Biomedical subjects

Thomas G Wilson

Publications and source records attributed to Thomas G Wilson.

At least 19 recordsLinked to original sources

PubMed2006

Drosophila melanogaster Methoprene-tolerant (Met) gene homologs from three mosquito species: Members of PAS transcriptional factor family.

The Methoprene-tolerant (Met) gene in Drosophila melanogaster has been shown to function in juvenile hormone (JH) action. Met homologs were isolated from three mosquito species, Culex pipiens, Aedes aegypti and Anopheles gambiae. Sequence similarity was found to be high in bHLH and PAS conserved domains, and the majority of the 7-9 introns in AaMet and AgMet are located in either identical or similar positions, indicating evolutionary relatedness. Sequence comparison with Met and the similar germ-cell expressed (gce) gene in D. melanogaster showed that the mosquito genes are more similar to gce than to Met. Moreover, the multiple introns in AgMet and AaMet are more similar in number with the 7 introns in Dmgce than to the single intron in DmMet; in fact, six intron positions in AaMet and AgMet are similar to those in Dmgce. Efforts to identify a second homologous gene in mosquitoes were unsuccessful, suggesting a single gene in lower Diptera, consistent with the single gene uncovered in genomic sequencing of Ae. aegypti and An. gambiae. These results suggest that a gene duplication occurred during the evolution of higher Diptera, resulting in Met and gce.

Amino Acid Sequence↗

PubMed2006

Wide mutational spectrum of a gene involved in hormone action and insecticide resistance in Drosophila melanogaster.

The Methoprene-tolerant (Met) bHLH-PAS gene in Drosophila melanogaster is involved in the molecular action of juvenile hormone (JH), and mutants result in resistance to the toxic and morphogenetic effects of JH and JH agonist insecticides such as methoprene. A detailed study of Met mutants can shed light on the poorly understood action of JH as well as the molecular basis of Met resistance to JH insecticides. Nine mutant alleles bearing point mutations in Met were examined for penetrance and expressivity of three phenotypic characters: resistance, defective oogenesis, and a novel eye defect. The collection ranged from two weak alleles having less severe phenotypes to strong alleles with severe phenotypes similar to that of a null allele. The point mutations were located in both conserved and nonconserved domains. Both the eye defect, seen as severely malformed ommatidial facets in the posterior margin of the compound eye, and the oogenesis phenotype are nonconditional, whereas expression of the resistance phenotype requires treatment with JH or JH analogs (JHAs) during early metamorphosis. A proposed basis for all the phenotypic characters centers on MET action as a transcriptional regulator of ecdysone secondary-response target genes during metamorphosis. Disruption of MET function either by mutation or by JHA presence during early metamorphosis results in transcriptional misregulation of different target genes, resulting in the pathology seen in either instance. The variety of amino acid changes in MET that resulted in resistance may portend a rapid rise in resistance in response to increased use of JH insecticides in field insect populations.

Alleles↗

PubMed2006

Interaction of bHLH-PAS proteins involved in juvenile hormone reception in Drosophila.

The Methoprene-tolerant (Met) bHLH-PAS gene is involved in juvenile hormone (JH) action in Drosophila melanogaster as a likely component of a JH receptor. We expressed Met in Drosophila S2 cells and explored for MET partners using pull-down assays. MET-MET interaction was found to occur. The germ-cell expressed (gce) gene is another D. melanogaster bHLH-PAS gene with high homology to Met, and GCE formed heterodimers with MET. In the presence of JH or either of two JH agonists, MET-MET and MET-GCE formation was drastically reduced. Interaction between GCE and MET having N- or C-terminus truncations, bHLH or PAS-A domain deletions, or a point mutation in the PAS-B domain failed to occur. However, JH-dependent interaction occurred between GCE and MET having point mutations in bHLH or PAS-A. During development, changes in JH titer may alter partner binding by MET and result in different gene expression patterns.

Animals↗

PubMed2005

Interaction between hormonal signaling pathways in Drosophila melanogaster as revealed by genetic interaction between methoprene-tolerant and broad-complex.

Juvenile hormone (JH) regulates insect development by a poorly understood mechanism. Application of JH agonist insecticides to Drosophila melanogaster during the ecdysone-driven onset of metamorphosis results in lethality and specific morphogenetic defects, some of which resemble those in mutants of the ecdysone-regulated Broad-Complex (BR-C). The Methoprene-tolerant (Met) bHLH-PAS gene mediates JH action, and Met mutations protect against the lethality and defects. To explore relationships among these two genes and JH, double mutants were constructed between Met alleles and alleles of each of the BR-C complementation groups: broad (br), reduced bristles on palpus (rbp), and 2Bc. Defects in viability and oogenesis were consistently more severe in rbp Met or br Met double mutants than would be expected if these genes act independently. Additionally, complementation between BR-C mutant alleles often failed when MET was absent. Patterns of BRC protein accumulation during metamorphosis revealed essentially no difference between wild-type and Met-null individuals. JH agonist treatment did not block accumulation of BRC proteins. We propose that MET and BRC interact to control transcription of one or more downstream effector genes, which can be disrupted either by mutations in Met or BR-C or by application of JH/JH agonist, which alters MET interaction with BRC.

Alleles↗

PubMed2005

Insulin signaling is necessary for vitellogenesis in Drosophila melanogaster independent of the roles of juvenile hormone and ecdysteroids: female sterility of the chico1 insulin signaling mutation is autonomous to the ovary.

It has been suggested that insulin signaling mutations of Drosophila melanogaster are sterile and long-lived because of juvenile hormone (JH) and ecdysteroid deficiency. However, female sterility of an insulin/IGF-like signaling mutant (chico(1)) of D. melanogaster is not mediated by downstream systemic signaling in terms of major alterations in JH or ecdysteroid levels. chico(1) is a null mutation in the insulin substrate protein (CHICO) gene of D. melanogaster. Homozygous chico(1) females are sterile and their oocytes do not mature beyond the last previtellogenic stage. Homozygous chico(1) females exhibit approximately wild-type rates of JH biosynthesis, ovarian release of ecdysteroids and haemolymph ecdysteroid levels, suggesting that these two major hormone systems play no role in producing the sterility. Previtellogenic wild-type ovaries transplanted into homozygous chico(1) females underwent vitellogenesis, showing that systemic factors present in mutant females are sufficient to support normal vitellogenesis. chico(1) ovaries transplanted into wild-type females did not undergo vitellogenesis indicating that CHICO is necessary in the ovary for vitellogenic maturation. The ovary transplant experiments corroborate the endocrine results and demonstrate that insulin/insulin-like signaling (IIS) is necessary for vitellogenesis even when sufficient levels of JH, ecdysteroids or other factors are present.

Animals↗

PubMed2005

Prospective assessment of the use of enamel matrix proteins with minimally invasive surgery.

BACKGROUND: Minimally invasive surgery (MIS) is a surgical technique using very small incisions, indicated for performing regenerative therapy in periodontal defects. Enamel matrix proteins (EMP) have been shown to enhance periodontal regeneration. This study was undertaken to determine the effect of using EMP in combination with an MIS approach. METHODS: Patients from two private periodontal practices with chronic periodontitis who, following non-surgical therapy, had one or more sites with probing depths (PD) of > or =6 mm were included in the study. An MIS approach was utilized for surgical access. Following surgical debridement, EMP was placed into the bony defect. The surgical sites were reevaluated after at least 11 months. RESULTS: Surgical treatment was performed at 160 sites in 16 patients. No significant differences were noted in the results between the two offices and the data were combined. Mean PD reduction (P = 0.002) and attachment level improvements (P = 0.012) were significantly greater than 3 mm with mean post-surgical PD of 3.17 mm and attachment levels of 4.05 mm, based on subject means. Mean change in recession following surgery was negligible (0.01 mm). All sites were considered to be clinically successful. CONCLUSION: The combination of MIS and EMP yields significant reductions in probing depths and improvements in attachment levels while producing little or no increase in recession.

Acid Etching, Dental↗

PubMed2005

Evaluation of the safety and efficacy of periodontal applications of a living tissue-engineered human fibroblast-derived dermal substitute. II. Comparison to the subepithelial connective tissue graft: a randomized controlled feasibility study.

BACKGROUND: The subepithelial connective tissue graft, traditionally harvested from the patient's palate, is commonly used for root coverage in periodontal recession defects. This study evaluates the safety and effectiveness of a living human fibroblast-derived dermal substitute (HF-DDS) compared to a connective tissue graft (CTG) for root coverage in these situations. METHODS: Thirteen patients were selected for this study. Each patient had Miller Class I or II bilateral facial recession defects > or =3 mm on two non-adjacent teeth. The test tooth received an HF-DDS graft, while a CTG was placed on the control site. The 10 test surgeries were performed by one operator and three pilot surgeries were performed by another surgeon. Eight of the HF-DDS sites received a single thickness of material; five received a double thickness. Clinical measurements were taken at baseline; 1 week; and 1, 3, and 6 months following surgery. Parameters measured were plaque index, recession depth, clinical attachment levels, recession width, probing depth, and width of keratinized tissue. All clinical readings were taken by a masked, calibrated examiner. RESULTS: There were no statistically significant differences between the test and control groups. The amount of root coverage was slightly greater for the control group than for the test group, but statistically the difference was insignificant. The width of the recession defect measured at the cemento-enamel junction (CEJ) for the test group was slightly smaller than that of the control group at the conclusion of the study. The amount of keratinized tissue was the same in both groups at 6 months. The probing depth was slightly greater in the control group as was the gain in clinical attachment, but neither was statistically significant. The amount of root coverage obtained when one layer of HF-DDS was used compared to the amount of coverage obtained when two layers were used approached statistical significance, but the small sample size may have been responsible for the difference. CONCLUSION: Within the limits of this study, the human fibroblast-derived dermal substitute may offer potential as a substitute to the connective tissue graft for covering areas of facial Miller Class I or Class II gingival recession in humans.

Adult↗

PubMed2005

Immediate restoration of implants placed into fresh extraction sockets for single-tooth replacement: a prospective clinical study.

The aim of the present clinical study was to evaluate the placement of transmucosal implants into fresh extraction sockets and their immediate restoration with temporary crowns. A series of 22 cases with a 12-month follow-up is presented. Twenty-two patients (15 women and 7 men; mean age 39 years) who needed a single tooth replaced because of vertical or horizontal root fracture, caries, endodontic lesions, or periodontal disease were treated with immediate postextraction implant placement. The implant was then restored with a screw-retained prosthetic restoration within 24 hours. Radiographic assessments were made at baseline and 12 months after implant placement. Clinical parameters, such as plaque score, mucositis score, probing attachment level, mucosal margin position, variation of gingival level, and variation of papilla position, were also measured at baseline and after 12 months of follow-up. At 12 months, no implants had failed. Radiographic examination revealed mean bone resorption of 0.5 mm at 12 months compared to baseline. The mean variation of gingival level, compared to the neighboring teeth, was -0.75 mm. Probing attachment levels were 0.79, 0.45, and 0.54 mm at proximal, buccal, and lingual sites, respectively. The values for the mucosal margin position were 2.9, 2.2, and 2.4 mm at proximal, buccal, and lingual sites, respectively. Regarding variation of papilla position, according to Jemt's index, 27 papillae presented with a score of 2 (61%) and 17 with a score of 3 (39%). An examination of oral hygiene and peri-implant soft tissue conditions at the 12-month follow-up visit revealed an overall frequency of plaque-carrying implant surfaces of 13%. Furthermore, mucositis (score 2) was not observed at any of the peri-implant units. Primary implant stability did not significantly increase over time. The immediate restoration of dental implants placed into fresh extraction sockets was shown to be a safe and predictable procedure. The success rate and radiographic and clinical results were comparable to those obtained following the standard protocol. Within the limits of the present investigation, immediate restoration of single-tooth implants placed in fresh extraction sockets can be considered a valuable option to replace a missing tooth. However, long-term clinical trials are needed to confirm the present results.

Adult↗

PubMed2004