A longitudinal study of interleukin-1 gene polymorphisms and periodontal disease in a general adult population

BACKGROUND

Cross-sectional studies have demonstrated that a specific polymorphism (allele 2 of both IL-1A +4845 and IL-1B +3954) in the IL-1 gene cluster has been associated with an increased susceptibility to severe periodontal disease and to an increased bleeding tendency during periodontal maintenance. The aim of the present study was to investigate the relationship between IL-1 genotype and periodontitis in a prospective longitudinal study in an adult population of essentially European heritage.

METHODS

From an ongoing study of the Oral Care Research Programme of The University of Queensland, 295 subjects consented to genotyping for IL-1 allele 2 polymorphisms. Probing depths and relative attachment levels were recorded at baseline, 6, 12, 24, 36, 48 and 60 months using the Florida probe. Periodontitis progression at a given site was defined as attachment loss > or =2 mm at any observation period during the 5 years of the study and the extent of disease progression determined by the number of sites showing attachment loss. Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans and Prevotella intermedia were detected using ELISA.

RESULTS

38.9% of the subjects were positive for the composite IL-1 genotype. A relationship between the IL-1 positive genotype and increased mean probing pocket depth in non-smokers greater than 50 years of age was found. Further, IL-1 genotype positive smokers and genotype positive subjects with P. gingivalis in their plaque had an increase in the number of probing depths > or =3.5 mm. There was a consistent trend for IL-1 genotype positive subjects to experience attachment loss when compared with IL-1 genotype negative subjects.

CONCLUSION

The results of this study have shown an interaction of the IL-1 positive genotype with age, smoking and P. gingivalis which suggests that IL-1 genotype is a contributory but non-essential risk factor for periodontal disease progression in this population.

Likelihood-based modeling and analysis of data underdispersed relative to the Poisson distribution

By using a generalization of the Poisson process, distributions can be constructed that show appropriate amounts of underdispersion relative to the Poisson distribution that may be apparent from observed data. These are then used to examine the differences between the distributions of numbers of fetal implants in mice corresponding to different doses of the herbicide 2,4,5-T.

Follicle dynamics during ovarian ageing

The human ovary is endowed at birth with a fixed number of primordial follicles which steadily declines throughout life as a result of atresia and recruitment towards ovulation. The pattern of this decline is not exponential, but more bi-exponential corresponding to a 'broken-stick' regression of logged total numbers of follicles against age. Such a model implies an abrupt change in the exponential rate of follicle loss at age 38 years, and is thus rather implausible biologically. A more refined model with an exponential rate of follicle loss that changes gradually throughout life also describes the data on declining follicle numbers but in addition leads to a distribution of age at menopause, corresponding to follicle numbers falling below a critical threshold, that shows quite remarkable agreement with independent data on menopausal ages of American women. When the follicles are classified into resting and growing stages, it is found that any changes in the consequent process of follicle development as the ovary ages relate mainly to the small resting follicles and not the larger growing ones.

Ante-dependence modeling in a longitudinal study of periodontal disease: the effect of age, gender, and smoking status

BACKGROUND

It is generally accepted that periodontal disease progresses by a series of bursts that are interspersed by periods of stability or even gain of attachment. In order to analyze longitudinal data on a patient's disease experience, it is necessary to use models which accommodate serial dependence. Ante-dependence between the results of a series of periodontal examinations over time can be modeled using a Markov chain. This model describes temporal changes in patients' levels of disease in terms of transition probabilities, which allow for both regression and progression of the disease. The aim of the present study was to demonstrate the use of a Markov chain model to analyze data from a longitudinal study investigating the progression of periodontal disease in an adult population.

METHODS

The study population consisted of 504 volunteers; however, only 456 were included in the analysis because the remaining 48 subjects did not give consecutive data. Subjects were examined at baseline, 6 months, and 1, 2, and 3 years. Probing depths (PD) were recorded using an automated probe. Disease was defined as four or more sites with PD > or = 4 mm. Markov chain modeling was used to determine the effect of age, gender, and smoking on the natural progression and regression (healing) of periodontal disease.

RESULTS

Smoking and increasing age had no effect on the progression of disease in this population, but did have a significant effect (P values < or = 0.05) in reducing the regression of disease; i.e., their effect on disease appears to be inhibition of the natural healing process. Gender had no significant effects.

CONCLUSIONS

These results demonstrate how ante-dependence modeling of longitudinal data can reveal effects that may not be immediately apparent from the data, with smoking and increasing age being seen to inhibit the healing process rather than promote disease progression.

Estimations of the efficacy and reliability of paternity assignments from DNA microsatellite analysis of multiple-sire matings

It is important for bovine DNA testing laboratories to provide the cattle industry with accurate estimates of the efficacy and reliability of DNA tests offered so that end users of this technology can adequately assess the cost-benefits of testing. To address these issues for bovine paternity testing, paternity exclusion probability estimates were obtained from breed panel data and were predictive of the efficacy of the DNA tests used in 39 multiple-sire mating groups, involving 5960 calves and 505 bulls. Paternity testing of these mating groups has demonstrated that the majority involve a variable proportion of unknown sires and this impacts on the reliability of sire allocation. Mathematical models based on binomial or beta-binomial probability distributions were used to estimate the reliability of single-sire allocations from multiple-sire matings involving unknown sires. Reliability of 98-99% is achieved when the exclusion probability is 0.99 or greater, after allowing for up to 20% unknown sires. When the exclusion probability drops below 0.90 and there are 20% unknown sires, the reliability is poor, bringing into question the benefits of testing. This highlights the need for DNA testing laboratories to offer paternity tests with an exclusion power of at least 99%.

Biological bases of premature ovarian failure

The ovary is endowed at birth with a fixed number of primordial follicles, which steadily dwindles throughout life as a result of atresia and recruitment towards ovulation. In addition to age, the number varies allometrically between species, larger and longer-lived animals tending to have more follicles initially and these disappear at a slower rate. A causal relationship between follicle depletion and menopause clearly exists, and there is a gradual acceleration of follicle wastage in the human ovary beginning more than a decade before the end of menstrual life. A mathematical model has provided confirmatory evidence of this relationship, and indicates that menopause is triggered by a threshold number of follicles which varies stochastically with a mean of 1100.

Permeation of human ovarian tissue with cryoprotective agents in preparation for cryopreservation

The recent improvements in the treatment of cancer by chemo- and radiotherapy have led to a significant increase in the survival rates of patients with malignant disease, but at the expense of distressing side effects. One major problem, especially for younger patients, is that aggressive therapy destroys a significant proportion of the follicular population, which can result in either temporary or permanent infertility. Freeze-banking pieces of ovarian cortex prior to treatment is one strategy for preserving fecundity. When the patient is in remission, fertility could, theoretically, be restored by autografting the thawed tissue at the orthotopic site or by growing isolated follicles to maturity in vitro. Recent studies have found good follicular survival in frozen-thawed human ovarian tissue but to optimize the process an effective cryopreservation method needs to be developed. An essential part of such a technique is to permeate the tissue with a cryoprotectant to minimize ice formation and the extent of this equilibration is an important determinant of post-thaw cellular survival. In the current study, we have investigated the diffusion of four cryoprotective agents into human tissue at both 4 degrees C and 37 degrees C. We have also studied the effect of adding different concentrations of the non penetrating cryoprotective agent, sucrose, to the freezing media using the release of lactate dehydrogenase as a measure of its protective effect. At 4 degrees C propylene glycol and glycerol penetrated the tissue significantly slower than either ethylene glycol or dimethyl sulphoxide. At the higher temperature of 37 degrees C all four cryoprotectants penetrated at a faster rate, however concern about enhanced toxicity prevents the use of these conditions in practice. Thus, the results suggest that the best method of preparing tissue for freezing is exposure for 30 min to 1.5 M solutions of ethylene glycol or dimethyl sulphoxide at 4 degrees C; this achieved a mean tissue concentration that was almost 80% that of the bathing solution. We also report that the addition of low concentrations of sucrose to the freezing medium does not have a significant protective effect against freezing injury.

Impact of congenital or experimental hypogonadotrophism on the radiation sensitivity of the mouse ovary

As the numbers of young people making a full recovery from haematological malignancy continue to rise, reproductive science must investigate ways of ameliorating the sterilizing effects of high-dose chemotherapy and total body irradiation. Because there is conflicting evidence as to whether lower serum gonadotrophin concentrations have any protective effect on the gonads, a study was designed to test whether either congenital or experimentally induced hypogonadism reduces the radiosensitivity of the mouse ovary. Test subjects were either homozygous for the hpg locus or animals of normal phenotype treated with a gonadotrophin-releasing hormone antagonist. At 14 days after receiving a single dose of 0.1, 0.2 or 0.3 Gy X-rays or a sham procedure, primordial follicles in the ovaries of the two experimental groups and controls were counted in serial histological sections. The doses at which half of the follicles were lost (LD50) were estimated as 0.11 +/- 0.02, 0.19 +/- 0.02 and 0.17 +/- 0.02 Gy respectively. There was no significant difference between the controls and the antagonist-treated animals, but the congenitally hypogonadal group was unexpectedly more sensitive to radiation. Either way, these results do not support the hypothesis that the ovary is protected from radiation injury by lower gonadotrophin concentrations.

Efficacy of a dentifrice and oral rinse containing sanguinaria extract in conjunction with initial periodontal therapy

In the treatment of periodontal disease initial therapy aims at reducing marginal inflammation so allowing assessment of residual disease and further treatment options. The aim of the present study was to determine whether the use of a dentifrice and oral rinse containing sanguinaria extract led to a more rapid resolution of gingival inflammation following initial therapy. Thirty-four subjects, randomly assigned to one of two treatment groups, took part in this randomized double-blind parallel study. All subjects received initial therapy including oral hygiene instruction and scaling and root planing as required. One group also received an active dentifrice and oral rinse containing sanguinaria extract (an antiplaque agent) and zinc chloride. The other group received a placebo dentifrice and oral rinse. The gingival index (GI), plaque index (PLI) and probing pocket depths (PD) were recorded at six sites per tooth at baseline, two weeks after initial therapy and six weeks after initial therapy. There was no significant difference between the groups for any of the parameters at the baseline examination. Two weeks following initial therapy both groups showed a statistically significant increase in the number of sites with PLI of 0 or 1 (p < 0.0001) and a statistically significant increase in the number of sites with a GI of 0 or 1 (that is, no bleeding on probing), (p < 0.0001). Also there was a statistically significant increase in the number of sites with probing depths < or = 3 mm (p < 0.0001) compared with baseline. These changes were maintained through to six weeks post therapy. There was no significant advantage to the sanguinaria group. Results demonstrate that initial therapy in the form of oral hygiene instruction, scaling and root planing leads to a significant improvement in periodontal status which is maintained at least in the short term. Further, use of a dentifrice and oral rinse containing sanguinaria did not improve the efficacy of initial therapy.

Regression pattern of beta human chorionic gonadotrophin in blood after chemotherapy for gestational trophoblastic neoplasia

Although beta human chorionic gonadotrophin (beta-HCG) is a clinically-useful tumour marker in gestational trophoblastic neoplasia, there is limited information on how serum beta HCG regresses in molar pregnancy and choriocarcinoma during chemotherapy. The study included 41 patients who had been treated by single- and multidrug regimens, and decay curves for regression of beta HCG in the circulation in these patients were fitted to the data. Thirty-three patients achieved a biochemical remission ('cured') by first-line chemotherapy; this gave an overall efficacy rate of 80%. The beta HCG decay curves convey useful information of the chemosensitivity of the tumour, and may assist in determining the time required for treatment and earlier change in treatment for the chemoresistant tumour.

A model conforming the decline in follicle numbers to the age of menopause in women

The store of primordial follicles in the ovary is fixed before birth and dwindles with age until it is unable to provide enough Graafian stages to sustain menstrual cyclicity. According to a simple bi-exponential model of ageing, the rate of follicle disappearance increases at age 37.5 years (or when 25 000 follicles remain) so that the numbers fall to approximately 1000 at 51 years, the median age of menopause in the population. This study attempts to produce a biologically more realistic model of follicle disappearance and harmonizes follicle dynamics with the distribution of menopausal ages from an American survey. The step-change in the rate of follicle attrition was replaced by a model which assumed that this rate changes more gradually with the size of the follicle store. This produced a distribution of predicted menopausal ages (based on an assumed threshold of 1000 follicles) which was closer to observed data. The fit further improved when the model was modified by having a threshold that varied across the population. Using such a stochastic threshold model for menopause, the number of fertile years remaining could be forecast with an acceptable margin of uncertainty if it ever becomes possible to estimate the size of the follicle store in vivo.

A mathematical model of follicle dynamics in the human ovary

A mathematical model has been developed to describe the rates of growth and death of follicles in human ovaries between 19 and 50 years of age. It was based on the numbers of follicles at three successive stages of development, which were obtained by counting follicles in histological sections of ovaries from 52 normal women. The model indicated that follicle dynamics were age dependent, with a transition at 38 years of age when the rate of follicle disappearance increased. The rates of follicle growth increased at successive stages but did not change with age. The annual egress from stage III (consisting of follicles with two or more granulosa cell layers) was affected by the declining numbers of small follicles, and corresponded to 31, nine and one follicles per day at 29-30, 39-40 and 49-50 years of age respectively. The rate of death at stage I (representing small, resting follicles) was the only parameter which varied significantly with age: no evidence of significant atresia was found for this stage in ovaries < or = 38 years old, but there was significant death above this age. As a consequence, only 40% of follicles leaving stage I reached stage III in older ovaries and just 1500 follicles in toto remained at 50 years of age from the 300,000 present at 19 years. This high death rate of small follicles appears to be responsible for advancing the timing of ovarian failure, and therefore of menopause, to midlife in our species.

Ovarian aging, follicular depletion, and steroidogenesis

The follicular population. Menopause occurs as a consequence of the continuous utilization of a fixed store of primordial follicles leading to almost total depletion at mid-life or sometimes earlier. The great majority of follicles that disappear are lost by atresia rather than by ovulation, and the rate of loss accelerates in the last decade of menstrual life. The numbers of growing follicles at a given age are correlated with those of the primordial stages, but there are always more being recruited than required for a single ovulation each month. The extent to which a dwindling number is responsible for the character of cycles of the menopausal transition remains unclear. Ovarian secretion. While menstrual cycles remain regular, circulating concentrations of estradiol and progesterone are relatively independent of age. On the other hand, serum levels of inhibin are substantially lower in women approaching menopausal age, probably reflecting smaller numbers of growing follicles at the beginning of the cycle. Alleviation of negative feedback on the pituitary gland results in a greater output of follicle-stimulating hormone (FSH), but the effects of chronic superstimulation on the aging ovary are not known. Follicular aging. Aging of long-lived oocytes could affect the developmental potential of the follicle unit as well as compromising the chances of late pregnancy. Another important field of investigation is therefore to determine the balance of responsibility between cumulated damage to molecules by toxins, on the one hand, and the effects of physiological aging and such epiphenomena as the changing hormonal or paracrine environments, on the other.

A structured compartmental model for drug kinetics

A compartmental model with a structure that describes drug kinetics by incorporating the ideas of diffusion and gamma distributed clearance times is proposed. The equations describing this model may be solved by elementary numerical techniques, and the model is shown to fit a data set describing renal gentamicin concentrations, better than a simple power-function model.

Diffusion approximations for stochastic compartmental models

A diffusion approximation is developed for one-compartment systems with nonlinear elimination rates. Both impulsive input and continuous infusion are considered. Explicit expressions for the mean and autocovariance functions of the contents of the compartment as time elapses are given.

Accelerated disappearance of ovarian follicles in mid-life: implications for forecasting menopause

Menopause is triggered by the number of ovarian follicles falling below a threshold number and is irreversible because oogonial stem cells disappear after birth. Since it is the result of programmed disappearance of a limited store of follicles, menopause can be predicted using mathematical models based on total follicle counts at different ages. Our model shows follicle numbers decline bi-exponentially rather than as a simple exponential function of age, as had been assumed, with a first exponential rate parameter of -0.097 and a second of -0.237. The change occurred when numbers had fallen to the critical figure of 25,000 at age 37.5 years. The unexpectedly faster rate of ovarian ageing afterwards lowers the follicle population to 1000 at approximately 51 years, and was adopted as the menopausal threshold because it corresponds to the median age of menopause in the general population. Had the earlier rate persisted menopause would not be expected until 71 years. The impact of step reductions of follicle numbers on the prospective span of menstrual life was predicted by the model. A reduction by 50% before age 30 years resulted in the threshold being reached at 44 years and 0.6 year later for every subsequent year until age 37.5 years after which it is reached at 48 years. A reduction of 90% in childhood before age 14 years could result in menopause as early as 27 years, with increments of 0.6 year per year afterwards until after 37.5 years when it is expected at age 41 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of exogenous progesterone on ovarian follicular dynamics and function in mice

Raising progesterone concentrations in young adult mice by subcutaneous implants resulted in ovulation being blocked and the cessation of oestrous cycles. The effect of this treatment on the numbers and dynamics of preantral follicles during 36 days of treatment was studied using a compartmental model to analyse differential follicle counts. Changes in growth and/or death rates were detected at all stages of follicular development. An increased rate of growth through preantral stages was predicted in the treatment group when compared with the controls, but most of these follicles did not reach the antral stage of development as an increased death rate was observed at large preantral stages (stage IV). Antral follicles were formed in the treatment group, but all succumbed to atresia. Increased atresia in the antral population of follicles in the treatment group was observed directly.

Ovarian cyclicity and follicular recruitment in unilaterally ovariectomized mice

Halving the numbers of follicles in young adult mice by unilateral ovariectomy resulted in compensatory Graafian follicle growth with a reduction by about 25% of the expected number of oestrous cycles. The impact of the operation on the numbers and dynamics of preantral follicles during the first 2 months after ovariectomy was studied using a compartmental mathematical model to analyse differential follicle counts. There were changes in growth and/or death rates at all stages of follicle development, and the patterns emerging were time-dependent. The rate of follicle survival from the pool of unilaminar stages was paradoxically reduced, but those forming two granulosa cell layers continued to develop towards Graafian size. As the frequency of follicle death declined, the numbers of healthy large preantral and antral stages in unpaired ovaries rose to approach those in pairs of age-matched control ovaries, suggesting that follicles otherwise undergoing atresia were being rescued. In the long-term, follicle dynamics after unilateral ovariectomy at young ages did not appear to compromise fecundity seriously.