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Biomedical subjects

P Molnar

Publications and source records attributed to P Molnar.

45 records · Page 3Linked to original sources
PubMed1983

Regional blood flow in avian sarcoma virus (ASV)-induced brain tumors.

Regional blood flow (F) was measured in avian sarcoma virus (ASV)-induced brain tumors in rats. Blood flow was variable in individual as well as different tumors; tumor F did not correlate with histologic classification, tumor size, central versus peripheral tumor regions, intraparenchymal location, cell density, or specific cytologic characteristics. Low values of F did correlate with tumor necrosis and hydrocephalus; high values of F correlated with tumorous invasion or association with choroid plexus. Mean tumor F was not significantly different from that of the same anatomic, tumor-free brain region of the contralateral hemisphere, but F in brain tissue adjacent to the tumor was depressed significantly. Depression of F was observed in tumor-free cortex and corpus callosum, especially in the hemisphere ipsilateral to the main tumor mass and in those animals with hydrocephalus.

Animals↗
PubMed1983

Regional blood-to-tissue transport in avian sarcoma virus (ASV)-induced brain tumors.

Regional blood-to-tissue transport of 14C-alpha-aminoisobutyric acid (AIB) was measured in avian sarcoma virus (ASV)-induced rat brain tumors and expressed as a unidirectional transfer rate constant (K). The magnitude of K was variable and did not correlate with histologic classification or specific features of the tumors, with the possible exception of sarcomas. Averaged mean K was highest for anaplastic astrocytomas and lowest for gemistocytic astrocytomas (GA); however, the range of measurement within the individual tumor classifications (except GA) was broad. K was not consistently related to tumor size or tumor location; choroid plexus and subependymal tumors were exceptions and had higher K values. The averaged mean K of tumor-free brain in the contralateral hemisphere (CBA) was comparable to that of control animals. The averaged mean K in brain adjacent to tumor was greater than in CBA and generally one-third to one-half of the value in tumor periphery, indicating that these tumors affect the permeability characteristics of adjacent brain capillaries. Estimates of the fractional extraction (E) of AIB by the tumors ranged between 0.009 and 0.2; E's in this range indicate that tumor capillaries are not freely permeable to this solute.

Animals↗
PubMed1983

Regional blood flow in RT-9 brain tumors.

Regional blood flow (BF) was measured in RT-9 experimental brain tumors using carbon-14 labeled iodoantipyrine, the Kety tissue-exchange equations, and quantitative autoradiographic techniques. Blood flow was variable within tumor tissue, and the range of BF increased with increasing tumor size; the overall range was 6 to 138 ml/100 gm/min and the maximum range within an individual tumor was 55 ml/100 gm/min. In all but one case, mean tumor BF was less than that in the same anatomic region of the contralateral hemisphere (CBA). The magnitude of BF within individual tumor foci generally could be related to tumor size, location (intraparenchymal versus extraparenchymal), and the presence of necrosis or cysts; it was lower in the geometric centers than in the periphery of medium-sized and large tumors. Brain adjacent to tumor had higher BF's than the tumor periphery; generally, the BF in the brain adjacent to the tumor was less than that in the CBA. A global depression of BF was observed within tumor-free cortex and corpus callosum of the hemisphere ipsilateral to tumor implantation and primary growth, suggesting a hemispheric reduction in metabolic and functional activity.

Animals↗
PubMed1983

Regional blood-to-tissue transport in RT-9 brain tumors.

Regional blood-to-tissue transport, expressed as a unidirectional transfer rate constant (K), was measured in experimental RT-9 brain tumors using 14C-alpha-aminoisobutyric acid (AIB) and quantitative autoradiographic techniques. The magnitude of K depends on the permeability, surface area, and blood flow of the tissue capillaries. The transfer rate constant was variable within tumor tissue (range 0.001 to 0.178 ml/gm/min) and depended on tumor size, location (intraparenchymal, meningeal, or choroid plexus associated), and to a lesser extent on necrosis and cyst formation. Brain adjacent to tumor had higher K values, particularly around larger tumors (0.004 to 0.014 ml/gm/min), than corresponding brain regions in the contralateral hemisphere (0.001 to 0.002 ml/gm/min). Estimates of the fractional extraction of AIB by intraparenchymal tumors were between 0.008 and 0.4 ml/gm/min. Values of fractional extraction in this range indicate that tumor capillaries are not freely permeable to this solute. The values of K measured with AIB in this study, for the most part, approximate the permeability-surface area product of tumor and brain capillaries. The experimental data suggest that the permeability-surface area characteristics of the microvasculature in small RT-9 tumors are similar to those of the host tissue, whereas the microvasculature of larger RT-9 tumors is influenced more by intrinsic tumor factors.

Aminoisobutyric Acids↗
PubMed1983

Increased blood-brain transfer in a rabbit model of acute liver failure.

The blood-to-brain transfer of [14C]alpha-aminoisobutyric acid was investigated by quantitative autoradiography in normal rabbits and rabbits with acute liver failure induced by the selective hepatotoxin galactosamine. The blood-to-brain transfer of alpha-aminoisobutyric acid was similar in control animals and animals 2 and 7 h after galactosamine injections, but was increased five- to tenfold in certain gray-matter areas of the brain in animals 11 and 18 h after galactosamine treatment. No detectable differences in white-matter uptake of [14C]alpha-aminoisobutyric acid were found between the control and treated groups. The increase in alpha-aminoisobutyric acid transfer within the gray-matter areas suggested that a general or nonspecific increase in brain capillary permeability occurred in these areas. No clinical signs of early hepatic encephalopathy were observed in the treated rabbits, except for 1 animal from the 18-h postgalactosamine group. Thus, enhanced blood-brain transfer of alpha-aminoisobutyric acid preceded the development of overt hepatic encephalopathy. The distribution of radioactivity after the intravenous administration of [14C]galactosamine showed that virtually none of the hepatotoxin localized in the brain, suggesting that the drug itself does not have a direct effect upon the blood-brain barrier or the brain. The increased uptake of alpha-aminoisobutyric acid at 11 and 18 h implies that the transfer of other solutes would also be enhanced, that central nervous system homeostasis would be compromised, and that the resulting changes in brain fluid composition could contribute to or cause hepatic encephalopathy.

Aminoisobutyric Acids↗
PubMed1983

Regional [14C]misonidazole distribution in experimental RT-9 brain tumors.

Regional [14C]misonidazole-derived radioactivity (MISO) was measured by quantitative autoradiography in experimental RT-9 brain tumors 0.5, 2, and 4 hr after an i.v. bolus (25 mg) and constant infusion (10 mg/hr). Misonidazole (MISO) concentration in plasma and brain was also measured by high-pressure liquid chromatography; the brain/plasma MISO ratio ranged between 0.5 and 0.7. MISO equivalents were calculated from tissue or plasma 14C radioactivity and [14C]MISO specific activity data. The MISO/MISO equivalents ratio, which represents the nonmetabolized fraction of [14C]MISO, fell gradually in plasma (0.89 at 4 hr) and more rapidly in brain (0.67 at 4 hr) and tumor (0.30 at 4 hr). MISO distributed uniformly throughout the brain at all three time periods. In contrast, MISO distribution in tumor was variable, and tumor concentrations relative to that in brain increased with time. The average tumor/brain MISO ratio was 1.3, 1.7, and 2.6 at 0.5, 2, and 4 hr, respectively, which suggests tumor uptake and binding of MISO or, more likely, MISO-derived 14C-labeled metabolites. In addition, MISO distribution in tumor tissue was strikingly heterogeneous at 4 hr, resulting in an average high/low tumor activity ratio of 4/1 and an average high tumor/brain ratio of 5/1. Tumor regions with high MISO activity correlated in part to viable-appearing cells around necrotic foci.

Animals↗
PubMed1970

Plate tectonics of the Red Sea and East Africa.

The relative motion between the plates on each side of the East African Rift Valley can be obtained from the opening of the Red Sea and the Gulf of Aden. The calculated direction of relative motion agrees well with fault plane solutions for earthquakes north of the equator.

Journal Article↗
PubMedDate not supplied

Hemangiopericytoma of the cerebello-pontine angle. Diagnostic pitfalls and the diagnostic value of the subunit A of factor XIII as a tumor marker.

The authors report on a case that during its 9-year-long history has repeatedly been misdiagnosed due to the misleading clinical and histopathological findings. The patient has been treated, in chronological order, for cerebrovascular disease, acoustic Schwannoma, glomus tympanicum tumor (chemodectoma) and finally turned out to have an intracranial hemangiopericytoma that originated from the area of the glomus tympanicum and eventually widely metastatized within and outside the intracranial compartment. The proper diagnosis was reached with the help of detailed immunohistochemical analysis. The subunit A of Factor XIII (FXIIIa) can be demonstrated on formaldehyde-fixed paraffin embedded sections. It has recently been shown that FXIIIa reactivity is characteristic and hence diagnostic of a subpopulation of cells within systemic and intracranial (central) hemangiopericytomas (HPCs). Since it is consistently missing from all cell components of ordinary meningiomas, glomus tumors (chemodectomas) and a host of other soft tissue tumors, its presence or absence is a helpful sign in various differential diagnostic dilemmas.

Biomarkers, Tumor↗