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Biomedical subjects

J Fisher

Publications and source records attributed to J Fisher.

At least 361 records · Page 20Linked to original sources
PubMed1990

A simple instrument for the measurement of maximum occlusal force in human dentition.

A simple instrument for the measurement of maximum occlusal force has been developed and the results of an initial clinical trial have been reported. The maximum occlusal force in subjects with dentures was significantly lower than in a group of young male subjects with natural dentition. In the young males the bite force between the molars and premolars was significantly greater than between the incisors. The maximum bite force was not dependent on position for subjects with dentures.

Adult↗
PubMed1990

Determination of contact area in 'cushion form' bearings for artificial hip joints.

Current forms of artificial hip joints produce wear debris, which contributes to loosening of the prostheses. These 'hard' joints articulate with boundary or mixed lubrication, whereas the natural joint articulates with full fluid film lubrication. An artificial joint that articulates with full fluid film lubrication could greatly reduce wear and frictional torque and hence reduce the incidence of loosening and inflammatory tissue reaction. The use of a thin lining of low elastic modulus in the acetabular cup is one possible way of promoting full fluid film lubrication. In the design of such cushion forms of bearings, it is important to be able to predict the contact area, stress distribution and film thickness. This paper presents experimental techniques to determine the contact area in low elastic modulus layers and compares these measured areas with theoretical predictions using linear elasticity theory. At low loads experimental results and theoretical predictions were close. However, at loads above 300 N, the theory overestimated the width of the contact area by up to 8.5 per cent. This difference is mainly attributed to the non-linear behaviour of the elastomer at the higher levels of stress.

Elasticity↗
PubMed1990

Management of large dural defects in skull base surgery: an update.

The use of a ventriculoatrial shunt for long-term CSF diversion for reconstruction after resection of large skull base tumors with intradural extension has been discontinued. The concern about placing a permanent foreign body in a wound open for 12 to 18 hours is our primary reason for changing the technique. Our present approach uses a rectus abdominis microvascular free flap over the fascial closure of the dural defect. Although our experience with this technique is limited, the advantages over the technique used previously warrant its continued use.

Abdominal Muscles↗
PubMed1989

c-myc and c-myb oncoproteins during induced maturation of myeloid and erythroid human leukemic cell lines.

c-myc and c-myb mRNAs have been found to be tightly regulated during hemopoietic differentiation. We have studied nuclear c-myc and c-myb oncoproteins through the cell cycle, during macrophage, granulocyte, erythroid, and megakaryocytic differentiation of KG1, HL60, and HEL cells. p62c-myc and p75c-myb content of propidium iodide-stained nuclei was quantitated by flow cytometry using fluoresceinated antibodies CT14-G4 and MB4.3, respectively. In uninduced cells p62c-myc content is highest in HL60, followed by HEL, then KG1, while p75c-myb is highest in HEL, followed by HL60 and KG1. All lines showed a less than 2-fold increment in both oncoproteins over the cell cycle. Macrophage induction of KG1 and HL60 resulted in early increase in both oncoproteins, followed by a decline to less than starting values by 48 h, concurrent with a reduction of S phase cells and the appearance of adherent alpha-naphthyl acetate esterase-positive cells. p62c-myc changes were more pronounced in HL60 and p75c-myb changes in KG1. Different patterns of oncoprotein expression were found when different inducing agents were used for granulocyte differentiation of HL60. Under all conditions, however, both oncoproteins declined to basal levels before granulocyte maturity. Hemin-induced erythroid differentiation of HEL to hemoglobin-containing cells resulted in biphasic p62c-myc and p75c-myb kinetics. In contrast, dimethyl sulfoxide-induced megakaryocytic differentiation of HEL was accompanied by an early and steady decline in both oncoproteins. Despite considerable reduction in oncoprotein levels, HEL cells were still actively cycling at 120 h. It appears that c-myc and c-myb proteins decline with differentiation, well before proliferation ceases in some lineages. The kinetics of the decline differ between the two oncogenes and vary with the lineage induced and the nature of the inducing agent used. The cell cycle distribution of the oncoproteins does not change during maturation. These data suggest disparate roles for c-myc versus c-myb during hemopoietic differentiation and the existence of multiple signal transduction pathways for down-regulation of these genes.

Antibodies, Monoclonal↗
PubMed1989

1H NMR studies of bovine and porcine phospholipase A2: assignment of aromatic resonances and evidence for a conformational equilibrium in solution.

Bovine and porcine pancreatic phospholipases A2, and porcine isophospholipase A2, have been investigated by one- and two-dimensional 1H NMR spectroscopy. Resonances have been assigned for 20-26 residues in each enzyme, including all the aromatic residues, by a strategy based on the semiquantitative comparison of proximity relationships deduced from NOE experiments with those seen in the crystal structure NOE experiments indicate that the loop comprising residues 59-70, which has a different conformation in the crystal structures of the bovine and porcine enzymes, has the same conformation in these two enzymes in solution. Selective changes in the line width of a limited number of resonances as a function of pH, temperature, and calcium concentration provide evidence for a local conformational equilibrium. This equilibrium involves a limited region of the protein structure around residues 25, 41, 106, and 111; it has been identified in the bovine enzyme and porcine isoenzyme but is not apparent in the porcine enzyme.

Animals↗
PubMed1989

Dimerization and activation of porcine pancreatic phospholipase A2 via substrate level acylation of lysine 56.

The porcine pancreatic phospholipase A2-catalyzed hydrolysis of the water-soluble chromogenic substrate 4-nitro-3-octanoyloxybenzoate shows an initial latency phase similar to the one observed in the hydrolysis of aggregated phospholipids by the same enzyme. We report here that during the latency phase the enzyme undergoes a slow, autocatalytic, substrate-level acylation whereby in a few of the catalytic events the scissile octanoyl group of the substrate, normally transferred to water, is transferred to the epsilon-amino group of lysine 56. The N epsilon 56-octanoylphospholipase shows a strong tendency to dimerize in solution and thus may be separated from the monomeric native enzyme by gel filtration. Octanoylation of Lys-56 activates the enzyme some 180-fold toward 4-nitro-3-octanoyloxybenzoate and more than 100-fold toward monolayers of 1,2-didecanoyl-sn-glycero-3-phosphocholine. Acylation also attends the enzymatic hydrolysis of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine with the incorporation of 1 eq of palmitate. Kinetic analysis of the early phase of reaction with 4-nitro-3-octanoyloxybenzoate shows that in this initial step the rate of activation is first order with respect to enzyme and substrate. A much more rapid, autocatalytic activation occurs in the later phases of the reaction where the activation of the enzyme is catalyzed by the activated enzyme itself. These findings with porcine pancreatic phospholipase A2, together with those relative to a snake venom enzyme monomer (Cho, W., Tomasselli, A. G., Heinrikson, R. L., and Kézdy, F. J. (1988) J. Biol. Chem. 263, 11237-11241), strongly support the proposal that interfacial activation of monomeric phospholipases is due to substrate-level autoacylation resulting in fully potentiated dimeric enzymes.

Acylation↗
PubMed1989

Acute effects of combination of IB and IC antiarrhythmics for the treatment of ventricular tachycardia.

There are limited data on the effects of Class IB and IC antiarrhythmic drug combination for the treatment of ventricular tachycardia. The present study evaluated this combination in 12 patients who had sustained ventricular tachycardia (SuVT) during programmed electrical stimulation (PES) and failed IC antiarrhythmic therapy. Following combination of lidocaine and a IC agent (7 with encainide and 5 with flecainide), two had no inducible ventricular tachycardia (VT) and one had nonsustained VT (NSVT). In seven of nine patients who still had SuVT, the mean VT cycle length increased 40 +/- 25 msec post combination compared to IC antiarrhythmic therapy. Seven patients who had a favorable response to the initial combination (less than 10 beats of NSVT, or greater than or equal to 10 beats of VT with a greater than 100 msec increase in cycle length compared to baseline and no hemodynamic compromise) were then placed on IC + oral IB agent (5 with mexiletine, 2 with tocainide). Similar effects on VT inducibility and cycle length were observed following the oral combination. In conclusion, the addition of lidocaine to IC therapy produced favorable effects on induced ventricular tachycardia in 58% of patients compared to IC agent alone. Also, a positive PES response to lidocaine and IC therapy corresponded to a similar positive response when either mexiletine or tocainide was substituted for lidocaine.

Anilides↗
PubMed1989

Microvascular surgery as an adjunct to craniomaxillofacial reconstruction.

Fifteen patients (8 female and 7 male) age 4 to 57 years underwent microsurgical free tissue transfers as a component of a craniomaxillofacial reconstruction. In 12 patients the free flap was performed simultaneously with the bony procedure and in three it was a secondary procedure. The patients included two craniosynostosis, four craniofacial tumours, five hemicraniofacial microsomias, one facial and skull base arteriovenous malformation, one orbitofacial neurofibromatosis and two hemifacial atrophies with extensive facial skeletal involvement. The rectus abdominis free flap was used in 9 patients, the latissimus dorsi in two, the omentum in three, and the first web-space in one. The choice of tissue varied according to the size of the defect and its location. The rectus abdominis musculofasciocutaneous flap was the most frequent source of tissue for contour restoration, and the omentum was used to fill intracranial spaces. One flap failed intraoperatively in a patient with hemifacial microsomia and inadequate and abnormal recipient vessels. One patient had an injury to the temporal branch of the facial nerve, with spontaneous recovery. In 13 patients the free tissue transfer was for soft tissue fill with cover of facial bone or skull base; secondary procedures were frequently required in these patients. In two patients with intracranial free flaps, no further procedures were necessary. In selected cases the association of microvascular techniques with craniomaxillofacial surgery can facilitate reconstruction and improve results.

Adolescent↗
PubMed1989

Combination therapy with gold and hydroxychloroquine in rheumatoid arthritis: a prospective, randomized, placebo-controlled study.

We studied combination therapy with two slow-acting antirheumatic drugs given concurrently in active rheumatoid arthritis (RA). A 12-month prospective randomized controlled trial compared gold and hydroxychloroquine in 52 patients to gold and placebo in 49. The patients continued to receive non-steroidal anti-inflammatory drugs and analgesics. They were selected from three rheumatology centres in the West Midlands. Combination therapy led to a greater number of withdrawals due to adverse reactions (18 cases compared to 10 receiving gold/placebo). Patients completing 12 months' therapy (27 taking gold/hydroxychloroquine and 32 on gold/placebo) were compared using five clinical, seven laboratory, and one radiological measure. All 13 variables favoured gold/hydroxychloroquine with an overall advantage of 20-25% for the combination. This only reached statistical significance (at the 1% level) for C-reactive protein. An overall disease activity index was better at 12 months (at the 5% level) and showed a more rapid response with gold/hydroxychloroquine. This is the first randomized prospective placebo-controlled trial to show a significant advantage from a combination of two slow-acting drugs. There are many different ways of giving such combinations and we consider these should be explored to maximize the effectiveness of treatment for RA.

Adult↗
PubMed1989

Experience with 80 rectus abdominis free-tissue transfers.

Eighty patients receiving rectus abdominis free-tissue transfers are discussed. The operations were performed between July of 1983 and December of 1986. Specifically, the patients were followed in the clinic to determine the extent and degree of donor-site morbidity. Sixty-two flaps were transferred to the lower extremities, 15 to the head and neck, 2 to the arm, and 1 was placed intrathoracically. Osteomyelitis was the most common indication for free-muscle transfer in 33 patients, soft-tissue defects in 26, and facial soft-tissue augmentation in 14 patients. In the 80 rectus abdominis free-muscle transfers, there were 9 local complications. A seroma occurred in 4 patients, wound infection in 3, and an abdominal wall hernia occurred in 1 patient. The success rate for muscle transfer was 93 percent with six flap losses. Because there is a low incidence of donor-site complications, the surgical dissection is relatively easy, and the relative consistency and size of the deep inferior epigastric pedicle are good, the rectus abdominis muscular unit is now one of the most frequently used free-tissue transfers at our institution.

Abdominal Muscles↗
PubMed1989

Immunoprophylaxis of Chlamydia trachomatis lymphogranuloma venereum pneumonitis in mice by oral immunization.

Groups of BALB/c mice were orally immunized with chlamydiae and challenged intranasally to determine whether oral immunization offers protection against pulmonary disease and to characterize the nature and kinetics of the chlamydial antibody response in the lung and other mucosal sites. Protection by oral immunization from chlamydial lung disease was demonstrated by lack of replication of the organism and the lack of chlamydial antigen in lung tissue. The chlamydial immunoglobulin A (IgA) antibody response was present at all body sites, reaching peak levels in the lung as well as in the serum. Classical IgA booster effect kinetics was observed after intranasal challenge, especially in the lung. Specific IgG antibody was detected at all body sites but at lower levels. Furthermore, animals immunized orally had no pneumonic process, as determined by histopathology. These studies also suggest that passively acquired specific serum IgG antibody may not significantly influence the course of mucosal replication of the organism. These observations indicate that oral immunization activating the gut-associated lymphoid tissue system gave total protection against chlamydial lung disease, suggesting migration of immunologically competent cells from the intestine to the lung.

Administration, Oral↗
PubMed1989

Failure and hydrodynamic function testing of explanted pericardial and porcine bioprosthetic valves.

The long-term durability and function of cardiac bioprostheses can be affected by both calcification and mechanical failure of the tissue. The mechanisms of failure and hydrodynamic function of 66 explanted bioprostheses have been studied. The majority of porcine valves were heavily calcified with leaflet tears adjacent to the calcification at the commissures. These tears caused prolapsed leaflets and regurgitation of between 30 and 70 per cent. Only three porcine valves had tissue failure in the absence of calcification. The majority of pericardial valves failed due to leaflet tears at the edge of the frame in the absence of macroscopic calcification. These tears also produced prolapsed leaflets and large regurgitation in hydrodynamic tests. Three pericardial valves were heavily calcified and stenotic without leaflet tears. Leaflet dynamics in the pericardial valves were affected by host tissue ingrowth which produced increased pressure drops across the valves, an asymmetrical open position and leaflet flutter. In the absence of calcification and leaflet tears, there was little change in the function of explanted porcine valves.

Bioprosthesis↗
PubMed1989

Severe "silent" mitral regurgitation. A potentially reversible cause of refractory heart failure.

Hemodynamically critical ("severe") mitral regurgitation is usually associated with an audible (if not loud) systolic murmur and signs of left ventricular volume overload. However, "silent" severe mitral regurgitation is being increasingly recognized. We review the case histories of nine patients with silent hemodynamically important mitral regurgitation (associated with acute myocardial infarction and chronic valvular, hypertrophic, and ischemic heart disease), six of whom survived mitral valve replacement, of whom five are alive and functioning well more than three years postoperatively. Performance of left ventriculography early in the hospital course of patients with severe unexplained congestive heart failure (with normal or near-normal left ventricular systolic function assessed noninvasively) identifies patients with severe silent mitral regurgitation who may have long-term benefit from mechanical therapy.

Adult↗
PubMed1989

Cardiopulmonary responses to Pseudomonas septicemia in swine: an improved model of the adult respiratory distress syndrome.

Bacteremia with resultant damage to multiple organ systems remains a serious problem in intensive care of human patients. We have developed a clinically relevant swine model of sepsis-induced adult respiratory distress syndrome (ARDS). Twenty-three animals were given various doses of Pseudomonas aeruginosa intravenously. Low cardiac output septic shock was prevented with massive fluid infusion. It was found that a dose of 1.0 X 10(7) colony forming units per 20 kg/min for 2 hours reliably produced respiratory failure in a setting of hyperdynamic sepsis which meets the diagnostic criteria of human ARDS.

Animals↗
PubMed1988

Relation of concentric left ventricular hypertrophy and extracardiac target organ damage to supranormal left ventricular performance in established essential hypertension.

Increased cardiac performance has been documented in patients with early systemic hypertension, but its prevalence and determinants in patients with uncomplicated sustained essential hypertension have not been characterized. Radionuclide cineangiography in 116 patients with uncomplicated essential hypertension showed that 12 of 116 (10%) had supranormal resting left ventricular (LV) ejection fraction (greater than 70%, above the highest value in normal subjects), while 104 patients had a normal resting ejection fraction (45 to 70%). Patients with a high resting ejection fraction had higher systolic and diastolic blood pressure compared with patients with normal resting ejection fraction (182 mm Hg vs 169, p less than 0.01, and 110 vs 103, p less than 0.05, respectively), markedly greater echocardiographic LV mass (136 vs 94 g/m2, p less than 0.01), smaller ventricular dimensions in systole (2.5 vs 3.1, p less than 0.01) and diastole (4.4 vs 4.9, p less than 0.05), and higher relative wall thickness (0.61 +/- 0.20 vs 0.39 +/- 0.98, p less than 0.001). Patients with supranormal resting ventricular performance had lower end-systolic wall stress than normal volunteers or patients with normal resting LV function (48 vs 64 vs 74 X 10(3) dynes/cm2, respectively). Patients with an elevated LV ejection fraction also had significantly more abnormal funduscopic examinations and greater proteinuria. Thus, a subset of essential hypertensive patients with moderately to severely elevated blood pressure developed marked concentric LV hypertrophy associated with subnormal end-systolic stress and supranormal LV performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomegaly↗
PubMed1988

Severe haemolysis with the St. Jude Medical prosthesis.

The St. Jude Medical prosthesis has become one of the most widely used mechanical heart valves because of its excellent haemodynamic function. Although subclinical haemolysis has been described with this prosthesis, there has only been a single report of frank haemolysis in the absence of a paravalvular leak. We report the occurrence of severe haemolysis in five patients following St Jude Medical prosthesis implantation, four of whom had combined aortic and mitral valve replacements. In no patient could the haemolysis be attributed either to a paravalvular leak or an obvious valve malfunction.

Aged↗