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Biomedical subjects

H Opitz

Publications and source records attributed to H Opitz.

At least 19 recordsLinked to original sources
PubMed2001

Assessment of chemoreflex sensitivity in free breathing young subjects by correction for respiratory influence.

BACKGROUND: The assessment of autonomic function is an important tool for risk stratification in critically ill patients. Peripheral cardiac chemoreflex sensitivity has been considered a marker for increased risk of sudden cardiac death. In normals, the evaluation of peripheral cardiac chemoreflex sensitivity is performed under controlled breathing conditions during inhalation of hypoxic gas. Since this is poorly tolerated by patients, they are commonly studied under hyperoxic conditions, which are not physiological. METHODS: We studied 20 healthy volunteers who underwent free and controlled breathing of a hypoxic gas mixture (10% O2 in N2) over 5 min. Values of peripheral cardiac chemoreflex sensitivity, corrected for respiratory influence, were compared with the results obtained experimentally under controlled breathing conditions in the same subjects. RESULTS: We found a substantial difference between values obtained during free and controlled breathing (3.64 +/- 0.81 vs. 1.53 +/- 0.32 ms/mmHg, respectively; P < 0.05). After application of a respiratory correction, described and validated in this article, no significant difference was seen for these values (0.89 +/-0.91 vs. 1.53 +/- 0.32 ms/mmHg, P = 0.46). CONCLUSIONS: This approach allows the evaluation of peripheral cardiac chemoreflex sensitivity in free breathing subjects. This correction could improve the assessment of cardiac chemoreflex sensitivity in patients with cardiorespiratory disorders, who find it difficult to control their breathing according to an experimental protocol.

Adult↗
PubMed2001

Exercise training for rehabilitation and secondary prevention of falls in geriatric patients with a history of injurious falls.

OBJECTIVE: To determine the safety and efficacy of an exercise protocol designed to improve strength, mobility, and balance and to reduce subsequent falls in geriatric patients with a history of injurious falls. DESIGN: A randomized controlled 3-month intervention trial, with an additional 3-month follow-up. SETTING: Out-patient geriatric rehabilitation unit. PARTICIPANTS: Fifty-seven female geriatric patients (mean age 82 +/- 4.8 years; range 75-90) admitted to acute care or inpatient rehabilitation with a history of recurrent or injurious falls including patients with acute fall-related fracture. INTERVENTION: Ambulatory training of strength, functional performance, and balance 3 times per week for 3 months. Patients of the control group attended a placebo group 3 times a week for 3 months. Both groups received an identical physiotherapeutic treatment 2 times a week, in which strengthening and balance training were excluded. MEASUREMENTS: Strength, functional ability, motor function, psychological parameters, and fall rates were assessed by standardized protocols at the beginning (T1) and the end (T2) of intervention. Patients were followed up for 3 months after the intervention (T3). RESULTS: No training-related medical problems occurred in the study group. Forty-five patients (79%) completed all assessments after the intervention and follow-up period. Adherence was excellent in both groups (intervention 85.4 +/- 27.8% vs control 84.2 +/- 29.3%). The patients in the intervention group increased strength, functional motor performance, and balance significantly. Fall-related behavioral and emotional restrictions were reduced significantly. Improvements persisted during the 3-month follow-up with only moderate losses. For patients of the control group, no change in strength, functional performance, or emotional status could be documented during intervention and follow-up. Fall incidence was reduced nonsignificantly by 25% in the intervention group compared with the control group (RR:0.753 CI:0.455-1.245). CONCLUSIONS: Progressive resistance training and progressive functional training are safe and effective methods of increasing strength and functional performance and reducing fall-related behavioral and emotional restrictions during ambulant rehabilitation in frail, high-risk geriatric patients with a history of injurious falls.

Accidental Falls↗
PubMed1999

Echo planar perfusion imaging with high spatial and temporal resolution: methodology and clinical aspects.

The purpose of the present study was to analyse specific advantages of calculated parameter images and their limitations using an optimized echo-planar imaging (EPI) technique with high spatial and temporal resolution. Dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) was performed in 12 patients with cerebrovascular disease and in 13 patients with brain tumours. For MR imaging of cerebral perfusion an EPI sequence was developed which provides a temporal resolution of 0.68 s for three slices with a 128 x 128 image matrix. To evaluate DSC-MRI, the following parameter images were calculated pixelwise: (1) Maximum signal reduction (MSR); (2) maximum signal difference (delta SR); (3) time-to-peak (Tp); and (4) integral of signal-intensity-time curve until Tp (SInt). The MSR maps were superior in the detection of acute infarctions and delta SR maps in the delineation of vasogenic brain oedema. The time-to-peak (Tp) maps seemed to be highly sensitive in the detection of poststenotic malperfused brain areas (sensitivity 90%). Hyperperfused areas of brain tumours were detectable down to a diameter of 1 cm with high sensitivity (> 90%). Distinct clinical and neuroradiological conditions revealed different suitabilities for the parameter images. The time-to-peak (Tp) maps may be an important advantage in the detection of post-stenotic "areas at risk", due to an improved temporal resolution using an EPI technique. With regard to spatial resolution, a matrix size of 128 x 128 is sufficient for all clinical conditions. According to our results, a further increase in matrix size would not improve the spatial resolution in DSC-MRI, since the degree of the vascularization of lesions and the susceptibility effect itself seem to be the limiting factors.

Adult↗
PubMed1998

Neurophysiological identification of the subthalamic nucleus in surgery for Parkinson's disease.

Microelectrode recording methods for stereotactic localization of the subthalamic nucleus (STN) and surrounding structures are described. These methods accurately define targets for chronic deep brain stimulation in the treatment of Parkinson's disease. Mean firing rates and a burst index were determined for all recorded neurons, and responses to active and passive limb and orofacial movements were tested. STN neurons had a mean firing rate of 37+/-17 Hz (n = 248) and an irregular firing pattern (median burst index, 3.3). Movement-related activity and tremor cells were identified in the STN. Ventral to the STN, substantia nigra pars reticulata neurons had a mean rate of 71+/-23 Hz (n = 56) and a more regular firing pattern (median burst index, 1.7). Short trains (1-2 seconds) of electrical microstimulation of STN could produce tremor arrest but were not found to be useful for localization. Compared with data from normal monkeys our findings suggest that STN neuronal activity is elevated in Parkinson's disease.

Adult↗
PubMed1998

Angiogenesis and brain oedema in intracranial meningiomas: influence of vascular endothelial growth factor.

The correlation between angiographic neovascularization, peritumoural brain oedema (PTBOe) and the expression of vascular endothelial growth factor (VEGF), was analysed in 30 patients with intracranial meningiomas. Pre-operative angiograms were examined for the existence of either an exclusively dural tumour blush or an additionally pial tumour supply from cerebral arteries. Furthermore the presence of macroscopic tumour-neovascularization and dysplastic changes of tumour-draining cerebral veins was evaluated. VEGF expression was investigated on histological tissue samples, using immunohistochemical techniques. VEGF immunohistochemistry and neuroradiological evaluations were performed in double blind fashion. Tumour volume and the amount of oedema were calculated by computerized tomography (CT) or magnetic resonance imaging (MRI). The oedema-tumour volume ratio was defined as oedema index (OeI). Compared to VEGF-negative meningiomas, tumours with striking VEGF staining revealed a significant higher mean oedema index (OeI = 4.2 vs. OeI = 1.5; p < 0.018), and a higher oedema incidence (91.7% vs. 44.4%; p < 0.046). Equally, meningiomas with additionally tumour supply from cerebral arteries were associated with a significant higher mean OeI (OeI = 4.1 vs. OeI = 1.2; p < 0.01) and oedema incidence (94.7% vs. 20.0%; p < 0.0023) than meningiomas with exclusively tumour supply from dural arteries. All meningiomas with striking VEGF-expression were associated with vascular tumour supply from cerebral arteries, but VEGF-negative tumours only in 50% (p < 0.029). These data suggest a link between VEGF-expression, arterial tumour supply and peritumoural brain oedema. The development of tumour supply from cerebral arteries may be important for formation of meningioma-related oedema. Therefore, VEGF may represent a potent mediator in the evolution of this type of vascularization in meningiomas.

Adult↗
PubMed1997

Chondroma of the cerebellopontine angle. Case report.

A patient is reported who had a solitary chondroma of the cerebellopontine angle. The tumor was totally removed. The diagnostic value of CT-scanning and MRI in this rare pathological condition are discussed.

Cerebellar Neoplasms↗
PubMed1997

The importance of pial blood supply to the development of peritumoral brain edema in meningiomas.

In a retrospective analysis, the authors studied the pial and dural blood supplies in 74 intracranial meningiomas and quantified their associated peritumoral brain edema (PTBE). The extent and localization of pial blush in relation to the total tumor volume were determined angiographically. The amount of edema and tumor size were calculated using computerized tomography. The edema-tumor volume ratio was defined as Edema Index (EI). There were 49 meningiomas with PTBE; of those tumors, 46 were supplied by pial vessels, and three were supplied exclusively by dural vessels. Tumors without PTBE showed no pial blush. The mean EI in meningiomas with pial blush was significantly larger (EI = 3) than in meningiomas without pial supply (EI = 1.1; p < 0.0001). Meningiomas with a smaller pial supply than dural supply had a significantly smaller mean EI than tumors with a pial supply equal to or greater than the dural supply (EI = 2.9 vs. EI = 3.7; p < 0.015). In 69.9% of cases with pial blood supply, major portions of the edema were located adjacent to the tumor region supplied by pial vessels. Edema index differences among tumors of different subgroups, as defined by size or histology, were significantly related to the pial supply in each subset. Thus, pial blood supply may be associated with the development of PTBE in meningiomas.

Adult↗
PubMed1996

Three-dimensional chemical shift-selective MRI of a ruptured intracranial dermoid cyst.

We report a man with a ruptured intracranial dermoid cyst, suffering from headache, nausea, vomiting and a generalised seizure. MRI was performed before and 2 weeks after surgical resection. On T1-weighted images the tumour gave high signal, as did fatty material in the frontal and parietal brain sulci. Identification of this hyper-intense material as lipids was possible by chemical-shift-selective 3D gradient-echo imaging, which provided excellent contrast between the subarachnoid lipids and the adjacent normal brain, with a good spatial resolution. Possible complications of subarachnoid and intraventricular lipid particles after dermoid cyst rupture are discussed and the diagnostic value of 3 D chemical-shift-selective additional to conventional T-1-weighted spin-echo images in identification of even small amounts of fat is emphasised.

Adult↗
PubMed1994

The "dural tail" adjacent to meningiomas studied by dynamic contrast-enhanced MRI: a comparison with histopathology.

We examined 32 patients with intracranial tumors (17 meningiomas, 8 neuromas, 7 pituitary adenomas) by conventional and dynamic contrast-enhanced MRI. Our aim was to clarify whether the pathological dural contrast enhancement adjacent to meningiomas (the "dural tail") is specific to meningiomas and, more important, whether it represents neoplastic dural infiltration or hypervascularization as a tumor accompanying reaction. A "dural tail" was found in 9 of 17 meningiomas. None of the other extra-axial tumours (neuromas, pituitary adenomas) showed comparable dural enhancement. Dynamic examinations with an ultrafast single slice imaging technique (snapshot-FLASH) after a bolus injection of contrast medium showed a "dural tail" in seven out of these nine meningiomas, while in two cases the "dural tail" turned out to be a cortical vein with a characteristic dynamic contrast enhancement pattern. In the dynamic study all seven "dural tails" were found to have earlier, steeper contrast enhancement than the corresponding tumours. All the tumours and part of the adjacent dura mater in four of the seven meningiomas with dural enhancement were examined histopathologically. In none of these four cases was neoplastic tissue found more than 2 mm away from the main tumour. The results strongly support the suggestion that the "dural tail" adjacent to meningiomas represents a hypervascular, non-neoplastic dural reaction.

Adenoma↗
PubMed1993

Collagen types I and III at the implant/tissue interface.

Collagen composition in tissue capsules around implants has been reported to differ histologically from collagen in subcutaneous connective tissue. In the present study, an immune histochemical analysis of collagen types I and III was undertaken in tissue capsules of various implant materials. The materials included polyvinyl chloride/polyacrylonitrile copolymer, poly(ethylene terephthalate), polysiloxane, titanium, and hydroxyapatite, which had been implanted into the dorsal subcutaneous space of rabbits for various time periods from 28 and to 90 days. The results indicate that collagen type III stained in all capsules independent of the evaluated materials, implantation periods, and material surface roughness. Collagen type I stained only in titanium implant capsules and dominated there over collagen type III. The staining sensitivity was highly specific and reproducible. The presence of collagen type III can be expected because it is the collagen of connective tissue healing. Collagen type I appears to be a response to chemical or electrochemical titanium surface properties but not to surface roughness. The quantitative relationship between the two collagen types may indicate capsule tissue stability and therefore serve as another biocompatibility measure.

Animals↗
PubMed1992

Very-late-onset adrenoleukodystrophy: possible precipitation of demyelination by cerebral contusion.

We report the clinical history, neuroradiology, and autopsy findings in a patient with very late onset, at age 57, of adrenoleukodystrophy (ALD) presenting with dementia, hemianopia, and gait apraxia. Open brain biopsy, elevated plasma very-long-chain fatty acids, and autopsy confirmed the diagnosis of ALD. Demyelinative lesions were most extensive at the site of a recent cerebral contusion. CNS trauma may have precipitated or accelerated demyelination in this patient carrying the ALD gene.

Adrenoleukodystrophy↗
PubMed1991

Myelinoclastic diffuse sclerosis (Schilder's disease): cliniconeuroradiologic correlations.

We report a 17-year-old boy with myelinoclastic diffuse sclerosis (Schilder's disease) presenting with left leg paresis, visual loss, and behavioral changes. CT and MRI showed two large lesions in the subcortical white matter of the occipital and parietal lobes of both hemispheres and increased intracranial pressure. Histology disclosed large areas of demyelination and perivascular infiltrates. The patient improved with coincident oral prednisolone treatment.

Adolescent↗
PubMed1990

[Chemoreflex modification of the myocardial contractility of rabbits].

The effects of arterial hypoxia on the minute ventilation (AMV), the heart interval (HI), the contractility index (KI = (P/P) max., the left ventricular systolic pressure (LVSP), and the pressure-increase-time RP were tested before and after infusion of a selective stimulator of the arterial chemoreceptors (0.5 mg/kg Almitrine-Bismesylate). The arterial blood-pH and the paO2 were increased by Almitrine whereas the paCO2 was decreased significantly. The AMV is elevated, the heart interval and the RP-interval are reduced, KI and LVSP increase after Almitrine. The hypoxia-effects after changing the paO2 from 19 to 9 kPa are an increase of AMV, KI, LVSP and a shortening of HI and RP. These effects were intensified by Almitrine. The hypoxia effects were not changed by vagotomy. A correlation between the increase of the respiration and the appertaining cardiac effects was not discovered.

Almitrine↗
PubMed1989

Afterload dependence of cardiac contraction parameters.

In rabbits the afterload dependence of baroreflex inotropy was studied, based on the contraction parameters CI = (dP/dt/P)max and a systolic time interval RP. These were estimated 1. for stepwise aortic coarctation and 2. for aortic nerve stimulation under pressure clamp conditions. CI is enhanced by aortic pressure elevation whereas RP is shortened. Aortic nerve stimulation caused higher CI and RP effects at free-running pressure than under pressure clamp conditions. The RP effects are always smaller. For clamping at low holding pressures the CI effects are higher and vice versa, whereas the RP effects are nearly independent of pressure. These results show that baroreflex inotropy, generally, is influenced by concomitant afterload changes, but the CI parameter and its inotropic effect is more afterload-dependent than RP.

Animals↗
PubMed1988

Altered expression of collagen type VI in brain vessels of patients with chronic hypertension. A comparison with the distribution of collagen IV and procollagen III.

The vascular extracellular matrix (ECM) plays an important role in the histopathology of cerebral microcirculation, but its characterization is still incomplete. For that reason we investigated paraffin-embedded and cryostat sections of intracerebral and meningeal vessels from eight normotensive and six hypertensive humans using monospecific affinity-purified polyclonal antibodies against human/monkey amino-terminal procollagen I + III peptide (P I P, P III P), collagen IV (7-S and NC1 domains), VI, and laminin (P 1 fragment) by applying peroxidase-antiperoxidase- and alkaline phosphatase-antialkaline phosphatase techniques. In normotensives, laminin and collagen IV were codistributed in the basal lamina of meningeal and intraparenchymal vessels. Collagen VI was only present in the adventitia of meningeal vessels and larger intraparenchymal arteries and veins, whereas it was absent from cortical vessels including capillaries. Intensive staining for collagen VI was observed in the choroid plexus, the superficial glia and sheath of cranial nerves. In hypertensives, the basement membrane constituents laminin and collagen IV appeared ubiquitously increased. Here, collagen VI was also deposited in the broadened vascular intima and media of larger arteries and in cortical vessels. In both groups collagen VI and P III P appeared to be codistributed. Our results indicate that significant qualitative change sin ECM of cerebral blood vessels are taking place during the development of hypertension, such as (1) an atypical deposition or an increase of collagen VI which by interconnecting collagen fibrils (I and III) might exert a stabilizing (sclerosing) function in the ECM, and (2) a thickening of vascular basement membranes caused by an accumulation of its major components laminin and collagen IV.

Aged↗
PubMed1986

[Negative inotropic reflex effects in the dog ventricle before and after beta-receptor blockade].

Myocardial contractility of the rabbit ventricle, expressed as contractility index KI = d log (p - p0)/dtmax, was altered by both aortic nerve reflex stimulation and by beta-receptor blockade with propranolol (Obsidan) and talinolol (Cordanum, (+)-Cordanum and (-)-Cordanum). In every case, beta-receptor blockade decreased negative reflex inotropy, whereas reflex hypotension was only reduced by Obsidan. The mean reflex inotropy was 11.8% after Obsidan application and 17.3% after Cordanum injection, the reflex hypotension 28.0% and 34.8%. From the results it is concluded that Cordanum acts in the rabbit ventricle cardioselectively. If neural and pharmacological effects are related to initial effects, we may conclude that the contractile state maintained by the resting sympathetic tone is diminished. The overall reduction of KI by Cordanum blockade and reflex inhibition amounts to 45.5%, that of blood pressure to 42%. Its optical isomers act also cardioselectively, the inotropic effects, however, are smaller than those of the racemate. Obviously, reflex stimulation and beta 1-blocking agents have a similar mode of inotropic action. From this we suggest that reflex inotropy is mediated by sympathetic nerve fibres and beta 1-adrenergic receptors.

Adrenergic beta-Antagonists↗