Analysis of PR subintervals in normal subjects and early studies in patients with abnormalities of the conduction system using surface His bundle recordings

Utilizing several different approaches to noise reduction, satisfactory beat by beat His bundle activity was recorded from the chest surface in 41 (80%) of 52 normal subjects. Surface atrial to His intervals (PAH) and His to ventricular intervals (HV) were measured in this group and compared with subintervals of the PR segment recorded endocardially from 47 persons with normal electrophysiologic findings. A recent modification in the selection algorithm allows on-line identification of the four of five possible recording sites for utilization in a spatial summation. The ability to record in less favorable circumstances has been improved to the extent that records of suitable clarity for measurement were also obtained in 17 (77%) of 22 individuals with conduction system abnormalities. Comparison of the surface and endocardially acquired data in the normal group reveals no statistically significant difference in the surface acquired PAH and endocardially acquired high right atrial to His (HRAH) intervals, nor in the HV intervals. In a small subset of patients data were acquired by both techniques and no significant differences were found. Thus, when programmed stimulation or endocardial mapping is not required to answer specific clinical questions, in the majority of persons it is possible to record meaningful subintervals from the body surface from each cardiac cycle. Additionally, in instances in which surface P wave activity is obscure in the routine electrocardiogram, this technique enhances atrial electrical activity.     

Changes in permeability of cell membranes and in composition and properties of hexokinase during induced carcinogenesis

The isozyme spectrum of hexokinase (HK) of the mucous membrane of the rat large intestine consists of three isozymes. In tumors induced by 1,2-dimethylhydrazine in this situation, the isozyme composition of HK is simplified through the loss or sharp reduction in content of the isozyme with the fastest speed of migration toward the anode. In metastatic tumors HK is represented by a single isozyme. The Michaelis constant (glucose) for KG in the tumors is reduced by 2–3 times. Starting from the first month of administration of the carcinogen, HK activity begins to appear in the blood serum of the animals and by the fifth month it is found in 80% of cases. HK was always absent from the blood serum of control animals.     

The role of multifunctional delivery scaffold in the ability of cultured myoblasts to promote muscle regeneration

Many cell types of therapeutic interest, including myoblasts, exhibit reduced engraftment if cultured prior to transplantation. This study investigated whether polymeric scaffolds that direct cultured myoblasts to migrate outwards and repopulate the host damaged tissue, in concert with release of angiogenic factors designed to enhance revascularizaton of the regenerating tissue, would enhance the efficacy of this cell therapy and lead to functional muscle regeneration. This was investigated in the context of a severe injury to skeletal muscle tissue involving both myotoxin-mediated direct damage and induction of regional ischemia. Local and sustained release of VEGF and IGF-1 from macroporous scaffolds used to transplant and disperse cultured myogenic cells significantly enhanced their engraftment, limited fibrosis, and accelerated the regenerative process. This resulted in increased muscle mass and, improved contractile function. These results demonstrate the importance of finely controlling the microenvironment of transplanted cells in the treatment of severe muscle damage.     

Secretory immunity in influenza

The dynamics of secretory antibody formation, the duration of secretory antibody preservation, and changes in the concentration of secretory antibodies to antigens other than influenza virus were studied in 64 patients with influenza A, 105 patients with influenza B, and 23 persons who had had influenza A. Severe forms of influenza A were accompanied by antibody accumulation in sera and nasal secretions; in some cases of mild forms of this infection, this process was limited by the humoral immunity system. In the first days of severe forms, transudation of antibodies from sera to nasal secretions was noted. Secretory antibodies to influenza A virus were preserved at titers of greater than or equal to 1:4 for four to eight months in persons with mild forms of the disease and for more than eight months in those with severe influenza A complicated with pneumonia. Decreases in the titer of antibodies to agents other than influenza A virus, including influenza B virus, respiratory syncytial virus, adenovirus, and staphylococcus toxin, were demonstrated in association with rises in titers of antibody to influenza A virus. Among patients with influenza B, who were infected with a new influenza virus variant, the formation of circulating antibodies was more intensely stimulated than was the formation of secretory antibodies. No correlation between the level of IgA and the antibody titer in nasal secretions was found.     

Signaling gradients in cascades of two-state reaction-diffusion systems

Biological networks frequently use cascades, generally defined as chain-like arrangements of similar modules. Spatially lumped cascades can serve as noise filters, time-delay, or thresholding elements. The operation and functional capabilities of spatially distributed cascades are much less understood. Motivated by studies of pattern formation in the early Drosophila embryo, we analyze cascades of 2-state reaction-diffusion systems. At each stage within such as a cascade, a diffusible particle is reversibly bound by immobile traps and can be annihilated in both mobile and immobile states. When trapped, these particles drive the next stage by converting mobile particles of a different type from a passive to active form. The cascade initiated by injection of mobile particles into the first stage. We derive analytical expressions for the steady-state concentration profiles of mobile and immobile particles and analyze how the output of a cascade is controlled by properties of the constituent stages.