Inactivation of Giardia lamblia and Giardia canis cysts by combined and free chlorine

Free chlorine and a combined organic N-chloramine (3-chloro-4,4-dimethyl-2-oxazolidinone, compound 1) were compared for efficacy as disinfectants against an admixture of cysts of Giardia lamblia and Giardia canis in water solution under a variety of test conditions; variables were pH, temperature, and water quality. In general, compound 1 was found to reduce the giardial excystation in the solutions at lower concentration or shorter contact time at a given total chlorine concentration than did free chlorine.     

Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium

Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel.     

pH dependence of the in situ formation of an organicN-chloramine water disinfectant

Summary Staphylococcus aureus was used to assess the bactericidal efficacy of aqueous solutions of the organicN-chloramine compound 3-chloro-4,4-dimethyl-2-oxazolidinone (agent I) formed in situ. The rate of in situ formation, accomplished by reacting free chlorine with the amine precursor, was a function of pH. When the reagents were combined under acidic conditions (pH5.5) and allowed to react for 22 h, sufficient residual free chlorine was present to inactivate the bacteria in less than 5 min. When combined under less acidic conditions (pH6.0), comparable bacterial inactivation required 30–60 min due to the extensive reaction of the free chlorine to form agent I. The kill rates present under less acidic and neutral conditions are equivalent to those for pre-formed agent I. In water disinfection applications for pH6.0, in situ formation of agent I would provide a combination of rapid initial and slower long-term disinfection.     

Rotational streaming in fiber cells and its role in translocation

All visible protoplasmic streaming in sections of various plant stems was reversibly stopped by 2,4-dinitrophenol (DNP). Sections contained epidermal, cortical, and fiber cell types. Cells treated with DNP retained their semipermeability as evidenced by their plasmolysis in sucrose solutions. Washing out the DNP resulted in the rapid resumption of protoplasmic streaming in all 3 cell types. Both the rate of movement of sodium fluorescein and the shape of the advancing dye front were greatly altered by DNP treatment. Dye transport was decreased in the fibers and little affected in cortical cells. The results suggest that rotational streaming accelerates the translocation of soluble substances in fiber cells.     

Non-neuronal cells of rat hypothalamus in dissociated cell culture

Summary The neurophysin that is biosynthesised in association with the neurohypophysial hormone vasopressin (vasopressin-neurophysin) affects the growth and DNA synthesis of rat hypothalamic non-neuronal cells in culture. Over a narrow range of concentrations vasopressin-neurophysin stimulated growth, as assessed by increase in cell numbers, about five-fold, in conditions where fetal calf serum concentration was limiting (0.2% fetal calf serum). Maximum stimulation occurred in the presence of 20 to 30 ng vasopressin-neurophysin per ml of medium. DNA synthesis was increased by a factor of three in the presence of 30 ng vasopressin-neurophysin per ml of medium. At least two populations of non-neuronal hypothalamic cells were present in the cultures, and these were both affected by vasopressin-neurophysin.This study allows the suggestion that neurophysin may be acting as a growth-regulating factor at its release site, playing a part in the interactions of neurones and glial cells in the hypothalamo-neurohypophysial system.     

6-d-glucopyranosyl fatty acid esters from Brassica napus pollen

6-d-Glucopyranosyl esters of palmitic, oleic, linoleic and linolenic acids were identified in Brassica napus (rape) pollen. These esters are inactive as plant growth promoters in the bean second-internode bioassay.     

Lipid surface charge does not influence conductance or calcium block of single sodium channels in planar bilayers.

We have studied the effects of membrane surface charge on Na+ ion permeation and Ca2+ block in single, batrachotoxin-activated Na channels from rat brain, incorporated into planar lipid bilayers. In phospholipid membranes with no net charge (phosphatidylethanolamine, PE), at low divalent cation concentrations (approximately 100 microM Mg2+), the single channel current-voltage relation was linear and the single channel conductance saturated with increasing [Na+] and ionic strength, reaching a maximum (gamma max) of 31.8 pS, with an apparent dissociation constant (K0.5) of 40.5 mM. The data could be approximated by a rectangular hyperbola. In negatively charged bilayers (70% phosphatidylserine, PS; 30% PE) slightly larger conductances were observed at each concentration, but the hyperbolic form of the conductance-concentration relation was retained (gamma max = 32.9 pS and K0.5 = 31.5 mM) without any preferential increase in conductance at lower ionic strengths. Symmetrical application of Ca2+ caused a voltage-dependent block of the single channel current, with the block being greater at negative potentials. For any given voltage and [Na+] this block was identical in neutral and negatively charged membranes. These observations suggest that both the conduction pathway and the site(s) of Ca2+ block of the rat brain Na channel protein are electrostatically isolated from the negatively charged headgroups on the membrane lipids.     

Highly Stable Plasmonic Nanostructures on a Nickel-Sputtered Glass and Polymeric Optical Fiber Sensors

Plasmonics - This study shows development of highly sensitive and stable localized surface plasmon resonance (LSPR)-active U-bent glass and polymeric optical fiber (GOF and POF) sensor probes by a...