Effects of Medicare Part D medication therapy management on racial/ethnic disparities in adherence to antidementia medications among patients with Alzheimer's disease and related dementias: An observational study

Background

Evidence is sparse on the effects of Medicare medication therapy management (MTM) on racial/ethnic disparities in medication adherence among patients with Alzheimer's disease and related dementias.

Objectives

This study examined the Medicare MTM program's effects on racial/ethnic disparities in the adherence to antidementia medications among patients with Alzheimer's disease and related dementias.

Methods

This is a retrospective analysis of 100% of 2010-2017 Medicare Parts A, B, and D data linked to Area Health Resources Files. The study outcome was nonadherence to antidementia medications, and intervention was defined as new MTM enrollment in 2017. Propensity score matching was conducted to create intervention and comparison groups with comparable characteristics. A difference-in-differences model was employed with logistic regression, including interaction terms of dummy variables for the intervention group and racial/ethnic minorities.

Results

Unadjusted comparisons revealed that Black, Hispanic, and Asian/Pacific Islander patients were more likely to be nonadherent than non-Hispanic White (White) patients in 2016. Differences in odds of nonadherence between Black and White patients among the intervention group were lower in 2017 than in 2016 by 27% (odds ratios [OR]: 0.73, 95% confidence interval [CI]: 0.65-0.82). A similar lowering was seen between Hispanic and White patients by 26% (OR: 0.74, 95% CI: 0.63-0.87). MTM enrollment was associated with reduced disparities in nonadherence for Black-White patients of 33% (OR: 0.67, 95% CI: 0.57-0.78) and Hispanic-White patients of 19% (OR: 0.81, 95% CI: 0.67-0.99).

Discussion

The Medicare MTM program was associated with lower disparities in adherence to antidementia medications between Black and White patients, and between Hispanic and White patients in the population with Alzheimer's disease and related dementias.

Conclusions

Expanding the MTM program may particularly benefit racial/ethnic minorities in Alzheimer's disease and related dementia care.

Solving racial/ethnic disparities associated with Medicare Part D Star Ratings

OBJECTIVE

Medicare Part D Star Ratings are instrumental in shaping healthcare quality improvement efforts. However, the calculation metrics for medication performance measures for this program have been associated with racial/ethnic disparities. In this study, we aimed to explore whether an alternative program, named Star Plus by us that included all medication performance measures developed by Pharmacy Quality Alliance and applicable to our study population, would reduce such disparities among Medicare beneficiaries with diabetes, hypertension, and/or hyperlipidemia.

METHOD

We conducted an analysis of a 10% random sample of Medicare A/B/D claims linked to the Area Health Resources File. Multivariate logistic regressions with minority dummy variables were used to examine racial/ethnic disparities in measure calculations of Star Ratings and Star Plus, respectively.

RESULTS

Adjusted results indicated that relative to non-Hispanic Whites (Whites), racial/ethnic minorities had significantly lower odds of being included in the Star Ratings measure calculations: the odds ratios (ORs) for Blacks, Hispanics, Asians, and Others were 0.68 (95% confidence interval [CI] = 0.66-0.71), 0.73 (CI = 0.69-0.78), 0.88 (CI = 0.82-0.93), and 0.92 (CI = 0.88-0.97), respectively. In contrast, every beneficiary in the sample was included in Star Plus. Further, racial/ethnic minorities had significantly higher increase in the odds of being included in measure calculation in Star Plus than Star Ratings. The ORs for Blacks, Hispanics, Asians, and Others were 1.47 (CI = 1.41-1.52), 1.37 (CI = 1.29-1.45), 1.14 (CI = 1.07-1.22), and 1.09 (CI = 1.03-1.14), respectively.

CONCLUSIONS

Our study demonstrated that racial/ethnic disparities may be eliminated by including additional medication performance measures to Star Ratings.

Racial and ethnic disparities in the enrolment of medicare medication therapy management programs

Objectives

Racial/ethnic disparities have been found in prior literature examining enrolment in Medicare medication therapy management programs. However, those studies were based on various eligibility scenarios because enrolment data were unavailable. This study tested for potential disparities in enrolment using actual MTM enrolment data.

Methods

Medicare Parts A&B claims, Medication Therapy Management Data Files, and the Area Health Resources File from 2013 to 2014 and 2016 to 2017 were analysed in this retrospective analysis. An adjusted logistic regression compared odds of enrolment between racial/ethnic minorities and non-Hispanic Whites (Whites) in the total sample and subpopulations with diabetes, hypertension, or hyperlipidaemia. Trends in disparities were analysed by including interaction terms in regressions between dummy variables for race/ethnic minority groups and period 2016-2017.

Key Findings

Disparities in MTM enrolment were detected between Blacks and Whites with diabetes in 2013-2014 (Odds Ratio = 0.78, 95% Confidence Interval = 0.75-0.81). This disparity improved from 2013-2014 to 2016-2017 for Blacks (Odds Ratio=1.08, 95% Confidence Interval = 1.04-1.11) but persisted in 2016-2017 (Odds Ratio = 0.84, 95% Confidence Interval = 0.81-0.87). A disparity was identified between Blacks and Whites with hypertension in 2013-2014 (Odds Ratio = 0.92, 95% Confidence Interval = 0.89-0.95) but not in 2016-2017. Enrolment for all groups, however, declined between periods. For example, in the total sample, the odds of enrolment declined from 2013-2014 to 2016-2017 by 22% (Odds Ratio=0.78, 95% Confidence Interval=0.75-0.81).

Conclusions

Racial disparities in MTM enrolment were found between Blacks and Whites among Medicare beneficiaries with diabetes in both periods and among individuals with hypertension in 2013-2014. As overall enrolment fell between periods, concerns about program enrolment remain.

Cost-Effectiveness of Medication Therapy Management Program Across Racial and Ethnic Groups Among Medicare Beneficiaries

OBJECTIVES

Equity and effectiveness of the medication therapy management (MTM) program in Medicare has been a policy focus since its inception. The objective of this study was to evaluate the cost-effectiveness of the Medicare MTM program in improving medication utilization quality across racial and ethnic groups.

METHODS

This study analyzed 2017 Medicare data linked to the Area Health Recourses File. A propensity score was used to match MTM enrollees and nonenrollees, and an incremental cost-effectiveness ratio between the 2 groups was calculated. Effectiveness was measured as the proportion of appropriate medication utilization based on medication utilization measures developed by Pharmacy Quality Alliance. Net monetary benefits were compared across racial and ethnic groups at various societal willingness-to-pay (WTP) thresholds. The 95% confidence intervals were obtained by nonparametric bootstrapping.

RESULTS

MTM dominated non-MTM among the total sample (N = 699 992), as MTM enrollees had lower healthcare costs ($31 135.89 vs $32 696.69) and higher proportions of appropriate medication utilization (87.47% vs 85.31%) than nonenrollees. MTM enrollees had both lower medication costs ($10 681.21 vs $11 003.08) and medical costs ($20 454.68 vs $21 693.61) compared with nonenrollees. The cost-effectiveness of MTM was higher among Black patients than White patients across the WTP thresholds. For instance, at a WTP of $3006 per percentage point increase in effectiveness, the net monetary benefit for Black patients was greater than White patients by $2334.57 (95% confidence interval $1606.53-$3028.85).

CONCLUSIONS

MTM is cost-effective in improving medication utilization quality among Medicare beneficiaries and can potentially reduce disparities between Black and White patients. Expansion of the current MTM program could maximize these benefits.

Racial and ethnic disparities in Medicare Part D medication therapy management services utilization

Background

The Medicare Part D medication therapy management (MTM) program has positive effects on medication and health service utilization. However, little is known about its utilization, much less so about the use among racial and ethnic minorities.

Objective

To examine MTM service utilization among older Medicare beneficiaries and to identify any racial and ethnic disparity patterns.

Methods

A retrospective cross-sectional analysis of 2017 Medicare administrative data, linked to the Area Health Resources Files. Fourteen outcomes related to MTM service nature, initiation, quantity, and delivery were examined using logistic, negative binomial, and Cox proportional hazards regression models.

Results

Racial and ethnic disparities were found with varying patterns across outcomes. For example, compared with White patients, the odds of opting out of MTM were 8% higher for Black patients (odds ratio [OR] = 1.08, 95% confidence interval [CI] = 1.03-1.14), 57% higher for Hispanic patients (OR = 1.57, 95% CI = 1.42-1.72), and 57% higher for Asian patients (OR = 1.57, 95% CI = 1.33-1.85). The odds of continuing MTM from the previous years were 12% lower for Black patients (OR = 0.88, 95% CI = 0.86-0.90) and 3% lower for other patients (OR = 0.97, 95% CI = 0.95-0.99). In addition, the probability of being offered a comprehensive medication review (CMR) after MTM enrollment was 9% lower for Hispanic patients (hazard ratio [HR] = 0.91, 95% CI = 0.85-0.97), 9% lower for Asian patients (HR = 0.91, 95% CI = 0.87-0.94), and 3% lower for other patients (HR = 0.97, 95% CI = 0.95-0.99). Hispanic and Asian patients were more likely to have someone other than themselves receive a CMR.

Conclusions

Racial and ethnic disparities in MTM service utilization were identified. Although the disparities in specific utilization outcomes vary across racial/ethnic groups, it is evident that these disparities exist and may result in vulnerable communities not fully benefiting from the MTM services. Causes of the disparities should be explored to inform future reform of the Medicare Part D MTM program.

Racial/ethnic disparities in the enrollment of Medication Therapy Management programs among Medicare beneficiaries with Alzheimer's disease and related dementias

OBJECTIVE

Previous analysis of policy scenarios reported potential disparities in eligibility in the Medicare Medication Therapy Management (MTM) program. With recently released MTM data, this study aimed to determine if racial/ethnic disparities exist in MTM enrollment among Medicare beneficiaries with Alzheimer's disease and related dementias (ADRD).

METHODS

Medicare claims/records (from 2013-2014 and 2016-2017) linked to the Area Health Resources File were examined. Included individuals were patients with ADRD and diabetes, hypertension or hyperlipidemia. The proportions of MTM enrollment were compared between non-Hispanic White (White) patients and racial/ethnic minority groups in descriptive analysis. Racial/ethnic disparities were then examined using a logistic regression adjusting for patient and community characteristics. Disparities across study periods were compared by estimating a logistic regression model with interaction terms between dummy variables for each racial/ethnic minority group and 2016-2017.

RESULTS

In unadjusted analyses, minorities had higher enrollment proportions than Whites. In 2016-2017, for example, enrollment percentages for Whites, Blacks, Hispanics, Asian/Pacific Islanders (Asians) and Others were respectively 14.44%, 16.71%, 19.83%, 16.66%, and 17.78%. In adjusted analyses, Blacks had lower enrollment odds than Whites within all cohorts. In the entire study sample in 2016-2017, for example, Blacks with ADRD had 9% lower odds of MTM enrollment (odds ratio 0.91, 95% confidence interval [CI] = 0.86-0.97) than Whites. These disparities decreased over time among the ADRD sample and all sub-groups. The interaction term between Blacks and 2016-2017, for instance, indicated that disparities were lowered by 11% (odds ratio 1.11, 95% CI = 1.05-1.16) across study periods among those with ADRD.

CONCLUSIONS

Blacks with ADRD, and diabetes, hypertension or hyperlipidemia have lower likelihood of MTM enrollment than Whites. Racial disparities were reduced over time but not eliminated.

Effects of Medicare comprehensive medication review on racial/ethnic disparities in nonadherence to statin medications among patients with Alzheimer's Disease: an observational analysis

Background

Alzheimer’s Disease (AD) is the mostcommon cause of dementia, a neurological disorder characterized by memory loss and judgment impairment. Hyperlipidemia, a commonly co-occurring condition, should be treated to prevent associated complications. Medication adherence may be difficult for individuals with AD due to the complexity of AD management. Comprehensive Medication Reviews (CMRs), a required component of Medicare Part D Medication Therapy Management (MTM), have been shown to improve medication adherence. However, many MTM programs do not target AD. Additionally, racial/ethnic disparities in MTM eligibility have been revealed. Thus, this study examined the effects of CMR receipt on reducing racial/ethnic disparities in the likelihood of nonadherence to hyperlipidemia medications (statins) among the AD population.

Methods

This retrospective study used 2015-2017 Medicare data linked to the Area Health Resources Files. The likelihood of nonadherence to statin medications across racial/ethnic groups was compared between propensity-score-matched CMR recipients and non-recipients in a ratio of 1 to 3. A difference-in-differences method was utilized to determine racial/ethnic disparity patterns using a logistic regression by including interaction terms between dummy variables for CMR receipt and each racial/ethnic minority group (non-Hispanic Whites, or Whites, as reference).

Results

The study included 623,400 Medicare beneficiaries. Blacks and Hispanics had higher statin nonadherence than Whites: Compared to Whites, Blacks’ nonadherence rate was 4.53% higher among CMR recipients and 7.35% higher among non-recipients; Hispanics’ nonadherence rate was 2.69% higher among CMR recipients and 7.38% higher among non-recipients. Differences in racial/ethnic disparities between CMR recipients and non-recipients were significant for each minority group (p < 0.05) except Others. The difference between Whites and Hispanics in the odds of statin nonadherence was 11% lower among CMR recipients compared to non-recipients (OR = 0.89; 95% Confidence Interval = 0.85-0.94 for the interaction term between dummy variables for CMR and Hispanics). Interaction terms between dummy variables for CMR and other racial/ethnic minorities were not significant.

Conclusions

Receiving a CMR was associated with a disparity reduction in nonadherence to statin medications between Hispanics and Whites among patients with AD. Strategies need to be explored to increase the number of MTM programs that target AD and promote CMR completion.

Effects of the Medicare Part D comprehensive medication review on medication adherence among patients with Alzheimer's disease

OBJECTIVE

Older patients with Alzheimer's disease (AD) are challenged with adhering to complex medication regimens. We examined effects of Comprehensive Medication Review (CMR), a required Medicare Part D Medication Therapy Management (MTM) program component, on medication adherence among AD patients.

METHODS

This retrospective study analyzed 100% of 2016-2017 Medicare claims covering the entire United States, linked to Area Health Resources Files. Medicare beneficiaries aged ≥65 years were included. Propensity score matching identified comparable intervention and comparison groups with the intervention defined as receiving a CMR in 2017. A difference-in-differences analysis included in multivariate logistic regressions an interaction term between CMR receipt and year 2017. The outcome measured was nonadherence to diabetes, hypertension and hyperlipidemia medications, with nonadherence defined as proportion of days covered <80% for study medications.

RESULTS

Unadjusted comparisons indicated the proportion of nonadherence for intervention group members decreased from 2016 to 2017 but increased for the comparison group. In adjusted analyses, reduction in medication nonadherence among the intervention group remained higher: odds ratios for the interaction term were 0.62 (95% confidence interval [CI] = 0.54-0.71), 0.54 (95% CI = 0.50-0.58) and 0.50 (95% CI = 0.47-0.53) respectively for diabetes, hypertension and hyperlipidemia medications. This suggests that the likelihood of nonadherence in the intervention group was respectively reduced by 38%, 46% and 50% more than the comparison group.

CONCLUSIONS

CMR was found to reduce nonadherence to diabetes, hypertension and hyperlipidemia medications among older Medicare beneficiaries with AD. This provides evidence that the MTM program is effective for a population with unique medication compliance challenges.

A non-electrolyte haemolysis assay for diagnosis and prognosis of sickle cell disease

Red blood cells (RBCs) from patients with sickle cell disease (SCD) lyse in deoxygenated isosmotic non-electrolyte solutions. Haemolysis has features which suggest that it is linked to activation of the pathway termed P_sickle. This pathway is usually described as a non-specific cationic conductance activated by deoxygenation, HbS polymerisation and RBC sickling. The current work addresses the hypothesis that this haemolysis will provide a novel diagnostic and prognostic test for SCD, dependent on the altered properties of the RBC membrane resulting from HbS polymerisation. A simple test represented by this haemolysis assay would be useful especially in less affluent deprived areas of the world where SCD is most prevalent. RBCs from HbSS and most HbSC individuals showed progressive lysis in deoxygenated isosmotic sucrose solution at pH 7.4 to a level greater than that observed with RBCs from HbAS or HbAA individuals. Cytochalasin B prevented haemolysis. Haemolysis was temperature- and pH-dependent. It required near physiological temperatures to occur in deoxygenated sucrose solutions at pH 7.4. At pH 6, haemolysis occurred even in oxygenated samples. Haemolysis was reduced in patients on long-term (>5 months) hydroxyurea treatment. Several manoeuvres which stabilise soluble HbS (aromatic aldehydes o-vanillin or 5-hydroxymethyl, and urea) reduced haemolysis, an effect not due to increased oxygen affinity. Conditions designed to elicit HbS polymerisation in cells from sickle trait patients (deoxygenated hyperosmotic sucrose solutions at pH 6) supported their haemolysis. These findings are consistent with haemolysis requiring HbS polymerisation and support the hypothesis that this may be used as a test for SCD.

Novel permeability characteristics of red blood cells from sickle cell patients heterozygous for HbS and HbC (HbSC genotype)

Individuals heterozygous for HbS and HbC (HbSC) represent about 1/3(rd) of sickle cell disease (SCD) patients. Whilst HbSC disease is generally milder, there is considerable overlap in symptoms with HbSS disease. HbSC patients, as well as HbSS ones, present with the chronic anaemia and panoply of acute vaso-occlusive complications that characterize SCD. However, there are important clinical and haematological differences. Certain complications occur with greater frequency in HbSC patients (like proliferative retinopathy and osteonecrosis) whilst intravascular haemolysis is reduced. Patients with HbSC disease can be considered as a discrete subset of SCD cases. Although much work has been carried out on understanding the pathogenesis of SCD in HbSS homozygotes, including the contribution of altered red blood cell permeability, relatively little pertains directly to HbSC individuals. Results reported in the literature suggest that HbSC cells, and particularly certain subpopulations, present with similar permeability to HbSS cells but there are also important differences - these have not been well characterized. We hypothesise that their unique cell transport properties accounts for the different pattern of disease in HbSC patients and represents a potential chemotherapeutic target not shared in red blood cells from HbSS patients. The distinct pattern of clinical haematology in HbSC disease is emphasised here. We analyse some of the electrophysiological properties of single red blood cells from HbSC patients, comparing them with those from HbSS patients and normal HbAA individuals. We also use the isosmotic haemolysis technique to investigate the behaviour of total red blood cell populations. Whilst both HbSS and HbSC cells show increased monovalent and divalent (Ca(2+)) cation conductance further elevated upon deoxygenation, the distribution of current magnitudes differs, and outward rectification is greatest for HbSC cells. In addition, although Gd(3+) largely abolishes the cation conductance of both HbSS and HbSC cells, only in HbSS ones are currents inhibited by the aminoglycosides like streptomycin. This distinction is retained in isosmotic lysis experiments where both HbSS and HbSC cells undergo haemolysis in sucrose solutions but streptomycin significantly inhibits lysis only in HbSS cells. These findings emphasise similarities but also differences in the permeability properties of HbSS and HbSC cells, which may be important in pathogenesis.

Abnormal permeability pathways in human red blood cells

A number of situations that result in abnormal permeability pathways in human red blood cells (RBCs) have been investigated. In sickle cell disease (SCD), RBCs contain HbS, rather than the normal HbA. When deoxygenated, an abnormal conductance pathway, termed P(sickle), is activated, which contributes to cell dehydration, largely through allowing Ca(2+) entry and subsequent activation of the Gardos channel. Whole-cell patch-clamp recordings from sickle RBCs show a deoxygenated-induced conductance, absent from normal RBCs, which shares some of the properties of P(sickle): equivalent Na(+) and K(+) permeability, significant Ca(2+) conductance, partial inhibition by DIDS and also Zn(2+). Gd(3+) markedly attenuates conductance in both normal and sickle RBCs. In addition, deoxygenated sickle cells, but not oxygenated ones or normal RBCs regardless of the oxygen tension, undergo haemolysis in isosmotic non-electrolyte solutions. Non-electrolyte entry was confirmed radioisotopically whilst haemolysis was inhibited by DIDS. These findings suggest that under certain circumstances P(sickle) may also be permeable to non-electrolytes. Finally, RBCs from certain patients with hereditary stomatocytosis have a mutated band 3, which appears able to act as a conductance pathway for univalent cations. These results extend our understanding of the abnormal permeability pathways of RBCs.

Inorganic phosphate transport in matrix vesicles from bovine articular cartilage

AIMS

In mineralizing tissues such as growth plate cartilage extracellular organelles derived from the chondrocyte membrane are present. These matrix vesicles (MV), possess membrane transporters that accumulate Ca(2+) and inorganic phosphate (P(i)), and initiate the formation of hydroxyapatite crystals. MV are also present in articular cartilage, and hydroxyapatite crystals are believed to promote cartilage degradation in osteoarthritic joints. This study characterizes P(i) transport in MV derived from articular cartilage.

METHODS

Matrix vesicles were harvested from collagenase digests of bovine articular cartilage by serial centrifugation. P(i) uptake by MV was measured using radioactive phosphate ((33)[P]HPO(4)(2-)). The Na(+) dependence, pH sensitivity and effects of P(i) analogues that inhibit P(i) transport were determined.

RESULTS

P(i) uptake was temperature-sensitive and comprised Na(+)-dependent and Na(+)-independent components. The Na(+)-dependent component saturated at high extracellular P(i) concentrations, with a K(m) of 0.16 mM. In Na(+)-free solutions, uptake did not fully saturate implying that carrier-mediated uptake is supplemented by a diffusive pathway. Uptake was inhibited by phosphonoacetate and arsenate, although a fraction of Na(+)-independent P(i) uptake persisted. Total P(i) uptake was maximal at pH 6.5, and reduced at more acidic or alkaline values, representing inhibition of both components.

CONCLUSION

These properties are highly similar to those of P(i) uptake by chondrocytes, suggesting that MV inherit P(i) transporters of the chondrocyte membrane from which they are derived. Na(+)-independent P(i) uptake has not previously been described in MV from growth plate cartilage and is relatively uncharacterized, but warrants further attention in articular cartilage, given its likely role in initiating inappropriate mineral formation.

Influences of buffer systems on chondrocyte growth during long-term culture in alginate

OBJECTIVE

Chondrocyte behavior is very sensitive to culture environment such as physical and biochemical conditions. As extracellular pH (pHo) and the existence of bicarbonate could affect the chondrocyte fate, hence, the purpose of this study is to investigate the buffer system effect on chondrocyte fate during relatively long-term culture.

METHODS

In order to examine whether effects seen were due to bicarbonate or to pHo, we had to devise a system which could differentiate between the two effects. Culture media buffered by N-2-hydroxyethyl piperazine-N'-2-ethanesulfonic acid (HEPES) only and the combination of HEPES and bicarbonate were used. Bovine articular chondrocytes were cultured in alginate beads for up to 12 days. pHo was kept constant by culture of 3 beads in 2 ml culture medium. Cell density, intracellular pH (pHi) and glycosaminoglycan (GAG) were measured at day 5 and day 12. Cell morphology, distribution and viability in alginate beads were monitored over 12 days of culture.

RESULTS

Compared to culture in the absence of bicarbonate, a higher proliferation rate of chondrocytes was observed in the presence of bicarbonate. pHi was more alkaline, about 0.2 pH unit, in the presence of bicarbonate than that in the absence of bicarbonate. About 50% more GAG was deposited in alginate beads when chondrocytes were cultured in the combination of HEPES and bicarbonate, compared to chondrocytes cultured in the absence of NaHCO3 at the end of 12 days of culture.

CONCLUSION

The presence of bicarbonate results in more alkaline in the pHi of bovine chondrocytes after long-term culture. The combination of bicarbonate and HEPES in culture medium improves cell growth, matrix production in three-dimensional alginate beads.

The effect of O2 tension on pH homeostasis in equine articular chondrocytes

OBJECTIVE

To determine the effects of varying O(2) on pH homeostasis, based on the hypothesis that the function of articular chondrocytes is best understood at realistic O(2) tensions.

METHODS

Cartilage from equine metacarpophalangeal/tarsophalangeal joints was digested with collagenase to isolate chondrocytes, and then loaded with the pH-sensitive fluorophore 2',7'-bis-2-(carboxyethyl)-5(6)-carboxylfluorescein. The radioisotope(22)Na(+) was used to determine the kinetics of Na(+)/H(+) exchange (NHE) and the activity of the Na(+)/K(+) pump, and ATP levels were assessed with luciferin assays. Levels of reactive oxygen species (ROS) were determined using 2',7'-dichlorofluorescein diacetate.

RESULTS

The pH homeostasis was unaffected when comparing tissue maintained at 20% O(2) (the level in water-saturated air at 37 degrees C) with that at 5% O(2) (which approximates the normal level in healthy cartilage); however, an O(2) tension of <5% caused a fall in intracellular pH (pH(i)) and slowed pH(i) recovery following acidification, an effect mediated via inhibition of NHE activity (likely through acid extrusion by NHE isoform 1). The Na(+)/K(+) pump activity and intracellular ATP concentration were unaffected by hypoxia, but the levels of ROS were reduced. Hypoxic inhibition of NHE activity and the reduction in ROS levels were reversed by treatment with H(2)O(2), Co(2+), or antimycin A. Treatment with calyculin A also prevented hypoxic inhibition of NHE activity.

CONCLUSION

The ability of articular chondrocytes to carry out pH homeostasis is compromised when O(2) tensions fall below those normally experienced, via inhibition of NHE. The putative signal is a reduction in levels of ROS derived from mitochondria, acting via altered protein phosphorylation. This effect is relevant to both physiologic and pathologic states of lowered O(2), such as in chronic inflammation.

Effects of anti-GLUT antibodies on glucose transport into human erythrocyte ghosts

We have studied the effects of anti-GLUT1 antibodies on the uptake of glucose into erythrocytes. Glucose transport into human erythrocyte ghosts was measured directly using 3H-2-deoxy-glucose, or indirectly by monitoring associated volume changes using light scattering. The uptake of glucose was significantly inhibited in ghosts resealed in solutions containing specific antibodies against GLUT1. Such an effect was not observed when an antibody against the oestrogen receptor, lacking specificity towards GLUT1, was employed instead. The antibodies were also without effect on the efflux of preloaded glucose from erythrocyte ghosts. The demonstration that anti-GLUT antibodies can inhibit glucose uptake is support for the hypothesis that they exaggerate the cytoplasmic barrier to glucose uptake created by endofacial segments of GLUT1.

Mechanisms contributing to intracellular pH homeostasis in an immortalised human chondrocyte cell line

The maintenance of chondrocyte pH is an important parameter controlling cartilage matrix turnover rates. Previous studies have shown that, to varying degrees, chondrocytes rely on Na(+)/H(+) exchange to regulate pH. HCO(3)(-)-dependent buffering and HCO(3)(-)-dependent acid-extrusion systems seem to play relatively minor roles. This situation may reflect minimal carbonic anhydrase activity in cartilage cells. In the present study, the pH regulation of the human chondrocyte cell line, C-20/A4 has been characterised. Intracellular pH (pH(i)) was measured using the H(+)-sensitive fluoroprobe BCECF. In solutions lacking HCO(3)(-)/CO(2), pH(i) was approximately 7.5, and the recovery from intracellular acidification was predominantly mediated by a Na(+)-dependent, amiloride- and HOE 694-sensitive process. A small additional component which was sensitive to chloro-7-nitrobenz-2-oxa-1,3-diazole, an inhibitor of the V-type H(+)-ATPase, was also apparent. In solutions containing HCO(3)(-)/CO(2), pH(i) was approximately 7.2. Comparison of buffering capacity in the two conditions showed that this variable was not significantly augmented in HCO(3)(-)/CO(2)-containing media. The recovery from intracellular acidification was more rapid in the presence of HCO(3)(-)/CO(2), although under these conditions it was again largely dependent on Na(+) ions and inhibited by amiloride and HOE 694. A small component was inhibited by SITS, although this effect did not reach the level of statistical significance. These findings indicate that HCO(3)(-)-dependent processes play only a minimal role in pH regulation in C-20/A4 chondrocytes. pH regulation instead relies heavily on the Na(+)/H(+) exchanger together with a H(+)-ATPase. The absence of extrinsic (HCO(3)(-)/CO(2)) buffering is likely to reflect the low levels of carbonic anhydrase in these cells. In addition to providing fundamental information about a widely-used cell line, these findings support the contention that the unusual nature of pH regulation in chondrocytes reflects the paucity of carbonic anhydrase activity in these cells.

The influence and interactions of hydrostatic and osmotic pressures on the intracellular milieu of chondrocytes

The intracellular milieu of chondroctyes is regulated by an array of proteins in the cell membrane which operate as transport pathways, allowing ions and nutrients such as glucose and amino acids and metabolites such as lactate to cross the plasma membrane. Here we investigated the influence of hydrostatic pressure on intracellular calcium concentrations ([Ca(2+)](i)) in isolated bovine articular chondrocytes. We found that short applications of high hydrostatic pressures led to a significant increase in [Ca(2+)](i). The pressure-induced rise was abolished for long (240 sec) but not short (30 sec) pressure applications by removal of extracellular Ca(2+). The rise in pressure was also blocked by the inhibitors neomycin and thapsigargin confirming that pressure, by generating IP(3), led to an increase in [Ca(2+)](i) by mobilising the pool of Ca(2+) ions contained within intracellular stores. We also found that intracellular [Na(+)] was affected by a rise in osmotic pressure and further affected by application of hydrostatic pressure. The effect of hydrostatic pressure on sulphate incorporation depended strongly on extracellular osmolality. Since significant gradients in extracellular osmolality exist across intact cartilage, the results imply that responses of chondrocytes to the same pressure will vary depending on location in the joint. The results also indicate that hydrostatic pressures can affect several different transporter systems thus influencing the intracellular milieu and chondrocyte metabolism.

Effects of high pressure on glucose transport in the human erythrocyte

The effects of raised hydraulic pressure on D-glucose exit from human red cells at 25 degrees C were determined using light scattering measurements in a sealed pressurized spectrofluorimeter cuvette. The reduction in the rates of glucose exit with raised pressure provides an index of the activation volume, deltaV++ (delta ln k/deltaP)(T) = -deltaV++/RT. Raised pressure decreased the rate constant of glucose exit from 0.077 +/- 0.003 s(-1) to 0.050 +/- 0.002 s(-1) (n = 5, P < 0.003). The Ki for glucose binding to the external site was 2.7 +/- 0.4 mm (0.1 MPa) and was reduced to 1.45 +/- 0.15 mm (40 MPa), (P < 0.01, Student's t test). Maltose had a biphasic effect on deltaV++. At [maltose] <250 microM, deltaV++ of glucose exit increased above that with [maltose = 0 mM], at >1 mm maltose, deltaV++ was reduced below that with [maltose = 0 mM]. Pentobarbital (2 mM) decreased the deltaV++ of net glucose exit into glucose-free solution from 30 +/- 5 ml mol(-1) (control) to 2 +/- 0.5 ml mol(-1) (P < 0.01). Raised pressure had a negligible effect on L-sorbose exit. These findings suggest that stable hydrated and liganded forms of GLUT with lower affinity towards glucose permit higher glucose mobilities across the transporter and are modelled equally well with one-alternating or a two-fixed-site kinetic models.

Human cervical cancer cells use Ca2+ signalling, protein tyrosine phosphorylation and MAP kinase in regulatory volume decrease

1. This study was aimed at identifying the signalling pathways involved in the activation of volume-regulatory mechanisms of human cervical cancer cells. 2. Osmotic swelling of human cervical cancer cells induced a substantial increase in intracellular Ca2+ ([Ca2+]i) by the activation of Ca2+ entry across the cell membrane, as well as Ca2+ release from intracellular stores. This Ca2+ signalling was critical for the normal regulatory volume decrease (RVD) response. 3. The activation of swelling-activated ion and taurine transport was significantly inhibited by tyrosine kinase inhibitors (genistein and tyrphostin AG 1478) and potentiated by the tyrosine phosphatase inhibitor Na3VO4. However, the Src family of tyrosine kinases was not involved in regulation of the swelling-activated Cl- channel. 4. Cell swelling triggered mitogen-activated protein (MAP) kinase cascades leading to the activation of extracellular signal-regulated kinase 1 and 2 (ERK1/ERK2) and p38 kinase. The volume-responsive ERK1/ERK2 signalling pathway linked with the activation of K+ and Cl- channels, and taurine transport. However, the volume-regulatory mechanism was independent of the activation of p38 MAP kinase. 5. The phosphorylated ERK1/ERK2 expression following a hypotonic shock was up-regulated by protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) and down-regulated by PKC inhibitor staurosporine. The response of ERK activation to hypotonicity also required Ca2+ entry and depended on tyrosine kinase and mitogen-activated/ERK-activating kinase (MEK) activity. 6. Considering the results overall, osmotic swelling promotes the activation of tyrosine kinase and ERK1/ERK2 and raises intracellular Ca2+, all of which play a crucial role in the volume-regulatory mechanism of human cervical cancer cells.

Chondrocyte regulation by mechanical load

The effects of load on articular cartilage are complex. Dynamic loading of cartilage is associated with slight cell and tissue deformation as well as cyclical fluctuations in the hydrostatic pressure of cartilage and in fluid movement. Static loading results in expression of fluid from the tissue, concentrating extracellular matrix macromolecules and consequently increasing the concentrations of cations, reducing extracellular pH and increasing extracellular osmolarity. Each of these alterations is implicated in regulating the synthetic response of chondrocytes to load. However, the mechanisms by which these changes affect matrix turnover are poorly understood. In this review we consider how load may affect chondrocyte behaviour through its influence on membrane transport processes and thus on the intracellular environment.

Variations of intracellular pH in human erythrocytes via K(+)(Na(+))/H(+) exchange under low ionic strength conditions

The change of intracellular pH of erythrocytes under different experimental conditions was investigated using the pH-sensitive fluorescent dye BCECF and correlated with (ouabain + bumetanide + EGTA)-insensitive K(+) efflux and Cl(-) loss. When human erythrocytes were suspended in a physiological NaCl solution (pH(o) = 7.4), the measured pH(i) was 7.19 + or - 0.04 and remained constant for 30 min. When erythrocytes were transferred into a low ionic strength (LIS) solution, an immediate alkalinization increased the pH(i) to 7.70 + or - 0.15, which was followed by a slower cell acidification. The alkalinization of cells in LIS media was ascribed to a band 3 mediated effect since a rapid loss of approximately 80% of intracellular Cl(-) content was observed, which was sensitive to known anion transport inhibitors. In the case of cellular acidification, a comparison of the calculated H(+) influx with the measured unidirectional K(+) efflux at different extracellular ionic strengths showed a correlation with a nearly 1:1 stoichiometry. Both fluxes were enhanced by decreasing the ionic strength of the solution resulting in a H(+) influx and a K(+) efflux in LIS solution of 108.2 + or - 20.4 mmol (l(cells) hr)(-1) and 98.7 + or - 19.3 mmol (l(cells) hr)(-1), respectively. For bovine and porcine erythrocytes, in LIS media, H(+) influx and K(+) efflux were of comparable magnitude, but only about 10% of the fluxes observed in human erythrocytes under LIS conditions. Quinacrine, a known inhibitor of the mitochondrial K(+)(Na(+))/H(+) exchanger, inhibited the K(+) efflux in LIS solution by about 80%. Our results provide evidence for the existence of a K(+)(Na(+))/H(+) exchanger in the human erythrocyte membrane.

Modulation of Na(+) x H(+) exchange by osmotic shock in isolated bovinearticular chondrocytes

The effects of hyperosmotic shock on intracellular pH (pHi) have been characterized in bovine articular chondrocytes. Osmotic shock is one of a variety of physicochemical stimuli experienced by chondrocytes upon cartilage loading. Cells were isolated from their extracellular matrix, and loaded with the pH-sensitive fluorophore 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Hyperosmotic shocks were imposed by addition of KCl or sucrose to the extracellular medium. For cells at steady-state pHi, resuspension in hyperosmotic solutions elicited an alkalinization, which was significantly inhibited by removal of extracellular Na+ ions, or treatment with amiloride (1 mM) or HOE-694 (10 microM), both inhibitors of Na+ x H+ exchange. For cells acidified by ammonium rebound, recovery of pHi towards resting levels was significantly stimulated by exposure to hyperosmotic solutions, and the effect was again attenuated by inhibition of Na+ x H+ exchange. Determination of the rate of acid extrusion at different levels of acidification indicated that the affinity of acid extrusion systems for H+ ions was increased by hypertonic shock. The response to hyperosmotic media could be abolished by treatment of chondrocytes with the non-specific kinase inhibitor staurosporine (10 nM), while the phosphatase inhibitor okadaic acid (1 mM) was able to augment recovery rates to values similar to those measured under hyperosmotic conditions. The osmotic sensitivity of recovery was unaffected by exposure to the protein kinase C inhibitor calphostin C, but was abolished in cells treated with ML-7, a specific inhibitor of myosin light chain kinase. These results confirm that - as for other components of mechanical load - increased osmolarity can modulate the activity of Na+ x H+ exchange, in this case by altered patterns of phosphorylation of transporter-associated myosin. The changes of pHi which will result dictate in part the rate of cartilage macromolecule synthesis.

Neuroleptic-induced striatal damage in rats: a study of antioxidant treatment using accelerometric and immunocytochemical methods

RATIONALE

Investigators have postulated that neuroleptic medications may affect the motor system through the creation of free radicals. Also, structural brain changes related to oxidative damage may disrupt normal striatal function.

OBJECTIVE

The goals of this study were to examine whether an antioxidant diet reduced the abnormal movements caused by long-term neuroleptic exposure and to examine structural effects within specific striatal regions in rats.

METHODS

Rats were given a basal diet or a diet high in antioxidants for 4 months, and treated with 10 mg/kg fluphenazine decanoate or sesame seed oil IM every 2 weeks. At baseline and after treatment, head movements were quantified by accelerometry, and immunocytochemically stained cholinergic neurons in the ventrolateral, mediodorsal, and ventromedial regions of the striatum were quantified.

RESULTS

Rats treated with fluphenazine had significantly lower neuron densities than those that did not receive antioxidants. Rats exposed to a diet consisting of antioxidants had significantly higher neuron densities than those that did not receive antioxidants in each of the three regions tested. Rats treated with fluphenazine had a greater increase in the number of accelerometric peaks recorded per minute compared with untreated animals. The increase in the number of accelerometric peaks recorded per minute was lower for animals exposed to antioxidant diets compared with unexposed animals. Lastly, there was a significant correlation between the accelerometric peak change score and cholinergic neuron density in all three regions.

CONCLUSIONS

Our results suggest that long-term neuroleptic treatment is associated with an increase in head movements and a reduction in ChAT-stained striatal cholinergic neurons and that these abnormalities are reduced by antioxidants.

Neural network analysis of the volumetric capnogram to detect pulmonary embolism

BACKGROUND

Pulmonary embolism (PE) produces ventilation/perfusion mismatch that may be manifested in various variables of the volume-based capnogram (VBC). We hypothesized that a neural network (NN) system could detect changes in VBC variables that reflect the presence of a PE.

METHODS

A commercial VBC system was used to record multiple respiratory variables from consecutive expiratory breaths. Data from 12 subjects (n = 6 PE+ and n = 6 PE-) were used as input to a fully connected back-propagating NN for model development. The derived model was tested in a prospective, observational study at an urban teaching hospital. Volumetric capnograms were then collected on 53 test subjects: 30 subjects with PE confirmed by pulmonary angiography or diagnostic scintillation lung scan, and 23 subjects without PE based on pulmonary angiography. The derived NN model was applied to VBC data from the test population.

RESULTS

Seventeen VBC variables were used by the derived NN model to generate a numeric probability of PE. When the derived NN model was applied to VBC data from the 53 test subjects, PE was detected with a sensitivity of 100% (95% CI = 89% to 100%) and a specificity of 48% (95% CI = 27% to 69%). The likelihood ratio positive [LR(+)] for the VBC-NN test was 1.82 and the LR (-) was 0.1.

CONCLUSION

This study demonstrates the feasibility of developing a rapid, noninvasive breath test for diagnosing PE using volumetric capnography and NN analysis.

Modulation of Na+ x H+ exchange by hydrostatic pressure in isolated bovine articular chondrocytes

The effects of increased hydrostatic pressure on Na+ x H+ exchange activity in bovine articular chondrocytes have been characterized. Chondrocytes were isolated from the cartilage matrix and the cells were loaded with the pH-sensitive fluorophore BCECF. Cells were acidified by ammonium rebound and the rate of recovery of pHi back to control levels was determined using cuvette fluorimetry. The application of hydrostatic pressure (1-300 atm) to cells within the fluorimeter was found to stimulate the rate of recovery from acidification, recorded as proton fluxes, in MOPS buffered media. This increase was dependent on the presence of extracellular Na+ ions and was inhibited by the Na+ x H+ exchange inhibitor EIPA. The pressure-stimulated increase in H+ flux is therefore mediated completely by Na+ x H+ exchange. In addition, the stimulation could be abolished by the kinase inhibitor staurosporine, was not additive with the stimulation of Na+ x H+ exchange elicited by the addition of serum and was unaffected by low concentrations of the myosin light chain kinase inhibitor ML-7. We therefore conclude that hydrostatic pressure activates Na+ x H+ exchange in this cell type by a pathway which involves direct phosphorylation of the transporter protein itself. This is the first demonstration of the activation of Na+ x H+ exchange by hydrostatic pressure and the relevance of this finding to the biology of cartilage tissue is discussed.

One phytopathologist's growth through ipm to holistic plant health: the key to approaching genetic yield potential

I relate my becoming a phytopathologist and my very satisfying growth into and beyond IPM to holistic plant health, and puzzle over paradigms that have prevented our accepting the overwhelming logic of (a) seeking defensible disease-loss data to justify funding and guide research and management priorities, (b) managing genetic diversity to retard pathogen development, (c) conserving genetic diversity in situ, and (d) educating and training general practitioner plant doctors. These multidisciplinary health care professionals are key to overcoming sources of stress that cause major world crops to yield only 15-20% of their genetic potential, on average. Thus, plant doctors give hope for approaching attainable yield and feeding a hungry world-if, simultaneously, human population growth is reduced. The plant health movement has the potential to effect the greatest change in world agriculture since the Green Revolution, and the DPH/M to become plant agriculture's most important single degree program.

The epidemiology of S. sonnei and S. flexneri in Pima County, Arizona: an exploratory study

Investigation of 189 cases of shigellosis reported to the Pima County, Arizona Health Department in 1986 revealed that 23 per cent of cases could be attributed to travel to Mexico, and 10 per cent to day care attendees and their household contacts. No source of infection or high-risk activity could be demonstrated for 43 per cent of the cases. Households in which S. flexneri occurred were more likely to be characterized by crowded living situations and to have no known source of infection.

Risk for measles related to immunization status in two Tucson high schools

An outbreak of measles occurred in Tucson, AZ, in 1985; 112 of the 225 cases were among students at two large high schools. A review of the immunization records of all students at both schools was undertaken in order to assess the risk of a person contracting measles in relation to that person's immunization status. Two factors, the lack of an immunization record and immunization prior to 12 months of age, showed a positive association with contracting measles. The association was statistically significant at one high school but not the other. At the first high school, students who were immunized at 12 to 14 months of age had a greater risk of infection than those immunized at 15 months or older. However, age at immunization of 12 to 14 months was not associated with a significantly higher risk when persons with multiple doses of vaccine were excluded from the analysis. Students of both schools showed a lower attack rate for those who had received multiple doses of vaccine, but the difference was not statistically significant.

The effects of a fluctuating Fio2 on metabolic measurements in mechanically ventilated patients

The determination of minute oxygen consumption (VO2) for metabolic studies on patients using either the Beckman Metabolic Cart (MMC) or the Respiratory Monitoring System (RMS) requires a stable fractional inspired oxygen concentration (FIO2). Measurement of VO2 on mechanically ventilated patients using the Bourns BEAR 1 and the Engstrom 311 and 312 was unsuccessful due to FIO2 variations greater than the acceptable limits. The inspiratory and expiratory O2 and CO2 waveforms were studied using various methods of supplying source gas to the ventilators. A method using an external air/oxygen blender was found that provided a stable FIO2 for metabolic measurements for each of the ventilators tested.