Gastrointestinal transit and digestibility of maltitol, sucrose and sorbitol in rats: a multicompartmental model and recovery study.

Using data obtained with a dye marker and the gavage technique, the kinetics of gastrointestinal transit of different loads of sugar substitutes (maltitol, sorbitol) and sugar (sucrose) in the rat were analysed using a linear multicompartmental model over a range from the realistic to the non-physiologic high, of carbohydrate intake levels and using only a few experimental time points. The model gave detailed insight into intestinal propulsion and gastrocecal transit time. Rate constants of transport between the compartments investigated were determined; they showed characteristics which could be related to the substance and the dosage administered. Analyses of the gastrointestinal content and calculations of the intestinal net water movement showed that the digestibility and absorption of the disaccharide sugar alcohol, maltitol, in the small gut depended inversely on the dose ingested. For all substances tested, caloric availability in the small intestine was calculated. At a physiological low level of maltitol intake, the results also indicated an insignificant calorie-saving effect in comparison to sucrose, an effect based mainly on the slow absorption rate of the maltitol cleavage product sorbitol.     

Piroxicam-induced analgesia: Evidence for a central component which is not opioid mediated

Piroxicam is a nonsteroidal anti-inflammatory drug with a potent analgesic effect. In order to establish whether the analgesic action of Piroxicam has a central component, we studied the effect of the drug on the nociceptive orbicularis oculi reflexes evoked by electrical stimulation of the cornea and supraorbital nerve in healthy subjects. Piroxicam significantly suppressed the corneal reflex and R3 component of the blink reflex by 28% (p<0.05) and 50% (p<0.01), respectively. This effect was not reversed by the i.v. injection of naloxone. Beta-endorphin levels did not change. Piroxicam administration induces distinct inhibitory changes in nociceptive reflexes, which suggests that the analgesic action of the drug has a central component. The ineffectiveness of naloxone, and the lack of beta-endorphin changes, indicate that this central action is independent of the opioid system; other pain regulatory systems are probably involved.     

Rapid generation of region specific probes by chromosome microdissection and their application.

The strategy presented here to identify unequivocally cryptic chromosomal rearrangements has relevance to both prenatal and postnatal cytogenetic analysis as well as the analysis of tumour-associated chromosome rearrangements. Microdissection and in vitro amplification of specific chromosomal regions are performed, followed by labelling for fluorescent in situ hybridization (FISH) to normal metaphase chromosomes (Micro-FISH). Micro-FISH probes have been used successfully to determine the derivation of chromosome segments unidentifiable by standard chromosome banding analysis. Micro-FISH probes (created in less than 24 hours) now make it possible to identify explicitly the chromosome constitution of virtually all cytologically visible chromosome rearrangements.     

Aberrant splicing of neural cell adhesion molecule L1 mRNA in a family with X-linked hydrocephalus.

A locus for X-linked hydrocephalus (HSAS), which is characterized by mental retardation and enlarged brain ventricles, maps to the same subchromosomal region (Xq28) as the gene for neural cell adhesion molecule L1. We have found novel L1 mRNA species in cells from affected members of a HSAS family containing deletions and insertions produced by the utilization of alternative 3' splice sites. A point mutation at a potential branch point signal in an intron segregates with the disease and is likely to be responsible for the abnormal RNA processing. These results suggest that HSAS is a disorder of neuronal cell migration due to disruption of L1 protein function.     

A candidate mouse model for Prader-Willi syndrome which shows an absence of Snrpn expression.

The best examples of imprinting in humans are provided by the Angelman and Prader-Willi syndromes (AS and PWS) which are associated with maternal and paternal 15q11-13 deletions, respectively, and also with paternal and maternal disomy 15. The region of the deletions has homology with a central part of mouse chromosome 7, incompletely tested for imprinting effects. Here, we report that maternal duplication for this region causes a murine imprinting effect which may correspond to PWS. Paternal duplication was not associated with any detectable effect that might correspond with AS. Gene expression studies established that Snrpn is not expressed in mice with the maternal duplication and suggest that the closely-linked Gabrb-3 locus is not subject to imprinting. Finally, an additional new imprinting effect is described.     

A survey of expressed genes in Caenorhabditis elegans.

As an adjunct to the genomic sequencing of Caenorhabditis elegans, we have investigated a representative cDNA library of 1,517 clones. A single sequence read has been obtained from the 5' end of each clone, allowing its characterization with respect to the public databases, and the clones are being localized on the genome map. The result is the identification of about 1,200 of the estimated 15,000 genes of C. elegans. More than 30% of the inferred protein sequences have significant similarity to existing sequences in the databases, providing a route towards in vivo analysis of known genes in the nematode. These clones also provide material for assessing the accuracy of predicted exons and splicing patterns and will lead to a more accurate estimate of the total number of genes in the organism than has hitherto been available.     

Caenorhabditis elegans expressed sequence tags identify gene families and potential disease gene homologues.

A database containing mapped partial cDNA sequences from Caenorhabditis elegans will provide a ready starting point for identifying nematode homologues of important human genes and determining their functions in C. elegans. A total of 720 expressed sequence tags (ESTs) have been generated from 585 clones randomly selected from a mixed-stage C. elegans cDNA library. Comparison of these ESTs with sequence databases identified 422 new C. elegans genes, of which 317 are not similar to any sequences in the database. Twenty-six new genes have been mapped by YAC clone hybridization. Members of several gene families, including cuticle collagens, GTP-binding proteins, and RNA helicases were discovered. Many of the new genes are similar to known or potential human disease genes, including CFTR and the LDL receptor.     

The peripheral myelin protein gene PMP-22 is contained within the Charcot-Marie-Tooth disease type 1A duplication.

Charcot-Marie-Tooth disease (CMT1) is the most common form of inherited peripheral neuropathy. Although the disease is genetically heterogeneous, it has been demonstrated that the gene defect is the most frequent type (CMT1A) is the result of a partial duplication of band 17p11.2. Recent studies suggested that the peripheral hypomyelination syndrome in the trembler (Tr) mouse, a possible animal model for CMT1 disease, is associated with a point mutation in the peripheral myelin protein-22 gene (pmp-22). Expression of pmp-22 is particularly high in Schwann cells, and the protein is found in peripheral myelin. We now report that the human PMP-22 gene is contained within the CMT1A duplication. We therefore, suggest that increased dosage of the PMP-22 gene may be the cause of CMT1A neuropathy.     

Isolation of a candidate gene for Norrie disease by positional cloning.

The gene for Norrie disease, an X-linked disorder characterized by progressive atrophy of the eyes, mental disturbances and deafness, has been mapped to chromosome Xp11.4 close to DXS7 and the monoamine oxidase (MAO) genes. By subcloning a YAC with a 640 kilobases (kb) insert which spans the DXS7-MAOB interval we have generated a cosmid contig which extends 250 kb beyond the MAOB gene. With one of these cosmids, microdeletions were detected in several patients with Norrie disease. Screening of cDNA libraries has enabled us to isolate and sequence a likely candidate gene for Norrie disease which is expressed in retina, choroid and fetal brain. No homologous sequences were found in DNA and protein databases indicating that this cDNA is part of a gene encoding a 'pioneer' protein.     

Small nuclear ribonucleoprotein polypeptide N (SNRPN), an expressed gene in the Prader-Willi syndrome critical region.

Prader-Willi syndrome (PWS) is associated with paternally derived chromosomal deletions in region 15q11-13 or with maternal disomy for chromosome 15. Therefore, loss of the expressed paternal alleles of maternally imprinted genes must be responsible for the PWS phenotype. We have mapped the gene encoding the small nuclear RNA associated polypeptide SmN (SNRPN) to human chromosome 15q12 and a processed pseudogene SNRPNP1 to chromosome region 6pter-p21. Furthermore, SNRPN was mapped to the minimal deletion interval that is critical for PWS. The fact that the mouse Snrpn gene is maternally imprinted in brain suggests that loss of the paternally derived SNRPN allele may be involved in the PWS phenotype.