Delineation of the QRS complex using the envelope of the e.c.g.

A new algorithm for QRS delineation has been developed. Based on the envelope of the e.c.g. signal a delineation function is defined, which yields a single positive pulse for each complex. From this function the onset and end of the QRS or, alternatively, a fiducial point is determined. To remove low-frequency component such as S-T abnormalities without distortion of the QRS complex, a filter with time-varying characteristics is used. The accuracy of the method has been evaluated in a test set of different QRS complexes obtained from coronary care patients. For QRS onset, the standard deviation of the difference between automated and manual determination was 7 ms in normal beats and 14 ms in ectopic beats. With simulated noise added to each waveform an average dispersion of 7 ms was observed in the recognition of the QRS onset at a signal-to-noise ratio of 15 dB. The corresponding dispersion in the location of a fiducial point was 2 ms. Using simulated e.c.g. data, the stability of the method is demonstrated for transitions between different waveform morphologies. Presented in part at ‘Computers in cardiology’, Florence, 23rd–25th September 1981     

Numerical solution of the bioelectric field of the e.r.g.

A numerical solution of a model of the bioelectric field of the e.r.g. was developed utilising a finited-difference successive overrelaxation technique. The difference equations implemented by the algorithms are applicable to any spherical volume conductor problem involving axial symmetry. The nodal network utilised was characterised by a variable and nonuniform spacing between the nodes and a pointwise variation of conductivity. An excellent accuracy was demonstrated when the numerical solutions were compared with the analytical solutions for several simplified test cases. When simulating the more realistic physiological configurations the model demonstrated a reasonably good agreement with the experimental data obtained from the literature.     

Recognition of shape from the frequency spectrum of the e.m.g.

Visual processing is one of the important aspects of research into an intelligent robot and upper extremity prostheses. The study has shown the relationship between the recognition of shape and the electromyogram generated in the human on the surface of the extensor carpi radialis muscle. To observe the corresponding electric signals, the subject was placed inside a shielded room with Ag?AgCl electrodes located at two points on his skin. The two electrodes were spaced 50 mm apart, but variation of the separation in the range 5–10 mm had no effect on the e.m.g. Three spectral peaks (100, 160 and 250 Hz) for the response are obtained for each shape. The frequencies corresponding with the peak values in the spectra are the same, and are independent of the shapes. Shape recognition can therefore be quantified as an e.m.g. spectral variation.     

Studies of the capillary basal lamina. I. Ultrastructure of the red body of the eel swimbladder.

The rete mirabile of the eel swimbladder is a vascular organ in which arterial andvenous capillaries alternate in regular fashion. The endothelium of the arterial capillaries is high, whereas that of the venous capillaries is thin and fenestrated. Endothelial cells and pericytes are the only cells found in the rete. A tubular systemin the arterial endothelial cells is connected with the organelles. The basal laminaeof both capillaries are similiar to those of mammalian capillaries of the same type. They present three layers of different electron density and have a high fibrillar pattern.A fine fibrillar material and dense fibrils appear in the cisternae of the rough endoplasmic reticulum and in large vacuoles of endothelial cells and pericytes: these cells areapparently involved in the synthesis of their lamina. Since the rete mirable ofthe eel swimbladder is a pure vascular preparation, it is most useful for the study of themorphology, the permeability, and the metabolism of the endothelial cells and for the analysis of the chemical structure of their basil laminae.     

Cellular composition of the bone marrow in the chicken. I. Identification of cells.

Incorporation of Fe55 in vivo was used for verifying on radioautographs the identity of chicken bone marrow cells that are in the process of hemesyntheses. Under the experimental conditions all labeled cells may be considered to be linked with erythroid differentiation. They were classified into five maturational stages according to their morphology and capacity for DNA synthesis. Granulocytes were identified by the presence of specific granules. All mononuclear cells were classified as lymphocytes which had a pachychromatic nucleus, a high nucleocytoplasmic ratio, lacked the capacity for DNA synthesis, and resembled small lymphocytes of the bursa, spleen and bone marrow that bound, in vitro, anti-chicken gamma globulins labeled with I125. Radioautography with H3TdR was used to identify proliferating and non-proliferating members of each cell population.     

Functional development of the interacting cells in the immune response. III. Role of the neonatal spleen.

Neonatal splenectomy and congenital absence of the spleen were shown to be associated with lack of primary IgM antibody synthesis, deficient bone marrow-thymus cell synergism. altered mitogen responsiveness and depressed homing patterns of thymocytes to the spleen. Using congenitally asplenic animals, altered B-T cell cooperation was manifest at the T cell but not B cell level. This correlated with the ability of thymus cells from either congenitally asplenic or neonatally splenectomized (NSx) animals to respond to the B cell mitogen lipopolysaccharide although there were no detectable Ig=ells present. To determine the role played by the spleen in the development of T cell function, NSx animals were given either irradiated or normal spleen grafts. Both irradiated and unirradiated grafts restored normal B-T cooperation and normal mitogenic responses of thymus cells. However, neither type of spleen graft was successful in restoring normal homing patterns to the spleen. It is concluded that the splenic microenvironment influences T cell maturation very early in life and that only some of the effects attributable to the absence of the spleen can be reversed by the reintroduction of this tissue as a graft.     

Host defence mechanisms in the bladder. II. Disruption of the layer of mucus.

The urinary bladder wall is lined by a layer of mucus which is believed to provide an important barrier to bacterial invasion of the urinary tract. Abnormal function of this protective layer could therefore be a factor predisposing the host to urinary tract infection (UTI). This study investigated the contribution of the bladder mucus to host defence in both acute and chronic lower UTI, using a non-obstructive animal model of infection which reproduces many features of the disease in man. The ultrastructural appearance of the infected bladder mucosa was assessed in tissue in which both the layer of mucus and bacterial glycocalyces were stabilized prior to examination by scanning and transmission electron microscopy. The protective role of the mucus layer was determined by disrupting the layer immediately prior to bacterial challenge. Both ultrastructural and bacteriological analyses have shown that infection was increased in those animals where the mucus barrier was disrupted.     

Mechanisms of immunity to leishmaniasis. II. Significance of the intramacrophage localization of the parasite.

The effect of initiating leishmanial infection in guinea-pigs with organisms contained within macrophages has been examined. Infection of animals in this way resulted in the development of metastatic disease with inocula 2 logs lower than required when free parasites were injected. The macrophage localization was found to protect the parasite from innate resistance, and, at certain times, from mechanisms of acquired immunity. Despite this, initiation of infection with parasites secluded in macrophages did result in the development of specific cell-mediated and humoral immunity. The results indicate that protection of the parasite by the macrophage contributes to the development of metastatic disease. Furthermore, it was revealed that metastatic disease can devlop in the face of acquired mechanisms of resistance. The possibility that non-healing diffuse leishmaniasis is the cause rather than the result of the suppressed immunological reactivity associated with this disease is discussed.