Volume 25, Issue 3
September 2000, pages 211-313
pp 221-228 Perspectives
pp 229-234 Articles
Drosophila nasuta albomicans (with 2n = 6), contains a pair of metacentric neo-sex chromosomes. Phylogenetically these are products of centric fusion between ancestral sex (X, Y) chromosomes and an autosome (chromosome 3). The polytene chromosome complement of males with a neo-X- and neo-Y-chromosomes has revealed asynchrony in replication between the two arms of the neo-sex chromosomes. The arm which represents the ancestral X-chromosome is faster replicating than the arm which represents ancestral autosome. The latter arm of the neo-sex chromosome is synchronous with other autosomes of the complement. We conclude that one arm of the neo-X/Y is still mimicking the features of an autosome while the other arm has the features of a classical X/Y-chromosome. This X-autosome translocation differs from the other evolutionary X-autosome translocations known in certain species of Drosophila.
pp 235-242 Articles
Expression of cytokeratins (CK), a subset of intermediate filament (IF) proteins in epithelia, is developmentally regulated. CK expression may also change after malignant transformation. Our earlier studies on CK expression in human oral tumours and pre-cancerous lesions have shown specific changes in CK expression. We analysed CK expression in human tongue and buccal mucosa (BM) in fetuses in the embryonic age group of 16 to 27 weeks using biochemical and immunohistochemical techniques to find out whether there is any similarity in CK expression in human oral squamous cell carcinomas (SCC) and fetal oral tissues. CK 1, 8 and 18 were detected in a majority of samples using both techniques. Our earlier studies had shown aberrant expression of CK 1 and 18 in many of the oral SCC and leukoplakias. Studies by immunohistochemistry showed that these different CK antigens were expressed in different cell layers. CK 1(2) were present in the stratified epithelial layers whereas CK 8 and 18 were restricted to glandular epithelium. Till 27 weeks of gestation, both tongue and BM expressed CK 1, 8 and 18 along with CK 6 and 16. Thus, fetal tissues showed some similarities in CK pattern with their respective SCC.
pp 243-252 Articles
Aggregating Dictyostelium cells release protons when stimulated with cAMP. To find out whether the protons are generated by acidic vesicles or in the cytosol, we permeabilized the cells and found that this did not alter the cAMP-response. Proton efflux in intact cells was inhibited by preincubation with the V-type H+ ATPase inhibitor concanamycin A and with the plasma membrane H+ ATPase blocker miconazole. Surprisingly, miconazole also inhibited efflux in permeabilized cells, indicating that this type of H+ ATPase is present on intracellular vesicles as well. Vesicular acidification was inhibited by miconazole and by concanamycin A, suggesting that the acidic vesicles contain both V-type and P-type H+ ATPases. Moreover, concanamycin A and miconazole acted in concert, both in intact cells and in vesicles. The mechanism of cAMP-induced Ca2+-fluxes involves phospholipase A2 activity. Fatty acids circumvent the plasma membrane and stimulate vesicular Ca2+-efflux. Here we show that arachidonic acid elicited H+-efflux not only from intact cells but also from acidic vesicles. The target of regulation by arachidonic acid seemed to be the vesicular Ca2+-relase channel.
pp 253-256 Articles
Young adult male rats, maintained either in an LD 12 : 12 or in continuous illumination (LL) for one week, were given a single injection of 25 𝜇g melatonin/100 g body wt or ethanolic-saline (control) at 17.00 h. Animals from each group were sacrificed at 11.00 h on the following day. The activity of two important steroidogenic enzymes, 17𝛽-hydroxysteroid dehydrogenase (17𝛽-HSD) and Δ5-3𝛽-hydroxysteroid dehydrogenase (Δ5-3𝛽-HSD), and serum concentrations of testosterone, were measured following highly specific and sensitive spectrophotometric techniques and RIA, respectively. A significant decrease in the activity of both the steroidogenic enzymes was noted in the testes of melatonin-treated rats maintained under normal light-dark schedules, but this response was found to be lacking in the LL rats. However, no significant changes in the level of serum testosterone were noted in either group of melatonin-treated rats from the values in respective groups of ethanolic saline-administered LD and LL rats. Exposure of ethanolic saline-injected rats to continuous light also did not cause any change in the steroidogenic activity of the testis from those in LD rats. The study indicates that continuous light as such does not affect the endocrine function of testis but abolishes suppressive effects of melatonin on the steroidogenic activity of the testis in rat.
pp 257-262 Articles
The nucleotide sequence of the complete genomes of two Indian isolates of Japanese encephalitis virus were compared. One of these isolates, GP78 was obtained from northern India in 1978. The other, the Vellore P20778 isolate, was obtained from southern India in 1958. There was 4.40% nucleotide sequence divergence between the two Indian isolates that resulted in a 1.86% amino acid sequence divergence. Phylogenetic analyses showed that in evolutionary terms the north Indian GP78 isolate was close to the SA14 isolate from China whereas the south Indian Vellore P20778 isolate was close to the Beijing-1 isolate, also from China. The two Indian isolates, however, appear to have evolved independently.
pp 263-266 Articles
Menthol is a highly valued monoterpene produced by Japanese mint (Mentha arvensis) as a natural product with wide applications in cosmetics, confectionery, flavours, beverages and therapeutics. Selection of high menthol yielding genotypes is therefore the ultimate objective of all genetic improvement programmes in Mentha arvensis. A positive correlation was observed in the present study between menthol content in oils of evaluated genotypes and the level of tolerance to externally supplied menthol of explants of these genotypes in culture medium. The easy use of this relationship as a selectable biochemical marker opens the practical applicability of large-scale in vitro screening of the germplasm, clones and breeders’ material for selection of elite genotypes.
pp 267-273 Articles
The ontogeny of kin recognition and influence of social environment on the development of kin recognition behaviour was experimentally investigated in tadpoles of Bufo melanostictus that lived in aggregations and showed low larval dispersion. Embryos and tadpoles of the toad were reared as
They were tested for the ability to discriminate between
All tadpoles were fed on boiled spinach before conducting trials. Preference of test tadpoles to associate near the end compartments whether empty or containing members of specific stimulus groups was assessed using a rectangular choice tank. When tested in tanks with empty end compartments, the test tadpoles showed random distribution and thus no bias for the apparatus or the procedure. In the presence of kin/non-kin in the end compartments a significantly greater number of test tadpoles spent the majority of the time near familiar or unfamiliar kin rather than near familiar or unfamiliar non-kin. Kin discrimination ability persisted throughout larval development. Familiarity with siblings is not required for discriminating kin from non-kin, and kin discrimination ability is not modified following exposure to non-kin. Also, involvement of dietary cues is unlikely to be the prime mechanism of kin recognition in B. melanostictus unlike in some other anurans.
pp 275-284 Review articles
Retinoic acids (RA) play a key role in myeloid differentiation through their agonistic nuclear receptors (RAR𝛼/RXR) to modulate the expression of target genes. In acute promyelocytic leukemia (APL) cells with rearrangement of retinoic acid receptor 𝛼 (RAR𝛼) (including: PML-RAR𝛼, PLZF-RAR𝛼, NPM-RAR𝛼, NuMA-RAR𝛼 or STAT5b-RAR𝛼) as a result of chromosomal translocations, the RA signal pathway is disrupted and myeloid differentiation is arrested at the promyelocytic stage. Pharmacologic dosage of all-trans retinoic acid (ATRA) directly modulates PML-RAR𝛼 and its interaction with the nuclear receptor co-repressor complex, which restores the wild-type RAR𝛼/RXR regulatory pathway and induces the transcriptional expression of downstream genes. Analysing gene expression profiles in APL cells before and after ATRA treatment represents a useful approach to identify genes whose functions are involved in this new cancer treatment. A chronologically well coordinated modulation of ATRA-regulated genes has thus been revealed which seems to constitute a balanced functional network underlying decreased cellular proliferation, initiation and progression of maturation, and maintenance of cell survival before terminal differentiation.
pp 285-290 Review articles
The visual and auditory systems are two major sensory modalities employed in communication. Although communication in these two sensory modalities can serve analogous functions and evolve in response to similar selection forces, the two systems also operate under different constraints imposed by the environment and the degree to which these sensory modalities are recruited for non-communication functions. Also, the research traditions in each tend to differ, with studies of mechanisms of acoustic communication tending to take a more reductionist tack often concentrating on single signal parameters, and studies of visual communication tending to be more concerned with multivariate signal arrays in natural environments and higher level processing of such signals. Each research tradition would benefit by being more expansive in its approach.
pp 291-299 Review articles
Under optimal conditions of growth, senescence, a terminal phase of development, sets in after a certain physiological age. It is a dynamic and closely regulated developmental process which involves an array of changes at both physiological and biochemical levels including gene expression. A large number of biotic and abiotic factors accelerate the process. Convincing evidence suggests the involvement of polyamines (PAs) and ethylene in this process. Although the biosynthetic pathways of both PAs and ethylene are interrelated, S-adenosylmethionine (SAM) being a common precursor, their physiological functions are distinct and at times antagonistic, particularly during leaf and flower senescence and also during fruit ripening. This provides an effective means for regulation of their biosynthesis and also to understand the mechanism by which the balance between the two can be established for manipulating the senescence process. The present article deals with current advances in the knowledge of the interrelationship between ethylene and PAs during senescence which may open up new vistas of investigation for the future.
pp 301-313 Review articles
The structure, growth, differentiation and function of crustacean chelipeds are reviewed. In many decapod crustaceans growth of chelae is isometric with allometry level reaching unity till the puberty moult. Afterwards the same trend continues in females, while in males there is a marked spurt in the level of allometry accompanied by a sudden increase in the relative size of chelae. Subsequently they are differentiated morphologically into crusher and cutter making them heterochelous and sexually dimorphic. Of the two, the major chela is used during agonistic encounters while the minor is used for prey capture and grooming. Various biotic and abiotic factors exert a negative effect on cheliped growth. The dimorphic growth pattern of chelae can be adversely affected by factors such as parasitic infection and substrate conditions. Display patterns of chelipeds have an important role in agonistic and aggressive interactions. Of the five pairs of pereiopods, the chelae are versatile organs of offence and defence which also make them the most vulnerable for autotomy. Regeneration of the autotomized chelipeds imposes an additional energy demand called “regeneration load” on the incumbent, altering energy allocation for somatic and/or reproductive processes. Partial withdrawal of chelae leading to incomplete exuviation is reported for the first time in the laboratory and field in Macrobrachium species.
Volume 42 | Issue 4