How mechanistic in silico modelling can improve our understanding of TB disease and treatment.

TB is one of the top 10 causes of death worldwide and the leading cause of death from a single infectious agent. Decreasing the length of time for TB treatment is an important step towards the goal of reducing mortality. Mechanistic in silico modelling can provide us with the tools to explore gaps in our knowledge, with the opportunity to model the complicated within-host dynamics of the infection, and simulate new treatment strategies. Significant insight has been gained using this form of modelling when applied to other diseases - much can be learned in infection research from these advances.

Clinical parameters of ovarian hyperstimulation syndrome following different hormonal triggers of oocyte maturation in IVF treatment.

OBJECTIVE: Ovarian hyperstimulation syndrome (OHSS) is a serious iatrogenic condition, predominantly related to the hormone used to induce oocyte maturation during IVF treatment. Kisspeptin is a hypothalamic neuropeptide that has recently been demonstrated to safely trigger final oocyte maturation during IVF treatment even in women at high risk of OHSS. However, to date, the safety of kisspeptin has not been compared to current hormonal triggers of oocyte maturation. DESIGN: We conducted a retrospective single-centre cohort study investigating symptoms and clinical parameters of early OHSS in women at high risk of OHSS (antral follicle count or total number of follicles on day of trigger ≥23) triggered with human chorionic gonadotrophin (hCG) (n = 40), GnRH agonist (GnRHa; n = 99) or kisspeptin (n = 122) at Hammersmith Hospital IVF unit, London, UK (2013-2016). RESULTS: Clinical Parameters of OHSS: Median ovarian volume was larger following hCG (138 ml) than GnRHa (73 ml; P < .0001), and in turn kisspeptin (44 ml; P < .0001). Median ovarian volume remained enlarged 20-fold following hCG, 8-fold following GnRHa and 5-fold following kisspeptin compared to prestimulation ovarian volumes. Mean (±SD) ascitic volumes were lesser following GnRHa (9 ± 44 ml) and kisspeptin (5 ± 8 ml) than hCG (62 ± 84 ml; P < .0001). Symptoms of OHSS were most frequent following hCG and least frequent following kisspeptin. Diagnosis of OHSS: The odds ratio for OHSS diagnosis was 33.6 (CI 12.6-89.5) following hCG and 3.6 (CI 1.8-7.1) following GnRHa, when compared to kisspeptin. CONCLUSION: Triggering oocyte maturation by inducing endogenous gonadotrophin release is preferable to the use of exogenous hCG in women at high risk of OHSS.

Non-growing follicle density is increased following adriamycin, bleomycin, vinblastine and dacarbazine (ABVD) chemotherapy in the adult human ovary.

STUDY QUESTION: Do the chemotherapeutic regimens of ABVD (adriamycin, bleomycin, vinblastine and dacarbazine) or OEPA-COPDAC (combined vincristine, etoposide, prednisone, doxorubicin (OEPA) and cyclophosphamide, vincristine, prednisone, dacarbazine (COPDAC)) used to treat Hodgkin lymphoma (HL), affect the density, morphology and in vitro developmental potential of human ovarian follicles? SUMMARY ANSWER: Ovarian tissue from women treated with ABVD contained a higher density of non-growing follicles (NGFs) per cubic millimetre and increased numbers of multiovular follicles but showed reduced in vitro growth compared with patients with lymphoma who had not received chemotherapy, patients treated with OEPA-COPDAC, age-matched healthy women and age-related model-predicted values. WHAT IS KNOWN ALREADY: Chemotherapy regimens can cause a loss of follicles within the ovary, which depends on the drugs given. Early stage HL is commonly treated by ABVD, a non-alkylating regimen that apparently has ovarian sparing qualities; thus it is important to investigate the histological appearance and distribution of follicles within ABVD-treated ovarian tissue. STUDY DESIGN, SIZE, DURATION: Thirteen ovarian biopsies were obtained from HL patients (six adolescents and seven adults) and one biopsy from a non-HL patient. Two HL patients and the non-HL patient had received no treatment prior to biopsy collection. The remaining 11 HL patients received one of two regimens: ABVD or OEPA-COPDAC. Tissue was analysed histologically and compared to biopsies from healthy women, and in a subgroup of patients, tissue was cultured for 6 days in vitro. PARTICIPANTS/MATERIALS, SETTING, METHODS: Ovarian biopsies were obtained from patients undergoing ovarian cryopreservation for fertility preservation and from healthy women at the time of Caesarian section ('obstetric tissue'). Follicle number and maturity were evaluated in sections of ovarian cortical tissue, and compared to an age-related model of mean follicle density and to age-matched contemporaneous biopsies. The developmental potential of follicles was investigated after 6 days of tissue culture. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 6877 follicles were analysed. ABVD-treated tissue contained a higher density of NGFs per cubic millimetre (230 ± 17) (mean ± SEM) than untreated (110 ± 54), OEPA-COPDAC-treated (50 ± 27) and obstetric (20 ± 4) tissue (P < 0.01), with follicle density 9-21 SD higher than predicted by an age-related model. Biovular and binucleated NGFs occurred frequently in ABVD-treated and in adolescent-untreated tissue but were not observed in OEPA-COPDAC-treated or obstetric tissue, although OEPA-COPDAC-treated tissue contained a high proportion of morphologically abnormal oocytes (52% versus 23% in untreated, 22% in ABVD-treated and 25% in obstetric tissue; P < 0.001). Activation of follicle growth in vitro occurred in all groups, but in ABVD-treated samples there was very limited development to the secondary stage, whereas in untreated samples from lymphoma patients growth was similar to that observed in obstetric tissue (untreated; P < 0.01 versus ABVD-treated, NS versus obstetric). LARGE SCALE DATA: N/A LIMITATIONS, REASONS FOR CAUTION: Although a large number of follicles were analysed, these data were derived from a small number of biopsies. The mechanisms underpinning these observations have yet to be determined and it is unclear how they relate to future fertility. WIDER IMPLICATIONS OF THE FINDINGS: This study confirms that the number of NGFs is not depleted following ABVD treatment, consistent with clinical data that female fertility is preserved. Our findings demonstrate that immature follicle density can increase as well as decrease following at least one chemotherapy treatment. This is the first report of morphological and follicle developmental similarities between ABVD-treated tissue and the immature human ovary. Further experiments will investigate the basis for the marked increase in follicle density in ABVD-treated tissue. STUDY FUNDING/COMPETING INTERESTS: Funded by UK Medical Research Council Grants G0901839 and MR/L00299X/1. The authors have no competing interests.

An externally validated age-related model of mean follicle density in the cortex of the human ovary.

PURPOSE: The ability to accurately estimate a woman's ovarian reserve by non-invasive means is the goal of ovarian reserve prediction. It is not known whether a correlation exists between model-predicted estimates of ovarian reserve and data generated by direct histological analysis of ovarian tissue. The aim of this study was to compare mean non-growing follicle density values obtained from analysis of ovarian cortical tissue samples against ovarian volume models. METHODS: Non-growing follicle density values were obtained from 13 ovarian cortical biopsies (16-37 years). A mean non-growing follicle density was calculated for each patient by counting all follicles in a given volume of biopsied ovarian cortex. These values were compared to age-matched model generated densities (adjusted to take into consideration the proportion of ovary that is cortex) and the correlation between data sets tested. RESULTS: Non-growing density values obtained from fresh biopsied ovarian cortical samples closely matched model generated data with low mean difference, tight agreement limits and no proportional error between the observed and predicted results. CONCLUSION: These findings validate the use of the adjusted population and ovarian volume models, to accurately predict mean follicle density in the ovarian cortex of healthy adult women.

The Relationship Between Variation in Size of the Primordial Follicle Pool and Age at Natural Menopause.

CONTEXT: Menopause has been hypothesized to occur when the nongrowing follicle (NGF) number falls below a critical threshold. Age at natural menopause can be predicted using NGF numbers and this threshold. These predictions support the use of ovarian reserve tests, reflective of the ovarian follicle pool, in menopause forecasting. OBJECTIVE: The objective of the study was to investigate the hypothesis that age-specific NGF numbers reflect age at natural menopause. DESIGN AND SETTING: Histologically derived NGF numbers obtained from published literature (n = 218) and distribution of menopausal ages derived from the population-based Prospect-European Prospective Investigation into Cancer and Nutrition (Prospect-EPIC) cohort (n = 4037) were combined. PARTICIPANTS: NGF data were from single ovaries that had been obtained postnatally for various reasons, such as elective surgery or autopsy. From the Prospect-EPIC cohort, women aged 58 years and older with a known age at natural menopause were selected. INTERVENTIONS: There were no interventions. MAIN OUTCOME MEASURE(S): Conformity between observed age at menopause in the Prospect-EPIC cohort and NGF-predicted age at menopause from a model for age-related NGF decline constructed using a robust regression analysis. A critical threshold for NGF number was estimated by comparing the probability distribution of the age at which the NGF numbers fall below this threshold with the observed distribution of age at natural menopause from the Prospect-EPIC cohort. RESULTS: The distributions of observed age at natural menopause and predicted age at natural menopause showed close conformity. CONCLUSION: The close conformity observed between NGF-predicted and actual age at natural menopause supports the hypothesis that that the size of the primordial follicle pool is an important determinant for the length of the individual ovarian life span and supports the concept of menopause prediction using ovarian reserve tests, such as anti-Müllerian hormone and antral follicle count, as derivatives of the true ovarian reserve.

Which follicles make the most anti-Mullerian hormone in humans? Evidence for an abrupt decline in AMH production at the time of follicle selection.

Anti-Müllerian hormone (AMH) is exclusively produced by granulosa cells (GC) of the developing pre-antral and antral follicles, and AMH is increasingly used to assess ovarian function. It is unclear which size follicles make the most AMH (total content) and are the main contributors to circulating AMH concentrations. To determine AMH gene expression in GC (q-RT-PCR) and follicular AMH production (Elisa and RIA) in relation to follicular development, 87 follicles (3-13 mm diameter) including both GC and the corresponding follicular fluid (FF) were collected in connection with fertility preservation of human ovaries. Further, follicle number and diameter, graded in 1 mm increments, were determined by 3D ultrasound in 113 women in their natural menstrual cycle to determine follicle number and diameter in relation to circulating AMH levels. This study demonstrates for the first time a positive association between AMH gene expression in human and both total follicular fluid AMH (P < 0.02) and follicular fluid AMH concentration (P < 0.01). AMH gene expression and total AMH protein increased until a follicular diameter of 8 mm, after which a sharp decline occurred. In vivo modelling confirmed that 5-8 mm follicles make the greatest contribution to serum AMH, estimated for the first time in human to be 60% of the circulating concentration. Significant positive associations between gene expression of AMH and FSHR, AR and AMHR2 expression (P < 0.00001 for all three) and significant negative association between follicular fluid AMH concentration and CYP19a1 expression were found (P < 0.0001). Both AMH gene expression (P < 0.02) and follicular fluid concentration of AMH (P < 0.00001) correlated negatively with estradiol concentration.

Ovarian cryopreservation: experimental or established and a cure for the menopause?

Long-term (>7 years) duration of function of ovarian cortical tissue grafts in three patients who have had several successful pregnancies is encouraging and requires us to carefully examine the risk benefit analysis of this technique for our future patients. However, the success rate for ovarian cryopreservation is unclear as the denominator (the number of women in whom frozen-thawed ovarian tissue has been re-implanted) is unknown. There still remain many unknowns and much more research is required before ovarian transplantation can be considered standard practice. The ability of ovarian cryopreservation to preserve fertility for some young survivors of cancer is proven, but the indications for which patients should be offered this exciting new technology are not yet established.

Data-driven assessment of the human ovarian reserve.

Human ovarian physiology is still poorly understood, with the factors and mechanisms that control initiation of follicular recruitment and loss remaining particularly unclear. Conventional hypothesis-led studies provide new data, results and insights, but datasets from individual studies are often small, allowing only limited interpretation. Great power is afforded by the aggregation of data from multiple studies into single datasets. In this paper, we describe how modern computational analysis of these datasets provides important new insights into ovarian function and has generated hypotheses that are testable in the laboratory. Specifically, we can hypothesize that age is the most important factor for variations in individual ovarian non-growing follicle (NGF) populations, that anti-Müllerian hormone (AMH) levels generally rise and fall in childhood years before peaking in the mid-twenties, and that there are strong correlations between AMH levels and both NGF populations and rates of recruitment towards maturation, for age ranges before and after peak AMH levels.

Individual ovarian volumes obtained from 2-dimensional and 3-dimensional ultrasound lack precision.

Measuring ovarian volume has been suggested as a possible screening test to assess a woman's ovarian reserve. For such a screening tool to be clinically useful, knowledge of its precision and reproducibility is essential. Recent advances in ultrasound scanning techniques allow the measurement of volumes in three dimensions rather than the traditional estimation from two dimensions. Transvaginal 2-dimensional (2D) and 3-dimensional (3D) ultrasound examinations were performed on 49 women attending a tertiary centre for investigation or treatment for subfertility between January and May 2006. Two observers calculated ovarian volume using both 2D (prolate ellipsoid formula) and 3D techniques [virtual organ computer-aided analysis (VOCAL)] with rotation steps of 30 degrees (3D-30). For the four comparisons (inter- and intra-observer; 2D and 3D-30) intraclass coefficients of 0.97 to 0.98, and standard errors ranging from 17% to 14% (for inter-observer 2D and intra-observer 3D, respectively) were obtained. The corresponding coefficients of repeatability ranged from 33% to 28%. These results suggest that measurement of transvaginal ovarian volumes using both 2D and 3D ultrasound is imprecise for individuals. The imprecision is greater for lower ovarian volumes, which may be important in clinical practice. The average of two or more measurements is likely to be more accurate than a single measurement.

The radiosensitivity of the human oocyte.

BACKGROUND: We determined the best model available for natural follicle decline in healthy women and used this to calculate the radiosensitivity of the human oocyte. METHODS: Ovarian failure was diagnosed in six patients with a median age of 13.2 years (range 12.5-16.0) who were treated with total body irradiation (14.4 Gy) at 11.5 years of age (4.9-15.1). We previously estimated the dose of radiation required to destroy 50% of the oocytes (LD(50)) to be <4 Gy. This estimate is an oversimplification, because decay represents an instantaneous rate of temporal change based upon the remaining population pool, expressed as a differential equation: dy/dx = -y[0.0595 + 3716/(11780 + y)], with initial value y(0) = 701 200. RESULTS: Solving the differential equation, we have estimated the number of follicles left after irradiation given as sol(51 - s + r), where r equals age at treatment, s equals age at diagnosis of ovarian failure, and 51 years is the average age of menopause. The surviving fraction of oocytes as a percentage is 100 times this value divided by sol(r). The mean surviving fraction for the six cases is 0.66%. We obtain a function, g(z), which decreases in value from 100% at zero dosage to mean value at dosage z = 14.4 Gy. We have g(z) = 10(mx+c), where c = log(10)100 = 2, and m = [log(10)(0.66) - c]/14.4. Solving g(z) = 50 gives an LD(50) of 1.99. CONCLUSIONS: Based on new data and a revised mathematical model of natural oocyte decline, we have determined the surviving fraction of oocytes following irradiation and estimate the LD(50) of the human oocyte to be <2 Gy.

Rural migration: what attracts new residents to non-metropolitan areas.

"This study uses the experience of three non-metropolitan counties in Pennsylvania to explore which community characteristics have the greatest influence on people's decisions to move to rural areas. Personal characteristics affected how in-migrants evaluated prospective rural residential locations. Higher income in-migrants placed a high priority on job opportunities, housing quality, a short commute to work, quality of schools, and low local taxes. Lower income in-migrants were more likely to value a location near family and friends. Ability to own a home, housing costs, and local taxes were also important."

Farm tractors, and the use of seat belts and roll-over protective structures.

Roll-over protective structures (ROPS) on farm tractors could significantly reduce the rate of fatal occupational injury on farms, but comparatively few tractors have them. Many of the policy discussions have focused on trying to identify the percentage of tractors that do not have ROPS, even though such a focus probably does not accurately represent effective protection by ROPS. This study investigates whether including differences in hours of usage, tractor activities, and seat belt use affects estimates of farm operators' protection by ROPS. In general, tractors used more hours a year were more likely to have ROPS. ROPS status also varied by tractor activity. When adjusting for seat belt use, effective ROPS protection is much less than when considering just ROPS status. Measures of the effective coverage of ROPS and policy responses should reflect these differences in hours, activities, and seat belt use.

The influence of insurance status and income on health care use among the nonmetropolitan elderly.

The objective of this research is to examine the influence of income and type of insurance coverage on the use of health services among the nonmetropolitan elderly. A model of health services utilization is used as the foundation for examining this issue with data from a telephone survey of a randomly selected sample of residents from four nonmetropolitan counties in Pennsylvania. Results indicated that those elders with Medicaid coverage were less likely to visit a doctor than respondents with private insurance or Medicare only, even after controlling for income and other relevant factors. Further, lower income respondents with Medicare were less likely to visit the dentist than those with private insurance (Medicare does not cover dental care). In contrast, neither income nor insurance predicted hospital use. As such, the health and dental care needs of many lower income nonmetropolitan elders may potentially be going unmet. In general, findings highlight the continued relevance of economic barriers to the use of such services among the nonmetropolitan elderly.

The agrarian myth and policy responses to farm safety.

Agriculture's status as one of the nation's most hazardous occupations has been an impetus for a reexamination of the federal role in agricultural safety and for various proposals to make farming safer. During the 1970s congressional debate and farm group testimony that led to agriculture's current exemption from the Occupational Safety and Health Administration's enforcement efforts, regulation foes made use of the "Agrarian Myth." The myth portrays farmers as the bedrock of democracy, suffering so that society may prosper and living a natural life away from the artificiality and evils of cities. Despite the inaccuracy of its images, the myth is a potent symbol in American culture, and its influence could arise again in current policy debates. This paper examines specific issues that may be obscured by the myth but that must be addressed in any agricultural safety policy debate. It then recommends that responses to agricultural safety be carefully considered and that value judgements about what the issues are, who would benefit, and who would bear the costs be explicitly discussed during debate.

Dairy barns and roll-over protection on farm tractors: work environment impacts on the adoption of roll-over protective structures.

A mailed survey of one group of dairy farmers supports the informal perception that roll-over protective structure (ROPS)-equipped tractors are considered unusable for in-barn tasks. This attitude must be addressed in order to achieve greater use of safety equipment.

Farm tractors and mandatory roll-over protection retrofits: potential costs of the policy in New York.

Tractor roll-overs are the leading cause of fatal farm accidents, accounting for more than one-fourth of all agriculturally related deaths. Most of these deaths could be prevented if the tractors were equipped with roll-over protective structures (ROPS). This study estimates the number of tractors in New York without ROPS, projects their retirement, and then estimates the number of lives which would be saved if ROPS were retrofitted on old tractors. The basic costs associated with mandating ROPS are calculated from these estimates. The minimum economic cost of mandating ROPS is $511,136 per life saved for the retrofits, and an additional $253,254 per life saved for every $1 million spent annually on enforcement. It is concluded that a policy mandating ROPS on all tractors would be expensive, but should be considered with particular attention to the need for and cost effectiveness of enforcement.