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R Salomon

Publications and source records attributed to R Salomon.

At least 55 records · Page 3Linked to original sources
PubMed1997

Development of polyclonal antibodies for detection of aflatoxigenic molds involving culture filtrate and chimeric proteins expressed in Escherichia coli.

Polyclonal antibodies (PAb) were raised against an aflatoxigenic strain of Aspergillus parasiticus by using two different sources for antibody elicitation: (i) filtrate of a culture on which the fungus had been grown (ii) and two chimeric proteins, expressed in Escherichia coli as separate products, of the genes ver-1 and apa-2, which are involved in aflatoxin biosynthesis. The gene products were amplified by PCR, and each was cloned into the E. coli expression vector pGEX2T. Upon induction, the bacteria overexpressed 38- and 33-kDa chimeric proteins corresponding to the N-terminal domains of the genes ver-1 and apa-2, respectively. The chimeric proteins were isolated and affinity purified for use as antigens. The specificity of the raised antibodies was examined by enzyme-linked immunosorbent assay (ELISA). The PAbs raised against the culture filtrate reacted with all the species of Aspergillus and Penicillium tested but not with Fusarium species or corn gain. However, the PAbs elicited against the chimeric proteins were highly specific, showing significantly higher ELISA absorbance values (A405) against A. parasiticus and A. flavus than against the other fungi tested and the corn grain. The approach of utilizing gene products associated with aflatoxin biosynthesis for antibody production therefore appears to be feasible. Such a multiantibody system combined with the PCR technique, could provide a useful tool for the rapid, sensitive, and accurate detection of aflatoxin producers present in grains and foods.

Aflatoxin B1↗
PubMed1997

[Mutations of the endothelin-3 gene in isolated and syndromic forms of Hirschsprung disease].

AIMS AND METHODS: Hirschsprung's disease is a frequent congenital malformation regarded as a multigenic neurocristopathy. Three susceptibility genes have been identified in Hirschsprung's disease, namely the RET proto-oncogene, the Glial cell line-Derived Neurotrophic Factor and the endothelin B receptor. A total of 174 probands with isolated Hirschsprung's disease (59 familial, 117 sporadic cases), and 4 patients with associated Waardenburg's syndrome and Hirschsprung's disease (1 familial, 3 sporadic cases) were screened for mutations in the coding sequence of the endothelin 3 gene. The coding sequence of the endothelin 3 gene was analyzed for point mutations, using a combination of SSCP analysis and direct DNA sequencing. RESULTS: Two heterozygous mutations (A17T and A224T) were identified in two patients with isolated Hirschsprung's disease. Two homozygous truncations mutations (E55X and GC262->T) were identified in patients with the Waardenburg's syndrome/Hirschsprung's disease association. CONCLUSION: The present data give further support to the role of the endothelin-signaling pathway in the development of neural crest-derived enteric neurons. They also suggest that either recessive and weakly penetrant dominant alleles could occur at the EDN3 locus, depending on the nature of the mutation.

Endothelin-3↗
PubMed1996

Re-evaluating genetic algorithm performance under coordinate rotation of benchmark functions. A survey of some theoretical and practical aspects of genetic algorithms.

In recent years, genetic algorithms (GAs) have become increasingly robust and easy to use. Current knowledge and many successful experiments suggest that the application of GAs is not limited to easy-to-optimize unimodal functions. Several results and GA theory give the impression that GAs easily escape from millions of local optima and reliably converge to a single global optimum. The theoretical analysis presented in this paper shows that most of the widely-used test functions have n independent parameters and that, when optimizing such functions, many GAs scale with an O(n ln n) complexity. Furthermore, it is shown that the current design of GAs and its parameter settings are optimal with respect to independent parameters. Both analysis and results show that a rotation of the coordinate system causes a severe performance loss to GAs that use a small mutation rate. In case of a rotation, the GA's complexity can increase up to O(nn) = O(exp(n ln n)). Future work should find new GA designs that solve this performance loss. As long as these problems have not been solved, the application of GAs will be limited to the optimization of easy-to-optimize functions.

Algorithms↗
PubMed1996

Germline mutations of the RET ligand GDNF are not sufficient to cause Hirschsprung disease.

Hirschsprung disease (HSCR, aganglionic megacolon) is a common congenital malformation leading to bowel obstruction, with an incidence of 1/5,000 live births. It is characterized by the absence of intrinsic ganglion cells in the myenteric and submucosal plexuses along variable lengths of the gastrointestinal tract. As enteric neurons are derived from the vagal neural crest, HSCR is regarded as a neurocristopathy. On the basis of a skewed sex-ratio (M/F = 4/1) and a risk to relatives much higher than the incidence in the general population, HSCR has long been regarded as a sex-modified multifactorial disorder. Accordingly, segregation analysis suggested an incompletely penetrant dominant inheritance in HSCR families with aganglionosis extending beyond the sigmoid colon. We and others have mapped a dominant gene for HSCR to chromosome 10q11.2 and have ascribed the disease to mutations in the RET proto-oncogene. However, the lack of genotype-phenotype correlation, the low penetrance and the sex-dependent effect of RET mutations supported the existence of one or more modifier gene(s) in familial HSCR. In addition, thus far, RET mutations only accounted for 50% and 15-20% of familial and sporadic HSCR patients, respectively. RET encodes a tyrosine kinase receptor whose ligand was unknown. Recently, the Glial cell line-derived neurotrophic factor (GDNF) has been identified to be a ligand for RET. Moreover, Gdnf-/- knockout mutant mice display congenital intestinal aganglionosis and renal agenesis, a phenotype very similar to the Ret-/- mouse. These data prompted us to hypothesize that mutations of the gene encoding GDNF could either cause or modulate the HSCR phenotype in some cases.

Drosophila Proteins↗
PubMed1996

Influence of loperamide on lactose handling and oral-caecal transit time.

BACKGROUND: The influence of pharmacologically prolonged oral caecal transit time on lactose handling is examined in the wake of finding improved lactose handling during naturally occurring prolonged oral-caecal transit time. METHODS: Sixteen normal male volunteers with lactose maldigestion were pretreated with 8 and 12 mg loperamide on different days and lactose handling was compared by measuring areas under the curve during lactose breath H2 testing (3 h). The oral-caecal transit time was similarly measured using lactulose and exhaled breath H2. Symptom scores were recorded and, in three subjects, blood sugar was simultaneously measured. RESULTS: The mean +/-S.E.M. baseline oral-caecal transit time was 56.9 +/- 5.9 min. Loperamide significantly prolonged oral-caecal transit time (90.3 +/- 11.1 and 82.1 +/- 13.9 min for 12 and 8 mg loperamide, respectively; P < 0.05). The lactose breath H2 area under the curve with 12 mg loperamide was significantly less than at baseline (7685 +/- 985.6 vs. 10243.1 +/- 1607, respectively; P < 0.05). Significantly fewer symptoms were recorded with both doses of loperamide during the 3 h test but with 12 mg loperamide only on follow-up. There was no significant rise in blood sugar at any time in the three subjects studied. CONCLUSIONS: Loperamide-induced graded prolongation of oral-caecal transit time is associated with significantly improved lactose handling as measured by a reduction of the area under the curve. Symptoms of lactose intolerance may also be improved with loperamide. Prolongation of oral-caecal transit time with loperamide may be useful as adjunctive or primary therapy of carbohydrate intolerance in patients with rapid transit.

Administration, Oral↗
PubMed1996

Detection of aflatoxigenic molds in grains by PCR.

Aflatoxins are carcinogenic metabolites produced by several members of the Aspergillus flavus group in grains and floods. Three genes, ver-1, omt-1, and apa-2, coding for key enzymes and a regulatory factor in aflatoxin biosynthesis, respectively, have been identified, and their DNA sequences have been published. In the present study, three primer pairs, each complementing the coding portion of one of the genes, were generated. DNA extracted from mycelia of five Aspergillus species, four Penicillium species, and two Fusarium species was used as PCR template for each of the primer pairs. DNA extracted from peanut, corn, and three insect species commonly found in stored grains was also tested. Positive results (DNA amplification) were achieved only with DNA of the aflatoxigenic molds Aspergillus parasiticus and A. flavus in all three primer pairs. The detection limit of the PCR was determined by using the primer pairs complementing the omt-1 and ver-1 genes. Sterile corn flour was inoculated separately with six different molds, each at several spore concentrations. Positive results were obtained only after a 24-h incubation in enriched media, with extracts of corn inoculated with A. parasiticus or A. flavus, even at the lowest spore concentration applied (10(2) spores per g). No DNA spores per g). It is concluded that genes involved in the aflatoxin biosynthetic pathway may form the basis for an accurate, sensitive, and specific detection system, using PCR, for aflatoxigenic strains in grains and foods.

Aflatoxins↗
PubMed1996

Caco-2 cell disaccharidase activities are unaffected by gestational hormones.

We previously reported that lactose handling was significantly improved during late-phase pregnancy in women with a genetically determined adult-type hypolactasia. However, the adaptive mechanisms underlying the enhanced lactose digestion during pregnancy are not clear. Progesterone therapy has been associated in animals with increased intestinal lactase activity. To investigate the potential role of progesterone and estrogen as modulators of human lactase activity during pregnancy, we employed the human-derived intestinal epithelial Caco-2 cell line. Measurements of lactase and sucrase activities were performed in parallel with DNA content in progesterone- and estrogen-treated cells after 5, 10, and 30 days of confluency. Caco-2 monolayer DNA content was observed to increase with duration of culture to an equivalent extent in both hormone-treated and control cultures. Lactase and sucrase activities were similarly unaltered by incubation with either progesterone or estrogen, at any time point tested. These data demonstrate that gestational hormones do not influence intestinal cell number nor disaccharidase activity in Caco-2 cells, at the doses tested. Although these studies were carried out in a malignant cell line, our data suggest that the improved lactose handling observed during pregnancy is probably related to prolonged intestinal transit.

Caco-2 Cells↗
PubMed1996

Determinants of prolonged oral cecal transit time during late phase pregnancy.

We examined the course of delayed oral cecal transit time (OCTT) and the impact of different variables in late pregnancy. Thirty-three women in late trimester were evaluated and 29 were re-tested post partum. Results were compared with 17 controls. A breath hydrogen test was used to measure OCTT. The impact of 3 demographic and 5 biochemical parameters was evaluated. Oral cecal transit time (99.2 +/- 7.8 min) during pregnancy was significantly prolonged compared both with controls (63.5 +/- 8.7 min) (p = 0.0042) and post partum (68.5 +/- 6.4 min) (p < 0.002). However, 40% during pregnancy had a normal OCTT. Post partum, 8 (29.6%) continued to have delayed OCTT. Serum free T4 levels were significantly lower than in controls (p < 0.0001) and post partum (p < 0.001), but did not correlate with OCTT. Gravidity rank correlated with OCTT (p = 0.022). By multivariate analysis, only 17% of the observed variability during pregnancy could be explained by these parameters. In controls, a formula including progesterone and gastrin levels was significant in explaining 54.7% of variability. Application of both formulae to post-partum returnees overpredicted OCTT; however, the one from pregnancy was more accurate. We conclude that in pregnancy multiple factors account for delayed OCTT and these may be different from controls and post partum. Pregnancy may still influence OCTT post partum.

Adult↗
PubMed1996

Lactose handling by women with lactose malabsorption is improved during pregnancy.

OBJECTIVE: To evaluate lactose handling among women in late pregnancy and post partum to determine whether lactose handling is altered in pregnancy. DESIGN: Prospective study of lactose intolerance among pregnant women with and without lactose malabsorption. SETTING: Gastroenterology service of the Sir Mortimer B. Davis-Jewish General Hospital, Montreal. PATIENTS: Thirty-three pregnant women, of whom 18 had lactose malabsorption, 12 did not and 3 were excluded. OUTCOME MEASURES: Lactose breath hydrogen (BH2) concentration after ingestion of lactose or lactulose; comparison before and after delivery of area under the curve (AUC) for lactose, oral-cecal transit time (OCTT) for lactulose, lactose-BH2-derived transit time and estimated dietary lactose consumption. RESULTS: After weaning (at a median time of 9 months after delivery), 28 of the women returned for follow-up. Of the 12 who could absorb lactose before delivery, 4 could no longer absorb lactose. Of the other 16 women, lactose intolerance worsened in 12, remained the same in 2 and improved in 2. The AUC was greater (p < 0.005), the maximal BH2 concentration was higher (p = 0.004) and the number of women whose BH2 concentration peaked was fewer (p < 0.025) post partum than before delivery. The women's symptoms during and after lactose BH2 tests were also greater post partum. The OCTT (based on the lactulose BH2 test) was shorter post partum (p = 0.001). Transit time derived from lactose BH2 tests was also shorter, but not significantly so. The OCTT was not inversely correlated with the change in AUC before and after delivery, but the lactose-BH2-derived transit time was inversely correlated. Pregnant women consumed more lactose before delivery than afterward (p < 0.004). CONCLUSIONS: Women with lactose malabsorption handle lactose better than usual in late pregnancy. Slow intestinal transit and bacterial adaptation to increased lactose intake may be primarily responsible.

Breath Tests↗
PubMed1996

[Genetics of Hirschsprung disease].

Hirschsprung's disease (HD) is one of the commonest gastrointestinal malformations, as it affects one child out of 5,000 births. It classically induces severe neonatal intestinal obstruction requiring surgical treatment which currently ensures a favourable prognosis for most of the affected children. Although the great majority of cases are sporadic, the existence of familial forms (10% of cases) has allowed localization and then identification of an autosomal dominant gene on chromosome 10, the RET proto-oncogene, responsible for 50% of familial forms and 15% of sporadic cases. A second gene has been recently localized on chromosome 13, the endothelium beta receptor (EDNRB) gene. Two homozygous mutations of the EDNRB gene have been identified in two consanguineous families, in which HD is associated with Waardenburg's syndrome (WS). Other heterozygous mutations have been identified in patients presenting with isolated HD and an 5% of cases of HD can be considered to present mutations of this gene. Finally, the authors have recently identified a mutation of the endothelium gene 3 (EDN3), one of the EDNRB ligands in a patient presenting with a combination of HD and WS. This mutation, present at the homozygous state in this patient, is predictive of complete absence of EDN3 protein: this is therefore the third known gene responsible for HD.

Drosophila Proteins↗
PubMed1996

[Genetics of Hirschsprung disease].

Hirschsprung disease (HD) is one of the commonest gastro-intestinal malformations, as it affects one child out of 5,000 births. It classically induces severe neonatal intestinal obstruction requiring surgical treatment which currently ensures a favourable prognosis for most of the affected children. Although the great majority of cases are sporadic, the existence of familial forms (10% of cases) has allowed the localization and then the identification of an autosomal dominant gene on chromosome 10, the RET proto-oncogene, responsible for 50% of familial forms and 15% of sporadic cases. A second gene has been recently localized on chromosome 13, the endothelin beta receptor (EDNRB) gene. Two homozygous mutations have been identified in two consanguineous families, in which HD is associated with Waardenburg syndrome (WS). Other heterozygous mutations have been identified in patients presenting with isolated HD and 5% of cases can be considered to present mutations of this gene. Finally the authors have recently identified a mutation of the endothelin 3 gene (EDN3), one of EDNRB ligands in a patient presenting a combination of HD and WS. This mutation, present at the homozygous state in this patient, is predictive of complete absence of EDN3 protein: this is therefore the third known gene responsible for HD.

Endothelin-3↗
PubMed1995

Inhibition of viral aphid transmission by the N-terminus of the maize dwarf mosaic virus coat protein.

Since removal of the exposed N-terminus of the coat protein of some potyviruses abolishes aphid transmission, the role of this coat protein region of maize dwarf mosaic potyvirus (MDMV) in aphid transmission was investigated. The viral cDNA encoding this region was cloned and expressed as a fusion protein in bacteria. The resulting purified N-terminus of the coat protein was used in controlled aphid transmission experiments in competition with MDMV. The results show that this region inhibits aphid transmission of MDMV, indicating a direct involvement of the N-terminal region of the coat protein in aphid transmission.

Amino Acid Sequence↗
PubMed1995

Craniosynostosis and kidney malformation in a case of Hennekam syndrome.

Hennekam syndrome is a rare autosomal recessive syndrome which was described for the first time in 1989. Here, we present a girl with intestinal lymphangiectasia, severe lymphedema of limbs, seizures, mild mental retardation, and facial anomalies consistent with the diagnosis of Hennekam syndrome. In addition, she had an ectopic kidney and craniosynostosis of the coronal suture, 2 manifestations not previously reported in this syndrome. While the molecular basis of Hennekam syndrome remains, as yet, unknown, this report illustrates its variable clinical expression.

Craniosynostoses↗
PubMed1994

Regional expression of epithelial dipeptidyl peptidase IV in the human intestines.

The expression of DPP IV/CD26 was studied in epithelial cells from different regions of the human small intestine and colon. The following data were obtained: 1) DPP IV/CD26 activity was highest in ileum and jejunum, low in duodenum and not detectable in colon; 2) The amount of DPP IV, as analyzed by Western blotting, was very low in duodenum and increased up to the ileum. No DPP IV protein was detected in colon; 3) RT-PCR analysis showed the expected 315-bp product in the small intestine with the highest signal in ileum and jejunum and a low signal in duodenum; a faint PCR signal could be detected in colon. Similar data were obtained by Northern blot analysis which revealed a 3.6-kb transcript only in small intestine. It is concluded that DPP IV/CD26 gene expression in human intestine is highest in the distal small intestine, and that is regulated at the mRNA level.

Adult↗
PubMed1994

Transgenic tomato plants expressing the tomato yellow leaf curl virus capsid protein are resistant to the virus.

The tomato yellow leaf curl virus (TYLCV) gene that encodes the capsid protein (V1) was placed under transcriptional control of the cauliflower mosaic virus 35S promoter and cloned into an Agrobacterium Ti-derived plasmid and used to transform plants from an interspecific tomato hybrid, Lycopersicon esculentum X L. pennellii (F1), sensitive to the TYLCV disease. When transgenic F1 plants, expressing the V1 gene, were inoculated with TYLCV using whiteflies fed on TYLCV-infected plants, they responded either as untransformed tomato or showed expression of delayed disease symptoms and recovery from the disease with increasingly more resistance upon repeated inoculation. Transformed plants that were as sensitive to inoculation as untransformed controls expressed the V1 gene at the RNA level only. All the transformed plants that recovered from disease expressed the TYLCV capsid protein.

Base Sequence↗
PubMed1993

Characterization of a common VIP-PACAP receptor in human small intestinal epithelium.

Vasoactive intestinal peptide (VIP) receptors were characterized in epithelial plasma membranes from human small intestine. Native VIP inhibited the binding of 125I-labeled VIP to jejunal membranes, and Scatchard analysis of these data was consistent with the existence of one class of receptor with a dissociation constant of 42 pM and a maximal binding of 256 fmol/mg membrane protein. VIP stimulated adenylyl cyclase activity in human jejunal membranes in the 0.01 nM-1 microM range [half-maximal effective dose = 0.7 nM]. Coupling of VIP receptors with a Gs protein was further assessed by the ability of GTP (10(-8) to 10(-3) M) to inhibit 125I-VIP binding to membranes. 125I-VIP binding was seven to eight times higher in villus cells than in crypt cells. Finally, 125I-VIP binding was detectable throughout the small and large intestines with the highest binding in jejunum. Among the natural peptides structurally related to VIP, some inhibited 125I-VIP binding with the following order of potency: VIP = pituitary adenylate cyclase-activating peptide (PACAP)-27 = PACAP-38 > helodermin >> peptide histidine methionineamide = human growth hormone-releasing factor > secretin. The same order of potency of peptides for inhibiting 125I-VIP or 125I-labeled PACAP was observed, supporting that the two tracers bound to a common VIP-PACAP receptor site. This order of potency was also observed for the stimulation of adenylyl cyclase activity by these peptides. 125I-VIP was cross-linked to membranes using disuccinimidyl suberate. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, one single band of 70,000 mol wt was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding, Competitive↗