Two homologous mitochondrial introns from closely related Saccharomyces species differ by only a few amino acid replacements in their Open Reading Frames: one is mobile, the other is not.

We have undertaken a comprehensive study of the gene conversion of all the mitochondrial introns of Saccharomyces capensis. The approach used involved the measurements of intron transmission amongst the progeny of crosses between a recipient strain (Saccharomyces cerevisiae intronless mitochondria) and various donor strains (Saccharomyces capensis, with various combinations of mitochondrial introns). We have shown that the S. capensis second intron (bi2 of cytochrome b gene) is extremely active as a donor in gene conversion whereas its homologous S. cerevisiae intron is not. Determination of sequence of the S. capensis intron demonstrates that it differs from that of the homologous S. cerevisiae intron (bi2) by a very small number of nucleotide substitutions.

[Individual variability in human requirements for food stuffs and energy and nutritional norms]. / Individualnata variabilnost na potrebnostite na khorata ot khranitelni veshtestva i energiia i normite za kranene.

The regular modifications in man's need of energy and protein substances primarily under the effect of a variety of factors are investigated. Emphasis is laid on the broad limits of individual variations in terms of alimentary requirements of people, and on a number of facts suggesting that in some ses the regularity of variations is by no means clarified. The problem of the minimum energy expenditure required by the organism is dealt with, underscoring the role played in this respect by basic metabolism values, and by the maximum energetic potential. The problem of the influence of deficient feeding and immobilization on man's need of alimentary substances is also discussed, as well as the issue of optimal protein balance level in the organism, considered as a level securing to the organism the optimal possibilities of metabolic adaptation to external milieu effects.

[Changes in protein metabolism in white rats with limited feeding and a varying physical load]. / Promeni v beltuchniia obmen na beli plukhove pri ogranicheno khranene i razlichno fizichesko natovarvane.

Changes in some protein metabolism indicators are studied in white rats at different levels of the energy balance. It is established that the level of the so-called labile protein in the organism is closely related to the level of energy metabolism and also, that it is not invariably directly dependent on protein concentration within the organism. The inference is reached that adaptivity of protein metabolism is manifested not merely through changes in the value of proteins, which might be employed in the capacity of reserve, but also through changes in the degree of their lability, resp. in the ability of the organism to mobilize them. The amount of protein reserves depends rather more on the increased protein intake with the while food, while the degree of reserve protein lability is related to a higher degree to the muscular activity of the organism. Restricted motor activity combined with a high protein intake, against the background of an even minimum hypercaloric feeding, leads to a considerable reduction of protein reserves. Deficient feeding combined with restricted motor activity leads to reduction both of the amount and lability of reserve proteins. Physical exertions have a favourable effect on the ability of organism both to increase its protein reserves and to mobilize them, with the latter being rather pronounced under conditions of limited feeding. It is stressed that excretion of nitrogen, urea and creatinine in the urine in conditions of protein poor diet is in a position to afford essential information on the adaptability of protein metabolism within the organism.