Changes in bone structure and metabolism during simulated weightlessness: Endocrine and dietary factors

The role of vitamin D, PTH and corticosterone in the skeletal alterations induced by simulated weightlessness was examined. The first objective was to determine if changes in the serum concentrations of Ca, P sub i, osteocalcin, 25-OH-D, 24,25(OH)2D or 1,25(OH)2D also occur following acute skeletal unloading. Animals were either suspended or pair fed for 2, 5, 7, 10, 12 and 15 days and the serum concentrations of Ca, P sub i, osteocalcin and the vitamin D metabolites measured. Bone histology was examined at day 5 after suspension. Acute skeletal unloading produced a transient hypercalcemia, a significant fall in serum osteocalcin and serum 1,25(OH)2D, a slight rise in serum 24,25(OH)2D, but did not affect the serum concentrations of P sub i or 25-OH-D. At the nadir in serum 1,25(OH)2D serum osteocalcin was reduced by 22%, osteoblast surface by 32% and longitudinal bone growth by 21%

Phylogenetic relationships and distribution of the enigmatic semislug Aillya (Gastropoda: Aillyidae)

Aillya is an enigmatic African semislug, which was originally classified into the American Amphibuliminae (Orthalicoidea) by Odhner. Later, Baker established a separate family for this group and placed it together with the Succineidae and Athoracophoridae in the suborder Heterurethra. Minichev & Slavoshevskaja subdivided the Heterurethra even into three separate orders and introduced the name Aillyida for the Aillyidae. In contrast, Pilsbry, Solem, Tillier and van Mol supposed that Aillya is most closely related to some limacoid groups, i.e. Helicarionidae or Urocyclidae. We investigated the phylogenetic relationships of Aillya based on ITS2 and partial 5.8S and 28S rDNA sequences. Furthermore, we examined the morphology of type specimens and newly collected material to clarify the taxonomy and distribution

Refuge theory and distribution patterns of land snails in Ugandan rain forests

Refuge theory assumes that the recent distribution of organisms is influenced by past, usually Pleistocene, environmental changes resulting in the contraction of ranges into refugia or the expansion of ranges from refugia. Refugia are areas that are less affected by environmental changes than the surrounding regions so that organisms that become extinct elsewhere can survive there. The existence and importance of Pleistocene refugia in the northern continents that were heavily affected by Pleistocene glaciations is universally accepted. However, the existence and role of refugia in the tropics is still controversial. Often the existence of refugia is inferred only from the recent distribution of species richness. However, several other patterns in the distribution of organisms are expected to originate, if retraction to refugia and expansion from refugia are processes that affect recent biogeography. Such patterns are nestedness of ranges (Hultén, 1937; Daubenmire, 1975; Hausdorf & Hennig, 2003a), clustering of ranges (***; Hausdorf & Hennig, 2004), and Rapoport effects (***; Pfenninger, 2004; Hausdorf, 2006). It is a long standing question whether the recent distribution of organisms can be explained by current ecological conditions alone or whether it shows the imprint of historical events (Endler, 1982a,b; ***). It has been assumed that the Pleistocene climatic cycles have resulted in cycles of retraction of ranges of organisms to refuges and expansions (***). Such hypotheses have been tested mainly for temperate regions. A retraction of biota into refugia and subsequent range expansions from such refugia will result is specific patterns in distribution data. Such processes should result in: 1. A decrease of species richness with increasing distance from the refuge; 2. Nestedness; that is the biota in regions more distant from the refuge will be subsets of the biota more closer to the refuge; 3. A Rapoport effect; that is the average range extension of the species belonging to a regional biota will increase with increasing distance from the refuge; 4. Clustering of ranges (biotic elements

The role of 1,25-dihydroxyvitamin D in the inhibition of bone formation induced by skeletal unloading

Skeletal unloading results in osteopenia. To examine the involvement of vitamin D in this process, the rear limbs of growing rats were unloaded and alterations in bone calcium and bone histology were related to changes in serum calcium (Ca), inorganic phosphorus (P sub i), 25-hydroxyvitamin D (25-OH-D), 24,25-dihydroxyvitamin D (24,25(OH)2D and 1,25-dihydroxyvitamin D (1,25(OH)2D. Acute skeletal unloading induced a transitory inhibition of Ca accumulation in unloaded bones. This was accompanied by a transitory rise in serum Ca, a 21% decrease in longitudinal bone growth (P 0.01), a 32% decrease in bone surface lined with osteoblasts (P .05), no change in bone surface lined with osteoclasts and a decrease in circulating (1,25(OH)2D. No significant changes in the serum concentrations of P sub i, 25-OH-D or 24,25(OH)2D were observed. After 2 weeks of unloading, bone Ca stabilized at approximately 70% of control and serum Ca and 1,25(OH)2D returned to control values. Maintenance of a constant serum 1,25(OH)2D concentration by chronic infusion of 1,25(OH)2D (Alza osmotic minipump) throughout the study period did not prevent the bone changes induced by acute unloading. These results suggest that acute skeletal unloading in the growing rat produces a transitory inhibition of bone formation which in turn produces a transitory hypercalcemia

Issues in modern bone histomorphometry

This review reports on proceedings of a bone histomorphometry session conducted at the Fortieth International IBMS Sun Valley Skeletal Tissue Biology Workshop held on August 1, 2010. The session was prompted by recent technical problems encountered in conducting histomorphometry on bone biopsies from humans and animals treated with anti-remodeling agents such as bisphosphonates and RANKL antibodies. These agents reduce remodeling substantially, and thus cause problems in calculating bone remodeling dynamics using in vivo fluorochrome labeling. The tissue specimens often contain few or no fluorochrome labels, and thus create statistical and other problems in analyzing variables such as mineral apposition rates, mineralizing surface and bone formation rates. The conference attendees discussed these problems and their resolutions, and the proceedings reported here summarize their discussions and recommendations

A Method for Evaluating the Cumulative Impact of Ground-Based Logging Systems on Soils

A method for determining the Effective Ground Pressure (EGP) of tracked or wheeled logging machines that can be directly and unambiguously related to their impact on soils is described. When several machines operate together in a logging system, the methodology allows their individual EGP's to be combined to derive a System Effective Ground Pressure (SEGP), which measures the impact of the system as a whole. The methodology has been applied to determine the relative impact of logging systems and influence the choice of machine running gear. Given also the temporal variability in the bearing capacity of soils, it has also been applied to forecasting the minimum level of disruption to operations on flat ground arising from limitations placed on soil disturbance. These applications have led to increased efficiency of operations through a reduction in wood stockpiling during wet weather. The method is sufficiently simplistic at the core, that contractors with the aid of appropriate charts have evaluated the relative impact of machines and systems on soils themselves

Factors driving Arabian gazelles (Gazella arabica) in Israel to extinction: time series analysis of population size and juvenile survival in an unexploited population

Wild populations of Arabian gazelles (Gazella arabica) were once common on the Arabian Peninsula, but today disappeared from large parts of their former range. In Israel only a small population of currently 30 individuals survived, although it was—and still is—well protected from illegal hunting and habitat destruction. In our study we aimed to identify the factors influencing the population growth of G. arabica in Israel over the last two decades (1995–2017). We tested the impact of five environmental variables including annual mean maximum temperature, rainfall, the availability of two major food plants, competition with sympatric dorcas gazelle (G. dorcas) and predation (mainly by wolves) on two dependent variables relating to population viability (population size, percentage fawn survival) using a retrospective time series analysis. After testing for autocorrelations, two generalized least squares (GLS) models with autocorrelations at 3 and 6 years [GLS-AR(3, 6)] were identified as the best models to explain environmental effects on populations size. Wolf encounter rate had a significant negative effect on G. arabica population size, while G. dorcas population size had a significant positive effect, suggesting that wolf predation shapes the population size of both gazelle species. For percentage fawn survival, model residuals did not reveal any significant autocorrelation and the best fit GLS-AR(0) model retained only wolf encounter rate and mean annual maximal temperature as significant predictors. This result suggests a strong impact of wolf predation and increasing temperatures on the fawn survival of Arabian gazelles. Changed rainfall patterns, food availability and competition between gazelle species had no impact on fawn survival

The conservation history of Arabian gazelles (Gazella arabica) in Israel — do fifty-five years monitoring help todefine future incentives

We aimed to review the population development and conservation history of Arabian gazelles (Gazella arabica acaciae) in Israel, to summarise conservation-related research and to provide future recommendations. 1. We researched published online material as well as files and archives of the Israel Nature and Park Authority, compiling old documents, field notes, numerous unpublished reports and photographs. 2. The population development-since monitoring started in 1964 is viewed in a historical context. The conservation history was critically revised and screened for the most eminent threats, including low fawn survival, high predation pressure, low genetic diversity (inbreeding), competition with dorcas gazelles (Gazella dorcas) and climate change. 3. We describe what conservation actions were implemented over a period of 30 years, the success and drawbacks of these measures, and what research projects were carried out to facilitate conservation. 4. Based on those results, we aimed to give future recommendations, delineating scenarios that might be useful to reverse the population decline, such as captive breeding and translocations, out-breeding, irrigation, water and food supply, predator control through fencing or culling and parasite surveillance. 5. Finally, we discussed the proposed capitulation, allowing the population to go extinct in the face of further emerging threats like climate change or disease outbreaks. We emphasise the importance of this population for the survival of the species in general, but also for the functional diversity of the hyper-arid desert ecosystem in the southern Negev

Early and late fawn mortality in a remnant population of Arabian gazelles (Gazella arabica)

The Arabian gazelle (Gazella arabica) population in Israel has experienced a turbulent conservation history and repeatedly faced local extinction. Low fawn survival was considered the main cause for the constant decline. In our study, we analyzed instantaneous fawn mortality rates, using a binomial coding at three different developmental stages, i.e., mortality rates to 3 months after parturition (weaning age), to 5 months after parturition (male fawns leave their mothers), and to the age of reproductive maturity, i.e., recruitment (12 months). We used a dataset obtained from 20 individually discernible mothers and their fawns (49 females and 48 males) born between June 2006 and September 2019. To explore causes for the fawn mortality rates, parental- (age of the mother at parturition) and offspring-related attributes (offspring sex), year of birth, together with one weather variable (mean monthly maximum temperature) were included as independent variables into three independent mixed effects cox regression models. Out of 97 fawns, 92 survived to weaning age, 73 to the age of 5 months and only 7 to the age of reproductive maturity. Temperature had significant effects on instantaneous fawn mortality rates, suggesting that low temperatures were detrimental to the survival of fawns after weaning (4–5 months) and male dispersal age (6–12 months). Male offspring encountered a higher instantaneous mortality rate than female offspring at the age of 6–12 months. Moreover, fawns from less experienced mother (young age at parturition) experienced higher mortality. Our results were in line with previous studies on fawn mortality observed in other desert dwelling ungulates

Bone Degeneration and Recovery after Early and Late Bisphosphonate Treatment of Ovariectomized Wistar Rats Assessed by In Vivo Micro-Computed Tomography

Bisphosphonates are antiresorptive drugs commonly used to treat osteoporosis. It is not clear, however, what the influence of the time point of treatment is. Recently developed in vivo micro-computed tomographic (CT) scanners offer the possibility to study such effects on bone microstructure in rats. The aim of this study was to determine the influence of early and late zoledronic acid treatment on bone in ovariectomized rats, using in vivo micro-CT. Twenty-nine female Wistar rats were divided into the following groups: ovariectomy (OVX, n = 5), OVX and zoledronic acid (ZOL) at week 0 (n = 8), OVX and ZOL at week 8 (n = 7), and sham (n = 9). CT scans were made of the proximal tibia at weeks 0, 2, 4, 8, 12, and 16; and bone structural parameters were determined in the metaphysis. Two fluorescent labels were administered to calculate dynamic histomorphometric parameters. At week 16, all groups were significantly different from each other in bone volume fraction (BV/TV), connectivity density, and trabecular number (Tb.N), except for the early ZOL and control groups which were not significantly different for any structural parameter. After ZOL treatment at week 8, BV/TV, structure model index, Tb.N, and trabecular thickness significantly improved in the late ZOL group. The OVX and ZOL groups showed, respectively, higher and lower bone formation rates than the control group. Early ZOL treatment inhibited all bone microstructural changes seen after OVX. Late ZOL treatment significantly improved bone microstructure, although the structure did not recover to original levels. Early ZOL treatment resulted in a significantly better microstructure than late treatment. However, late treatment was still significantly better than no treatment