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Biomedical subjects

D Chu

Publications and source records attributed to D Chu.

At least 19 recordsLinked to original sources
PubMed2003

Antibacterial and antifungal activity of Indonesian ethnomedical plants.

Methylene chloride and methanol extracts of 20 Indonesian plants with ethnomedical uses have been assessed for in vitro antibacterial and antifungal properties by disk diffusion method. Extracts of the six plants: Terminalia catappa, Swietenia mahagoni Jacq., Phyllanthus acuminatus, Ipomoea spp., Tylophora asthmatica and Hyptis brevipes demonstrated high activity in this bioassay system. These findings should stimulate the search for novel, natural product such as new antibacterial and antifungal agents.

Anti-Bacterial Agents↗
PubMed2001

Thermodynamics of denaturation of hisactophilin, a beta-trefoil protein.

Hisactophilin is a histidine-rich pH-dependent actin-binding protein from Dictyostelium discoideum. The structure of hisactophilin is typical of the beta-trefoil fold, a common structure adopted by diverse proteins with unrelated primary sequences and functions. The thermodynamics of denaturation of hisactophilin have been measured using fluorescence- and CD-monitored equilibrium urea denaturation curves, pH-denaturation, and thermal denaturation curves, as well as differential scanning calorimetry. Urea denaturation is reversible from pH 5.7 to pH 9.7; however, thermal denaturation is highly reversible only below pH approximately 6.2. Reversible denaturation by urea and heat is well fit using a two-state transition between the native and the denatured states. Urea denaturation curves are best fit using a quadratic dependence of the Gibbs free energy of unfolding upon urea concentration. Hisactophilin has moderate, roughly constant stability from pH 7.7 to pH 9.7; however, below pH 7.7, stability decreases markedly, most likely due to protonation of histidine residues. Enthalpic effects of histidine ionization upon unfolding also appear to be involved in the occurrence of cold unfolding of hisactophilin under relatively mild solution conditions. The stability data for hisactophilin are compared with data on hisactophilin function, and with data for two other beta-trefoil proteins, human interleukin-1beta, and basic fibroblast growth factor.

Animals↗
PubMed2001

Cloning and characterization of LUN, a novel ring finger protein that is highly expressed in lung and specifically binds to a palindromic sequence.

We isolated cDNAs encoding a novel RING finger protein (LUN), the mRNAs of which were expressed at high levels in the lung. In situ hybridization revealed that LUN mRNAs were expressed in the alveolar epithelium of the lung. The LUN gene locus was assigned to chromosome 9p21, which contains candidate tumor suppressor genes associated with loss of heterozygosity in more than 86% of small cell lung cancers. We clarified that LUN is localized to the nucleus and reveals Zn(2+)-dependent DNA binding activity. The region from amino acids 51 to 374 of LUN is responsible for DNA binding. Furthermore, we identified a novel palindromic binding consensus (5'-TCCCAGCACTTTGGGA-3') for the LUN binding. Interestingly, this LUN binding palindromic sequence is found in the upstream transcriptional regulatory region of the E-cadherin gene and two intervening regions of the talin gene. Our results suggested that LUN might be an important trans-acting transcriptional regulator for lung cancer-associated genes including E-cadherin and talin genes.

Amino Acid Sequence↗
PubMed2001

An fMRI study of the effect of amphetamine on brain activity.

Functional magnetic resonance imaging was used to evaluate the effects of oral d-amphetamine on brain activation elicited by auditory and simple motor tasks in ten normal right-handed subjects. We measured the percent signal change and number of voxels activated by a tone discrimination task and a right hand finger-tapping task after 20 mg of d-amphetamine and after placebo. Compared to placebo, amphetamine significantly increased the number of activated voxels in the left and right primary auditory cortices during the tone discrimination task and increased the number of activated voxels in the ipsilateral primary sensorimotor cortex and right middle frontal area during the motor task. Although highly specific vascular effects of drug cannot be ruled out as an explanation, these results could also mean that amphetamine increases the neuronal activity associated with each of these two tasks.

Adolescent↗
PubMed2001

Some aspects of sound extinction by zooplankton.

To address the importance of sound extinction (or the shadowing effect) in the presence of a densely aggregated zooplankton layer, acoustic scattering by weakly scattering fluid objects is studied theoretically. An analytical expression for the extinction cross section is obtained based on the forward scattering theorem and the analytical formula for the forward scattering amplitude is derived from the Modal Based-Deformed Cylinder Model (MB-DCM). The validity of the MB-DCM solution for the forward scattering amplitude and its sensitivity to geometrical and physical parameters is studied. Comparison with the PC-DWBA (Phase-Compensated-Distorted Wave Born Approximation) shows a reasonable agreement between the two models. The extinction cross section is shown to be proportional to (ka)2 and the induced attenuation is predicted for various species of zooplankton over a wide frequency range. It is shown that, under certain realistic conditions, such as the presence of a swarm of aggregated krill, sound extinction by zooplankton could influence the acoustic measurements significantly, as much as an 85% reduction in acoustic intensity for Euphausia superba with n = 5000 ind./m3 over a range of 50 m.

Journal Article↗
PubMed2001

The impact on clients of a community-based infant mortality reduction program: the National Healthy Start Program Survey of Postpartum Women.

OBJECTIVES: This study assessed the effect of the national Healthy Start Program on its clients. METHODS: We used a cross-sectional survey of a sample from Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) rosters of women less than 6 months postpartum who were residents of Healthy Start Program areas. RESULTS: Healthy Start clients revealed higher sociodemographic risk, but not behavioral risk, for adverse pregnancy outcome than other area residents. They did not differ from other residents in receipt of services except for a greater likelihood of receiving case management, using birth control at the time of the interview, and rating their prenatal care more highly. CONCLUSIONS: The Healthy Start Program succeeded in enrolling women at high risk. It had little effect on the immediately concluded pregnancy, but it might influence future outcomes.

Adolescent↗
PubMed2001

[A matched case-control study on direct economic costs of four kinds of nosocomial infections].

OBJECTIVE: To evaluate the direct economic costs of four major kinds of nosocomial infections such as nosocomial pneumonia, urinary tract infection, deep surgical wound infection and intracranial infection. METHODS: A matched case-control study was conducted among 95 pairs of hospitalized patients to investigate the direct economic costs of nosocomial infections. RESULTS: The average medical cost for patients in the case group was 38 741 RMB Yuan, 20 365 Yuan more than that in the control group patients (P < 0.0001). The largest part of extra costs was found in drug expenses, taking up 62.07%, while other extra costs such as non-drug therapies, blood transmission and laboratory examinations, accounted for 10.32%, 7.40% and 5.72% respectively. Extra economic burden caused by nosocomial infections varied in different degrees with different departments, with the heaviest found in the department of tumourology and hematology at an average extra cost of 34 944 Yuan. The average extra charges in case group caused by nosocomial pneumonia, urinary tract infection, deep surgical wound infection and intracranial infection were 31 940 Yuan, 7 436 Yuan, 17 332 Yuan and 17 349 Yuan respectively. The average length of hospital stay was 50.57 days in case group and 25.22 days in control group, showing a 25.53 extra days (P < 0.0001) of hospitalization due to nosocomial infections. CONCLUSION: Nosocomial infections had significantly added to the economic burden of managing the underlying diseases, led to prolonged hospitalization of the patients and lowered the turnover rate of hospital bed. There is a need to call for better infection control program, which would bring tremendous social and economic profits.

Case-Control Studies↗
PubMed2000

The mechanical state of intracranial tissues in elderly subjects studied by imaging CSF and brain pulsations.

The biomechanical properties of intracranial tissues influence the mechanical coupling of brain and CSF oscillations to the driving vascular pulsations. Dynamic phase contrast MRI was used to measure the transfer functions that characterize these couplings in normal elderly subjects and patients with Alzheimer's disease. The transfer functions of both groups were significantly different from the previously reported transfer functions of normal young subjects. The data show that vascular pulsations tend to cause greater spinal cord movements and smaller CSF oscillations in the older subjects than in the younger ones. These results are likely to be due to age-related changes in the mechanical state of intracranial tissues.

Adult↗
PubMed2000

Reorganization of the hand somatosensory cortex following perinatal unilateral brain injury.

Functional magnetic resonance imaging was used to map the hand somatosensory cortices of nine hemiparetic young adult patients with perinatal unilateral brain injury in the sensorimotor area and five normal subjects. Stimulation of the paretic hand by periodic manual squeezing produced activation in the contralateral hemisphere of three patients and in the ipsilateral hemisphere of three other patients. Paretic hand stimulation produced no activation in either hemisphere of the remaining three patients. Therefore, one-third of the patients demonstrated functional "plasticity" of the brain in the form of inter-hemispheric relocation of the hand somatosensory function. The volume and pattern of activation for both hands was altered for those patients that showed evidence of cortical reorganization to the opposite hemisphere. This differs from the hand motor system, which exhibited inter-hemispheric reorganization in a higher proportion of a related group of hemiparetic subjects.

Adolescent↗
PubMed2000

Acoustic scattering by benthic and planktonic shelled animals.

Acoustic backscattering measurements and associated scattering modeling were recently conducted on a type of benthic shelled animal that has a spiral form of shell (Littorina littorea). Benthic and planktonic shelled animals with this shape occur on the seafloor and in the water column, respectively, and can be a significant source of acoustic scattering in the ocean. Modeling of the scattering properties allows reverberation predictions to be made for sonar performance predictions as well as for detection and classification of animals for biological and ecological applications. The studies involved measurements over the frequency range 24 kHz to 1 MHz and all angles of orientation in as small as 1 degree increments. This substantial data set is quite revealing of the physics of the acoustic scattering by these complex shelled bodies and served as a basis for the modeling. Specifically, the resonance structure of the scattering was strongly dependent upon angle of orientation and could be traced to various types of rays (e.g., subsonic Lamb waves and rays entering the opercular opening). The data are analyzed in both the frequency and time domain (compressed pulse processing) so that dominant scattering mechanisms could be identified. Given the complexity of the animal body (irregular elastic shell with discontinuities), approximate scattering models are used with only the dominant scattering properties retained. Two models are applied to the data, both approximating the body as a deformed sphere: (1) an averaged form of the exact modal-series-based solution for the spherical shell, which is used to estimate the backscattering by a deformed shell averaged over all angles of orientation, and produces reasonably accurate predictions over all k1a(esr) (k1 is the acoustic wave number of the surrounding water and a(esr) is the equivalent spherical radius of the body), and (2) a ray-based formula which is used to estimate the scattering at fixed angle of orientation, but only for high k1a(esr). The ray-based model is an extension of a model recently developed for the shelled zooplankton Limacina retroversa that has a shape similar to that of the Littorina littorea but swims through the water [Stanton et al., J. Acoust. Soc. Am. 103, 236-253 (1998b)]. Applications of remote detection and classification of the seafloor and water column in the presence of shelled animals are discussed.

Acoustics↗
PubMed2000

[Clinical study on Shenning Mixture in treating IgA nephropathy].

OBJECTIVE: To study the clinical therapeutic effect of Shenning Mixture (SNM) in treating IgA nephropathy. METHODS: Patients were treated separately with SNM or prednisone by randomized grouping. The criteria, including clinical symptoms, signs, hematuria, albuminuria and immune globulin were observed. RESULTS: The total effective rate and the complete remission rate in the SNM group were 97.1% and 45.7% respectively, while in the control group, they were 37.1% and 8.6% respectively. Comparison of the two groups showed that the therapeutic effect in the former was better than that in the latter significantly, P < 0.01. The hematuria and albuminuria extenuated and serum IgA lowered more significantly in the SNM group than those in the control group (P < 0.05, P < 0.01). CONCLUSION: SNM has obvious therapeutic effect on the hematuria and albuminuria in treating IgA nephropathy.

Adolescent↗
PubMed1999

Second primary tumors in patients with cutaneous malignant melanoma.

BACKGROUND: Several studies report coexistent or subsequent primary tumors (SPT) among patients with malignant melanoma (MM), with the rate of incidence ranging from 1.5-20% depending on the sample size and the length and completeness of follow-up. METHODS: The authors followed a cohort of patients with cutaneous MM who were diagnosed and treated at the City of Hope National Medical Center to determine the incidence rate of SPT and associated risk factors. Five hundred eighty-five patients (median age at diagnosis, 43 years) were diagnosed and treated for MM between 1952 and 1996 and followed for a median of 6.5 years (range, 0.0-37.0 years). Ninety-six percent of the cohort had been treated by surgery alone. RESULTS: Thirty-seven patients developed an SPT. These included skin cancers (n = 23), carcinoma of the urinary bladder, breast carcinoma, and lymphoma (n = 3 each), lung carcinoma and prostate carcinoma (n = 2 each), and cervical carcinoma (n = 1). The estimated cumulative rate of incidence after MM was 5% at 5 years for any SPT, 3.7% for a second skin cancer, and 1.1% for a second solid tumor. Overall, the current cohort of MM patients was found to be at an increased risk for developing a subsequent melanoma (standardized incidence ratio [SIR], 4.5; 95% confidence interval [95% CI], 1.2-10.0) when compared with the general population. Older men (age > 50 years at the time of diagnosis of MM) were at an increased risk of developing subsequent bladder carcinoma (SIR, 6.4; 95% CI, 1.2-15.7). CONCLUSIONS: Patients diagnosed with MM are at an increased risk of developing subsequent MM and bladder carcinoma. Issues to be addressed in future studies include interactions between environmental exposures and genetic susceptibility and the identification of individuals at increased risk.

Adolescent↗
PubMed1999

Integrating the actin and vimentin cytoskeletons. adhesion-dependent formation of fimbrin-vimentin complexes in macrophages.

Cells adhere to the substratum through specialized structures that are linked to the actin cytoskeleton. Recent studies report that adhesion also involves the intermediate filament (IF) and microtubule cytoskeletons, although their mechanisms of interaction are unknown. Here we report evidence for a novel adhesion-dependent interaction between components of the actin and IF cytoskeletons. In biochemical fractionation experiments, fimbrin and vimentin coprecipitate from detergent extracts of macrophages using vimentin- or fimbrin-specific antisera. Fluorescence microscopy confirms the biochemical association. Both proteins colocalized to podosomes in the earliest stages of cell adhesion and spreading. The complex is also found in filopodia and retraction fibers. After detergent extraction, fimbrin and vimentin staining of podosomes, filopodia, and retraction fibers are lost, confirming that the complex is localized to these structures. A 1:4 stoichiometry of fimbrin binding to vimentin and a low percentage (1%) of the extracted vimentin suggest that fimbrin interacts with a vimentin subunit. A fimbrin-binding site was identified in the NH(2)-terminal domain of vimentin and the vimentin binding site at residues 143-188 in the CH1 domain of fimbrin. Based on these observations, we propose that a fimbrin-vimentin complex may be involved in directing the assembly of the vimentin cytoskeleton at cell adhesion sites.

Actins↗
PubMed1999

MR imaging of flow with locally high spatial resolution.

Locally focused magnetic resonance imaging (LF MRI) allows imaging with variable spatial resolution within the field of view (FOV). Because LF MRI uses a priori information to provide locally high resolution in regions with rapid spatial variations in intensity (e.g., blood/tissue interface), it allows accurate reproduction of intense sharp edges in the specimen without blurring and truncation artifacts. This study employs LF MRI for 3D imaging of stationary and pulsatile flow. In the implemented version of LF MRI analytically defined basis functions are used to determine image intensity in regions depicted with low or high resolution. It is demonstrated that LF MRI of flow allows a significant (i.e. 3-4 times) reduction in scan time as compared to conventional FT MRI. It is also shown that LF images of pulsatile flow have a decreased appearance of ghosting artifacts as compared to the images reconstructed by using the conventional method.

Carotid Arteries↗
PubMed1999

Rhizosphere bacteria enhance selenium accumulation and volatilization by indian mustard

Indian mustard (Brassica juncea L.) accumulates high tissue Se concentrations and volatilizes Se in relatively nontoxic forms, such as dimethylselenide. This study showed that the presence of bacteria in the rhizosphere of Indian mustard was necessary to achieve the best rates of plant Se accumulation and volatilization of selenate. Experiments with the antibiotic ampicillin showed that bacteria facilitated 35% of plant Se volatilization and 70% of plant tissue accumulation. These results were confirmed by inoculating axenic plants with rhizosphere bacteria. Compared with axenic controls, plants inoculated with rhizosphere bacteria had 5-fold higher Se concentrations in roots (the site of volatilization) and 4-fold higher rates of Se volatilization. Plants with bacteria contained a heat-labile compound in their root exudate; when this compound was added to the rhizosphere of axenic plants, Se accumulation in plant tissues increased. Plants with bacteria had an increased root surface area compared with axenic plants; the increased area was unlikely to have caused their increased tissue Se accumulation because they did not accumulate more Se when supplied with selenite or selenomethionine. Rhizosphere bacteria also possibly increased plant Se volatilization because they enabled plants to overcome a rate-limiting step in the Se volatilization pathway, i.e. Se accumulation in plant tissues.

Journal Article↗
PubMed1998

Assessment of the biomechanical state of intracranial tissues by dynamic MRI of cerebrospinal fluid pulsations: a phantom study.

We used a cranial phantom to investigate how intracranial mechanical factors [brain compliance and the resistance to the flow of cerebrospinal fluid (CSF)] affect the way in which CSF pulsations are driven by pulsatile transcranial blood flow. Dynamic phase-contrast magnetic resonance imaging (MRI) was used to measure the transfer function between vascular pulsations and pulsatile response of the CSF below the foramen magnum of the phantom. We found that the coupling between the high frequency components of cervical CSF flow and transcranial blood flow was decreased when the phantom was modified to simulate increased brain compliance and increased resistance to CSF flow.

Biomechanical Phenomena↗
PubMed1998

Sound scattering by several zooplankton groups. II. Scattering models.

Mathematical scattering models are derived and compared with data from zooplankton from several gross anatomical groups--fluidlike, elastic shelled, and gas bearing. The models are based upon the acoustically inferred boundary conditions determined from laboratory backscattering data presented in part I of this series [Stanton et al., J. Acoust. Soc. Am. 103, 225-235 (1998)]. The models use a combination of ray theory, modal-series solution, and distorted wave Born approximation (DWBA). The formulations, which are inherently approximate, are designed to include only the dominant scattering mechanisms as determined from the experiments. The models for the fluidlike animals (euphausiids in this case) ranged from the simplest case involving two rays, which could qualitatively describe the structure of target strength versus frequency for single pings, to the most complex case involving a rough inhomogeneous asymmetrically tapered bent cylinder using the DWBA-based formulation which could predict echo levels over all angles of incidence (including the difficult region of end-on incidence). The model for the elastic shelled body (gastropods in this case) involved development of an analytical model which takes into account irregularities and discontinuities of the shell. The model for gas-bearing animals (siphonophores) is a hybrid model which is composed of the summation of the exact solution to the gas sphere and the approximate DWBA-based formulation for arbitrarily shaped fluidlike bodies. There is also a simplified ray-based model for the siphonophore. The models are applied to data involving single pings, ping-to-ping variability, and echoes averaged over many pings. There is reasonable qualitative agreement between the predictions and single ping data, and reasonable quantitative agreement between the predictions and variability and averages of echo data.

Acoustics↗