Proof of safety vs proof of hazard

This paper refines and extends the work of Bross (1985, Biometrics 41, 785-793). One method to determine whether an environment is safe or hazardous is to frame the problem in the context of hypothesis testing. Any "proof" of safety or hazard will depend on the size of both the Type I and Type II errors associated with the test. Many past environmental monitoring programs, however, have ignored the power of the design, regardless of whether the objective was proof of safety or hazard.     

Enthalpy and entropy changes for the intercalation of small molecules to DNA. II. Ethidium and propidium fluoride

Enthalpy changes (ΔH_B) for the binding of ethidium (a monocation) and propidium (a dication) to calf thymus DNA have been determined calorimetrically in piperazine-N, N′-bis(2-ethanesulfonic acid) buffer with the fluoride ion as the counterion. Heats of dilution for the fluoride salts of ethidium and propidium were substantially less than the corresponding values found for other halide salts of these cations. At a Na⁺ ion concentrations of 0.019, ΔH_B = ?8.3 and ?7.9 ± 0.3 kcal mol^?1 for ethidium and propidium, respectively. For these two cations, just as was observed for the naphthalene monoimide (monocation) and diimide (dication) [H. P. Hopkins, K. A. Stevenson, and W. D. Wilson, (1986) J. Sol. Chem. 15 , 563–579], ΔH_B is within the same experimental error for both cations. Apparently, charge–charge interactions in DNA–cation complexes produce only small changes in the enthalpy for the system. In the concentration range 0.019–0.207, the ΔH_B values for propidium did not depend appreciably on the Na⁺ ion concentration, and a similar pattern was shown to exist for ethidium. When these results were combined with ΔG_B values for the binding of these cations to DNA, we found the variation of ΔS_B with Na⁺ ion concentration to be remarkably close to the predictions of modern polyelectrolyte theory, i.e., propidium binding to DNA causes approximately twice as many Na⁺ ions to be released into the bulk solution as does the binding of ethidium. The much stronger binding of propidium, relative to ethidium, at low ionic strengths is thus seen to be primarily due to entropic effects.     

Enzymic interesterification of fats: Laboratory and pilot-scale studies with immobilized lipase from Rhizopus arrhizus

An immobilized lipase suitable for fat interesterification has been prepared by precipitation with acetone of a commercial lipase from Rhizopus arrhizus onto diatomaceous earth. As observed previously with a less active enzyme from Aspergillus sp., the interesterification activity was enhanced by addition of purified lipase or by high loadings of commercial enzyme. The interesterification activities reached maximum values in both cases. For immobilized preparations with purified enzyme, interesterification activity was also enhanced by the presence of a precoat of glutaraldehyde cross-linked commercial lipase. A 2.9-L column of immobilized lipase was used to interesterify batches of shea oleine (67 kg) and shea oil (40 kg). Little activity was lost processing shea oleine, but slow poisoning of the bed occurred when shea oil was fed to the column.     

Production of and responsiveness to interleukin 2 in autoimmune BXSB mice

BXSB male mice serve as one of several murine models of human systemic lupus erythematosus. T-cell abnormalities in these mice involve decreased production of and responsiveness interleukin 2 (IL-2) and are age-related. The studies presented here investigated the mechanism of these T-cell defects. The results suggest that excessive suppressor-T-cell activity as well as soluble inhibitors of IL-2 production and activity, including PGE, are not responsible for the low levels of IL-2 observed in culture supernatants of Con A-stimulated lymphocytes from "old" (3-6 months) BXSB male mice. Supplementation of Con A-stimulated lymphocyte cultures from BXSB male mice with human IL-1 or normal murine accessory cells did not augment IL-2 production. Reduced proliferative responses were observed in bulk cultures of Con A- or alloantigen-stimulated "old" BXSB male lymphocytes, which were not enhanced by exogenous IL-2. Limiting dilution analysis revealed reduced frequencies of Con A- and alloantigen-inducible IL-2-reactive T cells in these mice. These results suggest intrinsic defects in the ability of T cells from "old" BXSB male mice to be activated to produce and respond to IL-2.     

Gibberellic acid by solid state fermentation: Consistent and improved yields

Five strains each of Gibberella fujikuroi and Fusarium monoliforme were screened to select G. fujikuroi P-3, a strain capable of giving consistent production of gibberellic acid (GA(3)) by solid state fermentation (SSF). The comparative production of GA(3) by SSF and submerged fermentation (SmF) indicated better productivity with the former technique. The accumulation of GA(3) was 1.626 times higher in the case of SSF. On the basis of available carbohydrates in the media, the percent conversions were 0.096 and 0.156 in SmF and SSF, respectively. The use of coarse wheat bran of the particle size of 0.3-0.4 cm resulted in an increase of 2.5 times in the yield of GA(3). The enrichment of commercial wheat bran with soluble starch gave enhanced accumulation to an extent of 3.5 times. The relation between GA(3) production and cell growth in SSF was similar to that encountered in SmF. The consistent and improved yields to a tune of 1.22 g GA(3) per kilogram dry moldy bran (DMB) establish the potential and feasibility of SSF for the production of GA(3) by G. fujikuroi P-3. On preliminary cost analysis, a net savings of about 60% and 50% on fermentation medium cost and the expenditure on down-stream processing, respectively, as compared to the presently employed SmF technique was evident.     

Phospholipase C from human sperm specific for phosphoinositides

Human sperm lysates were incubated in the presence of 1-[14C]stearoyl-2-acyl-sn-glycero-3-phosphocholine, 1-[14C]stearoyl-2-acyl-sn-glycero-3-phosphoethanolamine or 1-[14C]stearoyl-2-acyl-sn-glycero-3-phosphoinositol. Only the latter substrate was hydrolyzed to a significant extent, with a concomitant formation of 1-[14C]stearoyl-2-acyl-sn-glycerol. Furthermore, incubation of phosphatidyl[3H]inositol under the same conditions was accompanied by the formation, in roughly equal amounts, of [3H]inositol 1-phosphate and [3H]inositol 1:2-cyclic monophosphate. Finally [32P]phosphatidylinositol 4-phosphate and [32P]phosphatidylinositol 4,5-bisphosphate were degraded into [32P]inositol 1,4-bisphosphate and [32P]inositol 1,4,5-trisphosphate, respectively. The phosphoinositide-specific phospholipase C was activated by calcium (optimal concentration 5-10 mM) and inhibited by EGTA, although endogenous calcium supported a half-maximal activity. The enzyme displayed an optimal pH of 6.0 and an apparent Km of 0.08 mM. Its specific activity was around 10 nmol/min per mg protein, which is approximately the same as that found in human blood platelets. Subcellular fractionation revealed that 55% of the enzyme was solubilized under conditions where 80% of acrosin appeared in the supernatants. The majority of the particulate phospholipase C activity (37% of total) was found in the 1000 X g pellet, which contained only 8% of total acrosin activity. Further fractionation of spermatozoa into heads and tails indicated no specific enrichment of phospholipase C activity in any of these two fractions. However, owing to a 4-fold higher protein content in the head compared to the tail fraction, it is concluded that about 80% of particulate phospholipase C activity is located in sperm head. The physiological significance of this enzyme is discussed in relation to a possible role in acrosome reaction and (or) in egg fertilization.     

Labeling of phosphatidylcholines of retina subcellular fractions by [1-14C]eicosatetraenoate (20:4(n-6)), docosapentaenoate (22:5(n-3)) and docosahexaenoate (22:6(n-3))

The labeling of molecular species of phosphatidylcholine (PC) has been studied in bovine retinas incubated for 2 h with (1-14C)-labeled (n-6) eicosatetraenoate (n-3) docosapentaenoate and (n-3) docosahexaenoate (20:4, 22:5 and 22:6, respectively) and in four subcellular fractions isolated after such incubations. Of the total radioactivity incorporated in PC, the following percentages of the above fatty acids, respectively, are found in its dipolyunsaturated species: 58, 56 and 53% in rod outer segments; 29, 41 and 49% in mitochondria; 24, 28 and 39% in microsomes; 12, 14 and 16% in postmicrosomal supernatants; 28, 36 and 58% in entire retinas. The remainder percentages are in tetra-, penta- and hexaenoic species of PC, respectively. The levels of pentaenoic species in the PCs of all fractions are similar, while tetraenes are lowest and hexaenes highest in photoreceptor membranes. Dipolyunsaturated species are highly concentrated in photoreceptor membranes, but are minor components of mitochondrial, microsomal and cytosolic PC. The specific radioactivities of tetraenoic, pentaenoic and hexaenoic PCs are decreasingly lower in the following order: postmicrosomal supernatants, microsomes, mitochondria, photoreceptor membranes. In contrast, the specific radioactivities of dipolyunsaturated PCs are higher in mitochondria and microsomes than in the other fractions, especially with 22:5 and 22:6. It is suggested that mitochondria as well as the endoplasmic reticulum could play a role in the synthesis and further modifications of dipolyunsaturated PCs before being supplied to photoreceptor membranes.