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Biomedical subjects

M Anbar

Publications and source records attributed to M Anbar.

At least 19 recordsLinked to original sources
PubMed1991

Comparing assessments of students' knowledge by computerized open-ended and multiple-choice tests.

At the State University of New York at Buffalo School of Medicine and Biomedical Sciences, interactive computerized tests that accept unrestricted natural-language input were used to assess the knowledge of medical students in a sophomore course on clinical biophysics in 1989. The course covered the physical bases, scopes, and limitations of the most widely used diagnostic, therapeutic, and prosthetic technologies. The test was composed of both open-ended sequential questions and multiple-choice questions on the same material. The scores for the two testing modes were correlated, paying special attention to answers that demonstrated a flagrant lack of knowledge, corroborated by subsequent answers. The correlation between the qualities of the answers for the two testing modalities was found to be significantly positive for the lower half of the class of students and negative for the upper half, suggesting that the two modes of testing measure different aspects of competence. The implications of the findings to medical education and accreditation are discussed.

Clinical Competence↗
PubMed1989

Effect of physical activity on lumbar spine and femoral neck bone densities.

The lumbar spine and femoral neck densities of 123 and 141 normal adult women (50 +/- 10 years), respectively, measured by dual photon absorptiometry, were correlated with the number of hours of walking per day associated with their regular daily activities. This measure of exercise, obtained by detailed questionnaire and interview, was analyzed because it is regular, seasonally stable, and quantifiable. Both lumbar spine and femoral neck densities were significantly correlated with walking, with 0.8% and 1.9% increases in average bone density per hour of daily walking, respectively. This increase in density is substantial, considering that the age-related rate of bone loss in the same population is 0.7% and 0.5% per year of lumbar spine and femoral neck, respectively. This means that, on the average, a woman walking one additional hour per day has a femoral neck bone density comparable to that of a women 4 years younger who does not pursue this additional activity. This physical activity-associated enhancement of bone density may be critical at old age when osteoporosis is clinically manifested.

Adult↗
PubMed1989

Normal and abnormal features of the lumbar spine observed in dual photon absorptiometry scans.

Dual photon absorptiometry (DPA) is an extensively used technique for measuring the density of the lumbar spine. The presence of vertebral and extra-vertebral pathologies can lead to increased scatter of data and artifactual bias when constructing diagnostic reference value curves. The bone density of patients with such abnormalities cannot be compared with those of normals because it will appear artificially high. Furthermore, little effort has been made to identify and evaluate spinal abnormalities using the pictograms produced in this method. We have analyzed 60 DPA scans for morphologic changes, using x-rays for comparison, and have found practically complete concurrence between these two radiologic methods on features, though only the former is capable of accurately quantifying bone density. Examples of DPA presentation of anatomical morphology are shown to aid the user in interpreting DPA findings.

Adult↗
PubMed1988

Associations of parity, breast-feeding, and birth control pills with lumbar spine and femoral neck bone densities.

The relationships between parity, breast-feeding, and the use of birth control pills and the bone densities of the lumbar spine and the femoral neck, measured by dual-photon densitometry, were studied in normal women. Femoral neck density was found to decrease by 1.1% per live-birth, whereas lumbar spine density showed no significant association with parity. Breast-feeding was found to increase lumbar spine density by 1.5% per breast-fed child, whereas femoral neck density was not significantly correlated. No significant relationships between the use of birth control pills and the bone densities were found.

Adult↗
PubMed1988

Effects of natural menopause, hysterectomy, and oophorectomy on lumbar spine and femoral neck bone densities.

Lumbar spine and femoral neck bone densities of women, aged 35-65, were measured by dual photon bone densitometry. After exclusion of women with spinal and other abnormalities, this study included 233 subjects: 60 menstruant, 91 who underwent natural menopause (56 more than 2 years post-menopause), 45 bilaterally oophorectomized, and 37 hysterectomized without bilateral oophorectomy. No significant differences were found between the age-normalized average bone densities of the menstruant, early postmenopausal, and late postmenopausal women; nor was there a difference between the rates of their bone loss. The bone densities of the hysterectomized women were significantly lower than those of the normals. The bone densities of the oophorectomized women were significantly lower than those of the hysterectomized patients. The rates of bone loss, however, were comparable in all groups studied. The use of estrogen without progestin was associated with significantly higher lumbar spine densities in the oophorectomized women, but showed no significant effect in any of the other groups.

Adult↗
PubMed1985

Rate of non-adherent cell loss from long-term cultures of murine bone marrow: effect of medium conditioned by the adherent cell population.

The rate of random spontaneous cell loss from the non-adherent cell population of long-term cultures of murine bone marrow was determined. The measured rate of non-adherent cell loss is affected by previous conditioning of the medium in which the non-adherent cells are suspended. Specifically, the measured rate of non-adherent cell loss is significantly slowed when the non-adherent cells are suspended in medium conditioned in long-term haematopoietic cultures instead of fresh medium. It appears that a subset of the adherent cell population is the source of the factor or factors within the medium which result in this slower measured rate of non-adherent cell loss. This effect may be due to the stimulation to division of haematopoietic progenitor cells, offsetting the lysis of other non-adherent cells.

Animals↗
PubMed1979

Bioavailability of imipramine tablets relative to a stable isotope-labeled internal standard: increasing the power of bioavailability tests.

A new methodology for comparative bioavailability testing is described in which each drug formulation is compared with a stable isotope-labeled variant of the drug that is consumed orally in solution at the same time the tested formulation is ingested. The methodology is used to determine the comparative bioavailabilities of two commercially available brands of imipramine hydrochloride. The power of the new methodology to detect differences between drug formulations, when, in fact, such differences exist, is shown to be superior to that of conventional bioavailability tests.

Adolescent↗
PubMed1979

Localized fluoride release from fluorine-carrying polyphosphonates.

Fluoride release from fluorine-carrying copolymers of vinylphosphonate induced by calcium apatite and tooth enamel has been investigated. Fluoride ions were determined potentiometrically in the study of calcium hydroxyapatite, and Auger spectroscopy was used to study the fluoride release to enamel. The adsorbed copolymer of vinylphosphonic acid and vinylphosphonyl thiofluoride was shown to release fluoride to calcium hydroxyapatite and to enamel. The oxygen analog has shown a similar behavior with calcium hydroxyapatite, but not with tooth enamel. The results suggest a potential application of such copolymers as caries preventive agents which combine the effects of polyphosphonates and of fluoride ions.

Adsorption↗
PubMed1978

Determination of imipramine in plasma by high pressure liquid chromatography and field ionization mass spectrometry: increased sensitivity in comparison with gas chromatography mass spectrometry.

A quantitative method is reported for the determination of imipramine in plasma samples in the low nanogram and subnanogram range. The sensitivity and precision of the technique, which involves high pressure liquid chromatography and direct probe field ionization mass spectrometry, are approximately an order of magnitude greater than are offered by gas chromatography mass spectrometry with selected ion monitoring using deuterated or other types of internal standards. [2H6]Imipramine, labeled in the ethylene bridge and in the aromatic rings, serves as the isotopic diluent. The method has been used for the determination of the comparative bioavailabilities of two different commercial preparations of imipramine. In these tests, subjects ingested a 25 mg tablet of one or the other drug preparation together with a solution containing an equivalent amount of imipramine deuterated in the ethylene bridge ([2H2]imipramine). The latter served as an internal check for intrasubject variability in absorption of the imipramine tablets. Typical results from one of the subjects are presented.

Adolescent↗
PubMed1978

The measurement of cell turnover rates using stable isotope-labelled thymidine: experiments on the small intestine and on a transplantable lymphatic tumour of the mouse.

Multilabelled, non-radioactive thymidine and tritiated thymidine were incorporated simultaneously into the DNA of a rapidly-growing, transplantable mouse lymphoma and the DNA of mouse small intestine by a single intraperitoneal injection of both labelled nucleosides. Mice were killed at selected times during the next 7 days, and the specific activities of the tissues and extracted DNA and the 132/126 mass ratio of thymine isolated from the DNA were determined by scintillation counting and by field ionization mass spectrometry respectively. The rates of decrease of the concentrations of tritiated and stable isotope-labelled thymine in the DNA of the tumour or of the intestine were essentially identical. These results indicate the feasibility of using thymidine multilabelled with stable isotopes for measurement of cell turnover rates in conjunction with cancer therapy.

Animals↗
PubMed1977

Isotopic fractionation in thin-layer chromatography.

The thin-layer chromatography of imipramine on silica gel plates was studied in fifteen solvent systems. The mobility of imipramine labeled with deuterium in the methyl groups of the dimethylaminopropyl side chain differs markedly from that of unlabeled imipramine. Partial or complete separations between unlabeled and deuterated imipramine were observed in all basic and neutral solvent systems investigated, but not in weakly acidic solvents. Isotopic fractionations of imipramine were also found on alumina thin-layer plates, but were not detected in cellulose chromatography. In all thin-layer isotopic separations, the unlabeled compound migrates more rapidly than the deuterated molecule. These results can be explained by a stronger basicity of deuterated imipramine relative to its unlabeled counterpart.

Chromatography, Thin Layer↗
PubMed1977

A stable isotope method for measurement of thymidine incorporation into DNA.

A method has been developed for the measurement of DNA synthesis in vivo using the incorporation of multilabeled, non-radioactive thymidine. Simultaneous intraperitoneal injection of hexalabeled thymidine and tritiated thymidine into a normal adult rat resulted in the incorporation of both labeled nucelosides into the DNA of cells undergoing replication. The DNA of several tissues and organs was analysed, including liver, thymus, spleen, bone marrow, and small intestine. Following extraction with hot trichloroacetic acid, acid hydrolysis, and thin-layer chromatography of the hydrolysates, the isotopic compositions of the thymine products were determined by field ionization mass spectrometry and by scintillation counting. The relative incorporation of radioactive and stable isotope-labeled thymidine was similar in all tissues, and corresponded to the ratio of the two labeled nucleosides in the injected material. These results indicate the feasibility of utilizing thymidine multilabeled with stable isotopes for measurement of cellular proliferation rates in conjunction with cancer therapy.

Animals↗
PubMed1977

Improved adhesion of acrylic restorative materials to dental enamel by precoating with monomers containing phosphonate groups.

The adhesion of acrylic composite restorative materials to etched dental enamel is increased by a factor of two or more when the enamel is coated with a thin layer of vinyl-benzyl phosponic acid (VBPA) prior to forming the enamel-restorative bond. The present results support the suggestion that the enhanced adhesion is attributable to bonding between calcium ions in the enamel surface and phosphonate groups in the VBPA.

Acrylic Resins↗