Tissue distribution of bovine spongiform encephalopathy infectivity in Romney sheep up to the onset of clinical disease after oral challenge.

Sixty Romney sheep of three prion protein genotypes were dosed orally at six months of age with an inoculum prepared from the brains of cattle clinically affected with BSE, and 15 sheep were left undosed as controls. They were randomly assigned within genotype to groups and were sequentially euthanased and examined postmortem at intervals of six or 12 months, depending on their predicted susceptibility. Tissue pools prepared from the three, four or five dosed animals in each group were inoculated into groups of 20 RIII mice as a bioassay for infectivity. Separate inocula were prepared from the matched control sheep killed at each time. In the ARQ/ARQ sheep killed four months after inoculation, infectivity was detected in the Peyer's patch tissue pool, and at 10 months it was detected in the spleen pool; from 16 months, infectivity was detected in a range of nervous and lymphoreticular tissues, including the spinal cord pool, distal ileum excluding Peyer's patches, liver, Peyer's patches, mesenteric and prescapular lymph nodes, spleen, tonsil and cervical thymus. No infectivity was detected in the tissue pools from the ARQ/ARR and ARR/ARR sheep killed 10 months or 22 months after infection.

Evaluation of a biologically active cover for mitigation of landfill gas emissions.

Landfills are the third largest source of anthropogenic CH4 in the United States, and there is potential for reduction in this source of greenhouse gases and other contaminants. The objective of this work was to contrast emissions of CH4 and non-methane organic compounds (NMOCs) from landfill cells covered with soil or a biologically active cover consisting of yard waste compost. On the basis of four field campaigns over 14 months, CH4 emissions from the biocover (BC) varied from -1.73 to 1.33 g m(-2) d(-1), with atmospheric uptake measured in 52% of tests. BC emissions did not increase when the gas collection system was turned off. Uptake of atmospheric CH4 was measured in 54% of tests on the soil cover (SC) when the gas collection was system active and 12% when the gas collection system was off. Many (26%) relatively high fluxes (>15 g m(-2) d(-1)) were measured from the SC as were some dramatic effects due to deactivation of the gas collection system. In tests with positive emissions, stable isotope measurements showed that the BC and SC were responsible for oxidation of 55% and 21% of the CH4 reaching the bottom of the respective cover. Seven of the highest 10 NMOC emissions were measured in the SC, and 17 of 21 fluxes for speciated organic compounds were higher in the SC. The relationship between CH4, NMOC, and individual organic compound emissions suggested a correlation between CH4 and trace organic oxidation. BCs can reduce landfill gas emissions in the absence of a gas collection system and can serve as a polishing step in the presence of an active system.

Clusterin shortens the incubation and alters the histopathology of bovine spongiform encephalopathy in mice.

Clusterin accumulates in significant quantity in prion protein lesions associated with bovine spongiform encephalopathy (BSE) and we therefore sought to elucidate its ability to alter BSE pathogenesis and incubation time by comparison of wild type C57BL/6J mice and clusterin knock out (ko) mice. The ko mice had a 40 day increase in mean incubation time compared to wild type mice. PrP deposition in the medulla was less aggregated in clusterin knock out mice when compared to wild type BSE infected mice and a more marked astrocytosis, as determined by GFAP staining, was evident. The vacuolation profiles did not differ between the two strains of mice. Taken together these results suggest that clusterin alters the extracellular deposition of PrP(BSE) and accelerates BSE pathogenesis.

Preliminary observations on the pathogenesis of experimental bovine spongiform encephalopathy (BSE): an update.

Further preliminary observations are reported of an experiment to examine the spread of infectivity and the occurrence of pathological changes in cattle exposed orally to infection with bovine spongiform encephalopathy. Calves were dosed at four months of age and clinically monitored groups were killed sequentially from two to 40 months after inoculation. Tissues were collected for bioassay, for histopathological examinations and for the detection of PrP. Previous reported observations have included the presence of infectivity in the distal ileum of cattle killed after six to 18 months, the earliest onset of clinical signs in an exposed animal after 35 months, and diagnostic histopathological changes in the brain, in association with clinical disease, after 36, 38 and 40 months. In spite of the relative inefficiency of the bioassay of scrapie-like agents across a species barrier the new observations confirm that the onset of clinical signs and pathological changes in the central nervous system (CNS) occur at approximately the same time. The earliest pathological change, the presence of abnormal PrP 32 months after inoculation, coincided with the earliest detected infectivity in the CNS and occurred shortly before there was evidence of typical spongiform changes in the brain 36 months after inoculation. Infectivity has now been demonstrated in the peripheral nervous system, in the cervical and thoracic dorsal root ganglia 32 to 40 months after inoculation and in the trigeminal ganglion 36 and 38 months after inoculation. At the time of writing evidence of infectivity in other tissues is confined to the distal ileum, not only after six to 18 months but also after 38 and 40 months, but these findings may be supplemented by the results of further mouse assays. Nevertheless, they are in general agreement with current knowledge of the pathogenesis of scrapie.

Cyclic nucleotide-gated cation channels mediate sodium absorption by IMCD (mIMCD-K2) cells.

The inner medullary collecting duct cell line, mIMCD-K2, absorbs Na+ by an amiloride-sensitive, electrogenic mechanism. The goal of the present study was to characterize the amiloride-sensitive, Na+ -conducting channels responsible for electrogenic Na+ absorption. To this end, we measured Na+ currents in single cells with the patch-clamp technique and Na+ currents across monolayers mounted in Ussing-type chambers. In whole cell patch-clamp experiments, amiloride-sensitive, inward Na+ currents were mediated by nonselective cation channels. In single-channel patch-clamp experiments, amiloride- and guanosine 3',5'-cyclic monophosphate (cGMP)-sensitive, 20-pS nonselective cation channels (i.e., CNG channels) were identified in the apical membrane. CNG channels were inhibited by amiloride, diltiazem, ethylisopropylamiloride (EIPA), and 8-bromo-cGMP and were permeable to Ca2+ and Mg2+. Epithelial Na+ channels were never observed in whole cell or single-channel recordings. Na+ absorption across confluent monolayers was inhibited with a rank order potency of benzamil > amiloride > phenamil >> EIPA > diltiazem. Our data are most consistent with the view that CNG channels mediate electrogenic Na+ absorption across mIMCD-K2 cells.

Hyperosmolality inhibits sodium absorption and chloride secretion in mIMCD-K2 cells.

Previously we demonstrated that a cell line derived from mouse inner medullary collecting duct (mIMCD-K2) absorbs Na+ and secretes Cl- by electrogenic mechanisms and that arginine vasopressin (AVP) stimulates Cl- secretion. The objective of the present study was to determine whether hyperosmolality, both acute (minutes) and chronic (weeks), affects electrogenic Na+ absorption IscNa and electrogenic Cl- secretion IscCl across the IMCD. To this end, we measured IscNa and IscCl across monolayers of mIMCD-K2 cells mounted in Ussing-type chambers. Osmolality was increased from 290 to 590 mosmol/kgH2O by adding 200 mosmol/kgH2O of NaCl and 100 mosmol/kgH2O of urea or 300 mosmol/kgH2O of sucrose to the bathing solutions. Acute and chronic hyperosmolality reduced basal IscNa and IscCl and the AVP-stimulated rise in IscCl. These findings indicate that osmolality is an important determinant of IscNa and IscCl across IMCD cells and that the osmolality of the interstitial fluid should be considered when evaluating the effects of hormones and other factors on Na+ and Cl- transport by the IMCD.

Cell-specific expression of amiloride-sensitive, Na(+)-conducting ion channels in the kidney.

Amiloride-sensitive, electrogenic Na+ absorption across the distal nephron plays a vital role in regulating extracellular fluid volume and blood pressure. Recently, two amiloride-sensitive, Na(+)-conducting ion channel cDNAs were cloned. One, an epithelial Na(+)-selective channel (ENaC), is responsible for Na+ absorption throughout the distal nephron. The second, a guanosine 3',5'-cyclic monophosphate (cGMP)-inhibitable cation channel, is conductive to Na+ and Ca2+ and contributes to Na+ absorption across the inner medullary collecting duct (IMCD). As a first step toward understanding the segment-specific contributions(s) of cGMP-gated cation channels and ENaC to Na+ and Ca2+ uptake along the nephron, we used in situ reverse transcription-polymerase chain reaction (RT-PCR) hybridization, solution-phase RT-PCR, and Western blot analysis to examine the nephron and cell-specific expression of these channels in mouse kidney cell lines and/or dissected nephron segments. cGMP-gated cation channel mRNA was detected in proximal tubule, medullary thick ascending limb (mTAL), distal convoluted tubule (DCT), cortical collecting duct (CCD), outer medullary collecting duct (OMCD), and IMCD. cGMP-gated cation channel protein was detected in DCT, CCD, and IMCD cell lines. These observations suggest that hormones that modulate intracellular cGMP levels may regulate Na+, and perhaps Ca2+, uptake throughout the nephron. mRNA for alpha-mENaC, a subunit of the mouse ENaC, was detected in mTAL, DCT, CCD, OMCD, and IMCD. Coexpression of alpha-mENaC and cGMP-gated cation channel mRNAs in mTAL, DCT, CCD, OMCD, and IMCD suggests that both channels may contribute to Na+ absorption in these nephron segments.

Radial and tibial nerve pathology of two lactating ewes with "kangaroo gait".

Radial and tibial nerves of two ewes with clinical signs of chronic "kangaroo gait" were examined by qualitative and quantitative techniques and compared to the same nerves of a clinically normal ewe in late lactation. In affected ewes, there was extensive axonal degeneration of myelinated fibres in the radial nerve. Large and small myelinated fibres were affected equally and unmyelinated fibres were normal. Nerve fibre regeneration was present. In contrast, tibial nerve changes in the "kangaroo gait" ewes were minimal. The chronic nature of the radial nerve pathology was consistent with the clinical time course of "kangaroo gait". Regeneration may account for gradual improvement with eventual recovery in most chronically affected ewes. An episode of bilateral severe compression of a proximal radial nerve site is proposed as an explanation for the neuropathy, although the specific mechanism of this trauma is not known.

Behavior analysis in consumer affairs: Retail and consumer response to publicizing food price information.

A popular program among consumer action groups involves publicizing comparative food price information (CFPI) gathered from retail stores. Its significance is based on the assumption that publishing CFPI maximizes retail competition (i.e., moderates price levels or price increases) and occasions more frugal store selections among consumers. We tested these assumptions during a 2-year analysis. Specifically, we monitored the prices of two distinct market baskets in the supermarkets of two midwestern cities (target and contrast cities). Following a lengthy baseline, we published the prices of only one of the market baskets at stores in the target city in the local newspaper on five different occasions. The results suggested that reductions in price inflation occurred for both market baskets at the independently operated target stores. The corporate chain stores were not similarly affected. In addition, surveys indicated that many consumers used the CFPI as a basis for store selection. Finally, the analysis included a discussion of the politics, economics, and future of CFPI programs.

Turning the table on advice programs for parents: Using placemats to enhance family interaction at restaurants.

There are many opportunities in a family's daily routine to enrich the interactions among its members. One such opportunity arises at family restaurants. Surveys of restaurant personnel and customers suggested the possibility of enriching family interactions by redesigning indigenous materials such as table placemats. Accordingly, we developed Table-Talk placemats that provided conversational topics and illustrated games in which the entire family could participate. After some testing of these placemats in a preschool, a field experiment was conducted with families dining in restaurants. Table-Talk placements occasioned more social and educational dialogue among family members than either traditional-placemat or no-material conditions. Social validation ratings provided by mental health counselors and the parents suggested that Table-Talk placemats occasioned healthy and enjoyable interactions among family members.

Optogalvanic resonance detection of pulsed dye laser atomic absorption.

Resonance detection and quantification of atomic absorption have been demonstrated for Na, Cu, and Li using an optogalvanic effect. In this experiment, a pulsed dye laser tuned to an absorption transition of the analyte atom (i.e., the element to be determined) was directed through the analyte atomic vapor produced in a flame into a commercial hollow cathode lamp containing the element of interest. The optogalvanic signal was monitored and related to the analyte concentration in the flame. Detection limits were obtained for Na, Cu, and Li, the behavior of the sodium hollow cathode lamp was characterized, and future applications are suggested.