Amplitude Of Head Movement Research Articles

Risk factors for multiple gestation in women undergoing intrauterine insemination with ovarian stimulation

Objective: To identify whether sperm characteristics after washing and/or ovulation induction cycle characteristics can predict the occurrence of multiple conception in patients undergoing ovarian stimulation and IUI. Design: Retrospective study. Setting: A gynecology clinic and an andrology laboratory at a tertiary care facility. Patient(s): One hundred patients with single pregnancies and 22 patients with multiple pregnancies. Intervention(s): Patients underwent ovarian stimulation and IUI with their partner’s sperm. Main Outcome Measure(s): Relation of patient characteristics, ovarian stimulation, and sperm characteristics after washing to the occurrence of multiple pregnancy. Result(s): The mean serum E 2 level on the day of hCG injection was significantly higher in the multiple conception group, but the number of follicles was not. The total sperm count, total motile sperm count, and sperm motility after washing did not differ between the groups. However, couples with multiple pregnancies had sperm with a significantly higher amplitude of lateral head movement than couples with single pregnancies. A peak E 2 level of >583 pg/mL on the day of hCG injection and sperm with an ALH of >4 μm after washing predicted the occurrence of multiple pregnancy. Conclusion(s): Sperm with an amplitude of lateral head movement of >4 μm and a peak E 2 level of >583 pg/mL are significant risk factors for multiple pregnancy in patients undergoing IUI.

Role of pinnae and head movements in localizing pure tones 1The authors would like to thank Mr. Remi Humbert for implementing the experiment in Turbo Pascal and for his further assistance.

Twelve blindfolded subjects localized two different pure tones, randomly played by eight sound sources in the horizontal plane. Either subjects could get information supplied by their pinnae (external ear) and their head movements or not. We found that pinnae, as well as head movements, had a marked influence on auditory localization performance with this type of sound. Effects of pinnae and head movements seemed to be additive; the absence of one or the other factor provoked the same loss of localization accuracy and even much the same error pattern. Head movement analysis showed that subjects turn their face towards the emitting sound source, except for sources exactly in the front or exactly in the rear, which are identified by turning the head to both sides. The head movement amplitude increased smoothly as the sound source moved from the anterior to the posterior quadrant.

Cryopreservation of sperm from patients with leukemia

Intracytoplasmic sperm injection (ICSI) allows pregnancies to be established with a single sperm, improving the chances for men with severely impaired sperm quality to cause a pregnancy. Men with leukemia typically are of reproductive age and their fertility is threatened by initially impaired semen quality and cytotoxic chemotherapy. The authors examined the feasibility of sperm cryopreservation in men with leukemia before treatment and whether the type of leukemia is related to prefreeze or postthaw semen quality. Records of 25 patients with acute (n=13) or chronic (n=12) leukemia who banked their sperm were reviewed. Semen characteristics were compared with those of normal donors (n=50) and between the 2 patient groups before and after cryopreservation. Motile sperm count (MSC), motility, curvilinear velocity (VCL), linearity, and amplitude of lateral head movement were compared between patients and healthy donors. No patient had undergone chemotherapy before sperm banking. The nitrogen vapor technique was used for sperm cryopreservation. Patients with leukemia had significantly lower prefreeze and postthaw MSC (P=0.0001), motility (P<0.05), and VCL (P<0.05) compared with healthy donors. The percentage change from prefreeze to postthaw in MSC and motility (P<0.05) was significantly greater in patients than in healthy donors. The effect of cryopreservation on semen quality was similar in patients with both acute and chronic leukemia. Patients with leukemia have poor prefreeze and postthaw semen quality compared with healthy donors. In this study the type of leukemia did not appear to affect prefreeze or postthaw semen quality and the postthaw MSC was sufficient for use with ICSI. Sperm cryopreservation should be offered to all men of reproductive age before the initiation of therapy for leukemia.

Amplitude of human head movements associated with horizontal saccades.

Human saccades may or may not be associated with head movements. To date, little attention has been devoted to the mechanisms determining head movement recruitment and scaling. Normal human subjects made horizontal, centrifugal saccades along an encircling array of light-emitting diodes. Measurements of gaze, head, and eye-in-head angle were made at the conclusion of the head movement (or at the end of the eye movement in eye-only saccades). We found that head movement amplitude (deltaH) related in a simple fashion to the eye eccentricity that would have resulted if the gaze shift had been performed without a head movement. Plots of deltaH vs this predicted eye eccentricity (E(PRED)) had a central flat region in which gaze shifts were unaccompanied by head movements (the eye-only range) and two flanking lobes in which deltaH was a linear function of E(PRED) (the eye-head ranges). DeltaH correlated with EPRED better than with gaze shift amplitude, as would be expected if head movements were controlled so as to keep eye eccentricity within a particular range. Head movement tendencies were quantified by the width of the eye-only range, the slope of the eye-head range, and the width of the region within which the eye was likely to be found at the conclusion of the completed gaze-shifting behavior (the customary ocular motor range). The measures ranged widely in these normal subjects: 35.8+/-31.9 degrees for the eye-only range (mean+/-SD), 0.77+/-0.16 for the slope of the eye-head range, and 44.0+/-23.8 degrees for the customary ocular motor range. Yet for a given subject, the measurements were reproducible across experimental sessions, with the customary ocular motor range being the most consistent measure of the three. The form of the deltaH vs E(PRED) plots suggests that the neural circuitry underlying eye-head coordination carries out two distinct functions--gating the head movement and scaling the head movement. The reason for the large intersubject variability of head movement tendencies is unknown. It does not parallel intersubject differences in full-scale eye (in orbit) range or full-scale neck range.

Effect of insulin-like growth factors (IGFs) and IGF-binding proteins on in vitro sperm motility.

Previous studies have shown that exogenous growth hormone (GH) produces increases in sperm motility when given to subfertile men. Previous studies have also demonstrated the presence of IGFs and IGFBPs in seminal plasma. We have therefore investigated the effects of insulin-like growth factor-I (IGF-I), IGF-II, IGF-binding protein 2 (IGFBP-2) and intact IGFBP-3 on in vitro sperm motility. Using computer-aided sperm analysis, we investigated the effects of IGFs and IGFBPs on the in vitro sperm motility parameters: curvilinear velocity (CV), progressive velocity (PV), linearity (Ln), straightness (St), amplitude of lateral head movement (ALH), and beat frequency (BF). Washed motile sperm selected by the 'swim-up' method, from normozoospermic samples, were incubated at 37 degrees C in 5% CO2 in air with IGF-I, IGF-II, IGFBP-2, IGFBP-3, or control Earle's media, and were examined at time 0 and after 60 min incubation. Changes in motility parameters after 60 min incubation were compared with controls by analysis of variance (ANOVA). Compared to controls, statistically significant changes occurred at time 60 min after incubation: IGF-I decreased CV and ALH significantly (P < 0.05), but IGFBP-3 increased Ln, St, BF, and decreased ALH significantly (P < 0.05). In contrast, IGF-II, IGFBP-2, and a combination of IGF-I/IGFBP-3, had no significant effects. IGF-I and IGFBP-3 have differing and opposing effects on in vitro sperm motility parameters and thus may have a role in modulating in vivo sperm motility.

Follicular fluid and human granulosa cell cultures: Influence on sperm kinetic parameters, hyperactivation, and acrosome reaction

Objective: To evaluate the influence of human granulosa cell (GC) cultures and follicular fluid (FF) on sperm kinetic parameters, hyperactivation, and the acrosome reaction compared with the influence of human tubal fluid (HTF) and Ham's F-10 medium. Design: Sperm kinetic parameters, hyperactivation, and the acrosome reaction were evaluated after 6 hours of incubation in HTF, Ham's F-10 medium, FF, and GC cultures. Setting: Infertility and In Vitro Fertilization Centre, Reproductive Endocrinology Unit, Institute of Obstetrics and Gynaecology. Patient(s): Sixteen normal semen samples. Intervention(s): Sperm kinetic parameters and hyperactivation were analyzed using an automated videomicrography system, the acrosome reaction was performed using a triple-stain technique, and progesterone and 17OH-progesterone levels were measured with the use of commercially available kits. Main Outcome Measure(s): Sperm kinetic parameters, hyperactivation, acrosome reaction. Result(s): The percentage of motile sperm, the mean curvilinear velocity, and the mean of the maximum amplitude of lateral head movement were increased significantly after 6 hours of incubation in FF or GC cultures compared with incubation in HTF or Ham's F-10 medium, whereas the mean linearity was decreased significantly. Follicular fluid and GC cultures significantly increased hyperactivation and the acrosome reaction compared with the values obtained using HTF and Ham's F-10 medium. Progesterone and 17OH-progesterone levels were increased significantly after incubation in FF and GC cultures compared with HTF and Ham's F-10 medium. Conclusion(s): Follicular fluid and GC cultures increase sperm motility parameters, hyperactivation, and the acrosome reaction. This effect may be related to GC detoxification of the microenvironement or GC secretion of peptides, glycoproteins, growth factors (insulin-like growth factors 1 and 2), or steroids (progesterone and 17OH-progesterone).

Activity of cells in the deeper layers of the superior colliculus of the rhesus monkey: evidence for a gaze displacement command.

When the head is free to move, microstimulation of the primate superior colliculus (SC) evokes coordinated movements of the eyes and head. The similarity between these stimulation-induced movements and visually guided movements indicates that the SC of the primate is involved in redirecting the line of sight (gaze). To determine how movement commands are represented by individual collicular neurons, we recorded the activity of single cells in the deeper layers of the superior colliculus of the rhesus monkey during coordinated eye-head gaze shifts. Two alternative hypotheses were tested. The "separate channel" hypothesis states that two displacement commands are generated by the SC: one signal specifying the amplitude and direction of eye movements and a second signal specifying the amplitude and direction of head movements. Alternatively, a single gaze displacement command could be generated by the SC ("gaze displacement" hypothesis). The activity of collicular neurons was examined during three behavioral dissociations of gaze, eye, and head movement amplitude and direction (metrics). Subsets of trials were selected in which the amplitude and direction of either gaze shifts or eye movements or head movements were relatively constant but the metrics of the other two varied over wide ranges. Under these conditions, the separate channel and gaze displacement hypotheses make differential predictions about the patterns of SC activity. We tested these differential predictions by comparing observed patterns with predicted patterns of neuronal activity. We obtained data consistent with the predictions of the gaze displacement hypothesis. The predictions of the separate channel hypothesis were not confirmed. Thus microstimulation data, single-unit recording data, and behavioral data are all consistent with the gaze displacement hypothesis of collicular function--the hypothesis that a gaze displacement signal is derived from the locus of activity within the motor map of the SC and subsequently is decomposed into separate eye and head displacement signals downstream from the colliculus.

Eye-head coordination during head-unrestrained gaze shifts in rhesus monkeys.

We analyzed gaze shifts made by trained rhesus monkeys with completely unrestrained heads during performance of a delayed gaze shift task. Subjects made horizontal, vertical, and oblique gaze shifts to visual targets. We found that coordinated eye-head movements are characterized by a set of lawful relationships, and that the initial position of the eyes in the orbits and the direction of the gaze shift are two factors that influence these relationships. Head movements did not contribute to the change in gaze position during small gaze shifts (<20 degrees) directed along the horizontal meridian, when the eyes were initially centered in the orbits. For larger gaze shifts (25-90 degrees), the head contribution to the gaze shift increased linearly with increasing gaze shift amplitude, and eye movement amplitude saturated at an asymptotic amplitude of approximately 35 degrees. When the eyes began deviated in the orbits contralateral to the direction of the ensuing gaze shift, the head contributed less and the eyes more to amplitude-matched gaze shifts. The relative timing of eye and head movements was altered by initial eye position; head latency relative to gaze onset increased as the eyes began in more contralateral initial positions. The direction of the gaze shift also affected the relative amplitudes of eye and head movements; as gaze shifts were made in progressively more vertical directions, eye amplitude increased and head contribution declined systematically. Eye velocity was a saturating function of gaze amplitude for movements without a head contribution (gaze amplitude <20 degrees). As head contribution increased with increasing gaze amplitude (20-60 degrees), peak eye velocity declined by >200 degrees/s and head velocity increased by 100 degrees/s. For constant-amplitude eye movements (approximately 30 degrees), eye velocity declined as the velocity of the concurrent head movement increased. On the basis of these relationships, it is possible to accurately predict gaze amplitude, the amplitudes of the eye and head components of the gaze shift, and gaze, eye, and head velocities, durations and latencies if the two-dimensional displacement of the target and the initial position of the eyes in the orbits are known. These data indicate that signals related to the initial positions of the eyes in the orbits and the direction of the gaze shift influence separate eye and head movement commands. The hypothesis that this divergence of eye and head commands occurs downstream from the superior colliculus is supported by recent electrical stimulation and single-unit recording data.

Angiotensin II stimulates sperm motility

The physiological factors which induce and maintain mammalian sperm maturation and motility generally remain unclear, although several agents are known to be involved. We recently described the application of immunocytochemical and immunoblotting methods to identify the angiotensin II type 1 (AT1) receptor in the tails of ejaculated rat and human sperm, and gave evidence to show that angiotensin II may promote sperm motility. These data are extended here by the application of a computerised sperm tracking system (the Hobson Sperm Tracker) to demonstrate that AII has actions on specific motility parameters, including curvilinear velocity, straight line velocity, and amplitude of lateral head movement. Since local tissue renin-angiotensin systems are present in both male and female tracts, the data suggest that angiotensin II has a role in the maintenance of sperm function and fertility.

Value of Clinical Diagnosis in Predicting the Quality of Cryopreserved Sperm from Cancer Patients

Purpose Cryopreservation of semen from patients with malignant diseases (primarily testicular cancer, Hodgkin's disease and lymphoma) before specific chemotherapy, radiation or surgical therapy has become a realistic option to preserve fertility. Nevertheless, the post-thaw sperm quality in these patients is poor. Whether the clinical diagnosis of malignancy affects the cryopreservation of human sperm is unknown. Such an association could allow post-thaw sperm quality to be predicted. Materials and Methods We compared the effect of cryopreservation on sperm motility, velocity, linearity, amplitude of lateral head movement, motility index and motile sperm count in specimens from 30 normal men, 34 with testicular cancer, 39 with Hodgkin's disease, and 19 with leukemia and lymphoma who were referred for sperm banking during a 5-year period. Results The pre-freeze and post-thaw motility, motility index and motile sperm count were significantly lower in all patients than in normal men (p less than 0.01). No significant differences were noted among the patient groups. Similarly, no significant differences were noted after cryopreservation. Our results indicate that the poor pre-freeze sperm quality in some patients with malignancies explains the poor post-thaw results. However, the deterioration in sperm function after cryopreservation of semen among patients with different malignancies and normal donors appears to be similar. Conclusions Clinical diagnosis of malignancy is not an adequate predictor of the effect of cryopreservation on human semen.

Comparison of Horizontal Head Movements Evoked by Auditory and Visual Targets

Head movement propensity-the pattern of head saccades dependent on methods of target presentation-varies among individuals. The present group of 9 young adults was previously ranked in a visual saccadic task according to this propensity. The present report examines how and why this propensity changes if the saccades are made to auditory targets. 1) Spatially identical, interleaved, auditorily and visually elicited horizontal saccadic gaze shifts (jumps) differed in amplitude and in starting and/or ending position. The jumps were executed in two head movement modes: first, the non-aligned mode was a standard reaction-time single gaze step between two points. Second, the head-aligned mode required alignment of the head with the fixation (starting) point; thereafter both modes were identical. All results in the auditory task are expressed relative to the visual results. 2) In the non-aligned mode, head movement amplitudes were increased on average by 15% (for example, an 80 degrees jump elicited a 12 degrees larger head movement), and velocity decreased by 12%, reflecting the increased demands of the auditory task. More importantly, the differences between subjects was narrowed; that is, head movement propensity was homogenized in the auditory task. In the visual task, head-movers willingly move their heads off and across the midline, whereas non-movers are unwilling to leave the midline from eccentric starting points or to eccentric ending points. This is called the midline attraction effect and was previously linked to spatial reference frames. The homogenization in the auditory task was characterized by head-movers increasing, and non-movers decreasing, their midline attraction, suggesting altered spatial reference frames. 3) For heuristic purposes, the ideal head-mover is defined by a gain of 1.0 in the visual task, and by external earth-fixed reference frames. Similarly, the ideal non-mover has a gain of 0.0 and has a bias toward body (or some par of the body)-fixed reference frames. In the auditory task these gains (and reference frames) in head movers and non-movers are homogenized (close to 0.5), either by the participation of the head (movement of the ears in space) in sensory acquisition or by differences in central nervous processing of the two modalities, or both.

Effects of stimulus duration and task experience on gaze shift.

The effects of stimulus duration and prior task experience on gaze shift were studied to determine the spatial characteristics of gaze shift as affected by prior experience. Thirty-six subjects (with normal or corrected-to-normal vision) participated in two sessions of a task that required viewing two consecutively presented letters at either 15 degrees or 50 degrees eccentricity and deciding whether they were the same or different. In the first session (SS1) a letter was presented for either 500 (N = 18) or 1000 ms (N = 18), followed by a second letter. In session 2 (SS2), the groups were divided with half of the group performing the task under the same conditions as they did in SS1, while the other half was switched to the other first letter duration. Head and eye movements were recorded using a photoelectric transducer and electrooculogram (EOG), respectively. Few head movements occurred with targets presented at 15 degrees eccentricity. Approximately 80% of gaze shifts to the 50 degrees stimuli included a head movement component. DURATION had a significant effect on gaze shift. Head movement amplitude (HMA) increased, while saccade amplitude decreased with an increase in DURATION. On the average, the proportion of gaze shift accomplished via head movement was 24% if DURATION was 500 ms, and 37% when DURATION was extended to 1000 ms. SS1 task experience affected HMA in SS2. When DURATIONs differed between SS1 and SS2, HMA in SS2 were drawn toward the level of HMA in SS1. A positive and significant correlation was observed between head movement amplitude and head movement duration. The results suggest that both stimulus availability and prior experience affect head movement amplitude in gaze shift.

Chapter 7 Firing characteristics of neurones in the superior colliculus and the pontomedullary reticular formation during orienting in unrestrained cats

Cats were trained to fixate a center LED or light spot for 1-10 s and to orient to a target (LED or light spot), which appeared simultaneous with the disappearance of the fixation light. Firing characteristics of neurones in the superior colliculus (SC) and the pontomedullary reticular formation were examined systematically in cats performing the above orienting task. In the head-free condition, a majority of the superficial neurones in the SC was activated when a target appeared in a particular area in the visual field (receptive field) as in head fixed animals. We identified a new group of neurones in superficial layers of the SC, superficial fixation neurones, which fired tonically when fixated on a target light with little activity at fixating a center fixation light. In the intermediate and deep layers of the SC, many neurones fired when directed to a particular area in the visual field (movement field). In addition to these neurones, we found new groups of neurones fired tonically in a particular phase of orienting. These neurones were divided into three principal types, target activated, target suppressed and center fixation activated neurones. Target activated neurones fired tonically during the fixation of a target, but not during fixation of a center spot. Target suppressed neurones were characterized by a pause during fixation of targets irrespective of their location. They had clear phasic and tonic components. The phasic component was characterized by a movement field resembling that seen in a typical intermediate layer neurone. Center fixation activated neurones discharged during fixation of the center spot and exhibited suppression during fixation of the target. Many neurones in the pontomedullary reticular formation fired during orienting. Four major types of neurones, phasic, phasic sustained, pause and tonic neurones, were differentiated on the basis of their firing patterns. Phasic units were characterized by brief phasic firing during orienting and could be divided into four subtypes. Long lead phasic neurones began to fire 50-100 ms prior to the onset of a gaze shift and stopped well before the end of the gaze shift and the total number of firing was best correlated with the total angle of head rotation. Short lead phasic neurones started to fire 10-20 ms prior to a gaze shift and were further subdivided into decrement and plateau types. The decrement type exhibited a brief burst just prior to gaze shift and stopped discharging prior to the end of the gaze shift, while the plateau type fired tonically during the gaze shift and stopped firing after the gaze shift. Total number of discharges of both type was related to maximal angular velocity. The fourth type, gaze neurone, began firing coincident with the onset of the gaze shift and stopped firing at the completion of the gaze shift and the total number of discharges was closely related to total angle of head rotation Phasic sustained (PS) neurones fired 50-100 ms before the onset of a gaze shift and their discharges continued after the end of the gaze shift and were divided into three subtypes: augmenting, pause and plateau. The augmenting type was characterized by a transient increase of firing during the gaze shift and a maintained slow rate of firing following the gaze shift. Total number of discharges related to head movement amplitude and the sustained activity was correlated with head position. The pause type was suppressed during the gaze shift and was tonically active during a head movement. The plateau type had a weak phasic component and discharged at a fairly constant rate. The pause and plateau types appeared to be related to head amplitude and head position, respectively. Tonic units were classified into several types. Target fixation neurones exhibited sustained firing when the cat was fixating a target, irrespective of its location, but did not show sustained firing when the animal fixated the fixation light. Fixation neurones fired tonical

Optimum Abstinence Time for Cryopreservation of Semen in Cancer Patients

Although an abstinence period of 48 to 72 hours is the most commonly prescribed interval for diagnostic semen analysis, to our knowledge the association between the abstinence period and sperm quality after cryopreservation has not been identified. Patients with a malignant disease who are consulting for semen banking most often require urgent therapy. Consequently, defining the shortest abstinence period that allows for frequent semen collection within a limited interval and the best post-thaw sperm quality is necessary. We investigated the relationship between abstinence period, and the pre-freeze and post-thaw motility variables in semen specimens obtained from cancer patients for sperm banking. Samples collected from 95 patients were divided according to abstinence period: group 1--15 patients at 24 to less than 48 hours, group 2--53 at 48 to less than 72 hours and group 3--27 at more than 72 hours. Pre-freeze and post-thaw motile sperm count and motion variables (motility, velocity, linearity, amplitude of lateral head movement and motility index), and percentage decrease in sperm variables after cryopreservation were analyzed. Semen volume, the pre-freeze and post-thaw motile sperm count, motion parameters and the percentage decrease in semen variables did not differ significantly among the groups. We conclude that semen collection for cryopreservation after 24 to less than 48 hours of abstinence results in post-thaw quality comparable to that after an abstinence of 48 to less than 72 hours or longer. Thus, an abstinence period of 24 to less than 48 hours can be recommended for sperm banking in cancer patients.

Activity of neurons in the medial pontomedullary reticular formation during orienting movements in alert head-free cats

1. Single unit activities of 236 neurons were recorded in the medial pontomedullary reticular formation during visually triggered orienting gaze shifts in 10 alert cats under head-free conditions using movable tungsten-needle electrodes attached to the skull. The activities were analyzed mainly in relation to the head movement that was triggered by presentation of a light-emitting diode (LED) in one of eight directions separated radially by 45 deg after fixation of the center LED. Of these, 120 neurons were recorded in the pontine reticular formation, chiefly in the nucleus reticularis pontis caudalis, and the remaining 116 were in the medullary reticular formation, chiefly in the nucleus reticularis gigantocellularis. Activities of 65 pontine and 65 medullary neurons were modulated in relation to the dynamic phase of orienting movements ("orienting-related neurons"). Activities of the remaining neurons were modulated either irregularly or not at all during orienting movement ("irregular or no-response neurons"). Input from the contralateral superior colliculus and cerebral cortex and projections to the spinal cord were also investigated. 2. Among the orienting-related neurons, 62 pontine and 55 medullary neurons showed increases in activity preceding the onset of eye and head movement by 0-155 ms ("pretype"). Three pontine and 10 medullary neurons showed increases in activity only after the onset of movement ("posttype"). Of the pretype neurons, 61 pontine and 51 medullary neurons showed directional preference of activity ("directional" neurons). One pontine and four medullary neurons were classified as "omnidirectional" because these neurons increased activity preceding movements in all directions tested, and no directional preference was apparent. 3. In the pretype-directional cells, the average firing frequency during bursts was correlated with amplitude and angular velocity of head movements. Activities of the directional neurons during movements in the eight different directions could be well fitted with cosine functions in the majority of cases. The preferred directions of most pontine neurons and of about half the medullary neurons, as determined by first-degree sinusoidal regression analysis, were distributed around the ipsiversive horizontal axis. However, there were also a considerable number of neurons whose preferred directions were upward, downward, contraversive, or oblique in the medulla. 4. Among the directional cells preferring ipsiversive horizontal movements, 11 pontine neurons showed activity, the onset of which was locked to visual stimuli with latencies of 40-70 ms, in addition to phasic discharges locked to the onset of movement. This "stimulus-locked activity" was sometimes modulated depending on the attentional state of the animal.(ABSTRACT TRUNCATED AT 400 WORDS)

Cryopreservation and semen quality in patients with Hodgkin's disease.

Cryopreservation of semen from patients with Hodgkin's disease yields fewer motile sperm than from fertile men without Hodgkin's disease. However, although poor sperm quality and subfertility have been associated with Hodgkin's disease, whether the disease adversely affects sperm quality is not clear because many studies evaluated semen quality after chemotherapy or radiation therapy had begun. Furthermore, the effect of cryopreservation on semen quality in these patients is unknown. This study investigated pretreatment sperm quality and the effect of cryopreservation on semen quality in patients with Hodgkin's disease. Specimens from 39 patients with Hodgkin's disease and 30 normal volunteers who underwent sperm banking over a 5-year period were analyzed. No patient had undergone chemotherapy or radiation therapy before sperm banking. The nitrogen vapor technique, using Test-Yolk buffer with glycerol as a cryoprotective agent, was used for cryopreservation. Prefreeze and postthaw motile sperm count (MSC) and motion characteristics, namely motility, curvilinear velocity (VCL), linearity, amplitude of lateral head movement (ALH), and motility index, were compared between the two groups. Prefreeze values for MSC (P = 0.0001), motility (P = 0.0001), motility index (P = 0.0001), and VCL (P = 0.0019) differed significantly between patients and donors. Except for linearity and ALH, postthaw sperm MSC, motility, VCL, and motility index decreased significantly (P = 0.0001) in both groups. However, the percentage decline in semen quality from prefreeze to postthaw values did not differ significantly between donors and patients. The pretreatment semen quality in patients with Hodgkin's disease is poor compared with that of normal fertile men. However, half the patients had a normal MSC, so a clinical diagnosis of Hodgkin's disease does not predict cryopreservation outcome adequately. Semen cryopreservation should be encouraged as a routine part of the therapeutic management of men of reproductive age who will undergo chemotherapy or radiation therapy for Hodgkin's disease.

Effects of Visual Field Restriction on the Stability of Human Head Position During Walking.

The stability of human head position during walking was investigated, using angular velocity sensors, with emphasis on the effects of restriction of the visual field. The results (i) confirm the stability of head position during normal walking and (ii) demonstrate the importance of information from the peripheral visual field, as seen by differences in the amplitude of head movements. The effects of searching behavior on the head movements are discussed.

Human gaze shifts in which head and eyes are not initially aligned.

Most studies of rapid orienting gaze shifts generated by combined eye and head movements have focused on an experimental condition in which gaze displacements are started with the subject's eyes in the normal straight-ahead position in the orbit. Such an experimental approach does not permit a clear identification of the input signal to the head motor system, because target offset angle is the same for both the eye and head. We have studied gaze shifts in human subjects which began with the visual axis straight ahead relative to the body (i.e., gaze or line of sight aligned with body sagittal plane) and with head offset from straight ahead at various angular positions. In our experimental conditions, the amplitude of head movement during a gaze shift was nearly equal to the angular distance between the target position and the starting head position (target-re-head), even though subjects were not specifically instructed to move their heads. This observation contrasts with other published reports in the literature showing considerable variability amongst subjects in the amplitude of head rotation within a given task and between tasks. The difference may be related to the initial conditions which required subjects to align the eye and head on specific starting targets, since others have shown that requiring head alignment enhances head displacement. The amplitude of the saccadic eye movement was not determined by either the target's position relative to the starting eye or head positions. The value that best described the eye movement amplitude was the eye position in the orbit at the end of the saccade.(ABSTRACT TRUNCATED AT 250 WORDS)

Bypassing the Saccadic Pulse Generator: Possible Control of Head Movement Trajectory by Rat Superior Colliculus.

Saccades produced by electrical stimulation of the superior colliculus in primates are influenced primarily by the location of the stimulating electrode, with the suprathreshold intensity or frequency of the stimulating pulse train having little effect. Any given collicular site produces a characteristic movement of relatively fixed amplitude and velocity. In accordance with this finding, in models of the saccadic eye movement system the superior colliculus specifies the change of eye position: the velocity of movement components are determined by 'pulse generators' located between the superior colliculus and the oculomotor neurons. Previous findings in rodents, however, have suggested that eye and head movements induced by stimulation at some collicular sites may be critically dependent on stimulation parameters, implying that in these animals the superior colliculus has access to a non-saccadic control system. To investigate this possibility, rats with electrodes implanted into the lateral intermediate layers were stimulated with pulse trains of varying frequency and duration, and the resultant head movements analysed from video tape. At seven of the nine sites studied, amplitude of the horizontal component of the head movement was linearly related to stimulating frequency for fixed-duration trains, in some cases over a ten-fold range. Subsequent variation of train duration showed that amplitude was affected not by frequency as such, but by the number of pulses in the train; frequency was related to the mean velocity of the movement. By appropriate setting of these parameters, independent control of head movement amplitude and velocity could be achieved. These results suggest that the rodent superior colliculus may be able to control head movement without recourse to a pulse generator, and thus influence the trajectory of the movement directly. If so, it may prove to be a useful preparation for testing theories of trajectory formation.

Analysis of eye movements in different tasks related to the use of lift trucks

Fork-lift trucks are frequently involved in industrial injuries that happened during driving. Insufficient visibility is one of the leading causes of occurrence of these accidents. A previous study (Hella et al, 1988) showed that ± 75 mm is the maximal amplitude of head movements recorded to avoid the mast. However, very little is known about the areas of the forward field of view that are most frequently fixated by the eye. This article presents the results of two analyses of eye fixations during several driving situations of a lift truck that could provide a wealth of useful information for designers and for standardisation. The information it contains is also of interest in analysing visibility from all industrial vehicles.