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P Johnson

Publications and source records attributed to P Johnson.

At least 235 records · Page 13Linked to original sources
PubMed1995

Point mutation in the second phosphatase domain of CD45 abrogates tyrosine phosphatase activity.

CD45 is a transmembrane protein tyrosine phosphatase that possesses two phosphatase domains in its cytoplasmic region. Whether both domains function independently as phosphatase enzymes or whether both domains interact to form an active enzyme is unclear. A point mutation of a critical cysteine residue in domain I is known to abolish CD45 activity, implying that the catalytic activity resides in domain I. In this report, mutational analysis of purified, recombinant CD45 cytoplasmic domain protein was performed. It was found that a single amino acid change in domain II (glutamine 1180 to a glycine) resulted in an inactive phosphatase enzyme, whereas two other point mutations in the membrane proximal region of the molecule had no effect on activity. Deletion of the region linking the two phosphatase domains also abolished enzymatic activity. Amino acids crucial for phosphatase activity thus reside in both phosphatase domains of CD45, illustrating that the phosphatase domains of CD45 do not act independently, but are both required for the phosphatase activity of CD45.

Amino Acid Sequence↗
PubMed1995

When patients and pediatricians say good-bye in a pediatric resident continuity clinic.

Pediatric residency programs require a 3-year continuity clinic experience for residents. To our knowledge, no authors have examined the impact of termination at the end of the residency among the child, parent, and pediatrician. This article discusses an exploration that evolved in response to the questions that third-year pediatric residents asked concerning how to say good-bye to their primary care patients in the context of their continuity clinic. The first panel addressed parental and patient issues, and the second addressed the impact on the pediatrician. The parents on the panel stated that it was important that they be notified in advance of their pediatrician's departure, that they believed they had played an important role in the resident's education, and that they wanted a voice in the selection of their child's future pediatrician. The pediatricians on the panel all felt sadness, relief, and guilt as a result of the termination, but guilt that the family would feel abandoned was the strongest emotion. Few pediatricians on the panel acknowledged the impact of the relationship on themselves and the importance of including the parents in the decision to choose the child's future pediatrician. The issue of termination needs more deliberate attention in pediatric training programs. A structured system for teaching residents to manage the termination process is proposed.

Academic Medical Centers↗
PubMed1995

Detection of restricted isoform expression and tyrosine phosphatase activity of CD45 in murine dendritic cells.

CD45 is a cell surface transmembrane tyrosine phosphatase. It is expressed as distinct protein isoforms via alternative splicing of exons 4, 5 and 6. In T and B lymphocytes, CD45 is thought to play a critical role in antigen-dependent signaling through their respective antigen receptor complexes. However, the isoform expression and enzymatic activity of CD45 in other leukocytes remains largely unknown. Here, we examine the isoform expression and phosphatase activity of CD45 in murine dendritic cells (DC). Flow cytometric double-labeling analysis and biochemical analysis of purified splenic DC CD45 demonstrate that DC express both the CD45RB and CD45R0 isoforms. Flow cytometric analyses of freshly isolated splenic DC and thymic DC also indicate the expression of CD45RB and CD45R0 on these DC populations. In addition, we find that purified splenic DC CD45 possesses a high level of intrinsic tyrosine phosphatase activity. These data therefore establish the restricted isoform expression pattern of CD45 in murine DC and demonstrate that cells lacking specific antigen receptor complexes have active tyrosine phosphatase activity associated with CD45.

Animals↗
PubMed1995

Lactose fed-batch overexpression of recombinant metalloproteins in Escherichia coli BL21 (DE3): process control yielding high levels of metal-incorporated, soluble protein.

A method for producing recombinant proteins in pilot scale fermentation equipment using a glucose fed-batch initial growth, followed by a midlog phase feeding of a glucose and lactose mixture is described. Using the host strain Escherichia coli BL21(DE3), the diiron protein stearoyl-acyl carrier protein delta 9 desaturase has been overexpressed at a biomass level of up to 12 g x liter-1 dry cell weight, representing a 12-fold increase in volumetric productivity relative to that obtained from batch fermentations. Under these conditions, a maximum of 36% of the total cellular protein accumulates as the desaturase polypeptide. A correlation between the slowed growth rate of the fed-batch culture, a continued, albeit slower, exponential growth under inducing conditions, and a favorable partitioning between formation of the soluble holoprotein and inclusion bodies is reported. This correlation suggests that fed-batch techniques can be used to beneficially influence rate-limiting processes in the maturation of overexpressed proteins, such as metal uptake and incorporation proposed here. By using cells produced from the fed-batch method, the iron-containing, soluble desaturase can be purified in a yield of up to 66 mg x g-1 dry cell weight (approximately 500 mg x liter-1 culture), representing a three to fivefold increase in the yield relative to that obtained from batch fermentations. In addition, these methods are suitable for the production of the Anabena 7120 vegetative [2Fe 2S] ferredoxin in E. coli BL21(DE3) pLysS, a host strain used for the overexpression of toxic proteins.

Cell Division↗
PubMed1995

A retrospective study of the use of cisplatinum-5-fluorouracil neoadjuvant chemotherapy in cervical-node-positive nasopharyngeal carcinoma (NPC).

A retrospective study on 422 nasopharyngeal carcinoma (NPC) patients with cervical nodal metastases treated between 1984 and 1987 was performed. 169 received neoadjuvant chemotherapy (CHEMO) with cisplatinum and 5-fluorouracil for two or three courses prior to definitive radiotherapy and 253 were treated by radical radiotherapy alone (NCHEMO). While the primary tumour (T-stage) prognosticators had been comparable between the two groups, CHEMO had significantly more advanced cervical nodal metastases with bulkier nodes and more low-cervical and supraclavicular nodes (P < 0.05) which could account for its overall worse survival, poorer regional tumour control and a trend towards worse systemic tumour control. The worse regional control in CHEMO for Ho's N1 could be the result of more bulky nodes and more tumours infiltrating the skull base and/or causing cranial nerve(s) palsy. There was no statistical or apparent difference between CHEMO and NCHEMO for the same Ho's overall stages of NPC with comparable nodal and primary tumour characteristics for the clinical endpoints of actuarial survival rate (ASR), disease-free survival rate (DFS), free of local failure survival rate (FLF), and free from distant metastases survival rate (FDM), despite the presence of significantly more fixed nodes and bulky nodes. This suggests a possible beneficial effect of the neoadjuvant chemotherapy. However, multivariate analysis has not shown the administration of the neoadjuvant chemotherapy to be of prognostic significance. Even though the chemotherapy was well tolerated with little toxicity, we recommend against the routine use of neoadjuvant chemotherapy in cervical-node-positive NPC outside the context of a prospective randomised clinical trial.

Adolescent↗
PubMed1995

Antioxidant enzyme activities and lipid peroxidation levels in exercised and hypertensive rat tissues.

Previous studies have shown that exercise-induced changes in muscle antioxidant status occur shortly after exercise. The present studies were designed to determine if longer-term exercise-related changes in antioxidant enzyme activities in both normotensive (WKY) and hypertensive rats (SHR) occurred, and if these changes were related to the levels of lipid peroxidation. WKY and SHR rats were exercised over a 10-week period using a progressive treadmill regimen. After a 1-week detraining period, the animals were euthanized and measurements of tissue antioxidant enzyme activities and lipid peroxide levels were determined in both exercised and cage-sedentary groups. Decreases in antioxidant activities (particularly glutathione peroxidase and catalase) in liver, kidney, skeletal and cardiac were associated with exercise training in both WKy and SHR rats (e.g. left ventricular glutathione peroxidase specific activity in WKY rats was decreased from 234 +/- 25 [SD, n = 12] to 187 +/- 17 [SD, n = 11] units/mg protein). Elevations in activities of antioxidant enzymes were generally associated with hypertension in these tissues (e.g. left ventricular glutathione peroxidase specific activity in SHR rats was 275 +/- 30 [SD, n = 12] units/mg protein), but changes in activities were more variable than those seen in response to exercise. Exercise-related changes in tissue levels of thiobarbituric acid-reactive substances (an indirect measure of tissue lipid peroxide levels) generally did not correlate with exercise-related antioxidant enzyme activity changes, and hypertension had no effect on these levels except in liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Topical fibronectin ophthalmic solution in the treatment of persistent defects of the corneal epithelium. Chiron Vision Fibronectin Study Group.

PURPOSE: We sought to evaluate the efficacy of topical fibronectin ophthalmic solution, containing 3.5 mg/ml of human fibronectin, in the treatment of persistent epithelial defects of the cornea. METHODS: In a double-masked, randomized clinical trial, patients with a persistent, corneal epithelial defect of at least 14 days in duration, and at least 2 mm in width along the larger axis, were sought from the practices of 38 clinical investigators. After a 14-day washout period, 65 patients were randomly assigned to one of three treatment groups. One group (n = 20) received fibronectin drops; the second (n = 23) received drops of the vehicle from the fibronectin solution; and the third (n = 22) received a placebo. RESULTS: After 21 days of treatment, there was no difference in percentage reduction of the corneal epithelial defect size; the average percentage of reduction of defect area ranged from 46.5% to 54.3%. Fibronectin treatment showed a beneficial effect for patients with larger baseline defects (10 mm2 or greater in area); however, no such effect was observed among patients with smaller defects. Defect duration before treatment had a significant effect on outcome (P = .007); defects of longer duration were less likely to decrease in size over the course of the study. CONCLUSIONS: All three treatment groups showed similar reductions in defect size; therefore, this study provides no support for the efficacy of fibronectin treatment of persistent, corneal epithelial defects. Defect duration showed a negative association with reduction in defect size. Because strict control of topical applications during the washout and treatment periods resulted in beneficial responses, physicians should carefully consider the topical medications used by patients who have persistent, corneal epithelial defects.

Administration, Topical↗
PubMed1995

Obstructive jaundice secondary to hepatocellular carcinoma.

This prospective study aimed to identify different groups of patients with the rare pathology of biliary obstruction caused by hepatocellular carcinoma (HCC). Patients were evaluated with blood tests, chest radiography, ultrasound of the liver and endoscopic retrograde cholangiopancreatography/percutaneous transhepatic cholangiography. Patients who were potentially operable were further assessed with selective hepatic angiography and computed tomography (CT). Of the 38 patients with obstructive jaundice secondary to HCC, the levels of obstruction were extrahepatic in 19 patients and intrahepatic in 19 patients. The clinical presentations and blood biochemistry were similar in these two groups of patients. "Curative' resection was significantly more common in extrahepatic obstruction (8/19) than in intrahepatic obstruction (0/19) (chi 2 with Yates correction P = 0.001). All non-resectable tumours, except in four patients with terminally ill disease, were palliated with stents. Survival in patients who had "curative' liver resection was significantly better than in those who had no resection (median survival 25.3 vs. 2.1 months, log-rank test P = 0.004). Patients with extrahepatic biliary obstruction secondary to HCC had a better chance of being treated by liver resection, which resulted in a significantly improved survival rate compared to patients with intrahepatic obstruction.

Adult↗
PubMed1995

Transcervical electrosurgical resection of submucous leiomyomas for chronic menorrhagia.

STUDY OBJECTIVE: To evaluate the effectiveness and safety of transcervical electrosurgical resection (TSR) of submucous leiomyomas with or without concomitant transcervical endomyometrial resection (TEMR) for chronic menorrhagia. DESIGN: Prospective observational study, with 6-month follow-up of all 208 women and up to 6-year follow-up of 185 (88.9%). SETTING: Gynecology departments of teaching, community, and proprietary hospitals. PATIENTS: Two hundred eight women with submucous leiomyoma requiring surgical treatment of menorrhagia between March 1988 and March 1994. INTERVENTIONS: All 208 women (age range 32-63 yrs) underwent TSR with a continuous-flow gynecologic resectoscope. In 88 of these women who had no desire to preserve fertility, concomitant TEMR was performed. MEASUREMENTS AND MAIN RESULTS: Six months postoperatively 113 (94.2%) of the 120 women who underwent only TSR reported normal menses and 85 (96.6%) had satisfactory results; 62 (70.5%) who had both TSR and TEMR were amenorrheic. Eleven (73%) of the 15 women who had TSR and wanted to conceive subsequently became pregnant. One hundred eighty-five (88.9%) of the 208 patients have been followed for as long as 6 years. Ninety (84.1%) of the 107 women who had only the initial TSR and 69 (88.5%) of the 78 who had initial TSR and TEMR had satisfactory results. Only five women (2.7%) required major abdominal surgery. Among those undergoing TSR and TEMR, 49 (62.8%) were amenorrheic for as long as 6 years after TSR and one or two TEMRs. Eight (3.8%) of the 208 women had perioperative complications: 6 (2.9%) had fluid overload, 1 (0.5%) had dilutional hyponatremia, and 1 (0.5%) had excessive postoperative bleeding requiring tamponade. CONCLUSIONS: We believe that TSR with or without concomitant TEMR is an effective and safe treatment for women with submucous leiomyomas suffering from chronic menorrhagia.

Abdomen↗
PubMed1995

Where there is no family doctor: the development of family practice around the world.

Family physicians are generalists trained at the postgraduate level to address the majority of primary care needs of patients of all ages in communities they serve. Throughout the world there is a need for family physicians to serve as cornerstones of comprehensive health care systems that provide high-quality, cost-effective medical and public health services to the entire population. To meet this need, each country must value and adequately finance essential medical and public health services and must provide family physicians with a thorough education focused on the relevant health care problems of the population being served. The authors present an overview of the status of this training throughout the world, outline challenges to the development of such training, and suggest strategies for successful development accompanied by illustrative case studies from South Korea, Venezuela, and Pakistan.

Education, Medical↗
PubMed1995

Potential dangers of oxygen supplementation during facial surgery.

The use of local anesthesia and intravenous sedation has made same-day outpatient surgery a viable option for many aesthetic and reconstructive procedures. These procedures often include the use of supplemental oxygen. Oxygen-enriched environments increase the combustibility of most materials, and "oxygen pooling" has been suspected to play an integral role in intraoperative fires. A personal experience with an intraoperative explosion and fire during a cosmetic blepharoplasty compelled us to explore the potential danger inherent in the use of supplemental oxygen as well as potential strategies to minimize that danger. This study systematically examines the microenvironment created by the use of oxygen both in the operative field and beneath the surgical drapes under conditions simulating routine facial surgery and various recommended modifications of its delivery. With the use of oxygen supplementation, oxygen concentration beneath the drapes was found to be consistently elevated when compared with ambient air (20.9 percent) and reached levels as high as 53.5 percent. Oxygen concentration in the operative environment was mildly but not significantly elevated. Although criteria for the use of oxygen supplementation are not clear, when administration is deemed necessary, the use of a posterior pharyngeal catheter for its delivery had no advantage over nasal prongs. However, appropriate alternatives include the use of "open face" draping techniques, the use of compressed air beneath the drapes as a substitute for oxygen supplementation in unsedated patients, and cessation of oxygen supplementation for 60 seconds prior to the use of a possible ignition source with oxygen flow rates of less than 3 liters per minute.

Accidents↗
PubMed1995

Interferon-alpha and survival in renal cell cancer.

OBJECTIVE: To establish whether the use of interferon-alpha might result in improved survival, using two large series of patients with advanced renal cell cancer treated during studies of chemotherapy and biological therapy, respectively. PATIENTS AND METHODS: Patients treated either in the Eastern Cooperative Oncology Group (ECOG) chemotherapy protocols (327 patients) or in protocols employing interferon as part of a European randomized study or phase II studies at the Norwegian Radium Hospital (231 patients) were retrospectively analysed. Groups for comparison were matched by exclusion of those with an ECOG performance status > 2, no prior nephrectomy, brain metastases or prior chemotherapy. Univariate analysis of prognostic factors for survival was performed by the log rank method and multivariate analysis by Cox regression. RESULTS: Univariate analysis of the whole population showed that performance status, time from diagnosis to treatment, sites of metastases and the use of interferon carried the greatest prognostic significance. In multivariate analysis, the use of interferon remained a significant predictor of survival (P < 0.001). Subgroup analysis suggested that the impact of interferon treatment was greatest in those patients with two of the following characteristics: good performance status, an interval of > 2 years from diagnosis to treatment and no more than one site of metastasis. CONCLUSION: Although a prospective randomized trial is needed to establish definite benefit from the use of interferon in advanced renal cell cancer, this analysis supports the rationale for performing such a trial, particularly in patients with relatively good prognostic features. Patients should be entered into the Medical Research Council study comparing interferon with medroxyprogesterone acetate.

Adult↗
PubMed1995

Quality of life assessment in gynaecological cancer patients.

The feasibility of quality of life (QOL) assessment in a heterogeneous group of gynaecological cancer patients undergoing chemotherapy was determined. All new patients being prescribed cytotoxic chemotherapy were asked to complete a modified QOL assessment tool. The elected assessment tool is the Functional Assessment Cancer Therapy-General (FACT-G) tool, comprising 33 questions under 5 broad categories: physical well-being, social well-being, relationship with doctor, emotional well-being and functional well-being. Raw scores were calculated and then transformed to a 0-100 scale. Twenty eight patients received a total of 75 treatment cycles of chemotherapy. Four patients were not offered the assessment due to language difficulties. All patients offered the test satisfactorily completed the test to allow statistical analysis. The average number of chemotherapy courses received was 2.5 (range: 1-6). Of a total possible 2,475 study items (33 items x 75 cycles), 240 items were not answered (10%). Of these 240 unanswered items, 2 items (#14 and #15) comprised 38%. The mean transformed score for physical well-being was 32 (SE 2.5), for social well-being the mean transformed score was 50 (SE 1.7), relationship with doctor 86 (SE 2.4), emotional well-being 41 (SE 2) and functional well-being was 54 (SE 2.6). The assessment of QOL indices in gynaecological cancer patients undergoing chemotherapy is feasible. Further research needs to determine the optimal QOL tool for this patient population.

Adult↗