Biomedical subjects
Publications and source records attributed to R G Sherman.
Endocrine disorders are commonly seen in the general population. This article discusses the physiology, pathogenesis, and the medical and dental management of patients with thyroid, parathyroid, and pituitary gland disorders. In addition, the pharmacologic treatment, common side effects, and dental drug interactions of concern are discussed.
Bacteremias of dental origin have been implicated as sources of infection in specific cardiac conditions, diabetes, neutropenia, kidney disease, splenectomy, and patients with prosthetic joints. This article reviews the relative risks of dental bacteremias in these patients, discusses the merits of various regimens, and presents current prophylactic antibiotic recommendations.
This project sought to determine if a community-based habilitation program focusing on normalization and individual goal setting was effective in enhancing levels of independence in teenagers with spina bifida (myelomeningocele). The results of our formal and informal evaluation suggest that the program was effective. Using the goal-attainment scale for formal evaluation, the program averaged a score of 50.8, which reflects slightly better than expected outcomes. The greatest strength in the program was support and socialization among the teenagers. In addition, recommendations for practitioners in programming for teenagers are provided.
The objective of this study was to locate nerves arising from the CNS that have a cardioregulatory function in the tarantula, Eurypelma marxi Simon. Ramifications of the paired abdominal nerve VIIIb merge with the cardiac ganglion within the first heart segment. Electrical stimulation of the branches of nerve VIIIb that connect with the cardiac ganglion produce changes in heartbeat rate and amplitude. Nerve cutting experiments indicate that no other cardioregulatory nerves are present. Both increases and decreases in heart activity can be produced upon electrical stimulation of nerve VIIIb on each side of the heart. Only one action potential associated with the response of each type could be recorded in each member of the nerve pair. Therefore, we conclude that there are two inhibitory and two acceleratory neurons that arise in the central nervous system to modulate heartbeat activity. The inhibitory effect becomes maximal at a stimulation frequency of 20-30 Hz and the accelerator effect at 30-40 Hz. The aftereffect of acceleratory nerve activity exceeds that of inhibitory nerve activity. When the inhibitor and accelerator are activated simultaneously, the inhibitor dominates. The regulatory nerves interact with neurons in the cardiac ganglion. During inhibition, the number of externally recorded spikes in each ganglionic burst is decreased. The rate and magnitude of the heartbeat are decreased concomitantly. Stimulation of the accelerator enhances electrical activity in the cardiac ganglion at the same time that the heartbeat rate and amplitude are increased.
Cardiomyoblasts in the myocardium of embryonic lobsters at 3-4 weeks and 6 months of development were examined with the transmission electron microscope in order to describe the events in the formation of sarcomeres in a neurogenic cardiac system. Thick and thin myofilaments appear first in the cell periphery near the sarcolemma. They align in parallel in a sequential fashion to form consecutive sarcomeric units. Well-defined A and I bands appear before any semblance of a Z line is present. The initial sarcomere is anchored to the sarcolemma by the insertion of thin myofilaments into a region of electron dense material associated intimately with the sarcolemma. Myofibrils grow outward in several planes away from the electron-dense regions of membrane that serve as focal points for myofibril formation.
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Surface and volume densities of the invaginated membrane components of tonic muscle fibers of crayfish (Orconectes rusticus) were determined by stereological methods. Surface densities of the sarcolemma, sarcolemmal invaginations, T tubules and Z tubules were 2.0, 5.9, 26.3, and 3.3 micron2/100 micron3 of fiber, respectively, and volume densities of the sarcolemmal invaginations, T tubules, and Z tubules were 0.28, 0.29, and 0.08 micron3/100 micron3. The values obtained for surface density show that 95% of the membrane exposed to the extracellular environment is composed of invaginated membrane. Specific membrane capacitance, determined from square-wave pulse analysis and referred to the apparent area of surface sarcolemma, was 30.3 muF/cm2. However, after correction for the extent of invaginated membrane, the specific membrane capacitance was 1.6 muF/cm2.
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Structural and functional interrelationships between the pre- and postsynaptic elements of a singly motor innervated crab muscle (stretcher of Hyas araneus L.) were examined using electrophysiological and electron microscopic techniques. Excitatory postsynaptic potential (EPSP) amplitude at 1 Hz was found to be inversely related to the extent of facilitation, and directly related both to the amount of transmitter released at 1 Hz and the muscle fiber input resistance (R(in)). The extent of facilitation (F(e)), taken as the ratio of the EPSP amplitude at 10 Hz to that 1 Hz, was inversely related to muscle fiber R(in), tau(m), and sarcomere length. Sarcomere length was directly related to R(in) and tau(m). The excitatory nerve terminals of low F(e) muscle fibers had larger neuromuscular synapses than did those of high F(e) fibers. Inhibitory axo-axonal synapses were more often found in low F(e) muscle fibers. These structural features may account for the greater release of transmitter at low frequencies from the low F(e) nerve terminals as well as provide for a greater amount of presynaptic inhibition of low F(e) muscle fibers. The implications of these findings for the development and physiological performance of the crustacean motor unit are discussed. It is proposed that both nerve and muscle fiber properties may be determined by the developmental pattern of nerve growth.