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Biomedical subjects

M E Baker

Publications and source records attributed to M E Baker.

At least 127 records · Page 7Linked to original sources
PubMed1990

Hepatic hemangiomas vs metastases: MR differentiation at 1.5 T.

We retrospectively studied the value of MR imaging at 1.5 T in distinguishing hepatic hemangiomas (n = 15) from metastases (n = 15) by using (1) lesion/liver signal-intensity ratios, (2) contrast/noise ratios, and (3) T2 relaxation time on long TR/TE spin-echo (SE) sequences. Lesion/liver margin sharpness, lesion shape, and overall lesion morphologic pattern were evaluated also. Univariate logistic regression analysis of the quantitative data showed that T2 was the only statistically significant (p less than .02) variable for distinguishing a hemangioma from a metastasis. A receiver-operator-characteristic plot of T2 produced an area of 0.80 (+/- 0.08). T2 values for these lesions still overlapped with those for metastases. Morphologically, hemangiomas were sharply marginated (80%), rounded or oval (93%), homogeneous, hyperintense lesions (73%), whereas metastases were poorly marginated (66%) and inhomogenous (67%) lesions. The marked, hyperintense appearance was present in 27% of metastases. Retrospective, multivariate logistic regression analysis of T2 and the presence of hyperintense morphology did not improve results based on T2 alone. Morphologic criteria are helpful in differentiation, as some metastases have a prolonged T2 and are not homogenous, hyperintense lesions. In cases where T2 or morphology are equivocal, other diagnostic tests may help confirm the MR findings. We currently use a T2 of greater than 88 msec and the presence of hyperintense morphology to diagnose hemangiomas. Despite both quantitative and qualitative analysis, data for these hemangiomas and metastases still overlap.

Adult↗
PubMed1990

Ovarian vein thrombosis in oncology patients: CT detection and clinical significance.

During a 13-month period, ovarian vein thrombosis (OVT) was detected with CT in six patients with malignant tumors, five of whom were receiving high-dose chemotherapy at the time of diagnosis. None of these patients belonged to previously recognized risk groups. Unlike most patients with postpartum or postoperative OVT, only one of our patients was symptomatic, and none had related CT findings, such as uterine enlargement or other enhancing pelvic masses. Patients with malignant tumors, particularly those undergoing chemotherapy, are at risk for developing OVT. As OVT is often asymptomatic in these patients, and thrombus may resolve without treatment, anticoagulation may not be routinely necessary.

Adult↗
PubMed1990

Obliteration of the fat surrounding the celiac axis and superior mesenteric artery is not a specific CT finding of carcinoma of the pancreas.

Partial or complete obliteration of the fat surrounding the celiac axis and superior mesenteric artery on CT is considered so characteristic of pancreatic carcinoma that many consider it diagnostic. However, this finding may be present on CT scans of some treatable tumors. During a 2-year period, we retrospectively collected 10 cases of nonpancreatic tumors that obliterated the fat surrounding the celiac axis and/or superior mesenteric artery. Four patients had metastatic disease, three had lymphoma, two had primary small-bowel adenocarcinoma, and one had a diffuse retroperitoneal endocrine tumor. The scans were analyzed for presence, location, and morphology of the mass and biliary and/or pancreatic ductal dilatation. Of the patients with metastatic disease, three had focal, retropancreatic, periceliac masses without ductal dilatation. One had an infiltrative retroperitoneal process enveloping the pancreas and causing biliary dilatation. Of the patients with lymphoma, two had focal masses in the mesenteric root without ductal dilatation, and one had an infiltrative retroperitoneal process. Of the two patients with primary carcinoma of the small bowel, one had a mesenteric mass without ductal dilatation and the other had an infiltrative retroperitoneal process enveloping the pancreatic head and obstructing the ducts. The patient with the neuroendocrine tumor had an infiltrative retroperitoneal process enveloping the pancreas without ductal dilatation. Obliteration of the fat surrounding the celiac axis and superior mesenteric artery is not a specific CT finding of carcinoma of the pancreas. One cannot rely solely on its presence for the diagnosis of pancreatic carcinoma but should use other important findings such as a focal pancreatic mass and ductal dilatation.

Adenocarcinoma↗
PubMed1990

Computed tomography-guided fine-needle aspiration of retroperitoneal lymph nodes in gynecologic oncology.

Computed tomography-guided fine-needle aspiration was performed on 30 retroperitoneal lymph nodes in 29 patients with gynecologic cancer. There were no serious complications. Review of the cytologic material demonstrated malignant cells in 83% of the aspirates. Because the predictive value of a positive aspirate approaches 100%, therapy for metastatic disease can be initiated in these patients with the need for an open biopsy. Among five aspirates in which malignant cells were not seen, the cellularity of the specimen appeared to be the critical factor determining the predictive value of the aspirate. Whereas neither of two patients with negative aspirates of adequate cellularity has developed recurrent disease, two of three patients with hypocellular negative aspirates have. Because a hypocellular negative aspirate from a retroperitoneal lymph node may not be a true reflection of disease status, either repeat aspiration or open biopsy is advisable.

Adenocarcinoma↗
PubMed1989

Location of enzymatic and DNA-binding domains on E. coli protease La.

Escherichia coli protease La is an ATP-dependent enzyme that has a DNA-binding site. The locations of the enzymatic and DNA-binding sites are not known. We report that a 75-residue segment at the carboxy-terminus of the protease La is similar to part of Bacillus licheniformis beta-lactamase, a serine enzyme. The comparison score is 8.2 standard deviations higher than that obtained with 10,000 comparisons of randomized sequences of these segments. The probability of obtaining such a score by chance is 1.2 x 10(-16). We also find that a 107-residue segment in the amino-terminus half of protease La is similar to part of the sopB protein, a DNA-binding protein of the plasmid F of E. coli. The comparison score for these segments is 8 standard deviations (P = 6 x 10(-16)). These strong amino acid sequence similarities suggest the locations of the catalytic serine and the DNA-binding domains of protease La.

ATP-Dependent Proteases↗
PubMed1989

Similarity between phospholipase C and the regulatory domain of protein kinase C.

We report that a 100 residue segment in the carboxy-terminus half of phosphatidylinositol-specific phospholipase C is similar to a segment in the amino-terminus half of protein kinase C. The computer-based comparison score is 9.5 standard deviations higher than that of 2500 comparisons of randomized sequences of these segments (P = 10(-21), suggesting that the two segments have similar biological properties. Phospholipase C has a segment that is homologous to part of the non-catalytic domain of src kinase and other tyrosine protein kinases. The similarity of phospholipase C with protein kinase C, a serine/threonine kinase suggests that novel exon shuffling occurred among serine/threonine and tyrosine kinases and phospholipase C.

Amino Acid Sequence↗
PubMed1989

Dynamic, incremental computed tomography using a high heat capacity tube, solid-state detector, and automated injector. Potential in body imaging.

Using a new graphite tube, a prototype solid scintillating detector, and an automated injector, improvements were made in body computed tomography image quality. First, more scans with shorter interscan delay could be obtained with the improved tube. Second, liver image quality was improved with the use of higher techniques and a more consistent contrast bolus delivery with a mechanical injector. Last, body surveys were improved because the higher heat capacity tube provided the ability to rapidly scan and examine an entire region during the injection of contrast.

Automation↗
PubMed1989

Pulmonary septic emboli mimicking metastatic rhabdomyosarcoma.

Central venous catheters have proven to be an important aid for the care of pediatric patients with malignancies receiving chemotherapy. A rare complication of such catheters is pulmonary septic emboli. This report describes a 15-year-old white girl with rhabdomyosarcoma who developed pulmonary nodules while on chemotherapy. These lesions appeared to be metastatic rhabdomyosarcoma. However, an excisional biopsy showed the lesions to be septic emboli. The patient was placed on antibiotic therapy and responded well. She was able to continue with her "front-line" therapy because the nodules were confirmed not to be metastatic disease.

Adolescent↗
PubMed1989

Similarity between tyrosyl-tRNA synthetase and the estrogen receptor.

Residues 1-42 of Escherichia coli tyrosyl-tRNA synthetase are similar to residues 293-334 of the human estrogen receptor. A computer analysis yields a comparison score that is 8.2 standard deviations higher than that obtained with 10,000 comparisons of randomized sequences of these segments (P = 1.2 X 10(-16). This part of tyrosyl-tRNA synthetase binds ATP, which suggests that residues 293-334 of the human estrogen receptor are part of an ATP binding site.

Adenosine Triphosphate↗
PubMed1989

Human placental 17 beta-hydroxysteroid dehydrogenase is homologous to NodG protein of Rhizobium meliloti.

The amino acid sequence of human placental 17 beta-hydroxysteroid dehydrogenase (17 beta-OH-steroid dehydrogenase) was found to be similar to that of the NodG protein of Rhizobium meliloti. The computer-based comparison score is 11.5 SD higher than that obtained with 2500 comparisons of randomized sequences of these proteins. The probability of getting such a score by chance is 6 x 10(-31). 17 beta-OH-steroid dehydrogenase is also similar to Klebsiella aerogenes ribitol dehydrogenase and Escherichia coli glucitol-6-phosphate dehydrogenase. We propose that the steroid recognition site on 17 beta-OH-steroid dehydrogenase evolved from an ancestral recognition site for polyols such as ribitol and glucitol-6-phosphate.

17-Hydroxysteroid Dehydrogenases↗
PubMed1989

MR evaluation of adrenal masses at 1.5 T.

We retrospectively studied the value of MR imaging at 1.5 T to distinguish between nonadenomatous (n = 17) and adenomatous (n = 15) adrenal masses on the basis of (1) signal-intensity ratios on T1- and T2-weighted spin-echo images, (2) T2 relaxation times, and (3) T2 relaxation-time ratios. Univariate and then multivariate logistic regression were applied to these quantitative parameters to determine which of these best discriminated nonadenomas from adenomas, and whether or not more than one of these parameters improved the prediction. The adrenal mass/liver signal-intensity ratio on T2-weighted spin-echo images could not be used to differentiate nonadenomas from adenomas. Adrenal mass/fat signal-intensity ratios on T2-weighted spin-echo images, adrenal/liver T2 relaxation-time ratios, and adrenal mass T2 relaxation times were best for distinguishing nonadenomas from adenomas. By using a T2 value of greater than 61 msec, the true-positive ratio/false-positive ratio of differentiating nonadenomas from adenomas was 100%/20%; at greater than 82 msec, it was 64%/0.06%. The adrenal mass/fat signal-intensity ratios on T2-weighted spin-echo images and the adrenal/liver T2 relaxation-time ratios showed similar inherent discriminatory capacity. Overlap remains despite the use of these parameters. On the basis of this preliminary information, we conclude that MR has merit for the characterization of adrenal masses at 1.5 T. T2 relaxation time of the adrenal mass shows the greatest promise for discriminating nonadenomas from adenomas.

Adenoma↗
PubMed1988

Is vitellogenin an ancestor of apolipoprotein B-100 of human low-density lipoprotein and human lipoprotein lipase?

Vitellogenin, an ancient animal protein, is the major yolk protein of eggs, where it is used as a food source during embryogenesis. Here it is shown that vitellogenins, including those from the invertebrates Caenorhabditis elegans and Drosophila melanogaster, contain domains that are homologous with parts of apolipoprotein B-100 (apoB-100) of human low-density lipoprotein and human lipoprotein lipase. As vitellogenins are likely to have been used by invertebrates during embryogenesis well before the circulation of lipids appeared in vertebrates, it is suggested that copies of a precursor gene, serving a function similar to vitellogenin, were modified to code for part of apoB-100 and lipoprotein lipase in vertebrates. In addition to providing a link between invertebrates and vertebrates for proteins involved in lipid transport, these homologies suggest new functions for vitellogenin other than being a yolk food for the developing embryo.

Amino Acid Sequence↗