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Biomedical subjects

E Hsu

Publications and source records attributed to E Hsu.

At least 37 records · Page 2Linked to original sources
PubMed1998

Hardness and strength of endodontic instruments made from NiTi alloy.

Scant information could be found in the dental literature on the hardness or strength of the materials in nickel-titanium (NiTi) root canal instruments. Hardness testing is a convenient method for examining these products and strength properties can be deduced from strength-hardness data. The Vickers Hardness was determined for NiTi root canal files and reamers from five manufacturers for sizes 15, 25 and 40. Significant differences in hardness were found between manufacturers, with values ranging from 296 to 349. Some differences were found between the different sizes from each manufacturer, but these were generally not statistically significant. These values obtained for NiTi instruments are lower than the softest stainless steel files previously examined (296-347 cf. 403-651), and below the hardness required for many cutting instruments (550-650). The values obtained suggest that NiTi instruments may not be as sharp as, and become blunt more easily than, stainless steel instruments. The strengths are expected to be in the lower range of those for stainless steel instruments.

Analysis of Variance↗
PubMed1997

Abbreviated junctional sequences impoverish antibody diversity in urodele amphibians.

Of the six complementarity-determining regions (CDR) forming the structure of the Ab combining site, CDR3 of heavy chain is the most variable in length and sequence. Diversity of this loop is determined by the number of gene segments involved, extent of addition to or deletion from the joining genes, and imprecision of the site of recombination. In neonatal mice and Xenopus tadpoles, the last two factors occur less frequently than in adults, which in tadpoles result in low affinity Ab responses that do not mature. In contrast, adult urodele amphibians make larval-like responses and are notorious for lifelong poor immunocompetence. The mechanism for this is not known, and in this study we cloned germline VH genes from the axolotl and obtained rearrangements to these VH gene segments by reverse-transcriptase PCR. These sequences were analyzed for heavy chain junctional diversity and found to be even less variable than that in newborn mouse or Xenopus tadpoles, although for different reasons. Only 29% of the CDR3 loop in the axolotl consisted of somatically generated sequences, compared with 44% in tadpole, 39% in newborn mice, and 57% in both adult mice and Xenopus. This distinguishing feature of axolotl CDR3 results not only from shorter junctional sequences, but also unusually extensive integration of germline JH sequence. As the CDR3 loop is the most important portion of the Ig sequence for determining Ab combining site diversity, our data provide the molecular basis for a contributing factor in the deficient urodele amphibian Ab responses.

Aging↗
PubMed1997

New approaches for studying the permeability of fish embryos: toward successful cryopreservation.

This paper describes some new approaches for understanding the permeability of teleost embryos. The dechorionated zebrafish (Brachydanio rerio) was used as a model for basic studies of water and cryoprotectant permeability. These embryos are composed of two compartments, a large yolk (surrounded by the yolk syncytial layer) and differentiating blastoderm cells. Cellular water was distributed unequally in each compartment. Measurements indicated that the total water in the embryo was 74%, while the total water in the yolk was 42%, and total water in the blastoderm was 82%. The internal isosmotic value for the zebrafish embryo is unknown. However, for one-compartment modeling studies of membrane permeability, the mean Lp (+/- SEM) values were 0.022 +/- 0.002 to 0.049 +/- 0.008 microns x min-1 atm-1 at 40 mOsm (assuming this was one possible internal isosmotic value for the entire embryo) and 0.040 +/- 0.004 to 0.1 +/- 0.017 microns x min-1 atm-1 at 300 mOsm (assuming this was another possible internal isosmotic value for the entire embryo). When three- and six-somite embryos were placed in 1.5 and 2.0 M cryoprotectants (dimethyl sulfoxide and propylene glycol), osmometric measurements of volume changes indicated no cryoprotectant permeation. However, similar measurements with methanol revealed a small volume decrease (ca. 8%) and recovery (ca. 5%) for six-somite embryos in a 2.0 M solution. Magnetic resonance (MR) images of the spatial distribution of three cryoprotectants (dimethyl sulfoxide, propylene glycol, and methanol) demonstrated that only methanol permeated the entire embryo within 15 min. The other cryoprotectants exhibited little or no permeation into the yolk over 2.5 h. The results from MR spectroscopy and cryoprotectant microinjections into the yolk suggested that the yolk syncytial layer plays the critical limiting role for cryoprotectant permeation throughout the embryo.

Animals↗
PubMed1996

[The prevalence of hyperhomocysteinemia in thromboangiitis obliterans. Does homocysteine play a role pathogenetically?].

OBJECTIVE: As hyperhomocysteinaemia is known to be an important risk factor in the early onset of arteriosclerotic occlusive disease and leg-vein thrombosis, we investigated the prevalence of hyperhomocysteinaemia in patients with thromboangiitis obliterans (TAO), a condition predominantly affecting peripheral arteries and veins. PATIENTS AND METHODS: Plasma homocysteine (HC), before and after administration of methionine (0.1 g/kg) as well as serum folic acid, vitamins B6 and B12 were measured in 15 patients with TAO (12 men, 3 women; mean age 33.3 years: group 1), in 15 non-smokers without peripheral vascular disease (group 2) and 15 smokers without peripheral vascular disease (group 3). At the time of the study, of those in group 1 seven were active smokers, seven were ex-smokers and one was a non-smoker. RESULTS: Before methionine administration four patients (27%), none of the healthy non-smokers and one smoker without vascular disease (7%) had increased HC levels (> 13.9 nmol/ml). The difference between groups 1 and 2 was statistically significant (P < 0.05), but not that between groups 1 and 3 and between 2 and 3. 4 hours after methionine increased HC levels (> or = 31 nmol/ml) were measured in nine patients but in none of the healthy controls. The difference between patients and the two control groups without vascular disease was clearly significant (P = 0.0107). There was a difference in folic acid levels between the patients and the smokers without vascular disease: in eight patients (53%) the levels were in the lower third of normal, in six (40%) they were in the middle and in one (7%) in the upper third. Corresponding levels in group 3 were: four (27%), three (20%) and eight (53%). CONCLUSION: Hyperhomocysteinaemia occurs frequently in patients with TAO. It may play an important and nicotine-independent role in its pathogenesis.

Adult↗
PubMed1996

Characterization of keratinocyte growth factor binding to heparin and dextran sulfate.

Binding of keratinocyte growth factor (KGF) with heparin (molecular weight of 5000) and dextran sulfate (molecular weight of 8000) was studied using an online monitoring of size-exclusion chromatography with light scattering, refractive index, and uv absorbance detectors. This technique allows the determination of the molecular weight of KGF eluting as complexes with the above polymers. When mixtures of KGF with heparin were injected into the column, two peaks of heparin/KGF complexes were observed. The first peak corresponded to, on average, 3.4 KGF per complex and the second peak to an average of about 2 KGF per complex. These results suggest that the heparin/ KGF complex is heterogeneous, consisting of 1,2,3, and 4 KGF molecules per complex. To calculate the number of heparin molecules in these complexes, the rate of disappearance of free KGF was determined as heparin was added. The average number of KGF bound to 1 mol of heparin was calculated to be about 2 mol, suggesting that only one heparin molecule is present in these complexes. The heparin binding of two KGF mutants, i.e., (C1, 15S)KGF (with substitutions of serine for cysteines 1 and 15) and d28KGF (lacking 28 N-terminal amino acid residues), was essentially identical to that of the native sequence KGF. A similar experiment was carried out for KGF binding to dextran sulfate. The molecular weight of the complex corresponded to 2 to 2.6 KGF molecules per complex. The rate of disappearance of free KGF as the dextran sulfate added showed 2-3 mol of KGF bound to 1 mol of dextran sulfate, consistent with the idea that the complex contains only 1 dextran sulfate molecule.

Binding Sites↗
PubMed1996

The generation of antibody diversity in the turtle.

The Ab response in reptiles has been studied at the protein level, and in turtles some aspects resemble those of cold-blooded vertebrates from other classes. The genetic bases for these features are not clear. The present study is the first on the IgH organization and complexity of a reptilian Ig gene system. The approach to cloning turtle (Pseudemys scripta) sequences is entirely PCR based, and its efficacy is demonstrated by obtaining extensive information on a heretofore unexplored Ig gene system. A number of genomic VH sequences, representing possibly four families, were isolated, as was a genomic C mu 4 clone. These sequences, used as probes, provided proof that in the turtle there is a single IgH locus with multiple VH genes and one C mu gene. In Northern hybridizations, the C mu 4 probe detected two transcripts; of the four VH groups, only one was expressed, and multiple bands indicated the presence of at least two non-mu transcripts. Using reverse transcription-PCR on spleen or liver RNA, an IgM heavy chain sequence was obtained, as were a number of VDJ rearrangements. Among 32 unique VDJ rearrangements from one animal, there were 22 sequence variants at framework 4, suggesting either a very large number of J segments or somatic modification in the variable region. The latter interpretation is supported by point mutations found in framework 3 and CDR3. The number of changes is considerably greater than the deduced Taq misincorporation rate (0.05%).

Amino Acid Sequence↗
PubMed1996

Physical aggression is associated with preservation of substantia nigra pars compacta in Alzheimer disease.

OBJECTIVE: To investigate specific neuropathologic correlates of agitation and physical aggression in Alzheimer disease (AD). DESIGN: Neuronal counts in the nucleus basalis, locus ceruleus, and substantia nigra were compared in the brains of patients with pathologically definite AD with or without histories of agitation or interpersonal violence. SETTING: Alzheimer disease center of a university department of neurology. MAIN OUTCOME MEASURES: Neuron densities in the nucleus basalis and absolute neuron counts in the locus ceruleus and substantia nigra pars compacta. RESULTS: The patients with AD who had histories of unequivocal interpersonal violence had significantly greater neuron counts in the substantia nigra pars compacta than did the nonviolent patients with AD. This finding remained significant after multiple clinical and neuropathologic variables were adjusted for. Neuropathologic findings in the nucleus basalis and locus ceruleus were not different between violent and nonviolent patients. CONCLUSION: Preservation of pigmented substantia nigra neurons may be a risk factor for physical aggression in AD.

Aged↗
PubMed1996

Is Xenopus IgX an analog of IgA?

Using class specific monoclonal antibodies we analyzed the tissue distribution of B cells expressing the three immunoglobulin (Ig) isotypes (IgM, IgX, IgY) in Xenopus. Large numbers of IgM- and IgX-, but not IgY-, positive B cells are located in the gut epithelium of the intestine. In this organ up to 60% of all B cells can be IgX positive, while in the spleen or liver they are hardly detectable. The majority of IgX-producing cells resemble plasma cells. IgY-producing cells are found in the liver and spleen but not in the intestine. In contrast to IgY, the expression of IgM and IgX is thymus independent. Upon systemic immunization, a several-fold increase of specific IgM and IgY, but not IgX, antibodies was detected in the sera. This and its association with the mucosae of the intestine resembles results reported for mammalian IgA; therefore, IgX of Xenopus might be considered an analog of IgA.

Animals↗
PubMed1996

Innovations in acumoxa: acupuncture analgesia, scalp and ear acupuncture in the People's Republic of China.

This paper examines three 'innovations in acumoxa' (zhenjiu) that were promulgated by the Chinese government during the Maoist periods of the Great Leap Forward (1958-61) and the Cultural Revolution (1966-76): acupuncture analgesia (zhenjiu mazui), scalp acupuncture (touzhen) and ear acupuncture (erzhen). They all bear features of Chinese and Western medical practice, a characteristic which has been exploited in Chinese politics of health. On the one hand, the innovations have been promoted for the nationalistic reason in virtue of their being inherently Chinese. On the other hand, by equating Western medical practice with science, they signify modernity and progressiveness. In the late eighties, all still enjoyed official backing. Although they were no longer exclusively practised in government hospitals, they still stood for what they had originally been promulgated. Acupuncture analgesia, while no more practised in the clinic, is still the prototype of a Chinese scientific therapy, now subject to biomedical research in laboratories. Scalp acupuncture, which never became widely known as a modern Chinese-Western innovation, is still being practised exclusively by skilled doctors. Ear acupuncture is now practised also outside government institutions, for the same reasons of being easily applied, easily learnt and extremely economical as it had originally been promulgated. Paradoxically, ear acupuncture, the most popular of the three, was 'discovered' outside China, by a French doctor, and is founded on the principles of reflexology, a therapy that the biomedical establishment does not consider scientific.

Acupuncture Analgesia↗
PubMed1996

Canonical VH CDR1 nucleotide sequences are conserved in all jawed vertebrates.

The antibody combining site is formed from the complementarity-determining regions (CDR) of the heavy and light chains. Function, in antibodies, means diverse structures capable of binding a variety of ligands and the CDR have long been distinguished as the sites of a high incidence os non-homologous replacement. The present studies show, despite the apparent protein diversity, the existence of canonical nucleotide sequences in the heavy chain CDR1. These sequences were deduced from human and mouse CDR1, and their presence demonstrated experimentally in all representatives from the gnathostome vertebrate classes. This unexpected conservation suggests that selection pressure for sequence diversity is counter-balanced by properties of the encoded amino acids such as capacity for ligand interaction, structural requirements of the CDR loop and perhaps retention of certain ligand-binding sequences. Part of the canonical nucleotide sequence involves a motif that has been suggested as a hot spot for somatic hypermutation. The assay for the canonical sequence is PCR-based and provides a novel approach to cloning multigene family members by using the hypervariable portions as target sequence.

Amino Acid Sequence↗
PubMed1996

Sequencing homopolymer tracts and repetitive elements.

We investigated the use of Taq dye primer and Taq terminator sequencing chemistry to optimize the quality of sequence data obtained from templates containing homopolymer tracts and repetitive elements. In direct side-by-side comparisons using the Applied Biosystems Model 373A Fluorescent Sequencer, the Taq terminator sequencing chemistry gave much cleaner and more consistent results on long homopolymer tracts and dinucleotide repeats. We also investigated various thermal cycling conditions and determined that higher annealing temperatures and longer denaturation times improved the ability to sequence through these problem templates.

Base Sequence↗
PubMed1995

Three-dimensional structure of cat tibialis anterior motor units.

The motor unit is the basic unit for force production in a muscle. However, the position and shape of the territory of a motor unit within the muscle have not been defined precisely. The territories of five motor units in the cat tibialis anterior muscle were reconstructed three-dimensionally (3-D) from tracings of the glycogen-depleted fibers belonging to each unit. The motor unit territories did not span the entire length of the muscle and their cross-sectional areas tapered along the proximodistal axis producing a conical shape. In addition, the position of the territory of each unit shifted in an anterior-posterior plane along the longitudinal axis of the muscle, presumably as a consequence of the pinnation of the fibers. The area of the motor unit territory at any given level along the proximodistal axis was highly correlated with the number of fibers within the territory at that level. Connective tissue boundaries (outlining fascicles) appeared to have a strong influence on the shape of the territory, territories showed abrupt changes at connective tissue boundaries as groups of motor unit fibers within a fascicle often terminated together while motor unit fibers in neighboring fascicles did not terminate. It is likely that the mechanical impact of the recruitment of a motor unit is affected by the location and shape of motor units within the same muscle area.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Isolation and characterization of the Xenopus terminal deoxynucleotidyl transferase.

A cDNA clone containing the sequence of the Xenopus homologue of terminal deoxynucleotidyl transferase (TdT) was isolated and analyzed. The derived amino acid sequence shares > 50% identity with the human, mouse, and bovine TdT sequences. By hybridization and PCR analyses Xenopus TdT mRNA was found in the thymus and not in the spleen, kidney, intestine, or liver. During ontogeny TdT appears in significant amounts in the thymus of tadpoles at metamorphic climax but little in the earlier midlarval stages. The emergence of TdT only late in development correlates with the paucity of N region addition in larval Ig heavy chain sequences. Past experiments on the ontogeny of the Xenopus immune system revealed a less efficacious tadpole immune response in skin graft rejection and Ab heterogeneity; the absence of TdT in the tadpole stages fits well with the notion of lower larval TCR and Ab diversity.

Amino Acid Sequence↗
PubMed1994

Stimulation of all epithelial elements during skin regeneration by keratinocyte growth factor.

Keratinocyte growth factor (KGF), a recently discovered 18.9 kD member of the fibroblast growth factor family has been shown to selectively induce keratinocyte proliferation and differentiation in tissue culture. To explore its potential stimulating keratinocyte growth and differentiation in vivo, we analyzed for the influence of KGF on epithelial derived elements within a wound created through the cartilage on the rabbit ear. KGF accelerated reepithelialization (p = 0.004) and increased the thickness of the epithelium (p = 0.0005) when 4-40 micrograms/cm2 recombinant KGF was added at the time of wounding. The regenerating epidermis showed normal differentiation as detected by cytokeratin immunostaining. Remarkably, however, KGF stimulated proliferation and differentiation of early progenitor cells within hair follicles and sebaceous glands in the wound bed and adjacent dermis. There was a transient but highly significant increase in specific labeling of cycling cells in both basal and suprabasal layers that extended into the spinous layer of the regenerating epidermis. As an indication of specificity, the inflammatory cells and fibroblasts within the wound were not influenced by KGF. The results indicate that KGF is unique in its ability to accelerate reepithelialization and dermal regeneration by targeting multiple epithelial elements within the skin. These results suggest that KGF may induce specific epithelial progenitor cell lineages within the skin to proliferate and differentiate, and thus may be a critical determinant of regeneration of skin. Furthermore, these findings illustrate the potential capacity of this system to analyze epithelial differentiation programs and disorders of epidermis, dermal glandular elements, and hair follicles.

Animals↗
PubMed1994

Measuring CDR3 length variability in individuals during ontogeny.

The portion of the antibody sequence that contributes most to the conformation of the antigen-combining site is the third complementarity-determining region (CDR3). The CDR3 in antibody heavy chains are somatically produced by the rearrangement of three different immunoglobulin (Ig) gene segments, VH, D and JH, and are therefore highly variable in sequence and length. We have devised a technique for rapid analysis of CDR3 length variability from a large number of cDNA samples. This technique allows comparative evaluation of IgH heterogeneity in individuals without recourse to DNA cloning and sequencing. We also present data on Ig sequences from different stages of development in the amphibian, Xenopus laevis. Most of the larval and post-metamorphic Ig samples contained CDR3 of 3-10 codons, two codons shorter than those of the adult CDR3, which were 5-12 codons. Antibodies may by immunized tadpoles have been shown to be much less diverse than those produced by adults to the same antigen. The shorter tadpole CDR3 perhaps generates a more limited spectrum of antigen-combining site structures and, in this way, makes for a more restricted antibody repertoire.

Animals↗