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Biomedical subjects

C M Johnson

Publications and source records attributed to C M Johnson.

At least 19 recordsLinked to original sources
PubMed1992

Differential scanning calorimetry of thermal unfolding of the methionine repressor protein (MetJ) from Escherichia coli.

The thermal stability of the methionine repressor protein from Escherichia coli (MetJ) has been examined over a wide range of pH (pH 3.5-10) and ionic strength conditions using differential scanning calorimetry. Under reducing conditions, the transitions are fully reversible, and thermograms are characteristic of the cooperative unfolding of a globular protein with a molecular weight corresponding to the MetJ dimer, indicating that no dissociation of this dimeric protein occurs before unfolding of the polypeptide chains under most conditions. In the absence of reducing agent, repeated scans in the calorimeter show only partial reversibility, though the thermodynamic parameters derived from the first scans are comparable to those obtained under fully reversible conditions. The protein is maximally stable (Tm 58.5 degrees C) at about pH 6, close to the estimated isoelectric point, and stability is enhanced by increasing ionic strength in the range I = 0.01-0.4 M. The average calorimetric transition enthalpy (delta Hm) for the dimer is 505 +/- 28 kJ mol-1 under physiological conditions (pH 7, I = 0.125, Tm = 53.2 degrees C) and shows a small temperature dependence which is consistent with an apparent denaturational heat capacity change (delta Cp) of about +8.9 kJ K-1 mol-1. The effects of both pH and ionic strength on the transition temperature and free energy of MetJ unfolding are inconsistent with any single amino acid contribution and are more likely the result of more general electrostatic interactions, possibly including significant contributions from electrostatic repulsion between the like-charged monomers which can be modeled by a Debye-Hückel screened potential.

Bacterial Proteins↗
PubMed1992

Synthesis of renin by tubulocystic epithelium in autosomal-dominant polycystic kidney disease.

Evidence suggests an important role for the renin-angiotensin system in the pathogenesis of autosomal-dominant polycystic kidney disease (ADPKD). Therefore, we studied the presence of immunoreactive renin in renal biopsies and measured the concentrations of renin in cyst fluids. Normal kidneys and kidneys with renal artery stenosis were used for comparison. In ADPKD, immunoreactive renin was present in juxtaglomerular apparatus, associated arterioles, and in some cells within the connective tissue surrounding the cysts. Vascular immunoreactive renin was less prominent than in renal artery stenosis. Increased amounts of tubular immunoreactive renin were noted in polycystic kidneys, as compared to normal kidneys and kidneys with renal artery stenosis. Cyst fluids contained renin detected by Western analysis and enzymatic activity; concentrations were greater in gradient cysts than in nongradient cysts. Seventy-four percent of the renin in gradient cysts was active as compared to 23% in nongradient cysts and 15% in plasma. To determine whether cyst epithelial cells are capable of synthesizing renin, these cells were isolated in tissue culture. Enzymatic assay of extracts from these cells revealed the presence of renin-like enzymatic activity (1.3 +/- 0.8 ng AI/mg protein/hr). The synthesis of renin by tubulocystic epithelium was confirmed by [35S]-methionine radiolabeling of cyst-derived cells, followed by immunoprecipitation and SDS-PAGE and by detection of renin mRNA by the polymerase chain reaction. These results indicate that the tubulocystic epithelium has the potential to synthesize renin. Elevated levels of active renin in renal cysts may be linked to the pathogenesis of hypertension in ADPKD. The occurrence of renin in the lining epithelium of cyst walls raises the possibility that abnormal expression of the renin-angiotensin system may, by a paracrine or autocrine mechanism, regulate epithelial hyperplasia in growing renal cysts.

Base Sequence↗
PubMed1992

Beam-shaping device for long-film angiography.

Uniform radiologic exposure from the pelvis to the ankles is often difficult to achieve when long films (51-inch) are used for femoral angiography. A unique device developed to shape the x-ray beam accomplishes this task by using a movable shutter to obscure a portion of the x-ray beam. A microprocessor-controlled stepper motor modulates the amount of beam cutoff by regulating the movement of the shutter from the foot end of the film. The goal is to match exposure factors to the patient's body shape. This beam-shaping device has been evaluated and tested in examinations of 500 patients over the past year. A substantial improvement in image quality over that achieved with earlier systems of graduated screens and multiple wedge filters was seen in all cases. The system is esy to use, flexible, and especially valuable in imaging obese patients or those who have legs disproportionately smaller than their pelvis or abdomen.

Abdomen↗
PubMed1992

Pigs with von Willebrand disease may be resistant to experimental infective endocarditis.

Indirect evidence suggests that the blood platelet is important in the pathogenesis of experimental infective endocarditis. Mechanical injury to the endocardial surface causes deposition of fibrin and platelets; injected microorganisms quickly localize to this lesion. Endocarditis pathogens also bind to and activate platelets. We used our previously described animal model for inducing infective endocarditis in normal pigs and applied it to animals with severe von Willebrand disease. The model uses catheter-induced trauma to the aortic valve and endocardium, followed by intravenous injection of group C streptococci. Control animals all showed typical clinical and laboratory evidence of endocarditis. In contrast, in pigs with von Willebrand disease (n = 4) endocarditis failed to develop. Studies in vitro of platelet-bacteria interactions showed that platelets derived from both normal and diseased pigs were equal in their ability to bind to and be activated by group C streptococci. These data suggest that normal platelet function is important in the pathogenesis of experimental infective endocarditis.

Animals↗
PubMed1992

Analysis of 945 cases of pulmonary metastatic melanoma.

From 1970 to 1990, 7564 patients with melanoma were seen at Duke University Cancer Center. Complete follow-up data were available in all patients. The estimated probability of a pulmonary metastasis developing 5, 10, or 20 years after initial diagnosis was 0.13, 0.19, and 0.30, respectively. Pulmonary metastases were documented in 945 patients (12%), these having 1-, 3-, and 5-year survival rates of 30%, 9%, and 4%, respectively. The methods of diagnosis were chest radiograph (n = 544), computed tomography (n = 157), transthoracic needle biopsy (n = 121), bronchoscopy (n = 14), thoracotomy (n = 112), and autopsy (n = 7). Evidence of advanced pulmonic spread included bilateral disease in 543 and more than two nodules in 595. Univariate predictors for early formation of pulmonary metastases (p less than 0.001) were male sex, black race, increased primary thickness (millimeters), higher Clark's level, nodular or acral lentiginous histology, location on trunk or head and neck, and regional lymph nodes positive for metastasis. Multivariate predictors of improved survival (p less than 0.001) in order of importance were complete resection of pulmonary disease, longer time for formation of metastases, treatment with chemotherapy, one or two pulmonary nodules, lymph nodes negative for metastasis lymph nodes (p less than 0.005), and histologic type (p less than 0.04). Additionally, survival in patients with one nodule and resection (n = 84) was better than in those with similar disease and no resection (n = 142 months, p less than 0.001). These data comprise the largest series to date and emphasize the importance of long-term follow-up, as well as supporting the selective use of resection for isolated pulmonary metastases, increasing the 5-year survival rate from 4% to 20%.

Adult↗
PubMed1992

Primary venous leiomyosarcoma: a rare but lethal disease.

Primary venous leiomyosarcoma is rare, only 197 patients have been reported. To examine progress in diagnosis, treatment, and clinical outcome, we retrospectively reviewed data of 13 patients, 12 women and one man (mean age, 55 years; range, 19 to 75 years), who in the last 35 years underwent surgical treatment for primary venous leiomyosarcoma at our institution. The tumor arose from the inferior vena cava in eight, iliac vein in two, ovarian vein in one, and greater saphenous vein in two patients. Primary venous leiomyosarcoma was detected by physical examination in nine patients, symptoms were present in six. The 13 patients underwent 16 surgical procedures to resect primary (12), recurrent (2), or metastatic (2) tumors. Local excision alone was performed in seven, and local excision with reconstruction of the inferior vena cava or iliac vein was performed in six patients. The tumor was greater than 10 cm in eight patients. The perioperative mortality rate was 15% (2 of 13). Median survival of the 11 early survivors was 3.5 years (range, 6 months to 17 years). Currently five patients are alive (four of them free of known tumor), with a median survival of 3 years (6 months to 17 years) after surgery. Of the eight deceased patients, primary venous leiomyosarcoma recurred after resection in six. Tumor recurrence was not affected by tumor grade, size, or adjuvant treatment. Although early detection with modern imaging techniques could potentially be of benefit, wide local excision with selective venous reconstruction affords the only hope for prolonged survival.

Adult↗
PubMed1991

A comparison of the reactivity and stability of wild type and His388----Gln mutant phosphoglycerate kinase from yeast.

A variety of physico-chemical techniques have been used to probe the possible interactions between the characteristic structural domains of yeast phosphoglycerate kinase by comparison of the wild-type enzyme with the specific H388Q mutant in which a potential interaction between His388 and Glu190 in the crucial interdomain region is disrupted. Enzyme kinetic studies indicate that, despite being structurally remote from the active site, this mutation has significant effects on both the Vmax and Km values for various substrates. The single cysteine residue in the N domain of the protein is markedly more reactive in the mutant, and this enhanced accessibility is moderated by binding of substrates and various anions. Differences are also observed in the near-ultraviolet CD spectra of these proteins. The chemical and thermal stability of the mutant enzyme is reduced, as indicated from guanidinium chloride and differential-scanning calorimetry denaturation studies. Moreover, interdomain interactions seem to be altered in the mutant, resulting in the appearance of independent thermal transition for the two domains, in contrast to the single cooperative transition observed for the wild-type enzyme. The conformational and/or dynamic effects of the mutation on the H388Q enzyme are therefore various and not solely localised in the hinge region.

Amino Acid Sequence↗
PubMed1991

Topological and epitope mapping of the cellular retinaldehyde-binding protein from retina.

Cellular retinaldehyde-binding protein (CRALBP) carries 11-cis-retinol or 11-cis-retinaldehyde as endogenous ligands and may function as a substrate carrier protein that modulates interaction of these retinoids with visual cycle enzymes. As a first approach to identifying functional domains and protein recognition sites in CRALBP, a low resolution topological and epitope map has been developed using monoclonal and polyclonal antibodies and limited proteolysis. Fifteen peptides of 8-31 residues spanning 99% of the 316-residue bovine CRALBP were synthesized and used to prepare 13 anti-peptide polyclonal antibodies. Using a competitive ELISA procedure, peptide epitopes were classified as either accessible or inaccessible in the native protein based on the extent of their recognition by these site-specific antibodies. Use of the synthetic peptides to map the epitopes of a polyclonal antibody to intact CRALBP confirmed that the amino terminus and carboxyl terminus are immunodominate regions and hence likely to be exposed, at least in part. Limited tryptic proteolysis of native CRALBP produced three major fragments which were shown by microsequence and Western analysis to be derived from sequential loss of short peptides from the amino terminus. None of these major fragments reacted with four monoclonal antibodies (mAbs) to intact CRALBP although each mAb immunoprecipitated native CRALBP. These results and the lack of mAb recognition of any of the synthetic peptides indicates that the amino terminus of the protein is exposed and contains part of an assembly epitope recognized by the mAbs. Overall this study indicates that residues 1-30, 100-124, and 257-285 contain highly exposed segments in the native protein and therefore constitute potential interaction domains for CRALBP and visual cycle enzymes. Residues 30-99 and 176-229 are inaccessible in the native structure and may be involved with retinoid binding. These results provide a basis for a systematic higher resolution mutagenesis study directed toward correlating CRALBP structural domains with function.

Amino Acid Sequence↗
PubMed1991

Selective modification by transglutaminase of a glutamine side chain in the hinge region of the histidine-388----glutamine mutant of yeast phosphoglycerate kinase.

The transglutaminase-catalysed incorporation of putrescine and monodansylcadaverine into yeast phosphoglycerate kinase has been studied. There is little incorporation of the amines into wild-type enzyme, but nearly stoichiometric incorporation into the histidine-388----glutamine mutant enzyme. C.d. studies show that the overall structure of the mutant enzyme is very similar to that of the wild-type enzyme. Incorporation of the amines into the mutant enzyme causes no significant change in its activity. Glutamine-388 was shown, by isolation and sequencing of the modified peptide, to be the site of incorporation of monodansylcadaverine into the mutant enzyme. The specificity of the transglutaminase reaction is discussed in the light of available data.

Amino Acid Sequence↗
PubMed1991

Phase II trial of Bisantrene for metastatic melanoma: an Illinois cancer council study.

Sixteen patients with metastatic melanoma entered this phase II study of the efficacy of monthly cycles of Bisantrene. Toxicity was characterized by leukopenia, resulting in the hospitalization of one patient for a febrile incident, and superficial phlebitis. The results were similar to those of previous studies, in that among the 13 patients evaluable for response (six previously untreated with chemotherapy) there were no responses.

Adult↗
PubMed1991

Effect of inhibition of converting enzyme on renal hemodynamics and sodium management in polycystic kidney disease.

We compared the tubular transport of sodium and the erythrocyte sodium-lithium countertransport activity in hypertensive patients with autosomal dominant polycystic kidney disease (ADPKD) and in normotensive control subjects. In addition, we assessed the effects of inhibition of converting enzyme on renal hemodynamics and sodium excretion in hypertensive patients with ADPKD to provide information on mechanisms responsible for the increased renal vascular resistance and filtration fraction and the adjustment of the pressure-natriuresis relationship during saline expansion, observed in patients with ADPKD, hypertension, and preserved renal function. In comparison with normotensive control subjects, the hypertensive patients with ADPKD had lower renal plasma flows, higher renal vascular resistances and filtration fractions, and similar proximal and distal fractional reabsorptions of sodium. The administration of enalapril resulted in significant increases in the renal plasma flow and significant reductions in mean arterial pressure, renal vascular resistance, and filtration fraction, but the glomerular filtration rate remained unchanged. Despite the significant reduction in mean arterial pressure during inhibition of converting enzyme, the distal fractional reabsorption of sodium decreased while the total fractional excretion of sodium remained unchanged or increased slightly. No significant differences were detected between the normotensive control subjects and the hypertensive patients with ADPKD in erythrocyte sodium-lithium countertransport activity, plasma renin activity, plasma aldosterone concentration, or atrial natriuretic factor. These results suggest that the renal renin-angiotensin system plays a central role in the alterations in renal hemodynamics and sodium management associated with the development of hypertension in ADPKD.

Adult↗
PubMed1991

Efficacy and toxicity of pentostam against Panamanian mucosal leishmaniasis.

We tested the World Health Organization (WHO) recommended treatment for mucosal leishmaniasis in 16 Panamanians with disease due to Leishmania braziliensis panamensis. Disease was mild in this population because it was limited to the nasal mucosa and only one patient had septal perforation. The patients were administered 20 mg antimony (in the form of Pentostam) per kg intravenously each day for 28 days. Ten patients completed therapy and were cured at 12 month follow-up. Three patients completed therapy, healed their lesions, but relapsed at the six or 12 month follow-up. Three patients terminated therapy prematurely because of liver enzyme elevations in conjunction with either EKG abnormalities or musculoskeletal complaints; none of these patients were healed. This study indicates that in patients with mild mucosal leishmaniasis, the WHO regimen is curative in 77% patients who complete treatment and in 63% of all patients.

Adult↗
PubMed1991

Klippel-Trenaunay syndrome: the risks and benefits of vascular interventions.

Our experience with Klippel-Trenaunay syndrome (KTS), a rare congenital malformation, has increased considerably in recent years and now includes 144 patients (65 male and 79 female patients). Hemangioma was present in 137 patients (95.1%), varicosity in 110 (76.4%), and hypertrophy of the soft tissues or bones in 134 (93.1%). In most patients (71.5%) the disease involved one lower extremity. Diagnostic workup included roentgenogram to document limb length discrepancy, noninvasive arterial and venous evaluation, contrast venography, and nuclear magnetic resonance imaging. Most patients did well without treatment or with elastic compression only. Surgical treatment for the vascular malformation in KTS is rarely needed and it continues to be controversial. To evaluate the risks and benefits of vascular interventions, we examined in detail the clinical histories of nine patients who in the last decade underwent operation for a vascular malformation of the lower extremity. In seven patients we removed varicose veins or resected hemangioma of the lower extremity. Although none was cured, all five who underwent resection of varicose veins and one of the two patients who underwent resection of a hemangioma improved. Two additional patients, however, who underwent resection of varicose veins in another institution had worsening of the symptoms. In one patient we performed deep venous reconstruction for atresia of the superficial femoral vein, using the contralateral saphenous vein. Such operation in KTS has not been reported previously. The patient has a patent graft with a competent valve and clinical improvement 6 months after the operation. Although patients with severe chronic venous insufficiency, disturbing cosmetic appearance, or complications of hemangioma may benefit from surgical treatment, detailed preoperative imaging of the extremity and pelvis with magnetic resonance imaging and contrast venography is needed to decrease complications. Rarely, reconstruction for atresia or hypoplasia of the deep veins may be needed.

Adolescent↗
PubMed1991

Inducible release of an endothelial cell-specific protein.

The authors investigated the release of an endothelial cell-specific protein (E92) by cultured porcine aortic endothelial cell cultures. Under normal culture conditions, endothelial cells released little or no E92 into the culture supernatant. Treatment with thrombin (0.01 to 10 units/ml), endotoxin (0.01 to 10 micrograms/ml), or interleukin-1 (0.01 to 3.0 units/ml), however, caused significant, dose-dependent increases in E92 detectable in the culture supernatants. Time-course experiments showed that maximum release of E92 into cellular supernatants occurred 24 hours after stimulation with all mediators. Parallel experiments used 51Cr-loaded endothelial cells as a measure of lethal cellular injury. None of the mediators caused significant injury at the doses observed to induce release of E92. These results suggest that the release of E92 into the supernatants of cultured endothelial cells is an inducible event. The data also support the hypothesis that detection of E92 antigen in sera from patients with rheumatic disease represents a marker of in vivo vascular endothelial cell activity.

Animals↗
PubMed1991

Detection of circulating endothelial antigen.

In order to determine whether endothelial cell antigens are detectable in serum from patients with rheumatic disease characterized by vascular involvement, we developed an ELISA using a monoclonal antibody directed against a 92,000 molecular weight endothelial cell specific antigen designated E92. Sera were assayed from 191 patients and 34 healthy controls. E92 was undetectable or present in very low concentrations in healthy controls and was elevated in most patients with an active rheumatic disease. Our results indicate that circulating endothelial antigens are present in rheumatic vascular syndromes and may provide a measure of endothelial cell function.

Adolescent↗
PubMed1991

Infant and toddler sleep: a telephone survey of parents in one community.

A telephone survey was carried out to determine the prevalence of infant and toddler sleep disturbances. Parents of all 12- to 35-month-old children listed in one community were contacted, and 81% participated. Many children resisted going to bed (42%) or woke and cried during the night (35%). Approximately half the parents had changed their child's diet, naptime, or bedtime and about half these parents found changing routines helpful. Parents frequently reported that pacifiers or bottles in the crib quieted their children. Crying it out, scheduled awakenings, and progressive delay responding were all effective (70% or better) for parents who were aware of these procedures. Satisfaction did not necessarily correspond with effectiveness. Finally, parents were more likely to seek information about sleep from relatives, friends, or books and magazines than from their physician or from a psychologist.

Child, Preschool↗