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Biomedical subjects

Q Hu

Publications and source records attributed to Q Hu.

At least 37 records · Page 2Linked to original sources

Theoretical predictions of electromechanical deformation of cells subjected to high voltages for membrane electroporation.

An electromechanical analysis based on thin-shell theory is presented to analyze cell shape changes in response to external electric fields. This approach can be extended to include osmotic-pressure changes. Our calculations demonstrate that at large fields, the spherical cell geometry can be significantly modified, and even ellipsoidal forms would be inappropriate to account for the deformation. Values of the surface forces obtained from our calculations are in very good agreement with the 1--10 mN/m range for membrane rupture reported in the literature. The results, in keeping with reports in the literature, demonstrate that the final shape depends on membrane thickness. This has direct implications for tissues in which significant molecular restructuring can occur. It is also shown that, at least for the smaller electric fields, both the cellular surface area and volume change roughly in a quadratic manner with the electric field. Finally, it is shown that the bending moments are generally quite small and can be neglected for a simpler analysis.

Biomechanical Phenomena↗

Characterization of acute somatosensory pain transmission in P/Q-type Ca(2+) channel mutant mice, leaner.

To study the role of the Ca(v)2.1/alpha(1A) (P/Q-type) Ca(2+) channel in somatosensory pain processing, behavioral and electrophysiological studies were conducted using the leaner (tg(la)/tg(la)) mouse. Behavioral analyses in tg(la)/tg(la) revealed reduced responses to mechanical stimuli, and enhanced responses to heat stimuli. Electrophysiological analyses showed that tg(la)/tg(la) had a significantly reduced ability to evoke dorsal root potentials, suggesting a functional deficit in the spinal dorsal horn local circuitry responsible for presynaptic inhibition of primary sensory fibers. These results suggest the critical importance of the P/Q-type channel in modulation of acute somatosensory pain transmission in spinal cord.

Action Potentials↗

The role of acetylation in rDNA transcription.

Treatment of NIH 3T3 cells with trichostatin A (TSA), an inhibitor of histone deacetylase (HDAC), resulted in a dose-dependent increase in transcription from a rDNA reporter and from endogenous rRNA genes. Chromatin immunoprecipitation using anti-acetyl-histone H4 antibodies demonstrated a direct effect of TSA on the acetylation state of the ribosomal chromatin. TSA did not reverse inhibition of transcription from the rDNA reporter by retinoblastoma (Rb) protein, suggesting that the main mechanism by which Rb blocks rDNA transcription may not involve recruitment of deacetylases to rDNA chromatin. Overexpression of histone transacetylases p300, CBP and PCAF stimulated transcription in transfected NIH 3T3 cells. Recombinant p300, but not PCAF, stimulated rDNA transcription in vitro in the absence of nucleosomes, suggesting that the stimulation of rDNA transcription by TSA might have a chromatin-independent component. We found that the rDNA transcription factor UBF was acetylated in vivo. Finally, we also demonstrated the nucleolar localization of CBP. Our results suggest that the organization of ribosomal chromatin of higher eukaryotes is not static and that acetylation may be involved in affecting these dynamic changes directly through histone acetylation and/or through acetylation of UBF or one of the other components of rDNA transcription.

3T3 Cells↗

Programmable fusogenic vesicles for intracellular delivery of antisense oligodeoxynucleotides: enhanced cellular uptake and biological effects.

Programmable fusogenic vesicles (PFV) are liposomes composed of non-bilayer lipid components stabilized by the inclusion of an exchangeable poly(ethylene glycol) (PEG)-lipid conjugate. Vesicle destabilization by loss of the PEG-lipid results in recovery of the inherent fusogenic character. As a result, PFV can be designed to display a long circulation lifetime after i.v. administration, high accumulation at disease sites and full bioavailability of an encapsulated compound. In the present study, we investigated the potential application of PFV as carriers for intracellular delivery of antisense oligodeoxynucleotides (ODN). Antisense phosphorothioate ODN were encapsulated into PFV containing dioleoylphosphatidylethanolamine, cholesterol, dioleyldimethylammonium chloride and PEG-ceramides with different carbon chain length (C(8), C(14) and C(20)). In vitro fluorescent microscopy and flow cytometry analysis demonstrated that PFV containing PEG-ceramide C(14) provided enhanced intracellular delivery of FITC-labelled antisense ODN compared to PFV displaying faster or slower rates of destabilization (containing PEG-ceramide C(8) or C(20), respectively). Therapeutic efficacy of PFV-encapsulated antisense ODN against two proto-oncogenes, c-myc and bcl-2, was examined in various cell lines. At antisense concentrations of 0.5 microM, no significant downregulation of c-myc mRNA levels was observed in HEK293, B16 and MCA207 cells. However, treatment of 518A2 melanoma cells with PFV-encapsulated antisense targeting bcl-2 at concentrations of 0.5 microM and 1.0 microM resulted in reduced bcl-2 mRNA level by about 20% and 25% after 48 h incubation. Free antisense ODN did not affect bcl-2 mRNA expression at the concentrations used in this study and encapsulated control antisense (reverse polarity) led to a non-specific increase in mRNA levels. Our results suggest that PFV carriers displaying appropriate rates of destabilization have the potential to act as intracellular delivery vehicles and may improve the bioavailability and potency of antisense oligonucleotides.

Animals↗

CBF/NF-Y functions both in nucleosomal disruption and transcription activation of the chromatin-assembled topoisomerase IIalpha promoter. Transcription activation by CBF/NF-Y in chromatin is dependent on the promoter structure.

To understand the role of CCAAT-binding factor (CBF) in transcription in the context of chromatin-assembled DNA, we used regularly spaced nucleosomal DNA using topoisomerase IIalpha (topo IIalpha) and alpha2(1) collagen promoter templates, which were subsequently reconstituted in an in vitro transcription reaction. Binding of CBF to the nucleosomal wild-type topo IIalpha promoter containing four CBF-binding sites disrupted the regular nucleosomal structure not only in the promoter region containing the CBF-binding sites but also in the downstream region over the transcription start site. In contrast, no nucleosome disruption was observed in a mutant topo IIalpha promoter containing mutations in all CBF-binding sites. Interestingly, CBF also activated transcription from nucleosomal wild-type topo IIalpha promoter. In this experiment, a promoter containing one wild-type CBF-binding site was activated very weakly, whereas the promoter containing mutations in all sites was not activated by CBF. A truncated CBF that lacked the glutamine-rich domains did not activate transcription from nucleosomal wild-type topo IIalpha promoter but disrupted the nucleosomal structure about as much as did the binding of full-length CBF. Two nucleosomal mouse alpha2(1) collagen promoter DNAs, one containing a single and the other containing four CBF- binding sites, were also reconstituted in an in vitro transcription reaction. None of the nucleosomal collagen promoters was activated by CBF. However, both of these collagen promoters were activated by CBF when the transcription reaction was performed using naked DNA templates. Binding of CBF to the nucleosomal collagen promoter containing four binding sites disrupted the nucleosomal structure, similarly as observed in the topo IIalpha promoter. Altogether this study indicates that CBF-mediated nucleosomal disruption occurred independently of transcription activation. It also suggests that specific promoter structure may play a role in the CBF-mediated transcription activation of nucleosomal topo IIalpha promoter template.

3T3 Cells↗

Determinants of shear stress-stimulated endothelial nitric oxide production assessed in real-time by 4,5-diaminofluorescein fluorescence.

The extremely short biological half-life of endothelial-derived nitric oxide (NO) has impeded real-time measurements of NO synthesis. We used the membrane-permeable fluorescent probe 4,5-diaminofluorescein diacetate (DAF-2 DA) to study determinants of NO synthesis in bovine aortic endothelial cells (BAECs). A step increase in shear stress (SS) from 0.3 to 3.4 dyne/cm(2) triggered an increase in DAF-2 fluorescence starting 3.0 +/- 0.5 min after the flow rise and peaking at 44.7 +/- 7.2 min. This was abolished by intracellular Ca(2+) chelation, but was unaffected by blocking extracellular Ca(2+) influx or by inhibiting SS-related changes in intracellular pH. The increase in DAF-2 fluorescence occurred significantly earlier in BAECs transfected with either superoxide dismutase (SOD) or catalase (CAT), indicating concomitant reactive oxygen species (ROS) generation by SS and "competition" between ROS- and DAF-2-NO interactions. These data provide novel insights into several NO signaling determinants and reveal that DAF-2 can assess real-time SS-stimulated NO synthesis in endothelial cells. This should facilitate the analysis of NO-signaling pathways.

Animals↗

Self-consistent simulations of electroporation dynamics in biological cells subjected to ultrashort electrical pulses.

The temporal dynamics of electroporation of cells subjected to ultrashort voltage pulses are studied based on a coupled scheme involving the Laplace, Nernst-Plank, and Smoluchowski equations. A pore radius dependent energy barrier for ionic transport, accounts for cellular variations. It is shown that a finite time delay exists in pore formation, and leads to a transient overshoot of the transmembrane potential V(mem) beyond 1.0 V. Pore resealing is shown to consist of an initial fast process, a 10(-4) s delay, followed by a much slower closing at a time constant of about 10(-1) s. This establishes a time-window during which the pores are mostly open, and hence, the system is most vulnerable to destruction by a second electric pulse. The existence of such a time window for effective killing by a second pulse is amply supported by our experimental data for E. coli cells. The time constant for the longer process also matches experiments. The study suggests that controlled manipulation of the pore "open times" can be achieved through multiple, ultrashort pulses.

Biological Transport↗

Enhanced catharanthine production in catharanthus roseus cell cultures by combined elicitor treatment in shake flasks and bioreactors.

Chemical and fungal elicitors were added to Catharanthus roseus cell suspension cultures so as to improve the production of indole alkaloids. A synergistic effect on alkaloid accumulation was observed in C. roseus cell cultures when treated with some combined elicitors of fungal preparations and chemicals. Among them, the combination of tetramethyl amminium bromide and Aspergillum niger mycelial homogenate gave the highest ajmalicine yield (63 mg l(-1)) and an improved catharanthine accumulation (17 mg l(-1)). The combined elicitors of malate and sodium alginate resulted in the highest catharanthine yield (26 mg l(-1)) and a high ajmalicine accumulation (41 mg l(-1)) in the cell cultures. Based on the synergistic effect of malate and sodium alginate, a process with enhanced catharanthine production in Catharanthus roseus cell cultures was developed in shake flasks and a bioreactor. After 10 days of culture, 25 mg l(-1), 32 mg l(-1) and 22 mg l(-1) catharanthine yield were obtained in 500-ml flasks, 1000-ml flasks and in a 20-l airlift bioreactor, respectively. Upon malate-alginate combining treatments, peroxidase, catalase and superoxide dismutase activities decreased in elicited cells but phenylalanine ammonia lyase and lipoxygenase activities increased dramatically. That suggests a typical defense responses took place in the combined elicitors-treated cell cultures. Furthermore, the combined elicitors also caused a significant increase of malondialdehyde level in cell cultures, which suggests a serious lipid peroxidation occurred in the elicited cell cultures. Comparison of these results suggests that malate and alginate combining treatment also stimulates defense responses, such as lipid peroxidation, in all C. roseus culture processes and this may mediate the indole alkaloid production via jasmonate pathway.

Journal Article↗

Selection of fungal elicitors to increase indole alkaloid accumulation in catharanthus roseus suspension cell culture.

Various fungal elicitors derived from 12 fungi were tested to improve indole alkaloid production in Catharanthus roseus cell suspension cultures. Results show that different fungal mycelium homogenates stimulate different kinds of indole alkaloid (ajmalicine, serpentine and catharanthine) accumulation, which ranged from 2- to 5-fold higher than the control. Some fungal culture filtrates also efficiently elicited the biosynthesis of different indole alkaloids. The optimal elicitor addition and exposure time for the maximal alkaloid production were on day 7 after subculture and for 3 days of treatment but different fungal elicitors showed the different optimal treatment dosages. Additions of elicitor at the doses ranging from 5 mg/l to 30 mg/l of carbon hydrate equivalent resulted in varieous amounts and kinds of indole alkaloid accumulation. Exposed to a same fungal elicitor, several different cell lines generated the different responses regarding as growth rate, culture color and alkaloid production.

Journal Article↗

Intact LTP and fear memory but impaired spatial memory in mice lacking Ca(v)2.3 (alpha(IE)) channel.

To investigate the functional roles of the Ca(v)2.3 (alpha(1E)) channel in hippocampal CA1 pyramidal neurons, we studied in vitro synaptic properties and in vivo behaviors of the Ca(v)2.3 gene deficient mice. The Ca(v)2.3 channel mRNA was identified in the hippocampal formation of the wild-type mouse by in situ hybridization. The basic excitatory synaptic transmission and long-term potentiation by theta-burst stimulation were intact in CA1 region of Ca(v)2.3-/- mice. We performed two forms of behavioral tests to examine the hippocampus-dependent function, i.e., emotional and spatial learning tests. The Ca(v)2.3-/- mice were able to establish and maintain fear memories. Although general improvement in the performance of Morris water maze test was seen in Ca(v)2.3-/- mice, they displayed an obvious impairment in the probe test. These results suggest that the Ca(v)2.3 channel plays some role in formation of the accurate spatial memory but not of the fear memory.

Animals↗

A fast impingement detection algorithm for computer-aided orthopedic surgery.

OBJECTIVE: For simulation of computer-aided orthopedic interventions, the detection of impingement between parts of the patient's anatomy and/or implants is often of key importance. The impingement (collision) detection methods used in the existing literature seem to be unsuitable for two reasons. First, a polyhedral approximation of an anatomical model is not appropriate because medical images are quite irregular and are geometrically complex. Second, geometric and temporal coherences are not always available, because only the final results may be of interest. This article describes the development of a fast and accurate impingement detection algorithm for medical applications. MATERIALS AND METHODS: The presented algorithm takes implicit object models from reconstructions of anatomical CT data that represent complicated anatomical structures. To speed up the detection procedure, a lookup table and a linear transform are used so that searching for impingement between any two objects becomes a problem of calculating spatial indices and checking the lookup table. RESULTS: For any given transformation, the algorithm could perform impingement detection of two objects within 0.1 s on a 167 MHz Sun UltraSPARC1 workstation. Experimental results concerning accuracy, reliability and speed are given for a phantom and for a patient's data set. CONCLUSIONS: This algorithm provides a general-purpose impingement detection method in the sense that objects can be of any shape, and it can be extended to any number of objects in the scene.

Algorithms↗

The influence of enteral nutrition on gut barrier in the post-operative patients with damaged hepatic function.

The safety, rationality and the practicality of enteral nutrition (EN) support in the postoperative patients with damaged hepatic function were investigated and the protective effect of EN on the gut barrier and the clinical implication studied. Seventy-six adult patients whose hepatic function were in Child B or C grade were randomly assigned in EN group (30 cases), total parenteral nutrition (TPN) group (26 cases) and control group (CON, 20 cases). The patients received different nutritional support. The signs of nutritional condition and hepatic function were messured at 1 day before, 5 days and 10 days after the surgical operation respectively. The changes in the urine lactulose (L) and mannitol (M) contents and L/M ratio were observed by using pulsed electrochemical detection (HPLC-PED) to acquire the different effects among the different nutritional support performance. The results showed that the patients in the EN group and TPN group had no worse hepatic function damage after operation. The patients in the EN group reached the positive nitrogen balance earlier, had a less weight loss than in the TPN group with the difference being significant (P < 0.05). There was no obvious change in L/M ratio in the postoperative patients in the EN group (P > 0.05), but there was significant difference in L/M between TPN group and CON group (P < 0.05). It was concluded that EN was a rational, safe, effective and practical nutrition support method in the patients with damaged hepatic function patients after surgical operation and EN can effectively protect the structure and function of gut barrier from sever infection.

Child↗

Effects of stress factors, bioregulators, and synthetic precursors on indole alkaloid production in compact callus clusters cultures of Catharanthus roseus.

Compact callus cluster (CCC) cultures established from Catharanthus roseus consist of cohesive callus aggregates displaying certain levels of cellular or tissue differentiation. CCC cultures synthesize about two-fold more indole alkaloids than normal dispersed-cell cultures. Our studies here show that additions of KCl, mannitol, and a variety of synthetic precursors and bioregulators to the CCC cultures markedly improved indole alkaloid production and release of these alkaloids into the medium. Treatment with 250 mM mannitol and 4 g/l KCl yielded 42.3 mg l(-1) and 33.6 mg l(-1)of ajmalicine, respectively; these amounts were about four-fold higher than the control. Succinic acid, tryptamine, and tryptophan feedings also significantly increased ajmalicine (41.5 mg l(-1), 36.9 mg l(-1), and 31.8 mg l(-1), respectively) and catharanthine (21.1 mg l(-1), 17.2 mg l(-1), and 18 mg l(-1), respectively) production by the CCC cultures, while geraniol feeding inhibited biomass and alkaloid accumulation. We also found that tetramethyl ammonium bromide could significantly improve ajmalicine production (49.3 mg l(-1)) and catharanthine production (18.3 mg l(-1)) in C. roseus CCC cultures. The mechanisms responsible for these treatment effects are discussed herein.

Acyclic Monoterpenes↗

Transgenic rice plants expressing the ferredoxin-like protein (AP1) from sweet pepper show enhanced resistance to Xanthomonas oryzae pv. oryzae.

We used particle bombardment to cotransform mature seed-derived rice callus (Oryza sativa L., ssp. japonica, cv. Eyi 105) with plasmids containing the linked marker genes gusA and hpt, and the ap1 gene encoding an amphipathic protein previously shown to delay the hypersensitive response induced in non-host plants by the pathogen Pseudomonas syringae pv. syringae (Pss). Thirty-two independent lines of transgenic rice plants were regenerated, and 27 of these lines carried all three transgenes as shown by molecular analysis. A bacterial blight inoculation test was carried out on ten lines. In each case, plants carrying the ap1 gene showed enhanced resistance to Xanthomonas oryzae pv. oryzae (Xoo) race 6 at various levels. This suggests the ap1 gene could be a useful candidate for genetic engineering strategies in rice to provide bacterial blight resistance.

Journal Article↗

Field tracer-transport tests in unsaturated fractured tuff.

This paper presents the results of a field investigation in the unsaturated, fractured welded tuff within the Exploratory Studies Facility (ESF) at Yucca Mountain, NV. This investigation included a series of tests during which tracer-laced water was released into a high-permeability zone within a horizontal injection borehole. The tracer concentration was monitored in the seepage collected in an excavated slot about 1.6 m below the borehole. Results showed significant variability in the hydrologic response of fractures and the matrix. Analyses of the breakthrough curves suggest that flow and transport pathways are dynamic, rather than fixed, and related to liquid-release rates. Under high release rates, fractures acted as the predominant flow pathways, with limited fracture-matrix interaction. Under low release rates, fracture flow was comparatively less dominant, with a noticeable contribution from matrix flow. Observations of tracer concentrations rebounding in seepage water, following an interruption of flow, provided evidence of mass exchange between the fast-flowing fractures and slow- or non-flowing regions. The tests also showed the applicability of fluorinated benzoate tracers in situations where multiple tracers of similar physical properties are warranted.

Benzoic Acid↗

Study of the separation and determination of monosaccharides in soluble coffee by capillary zone electrophoresis with electrochemical detection.

A simple, fast and reliable method, based on capillary electrophoresis with electrochemical detection, for the separation and determination of six monosaccharides, namely glucose, galactose, arabinose, fructose, xylose and ribose, in soluble coffees was developed. A copper disk electrode was used as the working electrode. The optimum conditions for separation and detection were 50 mmol L-1 sodium hydroxide buffer (pH 12.7), separation voltage 5 kV and detection potential 0.65 V (vs. Ag/AgCl). The linear ranges were from 5.0 x 10(-3) to 0.5 mmol L-1 for all six sugars. All regression coefficients were > 0.99. The detection limits for all the sugars were 1.0 x 10(-3) mmol L-1. The RSD of the peak current was < 4.2% (n = 5). The proposed method was applied directly to the separation and determination of the six sugars without prior derivatization, and the assay results were satisfactory.

Journal Article↗

Evaluation of a combined calcium sodium alginate and bio-occlusive membrane dressing in the management of split-thickness skin graft donor sites.

The optimal treatment of the split-thickness skin graft (STSG) donor site remains an unresolved issue. This study was conducted to evaluate the combined use of calcium sodium alginate and a bio-occlusive membrane dressing in the management of STSG donor sites. This study was a prospective evaluation of all patients requiring an STSG over a 6-month period ending October 1998. There were 57 patients with a mean age of 61 years. All skin grafts were harvested with an electric dermatome from the anterior thigh and were 0.012 to 0.016 inches thick. Donor sites were dressed with calcium sodium alginate followed by a bio-occlusive dressing. Postoperatively, the skin graft donor site dressing was removed and replaced. The mean skin graft area was 114 cm2. The first dressing change occurred, on average, 3 days postoperatively. All dressings were taken down and the wounds reevaluated 7 days postoperatively. Fifty-two patients (91%) had achieved complete reepithelialization by this time. Five patients (9%) required an additional dressing. All wounds were healed completely by postoperative day 10. Donor site discomfort was minimal and limited to the time of dressing change. There were no wound-related complications. The average cost of dressing supplies was $48.00 per patient and $23.00 per dressing. This method of managing STSG donor sites allowed for unimpeded reepithelialization without wound complication. The bio-occlusive dressing eliminated the pain typically associated with fine mesh gauze dressings. The absorptive property of the calcium sodium alginate eliminated the problem of seroma formation and leakage seen routinely with the use of a bio-occlusive dressing alone. These results confirm that this technique is both efficacious and cost-effective.

Adult↗

[The electric pulse caused pore in the skin observed by fluorescence microscopy].

The objective of this study was to enunciate the difference in skin morphological changes between iontophroresis and electroporation for transdermal drug delivery (TDD). Fluorescence microscope was employed to observe the skin structure of human and snake in passive diffusion (control); iontophoresis was performed using direct current(0.5 mA/cm2) and electroporation was performed using intensive 380 V, pulse rate 4 ppm, pulse duration 5.5 ms, pulse number 100 and electric capacity 22 microF. Fluorescein was FITC. The results showed that for human skin in the passive, these were a few highlight fluorescent blots with scale of 15-30 microns and rough edge, but the edge of the blots became smooth and the scale did not change in the iontophoresis; when the scale of the blots was extended to 80-90 microns, the edge was smooth. For the snakes shin, the highlight blots were not sighted in the passive and iontophoresis, but they were found to be 25-30 microns in the electroporation. These data demonstrate that electric pulse can cause pore in the skin, thus creating a new route for drug permeation through skin.

Administration, Cutaneous↗