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Biomedical subjects

M F Mehler

Publications and source records attributed to M F Mehler.

At least 37 records · Page 2Linked to original sources
PubMed1994

Growth factor regulation of neuronal development.

Recent experimental investigations have redefined the spectrum of growth factors and developmental signalling pathways that are necessary to orchestrate the growth and differentiation of regional neuronal subpopulations. Gene knockout studies of the classic neurotrophins and their high-affinity tyrosine kinase (Trk) receptors have refined our definition of the cellular mechanisms and target populations of these neuronotrophic factors. Recognition of the significant parallels that exist between neuropoiesis and hematolymphopoiesis has fostered our study of the range and cellular actions of these hemopoietins in neuronal development. In addition, by activating receptor subunits that possess serine/threonine activity, bone morphogenetic proteins of the transforming growth factor-beta superfamily exhibit complex spatiotemporal regulation of regional neuronal subpopulations. These collective observations suggest that a complex hierarchy of epigenetic signals is required for the growth and maturation of regional neuronal lineage species in the central and peripheral mammalian nervous system.

Animals↗
PubMed1993

Cytokine regulation of neuronal differentiation of hippocampal progenitor cells.

The signalling mechanisms governing haematolymphopoiesis and those regulating neural development may be closely related, as indicated by similarities of higher-order structure and function of the cytokines involved, of the regional and temporal regulation of their transcription and translation, and of their bioactivity. Here we investigate this possible evolutionary connection using retroviral transduction of a temperature-sensitive mutant form of the SV40 large T antigen to develop conditionally immortalized murine embryonic hippocampal progenitor cell lines. Treatment of these cells with cytokines that are thought to participate in progressive lymphoid maturation, immunoglobulin synthesis and erythropoiesis causes progressive neuronal differentiation, as defined by morphological criteria, successive expression of increasingly mature neurofilament protein, and the generation of inward currents and action potentials. The cytokine interleukin(IL)-11 induces expression of action potentials that are insensitive to tetrodotoxin, which is indicative of developmentally immature sodium channels. By contrast, for expression of more mature action potentials (tetrodotoxin-sensitive) one of the interleukins IL-5, IL-7 or IL-9 must be applied in association with transforming growth factor-alpha after pretreatment with basic fibroblast growth factor. Our results suggest that the mechanisms regulating lineage commitment and cellular differentiation in the neural and haematopoietic systems are similar. Further, they define an in vitro model system that may facilitate molecular analysis of graded stages of mammalian neuronal differentiation.

Action Potentials↗
PubMed1992

Enhanced sensitivity of hippocampal pyramidal neurons from mdx mice to hypoxia-induced loss of synaptic transmission.

The gene at the Duchenne/Becker muscular dystrophy locus encodes dystrophin, a member of a protein superfamily that links the actin cytoskeleton to transmembrane plasmalemmal proteins. In mature skeletal myocytes, the absence of dystrophin is associated with decreased membrane stability, altered kinetics of several calcium channels, and increased intracellular calcium concentration. In the central nervous system, dystrophin is restricted to specific neuronal populations that show heightened susceptibility to excitotoxic damage and is localized in proximal dendrites and the neuronal somata. We report that CA1 pyramidal neurons in a hippocampal slice preparation from a dystrophin-deficient mouse genetic model of Duchenne muscular dystrophy (the mdx mouse) exhibit significant increased susceptibility to hypoxia-induced damage to synaptic transmission. This selective vulnerability was substantially ameliorated by pretreatment with diphenylhydantoin, an anticonvulsant that blocks both sodium-dependent action potentials and low-threshold transient calcium conductances. These findings suggest that dystrophin deficiency could predispose susceptible neuronal populations to cumulative hypoxic insults that may contribute to the development of cognitive deficits in Duchenne/Becker muscular dystrophy patients and that the effects of such periods of hypoxia may be pharmacologically remediable.

Animals↗
PubMed1992

Asymptomatic unilateral papilledema in pseudotumor cerebri.

A 32-year-old asymptomatic woman was found to have unilateral papilledema on routine ophthalmological examination. Subsequent visual field, neuroimaging, and cerebrospinal fluid examinations were consistent with the diagnosis of pseudotumor cerebri. This case demonstrates that pseudotumor cerebri may present as unilateral papilledema in any asymptomatic patient and illustrates the need for thorough neuro-ophthalmological evaluations to allow early detection of cases with atypical presentations to increase the efficacy of therapeutic intervention and prevent progressive visual loss.

Acetazolamide↗
PubMed1989

The rostral basilar artery syndrome: diagnosis, etiology, prognosis.

Vascular occlusive disease of the rostral basilar artery (RBAS) causes a myriad of clinical signs and symptoms reflecting rostral brainstem-diencephalic and posterior hemispheric dysfunction. To help define the clinical profile, we prospectively studied 61 patients with clinical/neuroimaging evidence of RBAS during a 7-year period. Fourteen patients mirrored classic descriptions: severe visual, oculomotor and behavioral signs without prominent motoric dysfunction, uniformly poor prognosis, and intimate association with hypertension and prior episodes of vertebrobasilar ischemia (VBI). In contrast, 47 individuals had a reversible syndrome with excellent short-term functional recoveries, and were distinguished by a lower frequency and severity of hypertension, a greater incidence of arrhythmias in the young, and no history of VBI. All patients had important neurobehavioral abnormalities including an invariable acute confusional state. Diagnosis required the integrated assessment of neurobehavioral, ophthalmologic, and imaging tests. The clinical syndrome is more common and etiologically diverse than previously reported and is frequently unrecognized in the young and elderly who present with acute confusion.

Adult↗
PubMed1988

Atypical psychosis with disseminated subpial demyelination.

A 34-year-old woman experienced three episodes of an atypical psychosis, characterized by confusion, agitation, delusional thinking, paranoid ideation, and auditory hallucinations, during the 14 months prior to her death. Findings of gross examination of the brain and spinal cord were unremarkable. Histologic examination revealed scattered subpial foci of demyelination throughout the brain stem, with involvement of the hippocampal formation bilaterally. Although occasional active lesions at early stages of development were noted, most lesions were gliotic and therefore quiescent. This case and one similar example of disseminated subpial demyelination found in the literature probably represent an unusual variant of multiple sclerosis.

Adult↗
PubMed1988

The neuro-ophthalmologic spectrum of the rostral basilar artery syndrome.

A broad range of neuro-ophthalmologic signs occurs with the rostral basilar artery syndrome (RBAS) and transient ischemia or infarction of the midbrain, thalamus, hypothalamus, paramedian diencephalon, and posterior temporal and occipital lobes. The pattern of affected neuroanatomic regions results in diverse patterns of interrelated functional disabilities in the areas of vertical gaze, nystagmus, oculomotor function, pupillary reactivity, visual fields, color vision, and visual illusions. With increasing recognition of more clinically benign forms of RBAS, it has become apparent that the vascular syndrome is often improperly diagnosed and may be associated with remediable occult medical disorders. To facilitate the acquisition of accurate diagnostic and therapeutic information, neuro-ophthalmologic signs were prospectively assessed in 61 patients with RBAS. The clinicoanatomic correlates of these diverse ocular manifestations are presented.

Adult↗
PubMed1988

Inflammatory myelinoclastic diffuse sclerosis.

We report on a 12-year-old girl with a severe subacute to chronic bifrontal leukoencephalopathy. By clinical, biochemical, radiological, and neuropathological criteria, a diagnosis of inflammatory myelinoclastic diffuse sclerosis was reached. This is the third fully documented case.

Child↗
PubMed1988

The clinical neuro-ophthalmologic spectrum of temporal arteritis.

The range of neuro-ophthalmologic signs in temporal arteritis is broad and includes diverse presentations of ischemic optic neuropathy, retinal infarction, transient ischemic phenomena, ophthalmoparesis, pupillary autonomic and anterior ocular segment dysfunction, cortical blindness and associated post-chiasmal field defects, and complex visual hallucinations. Neurovascular compromise can follow arteritic lesions at multiple neuroanatomic sites, and reflects different pathogenetic mechanisms and displays distinctive clinical features. A variety of temporal clinical profiles and differential responses to corticosteroids occur. This article reviews the broad range of neuroanatomic pathways affected by diverse and potentially interactive etiologic factors in this systemic arteritis.

Autonomic Nervous System Diseases↗
PubMed1988

Mixed transcortical aphasia in nonfamilial dysphasic dementia.

The neurolinguistic and cognitive profiles of a patient with mixed transcortical aphasia and non-familial dysphasic dementia associated with progressive, left perisylvian involution are presented. This clinicopathological entity has recently been shown to be an example of a novel class of intrinsic, focal cortical degenerations with sparing of the basal forebrain. The characteristics of the aphasia were unusual. There were occasional literal and verbal paraphasic errors, but no completion phenomenon, embellishment or significant echolalia. Evidence of a generalized lexical disruption was found on detailed analysis of residual abilities in reading, writing and spelling. A newly described form of non-lexical repetition was present, resulting in the patient's inability to correct syntactical and semantic errors. Affective prosodic repetition was intact. A combined paraphasic word-production and semantic anomia was found. These observations combined with evidence of evolving region-specific cognitive impairments suggest that the pathological process resulted in a relative disconnection of integral frontal and parieto-occipital areas from adjacent perisylvian language zones.

Agnosia↗
PubMed1988

The clinical spectrum of ocular bobbing and ocular dipping.

The term "ocular bobbing" defines a distinctive class of abnormal spontaneous vertical eye movements which occur in a variety of clinicopathological settings. Four cardinal forms, which correspond to the predicted permutations of the two characteristic clinical variables, initial vertical excursion and phasic velocity, have now been described. Reverse ocular dipping, with directional reversal and phasic inversion from typical ocular bobbing, is the last link in this functional tetrad and is newly presented. The four pathological forms share several basic phenomenological features but exhibit clinical and aetiological diversity and significant differences in prognosis. An analysis of the clinical spectrum of disorders subsumed under the general heading of "ocular bobbing" is presented.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Reverse ocular dipping.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Parasympathetic pupillary involvement in biopsy-proven temporal arteritis.

The neuro-ophthalmologic spectrum of temporal arteritis (TA) is broad and includes such diverse presentations as ischemic optic neuropathy, retinal infarction, anterior ocular segment dysfunction, ophthalmoparesis, and cortical blindness. A common clinical dictum suggests that third nerve palsies are associated with pupillary sparing in this systemic arteritis. We present a biopsy-proven case of TA with parasympathetic pupillary involvement and ophthalmoparesis. Relative light-near dissociation and differential clinical response to adrenocorticosteroids occurred. Previous pathologic studies have suggested that clinically apparent parasympathetic pupillary dysfunction could follow arteritic lesions at several neuroanatomic sites and may, therefore, reflect different pathogenetic mechanisms and display distinctive clinical features. Our case effectively broadens the clinicopathologic locus of neuro-ophthalmologic expression in TA.

Aged↗
PubMed1988

Primary spontaneous mesencephalic hemorrhage.

The case histories of two patients with clinically diverse forms of the very rare entity primary, spontaneous mesencephalic hemorrhage are presented. Each exhibited characteristic mesencephalic signs and neuroimaging profiles. However, both patients differed markedly in their predisposing factors, state of arousal, memory, temporal course and functional residua. One patient was unique in displaying a normal level of alertness throughout his clinical course and an isolated retrograde amnesia. The latter sign suggests a role for mesencephalic reticular activation in long-term retrieval and illustrates the differential effects of a subtle activation deficit on memory and arousal. These findings broaden the distinctive clinico-anatomical profile of primary, spontaneous mesencephalic hemorrhage.

Adult↗
PubMed1988

Reversible rostral basilar artery syndrome.

We prospectively studied 34 patients with clinical and radiologic evidence of rostral basilar artery syndrome, a vaso-occlusive disorder, who had uniformly excellent short-term functional recovery, in marked contrast to the classic syndrome. All patients displayed important neurobehavioral disturbances, including an acute confusional state, necessitating medical consultation. The composite group had minimal hypertension, significant arrhythmias in the young, and no history of vertebrobasilar insufficiency. Unsuspected cases of idiopathic orthostatic hypotension, as well as cardiac arrhythmias in the elderly, were discovered. A vascular cause was not considered in 79% of those presenting for emergency evaluation and prevented proper acute diagnostic evaluation in 88%. Recognition of this potentially reversible cerebrovascular syndrome may prevent hazardous diagnostic and therapeutic interventions.

Adult↗
PubMed1987

Giant cell arteritis causes recurrent posterior circulation transient ischemic attacks which respond to corticosteroid.

A 67-year-old man presented with recurrent clinically diverse posterior circulation transient ischemic attacks which continued despite full anticoagulation. Giant cell arteritis was suspected because of a markedly elevated erythrocyte sedimentation rate and confirmed by temporal artery biopsy. Treatment with corticosteroids resulted in a prompt and enduring resolution of clinical symptoms. Giant cell arteritis may represent a treatable cause of posterior circulation transient ischemic attacks, uniquely responsive to corticosteroids.

Aged↗