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Biomedical subjects

P A Heaton

Publications and source records attributed to P A Heaton.

14 recordsLinked to original sources
PubMed2001

Hypertrophy, hyperplasia, and infectious virus in gut-associated lymphoid tissue of mice after oral inoculation with simian-human or bovine-human reassortant rotaviruses.

Oral inoculation of infants with a vaccine that contains simian-human reassortant rotaviruses has been found to be a rare cause of intussusception. Because intussusception can be associated with enlargement of gut-associated lymphoid tissue, we studied the capacity of simian-human and bovine-human reassortant rotaviruses to cause lymphoid hypertrophy and hyperplasia of Peyer's patches (PP) of adult BALB/c mice. Neither hypertrophy nor hyperplasia was detected in PP after oral inoculation with simian-human or bovine-human reassortant rotaviruses. However, infectious virus was detected in PP and mesenteric lymph nodes after oral inoculation with simian, but not bovine, reassortant rotaviruses. Implications of these findings on the pathogenesis of intussusception are discussed.

Administration, Oral↗
PubMed1999

Congenital nephrotic syndrome responsive to captopril and indometacin.

Two children with congenital nephrotic syndrome are described (one with Finnish-type nephrosis, the other with diffuse mesangial sclerosis). Both children have had a prolonged and sustained clinical response with good physical health and normal growth patterns using captopril and indometacin as their sole treatment. No adverse effects have been noted. We recommend a trial of indometacin and captopril treatment in cases of congenital nephrotic syndrome.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

In vitro selection of a purine nucleotide-specific hammerheadlike ribozyme.

The in vitro selection for an intramolecular AUG-cleaving hammerhead-like ribozyme is described. One of the ribozymes selected was found to cleave after this triplet, both intramolecularly and intermolecularly, with rates comparable to the rate of the native GUC-cleaving hammerhead ribozyme. Although the selection was designed for cleavage 3' of the AUG triplet, the ribozyme also cleaves 3' of the AUA triplet. AUU and AUC triplets are, however, not cleaved, and thus the selected ribozyme is purine-specific for the third position in the triplet. In addition, cleavage 3' of the AAG triplet has been observed, thus the central U is not essential. Nuclease digestion indicates that the selected ribozyme has a secondary structure similar to that of the native hammerhead ribozyme, although with an altered core and stem-loop II sequence. All nucleotides in the core, except one, are essential for activity. The nucleotides in loop II are sensitive to changes and cannot, as in the hammerhead ribozyme, be replaced by other sequences or a nonnucleotide linker. Thus there are differences between these two ribozymes even though they have similar two-dimensional structures. The new ribozyme enlarges the application of hammerhead ribozymes for the inhibition of gene expression by extending the range of cleavable triplets.

Base Sequence↗
PubMed1997

Isolation of hammerhead ribozymes with altered core sequences by in vitro selection.

The hammerhead ribozyme has an invariant nucleotide sequence in the core region. In order to search for alternative sequences which can support the cleavage after the triplet GUC, the core region of 10 nucleotides was randomized and subjected to in vitro selection by repeated cycles of transcription, reverse transcription, and PCR. Active sequences were isolated after each transcription by denaturing PAGE, and after nine cycles of selection, two sequences dominated the pool. Both sequences conformed broadly to the consensus core region except that in one sequence a single A9U mutation was observed while in the other two mutations at A9U and U7A were seen. The catalytic efficiencies of these ribozymes were 6.4 and 14.1 microM(-1) min(-1), respectively, as compared to 163 microM(-1) min(-1) for the consensus sequence. Interestingly, the consensus was not found in any of the selected sequences. This discrimination against the consensus sequence was attributed to the specificity of the enzymes used in the selection procedure.

Base Composition↗
PubMed1997

The epidemiology of nontuberculous mycobacterial lymphadenitis affecting New Zealand children 1986-95.

AIMS: To study the epidemiological trends of nontuberculous mycobacterial lymphadenitis affecting New Zealand children from 1986-95. METHODS: Cases were identified from the records of the three regional reference laboratories in New Zealand. All children of less than 16 years with a positive culture of nontuberculous mycobacteria from a lymph node tissue sample were included. RESULTS: One hundred and sixty eight cases were identified, 43 in the first 5 years (no data available from Waikato) and 125 in the second 5 years of the study period. One hundred and fifty three (91%) of cases were in the 0-5 year age group and 101 (60%) were female. The head and neck was the most common site of infection accounting for 141 (84%) of all infection. In 161 (96%) of cases the causative organism was Mycobacterium avium intracellulare complex. CONCLUSION: Nontuberculous mycobacterial infections cause a subacute lymphadenitis in preschool children, usually affecting the lymph nodes of the head and neck. The annual number of microbiologically confirmed cases in New Zealand had increased substantially over recent years, most notably since 1992. The reason for the increase is unknown but possible explanations include increased awareness of mycobacterial disease, external factors causing either changes in the distribution or virulence of mycobacteria in the environment and alterations in the human immune response.

Adolescent↗
PubMed1997

The structure, function and application of the hammerhead ribozyme.

The hammerhead ribozyme is one of the smallest ribozymes known and catalyses the site-specific hydrolysis of a phosphodiester bond. This small ribozyme is of interest for two reasons. It offers a convenient system to study the structure/function relationship of a nucleotide sequence, and is a potential vehicle for the inhibition of gene expression. The first part of the review summarizes the sequence requirements of the hammerhead, its three-dimensional structure and the proposed mechanism, in addition to ribozyme specificity and turnover. The second part of the review focuses on the in vivo application of the ribozyme. The processes involved in designing ribozymes for efficient cleavage in vivo are described, together with possible delivery strategies.

Animals↗
PubMed1996

Diastereomeric specificity of 2',3'-cyclic nucleotide 3'-phosphodiesterase.

The diastereomers of adenosine and uridine 2',3'-cyclic phosphorothioates were tested as substrates for 2',3'-cyclic nucleotide 3'-phosphodiesterase from bovine brain. The enzyme cleaves the Sp (or exo) diastereomers efficiently, whereas the Rp (or endo) diastereomers are resistant to hydrolysis, even after long incubation. As the enzyme exhibits strong substrate inhibition the precise determination of kinetic parameters posed problems, particularly with phosphorothioates. The stereoselectivity of this enzyme is opposite to that of RNase T1 and RNase A and thus could be a useful complement in determination of the configuration of nucleoside 2',3'-cyclic phosphorothioates resulting from hydrolysis reactions of unknown stereochemical course.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1989

The pattern of burn injuries in childhood.

This was a retrospective study of all children aged less than 15 years who attended the accident and emergency department of a provincial hospital on account of burns over a 3 year period. There were a total of 372 patients of whom 58% were male and 66% were preschoolers. There was no seasonal variation of numbers attending, 85% of patients attended between the hours of 8 am and 8 pm and in 80% of cases burns involved the limbs. Of all burns 37% were due to hot liquids and 6.2% due to hot tap water. A total of 29 (7.8%) attending children were admitted of whom 6 (20% of admissions) were due to hot tap water burns. Sixteen (4.3%) of children received burns as a result of suspected or proven non-accidental injury. My findings suggest that burns continue to cause significant morbidity in preschool children and that hot tap water causes disproportionately severe and largely preventable injuries, the reasons for this are discussed.

Adolescent↗