Intracellular regulation of cell signaling cascades: how location makes a difference

Organelles such as endosomes and the Golgi apparatus play a critical role in regulating signal transmission to the nucleus. Recent experiments have shown that appropriate positioning of these organelles within the intracellular space is critical for effective signal regulation. To understand the mechanism behind this observation, we consider a reaction-diffusion model of an intracellular signaling cascade and investigate the effect on the signaling of intracellular regulation in the form of a small release of phosphorylated signaling protein, kinase, and/or phosphatase. Variational analysis is applied to characterize the most effective regions for the localization of this intracellular regulation. The results demonstrate that signals reaching the nucleus are most effectively regulated by localizing the release of phosphorylated substrate protein and kinase near the nucleus. Phosphatase release, on the other hand, is nearly equally effective throughout the intracellular space. The effectiveness of the intracellular regulation is affected strongly by the characteristics of signal propagation through the cascade. For signals that are amplified as they propagate through the cascade, reactions in the upstream levels of the cascade exhibit much larger sensitivities to regulation by release of phosphorylated substrate protein and kinase than downstream reactions. On the other hand, for signals that decay through the cascade, downstream reactions exhibit larger sensitivity than upstream reactions. For regulation by phosphatase release, all reactions within the cascade show large sensitivity for amplified signals but lose this sensitivity for decaying signals. We use the analysis to develop a simple model of endosome-mediated regulation of cell signaling. The results demonstrate that signal regulation by the modeled endosome is most effective when the endosome is positioned in the vicinity of the nucleus. The present findings may explain at least in part why endosomes in many cell types localize near the nucleus.     

Somatic embryogenesis and shoot regeneration from intact seedlings of Phaseolus acutifolius A., P. aureus (L.) Wilczek,P. coccineus L., and P. wrightii L.

A rapid, one-step procedure has been developed for inducing direct organogenesis and somatic embryogenesis in cultures of Phaseolus coccineus L., P. acutifolius A., P. aureus L. [Vigna radiata L. Wilczek] and P. wrightii L. Development of somatic embryos and shoot buds occurred within 6–8 weeks of culture from intact seedlings raised on MS (Murashige and Skoog 1962) medium supplemented with N⁶-benzylaminopurine (BAP). Shoot buds or embryoids originated from subepidermal tissue of the regions adjacent to the shoot apex, hypocotyl and cotyledonary axils. While P. acutifolius and P. aureus were regenerated via shoot formation and P. wrightii by somatic embryogenesis, both embryogenesis and shoot regeneration were observed in P. coccineus. Relatively higher levels of BAP, 50–80 M, were found to be optimal for inducing regeneration while lower concentrations were ineffective. About 40–70 shoots and 70–250 somatic embryos were produced per responding seedling. Regenerated shoots and somatic embryos developed into whole plants on a basal medium or the one supplemented with 1 M naphthaleneacetic acid.     

Proportions and variability in the Indian lorises: Bone weight observations onLoris tardigradus lydekkerianus andNycticebus coucang

Thirty uniformly prepared, disarticulated complete skeletons of adultLoris tardigradus lydekkerianus andNycticebus coucang have been weighed for preliminary study of the weight relations between different major skeletal parts. In these forms, combined relative weight of the precaudal vertebrae, ribs and sternum surpasses the averages for the rest of the skeletal parts. The weight of the skull equals one-fifth of the total skeletal weight inLoris andNycticebus. The weight of the skeletons of the limbs (including the shoulder girdle and the hip bones) contributes less than half of the total skeletal weight in lorises. The bones of the upper limbs are lighter than those of the lower limbs in the 2 series examined.Loris andNycticebus are distinguished by having the proportionately heaviest axial skeleton and skull and the lowest relative weights of the bones of the 4 limbs. The combined relative skeletal weight of the upper and lower limbs ranges between 45.34 and 50.01 inLoris andNycticebus. The relative weight of the skeletons of the hands and feet are almost similar to the corresponding weights in the 2 series.As far as the weights of the different skeletal parts are concerned, there is no relative asymmetry in the 2 series ofLoris andNycticebus examined.     

Role of purine metabolism in thidiazuron-induced somatic embryogenesis of geranium (Pelargonium × hortorum) hypocotyl cultures

Somatic embryogenesis in geranium ( Pelargonium × hortorum Bailey cv. Scarlet Orbit Improved) was achieved by culturing hypocotyl sections on Murashige and Skoog (1962) (MS) medium containing 10 μ M thidiazuron (TDZ) (induction medium) for 3 days and subsequently transferring the sections onto a basal medium lacking any plant growth regulators (expression medium). Addition of the purine analogue 2.6-diaminopurine (DAP) to the somatic embryo induction medium completely inhibited the embryogenic response as well as chlorophyll accumulation without affecting enlargement of the treated tissues. Addition of 20 μ M adenine sulphate to the expression medium, i.e during embryo growth and development phase, completely reversed the DAP-induced inhibition of the embryogenic response while addition during the induction phase caused only a 50% reversal of the inhibition. Analysis of endogenous levels of plant growth substances indicated that TDZ alone elevated the levels of auxins, cy-tokinins and abscisic acid while the presence of DAP during the induction phase caused a further increase in the levels of adenine and adenosine. These findings indicate a possible critical role for purines in embryogenesis from geranium hypocotyl tissues. However, the conversion of cytokinin bases to their corresponding nucleotide forms was not evident as the levels of isopentenyl adenine and zeatin increased during the second day of culture.     

Protective effects of lazaroids against oxygen-free radicals induced lysosomal damage

Lipid peroxidation of membranes by oxygen free radicals has been implicated in various disease states. Different antioxidants and iron chelators have been used to reduce lipid peroxidation. Lazaroids have been used for the acute treatment of central nervous system disorders such as trauma and ischemia wherein lipid peroxidative processes take place.In this study we evaluated the effect of lazaroids (U-785 18F and U-74389F) on the release of acid phosphatase activity and formation of malondialdehyde (MDA) in rat liver lyosomes subjected to exogenously generated oxygen free radicals. There was a significant increase in the acid phosphatase release and MDA formation in the presence of oxygen free radicals. This was prevented by both the lazaroids. In a separate study the effect of lazaroid U-74389F was seen on the zymosan-stimulated polymorphonuclear (PMN) leukocyte-derived chemiluminescence. The PMN leukocyte chemiluminescent activity was attenuated by the lazaroid in a dose-dependent manner. These studies suggest that lazaroids may inhibit lipid peroxidation and stabilize the membrane.     

Evaluation of Salmonella Porins as a Broad Spectrum Vaccine Candidate

Porins were prepared from smooth strain of Salmonella typhi 0–901 and chemotype of rough mutant of S. typhimurium Ra-30. Mice were immunized with both the porin preparations in different groups and challenged with S. typhimurium LT2–71 and S. enteritidis SH-1269. Porin immunized mice showed significant protection (P <0.01) against challenge with homologous as well as heterologous strains. Hence, the use of porins may be attempted in future to protect against salmonellosis.     

Modulation of somatic embryogenesis in hypocotyl-derived cultures of geranium (Pelargonium X hortorum bailey) CV ringo rose by a bacterium

Summary The Ringo Rose cultivar of zonal geranium (Pelargonium x hortorum Bailey) has been shown to be morphogenetically unresponsive. Attempts to improve somatic embryogenesis using various seed stress treatments before germination proved ineffective. However, bacterial contamination of one of the seed-stress treatments led to infected explants that had a significant increase in frequency of high-quality somatic embryos. The co-cultivation of explants with the isolated bacterium (tentatively identified asBacillus sp.) was found to be repeatable, and potentially represents a novel way to improve morphogenesis in geranium and possibly other species.     

Fish Gut Microbiome: Current Approaches and Future Perspectives

In recent years, investigations of microbial flora associated with fish gut have deepened our knowledge of the complex interactions occurring between microbes and host fish. The gut microbiome not only reinforces the digestive and immune systems in fish but is itself shaped by several host-associated factors. Unfortunately, in the past, majority of studies have focused upon the structure of fish gut microbiome providing little knowledge of effects of these factors distinctively and the immense functional potential of the gut microbiome. In this review, we have highlighted the recently gained insights into the diversity and functions of the fish gut microbiome. We have also delved on the current approaches that are being employed to study the fish gut microbiome with an aim to collate all the knowledge gained and make accurate conclusions for their application based perspectives. The literature reviewed indicated that the future research should shift towards functional microbiomics to improve the maximum sustainable yield in aquaculture.