Shear-dependent changes in the three-dimensional structure of human von Willebrand factor

The three-dimensional tertiary structure of human von Willebrand Factor (vWF) on a hydrophobic surface under aqueous conditions and different shear stress regimes was studied by atomic force microscopy (AFM). vWF was imaged by AFM at molecular level resolution under negligible shear stress, under a local applied shear force (7.4 to 19 nN) using the AFM probe in contact mode scanning, and after subjecting vWF to a range of shear stress (0 to 42.4 dyn/cm2) using a rotating disk system. The results demonstrate that vWF undergoes a shear stress-induced conformational transition from a globular state to an extended chain conformation with exposure of intra-molecular globular domains at a critical shear stress of 35 +/- 3.5 dyn/cm2. The globular vWF conformation (149 nm by 77 nm and height 3.8 nm) is representative of native vWF after simple diffusion to the hydrophobic surface, followed by adhesion and some spreading. In a shear stress field above the critical value, protein unfolding occurs and vWF is observed in extended chain conformations oriented in the direction of the shear stress field with molecular lengths ranging from 146 to 774 nm and 3.4 nm mean height. The shear stress-induced structural changes to vWF suggest a close conformation-function relationship in vWF properties for thrombogenesis in regions of high shear stress.

Eye movement desensitization and reprocessing: effectiveness and autonomic correlates

Eighteen subjects distressed by memories of a specific traumatic event were randomly assigned to a single session of one of three conditions: Eye Movement Desensitization and Reprocessing (EMDR), a Time Interval Condition (TIC), or Tapping Alternate Phalanges (TAP). All subjects treated in the EMDR group showed desensitization as monitored by SUDs, which correlated with the physiological data and cessation of pronounced symptomatology. Only one subject in a control group showed desensitization. Compared to TIC and TAP, autonomic measures showed distinct changes during EMDR: (1) respiration synchronized with the rhythm of the eye movements in a shallow, regular pattern; (2) heart rate slowed significantly overall; (3) systolic blood pressure increased during early sets, invariably declined during abreactions, and decreased overall; (4) finger tip skin temperature consistently increased; and (5) the galvanic skin response consistently decreased in a clear "relaxation response". This relaxing effect of the eye movements suggests that at least one of the mechanisms operating during EMDR is desensitization by reciprocal inhibition, by pairing emotional distress with an unlearned or "compelled" relaxation response.

Increased atherosclerosis in streptozotocin-induced diabetic mice

Premature and extensive atheroscleroses involving renal, peripheral, and cardiovascular sites remain major complications of diabetes mellitus. Controversy exists as to the contribution of hyperglycemia versus elevated local or systemic concentrations of insulin to atherosclerosis risk. In this report, we developed the first murine model susceptible to both atherosclerosis and diabetes to determine which diabetogenic factors contribute to vascular disease. C57BL/6 and BALB/c mice were treated with multiple low-dose streptozotocin (STZ) or control citrate buffer and fed rodent chow or an atherogenic-promoting (Ath) diet for 12-20 wk. STZ treatment resulted in sustained hyperglycemia (250-420 mg/dl) and a modest reduction in plasma insulin levels for both strains regardless of diet. Citrate-treated C57BL/6 mice fed the Ath diet showed extensive oil red O-staining fatty streak aortic sinus lesions (20,537+/-2,957 micron2), the size of which did not differ for Ath-fed mice treated with STZ (16,836+/-2,136 micron2). In contrast, hyperglycemic BALB/c mice fed the Ath diet showed a 17-fold increase in atherosclerotic lesion area (7,922+/-2,096 micron2) as compared with citrate-treated mice fed the Ath diet (467+/-318 micron2). Correlations between lesion size and plasma glucose levels were significant for BALB/c (r = 0.741, P < 0.009), but not C57BL/6 (r = 0.314, P<0.3) mice. Lesion size correlated significantly with plasma cholesterol for C57BL/6 (r = 0.612, P<0.03) but not BALB/c (r = 0.630, P<0.1) mice. Immunohistochemistry showed that aortic sinus lesions from both strains contained macrophages, but smooth muscle cells were clearly present in lesions of BALB/c mice. In summary, we present the first small animal model showing accelerated atherosclerosis in response to hyperglycemia. Fatty streaks resembled those of human type II lesions in that both macrophages and smooth muscle cells were evident. In addition, our results support the concept that hyperglycemia as opposed to hyperinsulinemia contributes heavily to risk of atherosclerosis.

How to screen for 222Rn in large buildings

222Rn measurements have been made in over 10,000 ground-contact rooms in 908 federal buildings. These data were examined statistically to compare parametric distributions that might be useful in the design and execution of future surveys of indoor 222Rn in large buildings. In 152 of the 365 buildings with the most measurements per building, the log-normal distribution was acceptable. Many other distributions were observed in the other 213 buildings, including bi- and tri-modal distributions. In contrast, when data from entire facilities were examined, the data were usually described by a lognormal distribution. Because of the above observations, we propose that any future surveys of indoor 222Rn in large buildings be done in two phases, screening and assessment. During the screening phase, all facilities may be surveyed with a comparatively low sampling density, perhaps, one measurement per 465 m2 (5,000 ft2) of floor space. Based on the results presented here, it is expected that statistical analysis of the screening data will reveal any facilities with substantial evidence of a high incidence of rooms with elevated indoor 222Rn concentrations (e.g., above 150 Bq m-3). In the assessment phase, the identified facilities will be surveyed with a sampling density of one measurement for every ground-contact room or about one per 84 m2 (900 ft2). Using numerical simulation techniques, we have tested the proposed screening phase protocol against data from sixteen facilities. The results of the simulated screenings support the feasibility of a two-phased approach to the task of identifying facilities having rooms with elevated 222Rn concentrations.

Experiences of cancer in children and adolescents

In an effort to understand the effect of cancer diagnosis and treatment in children and adolescents, and to identify issues that should be addressed with newly diagnosed patients, 85 patients with Ewing's sarcoma family tumors (ESFT) were interviewed about their experience of having cancer. This represents 90% of all eligible patients who survived at least 3 years since their diagnosis and who were treated for ESFT at the National Cancer Institute (NCI) from 1965-1993. The mean age of patients at the time of diagnosis was 15.8 +/- 5.3 years, and mean time since diagnosis was 13.6 +/- 6.4 years. Patients from this cohort had a disease usually related to poor outcome. Patients answered five open-ended written questions. Negative experiences that they described included transient and permanent discomfort and disabilities related to cancer; disruption of life or relationships; and emotional aspects of cancer diagnosis or treatment. Positive aspects of having cancer included changed attitudes about self and life, improved relationships with others, or better job performance. Advice for newly diagnosed patients most often dealt with the emotional aspects of cancer. The importance of patient-to-patient support was frequently described. Overall, having cancer was not an entirely negative experience, and it may result in introspection and improved relationships with others.

On the reduction of error in alpha track detector measurements of indoor 222Rn

Small plastic chambers containing alpha track detectors are often used for measuring indoor concentrations of 222Rn. This paper reports an experimental assessment of sources of error in measurements made with alpha track detector-containing chambers. The results demonstrate the feasibility of a nondestructive test for the identification of alpha track detector-containing chambers that are packaged in a way that does not effectively prevent ambient 222Rn from inducing tracks prior to field exposure. Results also indicate that there is statistically significant variation among manufacturing lots and among chemical processing batches. Error from these sources can be avoided or compensated if appropriate control measures are implemented as part of a quality assurance program during any survey using alpha track detector-containing chambers.

Metabolism of methoxyphenamine and 2-methoxyamphetamine in P4502D6-transfected cells and cell preparations

1. Control and P4502D6-transfected human B-lymphoblastoid cell lines (cHol and h2D6v2 respectively) were used to study 2D6-mediated metabolism of methoxyphenamine (MPA) and 2-methoxyamphetamine (2MA). The main metabolites were products of O-dealkylation and aromatic hydroxylation at the 5-position. In addition, N-desmethyl-methoxyphenamine (NDMP) was also identified as a minor metabolite of MPA in extracts of these cells, confirming previous reports of 2D6-mediated N-demethylation of MPA. 2. An additional ring-hydroxylated metabolite of MPA and 2MA has been tentatively identified as the corresponding 3-hydroxy-2-methoxy derivative. 3. MPA metabolism in whole cells was time dependent, with approximately 30% of the MPA metabolized after 72 h. A 35% conversion of MPA was achieved on average with cell lysates. Only 18% 2MA was metabolized. By contrast, control cells (cHol) showed no evidence of any MPA or 2MA metabolites even after 96-h incubation. 4. Continuous presence of haemin/dimethylsulphoxide (DMSO) throughout the 4-day incubation with MPA resulted in a shift in the metabolite profile towards the production of NDMP at the expense of the other products. 5. In summary, h2D6v2 cells, lysates and microsomes can form all metabolites of MPA and can be used in drug interaction studies.

Hyper- and hypo-responsiveness to dietary fat and cholesterol among inbred mice: searching for level and variability genes

A concept proposed by Berg (Berg, K. 1989. Arteriosclerosis. 9: I-50-I-58) is that a combination of level and variability genes determine an individual's overall plasma lipid levels and atherosclerotic risk. Our goal was to determine which inbred mouse strains could be used to identify candidate level and variability genes controlling lipid levels and atherosclerosis susceptibility. Nine common inbred mouse strains were examined for responsiveness with respect to plasma lipoprotein and tissue lipid levels upon feeding diets rich in cholesterol and fat. Marked quantitative variations were observed in plasma cholesterol and triglyceride levels among mice fed rodent chow and the high fat test diets. Mice of strains DBA/2 and AKR appeared to be hyporesponsive to diets containing high levels of fat and cholesterol as compared to rodent chow. In contrast, several strains were primarily hyperresponsive to either dietary fat or cholesterol, or both ingredients. Determination of cholesterol absorption for selected strains fed test diets suggested that decreased cholesterol absorption, in part, contributes to hyporesponsiveness as seen in DBA/2 mice. Levels of mRNA for cholesterol 7 alpha-hydroxylase were estimated and shown to vary markedly among strains. An inverse correlation was seen among strains between cholesterol 7 alpha-hydroxylase mRNA, and plasma and hepatic cholesterol levels for some diets. Thus, genes controlling cholesterol absorption and bile acid synthesis are candidates for further study as level and variability genes affecting plasma cholesterol levels. Overall, inbred mouse strains will prove useful for identifying genes controlling level and variability traits.

Mumps outbreak in a highly vaccinated school population. Evidence for large-scale vaccination failure

OBJECTIVES

To describe an outbreak and to identify risk factors for mumps occurring in a highly vaccinated high school population. (Note: Highly vaccinated means a population in which more than 95% have been vaccinated.)

DESIGN AND PARTICIPANTS

Survey and cohort study of 307 (97%) of 318 students.

OUTCOME MEASURES

Mumps was defined as an illness with 2 or more days of parotid swelling. Serologic confirmation of infection was obtained in eight cases, seven of which were evaluated for presence of IgM antibody using immunofluorescent antibodies. Vaccination records were verified for 297 (97%) students.

RESULTS

Between October 3 and November 23, 1990, clinical mumps developed in 54 students (attack rate, 18%), 53 of whom had been vaccinated. Most cases (40 [77%] of 52) occurred 12 to 20 days after a school-wide pep rally. Immunofluorescent antibody testing of all seven specimens demonstrated IgM antibody to mumps. Risk factors for clinical mumps identified in multivariate analyses included female gender (odds ratio, 3.0; 95% confidence interval, 1.6 to 5.7) and source of vaccination other than the local public health clinic (students vaccinated by private providers [odds ratio, 3.0; 95% confidence interval, 1.3 to 5.2] or in other districts [odds ratio, 2.4; 95% confidence interval, 1.1 to 5.3]).

CONCLUSIONS

The overall attack rate is the highest reported to date (and to our knowledge) for a population demonstrating virtually complete mumps vaccine coverage. Even verified documentation of vaccination may not be an accurate indicator of an individual's protection against mumps. Vaccination failure may play an important role in contemporary mumps outbreaks. We found no evidence to indicate that waning immunity (secondary vaccine failure) contributed significantly to this outbreak. A second dose of mumps vaccine, as recommended using measles-mumps-rubella vaccine, could potentially prevent similar outbreaks in secondary school populations in the future.

The influence of pregnancy on the biotransformation and urinary excretion of methoxyphenamine in mice

(i) The urinary elimination of methoxyphenamine (MPA) and its metabolites in underivatized samples was examined after single and multiple oral administration to pregnant and non-pregnant mice by GLC and GLC-MS. (ii) The major metabolite O-desmethylmethoxyphenamine (ODMP), along with lesser amounts of N-desmethylmethoxyphenamine (NDMP) and 2-hydroxyamphetamine (2OH), were the only metabolites detected in urine extracts of pregnant and non-pregnant mice. 5-Hydroxymethoxyphenamine (5HMP) was not detected. Enzyme hydrolysis did not increase the recovery of either substrate or metabolites in either the pregnant or non-pregnant animals. The results show that MPA metabolism in the Swiss-Webster mouse is distinctly different from that seen in man and other laboratory animals. (iii) The mean MPA:ODMP ratio in day-6 urine from pregnant mice after a single dose was 0.31 +/- 0.04. The NDMP:ODMP ratios were less than 0.10 in all samples. Non-pregnant mice urine had equivalent amounts of MPA, NDMP, ODMP, and 2OH after multiple dosing. (iv) While multiple dosing and pregnancy did not alter either the urinary recovery or profile of the metabolites detected, there was a linear decrease in the MPA:ODMP ratio during gestation. (v) MPA was extensively metabolized to ODMP in the male mice, and the MPA:ODMP ratio of 0.41 was slightly higher than that observed in the pregnant and non-pregnant females.

X-ray fluoroscopy spatio-temporal filtering with object detection

One potential way to reduce patient and staff X-ray fluoroscopy dose is to reduce the quantum exposure to the detector and compensate the additional noise with digital filtering. A new filtering method, spatio-temporal filtering with object detection, is described that reduces noise while minimizing motion and spatial blur. As compared to some conventional motion-detection filtering schemes, this object-detection method incorporates additional a priori knowledge of image content; i.e. much of the motion occurs in isolated long thin objects (catheters, guide wires, etc.). We create object-likelihood images and use these to control spatial and recursive temporal filtering such as to reduce blurring the objects of interest. We use automatically computed receiver operating characteristic (ROC) curves to optimize the object-likelihood enhancement method and determine that oriented matched filter kernels with 4 orientations are appropriate. The matched filter kernels are simple projected cylinders. We demonstrate the method on several representative X-ray fluoroscopy sequences to which noise is added to simulate very low dose acquisitions. With processing, we find that noise variance is significantly reduced with slightly less noise reduction near moving objects. We estimate an effective exposure reduction greater than 80%

Perception of fluoroscopy last-image hold

Last-image hold (LIH) is used in x-ray fluoroscopy systems as a convenience and dose savings feature. In the case of an image sequence, temporal filtering in the human visual system (HVS) reduces perceived noise. In the case of a constant, single image frame, this phenomenon is not present: the image looks noisier, and low-contrast objects disappear. Using low-contrast, stationary cylinder and disk phantoms in noise, perception of single frames are compared with that of conventional 30 acq/s continuous fluoroscopy (continuous). The dose of continuous is fixed at Q/acq, and the dose of single-frame presentations is varied in order to determine an "equivalent-perception dose" for a paired-comparison task. The equivalent-perception dose depends upon the shape and size of an object. As cylinder diameter increases from 1 to 21 pixels, the equivalent-perception dose decreases from 4.6 to 2.8 Q/acq. At equal equivalent-perception dose values, the relationship between cylinder and disk diameters are determined; a cylinder diameter of 10 pixels is roughly equivalent to a disk diameter of 20 pixels. For interventional angiography, an average equivalent-perception dose of approximately 3.5 Q/acq for a single-frame presentation is predicted. Thus processing by the HVS effectively reduces noise variance by a factor of 3.5, corresponding to an effective averaging time of 3.5 frames or 120 ms. Several variance reduction techniques are suggested to create an LIH frame having perception equal to the fluoroscopy sequence.

Volumetric intracoronary ultrasound: methods and validation

Intracoronary ultrasound (ICUS) not only allows visualization of the vessel lumen, it gives a unique view of the transmural components of the artery wall. Analysis of lumen and plaque volume is necessary for studying atherosclerotic disease progression or regression and the mechanisms of therapeutic coronary interventions. A real-time, ICUS pull-back data acquisition scheme was developed to acquire calibrated, cardiac-gated volumetric image data sets. A semiautomated border detection scheme was implemented using dynamic programming. In phantoms, estimated area profiles were very reproducible as measured by the root-mean-square from the mean (3.8-5.9%). In phantom volume estimates, improved reproducibility (standard deviation = 1.2-3.6%) was obtained as positive and negative errors in area profiles were averaged out. Phantom volumes were also accurate when compared to true water displacement volume. The mean error ranged from -2.59 to -8.94%. When compared to quantitative single and biplane angiographic analysis, ICUS volumetric estimates tended to be superior to single plane analysis (error -5.06 +/- 2.48% vs -9.96 +/- 8.01%), but similar to optimal biplane analysis (error -5.06 +/- 2.48% vs -6.34 +/- 3.08%). In vivo reproducibility was assessed by performing multiple cardiac-gated pull-backs through experimentally induced stenosis. Over the length of the stenosis, excellent reproducibility of area profiles (+/- 5.9%) and volumes (+/- 1.9%) was obtained for cardiac-gated acquisitions. We conclude that volumetric ICUS provides accurate and reproducible estimates of lumen volume. Thus this technique may be of use in clinical trials where changes lumen volumes and vessel area profiles are of interest.

Model for perception of pulsed fluoroscopy image sequences

Pulsed fluoroscopy at reduced frame rates can be used to lower x-ray dose with equivalent detection (hereafter called equivalent perception) of low-contrast, stationary objects. Experimentally average dose savings of 22%, 38%, and 49%, for pulsed fluoroscopy at 15, 10, and 7.5 acquisitions per second, respectively, are documented. Dose savings depend on object size, with fewer savings for smaller objects. To explain these data, we extend the framework of an ideal observer with three models for the spatiotemporal response of the human visual system (HVS). They are model 1, separable; model 2, nonseparable; and model 3, nonseparable with internal observer noise. With no free parameters, model 1 predicts the average dose savings within a 3% difference but does not describe the effect of object size. Models 2 and 3 explain the influence of size, and model 3, with a single free parameter, fits the measurements best. Perception of pulsed fluoroscopy is thus well described in terms of spatiotemporal processing by the HVS.

Optimal data acquisition for volumetric intracoronary ultrasound

Three-dimensional analysis using intracoronary ultrasound (ICUS) pull-back data provides the unique ability to quantitate lumen and atherosclerotic plaque volumes. Optimal data acquisition parameters for volumetric acquisition were established using simulations on computer phantoms of stenotic arteries. Eleven computer phantoms were generated using cross-sectional area data from quantitative angiography of stenotic coronary arteries. Three methods of data acquisition were simulated: conventional manual pull-back; motorized pull-back; and manual pull-back with measured displacement. Effects of pull-back velocity and cardiac gating on cross-sectional area profiles and volumes were studied. Cardiac gating eliminated errors introduced by vessel deformation within a cardiac cycle. With cardiac gating, pull-backs with mean velocities up to 1.2 mm/sec allowed reconstruction of cross-sectional area profiles within 5% RMS error. With faster pull-backs, cardiac gating resulted in sparse spatial sampling and significant errors in cross-sectional area profiles. The accuracy of both motorized and measured required equal displacements of the catheter proximal and distal ends. This assumption was validated with in vitro experiments where X-ray fluoroscopy was used to measure the displacement of the imaging tip. Excellent correlation was found between the two displacements (r = 0.99). Finally, slow pull-backs were performed by 3 operators, and pull-back velocities were measured. It was found that mean pull-back velocities as low as 0.8 mm/sec were achievable. From our simulations, we predict that accurate volumetric analysis requires cardiac gated, calibrated, slow (< 1.2 mm/sec) pull-backs.

The analysis of survival (mortality) data: fitting Gompertz, Weibull, and logistic functions

Survival functions are fitted to survival data from several large populations. The Gompertz survival function corresponds to exponential mortality rate increases with time. The Weibull survival function corresponds to mortality rates that increase as a power function of time. A two-parameter, logistic survival function is introduced, and corresponds to mortality rates that increase, and then decrease, with time. A three-parameter logistic-mortality function also is examined. It reflects mortality rates that rise, and then plateau, with age. Data are from published studies of medflies, Drosophila, house flies, flour beetles, and humans. Some survival data are better fit by a logistic survival function than by the more traditionally used Gompertz or Weibull functions. Gompertz, Weibull, or logistic survival functions often fit the survival of 95+% of a population, and the 'tails' of the survival curves usually appear to fall between the values predicted by the three functions. For some populations, such 'tails' appear to be too complex to be fit well by any simple function. Survival data for males and females in some populations are best fit by different functions. Populations of 100 or more are needed to distinguish among the functions. When testing effects of environmental or genetic manipulations on survival, it has been common to determine the changes in parameter values for a given function, such as Gompertz. It may be equally important to determine whether the best-fit function has changed as well.

The x-ray fovea, a device for reducing x-ray dose in fluoroscopy

The x-ray fovea (U.S. patents pending) is a device for reducing x-ray dose to patients and operations during x-ray fluoroscopy. It consists of a semitransparent collimator with an open, circular, central hole. The fovea collimator is placed at the exit of the x-ray tube, and the attenuation of the peripheral x-ray beam reduces x-ray exposure to patients and operators. The shadow caused by the x-ray fovea can be compensated using real-time image processing hardware. Accurate compensation is demonstrated for both linearly and logarithmically acquired images using a model that accounts for beam hardening in the fovea collimator. The central fovea region has improved image quality due to reduced scatter and veiling glare from the periphery. From beam-stop measurements, a 40% reduction in scatter plus veiling glare is measured using the fovea. A contrast improvement ratio of 1.5 is measured throughout the central region. In the compensated periphery, noise is increased by a factor of 1.66 because fewer photons are detected, but a small amount of temporal filtering compensates this degradation. The Roentgen area product (RAP) exposure to patients is reduced by approximately 70%, while scattered exposure to operators is reduced by approximately 60%.

Perceptual comparison of pulsed and continuous fluoroscopy

Pulsed fluoroscopy (hereafter called pulsed) at reduced acquisition rates, typically 15 acq/s (pulsed-15), is proposed to reduce x-ray dose in interventional procedures. However, since the human visual system (HVS) acts as a temporal low-pass filter that interacts with such acquisitions, the proper dose for pulsed must be obtained in perception experiments. We determine the dose for low-frame-rate pulsed that gives visualization equivalent to that of conventional 30 acq/s fluoroscopy, hereafter called continuous. Computer-generated phantoms are used. They consist of stationary, low-contrast disks on a flat background containing Poisson noise that mimics quantum noise in fluoroscopy. Image sequences are displayed on the video tachistoscope, a device with considerable display flexibility. Three experimental paradigms are used. (1) In a paired-comparison study, pulsed and continuous are displayed side-by-side on the same monitor, and the visibility of a contrast detail phantom is compared. (2) Using this same display, subjects record the minimally detectable disk contrast (the min-contrast measurement). (3) In a four-alternative forced-choice experiment, a disk is placed in one of four positions, and the subject determines the position of the disk. The methods are complementary--the forced-choice experiment properly eliminates the subjectivity of the observer threshold while the paired-comparison study is much more time efficient. With regard to pulsed and continuous comparisons, remarkable similarity is found between the supra-threshold experiments (1 and 2) and the detectability experiment (3); i.e., the average absolute differences in the equivalent-perception dose as determined by the three measures is approximately 3%. No difference is found between interlaced and noninterlaced display. A relatively small dependence of dose savings on disk size is found with larger disks giving increased dose savings. Average dose savings of 22%, 38%, and 49% are found for pulsed-15, pulsed-10, and pulsed-7.5, respectively.

Isolation and in situ localization of a cDNA encoding a Kex2-like prohormone convertase in the nematode Caenorhabditis elegans

1. A cDNA that encodes a Kex2-like prohormone convertase (PC) containing an active site similar to that of mammalian PC2 has been isolated from C. elegans. Total RNA was isolated from a mixed population of strain BA713 worms. After poly-(A)-selection and reverse transcription, degenerate/nested polymerase chain reactions (PCR) were performed using primers based on conserved regions within the active sites of the known vertebrate and invertebrate endoproteases. 2. Two distinct 300-bp PCR products that shared homologies with the active sites of known Kex2-like endoproteases were isolated. These two PCR products were used to screen a C. elegans cDNA library. 3. The complete cDNA for a Kex2-like endoprotease, designated CELPC2, was isolated and determined to be 2527 bp in length. This size was confirmed by northern analysis. The deduced amino acid sequence for the CELPC2 cDNA is very similar to the known Kex2-like endoproteases, especially at conserved regions within the active sites, but not identical to any one of them. The strongest structural homology was to vertebrate and invertebrate PC2 sequences. 4. In situ hybridization suggests that CELPC2 is synthesized primarily in cells associated with the circumpharyngeal nerve ring and the dorsorectal ganglion.

Analysis of job functions of top level nurse executives in acute, home, and long-term care: implications for education

The purpose of this study was to strengthen the empirical base for nursing administration curricula by analyzing the current job functions of top level nurse executives in acute, long-term, and home care settings. The survey of job functions was designed to identify the relative amount of "time spent" and "importance" attributed to the job activities of nurse executives. Course content areas providing preparation for key job responsibilities are identified, and recommendations for curriculum design are discussed.

Database tracking for pediatric home infusion outcomes

Until now national data-collection efforts for home infusion therapy have focused on adult patients, but as the number of children and infants who receive home infusion increases, so does the need for tracking their outcomes. Several pediatric home care directors met the challenge by creating the National Pediatric Home Care Database.

A comparison of methods for estimating mortality parameters from survival data

The Gompertz mortality function, Rm = R0e alpha t, is frequently used to describe changes in mortality rate (Rm) with time (t). In this paper, four methods for determining the best fit values of the two parameters, R0 and alpha, are compared. Three of the four methods use the Gompertz mortality function with mortality rate estimates derived from survival data to determine the best fit values for the two parameters. All three confront problems. The fourth method uses the Gompertz survival function, which can be derived from the Gompertz mortality function and which allows one to use survival data directly. It thereby avoids the problems and generally gives the best estimates for the two parameters. The use of the mortality function, with mortality rate estimates, confronts four distinct problems. One of these is caused by time intervals when zero organisms die. A second is caused by errors produced in estimating mortality rates from survival data. If too high a proportion of a population die in a given time interval, the mortality rate estimates are too low. A third problem is the sensitivity of the mortality-equation-based analyses to values at the end of the survival curve, where scatter in mortality values tends to be greater. A final problem occurs when time intervals greater than one time unit (day, week, year, etc.) are used in the analysis. Such problems with the use of mortality rates to estimate parameter values are revealed when the calculated parameters are used to produce a survival curve, or when known values of R0 and alpha are used to generate survival data. This paper introduces a non-linear regression analysis, using a Simplex algorithm to fit parameters R0 and alpha in the Gompertz Survival function and concludes that it gives more reliable and consistent results with a variety of data than do three methods that use the mortality function.

Biotransformation of tri-substituted methoxyamphetamines by Cunninghamella echinulata

1. Four trimethoxyamphetamine analogues were incubated with the filamentous fungus Cunninghamella echinulata. 2. 2,4,5-Trimethoxyamphetamine and 2,5-dimethoxy-4-ethoxyamphetamine were poorly metabolized by C. echinulata ATCC 9244 and C. echinulata var. elegans ATCC 9245. 2,5-Dimethoxy-4-(n)-propoxyamphetamine was mainly metabolized through N-acetylation and O-dealkylation with minor amounts of several aliphatic hydroxylation metabolites formed. 2,5-Dimethoxy-4-methylthioamphetamine was extensively metabolized to the corresponding sulphoxide. 3. 2,5-Dimethoxy-4-methylthioamphetamine metabolism was inhibited by ethanol and quinidine. Sparteine did not inhibit the formation of the sulphoxide and may have shunted the substrate through alternate metabolic pathways. 4. Incubation conditions can affect the rate and extent of fungal biotransformation of 2,5-dimethoxy-4-methylthioamphetamine, and influence dextrose utilization, ammonia formation and pH.

In vitro assessment of cytotoxicity and biotransformation of propranolol in Cunninghamella echinulata

1. Biotransformation studies with five concentrations of racemic propranolol were conducted using the filamentous fungus Cunninghamella echinulata ATCC 9244. 2. The rate of formation and subsequent disappearance of a new major metabolite, 8-hydroxypropranolol, was dose-dependent. Desisopropylpropranolol and 4-hydroxypropranolol were also formed. 4-Hydroxypropranolol was the major fungal metabolite in earlier studies. 3. Propranolol exerted a dose-dependent response on biotransformation, fungal growth, dextrose utilization, ammonia formation and incubation broth pH. Determination of dextrose utilization and incubation broth pH would provide reliable, cost-effective and convenient alternative methods for cytotoxicological evaluation.