Intestinal helminths of four species of skinks (Mabuya) (Sauria: Scincidae) from southern Africa

Intestinal helminths are reported from four species of scincid lizards from southern Africa: Mabuya occidentalis, Mabuya spilogaster, Mabuya striata and Mabuya variegata. The helminth fauna consisted of one species of Cestoda, Oochoristica truncata and five species of Nematoda, Abbreviata paradoxa, Maxvachonia dimorpha, Parapharyngodon rotundatus, Spauligodon petersi and Thubunaea fitzsimonsi. All findings represent new host records. Ascarid larvae were also found. It appears that Mabuya is infected by generalist helminths that occur in other species of African lizards.     

The pregnant Syrian hamster as a model to study intravascular trophoblasts and associated maternal blood vessel changes.

In pregnant Syrian hamsters (Mesocricetus auratus) used as an animal model for studying the migration of fetal trophoblasts and the associated changes in maternal blood vessels, intravascular trophoblasts migrated well beyond the blood vessels of the uterus and into the vessels of the mesometrium. They migrated beyond the decidua of the uterus, into the lumina of maternal uterine and mesometrial arteries, but not into veins. The arterial changes, which were often segmental, resembled those seen in the decidua and consisted of a replacement of normal smooth muscle cells by poorly differentiated stromal cells. Ultrastructurally, the trophoblasts were either above or below maternal endothelial cells. They occurred also as single or multiple layers within the lumina of arteries that lacked an endothelial lining. Apparent penetration of the elastic membrane by the fetal trophoblasts brought them into close apposition to maternal cells in the arterial wall. Histochemical studies showed heightened metabolic activity of the intravascular trophoblasts as suggested by strong histochemical reactions to nonspecific esterase, succinic dehydrogenase and the glycerophosphate dehydrogenase reactions. Thus, these metabolically active fetal trophoblasts actively migrate into the maternal arterial system, resulting in loss of endothelial cells and changes in the wall of the maternal arteries similar to those in the decidua at the uteroplacental junction.     

Fossil fuel combustion and the major sedimentary cycle

The combustion of the fossil fuels coal, oil, and lignite potentially can mobilize many elements into the atmosphere at rates, in general, less than but comparable to their rates of flow through natural waters during the weathering cycle. Since the principal sites of fossil fuel combustion are in the mid-latitudes of the Northern Hemisphere, changes in the composition of natural waters and air, as a consequence of this activity, will be most evident at these latitudes.     

Evaluation of contact exposure as a method for acclimatizing growing pigs to porcine reproductive and respiratory syndrome virus

OBJECTIVE: To determine whether 6.5-week-old gilts that have not previously been exposed to porcine reproductive and respiratory syndrome (PRRS) virus can be acclimatized to an endemic strain of the virus by commingling with age-matched gilts inoculated with the endemic PRRS virus strain and whether 10.5-week-old gilts can be acclimatized by commingling with age-matched inoculated or contact-exposed animals. DESIGN: Randomized controlled longitudinal study. ANIMALS: 80 gilts seronegative for PRRS on a farm in the Midwestern United States with a history of PRRS. PROCEDURES: 20 gilts were inoculated with the endemic PRRS virus strain at 6.5 weeks of age (group 1) and were commingled with 20 gilts that were not inoculated (group 2). Four weeks later, the remaining 40 gilts (group 3) were commingled with gilts in groups 1 and 2. Presence of viral RNA in the tonsils, seroconversion rate, serum neutralizing antibody titers, interferon-gamma-mediated cellular immunity, and reproductive outcomes were analyzed. RESULTS: Acclimatization of PRRS virus-na?ve pigs was achieved by means of contact exposure at both 6.5 and 10.5 weeks of age. No differences were observed among the 3 groups with respect to development of anti-PRRS virus-specific immune responses or reproductive outcomes. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that contact exposure of 6.5- to 10.5-week-old pigs that had not previously been exposed to PRRS virus to pigs inoculated with endemic PRRS virus may be an efficient acclimatization strategy for controlling outbreaks on commercial farms on which PRRS is endemic.     

Predicting land use change: comparison of models based on landowner surveys and historical land cover trends

To make informed planning decisions, community leaders, elected officials, scientists, and natural resource managers must be able to evaluate potential effects of policies on land use change. Many land use change models use remotely-sensed images to make predictions based on historical trends. One alternative is a survey-based approach in which landowners’ stated intentions are modeled. The objectives of our research were to: (1) develop a survey-based landowner decision model (SBM) to simulate future land use changes, (2) compare projections from the SBM with those from a trend-based model (TBM), and (3) demonstrate how two alternative policy scenarios can be incorporated into the SBM and compared. We modeled relationships between land management decisions, collected from a mail survey of private landowners, and the landscape, using remotely-sensed imagery and ownership parcel data. We found that SBM projections were within the range of TBM projections and that the SBM was less affected by errors in image classification. Our analysis of alternative policies demonstrates the importance of understanding potential effects of targeted land use policies. While policies oriented toward increasing enrollment in the Conservation Reserve Program (CRP) resulted in a large (11–13%) increase in CRP lands, policies targeting increased forest thinning on private non-industrial lands increased low-density forest projections by only 1%. The SBM approach is particularly appropriate for landscapes including many landowners, because it reflects the decision-making of the landowners whose individual actions will result in collective landscape change.     

Associations between genetics, farm characteristics and clinical disease in field outbreaks of porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome (PRRS) is a disease of domestic swine characterized by exceptionally high clinical variability. This study addresses the question of whether clinical variability in PRRS results from (a) genetic variation among viral isolates and/or (b) variation in management practices among farms on which isolates are found. Genetic data (open reading frame 5 gene sequences) and data on farm characteristics and associated clinical disease signs were collected for 62 PRRS virus (PRRSV) field isolates, representing 52 farms. Clinical disease signs were interrelated — confirming that a true reproductive syndrome exists (involving abortions, infertility in sows, deaths of sows and preweaning mortality).

Pairs of farms experiencing deaths in their sow populations also tended to share viral isolates which were more similar to one another than expected by chance alone. This implies that sow death (one of the more-severe manifestations of PRRS) is under genetic influence. Large herd size was a significant risk factor for the death of sows and for respiratory disease in nursery pigs. All-in–all-out management practices in the nursery were protective against reproductive signs in the sow herd. All-in–all-out management practices in the finishing stages of production were protective against respiratory disease in nursery pigs — but were paradoxically associated with an increased risk of infertility in sows. These results suggest that farm-management practices can also influence which PRRS clinical signs are manifested during an outbreak. In general, signs associated with PRRS appear to result from a combination of genetic factors and herd-management characteristics. The relative contributions of these two influences differ depending on the specific clinical sign in question.     

Fluxes of climate‐relevant trace gases between a Norway spruce forest soil and atmosphere during repeated freeze–thaw cycles in mesocosms

For this century, an increasing frequency of extreme meteorological boundary conditions is expected, presumably resulting in a changing frequency of freezing and thawing of soils in higher‐elevation areas. Our current knowledge about the effects of these events on trace‐gas emissions from soils is scarce. In this study, the effects of freeze–thaw events on the fluxes of the trace gases CO₂, N₂O, and NO between soil and atmosphere were investigated in a laboratory experiment. Undisturbed soil columns were collected from a mature Norway spruce forest in the “Fichtelgebirge”, SE Germany. The influence of freezing temperatures (–3°C, –8°C, –13°C) on gas fluxes was studied during the thawing periods (+5°C) in three freeze–thaw cycles (FTCs) and compared to unfrozen controls (+5°C). Two different types of soil columns were examined in parallel—one consisting of O layer only (O columns) and one composed of O layer and mineral soil horizons (O+M columns)—to quantify the contribution of the organic layer and the top mineral soil to the production or consumption of these trace gases. During the thawing period, we observed increasing emissions of CO₂, N₂O, and NO from the spruce forest soil, but the cumulative emissions of these gases did mostly not exceed the level of the controls. The results show that the O layers were mainly involved in the gas production. Severe soil frost increased CO₂ fluxes during soil thawing, whereas repetition of the freeze–thaw events decreased CO₂ fluxes from the thawing soil. Fluxes of N₂O and NO were neither influenced by freezing temperature nor by freeze–thaw repetition. Stable‐isotope analysis indicated that denitrification was mostly responsible for the N₂O production in the FTC columns. Furthermore, isotope data demonstrated a consumption of N₂O through microbial denitrification to N₂. It was further shown, that production of N₂O also occurred in the mineral horizons. The NO emissions were mainly driven by increasing soil temperature during thawing. In this freeze–thaw experiment up to 20 times higher NO than N₂O fluxes were recorded. Our results suggest that topsoil thawing has little potential to increase the emissions of CO₂, N₂O, and NO in spruce forest soils.     

Oxygen isotope ratios of juice water in Australian oranges and concentrates.

Australian orange juices from major growing regions have been surveyed over a 5 year period with a view to establishing a database of (18)O/(16)O isotope ratios against which retail samples can be tested for authenticity. The (18)O/(16)O ratios were found to follow a consistent pattern that had both a cyclic seasonal and a regional influence. Oxygen delta values ranged from a summer maximum of >+15 per thousand for oranges from inland regions to a winter minimum of approximately +1 per thousand for oranges grown in coastal areas. However, over a shorter time period, the range of values was markedly less than this. Concentrated orange juices, pulpwashes, and peel extracts, as well as other citrus types, were also tested. The effect of some industry practices that have an effect on (18)O/(16)O ratios was also investigated.