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Biomedical subjects

J Zhong

Publications and source records attributed to J Zhong.

At least 19 recordsLinked to original sources
PubMed2007

Human hydration level monitoring using embedded piezoresistive microcantilever sensors.

Embedded piezoresistive microcantilever (EPM) sensors were used to measure osmolality changes in both saliva mimic solutions and true human saliva. Osmolality changes in human saliva or urine may prove to be reliable, simple, and easy to measure markers for tracking human hydration levels. EPM sensors used in these experiments show good response to osmolality changes in both NaCl-based saliva mimic solutions and to human saliva. The addition of zero-point offset correction to EPM sensors allows for tracking of saliva osmolality changes with high accuracy. Also, the same EPM sensors exhibit a large enough range of osmolality response to make them potentially suitable for urine or blood serum osmolality monitoring.

Biosensing Techniques↗
PubMed2006

The activation of lytic replication of Epstein-Barr virus by baculovirus-mediated gene transduction.

A baculoviral mammalian-cell vector was constructed to express Rta, a protein of Epstein-Barr virus (EBV) responsible for the transition from latent infection to lytic replication. EBV lytic replication and cell-growth inhibition was observed in infected D98/HR1 cells. The baculovirus caused little cytotoxicity in the non-targeted HeLa cells, compared to an adenovirus vector. It is concluded that recombinant baculovirus might have the potential as a vector for the therapy of EBV-related cancer.

Baculoviridae↗
PubMed2006

Valproic acid adjunctive therapy for HIV-associated cognitive impairment: a first report.

In vitro and animal model data demonstrate that valproic acid (VPA) can ameliorate HIV-associated neurotoxicity. The authors conducted a pilot 10-week placebo-controlled study of VPA 250 mg twice daily in 22 HIV-infected individuals with (n = 16) and without (n = 6) cognitive impairment. VPA was safe and well tolerated, with trends toward improved neuropsychological performance and brain metabolism in the impaired subjects.

AIDS Dementia Complex↗
PubMed2006

Effects of number of diffusion gradient directions on derived diffusion tensor imaging indices in human brain.

BACKGROUND AND PURPOSE: The effects of a number of diffusion-encoding gradient directions (NDGD) on diffusion tensor imaging (DTI) indices have been studied previously with theoretic analysis and numeric simulations. In this study, we made in vivo measurements in the human brain to compare different clinical scan protocols and to evaluate their effects on the calculated DTI indices. METHODS: Fifteen healthy volunteers were scanned with a 1.5T MR scanner. Single-shot DTI images were acquired using 3 protocols different in NDGD and number of excitations (NEX) for each direction (NDGD/NEX = 6/10, 21/3, 31/2). Means and standard error of mean (SEM) were calculated and compared in 6 regions of interest (ROIs) for mean diffusivity (D), fractional anisotropy (FA), diffusion tensor eigenvalues (lambda(1), lambda(2), and lambda(3)), and correlation coefficients (r) of these indices among the 3 DTI protocols. RESULTS: At the ROI level, no significant differences were found for the mean and SEM of D and FA among protocols (P > .05). The 6-NDGD protocol, however, yielded higher values for lambda(1) and lambda(2) and lower values for lambda(3) in most ROIs (P < .05) compared with the other protocols. At the voxel level, the correlation between the protocols r(21-31) were higher than r(6-21) and r(6-31) in most ROIs. The correlation of FA among 3 protocols also increased with increasing anisotropy. CONCLUSION: For ROI analyses, different NDGDs lead to similar values of FA and D but different eigenvalues. However, different NDGDs at the voxel level provide varying values. The selection of the NDGD, therefore, should depend on the focus of different DTI applications.

Adult↗
PubMed2004

Parameters influencing augmentation of cerebral blood flow by cervical spinal cord stimulation.

BACKGROUND: Cervical spinal cord stimulation (SCS) has been shown to augment cerebral blood flow (CBF) and protect the brain from focal ischemia. However, the application of SCS in the treatment of cerebral ischemia requires a better understanding of the limits of the cerebrovascular effect and the optimal stimulation parameters. In the present study, we investigated the effects of various stimulation parameters on CBF augmentation, as well as the issue of tachyphylaxis of the CBF response. METHODS: SCS was performed in adult Sprague Dawley rats, and CBF was assessed using cortical laser Doppler flowmetry (LDF). In separate experimental series, stimulation amplitude, frequency, and pulse width were varied, and the effect on the LDF response was recorded. Finally, using the stimulation parameters found to elicit the strongest LDF response, we examined the effect of lengthening the period of SCS. FINDINGS: SCS elicited a robust increase in cortical LDF values as previously demonstrated. The magnitude of the response varied in a dose-dependent fashion with the stimulation amplitude. LDF values increased by more than 80% over baseline with an amplitude of 1.5 mA. The optimal pulse width and frequency of the stimulation were 0.25 ms and 50 Hz, respectively. Lengthening the stimulation period up to 20 minutes resulted in a persistent increase in cerebral LDF values during the entire stimulation period, although the magnitude of this effect diminished to approximately 50% over the baseline after 10 minutes. CONCLUSIONS: SCS elicits a robust augmentation in CBF, which lasts the entire stimulation duration. Stimulation parameters required for optimal cerebrovascular response are within normally used therapeutic ranges in the clinical settings. These results provide further evidence that SCS may provide a novel therapeutic strategy for the treatment of cerebral ischemia.

Animals↗
PubMed2003

A protein interaction map of Drosophila melanogaster.

Drosophila melanogaster is a proven model system for many aspects of human biology. Here we present a two-hybrid-based protein-interaction map of the fly proteome. A total of 10,623 predicted transcripts were isolated and screened against standard and normalized complementary DNA libraries to produce a draft map of 7048 proteins and 20,405 interactions. A computational method of rating two-hybrid interaction confidence was developed to refine this draft map to a higher confidence map of 4679 proteins and 4780 interactions. Statistical modeling of the network showed two levels of organization: a short-range organization, presumably corresponding to multiprotein complexes, and a more global organization, presumably corresponding to intercomplex connections. The network recapitulated known pathways, extended pathways, and uncovered previously unknown pathway components. This map serves as a starting point for a systems biology modeling of multicellular organisms, including humans.

Animals↗
PubMed2001

Independent control of cell survival by Raf-1 and Bcl-2 at the mitochondria.

Bcl-2 family proteins play a critical role in the regulation of cell survival by controlling the activation of the cell death executing caspase machinery. Recent work demonstrated that they also provide a link between growth factor signaling and cell survival control. Raf-1 has been identified initially as an essential component of the mitogenic Ras-Raf-MEK-ERK cascade. However, expression of oncogenic Raf-1 also efficiently suppresses apoptotic cell death. This process requires mitochondrial translocation of Raf-1 which can be achieved either by co-expression of the anti-apoptotic protein Bcl-2 or by fusion with the transmembrane domain of the yeast outer mitochondrial membrane protein Mas 70p. It is currently unclear how mitochondrial Raf-1 prevents apoptosis. One possible mechanism involves the phosphorylation of the pro-apoptotic protein Bad resulting in the restoration of Bcl-2 function. Alternatively, the role of Bcl-2 could be limited to the mitochondrial translocation of Raf-1 and survival signaling by Raf-1 is Bcl-2 independent. To test for the mutual requirement of Raf-1 and Bcl-2 in apoptosis suppression the individual proteins were singly tested for survival activity in a genetic background which precludes the expression of the other. The results obtained in these studies demonstrate that ablation of Raf-1 or Bcl-2 expression in fibroblast cells significantly increases the sensitivity towards doxorubicin induced cell death. Reversion of the mutant phenotype could be achieved in either case by introducing a functional bcl-2 gene or a mitochondria targeted version of oncogenic Raf-1, demonstrating that each protein by itself is sufficient to confer protection. Our data thus suggest the existence of two separate pathways of survival signaling at the mitochondria controlled either by Bcl-2 or by Raf-1.

Animals↗
PubMed2001

Acute cardiac allograft rejection in nitric oxide synthase-2(-/-) and nitric oxide synthase-2(+/+) mice: effects of cellular chimeras on myocardial inflammation and cardiomyocyte damage and apoptosis.

BACKGROUND: The contribution of nitric oxide synthase (NOS)-2 to myocardial inflammation and cardiomyocyte necrosis and apoptosis during allograft rejection was investigated through heterotopic cardiac transplantation in mice. METHODS AND RESULTS: In the first experiments, hearts from C3H donor mice were transplanted into NOS-2(-/-) and NOS-2(+/+) C57BL/6J.129J recipients. A second series of experiments included NOS-2(-/-) donor hearts transplanted into NOS-2(-/-) recipients and wild-type NOS-2(+/+) donor hearts transplanted into wild-type NOS-2(+/+) recipients. (All donors were C57BL/6J and recipients were C57BL/6J.129J.) In the first series of experiments, no significant differences were observed in allograft survival, rejection score, total number of apoptotic nuclei (TUNEL), total number of apoptotic cardiomyocytes, or graft NOS-2 mRNA and protein. Positive NOS-2 immunostaining occurred in endothelial cells and cardiomyocytes in the allografts; the inflammatory infiltrate was NOS-2 positive only when recipients were NOS-2(+/+). In the second series of experiments, cardiac allograft survival was significantly increased in the NOS-2(-/-) mice (26+/-13 versus 17+/-8 days, P<0.05), along with significant reductions in inflammatory infiltrate, rejection score, and total number of apoptotic nuclei (23.5+/-9.5 versus 56.4+/-15.3, P<0.01) and of apoptotic cardiomyocytes (2.9+/-1.6 versus 6.9+/-2.7, P<0.05). No NOS-2 or nitrotyrosine, a marker of peroxynitrite exposure, was detected in NOS-2(-/-) allografts transplanted into NOS-2(-/-) recipients. CONCLUSIONS: The data suggest that NO derived from NOS-2 contributes to the inflammatory response and to cardiomyocyte damage and apoptosis during acute cardiac allograft rejection.

Acute Disease↗
PubMed2001

Shape of the quantum diffusion front.

We show that quantum diffusion has well-defined front shape. After an initial transient, the wave packet front (tails) is described by a stretched exponential P(x,t) = A(t)exp(-absolute value of [x/w](gamma)), with 1 < gamma < infinity, where w(t) is the spreading width which scales as w(t) approximately t(beta), with 0 < beta < or = 1. The two exponents satisfy the universal relation gamma = 1/(1-beta). We demonstrate these results through numerical work on one-dimensional quasiperiodic systems and the three-dimensional Anderson model of disorder. We provide an analytical derivation of these relations by using the memory function formalism of quantum dynamics. Furthermore, we present an application to experimental results for the quantum kicked rotor.

Journal Article↗
PubMed2001

Functional inhibition of native volume-sensitive outwardly rectifying anion channels in muscle cells and Xenopus oocytes by anti-ClC-3 antibody.

Intracellular dialysis of NIH/3T3 cells with a commercially available anti-ClC-3 polyclonal antibody (Ab) for approximately 30 min completely inhibited expressed guinea-pig ClC-3 currents (IgpClC-3), while intracellular dialysis with antigen-preabsorbed anti-ClC-3 Ab failed to affect IgpClC-3. Anti-ClC-3 Ab was used as a selective probe to examine the relationship between endogenous ClC-3 expression and native volume-sensitive outwardly rectifying anion channels (VSOACs) in guinea-pig cardiac cells, canine pulmonary arterial smooth muscle cells (PASMCs) and Xenopus laevis oocytes. Intracellular dialysis or injection of anti-ClC-3 Ab abolished native VSOAC function in cardiac cells and PASMCs and significantly reduced VSOACs in oocytes. In contrast, native VSOAC function was unaltered by antigen-preabsorbed anti-ClC-3 Ab. It is suggested that endogenous ClC-3 represents a major molecular entity responsible for native VSOACs in cardiac and smooth muscle cells and Xenopus oocytes. Anti-ClC-3 Ab should be a useful experimental tool to directly test the relationship between endogenous ClC-3 expression and native VSOAC function, and help resolve existing controversies related to the regulation and physiological role of native VSOACs in a wide variety of different cells.

3T3 Cells↗
PubMed2001

beta-Adrenergic receptor stimulation of L-type Ca2+ channels in rabbit portal vein myocytes involves both alphas and betagamma G protein subunits.

1. Previous studies have shown that purified G protein alphas and betagamma subunits stimulate vascular L-type Ca2+ channels through protein kinase A and C (PKA and PKC), respectively. The present study tested whether activation of endogenous G proteins via beta-adrenergic receptor binding also stimulates vascular Ca2+ channels through both Galphas and Gbetagamma and the subsequent activation of PKA and PKC. 2. Peak Ba2+ current (IBa) in freshly isolated rabbit portal vein smooth muscle cells was significantly increased by bath application of 0.5 microM isoproterenol (isoprenaline; ISO) when measured using the whole-cell patch clamp method (53 +/- 3 % increase, n = 15). Stimulation of IBa by ISO was partially reversed by a PKA inhibitor, KT 5720, or a PKC inhibitor, calphostin C, and completely blocked when cells were pretreated with both KT 5720 and calphostin C. 3. Dialysis of cells with polyclonal antibody to Galphas significantly reduced but did not completely eliminate ISO-induced stimulation of IBa. The remaining stimulation was abolished by calphostin C. Dialysis of cells with a polyclonal antibody to Gbeta also significantly reduced ISO-induced stimulation and the remaining stimulation was abolished by KT 5720. Dialysis of cells with both antibodies completely prevented the stimulation of IBa by ISO. 4. ISO-induced stimulation of IBa was reversed by ICI-118,551, a specific beta2-adrenoceptor antagonist, but not by CGP 20712A, a specific beta1-adrenoceptor antagonist. In addition, the beta2-adrenoceptor agonist zinterol significantly increased peak IBa while the beta1-adrenoceptor agonist dobutamine and beta3-adrenoceptor agonist BRL 37344A had little effect on peak IBa. 5. These data suggest that beta-adrenergic receptor stimulation of vascular L-type Ca2+ channels involves both alphas and betagamma G-protein subunits, which exert their effects through PKA and PKC, respectively.

Adrenergic beta-Agonists↗
PubMed2001

Interleaved water and fat dual-echo spin echo imaging with intrinsic chemical-shift elimination.

A new technique was developed to simultaneously acquire water and fat dual-echo spin echo images in a single acquisition period. Chemical shifts between water and fat images are intrinsically eliminated, and the images are combined to form water-plus-fat image. In vivo water-only images show fat suppression superior to that of conventional spin echo images. This technique may be clinically useful for musculoskeletal imaging.

Adipose Tissue↗
PubMed2001

fMRI of auditory stimulation with intermolecular double-quantum coherences (iDQCs) at 1.5T.

An intermolecular double-quantum coherence (iDQC) imaging technique was used to study auditory activation in the human brain at 1.5T with a dual temporal lobe surface phased array coil and a quadrature head coil. Preliminary results demonstrate that it is feasible to obtain auditory activation maps using iDQC imaging at 1.5T, both in individual subjects using the surface coil array and with multisubject averaging of data using the head coil. The most robust activation map was obtained when a spin-echo (SE) acquisition was combined with an iDQC excitation. Since SE with conventional single quantum coherence (SQC) and similar parameters showed much reduced activation in spite of its higher signal-to-noise ratio (SNR), it was determined that activation resulting from the SE-iDQC acquisition almost entirely originates from iDQCs. In addition, the fact that the robust activation was obtained using signals at an evolution time more sensitive to changes in magnetic susceptibilities also suggests the sensitivity of iDQCs to the BOLD effect upon activation. iDQCs provide a novel MRI method which is potentially more sensitive to the BOLD effect traditionally measured with SQC. Magn Reson Med 45:356-364, 2001.

Acoustic Stimulation↗
PubMed2001

Primary and continuous midgut cell cultures from Pseudaletia unipuncta (Lepidoptera: Noctuidae).

Midgut epithelial cells were isolated from fifth-instar Pseudaletia unipuncta larvae by collagenase treatment of midgut tissue, and cultured in TNM-FH medium. Long-term continuous culture and maintenance of midgut cells were achieved with P. unipuncta armyworm intestinal cells. Several cells lines were obtained from these P. unipuncta primary cultures, and they have been subcultured and maintained for over 24 mo. The three major midgut cell types were present in the cultures, including stem (regenerative), columnar, and goblet cells. In vitro morphogenesis and differentiation of columnar and goblet cells from stem cells were observed. There appeared to be a cycle of cell death of goblet and columnar cells followed by their replacement from stem cells every 7-8 wk. After approximately six passages, the cell density in T-flasks appeared to be somewhat constant, reaching 10(3)-10(4) cells per milliliter of medium. The columnar cells are round to rectangular in shape and possess a brush border, while the goblet cells have a classic flask-like shape with a central cavity. Peritrophic membrane-like secretions were observed in all the culture flasks. Infection of these cells with multiply embedded nucleopolyhedrovirus was confirmed, and we conclude that these midgut cells can be used as an in vitro model system to study early events in baculovirus infection.

Animals↗
PubMed2001

Diffusion-weighted images of intracranial cyst-like lesions.

Magnetic resonance sequences may be designed to evaluate the diffusion movements of the protons (diffusion-weighted images, DWI). In these images, a bright signal identifies a region where the diffusion along a spatial axis is restricted. The contents of a cystic lesion frequently have the signal intensities of a generic homogeneous hyperproteinic fluid (hypointensity in T1-, hyperintensity in T2-weighted images). DWI may give further information about the microscopic organisation of these fluids: a hyperintense signal indicates the presence of a restricted diffusion, due to some kind of microscopic organisation, at the cellular or macromolecular level. This may provide additional information useful for clinical purposes. We obtained DWI in 24 consecutive patients with intracranial cystic lesions, (19 intra-axial: five abscesses, five gliomas, six metastases, two demyelinating lesions, one neurocysticercosis; five extraaxial: two arachnoid cysts, two epidermoid cysts, one cholesteatoma). We found a strongly hyperintense signal, indicating restricted diffusion, in brain abscesses, epidermoid cysts and cholesteatoma; all the remaining lesions were hypointense or mildly hyperintense. We found these data useful in critical diagnoses, such as in differentiating abscesses from tumours, and in identifying elusive tumours such as epidermoid cysts.

Adult↗
PubMed2001

Enhanced sensitivity to molecular diffusion with intermolecular double-quantum coherences: implications and potential applications.

Apparent molecular self-diffusion rates for (1)H intermolecular double-quantum coherences (iDQCs) were measured in solvents covering a wide range of intrinsic diffusion coefficients at 1.5, 9.4 and 14T, and water iDQC diffusion-weighted images were obtained at 1.5T in human brains and at 9.4T in rat brains. Conventional single quantum coherence (SQC) measurements were also made in the same samples. Experimental results indicate that iDQCs are approximately twice as sensitive to diffusion as SQC. A general theoretical expression was derived, and a model was proposed to explain the phenomenon. Potential applications in DWI and brain fMRI were also discussed.

Animals↗
PubMed2001

Diffusion-weighted echo-planar MR imaging of CNS involvement in systemic lupus erythematosus.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine the range of findings at diffusion-weighted magnetic resonance (MR) imaging in patients with systemic lupus erythematosus (SLE) and central nervous system involvement. MATERIALS AND METHODS: Diffusion-weighted MR images were reviewed in 20 patients with SLE and correlated with clinical symptoms and findings at computed tomography, conventional MR imaging, MR angiography, or conventional angiography. RESULTS: Diffusion-weighted MR imaging showed acute or subacute lesions in nine of 20 patients (45%). In the other 11, it showed no abnormal findings or chronic lesions. In four of the nine patients with lesions, diffusion-weighted imaging primarily showed hyperintense lesions with decreased apparent diffusion coefficient (ADC), which indicates acute or subacute infarcts. In four other patients, it primarily showed iso- or slightly hyperintense lesions with increased ADC, suggesting vasogenic edema. In two of these four patients, the findings were consistent with hypertensive encephalopathy. In the other two, small hyperintense foci on diffusion-weighted images with decreased ADC were seen within the vasogenic edema. These foci presumably represent microinfarcts associated with SLE vasculopathy. In the ninth patient, diffusion-weighted imaging showed a small linear hyperintense lesion with normal ADC in the left parietooccipital region. CONCLUSION: Diffusion-weighted imaging shows primarily two patterns of acute or subacute parenchymal lesions in patients with SLE: acute or subacute infarction and vasogenic edema with or without microinfarcts.

Adult↗