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Biomedical subjects

M E Baker

Publications and source records attributed to M E Baker.

At least 145 records · Page 8Linked to original sources
PubMed1988

Similarity between the estrogen receptor and the DNA-binding domain of the tetracycline repressor.

The amino-terminus region of tetracycline (tet) repressors contains a helix-turn-helix structure that binds to DNA. A computer-based comparison of a residues 18-61 of the tet repressor, which contains this DNA-binding domain, with a residues 304-347 of the human estrogen receptor (ER) yields a score that is 6.7 standard deviations higher than that obtained with 2,500 comparisons of randomized sequences of these segments. The probability of getting this score by chance is less than 10(-11). This part of the ER could be important in nuclear actions of ER in target tissues.

Amino Acid Sequence↗
PubMed1988

Benign retroperitoneal schwannoma.

A case of benign retroperitoneal Schwannoma is presented, with special attention to clarification of often confused pathologic nomenclature. The radiologic diagnosis and the literature on this rare tumor are reviewed.

Adult↗
PubMed1988

High resolution computed tomography of the cadaveric sternoclavicular joint: findings in degenerative joint disease.

High resolution, narrow collimation, axial computed tomography of the sternoclavicular joint was used to describe changes secondary to degenerative joint disease in 32 cadaveric specimens. The distribution and pattern of sclerosis, cystic changes, and osteophyte formation in the axial plane were well demonstrated using this technique. Joint space narrowing was sometimes difficult to assess. Subtle joint space calcification was exquisitely demonstrated using computed tomography. Clavicular head cupping, an anatomic variant, may predispose to more severe degenerative change. Computed tomography is an excellent means to analyze the sternoclavicular joint for the presence of degenerative joint disease and may be the imaging modality of choice in assessing articular disorders of the sternoclavicular joint.

Adolescent↗
PubMed1988

Evolution of alpha-fetoprotein: sequence comparisons among AFP species and with albumin species.

Alpha-fetoprotein (AFP) and albumin are related proteins, which contain about 585 amino acid residues that are organized in a characteristic structure of 3 homologous domains of about 195 amino acid residues. We have compared the domains of mouse, rat, and human AFP and rat, bovine, and human albumin using computer programs designed to quantify relationships between proteins. The comparisons of corresponding domains of the AFPs (e.g. domain I of rat and human AFP) reveal that each domain is well conserved. Similar results were found for the comparisons of corresponding domains in the albumins. In contrast, there was much less similarity between corresponding domains of albumin and AFP. These comparisons between AFP and albumin revealed that: (1) the amino acid sequences in domain III, which is at their carboxy terminus, are most conserved, and (2) the amino acid sequences in domain I, which is at their amino terminus, are least conserved. This suggests that there are differences in the constraints on amino acid substitutions among the domains of AFP and albumin during the approximately 400 million years since they diverged from a common ancestor. Also, computer studies revealed that there are substantial differences between domains I, II, and III in each AFP and albumin species, which indicates that these domains are significantly different from their approximately 195 residue ancestral domain. Finally, we find that mouse and rat AFP are more dissimilar to the albumins than is human AFP. Overall, our computer analyses indicate that AFP and albumin can be considered to be composed of distinct, but related, approximately 195 residue proteins, each of which could differ in some of their properties; for example, the binding of fatty acids.

Amino Acid Sequence↗
PubMed1988

Sonography of the low transverse incision, cesarean section: a prospective study.

Using sonography, the uterine incision site was prospectively studied in 36 asymptomatic patients, two days after cesarean section. The findings were compared with those seen in 21 symptomatic, postcesarean patients. In the asymptomatic patients, the incision site was visualized as an oval symmetric region of distinct echogenicity interposed between the lower uterine segment and the posterior wall of the urinary bladder. In eight of the 36 asymptomatic patients, a small (less than 1.5 cm) round hypoechoic mass was present in or adjacent to the uterine incision and distinct from the normal incision. These probably represented insignificant hematomas. Of the 21 symptomatic patients, 17 had either a subfascial hematoma, a bladder-flap hematoma, or endometritis. Two were sonographically normal, and one showed a hematoma in the paracolic gutter. In the remaining patient, there was a 5-mm asymmetrically placed hypoechoic mass representing an insignificant hematoma. Significant bladder-flap hematomas were characteristically round, greater than 2 cm masses asymmetrically placed in or adjacent to the uterine incision. Using sonography, the normal appearance of the lower uterine incision can be distinguished from significant hematomas.

Abdomen↗
PubMed1987

Vitamin K-dependent protein S is similar to rat androgen-binding protein.

Vitamin K-dependent protein S belongs to the family of clotting factors (e.g. Factors IX and X, and protein C). Unlike the other clotting factors, the C-terminal half (residues 250-634) of protein S is not a serine proteinase. In fact, the function of residues 250-634 of protein S is unknown. By using computer programs designed to detect evolutionary relationships between proteins, we find that this part of protein S is similar to rat androgen-binding protein, a protein produced and secreted by testicular Sertoli cells. The homology between protein S and androgen-binding protein suggests new approaches for elucidating their functions.

Amino Acid Sequence↗
PubMed1987

Augmentation of lymphoproliferative activity of tumor-bearing BALB/c mice to soluble tumor antigens by surgical manipulation: the possible role of macrophages.

Lymphoproliferative activity was assessed by 3H-thymidine incorporation in spleen cells of mammary tumor bearing BALB/c mice, mice which had their tumors surgically removed, and mice with sham surgery after stimulation in vitro with a soluble extract of syngeneic tumor antigens. Surgical removal of tumors caused an average of 65% decline in reactivity at 5 days postoperative as compared to reactivity of animals with their tumors intact. Sham surgery caused an average of 33% elevation in reactivity. Macrophages added to cultures at spleen cell/macrophage ratio of 100:1 caused an average 171%, 59%, and 12% elevation in the activity of surgery, tumor-bearing, and sham-surgery animals, respectively. Surgical manipulation of tumor-bearing mice, therefore, augmented in situ the ability of spleen cells to exhibit lymphoproliferative activity to a soluble syngeneic antigenic extract in vitro, possibly by a mechanism involving the activation of macrophages and requiring the presence of a sizable antigenic load.

Animals↗
PubMed1987

Polar infarct in a transplanted kidney: cause of a pseudomass.

Ultrasonography has become fairly standard for assessing common complications of renal transplantation such as hydronephrosis, urinomas, and lymphoceles. Infarctions are a less common complication that may occur in the setting of transplant rejection. We report a case in which an apparent solid mass on sonography proved to represent normal residual renal parenchyma in a kidney with a small shrunken lower pole due to infarction.

Female↗
PubMed1987

Benign adrenal lesions mimicking malignancy on MR imaging: report of two cases.

Two cases of nonmalignant adrenal masses with prolonged T2 relaxation time and increased adrenal/liver signal ratios are reported. These two cases, one a functioning adenoma with small areas of hemorrhage and the other tuberculosis, emphasize that increased signal intensity in an adrenal mass on T2-weighted images is not always due to malignancy or a pheochromocytoma. While the signal characteristics of an adrenal mass are useful in distinguishing malignancy or pheochromocytoma from benign adenomas, other studies (such as computed tomography for the detection of hemorrhage), clinical evaluation, and percutaneous biopsy remain useful in the investigation of an adrenal mass.

Adenocarcinoma↗
PubMed1987

Striated intramural gallbladder lucencies on US studies: predictors of acute cholecystitis.

Ultrasound scans of 51 consecutive patients with gallbladder wall thickening were reviewed, and specific sonographic features were correlated with surgical and clinical follow-up. Two patterns of thickening were identified as specific indicators of the presence or absence of acute cholecystitis. "Striated" wall thickening, consisting of several alternating, irregular, discontinuous, lucent and echogenic bands, was seen in eight of 13 patients (62%) with acute cholecystitis. This pattern was not encountered in any of the patients who did not have acute cholecystitis. Conversely, "three-layer" thickening, consisting of a single circumferential lucent zone between two relatively uniform echogenic layers, was seen in only one of 13 patients (8%) with acute cholecystitis but in 11 of 38 patients (29%) with other diagnoses. Other abnormalities, including the presence of intramural echogenic foci and wall irregularities, were more frequently seen in patients with acute cholecystitis but were not as helpful. Use of these features may suggest or help exclude a diagnosis of acute cholecystitis in those patients in whom the cause of gallbladder wall thickening is otherwise not apparent.

Acute Disease↗
PubMed1987

Diagnosis of acute colonic diverticulitis: comparison of barium enema and CT.

The contrast enema and CT studies in 102 patients with a clinical diagnosis (41%) or surgically confirmed (59%) diagnosis of colonic diverticulitis were reviewed retrospectively to determine the sensitivity of the two techniques. Combined results from all patients showed that the contrast enema was correct in 77% of patients. The contrast enema was falsely negative in 15% and was indeterminate in 7%. The CT examination was diagnostic in 41%, consistent with the diagnosis of diverticulitis in 38%, and falsely negative in 21% of patients. Both CT and contrast enemas were more accurate in patients with severe disease requiring surgery. No complications occurred from 109 enemas performed. Patient management was altered in only one patient as a result of the additional information provided by CT. The contrast enema should remain the initial and routine examination for the evaluation of patients with suspected diverticulitis. CT should be reserved for patients who are unable to have an adequate contrast enema, those with suspected distant or diffuse abdominal abscess, those who are unresponsive to medical therapy, and those who are candidates for percutaneous drainage.

Acute Disease↗
PubMed1987

Lumbar hernia: diagnosis by CT.

Lumbar hernias occur in the region of the flank bounded by the 12th rib, the iliac crest, and the erector spinae and external oblique muscles. We present the CT findings of seven lumbar hernias: six traumatic (four secondary to postoperative flank incisions, one secondary to an iliac bone-graft donor site, one secondary to nonunion of an iliac fracture) and one spontaneous. Because CT portrays the anatomic relationships in this region so well, it may be the only radiographic procedure necessary to make the diagnosis of a lumbar hernia. Furthermore, it can be helpful in the assessment of symptomatic patients after flank incision, to differentiate postincisional muscular weakness and intercostal neuralgia from a lumbar hernia.

Adult↗
PubMed1987

Sonography of subfascial hematoma after cesarean delivery.

Subfascial hematoma is an important complication of cesarean delivery that has received little attention in the radiologic literature. It results from extraperitoneal hemorrhage within the prevesical space, posterior to the rectus muscles and transversalis fascia but anterior to the peritoneum and umbilicovesical fascia. Subfascial hematomas were found in 12 (38%) of 32 patients referred for sonographic evaluation of a fever or a fall in hemoglobin that occurred after a cesarean delivery. In all cases, sonography revealed cystic or complex masses of various sizes anterior to the bladder. The use of high-frequency, short-focus transducers often was necessary to recognize these superficial abnormalities. Seven of the 12 patients had concomitant bladder-flap hematomas between the lower uterine segment and posterior bladder margin. Of the five remaining patients with isolated subfascial hematomas, the sonograms on four were misinterpreted as showing bladder-flap hematomas. The other was diagnosed correctly. Distinction of subfascial hematomas from bladder-flap hematomas and superficial-wound hematomas must be made if surgical evacuation is contemplated.

Abdominal Muscles↗
PubMed1986

Computer-based search for steroid and DNA binding sites on estrogen and glucocorticoid receptors.

The primary amino acid sequences of proteins that are receptors for estrogen, glucocorticoids, and ouabain were compared with each other using computer programs designed to detect and quantify similarities between proteins. Three regions of similarity between the estrogen receptor (ER) and the glucocorticoid receptor (GR) were identified. On the ER, residues 173-250, 323-395, and 426-458 are similar to residues 409-486, 540-612, and 644-676, respectively, on the GR. The ALIGN computer analysis of these segments on the ER and the GR gave comparison scores that were 16.8, 13.7, and 6.8 standard deviations higher, respectively, than that obtained with a comparison of randomized sequences of these proteins. The probability of getting these scores by chance is less than 10(-60), 10(-40), and 10(-11), respectively. Others have proposed that the segment on the ER and GR that is nearest their amino terminus (e.g. residues 173-250 of the ER) is part of their DNA binding domain and that the other two similar segments on each receptor, which are closer to their carboxy terminus, are part of their steroid binding domain. Here, we present evidence to support both of these hypotheses. First, an Align computer analysis indicates that residues 323-395 of the ER and residues 570-612 of the GR contain a region that is similar to a part of the alpha-subunit of the (Na+ + K+)ATPase that is hypothesized to bind the steroid ouabain. This similarity provides additional support for the proposed location of the steroid binding site on the ER, GR, and (Na+ + K+)ATPase. Second, a computer search of the protein sequence database revealed that protamine, a DNA binding protein, has some similarity to residues 255-281 of the ER, which are thought to be part of the DNA binding domain in the ER. Further, we find that residues 276-281 of the ER contain a structure that has been found at the nucleotide binding domain of some protein kinases. If this region on the ER binds ATP, then it may be involved in phosphorylation/dephosphorylation of the ER, which is thought to be important in its mechanism of action.

Amino Acid Sequence↗
PubMed1986

Bladder leiomyoma: advantages of sonography over computed tomography.

The complementary use of sonography in the evaluation of a bladder-base leiomyoma is reported. Sonography, as compared to computed tomography, was able to document the solid nature of the tumor, its submucosal location, and determined the site of origin and exact relationship to adjacent organs by virtue of the ability to image in multiple planes. The sonographic appearance of a submucosal, solid lobulated bladder-base mass is suggestive of a leiomyoma.

Adult↗
PubMed1986

Role of computed axial tomography of the chest in staging patients with nonmetastatic gestational trophoblastic disease.

Thirty-nine women with nonmetastatic gestational trophoblastic disease as determined by conventional staging studies were prospectively evaluated with computed axial tomography (CAT) of the lungs. Sixteen patients (41%) had pulmonary micrometastases detected by CAT, which were not detected by routine chest x-ray. Eight patients (20.5%) had indeterminate scans, and only 15 patients (38%) had negative scans. Eight of 16 patients (50%) with pulmonary micrometastases failed initial therapy with methotrexate-folinic acid rescue while one of eight (12.5%) patients in the indeterminate group and one of 15 (6.7%) patients in the true nonmetastatic group failed initial therapy (P less than .006). All patients who failed methotrexate-folinic acid rescue ultimately achieved prolonged remission with actinomycin D. Time to remission was significantly decreased in patients without evidence of pulmonary micrometastases (P = .03), but the total number of courses of chemotherapy was not significantly different (P = .06). No life-threatening toxicity occurred. Pulmonary micrometastases detected by CAT but not chest x-ray are predictive of an increased risk of methotrexate-folinic acid therapy failure. Computed axial tomography of the lungs identifies a group of patients at high risk for failure of methotrexate-folinic acid rescue, and, therefore, may be indicated for routine staging of patients with otherwise nonmetastatic gestational trophoblastic disease.

Adolescent↗