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T J Welch

Publications and source records attributed to T J Welch.

At least 37 records · Page 2Linked to original sources
PubMed1993

Stress response of Escherichia coli to elevated hydrostatic pressure.

The response of exponentially growing cultures of Escherichia coli to abrupt shifts in hydrostatic pressure was studied. A pressure upshift to 546 atm (55,304 kPa) of hydrostatic pressure profoundly perturbed cell division, nucleoid structure, and the total rate of protein synthesis. The number of polypeptides synthesized at increased pressure was greatly reduced, and many proteins exhibited elevated rates of synthesis relative to total protein synthesis. We designated the latter proteins pressure-induced proteins (PIPs). The PIP response was transient, with the largest induction occurring approximately 60 to 90 min postshift. Fifty-five PIPs were identified. Many of these proteins are also induced by heat shock or cold shock. The PIP demonstrating the greatest pressure induction was a basic protein of 15.6 kDa. High pressure inhibits growth but does not inhibit the synthesis of stringently controlled proteins. Cold shock is the only additional signal which has been found to elicit this type of response. These data indicate that elevated pressure induces a unique stress response in E. coli, the further characterization of which could be useful in delineating its inhibitory nature.

Autoradiography↗
PubMed1993

CT- and US-guided biopsy of the pancreas.

A retrospective review of 211 computed tomographic (CT)-guided and 58 ultrasound (US)-guided biopsies of pancreatic lesions performed between 1985 and 1989 was undertaken to evaluate the accuracy of diagnosis and the number of complications. Combined CT and US accuracy in the diagnosis of malignancy was 93%. CT-guided biopsies had an accuracy of 86%, and US-guided biopsies had an accuracy of 95%. Accuracy was higher with larger masses (> 3.0 cm, 92%; < or = 3 cm, 81%) and larger needle sizes (16-19 gauge, 92%; 20-22 gauge, 85%) and when the mass was located in the body or tail of the pancreas (93%) rather than the head (84%). Major complications developed in three cases (1.1%). No biopsy-related deaths occurred. Needle passage through the gastrointestinal tract, including the colon, did not cause complications.

Aged↗
PubMed1993

Pulmonary embolism: diagnosis with electron-beam CT.

Contrast material-enhanced electron-beam computed tomography (CT) (100-msec scan time) was performed to image the pulmonary vasculature in 86 patients, each suspected of having a pulmonary embolism (PE). Thromboembolic material was demonstrated in 39 patients; no emboli were demonstrated in 47. In 25 patients, angiographic or pathologic proof was available. There were 19 proved positive CT scans, four proved negative scans, one false-negative scan, and one false-positive scan. In the 21 patients with CT and angiographic correlation, evidence of thromboembolic disease was seen in 88 vascular zones. Fifty-three zones were positive for PE at both CT and angiography. Eighteen zones were positive for PE at angiography alone, and 17 zones were positive at CT alone. Electron-beam CT is a potentially effective noninvasive means of diagnosing PE.

Adult↗
PubMed1992

The role of intravenous fluorescein in the detection of colon ischemia during aortic reconstruction.

Intravenous fluorescein is an accurate predictor of small bowel viability, but its effectiveness in assessing colon perfusion during aortic surgery has not been evaluated. Over a 10 year period 186 of 3,306 patients undergoing aortic reconstruction received 500 to 1000 mg of intravenous fluorescein intraoperatively to evaluate colon viability. Prior history of colectomy, hypogastric or mesenteric arterial occlusive disease, or ruptured aneurysm placed these patients at risk to develop ischemic colitis. Patients were operated on for aneurysmal disease (n = 94), occlusive disease (n = 66), or a combination of both (n = 26): 171 exhibited uniform normal perfusion patterns under Wood's lamp illumination, while in 11 it was "patchy." None of these patients developed full-thickness ischemic colitis (observed specificity: 100%). Fluorescence of the rectosigmoid was absent in four patients. One of these patients with a ruptured aneurysm underwent immediate sigmoid resection, while three underwent inferior mesenteric artery reimplantation. The fluorescein pattern subsequently normalized in two patients, but one underwent sigmoid resection for an expanding mesenteric hematoma. The second patient recovered without complications. The final patient continued to show a segmental sigmoid defect and postoperatively developed full-thickness injury requiring sigmoidectomy. During the same period 18 other patients developed transmural colon ischemia from 3,120 aortic reconstructions (0.6%), with a mortality rate of 56%. None had received intraoperative fluorescein. Selective use of intravenous fluorescein may reduce the mortality of ischemic colitis following aortic reconstruction.

Aorta, Abdominal↗
PubMed1990

Radiologic evaluation of penetrating aortic atherosclerotic ulcer.

Patients with penetrating atherosclerotic ulcers of the aorta present with back or chest pain that mimics classic aortic dissection. The pathologic findings, however, are distinctly different from those of aortic dissection in that an atherosclerotic lesion with ulceration penetrates into the internal elastic lamina, allowing hematoma formation within the media of the aortic wall. This may lead to false aneurysm or, rarely, transmural rupture of the aorta. Imaging findings of penetrating aortic atherosclerotic ulcers are also different from those of classic aortic dissection. We have found computed tomography to be especially useful in differentiating between these entities and present several illustrative cases.

Aged↗
PubMed1990

Intravascular US of the distal aorta and iliac vessels: initial feasibility studies.

Intravascular ultrasound (US) imaging is a new, evolving technique in which a high-frequency transducer is placed on the tip of a catheter. With this device it is possible to obtain high-resolution images of vessel structure in real time. This may provide valuable information about the degree of stenosis, as well as the type and extent of atherosclerotic plaque, in relation to the underlying tunica media and adventitia. The intravascular US catheter was used in seven patients undergoing transfemoral angiography because of arteriosclerosis obliterans. High-resolution images were obtained in all seven patients, and no complications were noted. Various US findings were demonstrated and correlated with the angiographic findings.

Aged↗
PubMed1989

Imaging-guided biopsy.

In the past 10 years, imaging-guided biopsy has become an accepted technique of tissue retrieval for pathologic analysis. Fluoroscopy, ultrasonography, computed tomography, and magnetic resonance imaging are the current methods of guiding biopsy procedures. Each modality has advantages and disadvantages for various organ systems. High accuracy rates and low complication rates can be expected. Cost savings and rapid reporting of results add to the value of these procedures.

Biopsy↗
PubMed1989

Current applications of duplex and color Doppler ultrasound imaging: carotid and peripheral vascular system.

Recent advances in ultrasound technology have made possible the development of diagnostic instruments that combine cross-sectional imaging and Doppler analysis. These instruments have expanded the role of diagnostic ultrasonography to the assessment of carotid and peripheral vascular disease. The current applications of duplex Doppler and color Doppler imaging in evaluating the extracranial carotid arteries, vertebral artery, peripheral venous system, and peripheral arterial system are reviewed. The indications for and limitations of these examinations, as well as the potential future uses, are discussed.

Arteries↗
PubMed1989

Current applications of color Doppler imaging in the abdomen and extremities.

Recent advances in ultrasound technology have resulted in the development of diagnostic instruments that combine cross sectional imaging with spectral and color flow Doppler analysis. These instruments have expanded the role of diagnostic ultrasonography in the assessment of disease states involving the extracranial carotid artery, the peripheral vascular system, and the major abdominal vessels. The current applications of color Doppler imaging (CDI) combined with conventional spectral Doppler are demonstrated.

Abdomen↗
PubMed1989

CT-guided biopsy: prospective analysis of 1,000 procedures.

The authors prospectively analyzed 1,000 biopsies guided with computed tomography (CT) and performed in 955 patients over a 30-month period. All patients were followed up from 3 months to 2 years. The biopsies were performed in an average of 22 minutes (range, 3-85 minutes) by 26 different radiologists; five radiologists performed 547 of the procedures. Of the 1,000 biopsies, 722 were performed in areas in the liver, retroperitoneum, pancreas, pelvis, and adrenal glands. Of 69 errors in diagnosis, 67 were falsely negative and two were falsely positive; 747 true-positive and 184 true-negative diagnoses were made. CT-directed biopsy for accurate diagnosis was 91.8% sensitive and 98.9% specific, with a positive predictive value of 99.7% and a negative predictive value of 73.3%. Of 11 patients with complications, seven had hematomas, three had pneumothorax, and one had hematuria. No deaths occurred, and only one patient required surgery.

Adrenal Glands↗
PubMed1988

Percutaneous placement of the Greenfield vena caval filter.

During the period from August 1986 to August 1987, 50 patients underwent percutaneous placement of a Greenfield vena caval filter from the right femoral vein, left femoral vein, or right internal jugular vein at our institution. All 50 patients had a contraindication to anticoagulation therapy or had complications of anticoagulation for deep venous thrombosis or pulmonary emboli. The percutaneous placement was accomplished in the angiographic suite with use of local anesthesia and was well tolerated by all patients. Only three complications related to the percutaneous approach occurred during the short-term follow-up (3 months to 1 year). These complications were deep venous thrombosis of the leg in two patients and misplacement of the filter in one patient. The three patients tolerated these complications well. We conclude that placement of Greenfield vena caval filters can be readily accomplished by means of percutaneous entry. Our experience demonstrated minimal associated morbidity and no mortality.

Aged↗