Determinants of atherosclerosis susceptibility in the C3H and C57BL/6 mouse model: evidence for involvement of endothelial cells but not blood cells or cholesterol metabolism

Lipids, monocytes, and arterial wall cells are primary components involved in atherogenesis. Using the inbred mouse strains C57BL/6J (B6) and C3H/HeJ (C3H), which have been extensively studied as models of the genetic control of diet-induced atherosclerosis, we examined which of these components determine genetic susceptibility. To test whether dietary responsiveness is involved, a congenic strain of C3H carrying an apoE-null allele (apoE(-/-)) was constructed. Although C3H.apoE(-/-) mice had higher plasma cholesterol levels, they developed much smaller lesions than their B6.apoE(-/-) counterpart on either chow or Western diets. Reciprocal bone marrow transplantation between the strains, with congenics carrying the same H-2 haplotype, was performed to examine the role of monocytes. The atherosclerosis susceptibility was not altered in the recipient mice, indicating that variations in monocyte function were not involved. Endothelial cells isolated from the aorta of B6 mice exhibited a dramatic induction of monocyte chemotactic protein-1, macrophage colony-stimulating factor, vascular cell adhesion molecule-1, and heme oxygenase-1 in response to minimally modified LDL, whereas endothelial cells from C3H mice showed little or no induction. In a set of recombinant inbred strains derived from the B6 and C3H parental strains, endothelial responses to minimally modified LDL cosegregated with aortic lesion size. These data provide strong evidence that endothelial cells, but not monocytes or plasma lipid levels, account for the difference in susceptibility to atherosclerosis between the 2 mouse strains.

Correlation of immunohistochemical staining and mutations of p53 in human hepatocellular carcinoma

Mutations of the p53 tumor suppressor gene are common in hepatocellular carcinomas (HCCs). Detection of mutations by sequencing provides more information than immunohistochemical staining, but the equipment needed and the time required make it less practical for use in large-scale studies or in studies in developing countries. The degree of correlation between results obtained with these two methods has been studied in various tumors but has not been well-established in human HCCs. Paraffin sections of HCCs of 28 patients from Qidong, China were immunohistochemically stained using monoclonal antibody to p53. In addition, exons 5-8 of the p53 gene were sequenced in these HCCs. Of the 28 HCCs, nine had 0-9% of nuclei stained for p53, and 19 had 50-95% stained. Mutations in p53 exons 5-8 were found in 17/28 (61%) HCCs, including 15 at codon 249 (exon 7), one at codon 198 (exon 6), and one at codon 175 (exon 5). Among these 17 cases with p53 mutations, 16 cases (94%) had 50-95% of nuclei stained. Among 11 HCCs with no mutations by sequencing, 8 were also negative by immunohistochemistry (0-9% of nuclei stained) (73%) (the five HCCs with no staining whatsoever all had wild-type p53). Immunohistochemical staining to detect p53 mutations in human HCCs detected most mutations that were detected by sequencing (94% sensitivity, 73% specificity), and this method is therefore suitable when sequencing cannot be performed.

Government policies on fluoride utilization in the Nordic countries

In most but not all the Nordic countries, the National Boards of Health have issued guidelines governing the utilization of fluoride. The purpose of this paper is to outline the process of policy formation, describe the current fluoride guidelines in the Nordic countries, and discuss compliance with and appropriateness of the guidelines. The fluoride guidelines summarize current knowledge and make recommendations on choice of fluoride preparations (supplements, toothpaste, and varnish) and doses. Fluoride policies in the Nordic countries in the late 1990s state that use of fluoride toothpaste twice a day is the preferred and sufficient source of fluoride for the majority of the population. The policies of the Nordic countries are similar, but there are differences, some of them self-explanatory others not so obvious. In the case of supplements, for example, there are differences in the recommended dosage schedules. In the case of toothpaste, it is unclear what concentrations of fluoride are recommended both for children and for adults. Starting time for the use of fluoride, whether toothpaste or supplements, varies between countries. The clinicians' compliance with fluoride guidelines has not been systematically evaluated. Comparing the advice and treatments offered by dentists in the Nordic countries with current guidelines suggests that national policies influence the practice of clinicians. For government policy to be appropriate, it is imperative that the guidelines are based on sound scientific evidence. It is thus concluded that if nonevidence-based elements are included in national guidelines, this should be clearly stated to prevent confusion and enhance compliance from professionals and the public.

Fluoride supplements and caries in a non-fluoridated child population

In Norway, there is no water fluoridation and little naturally occurring fluoride in drinking water. Fluoride toothpaste is used by 95% of the population and there is a long tradition of use of fluoride supplements. The purpose of this study was to analyse whether children who used fluoride toothpaste regularly and complied with the recommendations for use of fluoride supplements had less caries than other children at the age of 8 years. Most fluoride supplements sold in Norway are lozenge-type tablets, which allow for extended enamel exposure to fluoride. All children (n = 551) born in 1988 living in a suburban community in Norway were invited to participate. In those who participated (n = 470), caries was registered clinically and radiographically and parents provided data on use of supplements. Thirty-eight percent of the children had used fluoride supplements regularly during the period 0.5 to 4.0 years of age and 66% used supplements regularly at the age of 6 to 8 years. Multivariate analyses showed that the children complying with the recommendations for use of fluoride supplements during the period 0.5 to 4.0 years of age had lower caries experience (dmfs) and fewer decayed surfaces (ds) in primary teeth than other children. No significant associations were found between supplement use in childhood and caries prevalence (DMFS) or number of decayed surfaces (DS) in permanent teeth at the age of 8 years. Supplement use from 6 to 8 years of age was not associated with caries occurrence either in primary or in permanent teeth. Both mother's education and the quality of dental hygiene were inversely associated with caries occurrence.

Caries-preventive methods used for children and adolescents in Denmark, Iceland, Norway and Sweden

Denmark, Iceland, Norway, and Sweden have all had a similar decline in dental caries during the last 20 years, although the decline has come later in Iceland. The purpose of this study was to compare the caries-preventive methods used for children and adolescents in these four countries. Questionnaires were sent to random samples of dentists, dental hygienists, and dental nurses working with children during 1995 and 1996. The results showed that the use of preventive methods was generally consistent between the countries. Nevertheless there were differences between the countries concerning the choice of preventive strategy for risk patients and also in how prevention was implemented. Danish dental care providers chose oral hygiene education as the priority, which they put into practice. Apart from fluoride varnish for some patients, most of them did not use or recommend fluoride except fluoride toothpaste. The Norwegian and Icelandic dental care providers chose both oral hygiene education and the use of fluoride as priorities, while most Swedish dental care providers preferred to provide dietary advice and oral hygiene education, and additional fluoride for risk patients. The differences could not be explained by other variables than nationality, implying that there are differences between the dental cultures in the four countries. The informational basis of decisions on preventive strategies varied between the different dental professionals in each country as well as between the countries, indicating that national professional cultures are being shaped differently. Despite the differences in choice of preventive methods, the dental health of children varies little across the frontiers. This raises the question of the significance of the choice of preventive methods to the decline of dental caries and points towards an urgent need to develop evidence-based preventive strategies.

Clinical judgement as a basis for choice of recall interval in child dental care?

OBJECTIVE

Extending recall intervals can be an important strategy for making children's dental care more efficient. The purpose of this study was to describe the recall intervals that the clinicians decided were appropriate for children and adolescents when they were instructed to extend and individualise the routines based on clinical judgement. In addition, the effect on recall interval of the profession of the clinician (dentist or dental hygienist), the child's age and the need for fillings were studied.

DESIGN

In a four week period in 1995, all dentists and dental hygienists in one county in Norway reported recall intervals for 2,513 children aged 3 to 18 years.

RESULTS

The mean current interval since the previous examination was 17.1 months (SD = 4.7 months) and the mean proposed interval until the next examination was 16.4 months (SD = 4.4 months). Approximately 50% of children were evaluated by the clinicians to be suitable for recall intervals of 20 months or more and 10% were assessed as requiring a new examination within 12 months. The length of the current recall interval, the age of the child, whether or not the child received fillings, and whether the decision-maker was a dentist or a dental hygienist were statistically significantly associated with the length of the proposed recall interval.

CONCLUSIONS

Basing recall intervals on clinical judgement resulted in intervals longer than 12 months for the majority of the children.

Caries preventive services for children and adolescents in Denmark, Iceland, Norway and Sweden: strategies and resource allocation

According to the dental acts of Denmark, Iceland, Norway and Sweden, emphasis is placed on preventive dental care. The purpose of this study was to describe and compare two aspects of the caries preventive services: the strategies and the resource allocation for preventive dental care of children and adolescents in Denmark, Iceland, Norway and Sweden. Questionnaires were sent to samples of dentists and other dental personnel who provided preventive care to children during 1995 and 1996. Comparisons between the countries showed significant differences in recall routines and in implementation of risk-based and population-based preventive strategies. Multivariate analyses showed that the time used for preventive care varied by country and was not associated with the DMFT of the children. More time was allocated for prevention when more operating dental auxiliaries were available at the clinic, when the recall interval was shorter, when the time used for routine examination was longer and when the clinician was an auxiliary rather than a dentist. In conclusion, resource allocation and strategies used for prevention were not consistent between the countries.

Preventive dental care of children and adolescents in the 1990s: Denmark, Iceland, Norway, and Sweden

This article describes the provision of preventive care for children and adolescents in Denmark, Iceland, Norway, and Sweden in the 1990s. It includes information on personnel giving preventive care, administration of the dental care system, strategies and methods used for prevention, and resources allocated for preventive dental care. In all these countries comprehensive and systematic dental care, subsidized or free of charge, has been instituted for children and adolescents. However, comparisons between the countries show significant differences in the organization of the dental care for children, the time used for preventive care, the recall routines, and the implementation of risk-based and population-based preventive strategies. The relative importance of different caries-prevention methods (fluorides, hygiene, and diet) reported by the clinicians varied between Denmark, Iceland, Norway, and Sweden. While variation poses rather than answers questions concerning effectiveness, available data provide evidence of differences in the input of resources. Unless the dental profession addresses the issue of effectiveness of preventive dental care, politicians and administrators in a cost-containment context will easily conclude that least is best.

Risk factors associated with fluorosis in a non-fluoridated population in Norway

In Norway, there is no water fluoridation and little naturally occurring fluoride in drinking water. Fluoride toothpaste is used by 95% of the population and there is a long tradition of fluoride supplement use. The purpose of this study was to record the prevalence and severity of dental fluorosis in 8-year-old children and relate this to systemic fluoride exposure (supplements and toothpaste). All children (n = 551, born 1988) in a municipality in Norway were invited to participate. Dental fluorosis on the buccal surface of the upper permanent incisors was recorded according to the Thylstrup-Fejerskov index (TF). Parents provided data on use of supplements and toothpaste. Complete data were obtained from 383 children. Sixty-seven percent of the children had used fluoride supplements regularly during childhood. At 8 months or earlier, the teeth of 26% of the children, and at age 14 months or earlier the teeth of 82%, were being brushed. Among children who used fluoride supplements regularly, periodically, seldom and not at all, 45%, 21%, 10% and 0%, respectively, had dental fluorosis. The dental fluorosis was mild (TF = 1) in 87% of the cases. Bivariate and multivariate analyses showed that, in addition to use of fluoride supplements, starting toothbrushing at an early age was associated with higher prevalence of dental fluorosis. The child's birth weight and liking for or swallowing of toothpaste did not influence the prevalence of fluorosis. Risk factors for fluorosis were use of toothpaste before the age of 14 months and regular use of fluoride supplements during childhood.

Analysis of transforming growth factor (TGF)-alpha/epidermal growth factor receptor, hepatocyte growth Factor/c-met,TGF-beta receptor type II, and p53 expression in human hepatocellular carcinomas

Experimental data suggest that dysregulation of growth factors and the cognate receptors may play an important role in hepatocarcinogenesis. The objective of the present study was to characterize the expression of two hepatotrophic growth factor/receptor systems [transforming growth factor-alpha/epidermal growth factor receptor (TGF-alpha/EGFR) and hepatocyte growth factor/c-met receptor (HGF/c-met)], both of which are implicated in the development of human liver tumors. In addition, we have analyzed the expression of transforming growth factor-beta receptor type II (TGF-beta-RII) and p53, genes associated with growth inhibition and tumor suppression, respectively. Surgical biopsy specimens from 86 human hepatocellular carcinomas were analyzed. TGF-alpha was overexpressed in 17%, equally expressed in 21%, and down-regulated in 62% of the hepatocellular carcinomas when compared to the surrounding hepatic tissue. No major changes were found with EGFR expression. HGF was over-expressed in 33% and down-regulated in 21% of the tumors. The c-met receptor was overexpressed in 20%, equally expressed in 48%, and down-regulated in 32% of the neoplasms. In contrast, TGF-beta-RII was overexpressed in only 8%, equal in 42%, and down-regulated in 50% of tumors. Nuclear staining of p53, indicative of a mutation(s), was observed in the great majority of the tumors (80%), whereas no nuclear p53 was detected in peritumoral tissues. Interestingly, simultaneous down-regulation of c-met and TGF-beta-RII was observed in 23% of the hepatocellular carcinomas, 85% of which also showed nuclear p53 staining. Taken together, our data suggest that down-regulation of c-met and TGF-beta-RII may, together with p53 mutations, play a significant role in human liver carcinogenesis.

Dental caries and resources spent for dental care among immigrant children and adolescents in Norway

The purpose of this study was to compare dental status and resource requirements in immigrants to Norway, three to 18 years of age, with Norwegians of the same age group. Data on dmft and DMFT, fillings placed and time spent for dental care were registered in the records of 9000 such children in the period 1992-93. Eleven per cent of the children were immigrant children. Immigrant children three to six years of age had fewer sound teeth and more decayed, missing and filled teeth than Norwegian children and the pre-school immigrant children had higher treatment needs. However, the time spent on a pre-school child with an immigrant background was shorter than the time spent on a Norwegian child with the same number of decayed teeth. The differences between immigrants and Norwegians disappeared with higher age. Immigrant children older than six years had dental health and resource requirements similar to those of Norwegian adolescents.

Individualizing recall intervals in child dental care

Individualizing and extending recall intervals for children have been recommended in Norway to target resources efficiently. Recall intervals were changed for children aged 3-18 years in Drammen from 1991. Clinical time spent by dentists and dental hygienists, dental health status and length of recall intervals were registered from 1990 to 1993. For the child population, the mean recall interval changed from 12.5 to 13.7 months and the annual time spent per child was reduced by 14% from 1990-91 to 1992-93. Adjusted for the decline in number of new decayed teeth, the reduction in time spent was 11%. Children with intervals of 17 to 20 months had fewer new decayed teeth and their care required less personnel time than other children. For children with new decayed teeth, time spent for dental care was not associated with recall interval, while for children without new decayed teeth, longer recall intervals were associated with shorter time for dental care. The variation in number of decayed teeth and time spent for dental care was substantial at all intervals. Individualizing and extending recall intervals to some extent targeted resources at children with more dental disease. However, in the short run, inequality in dental health persisted. Limited extension of recall intervals did not interrupt the long-term trend toward better dental health in the children and substantial resources were saved in the dental services.

Recall intervals, dental hygienists and quality in child dental care

Decline in dental disease and the need to provide dental care efficiently suggest changes in clinical and administrative routines in public dental care provision for children. A field project in Norway demonstrated productivity gains after the introduction of individualized recall intervals and using dental hygienists to conduct recall examinations. The purpose of the present study was to assess changes in the quality of dental health outcome and changes in the quality of the process of dental care provision. Recall intervals were increased from a target of 12 months to 16 and 18 months in two districts. Dental hygienists undertook all recall examinations and referred to dentists those patients who required operative care. Bitewing radiographs were inspected for all 18-yr-olds who were examined in 1989, 1990 and 1991 (n = 956) and for those who were examined before the changes were implemented in 1987 (n = 300). For each child, approximal caries on 24 surfaces was scored according to a 4-point severity scale. Clinical records were examined to determine what treatment had been provided. For each year after the changes were implemented, the quality of health outcome was assessed by comparing the radiographic caries prevalence and the number of sound surfaces with 1987 data. Quality in the process of care provision was indicated by the treatment decisions for approximal caries and by the proportion of uninterpretable surfaces on radiographs for each study year. The mean number of sound surfaces increased over time. A declining proportion of sound surfaces was restored over the study period, and almost all caries lesions extending deep into dentine were restored. Radiographic quality improved during the project period.(ABSTRACT TRUNCATED AT 250 WORDS)

Productivity in dental care for children. Factors influencing the time spent delivering dental care

The cost of dental services is related to their productivity. The purpose of the study was to identify factors influencing productivity, measured as time spent providing dental care per child under care, per year, in public dental clinics. The time was expected to vary with characteristics of the patients, the personnel and the clinics. Time spent by dentists and dental hygienists delivering dental care for children aged three to 18 years was obtained from 137 public dental clinics. The data showed substantial variation in productivity between clinics. Multiple regression analysis revealed that the time spent per child was associated with interval between examinations, proportion of male dentists, ratio of dental assistants to dentists, proportion of child treatment time given by dental hygienists and proportion of all treatment time spent on child patients. These variables explained 43 per cent of the variance in the total time spent by dentists and hygienists and 41 per cent of the variance in dentists' time. Individual dentists and hygienists may reduce the mean time spent per child by extending recall intervals. On an administrative level, dentists' time per child may be reduced by employing more dental assistants or dental hygienists and allowing dentists to treat patient groups other than children. It is concluded that productivity in dental care for children in the public dental services may be influenced in several ways, both by clinical and administrative decisions.

Use of dental hygienists and returns to scale in child dental care in Norway

The purpose of this study was to investigate, in the provision of dental care for children, technically and economically efficient combinations of dentists and dental hygienists and to study returns to scale by analyzing production functions. Data from 137 dental health clinics were analyzed. Output was registered as the number of 3-18-yr-old children to whom the clinic delivered complete dental care. Resource input was registered as hours spent by dentists, dental hygienists and dental assistants to deliver care to the children. The average clinic that employed dental hygienists used one hygienist hour per three dentist hours for child dental care. It would save dentist time, but not costs, to extent the use of hygienists. Increased use of dental hygienists might be economically efficient if the work distribution between the personnel groups were changed, for example, by delegating more examinations and preventive care to hygienists. There were technical opportunities for further substitution of dental hygienists for dentists both by introducing dental hygienists in the clinics that only used dentists in child dental care and by extending use of hygienists in clinics that already employed hygienists. This study found no productivity gain from centralizing treatment of children in large dental clinics.

Variation in clinical time spent by dentist and dental hygienist in child dental care

In a field project in the Public Dental Service in Norway, 4000 children aged 5 to 18 years were examined and given preventive care by dental hygienists. The study describes the clinical time spent providing child dental care when hygienists examined all children and referred to dentists those children who required care hygienists were not qualified to deliver. Of all clinical time spent, 56% was dentist time and 44% was hygienist time. A high proportion of children without dental caries did not consume dentist resources at all. More than 40% of the dentist time was consumed by the 10% of the children with most new decayed teeth. In conclusion, the project showed that in a child population with low caries increment, a substantial proportion of children received all dental care from hygienists, so that dentist resources were saved for other groups. However, although hygienists were used as first-line personnel, a considerable quantity of dentist time was spent on dental care for children.

[c-myc gene and p53 protein expression in human primary liver carcinoma]

Photobiotin-labelled c-myc gene probe was used to study primary liver carcinoma (PHC) by in situ hybridization on the paraffin sections as well as immunohistochemistry staining for p53 protein expression in 42 cases from high liver cancer incidence regions. The results are as follows: c-myc gene and p53 protein expression were both located in the nuclei. The positive incidences of overexpression of both c-myc gene and p53 protein in PHC were 76% and 55% respectively. The distribution and strength of the overexpression of c-myc gene and p53 protein in PHC are related to the degree of cell differentiation and the overexpression in the liver tissue surrounding the carcinoma is lower than that detected in the PHC tissue.

Alterations of tumor suppressor genes and allelic losses in human hepatocellular carcinomas in China

Aflatoxin B1 has been suggested as a causative agent for a G to T mutation at codon 249 in the p53 gene in human hepatocellular carcinomas (HCC) from southern Africa and Qidong in China. The objective of the present work was to test the hypothesis that exposure to aflatoxin B1 either alone or coincident with other environmental carcinogens might be associated with allelic losses occurring during development of human hepatocarcinogenesis in China. The HCCs were obtained from two different areas in China: Qidong, where exposure to hepatitis B virus (HBV) and aflatoxin B1 is high; and Beijing, where exposure to HBV is high but that of aflatoxin B1 is low. We analyzed the tumors for mutations in the p53 gene and loss of heterozygosity for the p53, Rb, and APC genes and at marker loci on chromosomes 4, 13, and 16. Frequencies of mutation, loss, and aberration (mutation and loss) of the p53 gene in 25 HCCs from Qidong were 60, 58, and 80%, respectively. The frequencies in 9 HCCs from Beijing were 56, 57, and 78%. However, the frequency of a G to T transversion at codon 249 in HCCs from Qidong and Beijing were 52 and 0%, respectively. These data indicate that mutation and/or loss of heterozygosity in the p53 gene, independent of the 249 mutation, play a critical role in the development of hepatitis B virus-associated HCCs in China. Loss of the Rb and APC genes was observed in 44 and 7% of HCCs from Qidong, respectively. Allelic losses on chromosome 4 and especially on chromosome 16 were frequent in HCCs from Qidong but were not observed in HCCs from Beijing, while loss of heterozygosity on chromosome 13 occurred at similar frequency in both Qidong and Beijing. These results show a distinct difference in the pattern of allelic losses between HCCs in Qidong and Beijing and suggest that aflatoxin B1 and/or other environmental carcinogens may contribute to this difference.

Aberrations of p53 gene in human hepatocellular carcinoma from China

Allele losses and mutations have been examined in 38 cases of primary hepatocellular carcinomas (HCC) from different geographic areas of China by Southern, single-strand conformational polymorphism (SSCP) and direct DNA sequencing analyses. Two of 12 samples from Qi-Dong and six of 18 HCCs from Shanghai showed loss of heterozygosity (LOH) at the loci on chromosome 17p13.3. All of the nine mutations in the p53 gene detected in HCC from Qi-Dong were clustered at the third base of codon 249, i.e. G:C to T:A, leading to an arginine to serine change. In contrast, 18 HCC samples from Shanghai contained three mutations at codons 249, 255 and 279. These results suggested a relationship between the spectrum of p53 aberration and environmental risk factors in these two geographic areas. Since no correlation between the state of HBV DNA and p53 aberration was observed, other factors such as dietary exposure to aflatoxin B1 (AFB1) might be responsible for the mutational hotspot at codon 249 in HCCs from Qi-Dong area.

[Clinical and pathological features of primary hepatocellular carcinoma in 26 patients survived over 10 years after operation]

The clinical and pathological features of primary hepatocellular carcinoma (PHC) in 26 patients who had survived over 10 years after operation were analyzed. The results were as follows: 84.62% (22 patients) were detected by AFP screening, 80.77% (21 patients) were in clinical stage I, 76.96% (20 patients) were younger than 45 years of age. Serum AFP of all patients turned negative within 2 months after operation. The tumor diameters ranged from 1.2 cm to 15 cm, and solitary tumors accounted for 80.77% (21 patients). All tumors were encapsulated and infiltrated by lymphocytes. Cirrhosis was found only in 9 cases (34.62%). The positive rates of HBsAg and HBcAg were 80% and 15% respectively in hepatic tissues surrounding the carcinoma. These results suggest that good prognosis or long survival is related to early detection, younger age of the patient, solitary tumor, better encapsulation, mild injury of the surrounding liver tissues, and rapid negative turning of AFP after operation.

Mutational hotspot in the p53 gene in human hepatocellular carcinomas

Human hepatocellular carcinomas (HCC) from patients in Qidong, an area of high incidence in China, in which both hepatitis B virus and aflatoxin B1 are risk factors, were analysed for mutations in p53, a putative tumour-suppressor gene. Eight of the 16 HCC had a point mutation at the third base position of codon 249. The G----T transversion in seven HCC DNA samples and the G----C transversion in the other HCC are consistent with mutations caused by aflatoxin B1 in mutagenesis experiments. No mutations were found in exons 5,6,8 or the remainder of exon 7. These results contrast with p53 mutations previously reported in carcinomas and sarcomas of human lung, colon, oesophagus and breast; these are primarily scattered over four of the five evolutionarily conserved domains, which include codon 249 (refs 4-9). We suggest that the mutant p53 protein may be responsible for a selective clonal expansion of hepatocytes during carcinogenesis.