Tracking of bone mass from childhood to puberty: a 7-year follow-up. The CHAMPS study DK.

Bone mass in childhood is highly influenced by puberty. At the same age, bone mass was higher for pubertal than pre-pubertal children. A high level of tracking during 7 years from childhood through puberty was shown, indicating that early levels of bone mass may be important for later bone health. INTRODUCTION: Bone mass development in childhood varies by sex and age, but also by pubertal stage. The objectives of this study were to (1) describe bone mass development in childhood as it relates to pubertal onset and to (2) determine the degree of tracking from childhood to adolescence. METHODS: A longitudinal study with 7 years of follow-up was initiated in 2008 to include 831 children (407 boys) aged 8 to 17 years. Participants underwent whole body dual-energy X-ray absorptiometry (DXA) scanning, blood collection to quantify luteinizing hormone levels, and Tanner stage self-assessment three times during the 7-year follow-up. Total body less head bone mineral content, areal bone mineral density, and bone area were used to describe development in bone accrual and to examine tracking over 7 years. RESULTS: Bone mass in pubertal children is higher than that of pre-pubertal children at the same age. Analysing tracking with quintiles of bone mass Z-scores in 2008 and 2015 showed that more than 80% of participants remained in the same or neighbouring quintile over the study period. Tracking was confirmed by correlation coefficients between Z-scores at baseline and 7-year follow-up (range, 0.80-0.84). CONCLUSIONS: Bone mass is highly influenced by pubertal onset, and pubertal stage should be considered when examining children's bone health. Because bone mass indices track from childhood into puberty, children with low bone mass may be at risk of developing osteoporosis later in life.

Retinal vascular diameters in relation to physical activity in Danish children - The CHAMPS Eye Study.

Our objective was to determine associations between retinal vascular caliber and physical activity (PA) in a school-based child cohort. In a prospective study, we created a childhood cumulative average PA-index using objectively measured PA (accelerometry) assessed at four periods between 2009 and 2015. Cumulative exposure to PA intensities was estimated. Cross-sectional examinations on biomarkers, anthropometry, and ophthalmological data including retinal fundus photographs were performed in 2015. Semi-automated measurements of retinal vascular diameters were performed and summarized into central retinal arteriolar and venular equivalents (CRAE, CRVE). We included 307 participants. Mean age in 2015 was 15.4 years (0.7). The mean CRAE and CRVE were 156.5 µm (2.8) and 217.6 µm (7.7), respectively. After adjusting for age, gender, and axial length, more time in PA was independently related to thinner retinal venules (ß-coefficient = -1.25 µm/%, 95% confidence interval = -2.20, -0.30, P < .01). Sedentary time was associated with wider venules (P < .01). Furthermore, birthweight (ß-coefficient = 0.56 µm/%, 95% confidence interval = 0.18, 0.95, P < .01) was associated with CRVE. Blood pressure was associated with thinner retinal arterioles (ß-coefficient = -0.19 µm/mmHg, 95% confidence interval = -0.36, -0.01, P = .04). We concluded that children with higher PA in childhood had thinner retinal venular caliber. Our results suggest that PA during childhood positively impacts the retinal microcirculation and that retinal vascular analysis may be a possible assessment to detect microvascular impairments in children with an increased risk of future cardiovascular disease.

Development of a Simple Hydroponic Assay to Study Vertical and Horizontal Resistance of Soybean and Pathotypes of Phytophthora sojae.

Phytophthora root rot, caused by Phytophthora sojae, is one of the most damaging diseases of soybean and the introgression of Rps (Resistance to P. sojae) genes into elite soybean lines is arguably the best way to manage this disease. Current bioassays to phenotype the gene-for-gene relationship are hampered with respect to reproducibility and long-term stability of isolates, and do not accurately predict horizontal resistance individually. The aim of our study was to investigate a new way of phenotyping P. sojae isolates and vertical and horizontal resistance in soybean that relies on zoospores inoculated directly into a hydroponic system. Inoculation of P. sojae isolates against a set of eight differentials accurately and reproducibly identified pathotypes over a period of two years. When applied to test vertical resistance of soybean lines with known and unknown Rps genes, the bioassay relied on plant dry weight to correctly identify all genes. In addition, simultaneous inoculations of three P. sojae isolates, collectively carrying eight major virulence factors against 64 soybean lines with known and unknown levels of horizontal resistance, separated the plants into five distinct groups of root rot, allowing the discrimination of lines with various degrees of partial resistance. Based on those results, this bioassay offers several advantages in facilitating efforts in breeding soybean for P. sojae resistance and in identifying virulence factors in P. sojae.

Fragile sites in domestic animal chromosomes: molecular insights and challenges.

Fragile sites are intriguing cytogenetic phenomena that have been extensively investigated in human and laboratory animal chromosomes over the past 40 years, but domestic animal species have been studied sporadically. Interest in the field has been recently renewed as increasing numbers of fragile site regions are cloned and characterized at the molecular level. Despite much effort, mechanisms by which specific DNA sequence confers fragility to a chromosome region remain unclear. Recent advancements in sequencing and mapping of domestic animal genomes provide tools for molecular characterization of fragile sites in animal chromosomes. Future comparative efforts may contribute insight into both the mechanisms that underlie chromosome fragility, and forces that drive rearrangements observed throughout evolution, and somatic changes that can result in disease or impair fertility.

An extended nomenclature of the canine karyotype.

In contrast to many other animals, knowledge about the canine karyotype is quite sparse. This is due in part to the rather difficult canine karyotypic pattern. Except for the X and the Y chromosome, there are only acrocentric chromosomes, which appear to be quite small and difficult to identify unambiguously. In previous reports, schematic representations of the canine karyotype have been described. However, a nomenclature comparable to that of the human karyotype or the karyotypes of sheep, cattle, or goats does not yet exist for the dog. Based on high-resolution banding of metaphase chromosomes from canine fibroblasts, we propose an ideogram of the canine karyotype with 460 numbered bands and characteristic landmarks. In addition, the centromere positions of the canine chromosomes are determined by a combined GTG-banding/FISH approach, and the R- and G-banding patterns are compared.

Frequency of sister chromatid exchange and hematological effects in pesticide-exposed greenhouse sprayers.

OBJECTIVES: A cross-sectional study was conducted to investigate whether exposure to pesticides in greenhouses causes hemato- or genotoxic damage in sprayers. METHODS: The frequency of sister chromatid exchange (SCE) in cultured lymphocytes and the number of blood erythrocytes, leucocytes, and thrombocytes were studied among 134 greenhouse sprayers exposed to a complex mixture of almost 50 insecticides, fungicides, and growth regulators and among 157 referents. RESULTS: The hematological profiles did not differ between the exposed and unexposed groups. The SCE frequency was elevated in nonsmoking, but not in currently smoking sprayers when compared with the referents. There was a slight tendency towards an increased SCE frequency with decreasing degree of protection during pesticide applications. The frequency of pesticide applications, lifetime pesticide exposure, and in-season plasma-cholinesterase inhibition (as an estimate of current exposure to organophosphates and carbamates) did not influence the SCE frequency or any of the hematological parameters. CONCLUSIONS: The present results suggest a genotoxic effect from combined subtoxic occupational pesticide exposure, whereas no hematogenic effects could be observed at the current exposure level.

The high resolution RBG-banded karyotype of Oryctolagus cuniculus. Comparison between different classifications of landmarks and bands.

Representative high resolution RBG-banded haploid karyotypes of Oryctolagus cuniculus and corresponding idiograms at the 550 band stage are presented. Classification of landmarks and bands based on high resolution RBG- and GTG-banding are compared with the standard classification and a translation between the three systems presented.

Minibands and chromosome structure. A theory.

Bright and dark field microscopy were used to examine interphase nuclei and RBG-banded human chromosomes. In dark field microscopy both chromosomes and interphase chromatin appeared to be composed of similar independent structures alternating between bright and dull light intensity. The position, colour, and number of these structures may support the theory that the transition from interphase chromatin to metaphase chromosomes, takes place without any dramatic changes in local chromatin structure. Although the resolution power of bright and dark field microscopy prevent a direct proof for the miniband model, our observations in combination with other data may add further support to this particular model of chromosome organization.

Localization of fragile sites in the karyotype of Felis catus.

High resolution RBG-banding was induced by exposure of cat fibroblast cultures to a folate antagonist and BUdR. After band induction the chromosomes displayed frequent breaks and gaps. To determine whether the observed aberrations were randomly or non-randomly distributed, a total of 300 metaphases were screened for the presence of breaks, gaps, and deletions. Statistical analysis was performed according to Mariani (1989). The 525 band idiogram presented by Rønne et al. (1994) was used for the calculations, and to determine which bands were harbouring an aberration. Bands with seven or more aberrations were considered to harbour a fragile site (Fh7 < 0.01).

Localization of fragile sites in the karyotype of Sus scrofa domestica: present status.

Fragile sites were induced to expression in pig lymphocyte chromosomes by in vitro exposure to folate antagonists and BUdR-Hoechst 33258. Expressed fragility was localized according to the presented idiograms and compared with the location of known spontaneous translocations.

Localization of landmarks and bands in the karyotype of Felis catus.

Using 5-bromodeoxyuridine and Giemsa solution, representative high resolution RBG-banded haploid karyotypes of Felis catus and corresponding idiograms at the 525 band stage were established and the results are discussed.

Localization of landmarks and bands in the karotype of Sus scrofa domestica. Comparison between different classifications.

Representative RBG-banded chromosomes of Sus scrofa domestica and diagrammatic representation of the banding patterns at the 600 band stage are presented. Comparison between different classification systems has been performed. It is suggested that the data presented can be applied to gene mapping, localization of chromosome aberrations, comparative cytogenetics, and translation between different classification systems.

The RBG-banded karyotype of Oryctolagus cuniculus at the 550-band stage.

Representative haploid RBG-banded karyotypes of Oryctolagus cuniculus and diagrammatic representation of the banding patterns at the 550 band stage are presented.

Myelin deficiency in female rats due to a mutation in the PLP gene.

Myelin deficiency (md) in female rats due to a mutation in the X-linked proteolipid protein (PLP) gene is caused by X-chromosome monosomy. Cytogenetic analysis revealed a single X karyotype [41,X(md/0)]. An immunocytochemical, electron microscopic, and biochemical study was performed on male and female md rats. The central nervous system (CNS) of the female md rat [41,X(md/0)] revealed the same total lack of PLP as the CNS of the affected male littermate [42,XY(md/Y)]. Immunocytochemistry for myelin basic protein (MBP), myelin-associated glycoprotein (MAG), and 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNP) revealed "islands" of myelin sheath-like reaction product in both. Electron microscopy showed great paucity of compact myelin sheaths in 41,X(md/0) and 42,XY(md/Y). Reduced levels of MPB, MAG, and CNP were confirmed for both sexes but MAG and CNP were substantially higher in 41,X(md/0). Sexual differentiation of the brain may account for the observed differences since normal female reproductive organs are present in the md female rat.

Synchronization, banding and in situ hybridization. A short laboratory manual.

A variety of culture, synchronization, banding and in situ hybridization techniques have been published in connection with chromosome studies. The present manual summarizes and discusses the most widely used techniques with special emphasis on the methods published by Rønne and coworkers from 1984-1991.

Putative fragile sites in the horse karyotype.

After fluorouracil/5-bromodeoxyuridine synchronization and subsequent FPG-staining, the karyotype of 15 phenotypically normal horses displayed several breaks and gaps. Twelve bands 1q24, 4p12, 8q23, 11p12, 16q21, 17q21, 23q31, 23q32, Xp21, Xq22, Xq25 and Xq27 showed relatively frequent fragility. After thymidine/cytidine synchronization and subsequent GWL-banding the same horses display karyotypes without any fragility. Hence it is suggested that the above listed bands harbour folate and/or 5-bromodeoxyuridine sensitive fragile sites.