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Biomedical subjects

W C Johnson

Publications and source records attributed to W C Johnson.

At least 163 records · Page 9Linked to original sources
PubMed1981

Information content in the circular dichroism of proteins.

A method is presented for predicting the secondary structure of a protein from its circular dichroism (CD) spectrum. Eight types of secondary structures are considered: helix; parallel and antiparallel beta strand; types I, II, and III beta turn; all other beta turns combined; and "other" structures. The method is based on mathematical calculation of orthogonal basis CD spectra from the CD spectra of proteins with known secondary structure. Five basis CD spectra are needed to reconstruct the 16 original protein CD spectra that extend into the vacuum ultraviolet region to 178 nm. Thus, one can expect to extract five independent pieces of information from the CD spectrum of a protein. Each basis CD spectrum corresponds to a known mixture of secondary structures so that the coefficients that reconstruct the protein CD spectrum can also be used to predict secondary structure. Furthermore, when the same method is applied to protein secondary structure rather than CD, it is found that only five basis secondary structure vectors are needed to reconstruct the original protein secondary structure vectors. Thus there are five independent "superstructures", consisting of a mixture of standard secondary structures, in the proteins studied. It would appear that there is enough information in the CD spectrum of a protein to predict all types of secondary structure. Our CD analyses compare favorably with the X-ray data.

Amino Acids↗
PubMed1981

Prognostic significance of cytomorphology in the cutaneous T-cell lymphomas.

In this retrospective study, the degree of differentiation of atypical lymphoid cells was assessed in pretreatment cutaneous biopsy specimens from 248 patients with cutaneous T-cell lymphomas (mycosis fungoides and Sézary syndrome) and the findings were correlated with the subsequent therapeutic results. Overall, patients with a predominance of cells with hyperchromatic nuclei (well-differentiated lymphoid cells) in cutaneous infiltrates responded better to treatment with improved survival rates than patients with infiltrates composed predominantly of cells with pale vascular nuclei (poorly differentiated lymphoid cells). Infiltrates with a predominance of poorly differentiated lymphoid cells were observed primarily in patients with advanced (tumor) stages of disease. However, comparison of the therapeutic results achieved for the two cytomorphologic patterns in patients at comparable stages of advanced disease did not reveal significant differences, indicating that the presence of poorly differentiated cells in large proportions does not have additional prognostic implications beyond those obtained from usual staging procedures. We speculate that the atypical cells with large, pale vesicular nuclei found in lesions of cutaneous T-cell lymphoma are not a more malignant cell population but rather evolve from more hyperchromatic cellular forms, perhaps a byproduct of malignant dedifferentiation.

Adolescent↗
PubMed1981

Prevention of renal insufficiency after abdominal aortic aneurysm resection by optimal volume loading.

A retrospective case review of 34 men was undertaken to evaluate the relationship between preoperative volume loading and renal function before, during, and after abdominal aortic aneurysm surgery. Volume expansion was guided by either central venous pressure (CVP) in 12 patients or pulmonary artery wedge pressure (PAWP) measurements in 22 patients. Statistically significant differences (P less than .05) were noted between the two groups where greater preoperative volume loading and urine output were associated with lower postoperative serum creatinine and renal function indices in the PAWP group. The age range, vascular risk factors, aneurysm size, and preoperative renal function were similar. The data indicate that (1) PAWP is a more accurate monitor for volume expansion than CVP and (2) when volume replacement is optimal, abdominal aortic aneurysm surgery is not associated with postoperative renal insufficiency.

Acute Kidney Injury↗
PubMed1981

Bleeding esophageal varices: treatment by embolization and shunting.

An assessment was made of the treatment of 120 consecutive, alcoholic, cirrhotic patients with bleeding esophageal varices. Percutaneous, transhepatic embolization of the esophagaogastric varices resulted in control of the hemorrhage and this approach was more effective than were the non-surgical methods used. Management of acute variceal bleeding by conservative non-surgical means, including embolization, appears preferable to emergency portal-systemic shunts. The combination of non-surgical control of the acute variceal hemorrhage plus subsequent selective distal splenorenal shunting resulted in minimal encephalopathy and the most effective treatment.

Embolization, Therapeutic↗
PubMed1981

Computed tomographic angiography.

Computed tomographic angiography performed by the intravenous administration of contrast medium was evaluated in 86 vascular patients. This experience demonstrates a new approach to the evaluation of patients with symptomatic aortic aneurysms, in whom computed tomographic angiography will aid in evaluating the need for emergency surgery. Nonoperative patients are serially evaluated by computed tomographic angiography to detect significant changes in the geometric configuration of their aneurysms. Computed tomographic angiography was beneficial in the evaluation of the patency of vascular reconstructive procedures such as femoropopliteal bypass, aortoiliac bypass and application of a vena caval device. More clinical experience and possibly a rapid sequence technique are needed to evaluate patients with portasystemic shunts.

Abdomen↗
PubMed1981

Treatment of abdominal abscesses: comparative evaluation of operative drainage versus percutaneous catheter drainage guided by computed tomography or ultrasound.

Computed tomography and, to a lesser extent, ultrasonography provide detailed anatomic localization of intra-abdominal abscesses that permit precise percutaneous placement of catheters large enough to effect drainage. Using routes similar to surgical approaches, the authors have used this technique as definitive therapy for intra-abdominal abscesses. To assess its efficacy, the results in the 27 patients treated percutaneously over the last five years have been compared with the results in the 43 patients treated by operative intervention over the past ten years. In the percutaneous group, complications (4%), inadequate drainage (11%), and duration of drainage (17 days) were less than in the operative group (16%, 21% and 29 days respectively). These results indicate that percutaneous drainage is at least as efficacious as operative drainage and avoids the risks of a major operative procedure.

Abdomen↗
PubMed1981

Comparison of various properties of low-molecular-weight proteins from dormant spores of several Bacillus species.

Several properties of the major proteins degraded during germination of spores of Bacillus cereus, Bacillus megaterium, and Bacillus subtilis have been compared. All of the proteins had low molecular weights (6,000 to 13,000) and lacked cysteine, cystine, and tryptophan. The proteins could be subdivided into two groups: group I (B. megaterium A and C proteins, B. cereus A protein, and B. subtilis alpha and beta proteins) and group II (B. cereus and B. megaterium B proteins and B. subtilis gamma protein). Species in group II had lower levels of (or lacked) the amino acids isoleucine, leucine, methionine, and proline. Similarly, proteins in each group were more closely related immunologically. However, antisera against a B. megaterium group I protein cross-reacted more strongly with the B. megaterium group II protein than with group I proteins from other spore species, whereas antisera against the B. megaterium group II protein cross-reacted most strongly with B. megaterium group I proteins. Analysis of the primary sequences at the amino termini and in the regions of the B. cereus and B. subtilis proteins cleaved by the B. megaterium spore protease revealed that the B. cereus A protein was most similar to the B. megaterium A and C proteins, and the B. cereus B protein and the B. subtilis gamma protein were most similar to the B. megaterium B protein. However, amino terminal sequences within one group of proteins varied considerably, whereas the spore protease cleavage sites were more highly conserved.

Amino Acid Sequence↗
PubMed1981

Acid-soluble spore proteins of Bacillus subtilis.

Acid-soluble spore proteins (ASSPs) comprise about 5% of the total protein of mature spores of different Bacillus subtilis strains. They consist of three abundant species, alpha, beta, and gamma, four less abundant species, and several minor species, alpha, beta, and gamma make up about 18, 18 and 36%, respectively, of the total ASSPs of strain 168, have molecular weights of 5,900, 5,9000, and 11,000, respectively, and resemble the major (A, C, and B) components of Bacillus megaterium ASSPs in several respects, including sensitivity to a specific B. megaterium spore endopeptidase. However, they have pI's of 6.58, 6.67, and 7.96, all lower than those of any of the B. megaterium ASSPs. Although strains varied in the proportions of different ASSPs, to overall patterns seen on gel electrophoresis are constant. ASSPs are located interior to the cortex, presumably in the spore cytoplasm, and are synthesized during sporulation and degraded during germination.

Bacillus subtilis↗
PubMed1980

Long-term follow-up of distal splenorenal shunts: evaluation by arteriography, shuntography, transhepatic portal venography, and cinefluorography.

Eight patients with patent distal splenorenal shunts were studied after a 22- to 36-month interval. Evolution of hemodynamic and anatomical changes was documented by percutaneous transhepatic portal catheterization, cinefluorography using ethiodized oil droplets, transfemoral splenorenal shuntography, and celiac arteriography. Changes included (a) a decrease in the portosystemic venous pressure gradient, (b) an increase in the size of and flow through both the shunt and the hepatic artery, (c) reversal of portal venous flow, (d) marked dilatation of collaterals and diversion of flow from the superior mesenteric vein to the shunt, and (e) an increase in cardiac output.

Cineradiography↗
PubMed1980

Further observations on the medical efficacy of computed tomography of the chest and abdomen.

A review of 262 consecutive 2-second CT scans (101 thoracic and 161 abdominal) revealed that 36% contributed information critical to diagnosis, prognosis or therapy. As a result of CT-derived data, major surgery was cancelled in 16 cases and planned surgery modified in 11. Similarly, CT contributed to treatment planning in 20 instances. Forty-four per cent of the studies produced new information but did not have definite clinical impact. Marked improvement in efficacy is noted when these data are compared to our previous study of 2 1/2-minute CT examinations. The improvement is ascribed to better imaging (faster scan speed), improved diagnostic skill, better patient selection, and improved credibility of CT-derived data.

Adenoma, Islet Cell↗
PubMed1980

Perforation of the inferior vena cava by the Kim-Ray Greenfield filter.

Perforation of the inferior vena cava has been reported following insertion of the Kim-Ray Greenfield filter. This report describes this complication as a consequence of a preventable technical error. However, the clinical implications of such a malpositioned filter may extend beyond the possible obvious complications of retroperitoneal hemorrhage or paracaval organ injury. Inadequate protection against pulmonary embolism may result. A three-dimensional concept is presented to illustrate the loss of equal "compartmentalization" of the cava.

Humans↗
PubMed1979

Carotid endarterectomy in the presence of contralateral carotid occlusion: the role of EEG and intraluminal shunting.

Patients undergoing carotid endarterectomy in the presence of occlusion of the contralateral carotid artery appear at greater risk for operative-related stroke or death. We had experience with 37 such patients in a five-year period. Routine intraluminal shunting without EEG monitoring was used in nine patients. Twenty-eight patients had continuous EEG monitoring during surgery. Of this group, 12 patients required intraluminal shunting based on intraoperative EEG criteria. In the early postoperative period, there was one death, and there were no instances of new, fixed neurological deficits. Life table analysis shows that 80% of the patients are neurologically stable in the five-year follow-up period. Electroencephalographic monitoring proved valuable in the detection of patients requiring intraluminal shunting, in the occasional recognition of poorly functioning shunts, and in the determination of the importance of alterations in blood pressure or cardiac rhythm on cerebral blood flow.

Arterial Occlusive Diseases↗
PubMed1979

Clinical and biochemical aspects of trichopoliodystrophy.

The clinical and biochemical evaluation of 6 patients with trichopoliodystrophy indicates that the disease process can begin in utero and is related to a selective abnormality in copper metabolism. Examination of 2 infants on the first day of life revealed abnormal neurological signs, a characteristic hair abnormality, and elevated levels of copper and ceruloplasmin. Decreased hepatic copper levels and increased urinary copper excretion were documented during the first week. The 2 neonates demonstrated a progressive decrease in blood copper levels in the first month of life. Four infants identified at ages 2 to 11 months had low values for blood copper and ceruloplasmin. All infants had progressive neurological dysfunction, and 4 of the 6 died at ages ranging from 2 1/2 months to 5 1/2 years. Parenteral copper therapy achieved normal blood and hepatic copper levels in 1 patient, but the copper values in the cerebral cortex and white matter were significantly decreased compared to control specimens.

Amniotic Fluid↗
PubMed1979

Circular dichroism and DNA secondary structure.

The change in average rotation of the DNA helix has been determined for the transfer from 0.05 M NaCl to 3.0 M CsCl, 6.2 M LiCl and 5.4 M NH4Cl. This work, combined with data at lower salt from other laboratories, allows us to relate the intensity of the CD of DNA at 275 nm directly to the change in the number of base pairs per turn. The change in secondary structure for the transfer of DNA from 0.05 M NaCl (where it is presumably in the B-form) to high salt (where the characteristic CD has been interpreted as corresponding to C-form geometry) is found to be -0.22 (+/- 0.02) base pairs per turn. In the case of mononucleosomes, where the CD indicates the "C-form", the change in secondary structure (including temperature effects) would add -0.31 (+/- 0.03) turns about the histone core to the -1.25 turns estimated from work on SV40 chromatin. Accurate winding angles and molar extinction coefficients were determined for ethidium.

Chemical Phenomena↗