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Biomedical subjects

J M Allen

Publications and source records attributed to J M Allen.

At least 73 records · Page 4Linked to original sources
PubMed1997

Identification and elimination of replication-competent adeno-associated virus (AAV) that can arise by nonhomologous recombination during AAV vector production.

Adeno-associated virus (AAV) vector preparations are often contaminated with variable amounts of replication-competent AAV (rcAAV), which may influence the behavior of these vectors both in cultured cells and in animals. A packaging plasmid/vector plasmid system containing no significant homology and lacking the wild-type AAV p5 promoter was constructed to eliminate the production of wild-type AAV by recombination. Still, rcAAV was detected in vector produced by cotransfection of these plasmids at large scale. Sequence analysis revealed that nonhomologous recombination was responsible for the generation of these novel rcAAVs. A new AAV packaging plasmid carrying separate rep and cap expression cassettes in opposite transcriptional orientations was constructed. AAV vector preparations produced by using this packaging construct did not contain rcAAV.

Animals↗
PubMed1996

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.

Bucladesine↗
PubMed1996

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.

Catalase↗
PubMed1996

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.

Adult↗
PubMed1996

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.

4-Aminobenzoic Acid↗
PubMed1996

Delayed-onset muscle soreness: lack of effect of combined phototherapy/low-intensity laser therapy at low pulse repetition rates.

A double-blind, placebo-controlled study using male subjects (n = 60), was conducted to investigate the efficacy of three different frequencies of combined phototherapy/low-intensity laser therapy (CLILT) in alleviating the signs and symptoms of delayed-onset muscle soreness (DOMS). The study was approved by the University's ethical committee. After screening for relevant pathologies, recent analgesic or steroid drug usage, current pain, diabetes, or current involvement in regular weight-training activities, subjects were randomly allocated to one of five experimental groups: Control, Placebo, or 2.5-Hz, 5-Hz, or 20-Hz CLILT groups (660-950 nm; 31.7 J/cm2; pulsed at the given frequencies for a duration of 12 min; n = 12 all groups). Once baseline measurements were obtained, DOMS was induced in the nondominant arm, which was exercised in a standardized fashion until exhaustion, using repeated eccentric contractions of the elbow flexors. The procedure was repeated twice more to ensure exhaustion was achieved, after which subjects were treated according to group allocation. In the CLILT/placebo groups, the treatment head was applied directly to the affected arm at the level of the musculotendinous junction. Subjects returned on two consecutive days for further treatment and assessment. The range of variables used to assess DOMS included range of movement (universal goniometer), mechanical pain threshold/tenderness (algometer) and pain (visual analogue scale and McGill Pain Questionnaire). Measurements were taken before and after treatment on each day, except for the McGill Pain questionnaire, which was completed at the end of the study. Analysis of results using repeated measures and one-factor analysis of variance with relevant post hoc tests showed significant changes in ranges of movement accompanied by increases in subjective pain and tenderness for all groups over time (p = 0.0001); however, such analysis failed to show any significant differences between groups on any of the days. These results thus provide no convincing evidence for any putative hypoalgesic effect of CLILT upon DOMS at the parameters used here.

Adult↗
PubMed1996

Manipulation of transcutaneous electrical nerve stimulation variables has no effect on two models of experimental pain in humans.

Two separate studies investigated the hypoalgesic effect of manipulation of Transcutaneous Electrical Nerve Stimulation (TENS) parameters on two models of experimental pain: the Submaximal Effort Tourniquet Technique and cold-pressor pain. For the first study, 32 healthy subjects (16 male and 16 female) attended once for the purpose of cold-pressor pain induction that involved immersion of the nondominant hand in a water bath at 0 degree C. Subjects were allocated to Control, Placebo, or 1 of 2 treatment groups (110 or 4-Hz TENS). Pain threshold measurements (time to withdrawal of hand in seconds) were obtained over six standardised cold pain cycles (i.e., two before stimulation onset, three during stimulation, and one cycle after stimulation). In the second study, 48 healthy volunteers (24 male and 24 female) attended on two occasions, 48 h apart, for the purposes of ischaemic pain induction. On the first attendance, baseline data were obtained and on the second, subjects were randomly allocated to Control, Placebo, or one of four treatment groups with different combinations of stimulation frequencies and pulse durations (4 or 110 Hz and 50 or 200 microseconds). Measurements of "current pain intensity" and "worst pain experienced" were obtained via the Visual Analogue Scale (VAS) and the McGill Pain Questionnaire (MPQ), respectively. Analysis of variance performed on both sets of collected data revealed no significant differences between any of the groups, thus indicating no apparent relevance of manipulation of TENS parameters using these models of pain. Several hypotheses are suggested to explain these findings.

Adult↗
PubMed1996

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.

Adolescent↗