Functional characterization of a human aquaporin 0 mutation that leads to a congenital dominant lens cataract

The aquaporin (AQP) transmembrane proteins facilitate the movement of water across the plasma membrane. In the lens, AQP0 is expressed in fiber cells and AQP1 in the epithelium. Recently, two individuals were identified with congenital polymorphic autosomal dominant cataract, due to a single nucleotide base deletion mutation in the lens AQP0. The deletion modified the reading frame resulting in the addition of a premature stop codon. In the present study, we examined the water permeability properties, trafficking and dominant negative effects as well as cytotoxicity due to the mutant AQP0 (Delta213-AQP0) protein. The membrane water permeability (P(w)) of Delta213-AQP0 expressing oocytes (14+/-1 microm/s) was significantly lower than those expressing WT-AQP0 (25+/-3 microm/s). P(w) of water injected control oocytes was 13+/-2 microm/s. Co-expression of WT-AQP0 with Delta213-AQP0 significantly lowered the P(w) (18+/-3 microm/s) compared to WT-AQP0. With or without the EGFP tag, WT-AQP0 protein localized in the plasma membranes of oocytes and cultured cells whereas Delta213-AQP0 was retained in the ER. Forster Resonance Energy Transfer (FRET) showed that WT-AQP0 partly localized with the co-expressed Delta213-AQP0. Co-localization studies suggest that the mutant AQP0 gained its dominant function by trapping the WT-AQP0 in the ER through hetero-oligomerization. Incubating the cells with chemical chaperones, namely, TMAO and DMSO, did not correct the folding/trafficking defects. Cell death in the Delta213-AQP0 expressing cells was due to necrosis caused by the accumulation of Delta213-AQP0 protein in the ER in cytotoxic proportions. The data show that replacement of the distal end of the 6th TM domain and the C-terminal domain of AQP0 due to the deletion mutation resulted in the impairment of cell membrane P(w), localization of the mutant protein in the ER without trafficking to the plasma membrane, and cytotoxicity due to the accumulation of the mutant protein. Cataracts in patients with this mutation might have resulted from the above mentioned consequences.

Management of temporo-mandibular joint ankylosis in growing children

Although temporo-mandibular joint (TMJ) ankylosis is one of the most common pathologies afflicting the facial skeleton, it is also the most overlooked and under-managed problem in children. The TMJ forms the very cornerstone of cranio-facial integrity and hence its ankylosis in growing children adversely affects the growth and development of the jaws and occlusion. Impairment of speech, difficulty in mastication, poor oral hygiene, rampant caries and acute compromise of the airway pose a severe psychologic burden on the tender minds of children. The aim of this article is to present an overview of efficient management strategies, based on a case report, so as to increase its awareness among all dental surgeons involved in the treatment of children.

Effect of toothpaste with natural calcium carbonate/perlite on extrinsic tooth stain

OBJECTIVE

The current study was designed to determine the effect of natural calcium carbonate toothpaste containing Perlite and microgranules (Whitening toothpaste) on extrinsic tooth stain compared to a standard commercial toothpaste formulation with precipitated calcium carbonate (PCC) as abrasive and a commercial toothpaste with dicalcium phosphate dihydrate (DCPD) as abrasive.

METHODS

The toothpastes were evaluated in a double blind, three-cell, stratified (tobacco use; baseline tooth stain level), parallel group design study involving 600 subjects with extrinsic tooth stain. Subjects brushed twice daily with their allocated toothpaste for four weeks. Extrinsic tooth stain was measured using the Macpherson modification of the Lobene stain index.

RESULTS

ANCOVA showed significant differences between toothpastes (p=0.037). Subsequent multiple comparisons using pairwise t-tests, showed the Whitening toothpaste to be superior to the DCPD toothpaste (p=0.014) and the PCC toothpaste (p=0.067). When a Box-Cox transformation was made to the data (y0.6) to improve normality, these two differences were more accurately estimated at p=0.004 and p=0.03 respectively.

CONCLUSION

The Whitening toothpaste has been shown to be significantly more effective in tooth stain removal than the two standard commercial toothpaste formulations.

Reactive fibrous hyperplasia associated with a natal tooth

A natal tooth is that which is present in the oral cavity at the time of birth. Fibrous hyperplasia is a non-specific reactive lesion of soft tissues of unknown etiology usually associated with trauma or local irritation. Natal teeth can occur as an isolated dental finding, but many times they are associated wilh syndromes and developmental disturbances. This is a rare case, where in a natal tooth has led to the formation of a reactive fibrous hyperplasia in a four and half month old infant, a relationship not reported previously.

"Moebius syndrome": a case report

Moebius syndrome is an extremely rare disorder characterized by a lifetime facial paralysis, involving sixth and seventh cranial nerves with malformations of orofacial structures and the limbs. In this case, an 8 year old girl with Moebius syndrome is presented, clinical findings are described and management aspects are discussed. Early dental evaluation and parental counselling as a part of preventive dental regimen can go a long way in providing complete psychosocial rehabilitation for such physically disabled children.

Labial talon cusp on permanent central incisor: a case report

Talon cusp is a supernumerary crown structure, a developmental disturbance in the shape of teeth that causes various diagnostic, functional and esthetic problems. Some synonyms for talon cusp are dens evaginatus of anterior teeth, interstitial cusp, tuberculated tooth, odontoma of the axial core type, evaginated odontoma, enamel pearl, supernumerary cusp etc. The lingual location on incisors, which frequently affects occlusion, is pathognomonic of the talon cusp. This report describes a rare odontogenic, isolated anomaly rather than an integral part of any disorder, a case of talon shaped cusp projecting from the labial surface of a maxillary permanent central incisor.

Herniation of the buccal fat pad into the oral cavity: a case report

An interesting lesion is presented, wherein a tiny traumatic perforation of the buccal mucosa and buccinator muscle forced a large portion of the buccal fat pad to extrude into the oral cavity. Such a situation can alarm any clinician & reinforces the importance of careful history taking and thorough examination, before treating patients.

Congenital muscular dystrophy--a case report

A rare case of congenital muscular dystrophy with unique oro-facial manifestations is presented. Dental considerations and successful management techniques are discussed.

Patients' values for health states associated with hepatitis C and physicians' estimates of those values

OBJECTIVES

Hepatitis C is the leading cause of chronic hepatitis in the United States. Little information is available regarding how persons with hepatitis C view health with their disease. We studied patients' perceptions about the value of hepatitis C health states and evaluated whether physicians understand their patients' perspectives about this disease.

METHODS

A total of 50 consecutive persons with hepatitis C were surveyed when they presented as new patients to a hepatology practice. Subjects provided utility assessments (preference values) for five hepatitis C health states and for treatment side effects. They also stated their threshold for accepting antiviral therapy. Five hepatologists used the same scales to estimate their patients' responses.

RESULTS

On average, patients believed that hepatitis C without symptoms was associated with an 11% reduction in preference value from that of life without infection, and the most serious condition (severe symptoms, cirrhosis) was believed to carry a 73% decrement. Patients judged the side effects of antiviral therapy quite unfavorably, and their median stated threshold for accepting treatment was a cure rate of 80%. Physicians' estimates were not significantly associated with patients' preference values for hepatitis C health states, treatment side effects, or with patients' thresholds for accepting treatment. In multivariate analysis, patients' stated thresholds for taking treatment were significantly associated with their decisions regarding therapy (beta = -2.72+/-1.21, p = 0.025).

CONCLUSIONS

There was little agreement between patients' preference values about hepatitis C and their physicians' estimates of those values. Utility analysis could facilitate shared decision making about hepatitis C.