Reduced shear stress: A major component in the ability of mammalian tissues to form three-dimensional assemblies in simulated microgravity

BHK-21 cells were cultured under various shear stress conditions in an Integrated Rotating-Wall Vessel (IRWV). Shear ranged from 0.5 dyn/cm² (simulated microgravity) to 0.92 dyn/cm². Under simulated microgravity conditions, BHK-21 cells complexed into three-dimensional cellular aggregates attaining 6 × 10⁶ cells/ml as compared to growth under 0.92 dyn cm² conditions. Glucose utilization in simulated microgravity was reduced significantly, and cellular damage at the microcarrier surface was kept to a minimum. Thus, the integrated rotating wall vessel provides a quiescent environment for the culture of mammalian cells. © 1993 Wiley-Liss, Inc.     

Enteropathogenicity of Vibrio parahaemolyticus in the ligated rabbit ileum.

The enteropathogenicity of Vibrio parahaemolyticus was investigated by contrasting the effects of whole cells, cell fragments, cell-free preparations, and media constituents injected into rabbit ileal loops. Three of 20 cultures utilized were Kanagawa-negative strains from seawater and sea fish. The remaining 17 cultures included both Kanagawa-positive and -negative strains from Japanese victims of gastroenteritis. Broth culture filtrates concentrated 10-fold by dialysis against 30% Carbowax were unreactive, whereas lyophilized filtrates, regardless of Kanagawa type, as well as all sterile broth preparations containing greater than or equal to 5% NaCl gave positive reactions in the rabbit gut. In contrast, crude lysates derived from broth cultures of Kanagawa-positive strains caused loop dilatation; lysate supernatants were unreactive. Lysates of cells washed from brain heart infusion agar were more reactive than lysates from Trypticase soy agar-grown cells. When agar-grown cell lysates prepared by disruption in saline were dialyzed against distilled water, they were devoid of gut reactivity. Reactivity was restored in dialysands resuspended in saline and in dialysates concentrated 10-fold. The agar-grown cell lysates exhibited Kanagawa-type hemolysis. Our data support the conclusion that the rabbit loop reactivity observed with lyophilized, cell-free culture filtrates may result from excessively elevated NaCl concentrations, and that a toxic factor associated with large-cell particles may be dialyzable, depends on saline for expression, and resembles the Kanagawa hemolysin.     

Characterization of aggregation and protein expression of bovine corneal endothelial cells as microcarrier cultures in a rotating-wall vessel

Rotating-wall vessels are beneficial to tissue engineering in that the reconstituted tissue formed in these low-shear bioreactors undergoes extensive three-dimensional growth and differentiation. In the present study, bovine corneal endothelial (BCE) cells were grown in a high-aspect rotating-wall vessel (HARV) attached to collagen-coated Cytodex-3 beads as a representative monolayer culture to investigate factors during HARV cultivation which affect three-dimensional growth and protein expression. A collagen type I substratum in T-flask control cultures increased cell density of BCE cells at confluence by 40% and altered the expression of select proteins (43, 50 and 210 kDa). The low-shear environment in the HARV facilitated cell bridging between microcarrier beads to form aggregates containing upwards of 23 beads each, but it did not promote multilayer growth. A kinetic model of microcarrier aggregation was developed which indicates that the rate of aggregation between a single bead and an aggregate was nearly 10 times faster than between two aggregate and 60 times faster than between two single beads. These differences reflect changes in collision frequency and cell bridge formation. HARV cultivation altered the expression of cellular proteins (43 and 70 kDa) and matrix proteins (50, 73, 89 and 210 kDa) relative to controls perhaps due to hypoxia, fluid flow or distortion of cell shape. In addition to the insight that this work has provided into rotating-wall vessels, it could be useful in modeling aggregation in other cell systems, propagating human corneal endothelial cells for eye surgery and examining the response of endothelial cells to reduced shear.     

Costs of Rapid HIV Screening in an Urban Emergency Department and a Nearby County Jail in the Southeastern United States

Emergency departments and jails provide medical services to persons at risk for HIV infection and are recommended venues for HIV screening. Our main objective in this study was to analyze the cost per new HIV diagnosis associated with the HIV screening program in these two venues. The emergency department’s parallel testing program was conducted at Grady Memorial Hospital in Atlanta, Georgia starting in 2008; the jail’s integrated testing program began at the Fulton County (GA) Jail in 2011. The two sites, four miles apart from one another, employed the same rapid HIV test. Ascertainment that cases were new differed by site; only the jail systematically checked identities against health department HIV registries. The program in the emergency department used dedicated HIV test counselors and made 242 diagnoses over a 40-month period at a cost of $2,981 per diagnosis. The jail program used staff nurses, and found 41 new HIV cases over 10.5 months at a cost of $6,688 per new diagnosis. Differences in methods for ascertainment of new diagnoses, previously undiagnosed HIV sero-positivity, and methodologies used for assessing program costs prevent concluding that one program was more economical than the other. Nonetheless, our findings show that testing in both venues yielded many new diagnoses, with the costs within the range reported in the literature.     

On the Unnecessary and Misleading Taxon “Cetartiodactyla”

Journal of Mammalian Evolution - The name “Cetartiodactyla” was proposed in 1997 to reflect the molecular data that suggested that Cetacea is closely related to Artiodactyla. Since...     

Simple finite element models for use in the design of therapeutic footwear

Therapeutic footwear is frequently prescribed in cases of rheumatoid arthritis and diabetes to relieve or redistribute high plantar pressures in the region of the metatarsal heads. Few guidelines exist as to how these interventions should be designed and what effect such interventions actually have on the plantar pressure distribution. Finite element analysis has the potential to assist in the design process by refining a given intervention or identifying an optimal intervention without having to actually build and test each condition. However, complete and detailed foot models based on medical image segmentation have proven time consuming to build and computationally expensive to solve, hindering their utility in practice. Therefore, the goal of the current work was to determine if a simplified patient-specific model could be used to assist in the design of foot orthoses to reduce the plantar pressure in the metatarsal head region. The approach is illustrated by a case study of a diabetic patient experiencing high pressures and pain over the fifth metatarsal head. The simple foot model was initially calibrated by adjusting the individual loads on the metatarsals to approximate measured peak plantar pressure distributions in the barefoot condition to within 3%. This loading was used in various shod conditions to identify an effective orthosis. Model results for metatarsal pads were considerably higher than measured values but predictions for uniform surfaces were generally within 16% of measured values. The approach enabled virtual prototyping of the orthoses, identifying the most favorable approach to redistribute the patient’s plantar pressures.