High-frequency and medium-frequency components of different inspiratory nerve discharges and their modification by various inputs.

In decerebrate paralyzed cats, spectral analysis was performed on simultaneous recordings of efferent inspiratory nerves (phrenic, recurrent laryngeal, hypoglossal). Spectral peaks were present both in the high-frequency (HFO) range (50-100 Hz) and the medium-frequency (MFO) range (20-50 Hz). Different activities were coherent only in the HFO range, indicating that the HFOs arise in a common inspiratory pattern generator that drives the different motoneuron populations, whereas the MFOs are specific to different systems.

Heparin prevention of tumor cell adherence and implantation on injured urothelial surfaces.

Increasing laboratory and clinical evidence supports the concept of tumor cell implantation as a cause of intravesical recurrence in transitional cell carcinoma of the bladder. The integrity of the surface mucopolysaccharide layer of the bladder has been shown to be crucial in preventing bacterial or crystalline adherence. The purpose of this study was to evaluate the effects of bladder surface mucin integrity on tumor cell adherence and implantation.

Tumor cell implantation following neodymium-YAG bladder injury: a comparison to electrocautery injury.

Recent clinical experience using the neodymium-YAG laser for the ablation of superficial bladder carcinoma seems to indicate a decreased local and second-site recurrence rate when compared to standard electrosurgical methods. Altered tumor cell implantation has been suggested as a mechanism explaining this phenomenon. The purpose of this study was to compare the effects of laser ablation and standard electrosurgical resection on tumor implantation.

Role of chemical afferents in the maintenance of rhythmic respiratory movements.

In seven anesthetized cats central chemosensitivity was eliminated (cold block) and peripheral chemoreceptors were either stimulated or eliminated (sectioned) to test whether nonchemical vagal afferents can maintain rhythmic ventilation and to determine the relative contribution of the carotid and aortic chemoreceptors to ventilatory drive without central chemosensitivity. Elimination of all chemical afferents invariably induced apnea, whereas ventilation was reduced from 533 to 159 ml X min-1 during cold block of central chemosensitivity and to 478 ml X min-1 after sectioning both sinus nerves. Cold block with only the aortic chemoreceptors and vagal afferents intact produced apnea in four of six cases tested.

Effect of halothane anesthesia on end-tidal PCO and pattern of respiration in the rat.

End-tidal Pco2 (petco2) and ventilation of the rat anesthetized with halothane were measured. The Petco2 measured by an infrared analyzer agreed well with the simultaneously measured Paco2 in the range from 20-60mm Hg (2.7-8.

H+-sensitivity and pattern of discharge of neurons in the chemosensitive areas of the ventral medulla oblongata of rats in vitro.

Effect of H+ on neuronal activity in medullary chemosensitive structures was analyzed in brain slices of the rat in vitro. Spontaneous discharges of spikes were recorded from two populations of neurons in the ventral surface layer of the medulla oblongata. Neurons located in the rostro-lateral part of the hypoglossal nerve root (area II) fired irregular phasic and/or continuous tonic discharges.

Respiratory response to hypoxia and hypercapnia after elimination of central chemosensitivity.

Central respiratory drive responding to pH changes was eliminated by bilateral coagulation or cold block of area S (intermediate area) on the ventral medullary surface in 7 anaesthetized cats. Arterial pH, PCO2, and PO2 (4 cats) and the respiratory response to hypoxia and hypercapnia (6 cats) were observed before and after coagulation. After coagulation in hyperoxia the arterial pH dropped from 7.

Chemosensitive neurons on the ventral medullary surface.

Central chemosensitivity is ascribed to three areas on the ventral medullary surface. The discharge frequency of neurons observed in these areas depends upon pH. Other neurons within the same areas do not change their frequency during acidosis or alkalosis.