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D C Fung

Publications and source records attributed to D C Fung.

10 recordsLinked to original sources
PubMed1999

An online locus-specific mutation database for familial hypertrophic cardiomyopathy.

The aim of this locus-specific mutation database was to provide an online resource that contains summarised and updated information on familial hypertrophic cardiomyopathy (FHC)-associated mutations and related data, for researchers and clinicians. It also serves as a means of publishing previously unpublished data, which could be of value in understanding genotype/phenotype correlations. There are 123 FHC-associated mutations catalogued along with ancillary information. By implementing the cgi/http method, remote users can query the database via the HTML interface on the Web browser and obtain data of relevance to them. The online service is available on http://www.angis.org.au/Databases/Heart.

Alternative Splicing↗
PubMed1998

UBE3A "mutations" in two unrelated and phenotypically different Angelman syndrome patients.

Angelman syndrome (AS) is a rare neurodevelopmental disorder. Recently, several mutations have been found in the E6-AP ubiquitin protein ligase gene (UBE3A) in a group of patients who are nondeleted and do not have uniparental disomy or imprinting defects. Most of the reported mutations cluster within exons 9 or 16 of the UBE3A gene, and nearly all are predicted to give rise to truncated E6-AP ligases. Here, we describe two AS patients with dissimilar phenotypes. At the molecular level, they are both nondeleted, do not display uniparental disomy, and have normal imprint patterns. One has the typical AS phenotype and carries the previously reported 1344delAG de novo mutation involving a functionally significant region of UBE3A. The other expresses an atypical phenotype in that she has less severe ataxia, no inappropriate laughing, or epilepsy, and her EEG was normal at an early age. A 14-bp deletion in the 3' untranslated region of exon 16 (3'UTRdel14) adjacent to the poly(A) signal was identified. Further investigation revealed that the DNA change was a neutral polymorphism. Haplotype analysis indicated that both the AS patient and her normal sibling had inherited the same maternal UBE3A gene and its 5' flanking region. Although the 14-bp change has no functional significance, it assists with counseling to determine future risks of recurrence in this family.

Angelman Syndrome↗
PubMed1998

Imaging techniques in microbiology.

Recent advances in optical imaging have dramatically expanded the capabilities of the light microscope and its usefulness in microbiology research. Some of these advances include improved fluorescent probes, better cameras, new techniques such as confocal and deconvolution microscopy, and the use of computers in imaging and image analysis. These new technologies have now been applied to microbiological problems with resounding success.

Cell Compartmentation↗
PubMed1998

Capillary electrophoresis: new technology for DNA diagnostics.

New innovations in the diagnostic laboratory achieve their full potential when they can be automated. Increasingly molecular biology (DNA) techniques are being utilised in traditional pathology disciplines, as well as the more recent ones of cytogenetics and molecular genetics. Molecular biology was first exploited for diagnostic purposes when Southern blotting became established. However the time-consuming nature of the methodology, as well as the skills required, made it difficult for Southern blotting to be used routinely in the service laboratory. Subsequently the invention of PCR facilitated the approach to DNA diagnostics. Today PCR in commercial or home-made kits is used for a range of procedures. The steps required to amplify DNA with PCR can also be fully automated. However the analysis of PCR products, which frequently requires slab gel electrophoresis and toxic chemicals or radioisotopes for visualisation, remains difficult to automate. An alternative way for analysing PCR products is now available through capillary electrophoresis. With this technique, automation can be extended to sample loading, electrophoresis and data analysis. The use of toxic chemicals or radioisotopes can be avoided.

Chromosome Mapping↗
PubMed1995

Powering the flagellar motor of Escherichia coli with an external voltage source.

Rotary motors of bacterial flagella are driven by ions that move across the cytoplasmic membrane down an electrochemical gradient. For Escherichia coli, the ions are protons, and the maximum work per unit charge that they can do is the protonmotive force. To test whether motor efficiency is limited by proton leakage or mechanical nonlinearities, we measured torque as a function of protonmotive force. Filamentous cells were drawn into micropipettes and energized with an external voltage source. Torque was proportional to protonmotive force up to -150 mV, twice the span accessible by earlier techniques. This is consistent with a mechanism in which a fixed number of protons, working at unit efficiency, carry the motor through each revolution. We also found that individual torque-generating elements inactivate at low potentials or potentials of reverse sign. When normal potentials are restored, they reactivate sequentially.

Cell Movement↗
PubMed1995

Mucus glycoconjugate complexes released from feline trachea by a bacterial toxin.

This paper describes low-density mucus glycoconjugates released from feline trachea by dirhamnolipid (DRL), a toxin from Pseudomonas aeruginosa. Mucus glycoconjugates in feline tracheas were radiolabeled in vivo with 3H-proline and 14C-glucose. Control mucus and that released by 200 micrograms/ml DRL were dissolved in guanidine hydrochloride buffer (GuHCl) and chromatographed on Sepharose CL-2B. Molecules eluting in the void volume (V0) of the column were isolated by isopycnic density gradient centrifugation in CsCl/GuHCl. All samples gave peaks of radiolabeled and periodic acid/Schiff (PAS)-reactive material at rho = approximately 1.50 and approximately 1.60 g/ml, but DRL-stimulated samples contained low-density material (rho < 1.32 g/ml), also PAS-reactive and radiolabeled. Control secretions incubated with DRL in vitro did not form low-density material. In Triton X-100 (1% vol/vol), a nonionic detergent, low-density material behaved as smaller molecules, running in the partially included volume (Vi) of the column of Sepharose CL-2B, but still in the V0 of Sephacryl S-300. Incubation with chondroitinase ABC, heparinase II and III, and keratanase failed to change its elution profile on S-300, evidence against glycosaminoglycans; but proteolysis with trypsin or proteinase K gave two peaks, peptide fragments near the totally included volume of the column and glycopeptides in V0. The V0 glycopeptides banded between 1.50 and 1.55 g/ml in a CsCl gradient and eluted as a single peak in the Vi of Sephacryl S-400, suggesting a distinct homogeneous glycopeptide, smaller than those from normal mucins. The main 14C-labeled sugars in this glycopeptide were fucose, glucosamine, galactosamine, and galactose, consistent with a mucin. Thus, DRL releases stable but noncovalent complexes containing one or more distinct mucinlike glycoconjugates, probably combined with lipids and peptides. We discuss their possible relevance to airway diseases, including cystic fibrosis.

Animals↗
PubMed1995

Analysis of respiratory mucus glycoproteins in asthma: a detailed study from a patient who died in status asthmaticus.

Airway mucus from asthmatics is often unusually solid. The death of a patient in status asthmaticus allowed the collection of 28 g of abnormal airway mucus at autopsy. Its chemical and physical properties were studied to reveal differences from more normal airway mucus. The gel plug taken from the airways could be dispersed in 6 M guanidinium chloride, but it took > 1 wk and 700 ml of extractant to disperse 3 g of exudate completely. In contrast, treatment with 10 mM dithiothreitol, which reduces disulfide bonds, dispersed the gel within seconds. Mucins accounted for 25% of the non-dialyzable material in the gel, while DNA constituted < 1% and proteoglycans could not be detected. The mucins were similar in architecture and general composition to other respiratory mucins and were present at a high concentration (approximately 40 mg/ml). The majority of mucins were of extreme size (mean M(r) 30-40 x 10(6)) and slow to dissolve, but sequential extraction experiments on the gel exudate demonstrated a proportion of mucins (15%), the most readily extracted, which had a higher density, 1.45-1.55 g/ml, a lower M(r) (11.5 x 10(6)) and were markedly more acidic than the bulk of the mucins. Both major and minor mucin populations were extremely heterogeneous in mass distribution. Electron microscopy of the major mucin species demonstrated extensive networks of molecules many microns in length. The major mucin species was distinctly less acidic than mucins previously described from either normal or diseased airways. Amino acid analysis of fractions across the charge distribution suggested the presence of at least two different mucin proteins occurring as distinct glycoforms.

Gels↗
PubMed1992

Vagal control of mucus glycoconjugate secretion into the feline trachea.

1. We examined the effects of frequencies and patterns of electrical stimulation of the peripheral cut ends of the vagus nerves on the release of mucus glycoconjugates into feline trachea in vivo. Mucus glycoconjugates, radiolabelled biosynthetically with [35S]sulphate and [3H]glucose, were washed from a tracheal segment in situ, and dialysed before being counted and assayed chemically by the periodic acid-Schiff (PAS) method. 2. Vagal stimulation with regular pulses (10 V, 2 ms duration) at 1, 2.25, 4.5, 9 and 18 Hz produced frequency-dependent increases in the output of mucus glycoconjugates. 3. The muscarinic agonist pilocarpine (0.1-10 microM), given intrasegmentally, produced dose-dependent increases in the output of mucus glycoconjugates. 4. Pretreatment with atropine, phentolamine and propranolol reduced but did not abolish the effects of vagal stimulation. Vagus nerve stimulation still caused frequency-dependent increases in the output of mucus glycoconjugates. 5. High frequency stimulations at 22.5 and 47.5 Hz given intermittently (1 s burst then 4 s rest), whether in the absence or presence of cholinergic and adrenergic blockade, produced similar secretory responses as the same number of pulses delivered in regular trains at 4.5 and 9.5 Hz. This suggests that neither cholinergic nor non-adrenergic, non-cholinergic (NANC) nerve mechanisms in this system are potentiated by high frequency, intermittent burst stimulation. 6. In the absence of atropine, regular vagal stimulation had a greater effect on heart rate than did the same number of pulses delivered in bursts. 7. High molecular weight glycoconjugates from secretions were taken from the void volume of a Sepharose CL-2B gel filtration column and separated further by density-gradient centrifugation. Macromolecular components were observed at two densities, a typical mucin at 1.52 g ml-1, and a high density atypical component at 1.63 g ml-1. In secretions collected during vagal stimulation, either in the absence or presence of cholinergic and adrenergic blockade, the ratio of low density to high density macromolecules was higher than in unstimulated secretions. This can be explained if both cholinergic and NANC nervous vagal mechanisms stimulate the output of typical (density = 1.52 g ml-1) mucins into the feline trachea.

Adrenergic Fibers↗
PubMed1992

NANC nerve pathways controlling mucus glycoconjugate secretion into feline trachea.

We used autonomic-blocking drugs to define nonadrenergic noncholinergic (NANC) vagus nerve pathways regulating tracheal mucus secretion. In anesthetized cats, mucus glycoconjugates, radiolabeled biosynthetically with [35S]sulfate and [3H]glucose, were washed from a tracheal segment in situ and dialyzed before scintillation counting and chemical assay with periodic acid-Schiff (PAS). Without autonomic blockade, vagal stimulation (9.5 Hz, 10 V, 2-ms pulse width, 10-min duration) increased outputs of radiolabeled and PAS-reactive glycoconjugates repeatably over four stimulation periods. In other animals, vagus nerves were stimulated with administration of autonomic blockers between stimulations. The first stimulation (no blockers) increased glycoconjugate output (delta 35S = 221 +/- 43.3%, delta 3H = 58 +/- 13.8%; delta PAS = +299 +/- 82.7%). Atropine, phentolamine, and propranolol reduced these responses (delta 35S = 67 +/- 15.6%; delta 3H = 26 +/- 5.3%; delta PAS = 88 +/- 25.6%). Guanethidine did not significantly lessen them further, although delta 3H was no longer significant. Ganglion blockade with hexamethonium prevented most of the remaining response to vagal stimulation (P less than 0.05 for diminution of delta 35S and delta PAS), but small effects persisted (delta 35S = 17 +/- 5.6%; delta PAS = 20 +/- 6.8%; P less than 0.05). We conclude that the main NANC vagal pathway controlling tracheal glycoconjugate secretion runs orthodromically.

Adrenergic Antagonists↗