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Biomedical subjects

J Maguire

Publications and source records attributed to J Maguire.

At least 37 records · Page 2Linked to original sources
PubMed1995

Evaluation of intrapedicular screw position using intraoperative evoked electromyography.

STUDY DESIGN: This study analyzed the parameters needed for electrical stimulation of vertebral pedicle drill bits and screws. OBJECTIVES: The feasibility of using electrically evoked electromyography was studied. SUMMARY OF BACKGROUND DATA: Considerable potential for damage of adjacent nerve roots with incorrectly placed bits and screws exists with pedicular fixation of the lumbar spine. METHODS: Ninety-five drill bits, one hundred forty-four screws, and thirty-four exposed nerve roots were electrically stimulated in thirty-six patients. Simultaneous evoked electromyographic activity was recorded from four muscle groups in each lower extremity during partial neuromuscular blockade. RESULTS: A constant current threshold of 6 mA or less correlated with misplaced drill bits and screws that broached the cortex. Evoked electromyography was 93% sensitive whereas radiography was only 63% sensitive to detecting bits and screws that had broached the cortex. CONCLUSIONS: Evoked electromyography is a valuable sensitive adjunct to radiographic examination of pedicle drill bit and screw placement.

Adult↗
PubMed1994

Gem: an induced, immediate early protein belonging to the Ras family.

A gene encoding a 35-kilodalton guanosine triphosphate (GTP)-binding protein, Gem, was cloned from mitogen-induced human peripheral blood T cells. Gem and Rad, the product of a gene overexpressed in skeletal muscle in individuals with Type II diabetes, constitute a new family of Ras-related GTP-binding proteins. The distinct structural features of this family include the G3 GTP-binding motif, extensive amino- and carboxyl-terminal extensions beyond the Ras-related domain, and a motif that determines membrane association. Gem was transiently expressed in human peripheral blood T cells in response to mitogenic stimulation; the protein was phosphorylated on tyrosine residues and localized to the cytosolic face of the plasma membrane. Deregulated Gem expression prevented proliferation of normal and transformed 3T3 cells. These results suggest that Gem is a regulatory protein, possibly participating in receptor-mediated signal transduction at the plasma membrane.

Amino Acid Sequence↗
PubMed1994

Intercellular interactions in PC12 cells overexpressing beta/A4 amyloid.

The amyloid precursor protein (APP) is an integral membrane component of eukaryotic cells. A variety of research approaches have addressed the contribution of the beta amyloid peptide region of the APP to neuritic plaque structure and formation in the Alzheimer disease brain as well as the relationship between beta amyloid accumulation and the occurrence of dementia. However, there is limited information available concerning the cellular consequences of amyloid deposition. The present studies were undertaken to investigate the relationship between beta amyloid and intercellular junctions. Transfected PC12 cell lines, that overexpress the beta amyloid peptide, exhibit structural and functional alterations at the cell surface and tend to form aggregates more readily than normal control cells. Intermediate junctions were the most common intercellular interactions of both normal and transfected cells. However, the control and transfected cells differed since areas of continuous and extensive junctions were readily seen in transfected cells and infrequently seen in control cells. The data suggest that excess accumulation of beta amyloid is associated with the junctional apparatus and may be related to increased intercellular adhesion.

Actins↗
PubMed1993

Intraoperative long-latency reflex activity in idiopathic scoliosis demonstrates abnormal central processing. A possible cause of idiopathic scoliosis.

Segmental reflex regulation in 37 patients with idiopathic scoliosis and 8 patients with nonidiopathic scoliosis was studied by recording evoked reflex muscle potentials from four muscle groups in each lower extremity during partial neuromuscular blockade. Effects on reflex activity mediated through descending systems arising in the brain stem were investigated by recording from proximal-distal and flexor-extensor muscles. Ipsilateral and contralateral long-latency complex polysynaptic activity was present in all 37 patients with idiopathic scoliosis. This reflex activity was absent in eight nonidiopathic scoliosis patients. Long-latency reflex activity may represent segmental disinhibition. The presence of long-latency reflex activity in patients with idiopathic scoliosis and the absence of this activity in nonidiopathic scoliosis patients with curves of equal magnitude demonstrates that the curve per se is not responsible for the activity. This would imply that abnormal reflex processing may play a role in the development of the spinal deformity in patients with idiopathic scoliosis.

Adolescent↗
PubMed1993

Correlation between lipids extracted from Bruch's membrane and age.

BACKGROUND: There is increasing circumstantial evidence that the chemical composition of the deposits in Bruch's membrane influences the clinical outcome in age-related macular disease. In particular, it has been postulated that deposition of neutral lipids in Bruch's membrane may cause hydrophobicity and predispose to detachment of the retinal pigment epithelium and cause functional loss. METHODS: Analysis of the lipid extracted from Bruch's membrane of eye bank eyes from donors of different ages has been undertaken using thin layer and gas chromatography. No clinical information was available concerning any previous eye disease. RESULTS: It is shown that the lipid extracted increases with the age of the donor, and that the total quantity and ratio of neutral fats to phospholipids varies widely from one specimen to another from donors older than 60 years of age. The ratios of the different phospholipids imply that they are not derived from blood. CONCLUSION: The results are compatible with the concept of hydrophobicity developing with age in Bruch's membrane.

Adolescent↗
PubMed1991

Lung edema formation following inhalation injury: role of the bronchial blood flow.

We investigated the contribution of the bronchial blood flow to the lung lymph flow (QL) and lung edema formation after inhalation injury in sheep (n = 18). The animals were equally divided into three groups and chronically prepared by implantation of cardiopulmonary catheters and a flow probe on the common bronchial artery. Groups 1 and 2 sheep were insufflated with 48 breaths of cotton smoke while group 3 received only room air. Just before injury, the bronchial artery of group 2 animals was occluded. The occlusion was maintained for the duration of the 24-h study period. At the end of the investigation, samples of lung were taken for determination of blood-free wet weight-to-dry weight ratio (W/D). Inhalation injury induced a sevenfold increase in QL in group 1 (7 +/- 1 to 50 +/- 9 ml/h; P less than 0.05) but only a threefold increase in group 2 (10 +/- 2 to 28 +/- 7 ml/h; P less than 0.05). The mean W/D value of group 1 animals was 23% higher than that of group 2 (5.1 +/- 0.4 vs. 3.9 +/- 0.2; P less than 0.05). Our data suggest that the bronchial circulation contributes to edema formation in the lung that is often seen after the acute lung injury with smoke inhalation.

Animals↗
PubMed1991

Isocratic reversed-phase HPLC method to measure pyrimethamine extracted from plasma of infants treated for toxoplasmosis.

An isocratic HPLC method for measuring pyrimethamine extracted from infant plasma is reported. The method is an improvement over previously published methods by requiring lower volumes of plasma (100 microL) and having increased sensitivity to pyrimethamine at 210 nm. The procedure, which entails a basic organic extraction and subsequent HPLC chromatography of the reconstituted extract, can detect 1.4 ng and quantify 4.0 ng of pyrimethamine per 40-microL injection, with two analyses per 100-microL sample. Analytical recovery of pyrimethamine added to plasma at 10, 50, and 125 ng/100 microL averaged 80%, 92%, and 101%, respectively (n = 20). Within- and between-day CVs were less than 7%. Studies of various plasma samples from adults and infants (n = 15) revealed no interference from other plasma peaks with the analyte of interest.

Chromatography, High Pressure Liquid↗
PubMed1990

The effects of siguazodan, a selective phosphodiesterase inhibitor, on human platelet function.

1. The effects of siguazodan (SK&F 94836) a selective phosphodiesterase (PDE) inhibitor with inotropic and vasodilator activity, were studied on human platelets. 2. Siguazodan selectively inhibited the major cyclic AMP-hydrolysing PDE in human platelet supernatants. The inhibited enzyme has been variously termed cyclic GMP-inhibited PDE or PDE-III. 3. In platelet-rich plasma (PRP), siguazodan inhibited U46619-induced aggregation more potently than that induced by ADP and collagen. Treatment of the PRP with aspirin had no effect on the potency of siguazodan. 4. In washed platelets, siguazodan increased cyclic AMP levels and reduced cytoplasmic free calcium [( Ca2+]i). ADP decreased the ability of siguazodan to raise cyclic AMP and this may explain its lower potency in inhibiting responses to ADP. 5. Siguazodan has anti-platelet actions over the same concentration range that it is an inotrope and vasodilator.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1989

[Respiratory and hemodynamic sequelae of unilateral inhalation injury of the lung].

Respiratory failure after smoke inhalation injury is usually preceded by a 12-48 h interval with only minor clinical symptoms. Since pulmonary lesions show a patchy distribution, it has been postulated that vasoconstriction in more severely damaged areas induces a shift of pulmonary blood flow to less severely damaged areas, minimizing venous admixture. This hypothesis was tested in a sheep model in which only one lung was exposed to smoke. Six chronically instrumented (arterial, central venous, pulmonary artery thermodilution, and left atrial catheters; ultrasonic transit time flow probe around the left pulmonary artery) range ewes were intubated with a modified Carlens tube under halothane anesthesia. Smoke from smoldering cotton was insufflated into the left lung until a carboxyhemoglobin level of 50% was achieved. After the smoking procedure, the animals were awakened, extubated, and studied for 24 h. During this time, the pulmonary vascular resistance of the left lungs increased fourfold while the pulmonary vascular resistance of both lungs only doubled. Left pulmonary artery blood flow decreased progressively to 37% of control at 24 h, while cardiac output decreased by only 25%. PaO2 decreased from 107 +/- 12 to 77 +/- 15 mmHg at 24 h. Mean pulmonary arterial pressure rose from 18 to 23 mmHg. Heart rate, mean arterial pressure, left atrial pressure, and PaCO2 showed no statistically significant changes. The results indicate that the response of the pulmonary vasculature to smoke inhalation injury is a two-phase phenomenon. In the first phase, vasoconstriction occurs to counterbalance injury-induced ventilation-perfusion mismatching.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗