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Biomedical subjects

T M Johnson

Publications and source records attributed to T M Johnson.

At least 19 recordsLinked to original sources
PubMed1992

Production and characterization of recombinant lignin peroxidase isozyme H2 from Phanerochaete chrysosporium using recombinant baculovirus.

Recombinant Phanerochaete chrysosporium lignin peroxidase isozyme H2 (pI 4.4) was produced in insect cells infected with a genetically engineered baculovirus containing a copy of the cDNA clone lambda ML-6. The recombinant enzyme was purified to near homogeneity and is capable of oxidizing veratryl alcohol, iodide, and, to a lesser extent, guaiacol. The Km of the recombinant enzyme for veratryl alcohol and H2O2 is similar to that of the fungal enzyme. The guaiacol oxidation activity or any other activity is not dependent upon Mn2+. The purified recombinant peroxidase is glycosylated with N-linked carbohydrate(s). The recombinant lignin peroxidase eluted from an anion exchange resin similar to that of native isozyme H1 rather than H2. However, the pI of the recombinant enzymes is different from both H1 and H2 isozymes. Further characterization of native isozymes H1 and H2 from the fungal cultures revealed identical N-terminus residues. This indicates that isozymes H1 and H2 differ in post-translational modification.

Amino Acid Sequence↗
PubMed1992

Epitopic mapping of linear and conformation-dependent antigenic determinants on GP5 of five U.S. bluetongue viruses.

Two distinct antigenic determinants of the major outer capsid protein, GP5, of five U.S. bluetongue viruses have been identified and mapped using monoclonal and oligoclonal antibodies. One antigenic site, identified by oligoclonal antibody AK-15, was found to be common and conserved in all five U.S. BTV serotypes. This linear epitope was located between amino acid residues 175 and 189 (ALQREAAERSEDEIK). The second determinant identified by monoclonal antibody 34.7 was present in BTV-2, -10, -11, and -17 but absent in BTV-13. The binding of this monoclonal antibody to GP5 could be blocked specifically by one of three short synthetic peptides located among amino acid residues 33-42 (KAAERFAESE), 159-168 (EKILKEEDSK), and 206-215 (EIERDGMQEE), indicating that this antigenic determinant is conformation-dependent. Oligoclonal antibody (AK-15) reacted with denatured GP5 immobilized on nitrocellulose membrane after Western transfer as well as with native GP5 present on the surface of purified BTV virions. Monoclonal antibody (34.7) reacted only with denatured GP5 but not native GP5 using an ELISA assay. However, these two antigenic epitopes alone did not elicit detectable neutralizing antibodies as determined by plaque reduction assay.

Amino Acid Sequence↗
PubMed1992

Squamous cell carcinoma of the skin (excluding lip and oral mucosa).

The striking impression obtained from reviewing the cancer literature is how difficult it is to analyze the data for answers to many important biologic, behavioral, prognostic, and therapeutic questions about squamous cell carcinoma of the skin. This article addresses current concepts, controversies, and management of cutaneous squamous cell carcinoma (excluding the lip and oral mucosa).

Carcinoma, Squamous Cell↗
PubMed1992

Soft tissue reconstruction with skin grafting.

Free skin grafts for soft tissue reconstruction can be classified into three types: full-thickness skin grafts, split-thickness skin grafts, and composite grafts. The indications, techniques, donor site considerations, and postoperative complications of each type of skin graft are reviewed.

Dermatologic Surgical Procedures↗
PubMed1992

Papulonodular dermal mucinosis in lupus erythematosus.

We report two cases of lupus erythematosus (LE) in which a truncal papulonodular eruption predominated. Histologically the lesions were characterized by diffuse dermal mucin without the usual inflammatory or epidermal changes of LE. It is uncommon in LE for dermal mucin to be present in a sufficient quantity to produce a papulonodular eruption in the absence of typical epidermal changes.

Adult↗
PubMed1992

Carbon dioxide laser treatment of actinic cheilitis. Clinicohistopathologic correlation to determine the optimal depth of destruction.

BACKGROUND: The carbon dioxide laser is an effective modality for the treatment of actinic cheilitis, but the number of passes required is unknown. After each pass different visual tissue qualities are observed. OBJECTIVE: Our purpose was to identify and characterize histologically the tissue zones seen after laser impact and thereby to determine the optimal depth of destruction of diseased tissue. METHODS: Twenty-three biopsy specimens from 14 patients were obtained from zones of different tissue qualities after one and three passes with the laser. Specimens were histologically examined for the presence or absence of diseased epithelium and degree of thermal necrosis. RESULTS: Complete destruction of the epithelial layer was observed in all specimens irrespective of the number of laser passes. The amount of dermal homogenization increased with multiple passes. CONCLUSION: Treatment to the first or second surgical zone is effective for actinic cheilitis.

Adult↗
PubMed1992

The paramedian scalp reduction with posterior Z-plasty. A technique to minimize the "slot" defect.

BACKGROUND: One consistent and undesired sequela resulting from scalp reductions has been the "slot" or "trough" defect, referring to the scar following the final reduction. Attempts to correct this have not been entirely satisfactory. OBJECTIVE: To present an approach to minimize the "slot" defect that consists of staged modified paramedian scalp reductions combined with a large posterior Z-plasty during the final reduction. METHODS: A paramedian crescent-shaped ellipse was marked onto the patient's scalp parallel and adjacent to the existing fringe hair. Subsequent reductions were performed in a similar manner approximately 2 months apart. The final reduction consisted of mobilization and transposition of the large flaps used in the posterior Z-plasty. RESULTS: Patients who underwent the staged modified paramedian reductions combined with a posterior Z-plasty had significant minimization and adequate camouflage of the undesirable "slot." CONCLUSION: Combining a large posterior Z-plasty with a paramedian reduction minimizes the slot defect.

Alopecia↗
PubMed1991

Heterologous expression and characterization of an active lignin peroxidase from Phanerochaete chrysosporium using recombinant baculovirus.

The cDNA clone lambda ML-1 encoding one of the extracellular lignin peroxidases from the white rot fungus, Phanerochaete chrysosporium, was heterologously expressed in an active form using a recombinant baculovirus system. The glycosylated extracellular form of the recombinant protein contained the ferriprotoporphyrin IX moiety and was capable of oxidizing both iodide and the model lignin compound, veratryl alcohol. In comparative peroxidase assays using guaiacol and Mn(II), the recombinant lignin peroxidase did not appear to be Mn(II) dependent. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that the heterologously expressed peroxidase had an apparent molecular weight similar to that of the native fungal isozyme H8. The elution profile of the active recombinant enzyme derived by ion-exchange chromatography and immunoblot analysis using an anti-H8 monoclonal antibody provided further evidence that the lambda ML-1 DNA encodes the lignin peroxidase H8.

Baculoviridae↗
PubMed1991

Combined curettage and excision: a treatment method for primary basal cell carcinoma.

A retrospective study of 403 primary basal cell carcinomas treated with aggressive curettage followed immediately by excision revealed microscopic tumor present in the curettage margin in 64 (15.9%) of the patients and in the excisional margin in 12 (2.5%) after curettage and excision. In 92% (11 of 12) of patients with persistent tumor after the combined curettage and excision technique the tumors were of the aggressive growth (fibrosing, sclerosing, scirrhous, and morpheaform) variety of basal cell carcinoma. Both lateral and deep margins were involved with tumor. The short-term cure rate was 97.6% for the combined technique. Excluding aggressive growth BCCs, the use of curettage allows the surgeon to define tumor borders better before excision. This proves especially beneficial in tumors with clinically indistinct borders.

Basal Cell Carcinoma↗
PubMed1991

Treatment of keratoacanthomas with intralesional methotrexate.

Multiple modalities exist for the treatment of keratoacanthoma. Excisional surgery is currently the treatment of choice for the majority of keratoacanthomas. This can result in functional and cosmetic defects when large or strategically located lesions are treated. An effective nonsurgical treatment would be desirable in such cases. Intralesional therapy, particularly with 5-fluorouracil, has been shown to be effective in the treatment of keratoacanthomas. Systemic methotrexate has been tried, with variable success. We report an open, noncontrolled study of nine consecutive patients with unusually large or strategically located solitary keratoacanthomas treated successfully with intralesional methotrexate. All lesions responded promptly, with complete resolution after a mean of 3.0 weeks and a mean of 1.7 injections. No side effects occurred, and scarring was minimal. We concluded that intralesional methotrexate is a simple and effective modality for the treatment of select keratoacanthomas and may offer greater efficacy, a more rapid response, decreased pain, and lower cost compared with intralesional 5-fluorouracil.

Adult↗
PubMed1991

The art and science of mechanical ventilator adjustments.

This article describes how information from mechanical ventilator settings, ABG, pulse oximetry, and capnography are useful in making therapeutic changes in mechanical ventilator settings. The nurse can use trial and error or apply scientific principles to adjust mechanical ventilator settings efficiently to correct abnormalities in ventilation or oxygenation. Consistent application of these principles improves nursing assessment and interventions as well as prevents undue pain and expense on the patient's behalf.

Blood Gas Analysis↗
PubMed1991

Carbonic anhydrase II deficiency syndrome in a Belgian family is caused by a point mutation at an invariant histidine residue (107 His----Tyr): complete structure of the normal human CA II gene.

Carbonic anhydrase II (CA II), which has the highest turnover number and widest tissue distribution of any of the seven CA isozymes known in humans, is absent from the red blood cells and probably from other tissues of patients with CA II deficiency syndrome. We have sequenced the CA II gene in a patient from a consanguinous marriage in a Belgian family and identified the mutation that is probably the cause of the CA II deficiency in that family. The change is a C-to-T transition which results in the substitution of Tyr (TAT) for His (CAT) at position 107. This histidine is invariant in all amniotic CA isozymes sequenced to date, as well as the CAs from elasmobranch and algal sources and in a viral CA-related protein. His-107 appears to have a stabilizing function in the structure of all CA molecules, and its substitution by Tyr apparently disrupts the critical hydrogen bonding of His-107 to two other similarly invariant residues, Glu-117 and Tyr-194, resulting in an unstable CA II molecule. We have also completed the intron-exon structure of the normal human CA II gene, which has allowed us to prepare PCR primers for all exons. These primers will facilitate the determination of the mutations in other inherited CA II deficiencies.

Base Sequence↗
PubMed1991

Changing trends in melanoma treatment and the expanding role of the dermatologist.

As the incidence of melanoma continues to increase, so does the role of the dermatologist as both medical and surgical oncologist for these patients, especially those with stage I disease. The dermatologist holds a key role in all phases of care, including prevention, diagnosis, treatment, and follow-up. The dermatologist is best trained to complete a full and thorough skin examination and is best able to recognize a melanoma at its earliest stages of radial growth. In large part because of advances in dermatology, the dysplastic nevus syndrome has been identified as an important marker and precursor lesion for melanoma; the dermatologist has the best knowledge base for the recognition and management of both sporadic and familial dysplastic nevi. Dermatologists also have the unique opportunity (by virtue of their patient population concerned with skin problems) to prevent melanoma through patient education concerning sun protection, self-examinations, and the ABCDs of melanoma recognition. The dermatologist is well trained to obtain an appropriate, full-thickness skin biopsy specimen and is also knowledgeable to interpret the pathologist's report, understanding the significance of the various histologic prognostic indices. Because of the changing trends in excisional margin size and fewer recommendations for ELND, the dermatologist is becoming more active in the surgical management of melanoma patients. In the MDMC, the dermatologist was clearly recognized as a capable surgeon to perform the wide local excisions for stage I patients. Almost one half of the patients seen (49%) were surgically treated in the department of dermatology. Of group I patients, 78% were treated by dermatologists. The dermatologist as surgeon should be capable of performing a wide local excision to the level of deep subcutaneous tissue or muscle fascia with an appropriate primary layered closure, local flap, or graft. Our experience confirms that the majority of patients present with local disease and a thin Breslow depth and thus can be skillfully treated in an outpatient setting under local anesthesia by a dermatologic surgeon. In follow-up, the dermatologist should provide continuity of care and should be knowledgeable in appropriate interval examinations and tests. The dermatologist is thoroughly skilled at the cutaneous examination and has the knowledge base to perform a careful and competent lymph node examination. As primary medical oncologist to these patients, the dermatologist needs to recognize stage II and stage III disease and be able to comprehensively discuss with the patient the options for treatment and how they affect their prognosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Combined Modality Therapy↗
PubMed1990

Immediate intraoperative tissue expansion.

We report a modification of the controlled tissue expansion technique, that is, immediate intraoperative tissue expansion. The procedure is performed by placing tissue expanders at the time of surgery. After placement, three to four cycles of inflation/deflation of the expander for 3 to 5 minutes are performed. In a one-stage procedure the stretched skin is then immediately used to close the surgical defect. Three case reports demonstrating the immediate intraoperative tissue expansion technique, in which the Foley catheter balloon was used as the tissue expander, are presented. These cases illustrate that this technique may allow the surgeon to cover defects more easily with less tension and with a better cosmetic result than with other closure techniques.

Adult↗