Nitrogen cycling in sheep

Nolan, John; Norton, B. W.; Leng, R. A.

doi:10.1079/pns19730021

Cited by 20 publications

(8 citation statements)

References 23 publications

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“…In mammals, urea N plays an important source of N during low protein intake [2]. Ruminants use recycled N in order to maintain microbial growth in the reticulorumen and hindgut [I].…”

mentioning

confidence: 99%

Isolation of a RT-PCR fragment from human colon and sheep rumen RNA with nucleotide sequence similarity to human and rat urea transporter isoforms

Ritzhaupt

Wood

Jackson

et al. 1998

Biochemical Society Transactions

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The main source of nitrogen (N) in the colon is ammonia derived from urea [I]. In mammals, urea N plays an important source of N during low protein intake [2]. Ruminants use recycled N in order to maintain microbial growth in the reticulorumen and hindgut [I]. Urea transporters (UT) have been identified in rat [3, 41, rabbit [5] and human kidney [6], and human bone marrow cells [7] and corresponding cDNAs cloned and sequenced. Recently, the rat equivalent to the human erythrocyte urea transporter cDNA (HUT1 1) was cloned and designated UT3 [4]. All three isofonns of the rat UT are expressed in the kidney [4].In our previous studies we investigated the mechanism for the transport of urea across sheep rumen and colonic epithelia. Our data suggested the presence of a carrier mediated, facilitated transport mechanism for urea across the epithelial cells of these tissues [8]. Northern blot analysis using the full length rabbit UT2 cDNA did not produce a signal with RNA isolated from colonic and rumen tissues [8]. A weak signal was detected in human colonic tissue using the HUT1 1 cDNA [6]. These findings raised the question of whether the UT in the human colon was structurally more closely related to HUT1 1 than HUTZ. Based on these data, we designed oligonucleotide primers against the human erythrocyte UT, HUT1 I, for use in reverse transcription polymerase chain reaction (RT-PCR). The RT-PCR reaction was performed in a single tube containing 1 pg total RNA isolated from human colon, sheep rumen or rat kidney.The antisense primer, nt 787-802 (5'-GCAGCATGCAGGCACATGAG-3') was used for the reverse transcription and the sense primer, nt 211-230 ( 5 ' -GGCATATCCCAAGTGGTGTT-3') was used for DNA amplification. Figure 1 : Analysis of RT-PCR products 1 pI of the RT-PCR reaction mixture was analysed on a 1.6 % agarose gel.The desired amplicons were directly subcloned into pGEM-T vector (Promega) and custom sequenced (University of Durham). SpeciesIdentity (%) human colon ShCW lumen human colon Fragment 100 sheep rumen fragment 87 rat kidney fragment 95.8 human erythrocyte UT (HUT1 1) 81.7 human kidney UT (HUT2) 70.9 rat kidney UT (UT3) 95.8 rabbit kidney UT (UT2) 72.4 rat kidney UT (rUT2) 70.5 87 100 87 81.5 68.8 87.2 70.1 69.5 ~~ "&le 1. C-son of nucleotide Folon and sheeo rumen RT-PCR fragments with & i transM)rters Comparisons are based on sequenced human colonic, sheep rumen and rat kidney RT-PCR fragments using LALIGN.Using primers against the human erythrocyte UT (HUTI1) in RT-PCR, we identified products of similar sizes in RNA samples isolated from rat kidney, human colon and sheep rumen (Figure 1). RNA isolated from rat kidney was used as a positive control for RT-PCR. Sequencing of the purified pmducts nvwled close similarities amongst the three. As expected, the rat kidney fragment was identical to rat UT3.In Table 1 the nucleotide sequences of the cloned human colon and sheep rumen RT-PCR products have been compared with other urea transport proteins identified to date. Interestingly, the sequence of the human colo...

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“…In mammals, urea N plays an important source of N during low protein intake [2]. Ruminants use recycled N in order to maintain microbial growth in the reticulorumen and hindgut [I].…”

mentioning

confidence: 99%

Isolation of a RT-PCR fragment from human colon and sheep rumen RNA with nucleotide sequence similarity to human and rat urea transporter isoforms

Ritzhaupt

Wood

Jackson

et al. 1998

Biochemical Society Transactions

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“…However the necessity of prolonged heating of oils at temperatures approaching 200 C prompted the concern of many researchers regarding the degradation products that could develop in such oils (1)(2)(3). Even though there is evidence that in commercial processing the level of degradation of the heat transfer agent is insignificant (4)(5)(6), commercial processes for the roasting of nut products in a blend of hexitols (mannitol and sorbitol), which are disclosed in two recently issued patents (7,8), could be expected to be challenged in a similar manner as the vegetable frying oils. The two processes (7,8) result in some pick-up of the heat-exchange medium by the food itself.…”

Section: Introductionmentioning

confidence: 99%

Analytical critique of hexitols used as a cooking medium

Waltking¹,

Bleffert²,

Brickman³

et al. 1973

J Americ Oil Chem Soc

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Analysis by differential scanning calorimetry and gas liquid chromatography of hexitol blends used as a roasting medium for peanuts demonstrated that there was no significant deterioration of the hexitol components due to prolonged repetitive heating. Small decreases in the hexitol content of the roasting medium, which were found after 72 hr at a temperature of 330 F, closely corresponded to the increases in the hexitan content. Furthermore no evidence could be found of any significant oxidative degradation products in any of the polyol samples analyzed.

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“…Although it can not be stated with surety, these investigations, along with the developing interest in cecal fermentation, must have led re searchers to consider similar transfers in the small and large intestine (Nolan and Leng, 1972;Nolan et , 1973;Mazanov and Nolan, 1976;Nolan et al, 1976;Okumura et al, 1976). Approximately 76% of the apparently degraded urea in the ruminant digestive tract was degraded by microbial fermentation postruminally according to Nolan and Leng (1972).…”

Section: Some Researchers Contend the Transfer To A Simple Diffusion mentioning

confidence: 99%

“…Fewer intestinal mucosa cells are shed into the lumen of germfree and antibiotic modi fied animals (Combe et al, 1965;Schaedler, 1973;Visek, 1978). Work by Snook and Meyer (1964) In subsequent papers from this same laboratory (Nolan and Leng, 1972;Nolan et al, 1973;Nolan et al, 1976;Mazanov and Nolan, 1976) an attempt was made to more specifically quantitate the amount and site of this degradation. From these data it was estimated that 75 to 80% of the blood urea degraded in the total intestine occurred out side of the rumen.…”

Section: Reutilization Of Intestinal Nitrogenmentioning

confidence: 99%

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The origin of the metabolic fecal nitrogen in relation to protein requirements

Nipper

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Energy and nitrogen intake Growth rate and final weight Carcass Weight and Composition Carcass weight Carcass nitrogen composition 106 Protein evaluation based on carcass composition 119 Liver weight 126 Cecal Weight and Composition 130 Cecal weight 130 Cecal nitrogen composition 138 Intestinal Nitrogen Movement and Blood Nitrogen Composition 160 Initial Slaughter Group Comparison 169 GENERAL DISCUSSION

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Nitrogen cycling in sheep

Cited by 20 publications

References 23 publications

Isolation of a RT-PCR fragment from human colon and sheep rumen RNA with nucleotide sequence similarity to human and rat urea transporter isoforms

Isolation of a RT-PCR fragment from human colon and sheep rumen RNA with nucleotide sequence similarity to human and rat urea transporter isoforms

Analytical critique of hexitols used as a cooking medium

The origin of the metabolic fecal nitrogen in relation to protein requirements

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