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Biomedical subjects

M C Townsend

Publications and source records attributed to M C Townsend.

At least 37 records · Page 2Linked to original sources
PubMed1989

Effective hepatic blood flow during cardiopulmonary bypass.

Hepatic dysfunction following cardiopulmonary bypass (CPB) is a relatively frequent finding, and jaundice occurring after CPB is associated with an increased mortality rate. Post-CPB jaundice may be a consequence of inadequate liver perfusion during CPB. To evaluate the potential impact of CPB on effective hepatic blood flow, 10 patients undergoing CPB for cardiac procedures were studied. Effective hepatic blood flow was measured in each patient during the operative procedure but before institution of CPB and during CPB as well. Effective hepatic blood flow was measured by the galactose clearance technique. Blood lactate and pyruvate levels were also measured before and during CPB. During CPB, effective hepatic blood flow was consistently reduced by an average of 19%. Although for most patients this reduction seems well tolerated, in a minority of patients it may contribute to postoperative hepatic dysfunction.

Cardiopulmonary Bypass↗
PubMed1989

Investigation of a cluster of deaths of adolescents from asthma: evidence implicating inadequate treatment and poor patient adherence with medications.

We investigated a cluster of five deaths of adolescents from asthma in St. Louis during a 3-month period in 1987. Although the cluster represented a statistically significant increase in the number of asthma deaths in this age group over that observed in previous years, no common exposure to environmental, infectious, or therapeutic agents could be identified. The patterns of hospital admissions for asthma and emergency room visits at the two pediatric hospitals in the community did not suggest an increase in the frequency or severity of asthma during this time. Despite the lack of evidence for common exposure, the decedents shared many personal and medical characteristics. All decedents were black patients and were of lower socioeconomic status. All were adolescents and were responsible for regulating their own medication schedules. Lack of appreciation of the severity of their asthma by medical personnel and the patients' families was evident. For example, two patients with severe asthma had not been prescribed inhaled corticosteroids. In addition, the four decedents tested had markedly subtherapeutic or zero serum theophylline levels measured at the time of the fatal episode, even though appropriate amounts of theophylline had been prescribed. Their theophylline levels were substantially lower than levels in patients of the same age observed at the emergency room or hospitalized for asthma during the same time period. Continued efforts to educate adolescent patients, their families, and medical care providers about the treatment of asthma are warranted.

Adolescent↗
PubMed1988

Femur fracture with associated soft-tissue injury produces hepatic ischemia. Possible cause of hepatic dysfunction.

Clinical studies demonstrate that early débridement and operative fixation of femur fractures in multiply injured patients lowers both the incidence and severity of hepatic failure. Perhaps the single most important determinant of hepatic function is nutrient hepatic perfusion. This study compares systemic and hepatic blood flow in rats that have sustained femur fractures with or without associated soft-tissue injury. Femur fracture without soft-tissue trauma resulted in a hyperdynamic state with normal blood flow distribution at 24 hours after injury and normal hemodynamics at 48 hours. When femur fracture was associated with soft-tissue trauma, the elevated cardiac output at 24 hours was not matched by a proportionately elevated hepatic blood flow. In this latter group, the cardiac output was normal at 48 hours, but the hepatic perfusion defect remained. Retained fracture fragments, hematoma, and injured and necrotic soft tissue may serve as a stimulus leading to a pathologic reduction in hepatic perfusion.

Animals↗
PubMed1988

Effects of muramyl dipeptide and core body temperature on peritoneal bacterial clearance.

To examine the interaction between muramyl dipeptide (MDP) and core body temperature in murine peritonitis, 120 Sprague-Dawley rats were randomized to receive either 0, 1, or 4 micrograms/g body weight of MDP. Twenty-four hours later a sublethal intraperitoneal inoculation of Escherichia coli was given after core body temperature regulation at 32 degrees C to 40 degrees C, which was maintained for 30 minutes. Killing of the rats at 1, 3, or 6 hours later allowed evaluation of peritoneal white blood cell and bacterial counts. Results demonstrated that MDP (independent of core body temperature) caused an increased peritoneal white blood cell response at one and six hours and an increased peritoneal bacterial clearance at three hours. Increasing core body temperature adversely affected peritoneal bacterial clearance. High-dose MDP was clearly significant in acceleration of peritoneal bacterial clearance. No interaction between MDP and core body temperature was seen.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1988

Radiographic abnormalities in relation to total dust exposure at a bauxite refinery and alumina-based chemical products plant.

A cross-sectional study of 788 male employees of an aluminum production company examined the relationship of radiographic abnormalities to smoking and dust exposure from the mining and refining of bauxite to alumina. Among the aluminas produced were low temperature range transitional forms. The present analyses were limited to nonsmokers and current smokers. Two National Institute of Occupational Safety and Health (NIOSH)-certified "B" readers interpreted the radiographs. The predominant radiographic abnormalities noted were scanty, small, irregular opacities in the lower zones of profusion 0/1 to 1/1. Rounded opacities were rare. Among nonsmokers with low dust exposures, the prevalence of opacities greater than or equal to 1/0 showed no trend with increasing age and duration of exposure, suggesting no relationship between age and prevalence of opacities of Category 1 or more in this cohort (p greater than 0.10). Nonsmokers who had accumulated higher dust exposures showed a trend of increasing prevalence of opacities with increasing duration, suggesting an effect of occupational exposure at higher cumulative exposure levels (p less than 0.05). In most exposure categories, smokers exceeded nonsmokers in their prevalence of opacities greater than or equal to 1/0; the overall prevalence among smokers being 12 and 11% according to Readers A and B, respectively, compared with 4% in nonsmokers (p less than 0.01). In conclusion, 7 to 8% of aluminum workers in this cohort had radiographic findings of scanty, small, irregular opacities, the prevalence of which was increased among smokers (p less than 0.01). There was a moderate increase in the prevalence of opacities with increasing tenure in nonsmokers with high cumulative exposures (p less than 0.05).

Aging↗
PubMed1987

Alterations in renal perfusion and renal energy charge in murine peritonitis.

Whether acute renal failure following overwhelming bacterial septicemia is a initially a consequence primarily of a cytotoxic insult or a perfusion insufficiency remains unclear. To assess the effects of intra-abdominal sepsis on the distribution of renal blood flow and renal cell bioenergy status, the glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and energy-charge ratios were measured in rats following cecal ligation/puncture (CLP) or sham laparotomies. The CLP animals demonstrated a decrease in ERPF of 42% and 58% from sham groups at ten and 20 hours, respectively. The GFR showed similar but more severe impairments of 53% and 71% at ten and 20 hours, respectively, following insult despite moderate increases in cardiac output. The disproportionate decrease in GFR over ERPF supports the hypothesis of a corticomedullary redistribution of renal blood flow in sepsis. Renal energy charge, unchanged at ten hours, decreased significantly at 20 hours. Diminished renal perfusion and the redistribution of renal blood flow precedes and may contribute to the renal cell bioenergy derangements in septic acute renal failure.

Adenine Nucleotides↗
PubMed1987

Galactose elimination kinetics in sepsis. Correlations of hepatic blood blow with function.

To study hepatic blood flow with clearance techniques during sepsis, it is essential to work within the limitations of the test being applied. Based on galactose elimination kinetics, this study validates galactose clearance at low concentrations as an estimate of effective hepatic blood flow in a rat peritonitis model of cecal ligation and puncture. Hepatic function as determined by galactose elimination capacity fell 25% at ten hours after induction of peritonitis, which correlated closely with the 20% reduction in effective hepatic blood flow at the same time point despite a normal cardiac output. The pattern of reduced flow and reduced function is consistent with intrahepatic flow redistribution. Inadequate flow at the microvascular level with secondary cellular injury may explain the liver dysfunction observed during sepsis.

Animals↗
PubMed1987

Hepatic microsomal adenosine triphosphatase and mitochondrial function. Response to cold and warm ischemia.

We investigated the response of mitochondrial function and microsomal adenosine triphosphatase (ATPase) activity in rat liver tissue subjected to in vitro ischemia at either 0 degree C to 4 degrees C or 37 degrees C for 30 to 60 minutes. Mitochondrial coupling, expressed as respiratory control index, was preserved at up to 60 minutes' cold ischemia. However, respiratory control index was decreased significantly from control by 30 minutes of warm ischemia. Both microsomal magnesium-activated ATPase and sodium-potassium ATPase activity were significantly increased by 60 minutes of warm ischemia yet were unaltered by 60 minutes of ischemia at 0 degree C to 4 degrees C. Warm ischemia produces deleterious effects on energy-generating (mitochondria) and energy-utilizing (ATPase) activity. Hypothermia provides a significant prolongation of cellular viability in ischemic tissue in terms of bioenergetic status. In addition to organ procurement and transplantation, hypothermic cytoprotection may prove valuable in areas such as shock, ischemia, and other clinical conditions of compromised visceral perfusion.

Adenosine Triphosphatases↗
PubMed1987

Flow redistribution in a hyperdynamic small animal burn: comparison to patterns in sepsis.

Visceral hypoperfusion with local accumulation of lactate in the ischemic tissues has been reported in a septic rat model despite a hyperdynamic systemic circulation. This visceral ischemia is felt to contribute to the multiple system organ failure (MSOF) syndrome associated with sepsis. The purpose of this study was to determine whether a similar redistribution of blood flow existed in rats after a severe thermal injury as it too is associated with MSOF. Twenty-four hours after animals were subjected to either a resuscitated 50% scald burn (BURN) or sham treatment (SHAM), thermodilution cardiac output (CO), effective hepatic blood flow (EHBF) by galactose clearance at low concentrations, effective renal plasma flow (ERPF) by para-aminohippurate clearance, and blood, liver, and skeletal muscle pyruvate (P), and lactate (L) concentrations were determined. CO increased 52% in BURN (46.5 +/- 2.8 ml/min/100 g, n = 21) versus SHAM (30.7 +/- 1.0 ml/min/100 g, n = 22; P less than 0.001) while EHBF increased only 18% (BURN: 6.81 +/- 0.36 ml/min/100 g, n = 8 vs SHAM: 5.77 +/- 0.29 ml/min/100 g, n = 8; P less than 0.025) and ERPF showed an insignificant 24% increase (BURN: 2.98 +/- 0.32 ml/min/100 g, n = 6 vs SHAM: 2.40 +/- 0.40 ml/min/100 g, n = 6; P less than 0.10), demonstrating a redistribution of flow. There was no local accumulation of lactate in blood, liver, or skeletal muscle and no derangement in P/L ratios. This study when compared to previous observations in sepsis suggests that (1) the flow redistribution of sepsis has features differentiating it from solely a "stress response".(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Effective hepatic blood flow and hepatic bioenergy status in murine peritonitis.

To assess the effects of sepsis on effective hepatic blood flow (EHBF) and hepatic tissue bioenergy status 250-350 g rats underwent either sham laparotomy or cecal ligation and perforation (CLP). At 5-, 10-, and 20-hr intervals cardiac output (CO), EHBF, and tissue adenine nucleotide levels were measured. CLP rats showed a hyperdynamic response to sepsis at 20 hr, with CO increased by 25% over sham rats. At all time intervals studied EHBF was decreased and at 20 hr it was maximally decreased by 35%. Hepatic energy charge (HEC) was calculated from tissue adenine nucleotide measurements. HEC was not statistically different in sham and CLP rats at 5 hr and was 11 and 9% reduced from sham levels in CLP rats at 10 and 20 hr, respectively. Thus, EHBF is decreased very early in sepsis; before any changes in hepatic bioenergy status are noted. In this hyperdynamic model of sepsis EHBF is decreased early and decreases progressively with time which may contribute to the significant decrease in HEC that is demonstrated.

Adenine Nucleotides↗
PubMed1987

Imidazole and indomethacin improve hepatic perfusion in sepsis.

Visceral microcirculatory insufficiency has been demonstrated in sepsis despite a hyperdynamic systemic circulation. This study examines the effect of the cyclo-oxygenase inhibitor indomethacin and the thromboxane synthetase inhibitor imidazole on septic hemodynamics and visceral perfusion in a septic rat model of cecal ligation and puncture. Animals received either indomethacin (INDO), imidazole (IMID), or saline intramuscularly at t = 0, 6, and 12 hr of peritonitis. Thermodilution cardiac output, mean arterial pressure, heart rate, hematocrit, effective hepatic blood flow, effective renal plasma flow, and arterial and mixed venous blood gases were determined at 15 hr. Both INDO and IMID improved effective hepatic blood flow in the septic animals to virtually sham, nonseptic levels without significantly altering systemic hemodynamics. This study suggests that the reduction in hepatic perfusion in sepsis may be mediated by thromboxane, the synthesis of which is suppressed by both INDO and IMID.

Animals↗
PubMed1987

Low-dose dopamine improves effective hepatic blood flow in murine peritonitis.

Diminished effective hepatic blood flow (EHBF) has been postulated as contributory to hepatocellular dysfunction in sepsis. In addition, dopamine has been demonstrated to increase perfusion to selective viscera. In order to examine the effects of peritonitis upon hepatic perfusion and its response to dopamine infusion, peritonitis was induced in rats via cecal ligation and perforation (CLP). Sixteen to 20 hours following insult, cardiac outputs were determined by thermodilution, and effective hepatic blood flow was determined by low-dose galactose clearance. Studies were performed in peritonitis-induced rats (CLP) and sham-operated controls with and without dopamine infusion for 30 minutes (0.5 microgram/100 g/min). Peritonitis resulted in a significant reduction in effective hepatic blood flow (p less than 0.01) despite a maintained cardiac output. Low-dose dopamine infusion resulted in a significant restoration of effective hepatic blood flow in CLP rats without altering cardiac output or hemodynamic status significantly. Dopamine may be beneficial in the maintenance of effective hepatic perfusion in peritonitis.

Animals↗
PubMed1986

Quality control aspects of expired air carbon monoxide measurement in the Multiple Risk Factor Intervention Trial.

The determination of carbon monoxide levels in the expired air of MRFIT participants was used to monitor the level of cigarette smoking in all participants and to assess the adherence of the SI participants to the MRFIT protocol, which required that they quit or reduce their cigarette smoking. Two problems affected the quality of the data. First, as with the measurements of pulmonary function (Chapter 12), the initial lack of training in adequate maintenance was responsible for inoperative instruments. Centralized training, both in the performance of the test and in equipment maintenance, helped to solve this problem. For future clinical trials, the importance of centralized training and certification of all technicians at the start of the study cannot be overemphasized. The second problem, the instability of the CO calibration gas in steel tanks over long periods, was not anticipated. The solution was to purchase small amounts of freshly prepared calibration gas, or to have such gas available to check the major gas supply. Many of the observed maintenance problems might have been avoided by the use of a checklist to ensure that preventive measures were taken before the equipment became inoperative.

Breath Tests↗
PubMed1986

Quality control aspects of pulmonary function testing in the Multiple Risk Factor Intervention Trial.

Pulmonary function testing was used in MRFIT to monitor the presence of airways disease and to assess changes in pulmonary function over time. The pulmonary function indices that were measured were FEV1, FVC, and MMEF, (FEF25-75). Quality control of technician training, equipment maintenance, data collection, and data measurement were essential to ensure that results, over time and from various clinics, could be compared. Based on the MRFIT experience, it is strongly recommended that centralized training in testing techniques and spirometer maintenance take place before a clinical trial begins, and periodically throughout a trial. Such training, combined with quality control follow-up, should prevent the loss of data due to inadequate spirometer maintenance and invalid testing procedures.

Allied Health Personnel↗
PubMed1986

Alterations of hepatic mitochondrial function in a model of peritonitis in immature rats.

Severe intra-abdominal infection results in significant metabolic dysfunction, multiple systems failure, and mortality. Although the course of peritonitis is particularly rapid and severe in neonates and small children, its physiologic consequences have been poorly studied in these age groups. In order to assess hepatic mitochondrial integrity in a model of fulminant peritonitis in immature animals, the following study was undertaken. Thirty-three immature Sprague-Dawley rats (21 to 28 days of age) and 32 mature rats (weight greater than 250 g) were anesthetized and laparotomies performed. The animals received either cecal ligation and gross perforation (CLP) or cecal manipulation alone (sham). Animals were killed at 2 and 4 hours and livers removed. Mitochondria were isolated by differential centrifugation. Mitochondrial respirations were studied polarographically with glutamate and succinate as substrates in the presence (state 3) and absence (state 4) of adenosine diphosphate (ADP). The Respiratory Control Index (RCI) is the ratio of state 3 to state 4 respiration and is a sensitive indicator of mitochondrial coupling. Results revealed that in mature animals, peritonitis produced a significant increase in RCI with glutamate as substrate (5.2 +/- 0.2) by 4 hours duration as compared with sham operated rats (4.3 +/- 0.1, P less than 0.01). Succinate as substrate revealed no significant alteration in mitochondrial coupling in mature rat hepatic mitochondria in animals subjected to peritonitis. By contrast, peritonitis in immature animals produced a significantly decreased RCI (3.6 +/- 0.2) with glutamate as substrate as compared with sham operated animals (4.8 +/- 0.2, P less than 0.01) by two hours duration.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1986

Validation of hospital discharge diagnosis data for chronic obstructive pulmonary disease and other allied conditions.

The assumption that discharge diagnoses of chronic obstructive pulmonary disease and other allied conditions accurately reflect patient medical records was tested using a sample of 553 hospital discharges from the Pittsburgh, Pennsylvania area. Three validation criteria were used in reviewing patient hospital records: 1) the presence of abnormal spirometry test results; 2) reference made to a previous diagnosis of one of the conditions; and 3) reports of respiratory symptoms consistent with these conditions. The findings were that 1 per cent of the 432 cases with a primary diagnosis in this disease category and 10 per cent of the 121 cases with a primary diagnosis of heart disease and a secondary diagnosis in this disease category were not supported by any of the selected criteria.

Adult↗
PubMed1986

Effective organ blood flow and bioenergy status in murine peritonitis.

Whether organ dysfunction frequently encountered in overwhelming bacterial sepsis is a result of a direct cellular "toxic" effect or diminished cellular perfusion remains controversial. To assess the effects of peritonitis on cellular energy status and visceral blood flow, peritonitis was induced in rats by means of cecal ligation and perforation. Five, 10, or 20 hours after cecal ligation and perforation, cardiac outputs were determined by thermodilution, effective hepatic blood flow was determined by low-dose galactose clearance, and effective renal plasma flow was determined by paraminohippuric acid clearance. In similar groups of rats with peritonitis or sham controls, tissue samples of liver, kidney, and skeletal muscle were obtained by freeze-clamp technique for analysis of adenine nucleotides, energy charge, pyruvate, lactate, and pyruvate/lactate ratios (P/L). Despite an increase in cardiac output (p less than 0.05), results indicated in this model that effective hepatic blood flow and effective renal plasma flow were significantly reduced (p less than 0.05). The energy charge and P/L ratios of hepatic (p less than 0.01) and renal (p less than 0.05) tissues were also decreased. In contrast, skeletal muscle energy charge and P/L ratio were unchanged by 20 hours duration. These data support the hypothesis of diminished visceral perfusion as contributory to the cellular dysfunction observed in sepsis. Skeletal muscle appears either nonischemic or more tolerant of ischemia in sepsis.

Adenosine Triphosphate↗