Differentiation of Neurosensory Cells in Hydra

The differentiation of neurosensory cells in Hydra has been studied at the level of the electron microscope. These cells arise from interstitial cells (undifferentiated cells) and not from pre-existing nerve cells. Furthermore, there is no evidence to suggest that neurosensory cells represent a stage in the development of other nerve cells, i.e. ganglionic and neurosecretory cells. Major cytoplasmic changes in fine structure during differentiation include development of a cilium and associated structures (basal body, basal plate, rootlets), development of microtubules and at least two neurites, increase in Golgi lamellae and formation of dense droplets typical of neurosecretory droplets, structural variations in mitochondria and a decrease in the number of ribosomes. Granular endoplasmic reticulum is characteristically poorly developed in all stages of differentiation, including the mature neurosensory cell. Nuclear and nucleolar changes also occur during differentiation but these are less dramatic than the cytoplasmic events.

The possibility of neurosensory cells being bi- or multiciliated and the presence of intercellular bridges between these cells are considered. The function of neurosensory cells is discussed briefly in relation to the function of the cilium and neurosecretory droplets.

Fluid transport and tubular intercellular spaces in reptilian kidneys

Renal tubules of crocodiles, lizards, snakes, and turtles have intercellular spaces similar in type to those observed in the mammalian gall bladder, but different from those of mammalian renal tubules. The fluid movements across renal tubules of reptiles are correlated with the width of the tubular intercellular spaces. In the proximal tubules, where transport is always isosmotic, the spaces are open whenever the tubular epithelium is tranporting, but closed when no transport is taking place. In distal tubules, intercellular spaces are wide open when the osmolality of the urine is close to that of the blood, that is, when the fluid resorbed is almost isosmotic to the tubular fluid. The apical two-thirds of the intercellular spaces are closed when the urine is hypoosmotic. They are also closed when the tubules are not transporting, as in collapsed tubules or tubules poisoned with ouabain. Thus, as in the gall bladder, the open intercellular spaces appear to be found whenever there is fluid transport across the epithelium.

Computer simulation of hospital patient scheduling systems

A method of analyzing alternative systems of scheduling hospital admissions by means of a computer simulation is described. The simulation is divided into three programs, dealing sequentially with requests for admission, scheduling, and evaluation of costs of three basic scheduling systems and using the output of each phase of the simulation as input to the following phase. The feasibility of using the scheduling program in a real-time automated patient-scheduling system is discussed, with indications of adaptations required and additional functions that could be handled by the system.

Virus-Like Particles in Normal and Tumorous Tissues of Drosophila

A new virus-like particle has been found in Drosophila. Thus far it has been detected only in electron micrographs of certain cells capable of division, such as those in larval imaginal disks, cell lines derived from imaginal disks, cells from a genetically controlled brain tumor, and adult gut cells. It appears to be slightly elliptical in shape, about 37 millimicrons by 45 millimicrons, and occurs in both the nucleus and cytoplasm. From the evidence it is suggested that the particle is a new virus.

The physician as an estimator of hospital stay

The abilities of physicians to estimate the length of stay of their hospital patients was investigated. Two estimates were made; one at admission request and another after a prescribed number of days of hospitalization. Data are presented as correlation coefficients between actual and estimated lengths of stay and as conditional frequency functions of actual given an estimated length of stay. Differences between physicians in surgical and medical service are shown. It is concluded that physicians' estimates may be a useful source of data for operating an elective patient scheduling system.

Prediction of hospital length of stay

Uncertainty in length of patient hospital stay is a major deterrent to effective scheduling for admission of elective patients. Various methods are presented for reducing this uncertainty, including use of diagnostic information, physicians' estimates, and nurses' discharge prediction. It is concluded that physicians' estimates prior to admission, revised by additional estimates after admission, are a useful tool for reducing the uncertainty in length of stay and permitting effective scheduling and manpower allocation.

A Progressive Staining Method for Mitochondria

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A Physio-Pathologic Study of the Choroid Plexus with the Report of a Case of Villous Hypertrophy

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