Genetic determination of the mitochondrial adenine nucleotide translocation system and ITS role in the eukaryotic cell

On integrating experimental data published previously, the following picture of the mitochondrial adenine nucleotide (AdN) translocation system is being presented: 1. The AdN translocation system serves not only to transport ATP synthesized within mitochondria into the cytosol but also to transport cytosolic ATP into the mitochondria when oxidative phosphorylation is not functioning. 2. The AdN translocator is coded for by nuclear genes and the mitochondrial protein synthesis is not involved in its formation. 3. The AdN translocation system must be preserved and functioning even in cells which could dispense with oxidative phosphorylation. It assures appropriate concentrations of intramitochondrial ATP. 4. The intramitochondrial ATP is required for normal replication of mitochondrial DNA. Tis supports the view that the mitochondrion is a self-replicating semi-autonomous organelle. 5. The appropriate concentration of ATP must be present in mitochondria to make possible cell growth or multiplication. This points to a direct or indirect role of mitochondria in the control of cell proliferation.     

Length of human constitutive heterochromatin in relation to chromosomal contraction

Summary Linear measurement of blocks of constitutive heterochromatin and the euchromatin portion 1q-h in three members of a family was used to study the dependence of the size of C blocks on the degree of chromosomal contraction. The results demonstrate that the size of heterochromatin portions decrease regularly with an increases of the degree of euchromatin contraction. The dependence was found to be linear, except for mitoses with an extremely high or low degree of contraction. The finding was used for the development of a new method of evaluation of constitutive heterochromatin.     

Metabolism of benzo(a)pyrene by human lung microsomal fractions

The metabolism of benzo(a)pyrene was studied using microsomal fractions obtained from human lung derived at either resection or autopsy. The rates of metabolism and metabolite distribution were monitored using high pressure liquid chromatography and the metabolic rates were noted to be similar to those obtained using rat lung microsomes. In contrast to the rat, human lung microsomes appear to form a higher percentage of the 7,8-dihydro-7, 8-diol or 9,10-dihydro-9, 10-diol of benzo(a)pyrene as a fraction of the total metabolites. However, there was a significant variation among the human lung microsomal preparations which might reflect the clinical diagnosis and/or individual variation.     

Leaf analysis as a diagnosis of nutritional deficiency or excess in the soilless culture of lettuce

Summary The results are given of experiments to test wether leaf analyses can be used for diagnostic determinations of deficiency and excess in mineral nutrition of lettuce in soilless culture. re]19760127     

Isolation and properties of crystalline ferredoxin from lactuca sativa

Lettuce ferredoxin has been purified to homogeneity, with a yield of 18 mg/kg of denerved leaves. It crystallizes in magnificent needles, often clustered in broom-like sheaves. The absorption spectrum showed maxima at 460, 422, 330 and 274 nm,with a ratio A₄₂₂/A₂₇₄, of 0.46. The mM absorption coefficient was 9.74 at 422 nm, and 21.62 at 274 nm. This ferredoxin showed a pI = 4.7 and an E′₀ = ?425 mV (at pH = 7.7). MWs of 12 400, 11480 and 13000 were obtained by sucrose gradient centrifugation, and on the basis of the amino acid composition and the iron content, respectively, with an average of 12 300. The amino acid analysis showed the existence of one methionine residue per mole, with 105 amino acid residues. There are two iron atoms and two labile sulfide groups per mole; 4 half-cystine residues were found by performic acid oxidation, and 5 cysteine groups when determined by titration with pHMB. The native protein is not fixed on thiol-Sepharose 4B, but it is quantitatively retained after incubation with 8 M urea. Lettuce ferredoxin showed a 62, 58 and 78% effectiveness with the spinach ferredoxin-NADP reductase, nitrite reductase and fructose-1,6-diphosphatase (FDPase), respectively, when compared with the spinach ferredoxin. This different behaviour of both ferredoxins is joined to genetic-structural relationships, and suggests that the role of ferredoxin in FDPase activation is more sophisticated than that of a mere nonspecific reductant.     

Germination inhibitors in the pine seed coat

Inhibitors from (Pinus pinea L.) seed coats were separated using paper chromatography, thin layer chromatography, and a Sephadex G-10 column. The inhibitory activity was resolved into several fractions. One of these behaved similarly to abscisic acid. It has exhibed the same properties as ABA in thin-layer chromatography, paper chromatography, and Sephadex G-10 chromatography and in UV absorption and fluorescence spectra. These germination inhibitors, present in the seed coats, are involved in the regulation of P. pinea seed germination.Abbreviations ABA abscisic acid - TLC thin-layer chromatography     

Adaptation to chronic hypobaric hypoxia and sexual hormones

The role of the gonads and their hormones on body weight was studied in rats of both sexes submitted to chronic hypoxia and their controls at sea level atmospheric pressure. Intact rats were exposed to either 4 700 or 6 000 m simulated altitude in a hypopressure chamber. Castrated rats and castrated rats daily injected with either 0.5 mg of testosterone or 20 microgram of estradiol or the vehicle, were exposed to the higher altitude. The rat weight was recorded for a period of at least eight weeks. All groups of hypoxic male animals increased their weight significantly less than the controls at sea level. Also in castrated females and in castrated injected with testosterone or the vehicle the same pattern of weight curves was observed. On the contrary, groups of intact females and castrated females injected with estradiol did not show significant differences between hypoxic and control animals. Only in a group of smaller intact females (50-80 g) the body weight increase was significantly diminished by exposure to either 4 700 or 6 000 m simulated altitude.     

Growth inhibition of a MC-induced mouse sarcoma by TCGF (IL 2)-containing preparations

Summary Supernatants from Con A-stimulated rat spleen cell cultures containing T cell growth factor inhibited growth of a transplantable 3-methylcholanthrene-induced sarcoma in syngeneic mice. The tumour-inhibitory effects were dependent on the concentration of T cell growth factor and repeated injections of the supernatants.