Lack of effect of transcutaneous electrical nerve stimulation upon experimentally induced delayed onset muscle soreness in humans

The aim of the current study, for which ethical approval was obtained, was to assess the hypoalgesic efficacy of transcutaneous electrical nerve stimulation (TENS) upon acute stage (72 h) experimentally induced delayed onset muscle soreness (DOMS). TENS naive subjects (n = 48; 24 male and 24 female) were recruited, screened for relevant pathology and randomly allocated to one of four experimental groups: control, placebo, low TENS (200 microseconds; 4 Hz) or high TENS group (200 microseconds; 110 Hz). DOMS was induced in a standardised fashion in the non-dominant elbow flexors of all subjects by repeated eccentric exercise. Subjects attended on three consecutive days for treatment and measurement of elbow flexion, extension and resting angle (Universal goniometer), Mechanical Pain Threshold/tenderness (algometer) and pain (Visual Analogue Scale (VAS)) on a daily basis, plus McGill Pain Questionnaire on the third day only. Measurements were taken before and after treatment under controlled double blinded conditions. Analysis of results using repeated measures analysis of variance (ANOVA) and post hoc tests showed some inconsistent isolated effects of high TENS (110 Hz) compared to the other conditions upon resting angle and flexion scores; no significant effects were found for any of the other variables. These results provide no convincing evidence for any measurable hypoalgesic effects of TENS upon DOMS-associated pain at the stimulation parameters used here.

The effect of H-wave therapy upon conduction in the human superficial radial nerve in vivo

This study was designed to investigate the putative neurophysiological effects of so-called 'H-wave therapy' (HWT), a form of electrical stimulation, upon conduction latencies in the human superficial radial nerve. Antidromic compound action potentials were recorded from the superficial radial nerve in the dominant forearms of thirty-two healthy human volunteers, who were randomly assigned to a control or one. of three HWT groups (2, 16 or 60 Hz). HWT was applied under double-blind conditions for three consecutive 5 min periods. Action potentials were recorded pre-HWT and immediately after each period of stimulation, i.e. at 5, 10 and 15 min. Analysis of results showed significant increases in negative and positive peak latencies in the 16 Hz and, to a greater extent, in the 60 Hz groups when compared with controls. No changes in conduction latency were observed in the low frequency 2 Hz group. The results of this study demonstrate that HWT applied at frequencies of 16 and 60 Hz may produce a direct, localized effect upon conduction in underlying peripheral nerves.

Differentiation of the human monocytic cell line U937 results in an upregulation of the calcium release-activated current, ICRAC

1. Single cell fura-2 fluorescence measurements and whole-cell patch clamp recordings were used to investigate the effects of macrophage-like differentiation, induced by dibutyryl cAMP (dbcAMP), on Ca2+ influx triggered by Ca2+ store depletion in the human monocytic cell line, U937. 2. In differentiated cells, the rise in intracellular [Ca2+] following store depletion by thapsigargin (TG) in nominally Ca(2+)-free solution was 94% greater and the [Ca2+]i rise on subsequent re-addition of external Ca2+ (2 mM) was 292% greater than in undifferentiated cells. 3. Under conditions where [Ca2+]i was buffered by BAPTA, TG-induced store depletion failed to activate a detectable inward Ca2+ current in undifferentiated U937 cells. Under identical conditions, store depletion of differentiated U937 cells generated an inwardly rectifying Ca(2+)-selective current which showed no reversal from -140 to +30 mV and was blocked by 1 microM external La3+; characteristics of the calcium release-activated Ca2+ current (ICRAC) identified in other cells. 4. We conclude that U937 cells show a differentiation-dependent upregulation of a store-mediated Ca2+ entry pathway, identified as ICRAC, which is not correlated with the small associated increase in the size of TG-sensitive Ca2+ pools.

Photochemical formation of singlet molecular oxygen in illuminated aqueous solutions of several commercially available sunscreen active ingredients

Evidence is presented for the photochemical formation of singlet molecular oxygen (1O2) in air-saturated aqueous solutions of several sunscreen active ingredients using sunlight-range illumination. This is of significance because (1) 1O2 is known to be cytotoxic, and (2) there have been several reports of toxic effects associated with the use of some sunscreens; most notably, with p-aminobenzoic acid (PABA). Illuminated aqueous solutions of PABA, 2-ethylhexyl p-(dimethylamino)benzate (ODPABA), 2-hydroxy-4-methoxybenzophenone (BZ3), 2,2'-dihydroxy-4-methoxybenzophenone (BZ8), 2-ethylhexyl 2-cyano-3,3-diphenylacrylate (OCR), 2-ethylhexyl p-methoxycinnamate (OMC), and 2-ethylhexyl salicylate (OCS) were evaluated individually for 1O2 formation. Furfuryl alcohol (FFA), a well-known chemical trap for 1O2, was added to each of the aqueous sunscreen solutions. The FFA was consumed when solutions of PABA, ODPABA, OMC, and OCR were illuminated, but no loss of FFA other than by direct photolysis occurred in solutions of BZ3, BZ8, or OCS. There was also no significant loss of FFA in any of these solutions kept in the dark. Further evidence for the formation of 1O2 in illuminated aqueous sunscreen solutions is provided by the results of experiments in which individual solutions containing sunscreen active ingredients and FFA that were diluted with D2O exhibited an increased rate of FFA consumption while the addition of azide ion (N3-) reduced the rate of FFA consumption. Continuous sunlight-range illumination of aqueous PABA solutions produced significantly higher steady-state concentrations of 1O2 than in solutions containing any of the other sunscreen active ingredients evaluated. The substituted benzophenone compounds (BZ3 and BZ8) and the salicylate-based compound (OCS) not only appear to produce no 1O2, but they also appear to produce no other reactive oxidant species that are capable of consuming FFA. This indicates that BZ3, BZ8, and OCS may be peferable, from the standpoint of toxic oxidant formation, for use as sunscreen active ingredients when compared to the other compounds evaluated in this study.

Photochemical formation of singlet molecular oxygen (1O2) in illuminated aqueous solutions of p-aminobenzoic acid (PABA)

Evidence is presented for the photochemical formation of singlet molecular oxygen (1O2) in air-saturated buffered aqueous solutions of p-aminobenzoic acid (PABA) using sunlight-range illumination. This is significant because PABA is widely used as an active ingredient in sunscreen preparations that are applied to the surface of the skin and 1O2 is known to cause oxidative damage to cells via the formation and subsequent reactions of lipid peroxides. Furfuryl alcohol (FFA), a well known chemical trap for 1O2, was added to aqueous PABA solutions prior to illumination. The FFA was consumed when the solution was illuminated, but no loss of FFA occurred in the dark and loss by direct photolysis was negligibly slow. Further evidence for the formation of 1O2 in illuminated aqueous PABA solutions is provided by the results of experiments in which individual solutions containing PABA and FFA that were diluted with D2O exhibited an increased rate of FFA consumption due to the increased lifetime and concentration of 1O2 in this solvent.

Reactive oxygen species inducible by low-intensity laser irradiation alter DNA synthesis in the haemopoietic cell line U937

BACKGROUND AND OBJECTIVE

The purpose of this study was to evaluate the possible role of reactive oxygen species (ROS) in mediating previously recorded alterations in DNA synthesis, inducible by low-intensity laser irradiation (LILI), in the haemopoietic cell line U937.

STUDY DESIGN/MATERIALS AND METHODS

The ability of LILI (660 nm, 12 mW, 5 kHz) to induce ROS from U937 cells was assessed spectrophotometrically at energy densities (E.D.) from 1.0 to 11.5 J/cm2. In order to assess whether laser-induced ROS could alter cellular proliferation DNA synthesis was measured post-irradiation, by the incorporation of tritiated thymidine (3H-TdR) into the cells in both the presence and absence of the antioxidant catalase (CAT).

RESULTS

Detectable ROS were produced post-irradiation only from the differentiated form of the cell line. Analysis by Student's t-test for unrelated groups showed a significant difference, at E.D.s 2.9 and 8.6 J/cm2, in the extent of DNA synthesis occurring in cells irradiated in the presence of CAT or in its absence.

CONCLUSION

These findings demonstrate that laser-inducible ROS can mediate laser's effects on this cell line.

IgG-induced Ca2+ oscillations in differentiated U937 cells; a study using laser scanning confocal microscopy and co-loaded fluo-3 and fura-red fluorescent probes

We have investigated, at the single cell level, intracellular Ca2+ ([Ca2+]i) modulations triggered by the high affinity receptor for IgG, Fc gamma RI, in the monocytic cell line, U937. Cells were co-loaded with the Ca(2+)-sensitive dyes, Fluo-3 and Fura-Red, by incubation with their acetoxymethyl (AM) esters and confocal ratio imaging was used to monitor the [Ca2+]i changes induced by antibody cross-linking of IgG-loaded Fc gamma RI. A single Ca2+ spike was observed in 81% of untreated cells whereas dibutyryl cAMP-induced differentiation into a more macrophage cell type resulted in a sub-population of cells (44%) responding to receptor cross-linking with calcium oscillations. This change in calcium signalling may explain the difference in functional responses triggered by Fc gamma RI in monocytes and macrophages. Analysis of the Fluo-3 and Fura-Red fluorescence, after AM-ester loading, showed that both dyes have similar photobleach rates and intracellular localization allowing compensation for shifts in focal plane, dye photobleaching and non-uniformity of dye loading. In addition, because the binding kinetics of both dyes are equivalent, accurate temporal information can be gained about [Ca2+] changes. There are, however, two major problems with this dual indicator technique. Firstly, loading from AM esters results in considerable variation between cells in the intracellular concentration ratio of the two dyes, making calibration difficult. Secondly, the fluorescence ratio, Fluo-3/Fura-Red, behaves non-linearly at Ca2+ concentrations less than approximately 500 nM and comparison with Fura-2-loaded single cell photometry studies suggests there is considerable amplitude distortion of the signal when the ratios are displayed on a linear scale. These problems may considerably limit the application of Fluo-3/Fura-Red ratiometric measurements.

The interaction between human Fc gamma RI and the gamma-chain is mediated solely via the 21 amino acid transmembrane domain of Fc gamma RI

We have established a biological assay to investigate the nature of the non-covalent interaction between two integral type I membrane proteins, Fc gamma RI and gamma-chain. Fc gamma RI, the human high affinity receptor for immunoglobulin G (IgG), is expressed on the surface of macrophages and monocytes and mediates a broad range of important immunological functions. Fc gamma RI relies on a functional interaction with a second integral type I membrane protein, gamma-chain, to mediate many of these functions. For example, Fc gamma RI can only mediate phagocytosis of IgG-coated particles in COS cells when co-expressed with gamma-chain. We have previously shown that the cytoplasmic domain of Fc gamma RI is not necessary for this functional interaction. In this study we have used the phagocytosis assay to investigate the role of the transmembrane region of Fc gamma RI in mediating this functional interaction with gamma-chain by using mutant and chimeric forms of the receptor. Three mutants, which introduce or remove charged residues from a conserved 10 amino acid stretch of amino acids in the proximal transmembrane region of Fc gamma RI, were able to mediate phagocytosis of IgG-coated particles. In contrast, two chimeric receptors, In which 21 of the amino acids in the distal transmembrane region of Fc gamma RI were replaced with the transmembrane region of the related receptors CD2 or LFA3, were expressed but failed to interact functionally with gamma-chain to mediate phagocytosis. Thus, these mutants demonstrate that the interaction between human Fc gamma RI and gamma-chain is mediated solely via these 21 amino acids in the transmembrane domain of Fc gamma RI.

Rapid reaction of singlet molecular oxygen (1O2) with p-aminobenzoic acid (PABA) in aqueous solution

The reaction of singlet molecular oxygen (1O2) with p-aminobenzoic acid (PABA) is quite rapid. The rate constant for reaction of 1O2 with PABA was measured in buffered aqueous solution by the method of competition kinetics and found to be 8.9 x 10(8) M-1 sec-1. The results of a Stern-Volmer analysis indicate that additional loss of 1O2 does not occur through physical quenching by PABA. Although illuminated PABA solutions are known to form 1O2, it appears that PABA is also a very efficient sink for 1O2.

Beta-adrenergic receptor downregulation and recovery in heart and lung in the Fischer 344 rat: effects of aging and correlation with mRNA levels

Using indirect methods to downregulate beta-adrenergic receptor (BAR) density, several investigators have observed an aging-related delay in the recovery of BAR density after downregulation and suggested this finding may in part explain the decreased beta-adrenergic responsiveness associated with aging. We downregulated BAR density in male Fischer 344 rats ages 3, 12, and 24 months using the direct BAR agonist, metaproterenol. Lung and heart BAR density and BAR mRNA levels were measured daily for 5 days during recovery. Heart BAR density was downregulated significantly more in the 24-month compared to the 3-month-old animals (ANOVA p < .05). The rate of recovery of heart BAR density was greater in the 24-month compared to the 3-month-old animals (ANOVA, p = .05). Lung BAR density showed no significant age-related differences at baseline, after downregulation, or during recovery. There was no significant change in lung or heart BAR mRNA levels observed in association with downregulation of BAR density. The previously documented decrease in myocardial beta-adrenergic responsiveness with aging in this animal appears to not be related to delayed or incomplete recovery of BAR density after agonist-induced downregulation, but may be associated with greater initial downregulation of heart BAR density.

Urinary Tamm-Horsfall protein increased after potassium citrate therapy in calcium stone formers

OBJECTIVES

To evaluate the effect of oral potassium citrate therapy on urinary excretion rates of citrate. Tamm-Horsfall protein (THP), and on calcium oxalate monohydrate crystal agglomeration inhibition [tm], in patients with recurrent calcium stone formation.

METHODS

To evaluate the effect of oral therapy with potassium citrate on urinary citrate, THP, and [tm], 24-hour urine samples were collected before and at least 2 months after initiation of oral potassium citrate therapy in 33 calcium stone-forming patients who had no dietary restrictions. The citrate concentration was measured by an adaptation of a citrate lyase method. Urinary disaggregated THP concentration was determined with a quantitative enzyme-linked immunosorbent assay. The [tm] was determined by observing the effects of patients' urine, before and after oral potassium citrate therapy, on the uptake of 45Ca2+ onto the surfaces of added preformed calcium oxalate crystals in a supersaturated solution of calcium oxalate, using the in vitro kinetic method described by other investigators.

RESULTS

We observed an increased urinary excretion rate of citrate from a mean of 1.9 mmol/24 h prealkali to 2.6 mmol/24 h postalkali (P < 0.0004) and of THP from a mean of 94.0 mg/24 h prealkali to 199.3 mg/24 h postalkali (P < 0.0016). A corresponding increase in [tm] from a mean of 177.1 minutes prealkali to 221.0 minutes postalkali (P < 0.024) was also observed.

CONCLUSIONS

To our knowledge this is the first report correlating increased urinary citrate with THP excretion rate following oral alkalinization with potassium citrate in calcium stone formers. Of clinical importance is the corresponding increase in [tm], which was previously shown to be inversely related to stone-forming activity. Moreover, urinary citrate and THP are known to have a synergistic effect on [tm]. Our data suggest that the effectiveness of potassium citrate therapy in calcium stone-forming patients may, at least in part, be due to increased levels of THP.

Increased capacity for store regulated calcium influx in U937 cells differentiated by treatment with dibutyryl cAMP

We have investigated the mechanisms underlying calcium signalling evoked by cross-linking of the high affinity IgG receptor (Fc gamma RI) in populations of the human monocyte-like cell line, U937, following activation of the cells by cytokine treatment, or differentiation to a more macrophage-like state by treatment with dibutyryl cAMP (Bt2cAMP). We have shown previously that a larger and more prolonged entry of external calcium occurs in Bt2cAMP-differentiated cells, although there is a smaller initial release from internal stores in these cells than in those activated by IFN-gamma treatment. In this paper we demonstrate, by use of the endomembrane Ca(2+)-ATPase inhibitor, thapsigargin, that this effect is explained (at least in part) by an enhanced capacity for store regulated entry of calcium in Bt2cAMP-differentiated cells.

Transcutaneous electrical nerve stimulation. Relevance of stimulation parameters to neurophysiological and hypoalgesic effects

Although Transcutaneous Electrical Nerve Stimulation (TENS) has become a popular modality in pain management over the past 20 yr, there is still debate over its mechanisms of action and the precise relevance of stimulation parameters to its hypoalgesic effects. Thus, confusion still surrounds the selection of optimal stimulation parameters. Two separate studies (total n = 88) were carried out to investigate the effect of four combinations of TENS pulse durations (50 microseconds & 200 microseconds) and frequencies (4 Hz and 110 Hz) on nerve conduction in the human superficial radial nerve and on Mechanical Pain Threshold (MPT) within the associated sensory distribution of the nerve over the dorsum of the hand. Results showed that application of one combination of TENS parameters (110 Hz, 200 microseconds) directly over the course of the nerve produced a significant increase in both peripheral nerve conduction latency (P < or = 0.05; analysis of variance (ANOVA)) and MPT (P < or = 0.01). In addition, there was a high correlation (r = 0.9) between shifts in MPT and negative peak latency for the groups treated with this combination of TENS parameters. The results of this study thus illustrate that combinations of TENS parameters are important to the peripheral neurophysiological effects of this modality and, further, its associated hypoalgesic effects, at least on the model of pain used here.

Detection of reverse transcriptase in culture medium for mammary tumour cell lines: a comparison of an established radio-labelling technique and a contemporary non-isotopic technique

Classically, radio-label techniques have been employed to analyse biological samples for reverse transcriptase (RT) activity. More recently, however, non-isotopic kits have been developed for retroviral quantification. Nevertheless, until the present investigation it has not been known if these contemporary methods are more sensitive at detecting reverse transcriptase activity. In our study, a non-isotopic ELISA method was shown to be considerably more sensitive than the radio-label technique at detecting reverse transcriptase in growth medium used to culture the murine breast cancer cell line GR/A. Using the ELISA, less reverse transcriptase activity was demonstrated in growth medium from human mammary adenocarcinoma MCF-7 cells than the murine source. This ELISA did not detect reverse transcriptase activity from a pure source of Moloney murine leukaemia virus. In light of this, the broad applicability of this ELISA for reverse transcriptase from different viral sources must be investigated before it can be used to monitor biological supernatants for the presence of retroviruses.

Fc gamma receptor-mediated phagocytosis requires tyrosine kinase activity and is ligand independent

Receptors for the invariant chain of immunoglobulins (FcR) define the cellular response to specific antigens. Fc gamma R recognize IgG and so elicit a variety of effector functions including phagocytosis. We are interested in the structural determinants for Fc gamma R-mediated phagocytosis, specifically Fc gamma RI(p135) and Fc gamma RIIa isoforms. The low-affinity receptor, Fc gamma RIIa, is found on macrophages and its cytoplasmic domain contains a tyrosine activation motif which has previously been shown to regulate endocytosis. In contrast, Fc gamma RI has no known signaling motifs, though a functional interaction has recently been demonstrated with the gamma chain of the high-affinity receptor for IgE, Fc epsilon RI. This accessory molecule has a cytoplasmic tyrosine activation motif implicated in signal transduction. Here we demonstrate that although Fc gamma RI transiently expressed on COS-7 cells is able to rosette opsonized SRBC, it cannot phagocytose them. If the cytoplasmic domain of either gamma chain or Fc gamma RIIa replaces that of Fc gamma RI in a chimeric receptor, efficient phagocytosis occurs. This particle ingestion is sensitive to the tyrosine kinase inhibitor genistein. Chimeric receptors where the extracellular domain of either Fc gamma RI or Fc gamma RIIa is replaced with that of CD2, a T cell antigen, indicate that Fc gamma R-mediated phagocytosis is ligand independent. We conclude that phagocytosis is dependent upon close particle apposition, tyrosine kinase activity, and that the process is ligand independent.