A spectrophotometric method for measuring the breakdown of hydrogen peroxide by catalase.

Publisher Summary This chapter discusses the assay of catalases and peroxidases are: (1) catalase assay by disappearance of peroxide; (2) method for crude cell extracts; (3) direct spectrophotometric assay of catalase and peroxidase in cells and tissues; and (4) peroxidase assay by spectrophotometric measurements of the disappearance of hydrogen donor or the appearance of their colored oxidation products. Two methods are described for the catalase assay by disappearance of peroxide are: ultraviolet spectrophotometry and permanganate titration. Ultraviolet spectrophotometryis a method devised, on the basis of the absorption curves for peroxide solutions, for determining the activity of catalase by direct measurements of the decrease of light absorption in the region 230 to 250 mμ caused by the decomposition of hydrogen peroxide by catalase. In the case of method for crude cell extracts, oxygen evolution caused by the decomposition of hydrogen peroxide is measured with the conventional manometric technique. Peroxidase assay by spectrophotometric measurements of the disappearance of hydrogen donor or the appearance of their colored oxidation products includes the guaiacol test and the pyrogallol test.

The assay of catalases and peroxidases.

Measurement of catalase activity in tissue extracts.

The safe disposal of human excreta is of paramount importance for the health and welfare of populations living in low income countries as well as the prevention of pollution to the surrounding environment. On-site sanitation (OSS) systems are the most numerous means of treating excreta in low income countries, these facilities aim at treating human waste at source and can provide a hygienic and affordable method of waste disposal. However, current OSS systems need improvement and require further research and development. Development of OSS facilities that treat excreta at, or close to, its source require knowledge of the waste stream entering the system. Data regarding the generation rate and the chemical and physical composition of fresh feces and urine was collected from the medical literature as well as the treatability sector. The data were summarized and statistical analysis was used to quantify the major factors that were a significant cause of variability. The impact of this data on biological processes, thermal processes, physical separators, and chemical processes was then assessed. Results showed that the median fecal wet mass production was 128 g/cap/day, with a median dry mass of 29 g/cap/day. Fecal output in healthy individuals was 1.20 defecations per 24 hr period and the main factor affecting fecal mass was the fiber intake of the population. Fecal wet mass values were increased by a factor of 2 in low income countries (high fiber intakes) in comparison to values found in high income countries (low fiber intakes). Feces had a median pH of 6.64 and were composed of 74.6% water. Bacterial biomass is the major component (25-54% of dry solids) of the organic fraction of the feces. Undigested carbohydrate, fiber, protein, and fat comprise the remainder and the amounts depend on diet and diarrhea prevalence in the population. The inorganic component of the feces is primarily undigested dietary elements that also depend on dietary supply. Median urine generation rates were 1.42 L/cap/day with a dry solids content of 59 g/cap/day. Variation in the volume and composition of urine is caused by differences in physical exertion, environmental conditions, as well as water, salt, and high protein intakes. Urine has a pH 6.2 and contains the largest fractions of nitrogen, phosphorus, and potassium released from the body. The urinary excretion of nitrogen was significant (10.98 g/cap/day) with urea the most predominant constituent making up over 50% of total organic solids. The dietary intake of food and fluid is the major cause of variation in both the fecal and urine composition and these variables should always be considered if the generation rate, physical, and chemical composition of feces and urine is to be accurately predicted.

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The Characterization of Feces and Urine: A Review of the Literature to Inform Advanced Treatment Technology

These companion volumes have been edited by two of the leading personalities in British obstetrics and gynaecology. Both have made notable contributions to their subjects, and each is an outstanding teacher who has always subscribed to the dictum that teaching needs research and research needs teaching. With such a philosophy inspiring their professional work, it would follow, therefore, that any publication of theirs would be devoid of pedantry. The reader will not be disappointed and will find an original, lucid, and constructive presentation. Their aim has been to present, so far as possible, a description of obstetrics and gynaecology as practised in Britain. It may be pertinently asked in what way British practice differs from that in other countries. The editors have forestalled this question. They believe that in obstetrics the chief modern contribution from Britain has been \" the results of the study of the relation of social and economic conditions to the health of the pregnant woman and the condition of her child.\" In gynaecology it is conservatism that has been the characteristic British contribution. Sir Eardley Holland has been responsible for the general editorship of the volume on obstetrics and has been assisted by 38 contributors selected from almost all the university and teaching centres. Professor Bruce Mayes, of Sydney University, is the sole overseas contributor. Included in this obstetric oligarchy are physicians, paediatricians, anatomists, a psychiatrist, a venereologist, a medical statistician, and a barrister. The co-authors have been allocated subjects in which they are acknowledged experts; thus each chapter is authoritative and at the same time original. Mr. Aleck Bourne has enlisted the help of 21 authors for the volume on gynaecology, and among these is an anatomist, a psychiatrist, a venereologist, and a barrister. He has always emphasized the importance of the basic sciences in relation to clinical medicine ; the reader will appreciate this from the contents and their presentation. It is doubtful whether a general work of this calibre should contain even brief accounts and exiguous illustrations of operations. The excellent chapter on the cervix uteri is impaired by the descriptions (and diagrams) of the operations for amputation of the cervix and trachelorrhaphy. Those who need pictorial assistance for their surgical technique would refer to a tome on operative surgery. Both volumes are illustrated with diagrams and plates of artistic distinction, and the publishers are to be congratulated on their production. The editors have succeeded in their aim. Their task has been sisyphean, but they have produced a magnunm opus which for many years will be indispensable to those who practise obstetrics and gynaecology. W. C. W. NIXON.

https://www.bmj.com/content/bmj/1/4957/29.2.full.pdf

Identification of enterobacteriaceae

Dielectric properties of carbohydrate-water mixtures at microwave frequencies

Suspensions of Escherichia coli and Bacillus subtilis spores were exposed to conventional thermal and microwave energy at 2,450 MHz. The degrees of inactivation by the different energy sources were compared quantitatively. During the transient heating period by microwave energy, approximately a 6 log cycle reduction in viability was encountered for E. coli. This reduction was nearly identical to what is expected for the same time-temperature exposure to conventional heating. Heating of B. subtilis spores by conventional and microwave energy was also carried out at 100 C, in ice and for transient heating. The degree of inactivation by microwave energy was again identical to that by conventional heating. In conclusion, inactivation of E. coli and B. subtilis by exposure to microwaves is solely due to the thermal energy, and there is no per se effect of microwaves.

Effect of Microwaves on Escherichia coli and Bacillus subtilis.

Photometric determination of catalase activity

The factors which affect the dielectric response of food materials are examined in an attempt to establish a predictive model and to obtain a more basic understanding of dielectric properties. Detailed dielectric measurements were performed on rehydrated non-fat dry milk using the precision slotted line technique, at temperatures of 25, 35, 45, and 55°C and at frequencies of 300, 1000, and 3000 MHz. Solute-solute and solute-solvent interaction were found to reduce the dielectric loss factors to levels substantially below those predicted by chemical composition alone; therefore, the dielectric loss cannot be predicted from a linear, additive model based on composition. The results of dielectric measurements of solid food products, beef and turkey were reported. Conductivities of beef juice obtained from cooking were measured and the dielectric losses at 5 to 65°C and 300, 915, and 2450 MHz calculated based on the measured conductivities.

Dielectric Properties of Food Materials

SUMMARY— The finished drying of potato chips represents the first large-scale use of microwaves in the food industry on a continuous basis. Hence it was deemed desirable to study the dielectric properties of various types of commercial cooking oils.

The dielectric constant (ɛ), and loss tangent (tans) of 11 commercial fats and oils have been determined at three different temperatures and at three different frequencies in the microwave range. The differences in dielectric properties among these fats and oils appear to be attributable to the phase (solid vs. liquid) of the material and generally correspond to the degree of unsaturation as evidenced by iodine values. The differences in loss factors among these fats and oils at any given temperature and frequency (within the range at which the measurements were made) are too small to be of any practical importance in selecting any one of them for use in heating processes using microwaves or in choosing an optimal frequency (300, 1000 or 3000 megahertz, MHz).

Data for one of the oils (number 9) were obtained over a wider range of frequencies and indicate that the loss factor peak(s) is/are found in the frequency range of 100 to 1000 MHz. Furthermore, from the data obtained for the other oils, it should be safe to assume that this oil is representative of dielectric properties of the entire group. The dielectric properties of bacon fat rendered by microwaves are almost identical to those of bacon fat rendered by conventional means.

Samuel A. Goldblith

Papers

Dielectric properties of carbohydrate-water mixtures at microwave frequencies

Effect of Microwaves on Escherichia coli and Bacillus subtilis.

Photometric determination of catalase activity

Dielectric Properties of Food Materials

Dielectric Properties of Commercial Cooking Oils