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Biomedical subjects

K Nielsen

Publications and source records attributed to K Nielsen.

At least 307 records · Page 17Linked to original sources

The generation of phospholipase A and hemolytic fatty acids by autolysing suspensions of Trypanosoma congolense.

When T. congolense undergoes autolysis there is a concomitant appearance of phospholipase A activity and hemolytic fatty acids. The generation of enzyme activity is exponential, and the appearance of hemolytic activity corresponds to a free fatty acid concentration of 0.02 to 0.03 mg. per ml. The concentration of the trypanosome suspension markedly affected the kinetics of the generation process. In contrast, the autolysis of T. lewisi did not generate hemolytic activity unless exogenous phospholipase A was added to the organisms.

Autolysis↗

Mechanisms of the anemia in trypanosomiasis: studies on the role of the hemolytic fatty acids derived from Trypanosoma congolense.

Trypanosoma congolense releases a number of hemolytic free fatty acids on autolysis of which the most potent is linoleic acid. These fatty acids can lyse washed rat and bovine erythrocytes in vitro. Autolysed T. congoleuse will cause increased fragility of erythrocytes in whole rat blood but not in whole bovine blood. The lack of effect of these fatty acids on bovine erythrocytes tends to be confirmed by the failure of this material to influence the survival of these cells in vivo. Calculations based on the amount of free fatty acids required to cause hemolysis in vivo also confirm that this mechanism of erythrocyte destruction is probably unimportant in bovine trypanosomiasis.

Anemia↗

Experimental bovine trypanosomiasis. Changes in the catabolism of serum immunoglobulins and complement components in infected cattle.

The turnover of serum proteins of calves experimentally infected with Trypanosoma congolense was compared to that of normal uninfected cattle. All proteins examined had much increased catabolic rates in infected animals. In normal animals the average half-lives in days for each protein were: IgG1 17.4, IgG2 22.4, IgM 4.8, IgA 3.4, IgE 1.9, C1 5.6 and C3 2.9. In trypanosome infected cattle the average half-lives were IgG1 1.9, IgG2 1.7, IgM 0.9, IgA 1.2, IgE 0.9, C1 1.2 and C3 1.1 days.

Animals↗

Experimental bovine trypanosomiasis. Changes in serum immunoglobulins, complement and complement components in infected animals.

In three calves experimentally infected with Trypanosoma congolense the amounts of IgG1 and IgG2 were little changed and similar to those of normal animals. IgM increased in amount early in the infection and the amount of the increase appeared related to the parasite burden. The amounts of IgA and IgE were both much decreased and this also appeared related to the numbers of parasites in the blood. There was a decrease in the amounts of total haemolytic complement and complement components C1, C1q and C3 in the infected calves. Furthermore the amounts of properdin fluctuated with the cyclical changes in numbers of T. congolense parasites in the individual calves. No significant change in the amount of C8 was observed. It is considered that activation of both the alternative and the classical complement pathways occurs in trypanosome infected animals but that neither pathway goes to its terminal stages.

Animals↗

Activation of complement by trypanosomes.

Factors exhibiting anti-complementary activity released from trypanosomes after incubation at 20 degrees C were described. The active material was shown to consume the first component of bovine complement. While the anti-complementary factor(s) from T. lewisi could activate bovine, human and guinea pig complement, the factor(s) from T. congolense was observed to activate bovine complement, but not guinea pig and only slightly human complement. The roles of complement activating factor(s) of trypanosomes in the pathology of the disease are discussed.

Animals↗

Application of the soluble antigen fluorescent antibody (SAFA) test to the serodiagnosis of rabies.

The adaptation and evaluation of the Soluble Antigen Fluorescent Antibody (SAFA) test for the serologic diagnosis of rabies is described. Evaluation of the SAFA test was based on a comparison between serum titers obtained in the SAFA test, the mouse Serum Neutralization (SN) test and in the Indirect Fluorescent Antibody (IFAT) test. Dog, fox, raccoon and skunk sera were used for the comparison with mouse SN titers. Human serum was used for the comparison with the IFAT titer. The purity and concentration of the test antigen is a crucial factor in determining the efficiency of the SAFA test for rabies serodiagnosis. Viral antigen obtained by the AIPO4 gel method for rabies virus purification and concentration was found to be sufficiently purified and concentrated for use in the SAFA test. Conjugate dilution decreased the level of non-specific staining. Although specific activity was also decreased, there was a statistically significant difference (P less than or equal to 0.05; Student's t test) between the rabies positive and the rabies negative serum samples at all conjugate dilutions for all species studied. In three cases (fox, raccoon, skunk) SAFA titers were greater than mouse SN titers. In one case (dog) the SAFA titer was less than the mouse SN titer. The IFAT titer of the human serum sample was greater than the SAFA titer. Comparison of Fluorometer Dial Readings (FDR) of sera obtained in separate protocols demonstrated satisfactory reproducibility of the SAFA test for rabies serodiagnosis.

Animals↗

Effects on rat urinary kallikrein excretion of bumetanide, bendroflumethiazide and hydralazine.

Single and/or repeated administrations of bumetanide, bendroflumethiazide and hydralazine to normotensive and spontaneously hypertensive rats resulted in an increase of urinary kallikrein excretion. No correlation was found with sodium output. The role of the increased plasma renin activity is discussed and it is suggested that the activation of the renal kallikrein-kinin system is related to the increase in renal blood flow.

Administration, Oral↗

The bovine immune response to Brucella abortus I. A water soluble antigen precipitated by sera of some naturally infected cattle.

Selected sera from cattle naturally infected with Brucella abortus precipitate water soluble antigens extracted by sonication from B. abortus. One of these antigens resembles antigen E (Baughn and Freeman) as it is excluded from Sephadex G-200 gels, migrates anodally when electrophoresed at pH 8.6, resists heating at 100 degrees C for ten minutes and appears to be susceptible to papain digestion. Precipitins specific for this antigen remained in sera from which all detectable Brucella agglutinating antibody had been removed by adsorption with live or heat killed B. abortus. The antigen has been extracted from smooth and rough strains of B abortus. Precipitins specific for this antigen have been detected in antisera produced against Brucella canis.

Agglutination Tests↗

A study of blood eosinophil counting in calves.

Blood eosinophils were determined in eight 7--13-month-old calves that had been reared under parasite-free conditions. Eosinophil counts were obtained by three methods, a) a direct count, b) a differential count and c) an indirect count (i.e. differential count x total leucocyte count). Methodological errors of these methods were determined. Upper limits of 1,000 eosinophils/micronl (direct count) and 9.5 per cent eosinophils (differential count) have been estimated an suitable working standards for calves of this age group. The distribution of eosinophils was skew, most direct counts being below 700 cells/micronl and most differential counts being below 7.5 per cent. A high degree of correlation was found between results obtained by either method, but an even higher correlation was found between direct and indirect counts.

Age Factors↗

Preparation of antisera to the mu chain of IgM.

The protein fraction in the first peak obtained by Sephadex G-200 gel filtration of normal bovine serum was reduced with 2-mercaptoethanol, alkylated with iodoactamide and recycled on a Sephadex G-200 column. The resultant chromatogram indicated the presence of two peaks the second of which was found to be pure monomeric IgM. Immunization of rabbits with the second peak protein resulted in the production of an antiserum with both heavy and light-chain activity. The light-chain activity was simply removed by absorption of the antiserum with glutaraldehyde-polymerized material obtained from the second peak of the initial Sephadex G-200 eluate, yielding an antiserum monospecific for the heavy chain of the IgM molecule.

Animals↗

Bovine reaginic antibody. I. Rat mast cell degranulation by bovine allergic serum.

A method of utilizing morphological changes in rat mast cells to determine reaginic antibody activity in bovine serum is described. This technique, which has been shown to be useful for the diagnosis of allergies in man, relies on the ability of antigen to degranulate mast cells sensitized with allergic serum. Experiments with radioactively-labelled allergic bovine globulin indicated the specificity of the binding of such proteins to rat mast cells. Cross-reaction between reaginic bovine antibody and human IgE was shown by a binding assay involving the uptake of 125I-labelled anti-human IgE globulin by mast cells incubated with bovine passive cutaneous anaphylaxis positive globulin.

Animals↗

[Intoxication in cattle caused by a batch of sugar beet pulp (author's transl)].

During the period from Dec. 7th 1972 to Jan. 8th 1973 76 cattle deaths were reported in 20 herds on the island of Møon and the adjacent south-eastern area of Sealand. The disease was characterized by a sudden onset and a rapid and invariably fatal course. Initially, there was a loss of appetite, depression, excessive salivation and incoordination. These symptoms progressed to paralysis and, in some animals, trmor and convulsions. Death usually ensued less than 2 hours after the first observation of symptoms. Losses in the herds varied from 1 to 12 animals. In herds with multiple incidents the majority of deaths occurred in the 24-hour-period following observation of the first case. Pathology: Gross lesions were few and inconclusive. Histology revealed marked dilatation of cerebral and maningeal blood vessels (arterioles, venoles and capillaries), with perivascular edema and haemorrhage. Adjacent neurons and glia cells showed various degrees of degeneration, apparently secondary to the vascular lesion. In all affected herds sugar beet pulp from one particular sugar mill had been used during the period preceding the outbreak. The syndrome was reproduced by feeding sugar beet pulp from this batch to two heifers. The heifers showed symptoms after 19 and 32 days' feeding, resp. and died after a few hours. Clinical and pathological features were identical with those observed in the spontaneous disease. Thus, it was proved that the particular batch of pulp was responsible for the disease. The investigation did not, however, reveal a toxic factor in this batch. Analyses for lead, arsenic, mercury, nitrite, alkyl phosphates, chlorinated insecticides and Cl. botulinum toxin were negative. Batches of the sugar beet pulp showed pronounced microbial deterioration, the flora being dominated by yeasts and filamentous fungi (moulds). Several species of fungi have been isolated but so fat their possible role in the etiology of the syndrome remains unsettled. The syndrome bears some resemblance to cerebrocortical necrosis (C.C.N.) but differs in several clinical and pathological details. It is tentatively suggested that the beet pulp may have contained one or more toxic substances that interfere with microbial activity in the rumen, resulting in a disturbance of synthesis or absorption of essential metabolites. The clinical, epidemiological and pathological findings are compatible with the hypothesis that the syndrome might be due to fungal toxins. Accordingly, the isolated fungi are now being studied in more detail.

Animal Feed↗