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T M Johnson

Publications and source records attributed to T M Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1996

Superoxide-mediated actin response in post-hypoxic endothelial cells.

The mechanism leading to changes in the superstructure of endothelial cells exposed to ischemia and reperfusion remains uncharacterized. We show that in post-hypoxic endothelial cells, the simple re-addition of oxygen induces a profound reorganization of the actin cytoskeleton. The total filamentous actin pool increases by 41% and translocation of actin filaments to the submembranous network is observed. Concurrent with the actin polymerization, increased tyrosine phosphorylation of endothelial cell substrates is detected on Western blots. Overexpression of superoxide dismutase using replication incompetent adenovirus inhibits the actin and tyrosine phosphorylation responses to reoxygenation. Inhibition of tyrosine kinases with the isoflavone genistein also suppressed the actin polymerization response to reoxygenation, but unlike superoxide dismutase, genistein also induced the collapse of the superstructure of endothelial cells upon reoxygenation. These experiments support the concept that reoxygenation following a period of hypoxia can induce the remodeling of the actin cytoskeleton in endothelial cells. Such a response requires the intact coupling of superoxide producing pathway(s) with tyrosine kinase pathway(s).

Actins↗
PubMed1996

Reactive oxygen species are downstream mediators of p53-dependent apoptosis.

Reactive oxygen species (ROS) have been implicated as potential modulators of apoptosis. Conversely, experiments under hypoxic conditions have suggested that apoptosis could occur in the absence of ROS. We sought to determine whether a central modulator of apoptosis, p53, regulates the levels of intracellular ROS and whether a rise in ROS levels is required for the induction of p53-dependent apoptosis. We transiently overexpressed wild-type p53, using adenoviral gene transfer, and identified cell types that were sensitive or resistant to p53-mediated apoptosis. Cells sensitive to p53-mediated apoptosis produced ROS concomitantly with p53 overexpression, whereas cells resistant to p53 failed to produce ROS. In sensitive cells, both ROS production and apoptosis were inhibited by antioxidant treatment. These results suggest that p53 acts to regulate the intracellular redox state and induces apoptosis by a pathway that is dependent on ROS production.

Adenoviruses, Human↗
PubMed1996

Detection of hyperdiploid malignant cells in pleural effusions with chromosome-specific probes and fluorescence in situ hybridization.

OBJECTIVE: To compare the efficacy of fluorescence in situ hybridization (FISH) by using chromosome-specific probes with standard cytology and cytogenetics for detection of hyperdiploid malignant cells in pleural effusions. MATERIAL AND METHODS: A blind study was done on 26 pleural effusions from 25 patients who had undergone thoracentesis (14 with and 11 without a malignant condition). Cytology, cytogenetics, and FISH with probes specific for chromosomes 7, 8, 12, 18, X, and Y were done on each pleural effusion. For FISH studies, malignant specimens were defined as having 8% or more of cells with hyperdiploidy. RESULTS: Results of cytology and FISH were both normal in each of the 11 patients with benign pleural effusions. Cytogenetic studies were successful in six of these patients: five were chromosomally normal, but one male patient had an abnormal clone that lacked a Y chromosome. Among the 14 patients with malignant pleural effusions, cytology and FISH were abnormal in 8 and 6, respectively. Cytogenetic studies were successful in 11 of these patients, and an abnormal clone was found in 5. CONCLUSION: FISH can detect hyperdiploid malignant cells in pleural effusions and can be useful in the work-up of patients suspected of having malignant pleural effusions.

Adult↗
PubMed1996

A comparison of wire brush and diamond fraise superficial dermabrasion for photoaged skin. A clinical, immunohistologic, and biochemical study.

BACKGROUND: Superficial dermabrasion has a proven beneficial effect on photoaged skin, but little is known about the differences between the two major modalities used in dermabrasion, the diamond fraise (DF) and the wire brush (WB). OBJECTIVE: We compared the clinical, immunohistologic, and biochemical changes after superficial dermabrasion with DF and WB. METHODS: Eight photoaged patients (mean age, 68 years; range, 49 to 80 years) underwent facial dermabrasion to the level of the papillary dermis. Clinical assessments were performed at baseline and at 3 and 12 weeks after dermabrasion. Biopsy specimens were taken from both dermabraded halves at the same time points and assessed by routine histologic and immunohistologic examinations, western blot analysis, and radioimmunoassay. Scoring of intracellular and extracellular transforming growth factor-beta 1 was based on a semiquantitative ordinal scale (0 = no staining to 4 = maximum staining) in half-unit increments. The score for each specimen represents the average of values obtained from four high-power fields. RESULTS: Both methods of dermabrasion resulted in significant resolution of actinic keratoses, lentigines, and wrinkling. No statistical significance was noted between the two methods in regard to clinical efficacy. Significantly fewer milia occurred after DF than after WB. Solar elastosis decreased with both the WB and DF. Immunohistologic examination demonstrated a highly significant increase in papillary dermal fibroblast staining for amino terminal procollagen I (type I pN-collagen) at 3 weeks for both DF and WB compared to baseline. Staining at 12 weeks had decreased from the peak noted at week 3, but was still significantly increased from baseline. Western blotting of type I pN-collagen demonstrated a 5.4-fold (p = 0.01) increase from baseline at 3 weeks and a 4.9-fold (p = 0.002) increase at 12 weeks after dermabrasion with the WB. Similarly, the DF produced a 4.9-fold (p = 0.006) increase at 3 weeks and a 5.1-fold (p = 0.008) increase at 12 weeks after dermabrasion. Western blotting of amino terminal procollagen III (type III pN-collagen) showed a 6.1-fold (p = 0.07) increase from baseline at 3 weeks and a 3.9-fold (p = 0.04) increase at 12 weeks after dermabrasion with the DF. The WB showed a 3.8-fold (p = 0.07) increase from baseline at 3 weeks and a 5.1-fold (p = 0.05) increase at 12 weeks. Transforming growth factor-beta 1 demonstrated a significant increase in extracellular staining with DF (3.3 +/- 0.2) and WB (3.7 +/- 0.2) from baseline (1.2 +/- 0.2, p < 0.001) at 3 weeks. CONCLUSION: Superficial dermabrasion with DF and WP appears to be similarly efficacious in the treatment of photoaged skin. Significant increases in type I pN-collagen, type III pN-collagen, and TGF-beta 1 occurred in the papillary dermis after both types of dermabrasion. These results suggest that increased fibroblast activity and consequent collagen I and III synthesis underlie the clinical improvement.

Aged↗
PubMed1996

Apoptosis in vascular disease: opportunities for genetic therapeutic intervention.

Apoptosis functions to efficiently eliminate normal cells no longer required in remodelling tissues, and abnormal cells exhibiting neoplastic phenotypes. Since injury is an important trigger to the development of vascular lesions, the balance of proliferation and apoptosis during the healing response, and aberrations of this process, may be important factors in lesion progression. The expression of genes that regulate this process, including c-myc and members of the bcl-2 and lce gene families, has been detected in the normal vasculature, and in atheromatous tissues. These observations suggest that the transfer of apoptosis-inducing genes into vascular lesions may be a feasible, non-inflammatory strategy to eliminate the cellular components of restenotic and atherosclerotic plaques.

Animals↗
PubMed1995

Autophosphorylation induces autoactivation and a decrease in the Src homology 2 domain accessibility of the Lyn protein kinase.

Lyn is a member of the Src family of protein-tyrosine kinases that can readily undergo autophosphorylation in vitro. The site of autophosphorylation is Tyr397 which corresponds to the consensus autophosphorylation site of other Src family tyrosine kinases. The rate of autophosphorylation is concentration-dependent, indicating that the reaction follows an intermolecular mechanism. Autophosphorylation results in a 17-fold increase in protein-tyrosine kinase activity. Kinetic analysis demonstrates that phosphorylation of a substrate peptide by Lyn following autophosphorylation occurs with a 63-fold decrease in Km but no significant change in Vmax, suggesting that autophosphorylation relieves the conformational constraint that prevents binding of the substrate peptide to the active site of the kinase. Using a phosphotyrosine-containing peptide (pYEEI) that has previously been shown to bind to the Src homology 2 (SH2) domain of Src family tyrosine kinases with high affinity, we found that autophosphorylation results in a significant decrease in accessibility of the Lyn SH2 domain, indicating that conformational changes in the protein kinase domain induced by autophosphorylation can be propagated to the SH2 domain. Our study suggests that autophosphorylation plays an important role in regulating Lyn by modulating both its kinase activity and its interaction with other phosphotyrosine-containing molecules.

Amino Acid Sequence↗
PubMed1995

Over-expression and characterization of active recombinant rat liver carnitine palmitoyltransferase II using baculovirus.

The cDNA encoding rat liver carnitine palmitoyltransferase II (CPT-II) was heterologously expressed using a recombinant baculovirus/insect cell system. Unlike Escherichia coli, the baculovirus-infected insect cells expressed mostly soluble active recombinant CPT-II (rCPT-II). CPT activity from crude lysates of recombinant baculovirus-infected insect cells was maximal between 50 and 72 h post-infection, with a peak specific activity of 100-200 times that found in the mock- or wild-type-infected control lysates. Milligram quantities (up to 1.8 mg/l of culture) of active rCPT-II were chromatographically purified from large-scale cultures of insect cells infected with the recombinant baculovirus. The rCPT-II was found to be: (1) similar in size to the native rat liver enzyme (approximately 70 kDa) as judged by SDS/PAGE; (2) immunoreactive with a polyclonal serum raised against rat liver CPT-II; and (3) not glycosylated. Kinetic analysis of soluble rCPT-II revealed Km values for carnitine and palmitoyl-CoA of 950 +/- 27 microM and 34 +/- 5.6 microM respectively.

Animals↗
PubMed1995

Cloning, sequencing and heterologous expression of a cDNA encoding pigeon liver carnitine acetyltransferase.

Two overlapping cDNA clones encoding pigeon liver carnitine acetyltransferase (EC 2.3.1.7) (CAT) were isolated from a pigeon liver lambda gt11 cDNA library by gene amplification using oligonucleotide primers based on the N-terminal amino acid sequence of the enzyme. The two clones, which represent the 5' and 3' ends of the gene, were spliced together to form a single cDNA construct containing the entire coding sequence for CAT, with an in-frame TGA stop codon 42 bases before the first ATG start site and a 3'-untranslated segment of 1057 bases. The largest open reading frame of 1942 nucleotides predicted a polypeptide of 627 amino acids and a molecular mass of 71.1 kDa. The N-terminus and four internal peptides from the amino acid sequence of pigeon breast muscle CAT were identified in the predicted sequence of the liver cDNA clone. The identity of the CAT cDNA was confirmed by heterologous expression of active recombinant CAT (rCAT) in insect cells using the baculovirus expression system. Western blots of rCAT from infected insect cell lysates and immunodetection with a rabbit anti-CAT polyclonal serum showed an immunoreactive protein band similar in size to native CAT from pigeon breast muscle. Like the native enzyme, rCAT was capable of acylating carnitine with a preference for small-chain acyl-CoAs of carbon chain lengths C2-C4.

Amino Acid Sequence↗
PubMed1995

Trichoblastic fibroma. A series of 10 cases with report of a new plaque variant.

BACKGROUND: Trichoblastic fibroma is a benign trichogenic tumor that has both epithelial and mesenchymal components and exhibits partial to complete follicular induction. We studied 10 cases of trichoblastic fibroma and reviewed their clinical and histologic features. OBSERVATIONS: All 10 tumors were located on the face. Nine of 10 patients were women. The mean age at presentation was 63.8 years (range, 35 to 81 years). Two distinct subsets of trichoblastic fibroma were identified: the nodular variant and the plaque variant. The nodular variant is well circumscribed, while the plaque variant is poorly circumscribed, has significant subclinical extension, and may represent the low-grade malignant counterpart of the classic nodular trichoblastic fibroma. Histologically, both variants demonstrate mesenchymal induction with keratin cysts, papillary mesenchymal bodies, and an inductive fibroblastic stroma. CONCLUSIONS: Trichoblastic fibroma may be confused clinically and/or histologically with basal cell carcinoma. Identification of the mixed epithelial-mesenchymal components is helpful in tumor recognition. The plaque variant trichoblastic fibroma has not been previously reported. Familiarity with this variant is important because of the potential for infiltrative growth.

Adult↗
PubMed1995

The importance of maintaining the alar-facial sulcus in nasal reconstruction.

The alar-facial sulcus is an important topographical region because it represents a junctional zone of three cosmetic units: the nasal base, the medial aspect of the cheek, and the upper lip. Too often, the sulcus is violated by transposition flaps that have been harvested from the cheek to reconstruct defects of the nasal-alar lobule. When the sulcus is violated by surgery, it is difficult to restore a completely natural appearance. For this reason, we suggest an alternative method of reconstructing the alar lobule through the use of an interpolated flap. When defects extend into the alar-facial sulcus, reconstruction of the sulcus is necessary and should be accomplished with a separate skin flap from that used to repair the nasal component of the defect. When a single flap is used to reconstruct both lobule and sulcus, restoration of a completely natural-appearing sulcus is rarely achieved and usually involves multiple surgical procedures often facilitated by aggressive flap contouring, secondary intention healing, and Z-plasty. We describe our methodology in restoring the alar-facial sulcus after nasal reconstruction.

Female↗
PubMed1995

The Rieger flap for nasal reconstruction.

OBJECTIVE: To repair surgical defects of the middle and distal third of the nose. DESIGN: The anatomic and technical design of the Rieger (dorsonasal) flap is described. CONCLUSION: When performed on properly selected patients, the Rieger flap is an aesthetically predictable, one-stage procedure.

Humans↗
PubMed1995

Sebaceous carcinoma.

Sebaceous carcinoma is a rare, aggressive, malignant tumor derived from the adnexal epithelium of sebaceous glands. It may arise in ocular or extraocular sites and exhibits such a variety of histologic growth patterns and diverse clinical presentations that the diagnosis is often delayed for months to years. We discuss incidence as well as clinical, histologic, diagnostic, prognostic, and management issues of this aggressive neoplasm.

Adenocarcinoma, Sebaceous↗
PubMed1995

Pilot histologic and ultrastructural study of the effects of medium-depth chemical facial peels on dermal collagen in patients with actinically damaged skin.

BACKGROUND: Chemical peels are employed for a variety of benign and premalignant skin disorders. OBJECTIVE: We compared clinical and histologic features with ultrastructural changes that occur after medium-depth chemical facial peel. METHODS: Three men with actinically damaged facial skin underwent a single 35% trichloroacetic acid peel. Biopsy specimens were taken before the peel, and 2 weeks and 3 months after the peel, for histologic examination, electron microscopy, and gel electrophoresis to assess total collagen type I content. RESULTS: Clinical resolution of actinic damage corresponded with restoration of epidermal polarity. Collagen type I was markedly increased after the peel. Characteristic ultrastructural features of skin after peeling include markedly decreased epidermal intracytoplasmic vacuoles, decreased elastic fibers, and increased activated fibroblasts. CONCLUSION: Electron microscopic studies after a medium-depth chemical peel of photodamaged skin reveal more profound changes than those seen histologically.

Aged↗
PubMed1995

The role of dermabrasion and chemical peels in the treatment of patients with xeroderma pigmentosum.

We describe our experience with two patients with xeroderma pigmentosum who underwent periodic trichloroacetic acid chemical peels. One also received a full-face dermabrasion. The effect of chemical peeling was more transient than dermabrasion but was associated with less morbidity. Both chemical peeling and dermabrasion provided a prophylactic effect against the development of skin malignancies; the latter had a more pronounced effect.

Adolescent↗