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R Myhrman

Publications and source records attributed to R Myhrman.

4 recordsLinked to original sources
PubMed1999

Evaluation of raw and heated velvet beans (Mucuna pruriens) as feed ingredients for broilers.

Velvet bean plants (Mucuna pruriens) are used widely outside the U.S. as a cover crop. The beans (VB), high in protein, contain toxic substances that possibly can be destroyed by heating. Few data are available on the use of VB in poultry nutrition. We examined the effects of raw and dry-roasted VB on broiler performance in two experiments. In Experiment 1, 10, 20, and 30% raw VB were substituted into nutritionally balanced rations fed 0 to 42 d of age. Raw VB caused progressive reductions in growth; at 42 d of age, broilers fed 30% VB weighed 39% of controls. Feed intake declined significantly only with 30% VB. Feed efficiency decreased significantly with 20 and 30% VB. In Experiment 2, 10% raw VB and 10, 20, and 30% heated VB were fed 0 to 42 d. With 10% raw VB, broilers grew significantly slower but feed intake was unchanged. Inclusion of 10% heated VB allowed better growth than raw VB, and by 42 d of age, growth was not significantly different from that of controls. At 20 and 30%, heated VB promoted much better growth and efficiency than raw VB in Experiment 1, but values were significantly lower than those of controls. With 30% heated VB, broilers grew to 66% of control, a marked improvement over raw VB. Carcass yield was unaffected. Trypsin inhibitor activity but not L-3,4-dihydroxyphenylalanine (L-DOPA) in VB was destroyed by heating. We conclude that dry heating of VB partially destroys its growth-inhibiting factor(s), allowing successful use of 10% heated VB in broiler rations. Higher levels of heated VB reduced broiler performance, although results were much better than those of raw VB.

Animal Feed↗
PubMed1988

Bacterial N-succinyl-L-diaminopimelic acid desuccinylase. Purification, partial characterization, and substrate specificity.

The enzyme N-succinyl-L-diaminopimelic acid desuccinylase from Escherichia coli has been purified 7,100-fold to apparent homogeneity. The enzyme is part of the diaminopimelic acid-lysine pathway in bacteria and catalyzes the hydrolysis of N-succinyl-L-diaminopimelic acid to produce L-diaminopimelic acid and succinate. The enzyme exists as a mixture of dimeric and tetrameric species of identical subunits of molecular weight approximately 40,000. Activity was completely abolished following dialysis of the enzyme against metal chelators. Cobalt(II) and zinc were effective in restoring the activity. The apparent affinities of the apoenzyme for cobalt and zinc were similar (Kd values near 1 microM) and the cobalt enzyme was 2.2-fold more active than the zinc enzyme. The Km and turnover number for the hydrolysis of the natural substrate, N-succinyl-L-diaminopimelic acid, were 0.4 mM and 16,000 min-1, respectively. The substrate specificity of the enzyme was defined by preparing a number of substrate analogues that systematically lack the various functional groups present in the molecule. These studies show that the enzyme is highly specific for the natural substrate. These properties of N-succinyl-L-diaminopimelic acid desuccinylase and the fact that the enzyme is essential for bacterial growth make it an ideal target for the development of inhibitors with potential antibacterial activity.

Amidohydrolases↗
PubMed1976

Complement activation by interaction of polyanions and polycations.

Interactions between heparin and protamine in normal human serum previously were found to activate the primary complement pathway and deplete the early-acting complement components. In the present investigation, the role of heparin-protamine complexes, immunoglobulins, C1q and C1-INH in this interaction was studied. Heparin and protamine, like antibody and antigen, were found to combine in multiple proportions; those proportions which resulted in optimal precipitation also induced maximal C consumption. Complexes formed in serum contained C1q and IgG, but the amount of C1q was insufficient to account for the total depletion of C1 haemolytic activity, and immunoglobulins were not required for activation of complement to occur: maximal consumption was observed in immunoabsorbed hypogammaglobulinaemic sera in which IgG, IgM and IgA were undetectable (less than 5, less than 10 and less than 7 mug/ml, respectively). Purified C1q aggregated heparin-protamine complexes formed or forming in the presence or absence of serum. The ability to induce maximal C consumption was rapidly lost as heparin and protamine interacted, and complexes preformed either in serum or buffer, or supernates thereof, were relatively ineffective in complement consumption. Thus, the consumption of complement seems to occur via transient reactivity with C1,probably at the level of C1q. It seems to be limited by the ability of free heparin to potentiate the activity of C1-INH, and perhaps also by its direct effect upon the early acting C components. These experiments support the concept that complement activation by interactions between polyelectrolytes such as heparin and protamine, like interactions between the antibodies and antigens, may have a role in the initiation of inflammatory reactions by direct activation of the complement system.

Agammaglobulinemia↗