Is Avian Malaria Playing a Role in Native Bird Declines in New Zealand? Testing Hypotheses along an Elevational Gradient

The mosquito-borne disease avian malaria (Plasmodium spp.) has impacted both captive populations and wild individuals of native New Zealand bird species. However, whether or not it is a cause of concern to their wild populations is still unclear. In Hawaii, the disease has been a major factor in the population declines of some native forest bird species, often limiting their elevational distribution due to an inverse relationship between force of infection and elevation. While studies have investigated latitudinal patterns of infection in New Zealand, elevational patterns are unexplored. To address this, a survey was conducted in Nelson Lakes National Park, a site experiencing native bird declines in which disease has been suggested as playing a role, to investigate whether there is a similar inverse relationship in New Zealand. Results from blood samples (n = 436) collected over three seasons across a broad elevational range (650–1400 m) support there being such a relationship. In addition, an overall higher prevalence in non-native (14.1%) versus native birds (1.7%) may indicate differential impacts on these two groups, while particularly high prevalence in non-native Turdus spp. supports previous suggestions that they are key reservoir hosts for the disease. Overall, these findings add weight to the hypothesis that avian malaria is playing a role in ongoing declines of native New Zealand birds.     

A developmental study of murine epidermal Langerhans cells

Prospective skin prior to invasion by neural crest cells was dissected from 10.5-day mouse embryos and cultivated in chick embryo hosts. The graft tissue was prepared for the demonstration of both mouse and chick cells, pigment cells, and Langerhans cells. Chick cells were not found in the graft mouse epidermis; however, ATPase-positive and osmium iodide-positive cells were present. Electron microscopic examination revealed that, in younger grafts, only indeterminate cells could be found among the keratinocytes. In older grafts, both indeterminate cells and Langerhans cells with granules were seen. The evidence affirms that epidermal Langerhans cells are not related to pigment cells.Based on the developmental nature of Birbeck (Langerhans) granules from the cytomembrane, it is proposed that the granule no longer be considered as specific to and characteristic of epidermal Langerhans cells. Rather, Langerhans cells should be defined as ATPase-positive, desmosome-free cells within stratified squamous, potentially keratinizing, epithelia. Thus epidermal, ATPase-positive indeterminate cells and such cells with Birbeck granules both should be considered as components of the Langerhans cell series.Normal chick skin does not show ATPase-positive cells. However, when 10.5-day mouse embryo ectoderm was inserted under the ectoderm of chick embryos, the resulting chimeric epidermis possessed ATPase-positive cells. It is proposed that epidermal Langerhans cells are of ectodermal origin.     

The importance of proline on long-term hepatocyte function in a collagen gel sandwich configuration: regulation of protein secretion

A serum-free culture system for primary hepatocytes which maintains stabel high-level hepatocyte function for prolonged periods in culture has been developed. Isolated rat primary hepatocytes were cultured in serum-free media between two layer of gelled collagen in a sandwich configuration which reinstates the cellular polarity necessary for long-term function in vitro. Thsee serum-free hepatocyte cultures maintained near physiological rates of albumin and transferrin secretion for a minimum of 26 days in culture. L-Proline was shown to be critical for both the approach to steady state and maximal level of protein secretion. Analysis of does-response data gave K(m) values of 2.9 and 1.7 mug/mL for albumin and transferrin secretion, respectively.     

Effects of dimethyl sulfoxide on cultured rat hepatocytes in sandwich configuration.

A recently developed sandwich culture system, in which hepatocytes are sandwiched between two layers of collagen, has been shown to be capable of maintaining long-term expression of hepatocellular function (J. C. Y. Dunn et al., Biotechnol. Prog. 7, 237-245, 1991). The development of an adequate technique for the cryopreservation of hepatocytes in such a stable culture configuration would ensure a ready supply of hepatocytes for use in bioreactors or bioartificial liver support devices. This report describes the effects of exposing hepatocytes in sandwich culture to different concentrations of the cryoprotectant dimethyl sulfoxide (Me2SO) at 22 degrees C on Day 7 of culture. Cell function, morphology, and cytoskeletal organization were followed for 14 days after exposure. Hepatocellular morphology and albumin secretion remained normal when cultures were exposed for up to 120 min to predicted final Me2SO concentrations up to 1.33 M. Exposure for less than 60 min to equilibrium concentrations of up to 3.33 M Me2SO did not adversely affect cell morphology or albumin secretion rate, but at the highest concentration (3.33 M), increase of the exposure time to 60 or 120 min resulted in dramatic, irreversible cell damage and loss of function. Actin filament organization was shown to be undisturbed when the cells were exposed to 1.33 M Me2SO for 60 min, but was irreversibly disrupted by exposure to 3.33 M for 120 min. Based on these results, a simple and safe procedure is suggested for the addition of Me2SO to hepatocytes in a sandwich culture configuration and its subsequent removal, which will be valuable for studies on hepatocyte cryopreservation.     

Cellular Deoxyribonucleic Acid Synthesis and Loss of Contact Inhibition in Irradiated and Contact-Inhibited Cell Cultures Infected with Fibroma Virus

Cultural changes that follow infection of rabbit kidney cells with fibroma virus were studied. Characteristic alterations of cell morphology and development of multilayered piles and cords of cells were found to occur in infected cultures in which cell division was blocked by gamma radiation or by cell crowding and serum deprivation, thus indicating no dependence upon cell division. Fibroma virus infection did not remove blocks to cell division, but it did exert distinct effects upon nuclear deoxyribonucleic acid synthesis in cells blocked by radiation or cell crowding. Use of tritium-labeled thymidine and autoradiography demonstrated that after infection initial inhibition of nuclear incorporation was followed by sharply increased nuclear labeling at a time that coincided with beginning alterations of cell morphology and development of cell piling.     

Amplification of Oral Streptococcal DNA from Human Incisors and Bite Marks

Challenges to the evidentiary value of morphometric determinations have led to a requirement for scientifically substantiated approaches to the forensic analysis of bite marks. Human teeth support genotypically distinctive populations of bacteria that could be exploited for forensic purposes. This study explored the feasibility of directly amplifying bacterial DNA from bite marks for comparison with that from teeth. Samples from self-inflicted experimental bite marks (n = 24) and human incisors were amplified by PCR using primers specific for streptococcal 16S ribosomal DNA. Amplicon profiles (resolved by denaturing gradient gel electrophoresis) from bite mark samples aligned significantly more closely with profiles generated from the teeth responsible than with those from other teeth. Streptococcal amplicons were generated from dental samples applied to excised porcine skin for up to 48 h. These findings indicate that streptococcal DNA can be amplified directly from bite marks, and have potential application in bite mark analysis.