Topography of the subunits of Micrococcus lysodeikticus F1-ATPase

Summary The combined use of proteolytic digestion and lactoperoxidase catalyzed labelling with [¹²⁵I] applied to membrane-bound or soluble pure F₁-ATPase from Micrococcus lysodeikticus has allowed us to establish the topography of its , , and subunits within the protein molecule and with respect to the plane of the membrane.The subunit is most externally located to the membrane bilayer looking towards the cytoplasmic face, a position consistent with its proposed catalytic role. The and subunits lie in an intermediate layer between the subunits and the membrane, in which the subunit occupies a central position within the F₁-ATPase molecule in contact with the subunit. The subunit appears to be tightly bound to the F₀ component of the ATPase complex, probably buried in the membrane bilayer. A molecular arrangement of M. lysodeikticus ATPase is proposed that, taking into account the subunit stoichiometry _{3 3 2 2} (MW 420 000), accommodates the role assigned to each subunit and most, if not all, the known properties of this bacterial energy-transducing protein.     

High Bulk Diet for Diverticular Disease of the Colon

In the past century diverticular disease of the colon has changed from being almost unknown to becoming the most common disease of the colon. Studies in Britain indicated that the pathological basis of the disease is a thickening of the colonic musculature, with diverticulosis and diverticulitis developing because of increased intracolonic pressures generated by the thickened colon wall. This pressure can be sharply reduced by increased colonic bulk. Geographical and anthropological data reveal that diverticular disease results from Western civilization''s food habits, specifically the reduced fiber content in food. There is evidence that increasing the dietary intake of fiber by the addition of bran can prevent formation of diverticula and relieve the symptoms of established disease. Large scale studies are recommended both as treatment and to further test the validity of this concept.     

Branched-chain glycosyl α-amino acids : Part II. Synthesis of 2-D- and 2-L-(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-yl)glycine. Analogs of the sugar moiety of the polyoxins

Stereospecific hydroxylation of 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-trans-and 3-C-cis-(methoxycarbonylmethylene)-α-D-ribo-hexofuranose (2 and 3, respectively), with potassium permanganate in pyridine afforded 3-C-[S- and R-hydroxy-(methoxycarbonyl)methyl]-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose, (6 and 7, respectively), in a combined yield, after chromatography, of 43%. Selective formation of monomethanesulfonates (9a and 10a) and p-toluenesulfonates (9b and 10b), followed by treatment with sodium azide and reduction of the azide, afforded the methyl 2-D-(and 2-L-)(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-yl)-glycinates (12a and 13a, respectively). Basic hydrolysis of the latter compounds yielded 2-D- and 2-L-(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-yl)glycine (12b and 13b, respectively). The structures of the glycosyl amino acids were correlated with that of L-alanine by circular dichroism.     

DISTRIBUTION OF PEROXISOMES (MICROBODIES) IN THE NEPHRON OF THE RAT : A Cytochemical Study

The distribution of peroxisomes (microbodies) in the rat nephron was studied cytochemically, using glutaraldehyde- or formaldehyde-fixed tissue, by means of α-hydroxy acid oxidase activity in light microscopy or oxidation of 3,3'-diaminobenzidine (DAB) at pH 9 in both light and electron microscopy.The two cytochemical methods show peroxisomes to be nearly sperical particles found only in cells of the proximal convoluted tubule. Lysosomes were identified in the same or parallel sections, with β-glycerophosphate or 5'-cytidylic acid as substrate. They are found in all cells of the nephron. These cytochemical methods visualize the two organelles for light microscopy; they also permit unequivocal differentiation of all kidney peroxisomes from lysosomes in electron micrographs. Peroxisomes are larger and more reactive in the cells of the pars descendens (P₃ segment) of the proximal convolution, located in the outer medulla and medullary rays, than in the cells of the pars convoluta (P₁ and P₂ segments), situated in the cortex. In contrast, lysosomes are much smaller in the P₃ segment and larger and more reactive in the P₁ and P₂ segments. In all cells of the proximal convolution, peroxisomes tend to be concentrated nearer the base of the cells than do lysosomes. Mitochondria in P₃ cells also show low levels of DAB oxidation at pH 6, in contrast to those in P₁ and P₂ cells. The possibility is discussed that P₃ cells possess an extramitochondrial means of oxidation in which peroxisome oxidases play an important role.     

Attempt at quantitative analysis of interindividual variability in stress response of leucocyte levels in mice from the viewpoint of control theory

Summary The authors studied the dependence between the ability of systems regulating the level of peripheral leucocytes to damp the fluctuations of this level, occurring under conditions of repeated stressing of the organism by non-specific stress factors (isolation, starvation, handling for blood withdrawal) and the tolerance of the organism to the action of ionizing radiation (summary exposure to X-rays leading to death at repeated irradiation). This regulatory ability was expressed with the aid of the slope (coefficientb) of regression between the leucocytary valuesx _i, fluctuating in time, and the subsequent differences _i ( _i =x _i+1–x _i ). The highest tolerance to lethal action of radiation is correlated to such a regulatory behaviour of the organism at which the time necessary for adaptation of the system is shortest. The authors point out the suitability of the employed regulatory characteristic for the quantitative study of adaptability and resistance of the organism and its relatedness to the damping ratio, used in the automatic control theory.     

Aspergilosis En Colombia

Resumen Se presentan 15 casos de aspergilosis recolectados en diferentes ciudades del país. Doce fueron casos autopsiados. Los tres restantes se refieren a pacientes en quienes se efectuó una lobectomía pulmonar superior derecha por aspergiloma gigante intracavitario. En los doce primeros existía una enfermedad básica que había alterado seriamente el estado general del paciente; once de ellos habían recibido antibióticos, cinco habían recibido esteroides, y dos, agentes citotóxicos. Se cree que, tanto el estado general del paciente, como la administración de dichas drogas, favorecieron la infección micótica. De los tres casos con aspergiloma intracavitario gigante, se cree que, en uno, la micosis se implantó en una caverna tuberculosa cicatrizada. En los otros dos, la cavidad era un bronquio localmente dilatado y se consideró que no existía una infección tuberculosa.ElAspergillus posee un amplio espectro de patogenicidad. Se le puede observar en lesiones que van desde una localización intrabronquial, acompañada de mínima o nula reacción inflamatoria, hasta casos en los cuales existen lesiones pulmonares necrotizantes con diseminación hematógena a otros órganos (sistema nervioso central, hígado, riñón).