Prevention of hemodialysis fistula thrombosis. Early detection of venous stenoses

Venous dialysis pressures were measured consecutively in 168 chronic hemodialysis patients for 265 patient-years of monitored dialysis. Venous dialysis pressure greater than 150 mm Hg measured by the protocol were considered elevated. Seventy-three patients had elevated venous dialysis pressures and 58 agreed to undergo elective venography (fistulogram). Fifty of 58 patients studied (86%) had significant venous stenoses. A combination of percutaneous transluminal angioplasty (PTA) and surgical revision were used to electively treat these stenoses. Early detection and treatment of these stenoses decreased fistula thrombosis and fistula replacement threefold compared with our earlier experiences. Patients with elevated venous dialysis pressure who were venogramed and treated had an occurrence of fistula thrombosis similar to patients with normal dialysis pressure (0.15 and 0.13 episodes per patient year of dialysis respectively, P = NS). In contrast patients with elevated venous dialysis pressure who refused elective fistulogram and treatment averaged 1.4 episodes of thrombosis per patient year of dialysis (P less than 0.001) compared to both other groups). We conclude that elevated venous dialysis pressure is a reliable method of detecting fistula stenoses and that the elective treatment of these stenoses significantly decreases fistula thrombosis and fistula loss.

Measurement of the distribution volume of gadopentetate dimeglumine at echo-planar MR imaging to quantify myocardial infarction: comparison with 99mTc-DTPA autoradiography in rats

PURPOSE

To measure the fractional distribution volume of gadopentetate dimeglumine in normal and reperfused infarcted myocardium at magnetic resonance (MR) imaging by using the fractional distribution volume of technetium 99m-diethylenetriaminepentaacetic acid (DTPA) as an independent reference.

MATERIALS AND METHODS

Rats were subjected to 1 hour of coronary artery occlusion and 1 hour of reperfusion before inversion-recovery echo-planar imaging or autoradiography. Regional change in relaxation rate (delta R1) ratios for myocardium over blood were compared with radioactivity ratios for myocardium over blood after the injection of 99mTc-DTPA.

RESULTS

Both delta R1 and radioactivity ratios demonstrated equilibrium distribution and hence represent partition coefficients (lambda). The fractional distribution volumes were greater in infarcted myocardium (0.90 +/- 0.05 for gadopentetate dimeglumine and 0.89 +/- 0.04 for 99mTc-DTPA) than in normal myocardium (0.23 +/- 0.02 for gadopentetate dimeglumine and 0.16 +/- 0.01 for 99mTc-DTPA). Area at risk at autoradiography was not significantly different from that at histomorphometry. The infarction size defined by using triphenyltetrazolium chloride was 13% +/- 4 smaller than that defined by using autoradiography.

CONCLUSION

The fractional distribution volumes of gadopentetate dimeglumine and 99mTc-DTPA are similar and indicate extracellular distribution in normal myocardium and intracellular as well as extracellular distribution in reperfused infarction. Because the failure of cells to exclude these agents is indicative of necrosis, contrast medium-enhanced MR imaging may be useful to quantify myocardial infarction.

Hemodialysis-associated subclavian vein stenosis

This study was undertaken to evaluate hemodialysis-associated subclavian vein stenosis (SVS) and to clarify treatment of this condition. Forty-seven patients underwent upper arm venography to evaluate fistula dysfunction. Subclavian vein stenosis was documented in 12. Eleven of 12 had elevated venous dialysis pressure (196 +/- 8.9 mm Hg), and six had arm edema. All 12 had previously undergone subclavian cannulation on the side of the fistula. Thirty-five patients showed no evidence of subclavian vein stenosis. Twelve of these 35 patients (mean venous dialysis pressure 113 +/- 2.3 mm Hg) had undergone previous subclavian cannulation on the side of the fistula. The mean age of the fistula at the time of venogram in patients with subclavian vein stenosis was 17.0 months versus 5.8 months in patients with ipsilateral subclavian cannulation without subclavian vein stenosis. Percutaneous transluminal angioplasty (PTA) was performed on 11 of 12 patients with SVS lowering venous dialysis pressure and restoring patency to the fistula in 100%. Lesions recurred in two of 11 patients and were successfully retreated with PTA. We conclude that SVS is a common dialysis problem that is amenable to treatment with PTA. Elevated venous dialysis pressures are a sensitive indicator of this condition.

Osteogenic sarcoma: noninvasive in vivo assessment of tumor necrosis with diffusion-weighted MR imaging

PURPOSE

To evaluate diffusion-weighted magnetic resonance (MR) imaging for detecting tumor necrosis in an animal model of osteogenic sarcoma.

MATERIALS AND METHODS

Twelve rats with osteogenic sarcoma underwent T1-weighted unenhanced and gadolinium-enhanced spin-echo and diffusion-weighted spin-echo MR imaging. Histologic correlation was performed. Signal intensities, T2 relaxation times, normalized apparent diffusion coefficients, and relative signal intensity increases were calculated.

RESULTS

On diffusion-weighted images, necrotic tumor showed low signal intensity (mean normalized apparent diffusion coefficient, 0.46 +/- 0.20 [1 standard deviation]), indicating rapid diffusion of water molecules as a result of loss of membrane integrity, while viable tumor showed high signal intensity (mean normalized apparent diffusion coefficient, 0.16 +/- 0.05; P < .0001). Differences in the T2 relaxation times and relative signal intensity increases between viable and necrotic tumor were not statistically significant.

CONCLUSION

Normalized apparent diffusion coefficients are more accurate in differentiating between viable and necrotic tumor than are T2 relaxation times or relative signal intensity increases on contrast-enhanced images. Signal intensity overlap between viable and necrotic tumor on gadolinium-enhanced images may be caused by the small molecular size of the agent, which permeates the interstitial space freely, thereby also enhancing necrosis. Diffusion-weighted MR imaging depicts differences in diffusion and, ultimately, in membrane integrity between viable and necrotic tumor and may be used to monitor tumor viability during treatment.

Magnetic resonance characterization of the peri-infarction zone of reperfused myocardial infarction with necrosis-specific and extracellular nonspecific contrast media

BACKGROUND

Because ischemically injured myocardium is frequently composed of viable and nonviable portions, a method to discriminate the two is useful for clinical management.

METHODS AND RESULTS

Ischemically injured myocardium was characterized with extracellular nonspecific (Gd-DTPA) and necrosis-specific (mesoporphyrin) MR contrast media in rats. Relaxation rates (R1) were measured on day 1 and day 2 by inversion-recovery echoplanar imaging. Spin-echo imaging was used to define contrast-enhanced regions and regional wall thickening. Gadolinium concentration, area at risk, and infarct size were measured at postmortem examination. DeltaR1 ratio (DeltaR1(myocardium)/DeltaR1(blood)) after administration of Gd-DTPA was greater in ischemically injured myocardium (1.20+/-0.15) than in normal myocardium (0.47+/-0.05, P<0.05), which was attributed to differences in gadolinium concentration and water content. The Gd-DTPA-enhanced region on day 2 was larger (32.8+/-0.9%) than true infarction as demonstrated by triphenyltetrazolium chloride (TTC) (24.6+/-1.4%, P<0.001, r=0.21). Bland-Altman analysis revealed that the Gd-DTPA-enhanced region overestimated true infarct size by 7.8+/-5.9%. On the other hand, the mesoporphyrin-enhanced region (26.9+/-1.8%, P=NS, r=0.87) and true infarct size were identical. The difference in the areas demarcated by the 2 agents is the peri-infarction. Systolic and diastolic MR images revealed no wall thickening in the mesoporphyrin-enhanced region (0.3+/-3.3%) but reduced thickening in the Gd-DTPA-enhanced rim (8.5+/-5.5%, P<0.05).

CONCLUSIONS

The Gd-DTPA-enhanced region encompasses both viable and nonviable portions of the ischemically injured myocardium. The Gd-DTPA-enhanced area overestimated infarct size, but the mesoporphyrin-enhanced area matched true infarct size. The salvageable peri-infarction zone can be characterized with double-contrast-enhanced and functional MR imaging; the mismatched area of enhancement between the 2 agents shows residual wall thickening.

Identification of a novel circular single-stranded DNA associated with cotton leaf curl disease in Pakistan

Recent reports have suggested that cotton leaf curl virus (CLCuV), a geminivirus of the genus Begomovirus, may be responsible for cotton leaf curl disease in Pakistan. However, the causal agent of the disease remains unclear as CLCuV genomic components resembling begomovirus DNA A are unable to induce typical disease symptoms when reintroduced into plants. All attempts to isolate a genomic component equivalent to begomovirus DNA B have been unsuccessful. Here, we describe the isolation and characterisation of a novel circular single-stranded (ss) DNA associated with naturally infected cotton plants. In addition to a component resembling DNA A, purified geminate particles contain a smaller unrelated ssDNA that we refer to as DNA 1. DNA 1 was cloned from double-stranded replicative form of the viral DNA isolated from infected cotton plants. Blot hybridisation using probes specific for either CLCuV DNA or DNA 1 was used to demonstrate that both DNAs co-infect naturally infected cotton plants from different geographical locations. DNA 1 was detected in viruliferous Bemisia tabaci and in tobacco plants infected under laboratory conditions using B. tabaci, indicating that it is transmitted by whiteflies. Sequence analysis showed that DNA 1 is approximately half the size of CLCuV DNA but shares no homology, indicating that it is not a defective geminivirus component. DNA 1 has some homology to a genomic component of members of Nanoviridae, a family of DNA viruses that are normally transmitted by aphids or planthoppers. DNA 1 encodes a homologue of the nanovirus replication-associated protein (Rep) and has the capacity to autonomously replicate in tobacco. The data suggest that a nanovirus-like DNA has become whitefly-transmissible as a result of its association with a geminivirus and that cotton leaf curl disease may result from a mutually dependent relationship that has developed between members of two distinct DNA virus families that share a similar replication strategy.

Transpupillary thermotherapy (TTT) for the treatment of choroidal neovascularisation

AIM

To assess the effectiveness of transpupillary thermotherapy (TTT) for the treatment of classic and occult choroidal neovascularisation (CNV).

METHOD

In a retrospective, case selected, open label trial 44 eyes of 42 patients with CNV secondary to age related macular degeneration (ARMD) were studied. 44 eyes with angiographically defined CNV were treated with diode laser (810 nm) TTT. Laser beam sizes ranged between 0.8 and 3.0 mm and power settings between 250-750 mW. Treatment was given in one area for 1 minute, the end point being no visible change, or a slight greying of the retina. Outcome was assessed with Snellen visual acuity and clinical examination; in 24/44 patients angiographic follow up was available.

RESULTS

12 predominantly classic CNV and 32 predominantly occult membranes were followed up for a mean of 6.1 months (range 2-19). Mean change in vision for classic membranes was -0.75 (SD 1.75) Snellen lines and occult membranes was -0.66 Snellen lines (2.1) (p>0.05). Predominantly classic membranes were closed in 75% (95% CI: 62.5-87.5) of eyes, remained persistent in 25% (95% CI: 12.5-37.5); no recurrences occurred. Predominantly occult membranes were closed in 78% (95% CI: 70.1-85.3) of eyes, remained persistent in 12.5% (95% CI: 6.6-18.5), and were recurrent in 5.1% (95% CI: 4.2-14.3).

CONCLUSIONS

Transpupillary thermotherapy is a potential treatment for CNV. It is able to close choroidal neovascularisation while maintaining visual function in patients with classic and occult disease. Further trials of TTT are needed to compare this intervention with the natural history and other treatment modalities.

Cotton leaf curl disease is associated with multiple monopartite begomoviruses supported by single DNA beta

For bipartite begomoviruses (family Geminiviridae) trans-replication of the DNA B component by the DNA A-encoded replication-associated protein (Rep) is achieved by virtue of a shared sequence, the "common region", which contains repeated motifs (iterons) which are sequence-specific Rep binding sites and form part of the origin of replication. Recently cotton leaf curl disease (CLCuD), a major constraint to cotton production on the Indian subcontinent, has been shown to be caused by a monopartite begomovirus ( Cotton leaf curl Multan virus [CLCuMV]) and a novel single-stranded DNA satellite molecule termed CLCuD DNA beta. The satellite molecule is trans-replicated by CLCuMV but does not possess the iteron sequences of this virus. We have investigated the ability of CLCuD DNA beta to interact with three further clones of monopartite begomoviruses, isolated from cotton, that have distinct Rep binding specificities. All three cloned viruses were capable of trans-replicating the satellite molecule and inducing CLCuD symptoms in cotton, indicating that the interaction between begomovirus and DNA beta is relaxed in comparison to the interaction between DNA A and DNA B components. Field surveys across all the cotton growing regions of Pakistan indicate that dual and multiple infections are the norm for CLCuD with no evidence of synergism. Despite the diversity of begomoviruses associated with CLCuD, only a single class of DNA beta has been detected, suggesting that this satellite has the capacity to be recruited by unrelated begomoviruses.

Reperfused rat myocardium subjected to various durations of ischemia: estimation of the distribution volume of contrast material with echo-planar MR imaging

PURPOSE

To estimate and compare the fractional distribution volume (fDV) of gadodiamide injection and technetium 99m-diethylenetriaminepentaacetic acid (DTPA) in the reperfused myocardium of rat hearts subjected to various durations of ischemia.

MATERIALS AND METHODS

Magnetic resonance (MR) imaging and autoradiography were performed in rats subjected to 20, 30, 40, or 60 minutes of regional ischemia followed by 1 hour of reperfusion. The fDVs of gadodiamide injection and (99m)Tc-DTPA were measured and compared by using inversion-recovery echo-planar imaging and autoradiographic phosphor imaging, respectively.

RESULTS

The mean fDV of both tracers (gadodiamide and (99m)Tc-DTPA) in normal myocardium was 18% +/- 1, whereas that in the entire area at risk increased significantly (P <.05) with 20, 30, 40, and 60 minutes of ischemia to 32% +/- 1, 57% +/- 4, 66% +/- 2, and 68% +/- 2, respectively. The fDV was significantly (P <.05) greater in the core of infarction-78% +/- 4, 89% +/- 5, and 88% +/- 5 with 30, 40, and 60 minutes of ischemia, respectively-than in the normal myocardium or in the area at risk.

CONCLUSION

The fDV of MR contrast material in the periinfarcted rim was significantly (P <. 05) greater than that in the normal myocardium, but significantly less than that in the core of infarcted myocardium.

Gastric adenocarcinoma: CT versus surgical staging

Seventy-five patients with gastric carcinoma underwent preoperative staging with computed tomography (CT). In 14 patients, CT failed to demonstrate lymphadenopathy despite the presence of malignant lymph nodes at surgery. In 13 patients, CT demonstrated enlarged nodes, but no malignant involvement was found at surgery. Although spread to the pancreas was correctly predicted in three patients with lack of fat plane between tumor and pancreas, five patients lacking a fat plane had no invasion, whereas eight patients with an intact fat plane had invasion. Thirty-five patients (47%) were incorrectly staged with CT:23 (31%) were understaged and 12 (16%) were overstaged. CT does not accurately display the true extent of disease in patients with gastric carcinoma and therefore should not be used routinely for staging.

Reperfused myocardial infarction as seen with use of necrosis-specific versus standard extracellular MR contrast media in rats

PURPOSE

To measure the difference in size of reperfused myocardial infarction with necrosis-specific (bis-gadolinium-mesoporphyrin [hereafter, mesoporphyrin]) and standard extracellular (gadopentetate dimeglumine) magnetic resonance (MR) contrast media.

MATERIALS AND METHODS

Echo-planar (for T1 measurement) and spin-echo (for infarction size) MR imaging were conducted in 32 rats subjected to reperfused reversible (n = 16) and irreversible (n = 16) myocardial injuries. All animals received gadopentetate dimeglumine 1 hour after reperfusion and underwent imaging. Sixteen rats received mesoporphyrin at 2 hours, the other 16 rats received gadopentetate dimeglumine at 24 hours, and all animals underwent imaging at 24 hours.

RESULTS

Mesoporphyrin produced prolonged (22 hours) reduction in T1 in irreversibly, but not in reversibly, injured myocardium. The size of the mesoporphyrin-enhanced region (37% +/- 4 [SEM] of left ventricular surface area) closely correlated with the true infarction size as measured by means of histomorphometry (36% +/- 3, r = 0.90). The size of the gadolinium-enhanced region overestimated (48% +/- 2 and 43% +/- 1 at 1 and 24 hours of reperfusion, respectively) the size of true infarction (36% +/- 3, P < .05, r = 0.02), but it was close to the size of the area at risk (r = 0.93).

CONCLUSION

The sizes of hyperenhanced regions displayed by using mesoporphyrin and gadopentetate dimeglumine differed from each other. The difference in size of the hyperenhanced region demarcated by mesoporphyrin and gadopentetate dimeglumine may provide an estimation of potentially salvageable myocardium.

Paraoxonase cluster polymorphisms are associated with sporadic ALS

BACKGROUND

Paraoxonases (PONs) are involved in the detoxification of organophosphate pesticides and chemical nerve agents. Due to a reported possible twofold increased risk of ALS in Gulf War veterans and the associations of PON1 polymorphisms with the neurologic symptom complex of the Gulf War syndrome, the authors investigated the association between sporadic ALS (SALS) and PON gene cluster variants in a large North American Caucasian family-based and case-control cohort (N = 1,891).

METHODS

Clinically definite and probable ALS was diagnosed according to the revised El Escorial criteria, exclusion of family history of ALS, and SOD1 mutation analysis. Single nucleotide polymorphism (SNP) genotyping was done using TaqMan assays on ABI7900HT. Data were analyzed using SPSS, Haploview, FBAT, and THESIAS.

RESULTS

A haploblock of high linkage disequilibrium (LD) spanning PON2 and PON3 was associated with SALS. The SNPs rs10487132 and rs11981433 were in strong LD and associated with SALS in the trio (parents-affected child triad) model. The association of rs10487132 was replicated in 450 nuclear pedigrees comprising trios and discordant sibpairs. No association was found in case-control models, and their haplostructure was different from that of the trios with overall reduced LD. Resequencing identified an intronic variant (rs17876088) that differentiated between detrimental and protective SALS haplotypes.

CONCLUSION

This study demonstrates evidence of significant association of variants in the Paraoxonase gene cluster with sporadic ALS and is compatible with the hypothesis that environmental toxicity in a susceptible host may precipitate ALS.

Reperfused myocardial infarctions on T1- and susceptibility-enhanced MRI: evidence for loss of compartmentalization of contrast media

The purpose of this study was to characterize the contrast caused by a susceptibility MRI contrast agents, on spin echo T2-weighted imaging of reperfused myocardial infarction. Our interest in this model focused on the expected requirement that such agents be compartmentalized in the tissue to cause signal loss on spin echo images, a condition which may not be present in reperfused infarcted myocardium. Accordingly, nine rats were subjected to 2 h of left coronary artery occlusion followed by 3 +/- 0.5 h of reperfusion prior to administration of contrast media. Three sets of MR images were acquired: (a) baseline axial images at the midventricle, both T1-weighted (TR/TE = 300/20) and T2-weighted (TR/TE = 1500/60); (b) T1-weighted images after administering a T1-enhancing agent, Gd-DTPA-BMA (0.2 mmol/kg), to document that contrast media is delivered to the reperfused infarction; and (c) T2-weighted images after administering the susceptibility agent, Dy-DTPA-BMA (1.0 mmol/kg). Gadolinium-enhanced T1 images depicted reperfused infarction as regions with greatly enhanced signal intensity compared with uninfarcted myocardium, indicating that contrast agent was delivered to the infarcted zone. Dysprosium-enhanced T2 images depicted the injury as a region of persistent signal intensity relative to depletion of signal in normal myocardium, consistent with failure of the contrast agent to cause signal loss. Similar infarction sizes were observed for unenhanced T2-weighted images (33 +/- 5%), gadolinium-enhanced T1-weighted images (36 +/- 5%) and postmortem staining (30 +/- 6%); strong correlations (r > 0.9) were noted in comparisons of these data.(ABSTRACT TRUNCATED AT 250 WORDS)

An ALMT1 gene cluster controlling aluminum tolerance at the Alt4 locus of rye (Secale cereale L)

Aluminum toxicity is a major problem in agriculture worldwide. Among the cultivated Triticeae, rye (Secale cereale L.) is one of the most Al tolerant and represents an important potential source of Al tolerance for improvement of wheat. The Alt4 Al-tolerance locus of rye contains a cluster of genes homologous to the single-copy Al-activated malate transporter (TaALMT1) Al-tolerance gene of wheat. Tolerant (M39A-1-6) and intolerant (M77A-1) rye haplotypes contain five and two genes, respectively, of which two (ScALMT1-M39.1 and ScALMT1-M39.2) and one (ScALMT1-M77.1) are highly expressed in the root tip, typically the main site of plant Al tolerance/susceptibility. All three transcripts are upregulated by exposure to Al. High-resolution genetic mapping identified two resistant lines resulting from recombination within the gene cluster. These recombinants exclude all genes flanking the gene cluster as candidates for controlling Alt4 tolerance, including a homolog of the barley HvMATE Al-tolerance gene. In the recombinants, one hybrid gene containing a chimeric open reading frame and the ScALMT1-M39.1 gene each appeared to be sufficient to provide full tolerance. mRNA splice variation was observed for two of the rye ALMT1 genes and in one case, was correlated with a approximately 400-bp insertion in an intron.

Influence of severity of myocardial injury on distribution of macromolecules: extravascular versus intravascular gadolinium-based magnetic resonance contrast agents

OBJECTIVES

This study sought to 1) compare the distribution of extravascular (573 Da) and intravascular (92 kDa) magnetic resonance (MR) contrast agents in reperfused infarcted myocardium, and 2) investigate the effect of injury severity on these distribution patterns.

BACKGROUND

Myocardial distribution of low and high molecular weight contrast agents depends on vascular permeability, diffusive/convective transport within the interstitium and accessibility of the intracellular compartment (cellular integrity).

METHODS

To vary the severity of myocardial injury, 72 rats were subjected to 20, 30, 45 or 75 min (n = 18, respectively) of coronary artery occlusion. After 2 h of reflow, the animals received either 0.05 mmol/kg of gadolinium-diethylenetriaminepentaacetic acid-bismethylamide (Gd-DTPA-BMA) (n = 24), (Gd-DTPA)30-albumin (n = 24) or saline (control group, n = 24). Three minutes after injection, the hearts were excised and imaged (spin-echo imaging parameters: repetition time 300 ms, echo time 8 ms, 2-tesla system), followed by triphenyltetrazolium chloride staining for infarct detection and sizing.

RESULTS

Histomorphometric and MR infarct size (expressed as percent of slice surface) correlated well: r = 0.96 for Gd-DTPA-BMA; r = 0.95 for (Gd-DTPA)30-albumin. On Gd-DTPA-BMA-enhanced images, reperfused myocardial infarctions were homogeneously enhanced. The ratio of signal intensity of infarcted/ normal myocardium increased with increasing duration of ischemia (overall p < 0.0001, analysis of variance [ANOVA]), indicating an increase in the distribution volume of Gd-DTPA-BMA in postischemic myocardium. On (Gd-DTPA)30-albumin-enhanced images, reperfused infarctions consisted of a bright border zone and a less enhanced central core. The extent of the core increased with increasing duration of ischemia (overall p value < 0.0001, ANOVA).

CONCLUSIONS

At 2 h of reperfusion, the distribution of MR contrast agents in postischemic myocardium is 1) specific for extravascular and intravascular agents, and 2) modulated by the duration of ischemia.

Inversion recovery EPI of bolus transit in rat myocardium using intravascular and extravascular gadolinium-based MR contrast media: dose effects on peak signal enhancement

Inversion recovery gradient recalled echo planar imaging (TI/TR/TE = 700/2000/10 ms) was used to dynamically monitor the first pass of an intravascular (GdDOTA-polylysine) and an extravascular (GdDTPA-BMA) contrast agent through normal rat myocardium. It was found that myocardial enhancement increased with dose of the intravascular agent to a limiting value of approximately 50% of fully relaxed intensity, consistent with enhancement of 40% of myocardial water content during the first pass. Larger doses produced no further increase in peak response. On the other hand, the extravascular agent caused incrementally increased enhancement throughout the dose range examined to a final value of 68 +/- 2% of fully relaxed intensity. The profile of dose dependence for both agents was inconsistent with monoexponential T1 relaxation. It was concluded that: (a) compartmentalization of myocardial water combined with restricted myocardial water diffusion limits the peak response during bolus transit; (b) extraction of the extravascular agent during transit elevates the peak response over that obtained from agent confined to the vascular volume; and (c) models that assume simple monoexponential T1 relaxation to derive time-density curves do not adequately describe the relationship between changes in signal intensity, R1 and contrast concentration.

Norepinephrine constricts the canine coronary bed via postsynaptic alpha 2-adrenoceptors

The effect of alpha 2-blockade (0.3 mg/kg i.v. rauwolscine) and alpha 1-blockade (1.2 mg/kg i.v. prazosin) on coronary constrictions induced by intracoronary injections of azepexole (B-HT 933, alpha 2-agonist, 0.1-10 microgram/kg), phenylephrine (0.3-3 microgram/kg) and norepinephrine (0.001-0.1 microgram/kg) were studied in dog hearts perfused in situ under beta-blockade. Constrictions by azepexole (antagonized by rauwolscine, yet resistant to prazosin and methysergide) demonstrated coronary alpha 2-adrenoceptors. Norepinephrine-induced constrictions were more attenuated (22-fold) by alpha 2-blockade than by alpha 1-blockade (2.6-fold) and thus were mediated mainly by activation of postsynaptic alpha 2-receptors.

Rheumatoid arthritis of the craniocervical region by MR imaging: detection and characterization

OBJECTIVE

The purpose of our study was to evaluate the potential of contrast-enhanced MR imaging to detect and to characterize craniocervical rheumatoid arthritis in a large population group, to compare MR imaging with clinical and conventional radiographic findings, and to examine the relationship between the histopathologic and MR imaging findings in seven patients.

SUBJECTS AND METHODS

We performed contrast-enhanced MR imaging using T2-weighted gradient-echo sequences and T1-weighted spin-echo sequences in 136 patients with rheumatoid arthritis. Sequential T1-weighted images were obtained before, 3 min after, and 15 min after injection of contrast material. Plain films were acquired in all patients. Serologic status and neurologic status were determined in each patient within 2 days of MR imaging. Patients were categorized into one of four groups, depending upon whether they had joint effusion, hypervascular pannus, hypovascular pannus, or fibrous pannus according to signal patterns on contrast-enhanced MR images. Signal intensity was measured to assess the enhancement of synovial hypertrophy, joint capsule, joint effusion, and the various stages of pannus tissue. Histologic specimens were obtained from seven patients and were correlated with MR imaging findings.

RESULTS

Acute and chronic synovitis were differentiated with contrast-enhanced MR imaging as follows: joint effusion (n = 29), hypervascular pannus (n = 54), hypovascular pannus tissue (n = 8), and fibrous pannus (n = 22). Signal intensity differed significantly among the four groups on contrast-enhanced T1-weighted images. In 59 patients with effusion or hypervascular pannus tissue, atlantoaxial subluxation was diagnosed with plain films. Patients with negative findings on radiographic studies (n = 20) had joint effusion, hypervascular pannus tissue, hypovascular pannus formation, or fibrous pannus tissue on MR imaging studies. Cord compression was found in 10% of all cases and isolated sac compression in 16%. Neurologic findings showed no correlation with MR imaging features.

CONCLUSION

Contrast-enhanced T1-weighted spin-echo MR imaging can discriminate between joint effusion and various forms of pannus in patients with rheumatoid arthritis of the craniocervical region. MR imaging also can detect joint effusion and pannus tissue in patients with negative radiographic findings. No relationship between MR imaging findings and clinical symptoms were found. Tissue enhancement and histopathologic findings correlated in a limited number of autopsies.

Echo-planar MR imaging of normal and ischemic myocardium with gadodiamide injection

Rapid echo-planar (EP) magnetic resonance (MR) imaging was used to monitor the first pass of a bolus of gadodiamide injection in the hearts of normal rats and rats subjected to left coronary artery occlusion. Inversion-recovery EP imaging combined with a low dose (0.05 mmol/kg) of the contrast agent caused signal enhancement of normal myocardium from 19% +/- 4 to 63% +/- 5 (mean +/- 1 standard error of the mean) of fully relaxed intensity at the peak of the bolus but only slight increase in signal intensity of the ischemic zone. Thus, ischemic myocardium was demarcated as a hypointense zone (cold spot) during passage of the bolus. A higher dose (0.20 mmol/kg) of the same agent caused signal loss of normal myocardium from 100% to 39% +/- 7 of control at the peak of the bolus on gradient-recalled echo EP images, and ischemic myocardium was visualized as a hyperintense zone (hot spot). With either method of monitoring bolus transit, myocardial signal intensity recovered slowly following the peak bolus effect, consistent with substantial extraction of the agent during the first pass through the heart. Use of gadodiamide injection can allow discrimination between ischemic and nonischemic myocardium on both T1- and susceptibility-weighted EP images during bolus transit.

A MRI spatial mapping technique for microvascular permeability and tissue blood volume based on macromolecular contrast agent distribution

A rapid and automated method for two-dimensional spatial depiction (mapping) of quantitative physiological tissue characteristics derived from contrast enhanced MR imaging was developed and tested in disease models of cancer, inflammation, and myocardial reperfusion injury. Specifically, an established two-compartment kinetic model of unidirectional mass transport was implemented on a pixel-by-pixel basis to generate maps of tissue permeability surface area product (PS) and fractional blood volume (BV) based on dynamic MRI intensity data after administration of albumin-(Gd-DTPA)30, a prototype macromolecular contrast medium (MMCM) designed for blood pool enhancement. Maps of PS and BV in disease models of adenocarcinoma, intramuscular abscess inflammation, and myocardial reperfusion injury clearly depicted zones of increased permeability (up to approximately 500 microl/cc/h--compared to <25 microl/cc/h in normal tissues). As revealed on PS maps, the rank ordering of studied permeability abnormalities was reperfusion injury > inflammation > tumors. A rapid, automated mapping technique derived from dynamic contrast-enhanced MRI data can be used to facilitate the identification and characterization of pathophysiologic abnormalities, specifically relative increases in blood volume and/or microvascular permeability.

Predicting death from initial disease severity in very low birthweight infants: a method for comparing the performance of neonatal units

OBJECTIVES

To investigate (a) which clinical variables and physiological measures of disease severity best predict death in very low birthweight infants and (b) their use in comparing mortality between two neonatal units.

DESIGN

Retrospective study of two cohorts of very low birthweight infants from overlapping time periods who received mechanical ventilation.

SETTING

Two neonatal intensive care units (hospitals A and B).

SUBJECTS

262 Very low birthweight infants, 130 in hospital A, 132 in hospital B.

MAIN OUTCOME MEASURE

Death in hospital.

RESULTS

In hospital A the mean level of oxygenation in the first 12 hours of life, whether measured as inspired oxygen requirement (FIO2), arterial/alveolar oxygen (a/AO2) ratio, or alveolar-arterial oxygen difference (A-aDO2), was more closely associated with death than any of four "traditional" risk factors: low birth weight, short gestation, the diagnosis of respiratory distress syndrome, and male sex. Mean pH in the first 12 hours was as strongly associated with death as birth weight. Multiple logistic regression models were derived in infants from hospital A using the four traditional risk factors with measures of oxygenation and pH. The validity of each model was then tested in infants from hospital B. The model based on the four traditional risk factors alone predicted death in hospital B with only 31% sensitivity. Adding mean a/AO2 ratio and mean pH increased its sensitivity to 75%, and when mean a/AO2 ratio was replaced by mean FIO2 its sensitivity increased further to 81%. Based on crude mortality rates alone, the odds of death in hospital A versus hospital B were 0.67 (95% confidence interval 0.37 to 1.23). After correcting for traditional risk factors and mean FIO2 and mean pH, however, the odds of death in hospital A increased to 3.27 (1.35 to 7.92; p less than 0.01). This increased risk persisted after adjusting for the time difference between each cohort.

CONCLUSIONS

Crude comparisons of hospital mortality can be highly misleading. Reliable assessment of neonatal outcome is impossible without correcting for major risk factors, particularly initial disease severity. International agreement on a minimum core dataset of clinical and physiological information could improve neonatal audit and help to identify effective treatments and policies.

Age and founder effect of SOD1 A4V mutation causing ALS

BACKGROUND

The alanine to valine mutation at codon 4 (A4V) of SOD1 causes a rapidly progressive dominant form of amyotrophic lateral sclerosis (ALS) with exclusively lower motor neuron disease and is responsible for 50% of SOD1 mutations associated with familial ALS in North America. This mutation is rare in Europe. The authors investigated the origin (geographic and time) of the A4V mutation.

METHODS

Several cohorts were genotyped: North American patients with confirmed A4V mutation (n = 54), Swedish (n = 3) and Italian (n = 6) A4V patients, patients with ALS with SOD1 non-A4V mutations (n = 66) and patients with sporadic ALS (n = 96), healthy white (n = 96), African American (n = 17), Chinese (n = 53), Amerindian (n = 11), and Hispanic (n = 12) subjects. High-throughput SNP genotyping was performed using Taqman assay in 384-well format. A novel biallelic CA repeat in exon 5 of SOD1, tightly linked to A4V, was genotyped on sequencing gels. Association statistics were estimated using Haploview. p Values less than 0.05 were considered significant. Age of A4V was estimated using a novel method based on r(2) degeneration with genetic distance and a Bayesian method incorporated in DMLE+.

RESULTS

A single haplotype of 10 polymorphisms across a 5.86-cM region was associated with A4V (p = 3.0e-11) when white controls were used, suggesting a founder effect. The strength of association of this haplotype progressively decreased when African American, Chinese, Hispanic, and Amerindian subjects were used as controls. The associated European haplotype was different from the North American haplotype, indicating two founder effects for A4V (Amerindian and European). The estimated age of A4V with the r(2) degeneration method was 458 +/- 59 years (range 398-569) and in agreement with the Bayesian method (554-734 years with 80-90% posterior probability).

CONCLUSIONS

North American SOD1 alanine to valine mutation at codon 4 descended from two founders (Amerindian and European) 400-500 years ago.

T1-relaxation kinetics of extracellular, intracellular and intravascular MR contrast agents in normal and acutely reperfused infarcted myocardium using echo-planar MR imaging

The objective of this study was to determine and compare if MR contrast agents distributed into various compartments can provide estimation of fractional distribution volume (FDV) in normal and infarcted myocardium using inversion recovery echo-planar MR imaging (IR EPI). Three different types of MR agents were investigated: (a) an extracellular agent, GdDTPA-BMA (0.1 mmol/kg); (b) an intravascular agent, GdDTPA-albumin (0.025 mmol/kg); and (c) an intracellular agent, manganese chloride (0.025 mmol/kg). The null point was determined from a series of IR EPI images in which TI was varied. Temporal changes in DeltaR1 (DeltaR1 = 1/T1(post)-1/T1(pre)) were measured during the initial 29-59 min after administration. Rats (n = 24) were subjected to 1-h coronary artery occlusion/reperfusion. Histochemical staining confirmed the presence and location of infarction. GdDTPA-BMA caused increase in DeltaR1 of infarction < blood < < normal myocardium. DeltaR1 ratios were 1.55 +/- 0.08 for infarction and 0.33 +/- 0.03 for normal myocardium, consistent with FDV of 0.82 +/- 0.04 and 0.18 +/- 0.01. The fractional distribution of this agent in normal myocardium approximated the extracellular space of myocardium. GdDTPA-albumin caused increase in DeltaR1 of blood < < infarction < < normal myocardium. DeltaR1 ratio in normal, but not infarcted, myocardium was constant at 0.10 +/- 0.02 and approximated fractional blood volume. MnCl(2) caused equivalent increase in DeltaR1 of normal and infarcted myocardium. DeltaR1 of normal myocardium did not change overtime, whereas DeltaR1 of blood rapidly decreased, leading to overestimation of FDV in normal and infarcted myocardium. In conclusion, extracellular, intravascular and intracellular MR contrast agents exhibited different T1-relaxation kinetics in both normal and infarcted myocardium. Constant DeltaR1 ratio (myocardium/blood) after administration of MR contrast agent is a prerequisite for estimation of FDV of MR contrast agent in myocardium.

Occlusive and reperfused myocardial infarcts: differentiation with Mn-DPDP--enhanced MR imaging

To assess whether the administration of manganese N,N'-bis(pyridoxal-5-phosphate)ethylenediamine-N,N'-diacetic acid (DPDP) permits differentiation between occlusive and reperfused infarcts, the authors subjected rats to either 6 hours of left coronary artery occlusion (n = 13) or 2 hours of occlusion followed by 4 hours of reperfusion (n = 10) before magnetic resonance (MR) imaging. Electrocardiographic-gated T1-weighted images were obtained before and for 1 hour after injection of 400 mumol/kg of Mn-DPDP. On T1-weighted images obtained before injection of Mn-DPDP. no significant differences in signal intensity were observed between normal and infarcted regions. Use of Mn-DPDP permitted delineation of the area of infarction. The pattern of enhancement in the injured zone was different for occlusive and reperfused myocardial infarcts. In rats with occlusive infarcts, In rats with occlusive infarcts, three well-defined zones were seen. Epicardium and endocardium were enhanced, while the midmyocardial zone was hypointense. The midmyocardial signal intensity gradually increased during the 60 minutes after injection. In rats with reperfused infarcts, the injured area was uniformly and intensely enhanced. Histologic examination confirmed the presence and location of myocardial infarct. Mn-DPDP may improve the detection and delineation of acute myocardial infarcts, demonstrate perfusion of the infarct, and permit discrimination between reperfused and occlusive infarcts.