Summary Parturient paresis affects about 10% of all cows. The most common treatment is injection of various Ca‐salts and MgCl2 and about 80% recover after repeated injections. The effect of IgG on the Arrhenius plot of bovine erythrocyte AChE was studied. The plot was normal, i. e. biphasic (a broken line) in the presence of IgG from healthy cows. The highest concentration tested was 10 mg/ml. Before one injection of the Ca‐Mg solution 5 mg/ml IgG from sera of paretic cows (n=10) changed the Arrhenius plots to monophasic (linear). Thus, paretic cows have antibodies against AChE. After injection the change to linear plots was observed already with 1 mg/ml IgG. Apparently, the level of antibodies in serum affecting AChE increased about 5‐fold. This is considered to be due to dissociation of bound antibodies from various AChEs. All cows recovered after one injection and release of AChE antibodies might be important for the recovery. Incubation of blood from paretic cows (n = 3) with Ca‐salts and MgCl2 increased the amount of free AChE‐antibodies about twofold; the Arrhenius plots became linear at 2.5 mg/ml IgG compared with 5 mg/ml before the incubation. This should be due to release from AChEs on blood corpuscles as erythrocytes and lymphocytes. But the increase of antibodies after incubation of blood does not account for the whole increase following the treatment of paretic cows. AChE antibodies are probably also dissociated from other sites, such as neuromuscular junctions.

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Summary Before the onset of bovine paresis a stage of hyperactivity and hypersensitivity was observed in clinical as well as in immunologically provoked cases. By gas chromatographic analysis of choline (Ch) in plasma and serum from four immunologically provoked cows this stage was verified to be an initial immunocholinergic hyperactivation. In the first hour after antigen challenge with 0.5 mg nematode AChE there was a very sharp rise in Ch mainly from agonist‐stimulated and phospholipase mediated phosphatidylcholine (PC) breakdown. A secondary massive influx of Ca into cells was mirrored in a 1 mmol/l depression of serum‐Ca values during the first hours. The hyperagonism mediated Ca‐translocation brought water into cells, resulting in reduced plasma volume. The generally supposed mechanism of secondary, Ca‐mediated cell damage and cell death was initiated and sometimes resulted in “Downers” with persisting paralysis. All acetylcholine (ACh)‐stimulated parts from CNS to the periphery are irregularily involved explaining the very varied clinical appearence of bovine paresis, and the influence on for instance the autonomous nerve system, adrenals and pancreas. In the experimental group, ACh in plasma showed a sharp fall within the first hour, while there were fairly constant values of serum‐ACh in the first four hours, possibly indicating some antibody protection. When paresis was established between 15–28 hours after challenge the general anergetic state was characterised by low ACh‐levels. Also in a larger field group ACh‐levels were significantly depressed in paretic compared to healthy cows. The unexpected finding in this group was considerably higher levels of ACh and especially Ch in serum compared to plasma. The origin of ACh and Ch had to be blood cells. Preliminary gaschromatographic analysis has confirmed ACh‐synthesis by leucocytes and an integrated immuno‐cholinergic system of great importance can be anticipated. The general feature of bovine paresis is updated by immune‐etiological, pathophysiological, blood chemical, clinical‐experimental and nomenclature considerations. The exact mechanism of pathogenesis is not revealed in this investigation, though many circumstances favour an anti‐Id mediated hyperagonism. Other types of investigations and above all more basic knowledge of distribution and functional character of cholinergic components on immune cells are required.

This investigation was supported by the Swedish Council for Agricultural Sciences. U. S. Copyright Clearance Center Code Statement: 0721-4981/83/3007-0485$02.50/0 486 AXELSSON and LUTHMANN A brief communication on the subject of which this investigation is part has been given elsewhere (AXELSSON, 1981). Material and Methods AnimalsGroup A . Eleven paresis-prone cows. Seven were of the Swedish Red Breed (SRB), two were Group B. Four SRB cows without a history of parturient paresis. Group C. Eight indoor born and kept calves, six SRBs and two SLBs, all 3 4 months old. Group D. Three parasite-free female Swedish Landrace sheep, 6 months old at the beginning of Group E. Three parasite-free female Swedish Landrace sheep, 6 months old at the beginning of Swedish Friesians (SLB) and two were of the Jerseys.immunization with crude 0-AChE. immunization with electric eel AChE. AntigensAntigens were isolated and purified as briefly described by AXELSSON (1981). The worm incubation medium was concentrated in an ultrafiltration cell (Amicon 30,000) and Hanks's balanced salt solution was at the same time changed to Tris buffer p H 7.4. The enzyme preparation was centrifuged at 20,000 g for one hour. The clear supernatant is referred to as crude 0-AChE. Pellets were discarded.The crude 0-AChE was used to provoke and immunize but was also further purified. The purification steps were chromatography on ConA Sepharose, affinity chromatography on CH Sepharose 4 B with specific ligand and gel filtration on Sephadex G 100 (all matrix from Pharmacia Fine Chemicals, Uppsala). Enzyme activity was measured by the spectrophotometric method of ELLMAN et al. (1961) and protein by the method of LOWRY et al. (1951) in order to get the specific activity of pkat/mg protein. The clinically used purified 0-AChE was the de-salted specific elution pool from the affinity column, with a 2C-25 fold purification compared with the crude 0-AChE. The most highly purified gel filtration product had limited stability even when deep-frozen, which made it difficult to use and quantify for clinical trials. This preparation gave a single band on polyacrylamide gel electrophoresis and was used to characterize the enzyme as a soluble, monomeric AChE with a molecular weight of 65,000. Antigen doses were for reasons of convenience measured as activities, and were expressed as the product of volume and activity in pkat/l. A dose of 50 represents, for example, 10 ml of an enzyme preparation with the activity of 5 pkat/l. Groups A and B were given 5C-60 and C, D and E 25-30pkadl. Relative to specific activity in peak gel filtration pool, the enzyme protein contents of these doses were 0.5-0.6 mg in groups A and B, 0.25-0.30 mg in groups C and D, and 0.28 mg in group E.All antigens were given as a single intravenous injection except in the first three cows where onethird was given subcutaneously and two-thirds intravenously.The immunization in sheep was done with at least one month and sometimes 6 months interval. Electric eel AChE was purchased from Sigma. Acetylch...