Search PubMed⌕ Search

Biomedical subjects

P Marx

Publications and source records attributed to P Marx.

At least 55 records · Page 3Linked to original sources
PubMed1997

Cutaneous dendritic cells promote replication of immunodeficiency viruses.

The cutaneous or mucosal DC-T cell environments seem extremely supportive of immunodeficiency virus replication. Apart from very early after SIV infection, similar virus producing cells have been difficult to detect in the lymphoid tissues where DCs and T cells are also known to interact. Large amounts of virus can be visualized in the germinal centers of the lymph nodes, much of which represents immune complexed virus that is trapped on the follicular dendritic cell surface. However, whether these virus-carrying cells actually make virus or even virus proteins requires further investigation. We believe that once an individual is systemically infected, free virus and/or virus-infected cells will seed peripheral tissues and when encountering similar DC-T cell environments as described in the oral mucosae, can set up sites of chronic virus replication. For instance, a virus-carrying T cell that migrates to the periphery would, on entering this milieu, interact with the mature DCs and activate virus production. This likely occurs at similar sites around the body, such as the mucosal associated lymphoid tissue of the gut, and is probably independent of the route of infection.

Animals↗
PubMed1997

[Association of hypertension and diabetes mellitus with microangiopathic cerebral infarct patterns].

OBJECTIVE: To test the hypothesis of a positive association of hypertension and diabetes mellitus with cerebral small-vessel disease infarct patterns. METHODS: Using a prospective stroke database, the 152 patients with computertomographic signs of small-vessel disease (lacunes and/or leucoaraiosis)--including as a subgroup of 85 cases with multiple lacunes and/or leucoaraiosis-were compared with 106 patients featuring pial artery infarcts. Statistical analyses of the rates of hypertension and diabetes included univariate tests (odds ratios) and a logistic regression model comprising the additional variables hypercholesterolemia, cigarette smoking, carotid stenosis, atrial fibrillation, and left cardiac thrombus. RESULTS: Multivariate testing revealed a significant association of hypertension and diabetes with multiple lacunar infarcts and/or leucoaraiosis (hypertension: odds ratio 2.0; 95% confidence interval 1.04-3.7; diabetes: odds ratio 1.9; 95% confidence interval 1.01-3.8), whereas for the total group of patients with small-vessel disease lesions no such effect was found. Among the other tested variables, only atrial fibrillation/left cardiac thrombus showed a significant negative association (odds ratio 0.5; 95% confidence interval 0.2-0.9) with lacunes/leucoaraiosis. CONCLUSION: Independent of other risk factors and other possible causes of stroke, both hypertension and diabetes appear to be strong determinants of multiple lacunar infarcts and/or leucoaraiosis.

Adult↗
PubMed1997

Mapping of tibial nerve evoked magnetic fields over the lower spine.

Using a low-noise 49-channel dc-SQUID system spinal somatosensory evoked fields (SEF) were recorded which were generated by compound action currents evoked upon posterior tibial nerve stimulation. The SEF mapping showed the action current propagation along the sciatic nerve, lumbosacral plexus and cauda equina in parallel to simultaneously recorded electrical potentials (SEP). For a reliable intraindividual side-to-side comparison of spinal SEFs the right and left tibial nerves were stimulated in alternating order; this procedure minimizes artifactual inter-nerve SEF map differences due to eventual patient-to-sensor displacements which might occur in serial measurements. These large-area lumbar SEF mappings open up several clinical perspectives for magnetoneurography, in particular with respect to the 3D-localization of proximal conduction blocks.

Adult↗
PubMed1997

MR evaluation of age-related increase of brain iron in young adult and older normal males.

The purposes of this study were to extend the investigation of age-related increases in brain iron to a younger age group, replicate previously published results, and further evaluate the validity of a novel noninvasive magnetic resonance (MR) method for measuring tissue iron (ferritin) levels with specificity. The method consists of measuring the dependence of tissue transverse relaxation rates (R2) on the field strength of MR instruments. Two MR instruments operating at 1.5 and 0.5 T were used to measure the field-dependent R2 increase (FDRI) in the frontal white matter, caudate, putamen, and globus pallidus. A group of 13 normal adult males (ages 21-77), with seven subjects below and six above age 35, was examined. As expected from postmortem and prior FDRI data, robust and significant age-related increases in FDRI were observed in the caudate, putamen, and globus pallidus, with the globus pallidus FDRI increasing sharply in the second decade and reaching a plateau after age 30. In addition, we replicated previous reports showing very high correlations between FDRI and published brain iron levels for the four regions examined. The data replicate and extend previous FDRI observations on brain aging and are consistent with postmortem data on age-related increases in brain iron. These results are relevant to the investigation of age-related neurodegenerative diseases in which iron may catalyze toxic free radical reactions.

Adult↗
PubMed1997

Side effects of high-dose intravenous immunoglobulins.

Intravenous immunoglobulins (IVIgs) are used increasingly as therapy for neuroimmunologic and other autoimmune diseases. With broader use, the number of reported side effects also is growing. Here we review the literature on adverse reactions reported after administration of i.v.Igs. Despite a few recent reports about a high frequency of complications of IVIgs, by and large they can be considered as safe. Mild and self-limited side effects may occur, but severe complications are rare and often associated with other risk factors for these complications. A careful screening for preexisting illnesses and monitoring of some laboratory parameters can minimize the risks of IVIg therapy.

Dose-Response Relationship, Drug↗
PubMed1996

[Diagnostic advantage by transthoracic and transesophageal echocardiography in acute ischemic infarct. A contribution to indications for transesophageal echocardiography].

The yield of TTE and TEE in identifying cardiac sources of embolism in patients with TIA or stroke was calculated from data from the Berlin Stroke Data Bank. High risk sources of embolism were detected by TTE in 4.2% with and in 1.6% of patients without evidence of cardiac disease from case history, clinical symptomatology, and ECG respectively. TEE yielded high risk sources of embolism in 10.6% of patients with and in 4.2% of patients without evidence of cardiac disease from case history, clinical symptomatology, ECG, and TTE respectively. Pathological findings were 12 atrial thrombi, 4 ventricular thrombi, and 1 atrial myxoma. 12 out of 14 atrial thrombi were only detected by TEE and not by TTE. There was a significant association of high risk cardiac sources of embolism with pial artery infarct pattern in CCT compared with lacunes. The yield of TEE in detecting high risk sources was not significantly associated with CCT infarct pattern probably due to the small numbers of investigations.

Adult↗
PubMed1996

Prevalence of antibodies against simian immunodeficiency virus (SIV) and simian T-lymphotropic virus (STLV) in a colony of non-human primates in Kenya, East Africa.

Sera (165 samples in 1988 and 66, follow-up samples in 1989) were collected from olive baboons, African green monkeys, Syke's monkeys and grey mangabeys kept in a semi-free, breeding colony at the Institute of Primate Research (IPR) in Nairobi, Kenya. The levels of antibodies to simian T-lymphotropic virus (STLV) or simian immunodeficiency virus (SIV), and the reactivity patterns of positive sera to various lentivirus subgroup antigens, were then determined. The results of tests using enzyme-immunoassay kits were confirmed by western blots. The prevalence of antibodies which reacted with the Kenyan SIVagm(KEN) isolate was 28% in the African green monkeys tested and 34% in the Syke's monkeys. STLV seroprevalence was 25% in the African greens and 20% in the Syke's. No antibodies to either SIV or STLV were detected in the olive baboons or grey mangabeys. More SIV-positive samples were detected in western blots when SIVagm(KEN) was used as antigen than when SIVagm(CAR014), a geographically distinct isolate from the Central African Republic, was used. However, SIVagm(KEN)-positive sera were more reactive against SIVagm(CAR014) than SIVsmm and SIVmac subgroup antigens, indicating that the two isolates from the African green monkey, CAR014 and KEN, remain antigenetically close even though they were recovered in two geographically distinct regions. To date, no clinical disease has been linked with SIV and STLV infection in the African green or Syke's monkeys in the colony. However, the relatively high prevalence of anti-SIV and anti-STLV antibodies in these monkeys offers an opportunity for prospective studies on the transmission and natural history of both viruses in a single colony.

Animals↗
PubMed1996

Percutaneous techniques for endoluminal carotid interventions.

PURPOSE: To describe the evolving techniques for stent implantation in the proximal and cervical carotid arteries. METHODS AND RESULTS: Percutaneous access to proximal and cervical carotid lesions is either via direct puncture of the common carotid artery or through the more familiar retrograde common femoral (RCF) artery approach. Both techniques and their variations are described in detail, along with their benefits, disadvantages, and possible complications. Dual lesions at the arch and higher up the neck can be treated either from the RCF route or, if the cervical lesion requires endarterectomy, with open exposure at the bifurcation and stenting of the proximal lesion. CONCLUSIONS: While the RCF route is more familiar to the majority of interventionists and provides adequate access in most situations, traversing the arch and negotiating acute angles at the ostia of the great vessels may render this method infeasible. The direct puncture technique is a useful alternative; however, it requires more expertise to prevent potentially disastrous access-site complications. One further caveat must be stated: regardless of the access approach selected, the opportunity for serious, debilitating-and lethal-complications is always present in cerebrovascular interventions. At this earliest phase in our experience with carotid stenting, cautious investigative methodologies must prevail.

Angioplasty, Balloon↗
PubMed1996

Intravascular ultrasound assessment in carotid interventions.

PURPOSE: To demonstrate the clinical value of intravascular ultrasound (IVUS) imaging in monitoring stent deployment in the cervical carotid arteries. METHODS AND RESULTS: Two-dimensional (2D) and three-dimensional (3D) IVUS imaging has been used routinely in more than 100 patients following carotid stenting and the completion angiogram to detect evidence of inaccurate stent deployment. Axial 2D views were used to measure diameters and cross-sectional areas and provide the basis for 3D reconstruction. These composited images produced single-frame views of entire vascular segments, with definition of vessel wall morphology, stent placement, and angioplasty-induced defects. This information was used in the decision to apply further treatment to the area in order to maximize luminal diameter and/or correct defects. CONCLUSIONS: IVUS imaging is an important component of carotid artery stent procedures. It more accurately visualizes stent placement and vessel wall morphology than arteriography, information critical to the intraprocedural assessment process.

Angioplasty, Balloon↗
PubMed1996

[Potential embolism sources in transesophageal echocardiography--prognostic value in patients with cerebral ischemia].

To determine whether potential sources of embolism such as atrial septal aneurysm (ASA), patent foramen ovale (PFO), mitral valve prolapse and atherosclerotic aortic debris can influence the outcome of patients after first cerebral ischemic event (CIE), 214 patients (124 stroke, 21 RIND, 69 TIA) were examined by transesophageal echocardiography (TEE) up to 3 weeks after CIE and followed up for 12 months. For risk estimation, the patients were subdivided into group I = without and group II = with potential sources of embolism. We additionally took into account cardiovascular diseases and atherosclerotic risk factors (group la + IIa without, Ib + IIb with). Recurrence occurred in 14 out of 214 patients (6.5%). Univariate analysis demonstrated that the presence of ASA, PFO and aortic debris as well as cardiovascular diseases and atherosclerotic risk factors was associated with a twofold to threefold higher incidence of recurrent events. While potential sources of embolism alone had no influence on the recurrence rate (group I:8/111 = 7.2% versus group II: 6/103 = 5.8%, n.s.), this was significantly different in relation to cardiovascular diseases and atherosclerotic risk factors (groups Ia + IIa: 0/66 = 0%, groups Ib + IIb: 14/148 = 9.8%, p < 0.01). Our results show that potential sources of embolism do not appear to influence the recurrence rate in cardiac healthy subjects. In patients with cardiovascular diseases, however, potential sources of embolism are associated with a higher risk of recurrence, and should therefore be imaged by TEE.

Adult↗
PubMed1994

[Intraspinal neurinoma in the thoracolumbar junction presenting unusual symptoms. The differential diagnosis of lumbago].

After more than a year of persistent lumbosacral pain a 53-year-old woman suddenly developed unilateral monoradicular pain over the S1 dermatome. Neurological, general medical and biochemical examinations were unremarkable, but myelography and magnetic resonance imaging revealed a cystic intraspinal space-occupying lesion at the level of L1, which was completely excised surgically. It proved to be a neurinoma, 5 x 3 x 3 cm, completely filling the spinal canal at the junction between the conus medullaris and the cauda equinus. The patient was without symptoms and neurological deficit after the operation. The tumour having been completely removed, the prognosis is good.

Diagnosis, Differential↗
PubMed1994

In vivo evaluation of brain iron in Alzheimer's disease and normal subjects using MRI.

Magnetic resonance imaging (MRI) can measure transverse relaxation rate (R2) of tissues. Although R2 is increased by tissue iron levels, R2 is not a specific measure of iron. A new method, based on the fact that ferritin (the primary tissue iron storage protein) affects R2 in a field-dependent manner, can quantify tissue iron with specificity by measuring the Field Dependent R2 Increase (FDRI). Using the FDRI method, we compared brain iron stores in frontal white matter, caudate nucleus, putamen, and globus pallidus of five male patients with Alzheimer disease (AD) and eight age and gender-matched normal controls. FDRI values were significantly higher among AD patients in the caudate and globus pallidus. The data suggest that AD may involve disturbances in brain iron metabolism and that the involvement of iron in the pathophysiology of age-related neurodegenerative disorders can be investigated in vivo using MRI.

Aged↗
PubMed1994

Cardiac sources of embolism in patients with pial artery infarcts and lacunar lesions.

BACKGROUND AND PURPOSE: On the assumption that the majority of lacunes are caused by small-vessel diseases and that pial artery infarcts arise from cardio-embolic or large-vessel diseases, 194 patients from the Berlin Cerebral Ischemia Data Bank with either lacunar or pial artery infarcts were analyzed for the frequency of cardiac sources of embolism. The primary hypothesis was that the frequency of cardiac sources of embolism is higher among pial artery infarct subjects. METHODS: The presence of cardiac sources of embolism was estimated by electrocardiographic and transthoracic and transesophageal echocardiographic studies. Cranial computed tomography scans were evaluated by two masked observers. RESULTS: The overall rate of cardiac sources of embolism did not differ significantly between the lacunar and the pial artery infarct group (66% versus 71%; odds ratio, 0.80; confidence interval, 0.43 to 1.50). Echocardiographic evidence of cardiac thrombi was positively associated with pial artery infarcts (odds ratio, 0.18; confidence interval, 0.04 to 0.80); atrial fibrillation and all other cardiac sources were not. CONCLUSIONS: Left cardiac thrombi are significantly associated with pial artery infarcts. Other presumed cardiac sources of embolism, including atrial fibrillation, may often represent coincidental findings or have a less strong tendency to result in pial artery infarcts.

Adolescent↗
PubMed1994

[Lacunar brain infarct in carotid occlusion].

The etiology of lacunar CCT lesions is controversial. We report a patient with recurrent ischemia in the territory of the right internal carotid artery. CCT initially showed a fresh non-lacunar lesion in the area of the basal ganglia and internal capsule. Subsequently, repeat CCT revealed a singular lacunar defect in the internal capsule. The Doppler sonographic investigations showed an internal carotid artery occlusion. This case supports the hypothesis that an embolic or hemodynamic etiology of the lacunae is possible.

Aged↗
PubMed1994

In vivo MR evaluation of age-related increases in brain iron.

PURPOSE: To assess the validity of an MR method of evaluating tissue iron. METHODS: The difference between the transverse relaxation rate (R2) measured with a high-field MR instrument and the R2 measured with a lower field instrument defines a measure termed the field-dependent R2 increase (FDRI). Previous in vivo and in vitro studies indicated that FDRI is a specific measure of tissue iron stores (ferritin). T2 relaxation times were obtained using two clinical MR instruments operating at 0.5 T and 1.5 T. T2 relaxation times were measured in the frontal white matter, caudate nucleus, putamen, and globus pallidus of 20 healthy adult male volunteers with an age range of 20 to 81 years. R2 was calculated as the reciprocal of T2 relaxation time. These in vivo MR results were correlated with previously published postmortem data on age-related increases of nonheme iron levels. RESULTS: The FDRI was very highly correlated with published brain iron levels for the four regions examined. In the age range examined, robust and highly significant age-related increases in FDRI were observed in the caudate and putamen. The correlations of age and FDRI in the globus pallidus and white matter were significantly lower and did not have statistical significance. CONCLUSIONS: The data provide additional evidence that FDRI is a specific measure of tissue iron stores. The data also show that age-related increases in tissue iron stores can be quantified in vivo despite significant age-related processes that oppose the increase in R2 caused by iron. These results are relevant to the investigation of neurodegenerative processes in which iron may catalyze toxic free-radical reactions.

Adult↗