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Biomedical subjects

W Fries

Publications and source records attributed to W Fries.

At least 55 records · Page 3Linked to original sources
PubMed1992

Disturbances of mineral and bone metabolism following gastric antrectomy in the rat.

In antrectomized (B-I) and control rats, bone mineralization, the fractional intestinal absorption of calcium, magnesium and phosphorus, the balances of these minerals, their serum concentration and renal excretion, together with serum gastrin, calciotropic hormones (parathyroid hormone, calcitonin, 1,25-dihydroxyvitamin D), and osteocalcin were assessed four months after surgery. B-I evoked hypogastrinemia, but no changes in the serum concentrations of minerals and calciotropic hormones, or urinary cyclic AMP. The major significant changes brought about by B-I were: (1) a decrease in bone dry weight, specific density, bone ash calcium and magnesium content; (2) a decrease in the fractional absorption and urinary excretion of calcium and magnesium; (3) an increase in urinary hydroxyproline and serum osteocalcin in the presence of normal serum bone isoenzyme of alkaline phosphatase. It is concluded that in the rat (1) B-I over the long term decreases both bone mineral content and calcium and magnesium absorption, in the absence of any counterregulation; (2) B-I rats may have attained a new equilibrium which is characterized by decreased absorption and urinary excretion of calcium and magnesium, but maintenance of normocalcemia at the expense of bone; (3) the concomitant changes of serum bone markers are contradictory, which makes their interpretation and use in the present context difficult.

Animals↗
PubMed1991

Motor responses after transcranial electrical stimulation of cerebral hemispheres with a degenerated pyramidal tract.

Motor responses were evoked in the thenar muscles by transcranial electrical cortex stimulation in 5 stroke patients with an isolated lacuna in the internal capsule, in whom wallerian degeneration of the pyramidal tract was demonstrated in vivo. Suprathreshold stimulation of the affected hemisphere elicited bilateral motor responses; whereas, stimulation at identical intensities of the undamaged hemisphere yielded strictly unilateral responses in the contralateral hand, like the responses of all normal control subjects. Focused magnetic brain stimulation was performed in 1 patient and gave identical results. Because muscular excitability to cortical stimulation is preserved in spite of pyramidal tract disruption, other pathways must bypass the lesion. Because of the bilaterality of responses, we suggest polysynaptic corticoreticulospinal connections.

Cerebrovascular Disorders↗
PubMed1991

Fibre divergence in the distal optic radiation: possible basis of functional plasticity in adult primate visual cortex.

The precision of retinotopy in primate visual cortex is commonly thought to result from highly ordered arrangement of fibres in the visual pathways. However, rigid point-to-point representation is hardly compatible with findings of a substantial reorganization of visual cortical maps after peripheral and central lesions. Such observations could be accounted for by divergence in the optic radiation. To explore the hypothesis of fibre divergence, we made small knife cuts in the distal optic radiation of macaca fascicularis. After subsequent axonal tracing by injecting WGA-HRP into lateral geniculate nucleus, we studied the course of distal fibres in white matter. The amount of divergence was assessed by measuring, relative to the prevailing fibre course, length and orientation of labelled fibres between lesion and entry into cortex. Lesion sizes between 1 mm to 3 mm did not result in any detectable diminution of terminal labelling in layer IVC of striate cortex. Individual labelled fibres were found to diverge symmetrically from both sides into the gap distal to the lesion. Divergence starts at a distance of about 3 mm before cortex. At the white matter boundary, less than 10% of all fibres still retain the original direction, with the remaining fibres taking any other orientation without preference. We estimate that this corresponds to a divergence of visual afferents encompassing about 6-10 mm of cortical distance, if intracortical arborization of terminal fibres is taken into account. Possible consequences for functional plasticity in the adult primate visual cortex are discussed.

Animals↗
PubMed1991

[Epidemiology of attempted suicide].

We studied 153 patients admitted to our observation ward after attempted suicide within the last 12 months. The time of attempt, age and sex distribution, social status, kind of suicide attempt and therapeutic procedures were registered. Our analysis showed, that exogenous factors like weather and season (April, November/December) must be considered as important for the time of suicide attempt. Furthermore we noted, that vacations, young age, isolation and unemployment were conducive to suicide attempt. Geriatric attempted suicides differed from those of other age groups in motivation and methods. They may represent on own entity of disease.

Adult↗
PubMed1990

Disturbance of rhythm sense following right hemisphere damage.

In a patient with right temporal lobe and additional right basal ganglia damage following a stroke, recognition and reproduction of simple rhythmical Gestalten were examined and found grossly undisturbed. In contrast to this undisturbed perception and production of rhythm, the patient could not tap or move rhythmically in beat with an auditory pacer such as a metronome or marching band music, yet he could do so to rhythmically presented light or touch stimuli. Thus, the impairment seems to be a previously undescribed, modality specific disturbance of auditorily paced predictive motor behaviour affecting, for example, walking, dancing, singing and speech.

Cerebral Cortex↗
PubMed1990

Pontine projection from striate and prestriate visual cortex in the macaque monkey: an anterograde study.

The projection from striate and prestriate visual cortex to the pontine nuclei has been studied in the macaque monkey by means of anterograde tracer techniques in order to assess the contribution of anatomically and functionally distinct visual cortical areas to the cortico-ponto-cerebellar loop. No projection to the pons was found from central or paracentral visual-field representations of V1 (striate cortex) or prestriate visual areas V2, and V4. Small patches of terminal labeling occurred after injections of tracer into more peripheral parts of V1, V2 and V3, and into V3A. The terminal fields were located most dorsolaterally in the anterior to middle third of the pons and were quite restricted in their rostro-caudal extent. Injections of V5, however, yielded substantial terminal labeling, stretching longitudinally throughout almost the entire pons. This projection could be demonstrated to arise from parts of V5 receiving input from central visual-field representations of striate cortex, whereas parts of V4 receiving similarly central visual-field input had no detectable projection to the pons. Its distribution may overlap to a large extent with the termination of tecto-pontine fibers and with the termination of fibers from visual areas in the medial bank (area V6 or PO) and lateral bank (area LIP) of the intraparietal sulcus, as well as from frontal eye fields (FEF). It appears that the main information relayed to the cerebellum by the visual corticopontine projection is related to movement in the field of view.

Animals↗
PubMed1989

Otolith function in man. Results from a case of otolith Tullio phenomenon.

An otolith disorder is described in a patient with a subluxed stapes footplate. Otoneurological examination, including tympanoscopy, showed that nonphysiological mechanical stimulation of the otoliths by a (pathologically) hypermobile stapes footplate typically manifests with a pattern of sound-induced paroxysms of ocular tilt reaction (OTR), oscillopsia and postural imbalance (otolith Tullio phenomenon). The rare condition of sound-induced otolithic stimulation in an otherwise healthy young man offered a unique opportunity to investigate otolith reflex control of the eye, head and posture in man. Electro-oculographic recordings and special video analysis (time resolution: 1000 images/s) revealed an initial rapid and phasic counterclockwise rotatory upward deviation with a latency of 22 ms, followed by a smaller tonic effect which lasted as long as sound stimulation (480 +/- 20 Hz, 95 dB A). Latencies of the otolithic vestibulospinal reflex, recorded using surface EMG during upright stance with the eyes closed, were surprisingly short with activation of the ipsilateral tibialis anterior muscle 47 ms after the stimulus, and of the ipsilateral gastrocnemius muscle after 52 ms. A considerable postural pertubation was measured by means of a Kistler platform, with the shortest latency for displacement of the centre of pressure of 80 ms and a preferred body sway direction from right-backward to left-forward. When the Valsalva manoeuvre was performed, tonic eye movements and oscillopsia were induced opposite in direction to those produced by the sound reflecting a push-and-pull deviation of the otoliths.

Adult↗
PubMed1988

Raphe nucleus of the pons containing omnipause neurons of the oculomotor system in the monkey, and its homologue in man.

Omnipause neurons take part in the generation of saccadic eye movements. They lie around the midline in the caudal pontine reticular formation, in an area usually ascribed to the nucleus raphe pontis (rp). In this study of the monkey (Macaca fascicularis and M. mulatta), we describe four series of experiments aimed at establishing that omnipause neurons lie within a distinctive cytoarchitectonic entity, which we call the nucleus raphe interpositus (rip): (1) cytoarchitectural study, (2) recording-lesion experiments to establish in which cell group omnipause neurons lie, (3) cytochrome oxidase distribution in the omnipause region and neighboring structures, and (4) neuroanatomical tracing experiments to demonstrate afferents to the omnipause region. In the detailed cytoarchitectural study of the midline structures in the caudal pons and rostral medulla, a distinctive group of neurons (rip) adjoining the ventrocaudal border of rp and dorsal to the nucleus raphe magnus (rm) is described. The striking features of rip are the uniformly arranged, narrow row of the cells either side of the midline, and the extensive horizontally oriented dendritic trees of its neurons. The abducens rootlets (NVI) pass through the reticular formation at the same rostrocaudal level as rip and form a reliable landmark for its location. Cytochrome-oxidase-stained sections demonstrated additional differences between rip and adjacent cell groups: in rip the neurons and their extensive dendrites stained strongly, but not the surrounding neuropile, whereas in rp both the neurons and the neuropile stained darkly, so that individual neurons were difficult to see. Unlike rp, rip coincides with the location of omnipause neurons, and lesions marking the sites of individual omnipause units lay within its boundaries. Tritiated leucine was injected into superior colliculus (sc), which is known to have monosynaptic connections with omnipause neurons. Labelled axons and patterns of silver grains taken to indicate the presence of terminal branching were found in and around rip, but no significant labelling was seen in rp or rm. It is concluded that the omnipause neurons lie within the rip in the monkey. These functional and morphological differences between rip and the adjacent raphe nuclei are used to justify its characterization as an independent cell group in the monkey. In order to relate these findings to man, cytochrome oxidase experiments were carried out on the human brainstem, and the pattern of staining at the level of the abducens rootlets was correlated with the cytoarchitecture.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Plasticity and rigidity in the representation of the human visual field.

Neuronal plasticity in the mammalian visual system has been studied with a variety of experimental methods like induction of artificial squint and eye rotation. To investigate neuronal plasticity in the human visual system, we examined a patient with a congenital convergent squint of his left eye, who later suffered a vascular lesion in his left occipital lobe that led to an incomplete hemianopia in his right visual field. The examination revealed that the visual field representation in the striate cortex is rigidly prewired with reference to the anatomical fovea. In contrast, plasticity in the oculomotor system enables the patient to use a functional visual axis that does not correspond to the anatomical fovea. Local alterations of sensitivity within the visual field that indicate interactions among non-corresponding retinal points provide additional evidence of functional plasticity.

Esotropia↗
PubMed1985

Large layer VI cells in macaque striate cortex (Meynert cells) project to both superior colliculus and prestriate visual area V5.

Layer VI of macaque striate cortex contains a number of large solitary neurones called Meynert cells. It has been shown earlier that these Meynert cells project to the posterior bank of the superior temporal sulcus (area V5), but it has also been shown that they project to the superior colliculus. In retrograde fluorescent double-labelling experiments, it was found that Meynert cells represent a class of neurones which distribute divergent axon collaterals to the posterior bank of the superior temporal sulcus and to the superior colliculus, i.e. to a distant cortical and a subcortical structure. This feature appears to be unique among projecting neurones in monkey visual cortex.

Amidines↗
PubMed1984

Cortical projections to the superior colliculus in the macaque monkey: a retrograde study using horseradish peroxidase.

The topical and laminar distribution of corticotectal cells, as well as their size and morphology, were studied in the macaque monkey with the horseradish peroxidase (HRP) technique. After HRP injections restricted primarily to the superficial layers of the colliculus, labelled cells were found in visual cortex (areas 17, 18, and 19) and both in the frontal eye field (area 8) and the adjacent part of premotor cortex (area 6). The clustering of labelled cells in visual cortex indicated that each of the anatomically and functionally distinct visual areas has its own set of collicular projections. When intermediate and deeper layers of the colliculus were injected, labelled cells were found also in posterior parietal cortex (area 7) where they were concentrated mainly on the posterior bank of the intraparietal fissure, in inferotemporal cortex (areas 20 and 21), in auditory cortex (area 22), in the somatosensory representation SII (anterior bank of sylvian fissure, area 2), in upper insular cortex (area 14), in motor cortex (area 4), in premotor cortex (area 6), and in prefrontal cortex (area 9). In the motor and premotor cortex, labelled cells formed a continuous band which appeared to stretch across finger-hand-arm-shoulder-neck representation. Similarly, the cluster of labelled cells in area 2 may correspond to the finger-hand representation of SII. The cortical regions not containing labelled cells were the somatosensory representation SI (areas 3, 1 and 2) and the infraorbital cortex. Labelled cells were restricted to layer V of all cortical areas except in the primary visual cortex, where labelled cells were found in both layer V and layer VI. The size spectrum of corticotectal cells ranged from 14.8 micron (average diameter) in area 17 to 27.8 micron in area 6, comprising cells as small as 8 micron and as large as 45 micron. Labelled cells in posterior parietal (area 7), in auditory (area 22), and in motor cortex (area 4) were small and distributed over only a narrow range of sizes. Those in premotor cortex (area 6) were often large and had a wide range in size distribution. The differences in size and morphology of corticotectal neurons suggest that they do not form a uniform class of neurons.

Animals↗
PubMed1984

Effects of diazepam on mitosis and basal body duplication of synchronously dividing flagellate cells.

We report here that diazepam (Valium, Roche) has an inhibitory effect on proliferation of synchronously dividing cultures of Dunaliella, whenever the drug is added during the cell cycle. The drug induced an accumulation of abnormal mitotic figures after 17 to 24 hr of treatment with the chromosomes distributed around the nuclei and a monopolar spindle, although the pole-to-chromosome microtubules were well-formed. Diazepam seemed to affect mitosis by inhibiting the separation of the basal bodies, whose duplication was perturbed in a dose-related manner. After 48 hr of treatment, the nucleus returned to interphase without having undergone mitosis, but cytokinesis might have taken place. The mechanism of this action of diazepam on mitosis remains to be elucidated. However, it does not appear to act in the same way here as it does on the central nervous system.

Cell Cycle↗
PubMed1983

Large layer VI neurons of monkey striate cortex (Meynert cells) project to the superior colliculus.

After injections of the enzyme horseradish peroxidase (HRP) into the superior colliculus of macaque monkeys, labelled cells in the neocortex were found to be restricted to layer V in all areas except striate visual cortex. In striate visual cortex, cortico-tectal cells were found both in layer V and in layer VI. The labelled cells in the two layers belonged to morphologically different populations: those of layer V were the common pyramidal cells and those of layer VI were identified as solitary cells of Meynert. This finding may provide new insights into the physiology of the cortico-collicular pathways. It also shows that the striate area in primates differs, with respect to cortico-tectal laminar specificity, from other neocortex.

Animals↗
PubMed1982

Contralateral cortical projections to the superior colliculus in the macaque monkey.

Cortical projections from the contralateral hemisphere to the superior colliculus (SC) were studied in macaque monkey using retrograde transport of the enzyme horseradish peroxidase (HRP). After single or multiple injections of HRP into SC, labelled cells were found contralaterally in layer V of the anterior bank of the arcuate sulcus, the origin of this contralateral projection being confined to the anterior part of Brodmann's area 6. Only a few labelled cells appeared in adjacent area 8. Labelled cells occurred in patches, forming bands which were found to run in a ventromedial direction. A similar pattern was seen homotopically in ipsilateral area 6. Thus, this anterior part of area 6 gives rise to a bilateral projection to the SC. The findings emphasize structural differences in a region of the frontal lobe which has been considered functionally uniform as frontal eye field.

Afferent Pathways↗