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Biomedical subjects

G Rosner

Publications and source records attributed to G Rosner.

85 records · Page 5Linked to original sources
PubMed1986

Cortical deafferentation in cat focal ischemia: disturbance and recovery of sensory functions in cortical areas with different degrees of cerebral blood flow reduction.

During and after 15-min occlusion of the middle cerebral artery (MCA) in cats, local CBF and neuronal activity were measured in cortical areas varying in the degree of CBF reduction. In an area within the ischemic center (primary auditory cortex, middle ectosylvian gyrus), CBF was severely suppressed. Click-induced auditory evoked potentials and evoked as well as spontaneous single-unit activity ceased within 1 min after occlusion. Recirculation resulted in a recovery of the different neurophysiological parameters with a time delay ranging from several minutes to 2 h. In two areas surrounding the ischemic focus (a visual area in the marginal gyrus and the forelimb representation area in the primary somatosensory cortex), CBF was reduced but remained above 30 ml/100 g/min during MCA occlusion. Visual flash-induced evoked potentials and somatosensory evoked potentials induced by median nerve electrical stimulation ceased in the corresponding areas with a somewhat slower time course as compared to the auditory responses and they recovered faster after recirculation. In another somatosensory area (hindlimb projection area in the primary somatosensory cortex), CBF stayed nearly at control levels during occlusion. Evoked potentials and single-unit activity induced by tibial nerve electrical stimulation decreased approximately 5 min after occlusion and were abolished approximately 5 min later. At that time, single-unit activity had changed to a nonresponsive pattern but persisted. However, potentials evoked transcallosally by electrical stimulation of the contralateral hemisphere were still recorded. After reopening the MCA, the recovery of neuronal functions was usually complete and occurred within approximately 5 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

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Journal Article↗
PubMed1984

BCVPP chemotherapy for advanced Hodgkin's disease: evidence for greater duration of complete remission, greater survival, and less toxicity than with a MOPP regimen. Results of the Eastern Cooperative Oncology Group study.

Two chemotherapy regimens for treatment of patients with advanced Hodgkin's disease, BCVPP (carmustine, cyclophosphamide, vinblastine, procarbazine, and prednisone) and MOPP (mechlorethamine hydrochloride, vincristine, procarbazine, and prednisone), were compared in a randomized prospective study. Two hundred ninety-three patients were evaluable in the induction phase of this study. The complete remission rate with BCVPP was 76% (112/147) and with MOPP, 73% (106/146) (p = 0.51). The duration of complete remissions for previously untreated patients given BCVPP was significantly longer than that for previously untreated patients given MOPP (p = 0.02). Although hematologic toxicities were similar, BCVPP caused less gastrointestinal (p = 0.0001) and neurologic toxicity (p = 0.01) than MOPP. Previously untreated patients achieving complete remission with BCVPP survived significantly longer than those receiving MOPP (p = 0.03). As primary induction chemotherapy for advanced Hodgkin's disease, BCVPP is an effective alternative to MOPP, having equal or greater therapeutic benefit with less toxicity.

Adult↗
PubMed1983

Functional recovery of cortical neurons as related to degree and duration of ischemia.

Simultaneous recordings of spontaneous single cell activity and local cerebral blood flow were obtained from 72 cortical neurons and adjacent brain in 54 cats before, during, and after ischemia induced by reversible occlusion of the middle cerebral artery. In most cells spontaneous electrical activity ceased at flow values of about 0.18 ml/gm/min (range, 0.06 to 0.22 ml/gm/min). No signal was obtained from 28 neurons during reperfusion following ischemia of varying degree and duration. Overall, neurons exposed to a residual flow of 0.14 ml/gm/min or less for more than 45 minutes had a poorer prognosis compared to any other combination of degree and duration of ischemia. A discriminant curve was estimated to define the border line between recovering and nonrecovering cells. Regions showing irreversible neuronal failure contained selective neuronal necrosis or areas of infarction by histological examination. Reperfusion restored neuronal function in 44 cells. In this group of neurons, there was a joint interaction of duration of ischemia, ischemic residual flow, and recovery time: cells exposed to moderate ischemia (0.09 to 0.22 ml/gm/min) for up to 20 minutes recovered rapidly; most neurons subjected either to extreme ischemia (less than 0.09 ml/gm/min) of short duration (less than 20 minutes) or to moderate ischemia (0.09 to 0.22 ml/gm/min) for longer periods (20 to 141 minutes) required from 19 to 50 minutes for recovery. A few resistant neurons tolerated less than 0.09 ml/gm/min for more than 20 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Response latency of brisk-sustained (X) and brisk-transient (Y) cells in the cat retina.

1. Several methods for evaluating light-evoked response latency and its variability in brisk-sustained (X) and brisk-transient (Y) retinal ganglion cells were tested. The most accurate procedure proved to be that described by Levick (1973), in which the time of the occurrence of the fourth impulse after stimulus onset is taken as an estimate of the latency.2. The shortest response latencies are obtained when the stimuli are the same size as the receptive field centre. At medium and high response amplitudes (> 150 impulses/sec) the response of brisk-transient (Y) cells to these optimal stimuli is 10-15 msec faster than that of adjacent brisk-sustained (X) cells.3. The response latency of brisk-sustained (X) cells for stimuli larger than the receptive field centre increases, whereas that of brisk-transient (Y) cells remains constant. Brisk-sustained (X) cells respond faster than do brisk-transient (Y) cells to stimuli smaller than the receptive field centre.4. No systematic difference exists between brisk-sustained (X) and brisk-transient (Y) cells in regard to the temporal variability of the response. The standard deviation of the latency for stimuli of optimal size decreases from 2.0-8.0 msec at medium stimulus contrast to 0.6-2.0 msec at high stimulus contrast.5. The response of OFF-centre cells to the disappearance of a light spot is always slower than that of an ON-centre cell of the same class to the onset of this stimulus. However, when OFF-centre cells are stimulated with dark spots, their response latency does not differ from that of ON-centre cells of the same class.6. No simple relationship exists between the response latency and the response amplitude. At medium and high discharge rates, most brisk-transient (Y) cells respond faster than an adjacent brisk-sustained (X) cell with equal response. At the same response amplitude, the latencies become shorter as the background illumination is raised. The same discharge rate can be obtained with stimuli of sub-optimal and supra-optimal size, but the latency for the larger stimulus is shorter than that for the smaller one. Latency, therefore, is an additional parameter characterizing the light-evoked response.

Action Potentials↗
PubMedDate not supplied

Selective functional vulnerability of cortical neurons following transient MCA-occlusion in the cat.

Simultaneous recordings of several cortical neurons were obtained before, during and after transient 15 min occlusion of the middle cerebral artery in cats. With the use of a multiple electrode array consisting of 4-7 platinum/iridium microelectrodes, the cortical pericellular blood flow was concurrently measured by means of the hydrogen clearance technique. Hydrogen clearance measurements revealed a homogeneous blood flow distribution throughout all phases of the experiment in the area covered by the different microelectrodes. Considering only the results of experiments with low residual blood flow during ischemia (less than 0.1 ml/g/min), single unit activity ceased immediately after occlusion and remained so during the ischemic period. The recovery time of action potentials after reperfusion ranged from 10 min to 3 hours depending on the examined neuron. Lower values for discharge rates of the individual cells were generally observed after reoccurrence, although some units exhibited temporarily an even higher spike frequency. Furthermore, the spike form usually changed in that the hyperpolarizing afterpotentials were enlarged after recirculation. However, some cells with a nearly unchanged spike form were found as well. The results indicate that the recovery of cell function largely depends on the individual neuron which supports the idea of a selective functional vulnerability of cortical neurons in response to ischemia.

Action Potentials↗
PubMedDate not supplied

Experimental focal ischemia in cats: changes in multimodality evoked potentials as related to local cerebral blood flow and ischemic brain edema.

Somatosensory and auditory evoked cortical potentials (SEP's and AEP's), regional cerebral blood flow, regional brain water content, and alteration of the blood-brain barrier were investigated in 3 cortical areas during permanent and 1- and 2-hour transient occlusion of the left middle cerebral artery and after restoration of blood flow in cats. During occlusion, blood flow in the auditory cortex was severely suppressed. In the fore limb projection area of the somatosensory cortex, blood flow was moderately reduced while it was nearly unaffected in the hind limb projection area. Despite different degrees of ischemia in the 3 cortical areas, all evoked responses were completely abolished within 10 minutes after occlusion. During permanent occlusion, the pattern of blood flow reduction persisted, and all evoked potentials stayed abolished. Recirculation after occlusion restored blood flow rapidly. AEP's recovered poorly after both 1 and 2 hours of ischemia. SEP's regained normal amplitudes soon after recirculation in the group with 1-hour occlusion. After 2 hours of ischemia, the recovery of SEP's was variable but better than that of the AEP's. Remarkable water accumulation was observed in the auditory cortex of all 3 groups and was accompanied in the 2-hour ischemia group by a disruption of the blood-brain barrier. In the 2-hour group, water accumulation was also found in the subcortical white matter radiation, whereas significant changes in regional water content were not observed in the somatosensory areas. The present study indicates that abolition of SEP's during middle cerebral artery occlusion in cats is caused by lesions in the afferent pathway leading to cortical deafferentation rather than by cortical ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

The use of hydralazine to manipulate tumour temperatures during hyperthermia.

Hydralazine is an antihypertensive drug which theoretically could increase tumour temperatures during hyperthermia via reduction in tumour blood flow from a vascular 'steal' phenomenon. Doses that are therapeutically effective in reducing blood pressure in hypertensive patients would probably cause postural hypotension and other side-effects in normotensive patients beyond the hyperthermia treatment session, however. This study was designed to evaluate whether hydralazine, when administered at a safe dose for normotensive patients (0.125 mg/kg, i.v.) would be effective in increasing tumour temperatures during hyperthermia. The working hypothesis was that hydralazine at a dose of 0.125 mg/kg would be effective in raising tumour temperatures during hyperthermia treatment with minimal change in blood pressure. Fourteen human and five canine subjects were given hydralazine (0.125 mg/kg, i.v.) at the midpoint of a hyperthermia session. Temperatures and blood pressures were monitored before and after drug administration. Although hydralazine resulted in slight reduction in blood pressure, it was ineffective in increasing tumour temperatures in human patients (average maximum rise in median temperature was 0.26 +/- 0.32 degrees C). In canine subjects the same dose of hydralazine was effective in reducing blood pressure in four of five subjects studied (mean maximum drop was 22.7 +/- 4.1 mmHg) and the median temperature rose 0.8 +/- 0.7 degrees C. In the canine subjects the greater the decrease in blood pressure, the greater the increase in temperature. These results suggest that a rise in tumour temperature induced by hydralazine is dependent on creating a drop in blood pressure. Future studies in this laboratory will include tumour blood flow manipulation with antihypertensives which have a shorter half-life and a titratable effect. Using this approach, hypotension, which seems to be required to raise tumour temperature, will be more controllable in terms of magnitude and duration.

Animals↗
PubMedDate not supplied

Response of canine soft tissue sarcomas to radiation or radiation plus hyperthermia: a randomized phase II study.

Sixty-four dogs with spontaneous soft tissue sarcomas without evidence of metastases were stratified by tumour volume and randomized to receive graded doses of radiotherapy (XRT) alone or radiotherapy plus hyperthermia (HT). An improvement in duration of local control was achieved with the addition of hyperthermia as compared with XRT alone (Wilcoxon, p = 0.040; log rank, p = 0.064). Overall frequency of late complications was not different for the two treatment arms when comparing across equivalent XRT dose groups. Frequency of distant metastases after therapy completion was not significantly different for the two treatment arms at 1 year (7.4% for XRT versus 20% for HT plus XRT) or 2 years (11.5% for XRT versus 25% for HT plus XRT) post therapy. These results suggest that a therapeutic gain was achieved for this group of tumour-bearing animals. Uni- and multivariate analyses were performed to examine the potential for various factors to influence treatment outcome. Patient related variables included tumour stage, histologic subtype and grade and tumour site. Treatment related variables included total radiation dose and 15 descriptors of temperature distributions achieved during hyperthermia. When considering patient related factors, tumour histology, grade and location were important predictors of time to minimum volume, but only tumour location influenced time to tumour regrowth. When considering treatment related factors, radiation dose was not significantly correlated with time to minimum volume or time to local regrowth, but it was correlated with probability for late normal tissue damage in the XRT alone group (p = 0.005). For the hyperthermia treatments, 13 of 15 tumour temperature distribution descriptors were correlated with time to minimum volume, but none were correlated with time to local regrowth. These results suggest that caution should be used in interpreting the value of temperature distribution descriptors in predicting for long-term local control after hyperthermia and radiotherapy, based on analysis of short-term responses.

Animals↗