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Biomedical subjects

A A Alexander

Publications and source records attributed to A A Alexander.

At least 37 records · Page 2Linked to original sources
PubMed1994

High-resolution endoluminal sonography of the anal sphincter complex.

The ability of a high-frequency miniature ultrasonographic transducer to image the anatomy of the anal sphincter complex was investigated in 20 normal subjects. A 9 Fr catheter containing a 12.5 MHz transducer was inserted into the anal canal. Cross-sectional ultrasonographic images of the canal were acquired as the catheter was advanced through the canal into the distal rectum. Three analog images were digitally stored on a computer system, and measurements of the anal sphincters were made from an eight octant grid by two independent investigators. In all 20 subjects the hypoechoic mucosa, hyperechoic submucosa, and hypoechoic internal anal sphincter (IAS) were identified. The first band of the external anal sphincter (EAS) was imaged in 12 of 20 subjects. The mean width of the IAS was 3.5 +/- 0.5 mm (range, 2.6-4.3 mm). The mean width of the first band of the EAS was 2.3 +/- 0.5 mm (range, 1.6-3.2 mm). High-resolution sonography of the anal canal allows detailed evaluation of anatomic structures that cannot be achieved by conventional imaging technology.

Anal Canal↗
PubMed1994

Endorectal color and duplex imaging of the normal rectal wall and rectal masses.

This study investigates the ability of endorectal ultrasonography aided by color flow and pulse wave Doppler techniques to identify submucosal arterial plexuses of the normal rectal wall and to detect vessels supplying rectal wall masses. Color flow and pulsed wave Doppler analysis of 62 normal submucosal arterial plexuses and vessels feeding rectal wall masses (one rectal endometriosis and seven rectal cancers) was performed. The color signals from normal submucosal arterial plexuses and the one case of rectal endometriosis were judged to be sparse or decreased in comparison to color signals from rectal cancers. The median and mean P1 values for normal submucosal arterial plexuses were significantly greater than those for the central feeding vessels or small peripheral vessels within rectal masses. Our experience with color and duplex endorectal ultrasonography suggests that different vascular structures exist in normal persons compared to those in rectal wall masses. Pathologically, rectal cancers possess vessels with and without a smooth muscle layer, which may produce the high and low resistance signals identified by pulse Doppler.

Adult↗
PubMed1993

Intravesical growth of murine bladder tumors assessed by transrectal ultrasound.

Experimental studies in the therapy of intravesically growing bladder tumors in mice have been hampered by an inability to monitor tumor growth before and during treatment. To establish a repeatable, noninvasive method to monitor the intravesical growth of bladder tumors, MB49 murine bladder tumor cells were instilled into the bladders of syngeneic C57BL/6 mice. Following 3 weeks of growth, the bladders of tumor-bearing and control mice were imaged using a 20 mHz, 6.2 F catheter-based ultrasound transducer inserted rectally. Bladders of tumor implanted and control mice were identified by high resolution endoluminal ultrasound after distension with 0.15 ml. of normal saline. When compared with the results of histologic analysis, transrectal ultrasound (TRUS) accurately identified tumor presence, size, and location.

Animals↗
PubMed1993

Prostate: techniques, results, and potential applications of color Doppler US scanning.

Color Doppler ultrasound (US) scanning and conventional endorectal gray-scale US of the prostate were performed in 619 patients. Pathologic correlation was available in all cases after US-guided transrectal biopsy. There were 132 cancers in 121 men, 13 foci of atypia in 10 men, 33 foci of inflammation in 31 men, and 469 benign lesions in 457 men. Two hundred seventy patients with abnormal areas of flow identified at color Doppler scanning also underwent spectral waveform analysis of the area of potential concern. No statistical difference in the mean resistive indexes was identified in any patient (P = .25; Scheffe F test, analysis of variance). All malignant lesions had abnormalities demonstrated at gray-scale US and/or focal or diffuse abnormal flow demonstrated at color Doppler scanning. Of the 132 cancers, 123 (93%) had corresponding gray-scale abnormalities and 114 (86%) demonstrated abnormal flow at color Doppler imaging. Nine of the 132 cancers (7%) had no obviously identifiable abnormality at gray-scale scanning but had distinctly abnormal flow at color Doppler scanning. Abnormal findings at color scanning without abnormal findings at gray-scale scanning occurred in eight of the 33 cases of inflammatory foci (24%) and in 24 of the 469 (5%) benign lesions.

Adult↗
PubMed1993

Multicentric fibromatosis with metaphyseal dysplasia.

A new association between multicentric fibromatosis and a bone dysplasia is reported. Three patients are described, each of whom had multicentric fibromatosis of the lower extremity and a skeletal dysplasia. One of the patients had dysplastic changes restricted to the involved extremity. The other two had dysplastic changes of all the long bones. The dysplasia consisted predominantly of undertubulation reminiscent of the findings seen in Pyle disease. No clinical or radiographic abnormalities of the marrow were found in any of these patients. It is believed that this association represents mesenchyme that is predisposed to develop both dysplastic bone changes and tumor.

Adult↗
PubMed1993

Clinical and US findings in prostate cancer: patients with normal prostate-specific antigen levels.

PURPOSE: To determine guidelines for biopsy in men with normal prostate-specific antigen (PSA) levels and suspected prostate cancer. MATERIALS AND METHODS: The clinical-sonographic features of 91 lesions of reduced echogenicity in 83 men with normal PSA levels who underwent transrectal ultrasound-guided biopsy were analyzed. RESULTS: Sixteen men (19%) had cancer, two with bilateral foci, and four had prostatic intraepithelial neoplasia (PIN). Fourteen of 47 discrete hypoechoic lesions yielded cancer or PIN versus only five of 44 ill-defined vaguely hypoechoic lesions (P = .03). Fifteen of 18 malignant lesions exceeded 1 cm in longest dimension. In 47 men, sonographic and digital rectal examination (DRE) findings corresponded; 17 (36%) had cancer or PIN. By contrast, of 36 patients with differing sonographic and DRE findings, only three (8%) had malignancy at biopsy (P < .01). CONCLUSION: Predictors of malignancy at sonography of the peripheral prostate gland in men with normal PSA levels include (a) lesion size, (b) degree and focality of hypoechogenicity, and (c) correspondence with the site of DRE abnormality.

Aged↗
PubMed1993

Occluded coloanal anastomosis: transrectal US-guided balloon dilation.

Balloon dilation is a well-described, nonoperative, alternative treatment for postoperative strictures of the colon and rectum. This procedure may not be technically feasible when an occluded lumen prevents passage of a guide wire across the obstruction. The authors describe the use of transrectal ultrasound guidance to initially pass a needle across an occlusive web at the coloanal anastomosis after proctosigmoidectomy. This allowed placement of a guide wire across the occlusion and subsequent successful balloon dilation.

Anal Canal↗
PubMed1992

Cannula-induced vertebral steal in neonates during extracorporeal membrane oxygenation: detection with color Doppler US.

To determine whether flow through the subclavian artery might be affected during extracorporeal membrane oxygenation (ECMO), 40 neonates were examined with color Doppler ultrasound during and after ECMO. Retrograde flow in the right vertebral artery, noted in 12 of the 40 neonates (30%), was consistent with vertebral steal. Brachial systolic velocity was significantly less (P less than .01) on the right than on the left side in neonates both with and without vertebral steal. When the arterial cannula was removed after ECMO, vertebral artery flow became antegrade with symmetric velocity. Brachial velocities became symmetric in infants without vertebral steal, but mild asymmetry persisted in neonates who had had vertebral steal. Only one neonate had clinical signs of arm ischemia, which resolved promptly after removal of the cannula. No surviving neonates (n = 11) had neurologic findings related to the vertebrobasilar insufficiency over a 12-22-month period of observation. Vertebral steal appears to be common during ECMO and is resolved after removal of the cannula.

Basilar Artery↗
PubMed1992

Transnasal US of the esophagus: preliminary morphologic and function studies.

High-frequency catheter-based ultrasound (US) transducers can be inserted into the esophagus transnasally to evaluate esophageal wall structures. Studies were performed in two sheep esophagus specimens in vitro, in 17 healthy human subjects, and in 16 patients with esophageal abnormalities (eight with achalasia, four with scleroderma, three with esophageal carcinoma, and one with esophagitis). In the sheep specimens, endoluminal US delineated seven layers of the esophageal wall; these results correlated closely with histologic findings. Real-time US of the normal esophageal wall was performed during resting and swallowing. Muscles at the lower esophageal sphincter (LES) were shown to be thicker than muscles in the body of the esophagus. Thickening of the muscular layers at the LES in achalasia, dilated blood vessels within the submucosa in esophagitis, and fibrotic changes within the muscular layers in scleroderma were demonstrated. Extramural structures adjacent to the esophagus were also seen. These preliminary results suggest that transnasal esophageal US may become an important diagnostic tool in evaluation of the esophagus.

Adult↗
PubMed1991

Palpable masses in the prostate: superior accuracy of US-guided biopsy compared with accuracy of digitally guided biopsy.

The accuracies of digitally guided biopsy versus ultrasound (US)-guided biopsy of the prostate were compared in 112 consecutive men with palpable prostatic lesions who had previously undergone conventional digitally guided biopsy and in which the results were negative for carcinoma. US-guided biopsies were performed with either the transperineal (n = 51) or transrectal (n = 61) approach, by means of previously described methods. All US-guided biopsies were performed within 3 months after the most recent conventional biopsy. In 44 patients (39.3%) with negative results of conventional biopsies, the results of US-guided biopsy revealed cancer. The transrectal and transperineal digitally guided biopsies were equally inaccurate, and the transrectal and transperineal US-guided biopsies showed no statistically significant differences in accuracy. The patients accepted and tolerated both US techniques equally well; neither technique was associated with significant complications. It is concluded that all patients with a palpable nodule should undergo US-guided biopsy if the result of conventional digitally guided biopsy is negative for cancer and the diagnostic US scan suggests an abnormality.

Biopsy, Needle↗
PubMed1991

Color Doppler as an adjunct to prostate ultrasound.

Endorectal ultrasound of the prostate with color Doppler is a new technique to identify internal vasculature and flow. In a period of one year more than 500 men have been examined with this technique. The normal prostate will demonstrate flow within the surrounding vasculature; there is no distinguishing flow among the various zones. In prostate cancer there is an increased flow within or surrounding the lesion. Diffuse prostatitis exhibits a diffusely abnormal flow; in focal prostatitis the flow is not significantly different from cancer. In benign prostatic hyperplasia a significant abnormal flow was seen, usually in the inner gland, and flow was frequently identified in the area of the surgical capsule. Color Doppler can provide additional physiologic information for prostate ultrasound and may increase the specificity and sensitivity of the examination in the evaluation of potential prostatic malignancy.

Humans↗
PubMed1990

Interhemispheric fissure width in neonates on ECMO.

The neurosonograms of fifty-eight patients treated over a four-year period with ECMO support were retrospectively reviewed for analysis of changes in interhemispheric (IHF) width while on ECMO. To correlate these measurements with patterns of development of total body edema as reflected by chest wall thickening on portable chest radiographs, patients were divided into three categories based on the pattern and severity of body edema development. Patterns of IHF widening were compared between these categories, and to the pattern of development of chest wall edema within each category. Results indicate that IHF width tends to progressively increase during ECMO and that the pattern of IHF widening tends to parallel development of overall body edema. Additionally, IHF widening was found to resolve following termination of ECMO support, as demonstrated on follow-up cranial CT examinations. Our results suggest that IHF widening in infants on ECMO is an intracranial manifestation of the generalized edema accumulation that frequently occurs during ECMO.

Analysis of Variance↗
PubMed1989

A Thy-1 negative lymphoma cell variant defective in the formation of glycosyl-phosphatidylinositol membrane protein anchors.

Thy-1 is a glycoprotein present on the membrane of murine cells of the T-lineage. The mature Thy-1 is anchored to the membrane via a glycolipid, phosphatidylinositide. In order to study the regulation of the synthesis and membrane insertion of this protein, the biochemical properties of a Thy-1.2 negative variant T-lymphoma cell (RL male 1.4) were studied. It contains intracellular Thy-1 protein but fails to express it on the cell surface. While the wild type and the mutant show similar labelling of the intracellular Thy-1 glycoprotein with amino acids, no ethanolamine is incorporated into the Thy-1 molecule of RL male 1.4. A plasmid, pT1, containing the normal Thy-1.2 gene and bacterial gpt gene was transfected into RL male 1.4 and into the murine plasmacytoma cell, J558L. A transfected plasmacytoma, T1J2, synthesized a normal sized Thy-1 protein and displayed the antigen on the membrane. In contrast, the mycophenolic acid resistant RL male 1.4 transfectants did not display Thy-1.2 on the cell surface, despite the presence of substantial amounts of Thy-1 intracellularly. Two other antigens known to be anchored in the membrane by phospholipid, Ly-6e and Qa-2, were also examined in RL male 1.4. RL male 1.4 did not express Ly-6e after alpha interferon induction. In addition, the expression of Qa-2 antigen was greatly diminished in RL male 1.4 in comparison to RL male 1.3. Thus, the defect in RL male 1.4 is not restricted to Thy-1.2, but includes other similarly anchored glycoproteins as well. This implies that the addition of phospholipid to core proteins is similar, if not identical, for all these molecules and that the RL male 1.4 cell lacks the capacity to from the lipid glycoprotein linkage required for the expression of these proteins on the cell surface.

Animals↗