Extracellular potassium can simulate the role of serum as an activator of uridine uptake by quiescent hamster cells in culture

Replacement of ~100 mM of sodium chloride in the extracellular medium of quiescent hamster fibroblasts (Nil 8 and BHK cells) by potassium chloride causes an increase in the rate of uridine uptake. This increase is identical with that achieved by addition of 10% serum to the same cultures. The effects of serum and KCl are not additive. The dependence of the rate of uridine uptake on extracellular KCl concentration is of a sigmoid nature. The time course of the activation process is similar to that of serum activation of uridine uptake in the same cells. The high rate of uridine uptake persists for at least 30 min after return to an extracellular medium containing a high concentration of sodium.     

Oil palm (Elaeis guineensis) protoplasts: isolation, culture and microcallus formation

Procedures are deseribed for the efficient isolation of protoplasts from a variety of oil palm (Elaeis guineensis Jacq.) tissues. Various factors including donor source, composition of enzyme mixture and culture medium affected the yield and viability of the protoplasts Polyembryogenic cultures of oil palm were the most suitable starting material in terms of yield, viability and metabolic competence. Pectolyase Y-23 in association with cellulase and hemicellulase was required for the efficient release of protoplasts from the oil palm tissues. Limited cell division to form microcallus was observed at very low frequency (<0.01%) when glutathione and catalase were incorporated in the culture medium.Abbreviations 2,4-d dichlorophenoxyacetic acid - DTT dithiothreitol - MES 2[N-morpholino] ethanesulphonic acid - NAA 1-naphthalene acetic acid - PVP polyvinylpyrrolidone     

Avian epidermis contains ATPase- and Ia-positive Langerhans-like cells

Summary The occurrence of cells resembling mammalian Langerhans cells in the avian epidermis was studied by ATPase histochemistry, Ia immunoreactivity and electron microscopy. The existence of MHC class II antigen-(Ia) expressing, ATPase-positive dendritic cells, which are ultrastructurally similar to mammalian Langerhans cells except for the absence of Birbeck granules, was demonstrated. These cells may be a basic component of the immune system of birds.     

New chromogenic dipeptide substrate for continuous assay of the D-alanyl-D-alanine dipeptidase VanX required for high-level vancomycin resistance.

A direct continuous UV-Vis spectrophotometric assay has been developed for VanX, a D-alanyl-D-alanine aminodipeptidase necessary for vancomycin resistance. This method is based on the hydrolysis of the alternative substrate D-alanyl-alpha-(R)-phenylthio-glycine D-Ala-D-Gly(S-Ph)-OH (H-DAla-DPsg-OH, 5a). Spontaneous decomposition of the released phenylthioglycine generates thiophenol, which is quantified using Ellman's reagent. The dipeptide behaved as an excellent substrate of VanX, exhibiting Michaelis-Menten kinetics with a kcat of 76 +/- 5/s and a KM of 0.83 +/- 0.08 mm (kcat = 46 +/- 3/s and KM = 0.11 +/- 0.01 mm for D-Ala-D-Ala). Determination of the kinetic parameters of the previously reported mechanism-based inhibitor D-Ala-D-Gly(SPhip-CHF2)-OH (H-D-Ala-DPfg-OH, 5c) [Araoz, R., Anhalt, E., René, L., Badet-Denisot, M.-A., Courvalin, P. & Badet, B. (2000) Biochemistry 39, 15971-15979] using the substrate reported in the present study yielded values of Kirr of 22 +/- 1 microM and kinact of 9.3 +/- 0.4/min in good agreement with values previously obtained in our laboratory (Kirr = 30 +/- 1 mm; kinact = 7.3 +/- 0.3/min). In addition, inhibition by the competing substrate D-Ala-D-Ala resulted in determination of a Ki = 70 +/- 6 microM close to the previously reported KM value. These results demonstrate that the present assay is a convenient, rapid and sensitive tool in the search for VanX inhibitors.     

On a new charophyte from India

Chara indica is described as a new species on morphological and cytological grounds.Part of Ph. D. Thesis of Ranchi University.     

Effect of papaya (Carica papaya) leaf extract as dietary growth promoter supplement in red hybrid tilapia (Oreochromis mossambicus × Oreochromis niloticus) diet

The purpose of this experiment was to examine the potential use of Carica papaya leaf extract as a supplement to promote growth and improve feed utilization in red hybrid tilapia. Five diets were formulated containing isolipidic (80 g/kg) and isonitrogenic (350 g/kg) levels. All feeds contained similar types and amounts of raw materials but differed in the inclusion of papaya leaf extract (0, 5, 10, 20 and 40 g/kg feed). The initial size of fish used was 2.3 ± 0.01 g. Each diet was performed in triplicate tanks, and the feeding period was 12 weeks. Fish fed diet containing 2% papaya leaf extract (PLE) had the highest final weight, 31.14 ± 1.47 g, followed by 1% PLE (27.27 ± 1.75 g). These two diets (1% and 2%) were also showed significant improvements of weight gain, SGR, and feed efficiency of the red hybrid tilapia (p < 0.05). However, papaya leaf extract did not affect the HSI, VSI, PER, digestive enzymes activity, blood composition, and survival rate. Supplementing the diets with papaya leaf extract lowered serum urea. Findings of this research suggest that adding papaya leaf extract to the diet of red hybrid tilapia improves growth and feed efficiency without adversely affecting blood parameters. Therefore, an inclusion level between 1% and 2% of the papaya leaf extract is recommended as a feed additive to promote red hybrid tilapia fry growth.     

Synthesis and structure–activity relationships of cassiarin A as potential antimalarials with vasorelaxant activity

Cassiarin A 1, a tricyclic alkaloid, isolated from the leaves of Cassia siamea (Leguminosae), shows powerful antimalarial activity against Plasmodium falciparum in vitro as well as P. berghei in vivo, which may be valuable leads for novel antimalarials. Interactions of parasitized red blood cells (pRBCs) with endothelium in aorta are especially important in the processes contribute to the pathogenesis of severe malaria. Nitric oxide (NO) reduces endothelial expression of receptors/adhesion molecules used by pRBC to adhere to vascular endothelium, and reduces cytoadherence of pRBC to vascular endothelium. Cassiarin A 1 showed vasorelaxation activity against rat aortic ring, which may be related with NO production. A series of a hydroxyl and a nitrogen-substituted derivatives and a dehydroxy derivative of 1 have been synthesized as having potent antimalarials against P. falciparum with vasodilator activity, which may reduce cytoadherence of pRBC to vascular endothelium. Cassiarin A 1 exhibited a potent antimalarial activity and a high selectivity index in vitro, suggesting that the presence of a hydroxyl and a nitrogen atom without any substituents may be important to show antimalarial activity. Relative to cassiarin A, a methoxy derivative showed more potent vasorelaxant activity, although it did not show improvement for inhibition of P. falciparum in vitro. These cassiarin derivatives may be promising candidates as antimalarials with different mode of actions.     

Preoptic hypothalamic warming suppresses laryngeal dilator activity during sleep

Upper airway dilator activity during sleep appears to be diminished under conditions of enhanced sleep propensity, such as after sleep deprivation, leading to worsening of obstructive sleep apnea (OSA). Non-rapid eye movement (NREM) sleep propensity originates in sleep-active neurons of the preoptic area (POA) of the hypothalamus and is facilitated by activation of POA warm-sensitive neurons (WSNs). We hypothesized that activation of WSNs by local POA warming would inhibit activity of the posterior cricoarytenoid (PCA) muscle, an airway dilator, during NREM sleep. In chronically prepared unrestrained cats, the PCA exhibited inspiratory bursts in approximate synchrony with inspiratory diaphragmatic activity during waking, NREM, and REM. Integrated inspiratory PCA activity (IA), peak activity (PA), and the lead time (LT) of the onset of inspiratory activity in PCA relative to diaphragm were significantly reduced in NREM sleep and further reduced during REM sleep compared with waking. Mild bilateral local POA warming (0.5-1.2 degrees C) significantly reduced IA, PA, and LT during NREM sleep compared with a prewarming NREM baseline. In some animals, effects of POA warming on PCA activity were found during waking or REM. Because POA WSN activity is increased during spontaneous NREM sleep and regulates sleep propensity, we hypothesize that this activation contributes to reduction of airway dilator activity in patients with OSA.