Continuous daily assessment of multiple sclerosis disability using remote step count monitoring.

Disability measures in multiple sclerosis (MS) rely heavily on ambulatory function, and current metrics fail to capture potentially important variability in walking behavior. We sought to determine whether remote step count monitoring using a consumer-friendly accelerometer (Fitbit Flex) can enhance MS disability assessment. 99 adults with relapsing or progressive MS able to walk ≥2-min were prospectively recruited. At 4 weeks, study retention was 97% and median Fitbit use was 97% of days. Substudy validation resulted in high interclass correlations between Fitbit, ActiGraph and manual step count tally during a 2-minute walk test, and between Fitbit and ActiGraph (ICC = 0.76) during 7-day home monitoring. Over 4 weeks of continuous monitoring, daily steps were lower in progressive versus relapsing MS (mean difference 2546 steps, p < 0.01). Lower average daily step count was associated with greater disability on the Expanded Disability Status Scale (EDSS) (p < 0.001). Within each EDSS category, substantial variability in step count was apparent (i.e., EDSS = 6.0 range 1097-7152). Step count demonstrated moderate-strong correlations with other walking measures. Lower average daily step count is associated with greater MS disability and captures important variability in real-world walking activity otherwise masked by standard disability scales, including the EDSS. These results support remote step count monitoring as an exploratory outcome in MS trials.

Ion transport studies and determination of the cell wall elastic modulus in the marine alga Halicystis parvula.

Using cultured cells of the marine alga, Halicystis parvula, we measured the concentrations of 11 inorganic ions in the vacuolar sap and the electrical potential difference (PD) between the vacuole and the external solution. In normal cells under steady-state conditions a comparison of the electrochemical equilibrium (Nernst) potential for each ion with the PD of -82 mV (inside negative) indicates that Na+ and K+ are actively transported out of the vacuole whereas all anions are pumped into the cell. Although the [K+] in the vacuole is only 9 mM, the cytoplasmic [K+] is about 420 mM, which suggests that the outwardly directed pump is at the tonoplast. Using large Halicystis cells we perfused the vacuole with an artificial seawater and conducted a short-circuit analysis of ion transport. The short-circuit current (SCC) of 299 peq - cm-2-s-1 is not significantly different from the net influx of Cl-. There is a small, but statistically significant net efflux of K+ (less than 1 pmol-cm-2.-1), while the influx and efflux of Na+ are not significantly different. Therefore, the SCC is a good measure of the activity of the Cl- pump. Finally, we measured the volumetric elastic modulus (epsilon) of the cell wall by measuring the change in cell volume when the internal hydrostatic pressure was altered. The value of epsilon at applied pressures between 0 and 0.4 atm is about 0.6 atm, which is at least 100-fold lower than the values of epsilon for all other algae which have been studied.

Electrically silent anion transport through lipid bilayer membranes containing a long-chain secondary amine.

The permeability properties of planar lipid bilayers made from egg lecithin, n-decane and a long-chain secondary amine (n-lauryl [trialkylmethyl]amine) are described. Membranes containing the secondary amine show halide selectivity and high conductance at pH less than 6, as estimated by measurements of zero-current potentials generated by NaBr activity gradients. In the absence of halide ions, the membranes show H+ selectivity, although the total membrane conductance is relatively low. In 0.1 M NaBr both the membrane conductance (Gm) and the Br- self-exchange flux (JBr) are proportional to H+ concentration over the pH range of 7 to 4, and both JBr and Gm saturate at pH less than 4. However, JBr is always more than 100 times the flux predicted from Gm and the transference number for Br-. Thus, greater than 99% of the observed (tracer) flux is electrically silent and is not a Br2 or HBrO flux because the reducing agent, S2O3=, has no effect on JBr. At pH 7, JBr is proportional to Br- concentration over the range of 1-340 mM, with no sign of saturation kinetics. Both urea and sulfate tracer permeabilities are low and are unaffected by pH. The results can be explained by a model in which the secondary amine behaves as a monovalent, titratable carrier which exists in three chemical forms (C, CH+, and CHBr). Br- crosses the membrane primarily as the neurtal complex (CHBr). The positively charged carrier (CH+) crosses the membrane slowly compared to CHBr, but CH+ is the principal charge carrier in the membrane. At neurtal pH greater than 99% of the amine is in the nonfunctional form (C), which can be converted to CH+ or CHBr by increasing the H+ or Br- concentrations. The permeability properties of these lipid bilayers resemble in many respects the permeability properties of red cell membranes.

Living with mania: a study of outpatient group psychotherapy for bipolar patients.

This article describes an outpatient group psychotherapy with fourteen bipolar patients. Contrary to previous pessimistic reports in the literature, the author demonstrates that group therapy with these patients is both feasible and beneficial, and that it contributes to an ameloriation of the natural course of this illness. Group psychotherapy, with its enhancement of medication compliance, effective challenge of denial mechanisms, and facilitation of increased awareness of internal and external stressors, can thus be an effective tool in the therapeutic armamentarium against the ravages of bipolar illness. Significant themes arising in the group, common defensive operations, and therapeutic techniques are discussed. In addition, phases of recovery and group development are reviewed in the context of relevant interventions. Treating bipolars in group therapy is a fascinating and rewarding experience, full of potential gains in understanding and influencing the course of this complicated illness.

Increase in K+ and alpha-AIB active transport in CHO cells after low [K+] treatment.

We have studied the effects of prolonged incubation in low [K+] medium (approximately 0.3 mM) on both K+ and amino acid transport in Chinese hamster ovary (CHO) cells. When incubated in low [K+] medium, CHO cells redressed partially the loss of intracellular K+ after 12 h. After 24 h of incubation, both the activity of Na+-K+-ATPase in crude homogenates, and the transport capacity (Vmax) for ouabain-sensitive (i.e., active) K+ influx approximately doubled. The magnitude of the ouabain-insensitive (i.e., passive) K+ influx decreased by 50%. Thus the regulatory response involves an apparent increase in Na+-K+ pump and a decrease in K+ leak. The transport capacity for the nonmetabolized amino acid, alpha-aminoisobutyric acid (alpha-AIB), also increased after 24 h in low [K+] medium. The Vmax for the Na+-dependent (i.e., active) alpha-AIB influx increased by about 150%, and the magnitude of the Na+-independent influx increased by 20-40%. These changes in alpha-AIB transport result in a twofold greater capacity to accumulate this amino acid. Thus the regulation of K+ and alpha-AIB transport systems appears to be linked and possible mechanisms of this linkage are discussed.

Development of calcium reabsorption by the allantoic epithelium in chick embryos grown in shell-less culture.

The allantoic sac of the chick embryo functions as a primitive urinary bladder, storing and modifying the excretory fluid produced by the embryo. We have used chick embryos grown in shell-less culture to study the in situ handling of Ca2+ by the allantoic epithelium. Between Days 8 and 13 of incubation (38 degrees C, 5% CO2), the [Ca2+] of the allantoic sac fluid declines from about 1.5 mM to less than 0.3 mM, with most of this Ca2+ reabsorption occurring between Days 10 and 11. In 13-day-old embryos, the allantoic epithelium reabsorbs within 24 hr 85-92% of 45Ca2+ injected into the allantoic sac, while in 9-day-old embryos 45Ca2+ reabsorption is less than 40% by 24 hr. This is evidence for the developmental onset of a Ca2+ reabsorption process in the allantoic epithelium. The allantoic fluid Ca2+ is reabsorbed into the embryo's blood in which the serum [Ca2+] is about 1.5 mM. Also, electrical potential profiles reveal that the serosal (mesenchymal) side of the allantoic epithelium is 15-30 mV positive compared to the mucosal (luminal) side. Thus, by electrochemical criteria this reabsorption process appears to be active.

Regulation of 25-hydroxyvitamin D3 metabolism in chick embryo.

We investigated the time course of the development of renal 25-hydroxyvitamin D-1-hydroxylase and 25-hydroxyvitamin D-24-hydroxylase in chick embryos grown in the presence and absence of the eggshell. In embryos with the eggshell, the specific activity (SA) of 25-hydroxyvitamin D-1-hydroxylase in kidney homogenates increased from 0.68 fmol X min-1 X mg protein-1 at 12 days of gestation to a peak of 2.55 +/- 0.50 fmol X min-1 X mg-1 protein-1 at 17 days. In contrast, the SA of 25-hydroxyvitamin D-24-hydroxylase decreased from 2.5 fmol X min-1 X mg protein-1 to 0.90 +/- 0.25 fmol X min-1 X mg protein-1 during the interval. The total plasma calcium was significantly reduced in embryos without shells at 14 to 15 days of gestation (1.1 +/- 0.1 mM, mean +/- SE) compared with normal embryos of the same gestation (2.3 +/- 0.3 mM, P less than 0.002). In embryos without the eggshell, renal 25-hydroxyvitamin D-1-hydroxylase increased from 6.0 to 8.2 +/- 0.6 fmol X min-1 X mg protein-1 at 17 days of gestation and was from four- to sixfold higher than corresponding enzymatic activities for intact embryos. The increased enzyme activity resulting from loss of the eggshell was due to an increase in Vmax. The findings indicate that renal 25-hydroxyvitamin D-1-hydroxylase and 25-hydroxyvitamin D-24-hydroxylase in the chick embryo exhibit activity and show a large capacity for regulation in response to changes in calcium metabolism.

Embryonic chick allantois: functional isolation and development of sodium transport.

By removing the shell membranes from the chorioallantoic membrane, the chorion is damaged, as visualized by electron microscopy, and rendered permeable, as evidenced by penetration of horseradish peroxidase and increased inhibition of the allantoic Na+-K+ pump by ouabain applied on the chorionic side. The short-circuit current (SCC) of this functionally isolated allantoic epithelium is augmented by nystatin, a channel-forming ionophore, when applied to the mucosal surface. Electrical parameters were determined for three age groups between 12 and 19 days of incubation. The SCC approximately doubled from the youngest (12-13 days) to the oldest (18-19 days) groups, whereas the transepithelial resistance (Re) of 700-900 omega X cm2 remained the same. Amiloride, an inhibitor of apical Na+ uptake, inhibited 98-100% of the SCC at 10(-4) M in both 15-16 and 18-19 day epithelia. In the 12- to 13-day preparation 20-25% of the SCC was insensitive to 10(-3) M amiloride. The Ki's for amiloride were similar in all preparations, at about 5 X 10(-7) M. Determination of the Hill coefficients for inhibition revealed a lower value (0.75 +/- 0.03) for the 12-13 day preparation compared with the two older preparations with coefficients not significantly different from unity. Replacing Na+ in the bathing solutions abolished the SCC of 18-19 day epithelia, whereas about 15% of the SCC remained at 12-13 days. Thus, during development, the SCC of the allantoic epithelium increases in magnitude and becomes increasingly (to 100%) amiloride-sensitive and Na+-dependent.

Evidence for an electrogenic ion transport pump in cells of higher plants.

Cyanide (CN) and dinitrophenol (DNP) rapidly depolarize the cells of oat coleoptiles (Avena sativa L., cultivar Victory) and of pea epicotyls (Pisum sativum L., cultivar Alaska); the effect is reversible. This indicates that electrogenesis is metabolic in origin, and, since active transport is blocked in the presence of CN and DNP, perhaps caused by interference with ATP synthesis, that development of cell potential may be associated with active ion transport. Additional evidence for an electrogenic pump is as follows. (1) Cell electropotentials are higher than can be accounted for by ionic diffusion. (2) Inhibition of potential, respiration, andactive ion transport is nearly maximal, but a potential of -40 to -80 mV remains. This is probably a passive diffusion potential since, under these conditions, a fairly close fit to the Goldman constant-field equation is found in oat coleoptile cells.

Amiloride-sensitive ammonium and sodium ion transport in the blue crab.

In the estuarine crab, Callinectes sapidus, net NH4+ efflux was twice as high in animals acclimated to 17% salinity seawater (SW) (0.495 +/- 0.084 mumol . h-1 . g wet wt-1, n = 7) than in animals acclimated to full-strength 35% SW (0.212 +/- 0.028 mumol . h-1 . g-1, n = 7). Amiloride (3 X 10(-4) M) in the external SW reversibly inhibited these effluxes by 63 +/- 6% (n = 6) and 67 +/- 6% (n = 5), respectively. Unidirectional Na+ influx was reversibly inhibited 42 +/- 6% (n = 7) by amiloride in 17% SW-acclimated crabs and 49 +/- 7% (n = 8) in 35% SW-acclimated crabs. This mutual sensitivity to amiloride is evidence for a Na+/NH4+ exchanger. Inhibition of unidirectional Na+ efflux by Na+-free SW indicates the presence of an obligate Na+/Na+ exchange component that accounts for at least 42% of the Na+ flux and is also amiloride sensitive. The lack of inhibition by amiloride of the net H+ efflux does not support the presence of a Na+/H+ exchanger. Acclimation of the crab to dilute SW may involve an increase in the activity of the Na+/NH4+ exchanger in the gills, but this mechanism contributes only a small fraction of the total Na+ transport.

Freeze fracture morphology of the tight junctions of the eccrine sweat gland from patients with cystic fibrosis.

The resorption of Na+ and Cl- across the duct of the human eccrine sweat gland is markedly decreased in individuals with cystic fibrosis (CF). Conceivably, a defective transcellular ion transport mechanism or an increased paracellular backflux of ions could account for the abnormal salt resorption in the sweat gland duct and other organs affected in CF. Tight junctions are thought to regulate paracellular ion flow. Specifically, the number of junctional elements observed by freeze fracture are believed to correspond with the extent of paracellular transport. We compared the freeze fracture morphology of tight junctions of eccrine sweat glands taken from 11 control and seven CF patients. In an attempt to "fingerprint" the junctions morphometrically, the following parameters were measured: the number of strands, the depth of the junction from the apical to the basal strand, the angle of intersection between strands, and the mean distance along a strand between intersections with two other strands. No significant difference was observed between control and CF sweat glands in the freeze fracture morphology of the tight junctions of the duct, the segment where the net reabsorption of Na+ and Cl- is abnormally decreased in CF. Significant changes were observed, however, in the means of the number of strands, the depth, and the distance between intersections for the tight junctions of the intercellular canaliculus of the secretory coil, which appears to function normally in CF.

Cross-reactivity of an antiserum to the alpha-subunit of the Na+, K+-ATPase of toad (Bufo marinus) kidney with basal and apical membranes of transporting epithelia of the rat.

An antibody to the 96 kD alpha-subunit of the Na+, K+-ATPase from Bufo marinus has been used in immunostaining rat kidney and salivary glands. Intense staining was observed on basolateral membranes of distal tubules of the kidney and striated ducts of the three major salivary glands. Less intense staining was seen on the basolateral membranes of parotid acinar cells, but no staining was seen on the acinar cells of submandibular or sublingual glands. These sites of staining have been shown, by other methods, to posses substantial Na+, K+-ATPase, indicating that the antibody recognizes antigenic determinants of the sodium pump highly conserved in the course of evolution. In addition, staining with this antibody was observed at the apical region of cells of the proximal straight tubule and of the papillary collecting duct in the kidney. Absorption studies suggest that the apical antigenic determinants are the same or closely related to each other but are distinct from basolateral antigenic determinants.

Electrical potential differences in cells of barley roots and their relation to ion uptake.

Single cell electropotentials of barley (Hordeum vulgare L., cv. ;Compana') root cortex were measured at different external concentrations of KCl in the presence of Ca(2+). The roots were low in salt from seedlings grown on 0.5 mm aerated CaSO(4) solution. Thus, the conditions were equivalent to those used to define the dual mechanisms found with radioactive tracer-labeled ion uptake. In 0.5 mm CaSO(4) alone, there is an increase with time of cell negativity from about -65 millivolts 15 minutes after cutting segments to about -185 millivolts in 6 to 8 hours. Two possible hypotheses, not mutually exclusive, are offered to explain this aging effect: that cutting exposes plasmodesmata which are leaky initially but which seal in time, and that some internal factors, e.g., hormones diffusing from the apex, have a regulatory effect on the cell potential, an influence which becomes dissipated in isolated segments and permits the development of a higher potential difference. In any case changes in selective ion transport must be involved. The cell potentials at KCl concentrations above 2.0 mm are more negative than would be expected for a passive diffusion potential. It is suggested that this discrepancy may be due to an electrogenic pump or to a higher K(+) concentration in the cytoplasm than in the remainder of the cell, or perhaps to both. Whether there is a clear relationship between cell potential and mechanisms 1 and 2 of cation transport depends upon whether the cell potentials of freshly cut or of aged tissue represent the values relevant to intact roots.

The intracellular localization of amiloride in frog skin.

The diuretic compound amiloride is often used as a specific inhibitor of the passive Na+ entry step in the transepithelial transport of Na+ across frog skin. We have utilized the fluorescence properties of amiloride to study the distribution of this transport inhibitor in the ventral skin of Rana pipiens. After a 30 s exposure of 1-100 microM amiloride to the external surface of frog skin, amiloride fluorescence was evident in the cytoplasm of all cell layers of the epidermis and alveolar gland epithelium. Changes in the conditions of incubation which alter the pharmacological activity of amiloride did not affect the intracellular distribution of amiloride or the washout profile of [14C]amiloride. The presence of amiloride fluorescence in the cytoplasm prevented our examination of changes in the amiloride fluorescence at the cell surface with various conditions of incubation. Four derivatives of amiloride that differed in their ability to inhibit short-circuit current were also localized intracellularly but varied in their relative distribution among the cell layers of the epidermis. Our results indicate that when incubated at concentrations from 1 to 100 microM, a large fraction of the amiloride taken up by frog skin is not directly involved with the inhibition of passive Na+ transport at the apical surface of the stratum granulosum. The mechanism of intracellular uptake of amiloride is not clear. However, the cytoplasmic localization of amiloride could explain the action of the drug on intracellular enzymes and may account for the large proportion of non-displaceable [14C]amiloride that has been observed in frog skin.

Structure of the tight junctions of the human eccrine sweat gland.

The human eccrine sweat gland contains two anatomically and functionally discrete segments: the secretory coil, which produces an isotonic or slightly hypertonic precursor fluid, and the coiled duct, which reabsorbs Na+ and Cl- to yield a hypotonic sweat. We examined the freeze-fracture morphology of tight junctions from isolated secretory coil and coiled duct segments to assess indirectly the contribution of paracellular ion transport in secretion and resorption in the sweat gland. In the secretory coil, tight junctions of the intercellular canaliculus and main lumen consisted of approximately 9 and 6, closely spaced, parallel or anastomosing elements, respectively. Tight junctions of the coiled duct were similar in appearance to those at the main lumen of the secretory coil. In both the secretory coil and coiled duct, and average of 2 to 3, widely spaced junctional elements were usually observed basolateral to the closely spaced junctional elements in the region corresponding to the location of the zonula adherens in Epon sections. The complexity of the tight junctions of the secretory coil exceeded what we expected for an epithelium secreting an isosmotic fluid. The elaborate tight junctions of the coiled duct support other evidence for an intermediate to high transepithelial resistance.