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Biomedical subjects

E Oldfield

Publications and source records attributed to E Oldfield.

At least 55 records · Page 3Linked to original sources
PubMed1993

Secondary and tertiary structural effects on protein NMR chemical shifts: an ab initio approach.

Recent theoretical developments permit the prediction of 1H, 13C, 15N, and 19F nuclear magnetic resonance chemical shifts in proteins and offer new ways of analyzing secondary and tertiary structure as well as for probing protein electrostatics. For 13C, phi, psi torsion angles dominate shielding for C alpha and C beta, but the addition of hydrogen bonding and electrostatics gives even better accord with experiment. For 15NH, side chain (chi 1) torsion angles are also important, as are nearest neighbor sequence effects, whereas for 1HN, hydrogen bonding is particularly significant. For 19F, weak or long-range electrostatic fields dominate 19F shielding nonequivalencies. The ability to predict chemical shifts in proteins from known or test structures opens new avenues to structure refinement or determination, especially for condensed systems.

Bacterial Proteins↗
PubMed1993

Carbon-13 "magic-angle" sample-spinning nuclear magnetic resonance studies of human myelin, and model membrane systems.

We have obtained high-field (11.7 Tesla), high-resolution carbon-13 solid-state "magic-angle" sample-spinning nuclear magnetic resonance (NMR) spectra of a variety of phospholipids, sphingolipids, myelin and white matter samples, resolving and assigning over 40 resonances in the spectra of human and bovine myelin. The NMR results indicated no large spectral changes due to sample preparation, sample freezing, or brain location, and also no changes in myelin structure detectable via light microscopy, electron microscopy, thin layer chromatography, or sodium dodecyl sulfate-polyacrylamide gel electrophoresis, attributable to the sometimes lengthy NMR data acquisition process. Human myelin and white matter chemical shift assignments were made based on 13C "magic angle" sample spinning (MAS) NMR spectra of individual model lipids, as well as on spectra of lipid mixtures. In all myelin samples there were essentially no features attributable to membrane proteins, with the exception of one small feature due to C zeta of Arg residues, primarily in the myelin basic proteins. The general similarity between the model lipid and intact myelin spectra suggested no major effects of protein on lipid mobility. We have also investigated human myelin samples as a function of developmental age (4, 15, 48 months and adult), and our results showed only small changes in overall lipid composition, although there were significant decreases in lipid hydrocarbon chain unsaturation with age, as determined by computer line-shape simulations of myelin and model compounds. The spectrum of an infant leukoencephalopathy myelin showed marked decreases in galactocerebrosides. Overall, the ability to resolve and assign over 40 resonances in the 13C MAS NMR spectra of myelin, and to detect changes as a function of development and disease, should provide a useful starting point for further more detailed studies of myelin membrane molecular motions, and function.

Adult↗
PubMed1993

NMR chemical shifts and structure refinement in proteins.

Computation of the 13C alpha chemical shifts (or shieldings) of glycine, alanine and valine residues in bovine and Drosophila calmodulins and Staphylococcal nuclease, and comparison with experimental values, is reported using a gauge-including atomic orbital quantum-chemical approach. The full approximately 24 ppm shielding range is reproduced (overall r.m.s.d. = 1.4 ppm) using 'optimized' protein structures, corrected for bond-length/bond-angle errors, and rovibrational effects.

Alanine↗
PubMed1993

Leishmaniasis among Desert Storm veterans: a diagnostic and therapeutic dilemma.

Troops stationed in the Middle East during Operations Desert Shield/Storm were potentially exposed to leishmaniasis, a parasitic infection transmitted by sandflies. In this region, infection primarily causes cutaneous and, less often, visceral disease. Visceral leishmaniasis, which typically has an incubation period of several months, can be a difficult diagnosis as it presents with a wide range of symptoms and there are no non-invasive, reliable diagnostic tests. Cutaneous leishmaniasis is more easily diagnosed using culture and stained smears of biopsy and aspirate samples from skin lesions. Pentavalent antimonials are most often used to treat leishmaniasis; however, treatment is potentially toxic and not recommended except in cases of documented disease.

Humans↗
PubMed1992

Cytotoxic ribonuclease chimeras. Targeted tumoricidal activity in vitro and in vivo.

Monoclonal antibodies to the transferrin receptor or to the T cell antigen, CD5, were chemically linked to mammalian RNase A and found to specifically inhibit protein synthesis in antigen-positive cells. Antibody-mediated specificity of these cytotoxic ribonuclease chimeras (CRCs) was demonstrated in three ways. 1) Toxicity was due to the chemical linkage of RNase to antibody, as the individual components added separately or in combination did not inhibit protein synthesis; 2) the anti-transferrin receptor CRCs inhibited protein synthesis in those cells expressing the human transferrin receptor (K562, U251, Jurkat cells) but had no detectable toxicity to cells lacking the human transferrin receptor (Vero or NIH 3T3 cells); 3) free antibody to either the human transferrin receptor (454A12 or 5E-9) or to the T cell antigen, CD5 (T101), blocked the cytotoxicity of the respective CRC. Two CRC species, designated P1 and P2, that differed in size and stoichiometry of RNase A to antibody, were purified by size-exclusion high performance liquid chromatography. The higher molecular weight P1 conjugate had an IC50 of 20-30 nM, whereas the P2 conjugate had a higher IC50 of 300-500 nM. Bioactivity could be reversibly increased more than 10-fold by freezing. The cytotoxicity of the CRCs was examined in vivo in a solid tumor animal model. Intratumoral injections of an anti-transferrin receptor CRC into established U251 human glioblastoma tumors grown in the flanks of nude mice prevented tumor growth, whereas RNase A mixed with antibody was ineffective. CRCs, therefore, express cytotoxicity in vitro and in vivo. Mammalian nucleases coupled to antibodies may be utilized as cell type-selective cytotoxins and have potential as pharmacologic reagents. The systemic toxicity and immunogenicity observed with mammalian derived cytotoxins may be significantly less than that of the currently employed plant- and bacterial-derived immunotoxins.

Animals↗
PubMed1992

Spectroscopic studies of lipids and biological membranes: carbon-13 and proton magic-angle sample-spinning nuclear magnetic resonance study of glycolipid-water systems.

We have obtained 1H and 13C magic-angle sample-spinning (MAS) nuclear magnetic resonance (NMR) spectra of three glycosyldiacylglycerol-water (1:1, weight ratio) mesophases, at 11.7 T, as a function of temperature, in order to probe lipid headgroup, backbone, and acyl chain dynamics by using natural-abundance NMR probes. The systems investigated were monogalactosyldiacyldiglyceride [MGDG; primarily 1,2-di[(9Z,12Z,15Z)octadec-9,12,15-trienoyl++ +]-3-beta-D-galactopyranosyl- sn-glycerol]; digalactosyldiacyldiglyceride [DGDG; primarily 1,2-di[(9Z,12Z,15Z)octadec-9,12,15-trienoyl++ +]-3- (alpha-D-galactopyranosyl-1-6-beta-D-glactopyranosyl)-sn-glycerol] ; and sulfoquinovosyldiacyldiglyceride [SQDG; primarily 1-[(9Z,12Z,15Z)octadec-9,12,15-trienoyl]-2 -hexadecanoyl-3-(6-deoxyl-6- sulfono-alpha-D-glucopyranosyl)-sn-glycerol]. At approximately 22 degrees C, all three lipid-water systems give well-resoled 13C and 1H MAS NMR spectra, characteristic of fluid, liquid-crystalline mesophases. 13C spin-lattice relaxation times of the headgroup and glycerol backbone carbons of all three materials give, within experimental error, the same NT1 values (approximately 400 ms), implying similar high-frequency motions, independent of headgroup size and charge. Upon cooling, pronounced line broadenings are observed, due to an increase in slow motional behavior. For each lipid, the onset of line broadening is seen with the glycosyl headgroup, glycerol backbone, and the first two or three carbons of the acyl chains. By approximately -20 degrees, all headgroup carbon resonances are broadened beyond detection. Both galactose moieties in DGDG "freeze out" together, implying a rigid-body motion of the disaccharide unit. Upon further cooling, the bulk polymethylene chain resonances in all three systems (in both 13C and 1H MAS) broaden greatly, followed by the olefinic and allylic carbon resonances.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate Conformation↗
PubMed1991

Carbon-13 nuclear magnetic resonance spectroscopy of lipids: differential line broadening due to cross-correlation effects as a probe of membrane structure.

We have obtained proton-coupled carbon-13 nuclear magnetic resonance (NMR) spectra of a variety of lipid-water and lipid-drug-water systems, at 11.7 T, as a function of temperature, using the "magic-angle" sample-spinning (MAS) NMR technique. The resulting spectra show a wide range of line shapes, due to interferences between dipole-dipole and dipole-chemical shielding anisotropy interactions. The differential line-broadening effects observed are particularly large for aromatic and olefinic (sp2) carbon atom sites. Coupled spectra of the tricyclic antidepressants desipramine and imipramine, in 1,2-dimyristoyl-sn-glycero-3-phosphocholine-water mesophases, show well-resolved doublets having different line shapes for each of the four aromatic methine groups, due to selective averaging of the four C-H dipolar interactions due to rapid motion about the director (or drug C2) axis. 2H NMR spectra of [2,4,6,8-2H4]desipramine (and imipramine) in the same 1,2-dimyristoyl-sn-glycero-3-phosphocholine-water mesophase exhibit quadrupole splittings of approximately 0-2 and approximately 20 kHz, indicating an approximate magic-angle orientation of the C2-2H(1H) and C8-2H(1H) vectors with respect to an axis of motional averaging, in accord with the 13C NMR results. Selective deuteration of imipramine confirms these ideas. Spectra of digalactosyl diglyceride [primarily 1,2-di[(9Z,12Z,15Z)-octadeca-9,12,15-trienoyl ]-3- (alpha-D-galactopyranosyl-1-6-beta-D-galactopyranosyl)-sn-glycerol]-H2O (in the L alpha phase) show a large differential line broadening for C9 but a reduced effect for C10, consistent with the results of 2H NMR of specifically 2H-labeled phospholipids [Seelig, J., & Waespe-Saracevic, N. (1978) Biochemistry 17, 3310-3315].(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon Isotopes↗
PubMed1991

Distal and proximal ligand interactions in heme proteins: correlations between C-O and Fe-C vibrational frequencies, oxygen-17 and carbon-13 nuclear magnetic resonance chemical shifts, and oxygen-17 nuclear quadrupole coupling constants in C17O- and 13CO-labeled species.

We have obtained the oxygen-17 nuclear magnetic resonance (NMR) spectra of a variety of C17O-labeled heme proteins, including sperm whale (Physeter catodon) myoglobin, two synthetic sperm whale myoglobin mutants (His E7----Val E7; His E7----Phe E7), adult human hemoglobin, rabbit (Oryctolagus cuniculus) hemoglobin, horseradish (Cochlearia armoracia) peroxidase (E.C. 1.11.1.7) isoenzymes A and C, and Caldariomyces fumago chloroperoxidase (E.C. 1.11.1.10), in some cases as a function of pH, and have determined their isotropic 17O NMR chemical shifts, delta i, and spin-lattice relaxation times, T1. We have also obtained similar results on a picket fence prophyrin, [5,10,15,20-tetrakis(alpha, alpha, alpha, alpha, alpha-pivalamidophenyl)porphyrinato]iron(II) (1-MeIm)CO, both in solution and in the solid state. Our results show an excellent correlation between the infrared C-O vibrational frequencies, v(C-O), and delta i, between v(C-O) and the 17O nuclear quadrupole coupling constant (e2qQ/h, derived from T1), and as expected between e2qQ/h and delta i. Taken together with the work of others on the 13C NMR of 13CO-labeled proteins, where we find an excellent correlation between delta i(13C) and v(Fe-C), our results suggest that IR and NMR measurements reflect the same interaction, which is thought to be primarily the degree of pi-back-bonding from Fe d to CO pi* orbitals, as outlined previously [Li, X.-Y., & Spiro, T.G. (1988) J. Am. Chem. Soc. 110, 6024]. The modulation of this interaction by the local charge field of the distal heme residue (histidine, glutamine, arginine, and possibly lysine) in a variety of species and mutants, as reflected in the NMR and IR measurements, is discussed, as is the effect of cysteine as the proximal heme ligand.

Carbon Isotopes↗
PubMed1991

Von Hippel-Lindau (VHL) disease: distinct phenotypes suggest more than one mutant allele at the VHL locus.

As part of an attempt to locate the von Hippel-Lindau locus (VHL) on chromosome 3, we evaluated 41 families with von Hippel-Lindau disease from the United States and Canada. One large family was identified whose disease phenotype was distinct from typical VHL. The most common disease manifestation was pheochromocytoma occurring in 57% (27/47) of affected family members. Few (4/47) affected family members had symptomatic spinal or cerebellar hemangioblastomas; no affected family member had renal cell carcinoma (0/47) or pancreatic cysts (0/24). Previously, genetic analysis demonstrated that the disease manifestations in this family were linked to RAF1 and D3S18, markers shown to be linked to typical VHL. These results suggest that there are mutant alleles at the VHL locus associated with distinct tissue specificities.

Adrenal Gland Neoplasms↗
PubMed1991

Sequential cerebrospinal fluid and plasma sampling in humans: 24-hour melatonin measurements in normal subjects and after peripheral sympathectomy.

Simultaneous measurements of plasma and cerebrospinal fluid (CSF) melatonin and urinary excretion of 6-hydroxymelatonin were performed in four normal volunteers and one patient before and after upper thoracic sympathectomy for the control of essential hyperhidrosis. For normal individuals, hourly 24-h melatonin concentrations in plasma and CSF exhibited similar profiles, with low levels during the day and high levels at night. Peak plasma levels varied from 122-660 pmol/L, and the peak CSF levels from 94-355 pmol/L. The onset of the nocturnal increase in melatonin did not occur at the same time for each individual. Urinary 6-hydroxymelatonin levels also exhibited a daily rhythm, with peak excretion at night. The individual with the lowest nocturnal levels of circulating melatonin also had the lowest excretion of 6-hydroxymelatonin. In the patient with hyperhidrosis, a prominent melatonin rhythm was observed preoperatively in the CSF and plasma. After bilateral T1-T2 ganglionectomy, however, melatonin levels were markedly reduced, and the diurnal rhythm was abolished. These results provide direct evidence in humans for a diurnal melatonin rhythm in CSF and plasma as well as regulation of this rhythm by sympathetic innervation.

Adult↗
PubMed1991

Central nervous system involvement in Von Hippel-Lindau disease.

Fifty individuals with Von Hippel-Lindau disease (VHL) were studied with gadolinium-enhanced magnetic resonance imaging (MRI) to determine the frequency and distribution of CNS lesions. The associated clinical features were also reviewed. Thirty-six (72%) of the 50 had 1 or more CNS tumors. The most frequently affected sites in the CNS excluding the retina were the cerebellum (52%), spinal cord (44%), and brainstem (18%). New regional predilections for the craniocervical junction and conus medullaris were demonstrated by this study. Forty-one percent of all VHL patients with CNS tumors were neurologically asymptomatic: cerebellar tumors (50%), spinal cord tumors (50%), and brainstem tumors (44%) were often without clinical signs or symptoms. Multiple lesions were common. The mean age of all VHL patients (34.5 years) was similar to the mean age of all CNS VHL patients (34.4 years), suggesting a lack of age association. CNS lesions commonly occurred in the 2nd decade of life. All patients at risk for VHL should be evaluated using gadolinium-enhanced MRI after 10 years of age, although ophthalmic examination should be initiated within the 1st 2 years of life. Enhanced MRI is particularly useful in the detection of CNS tumors in patients with the VHL gene.

Adolescent↗
PubMed1990

Localization of the von Hippel-Lindau disease gene to a small region of chromosome 3.

We studied 25 families with von Hippel-Lindau disease (VHL) to locate VHL more precisely on chromosome 3. We found that VHL was linked to RAF1, confirming previous observations, and to two polymorphic DNA markers, D3S18 and D3S191. Multipoint linkage analysis indicated that the most likely location for VHL was in the interval between RAF1 and D3S18. D3S18 was located at 3p26. Genetic heterogeneity was not detected in this panel of von Hippel-Lindau disease families. The polymorphic markers RAF1, D3S18, and D3S191 should be useful in identifying asymptomatic gene carriers in VHL families and in guiding efforts at gene isolation.

Chromosome Mapping↗
PubMed1990

Pulsatile growth hormone secretion in patients with acromegaly and normal men: the effects of growth hormone-releasing hormone infusion.

Twenty-four GH secretory patterns were studied before and during continuous infusions of GHRH in six patients with active acromegaly and in six normal adult men. GH release was episodic in both groups. Control subjects showed a normal diurnal variation in GH release, with the majority of GH released at night (2200-0800 h); mean levels were 1.5 +/- 0.4 (SE) ng/mL (day) and 4.2 +/- 0.8 ng/mL (night). Acromegalics had no diurnal variation in GH; levels were 45.3 +/- 13.7 ng/mL (day) and 39.8 +/- 12.2 ng/mL (night). Acromegalics demonstrated an increased frequency of GH pulses compared to normals (11.8 +/- 0.8 vs. 2.2 +/- 0.3/24 h). During continuous 24-h infusions of GHRH, the normal subjects continued to show a diurnal variation in GH release, but GH pulse frequency increased to a rate (11.7 +/- 1.4 pulses/24 h) very similar to that of the patients with acromegaly. In contrast, GHRH infusion did not alter the GH pulse frequency in the acromegalics. GHRH increased the mean levels of GH in both groups (patients 80.2 +/- 20.3 vs. 41.0 +/- 12.1 ng/mL, x +/- SE. P less than 0.05; controls 10.2 +/- 2.0 vs. 3.33 +/- 0.5 ng/mL, P less than 0.01). Some of the patients with acromegaly showed a progressive decline in GH levels during the infusion period, suggesting desensitization or exhaustion of releaseable stores; however, GH levels remained above basal values in all patients. After the 24-h GHRH infusions, the GH response to a bolus of GHRH was diminished in the normal subjects (2.1 +/- 0.9 vs. 16.8 +/- 5 ng/mL, x +/- SE; P less than 0.01) but not in the acromegalic patients (30.2 +/- 8.9 vs. 35.5 +/- 12.5 ng/mL; NS). These results indicate that GH release is episodic under basal conditions and during continuous GHRH infusion in both acromegalic and normal subjects, indicating the importance of other modulators of GH release, such as somatostatin, which may remain pulsatile even in acromegaly.

Acromegaly↗
PubMed1989

Specific genetic change in tumors associated with von Hippel-Lindau disease.

Previous reports showed that the loss of DNA sequences on the short arm of chromosome 3 (3p) is consistently found in sporadic renal cell carcinomas. To evaluate the significance of this genetic change, we looked for the loss of 3p alleles in hereditary renal cell carcinomas and other tumors from patients with von Hippel-Lindau disease. Specific loss of alleles from chromosome 3p was detected with polymorphic DNA markers in 11 renal cell carcinomas, one pheochromocytoma, two spinal hemangioblastomas and one cerebellar hemangioblastoma from von Hippel-Lindau patients. Multiple renal cell carcinomas in individuals with von Hippel-Lindau disease showed loss of the same chromosome 3p alleles, which demonstrated that the same chromosome was deleted in each tumor. Analysis of haplotypes indicated that the loss of chromosome 3p alleles was from the chromosome bearing the balancing, wild-type allele of the VHL gene. These results are consistent with the concept that the VHL gene is a recessive oncogene. Renal cell carcinoma, pheochromocytoma, and spinal and cerebellar hemangioblastomas develop in predisposed family members when somatic mutational events lead to loss of chromosome 3p sequences bearing the wild-type allele of the VHL gene.

Alleles↗