Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Yaws”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMed1956

Yaws eradication campaign in Nsukka Division, Eastern Nigeria.

Nsukka Division in Eastern Nigeria was chosen as the starting point for a yaws eradication campaign undertaken by the Government assisted by WHO and UNICEF. Yaws was found to be hyper-endemic, and a policy of total mass treatment was therefore adopted. The objectives of the campaign, the field organization and methods of operation, and the clinical findings and treatment schedules used are described.A total of 383 769 persons were examined and treated with penicillin; of these 12 221 were infectious cases, 42 553 were late cases, and 328 995 were latent cases and contacts. It is believed that over 95% of the population was seen. Resurveys at intervals of six months showed a dramatic fall in the reservoir of infectious cases.The campaign was also used to stimulate better rural health services, and a network of local health centres was built by the people themselves.

Biomedical Research↗
PubMed1985

Resurgent yaws and other skin diseases in the Western Province of the Solomon Islands.

A clinical study of the extent and nature of skin disease was undertaken among 10,224 Melanesians in the Western Province of the Solomon Islands. It was performed concurrently with a survey and selective mass treatment campaign for yaws which has reappeared in the area for the first time in 20 years. For children under 15 years old, prevalence rates for pyoderma and infectious yaws were 52% and 8.5%, respectively. Tinea versicolor was the commonest superficial dermatomycosis affecting nearly half of all adults seen. Glabrous skin (16% of all cases) and nails (25% of all cases) were the principle sites infected by the dermatophytes. Tinea imbricata, whilst uncommon, was restricted to small endemic foci. Pediculosis capitis was universal but scabies was present in only 4% of young children. Unfavourable environmental conditions and misconceptions about personal hygiene are important aetiological determinants. Education and motivation at a village level will be the mainstay of future control with specific therapy generally reserved for treponematoses, extensive dermatophytoses and scabies.

Adolescent↗
PubMed1991

The squirrel monkey vestibulo-ocular reflex and adaptive plasticity in yaw, pitch, and roll.

The vestibulo-ocular reflex (VOR) was studied in adult squirrel monkeys before and after adaptation to magnifying and minifying viewing conditions. Monkeys were subjected to broadband (0.05-0.71 Hz) conditioning rotation for six hours in head yaw, pitch, and roll on separate occasions, and the VORs in these three planes were studied in darkness to assess adaptive plasticity in the reflexes. The gain of the horizontal VOR (H-VOR) averaged 0.8 across the frequency bandwidth studied (0.025-4 Hz). Phase was near 0 degrees from 4 to around 0.1 Hz, but developed a progressive lead as frequency declined further. Normal vertical VOR (V-VOR) gain climbed from 0.6 at 0.025 Hz to near 1 as frequency increased to 4 Hz. Phase lead was more pronounced at low frequencies than in the H-VOR. The normal torsional VOR (T-VOR) qualitatively resembled the V-VOR, showing similar phase but lower gains (0.3-0.7) across the frequency bandwidth. These findings suggest that the dynamics of the V-VOR and T-VOR resemble canal characteristics more closely than does the H-VOR. After adaptation to visual minification and conditioning rotation (0.5X for yaw and pitch, 0X for roll), gain decreased in each of the planes of conditioning. Similarly, gain increased in the plane of conditioning after adaptation to visual magnification (2X). The adaptive changes were greater at low (0.025-1 Hz) than at high (2.5-4 Hz) frequencies, and were more robust when gain was driven downward than upward. However, control (sham) adaptation experiments showed that VOR gain tended to drop slightly over 6 h in the absence of adaptive drive to do so, suggesting that the gain modifications may be more symmetric when referenced to the control. Adaptive VOR gain enhancement or decrement in the plane of conditioning did not result in systematic and parallel changes in orthogonal VOR planes.

Acclimatization↗
PubMed1996

Modulation of vergence by off-vertical yaw axis rotation in the monkey: normal characteristics and effects of space flight.

Horizontal movements of both eyes were recorded simultaneously using scleral search coils in 2 rhesus monkeys before and after the COSMOS 2229 space-flight of 1992-1993. Another 9 monkeys were tested at comparable time intervals and served as controls. Ocular vergence, defined as the difference in horizontal position between the left and right eyes, was measured during off-vertical yaw axis rotation (OVAR) in darkness. Vergence was modulated sinusoidally as a function of head position with regard to gravity during OVAR. The amplitude of peak-to-peak modulation increased with increments in tilt of the angle of the rotational axis (OVAR tilt angle) that ranged from 15 degrees to 90 degrees. Of the 11 monkeys tested, 1 had no measurable modulation in vergence. In the other 10, the mean amplitude of the peak to peak modulation was 5.5 degrees +/- 1.3 degrees at 90 degrees tilt. Each of these monkeys had maximal vergence when its nose was pointed close to upward (gravity back; mean phase: -0.9 degree +/- 26 degrees). After space flight, the modulation in vergence was reduced by over 50% for the two flight monkeys, but the phase of vergence modulation was not altered. The reduction in vergence modulation was sustained for the 11-day postflight testing period. We conclude that changes in vergence are induced in monkeys by the sinusoidal component of gravity acting along the naso-occipital axis during yaw axis OVAR, and that the modulation of the vergence reflex is significantly less sensitive to linear acceleration after space flight.

Animals↗
PubMed1986

European vestibular experiments on the Spacelab-1 mission: 6. Yaw axis vestibulo-ocular reflex.

In two Spacelab-1 crew members the lateral eye movements evoked by active angular oscillation of the head in yaw at 1 Hz were recorded in-flight and post-flight. In one, the responses to passive angular oscillation in yaw at 0.2-1 Hz were also studied pre- and post-flight. In the absence of visual fixation there was no significant change in the gain of either the active or passive vestibulo-ocular reflex (VOR) attributable to exposure to microgravity. However, when the subject fixated on a visual target that moved with his head the suppressed VOR gain was lower on the first post-flight test (performed 16 h after landing) than that obtained pre-flight or on subsequent post-flight tests.

Adaptation, Physiological↗
PubMed2001

Control of steering in the presence of unexpected head yaw movements. Influence on sequencing of subtasks.

Control of the head during locomotion has been suggested as a means of facilitating overall postural control of the body. The control of online steering is challenging, as it requires the central nervous system (CNS) to simultaneously control body reorientation in a new direction while modifying the ongoing step cycle. Stable body posture during steering is maintained via appropriately organized postural responses to error signals detected by the visual, vestibular, and/or proprioceptive systems. Modifications to the gait cycle include step-width regulation and movement of body center of mass (COM) in the direction of travel, and may be preceded by independent control of head orientation to see where one is going. The purpose of this investigation was to examine how the ability to successfully steer is influenced by unexpected head perturbations and how various body segments are coordinated and controlled to successfully steer along different pathways. Body kinematics were monitored as participants changed their direction of travel by varying amounts when visually cued one stride before the turn. Perturbations to the head were applied to either assist or oppose the change in direction one step prior to initiation of the turn. Analyses focused on the timing of the changes in head yaw, trunk yaw, and COM trajectories in the mediolateral plane. Results indicate that the order of control over the body segments was head and trunk reorientation in the direction of travel and finally movement of the COM in the intended direction. Thus gaze, inferred from head movement, preceded changes in COM trajectory. This suggests that looking where you are going is critical for steering. When steering is potentially compromised by unexpected head movements, the CNS delays committing movement of the COM until it has a chance to look at the new travel path.

Adult↗
PubMed2004

Eye-position dependence of torsional velocity during interaural translation, horizontal pursuit, and yaw-axis rotation in humans.

The translational vestibulo-ocular reflex (tVOR) stabilizes an image on the fovea during linear movements of the head. It has been suggested that the tVOR may share pathways with the pursuit system. We asked whether the tVOR and pursuit would be similar in their behavior relative to Listing's Law. We compared torsional eye velocity as a function of vertical orbital position during interaural translation, pursuit, and yaw-axis rotation. We found that the eye-position-dependence of torsion was similar during translation and pursuit, which differed from that during yaw-axis rotation. These findings further support a close relationship between the mechanisms that generate pursuit and the tVOR.

Adult↗
PubMed2005

Kinematics of vertical saccades during the yaw vestibulo-ocular reflex in humans.

PURPOSE: Listing's law (LL) constrains the rotational axes of saccades and pursuit eye movements to Listing's plane (LP). In the velocity domain, LL is ordinarily equivalent to a tilt in the ocular velocity axis equal to half the change in eye position, giving a tilt angle ratio (TAR) of 0.5. This study was undertaken to investigate vertical saccade behavior after the yaw vestibulo-ocular reflex (VOR) had driven eye torsion out of LP, an initial condition causing the position and velocity domain formulations of LL to differ. METHODS: Binocular eye and head motions were recorded with magnetic search coils in eight humans. With the head immobile, LP was determined for each eye, and mean TAR was 0.50 +/- 0.07 (mean +/- SD) for horizontal and 0.45 +/- 0.11 for vertical saccades. The VOR was evoked by transient, whole-body yaw at 2800 deg/s2 peak acceleration, capable of evoking large, uninterrupted VOR slow phases. Before rotation, subjects viewed a target at eye level, 20 degrees up, or 20 degrees down. In two thirds of the trials, the target moved upward or downward at systematically varying times, triggering a vertical saccade during the horizontal VOR slow phase. RESULTS: Because the head rotation axis was generally misaligned with LP, the eye averaged 3.6 degrees out of LP at vertical saccade onset. During the saccade, eye position continued to depart LP by an average 0.8 degrees. The horizontal TAR at saccade onset was 0.29 +/- 0.07. At peak saccade velocity 35 +/- 3 ms later, the vertical TAR was 0.45 +/- 0.07, statistically similar to that of head fixed saccades. Saccades did not return to LP. CONCLUSIONS: Although they did not observe the position domain formulation of LL, vertical saccades, during the VOR, observed the half-angle velocity domain formulation of LL.

Adult↗
PubMed1995

Unilateral vestibular deafferentation (UVD) causes permanent asymmetry in the gain of the yaw VOR to high acceleration head impulses in guinea pigs.

Using an acute scleral search coil technique for measuring eye position in alert animals we have shown that after UVD the yaw VOR in the guinea pig shows a permanent gain asymmetry. There is a reduced gain during the first 100 ms of brief, high acceleration horizontal head rotations ("yaw head impulses") towards the operated side, but only a small loss in gain for similar rotations towards the intact side. This result confirms that the horizontal E response during the first 100 ms of an abrupt high acceleration head rotation is a clear indicator of the function of the horizontal canal. These results are similar to those in human patients after unilateral acoustic neuroma operations. The asymmetry in response is large shortly after UVD and decreases over time but is permanent.

Acceleration↗
PubMed1995

Torsional eye velocity components during yaw angular acceleration identify the side of unilateral vestibular deafferentation.

Using dual torsion scleral search coils we have recorded 3-dimensional eye position during yaw angular accelerations of 20 degrees/s2 about an earth vertical axis in healthy subjects and in patients with unilateral vestibular deafferentation (UVD). These experiments produced two interesting results: i) even in healthy subjects, the axis of eye velocity did not coincide with the (earth vertical) stimulus axis during centred rotation; ii) Patients with UVD had torsional eye velocity components that were systematically different from those in normal subjects. While in normals the direction of the torsional component of the eye velocity depended on the direction of rotation and was on average approximately symmetric for CW and CCW yaw rotation, there was a clear asymmetry in patients, which was distinctly different for left and right UVD.

Acceleration↗
PubMed1997

Yaw sensory rearrangement alters pitch vestibulo-ocular reflex responses.

Ten male subjects underwent two types of adaptation paradigm designed either to enhance or to attenuate the gain of the canal-ocular reflex (COR), before undergoing otolith-ocular reflex (OOR) testing with constant velocity, earth horizontal axis and pitch rotation. The adaptation paradigm paired a 0.2 Hz sinusoidal rotation about an earth vertical axis with a 0.2 Hz optokinetic stimulus that was deliberately mismatched in peak velocity or phase and was designed to produce short-term changes in the COR. Preadaptation and postadaptation OOR tests occurred at a constant velocity of 60 degrees/sec in the dark and produced a modulation component of the slow phase velocity with a frequency of 0.16 Hz due to otolithic stimulation by the sinusoidally changing gravity vector. Of the seven subjects who showed enhancement of the COR gain, six also showed enhancement of the OOR modulation component. Of the seven subjects who showed attenuation of the COR gain, five also showed attenuation of the OOR modulation component. The probability that these two cross-axis adaptation effects would occur by chance is less than 0.02. This suggests that visual-vestibular conditioning of the yaw axis COR also induced changes in the pitch axis OOR. We thus postulate that the central nervous system pathways that process horizontal canal yaw stimuli have elements in common with those processing otolithic stimuli about the pitch axis.

Adaptation, Psychological↗
PubMed2003

Eye movement responses to active, high-frequency pitch and yaw head rotations in subjects with unilateral vestibular loss or posterior semicircular canal occlusion.

This study assessed the eye movement responses to active head rotation in six subjects with complete unilateral vestibular loss (UVL), five subjects with posterior canal plugging (PCP) and age- and sex-matched normal subjects. Subjects performed head rotations in the pitch and yaw planes at frequencies ranging from 2 to 6 Hz, while looking at an earth-fixed target. Vertical eye movement gains obtained in UVL, PCP and normal subjects were not significantly different. Vertical phases decreased with increasing head movement frequencies in both UVL and PCP subjects. Although this decrease produced significantly different vertical phases between UVL and normal subjects for head movements above 3.9 Hz, vertical phases in some normal subjects were similar to those obtained in UVL subjects. We conclude that active head oscillations in the pitch plane are not clinically useful for the detection of vertical canal impairment limited to one ear. As expected, UVL subjects showed reduced horizontal gains, and eye velocity asymmetries during active head rotation in the yaw plane. Results in some PCP subjects suggested possible minor impairments of horizontal vestibulo-ocular reflexes.

Adolescent↗
PubMed1986

Vestibular-visual conflict in pitch and yaw planes in the squirrel monkey.

Direction conflicting vestibular and visual (optokinetic) stimuli either in the pitch or yaw plane were given to squirrel monkey subjects. The conflict sickness symptom score in the pitch plane was significantly higher than that in the yaw plane for the initial exposure session (p less than 0.01). A significant score difference was also encountered when the exposure sessions were repeated (p less than 0.05).

Animals↗
PubMedDate not supplied

An earth-stationary perceived visual scene during roll and yaw motions in a flight simulator.

A flight simulator was used for two experiments to determine the amplitude combinations of visual scene motion (with respect to the observer) and inertial body motion (with respect to an earth-fixed frame) that provide the perception of an earth-stationary visual scene and realistic simulated self-motion. In the first experiment, this range was determined for simulated self-motion about the longitudinal body axis, while in the second, self-motion about the vertical body axis was considered. Both the inertial and the visual motions consisted of 0.75 a accelerations, followed by 1.50 s decelerations, and 0.75 s accelerations. The visual scene acceleration amplitude, W, was fixed at either 0, 2, 4, 8, or 12 degrees/s2 while the inertial acceleration amplitude, I, was varied by a staircase procedure. Following the visual and inertial motions, the subjects pushed a button when they perceived the scene to be not earth-stationary. At each visual scene acceleration amplitude, the lower and upper inertial threshold amplitudes were determined, which bounded the range in which the visual scene was perceived to be earth-stationary. The lower and upper inertial thresholds were defined as the inertial motion amplitudes for which the inertial stimulations were too small or too large, respectively, to provide the perception of an earth-stationary visual scene. The lower inertial thresholds were determined for W = 2 through W = 12 degrees/s2 and were found to be well approximated by the linear relation I = -0.37 + 0.60 W for the roll motions tested, and I = 1.1 + 0.33 W for the yaw motions tested. The upper inertial thresholds were determined for W = 0 through W = 12 degrees/s2 and were found to be well approximated by the linear relation I = 2.7 + 1.7 W for roll and I = 2.2 + 1.4 W for yaw. With the assumption that the lower and upper inertial threshold amplitudes are symmetric about the W = 0 condition, the present results infer a strong nonlinearity of the thresholds near W = 0.

Adult↗
PubMed1963

ON THE ORIGIN OF THE HUMAN TREPONEMATOSES (PINTA, YAWS, ENDEMIC SYPHILIS AND VENEREAL SYPHILIS).

A close relationship between the four human treponematoses is suggested by their clinical and epidemiological characteristics and by such limited knowledge of the treponemes as there is at present. No treponeme of this group (except for that of the rabbit) is known other than in man, but the human treponemes probably arose long ago from an animal infection. The long period of infectiousness of pinta suggests that it may have been the earliest human treponematosis. It may have been spread throughout the world by about 15 000 B.C., being subsequently isolated in the Americas when the Bering Strait was flooded. About 10 000 B.C. in the Afro-Asian land mass environmental conditions might have favoured treponeme mutants leading to yaws; from these, about 7000 B.C., endemic syphilis perhaps developed, to give rise to venereal syphilis about 3000 B.C. in south-west Asia as big cities developed there. Towards the end of the fifteenth century A.D. a further mutation may have resulted in a more severe venereal syphilis in Europe which, with European exploration and geographical expansion, was subsequently carried throughout the then treponemally uncommitted world. These suggestions find some tentative support in climatic changes which might have influenced the selection of those treponemes which still survive in humid or arid climates. Venereal transmission would presumably remove the treponeme from the direct influence of climate. The author makes a plea for further investigation of many aspects of this subject while this is still possible.

Americas↗
PubMed1992

Case report 724. Yaws.

A 15-year-old girl presented with the typical clinical, serological, and pathological lesions of yaws. The patient was a native of Sumatra. The important diagnostic criteria and the relationship to venereal syphilis were discussed.

Adolescent↗
PubMed1983

Resurgence of yaws in Ghana.

This paper reports on the first 1 1/2 years of a new effort to control yaws in Ghana, where the disease has been resurgent since a previous mass campaign ended over 10 years ago.

Adolescent↗
PubMed1988

Imported yaws in Johor, Malaysia.

Yaws was detected in a six-member family in the southern Malaysia state of Johor. This stresses the need to be vigilant against a long-forgotten disease of childhood which was of great public health concern in the past.

Child↗