Brown fat cells isolated from adult golden hamsters have earlier been found to respond to addition of the physiological agonist norepinephrine with an increased rate of oxygen consumption and with fatty acid release. Working with these cells, we found the following. 1. The presence of albumin in the incubation medium (phosphate buffer) increases norepinephrine-induced fatty acid release and tends to stabilize the rate of oxygen consumption; bubbling of phosphate buffer with 5% CO2 in air has only a slight effect on fatty acid release. 2. In the presence of albumin, the norepinephrine-induced rate of oxygen consumption is also stable in bicarbonate buffer; it is higher than in the phosphate + CO2 buffer and the brown fat cells have a higher sensitivity to norepinephrine. 3. 20 mM phosphate (as e.g. present in a phosphate buffer) inhibits both fatty acid release and oxygen consumption. 4. Insulin inhibits the rate of oxygen consumption, but only at suboptimal concentrations of norepinephrine. 5. Atractylate inhibits submaximal norepinephrine-induced respiration, indicating that some oxidative phosphorylation takes place in norepinephrine-stimulated brown fat cells. 6. Fatty acid export from brown fat should be regarded as physiologically important. 相似文献
The structure of the polysaccharide antigen produced by Eubacterium saburreum, strain L 32, has been investigated. The principal methods used were methylation analysis, graded hydrolysis with acid, and n.m.r. spectroscopy. The polysaccharide, which contains the unusual sugar 3,6-dideoxy-D-arabino-hexose (tyvelose, Tyv), is composed of trisaccharide repeating-units having the following structure: 相似文献
The polysaccharide antigen produced by Eubacterium saburreum, strain L 49, is composed of D-glycero-D-galacto-heptose and a new sugar, tentatively identified as 6-deoxy-D-altro-heptose. It contains chains of alternating (1 leads to 3)- and (1 leads to 6)- linked beta-D-glycero-D-galacto-heptopyranosyl residues, the latter being substituted with 6-deoxy-alpha-heptofuranosyl groups at O-3. The polysaccharide further contains 0-acetyl groups, linked to O-7 of part of the heptosyl residues and to O-2 of part of the 6-deoxyheptosyl groups. 相似文献
The structure of the capsular polysaccharide from Klebsiella type 59 has been investigated by methylation analysis, a modified Smith-degradation procedure, and uronic acid degradation followed by oxidation and elimination of the substituents of the oxidized residue. The oligomeric fragments produced by these degradative procedures were isolated and characterized. O-Acetyl groups were identified and their position determined. The polysaccharide consists of the following pentasaccharide repeating-unit (dotted lines indicate that only some of the residues carry the O-acetyl substituent). See article. 相似文献
1. Brown adipose tissue of the hamster possesses high specific activities of soluble, cytoplasmic NAD-linked, as well as mitochondrial flavin-coupled, glycerol-3-phosphate dehydrogenases. The ratio of the two enzyme activities is high (close to 1), when compared with other tissues of the hamster. 2. In the presence of rotenone, NADH is oxidised very poorly by homogenates of brown adipose tissue. A high rate of oxidation is obtained upon further addition of dihydroxyacetone phosphate, which itself is negligible oxidised. When followed fluorimetrically glycerol 3-phosphate can also be observed to induce NADH oxidation, but only after a significant lag time. Similar results are obtained with isolated mitochondria plus high-speed supernatant. With high-speed supernatant alone, only dihydroxyacetone phosphate has any effect, whereas with isolated mitochondria neither dihydroxyacetone phosphate nor glycerol 3-phosphate induce any NADH disappearance. 3. Respiration induced by NADH plus dihydroxyacetone phosphate in homogenates equals 56% of the respiration induced by glycerol 3-phosphate alone. 4. Respiration induced by NADH plus dihydroxyacetone phosphate, as well as that induced by glycerol 3-phosphate, is inhibited by the same concentrations of inhibitors as are required for inhibition of the mitochondrial dehydrogenase i.e. EDTA, long-chain unsaturated fatty acids, long-chain fatty acyl CoA esters. 5. In isolated brown adipocytes in the presence of rotenone, norepinephrine significantly inhibits respiration induced by glycerol 3-phosphate. 6. The results obtained are discussed with respect to the role of glycerol 3-phosphate as an electron sink for cytosolic reducing equivalents to maintain a low level of extramitochondrial NADH. A means of maintaining a level of glycerol 3-phosphate adequate for triglyceride synthesis is also considered. 相似文献
Variation in inhibition of real-time PCR was investigated with DNA extracts from 50 aquifer sediment core samples of 5 cm length collected through a 2.5 meter vertical profile across a landfill leachate plume. The inhibition was quantified using an internal control of the green fluorescent protein (gfp) gene, which was spiked into the real-time PCR reactions. The inhibition was investigated at twogfpgene concentrations: at 1.7 · 107gfpgene copies/g sediment (5.1 · 104gfpgene copies/PCR reaction) and at 1.7 · 105gfpgene copies/g sediment (5.1 · 102gfpgene copies/PCR reaction). Despite the low TOC content of the sediment (average 0.4 mg C/g dw) the average real-time PCR response was partially inhibited, compared to a reference (pure water), at both high and lowgfpconcentrations. The relative amplification (reference = 1) was 0.85 ± 0.20 (high) and 0.66 ± 0.23 (low), showing significantly (P < 0.05) stronger inhibition at the lower target gene concentration. The inhibition of the real-time PCR did not show a systematic variation in the vertical profile related to plume position but variations were significant on a small scale of 5–15 cm depth intervals. One of the 50 samples failed to produce a signal with either concentration of thegfpinternal control and three other samples inhibited real-time PCR at both high and lowgfp concentration. These 4 samples, which were the samples with the highest inhibition, were the only DNA extracts with a visible brown colouration, indicating contents of humic-like substances. Elevated absorbance at 400 nm of these samples also indicated that humic-like substances were responsible for inhibition. However, other factors not associated with either absorbance or TOC may have contributed to the inhibition in less inhibited samples since the variation in real-time PCR response could not be sufficiently explained by absorbance or TOC. The results of this study suggest that an internal control is needed in real-time PCR reactions with DNA from environmental samples due to variation in inhibition to correctly quantify the number of target genes, especially at low target gene concentrations, when dilution of DNA extracts is not practical. 相似文献
Zygaena filipendulae accumulates the cyanogenic glucosides linamarin and lotaustralin by larval sequestration from the food plant or de novo biosynthesis. We have previously demonstrated that the Z. filipendulae male transfers linamarin and lotaustralin to the female in the course of mating. In this study we report the additional transfer of 5-hydroxytryptophan glucoside (5-(β-d-glucopyranosyloxy)-l-Tryptophan) from the Z. filipendulae male internal genitalia to the female spermatophore around 5 h into the mating process. 5-Hydroxytryptophan glucoside is present in the virgin male internal genitalia, and production continues during the early phase of mating. Following initiation of 5-hydroxytryptophan glucoside transfer to the female, the amount in male internal genitalia is drastically reduced until after mating where it is slowly replenished. For unambiguous structural identification, 5-hydroxytryptophan glucoside was chemically synthesized and used as an authentic standard. The biological function of 5-hydroxytryptophan glucoside remains to be established, although we have indications that it may be involved in inducing the female to stay in copula and delay egg-laying to prevent re-mating of the female. To our knowledge 5-hydroxytryptophan glucoside has not previously been reported present in animal tissues. 相似文献