Constitutive choline transport in Pseudomonas aeruginosa.

Pseudomonas aeruginosa has a choline uptake system which is expressed in bacteria grown in the presence of succinate and ammonium chloride as the carbon and nitrogen source, respectively. This system obeys Michaelis-Menten kinetics with an apparent Km value of 53 microM; its activity is not inhibited by high osmolarities in the medium but is partially inhibited by choline metabolites such as betaine and dimethylglycine.

Cloning and characterization of the phenylalanyl-tRNA synthetase beta subunit gene from Candida albicans.

A Candida albicans expression library was constructed from RNA isolated from regenerating protoplasts. A 1.4-kb cDNA clone was used to isolate a genomic fragment. Sequence analysis revealed an open reading frame of 593 amino acids with an overall identity of 63.6% with the phenylalanyl-tRNA synthetase beta subunit (FRS1) of Saccharomyces cerevisiae. We named it CaFRS1. It is located in a single copy in chromosome R, SfiI fragment M. Its expression showed a decrease during the cell wall regeneration process in protoplasts of both yeast and mycelial cells of C. albicans, suggesting its requirement thereof in initial steps of the cell wall synthesis.

A simple model of blood flow rate reduction in haemodynamic disorders of the spleen.

The structural rearrangement of human sheathed capillaries in congestive splenomegaly has been considered. In abnormal spleens the external diameter and wall thickness were decreased, while the internal diameter was increased. Moreover, the total length and the absolute number of sheathed capillaries were increased, though not as much as the whole red pulp volume. Thus, in congestive splenomegaly, in addition to the well-known changes of the sinuses, the terminal arterial passages also appear to participate in the morphological rearrangement of the red pulp. The purpose of this paper is to formulate a simple dynamic model explaining the reduction of blood flow rate in the pathologically modified spleen. The main advantage of the present approach is that the coefficients inserted in equations describing the physical phenomena have been eliminated from the final formulae. Consequently, the model does not require the determination of parameters by means of difficult experimental measurements.

Ultrastructural and immunohistochemical study of the telencephalo-habenulo-interpeduncular connections of the goldfish.

Surgical ablations of telencephalon or telencephalon plus habenular nuclei (HBN) have been performed for studying anatomical connections of the telencephalo-habenulo-interpeduncular system of the goldfish. The results of the ultrastructural studies confirmed the presence of massive telencephalo-habenular and habenulo-interpeduncular projections and, in addition, demonstrated a minor direct telencephalo-interpeduncular connection. Immunohistochemical localization of substance P in the interpeduncular nucleus (IPN) after telencephalic ablation failed to demonstrate the involvement of this neurotransmitter in the direct telencephalo-interpeduncular projection, while telencephalon plus HBN ablation reduced substance P immunoreactivity in the IPN. The different distribution of degenerating terminals converging on the IPN from the HBN and from the telencephalon suggested a subnuclear organization of this area, as described in mammals.

Carotid wall as an isotropic mechanical system.

The morphological organization of the structural components in the dog carotid wall is investigated by X-ray diffraction and microscopic analysis. Histological analysis confirms an anisotropic morphology of smooth muscle cells and elastic fibers in the tissue. Collagen fibers, as revealed by X-ray diffraction technique, are organized in an isotropic network in the unstretched carotid media. Collagen fibers stretch without a preferential direction of orientation when a carotid segment is deformed in the physiological range under intraluminal pressure. A mathematical model which takes into account the isotropic distribution of the collagen fibers is developed. The validity of this model has been tested by computing several mechanical parameters using Anliker's data on the axial and radial oscillation obtained for carotids of living dogs. In spite of the anisotropic morphology of the main constituents of the carotid media layer, from a mechanical point of view the tissue can be considered as an isotropic material for the random distribution of the collagen fibers which represent the component of higher tensile strength.

[The electrical resistance and impedance of mammalian muscles during the first days after slaughter. I: bovine diaphragm]. / Osservazioni sulla resistenza ed impedenza elettrica del tessuto muscolare dei mammiferi nel periodo postvitale. Nota I: nel muscolo diaframmatico di bovino.

In the view of characterizing the animal tissues with respect to their physical properties, the AA. have investigated on the behaviour of the electrical responses of bovine diaphragmatic muscle. In particolar the resistance and the impedance (at a fixed frequency of 20 Hz, sinusoidal wave) have been checked in samples from the 4th up to the 148th hour after slaughter. The results of these experiments show that, during the maturation of the meat, there is a decrease of the values of the resistance and of the capacitive reactance. On the basis of the data acquired, the only hypothesis explaining the course of the research could be that the electrical properties of the meat are greatly influenced in a very relevant way by capacitive structures and in lower degree by a pure resistive medium.

[The electrical resistance and impedance of mammalian muscles during the first days after slaughtering. II: femoral biceps of swine]. / Osservazioni sulla resistenza ed impedenza elettrica del tessuto muscolare dei mammiferi nel periodo postvitale. Nota II: nel muscolo bicipite femorale di suino.

The Authors continuing a program of research on the characterization of physical properties of muscular tissues of Mammalia after slaughtering, have performed a new series of observations on the electrical conductance of femoral biceps of swine. Using two groups of specimen (one cut along the axis of the muscular fibers, the other at right angle of them), the AA. checked different values of resistance and of impedance, particularly during the first hours. On the contrary in the final stage of the research the data are quite similar in both the groups of samples. In the comment has taken into account the hypothesis that, on the basis of changes in the tissue structures, electrochemical processes could explain the results.

Measurements in microscopic images: an inexpensive device for semi-automatic analysis of microscopic images.

Measurement of histological and cytological parameters can be performed much faster and more accurate by means of a semi-automatic device that is described in detail. The system consists mainly of a medium-sized computer and one or more peripheral terminals. Each terminal incorporates a special measurement table for data acquisition, a keyboard for manual data input, and an interface. The software program for the evaluation and storage of the digital data is simple to write and offers a high degree of flexibility to the user. The system can be operated in real time.