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PubMed1994

Head movement in normal subjects during simulated PET brain imaging with and without head restraint.

UNLABELLED: Head movement during brain imaging is recognized as a source of image degradation in PET and most other forms of medical brain imaging. However, little quantitative information is available on the kind and amount of head movement that actually occurs during these studies. We sought to obtain this information by measuring head movement in normal volunteers. METHODS: Head position data were acquired for 40 min in each of 13 supine subjects with and without head restraint. These data were then used to drive a mathematically simulated head through exactly the same set of movements. The positions of point sources embedded in this head were computed at each location and these data summarized as movement at FWHM in each of the three coordinate directions. RESULTS: Head movement increased with the length of the sampling interval for studies of either type (with or without head restraint), but the amount and rate of increase with restraint was much smaller. In contrast, head movement during consecutive, short sampling intervals was small and did not increase with time. Spatial gradients in head movement were detected within each study type, and significant spatial differences in head movement were found between study types. CONCLUSIONS: Head movements in normal, supine subjects, though small, can cause the effective resolution of a brain imaging study to appear to vary in space and time. These effects can be reduced significantly with head restraint and may also be reduced by dividing the acquisition of a single image into a sequence of short images (instead of a single long image), aligning these images spatially and summing the result.

Adult↗
PubMed1987

Stability of the head: studies in normal subjects and in patients with labyrinthine disease, head tremor, and dystonia.

The dynamics of postural control of the head were investigated in normal human subjects and patients with neurological disease. The technique adopted was to measure the head movements provoked by passive, unpredictable oscillations of the trunk in the frequency range 0-6-7 Hz when subjects were required (a) to try to stabilise their head "in space" and (b) to try to make their heads move "en bloc" with the trunk. Head movement responses were characterised by the gain and phase with respect to trunk movement (transfer function) and degree of linear relationship between head and trunk (coherence). The normal transfer function approximated a cascade of two second-order, underdamped, systems representing the passive inertial, viscous, and elastic properties of the muscle and joints of the head and neck. Stabilisation of the head "in space" produced about 40% reduction in transmission of body movement, was only evident at frequencies less than 1 Hz and was affected partly by voluntary movements. An alabyrinthine patient could also achieve some spatial stabilisation. The findings indicate a weak role for vestibular-collic reflexes and emphasise that the primary control of head posture during unpredictable movement is through the tonic visco-elastic properties of neck muscles that work to stabilise the head on the shoulders. In patients with dystonia of the neck and essential and cerebellar head tremor, the head showed a tendency to unstable oscillation (resonance). The instability and dystonia could be measured in terms of visco-elastic constants and damping ratios. The head movements of some tremor patients did not linearly follow the trunk movement, showing that the motion stimulus provoked abnormal phasic muscle activity at frequencies other than those of the tremor. The technique quantifies head control in movement disorders and is sensitive to abnormal function.

Adolescent↗
PubMed2000

Role of cyclic adenosine 3',5'-monophosphate and serum albumin in head-to-head agglutination of boar spermatozoa.

It has previously been shown that when boar spermatozoa are incubated in a modified Krebs-Ringer bicarbonate (mKRB), head-to-head agglutination occurs in many cells. The aim of the present study was to investigate the effects of cyclic adenosine 3',5'-monophosphate (cAMP) and serum albumin on sperm agglutination and to discuss a possible mechanism for sperm agglutination. Spermatozoa were collected from four mature boars, washed and incubated in mKRB. After a 1-h incubation, a sample of each sperm suspension was smeared gently on a separate glass slide, dried and stained in a phosphate-buffered solution of Giemsa to assess the percentage of head-to-head agglutinated cells in each suspension. In the samples incubated in mKRB, approximately 50% of the spermatozoa were agglutinated with one another at the acrosome. However, the percentages of head-to-head agglutinated spermatozoa were greatly reduced by a lack of calcium chloride in mKRB, but were recovered by the addition of dibutyryl cAMP (dbcAMP, a cAMP analogue) in a dose-dependent manner between 1 and 1000 microM. Addition of 3-isobutyl-1-methylxanthine (IBMX, 100 and 500 microM) instead of dbcAMP also significantly increased the percentages of head-to-head agglutinated spermatozoa. Moreover, the effects of adding dbcAMP were attenuated by treatment with Rp-adenosine 3',5'-cyclic monophosphorothioate triethylamine salt (0.25-1.0 mM, a cAMP antagonist) or H-89 (5 microM, a protein kinase-A inhibitor), but were enhanced by treatment with okadaic acid (500 nM) and calyculinA (500 nM) (inhibitors of protein serine/threonine phosphatase). In sperm samples incubated in mKRB containing 0.1% polyvinyl alcohol (mKRB-P) or mKRB-P lacking calcium chloride and supplemented with 1 mM dbcAMP, a lack of bovine serum albumin (BSA) resulted in a significant decrease in the percentages of head-to-head agglutinated spermatozoa. Addition of porcine serum albumin (PSA, 1-4 mg mL(-1)) or methyl-beta-cyclodextrin (MBC, 5-10 mg mL(-1)) instead of BSA was as effective as BSA (4 mg mL(-1)) in enhancing sperm agglutination. However, the effects of BSA (4 mg mL(-1)) or MBC (5 mg mL(-1)) were reduced by pre-mixing these reagents with cholesterol 3-sulfate (a cholesterol analogue, 5 microg mL(-1) for BSA and 375 microg mL(-1) for MBC). In addition, a protein 'anti-agglutinin' inhibiting sperm agglutination, was extracted from spermatozoa incubated with serum albumin or MBC and detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting techniques. The obtained Western blots revealed that sperm-bound anti-agglutinin was detected less in the samples incubated with either BSA (4 mg mL(-1)) or MBC (5-10 mg mL(-1)), compared with control samples. Moreover, pre-mixing MBC (5 mg mL(-1)) with cholesterol 3-sulfate (375 microg mL(-1)) reduced this reagent's effects on the loss of sperm-bound anti-agglutinin. Additionally, the assay of sperm agglutination and a chlortetracycline staining assay revealed that the percentages of head-to-head agglutinated spermatozoa were positively correlated with those of spermatozoa classified into B pattern (capacitated spermatozoa). These results are consistent with the following suggestions: (i) an adenylyl cyclase-cAMP-protein kinase system mediates a signalling pathway leading to head-to-head agglutination; and (ii) loss of anti-agglutinin from the spermatozoa may be modulated by changes in the plasma membrane induced by actions of serum albumin or MBC contained in a medium.

1-Methyl-3-isobutylxanthine↗
PubMed2005

Countermanding eye-head gaze shifts in humans: marching orders are delivered to the head first.

The countermanding task requires subjects to cancel a planned movement on appearance of a stop signal, providing insights into response generation and suppression. Here, we studied human eye-head gaze shifts in a countermanding task with targets located beyond the horizontal oculomotor range. Consistent with head-restrained saccadic countermanding studies, the proportion of gaze shifts on stop trials increased the longer the stop signal was delayed after target presentation, and gaze shift stop-signal reaction times (SSRTs: a derived statistic measuring how long it takes to cancel a movement) averaged approximately 120 ms across seven subjects. We also observed a marked proportion of trials (13% of all stop trials) during which gaze remained stable but the head moved toward the target. Such head movements were more common at intermediate stop signal delays. We never observed the converse sequence wherein gaze moved while the head remained stable. SSRTs for head movements averaged approximately 190 ms or approximately 70-75 ms longer than gaze SSRTs. Although our findings are inconsistent with a single race to threshold as proposed for controlling saccadic eye movements, movement parameters on stop trials attested to interactions consistent with a race model architecture. To explain our data, we tested two extensions to the saccadic race model. The first assumed that gaze shifts and head movements are controlled by parallel but independent races. The second model assumed that gaze shifts and head movements are controlled by a single race, preceded by terminal ballistic intervals not under inhibitory control, and that the head-movement branch is activated at a lower threshold. Although simulations of both models produced acceptable fits to the empirical data, we favor the second alternative as it is more parsimonious with recent findings in the oculomotor system. Using the second model, estimates for gaze and head ballistic intervals were approximately 25 and 90 ms, respectively, consistent with the known physiology of the final motor paths. Further, the threshold of the head movement branch was estimated to be 85% of that required to activate gaze shifts. From these results, we conclude that a commitment to a head movement is made in advance of gaze shifts and that the comparative SSRT differences result primarily from biomechanical differences inherent to eye and head motion.

Adult↗
PubMed2002

Internal loads in the cervical spine during motor vehicle rear-end impacts: the effect of acceleration and head-to-head restraint proximity.

STUDY DESIGN: This study used rigid-body and finite-element models of forces in the cervical spine resulting from a rear-end motor vehicle impact based on data from 26 volunteer experiments. OBJECTIVES: To define the magnitudes and directions of internal forces acting on the cervical spine during rear-end impact, and to determine the effects of increasing the impact acceleration and the initial position of the occupant's head with respect to the head restraint. SUMMARY OF BACKGROUND DATA: In a number of studies using volunteers or cadavers, the kinematics of the occupant during a rear-end impact related to "whiplash" of the cervical spine have been reported. Few studies have described the mechanism by which internal spine forces are produced and how they may be affected by interaction of the occupant with the seat and head restraint during impact. METHODS: From a companion study on the response of 26 volunteers to rear-end impact, experimental data on head and torso accelerations were developed. Rigid-body mathematical dynamic modeling of a 50th-percentile male was implemented, along with a finite-element seat model, lap belt, and shoulder belt. The model was first subjected to a rear-impact pulse similar to that used in the volunteer study, first with a peak of 3.5 G, then with a peak up to 12 G. Initial head-to-head restraint distance in the model was varied from 1 to 12.5 cm. RESULTS: The major cervical spine forces were upper and lower neck shear causing intervertebral relative anterior displacements. Increasing the peak acceleration magnitude caused increased neck shear force magnitudes. With the head initially positioned closer to the head restraint, the time difference between the occurrences of the peak upper and lower neck shear forces was smaller; the C7-T1 intervertebral shear displacements were reduced; the head moved more in phase with the torso; extension of the head and neck was reduced; and late head flexion was increased. CONCLUSIONS: In this simulation, anterior shear was the major internal force acting in the cervical spine during rear-end impact. Increasing impact acceleration magnitude directly increased shear force. When the head was initially closer to the head restraint, the magnitude of the shear force was unaffected, but the time difference between its occurrences in the upper and lower neck was decreased and intervertebral translations were reduced. These results suggest how the seat could be improved to reduce peals forces and the time differences between them.

Acceleration↗
PubMed1997

Primate head-free saccade generator implements a desired (post-VOR) eye position command by anticipating intended head motion.

Primate head-free saccade generator implements a desired (post-VOR) eye position command by anticipating intended head motion. J. Neurophysiol. 78: 2811-2816, 1997. When we glance between objects, the brain ultimately controls gaze direction in space. However, it is currently unclear how this is allocated into separate commands for eye and head movement. To determine the role of desired final eye position commands, and their coordination with intended head movement, we trained three monkeys to make large gaze shifts while wearing opaque goggles with a monocular 8 degrees aperture. Animals eventually developed a new set of context-dependent eye-head coordination strategies, in particular expanding the head range and compressing the eye-in-head range toward the aperture (while wearing the goggles). However, when we shifted the location of the aperture to a different subsection of the normal head-free oculomotor range (by covering the original aperture and creating a new one), eye-head saccades failed to acquire visual targets, because they continued to drive the eye ultimately toward the now occluded original aperture. Even when a head-stationary saccade acquired the new aperture, subsequent head-free saccades drove the eye eccentrically toward a point that anticipated the intended head movement, such that the subsequent vestibuloocular reflex slow phase brought the eye onto the location of the original aperture. Animals could only acquire the new aperture consistently after several days of retraining. These results suggest that 1) eye-head coordination is achieved by a plastic, context-dependent neural operator that uses information about initial eye/head position and intended movement to compute desired combinations of final eye/head position and 2) acquisition of these positions involves sophisticated anticipatory compensations for subsequent movement components, akin to those observed previously in complex oral and manual behaviors.

Animals↗
PubMed1995

Head perturbations during walking while viewing a head-fixed target.

BACKGROUND: Inexpensive, head-fixed computer displays are now available that subjects can wear during locomotion. HYPOTHESIS: Viewing a head-fixed visual display will change the characteristics of rotational head perturbations during natural walking. METHODS: Using a 3-axis angular rate sensor, we measured head rotations during natural or treadmill walking, in 10 normal subjects and 2 patients with deficient vestibular function, as they attempted to view (A) a stationary target at optical infinity; and (B) a target at a distance of 20 cm rigidly attached to the head. RESULTS: Normal subjects and patients showed no significant change in the predominant frequency of head rotations in any plane (ranging 0.7-5.7 Hz) during the two different viewing tasks (p > 0.1). Mean peak head velocities (ranging 6-36 degrees.s-1) also showed no difference during the two viewing conditions except in the yaw plane, in which values were greater while viewing the near target (p < 0.005). Predominant frequencies of head rotations were similar in the pitch plane during natural or treadmill walking; however, peak velocities of pitch head rotations were substantially greater during natural walking (p < 0.05). One vestibular patient showed modest increases of head velocity during natural walking compared with normal subjects. CONCLUSIONS: Rotational head perturbations that occur during natural walking are largely unaffected when subjects view a head-fixed target. There is need to study how such perturbations, which induce vestibular eye movements, affect vision of head-fixed displays.

Adult↗
PubMed2006

Combined head and abdominal computed tomography for blunt trauma: which patients with minor head trauma benefit most?

The widespread availability of computed tomography (CT) in the diagnosis and management of blunt trauma has created the possibility of overuse without clear indications. Some clinicians believe that patients with head injury, intoxication, and/or distracting injury have an unreliable abdominal examination and should undergo combined head and abdomen CT. The objective of this study was to evaluate which patients with minor head trauma benefit most from combined head and abdomen CT. Consecutive blunt trauma patients, with a Glasgow coma scale (GCS) of 14 or 15, who underwent concomitant head and abdomen CT upon admission to a level I trauma center over a 2-year period were retrospectively reviewed. Patient demographics, mechanism of injury, physical exam, hospital course, and radiological and laboratory findings were recorded. Patients were divided into four subgroups based upon the presence or absence of intracranial and/or intraabdominal injury detected by CT. Among the 1,478 blunt head trauma patients, only 18 (1%) patients had both head and abdominal injuries detected by combined CT. One-hundred twelve (8%) patients had only head injuries, and 131 (9%) had only intraabdominal injuries detected. Patients with a GCS of 14 were more likely to have isolated head injury [odds ratio (OR) 3.1, P=0.001], while those with loss of consciousness were more likely to have combined head and intraabdominal injury (OR 6.8, P=0.03) or isolated head injury (OR 1.7, P=0.02). Abdominal tenderness was associated with increased risk of isolated intraabdominal injury (OR 1.8, P=0.0015). Hematuria was associated with increased risk of combined head and intraabdominal injury (OR 8.3, P=0.0004) or isolated intraabdominal injury (OR 7.9, P=0.0001). Patients with loss of consciousness and/or GCS of 14 frequently undergo head CT. The addition of an abdomen CT scan in this patient population should be based on objective clinical criteria such as presence of abdominal tenderness and/or hematuria.

Abdominal Injuries↗
PubMed1999

The relationship in neonates between clinically measured head circumference and brain volume estimated from head CT-scans.

OBJECTIVE: To determine if the frontal-occipital head circumference correlates with brain volume on CT and to investigate correlations between the volumes of different brain subdivisions in live neonates. METHODS: Records were studied from 27 neonates with anatomically normal head CT-scans which were ordered for clinical reasons, and which were performed at Johns Hopkins Hospital. Clinical data were abstracted from medical records. Brain volumes were estimated by digitizing the structures of interest on each slice of head CT-scans. RESULTS: In this sample of 27 infants with a mean birth weight of 3000.4 +/- 668 g, mean head circumference of 33.5 +/- 1.8 cm, and mean gestational age of 37 weeks and 4 days +/- 24 days, the mean of total brain volume was 333.0 +/- 78.3 ml. The correlation between clinically measured head circumference and total brain volume was 0.55 (P < 0.003). Regression of total brain volume on head circumference and its second and third powers accounted for 43% of the variation in total brain volume. Other predictor variables, namely infant race, sex, gestational age, and maternal age, were not significant in this regression once head circumference was included. The slope of the cubic function of head circumference as a predictor of brain volume was greatest below the mean head circumference of 33.5 cm. Brain volume leveled off at head circumferences greater than the mean. CONCLUSION: Head circumference is a powerful predictor of total brain volume in the neonate: below the approximate head-circumference mean of 33.5 cm, smaller head circumference indicates smaller total brain volume.

Birth Weight↗
PubMed1981

Motions and interactions of phospholipid head groups at the membrane surface. 3. Dynamic properties of amine-containing head groups.

The dynamic properties of the amine-containing head groups of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and a new phospholipid, phosphatidylserine methyl ester, were studied. Deuterium NMR spin-lattice (T1) relaxation times of deuterium labels specifically incorporated in the head groups were measured in multilamellar dispersions of these phospholipids. As a reference point, the data were compared with T1 values from a phospholipid with a simple phosphopropanol head group. In the liquid-crystalline state at both the alpha (P--O--CD2--CH) and beta (P--O--CH2--CD) head-group segments, the values of the T1 relaxation times decreased in the order propyl greater than choline greater than ethanolamine greater than serine = serine methyl ester. In the propyl and choline head groups, the beta-segment T1 values were longer than those of the alpha segment, indicating increasing flexibility as one progressed toward the free end of the head group. The ethanolamine and serine head groups had essentially identical T1 values at all positions. Phosphorus-31 NMR spin-lattice relaxation times were found to parallel the deuterium results for the neighboring alpha segment. These data indicate that the phosphatidylserine head group is less flexible than that of phosphatidylethanolamine which in turn was more rigid than the phosphatidylcholine head group. The phosphatidylserine head-group T1 values were as short as those of the glycerol backbone moiety of phosphatidylcholine which is known to be a relatively rigid section of the phospholipid molecule. The relaxation time data for liquid-crystalline phase phosphatidylserine and gel phase phosphatidylglycerol were quantitatively similar, indicating that for those motions which contribute to T1 relaxation, the two head groups are in similar states. These differences in head-group rigidity are discussed in terms of the capacity of the various head groups to bind noncovalently to their neighbors in the plane of the membrane surface.

Amines↗
PubMed2005

Heading in football. Part 3: effect of ball properties on head response.

OBJECTIVES: Head impacts from footballs are an essential part of the game but have been implicated in mild and acute neuropsychological impairment. Ball characteristics have been noted in literature to affect the impact response of the head; however, the biomechanics are not well understood. The present study determined whether ball mass, pressure, and construction characteristics help reduce head and neck can impact response. METHODS: Head responses under ball impact (6-7 m/s) were measured with a biofidelic numerical human model and controlled human subject trials (n = 3). Three ball masses and four ball pressures were investigated for frontal heading. Further, the effect of ball construction in wet/dry conditions was studied with the numerical model. The dynamic ball characteristics were determined experimentally. Head linear and angular accelerations were measured and compared with injury assessment functions comprising peak values and head impact power. Neck responses were assessed with the numerical model. RESULTS: Ball mass reductions up to 35% resulted in decreased head responses up to 23-35% for the numerical and subject trials. Similar decreases in neck axial and shear responses were observed. Ball pressure reductions of 50% resulted in head and neck response reductions up to 10-31% for the subject trials and numerical model. Head response reductions up to 15% were observed between different ball constructions. The wet condition generally resulted in greater head and neck responses of up to 20%. CONCLUSION: Ball mass, pressure, and construction can reduce the impact severity to the head and neck. It is foreseeable that the benefits can be extended to players of all ages and skill levels.

Biomechanical Phenomena↗
PubMed2000

A comparison of head-unrestrained and head-restrained pursuit: influence of eye position and target velocity on latency.

Horizontal step-ramp target trajectories were used to study the initiation of head-unrestrained and head-restrained pursuit in the monkey. In a first series of experiments, initial target position (0 degrees, 5 degrees, or 30 degrees, contraversive to the direction of pursuit), fixation duration, target velocity (20 degrees, 40 degrees, 60 degrees and 80 degrees/s), and target direction were randomized in order to minimize predictive responses. Animals pursued the target either with their eyes alone (head-restrained: HR condition) or with a combination of eye and head movements (head-unrestrained: HU condition). Head motion onset consistently lagged pursuit onset (i.e., eye motion) by 50 ms or more in the HU condition, and was influenced by target velocity as well as by initial target position. Pursuit onset latencies did not vary systematically as a function of target velocity in either the HR or HU conditions. However, pursuit initiation latencies tended to be longer in the HU condition as compared to the HR condition when target motion started from the most contraversive position. A second series of experiments revealed that this difference in HR and HU pursuit onset latencies could be explained by the effects of initial eye-in-head position; more contraversive initial eye positions yielded shorter pursuit latencies in both conditions, and the monkeys generally moved their head towards the target in the HU condition, resulting in smaller eye-in-head eccentricities. Furthermore, we found that initial gaze and head positions had little or no effect on pursuit latencies. We conclude that the latency for pursuit initiation is similar irrespective of whether an animal is head-restrained or head-unrestrained, when initial eye position is held constant.

Animals↗
PubMed2000

Neck pain and head restraint position relative to the driver's head in rear-end collisions.

This two-year investigation was designed to estimate the incidence of driver neck pain in rear-struck vehicles involved in two-vehicle collisions and to determine the relationship between neck pain and specific vehicle, human, and environmental factors. Neck pain percentages were significantly higher for female (45%) than for male (28%) drivers. For female and male drivers, neck pain likelihood increased as head restraint height decreased below the head's center of gravity, although this effect was significant only for females. Head restraint backset, the horizontal distance measured from the back of the driver's head to the front of the head restraint, was not found to be related to neck pain for female drivers. Backset trends for male drivers could not be evaluated because few male drivers had head restraints that were high enough for backset to be relevant. Reported neck pain decreased for older drivers (females only), drivers in less severe crashes, and drivers in heavier cars (females only); all head restraint analyses were adjusted for these characteristics. Women, and most likely men, in the United States would benefit greatly from international harmonization to European head restraint standards. Until then, both women and men should be encouraged to adjust their adjustable head restraints, if possible, behind their heads' centers of gravity and to sit with the backs of their heads as close as possible to their head restraints.

Accidents, Traffic↗
PubMed2001

Insulin, insulin-like growth factors-I and -II and insulin-like growth factor binding protein-3 in newborn serum: association with normal fetal head growth and head circumference.

The insulin-like growth factors (IGF) and their binding proteins (IGFBP) have been implicated in the regulation of fetal weight and length. The aim of our study was to determine the relationship between head circumference at birth and serum levels of IGF-I, IGF-II, IGFBP-3 and insulin in full-term appropriate-for-gestational age (AGA) infants. Serum samples were obtained from 77 singleton full-term neonates, 69 AGA and 8 small-for-gestational age (SGA). The AGA infants were divided into three groups by head circumference: Group 1: < or = 3rd percentile; Group 2: at 50th percentile; Group 3: > or = 97th percentile. Serum levels of IGF-I, IGF-II, IGFBP-3 and insulin were determined with commercial kits and immunometric methods. There were no statistically significant differences in mean serum levels of IGF-I, IGF-II and IGFBP-3 between the groups. A significantly higher mean serum insulin level was noted in the AGA infants with a head circumference > or = 97th percentile compared to those with a head circumference < or = 3rd percentile (4.6 +/- 0.3 vs 3.3 +/- 0.6 microU/ml; p = 0.04), and in AGA infants with a head circumference above the 50th percentile compared to those with a head circumference below the 50th percentile (4.4 +/- 0.4 vs 3.3 +/- 0.3 microU/ml; p = 0.01). AGA infants with a head circumference above or below the 50th percentile did not differ statistically in their mean IGF-II and IGFBP-3 serum level, while IGF-I differed statistically between the groups (18 +/- 2.7 vs 11.6 +/- 1.6 ng/ml, respectively; p = 0.045). Using univariate analysis, head circumference correlated positively with insulin (r = 0.29; p = 0.016) and with IGF-I (r = 0.26; p = 0.03). A stepwise multivariate linear regression analysis, however, did show statistically significant correlation of head circumference with birth weight (f = 36; p = 0.0001), and only marginally with birth length (f = 4.7; p = 0.06) and insulin (f = 3.4; p = 0.07). No correlations were found between head circumference and IGF-I, IGF-II or IGFBP-3. These data suggest that apart from genetic and nutritional factors, insulin may play a role in promoting intrauterine head growth, as reflected by head circumference at birth.

Cohort Studies↗
PubMed1992

Non-icteric pancreas head carcinoma fares worse than icteric pancreas head carcinoma.

A total of 22 patients with non-icteric pancreas head carcinoma were retrospectively compared with 61 patients with icteric pancreas head carcinoma. No significant difference was found regarding age, sex, greatest diameter, macroscopic type, microscopic type, stage, lymphatic permeation, perineural infiltration, venous invasion, lymph node metastasis, and the presence of cancer cells at the surgical margins. The main location of pancreas head carcinoma could be divided into two sites: the superior (pericholedochal), and inferior or distal (excholedochal) areas of the pancreas head. Sixteen (73%) of the 22 non-icteric pancreas head carcinomas were located in the inferior or distal area (excholedochal), while 28 (46%) of the 61 icteric pancreas head carcinomas were situated in the superior portion (pericholedochal) (P less than 0.05). One (5%) of the 22 non-icteric pancreas head carcinomas was small pancreas carcinoma, compared with 11 (18%) of the 61 icteric pancreas head carcinomas. The cumulative 2-year and 4-year survival rates of the 22 patients with non-icteric pancreas head carcinoma were significantly worse than those of the 61 patients with icteric pancreas head carcinoma [7.9% vs. 24.6% (P less than 0.05) and 0% vs. 13.4% (P less than 0.01)]. These findings suggest that non-icteric pancreas head carcinomas normally arise in an area far from the biliary tree, and include a greater number of large tumors. Any resulting difficulty and delay in the diagnosis and treatment of this disease will usually lead to a worsening of the clinical course of non-icteric pancreas head carcinoma.

Age Factors↗
PubMed1997

Myosin head configuration in relaxed fish muscle: resting state myosin heads must swing axially by up to 150 A or turn upside down to reach rigor.

The arrangement and shape of myosin heads in relaxed muscle have been determined by analysis of low-angle X-ray diffraction data from a very highly ordered vertebrate muscle in bony fish. This reveals the arrangement and interactions between the two heads of the same myosin molecule, the shape of the resting myosin head (M.ADP.Pi) assuming a putative hinge between the myosin catalytic domain and the light chain binding-domain, and the way that the actin-binding sites on myosin are arrayed around the actin filaments in the bony fish muscle A-band cell unit. The results are discussed in terms of possible force-generating mechanisms. Changes in myosin head shape or tilt have been implicated in the mechanism of force generation. The myosin head arrangement, including perturbations from perfect helical symmetry, has all heads oriented roughly the same way up (there is only a small range of rotations around the head long axis). X-ray data do not define the absolute polarity of the myosin head array. The resting head rotation is either similar to (65 degrees difference) or opposite to (115 degrees difference) the rotation in the rigor state. If the rotations are similar, probably the more likely possibility, then the average relative axial displacement of the inner and outer ends of the heads from the resting state to rigor is about 140 to 150 A. If (less likely) the resting head rotation is opposite to rigor, then the heads would need to turn over (i.e. rotate about 115 degrees around their own long axes) and the mean relative axial displacement from relaxed to rigor would only be 20 to 30 A.

Actins↗
PubMed1987

The role of the aural head shake reflex in serotonin-mediated head shaking behavior.

The head shake reflex is a rapid rhythmic shaking of the head in a radial motion and is a prominent part of the behavior of most mammalian species. The administration of agonists at 5-hydroxytryptamine (5-HT) receptors to rats increases apparently-spontaneous head shaking behavior. The present study examined the relationship between the head shake reflex, elicited by stimulation of the aural ampullae with Tween 80, with a similar-appearing behavior, the head shake response caused by the administration of 5-HT agonists to rats. Head shaking was attenuated by the subcutaneous infiltration of the local anesthetic procaine into the posterior border of the external auditory meatus. However, the local anesthetic did not alter head shake behavior produced by administering either the 5-HT agonist quipazine or the 5-HT precursor 5-hydroxy-L-tryptophan (L-5-HTP). The magnitude of the head shake reflex was also diminished after habituation of the reflex by repeatedly applying Tween 80 to the ampullae, yet this treatment had no effect on the head shaking behavior caused by quipazine. In a complementary manner, pretreatment with the 5-HT2 receptor antagonist ketanserin potently blocked shaking behavior caused by quipazine without significantly altering the head shake reflex. Chronic administration of the atypical antidepressant drug iprindole to rats for 7 days reduced quipazine-induced shaking behavior without affecting the head shake reflex. In contrast, chronic administration of the monoamine oxidase inhibitor phenelzine to rats for 7 days reduced head shaking behavior caused by either stimulus, indicating that an attenuation of motor reflex activity could play a role in the reduced response to quipazine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗