Epilepsy surgery as a treatment option for select patients with PCDH19-related epilepsy

PCDH19 is a common epilepsy gene causing medication resistant epilepsy with fever-related seizures. Traditionally, patients with PCDH19-related epilepsy have not been considered surgical candidates. This retrospective review evaluated three patients with pathogenic variants in PCDH19 who presented with seizures in childhood, had one seizure semiology, became medication resistant, and had concordant imaging, seizure semiology and electrographic findings. All three patients ultimately underwent temporal lobectomy, resulting in seizure freedom. These findings suggest epilepsy surgery can be an effective treatment option for select patients with PCDH19-related epilepsy and a single seizure semiology.

Association of Body Mass Index in Midlife With Morbidity Burden in Older Adulthood and Longevity

IMPORTANCE

Abundant evidence links obesity with adverse health consequences. However, controversies persist regarding whether overweight status compared with normal body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) is associated with longer survival and whether this occurs at the expense of greater long-term morbidity and health care expenditures.

OBJECTIVE

To examine the association of BMI in midlife with morbidity burden, longevity, and health care expenditures in adults 65 years and older.

DESIGN, SETTING, AND PARTICIPANTS

Prospective cohort study at the Chicago Heart Association Detection Project in Industry, with baseline in-person examination between November 1967 and January 1973 linked with Medicare follow-up between January 1985 and December 2015. Participants included 29 621 adults who were at least age 65 years in follow-up and enrolled in Medicare. Data were analyzed from January 2020 to December 2021.

EXPOSURES

Standard BMI categories.

MAIN OUTCOMES AND MEASURES

(1) Morbidity burden at 65 years and older assessed with the Gagne combined comorbidity score (ranging from -2 to 26, with higher score associated with higher mortality), which is a well-validated index based on International Classification of Diseases, Ninth Revision codes for use in administrative data sets; (2) longevity (age at death); and (3) health care costs based on Medicare linkage in older adulthood (aged ≥65 years).

RESULTS

Among 29 621 participants, mean (SD) age was 40 (12) years, 57.1% were men, and 9.1% were Black; 46.0% had normal BMI, 39.6% were overweight, and 11.9% had classes I and II obesity at baseline. Higher cumulative morbidity burden in older adulthood was observed among those who were overweight (7.22 morbidity-years) and those with classes I and II obesity (9.80) compared with those with a normal BMI (6.10) in midlife (P < .001). Mean age at death was similar between those who were overweight (82.1 years [95% CI, 81.9-82.2 years]) and those who had normal BMI (82.3 years [95% CI, 82.1-82.5 years]) but shorter in those who with classes I and II obesity (80.8 years [95% CI, 80.5-81.1 years]). The proportion (SE) of life-years lived in older adulthood with Gagne score of at least 1 was 0.38% (0.00%) in those with a normal BMI, 0.41% (0.00%) in those with overweight, and 0.43% (0.01%) in those with classes I and II obesity. Cumulative median per-person health care costs in older adulthood were significantly higher among overweight participants ($12 390 [95% CI, $10 427 to $14 354]) and those with classes I and II obesity ($23 396 [95% CI, $18 474 to $28 319]) participants compared with those with a normal BMI (P < .001).

CONCLUSIONS AND RELEVANCE

In this cohort study, overweight in midlife, compared with normal BMI, was associated with higher cumulative burden of morbidity and greater proportion of life lived with morbidity in the context of similar longevity. These findings translated to higher total health care expenditures in older adulthood for those who were overweight in midlife.

Yoga therapy as a supportive care strategy for family caregivers of patients with primary brain tumor: Results of 3-arm pilot randomized controlled trial

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Background: Seeking to address the well-documented burden of caring for a loved one with a high-grade glioma, this pilot RCT compared the feasibility and preliminary efficacy of a dyadic versus individual yoga intervention as a supportive care strategy for family caregivers. Methods: Caregivers completed self-reported assessments of QOL (SF-36) and caregiver burden (CRA) at baseline. Then, patients and caregivers were randomized to either a dyadic yoga (DY) arm in which caregivers attended the sessions together with the patient, a caregiver yoga (CY) arm in which the caregiver attended all sessions individually or a usual care (UC) arm. Both yoga programs were delivered over 15 sessions either in-person or via videoconference (Zoom) concurrently while patients were undergoing standard radiotherapy. All arms were re-assessed at the end of treatment and then again 3-months later. Results: We consented 76 patient-caregiver dyads (59%) and randomized 23 dyads to the DY, 22 to the CY, and 22 to the UC arm. Attendance in the DY was higher than in the CY group (session means, DY = 12.23, CY = 9.00; P =.06, d =.57). Caregivers (80% female; 78% non-Hispanic White; mean age = 53 yrs) reported significantly more overall subjective benefit in the CY compared to the DY arm (means, CY = 1.39, DY = 1.81, P <.05, d = 1.45). Caregivers slightly favored the in-person delivery over the Zoom-based sessions (means, in person: 1.48; Zoom: 1.82, P =.10; d =.77). A clinically significant, medium effect size was found for improved QOL in favor of the CY over the DY group (means, CY = 49.45, DY = 44.45; F = 3.58, P =.07; d =.67). Caregivers in the CY group also reported less caregiving-related health declines compared to the DY group (means, CY = 2.18; DY = 2.48; F = 4.23, P <.05; d =.42). Caregivers in the CY group reported less caregiving-related financial burden than the UC group (means: CY = 2.79; UC = 3.21; F = 3.32, P =.08; d =.35). Conclusions: Despite lower attendance, caregivers in the CY arm reported greater subjective overall benefit, experienced better mental QOL and less caregiver burden compared with those in the DY and UC comparison arms. It appears that individual rather than dyadic delivery may be a superior supportive care approach for this vulnerable caregiver population. An adequately powered, larger efficacy trial of this intervention strategy is warranted. Clinical trial information: NCT02481349.

A research protocol for a pilot, randomized controlled trial designed to examine the feasibility of a dyadic versus individual yoga program for family caregivers of glioma patients undergoing radiotherapy

BACKGROUND

Although the diagnosis and treatment of a primary brain tumor present unique challenges to patients and their family caregivers, evidence-based supportive care interventions are generally lacking. The primary aim of this research protocol is to determine the feasibility of implementing a dyadic yoga (DY) versus a caregiver yoga (CY) intervention or a wait-list control (WLC) group using a randomized controlled trial design.

METHODS

Seventy-five glioma patients undergoing radiotherapy and their family caregivers are randomized to the DY, CY, or a WLC group. Patient-caregiver dyads in the DY group and caregivers in the CY group receive 15 sessions (45 min each) over the course of patients' standard radiotherapy (6 weeks). Patients and caregivers in all groups complete baseline assessments of symptoms, quality of life (QOL), and health utilization outcomes prior to randomization. Follow-up assessments are performed 6 weeks and then again 3 months later. The primary outcome is feasibility (i.e., ≥ 50% of eligible dyads consent, ≥ 70% of enrolled dyads complete all assessments, and ≥ 50% of all practice sessions are attended). We will also perform primarily descriptive analyses of the self-reported outcomes (e.g., fatigue, overall QOL) and explore potential intervention moderators (e.g., performance status) to inform a larger future trial.

CONCLUSION

This trial will provide important information regarding the feasibility of a dyadic versus a caregiver yoga intervention regarding symptom, QOL, and health utilization outcomes in glioma patients and their caregivers.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02481349.

Cancer-Related Risk Perceptions and Beliefs in Texas: Findings from a 2018 Population-Level Survey

BACKGROUND

Cancer beliefs and perceptions of cancer risk affect the cancer continuum. Identifying underlying factors associated with these beliefs and perceptions in Texas can help inform and target prevention efforts.

METHODS

We developed a cancer-focused questionnaire and administered it online to a nonprobability sample of the Texas population. Weighted multivariable logistic regression analysis identified key factors associated with perceptions and beliefs about cancer.

RESULTS

The study population comprised 2,034 respondents (median age, 44.4 years) of diverse ethnicity: 45.5% were non-Hispanic white, 10.6% non-Hispanic black, and 35.7% Hispanic. Self-reported depression was significantly associated with cancer risk perceptions and cancer beliefs. Those indicating frequent and infrequent depression versus no depression were more likely to believe that: (i) compared to other people their age, they were more likely to get cancer in their lifetime [OR, 2.92; 95% confidence interval (CI), 1.95-4.39 and OR, 1.79; 95% CI, 1.17-2.74, respectively]; and (ii) when they think about cancer, they automatically think about death (OR, 2.05; 95% CI, 1.56-2.69 and OR, 1.46; 95% CI, 1.11-1.92, respectively). Frequent depression versus no depression was also associated with agreement that (i) it seems like everything causes cancer (OR, 1.67; 95% CI, 1.26-2.22) and (ii) there is not much one can do to lower one's chance of getting cancer (OR, 1.44; 95% CI, 1.09-1.89). Other predictors for perceived cancer risk and/or cancer beliefs were sex, age, ethnicity/race, being born in the United States, marital status, income, body mass index, and smoking.

CONCLUSIONS

Depression and other predictors are associated with cancer risk perceptions and beliefs in Texas.

IMPACT

Increased attention to reducing depression may improve cancer risk perceptions and beliefs.

Trends in the Incidence, Prevalence, and Survival Outcomes in Patients With Neuroendocrine Tumors in the United States

Importance

The incidence and prevalence of neuroendocrine tumors (NETs) are thought to be rising, but updated epidemiologic data are lacking.

Objective

To explore the evolving epidemiology and investigate the effect of therapeutic advances on survival of patients with NETs.

Design, Setting, and Participants

A retrospective, population-based study using nationally representative data from the Surveillance, Epidemiology, and End Results (SEER) program was conducted to evaluate 64 971 patients with NETs from 1973 to 2012. Associated population data were used to determine annual age-adjusted incidence, limited-duration prevalence, and 5-year overall survival (OS) rates. Trends in survival from 2000 to 2012 were evaluated for the entire cohort as well as specific subgroups, including distant-stage gastrointestinal NETs and pancreatic NETs. Analyses were conducted between December 2015, and February 2017.

Main Outcomes and Measures

Neuroendocrine tumor incidence, prevalence, and OS rates.

Results

Of the 64 971 cases of NETs, 34 233 (52.7%) were women. The age-adjusted incidence rate increased 6.4-fold from 1973 (1.09 per 100 000) to 2012 (6.98 per 100 000). This increase occurred across all sites, stages, and grades. In the SEER 18 registry grouping (2000-2012), the highest incidence rates were 1.49 per 100 000 in the lung, 3.56 per 100 000 in gastroenteropancreatic sites, and 0.84 per 100 000 in NETs with an unknown primary site. The estimated 20-year limited-duration prevalence of NETs in the United States on January 1, 2014, was 171 321. On multivariable analyses, the median 5-year OS rate varied significantly by stage, grade, age at diagnosis, primary site, and time period of diagnosis. The OS rate for all NETs improved from the 2000-2004 period to the 2009-2012 period (hazard ratio [HR], 0.79; 95% CI, 0.73-0.85). Even larger increases in OS between these periods were noted in distant-stage gastrointestinal NETs (HR, 0.71; 95% CI, 0.62-0.81) and distant-stage pancreatic NETs (HR, 0.56; 95% CI, 0.44-0.70).

Conclusions and Relevance

The incidence and prevalence of NETs are steadily rising, possibly owing to detection of early-stage disease and stage migration. Survival for all NETs has improved over time, especially for distant-stage gastrointestinal NETs and pancreatic NETs in particular, reflecting improvement in therapies. These data will help to prioritize future research directions.

Prevalence of co-morbidities in elderly patients with distant stage neuroendocrine tumors

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Background: The median age of diagnosis of neuroendocrine tumors (NETs), an indolent tumor characterized by hormone production (carcinoid syndrome, CS) when metastatic is 63 years. Patients (pts) in this age group have multiple co-morbidities. However, their prevalence among elderly pts with metastatic NET is unknown. Methods: The Surveillance, Epidemiology and End Results (SEER)-Medicare database was used to identify 2,388 elderly patients with distant stage NET (Age: < 70: 631; 70-79: 1200; > 80: 557; Race: white: 83.4%, black: 8.6%) diagnosed between 1/03 and 12/11 identified by ICD-O-3 codes with continuous Medicare Parts A and B enrollment during the one year after NET diagnosis. We examined the prevalence of common co-morbidities in the elderly population: dementia, heart conditions including ischemic heart disease (IHD), hypertension (HTN) & congestive heart failure, chronic obstructive pulmonary disease, chronic kidney disease, hyperlipidemia, diabetes, arthritis, and two additional relevant comorbidities: osteoporosis (OP) and non-rheumatic tricuspid valve (TV) disorders. Pts were considered to have a condition if they had ≥ 1 inpt or ≥ 2 outpt visits indicative of the condition. We compared the prevalence in the NET group with that in a propensity score matched non-cancer group using chi-square test. Within the NET group, we also examined the association between pt characteristics and the presence of the conditions using a logistic regression model. Results: Compared to the matched non-cancer control group, NET pts were significantly (P < 0.01) more likely to have HTN (74% vs. 66%), OP (14% vs. 11%) & TV disorders (1.72% vs. 0.98%) and less likely to have dementia (7.3% vs 17.4%), IHD (23.2% vs 29%) and diabetes (30.3% vs 33.5%). CS was noted in 25.7% of the NET group and logistic regression showed that these pts with were significantly more likely to have TV disorders (AOR = 2.52, 95% CI: 1.24-5.14) and osteoporosis (AOR: 1.34, 95% CI: 1.01-1.81). Conclusions: This population-based study showed that elderly NET pts have significantly different prevalence of co-morbidities compared to non-cancer controls. The impact of these conditions on survival and therapeutic decisions is being evaluated.

Influence of Surveillance PET/CT on Detection of Early Recurrence After Definitive Radiation in Stage III Non-small-cell Lung Cancer

BACKGROUND

There are few data to support the use of varying imaging modalities in evaluating recurrence in non-small-cell lung cancer (NSCLC). We compared the efficacy of surveillance positron emission tomography (PET)/computed tomography (CT) versus CT scans of the chest in detecting recurrences after definitive radiation for NSCLC.

MATERIALS AND METHODS

We retrospectively analyzed 200 patients treated between 2000 and 2011 who met the inclusion criteria of stage III NSCLC, completion of definitive radiation treatment, and absence of recurrence within the initial 6 months. These patients were then grouped on the basis of the use of PET/CT imaging during postradiation surveillance. Patients who received ≥ 1 PET/CT scans within 6 months of the end of radiation treatment were placed in the PET group whereas all others were placed in the CT group. We compared survival times from the end of treatment to the date of death or last follow-up using log rank tests. Multivariate analysis was conducted to identify factors associated with decreased survival.

RESULTS

In the entire cohort, median event-free survival (EFS) was 26.7 months, and median overall survival (OS) was 41.2 months. The CT group had a median EFS of 21.4 months versus 29.4 months for the PET group (P = .59). There was no difference in OS between the CT and PET groups (median OS of 41.2 and 41.3 months, respectively; P = .59). There was also no difference in local recurrence-free survival or distant metastases-free survival between the CT-only and PET/CT groups (P = .92 and P = .30, respectively). Similarly, in multivariate analysis, stratification into the PET group was not associated with improved EFS (hazard ratio [HR], 0.90; 95% confidence interval [CI], 0.61-1.34; P = .60) or OS (HR, 1.2; 95% CI, 0.83-1.7; P = .34).

CONCLUSIONS

In stage III NSCLC patients treated with definitive radiation and without early recurrence, PET/CT scan surveillance did not result in decreased time to detection of locoregional or distant recurrence or improved survival.

Design architectures for optically multiplexed imaging

Optically multiplexed imaging is the process by which multiple images are overlaid on a single image surface. Uniquely encoding the discrete images allows scene reconstruction from multiplexed images via post processing. We describe a class of optical systems that can achieve high density image multiplexing through a novel division of aperture technique. Fundamental design considerations and performance attributes for this sensor architecture are discussed. A number of spatial and temporal encoding methods are presented including point spread function engineering, amplitude modulation, and image shifting. Results from a prototype five-channel sensor are presented using three different encoding methods in sparse-scene star tracking demonstration. A six-channel optically multiplexed prototype sensor is used to reconstruct imagery from information rich dense scenes through dynamic image shifting.

Transient aphasias after left hemisphere resective surgery

OBJECT

Transient aphasias are often observed in the first few days after a patient has undergone resection in the language-dominant hemisphere. The aims of this prospective study were to characterize the incidence and nature of these aphasias and to determine whether there are relationships between location of the surgical site and deficits in specific language domains.

METHODS

One hundred ten patients undergoing resection to the language-dominant hemisphere participated in the study. Language was evaluated prior to surgery and 2-3 days and 1 month postsurgery using the Western Aphasia Battery and the Boston Naming Test. Voxel-based lesion-symptom mapping was used to identify relationships between the surgical site location assessed on MRI and deficits in fluency, information content, comprehension, repetition, and naming.

RESULTS

Seventy-one percent of patients were classified as aphasic based on the Western Aphasia Battery 2-3 days postsurgery, with deficits observed in each of the language domains examined. Fluency deficits were associated with resection of the precentral gyrus and adjacent inferior frontal cortex. Reduced information content of spoken output was associated with resection of the ventral precentral gyrus and posterior inferior frontal gyrus (pars opercularis). Repetition deficits were associated with resection of the posterior superior temporal gyrus. Naming deficits were associated with resection of the ventral temporal cortex, with midtemporal and posterior temporal damage more predictive of naming deficits than anterior temporal damage. By 1 month postsurgery, nearly all language deficits were resolved, and no language measure except for naming differed significantly from its presurgical level.

CONCLUSIONS

These findings show that transient aphasias are very common after left hemisphere resective surgery and that the precise nature of the aphasia depends on the specific location of the surgical site. The patient cohort in this study provides a unique window into the neural basis of language because resections are discrete, their locations are not limited by vascular distribution or patterns of neurodegeneration, and language can be studied prior to substantial reorganization.

Seizures and epileptiform activity in the early stages of Alzheimer disease

IMPORTANCE

Epileptic activity associated with Alzheimer disease (AD) deserves increased attention because it has a harmful impact on these patients, can easily go unrecognized and untreated, and may reflect pathogenic processes that also contribute to other aspects of the illness. We report key features of AD-related seizures and epileptiform activity that are instructive for clinical practice and highlight similarities between AD and transgenic animal models of the disease.

OBJECTIVE

To describe common clinical characteristics and treatment outcomes of patients with amnestic mild cognitive impairment (aMCI) or early AD who also have epilepsy or subclinical epileptiform activity.

DESIGN

Retrospective observational study from 2007 to 2012. SETTING Memory and Aging Center, University of California, San Francisco.

PATIENTS

We studied 54 patients with a diagnosis of aMCI plus epilepsy (n = 12), AD plus epilepsy (n = 35), and AD plus subclinical epileptiform activity (n = 7).

MAIN OUTCOMES AND MEASURES

Clinical and demographic data, electroencephalogram (EEG) readings, and treatment responses to antiepileptic medications.

RESULTS

Patients with aMCI who had epilepsy presented with symptoms of cognitive decline 6.8 years earlier than patients with aMCI who did not have epilepsy (64.3 vs 71.1 years; P = .02). Patients with AD who had epilepsy presented with cognitive decline 5.5 years earlier than patients with AD who did not have epilepsy (64.8 vs 70.3 years; P = .001). Patients with AD who had subclinical epileptiform activity also had an early onset of cognitive decline (58.9 years). The timing of seizure onset in patients with aMCI and AD was nonuniform (P < .001), clustering near the onset of cognitive decline. Epilepsies were most often complex partial seizures (47%) and more than half were nonconvulsive (55%). Serial or extended EEG monitoring appeared to be more effective than routine EEG at detecting interictal and subclinical epileptiform activity. Epileptic foci were predominantly unilateral and temporal. Of the most commonly prescribed antiepileptics, treatment outcomes appeared to be better for lamotrigine and levetiracetam than for phenytoin.

CONCLUSIONS AND RELEVANCE

Common clinical features of patients with aMCI- or AD-associated epilepsy at our center included early age at onset of cognitive decline, early incidence of seizures in the disease course, unilateral temporal epileptic foci detected by serial/extended EEG, transient cognitive dysfunction, and good seizure control and tolerability with lamotrigine and levetiracetam. Careful identification and treatment of epilepsy in such patients may improve their clinical course.

Comparison of seizure control outcomes and the safety of vagus nerve, thalamic deep brain, and responsive neurostimulation: evidence from randomized controlled trials

Epilepsy is a devastating disease, often refractory to medication and not amenable to resective surgery. For patients whose seizures continue despite the best medical and surgical therapy, 3 stimulation-based therapies have demonstrated positive results in prospective randomized trials: vagus nerve stimulation, deep brain stimulation of the thalamic anterior nucleus, and responsive neurostimulation. All 3 neuromodulatory therapies offer significant reductions in seizure frequency for patients with partial epilepsy. A direct comparison of trial results, however, reveals important differences among outcomes and surgical risk between devices. The authors review published results from these pivotal trials and highlight important differences between the trials and devices and their application in clinical use.

Abstract P3-14-06: Pharmacokinetic (PK) Interaction Potential of Trastuzumab-DM1 (T-DM1) and Pertuzumab (P) in Pts with HER2-Positive, Locally Advanced or MBC: Results from a Phase 1b/2 Study

Introduction

T-DM1 is an antibody-drug conjugate (ADC) composed of the cytotoxic DM1 conjugated to trastuzumab and retaining its antitumor properties. P is a HER2-directed monoclonal antibody that inhibits HER2 dimerization and subsequent signaling. The combination of T-DM1 and P has demonstrated synergistic antitumor activity in HER2-positive xenograft models. T-DM1 and P are expected to undergo proteolytic degradation with no significant involvement of cytochrome P450 isoenzymes. In contrast, DM1 is metabolized mainly by CYP3A4 and to a limited extent by CYP3A5. Therefore, a key component in evaluating this combination clinically is determining whether a PK-based drug interaction potential exists when these drugs are administered together. Assessment of PK-based therapeutic protein-ADC interaction potential is novel, as antibodies have typically been combined with chemotherapy in clinical studies. Methods

This 3+3 dose escalation, open-label, phase 1b/2 study evaluated the safety, tolerability, PK, and efficacy of T-DM1 (3.0 mg/kg q3w or 3.6 mg/kg q3w [established phase 2 dose]) in combination with P (840 mg loading dose; 420 mg q3w thereafter) in pts with HER2-positive locally advanced or MBC. Because of the half-life of both agents, staggered dosing was not a practical approach to assess the PK interaction. Thus, both drugs were administered sequentially on Day 1 of each cycle. All pts receiving study treatment were evaluated for serum concentrations of T-DM1, total trastuzumab (conjugated and unconjugated to DM1), and plasma concentrations of DM1, at pre-specified time points. To avoid the interference of P with the quantification of total trastuzumab, a new assay that allows capturing trastuzumab in the presence of P was developed and validated. PK of T-DM1 and related analytes were compared with historical single agent data by population and/or noncompartmental analyses. Whether combination with P was a significant covariate of T-DM1 clearance and central volume of distribution (V1) was tested. The confidence intervals (CIs) of the ratios of clearance and V1 of combination to monotherapy were estimated. A CI containing 1 is indicative of comparable parameters. Results

PK data were available for 63 pts. Combination with P was not a significant covariate of T-DM1 clearance and V1 (P&gt;0.05 by the log likelihood ratio test). The combination to monotherapy ratios for clearance and V1 had a 95% CI of [0.90-1.04] and [0.95-1.06], respectively, indicating comparable clearance and V1 of combination and monotherapy. The average post-hoc Bayesian estimates of T-DM1 clearance and V1 in the presence of P were 0.69±0.14 L/day and 3.3±0.41 L, which were comparable with historical measures of 0.73±0.19 L/day and 3.4±0.57 L with monotherapy. The average maximal concentration of total trastuzumab in cycle 1 was 101±29 μg/ml in the 3.0 mg/kg TDM1 dose (n=3) and 98±32 μg/ml for the 3.6 mg/kg dose (n=60). The maximum DM1 level was &lt;17 ng/mL at both T-DM1 doses. The PK of total trastuzumab and DM1 were also comparable with monotherapy (data not shown).

Conclusions

This assessment suggests that P does not alter the PK of T-DM1 when these drugs are administered together.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-14-06.

Nonlinear spectra of ZnO: reverse saturable, two- and three-photon absorption

We present a broadband (460 - 980 nm) analysis of the nonlinear absorption processes in bulk ZnO, a large-bandgap material with potential blue-to-UV photonic device applications. Using an optical parametric amplifier we generated tunable 1-kHz repetition rate laser pulses and employed the Z-scan technique to investigate the nonlinear absorption spectrum of ZnO. For excitation wavelengths below 500 nm, we observed reverse saturable absorption due to one-photon excitation of the sample, agreeing with rate-equation modeling. Two- and three-photon absorption were observed from 540 to 980 nm. We also determined the spectral regions exhibiting mixture of nonlinear absorption mechanisms, which were confirmed by photoluminescence measurements.

Sociodemographic disparities in epilepsy care: Results from the Houston/New York City health care use and outcomes study

PURPOSE

The purpose of this study was to identify sociodemographic disparities in health care use among epilepsy patients receiving care at different sites and the extent to which the disparities persisted after adjusting for patient characteristics and site of care.

METHODS

Three months of health care use data were obtained from baseline interviews of approximately 560 patients at four sites. One-half of the patients were from a Houston site and two NYC sites that serve predominantly low-income, minority, publicly insured, or uninsured patients. The other half were at the remaining site in Houston that serves a more balanced racial/ethnic and higher sociodemographic population. Differences in general and specialist visits, hospital emergency room (ER) care, and hospitalizations were associated with race/ethnicity, income, and coverage. Logistic regression was used to assess the extent to which the differences persisted when adjusting for individual patient characteristics and site of care.

RESULTS

Compared to whites, blacks and Hispanics had higher rates of generalist visits [odds ratio (OR) = 5.3 and 4.9, p < 0.05), ER care (OR = 3.1 and 2.9, p < 0.05) and hospitalizations (OR = 5.4 and 6.2, p < 0.05), and lower rates of specialist visits (OR = 0.3 and 0.4, p < 0.05). A similar pattern was found related to patient income and coverage. The magnitude and significance of the disparities persisted when adjusting for individual characteristics but decreased substantially or were eliminated when site of care was added to the model.

DISCUSSION

There are sociodemographic disparities in health care for people with epilepsy that are largely explained by differences in where patients receive care.

Femtosecond laser waveguide micromachining of PMMA films with azoaromatic chromophores

We report on the femtosecond-laser micromachining of poly(methyl methacrylate) (PMMA) films doped with nonlinear azoaromatic chromophores: Disperse Red 1, Disperse Red 13 and Disperse Orange 3. We study the conditions for controlling chromophore degradation during the micromachining of PMMA doped with each chromophore. Furthermore, we successfully used fs-micromachining to fabricate optical waveguides within a bulk sample of PMMA doped with these azochromophores.

Plasma pharmacokinetics and cerebrospinal fluid concentrations of erlotinib in high-grade gliomas: A novel, phase I, dose escalation study

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Background: Erlotinib (ERL) is an inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase. EGFR is overexpressed in glioblastoma multiforme (GBM). The primary objectives of this study were to determine the maximum tolerated dose (MTD), dose limiting toxicity (DLT) and to evaluate plasma and cerebrospinal fluid (CSF) ERL concentrations using a novel every 72 hour ERL dosing schedule. Methods: Patients = 18 years of age with GBM or high grade glioma with evidence of disease progression following first line therapy (surgery/XRT/chemotherapy) and Karnofsky performance status = 60 % were included. Patients were stratified based on use of enzyme-inducing antiepileptic drugs (EIAED). Patients not on EIAED were initiated on ERL 450 mg PO every 72h, while those on EIAED were initiated on 900 mg PO every 72 h. Results: Six patients have been enrolled and assessed for safety, 5 for plasma PK and 3 for CSF concentrations. For ERL, the area under the plasma concentration versus time curve (AUC) was greater and the half-life longer in patients not receiving EIAED. However, the AUC of OSI-420, the major metabolite of ERL, was lower in patients not receiving EIAED. The OSI-420 AUC: ERL AUC ratio was increased 3 fold among patients receiving EIAED, indicative of increased hepatic metabolism and increased clearance. CSF concentrations were detectable and ranged from 1 to 3% of peak plasma concentrations. Neither group has experienced a DLT or reached the MTD. The most common side effects (grade 1/2) have been diarrhea (83%), rash (100%) and fatigue (33%). To date, there has been 1 partial response, 1 patient with stable disease and 4 patients with disease progression. The partial response and stable disease have occurred in patients with GBM. Conclusions: ERL is a well tolerated therapy. Patient enrollment and subsequent dose escalation is ongoing and updated results will be presented at the ASCO 2007 meeting.

[Table: see text]

No significant financial relationships to disclose.

Faraday rotation in femtosecond laser micromachined waveguides

We demonstrate magneto-optic switching in femtosecond-laser micromachined waveguides written inside bulk terbium-doped Faraday glass. By measuring the polarization phase shift of the light as a function of the applied magnetic field, we find that there is a slight reduction in the effective Verdet constant of the waveguide compared to that of bulk Faraday glass. Electron Paramagnetic Resonance (EPR) measurements confirm that the micromachining leaves the concentration of the terbium ions that are responsible for the Faraday effect virtually unchanged.

Volume holographic imaging in transmission geometry

We address the performance of transmission geometry volume holograms as depth-selective imaging elements. We consider two simple implementations using holograms recorded with spherical and plane beams. We derive the point-spread function (PSF) of these systems using volume diffraction theory and use the PSF to estimate depth resolution. Furthermore, we show that appropriately designed objective optics can significantly improve the depth resolution or the working distance of plane-wave reference holographic imaging systems. These results are confirmed experimentally and demonstrated for objects with millimeter axial features, imaged from the 5- to 50-cm range.

Premorbid weight, body mass, and varsity athletics in ALS

Several famous athletes have been affected by ALS, and some epidemiologic studies have indicated that vigorous physical activity (heavy labor or athletics) is a risk factor for the disease. In a case-control study of 279 patients with motor neuron diseases and 152 with other neurologic diseases, the authors found that subjects with motor neuron diseases were more likely than controls to report they had always been slim or they had been varsity athletes. For slimness, the odds ratio (OR) was 2.21; 95% CI, 1.40 to 3.47. For varsity athletics, the OR was 1.70; CI, 1.04 to 2.76.

Liquid chromatographic-tandem mass spectrometric urine assay for a highly metabolized cyclic ureidobenzenesulfonamide: issues concerning assay specificity and quality control preparation

An LC-MS-MS method was validated for the quantitation of a beta(3) agonist (A) in human urine to support Phase I studies. A was designed to accelerate metabolism for weight reduction. During assay development a significant loss of A was apparent from frozen urine quality control samples. The addition of 0.75% bovine serum albumin (BSA) in urine (v/v) was required to maximize the recovery of A from urine. Urine samples were basified and extracted into methyl t-butyl ether-isopropyl alcohol (90:10, v/v). The organic layer was washed, evaporated, reconstituted, and injected onto a 5 cm, C8 HPLC column prior to MS-MS analysis. The standard curve was linear from 5 to 500 ng/ml. Intraday precision for peak area ratios from BSA urine samples at seven separate concentrations over a range of 5-500 ng/ml (n=5) was <4.0% and calculated concentrations were within 91-115% of nominal concentrations. Interday precision for BSA urine quality control (QC) samples at four separate concentrations (n=10 of each) was <5.0% and individual calculated concentrations were within 90-111% of nominal concentrations. This work emphasizes that potential metabolites and quality control standards should be prepared and assayed as early as possible in method development, especially before the sample collection section of the clinical protocol is prepared. The methods described here have wide utility to other compounds containing basic benzene sulfonamides and to beta3 agonist candidates.

Beta(3)-adrenoceptor agonist-induced increases in lipolysis, metabolic rate, facial flushing, and reflex tachycardia in anesthetized rhesus monkeys

The effects of two beta(3)-adrenergic receptor agonists, (R)-4-[4-(3-cyclopentylpropyl)-4,5-dihydro-5-oxo-1H-tetrazol-1-yl]-N-[4-[2-[[2-hydroxy-2-(3-pyridinyl)ethyl]amino]ethyl]phenyl]benzenesulfonamide and (R)-N-[4-[2-[[2-hydroxy-2-(3-pyridinyl)- ethyl]amino]ethyl]phenyl]-1-(4-octylthiazol-2-yl)-5-indolinesulfonamide, on indices of metabolic and cardiovascular function were studied in anesthetized rhesus monkeys. Both compounds are potent and specific agonists at human and rhesus beta(3)-adrenergic receptors. Intravenous administration of either compound produced dose-dependent lipolysis, increase in metabolic rate, peripheral vasodilatation, and tachycardia with no effects on mean arterial pressure. The increase in heart rate in response to either compound was biphasic with an initial rapid component coincident with the evoked peripheral vasodilatation and a second more slowly developing phase contemporaneous with the evoked increase in metabolic rate. Because both compounds exhibited weak binding to and activation of rhesus beta(1)-adrenergic receptors in vitro, it was hypothesized that the increase in heart rate may be reflexogenic in origin and proximally mediated via release of endogenous norepinephrine acting at cardiac beta(1)-adrenergic receptors. This hypothesis was confirmed by determining that beta(3)-adrenergic receptor agonist-evoked tachycardia was attenuated in the presence of propranolol and in ganglion-blocked animals, under which conditions there was no reduction in the evoked vasodilatation, lipolysis, or increase in metabolic rate. It is not certain whether the beta(3)-adrenergic receptor-evoked vasodilatation is a direct effect of compounds at beta(3)-adrenergic receptors in the peripheral vasculature or is secondary to the release or generation of an endogenous vasodilator. Peripheral vasodilatation in response to beta(3)-adrenergic receptor agonist administration was not attenuated in animals administered mepyramine, indomethacin, or calcitonin gene-related peptide(8-37). These findings are consistent with a direct vasodilator effect of beta(3)-adrenergic receptor agonists.

ATP depletion increases tyrosine phosphorylation of beta-catenin and plakoglobin in renal tubular cells

This study examines the hypothesis that the loss of integrity of the junctional complex induced by ATP depletion is related to alterations in tyrosine phosphorylation of the adherens junction proteins beta-catenin and plakoglobin. ATP depletion of cultured mouse proximal tubular (MPT) cells induces a marked increase in tyrosine phosphorylation of both beta-catenin and plakoglobin. The tyrosine phosphatase inhibitor vanadate has the same effect in ATP-replete (control) monolayers, whereas genistein, a tyrosine kinase inhibitor, reduces phosphorylation of both proteins in ATP-replete monolayers and prevents the hyperphosphorylation of these proteins with ATP depletion. This study also demonstrates that the fall in the transepithelial resistance of MPT monolayers induced by ATP depletion can be reproduced by treatment of ATP-replete monolayers with vanadate, whereas genistein substantially ameliorates the fall in transepithelial resistance induced by ATP depletion. Also, using immunofluorescence microscopy it was demonstrated that ATP depletion results in a marked diminution of E-cadherin staining in the basolateral membrane of MPT cells. Vanadate mimics this effect of ATP depletion, whereas genistein ameliorates the reduction in the intensity of E-cadherin staining induced by ATP depletion. Because it is has been well established that hyperphosphorylation of the catenins leads to dissociation of the adherens junction and to dysfunction of the junctional complex, it is proposed that the increase in tyrosine phosphorylation of catenins observed in MPT cells during ATP depletion contributes to the loss of function of the junctional complex associated with sublethal injury.

SNARE proteins regulate H(+)-ATPase redistribution to the apical membrane in rat renal inner medullary collecting duct cells

The interaction of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins provides the necessary steps for vesicle docking fusion. In inner medullary collecting duct (IMCD) cells, acid secretion is regulated in part by exocytotic insertion and endocytotic retrieval of an H(+)-ATPase to and from the apical membrane. We previously suggested a role for SNARE proteins in exocytotic insertion of proton pumps in IMCD cells. The purpose of the present study was to determine whether SNARE proteins are associated with the 31-kDa subunit of H(+)-ATPase in IMCD cells during exocytosis and to determine the effects of clostridial toxins on SNARE-mediated trafficking of H(+)-ATPase. Cell acidification induced a marked increment of H(+)-ATPase in the apical membrane. However, pretreating cells with clostridial toxins blocked the cellular translocation of the 31-kDa subunit. Immunoprecipitation of IMCD cell homogenate, using antibodies against either the 31-kDa subunit of H(+)-ATPase or vesicle-associated membrane protein-2, co-immunoprecipitated N-ethylmaleimide-sensitive factor, alpha-soluble NSF attachment protein (alpha-SNAP), synaptosome-associated protein-23, syntaxin, and vesicle-associated membrane protein-2. Pretreatment with clostridial toxin resulted in reduced co-immunoprecipitation of H(+)-ATPase and syntaxin. These experiments document, for the first time, a putative docking fusion complex in IMCD cells and a physical association of the H(+)-ATPase with the complex. The sensitivity to the action of clostridial toxin indicates the docking-fusion complex is a part of the exocytotic mechanism of the proton pump.

Prior heat stress inhibits apoptosis in adenosine triphosphate-depleted renal tubular cells

BACKGROUND

This study tested the following hypotheses: (a) renal tubular epithelial cells subjected to transient adenosine triphosphate (ATP) depletion undergo apoptosis, and (b) induction of heat stress proteins (HSPs) inhibits cell death following ATP depletion, possibly by interacting with anti-apoptotic signal proteins.

METHODS

To simulate ischemia in vivo, cells derived from opossum kidney proximal tubule (OK) were subjected to ATP depletion (5 mM cyanide, 5 mM 2-deoxy-D-glucose, and 0 mM glucose) for 1 to 1. 5 hours, followed by recovery (10 mM glucose without cyanide). The presence of apoptosis was assessed by morphological and biochemical criteria. The effect of prior heat stress or caspase inhibition on apoptosis and cell survival were assessed.

RESULTS

In the ATP-depleted cell, both Hoechst dye and electron microscopy revealed morphological features that are typical of apoptosis. On an agarose gel, a "ladder pattern" typical of endonucleosomal DNA degradation was observed. Prior heat stress reduced the number of apoptotic-appearing cells, significantly decreased DNA fragmentation, and improved cell survival compared with controls (73.0 +/- 1% vs. 53.0 +/- 1.5%; P < 0.05). Two different caspase inhibitors also improved survival, suggesting that apoptosis is a cause of cell death in this model. Compared with ATP-depleted controls, prior heat stress inhibited the pro-apoptotic changes in the ratio of Bcl2 to BAX, proteins known to regulate the apoptotic set point in renal cells. HSP 72, a known cytoprotectant, co-immunoprecipitated with Bcl2, an anti-apoptotic protein. Prior heat stress markedly increased the interaction between HSP 72 and Bcl2.

CONCLUSIONS

Transient ATP depletion causes apoptosis in tubular epithelial cells. Prior HS inhibits apoptosis and improves survival in these cells. Novel interactions between HSP 72 and Bcl2 may be responsible, at least in part, for the protection afforded by prior heat stress against ATP depletion injury.

Effect of acidification on the location of H+-ATPase in cultured inner medullary collecting duct cells

In previous studies, our laboratory has utilized a cell line derived from the rat inner medullary collecting duct (IMCD) as a model system for mammalian renal epithelial cell acid secretion. We have provided evidence, from a physiological perspective, that acute cellular acidification stimulates apical exocytosis and elicits a rapid increase in proton secretion that is mediated by an H+-ATPase. The purpose of these experiments was to examine the effect of acute cellular acidification on the distribution of the vacuolar H+-ATPase in IMCD cells in vitro. We utilized the 31-kDa subunit of the H+-ATPase as a marker of the complete enzyme. The distribution of this subunit of the H+-ATPase was evaluated by immunohistochemical techniques (confocal and electron microscopy), and we found that there is a redistribution of these pumps from vesicles to the apical membrane. Immunoblot evaluation of isolated apical membrane revealed a 237 +/- 34% (P < 0.05, n = 9) increase in the 31-kDa subunit present in the membrane fraction 20 min after the induction of cellular acidification. Thus our results demonstrate the presence of this pump subunit in the IMCD cell line in vitro and that cell acidification regulates the shuttling of cytosolic vesicles containing the 31-kDa subunit into the apical membrane.

Anticonvulsants for soman-induced seizure activity

This report describes studies of anticonvulsants for the organophosphorus (OP) nerve agent soman: a basic research effort to understand how different pharmacological classes of compounds influence the expression of seizure produced by soman in rats, and a drug screening effort to determine whether clinically useful antiepileptics can modulate soman-induced seizures in rats. Electroencephalographic (EEG) recordings were used in these studies. Basic studies were conducted in rats pretreated with HI-6 and challenged with 1.6 x LD50 soman. Antimuscarinic compounds were extremely effective in blocking (pretreatment) or terminating soman seizures when given 5 min after seizure onset. However, significantly higher doses were required when treatment was delayed for more than 10 min, and some antimuscarinic compounds lost anticonvulsant efficacy when treatment was delayed for more than 40 min. Diazepam blocked seizure onset, yet seizures could recur after an initial period of anticonvulsant effect at doses </=2.5 mg/kg. Diazepam could terminate ongoing seizures when given 5 min after seizure onset, but doses up to 20 mg/kg were ineffective when treatment was delayed for 40 min. The GABA uptake inhibitor, tiagabine, was ineffective in blocking or terminating soman motor convulsions or seizures. The glutamate receptor antagonists, NBQX, GYKI 52466, and memantine, had weak or minimal antiseizure activity, even at doses that virtually eliminated signs of motor convulsions. The antinicotinic, mecamylamine, was ineffective in blocking or stopping seizure activity. Pretreatment with a narrow range of doses of alpha2-adrenergic agonist, clonidine, produced variable protection (40-60%) against seizure onset; treatment after seizure onset with clonidine was not effective. Screening studies in rats, using HI-6 pretreatment, showed that benzodiazepines (diazepam, midazolam and lorazepam) were quite effective when given 5 min after seizure onset, but lost their efficacy when given 40 min after onset. The barbiturate, pentobarbital, was modestly effective in terminating seizures when given 5 or 40 min after seizure onset, while other clinically effective antiepileptic drugs, trimethadione and valproic acid, were only slightly effective when given 5 min after onset. In contrast, phenytoin, carbamazepine, ethosuximide, magnesium sulfate, lamotrigine, primidone, felbamate, acetazolamide, and ketamine were ineffective.

H+ secretion is inhibited by clostridial toxins in an inner medullary collecting duct cell line

Renal epithelial cell H+ secretion is an exocytic-endocytic phenomenon. In the inner medullary collecting duct (IMCD) cell line, which we have utilized as a model of renal epithelial cell acid secretion, we found previously that acidification increased exocytosis and alkalinization increased endocytosis. It is likely, therefore, that the rate of proton secretion is regulated by the membrane insertion and retrieval of proton pumps. There is abundant evidence from studies in the nerve terminal and the chromaffin cell that vesicle docking, membrane fusion, and discharge of vesicular contents (exocytosis) involve a series of interactions among so-called trafficking proteins. The clostridial toxins, botulinum and tetanus are proteases that specifically inactivate some of these proteins. In these experiments we demonstrated, by immunoblot and immunoprecipitation, the presence in this IMCD cell line of the specific protein targets of these toxins, synaptobrevin/vesicle-associated membrane proteins (VAMP), syntaxin, and synaptosomal-associated protein-25 (SNAP-25). Furthermore, we showed that these toxins markedly inhibit the capacity of these cells to realkalinize after an acid load. Thus these data provide new insight into the mechanism for H+ secretion in the IMCD.

Effect of neuromuscular blockade on facial nerve monitoring

Direct facial nerve stimulation and monitoring during cerebellopontine angle (CPA) tumor surgery are critical for identification and preservation of function. Electrically evoked facial nerve monitoring was compared with ulnar train-of-four monitoring under progressive neuromuscular blockade. Using a rabbit model, the facial nerve function of six controls was compared to that of six specimens with acute or chronic injuries. Eight of 18 patients who had undergone CPA tumor resection during one year were also studied. Regression analysis correlated between ulnar nerve monitoring and facial electromyographic (EMG) peak voltage in all groups. Facial EMG was measurable, even with 75 percent receptor blockade. The results of this study support the hypothesis that high degrees of neuromuscular blockade do not preclude satisfactory EMG monitoring of the facial nerve during CPA tumor surgery. This study did demonstrate that chronically injured facial nerves may show greater sensitivity to the effects of neuromuscular blockade. Lower levels or avoidance of neuromuscular blockade should be employed under these circumstances.

Laser discectomy. Comparison of systems

Percutaneous methods of lumbar disc removal have gained wide popularity since the introduction of the automated suction device. Newer methods to enter this field include the Nd:YAG and Ho:YAG lasers. To date, no experimental model exists to compare the efficacy of disc removal of these devices. An in vitro disc elastance (pressure/volume) model was designed that accurately reflects the mass of dry disc removed after any type of discectomy procedure. The experimental design consists of an infusion pump compressing a static column of air in line with the disc through a 12-gauge needle. Both mechanical and laser devices exhibited a reproducible treatment plateau, beyond which no disc removal was effected. Total energy, as opposed to power, was found to be the main determinant of the extent of disc removal during laser discectomy. Finally, in the experimental model of juvenile swine the automated suction device exhibited superior disc removal compared to the two lasers, but the clinical applicability of this is debatable. Disc space elastance offers a rapid and reproducible method to quantitate the extent of disc removal after intradiscal treatment methods and if employed in human cadaver spines may minimize the need for clinical trials to compare different devices and techniques.

Intracranial cryosurgery in a canine model: a pilot study

Although virtually abandoned decades ago following the introduction of levodopa for the treatment of movement disorders, intracranial cryosurgery potentially offers a simple and accurate means of destroying deep-seated lesions when coupled with computed tomographic-stereotaxic placement techniques. We performed a pilot investigation of the size and histology of brain cryolesions in six dogs, using a 3-mm probe maintained at -160 degrees C for 6 minutes while simiultaneously monitoring the process by real-time ultrasound. Lesion diameter was 1.4 +/- 0.1 cm at less than or equal to 2 days but enlarged to 2.25 +/- 0.21 cm at 1 week, primarily at the expense of white matter. Ultrasound appearance of the lesion was characterized by a hyperechoic ice ball, the size of which consistently underestimated true size (determined by histology). By microscopy, the lesion was a hemorrhagic infarction that incited little surrounding edema and exhibited a sharp transitional zone. These data indicate that the cryosurgical probe can lesion significant volumes of brain in a reproducible and discrete fashion with minimal reaction to the surrounding tissue. Further work is required to clarify the observed "growth" of lesion size between days 2 and 7.

Percutaneous laser discectomy with the Ho:YAG laser

A prototype Ho:YAG (2.15 microns) laser operating at 2-J/pulse, 3 Hz through a 600-microns fiber was employed to perform laser discectomies at the L3-4 disc through an 18G needle in five juvenile pigs. No temperature elevations were recorded in the posterior longitudinal ligament at the disc level and all animals recovered fully with no adverse sequelae, even immediately upon awakening from anesthesia. Pathologic examination demonstrated a wide swath of coagulation necrosis confined to the disc space. The Ho:YAG laser, owing to its close approximation to the intense 2.0 microns absorption band of water, appears to be a viable candidate for clinical trials of laser discectomy.

A comparison of cholinergic effects of HI-6 and pralidoxime-2-chloride (2-PAM) in soman poisoning

The effects of HI-6 and pralidoxime chloride (2-PAM) on soman-induced lethality, time to death and several cholinergic parameters in rats were compared to understand the beneficial action of HI-6. Treatment with atropine sulfate (ATS) or HI-6 alone protected against 1.2 and 2.5 LD50s of soman respectively, whereas 2-PAM or methylated atropine (AMN) alone afforded no protection. Addition of ATS, but not AMN, to HI-6-treated rats enhanced the protection from 2.5 to 5.5 LD50s. HI-6 increased the time-to-death, while 2-PAM had no effect; a combination of HI-6 and ATS provided the most significant increase in time-to-death. Cholinesterase (ChE) activity was not altered in any tissue by ATS, HI-6 or 2-PAM treatment individually, but was markedly inhibited in all tissues by 100 micrograms/kg of soman. In soman-poisoned rats, the HI-6, but not the 2-PAM, group had significantly higher levels of ChE in blood and other peripheral tissues than did the group given soman alone. Neither HI-6 nor 2-PAM affected soman-inhibited ChE in the brain. Additional ATS treatment had no effect on ChE activity. HI-6 and 2-PAM neither modified baseline brain acetylcholine (ACh) or choline (Ch) levels nor protected against soman-induced ACh or Ch elevation. 2-PAM exhibited a 4-fold more potent in vitro inhibition of 3H-quinuclidinyl benzilate (3H-QNB) binding and sodium-dependent high-affinity Ch uptake (HACU) than did HI-6 in brain tissues. The findings that 2-PAM is a more potent in vitro inhibitor of muscarinic receptor binding and HACU than HI-6, and yet neither elevates ChE activity in the periphery nor protects rats against soman poisoning, indicate the importance of higher ChE activity in the periphery of HI-6-treated rats. Maintenance by HI-6 of a certain amount of active ChE in the periphery appears to be important for survival after soman exposure.

Effects of hematocrit on thixotropic properties of human blood

The rheological properties of whole human blood exhibit thixotropic behavior at low shear rates up to about ten reciprocal seconds (1). The accepted cause of this shear rate-dependent and time-dependent behavior is the progressive breakdown of rouleaux into individual red cells. Huang developed a rheological equation which incorporates the kinetics of rouleau breakdown in his models (2). This five-parameter equation was used successfully to represent the hysteresis loop and the torque-decay curve of whole human blood. Numerical values of these five thixotropic parameters, which characterize the rheological behavior of the blood from apparently healthy human subjects, were established (3). In this communication, we examined the effect of hematocrit on each of the above mentioned parameters. The results show that the following parameters will increase their values with an increase in hematocrit: the yield stress, Newtonian contribution of viscosity, non-Newtonian contribution of viscosity, apparent viscosity and the equilibrium value of the structural parameter which indicates the relative amount of rouleaux in blood. Mathematical equations were developed to give the relationship between parameters and hematocrit. Two other thixotropic parameters, viz. the kinetic rate constant of rouleaux breakdown into individual red cells and the order of the breakdown reaction, were found to be independent of the hematocrit. It is consistent with reaction kinetic theory that the rate constant and the order of reaction are independent of the concentration of reactants.

Reconstruction of large fronto-orbital defects with Dacron polyurethane custom prosthesis and autogenous bone

Reconstruction of large defects of the frontal bone and bony orbit may be required following trauma or ablative tumor surgery. Autogenous bone or alloplastic implants used alone may prove inadequate due to difficulties obtaining symmetric contours with bone and lack of strength and resistance to infection with alloplastic materials. These problems can be overcome with the combined use of a prefabricated Dacron polyurethane mesh prosthesis (Osteo-Mesh, Xomed, Inc.) to establish contour of the forehead and superciliary ridges, and underlying split-rib grafts to protect the brain and isolate the paranasal sinuses. This technique is not indicated for small frontal defects, but it should be considered for use by the head and neck surgeon who is faced with the challenge of reconstructing a major fronto-orbital defect.

Involvement of His HC3 (146) beta in the Bohr effect of human hemoglobin. Studies of native and N-ethylmaleimide-treated hemoglobin A and hemoglobin Cowtown (beta 146 His replaced by Leu)

The involvement of the COOH-terminal histidines of the beta chains of human hemoglobin in the allosteric mechanism of oxygen binding has been the topic of intensive discussion. Data presented here on the functional properties of native and chemically modified forms of Hb Cowtown (beta 146 His replaced by Leu) suggest that approximately half of the alkaline Bohr effect is attributable to the imidazole of His HC3(146) beta. The contribution of this residue to the alkaline Bohr effect has been estimated variably as 40-60% and 15% or less. Equilibrium and kinetic studies show that the amino acid substitution in Hb Cowtown decreases the stability of the low affinity conformation, resulting in an increased oxygen affinity and altered sensitivity to anionic effectors. Detailed analysis of Hill plots of oxygen binding according to the Adair scheme reveals that, under conditions of moderate ionic strength (chloride = 0.1 M), the K2 and K3 values for Hb A and Hb Cowtown differ, whereas the K1 and K4 values are closely similar over the physiological pH range. The decreased pH sensitivity of Hb Cowtown is associated with a decreased pH sensitivity of K1, the first Adair constant. In contrast to des-His(146 beta) hemoglobin, the cooperative interactions shown by Hb Cowtown under conditions of moderate ionic strength are not reduced in comparison to those of Hb A. This and the similarity of K1 and K4 values for Hb A and Hb Cowtown indicate that under these conditions the salt bridge formed by the COOH-terminal imidazole group does not significantly contribute to the free energy difference between "T-state" and "R-state" hemoglobin. It appears that the salt bridge formed by the COOH-terminal carboxyl group stabilizes the deoxy, T-state, conformation to a greater degree than previously appreciated. Chemical modification of the Cys(93 beta) residue of Hb Cowtown with N-ethylmaleimide causes a decrease in its oxygen affinity, in contrast to the increase in affinity exhibited by N-ethylmaleimide-modified Hb A. Hemoglobins A and Cowtown have remarkably similar oxygen binding properties after this modification and are shown to have K1 and K4 values distinctly different from those of unmodified Hb A. The properties of native and chemically modified forms of Hb Cowtown are indicative of a large contribution of the His HC3 (146) beta residue to the alkaline Bohr effect and also illustrate how chemical modifications or changes of strategic amino acid residues can result in pronounced differences in the conformational equilibrium of an allosteric protein.

Oxygen equilibrium studies of Hb Willamette alpha 2 beta (2)51(D2)Pro leads to Arg

The homotropic and heterotropic effects of isolated Hb Willamette were studied using an automatic recording oxygen equilibrium analyzer. The results indicate that Hb Willamette displays normal intrinsic oxygen binding in the stripped condition. An apparent decrease of the Bohr effect is explained by the decrease of allosteric effects in this abnormal hemoglobin. Furthermore, the lack of clinical manifestations in the original patient is consistent with the red cell oxygen equilibrium studies.