Biomedical subjects

G C Hung

Publications and source records attributed to G C Hung.

10 recordsLinked to original sources

PubMed2001

Clinical features and outcome of appendicitis in children younger than three years of age.

BACKGROUND: Acute appendicitis is the most common surgically amenable cause of acute abdominal pain in children. We analyzed our past experience of appendectomies in children and present the clinical characteristics of appendicitis in children younger than 3 years of age. A better understanding of appendicitis in early childhood would allow us to achieve an earlier diagnosis. METHODS: A group of 475 children from 4 months to 15 years of age who underwent appendectomy for appendicitis was studied over a 5-year period from July 1994 to June 1999. Excluding cases with negative pathological findings (n = 34), they were divided into 2 age groups: group I (< or = 3 years old) and group II (> 3 years old). Medical records were reviewed and comparisons between clinical findings, laboratory data, pathology findings, and complications were made. RESULTS: Of 441 cases enrolled in our study, 24 (5.4%) were 3 years of age or younger. Of all children older than 3 years of age, 32 (7.1%) had negative pathological findings compared to children younger than 3 years of age (7.7%). The duration of symptoms prior to diagnosis in group I was 3.6 days compared to group II at 2.0 days. Children from group I frequently showed a higher incidence of fever (90% vs. 53.4%), abdominal distention (50% vs. 9.8%), perforation (50% vs. 40.1%), and missed first impression (29% vs. 2.4%) than those from group II. Children of group I also had a higher complication rate (41.7% vs. 11.5%). CONCLUSIONS: In early childhood the symptoms and signs of appendicitis usually are nonspecific. There is a longer duration before diagnosis, more instances of fever and abdominal distention, less right lower quadrant pain, less local tenderness and rebounding pain, and no obturator sign. Close observation and on-going evaluation of patients are essential.

Appendicitis↗

PubMed2000

Relationships among some ascaridoid nematodes based on ribosomal DNA sequence data.

The nuclear ribosomal DNA (rDNA) region spanning the first (ITS-1) and second (ITS-2) internal transcribed spacers was sequenced for 15 taxa of ascaridoid nematodes. The length of the ITS-1 and ITS-2 sequences in the 15 taxa ranged from 392-500 bp and 240 348 bp, respectively. While nucleotide variation of 0-2.9% in the ITS-1 and/or ITS-2 sequences was detected within taxa where multiple samples were sequenced, significantly higher level of nucleotide difference (9.4-66.6%) was detected between the taxa, except for Ascaris suum and A. lumbricoides whose taxonomic status remains uncertain. These interspecific differences were linked with the considerable size differences (0-108 bp) in the rDNA spacers. Phenograms based on the genetic differences among the 15 taxa showed some concordance with previous classification schemes derived from morphological data.

Animals↗

PubMed2000

A molecular systematic framework for equine strongyles based on ribosomal DNA sequence data.

In this study, molecular data sets were used to address the controversies relating to the systematics of strongyloid nematodes of equids utilising morphological data sets. DNA sequences of the first and second internal transcribed spacers (ITS-1 and ITS-2) of ribosomal DNA were determined for 30 species of equine strongyles and the systematic relationships reconstructed using phenetic and phylogenetic tree-building methods. The molecular data provided support for the hypothesis that the genera with large subglobular buccal capsules are ancestral to those with small cylindrical buccal capsules, but did not provide support for the current division of the subfamilies Strongylinae and Cyathostominae or for some taxonomic groupings (i.e. generic designations of species) within the Cyathostominea based on morphological data. Although not entirely concordant, the current molecular data provide a systematic framework for future studies of equine strongyles, which could be exploited in combination with new, phylogenetically informative morphological data sets.

Animals↗

PubMed1999

Molecular evidence for cryptic species within Cylicostephanus minutus (Nematoda: Strongylidae).

The nucleotide sequences of the first and second internal transcribed spacers of nuclear ribosomal DNA were determined for adults of Cylicostephanus minutus from different geographical origins. The lengths of first and second internal transcribed spacer sequences ranged from 370 to 372bp and 215 to 216bp, respectively. Pairwise sequence comparisons revealed that some individuals of C. minutus had identical first and second internal transcribed spacer sequences, whereas others differed by 3.0% and 7.4% in their first and second transcribed spacers, respectively. Some individuals with sequence differences originated from the same host. The levels of difference within C. minutus were higher than that between the morphologically distinct species, Cylicostephanus goldi and Cylicostephanus longibursatus (0.8% for the first internal transcribed spacer and 3.8% for the second internal transcribed spacer). The data provide support for the proposal that C. minutus represents a complex of at least two species. In order to study the population genetic structure of C. minutus, a PCR-linked single-strand conformation polymorphism technique was also established.

Animals↗

PubMed1999

Secondary structure model for the ITS-2 precursor rRNA of strongyloid nematodes of equids: implications for phylogenetic inference.

In order to maximise the positional homology in the primary sequence alignment of the second internal transcribed spacer for 30 species of equine strongyloid nematodes, the secondary structures of the precursor ribosomal RNA were predicted using an approach combining an energy minimisation method and comparative sequence analysis. The results indicated that a common secondary structure model of the second internal transcribed spacer of these nematodes was maintained despite significant interspecific differences (2-56%) in primary sequences. The secondary structure model was then used to refine the primary second internal transcribed spacer sequence alignment. The 'manual' and 'structure' alignments were both subjected to phylogenetic analysis to compare the effect of using different sequence alignments on phylogenetic inference. The topologies of the phylogenetic trees inferred from the manual second internal transcribed spacer alignment were usually different to those derived from the structure second internal transcribed spacer alignment. The results suggested that the positional homology in the second internal transcribed spacer primary sequence alignment was maximised when the secondary structure model was taken into consideration.

Animals↗

PubMed1999

Species-specific amplification by PCR of ribosomal DNA from some equine strongyles.

The first and second internal transcribed spacer sequences of 28 morphologically-defined species of horse strongyle were characterized, and specific oligonucleotide primers were designed for some species based on the nucleotide differences. Utilizing these primers, a PCR approach was developed for the specific amplification of ribosomal DNA of Strongylus vulgaris, Cyathostomum catinatum, Cylicocyclus nassatus, Cylicostephanus longibursatus or Cylicostephanus goldi. The method allowed the species-specific amplification of parasite DNA derived from faecal samples and/or copro-cultures, demonstrating the potential of the approach for the diagnosis of equine strongyloidosis. The establishment of this PCR assay also has implications for studying the biology and epidemiology of equine strongyles and anthelmintic resistance using faecal egg count reduction tests.

Animals↗

PubMed1997

Polymerase chain reaction-linked single-strand conformation polymorphism of ribosomal DNA to fingerprint parasites.

To overcome limitations of the morphological identification of some parasites (and their different developmental stages) to species, we have established a polymerase chain reaction-linked single-strand conformation polymorphism technique (PCR-SSCP) utilizing the second internal transcribed spacer (ITS-2) of ribosomal (r)DNA. This spacer was specifically chosen in the study of strongylid and ascarid nematodes because it is known to provide reliable species markers. The ITS-2 from individual parasites was amplified by PCR, then denatured and subjected to electrophoresis on a mutation detection enhancement (MDE) (nondenaturing) gel matrix. PCR-SSCP analysis showed that the single-strand ITS-2 patterns produced allowed the accurate identification of species. The method also allowed the display of (low-level) variation in patterns within some species between different geographical isolates. These findings demonstrate the usefulness of PCR-SSCP of ITS-2 for the identification of nematode species and indicate its potential for resolving variation in the ITS-2 sequence within species.

Animals↗

PubMed1997

The 5.8S rDNA sequences of 18 species of bursate nematodes (order Strongylida): comparison with rhabditid and tylenchid nematodes.

The 5.8S rDNA sequences of 18 species of bursate nematode were 153 bp in length and had a G + C content of 47-50%. Interspecific differences in rDNA sequence among the bursate nematodes were low (0-5.2%), but the extent of the sequence differences between the parasitic bursate nematodes, a free-living rhabditid nematode and 2 species of parasitic tylenchid nematodes (12-33%) suggests that the 5.8S rRNA gene may provide useful phylogenetic information with respect to the relationships of the different orders within the phylum Nematoda.

Animals↗

PubMed1997

Molecular delineation of Cylicocyclus nassatus and C. ashworthi (Nematoda:Strongylidae).

The nucleotide sequences of the first internal transcribed spacer (ITS-1), 5.8S gene and second internal transcribed spacer (ITS-2) of ribosomal DNA have been determined for Cylicocyclus nassatus, C. ashworthi and C. insignis. Pairwise comparisons revealed sequence differences between the taxa ranging from 3.8 to 6.2% for the ITS-2 and 2.2-2.7% for the ITS-1. For the ITS-1, the level of the sequence difference between C. ashworthi and C. nassatus (2.2%) was equivalent to that between C. nassatus and C. insignis (2.2%), indicating that C. ashworthi and C. nassatus represent separate species. Theoretical restriction maps were constructed from the sequence data, and a polymerase chain reaction-linked restriction fragment length polymorphism (PCR-linked RFLP) technique was established to unequivocally distinguish C. ashworthi from C. nassatus.

Animals↗

PubMed1996

Strongylus asini (Nematoda, Strongyloidea): genetic relationships with other Strongylus species determined by ribosomal DNA.

Genomic DNA was isolated from adult Strongylus asini collected from zebra. The second ribosomal transcribed spacer (ITS-2) was amplified and sequenced using polymerase chain reaction (PCR) based techniques. The DNA sequence was compared with previously published data for 3 related Strongylus species. A PCR-linked restriction fragment length polymorphism method allowed the 4 species to be differentiated unequivocally. The ITS-2 sequence of S. asini was found to be more similar to those of S. edentatus (87.1%) and S. equinus (95.3%) than to that of S vulgaris (73.9%). This result confirms that S. Asini and S vulgaris represent separate species and supports the retention of the 4 species within 1 genus.

Animals↗