A New Technique for Monitoring Heart Signals?Part II: Orthogonal Lead Extraction

In Part I, instrumentation design is given for recording ECG signals from a home bathtub setup. In Part II, it is asserted that these bathtub signals are the projections of the heart dipole vector. This assertion is tested and the corresponding coefficients of the projection matrix are computed by monitoring the bathtub ECG signals for a subject as well as his orthogonal X, Y, Z leads on a PDP-9 computer. The least-squares estimation technique is used to determine the projection matrix. To compensate for the magnitude and phase distortion of the bathtub ECG signals, suitable digital as well as analog compensators are designed. A comparison of orthogonal leads extracted from bathtub leads and similar leads obtained from the HP1520A vectorcardiograph is given for five different subjects. It is shown that the average standard deviation obtained for these five subjects is 12.6 percent.     

Selection of a Set of Part Delivery Dates in a Multi-Job Stochastic Assembly System

The problem of determining part delivery dates in a low-volume assembly line manufacturing large and costly products is studied. At each workstation a part is assembled to the subassembly. These parts are supplied by external vendors with unreliable delivery schedules. The arrival date of a part is assumed to follow a normal distribution whose mean is to be specified. A dynamic programming approach in combination with a heuristic procedure is used to prescribe the vendor delivery dates for a batch of products. Simulation results show the procedure to be significantly superior to a deterministic approach to the problem. Comparisons are also made with a safety buffer method.     

Imaging intracellular elemental distribution and ion fluxes in cultured cells using ion microscopy: a freeze-fracture methodology

A freeze-fracture methodology was standardized for tissue culture cells to study intracellular distribution of diffusible elements with ion microscopy. Chinese hamster ovary (CHO) and normal rat kidney (NRK) cells grown on a silicon substrate were sandwiched using another smooth surface (silicon, glass, mica) in the presence of spacers and fast frozen in liquid nitrogen slush. The sandwich was fractured by prying the two halves apart under liquid nitrogen. This procedure produced large areas on the silicon substrate containing hundreds of cells grouped together and fractured at the apical cell surface. After freeze-drying, these cells revealed a subcellular distribution of Na, K, Ca, Mg, P, Cl and S with the ～0·5 μm lateral resolution of the ion microscope. Between the nuclei and the cytoplasm of cells, no major differences were observed for Na, K, Mg, P, Cl and S intensities. Calcium alone, however, exhibited a remarkable distribution. Calcium accumulated more in the cytoplasm than in the nuclei of cells. Even within the cytoplasm its distribution was heterogeneous, suggesting Ca binding sites. The fractured cells consistently exhibited high K-low Na intensities. The injured or dead cells were easily recognized among the healthy ones due to their abnormal ion composition. This simple freeze-fracture methodology allowed fracturing of cells without removing the cells from the substrate. In addition, it eliminated the need for washing the nutrient media away and cryo-sectioning before ion microanalysis. The methodology was successfully extended to 3T3 mouse fibroblast, PtK₂ rat kangaroo and L5 rat myoblast cultures.     

Stimulation of liver growth and DNA synthesis by glucosylceramide

The nature of the growth-stimulating effect of glucosylceramide was studied. Mice were injected intraperitoneally with emulsified glucosylceramide and conduritol B epoxide, an inhibitor of cerebroside glucosidase. Within one or two days, the liver grew 18–24%, as reported. Two enzymes involved in DNA synthesis also increased more than the weight. The total liver activity of thymidine kinase increased 46–73%, and the total activity of ornithine decarboxylase increased as much as 101%. It is suggested that elevated liver levels of glucocerebroside stimulate cell proliferation through a relatively direct mechanism.