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Biomedical subjects

T Brandt

Publications and source records attributed to T Brandt.

At least 91 records · Page 5Linked to original sources
PubMed2000

Mutations in the tropoelastin gene (ELN) were not found in patients with spontaneous cervical artery dissections.

BACKGROUND AND PURPOSE: The majority of patients with spontaneous cerebral artery dissection show ultrastructural alterations in dermal collagen and elastic fibers. METHODS: We studied the gene encoding tropoelastin (ELN) by reverse transcription-polymerase chain reaction and subsequent sequence analysis in 10 patients with abnormalities in their elastic fibers. RESULTS: No mutations were found in the whole coding region of the ELN gene. The simultaneous visualization and quantification of ELN splice variants by gene scanning enabled the analysis of the regulation of alternative splicing of ELN mRNA. No differences could be detected between fibroblast cultures of the patients and a control subject. CONCLUSIONS: Neither mutations in the ELN gene nor dysregulation of its activity appears to be the cause of the connective tissue disorder that is found in most patients with spontaneous dissections.

Adult↗
PubMed2000

Perceived vertical and lateropulsion: clinical syndromes, localization, and prognosis.

We present a clinical classification of central vestibular syndromes according to the three major planes of action of the vestibulo-ocular reflex: yaw, roll, and pitch. The plane-specific syndromes are determined by ocular motor, postural, and perceptual signs. Yaw plane signs are horizontal nystagmus, past pointing, rotational and lateral body falls, deviation of perceived straight-ahead to the left or right. Roll plane signs are torsional nystagmus, skew deviation, ocular torsion, tilts of head, body, and perceived vertical in a clockwise or counterclockwise direction. Pitch plane signs are upbeat/downbeat nystagmus, forward/backward tilts and falls, deviations of the perceived horizon. The thus defined vestibular syndromes allow a precise topographic analysis of brainstem lesions according to their level and side. Special emphasis is placed on the vestibular roll plane syndromes of ocular tilt reaction, lateropulsion in Wallenberg's syndrome, thalamic and cortical astasia and their association with roll plane tilt of perceived vertical. Recovery is based on a functionally significant central compensation of a vestibular tone imbalance, the mechanism of which is largely unknown. Physical therapy may facilitate this central compensation, but this has not yet been proven in prospective studies.

Animals↗
PubMed2000

Long chain arginine esters: a new class of cationic detergents for preparation of hydrophobic ion-paired complexes.

The ability of stoichiometric amounts (based on charged groups) of ionic detergents to bind to oppositely charged ionic compounds has been recently reviewed. These hydrophobic ion-paired (HIP) complexes display altered solubility properties. Most of the work to date on HIP compelxes has focused on basic drugs and anionic detergents. It would be extremely useful to extend this approach to acidic compounds, including DNA and RNA. However, most cationic detergents are relatively toxic. It is hypothesized that detergents constructed from naturally occurring or well tolerated components, coupled by labile linkages, will be less toxic and still able to form strong HIP complexes. This study describes the synthesis and characterization of long chain alkyl esters of arginine. This class of cationic detergents, which have not been reported previously, are less cytotoxic than alkyltrimethylammonium detergents, possibly making them more acceptable in drug delivery applications. These arginine esters exhibit detergent-like properties. For example, the dodecyl ester of arginine has a critical micelle concentration of 0.07 mM, while being approximately 5-10 fold less toxic than tetradecyltrimethylammonium bromide. The arginine dodecyl ester forms stable HIP complexes with plasmid DNA. The complex is sufficiently stable to allow some modest level of transfection with Cos-7 cells in a time- and concentration-dependent fashion. This work demonstrates that arginine-based cationic detergents are effective ion-pairing agents, appear to be less toxic than alkyltrimethylammonium compounds, and form stable complexes with DNA.

Animals↗
PubMed2000

Measurement of respiratory impedance by impulse oscillometry--effects of endotracheal tubes.

Impulse Oscillometry is a new, noninvasive method to measure respiratory impedance, i.e. airway resistance and reactance at different oscillation frequencies. These parameters are potentially useful for the monitoring of respiratory mechanics in the critically ill patent with respiratory dysfunction. The endotracheal tube, used to mechanically ventilate these patients, however, represents an additional nonlinear impedance that introduces artifacts into the measurements. The objective of this work was therefore to investigate the effects of clinically available endotracheal tubes on resistance and reactance of an in vitro analogue of the respiratory system. Additionally, the effects of decreasing the compressible gas volume in this experimental model, as a simulation of decreased lung capacity and compliance, was investigated. Impulse oscillometric measurements of the test analogue gave highly reproducible results with and without an endotracheal tube. The tubes had significant influence on the measurement of the test object at all frequencies investigated. Changes of low frequent reactance were negligible - at least if repetitive measurements of the same system are performed - for realistic measurement of airway resistance, a correction of the tube impedance or measurement of the pressure distal of the tube is required. Resistance increased and low frequent reactance decreased significantly with decreasing gas volume. These changes were of magnitudes higher than the variations due to the introduction of the endotracheal tubes. Our results suggest that changes of respiratory reactance measured with impulse oscillometry may be used as a monitoring parameter in intubated patients.

Airway Resistance↗
PubMed1999

Galvanic stimulation in bilateral vestibular failure: 3-D ocular motor effects.

Bilateral galvanic vestibular stimulation (GVS) with current intensity of 3 mA was applied at mastoid level in 11 patients with chronic bilateral vestibular failure, in order to determine ocular motor responses by 3-D video-oculography. The following abnormal features were found: (1) a predominantly torsional or mixed torsional-horizontal nystagmus at the onset of stimulation with lower current intensities (1.0-3.0 mA) in nine patients; (2) a reduced amplitude of tonic ocular torsion by about 50% in nine patients (1.3 +/- 0.6 degrees at 3 mA); (3) a nystagmus in the opposite direction at stimulation offset in five patients (rebound); (4) no eye movements at all in a patient with bilateral nerve failure. GVS stimulates the vestibular nerve, thus allowing differentiation of nerve failure from labyrinthine failure. The low thresholds for initiating nystagmus and the rebound, which appear to be the most typical features of bilateral labyrinthine failure, can be explained by central compensation mechanisms.

Acceleration↗
PubMed1999

Subjective straight-ahead during neck muscle vibration: effects of ageing.

The subjective visual straight-ahead (SVA) was measured psychophysically before and during unilateral vibration of the posterior neck muscles in order to determine the particular contribution of neck muscle spindles to the perception of body orientation during ageing. We found a symmetrical increase of the vibration-induced displacement of the SVA with advancing age (R = +0.73, p < 0.01, n = 60) in 30 healthy subjects of different ages (range 20-81 years). These data indicate the cervical proprioceptive contribution to multisensory body orientation increases with ageing. One possible interpretation is that the sensorial weight of proprioception increases as the peripheral vestibular input decreases with advancing age, thereby substituting for the lack of vestibular function.

Adult↗
PubMed1999

Simulation of pathological ocular counter-roll and skew-torsion by a 3-D mathematical model.

A basic version of a 3-D mathematical model for simulation of otolithic control of binocular static eye position was extended by introducting excitatory commissural fibers between the vestibular nuclei, and physiological non-linearities: the force-response relationship of utricular neurons and a quadratic relationship between eye muscle innervation and force. These modifications appeared to be necessary in order to simulate the gain asymmetry of ocular counter-roll to lateral head tilt in patients with unilateral utricular loss. The current model can adequately simulate skew-torsion in patients with unilateral utricular loss, lesions of the vestibular nuclei, and central graviceptive pathway lesions. The direction of simulated skew-torsion corresponds satisfactorily to data from normals and patients with acute vestibular loss. The relatively low values of predicted eye deviations for peripheral vestibular lesions suggest that part of the effects seen in patients is caused by affection of the semicircular canals.

Action Potentials↗
PubMed1999

[Progressive multifocal leukoencephalopathy as a result of immunosuppressive therapy].

HISTORY AND ADMISSION FINDINGS: A 62-year-old woman developed paresis in her right arm within several weeks. She was being treated with methylprednisolone (4 mg daily) and chlorambucil (2 mg every other day) for systemic lupus erythematodes (SLE), which was now in remission. Neurological examination on admission revealed a right flaccid hemiparesis, predominantly of the right arm. The physical examination was otherwise unremarkable. INVESTIGATIONS: Magnetic resonance imaging (MRI) (T2 weighted) showed hyperintense changes in the subcortical medullary layer of the left precentral gyrus without perifocal oedema or abnormal contrast medium uptake, which argued against progressive cerebral ischaemia or tumour. Blood and cerebrospinal fluid (CSF) showed no abnormalities except leukopenia and a raised antinuclear antibody titre. Progressive paralysis of the right side of the body after 2 years of immunosuppressive treatment, the MRI findings and an essentially normal CSE suggested progressive multifocal leucoencephalopathy (PML), confirmed by polymerase chain reaction (PCR) demonstrating JC-virus DNA in serum and CSF. TREATMENT AND COURSE: As a result of the CNS infection with papovavirus JC, an opportunistic infection of the central nervous system, which is usually fatal, occurred. The cerebral changes spread within a few weeks, despite of the immunosuppressive drugs having been discontinued. The pareses progressed further and a marked personality disorder of organic origin ensued. CONCLUSION: While efficacious immunosuppressive drugs against autoimmune disease are available, their use risks the occurrence of life-threatening opportunistic infections.

Brain↗
PubMed1999

The vestibular cortex. Its locations, functions, and disorders.

Evidence is presented that the multisensory parieto-insular cortex is the human homologue of the parieto-insular vestibular cortex (PIVC) in the monkey and is involved in the perception of verticality and self-motion. Acute lesions (patients with middle cerebral artery infarctions) of this area caused contraversive tilts of perceived vertical, body lateropulsion, and, rarely, rotational vertigo. Brain activation studies using positron emission tomography or functional magnetic resonance tomography showed that PIVC was activated by caloric irrigation of the ears or by galvanic stimulation of the mastoid. This indicates that PIVC receives input from both the semicircular canals and otoliths. PIVC was also activated during small-field optokinetic stimulation, but not when the nystagmus was suppressed by fixation. Activation of vestibular cortex areas, visual motion-sensitive areas, and ocular motor areas exhibited a significant right-hemispheric dominance. The vestibular cortex intimately interacts with the visual cortex to match the two 3-D orientation maps (perception of verticality, room-tilt illusion) and mediates self-motion perception by means of a reciprocal inhibitory visual-vestibular interaction. This mechanism of an inhibitory interaction allows a shift of the dominant sensorial weight during self-motion perception from one sensory modality (visual or vestibular) to the other, depending on which mode of stimulation prevails: body acceleration (vestibular input) or constant velocity motion (visual input).

Animals↗
PubMed1999

[Spectrum of neurological symptoms in dissections of brain-supplying arteries].

BACKGROUND AND OBJECTIVE: Dissection of extracranial arteries that supply the brain is a common cause of ischemic stroke in youngish persons. Yet this disease, with its warning and early symptoms, is inadequately known among the population as well as doctors. This study was undertaken to demonstrate the incidence, severity and sequelae of this condition, important in both routine general and hospital practice, with particular emphasis on early signs and diagnosis. PATIENTS AND METHODS: The data from 33 patients (20 men, 13 women, average age 42 [21-72] years) who during one year had been treated in the authors' hospital for carotid (n = 23) or vertebral (n = 10) artery dissection were analysed. RESULTS: The admission diagnosis of dissection, based on the history and ultrasound findings was in almost all cases confirmed by magnetic resonance imaging (wall haematoma), magnetic resonance angiograhy, computed tomography-angiography or conventional angiography. Typical warning and early symptoms such as whiplash sensation unilateral pain in the throat, neck and head or Horner's syndrome were elicited in nearly 50% of patients, while known causes such as trauma or connective tissue disease were confirmed in only 27%. Neurological deficits of ischemic infarction, some of them severe, persisted in two-thirds of patients, brain death occurred in one. CONCLUSIONS: Dissection of carotid or vertebral arteries is a statistically and medically relevant cause of stroke in youngish persons that can be diagnosed by attention to typical warning and early symptoms and the performance of noninvasive tests. The often life-threatening sequelae of possible cerebral ischemia can be diagnosed and even averted by early recognition of the cause.

Acute Disease↗
PubMed1999

Increased body sway at 3.5-8 Hz in patients with phobic postural vertigo.

Postural sway during upright stance was analyzed in 12 patients with phobic postural vertigo (PPV) and in 12 age-matched healthy volunteers. Recordings were made under different conditions (with the eyes open or closed): when standing on a foam rubber pad with the head upright, turned 30 degrees to the right or left, or during 1 Hz horizontal head oscillations. Sway analysis included calculation of sway path, of root mean square values of sway and of the power spectrum of sway in fore/aft and lateral directions. There was a significant increase in sway activity in the 3.53-8 Hz frequency band in patients with PPV. This did not impair objective postural stability. Increase in higher frequency sway activity may simply reflect a change in postural strategy rather than a sensorimotor dysfunction. The patients' conscious control of stance may augment co-activation of anti-gravity muscles, a strategy applied by normal subjects when performing demanding balancing tasks.

Adult↗
PubMed1999

Association of cervical artery dissection with recent infection.

BACKGROUND: Cervical artery dissection (CAD) is an important cause of ischemic stroke in younger patients. However, its cause is insufficiently understood. OBJECTIVE: To test the hypothesis that CAD is frequently associated with recent infection. SUBJECTS AND METHODS: We compared the prevalence of infection during the preceding week in 43 consecutive patients with acute CAD and 58 consecutive patients younger than 50 years with acute cerebral ischemia from other causes (control patients). In subgroups of patients, we correlated infectious status with electron microscopic studies of skin biopsy specimens and investigated pathways potentially linking infection and CAD. RESULTS: Recent infection was more common in patients with CAD (25/43 [58.1%]) than in control patients (19/58 [32.8%]; P=.01). Respiratory tract infection was preponderant in both groups. Recent infection, but not the mechanical factors cough, sneezing, or vomiting, was independently associated with CAD in multivariate analysis. Investigation of serum antibodies against Chlamydia pneumoniae, smooth muscle cells, endothelial cells, collagen types I through IV, and heat shock protein 65 and assessment of serum alpha1-antitrypsin and HLA did not contribute to the understanding of the pathogenesis of CAD. More patients with pathologic findings in skin biopsy specimens tended to have had a recent infection (13/21 [62%]) than patients without pathologic findings (2/9 [22%]; P=.11). CONCLUSION: Our results suggest a significant association between recent infection and CAD that is not explained by mechanical factors occurring during infection.

Acute Disease↗
PubMed1999

Distribution of herpes simplex virus type 1 in human geniculate and vestibular ganglia: implications for vestibular neuritis.

Vestibular neuritis is a common cause of partial unilateral vestibular paralysis, which usually spares posterior semicircular canal function. The cause is assumed to be a viral reactivation of latent herpes simplex virus type 1 (HSV-1) in human vestibular ganglia. The existence of an anastomosis between the intermediate nerve and the superior vestibular nerve suggests the question of whether selective affliction of the superior vestibular nerve is the result of migration of HSV-1 from the geniculate ganglion along this faciovestibular anastomosis. We determined the distribution of HSV-1 among geniculate ganglia, vestibular ganglia, and within Scarpa's ganglion by examining 35 human temporal bones by polymerase chain reaction. HSV-1 was found in 66% of geniculate ganglia and 60% of vestibular ganglia; all examined parts of vestibular ganglia were almost equally HSV-1 infected. Our data provided no support for viral migration along this anastomosis or for a preferential latency of HSV-1 in the superior vestibular nerve. We suggest that the common double innervation of the posterior ampulla by two nerves running in two separate bony canals could offer an alternative explanation for the regular sparing of posterior canal function in vestibular neuritis.

Adolescent↗