Diarrhea associated with Cryptosporidium parvum among young children of the Nile River Delta in Egypt

Over a 2-year period, the prevalence and clinical characteristics of Cryptosporidium-associated diarrhea in the Nile River Delta of Egypt was studied. A stool sample was obtained from children with diarrhea attending one of two study hospitals and of the 1275 children evaluated, 214 (17%) were found to be infected with Cryptosporidium. Younger age was a risk factor for developing Cryptosporidium-associated diarrhea. Children <12 months of age were 2.4 times more likely to be infected with Cryptosporidium (p<0.01) and children 12 to 23 months were 1.9 (p<0.05) times more likely to be infected with the organism as compared to older children. Breastfeeding had a trend towards protection against Cryptosporidium-associated diarrhea (p=0.07). Clinical findings associated with Cryptosporidium diarrhea included vomiting, persistent diarrhea and the need for hospitalization. Our data suggest that Cryptosporidium is common in Egyptian children and may be associated with severe diarrhea.

Expression of intron-containing GUS constructs is reduced due to activation of a cryptic 5' splice site

An intron-containing beta-glucuronidase (GUS) gene has been used widely in promoter analyses and as a plant transformation marker. Maximal plant gene expression requires accurate and efficient removal of the intron from the expressed pre-mRNA transcripts by splicing. Detailed analysis of splicing of potato ST-LS1 and pea legumin introns from GUS constructs revealed the activation of a cryptic 5' splice site in the GUS coding sequence 4 nt upstream from the authentic intron 5' splice site. About 40% of transcripts utilised the cryptic 5' splice site in tobacco protoplasts, reducing the translational potential of expressed pre-mRNA. The same cryptic splicing event was evident in transgenic tobacco leaves but at reduced levels. Mutations that removed the cryptic 5' splice site are associated with a two-fold enhancement in GUS activity in tobacco protoplasts, highlighting the need for careful examination of introns and their sites of insertion into gene constructs to minimise variability in gene activity and maximise gene expression.

Differential expression of potato U1A spliceosomal protein genes: a rapid method for expression profiling of multigene families

The spliceosomal protein, UIA, is a component of the U1snRNP essential to pre-mRNA splicing. From the ubiquitous nature of the splicing machinery, expression of U1A genes is expected to be constitutive. However, many plant genes are organised in multigene families that exhibit variation in expression profiles. Without detailed knowledge of the size of the U1A gene family or their degree of sequence variation, we examined the expression of the U1A genes using a novel approach. The approach was based on 5' RACE with [32P]-labelled primers and separation of products on high-resolution DNA sequencing gels to give a 'snapshot' of the expression of U1A genes. This was followed by sequencing of cloned 5' RACE products and of products re-amplified from excised bands. In combination with RT-PCR/SSCP, these analyses allowed the rapid identification of different gene transcripts and assessment of their relative expression profiles. Transcripts from four U1A genes (U1A-1 to U1A-4) were identified, of which U1A-1 and U1A-2 were expressed much more highly than U1A-3 and U1A-4. Differential expression of the two most highly expressed genes, U1A-1 and UIA-2, was observed in that only U1A-2 was expressed in flowers. Upstream sequences of U1A-1 and U1A-2 were cloned and the gene-specific promoters identified on the basis of the sequence variation defined from the 5' RACE products. The differential expression of these genes may be due to a 1.3 kb insertion less than 200 bp upstream of the U1A-1 coding sequence. This approach can be used more generally to examine expression profiles of multigene families, and in particular to refine information from EST or microarray analyses, and to isolate rapidly gene-specific promoters.