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Biomedical subjects

M Gardner

Publications and source records attributed to M Gardner.

At least 73 records · Page 4Linked to original sources
PubMed1995

Identification of arteriovenous anastomoses by duplex ultrasound. Implications for the treatment of varicose veins.

BACKGROUND: It has been suggested that arteriovenous anastomoses (AVA) may contribute to the etiology of varicose vein disease. Duplex ultrasound has recently assumed a major role in the diagnosis of venous disease. This noninvasive method can serve as a research tool to better elucidate the role of AVA, and as a guide to the treatment of varicose veins. OBJECTIVE: To determine the incidence and location of AVA identifiable by duplex ultrasound in a population with clinically apparent varicose veins due to underlying saphenous vein reflux. METHODS: The presence and location of AVA detected by duplex ultrasound were noted in 510 patients with varicose veins due to Doppler-positive saphenous vein reflux from three private practices. RESULTS: Twenty-six AVA were found in 19 patients (incidence 3.7%), mostly in the distal half of the long saphenous system. AVA were represented equally on both right and left sides, and regardless of previous vein stripping. Three AVA were found at the base of venous ulcers. AVA were more easily detected using higher resolution ultrasound. CONCLUSION: AVA occurring in association with saphenous vein disease and identified using duplex ultrasound are usually found below the knee in the long saphenous system, and sometimes at the base of venous ulcers. Knowledge of their presence and location may help to avert complications of sclerotherapy, and guide the approach to treatment.

Adult↗
PubMed1995

Application of an electrocardiographic inverse solution to localize ischemia during coronary angioplasty.

Localization of Ischemia. This study demonstrates the utility of an electrocardiographic inverse solution, coupled with body surface potential mapping (BSPM), in localizing acute ischemia in patients undergoing percutaneous transluminal coronary angioplasty (PTCA). PTCA balloon inflations produce complete occlusion and acute transient ischemia, which can be detected electrocardiographically with BSPM. Comparisons between maps recorded both during and before the inflation of the PTCA balloon allow patient- and artery-specific characterizations of the resulting ischemia. Knowledge of the patient's coronary anatomy and the location of the occlusion site by coronary angiography permit an estimation based on cardiac hemodynamics of the region of myocardium most likely to suffer from PTCA-induced ischemia. Electrocardiographic inverse solutions provide a means of predicting cardiac potentials from body surface maps. In this study, we describe an inverse solution we have developed to localize the transient ischemia produced by PTCA. To validate the procedure, we compared the locations of predicted ischemia in seven patients with a qualitative estimate of the perfusion region based on fluoroscopic examination of each patient's coronary anatomy and PTCA balloon location. In each case, the region of ischemia predicted by the model included the perfusion zone determined fluoroscopically. These results suggest that electrical changes induced by acute ischemia can be localized with an electrocardiographic inverse solution.

Angioplasty, Balloon, Coronary↗
PubMed1995

Comparison of dual chamber and ventricular rate responsive pacing in patients over 75 with complete heart block.

OBJECTIVE: To compare symptoms and exercise tolerance during dual chamber universal (DDD) and ventricular rate response (VVIR) pacing in elderly (> or = 75) patients. DESIGN: Randomised, double blind, crossover study. SETTING: Regional cardiac department. PATIENTS: Twenty elderly patients (mean age 80.5 (1) years) with high grade atrioventricular block and sinus rhythm. Patients with pre-existing risk factors for the pacemaker syndrome and chronotropic incompetence were excluded. INTERVENTION: After four weeks of VVI pacing following pacemaker implantation, patients underwent consecutive two week periods of VVIR and DDD pacing. MAIN OUTCOME MEASURES: Patient preference, symptom scores, "daily activity exercises," and perceived level of exercise (Borg score). RESULTS: Eleven patients preferred DDD mode to either VVI or VVIR mode. Mean (SE) total symptom scores during VVI, VVIR, and DDD pacing were 5.9 (1.1), 6.1 (1.0), and 3.5 (0.9) respectively (P < 0.01). The corresponding mean (SE) pacemaker syndrome symptom scores were 4.8 (0.7), 5.2 (0.8), and 2.9 (0.8) (P < 0.05). Symptom scores during VVI and VVIR pacing were not significantly different. Exercise performance and Borg scores were significantly worse during VVI pacing compared with VVIR or DDD pacing but did not significantly differ between VVIR and DDD modes. CONCLUSIONS: In active elderly patients with complete heart block both DDD and VVIR pacing are associated with improved exercise performance compared with fixed rate VVI pacing. The convenience and reduced cost of VVIR systems, however, may be offset by a higher incidence of the pacemaker syndrome. In elderly patients with complete heart block VVIR pacing results in suboptimal symptomatic benefit and should not be used instead of DDD pacing.

Aged↗
PubMed1995

Pharmacokinetics of fluconazole in renal failure.

Fluconazole (FLU) is a widely used antifungal agent. The multiple-dose pharmacokinetics of FLU in renal impairment have not been previously investigated. The following groups were studied: volunteers with creatinine clearances (CLcr, > 50 mL/min) of 107 mL/min, given a loading dose of 400 mg and a daily dose of 200 mg/day for 9 days (Group 1); subjects with CLcr between 21 and 50 mL/min with a mean of 38 mL/min, given a loading dose of 200 mg and a maintenance dose of 100 mg/day for 9 days (Group 2); subjects with CLcr between 11 and 20 mL/min with a mean of 14.8 ml/min, given a loading dose of 100 mg and a maintenance dose of 50 mg/day for 9 days (Group 3); and subjects on hemodialysis (three times per week) receiving a loading dose of 200 mg and then 100 mg after each of four dialysis sessions (Group 4) (N = 10 per group). After the administration of the loading dose on Day 1, the mean area under the curve (AUC) (0-24) measurements were approximately proportional to the dose of FLU and independent of renal function. After 10 days of FLU dosing, the mean renal clearance of FLU decreased as CLcr decreased for Groups 1 to 3, and the Day 10 mean half-lives were inversely related to mean CLcr (36.7 h in Group 1, 84.5 h in Group 2, and 101.9 h in Group 3). The mean AUC (0-24) on Day 10 was similar for Group 1 compared with Group 2, despite a reduction in the maintenance dose by 50%. (ABSTRACT TRUNCATED AT 250 WORDS)

Creatinine↗
PubMed1994

Outcome five years after percutaneous transluminal coronary angioplasty or coronary artery bypass grafting for significant narrowing limited to the left anterior descending coronary artery.

Percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting (CABG) are both used widely for angina but information about their comparative efficacy is limited. This study compared the outcome of 358 consecutive patients undergoing initial revascularization for significant narrowing of the left anterior descending artery (LAD) by PTCA (n = 254) or CABG (n = 104) from 1987 to 1989. PTCA was successful in 93% but complicated by urgent CABG in 3%. A left internal mammary graft was used in 88% of those having elective CABG. There was 1 perioperative death. Follow-up data were obtained after a median interval of 5.5 years (maximum 7.1). Rates for freedom from death (97% PTCA vs 93% CABG, p = 0.06) were similar, but CABG patients had greater rates for freedom from chest pain recurrence (74% CABG vs 48% PTCA, p < 0.0001), myocardial infarction (98% vs 92%, p = 0.04), and from need for further revascularization (99% vs 67%, p < 0.0001). Both groups achieved similar status, with 81% of PTCA and 90% of CABG patients having angina no worse than functional class I. Quality-of-life index was high for both groups (0.983 +/- 0.034/1.000 vs 0.987 +/- 0.032/1.000, p = 0.3). Both PTCA and CABG result in excellent survival, functional ability, and quality of life, but patients undergoing PTCA require more procedures to achieve this.

Adult↗
PubMed1994

Perseveration in healthy subjects: an impressive classroom demonstration for educational purposes.

Perseveration, that is, the inappropriate maintenance of an activity, is not exclusively observed in patients with brain pathology. We present a brief calculation task that requires healthy subjects to add eight numbers sequentially. While the first seven steps of the addition involve the repeated application of a particular rule, this rule does not apply for the last step. However, a high percentage of subjects (approximately 70%) will commit a perseverative error at this last step and hence obtain an incorrect final result. This simple task is a highly informative illustration of the principle of perseverative behavior. When applied in a classroom setting, it is an impressive demonstration of the ease with which perseveration can be evoked in healthy persons.

Attention↗
PubMed1994

Evidence that growth hormone stimulates milk synthesis by direct action on the mammary gland and that prolactin exerts effects on milk secretion by maintenance of mammary deoxyribonucleic acid content and tight junction status.

Both PRL and GH play a role in maintaining lactation in the rat, although GH can only maintain pup weight gain at around 50% of the control value, whereas PRL can maintain weight gain close to 90% in the absence of GH. In this study we examined the effects of PRL and GH deficiency (using bromocriptine and an antiserum to rat GH) on milk yield and composition in lactating rats. Treatment with bromocriptine to suppress PRL secretion for 48 h led to a 57% decrease in milk yield with a concomitant decrease in milk protein and lactose yields, but no decrease in fat output. This led to the production of milk with a lower lactose concentration but increased concentrations of protein and particularly fat (increased 100%), which suggests that GH serves an auxiliary role by maintaining an energy-rich milk for the neonate when PRL secretion is reduced. This decrease in milk synthesis was accompanied by decreases in total mammary DNA content and increased milk sodium concentrations. The latter indicates the opening of tight junctions between mammary epithelial cells, which normally occurs during dedifferentiation and involution of the mammary gland. This suggests that PRL maintains milk synthesis at least in part by inhibiting epithelial cell loss and maintaining cellular differentiation. A deficiency in GH, by contrast, caused only a small decrease (24%) in milk yield and had no effect on the major constituents of milk or on milk sodium concentrations or total mammary DNA content. When animals were made deficient in both PRL and GH, however, there was a further marked decrease (88%) in milk volume along with the yields of all major milk constituents, confirming our previous findings that PRL and GH are the major regulators of milk synthesis. Recent studies have indicated that GH exerts direct effects on mammary gland growth, but its actions on milk secretion have been proposed to be mediated indirectly via insulin-like growth factor-I (IGF-I). We, therefore, inhibited lactation by inducing PRL and GH deficiency for 48 h and then attempted to reinitiate it by administering GH either systemically or by local oil-based implants into the mammary gland. Oil-based GH implants were as effective in stimulating milk secretion in the treated (but not contralateral, control) gland as was systemic GH treatment. Thus, GH does act directly on the mammary gland to stimulate milk synthesis, although this does not rule out the possibility that GH acts by stimulating local production of IGF-I.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Several insulin-like growth factor-I analogues and complexes of insulin-like growth factors-I and -II with insulin-like growth factor-binding protein-3 fail to mimic the effect of growth hormone upon lactation in the rat.

Lactation was suppressed in rats using a combined treatment of bromocriptine (to reduce prolactin concentrations) and a specific antiserum to rat GH administered twice daily for 2 days. When milk production had ceased, as determined by litter weight loss and the absence of milk in the stomachs of pups, attempts were made to reinitiate lactation using prolactin, GH, insulin-like growth factor-I (IGF-I) precomplexed to recombinant human IGF-binding protein-3 (hIGFBP-3) or IGF-I plus IGF-II precomplexed to hIGFBP-3. Despite the fact that all treatments except prolactin led to increases in serum IGFs and IGFBP-3, only prolactin and GH provoked the reinitiation of milk production as determined by increased litter weight gain, milk in the stomach of pups and a significant increase in the weight of the mammary glands. Since the mammary gland has been shown to produce IGFBPs which may inhibit IGF action we also tested three IGF-I analogues, R3-IGF-I, Long-IGF-I and Long-R3-IGF-I. R3-IGF-I has a single amino acid substitution (Glu to Arg) at position 3 whereas Long-IGF-I has a 13 amino acid N-terminal extension. These modifications dramatically reduce the ability of these analogues to bind to IGFBPs although they remain active at the IGF-I receptor. Such IGF analogues would therefore be expected to be active irrespective of the production of inhibitory IGFBPs. However, none was effective in reinitiating lactation, even at doses which have been shown to be biologically effective in terms of nitrogen retention.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Effect of aqueous neem (Azadirachta indica) extract on testosterone and other blood constituents in male rats. A pilot study.

Effect of oral administration of crude aqueous neem extract on serum testosterone and other blood constituents was studied in the male Wistar rats for 10 weeks. The neem treatment resulted in significant decreases (p < 0.01) in total testosterone, total bilirubin and K+ in serum. There were also increases (p < 0.05) in packed cell volume, mean corpuscular haemoglobin concentration, red blood cell, white blood cell and lymphocyte counts without showing any cytotoxic effects in the body.

Administration, Oral↗
PubMed1994

Unit-based shared governance can work!

The Nurse Executive Council at a 540-bed community teaching health center planned and implemented Shared Governance in a 10-bed Medical Intensive Care Unit (MICU). Paid time was provided for nurses to take part in one of four councils. After a pilot year resulting in satisfaction with job autonomy and input into decision-making, staff reaffirmed their commitment to shared governance as a permanent "way of life" in the MICU. During the second year, patient care assistants and unit clerks were integrated into the Councils and staff began serving as consultants to other units and institutions.

Decision Making, Organizational↗
PubMed1994

DDD vs. VVI pacing in patients aged over 75 years with complete heart block: a double-blind crossover comparison.

We studied 16 patients aged 77-88 years to determine whether elderly patients gain significant benefit from dual-chamber (DDD) compared with single-chamber ventricular demand (VVI) pacing. The study was designed as a double-blind randomized two-period crossover study--each pacing mode was maintained for 7 days. End points included: (i) overall symptoms scores; (ii) exercise tests related to daily activities; and (iii) perceived level of difficulty (Borg score). The mean symptom score in DDD mode was 7.07 (6.38) vs. 12.27 (7.29) in VVI mode (p < 0.006). Dizziness, breathlessness and fatigue were the most noticed symptoms during VVI pacing. One patient dropped out from follow-up and three patients requested early reprogramming, all from VVI mode. Overall, no patient preferred VVI mode, 11 preferred DDD mode and four expressed no preference. There were significant improvements in all objective test performances in DDD mode. Mean (SD) total Borg scores in DDD mode and VVI mode were 36.57 (5.85) and 41.93 (6.49), respectively (p < 0.002). Ventricular demand pacing in elderly patients with complete heart block is associated with higher symptom scores, reduced exercise ability and greater perceived exercise difficulty compared with dual-chamber pacing.

Aged↗
PubMed1993

The pathogenesis of murine retroviral infection of the central nervous system.

Several decades have lapsed since the original description of retroviral infection of the central nervous system (CNS) appeared. With the recent arrival of the autoimmune deficiency syndrome (AIDS) epidemic and the associated human retroviral encephalitis, interest in murine models has been rekindled. In most of the published studies, susceptible mouse strains are infected as neonates with molecularly cloned type-C retroviruses. In most models, a spongiform encephalopathy follows an early CNS endothelial cell infection. The subsequent pathogenesis of this encephalopathy is unknown. In some models neuronal and glial infection is seen, while in others only non-neuroglial elements are infected. This variation can be traced to differences in strains of mice and viruses in addition to differences in assays. The different models offer fertile experimental ground to decipher the role of direct versus indirect neuroglial damage. Reconciliation of these various models where the final neuropathology appears so similar, may be the key to understanding their pathogenesis.

Animals↗
PubMed1992

The use of drugs in emergency airway management in pediatric trauma.

Most patients who require emergency airway control receive drugs to induce rapidly sufficient anesthesia for direct laryngoscopy and endotracheal intubation, but there are no protocols that outline the use of specific drugs in general use. Drugs should safely and rapidly produce (1) unconsciousness; (2) paralysis; and (3) blunt intracranial pressure (ICP) responses to airway procedures. Consequences to be considered include increased ICP, hemorrhagic shock, and a full stomach. To refine the use of drugs used for airway procedures in pediatric trauma patients, the authors reviewed all cases of emergency endotracheal intubation over a recent 12-month period (1) to see whether medications used met the goals of producing unconsciousness and paralysis and blunting ICP responses were met safely; and (2) to identify potential drug-related complications. From July 1, 1990, to June 30, 1991, 60 of 791 children (7.6%) required endotracheal intubation at the scene of injury, at the referring hospital, or in our emergency department (15; 25%). Ten patients died (16.7%). Three fourths were younger than 9 years of age. All except one suffered blunt injuries. Nearly all (95%) suffered head injuries, isolated in 39 of 57 (68.4%) and combined with injuries in other regions in 18 (31.6%). Fifteen patients were in apnea (25%); seven were both apneic and pulseless. Three fourths (45 of 60) had diminished levels of consciousness; one fourth (15 of 60) were awake. Immediate endotracheal intubation proceeded appropriately without drugs in all seven patients in cardiopulmonary arrest. Only eight of the remaining 53 patients (15.1%) received an optimal medication regimen. Many patients with head injury were inadequately protected against increases in ICP. Thiopental, an effective anesthetic agent that effectively lowers intracranial pressure, was not used in 25 of 35 stable patients with isolated head injury (71.4%). Intravenous lidocaine was not used in 38 of 50 head-injured patients in whom it would have been an appropriate adjunct to control increases in ICP (76%). Eight patients received paralyzing agents alone, without sedatives or narcotics. Medications were thought inadequate to relieve the pain and discomfort of laryngoscopy and endotracheal intubation in 32 of the 53 patients who should have received them (60.4%). No paralyzing agents were used in 36 of the 53 instances where it would have been appropriate (67.9%). In two of 11 instances (18.3%) where succinylcholine was administered, no prior nondepolarizing agent was used. Complications of a full stomach at the time of emergency endotracheal intubation became evident in 10 patients (16.7%) who vomited during procedures to control the airway. Two patients (3.3%) aspirated.(ABSTRACT TRUNCATED AT 400 WORDS)

Adjuvants, Anesthesia↗
PubMed1992

Protection of macaques against infection with simian type D retrovirus (SRV-1) by immunization with recombinant vaccinia virus expressing the envelope glycoproteins of either SRV-1 or Mason-Pfizer monkey virus (SRV-3).

Rhesus macaques were immunized with live vaccinia virus recombinants expressing the envelope glycoproteins (gp70 and gp22) of simian type D retrovirus (SRV), serotype 1 or 3. All of the animals immunized with either the SRV-1 env or the SRV-3 env vaccinia virus recombinant developed neutralizing antibodies against the homologous SRV. In addition, both groups developed cross-reactive antibodies and were protected against an intravenous live-virus challenge with SRV-1. The four control animals immunized with a vaccinia virus recombinant expressing the G protein of respiratory syncytial virus were not protected against the same SRV-1 challenge. Although SRV-1 and SRV-3 immune sera showed cross-neutralization, they failed to neutralize a separate, more distantly related serotype, SRV-2, in an in vitro assay. These findings are consistent with the known degree of serologic and genetic relatedness of these three SRV strains.

Animals↗
PubMed1992

"Michael.".

Explore the source record for details and available documents.

Adult↗
PubMed1992

Toxic effects of ackee oil (Blighia sapida L) following subacute administration to rats.

Subacute intraperitoneal administration of the lipid portion of the unripe ackee arillus, referred to as "ackee oil", resulted in marked neutropenia (p less than 0.001) and increase in platelets (p less than 0.01) without anaemia, in rats. Blood urea, sodium and aspartate aminotransferase levels were significantly decreased but glucose and bilirubin levels were similar to those of controls. The lungs showed areas of petechial haemorrhages and a dose-related perivascular and peribronchial mononuclear cell infiltration. The pulmonary toxicity may be interpreted as a hypersensitive reaction to ackee oil. Further research is in progress on the neutropenic effects of ackee oil.

Animals↗
PubMed1991

Open to suggestions.

A survey of patients' attitudes to GP opening hours produced strong evidence for extending surgery times for patients' convenience and to meet specific health needs, say Chris Atkinson and Marjorie Gardner.

Appointments and Schedules↗