Pretreatment to reduce somatic Salmonella phage interference with FRNA coliphage assays : successful use in a one-year survey of vulnerable groundwaters.

Somatic salmonella (SS) phages were commonly found in higher numbers than F-specific RNA (FRNA) coliphages in a multi-site survey of contamination-vulnerable groundwaters. The relative abundance of SS phages required that a pretreatment procedure be implemented to reduce the SS phage content of samples before FRNA coliphage assay with Salmonella typhimurium WG49. Pretreatment involved selective SS phage removal by Salm. typhimurium WG45 cells. This pretreatment proved effective in producing interference-free samples throughout the one-year survey period and in seeded evaluation, was shown not to affect the detection of representative FRNA coliphage MS2. During the survey, 30 groundwater sites located in the continental United States, Puerto Rico and the Virgin Islands were examined for FRNA coliphages and SS phages at monthly intervals. FRNA coliphages were detected at six of the 30 sites and in 33 of 329 monthly samples. SS phages were also detected at six sites and in 28 of 329 monthly samples. Five of the phage-positive sites were positive for both phage groups. At those five sites, 58 monthly samples were collected during the survey period. Those 58 samples yielded an average FRNA coliphage concentration of 140 pfu per 100 l of groundwater as compared to an average SS phage concentration of 565 pfu per 100 l of groundwater. Twenty of the 58 samples were positive for both the FRNA coliphages and SS phages. In those samples, FRNA coliphages were more abundant in five samples; SS phages were more abundant in 15 samples. Because these results demonstrate that SS phage levels may often exceed FRNA coliphage levels in environmental waters, it is clear that SS phage removal procedures will greatly enhance the effectiveness of the WG49-based FRNA coliphage assay.

Detection of viruses in environmental samples: suitability of commercial rotavirus and adenovirus test kits.

Commercially marketed kits are now available for rapid viral assay of clinical specimens. This study was conducted to determine the suitability of these kits for use in environmental testing. Eight rotavirus kits and one enteric adenovirus kit were screened for sensitivity using simian rotavirus SA11, human rotavirus Wa, and adenovirus 41. The most sensitive rotavirus kit and the adenovirus kit were selected for further evaluation using virus-seeded and unseeded sewage samples. The selected rotavirus kit proved capable of detecting virus at the 10(1) PFU/ml level. The enteric adenovirus kit was similarly sensitive, detecting virus at the 10(1) TCID50/ml level. Neither kit was adversely affected by the presence of sewage. Kit assay revealed 3 of 30 unseeded sewage samples to be positive for rotavirus. Adenovirus positive samples were not detected among the 30 samples. These results were confirmed using electron microscopy. It was concluded that sensitive commercial kits could provide a reasonable alternative to cell culture for the presumptive testing of environmental samples.

Electron microscopy of stool-shed viruses: retention of characteristic morphologies after long-term storage at ultralow temperatures.

Storage of stool specimens at -70 degrees C has been reported to destroy the characteristic morphology of calicivirus. To determine if other stool-shed viruses are similarly affected, stool specimens previously examined by electron microscopy and observed to contain virus particles were reexamined after 6-10 years of storage at -70 degrees C to -85 degrees C. The stools contained virus particles of different morphological types, including astrovirus, small round structured virus, adenovirus, and rotavirus as well as calicivirus. Also reexamined were stools containing coronavirus-like particles and T = 19 virus-like particles. Characteristic virus particles, including calicivirus particles, were recognized in all the stools reexamined. The results indicate that long-term storage of stools at ultralow temperatures does not present a significant problem for the morphological identification of stool-shed viruses.

Review of hydrodynamic principles for the cardiologist: applications to the study of blood flow and jets by imaging techniques.

An understanding of the basic concepts of the physics of blood flow is of vital importance to the cardiologist as he or she attempts to utilize new blood flow imaging modalities, such as Doppler ultrasound and nuclear magnetic resonance imaging. Concepts such as the Bernoulli equation and its limitations, the continuity equation and volume flow calculations and the theory of free and confined jets have applications in cardiac blood flow-related problems. For example, mitral regurgitant flow may be treated with the free jet theory. Aortic stenosis results in confined jet flow. It is important that the cardiologist understand the basic principles behind these hydrodynamic concepts so that he or she can use them in appropriate applications. The limitations of the simplification of complex hydrodynamic relations that are used clinically need to be clearly understood so that these simplified principles are not used improperly or used to draw oversimplified conclusions.

In vitro hemodynamic characteristics of tissue bioprostheses in the aortic position.

The in vitro hemodynamic characteristics of a variety of old and new generation porcine and bovine pericardial bioprostheses were investigated in the aortic position under pulsatile flow conditions. The following valves were studied: Carpentier-Edwards porcine (Models 2625 and 2650), Carpentier-Edwards pericardial, Hancock porcine (Models 242, 250, and 410), Hancock pericardial, and Ionescu-Shiley (standard and low-profile) bioprostheses. The pressure drop results indicated that the old design valves had performance indices in the range of 0.30 to 0.42, whereas the new low-pressure fixed designs have performance indices of 0.50 to 0.70. Flow visualization and velocity and turbulent shear stress measurements, conducted with a two-dimensional laser Doppler anemometer system, indicated that all tissue valve designs created jet-type flow fields. The intensity of the jets and turbulence levels were less severe with the new designs. The old designs created higher peak jet velocities and higher levels of turbulent shear stresses. On the whole, pericardial bioprostheses have better in vitro hemodynamic characteristics than porcine bioprostheses. These observations should have applications regarding the clinical choice of bioprosthetic valves and have implications regarding further improvements in the preparation and design of bioprosthetic valves.

In vitro fluid dynamic characteristics of aortic bioprostheses: old versus new.

The in vitro fluid dynamic characteristics of a variety of old- and new-generation porcine and pericardial aortic bioprostheses were investigated under pulsatile flow conditions. The pressure drop results indicate that the old valve designs have performance indices in the range of 0.30 to 0.42, while the new, low-pressure fixed designs have performance indices of 0.50 to 0.70. Leaflet photography indicated that the new designs also have superior opening and closing characteristics. Flow visualization, and velocity and turbulent shear stress measurements, conducted with a two-dimensional laser Doppler anemometer system, indicated that all the tissue valve designs create jet-type flow fields. The intensity of the jets and turbulence levels were less severe with the new designs. The old designs created turbulent shear stresses of as little as 1500 dynes/cm2, while the new designs created turbulent shear stresses of as little as 750 dynes/cm2.

Analysis of candidate anticancer drugs by thermospray high-performance liquid chromatography-mass spectrometry and by high-resolution mass spectrometry.

Thermospray high-performance liquid chromatography-mass spectrometry (TSP-HPLC-MS) and direct probe high-resolution MS was used to analyze four candidate anticancer drugs. The techniques were used to confirm the identity of the bulk drug and to identify impurities. Analysis by TSP-HPLC-MS resulted in molecular weight information from the separated components using as little as 50 ng of each drug. The high-resolution direct probe MS analysis provided additional structural information and possible empirical formulas for the parent drugs and their impurities. The use of both of these complimentary techniques proved to be very specific for the detection of the anticancer drugs and for postulating the identity of impurities.

Membrane-associated viral complexes observed in stools and cell culture.

Viral complexes observed to be membrane associated rather than clumped by antibody were detected in a rotavirus-containing stool specimen by negative-stain electron microscopy. These "viral packets" were also observed in cell culture fluids after repeated passaging and contained up to 100 virions. Other stool specimens have been observed to contain similar packets of parvovirus-like particles. Such complexes must be expected in fecally contaminated water.

Numerical simulation of steady turbulent flow through trileaflet aortic heart valves--II. Results on five models.

Turbulent flow simulations are run for five aortic trileaflet valve geometries, ranging from a valve leaflet orifice area of 1.1 cm2 (Model A1--very stenotic) to 5.0 cm2 (Model A5--natural valve). The simulated data compares well with experimental measurements made downstream of various aortic trileaflet valves by Woo (PhD Thesis, 1984). The location and approximate width and length of recirculation regions are correctly predicted. The less stenotic valve models reattach at the end of the aortic sinus region, 1.1 diameters downstream of the valve. The central jet exiting the less stenotic valve models is not significantly different from fully developed flow, and therefore recovers very quickly downstream of the reattachment point. The more stenotic valves disturb the flow to a greater degree, generating recirculation regions large enough to escape the sinuses and reattach further downstream. Peak turbulent shear stress values downstream of the aortic valve models which approximated prosthetic valves are 125 and 300 Nm-2, very near experimental observations of 150 to 350 Nm-2. The predicted Reynolds stress profiles also present the correct shape, a double peak profile, with the location of the peak occurring at the location of maximum velocity gradient, which occurs near the recirculation region. The pressure drop across model A2 (leaflet orifice area 1.6 cm2) is 20 mmHg at 1.6 diameters downstream. This compares well with values ranging from 19.5 to 26.2 mmHg for valves of similar orifice areas. The pressure drop decreases with decreasing valve stenosis, to a negligible value across the least stenotic valve model. Based on the good agreement between experimental measurements of velocity, shear stress and pressure drop, compared to the simulated data, the model has the potential to be a valuable tool in the analysis of heart valve designs.

A community waterborne gastroenteritis outbreak: evidence for rotavirus as the agent.

A community waterborne nonbacterial gastroenteritis outbreak occurred in Eagle-Vail, Colorado in March 1981. Illness (defined as vomiting and/or diarrhea) was statistically associated with water consumption (chi 2 for linear trend = 7.07, p less than .005). Five of seven persons associated with the outbreak were infected with rotavirus as shown by virus detection or serological methods. Bacterial pathogens, Giardia lamblia, and Norwalk virus were excluded as responsible agents. Rotavirus should be looked for as a cause of waterborne outbreaks.

Bileaflet, tilting disc and porcine aortic valve substitutes: in vitro hydrodynamic characteristics.

The desire for a low profile mechanical valve with better fluid dynamic performance led to the design and development of the St. Jude Medical bileaflet prosthesis. Comparative in vitro flow studies indicate that it has better pressure drop characteristics than the Björk-Shiley (convexo-concave) and Carpentier-Edwards porcine valves in current clinical use, especially in the small sizes. In the 21 to 27 mm aortic valve size range the St. Jude valve has an average performance index of 0.66, compared with 0.46 and 0.32 for the Björk-Shiley and Carpentier-Edwards valves, respectively. In contrast, the St. Jude valve has larger regurgitant volumes than both the Björk-Shiley and Carpentier-Edwards valves. Velocity measurements with a laser-Doppler anemometer indicate relatively centralized flow with small amounts of turbulence downstream of the St. Jude valve. The flow is unevenly distributed between the central and side orifices. The turbulent shear stresses are, however, large enough to cause sublethal or lethal damage to blood elements. Wall shear stresses are smaller than those measured downstream of the Björk-Shiley valve. Regions of flow separation were observed just downstream from the sewing ring, which could lead to excess tissue growth along the sewing ring. The results of this study indicate that overall in vitro fluid dynamic performance of the St. Jude valve is superior to that of the two other commonly used prostheses.

In-vitro fluid dynamic characteristics of the abiomed trileaflet heart valve prosthesis.

The need for better and longer lasting trileaflet valves has led to the design and development of the Abiomed polymeric trileaflet valve prosthesis. In-vitro fluid dynamic studies on sizes 25 and 21 mm valves in the aortic position indicate an overall improvement in performance compared to the Carpentier-Edwards and Ionescu-Shiley tissue valves in current clinical use. The pressure drop studies yielded effective orifice areas of 1.99 and 1.54 cm2, and performance indices of 0.41 and 0.45 for the Nos. 25 and 21 valves, respectively. Leaflet photography studies indicated that the two valve sizes had maximum opening areas of 225 and 145 mm2, respectively, at a normal resting cardiac output. Steady and pulsatile flow velocity measurements with a laser-Doppler anemometer (LDA) system indicate that the flow field downstream of the Abiomed valve is jetlike and turbulent. Maximum mean square axial velocity fluctuations of 55 and 83 cm/s, and turbulent shear stresses of 220 and 450 N/m2 were measured in the immediate vicinity of the nos. 25 and 21 valves, respectively. The Abiomed valves studied had been originally configured for use in valved conduits, and it is therefore our opinion that further improvements can be made to the valve and stent design, which would enhance its fluid dynamic performance.

In vitro fluid dynamic characteristics of Ionescu-Shiley and Carpentier-Edwards tissue bioprostheses.

In the study reported here, the in vitro fluid dynamic characteristics of the Ionescu-Shiley (calf pericardial) and Carpentier-Edwards (porcine) aortic tissue valves were studied. The experiments conducted were pressure drop measurements, leaflet photography, flow visualization, and velocity measurements. The pressure drop studies indicated that both types of tissue valves created relatively large pressure drops. These pressure drops were larger than those observed with the corresponding sizes of Bjork-Shiley, Hall-Kaster, and St. Jude aortic prostheses. The photographs of the opening of the valve leaflets indicated that the tissue valves do not open as ideally as do the natural valves. It was also observed that the Ionescu-Shiley aortic valves opened more symmetrically and with reproducibility than the corresponding Carpentier-Edwards aortic valves. Velocity and shear stress measurements made with a laser-Doppler anemometer indicated that the flow that emerged from the leaflets for both types of tissue valves was like a jet and could lead to turbulent shear stress on the order of 1,000-3,000 dynes/cm2. Such turbulent shear stresses could be harmful to blood components. The jet-type flow could also damage the endothelial lining of the wall of the ascending aorta. The velocity measurements also indicated an annular region of stagnant fluid between the outflow surfaces of the leaflets and the flow channel wall. Such a region could lead to the build-up of thrombotic, fibrotic, and/or calcific material on the outflow surfaces of the leaflets. Both types of valve designs, however, created relatively low wall shear stresses and regurgitant volumes.

Steady and pulsatile flow studies on a trileaflet heart valve prosthesis.

The need for better and longer lasting trileaflet valves has led to the design and development of the ABIOMED polymeric trileaflet valve prosthesis. In vitro fluid dynamic studies in the aortic position indicate that overall it has improved leaflet motion characteristics and pressure drop characteristics compared to the Carpentier-Edwards porcine and Ionescu-Shiley pericardial tissue valves in current clinical use. The ABIOMED valve is, however, more stenotic compared to the St. Jude and Medtronic-Hall low profile mechanical valves, at normal cardiac outputs. Steady and pulsatile flow velocity measurements with a laser-Doppler anemometer system indicate that the flow field downstream of the ABIOMED valve is jet-like and leads to elevated shear stresses. These shear stresses are, however, lower than those observed with the Ionescu-Shiley and Carpentier-Edwards tissue valves. The ABIOMED valves tested had been originally configured for use in valved conduits, and it is therefore our opinion that further improvements can be made to the valve and stent design which would enhance its fluid dynamic performance.

In vitro fluid dynamic characteristics of the Medtronic-Hall pivoting disc heart valve prosthesis.

The need for better low-profile mechanical valves led to the design and development of the Medtronic-Hall (formerly known as the Hall-Kaster valve) pivoting disc heart valve prosthesis in 1976. In vitro flow studies indicate that it has improved pressure drop characteristics compared to the Lillehei-Kaster and convexoconcave Björk-Shiley (60 degrees model) tilting disc valves. It does, however, have a somewhat larger regurgitant volume compared to the Björk-Shiley valve design. Velocity measurements with a laser-Doppler anemometer in the immediate downstream vicinity of the Medtronic-Hall valve indicate no region of stagnation near the outflow face of the disc. Regions of stagnation were, however, observed adjacent to the two titanium "pivot stops" situated on either side of the disc in the major orifice and along the pivot post in the minor orifice, together with a region of flow separation adjacent to the sewing ring of the minor outflow region. The results of the present in vitro study indicate a small but significant improvement in the overall fluid dynamic performance of the Medtronic-Hall valve, compared to the convexo-concave Björk-Shiley (60 degrees model) and Lillehei-Kaster tilting disc prostheses in current clinical use.

Astrovirus-like, coronavirus-like, and parvovirus-like particles detected in the diarrheal stools of beagle pups.

Astrovirus-like, coronavirus-like, and parvovirus-like particles were detected through electron microscopic (EM) examination of loose and diarrheal stools from a litter of beagle pups. Banding patterns obtained from equilibrium centrifugations in CsCl supported the EM identification. Densities associated with the identified particles were: 1.34 g/ml for astrovirus, 1.39 g/ml for "full" parvovirus and 1.24-1.26 g/ml for "typical" coronavirus. Convalescent sera from the pups aggregated these three particle types as observed by immunoelectron microscopy (IEM). Only coronavirus-like particles were later detected in formed stools from these same pups. Coronavirus and parvo-like viruses are recognized agents of canine viral enteritis, however, astrovirus has not been previously reported in dogs.

Experimental respiratory infection with Pasteurella multocida and Bordetella bronchiseptica in rabbits.

Eight-to-10-wk-old offspring of a colony of specific pathogen free [Eda:(NZW x FG)F1BR] rabbits were exposed to cultures of Pasteurella multocida and Bordetella bronchiseptica. Two groups of 9 animals each were exposed to cultures of either species of bacteria intranasally and killed 2, 7, 14, and 21 da postinoculation. Five of 9 rabbits in each group developed a mucopurulent nasal discharge 4-7 da postinoculation. The remaining 4 rabbits in each group failed to develop clinical signs. The gross and microscopic lesions did not differ in character or distribution among the inoculated rabbits. The infection was characterized by an acute upper respiratory syndrome accompanied by a mild bronchopneumonia.