Mechanical characterization of structurally porous biomaterials built via additive manufacturing: experiments, predictive models, and design maps for load-bearing bone replacement implants.

Porous biomaterials can be additively manufactured with micro-architecture tailored to satisfy the stringent mechano-biological requirements imposed by bone replacement implants. In a previous investigation, we introduced structurally porous biomaterials, featuring strength five times stronger than commercially available porous materials, and confirmed their bone ingrowth capability in an in vivo canine model. While encouraging, the manufactured biomaterials showed geometric mismatches between their internal porous architecture and that of its as-designed counterpart, as well as discrepancies between predicted and tested mechanical properties, issues not fully elucidated. In this work, we propose a systematic approach integrating computed tomography, mechanical testing, and statistical analysis of geometric imperfections to generate statistical based numerical models of high-strength additively manufactured porous biomaterials. The method is used to develop morphology and mechanical maps that illustrate the role played by pore size, porosity, strut thickness, and topology on the relations governing their elastic modulus and compressive yield strength. Overall, there are mismatches between the mechanical properties of ideal-geometry models and as-manufactured porous biomaterials with average errors of 49% and 41% respectively for compressive elastic modulus and yield strength. The proposed methodology gives more accurate predictions for the compressive stiffness and the compressive strength properties with a reduction of the average error to 11% and 7.6%. The implications of the results and the methodology here introduced are discussed in the relevant biomechanical and clinical context, with insight that highlights promises and limitations of additively manufactured porous biomaterials for load-bearing bone replacement implants. STATEMENT OF SIGNIFICANCE: In this work, we perform mechanical characterization of load-bearing porous biomaterials for bone replacement over their entire design space. Results capture the shift in geometry and mechanical properties between as-designed and as-manufactured biomaterials induced by additive manufacturing. Characterization of this shift is crucial to ensure appropriate manufacturing of bone replacement implants that enable biological fixation through bone ingrowth as well as mechanical property harmonization with the native bone tissue. In addition, we propose a method to include manufacturing imperfections in the numerical models that can reduce the discrepancy between predicted and tested properties. The results give insight into the use of structurally porous biomaterials for the design and additive fabrication of load-bearing implants for bone replacement.

Achieving long-term use of solar water disinfection in Zimbabwe.

OBJECTIVES: To use a psychological theory of behavioural change to measure and interpret the effectiveness of different promotional strategies for achieving long-term usage of a household water treatment and safe storage (HWTS) system in peri-urban Zimbabwe. STUDY DESIGN: Solar disinfection (SODIS) was introduced into five peri-urban communities near Harare, Zimbabwe. Six different interventions were developed and were applied in four communities in different combinations, with the fifth remaining as a control area where no interventions were implemented. METHODS: Throughout the 26 months of the study nine longitudinal panel surveys were conducted in which SODIS usage was estimated using three separate metrics: reported, calculated, and observed. A total of 1551 people were interviewed. RESULTS: The three indicators of SODIS usage broadly agreed with one another. By any measure, the most effective intervention was household visits by trained promoters in combination with persuasion. Households which received household visits maintained SODIS usage rates of 65% or more, even six months after the cessation of all promotional activities. Households receiving other interventions were significantly less effective. Interventions like prompts or public commitment after the application of household visits were effective at maintaining good practices once these were established. CONCLUSIONS: Household promotion in combination with persuasion appears more effective than other approaches, especially when followed with interventions targeting the maintenance of the new behaviour. With this intervention it is possible that around 65% of the households continue to use solar water disinfection (SODIS) more than two years after the initial promotion, and six months after the end of all interventions.

International multicentre study examining selection criteria for active surveillance in men undergoing radical prostatectomy.

BACKGROUND: The controversies concerning possible overtreatment of prostate cancer, highlighted by debate over PSA screening, have highlighted active surveillance (AS) as an alternative management option for appropriate men. Regional differences in the underlying prevalence of PSA testing may alter the pre-test probability for high-risk disease, which can potentially interfere with the performance of selection criteria for AS. In a multicentre study from three different countries, we examine men who were initially suitable for AS according to the Toronto and Prostate Cancer Research International: Active Surveillance (PRIAS) criteria, that underwent radical prostatectomy (RP) in regards to:1.the proportion of pathological reclassification(Gleason score ≥7, ≥pT3 disease),2.predictors of high-risk disease,3.create a predictive model to assist with selection of men suitable for AS. METHODS: From three centres in the United Kingdom, Canada and Australia, data on men who underwent RP were retrospectively reviewed (n=2329). Multivariable logistic regression was performed to identify predictors of high-risk disease. A nomogram was generated by logistic regression analysis, and performance characterised by receiver operating characteristic curves. RESULTS: For men suitable for AS according to the Toronto (n=800) and PRIAS (410) criteria, the rates for upgrading were 50.6, 42.7%, and upstaging 17.6, 12.4%, respectively. Significant predictors of high-risk disease were:•Toronto criteria: increasing age, cT2 disease, centre of diagnosis and number of positive cores.•PRIAS criteria: increasing PSA and cT2 disease.Cambridge had a high pT3a rate (26 vs 12%). To assist selection of men in the United Kingdom for AS, from the Cambridge data, we generated a nomogram predicting high-risk features in patients who meet the Toronto criteria (AUC of 0.72). CONCLUSION: The proportion of pathological reclassification in our cohort was higher than previously reported. Care must be used when applying the AS criteria generated from one population to another. With more stringent selection criteria, there is less reclassification but also fewer men who may benefit from AS.

Tubewell water quality and predictors of contamination in three flood-prone areas in Bangladesh.

AIMS: To measure enteric bacterial contamination of tubewells in three flood prone areas in Bangladesh and the relationship of bacteriological contamination with tubewell sanitary inspection scores. METHODS AND RESULTS: Microbiologists selected 207 tubewells in three flood prone districts, assessed physical characteristics of the tubewells and collected a single water sample from each tubewell. Tubewell water samples were contaminated with total coliforms (41%, n = 85), thermotolerant coliforms (29%, n = 60) and Escherichia coli (13%, n = 27). Among contaminated wells, the median CFU of contamination per 100 ml was 8 (interquartile range, 2-30) total coliforms, 5 (interquartile range, 2-23) thermotolerant coliforms and 6 (interquartile range, 1-30) E. coli. There was no significant association between tubewell contamination with E. coli, thermotolerant coliforms or total coliforms and a poor sanitary inspection score, though a history of inundation was associated with contamination with both E. coli and thermotolerant coliforms. CONCLUSIONS: Tubewells in flood-prone regions of Bangladesh were commonly contaminated with low levels of faecal organisms, contamination that could not be predicted by examining the tubewell's external characteristics. SIGNIFICANCE AND IMPACT OF THE STUDY: The forms currently used for sanitary inspection do not identify the most important causes of drinking water contamination in these communities.

Clinical aspects of chronic granulomatous disease.

Data from a registry of 368 patients with chronic granulomatous disease (CGD) documenta shift in the most common infecting organisms away from staphylococci and enteric bacteria to Aspergillus species, although staphylococci remain a threat. A. nidulans appears to have a particular virulence in CGD. Burkholderia cepacia sepsis/pneumonia was the second most lethal infection in patients in the registry. Seventy-six percent of registry patients had the X-linked recessive (XLR) form of CGD. Chorioretinitis may be more common than previously appreciated, and boys with the XLR disease should probably have routine full eye exams. A new variant of CGD has been described that is caused by an inhibitory mutation in Rac2, which regulates activity of the neutrophil respiratory burst and actin assembly. Interferon-gamma, antibacterial prophylaxis, and, probably, antifungal prophylaxis with itraconazole reduce the rate of infection, and bone marrow transplantation can cure the disease if a histocompatible donor is available. Gene therapy can cure CGD in knockout mouse models. Having even a small percentage of phagocytes that are nicotinamide adenine dinucleotide phospate oxidase-positive can reduce the risk of serious infection, and procedures now under study appear close to achieving that goal, if not a cure.

The phagocytosis-associated respiratory burst in human monocytes is associated with increased uptake of glutathione.

During the phagocytic respiratory burst, oxygen is converted to potent cytotoxic oxidants. Monocytes and macrophages are potentially long-lived, and we have hypothesized that protective mechanisms against oxidant stress are varied and fully expressed in these cells. We report here that the respiratory burst in monocytes is accompanied by an increase in the uptake of [35S]glutathione ([35S]GSH) after 20-30 min to levels up to 10-fold greater than those at baseline. By 30 min, 49% of the cell-associated radioactivity was in the cytosol, 41% was in membrane, and 10% was associated with the nuclear fraction. GSH uptake was inhibited by catalase, which removes hydrogen peroxide (H2O2), and micromolar H2O2 stimulated GSH uptake effectively in monocytes and also lymphocytes. Oxidation of GSH to glutathione disulfide with H2O2 and glutathione peroxidase prevented uptake. Acivicin, which inhibits GSH breakdown by gamma-glutamyl transpeptidase (GGT), had no effect on the enhanced uptake seen during the respiratory burst. Uptake of cysteine or cystine, possible products of GGT activity, stayed the same or decreased during the respiratory burst. These results suggest that a GGT-independent mechanism is responsible for the enhanced GSH uptake seen during the respiratory burst. We describe here a sodium-independent, methionine-inhibitable transport system with a Km (8.5 microM) for GSH approximating the plasma GSH concentration. These results suggest that monocytes have a specific GSH transporter that is triggered by the release of H2O2 during the respiratory burst and that induces the uptake of GSH into the cell. Such a mechanism has the potential to protect the phagocyte against oxidant damage.

Chronic granulomatous disease. Report on a national registry of 368 patients.

A registry of United States residents with chronic granulomatous disease (CGD) was established in 1993 in order to estimate the minimum incidence of this uncommon primary immunodeficiency disease and characterize its epidemiologic and clinical features. To date, 368 patients have been registered; 259 have the X-linked recessive form of CGD, 81 have 1 of the autosomal recessive forms, and in 28 the mode of inheritance is unknown. The minimum estimate of birth rate is between 1/200,000 and 1/250,000 live births for the period 1980-1989. Pneumonia was the most prevalent infection (79% of patients; Aspergillus most prevalent cause), followed by suppurative adenitis (53% of patients; Staphylococcus most prevalent cause), subcutaneous abscess (42% of patients; Staphylococcus most prevalent cause), liver abscess (27% of patients; Staphylococcus most prevalent cause), osteomyelitis (25% of patients; Serratia most prevalent cause), and sepsis (18% of patients; Salmonella most prevalent cause). Fifteen percent of patients had gastric outlet obstruction, 10% urinary tract obstruction, and 17% colitis/enteritis. Ten percent of X-linked recessive kindreds and 3% of autosomal recessive kindreds had family members with lupus. Eighteen percent of patients either were deceased when registered or died after being registered. The most common causes of death were pneumonia and/or sepsis due to Aspergillus (23 patients) or Burkholderia cepacia (12 patients). Patients with the X-linked recessive form of the disease appear to have a more serious clinical phenotype than patients with the autosomal recessive forms of the disease, based on the fact that they are diagnosed significantly earlier (mean, 3.01 years of age versus 7.81 years of age, respectively), have a significantly higher prevalence of perirectal abscess (17% versus 7%), suppurative adenitis (59% versus 32%), bacteremia/fungemia (21% versus 10%), gastric obstruction (19% versus 5%), and urinary tract obstruction (11% versus 3%), and a higher mortality (21.2% versus 8.6%).

Preclinical evaluation of a rheolytic catheter for percutaneous coronary artery/saphenous vein graft thrombectomy.

The presence of thrombus increases the rate of acute complications and restenosis in percutaneous revascularization of native coronary arteries and saphenous vein grafts. Rheolytic thrombectomy uses high velocity saline jets to create a Bernoulli effect for thrombus entrainment, dissociation, and evacuation of debris, providing a novel approach to the treatment of thrombotic lesions. The study objective was to determine the preclinical safety and effectiveness of a 5 French rheolytic thrombectomy catheter designed for use in coronary arteries and saphenous vein grafts. In vitro testing was performed to evaluate catheter effectiveness (clot removal rate) and safety (particle generation and hemolysis). This was followed by acute (n = 6) and chronic (n = 6) canine studies to determine hemodynamic, angiographic, and histopathologic effects of the catheter. The results showed effective clot removal with minimal embolization: 99.4% of the total clot volume was removed with only 0.1% proximal embolization and 0.5% distal embolization. 98.4% of the embolic particles were less than 10 microm. Canine studies revealed no significant angiographic, hemodynamic, histopathologic, or electrocardiographic abnormalities with the exception of transient heart block in one animal. There was transient hemolysis which normalized within 24 hours with no adverse effects. These results demonstrate the effectiveness and safety of coronary rheolytic thrombectomy and provided the basis for clinical trials to further evaluate this promising new approach for coronary thrombectomy.

The effect of using "race of child" instead of "race of mother" on the black-white gap in infant mortality due to birth defects.

OBJECTIVE: For at least 20 years, birth defects have been the leading cause of infant mortality in the United States. Some studies have reported higher rates for black infants than white infants of mortality due to birth defects, while other studies have reported no black-white differences. The authors analyzed the effect on these rates of a change in the way the National Center for Health Statistics (NCHS) tabulates "race" for newborns. METHODS: The authors calculated infant mortality rates due to birth defects for 1980-1993 using two standard methods of assigning newborns to "racial" categories: a "race of child" algorithm and the "race of mother" approach currently used by NCHS. RESULTS: From 1980 through 1993, birth defect-specific infant mortality rates (BD-IMRs) were significantly higher for black infants than white infants 12 of the 14 years by "race of mother" and only 5 of 14 years by "race of child." Calculation of BD-IMRs by "race of mother" reduced the rate for white infants and increased the rate for black infants in each of the 14 years. The choice of method for assigning newborns to "racial" categories had a progressively greater effect over time on the black-white gap in BD-IMRs. CONCLUSIONS: Calculations of trends in "race"-specific BD-IMRs by may vary substantially by whether "race of mother" or "race of child" is used. Identifying the method of tabulation is imperative for appropriate comparisons and interpretations.

Effect of lower extremity muscular fatigue on motor control performance.

PURPOSE: The purpose of this study was to determine whether lower extremity fatigue affects the ability of an individual to balance on an unstable platform. METHODS: Twenty healthy subjects (average age, 29 yr, range, 20 to 39 yr) were tested on an instrumented balance assessment system. Static tests were done on the limbs unilaterally and then bilaterally, and finally a dynamic test was performed in which the subject moved the platform in a circular manner to chase a moving object on a computer screen. After testing, subjects were fatigued using an isokinetic dynamometer, which imposes closed kinetic chain antagonistic exercise on the ankle, knee, and hip, similar to a stair stepper. No rest was allowed, and subjects were fatigued to less than 50% of their initial tested force. Subjects were then immediately retested on the unstable platform using the same testing protocol. All subjects completed the testing. RESULTS: Analysis of pre- and post-fatigue balance results demonstrated significant decreases in motor control performance on the three static tests following exercise to fatigue in all subjects (P < 0.001). CONCLUSIONS: Our findings support anecdotal evidence that fatigued individuals are at increased risk of injury because of loss of balance. Avoidance of fatigue and preconditioning may prevent injury.

Augmentation of human macrophage candidacidal capacity by recombinant human myeloperoxidase and granulocyte-macrophage colony-stimulating factor.

Phagocyte myeloperoxidase (MPO) is believed to be particularly important in defense against candida infection. We reported earlier that monocytes, rich in MPO, killed Candida albicans at a significantly higher rate and extent than did monocyte-derived macrophages, known to lack MPO, and that C. albicans is less resistant to MPO-dependent oxidants than less pathogenic Candida species. We hypothesized, therefore, that the capacity of macrophages to kill C. albicans might be improved in the presence of MPO. In this study, we evaluated the ability of recombinant human MPO (rhMPO) to augment the killing of C. albicans by resident macrophages and macrophages activated by recombinant human granulocyte-macrophage colony-stimulating factor. Addition of rhMPO (concentration range, 0.8 to 6.4 U/ml) to suspensions of resident and activated macrophages and opsonized C. albicans resulted in concentration-dependent and significant increases in candida killing. This enhancement was particularly pronounced with activated macrophages, whether C. albicans was opsonized or unopsonized and ingested through the macrophage mannose receptor. rhMPO did not affect the killing of C. albicans by monocytes, nor did it affect phagocytosis of opsonized or unopsonized C. albicans. These results indicate that exogenous rhMPO can augment the candidacidal capacity of both resident and activated macrophages, with a more profound effect on activated cells. We suggest that rhMPO may be effective in the treatment of invasive candidiasis.

Characterization of multiple cysteine and cystine transporters in rat alveolar type II cells.

Cysteine availability is rate limiting for the synthesis of glutathione, an important antioxidant in the lung. We used rat alveolar epithelial type II cells to study the mechanism of cysteine and cystine uptake. Consistent with carrier-mediated transport, each uptake process was saturable with Michaelis-Menten kinetics and was inhibited at 4 degrees C and by micromolar levels of amino acids or analogs known to be substrates for a specific transporter. A unique system XAG was found that transports cysteine and cystine (as well as glutamate and aspartate, the only substrates previously described for system XAG). We also identified a second Na(+)-dependent cysteine transporter system, system ASC, and two Na(+)-independent transporter systems, system xc for cystine and system L for cysteine. In the presence of glutathione at levels measured in rat plasma and alveolar lining fluid, cystine was reduced to cysteine and was transported on systems ASC and XAG, doubling the transport rate. Cysteinylglycine, released from glutathione at the cell surface by gamma-glutamyl transpeptidase, also stimulated uptake after reduction of cystine. These findings suggest that, under physiological conditions, cysteine and cystine transport is influenced by the extracellular redox state.

Folic acid supplementation--when and how.

The periconceptional intake of 400 micrograms of folic acid can prevent 50-70% of neural tube defects. It is difficult to achieve this intake with diet alone, even with the recently approved levels for grain-food fortification. Therefore, a daily multivitamin with folic acid is recommended for all women of childbearing potential. Obstetrician-gynecologists should exercise every opportunity to educate their patients to this end. Although raised as a concern, the potential of masking the megaloblastic anemia of pernicious anemia is unlikely with these levels of supplementation, and considering the rarity of the disease in women of reproductive age.

Diamide primes neutrophils for enhanced release of superoxide anion: relationship to S-thiolation of cellular proteins.

Stimulation of the respiratory burst in phagocytes induces the formation of mixed disulfides between sulfhydryl groups of proteins and low-molecular-weight thiols. We hypothesized that this process (S-thiolation) might be involved in turning off the respiratory burst. However, induction of S-thiolation by pretreatment of neutrophils with diamide, a direct thiol oxidizing agent, actually primed the cells for a two- to fivefold increase in total release and fourfold increase in rate of release of 02- on stimulation by f-Met-Leu-Phe. Generation of intracellular oxidants (hydroethidine fluorescence) was increased ninefold. Priming and S-thiolation were apparent at 1 min of incubation and peaked at 5-10 min. Diamide pretreatment also reduced the lag time between addition of phorbol diester and release of 02- by a mean of 23 s (41%). Dithioerythritol, a sulfhydryl-reducing agent, abolished both the S-thiolation and priming mediated by diamide. H202 also induced priming and S-thiolation; and these were eliminated by dithioerythritol. In contrast to the effect of endotoxin, diamide priming did not affect Ca2+ homeostasis of the neutrophils. Diamide did not significantly alter NADPH oxidase activity in a cell-free system. These findings suggest that sulfhydryl groups on one or more proteins play an important role in modulating the respiratory burst.