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Biomedical subjects

G A Robertson

Publications and source records attributed to G A Robertson.

At least 37 records · Page 2Linked to original sources
PubMed1993

An anatomical study of the deep transverse metacarpal ligament.

The anatomy of the deep transverse metacarpal ligament was examined in cadaveric dissections. Previously unreported findings were transverse muscular slips from abductor digiti minimi that inserted into the medial border of the ligament and, in 1 case, an extension from the medial half of the tendon of extensor carpi ulnaris that inserted into the medial aspect of the ligament. Applied anatomy in relation to the dynamics of the transverse metacarpal arch is reviewed.

Finger Joint↗
PubMed1992

A biomechanical analysis of a new interlock suture technique for flexor tendon repair.

Using a computerised tensometer, both the gap-producing and breaking forces of a new interlocking suture for flexor tendon repair were compared to the modified Kessler and the Strickland techniques. 30 porcine deep flexor tendons were used in each group and all repairs were performed with 3/0 polypropylene sutures. The interlock technique withstood gap-producing and breaking forces significantly better than the modified Kessler and Strickland techniques. Also, the gap-producing force was closer to the breaking force with the interlock technique than with the other two techniques.

Animals↗
PubMed1991

A component of calcium-activated potassium channels encoded by the Drosophila slo locus.

Calcium-activated potassium channels mediate many biologically important functions in electrically excitable cells. Despite recent progress in the molecular analysis of voltage-activated K+ channels, Ca(2+)-activated K+ channels have not been similarly characterized. The Drosophila slowpoke (slo) locus, mutations of which specifically abolish a Ca(2+)-activated K+ current in muscles and neurons, provides an opportunity for molecular characterization of these channels. Genomic and complementary DNA clones from the slo locus were isolated and sequenced. The polypeptide predicted by slo is similar to voltage-activated K+ channel polypeptides in discrete domains known to be essential for function. Thus, these results indicate that slo encodes a structural component of Ca(2+)-activated K+ channels.

Amino Acid Sequence↗
PubMed1991

Iliac-enteric fistula following Dacron patch angioplasty.

We report a patient who developed fistulization between the jejunum and a Dacron patch placed at the bifurcation of the right common iliac artery during endarterectomy 14 years previously. The patient was successfully managed by resection of the iliac bifurcation and a segment of the involved bowel. While arterio-enteric fistulae typically involve prosthetic grafts, they may occur in association with artificial materials used to patch endarterectomy sites; hence, knowledge of technical detail is important in the diagnosis of this complication following endarterectomy.

Aged↗
PubMed1991

Acquired nostril stenosis.

Acquired nostril stenosis is an uncommon but challenging problem. Etiology, pathophysiology, presentation, and treatment options are presented, together with two patient reports. A classification is offered that allows for appropriate selection of the surgical procedure.

Child↗
PubMed1988

A microtiter cell-culture assay for the determination of anti-human immunodeficiency virus neutralizing antibody activity.

A microtiter cell-culture assay is described for measuring neutralizing antibody activity directed against the human immunodeficiency virus (HIV). The assay relies upon inhibition of HIV-mediated cell killing of infected MT-4 lymphoid cells. The assay exhibits comparable sensitivity to two other methods used for such measurements, is relatively rapid, may be adapted for screening large numbers of samples and involves minimal handling of infectious virus.

Antibodies, Viral↗
PubMed1988

Synaptic control of hindlimb motoneurones during three forms of the fictive scratch reflex in the turtle.

1. The turtle spinal cord produces three forms of the fictive scratch reflex in response to tactile stimulation of sites on the body surface. Common to all three forms is the rhythmic alternation of activity between hip protractor and hip retractor motoneurones. Hip protractor motoneurone activity is monitored via nerves innervating the hip protractor muscle puboischiofemoralis internus pars anteroventralis (VP-HP). Hip retractor activity is monitored via nerves innervating several monoarticular hip retractor muscles, one hip adductor muscle, and several biarticular hip retractor-knee flexor muscles (HR-KF). Each form is characterized by the timing of activity of motoneurones innervating femorotibialis (FT-KE), a monoarticular knee extensor muscle, within this alternating cycle (Robertson, Mortin, Keifer & Stein, 1985). In the present study, intracellular recordings revealed a corresponding regulation of synaptic drive to knee extensor motoneurones with respect to the synaptic drive to the motoneurones innervating antagonist muscles of the hip. These patterns of synaptic activation give rise to the distinct motor pattern underlying each form of the scratch reflex. 2. VP-HP, HR-KF and FT-KE motoneurones all exhibited phasic depolarizing and hyperpolarizing changes in membrane voltage during the production of the rhythmic motor patterns underlying each stratch form. Membrane depolarization is caused by synaptic excitation (EPSPs) and gives rise to motoneurone discharge. Hyperpolarization is primarily the result of postsynaptic inhibition (IPSPs) mediated by an increased conductance of chloride ions (Cl-) and ensures motor pool quiescence during antagonist activation. 3. VP-HP motoneurones depolarized during activation of the VP-HP motor pool and hyperpolarized during activation of the HR-KF motor pool. HR-KF motoneurones depolarized during activation of the HR-KF motor pool and hyperpolarized during activation of the VP-HP motor pool. In many cases, the amplitude of hyperpolarization was directly related to the intensity of the antagonist motor pool burst. During the rostral scratch, HR-KF motor pool activity was sometimes deleted, along with the depolarizing wave in HR-KF motoneurones and the hyperpolarizing wave in VP-HP motoneurones. The interneurones providing the synaptic drive to these antagonist motoneurones appear, therefore, to have reciprocal activation patterns. 4. FT-KE motoneurones depolarized during FT-KE motor pool activation and hyperpolarized during FT-KE motor pool quiescence. This alternation of opposing synaptic drive underlies the rhythmic activation of the FT-KE motor pool during all scratch forms.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1986

The role of sternum in osteomyocutaneous reconstruction of major mandibular defects.

Replacement of skeletal support after extensive intraoral resection demands the use of a vascularized bone graft. This can be provided by microvascular free transfer using the ilium or metatarsal bones or by using muscle as a vascular carrier, employing the rib, the spine of the scapula, or the clavicle. Over a 5 year period, 27 patients underwent mandibular reconstruction with a vascularized segment of the outer table of sternum transposed together with a skin island on the pectoralis major muscle. Loss of bone occurred in two patients. A 93 percent survival rate was achieved. An earlier, smaller series of six patients using rib for reconstruction resulted in an unacceptably high complication rate. Success in survival of the bone graft, however, is not enough to procure a satisfactory result. Specific aspects of surgical technique are described that create an alveolar ridge with a sulcus on either side that can accept a denture; a diaphragm to replace the floor of the mouth and eliminate dead space; and an esthetically acceptable appearance, with definition of the jawline and a properly supported lower lip.

Adult↗
PubMed1986

A comparison between sternum and rib in osteomyocutaneous reconstruction of major mandibular defects.

Following major mandibular resection for intraoral malignancy, 6 patients underwent reconstruction using rib and 22 patients underwent reconstruction using the outer table of the sternum; the pectoralis major muscle was used as the vascular carrier for both bone and skin in all patients. Five of the 6 patients in the rib group encountered major complications. In the sternal group, loss of bone occurred in only 2 of 22 patients. Those aspects of technique considered important to the outcome are detailed. Results are discussed in terms of bone survival, intraoral features including denture placement, and the patient's appearance. The sternal transfer has consistently shown itself to be superior to rib, in terms of both early morbidity and later functional and aesthetic results. It is our present method of choice for reconstruction following major intraoral resection.

Bone Transplantation↗
PubMed1986

Etiologic aspects of cold agglutinin disease: evidence for cytogenetically defined clones of lymphoid cells and the demonstration that an anti-Pr cold autoantibody is derived from a chromosomally aberrant B cell clone.

This study investigated the clonal nature of cold agglutinin disease in a series of nine patients, which included the benign or idiopathic form as well as cases with an underlying lymphoma. Surface marker phenotyping and karyotypic analysis were performed on peripheral blood lymphocytes. An increased proportion of B cells was found in four cases and in three of these patients a monoclonal B cell population was identified with a mu, kappa phenotype. In the same three cases, as well as an additional patient, an aberrant karyotype was demonstrated. The cytogenetic abnormality present in all four cases included trisomy 3; two patients also had a trisomy 12. One of these four patients had a well-differentiated lymphoma and underwent a splenectomy. Splenic lymphocytes were transformed with Epstein-Barr virus and cultured en masse. Eight clones were established producing the same cold agglutinin with identical specificity as that present in the patient's plasma. Five of these clones were studied cytogenetically, and all had the same abnormal karyotype (51,XX,+3,+9,+12,+13,+18) found in peripheral blood and splenic lymphocytes. Thus, in this case, the cold reactive autoantibody was produced by the chromosomally abnormal, neoplastic clone of lymphocytes. Our findings support the view that cold agglutinin disease represents a spectrum of clonal disorders.

Adult↗
PubMed1986

Blends of rostral and caudal scratch reflex motor patterns elicited by simultaneous stimulation of two sites in the spinal turtle.

Simultaneous tactile stimulation of 2 sites on the body surface of a spinal turtle elicits complex blends of the scratch forms and motor patterns associated with each site. Our previous work has utilized 1-site stimulation to elicit distinct forms of the scratch reflex in the spinal turtle (Mortin et al., 1985; Robertson et al., 1985). Using this paradigm, stimulation of a site on the shell bridge anterior to the hindlimb elicits a rostral scratch reflex in which the dorsum of the foot rubs against the stimulated site; stimulation of a site near the tail elicits a caudal scratch reflex in which the heel or side of the foot rubs against the stimulated site (Mortin et al., 1985). During each scratch cycle, the monoarticular knee extensor muscle is active when the limb rubs against the stimulated site, and there is rhythmic alternation between hip protractor and hip retractor muscle activity (Robertson et al., 1985). In a rostral scratch, the monoarticular knee extensor muscle is active during the latter portion of hip protractor muscle activity; in a caudal scratch, the monoarticular knee extensor muscle is active near the end of hip retractor muscle activity. Pure-form motor patterns that are similar to those recorded from these muscles during movement can be recorded from the corresponding nerves in a spinal turtle immobilized with a neuromuscular blocking agent (Robertson et al., 1985). In this paper, we describe blend responses to simultaneous stimulation of 2 sites, one in the rostral scratch and the other in the caudal scratch receptive field. During these blends, the responding hindlimb rubs against both stimulated sites in one continuous movement sequence.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Silastic sheet interposition arthroplasty for the painful rheumatoid wrist: a long-term review.

Silastic sheet interposition arthroplasty was performed in 20 patients with persistently painful but stable wrists. Synovial recurrence with progression of symptoms was seen in one patient. Quantitative analysis of pain demonstrated an 87% improvement in their perception of pain in the remaining 19 patients, with an average follow-up of 8.5 years. The postoperative range of motion was 58 degrees Total Active range of Motion (TAM) (range 27 degrees - 97 degrees). Nine patients showed later ulnar translocation of the carpus, and 10 patients had continuing carpal collapse. There was no relation between these changes and the degree of pain relief at the radio-carpal joint. Those patients operated on within 18 months of the onset of symptoms showed a significantly greater post-operative range of motion (68 degrees) compared to those whose symptoms had persisted from 2 to 4 years (48 degrees).

Adult↗
PubMed1985

Three forms of the scratch reflex in the spinal turtle: central generation of motor patterns.

A turtle with a complete transection of the spinal cord, termed a spinal turtle, exhibits three types or "forms" of the scratch reflex: the rostral scratch, pocket scratch, and caudal scratch (21). Each scratch form is elicited by tactile stimulation of a site on the body surface innervated by afferents entering the spinal cord caudal to the transection. We recorded electromyographic (EMG) potentials from the hindlimb during each of the three forms of the scratch in the spinal turtle (see Fig. 1). Common to all scratch forms is the rhythmic alternation of the activity of the hip protractor muscle (VP-HP) and hip retractor muscle (HR-KF). Each form of the scratch displays a characteristic timing of the activity of the knee extensor muscle (FT-KE) with respect to the cycle of activity of the hip muscles VP-HP and HR-KF. In a rostral scratch, activation of FT-KE occurs during the latter portion of VP-HP activation. In a pocket scratch, activation of FT-KE occurs during HR-KF activation. In a caudal scratch, activation of FT-KE occurs after the cessation of HR-KF activation. The timing characteristics of these muscle activity patterns correspond to the timing characteristics of changes in the angles of the knee joint and the hip joint obtained with movement analyses (21). We recorded electroneurographic (ENG) potentials from peripheral nerves of the hindlimb during each of the three forms of the "fictive" scratch in the spinal turtle immobilized with neuromuscular blockade (see Fig. 4). Common to all forms of the fictive scratch is the rhythmic alternation of the activity of hip protractor motor neurons (VP-HP) and hip retractor motor neurons (HR-KF). Each form displays a characteristic timing of the activity of knee extensor motor neurons (FT-KE) with respect to the cycle of VP-HP and HR-KF motor neuron activity. The timing characteristics of these motor neuron activity patterns are similar to the timing characteristics of the muscle activity patterns obtained in the preparation with movement (cf. Figs. 1 and 4). The motor pattern for each scratch form is generated centrally within the spinal cord. In the spinal immobilized preparation, neuromuscular blockade prevents both limb movement and phasic sensory input, and complete spinal transection isolates the cord from supraspinal input.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Translation of type IV procollagen messenger RNA from cultured cat retinal pigment epithelial cells.

The activity of type IV procollagen mRNA was detected in the total cytoplasmic RNA prepared from normal feline retinal pigment epithelial cells in culture. The translation products contained two distinct bands in the pro alpha chain region on SDS-PAGE, which were sensitive to collagenase digestion. Corresponding bands were identified in the immunoprecipitate of the translation products after reaction with an anti-type IV collagen antiserum and separation by protein A-Sepharose column chromatography.

Animals↗
PubMed1984

Sealing the postpneumonectomy space: use of a pectoralis major myodermal flap.

Reconstruction of chest wall defects is performed by a variety of surgical procedures. Use of the pectoralis major myodermal flap following a Clagett procedure appears to be a reliable technique providing satisfactory results. The application of this technique demands a close interaction between the plastic surgeon and the thoracic surgeon.

Aged↗
PubMed1984

Increased solubility of newly synthesized collagen in retinal capillary pericyte cultures by nonenzymatic glycosylation.

The effect of increasing glucose concentration on the solubility of newly synthesized collagen was studied in bovine retinal capillary pericyte (BRCP) cultures. Synchronized pericytes were labeled with [3H]-proline in media containing either 5, 10, 20 or 40 mM glucose, or 5 mM glucose and 100 micrograms/ml beta-aminopropionitrile fumarate (BAPN). The relative rate of collagen synthesis in the medium (soluble collagen) was significantly increased, and the rate in the cell layer (insoluble collagen) was decreased, by an elevated glucose concentration. The increase in collagen solubility with 20 and 40 mM glucose (over normal, 5 mM glucose) was 14 and 42%, respectively, of that obtained with BAPN. BAPN and 4-deoxypyridoxine inhibited BRCP lysyl oxidase activity, but elevated glucose concentrations did not. Increased nonenzymatic glycosylation of newly synthesized collagen was demonstrated in BRCP cultures co-labeled with L-[14C]-glucose and L-[3H]-proline. The increase in collagen solubility with elevated glucose concentrations therefore appears to be the result of the inhibition of lysyl-derived cross-link formation because of an increased nonenzymatic glycosylation of the epsilon-amino groups of lysyl residues of newly synthesized collagen in culture.

Aminopropionitrile↗
PubMed1984

Resection of a metastatic sternal carcinoma and reconstruction of the chest wall: a case report.

A large metastatic squamous carcinoma of the anterior chest wall was managed by en-bloc resection of the thoracic wall. The extensive defect resulting from the resection was bridged with Marlex mesh superimposed on an omental flap that served as recipient to partial-thickness skin grafts. This composite reconstruction restored an efficient bellows action to the chest cage, manifested by the lack of anterior flailing and postoperative spirometry values, measured at the bedside, that were 75% of those obtained preoperatively. During the initial postoperative period, however, mechanical ventilatory assistance was required to treat an adult respiratory distress syndrome that together with mild anterior flailing made early extubation impossible.

Carcinoma, Squamous Cell↗