scholarly journals Formation of ketone bodies from [14C]palmitate and [14C]glycerol by tissues from ketotic sheep

1968 ◽  
Vol 106 (1) ◽  
pp. 289-292 ◽  
Author(s):  
J. A. Taylor ◽  
H. D. Jackson
Keyword(s):  
Carbon Dioxide ◽  
Ketone Bodies ◽  
Epithelial Tissue ◽  
Complete Oxidation ◽  
Long Chain Fatty Acids ◽  
Rumen Epithelium ◽  
Extrahepatic Tissues ◽  
Sheep Rumen ◽  
Tissue Nitrogen

Labelled ketone bodies were produced readily from [U−14C]palmitate, [2−14C]palmitate and [1−14C]glycerol by sheep rumen-epithelial and liver tissues in vitro. On a tissue-nitrogen basis, both tissues had similar capacities for ketogenesis. Palmitate was a ketogenic substrate in both rumen-epithelial tissue and liver, and more of its 14C appeared in ketone bodies than in the 14CO2 liberated. Glycerol was actively metabolized to ketone bodies, but more readily underwent complete oxidation to carbon dioxide; this complete oxidation was most pronounced in rumen-epithelial tissue from ketotic ewes. These experiments with labelled compounds confirm earlier observations that rumen-epithelial tissue, like liver, actively forms ketone bodies from long-chain fatty acids and show further that normal rumen-epithelial tissue can convert palmitate into ketone bodies as readily as into carbon dioxide. Free glycerol, which is metabolized only by liver tissue in non-ruminants, is also metabolized by rumen epithelium. The rumen epithelium thus has unique metabolic capacity among extrahepatic tissues.

EFFECT OF AGE AND DIET ON IN VITRO METABOLISM IN RUMEN EPITHELIUM FROM HOLSTEIN CALVES

1988 ◽  
Vol 68 (4) ◽  
pp. 1245-1251 ◽  
Author(s):  
ROY S. BUSH
Keyword(s):  
Volatile Fatty Acids ◽  
Acid Metabolism ◽  
Ketone Bodies ◽  
Glucose Production ◽  
Major Product ◽  
Epithelial Tissue ◽  
Rumen Epithelium ◽  
Holstein Calves ◽  
Effect Of Age

Fresh rumen epithelial tissue was collected from calves slaughtered at 3, 12, 19, 30 and 60 d of age. These calves were fed milk until 28 d of age and had received starter and hay after 10 d of age. Samples also were collected at 30 and 60 d of age from calves fed only milk. Epithelial tissue was incubated with combinations of volatile fatty acids and sources of ammonia to measure some of the metabolic end products as indicators of metabolism and physiological development. Ketone bodies were the major product of volatile fatty acid metabolism by epithelial tissue under these incubation conditions. By 60 d of age, the weaned calves were producing ketones at rates similar to those reported previously for mature tissue and at approximately 40% of the mature rate at 30 d of age. At 60 d of age, milk-fed calves were producing ketones at 10–15% of mature levels. Very young and milk-fed calves appeared to produce more lactic acid than did older calves that were weaned onto dry feeds. There was no net glucose production, however, there was some accumulation of glucose in the incubations of epithelium from calves at 19 d of age. This may be related to a shift in epithelial metabolism occurring at this age. Key words: Rumen epithelium, metabolism, ketogenesis, milk-fed calf

scholarly journals Ketogenesis from butyrate and acetate by the caecum and the colon of rabbits

1972 ◽  
Vol 130 (3) ◽  
pp. 785-790 ◽  
Author(s):  
S. J. Henning ◽  
F. J. R. Hird
Keyword(s):  
Carbon Dioxide ◽  
Liver Tissue ◽  
Ketone Bodies ◽  
Distal Colon ◽  
Proximal Colon ◽  
Enzyme Assays ◽  
Liver Slices

1. When studied in vitro, tissue from the caecum and the proximal colon of rabbits converted butyrate into ketone bodies. The conversion was similar to that observed with liver slices. The ketogenic activity was associated with the mucosa rather than the muscle of the gut wall and, in the colon, diminished as the distance from the caecal–colonic junction increased. 2. Tissue from the wall of the ileum, caecum, proximal colon and distal colon was also shown to metabolize [1-14C]butyrate to carbon dioxide. 3. Enzyme assays showed that in both liver tissue and caecal mucosa the activity of hydroxymethylglutaryl-CoA synthase was more than ten times that of acetoacetyl-CoA deacylase. Labelling experiments in vitro gave confirmation of the hydroxymethylglutaryl-CoA pathway. 4. The significance of the conversion of butyrate into ketone bodies is discussed.

scholarly journals The relationships between potassium intakes, transmural potential difference of the rumen epithelium and magnesium absorption in wethers

2004 ◽  
Vol 91 (2) ◽  
pp. 183-189 ◽  
Author(s):  
S. Jittakhot ◽  
J. Th. Schonewille ◽  
H. S. Wouterse ◽  
C. Yuangklang ◽  
A. C. Beynen
Keyword(s):  
Latin Square ◽  
Potential Difference ◽  
Serosal Side ◽  
Rumen Epithelium ◽  
K Concentration ◽  
Sheep Rumen

In vitro studies with isolated sheep rumen epithelium have shown that an increase in the lumen K concentration induces an increase in the transmural potential difference across the rumen epithelium (serosal side: positive), which is associated with a decrease in Mg transport. However, at lumen K concentrations >80 mmol/l, Mg transport across the epithelium became independent of the lumen K concentration. The present study was carried out to determine whether this observation also occurs in vivo. Four ruminally fistulated wethers were fed four rations supplemented with KHCO3 (15·7, 37·6, 59·4 or 77·4 g K/kg DM) in a 4×4 Latin square design. Increased K intakes significantly increased the rumen K concentration. For all data combined, Mg absorption expressed as % intake was negatively correlated with the rumen K concentration. However, apparent Mg absorption either expressed in absolute terms (g/d) or as % intake was not significantly affected when the dietary K concentration was increased from 59·4 to 77·4 g/kg DM. Rumen K concentration was inversely correlated with the transmural potential difference (blood side: positive) (Pearson's r −0·709; R2adj 0·468, P=0·002, n 16). It is concluded that in wethers apparent Mg absorption becomes independent of the dietary K concentration when the K concentration is >60 g/kg DM or equivalent to a postprandial rumen K concentration of about 125 mmol/l.

scholarly journals Novel Transcriptional Regulons for Autotrophic Cycle Genes in Crenarchaeota

2015 ◽  
Vol 197 (14) ◽  
pp. 2383-2391 ◽  
Author(s):  
Semen A. Leyn ◽  
Irina A. Rodionova ◽  
Xiaoqing Li ◽  
Dmitry A. Rodionov
Keyword(s):  
Carbon Dioxide ◽  
Transcriptional Regulation ◽  
Comparative Genomics ◽  
Dna Binding ◽  
Transcriptional Control ◽  
Binding Assays ◽  
Promoter Regions ◽  
Content Type ◽  
Genome Context

ABSTRACTAutotrophic microorganisms are able to utilize carbon dioxide as their only carbon source, or, alternatively, many of them can grow heterotrophically on organics. Different variants of autotrophic pathways have been identified in various lineages of the phylumCrenarchaeota. Aerobic members of the orderSulfolobalesutilize the hydroxypropionate-hydroxybutyrate cycle (HHC) to fix inorganic carbon, whereas anaerobicThermoprotealesuse the dicarboxylate-hydroxybutyrate cycle (DHC). Knowledge of transcriptional regulation of autotrophic pathways inArchaeais limited. We applied a comparative genomics approach to predict novel autotrophic regulons in theCrenarchaeota. We report identification of two novel DNA motifs associated with the autotrophic pathway genes in theSulfolobales(HHC box) andThermoproteales(DHC box). Based on genome context evidence, the HHC box regulon was attributed to a novel transcription factor from the TrmB family named HhcR. Orthologs of HhcR are present in allSulfolobalesgenomes but were not found in other lineages. A predicted HHC box regulatory motif was confirmed byin vitrobinding assays with the recombinant HhcR protein fromMetallosphaera yellowstonensis. For the DHC box regulon, we assigned a different potential regulator, named DhcR, which is restricted to the orderThermoproteales. DhcR inThermoproteus neutrophilus(Tneu_0751) was previously identified as a DNA-binding protein with high affinity for the promoter regions of two autotrophic operons. The global HhcR and DhcR regulons reconstructed by comparative genomics were reconciled with available omics data inMetallosphaeraandThermoproteusspp. The identified regulons constitute two novel mechanisms for transcriptional control of autotrophic pathways in theCrenarchaeota.IMPORTANCELittle is known about transcriptional regulation of carbon dioxide fixation pathways inArchaea. We previously applied the comparative genomics approach for reconstruction of DtxR family regulons in diverse lineages ofArchaea. Here, we utilize similar computational approaches to identify novel regulatory motifs for genes that are autotrophically induced in microorganisms from two lineages ofCrenarchaeotaand to reconstruct the respective regulons. The predicted novel regulons in archaeal genomes control the majority of autotrophic pathway genes and also other carbon and energy metabolism genes. The HhcR regulon was experimentally validated by DNA-binding assays inMetallosphaeraspp. Novel regulons described for the first time in this work provide a basis for understanding the mechanisms of transcriptional regulation of autotrophic pathways inArchaea.

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