Search PubMed⌕ Search

Biomedical subjects

R Ma

Publications and source records attributed to R Ma.

At least 55 records · Page 3Linked to original sources
PubMed1999

Bone mineral measurements: a comparison of delayed gamma neutron activation, dual-energy X-ray absorptiometry and direct chemical analysis.

A system in vitro consisting of a femur from a cadaver and soft-tissue equivalent material was used to test the agreement between several techniques for measuring bone mineral. Calcium values measured by delayed gamma neutron activation (DGNA) and bone mineral content (BMC) by Lunar, Hologic and Norland dual-energy X-ray absorptiometers (DXA) were compared with calcium and ash content determined by direct chemical analysis. To assess the effect of soft-tissue thickness on measurements of bone mineral, we had three phantom configurations ranging from 15.0 to 26.0 cm in thickness, achieved by using soft-tissue equivalent overlays. Chemical analysis of the femur gave calcium and ash content values of 61.83 g +/- 0.51 g and 154.120 +/- 0.004 g, respectively. Calcium measured by DGNA did not differ from the ashed amount of calcium at any of the phantom configurations. The BMC measured by DXA was significantly higher, by 3-5%, than the amount determined by chemical analysis for the Lunar densitometer and significantly lower, by 3-6%, for the Norland densitometer (p<0.001-0.024), but only 1% lower (not significant) for the Hologic densitometer. DXA instruments showed a decreasing trend in BMC as the thickness increased from 20.5 to 26.0 cm (p<0.05). However, within the entire thickness range (15.0-26.0 cm), the overall influence of thickness on BMC by DXA was very small. These findings offer insight into the differences in these currently available methods for bone mineral measurement and challenge the comparability of different methods.

Absorptiometry, Photon↗
PubMed1999

Total-body calcium estimated by delayed gamma neutron activation analysis and dual-energy X-ray absorptiometry.

Total body calcium (TBCa) in 270 black and white women age 21-79 years was measured concurrently by delayed gamma neutron activation analysis (DGNA) and dual-energy X-ray absorptiometry (DXA). The mean value for TBCa calculated from DXA was 933 g compared with 730 g for DGNA. By regression, TBCa(DXA(g)) = 1.35 x TBCa(DGNA(g)) -54 (r = 0. 90, r(2) = 81.4%, SEE = 66.9 g). This remarkable difference of 203 g suggests that one or both these methods is not accurate. Adjustment of the regression of DXA versus DGNA for body mass index or trunk thickness explained 8.5-10% of the variability between methods. The unadjusted slope for the DXA values regressed against the DGNA values was 1.35, indicating significant discordance between the methods. There is greater agreement between the two DGNA facilities (Brookhaven National Laboratory and Baylor College of Medicine) and between the various DXA instruments. Either DGNA underestimates TBCa or DXA overestimates total-body bone mineral content. Resolution of these disparate results may possibly be achieved by concurrent measurement of whole human cadavers of different sizes with chemical determination of the calcium content of the ash. In the interim, cross-calibration equations between DGNA and standardized values for DXA for total-body bone mineral content may be used, which will permit reporting of consistent values for TBCa from the two technologies.

Absorptiometry, Photon↗
PubMed1999

Phylogenetic relationships of Cheju horses to other horse breeds as determined by mtDNA D-loop sequence polymorphism.

Historical records suggest that horses inhabiting the island of Cheju in Korea are descendants of Mongolian horses introduced in 1276. Other studies, however, suggest that horses may have been present on the island prior to the Mongolian introduction. To determine the origin of the Cheju horses we used a phylogenetic analysis of sequences of the mitochondrial DNA (mtDNA) D-loop region, including tRNA Pro and parts of tRNA thr and tRNA Phe sequences (1102-bp excluding the tandem repeat region). Maximum parsimony and neighbor-joining trees were constructed using sequences determined for seven Cheju, four Mongolian, one Przewalskii and two Chinese Yunnan horses, and published sequences for one Swedish and three Thoroughbred horses. Donkey mtDNA was used as an outgroup. We found that the mtDNA D-loop sequence varies considerably within Mongolian, Cheju and Thoroughbred horse breeds, and that Cheju horses clustered with Mongolian horses as well as with horses from other distantly related breeds. On the basis of these findings we propose that horses on Cheju Island are of mixed origin in their maternal lineage, and that horses may have existed and been traded on the island before the Mongolian introduction.

Animals↗
PubMed1999

The comet assay in clinical practice.

The comet assay is a single-cell gel electrophoresis technique that measures DNA damage in individual cells. Since radiation produces 3-4 times more DNA damage in well-oxygenated cells compared with hypoxic cells, this assay can quantify the fraction of radiation-resistant hypoxic cells found in many solid tumours. This paper summarizes our results with 73 accessible metastatic tumours irradiated with palliative intent. Hypoxic fractions ranged from 0.0 to 0.67 with a mean of 0.15; 62% of these advanced tumours showed a hypoxic fraction > 0.05. Comparisons between two sequential aspirates in 33 tumours gave a slope of 0.92 (r2 = 0.88), suggesting that a single aspirate is generally representative of the tumour. A limitation, however, is that the hypoxic fraction could not be measured in clinical samples given a conventional dose of 2 Gy.

Animals↗
PubMed1999

Standardization and conversion of marker polymorphism measures.

Large scale gene mapping efforts in domestic animals have generated and mapped a large number of genetic markers that are useful for mapping quantitative trait and disease loci and for DNA diagnostic purposes such as parentage testing. Marker polymorphism is an important criterion for selecting genetic markers in planning experiment for mapping quantitative trait loci or for DNA diagnostic purposes. Current formulations of marker polymorphism measures are functions of marker allele frequencies. In this study, two measures of marker polymorphism that are available from gene mapping studies and do not require allele frequencies were proposed and analyzed: the observed polymorphic information content (PIC) and the observed family information content (FIC). The observed FIC was more stable than the observed PIC because the observed FIC is unaffected by the variation in the frequency of heterozygous parents. However, both FIC and PIC are dependent on the gene mapping design. The effective number of alleles is recommended as a tool to standardize marker polymorphism measures so that polymorphism of different markers can be compared on an equal basis, and to obtain a new polymorphism measure (such an exclusion probability) from an existing measure (such as FIC). The usage of the effective number of alleles to standardize FIC, PIC and exclusion probabilities is illustrated using genetic markers in a published linkage map.

Animals↗
PubMed1999

Total body-calcium measurements: comparison of two delayed-gamma neutron activation facilities.

This study compares two independently calibrated delayed-gamma neutron activation (DGNA) facilities, one at the Brookhaven National Laboratory (BNL), Upton, New York, and the other at the Children's Nutrition Research Center (CNRC), Houston, Texas that measure total body calcium (TBCa). A set of BNL phantoms was sent to CNRC for neutron activation analysis, and a set of CNRC phantoms was measured at BNL. Both facilities showed high precision (< 2%), and the results were in good agreement, within 5%.

Calcium↗
PubMed1999

Boron neutron capture therapy for glioblastoma multiforme: interim results from the phase I/II dose-escalation studies

OBJECTIVE: The primary objective of these Phase I/II dose-escalation studies is to evaluate the safety of boronophenylalanine (BPA)-fructose-mediated boron neutron capture therapy (BNCT) for patients with glioblastoma multiforme (GBM). A secondary purpose is to assess the palliation of GBM by BNCT, if possible. METHODS: Thirty-eight patients with GBM have been treated. Subtotal or gross total resection of GBM was performed for 38 patients (median age, 56 yr) before BNCT. BPA-fructose (250 or 290 mg BPA/kg body weight) was infused intravenously, in 2 hours, approximately 3 to 5 weeks after surgery. Neutron irradiation was begun between 34 and 82 minutes after the end of the BPA infusion and lasted 38 to 65 minutes. RESULTS: Toxicity related to BPA-fructose was not observed. The maximal radiation dose to normal brain varied from 8.9 to 14.8 Gy-Eq. The volume-weighted average radiation dose to normal brain tissues ranged from 1.9 to 6.0 Gy-Eq. No BNCT-related Grade 3 or 4 toxicity was observed, although milder toxicities were seen. Twenty-five of 37 assessable patients are dead, all as a result of progressive GBM. No radiation-induced damage to normal brain tissue was observed in postmortem examinations of seven brains. The minimal tumor volume doses ranged from 18 to 55 Gy-Eq. The median time to tumor progression and the median survival time from diagnosis (from Kaplan-Meier curves) were 31.6 weeks and 13.0 months, respectively. CONCLUSION: The BNCT procedure used has been safe for all patients treated to date. Our limited clinical evaluation suggests that the palliation offered by a single session of BNCT is comparable to that provided by fractionated photon therapy. Additional studies with further escalation of radiation doses are in progress.

Journal Article↗
PubMed1999

Reduced NO enhances the central gain of cardiac sympathetic afferent reflex in dogs with heart failure.

The aim of the present study was to test the hypothesis that a decrease in central nitric oxide (NO) is involved in the enhancement of the central gain of the cardiac "sympathetic afferent" reflex (CSAR) in dogs with congestive heart failure (CHF). Thirteen dogs with pacing-induced CHF and sixteen sham dogs were anesthetized with alpha-chloralose and were baroreceptor denervated and vagotomized. The CSAR was evoked by stimulation of the left ventral ansa. A lateral cerebroventricular cannula was inserted to deliver sodium nitroprusside (SNP) and NG-nitro-L-arginine methyl ester (L-NAME). Arterial pressure, heart rate, and renal sympathetic nerve activity (RSNA) were recorded at baseline and during elicitation of the CSAR. We found that 1) the responses of RSNA to stimulation were augmented in dogs with CHF, 2) SNP depressed the increase in RSNA induced by the CSAR in CHF dogs but had no effect in sham dogs, and 3) L-NAME potentiated the CSAR-induced increase in RSNA in sham dogs but not in dogs with CHF. We conclude that reduced central NO is involved in the enhanced central gain of the CSAR in CHF dogs.

Afferent Pathways↗
PubMed1999

Chronic central infusion of ANG II potentiates cardiac sympathetic afferent reflex in dogs.

The aims of this study were to determine whether ANG II is involved in the central integration of the cardiac sympathetic afferent reflex (CSAR), and if this central effect of ANG II is mediated by the AT(1) receptor. Experiments were undertaken in dogs that were anesthetized with alpha-chloralose, sinoaortic denervated, and vagotomized. The renal sympathetic nerve activity (RSNA) responses to varying frequency and voltage stimulation of cardiac sympathetic afferent nerves were used to evaluate the central sensitivity of the CSAR. In two groups of dogs, two doses (50 and 100 ng/min icv) of ANG II were acutely infused. In a third group of dogs, ANG II was chronically infused for 3 days (100 ng/min, 1 microliter/h icv). We found that acute infusion into the cerebroventricle of two doses of ANG II did not affect the central sensitivity of the CSAR or the baseline hemodynamics, but the baseline RSNA increased significantly during the infusion of the higher dose of ANG II. However, chronic intracerebroventricular infusion of ANG II enhanced the central sensitivity of the CSAR significantly. In addition, chronic intracerebrovetricular infusion of ANG II elicited a significant increase in water intake and in arterial pressure from the first and second day of infusion, respectively. In the group that received chronic intracerebroventricular infusion of ANG II, the administration of an AT(1)-receptor antagonist losartan (0.125 mg/kg icv) abolished ANG II-induced augmentation of the CSAR. These results suggest that chronic elevation of central ANG II can sensitize the CSAR via central AT(1) receptors.

Angiotensin II↗
PubMed1999

Cardiac sympathetic afferent sensitivity is enhanced in heart failure.

A previous study from this laboratory has shown that cardiac sympathetic afferent stimulation by epicardial application of bradykinin (BK) and capsaicin was significantly enhanced in the dog with experimental heart failure (HF). The present study determined whether activity from cardiac sympathetic chemosensitive afferent endings is enhanced in HF. Rapid ventricular pacing was induced in six dogs. Five sham dogs served as controls. At the time of the acute experiment, the dogs were anesthetized with pentobarbital sodium (30 mg/kg iv). A thoracotomy was performed in the second intercostal space, and single afferent fiber discharge from the left cardiac sympathetic nerve was recorded. Baseline cardiac sympathetic afferent discharge rate (spikes/s) and its responses to intra-atrial injection of BK were compared between sham and HF groups. Baseline cardiac sympathetic afferent discharge rate in the HF group was significantly elevated compared with the sham group (4.3 +/- 0.5 vs. 2.2 +/- 0.6 spikes/s, P < 0.05). In addition, cardiac sympathetic afferent responses to left intra-atrial injection of bradykinin (2 and 5 microgram/kg) and capsaicin (5 and 10 microgram/kg) were also significantly augmented. The sensitized cardiac sympathetic afferent responses to BK (2 and 5 microgram/kg, left intra-atrial injection) in the HF group were significantly reduced by the cyclooxygenase inhibitor indomethacin (5 mg/kg iv). The sensitized cardiac sympathetic afferent response to capsaicin (5 and 10 microgram/kg, left intra-atrial injection) in the HF group was preserved. It is suggested that the cardiac sympathetic chemosensitive afferent sensitivity is significantly enhanced in dogs with HF even though the baseline cardiac sympathetic afferent discharge is elevated.

Afferent Pathways↗
PubMed1999

The effects of boron neutron capture irradiation on oral mucosa: evaluation using a rat tongue model.

The ventral surface of the tongue of male Fisher 344 rats was used to evaluate the response of oral mucosa to boron neutron capture irradiation. Three hours after i.p. injection of 700 mg/kg of the boron delivery agent p-boronophenylalanine (BPA), the boron concentrations in blood and tongue mucosal epithelium were approximately 21 and 23 microgram (10)B/g, respectively. The doses required to produce a 50% incidence of ulceration with X rays, the Brookhaven Medical Research Reactor thermal neutron beam alone, or the thermal neutron beam in the presence of BPA were 13.4 +/- 0.2, 4. 2 +/- 0.1, and 3.0 +/- 0.1 Gy, respectively. Ulceration of the tongue was evident by 6 to 7 days after irradiation, irrespective of the irradiation modality; healing was related to dose and was relatively rapid (</=19 days). Compared to 100 kVp X rays, the relative biological effectiveness factors were 3.2 for the thermal neutron beam and 4.9 for the products of the boron neutron capture reaction, (10)B(n,alpha)(7)Li. Oral mucosa is highly sensitive to BPA-mediated BNC irradiation and could be a dose-limiting normal tissue in BNCT of brain tumors, or if BPA-based BNCT is applied to the treatment of head and neck tumors.

Animals↗
PubMed1999

[Clinical and experimental study on the treatment of myelodysplastic syndromes with fuzheng quxie tablet].

OBJECTIVE: To study the mechanism of Fuzheng Quxie Tablet (FZQXT) in treating myelodysplastic syndromes (MDS). METHODS: Thirty-three cases of MDS were treated with FZQXT, changes of peripheral blood cells, morphology of bone marrow smear, bone marrow pathology and immunology were monitored before and after treatment. The effects of FZQXT on hematopoietic stem cells of mice were also observed. RESULTS: The remission rate and total effective rate were 24.24% and 72.72% respectively. FZQXT had obvious effect in promoting the proliferation of colony forming unit-erythrocytes (CFU-E). CONCLUSION: The beneficial effect of FZQXT in treating refractory anemia might be reached through promoting the proliferation of erythrocytic hematopoietic stem cells.

Adolescent↗
PubMed1999

[Clinical study on treatment of chronic idiopathic thrombocytopenic purpura by Decoction of Nourishing Blood and Eliminating Purpura].

OBJECTIVE: To observe the clinical effect of treatment of chronic idiopathic thrombocytopenic purpura (CITP) by Decoction of Nourishing Blood and Eliminating Purpura (DNBEP), and study the possible mechanism. METHODS: Effect of 55 patients of CITP in treatment group treated by DNBEP and 22 patients in the control group treated by Antaisu were observed and compared. Their immunologic indexes were determined for exploring the mechanism. RESULTS: The markedly effective, improved and total effective rate of the treatment group were 32.7%, 20.0% and 87.3%, while those of the control group were 4.5%, 9.1% and 45.5% respectively, the difference between the two groups was significant (P < 0.001). The effect of the treatment group was better than the control group in platelet count restoring, hemorrhagic symptoms improving and effect initiating, P < 0.01. Immunologic test showed that the humoral and cell immune function as well as platelet function were abnormal in CITP patients. These functions were improved after treatment, and the effectiveness of the treatment group was significantly superior to that of the control group. CONCLUSIONS: DNBEP is reliable in treating CITP clinically. Its mechanism might be better due to its selective suppression of humoral immune function, bi-directional regulation of cell immune function and recovery of platelet function.

Adolescent↗
PubMed1999

[Determination of acemetacin and indometacin in human serum by high performance liquid chromatography].

A method of HPLC for the quantitative determination of acemetacin and indometacin in human serum is described. After being extracted with diethyl ether, acemetacin and indometacin were analyzed by reversed-phase HPLC(Spherisorb-C8) and UV-detector(254 nm), with tolbutamide as internal standard. The mobile phase was a mixture of V(acetate buffer solution, pH 4.6):V(methyl alcohol):V(acetonitrile) = 55:5:40 and at a rate of 1.0 mL/min. Over the mass concentration range of 12.5 micrograms/L-1.6 mg/L, both the calibration curves were linear, r = 0.9996, n = 8. The average recoveries of acemetacin and indometacin were 77.2% and 86.7% respectively. The within-day and between-day RSD of acemetacin and indometacin were less than 5% and 10% respectively.

Adult↗
PubMed1998

Relationship of body water compartments to age, race, and fat-free mass.

Water compartments were studied in 72 black and 128 white women, aged 20 to 70 years. Total body water (TBW) was measured by tritiated water dilution, and extracellular water (ECW) was measured by using delayed gamma neutron activation for the determination of total body chloride. Intracellular water (ICW) was assessed as the difference between TBW and ECW. Fat-free mass (FFM) was estimated by the measurement of total body potassium (TBK) and total body fat (TBF) by measurement of total body carbon (TBC). Total body protein was calculated from total body nitrogen (TBN). TBW was found to decline with age and to also be significantly influenced by body size. The extracellular water space was 41.5% of TBW. The decline of TBW with age is due primarily to a decline in ICW. The hydration of the FFM increased with age for the overall population because of a decline in TBK and TBN and an increase in ECW. Body composition models that have assumed constancy of hydration should be adjusted not only for gender but for age and body size.

Adipose Tissue↗
PubMed1998

British urological surgery practice: 2. Renal, bladder and testis cancer.

OBJECTIVE: To investigate the management of urological malignancies in the United Kingdom. METHODS: A postal survey of consultant urologists and general surgeons with an interest in urology was conducted to examine current clinical practice in urological malignancies. RESULTS: Completed questionnaires were received from 273 consultant surgeons who saw an estimated total of 13241 new patients with renal, bladder or testis cancer per year; 82% had access to on-site oncology services and in general there was a consensus in the answers given. Most respondents advised active treatment of an asymptomatic primary renal cancer in the presence of metastases and a significant proportion of patients with metastases were not prescribed immunotherapy nor were offered a multidisciplinary approach for their condition. Forty-six per cent of patients with testis cancer received no advice to store sperm before chemotherapy and there were varied opinions as to the need for surgical resection of residual masses after completion of chemotherapy. CONCLUSION: This survey showed minor variations in the management of renal, bladder and testis tumours in the UK. Consensus management guidelines for urological malignancies and a change in the working relationships between urologists and oncologists is required, to improve the outcome of patients with urological malignancy.

Carcinoma, Renal Cell↗
PubMed1998

Improvement of the prompt-gamma neutron activation facility at Brookhaven National Laboratory.

The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its shielding, repositioning the system's two NaI(Tl) detectors, and improving the neutron and gamma shielding of these detectors. The new source collimator has a graphite reflector around the 238PuBe neutron source to enhance the low-energy region of the neutron spectrum incident on the patient. The gamma detectors have been relocated from positions close to the upward-emerging collimated neutron beam to positions close to and at the sides of the patient. These modifications substantially reduced spurious counts resulting from the capture of small-angle scattered neutrons in the NaI detectors. The pile-up background under the 10.8 MeV 14N(n, gamma)15N spectral peak has been reduced so that the nitrogen peak-to-background ratio has been increased by a factor of 2.8. The resulting reduction in the coefficient of variation of the total body nitrogen measurements from 3% to 2.2% has improved the statistical significance of the results possible for any given number of patient measurements. The new system also has a more uniform composite sensitivity.

Gamma Rays↗