An alcohol-soluble Schiff's reagent: a histochemical application of the complex between Schiff's reagent and phosphotungstic acid.

A schedule for staining partially hydrated PAS-positive structures using non-aqueous solutions has been devised. Tissues are dewaxed, taken down to 70% alcohol, oxidised for 10 min in a 1% w/v alcoholic solution of periodic acid, treated with an alcoholic solution of phosphotungstic acid-Schiff reagent complex (PTA-Schiff reagent) for 25 min, washed in alcohol, cleared in xylene and mounted in a synthetic medium. The PTA-Schiff reagent complex prepared from de Tomasi Schiff reagent by precipitation with PTA may be stored in the deep freeze for many months and dissolved freshly in alcohol for use. The PTA-Schiff reagent used as above allows staining of highly water soluble materials such as dextran. From blocking and digestion studies the mode of action seems similar to de Tomasi Schiff reagent. The partial hydration of the tissues prior to reaction was found to be essential for effective staining.     

Sequential staining of DNA-aldehyde with Schiff's reagent and acriflavine-SO2.

Acid hydrolysed DNA of rat liver was stained with Schiff's reagent at pHs 1.7 or 3.0 followed by staining with acriflavine-SO2 at pH 2.0 as well as with acriflavine-SO2 followed by Schiff's reagent at pH 1.7 or 3.0. Nuclei stained with Schiff's reagent at pH 1.7 were brown-yellow and an analysis of their absorption characteristics revealed two peaks--one at 470 nm and the other at 570 nm. Although nuclei stained with Schiff's reagent at pH 3.0 followed by acriflavine-SO2 were deep magenta in colour, they also showed similar peaks of maximum absorption. Identical peaks were also seen when the sequence of staining was reversed. It is suggested that in the conventional Feulgen-type reactions only some of the DNA-aldehyde molecules are stained; the remaining molecules can be stained by sequential application of another Schiff or Schiff-type reagent such as acriflavine-SO2. The possible mechanism of staining in these cases has been discussed.     

An alcohol-soluble Schiff's reagent: A histochemical application of the complex between Schiff's reagent and phosphotungstic acid

Summary A schedule for staining partially hydrated PAS-positive structures using non-aqueous solutions has been devised. Tissues are dewaxed, taken down to 70% alcohol, oxidised for 10 min in a 1% w/v alcoholic solution of periodic acid, treated with an alcoholic solution of phosphotungstic acid-Schiff reagent complex (PTA-Schiff reagent) for 25 min, washed in alcohol, cleared in xylene and mounted in a synthetic medium. The PTA-Schiff reagent complex prepared from de Tomasi Schiff reagent by precipitation with PTA may be stored in the deep freeze for many months and dissolved freshly in alcohol for use. The PTA-Schiff reagent sued as above allows staining of highly water soluble materials such as dextran. From blocking and digestion studies the mode of action seems similar to de Tomasi Schiff reagent. The partial hydration of the tissues prior to reaction was found to be essential for effective staining.     

Studies on groundnut proteins. III. Physicochemical properties of arachin prepared by different methods

The homogeneity of arachin prepared by different methods was determined by the techniques of polyacrylamide gel electrophoresis, DEAE-cellulose chromatography, and ultracentrifugation. Arachin obtained by the method of Tombs (Biochem. J.96, 119, 1965) or Dawson (Anal. Biochem.41, 305, 1971) appeared to be homogeneous by these techniques. Total groundnut proteins, extracted in 1 m NaBr solution and subjected to double precipitation with 23% (NH₄)₂SO₄, also gave a homogeneous arachin preparation. These three homogeneous arachin preparations differed in their rate of hydrolysis by alpha-chymotrypsin, heat coagulation, and dissociation into subunits. However, SDS¹ and GuHCl denatured them to the same extent, as could be judged by the difference spectra. The phosphorus and carbohydrate content of the three preparations did not differ significantly.     

Studies on groundnut proteins. V. Physico-chemical properties of arachin prepared by different methods.

ORD,¹ CD, and fluorescence spectra of arachin prepared by Tombs' (Biochem. J., 96, 119; 1965), Dawson's (Anal. Biochem., 41, 305; 1971) or Shetty and Rao's (Anal. Biochem., 62, 108; 1974) procedure were measured; the effect of denaturants such as SDS, GuHCl, and acid was also determined. ORD and CD spectra showed differences, whereas fluorescence spectra did not show any difference. The effect of the denaturants was the same on the three arachins. At low concentrations of GuHCl (<2 m), the denaturant was bound by the protein molecule without causing any conformational change. The binding affinity varied among the arachins.     

Bacteriological quality and shelf life of ground beef.

The bacteriological quality of unfrozen raw ground beef was evaluated after 0, 3, 6, 9, 12, 15, and 18 days of storage at 29 +/- 1 F (-1.7 +/- 0.6 C). At the time of fabrication, all of the ground beef samples contained 10(6) or fewer total aerobic and psychrotrophic bacteria/g; 81% contained 100 or fewer coliforms/g; 94% contained 100 or fewer Escherichia coli/g; and all of the samples contained 100 or fewer coagulase-positive Staphylococcus aureus and Clostridium perfringens/g. Total aerobic and psychrotrophic bacteria increased by 1 log between 3 and 18 days of storage. Coliform and E. coli counts decreased during storage, whereas coagulase-positive S. aureus and C. perfringens counts did not change significantly. These data indicate that meat processors, wholesalers, and retailers could improve the bacteriological quality and prolong the shelf life of ground beef packaged in oxygen-impermeable film if the temperature of product never exceeded 29 +/- 1 F (-1.7 +/- 0.6 C).     

Bacteriological quality and shelf life of ground beef.

The bacteriological quality of unfrozen raw ground beef was evaluated after 0, 3, 6, 9, 12, 15, and 18 days of storage at 29 +/- 1 F (-1.7 +/- 0.6 C). At the time of fabrication, all of the ground beef samples contained 10(6) or fewer total aerobic and psychrotrophic bacteria/g; 81% contained 100 or fewer coliforms/g; 94% contained 100 or fewer Escherichia coli/g; and all of the samples contained 100 or fewer coagulase-positive Staphylococcus aureus and Clostridium perfringens/g. Total aerobic and psychrotrophic bacteria increased by 1 log between 3 and 18 days of storage. Coliform and E. coli counts decreased during storage, whereas coagulase-positive S. aureus and C. perfringens counts did not change significantly. These data indicate that meat processors, wholesalers, and retailers could improve the bacteriological quality and prolong the shelf life of ground beef packaged in oxygen-impermeable film if the temperature of product never exceeded 29 +/- 1 F (-1.7 +/- 0.6 C).     

不同有机酸对铅胁迫小麦幼苗的缓解作用

研究了在铅胁迫条件下,加入外源有机酸对小麦铅毒害的缓解效应。结果表明,低浓度的草酸和乙酸能增加铅胁迫小麦叶绿素含量,不同程度地提高SOD、CAT、POD活性,降低MDA含量,而高浓度草酸和乙酸及柠檬酸对此则无明显的缓解作用;乙酸处理减少根系活跃吸收面积,柠檬酸能明显提高根系活力。草酸对铅胁迫的缓解效果最明显。     

Effects of different organic acids on 2,3-butanediol production by Serratia marcescens

考察了不同的短链有机酸对粘质沙雷氏菌合成2,3-丁二醇的影响,结果表明乙酸、乳酸、丙酮酸、琥珀酸、延胡索酸和柠檬酸均能在一定程度上提高2,3-丁二醇的产量,其中乙酸的效果最为明显,在基础培养基中添加6 g/L乙酸,与对照相比,2,3-丁二醇的产量提高了91.06％,此外菌体干重也提高了58.28％.为了揭示其中的调控机制,构建了启动子:lacZ融合报告载体,lacZ活性测定显示六种有机酸均可提高报告基因β-半乳糖苷酶的表达,其中乙酸提高β-半乳糖苷酶活性近4倍,暗示六种有机酸促进2,3-丁二醇的合成可能与诱导该合成途径相关基因的表达有关.     

不同有机酸对粘质沙雷氏菌合成2,3-丁二醇的影响

考察了不同的短链有机酸对粘质沙雷氏菌合成2,3－丁二醇的影响,结果表明乙酸、乳酸、丙酮酸、琥珀酸、延胡索酸和柠檬酸均能在一定程度上提高2,3－丁二醇的产量,其中乙酸的效果最为明显,在基础培养基中添加6g／L乙酸,与对照相比,2,3．丁二醇的产量提高了91．06％,此外菌体干重也提高了58．28％。为了揭示其中的调控机制,构建了启动子：lacZ融合报告载体,fncz活性测定显示六种有机酸均可提高报告基因B．半乳糖苷酶的表达,其中乙酸可提高B．半乳糖苷酶活性近4倍,暗示六种有机酸促进2,3－丁二醇的合成可能与诱导该合成途径相关基因的表达有关。     

The production of organic acids.

The production of organic acids covers two aspects: first, the metabolic pathways involved in the biosynthesis, and, second, the industrial process strategy adopted. The review seeks to show the underlying biochemical similarities in the biosynthesis of organic acids and the resulting similarities in the commercial processes. Two groups of acids are defined, those with a "long" biosynthetic path from glucose, involving much of the glycolytic pathway and the tricarboxylic acid cycle, and those acids with a "short pathway", essentially a biotransformation of glucose. The regulation of the pathways and the future developments in metabolic control theory and genetic manipulations relating to them are considered. The organisms used industrially are also limited, Aspergillus sp. and Candida yeasts; again the underlying metabolic similarities lead to similar strategies for all the acids discussed.     

A chemical-modification approach to the olfactory code. Studies with a thiol-specific reagent

The effects of thiol-specific reagents on the amplitude of the electro-olfactogram (E.O.G.) responses elicited from frog olfactory mucosa by pulses of odorant vapours was studied. The impermeant thiol-specific reagent mersalyl [(3-{[2-(carboxymethoxy)-benzoyl]amino}-2-methoxypropyl)hydroxymercury monosodium salt] brings about a rapid decrease in the E.O.G. signal obtained with the odorant pentyl acetate. The extent of the decrease is proportional to the concentration of the mersalyl applied and the effect of the reagent is partially but incompletely reversed by treatment of the labelled mucosa with dithiothreitol. The sites labelled by mersalyl can be protected by pretreating the mucosa with a dilute solution of the odorant pentyl acetate and leaving the solution in contact with the tissue after the addition of mersalyl. When the protecting odorant is washed out of the tissue, the original E.O.G. amplitude is regained. Pentyl acetate applied to the mucosa protected the E.O.G. response to vapour pulses of the following odorants from the effects of mersalyl: n-butyric acid, n-butyl acetate, phenylacetaldehyde and cineole (1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane). The pentyl acetate applied to the mucosa failed to protect the E.O.G. response to vapour pulses of the following odorants from the effects of mersalyl: butan-1-ol, benzyl acetate, nitrobenzene, beta-ionone and linalyl acetate. The significance of the differential protection effects for the odour-quality-coding mechanism in the olfactory primary neurons is discussed. It is suggested that the olfactory code at this level of the olfactory system may be elucidated by chemical-modification methods.