Search PubMed⌕ Search

Biomedical subjects

M D Davis

Publications and source records attributed to M D Davis.

At least 19 recordsLinked to original sources
PubMed2001

A Rep recognition sequence is necessary but not sufficient for nicking of DNA by adeno-associated virus type-2 Rep proteins.

The strand-specific, site-specific endonuclease (nicking) activity of the Rep68 and Rep78 (Rep68/78) proteins of adeno-associated virus type 2 (AAV) is involved in AAV replication, and appears to be involved in AAV site-specific integration. Rep68/78 cuts within the inverted terminal repeats (ITRs) of the AAV genome and in the AAV preferred integration locus on human chromosome 19 (AAVS1). The known endonuclease cut sites are 11-16 bases away from the primary binding sites, known as Rep recognition sequences (RRSs). A linear, double-stranded segment of DNA, containing an RRS and a cut site, has previously been shown to function as a substrate for the Rep68/78 endonuclease activity. We show here that mutation of the Rep recognition sequence, within such a DNA segment derived from the AAV ITRs, eliminates the ability of this substrate to be cleaved detectably by Rep78. Rep78 nicks the RRS-containing site from AAVS1 about half as well as the linear ITR sequence. Eighteen other RRS-containing sequences found in the human genome, but outside AAVS1, are not cleaved by Rep78. These results may help to explain the specificity of AAV integration.

Animals↗
PubMed2001

Beard dermatitis due to para-phenylenediamine use in Arabic men.

The most common active ingredient in hair coloring is para-phenylenediamine (PPDA), which can produce contact dermatitis, particularly in persons who dye their scalp hair and in hairdressers. We have identified another group of patients also at risk, namely men from Arab countries, who commonly grow beards and dye them. We searched the computerized patient database at the Mayo Clinic for patients with beard dermatitis associated with dye use. Eight Arabic men presented to the Mayo Clinic between 1994 and 1999 with beard dermatitis and a positive patch test to PPDA. The lesions were described as pruritic, erythematous, papular eruptions that developed in the jaw area after each application of beard dye. The symptoms subsided after the patients discontinued use of the PPDA-containing dye and received treatment with topical corticosteroids. Allergic contact dermatitis in the beard area due to PPDA occurs in Arabic men as a result of their propensity to dye their beards.

Arabs↗
PubMed2001

Heat transfer properties, moisture loss, product yield, and soluble proteins in chicken breast patties during air convection cooking.

Chicken breast patties were processed in an air convection oven at air temperatures of 149 to 218 C, air velocities of 7.1 to 12.7 m3/min, and air relative humidities of 40 to 95%. The air humidity was controlled via introducing steam into the oven. The patties were processed to a final center temperature of 50 to 80 C. Heat flux, heat transfer coefficient, moisture loss in the cooked chicken patties, the product yield, and the changes of soluble proteins in the product were evaluated for the cooking system. During cooking, heat flux varied with the processing time. Heat flux increased with increasing air humidity. The effective heat transfer coefficient was obtained for different cooking conditions. Air humidity in the oven affected the heat transfer coefficient. The moisture loss in the cooked products increased with increasing the final product temperature and the oven air temperature. The soluble proteins in the cooked patties decreased with increasing the final product temperature. Increasing humidity increased heat transfer coefficient and therefore reduced cooking time. Reducing oven temperature, reducing internal temperature, and increasing air humidity increased the product yield. Soluble proteins might be used as an indicator for the degree of cooking. The results from this study are important for evaluating commercial thermal processes and improving product yields.

Animals↗
PubMed2000

PD 158771, a potential antipsychotic agent with D(2)/D(3) partial agonist and 5-HT(1A) agonist actions. I. Neurochemical effects.

The neurochemical effects of a novel dopamine (DA) D(2)-like and serotonin (5-HT) 5-HT(1A) agonist, PD 158771, are described. PD 158771 exhibited affinities for human D(2L), D(3) and D(4.2) receptors expressed in Chinese hamster ovary (CHO)-K1 cells with K(i) (nM) values of 5.2, 13.7 and 34.8 respectively. PD 158771 showed high affinity for cloned human 5-HT(1A) (K(i) = 2.6 nM) and rat hippocampal 5-HT(1A) receptors (K(i) = 3.5 nM). Weaker affinities were observed at alpha 1-adrenergic (K(i) = 43 nM), histamine H(1) (IC(50) = 30 nM), 5-HT(2A) (K(i) = 24.5 nM) and sigma (sigma) -1 binding sites (K(i) = 24.5 nM). In measures of in vitro functional activity, PD 158771 stimulated [(3)H]thymidine uptake in CHO p-5 cells transfected with hD(3) receptors with a maximal effect of 23% relative to quinpirole. In hD(2)L, the corresponding value was 60% with an EC(50) of 29 nM, again indicating partial DA agonist action of PD 158771. In vivo, PD 158771 produced a dose-related decrease in DA synthesis in the striatum and mesolimbic regions of rat brain treated with gamma-butyrolactone (GBL), indicating a DA autoreceptor agonist action. In animals not treated with GBL, PD 158771 produced a dose-related decrease in DA synthesis and extracellular DA. A decrease in 5-HT synthesis in several brain areas was observed consistent with an agonist response. Further support for DA autoreceptor agonist action is that PD 158771 produced a partial inhibition of the firing of substantia nigra zona compacta DA neurons, an effect reversed by haloperidol. In conclusion, PD 158771 exhibited affinities for DA and 5-HT receptors, appears to possess DA and 5-HT agonist actions; and it could provide improved antipsychotic profile with minimal side effects.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2000

Natural history of erythromelalgia: presentation and outcome in 168 patients.

OBJECTIVE: To describe the demographics, presentation, and outcome in patients with erythromelalgia--a rare and poorly understood clinical syndrome defined by the triad of red, hot, painful extremities. DESIGN: Retrospective medical record review with follow-up by survey questionnaire. SETTING: Large tertiary care medical center. SUBJECTS: Patients with erythromelalgia examined at the Mayo Clinic, Rochester, Minn, between 1970 and 1994. INTERVENTION: The medical records of 168 patients were analyzed. Follow-up data, which consisted of answers to 2 survey questionnaires or the most recent information in the medical record from patients still alive and death certificates or reports of death for those deceased patients, were obtained for all but 13 patients. MAIN OUTCOME MEASURES: Survival, morbidity, and quality of life. RESULTS: All patients were white; 122 (72.6%) were female, and 46 (27.4%) were male. At presentation, the patients' mean age was 55.8 years (age range, 5-91 years). Symptoms had been present since childhood in 7 patients (4.2%). Six patients (3.6%) had a first-degree relative with erythromelalgia. Symptoms were intermittent in 163 patients (97.0%) and constant in 5 (3.0%). Symptoms predominantly involved feet (148 patients [88.1%]) and hands (43 patients [25.6%]). Kaplan-Meier survival curves revealed a significant decrease in survival compared with that expected in persons of similar age and of the same sex (P<.001). After a mean follow-up of 8.7 years (range, 1.3-20 years), 30 patients (31.9%) reported worsening of, 25 (26.6%) no change in, 29 (30.9%) improvement in, and 10 (10.6%) complete resolution of the symptoms. On a standard health status questionnaire, scores for all but one of the health domains were significantly diminished in comparison with those in the US general population. CONCLUSION: Erythromelalgia is a syndrome with significantly increased mortality and morbidity compared with the US general population.

Adolescent↗
PubMed2000

Swelling and loss of photoreceptors in chronic human and experimental glaucomas.

OBJECTIVE: To determine whether outer retinal changes occur in chronic, presumed primary open-angle glaucoma (POAG). METHODS: The outer retinas from 128 human eyes with a diagnosis of chronic glaucoma (presumably POAG in most cases) and 90 control eyes were examined histologically by 3 masked observers for photoreceptor swelling and loss. Retinas from 9 rhesus monkeys with glaucoma induced experimentally by laser trabecular destruction were compared with 7 fellow (control) eyes. The mean pressure elevations in the eyes with laser trabecular destruction ranged from 26.6 to 53.6 mm Hg with durations varying from 7 to 33 weeks. RESULTS: Swelling of the red- and green-sensitive cones was observed in a statistically significantly greater proportion of human eyes with presumed POAG compared with the control eyes. Patchy loss of red/green cones and rods was also found in some of the glaucomatous retinas. In a subset of the human eyes with end-stage disease, cone swelling was a variable finding. Although no photoreceptor loss was found in the 9 monkey eyes with experimental glaucoma, 8 had swelling of their red/green cones that was remarkably similar to that seen in the human eyes. Swelling was not present in any of the control monkey eyes. CONCLUSIONS: The photoreceptors are affected by chronically elevated intraocular pressure. CLINICAL RELEVANCE: These findings may explain some of the abnormalities of color vision and the electrophysiological effects that have been observed in patients with POAG.

Aged↗
PubMed2000

Risk factors for advancement of cytomegalovirus retinitis in patients with acquired immunodeficiency syndrome. Studies of Ocular Complications of AIDS Research Group.

OBJECTIVE: To identify ocular and systemic factors that predict advancement of cytomegalovirus (CMV) retinitis during treatment. METHODS: Patients with acquired immunodeficiency syndrome were enrolled in a multicenter clinical trial designed to evaluate foscarnet sodium and ganciclovir sodium as therapy for newly diagnosed CMV retinitis. Ocular characteristics at baseline and measurements of retinitis were assessed from fundus photographs by graders at a fundus photograph reading center. The following measures of advancement were assessed: (1) lesion border movement of at least 750 microm or development of a new lesion in involved eyes; (2) rate of increase in retinal area with CMV in involved eyes; and (3) development of retinitis in uninvolved eyes of patients with unilateral disease at baseline. RESULTS: In eyes with retinitis, risk factors at baseline for advancement while receiving treatment included smaller area involved, active margins of retinitis, and posterior location. Risk factors for development of retinitis in uninvolved fellow eyes included blood and urine cultures positive for CMV and lower CD8(+) T-lymphocyte count. CONCLUSIONS: Lesion characteristics can be used to predict advancement of preexisting disease, whereas only systemic factors are associated with development of bilateral disease. These analyses describe retinitis activity before the introduction of potent antiretroviral therapies but provide an important reference point for patients in whom CMV retinitis develops after failure or intolerance of antiretroviral agents. Arch Ophthalmol. 2000;118:1196-1204

AIDS-Related Opportunistic Infections↗
PubMed2000

Infiltrating basal cell carcinoma in the setting of a venous ulcer.

A 77-year-old man was referred with a 5-year history of an intermittently painful, nonhealing right medial ankle ulcer. The ulcer had not responded to multiple treatment modalities, including Unna boots, compression therapy, sclerotherapy, and split-thickness skin grafting. The past medical history was significant for a deep venous thrombosis in the right leg 30 years earlier (treated with warfarin for 3 months) and a history of greater saphenous vein harvesting for coronary bypass grafting 28 years previously. After the vein stripping, the patient had suffered from increasing right leg edema and stasis changes in the right leg. His history was also remarkable for coronary artery disease, dyslipidemia, and lymphoma treated with chemotherapy 8 years before presentation, with no evidence of recurrence. He had stopped smoking approximately 20 years earlier. Medications included atenolol, simvastatin, nicardipine, nitroglycerin, and aspirin. Skin examination revealed a 3.0 x 3.5-cm ulcer adjacent to the medial malleolus. The edges of the ulcer appeared raised and rolled (Fig. 1). Centrally, there was granulation tissue, which appeared healthy. There were surrounding dermatitic changes. Dorsalis pedis and the posterior tibial pulses were normal. Noninvasive vascular studies revealed severe venous incompetence of the right popliteal and superficial veins. Arterial studies and transcutaneous oximetry were normal. Computed tomographic scan of the pelvis did not reveal any adenopathy, and radiographic imaging did not reveal any bony changes suggestive of osteomyelitis. Biopsy of the ulcer edge and base showed infiltrating basal cell carcinoma (Fig. 2). Mohs' micrographic surgery required three layers; the final extent of the ulcer was 7.8 x 6.9 cm. A split-thickness skin graft was placed.

Aged↗
PubMed2000

Large plantar wart caused by human papillomavirus-66 and resolution by topical cidofovir therapy.

Warts can be difficult to diagnose and to treat in the setting of human immunodeficiency virus (HIV) infection. A 37-year-old woman with a background of HIV presented with a large verrucous plaque involving her right foot. Human papillomavirus (HPV)-66 was identified in the lesional skin biopsy sample and in scrapings obtained from her cervix. The wart rapidly responded to topical cidofovir therapy. HPV-66 is a novel HPV type to be associated with verruca vulgaris. Topical cidofovir should be further investigated as an alternative treatment modality for verruca vulgaris.

AIDS-Related Opportunistic Infections↗
PubMed2000

Mutational analysis of adeno-associated virus type 2 Rep68 protein endonuclease activity on partially single-stranded substrates.

The endonuclease activity of the Rep68 and Rep78 proteins (Rep68/78) of adeno-associated virus type 2 (AAV) cuts at the terminal resolution site (trs) within the hairpin structure formed by the AAV inverted terminal repeats. Recent studies suggest that a DNA unwinding function of Rep68/78 may be required for endonuclease activity. We demonstrate that several mutant proteins which are endonuclease negative on a fully duplex hairpin substrate are endonuclease positive on a partially single-stranded hairpin substrate. Truncation analysis revealed that the endonuclease function is contained within the first 200 amino acids of Rep68/78. This endonucleolytic cleavage is believed to involve the covalent attachment of Rep68/78 to the trs via a phosphate-tyrosine linkage. A previous report (S. L. Walker, R. S. Wonderling, and R. A. Owens, J. Virol. 71:2722-2730, 1997) suggested that tyrosine 152 was part of the active site. We individually mutated each tyrosine within the first 200 amino acids of the Rep68 moiety of a maltose binding protein-Rep68/78 fusion protein to phenylalanine. Only mutation of tyrosine 156 resulted in a protein incapable of covalent attachment to a partially single-stranded hairpin substrate, suggesting that tyrosine 156 is part of the endonuclease active site.

Base Sequence↗
PubMed2000

Naproxen-associated linear IgA bullous dermatosis: case report and review.

Linear IgA bullous dermatosis (LABD) is an acquired autoimmune subepidermal blistering disorder in which linear deposits of IgA are found along the basement membrane. Idiopathic, systemic disorder-related, and drug-induced forms of LABD have been described. Drug-induced LABD occurs in association with drug administration and resolves when the offending agent is discontinued. Other forms of LABD assume a more chronic course. The nonsteroidal anti-inflammatory drugs piroxicam and diclofenac have been previously reported to induce LABD. To our knowledge, this article describes the first documented case of LABD associated with naproxen administration, which resolved after discontinuation of the drug.

Aged↗
PubMed1999

Ectonucleotidases of avian gizzard smooth muscle and liver plasma membranes: a comparative study.

Extracellular nucleotides, e.g., ATP, ADP, and UTP, are important signaling molecules which elicit various physiological responses in different tissues. Their degradation is catalyzed by ectonucleotidases which are located on cell surfaces. Most tissues have a mixed population of ectonucleotidases. In this report, the ATP and ADP hydrolyzing ectonucleotidases of chicken gizzard smooth muscle and liver plasma membranes were studied. The two membranes exhibited marked differences in the ratio of ATPase/ADPase activities, activation by divalent cations, thermal stability, responses to detergents and cross-linking agents, and sensitivity to several enzyme inhibitors. The ATPase activity of chicken gizzard membranes is (i) labile to heat and detergents; (ii) activated by concanavalin A and disuccinimidyl suberate, both cross-linking agents; (iii) inhibited by mercurials; and (iv) insensitive to high concentrations of azide, a known inhibitor of ecto-ATP diphosphohydrolases (ecto-ATP/Dase). In contrast, the liver membrane ATPase and ADPase activities are more stable to treatment by heat and detergents and insensitive to cross-linking agents and mercurials, but are inhibited by azide. A low ADP hydrolase activity in the gizzard membranes could be distinguished from both the gizzard ATPase and the liver ATPase/ADPase. This ADP hydrolase, which is markedly stimulated by NBD-Cl, accounts for most of the ADP hydrolysis activity in gizzard membranes. It is concluded that the major ectonucleotidase in the gizzard membranes is an ecto-ATPase whereas that in the liver membranes is an ecto-ATP/Dase. That both membranes contain a mixed population of the ecto-ATPase and ecto-ATP/Dase, but in different proportions, is further demonstrated by immunochemical characterization. The different composition of ectonucleotidases in the two membranes is expected to have an important effect on the regulation of hydrolysis of extracellular ATP as well as the concentration of extracellular adenine nucleotides in the gizzard and liver tissues.

4-Chloro-7-nitrobenzofurazan↗
PubMed1999

Idiopathic reactive hyperplasia of the retinal pigment epithelium.

OBJECTIVES: To present and discuss 2 patients with acquired peripapillary pigmented lesions. METHODS: We reviewed the patients' clinical records and histopathologic findings. RESULTS: The first patient was diagnosed with a pigmented papillary lesion that was followed up for 38 years. The second patient was a child with neurofibromatosis type 1 who developed a pigmented peripapillary lesion following excision of an optic nerve glioma. Histologic findings in both cases demonstrated hyperplasia of the retinal pigment epithelium with associated findings. CONCLUSIONS: The lesions presented an idiopathic reactive hyperplasia of the retinal pigment epithelium. The clinical and histopathologic findings resemble findings reported with the combined hamartoma. We suggest that such lesions are reactive in nature, rather than hamartomatous.

Child, Preschool↗
PubMed1999

Causes of severe visual loss in the early treatment diabetic retinopathy study: ETDRS report no. 24. Early Treatment Diabetic Retinopathy Study Research Group.

PURPOSE: To describe the causes of and risk factors for persistent severe visual loss occurring in the Early Treatment Diabetic Retinopathy Study (ETDRS). METHODS: The ETDRS was a randomized clinical trial investigating photocoagulation and aspirin in 3,711 persons with mild to severe nonproliferative or early proliferative diabetic retinopathy. Severe visual loss, defined as best-corrected visual acuity of less than 5/200 on at least two consecutive 4-month follow-up visits, developed in 257 eyes (219 persons). Of these 257 eyes, 149 (127 persons) did not recover to 5/200 or better at any visit (persistent severe visual loss). Ocular characteristics of these eyes were compared with those of eyes with severe visual loss that improved to 5/200 or better at any subsequent visit. Characteristics of patients with severe visual loss that did and did not improve and those without severe visual loss were also compared. RESULTS: Severe visual loss that persisted developed in 149 eyes of 127 persons. In order of decreasing frequency, reasons recorded for persistent visual loss included vitreous or preretinal hemorrhage, macular edema or macular pigmentary changes related to macular edema, macular or retinal detachment, and neovascular glaucoma. Compared with all patients without persistent severe visual loss, patients with persistent severe visual loss had higher mean levels of hemoglobin A1c (10.4% vs 9.7%; P = .001) and higher levels of cholesterol (244.1 vs 228.5 mg/dl; P = .0081) at baseline. Otherwise, patients with persistent severe visual loss were similar to patients with severe visual loss that improved and to those without severe visual loss. CONCLUSIONS: Persistent severe visual loss was an infrequent occurrence in the ETDRS. Its leading cause was vitreous or preretinal hemorrhage, followed by macular edema or macular pigmentary changes related to macular edema and retinal detachment. The low frequency of persistent severe visual loss in the ETDRS is most likely related to the nearly universal intervention with scatter photocoagulation (either before or soon after high-risk proliferative diabetic retinopathy developed) and the intervention with vitreous surgery when clinically indicated.

Aspirin↗