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Biomedical subjects

W Graf

Publications and source records attributed to W Graf.

At least 145 records · Page 8Linked to original sources
PubMed1976

Visual-vestibular interactions in the vestibular nuclei of the goldfish.

The responses of vestibular nuclei neurons of relaxed unanaesthetized goldfish have been examined with trapezoid velocity stimuli under three conditions. Responses to horizontal body rotation in the dark (pure vestibular stimulation) resemble those observed in vestibular nerve afferents. Optokinetic responses to exclusive visual surround-motion are also direction-specific and, in contrast to vestibular responses, exhibit a tonic response to constant velocity. They show three different response profiles, classified A,B or C, based on the neuron's discharge rate: either increasing, decreasing or remaining constant once surround motion is maintained at constant velocity. Following these dynamic effects, optokinetic responses have a maintained modulation of resting discharge until deceleration commences. The time constants associated with the dynamic effects vary between 1 and 11 seconds. Steady-state modulation of optokinetic responses shows a weak relation to stimulus velocities exceeding 10 deg/sec. Responses to body rotation in the light were found to linearly combine the weighted vestibular and optokinetic responses so that accurate velocity information is available for sensory and motor functions independent of the neuron's vestibular (I,II) or optokinetic (A,B,C) response type. The principle of this visual-vestibular interaction is discussed with respect to multisensory processing within the vestibular nuclei.

Action Potentials↗
PubMed1976

A technique for study of lung function in birds by blocking the primary bronchus.

The technique described allows in vivo placement of a blocking balloon in the avian primary bronchus between the origins of the two sets of secondary bronchi, the medioventrals and mediodorsals. With caudal air sacs cannulated the animal may then be ventilated with a constant flow of gas passing entirely through the gas-exchanging parabronchi. This technique has been found useful particularly in studies of pulmonary gas exchange in birds.

Animals↗
PubMed1976

Effects of CO2 on pulmonary air flow resistance in the duck.

Effects of CO2 on pulmonary smooth muscle were assessed by measuring the air flow resistance of secondary bronchi and parabronchi in ducks unidirectionally ventilated with a constant gas flow through the parabronchial lung, the bypass of the primary bronchus being occluded by a blocking catheter. Pressure differences across the blocking balloon (deltaP), corresponding to the pressure drop in the gas flowing through the mediodorsal and medioventral secondary bronchi (MD and MV) and parabronchi, were measured at flow rates (V) varied from 0.5 to 3 L-min-1 and at CO2 concentrations of ventilating gas (FICO2) varied from 0 to 10%. 1) deltaP increased more than linearly with V. The resulting flow resistance R(= deltaP/V) averaged 43 and 95 cm H2O-L-1-sec at V = 0.5 and 3 L-min-1, respectively. 2) Step changes in FICO2 at constant V were followed within 0.5 to 5 sec by changes in R. 3) Lowering FICO2 from 5% resulted in marked increases in R, the value at FICO2 = 0% being more than twice the average value at 5%. Raising FICO2 from 5% up to 10% was followed by only slight changes in R. 4) Vagotomy did not consistently change R at any level of CO2; it did, however, slightly increase the delay time for changes in R on step changes of FICO2. 5)The medioventral secondary bronchi and their orifices into the primary bronchus appeared to be mainly responsible for the resistance measured and its changes with CO2. The resistance offered by the parabronchi appeared to be much smaller and much less dependent on CO2. The results suggest importance of lung gas CO2 in aerodynamic valving of respiratory flow in avian lungs during normal breathing and particularly during thermal panting to prevent alkalosis.

Airway Resistance↗