Quantitative three-dimensional reconstruction of aneurysmal left ventricles. In vitro and in vivo validation

BACKGROUND

Current two-dimensional (2D) echocardiographic measures of left ventricular (LV) volume are most limited by aneurysmal distortion, which restricts application of simple geometric models that assume symmetrical shape. 2D methods also fail to provide separate volumes of the aneurysm and nonaneurysmal residual LV cavity, which could help assess the stroke volume wasted by dyskinesis and the potential residual LV body to guide surgical approaches and predict their outcome. Three-dimensional (3D) echocardiographic reconstruction has potential advantages for assessing aneurysmal left ventricles because it is not dependent on geometric assumptions, does not require standardized views that may exclude portions of the aneurysm, and can potentially measure separate aneurysm and nonaneurysm cavity volumes of any shape. The purpose of this study was first, to validate the accuracy of 3D echocardiographic reconstruction for quantifying total LV and separate LV body and aneurysm volumes in vitro so as to provide direct standards for the separate volumes; and second, to determine the feasibility and accuracy of 3D echocardiographic reconstruction for quantifying the total volume and function of aneurysmal left ventricles in an animal model, providing a reference standard for instantaneous LV volume.

METHODS AND RESULTS

A recently developed 3D system that automatically combines 2D images and their locations was applied (1) to reconstruct 10 aneurysmal ventricular phantoms and 12 gel-filled autopsied human hearts with aneurysms, comparing cavity volumes (total and aneurysm) to those measured by fluid displacement; and (2) to reconstruct the left ventricle during 19 hemodynamic stages in four dogs with surgically created LV aneurysms, comparing total volumes with actual instantaneous values measured by an intracavitary balloon attached to an external column for validation and also calculating the stroke volume wasted by aneurysmal dyskinesis. 3D reconstruction reproduced the distorted aneurysmal LV shapes. In vitro, calculated volumes (aneurysm, nonaneurysm, and total) agreed well with actual values, with correlation coefficients of .99 and SEEs of 3.2 to 6.1 cm3 for phantoms and 3.4 to 4.2 cm3 for autopsied hearts (mean error, < 4% for both). In vivo, LV end-diastolic, end-systolic, and stroke volumes as well as ejection fraction calculated by 3D echocardiography correlated well with actual values (r = .99, .99, .95, and .99, respectively) and agreed closely with them (SEE = 4.3 cm3, 3.5 cm3, 1.7 cm3, and 2%, respectively). The stroke volumes wasted by the aneurysm were -20.1 +/- 19.3% of LV body (nonaneurysm) stroke volume.

CONCLUSIONS

Despite distorted ventricular shapes, a recently developed 3D echocardiographic system and surfacing algorithm can accurately reconstruct aneurysmal left ventricles and quantify total LV volume (validated in vivo and in vitro) as well as the separate volumes of the aneurysm and residual LV body (validated in vitro). This should improve our ability to evaluate such ventricles and guide surgical approaches.

Hypertonic activation of AE2 anion exchanger in Xenopus oocytes via NHE-mediated intracellular alkalinization

Xenopus oocytes express endogenous Na+/H+ exchange activity but lack significant endogenous Cl-/HCO3- exchange activity. Coupled operation of Na+/H+ exchange and Cl-/HCO3- exchange contributes in many cell types to the cellular response to hypertonic stress. We therefore examined in Xenopus oocytes the osmotic regulation of chloride transport mediated by recombinant anion exchanger proteins AE2 and AE1. Hypotonicity was without effect on either anion transporter. Hypertonicity activated AE2-associated 36Cl- influx and efflux in a time- and osmolarity-dependent manner, whether incremental osmoles were charged or uncharged, but had no measurable effect on AE1 function. Hypertonic stimulation of AE2 was completely inhibited by Na+ removal or by addition of amiloride. In contrast, neither maneuver altered isotonic activity of AE2. Hypertonicity also induced amiloride-sensitive elevation of oocyte intracellular pH (pHi), and shifted the sigmoidal relationship of extracellular pH vs. AE2 activity > or = 0.5 units to the acid. Injection of pH 7.4 buffer into oocytes attenuated both hypertonic alkalinization and activation of AE2-associated 36Cl- influx, without inhibition of isotonic AE2 function. These data demonstrate that recombinant AE2 expressed in Xenopus oocytes is activated by increased pHi and that hypertonic activation of AE2 is secondary to hypertonic activation of Na+/H+ exchange.

Breath ethane generation during clinical total body irradiation as a marker of oxygen-free-radical-mediated lipid peroxidation: a case study

Total body irradiation (TBI) is used therapeutically for treatment of leukemias and other malignancies of the hemopoietic system. Ionizing radiation produces oxygen free radicals that contribute to cytotoxicity. Breath collected from one patient undergoing therapeutic TBI showed measurable changes in levels of ethane during treatment. Breath ethane is a marker of lipid peroxidation of n-3 fatty acids. The TBI treatment involved 4 days of irradiation. The largest changes in breath ethane occurred on Day 2. The increased levels of breath ethane on Day 2 were correlated to clinical manifestations of toxicity. The correlation of the onset of gastrointestinal side effects with higher levels of breath ethane suggests that breath ethane may be a clinically useful measure of the toxicity of various TBI fractionation treatment protocols currently in use at different medical centers. The levels of breath ethane on the other days of treatment were lower, suggesting that the oxidative-antioxidative balance of the patient may be important in protection against free radical mediated injury. These results for a single patient suggest that breath ethane may be a promising approach to elucidate the role of antioxidants in clinical TBI and should be extended for verification to a larger volunteer patient population.

Functional characterization and regulation by pH of murine AE2 anion exchanger expressed in Xenopus oocytes

cRNA encoding the murine band 3-related protein AE2 was expressed in Xenopus oocytes. AE2-mediated transport function and regulation were analyzed by unidirectional 36Cl- influx and efflux studies. AE2 cRNA-injected oocytes took up 36Cl- as much as 40-fold faster than did water-injected oocytes. AE2-mediated 36Cl- uptake increased as a function of increasing uptake time, number of days after cRNA injection, and amount of injected cRNA. Among the functional properties of AE2 evaluated were transport mechanism and substrate specificity, inhibitor pharmacology, and regulation by pH. The apparent Km for external Cl- was 5.6 mM. AE2 was defined as a Cl-/anion exchanger by two criteria: 1) 36Cl- efflux from AE2-expressing oocytes was maximally stimulated by extracellular Cl- or nitrate; AE2-associated 36Cl- efflux was supported by substitution of extracellular Cl- with other anions in the rank order bromide > isethionate > or = gluconate > iodide and 2) prolonged preincubation of AE2 cRNA-injected oocytes in Cl(-)-free media containing isethionate, gluconate, or glutamate decreased subsequent AE2-associated 36Cl- uptake from Cl- media in rough proportion to the degree of intracellular Cl- depletion, whereas preincubation in nitrate medium had no effect. AE2-associated 36Cl- uptake was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid at half-maximally inhibitory concentrations between 0.5 and 19 microM, depending on extracellular Cl- concentration, and progressed to irreversibility at 20 degrees C with a half-time of 20-30 min. Many additional inhibitors showed lower potency for AE2 than previously reported for AE1. Although AE2 expression did not change oocyte resting intracellular pH, AE2-associated 36Cl- influx and efflux were each decreased in acid incubation medium and increased in alkaline medium.

pHi and serum regulate AE2-mediated Cl-/HCO3- exchange in CHOP cells of defined transient transfection status

Anion exchanger (AE) protein-mediated anion exchange contributes to regulation of intracellular pH (pHi), Cl- concentration, and volume in vertebrate cells. We have extended the functional characterization of recombinant AE2-mediated Cl-/HCO3- exchange in single Chinese hamster ovary cells stably transfected with the polyoma large T antigen (CHOP cells) of defined transient transfection status using a novel surface marker coexpression vector. Marker expression and detection had minimal effect on the low endogenous Cl-/HCO3- exchange activity of CHOP cells, whereas coexpression of marker with AE2 elevated CHOP cell Cl-/HCO3- exchange activity 16-fold. Between pHi of 7.3 and 7.8, AE2-mediated flux of proton equivalents was activated > 11-fold by increasingly alkaline pHi without reaching saturation. This activation may be secondary to allosteric effects of pHi on AE2, in parallel with the obligatory increase in substrate intracellular HCO3- concentration. Nominal removal of CO2/HCO3- reduced AE2 activity by 90%. Addition of 10% calf serum slowly activated AE2 activity severalfold. This activation was slowly reversed after serum removal. Surface marker coexpression vectors improve both the efficiency and reliability of studies of recombinant protein function for a wide range of single cell assays in many cell types.

Intracardiac ultrasound measurement of volumes and ejection fraction in normal, infarcted, and aneurysmal left ventricles using a 10-MHz ultrasound catheter

BACKGROUND

Our objective was to examine the accuracy of intracardiac ultrasound (ICUS) measurement of left ventricular (LV) volumes and ejection fraction (EF) using a 10-MHz ultrasound catheter. ICUS can image the LV in cross sections at all levels along the long axis with a transducer mounted on the tip of a catheter. Sequential serial LV cross-sectional images can be obtained during cardiac catheterization and used to calculate LV volumes by Simpson's rule. This technique may be an alternative to contrast LV angiography.

METHODS AND RESULTS

A beating-heart in vivo model was created to measure LV volume directly and continuously with an intracavity high-compliance latex balloon connected to a calibrated extracardiac reservoir in eight dogs in 35 experimental stages. A 10F ICUS catheter with a 10-MHz single-element transducer was introduced retrogradely via the aortic valve to the apex. Series of sequential LV cross-sectional images were recorded from the apex to the base during a calibrated pullback of the catheter. At each 5-mm interval, the LV cross section was traced at end diastole and end systole. LV volume was calculated by Simpson's rule by integrating all segmental areas multiplied by segmental height. The effect on accuracy of selecting 5-, 10-, or 15-mm heights or a single section at the midventricular level for measurement was assessed. The influence of distorted ventricular shape on the accuracy of ICUS measurements of LV volume was evaluated. This method was applied in 19 experimental stages in 10 intact dogs and pigs catheterized via the femoral artery. In the in vivo canine model, LV end-diastolic volume, end-systolic volume, and EF determined by ICUS using 5-, 10-, or 15-mm segments were not different from the actual measurements. But correlation and agreement between ICUS end-diastolic volume and direct measurements for 5- and 10-mm segments were significantly better than for 15-mm segments or a single section. Similar excellent correlations and agreement were observed for actual and ICUS-derived end-systolic volumes using 5-, 10-, or 15-mm segments. The ICUS-derived EF correlated very well with actual EF with a small measurement error of 3.91 +/- 2.59% for 5-mm or 4.13 +/- 2.79% for 10-mm segments but a significantly greater measurement error for 15-mm segments (5.35 +/- 3.76%) or single sections (14.8 +/- 12.2%). The presence of LV infarction or aneurysm did not significantly influence the accuracy of ICUS calculations for segmental heights < or = 10 mm. Application in intact animals demonstrated a good correlation between stroke volume measured by ICUS and by thermodilution or flowmeter. ICUS-derived LV volumes correlated well with biplane angiographic volumes, with a tendency toward underestimation. There was no significant difference between ICUS-determined LV EF and EF determined by angiography.

CONCLUSIONS

Intracardiac echocardiography accurately measures LV volumes and global systolic function in both regularly shaped and distorted left ventricles. This technique directly and continuously visualizes circumferential LV endocardium and wall thickness without contrast agents or geometric assumptions for calculation of LV volume. Thus, it should be particularly useful in patients at high risk for contrast-related complications or distorted LV shapes in which geometric assumptions may not be valid.

Kinetics of uptake, transport, and accumulation of liposome-associated fluorescent dolichol esters in human fibroblasts

The anthroyl and n-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino (NBD) hexanoyl esters of dolichol were synthesized and incorporated into phospholipid liposomes. Fluorescence spectrometric methods were used to estimate the kinetics and dynamics of the incorporation and turnover of these esters in normal human fibroblasts. For anthroyl dolichol a saturable uptake of 2.5 x 10(3) pmol/10(6) fibroblasts was obtained. Half-maximum uptake was seen at a labeling concentration of 19 microM. The time required for half-maximum uptake of fluorescence (t1/2) was about 10 h. Over 50% of the anthroyl dolichol taken up remained in fibroblasts 24 h after the labeling medium was removed. Uptake was higher for esters of 9 isoprenes than for those with 16-21. Dolichol labeled with the NBD fluorophore appeared to enter fibroblasts in higher concentration than the same dolichol labeled with anthracene. Uptake was not influenced by the presence of agents that disrupt lysosome function (leupeptin and chloroquine) prior to or during fluorescence labeling. The amount of fluorescent dolichol in the (i) lysosomes and endosomes and (ii) nuclei of labeled fibroblasts was determined after Percoll density gradient centrifugation and cell lysis in culture, respectively. Most of the fluorescent dolichyl ester (and most of the free alcohol form) taken up by fibroblasts was recovered in lysosomes.

Quantification of pericardial effusions by three-dimensional echocardiography

OBJECTIVES

The purpose of this study was to examine the accuracy of three-dimensional echocardiography for the quantification of asymmetric pericardial effusion volume and to compare this new technique with two-dimensional echocardiography.

BACKGROUND

Quantification of pericardial effusion by two-dimensional echocardiography relies on a symmetric distribution of the fluid. Three-dimensional echocardiography can quantitate volume without these limitations, but its accuracy for pericardial effusion volume has not yet been assessed.

METHODS

In six open chest dogs, 41 different asymmetrically distributed pericardial effusions of known volume were created by serial infusions of fluid through a pericardial catheter. The hearts were imaged using an automated echocardiographic method that integrates three-dimensional spatial and imaging data. The surfaces of the pericardial sac and heart were then reconstructed, and the volumes of pericardial effusions were calculated. Two-dimensional echocardiography was performed simultaneously, and volumes were calculated using the prolate ellipsoid method. Asymmetric distribution of the fluid was obtained by applying localized hydrostatic pressure to the pericardium.

RESULTS

The volumes of pericardial effusion quantified using three-dimensional echocardiography correlated well with actual volumes (y = 1.0x - 1.4, SEE = 7.7 ml, r = 0.98). Two-dimensional echocardiography had an acceptable correlation (y = 1.0x + 2.3, SEE = 23 ml, r = 0.84), but a marked degree of variation from the true value was observed for any individual measurement.

CONCLUSIONS

Three-dimensional echocardiography accurately quantifies pericardial effusion volume in vivo, even when the fluid is distributed asymmetrically, whereas two-dimensional echocardiography is less reliable. This new technique may be of clinical value in quantitating pericardial effusion, especially in the serial evaluation of asymmetric or loculated effusions.

Three-dimensional echocardiography: in vivo validation for right ventricular free wall mass as an index of hypertrophy

OBJECTIVES

This study tested the ability of three-dimensional echocardiography to reconstruct the right ventricular free wall and determine its mass in vivo using a system that automatically combines two-dimensional images with their spatial locations.

BACKGROUND

Right ventricular free wall thickness is limited as an index of right ventricular hypertrophy because right ventricular mass may increase by dilation without increased thickness and because trabeculations and oblique views can exaggerate thickness in individual M-mode and two-dimensional scans. Three-dimensional echocardiography may have potential advantages because it can integrate the entire free wall mass, uninfluenced by oblique views or geometric assumptions.

METHODS

The three-dimensional system was applied to 12 beating canine hearts to reconstruct the right ventricular free wall in intersecting views. The corresponding mass was compared with actual weights of the excised right ventricular free wall (15.5 to 78 g). For comparison, right ventricular sinus and outflow tract thickness were also measured by two-dimensional echocardiography, and the ability to predict mass from these values was determined.

RESULTS

The three-dimensional algorithm successfully reproduced right ventricular free wall mass, which agreed well with actual values: y = 1.04x + 0.02, r = 0.985, SEE = 2.7 g (5.7% of the mean value). The two-dimensional predictions showed increased scatter: The variance of mass estimation, based on thickness, was 9.5 to 12.5 (average 11) times higher than the three-dimensional method (p < 0.02).

CONCLUSIONS

Despite the irregular crescentic shape of the right ventricle, its free wall mass can be accurately measured by three-dimensional echocardiography in vivo, providing closer agreement with actual mass than predictions based on wall thickness. This method, with the increased efficiency of the three-dimensional system, can potentially improve our ability to evaluate the presence and progression of right ventricular hypertrophy.

The binding site for ribosomal protein S8 in 16S rRNA and spc mRNA from Escherichia coli: minimum structural requirements and the effects of single bulged bases on S8-RNA interaction

Through specific interactions with rRNA and mRNA, ribosomal protein S8 of Escherichia coli plays a central role in both assembly of the 30S ribosomal subunit and translational regulation of spc operon expression. To better understand S8-RNA association, we have measured the affinity of S8 for a number of variants of its rRNA and mRNA binding sites prepared by in vitro transcription or chemical synthesis. With the aid of site-directed deletions, we demonstrate that an imperfect, 33-nucleotide helical stem encompassing nucleotides 588-603 and 635-651 possesses all of the structural information necessary for specific binding of S8 to the 16S rRNA. This segment consists of two short duplexes that enclose a conserved, asymmetric internal loop which contains features crucial for protein recognition. The S8 binding site in spc operon mRNA is very similar in both primary and secondary structure to that in 16S rRNA except for the presence of two single bulged bases in one of the duplex segments. In addition, the apparent association constant for the S8-mRNA interaction is approximately fivefold less than that for the S8-rRNA interaction. We show that the difference in affinity can be attributed to the effects of the bulged bases. Deletion of the bulged bases from the mRNA site increases its affinity for S8 to a level similar to that of the rRNA, whereas insertion of single-base bulges at equivalent positions within the rRNA site reduces its affinity for S8 to a value typical of the mRNA. Single-base bulges in the proximity of essential recognition features are therefore capable of modulating the strength of protein-RNA interactions.

Three-dimensional echocardiography. In vivo validation for right ventricular volume and function

BACKGROUND

Current two-dimensional echocardiographic measures of right ventricular volume are limited by the asymmetrical and crescentic shape of the ventricle and by difficulty in obtaining standardized views. Three-dimensional echocardiographic reconstruction, which does not require geometric assumptions or standardized views, may therefore have potential advantages for determining right ventricular volume. Three-dimensional techniques, however, have not been applied to the right ventricle in vivo, where cardiac motion and contraction could affect accuracy. The purpose of this study was to determine the feasibility and accuracy of three-dimensional echocardiographic reconstruction for quantifying right ventricular volume and function in vivo. In particular, it was designed to test the accuracy of a newly developed system that provides rapid, efficient, and automated three-dimensional data collection (minimizing motion effects) and takes advantage of the full three-dimensional data set to obtain volume.

METHODS AND RESULTS

The three-dimensional system was applied to reconstruct the right ventricle and measure its volume and function during 20 hemodynamic stages created in five dogs. Actual instantaneous volumes were measured continuously by an intracavitary balloon connected to an external column. Hemodynamics were varied by volume loading and induction of ischemia. Three-dimensional reconstruction successfully reproduced right ventricular volume compared with actual values at end diastole (y = 1.0 chi-3.4, r = .99, SEE = 1.8 mL) and end systole (y = 1.0 chi+ 2.0, 4 = .98, SEE = 2.5 mL). The mean difference between calculated and actual volumes throughout the cycle was 2.1 mL, or 4.9% of the mean. Ejection fraction also correlated well with actual values (y = 0.96 chi-0.3, r = .98, SEE = 3.3%).

CONCLUSIONS

Despite the irregular crescentic shape of the right ventricle, this newly developed three-dimensional system and surfacing algorithm can accurately reconstruct its shape and quantitate its volume and function in vivo without geometric assumptions. The increased efficiency of the system should increase applicability to issues of clinical and research interest.

Three-dimensional echocardiographic reconstruction of right ventricular volume: in vitro comparison with two-dimensional methods

Two-dimensional echocardiographic measures of right ventricular volume are limited by the asymmetric and crescentic shape of that ventricle and the difficulty in obtaining standardized views. We have developed a three-dimensional echocardiographic system that automatically integrates images and positional data and calculates right ventricular volume without the need for geometric assumptions or standardized views and a surfacing algorithm that takes advantage of the full three-dimensional data set. The accuracy of this system was studied and compared with two-dimensional methods in 12 gel-filled excised human right ventricles (18 to 74 ml). Volumes calculated by three-dimensional echocardiography correlated well with actual values (r = 0.99) and agreed more closely with them than did those obtained by two-dimensional methods (p < 0.02).

Skin elicitation threshold of ethylbutyl thiourea and mercaptobenzothiazole with relative leaching from sensitizing products

We studied 3 contact sensitizers present in rubber products, ethylbutyl thiourea (EBT), 2-mercaptobenzothiazole (MBT) and 2,2-dithio-bis-benzothiazole (MBTS), to relate the amount of sensitizer eliciting allergic contact dermatitis to the quantity leaching from a product into various biological fluids: normal saline, human plasma and 3 synthetic sweat solutions of pH 5.5 to 7.5. To determine the amount of sensitizer remaining after leaching, Soxhlet extraction with acetonitrile was subsequently performed. High-performance liquid chromatography was used for chemical analysis. 12 MBT-sensitive patients were patch tested with serial dilutions of MBT and MBTS in petrolatum. A Latin Square design was used in statistical analysis of variance of the patch test results. Large amounts of thioureas leached from 2 rubber articles eliciting thiourea dermatitis, the literature suggesting that these would have been well above the elicitation threshold. Leaching of MBTS was relatively greater than MBT into most media, whereas MBT was a more potent elicitor than MBTS at equivalent concentrations. The lowest eliciting concentration of MBT in 1 subject was 0.01%. Such information should prove helpful to manufacturers in designed products that do not release allergens sufficiently to cause reactions in consumers.

[Studies on the chemical constituents of Epimedium acuminatum Franch]

Five flavonoids were isolated from the aerial parts of Epimedium acuminatum. Their structures were determined chemically and spectroscopically to be baohuoside VI, tricin, icaritin, icariside I and baohuoside I.

The crystal structure and conformational analysis of substituted 2,7-dioxabicyclo[4,1,0]heptanes: 1,2-anhydro-3,4,6-tri-O-benzyl-beta-D-talopyranose

The title compound, C28H27O5, is triclinic, space group P1 with unit cell dimensions a = 12.763(2), b = 11.130(2), c = 4.764(3) A, alpha = 73.78(3), beta = 82.89(3), gamma = 62.16(1) degrees, V = 574.8(4) A3, and Z = 1. The pyranose ring has an 4H5 conformation with some flattening at C-4. Molecular mechanisms calculations indicate that the 4H5 conformation of the pyranose ring in the title compound is the most stable conformation.

Isolation of new nonsense and frameshift mutants in the immunoglobulin mu heavy-chain gene of hybridoma cells

In order to expand the experimental material available for genetic and biochemical analyses of the natural immunoglobulin genes, we have isolated a variety of mutant mouse hybridoma cell lines. Some of these mutants have partial or complete deletions of the mu gene. Other mutants have nonsense or frameshift mutations in the exons encoding the variable and the second and third constant region domains of the mu heavy chain. When combined with earlier mutant data, this collection of genotypically and phenotypically tight mutants of known sequence spans most of the 10 kb of the mu gene, providing material for a variety of studies of genetic recombination and mRNA metabolism.

[Hepatic schistosomiasis. X-ray computed tomographic aspects. Apropos of 97 cases]

Ninety seven patients with liver cirrhosis of schistosomiasis were collected. Its CT findings and features were analysed on the clinicopathological basis including (1) the high percentage of the hepatomegaly and of the enlargement of the left lobe; (2) occurrence of deposition and calcification of eggs in large bowel wall (5/5), the portal vein system (22/97), the root of the mesentery (9/97) and the liver (93/97); (3) the variety and characteristics of the appearances of the intrahepatic calcification; (4) widened and fibrotic changes in the portal canal region. It was also noted that high percentage of hepatocellular carcinoma associated with this disease in the present series (25/97).

Mutation of the gene for the human lysosomal serine protease cathepsin G is not the cause of aberrant APP processing in familial Alzheimer disease

Recent genetic linkage studies have implicated a gene on chromosome 14 in the pathogenesis of FAD. The identity of this gene remains unknown but it has been speculated that it may be involved in the cellular processing of the amyloid precursor protein (APP). We have analyzed the nucleotide sequence of the entire open reading frame of the cathepsin G gene located on chromosome 14q. No mutations were observed, suggesting that defects in this lysosomal protease are not responsible for aberrant accumulation of proteolytic products of APP in FAD brain tissue.

Land reforms in China

Describes the recent economic and land reforms in China, and the consequent changes in the emerging Chinese property market. Analyses the need for property management valuation skills in China in the light of problems of country size, regional differences, the scale of economic reforms and the speed with which they are being implemented, administration and the difficulty of educating a large number of property professionals.

Ultramark 1621 as a reference compound for positive and negative ion fast-atom bombardment high-resolution mass spectrometry

Ultramark 1621, a commercially available mixture of fluorinated phosphazines, was found to be a useful calibration compound for negative and positive ion fast-atom bombardment (FAB) high-resolution mass spectrometry. Ultramark 1621 worked very well with the most widely used matrices such as glycerol, nitrobenzyl alcohol, and triethanolamine. The negative and positive ion FAB mass spectra of Ultramark include a series of intense peaks extending from 700 to 1900 u.

Identification of calcitonin gene related peptide in ovine hypothalamic extract

Calcitonin gene-related polypeptide (CGRP) was purified from ovine hypothalamic extracts. Its amino acid sequence was determined as: Ser-(Cys)-Asn-Thr-Ala-Thr-(Cys)-Val-Thr-His-Arg-Leu-Ala-Gly-Leu-Leu-Ser- Arg-Ser - Gly-Gly-Val-Val-Lys-Ser-Asn-Phe-Val-Pro-Thr-Asn-Val-Gly-Ser-Gln-Ala-Phe- NH2. This sequence differs from rat CGRP by two amino acid substitutions (Ser for Asp25 and Gln for Glu35). Adenylate cyclase stimulating activity in rat pituitary cell cultures was monitored during the isolation. CGRP had adenylate cyclase stimulating activity comparable to corticotropin-releasing hormone, suggesting a hypophysiotropic role for CGRP. This is the first chemical characterization of CGRP in the brain (hypothalamus).

Effects of mutation position on frequency of marker rescue by homologous recombination

Homologous recombination between transferred and chromosomal DNA can be used for mapping mutations by marker rescue, i.e., by identifying which segment of wild-type DNA can recombine with the mutant chromosomal gene and restore normal function. In order to define how much the fragments should overlap each other for reliable mapping, we have measured how the frequency of marker rescue is affected by the position of the chromosomal mutation relative to the ends of the transferred DNA fragments. For this purpose, we used several DNA fragments to effect marker rescue in two mutant hybridomas which bear mutations 673 bp apart in the exons encoding the second and third constant region domains of the immunoglobulin mu heavy chain. The frequency of marker rescue decreased greatly when the mutation was located near one of the ends of the fragments, the results indicating that fragments should be designed to overlap by at least several hundred base pairs. Possible explanations for this "end effect" are considered.