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Biomedical subjects

W C Small

Publications and source records attributed to W C Small.

At least 37 records · Page 2Linked to original sources
PubMed1991

Magnetic resonance imaging of the pancreas with gadolinium-DTPA.

Gadolinium (Gd)-DTPA was evaluated as a contrast agent for magnetic resonance (MR) imaging of the pancreas at 1.5T. Twenty-five patients were imaged with identical gradient-echo (GE) (TR 47, TE 13, 80 degree pulse angle) and spin-echo (SE) (TR 300, TE 15) MR sequences prior to and following an intravenous bolus of 0.1 mmol/kg Gd-DTPA. Marked pancreatic enhancement was demonstrated on dynamic sequential breath-hold GE images obtained immediately following the Gd-DTPA bolus (116% mean enhancement over pre-Gd-DTPA images). Enhancement decreased but persisted on the SE images obtained approximately 5 and 15 min following the Gd-DTPA bolus (65 and 60% mean enhancement, respectively). Five of the patients had a pancreatic mass. In these five patients, the enhancement of pancreatic tissue resulted in improved conspicuity of the mass. These initial results suggest that pancreatic enhancement occurs following an intravenous bolus of Gd-DTPA and has the potential to improve MR visualization of pancreatic masses.

Adenocarcinoma↗
PubMed1991

Gd-DTPA adrenal gland enhancement at 1.5 T.

The change in relative signal intensity of normal adrenal glands in 31 patients was evaluated following bolus administration of 0.1 mmol/kg of gadolinium diethylenetriamine pentacetic acid (Gd-DTPA). A marked increase in relative intensity of greater than 300% was observed within 2.5 min following contrast administration upon comparison of pre- and postcontrast T1-weighted gradient-echo images (TR = 47 msec, TE = 13 msec, pulse angle 80 degrees). Significantly elevated relative intensities of 55% and 44% persisted on postcontrast T1-weighted spin-echo images obtained at further delay times averaging 8 and 20 min, respectively, when compared to the identical precontrast sequence.

Adrenal Glands↗
PubMed1991

Intramitochondrial functions regulate nonmitochondrial citrate synthase (CIT2) expression in Saccharomyces cerevisiae.

We have examined the effects of perturbation of mitochondrial function on expression of two nuclear genes encoding the mitochondrial and peroxisomal forms of citrate synthase in Saccharomyces cerevisiae, CIT1 and CIT2. CIT2 expression was as much as 30-fold higher in [rho0] petites, than in isochromosomal [rho+] cells, whereas CIT1 expression was slightly down regulated in [rho0] cells. CIT2 expression was also increased in [rho+] cells by inhibition of respiration with antimycin A or in [rho+] cells containing a disruption of the CIT1 gene. These effects were additive, and together they approached the level of CIT2 expression seen in [rho0] cells. Experiments using heterologous gene fusions showed that all of the effects leading to increased expression of CIT2 were transcriptionally controlled through 5'-flanking CIT2 DNA sequences. Analysis of [rho+] and [rho0] cells containing disruptions of CIT1 and CIT2, singly and in combination, showed that the peroxisomal citrate synthase could partially spare the mitochondrial isoform for growth yield in [rho+] but not in [rho0] cells. These studies suggest a physiological role for increased expression of CIT2 in cells with altered mitochondrial function. They also provide additional evidence for a retrograde path of communication from mitochondria to the nucleus in yeast cells.

Amino Acid Sequence↗
PubMed1990

Pyrroline 5-carboxylate dehydrogenase of the mitochondrial matrix of rat liver. Purification, physical and kinetic characteristics.

The oxidation of proline to glutamate in mitochondria requires two enzymes, proline oxidase and pyrroline 5-carboxylate (P5C) dehydrogenase. In this paper we report an 800-fold purification P5C dehydrogenase from rat liver mitochondria to yield an essentially homogenous protein. The protein, whose Mr is 59,000, is an alpha 2 dimer (Mr = 115,000) in solution with an isoionic point at pH 5.7. The substrates P5C and NAD+ have apparent dissociation constants of 0.16 and 1.0 mM, respectively. Studies have been conducted to see if the conversion of glutamate and NADH to P5C and NAD+ is catalyzed by this enzyme. These studies have established that if the reverse reaction occurs the rate is 1/15,000th of the rate at which P5C is oxidized to glutamate. The concentration of the substrates needed in the assay results in a high background that interferes with accurate spectrophotometric analysis of the rate of NADH production; therefore a radiochemical (2) or a new colorimetric (3) assay was used here. A number of aldehydes were tested as substrates. It was found that the rat and human enzymes (4) have similar requirements for an aldehyde to be a substrate. Both of these proteins interacted with a polyclonal rabbit anti-rat P5C dehydrogenase serum.

1-Pyrroline-5-Carboxylate Dehydrogenase↗
PubMed1990

A quantitative colorimetric assay for semialdehydes.

We have studied the ability of the enzyme pyrroline-5-carboxylate dehydrogenase to oxidize aldehydes which are structurally similar to pyrroline-5-carboxylate, the enamine of gamma-glutamyl semialdehyde. These studies required the organic synthesis of semialdehydes not commercially available. Accurate quantitation of the concentration of these compounds in solution is necessary because they polymerize upon evaporation to dryness. Reported here is a method for colorimetric measurement of semialdehydes in solution by formation of an oxidized covalent adduct with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole. This adduct after oxidation produces a product that has an absorption maximum at 302 +/- 2 nm. This characteristic absorbance maximum was not found in the spectra of the covalent adducts of simple aliphatic aldehydes with the chromophore. Using glyoxylic acid as standard, the values obtained for the concentration of semialdehydes in solution were independently verified from quantitation of the proton concentration of the oxidized adducts by integration of the area under the peaks of their 1H NMR signals. These latter values were compared to the signal strengths of an internal standard. The values obtained by the colorimetric and NMR techniques were in excellent agreement, thus allowing use of the colorimetric technique as a simple method for routine laboratory analysis of semialdehydes.

Aldehydes↗
PubMed1990

CT and chest radiography are equally sensitive in the detection of pneumothorax after CT-guided pulmonary interventional procedures.

Pneumothorax is the most common complication after CT-guided pulmonary interventional procedures and should be promptly diagnosed and treated. Because it is easier to obtain CT scans than chest radiographs after CT-guided interventional procedures, it is important to know the sensitivity of CT in detecting pneumothoraces. To determine the sensitivity of CT for detecting procedure-induced pneumothoraces, we retrospectively reviewed 70 pulmonary interventional procedures performed under CT guidance. The sensitivity for detecting pneumothoraces with CT was compared with the detection rate with expiratory chest radiographs. Thirty-two (46%) of 70 procedures resulted in pneumothorax. Twenty-nine (91%) of the pneumothoraces were detected on CT scans and 27 (84%) were detected on chest radiographs. The difference between these two detection rates was not statistically significant (p less than .90). We conclude that postprocedure CT scans can replace expiratory chest radiographs for the detection of pneumothoraces after CT-directed pulmonary procedures.

Adult↗
PubMed1985

S-Adenosylhomocysteine hydrolase from human placenta. Affinity purification and characterization.

S-Adenosylhomocysteine hydrolase (EC 3.3.1.1) was purified to homogeneity from human placenta by using S-adenosylhomocysteine-agarose affinity chromatography. The enzyme is a tetramer with a native Mr of 189 000 and subunit Mr of 47 000-48 000; there were nine cysteine residues per subunit and no disulphide bonds. The pI was 5.7. H.p.l.c. analysis revealed that the enzyme contained four molecules of tightly bound cofactor (NAD) per tetramer, of which 10-50% was in the reduced form. The enzyme had four binding sites per tetramer for adenosine, of which 10-35% were found to be occupied. Two types of adenosine-binding sites could be distinguished on the basis of differences in rates of dissociation of the enzyme-adenosine complex, and by examining binding of adenosine at 0 degree C and 37 degrees C. The enzyme catalysed the interconversion of adenosine and 4',5'-dehydroadenosine; the equilibrium constant for this reaction was 2.1 and favoured 4',5'-dehydroadenosine formation. Variability in the specific activity of preparations of S-adenosylhomocysteine hydrolase was related to the NAD+/NADH ratio of the preparation. The capacity to bind radioactively labelled adenosine depended on the adenosine content of the purified enzyme. The rate of adenosine binding and the sensitivity of S-adenosylhomocysteine hydrolase to inactivation by adenosine were both diminished in the absence of dithiothreitol.

Adenosine↗
PubMed1984

Magnetic resonance imaging in the diagnosis of breast disease: use of transverse relaxation times.

The ability of magnetic resonance imaging (MR) to demonstrate breast carcinoma depends upon significantly different relaxation times in benign and malignant tissues. The authors conducted an in vitro study of transverse relaxation times (T2) of 393 breast tissue samples in order to establish a range of values for normal tissue, benign lesions, and carcinoma. All T2 values were multiexponential. Benign lesions were readily distinguished from both invasive and noninvasive carcinoma in samples containing fat or a mixture of fat and fibrous tissue; however, in purely fibrous samples there was some overlap of T2 values in benign and malignant tissues. Although the data acquisition and analysis requirements involved in this in vitro study exceed the capabilities of present whole-body MR imagers, the added understanding gained through efforts of this type may aid both interpretation of current images and future developments.

Adenofibroma↗
PubMed1983

Effects of alkyl-lysophospholipids on human leukemic cell lines measured by nuclear magnetic resonance.

Part of the cytotoxic action of alkyl-lysophospholipids (ALP) on leukemic cells is known to result from the lack of an O-alkyl cleavage enzyme and its antimetabolic effect which results in a toxic lysophospholipid buildup. Further, ALP (5 micrograms/ml) suppresses clonogenicity and tritiated thymidine uptake in HL60 cultures after 24 hr of exposure. The effect of ALP on two leukemic cell lines, HL60 and K562, measured by two nuclear magnetic resonance (NMR) techniques and examined by electron microscopy is reported. 31P-NMR spectroscopy indicates that the adenosine 5'-triphosphate:adenosine 5'-diphosphate ratios are unaffected after 24 hr, as is mitochondrial morphology, judging by electron micrographs. However, cell membrane integrity in HL60 is altered at that time. The earliest ALP effects occur in NMR internal water relaxation at 1 hr after ALP exposure, followed by a small reduction in tritiated thymidine uptake at 4 hr. No effect is observed in K562 cell cultures in morphology or NMR measurements. No new 31P-labeled metabolites were detected in either cell line as a result of drug treatment.

Adenosine Diphosphate↗
PubMed1982

The effect of the cryoprotectants, dimethylsulfoxide and glycerol on water transport in the human red blood cell.

The response of human red blood cells to the cryoprotective agents, DMSO and glycerol, has been investigated using a pulsed NMR method. The experimentally determined parameters are: (1) the intracellular transverse relaxation time, T2a; (2) the mean residence time of intracellular water, tau a, which is effectively a reciprocal measure of the rate of water transport across the red blood cell membrane; and (3) the activation energy for this process. The quantitative data indicate that the observed effects are colligative rather than species-specific in origin.

Biological Transport↗
PubMed1981

The effect of changing extracellular osmolality on water transport in the human red blood cell as measured by the cell water residence time and the activation energy of water transport.

A pulse NMR technique employing low extracellular Mn2+ concentrations has been used in following the effect of variations in extracellular osmolality on water transport through the human red blood cell membrane. We report results including the effect of osmolality on the cell water lifetime (tau a) and, for the first time, the effect on the proton spin-spin relaxation of the intracellular water (T2a) and the activation energy for the water transport process. Current results are encouraging in correlating the effects seen in this study with suspected membrane functional changes occurring in both in vivo and in vitro aging and during in vitro preservation attempts.

Adult↗
PubMedDate not supplied

Citrate synthase 1 interacts with the citrate transporter of yeast mitochondria.

We have previously shown that citrate synthase binds to an intrinsic protein of the mitochondrial inner membrane (D'Souza and Srere, 1983). In this paper we present evidence that this citrate synthase binding protein is the citrate transporter. We have used citrate synthase 1 mutants of Saccharomyces cerevisiae and transformants containing citrate synthase inactivated by site-directed mutagenesis to study the effect of the CS1 protein upon mitochondrial function (Kispal and Srere). In the present study citrate uptake and oxidation were measured during state 3 conditions (presence of 200 microM ADP) in the mitochondria of several strains of Saccharomyces cerevesiae: a parental strain containing wild-type mitochondrial citrate synthase (CS1) and strains derived from a CS1 deficient strain in which the CS1 gene was disrupted by insertion of the LEU2 gene. These strains were generated from the CS1- cells by transformation with vectors encoding site-specific mutants of CS1 possessing very low levels of enzymatic activity. One such strain in this study was subsequently found to have undergone reversion to produce a strain which had activity very similar to wild type. Positive correlation between citrate uptake and the rate of citrate oxidation was found, suggesting coupling of the two processes. Both mitochondrial citrate uptake and oxidation were decreased in the mutant lacking any form of CS1 protein. Reintroduction of mutagenized CS1 into yeast causes an enhancement in the rate of state 3 oxygen consumption and of citrate uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Carrier Proteins↗
PubMedDate not supplied

Immunological mapping of fine molecular surface structures of citrate synthase enzymes from different cell types.

Citrate synthase (EC 4.1.3.7), which is present in all living organisms as a key enzyme in aerobic energy metabolism, is one of the most highly phylogenetically conserved enzymes known in terms of its primary and active site structure. However, in terms of other parameters such as in vitro stability, tolerance to changes in pH, degree of self-polymerization, etc., citrate synthases from different sources are markedly different. These divergences can be observed even between isoforms of the enzyme within the same species. Data documenting these diversities suggest that a high degree of difference in tertiary structures may occur. Therefore, the surface profiles of citrate synthase enzymes from yeast, pig, rat, tomato and Escherichia coli were investigated with immunological methods using monoclonal antibody families generated against either pig citrate synthase (alpha-PCS) or yeast citrate synthase-2 (alpha-YCS-2). A high degree of homology of enzyme epitopes was detected on the mitochondrial citrate synthases originating from yeast, tomato, pig and rat cells. Major differences were found between the hexameric citrate synthase originating from E. coli compared with those dimeric forms prepared from eukaryotic cells. Only modest similarities were detected between the highly homologous peroxisomal and mitochondrial yeast citrate synthases. Furthermore, a point mutation of one of the catalytic residues (H274R on recombinant pig and H313R on yeast enzyme) of mitochondrial citrate synthase (CS-1) resulted in a significant increase in immunological similarity with the peroxisomal isoenzyme (CS-2). These findings are discussed in terms of the possible mechanism of evolution of CS-2 in yeast.

Animals↗
PubMedDate not supplied

Enhancement effects of a hepatocyte receptor-specific MR contrast agent in an animal model.

The enhancement characteristics of the liver and spleen produced by a hepatocyte-specific magnetic resonance imaging agent, an arabinogalactan-coated ultrasmall superparamagnetic iron oxide derivative, BMS 180550, were evaluated. Both heavily T1- and T2-weighted sequences were used. Imaging was performed in the farm pig model, as a function of contrast agent concentration (5, 10, and 20 mumol of iron per kilogram) and delay (immediate, 0.5, 2.5, 5.0, 7.5, and 9.0 hours) after bolus injection of BMS 180550. BMS 180550 provided excellent contrast enhancement characteristics by producing marked positive enhancement with T1-weighted sequences and marked negative enhancement with T2-weighted sequences. The T1-weighted enhancement immediately after contrast agent injection was of greater magnitude in the spleen (329% +/- 83) than in the liver (66% +/- 16). Postcontrast negative enhancement with T2-weighted sequences was largely hepatocyte specific at 5 and 10 mumol/kg but was also seen within the spleen at 20 mumol/kg. The authors discuss the possible mechanisms that produce these changes and conclude that 10 mumol/kg BMS 180550 is near the optimum dose for maximizing the enhancement properties of this agent with all sequences in the farm pig.

Animals↗
PubMedDate not supplied

Safety and optimum concentration of a manganese chloride-based oral MR contrast agent.

To determine the safety of a manganese chloride-based oral magnetic resonance (MR) contrast agent and the ideal concentration of the agent for marking in three different anatomic sites (stomach, middle of the small bowel, and ileocecal region), six healthy volunteers were evaluated before and after administration of 900 mL of three different concentrations of the contrast agent. Images were evaluated subjectively and objectively. No adverse events were noted. There was a minimal rise in manganese blood levels at 6 hours after administration, with a return to baseline at 24 hours. The imaging data demonstrated good-to-excellent bowel marking on T1-weighted images at all three concentrations. However, on T2-weighted images, the 40 mg Mn+2/L concentration provided improved hypointense bowel marking relative to the 20 mg/L concentration. Little difference was seen between the 40 and 60 mg/L concentrations. Fast T1- and T2-weighted sequences provided superior image quality to that of conventional spin-echo sequences.

Administration, Oral↗
PubMedDate not supplied

Does CTAP prior to hepatic resection improve patient survival rates?

The purpose of our study was to compare survival rates of colon carcinoma patients who had undergone attempted curative hepatic resection based on liver staging by computed tomographic angiography (CTA) or portography (CTAP) with previously reported survival rates of patients who underwent similar surgery without preoperative CTAP evaluations. A total of 404 CTAP studies performed at three institutions were reviewed. Of this group, 197 had colon carcinoma. Sixty-nine of the colon patients went to surgery. Actuarial adjusted yearly survival rates were calculated for the prior CTAP colon group and compared to historical controls. The control survival data were taken from reports published prior to the CTAP era. Our study demonstrated no difference in the 1-year survival data between the groups. However, the CTAP patients had greater survival in years 2-4. This greater survival may be multifactorial but in part due to better surgical selection caused by CTAP.

Actuarial Analysis↗