The effect of age on the attentional demands of postural control.

A dual-task paradigm was used to determine the attentional demands of several postural control tasks in 16 older women (age, 71.5+/-3.4 years) and 14 young women (age, 25.5+/-2.4 years). Older women had slower verbal reaction times (VRT) compared with the younger women and increased reaction time more from a sitting to standing posture. Compared with the younger women, older women required more cognitive resources to maintain a simple eyes open standing posture versus an eyes open seated posture. Further, older women had significantly greater VRT during the dual-task conditions compared with younger women. However, VRT did not significantly change as the difficulty of the primary task increased in either group. These data have implications for older adults who may be at risk for falls in situations where they may be engaged in concurrent tasks, even when those tasks are considered automated and/or lower order operations.

The fibromyalgia syndrome: musculoskeletal pathophysiology.

Fibromyalgia (FM) is a chronic pain disorder that afflicts predominantly middle-aged women with cardinal symptoms of diffuse musculoskeletal pain, defined tender points, deprived sleep, and fatigue. The etiology and pathological mechanisms are poorly understood, and treatment approaches are largely ineffective. The clinical features of the syndrome are presented, and the relevance of muscle dysfunction in the etiopathogenesis of the disorder is explored. The evidence for involvement of muscle pathophysiology as a primary mechanism mediating the onset of symptoms is not compelling. Musculoskeletal dysfunction can be considered secondary to central abnormalities of pain modulation and altered sleep physiology precipitated by emotional stress in genetically predisposed individuals. Contemporary evidence favors treatment strategies that emphasize pain control, sleep enhancement, and a program of conditioning.

Properties of triiodothyronine binding sites in cerebral cortical cytosol.

Some properties of brain cytosol components that specifically bind L-triiodothyronine (T3) were examined in order to resolve their relevance and relationship to nuclear receptors. A marked variation in T3 binding activity was apparent among different brain areas. Binding exhibited temperature dependence and was maximal at 0 degrees C. The binding component was shown to be a protein that migrated as a single included peak on Sephadex G-100 columns at a position corresponding to a Stokes radium of 30A degrees and a M.W. of 54,000. On a linear glycerol gradient the T3-macromolecular complex was estimated to have a sedimentation constant of .4.2S. By combining sedimentation and gel filtration data the calculated M.W. was 53,000. With DEAE-cellulose chromatography the T3 complex eluted as a single peak at 115mM KH2PO4. The results indicate that the properties of the cytosol thyronine-binding protein are similar in many respects to those reported for nuclear receptors. In addition, the regional and developmental binding parameters parallel those for nuclei. We conclude that cytosolic recognition sites may function in the modulation of nuclear receptors and in addition serve to distinguish target from non-target tissue.

Thyroid hormone state and the incorporation of (14C) leucine by brain microsomes in developing rats.

Cell-free incorporation of (14C) leucine into protein was 38% greater for cerebral cortical microsomes from 22-day old neonatally thyroidectomized rats compared to littermate controls. In contrast, incorporation by liver microsomes of hypothyroid rats was 33% lower compared to controls, confirming their deficient hormonal state. Incubation of cerebral microsomes from either hypothyroid or euthyroid rats with both homologous and heterologous pH 5 enzyme fractions clearly implicated the pH 5 fraction as the source of the apparent increase in protein synthetic capacity in the hypothyroid brain. Daily administration of L-thyroxine (20 microgram/100 g body wt) to hypothyroid animals between 22 and 25 days of age produced an additional increase in (14C) leucine incorporation into protein by cerebral microsomes, whereas the cell-free protein synthesis rate of euthyroid rats was unaffected by similar hormonal treatment. Liver preparations from both hypothyroid and euthyroid rats exhibited the expected increase in cell-free protein synthesis following thyroxine administration. The results support the hypothesis that the young hypothyroid brain exhibits delayed maturation and that thyroid hormones play a regulatory role in cerebral protein synthesis during a defined developmental period.

Brain colchicine-binding protein (tubulin) during postnatal development in the rat.

A time-decay colchicine-binding assay was used under optimal conditions for measuring tubulin concentration in the cerebral cortex and cerebellum during postnatal development. In both brain areas soluble tubulin concentration (pmoles colchicine bound/mg tissue) declined by about 35% between 4 and 12 days of age after which the decrease was more gradual up to adulthood. Colchicine-binding protein concentration of particulate fractions, on the other hand, increased between 4 and 12 days of age followed by relatively little change. The concentration of tubulin in the soluble and particulate fractions of the cerebral cortex was 45% and 75% greater, respectively, than corresponding fractions of the cerebellum. The expression of tubulin on the basis of DNA, revealed marked regional differences which can be considered a reflection of differences in the relative extent of morphological differentiation in these areas during the postnatal period. Tubulin in both soluble and particulate fractions exhibited a marked increase in lability for colchicine binding from approximately 12 days of age. The half-life for loss of colchicine-binding activity was 2,5-fold greater in particulate compared to soluble fractions. An analysis of the characteristics of the particulate colchicine-binding reaction provides additional support for the hypothesis that it represents a functionally significant association of tubulin with the membranous components.