Glucokinase (GK) plays a central role in glucose homeostasis in mammals. The absence of an inducible GK has been suggested to explain the poor utilization of dietary carbohydrates in rainbow trout. In this context, we analyzed GK expression in three fish species (rainbow trout, gilthead seabream, and common carp) known to differ in regard to their dietary carbohydrate tolerance. Fish were fed for 10 wk with either a diet containing a high level of digestible starch (>20%) or a diet totally deprived of starch. Our data demonstrate an induction of GK gene expression and GK activity by dietary carbohydrates in all three species. These studies strongly suggest that low dietary carbohydrate utilization in rainbow trout is not due to the absence of inducible hepatic GK as previously suggested. Interestingly, we also observed a significantly lower GK expression in common carp (a glucose-tolerant fish) than in rainbow trout and gilthead seabream, which are generally considered as glucose intolerant. These data suggest that other biochemical mechanisms are implicated in the inability of rainbow trout and gilthead seabream to control blood glucose closely.

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Klebsiella oxytoca mutants resistant to a variety of ␤-lactams were obtained in vitro on aztreonam. Constitutive ␤-lactamase production was much higher in the mutants than in the susceptible strains (75-fold). The only difference observed in these mutants compared with the susceptible strains were point mutations in the Pribnow box: a transversion (G3T) in the first base for one mutant or a transition (G3A) in the fifth base of the ؊10 consensus sequence for the other three mutants. The transcriptional output of the ␤-lactamase gene (bla OXY ) from the mutants was significantly higher than that of the bla OXY gene from the susceptible strains.

Two blaTEM-like genes were characterized that encoded IRT beta-lactamases (previously called TRI) in clinical isolates of Escherichia coli resistant to amoxycillin alone and to combinations of amoxycillin with beta-lactamase inhibitors. Plasmids carrying this resistance were isolated from E. coli K 12 transconjugants and the genes were sequenced after amplification of defined fragments, using TEM-1-specific primers. The gene for IRT-1 beta-lactamase resembled the blaTEM-1B gene, and that for IRT-2 resembled blaTEM-2. However, both IRT enzymes have a glutamine residue at position 37, which is characteristic of TEM-1. The unique nucleotide difference with parental genes corresponding to amino acid variation was observed at nucleotide position 929. The consequence of C to T transition in the blaIRT-1 gene and C to A transversion in the blaIRT-2 gene was the substitution of arginine 241 in the native protein by cysteine and serine, respectively, in the mutants. Thus, the nature of amino acid 241 is critical in conferring resistance or susceptibility to beta-lactamase inhibitors. Furthermore, these basic to neutral amino acid replacements explain the more acidic pI (pI = 5.2) of these IRT enzymes compared to that of TEM-1 (pI = 5.4). The presence of cysteine-241 in IRT-1 also explains the selective sensitivity of this beta-lactamase to inhibition by p-chloromercuribenzoate.

The majority of the chromosomes with the ␤ S gene have one of the five common haplotypes, designated as Benin, Bantu, Senegal, Cameroon, and Arab-Indian haplotypes. However, in every large series of sickle cell patients, 5-10% of the chromosomes have less common haplotypes, usually referred to as "atypical" haplotypes. In order to explore the genetic mechanisms that could generate these atypical haplotypes, we extended our analysis to other rarely studied polymorphic markers of the ␤ S -gene cluster, in a total of 40 chromosomes with uncommon haplotypes from Brazil and Cameroon. The following polymorphisms were examined: seven restriction site polymorphisms of the ␥␦␤-cluster, the pre-G ␥ framework sequence including the 6-bp deletion/insertion pattern, HS-2 LCR (AT)xR(AT)y and pre-␤ (AT)xTy repeat motifs, the GC/TT polymorphism at −1105-1106 of G ␥-globin gene, the C/T polymorphism at −551 of the ␤-globin gene, and the intragenic ␤-globin gene framework. Among the Brazilian subjects, the most common atypical structure (7/16) was a Bantu 3-subhaplotype associated with different 5-sequences, while in two chromosomes a Benin 3-subhaplotype was associated with two different 5-subhaplotypes. A hybrid Benin/Bantu configuration was also observed. In three chromosomes, the atypical haplotype differed from the typical one by the change of a single restriction site. In 2/134 chromosomes identified as having a typical Bantu RFLPhaplotype, a discrepant LCR repeat sequence was observed, probably owing to a crossover 5 to the -gene. Among 80 ␤ S chromosomes from Cameroon, 22 were associated with an atypical haplotype. The most common structure was represented by a Benin haplotype (from the LCR to the ␤-gene) with a non-Benin segment 3 to the ␤-globin gene. In two cases a Bantu LCR was associated with a Benin haplotype and a non-Benin segment 3 to the ␤-globin gene. In three other cases, a more complex structure was observed that can be considered as a hybrid of Benin, Bantu, Senegal, or other chromosomes was observed. These data suggest that the atypical ␤ S haplotypes are not uncommon in America and in Africa. These haplotypes are probably generated by a variety of genetic mechanisms including (a) isolated nucleotide changes in one of the polymorphic restriction sites, (b) simple and double crossovers between two typical ␤ S haplotypes or much more frequently between a typical ␤ S haplotype and a different ␤ Aassociated haplotype that was present in the population, and (c) gene conversions. Am.

The association between Down's syndrome (DS) and celiac disease (CD) has been confirmed by several authors. The sensitivity and specificity of antigliadin antibodies (AGAs), the clinical features of subjects with DS and CD (DS-CD+), the incidence of CD, and the results of serological and molecular class I and II HLA typing were determined in a sample of 57 Sicilian subjects with DS. Six (10.5%) and 17 subjects (29.8%) showed high levels of IgA AGAs and IgG AGAs, respectively. AGAs sensitivity and specificity were lower than in the population without DS. Ten people with DS were submitted to jejunal biopsy, and seven (12.2%) showed CD according to ESPGAN criteria. All seven patients were put on gluten-free diet, followed by rapid disappearance of symptoms. Class I and II HLA serological and molecular typing was carried out in seven DS-CD + subjects, 22 people with DS without CD (DS-CD-), five subjects with CD without DS, and 20 controls. Between DS-CD + and DS-CD- subjects, no statistically significant difference regarding serum HLA class I antigens was found. DQA1*0101 allele appears significantly in DS-CD + patients and deserves to be searched for in a larger sample to assess its meaning in the DS-CD association.

Sixty-four homozygous ␤-thalassemia patients comprising 40 patients with ␤-thalassemia major and 24 patients with ␤-thalassemia intermedia were investigated for the nature of their ␤-thalassemia mutations, associated ␣-thalassemia, and XmnI polymorphism in the gamma gene which are known to affect the clinical course of the disease. This study was undertaken to look for the contribution of these associated factors in reducing the clinical severity of homozygous ␤-thalassemia from a severe disease to a ␤-thalassemia intermedia phenotype. Clinical severity of these patients was assessed by the degree of transfusion dependency and the age at which the patient presented with symptoms. Globin chain synthetic ratio was taken as the biochemical pointer of severity of the disease. Eleven different ␤-thalassemia mutations were encountered among 128 ␤-thalassemia chromosomes. It was observed that the nature of the ␤-thalassemia mutations was not very different between the ␤-thalassemia major and ␤-thalassemia intermedia groups in our patients, but co-inheritance of one or more ␣-globin gene deletions (−␣