An asymptotic description of a basic FcRn-regulated clearance mechanism and its implications for PBPK modelling of large antibodies.

A basic FcRn-regulated clearance mechanism is investigated using the method of matched asymptotic expansions. The broader aim of the work is to obtain further insight on the mechanism, thereby providing theoretical support for future pharmacologically-based pharmacokinetic modelling efforts. The corresponding governing equations are first non-dimensionalised and the order of magnitudes of the model parameters are assessed based on their values reported in the literature. Under the assumption of high FcRn-binding affinity, analytical approximations are derived that are valid over the characteristic phases of the problem. Additionally, relatively simple equations relating clearance and AUC to physiological model parameters are derived, which are valid over the longest characteristic time scale of the problem. For lower to moderate doses clearance is effectively linear, whereas for higher doses it is nonlinear. It is shown that for all doses sufficiently high the leading-order approximation for the IgG concentration in plasma, over the longest characteristic time scale, is independent of the initial dose. This is because IgG that is in 'excess' of FcRn is eliminated over a time scale much shorter than that of the terminal phase. In conclusion, analytical approximations of the basic FcRn mechanism have been derived using matched asymptotic expansions, leading to a simple equation relating clearance to FcRn binding affinity, the ratio of degradation and FcRn concentration, and the volumes of the system.

Assessing the performance of QSP models: biology as the driver for validation.

Validation of a quantitative model is a critical step in establishing confidence in the model's suitability for whatever analysis it was designed. While processes for validation are well-established in the statistical sciences, the field of quantitative systems pharmacology (QSP) has taken a more piecemeal approach to defining and demonstrating validation. Although classical statistical methods can be used in a QSP context, proper validation of a mechanistic systems model requires a more nuanced approach to what precisely is being validated, and what role said validation plays in the larger context of the analysis. In this review, we summarize current thoughts of QSP validation in the scientific community, contrast the aims of statistical validation from several contexts (including inference, pharmacometrics analysis, and machine learning) with the challenges faced in QSP analysis, and use examples from published QSP models to define different stages or levels of validation, any of which may be sufficient depending on the context at hand.

Half-Century Ammonia Emissions From Agricultural Systems in Southern Asia: Magnitude, Spatiotemporal Patterns, and Implications for Human Health.

Much concern has been raised about the increasing threat to air quality and human health due to ammonia (NH3) emissions from agricultural systems, which is associated with the enrichment of reactive nitrogen (N) in southern Asia (SA), home of more than 60% the world's population (i.e., the people of West, central, East, South, and Southeast Asia). Southern Asia consumed more than half of the global synthetic N fertilizer and was the dominant region for livestock waste production since 2004. Excessive N application could lead to a rapid increase of NH3 in the atmosphere, resulting in severe air and water pollution in this region. However, there is still a lack of accurate estimates of NH3 emissions from agricultural systems. In this study, we simulated the agricultural NH3 fluxes in SA by coupling the Bidirectional NH3 exchange module (Bi-NH3) from the Community Multi-scale Air Quality model with the Dynamic Land Ecosystem Model. Our results indicated that NH3 emissions were 21.3 ± 3.9 Tg N yr-1 from SA agricultural systems with a rapidly increasing rate of ~0.3 Tg N yr-2 during 1961-2014. Among the emission sources, 10.8 Tg N yr-1 was released from synthetic N fertilizer use, and 10.4 ± 3.9 Tg N yr-1 was released from manure production in 2014. Ammonia emissions from China and India together accounted for 64% of the total amount in SA during 2000-2014. Our results imply that the increased NH3 emissions associated with high N inputs to croplands would likely be a significant threat to the environment and human health unless mitigation efforts are applied to reduce these emissions.

Targeted purification development enabled by computational biophysical modeling.

Chromatographic and non-chromatographic purification of biopharmaceuticals depend on the interactions between protein molecules and a solid-liquid interface. These interactions are dominated by the protein-surface properties, which are a function of protein sequence, structure, and dynamics. In addition, protein-surface properties are critical for in vivo recognition and activation, thus, purification strategies should strive to preserve structural integrity and retain desired pharmacological efficacy. Other factors such as surface diffusion, pore diffusion, and film mass transfer can impact chromatographic separation and resin design. The key factors that impact non-chromatographic separations (e.g., solubility, ligand affinity, charges and hydrophobic clusters, and molecular dynamics) are readily amenable to computational modeling and can enhance the understanding of protein chromatographic. Previously published studies have used computational methods such as quantitative structure-activity relationship (QSAR) or quantitative structure-property relationship (QSPR) to identify and rank order affinity ligands based on their potential to effectively bind and separate a desired biopharmaceutical from host cell protein (HCP) and other impurities. The challenge in the application of such an approach is to discern key yet subtle differences in ligands and proteins that influence biologics purification. Using a relatively small molecular weight protein (insulin), this research overcame limitations of previous modeling efforts by utilizing atomic level detail for the modeling of protein-ligand interactions, effectively leveraging and extending previous research on drug target discovery. These principles were applied to the purification of different commercially available insulin variants. The ability of these computational models to correlate directionally with empirical observation is demonstrated for several insulin systems over a range of purification challenges including resolution of subtle product variants (amino acid misincorporations). Broader application of this methodology in bioprocess development may enhance and speed the development of a robust purification platform.

The impact of group B Streptococcus prophylaxis on early onset neonatal infections.

OBJECTIVE: To determine if changes have occurred in the causative pathogens and/or antibiotic susceptibility profiles in early onset neonatal infections since initiation of group B Streptococcus (GBS) prophylaxis and to determine risk factors for ampicillin/penicillin resistant microorganisms. STUDY DESIGN: Data on 220 infants with positive blood, urine, or cerebrospinal fluid cultures for bacteria or fungi at ≤seven days of age from 1990-2007 were examined and divided into three epochs, based on intrapartum antibiotic prophylactic (IAP) practices. Pathogens and antibiotic resistance were compared among epochs. RESULTS: A significant decrease in the incidence of GBS infections occurred over time, with no change in the incidence of other pathogens or the emergence of antibiotic resistance, including the very low-birthweight population. In regression analysis, ampicillin resistance was associated with male gender (OR 3.096). CONCLUSIONS: No emergence of antibiotic resistant pathogens was found following IAP use. Changing microorganisms and increasing antibiotic resistance found in prior studies are likely multifactorial. Further study is needed to continue to reduce the rates of common early onset pathogens.

The impact of group B streptococcus prophylaxis on late-onset neonatal infections.

OBJECTIVE: To determine trends in late-onset neonatal infections and risk factors for ampicillin/penicillin-resistant microorganisms. STUDY DESIGN: Data on 584 infants with positive blood, urine or cerebrospinal fluid cultures for bacteria or fungi at 8-30 days of age from 1990 to 2007 were examined and divided into three epochs, based on intrapartum antibiotic prophylactic (IAP) practices. Pathogens and antibiotic resistance were compared among epochs. RESULT: The number of candidal infections increased over time for the entire population (P=0.006). There was an increased incidence of Gram-negative (P=0.009) and candidal infections (P=0.014) among very low-birthweight infants. Only Escherichia coli infections showed increasing ampicillin resistance over epochs (P=0.006). In regression analysis, ampicillin/penicillin resistance increased with IAP use (odds ratio 2.05). CONCLUSION: Changing microorganisms and increasing antibiotic resistance in late-onset neonatal infections are likely multifactorial but are increased with IAP use, which may identify an at-risk population. Increasing Candida infections require further investigation.

Mother-clinician discussions in the neonatal intensive care unit: agree to disagree?

OBJECTIVE: To compare mothers' and clinicians' understanding of an infant's illness and perceptions of discussion quality in the neonatal intensive care unit. STUDY DESIGN: English-speaking mothers with an infant admitted to the intensive care unit for at least 48 h were interviewed using a semi-structured survey. The clinician whom the mother had spoken to and identified was also surveyed. Interviews were audiotaped and transcribed. RESULT: A total of 101 mother-clinician pairs were interviewed. Most mothers (89%) and clinicians (92%) felt that their discussions had gone well. Almost all mothers could identify one of their infant's diagnoses (100%) and treatments (93.4%). Mothers and clinicians disagreed on infant illness severity 45% of the time. The majority of mothers (62.5%) who disagreed with clinician estimate of infant illness severity believed their infant to be less sick than indicated by the clinician. CONCLUSION: Mother-clinician satisfaction with communication does not ensure mother-clinician agreement about an infant's medical status.

Relationship between cerebrovascular dysautoregulation and arterial blood pressure in the premature infant.

OBJECTIVE: To evaluate cerebrovascular autoregulation as a function of arterial blood pressure (ABP) in the critically ill, premature infant. STUDY DESIGN: A prospective observational pilot study was conducted in two tertiary care Neonatal Intensive-Care Units. Premature infants (n=23, ≤30 weeks estimated gestational age with invasive ABP monitoring) were enrolled and received routine care while undergoing continuous autoregulation monitoring, using the cerebral oximetry index (COx). The COx is a moving, linear correlation coefficient between cortical reflectance oximetry and ABP. COx values were stratified as a function of ABP for individual subject recordings and for the cohort. RESULT: The mean duration of autoregulation monitoring was 3.2 days (median: 2.97, range: 0.61-3.99). A total of 10 of 23 (43%) developed intraventricular hemorrhage and 1 of 23 (4%) developed periventricular leukomalacia by head ultrasound. No association was found between neurologic injury and percentage of the monitoring periods with autoregulation impairment (defined as COx>0.5). Lower ABP was associated with dysautoregulation (higher COx values, P<0.01). The percentage of time with impaired autoregulation was greater with lower ABP (P=0.013, Spearman r=0.51). CONCLUSION: All infants studied had periods with intact and periods with impaired cerebrovascular autoregulation, measured with the COx. Low ABP was associated with impaired autoregulation.

Significance of internal mammary lymph nodes in patients after mastectomy with tissue-expander reconstruction: a case-control study.

AIM: To retrospectively assess the frequency of internal mammary lymph nodes (IMNs) in patients after mastectomy and tissue-expander reconstruction. MATERIALS AND METHODS: Statistical analysis was performed for all available data in patients with mastectomy and tissue-expander reconstruction from 2004-2007 (study group). The data were compared with that of a control population with mastectomy who did not have reconstruction (control group). Patients with recurrent breast cancers, previous breast reconstruction, surgeries performed at outside hospitals, no available pre- or postoperative computed tomography (CT) or magnetic resonance imaging (MRI) data, or inadequate imaging follow-up were excluded. RESULTS: There were eight patients in the study group (median age 50.5 years, seven breast cancers), and eight patients in the control group (median age 52 years, seven breast cancers). No patients had IMNs on their preoperative imaging examinations. New IMNs were present in postoperative imaging in seven of eight patients (7/8, 87.5%) in the study group. All of them were stable or decreased in size on subsequent imaging examinations. None of the patients in the control group had IMNs (0/8). CONCLUSION: IMNs are common on imaging after mastectomy and tissue-expander placement. The IMNs decreased or remained stable on follow-up imaging and may represent reactive nodes.

Pathologic gambling in patients with restless legs syndrome treated with dopaminergic agonists.

Pathologic gambling is an impulse control disorder previously reported to complicate dopamine agonist therapy in patients with Parkinson disease. It has not been described in association with dopamine agonist therapy of other conditions. We report three patients treated in our sleep disorders center who developed pathologic gambling while receiving treatment with dopamine agonists for restless legs syndrome.

Insights into REM sleep behavior disorder pathophysiology in brainstem-predominant Lewy body disease.

BACKGROUND AND PURPOSE: Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia reflecting changes in the brain, but which specific neuronal networks are involved in human RBD pathogenesis has not yet been determined. To date, only one case of idiopathic RBD has undergone autopsy, in which "incidental Lewy body disease" was found. Due to the severe neuronal loss and gliosis in the substantia nigra (SN) and locus ceruleus (LC) in this case, degeneration of brainstem monoaminergic neurons was postulated as the underlying substrate for RBD. Additional cases of idiopathic RBD with neuropathologic examination may help clarify which key brainstem structures are involved. PATIENT AND METHODS: Case report with neuropathologic analysis. RESULTS: A man with polysomnographically proven RBD (onset age 57 years), but no other neurologic signs or symptoms, underwent neuropathologic examination upon his death at age 72. Histopathologic analysis showed Lewy body disease, but no significant neuronal loss or gliosis was present in the SN or LC. CONCLUSIONS: This case represents another example of Lewy body disease associated with RBD. The minimal degenerative changes in the SN and LC call into question the role of these nuclei in RBD, at least in our case. We suggest additional cases of idiopathic RBD undergo neuropathologic analyses to better delineate the neurologic substrate of this intriguing parasomnia.

Acquired tracheomalacia: detection by expiratory CT scan.

PURPOSE: The purpose of this work was to determine whether cross-sectional area and coronal and sagittal diameter measurements of the trachea between inspiration and end-expiration on CT are significantly different between patients with acquired tracheomalacia and those without this condition. METHOD: Inspiratory and end-expiratory CT scans of the trachea of 23 normal patients and 10 patients with acquired tracheomalacia were analyzed. Percent changes in cross-sectional area, coronal, and sagittal diameters were calculated. RESULTS: For patients with tracheomalacia, mean percent changes in the upper and middle trachea between inspiration and expiration were 49 and 44%; mean changes in the coronal and sagittal diameters in the upper and middle tracheal were 4 and 10% and 39 and 54%, respectively. Control group mean percent changes in the upper and middle tracheal area were 12 and 14%, respectively, and mean changes in the coronal and sagittal diameters in the upper and middle trachea were 4 and 4% and 11 and 13%, respectively. Significant differences were calculated for changes in cross-sectional area and sagittal diameter between groups (p < 10-5). Based on receiver operator curve analysis, a > 18% change in the upper trachea and 28% change in the midtrachea between inspiration and expiration were observed; the probability of tracheomalacia was 89-100%. The probability of tracheomalacia was > 89%, especially if the change in sagittal diameter was > 28%. CONCLUSION: By measuring changes in tracheal cross-sectional area and sagittal diameters between inspiratory and end-expiratory CT, a significant difference can be identified between normal patients and those with acquired tracheomalacia.

Factors influencing pneumothorax rate at lung biopsy: are dwell time and angle of pleural puncture contributing factors?

PURPOSE: To study factors that may influence pneumothorax and chest tube placement rate, especially needle dwell time and pleural puncture angle. MATERIALS AND METHODS: In 159 patients, 160 coaxial computed tomography (CT)-guided lung biopsies were performed. Dwell time, the time between pleural puncture and needle removal, was calculated. The smallest angle of the needle with the pleura ("needle-pleural angle") was measured. These and other variables were correlated with pneumothorax and chest tube rates. RESULTS: One hundred fifty biopsies were included. There were 58 (39%) pneumothoraces (14 noted only at CT), with eight (5%) biopsies resulting in chest tube placement. Longer dwell times (mean, 29 minutes; range, 12-66 minutes) did not correlate with pneumothoraces (P =.81). Smaller needle-pleural angles (< 80 degrees) [corrected], decreased forced expiratory volume in 1 second to vital capacity ratio (<50%), lateral pleural puncture, and lesions along fissures were associated with higher [corrected] pneumothorax rates (P <.05). Emphysema along the needle path, pulmonary function tests showing ventilatory obstruction, and lesions along fissures predisposed patients to chest tube placement (P <.05). Pleural thickening and prior surgery were associated with lower pneumothorax rates (P <.05). CONCLUSION: Longer dwell times do not correlate with pneumothorax and should not influence the decision to obtain more biopsy samples. A shallow pleural puncture angle may increase the pneumothorax rate.

Stereotaxic delivery of corticosterone to the amygdala modulates colonic sensitivity in rats.

Episodes of anxiety are often associated with the onset or exacerbation of visceral pain in patients with irritable bowel syndrome (IBS). The central amygdaloid nucleus (CeA) is a key limbic structure involved in the expression of anxiety as well as a major site for regulating autonomic and visceral responses to stress. Previous experiments have shown that glucocorticoids can act directly at the CeA to increase the level of anxiety in rats. Therefore, the goal of this study was to examine the effect of stereotaxic delivery of corticosterone into the CeA on the development of visceral hypersensitivity by measuring visceromotor response to colorectal distention in rats. Stereotaxic delivery of corticosterone to the CeA increases indices of anxiety and produces a hypersensitive colon as demonstrated by an exaggerated visceromotor response to colorectal distention in the F344 rat strain. Our findings suggest that modulation of anxiety by manipulating amygdala function with corticosterone induced colonic hypersensitivity via descending neuronal pathways from the CeA.

Evidence for visceral hypersensitivity in high-anxiety rats.

In patients with irritable bowel syndrome, anxiety is often associated with visceral pain. Based on this information we hypothesized that rats genetically predisposed to anxiety have an increased visceral sensitivity. To test this hypothesis, visceromotor reflex recordings in response to colorectal distention were used to estimate the level of visceral stimulation in high; moderate-, and low-anxiety rats. We compared the effect of innocuous colorectal distension in rats with and without sensitized colons. In nonsensitized rats visceromotor responses were increased by colorectal distention with the greatest response in the high-anxiety Wistar-Kyoto strain. Sensitization of the colon significantly increased visceromotor responses to colorectal distention in all rat strains. In summary, our data suggested that a manifestation of a genetically determined anxiety level appeared to be abnormal neural responsiveness of the gastrointestinal tract leading to visceral hypersensitivity in high-anxiety animals.

Identification of four new quantitative trait loci regulating arthritis severity and one new quantitative trait locus regulating autoantibody production in rats with collagen-induced arthritis.

OBJECTIVE: Collagen-induced arthritis (CIA) is a polygenic model of experimentally induced autoimmunity and chronic joint inflammation. This study maps genetic loci that regulate CIA susceptibility in DA/Bkl (DA) and BN/SsNHsd (BN) rats. METHODS: Genome scans covering chromosomes 1-20 and interval mapping techniques using 159 simple sequence-length polymorphism markers were used to identify quantitative trait loci (QTLs) that regulate CIA in (DA x BN)F2 hybrids. Serum antibody titers to type II collagen were determined by enzyme-linked immunosorbent assay. RESULTS: DA rats were high responders to porcine type II collagen (PII) and developed severe CIA (100%). BN rats were low responders to PII and resistant to CIA (0%). BN genes strongly repressed PII-induced CIA. Only 12% of (DA x BN)F1 rats (7 of 60) and 31% of (DA x BN)F2 rats (307 of 1,004) developed CIA. Three new QTLs (Cia11, Cia12, and Cia13) with significant logarithm of odds (LOD) scores of 5.6, 4.6, and 4.5, respectively, plus a suggestive QTL (Cia14*, LOD 3.0) regulating arthritis severity were identified on chromosomes 3, 12, 4, and 19. A new QTL, Ciaa3, associating with anticollagen antibody titer (antibody to PII LOD 6.5; antibody to rat type II collagen LOD 5.2) mapped to chromosome 9. Of 10 CIA QTLs previously identified in (DA x F344) and (DA x ACI) rats, only Cia1 in the major histocompatibility complex and a region coincident to Cia5 on chromosome 10 (LOD >8.0) influenced CIA severity in (DA x BN)F2 rats. CONCLUSION: Since CIA exhibits many of the pathologic features of rheumatoid arthritis, the data indicate that the variety of genetic elements regulating human autoimmune and rheumatic diseases may be much larger and more varied than originally envisioned.

Additive pressor effects of caffeine and stress in male medical students at risk for hypertension.

The effects of caffeine on blood pressure (BP) and cortisol secretion were examined during elevated work stress in medical students at high versus low risk for hypertension. Among 31 male medical students who were regular consumers of caffeine, 20 were considered at low risk for hypertension (negative parental history and all screening BP < 125/78 mm Hg) and 11 at high risk based on epidemiologic criteria (positive parental history and average screening BPs between 125/78 and 139/89 mm Hg). Cortisol levels and ambulatory BP were measured with and without caffeine during two lectures (low work stress) and two exams (high work stress) in a randomized, double-blind, crossover trial. Caffeine consumption and exam stress increased cortisol secretion in both groups (P < .05). BP increased with caffeine or exam stress in both groups, low versus high risk, respectively (Caffeine: + 5/4 vs + 3/3 mm Hg; Stress: + 4/1 vs + 7/3 mm Hg; P < .05). The combination of stress and caffeine caused additive increases in BP (Low Risk + 9/5 mm Hg, High Risk + 10/6 mm Hg) such that 46% of high-risk participants had average systolic BP > or = 140 mm Hg. This combined effect of stress and caffeine on BP suggests that it may be beneficial for individuals at high risk for hypertension to refrain from the use of caffeinated beverages, particularly at times when work demands and attendant stressors are high. For the same reasons, recent intake of caffeine should be controlled in patients undergoing BP measurement for the diagnosis of hypertension.

Corticosterone delivery to the amygdala increases corticotropin-releasing factor mRNA in the central amygdaloid nucleus and anxiety-like behavior.

The present study examined the effects of stereotaxic delivery of corticosterone to the amygdala on anxiety-like behavior and corticotropin-releasing factor (CRF) mRNA level in the central nucleus of the amygdala (CeA). Micropellets (30 microg) of crystalline corticosterone or cholesterol (control) were implanted bilaterally at the dorsal margin of the CeA in Wistar rats. Seven days post-implantation, anxiety-like behavior was accessed using an elevated plus-maze. CRF mRNA level in the CeA was determined by in situ hybridization 4 h after being tested on the elevated plus-maze. Corticosterone implants increased indices of anxiety on the elevated plus-maze and produced a concomitant increase in both basal level of CRF mRNA per neuron and the number of neurons with CRF hybridization signal in the CeA. The plus-maze increased CRF mRNA levels in the CeA of cholesterol implanted rats to the elevated basal levels observed in corticosterone treated animals. Exposure to the plus-maze did not increase CRF mRNA level in the CeA of corticosterone implanted rats beyond elevated basal levels. Taken together, these findings support the involvement of the amygdala in anxiety-like behaviors in response to chronically elevated corticosterone and suggests that elevated glucocorticoids may increase anxiety by inducing CRF expression in the CeA.