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Biomedical subjects

M L Dalton

Publications and source records attributed to M L Dalton.

At least 19 recordsLinked to original sources
PubMed2005

Hemodynamic and pulmonary fluid status in the trauma patient: are we slipping?

Recent reports point to problems in the clinical assessment of the cardiopulmonary system in hemodynamically unstable patients, especially with the decreasing usage of pulmonary artery catheters. Our purpose was to evaluate the hypothesis that clinical judgment alone is inadequate for a reliable estimate of cardiopulmonary status in critically ill patients. Physician assessments (high, normal, or low) of cardiac index (CI) and thoracic fluid content (TFC) were made in 68 acute trauma cases and compared to the results obtained with impedance cardiography (ICG). Physician assessment using clinical judgment alone was correct only 42 per cent and 57 per cent, respectively, for CI and TFC. There was very little difference in heart rate (HR), blood pressure (BP), Glasgow Coma Score (GCS), and the number of injured systems between the incorrect and correct assessments of CI. However, the mean Injury Severity Score (ISS) was markedly higher for the incorrect than the correct CI values (18.8 +/- 9.3 vs 14.2 +/- 9.8, P = 0.0589). Thus, there is a need for an objective measurement of CI and TFC especially in the more severely injured patient. The inaccuracy of the clinical exam strongly suggests the need for a supplemental measurement, which the new and improved ICG monitor could provide.

Adult↗
PubMed2001

The history of the Gold Medal Papers of the Southeastern Surgical Congress: 1960-2000.

Since 1960 at its annual meeting the Southeastern Surgical Congress has selected a varying number of "Gold Medal Papers" to be presented. Customarily a prize is awarded for the first place among the Gold Medal Papers and in some instances a second and third place. A brief history of the origin of these Gold Medal Papers is presented. With the assistance of the Executive Secretary of the Southeastern Surgical Congress a list of the Gold Medal presenters insofar as can be ascertained from the Council minutes is presented. It is unfortunate that all of the names of the Gold Medal Paper presenters have not been preserved.

Awards and Prizes↗
PubMed2001

Magnetically guided nasoenteral feeding tubes: a new technique.

Our objective was to evaluate a new technique for the bedside placement of nasoenteral feeding tubes into the duodenum using an external hand-held magnet to maneuver the tube from the stomach to the distal duodenum. We conducted a prospective case series of 20 consecutive patients requiring nasoenteral tube feeding in the intensive care units of a university-affiliated hospital. Twenty patients were entered into the study after the attending physician requested assistance in tube placement. A flexible nasoenteral feeding tube (12 F), modified to include a magnet and a magnetic field sensor in the distal tip connected by a thin insulated wire to a small light at the proximal end, was passed per nares into the stomach. A larger hand-held magnet held over the epigastrium was used to magnetically "capture" the tube tip, indicated by the illumination of the proximal light. The tube tip was then maneuvered by the hand-held magnet along the lesser curvature of the stomach, through the pylorus, and into the duodenum. Procedure time and anatomic location of the tube tip as determined by an abdominal radiograph was recorded. The 12 men and eight women had a mean age of 60 years (range 30-84). The procedure time averaged 9.6 minutes (range 1-30). In 19 of the 20 patients (95%) radiographs revealed successful placement of the tip of the feeding tube into the duodenum. There were no complications related to the procedure. Using a novel magnetically guided nasoenteral feeding tube transpyloric tube placement was achieved in 95 per cent of cases with an average procedure time of 9.6 minutes. This new and inexpensive bedside technique will allow prompt and safe initiation of enteral nutrition.

Adult↗
PubMed2001

William Osler's influence on the career of Tinsley Randolph Harrison.

In 1957, I was graduated from what was then the Medical College of Alabama, a division of the University of Alabama. It was a privilege and honor to be on Dr. Harrison's service on two occasions during my last 2 years of medical school. He was the most influential role model during my student years and has remained so throughout my professional life. I have always benefitted from his writings, his profound philosophical approach to medicine, and his numerous aphorisms. Only in later years have I come to know of the tremendous influence of William Osler on Tinsley Harrison through his father, William Groce Harrison. Unfortunately, Tinsley Harrison never knew Sir William Osler because he died the year Tinsley Harrison began his second year of medical school at Johns Hopkins. This connection is interesting from many standpoints. For instance, Osler advised Groce Harrison to make Tinsley a "teacher of medicine" when Tinsley was only 3 years old. Through the advice of his father, Tinsley followed the Oslerian tradition throughout his life. This paper presents several similarities between Osler and Harrison.

History, 20th Century↗
PubMed2001

Osteogenesis in a rat model: use of bone marrow cells and biodegradable gelatin matrix carrier.

We investigated the use of a biodegradable porcine gelatin matrix (Gelfoam) as a carrier for marrow cells that induce osteogenesis at ectopic sites in rats. Bone marrow cells obtained from the long bones of 6-week-old Sprague-Dawley rats were dissociated enzymatically and the cells reconstituted in rat serum. Twenty million cells in 0.1 mL of serum were then adsorbed into 1-cm3 pieces of gelatin matrix substrate and implanted into ectopic sites in live Sprague-Dawley rats. The implants were retrieved and analyzed histologically for bone and cartilage formation 3, 4, 6, and 8 weeks after implantation. Woven bone was seen as early as 3 weeks and persisted through 8 weeks. No cartilage was observed. Osteoclasts first appeared at 3 weeks, peaking in number at 4 weeks. By 6 and 8 weeks, only small islets of substrate remained, surrounded by dense, woven bone. Control implants, consisting only of serum adsorbed into the carrier, showed no bone formation. We conclude that biodegradable gelatin matrix can serve as a carrier for the osteogenic cells of bone marrow in rats in ectopic sites. Such a system may be further developed to augment bone healing.

Animals↗
PubMed2000

Schwannoma of the cervical sympathetic chain: it's not a carotid body tumor.

Schwannoma of the cervical sympathetic chain is a rare nerve tumor with fewer than 40 confirmed cases in the English literature. These lesions typically present as an asymptomatic neck mass and are easily mistaken for a carotid body tumor during the initial workup. We report a case of schwannoma of the cervical sympathetic chain in a 35-year-old man followed by a review of the current literature.

Adult↗
PubMed2000

Isoproterenol inhibits bacterial lipopolysaccharide-stimulated release of tumor necrosis factor-alpha from human heart tissue.

Recent evidence suggests that inflammatory cytokines, particularly tumor necrosis factor alpha (TNF-alpha), may play a role in heart disease. Elevated plasma levels of the cytokine have been reported in congestive heart failure and severe angina and after myocardial infarction. The exact role of TNF-alpha in heart disease and how production is stimulated and regulated in the heart are current areas of investigation. Regarding regulation of production, isoproterenol elevates cyclic AMP and inhibits TNF-alpha release in macrophages. Therefore we hypothesized that stimulation of beta-adrenergic receptors of the sympathetic nervous system would inhibit release of the cytokine from heart tissue. With Institutional Review Board approval and patient consent atrial tissue was obtained during preparation for cardiac bypass. The tissue was divided into segments, placed in culture medium, and incubated for various times in the presence or absence of lipopolysaccharide (LPS) (20 microg/mL) and/or isoproterenol (1 microM). The medium was removed and analyzed for biologically active TNF-alpha by the L929 cell cytotoxicity assay. Tissue samples were weighed and TNF-alpha release was expressed as pg TNF-alpha/mg tissue. Initially, to determine the time course of release, measurements were made at 2, 5, 10, 15, 30, 60, 120, 180, and 360 minutes after the addition of LPS. Elevated TNF-alpha levels in the culture medium were reliably detected at 360 minutes after exposure to LPS. In atrial tissue obtained from seven patients TNF-alpha released into the culture medium at 360 minutes was 6 +/- 3 pg/mg tissue. In the presence of LPS, levels of the cytokine in the culture medium increased to 604 +/- 233 pg/mg tissue (P < 0.05 vs LPS alone). When isoproterenol and LPS were simultaneously added to the culture medium release of TNF-alpha was reduced by 87 per cent to 82 +/- 40 pg/mg tissue (P < 0.05 vs LPS alone). Our results show that activation of the beta-adrenergic receptor inhibits myocardial production of TNF-alpha. This finding suggests that the sympathetic nervous system inhibits production of the cytokine and that impaired sympathetic function in heart failure may play a role in the elevated levels of TNF-alpha.

Animals↗
PubMed1999

A reactive oxygen-generating system activates nuclear factor-kappaB and releases tumor necrosis factor-alpha in coronary smooth muscle cells.

BACKGROUND: Recently we reported that bacterial lipopolysaccharide (LPS) stimulates release of tumor necrosis factor alpha (TNF-alpha) from porcine coronary arteries and smooth muscle cells cultured from those vessels. It has also been reported that plasma levels of TNF-alpha are elevated after myocardial infarction. Since it is known that the production of reactive oxygen intermediates (ROI) occurs during ischemia and ROI are suggested activators of the nuclear regulatory factor kappaB (NF-kappaB), we tested the hypothesis that release of TNF-alpha from smooth muscle cells could also be stimulated with a ROI-generating system. MATERIALS AND METHODS: Smooth muscle cells were isolated from porcine coronary arteries. Confluent cells in 48-well culture dishes were treated for 30 min with 0.003 units/ml xanthine oxidase (XO) and 2 mM hypoxanthine (HX) added to the culture medium. The medium was then removed and the cells were washed three times and fresh medium without HX-XO was added. Then, at 1, 3, and 6 h the medium was removed and analyzed for biologically active TNF-alpha. In other experiments, smooth muscle cells were treated with 20 micrograms/ml LPS for 6 h and aliquots of medium analyzed for TNF-alpha. Untreated cells served as controls. Data were analyzed by two-way ANOVA with repeated measures. Extracts of total cell protein were prepared and activation of NF-kappaB was determined by electrophoretic mobility shift assay. RESULTS: Treatment of cells with HX-XO stimulated release of TNF-alpha, which rose to a maximum of 17.5 +/- 1.7 units/mg cell protein at 6 h. This was significantly higher (P < 0. 05) than release stimulated by LPS (10.2 +/- 1.0 units/mg at 6 h) or TNF-alpha detected in the culture medium from untreated control cells (4.2 +/- 0.9 units/mg protein at 6 h). Both HX/XO and LPS activated NF-kappaB. CONCLUSIONS: These results support the conclusion that coronary smooth muscle cells are a potential source of TNF-alpha during events that are associated with formation of ROI such as myocardial ischemia.

Animals↗
PubMed1999

Bilateral recurrent nerve paralysis associated with multinodular substernal goiter: a case report.

Substernal goiter is an infrequent occurrence and is found in two to five per cent of all patients undergoing thyroid surgery. These lesions are well known to cause respiratory symptoms and alterations in phonation due to direct compression of airway structures. Infrequently, unilateral recurrent nerve palsy has been reported in patients with substernal goiter. We report a case of bilateral recurrent nerve palsy associated with multinodular substernal goiter in an 89-year-old female who presented in respiratory distress.

Aged↗
PubMed1998

Release of tumor necrosis factor-alpha from coronary smooth muscle: activation of NF-kappaB and inhibition by elevated cyclic AMP.

BACKGROUND: Evidence suggests that tumor necrosis factor-alpha (TNF-alpha) is involved in heart diseases such as atherosclerosis. We used porcine coronary arteries and smooth muscle cells cultured from these vessels to study the regulation of production of TNF-alpha. The aims were to determine if bacterial lipopolysaccharide (LPS) could stimulate production; if activation of the nuclear regulatory factor, NF-kappaB, was associated with production; and if intracellular cAMP regulates TNF-alpha in coronary vasculature through a mechanism involving NF-kappaB. MATERIAL AND METHODS: LPS was used to stimulate TNF-alpha production. Forskolin (FSK) and 8-Br-cAMP were added to tissue and cells in order to elevate intracellular cAMP. TNF-alpha release into the bathing medium was measured by the L929 cell cytotoxicity assay. Intracellular cAMP was determined by radioimmunoassay. NF-kappaB activation was determined in whole cell extracts by electrophoretic mobility shift assay. RESULTS: In segments of coronary arteries, LPS stimulated TNF-alpha release which increased with time to a maximum at 6 h (485 +/- 19 units/g tissue) and remained elevated at this level for 24 h. In contrast, the level of TNF-alpha measured at 24 h in medium from coronary tissue not exposed to LPS was 11.1 +/- 4.1 units/g tissue. In the presence of LPS, both FSK and 8-Br-cAMP significantly reduced TNF-alpha release. For instance at 6 h in the presence of LPS and FSK or 8-Br-cAMP, TNF-alpha was 126 +/- 24 and 71.6 +/- 22 units/g tissue, respectively (P < 0.05 vs LPS alone). Tissue levels of cAMP were significantly elevated in the presence of FSK. Similar results were obtained with smooth muscle cells cultured from the coronary arteries; i.e., LPS stimulated TNF-alpha release which was inhibited in a concentration-dependent manner by a rise in intracellular cAMP induced by FSK. In cultured cells release of TNF-alpha stimulated by LPS was associated with activation of NF-kappaB. Neither FSK nor 8-Br cAMP inhibited activation of NF-kappaB by LPS. CONCLUSIONS: Porcine coronary arteries produce TNF-alpha from a smooth muscle cell source. Production stimulated by LPS was inhibited by elevated intracellular cAMP and was associated with activation of NF-kappaB. However, activation of NF-kappaB was not inhibited by elevated cAMP, suggesting that the regulatory action of this cyclic nucleotide could lie downstream from activation of the TNF-alpha gene. These results support the view that coronary vessels can be a source of TNF-alpha possibly involved in heart disease.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1997

Differential response of mesoderm- and neural crest-derived smooth muscle to TGF-beta1: regulation of c-myb and alpha1 (I) procollagen genes.

Previously, we demonstrated that avian vascular smooth muscle cells (VSMC) derived from embryonic abdominal and thoracic aorta grow differently in the presence of transforming growth factor beta (TGF-beta1) and platelet-derived growth factor (PDGF-BB) (Wrenn et al., In Vitro Cell. Dev. Biol. 29, 73-78, 1992). The thoracic VSMC (N-VSMC) are derived from neural crest, and therefore differentiate from ectoderm; the abdominal VSMC (M-VSMC) are derived from mesoderm. The present study was designed to identify factors that mediate the differential responses of the VSMC to TGF-beta1. We found that TGF-beta1 increased DNA synthesis by approximately sevenfold in N-VSMC. Levels of both alpha1 (I) procollagen and c-myb mRNAs were markedly induced in N-VSMC treated with TGF-beta1. Chimeric plasmids containing up to 3.5 kb of alpha1 (I) procollagen 5' flanking DNA were induced to equivalent levels as procollagen mRNA in N-VSMC. However, TGF-beta1 increased DNA synthesis by threefold in M-VSMC; there was no effect on alpha1 (I) procollagen expression, and c-myb was not expressed, as demonstrated by immunohistochemistry staining and RNA analyses. Antisense c-myb oligodeoxynucleotides blocked the TGF-beta1 induction of alpha1 (I) procollagen and the growth of N-VSMC. The increase in DNA synthesis by M- and N-VSMC was correlated with the secretion of PDGF-AA, and staurosporine and antibodies directed against PDGF-AA suppressed DNA synthesis. Our results demonstrate that TGF-beta1 activity and c-myb expression modulate the expression of alpha1 (I) collagen and cell proliferation in neural crest-derived smooth muscle. The regulation of these events by TGF-beta1 may be important during morphogenesis of blood vessels and vascular diseases.

Animals↗
PubMed1997

Homocysteine signal cascade: production of phospholipids, activation of protein kinase C, and the induction of c-fos and c-myb in smooth muscle cells.

Hyperhomocysteinemia has been recognized as an independent risk factor for cerebral, coronary, and peripheral atherosclerosis. To examine the contribution of homocysteine (H[cys]) in the pathogenesis of vascular diseases, we sought to determine whether the H[cys] effect on vascular smooth muscle (VSMC) proliferation is mediated by a specific receptor/transporter or is due to an interaction with growth factors or cytokines. We show that H[cys] induced c-fos and c-myb and increased DNA synthesis and cell proliferation 12-fold in neural crest-derived VSMC (N-VSMC). The H[cys] effect on N-VSMC proliferation is inhibited by Mk-801, a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, a glutamate-gated calcium ion channel receptor, and CGS 19755, a competitive antagonist of NMDA-type glutamate receptor. H[cys] stimulates the synthesis of mass amounts of sn-1,2 diacylglycerol, and activates protein kinase C translocation from the nucleus and cytoplasm to cell membranes. Furthermore, protein kinase C inhibitors block the growth effect mediated by H[cys]. These findings indicate that H[cys]-mediated responses are coupled to diacylglycerol-dependent protein kinase C activation. Our results suggest that homocysteine activates a receptor/transporter-like factor in neural crest derived smooth muscle.

Aorta, Abdominal↗
PubMed1997

Increased intracellular cyclic adenosine 3', 5'-monophosphate inhibits release of tumor necrosis factor-alpha from human vascular tissue and cultured smooth muscle cells.

OBJECTIVES: We recently reported that bacterial lipopolysaccharide stimulates release of tumor necrosis factor (TNF)-alpha from both human vascular tissue and cultured smooth muscle cells. In the current study, we tested the hypothesis that increased intracellular cyclic adenosine 3',5'-monophosphate (cAMP) could inhibit TNF-alpha release. DESIGN: Prospective, repeated-measures analysis. SETTING: Academic research laboratory. SUBJECTS: Segments of internal mammary artery and saphenous vein from patients undergoing coronary artery bypass surgery. MEASUREMENTS AND MAIN RESULTS: Segments of saphenous vein and internal mammary artery and confluent smooth muscle cells cultured from these vessels were incubated in the presence of 20 micrograms/mL bacterial lipopolysaccharide, alone or with the addition of forskolin or 8-Br-cAMP. At 0, 1, 3, 6, 18, and 24 hrs, the incubation medium was removed from vessel segments or cells and was analyzed for biologically active TNF-alpha, using the L929 cell cytotoxicity assay. cAMP was extracted from tissue and cells with 0.1 N HCl and was analyzed by radioimmunoassay. Bacterial lipopolysaccharide stimulated the release of TNF-alpha from internal mammary smooth muscle cells at all time points. For example, at 6 hrs, TNF-alpha concentration in the medium from lipopolysaccharide-stimulated cells was 20 +/- 1.6 U/mg of cell protein, compared with 0.9 +/- 0.5 U/mg of cell protein in control cell medium (p < .05). Forskolin-inhibited bacterial lipopolysaccharide stimulated TNF-alpha release. In the presence of lipopolysaccharide and forskolin, TNF-alpha release at 6 hrs was 8.6 +/- 1.5 U/mg of cell protein (p < .05 vs. in the presence of bacterial lipopolysaccharide alone). Bacterial lipopolysaccharide, alone, had no effect on intracellular cAMP. Forskolin increased intracellular cAMP levels to 74.0 +/- 12 pmol/mg of cell protein at 6 hrs from a control level of 7.7 +/- 0.4 pmol/mg (p < .05). The 8-Br-cAMP, an agent that mimics the action of intracellular cAMP, also inhibited TNF-alpha release stimulated by lipopolysaccharide. Similar inhibition by forskolin and 8-Br-cAMP on TNF-alpha release was obtained with smooth muscle cells from saphenous vein. Finally, in tissue segments from either internal mammary artery or saphenous vein, both forskolin and 8-Br-cAMP inhibited lipopolysaccharide-stimulated TNF-alpha release. CONCLUSIONS: These results are consistent with the conclusion that vascular tissue, particularly the smooth muscle cell, is a source of TNF-alpha. Further, bacterial lipopolysaccharide-stimulated tumor TNF-alpha release can be inhibited by increased intracellular cAMP.

Animals↗
PubMed1996

Surgical clerkship performance of traditional and nontraditional students in a problem-based learning environment.

BACKGROUND: To determine whether nontraditional students perform better than traditional students during surgical clerkships as reflected on the surgical clerkship final examination. METHODS: Retrospective review of medical student records from the classes of 1986 through 1993. Students admitted soon after completing undergraduate training were identified as "traditional," and those having prior careers as "nontraditional." RESULTS: There were 150 traditional and 72 nontraditional students. The ratio of men to women and admission MCAT scores were not significantly different. Traditional students were significantly younger and had higher admission grade point averages (GPAs). Nontraditional students were more likely to be married and have children. Final examination scores of traditional and nontraditional students were not significantly different. MCAT scores and college GPAs were the best predictors of final examination performance. Married students performed significantly better than single students. CONCLUSIONS: There was no significant difference between nontraditional and traditional student performance on the surgical clerkship final examination.

Adult↗
PubMed1996

Multifocal mesenchymal hamartoma of the chest wall in infancy.

The authors report on an infant who had multifocal mesenchymal hamartoma of the right posterior chest wall. The tumors were found incidentally, on a chest radiograph, during routine evaluation for upper respiratory tract infection. Resection of both lesions with chest wall reconstruction was performed, with a good result. Only 46 cases of this unusual tumor have been reported previously, and only two of them were multifocal.

Female↗
PubMed1996

Major vascular injury from high-pressure water jet.

High-pressure water jets are used in industry as a cleaning and cutting tool. Penetrating injuries by these devices can produce minimal external evidence of extensive internal damage. We report a literature review and the case of a limb-threatening injury to the lower extremity caused by such a device.

Accidents, Occupational↗