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Biomedical subjects

R A Müller

Publications and source records attributed to R A Müller.

At least 19 recordsLinked to original sources
PubMed2005

Retention of Escherichia coli in municipal sewage by means of planted soil filters in two-stage pilot plant systems.

Different types of constructed wetlands in a pilot-plant system were fed with identical municipal waste water to compare the sanitisation process in two-stage systems. With combinations of a vertical and a horizontal flow filter an E. coli reduction of 5 log10 with an E. coli influent concentration of 10(7) MPN/100 ml was achieved. Using different filter materials in each stage the total performance of the two-stage system was independent from the sequence of these materials. However, using coarser filter material in the first stage makes the filter less prone to clogging and is thus the preferential option with regard to operational reliability.

Biodegradation, Environmental↗
PubMed2003

Effects of plants and microorganisms in constructed wetlands for wastewater treatment.

Constructed wetlands are a natural alternative to technical methods of wastewater treatment. However, our understanding of the complex processes caused by the plants, microorganisms, soil matrix and substances in the wastewater, and how they all interact with each other, is still rather incomplete. In this article, a closer look will be taken at the mechanisms of both plants in constructed wetlands and the microorganisms in the root zone which come into play when they remove contaminants from wastewater. The supply of oxygen plays a crucial role in the activity and type of metabolism performed by microorganisms in the root zone. Plants' involvement in the input of oxygen into the root zone, in the uptake of nutrients and in the direct degradation of pollutants as well as the role of microorganisms are all examined in more detail. The ways in which these processes act to treat wastewater are dealt with in the following order: Technological aspects; The effect of root growth on the soil matrix; Gas transport in helophytes and the release of oxygen into the rhizosphere; The uptake of inorganic compounds by plants; The uptake of organic pollutants by plants and their metabolism; The release of carbon compounds by plants; Factors affecting the elimination of pathogenic germs.

Biodegradation, Environmental↗
PubMed2001

Atypical patterns of cerebral motor activation in autism: a functional magnetic resonance study.

BACKGROUND: Early neurodevelopmental pathogenesis in autism potentially affects emerging functional maps, but little imaging evidence is available. METHODS: We studied eight male autistic and eight matched normal subjects, using functional magnetic resonance imaging during visually paced finger movement, compared to a control condition (visual stimulation in the absence of motor response). RESULTS: Groupwise analyses showed activation in contralateral perirolandic cortex, basal ganglia, and thalamus, bilateral supplementary motor area, and ipsilateral cerebellum for both groups. However, activations were less pronounced in the autism group. Direct group comparisons demonstrated greater activation in perirolandic and supplementary motor areas in the control group and greater activation (or reduced deactivation) in posterior and prefrontal cortices in the autism group. Intraindividual analyses further showed that strongest activations were consistently located along the contralateral central sulcus in control subjects but occurred in locations differing from individual to individual in the autism group. CONCLUSIONS: Our findings, though based on a rather small sample, suggest abnormal individual variability of functional maps and less distinct regional activation/deactivation patterns in autism. The observations may relate to known motor impairments in autism and are compatible with the general hypothesis of disturbances of functional differentiation in the autistic cerebrum.

Adolescent↗
PubMed2001

Broca's area and the discrimination of frequency transitions: a functional MRI study.

The left inferior frontal lobe has been traditionally viewed as a "language area," although its involvement in the discrimination of rapid nonverbal frequency changes has been also shown. Using functional MRI, we studied seven healthy adults during discrimination of relatively slow (200 ms) tonal frequency glides. Compared to a control task, in which subjects indiscriminately responded to white noise bursts, tonal discrimination was associated with bilateral superior and middle temporal and medial frontal activations. Inferior frontal activations were bilateral, but stronger on the left. Contrary to previous studies comparing discrimination of slow frequency changes to rest, our results suggest that such discriminations-when compared to an auditory control task-activate the left inferior frontal gyrus. Our findings are consistent with a participation of Broca's area in nonlinguistic processes besides its known roles in semantic, syntactic, and phonological functions.

Adult↗
PubMed2001

Verbal recall and recognition following traumatic brain injury: a [0-15]-water positron emission tomography study.

Although several studies exist which have examined static functional neuroimaging following traumatic brain injury (TBI), controlled cognitive activation studies of episodic memory in this population have not been published. The present investigation studied verbal recall using [O-15]-water positron emission tomography (PET) in 5 individuals who sustained severe TBI (M GCS=6.8; M years post-injury=3.18), and 4 non-injured control participants. Statistical image analysis demonstrated changes in frontoparietal regional cerebral blood flow (rCBF) in both groups, but there were interesting differences between groups and across conditions. Frontal lobe rCBF changes in TBI patients were reduced during free recall but enhanced during recognition, when compared to controls. Changes in cerebellar rCBF were observed in the control group during free recall, but not in the TBI sample. In both groups, bifrontal rCBF increases were noted on recognition tasks. The present findings provide evidence of alterations in specific substrates involved in verbal recall following brain injury.

Adult↗
PubMed2001

Face processing occurs outside the fusiform 'face area' in autism: evidence from functional MRI.

Processing the human face is at the focal point of most social interactions, yet this simple perceptual task is difficult for individuals with autism, a population that spends limited amounts of time engaged in face-to-face eye contact or social interactions in general. Thus, the study of face processing in autism is not only important because it may be integral to understanding the social deficits of this disorder, but also, because it provides a unique opportunity to study experiential factors related to the functional specialization of normal face processing. In short, autism may be one of the only disorders where affected individuals spend reduced amounts of time engaged in face processing from birth. Using functional MRI, haemodynamic responses during a face perception task were compared between adults with autism and normal control subjects. Four regions of interest (ROIs), the fusiform gyrus (FG), inferior temporal gyrus, middle temporal gyrus and amygdala were manually traced on non-spatially normalized images and the percentage ROI active was calculated for each subject. Analyses in Talairach space were also performed. Overall results revealed either abnormally weak or no activation in FG in autistic patients, as well as significantly reduced activation in the inferior occipital gyrus, superior temporal sulcus and amygdala. Anatomical abnormalities, in contrast, were present only in the amygdala in autistic patients, whose mean volume was significantly reduced as compared with normals. Reaction time and accuracy measures were not different between groups. Thus, while autistic subjects could perform the face perception task, none of the regions supporting face processing in normals were found to be significantly active in the autistic subjects. Instead, in every autistic patient, faces maximally activated aberrant and individual-specific neural sites (e.g. frontal cortex, primary visual cortex, etc.), which was in contrast to the 100% consistency of maximal activation within the traditional fusiform face area (FFA) for every normal subject. It appears that, as compared with normal individuals, autistic individuals 'see' faces utilizing different neural systems, with each patient doing so via a unique neural circuitry. Such a pattern of individual-specific, scattered activation seen in autistic patients in contrast to the highly consistent FG activation seen in normals, suggests that experiential factors do indeed play a role in the normal development of the FFA.

Adult↗
PubMed1999

Brain weight in autism: normal in the majority of cases, megalencephalic in rare cases.

The brain weights of 21 postmortem autism cases (5 new and 16 previously published) were compared with normal brain weights from six autopsy studies. Of the 21 cases, 17 had normal brain weights and 1 was micrencephalic. Compared with the normal median (1,460 g), three autism cases were megalencephalic: two (1,810 g and 1,820 g) had been previously reported and one (1,880 g) was a new case. Brain weight is thus normal in most postmortem cases of autism. There are, however, rare cases of megalencephaly and possibly micrencephaly.

Adolescent↗
PubMed1999

Language organization in patients with early and late left-hemisphere lesion: a PET study.

Functional neuroimaging studies have shown enhanced right-hemisphere language activations in adults with left-hemisphere damage. We hypothesized that this effect would be stronger in patients with lesion occurring early in development. Using [15O]-water PET, we studied eight normal adults and 23 patients with unilateral left lesion during rest, listening to sentences, and sentence repetition. Thirteen patients had lesions with early onset (< 5 years) and ten had lesions with late onset (> 20 years). For listening to sentences, frontotemporal blood flow increases were significantly stronger in the left than in the right hemisphere in normal adults. This normal asymmetry was reduced in patients with late lesion and reversed in those with early lesion. For sentence repetition, analogous group differences were significant for the basal ganglia, but failed to reach significance for the (pre)motor and insular regions. We conclude that left lesion leads to alterations in the asymmetry of language activations (in and beyond the perisylvian areas). In addition, rightward shifts of language activation tend to be stronger as a consequence of early (as compared to late) lesion. Finally, postlesional reorganization appears to reflect a coexistence of 'additive' and 'subtractive' effects, i.e., activation in some regions that are not normally involved in language processing and lack of activation in other (undamaged) regions that are normally activated by language tasks.

Adolescent↗
PubMed1999

Brain organization for language in children, adolescents, and adults with left hemisphere lesion: a PET study.

1. There is evidence for pronounced brain plasticity during postnatal maturation. The authors hypothesized that left-hemisphere lesion would be associated with greater than normal language participation of the right hemisphere and that atypical asymmetry of perisylvian language activations would be enhanced after lesion occurring in early childhood as compared to lesion occurring later in life. 2. Eleven patients with left-hemisphere lesion (aged 8-33 yrs.) and 9 normal adult comparison subjects were studied, using [15O]-water positron emission tomography. One patient group (N = 6) had early lesion onset (< or = 6 years of age), a second group (N = 5) had lesion onset later in life (> or = 10 years of age). Regional cerebral blood flow (rCBF) changes during listening to sentences (minus rest) and sentence generation (minus repetition) were compared between groups in predefined regions of interest. 3. Variance of regional activations within early and late lesion onset groups was considerable and qualitative inspection revealed only few robust group differences. However, when 4 patient pairs were approximately matched for chronological age, lesion site and VIQ, significantly reduced leftward asymmetry of activations in early lesion patients was found in the prefrontal, inferior frontal, and inferior parietal regions for expressive language, with concordant and marginally significant trends in the inferior frontal and superior temporal regions for receptive language. 4. The results suggest enhanced postlesional plasticity in childhood, while also reflecting strong individual variability probably due to clinical and demographic factors beside lesion onset.

Adolescent↗
PubMed1999

Brain mapping of language and auditory perception in high-functioning autistic adults: a PET study.

We examined the brain organization for language and auditory functions in five high-functioning autistic and five normal adults, using [15O]-water positron emission tomography (PET). Cerebral blood flow was studied for rest, listening to tones, and listening to, repeating, and generating sentences. The autism group (compared to the control group) showed (a) reversed hemispheric dominance during verbal auditory stimulation; (b) a trend towards reduced activation of auditory cortex during acoustic stimulation; and (c) reduced cerebellar activation during nonverbal auditory perception and possibly expressive language. These results are compatible with findings of cerebellar anomalies and may suggest a tendency towards atypical dominance for language in autism.

Adolescent↗
PubMed1999

Brain activation during intermittent photic stimulation: a [15O]-water PET study on photosensitive epilepsy.

PURPOSE: Intermittent photic stimulation (IPS) is an activation procedure used during electroencephalogram (EEG) recording to elicit paroxysmal discharges in individuals with photosensitivity. Specific responses on EEG recording may be provoked by IPS at different frequencies of flickering in normal individuals and in patients with photosensitive epilepsy. METHODS: Changes in regional cerebral blood flow (rCBF) were studied during IPS in two groups of subjects by using [15O]-water positron emission tomography (PET): a control group consisting of eight healthy adults with photic driving response during IPS on EEG recording (mean age, 25 +/- 10.5 years) without history of neurologic or psychiatric abnormalities and a patient group consisting of four adults (mean age, 33 +/- 7.5 years) with history of photosensitive epilepsy. [15O]-water PET scanning with concomitant EEG monitoring was performed during baseline and IPS at 4-, 14-, and 30-Hz frequencies. RESULTS: The control group showed photic driving response at 14-Hz IPS frequency. The patient group showed photoparoxysmal response at 14 and 30 Hz, but not at 4 Hz. Changes in rCBF were determined by means of statistical parametric mapping. Increases in rCBF in occipital cortex (Brodmann's areas 17, 18, and 19) were observed in both groups. In addition, during photic driving responses, the control group showed rCBF increases in the insula and in the thalamus, on the right side. The patient group showed a significant rCBF increase in the hypothalamic region inferior to the left caudate nucleus during photoparoxysmal response. This activation was not found in the control group. Increased rCBF also was observed in the patient group in the head of the left caudate nucleus, in the left hippocampus, and in left insula during IPS without photoparoxysmal response. No activations in these regions were observed during photoparoxysmal response. CONCLUSIONS: These data may indicate involvement of the hypothalamus in photosensitive epilepsy and may suggest a modulatory function of the caudate nucleus, which might be associated with an inhibition of epileptic discharges during IPS in patients with photosensitive epilepsy.

Adult↗
PubMed1998

Task-related activations in heterotopic brain malformations: a PET study.

Positron emission tomography (PET) studies have shown normal or elevated levels of glucose metabolism in neuronal heterotopia, raising the issue of potential participation of heterotopic neurons in cognitive processing. We studied three patients with heterotopic malformations, using [(15)O]water PET and experimental conditions selected according to the location of the malformations. Task performance was associated with blood flow increases of > 17% within the heterotopia in each patient. In two, these occurred in left frontal heterotopia during sentence generation. In the third patient, activations for facial and visuospatial discrimination and picture naming were found in a right posterior heterotopion. Our findings may reflect participation of heterotopia in cognitive function and suggest that heterotopic neurons synapse with neurons in other brain regions.

Adolescent↗
PubMed1998

Impairment of dentato-thalamo-cortical pathway in autistic men: language activation data from positron emission tomography.

Recent evidence suggests disturbances of serotonin synthesis affecting the dentato-thalamo-cortical pathway in autistic boys. We studied possible effects of such disturbances on brain activations for language in autistic adults. Four autistic and five normal men were studied while listening to, repeating, and generating sentences, using [15(O)]-water positron emission tomography (PET). Activation in the right dentate nucleus and in the left frontal area 46 was reduced during verbal auditory and expressive language and enhanced during motor speech functions in the autism as compared to the control group. The thalamus showed group differences concordant with area 46 for expressive language. The results may indicate atypical functional specialization of the dentato-thalamo-cortical pathway and are compatible with a model of region-specific biochemical disturbances in the developing autistic brain.

Adolescent↗
PubMed1998

Differential patterns of language and motor reorganization following early left hemisphere lesion: a PET study.

OBJECTIVE: There is extensive evidence for post-lesional plasticity in the language and motor domains. We examined possible domain-specific differences in reorganizational patterns, hypothesizing that interhemispheric reorganization would be predominantly homotopic for language, but predominantly nonhomotopic for motor control. DESIGN: Using oxygen 15-water positron emission tomography, regional cerebral blood flow was studied during rest, listening to sentences, repetition of sentences, and finger tapping of the right hand. Task-specific primary, secondary, and tertiary regions of interest were defined according to the degree of regional involvement in language/motor functions as documented in previous studies. Regional activations were compared within and across functional domains. PATIENTS: Nine patients (aged 4-20 years) with unilateral left hemisphere lesion involving both the primary motor and perisylvian language cortices were studied. Two samples of healthy adults were included for additional comparisons. MAIN OUTCOME MEASURE: Hemispheric asymmetry of blood flow changes within regions of interest. RESULTS: As predicted, rightward asymmetry of activations in primary and secondary regions was stronger for language than for movement, but the expected inverse difference for tertiary regions (greater rightward asymmetry of motor activations) was not found. Within-domain comparisons showed that for listening to sentences, rightward asymmetry was strongest in primary and weakest in tertiary regions, whereas the inverse differences were found for movement. CONCLUSION: The findings suggest a greater potential for homotopic interhemispheric reorganization in the language than in the motor domain. Interhemispheric motor reorganization was generally limited.

Adolescent↗
PubMed1998

Brain organization of language after early unilateral lesion: a PET study.

Neuropsychological studies suggest that good long-term language outcome is possible following extensive early left-hemisphere damage. We explored the brain organization for language in children with early unilateral lesion, using [15O]-water PET. In 12 patients with left lesion (LL) and 9 patients with right lesion (RL), cerebral blood flow changes during listening to sentences and repetition were studied. A rightward shift of language activations in the LL group was found in perisylvian areas and multiple other, mostly temporo-parietal, regions. The hypothesis of intrahemispheric reorganization in the LL group found only limited support. The number of activated regions was overall greater in the RL group. Unexpected findings included a stronger subcortical and cerebellar language involvement in the RL group. We suggest that (a) early left lesion is associated with enhanced language participation of the right hemisphere in and beyond the classical language areas, and (b) postlesional effects are in part additive (recruitment of noncanonical areas), in part subtractive (functional depression in areas normally involved in language).

Adolescent↗
PubMed1998

Motor organization after early middle cerebral artery stroke: a PET study.

The brain organization for movement in a 20-year-old man with a history of intrauterine or perinatal right middle cerebral artery stroke was studied. [(15)O]-water positron emission tomography demonstrated a normal pattern of activation during finger movement in the right hand. Movement of the hemiparetic left hand was associated with activation in the supplementary motor area bilaterally and in the left premotor cortex. Blood flow increase was observed in the right temporal lobe adjacent to an extensive area of encephalomalacia, suggesting atypical motor function in the temporal lobe.

Adult↗