Pigment,abnormal mitochondria and laminar bodies in human sympathetic neurons

Summary A study was made of the fine structure of neurons in lumbar sympathetic ganglia which were surgically removed from a 52 year old male patient. Some samples were fixed by direct immersion into osmium tetroxide, others were first prefixed with an aldehyde solution. Large vesiculated pigment granules were described, compared with similar particles, previously seen in human and animal autonomic neurons, and their glycogen and lipid-soluble components were tentatively identified. These granules increase numerically during aging, are probably derivatives of lysosomes, and may incorporate both lipofuscin and melanin in the same particle. Mitochondrial changes (enlargement, disappearance of cristae and deposit of opaque central material) in sympathetic perikarya occurred under all conditions of preservation, and were interpreted as hypoxia-induced structures which developed during life. Abnormal aggregates of mitochondria were seen in nerve processes. Laminar bodies, chiefly associated with mitochondria were present, especially, in aldehyde prefixed material. It remained undecided whether these structures occurred during life or were artifacts. Compared with direct osmium tetroxide fixation, prefixation with aldehyde, followed by osmium tetroxide proved to be a superior, but not entirely adequate method of preserving deep layers of neuronal tissue. This investigation was supported (in whole) by United States Public Health Service Grant NB 1879-09, Institute for Nervous Diseases and Blindness.The author is greatly indebted to Dr. Jere W. Lord, Jr., Department of Surgery, New York University Medical Center, for the surgically removed tissues used in this study; he is grateful to Dr. Sanford L. Palay, Department of Anatomy, Harvard Medical School, for suggesting the use of the then unpublished method of prefixation with the aldehyde solution. It is a pleasure to acknowledge the expert skill with which Miss Carmen DeLemos and Mr. Arnlod Cianella assisted in completing this work.     

Role of Differential Air Pressure Zones in the Control of Aerosols in a Large Animal Isolation Facility

The uncontrolled transmission of hog cholera in a large animal isolation facility, designed to control the movement of aerosols within and between individual wings of a multiunit building, indicated the need for a critical study of aerosol behavior under existing conditions of operation. Studies with aerosols of Escherichia coli B T3 bacteriophage (T3 coliphage) conclusively demonstrated the impossibility of obtaining the desired control by means of a "static" air balance relationship between adjacent areas within the facility. Modifications needed to provide the desired control of the air-handling system are outlined and discussed.     

Production planning of a flexible manufacturing system in a material requirements planning environment

Early flexible manufacturing system (FMS) production planning models exhibited a variety of planning objectives; typically, these objectives were independent of the overall production environment. More recently, some researchers have proposed hierarchical production planning and scheduling models for FMS. In this article, we examine production planning of FMS in a material requirements planning (MRP) environment. We propose a hierarchical structure that integrates FMS production planning into a closed-loop MRP system. This structure gives rise to the FMS/MRP rough-cut capacity planning (FMRCP) problem, the FMS/MRP grouping and loading (FMGL) problem, and the FMS/MRP detailed scheduling problem. We examine the FMRCP and FMGL problems in detail and present mathematical programming models for each of these problems. In particular, the FMRCP problem is modeled as a generalized assignment problem (GAP), and a GAP-based heuristic procedure is defined for the problem. We define a two-phase heuristic for the FMGL problem and present computational experience with both heuristics. The FMRCP heuristic is shown to solve problems that exhibit a dependent-demand relation within the FMS and with FMS capacity utilization as high as 99 percent. The FMGL heuristic requires very little CPU time and obtains solutions to the test problems that are on average within 1.5 percent of a theoretical lower bound. This FMS/MRP production planning framework, together with the resulting models, constitutes an important step in the integration of FMS technology with MRP production planning. The hierarchical planning mechanism directly provides for system-level MRP planning priorities to induce appropriate production planning and control objectives on the FMS while simultaneously allowing for necessary feedback from the FMS. Moreover, by demonstrating the tractability of the FMRCP and FMGL problems, this research establishes the necessary groundwork upon which to explore systemwide issues pertaining to the coordination of the hierarchical structure.     

Oxidant inhibition of epithelial active sodium transport

The purpose of this study was to quantify the effects of extracellularly generated partially reduced oxygen species on active sodium (NA⁺) transport across the ventral toad skin, a well-studied epithelium. Sections of skin from decapitated toads were mounted in an Ussing chamber, bathed on both sides with electrolyte solution containing 500 μM xanthine and bubbled continuously with room air. The tissues were short-circuited, and short circuit current (Isc) and tissue resistance (R_t were monitored continuously with an automatic voltage clamp apparatus. Fifteen mU/ml of xanthine oxidase (XO), either purchased from Calbiochem or purified from cream, were instilled in either the apical (mucosal) or basolateral (serosal) baths at t = 0 and T = 10 min. Hydrogen peroxide (H₂O₂) concentrations increased to 200 μM within the first 20 min and then decreased, reaching a value of 40 μM by 60 min. Mean [H₂O₂] was 90 μM. Instillation of XO in the apical bath resulted in a large decrease in Isc and an increase in R_t, their values being 43% and 160% of their corresponding controls 85 min after the first instillation. Addition of superoxide dismutase and catalase completely prevented these changes. Instillation of XO in the basolateral bath had no effect. Similar physiological responses were obtained using the Calbiochem XO or the purified XO, which contained no measurable protease activity. It was concluded that extracellularly generated partially reduced oxygen species may interfere with active Na⁺ transport by possibly damaging apical Na⁺ channel proteins.