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.     

Effect of pH on the Immunogenicity of Mycoplasma pneumoniae

Mycoplasma pneumoniae harvested from media which had become acid lost the ability both to induce formation of tetrazolium reduction inhibition antibody and to act as antigens in immunodiffusion against human convalescent-phase sera. Incorporation of N-tris(hydroxymethyl)-2-aminoethane sulfonic acid and N-2-hydroxyethylpiperazine-N'-2-ethane sulfonic acid buffers into a new medium containing PPLO Serum Fraction instead of horse serum delayed the pH decline. Tris(hydroxymethyl)aminomethane, triethanolamine, and 3,6-endomethylene-1,2,3,6-tetrahydrophthalic acid buffers inhibited growth. Mycoplasmas obtained from buffered cultures retained antigenicity as measured by immunodiffusion and could stimulate tetrazolium reduction inhibition antibody formation in animals.     

Ultrastructural observations on the kinetosomes,and Golgi bodies during the asexual life cycle ofSaprolegnia

Summary At the onset of zoospore cleavage the centrioles ofSaprolegnia ferax reorientate, develop into kinetosomes and become associated with microtubular roots and a striate fibre. After cytoplasmic cleavage a flagellum, with a hitherto undescribed transition zone structure, develops from each kinetosome. Flagellum axonemes occur inside recently encysted primary spores. In vegetative hyphae and germinating cysts most recognizable Golgi bodies are characteristically associated with a cisternum of the endoplasmic reticulum and a mitochondrion but during sporogenesis they all lie adjacent to nuclei where they are apparently active in vesicle production. The structural details of these changes are described and their significance discussed. We wish to acknowledge the numerous helpful discussions with Dr. J. L. Gay. The senior author held a S.R.C. studentship during the course of this work, part of which was submitted in partial fulfillment of the requirements for the degree of Ph. D. at the University of London.     

Further environmental factors affecting the antigenicity of Trichophyton rubrum

Biochemical determinations performed on ammonium sulfate soluble and insoluble fractions of crude mycelial extracts ofTrichophyton rubrum indicated that these antigens were either carbohydrates or carbohydrates with peptide side chains. The antigens contained considerable amounts of galactose and mannose.Gel filtration techniques proved to be effective in separating these antigens. One antigen had a molecular weight greater than or equal to 2.0 × 10⁶. A smaller, more reactive antigen was also found; however, the elution time of this antigen varied with the concentration of dextrose in the medium.Quantitative precipitation tests used to differentiate the serological reactivity of crude antigens, recovered from mycelia grown on media containing variable concentrations of dextrose, indicated that the serological reactivity of the crude antigen was inversely proportional to the concentration of the carbohydrate source, with an optimum reactivity occurring with antigens prepared from mycelia grown in low dextrose concentrations.Nitrogen and carbohydrate concentrations performed on whole mycelia and cell free extracts demonstrated that the total nitrogen, soluble nitrogen, total carbohydrate and soluble carbohydrate concentrations were influenced by the concentration of the carbohydrate source. The optimum carbohydrate concentration necessary for the maximum ratio of protein and carbohydrates per gram of mycelium was 15.0 g/l. This is less than the amount used in most Sabouraud's dextrose media formulations. The effect of these environmental factors on the serological reactivity was discussed.Supported in part by NIH Environmental Health Tranining Grant ES00081-02. The help of Mrs. Gary Swecker is gratefully acknowledged for preparing the graphs.     

The Hemodynamic Response of the Right Ventricle Following Acute and Chronic Partial Obstruction of the Main Pulmonary Artery in Dogs

In eight adult dogs the main pulmonary artery was constricted to elevate the right ventricular peak systolic pressure to 50% of the peak aortic pressure at rest. The response of the right ventricle was assessed immediately, at 30 minutes and at six months. The right ventricle responded to acute systolic loading by complete compensation. After 30 minutes there was a reduction in the right ventricular outflow tract resistance. The cardiac output, heart rate and aortic pressure were maintained. The right ventricular systolic ejection period, end-diastolic pressure, peak pressure time, mean systolic pressure, right ventricular—main pulmonary artery mean systolic gradient, right ventricular work index, systolic work and outflow tract resistance were all increased.The right ventricle in the dog was shown to have an immediate capacity to compensate for systolic loading and retains this capacity for long periods of time. The ability to increase work is accomplished by adaptations in right ventricular physiology which increase right ventricular mean systolic pressures and prolong the right ventricular ejection period.     

Medical Radiation to Children with Congenital Heart Disease

A retrospective analysis was made of the source of medical radiation received by 25 children who were investigated by cardiac catheterization techniques and followed in the Cardiac Outpatient Clinic of the Health Centre for Children, Vancouver General Hospital. The source of radiation was analyzed. The r dose per year received from plane films averaged 0.05 r, from cardiac fluoroscopy 6.7 r, and from catheterization and angiocardiography studies 1.58 r per year. In six of the 25 children, radiation doses to the thorax exceeded the LD₅₀ for adult humans. In these six patients 95.8% of the radiation received was during cardiac fluoroscopy. Routine fluoroscopy for the radiological re-evaluation of pediatric patients with congenital heart disease should be replaced by plain chest radiographs.     

LYSOSOMES IN THE RAT SCIATIC NERVE FOLLOWING CRUSH

Peripheral nerves undergoing degeneration are favorable material for studying the types, origins, and functions of lysosomes. The following lysosomes are described: (a) Autophagic vacuoles in altered Schwann cells. Within these vacuoles the myelin and much of the axoplasm which it encloses in the normal nerve are degraded (Wallerian degeneration). The delimiting membranes of the vacuoles apparently form from myelin lamellae. Considered as possible sources of their acid phosphatase are Golgi vesicles (primary lysosomes), lysosomes of the dense body type, and the endoplasmic reticulum which lies close to the vacuoles. (b) Membranous bodies that accumulate focally in myelinated fibers in a zone extending 2 to 3 mm distal to the crush. These appear to arise from the endoplasmic reticulum in which demonstrable acid phosphatase activity increases markedly within 2 hours after the nerve is crushed. (c) Autophagic vacuoles in the axoplasm of fibers proximal to the crush. The breakdown of organelles within these vacuoles may have significance for the reorganization of the axoplasm preparatory to regeneration. (d) Phagocytic vacuoles of altered Schwann cells. As myelin degeneration begins, some axoplasm is exposed. This is apparently engulfed by the filopodia of the Schwann cells, and degraded within the phagocytic vacuoles thus formed. (e) Multivesicular bodies in the axoplasm of myelinated fibers. These are generally seen near the nodes of Ranvier.