Interactions of lanthanum with purified and intact cell acetylcholinesterase of electrophorus electricus

Summary The effects of lanthanum on the activity of purified preparations of acetylcholinesterase (AChE) from the electric organ ofE. electricus and on the activity of AChE in intact electro-plaques from the same species were studied. 0.1mm LaCl₃ produced an initial inhibition of purified AChE which was followed by a delayed activation of the enzyme. Upon pretreatment of purified enzyme with LaCl₃, initial activity was markedly increased. LaCl₃ exerted a marked, concentration-dependent inhibition of intact cell AChE.La³⁺ and Ca²⁺ appear to interact competitively. In the presence of both 10mm CaCl₂ and 0.1mm LaCl₃, the initial activity of purified AChE was increased at lower ACh concentrations and inhibited at ACh concentrations greater than 3 × 10^–4 m. Inhibition of intact cell enzyme by 0.1mm LaCl₃ was relieved by increasing the CaCl₂ concentration to 10mm at ACh concentrations less than 2 × 10^–4 m.The data were analyzed assuming Michaelis-Menten kinetics and interpreted with reference to the differential binding of divalent and trivalent cations to regulatory anionic sites which are separate and distinct from the anionic site of the active center of the enzyme.     

Two early mississippian seeds from the price formation of Southwestern Virginia

Lagenospermum imparirameum Arnold, originally described from a few specimens of cupulate seeds borne on two or three times dichotomous branches, is now shown to be borne on more complex branching systems. Details of the cupule and seed morphology are added and an emended diagnosis of the taxon is given. A new species,Gnetopsis hispida, is described as the third occurrence of this genus and the first occurrence in beds of Lower Mississippian Age in North America. The classification, evolutionary implications, and dispersal biology are discussed for each of the seeds     

Receptor-mediated phagocytosis of zymosan is unaffected by some conditions which reduce macrophage lysosomal enzyme secretion

We have previously shown that several agents which interfere with binding of ligands to the mannose-glycoprotein receptor on macrophages can inhibit zymosan-induced lysosomal enzyme secretion. Here we show that mannose only reduces the association of zymosan with macrophages during the first hour of exposure; after longer periods of uptake no effect is detectable. We have previously shown that mannose reduces surface binding of zymosan, probably by interfering selectively with binding to the mannose receptor. The present inhibition of association of zymosan with macrophages during short exposures can be entirely explained by this reduction of binding. Macrophages must therefore internalize zymosan at sites in addition to the mannose receptor. In contrast to macrophages the murine macrophage-like cell line P388D1 is lacking the mannose-glycoprotein receptor. Accordingly we find that binding of zymosan to P388D1 is much slighter than to macrophages and is unaffected by mannose or mannose-6-phosphate. The spontaneous lysosomal enzyme secretion of P388D1 is also unaffected by mannose. The data on macrophages confirm our previous suggestion that agents interfering with the mannose receptor inhibit the induction of lysosomal enzyme secretion by acting directly on the receptor. The data on P388D1 cells support this assertion by excluding effects at later steps in the secretory pathway.     

Development and characterization of monoclonal antibodies to human type III procollagen

Hybridomas which secrete monoclonal antibodies against human type III procollagen have been developed. By an enzyme-linked immunosorbent assay, three of the monoclonal antibodies have been determined to be against non-helical extensions of the molecules while two of the antibodies are against helical portion of the molecules which is sensitive to bacterial collagenase action. These findings have been further confirmed by carrying out immuno-reaction of the pro α-chains transferred on nitrocellulose paper from sodium dodecyl sulfate polyacrylamide gels. These monoclonal antibodies have been found to be suitable reagents for immunohistochemical studies as well as for immunoassays of type III procollagen and collagen.     

The effect of temperature, water activity and sorbic acid on ketone rancidity produced by Penicillium crustosum Thom in coconut and palm kernel oils

In a model system medium-chain fatty acids (MCFA) C₆–C₁₂ in coconut and palm kernel oil are converted to methyl ketones, one carbon atom less than the parent fatty acids, by two strains of Penicillium crustosum Thom. Conversion rates of up to 32% were seen for decanoic acid at 25°C. The optimum temperature for ketone production was 25°C in liquid suspension culture. Coconut oil contains 3.23 mmol/g MCFAs compared with 2.34 mmol/g for palm kernel oil. Coconut oil is more prone to fungal spoilage (growth and ketone production) than palm kernel oil. The main end product of fermentation was 2-undecanone reflecting the high concentration of dodecanoic acid in the substrates. Ketonic rancidity is fungal engendered. The reaction can be controlled by reducing the temperature (4°C), reducing the water activity (0.91) or by addition of sorbic acid (20 mmol/l).     

Sex Determination in Caenorhabditis elegans

In Caenorhabditis elegans, the decision to develop as a hermaphrodite or male is controlled by a cascade of regulatory genes. These genes and other tissue-specific regulatory genes also control sexual fate in the hermaphrodite germline, which makes sperm first and then oocytes. In this review, we summarize the genetic and molecular characterization of these genes and speculate how they mutually interact to specify sexual fate.     

Monoamines and Their Precursors and Metabolites in the Chicken Brain, Pineal, and Retina: Regional Distribution and Day/Night Variations

Levels of norepinephrine, epinephrine, dopamine, and serotonin (5-HT) and their precursors [tyrosine, L-3,4-dihydroxyphenylalanine, tryptophan, and 5-hydroxytryptophan (5-HTP)] and metabolites [3,4-dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3-MT), homovanillic acid, 3-methoxy-4-hydroxyphenylglycol, and 5-hydroxyindoleacetic acid (5-HIAA)] were determined concurrently in samples of chick retina, pineal gland, and nine selected areas of the brain (optic lobes, thalamus, hypothalamus, optic chiasm, pons/medulla, cerebellum, neostriatum/ectostriatum, hyperstriatum, and basal forebrain) using HPLC coupled with a coulometric electrode array detection system. The norepinephrine level was highest in the pineal gland, but it was also widely distributed throughout the chick brain, with the thalamus and hypothalamus showing substantial levels. The dopamine level was highest in the basal forebrain. The epinephrine level was highest in the hypothalamus. The thalamus and hypothalamus showed the highest levels of 5-HT. Daytime levels (1100 h) of these compounds were compared with levels in chicks killed in the middle of the dark phase (2300 h). In the brain areas examined, no day/night variations in levels of norepinephrine, epinephrine, dopamine, or 5-HT were seen, although significant nocturnal changes in levels of their metabolites were observed in some areas. Pineal levels of 5-HIAA decreased significantly at night. The retina showed significant nocturnal increases in 5-HTP, 5-HT, and 5-HIAA levels. Retinal levels of 3-MT and DOPAC were significantly decreased at night.     

Five novel elements involved in the regulation of mitosis in fission yeast

Summary Five new elements of the mitotic control in the fission yeast Schizosaccharomyces pombe were isolated from gene libraries as multicopy suppressors of the conditional lethal phenotype of win1-1 weel ^ts cdc25^ts triple mutant strains. These genes were designated wisl ⁺ –wis5⁺for win suppressing, and do not correspond to winl ⁺ or any of the previously characterised mitotic control genes. None of the wis genes is capable of suppressing the cdc phenotype of cdc25 ^ts strains, suggesting that their effect is not simply to reverse the effect of loss of cdc25 function. wisl ⁺ has been previously reported to encode a putative serine/threonine protein kinase that acts as a dosage-dependent inducer of mitosis. wis4 ⁺ appears to be a specific suppressor of the winl-1 mutation. wis2 ⁺ and wis3 ⁺ are capable of suppressing a wide range of cdc phenotypes arising from the combination of various mutations with wee1 ^ts and cdc25 ^ts, suggesting that the wis2 ⁺ and wis3 ⁺ products may interact with elements central to the mitotic control.