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Biomedical subjects

E Koenig

Publications and source records attributed to E Koenig.

At least 19 recordsLinked to original sources
PubMed1995

Screening for active tuberculosis in HIV testing centre.

In industrialised nations HIV-seropositive individuals can be offered skin testing for tuberculosis (TB) and isoniazid prophylaxis, but this approach is neither practicable nor affordable in most developing countries. In Santo Domingo, Dominican Republic, we offered skin testing and a brief clinical examination for active TB to people requesting HIV testing at one centre. 200 newly detected HIV-positive individuals and 200 age and sex-matched HIV-negative ones were compared. 39 (9.7%) of the 400 individuals seeking HIV testing had active TB; 29 were HIV positive and 10 were HIV negative (adjusted odds ratio 3.3, 95% CI 1.3-8.7; p = 0.01). In multivariate analysis, the strongest independent predictors of active TB were 10 mm or more of induration on skin testing, a history of chronic cough, lymphadenopathy, and HIV infection. Of the patients diagnosed with TB, 85% had one or more symptoms readily ascertainable in a brief screening questionnaire. Screening for TB at HIV-testing sites could be an effective approach to early detection of active TB among not just HIV-positive but also HIV-negative people. Integrating screening for TB into HIV testing schemes could help to reduce the spread of TB and allow patients with TB to be diagnosed and treated earlier.

Adolescent↗
PubMed1995

Clinical manifestations of trisomy 4p syndrome.

UNLABELLED: Trisomy 4p syndrome is a distinct clinical entity which was noted almost a quarter century ago by Wilson et al. [71] and later was delineated by Gonzalez and colleagues [29]. The variation in the length of duplicated segment usually associated with monosomy of other genetic material which has resulted in confusion and as a result a so-called 4p syndrome could not be recognized without cytogenetic analysis. We wish to draw the attention of clinicians to this subject by presenting the description of over 75 cases including one from our clinic and stress the point that molecular approaches are imperative to characterize this anomaly. After extensive review, it appears that patients retaining at least the distal two-thirds to the entire short arm share an overlapping phenotypic expression that constitutes pure trisomy 4p syndrome which includes prominent glabella, bulbous nose with flat or depressed nasal bridge, retrognathia, pointed chin, short neck with low hairline, enlarged ears with abnormal helix and antihelix, rocker-bottom feet with prominent heel. Arachnodactyly and camptodactyly. Molecular characterization of 4p is imperative. We have also included an extensive bibliography for clinicians who may find it useful as a single reference source for evaluating their future cases. CONCLUSION: The 4p-syndrome is a distinct entity but without cytogenetic evaluation, the syndrome can not be recognized.

Abnormalities, Multiple↗
PubMed1995

Self-rotation estimate about the vertical axis.

The aim of this paper was to examine the accuracy of passive whole-body self-rotation estimate around the earth-vertical (yaw) axis. Subjects were required to reach an imposed angle of +/- 90 degrees, 180 degrees or 360 degrees (outward way), and then to rotate back to the initial position (return way), through passive rotation controlled by the subject, in darkness. During these rotations, only the semi-circular canals were stimulated. On the outward way, subjects were required to elaborate the correct imposed angle, without any external reference. In average, subjects undershot the expected angles on outward way, which suggests an overestimate of self-rotation, and the error increased with increasing expected angle. On the return way, subjects had to rotate back to the starting point, through a path integration process. There was no effect of the imposed angle on the error, and the variability was lower than on the outward way. The data suggests that the subjects could construct the internal representation of a virtual starting point: the initial body position, which became a goal to reach clearer than the outward rotation angle, which the subjects also have defined, in an environment deprived of any external spatial reference.

Adult↗
PubMed1994

Oculomotor abnormalities and MRI findings in idiopathic cerebellar ataxia.

Extensive oculomotor testing and quantitative MRI evaluation was performed in seven patients with idiopathic cerebellar ataxia without extracerebellar symptoms (IDCA-C) and in ten patients with additional extracerebellar symptoms (IDCA-P). The most severe oculomotor deficits were disturbed smooth pursuit, optokinetic nystagmus and suppression of the vestibulo-ocular reflex (VOR). The symptoms correlated well and consistently with the amount of atrophy of the flocculus and the dorsal vermis. These correlations, however, were not specific, and deficits also correlated with the amount of atrophy of other cerebellar structures. No correlation was found between saccade velocity and brainstem atrophy or between saccade metrics and atrophy of the dorsal vermis. Although patients with IDCA-P had more severe oculomotor deficits than patients with IDCA-C, the pattern of the oculomotor disturbances was the same for both groups. Thus, eye movement analysis alone is not sufficient to distinguish between patients with pure cerebellar ataxia and those with additional extracerebellar symptoms.

Adult↗
PubMed1994

Rotational kinematics of the human vestibuloocular reflex. I. Gain matrices.

1. This series of three papers aims to describe the three-dimensional, kinematic input-output relations of the rotational vestibuloocular reflex (VOR) in humans, and to identify the functional advantages of these relations. In this first paper the response to sinusoidal rotation in darkness at 0.3 Hz, maximum speed 37.5%/s, was quantified by the use of the three-dimensional analogue of VOR gain: a 3 x 3 matrix where each element describes the dependence of one component (torsional, vertical, or horizontal) of eye velocity on one component of head velocity. 2. The three matrix elements indicating collinear gains (i.e., dependence of torsional eye velocity on torsional head velocity, vertical on vertical, and horizontal on horizontal) were smaller than the -1's required for optimal retinal image stabilization. Of these three the torsional gain was weakest: -0.37 for rotation about an earth-vertical axis, versus -0.73 and -0.64 for vertical and horizontal gains. Matrix elements indicating cross talk were mostly negligible. There was a tendency to leftward eye rotation in response to clockwise head motion, but this was not statistically significant. 3. VOR responses were compared for rotation about earth-vertical and earth-horizontal axes. The varying otolith input due to the rotation of the gravity vector relative to the head during earth-horizontal axis rotation made no difference to the collinear gains. 4. There were no consistent phase leads or lags except for a torsional phase lead of up to 10 degrees, usually more marked for clock-wise head rotation versus counterclockwise, and for oblique axis rotations versus purely torsional. 5. Torsional gain was magnified, averaging -0.52, when the torsional component of head rotation was only a small part of a predominantly vertical or horizontal rotation, i.e., when the axis of head rotation was near the frontal plane. Because most natural head rotations occur about such axes, the torsional VOR is probably somewhat stronger than the response to pure torsion would suggest. 6. The speed of eye rotation in response to a given stimulus varied widely among subjects, but the direction of rotation was much more uniform. For head rotations about oblique axes out of the frontal plane, there was a systematic misalignment of eye and head axes, with eye axes tilted toward the frontal plane. These findings can be explained on the basis of a strategy where the VOR balances the muscular effort of rotating the eyes against the cost of retinal slip.

Acceleration↗
PubMed1994

Rotational kinematics of the human vestibuloocular reflex. II. Velocity steps.

1. Gain matrices were used to quantify the three-dimensional vestibuloocular reflex (VOR) in five human subjects who were accelerated over 1 s and then spun at a constant 150 degrees/s for 29 s in darkness. Rotations were torsional, vertical and horizontal, about earth-vertical and earth-horizontal axes. 2. Elements on the main diagonal of the gain matrices were much smaller than the optimal value of -1, and torsional gain was weaker than vertical or horizontal. Off-diagonal elements, indicating cross talk, were minimal except for a small but consistent horizontal response to torsional head rotation. 3. Downward slow phases were more than twice as fast as upward at the start of rotation about both earth-vertical and earth-horizontal axes, but the asymmetry vanished later in the rotation. 4. During earth-vertical-axis rotation, all matrix elements decayed to zero. The main-diagonal torsional and vertical gains waned with time constants close to that of the cupula (6.7 and 7.3 s). Velocity storage prolonged the horizontal response to horizontal head rotation (time constant 14.2 s) but not the horizontal response to torsion (7.7 s). A simple explanation is that velocity storage acts on a central estimate of head motion that accurately distinguishes horizontal from torsional and that the inappropriate horizontal eye velocity response to torsion occurs because of cross talk downstream from velocity storage. 5. During earth-horizontal-axis rotation, the torsional, vertical, and horizontal main-diagonal elements declined, with time constants of 7.6, 8.2, and 7.9 s, to maintained nonzero values, all equal to about -0.1. Off-diagonal elements, including the horizontal response to torsion, decayed to zero, so that the otolith-driven reflex, late in the rotation, was equally strong in all dimensions and almost free of detectable cross talk. 6. The difference between gain curves over the course of earth-vertical- and earth-horizontal-axis rotations was not constant but increased with time, suggesting that the VOR response to earth-horizontal-axis rotation is not a simple sum of canal and otolith reflexes.

Acceleration↗
PubMed1994

Rotational kinematics of the human vestibuloocular reflex. III. Listing's law.

1. Do slow phase eye velocities generated by the vestibuloocular reflex (VOR) depend on eye position? If the purpose of the VOR is simply to stabilize the retinal image, there can be no such dependence, because eye velocity must always be equal and opposite to head velocity. But if the VOR tolerates some retinal slip to achieve other goals, such as reducing eye velocity or following Listing's law, then one should see specific patterns of dependence. We examined VOR responses of human subjects to yaw, pitch, and roll rotation looking in various directions to quantify how the input-output properties of the VOR vary with eye position. 2. Eye rotation axes during yaw and pitch tilted in the same direction as the gaze line but only one-quarter as far on average. Thus, during yaw head rotation, the axis of eye rotation was roughly aligned with the head axis when the subject looked straight ahead, but tilted up when the gaze direction was up, and down when gaze was down. The amount of tilt varied between subjects, but on average a 30 degrees change in eye position caused a 7.5 degrees tilt in the eye rotation axis. During pitch, the eye axis tilted right when gaze was right and left when gaze was left, also moving 7.5 degrees on average for a 30 degrees change in the gaze direction. 3. During roll stimulation, the axis of eye rotation tilted in the opposite direction to the gaze line, and about one-half as far. On average, when the gaze line moved 30 degrees down, the eye rotation axis tilted 12.0 degrees up; when the gaze moved 30 degrees left, the eye axis tilted 15.3 degrees right. 4. It is often argued that the torsional VOR is weak because head rotation about the line of sight causes little image displacement on the fovea. But the line of sight is collinear with the torsional axis only when the subject looks straight ahead. Does the "weak axis" of the VOR stay collinear with the gaze line when the subject looks eccentrically? We calculated the axis of head rotation for which the VOR response is weakest and found that it does vary with eye position, but does not stay parallel with the gaze direction. When subjects looked straight ahead, the weak axis was roughly collinear with the gaze line; when gaze shifted eccentrically, the weak axis shifted in the same direction but only about one-half as far.(ABSTRACT TRUNCATED AT 400 WORDS)

Acceleration↗
PubMed1994

Head position dependent adjustment of the three-dimensional human vestibuloocular reflex.

We studied the influence of static head position relative to the rotation axis on the three-dimensional (3-D) vestibuloocular reflex (VOR). By means of a 3-D rotating chair and a 3-D magnetic search-coil system, eye movements were recorded in 6 normal human subjects during sinusoidal rotation about an earth-vertical axis (yaw) with the head positioned at different pitch angles and about an earth-horizontal axis (pitch) with the head positioned at different yaw angles. We confirmed that torsional VOR gain is about 2/3 of horizontal and vertical VOR gain leading to non-collinear axes of eye and head rotation whenever torsional head movement components were present with eye movement axes tilting away from the torsional direction. Despite this non-collinearity of stimulus and eye movement rotation axes there was close to perfect adjustment of the different VOR components depending on the angle between gaze direction and stimulation axis, indicating a vectorial summation of gains obtained for rotations in the major body axes (roll, pitch and yaw). The horizontal and vertical eye movement components followed a cosine function of the angle between the plane of rotation and gaze direction. The torsional component followed a sine function.

Adult↗
PubMed1993

Monoclonal antibody 8A2-induced retraction appears to be mediated by protein phosphorylation in goldfish retinal ganglion cell axons.

We have recently demonstrated that binding by monoclonal antibody (mAb) 8A2 to regenerating retinal ganglion cell axons in goldfish explants specifically induces a sustained, actin-based retraction response that is similar in most respects to a spontaneous retraction (S.G. Finnegan, V. Lemmon, and E. Koenig, Cell Motil. Cytoskeleton, 1992). Experiments were conducted to evaluate potential signal transduction pathways that may play a role in mediating retraction, using the mAb 8A2 retraction model system. Potential roles of cAMP, elevated intracellular calcium, or calmodulin-dependent processes were probed and the results did not appear to implicate them in either the induction or the maintenance of the axon retraction response. In contrast, treatment with phorbol 12-myristate 13-acetate, but not with inactive phorbol esters, induced a retraction response, although the response was more variable and less robust than that produced by mAb 8A2. However, both forms of induction were blocked by staurosporine, a nonspecific kinase inhibitor. Okadaic acid, a potent serine/threonine phosphatase inhibitor produced a very robust retraction response, and subthreshold doses significantly potentiated the retraction response induced by mAb 8A2. Genistein inhibited the mAb 8A2-induced retraction response at concentrations selective for tyrosine kinase activity in a dose-dependent manner. These findings are consistent with the hypothesis that an augmented phosphorylation state of one or more axonal proteins, perhaps catalyzed in part by protein kinase C, produces a sustained physiological retraction. In addition, tyrosine kinase may be involved in transducing surface-mediated interactions that trigger retraction, including the binding reaction signal of mAb 8A2.

Alkaloids↗
PubMed1993

Vestibular perception of passive whole-body rotation about horizontal and vertical axes in humans: goal-directed vestibulo-ocular reflex and vestibular memory-contingent saccades.

This study was aimed at complementing the existing knowledge about vestibular perception of self-motion in humans. Both goal-directed vestibulo-ocular reflex and vestibular memory-contingent saccade (VMCS) tasks were used, respectively as concurrent and retrospective magnitude estimators for passive whole-body rotation. Rotations were applied about the earth-vertical and earth-horizontal axes to study the effect of the otolith signal in self-rotation evaluation, and both in yaw and pitch to examine the horizontal and vertical semi-circular canals. Two different magnitudes of constant angular acceleration (50 degrees/s2 and 100 degrees/s2) were used. The main findings were (1) strong correlation between both oculomotor responses of both tasks, (2) greater accuracy with rotations about the earth-vertical than the earth: -horizontal axis, (3) greater accuracy for yaw than for pitch rotations, (4) greater accuracy for high acceleration than for low, and (5) no effect of the delay (2 s or 12 s) in the VMCS task. Adequacy of both tasks as subjective magnitude estimators of vestibular perception of self-motion is discussed.

Adult↗
PubMed1992

The influence of head position and head reorientation on the axis of eye rotation and the vestibular time constant during postrotatory nystagmus.

Reorienting the head with respect to gravity during the postrotatory period alters the time course of postrotatory nystagmus (PRN), hastening its decline and thereby reducing the calculated vestibular time constant. One explanation for this phenomenon is that the head reorientation results in a corresponding reorientation of the axis of eye rotation with respect to head coordinates. This possibility was investigated in 10 human subjects whose eye movements were monitored with a three-dimensional magnetic field - search - coil technique using a variety of head reorientation paradigms in a randomized order during PRN following the termination of a 90 degrees/s rotation about earth vertical. Average eye velocities were calculated over two time intervals: from 1 s to 2 s and from 7 s to 8 s after cessation of head rotation. The time constant was estimated as one third of the duration of PRN. For most conditions, a reorientation of the head with respect to gravity 2 s after the rotation had stopped did not significantly alter the direction of the eye velocity vector of PRN with respect to head coordinates. This strongly indicates that, in humans, PRN is mainly stabilized in head coordinates and not in space coordinates, even if the otolith input changes. This finding invalidates the notion that the shortening of PRN due to reorientation of the head could be due to a change of the eye velocity vector towards a direction (torsion), which is not detectable with the eye recording methods (electrooculography) used in earlier studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Three-dimensional properties of human pursuit eye movements.

For any given location and velocity of a point target, there are infinitely many different eye velocities that the pursuit system could use to track the target perfectly. Three-dimensional recordings of eye position and velocity in 8 normal human subjects showed that the system chooses the unique tracking velocity that keeps eye position vectors (a particular mathematical representation of three-dimensional eye orientation) confined to a single plane, i.e. pursuit obeys Listing's law. One advantage of this strategy over other possible ones, such as choosing the smallest eye velocity compatible with perfect tracking, is that it permits continuous pursuit without accumulation of ocular torsion. For nonpoint targets, there is at most one eye velocity compatible with perfect retinal image stabilisation, and the optimal velocity may not fit Listing's law; we observed small but consistent deviations from the law during pursuit of rotating line targets.

Adult↗
PubMed1991

Selective impairment of smooth-pursuit eye movements due to an ischemic lesion of the basal pons.

Voluntary and reflex-like eye movements were measured in a patient with an ischemic lesion of the right basal pons. Ipsilateral smooth-pursuit eye movements were predominantly impaired and interrupted by saccades. This profound smooth-pursuit deficit contrasted with only minor abnormalities of visually guided saccades and the vestibulo-ocular reflex. A selective disturbance of smooth-pursuit eye movements due to a lesion of the basal pons in this patient concurs with recent work in monkeys suggesting that smooth-pursuit eye movements are mediated by a parietooccipito-ponto-cerebellar pathway.

Brain Ischemia↗
PubMed1991

Transmembrane cytoskeletal modulation in preterminal growing axons. II. Limax flavus agglutinin-induced receptor redistribution, capping and internalization in varicosities of growing axons.

Growing retinal ganglion cell axons of the goldfish exhibit varicosities of varying sizes and smaller non-protruding phase-dense inclusions that are mobile and mediate rapid bulk redistribution of axoplasm. In fixed axons, Limax flavus agglutinin, a lectin specific for sialic acid which has been shown to inhibit organelle transport in these axons, preferentially labels surface membrane associated with varicosities and inclusions in preterminal axons. In viable axons, Limax flavus agglutinin causes: (1) agglutination of closely apposed axons, (2) redistribution of lectin-binding sites on varicosities to surfaces of interaxonal contact with other varicosities, forming 'fused' multivaricosity complexes, and (3) formation of vacuoles in many single varicosities and some multivaricosity complexes. Vacuoles contain Limax flavus agglutinin binding sites distributed circumferentially. On the basis of immunocytochemistry, actin, myosin, calmodulin and alpha-spectrin are co-localized with redistributed Limax flavus agglutinin binding sites. The agglutination, redistribution of lectin binding sites and changes in the cytoskeleton can be reversed by treatment with sialic acid. The lectin-induced vacuole formation and internalization of Limax flavus agglutinin receptors can also be blocked either by sodium azide in a glucose-free medium, or by pretreatment with cytochalasin D and indicate an energy and a cytoskeletal dependence. The Limax flavus agglutinin-induced structural rearrangements are not altered after limited digestion with pronase. Western blots after ultramicroelectrophoresis of retinal ganglion cell axons subjected to limited digestion reveal Limax flavus agglutinin labelling of bands with apparent Mr of 64 and 70 KDa. In undigested axons, some 70 KDa protein remains unextracted with Triton X-100 lysis of axonal fields, and more remains unextracted when axonal fields are pretreated with Limax flavus agglutinin before Triton lysis, suggesting increased association with the cytoskeleton in response to lectin binding. The results indicate that cross-linking of one or more sialoglycoconjugates on the surface of varicosities of preterminal growing retinal ganglion cell axons causes a constellation of transmembrane-mediated cytoskeletal and membrane changes that are akin to those described for capping in motile cells.

Actins↗
PubMed1991

T-wave response in cervical root lesions.

T-wave responses of biceps and triceps brachii muscles were recorded electrophysiologically from 31 normal subjects and 15 patients with unilateral lesions of the cervical C6 or C7 roots. Pathological T-wave responses were found in 11 (73%) patients. Patients with radiological correlate showed electromyographic (EMG) pathology in 60% but a pathological T-wave response in 90%. All patients with radiological correlate also showed pathological electrophysiological tests (EMG or T-wave responses). Electrophysiological measurement of the T-wave response appears to be a potentially useful tool in the diagnosis of cervical radiculopathies.

Adult↗
PubMed1990

Volume regulation in response to hypo-osmotic stress in goldfish retinal ganglion cell axons regenerating in vitro.

Goldfish retinal ganglion cell (RGC) axons regenerating in vitro were used to investigate the volume regulatory response to hypo-osmotic stress. Reducing the tonicity of the bathing medium to half strength caused an immediate swelling of axons; however, within 1 min a progressive volume reduction ensued which stabilized at near control volume over a period of 10 min. This regulatory volume decrease (RVD) was attenuated by elevated [K+]o, Ca2(+)-activated K+ channel antagonists, and calmidazolium, a potent calmodulin inhibitor. Inclusion of ATP-gamma S in the hypotonic bathing medium led to a loading of stressed axons which resulted in an excessive volume reduction that reflected an overshooting of the RVD response. The latter suggested the importance of phosphorylation/dephosphorylation reactions in the RVD response pathway. Cytochalasin D and colchicine had no effect on the development of the typical RVD response, providing no evidence of involvement of actin or microtubule cytoskeletons in the volume reduction mechanism of the immature axons. The results are consistent with the hypothesis that hypo-osmotic stress activates a calcium/calmodulin dependent membrane pathway, which probably involves transient phosphorylation, leading to a loss of cellular K+ and osmotically obligated water which restorates normal axonal volume.

Adenosine Triphosphate↗