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Biomedical subjects

R D Neumann

Publications and source records attributed to R D Neumann.

At least 37 records · Page 2Linked to original sources
PubMed1999

Glut-1 and hexokinase expression: relationship with 2-fluoro-2-deoxy-D-glucose uptake in A431 and T47D cells in culture.

Uptake of 2-[18F]-2-deoxy-D-glucose (FDG) has been used as a marker of increased glucose metabolism to visualize, stage, and monitor progression of human cancers with positron emission tomography. Many human tumors have been shown to overexpress the Glut-1 glucose transport protein. The aim of this study is to define whether a quantitative relationship exists between the amount of Glut-1 expressed by cells and their ability to accumulate FDG. We characterized the expression of the known facilitative and sodium-dependent glucose transporter isoforms in six different cancer cell lines used in our laboratory (A431, MDA-MB-231, T47D, CaCo II, MCF7, and HepG2). A431 and T47D cells express, respectively, the highest and lowest amount of Glut-1 mRNA by Northern blot of all of the cells analyzed, and no other glucose transporter isoforms were detectable by this method in both cell lines. Both total and plasma membrane-associated Glut-1 protein levels were higher in A431 than in T47D cells, consistent with the higher Glut-1 mRNA levels. However, T47D cells accumulate FDG more rapidly than do A431 cells. 3-O-Methylglucose transport is higher in A431 cells. Although hexokinase I and II mRNA levels are higher in A431 cells than in T47D cells, the ability of mitochondrial preparations to phosphorylate FDG is higher in T47D cells. Our data indicate that in these cultured cells, FDG uptake correlates better with FDG phosphorylating activity of mitochondrial preparations rather than the level of expression of the Glut-1 or hexokinase I and II genes.

Biological Transport↗
PubMed1999

Determination of human DNA polymerase utilization for the repair of a model ionizing radiation-induced DNA strand break lesion in a defined vector substrate.

Human DNA polymerase and DNA ligase utilization for the repair of a major class of ionizing radiation-induced DNA lesion [DNA single-strand breaks containing 3'-phosphoglycolate (3'-PG)] was examined using a novel, chemically defined vector substrate containing a single, site-specific 3'-PG single-strand break lesion. In addition, the major human AP endonuclease, HAP1 (also known as APE1, APEX, Ref-1), was tested to determine if it was involved in initiating repair of 3'-PG-containing single-strand break lesions. DNA polymerase beta was found to be the primary polymerase responsible for nucleotide incorporation at the lesion site following excision of the 3'-PG blocking group. However, DNA polymerase delta/straightepsilon was also capable of nucleotide incorporation at the lesion site following 3'-PG excision. In addition, repair reactions catalyzed by DNA polymerase beta were found to be most effective in the presence of DNA ligase III, while those catalyzed by DNA polymerase delta/straightepsilon appeared to be more effective in the presence of DNA ligase I. Also, it was demonstrated that the repair initiating 3'-PG excision reaction was not dependent upon HAP1 activity, as judged by inhibition of HAP1 with neutralizing HAP1-specific polyclonal antibody.

Base Sequence↗
PubMed1999

Detecting the DNA kinks in a DNA-CRP complex in solution with iodine-125 radioprobing.

Auger-electron-emitting radioisotopes such as 125I produce DNA strand breaks within nanometer range of the decay site. Here we analyze these breaks in order to study changes in DNA conformation upon binding with cyclic AMP receptor protein (CRP) in solution. The clear difference we found in break frequency in the CRP-DNA complex, as compared to the naked DNA duplex, correlates with the increased distances between the deoxyriboses and the radioiodine atom caused by the CRP-induced kink observed in the cocrystal. Thus, we demonstrate that 125I radioprobing can be used to study fine conformational changes of DNA within DNA-protein complexes.

Base Sequence↗
PubMed1999

Targeting of transferrin receptors in nude mice bearing A431 and LS174T xenografts with [18F]holo-transferrin: permeability and receptor dependence.

UNLABELLED: The goal of this study was to investigate whether 18F-labeled transferrin (Tf), which has a molecular weight (Mr) of approximately 79,000, binds to Tf receptor sites in tumors in a specific manner within the time frame commensurate with the half-life of 18F (109.7 min). We have previously shown that [18F]holo-Tf ([18F]Tf) maintains all properties of native Tf in vitro and that it can specifically target liver Tf receptor sites in vivo. METHODS: The distribution of [18F]Tf, using [18F]albumin (Alb) or [14C]Alb as a control, was studied over a 6-h period in nude mice bearing LS174T and A431 xenografts of a high- and low-permeability tumor, respectively. RESULTS: Measurements of Tf receptor concentration in the tumor extracts suggest similar binding capacities. In vivo, liver uptake values were higher for [18F]Tf than for both [18F]Alb and [14C]Alb throughout the study, indicating specific binding. In contrast, tumor Tf uptake values remained below those of the Alb tracers, and tumor-to-blood ratios of [18F]Tf in each xenograft increased in parallel with those of the Alb tracers. The permeabilities of [14C]Alb and [18F]Tf in LS174T were calculated to be 1.29+/-0.49 and 1.03+/-0.38 microL/min/g (mean +/- SD), respectively, whereas the permeabilities of the two tracers in A431 were 0.79+/-0.24 and 0.44+/-0.04 microL/min/g. Pharmacokinetic modeling of the data using these permeabilities and the high plasma and extracellular concentrations of endogenous Tf showed that the observed uptake values in the two xenografts are consistent with a non-receptor-mediated distribution. In the liver, the absence of permeability barriers yields specific [18F]Tf binding to receptors compared with the [14C]Alb control, within 5 min after injection. CONCLUSION: Receptor-mediated accumulation of [18F]Tf in tumor xenografts is impaired by rate-determining permeability and competition from endogenous Tf and is not achieved in a time frame of 6 h.

Albumins↗
PubMed1999

What is new in nuclear medicine imaging?

Modern nuclear medicine tests can be of great help to today's surgical oncologists. The new techniques of positron emission tomography (PET) and single photon emission computed tomography (SPECT), and the availability of new radiopharmaceuticals for localization of tumors and assessment of organ function provide information vital to the management of oncology patients.

Fluorodeoxyglucose F18↗
PubMed1998

Radiotoxicity of iodine-125-labeled oligodeoxyribonucleotides in mammalian cells.

UNLABELLED: We investigated the distribution, stability and radiotoxicity of 125I-oligodeoxyribonucleotides (125I-ODN) in human fibrosarcoma HT-1080 cells to study the radiotoxic effects of the Auger electron emitter 125I delivered to the cells by ODN. METHODS: We delivered 125I-ODN into the cells via complexing with a liposomal delivery system. To assess the intracellular distribution and stability of 125I-ODN delivered by the liposomal delivery system, we used autoradiography, fluorescent and confocal microscopy and electrophoresis. To study the radiotoxicity of the unbound 125I-ODN, we used a clonogenic assay. The radiotoxicity of 125I-ODN delivered by the liposomal delivery system was compared with that of freely diffusible 125I-antipyrine, membrane-excluded 125I-bovine serum albumin and DNA incorporated 125I-deoxyuridine (125I-UdR). RESULTS: Oligodeoxyribonucleotides accumulated in the cell nucleus within a few hours of incubation. On the basis of the number of decays at 37% survival, 125I-ODN are 2 times more radiotoxic than 125I-antipyrine, which is freely diffusible into cells, and 8 times more radiotoxic than 125I-bovine serum albumin, which remains outside cells. However, the radiotoxicity of unbound 125I-ODN is almost 3 orders of magnitude lower than that of DNA-incorporated 125I-UdR. The 125I-ODN are not significantly degraded by intracellular nucleases during the time of uptake incubation. CONCLUSION: The dramatic difference in radiotoxicity between 125I-ODN and 125I-UdR confirms that, despite the nuclear localization, 125I-ODN are not bound to or incorporated within the genomic DNA. Our data demonstrate that the radiotoxicity of Auger electron emitters is determined by the radiation dose delivered to nuclear DNA, not necessarily to the nucleus. Therefore, relatively high intracellular concentrations of unbound 125I-ODN can be achieved without causing significant cell death.

Animals↗
PubMed1998

Phase I study of the pharmacokinetics of a radioimmunoconjugate, 90Y-T101, in patients with CD5-expressing leukemia and lymphoma.

Ten patients with advanced or refractory CD5-expressing hematologic neoplasms [two with chronic lymphocytic leukemia and eight with cutaneous T-cell lymphoma (CTCL)] were treated in a Phase I study with the radioimmunoconjugate 90Y-T101, which targets CD5+ lymphocytes. Prior imaging studies using 111In-T101 demonstrated uptake in involved lymph nodes and skin in patients with CTCL, and Phase I studies with unmodified T101 demonstrated transient responses. In this study, patients were treated with 5 or 10 mCi of 90Y chelated to T101 via isothiocyanatobenzyl diethylenetriamine pentaacetic acid, along with tracer doses of 111In-T101 for imaging. The biodistribution of the radioimmunoconjugate was determined by measuring 90Y and 111In blood clearance, urine excretion, and accumulation in bone marrow and in involved skin lesions. The intravascular pharmacokinetics of 90Y were predicted by 111In-labeled T101. The greatest differences in biodistribution between 111In and 90Y were in the higher bone accumulation of 90Y and its lower urinary excretion. Imaging studies demonstrated targeting of skin lesions and involved lymph nodes in CTCL patients. The predominant toxicity was bone marrow suppression. Rapid antigenic modulation of CD5 on circulating T and B cells was observed. Recovery of T-cell populations occurred within 2-3 weeks; however, suppression of B-cell populations persisted after 5+ weeks. All CTCL patients developed human antimouse antibody after one cycle and thus were not retreated; one patient with chronic lymphocytic leukemia received a second cycle of therapy. Partial responses occurred in five patients, two with chronic lymphocytic leukemia and three with CTCL. The median response duration was 23 weeks. One CTCL patient who subsequently received electron beam irradiation to a residual lesion is disease-free after 6 years.

Adult↗
PubMed1997

Radioprobing of DNA: distribution of DNA breaks produced by decay of 125I incorporated into a triplex-forming oligonucleotide correlates with geometry of the triplex.

The distribution of breaks produced in both strands of a DNA duplex by the decay of 125I carried by a triplex-forming DNA oligonucleotide was studied at single nucleotide resolution. The 125I atom was located in the C5 position of a single cytosine residue of an oligonucleotide designed to form a triple helix with the target sequence duplex. The majority of the breaks (90%) are located within 10 bp around the decay site. The addition of the free radical scavenger DMSO produces an insignificant effect on the yield and distribution of the breaks. These results suggest that the majority of these breaks are produced by the direct action of radiation and are not mediated by diffusible free radicals. The frequency of breaks in the purine strand was two times higher that in the pyrimidine strand. This asymmetry in the yield of breaks correlates with the geometry of this type of triplex; the C5 of the cytosine in the third strand is closer to the sugar-phosphate backbone of the purine strand. Moreover, study of molecular models shows that the yield of breaks at individual bases correlates with distance from the 125I decay site. We suggest the possible use of 125I decay as a probe for the structure of nucleic acids and nucleoprotein complexes.

DNA↗
PubMed1997

Effect of radionuclide linker structure on DNA cleavage by 125I-labeled oligonucleotides.

We studied the yield and distribution of DNA strand breaks produced by decay of 125I introduced into triplex-forming and duplex-forming oligodeoxyribonucleotide (ODNs) through linkers of various lengths. ODNs were prepared with 125I attached at the 5'-end with a long linker or to an internal nucleotide position with a short linker. The 125I-ODNs were hybridized to either a single-stranded target to form duplexes or to a double-stranded target to form triplexes. After decay accumulation, the duplex and triplex samples were assayed for strand breaks in a sequencing gel. The yield of strand breaks per decay was 0.34 for duplex with the 5'-modified ODN and 0.66 for duplex with internally modified ODN. The triplex samples with internal 125I have different yields of DNA breaks in the pyrimidine and purine strands, 0.16 and 0.37, respectively. The yield of DNA breaks in the pyrimidine strand of the triplex with the 5'-modified ODN is 0.46. The majority of breaks are located within 5 nucleotides from the decay site. The yield of strand cleavage per decay of 125I was nearly two-fold lower with the described linkers in comparison with the results obtained when 125I is directly attached to the C-5 position of cytosine. Nevertheless, the rapid iodination procedure reported here combined with the possibility of multiple incorporations of 125I on the linkers makes such 125I-ODNs promising agents for sequence-specific cleavage of DNA.

Base Sequence↗
PubMed1996

Transferrin dependence of Ga (NO3)3 inhibition of growth in human-derived small cell lung cancer cells.

The effect of a combination of anti-transferrin receptor (TFR) antibody, 42/6, and Ga(NO3)3 on cell growth was examined in small cell lung cancer (SCLC) cell lines: classic, NCI-H209, NCI-H345, NCI-H510; and variant, NCI-H82 and NCI-N417. The role of TFR and transferrin (TF) in Ga(NO3)3 cellular uptake was also tested. Exogenous TF did not enhance the cytotoxicity of Ga. At > 3 micrograms/mL, Ga(NO3)3 inhibited growth in all cell lines in TF-supplemented or deficient media. At < 3 micrograms/mL, Ga stimulated growth for all cells but this effect was eliminated by TF or 42/6. Classic SCLC lines required 3-4-fold less exogenous gallium than variant lines to reduce cell number by 50%. The mean Ga uptake (ng/10(6) cells) in H345 and H209 cell lines was 4-5-fold compared to H82 and N417 uptake (P < 0.001). 42/6 reduced exogenous TF-stimulated growth. Antibody plus Ga(NO3)3 caused a slight further cell number decline in all cell lines in TF-supplemented or deficient media. These results suggest that the addition of 42/6 antibody treatment would not increase the effectiveness of Ga(NO3)3 in patients. Both exogenous and endogenous TF and TFR play an important role in Ga uptake in these cells.

Antibodies, Monoclonal↗
PubMed1996

Radiolabeled peptides and other ligands for receptors overexpressed in tumor cells for imaging neoplasms.

For better detection of neoplasms by scintigraphy, ligands that bind specifically to surface receptors overexpressed in tumor cells are being developed. These ligands must be labeled with the readily available radionuclides of iodine, [111In] or [99mTc], without blocking their interaction with the specific cell membrane receptors. The promising ligands include bioactive endogenous peptides or their analogues, inhibitors of glucose transport proteins, estrogen and sigma receptor ligands, growth factors, and cytokines.

Animals↗
PubMed1996

Sequence-specific DNA breaks produced by triplex-directed decay of iodine-125.

Triplex forming oligonucleotides (TFO) labeled with Auger emitters could be ideal vehicles to deliver radioactive-decay energy to specific DNA sequences, causing DNA breaks and, subsequently, inactivation of these sequences. To demonstrate this approach we labeled with 125I (two 125I per molecule on average) a purine-rich 38-mer which forms a stable triplex with a polypurine x polypyrimidine stretch in the human HPRT gene. Decay of 125I in the bound TFO was shown to cause sequence-specific double strand breaks (DSB) in the target HPRT sequence cloned into plasmid DNA. No sequence-specific breaks were observed if 125I-labeled TFO were not bound to the plasmid DNA. After 60 days of decay accumulation (one 125I half-life) approximately a quarter of all plasmid molecules contained sequence-specific DSB, corresponding to 0.3 site-specific DSB per decay. Sequencing gel analysis shows that the DNA breaks are distributed within a few bases of the maxima at those bases opposite to the positions of 125I in the TFO.

Base Sequence↗
PubMed1996

Evaluation of human transferrin radiolabeled with N-succinimidyl 4-[fluorine-18](fluoromethyl) benzoate.

UNLABELLED: Iron metabolism plays a key role in cell proliferation and survival in rapidly growing cancer cells. Uptake is mediated by the carrier protein transferrin. The increased need for iron has been used as a method to target tumors and there is well-documented evidence that certain tumors can be imaged with tracers such as 67Ga, that mimic transferrin-mediated iron uptake. To obtain a tracer that would be better able to quantitate transferrin kinetics and indirectly evaluate iron metabolism, we have labeled human transferrin with the positron emitter, 18F, with a one-step high-specific activity method developed in our laboratory. METHODS: We measured the binding affinities of [18F]diferric (holo-) and iron-free (apo-) transferrin on two human cell lines. We also compared cellular uptake of [18F]holo-transferrin and [67Ga]citrate in various conditions, and washout of label incorporated into cells. RESULTS: The binding affinity of [18F]holo-transferrin was found to be the same as that reported for [125I]holo-transferrin. In our hands there was no significant difference in binding affinity between diferric holo-transferrin and iron-free apo-transferrin. [18F]holo-transferrin uptake rapidly reaches a steady-state equilibrium between the intracellular and extracellular environment, while gallium accumulation linearly increases with time. [18F]holo-transferrin is rapidly recycled out of the cell with similar kinetics to those reported for [125I]holo-transferrin. CONCLUSION: [18F]holo-transferrin displays the properties of native transferrin and appears suitable for quantitative evaluation of transferrin kinetics in vivo.

Benzoates↗
PubMed1996

Ultrastructure of selected struvite-containing urinary calculi from cats.

OBJECTIVE: To elucidate the ultrastructural details of struvite-containing urinary calculi from cats. DESIGN: Specimens studied were inclusive of the range of textures visible during preliminary analysis by use of a stereoscopic dissecting microscope. Textural types, which were used to infer crystal growth conditions, were differentiated with regard to crystal habit, crystal size, growth orientation, and primary porosity. SAMPLE POPULATION: Thirty specimens were selected from a collection of approximately 1,600 feline urinary calculi: 20 of these were composed entirely of struvite, and 10 consisted of struvite and calcium phosphate (apatite). PROCEDURE: Qualitative and quantitative analyses of specimens included use of plain and polarized light microscopy, x-ray diffractometry, scanning electron microscopy with backscattered electron imagery, x-ray fluorescence scans, and electron probe microanalysis. RESULTS: Four textural types were recognized among struvite calculi, whereas 2 textural types of struvite-apatite calculi were described. CONCLUSIONS: The presence of minute, well interconnected primary pores in struvite-containing urinary calculi from cats is an important feature, which may promote possible interaction of calculi with changes in urine composition. CLINICAL RELEVANCE: Primary porosity, which can facilitate interaction between the calculus and changing urine composition, may explain the efficacy of dietary or medicinal manipulations to promote the dissolution of struvite-containing uroliths from this species.

Animals↗
PubMed1996

Diagnostic imaging in patients with paragangliomas. Computed tomography, magnetic resonance and MIBG scintigraphy comparison.

OBJECTIVE: We compared iodine-131 metaiodobenzylguanidine (MIBG), computed tomography (CT) and magnetic resonance (MR) imaging studies in 40 patients with suspected or proven paragangliomas. PATIENTS: 21 patients were studied during the initial evaluation, while 19 were evaluated after surgery for paragangliomas. Furthermore, in 18 patients with benign (n = 10) or malignant (n = 8) tumors, MIBG uptake, MR signal intensity ratios (SIR) and CT parameters were analyzed. RESULTS: In patients studied during the initial evaluation, CT and MR had a significant (p < 0.05) higher diagnostic sensitivity (100% for both) compared to MIBG (82%); conversely, MIBG showed a higher specificity (100%) compared to CT and MR (50% for both); the accuracy of MIBG (86%), CT and MR (91% for both) were similar. In patients evaluated after surgery, MIBG and MR had slightly better sensitivity (85% for both) compared to CT (77%). MIBG showed again better specificity (100%) than CT and MR (83% for both); the accuracy of MIBG, MR and CT were respectively 90%, 84% and 79%. While no significant differences were observed in MR SIR and CT findings between benign and malignant tumors, MIBG uptake was significantly higher in malignant compared to benign lesions (p < 0.03). CONCLUSIONS: Our results suggest that CT and MR are particularly useful in the initial evaluation of patients with suspected paragangliomas. MIBG should be recommended during the post-surgical follow-up of such patients since recurrent, malignant or extra-adrenal disease frequently occur. Finally, while MR SIR and CT features are not able to distinguish malignant paragangliomas from benign tumors, MIBG uptake is higher in malignant lesions compared to benign tumors providing a diagnostic criterion to differentiate these lesions.

3-Iodobenzylguanidine↗
PubMed1995

Targeting cancer micrometastases with monoclonal antibodies: a binding-site barrier.

Monoclonal antibodies penetrate bulky tumors poorly after intravenous administration, in part because of specific binding to the target antigen. Experiments presented here demonstrate an analogous phenomenon in micrometastases; poor antibody penetration, attributable to a "binding-site barrier" phenomenon, can be seen in guinea pig micrometastases as small as 300 microns in diameter. Increasing the dose of antibody can partially overcome this limitation, but at a cost in specificity.

Animals↗
PubMed1995

Kinetic analysis of muscarinic receptors in human brain and salivary gland in vivo.

Previous studies in rats have suggested that the muscarinic acetylcholine receptor (mAChR) antagonist (S)-3-quinuclidinyl-(S)-4-[123I]iodobenzilate [(SS)-IQNB] may be useful for the in vivo evaluation of mAChRs in humans as a control for the higher-affinity compound (RR)-IQNB. We have directly tested this hypothesis and examined the distribution of mAChRs in brain regions and parotid glands of healthy human volunteers in vivo using (RR)- and (SS)-IQNB (relatively high- and low-affinity antagonists, respectively), planar imaging, and pharmacokinetic analysis. This is the first in vivo study of mAChRs in humans that has employed stereoisomeric ligands and metabolic analysis to determine specific receptor binding. We observed that (SS)-IQNB showed much faster clearance from blood than (RR)-IQNB and different metabolite profiles. Also, the transport kinetics of the enantiomers were different. The estimated binding potential (approximately Bmax/Kd) of (RR)-IQNB was highest in two cortical regions, intermediate in parotid gland, and lowest in cerebellum. The aggregate results show that in humans (SS)-IQNB does not act as an ideal general probe to measure the nonspecific IQNB distribution. However, (RR)-IQNB does appear to have value when used for studies of human brain mAChRs.

Adult↗