Dry-season spawning in a cyprinid fish of southern India

Synopsis A population of the S. Indian cyprinid fishBarbus melanampyx was sampled monthly through 24 months. Seasonal cycles of the gonado-somatic index (GSI), ovarian stages, male breeding tubercles, spawning behaviour and population structure were assessed. These fish breed strictly seasonally during the main dry period: December/January through April. Comparison with other Barbus species of the same general region led to the conclusion that the patterns of reproductive investment ofB. melanampyx are similar to those of perennial species, and different from those of wet-season spawners. The reasons for this rather unexpected result were found in the more constant conditions prevailing during a dry season as compared to the monsoon. It was argued thatB. melanampyx and the species spawning perennially are in effect small-brood spawners, rather than partial spawners.     

Assessment of the genotoxic potential of riboflavin and lumiflavin. B. Effect of light.

On exposure to visible light, riboflavin and lumiflavin produced reactive oxygen species such as singlet oxygen and superoxide radicals. The reaction was found to be time- and concentration-dependent. Both riboflavin and lumiflavin, upon illumination, showed mutagenic response in the umu test as well as in the Ames/Salmonella assay with Salmonella typhimurium TA102. The mutagenic response was partially abolished by superoxide dismutase while sodium azide did not have any effect. No mutagenicity was observed if the compounds were not illuminated. The results suggested the involvement of superoxide radicals in light-induced mutagenicity of riboflavin as well as lumiflavin.     

Ligand Binding Characteristics of the Human Serotonin<Subscript>1<Emphasis Type="Italic">A</Emphasis></Subscript> Receptor Heterologously Expressed in CHO Cells

The serotonin_1A (5-HT_1A) receptors are important members of the superfamily of seven transmembrane domain G-protein coupled receptors. They appear to be involved in various behavioral, cognitive and developmental functions. Mammalian cells in culture heterologously expressing membrane receptors represent convenient systems to address problems in receptor biology. We report here the pharmacological characterization of one of the first isolated clones of CHO cells stably expressing the human 5-HT_1A receptor using the selective agonist 8-OH-DPAT and antagonist p-MPPF. In addition, we demonstrate that agonist and antagonist binding to the receptor exhibit differential sensitivity to the non-hydrolyzable GTP analogue, GTP--S, as was observed earlier with the native receptor from bovine hippocampus. These results show that the human 5-HT_1A receptor expressed in CHO cells displays characteristic features found in the native receptor isolated from bovine hippocampus and promises to be a potentially useful system for future studies of the receptor.These authors have contributed equally to the work     

Heterodimerization of type A and B cholecystokinin receptors enhance signaling and promote cell growth

Dimerization of several G protein-coupled receptors has recently been described, but little is known about its clinical and functional relevance. Cholecystokinin (CCK) and gastrin are structurally related gastrointestinal and neuronal peptides whose functions are mediated by two structurally related receptors in this superfamily, the type A and B CCK receptors. We previously demonstrated spontaneous homodimerization of type A CCK receptors and the dissociation of those complexes by agonist occupation (Cheng, Z. J., and Miller, L. J. (2001) J. Biol. Chem. 276, 48040-48047). Here, for the first time, we also demonstrate spontaneous homodimerization of type B CCK receptors, as well as heterodimerization of that receptor with the type A CCK receptor. Unlike type A CCK receptor dimers, the homodimerization of type B CCK receptors was not affected by ligand occupation. However, although heterodimers of type A and B CCK receptors bound natural agonists normally, they exhibited unusual functional and regulatory characteristics. Such complexes demonstrated enhanced agonist-stimulated cellular signaling and delayed agonist-induced receptor internalization. As a likely consequence, agonist-stimulated cell growth was markedly enhanced in cells simultaneously expressing both of these receptors. Our results provide the first evidence that heterodimerization of G protein-coupled receptors can form a more "powerful" signaling unit, which has potential clinical significance in promoting cell growth.     

Fluorescent indicators distributed throughout the pharmacophore of cholecystokinin provide insights into distinct modes of binding and activation of type A and B cholecystokinin receptors

Ligand probes with fluorescent indicators positioned throughout the pharmacophoric domain can provide important insights into the molecular basis of receptor binding and activation as reflected in the microenvironment of each indicator while docked at a receptor. We developed three cholecystokinin-like probes with Aladan situated at the N terminus, in the mid-region, and at the C terminus (positions 24, 29, and 33, respectively). These were studied in solution and docked at type A and B cholecystokinin receptors. This study demonstrated clear differences in mechanisms of cholecystokinin binding and activation of these structurally related receptors with distinct agonist structure-activity relationships. The fluorescence characteristics of Aladan are highly sensitive to the polarity of its microenvironment. The mid-region probe was least accessible to the aqueous milieu as determined by fluorescence emission spectra and iodide quenching, which was not altered by changes in conformation from active to inactive. Accessibility of the N- and C-terminal probes was affected by receptor conformation. The position 24 probe was more easily quenched in the active than in the G protein-uncoupled conformation for both receptors. However, the position 33 probe docked at the type A cholecystokinin receptor was more easily quenched in the active conformation, whereas the same probe docked at the type B cholecystokinin receptor was more easily quenched in the inactive conformation. Fluorescence anisotropy and red edge excitation shift determinations confirmed these observations and supported the proposed movements. Although both type A and B cholecystokinin receptors bind cholecystokinin with high affinity, resulting in fully efficacious biological responses, these receptors utilize distinct molecular modes of binding.     

Peroxisome proliferator-activated receptor β/δ induces myogenesis by modulating myostatin activity

Classically, peroxisome proliferator-activated receptor β/δ (PPARβ/δ) function was thought to be restricted to enhancing adipocyte differentiation and development of adipose-like cells from other lineages. However, recent studies have revealed a critical role for PPARβ/δ during skeletal muscle growth and regeneration. Although PPARβ/δ has been implicated in regulating myogenesis, little is presently known about the role and, for that matter, the mechanism(s) of action of PPARβ/δ in regulating postnatal myogenesis. Here we report for the first time, using a PPARβ/δ-specific ligand (L165041) and the PPARβ/δ-null mouse model, that PPARβ/δ enhances postnatal myogenesis through increasing both myoblast proliferation and differentiation. In addition, we have identified Gasp-1 (growth and differentiation factor-associated serum protein-1) as a novel downstream target of PPARβ/δ in skeletal muscle. In agreement, reduced Gasp-1 expression was detected in PPARβ/δ-null mice muscle tissue. We further report that a functional PPAR-responsive element within the 1.5-kb proximal Gasp-1 promoter region is critical for PPARβ/δ regulation of Gasp-1. Gasp-1 has been reported to bind to and inhibit the activity of myostatin; consistent with this, we found that enhanced secretion of Gasp-1, increased Gasp-1 myostatin interaction and significantly reduced myostatin activity upon L165041-mediated activation of PPARβ/δ. Moreover, we analyzed the ability of hGASP-1 to regulate myogenesis independently of PPARβ/δ activation. The results revealed that hGASP-1 protein treatment enhances myoblast proliferation and differentiation, whereas silencing of hGASP-1 results in defective myogenesis. Taken together these data revealed that PPARβ/δ is a positive regulator of skeletal muscle myogenesis, which functions through negatively modulating myostatin activity via a mechanism involving Gasp-1.     

G-protein-dependent cell surface dynamics of the human serotonin1A receptor tagged to yellow fluorescent protein

Serotonergic signaling appears to play a key role in the generation and modulation of various cognitive, behavioral, and developmental processes. The serotonin(1A) receptor is an important member of the superfamily of seven transmembrane domain G-protein-coupled receptors and is the most extensively studied among the serotonin receptors. Several aspects of serotonin(1A) receptor biology such as cellular distribution and signal transduction characteristics are technically difficult to address in living cells on account of the inability to optically track these receptors with fluorescence-based techniques. We describe here the characterization of the serotonin(1A) receptor tagged to the enhanced yellow fluorescent protein (EYFP) stably expressed in Chinese hamster ovary (CHO) cells. These receptors were found to be essentially similar to the native receptor in pharmacological assays and can therefore be used to reliably explore aspects of receptor biology such as cellular distribution and dynamics on account of their intrinsic fluorescent properties. Analysis of the cell surface dynamics of these receptors by fluorescence recovery after photobleaching (FRAP) experiments has provided novel insight into the molecular mechanism of signal transduction of serotonin(1A) receptors in living cells. Interestingly, addition of pharmacologically well-characterized ligands or activators of G-proteins altered the diffusion characteristics of the receptor in a manner consistent with the G-protein activation model. These results demonstrate, for the first time, that membrane dynamics of this receptor is modulated in a G-protein-dependent manner.     

Recent advances in mRNA-based vaccine for cancer therapy; bench to bedside

The messenger RNA (mRNA) vaccines have progressed from a theoretical concept to a clinical reality over the last few decades. Compared to conventional vaccination methods, these vaccines have a number of benefits, such as substantial potency, rapid growth, inexpensive production, and safe administration. Nevertheless, their usefulness was restricted up to now due to worries about the erratic and ineffective circulation of mRNA in vivo. Thankfully, these worries have largely been allayed by recent technological developments, which have led to the creation of multiple mRNA vaccination platforms for cancer and viral infections. The mRNA vaccines have been demonstrated as a powerful alternative to traditional conventional vaccines because of their high potency, safety and efficacy, capacity for rapid clinical development, and potential for rapid, low-cost manufacturing. The paper will examine the present status of mRNA vaccine technology and suggest future paths for the advancement and application of this exciting vaccine platform as a common therapeutic choice.