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A variety of methods was developed to characterize mtDNA. The initial aim of these techniques was to try and link diseases with specific mitochondrial defects. As a result of the maternal inheritance trait of mtDNA these techniques facilitate studies of the phylogenetic history and population structure of the human population. It has been shown that mitochondrial DNA typing can be of great value for human identification in forensic cases. The identification of victims of mass-disasters or mass-murders, where human remains can be recovered only after many years have passed, is one of the most challenging fields of forensic identification. By using automated DNA sequencing with fluorescent labels, mitochondrial DNA sequences can be generated rapidly and accurately. Computer software facilitates the rapid comparison of individual and reference sequences.

A variety of methods was developed to characterize mtDNA. The initial aim of these techniques was to try and link diseases with specific mitochondrial defects. As a result of the maternal inheritance trait of mtDNA these techniques facilitate studies of the phylogenetic history and population structure of the human population. It has been shown that mitochondrial DNA typing can be of great value for human identification in forensic cases. The identification of victims of mass-disasters or mass-murders, where human remains can be recovered only after many years have passed, is one of the most challenging fields of forensic identification. By using automated DNA sequencing with fluorescent labels, mitochondrial DNA sequences can be generated rapidly and accurately. Computer software facilitates the rapid comparison of individual and reference sequences.

A unique heparinase was isolated from a recently discovered Gram-negative soil bacterium. The enzyme (heparinase III) was purified by hydroxylapatite chromatography, chromatofocusing, and gel permeation chromatography. The enrichment was 48x, and the specific activity of catalytically pure heparinase was 127 IU/mg of protein. Similar to the heparinase I from Flavobacterium heparinum, heparinase III also degrades heparin to mainly disaccharide fragments. It is specific for heparin and also breaks down heparan sulfate, but not hyaluronic acid and chondroitin sulfate. Heparinase III, however, differs markedly from heparinase I in several other aspects: it has a higher molecular mass (94 versus 43 kDa), pI (9.2 versus 8.5), its Km and kcat are different, and it has a higher energy of activation (15.6 versus 6.3 kcal/mol). Optimal activity was also found at higher pH (7.6 versus 6.5) and temperature (45 versus 37 degrees C). Furthermore, the amino acid composition of heparinase III is quite different from that of heparinase I.

Oxygen has been discovered about 200 years ago. Since then the vital physiological involvement of oxygen in various biologi­cal processes, mainly energy production, has been established. However, in the body molecular oxygen can be converted to toxic oxygen metabolites such as superoxide anion, hydrogen peroxide, the hydroxyl radical and singlet oxygen. These toxic metabolites are produced mainly in the mitochondria, plasma membranes and endoplasmic reticulum.

Oxygen has been discovered about 200 years ago. Since then the vital physiological involvement of oxygen in various biologi­cal processes, mainly energy production, has been established. However, in the body molecular oxygen can be converted to toxic oxygen metabolites such as superoxide anion, hydrogen peroxide, the hydroxyl radical and singlet oxygen. These toxic metabolites are produced mainly in the mitochondria, plasma membranes and endoplasmic reticulum.

Good sperm motility in normozoospermic men was associated with high bound and total sialic acid (SA) and pyruvate concentrations in the seminal plasma, as well as high endogenous (sperm) pyruvate concentrations. The presence of sialidase in the seminal plasma was also demonstrated for the first time. The results suggest that SA is metabolized to pyruvate by a N-acetylneuraminic acid (NANA)-aldolase in the seminal plasma and that pyruvate subsequently serves as an energy source for sperm.

Despite the low fluoride (F) content of the drinking water (less than 0.05 mg/l), an optimum to above optimum daily F intake was shown for the community in Tshikundamalema (Republic of Venda, Southern Africa). In order to evaluate the biological availability of fluoride in the diet, the assimilation of the fluoride ion in enamel was tested. Six age groups (selected according to WHO criteria) consisting of 10 individuals each were used in the study. Enamel biopsies (2N HCl0(4); 3,143 mm2; 8 seconds) were conducted on the mid-labial surfaces of the central maxillary incisors. The fluoride concentrations of the etching solutions were analyzed according to the potentiometric analytical method. The calcium concentrations were determined by means of a flame spectrophotometer. The F content of the outer 10 microns in the enamel of the community was examined in relation to the total daily intake of fluoride for the community. The results obtained from the study showed that, the F content of the enamel of the community (x = 1,133 pg/micrograms; 10 microns depth of etch) correlated with the F intake of the community (x = 3.15 mg F/day). Thus the F content of the diet was biologically available to the body. However, between age groups and sexes, no correlation could be found between the fluoride status and the fluoride intake.

Plasma carcinoembryonic antigen (CEA) levels were performed by radioimmunoassay in 234 patients with histologically proved breast cancer: 181 with advanced metastatic disease and 53 without distant metastases but nodal involvement at time of mastectomy. Four hundred and thirty-four assays were done and correlated with the clinical status of the patients. Values above 2.5 ng/ml were taken as abnormal. Active disease was associated with elevated plasma CEA levels. Very high values were not recorded in 109 patients when they were considered to be in complete remission, while only 22 patients out of 63 patients with progressive disease had normal values. In 16 of these values remained normal despite progression of disease. In 6 patients clinical relapse preceded CEA elevation by 2--5 months. Tumor burden and abnormal serial CEA values showed positive correlation in 38 patients. In 30 patients, change in clinical status and CEA values occurred simultaneously. In only 2 patients an increase in CEA value occurred 2--3 months before clinical documentation of relapse.

Coetzee, Smit & Prozesky (1966) described three serologically related phages PL25, PL26 and PL37 which produce generalized transduction in the Providence hosts. It was decided to investigate the physical properties of the nucleic acid of phage PL25 because this phage could usually be prepared in higher titre than its relatives. Crude lysates (5 × 1010 p.f.u./ml.) were partially purified by differential centrifugation. Pellets were resuspended in saline-citrate buffer (0.15 m-NaCl + 0.015 m-citrate) at pH 7.0 to a titre of about 5 × 1012 p.f.u./ml. Phage DNA was prepared by the method of Mandell & Hershey (1960). The presence and concentration of DNA were determined by the diphenylamine reaction (Kupila, Bryan & Stern, 1961) and ultraviolet absorption at 260 nm. (1 µg. DNA/ml. = 0.0205 absorbency units). Concentrations of DNA ranged from 400 to 600 µg./ml. and no protein was detected by the Lowry procedure (Lowry et al. 1951).

Presumed diploid and haploid cultures ofSporobolomyces salmonicolor andCandida albicans were analysed for their DNA content per cell. Ratios of approximately 2 ∶ 1 were obtained by relating the DNA content of the two phases to ploidy.

In vivo metabolic studies on rats and mice revealed a marked difference in the fluorescent compounds produced after ingestion of aflatoxin B(1). The mouse converted aflatoxin B(1) to three unknown fluorescent compounds, designated x(1), x(2) and x(3) and the known aflatoxin M(1), while the rat was only capable of producing aflatoxin M(1). The results suggested that metabolites x(1), x(2), x(3) and aflatoxin M(1) were not part of a major metabolic pathway, but produced independently. These unknown yellowish-green fluorescent compounds did not seem to be conjugated with sulphate or glucuronic acid.In vitro incubations of various mouse liver cell fractions with aflatoxin B(1) showed that metabolites x(1), x(2), x(3) and aflatoxin M(1), could only be produced by the microsomal fraction and that NADPH was needed as a co-factor. The differences in aflatoxin metabolism by mice and rats are discussed in relation to the apparent resistance of the mouse to the carcinogenic effects of this toxin.

Die handhawing van suur-basisewewig in soogdiere word as ’n goeddeurtrapte paadjie beskou. Ongelukkig verskyn daar gedurig verwarrings in die literatuur, met spesifieke verwysing na die rol van die ammoniumbuffersisteem in die nier gedurende asidose. Dit is ‘n jammerte dat die korrekte stoichiometrie van die regulering van suurbasisewewig nie altyd na waarde geskat word nie. Onlangs is beweer dat die lewer ook ’n rol in pH-regulering speel en wel deur die proses van ureumsintese. Die doel van hierdie oorsigartikel is om die rol van die hepatorenale sisteem in pH-regulering te bespreek.

The regulation of the acid-base balance is generally regarded as a well entrenched area. However, a number of confusing views on pH-homeostasis, especially with reference to the relationship between the kidney and the ammonium buffer system, appear regularly in textbooks. One reason is that the correct stoichiometry of acid-base regulation is not mentioned. Recently the rote of the liver in pH regulation by controlling the bicarbonate concentration through urea synthesis is proposed. In this paper the role of the liver and kidneys as a team is discussed.

Plasma carcinoembryonic antigen (CEA) levels were performed by radioimmunoassay in 234 patients with histologically proved breast cancer: 181 with advanced metastatic disease and 53 without distant metastases but nodal involvement at time of mastectomy. Four hundred and thirty-four assays were done and correlated with the clinical status of the patients. Values above 2.5 ng/ml were taken as abnormal. Active disease was associated with elevated plasma CEA levels. Very high values were not recorded in 109 patients when they were considered to be in complete remission, while only 22 patients out of 63 patients with progressive disease had normal values. In 16 of these values remained normal despite progression of disease. In 6 patients clinical relapse preceded CEA elevation by 2--5 months. Tumor burden and abnormal serial CEA values showed positive correlation in 38 patients. In 30 patients, change in clinical status and CEA values occurred simultaneously. In only 2 patients an increase in CEA value occurred 2--3 months before clinical documentation of relapse.

The importance of vitamin B6 in human nutrition is discussed with special reference to the possibility of undetected long-term subclinical deficiencies in the population at large. It is well known that this vitamin plays a vital role in many physiological processes, such as amino acid metabolism, lipid metabolism and the immune process. In view of the well-documented photo- and thermolability of the different B6 vitamers it stands to reason that serious dangers to health may be associated with undetected, lingering subclinical deficiencies, e.g. induction of and predisposition to various diseases (such as atherosclerosis, multiple sclerosis, degeneration of the myelin sheath of the central nervous system). With the advent of modern analytical techniques it is now imperative that a survey of the vitamin B6 status of a representative sample of the population at large be performed, and that fortification of key food items and/or other means of B6 supplementation be considered pending the outcome of such a survey.

The fluoride content of representative samples of the drinking water and diet of the inhabitants of Tshikundamalema (Republic of Venda, southern Africa) was determined according to the potentiometric method of fluoride analysis. The mean daily intake of fluoride of the inhabitants was compared with the recommended daily intake of fluoride, as advocated by the Mayo Clinic (USA). Despite the low fluoride ion concentration ([F-]) of the drinking water (less than 0.05 mg/l), there exists an optimum to above optimum (3,54-5,32 mg F-) daily intake of fluoride for the adults in Tshikundamalema. The main source of fluoride intake was from beer and green leafy vegetables. The intake of fluoride for the children in Tshikundamalema is sub-optimal (0.598 mg F-/day).

Notwithstanding a close similarity in their chemical structures, the aflatoxins were found to have a wide variation in toxicity as well as a variation in their carcinogenicity.1–5 Clifford, Rees and Stevens6 found a correlation between the magnitude of spectral changes obtained in the DNA-aflatoxin interactions and inhibition of RNA synthesis in liver slices by aflatoxins B1, G1 and G2 and postulated that the degree of interaction with DNA might determine their degree of toxicity. The inhibition of DNA dependent RNA-polymerase after aflatoxin B1, poisoning supports the proposals that the inhibition of nuclear RNA synthesis by aflatoxin B1 was the result of the toxin interacting with the DNA and thereby preventing a transcription of the DNA.

The influence of the metabolites of carcinogens and toxins on macromolecules is becoming of increasing interest in the study of the biochemistry of tumours. Sterigmatocystin, with a chemical structure closely related to aflatoxin, is carcinogenic to rats1 and there are indications that it may also be carcinogenic to Vervet monkeys.2 The type of tumour produced experimentally with sterigmatocystin is morphologically similar to tumours seen in the Bantu races of Southern Africa.

Summary Bacteriophage PL25 was purified by centrifugation in caesium chloride. It has S°20,w = 485; D°20,w = 0.68 × 10-7 cm.2/sec. and m.w. = 54.3 × 106. An equation was derived relating S°20,w and molecular weight of bacteriophages.

Ochratoxin A is one of three chemically related metabolites isolated from Aspergillus ochraceus Wilh. 1 It has been structurally characterised as 7-carboxyl-5-chloro-8-hydroxy-3,4-dihidro-methylisocoumarin linked over its 7-carboxyl group to L-β-phenylalanine.2 The LD50 in rats dosed per os is 20 mg/kg and the toxin causes enteritis, renal necrosis and an increase in the quantity of glycogen in rat liver.3 The route and time course of the metabolism of ochratoxin A was investigated by Nel and Purchase4 in view of the fact that the increase in glycogen only became evident 4 to 5 days after dosing. They concluded that ochratoxin A is hydrolysed in vivo to the isocoumarin moiety (ochratoxin α) most probably by proteolytic enzymes.

THE isolation of intact DNA of the same size and form as that present in the organism is possible in the case of viruses1 but presents problems in bacteria and higher organisms, principally as a result of the action of degrading enzymes and mechanical shear. Isolated bacterial DNA usually has a relatively low molecular weight (S°20,w between 11–33)2,3 except in the cases of E. coli4, B. subtilis4 (S°20,w of 81) and H. influenzae5 (S°20,w of 94).

The isolation of a small gram-negative rod, lacking flagella or pili, and tentatively identified as aFlavobacterium sp., giving exceptionally high yields of heparinase, is reported. The enzyme was partially purified.