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Biomedical subjects

B Kiefer

Publications and source records attributed to B Kiefer.

48 records · Page 3Linked to original sources
PubMed1984

Adriamycin impairs phagocytic function and induces morphologic alterations in human neutrophils.

Normal human polymorphonuclear leukocytes (PMNL) were preincubated in vitro with methotrexate, 5-fluorouracil, vincristine, cisplatin, Adriamycin (doxorubicin), and daunomycin for 15 hours before being tested in a phagocytic-bactericidal assay. Anthracycline-treated PMNL were defective in phagocytosis and killing of the bacteria, in contrast to the other chemotherapeutic agents which allowed the PMNL to remain functional. The defect of Adriamycin-treated PMNL resulted from decreased ingestion: 3 micrograms/ml Adriamycin inhibited by 50% of the uptake of Oil Red-O particles. In this assay, the proportion of noningesting PMNL increased from less than or equal to 20% with 0.62 micrograms/ml to greater than or equal to 90% with 10 micrograms/ml Adriamycin. Electron microscopy revealed that Adriamycin-inactivated PMNL had rounded up, were depleted in glycogen, and had undergone profound nuclear changes. RNA and protein synthesis in PMNL were also affected. Adriamycin, besides producing neutropenia, may decrease the phagocytic function of circulating PMNL.

Antineoplastic Agents↗
PubMedDate not supplied

MR imaging of focal liver lesions: comparison between turbo spin-echo and conventional spin-echo pulse sequences.

The aim of this study was to compare conventional spin-echo (CSE) T2-weighted (T2W) images with turbo spin-echo (TSE) T2W pulse sequences in their ability to detect focal liver lesions. Seventy-eight consecutive patients with focal liver lesions were entered into this study. All patients were imaged using the gradient-echo (GE) sequence with the breath-hold technique for T1-weighted (T1W) images, and CSE and TSE sequences for T2W images. Qualitative evaluation included lesion detection (number of lesions detected) and conspicuity (extent of visualization of lesional borders); quantitative evaluation included the signal-to-noise (S/N) ratio and the contrast-to-noise (C/N) ratio. TSE showed the best performance in terms of lesion detection; however, the difference between TSE and CSE was significant only in the case of benign cysts (p < 0.01). Conspicuity was higher with TSE and CSE, and lower with GE. The S/N and C/N ratios of the two T2W sequences were also comparable, and better than those of GE. However, the combined use of GE and TSE resulted in improved lesion detection. The results show that, because the acquisition time is greatly reduced with TSE sequences, these should be considered as first-line approach to magnetic resonance imaging of the liver for the study of focal lesions.

Adenoma↗
PubMedDate not supplied

High resolution GRASE MRI of the brain and spine: 512 and 1024 matrix imaging.

OBJECTIVE: Our goal was to implement 512 and 1024 matrix MRI of the brain in clinically acceptable imaging times. MATERIALS AND METHODS: With use of the GRASE (gradient-SE) imaging technique, 3 signals are refocused from each of 16 SEs, giving a total of 48 echoes per echo train, for a speed advantage of 1/48 over conventional SE imaging. Images in 1024 matrices are acquired in 2D Fourier transform (FT) multisectional MRI. In related experiments, multislab 3D FT GRASE imaging is performed using 16 partitions/slab, providing thinner 1 to 2 mm sections. In all imaging experiments, higher spatial resolution is obtained with stronger and faster gradients, 24 mT/m in 625 microseconds rise time, on a standard commercial MRI system. RESULTS: The 2D FT 1024 matrix images of the head were acquired in 4:20 min, with 20 sections and TR/TE 7040/115 ms in a rectangular FOV to obtain .28 x .27 mm2 spatial resolution. Small anatomic structures, including cochlea of inner ear, cranial nerves, and vascular detail, are readily demonstrated. The 512 matrix images were obtained in 4:40 min, with 16 sections and TR/TE 3,500/104 ms in a 24 cm FOV. The 3D FT technique substantially increased slice coverage as well as image signal-to-noise ratio. CONCLUSION: The results show that 1024 matrix MRI is technically feasible in clinically acceptable imaging time and offers advantage for high resolution imaging. Optimization of 1024 matrix and 3D FT GRASE imaging should improve the delineation of anatomic regions of interest.

Adult↗
PubMedDate not supplied

On the origin of the non-haemic iron transferrin ESR signal: ESR investigations on histidine-iron-ascorbic acid systems.

The nature of the ferric high spin iron complex located at g = 4.3 has been investigated by means of electron spin resonance spectroscopy. It could be shown that the iron is bound to two histidines, three ascorbic acids, and one bicarbonate. This agrees well with previous findings according to which the ligand field of iron is composed mainly of oxygen and nitrogen atoms. Another low-field signal located at g = 9.5 appears always concomitantly with the g = 4.3 signal. It should be due, therefore, to a transition between the two sublevels of the low-lying Kramers doublet in one principal direction.

Ascorbic Acid↗
PubMedDate not supplied

On the origin of the non-haemic iron transferrin ESR signal: ESR investigations on histidine-iron-citric acid systems.

The nature of the high spin ferric iron complex located at g = 4.3 has been investigated by means of electron spin resonance spectroscopy and polarography. It could be shown that two complexes each exist in the acid and alkaline pH region, and that the iron is bound to two histidines, three citric acids, and probably to one bicarbonate. These results agree well with previous findings according to which the ligand field of iron should be composed mainly of oxygen and nitrogen atoms. Another low-field signal located at g = 3.6 appears in the pH range from 2 to 7 only and exhibits its maximum where the g = 4.3 signal has its minimum. Its exact nature is still unknown but it seems to represent some intermediate state of the ternary Fe3+-histidine-citric acid complex. When citric acid is used, the spin concentration seems to be always larger than in the case of ascorbic acid. Since the effect obtained with ascorbic acid and citric acid seems to be similar, it may be concluded that the biological function of both of the acids might be somehow related to each other.

Ascorbic Acid↗
PubMedDate not supplied

ESR investigations on the modification of the ascorbic acid-erythrocyte interaction by ferrous ions.

An ascorbic acid-erythrocyte interaction results in the formation of the semidehydroascorbate (SDA) radical and an increase in spin concentration. Addition of a more than ten-fold concentration of Fe2+ (as FeSO4) to such a system compensates the effect produced by ascorbic acid, that is the electron spin resonance spectrum obtained resembles very closely that of erythrocytes only. With the disappearance of the SDA radical a high spin ferric ion signal appears concomitantly at g = 4.3.

Ascorbic Acid↗
PubMedDate not supplied

The influence of amino acid ligands and vitamin C on the reduction potential of Fe (III): polarographic and electron spin resonance investigations.

The pH dependence of Fe(III)-amino acid complexes has been studied polarographically and by means of ESR spectroscopy. It could be shown that, at least, two complexes exist: one with a low molecular weight, ESR detectable at acid pH, and one with a high molecular weight at alkaline pH, ESR non detectable. The half wave potential of Fe(III) is lowered by amino acid ligands. The redox interaction of the Fe(III)-amino acid complexes with vitamin C results in a decrease of the ascorbyl radical concentration. Ascorbic acid also forms a complex with Fe(III) as indicated by a polarographic half wave potential near -0.55 V vs. S.C.E. at pH 7.

Alanine↗
PubMedDate not supplied

Interaction between spin labels and DPPC vesicles.

1H NMR studies on DPPC vesicles labeled with the spin labels (1,14) or (12,3) have shown that both of the spin labels influence the fatty acid side chains as well as the choline head groups. The spin label (12,3) affects, naturally, the head groups stronger than the spin label (1,14), while the reversed effect can be observed at the side chains. This effect progresses with time after vesicle preparation and is fully developed after about 24 h. Addition of Na-ascorbate, at this time, seems to reverse the effect indicating a stabilizing effect of the vitamin on the membrane. These results could be confirmed by ESR investigations according to which the high-field signal seems to be indicative for changes occurring at the side chains, while the low-field signal seems to reflect modifications of the head groups. Since the spin label (1,14) affects considerably the head groups at temperatures less than 6 degrees C, in which case the spectrum is very similar to that obtained with spin label (12,3) at 24 degrees C, one might conclude that there might be a phase transition in regard to the head groups.

1,2-Dipalmitoylphosphatidylcholine↗