Methyl bromide as a microbicidal fumigant for tree nuts.

Methyl bromide (MeBr) has broad microbicidal activity, but its use as a disinfectant for food is limited by the resulting bromide residues. Increasing the MeBr concentration, exposure temperature, or exposure period of a treatment tended to increase both the microbicidal efficacy of MeBr and the bromide residues. Its sporicidal activity was less at high than at low relative humidity within the range of 20 to 99%. Both the efficacy and the resulting residues of a MeBr treatment varied inversely with the load of product in a fumigation chamber due to sorption of the fumigant. Fumigation tests with almond kernels inoculated with Escherichia coli or Salmonella typhimurium indicated that MeBr can be used to disinfect whole nut kernels without resulting in excessive bromide residues, although the MeBr level necessary is higher than that normally used for insect control.     

Purification and Chemistry of Bacteriophage ?

From a stock of varkappa phage grown on Salmonella, a host-range mutant which attacks Escherichia coli was isolated. As in the case of Salmonella, only motile strains of E. coli are sensitive to varkappa. The phage shows an eclipse period of 35 min and a minimal latent period of 52 min. The adsorption rate constant is 3 x 10(-9) ml/min. Adsorption shows a marked dependence on temperature. Bacteriophage varkappa was purified by differential centrifugation and CsCl density gradient centrifugation. It contains deoxyribonucleic acid (DNA) which is double-stranded. The DNA has a molecular weight of 42 million and a guanine plus cytosine content of 57%. Of 68 molecules of DNA inspected, 7 were circular. The phage particle weight is about 90 million.     

Stoichiometric relations in an ant-treehopper mutualism

Carbon : nitrogen : phosphorus (C : N : P) stoichiometry can underlie physiological and life history characteristics that shape ecological interactions. Despite its potential importance, there is much to learn about the causes and consequences of stoichiometric variation in terrestrial consumers. Here we show that treehoppers (Publilia modesta) tended by ants (Formica obscuripes) contained lower N concentrations than treehoppers on plants from which ants were excluded. Ant presence also affected nutrient concentrations in host plants: on plants with ants, leaves contained uniformly low concentrations of N; on plants without ants, N concentrations were low only in the few leaves fed upon by treehoppers at the time of collection. We suggest treehopper feeding reduces leaf nutrient levels and ants positively affect treehopper abundance, producing a top–down effect on plant quality. Determining the causes of these stoichiometric changes should help elucidate factors guiding the dynamics of conditional mutualisms between ants and homopterans.     

Role of the tubulin-microtubule system in lymphocyte activation

The role of the tubulin-microtubule system was examined in human peripheral blood leukocytes after activation with phytohemagglutinin (PHA). Soluble tubulin and microtubules were measured with a [(3)H]colchicine-binding assay. It was found that the tubulin content of PHA-activated lymphocytes was consistently increased relative to total protein content after 36 h of culture. There was no increase in the proportion of total tubulin synthesis which was present as microtubules at 36 h. Nevertheless, as a result of increased tubulin synthesis, there was a two-to three-fold increase in total microtubular mass. Colchicine, which disrupts microtubles, was used to assess the role of microtubule assembly in the sequence of events which follow lymphocyte activation, namely lymphokine release, protein synthesis, RNA synthesis, and DNA synthesis. Colchicine consistently inhibited DNA synthesis but did not inhibit release of the lymphokine, osteoclast activating factor (OAF). Protein and RNA syntheses were inhibited much less than DNA synthesis. The fact that some effects of PHA on lymphocytes appear to require intact microtubules and at least one does not suggest that the microtubule dependent step in PHA-stimulated lymphocyte activation occurs at a stage after propagation of the signal from the membrane to the cell interior.     

Species differences in biotransformation of 17α-cyanomethylestradiol 3-methyl ether

Following oral administration of 9,11- ³H-17α-cyano-methylestra-1,3,5(10)-triene-3,17-diol 3-methyl ether, urinary metabolites were studied in man, baboon, beagle dog, minipig and rat. The metabolite pattern revealed remarkable species differences, especially in quantitative respects. 17α-Cyanomethylestra-1,3,5(10)-triene-3,17-diol, 17α-cyanomethylestra-1,3,5(10)-triene-2,3,17-triol 2-methyl ether, 17α-hydroxymethylestra-1,3,5(10)-triene-3,17-diol and 17α-cyanomethylestra-1,3,5(10)-triene-3,16$\text{6}\text{5}$,17-triol were isolated as principal metabolites. In rat bile, a metabolite was tentatively identified as aγ-lactone of a 17α-carbozymethyl-16α-hydroxy compound.     

Cytokines involved in monocyte mediated tumor cell death and growth inhibition in serum-free medium.

In a serum-free culture system, the release of TNF, lI-1, lI-6, IFN-alpha, and IFN-beta during interaction of elutriated human monocytes (MO) with human tumor cells (TC) was studied by ELISA-technique. Contributions of these cytokines to inhibition of TC-growth and to induction of TC-death by supernatants (SU) gained from such MO/TC-interaction cultures were investigated using affinity chromatography for removal of individual cytokines. Although the TC used are relatively insensitive to recombinant human TNF, withdrawal of TNF causes 50% to 75% reduction of SU-induced TC-death rates, suggesting that susceptibility to TNF is raised during MO/TC-interaction by the other cytokines. Individual removal of other cytokines does not cause reduction of SU-mediated TC-death. However, combined withdrawal of lI-1 and IFN-alpha/beta causes in 2 of 4 TC-lines significant reduction of TC-death. Combined removal of TNF, IFN-alpha/beta, lI-1, and lI-6 leads to complete prevention of SU-mediated growth inhibitory and lytic effects, suggesting that besides these cytokines other signals are not involved significantly. SU-effects can be mimicked by appropriate combinations of authentic cytokines. The response of TC to SU- or cytokine-exposure is strikingly dependent on TC-density, leading at subconfluent TC-density exclusively to inhibition of growth and at postconfluent TC-density to induction of cell death. The principal effect of SU or cytokine combinations in this context seems to be the activation of growth inhibitory signal transduction pathways leading to TC-death in postconfluent TC-populations exclusively if growth stimulatory pathways are activated at the same time. Mouse L cells do not follow this reaction pattern: Their death is exclusively dependent on the presence of TNF in SU and they die upon SU-exposure at postconfluent as well as at subconfluent cell density.     

Influence of contraceptive pill and menstrual cycle on serum lipids and high-density lipoprotein cholesterol concentrations.

The fluctuations of serum lipid and lipoprotein concentrations within one cycle were studied both in women using and not using oral contraceptives. High-density lipoprotein cholesterol decreased significantly from 1.47 mmol/l (57 mg/100 ml) to 1.30 mmol/l (50 mg/100 ml) during one contraceptive cycle in eight women and rose again to the initial value during the pill-free days. The mean concentration of total cholesterol also fell significantly as a result of the decrease of high-density lipoprotein cholesterol and of a not significant decrease of low-density lipoprotein cholesterol. The mean serum triglyceride concentration did not change significantly. The fluctuations in the concentration of serum lipids and lipoproteins in 10 women not using oral contraceptives were smaller than in the women using oral contraceptives and no significant changes in the concentrations were found during one cycle. Thus, high-density lipoprotein cholesterol concentration decreases during each contraceptive cycle. The time of blood sampling during the cycle is, therefore, of vital importance in interpreting the effect of oral contraceptives on high-density lipoprotein cholesterol. In women not using oral contraceptives blood can be sampled on random days during the cycle.     

Incidence of Aflatoxin in California Almonds

In a survey of California almonds, aflatoxin was found in 14% of 74 samples of unsorted, in-shell almonds as received by the processor in 1972, but it occurred at very low levels (below 20 parts per billion [ppb]) in 90% of the contaminated samples. The overall proportion of individual nuts contaminated was especially low and is estimated with 95% probability to have been in the range of 1 nut/55,300 nuts to 1 nut/14,700 nuts. Aflatoxin contamination is not restricted to any particular section of the almond-growing region of California. Commercial sorting procedures are effective in removing most aflatoxin-contaminated nutmeats, since none of 26 samples of processed, whole nutmeats contained aflatoxin. In contrast, 13 of 27 samples of diced almonds were contaminated, but nine of these 13 samples contained less than 20 ppb. Only one of 25 samples of sliced nutmeats contained aflatoxin (4 ppb). Thus, aflatoxin incidence in almonds varies greatly with the category of finished product. The apparent high incidence in diced nutmeats is probably due mostly to the more uniform distribution of aflatoxin occurring in this product (because of its small particle size) than that occurring in the other products. Sample size requirements for monitoring aflatoxin in almonds are discussed.     

Estrogen biosynthesis and its inhibition--a review

A short review is given about extragonadal sources of estrogens via androgen aromatization; the possible importance of this aromatization; the mechanism of aromatization, the inhibition of androgen aromatization by steroidal compounds; the importance and possible usefulness of such an inhibition.