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Biomedical subjects

R E Weiner

Publications and source records attributed to R E Weiner.

15 recordsLinked to original sources
PubMed1992

Loss of radiogallium from lymphoma after initiation of chemotherapy.

A man with a high-grade lymphoma had radiogallium imaging at 48 hours postinjection, revealing three distinct sites of uptake (neck and thorax). Unknown to the authors, the patient was given cytoxan, vincristine, and prednisone intravenously 27 hours after radiogallium administration. The images at 120 hours showed markedly reduced radiogallium activity at all three sites. Possible reasons for the loss of radiogallium from the tumor sites were presented.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1992

Gallium-67 distribution in a man with a decrease in both transferrin and hepatic gallium-67 concentration.

A patient with reduced transferrin concentration had a 67Ga scintigram that showed uptake in a peritoneal abscess, pericarditis and pleural effusion but only faint liver uptake. Gallium-67 activity was measured in liver, lung, muscle and plasma samples obtained at autopsy. The percent injected dose/kg for liver and plasma samples was considerably lower than previously reported while that in muscle and lung tissues values were comparable to prior data. In this patient, sites on transferrin available to bind 67Ga were reduced from the normal 40 microM to 5.2 microM; this in turn increased the concentration of radiogallate from 1% to 7%. This elevated free activity increased 67Ga excretion and reduced the amount of 67Ga*transferrin species. These results and those of previous studies suggest that liver uptake is slower than abscess uptake and more sensitive to concentration of 67Ga*transferrin. Iron status is an important facet of the interpretation of 67Ga scintigrams.

Abscess↗
PubMed1989

Role of phosphate-containing compounds in the transfer of indium-111 and gallium-67 from transferrin to ferritin.

Physiologic concentrations of ATP stimulate the translocation of gallium-67 (67Ga) from human transferrin (TF) to horse ferritin (HoFE). The mechanism of this translocation was examined. One millimolar ATP did not speed the binding of 67Ga or indium-111 (111In) to HoFE. ATP and pyrophosphate (PPi) at 1 mM, did not form high affinity complexes with 67Ga or 111In. ATP and PPi interacted directly with the [67Ga]TF complex and could within minutes increase the amount of nonprotein-bound 67Ga. Serum HCO3- concentration, 30 mM, prevented the ATP-induced dissociation of 67Ga from TF, whereas intracellular concentrations (0.4 and 5 mM) did not. Using a dialysis technique, ATP also stimulated the translocation of 111In from TF to HoFE; however, this process was much slower than with 67Ga. ATP caused an increase in the nonprotein-bound 111In compared to the control. These results suggest the formation of nonprotein-bound nuclide by these phosphate-containing compounds in a kinetically labile form is important to the translocation mechanism.

Adenosine Triphosphate↗
PubMed1988

Scintigraphic and electrophysiological evidence of canine myocardial sympathetic denervation and reinnervation produced by myocardial infarction or phenol application.

Epicardial phenol application or transmural myocardial infarction in dogs produces sympathetic denervation of myocardium apical to the site of the intervention. Because efferent denervation is probably postganglionic, reinnervation most likely occurs but has not been shown. We investigated whether 123I-labeled metaiodobenzylguanidine (MIBG), a norepinephrine analogue taken up by sympathetic nerve terminals, could provide a scintigraphic image that would detect apical sympathetic denervation and possible reinnervation. Dogs underwent MIBG scintigraphic imaging at various times after phenol application or transmural myocardial infarction. The results of MIBG scintigraphy were correlated with electrophysiological responses obtained during ansae subclaviae and norepinephrine stimulation to establish the presence of neural denervation and reinnervation. Apical defects in the MIBG scan, which were associated with either normal perfusion by thallium or a smaller-sized defect, were found consistently in dogs that had apical sympathetic innervation. MIBG scintigraphic images returned to normal after 14 weeks (mean) at a time when reinnervation was shown to have occurred. Thus, the results of MIBG scintigraphy correlated accurately with the presence of denervation and reinnervation established by neuroelectrophysiological testing. Supersensitive refractory period shortening in response to norepinephrine infusion was present after denervation and persisted for more than 3 weeks after scintigraphic and electrophysiological evidence of reinnervation. Conclusions are that 1) MIBG can be used noninvasively to determine the presence of regional myocardial efferent sympathetic denervation and subsequent reinnervation, 2) reinnervation occurs after phenol application or transmural myocardial infarction, and 3) denervation supersensitivity persists even after reinnervation occurs.

3-Iodobenzylguanidine↗
PubMed1987

Influence of various factors on binding of 67Ga to polymorphonuclear leukocytes.

We have studied in vitro, factors that influence the uptake of 67Ga-citrate by human polymorphonuclear leukocytes. Citrate at 20 mM concentration decreased the uptake to 1% of control values. Uptake increased as a function of increased microCi of 67Ga/10(7) cells added and incubation time from 0 to 120 min. Uptake decreased somewhat as the incubation pH was lowered from 7.4 to 6.0. Our results suggest that, in vivo, these cells would accumulate 67Ga as the inflammatory lesion progresses while the acidic milieu would modestly reduce uptake.

Citrates↗
PubMed1985

Compounds which mediate gallium-67 transfer from lactoferrin to ferritin.

The influence of various low molecular weight compounds on the transfer of 67Ga from human lactoferrin (LF) to horse spleen ferritin (HoFE) has been examined in vitro. When LF*67Ga complex was placed in competition with HoFE using a dialysis system the initial transfer rate (TR) of 67Ga to HoFE was slow and continuous. In the presence of 1 mM pyrophosphate (PPi) ascorbate and adenosine triphosphate (ATP), the TR was dramatically enhanced. This effect was concentration sensitive since reduction of the ATP to 0.1 mM eliminated the enhancement. Other intracellular compounds did not significantly influence the TR. Although PPi and ascorbate ions yielded larger TR's, ATP was more effective in the promotion of 67Ga transfer to HoFE. When the LF/HoFE concentration ratio was decreased, in the presence of ATP, the transfer of 67Ga was significantly increased. These results suggest that ferritin present intracellularly could remove and retain 67Ga entering the cell in the form of a LF*67Ga complex. Moreover, increased synthesis of ferritin and cytosolic phosphate compounds would appear to enhance this process.

Adenosine Triphosphate↗
PubMed1977

Fluorescence properties of the copper enzyme galactose oxidase and its tryptophan-modified derivatives.

Galactose oxidase contains a single nonblue Cu(II) atom and 18 tryptophan residues per molecule. Removal of the copper atom reveals that it has an approximately 29% quenching effect on the relative quantum yield of fluorescence. While saturating concentrations of the sugar substrate of galactose oxidase also reduce the quantum yield, the second substrate, oxygen, has no significant effect on fluorescence in the absence of the sugar substrate. N-Bromosuccinimide (NBS) inactivates galactose oxidase as two tryptophans are oxidized (Kosman, D. J., Ettinger, M. J., Bereman, R. D., and Giordano, R. S. (1977), Biochemistry, 16). Oxidation of two tryptophans also leads to a disproportionately large decrease in fluorescence intensity. A 23% reduction in quantum yield with blue-shift occurs with oxidation of 0.85 tryptophan equiv and a further 25% quenching is obtained as the reaction proceeds to 2.0 residues oxidized. Fluorescence experiments with the modified enzyme show that it contains at least one tryptophan residue which is unreactive towards NBS, but which also interacts with the Cu(II) atom and substrate. These results taken together substantiate the postulate that one or more tryptophan residues, the Cu(II) atom, and the sugar substrate mutually interact within the native enzyme. Energy-transfer calculations suggest that this residue(s) which must be within a relatively hydrophobic environment is at least 12 A from the Cu(II) atom.

Alcohol Oxidoreductases↗
PubMed1975

The molecular weight of bovine lactoferrin.

The molecular weight of bovine lactoferrin in a neutral solvent (e.g. 0.2 M NaC1, pH 7.8 20 degrees C) has been determined using high-speed sedimentation equilibrium at various concentrations and speeds. Under these conditions the protein behaved as a single thermodynamic component with a weight-average molecular weight [MW]C=0 = 93000 plus or minus 2000 and a second virial coefficient B = 4.3-10(-5) mol-ml(-1)-g(-2). This value of the molecular weight is in good agreement with values previously reported by Groves (J. Am. Chem. Soc. 82, 3345-3350, 1960) and Szuchet and Johnson (Eur. Polym. J. 2, 115-128, 1966); it is, however, in disagreement with the more recent value given by Castellino et al. (J. Biol. Chem. 245, 4269-4275, 1970). The possible reasons for this discrepancy are discussed.

Animals↗