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Biomedical subjects

T J Lyons

Publications and source records attributed to T J Lyons.

At least 55 records · Page 3Linked to original sources
PubMed1996

Brain cancer, flying, and socioeconomic status: a nested case-control study of USAF aircrew.

UNLABELLED: We compared the brain cancer risk of male United States Air Force (USAF) aircrew (37 cases) with nonflying Air Force personnel (193 cases) between 1970 and 1989. METHODS: Incident brain cancer cases for both aviators and nonflying USAF personnel were obtained from USAF hospitalization records. Age, race, and calendar time matched controls were randomly selected for each case from the remaining USAF cohort. We estimated brain cancer risks using conditional logistic regression models. RESULTS: Initially, we observed a statistically significant brain cancer excess for USAF aircrew compared to nonflying USAF personnel (Odds Ratio [OR] = 1.77, 95% Confidence interval [95% CI] 1.17-2.68). However, following adjustment for senior military rank, a socioeconomic status indicator, the USAF aircrew brain cancer risk was markedly reduced (OR = 1.22, 95% CI 0.76-1.95), demonstrating that much of the previously observed USAF aircrew brain cancer risk was attributable to factors other than flying. CONCLUSION: The results of this investigation indicate that flying is not an important brain cancer risk factor, at least for USAF aircrew. The positive relationships observed in other studies between commercial aircrew and brain cancer risk may have been confounded by social class differentials.

Adult↗
PubMed1995

Non-cholesteatomatous suppurative otitis media: facial nerve palsy in an immunocompromised patient.

A 47-year-old man developed a complete facial nerve palsy secondary to non-cholesteatomatous suppurative otitis media. At operation, this was seen to be due to destruction of the nerve from halfway along the horizontal segment to a point just distal to the second genu. The history of recent renal transplantation and subsequent immunosuppression was judged to be significant in the pathogenesis of the palsy.

Facial Paralysis↗
PubMed1995

External ear canal cholesteatoma. Case report.

External ear canal cholesteatoma is a rare condition in otologic practice. A case in a 43-year-old woman is presented in which despite the extensive nature of the lesion, minimal symptoms and absence of signs delayed diagnosis. The cause of the lesion and its treatment are discussed.

Adult↗
PubMed1995

A review of United States Air Force aeromedical evacuation of acute myocardial infarction patients in Europe.

United States Air Force regulations currently do not recommend the routine movement of recently stabilized patients diagnosed with acute myocardial infarctions. However, U.S. Department of Defense and embassy physicians throughout Europe continually request aeromedical movement of these patients. Therefore, a year-long prospective case review of acute myocardial infarction (AMI) patient movement within the military aeromedical system in Europe was undertaken to evaluate the need for and safety of transporting these patients. This case review, combined with the literature, suggests that recently stabilized AMI patients, with appropriate pre-flight preparation and in-flight care, can tolerate exposure to the stresses of flight and can be safely airlifted.

Air Ambulances↗
PubMed1995

Increased flight surgeon role in military aeromedical evacuation.

BACKGROUND: Physicians were involved in the development of aeromedical evacuation (medevac) and flight surgeons flew as crewmembers on the first U.S. military medevac flights. However, since World War II flight surgeons have not been routinely assigned to operational medevac units. The aeromedical literature addressing the role of physicians in medevac is controversial. Recent contingencies involving the U.S. Air Force (USAF) have required the augmentation of medevac units with flight surgeons. RECENT CHANGES IN THE EUROPEAN THEATER: Beginning in 1992, the United States Air Forces Europe (USAFE) assigned three flight surgeons to the medevac squadron. Between 2 February 1993 and 24 March 1994 USAFE moved 241 patients on 29 missions out of the former Yugoslavia--most of these missions had a flight surgeon on the crew. Because advance medical information on the status of these patients is often nonexistent, the presence of a physician on the crew proved life-saving in some instances. In peacetime operations, there has been a recent trend in the European theater for the USAF to move more unstable patients. OBSERVED BENEFITS OF PHYSICIANS IN MEDEVAC: Dedicated medevac flight surgeons have proven to have the specific experience and training to perform effectively in the role of in-flight medical attendant. In addition, they are effective in negotiating with referring physicians about the urgency of movement, required equipment, the need for medical attendants, etc. These flight surgeons also provide medical coverage of transiting patients in the Aeromedical Staging Flight (ASF), thus providing needed continuity in the medevac system. CONCLUSION: Dedicated medevac flight surgeons fill a unique and valuable role in medevac systems. Agencies with medevac units should consider assigning flight surgeons to these units.

Aerospace Medicine↗
PubMed1995

U.S. Air Force aeromedical evacuation of obstetric patients in Europe.

U.S. Air Force (USAF) regulations do not recommend the routine movement of obstetrical patients greater than 34 weeks gestation. However, U.S. Department of Defense and embassy physicians throughout Europe continually request aeromedical movement of obstetrical patients greater than 34 weeks gestation. Therefore, a year-long prospective review of obstetric patient movement within the military aeromedical system in Europe was undertaken to evaluate the need for and safety of transporting pregnant women over 34 weeks gestation. Civilian studies demonstrate the safety of transporting these patients, but these studies generally address short-range transport by helicopter. By contrast, the USAF operates a high-volume, long-range aeromedical evacuation system with large fixed-wing aircraft. Of the 13,095 patients reported for military aeromedical movement within the study time frame, 329 patients were uneventfully airlifted for obstetrical reasons. This study suggests that long distance movement by fixed-wing aircraft of obstetric patients at any gestational age can be done safely in the USAF military aeromedical system.

Air Ambulances↗
PubMed1994

Glycation, glycoxidation, and cross-linking of collagen by glucose. Kinetics, mechanisms, and inhibition of late stages of the Maillard reaction.

The Maillard or browning reaction between sugar and protein contributes to the increased chemical modification and cross-linking of long-lived tissue proteins in diabetes. To evaluate the role of glycation and oxidation in these reactions, we have studied the effects of oxidative and antioxidative conditions and various types of inhibitors on the reaction of glucose with rat tail tendon collagen in phosphate buffer at physiological pH and temperature. The chemical modifications of collagen that were measured included fructoselysine, the glycoxidation products N epsilon-(carboxymethyl)lysine and pentosidine and fluorescence. Collagen cross-linking was evaluated by analysis of cyanogen bromide peptides using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by changes in collagen solubilization on treatment with pepsin or sodium dodecylsulfate. Although glycation was unaffected, formation of glycoxidation products and cross-linking of collagen were inhibited by antioxidative conditions. The kinetics of formation of glycoxidation products proceeded with a short lag phase and were independent of the amount of Amadori adduct on the protein, suggesting that autoxidative degradation of glucose was a major contributor to glycoxidation and cross-linking reactions. Chelators, sulfhydryl compounds, antioxidants, and aminoguanidine also inhibited formation of glycoxidation products, generation of fluorescence, and cross-linking of collagen without significant effect on the extent of glycation of the protein. We conclude that autoxidation of glucose or Amadori compounds on protein plays a major role in the formation of glycoxidation products and cross-liking of collagen by glucose in vitro and that chelators, sulfhydryl compounds, antioxidants, and aminoguanidine act as uncouplers of glycation from subsequent glycoxidation and cross-linking reactions.

Animals↗
PubMed1994

Toxicity of mildly modified low-density lipoproteins to cultured retinal capillary endothelial cells and pericytes.

To investigate the role of modified low-density lipoproteins (LDL) in the pathogenesis of diabetic retinopathy, we studied the cytotoxicity of normal and mildly modified human LDL to bovine retinal capillary endothelial cells and pericytes in vitro. Pooled LDL was incubated (in phosphate-buffered saline-EDTA, 3 days, 37 degrees C) under 1) nitrogen with additional chelating agents and 2) air, to prepare normal and minimally oxidized LDL, respectively. Similar conditions, but with the addition of 50 mM D-glucose, were used to prepare glycated and glycoxidized LDL. None of the LDL preparations was recognized by the macrophage scavenger receptor, confirming limited modification. Retinal capillary endothelial cells and pericytes were grown to confluence and then exposed for 2 or 3 days to serum-free medium (1% albumin) supplemented with normal or modified LDL (100 mg/l) or to serum-free medium alone. Cytotoxicity was assessed by cell counting (live and total cells) and by cell protein determination. Compared with normal LDL, modified LDL were cytotoxic to both cell types at both time points, causing highly significant decreases in live and total cell counts (P < 0.001) (analysis of variance). Reductions in cell protein also were significant for pericytes at day 3 (P = 0.016) and of borderline significance for endothelial cells at day 2 (P = 0.05) and day 3 (P = 0.063). Cytotoxicity increased as follows: normal < glycated < or = minimally oxidized < glycoxidized LDL. We conclude that, in diabetes, mild modification of LDL resulting from separate or combined processes of glycation and oxidation may contribute to chronic retinal capillary injury and thus to the development of diabetic retinopathy.

Analysis of Variance↗
PubMed1994

3-Deoxyfructose concentrations are increased in human plasma and urine in diabetes.

3-Deoxyglucosone (3-DG) is a reactive dicarbonyl sugar thought to be a key intermediate in the nonenzymatic polymerization and browning of proteins by glucose. 3-DG may be formed in vivo from fructose, fructose 3-phosphate, or Amadori adducts to protein, such as N epsilon-fructoselysine (FL), all of which are known to be elevated in body fluids or tissues in diabetes. Modification of proteins by 3-DG formed in vivo is thought to be limited by enzymatic reduction of 3-DG to less reactive species, such as 3-deoxyfructose (3-DF). In this study, we have measured 3-DF, as a metabolic fingerprint of 3-DG, in plasma and urine from a group of diabetic patients and control subjects. Plasma and urinary 3-DF concentrations were significantly increased in the diabetic compared with the control population (0.853 +/- 0.189 vs. 0.494 +/- 0.072 microM, P < 0.001, and 69.9 +/- 44.2 vs. 38.7 +/- 16.1 nmol/mg creatinine, P < 0.001, respectively). Plasma and urinary 3-DF concentrations correlated strongly with one another, with HbA1c (P < 0.005 in all cases), and with urinary FL (P < 0.02 and P = 0.005, respectively). The overall increase in 3-DF concentrations in plasma and urine in diabetes and their correlation with other indexes of glycemic control suggest that increased amounts of 3-DG are formed in the body during hyperglycemia in diabetes and then metabolized to 3-DF. These observations are consistent with a role for increased formation of the dicarbonyl sugar 3-DG in the accelerated browning of tissue proteins in diabetes.

Adolescent↗
PubMed1994

Platelet plasminogen activator inhibitor 1 in patients with type II diabetes.

OBJECTIVE: To compare platelet plasminogen activator inhibitor 1 (PAI-1) concentration in type II diabetic patients and healthy control subjects. RESEARCH DESIGN AND METHODS: We studied a group of 12 diabetic patients whose disease was controlled by diet or sulfonylurea therapy and a group of 17 nondiabetic control subjects. All subjects were free of clinically advanced vascular disease. PAI-1 antigen concentrations were measured in 5 x 10(8) isolated platelets, which were lysed by 1% Triton X-100. RESULTS: Mean platelet PAI-1 was significantly higher in diabetic patients (264 +/- 83 ng/5 x 10(8) platelets) compared with control subjects (202 +/- 71 ng/5 x 10(8) platelets) (P < 0.05). A significant independent positive correlation was found between platelet PAI-1 concentrations and fasting plasma specific insulin levels in the diabetic patients (r = 0.63, P = 0.03). CONCLUSIONS: These findings suggest that 1) a higher platelet PAI-1 concentration may contribute to enhanced thrombosis in type II diabetes and 2) megakaryocyte PAI-1 synthesis may be under the control of insulin.

Blood Platelets↗
PubMed1994

Classification problems of U.S. Air Force spatial disorientation accidents, 1989-91.

Spatial disorientation (SD) continues to contribute to a fairly constant proportion of military aircraft accidents. The U.S. Air Force (USAF) fielded a new accident investigation reporting form in July 1989, which for the first time specified Type I SD, Type II SD, and Type III SD as possible causes of aircraft accidents. Of a total of 91 major accidents that occurred over the 2-year period beginning in October 1989, SD was rated as contributing significantly to 13 (14%). Coding for SD on accident investigation reporting forms was not consistent, however. Individual flight surgeons differed in their approaches to coding accidents as SD-related; other differences were noted between flight surgeons and pilots, and additional procedural differences resulted in inconsistent reporting over time. There is a consensus that SD represents a major problem in military aviation, but a scientific approach to this important problem would be facilitated if agreement could be reached on definitional and semantic issues.

Accidents, Aviation↗
PubMed1993

Glycation and oxidation: a role in the pathogenesis of atherosclerosis.

Reactions involving glycation and oxidation of proteins and lipids are believed to contribute to atherogenesis. Glycation, the nonenzymatic binding of glucose to protein molecules, can increase the atherogenic potential of certain plasma constituents, including low-density lipoprotein (LDL). Glycation of LDL is significantly increased in diabetic patients compared with normal subjects, even in the presence of good glycemic control. Metabolic abnormalities associated with glycation of LDL include diminished recognition of LDL by the classic LDL receptor; increased covalent binding of LDL in vessel walls; enhanced uptake of LDL by macrophages, thus stimulating foam cell formation; increased platelet aggregation; formation of LDL-immune complexes; and generation of oxygen free radicals, resulting in oxidative damage to both the lipid and protein components of LDL and to any nearby macromolecules. Oxidized lipoproteins are characterized by cytotoxicity, potent stimulation of foam cell formation by macrophages, and procoagulant effects. Combined glycation and oxidation, "glycoxidation," occurs when oxidative reactions affect the initial products of glycation, and results in irreversible structural alterations of proteins. Glycoxidation is of greatest significance in long-lived proteins such as collagen. In these proteins, glycoxidation products, believed to be atherogenic, accumulate with advancing age: in diabetes, their rate of accumulation is accelerated. Inhibition of glycation, oxidation, and glycoxidation may form the basis of future antiatherogenic strategies in both diabetic and nondiabetic individuals.

Animals↗
PubMed1993

Type I aortic dissection in a patient with osteogenesis imperfecta.

The previously undescribed association between aortic dissection and osteogenesis imperfecta is reported in a 39-year-old man with known osteogenesis imperfecta, who presented with a type I aortic dissection. His ascending aorta was repaired using a Dacron tube graft under hypothermic circulatory arrest but the patient died 12 h later, following re-dissection around the left coronary ostium resulting in massive myocardial infarction of the left ventricle.

Adult↗
PubMed1993

Inflammatory pseudotumour of the liver: antecedent causes and clinical experience.

We present a case in which inflammatory pseudotumour of the liver which appears to complicate Caroli's disease. We have reviewed the literature in hepatic inflammatory pseudotumour with particular emphasis on underlying causes. We were able to find 45 reported cases, with adequate clinical data in 42; in these only 7 showed a probable antecedent cause. There were gallstones in another 5, giving a prevalence not significantly different to that within the general population. Hepatic inflammatory pseudotumour typically presents with a history of fever, anorexia, loss of weight, hepatic pain, jaundice and a detectable liver mass (or masses). The diagnosis of inflammatory pseudotumour should be particularly considered when there is a history of previous inflammatory hepato-biliary disease. Preoperative or intra-operative diagnosis might then avoid major hepatic surgery.

Adult↗
PubMed1993

Accumulation of Maillard reaction products in skin collagen in diabetes and aging.

To investigate the contribution of glycation and oxidation reactions to the modification of insoluble collagen in aging and diabetes, Maillard reaction products were measured in skin collagen from 39 type 1 diabetic patients and 52 nondiabetic control subjects. Compounds studied included fructoselysine (FL), the initial glycation product, and the glycoxidation products, N epsilon-(carboxymethyl) lysine (CML) and pentosidine, formed during later Maillard reactions. Collagen-linked fluorescence was also studied. In nondiabetic subjects, glycation of collagen (FL content) increased only 33% between 20 and 85 yr of age. In contrast, CML, pentosidine and fluorescence increased five-fold, correlating strongly with age. In diabetic patients, collagen FL was increased threefold compared with nondiabetic subjects, correlating strongly with glycated hemoglobin but not with age. Collagen CML, pentosidine and fluorescence were increased up to twofold in diabetic compared with control patients: this could be explained by the increase in glycation alone, without invoking increased oxidative stress. There were strong correlations among CML, pentosidine and fluorescence in both groups, providing evidence for age-dependent chemical modification of collagen via the Maillard reaction, and acceleration of this process in diabetes. These results support the description of diabetes as a disease characterized by accelerated chemical aging of long-lived tissue proteins.

Adolescent↗