CFD-based bioreactor model with proportional-integral-derivative controller functionality for dissolved oxygen and pH.

A physics-based model for predicting cell culture fluid properties inside a stirred tank bioreactor with embedded PID controller logic is presented. The model evokes a time-accurate solution to the fluid velocity field and overall volumetric mass transfer coefficient, as well as the ongoing effects of interfacial mass transfer, species mixing, and aqueous chemical reactions. The modeled system also includes a direct coupling between process variables and system control variables via embedded controller logic. Satisfactory agreement is realized between the model prediction and measured bioreactor data in terms of the steady-state operating conditions and the response to setpoint changes. Simulation runtimes are suitable for industrial research and design timescales.

Modeling multiphase fluid flow, mass transfer, and chemical reactions in bioreactors using large-eddy simulation.

We present a transient large eddy simulation (LES) modeling approach for simulating the interlinked physics describing free surface hydrodynamics, multiphase mixing, reaction kinetics, and mass transport in bioreactor systems. Presented case-studies include non-reacting and reacting bioreactor systems, modeled through the inclusion of uniform reaction rates and more complex biochemical reactions described using Contois type kinetics. It is shown that the presence of reactions can result in a non-uniform spatially varying species concentration field, the magnitude and extent of which is directly related to the reaction rates and the underlying variations in the local volumetric mass transfer coefficient.

Experimental and computational characterization of mass transfer in high turndown bioreactors.

Single-use bioreactors (SUBs, or disposable bioreactors) are extensively used for the clinical and commercial production of biologics. Despite widespread application, minimal results have been reported utilizing the turndown ratio; an operation mode where the working range of the bioreactor can be expanded to include low fluid volumes. In this work, a systematic investigation into free surface mass transfer and cell growth in high turndown single-use bioreactors is presented. This approach, which combines experimental mass transfer measurements with numerical simulation, deconvolutes the combined effects of headspace mixing and the free surface convective mass transfer on cell growth. Under optimized conditions, mass transfer across the interface alone may be sufficient to satisfy oxygen demands of the cell culture. Within the context of high turndown bioreactors, this finding provides a counterpoint to traditional sparge-based bioreactor operational philosophy. Multiple monoclonal antibody-producing cell lines grown using this high turndown approach showed similar viable cell densities to those cells expanded using a traditional cell bag rocker. Furthermore, cells taken directly from the turndown expansion and placed into production showed identical growth characteristics to traditionally expanded cultures. Taken together, these results suggest that the Xcellerex SUB can be run at a 5:1 working volume as a seed to itself, with no need for system modifications, potentially simplifying preculture operations.

Mapping the protein profile involved in the biotransformation of organoarsenicals using an arsenic metabolizing bacterium.

Alkaliphilus oremlandii strain OhILAs, a gram-positive bacterium, has been shown to ferment lactate as well as use arsenate and roxarsone as a terminal electron acceptor. This study examines the proteome expressed under four growth conditions to further elucidate the bacterial metabolism of inorganic and organic arsenic. The four growth conditions include, sodium lactate (as fermentative control), sodium lactate with 3-nitro-4-hydroxybenzenearsonic acid (roxarsone), sodium lactate with 3-amino-4-hydroxybenzenearsonic acid (3A4HBAA), and sodium lactate with sodium arsenate. Shotgun proteomics using LC-MS/MS was performed on the soluble cytoplasm as well as solubilized membrane proteins using perfluorooctanoic acid, a surfactant with properties similar to sodium dodecyl sulfate. The MS/MS data were analyzed using the Spectrum Mills Proteomic Workbench. Positive protein matches were confirmed with protein scores of 20 or greater and the presence of two or more peptides among the three technical replicates. A total of 1357 proteins (out of 2836 predicted) were identified with 791 in sodium lactate, 816 in sodium lactate and roxarsone, 715 in sodium lactate and 3A4HBAA, and 733 in sodium lactate and arsenate. The relative abundance of each protein was determined using a method called normalized spectral abundance factor (NSAF). Proteins that were identified in both the control and the experimental conditions were compared using the Power Law Global Error Model (PLGEM) to determine proteins that were significantly up or down regulated. All putative proteins were assigned functions and pathways using the COG databases. However, a large number of proteins were classified as hypothetical or had unknown function. Using the statistical information and known functionalities of the identified proteins, a pathway for the degradation of roxarsone and 3A4HBAA by A. oremlandii strain OhILAs is proposed.

A randomized controlled comparison between combined spinal-epidural and single-shot spinal techniques in morbidly obese parturients undergoing cesarean delivery: time for initiation of anesthesia.

BACKGROUND: There is no current consensus on the optimal technique for subarachnoid anesthesia in morbidly obese parturients even though some providers prefer the combined spinal-epidural (CSE) over single-shot spinal (SSS) technique. In this randomized controlled study, we compared the time required for initiation of subarachnoid anesthesia between SSS and CSE techniques in morbidly obese parturients undergoing elective cesarean delivery. METHODS: Morbidly obese parturients presenting for elective cesarean delivery were randomized to receive subarachnoid anesthesia performed either with a SSS or a CSE technique. The spinal procedure in the sitting position was attempted by an experienced resident for up to 10 minutes, and if unsuccessful, the attending obstetric anesthesiologist assumed control of the procedure. The primary outcome was the time it took from the insertion of the introducer needle (SSS group) or insertion of the epidural needle (CSE group) to the end of intrathecal injection of drugs (procedure time). RESULTS: Forty-four patients were enrolled and completed the study. Three were excluded due to protocol violations. Of the remaining, 21 patients were in the SSS group and 20 in the CSE group. Demographic variables and mean (SD) body mass index (48.7 ± 7.6 kg/m for SSS; 49.9 ± 8.6 kg/m for CSE) were not different between groups. The median [interquartile range] for procedure time was 210 [116-692] seconds and 180 [75-450] seconds for SSS and CSE groups, respectively (P = 0.36), while the 95% confidence interval (CI) of the difference was -80 to +180 seconds. The first operator completed the procedure in <10 minutes in 71% of subjects in the SSS group and 95% of those in the CSE group (P = 0.09) and the 95% CI of the difference was -2% to +45%. There were more attempts to successful completion of the procedure in the SSS group (P = 0.007) with its 95% CI of the difference being +1 to +6. CONCLUSION: Our results suggest that the CSE technique is noninferior to the SS technique in morbidly obese parturients for time of initiation of subarachnoid anesthesia and may be accomplished with fewer attempts than the SSS technique with experienced residents.

An injectable thiol-acrylate poly(ethylene glycol) hydrogel for sustained release of methylprednisolone sodium succinate.

Clinically available injectable hydrogels face technical challenges associated with swelling after injection and toxicity from unreacted constituents that impede their performance as surgical biomaterials. To overcome these challenges, we developed a system where chemical gelation was controlled by a conjugate Michael addition between thiol and acrylate in aqueous media, with 97% monomer conversion and 6 wt.% sol fraction. The hydrogel exhibited syneresis on equilibration, reducing to 59.7% of its initial volume. It had mechanical properties similar to soft human tissue with an elastic modulus of 189.8 kPa. Furthermore, a mesh size of 6.9 nm resulted in sustained release of methylprednisolone sodium succinate with a loading efficiency of 2 mg/mL. Functionalization with 50 µg/mL of an oligolysine peptide resulted in attachment of freshly isolated murine mesenchymal stem cells. The rational design of the physical, chemical and biological properties of the hydrogel makes it a potentially promising candidate for injectable applications.

Personal care products and endocrine disruption: A critical review of the literature.

This article reviews laboratory and epidemiological research into the endocrine disruptive effects of components of personal care products, namely, phthalate esters, parabens, ultraviolet (UV) filters, polycyclic musks, and antimicrobials. High doses of phthalates in utero can produce “phthalate syndrome,” demasculinizing effects in male rat offspring due to impaired testosterone production by fetal testes. However, evidence linking phthalate exposure to similar effects in humans appears inconclusive. Furthermore, phthalate exposure derived from personal care products is within safe limits and its principal bioavailable phthalate, diethyl phthalate (DEP), does not produce “phthalate syndrome.” Parabens exhibit very weak estrogen activity in vitro and in vivo, but evidence of paraben-induced developmental and reproductive toxicity in vivo lacks consistency and physiological coherence. Evidence attempting to link paraben exposure with human breast cancer is nonexistent. Select UV filters at high doses produce estrogenic, antithyroid, and other effects in rats in vivo. Again, no evidence links UV filter exposure to endocrine disruptive effects in humans. Some polycyclic musks weakly bind to estrogen, androgen, or progestin receptors and exhibit primarily antagonistic activity in vitro, which for the most part, has yet to be confirmed in vivo in mammals. The antimicrobials triclocarban and triclosan evoke weak responses mediated by aryl hydrocarbon, estrogen, and androgen receptors in vitro, which require confirmation in vivo. Preliminary observations suggest a novel interaction between triclocarban and testosterone. In conclusion, although select constituents exhibit interactions with the endocrine system in the laboratory, the evidence linking personal care products to endocrine disruptive effects in humans is for the most part lacking.

Water flow in carbon nanotubes: transition to subcontinuum transport.

The structure and flow of water inside 75 and 150 nm-long carbon nanotubes with diameters ranging from 0.83 to 1.66 nm are examined using molecular dynamics simulation. The flow rate enhancement, defined as the ratio of the observed flow rate to that predicted from the no-slip Poiseuille relation, is calculated for each tube and the liquid structure is examined using an axial distribution function. The relationship between the intermolecular water structure and water flow is quantified and differences between continuum and subcontinuum flow are discussed.

Reassessing fast water transport through carbon nanotubes.

Pressure-driven water flow through carbon nanotubes (CNTs) with diameters ranging from 1.66 to 4.99 nm is examined using molecular dynamics simulation. The flow rate enhancement, defined as the ratio of the observed flow rate to that predicted from the no-slip Hagen-Poiseuille relation, is calculated for each CNT. The enhancement decreases with increasing CNT diameter and ranges from 433 to 47. By calculating the variation of water viscosity and slip length as a function of CNT diameter, it is found that the results can be fully explained in the context of continuum fluid mechanics. The enhancements are lower than previously reported experimental results, which range from 560 to 100 000, suggesting a miscalculation of the available flow area and/or the presence of an uncontrolled external driving force (such as an electric field) in the experiments.

Dural puncture with a 27-gauge Whitacre needle as part of a combined spinal-epidural technique does not improve labor epidural catheter function.

BACKGROUND: This prospective, double-blind, randomized study was designed to examine whether the combined spinal-epidural technique without subarachnoid drug administration improved epidural catheter function when compared with the traditional epidural technique. METHODS: After institutional review board approval and informed consent, 251 healthy laboring parturients were randomly assigned to either group DP (combined spinal-epidural technique with 27-gauge Whitacre needle dural puncture but without subarachnoid drug administration) or group NoDP (traditional epidural technique). Patient-controlled epidural analgesia was initiated with 0.11% bupivacaine and 2 microg/ml fentanyl. Top-up doses in 5-ml increments of 0.25% bupivacaine were administered if needed. Previous power analysis revealed that a sample size of 108 patients/group was needed to show a clinically useful reduction of the catheter manipulation rate from 32% to 15%. RESULTS: In groups DP and NoDP, 107 and 123 evaluable patients, respectively, completed the study. Demographics and outcome variables measured, including epidural catheter manipulation and replacement rate, sacral sparing, unilateral block, number of top-up doses, average hourly epidural drug usage, highest sensory blockade level, and labor analgesia quality, were not different between groups. A subgroup of 18 patients without cerebral spinal fluid return during dural puncture had a higher catheter replacement rate than those of groups DP and NoDP, but it did not reach statistical significance. CONCLUSIONS: Dural puncture with a 27-gauge Whitacre needle without subarachnoid drug administration during combined spinal-epidural labor analgesia did not improve epidural labor analgesia quality or reduce catheter manipulation or replacement rate when compared with a traditional epidural technique.

Relation of residency selection factors to subsequent orthopaedic in-training examination performance.

OBJECTIVES: Orthopaedic surgery remains one of the most competitive specialties, with more than a 99% match fill rate in the past several years. An oversupply of qualified applicants leads to intense competition for these residency spots, allowing program directors to be more selective in choosing their future residents. Although many previous studies have documented factors important to program directors in the admission process, less is known about how preselection factors correlate with subsequent performance in a residency program. METHODS: The relation of both demographic and academic factors with subsequent performance on the Orthopaedic In-Training Examination (OITE) were studied. These factors include United States Medical Licensing Examination (USMLE) step I scores, Alpha Omega Alpha (AOA) status, research publications, age entering residency, marital status, and medical school affiliation. RESULTS: In this study, the only statistically significant correlations to OITE scores were USMLE step I performance and marital status. Those residents who had previously scored above 220 on the USMLE step I had higher average OITE scores than those scoring below 220. Residents who were married also had higher average OITE scores. A trend with regard to AOA status also was found, with residents scoring slightly higher on the OITE if they were members of AOA. CONCLUSIONS: Few preresidency variables correlate to success during an orthopaedic residency.

Sudden cardiac death in children and adolescents: introduction and overview.

Sudden unexpected cardiac death (SCD) in a child or adolescent is a devastating event with serious impact on the family, the school, and the community. This article reviews the epidemiology of SCD in children and adolescents and includes a discussion of its incidence and etiologies. It also discusses strategies for prevention.

Impact of implant design on femoral head hemiresurfacing arthroplasty.

Two consecutive series of cemented femoral hemiresurfacing arthroplasty for patients with Ficat Stage III and early Stage IV osteonecrosis of the femoral head were studied to identify the impact of design on the clinical and radiographic results. Group I (30 patients, 33 hips) components had a cobalt chrome shell with a tapered inner dimension, no stem, and sizes in 2-mm increments. Group II (37 patients, 51 hips) components differed by adding a proportional stem, increased spherical coverage, and sizes in 1-mm increments. The average age for the patients in both groups was 40 years. Fifty percent of the patients in Group I were men: in 43% of patients osteonecrosis was associated with steroid use and in 21% of patients it was associated with alcohol use. Thirty-three percent of the patients in Group II were men: in 41% of patients osteonecrosis was associated with steroid use and in 17% of patients it was associated with alcohol use. The average followup is 42 months for Group I and 24 months for Group II. Neither group experienced infections, nerve palsies, dislocations, or loosening. In Group I, two patients died of unrelated causes and five patients had reoperations, two for femoral neck fractures, and three for unsatisfactory pain relief. No patients in Group II had femoral neck fractures but three patients had reoperations for unsatisfactory pain relief. The stemmed component in Group II has resulted in an improvement in component position and elimination of femoral neck fractures in this series.

Cystatin C in cerebrospinal fluid is not a diagnostic test for pain in humans.

A recent subtractive cDNA cloning study in rats demonstrated an unexpected increase in expression of the proteinase inhibitor, cystatin C in the spinal cord during acute peripheral inflammation, suggesting this protein may be involved in the pathogenesis of persistent pain. A subsequent study of 10 women suggested that prolonged labor pain resulted in increased cystatin C concentrations in cerebrospinal fluid, and that this could be used as a biomarker for pain. To confirm and extend these observations, we measured cystatin C concentrations in cerebrospinal fluid in 131 subjects: 30 normal volunteers without pain, 25 women at elective cesarean section without pain, 60 women in labor with severe pain, and 16 patients with chronic neuropathic pain and tactile allodynia. The median cystatin C concentration in normal volunteers, 2.2 microg/ml, was similar to that previously reported by multiple investigators, and cystatin C concentrations were increased in women in labor (3.9 microg/ml). However, contrary to the previous report, cystatin C concentrations in laboring women with pain did not differ from those of pregnant women without pain (3.7 microg/ml). There was no relationship between duration of painful labor and cystatin C concentration. Patients with neuropathic pain had similar cystatin C concentrations (2.4 microg/ml) to controls. Logistic regression analysis indicated that cystatin C concentrations could not be used to reliably predict the presence of pain in either acute or chronic settings. These data suggest that cystatin C concentration in cerebrospinal fluid is an unreliable diagnostic marker for pain in humans.

Safety of foods derived from genetically modified plants.

Biopharmaceuticals have been available for clinical use for nearly three decades, but foods derived from agribiotechnology have been available for just under a decade. Controversy surrounding foods from genetically modified (GM) plants has focused primarily upon their allergenicity, with lesser concerns about antibiotic resistance genes. Concerns are related to possible environmental impacts on non-human species, including effects on non-target species (e.g., butterflies) and on the development of so-called "super weeds." Food allergies are no more prevalent in foods from GM plants than in conventional foods. Further, the use of antibiotics in the development of GM plants does not pose a significant risk to the human population. Foods from the current GM plant products have been shown not to pose any detrimental effects to humans, and, in fact, nutritionally enhanced products are being developed. GM foods are subjected globally to intense regulatory scrutiny, and extensive data have been provided consistently to regulatory agencies in the United States on a voluntary basis, with mandatory reporting of data soon to be in force. Existing environmental concerns appear to be unjustified on the basis of existing data and experience.

Influence of volunteer wheat plant condition on movement of the wheat curl mite, Aceria tosichella, in winter wheat.

The wheat curl mite (WCM), Aceria tosichella Keifer, is the vector of wheat streak mosaic virus and high plains virus which cause significant crop loss in winter wheat throughout the western Great Plains. Volunteer wheat emerging before harvest, as a result of severe hail, is the primary source of mites and virus that infect fall-planted winter wheat. Wind-borne movement of the WCM is of key importance in the spread and infection of the virus complex. Significant movement of WCM from wheat has been thought to be closely tied to the senescence or deterioration of the host. Results from field and greenhouse studies indicated that movement from un-vernalized winter wheat was not closely associated with the deterioration of the wheat host. Greenhouse studies showed no correlation between WCM movement and plant condition, but there was a highly significant relationship between WCM movement and mite population on the host plant. Field studies did not demonstrate increased movement associated with deteriorating un-vernalized winter wheat. However, healthier hosts which were able to support a larger population of mites were associated with increased movement. The main influence on the level of mite movement relates to the size of the source population and not the condition of the host plant, but plant condition appears to be a factor in limiting the increase of the WCM population.

Aspartame: review of safety.

Over 20 years have elapsed since aspartame was approved by regulatory agencies as a sweetener and flavor enhancer. The safety of aspartame and its metabolic constituents was established through extensive toxicology studies in laboratory animals, using much greater doses than people could possibly consume. Its safety was further confirmed through studies in several human subpopulations, including healthy infants, children, adolescents, and adults; obese individuals; diabetics; lactating women; and individuals heterozygous (PKUH) for the genetic disease phenylketonuria (PKU) who have a decreased ability to metabolize the essential amino acid, phenylalanine. Several scientific issues continued to be raised after approval, largely as a concern for theoretical toxicity from its metabolic components--the amino acids, aspartate and phenylalanine, and methanol--even though dietary exposure to these components is much greater than from aspartame. Nonetheless, additional research, including evaluations of possible associations between aspartame and headaches, seizures, behavior, cognition, and mood as well as allergic-type reactions and use by potentially sensitive subpopulations, has continued after approval. These findings are reviewed here. The safety testing of aspartame has gone well beyond that required to evaluate the safety of a food additive. When all the research on aspartame, including evaluations in both the premarketing and postmarketing periods, is examined as a whole, it is clear that aspartame is safe, and there are no unresolved questions regarding its safety under conditions of intended use.