Metabolism of [1-14C]glyoxylate, [1-14C]-glycollate, [1-14C]glycine and [2-14C]-glycine by homogenates of kidney and liver tissue from hyperoxaluric and control subjects

1. The metabolism of [1-(14)C]glyoxylate to carbon dioxide, glycine, oxalate, serine, formate and glycollate was investigated in hyperoxaluric and control subjects' kidney and liver tissue in vitro. 2. Only glycine and carbon dioxide became significantly labelled with (14)C, and this was less in the hyperoxaluric patients' kidney tissue than in the control tissue. 3. Liver did not show this difference. 4. The metabolism of [1-(14)C]glycollate was also studied in the liver tissue; glyoxylate formation was demonstrated and the formation of (14)CO(2) from this substrate was likewise unimpaired in the hyperoxaluric patients' liver tissue in these experiments. 5. Glycine was not metabolized by human kidney, liver or blood cells under the conditions used. 6. These observations show that glyoxylate metabolism by the kidney is impaired in primary hyperoxaluria.     

The chemical synthesis and biological oxidation of 7α-hydroxy[26-14C]cholesterol, 7-dehydro[26-14C]cholesterol and 26-hydroxy[26-14C]cholesterol

1. 26-Hydroxycholesterol was obtained by reducing the methyl ester of (±)-3β-hydroxycholest-5-en-26-oic acid, which was synthesized from 25-oxonorcholesterol. 2. Methods for preparing 7α-hydroxycholesterol and 7-dehydrocholesterol were modified to allow the micro-scale preparation of these [¹⁴C]sterols from [26-¹⁴C]-cholesterol. 3. 26-Hydroxycholesterol was oxidized more readily than 7α-hydroxycholesterol, 7-dehydrocholesterol or cholesterol by mitochondrial preparations from livers of mice, rats, guinea pigs, common toads (Bufo vulgaris) and Caiman crocodylus. 4. (±)-3β-Hydroxy[26-¹⁴C]cholest-5-en-26-oic acid was oxidized very rapidly to ¹⁴CO₂ by mouse and guinea-pig mitochondria without evident discrimination between the two optical isomers. 5. An enzyme system that oxidizes 26-hydroxycholesterol to 3β-hydroxycholest-5-en-26-oic acid was identified in the soluble extract of rat-liver mitochondria. This enzyme could use NADP in place of NAD but was not identical with liver alcohol dehydrogenase (EC 1.1.1.1). 6. [26-¹⁴C]Cholesteryl 3β-sulphate was not oxidized by fortified mouse-liver preparations that oxidized [26-¹⁴C]cholesterol to ¹⁴CO₂.     

Sequences 5'' to translation start regulate expression of petunia rbcS genes.

The promoter sequences that contribute to quantitative differences in expression of the petunia genes (rbcS) encoding the small subunit of ribulose bisphosphate carboxylase have been characterized. The promoter regions of the two most abundantly expressed petunia rbcS genes, SSU301 and SSU611, show sequence similarity not present in other rbcS genes. We investigated the significance of these and other sequences by adding specific regions from the SSU301 promoter (the most strongly expressed gene) to equivalent regions in the SSU911 promoter (the least strongly expressed gene) and assaying the expression of the fusions in transgenic tobacco plants. In this way, we characterized an SSU301 promoter region (either from -285 to -178 or -291 to -204) which, when added to SSU911, in either orientation, increased SSU911 expression 25-fold. This increase was equivalent to that caused by addition of the entire SSU301 5'-flanking region. Replacement of SSU911 promoter sequences between -198 and the start codon with sequences from the equivalent region of SSU301 did not increase SSU911 expression significantly. The -291 to -204 SSU301 promoter fragment contributes significantly to quantitative differences in expression between the petunia rbcS genes.     

Influence of nutrient-limited growth on pathogenesis-associated outer membrane proteins of Yersinia enterocolitica

From studies based on batch culture, it has been postulated that the expression of the virulence-associated proteins of Yersinia spp. is controlled by temperature and Ca²⁺, such that these proteins are synthesized only at the higher temperature (37°C) and calcium-scarce conditions of the intracellular environment. It was found, however, that in Yersinia enterocolitica one of these proteins (140 kDa) is not synthesized at submaximal growth rates under any of the relevant conditions, and that another of the implicated proteins (34 kDa), is synthesized even at 28°C during nutrient-limited growth. Thus, temperature and Ca²⁺ influence the synthesis of these proteins differently under growth conditions that better approximate the natural environments than do batch cultures.