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Biomedical subjects

R Ma

Publications and source records attributed to R Ma.

At least 37 records · Page 2Linked to original sources
PubMed2001

Results of curative surgery and postoperative chemoradiation for rectal adenocarcinoma in British Columbia, 1985 to 1994.

OBJECTIVE: To assess factors affecting survival and pelvic recurrence after surgery and postoperative chemoradiation for rectal cancer in order to design improved management strategies. DESIGN: A chart review. SETTING: The British Columbia Cancer Agency. PATIENTS: One hundred and ninety-one consecutive patients who had rectal cancer treated between 1985 and 1994. Median follow-up was 39 months. INTERVENTIONS: Surgical excision of the cancer with intent to cure followed by chemoradiation. OUTCOME MEASURES: Multivariate analysis, to determine whether survival and pelvic recurrence were affected by tumour stage, nodal status, type of surgical procedure and presence of residual disease, and the quality of pathology reporting with respect to evaluation of radial resection margins and number of lymph nodes examined. RESULTS: Overall 5-year disease-specific survival was 60% and pelvic recurrence was 25%. Survival was affected by tumour stage (p < 0.02), nodal status (p < 0.001), type of surgical procedure (p < 0.04), presence of residual disease (p < 0.02) and pelvic recurrence (p < 0.0001). Pelvic recurrence was affected by the presence of residual disease (p < 0.001) but not by tumour stage (p < 0.14), nodal status (p < 0.37) or type of surgcial procedure (p < 0.20). Radial margins were evaluated in 44% of pathology reports and the median number of lymph nodes assessed was 6. CONCLUSIONS: Survival was most significantly affected by pelvic recurrence. Strategies to minimize pelvic recurrence including preoperative radiation and the principle of careful mesorectal excision to maximize the achievement of negative radial resection margins and negative residual disease are recommended. Also needed are standards for evaluating radial margins and lymph nodes to improved pathology reports.

Adenocarcinoma↗
PubMed2001

[Study on effect of nephropathy mixture on genetic expression of liver albumin in rats with adriamycin-induced nephrotic syndrome].

OBJECTIVE: To explore the effect of Nephropathy mixture on genetic expression of liver albunin in rats with adriamycin-induced nephrotic syndrome. METHODS: The rat model of adriamycin-induced nephrotic syndrome was established and the liver albumin mRNA expression level was observed with Northern hybridization and Dot-blot quantitative analysis. RESULTS: The liver albumin mRNA expression level in the Nephropathy Mixture treated group was significantly higher than that in the model group and the normal control group (P < 0.05). CONCLUSION: Nephropathy Mixture could up-regulate the liver albumin mRNA expression level and promote the synthesis of albumin in rats with adriamycin-induced nephrotic syndrome.

Albumins↗
PubMed2001

[Effect of fuzheng kangbai granule on immune function and survival time in minimal residual leukemia model in mice].

OBJECTIVE: To observe the effects of Fuzheng Kangbai Granule (FZKBG) on immune function and survival time in minimal residual leukemia (MRL) model mice and study its mechanism. METHODS: MRL model mice were established by hypodermic inoculation with L7212 cells following intraperitoneal injection of cytoxan (CTX) 25 mg/kg 3 days later, and divided into the control group and FZKBG group. The changes of T-lymphocyte subsets, including CD3+, CD4+ and CD8+, and the survival time in model mice were observed. RESULTS: Comparing with the control group, FZKBG could obviously increase both the percentage and absolute value of CD3+ and CD4+ lymphocytes and prolong the survival time of model mice, the prolongation rate being 29.6%-60.4%. CONCLUSION: FZKBG could markedly prolong the survival time of MRL mice, its mechanism might be through elevating the immune function and inhibiting the leukemic cells in model mice.

Adjuvants, Immunologic↗
PubMed2000

A new one-Pot method for the synthesis of alpha-siloxyamides from aldehydes or ketones and its application to the synthesis of (-)-bestatin

A new one-pot method for the synthesis of alpha-siloxyamides is described. The three substrates, H-C(CN)(2)O-SiMe(2)t-Bu, aldehydes or ketones, and primary or secondary amines, are simply mixed in one portion in acetonitrile or ether; the alpha-siloxyamides are obtained within short peroids in excellent yields in many cases. As a demonstration of our method, the synthesis of (-)-bestatin was carried out.

Journal Article↗
PubMed2000

Isotopic analysis of uranium in tree bark by ICP mass spectrometry: a strategy for assessment of airborne contamination

Isotopic analysis of uranium in tree bark by ICP mass spectrometry is proposed as a new measurement strategy for monitoring airborne contamination and for discrimination of nuclear and nonnuclear emission sources. A quadrupole-based ICP mass spectrometer equipped with a microconcentric nebulizer and membrane desolvator was used to provide high-sensitivity measurement. The limit of detection for uranium (238U) was 0.004 ng L(-1). Measurement precision (235U/238U) was between 0.2 and 0.5% RSD for isotopic SRMs (U005 and U015; concentration, 1 microg L(-1)) and ranged from 0.4 to 3.1% RSD for tree bark extracts (U concentration, 0.03-0.08 microg L(-1)). Bark samples collected from the Peak District National Park in Derbyshire (U.K.) exhibited a natural 235U/238U isotope ratio value (0.0072) whereas samples from Sellafield, West Cumbria (U.K.) showed depletion in 235U (235U/238U = 0.0053-0.0064).

Journal Article↗
PubMed2000

Platinum-group elements: quantification in collected exhaust fumes and studies of catalyst surfaces.

Automotive catalytic converters, in which Pt, Pd and Rh (platinum-group elements; PGEs) are the active components for eliminating several noxious components from exhaust fumes, have become the main source of environmental urban pollution by PGEs. This work reports on the catalyst morphology through changes in catalyst surface by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and laser-induced breakdown spectrometry (LIBS) from fresh to aged catalytic converters. The distribution of these elements in the fresh catalysts analysed (Pt-Pd-Rh gasoline catalyst) is not uniform and occurs mainly in a longitudinal direction. This heterogeneity seems to be greater for Pt and Pd. PGEs released by the catalysts, fresh and aged 30,000 km, were studied in parallel. Whole raw exhaust fumes from four catalysts of three different types were also examined. Two of these were gasoline catalysts (Pt-Pd Rh and Pd-Rh) and the other two were diesel catalysts (Pt). Samples were collected following the 91,441 EUDC driving cycle for light-duty vehicle testing. The results show that at 0 km the samples collected first have the highest content of particulate PGEs and although the general tendency is for the release to decrease with increasing number of samples taken, exceptions are frequent. At 30,000 km the released PGEs in gasoline and diesel catalysts decreased significantly. For fresh gasoline catalysts the mean of the total amount released was approximately 100, 250 and 50 ng km(-1) for Pt, Pd and Rh, respectively. In diesel catalysts the Pt release varied in the range 400-800 ng km-1. After ageing the catalysts up to 30,000 km, the gasoline catalysts released amounts of Pt between 6 and 8 ng km(-1), Pd between 12 and 16 ng km(-1) and Rh between 3 and 12 ng km(-1). In diesel catalysts the Pt release varied in the range 108-150 ng km(-1). The soluble portion of PGEs in the HNO3 collector solution represented less than 5% of the total amount for fresh catalysts. For 30,000 km the total amount of soluble PGEs released was similar or slightly higher than for 0 km.

Electrochemistry↗
PubMed2000

The aconitase function of iron regulatory protein 1. Genetic studies in yeast implicate its role in iron-mediated redox regulation.

Iron regulatory proteins (IRP) are sequence-specific RNA-binding proteins that mediate iron-responsive gene regulation in animals. IRP1 is also the cytosolic isoform of aconitase (c-aconitase). This latter activity could complement a mitochondrial aconitase mutation (aco1) in Saccharomyces cerevisiae to restore glutamate prototrophy. In yeast, the c-aconitase activity of IRP1 was responsive to iron availability in the growth medium. Although IRP1 expression rescued aco1 yeast from glutamate auxotrophy, cells remained growth-limited by glutamate, displaying a slow-growth phenotype on glutamate-free media. Second site mutations conferring enhanced cytosolic aconitase-dependent (ECA) growth were recovered. Relative c-aconitase activity was increased in extracts of strains harboring these mutations. One of the ECA mutations was found to be in the gene encoding cytosolic NADP(+)-dependent isocitrate dehydrogenase (IDP2). This mutation, an insertion of a Ty delta element into the 5' region of IDP2, markedly elevates expression of Idp2p in glucose media. Our results demonstrate the physiological significance of the aconitase activity of IRP1 and provide insight into the role of c-aconitase with respect to iron and cytoplasmic redox regulation.

Aconitate Hydratase↗
PubMed2000

Tolerance of the normal canine brain to epithermal neutron irradiation in the presence of p-boronophenylalanine.

Twelve normal dogs underwent brain irradiation in a mixed-radiation, mainly epithermal neutron field at the Brookhaven Medical Research Reactor following intravenous infusion of 950 mg of 10B-enriched BPA/kg as its fructose complex. The 5 x 10 cm irradiation aperture was centered over the left hemisphere. For a subgroup of dogs reported previously, we now present more detailed analyses including dose-volume relationships, longer follow-ups, MRIs, and histopathological observations. Peak doses (delivered to 1 cm3 of brain at the depth of maximum thermal neutron flux) ranged from 7.6 Gy (photon-equivalent dose: 11.8 Gy-Eq) to 11.6 Gy (17.5 Gy-Eq). The average dose to the brain ranged from 3.0 Gy (4.5 Gy-Eq) to 8.1 Gy (11.9 Gy-Eq) and to the left hemisphere, 6.6 Gy (10.1 Gy-Eq) to 10.0 Gy (15.0 Gy-Eq). Maximum tolerated 'threshold' doses were 6.7 Gy (9.8 Gy-Eq) to the whole brain and 8.2 Gy (12.3 Gy-Eq) to one hemisphere. The threshold peak brain dose was 9.5 Gy (14.3 Gy-Eq). At doses below threshold, some dogs developed subclinical MRI changes. Above threshold, all dogs developed dose-dependent MRI changes, neurological deficits, and focal brain necrosis.

Animals↗
PubMed2000

Cardiac sympathetic afferent reflexes in heart failure.

Heart failure is characterized by an elevation in sympathetic tone. The mechanisms responsible for this sympatho-excitation of heart failure are not completely understood. Several studies from this laboratory have compared differences in the cardiac "sympathetic afferent" reflex between sham dogs and dogs with pacing-induced heart failure. We found 1) that the cardiac sympathetic afferent reflex is augmented in heart failure, 2) tonic cardiac sympathetic afferent inputs play an important role in the elevated sympathetic tone in heart failure, 3) cardiac sympathetic afferents are sensitized in heart failure and 4) the central gain of the cardiac sympathetic afferent reflex in heart failure is sensitized and that this sensitization may be related to augmented central Ang II and blunted NO mechanisms. These studies integrate into the regulation of sympathetic outflow in heart failure which is likely to be mediated by a variety of peripheral inputs modulated by central substances. If the cardiac sympathetic afferent reflex is one of the excitatory reflexes which contribute to sympathetic activation in heart failure, a comprehensive understanding of neuro-humoral regulation of this reflex may result in more definitives and rational therapy targeted to the sympathetic nervous system in this disease state.

Afferent Pathways↗
PubMed2000

Calibration of the Brookhaven National Laboratory delayed gamma neutron activation facility to measure total body calcium.

Differences in body size and shape can cause large variances in the in vivo results of neutron activation analysis. To introduce corrections for body size for the delayed gamma neutron activation facility at Brookhaven National Laboratory, "reference man"-sized and "reference woman"-sized phantoms were constructed. Simulation results using the Monte Carlo Neutron and Photon Transport code also provided correction factors for people of different sizes. For individuals with a body mass index (BMI = weight (kg)/height (m)2) between 20 and 30, no correction was required. At BMIs greater than 30, the effects of neutron attenuation were significant and a correction factor of CF = -0.0192 x BMI + 1.5635 can be applied.

Body Composition↗
PubMed2000

A conducting plastic simulating brain tissue.

A new conducting plastic has been composed which accurately simulates the photon and neutron absorption properties of brain tissue. This tissue-equivalent (TE) plastic was formulated to match the hydrogen and nitrogen constituents recommended by ICRU Report #44 for brain tissue. Its development was initiated by the inability of muscle tissue-equivalent plastic to closely approximate brain tissue with respect to low-energy neutron interactions. This new plastic is particularly useful as an electrode in TE dosimetry devices for boron neutron capture therapy (BNCT), which utilizes low-energy neutrons for radiotherapy of the brain. Absorbed dose measurements in a clinical BNCT beam using a proportional counter constructed from this TE plastic show good agreement with Monte Carlo calculations.

Boron Neutron Capture Therapy↗
PubMed2000

Differences in skeletal and muscle mass with aging in black and white women.

Previous cross-sectional studies using delayed gamma neutron activation analysis and whole body counting suggested that the relationship of total body calcium (TBCa) to total body potassium (TBK) (muscle mass, body cell mass) remained constant with age. This led to the hypothesis that the muscle mass and skeletal mass compartments are integrated in their response to aging. It had also been hypothesized that loss of skeletal and muscle mass was similar between races. In the current study, delayed gamma neutron activation analysis and whole body counting were performed on 90 black and 143 white women 20-69 yr of age. Black women had higher TBCa and TBK values than white women, even when the data were adjusted for age, height, and weight. TBCa was correlated with height and TBK with weight. The estimated decline of skeletal mass (TBCa) from 20 to 70 yr was 18% in black women and 19% in white women. However, the lifetime decline of TBK was only 8% for black women, compared with 22% for white women. Black women may lose TBK more slowly than TBCa with aging, compared with white women. In particular, correlation of TBCa and age was similar for blacks and whites (r = -0.44 and r = -0.54, respectively). However, for TBK these correlations were r = -0.14 and r = -0.42. These data confirm a higher musculoskeletal mass in black women and suggest that the loss of muscle mass with age may be lower in black than in white women. These ethnic differences do not support the hypothesis of an integrated musculoskeletal system, so that these two components should be considered separately. A prospective study is needed to confirm these findings.

Adult↗
PubMed2000

Store-operated Ca(2+) channels in human glomerular mesangial cells.

Experiments were performed to identify the biophysical properties of store-operated Ca(2+) channels (SOC) in cultured human glomerular mesangial cells (MC). A fluorometric technique (fura 2) was utilized to monitor the change in intracellular calcium concentration ([Ca(2+)](i)) evoked by elevating external [Ca(2+)] from 10 nM to 1 mM (Delta[Ca(2+)]). Under control conditions, Delta[Ca(2+)] averaged 6 nM and was unaffected by elevating bath [K(+)]. After treatment with 1 microM thapsigargin to deplete the intracellular Ca(2+) store, the change in [Ca(2+)](i) (Delta[Ca(2+)](th)) averaged 147 +/- 16 nM. In thapsigargin-treated MC studied under depolarizing conditions (75 mM bath K(+)), Delta[Ca(2+)](th) was 45 +/- 7 nM. The Delta[Ca(2+)](th) response of thapsigargin-treated cells was inhibited by La(3+) (IC(50) = 335 nM) but was unaffected by 5 microM Cd(2+). In patch clamp studies, inward currents were observed in cell-attached patches with either 90 mM Ba(2+) or Ca(2+) in the pipette and 140 mM KCl in the bathing solution. The single-channel conductance was 2.1 pS with Ba(2+) and 0.7 pS with Ca(2+). The estimated selectivities were Ca(2+) > Ba(2+) >> K(+). These channels were sensitive to 2 microM La(3+), insensitive to 5 microM Cd(2+), and voltage independent, with an average channel activity (NP(o)) of 1.02 at command potential (-V(p)) ranging from 0 to -80 mV. In summary, MC exhibited an electrogenic Ca(2+) influx pathway that is suggestive of Ca(2+) entry through SOC, as well as a small-conductance divalent-selective channel displaying biophysical properties consistent with SOC. Based on estimates of whole cell Ca(2+) influx derived from our data, we conclude that SOC with low single-channel conductance must be highly abundant in MC to allow significant capacitative Ca(2+) entry in response to depletion of the intracellular store.

Biophysical Phenomena↗
PubMed2000

Regulation of Ca(2+)-activated K(+) channels by multifunctional Ca(2+)/calmodulin-dependent protein kinase.

Activation of mesangial cells by ANG II provokes release of intracellular Ca(2+) stores and subsequent Ca(2+) influx through voltage-gated channels, events that are reflected by a large transient increase in intracellular concentration [Ca(2+)](i) followed by a modest sustained elevation in [Ca(2+)](i). These ANG II-induced alterations in [Ca(2+)](i) elicit activation of large Ca(2+)-activated K(+) channels (BK(Ca)) in a negative-feedback manner. The mechanism of this BK(Ca) feedback response may involve the direct effect of intracellular Ca(2+) on the channel and/or channel activation by regulatory enzymes. The present study utilized patch-clamp and fura 2 fluorescence techniques to assess the involvement of multifunctional calcium calmodulin kinase II (CAMKII) in the BK(Ca) feedback response. In cell-attached patches, KN62 (specific inhibitor of CAMKII) either abolished or reduced to near zero the ANG II-induced BK(Ca) feedback response. This phenomenon did not reflect direct effects of KN62 on the BK(Ca) channel, because this agent alone did not significantly alter BK(Ca) channel activity in inside-out patches. KN62 also failed to alter either the transient peak or sustained plateau phases of the [Ca(2+)](i) response to ANG II. In inside-out patches (1 microM Ca(2+) in bath), calmodulin plus ATP activated BK(Ca) channels in the presence but not the absence of CAMKII. These observations are consistent with the postulate that CAMKII is involved in the BK(Ca) feedback response of mesangial cells, acting to potentiate the influence of increased [Ca(2+)](i) on the BK(Ca) channel or a closely associated regulator of the channel. An additional effect of CAMKII to activate a voltage-gated Ca(2+) channel cannot be ruled out by these experiments.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2000

Boron neutron capture therapy for malignant gliomas.

Boron neutron capture therapy (BNCT) represents a promising modality for a relatively selective radiation dose delivery to the tumour tissue. Boron-10 nuclei capture slow 'thermal' neutrons preferentially and, upon capture, promptly undergo 10B(n,alpha)7Li reaction. The ionization tracks of energetic and heavy lithium and helium ions resulting from this reaction are only about one cell diameter in length (approximately 14 microm). Because of their high linear energy transfer (LET) these ions have a high relative biological effectiveness (RBE) for controlling tumour growth. The key to effective BNCT of tumours, such as glioblastoma multiforme (GBM), is the preferential accumulation of boron-10 in the tumour, including the infiltrating GBM cells, as compared with that in the vital structures of the normal brain. Provided that a sufficiently high tumour boron-10 concentration (approximately 10(9) boron-10 atoms/cell) and an adequate thermal neutron fluence (approximately 10(12) neutrons/cm2) are achieved, it is the ratio of the boron-10 concentration in tumour cells to that in the normal brain cells that will largely determine the therapeutic gain of BNCT.

Boron Neutron Capture Therapy↗
PubMed2000

[Determination of trace elements Cu, Zn, Mg, Cr, Mn in serum of people with hepatoma, cirrhosis, hepatapstema disease].

Using AAS method, we detected serum Zn, Cu, Mn, Cr, Mg in the people with hepatoma, cirrhosis and hepatophyma disease. The results showed that the level of serum Cu of people with hepatoma and cirrhosis were significantly higher than those in the healthy control and with hepatophyma disease (P < 0.01). The levels of serum Mn, Cr of those with hepatoma and cirrhosis disease were significantly lower than those with hepatophyma and the healthy control (P < 0.01). It is concluded that determination of Cu, Mn, Cr may be one of the methods to diagnose hepatoma and cirrhosis disease.

Adolescent↗
PubMed1999

Serotonin receptor subtypes that depolarize guinea pig inferior mesenteric ganglion neurons.

Our previous studies indicated that serotonin (5-HT) depolarized a majority of guinea pig inferior mesenteric ganglion (IMG) neurons and may be another transmitter for the noncholinergic late slow excitatory postsynaptic potential (ls-EPSP) in the IMG. However, the subtypes of 5-HT receptor mediating these responses have not yet been identified. Using intracellular recording, we examined the effect of 5-HT receptor antagonists with specificity to various 5-HT receptor subtypes on the 5-HT-mediated depolarization and ls-EPSP in IMG neurons in vitro. Cyproheptadine, a 5-HT(1/2) receptor antagonist, reversibly inhibited the slow, but not the fast, depolarization and ls-EPSP in the 5-HT-sensitive neurons. Both mianserin and spiperone, 5-HT(2) and 5-HT(1A) receptor antagonists, did not significantly alter either the fast or slow depolarizing responses or the ls-EPSP. The 5-HT(3) receptor antagonist MDL 72222 (Bemesetron) completely inhibited the fast depolarization with little diminution of the slow depolarization and ls-EPSP. Superfusion of putative 5-HT(1P) receptor antagonist, BRL 24924 (Renzapride), reversibly attenuated both the depolarization and ls-EPSP. However, 5-HT-insensitive neurons with ls-EPSP were found to be insensitive to both cyproheptadine and BRL 24924. In most 5-HT-sensitive neurons, the 5-HT(3) receptor agonist, 2-methyl-5-HT, and the selective 5-HT(1P) agonist, MCPP or 5-OHIP, evoked a fast and a slow depolarization in 55.6 and 71.4% of the neurons, respectively, without a significant effect on the membrane potential in 85.7 and 100% of the 5-HT-insensitive neurons. In 5-HT-sensitive neurons, MDL 72222 reversibly abolished the fast depolarization induced by 2-methyl-5-HT; BRL 24924 significantly inhibited the slow depolarization induced by MCPP or 5-OHIP, but not by SP. Prolonged superfusion of 5-HT-sensitive neurons with MCPP abolished the evoked ls-EPSP without inhibition of action potential. These results suggest that the fast and slow depolarizations in these neurons are mediated by 5-HT(3) and 5-HT(1P) receptor subtypes, respectively. The latter may also mediate the ls-EPSP in 5-HT-sensitive neurons.

Animals↗