Purpose
To investigate the relationship between the atherosclerotic lesion load determined on magnetic resonance angiography (MRA) and phosphocreatine (PCr) kinetics during incremental, exhaustive ...calf exercise in patients with bilateral, symptomatic peripheral arterial disease (PAD).
Procedures
Using a 1.5 Tesla MR scanner, 26 patients with bilateral symptomatic PAD and 24 healthy male controls underwent serial phosphorus-31 MR spectroscopy (31P MRS) during incremental exercise at 2, 3, 4, and 5 Watts. For each increment and recovery, PCr time constants, amplitudes of PCr changes and pH values were calculated from the MR spectra. In patients, the run-off resistance (ROR) was determined on MRA.
Results
The patients exhibited significantly (
p
≤ 0.002) increased PCr time constants at the first (36.7, 13.8–360.3 vs. 22.9, 9.2–60.7 s), at the second (68.1, 4.2–757.2 vs. 18.3, 5.2–57.6 s), at the third (65.3, 14.7–277.7 vs. 29.0, 4.48–97.2 s), the fourth increment (64.1, 34.2–548.8 vs. 34.6, 4.9–106.2 s), and during recovery (53.2, 11.1–353.2 vs. 41.4, 15.1–122.4 s) compared to the normal controls. The PCr on-kinetics during the increments correlated significantly with the pH levels (
r
= −0.39 to −0.66,
p
≤ 0.005) at the end of the corresponding increments, but not with the RORs.
Conclusions
The correlation between PCr on-kinetics and end-increment pH values might indicate remodelling processes within the muscle that probably affect mitochondrial performance, diffusion of oxygen, and muscle fiber distribution. These parameters could be improved by exercise training.
It is known that the relevance of a peripheral stenosis for muscle function increases with exercise. Our intention was to investigate the impact of a moderate cuff stenosis (CS) at 120 mmHg of the ...superficial femoral artery on high-energy phosphate (HEP) metabolism during isotonic, incremental calf exercise. Serial phosphorus 31 magnetic resonance spectroscopy (31P MRS) and velocity-encoded phase-contrast MR imaging (VEPC MRI) were carried out in each leg of ten healthy male volunteers. Each leg underwent four increments of calf exercise (2, 3, 4 and 5 W) followed by recovery during separate exercise sessions with and without a CS at 120 mmHg. The serial 31P MRS measurements had a time resolution of 10 s. VEPC MRI was performed at the end of each increment during separate sessions. During all increments, we detected significant differences (P < 0.05) in the phosphocreatine (PCr) time constants and the amount of PCr hydrolysis between the sessions without and with CS. Regarding the time courses of the PCr, inorganic phosphate (Pi) and pH level, we observed significant differences (P < 0.002) during exercise and recovery. During both conditions, the end-increment PCr levels as well as blood flow correlated significantly with the mechanical power. The PCr time constants during exercise significantly correlated with the intramuscular pH, but not with blood flow or mechanical power. However, the PCr recovery time constants correlated significantly with blood flow and end-exercise pH. Our study shows that reduction of blood flow due to a peripheral stenosis results in a prolongation of PCr time constants, decreased PCr and pH level as well as increased Pi level during exercise. We believe that 31P MRS during incremental exercise might provide additional information for assessing the relevance of a peripheral stenosis and its impact on muscle function.
The first part of this article deals with the concept of Mild Cognitive Impairment and its role in the pathogenesis of dementia. In the second part neuroradiologic diagnostic methods which can ...potentially help to predict the conversion of MCI to Alzheimer s disease (DAT) are discussed.
We reviewed in PubMed published literature for reports which investigated diagnosis and progress of patients with MCI and DAT.
Patients with MCI older than 65 years have a risk of 10-15%/year to develop dementia in comparison to the healthy population with a risk of 2%/year. Neuroradiologic methods such as MR-spectroscopy, FDGPET, DWI and VBM are able to differentiate patients who will convert to DAT from patients who remain stable. Structural changes can be detected prior to clinically measurable cognitive deficits.
The neuroradiologic examination using MR- Spectroscopy, VBM, DWI or FDG-PET show early structural and functional changes which can predict a conversion from MCI to DAT.
We report the case of a newborn infant affected by congenital hyperinsulinism who developed cholelithiasis associated with cholestatic jaundice following treatment with octreotide, a somatostatin ...analogue.
Among the molecular variants of human GH, the monomeric 22-kD is the predominant isoform, whereas the 20-kD is the second most abundant isoform. Because little is known on the pattern of human GH ...isoforms in the early postnatal period, we evaluated serum levels of 22-kD GH by an immunofluorometric assay and of 20-kD GH by an ELISA using an anti-20-kD antibody, and measured GH bioactivity with the Nb2 cell bioassay in 19 preterm neonates (gestational age, 32 +/- 0.5 wk; mean +/- SEM) on the fourth and 15th days of life. As control subjects, we studied 19 full-term neonates (gestational age, 39 +/- 0.3 wk) on the fourth day of life and 20 healthy adults, aged 20 +/- 0.3 y. Four-day-old preterm neonates showed significantly higher serum values of 20-kD GH (0.99 - 0.14 ng/mL) than full-term neonates (0.33 +/- 0.07 ng/mL; p < 0.001) and adults (0.09 +/- 0.02; p < 0.0001). Likewise, 22-kD GH and GH levels by Nb2 cell bioassay were also significantly higher (p < 0.001) in preterm than in full-term neonates and young adults. A significant decrease (p < 0.01) in 20-kD, 22-kD, and Nb2-determined GH was observed in preterm neonates on the 15th day of life The percentage of the 20-kD isoform was similar in the preterm infants at the fourth and 15th day, in full-term-infants, and in adults (2.7%, 2.7%, 2.8%, and 3.16%, respectively). Our results indicate that 20-kD GH serum levels change throughout life as regards total amount, but not as regards percentage.
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 15, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf ...file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Phillip E. Messner. Vita. Includes bibliographical references.
Unconventional resource development has been enabled by advanced completion methods such as horizontal drilling and multistage hydraulic fracturing. However, unconventional reservoir production rates ...decline more rapidly relative to conventional reservoirs, and recovery factors remain relatively low. Enhancing hydrocarbon recovery can be improved through a fundamental understanding of transport processes inside unconventional rocks. This work provides unique insights into fluid transport mechanisms in unconventional rocks during miscible displacement using a direct and noninvasive method to quantitatively detect hydrocarbons and their distribution inside rock samples by proton NMR imaging coupled with theoretical analysis of experimental results. This study shows the importance of unconventional rock morphology and pore structure to better understanding fluid transport and overall mass transfer rates. Different transport mechanisms in representative homogeneous and heterogeneous unconventional tight rocks are demonstrated. For homogeneous tight rocks, viscous or hydraulic flow is the dominant fluid transport mechanism in the direction of an applied pressure differential. However, a more complex behavior is observed in heterogeneous tight rocks. Despite smaller average pore sizes, the heterogeneous tight rocks can possess macroscopic permeabilities comparable to larger-pore rocks due to microfracture(s) in the sample that remain open at field relevant net confining stresses. Such microfractures enable a dual fluid transport mechanism inside the heterogeneous tight rock: hydraulic fluid transport along microfracture(s) and diffusion dominated fluid exchange across microfracture(s) inside the rock matrix. Overall mass transfer rates through heterogeneous tight rocks depends on the interplay of these two transport mechanisms, relative rates and travel distances. Experiments with lab cores showed that for fluid exchange of an injected fluid with the in situ fluid, diffusion in the matrix is a rate limiting step. More study is required to upscale our observations to a field relevant scale.
Static cold storage is the cheapest and easiest method and current gold standard to store and preserve donor organs. This study aimed to compare the preservative capacity of ...gluconate-lactobionate-dextran (Unisol) solutions to histidine-tryptophan-ketoglutarate (HTK) solution. Murine syngeneic heterotopic heart transplantations (Balb/c-Balb/c) were carried out after 18 h of static cold storage. Cardiac grafts were either flushed and stored with Unisol-based solutions with high-(UHK) and low-potassium (ULK) ± glutathione, or HTK. Cardiac grafts were assessed for rebeating and functionality, histomorphologic alterations, and cytokine expression. Unisol-based solutions demonstrated a faster rebeating time (UHK 56 s, UHK + Glut 44 s, ULK 45 s, ULK + Glut 47 s) compared to HTK (119.5 s) along with a better contractility early after reperfusion and at the endpoint on POD 3. Ischemic injury led to a significantly increased leukocyte recruitment, with similar degrees of tissue damage and inflammatory infiltrate in all groups, yet the number of apoptotic cells tended to be lower in ULK compared to HTK. In UHK- and ULK-treated animals, a trend toward decreased expression of proinflammatory markers was seen when compared to HTK. Unisol-based solutions showed an improved preservative capacity compared with the gold standard HTK early after cardiac transplantation. Supplemented glutathione did not further improve tissue-protective properties.
