Distribution and uptake of magnesium by developing deciduous bovine incisor enamel

Magnesium concentrations determined in deciduous bovine enamel at different stages of development were similar to those previously published for human and rat enamel ranging from 0.1 to 0.4 per cent. Highest concentrations, i.e. greatest uptake, occurred after secretion, in the transitional and maturing enamel. Uptake had occurred throughout the tissue thickness and was not confined to the surface. Magnesium probably enters enamel in the tissue fluid which replaces the organic matrix. Some magnesium is lost as fluid is replaced by calcium and phosphate but part is retained probably on or near crystal surfaces.     

Lesion volume, lesion location, and outcome after middle cerebral artery territory stroke.

AIM: To investigate the relation between lesion volume, lesion location, and clinical outcome in children with infarction in the territory of the middle cerebral artery (MCA). PATIENTS AND METHODS: Children with MCA territory infarcts were selected retrospectively from a database of children with ischaemic stroke. Lesion volumes were expressed as a percentage of the supratentorial intracranial volume and were categorised as "small", "moderate", or "large". Lesion location was categorised as cortical or purely subcortical. Outcome was ascertained by parental questionnaire and was categorised as "good" or "poor". RESULTS: 38 patients were identified (median age 6 years); 21 patients had lesions that involved cortical tissue. Outcome was good in 12 cases and poor in 26 cases (including 2 children who died). Although there was no significant effect of lesion size or lesion location on outcome for the group as a whole, all children who had infarcted more than 10% of intracranial volume had a poor outcome. Of note, some children with small subcortical lesions had pronounced residual deficits. CONCLUSIONS: Although the outcome after a small infarct in the MCA territory is variable and unpredictable, infarction of more than 10% of intracranial volume is universally associated with a poor outcome. Characterisation of lesion volume and topography might be helpful in identification of such children for participation in future trials of treatments for acute stroke.     

Isothiocyanates and freeze-dried strawberries as inhibitors of esophageal cancer

A group of arylalkyl isothiocyanates were tested for their abilities to inhibit tumorigenicity and DNA methylation induced by the esophageal- specific carcinogen, N-nitrosomethylbenzylamine (NMBA) in the F344 rat esophagus. Phenylpropyl isothiocyanate (PPITC) was more potent than either phenylethyl isothiocyanate (PEITC) or benzyl isothiocyanate (BITC). Phenylbutyl isothiocyanate (PBITC), however, had a lesser inhibitory effect on esophageal tumorigenesis, and phenylhexyl isothiocyanate (PHITC) actually enhanced esophageal tumorigenesis. Thus, the two- and three-carbon isothiocyanates were more effective inhibitors of NMBA-esophageal carcinogenesis than the longer chain isothiocyanates. The effects of the isothiocyanates on tumorigenesis were well correlated as to their effects on DNA adduct formation. The most likely mechanism of inhibition of tumorigenesis by these isothiocyanates is via inhibition of the cytochrome P450 enzymes responsible for the metabolic activation of NMBA in rat esophagus. A freeze-dried strawberry preparation was also evaluated for its ability to inhibit NMBA-esophageal tumorigenesis. It proved to be an effective inhibitor, although not as potent as either PEITC or PPITC. The inhibitory effect of the berries could not be attributed solely to the content of the chemopreventive agent, ellagic acid, in the berries.      

Architecture of intact natural human plaque biofilms studied by confocal laser scanning microscopy

Determination of the structure of human plaque will be of great benefit in the prediction of its formation and also the effects of treatment. However, a problem lies in the harvesting of undisturbed intact plaque samples from human volunteers and the viewing of the biofilms in their natural state. In this study, we used an in situ device for the in vivo generation of intact dental plaque biofilms on natural tooth surfaces in human subjects. Two devices were placed in the mouths of each of eight healthy volunteers and left to generate biofilm for 4 days. Immediately upon removal from the mouth, the intact, undisturbed biofilms were imaged by the non-invasive technique of confocal microscopy in both reflected light and fluorescence mode. Depth measurements indicated that the plaque formed in the devices was thicker round the edges at the enamel/nylon junction (range = 75-220 microm) than in the center of the devices (range = 35-215 microm). The reflected-light confocal images showed a heterogeneous structure in all of the plaque biofilms examined; channels and voids were clearly visible. This is in contrast to images generated previously by electron microscopy, suggesting a more compact structure. Staining of the biofilms with fluorescein in conjunction with fluorescence imaging suggested that the voids were fluid-filled. This more open architecture is consistent with recent models of biofilm structure from other habitats and has important implications for the delivery of therapeutics to desired targets within the plaque.     

Altered interface adhesion molecules in oral lichen planus

OBJECTIVE: To evaluate expression of key epithelial-connective tissue interface adhesion molecules (basal keratinocyte integrins and extracellular matrix receptors) in oral lichen planus (LP).
DESIGN: Integrins α3, α6, β1, β4 and basement membrane proteins laminin 1, laminin 5, collagen IV, and collagen VII were immunohistochemically identified in frozen biopsy specimens (14 oral LP and 11 matched controls) using a standard avidin-biotin-peroxidase technique.
RESULTS: An increased staining intensity of all antigens in LP was shown, as compared to controls. Integrin expression by LP keratinocytes was generally more intense and appeared on more upper level cells. Staining for basement membrane-associated extra-cellular matrix proteins was also generally more intense, although fragmentation and gaps were typically seen. Reactions for α6, β4, laminin 5, and collagen VII stains were particularly intense along the basement membrane. In LP, strands of laminin 5, collagen IV, and collagen VII appeared in the submucosa approximating or duplicating the basement membrane.
CONCLUSIONS: The apparent increased expression of the interface-associated adhesion molecules may be reflective of a keratinocyte compensatory response (due to lymphocyte-mediated damage) that would functionally help resist epithelial separation (ulceration). Expression of α3β1 and α6β4 would also assist in epithelial migration associated with wound repair. We interpret the submucosal extensions and deposits of basement membrane proteins as representing remnants of basement membrane, indicating recent remodeling or atrophy of epithelial rate ridges.     

瓷贴面生物力学研究及临床应用

贴面已经成为一种广泛应用于前牙美容的修复方法。本文主要总结近年来国内外学者在瓷贴面设计及操作方面的生物力学研究成果,以期更好地指导临床工作。     

Young people of minority ethnic origin in England and early parenthood: views from young parents and service providers

The paper explores the phenomenon of early parenthood in minority ethnic communities in England. The data were collected using focus group interviews, in-depth semi-structured interviews and a telephone survey. The sample consisted of 139 participants (41 service providers, 10 grandmothers, 88 young parents). The findings map out the complexity and diversity of experience of early parenthood amongst young people of minority ethnic origin, not least the multiple attachments many experience in relation to their social groups, religious affiliations and the traditional patterns of parenting within their immediate and extended family. Both the young parents and professionals in this study constructed early parenthood in more positive terms than is currently portrayed in the contemporary policy. The findings are analysed and discussed in relation to ethnic identity, social inclusion and exclusion. We explore participants' attempts to counter negative 'deficit' models of early parenthood with reference to perspectives on youth, parenthood and contemporary strategic policy. In conclusion, we suggest an unambiguous focus on the reduction of pregnancy is not a credible message when teenage pregnancy is a social norm for a particular ethnic or cultural group. For young parents of Muslim faith in particular, teenage parenting within marriage is not necessarily considered a 'problem' or seen as a distinctive event. Most participants did not view early parenthood as a barrier to re-establishing career and educational aspirations. A wide diversity of experience amongst young parents is evidenced in the communities studied; this needs to be reflected more comprehensively both in UK policy and in support services.