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Biomedical subjects

C R Bridges

Publications and source records attributed to C R Bridges.

At least 19 recordsLinked to original sources
PubMed2005

The canine right caudal and accessory lobe pulmonary veins: revised anatomical description, clinical relevance, and embryological implications.

Necropsy dissections were performed on nine dogs to provide an anatomical description of the right caudal and accessory lobe pulmonary veins. In all dogs, the pulmonary vein from the right caudal lung lobe initially paralleled the right caudal lung lobe bronchus, running cranially, medially, and ventrally. It diverged from the bronchus at the level of the pulmonary artery and bronchus of the accessory lung lobe. At this point, the pulmonary vein from the right caudal lung lobe coursed dorsal to the pulmonary artery and bronchus of the accessory lung lobe. Medial to the bronchus of the accessory lung lobe, it received the pulmonary vein from the accessory lung lobe on its ventral surface. Within the pericardium, this common venous trunk merged with the caudal aspect of the left atrium either with or immediately adjacent to the left caudal lobe pulmonary vein. These findings were corroborated during surgical dissection to achieve isolation of the heart in five dogs as part of an experimental study on intravascular gene delivery to the heart. These anatomical findings are relevant to clinical and experimental surgery and raise interesting questions about the embryological development of pulmonary veins in the dog.

Animals↗
PubMed2004

Immunohistochemical localization of CYP1A, vitellogenin and Zona radiata proteins in the liver of swordfish (Xiphias gladius L.) taken from the Mediterranean Sea, South Atlantic, South Western Indian and Central North Pacific Oceans.

Cytochrome P4501A (CYP1A) monoxygenase, vitellogenin (Vtg) and Zona radiata proteins (Zrp) are frequently used as biomarkers of fish exposure to organic contaminants. In this work, swordfish liver sections obtained from the Mediterranean Sea, the South African coasts (South Atlantic and South Western Indian Oceans) and the Central North Pacific Ocean were immunostained with antisera against CYP1A, Zrp, and Vtg. CYP1A induction was found in hepatocytes, epithelium of the biliary ductus and the endothelium of large blood vessels of fish from the Mediterranean Sea and South African waters, but not from the Pacific Ocean. Zrp and Vtg were immunolocalized in hepatocytes of male swordfish from the Mediterranean Sea and from South African waters. Plasma Dot-Blot analysis, performed in Mediterranean and Pacific specimens, revealed the presence of Zrp and Vtg in males from Mediterranean but not from Pacific. These results confirm previous findings about the potential exposure of Mediterranean swordfish to endocrine, disrupting chemicals and raise questions concerning the possible presence of xenobiotic contaminants off the Southern coasts of South Africa in both the South Atlantic and South Western Indian Oceans.

Animals↗
PubMed2003

Evidence of a high percentage of intersex in the Mediterranean swordfish (Xiphias gladius L.).

The first evidence of the presence of intersexuality in a wild population of Mediterranean swordfish (Xiphias gladius L.) is reported. Forty of 162 specimens (25%) macroscopically classified as males, showed the presence of female germ cells within the testes. In two specimens grouped previtellogenic oocytes were present; all the other specimens possessed single scattered previtellogenic oocytes. The presence of vitellogenin was demonstrated immunohistochemically in the liver of both intersex and normal males. These findings could be due to the exposure to oestrogen-mimicking substances.

Animals↗
PubMed2001

Structural and functional properties of hemocyanin from Cyanagraea praedator, a deep-sea hydrothermal vent crab.

Cyanagraea praedator (Crustacea: Decapoda: Brachyura) is an endemic species of the East Pacific Rise hydrothermal vents, living in the upper part of black smoker chimneys. Because we were seeking species that have made respiratory adaptations to the hydrothermal environment, we looked at Cyanograea hemocyanin (Hc) and determined its quaternary structure and the oxygen-binding properties in relation to temperature, pH, and lactate. C. praedator Hc is composed of dodecamers and hexamers, with dodecamers formed by the perpendicular association of two hexamers. The composition of these polymers was determined by electrophoresis and, for the first time, by electrospray mass spectrometry. Dodecamers and hexamers are composed of six subunits common to the two forms, with molecular mass ranging from 75,008 Da to 75,534 Da. In addition, we found two dodecamer-specific subunits, at 75,419 Da and 75,629 Da. The native hemocyanin possesses a high oxygen affinity (P(50) varies between 4 and 10 Torr at pH 7.5, 15 degrees C) and a large Bohr coefficient (Delta log P(50)/DeltapH approximately -1.8). Oxygen affinity is not affected by lactate or, surprisingly, temperature between 5 degrees C and 35 degrees C (DeltaH = 1.16 kJ/mol(1) 5-35 degrees C). Dialysis of native hemolymph elicited a significant increase in Hc-O(2) affinity (DeltaP(50) = 2.5 Torr at pH 7.5), an effect opposite the usual trend observed for crustacean hemocyanins. In this article these functional properties are interpreted in relation to characteristics of the environment.

Adaptation, Physiological↗
PubMed2001

Modulation of haemocyanin oxygen affinity: properties and physiological implications in a changing world.

Crustacean haemocyanin oxygen affinity may be modified through changes in concentration of various inorganic and organic allosteric modulators. These may act in both positive and negative directions, increasing or decreasing haemocyanin oxygen affinity, and assist both in oxygen loading at the gills and oxygen release in the tissues. Inorganic ions, except for Mg(2+), do not normally influence cooperativity or the Bohr effect, whereas most of the organic modulators decrease cooperativity without affecting the Bohr coefficient. Several new findings on the influence of sulphide and thiosulphate are reviewed together with evidence for unidentified factors that decrease haemocyanin oxygen affinity. The physiological implications of all these findings are discussed in the context of maintaining a flexible response to a changing environment.

Animals↗
PubMed2001

The Batista procedure. Theoretical analysis and clinical implications.

BACKGROUND: The Batista procedure leads to dramatic early improvement in left ventricular function in some patients and a worsening in function in others. The theoretical and actual clinical effects of the procedure on early postoperative left ventricular function remain controversial. The purpose of this study is to utilize an appropriate mathematical model to determine the effects of the Batista procedure on stroke volume and myocardial wall stress. Our hypothesis is that the preoperative end-systolic stress (ses) is an important predictor of early postoperative myocardial function after this procedure. A corollary is that an index related to ses may be useful in selecting patients for this procedure. METHODS: An analysis of the Batista procedure is developed, based upon a spherical membrane model of the ventricle. This model shows how ventricular dilatation distorts the systolic and diastolic pressure-volume relations. RESULTS: Dilatation initially improves ventricular performance; but further dilatation, beyond a critical value, produces an unstable state with sharply falling performance. For a ventricle operating significantly beyond the point of critical dilatation, our theoretical results suggest that the Batista procedure not only reduces myocardial stress but may improve stroke volume. The end-systolic stress, ses is an indicator of how close a ventricle is to the critical dilatation point. CONCLUSIONS: There is a theoretical basis for the Batista procedure. Resection of myocardium not only decreases wall stress but may improve stroke volume for sufficiently dilated and depressed ventricles. Patients with markedly elevated end-systolic stress may benefit most from the Batista procedure.

Cardiac Surgical Procedures↗
PubMed2000

The effect of race on coronary bypass operative mortality.

OBJECTIVES: The study was done to determine whether race is an independent predictor of operative mortality after coronary artery bypass graft (CABG) surgery. BACKGROUND: Blacks are less frequently referred for cardiac catheterization and CABG than are whites. Few reports have investigated the relative fate of patients who undergo CABG as a function of race. METHODS: The Society of Thoracic Surgeons National Database was used to retrospectively review 25,850 black and 555,939 white patients who underwent CABG-alone from 1994 through 1997. A multivariate logistic regression model was developed to determine whether race affected risk-adjusted operative mortality. RESULTS: Operative mortality was 3.83% for blacks versus 3.14% for whites (unadjusted black/white odds ratio [OR] 1.23 [1.15-1.31]). Blacks were younger, more likely female, hypertensive, diabetic and in heart failure. Nonetheless, the influence of these and other preoperative risk factors on procedural mortality was quite similar in black and white patients. After controlling for all risk factors, race remained a significant independent predictor of mortality in the multivariate logistic model (adjusted black/white OR 1.29 [1.21, 1.38]). Proportionately, these differences were greatest among lower-risk patients. The race-by-gender interaction was significant (p<0.05). The unadjusted mortality for black men, 3.30% and white men, 2.64% differed significantly (p<0.05), whereas for women there was no difference (black, 4.49%; white 4.41%). CONCLUSIONS: Black race is an independent predictor of operative mortality after CABG except for very high-risk patients. The difference in mortality is greatest for male patients and, though statistically significant, is small in absolute terms. Therefore, patients should be referred for CABG based on clinical characteristics irrespective of race.

Aged↗
PubMed2000

Angiogenesis in myocardial laser "revascularization".

The clinical and experimental data relevant to the theoretical mechanisms and clinical results of laser myocardial "revascularization" are reviewed. Both transmyocardial (TMR) and percutaneous (PMR) approaches are considered. Special attention is paid to the issue of TMR-induced angiogenesis. Both TMR and PMR result in a reduction in angina symptoms in patients refractory to conventional therapy and are likely to act through common pathways. TMR-induced angiogenesis appears to result from the up-regulation of vascular growth factors. However, the available data suggest that the angiogenic response is not a unique consequence of laser revascularization. Rather, the angiogenesis associated with TMR is likely to be a non-specific response of the myocardium to injury.

Animals↗
PubMed2000

Acute type A aortic dissection: retrograde perfusion with left superior vena cava.

Retrograde cerebral perfusion with hypothermic circulatory arrest confers additional cerebral protection during repair of type A aortic dissection. We present a 42-year-old man with acute type A aortic dissection and a persistent, left superior vena cava. Cannulation of the right and left superior vena cava is used for retrograde perfusion of both hemispheres with bilateral monitoring of electroencephalogram and somatosensory-evoked potentials during and after the hypothermic circulatory arrest interval.

Adult↗
PubMed2000

Myocardial laser revascularization: the controversy and the data.

The clinical and experimental data relevant to the theoretical mechanisms and clinical results of laser myocardial revascularization are reviewed. Both transmyocardial and percutaneous approaches are considered. Both types result in a reduction in anginal symptoms in patients refractory to conventional therapy and are likely to act through common pathways. The proximate mechanisms for the transmyocardial revascularization effect most likely relate to myocardial inflammation, secondary stimulation of growth factors, and denervation of the myocardium.

Angina Pectoris↗
PubMed2000

Management of postoperative arrhythmias.

Arrhythmias occur commonly in patients after cardiac surgery. Atrial fibrillation is the most common arrhythmia in the postoperative period; it accounts for significant morbidity to the patient and prolonged hospital stays, and it contributes significantly to the cost of hospitalization. It occurs more commonly in elderly men and in patients undergoing valvular procedures. Beta blockers are effective agents that keep patients from developing postoperative atrial fibrillation and help maintain ventricular rate control. Prophylaxis with antiarrhythmic agents such as amiodarone and sotalol and recently with atrial pacing have shown promise in recent randomized trials. Patients with atrial fibrillation that persists for longer than 48 hours appear to be at a greater risk for cerebroembolic events and should receive anticoagulation unless a contraindication exists. Although frequent premature ventricular contractions and nonsustained ventricular tachycardia (NSVT) occur frequently in patients after cardiac surgery, sustained ventricular tachycardia and ventricular fibrillation are rare and are associated with a poor prognosis. Polymorphic ventricular tachycardia may occur in the setting of myocardial ischemia, metabolic disturbances, and drug toxicities (including antiarrhythmic agents used to treat atrial fibrillation). Poor left ventricular function is a potent risk factor for sudden death in patients with NSVT. Patients with persistent NSVT and ischemic cardiomyopathy with left ventricular ejection fractions of less than 40% should undergo electrophysiologic testing. Conduction abnormalities that may be encountered in patients after cardiac surgery are rarely life threatening. Patients who have undergone valve replacement or repair are at higher risk of developing significant bradyarrhythmias that may require temporary pacing.

Arrhythmias, Cardiac↗
PubMed1998

Angiogenesis in transmyocardial laser revascularization. A nonspecific response to injury.

BACKGROUND: The mechanism of action of transmyocardial laser revascularization (TMR) is poorly understood. TMR has been shown to stimulate angiogenesis in porcine and canine myocardium. METHODS AND RESULTS: We examined the possibility that angiogenesis also occurs in ovine myocardium and that it is a nonspecific tissue injury response. Five Dorset sheep underwent creation of transmyocardial channels of equal diameter in both the apical and basal regions of the left ventricle through the use of both CO2 laser in 1 region and a power drill in the alternate region of the same heart. All channels were closed at 4 weeks. Histology showed channel remnants composed of granulation tissue, fibrosis, and new vessels (NV). These changes were not distinguishable on the basis of the method of channel creation. The average diameter of the channels was similar (laser, 630 +/- 180 microns; drill, 750 +/- 280 microns) (P = NS). NV with smooth muscle media were seen within the channel remnant and immediately surrounding this region using Verhoeff-Van Gieson (elastic) stain. The densities of the NV within the channel remnants were similar (laser, 1.87 +/- 1.05 NV/high-power field [hpf]; drill, 1.92 +/- 1.09 NV/hpf; P = NS), and both were significantly greater than the density of vessels in remote regions, > 5 mm from the channel center (remote laser area, 0.09 +/- 0.28 NV/hpf; remote drill area, 0.04 +/- 0.21 NV/hpf; P = NS for remote areas, P < 0.001 for laser versus remote laser, P < 0.001 for drill versus remote drill area). CONCLUSIONS: These findings demonstrate that the CO2 laser stimulates angiogenesis in normal ovine myocardium and suggest that this response represents a nonspecific reaction to tissue injury.

Animals↗
PubMed1998

Transmyocardial laser revascularization fails to prevent left ventricular functional deterioration and aneurysm formation after acute myocardial infarction in sheep.

OBJECTIVE: Transmyocardial laser revascularization is an investigational technique for revascularizing ischemic myocardium in patients with inoperable coronary arterial disease. This study tests the hypothesis that laser revascularization prevents left ventricular functional deterioration and aneurysm formation after acute anteroapical myocardial infarction. METHODS: An ultrasonic ascending aortic flow probe and snares around the distal left anterior descending and second diagonal coronary arteries were placed in 26 Dorsett hybrid sheep. Ten to 14 days later, snared arteries were occluded to produce an anteroapical infarction of 23% of left ventricular mass. Before infarction 14 animals had 34 +/- 4 transmyocardial perforations in the area of the anticipated infarction made with a carbon dioxide laser. Twelve animals served as controls. Hemodynamic measurements and transdiaphragmatic quantitative echocardiograms were obtained before, immediately after, and 2, 5, and 8 weeks after infarction. Eighteen sheep completed the protocol. RESULTS: All animals had large anteroapical left ventricular aneurysms with massive ventricular enlargement. Immediately after infarction the anterior wall became thinner and dyskinetic in all sheep. At 8 weeks aneurysmal size and shape were indistinguishable between groups. Two days after infarction, laser holes were filled with fibrin. At 5 and 8 weeks the infarct consisted of dense collagen, fibroblasts, scattered calcifications, myocyte fragments, neutrophils, macrophages, and no laser holes. There were no significant differences at any time between groups for cardiac pressures or output, ventricular volumes, ejection fraction, stroke work, and the stroke work-left ventricular end-diastolic pressure index. CONCLUSION: Transmyocardial laser perforations do not revascularize acute myocardial infarction in sheep.

Animals↗
PubMed1998

Physiology and biochemistry of the pseudobranch: an unanswered question?

The structure and function of the pseudobranch has long interested scientists, but its overall role has remained a mystery. Previous studies have attributed respiratory, endocrine, osmoregulatory and sensory roles to the pseudobranch, and the present review concentrates on new findings. Perfusion experiments on the pseudobranch of the rainbow trout (Oncorhynchus mykiss) using both erythrocyte suspensions and Ringer solution have shown that this organ is able to generate values for the respiratory quotient (RQ) greater than 1.0. The release of carbon dioxide into the perfusate was found to be largely independent of flow between perfusion rates of 120-190 microl/min and could be inhibited by acetazolamide (10(-5) M), indicating a role for carbonic anhydrase. Noradrenaline (10(-5) M) had no effect on oxygen consumption or carbon dioxide release of the pseudobranch. The rate of carbon dioxide release was also dependent on the pH of the pre-pseudobranch perfusate, carbon dioxide release being reduced at lower perfusate pH values. Based on the glucose balance of the isolated saline-perfused rainbow trout pseudobranch and on the enzyme profiles for the rainbow trout, cod, swordfish and deep-water grenadier pseudobranch, it is suggested that the pentose phosphate shunt might be a source of carbon dioxide, yielding the high RQ values found for this organ. Most evidence now available indicates that the pseudobranch is integrally linked with the choroid rete and the supply of oxygen to the retina of the fish eye.

Animals↗
PubMed1991

Skeletal muscle bioenergetics during frequency-dependent fatigue.

The bioenergetic correlates of skeletal muscle fatigue were assessed in vivo with phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy. After surgical construction of latissimus dorsi muscle ventricles, seven beagles underwent 31P-NMR spectroscopy during 12-min exercise protocols at 25- and 85-Hz stimulation frequencies and during both isovolumetric and dynamic contractions. Exercise at 85 Hz was associated with significantly greater fatigue than exercise at 25 Hz. At both frequencies, the onset of exercise was associated with a marked increase in inorganic phosphate (Pi) and a decrease in phosphocreatine (PCr). As the muscle fatigued at 85 Hz but not at 25 Hz, the phosphorus spectra returned to near baseline with a decrease in Pi and increase in PCr. For a given amount of force generated, the Pi-to-PCr ratio was higher for dynamic contractions than for isovolumetric contractions. This study indicates that high-frequency fatigue is unlikely to result from the direct effects of high-energy phosphate metabolism and that contractions producing external work consume more metabolic energy than equally forceful isometric contractions.

Animals↗
PubMed1991

Reversible hexadimethrine-induced alterations in glomerular structure and permeability.

Female Munich-Wistar rats received hexadimethrine (HDM) i.v. until the onset of proteinuria (PEAK)--a period of not more than 30 min. There were four experimental groups: C (control), H (HDM only), HH (HDM and heparin), and HHD (identical to HH but with dextran clearances measured). Rats in groups HH and HHD received a heparin bolus after the PEAK period, whereas rats in group H did not. HDM led to dramatic increases in both albumin and IgG excretion. Glomerular filtration rate and renal plasma flow rate were reduced by 30 to 50% after HDM infusion. Neutral dextran clearances for radii greater than 30 A were elevated during the PEAK period, and, concurrently, there was extensive intraglomerular microthrombosis, obliteration of foot processes, and disruption of filtration slit diaphragms. One hour later, glomerular filtration rate, renal plasma flow rate, dextran clearances, and proteinuria returned to baseline in groups HH and HHD but not in group H. Recovery in heparin-treated rats was associated with reversal of HDM-associated morphological alterations. Membrane pore-size parameters calculated from the dextran clearances indicate that HDM leads to a detect in glomerular size-selectivity. The facts that maximal albuminuria tended to precede maximal excretion of IgG and that increases in albumin excretion were proportionately greater than those of dextran or IgG suggest that HDM also leads to a time-dependent defect in glomerular charge-selectivity.

Albuminuria↗
PubMed1991

Autogenously lined skeletal muscle ventricles in circulation. Up to nine months' experience.

Skeletal muscle ventricles were constructed in fifteen dogs. After a delay period of 4 weeks the skeletal muscle ventricles were connected to the descending thoracic aorta with a polytetrafluoroethylene bifurcation graft (Gore-Tex bifurcation graft, W.L. Gore & Associates, Inc., Elkton, Md.). The aorta was ligated between the two limbs of the graft so that there was obligatory blood flow through the skeletal muscle ventricle. Nine skeletal muscle ventricles were lined with autogenously derived tissue, either pleura or pericardium, whereas six had no specific lining other than an induced fibrous reaction. The skeletal muscle ventricles were activated to contract during cardiac diastole. Aortic diastolic counterpulsation was achieved in all dogs, with ten surviving from 1 week to beyond 9 months. Thrombus eventually developed in all but three of the skeletal muscle ventricles, but no dog had clinical evidence of thromboemboli. The three thrombus-free skeletal muscle ventricles were lined with pleura, including the animal surviving beyond 9 months. These results indicate that canine skeletal muscle can provide aortic diastolic counterpulsation for 9 months without clinically apparent thromboembolic complications.

Animals↗