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Biomedical subjects

R Laas

Publications and source records attributed to R Laas.

31 records · Page 2Linked to original sources
PubMed1984

Common carotid artery stump pressure in the gerbil stroke model.

In 106 slightly anaesthetised adult mongolian gerbils one common carotid artery (CCA) was ligated and the blood pressure in the distal and in the proximal stump was monitored for 8 minutes. The mean distal CCA stump pressure of the 39 nonsurvivors was 15 (+/- 6) mm Hg, that of the 25 survivors with retinocerebral infarcts was 25 (+/- 6) mm Hg, and that of the 42 intact survivors was 31 (+/- 7) mm Hg. The corresponding mean arterial blood pressures (MABP), as measured in the proximal CCA stump, were 81 (+/- 12) mm Hg, 84 (+/- 13) mm Hg, and 87 (+/- 11) mm Hg, respectively. There were no differences between the samples concerning sex, body weight, rectal temperature, arterial blood gases, arterial pH, and haematocrit. Measurements in a second series of 10 awake gerbils showed that the mean values of MABP, heart rate, and respiratory rate of the nonsurvivors were less than those of the survivors during 90 minutes after CCA ligation. It is inferred that in the mongolian gerbil the lower threshold of the arterial blood pressure for the development of brain infarcts ranges within 22 and 25 mm Hg, that is, within the values found in monkeys and cats. The longlasting depression of respiration and circulation in the nonsurvivors is considered to be related to the phenomenon of diaschisis .

Animals↗
PubMed1983

Cerebral infarction due to carotid occlusion and carbon monoxide exposure. I. Pathophysiological and neuropathological investigations.

Ligation of one common carotid artery and exposure to carbon monoxide has proved to be a reliable method of producing unilateral cerebral infarcts in the rat, allowing controlled experiments in any given sample size. Pathophysiological measurements in awake and narcotized rats has shown that, in contrast to hypoxic hypoxia, the carbon monoxide-induced functional anaemia (3000 ppm in room air) did not stimulate chemoreceptors, thus causing a severe systemic hypotension owing to peripheral vascular dilatation. This hypotension is likely to represent the main pathogenetic factor in this model. An inhibition of ferro-enzymes by carbon monoxide did not seem to be involved. The only cause of death was shown to be diffuse ipsilateral brain oedema with or without extra-vasation of serum proteins. The EEG, the systemic arterial pressure, rotational behaviour, and carotidal stump pressure proved to be reliable predictors of outcome.

Animals↗
PubMed1983

Cerebral infarction due to carotid occlusion and carbon monoxide exposure. II. Influence of preganglionic cervical sympathectomy.

Unilateral cerebral infarcts were produced in the rat by ligation of one common carotid artery and subsequent exposure to carbon monoxide. The incidence and extension of brain infarcts was increased in animals with additional ipsilateral cervical preganglionic sympathectomy. Sympathectomy did not affect markedly the respiration and systemic circulation. The effect of sympathectomy was attributed to a cutaneous vasodilation, leading to an extracranial steal phenomenon.

Animals↗
PubMed1983

Cerebral infarction due to carotid occlusion and carbon monoxide exposure III. Influence of neck vein occlusion.

Unilateral cerebral infarcts were produced in the rat by ligation of one common carotid artery and a subsequent exposure to carbon monoxide. In animals which had undergone an additional ligation of the external jugular veins leading to a moderate increase of the cephalic venous pressure the outcome of the procedure was ameliorated significantly. Venous pressure elevation was thought to reduce the venous vascular resistance effectively by preventing the leptomeningeal veins from collapsing. Collapse of the leptomeningeal veins probably occurred during the severe carbon monoxide-induced hypotension causing a steep increase of cerebral vascular resistance.

Animals↗
PubMed1981

Compression of the outlets of the leptomeningeal veins--the cause of intracranial plateau waves.

The hypothesis is developed that plateau waves (PW) are caused by an abrupt elevation of postcapillary flow resistance induced by compression of the outlets of the leptomeningeal veins. It is shown by means of a physical model that the main prerequisite for venous outlet compression consists in an elevation of the outflow resistance of the cerebrospinal fluid. Resolution of PW is demonstrated to be brought about by expulsion of fluid from the cranial vault during the plateau phase, thus allowing the outlets of the leptomeningeal veins to re-open. Brain shifting seems also to participate in this redistribution of the intracranial space in favour of the vasculature. It is further proven that PW may occur in rats with chronically or acutely increased CSF outflow resistance. PW triggering was investigated in these animals. All phenomena known to be related to PW are explained by the concept developed.

Animals↗
PubMed1981

An improved balloon catheter technique for the occlusion of carotid-cavernous sinus fistulas (CCF).

By means of a case report a shortcoming of balloon catheter techniques for intravascular occlusion of CCF is demonstrated: the procedure by which the balloon is detached from the filling catheter is unreliable and may further traumatise the vessel wall. We describe a new technique that allows careful, gentle, and effortless detachment of the balloon by means of a melting-off technic.

Adolescent↗
PubMed1980

[Animal studies on pancreatic encephalopathy (author's transl)].

In the albino rat pancreatic juice was chronically introduced into the circulatory system. Even when the blood brain barrier was transiently opened this procedure did not affect the central nervous system, as revealed by polyphysiographic and neuropathologic analysis.

Animals↗
PubMedDate not supplied

Hormone production in pituitary adenomas following external irradiation: an experimental study in rats.

INTRODUCTION: The aim of this study was to investigate the hormone production in pituitary gland tumors following fractionated external irradiation in rats. MATERIALS AND METHODS: Sixty female Wistar rats 3 to 4 month of age at the beginning of the experiments, were subjected to fractionated roentgen-rays exposure, 2 Grays (Gy) daily, either up to 20, 40 or 60 Gy. The animals were sacrificed either 6 month or 1 year after completion of the randomly assigned irradiation protocol. RESULTS: We found 9 pituitary tumors in 60 irradiated rats (15%). All tumors proved to be adenomas. Immunohistochemical analysis of hormone production in remnants of the normal adenohypophysis revealed immunoreactivity for growth hormone (GH), adrenocorticotropic hormone (ACTH), prolactin (PRL), thyroid-stimulating hormone (TSH), and follicle-stimulating hormone (FSH). In adenomas, 4 cases were immunoreactive for TSH, 4 for GH, 2 for PRL, and 2 for FSH. The tumors were not reactive with anti-ACTH and anti-LH (luteinizing hormone). DISCUSSION: We concluded that irradiation accelerates the development of pituitary gland adenomas. In our series these tumors were predominantly incidental findings at necropsies after pre-termed follow-up, with a variety of hormone producing tumor cells. However, 4 of 9 tumors in our study were not producing hormones.

Animals↗
PubMedDate not supplied

Hypoxia-ischemia and thiamine deficiency.

In order to test the hypothesis that Wernicke's encephalopathy is of topographic rather than of pathogenetic specificity we examined the brains of 49 patients without any evidence of chronic alcoholism. They had died at least four days after an event of severe hypoxia-ischemia. They all showed extensive lesions in the cortex, in the thalamus and in other regions. In 19 of them there was additional necrosis in the mamillary bodies which apparently was of the same age as the associated cortical and thalamic lesions and which could not be distinguished from Wernicke's encephalopathy. In three of the 19 cases there was a total necrosis within the mamillary bodies. By re-examining the mamillary bodies of 12 known alcoholics without any evidence for an ischemic impact we could affirm that total necrosis may fit into the spectrum of Wernicke's encephalopathy. Our findings demonstrate that the morphological changes in the mamillary bodies due to thiamine deficiency and those due to hypoxia-ischemia may be identical.

Adult↗
PubMedDate not supplied

Comparative brain pathology of HIV-seronegative and HIV-infected drug addicts.

Early stages of infection with human immunodeficiency virus (HIV) were studied in HIV-seropositive drug addicts. Since heroin users are immunocompromized even in the absence of HIV infection, the aim of the present study was to compare the morphological alterations present in HIV-seronegative and HIV-seropositive drug addicts. A total of 60 cases (32 HIV-seronegative subjects, 21 HIV-seropositive patients without signs of acquired immunodeficiency syndrome (AIDS), and 7 HIV-seropositive patients with signs of AIDS) were investigated macroscopically, histologically, and immunohistochemically HIV-seronegative patients presented more frequently with acute drug intoxication, died at a significantly younger age than HIV-seropositive patients, and were found to suffer more frequently from alcohol-related changes. These results indicated that HIV-seronegative and HIV-seropositive patients differed possibly in their drug consumption and also in their general conditions of life. In accordance with previous reports activated microglia and a diffuse astrogliosis in the white matter were detected at a significantly higher frequency and found to be more severe in HIV-seropositive subjects than in HIV-seronegative addicts. A lymphocytic meningitis was present in 6 of 21 HIV-seropositive patients but in none of the HIV-seronegative patients. Perivascular infiltrates consisting of lymphocytes and macrophages were detected at similar frequencies in HIV-seronegative and HIV-seropositive patients but were significantly more severe in patients suffering from lymphocytic meningitis or purulent encephalitis. Opportunistic infections were only demonstrated in 2 AIDS cases. In 10 of the HIV-seronegative patients and in 3 of the HIV-seropositive patients CD68-and Ham56-positive multinucleated cells were detected scattered in the subarachnoidal space exclusively over the frontal cortex.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Xanthogranuloma and xanthoma of the choroid plexus: evidence for different etiology and pathogenesis.

Xanthogranulomas of the choroid plexus (XGCP) and xanthomas of the choroid plexus (XCP) are generally held to be closely related to each other. Obtained by autopsy 17 cases with XGCP and 21 cases with XCP were investigated. Foamy cells were confirmed to be constitutional for both lesions. Immunohistochemically their antigen profile was shown to be of histiocytic type. A dense siderosis emerged as a consistent feature of XGCP but not of XCP. In no case both tumors were found associated. Analysis of clinical data revealed hyperlipidemia in 15 out of 17 cases with XCP but in only 3 out of 13 cases with XGCP (p < 0.01; in 4 cases of each sample pertinent data were pending). The male-to-female ratio was 14:3 in cases with XGCP and 13:8 in cases with XCP; when combined with data of other authors the male preponderance in XGCP became statistically significant. In conclusion, XGCP and XCP emerged as different independent lesions. XCP appeared to be closely related for example to tendon xanthomas of the skin which are well established as being diagnostic of hyperlipidemia. XGCP, on the other hand, are most likely to correspond to cholesterol granulomas of extracranial provenance. Thus, the data presented strongly recommend the replacement of the term "xanthogranuloma of choroid plexus" with the term "cholesterol granuloma of choroid plexus".

Adult↗