A chronobiological study of delta-amino levulinic acid urinary excretion

Determination of urinary delta-amino levulinic acid (ALA) is now systematically used in occupational health to detect an excessive exposure to lead in professionally exposed workers. However, to determine whether circadian changes of the urinary excretion of ALA alter the significance of the test, we quantified the ALA levels in the urine of 19 healthy young adults. Urine samples were taken every 3 hr between 0700 and 2300 hr and ALA levels were determined by a spectrocolorimetric method. The data indicated that the 24-hr mean ALA level was: 1.81 mg/g creatinine. The peak values (2.24 +/- 0.24) were obtained between 1400 and 1700 hr whereas the lowest ALA levels were found between 2200 and 0300 hr. Cosinor analysis revealed a significant circadian rhythm while no significant difference could be found according to sex. Possible explanations of our findings are discussed.     

Effect of detergent on protein structure. Action of detergents on secondary and oligomeric structures of band 3 from bovine erythrocyte membranes

With special interest in the mode of action of zwitterionic detergents on proteins, a variety of detergents were examined for their ability to disrupt the secondary and quaternary structures of an anion transport protein, band 3, and its cytoplasmic 38 kDa fragment from bovine erythrocyte membranes and for their effect on the binding of an anion transport inhibitor to band 3. Nonionic detergents and Chaps also acted as a nondenaturant in these instances, as well accepted for other proteins. Though deoxycholate and cholate inhibited the binding of an anion transport inhibitor to band 3, these detergents did not show any effect on the native structure of band 3. Zwitterionic detergents (Zwittergent 3-10, Zwittergent 3-12 and N, N-dimethyl-N-dodecyl glycine) were suggested to denature the water-soluble 38 kDa fragment at concentrations above the critical micelle concentration, but to be weak in disrupting interacting forces between hydrophobic membrane-bound domains of band 3. The results indicated that these zwitterionic detergents are similar in the mode of denaturing action to dodecyltrimethylammonium bromide rather than sodium dodecyl sulfate.     

Cytotoxicity of cholesterol oxidase to cells of hypercholesterolemic guinea pigs

1. A high cholesterol diet caused guinea pig erythrocytes to become sensitive to lysis by cholesterol oxidase (CO), a protein not hemolytic to normal cells. 2. Lysis was associated with conversion of membrane cholesterol to its oxidation product (delta-4-cholesten-3-one). 3. Intravenous injection of CO to hypercholesterolemic guinea pigs produced a reduction in serum cholesterol, but was not lethal as it was in rabbits. 4. Homogenized spleen, liver and kidney from the hyperlipidemic animals were sensitive to in vitro cholesterol oxidation while tissues from non-lipemic animals were resistant to modification.     

Regulation of ornithine decarboxylase activity by spermidine and the spermidine analogue N1N8-bis(ethyl)spermidine.

Polyamine biosynthesis in intact cells can be exquisitely controlled with exogenous polyamines through the regulation of rate-limiting biosynthetic enzymes, particularly ornithine decarboxylase (ODC). In an attempt to exploit this phenomenon as an antiproliferative strategy, certain polyamine analogues have been identified [Porter, Cavanaugh, Stolowich, Ganis, Kelly & Bergeron (1985) Cancer Res. 45, 2050-2057] which lower ODC activity in intact cells, have no direct inhibitory effects on ODC, are incapable of substituting for spermidine (SPD) in supporting cell growth, and are growth-inhibitory at micromolar concentrations. In the present study, the most effective of these analogues, N1N8-bis(ethyl)SPD (BES), is compared with SPD in its ability to regulate ODC activity in intact L1210 cells and in the mechanism(s) by which this is accomplished. With respect to time and dose-dependence of ODC suppression, both polyamines closely paralleled one another in their response curves, although BES was slightly less effective than SPD. Conditions of minimal treatment leading to near-maximal ODC suppression (70-80%) were determined and found to be 3 microM for 2 h with either SPD or BES. After such treatment, ODC activity was fully recovered within 2-4 h when cells were re-seeded in drug-free media. By assessing BES or [3H]SPD concentrations in treated and recovered cells, it was possible to deduce that an intracellular accumulation of BES or SPD equivalent to less than 6.5% of the combined cellular polyamine pool was sufficient to invoke ODC regulatory mechanisms. Decreases in ODC activity after BES or SPD treatment were closely paralleled by concomitant decreases in ODC protein. Since cellular ODC mRNA was not similarly decreased by either BES or SPD, it was concluded that translational and/or post-translational mechanisms, such as increased degradation of ODC protein or decreased translation of ODC mRNA, were probably responsible for regulation of enzyme activity. Experimental evidence indicated that neither of these mechanisms seemed to be mediated by cyclic AMP or ODC-antizyme induction. On the basis of the consistent similarities between BES and SPD in all parameters studied, it is concluded that the analogue most probably acts by the same mechanisms as SPD in regulating polyamine biosynthesis.     

Origin of abnormality in a human simelian foetus as elucidated by our knowledge of vertebrate development

In this paper we attempt to explain the abnormality of a simelian foetus with reference to our present knowledge of vertebrate development. The various developmental defects seem to have a single common origin: the speeding-up of the progression of cell differentiation in the notochord anlage--which is the organization centre of the embryo--during the regression of the Hensen's node. Cell activity involved in the morphogenetic movements in the chordamesoderm probably stopped before it should have. The elongation of the notochord anlage was not completed, resulting in the defective development of the posterior part of the foetus. A number of pairs of posterior trunk somites were not induced. Consequently (1) the pelvic limb buds, whose posterior parts were missing, fused, bringing in further developmental deviations in the limb skeleton and abdominal muscles; (2) there are no vertebrae between the first sacral vertebra and the misshaped coccyx formed by the tail bud. The derivatives of the posterior endoderm (hindgut, bladder and ureters) were not induced either. The cauda equina is deficient. The absence of functional kidneys and the presence of embryonic urinary tubules in the pelvic cysts which are wrapped up by gut epithelium suggest the induction of the metanephric mesenchyme by ectopic endoderm. The speeding-up of differentiation in the notochord anlage also probably resulted in the excessive extension of its anterior region which is the organizer of brain structures. This explains the overdevelopment of the nose and of the neurocranium, and the low position of the ear. A gene mutation as well as a mechanical stress are the possible causes of the abnormal behaviour of the notochord anlage.