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Biomedical subjects

H Wassmann

Publications and source records attributed to H Wassmann.

At least 37 records · Page 2Linked to original sources
PubMed2000

Acute protective effect of nimodipine and dimethyl sulfoxide against hypoxic and ischemic damage in brain slices.

Nimodipine and dimethyl sulfoxide (DMSO) were tested (alone and in combination) regarding their ability to increase hypoxic tolerance of brain slices under 'hypoxic' (deprivation of oxygen) or 'ischemic' (hypoxia+withdrawal of glucose) conditions. Direct current (DC) and evoked potentials were recorded in the CA1 region of hippocampal slices of adult guinea pigs. After induction of hypoxia or ischemia, the latency of anoxic terminal negativity (ATN) of the DC potential was determined during superfusion with artificial cerebrospinal fluid alone (aCSF), and during superfusion with aCSF containing DMSO [0.1% (14.1 mmol/l) and 0.4% (56.3 mmol/l)] with the addition of nimodipine (40 micromol/l). Latencies of ATN with first hypoxia were 6.7+/-3.7 min in the control group, 9. 3+/-4.2 min in the 0.4% DMSO group and 12.3+/-5.5 min (P=0.007) in the nimodipine/0.4% DMSO group. Latencies of ATN with first ischemia were 2.9+/-2 min in the control group, 4.1+/-1.6 min in the 0.1% DMSO group, 7.1+/-3.9 min in the 0.4% DMSO group (P=0.006), 5.3+/-1. 5 min in the nimodipine/0.1% DMSO group and 7.6+/-3 min (P<0.001) in the nimodipine/0.4% DMSO group. DMSO (0.4%), either alone or in combination with nimodipine, increase the latency of the ATN after acute onset of hypoxia and ischemia.

Animals↗
PubMed2000

COL9A2 allelotypes in intervertebral disc disease.

An allelic variation of the COL9A2 gene encoding the alpha(2)-chain of collagen IX has recently been identified as a genetic risk factor for intervertebral disc prolapse, resulting in a tryptophane (Trp) substitution at position 326 of the protein. To enable quick screening of a large population we established a single enzyme (BsmFI) restriction assay which was validated by screening disc tissue samples of 250 patients (age, 47.1 +/- 13.7 years). Positive results were confirmed by nucleotide sequencing. The Trp allele was found in three patients (1.2%) who suffered from their first prolapse and were significantly older (70.7 +/- 8.5 years) than the other 247 patients. Since the substitution affects a domain covalently linked to collagen II fibrils, we conclude that this allelotype may contribute to reduced collagen crosslinking, disc instability and eventually prolapse in the elderly.

Adolescent↗
PubMed2000

Evaluation of the extension of cerebral gliomas by scintigraphy.

BACKGROUND: Single photon emission computed tomography (SPECT) with 201Tl and 123I-alpha-methyl tyrosine (123I-IMT) are routine methods for the evaluation of brain tumors. 123I-IMT transport across the blood brain barrier is mediated by an amino acid carrier, 201Tl accumulation is analogous to cerebral potassium uptake. PATIENTS AND METHODS: To determine the differences in glioma extension as shown by the 2 methods, 17 patients with malignant gliomas were included in this comparative imaging study: astrocytoma III: n = 6, ependymoma III: n = 1, oligodendroglioma III: n = 1, glioblastoma IV: n = 9. The tomographic image sets were matched anatomically and the slices showing maximal tumor extension were identified in both image sets respectively. Tumor spread was compared visually and the tumor extension was quantified. RESULTS: In gliomas WHO III tumor extension was delineated significantly larger by 123I-IMT-SPECT than by 201Tl-SPECT (mean +/- SD: 816 +/- 281 pixels vs 600 +/- 220 pixels, n = 8, p < 0.05). The size of glioblastomas was shown in a comparable manner by the 2 methods (977 +/- 571 vs 1.051 +/- 588, n = 9, ns, p = 0.57), but there were considerable regional differences between the area of 201Tl uptake and amino acid retention. In the whole group a weak but significant negative correlation between intensity of 201Tl uptake on the one hand and a ratio of the area as depicted by 123I-IMT vs area as depicted by 201Tl on the other hand, was found (n = 17, r = 0.49, p < 0.05). Thus the differences in the delineation of areas became smaller with increasing 201Tl uptake. CONCLUSIONS: These preliminary data indicate that the extension of gliomas is depicted differently by the 2 methods. 123I-IMT-SPECT shows a larger tumor extension especially in gliomas WHO III. Since 201Tl uptake has previously been shown to correlate with disruption of the blood brain barrier, 123I-IMT-SPECT may delineate tumor parts without endothelial leakage. This additional information may be helpful in planning surgical or radiation therapy. The advantages of 123I-IMT in this respect decrease with increasing 201Tl uptake and with increasing malignancy.

Adult↗
PubMed2000

Sequential scintigraphic strategy for the differentiation of brain tumours.

Both thallium-201 and iodine-123 alpha-methyltyrosine (123I-IMT) have been shown to be useful in the diagnostic evaluation of brain tumours. The aim of this study was to investigate the respective contributions of 201Tl and 123I-IMT single-photon emission tomography (SPET) in the non-invasive evaluation of intracerebral tumours. We analysed 65 patients with the following brain tumours: 8 non-neoplastic lesions, 4 meningiomas, 12 low-grade gliomas, 28 high-grade gliomas, 11 metastases and 2 high-grade lymphomas. 201Tl SPET and 123I-IMT SPET were performed [start of 201Tl SPET: 15 min p.i. (early) and 180 min p.i. (delayed); start of 123I-IMT SPET: 15 min p.i.]. The intensity of uptake was quantified as the ratio between tracer accumulation in the tumour and in the contralateral hemisphere. None of the non-neoplastic lesions or low-grade gliomas expressed marked 201Tl uptake. All malignant tumours except one small metastasis and all meningiomas except one small, cystic and degenerated lesion showed significant 201Tl accumulation [Tl(15')>2.0]; 123I-IMT uptake was either absent or intermediate in non-malignant lesions except in two low-grade gliomas; the highest levels were observed in high-grade gliomas followed by metastases and lymphomas (mean IMT: 2.7 vs. 2.1 vs. 1.8), with metastases showing a high variability in 123I-IMT uptake (range: 0.8-3.6). Using 201Tl to distinguish non-neoplastic lesions from malignant tumours and meningiomas, 63 of 65 patients were characterised correctly. In the latter group, high-grade gliomas were correctly identified in 27 of 28 cases by their amino acid uptake. It is concluded that the combination of 201Tl and 123I-IMT surpasses the accuracy of each single test in the differentiation of space-occupying lesions of the brain. Based on these preliminary results, a sequential strategy is proposed involving an initial 201Tl SPET study and an additional 123I-IMT SPET study in the event of positive 201Tl uptake.

Adult↗
PubMed2000

In vivo glioma model enabling regulated gene expression.

Experimental investigation of glioma biology and therapy requires a representative model and a convenient technique for regulating gene expression. We have established an in vivo model in which genetically modified rat C6 glioma cells (C6TL cells) are transplanted into nude mice brain, followed by specific transcriptional control of a transgene. Histologically, the tumors exhibit an astrocytic phenotype and closely resemble human malignant gliomas including diffuse brain invasion. Due to a stably integrated lacZ gene, individual tumor cells can be unequivocally identified in tissue sections by histochemistry for beta-galactosidase. Since C6TL cells carry the tet transactivator (tTA) gene, any additional gene under control of a tetracycline/tTA-responsive promoter can be transcriptionally regulated by the concentration of tetracycline. C6TL cells stably transfected with a tetracycline/tTA-responsive luciferase reporter gene showed 23-fold regulation of luciferase activity in vitro. After intracerebral transplantation a regulation of 4.5- to 8.3-fold was obtained, dependent on the concentration and the type of tetracycline in the drinking water. This model should be useful for studying the functional role of candidate genes in tumor biology as well as for experimental gene therapy studies.

Animals↗
PubMed1999

Dimethyl sulfoxide increases latency of anoxic terminal negativity in hippocampal slices of guinea pig in vitro.

Dimethyl sulfoxide (DMSO), which is widely used as a solvent for a variety of drugs, was used in the present study to investigate its ability to increase the hypoxic tolerance of brain tissue in vitro. DC-potentials and evoked potentials (EP, Schaffer collateral stimulation) were recorded in the CA1 region of hippocampal slices from adult guinea pigs. The latencies of the negative DC-potential shift (anoxic terminal negativity, ATN) after onset of hypoxia (95% N2, 5% CO2) were determined during superfusion with artificial cerebrospinal fluid (aCSF) or DMSO 0.4% dissolved in aCSF, respectively. The latencies of ATN were increased by DMSO application from 7.5+/-0.9 min (mean +/- SEM) under control conditions (n = 38) to 11.1+/-1.3 min with DMSO (n = 22, P < 0.01). These results demonstrate a neuroprotective effect of DMSO.

Animals↗
PubMed1999

Neuroprotection by 21-aminosteroids: insights from latencies of anoxic terminal negativity in hippocampus slices of guinea pig.

The protection of neuronal function by 21-aminosteroids against a hypoxic challenge was tested in guinea pig hippocampal slices. 21-aminosteroids, which apart from a protective mechanism against membrane lipid peroxidation, provide direct membrane stabilizing effects, are reported. We tested whether the 21-aminosteroid U-74389G delays the anoxic terminal negativity (ATN) of the DC-potential during hypoxia. Hippocampal slices were placed at the interface of artificial cerebrospinal fluid (aCSF) and gaseous phase (normoxic: 95% O2, 5% CO2; hypoxic: 95% N2, 5% CO2). Population spikes obtained by stimulation of Schaffer-collaterals as well as the DC-Potential were recorded in the CA1 region. The latency of appearance of ATN after oxygen deprivation was determined. In control experiments, the latency of ATN was 12.6 +/- 3.1 min (n = 6, mean +/- SEM). With application of U-74389G, the ATN-latency was 8.8 +/- 3.2 min (n = 6). We conclude that the cerebroprotective effect of the 21-aminosteroid is not mediated via direct membrane stabilization.

Animals↗
PubMed1998

Optical monitoring of PO2 changes and simultaneous recording of bioelectric activity in human and animal brain slices.

For investigations of hypoxic effects in nervous tissue, brain slices are often used as a model system. This provides the advantage that parameters of the micromilieu, e.g. pH and temperature can easily be controlled and measurements of different data, e.g. bioelectric potentials, ion activities etc. can be performed. It is of special importance that the PO2 the slice preparation is exposed to is equally controlled under these conditions. Therefore, a PO2 monitoring system is needed which provides representative values for the tissue environment. This requirement is fulfilled by an optical PO2 sensing method based on phosphorescence quenching as a function of PO2. Here, the application of this method as adapted for use in in vitro models is described and compared to the polarographic oxygen-sensing method. Both the optical and polarographic methods are comparable regarding accuracy and response time of measurements. Furthermore, both the optical method and electrophysiological measurements can be combined. Lastly, under experimental conditions, neither the phosphorescent dye Palladium-meso-tetra-4-carboxyphenyl-porphine nor the illumination necessary for excitation of the dye influence bioelectric activity of neuronal tissue in vitro. In conclusion, the optical PO2 sensing method presented here provides a tool for reliable and continuous monitoring of PO2 in the immediate environment of brain slice preparations.

Animals↗
PubMed1998

Flat and steep terminal negativity in the DC-potential after deprivation of oxygen and glucose in human neocortical slices.

The so-called terminal negativity (TN) of the DC-potential is a characteristic reaction of neuronal tissue to hypoxia or ischemia. In a previous study on human neocortical slices, two types of TN with flat and steep slopes of rise (< or >10 mV/min) were found with hypoxia. The aim of the present study was to further investigate causes underlying the occurrence of flat and steep TN. Experiments were performed on 23 human neocortical slices (500 micron) resected from 13 patients (epilepsy and tumour surgery). DC-potential and evoked potentials (white matter stimulation) were recorded in layer III. The extracellular potassium concentration ([K+]o) was measured by K+-sensitive microelectrodes. In an interface type chamber, ischemic episodes were induced by oxygen and glucose deprivation. They were terminated when TN had peaked. Both flat and steep TN also existed with ischemic conditions. There was a linear correlation between the slope of rise of TN and the associated slope of rise in [K+]o, respectively, but none regarding latencies of TN or recovery of evoked potentials. Peak levels in [K+]o were 13.9+/-0.9 mmol/l. Compared to control, the slope of rise and latency of TN were clearly increased by addition of dimethyl sulfoxide (DMSO, 0.4%) to the bath solution, whereas nimodipine (40 micromol/l) in 0.4% DMSO had neither an effect on slope of rise of TN nor on latency of TN. As a whole, our observations suggest, that the actual metabolic state determines the occurrence of flat or steep TN.

Brain Ischemia↗
PubMed1998

Neuroprotection of mild hypothermia: differential effects.

To estimate whether mild hypothermia during repetitive hypoxia provides a neuroprotective effect on brain tissue, hippocampal slice preparations were subjected to repetitive hypoxic episodes under different temperature conditions. Slices of guinea pig hippocampus (n=40) were placed at the interface of artificial cerebrospinal fluid (aCSF) and gas (normoxia: 95% O2, 5% CO2; hypoxia: 95% N2, 5% CO2). Evoked potentials (EP) and direct current (DC) potentials were recorded from hippocampal CA1 region. Slices were subjected to two repetitive hypoxic episodes under the following temperature conditions: (A) 34 degrees C/34 degrees C, (B) 30 degrees C/30 degrees C and (C) 34 degrees C/30 degrees C. Hypoxic phases lasted until an anoxic terminal negativity (ATN) occurred. The recovery after first hypoxia lasted 30 min. Tissue function was assessed regarding the latency of ATN and the recovery of evoked potentials. The ATN latencies with protocol A (n = 25) for the first and second hypoxia were 5.9+/-1.3 min (mean+/-S.E.M., 1st hypoxia) and 2.4+/-0.9 min (2nd hypoxia), with protocol B the latencies (n = 7) were significantly longer: 25.2+/-7.1 min and 15.6+/-7.7 min. With protocol C (n=8), the latencies were 5.6+/-1.8 and 3.3+/-0.5 min. No differences were seen in the recovery of the EPs with protocols A-C. Our results suggest that a mild hypothermia is only neuroprotective if applied from an initial hypoxia onwards.

Animals↗
PubMed1998

Surgical management of intraosseous skull base tumors with aid of Operating Arm System.

Invasion of bone and critical neurovascular structures often impedes complete resection of intraosseous skull base neoplasms, and these lesions tend to recur unless all infiltrated bone is removed. Evolving experience with image guidance over the past few years indicates the potential value of neuronavigation in skull base lesions diffusely infiltrating or fixed to bone structures. We report our early experience with the Radionics Operating Arm System (OAS), specifically emphasizing its utility as an adjunct in the treatment of intraosseous skull base tumors, mainly meningiomas. In April 1995 the OAS was introduced into clinical use at the neurosurgical university clinic in Münster, Germany. Since then, the system's utility has been explored in 10 patients out of the total neuronavigation series presenting with intraosseous skull base tumors (nine females and one male, mean age 47 years; nine meningiomas, one chordoma). For navigational planning, both 3-mm computed tomography scans and a set of 3-mm fat-suppression magnetic resonance images were chosen. At least four adhesive skin markers were used for system calibration. The system was technically usable in all cases in this small series. Because of the relative immobility of the bone structures and/or the tumor, no significant deviation from the preoperative registration accuracy was noted at the end of the procedures. The main advantages were easier localization and resection of infiltrated bone, which is often not grossly identifiable, even under the microscope. Our preliminary experience with the OAS suggests that image guidance is helpful in this type of lesion, providing better anatomical orientation during surgery and delineating tumor margins and their relation to critical neurovascular structures. The problem of a possible intracranial tumor and brain shift can be neglected in these lesions. The system facilitates resection by volumetric contour information, allowing more aggressive and complete resection.

Adult↗
PubMed1998

High amino acid uptake in a low-grade desmoplastic infantile ganglioglioma in a 14-year-old patient.

Amino acid uptake is higher in high-grade than in low-grade gliomas; this is the rationale for using radioactively labelled amino acids for the non-invasive grading of brain neoplasms. We present a 14-year-old boy with a low-grade desmoplastic infantile ganglioglioma (DIG) that exhibited marked contrast enhancement on magnetic resonance imaging (MRI), but no signs of infiltration and only minimal surrounding edema. In this benign neoplasm the relative uptake of the radioactively labelled amino acid I-123-alpha-methyl tyrosine (IMT), determined using single-photon emission computed tomography (SPECT), was 3.24; it was considerably higher than that of eleven other pretherapeutic low-grade gliomas where it ranged from 1.06 to 1.94 and also markedly above that average value of 2.37 found in 20 high-grade gliomas. This case report illustrates that results from emission tomography with radioactively labelled amino acids must be interpreted with caution, particularly when rare tumor entities are considered in view of uncommon clinical or radiological findings.

Adolescent↗
PubMed1998

Intracranial metastasis of a spinal myxopapillary ependymoma. A case report.

A 37-year-old man exhibited a suprasellar tumor which histologically proved to be a myxopapillary ependymoma. Since these gliomas are virtually restricted to the cauda equina region, magnetic resonance imaging (MRI) was performed which revealed multiple spinal tumors. The present case seems to be the first report on spontaneous intracranial seeding of a spinal myxopapillary ependymoma.

Adult↗
PubMed1998

Management of a ruptured cerebral aneurysm in infancy. Report of a case of a ten-month-old boy.

A ten month old unconscious boy with hemiplegia (Hunt and Hess IV) was first admitted to a district hospital without a CT scanner or a neurosurgical service (Glasgow-Coma-Score 4, no pathological pupillary signs). Therefore, he was transferred to the Pediatric Department of the University Hospital the same night. An emergency CT scan that night showed intracerebral and subarachnoid hemorrhage with enlarged ventricle (Fisher grade 5). Angiography was not available within reasonable time. Thus in the stage of progressively increasing clinical deterioration, still without pupillary signs, an external ventricular drain-age was placed. Immediately after reduction of the cerebrospinal fluid volume, arterial hypertension was noticed--the right pupil was mydriatic and fixed. Without further apparative diagnosis an emergency craniotomy was performed for decompression under the suspicion of a secondary hemorrhage due to a rerupture of a middle cerebral artery aneurysm. A bleeding aneurysm of the right middle cerebral artery was found and clipped. A mass transfusion was necessary and a pulmonary air embolism occurred. The infant died in tabula. The histological specimens revealed disruption of the internal elastic membrane of both MCA. This emphasizes a congenital nature of the aneurysm. We conclude that cerebral arterial aneurysms have to be considered in the differential diagnosis of stroke-like symptoms in infancy and early childhood, although the incidence of reported cases is less than one case per year. Since no valid screening parameter is available, diagnosis is often made only after rupture of the aneurysm. This causes problems for emergency management. Infants and children with stroke or stroke-like symptoms should immediately be transferred to a hospital with a neurosurgical unit.

Cerebral Hemorrhage↗
PubMed1998

[Aneurysmal hemorrhage as a complication of paracentesis].

Aneurysms of the temporal part of the carotid artery are unusually rare. The literature contains only a few previous reports dealing with hemorrhage from such malformations. In the present case massive bleeding occurred from a right-sided intrapetrous aneurym after myringotomy, which was performed as treatment for bilateral secretory otitis media. Due to the absence of any specific symptoms and the masking effect of middle ear glue preoperative identification of the aneurysm was not possible. Subsequent angiography showed the large fusiform extension of the intrapetrous aneurysm as well as multiple intracranial aneurysms. Leakage from the aneurism was closed definitively with muscle, fascia lata and a gelatin-resorcin-formalin-glue (Cardial). In order to apply the tissue patch the hypotympanic site of the aneurism was exposed using a posterior otosurgical approach. Due to extensive intracranial collateralization to the vertebral arteries bleeding persisted even after ligation of both carotid arteries. Temporary cardiac asystole was then induced to allow safe closure of the aneurysm. Following surgery the patient sustained loss of hearing in her ear and a partial peripheral facial palsy.

Aneurysm, Ruptured↗
PubMed1998

Hypothermia as cerebroprotective measure. Experimental hypoxic exposure of brain slices and clinical application in critically reduced cerebral perfusion pressure.

An in vitro human neocortical and rodent hippocampus brain slice technique was used under repeated hypoxia to investigate the cerebroprotective effect of hypothermia. As a hallmark of the neuronal hypoxic reaction anoxic terminal negativity (ATN) was registered to test whether hypothermia delays the onset of ATN. The experiments clearly confirm an assumed protective effect of hypothermia in vitro and in vivo and give for the first time evidence of the lack of the protective effect of hypothermia once hypoxia has occurred under normothermic conditions, probably by a critical depletion of cellular ATP-stores. In patients with severe traumatic brain injury and critically low cerebral perfusion pressure mild hypothermia is able to improve clinical outcome.

Adult↗