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The objective of the present study was to examine the interaction between graded levels of leucine and dietary crude protein. Dose-response curves were generated using four 3 x 3 Latin squares (two dogs/square). Each square represented one of two concentrations of crude protein (140 or 280 g/kg diet) and one of two combinations of three concentrations of leucine (5.0, 7.0 and 9.0 g/kg diet or 9.0, 11 and 13 g/kg diet). An additional experiment was performed by feeding crude protein at 210 g/kg diet with either 7.0 or 11 g leucine/kg diet. Weight gain, food intake, nitrogen retention, plasma albumin and plasma amino acids were measured. The requirement was determined to be the minimum leucine concentration required to maximize weight gain and nitrogen retention. For 8-14-week-old male Beagle dogs, 140 g crude protein/kg diet in a diet containing 18 kJ metabolizable energy/g does not appear to support maximal growth. The leucine requirement was not affected by doubling the dietary crude protein level from 140 to 280 g/kg diet. From these results, the leucine requirement of 8-14-week-old Beagle dogs appears to be 11 g leucine/kg diet independent of the level of dietary crude protein, whereas dogs over 14 weeks require only 7 g leucine/kg diet for maximal nitrogen retention.

Jack pine (Pinus banksiana Lamb.) seedlings were inoculated with either one of the ectomycorrhizal (ECM) fungi, Laccaria bicolor (Miare) Orton or Pisolithus tinctorius (Pers.) Coker and Couch, and grown for 16 weeks in a growth chamber along with non-ECM controls. Five enzymes involved with the assimilation of nitrogen or the synthesis of amino acids were measured in the 3 jack pine root systems as well as in the pure fungal cultures. Pisolithus tinctorius in pure cultures. Pisolithus tinctorius in pure culture had no detectable activity of nitrate reductase (NR, EC 1.6.6.1), glutamate dehydrogenase (GDH, EC 1.4.1.2), glutamate oxoglutarate aminotransferase (GOGAT, EC 1.4.1.13) but did have some glutamine synthetase (GS, EC 6.3.1.2) activity. Laccaria bicolor in pure culture had no NR activity, small levels of GDCO activity, and high GS, GDH and GOGAT activity. The high levels of enzymatic activity present in L. bicolor indicate that it may play a greater role in the nitrogen metabolism of its host plant than P. tinctorius. ECM infection clearly altered the enzymatic activity in jack pine roots but the nature of these changes depended on the fungal associate. Non-ECM root systems had higher specific activities than ECM root systems for NR, GS, GDH and GDCO but GOGAT activities were the same for both the ECM and non-ECM roots. Root systems infected with L. bicolor had significantly greater NR and GDCO activity than those infected with P. tinctorius. Differences in the GS activity of the two fungi in pure culture corresponded to the GS activity of jack pine roots in symbiotic association with these fungi. While the free amino acids profiles in foots were significantly affected by ECM infection, the profile of free amino acids exported to the stem was the same for all treatments. High asparagines and low glutamine in roots infected with P. tinctorius indicates that asparagines synthetase (EC x.x.x.x) activity should be higher within this symbiotic association than in the L. bicolor association or in the non-mycorrhizal roots. [ABSTRACT FROM AUTHOR]

The fimbrial subunit genes of Bacteroides nodosus may be divided into two distinct classes, based on the sequence of the major subunit gene fimA (accompanying paper -- Mattick et al., 1991). The genetic organization of the fimbrial germ region in these two clams is also distinct. Upstream of fimA in both classes in opposite transcriptional orientation is the gene aroA which encodes amino acid biosynthetic enzyme 5-enolpyruvylshikimate-3-phosphate synthase. However, downstream of fimA the two classes are quite different until homology is restored at a bidirectional transcription termination signal separating the fimbrial operon from a gene clpB, which appears to encode the regulatory subunit of an ATP-dependent protease. Between aroA and clpB class I strains contain, apart from fimA, only one other germ (fimB). Sequence and polymorase chain reaction analyses indicate that fimB does not have a separate promoter but rather is co-transcribed with fimA at a level attenuated by the strength of the transcription termination signal in the intergenic region. In class II strains fimA is followed by a more extended region containing three genes, which appear to have the same transcriptional arrangement as fimB. The second of these genes (fimD) may represent a functional analogue of fimb although there is no close sequence homology. The first gene (fimC) has no obvious similarity to either fimB or fimD. Beyond fimD, at the 3′ end of the class II-specific region, is a variant fimbrial subunit germ (fimZ) which is virtually identical in serogroups D and H and which appears to represent a duplicate, possibly redundant, gene closely related to the progenitor of the more divergent structural subunit fimA gene found in these strains. Comparisons of the predicted fimZ... [ABSTRACT FROM AUTHOR]