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B T Baxter

Publications and source records attributed to B T Baxter.

49 records · Page 3Linked to original sources
PubMed1992

Elastin content, cross-links, and mRNA in normal and aneurysmal human aorta.

Although elastin depletion is thought to be an etiologic factor in abdominal aortic aneurysm, little is known about its transcription and posttranslational modification in normal and diseased human aorta. Our objectives were to quantify total elastin and elastin cross-links (desmosine/isodesmosine [DID]) and to determine if elastin mRNA was detectable in the disease-prone infrarenal aorta from patients with abdominal aortic aneurysm and a comparative group with no aneurysmal diseases. After preliminary extraction and thermolysin digestion, content of DID and the elastin tetrapeptide, valine-alanine-proline-glycine (VAPG), were determined by high-performance liquid chromatography. Tissue mRNA was studied by Northern blot analysis. Mean values (+/- SE) were compared by Student's t test. The proportion of insoluble elastin was markedly decreased in abdominal aortic aneurysm tissue (1.3% +/- 0.04% vs 12% +/- -2.8%; p less than 0.001). There was no difference in the small percentage of elastin solubilized during extraction in abdominal aortic aneurysm (5.3% +/- 1%) and no aneurysmal disease (6.0% +/- 1.2%; p = 0.71) tissues. The DID concentration of insoluble elastin was not different for abdominal aortic aneurysm and no aneurysmal disease tissue (0.18% +/- 0.07 vs 0.18 +/- 0.05 nm DID/nm VAPG; p = 0.97). On the basis of VAPG content, only 26% +/- 4% of the sodium hydroxide insoluble residue from abdominal aortic aneurysm was elastin; the predominate protein(s) was high in polar amino acids. Elastin mRNA was detectable in all tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Collagen and elastin gene expression in aortic aneurysms.

BACKGROUND: The decreased elastin concentration found in abdominal aortic aneurysms (AAAs) may result from a differential synthetic response wherein elastin gene expression fails to increase in parallel with type I procollagen (COL I) gene expression. The purpose of this study is to determine tissue mRNA levels for elastin and COL I in AAAs compared with levels in normal, age-matched aorta and to determine the relationship between aging and COL I gene expression. METHODS: Total RNA exacted from normal infrarenal aortic tissue (n = 7) and AAA (n = 10) tissue was subjected to Northern analysis. Mean values for COL I, elastin, and alpha-tubulin mRNA levels were compared by use of the Student t test. Age and COL I mRNA levels were analyzed by regression analysis. RESULTS: COL I mRNA was increased significantly in AAAs (1.18 +/- 0.13) compared with normal aortas (0.14 +/- 0.05). A commensurate increase in elastin mRNA (AAAs, 0.11 +/- 0.02, vs normal aortas, 0.39 +/- 0.2) was absent. There was no correlation between age and COL gene expression. CONCLUSIONS: The decreased elastin concentration relative to collagen in AAAs may be explained, in part, by the changes in message level of elastin and collagen. The enhanced COL I gene expression in AAAs is unrelated to age.

Aging↗
PubMed1991

Aneurysm or occlusive disease--factors determining the clinical course of atherosclerosis of the infrarenal aorta.

Atherosclerosis of the infrarenal aorta results in distinct clinical entities--aortoiliac occlusive disease (AOD) and abdominal aortic aneurysm (AAA). Although loss of collagen has been implicated in AAA, collagen accumulation plays a role in AOD. In vivo collagen-gene expression can be assessed using complementary DNA for collagen types I and III alpha-chains. The purpose of this study is to compare total collagen (type I + III) and collagen types I and III messenger RNA in AAA, AOD and normal aorta. Specimens were collected from the infrarenal aorta during operation for AOD (n = 7), AAA (n = 7), autopsy, or organ procurement (normal; n = 7). Northern transfer analysis of total RNA was used to compare mRNA levels for type I and III collagen. After preliminary extraction, specimens were hydrolyzed for hydroxyproline analysis used to calculate total collagen (type I + III). Relative levels of type I (pro-a1[1]) mRNA were greater in both AOD (0.77 +/- 0.35) and AAA tissue (0.94 +/- 0.24; p = 0.6) than in normal aorta (0.02 +/- 0.03). Type III (pro-a1[III]) mRNA levels were also greater in AOD (2.52 +/- 0.19; p = 0.09) and AAA tissue (3.15 +/- 1.3) than in normals (0.97 +/- 0.47). Total collagen concentration was increased in AOD (45.6% +/- 3.1% dry weight; p less than 0.05) but not AAA tissue (27.8% +/- 4%) when compared to normal aorta (34.7% +/- 2.3%). Collagen type I and III gene expression is greater in older, diseased aorta, yet collagen accumulated only in AOD. This implies a similar synthetic response in both AOD and AAA. Thus, proteolytic degradation in AAA appears to determine collagen content and possibly the clinical course of the atherosclerotic process.

Aged↗
PubMed1990

A comparative study of intraoperative angioscopy and completion arteriography following femorodistal bypass.

A prospective comparison of the findings on standard completion arteriography with those seen using videoangioscopy was done following 49 cases of "femorodistal" bypass grafting in 47 patients. The two techniques were compared with respect to the detection of technical defects, modification of the surgical procedures, early graft patency (72 hours), and complications. Completion arteriography was specific (95%) but only moderately sensitive (67%) compared with angioscopy for detection of technical problems. Following angioscopy, significant alterations in the surgical procedure were noted in 5 (10%) of the 49 cases. Early graft failure occurred in 3 (6.1%) cases but none were identifiably due to technical problems. Four patients suffered postoperative myocardial infarctions, 2 (4.2%) of which were fatal; no patients had contrast-induced allergies or renal failure. Angioscopy was measurably more accurate for the detection of technical problems than completion arteriography, but offered little information about distal arterial anatomy that may have an impact on graft patency or the use of antithrombotic therapy.

Aged↗
PubMed1990

Distal embolization as a presenting symptom of aortic aneurysms.

The records of 302 patients who underwent abdominal aortic aneurysm (AAA) repair between 1985 and 1990 were reviewed. Two hundred and forty-eight patients (82%) were asymptomatic, while 32 patients (11%) had ruptured aneurysms. During this period, 15 patients (5%) presented with distal embolization as the first manifestation of their AAA. The preoperative embolic event resulted in limb-threatening ischemia in 3 patients, digital ischemia in 11, and calf myonecrosis in 1. CT scan was performed in 14 of 15 patients demonstrating irregular, heterogeneous thrombus within the AAA. Only two of the AAAs were larger than 5 cm. Angiography demonstrated occlusive lesions but was not diagnostic for AAA in seven patients and resulted in three episodes of embolization. AAA was repaired with a tube graft in 4 patients while a bifurcated graft was required in 11 patients for aneurysmal (in 4 patients) and occlusive disease (in 7 patients) of the iliac arteries. All cases employed a transperitoneal approach, systemic heparin, and distal occlusion prior to aortic clamping. Complications included three major (below-knee) and five minor amputations, developing or worsening renal failure in five patients (33%), and death in two (13%). In comparison, mortality was 5% for elective repair and 66% for rupture during this same period. CT scan was safer and more informative than angiography. The morbidity of patients with AAA presenting with emboli is comparable with rupture. The risk of embolization does not correlate with size and indicates the potentially dangerous nature of small AAAs.

Aged↗
PubMed1990

Noninvasive evaluation of the upper extremity.

Vascular problems of the arm and hand can be assessed by a number of noninvasive modalities that are chosen on the basis of the history and physical examination. For suspected upper-extremity ischemia, we begin with SLPs and velocity-waveform analysis. The former test will define the extent and approximate location of the disease process, and subjective assessment of the waveform will further determine the degree and location of occlusive disease. When digital ischemia is suspected, the Doppler examination combined with intermittent compression of the radial and ulnar arteries is valuable for defining the variable arterial anatomy of the hand and the patency of the common and proper digital arteries. The extent of distal ischemia can be assessed by digital pressures. Duplex scanning has been found to be of value in determining the source of upper-extremity micro-emboli, in imaging suspected aneurysmal changes, and for evaluating arteriovenous fistulae and bypass grafts. Cold testing is used to confirm the diagnosis of Raynaud's disease after excluding proximal occlusive disease. When symptoms suggest intermittent arterial obstruction, arterial compression at the thoracic outlet is assessed by monitoring the arterial waveform during a series of maneuvers that change the anatomy of the outlet. Although a combination of IPG and venous Doppler examination accurately identifies venous occlusion, we routinely use duplex scanning in this setting. In addition to providing both anatomic and hemodynamic information about the subclavian vein, the jugular vein and the junction of the innominate vein can also be studied. Because of its ability to image in a coronal plane, MRI scanning is another nonivasive study that we have found useful for evaluation of venous anatomy and patency of the subclavian, jugular, and innominate veins. Venous thrombosis, often the first manifestation of subclavian vein compression at the thoracic inlet, is best evaluated using duplex scanning.

Arm↗
PubMed1989

A plea for sensible management of myocardial contusion.

The purpose of this study was to define the relative risk of life-threatening sequelae in patients at risk for myocardial contusion. During a 3-year period, 280 patients sustaining blunt chest trauma were admitted to the surgical intensive care unit to exclude myocardial contusion. Patients were evaluated by electrocardiogram and creatine phosphokinase (CPK) MB enzyme levels every 8 hours for a minimum of 48 hours. Myocardial contusion was identified in 35 patients (13 percent); the diagnosis was established by transient electrocardiographic changes (30), CPK-MB more than 3 percent (9) or both criteria (4). Two patients (1 percent) died from cardiac decompensation 4 and 12 hours postinjury, and seven (3 percent) required early (12 hours postinjury) intensive care unit treatment of arrhythmias or myocardial failure. None of the remaining 271 patients developed cardiac symptoms. This clinical experience underscores the low incidence of cardiac sequelae among patients at risk for myocardial contusion. Complications were always manifest within 12 hours of injury. The clinical diagnosis of myocardial contusion can be excluded pragmatically in the asymptomatic patient with a normal electrocardiogram and CPK-MB levels during the initial 24-hour postinjury period.

Adolescent↗
PubMed1989

Emergency Department thoracotomy in children--a critical analysis.

Recent clinical reviews have helped to clarify the role of Emergency Department (E.D.) thoracotomy in critically injured adults. However, guidelines in the pediatric population remain ill defined. The purpose of this report is to examine the yield of E.D. thoracotomy in patients less than or equal to 18 years of age to allow for a more cost-effective application of this heroic measure. From an 11-year experience of 689 consecutive E.D. thoracotomies, 83 patients (12%) were less than or equal to 18 years old. Mechanism of injury was blunt trauma in 57%, gunshot wound in 30%, and stab wound in 13%. Mean age was 15 years and 71% were male. Survival by injury mechanism was 9% (1/11) for stab wound, 4% (1/25) for gunshot wound, and 2% (1/47) for blunt trauma. Sixty-nine patients presented to the E.D. without vital signs and only one, a 16-year-old with stab wounds to the chest and abdomen, survived. In contrast, two (14%) among 14 patients presenting with vital signs were salvaged. As in adults, outcome was largely determined by injury mechanism and physiologic status on E.D. presentation. Blunt trauma, the predominant mechanism of lethal injuries in children, had a dismal outcome, with only 2% salvage and no survivors when vital signs were absent. This study demonstrates a similar outcome for E.D. thoracotomy in children compared to adults, and supports a selective policy of liberal use in penetrating injury irrespective of physiologic status but limited in those arriving lifeless following blunt trauma.

Adolescent↗
PubMed1989

Intraoperative cardiac sampling following penetrating wounds: a technique for early detection of traumatic intracardiac shunts--case report.

Intracardiac shunts complicating penetrating heart wounds may be unrecognized during the early postoperative period due to the insensitivity of noninvasive diagnostic tests. This case demonstrates the value of intraoperative cardiac sampling for oxygen saturation to identify an otherwise occult aorta-right ventricular fistula secondary to a precordial stab wound, ultimately progressing to a 1.9:1 shunt requiring operative repair.

Adult↗
PubMed1988

Graded experimental myocardial contusion: impact on cardiac rhythm, coronary artery flow, ventricular function, and myocardial oxygen consumption.

Current management of myocardial contusion is based on experience with ischemic heart disease, but the mechanism responsible for cardiac dysfunction may be quite different. The purpose of this study was to characterize the pathophysiology of myocardial contusion in a controlled animal model. Sprague-Dawley rat hearts were prepared on a standard Langendorff apparatus, and myocardial function (DP, + dP/dT, - dP/dT) measured via a left ventricular balloon. Bipolar atrial and ventricular leads were placed to define conduction changes. Coronary sinus effluent was sampled for pO2, pH, creatine phosphokinase (CPK), and lactic dehydrogenase (LDH). The hearts were freeze-clamped to measure phosphocreatine (PC) and adenosine triphosphate (ATP). Myocardial contusion was produced by a single blow with a weighted pendulum. Hearts were divided into control (n = 5), moderate impact--Group I (n = 5), and major impact--Group II (n = 5). Group I sustained a 25% decrease in function after an impact of 78 +/- 5 mJoules/gm, and Group II a 50% deficit after 87 +/- 7 mJoules/gm. Impact resulted in complete electrical arrest, followed by sequential ventricular, atrial, and AV nodal recovery; recovery time correlated directly with degree of injury. Coronary flow at 2 min postinjury was decreased (p less than 0.05) in Group I (12.8 +/- 0.8 ml/min) and Group II (11.5 +/- 1.3) compared to control (17.2 +/- 0.5), and returned to baseline levels at 20 min. LDH and CPK levels were twice as high in Group II as in Group I. The PC/ATP ratio in Group II increased from 1.63 at baseline to 2.54 (p less than 0.05) at 25 min, confirming ischemic reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Angioplasty with stenting is effective in treating blue toe syndrome.

Blue toe syndrome is a manifestation of distal embolization associated with significant pain and risk of tissue loss. The recommended treatment options for this problem include endarterectomy or bypass with exclusion of the source of emboli. Although focal arterial stenosis can be effectively treated with angioplasty,it is unclear whether performing angioplasty in a lesion suspected of causing distal embolization might actually worsen the condition or what long-term effects this would have in preventing future embolization. The purpose of this study was to evaluate the treatment and outcome of a series of patients with unilateral blue toe syndrome treated with percutaneous angioplasty and stenting. During a 5-year period, a total of 8 patients were identified with unilateral blue toe syndrome. Ankle/brachial indices (ABIs) were obtained, followed by arteriography. The study group included 4 men and 4 women with an age range of 35 to 83 years. Their atherosclerotic risk factors included smoking (8), hypertension (5), diabetes mellitus (3), and hypercholesterolemia (1). One patient had a history of illicit drug use. The patients were followed up by repeat clinical examinations and vascular laboratory studies. Arteriography typically demonstrated a focal preocclusive lesion with thrombus at the distal end of the lesion. Angioplasty and stent placement was technically successful in all cases. The ABIs increased following angioplasty (before 0.81 +/- 0.05; after 1.02 +/-.05). The symptoms resolved in all 8 patients over the ensuing month, and there were no recurrences with a mean follow-up of 18.5 months (range 4 to 36 months). There was 1 death at 4 months associated with preexisting colon carcinoma. Unilateral arterial to arterial emboli were found in association with focal preocclusive lesions. Despite the presence of thrombus in some of the lesions, these patients were not acutely worse following angioplasty. There was good initial angiographic success in all cases. There was also hemodynamic improvement as shown by the increased ankle/brachial indices. Although long-term follow-up is not available, these intermediate results suggest that angioplasty and stenting should be considered a reasonable alternative to standard operative approaches for patients with blue to syndrome associated with embolization from a focal stenosis.

Adult↗