Expressions of visual pigments and synaptic proteins in neonatal chick retina exposed to light of variable photoperiods

Light causes damage to the retina, which is one of the supposed factors for age-related macular degeneration in human. Some animal species show drastic retinal changes when exposed to intense light (e.g. albino rats). Although birds have a pigmented retina, few reports indicated its susceptibility to light damage. To know how light influences a cone-dominated retina (as is the case with human), we examined the effects of moderate light intensity on the retina of white Leghorn chicks (Gallus g. domesticus). The newly hatched chicks were initially acclimatized at 500 lux for 7 days in 12 h light: 12 h dark cycles (12L:12D). From posthatch day (PH) 8 until PH 30, they were exposed to 2000 lux at 12L:12D, 18L:6D (prolonged light) and 24L:0D (constant light) conditions. The retinas were processed for transmission electron microscopy and the level of expressions of rhodopsin, S- and L/M cone opsins, and synaptic proteins (Synaptophysin and PSD-95) were determined by immunohistochemistry and Western blotting. Rearing in 24L:0D condition caused disorganization of photoreceptor outer segments. Consequently, there were significantly decreased expressions of opsins and synaptic proteins, compared to those seen in 12L:12D and 18L:6D conditions. Also, there were ultrastructural changes in outer and inner plexiform layer (OPL, IPL) of the retinas exposed to 24L:0D condition. Our data indicate that the cone-dominated chick retina is affected in constant light condition, with changes (decreased) in opsin levels. Also, photoreceptor alterations lead to an overall decrease in synaptic protein expressions in OPL and IPL and death of degenerated axonal processes in IPL.     

Cytokeratin localization in toe pads of the anuran amphibian Philautus annandalii (Boulenger, 1906)

We have examined cytokeratin distribution and their nature in toe pads of the Himalayan tree-frog Philautus annandalii. Toe pads are expanded tips of digits and show modifications of their ventral epidermis for adhesion. The toe pad epidermal cells, being organized into 3–4 rows, possess keratin bundles, especially in surface nanostructures that are involved in adhesion. Immunohistochemical localization using a pan-cytokeratin antibody revealed that cytokeratin immunoreactivity is the strongest in the mid- to basal cell rows of the epidermis, which parallels our previous ultrastructural observation of dense keratin bundles present in this part of the epidermis. The remainder of the epidermis (i.e., the superficial cell layer) showed little immunoreactivity. Immunoblot analysis revealed that toe-pads possessed keratins prominently in the molecular mass of 50 kDa. Possible presence of keratin 5 in toe pad epidermis has been correlated with its usual distribution pattern in mammalian epidermis.     

Age variations in adiposity and body fat composition among older Bengalee Hindu women of Calcutta, India

A cross-sectional study of 279 older (50+ years) urban Bengalee Hindu women was undertaken to study age variations in adiposity, body composition, obesity and central fat distribution. The women were divided into three groups: Group I (G I, 50-59 years), Group II (G II, 60-69 years) and Group III (G III, 70+ years). A significant decreasing age trend was observed in adiposity and body fat composition measures. Women in G I had significantly higher means compared with those in G III. Individuals in G II had intermediate values. However, there was no significant age trend in muscle measures and indices of central body fat distribution. The results revealed that significantly more women in G III (45.8%) were malnourished (BMI < 18.5), while significantly more women in G I (28.7%) were obese (BMI > or = 25). The levels of malnourishment (21.6%) and obesity (24.5%) in G II were intermediate between G I and G III. Age had significant negative correlations with measures of adiposity and body fat composition. Regression analysis revealed that age had significant negative effect on these anthropometric measures. This significant negative impact of age remained even after controlling for the effect of BMI. In conclusion, the present investigation revealed that among older Bengalee Hindu women, there is a significant inverse age trend in adiposity and body fat composition, which is independent of overall adiposity (BMI). However, with ageing, muscle and central body fat distribution remain the same. Furthermore, with increasing age, there is a trend of increasing levels of malnourishment and decreasing levels of obesity.     

Immunohistochemical identification of aquaporin 2 in the kidneys of young beef cattle

Aquaporin 2 (AQP2) is a small, integral tetrameric plasma membrane protein that is expressed in mammalian kidneys. The specific constitution of this protein and its selective permeability to water means that AQP2 plays an important role in hypertonic urine production. Immunolocalization of AQP2 has been studied in humans, monkeys, sheep, dogs, rabbits, rats, mice and adult cattle. We analyzed the expression of AQP2 in kidneys of 7-month-old Polish-Friesian var. black and white male calves. AQP2 was localized in the principal cells of collecting ducts in medullary rays penetrating the renal cortex and in the collecting ducts of renal medulla. AQP2 was expressed most strongly in the apical plasma membrane, but expression was observed also in the intracellular vesicles and basolateral plasma membrane. Our study provides new information concerning the immunolocalization of AQP2 in calf kidneys.     

The root: a potential new source of competent cells for high-frequency regeneration in Tylophora indica

The purpose of this study was to develop a new micropropagation system for Tylophora indica, an important medicinal plant in India, using root explants as starting material. Root explants cultured on MS medium supplemented with 6-benzyladenine (BA) or 2-isopentyladenine (2iP) produced organogenic nodular meristemoids (NMs) within 4 weeks. NMs induced from the cut ends of root segments showed two types of organogenic response—direct shoot bud formation and somatic embryogenesis—when maintained on induction medium. In 42% of the explants, NMs developed shoot buds directly in the presence of 10.72–26.80 M BA. On average, 18.5±0.7 shoots per gram of NM tissue were obtained after each 4-week subculture. Elongation of microshoots and root initiation were correlated with the auxin used, with the optimal response occurring in the presence of 28.54 M indole-3-acetic acid. In 39% of the explants, NMs dedifferentiated into friable embryogenic callus (FEC) in the presence of BA or 2iP after 12 weeks of culture. Of the different treatments, MS medium supplemented with 10.72 M BA was the most effective in inducing FEC and somatic embryogenesis: at this concentration 64% of the cultured NMs developed FEC and, on the same medium, 89% of the FEC produced globular somatic embryos (SEs). FEC biomass increased nearly five-fold with every 4-week subculture, and about 30 SEs were recovered per gram of FEC during this period. The best conversion of mature SEs to complete plantlets was obtained on basal MS medium–42%. Plantlets derived via somatic embryogenesis and shoot organogenesis were successfully hardened (88–96%) and transferred to the field.Abbreviations BA: 6-Benzyladenine - 2,4-D: 2,4-Dichlorophenoxyacetic acid - FEC: Friable embryogenic callus - GRS: Green root segment - IAA: Indole-3-acetic acid - IBA: Indole-3-butyric acid - 2ip: 2-Isopentyladenine - Kin: Kinetin - NAA: -Naphthaleneacetic acid - NM: Nodular meristemoid - SE: Somatic embryo - WRS: White root segmentCommunicated by P. Lakshmanan     

Synthesis and structure-activity relationship studies of cinnamic acid-based novel thiazolidinedione antihyperglycemic agents

A number of 2,4-thiazolidinedione derivatives of -phenyl substituted cinnamic acid were synthesized and studied for their PPAR agonist activity. The E-isomer of cinnamic acid, 11, showed moderate PPAR transactivation. The corresponding Z-isomer, 23, and double bond reduced derivative, 15, were found to be much less potent. Although the E-isomer showed a moderate PPAR gamma transactivation, it demonstrated a strong glucose-lowering effect in a genetic rodent model of diabetes. Results of pharmacokinetic, metabolism and permeability studies are consistent with 11 being an active prodrug with an active metabolite, 14, that has similar glucose lowering and PPAR gamma agonist properties.     

Crystal structure of imidazole glycerol phosphate synthase: a tunnel through a (beta/alpha)8 barrel joins two active sites

BACKGROUND: Imidazole glycerol phosphate synthase catalyzes a two-step reaction of histidine biosynthesis at the bifurcation point with the purine de novo pathway. The enzyme is a new example of intermediate channeling by glutamine amidotransferases in which ammonia generated by hydrolysis of glutamine is channeled to a second active site where it acts as a nucleophile. In this case, ammonia reacts in a cyclase domain to produce imidazole glycerol phosphate and an intermediate of purine biosynthesis. The enzyme is also a potential target for drug and herbicide development since the histidine pathway does not occur in mammals. RESULTS: The 2.1 A crystal structure of imidazole glycerol phosphate synthase from yeast reveals extensive interaction of the glutaminase and cyclase catalytic domains. At the domain interface, the glutaminase active site points into the bottom of the (beta/alpha)(8) barrel of the cyclase domain. An ammonia tunnel through the (beta/alpha)(8) barrel connects the glutaminase docking site at the bottom to the cyclase active site at the top. A conserved "gate" of four charged residues controls access to the tunnel. CONCLUSIONS: This is the first structure in which all the components of the ubiquitous (beta/alpha)(8) barrel fold, top, bottom, and interior, take part in enzymatic function. Intimate contacts between the barrel domain and the glutaminase active site appear to be poised for crosstalk between catalytic centers in response to substrate binding at the cyclase active site. The structure provides a number of potential sites for inhibitor development in the active sites and in a conserved interdomain cavity.     

Plastid transformation in Arabidopsis thaliana

Plastid transformation is reported in Arabidopsis thaliana following biolistic delivery of transforming DNA into leaf cells. Transforming plasmid pGS31A carries a spectinomycin resistance (aadA) gene flanked by plastid DNA sequences to target its insertion between trnV and the rps12/7 operon. Integration of aadA by two homologous recombination events via the flanking ptDNA sequences and selective amplification of the transplastomes on spectinomycin medium yielded resistant cell lines and regenerated plants in which the plastid genome copies have been uniformly altered. The efficiency of plastid transformation was low: 2 in 201 bombarded leaf samples. None of the 98 plants regenerated from the two lines were fertile. Received: 13 February 1998 / Revision received: 24 April 1998 / Accepted: 5 June 1998     

Bacterial flagellar diversity in the post-genomic era

Flagellar biosynthesis has been studied most thoroughly in laboratory strains of Escherichia coli and Salmonella enterica. However, genome sequencing has uncovered flagellar loci in distantly related bacteria. We have used homology searches to determine how far the E. coli/S. enterica paradigm can be generalised to other flagellar systems. Numerous previously unrecognized homologues of flagellar components were discovered, including novel FlgM, FlgN, FliK and FliO homologues. Homology was found between the FliK proteins and a molecular ruler, YscP, from a virulence-associated type-III secretion system. Also described is a new family of flagellar proteins, the FlhX proteins, which resemble the cytoplasmic domain of FlhB.