decrement but these too improved at pH 9 to almost 105% and 130% respectively compared to untreated muscle at pH 7. Using the number of short duration tetanic contractions, which reduce To and Vmax by half, as an index for the onset of fatigue, high pH was found to have a positive effect in both normal and DNFB-treated muscle. Thus, the crucial factor for onset of fatigue is not a fall in ATP level but acidification and treatment with high pH Ringer's solution partially annuls the effect of acidosis, arising either naturally or from DNFB treatment. One additional role of creatine kinase activity to that of ATP regeneration is suggested to be the maintenance of neutral pH in the sarcoplasm.

A New Record on the Morphometric Variations in the Populations of Horseshoe Crab (Carcinoscorpius rotundicauda Latreille) Obtained from Two Different Ecological Habitats of Peninsular Malaysia

The allometric analysis was used to study the morphometric variability in two different populations of horseshoe crab (Carcinoscorpius rotundicauda, Latreille) collected from Setiu and Gelang Patah (Johor) of Peninsular Malaysia. Values of all parameters in male and female populations of Setiu were recorded high as compared to the horseshoe crab collected from Gelang Patah. In all relationships (total length, carapace length, carapace width and telson length) either with normal values or when values were converted into their logarithmic values, it showed a straight line which indicated that in both populations the increment of all body parts followed an isometric growth.DOI: 10.3126/on.v8i1.4329