Search

Acceleration of particles by intense laser-plasma interactions represents a rapidly evolving field of interest, as highlighted by the recent demonstration of laser-driven relativistic beams of monoenergetic electrons. Ultrahigh-intensity lasers can produce accelerating fields of 10 TV m(-1) (1 TV = 10(12) V), surpassing those in conventional accelerators by six orders of magnitude. Laser-driven ions with energies of several MeV per nucleon have also been produced. Such ion beams exhibit unprecedented characteristics--short pulse lengths, high currents and low transverse emittance--but their exponential energy spectra have almost 100% energy spread. This large energy spread, which is a consequence of the experimental conditions used to date, remains the biggest impediment to the wider use of this technology. Here we report the production of quasi-monoenergetic laser-driven C5+ ions with a vastly reduced energy spread of 17%. The ions have a mean energy of 3 MeV per nucleon (full-width at half-maximum approximately 0.5 MeV per nucleon) and a longitudinal emittance of less than 2 x 10(-6) eV s for pulse durations shorter than 1 ps. Such laser-driven, high-current, quasi-monoenergetic ion sources may enable significant advances in the development of compact MeV ion accelerators, new diagnostics, medical physics, inertial confinement fusion and fast ignition.

Intertester reliability is important for longitudinal assessment of patients by two different clinicians. The purpose of this study was to investigate the intertester reliability of the cervical range of motion device (CROM). The CROM was used to measure subjects with a history of cervical dysfunction. The sample consisted of 22 subjects (15 female and 7 male). Active cervical flexion, extension, right and left rotation, and right and left lateral flexion were measured with the client in the sitting position. Moderate to high intraclass correlation coefficients (ICC = +.76 to +.98) were found between testers. Furthermore, the mean differences between testers were also consistently low for all six measurements (.5-3.6 degrees ). These data suggest the CROM is a reliable measuring tool between testers for cervical range of motion. J Orthop Sports Phys Ther 1992;15(3):147-150.

In raccoons and other mammals, a pathway for kinesthetic sensation (from muscles, fascia, tendons, and joints) reaches the anterodorsal cap of the ventrobasal thalamus and the anteriormost part of the somatic sensory cerebral cortex. To find the medullary component of this kinesthetic pathway in raccoons, small injections of horseradish peroxidase were made in the thalamus under guidance of simultaneous electrophysiological recording from kinesthetic projections. As determined by retrograde labeling following these injections, kinesthetic thalamic subregions receive projections as follows: caudomedial from cells in the external cuneate nucleus and its medial tongue, rostromedial from cells in basal cuneate nucleus, and rostrolateral from cells in cell group z and the reticular division of cell group x. Electrophysiological recording showed kinesthetic representations in each of these medullary regions. Labeled cells were also observed in the infratrigeminal subnucleus of the lateral reticular nucleus. Cats have kinesthetic projections to the thalamus from the basal cuneate and cell group z; raccoons (and monkeys) have these plus projections from the external cuneate and cell group x. This suggests that the kinesthetic projection system in raccoons and monkeys is expanded in correlation with their more dextrous use of the hand.

The morphology and brachial cord primary afferent projections of the cuneate and lateral cuneate nuclei have been studied in the lesser bushbaby. The cuneate nucleus was divided into three regions. From caudal to rostral these were the large cell, cell column and rostral regions. Primary afferents from C2, C4, C6, C7, C8, T1 and T3 terminated within distinct partially overlapping terminal zones in the ipsilateral large cell and cell column regions of the cuneate nucleus (CN) and the lateral cuneate nucleus (LCN). Segmentotopic was the greatest in the rostal region of the CN due to a more diffuse projection pattern. In the LCN, the transverse terminal fields appeared as curved mediolaterally oriented laminae. In each case, ascending fibers of passage from C4, C6, and C7 in the cuneate fasciculus were organized so that two distinct fiber laminae were present. The separation of fibers and the formation of the two ascending laminae were completed either within two segments rostral to their respective level of entry (for C6 and C7 lesions) or in the caudal medulla (for C4 lesion). For each of these segments, the laminae consisted of a small dorsomedial one and a large lateral one. The organization of primary afferents from one segment into two ascending fiber laminae in the cuneate fasciculus was reflected in a differential termination pattern within both the CN and LCN. The results of this study were discussed relative to earlier anatomical and physiological studies on the DCN in other animals.

In 1979, the National Institute for Occupational Safety and Health (NIOSH) conducted a cross-sectional medical and industrial hygiene survey of workers exposed to carbon disulfide in the manufacture of rayon staple. The purpose of the study was to define dose-response relationships at levels near the existing United States standard of 20 ppm. The plant chosen has been historically well controlled, with levels between 10 and 30 ppm for most of its history. Medical tests were designed to examine effects on the central and peripheral nervous systems, on the cardiovascular system (including the retinal vessels), on carbohydrate, trace mineral, and lipid metabolism, on testicular function, and on thyroid function. This paper describes the plant, the exposed and reference populations, and the tests used to determine the health effects of carbon disulfide. The data are still being analyzed, but preliminary evidence suggests that carbon disulfide exposure at levels below the present standard of 20 ppm is associated with adverse effects. On the basis of the analysis completed to date the safety of the standard of 1 ppm recommended by NIOSH does not appear to be established.

An evaluation of the effects of occupational exposure to carbon disulfide was performed in a sample of 156 male viscose rayon workers. A composite group of 233 workers drawn from two other artificial fiber plants located on the same premises as the rayon plant was used for comparison. Effects of CS2 on the peripheral nervous system (PNS) were evaluated in ulnar and peroneal nerves using measurements of maximum motor nerve conduction velocity (MCV) and distal latency; and sensory conduction velocity (SCV) in the sural nerve. Self-reported symptoms related to PNS disorders were also obtained from each study participant. Industrial hygiene records showed the rayon workers to have had CS2 exposures that generally had not exceeded 20 ppm. The overall mean number of years of CS2 exposure was 12.1 years (+/- 6.9 S.D.). The viscose rayon workers were divided prior to the study into three groups according to historical mean CS2 levels calculated for job titles, and area and personal CS2 samples were obtained during the conduct of the study to characterize each job. For these three groups the median CS2 levels were measured to be 1.0, 4.1 and 7.6 ppm. The comparison group's median CS2 level approximated 0.2 ppm. Results showed CS2-exposed workers to have small but statistically significant (p less than .05) reductions in sural SCV and peroneal MCV. Other neurophysiological measures consisting of distal latency, residual latency, and muscle or nerve action potential amplitudes showed no significant differences between study groups. A reduction in the ratio of amplitudes of muscle action potentials obtained from peroneal nerve stimulation was significant (p less than .05). Reductions in the peroneal nerve MCV were found to be related, in a dose response sense, to workers' cumulative exposure to CS2. No increase attributable to CS2 was found in the prevalence of symptoms related to PNS disorders. The results from this study generally agree with similar findings from Finland, Sweden and Italy, but at CS2 exposure levels lower than those previously reported for occupational exposure.

The distribution and organization of mechanosensory projections to the cuneate, gracile and external cuneate nuclei were mapped in tree squirrels anesthetized with ketamine and urethane. Tungsten microelectrodes were used to record unit and unit cluster responses to mechanical stimulation. Most responses in the gracile nucleus were to stimulation of skin and hairs of the tail, hind foot and leg, and trunk, in that order going from dorsal to ventral in the nucleus. A similar distribution of responses was found in the cuneate nucleus to stimulation of forelimb, neck and pinna going from dorsomedial to ventrolateral in the nucleus. Some responses to stimulation or movement of subcutaneous tissue were found in the cuneate and gracile nuclei. Responses in the external cuneate were to stimulation of deep-lying tissues in the hand medially, the lower arm centrally and the shoulder and trunk laterally. The pattern of projections in the tree squirrel differed most strikingly from that seen in raccoons and opossums in the relatively small extent of projections from the glabrous skin of the forepaws which were concentrated in a small region near the obex in squirrels. In contrast, there was a large representation of hairy receptive fields located on the forelimb in all regions of the squirrel cuneate nucleus. Otherwise, the somatotopic organization of mechanosensory projections to these dorsal column nuclei in tree squirrels was similar to that reported in other mammals.

A case report in which the management of a patient with hereditary angioneurotic edema requiring oral surgery is presented. A review of the literature with emphasis on the clinical features, etiology, diagnosis, and treatment is also presented.

The projection of hindlimb dorsal root afferents to Clarke's column has been studied in the tree shrew (Tupaia glis) and lesser bushbaby (Galago senegalensis). In the bushbaby, fibers from K12, L1 and L3 projected ipsilaterally to Clark's nucleus from levels L3 to T3, L2 to T4 and L3 to T5 respectively. In Tupaia, afferents from T11, L1, and L3 terminated ipsilaterally within the nucleus from segments L2 to T4, L3 to T6, and L3 to T8. Fibers from T12, L1, and L3 in Galago and T11 in Tupaia terminated within the even to lateral aspect of the nucleus at lower levels, throughout the nucleus at middle levels and in the dorsal aspect of the column at rostral levels. Fibers from T11 and L1 have a similar ventrolateral pattern of termination in lower levels, however, at rostral levels preterminal debris was present throughout the width of the nucleus. Fibers from L1 and L3 in the bushbaby form a complex longitudinal network with the medullary region of the nucleus in segments T11 to T8. Afferents from levels T5 in Tupaia and L6 in Galago projected ipsilaterally to the nucleus from level L3 to T10, and T8, respectively. Fibers from these segments terminated throughout the extent of the column at L3 and, rostrally projected to more dorsal regions of the nucleus. In this study, fibers from S2, and S3 and CCO2 did not terminate in Clark's column. Both the segmental distribution of hindlimb dorsal root fibers and their pattern of termination in Clark's nucleus in the tree shrew were similar to that reported in quadrupedal primates and other quadrupedal mammalian forms. The results of this study were interpreted as evidence which relates the complex organization of the Clark column system in the lesser bushbaby to its vertical clinging and leaping style of locomotion.

Because murine rodents have no complex synaptic arrangements in the ventral posterolateral nucleus (VPL), we sought to determine if the lack of complexity was a characteristic common to all rodents. We studied the synaptology of VPL in the fox squirrel, Sciurus niger, using electron microscopy. We found vesicle-containing dendrites and complex synaptic arrangements in the squirrel VPL. Therefore, the relative simplicity of the rat and mouse VPL is not a general feature of the rodent somatosensory thalamus.

The distribution of lateral funicular and cerebral corticofugal fibers to the dorsal column, Z and X nuclei were studied in the prosimian primate Galago senegalensis. Lesions of the lateral funiculus resulted in a differential distribution pattern of preterminal degeneration within the nuclei studied. In the nucleus gracilis, spinal lesions produced moderate amounts of debris in ventral cell nest and rostral areas. Diffuse degeneration was present in both the dorsal cell nest area of the nucleus gracilis and the rostral nucleus cuneatus. Extremely dense debris was present within both ipsilateral Z and X nuclei. Cortical ablations of predominantly hind-limb motor-sensory areas resulted in degeneration throughout most of the longitudinal and transverse extent of the contralateral dorsal column nuclei. Degeneration appeared to be more concentrated in ventral nuclear areas. The distribution of cortical fibers to the rostral gracile and Z nuclei was essentially the inverse of that observed for lateral funicular fibers. The contralateral nucleus Z received only a sparse corticobulbar input while the rostral gracile contained more moderate amounts of preterminal degeneration. The results are in agreement with previous reports on the morphology and fiber connections of the dorsal column, Z and X nuclei in Galago and other animals. They support the concept that the Z and X nuclei are functional components of the dorsal column nuclear system.

This report describes the medullary course and projection patterns of cervical dorsal root nerve fibers in five mammalian species (bushbaby, tree squirrel, raccoon, potoroo, and brush-tailed possum). After cutting a single cervical dorsal root and allowing appropriate postoperative survival, we studied serial, Fink-Heimer impregnated sections of the medulla from each individual to locate degenerated afferent fibers and endings. Fibers from those rostral (C2) or caudal (C8) cervical roots studied traverse the medulla as a single bundle, forming collaterals en route into the nucleus cuneatus and external cuneate nucleus at all levels. Fibers from most cervical roots (C4 through C7, sometimes C3), however, separate into two discrete bundles as they project rostrally. A more medial, superficially placed group of fibers projects predominately to the dorsal part of nucleus cuneatus, which seems to be somatotopically arranged. The second fiber group, larger, deeper, and more laterally situated, projects mainly to ventral and ventrolateral nucleus cuneatus (asomatotopically) and to the external cuneate nucleus. Based on segmental and species differences in the presence of this fiber separation, and on prior physiologic and anatomic evidence, we suggest that this form of fiber sorting in the cuneate fasciculus is modality based. It appears likely that fibers in the medial group are of primarily cutaneous origin, and that many if not most of those in the larger lateral population arise from deep receptors in muscle and joints.

The present study was conducted with a group of 298 textile workers. Of the workers studied 131 had worked at least one year in a rayon plant where there were CS2 exposures of varying degree, but generally below 20 ppm, which is the U.S. occupational exposure limit. The remaining 167, who worked in plants that manufactured other textiles where any CS2 exposure was considered inconsequential, comprised a comparison group. The 298 workers completed a checklist of symptoms characteristic of various neurobehavioral syndromes. Mood and excitability were measured by the Profile of Mood States, and by a mania scale from the Minnesota Multiphasic Personality Inventory, respectively. Cognitive and psychomotor performance was studied by application of four standard tasks: the Neisser letter search, the memory span test, the eye-hand coordination test, and a combined simple and complex reaction time test. The results indicated an absence of behavioral changes of any major significance, suggesting that effects here may only be marginal. The major finding related to the significant cluster of reported symptoms of neurobehavioral ailments.

The course and terminal distribution of cervical primary afferents in the dorsal column nuclei were studied in the fox squirrel, Sciurus niger. Unilateral rhizotomies were performed at cervical levels C3, C4, C5, C6 and C8. For all spinal levels studied except C8, degeneration in the medullary cuneate fasciculus was present within two distinct groups. They included a large oblique lateral lamina and a small superficial group of degeneration. The superficial group was horizontal, located medial to the large lamina and appeared to be formed by the medial shifting of fibers away from the initial larger group. Fibers in the large primary lamina appeared to terminate primarily in the ventrolateral areas of the cuneate nucleus. Fibers from the superficial group, however, appeared to project mostly to dorsal cuneate nuclear areas. Hence, the dual transverse terminal patterns for cervical fibers in the cuneate nucleus appeared to be related directly to a fiber sorting process that involved the formation of two often separate ascending fiber groups in the cuneate fasciculus. The results of this study are compared with the mechanosensory mapping of the dorsal column nuclei in the squirrel.