Long-term stability of hand-held dynamometric measurements in children who have myelomeningocele

The long-term stability of hand-held dynamometric measurements was assessed in 30 muscle groups of 12 children with myelomeningocele, before and after a 23-day interval. Measurements from a majority of the muscle groups had excellent stability, based on statistical indicators of association (Pearson Product-Moment Correlation Coefficients, r =.76-.98) and agreement (intraclass correlation coefficients, ICC = .75-.99). Muscle groups with lower long-term stability were the right and left wrist extensors and flexors, the left hip adductors and extensors, the left knee flexors, and the right and left knee extensors. Upper-extremity muscle groups had higher long-term stability than did lower-extremity muscle groups. The results indicate that the dynamometric measurements were highly reliable when the test-retest interval was 23 days. Other researchers have previously shown high reliability for these measurements over shorter periods of time. Improved reliability might be obtained by supporting the lower extremity during hip extension tests; padding the dynamometer end pieces, especially when testing over bony prominences; and using a smaller, digital dynamometer. The hand-held dynamometer appears to warrant use and further investigation with pediatric populations.

Cannabinoid receptor agonists inhibit Ca current in NG108-15 neuroblastoma cells via a pertussis toxin-sensitive mechanism

Cannabinoid receptor ligands irreversibly inhibited peak voltage-activated Ca currents (44%) in NG108-15 cells; this inhibition was Pertussis toxin-sensitive. Inhibition was largely due to a reduction in the omega-conotoxin sensitive portion of high-voltage activated (HVA) current, although there was also a significant decrease in low-voltage activated current (56%) and in the nifedipine-sensitive portion of HVA current (41%).

Goal attainment scaling as a measure of change in infants with motor delays

Goal attainment scaling (GAS) is an individualized criterion-referenced measure of change that has several unique features, compared with the behavioral objective, and five possible levels of attainment for each goal. The validity of GAS as a measure of motor change was investigated in 65 infants, 3 to 30 months of age, with motor delays. For each infant, two goals to be attained within a 6-month period of intervention were established. After the 6-month period, the mean GAS T-score of 55.4 was significantly higher than the expected mean of 50. This finding indicated that the infants' motor change exceeded the therapists' expectations. Neither the type nor the category of goal influenced the therapists' ability to select outcomes that the infants were capable of achieving. Because moderate and low correlations were found between GAS T-scores and Peabody gross motor and fine motor change scores, the two assessments appear to measure different aspects of motor development. Selected child, family, and program variables were examined as sources of bias in GAS T-scores. Motor delay was the only variable that biased GAS T-scores; infants who were less delayed had higher GAS T-scores. The results indicate that GAS was responsive to change in individualized motor goals and support the model of GAS as an idiosyncratic measure. The unique features of GAS offer advantages for measurement of motor change compared with the behavioral objective and norm-referenced developmental scales.

Synapse formation between dissociated basal forebrain neurones and hippocampal cells in culture

Dissociated neurones from rat basal forebrain and hippocampus were co-cultured in vitro for 8-15 days. Patch-clamp recordings from individual presumed hippocampal pyramidal cells revealed synaptic currents following focal extracellular stimulation of single presumed basal forebrain neurones. Of 18 neurone pairs, 13 showed inward (excitatory) synaptic currents, 4 showed outward (inhibitory) synaptic currents, and 1 showed a mixed current. Latencies varied from 4 to 15 ms, suggesting both mono- and polysynaptic currents. These experiments indicate that synaptic connections can be established between basal forebrain and hippocampal cells in dissociated cell culture.

Neurotransmitters inhibit the omega-conotoxin-sensitive component of Ca current in neuroblastoma x glioma hybrid (NG 108-15) cells, not the nifedipine-sensitive component

Voltage-dependent calcium currents (ICa) in NG 108-15 cells consisted of three pharmacologically distinct components: a transient low-voltage-activated (LVA) current, sensitive to Ni2+; a high-voltage-activated (HVA) current sensitive to the dihydropyridine antagonist, nifedipine and a HVA current sensitive to omega-conotoxin GVIA (CgTx). The voltage sensitivities and decay kinetics of the two HVA currents were indistinguishable. The neurotransmitters acetylcholine (ACh) and noradrenaline inhibited ICa. This inhibition was not occluded by Ni2+ or nifedipine, but was abolished by CgTx. It is therefore concluded that the neurotransmitter-sensitive component of ICa is restricted to that component of HVA current inhibitable by omega-conotoxin.

Intracellular Mg2+ inhibits the IP3-activated IK(Ca) in NG108-15 cells. [Why intracellular citrate can be useful for recording IK(Ca)]

Receptor-mediated formation of inositol 1,4,5-trisphosphate (IP3) can induce an outward Ca(2+)-activated K+ current [IK(Ca)] in some neural cells. We have investigated IK(Ca) activated by intracellular injections of IP3 in whole-cell patch-clamped neuroblastoma x glioma hybrid cells. The current could only be recorded reliably using citrate as the anion in the pipette, but not using acetate, aspartate, chloride, fluoride, gluconate or methylsulphate. This could be attributed to buffering of intracellular Mg2+ by citrate. Theoretical calculations suggested free [Mg2+] of 1.0 and 0.07 mM respectively in the acetate- and citrate-based recording solutions. Further, IP3-activated IK(Ca) could be recorded when the free Mg2+ level in the acetate, chloride or methylsulphate solutions was lowered to the range (0.05 mM) calculated for the citrate solution. Thus, raised [Mg2+] blocks IK(Ca). This appeared to be due to inhibition of the response to released Ca2+, since high [Mg2+] also blocked the response to intracellular injections of Ca2+ ions. Mean Mg2+ levels in intact neuroblastoma x glioma hybrid cells measured by Mag-Indo-1/AM fluorescence were estimated to be less than 0.14 mM. We therefore conclude that IP3-induced IK(Ca) is expressed under normal conditions, but may be subject to regulation by intracellular Mg2+.

Sorting of GPI-anchored proteins to glycolipid-enriched membrane subdomains during transport to the apical cell surface

We show that a protein with a glycosylphosphatidyl inositol (GPI) anchor can be recovered from lysates of epithelial cells in a low density, detergent-insoluble form. Under these conditions, the protein is associated with detergent-resistant sheets and vesicles that contain other GPI-anchored proteins and are enriched in glycosphingolipids, but do not contain a basolateral marker protein. The protein is recovered in this complex only after it has been transported to the Golgi complex, suggesting that protein-sphingolipid microdomains form in the Golgi apparatus and plasma membrane and supporting the model proposed by Simons and colleagues for sorting of certain membrane proteins to the apical surface after intracellular association with glycosphingolipids.

Kinetic and pharmacological properties of the M-current in rodent neuroblastoma x glioma hybrid cells

1. The M-like current IK(M,ng) in differentiated NG108-15 mouse neuroblastoma x rat glioma hybrid cells has been studied using tight-seal, whole-cell patch-clamp recording. 2. When calculated from steady-state current-voltage curves, the conductance underlying IK(M,ng) showed a Boltzmann dependence on voltage with half-activation voltage Vo = -44 mV (in 3 mM [K+]) and slope factor (a) = 8.1 mV/e-fold increase in conductance. In 12 mM [K+] Vo = -38 mV and a = 6.9 mV. The deactivation reciprocal time constant accelerated with hyperpolarization with slope factor 17 mV/e-fold voltage change. 3. The reversal potential for deactivation tail currents varied with external [K+] as if PNa/PK were 0.005. 4. Steady-state current was increased on removing external Ca2+. In the presence of external Ca2+, reactivation of IK(M, ng) after a hyperpolarizing step was delayed. This delay was preceded by an inward Ca2+ current, and coincided with an increase in intracellular [Ca2+] as measured with Indo-1 fluorescence. Elevation of intracellular [Ca2+] with caffeine also reduced IK(M, ng). 5. IK(M, ng) was inhibited by external divalent cations in decreasing order of potency (mM IC50 in parentheses): Zn2+ (0.011) greater than Cu2+ (0.018) greater than Cd2+ (0.070) greater than Ni2+ (0.44) greater than Ba2+ (0.47) greater than Fe2+ (0.69) greater than Mn2+ (0.86) greater than Co2+ (0.92) greater than Ca2+ (5.6) greater than Mg2+ (16) greater than Sr2+ (33). This was not secondary to inhibition of ICa since: (i) inhibition persisted in Ca(2+)-free solution; (ii) La3+ did not inhibit IK(M, ng) at concentrations which inhibited ICa; and (iii) organic Ca2+ channel blockers were ineffective. Inhibition comprised both depression of the maximum conductance and a positive shift of the activation curve. Addition of Ca2+ (10 microM free [Ca2+]) or Ba2+ (1 mM total [Ba2+]) to the pipette solution did not significantly change IK(M, ng). 6. IK(M, ng) was reduced by 9-amino-1,2,3,4-tetrahydroacridine (IC50 8 microM) and quinine (30 microM) but was insensitive to tetraethylammonium (IC50 greater than 30 mM), 4-aminopyridine (greater than 10 mM), apamin (greater than 3 microM) or dendrotoxin (greater than 100 nM). 7. IK(M, ng) was inhibited by bradykinin (1-10 microM) or angiotensin II (1-10 microM), but not by the following other receptor agonists: acetylcholine (10 mM), muscarine (10 microM), noradrenaline (100 microM), adrenaline (100 microM), dopamine (100 microM), histamine (100 microM), 5-hydroxytryptamine (10 microM), Met-enkephalin (1 microM), glycine (100 microM), gamma-aminobutyric acid (100 microM) or baclofen (500 microM).(ABSTRACT TRUNCATED AT 400 WORDS)

Potassium currents contributing to action potential repolarization in dissociated cultured rat superior cervical sympathetic neurones

Pharmacological blocking agents were used to assess the contributions of different K(+)-currents to spike-repolarization and early spike-afterhyperpolarization recorded in dissociated, tissue-cultured rat superior cervical sympathetic neurones using both patch-clamp and impalement microelectrode techniques. Effects of 4-aminopyridine (4-AP) and tetraethylammonium (TEA), in concentrations which selectively reduced the delayed rectifier current IK(DR) and Ca(2+)-activated K(+)-current IK(Ca, fast), respectively, indicated that IK(DR) made a significant contribution to both spike repolarization and spike afterhyperpolarization under all recording conditions, whereas the contribution of IK(Ca,fast) depended on the level of intracellular Ca(2+)-buffering. No evidence for a significant role for the transient current IK(A) could be adduced in these experiments.

Pharmacology of the putative M4 muscarinic receptor mediating Ca-current inhibition in neuroblastoma x glioma hybrid (NG 108-15) cells

1. We have assessed the potency of a range of agonists and antagonists on the muscarinic receptor responsible for inhibiting the Ca-current (ICa) in NG 108-15 hybrid cells. 2. Acetylcholine (ACh), oxotremorine-M and carbachol were potent 'full' agonists (EC50 values were 0.11 microM, 0.14 microM and 2 microM, respectively). Maximum inhibition of peak high-threshold ICa by these agonists was 39.5%. (+/-)-Muscarine, methylfurmethide and arecaidine propargyl ester (APE) were 'partial' agonists, with EC50 values of 0.54 microM, 0.84 microM and 0.1 microM, respectively. 3. Atropine, pirenzepine and himbacine were potent antagonists of muscarinic inhibition of ICa, with apparent pKB values of 9.8, 7.74 and 8.83, respectively. Methoctramine was relatively weak (pKB = 7.63). Atropine and pirenzepine depressed maximum responses to agonists, probably because these antagonists have relatively slow dissociation rates. 4. The characteristic pharmacological profile found for the M4 receptors in these functional experiments (himbacine high affinity, pirenzepine moderate to high affinity, methoctramine low affinity) corresponds well with data from earlier binding experiments (Lazareno et al., 1990). Since mRNA hybridising to probes for the m4 receptor genotype can be detected in these cells, it is suggested that these pharmacological characteristics identify the equivalent expressed receptor subtype M4.

An objective method for assessing graded electrically evoked afferent activity in humans

A problem arises in human sensorimotor studies when attempts are made to equate the intensity of electrical stimulation of a peripheral nerve with the amount of afferent activity generated. Results presented here reveal that sural recruitment curves exhibit large session to session differences both within and among subjects. These differences hinder the prediction of afferent activation based solely upon stimulus intensity. An alternative method based upon measurement of the evoked potentials is described for improving on these predictions. Sural nerve stimulation is used to demonstrate this method, but the method should be applicable wherever a peripheral nerve is accessible for electrical stimulation and evoked recordings.

The human interferon-gamma gene contains an inducible promoter that can be transactivated by tax I and II

T cells infected with the HTLV (human T cell leukemia virus)-I and -II retroviruses often express the lymphokine interferon-gamma (IFN-gamma). We sought the molecular explanation for this phenomena by co-transfecting the transactivator genes of these human retroviruses together with 5' flanking sequences of the human IFN-gamma gene linked to a heterologous reporter gene. In the presence of phytohemagglutinin or anti-T cell receptor monoclonal antibodies and phorbol 12-myristate 13-acetate, the IFN-gamma promoter is activated in human T cells, which can be further enhanced by co-transfection of the tax I or II genes. Using Bal-31 deletion analysis, we have found that induction by mitogens can be mapped to a region between -284 to -260 (bp) 5' of the transcriptional start site, which is separable from the sequence(s) further upstream which transmit the synergistic transactivation by tax I or II.

T lymphocyte-synovial fibroblast interactions induced by mycobacterial proteins in rheumatoid arthritis

An in vitro system was established in which single-cell suspensions of lymphocytes and synovial cells from the joints of patients with rheumatoid arthritis were cultured and produced an outgrowth of an organized inflammatory tissue with an extracellular matrix and capsule. The tissue outgrowth, which had histologic features of pannus, required the addition of mycobacterial antigen and interleukin-2 to the tissue culture medium and was dependent upon the presence of T lymphocytes and their interaction with synovial fibroblasts.

The naphthalenesulphonamide calmodulin antagonist W7 and its 5-iodo-1-C8 analogue inhibit potassium and calcium currents in NG108-15 neuroblastoma x glioma cells in a manner possibly unrelated to their antagonism of calmodulin

Patch clamp techniques were used to record voltage-sensitive calcium and potassium currents from NG108-15 cells. N-(6-aminohexyl)-5-chloro-1-naphthalene- sulphonamide (W7), a calmodulin (CaM) antagonist and its more potent (10 times) 5-iodo-1-C8 analogue (J8) inhibited these currents in a dose-dependent manner. The inhibition was not dependent on internal or external Ca2+. W7 was about four times more potent as an inhibitor of the transient potassium current (IC50 = 8 microM) than of the M-current or of the calcium current. J8 was also selective for the potassium currents (IC50 values: transient current 4 microM, M-current 11 microM) compared to the calcium current (IC50 36 microM). It is suggested that the inhibition does not result from an anti-CaM action of the compounds.

M-current noise and putative M-channels in cultured rat sympathetic ganglion cells

1. Whole-cell recordings of M-currents and single-channel recordings have been made in cultured rat sympathetic ganglion (SCG) neurones using the patch clamp technique. 2. Muscarine caused a reduction in macroscopic M-current relaxations, induced by voltage steps, and a concomitant reduction in whole-cell current noise. Power spectra of the muscarine-sensitive component of current noise were fitted with two Lorentzian components corresponding, on average, to 162 and 15 ms. The longer time constant was very similar to that of deactivation tail currents measured at the same potential. 3. The single-channel conductance at -30 mV was estimated from power density spectra and whole-cell current-variance relationships to be 1-2 pS. 4. Putative single M-channels, activated by depolarization, were identified in cell-attached and outside-out patches from cultured SCG neurones. In particular, the ensemble average of a small amplitude channel (estimated to be ca4 pS in physiological [K+]) in a cell-attached patch, exhibited a similar time dependence to whole-cell M-current.

Selective coupling of different muscarinic acetylcholine receptors to neuronal calcium currents in DNA-transfected cells

Acetylcholine (ACh) can inhibit calcium currents (ICa) in nerve cells by activating muscarinic ACh receptors (mAChR). There are several different genetic subtypes of mAChR. It is not known which subtype(s) are responsible for ICa inhibition. To resolve this issue, we measured ICa inhibition by ACh with patch-clamp recording, by using Ba2+ as charge carrier, in clones of NG108-15 neuroblastoma x glioma hybrid cells transfected with DNA for mAChRI, II, III and IV. Control (non-transfected) cells showed a mean maximum inhibition of peak ICa of 12.8 +/- 1.8% (n = 36) at 1 mM ACh. No consistent increase in inhibition was detected in vector-transfected cells, or in cells transformed to express mAChRI or mAChRIII. In contrast, inhibition was significantly increased in clones transformed to express mAChRII or mAChRIV. Inhibition was not correlated with the number of muscarinic receptors as determined by 3H-quinuclidinyl benzilate binding. Inhibition in both control and transfected cells was prevented by pretreatment with pertussis toxin (PTx). Inhibition persisted in the presence of extracellular or intracellular dibutyryl cyclic AMP, and hence is not because of inhibition of adenylate cyclase. We conclude that the inhibition of neuronal ICa is mediated preferentially by mAChRII and mAChRIV, via a PTx-sensitive GTP-binding protein.

Muscarinic and beta-adrenergic depression of the slow Ca2(+)-activated potassium conductance in hippocampal CA3 pyramidal cells is not mediated by a reduction of depolarization-induced cytosolic Ca2+ transients

Combined intracellular and microfluorometric recording techniques were used to evaluate whether the inhibition by cholinergic or adrenergic transmitters of the Ca2(+)-activated potassium current (IAHP) in hippocampal CA3 pyramidal cells was mediated by an alteration of depolarization-induced change in cytosolic free Ca2+ concentration [(Ca2+]i). Low concentrations of isoproterenol (1-10 microM) and muscarine (0.25-1 microM) reversibly abolished IAHP without affecting concomitant Ca2+ transients or the steady-state [Ca2+]i. Only after application of higher concentrations of muscarine, [Ca2+]i increased; in the presence of potassium channel blockers, muscarine depressed Ca2+ currents and concomitant Ca2+ transients. These observations provide direct evidence that the inhibition of IAHP by isoproterenol and muscarine are not mediated by an alteration of Ca2+ dynamics.

Neuronal properties and trophic activities of immortalized hippocampal cells from embryonic and young adult mice

The hippocampal formation elaborates trophic factors such as nerve growth factor (NGF) to support the cholinergic innervation it receives from the septal region. To further study the trophic interactions of this pathway, hippocampal cells from embryonic day 18 and postnatal day 21 mice were immortalized via somatic cell fusion to N18TG2 neuroblastoma cells. The hippocampal cell lines exhibit morphological and cytoskeletal features which are typical of their neuronal parents but which are not expressed by the neuroblastoma parent. When differentiated with retinoic acid, the hippocampal cell lines exhibit electrophysiological features similar to cultured hippocampal neurons. Many of the lines constitutively express high levels of NGF, and at least one cell line exerts a non-NGF trophic effect on the expression of choline acetyltransferase by septal neurons in vitro. These cell lines are potentially useful for investigating the neurochemical and excitable properties of hippocampal neurons and identifying novel trophic activities that promote the development and maintenance of the septohippocampal pathway.

Cancer-related maternal mortality in Massachusetts, 1954-1985

Cancer-related maternal mortality is a rare event. We report the first population-based study of this issue using data collected by the Committee on Maternal Welfare of the Massachusetts Medical Society between 1954 and 1985. The incidence of cancer-related maternal mortality during the study period fell from 3.16 to 0 per 100,000 live births. The most common cancer-associated maternal deaths were due to central nervous system tumors and hematological cancers. To determine the effects of pregnancy on cancer mortality, we compared our data with figures from the Connecticut Register of Mortality for Women aged 15-44. In the pregnant group there was a significantly higher incidence of mortality due to central nervous system tumors and a significantly lower incidence of mortality due to breast cancer. The data suggest that pregnancy may not be contraindicated for a woman with a history of breast cancer, but may be contraindicated for a woman with a history of a central nervous system tumor.

Cytosolic free calcium in hippocampal CA3 pyramidal cells

The dynamics of cytosolic free Ca2+ ([Ca2+]i) of single voltage-clamped CA3 pyramidal cells in hippocampal slice cultures is reviewed. [Ca2+]i amounts to about 30 nM at resting membrane potential and increases slowly when the membrane potential is clamped at more positive values (up to 500 nM at -30 mV). Short lasting depolarizations (40-100 ms) induce a transient rise in [Ca2+]i which activates a slow aftercurrent (IAHP). The muscarinic or beta-adrenergic depression of IAHP is not accompanied by any change in the dynamics of Ca2+ and appears, therefore, to result primarily from an inhibition of the K(+)-current itself or of the ability of Ca2+ to activate the current. At higher concentrations than those required to inhibit IAHP, muscarine produces a pronounced inward current and this is accompanied by a rise in resting [Ca2+]i concentration.

Membrane currents in hippocampal neurons

This chapter reviews properties and functions of endogenous ionic currents in hippocampal neurones. Currents considered are: Na currents INa(fast) and INa(slow); Ca currents; K currents--delayed rectifier IK(DR), transient IK(A), 'delay' current IK(D) and M current IK(M); inward rectifiers IQ, IK(IR) and ICl(V); Ca-activated currents IK(Ca) (IC and IAHP), ICl(Ca) and Ication(Ca); Na-activated currents; and anoxia-induced currents.