Active elimination of radio frequency interference for improved signal-to-noise ratio for in-situ NMR experiments in strong magnetic field gradients.

Improvement in the signal-to-noise ratio of Nuclear Magnetic Resonance (NMR) systems may be achieved either by increasing the signal amplitude or by decreasing the noise. The noise has multiple origins - not all of which are strictly "noise": incoherent thermal noise originating in the probe and pre-amplifiers, probe ring down or acoustic noise and coherent externally broadcast radio frequency transmissions. The last cannot always be shielded in open access experiments. In this paper, we show that pulsed, low radio-frequency data communications are a significant source of broadcast interference. We explore two signal processing methods of de-noising short T2∗ NMR experiments corrupted by these communications: Linear Predictive Coding (LPC) and the Discrete Wavelet Transform (DWT). Results are shown for numerical simulations and experiments conducted under controlled conditions with pseudo radio frequency interference. We show that both the LPC and DWT methods have merit.

Regulation of peroxisome size and number by fatty acid beta -oxidation in the yeast yarrowia lipolytica.

The Yarrowia lipolytica MFE2 gene encodes peroxisomal beta-oxidation multifunctional enzyme type 2 (MFE2). MFE2 is peroxisomal in a wild-type strain but is cytosolic in a strain lacking the peroxisomal targeting signal-1 (PTS1) receptor. MFE2 has a PTS1, Ala-Lys-Leu, that is essential for targeting to peroxisomes. MFE2 lacking a PTS1 can apparently oligomerize with full-length MFE2 to enable targetting to peroxisomes. Peroxisomes of an oleic acid-induced MFE2 deletion strain, mfe2-KO, are larger and more abundant than those of the wild-type strain. Under growth conditions not requiring peroxisomes, peroxisomes of mfe2-KO are larger but less abundant than those of the wild-type strain, suggesting a role for MFE2 in the regulation of peroxisome size and number. A nonfunctional version of MFE2 did not restore normal peroxisome morphology to mfe2-KO cells, indicating that their phenotype is not due to the absence of MFE2. mfe2-KO cells contain higher amounts of beta-oxidation enzymes than do wild-type cells. We also show that increasing the level of the beta-oxidation enzyme thiolase results in enlarged peroxisomes. Our results implicate peroxisomal beta-oxidation in the control of peroxisome size and number in yeast.

Mutants of the Yarrowia lipolytica PEX23 gene encoding an integral peroxisomal membrane peroxin mislocalize matrix proteins and accumulate vesicles containing peroxisomal matrix and membrane proteins.

pex mutants are defective in peroxisome assembly. The mutant strain pex23-1 of the yeast Yarrowia lipolytica lacks morphologically recognizable peroxisomes and mislocalizes all peroxisomal matrix proteins investigated preferentially to the cytosol. pex23 strains accumulate vesicular structures containing both peroxisomal matrix and membrane proteins. The PEX23 gene was isolated by functional complementation of the pex23-1 strain and encodes a protein, Pex23p, of 418 amino acids (47,588 Da). Pex23p exhibits high sequence similarity to two hypothetical proteins of the yeast Saccharomyces cerevisiae. Pex23p is an integral membrane protein of peroxisomes that is completely, or nearly completely, sequestered from the cytosol. Pex23p is detected at low levels in cells grown in medium containing glucose, and its levels are significantly increased by growth in medium containing oleic acid, the metabolism of which requires intact peroxisomes.

Complications of the anterior retropharyngeal approach in cervical spine surgery: a technique and outcomes review.

The retropharyngeal approach is used to avoid the risks and limitations of transmucosal surgery. The standard Smith-Robinson approach does not allow complete exposure of the C3 body/disk in patients requiring instrumentation of C3 or in patients with a short, thick neck. The anterior retropharyngeal approach provides additional exposure to the entire cervical spine in these patients. Our results in 14 cases show the anterior retropharyngeal approach to the upper and lower cervical spine to be an effective surgical technique in cases of upper cervical spine abnormalities and for multilevel abnormalities in patients with a short, thick neck. Although complications occurred as a result of the procedure, no permanent disorders were encountered. Adequate exposure to the entire cervical spine can be achieved without the high incidence of infection associated with the transoral approach.

Activation of phosphatidylinositol 3-kinase is sufficient for cell cycle entry and promotes cellular changes characteristic of oncogenic transformation.

Using a new inducible form of phosphatidylinositol 3-kinase (PI 3-kinase) we have found that PI 3-kinase activation has the following effects on cell growth and proliferation. (i) Activation of PI 3-kinase was sufficient to promote entry into S phase of the cell cycle within several hours. This was shown by activation of cyclin-dependent kinase 4 (Cdk4) and Cdk2 and by the induction of DNA synthesis. (ii) PI 3-kinase activation alone was not, however, sufficient to provide for progression through the entire cell cycle. Instead, prolonged activation of PI 3-kinase in the absence of serum stimulation resulted in apoptosis. It is possible that the cells undergo apoptosis because the PI 3-kinase-induced entry into the cell cycle is abnormal. For example, we found that the cyclin E-Cdk2 complex, which normally disappears after entry into S phase of the cell cycle, fails to be downregulated following induction by PI 3-kinase. (iii) Finally, we found that prolonged activation of PI 3-kinase in the presence of serum resulted in cellular changes that resemble those associated with oncogenic transformation. The cells reached high densities, were irregular and refractile in appearance, and formed colonies in soft agar. In contrast, neither PI 3-kinase nor serum stimulation alone could induce these changes. Our results suggest that activation of PI 3-kinase promotes anchorage-independent cell growth and entry into the cell cycle but does not abrogate the growth factor requirement for cell proliferation.

Dual hemodynamic mechanisms for salt-induced hypertension in Dahl salt-sensitive rats.

Cardiac output, blood volume, total peripheral resistance, and renal blood flow were measured in awake salt-sensitive and salt-resistant Dahl rats on normal rat chow (1% NaCl) and on high salt (8% NaCl) diets. Rats were studied after 4, 8, and 46 weeks on a 1% NaCl diet and after 4 and 8 weeks on an 8% NaCl diet. Salt-sensitive rats on 8% NaCl for 4 weeks developed systolic hypertension; by 8 weeks they developed greater systolic and also diastolic hypertension. Salt-resistant rats on 8% NaCl remained normotensive throughout the studies, although renal resistance decreased (p less than 0.05). At 4 weeks, hypertension in salt-sensitive rats on 8% NaCl was caused by increased blood volume and cardiac output (p less than 0.05), with normal total peripheral resistance. At 8 weeks, hypertension was due to increased total peripheral resistance (p less than 0.05); cardiac output was below normal despite persistent elevation of blood volume (p less than 0.05). Salt-sensitive rats on 1% NaCl for 46 weeks were hypertensive, with elevated total peripheral resistance (p less than 0.05); cardiac output decreased (p less than 0.05), whereas blood volume remained unchanged. Salt-resistant rats on 1% NaCl remained normotensive with no charges in hemodynamics. Salt-sensitive rats on 8% NaCl for 4 weeks had an increase in renal vascular resistance but no significant change in nonrenal resistance or total peripheral resistance. The increased total peripheral resistance in salt-sensitive rats on 8% NaCl for 8 weeks and on 1% NaCl for 46 weeks was a reflection of increases of both renal and nonrenal vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Atraumatic osteolysis of the distal clavicle: histologic evidence of synovial pathogenesis. A case report.

Osteolysis of the distal clavicle was diagnosed in a young male athlete following many years as a baseball pitcher with a supplementary weightlifting program. There was no history of ligamentous injuries, contusions, fractures or separation of the acromioclavicular joint. As such, this case was categorized as "atraumatic" osteolysis. Non-decalcified histologic sections from the resected clavicle suggest that the pathogenesis of this atraumatic osteolysis arose from the synovium.

Ultrasonic evaluation of patients with acute right upper quadrant pain.

To define the role of ultrasound in evaluating acute right upper quadrant pain, a prospective study was performed on 52 patients having clinically suspected acute cholecystitis. Ultrasonographic determination of acute or chronic cholecystitis, or diagnosis of a normal gallbladder, was based on analysis of location of tenderness, calculi, sludge, and wall thickness. The diagnosis of acute cholecystitis (34.6% of patients) was based on the highly significant observations of focal gallbladder tenderness and calculi. Sludge and wall thickening were also statistically significant, but to a lesser degree. Cholelithiasis allowed differentiation of patients with chronic cholecystitis (32.7%) from patients with normal gallbladders (32.7%). Neither of these two groups had significant focal gallbladder tenderness, sludge, or thickened walls. Because acute cholecystitis is found in the minority of patients with acute right upper quadrant pain, and because ultrasound is rapid, accurate, and noninvasive, it should be the initial modality used to evaluate these patients.

Ultrasonic demonstration of endometrial fluid collections unassociated with pregnancy.

Intrauterine fluid collections were demonstrated by ultrasound in 17 non-pregnant patients. In nearly all instances, the surrounding echoes were of low to moderate amplitude. This has been noted previously in women with an ectopic or abnormal intrauterine pregnancy. In 2 patients, a well-defined thick rind of high-amplitude echoes encompassed the fluid, simulating an early gestational sac. Small intrauterine fluid collections were seen most frequently in non-pregnant patients who had vaginal bleeding or inflammation of the endometrium or adnexa.

Sonographic demonstration of portal hypertension: the patent umbilical vein.

The remnant of the umbilical vein, the ligamentum teres, is seen on a high percentage of normal ultrasonograms. In patients with portal hypertension, the umbilical vein often reopens as a collateral vessel and can be visualized sonographically; the authors have recently demonstrated this finding in 30 patients. Recognition of a patent umbilical vein is important, since it currently is the only ultrasonographic finding specific for portal hypertension.

Ultrasonographic evidence of gallbladder wall thickening in association with hypoalbuminemia.

Retrospective evaluation of 125 consecutive gallbladder sonograms was done to determine the conditions under which a thickened gallbladder wall is identified. The population studied included a large number of chronic alcoholics. Forty-two patients (Group A) had thickened (greater than or equal to 3 mm) gallbladder walls, while 48 patients (Group B) had walls of normal thickness. Forty patients in Group A had markedly depressed serum albumin levles, significantly lower (p less than 0.001) than albumin levels in Group B. Ten patients in Group B had cholecystitis, compared to two in Group A. The authors conclude that a thick gallbladder wall can be seen in severe hypoalbuminemic states in the absence of acute or chronic cholecystitis.

Analysis of ultrasonographic criteria in the evaluation for ectopic pregnancy.

To assess the usefulness of ultrasound in diagnosing ectopic pregnancy, the ultrasonographic findings, pregnancy test results, and proven diagnoses in 148 patients referred for evaluation for ectopic pregnancy were reviewed. Of these patients, 33 were subsequently proven to have ectopic gestations. The ultrasonograms were coded for uterine size, intrauterine gestation sac, adnexal mass, adnexal ring, cul-de-sac fluid, or normal findings. With a positive pregnancy test, the presence of an intrauterine gestation sac excludes the diagnosis of ectopic pregnancy. Of those patients with positive pregnancy tests and no intrauterine gestation sac, 73% had ectopic pregnancy. All patients with normal ultrasonograms had other diagnoses. With a negative pregnancy test, the intrauterine findings are not helpful, and evaluation of the adnexa is more important. An adnexal ring is a significant, though not absolute, indicator of ectopic pregnancy. A normal scan excludes this diagnosis. Other criteria were not significant. A clinical approach to the evaluation for ectopic pregnancy, based on the data accumulated in this study, is suggested.

Mature placenta simulating fetus papyraceus on ultrasonic examination.

A case of a heavily calcified, mature placenta simulating the appearance of a fetus papyraceus is presented. Calcification surrounding the more sonolucent cotyledons simulated the body and limbs of a dead fetus. Awareness of the morphologic alterations which occur as the placenta matures should prevent confusion of normal placental changes with a pathologic entity.