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Biomedical subjects

S Miller

Publications and source records attributed to S Miller.

At least 145 records · Page 8Linked to original sources
PubMed1999

A novel mitochondrial DNA-like sequence in the human nuclear genome.

We describe here a nuclear mitochondrial DNA-like sequence (numtDNA) that is nearly identical in sequence to a continuous 5842 bp segment of human mitochondrial DNA (mtDNA) that spans nucleotide positions 3914 to 9755. On the basis of evolutionary divergence among modern primates, this numtDNA molecule appears to represent mtDNA from a hominid ancestor that has been translocated to the nuclear genome during the recent evolution of humans. This numtDNA sequence harbors synonymous and nonsynonymous nucleotide substitutions relative to the authentic human mtDNA sequence, including an array of substitutions that was previously found in the cytochrome c oxidase subunit 1 and 2 genes. These substitutions were previously reported to occur in human mtDNA, but subsequently contended to be present in a nuclear pseudogene sequence. We now demonstrate their exclusive association with this 5842-bp numtDNA, which we have characterized in its entirety. This numtDNA does not appear to be expressed as a mtDNA-encoded mRNA. It is present in nuclear DNA from human blood donors, in human SH-SY5Y and A431 cell lines, and in rho(0) SH-SY5Y and rho(0) A431 cell lines that were depleted of mtDNA. The existence of human numtDNA sequences with great similarities to human mtDNA renders the amplification of pure mtDNA from cellular DNA very difficult, thereby creating the potential for confounding studies of mitochondrial diseases and population genetics.

Cell Nucleus↗
PubMed1999

An experimental model for the endometriosis in athymic mice.

Endometriosis is an adhesion disorder characterized by the presence of endometrial tissue in ectopic sites outside the uterus. The disease is associated with dysmenorrhea, pelvic pain and infertility. Although endometriosis is the most common gynecologic disorder, relatively little is known regarding its etiology, pathogenesis and the course of the disease. This situation is primarily due to the absence of experimental systems to examine the mechanism of endometrial cell adhesion, role of inflammatory cells and the interactions of epithelial, and stromal cells with the peritoneum and ovarian tissue leading to the development of this disorder. Dissociated human endometrial cells were suspended in peritoneal fluids of individuals with and without endometriosis and were injected into the peritoneal cavity of athymic mice. This led to development of ectopic adhesions of endometrial cells at the peritoneal and ovarian surfaces. Endometrial cells which were marked with fluorescent lipophylic dyes, prior to intraperitoneal injection, could be visualized without surgery at such sites. The studies demonstrate a model for endometriosis in athymic mice.

Adult↗
PubMed1999

Inhibition of the peroxidative degradation of haem as the basis of action of chloroquine and other quinoline antimalarials.

The malaria parasite feeds by degrading haemoglobin in an acidic food vacuole, producing free haem moieties as a by-product. The haem in oxyhaemoglobin is oxidized from the Fe(II) state to the Fe(III) state with the consequent production of an equimolar concentration of H2O2. We have analysed the fate of haem molecules in Plasmodium falciparum-infected erythrocytes and have found that only about one third of the haem is polymerized to form haemozoin. The remainder appears to be degraded by a non-enzymic process which leads to an accumulation of iron in the parasite. A possible route for degradation of the haem is by reacting with H2O2, and we show that, under conditions designed to resemble those found in the food vacuole, i.e., at pH5.2 in the presence of protein, free haem undergoes rapid peroxidative decomposition. Chloroquine and quinacrine are shown to be efficient inhibitors of the peroxidative destruction of haem, while epiquinine, a quinoline compound with very low antimalarial activity, has little inhibitory effect. We also show that chloroquine enhances the association of haem with membranes, while epiquinine inhibits this association, and that treatment of parasitized erythrocytes with chloroquine leads to a build-up of membrane-associated haem in the parasite. We suggest that chloroquine exerts its antimalarial activity by causing a build-up of toxic membrane-associated haem molecules that eventually destroy the integrity of the malaria parasite. We have further shown that resistance-modulating compounds, such as chlorpromazine, interact with haem and efficiently inhibit its degradation. This may explain the weak antimalarial activities of these compounds.

Animals↗
PubMed1999

Random monoallelic expression of the imprinted IGF2 and H19 genes in the absence of discriminative parental marks.

The IGF2 and H19 genes are genomically imprinted and expressed preferentially from the paternal and maternal alleles, respectively, during human prenatal development. The exact role of the parental imprint(s), however, is not known. To explore this issue in some detail, we have examined human androgenetic cells which by definition should be incapable of allelic discrimination given the paternal origin of both genomes. Allele-specific in situ hybridisation analysis of dispermic complete hydatidiform moles shows that IGF2 and H19 can be found to be transcriptionally active in a variegated manner, which results in the generation of random monoallelic expression patterns. This data shows that imprinted genes can be expressed monoallelically in the absence of discriminating parental marks and raises the question whether or not mechanisms underlying monoallelic expression preceded the acquisition of parental imprints during evolution.

Alleles↗
PubMed1999

The role of glutamine in skeletal muscle ischemia/reperfusion injury in the rat hind limb model.

OBJECTIVES: Ischemia/reperfusion injury is a commonly occurring event with severe pathologic consequences. Reperfusion initiates both the local and systematic damage in part through rapid oxygen generation. The glutathione system is a major mechanism of reducing this oxidative stress. If this system can be maintained or augmented during this stress then less damage may occur. Glutamine provides the source of glutamate to this system and has been shown to preserve total glutathione levels after injury/ischemia to both hepatic and gut models. To test this effect, we looked at glutamine and its role in ischemia/reperfusion injury in a rat hind limb model. METHODS: Fifty male HSD/Holtzman rats weighing 350-400 g were randomized to receive glutamine (3% sol) or normal saline via intraperitoneal injections. The groups were then subjected to 2 hours of ischemia to their hind limbs using the Tourni-Cot method. Animals were then randomized to reperfusion groups of 30 minutes, 2 hours, and 4 hours. Muscle tissue assays were performed for lipid peroxidation (LPO), total glutathione (GSH), and myeloperoxidase (MPO). Peripheral blood was analyzed for creatinephosphokinase levels (CPK). RESULTS: Animals that received glutamine showed a general trend of less lipid peroxidation products than the normal saline groups. In animals that received glutamine and underwent 2 hours of ischemia and reperfusion times of 0 minutes, 30 minutes, and 2 hours, there were significantly less percent changes in lipid peroxidation products from controls (4.6% vs 48.2%, P <0.05), (18.9% vs 123%, P <0.05), (12.6% vs 115%, P <0.05). A general trend upward was noted in CPK levels in both groups. In animals receiving 2 hours of ischemia and 30 minutes of reperfusion, there was a significantly greater level of creatinephosphokinase (CPK) calculated as percent change from control in the normal saline group as compared with the glutamine group (209.2% vs 92.7%). Myeloperoxidase assay of muscle tissue revealed a progressive increase as the reperfusion times grew. In animals receiving 2 hours of ischemia and 30 minutes of reperfusion, the normal saline group had a significantly larger percent increase from controls than the group that received glutamine (1126.4% vs 108%, P <0.05). Also, in those animals receiving 4 hours of reperfusion, the normal saline group had a significantly higher percent increase in MPO content than the glutamine group (6245% vs 108%, P <0.05). Total glutathione levels decreased rapidly as reperfusion occurred in both the normal saline and glutamine groups. No significant difference between the groups was noted. CONCLUSIONS: Total glutathione levels during reperfusion were not significantly different in the groups receiving glutamine versus normal saline. Glutamine may provide an initial protective effect on reperfusion injury after moderate reperfusion times in the hind limb model as defined by CPK and LPO levels. Glutamine may blunt neutrophil recruitment after longer reperfusion times (4 hours) in the ischemic hind limb. Total glutathione levels decreased significantly after moderate levels of ischemia (2 hours) and reperfusion (30 minutes, 2 hours).

Animals↗
PubMed1999

Cellular and molecular mechanisms of memory: the LTP connection.

Studies of the cellular and molecular mechanisms of memory formation have focused on the role of long-lasting forms of synaptic plasticity such as long-term potentiation (LTP). A combination of genetic, electrophysiological and behavioral techniques have been used to examine the possibility that LTP is a cellular mechanism of memory storage in the mammalian brain. Although a definitive answer remains elusive, it is clear that in many cases manipulations that alter LTP alter memory, and training regimens that produce memory can produce LTP-like potentiation of synaptic transmission.

Animals↗
PubMed1999

Transmyocardial laser revascularization in the acute ischaemic heart: no improvement of acute myocardial perfusion or prevention of myocardial infarction.

OBJECTIVE: Transmyocardial laser revascularization (TMLR) has been used to provide enhanced myocardial perfusion in patients not suitable for coronary revascularization or angioplasty. This study investigates the acute changes in myocardial perfusion after TMLR with a Holmium:Yttrium-Aluminium-Garnet (YAG) laser with a thermal imaging camera in a model of acute ischaemia, and confirms its midterm effects by post-mortem investigation of magnetic resonance imaging and histopathological examination. METHODS: Acute myocardial ischaemia was induced by occlusion of the dominant diagonal branch in ten sheep. Perfusion measurements were undertaken first in the unaffected myocardium, then after temporary occlusion of the coronary to obtain a control measurement for ischaemic myocardium. Myocardial perfusion was then evaluated during reperfusion after release of coronary occlusion. Then the coronary was permanently occluded and 20.5+/-2 channels were drilled with the Holmium:YAG laser and perfusion was measured again. The other four sheep served as control with untreated ischaemia. All animals were sacrificed after 28 days following administration of gadolinium i.v. to serve as contrast medium for magnetic resonance tomography. The hearts were subjected to magnetic resonance tomography and histopathological examination. RESULTS: Intraoperative perfusion measurements revealed a decreased perfusion after temporary occlusion and an increased perfusion in reperfused myocardium. After TMLR, no improvement of myocardial perfusion above the ischaemic level could be shown. Magnetic resonance images could neither confirm patent laser channels nor viable myocardium within ischaemic areas. On histology no patent endocardial laser channel could be detected. The transmural features were myocardial infarct with scar tissue. CONCLUSIONS: In the presented sheep model with acute ischaemia, TMLR with a Holmium:YAG laser did not provide acute improvement of myocardial perfusion as assessed by a thermal imaging camera. This would suggest no direct contribution of newly created laser channels to myocardial perfusion. As chronic effects are concerned, no perfused laser channels could be identified by later magnetic resonance imaging or histology.

Animals↗
PubMed1999

Folding of coliphage T4 short tail fiber in vitro. Analysing the role of a bacteriophage-encoded chaperone.

The morphogenesis of the Escherichia coli bacteriophage T4 depends on the presence of helper proteins which are not components of the mature virion. Two bacteriophage-encoded proteins, p57 and p38, are required for the assembly of the bacteriophage T4 tail fibers. In the absence of p57, two polypeptides of the long fiber (p34 and p37) and that of the short tail fiber (p12) fail to trimerize. Instead they form water-insoluble aggregates. Co-expression of the genes 12 and 57 in vivo caused the formation of only trimeric, water-soluble p12. The function of g57 cannot be replaced by overexpression of the host proteins GroEL/ES or parvulin. The mechanism of action of this helper protein has remained unknown, mainly because it has not been possible to determine its activity in vitro. Purified p12, denatured in 7 M urea, trimerized spontaneously in a slow reaction (half-time approximately 6 h) and with low yield. Upon renaturation, p12 forms native SDS-resistant trimers as indicated by spectroscopic and hydrodynamic measurements. Addition of p57 increased the rate of folding threefold and nearly doubled the yield. These experiments demonstrate that p57 acts as a molecular chaperone during folding of T4 tail fibers.

Bacteriophage T4↗
PubMed1999

Back to basics: exploring the conceptual basis of nursing.

It has long been recognized that nursing is essentially a practice-based discipline, underpinned by fundamental concepts which inform practice. The purpose of this paper is two-fold: first, to discuss the need for an exploration of these concepts of nursing as a foundation to pre-registration nursing programmes. Second, by utilizing a continuous quality improvement perspective, an evaluation of teachers' experiences with a cohort of adult and child health branch students is considered. It is concluded that a significant proportion of students found that a raised conceptual awareness served to promote theory-practice links.

Adult↗
PubMed1999

[Cardiac MRI for determining functional left ventricular parameters].

PURPOSE: To prove the accuracy of MR methods in the determination of left ventricular (LV) functional parameters and anatomy. MATERIALS AND METHODS: At 1.5 T, 20 healthy volunteers and 22 patients with aortic valvular disease (stenosis n = 15, regurgitation n = 7) were examined. Functional parameters like cardiac output, ejection fraction, end-diastolic volume, aortic flow maximum, and time interval from the R-wave to maximum flow were obtained using a velocity encoding 2D FLASH sequence (TR 24 ms, TE 5 ms, venc 250 cm/sec) and segmented breath-hold cine FLASH 2D technique (TR 100 ms, TE 4.8 ms, flip angle 25 degrees, temporal resolution 50 ms). Invasive measurements (Fick principle) served as gold standard, intra- and interobserver variability were determined. RESULTS: Differences of functional parameters between normal volunteers and patients were detectable at a high level of significance (p < 0.0001). For cardiac output a superior correlation with the gold standard was found using flow measurements (r = 0.66, p < 0.0007) compared to volumetric calculations from cine studies (r = 0.47, p < 0.02). Interobserver variability was 2.5 +/- 2.7%/4.5 +/- 6.9% (flow quantification/calculations from cine studies), intraobserver variability was 1.7 +/- 1.6%/3.3 +/- 2.2%. CONCLUSIONS: MRI is an appropriate tool for determining LV functional parameters and anatomy. Differences between normal volunteers and patients with aortic valvular disease can be detected reliably. Flow measurements turned out to be more accurate than calculations from cine images. Therefore, flow quantification techniques should be preferred for clinical use.

Adult↗
PubMed1999

[Optimization of numerical measurement parameters for ECG-triggered MRI snapshot-FLASH myocardial perfusion studies].

BACKGROUND AND AIMS: In MR examinations of myocardial perfusion by the use of Snapshot-FLASH sequences it is of major importance that the achievable signal difference between pre- and normal postcontrast myocardium be maximized. METHODS: In ECG-triggered Snapshot-FLASH sequences the signal intensity of the myocardium depends on the flip angle alpha, the inversion time TI and the trigger delay TD (both depending on the cardiac frequency f) for unchanged slice thickness (SL), matrix size (MA), repetition time (TR) and echo time (TE). Therefore a simulation of the signal behavior of pre- and postcontrast myocardium based on Bloch's equations was performed by varying the flip angle alpha, TI and TD for different cardiac frequencies in order to determine an optimized combination of the measurement parameters. RESULTS: In normal heart rates (50-70 beats/min) maximal signal differences between pre- and normal postcontrast myocardium can be reached for inversion times TI = 170-200 ms and a flip angle alpha = 11 degrees. For higher heart rates again alpha = 11 degrees and TI = 200-220 ms with shortened TD (TD = 0 for f > 90 beats/min) were found to be optimal. The calculated values were semiquantitatively confirmed in phantom and volunteer measurements. CONCLUSIONS: The described method allows cardiac frequency dependent optimization of the Snapshot-FLASH measurement parameters alpha, TI and TD in order to reach a maximum in signal contrast between normal and malperfused myocardium.

Computer Graphics↗
PubMed1999

[Diagnosis of renal artery stenosis in 1.0 T using 3D phase contrast magnetic resonance angiography and dynamic contrast medium perfusion].

PURPOSE: To assess renal artery stenosis (RAS) by 3D phase contrast (PC) MR angiography and dynamic perfusion imaging of the kidneys. METHODS: On a standard 1.0 T MR imaging system (Magnetom Expert, Siemens), 32 patients with angiographically proven unilateral RAS were examined using a 3D PC sequence (TR 40 ms/TE 9 ms/venc 30 cm/s). An ECG-gated Turbo-FLASH 2D sequence (TR 4.5 ms/TE 2.2 ms/TIeff. 400 ms) was applied to study the first pass of paramagnetic contrast agent (0.1 mmol Gd-DTPA/kg) through the kidneys. Signal intensity (SI) over time curves of the renal cortex were obtained and evaluated considering temporal relation and percentage of maximum SI compared to the aorta and normal kidneys. Analysis of the MRA was performed by two independent blinded readers. The gold-standard DSA was interpreted by consensus reading of two experienced radiologists. RESULTS: RAS was detected by 3D PC MRA with a sensitivity of 93% and specificity of 81% (ppv 82%, npv 93%, accuracy 87%, kappa = 0.61). Maximum SI in RAS was significantly decreased (p < 0.001-0.0001). A temporally delayed enhancement of 1.5 +/- 1.3 s was found for RAS > 75% (p < 0.002) but not for RAS < 75% (p > 0.1). CONCLUSIONS: 3D PC MRA is capable of detecting RAS in a high percentage of patients. Dynamic perfusion imaging of the kidneys, applied additionally, can confirm the diagnosis and give valuable information about the hemodynamic relevance of RAS in suspected unilateral disease.

Contrast Media↗
PubMed1999

[MR proton spectroscopy to monitor the concentration changes in cerebral metabolites following a TIPS placement].

BACKGROUND AND AIMS: In chronic liver dysfunction with portal hypertension the risk of variceal bleeding can be lowered by intrahepatic portosystemic shunting (TIPS). Although less pronounced than in surgical shunting, hepatic encephalopathy (HE) is a well-known undesired side effect. In cerebral proton MR spectroscopy (MRS), HE can be detected by a specific pattern of brain metabolite changes (increase of glutamine/glutamate (Glx) and decrease of myo-inositol (ml) and choline (Cho)). The aim of this study was to examine whether, after TIPS implantation, there is a correlation of the reduction of the portosystemic pressure gradient (PSPG) and the cerebral metabolite changes and their correspondence to the clinical status. METHODS: We examined 10 cirrhotic patients (Child B, C) before and 3-20 days after TIPS implantation. Clinical examination was performed by a senior hepatologist. Localized MR spectra were acquired in parieto-occipital gray/white matter using a short echo time (TE = 5 ms) STEAM sequence. RESULTS: After TIPS we found an increase of Glx/(Cr + PCr) of 13%-40% and a decrease of ml(Cr + PCr) of 6%-46% with a positive (Glx: r = 0.71) respectively negative (ml: r = -0.59) correlation to the reduction of the PSPG. 7/10 patients with a reduction of the PSPG of more than 9 mmHg (9-17 mmHg) showed a clinical impairment of their HE. CONCLUSIONS: Short echo time cerebral MRS allows detection of finest HE specific metabolite changes and can therefore contribute positively to an individually optimized reduction of the PSPG during TIPS implantation.

Adult↗
PubMed1999

Refrigerated storage improves the stability of the complete blood cell count and automated differential.

A CBC count was performed on 113 random patient and 21 control specimens before and after 24-hour room temperature (RT) storage; 98 random patient and 20 control specimens also were analyzed before and after 24 hour 4 degrees C storage. The Cell-Dyn 3500 (Abbott Laboratories, Abbott Park, IL) was used for analysis. RT storage showed a decline in WBC count using the optical but not the impedance method, resulting in a large number of WBC flags. An increase in mean corpuscular volume also was seen for patient specimens. The automated WBC differential showed a decrease in the percentage of neutrophils and an increase in the percentage of lymphocytes, owing primarily to neutrophil degeneration. These changes also were seen in the manual differential to a similar degree. Storage of specimens at 4 degrees C largely prevented all of these changes. The implementation of refrigerated specimen storage is a simple, inexpensive method to improve the accuracy of CBC results for aged specimens on automated hematology analyzers.

Autoanalysis↗
PubMed1999

Embryo and yolk compositional relationships in broiler hatching eggs during incubation.

Developmental relationships between yolk, embryo body, and embryo liver compositions during incubation were determined in two trials. In Trial 1, embryo body moisture, fat, and CP contents and embryo liver moisture and fat contents were determined. In Trial 2, relative yolk weights, moisture, fat, and fatty acid contents, relative wet and dry embryo weights and moisture contents, and relative wet and dry liver weights and moisture contents were determined. In Trial 1, embryo moisture decreased sigmoidally between Days 6 and 21, whereas embryo fat increased between Days 12 and 21 of incubation; embryo CP displayed sequential fluctuations throughout incubation. However, an overall significant decrease in embryo CP occurred between Days 6 and 21. Liver fat content increased between Days 12 and 21, whereas liver moisture decreased through Day 18, with a subsequent increase by Day 21. In Trial 2, relative yolk weight and moisture content decreased, whereas percentage yolk lipid content increased between Days 6 and 15. Relative wet and dry embryo weights changed in a similar manner, with rapid increases between Days 12 and 18 of incubation. Embryo moisture and CP were negatively correlated to embryo fat content. Furthermore, relative embryo and liver DM were related to yolk palmitic acid concentration, whereas yolk oleic acid was correlated only with liver DM. In conclusion, embryos and their livers displayed differential accumulations of moisture and DM during incubation, and these differences exhibited distinctive associations with various yolk fatty acids.

Animals↗
PubMed1999

"Slow" code: perspectives of a physician and critical care nurse.

"Slow" codes are not conducted frequently, but even their limited use is controversial from an ethical point of view. Physicians and nurses may view the rationale for a "slow" code differently. A critical care nurse and a physician were interviewed regarding their experiences with and their views about "slow" codes.

Attitude of Health Personnel↗