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Background: Persistent diarrhoea has recently been reported as a common problem following surgical resection for advanced abdominal neuroblastoma. Case study: A 10-month-old child, who had previously had no nutritional problems whilst undergoing chemotherapy treatment for a stage IV neuroblastoma, developed severe diarrhoea following tumour resection. He required nutritional support and was commenced on a continuous overnight nasogastric feed of a non-milk protein hydrolysate feed (MCT Pepdite 0-2, S.H.S. International Ltd, UK) His diarrhoea persisted and it was assumed that this was a postoperative problem which in time would regress. Two months later the child was admitted with a rectal prolapse, and a colonoscopy and biopsy suggested allergic protocolitis. The diarrhoea resolved rapidly on stopping the feed. Conclusion: Although he was never re-challenged with the non-milk protein hydrolysate, it appears that he had a rare intolerance to an extensively hydrolysed protein formula which was masked by the assumption that his diarrhoea was a postoperative problem. [ABSTRACT FROM AUTHOR]

In the years since we last reviewed the use of mutants to study tomato fruit ripening (Grierson et al. 1987), considerable information has been gained by the cloning, sequencing and identification of many mRNAs implicated in this developmental process. Genes involved in cell wall degradation, colour change and ethylene synthesis have been cloned, and antisense techniques have been developed and used to produce genetically engineered mutant fruit deficient in these aspects of ripening (see Gray et al 1992). Recently, a previously cloned ripening gene has been used to complement a naturally occurring fruit colour mutant, yellow flesh (Fray & Grierson 1993a), and a ripening impaired mutant, ripening inhibitor, has been used to identify several new ripening-related mRNAs (Picton et al 1993b). The chromosomal region bearing the ripening inhibitor mutation has been subjected to high-resolution mapping (Churchill, Giovannoni & Tanksley 1993) and chromosome walking experiments are in progress to identify this gene. [ABSTRACT FROM AUTHOR]

Ripening tomato fruits incubated at 35°C fail to achieve normal pigmentation, soften little and show a marked decline in ethylene evolution. Labelling studies in vivo indicate that protein synthesis continues throughout incubation at 35°C although the spectrum of labeled proteins is different to that observed at 25°C. Translation of mRNAs in vitro shows traces of several 'heat-shock' mRNAs at 35°C and the loss of several others normally found in fruit ripened at 25°C. Using ripening-related cDNA clones as hybridization probes the expression of 12 ripening-related genes was followed during incubation at 25°C and 35°C. In general, there was a marked decline in the amounts of there was a marked decline in the amounts of these mRNAs following incubation of ripening fruit at 35°C. In particular, mRNA homologous to pTOM 6, cDNA clone coding for polygalacturonase, a major cell wall degrading enzyme, showed a rapid decline following incubation at 35°C and after 72-h at elevated temperature was undetectable. There was no recovery of expression during 120 h at 35°C and the application of exogenous ethylene did not overcome the inhibition of ripening or lead to the renewed accumulation of polygalacturonase mRNA. It is proposed that the failure to soften normally at elevated temperature is due, in part, to the suppression of polygalacturonase mRNA and that the inhibition of other facets of ripening at 35°C is due to the inhibition or reduced expression of other, as yet unidentified, ripening-related genes. [ABSTRACT FROM AUTHOR]

Background: Embryonic stem (ES) cells have the potential to produce unlimited numbers of surrogate insulin-producing cells for cell replacement therapy of type 1 diabetes mellitus. The impact of the in vivo environment on mouse ES cell differentiation towards insulin-producing cells was analysed morphologically after implantation., Methods: ES cells differentiated in vitro into insulin-producing cells according to the Lumelsky protocol or a new four-stage differentiation protocol were analysed morphologically before and after implantation for gene expression by in situ reverse transcription polymerase chain reaction and protein expression by immunohistochemistry and ultrastructural analysis., Results: In comparison with nestin positive ES cells developed according to the reference protocol, the number of ES cells differentiated with the four-stage protocol increased under in vivo conditions upon morphological analysis. The cells exhibited, in comparison to the in vitro situation, increased gene and protein expression of Pdx1, insulin, islet amyloid polypeptide (IAPP), the GLUT2 glucose transporter and glucokinase, which are functional markers for glucose-induced insulin secretion of pancreatic beta cells. Renal sub-capsular implantation of ES cells with a higher degree of differentiation achieved by in vitro differentiation with a four-stage protocol enabled further significant maturation for the beta-cell-specific markers, insulin and the co-stored IAPP as well as the glucose recognition structures. In contrast, further in vivo differentiation was not achieved with cells differentiated in vitro by the reference protocol., Conclusions: A sufficient degree of in vitro differentiation is an essential prerequisite for further substantial maturation in a beta-cell-specific way in vivo, supported by cell-cell contacts and vascularisation.

In pancreatic islets prepared from fed rats and incubated at a low concentration (1.7 mM) of D-glucose, D-mannoheptulose (10.0 mM) virtually fails to affect the metabolism of the hexose. Likewise, in islets from starved rats, the relative extent of the inhibitory action of D-mannoheptulose upon D-glucose metabolism is much more marked at high (16.7 mM) than low (1.7 mM) hexose concentration. Nevertheless, despite decreasing the metabolism of D-glucose, starvation augments the sensitivity to D-mannoheptulose in the islets incubated at a low concentration of the hexose, D-galactose, but not D-fructose, also augments the inhibitory action of D-mannoheptulose upon D-glucose metabolism in islets prepared from fed rats and exposed to the low concentration of D-glucose. A comparable situation prevails in islets exposed to 2-ketoisocaproate. Forskolin, however, which decreases D-glucose catabolism in the islets from fed rats exposed to 1.7 mM D-glucose, fails to affect significantly the inhibitory action of D-mannoheptulose on D-glucose metabolism. It is proposed that hexoses transported by the same carrier as D-glucose and non-glucidic nutrient secretagogues somehow increase D-mannoheptulose uptake by the islet cells. The latter two conditions may be operative in islets exposed to a high concentration of D-glucose, this accounting for the exquisite sensitivity to D-mannoheptulose of glucose-stimulated islets.

The esterification of several monosaccharides, such as D-glucose, D-mannoheptulose and 2-deoxy-D-glucose was recently reported to increase their biological efficiency as either nutrient or antimetabolic agent. In the present study, however, the tetraacetate ester of streptozotocin was unexpectedly found to be less potent than unesterified streptozotocin in inhibiting D-glucose metabolism and insulinotropic action in isolated rat pancreatic islets. This coincided with a much lower rate for the hydrolysis of streptozotocin tetraacetate than D-glucose pentaacetate in islet homogenates. These findings document that the esterification of single sugars is not always a successful procedure to enhance their biological potency, for instance because of too low a rate for the intracellular hydrolysis of the ester. To the extent that the activity of the concerned esterase(s) may differ in distinct cell types, as suggested by a prior observation, advantage could be taken of such a situation to target selected esters towards specific, e.g. tumoural cells.