Calcium is necessary for light excitation in barnacle photoreceptors

Summary Illumination of barnacle (Balanus amphitrite) photoreceptors is known to increase the membrane permeability to sodium and Ca²⁺ ions resulting in a depolarizing receptor potential. In this report, we show that lanthanum (La³⁺), a known inhibitor of Ca-binding proteins, reversibly eliminates the receptor potential of barnacle photoreceptors when applied to the extracellular space. Similar reversible elimination of the light response was obtained by removing extracellular Ca²⁺ by application of the calcium chelating agent EGTA. Iontophoretic injection of Ca²⁺, but not K⁺ into the cells protected both the transient and the steady-state phases of the receptor potential from elimination by EGTA while only the transient phase was protected in the presence of La³⁺. The EGTA experiments suggest that internal Ca²⁺ is necessary for light excitation of barnacle photoreceptors while the La³⁺ experiments suggest that La³⁺-sensitive inward current is necessary to maintain excitation during prolonged light.Abbreviations EGTA ethylenglyol-bis-(-aminoethylether) N, N, N¹, N¹-tetraacetate - BAPTA bis-(0-aminophenoxy)-ethane-N, N, N¹, N¹-tetraacetic acid - DMSO dimethyl sulfoxide - trp transient receptor potential - nss no steady state - ASW artificial sea water     

Changes in soil microflora associated with control of Sclerotium Rolfsii by Furfuraldehyde

The efficacy of 2‐furfuraldehyde for control of Sclerotium rolfsii was studied in laboratory and greenhouse experiments. Mycelial growth of the fungus was reduced proportionally with concentrations of 0.1–0.5 ml furfuraldehyde l^‐1 agar medium, and viability of sclerotia diminished on exposure to 2‐furfuraldehyde vapours. Detectable populations of bacteria and fungi, including Trichoderma spp., were reduced significantly (9=0.05) when furfuraldehyde was added to the agar used for soil dilution plates of untreated soil. Repeated treatments of natural soil with the fumigant significantly increased populations of Trichoderma spp. and bacteria, but diminished numbers of actinomycetes. Increasing dosages applied to soil artificially infested with S. rolfsii caused a reduction of disease on lentil, Lens culinaris. Results indicate that the compound, when applied to field soil, changes the composition of soil microflora and has potential for integrated control of S. rolfsii.     

A Comparison of the Efficacy of Nuclear Polyhedrosis and Granulosis Viruses in Spray and Bait Formulations for the Control of Agrotis segetum (Lepidoptera: Noctuidae) in Maize

Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to four‐leaf stage of growth. Plots were arranged in a 6 x 6 Latin square design and infested with second‐instar A. segetum larvae (the common cutworm). Each virus was applied in separate treatments by two application methods; as an aqueous spray containing 0.1% Agral as a wetting agent, and as a bran bait. The NPV was applied at a rate of 4 X 10¹² polyhedra/ha, and the GV at 4 X 10¹³ granules/ha. Soil and plants were sampled for larvae on three occasions following virus treatment: 24 h, 4 days and 11 days. The larvae were reared on diet in the laboratory, until death or pupation, to examine the rate and level of viral infection. Infection data showed 87.5% and 91% NPV infection and 12.5% and 55% GV infection in spray and bait treatments, respectively, in larvae sampled 24 h after treatment. In larvae sampled 4 days after treatment, the results were 78% and 100% NPV infection, and 13% and 6% GV infection. A total of only six larvae were retrieved on day 11. In both treatments larvae infected with AsNPV died significantly more rapidly and at an earlier instar than those infected with AsGV, indicating that AsNPV appears to have better potential as a control agent for A. segetum.     

Effects of nitrogen source, calcium concentration and osmotic stress on protoplasts and protoplast-derived cell cultures of Pinus Pinaster cotyledons

The experiments described emphasize the effects of several factors crucial to the maintenance of cell divisions leading to increased cell numbers in suspension and colony formation from cotyledon protoplasts of Pinus Pinaster Ait. Osmotic potential of the incubation and culture media are critical. Reducing the osmolality from 680 mOsm kg H₂O⁻¹ during protoplast isolation to 610 mOsm kg H₂O⁻¹ during washing and culture was essential to achieve a high frequency of cell division. Survival of the cells beyond 3 weeks of culture occurs only if the calcium concentration is decreased from 5.6 m M to 1.5 m M . Glutamine as sole source of nitrogen shortens the lag phase of response of the protoplasts and increases their plating efficiency. After 6 weeks of culture, a combination of low osmolality (225 mOsm kg H₂O⁻¹) and high level of glutamine (40 m M ) is a prerequisite for obtaining actively growing cell suspensions.     

Optimization of fetal lung organ culture for surfractant biosynthesis

Summary Lung organ culture has been a widely used system for studying differentiation and maturation of alveolar epithelium through various culture conditions. The purpose of this work was to carefully characterize in vitro lung biochemical diffeentiation through isolation of surfactant fraction from tissue and to search for optimal culture conditions. Fetal rat lung was explanted on the 18th gestational day for studying glycogen storage, and on the 20th gestational day for studying surfactant accretion, and cultivated for 48 h. Morphologic differentiation was studies byelectron microscopy tissue explanted on the 17th or 18th gestational days and cultivated for various times. Glycogen storage was greater on fluid medium, although less than occurring in vivo. Cellular integrity and surfactant accumulation were maximal on a semisolid medium containing 0.5% agar. Use of O₂-CO₂ instead of air-CO₂ for gassing the explants slighlty decreased phospholipid accumulation. Among media used in previous lung culture studies, Waymouth MB 752/1 was the only one to allow net glycogen accumulation in vitro. The most favorable media for surfactant phospholipid accretion were Waymouth MB 752/1, Eagle’s minimum essential and its Dulbeccco’s modification, CMRL 1066, and NCTC 109. They allowed a 12- to 14-fold increase of surfactant fraction phospholipids in vitro, which is similar to the increase occurring in vivo during the same peiod. Ham’s F10 and F12 media allowed a six fold increase. RPMI 1640 and medium 199 (M199) allowed only a three fold increase. Phospholipid concentration in nonsurfactant fraction only doubled during culture, and differences between various media were much less marked. DNA concentration changed little during culture. Morphologic differentiation of epithelial cells was advanced as compared with in vivo timing in a medium allowing maximal surfactant accretion (Waymouth MB 752/1) but not in a medium allowing low surfactant increase (RPMI 1640). The possible role of compositional differences between media is discussed.     

Monoclonal antibodies against human ovarian tumor associated antigen NB/70K: Preparation and use in a radioimmunoassay for measuring NB/70K in serum

Summary Murine monoclonal antibodies (MCAs) against human ovarian tumor associated antigen NB/70K have been prepared. One of these MCAs, NB12123, was chosen for the development of a radioimmunoassay for measuring serum NB/70K levels. In this assay, the average NB/70K level in 75 normal, healthy controls was 11.9 activity units (AU) with an SD of 14.9 AU. The normal cut off value for this assay was set at 45 AU (mean +2 SD). 24 of 46 (52%) ovarian cancer patients, 7 of 18 (39%) patients with benign ovarian cysts or tumors and 3 of 85 (4%) control samples had elevated serum NB/70K levels. Comparison of NB/70K levels measured in the NB12123 assay with levels measured in an assay using a polyclonal antiNB/70K previously developed in our laboratory [13] indicated that although both assays had approximately the same percentage of positive ovarian cancer patient samples, there appeared to be no correlation between the absolute NB/70K levels measured by the two assays. The rank of ovarian cancer patient samples was also different for the two assays. Also, almost 40% of patients with benign ovarian cysts and tumors had elevated serum NB/70K levels as measured by the NB12123 assay as compared to 0% for the polyclonal assay. Reciprocal cross-blocking experiments, absorption studies, and immune precipitate analysis indicated that both the monoclonal NB12123 assay and the polyclonal antiNB/70K assay measured the same population of NB/70K molecules. However, the polyclonal antibody recognizes epitopes in addition to that recognized by NB12123. Taken together, these results suggest that the epitope recognized by NB12123 is not as specific for malignant ovarian tumors as the epitope(s) recognized by polyclonal antiNB/70K and/or that more than the one epitope detected by the MCA is responsible for the specificity for ovarian cancer of the polyclonal NB/70K assay. In spite of this, the greater sensitivity and range of the monoclonal NB12123 assay make it possible to monitor serum NB/70K levels in ovarian cancer patients. In four patients examined, the fluctuating serum NB/70K levels appeared to correlate well with clinical statusSupported in part by ACS # PDT 231 and a grant from the Elsa U. Pardee Foundation     

Stereochemistry of the hydrolysis of α,α-trehalose by trehalase,determined by using a labelled substrate

(1,1′-¹³C)α,α-Trehalose was obtained in 37% yield from the Pavia condensation of 2,3,4,6-tetra-O-benzyl-d-(1-¹³C)glucopyranose, in dichloromethane in the presence of trifluoromethanesulfonic anhydride, followed by the usual deprotection techniques. The hydrolysis of this substrate by cockchafer trehalase was monitored at 37° by using ¹³C-n.m.r. spectroscopy with short recording times. Equimolecular amounts of α- and β-d-glucopyranose are released simultaneously by the action of the enzyme. This result is consistent with a bimolecular substitution mechanism, taking into account previous results involving C-2 asymmetric participation in the catalytic step of hydrolysis of α,α-trehalose. For comparative evaluation of its accuracy, the usual polarimetric technique was also used for the determination of the anomeric configuration of the d-glucose released by the action of the enzyme on α,α-trehalose.