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T O'Halloran

Publications and source records attributed to T O'Halloran.

17 recordsLinked to original sources
PubMed2003

Modified implanted drop foot stimulator system with graphical user interface for customised stimulation pulse-width profiles.

A modified implanted drop foot stimulator that allows cyclic modulation of the stimulation pulse-width during gait has been developed. Stimulation was on two channels of a four-channel 12 polar cuff electrode. The stimulator allowed modulation of stimulation pulse-width, between 0 and 255 micros, on both channels throughout the swing and stance phases of gait. Stimulation was applied between 17 and 40 Hz. The clinician can specify an infinite range of stimulation profiles on a desktop computer, using a user-friendly LabVIEW interface. The desktop program generated a stimulation profile table of 100 values, which was then downloaded to the drop foot stimulator. As each phase of gait imposed different biomechanical demands on the ankle dorsiflexor muscles, different stimulation intensities were desirable, throughout gait, to match these demands. Moreover, as the gait of each person with hemiplegia is unique, the biomechanical demands imposed throughout the gait cycle for each user of a drop foot stimulator are unique. This stimulator architecture allowed the clinician to, specify stimulation intensities individually, at each phase of the gait cycle for each drop foot stimulator user. The stimulator was evaluated on a male hemiplegic subject. It was used to increase the stimulation pulse-width by 150% at 5% of gait cycle prior to heel strike. The system performed well, with the ankle angle at heel strike increasing by 5 degrees owing to this increased pulse-width.

Electric Stimulation Therapy↗
PubMed1999

Molecular characterization of rabE, a developmentally regulated Dictyostelium homolog of mammalian rab GTPases.

The superfamily of small GTPases includes a subgroup, rab proteins, thought to function in the regulation of discrete steps of membrane traffic. Using a screen based on the polymerase chain reaction, we identified six partial gene sequences of novel rab genes from the soil slime mold amoeba, Dictyostelium. Stretches of conserved sequence for these genes identified them clearly as rab GTPases; unique sequences showed these were novel rab genes. A full-length clone for one gene, which we named rabE, was characterized in detail. The coding sequence of rabE was 1.1 kb in length and contained three introns. RNAse protection analysis revealed rabE expression to be under developmental regulation, with an onset of message expression after 8 h of development. Comparison of the rabE amino acid sequence with the database showed that its unique domains were most similar to the products of four mammalian rab genes. Interestingly, only the rabE protein and its four mammalian homologs contained the sequence WDIAGQE, a variation of a conserved GTPase domain. The WDIAGQE motif thus defines a subgroup of rab proteins. Identification of a Dictyostelium homolog of this group of proteins opens an experimental system to explore the structure and function of this group of WDIAGQE-containing rab proteins.

Amino Acid Sequence↗
PubMed1997

The effect of continuous passive motion duration and increment on range of motion in total knee arthroplasty patients.

There is insufficient information on continuous passive motion (CPM) parameters in total knee arthroplasty patients for optimal patient outcomes. We compared CPM duration and increments on active and passive range of motion (ROM) in patients who underwent a unilateral total knee arthroplasty due to degenerative joint disease. Forty-five total knee arthroplasty patients were randomly assigned to either a control group, a short CPM duration (3-5 hours per day) group with CPM ROM increased 5 degrees twice daily, a short CPM duration group with CPM ROM increased daily to patient tolerance, a long CPM duration (10-12 hours per day) group with CPM ROM increased 5 degrees twice daily, or a long CPM duration group with CPM ROM increased daily to patient tolerance. Active and passive flexion and extension were measured goniometrically on each postoperative day that the patient was treated by physical therapy. No statistically significant differences between groups were found for baseline and final postoperative ROM. The CPM groups did not maintain the parameters assigned and were combined, revealing an enhanced rate of change of flexion. Most patients opted for a CPM duration of between 4 and 8 hours per day and the patient-preferred CPM incremental increase in ROM was 6-7 degrees/day.

Aged↗
PubMed1994

A Rab4-like GTPase in Dictyostelium discoideum colocalizes with V-H(+)-ATPases in reticular membranes of the contractile vacuole complex and in lysosomes.

In the course of screening a cDNA library for ras-related Dictyostelium discoideum genes, we cloned a 0.7 kb cDNA (rabD) encoding a putative protein that was 70% identical at the amino acid level to human Rab4. Rab4 is a small M(r) GTPase, which belongs to the Ras superfamily and functions to regulate endocytosis in mammalian cells. Southern blot analysis indicated that the rabD cDNA was encoded by a single copy gene while Northern blot analysis revealed that the rabD gene was expressed at relatively constant levels during growth and differentiation. Affinity-purified antibodies were prepared against a RabD fusion protein expressed in bacteria; the antibodies recognized a single 23 kDa polypeptide on western blots of cell extracts. Density gradient fractionation revealed that the RabD antigen co-distributed primarily with buoyant membranes rich in vacuolar protons pumps (V-H(+)-ATPases) and, to a lesser extent, with lysosomes. This result was confirmed by examining cell lines expressing an epitope-tagged version of RabD. Magnetically purified early endocytic vesicles and post-lysosomal vacuoles reacted more weakly with anti-RabD antibodies than did lysosomes. Other organelles were negative for RabD. Double-label indirect immunofluorescence microscopy revealed that RabD and the 100 kDa V-H(+)-ATPase subunit colocalized in a fine reticular network throughout the cytoplasm. This network was reminiscent of spongiomes, the tubular elements of the contractile vacuole system. Immunoelectron microscopy confirmed the presence of RabD in lysosome fractions and in the membranes rich in V-H(+)-ATPase. We conclude that a Rab4-like GTPase in D. discoideum is principally associated with the spongiomes of contractile vacuole complex.

Amino Acid Sequence↗
PubMed1992

Nitrogen chemical structure in DNA and related molecules by X-ray absorption spectroscopy.

The electronic environment of nitrogen in nucleic acid bases, nucleotides, polynucleotides and DNA has been studied, for the first time using X-Ray Absorption Near-Edge Spectroscopy (XANES). Generally, the spectra of these complex molecules consist of low energy bands corresponding to 1s-->pi* transitions and high energy bands corresponding to 1s-->sigma* transition, as illustrated using several nitrogen model compounds. The 1s-->pi* transitions show particular sensitivity to the chemical environment of the nitrogen. Oxygen substitution on ring carbon atoms generally results in a significant blue shift of the lowest 1s-->pi* bands while halogen substitution results in a small blue shift. These observations illustrate the significance of the disturbance of the aromatic ring system produced by exocyclic carbonyl groups. Direct substitution on the nitrogen frequently results in significant spectral perturbations. Differences between the spectra of the polynucleotides and the sums of spectra of the individual nucleotides point to the effects of hydrogen-bonding in complementary double-helix structures. The XANES spectrum of a DNA sample with a known ratio of the polynucleotides is equivalent to the weighted sum of the spectra of individual polynucleotides, indicating that the difference in base stacking interactions produces negligible spectral effects. The variability of nitrogen K-edge spectra in these samples and in protein may be useful for chemically specific imaging using X-ray microscopes.

Animals↗
PubMed1987

Metalloregulatory DNA-binding protein encoded by the merR gene: isolation and characterization.

The MerR protein mediates the induction of the mercury resistance phenotype in bacteria; it has been isolated in order to study the effects of metal-ion induced changes in the metabolism of prokaryotic cells at the molecular level. After DNA sequences responsible for negative autoregulation were removed, the 16-kilodalton protein was overproduced and purified to more than 90 percent homogeneity by a salt extraction procedure that yields about 5 milligrams of protein per gram of cells. Complementation data, amino terminal analysis, gel filtration, and deoxyribonuclease I protection studies demonstrate that the purified merR gene product is a dimer under nondenaturing conditions and that it binds specifically to DNA, in the presence and absence of mercury, at a palindromic site which is directly between the -10 and -35 regions of the structural genes and adjacent to its own promoter. These initial results indicate that MerR is a DNA-binding metalloregulatory protein that plays a central role in this heavy metal responsive system and they delineate an operator site in the mer operon.

Amino Acid Sequence↗
PubMed1986

Purification of a 190 kDa protein from smooth muscle: relationship to talin.

Several studies of vinculin-binding proteins have described a 190 kDa protein in chicken gizzard smooth muscle which binds radioiodinated vinculin. We have purified and studied the 190 kDa protein from chicken gizzard smooth muscle. By indirect immunofluorescence, an antiserum raised against the 190 kDa protein stains adhesion plaques (focal contacts), ruffling membranes, and fibrillar streaks on the dorsal and ventral surfaces of fibroblasts. Both the binding to vinculin and the location of the protein in fibroblasts are properties shared with talin, a 215 kDa protein in smooth muscle and fibroblasts. Because antisera against talin and the 190 kDa cross-react the relationship of these two proteins has been investigated further. Upon prolonged storage at 4 degrees C, purified talin degrades into a 190 kDa fragment. A 190 kDa fragment is also generated from talin by the Staphylococcus aureus V-8 proteinase and by trypsin. Comparison of partial peptide maps of talin and the 190 kDa protein reveal that the proteins are very similar and when the 190 kDa fragment of talin is compared with the purified 190 kDa protein by partial proteolytic digestion no differences are found in the pattern of peptides generated. In addition, the amount of 190 kDa protein detected in muscle tissues excised from chick embryos can be drastically reduced if proteinase inhibitors are added to the tissue homogenates. We conclude that the purified 190 kDa dalton protein is a proteolytic fragment of talin. Although markedly reduced by proteinase inhibitors, detection of the 190 kDa protein is not completely abolished, suggesting that some talin may already be cleaved within living cells.

Animals↗
PubMed1986

Demonstration of a relationship between talin and P235, a major substrate of the calcium-dependent protease in platelets.

Talin is a 225,000-Dalton protein we have purified from smooth muscle. In chick embryo fibroblasts talin is found in adhesion plaques (focal contacts), areas where the cell is closely apposed to the substratum. In comparison with other cytoskeletal proteins, we found talin to be unusually susceptible to proteolysis and have identified a 190,000-Dalton proteolytic fragment of talin in the immunoblots of many tissues. These observations raised the possibility that the cleavage of talin to this fragment has physiological relevance. One system that we have investigated in which significant proteolysis occurs is platelets. During platelet activation several high-molecular-weight proteins are cleaved to lower-molecular-weight forms. Here we demonstrate that talin is closely related to one of these platelet high-molecular-weight proteins, P235. The purification of talin is comparable to that developed for P235, and the two proteins have similar biophysical properties. In addition, antibodies raised against chicken gizzard talin recognize P235 in purified form as well as in crude platelet extracts. The platelet protein also resembles smooth-muscle talin in its susceptibility to endogenous proteolysis: P235 is rapidly cleaved to a 190-200 kD polypeptide by a calcium-activated protease found in platelet extracts. Moreover, partial proteolysis of P235 and talin with chymotrypsin, elastase, or trypsin also generates remarkably similar one-dimensional peptide maps. Because of their similar biophysical properties, immunological crossreactivity, and similar one-dimensional partial peptide maps, we conclude that P235 is the platelet form of talin.

Animals↗
PubMed1986

Talin at myotendinous junctions.

Junctions formed by skeletal muscles where they adhere to tendons, called myotendinous junctions, are sites of tight adhesion and where forces generated by the cell are placed on the substratum. In this regard, myotendinous junctions and focal contacts of fibroblasts in vitro are analogues. Talin is a protein located at focal contacts that may be involved in force transmission from actin filaments to the plasma membrane. This study investigates whether talin is also found at myotendinous junctions. Protein separations on SDS polyacrylamide gels and immunolabeling procedures show that talin is present in skeletal muscle. Immunofluorescence microscopy using anti-talin indicates that talin is found concentrated at myotendinous junctions and in lesser amounts in periodic bands over nonjunctional regions. Electron microscopic immunolabeling shows talin is a component of the digitlike processes of muscle cells that extend into tendons at myotendinous junctions. These findings indicate that there may be similarities in the molecular composition of focal contacts and myotendinous junctions in addition to functional analogies.

Animals↗
PubMedDate not supplied

Identification of talin as a major cytoplasmic protein implicated in platelet activation.

During platelet activation there is a major reorganization in the platelet cytoskeleton that accompanies a rapid change in platelet shape. Many of the events associated with activation are attributed to a rise in calcium concentration within the platelet cytoplasm. One direct consequence of the elevated calcium is the activation of a calcium-dependent protease that cleaves a major platelet protein of relative molecular mass (Mr) approximately 235,000 (235K) to 200K. This protein, P235, has been purified and reported to interact with actin, but the significance of the proteolytic cleavage is unknown. Talin, a cytoskeletal protein in smooth muscle and fibroblasts, binds vinculin and, together with vinculin, is localized in fibroblasts at sites of actin-membrane attachment. Talin and P235 have similar purification procedures, sedimentation coefficients and Stokes' radii (ref. 6 and Molony et al., unpublished observations). Of particular significance, talin is readily cleaved by proteases from approximately 215K to a fragment of approximately 190K. Given these similarities we have investigated the possible relationship between these proteins. Here we demonstrate that platelet P235 is recognized by anti-talin antibody and that it binds vinculin. Both proteins are cleaved in vitro by the calcium-activated protease to yield similar fragments. We conclude that P235 corresponds to the platelet form of talin.

Actins↗
PubMedDate not supplied

47 years of phaeochromocytomas.

Thirty three patients with phaeochromocytomas had surgery in St. Vincent's Hospital between 1950 and 1997. 32 patients had hypertension, 32 had palpitations and 30 had excessive sweating. All patients had at least one of these cardinal symptoms. Diagnostic tests changed over this period. In the early cases the phentolamine test was used, later diagnosis was confirmed by measurement of urinary VMA and catecholamines. IVP, CT, ultrasound or MIBG scanning were used to locate the tumours. Before 1967, 3 of 17 patients died peri-operatively, 2 of these from strokes and one from pulmonary embolism. Since then, all patients have survived surgery. Four of the women had phaeochromocytomas diagnosed during pregnancy. Two of the 33 patients had tumours that were malignant, the remainder being benign. One patient has died from metastatic disease. This series illustrates the changing trends in the surgical management of phaeochromocytomas.

Adolescent↗
PubMedDate not supplied

Diabetes mellitus in childhood cystic fibrosis.

Since 1984, five patients in the cystic fibrosis (CF) clinic at Cork Regional Hospital have developed diabetes mellitus (DM) and were treated with Insulin. None had received systemic corticosteroids but two had high calorie naso-gastric feeding regimes. Two died from lung disease. A fifteen year old boy developed bilateral cataracts. In nine other paediatric CF clinics in the Republic of Ireland (total: 420 patients), three patients have DM, two receiving Insulin. Abnormal glucose tolerance is becoming more common in CF as patients survive longer. The possible role of corticosteroid treatment and intensive carbohydrate feeding regimes in development of glucose intolerance must be considered. DM in CF differs from the usual childhood DM. Regular screening and early Insulin supplementation may be beneficial.

Adolescent↗