Putative melatonin receptor in human spermatozoa.

Melatonin is present in human semen, and may affect sperm motility. The presence of melatonin receptors on spermatozoa has not yet been reported. Detection of melatonin-binding sites may be limited because of the masking of such sites by sialic acid. Spermatozoa were obtained from eligible human donors, incubated with neuraminidase to remove sialic acid residues, and saturation binding assays were carried out using 2-125I-melatonin as a receptor probe. Consistent 125I-melatonin binding could only be obtained after spermatozoa were treated with neuraminidase. Scatchard analysis revealed a low-affinity binding site (ML-2) with a Kd value of 127 +/- 6 nM and a Bmax of 25 +/- 4.5 fmol/mg protein. These results present evidence of melatonin-binding sites in spermatozoa. Sialic acid possibly regulates the binding of melatonin to these sites.

Amino acid composition of dentine in permanent human teeth.

Dentine of permanent mandibular incisors from nine individuals was hydrolysed and the amino acid composition determined by ion-exchange chromatography against a standard calibrant of 41 amino acids. Nineteen amino acids were detected, including small quantities of 1-methylhistidine and asparagine, two amino acids whose existence had apparently not been recorded before in human dentine. The total content of hydroxylysine plus lysine varied between 2.6 and 3.3 residues per 100 (SD, 0.74) in different teeth, which therefore did not support previous studies that had proposed a constant total value. This and other quantifiable differences between present and previous findings may be the result of the different methods and the influence of dietary and other regional factors on dentinogenesis.

[Fluoride intake in a community with low fluoride concentration in drinking water]. / Fluoriedinname van'n gemeenskap met 'n lae fluoriedioonkonsentrasie in die drinkwater.

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).

A comparative study on aflatoxin B 1 metabolism in mice and rats.

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.

Vitamin B6 revisited. Evidence of subclinical deficiencies in various segments of the population and possible consequences thereof.

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.

Conversion of monomeric human growth hormone and big growth hormone into different molecular weight forms in vitro and after injection into humans.

Monomeric human growth hormore (hGH) and big hGH obtained by a new purification procedure from human pituitary glands were examined for a possible conversion into different molecular weight forms under in vitro and in vivo conditions. Sephadex G-150 gel filtration was used for separation. Big or monomeric hGH was incubated in hormone-free serum or injected into normal individuals in order to induce a peak of immunoreactive hGH. Specimens from early and late stages of the surge were subjected to gel filtration. It could be shown that not only the big hGH is converted to the smaller form but that monomeric hGH is also recovered in two higher molecular weight regions by gel filtration in vitro and in vivo experiments. A significantly higher conversion of monomeric to big hGH was found in vitro. This suggests an inhibition of big hGH formation from monomeric hGH in normal individuals. There was no apparent time relation of big hGH formation from monomeric hGH in vivo. Regarding the conversion of big hGH, more of this material remained in its original form in vitro. The immunoreactivity recovered in the region of the very large form was found to be higher in vivo. The formation of the monomer from big hGH was similar under in vitro and in vivo conditions.

Purification and characterization of a novel heparinase.

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.

Carcinoembryonic antigen in patients with breast cancer: an adjunctive tool to monitor response and therapy.

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.

Sialic acid in semen of normozoospermic men.

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.

[Fluoride status of a community and fluoride concentration in its drinking water]. / Fluoriedstatus van'n gemeenskap met'n lae fluoriedioonkonsentrasie in die drinkwater.

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.

A modified neutral sucrose centrifugation method for rapid detection of DNA damaged by gamma-radiation and repair in human lymphocytes.

1. The influence of 60Co gamma-radiation on the sedimentation behaviour of human lymphocyte nucleoids in neutral sucrose gradients was studied with the aid of a modified fluorescent monitor system consisting of the DNA-binding dye, Hoechst 33258 and a vertical centrifuge rotor. 2. A combined method employing the sedimentation procedure and the incorporation of tritiated nucleosides was utilized to evaluate the repair of gamma-radiated DNA.