Studies on the biosynthesis of collagen. I. The growth of fowl osteoblasts and the formation of collagen in tissue culture

1. A tissue culture method was devised in which suspensions of osteoblasts, obtained directly from frontal bones of fowl embryos, were grown in a fluid, fibrin-free medium. 2. Maximum growth of the tissue, as measured by dry weight, with the formation of collagen protein, based on the estimation of hydroxyproline, was obtained in periods of up to 6 days. 3. Appreciable amounts of protein-bound hydroxyproline were formed during the first 24 hour growth period, but electron microscopy of portions of the same cultures failed to demonstrate the presence of any typical collagen fibrils. 4. The subsequent formation of many characteristic collagen fibrils was not associated with a significant rise in the mean hydroxyproline content of the tissue. 5. The cytoplasmic granules of the osteoblasts stained intensely with the P.A.S. technique when the collagen fibrils were being formed. 6. It is suggested that collagen-forming cells synthesise and secrete a hydroxyproline-rich precursor of protein or large peptide nature, which subsequently becomes directly transformed into typical collagen fibrils.     

Evaluating Detection Probabilities for American Marten in the Black Hills,South Dakota

ABSTRACT Assessing the effectiveness of monitoring techniques designed to determine presence of forest carnivores, such as American marten (Martes Americana), is crucial for validation of survey results. Although comparisons between techniques have been made, little attention has been paid to the issue of detection probabilities (p). Thus, the underlying assumption has been that detection probabilities equal 1.0. We used Presence-Absence data obtained from a track-plate survey in conjunction with results from a saturation-trapping study to derive detection probabilities when marten occurred at high (>2 marten/10.2 km²) and low (≤1 marten/10.2 km²) densities within 8 10.2-km² quadrats. Estimated probability of detecting marten in high-density quadrats was p = 0.952 (SE = 0.047), whereas the detection probability for low-density quadrats was considerably lower (p = 0.333, SE = 0.136). Our results indicated that failure to account for imperfect detection could lead to an underestimation of marten presence in 15–52% of low-density quadrats in the Black Hills, South Dakota, USA. We recommend that repeated site-survey data be analyzed to assess detection probabilities when documenting carnivore survey results.     

Habitat Use of Sympatric Rattlesnake Species Within the Gulf Coastal Plain

Abstract: The eastern diamondback rattlesnake (Crotalus adamanteus) and timber rattlesnake (Crotalus horridus) are sympatric throughout most of southern Georgia, USA. We used rattlesnake sightings to quantify and compare habitat use by these 2 species in the Gulf Coastal Plain. At the largest scale examined, univariate statistics and logistic regression models indicated that eastern diamondback rattlesnakes were associated with roads but not with any of the specific habitat types we examined. In contrast, timber rattlesnakes were closely associated with hardwood habitat and riverine systems but not with roads and edges. To effectively conserve and manage both species in the Southeast, a habitat matrix of large intact patches of both hardwood and pine (Pinus spp.) forest may be necessary.     

Identifying Rattus species using mitochondrial DNA

In recent years, research has shown that geographical variation in mitochondrial DNA of commensal rats provides a strong signal of human dispersal and migration. However, interpretation of genetic variation is complicated by the presence of multiple species of Rattus especially in Island Southeast Asia, by the occurrence of some of these Rattus sp. as subfossils in archaeological and natural sites, and by the difficulty of osteological identification of these remains. Amplification of DNA from ancient sources usually yields only small fragments (～200 bp). We assessed whether we could identify Rattus sp. reliably with DNA barcoding using cytochrome oxidase I (COI) sequences, or tree‐based methods using D‐loop, cytochrome b and COI sequences. Species forming well‐differentiated clades in a molecular phylogeny were accurately identified by both methods, even when we used short DNA fragments. Identification was less accurate for paraphyletic and polyphyletic species. We suggest that taxonomic revisions that recognize cryptic or polytypic species will lead to even greater accuracy of DNA‐based identification methods.     

Habitat change and woodland birds in Britain: implications for management and future research

There is increasing evidence that changes in habitat structure in the form of reduced understorey and loss of open habitats, both probably a result of increases in shading and deer browsing, may be responsible for causing recent changes in the composition of breeding bird communities in many lowland British woods and forests. In contrast, management of upland coniferous forests may prevent the attainment of mature and old-growth structures which would benefit community development in these new ecosystems. We suggest that the key challenge for woodland conservation policy is to create larger areas of both young-growth and old-growth habitat. These objectives need not necessarily conflict with each other, or with other multipurpose forestry objectives, provided that they inform strategic plans and are targeted at appropriate locations and scales. In the lowlands, the current large stock of middle-aged, often unmanaged and species-poor woodland provides an opportunity to restore or create new woodland habitats of high biodiversity value. The development of woodfuel markets may effectively increase the amount of young-growth but it is unclear exactly what habitat structures might be created. In the uplands, allowing more natural development of native woodland in mosaics with other habitats may provide opportunities for both old- and young-growth species. For the foreseeable future, deer impacts will continue to be widespread and probably increasingly severe in many areas. In view of the uncertainty about the implications of climate change for woodland ecosystems, a strong case can be made for attempting to buffer valued wildlife communities against damaging effects by creating and maintaining high structural diversity at a range of scales and increasing the area of woodland.