Differential regulation of matrix Gla protein (MGP) gene expression by retinoic acid and estrogen in human breast carcinoma cells

Expression of matrix Gla protein (MGP) gene and its regulation by retinoic acid (RA) and estrogen was investigated in eight human breast cancer cell lines. The promoter region of the MGP gene contains a consensus retinoic acid response element (RARE) and the MGP gene expression has been shown to be strongly induced by RA in other systems. Our results suggest that RA negatively regulates MGP mRNA expression in human breast cancer cells that have high levels of estrogen receptors (ER), i.e. MCF-7, ZR-75 and BT474 and positively regulates its expression in cells with either no ERs, i.e. MDA-MB-468 or very low levels of ERs, i.e. T47D. This indicates that ER levels may affect RA modulation of MGP gene expression in human breast cancer cells. The inhibitory effect of RA on MGP gene expression was abolished in RRO-I, the RA-resistant MCF-7 subline. We also demonstrate for the first time that estrogen strongly induces MGP gene expression in ER-positive cells and that estrogen-mediated induction of MGP is blocked by RA even in otherwise RA-resistant cells.

The mode of action of primary bile salts on human platelets

Cholate and its conjugated amide derivatives glycocholate and taurocholate solubilized human platelets differently as studied by the observations on: (1) the change in optical absorbance of platelet suspension, (2) marker leakiness and (3) component solubility. Cholate ruptures the membrane in an all-or-none process, while both conjugated derivatives shed off both proteins and lipids. The shed lipids formed vesicles and could be separated from the proteins. The conjugated salts gradually chop off the cell membrane into pieces causing the cells to become small spheres (1.5 microns in diameter) as revealed by scanning electron microscopy, which also revealed that morphological change of platelet in these bile salts depended on both concentration and incubation period. Platelets at the prelytic-stage concentration of these three salts deformed initially to spiculate disc and finally to a stretched-out flat form. Also, in the prelytic stage of these bile salts, platelets showed inhibited responses to thrombin which did not happen to platelets in deoxycholate (Shiao et al. (1989) Biochim. Biophys. Acta 980, 56-68.).

[Intrathecal meperidine attenuates shivering induced by spinal anesthesia]

Shivering is a common and complex phenomenon that occurs in many patients during spinal anesthesia. Shivering can increase oxygen consumption up to 500 per cent which may be detrimental to patients with decreased myocardial reserve. The metabolic costs and cardiorespiratory consequences of shivering are important particularly for patients with anemia, coronary arterial disease, cardiopulmonary insufficient, debilitated status or are elderly. We studied whether intrathecal meperidine could prevent shivering after spinal anesthesia. 60 patients with ASA class I-II were divided into intrathecal meperidine group (Group I) (n = 30) and control group (Group II) (n = 30). Group I received spinal tetracaine 12-16 mg with meperidine 0.2 mg/kg and Group II received spinal tetracaine 12-16 mg without meperidine. During operation the highest level of spinal anesthesia, ambient and rectal temperatures, blood pressure (BP) and heart rate (HR), presence or absence of shivering, intensity of shivering in both groups were recorded. Close observation for side effects was given post-operatively. There was a significant reduction (p < .005) in incidence of shivering in group I patients (16.7%) when compared with group II (56.7%). There was no or less side effects observed with other neuraxial opioids except nausea. We concluded that intrathecal meperidine could suppress shivering induced by spinal anesthesia.

[Nifedipine in preeclampsia for cesarean section]

The patients with preeclampsia undergoing emergent cesarean section is always a challenge to an anesthesiologist, because severe hypertensive response after laryngoscopy and tracheal intubation may result in life-threatening complication such as cerebral hemorrhage. Most of these patients receive magnesium sulfate for the prevention of convulsion. An ideal anti-hypertensive drug for preeclampsia should be effective, limited fall in blood pressure, rapid onset, maintaining uteroplacental blood flow, and less maternal and fetal side effects. We studied the efficacy of 10 mg sublingual nifedipine in attenuating the pressor response to intubation. We were also concerned about whether this calcium antagonist may inhibit uterine contraction and increase intra and postpartum hemorrhage when it is used with magnesium sulfate and general anesthesia. There were thirty-three patients in our study (16 in nifedipine group and 17 in control group). This study revealed that nifedipine attenuate the hypertensive response effectively. Uterine contraction response to oxytocic drugs was quite well in both groups. There was no significant difference in blood loss between nifedipine and control group. And no severe maternal and fetal adverse effect.

A stationary hemispherical SPECT imager for three-dimensional brain imaging

A completely stationary, hemispherical-coded aperture SPECT imaging system was designed to produce three-dimensional images of the brain. The system consisted of a hemispherical multiple-pinhole coded aperture and 20 small (100 x 100 mm crystal area) digital gamma cameras. Reconstructions and measured performance specifications from two laboratory versions of the imager are presented. The reconstructed field of view of these systems was an ellipsoidal region with semi-diameters of 100 x 100 x 50 mm. The reconstructed spatial resolution for a point source in air at the center of this field was found to be 4.8 mm FWHM and the corresponding system sensitivity was 36 cps/microCi. An analysis using an ideal-observer model indicated that the multiplexed projection data suffered a 21% degradation relative to similar, but nonmultiplexed SPECT data. Therefore, by this measure, the effective sensitivity of the brain imager was 79% of the measured value.

Cloning and characterization of an alpha-amylase gene from Streptomyces lividans

The alpha-amylase gene (amy) of Streptomyces lividans TK24 was cloned in an amylase deficient mutant strain S. lividans M2. The cloned gene contained an open reading frame (ORF) of 2757 nucleotides (919 amino acids) coding for a protein of 100 kDa. Sequencing of the amino terminus of the extracellular alpha-amylase protein revealed the presence of a signal peptide of 33 amino acid residues. The transcriptional initiation site was mapped by the primer extension method with T4 DNA polymerase and was found to be transcribed from an unique promoter. The alpha-amylase protein produced by S. lividans was larger than those derived from other origins. It also contained the four common conserved regions characteristic of other alpha-amylase proteins.

The opioid receptor binding of dezocine, morphine, fentanyl, butorphanol and nalbuphine

The ability of morphine, fentanyl, butorphanol, nalbuphine, and dezocine to compete with radiolabeled ligands for binding at the mu1, mu2, kappa1, and delta opioid receptors and the sigma receptor was characterized. In the absence of sodium, the potency of opioid receptor competition at each receptor site was found to be: mu1-fentanyl > butorphanol > morphine > or = dezocine = nalbuphine; mu2-butorphanol > fentanyl > nalbuphine > morphine = dezocine; kappa1-butorphanol > nalbuphine >> morphine > or = dezocine > fentanyl; and delta-butorphanol > nalbuphine > or = dezocine > morphine > fentanyl. For all five compounds, competition at the sigma receptor was weak, with nalbuphine and dezocine having Kis of approximately 0.5 microM and the other opioids having Kis of greater than 1 microM. Since the presence of 100 mM NaCl during the competitive binding decreased the K(i), to varying degrees, of all five opioids at the mu1 and delta receptors and of some of the opioids at the mu2 and kappa1 receptors, the five compounds studied appear to differ in efficacy at the five receptor sites.

MR of human postmortem brain tissue: correlative study between T2 and assays of iron and ferritin in Parkinson and Huntington disease

PURPOSE

To test the hypothesis that the T2 shortening observed on MR images of the brain in patients with Parkinson and Huntington diseases is due to tissue iron deposition.

METHODS

Tissue iron and ferritin assays were performed on postmortem putamen and globus pallidus samples from subjects with Huntington and Parkinson disease. The assays were correlated with T2 measurements. Normal samples were included as controls.

RESULTS

There were significant differences in T2 values, and iron and ferritin concentrations among the putamen samples. Compared with normal controls, subjects with Huntington disease had approximately a threefold increase in iron and a sixfold increase in ferritin concentrations; however, they also had the longest T2 values. Parkinson disease putamens had milder elevations of iron concentrations above that of controls (33%) and demonstrated slightly shorter T2 values. The globus pallidus samples demonstrated a similar trend in their T2s, iron, and ferritin levels, but there was a larger overlap in the T2 values.

CONCLUSIONS

Our results indicate that tissue iron and ferritin concentrations are elevated in the brains of subjects with both Parkinson and Huntington disease but the elevated concentrations do not correlate with T2 shortening. Although iron and ferritin can shorten T2, we conclude that other factors must play a significant role in determining the T2 relaxation time and that iron or ferritin are not dominant in this regard.

Etonitazene: an opioid selective for the mu receptor types

Specific radioligand binding protocols were utilized to compare the affinity of morphine and the high-potency opioid etonitazene at mu 1, mu 2, delta, kappa 1 and sigma receptors. Both etonitazene and morphine displayed a mu 1-selective binding profile; however, etonitazene had a 2500-fold higher affinity at this receptor type. The latter result is consistent with the relative potencies or morphine and etonitazene in various behavioral tests.

[Intramuscular meperidine for the prevention of shivering in spinal anesthesia]

Intravenous meperidine 25mg has been employed effectively to treat shivering following regional anesthesia and general anesthesia. The study was designed to evaluate the effectiveness of intramuscular meperidine for the prevention of shivering in spinal anesthesia. The series consisted of 60 patients who were divided into 2 groups with 30 patients in each, undergoing lower abdominal or lower extremity surgery. All patients were given diazepam 0.1mg/kg i.v. for anxiolysis when they came to the operating room. In a double blind and randomized fashion, patients in the study (meperidine) group received meperidine 25mg IM (= 0.5ml). In the control group 0.9% N/S 0.5ml IM was given instead. All patients received spinal anesthesia 15 minutes later. Measurement of the levels of sensory loss to pinprick was made. The ambient temperature and the rectal temperature were continuously monitored to evaluate the effect of the change in body temperature on shivering during operation. The degree and the occurrence of shivering were carefully evaluated and recorded by a blind-trust observer. There was no significant difference in maximal analgesic level, ambient temperature and change of rectal temperature during operation between the groups. Shivering occurred in 17 patients (56.7%) in the saline group with an onset time of 7.9 +/- 2.5min following spinal anesthesia. In the meperidine group, shivering occurred only in 3 patients (10%) with an onset time of 54 +/- 29.5min after spinal anesthesia. There was a significantly lower incidence of shivering in the meperidine group than in the saline group (p < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin-like growth factor binding protein-5 gene expression is differentially regulated at a post-transcriptional level in retinoic acid-sensitive and resistant MCF-7 human breast carcinoma cells

Insulin-like growth factor binding protein (IGFBP) gene expression and IGFBP secretion were investigated in a retinoic acid (RA)-resistant subline (RROI) of MCF-7 human breast carcinoma cells. Our results demonstrate that RRO-I cells constitutively secrete higher levels of IGFBP-3 and IGFBP-5. In addition, we found that a 5-fold increase in IGFBP-5 mRNA levels observed in RRO-I cells, which eventually leads to a similar increase in the secreted levels of IGFBP-5, was partly due to an increase in the stability of IGFBP-5 mRNA. Actinomycin D and cycloheximide differentially stabilized IGFBP-5 mRNA in MCF-7 cells but not in RRO-I cells, indicating a difference in the control of IGFBP-5 gene regulation at the level of mRNA stability in these cell lines.

Expression of growth factor mRNA in rabbit PVR model systems

Proliferative vitreoretinopathy (PVR) involves the formation of intravitreal fibrocellular membranes which may lead to traction retinal detachment and blindness. The cellular component of epiretinal membranes originates from the proliferation and migration of cells within the eye. Several growth factors and other cytokines are plausible candidates for directing the processes leading to membrane formation. A reproducible animal model is needed for experimental studies of cytokine expression during PVR induction or treatment. We found that intravitreal injection of > 10(6) mixed mononuclear leukocytes or adherent monocytes along with a trans-scleral incision through the pars plana leads to the development of PVR-like disease in rabbit eyes. The severity of the disease was related to the number of monocytes injected. Typically, organized membranes extending from the incision toward the optic nerve formed within one week. Progression to extensive traction retinal detachment required 1 to 4 weeks. Injection of up to 5 x 10(6) lymphocytes or freeze-thaw killed monocytes was ineffective, and coinjecting 100 micrograms endotoxin with the monocytes did not result in enhanced disease. The histological appearance of the epiretinal membranes was similar to human PVR membranes. Macrophage, cytokeratin-positive (epithelial), and fibroblast-like cells were present. Northern blot analysis of RNA extracted from the rabbit membranes revealed the presence of mRNA for acidic fibroblast growth factor (aFGF). Acidic FGF mRNA was not expressed by the injected monocytes. A comparable level of aFGF mRNA and also mRNAs for basic FGF, platelet-derived growth factor-B, and transforming growth factor beta were found in epiretinal membranes induced by a scleral incision in association with cryopexy.(ABSTRACT TRUNCATED AT 250 WORDS)

Prenatal protein malnutrition in rats enhances serotonin release from hippocampus

The effect of prenatal protein malnutrition on central serotonin metabolism was assessed in 220- to 240-d-old male rats. The malnourished rats (denoted 6,25 group) were males born to dams fed a 6% casein diet during pregnancy and fostered at birth to dams fed a control (25% casein) diet. They were compared with males born to dams fed 25% casein diet. Tissue concentrations of serotonin, 5-hydroxyindoleacetic acid, 5-hydroxytryptophan, L-tryptophan and catecholamines in the hippocampal formation in the 6,25 group were similar to those of well-fed controls (25,25 group). However, a twofold greater basal serotonin efflux from hippocampal slices of 6,25 rats compared with slices from 25,25 rats was observed during a 20-min incubation period. Hippocampal [3H]paroxetine binding indicated that there was no alteration of apparent maximal binding and affinity of the serotonin transporter in the 6,25 rats. In addition, there was no difference in serotonin receptor binding in hippocampal membranes from 6,25 and 25,25 rats. The results indicate that prenatal protein malnutrition causes selective changes in central serotonin metabolism.

Insulin-like growth factor-I (IGF-I) and retinoic acid modulation of IGF-binding proteins (IGFBPs): IGFBP-2, -3, and -4 gene expression and protein secretion in a breast cancer cell line

Retinoic acid (RA) blocks insulin-like growth factor-I (IGF-I) stimulation of proliferation in the MCF-7 breast carcinoma cell line, and this is associated with the appearance of 42- to 46-kilodalton (kDa) IGF-binding proteins(s) (IGFBPs) in the conditioned medium (CM), in addition to the approximately 34- and 27-kDa IGFBPs present in the CM of unstimulated cells. Using immunological, biochemical, and molecular biological criteria, we have identified the 27-kDa band as IGFBP-4, the 34-kDa band as IGFBP-2, and the 42- to 46-kDa band as IGFBP-3. IGF-I alone stimulated MCF-7 cell proliferation, and this was associated with a large increase in IGFBP-2 in the CM. RA alone resulted in increased IGFBP-4 levels and the appearance of IGFBP-3 in the CM. The combination of RA and IGF-I, which resulted in decreased cellular proliferation, was associated with the appearance of IGFBP-3 in the CM at levels far exceeding those seen with RA alone. The effect of IGF-I on IGFBP-2 levels and the synergistic action of IGF-I and RA on IGFBP-3 levels in CM were blocked by alpha IR3, a monoclonal antibody to the human IGF-I receptor, indicating that these effects required signal transduction through the IGF-I receptor. IGFBP-2, -3, and -4 mRNAs were detected in unstimulated MCF-7 cells. RA increased IGFBP-3 mRNA levels, suggesting that transcriptional events contribute to the RA stimulation of IGFBP-3 appearance in CM. In contrast, the increase in IGFBP-2 protein in CM after IGF-I treatment appeared to be greater than the increase in IGFBP-2 mRNA levels. The increase in IGFBP-3 protein in CM in response to the combination of RA and IGF-I was much greater than the increase in IGFBP-3 mRNA. These results suggest that the action of RA and IGF-I in combination to increase IGFBP-3 protein in CM is principally translational or posttranslational. We speculate that RA inhibition of IGF-I-stimulated MCF-7 cell proliferation may be due to IGFBP-3, or that increased levels of IGFBP-3 in response to growth inhibition represent a compensatory response.

Conversion of premalignant human cells to tumorigenic cells by methylmethane sulfonate and methylnitronitrosoguanidine

Nine human tumor cell lines derived from both epithelial and mesenchymal tumors exhibited either an anchorage-independent growth non-tumorigenic phenotype or an anchorage-independent tumorigenic phenotype. Transformed epithelial cell lines with the non-tumorigenic phenotype could be converted to a progressively growing tumor phenotype following treatment with either methylmethane sulfonate (MMS) or N-methyl-N'-nitro-N-nitro-soguanidine (MNNG). In contrast, sarcoma derived cell lines with a non-tumorigenic phenotype could be converted to a progressively growing tumor phenotype only with MNNG. SV40 immortalized HET-1A non-tumorigenic phenotype cells could be converted to a progressively growing tumorigenic phenotype, infrequently, when treated with MNNG, but not MMS. Progressively growing tumors produced by either MMS or MNNG treated non-tumorigenic phenotypes exhibited metastatic potential in nude mice. Chemically treated HET-1A cells acquired the ability to produce tumor in mice but the tumor did not exhibit metastatic potential. In contrast, populations of tumorigenic cells were not rendered more biologically aggressive after treatment with either MMS or MNNG; i.e., the latency period for tumor development was not accelerated and the tumors did not exhibit metastatic potential. These results suggest that the biological effects of MMS and MNNG on non-tumorigenic, tumorigenic and immortalized cell lines are phenotype specific.

IGFBP-3 gene expression and estrogen receptor status in human breast carcinoma

Insulin-like growth factors (IGF) I and II are potent mitogens for breast carcinoma proliferation. IGF-mediated proliferative activity can be markedly enhanced by the presence of specific IGF-binding proteins (IGFBPs). IGFBP-3 has been shown to enhance IGF-mediated growth in a number of systems. Studies have demonstrated IGFBP-3 secretion only in estrogen receptor (ER)-negative breast carcinoma cell lines while IGFBP-3 could not be detected in media conditioned by ER-positive cell lines. We investigated whether a relationship exists between ER status and IGFBP-3 mRNA expression in human breast carcinoma biopsy specimens. We have detected IGFBP-3 mRNA in breast carcinoma tissue obtained from patients utilizing in situ hybridization. Quantitation of IGFBP-3 mRNA levels was performed utilizing image cytometry. There was a significantly higher expression of IGFBP-3 mRNA in ER-negative breast carcinoma specimens when compared to the ER-positive specimens. Whether this higher expression of IGFBP-3 mRNA and presumed secretion of IGFBP-3 by ER-negative tumors play a role in the rapid proliferation and poor prognosis of these tumors remains to be determined.

pH transients evoked by excitatory synaptic transmission are increased by inhibition of extracellular carbonic anhydrase

Excitatory synaptic transmission has been associated with a rapid alkalinization of the brain extracellular space. These pH shifts are markedly increased by acetazolamide, an inhibitor of carbonic anhydrase. Although this effect can be readily explained by inhibition of extracellular carbonic anhydrase, this enzyme has been considered strictly intracellular in the central nervous system. To determine whether these alkaline shifts are regulated by extracellular carbonic anhydrase, we studied the effects of a membrane impermeant, dextran-bound inhibitor of this enzyme. Extracellular alkaline transients, measured with pH-sensitive microelectrodes, were generated in the CA1 region of rat hippocampal slices by repetitive electrical stimulation of Schaeffer collateral fibers or by local ejection of glutamate. More direct alkalinizations were elicited by focal ejection of NaOH in the vicinity of a pH microelectrode. These pH transients were reversibly enhanced by addition of the dextran-bound inhibitor. We conclude that there is significant carbonic anhydrase activity in the extracellular space of the brain. We postulate that this enzyme functions in the regulation and modulation of extracellular pH transients associated with neuronal activity.

Extracellular alkaline shifts in rat hippocampal slice are mediated by NMDA and non-NMDA receptors

1. The pharmacology of synaptically evoked extracellular alkaline shifts was studied in the CA1 area of rat hippocampal slices. 2. Stimulus-evoked alkalinizations were unaffected by 2-amino-5-phosphonovalerate (APV) (20 microM). 3. 6-Cyano-7-nitro-nitroquinoxaline-2,3-dione (CNQX) (10 microM) inhibited the alkalinizations. In the continued presence of CNQX, an APV-sensitive, picrotoxin-insensitive, alkaline shift was elicited in low Mg2+ media. 4. Antidromic stimulation produced small alkaline shifts in comparison with orthodromic activation. 5. Our results demonstrate that in the hippocampal CA1 region, synaptically evoked alkalinizations can arise through both N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors. These responses cannot be explained by cell firing per se.

Identification of six open reading frames from a region of the Azotobacter vinelandii genome likely involved in dihydrogen metabolism

We reported earlier the identification of two Azotobacter vinelandii open reading frames (ORFs), ORF1 and ORF2, downstream from the hydrogenase structural genes (Chen, J.C. and Mortenson, L.E. (1992) Biochim. Biophys. Acta 1131, 122-124). Sequencing of 6008 base pairs of DNA immediately downstream from ORF2 revealed six additional ORFs (ORF3 through ORF8). All six ORFs are transcribed from the same DNA strand as that of the ORF1 and ORF2. Deduced amino acid sequences of ORF3 through ORF5, and those of ORF4, ORF5, ORF7 and ORF8 have strong homology with genes required for dihydrogen (H2) metabolism in Rhodobacter capsulatus and in Escherichia coli, respectively. ORF4, ORF5, ORF6 and ORF8 would encode for polypeptides containing one or more 'Cys-X-X-Cys' motifs. The predicted products of ORF5 and ORF6 each contain a histidine-rich region, and the product of ORF5 also includes a 'Cys-Thr-Val-Cys-Gly-Cys' region near its amino-terminus. Implications of these findings with respect to metal binding, transport and incorporation, to hydrogenase assembly and to H2 metabolism are discussed.

Oxygen consumption and ammonia-N excretion of Penaeus chinensis juveniles exposed to ambient ammonia at different salinity levels

1. Oxygen consumption rate (O2 mg/g/hr) and ammonia-N (un-ionized plus ionized ammonia as nitrogen) excretion rate (microgram/g/hr) of Penaeus chinensis juveniles (0.54 +/- 0.11 g) decreased with increase of salinity among 10, 20 and 30 ppt. 2. Oxygen consumption rate increased with increase of ambient ammonia-N at three salinity levels. 3. Ammonia-N excretion rate was highest (204 micrograms/g/hr) in P. chinensis exposed to 0.985 mg/l ammonia-N at 10 ppt, and lowest (-416 micrograms/g/hr) in that exposed to 9.897 mg/l ammonia-N at 30 ppt. 4. In the prawns exposed to 9.921 mg/l ammonia-N at 20 ppt, and to 5.087 and 9.897 mg/l ammonia-N at 30 ppt, ammonia-N excretion was heavily depressed and ammonia-N influx occurred (ammonia-N uptake was much higher than ammonia-N excretion).

Alkaline extracellular pH shifts generated by two transmitter-dependent mechanisms

Recent studies of the effect of γ-aminobutyric acid (GABA) on brain extracellular pH are reviewed. Experiments were performed on isolated turtle cerebellum, using double-barrelled pH-sensitive microelectrodes. Superfusion of GABA (1 mM) caused a rapid extracellular alkaline shift accompanied by a rise in extracellular K+. Washout of GABA was often associated with an acid rebound, concomitant with an undershoot of extracellular K+. The GABA-evoked alkaline shift was blocked by picrotoxin and mimicked by the GABA-A agonists isoguvacine and muscimol. The response persisted in the nominal absence of extracellular calcium, but it was reversibly abolished in nominally bicarbonate free media. In contrast, extracellular alkaline shifts evoked by repetitive stimulation of the parallel fibers were amplified in bicarbonate-free media and were insensitive to picrotoxin. These results indicate the existence of separate, transmitter-dependent mechanisms of extracellular alkalinization: (i) a GABA-A receptor mediated process, most likely associated with efflux of bicarbonate ions across GABA-A anion channels and (ii) a bicarbonate-independent process associated with excitatory synaptic transmission.Key words: GABA, bicarbonate, extracellular pH, alkaline shift.

Two open reading frames (ORFs) identified near the hydrogenase structural genes in Azotobacter vinelandii, the first ORF may encode for a polypeptide similar to rubredoxins

Sequencing of 744 base pairs (bp) of a cloned section of DNA from Azotobacter vinelandii reveals two complete, closely-spaced open reading frames (ORF1 and ORF2). Both ORFs are transcribed from the same DNA strand as that of the structural genes for hydrogenase (hoxK and hoxG, Menon, A.L. et al. (1990) Gene 96, 67-74), and are located downstream from the latter genes. The distance between the end of hoxG and the beginning of ORF1 is approx. 3.0 kilobases (kb). Most of the deduced amino acid sequence of ORF1 shares high homology with rubredoxin sequences. Some of the deduced amino acid sequence of ORF2 shares homology with that of a reported partial ORF from Rhodobacter capsulatus, ORF located within a region of DNA required for dihydrogen oxidation in that organism. Implications of these findings with respect to dihydrogen metabolism are discussed.

Suspected dural arteriovenous fistula: results with screening MR angiography in seven patients

Previous studies have shown that spin-echo (SE) magnetic resonance (MR) imaging has been helpful in the assessment of dural arteriovenous fistula (DAVF); however, direct visualization of the fistula site is limited. Thus, conventional plain angiography is required to establish the diagnosis. Because of this limitation, the additional use of MR angiography may improve noninvasive screening for this disorder. Seven patients with DAVFs proved at plain angiography were evaluated with SE MR imaging and with three-dimensional (3D) time-of-flight (TOF) MR angiography. In six of seven cases, 3D TOF MR angiography demonstrated the fistula site. Correlation was good when compared with findings at plain angiography. Occlusion of the dural sinus was found at plain angiography in three of seven patients but was missed at SE imaging in all three. MR angiography also failed to demonstrate sinus occlusion in two of three patients. Arterial feeders could not be seen on SE MR images, but MR angiography improved their depiction. Plain angiography demonstrated abnormal venous drainage into distended cortical veins in three patients, but dilated cortical veins were noted in only two of the patients on both SE MR images and MR angiograms.