Field measurement of beef pen manure methane and nitrous oxide reveals a surprise for inventory calculations.

Few data exist on direct greenhouse gas emissions from pen manure at beef feedlots. However, emission inventories attempt to account for these emissions. This study used a large chamber to isolate NO and CH emissions from pen manure at two Australian commercial beef feedlots (stocking densities, 13-27 m head) and related these emissions to a range of potential emission control factors, including masses and concentrations of volatile solids, NO, total N, NH, and organic C (OC), and additional factors such as total manure mass, cattle numbers, manure pack depth and density, temperature, and moisture content. Mean measured pen NO emissions were 0.428 kg ha d (95% confidence interval [CI], 0.252-0.691) and 0.00405 kg ha d (95% CI, 0.00114-0.0110) for the northern and southern feedlots, respectively. Mean measured CH emission was 0.236 kg ha d (95% CI, 0.163-0.332) for the northern feedlot and 3.93 kg ha d (95% CI, 2.58-5.81) for the southern feedlot. Nitrous oxide emission increased with density, pH, temperature, and manure mass, whereas negative relationships were evident with moisture and OC. Strong relationships were not evident between NO emission and masses or concentrations of NO or total N in the manure. This is significant because many standard inventory calculation protocols predict NO emissions using the mass of N excreted by the animal.

K(+)-dependent gating of K(ir)1.1 channels is linked to pH gating through a conformational change in the pore.

1. We have used giant patch-clamp recording to investigate the interaction between pH gating and K(+)-dependent gating in rat K(ir)1.1 (ROMK) channels heterologously expressed in Xenopus oocytes. 2. Gating by intracellular protons (pH gating) and extracellular K(+) ions (K(+)-dependent gating) is a hallmark of K(ir)1.1 channels that mediate K(+) secretion and control NaCl reabsorption in the kidney. pH gating is driven by protonation of an intracellular lysine residue (K80 in K(ir)1.1). K(+)-dependent gating occurs upon withdrawal of K(+) ions from the extracellular side of the channel. Both gating mechanisms are thought to interact allosterically. 3. K(+)-dependent gating was shown to be strictly coupled to pH gating; it only occurred when channels were in the pH-inactivated closed state, but not in the open state. Moreover, K(+)-dependent gating was absent in the non-pH-gated mutant K(ir)1.1(K80 M). 4. Channels inactivated by K(+)-dependent gating were reactivated upon addition of permeant ions to the extracellular side of the membrane, while impermeant ions failed to induce channel reactivation. Moreover, mutagenesis identified two residues in the P-helix (L136 and V140 in K(ir)1.1) that are crucial for K(+)-dependent gating. Replacement of these residues with the ones present in the non-K(+)-gated K(ir)2.1 abolished K(+)-dependent gating of K(ir)1.1 channels without affecting pH gating. 5. The results indicate that pH gating and K(+)-dependent gating are coupled to each other via structural rearrangements in the inner pore involving the P-helix.

A new module arrangement for plasmapheresis.

On-line plasmapheresis using microporous membranes for filtration normally requires two external circulations (double treatment) before the detoxified plasma can be returned to the patient. The duomodule, a new filter arrangement developed by our group, integrates both steps in one equipment module using only one external circuit. Separations of aqueous polyethylene glycol (PEG) solutions as well as human plasma were carried out using the duomodule arrangement. The results revealed a considerable decrease of higher molecular substances in the feed solutions and a significant increase of these components in the permeate solution accumulated in the external compartment of the module. In conclusion, the duomodule arrangement seems to be an useful tool for the therapeutic apheresis.

pH gating of ROMK (K(ir)1.1) channels: control by an Arg-Lys-Arg triad disrupted in antenatal Bartter syndrome.

Inward-rectifier K(+) channels of the ROMK (K(ir)1.1) subtype are responsible for K(+) secretion and control of NaCl absorption in the kidney. A hallmark of these channels is their gating by intracellular pH in the neutral range. Here we show that a lysine residue close to TM1, identified previously as a structural element required for pH-induced gating, is protonated at neutral pH and that this protonation drives pH gating in ROMK and other K(ir) channels. Such anomalous titration of this lysine residue (Lys-80 in K(ir)1.1) is accomplished by the tertiary structure of the K(ir) protein: two arginines in the distant N and C termini of the same subunit (Arg-41 and Arg-311 in K(ir)1.1) are located in close spatial proximity to the lysine allowing for electrostatic interactions that shift its pK(a) into the neutral pH range. Structural disturbance of this triad as a result from a number of point mutations found in patients with antenatal Bartter syndrome shifts the pK(a) of the lysine residue off the neutral pH range and results in channels permanently inactivated under physiological conditions. Thus, the results provide molecular understanding for normal pH gating of K(ir) channels as well as for the channel defects found in patients with antenatal Bartter syndrome.

Extracellular K+ and intracellular pH allosterically regulate renal Kir1.1 channels.

The channels that control K+ homeostasis by mediating K+ secretion across the apical membrane of renal tubular cells have recently been cloned and designated ROMK1, -2, and -3. Native apical K+ channels are indirectly regulated by the K+ concentration at the basolateral membrane through a cascade of intracellular second messengers. It is shown here that ROMK1 (Kir1.1) channels are also directly regulated by the extracellular (apical) K+ concentration, and that this K+ regulation is coupled to intracellular pH. The K+ regulation and its coupling to pH were assigned to different structural parts of the channel protein. K+ regulation is determined by the core region, which comprises the two hydrophobic segments M1 and M2 and the P region. Decoupling from pH was achieved by exchanging the N terminus of ROMK1 by that of the pH-insensitive channel IRK1 (Kir2.1). These results suggest an allosteric regulation of ROMK1 channels by extracellular K+ and intracellular pH, which may represent a novel link between K+ homeostasis and pH control.

Strong voltage-dependent inward rectification of inward rectifier K+ channels is caused by intracellular spermine.

Inward rectifier K+ channels mediate the K+ conductance at resting potential in many types of cell. Since these K+ channels do not pass outward currents (inward rectification) when the cell membrane is depolarized beyond a trigger threshold, they play an important role in controlling excitability. Both a highly voltage-dependent block by intracellular Mg2+ and an endogenous gating process are presently assumed to underly inward rectification. It is shown that strong voltage dependence of rectification found under physiological conditions is predominantly due to the effect of intracellular spermine. Physiological concentrations of free spermine mediate strong rectification of IRK1 inward rectifier K+ channels even in the absence of free Mg2+ and in IRK1 mutant channels that have no endogenous rectification.

ANCA in haemodialysis patients.

The prevalence of positive ANCA as well as the prevalence of PR-3 and MPO antibodies were examined in a cross-sectional sample of 1277 haemodialysis patients from 16 German haemodialysis centres. We found 32 patients positive for c-ANCA (median titre 1:40; range 1:20-1:320) and 65 for p-ANCA (1:80; 1:20-1:1280). Twenty-two percent of the c-ANCA-positive and 31% of the p-ANCA-positive patients had PR-3 and MPO antibodies by ELISA respectively. Clinical evidence of vasculitis was found in 11 of 32 c-ANCA-positive and 19 of 65 p-ANCA-positive patients. Of the 11 c-ANCA-positive, four had a known diagnosis of Wegener's granulomatosis (WG); WG was recognized after the test in a further five patients and two had renal limited RPGN. Of the 19 p-ANCA-positive patients, three had a clinical diagnosis of microscopic polyarteritis (MP), MP was newly diagnosed in a further 12, WG in one and renal limited RPGN in three. The patients had not received cyclophosphamide (the diagnosis had been non-specified 'systemic disease'). Thus false-positive ANCA, as defined by absence of vasculitis, was found in 5% of dialysis patients versus 0% in patients with preterminal renal failure (n = 152) or blood donors (n = 150). Patients with vasculitis tended to have higher c-ANCA and p-ANCA titres respectively, but there was a considerable overlap. Titres were not higher in patients symptomatic at the time of examination (6 of 11 c-ANCA and 10 of 19 p-ANCA), but PR-3 and MPO ELISA were positive in all but two.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence of ANCAs in patients on maintenance haemodialysis.

ANCA analysis as evaluated by concomitant determination of ANCA-IF, PR3-AB and MPO-AB in a larger cohort of dialysis patients disclosed that the prevalence of Wegener's granulomatosis and microscopic polyarteritis in Germany is 4 fold higher than hitherto believed. Low ANCA-IF titers without measurable PR3-AB or MPO-AB are not pathological- they resemble an increased autoimmune tendency of the dialysis patients. According to the european dialysis and transplantation association (EDTA)-registry the incidence of Wegener's granulomatosis (WG) and microscopic polyarteritis (MP) on haemodialysis (HD) in Germany is 0.5% and the prevalence is in the same range (1). In contrast to Germany the incidence in France and Great Britain is above 2%. This is mainly based on histologically proven diseases, which can identify only 1/3 of all affected cases, corresponding to our own experience. With the advent of ANCA serology, WG and MP can be diagnosed more easily. C-ANCA with proteinase 3-antibodies (PR3-AB) is typical of WG, and p-ANCA with myeloperoxidase-antibodies (MPO-AB) is typical of MP in our country. Since a considerable number of patients are on chronic HD without knowledge of their underlying renal disease we studied the prevalence of ANCAs in a larger cohort of HD patients.

Species-specific sound production in three ephippigerine bushcrickets.

Songs of three Ephippigerine species (Ephippiger ephippiger, E. discoidalis and E.perforatus) have been recorded and analysed. Manipulation experiments have been carried out by removing single teeth from the pars stridens. The songs of manipulated animals show characteristic gaps within the impulse structure of the opening and closing syllables. Morphological measurements were carried out by means of SEM-photographs of the pars stridens. Combining both the bioacoustic and morphological results reveals that only the lateral part of the pars stridens is used during stridulation. Furthermore it could be shown that the individual impulse interval pattern within one syllable is also highly constant between syllables. The impulse interval pattern correlates with the pattern of tooth spacing on the pars stridens.