Care Quality and Spending Among Commercially Insured Children With Disabilities

OBJECTIVE

To identify opportunities to improve care value for children with disabilities (CWD), we examined CWD prevalence within a commercially insured population and compared outpatient care quality and annual health plan spending levels for CWD relative to children with complex medical conditions without disabilities; children with chronic conditions that are not complex; and children without disabling, complex, or chronic conditions.

METHODS

This cross-sectional study comprised 1,118,081 person-years of Blue Cross Blue Shield Massachusetts data for beneficiaries aged 1 to 19years old during 2008 to 2012. We combined the newly developed and validated Children with Disabilities Algorithm with the Pediatric Medical Complexity Algorithm to identify CWD and non-CWD subgroups. We used 14 validated or National Quality Forum-endorsed measures to assess outpatient care quality and paid claims to examine annual plan spending levels and components.

RESULTS

CWD constituted 4.5% of all enrollees. Care quality for CWD was between 11% and 59% for 8 of 14 quality measures and >80% for the 6 remaining measures and was generally comparable to that for non-CWD subgroups. Annual plan spending among CWD was a median and mean 23% and 53% higher than that for children with complex medical conditions without disabilities, respectively; CWD mean and median values were higher than for all other groups as well.

CONCLUSIONS

CWD were prevalent in our commercially insured population. CWD experienced suboptimal levels of care, but those levels were comparable to non-CWD groups. Improving the care value for CWD involves a deeper understanding of what higher spending delivers and additional aspects of care quality.

Adverse Events in Hospitalized Pediatric Patients

: media-1vid110.1542/5789657761001PEDS-VA_2017-3360Video Abstract BACKGROUND: Patient safety concerns over the past 2 decades have prompted widespread efforts to reduce adverse events (AEs). It is unclear whether these efforts have resulted in reductions in hospital-wide AE rates. We used a validated safety surveillance tool, the Global Assessment of Pediatric Patient Safety, to measure temporal trends (2007-2012) in AE rates among hospitalized children.

METHODS

We conducted a retrospective surveillance study of randomly selected pediatric inpatient records from 16 teaching and nonteaching hospitals. We constructed Poisson regression models with hospital random intercepts, controlling for patient age, sex, insurance, and chronic conditions, to estimate changes in AE rates over time.

RESULTS

Examining 3790 records, reviewers identified 414 AEs (19.1 AEs per 1000 patient days; 95% confidence interval [CI] 17.2-20.9) and 210 preventable AEs (9.5 AEs per 1000 patient days; 95% CI 8.2-10.8). On average, teaching hospitals had higher AE rates than nonteaching hospitals (26.2 [95% CI 23.7-29.0] vs 5.1 [95% CI 3.7-7.1] AEs per 1000 patient days, P < .001). Chronically ill children had higher AE rates than patients without chronic conditions (33.9 [95% CI 24.5-47.0] vs 14.0 [95% CI 11.8-16.5] AEs per 1000 patient days, P < .001). Multivariate analyses revealed no significant changes in AE rates over time. When stratified by hospital type, neither teaching nor nonteaching hospitals experienced significant temporal AE rate variations.

CONCLUSIONS

AE rates in pediatric inpatients are high and did not improve from 2007 to 2012. Pediatric AE rates were substantially higher in teaching hospitals as well as in patients with more chronic conditions.

Quality of Primary Care for Children With Disabilities Enrolled in Medicaid

OBJECTIVE

The quality of primary care delivered to Medicaid-insured children with disabilities (CWD) is unknown. We used the newly validated CWD algorithm (CWDA) to examine CWD prevalence among Medicaid enrollees 1 to 18 years old, primary care quality for CWD, and differences in primary care quality for CWD and non-CWD.

METHODS

Cross-sectional study using 2008 Medicaid Analytic eXtract claims data from 9 states, including children with at least 11 months of enrollment (N = 2,671,922 enrollees). We utilized CWDA to identify CWD and applied 12 validated or endorsed pediatric quality measures to assess preventive/screening, acute, and chronic disease care quality. We compared quality for CWD and non-CWD unmatched and matched on age, sex, and number of nondisabling chronic conditions and outpatient encounters.

RESULTS

CWDA identified 5.3% (n = 141,384) of our study population as CWD. Care quality levels for CWD were below 50% on 8 of 12 quality measures (eg, adolescent well visits [44.9%], alcohol/drug treatment engagement [24.9%]). CWD care quality was significantly better than the general population of non-CWD by +0.9% to +15.6% on 9 measures, but significantly worse for 2 measures, chlamydia screening (-3.4%) and no emergency department visits for asthma (-5.0%; all P < .01 to .001). Differences in care quality between CWD and non-CWD were generally smaller or changed direction when CWD were compared to a general population or matched group of non-CWD.

CONCLUSIONS

One in 20 Medicaid-insured children is CWD, and the quality of primary care delivered to CWD is suboptimal. Areas needing improvement include preventive/screening, acute care, and chronic disease management.

Performance of the Global Assessment of Pediatric Patient Safety (GAPPS) Tool

BACKGROUND AND OBJECTIVE

Efforts to advance patient safety have been hampered by the lack of high quality measures of adverse events (AEs). This study's objective was to develop and test the Global Assessment of Pediatric Patient Safety (GAPPS) trigger tool, which measures hospital-wide rates of AEs and preventable AEs.

METHODS

Through a literature review and expert panel process, we developed a draft trigger tool. Tool performance was tested in 16 academic and community hospitals across the United States. At each site, a primary reviewer (nurse) reviewed ∼240 randomly selected medical records; 10% of records underwent an additional primary review. Suspected AEs were subsequently evaluated by 2 secondary reviewers (physicians). Ten percent of records were also reviewed by external expert reviewers. Each trigger's incidence and positivity rates were assessed to refine GAPPS.

RESULTS

In total, 3814 medical records were reviewed. Primary reviewers agreed 92% of the time on presence or absence of a suspected AE (κ = 0.69). Secondary reviewers verifying AE presence or absence agreed 92% of the time (κ = 0.81). Using expert reviews as a standard for comparison, hospital-based primary reviewers had a sensitivity and specificity of 40% and 91%, respectively. As primary reviewers gained experience, their agreement with expert reviewers improved significantly. After removing low-yield triggers, 27 and 30 (of 54) triggers met inclusion criteria to form final manual and automated trigger lists, respectively.

CONCLUSIONS

GAPPS reliably identifies AEs and can be used to guide and monitor quality improvement efforts. Ongoing refinement may facilitate future interhospital comparisons.

Development of the Children With Disabilities Algorithm

BACKGROUND

A major impediment to understanding quality of care for children with disabilities (CWD) is the lack of a method for identifying this group in claims databases. We developed the CWD algorithm (CWDA), which uses International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes to identify CWD.

METHODS

We conducted a cross-sectional study that (1) ensured each of the 14,567 codes within the 2012 ICD-9-CM codebook was independently classified by 3 to 9 pediatricians based on the code's likelihood of indicating CWD and (2) triangulated the resulting CWDA against parent and physician assessment of children's disability status by using survey and chart abstraction, respectively. Eight fellowship-trained general pediatricians and 42 subspecialists from across the United States participated in the code classification. Parents of 128 children from a large, free-standing children's hospital participated in the parent survey; charts of 336 children from the same hospital were included in the abstraction study.

RESULTS

CWDA contains 669 ICD-9-CM codes classified as having a ≥75% likelihood of indicating CWD. Examples include 318.2 Profound intellectual disabilities and 780.72 Functional quadriplegia. CWDA sensitivity was 0.75 (95% confidence interval 0.63-0.84) compared with parent report and 0.98 (0.95-0.99) compared with physician assessment; its specificity was 0.86 (0.72-0.95) and 0.50 (0.41-0.59), respectively.

CONCLUSIONS

ICD-9-CM codes can be classified by their likelihood of indicating CWD. CWDA triangulates well with parent report and physician assessment of child disability status. CWDA is a new tool that can be used to assess care quality for CWD.

A gene on the HER2 amplicon, C35, is an oncogene in breast cancer whose actions are prevented by inhibition of Syk

Background:

C35 is a 12 kDa membrane-anchored protein endogenously over-expressed in many invasive breast cancers. C35 (C17orf37) is located on the HER2 amplicon, between HER2 and GRB7. The function of over-expressed C35 in invasive breast cancer is unknown.

Methods:

Tissue microarrays containing 122 primary human breast cancer specimens were used to examine the association of C35 with HER2 expression. Cell lines over-expressing C35 were generated and tested for evidence of cell transformation in vitro.

Results:

In primary breast cancers high levels of C35 mRNA expression were associated with HER2 gene amplification. High levels of C35 protein expression were associated with hallmarks of transformation, such as, colony growth in soft agar, invasion into collagen matrix and formation of large acinar structures in three-dimensional (3D) cell cultures. The transformed phenotype was also associated with characteristics of epithelial to mesenchymal transition, such as adoption of spindle cell morphology and down-regulation of epithelial markers, such as E-cadherin and keratin-8. Furthermore, C35-induced transformation in 3D cell cultures was dependent on Syk kinase, a downstream mediator of signalling from the immunoreceptor tyrosine-based activation motif, which is present in C35.

Conclusion:

C35 functions as an oncogene in breast cancer cell lines. Drug targeting of C35 or Syk kinase might be helpful in treating a subset of patients with HER2-amplified breast cancers.

4-Methylumbelliferone inhibits tumour cell growth and the activation of stromal hyaluronan synthesis by melanoma cell-derived factors

BACKGROUND

There is a close correlation between tumour progression and hyaluronan production, either by tumour cells or by stromal cells that are stimulated by tumour-derived factors. Inhibition of tumour stimulation of fibroblast hyaluronan may suppress tumour growth and invasion.

OBJECTIVES

To examine the effect of the hyaluronan synthesis inhibitor 4-methylumbelliferone (4-MU) on the growth of and hyaluronan synthesis by fibroblasts and C8161 and MV3 melanoma cell lines, invasion, and inhibition of tumour cell-derived factor activation of fibroblasts.

METHODS

Effects of 4-MU on growth and hyaluronan synthesis by fibroblasts and melanoma cells were examined in monolayer culture and fibroblast-contracted collagen lattices, and their effects on the growth and invasion of tumour cells into collagen lattices were also studied.

RESULTS

4-MU caused a dose-dependent growth inhibition of fibroblast and melanoma cells with maximum inhibition at 0·5 mmol L(-1) 4-MU. At this dose, 4-MU inhibited (3) H-glucosamine incorporation into fibroblast glycosaminoglycans by 52%, and hyaluronan synthesis by 64%. The relative inhibition was more pronounced when fibroblasts were stimulated with C8161 melanoma cell-conditioned medium. 4-MU reduced the level of hyaluronan in fibroblast-contracted collagen lattices, and inhibited both the growth on and invasion into the lattices by melanoma cells. This growth inhibition appears to be predominantly independent of inhibition of hyaluronan synthesis. The effect on growth inhibition was reversible, and 4-MU had no effect on apoptosis.

CONCLUSIONS

4-MU is a potent inhibitor of hyaluronan synthesis, induction of stromal hyaluronan accumulation by tumour cells, and fibroblast and melanoma cell proliferation, and results suggest that 4-MU may have potential as a tumour cell anti-invasive and antiproliferative agent.

Gadodiamide contrast agent 'activates' fibroblasts: a possible cause of nephrogenic systemic fibrosis

Nephrogenic systemic fibrosis (NSF) is a fibrotic disease generating intense interest due to its recent discovery, and unknown cause. It appears confined to patients with renal disease and presents as grossly thickened, indurated, tight skin that is woody to palpation. Histologically, the dermis contains thickened collagen bundles, numerous plump fibroblast-like cells, and elevated hyaluronan expression. Recent data suggest a link between the use of gadolinium chelate as an MRI contrast agent and the onset of the disease. Fibroblasts from the lesions of six NSF patients, all of whom were exposed to gadodiamide, were compared with control fibroblasts for hyaluronan and collagen synthesis. Serum from NSF patients was assessed for fibroblast hyaluronan-stimulating activity, collagen synthesis, and gadodiamide for its effect on fibroblast proliferation and matrix synthesis. NSF fibroblasts synthesized excess levels of hyaluronan and collagen compared with control fibroblasts, with up to 2.8-fold and 3.3-fold increases, respectively. NSF patient serum stimulated control fibroblast hyaluronan synthesis by up to 7-fold, and collagen synthesis by up to 2.4-fold. 1 mM gadodiamide added to culture medium stimulated fibroblast growth in a dose-dependent manner, decreasing their doubling time from 28 h to 22 h, and increasing the maximum cell density. Even a short exposure to gadodiamide stimulated cell growth, suggesting that the cells were activated by the gadodiamide. The growth of fibroblasts within contracted collagen lattices was also significantly stimulated by gadodiamide, while fibroblasts exposed to gadodiamide synthesized increased levels of hyaluronan. Control fibroblasts exposed to gadodiamide, and NSF fibroblasts exhibited an extensive pericellular coat of hyaluronan, and expressed alpha-smooth muscle actin. Gadolinium chloride did not affect fibroblast growth. This report demonstrates that NSF fibroblasts synthesize excess levels of hyaluronan and collagen, and that gadodiamide stimulates control fibroblast growth, matrix synthesis, and differentiation into myofibroblasts, suggesting a possible role for gadodiamide in the pathophysiology of NSF.

What about the other breast? A review of a series of bilateral breast carcinomas

The BreastScreen Queensland Brisbane Southside BreastScreen Service reports on a study of 10 cases of bilateral breast carcinomas from a total cancer population of 217 cases. All cases were patients of screening examinations that were recalled for a suspicious lesion in one breast. Two cases were mammographically suspicious of bilateral tumours. In eight cases, tumours were ultrasonically visible in both breasts and in two further cases, the suspicion of bilateral malignancy was raised by the presence of bilateral microcalcification. It is not the purpose of this paper to provide a statistical analysis of the occurrence of bilateral breast cancer. This is a radiological paper from a breast screening service reporting on findings that conventional wisdom may find unusual. The incidence of bilateral breast malignancy in the study was found to be somewhat higher than expected. These cases have been diagnosed by the utilization of a particularly high standard of ultrasound and mammography, performed and interpreted by diagnosticians possessing an elevated level of suspicion of the possible presence of a second primary lesion. It is therefore proposed that an increased rate of diagnosis of bilateral tumours is possible with an evolution of assessment protocols, combined with quality ultrasound and mammography.

Phase I study of Gliadel wafers plus temozolomide in adults with recurrent supratentorial high-grade gliomas

Both Gliadel wafers [1,3-bis(2-chloroethyl)-1-nitrosourea] and temozolomide (TEMO) have been shown in independent studies to prolong survival of patients with recurrent malignant glioma following surgery and radiotherapy. On the basis of preclinical evidence of synergism between Gliadel wafers and TEMO, a phase I study was designed to evaluate the toxicity of combining these 2 agents in the treatment of patients with recurrent supratentorial malignant glioma. All patients had surgical resection of the tumor at relapse, and up to 8 Gliadel (3.85%) wafers were placed in the surgical cavity following resection. Two weeks after surgery, TEMO was given orally daily for 5 days. Cohorts of 3 patients received TEMO at daily doses of 100 mg/m2, 150 mg/m2, and 200 mg/m2, respectively. Patients were assessed for toxicity 4 weeks after start of the first course of TEMO. Contrast-enhanced MRI of the brain was used to assesstumor response after the first cycle of TEMO. Patients with stable disease or response after the first cycle of TEMO were allowed to continue treatment at the same dose every 4 weeks for 12 cycles or until disease progression or unacceptable toxicity. Ten patients with a median age of 47 years (range, 22-66 years) were enrolled in this study. There were 7 patients with glioblastoma multiforme and 3 patients with anaplastic astrocytoma. Three patients were treated with TEMO at the first dose level of 100 mg/m2, 4 at the second dose level of 150 mg/m2, and 3 at the third dose level of 200 mg/m2. The 10 patients received a median of 3 cycles (range, 1-12 cycles) of TEMO following placement of Gliadel wafers. The treatment was well tolerated, with only 1 patient suffering grade III thrombocytopenia at the highest dose level. Two patients at each dose level had no evidence of disease progression after treatment. Four patients suffered progressive disease on therapy. Our study demonstrates that TEMO can be given safely after placement of Gliadel (3.85%) wafers. The recommended dosage for TEMO for a phase II study of this combination is 200 mg/m2 per day for 5 days.

Analysis of the pobA and pobR genes controlling expression of p-hydroxybenzoate hydroxylase in Azotobacter chroococcum

We report the cloning and analysis of a gene and its cognate regulatory element from a member of the Azotobacteriaceae which are involved in the breakdown of an aromatic compound. The genes from Azotobacter chroococcum encoding p-hydroxybenzoate hydroxylase (pobA) and its regulatory protein (pobR) were cloned from a genomic library and sequenced. Sequence analysis of pobA revealed homology with other bacterial p-hydroxybenzoate hydroxylase enzymes. Residues essential to the structure and function of the enzyme have been conserved. The pobR gene encodes a DNA binding regulatory protein with similarity to proteins from the AraC/XylS family of transcriptional activators. A fragment containing both pobA and pobR was cloned into pUC19 and p-hydroxybenzoate hydroxylase activity was induced in Escherichia coli by the addition of p-hydroxybenzoate. A frame-shift mutation introduced into the pobR gene prevented expression of p-hydroxybenzoate hydroxylase, indicating that PobR is the protein required for transcription of pobA. Interestingly, A. chroococcum PobR has no homology to the PobR protein that is the transcriptional activator of pobA in Acinetobacter strain ADP1, a protein that is homologous to the IclR family of transcriptional regulators. However, PobR from A. chroococcum is homologous to several other proteins, suggesting that these proteins will also function as transcriptional activators of pobA.

Sex expression, sex-specific traits, and the effects of salinity on growth and reproduction of Amaranthus cannabinus (Amaranthaceae), a dioecious annual

Amaranthus cannabinus was studied to investigate some of the ecological factors thought to be involved in the evolution of dioecy and to investigate the effects of salinity on sex expression and sex-specific selection. In the field portion of this study, sex ratios, stability of sex expression, spatial distribution, allocation strategies, and phenologies of the sexes were investigated in New Jersey freshwater and salt marsh populations of water hemp. To examine the effects of salinity on vegetative and reproductive development of males and females, plants were grown in the greenhouse at three salinity levels. Adult sex ratios were found to be 1:1. Temporal deviations from a 1:1 sex ratio varied by population and were due to differences in flowering phenology and mortality between the sexes. No plants were observed to change sex expression, and there was no evidence of spatial segregation of the sexes in the field. In both the field and the greenhouse, females allocated more resources to vegetative tissues and had a longer growing period than males. The results of this study suggest that increased reproductive efficiency through sex-specific growth patterns may have been an important selective factor involved in the evolution of dioecy in A. cannabinus.

Phase I trial of carmustine plus O6-benzylguanine for patients with recurrent or progressive malignant glioma

PURPOSE

The major mechanism of resistance to alkylnitrosourea therapy involves the DNA repair protein O(6)-alkylguanine-DNA alkyltransferase (AGT), which removes chloroethylation or methylation damage from the O(6) position of guanine. O(6)-benzylguanine (O(6)-BG) is an AGT substrate that inhibits AGT by suicide inactivation. We conducted a phase I trial of carmustine (BCNU) plus O(6)-BG to define the toxicity and maximum-tolerated dose (MTD) of BCNU in conjunction with the preadministration of O(6)-BG with recurrent or progressive malignant glioma.

PATIENTS AND METHODS

Patients were treated with O(6)-BG at a dose of 100 mg/m(2) followed 1 hour later by BCNU. Cohorts of three to six patients were treated with escalating doses of BCNU, and patients were observed for at least 6 weeks before being considered assessable for toxicity. Plasma samples were collected and analyzed for O(6)-BG, 8-oxo-O(6)-BG, and 8-oxoguanine concentration.

RESULTS

Twenty-three patients were treated (22 with glioblastoma multiforme and one with anaplastic astrocytoma). Four dose levels of BCNU (13.5, 27, 40, and 55 mg/m(2)) were evaluated, with the highest dose level being complicated by grade 3 or 4 thrombocytopenia and neutropenia. O(6)-BG rapidly disappeared from plasma (elimination half-life = 0. 54 +/- 0.14 hours) and was converted to a longer-lived metabolite, 8-oxo-O(6)-BG (elimination half-life = 5.6 +/- 2.7 hours) and further to 8-oxoguanine. There was no detectable O(6)-BG 5 hours after the start of the O(6)-BG infusion; however, 8-oxo-O(6)-BG and 8-oxoguanine concentrations were detected 25 hours after O(6)-BG infusion. The mean area under the concentration-time curve (AUC) of 8-oxo-O(6)-BG was 17.5 times greater than the mean AUC for O(6)-BG.

CONCLUSION

These results indicate that the MTD of BCNU when given in combination with O(6)-BG at a dose of 100 mg/m(2) is 40 mg/m(2) administered at 6-week intervals. This study provides the foundation for a phase II trial of O(6)-BG plus BCNU in nitrosourea-resistant malignant glioma.

Estrogen-induced activation of Erk-1 and Erk-2 requires the G protein-coupled receptor homolog, GPR30, and occurs via trans-activation of the epidermal growth factor receptor through release of HB-EGF

Estrogen rapidly activates the mitogen-activated protein kinases, Erk-1 and Erk-2, via an as yet unknown mechanism. Here, evidence is provided that estrogen-induced Erk-1/-2 activation occurs independently of known estrogen receptors, but requires the expression of the G protein-coupled receptor homolog, GPR30. We show that 17beta-estradiol activates Erk-1/-2 not only in MCF-7 cells, which express both estrogen receptor alpha (ER alpha) and ER beta, but also in SKBR3 breast cancer cells, which fail to express either receptor. Immunoblot analysis using GPR30 peptide antibodies showed that this estrogen response was associated with the presence of GPR30 protein in these cells. MDA-MB-231 breast cancer cells (ER alpha-, ER beta+) are GPR30 deficient and insensitive to Erk-1/-2 activation by 17beta-estradiol. Transfection of MDA-MB-231 cells with a GPR30 complementary DNA resulted in overexpression of GPR30 protein and conversion to an estrogen-responsive phenotype. In addition, GPR30-dependent Erk-1/-2 activation was triggered by ER antagonists, including ICI 182,780, yet not by 17alpha-estradiol or progesterone. Consistent with acting through a G protein-coupled receptor, estradiol signaling to Erk-1/-2 occurred via a Gbetagamma-dependent, pertussis toxin-sensitive pathway that required Src-related tyrosine kinase activity and tyrosine phosphorylation of tyrosine 317 of the Shc adapter protein. Reinforcing this idea, estradiol signaling to Erk-1/-2 was dependent upon trans-activation of the epidermal growth factor (EGF) receptor via release of heparan-bound EGF (HB-EGF). Estradiol signaling to Erk-1/-2 could be blocked by: 1) inhibiting EGF-receptor tyrosine kinase activity, 2) neutralizing HB-EGF with antibodies, or 3) down-modulating HB-EGF from the cell surface with the diphtheria toxin mutant, CRM-197. Our data imply that ER-negative breast tumors that continue to express GPR30 may use estrogen to drive growth factor-dependent cellular responses.

Neurologic emergencies in the cancer patient

Neurologic complications of cancer and its therapy are varied and common, but there are few true neurologic emergencies. However, when a neurologic emergency does occur, rapid diagnosis and treatment can preserve neurologic function and, in some circumstances, save a life. Epidural spinal cord compression, raised intracranial pressure (ICP), status epilepticus, and intracerebral hemorrhage (ICH) are the most common neurologic emergencies in the cancer patient. This chapter details the clinical features, possible etiologies, diagnostic tests, and treatment options for each of these complications.

The Directional Dependence of Water Penetration into Langmuir-Blodgett Multilayers

The relationship between the mass uptake and the swelling of arachidic acid Langmuir-Blodgett (LB) films exposed to water vapor was investigated. Combining sorption data from the quartz crystal microbalance with swelling data from the surface forces apparatus (SFA), it was found that films exposed to water vapor ( approximately 75% RH) absorb 0.22 moles water/mole LB film with an associated swelling of 0.2 Å/film layer. This degree of film swelling is less than that predicted if the water taken up exhibits the molar volume of bulk liquid water. The configuration of the films in the SFA, where they are trapped between impermeable surfaces, makes possible the measurement of the lateral diffusion coefficient of water in these layered materials. This was found to be 1.5 x 10(-10) cm(2)/s, which is at least 100 times faster than diffusion normal to the layers as measured with the microbalance. Copyright 1999 Academic Press.

Maximal migration of human smooth muscle cells on fibronectin and type IV collagen occurs at an intermediate attachment strength

Although a biphasic dependence of cell migration speed on cell-substratum adhesiveness has been predicted theoretically, experimental data directly demonstrating a relationship between these two phenomena have been lacking. To determine whether an optimal strength of cell-substratum adhesive interactions exists for cell migration, we measured quantitatively both the initial attachment strength and migration speed of human smooth muscle cells (HSMCs) on a range of surface concentrations of fibronectin (Fn) and type IV collagen (CnIV). Initial attachment strength was measured in order to characterize short time-scale cell-substratum interactions, which may be representative of dynamic interactions involved in cell migration. The critical fluid shear stress for cell detachment, determined in a radial-flow detachment assay, increased linearly with the surface concentrations of adsorbed Fn and CnIV. The detachment stress required for cells on Fn, 3.6 +/- 0.2 x 10(-3) mu dynes/absorbed molecule, was much greater than that on CnIV, 5.0 +/- 1.4 x 10(-5) mu dynes/absorbed molecule. Time-lapse videomicroscopy of individual cell movement paths showed that the migration behavior of HSMCs on these substrates varied with the absorbed concentration of each matrix protein, exhibiting biphasic dependence. Cell speed reached a maximum at intermediate concentrations of both proteins, with optimal concentrations for migration at 1 x 10(3) molecules/micron2 and 1 x 10(4) molecules/micron2 on Fn and CnIV, respectively. These optimal protein concentrations represent optimal initial attachment strengths corresponding to detachment shear stresses of 3.8 mu dyne/micron2 on Fn and 1.5 mu dyne/micron2 on CnIV. Thus, while the optimal absorbed protein concentrations for migration on Fn and CnIV differed by an order of magnitude, the optimal initial attachment strengths for migration on these two proteins were very similar. Further, the same minimum strength of initial attachment, corresponding to a detachment shear stress of approximately 1 mu dyne/micron2, was required for movement on either protein. These results suggest that initial cell-substratum attachment strength is a central variable governing cell migration speed, able to correlate observations of motility on substrata differing in adhesiveness. They also demonstrate that migration speed depends in biphasic manner on attachment strength, with maximal migration at an intermediate level of cell-substratum adhesiveness.

High mortality of domestic turkeys associated with Highlands J virus and eastern equine encephalitis virus infections

High mortality occurred in two flocks of commercial turkey hens placed in southern North Carolina in fall 1991. Daily mortality peaked at 3.19% in Flock 1 and 3.79% in Flock 2. Clinical signs included restlessness, somnolence, vocalization, and acute death. Gross lesions included atrophy of the bursa of Fabricius, thymus, and spleen, and watery intestinal contents. Microscopic changes included moderate to marked lymphocyte necrosis and depletion in the bursa, thymus, and spleen, widely scattered necrosis of pancreatic acinar cells, and mild villous atrophy and fusion in the jejunum and ileum with cuboidal to low columnar epithelial cells covering the villous tips. In Flock 1, at 27 days of age, reovirus and picornavirus particles were detected in the feces. One week later, togavirus-like particles were observed in fecal contents, and two of seven serum samples showed seroconversion to Highlands J virus. Eleven days later, five of six serum samples were positive for antibodies against Highlands J virus, with a fourfold increase in the geometric mean titer. In Flock 2, seroconversion to eastern equine encephalitis virus was observed in four of 10 serum samples 11 days after the onset of clinical signs. Based on the above observations, it is suspected that these alphaviruses were the cause of the clinical syndrome.

Stopped-flow chamber and image analysis system for quantitative characterization of bacterial population migration: Motility and chemotaxis ofEscherichia coli K12 to fucose

The directed movement of a bacterial population in response to a chemical gradient is known as bacterial chemotaxis and plays a critical role in the distribution and dynamic interaction of bacterial populations. A quantitative characterization of the chemotactic response in terms of intrinsic cell properties is necessary for making reliable predictions about the migratory behavior of bacterial populations within the environment.The design of the stopped-flow diffusion chamber (SFDC) provides a well-characterized chemical gradient and reliable method for measuring bacterial migration behavior. During flow through the chamber a step change in the chemical concentration is imposed on a uniform suspension of bacteria. Once flow is stopped a transient chemical gradient forms due to diffusion; bacteria respond by forming a band of high cell density that travels toward higher concentrations of the attractant. Sequential observations of bacterial spatial distributions over a period of about ten minutes are recorded on photomicrographs. Computer-aided image analysis of the photographic negatives converts light-scattering information to a digital representation of the bacterial density profiles. A mathematical model is used to quantitatively characterize these observations in terms of intrinsic cell parameters: a chemotactic sensitivity coefficient, χ0, from the aggregate cell density accumulated in the band and a random motility coefficient, μ0, from population dispersion in the absence of a chemical gradient.Using the SFDC assay and an individual cell-based mathematical model we successfully determined values for both of these population parameters forEscherichia coli K12 responding to fucose. The values we obtained were μ0=1.1 ± 0.4 x 10(-5) cm(2)/sec and χ0=8 ± 3 x 10(-5) cm(2)/sec. These parameters will be useful for predicting population behavior in application systems such as biofilm development, population dynamics of genetically-engineered bacteria released into the environment, and in situ bioremediation technologies.

Skeletal lesions associated with a naturally occurring poult enteritis

One-day-old poults were placed on contaminated litter on which poults previously had developed an enteric disease characterized by diarrhea, increased mortality, and stunting. These exposed birds were examined for clinical signs and pathologic changes in bone and parathyroid glands compared with controls. Intestinal and fecal samples were examined for potential pathogens. Exposed poults varied in size as early as day 8 and had significantly decreased weight gains and reduced shank lengths on days 8, 12, 16, and 21. The proximal tibial growth plate was narrowed. The mineralized hypertrophy zone was decreased in length and contained multiple non-mineralized bands on days 8, 12, 16, and 21. Metaphyseal trabeculae were reduced in amount on days 16 and 21. Parathyroid glands were hyperplastic on days 16 and 21. The bone and parathyroid gland lesions indicated that mineral homeostasis was being maintained at the expense of the skeleton during the enteric disease. A specific etiology for the enteric disease was not determined. Cryptosporidium, rotavirus, paramyxovirus, and Salmonella were identified in the exposed poults, and paramyxovirus and Salmonella were identified in the controls.

Receptor-mediated cell attachment and detachment kinetics. II. Experimental model studies with the radial-flow detachment assay

Quantitative information regarding the kinetics of receptor-mediated cell adhesion to a ligand-coated surface are crucial for understanding the role of certain key parameters in many physiological and biotechnology-related processes. Here, we use the probabilistic attachment and detachment models developed in the preceding paper to interpret transient data from well-defined experiments. These data are obtained with a simple model cell system that consists of receptor-coated latex beads (prototype cells) and a Radial-Flow Detachment Assay (RFDA) using a ligand-coated glass disc. The receptors and ligands used in this work are complementary antibodies. The beads enable us to examine transient behavior with particles that possess fairly uniform properties that can be varied systematically, and the RFDA is designed for direct observation of adhesion to the ligand-coated glass surface over a range of shear stresses. Our experiments focus on the effects of surface shear stress, receptor density, and ligand density. These data provide a crucial test of the probabilistic framework. We show that these data can be explained with the probabilistic analyses, whereas they cannot be readily interpreted on the basis of a deterministic analysis. In addition, we examine transient data on cell adhesion reported from other assays, demonstrating the consistency of these data with the predictions of the probabilistic models.

Receptor-mediated cell attachment and detachment kinetics. I. Probabilistic model and analysis

The kinetics of receptor-mediated cell adhesion to a ligand-coated surface play a key role in many physiological and biotechnology-related processes. We present a probabilistic model of receptor-ligand bond formation between a cell and surface to describe the probability of adhesion in a fluid shear field. Our model extends the deterministic model of Hammer and Lauffenburger (Hammer, D.A., and D.A. Lauffenburger. 1987. Biophys. J. 52:475-487) to a probabilistic framework, in which we calculate the probability that a certain number of bonds between a cell and surface exists at any given time. The probabilistic framework is used to account for deviations from ideal, deterministic behavior, inherent in chemical reactions involving relatively small numbers of reacting molecules. Two situations are investigated: first, cell attachment in the absence of fluid stress; and, second, cell detachment in the presence of fluid stress. In the attachment case, we examine the expected variance in bond formation as a function of attachment time; this also provides an initial condition for the detachment case. Focusing then on detachment, we predict transient behavior as a function of key system parameters, such as the distractive fluid force, the receptor-ligand bond affinity and rate constants, and the receptor and ligand densities. We compare the predictions of the probabilistic model with those of a deterministic model, and show how a deterministic approach can yield some inaccurate results; e.g., it cannot account for temporally continuous cell attach mentor detachment, it can underestimate the time needed for cell attachment, it can overestimate the time required for cell detachment for a given level of force, and it can overestimate the force necessary for cell detachment.

Receptor-mediated adhesion phenomena. Model studies with the Radical-Flow Detachment Assay

Receptor-mediated cell adhesion phenomena play a vital role in many physiological and biotechnology-related processes. To investigate the physical and chemical factors that influence the cell/surface interaction, we have used a radial flow device, a so-called Radial-Flow Detachment Assay (RFDA). The RFDA allows us to make direct observations of the detachment process under specified experimental conditions. In results reported here, we have studied the detachment of receptor-coated latex beads (prototype cells) from ligand-coated glass surfaces. The receptors and ligands used in this work are complementary antibodies. The beads enable us to examine several aspects of the adhesion process with particles having uniform properties that can be varied systematically. Advantages of the RFDA are many, especially direct observation of cell detachment over a range of shear stresses with quantitative measurement of the adhesive force. We focus our studies on the effects of ligand and receptor densities, along with the influence of pH and ionic strength of the medium. These data are analyzed with a mathematical model based on the theoretical framework of Bell, G. I. (1978. Science [Wash. DC]. 200:618-627) and Hammer, D. A. and D. A. Lauffenburger (1987. Biophys. J. 52:475-487). We demonstrate experimental validation of a theoretical expression for the critical shear stress for particle detachment, and show that it is consistent with reasonable estimates for the receptor-ligand bond affinity.

Permeation of inert gases through human skin: modeling the effect of skin blood flow

We present an analytic method for determining the effects of skin perfusion--vasculature and flow rates--on the flux of inert gases through human skin. We systematically specify the underlying blood flow and examine the resulting fluxes of several gases, allowing for the appropriate tissue resistances. For physiological flows, the stratum corneum has an effect equivalent to a series resistance. Helium flux at low total flow depends primarily on subdermal perfusion, but at higher flow, middermal and subpapillary effects become important. The fluxes of less permeable gases, such as argon and xenon, depend on middermal and subpapillary flow at lower total flows. From any single measurement of gas flux, it is difficult to establish an unambiguous value for the underlying blood flow, but the simultaneous measurement of different gases narrows the range of plausible conditions.

Association of amoebae and actinomyces in an intrauterine contraceptive device user

A patient wearing an intrauterine contraceptive device (IUD) was diagnosed as being colonized by Actinomyces and amoebae by examination of a routine Papanicolaou smear. The patient received vaginal treatment with metronidazole, which temporarily eliminated the protozoa; however, it was necessary to remove the IUD to definitively eradicate the microorganisms. Follow-up Papanicolaou smears taken after removal of the IUD have been normal and free of both microorganisms.

The role of seed depth, litter, and fire in the seedling establishment of amphicarpic peanutgrass (Amphicarpum purshii)

Amphicarpum purshii is an annual grass which mostly grows in disturbed areas of the New Jersey Pine Barrens, USA. It is amphicarpic, producing spikelets (and seeds) both above and below the soil surface. Previous research has shown that subterranean seed production ensures reproduction in the event of a major disturbance such as fire and results in rapid post-burn colonization of these sandy habitats. The effects of fire, litter, and seed depth were further examined by planting subterranean seeds at four depths in 16 litter-covered flats buried at ground level and comparing plants arising from burned flats with those in undisturbed litter-covered flats. At 0 and 1 cm depth, rates of seedling emergence were lowest in burned flats. Surface-sown seeds produced seedlings more likely to desiccate. Sowing depth had a greater influence on most measured characters than burning treatments. The mean depth of subterranean seed placement by Amphicarpum is 3.5 cm and this coincides with the seed depth from which plants showed the greatest height growth, shoot biomass, and reproductive output. In a second experiment, subterranean seeds on the bare soil surface in clay pots were more likely to lose viability and less likely to germinate than seeds protected by litter or burial in soil. In addition to providing protection from fire, placement of seeds below ground in the sandy habitat of peanutgrass provides conditions more suitable for seed survival and subsequent seedling establishment.

Gas flux through human skin: effect of temperature, stripping, and inspired tension

The flux of He and O2 through intact adult human skin was measured at various inspired concentrations and skin temperatures. The skin surface was then stripped with cellophane tape to alter the diffusional conductance of the stratum corneum. He flux for stripped skin was used to estimate skin perfusion as a function of local temperature, and diffusional conductance for O2 was estimated from O2 flux and perfusion. The flux of He or O2 at constant skin temperature can be related to inspired concentration by a simple linear model. Increasing surface temperature in the range 33-43 degrees C produced a much larger increase in O2 flux than in He flux for intact skin. Skin stripping greatly increased skin O2 flux. Estimated skin conductance for O2 showed a more marked temperature dependence than estimated skin perfusion. The results suggest that raising skin temperature in the range 38-43 degrees C has only a modest effect on skin perfusion and that stratum corneum conductance may have a major role in the large increase of O2 flux with temperature.

Kinetic constants determined from membrane transport measurements: carbonic anhydrase activity at high concentrations

Facilitated diffusion rates can be used to determine kinetic constants for rapid reactions occurring within membranes and thin fluid layers. We have applied this technique to the study of the reversible CO(2) hydration reactions catalyzed by carbonic anhydrase (EC 4.2.1.1; carbonate hydro-lyase). The experimental method entails the diffusion of tracer (14)CO(2) through Millipore filter membranes impregnated with aqueous bicarbonate solutions containing various concentrations of dissolved enzyme. A mathematical model of the simultaneous diffusion/reaction transport process is analyzed to predict the effective diffusion rate in terms of the relevant kinetic parameters. The solution to the mathematical model can be transformed to yield straight-line relations analogous to Lineweaver-Burk plots. The pseudo-first-order enzymatic rate constant for the hydration reaction can be determined from the slope or intercept of a plot of this straight-line relationship. Rate constants were accurately measured at high enzyme concentrations for reactions having half-times under a millisecond. The rate constants agree well with other reported kinetic constants for carbonic anhydrase, and the known pH-activity dependence and bicarbonate inhibition are quantitatively demonstrated. The specific activity is constant up to 4.0 mg/ml, which is believed to be the highest concentration at which the activity has been measured. The membrane transport technique has general applicability for other rapid reaction systems.

Restricted transport in small pores. A model for steric exclusion and hindered particle motion

The basic hydrodynamic equations governing transport in submicron pores are reexamined. Conditions necessary for a simplified, one-dimensional treatment of the diffusion/convection process are established. Steric restrictions and Brownian motion are incorporated directly into the resulting model. Currently available fluid mechanical results are used to evaluate an upper limit on hindered diffusion; this limit is valid for small particle-to-pore ratios. Extensions of the analysis are shown to depend on numerical solutions of the related hydrodynamic problem, that of asymmetrical particle motion in a bounded fluid.

Bubble formation in physical and biological systems: a manifestation of counterdiffusion in composite media

The counterdiffusion of gases across a composite layer can lead to supersaturation and development of bubbles within the layer. A physicochemical model has been derived to predict the extent of such supersaturation; experiments with inert liquid layers confirm predictions. These findings explain the evolution of cutaneous lesions observed in man during simulated deep-sea dives and the cutaneous lesions and intravascular bubbles experimentally induced in pigs by exchanging certain inert gases across the skin. The phenomena associated with counterdiffusion have widespread physical and biological implications.

Model pores of molecular dimension. The preparation and characterization of track-etched membranes

Extremely uniform pores of near molecular dimension can be formed by the irradiation-etching technique first demonstrated by Price and Walker. The technique has now been developed to the stage where it can be used to fabricate model membranes for examining the various steric, hydrodynamic, and electrodynamic phenomena encountered in transport through molecular-size pores. Methods for preparing and characterizing membranes with pores as small as 25 A (radius) are described in this paper. Results on pore size determination via Knudsen gas flow and electrolyte conduction are compared. Pore wall modification by monolayer deposition is also discussed.

Calibrated membranes with coated pore walls

Extremely uniform small-radius pores, formed in thin mica membranes, have been coated with monoand multimolecular layers of fatty acids. Stearate monolayers orient themselves on the pore walls in layers 25 to 28 angstroms thick. The resulting membranes, with radii of the order 100 angstroms or less, may have applications in simulating certain features of biological membranes and in fabricating highly selective membranes for differential dialysis or ultrafiltration.

Composite Membranes: The Permeation of Gases through Deposited Monolayers

We have measured permeabilities of deposited monolayers of stearic acid varying in thickness from 8 to 48 deposited layers. These results are compared with permeabilities of polymeric films and insoluble monolayers. The technique may have applicability in the fabrication of synthetic membranes.