Biomedical subjects

Y C Yu

Publications and source records attributed to Y C Yu.

At least 19 recordsLinked to original sources

PubMed2006

Effects of immunisation against leptin on feed intake, weight gain, fat deposition and laying performance in chickens.

1. Three experiments were conducted to study the effects of leptin on weight gain and body composition in laying hens. 2. The effects of immunisation against chicken leptin on feed intake (FI), fat deposition and laying rate were observed in laying Guangdong yellow-feathered hens. Ten hens were inoculated with leptin immunogen on d 3, 31, 63 and 84, together with 10 control hens immunised with bovine serum albumin (BSA). In the 100-d experiment, immunisation against leptin increased blood anti-leptin antibody titres, slightly reduced plasma T3 concentrations, slightly decreased FI and increased live weight; however, laying rate was significantly depressed and abdominal fat mass was increased by the end of the 100-d experiment. 3. Passive immunisation of 50-d-old pullets with yolk extract containing anti-leptin antibody IgY significantly increased FI within 6 h of treatment compared with physiological saline treated controls. 4. In growing 70-d-old pullets, inoculation with 0.5 (group 1) or 1 (group 2) ml leptin immunogen on d 1 and 28 of the experiment slightly increased FI and significantly increased daily gain compared with BSA-immunised control pullets. Abdominal fat mass on d 49 increased from 48+/-4.5 g in controls to 66+/-3.5 and 80+/-3.1 g in groups 1 and 2, respectively. 5. It was suggested that immunisation against leptin mimicked loss of leptin bioactivity and might become a novel technique to stimulate fat growth in certain types of animal production.

Adipose Tissue↗

PubMed2001

Minimally invasive estimation of systemic vascular parameters.

A cardiovascular parameter estimator to identify the systemic vascular parameters was developed using an extended Kalman filter (EKF) algorithm. Measurements from a ventricular assist device (VAD) and arterial pressure were used in the estimator. The systemic vascular parameters are important indices of heart condition. However, obtaining these parameters usually requires invasive measurements, which are difficult to obtain under most clinical environments. Including a VAD model into the estimator and using the signals from a VAD to identify the cardiovascular parameters for VAD patients would minimize the need for indwelling sensors. This paper illustrates the use of a Novacor left ventricular assist system (LVAS) model with a cardiovascular model in the estimator to identify the systemic vascular parameters: characteristic resistance, blood inertance at the aorta, systemic compliance, and systemic resistance. Performance of the estimator was evaluated using data from a computer simulation and from a mock circulatory system experiment. Robustness of the estimator to the available measurements was also described. The estimation results showed that the estimates converged with reasonable accuracy in a limited time when the LVAS pump volume and arterial pressure were used as measurements. These parameter estimates can provide additional diagnostic information for patient and device monitoring and can be used for future VAD control development.

Algorithms↗

PubMed1999

Structure and dynamics of peptide-amphiphiles incorporating triple-helical proteinlike molecular architecture.

Organized polymeric assemblies that incorporate bioactive sequences and structures are finding important applications for the study of protein structure-function relationships. We have recently described a heteropolymeric peptide-amphiphile system that forms organized structures in solution and on surfaces. While the overall three-dimensional features of peptide-amphiphiles have been studied previously, the precise environment of specific residues, particularly those within biologically active regions, have not been examined in detail. In the present study, we have used heteronuclear single quantum coherence (HSQC) and inverse-detected 1H-15N NMR spectroscopy to examine the structure and dynamics of a peptide and peptide-amphiphile that incorporate the alpha1(IV)1263-1277 ([IV-H1]) amino acid sequence from type IV collagen. Three variants of the sequence (Gly-Pro-Hyp)4-[IV-H1]-(Gly-Pro-Hyp)4 were constructed with a single 15N-labeled Gly placed in the middle of the N-terminal (Gly-Pro-Hyp)4 region (residue Gly7), in the middle of the [IV-H1] sequence (residue Gly19), or in the middle of the C-terminal (Gly-Pro-Hyp)4 region (residue Gly34). These peptides were also N-terminally acylated with hexanoic acid to create an analogous series of 15N-labeled peptide-amphiphiles. HSQC spectra indicated that both the peptide and the peptide-amphiphile were in triple-helical conformation at low temperature, supporting prior circular dichroism (CD) spectroscopic results. The intensities of the triple-helical cross-peaks were stronger for the peptide-amphiphile, consistent with an enhanced triple-helical thermal stability within the peptide-amphiphile construct compared to that of the peptide alone. Relative relaxation values for the peptide-amphiphile monomeric and trimeric species were consistent with those reported previously for other triple-helical peptides. Relaxation measurements indicated that the triple-helical [IV-H1] region did not appear to be dramatically more flexible than the Gly-Pro-Hyp regions. The angle between Gly N-H bonds and the helix dyad axis, determined from the relaxation data, was within the range expected for triple helices. Overall, the peptide headgroup of the C6-(Gly-Pro-Hyp)4-[IV-H1]-(Gly-Pro-Hyp)4 peptide-amphiphile appears to form a continuous triple helix that behaves similarly, in a dynamic sense, to a triple-helical peptide. The enhanced thermal stability of the peptide-amphiphile compared to the analogous triple-helical peptide, along with the multitude of organized structures formed by lipidlike compounds, suggest that peptide-amphiphiles could be utilized as targeted liposomes, sensors, receptors, or enzymes.

Amino Acid Sequence↗

PubMed1999

Elderly use of the ED in an Asian metropolis.

To compare emergency department (ED) use by elderly patients (age 65 yrs or older) with that by younger adult patients (age 15-64 yrs), a prospective consecutive chart review study was conducted from August 1, 1995 through May 31, 1996 in eight designated hospitals in Taipei city (which has 2.6 million residents, 8.4% of whom are 65 yrs or older). Patient age, sex, mode of arrival, living status, triage category, advanced life support (ALS) eligibility, referral, confinement to bed, intensive care unit (ICU) admission, impression, trauma mechanism, and disposition were recorded and compared between the two groups. Of 27,765 adult emergency patients studied during the 10 months, 24% were elderly. The elderly were more likely to be ambulance cases, of high acuity and ALS eligibility, living alone, bed-ridden, and ICU cases (19.4% v 10.5%, 14.8% v 5.5%, 14.7% v 4.3%, 9.7% v 4.1%, 16% v 1.1%, and 4.0 v 1.1%, respectively). The three leading illnesses in the elderly were cerebral vascular accident (6.6%), cancer (5.6%), and cardiovascular disease (5.6%), and the two most common trauma mechanisms were trip (fall from the same level surface) (57.2%) and traffic accident (20.7%). Twenty-seven percent and 22.7% of elderly were disposed to admission and observation, respectively, compared with the 10.9% and 11.4% of the younger patients. Elderly patients have significantly different and more severe presentations to the ED compared with younger adults.

Adolescent↗

PubMed1999

Stepwise chromosome evolution in Drosophila albomicans.

A 'stepwise chromosome evolution model' is proposed to elaborate the two stages of the sex chromosome evolution of Drosophila albomicans. To explain the occurrence of both a 3-X and a 3-Y in this species it is proposed that these chromosomes evolved sequentially. The selection forces acting in the two stages are different. The genic composition in the first fused sex chromosome of D. albomicans was supposed to be selectively superior to the primitive unfused chromosomes, thus the fused chromosome could overcome the meiotic structural incompatibility and be maintained in the population during the first stage. When the second fusion occurred, the newly fused sex chromosome was preferentially selected, as it could provide a meiotic pairing partner for the first fusion. The fused sex chromosomes were eventually fixed in the population. Based on this model, we tried to determine which fused chromosome, 3-X or 3-Y, established first. The karyotyping result of four experimental hybrid populations showed that the fused 3-X, as opposed to 3-Y, chromosome has higher fitness values. However, without the coexistence of 3-X, 3-Y is excluded rapidly. Therefore, 3-X is likely to be the first fused chromosome in the stepwise chromosome evolution model. The formation and fixation of the fused 3-Y chromosome occurred subsequently.

Animals↗

PubMed1999

Epstein-Barr virus-encoded latent membrane protein 1 co-expresses with epidermal growth factor receptor in nasopharyngeal carcinoma.

Latent membrane protein 1 (LMP-1) is the only Epstein-Barr virus (EBV)-encoded oncogenic protein that has been detected in nasopharyngeal carcinoma (NPC), a cancer that is closely associated with EBV. Previous in-vitro studies have demonstrated that LMP-1 can upregulate epidermal growth factor receptor (EGFR) in epithelial cells. It was not established whether this cellular effect exists in NPC. To assess the association between LMP-1 and EGFR in NPC tissues, 60 NPC specimens were examined by immunohistochemistry using anti-LMP-1 antibody (CS 1-4) and anti-EGFR antibodies (EGFR 1, EGFR 1005). The results revealed that 41 (68.3%) specimens were immunopositive for LMP-1 and 44 (73.3%) specimens over-expressed EGFR. Morphologically, the expressions of LMP-1 and EGFR were homogeneously distributed in the tumor nests. In addition, the correlation between LMP-1 and EGFR was statistically significant (P<0.001, chi2 test, d.f. = 1). To elucidate further the correlation between LMP-1 and EGFR in vivo and in situ, an indirect dual immunofluorescence assay was conducted, using secondary antibodies conjugated with fluorescein isothiocyanate (FITC) or indocarbocyanine (Cy3). The results disclosed an intimate co-expression of LMP-1 and EGFR. In summary, the data indicate that over-expression of EGFR is a common phenomenon in NPC, and that EGFR is co-expressed with LMP-1 in NPC. Thus, EBV may play a role in the tumorigenesis of NPC through the effects of LMP-1 and EGFR.

ErbB Receptors↗

PubMed1999

[Rabbit facial nerve damager after Nd: YAG laser irradiation: an experimental study]

OBJECTIVE:To investigate the change effects of rabbit facial nerve after Nd:YAG laser irradiation.METHODS: According to therapeutic laser energy density,the facial nerves of 28 rabbits were irradiated by Nd:YAG laser with 5 different laser dosages.RESULTS: The facial nerves were functionally intact with mild degeneration histologically at three weeks postoperatively,when the energy density of Nd: YAG laserlaser lower than 70J/cm(2).In the group with energy density of 140J/cm(2),facial nerve density functionally impaired with moderate degeneration which rehabilitated within six weeks. While the laser power increaseed to more than 240J/cm(2),irreversible nerve damages happened.CONCLUSION: laser thermal effect is the main cause of nerve damage,there is a positive correlation between laser dosage and nerve impairment.

Journal Article↗

PubMed1998

Protein-like molecular architecture: biomaterial applications for inducing cellular receptor binding and signal transduction.

The development of biomaterials with desirable biocompatibility has presented a difficult challenge for tissue engineering researchers. First and foremost, materials themselves tend to be hydrophobic and/or thrombogenic in nature, and face compatibility problems upon implantation. To mediate this problem, researchers have attempted to graft protein fragments onto biomaterial surfaces to promote endothelial cell attachment and minimize thrombosis. We envisioned a novel approach, based on the capability of biomolecules to self-assemble into well-defined and intricate structures, for creating biomimetic biomaterials that promote cell adhesion and proliferation. One of the most intriguing self-assembly processes is the folding of peptide chains into native protein structures. We have developed a method for building protein-like structural motifs that incorporate sequences of biological interest. A lipophilic moiety is attached onto a N alpha-amino group of peptide chain, resulting in a "peptide-amphiphile." The alignment of amphiphilic compounds at the lipid-solvent interface is used to facilitate peptide alignment and structure initiation and propagation, while the lipophilic region absorbs to hydrophobic surfaces. Peptide-amphiphiles containing potentially triple-helical or alpha-helical structural motifs have been synthesized. The resultant head group structures have been characterized by CD spectroscopy and found to be thermally stable over physiological temperature ranges. Triple-helical peptide-amphiphiles have been applied to studies of surface modification and cell receptor binding. Cell adhesion and spreading was promoted by triple-helical peptide-amphiphiles. Cellular interaction with the type IV collagen sequence alpha 1(IV) 1263-1277 increased signal transduction, with both the time and level of induction dependent upon triple-helical conformation. Collectively, these results suggest that peptide-amphiphiles may be used to form stable molecular structure on biomaterial surfaces that promote cellular activities and improve biocompatibility.

Amino Acid Sequence↗

PubMed1998

Do in vitro susceptibility data predict the microbiologic response to amphotericin B? Results of a prospective study of patients with Candida fungemia.

Outcome for 105 patients with candidemia treated with amphotericin B was correlated with amphotericin B in vitro susceptibility results. Thirty-three patients had microbiologic failure, which was defined as persistence of Candida in the bloodstream despite > or = 3 days of amphotericin B. Amphotericin B minimum inhibitory concentrations (MICs) were determined by the National Committee for Clinical Laboratory Standards methodology. After determination of MICs, the minimal lethal concentrations (MLCs) were determined. The isolates tested yielded a narrow range of amphotericin B MICs (0.06-2 microg/mL); only 5% (5/105) exhibited MICs > or = 1 microg/mL. The MLC range, on the other hand, was significantly broader (0.125 to > 16 microg/mL); 24% (25/105) exhibited MLCs > or = 1 microg/mL. The strongest predictor for microbiologic failure was 48-h MLC (P < .001), followed by 24-h MLC (P = .03) and 48-h MIC (P = .11). A resistant break point for amphotericin B of > 1 microg/mL for MLC and > or = 1 microg/mL for MIC could be inferred from this study.

Amphotericin B↗

PubMed1998

Inhibition of RNA synthesis as a therapeutic strategy against Aspergillus and Fusarium: demonstration of in vitro synergy between rifabutin and amphotericin B.

We investigated the in vitro antifungal activity of amphotericin B, alone and in combination with rifabutin, an inhibitor of bacterial RNA polymerase, against 26 clinical isolates of Aspergillus and 25 clinical isolates of Fusarium. Synergy or additivism between these drugs was demonstrated against all isolates tested. Amphotericin B MICs were reduced upon combination with rifabutin from a mean of 0.65 microg/ml to a mean of 0.16 microg/ml against Aspergillus, and from a mean of 0.97 microg/ml to a mean of 0.39 microLg/ml against Fusarium (P < 0.000001 for both). Similarly, the MICs of rifabutin were reduced upon combination with amphotericin B from a mean of >32 microg/ml to a mean of 1.1 microg/ml against both fungi (P < 0.000001 for both). These positive interactions were corroborated by a colony count study with two Fusarium isolates, for which treatment with the combination of subinhibitory concentrations of amphotericin B (at concentrations 2- and 4-fold less than the MIC) and rifabutin (at concentrations ranging from 4- to 64-fold less than the MIC) resulted in 3.2-log reductions in colony counts compared to those after treatment with either drug alone. Inhibition of RNA synthesis was shown to be the mechanism of antifungal activity. These results suggest that inhibition of fungal RNA synthesis might be a potential target for antifungal therapy.

Amphotericin B↗

PubMed1997

Potentiation of antifungal activity of amphotericin B by azithromycin against Aspergillus species.

The potential role of azithromycin in combination with amphotericin B against 25 clinical isolates of Aspergillus was assessed. The MIC of amphotericin B was 1 microg/ml for 44% of the isolates, 0.5 microg/ml for 48%, and 0.25 microg/ml for 8%. All isolates were resistant to azithromycin. Synergism, defined as a > or = twofold reduction in the MIC of both drugs upon combination, was demonstrated between amphotericin B and azithromycin for all 25 isolates. To prove that azithromycin exerts its antifungal effect by inhibiting protein synthesis, we studied [35S]-methionine incorporation into protein in one Aspergillus isolate. Neither amphotericin B at 0.125 microg/ml (fourfold below its MIC) nor azithromycin at 16 microg/ml (> or = 16-fold below its MIC) had any effect on protein synthesis when tested alone. Upon combination, however, a 68% inhibition in protein synthesis was evident by the inhibition of [35S]-methionine incorporation.

Amphotericin B↗

PubMed1997

Construction of biologically active protein molecular architecture using self-assembling peptide-amphiphiles.

The peptide-amphiphiles described here provide a simple approach for building stable protein structural motifs using peptide head groups. One of the most intriguing features of this system is the possible formation of stable lipid films on solid substrates, or the use of the novel amphiphiles in bilayer membrane systems, where the lipid tail serves not only as a peptide structure-inducing agent but also as an anchor of the functional head group in the lipid assembly. The peptide-amphiphile system potentially offers great versatility with regard to head and tail group composition and overall geometries and macromolecular structures. For building materials with molecular and cellular recognition capacity, it is essential to have a wide repertoire of tools to produce characteristic supersecondary structures at surfaces and interfaces.

Drug Design↗

PubMed1997

Effects of moxibustion on blood pressure and renal function in spontaneously hypertensive rats.

The aim of this study was to investigate the effects of moxibustion at the meridian points BL-15 (Xin-shu) and BL-27 (Xiao-chang-shu) on renal function, systolic blood pressure, plasma levels of renin activity, aldosterone and atrial natriuretic peptide in spontaneously hypertensive rats. The results showed that urine volume increased significantly after moxibustion at the meridian points BL-15, but decreased at BL-27. Urinary excretion of Na+ decreased after moxibustion at the meridian points BL-15 and BL-27. Systolic blood pressure decreased after moxibustion at the meridian point BL-15. No effect was observed at BL-27. Plasma levels of aldosterone and renin activity increased significantly, but the levels of atrial natriuretic peptide decreased significantly after moxibustion at BL-15. Plasma levels of aldosterone and atrial natriuretic peptide increased significantly after moxibustion at the meridian points BL-27. These results suggest that the meridian points BL-15 and BL-27 are related to the regulation of renal function and the secretion of hormone with body fluid metabolism.

Acupuncture Points↗

PubMed1996

Neuroendocrine cells in the cat laryngeal epithelium.

The structure and distribution of neuroendocrine cells in the feline laryngeal epithelium were examined using immunohistochemical techniques. Neuroendocrine cells were often spindle shaped, with cytoplasmic processes directed towards the lumen and basement membrane. The apical portion of the cells usually reached the laryngeal lumen with microvillous projections. The cytoplasm always contained variable numbers of electrondense cored vesicles. The number of neuroendocrine cells decreased in the following order: subglottis, posterior glottis, supraglottis, anterior glottis. Neuroendocrine cells contained calcitonin gene-related peptide, substance P and/or 5-hydroxytryptamine. They also showed protein gene product 9.5 or neuron-specific enolase immunoreactivity. These observations suggest that neuroendocrine cells play a part in the regulatory function of the cat larynx by releasing various peptides. These substances may contribute to allergic reactions or control mucus secretion by acting via the endocrine or paracrine pathways and/or neurosecretory pathways.

Animals↗

PubMed1996

[Surgical approach plus Nd:YAG laser irradiation for the management of hemangioma in deep maxillofacial region]

This article introduces a new method for the management of cavernous hemangioma in deep maxillofacial region.Common surgical approach was carried out to expose the mass of hemangioma,then Nd:YAG laser was irradiated it without tumor removal.Immediatelly shrinking of hemangioma can be seen in all these seven cases.The therapeutic effect was satisfied in 3-12 months follow up.With the basic research of the rabbit facial nerve's Nd:YAG laser injured detecting experiment.We discussed its indication,advantage and interaction between laser and peripheral tissue.Our result shown that this new way is a good method for hemangioma in deep maxillofacial region as its advantages of skin preventing and peripheral normal tissue preserving

Journal Article↗

PubMed1994

The effect of endodontic access cavity preparation and subsequent restorative procedures on incisor crown retention.

Endodontic treatment often will require access through existing crowns. This study was undertaken to determine whether endodontic access cavity preparation affected the retention of crowns in anterior teeth and then to determine whether this retention can be regained by amalgam or post-retained amalgam restorations. Twenty extracted human incisors were mounted in acrylic blocks and prepared for crowns. Metal copings were fabricated and cemented with zinc phosphate cement and the forces required to displace the copings after various procedures were measured with a tensile testing machine. Retention values for all stages were compared with the initial retentive value for each coping without an access cavity which was set at 100 per cent. Group one specimens had the following means: copings with access cavity, 85.64 +/- 28.65 per cent of the initial values; amalgam flush with lingual dentine, 95.81 +/- 36.2 per cent; amalgam flush with coping, 114.89 +/- 34.5 per cent. Group two means were: copings with access cavity, 89.95 +/- 21.42 per cent; posts and amalgam, 177.37 +/- 77.5 per cent. Statistical analysis with the two sample t test showed that retention with post-retained amalgam restorations showed significantly higher values when compared with access cavities without restorations (p < 0.05). Retention values for post-retained restorations were significantly different from those just using amalgam. This study demonstrated that endodontic access cavities reduced the retention of the crowns, and subsequent restoration with amalgam or a post can regain the retention.(ABSTRACT TRUNCATED AT 250 WORDS)

Crowns↗

PubMed1991

Intrathoracic extramedullary hematopoiesis simulating posterior mediastinal mass--report of a case in patient with beta-thalassemia intermedia.

Intrathoracic involvement of the extramedullary hematopoiesis is a rare condition. It is usually found in patients with thalassemia or hereditary spherocytosis. In the literature, only 79 cases have been reported. Here, in Taiwan, a 22 year-old female patient of beta-thalassemia intermedia presented with posterior mediastinal mass proved as an intrathoracic extramedullary hematopoiesis by thoracoscopic biopsy was reported.

Adult↗

PubMed1990

Cholinergic mechanisms in the rat's hypothalamus mediate the stimulatory effect of thyrotropin-releasing hormone on gastric secretion.

To assess the possible involvement of cholinergic mechanisms in the hypothalamic nuclei in the stimulatory effect of TRH on gastric secretion, rats were infused with thyrotropin-releasing hormone (TRH), cholinergic agonist or antagonist, and normal saline through previously implanted hypothalamic cannulae. Administration of TRH or pilocarpine into the lateral cerebral ventricle or the anterior hypothalamus caused a dose-related increase in gastric volume and acidity in rats. On the other hand, administration of either atropine or D-tubocurarine into the same brain sites caused the opposite effects. Furthermore, the stimulatory effect of TRH or pilocarpine on gastric secretion was completely abolished by pretreatment of the CSF or the anterior hypothalamus with atropine and to a lower degree, D-tubocurarine. Administration of TRH, pilocarpine, atropine or D-tubocurarine into the lateral hypothalamus produced only a slight effect on gastric volume and acidity. However, the gastric volume or acidity was not affected by administration of either TRH, pilocarpine, atropine or D-tubocurarine into the ventromedial hypothalamus in our rats. The data indicate that the cholinergic muscarinic receptor mechanisms in the anterior hypothalamus may mediate the stimulatory effect of TRH on gastric secretion in rats.

Animals↗