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Biomedical subjects

M Rich

Publications and source records attributed to M Rich.

At least 55 records · Page 3Linked to original sources
PubMed1989

Motor nerve terminal loss from degenerating muscle fibers.

The fate of nerve terminals following elimination of postsynaptic target cells was studied in living mouse muscle. Several days after muscle fiber damage, observations of previously identified neuromuscular junctions showed that motor nerve terminal branches had rapidly disappeared from degenerating muscle fibers. Following muscle fiber regeneration, loss of terminal branches ceased and nerve terminals regrew, reestablishing some of the original sites and adding new branches. The distribution of acetylcholine receptors reorganized in the regenerated muscle so that perfect alignment was reestablished with the newly configured nerve terminals. These results argue that the maintenance of the full complement of nerve terminal branches at a neuromuscular junction is dependent on the presence of a healthy muscle fiber. Similarly, regenerating muscle is dependent on the nerve terminal for the organization and maintenance of postsynaptic receptors.

Animals↗
PubMed1989

Persistent cloaca and phallic urethra.

During the last 8 years 54 children with a persistent cloaca have been treated by one of us (A. P.). The most common associated anomalies involved the urinary tract, with renal agenesis, renal dysplasia, vesicoureteral reflux and megaureter encountered most frequently. Four patients demonstrated the rare entity of an opening at the tip of a pseudophallus and 2 also had an accessory urethra in association with the cloacal malformation. These children exhibited some form of masculinization of the external genitalia with the accessory urethra or cloacal channel assuming a phallic position in an enlarged clitoris. No adrenal, metabolic or chromosomal abnormalities were detected and virilization was limited to the genitalia. These cases illustrate the greater predilection of these patients to more complex congenital malformations than patients with an isolated cloaca. The posterior sagittal approach has been used effectively for repair of these congenital malformations.

Abnormalities, Multiple↗
PubMed1989

Imaging rounds #97. Salter II fracture of the proximal tibia.

Proximal tibial physeal injury is extremely rare. It occurs most often in adolescents and is the result of a significant abduction force applied to the lower leg with the foot firmly fixed. Management of this injury follows the same principles as other Salter-Harris epiphyseal plate fractures. Prognosis is generally good, although there is a somewhat higher than anticipated incidence of angulatory and longitudinal deformities of Type I and Type II fractures, much as has been observed in distal femoral physeal fractures. This is probably due to direct injury to the germinal layer of the growth plate with subsequent partial physeal closure.

Adolescent↗
PubMed1988

Flexible cystoscopy in surgical repair of traumatic urethral strictures in children.

Flexible cystoscopy via a suprapubic cystostomy tract was utilized to locate the proximal segment of a complete traumatic disruption of the bulbar urethra secondary to a pelvic fracture. With the fiberoptic light of the instrument visible in the perineum, the proximal urethra was easily and safely dissected free from the enveloping fibrotic scar tissue and a simple one-stage urethroplasty performed. The patient is voiding normally eight months postoperatively.

Child↗
PubMed1987

Applications of the peel-away introducer sheath.

The peel-away introducer sheath set, originally designed for the antegrade insertion of the silicone rubber Universal stent, also is useful for antegrade or retrograde basketing of ureteral stones, negotiation of a dilated renal pelvis and tortuous ureter with minimal trauma, retrograde flushing of ureteral stones for percutaneous extraction, removal of dislodged stents from the renal pelvis and ureteral examination with a flexible endoscope or rigid ureteropyeloscope.

Dilatation↗
PubMed1987

Use of elevated pressure to promote the difference in permeability of Adriamycin and hematoporphyrin between neoplastic and normal lung cells.

The effect of increased pressure on the permeability of Adriamycin into human lung cells was studied as a function of a combination of pressure and temperature. Normal diploid lung cells as well as cells with adenocarcinoma were subjected to elevated pressures of up to 225 bars. The penetration of Adriamycin and hematoporphyrin into the cells, were assayed by use of fluorescence and absorption spectroscopy. After cells were subjected to pressure in the presence of Adriamycin, there was a greater concentration of Adriamycin in malignant cells than in normal cells. Malignant cells subjected to a pressure of 8 bars, for 210 min at 37 degrees C were found to contain twice the concentration of Adriamycin than normal cells, under the same conditions. The present results suggest that elevated pressure techniques may serve to increase the permeability of malignant cells to antineoplastic drugs.

Cell Membrane Permeability↗
PubMed1986

Importance of continued activation of thrombin reflected by fibrinopeptide A to the efficacy of thrombolysis.

Factors responsible for initial success or failure of coronary thrombolysis and persistent recanalization or early reocclusion have not been thoroughly elucidated. Both adequate initial clot lysis and preclusion of rethrombosis are required. Failure may reflect clot lysis followed immediately or somewhat later by rethrombosis. To determine whether differences in the intensity and persistence of the activation of thrombin are determinants of success or failure of recanalization, plasma fibrinopeptide A, a fibrinogen product liberated by thrombin, was serially assayed in 19 patients treated with intravenous streptokinase. In patients exhibiting recanalization (n = 9), plasma fibrinopeptide A decreased after administration of streptokinase but before administration of heparin. In patients without initially apparent recanalization, fibrinopeptide A increased, suggesting ongoing thrombosis, and subsequently decreased promptly after heparin. In patients with initial recanalization followed by overt reocclusion the pattern was different. Despite recanalization, fibrinopeptide A continued to rise markedly. Elevations persisted despite administration of heparin. Thus, inhibition of activation of thrombin is associated with successful recanalization. Conversely, persistent activation of thrombin may be a predisposing factor to both apparent initial failure of recanalization and overt early reocclusion.

Coronary Disease↗
PubMed1986

A comparative evaluation of three neonatal ventilators.

The comparative reliability of three neonatal ventilators was evaluated using an infant model lung to simulate airway resistance and lung compliance. The ventilators tested were the Bourns BP200, the Healthdyne TI-11, and a positive-pressure ventilator called the PREEMIE (not commercially manufactured) used in several neonatal units in the Milwaukee area. The Bourns and Healthdyne ventilators generated similar airway and alveolar pressures while the PREEMIE produced alveolar, peak inspiratory, and positive end-expiratory pressures that exceeded the respective ventilator pressure settings by up to 11 cm H2O. The simple method described here should be generally useful for the evaluation of neonatal ventilator output.

Airway Resistance↗
PubMed1986

Roentgen rounds #85. Compression fractures of lumbar vertebrae 3, 4, and 5.

Vertebral fractures in children are very rare and usually result from hyperflexion. Symptoms may be minimal, and most children are neurologically normal. Multiple vertebral fractures are common. The active growth plate, if uninjured, allows restoration of the vertebral body height, and growth of adjacent vertebrae can compensate for angular deformity.

Braces↗
PubMed1984

Long-term high-frequency jet ventilation in neonates.

High-frequency jet ventilation (HFJV) markedly improved the ventilatory status of 2 neonates with severe respiratory failure refractory to conventional mechanical ventilatory support. However, after approximately 1 wk of HFJV, both patients expired from causes not directly related to ventilatory compromise. Autopsy showed no gross alterations in tracheal or bronchial mucosa but did reveal microscopic lesions which could be attributable to HFJV.

Bronchi↗
PubMed1976

Hydrodynamic diameters of murine mammary, Rous sarcoma, and feline leukemia RNA tumor viruses: studies by laser beat frequency light-scattering spectroscopy and electron microscopy.

We have studied purified preparations of murine mammary tumor virus (MuMTV), Rous sarcoma virus (RSV; Prague strain), and feline leukemia virus (FeLV) by laser beat frequency light-scattering spectroscopy, ultra-centrifugation, and electron microscopy. The laser beat frequency light-scattering spectroscopy measurements yield the light-scattering intensity, weighted diffusion coefficients. The corresponding average hydrodynamic diameters, as calculated from the diffusion coefficients by the Stokes-Einstein equation for MuMTV, RSV, and FeLV, respectively, are: 144 +/- 6 nm, 147 +/- 7 nm, and 168 +/- 6 nm. Portions of the purified RSV and MuMTV preparations, from which light-scattering samples were obtained, and portions of the actual FeLV light-scattering samples were examined by negatively stained, catalase crystal-calibrated electron microscopy. The light-scattering intensity weighted averages of the electron micrograph size distributions were calculated by weighing each size by its theoretical relative scattering intensity, as obtained from published tables computed according to the Mie scattering theory. These averages and the experimentally observed hydrodynamic diameters agreed to within +/- 5%, which is the combined experimental error in the electron microscopic and light-scattering techniques. We conclude that the size distributions of singlet particles observed in the electron micrographs are statistically true representations of the sedimentation-purified solution size distributions. The sedimentation coefficients (S20, w) for MuMTV, RSV, and FeLV, respectively, are: 595 +/- 29S, 689 +/- 35S, and 880 +/- 44S. Virus partial specific volumes were taken as the reciprocals of the buoyant densities, determined in sucrose density gradients. The Svedberg equation was used to calculate particle weights from the measured diffusion and sedimentation coefficients. The particle weights for MuMTV, RSV, and FeLV, respectively, are: (3.17 +/- 0.32) x 10(8), (4.17 +/- 0.42) x 10(8), and (5.50 +/- 0.55) x 10(8) daltons.

Avian Sarcoma Viruses↗