Swelling behavior of bisensitive interpenetrating polymer networks for microfluidic applications.

Bisensitive interpenetrating polymer network (IPN) hydrogels of temperature sensitive net-poly(N-isopropylacrylamide) and pH sensitive net-poly(acrylic acid-co-acrylamide) for microfluidic applications were prepared via a sequential synthesis using free radical polymerization. The IPN indicated a suitable reversible alteration of swelling in response to the change in pH and temperature. The adequate change of the hydrogel volume is a basic requirement for microfluidic applications. Using the introduced correction factor f, it is possible to determine the cooperative diffusion coefficient (Dcoop) of cylindrical samples at any aspect ratio. The determined cooperative diffusion coefficient allowed the evaluation of varying swelling processes of different network structures. The presence of the second sub-network of the IPN improved the swelling behaviour of the first sub-network compared to the individual networks.

Motor control of the stomach.

Gastric motility is controlled at various levels including the enteric nervous system (ENS). The gastric ENS is involved in the regulation of accommodation reflexes as well as of the peristaltic waves which are responsible for grinding and emptying. Polarised projections consisting of ascending cholinergic and descending nitrergic muscle motor neurons make up the hard wired circuits for control of muscle activity. In an isolated flat sheet preparation of the gastric corpus we investigated stretch evoked responses. The responses at the site of the distension as well as proximal and distal to the distension consisted of a cholinergic excitation whereas a nitrergic inhibition was only observed at the site of the distension stimulus. At all sites the responses were significantly reduced by the neurotoxin tetrodotoxin suggesting a neural component. In addition the nicotinic blocker hexamethonium reduced the responses at all sites to the same degree as tetrodotoxin which indicated the strong contribution of ascending and descending cholinergic interneurons. The reflexes of isolated gastric corpus preparations to distension are dominated by excitatory responses. Only the muscle response at the site of distension exhibited an inhibitory response which is usually dominated by the cholinergic excitatory response.

Survival of dairy cows after surgery to correct abomasal displacement: 1. Clinical and laboratory parameters and overall survival.

The objective of this study was to compare the clinical and laboratory consequences of left and right displacement of the abomasum (LDA and RDA), short- and long-term survival after surgery and the findings in cows, that could not be cured by omentopexy. Data from 564 cases of displaced abomasum (466 LDA, 98 RDA) were analysed retrospectively. Clinical and laboratory findings were compared between the two manifestations of DA. Survival was assessed after 10 days and after 15 months. Necropsy was carried out on cows that died or were killed. On arrival at the clinic, left displacement of the abomasum (LDA) cows had been recognized as diseased for longer. LDA occurred earlier in lactation, and more cows with right displacement of the abomasum (RDA) were pregnant. Overall clinical symptoms were more severe in RDA than in LDA cows. Heart rate was higher, body temperature was lower, inanition, abnormal faeces and ruminal stasis were more frequent in RDA cows. Leucocyte counts were higher, and potassium and chloride levels were lower in RDA cows. Acetonuria was more frequent in LDA cows. More LDA than RDA cows were released from the clinic as cured (82.0% versus 74.5%). However, survival after the early post-surgical period was similar for RDA and LDA cows. At necropsy, diseases of the gastrointestinal system were the predominant finding in RDA cows, while in LDA cows, diseases of the liver and other concurrent diseases were more important.

Survival of dairy cows after surgery to correct abomasal displacement: 2. Association of clinical and laboratory parameters with survival in cows with left abomasal displacement.

This study examines the association of pre-surgical clinical parameters in cows with left displacement of the abomasum (LDA) with the probability of cure. Data from 466 cases of LDA in which omentopexy was performed were analysed. Cows were classified in three categories according to the outcome of treatment. Cows in the first category were cured, i.e. sent back to the farm for further milk production. Cows in the second category were sent for slaughter because of an unfavourable prognosis concerning productivity. Cows in the third category either died or were salvaged because of poor prognosis concerning survival. Factors were examined for their possible influence on the outcome of treatment by comparing the values of successfully treated cows to those cows that either died or had to be sent for slaughter. Factors that were associated with a favourable prognosis were a short duration of disease, an undisturbed general condition, good appetite, normal faeces, a higher body weight, lower haematocrit, haemoglobin and erythrocyte counts, lower urea, AST and bilirubin, and higher sodium, potassium and chloride concentrations compared with cows with an unfavourable prognosis. Haemoconcentration was associated with higher AST, bilirubin and urea and with low sodium, potassium and chloride. Acetonuria was associated with increased AST and bilirubin and low urea. Low sodium and potassium concentrations were associated with an impaired general condition. It is concluded that a thorough clinical examination with special emphasis on general condition, liver function and dehydration status is of great importance in determining the prognosis of abdominal surgery in cows with LDA.

Blockade of capacitive Ca2+ influx by Cl- channel blockers inhibits secretion from rat mucosal-type mast cells.

Whole-cell patch-clamp recordings of membrane currents were performed in combination with measurements of mediator secretion from mucosal-type mast cells (rat basophilic leukemia cells, subline 2H3), to determine the involvement of membrane conductances induced upon depletion of intracellular Ca2+ stores. In patch-clamp experiments, ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-induced depletion of internal Ca2+ stores led to activation of two distinct membrane conductances, a Ca2+ current and a Cl- current. The Ca2+ current was blocked by 100 microM La3+, which did not affect the Cl- current. In contrast, 500 microM 4,4'-diisothiocyanato-2,2'-disulfonic acid produced selective blocked of the Cl- current. Remarkably, the Cl- channel blockers 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), niflumic acid, and N-phenylanthranilic acid (NPAA) inhibited not only the Cl- current but also the Ca2+ current. IC50 values for the blockade of the Ca2+ inward current by NPPB, niflumic acid, and NPAA were determined to be 23, 150, and 190 microM, respectively. In secretion experiments, thapsigargin-induced depletion of internal Ca2+ stores stimulated serotonin release, which was found to be strictly dependent on extracellular Ca2+. In the presence of 100 microM La3+ secretion was almost completely inhibited. In contrast, only 50% of secretion was suppressed by 500 microM 4,4'-diisothiocyanato-2,2'-disulfonic acid, which fully blocked the Cl- current without affecting Ca2+ influx, as monitored by electrophysiological experiments. The other Cl- channel blockers produced a very different pattern for the inhibitory dose dependence of secretion, with IC50 values for NPPB, niflumic acid, and NPAA of 23, 60, and 180 microM, respectively. Taken together, these findings suggest that Ca2+ store depletion leads to concomitant activation of Cl- and Ca2+ currents. Blockade of the latter is apparently an additional mode of action for diarylaminocarboxylate-type Cl- channel blockers inhibiting mast cell secretory responses.