Substance use patterns in 9-10 year olds: Baseline findings from the adolescent brain cognitive development (ABCD) study

BACKGROUND

The Adolescent Brain Cognitive Development ™ Study (ABCD Study®) is an open-science, multi-site, prospective, longitudinal study following over 11,800 9- and 10-year-old youth into early adulthood. The ABCD Study aims to prospectively examine the impact of substance use (SU) on neurocognitive and health outcomes. Although SU initiation typically occurs during teen years, relatively little is known about patterns of SU in children younger than 12.

METHODS

This study aims to report the detailed ABCD Study® SU patterns at baseline (n = 11,875) in order to inform the greater scientific community about cohort's early SU. Along with a detailed description of SU, we ran mixed effects regression models to examine the association between early caffeine and alcohol sipping with demographic factors, externalizing symptoms and parental history of alcohol and substance use disorders (AUD/SUD).

PRIMARY RESULTS

At baseline, the majority of youth had used caffeine (67.6 %) and 22.5 % reported sipping alcohol (22.5 %). There was little to no reported use of other drug categories (0.2 % full alcohol drink, 0.7 % used nicotine, <0.1 % used any other drug of abuse). Analyses revealed that total caffeine use and early alcohol sipping were associated with demographic variables (p's<.05), externalizing symptoms (caffeine p = 0002; sipping p = .0003), and parental history of AUD (sipping p = .03).

CONCLUSIONS

ABCD Study participants aged 9-10 years old reported caffeine use and alcohol sipping experimentation, but very rare other SU. Variables linked with early childhood alcohol sipping and caffeine use should be examined as contributing factors in future longitudinal analyses examining escalating trajectories of SU in the ABCD Study cohort.

Baseline brain function in the preadolescents of the ABCD Study

The Adolescent Brain Cognitive Development (ABCD) Study® is a 10-year longitudinal study of children recruited at ages 9 and 10. A battery of neuroimaging tasks are administered biennially to track neurodevelopment and identify individual differences in brain function. This study reports activation patterns from functional MRI (fMRI) tasks completed at baseline, which were designed to measure cognitive impulse control with a stop signal task (SST; N = 5,547), reward anticipation and receipt with a monetary incentive delay (MID) task (N = 6,657) and working memory and emotion reactivity with an emotional N-back (EN-back) task (N = 6,009). Further, we report the spatial reproducibility of activation patterns by assessing between-group vertex/voxelwise correlations of blood oxygen level-dependent (BOLD) activation. Analyses reveal robust brain activations that are consistent with the published literature, vary across fMRI tasks/contrasts and slightly correlate with individual behavioral performance on the tasks. These results establish the preadolescent brain function baseline, guide interpretation of cross-sectional analyses and will enable the investigation of longitudinal changes during adolescent development.

Relative contribution of clinicopathological variables, genomic markers, transcriptomic subtyping and microenvironment features for outcome prediction in stage II/III colorectal cancer

BACKGROUND

It remains unknown to what extent consensus molecular subtype (CMS) groups and immune-stromal infiltration patterns improve our ability to predict outcomes over tumor-node-metastasis (TNM) staging and microsatellite instability (MSI) status in early-stage colorectal cancer (CRC).

PATIENTS AND METHODS

We carried out a comprehensive retrospective biomarker analysis of prognostic markers in adjuvant chemotherapy-untreated (N = 1656) and treated (N = 980), stage II (N = 1799) and III (N = 837) CRCs. We defined CMS scores and estimated CD8+ cytotoxic lymphocytes (CytoLym) and cancer-associated fibroblasts (CAF) infiltration scores from bulk tumor tissue transcriptomes (CMSclassifier and MCPcounter R packages); constructed a stratified multivariable Cox model for disease-free survival (DFS); and calculated the relative proportion of explained variation by each marker (clinicopathological [ClinPath], genomics [Gen: MSI, BRAF and KRAS mutations], CMS scores [CMS] and microenvironment cells [MicroCells: CytoLym+CAF]).

RESULTS

In multivariable models, only ClinPath and MicroCells remained significant prognostic factors, with both CytoLym and CAF infiltration scores improving survival prediction beyond other markers. The explained variation for DFS models of ClinPath, MicroCells, Gen markers and CMS4 scores was 77%, 14%, 5.3% and 3.7%, respectively, in stage II; and 55.9%, 35.1%, 4.1% and 0.9%, respectively, in stage III. Patients whose tumors were CytoLym high/CAF low had better DFS than other strata [HR=0.71 (0.6-0.9); P = 0.004]. Microsatellite stable tumors had the strongest signal for improved outcomes with CytoLym high scores (interaction P = 0.04) and the poor prognosis linked to high CAF scores was limited to stage III disease (interaction P = 0.04).

CONCLUSIONS

Our results confirm that tumor microenvironment infiltration patterns represent potent determinants of the risk for distant dissemination in early-stage CRC. Multivariable models suggest that the prognostic value of MSI and CMS groups is largely explained by CytoLym and CAF infiltration patterns.

Prediction of overall survival in stage II and III colon cancer beyond TNM system: a retrospective, pooled biomarker study

Background

TNM staging alone does not accurately predict outcome in colon cancer (CC) patients who may be eligible for adjuvant chemotherapy. It is unknown to what extent the molecular markers microsatellite instability (MSI) and mutations in BRAF or KRAS improve prognostic estimation in multivariable models that include detailed clinicopathological annotation.

Patients and methods

After imputation of missing at random data, a subset of patients accrued in phase 3 trials with adjuvant chemotherapy (n = 3016)-N0147 (NCT00079274) and PETACC3 (NCT00026273)-was aggregated to construct multivariable Cox models for 5-year overall survival that were subsequently validated internally in the remaining clinical trial samples (n = 1499), and also externally in different population cohorts of chemotherapy-treated (n = 949) or -untreated (n = 1080) CC patients, and an additional series without treatment annotation (n = 782).

Results

TNM staging, MSI and BRAFV600E mutation status remained independent prognostic factors in multivariable models across clinical trials cohorts and observational studies. Concordance indices increased from 0.61-0.68 in the TNM alone model to 0.63-0.71 in models with added molecular markers, 0.65-0.73 with clinicopathological features and 0.66-0.74 with all covariates. In validation cohorts with complete annotation, the integrated time-dependent AUC rose from 0.64 for the TNM alone model to 0.67 for models that included clinicopathological features, with or without molecular markers. In patient cohorts that received adjuvant chemotherapy, the relative proportion of variance explained (R2) by TNM, clinicopathological features and molecular markers was on an average 65%, 25% and 10%, respectively.

Conclusions

Incorporation of MSI, BRAFV600E and KRAS mutation status to overall survival models with TNM staging improves the ability to precisely prognosticate in stage II and III CC patients, but only modestly increases prediction accuracy in multivariable models that include clinicopathological features, particularly in chemotherapy-treated patients.

Understanding and measuring health care insecurity

PURPOSE

To define the concept of "health care insecurity,” validate a new self-report measure, and examine the impact of beginning care at a free clinic on uninsured patients' health care insecurity.

METHODS

Consecutive new patients presenting at a free clinic completed 15 items assessing domains of health care insecurity (HCI) at their first visit and again four to eight weeks later. Psychometrics and change of the HCI measure were examined.

RESULTS

The HCI measure was found to have high internal consistency (α=0.94). Evidence of concurrent validity was indicated by negative correlation with VR-12 health-related quality of life physical and mental health components and positive correlation with the Perceived Stress Scale. Predictive validity was shown among the 83% of participants completing follow-up: HCI decreased after beginning care at a free clinic (p<.001).

CONCLUSION

Reliably assessing patient experience of health care insecurity is feasible and has potential to inform efforts to improve quality and access to care among underserved populations.

How well do physician and patient visit priorities align?

This study found that there is alignment between a patient's reason for a visit and the physician's main concern 69% of the time. Less than fully aligned priorities were associated with insurance status and the number of problems addressed.

Teachable moments for health behavior change and intermediate patient outcomes

OBJECTIVE

Teachable moments (TM) are opportunities created through physician-patient interaction and used to encourage patients to change unhealthy behaviors. We examine the effectiveness of TMs to increase patients' recall of advice, motivation to modify behavior, and behavior change.

METHODS

A mixed-method observational study of 811 patient visits to 28 primary care clinicians used audio-recordings of visits to identify TMs and other types of advice in health behavior change talk. Patient surveys assessed smoking, exercise, fruit/vegetable consumption, height, weight, and readiness for change prior to the observed visit and 6-weeks post-visit.

RESULTS

Compared to other identified categories of advice (i.e. missed opportunities or teachable moment attempts), recall was greatest after TMs occurred (83% vs. 49-74%). TMs had the greatest proportion of patients change in importance and confidence and increase readiness to change; however differences were small. TMs had greater positive behavior change scores than other categories of advice; however, this pattern was statistically non-significant and was not observed for BMI change.

CONCLUSION

TMs have a greater positive influence on several intermediate markers of patient behavior change compared to other categories of advice.

PRACTICE IMPLICATIONS

TMs show promise as an approach for clinicians to discuss behavior change with patients efficiently and effectively.

Creating a culture of inquiry in family medicine

BACKGROUND AND OBJECTIVES

Strengthening the contribution of reflective practice and new knowledge generation to the learning relationships forged during graduate and undergraduate medical training offers a possibility to create a climate more conducive to the recruitment and retention of family physicians. The Culture of Inquiry (CI) fellowship, an immersive, experientially based training program, combines didactic instruction, workshops, and mentoring to develop the capacity of family medicine's teachers to imagine, implement, and disseminate clinically relevant research and stimulate collaborations with those whom they train. This article outlines the CI fellowship program, summarizes its outcomes, and offers insights about programmatic features contributing to its success.

METHODS

The Department of Family Medicine and Community Health at Case Western Reserve University selected CI fellows from interested local family physicians who train residents and medical students. Over 10 months, with 10% effort expected from fellows, the CI fellowship exposed each fellow to the entire research process and provided technical and logistical support for the design and completion of two research projects. Quantitative and qualitative program evaluation were used to assess outcomes.

RESULTS

Scholarly productivity of fellows exceeded expectations. Collaborations with students and residents produced a ripple effect that amplified the fellowship's impact by strengthening those relationships crucial to the creation of a culture of inquiry among family medicine's teachers, learners, and practitioners.

CONCLUSIONS

The CI fellowship represents a highly replicable program to connect committed and interested clinicians to research mentors with the goal of increasing scholarship and creating a growing culture of inquiry in family medicine.

Direct observation of weight counselling in primary care: alignment with clinical guidelines

Primary care physicians provide care to a disproportionate number of overweight and obese patients and are uniquely positioned to help patients manage their weight in the context of a continuity relationship. The US National Heart, Lung and Blood Institute (NHLBI) developed evidence-based guidelines for the effective and efficient care of overweight/obese patients, but little is known about the use of these guidelines in practice. To determine the content of weight discussions and assess the elements of the NHLBI guidelines that were accomplished, office visits of 544 adult, overweight/obese patients to 28 primary care physicians were observed and audio recorded. Associations between type of weight management discussion and patient, physician and visit characteristics were examined. Fifty per cent (n = 270) of visits included weight discussions; 47% and 38% included use of at least one NHLBI assessment or treatment element during discussions about weight, respectively. Only 35% (n = 193) of discussions included an assessment and treatment strategy; none included all NHLBI-recommended elements. Overall, adherence to guidelines was poor, particularly with regard to reporting body mass index to the patient, measuring waist circumference and setting realistic weight loss goals. Weight discussions did not clearly vary by the patient, physician or visit characteristics examined. These findings suggest opportunities to develop and further tailor resources for improved physician training in patient weight management communication and treatment techniques that are both consistent with current standards for effective, evidence-based care and efficient enough for routine use during busy primary care visits.

A case control study of bacterial species and colony count in milk of breastfeeding women with chronic pain

BACKGROUND

An infectious etiology for chronic breast pain in breastfeeding women continues to be debated. Although recent data suggest that Staphylococcus aureus and coagulase-negative Staphylococcus (CNS) may cause chronic breast pain, no studies have used quantitative cultures to address this question. In this study we compared bacterial species and colony counts between breastfeeding women with (cases) and without (controls) chronic pain.

SUBJECTS AND METHODS

We enrolled 114 breastfeeding women in a prospective cohort study. Cases (n=61), breastfeeding women with breast pain for >1 week and no signs of acute infection, were matched with controls (n=53) by weeks postpartum and parity.

RESULTS

More cases had a history of mastitis (14% vs. 2%, p=0.036), cracked nipples (64% vs. 17%, p=0.001), and other breastfeeding difficulties. Enterobacter species growth was less likely in cases (0% vs. 7.5%, p=0.029). Cases had a significantly higher growth of S. aureus (19.7% vs. 1.9%, p=0.003). CNS frequency was similar between groups (75% vs. 79%, p=0.626), but median colony count growth was significantly lower in cases (900 colony-forming units/mL vs. 5,000 colony-forming units/ml, p=0.003). Growth of CNS and S. aureus was negatively correlated (r=-0.265, p=0.004).

CONCLUSIONS

Higher S. aureus growth in cases supports a pathogenic role for S. aureus and reinforces the need for future antibiotic treatment studies in breastfeeding women with chronic pain. In contrast, similar CNS frequency between groups, lower CNS colony counts in cases, and a negative correlation between S. aureus and CNS growth suggest that neither CNS, nor its overgrowth, causes chronic breast pain.

The effect of insurance-driven medication changes on patient care

PURPOSE

Insurance plans periodically change their formularies to enhance medical efficacy and cost savings. Patients face challenges when formulary changes affect their treatment. This study assessed the impact of insurance-driven medication changes on primary care patients and examined implications for patient care.

METHODS

We mailed questionnaires to a cross-sectional random sample of 1200 adult patients who had visited one of 3 family medicine practices within the past 6 months, asking them to describe problems they had encountered in filling medication prescriptions. We performed descriptive analyses of the frequency and distribution of demographic variables and conditions being treated. Using logistic regression analysis, we identified demographic and health-related variables independently associated with patient-reported problems caused by formulary changes.

RESULTS

Three variables-a greater number of prescription medications taken, younger patient age, and reliance on government insurance-were independently associated with an increased likelihood of encountering a problem filling a medication. Patients who reported an insurance-related issue filling a new or existing prescription over the past year (23%) encountered an average of 3 distinct problems. Patients experienced adverse medical outcomes (41%), decreased satisfaction with the health care system (68%), and problems that burdened the physician practice (83%). Formulary changes involving cardiac/hypertension/lipid and neurologic/psychiatric medications caused the most problems.

CONCLUSIONS

Insurance-driven medication changes adversely affect patient care and access to treatment, particularly for patients with government insurance. A better understanding of the negative impact of formulary changes on patient care and indirect health care expenditures should inform formulary change practices in order to minimize cost-shifting and maximize continuity of care.

A Teachable Moment Communication Process for smoking cessation talk: description of a group randomized clinician-focused intervention

BACKGROUND

Effective clinician-patient communication about health behavior change is one of the most important and most overlooked strategies to promote health and prevent disease. Existing guidelines for specific health behavior counseling have been created and promulgated, but not successfully adopted in primary care practice. Building on work focused on creating effective clinician strategies for prompting health behavior change in the primary care setting, we developed an intervention intended to enhance clinician communication skills to create and act on teachable moments for smoking cessation. In this manuscript, we describe the development and implementation of the Teachable Moment Communication Process (TMCP) intervention and the baseline characteristics of a group randomized trial designed to evaluate its effectiveness.

METHODS/DESIGN

This group randomized trial includes thirty-one community-based primary care clinicians practicing in Northeast Ohio and 840 of their adult patients. Clinicians were randomly assigned to receive either the Teachable Moments Communication Process (TMCP) intervention for smoking cessation, or the delayed intervention. The TMCP intervention consisted of two, 3-hour educational training sessions including didactic presentation, skill demonstration through video examples, skills practices with standardized patients, and feedback from peers and the trainers. For each clinician enrolled, 12 patients were recruited for two time points. Pre- and post-intervention data from the clinicians, patients and audio-recorded clinician‒patient interactions were collected. At baseline, the two groups of clinicians and their patients were similar with regard to all demographic and practice characteristics examined. Both physician and patient recruitment goals were met, and retention was 96% and 94% respectively.

DISCUSSION

Findings support the feasibility of training clinicians to use the Teachable Moments Communication Process. The next steps are to assess how well clinicians employ these skills within their practices and to assess the effect on patient outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01575886.

Integrating routine lactation consultant support into a pediatric practice

BACKGROUND

Although research shows that healthcare professionals' support improves breastfeeding duration, many physicians do not believe they have adequate time to address breastfeeding concerns during office visits. This study evaluated the impact of a pediatric practice's postnatal lactation consultant intervention. To improve breastfeeding support, the study practice changed policy and began using a lactation consultant overseen by a physician, to conduct the initial postpartum office visit for all breastfeeding infants.

METHODS

A retrospective chart review was performed on consecutive newborns before (n = 166) and after (n = 184) implementation of the program. Feeding method was assessed at each well child visit during the infant's first 9 months. χ² and logistic growth curve analyses were used to test the association between implementation status and non-formula feeding (NFF).

RESULTS

Mothers and infants in 2007 and 2009 were similar with regard to type of insurance, parity, gestational age, multiple births, and cesarean sections. Overall, NFF improved after program implementation (odds ratio = 1.12, 95% confidence interval 1.02-1.23). In 2009, NFF rates at 2 months, 4 months, 6 months, and 9 months were greater than 2007 rates by 10%, 15%, 11%, and 9%, respectively. Logistic growth curve analysis indicated the difference across these time points was significant between 2007 and 2009.

CONCLUSION

A routine post-discharge outpatient lactation visit coordinated within a primary care practice improved breastfeeding initiation and intensity. This effect was sustained for 9 months.

Monitoring the intracellular store Ca2+ concentration in agonist-stimulated, intact human platelets by using Fluo-5N

BACKGROUND

Most Ca(2+) signaling research in platelets has relied solely on monitoring the cytosolic Ca(2+) concentration ([Ca(2+)](cyt)). Changes in [Ca(2+)](cyt) constitute the net effect of Ca(2+) fluxes into the cytosol across the plasma membrane (PM) and from intracellular stores, and Ca(2+) sequestration into the stores and Ca(2+) removal across the PM. This makes interpretation of the effects of pharmacologic or genetic interventions on Ca(2+) signaling difficult and subject to error.

OBJECTIVES

To validate the use of the low-affinity Ca(2+) indicator Fluo-5N to monitor the concentration of Ca(2+) in the intracellular stores ([Ca(2+)](st)) of human platelets as a first step in developing assays for a systems-level analysis of platelet Ca(2+) signaling.

METHODS

Fluo-5N-loaded and Fura-2-loaded human platelets were used to observe the effects of agonist stimulation and other manipulations on [Ca(2+)](cyt) and [Ca(2+)](st).

RESULTS

Fluo-5N fluorescence changed appropriately in response to compounds that induce passive depletion of intracellular Ca(2+) stores and to physiologic agonists. Ca(2+) reuptake inhibitors and blockers of Ca(2+) release channels had the expected effects on Fura-2 and Fluo-5N fluorescence. Agonist-evoked Ca(2+) release was reversed by Ca(2+) addition to the medium, and required intact Ca(2+) reuptake mechanisms. Store refilling was observed in the presence of sarcoplasmic/endoplasmic reticulum Ca(2+) -ATPase (SERCA) inhibitors and ionomycin, suggesting the presence of a non-SERCA Ca(2+) reuptake mechanism. Evidence for a role for Ca(2+) -induced Ca(2+) release in agonist-evoked responses was obtained.

CONCLUSIONS

Our data provide a validation of the use of Fluo-5N as a method for monitoring changes in [Ca(2+)](st) in human platelets.

Phorbol ester-evoked Ca2+ signaling in human platelets is via autocrine activation of P(2X1) receptors, not a novel non-capacitative Ca2+ entry

SUMMARY BACKGROUND

Platelets are reported to possess a protein kinase C (PKC)-dependent non-capacitative Ca(2+)entry (NCCE) pathway. The phorbol ester, phorbol, 12-myristate, 13-acetate (PMA) has been suggested to stimulate platelet NCCE. Recently we demonstrated important roles in store-operated Ca(2+)entry in human platelets for Na(+)/Ca(2+) exchangers (NCXs) and autocrine signaling between platelets after dense granule secretion. As PMA evokes dense granule secretion, we have investigated the role of NCXs and autocrine signaling in PMA-evoked Ca(2+)entry.

OBJECTIVES

To investigate the roles of NCXs and dense granule secretion in PMA-evoked Ca(2+)signaling in human platelets.

METHODS

Fura-2- or sodium-binding benzofuran isophthalate (SBFI)-loaded platelets were used to monitor cytosolic Ca(2+)or Na(+) concentrations. Dense granule secretion was monitored as ATP release using luciferin-luciferase.

RESULTS

The NCX inhibitors KB-R7943 or SN-6, and removal of extracellular Na(+), significantly reduced PMA-evoked Ca(2+)entry. PMA-evoked dense granule secretion was almost abolished by pretreatment with the PKC inhibitor Ro-31-8220 and significantly slowed by KB-R7943. The P(2X1) antagonists Ro-0437626 or MRS-2159, or desensitization of P(2X1) receptors by prior treatment with alpha,beta-Methylene-ATP or omitting apyrase from the medium, reduced PMA-evoked Ca(2+)entry. Ro-0437626 or chelation of extracellular Ca(2+) slowed but did not abolish PMA-evoked ATP release, indicating that PMA-evoked dense granule secretion does not require P(2X1) receptor activation but is accelerated by P(2X1)-mediated Ca(2+)entry. The presence of NCX3 in human platelets was demonstrated by Western blotting.

CONCLUSION

PMA-evoked Ca(2+)entry results from an NCX3-dependent dense granule secretion and subsequent P(2X1) receptor activation by secreted ATP, rather than activation of a novel NCCE pathway.

The effect of auditory stimulation on the tensor tympani in patients following stapedectomy

CONCLUSION

We believe that a tensor tympani reflex, in response to loud sound, is present in a minority of people, although its functional significance with regard to sound transmission is questionable. The absence of startle response in our stapedectomized subjects makes us question whether the tensor component of the startle response is large enough to be identified by manometry.

OBJECTIVES

This study was organized to examine reflex activity to stimulation by loud sound or by startle in the tensor tympani. Although many previous studies have been carried out, results have been contradictory, and methodological flaws have rendered the interpretations questionable.

PATIENTS AND METHODS

Stapedectomized patients were invited to take part in the study. Thirteen patients underwent testing by extratympanic manometry, using a standard tympanometer. Responses were observed during repeated stimuli with loud sound at 500, 1000, 2000 and 4000 Hz to the ipsilateral and contralateral ears, and with an air jet against the closed eye. A control group was also studied for the startle test.

RESULTS

Three clear ipsilateral (23%) and two clear contralateral (14%) responses to auditory stimuli were seen in the 13 patients. We found responses to startle stimuli in none of our study group and eight (42%) of control ears.

Differential role of cation and anion exchange in lymphocyte pH regulation

In lymphocytes, the Na+/H+ antiport is well suited to function in cytoplasmic pH (pHi) regulation. It is activated by departures from the physiological pHi and is thermodynamically poised to compensate for the tendency of the cells to become acidic. The driving force for H+ (equivalent) efflux is indirectly provided by the Na+ pump. Lymphocytes also possess a cation-independent anion (Cl-/HCO3-) exchange system, which, under the appropriate conditions, tends to restore pHi after an alkali load. Unlike the cation antiport, the source of energy driving the anion exchanger, i.e. the factors that determine the transmembrane Cl- distribution, is not well understood. The contribution of conductive pathways appears to be minimal, resulting in a marked difference between the membrane potential and ECl-. Instead, ECl- is very similar to EH+. Moreover, changes in the distribution of Cl- lead to alterations in the transmembrane delta pH and vice versa, suggesting a relationship between these parameters. Evidence is presented which suggests that the transmembrane distribution of HCO3-, dictated by delta pH, is a major determinant of the intracellular Cl- concentration, a process mediated by the anion exchanger. Thus, if Cl- is driven by the gradient of HCO3-, the cation-independent anion exchanger cannot play an active role in determining pHi. Instead, Cl-/HCO3- exchange may simply stabilize pHi by increasing the dynamic buffering power of the cells. Cation-independent Cl-/HCO3- exchange could be involved in pHi regulation only if coupled to a separate mechanism of intracellular Cl- accumulation, such as Na+-K+-2Cl- co-transport or an inward Cl- pump, which have not been detected in lymphoid cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Antecedent moisture and seasonal precipitation influence the response of canopy-scale carbon and water exchange to rainfall pulses in a semi-arid grassland

The influences of prior monsoon-season drought (PMSD) and the seasonal timing of episodic rainfall ('pulses') on carbon and water exchange in water-limited ecosystems are poorly quantified. *In the present study, we estimated net ecosystem exchange of CO(2) (NEE) and evapotranspiration (ET) before, and for 15 d following, experimental irrigation in a semi-arid grassland during June and August 2003. Rainout shelters near Tucson, Arizona, USA, were positioned on contrasting soils (clay and sand) and planted with native (Heteropogon contortus) or non-native invasive (Eragrostis lehmanniana) C4 bunchgrasses. Plots received increased ('wet') or decreased ('dry') monsoon-season (July-September) rainfall during 2002 and 2003. Following a June 2003 39-mm pulse, species treatments had similar NEE and ET dynamics including 15-d integrated NEE (NEE(pulse)). Contrary to predictions, PMSD increased net C uptake during June in plots of both species. Greater flux rates after an August 2003 39-mm pulse reflected biotic activity associated with the North American Monsoon. Furthermore, August NEE(pulse) and ecosystem pulse-use efficiency (PUE(e) = NEE(pulse)/ET(pulse)) was greatest in Heteropogon plots. PMSD and rainfall seasonal timing may interact with bunchgrass invasions to alter NEE and ET dynamics with consequences for PUE(e) in water-limited ecosystems.

The interpretation of current-clamp recordings in the cell-attached patch-clamp configuration

In these experiments we have investigated the feasibility and accuracy of recording steady-state and dynamic changes in transmembrane potential noninvasively across an intact cell-attached patch using the current-clamp mode of a conventional patch-clamp amplifier. Using an equivalent circuit mimicking simultaneous whole-cell voltage-clamp and cell-attached current-clamp recordings we have defined both mathematically and experimentally the relationship between the membrane patch resistance, the seal resistance, and the fraction of the whole-cell potential recorded across an intact membrane patch. This analysis revealed a steep increase in the accuracy of recording of steady-state membrane potential as the seal/membrane ratio increases from 0. The recording accuracy approaches 100% as the seal/membrane ratio approaches infinity. Membrane potential measurements across intact cell-attached patches in rat basophilic leukemia cells and rat megakaryocytes revealed a surprisingly high degree of accuracy and demonstrated the ability of this noninvasive technique to follow dynamic changes in potential in nonexcitable cells.

Sex differences in the middle ear of the bullfrog (Rana catesbeiana)

Impedance transformation by the middle ear of terrestrial vertebrates is considered to be a function of the ossicular lever apparatus, which increases force and decreases velocity at the stapes footplate relative to the tympanic membrane, and the ratio of tympanic membrane area to stapes footplate area (the area ratio), which increases pressure at the stapes. A recent vibrometric study has found that the velocity ratio between tympanic membrane and stapes footplate is higher in male bullfrogs (Rana catesbeiana) than in females. Although the tympanic membrane area is known to be larger in male bullfrogs, the area ratio has apparently never been compared between the sexes. The hypothesis that a lower area ratio in males helps to compensate for the higher velocity ratio was investigated by comparing tympanic membrane, stapes footplate and operculum areas in frogs of both sexes. Contrary to expectation, the difference in stapes footplate area between males and females is very small, and area ratios are considerably higher in males. Area ratios increase with increasing body size in both sexes. Operculum area does not differ between the sexes. The apparent difference in impedance transformation between male and female frogs might be necessary due to different inner ear impedances, or might reflect serious inadequacies in the conventional models of middle ear function.

Depolarisation-evoked Ca2+ waves in the non-excitable rat megakaryocyte

1. A combination of patch clamp, confocal microscopy and immunohistochemistry was used to examine the spatial properties of Ca2+ signalling in the rat megakaryocyte, a non-excitable cell type in which membrane potential can markedly modulate agonist-evoked Ca2+ release. 2. Intracellular calcium ion concentration ([Ca2+]i) increases, stimulated by both ADP and depolarisation, frequently originated from a peripheral locus and spread as a wave throughout the cell. Spatially restricted [Ca2+]i increases, consistent with elementary Ca2+ release events, were occasionally observed prior to ADP-evoked waves. 3. ADP- and depolarisation-evoked Ca2+ waves travelled approximately twice as fast around the periphery of the cell compared to across its radius, leading to a curvilinear wavefront. There was no significant difference between wave velocities generated by the two stimuli. 4. Immunohistochemical staining of type III IP3 receptors, the endoplasmic reticulum-specific protein GRP78/BiP and calreticulin indicated a major peripheral location of the cellular Ca2+ stores which probably accounts for the accelerated wave velocity at the cell periphery. 5. These data demonstrate that [Ca2+]i increases, stimulated by depolarisation or the agonist ADP, have indistinguishable spatial properties, providing evidence that similar underlying mechanisms are responsible for their generation.

Investigation of Head Injury Mechanisms Using Neutral Density Technology and High-Speed Biplanar X-ray

The principal focus of this study was the measurement of relative brain motion with respect to the skull using a high-speed, biplanar x-ray system and neutral density targets (NDTs). A suspension fixture was used for testing of inverted, perfused, human cadaver heads. Each specimen was subjected to multiple tests, either struck at rest using a 152-mm-diameter padded impactor face, or stopped against an angled surface from steady-state motion. The impacts were to the frontal and occipital regions. An array of multiple NDTs was implanted in a double-column scheme of 5 and 6 targets, with 10 mm between targets in each column and 80 mm between columns. These columns were implanted in the temporoparietal and occipitoparietal regions. The impacts produced peak resultant accelerations of 10 to 150 g, and peak angular accelerations between 1000 and 8000 rad/s(2). For all but one test, the peak angular speeds ranged from 17 to 22 rad/s. The relative 3D displacements between the skull and the NDTs were analyzed. The localized motions of the brain generally followed loop or figure eight patterns, with peak displacements on the order of +/- 5 mm. These results can be used to further finite-element modeling efforts.

Voltage-dependent Ca2+ release in rat megakaryocytes requires functional IP3 receptors

Using simultaneous whole-cell patch-clamp and fluorescence measurements of [Ca2+]i in rat megakaryocytes we have investigated the requirement for functional inositol 1,4,5-trisphosphate (IP3) receptors in Ca2+ release induced by membrane depolarization during agonist stimulation. Voltage-dependent Ca2+ release was observed during application of the IP3-generating agonists U46619 (a thromboxane A2 analogue) and ADP. Furthermore, voltage-dependent Ca2+ release was observed in the absence of exogenous agonist following sensitization of IP3 receptors with thimerosal. Depolarization-induced Ca2+ release was not detected during depletion of intracellular Ca2+ stores by thapsigargin. Thus, depletion of stores alone is not sufficient to confer voltage dependence upon the Ca2+ release mechanism. Block of IP3 receptors by carbacyclin-stimulated elevations in cAMP, uncaging of cAMP or exposure to a high concentration of caffeine reversibly abolished Ca2+ increases stimulated by both ADP and depolarization. The cAMP-dependent block was prevented by a peptide inhibitor of protein kinase A, indicating that an alteration of adenylate cyclase activity leading to modulation of protein kinase A activity does not underlie the control of Ca2+ release by voltage. These results are consistent with the requirement for functional IP3 receptors for voltage control of Ca2+ release from intracellular stores during inositol lipid signalling. The data also indicate the involvement of a voltage sensor downstream of surface membrane receptors in the depolarization-evoked Ca2+ response.

A study of the corrosion products of mild steel in high ionic strength brines

The corrosion layer on steel surfaces that formed after exposure to waste isolation pilot plant (WIPP) brines under anoxic conditions was characterized for chemical composition, thickness and phase composition. The chemical composition of the corrosion layer was determined both by X-ray photoelectron spectroscopy (XPS) and by chemical analysis of acid solutions used to remove the corrosion layer. Atomic force microscopic (AFM) images indicated that the brine-corroded surface layer shows extensive granulation along the contours of the steel surface that is characteristic of sharp polishing marks. The corrosion layer seemed to be porous and could be dissolved and detached in dilute hydrochloric acid. The corrosion layer appears to be composed of iron oxides with some ionic substitutions from the brines. The 77 K Mössbauer spectrum recorded for iron powder leached under similar conditions indicated the corrosion layer was comprised principally of green rust.

Influence of clinical and angiographic factors on development of collateral channels

BACKGROUND

The degree of coronary collateralization is believed to be related to several clinical and angiographic factors. The duration and frequency of angina may be important factors in determining development of collateral channels.

OBJECTIVE

To assess these factors for a consecutive series of patients suspected to have coronary artery disease.

METHODS

Patients without at least one stenosis of < 50% and patients who had previously undergone bypass surgery were excluded from our study. Severity of stenosis was quantified by digital analysis, antegrade flow in terms of TIMI grade, and collaterals using the Rentrop classification.

RESULTS

We reviewed 106 patients [mean age 61 years (range 35-84), 77.6% men]. Of these, 22 (21%) had presented with an acute coronary syndrome on this admission, whilst 46 patients (43%) had previously had an acute coronary syndrome. Collaterals were more likely in patients with stenoses of > 90% (Spearman correlation 0.65, P < 0.001) in patients with lower than normal TIMI flow grade (Spearman correlation 0.86, P < 0.01) and were related to regions of hypokinesis (Spearman correlation 0.35, P < 0.01). Significant collaterals were present in 14 patients (13%) despite their having TIMI grade II/III flow. Two of these patients had grade 2/3 collaterals with TIMI grade II/III antegrade flow. Degree of collateralization was not related to chronicity and frequency of symptoms, age, risk factors for atherosclerosis and nature of presentation (i.e. acute or stable symptoms).

CONCLUSION

The likelihood of coronary collateralization cannot be prospectively predicted from clinical history alone, but appears to be largely a function of severity of stenosis and level of antegrade flow. A few patients develop high-grade collateral channels despite the presence of good antegrade flow.

A novel role for membrane potential in the modulation of intracellular Ca2+ oscillations in rat megakaryocytes

1. The effect of membrane potential (Vm) on ADP-evoked [Ca2+]i oscillations was investigated in rat megakaryocytes, a non-excitable cell type recently shown to exhibit depolarisation-evoked Ca2+ release from intracellular stores during metabotropic purinoceptor stimulation. 2. Hyperpolarising voltage steps caused a transient fall in [Ca2+]i and either abolished Ca2+ oscillations or reduced the oscillation amplitude. These effects were observed in both the presence and absence of extracellular Ca2+ and also in Na+-free saline solutions, suggesting that hyperpolarisation leads to a reduction in the level of ADP-dependent Ca2+ release without a requirement for altered transmembrane Ca2+ fluxes. 3. In the presence of Ca2+ oscillations, depolarising voltage steps transiently enhanced the amplitude of Ca2+ oscillations. Following run-down of Ca2+ oscillations, depolarisation briefly restimulated oscillations. 4. Simultaneous [Ca2+]i and current-clamp recordings showed that Ca2+ and Vm oscillate in synchrony, with an average fluctuation of approximately 30-40 mV, due to activation and inactivation of Ca2+-dependent K+ channels. Application of a physiological oscillating Vm waveform to non-oscillating cells under voltage clamp stimulated [Ca2+]i oscillations. 5. Analysis of the relationship between [Ca2+]i and Vm showed a threshold for activation of hyperpolarisation at about 250-300 nM. The implications of this threshold in the interaction between Vm and Ca2+ release during oscillations are discussed. 6. We conclude that the ability of voltage to control release of endosomal Ca2+ in ADP-stimulated megakaryocytes is bipolar in nature. Our data suggest that Vm changes are active components of the feedback/feedforward mechanisms contributing to the generation of Ca2+ oscillations.

Substance P activates NF-kappaB independent of elevations in intracellular calcium in murine macrophages and dendritic cells

Professional antigen presenting cells, such as macrophages, can be activated by intracellular calcium-dependent as well as calcium-independent mechanisms, depending upon the stimulus used. In this report, we addressed the mechanism of substance P-induced intracellular signalling in murine macrophages and dendritic cells. While no increases in intracellular calcium concentration were detected in macrophages or dendritic cells using sensitive fluorimetric techniques, substance P did induce rapid enhanced activation of NF-kappaB, a transcriptional activator known to regulate pro-inflammatory cytokines. These data provide an important mechanism by which substance P may augment the production of pro-inflammatory molecules.

Clinical mental health training within a multidisciplinary school-based health clinic

A model is presented to illustrate a clinical mental health training program within a multidisciplinary School-Based Health Clinic (SBHC). In collaboration with schools of education, medicine, nursing, and social work, a multidisciplinary training and treatment program was established that provided unique opportunities for clinical training. An ecological/public health model was utilized as the conceptual framework for clinical mental health training, treatment, and research. Preliminary clinical outcome data suggest that out of a sample of 381 patients, 15% of those utilizing the SBHC's mental health services were being treated for substance abuse disorders. This finding supports current research that has demonstrated that the SBHCs are providing access to students who are in the most serious need to mental health services. Process data suggest that the SBHC is an effective site for multidisciplinary clinical mental health training.

Isolation of sublethally injured campylobacters from poultry and water sources

Campylobacters are the most common cause of bacterial food poisoning in the UK and are prominent in many other countries worldwide. Sources that have acted as vehicles of infection in many outbreaks include milk, water and poultry, and these may contain campylobacter cells that are sublethally injured and not detected by routine laboratory techniques. Current culture media contain antibiotics to suppress competing flora, and injured campylobacter cells are more sensitive to the antibiotics used and may not grow in these selective media. Therefore, the use of selective broth as the primary culture medium may reduce the isolation rate from samples containing injured cells. To examine this, various experiments were carried out using naturally contaminated river water and fresh chicken samples. In these samples, campylobacter cells showed varying degrees of sublethal injury, with the greatest found in water. A delay of four to eight hours before adding antibiotics to broth significantly increased isolation rate, compared with direct culture in selective broth. With chicken, however, significantly better results were obtained with selective broth as the primary medium.

Transitional changes in membrane potential and intracellular [Ca2+] in rat basophilic leukemia cells

Using whole-cell current-clamp measurements we have found that thapsigargin-mediated activation of store-regulated Ca2+ entry in rat basophilic leukemia cells is accompanied by complex changes in membrane potential. These changes consisted of: (i) an initial slow, small depolarization, (ii) a transitional change in potential to a depolarized value and (iii) transitional changes between a hyperpolarized and a depolarized potential. These complex changes in potential can be explained by the interaction between the endogenous inwardly rectifying K+ conductance and the generation of a small inward current. To investigate the possible influence of these changes of potential on [Ca2+]i, single cell measurements of fura2 fluorescence were undertaken alone or in combination with current-clamp measurements. Thapsigargin-mediated activation of the store-regulated Ca2+ entry pathway was accompanied by a marked increase of [Ca2+]i. During this increase, transient, abrupt declines in [Ca2+]i were detected in approximately 60% of the cells investigated. These changes of [Ca2+]i are consistent with the observed changes of membrane potential recorded under current-clamp.

Stabilisation of medically refractory ventricular arrhythmia by intra-aortic balloon counterpulsation

OBJECTIVE

To review the efficacy of intra-aortic balloon counterpulsation (IABCP) in medically refractory ventricular arrhythmia.

DESIGN

Retrospective analysis of the outcome of patients with ventricular arrhythmia treated with IABCP after transfer between 1992 and 1997.

SETTING

Tertiary cardiac referral centre.

PATIENTS

21 patients (mean age 58 years) who underwent IABCP for control of ventricular arrhythmia. All had significant left ventricular impairment (mean ejection fraction 28.6%); 18 had coronary artery disease.

RESULTS

Before IABCP, 10 patients had incessant monomorphic ventricular tachycardia and 11 had paroxysmal ventricular tachycardia and/or ventricular fibrillation (VT/VF). IABCP resulted in suppression of ventricular arrhythmia in 18 patients, of whom 13 were weaned from IABCP. After stabilisation of ventricular arrhythmia, 10 patients were maintained on medical treatment alone and one underwent endocardial resection. IABCP was maintained until cardiac transplantation in five patients. One patient had a fatal arrest before discharge and one died from progressive heart failure. IABCP failed to control ventricular arrhythmia in three patients and was subsequently discontinued. A cardiac assist device was employed in one of these until cardiac transplantation; the other two were eventually stabilised on medical treatment. Nineteen patients were discharged from hospital. Overall survival was 95% at mean follow up of 25.7 months.

CONCLUSIONS

IABCP can be an effective means of controlling refractory ventricular arrhythmia, allowing time for the institution of more definitive treatment.

Depolarization-evoked Ca2+ release in a non-excitable cell, the rat megakaryocyte

1. The effect of membrane potential on [Ca2+]i in rat megakaryocytes was studied using simultaneous whole-cell patch clamp and fura-2 fluorescence recordings. 2. Depolarization from -75 to 0 mV had no effect on [Ca2+]i in unstimulated cells, but evoked one or more spikes of Ca2+ increase (peak increase: 714 +/- 95 nM) during activation of metabotropic purinoceptors by 1 microM ADP. 3. The depolarization-evoked Ca2+ increase was present in Ca2+-free medium and also following removal of Na+. Thus depolarization mobilizes Ca2+ from an intracellular store without a requirement for altered Na+-Ca2+ exchange activity. 4. Intracellular dialysis with heparin blocked the depolarization-evoked Ca2+ increase, indicating a role for functional IP3 receptors. 5. Under current clamp, ADP caused the membrane potential to fluctuate between -43 +/- 1 and -76 +/- 1 mV. Under voltage clamp, depolarization from -75 to -45 mV evoked a transient [Ca2+]i increase (398 +/- 91 nM) during exposure to ADP. 6. We conclude that during stimulation of metabotropic purinoceptors, membrane depolarization over the physiological range can stimulate Ca2+ release from intracellular stores in the rat megakaryocyte, a non-excitable cell type. This may represent an important mechanism by which electrogenic influences can control patterns of [Ca2+]i increase.

Differential kinetics for induction of interleukin-6 mRNA expression in murine peritoneal macrophages: evidence for calcium-dependent and independent-signalling pathways

It is presently unclear what role elevations in intracellular calcium concentration ([Ca2+]i) play in the control of monokine secretion, or whether such alterations underlie the ability of physiologic stimuli to induce production of these important signalling molecules. To address these issues, we have performed experiments in murine peritoneal macrophages to determine whether lipopolysaccharide (LPS) or interferon gamma (IFN-gamma) initiate production of the proinflammatory monokine interleukin 6 (IL-6) concomitant with elevations in [Ca2+]i and with kinetics similar to that seen with known Ca2+ mobilizing agents. Alterations in [Ca2+]i after treatment with LPS, IFN-gamma, platelet activating factor (PAF), or thapsigargin were measured by fluorimetric methods. These effects were compared with the ability of each to induce IL-6 mRNA expression as measured by semiquantitative reverse-transcribed polymerase chain reactions. We report that neither LPS nor IFN-gamma elicited detectable elevations in [Ca2+]i but that both up-regulated expression of IL-6 mRNA expression within 60 min. In contrast, experiments using either thapsigargin or PAF showed rapid and dramatic elevations in [Ca2+]i with marked increases in IL-6 mRNA expression, as quickly as 15 min after initial exposure. Elevations in mRNA encoding IL-6 by thapsigargin and PAF were found to occur in a dose-dependent manner, mirroring their ability to elicit elevations in [Ca2+]i. These data demonstrate that LPS and IFN-gamma induce IL-6 message expression by means of Ca2+-independent signalling pathways. Furthermore, Ca2+-mobilizing agents that evoke monokine message expression do so far more rapidly than do LPS or IFN-gamma. Taken in concert, these data are consistent with the hypothesis that multiple signalling pathways exist by which production of proinflammatory monokines are initiated.

School-based health clinics and the role of mental health services: a review of the literature

A review of school-based health clinics is provided with special attention to the role of mental health services. An historical account of the development of school-based health clinics is delineated as well as a description of school-based health clinics' purpose and unique role in providing health care for children and adolescents. Critical policy issues are reviewed, such as managed care's role in the school-based health clinics, research issues, and funding concerns.

Thrombin-dependent calcium signalling in single human erythroleukaemia cells

1. A combination of single cell fluorescence and patch clamp techniques were used to study the mechanisms underlying thrombin-evoked Ca2+ signals in human erythroleukaemia (HEL) cells, a leukaemic cell line of platelet-megakaryocyte lineage. 2. Thrombin caused a transient increase in intracellular Ca2+ ([Ca2+]i), consisting of both release of Ca2+ from intracellular stores and influx of extracellular Ca2+. Mn2+ quench studies indicated that the thrombin-evoked divalent cation-permeable pathway was activated during, but not prior to, release from internal stores. 3. Thapsigargin (1 microM) irreversibly released internal Ca2+ from the same store as that released by thrombin and continuously activated a Ca(2+)-influx mechanism. The amplitude of the thrombin- and thapsigargin-induced Ca2+ influx displayed a marked single cell heterogeneity which showed no correlation with the size of the store Ca2+ transient. 4. In whole-cell patch clamp recordings, both thrombin and thapsigargin evoked an inwardly rectifying Ca2+ current which developed with little or no increase in current noise, showed no reversal in the voltage range -110 to +60 mV and was blocked by 1 mM Zn2+. The apparent divalent cation permeability sequence of this pathway was Ca2+ > > Ba2+ > Mn2+, Mg2+. The thapsigargin-evoked current density at -100 mV varied between 0.42 and 2.1 pA pF-1 in different cells. Thrombin failed to activate additional Ca2+ current if it was added after the thapsigargin-induced inward current had fully developed. 5. These studies indicate that thrombin activates Ca2+ influx in HEL cells entirely via a Ca(2+)-store-release-activated Ca2+ current (Icrac) rather than via receptor-operated or second messenger-dependent Ca2+ channels. The level of expression of Icrac appears to be a major factor in determining the duration of the thrombin-evoked [Ca2+]i response and therefore represents a means by which cells can exert control over [Ca2+]i-dependent events.

Agonist-induced calcium regulation in freshly isolated renal microvascular smooth muscle cells

The studies presented here were performed to determine the effect of agonist stimulation on the cytosolic free Ca2+ concentration ([Ca2+]i) in single smooth muscle cells, freshly isolated from afferent arterioles and interlobular arteries averaging between 10 to 40 microns in diameter. Microvessels were obtained from male Sprague-Dawley rats using an iron oxide collection technique followed by collagenase digestion. Freshly isolated microvascular smooth muscle cells (MVSMC) were loaded with fura 2 and studied using fluorescence photometry techniques. The resting [Ca2+]i averaged 67 +/- 3 nM (N = 82 cells). Increasing the extracellular K+ concentration significantly increased [Ca2+]i dose-dependently (P < 0.05). Involvement of extracellular Ca2+ in the response to KCl-induced depolarization was also evaluated. Resting [Ca2+]i increased approximately 132% from 40 +/- 5 nM to 93 +/- 26 nM in response to 90 mM extracellular KCl. This change was abolished in nominally Ca(2+)-free conditions and markedly attenuated by diltiazem. Inhibition of K+ channels with charybdotoxin or tetraethylammonium chloride produced a modest transient increase in [Ca2+]i during the response to 30 mM K+ and had no detectable effect on responses to 90 mM K+. Studies were also performed to establish whether freshly isolated renal MVSMC exhibit appropriate responses to receptor-dependent physiological agonists. Angiotensin II (100 nM) increased cell Ca2+ from 97 +/- 10 nM to 265 +/- 47 nM (N = 12 cells). Similarly, 100 microM ATP increased MVSMC [Ca2+]i from a control level of 71 +/- 14 nM to 251 +/- 47 nM (N = 11 cells). Norepinephrine administration caused [Ca2+]i to increase from 63 +/- 4 nM to 212 +/- 47 nM (N = six cells), and vasopressin increased [Ca2+]i from 86 +/- 10 nM to 352 +/- 79 nM (N = five cells). These data demonstrate that receptor-dependent and -independent vasoconstrictor agonists increase [Ca2+]i in MVSMC, freshly isolated from rat preglomerular vessels. Furthermore, the ability to measure [Ca2+]i in responses to physiological stimuli in these single cells permits investigation of signal transduction mechanisms involved in regulating renal microvascular resistance.

Patterns of service utilization for Mexican American majority students who use alcohol or other drugs

A substance use and attitude survey was given to 436 students ranging in grades from fourth to twelfth in a Southwestern United States school district. Unique features of this district include a student body that is 90% Mexican American and the proximity to the Mexico border. The data revealed that eighth grade students were significantly more likely to seek a school counselor for help with drug use than tenth or twelfth grade students.

Evidence for a phorbol ester-insensitive phosphorylation step in capacitative calcium entry in rat thymic lymphocytes

Experiments were undertaken to investigate the regulation of capacitative Ca2+ entry by phorbol ester-sensitive protein kinase C and serine/threonine protein phosphatase activity. The thapsigargin-activated Ca2+ entry pathway was probed in control cells and cells treated with phosphatase type 1/2A inhibitors, okadaic acid and calyculin A, or with the phorbol ester, phorbol 12-myristate 13-acetate. The permeability state of this pathway was monitored in the presence or absence of these agents using fluorometric measurements of intracellular Ca2+ concentration, unidirectional Mn2+ entry, and membrane potential and unidirectional measurements of Ca2+ uptake using 45Ca2+. The results of these studies demonstrate that modification of the phosphorylation state of target protein(s) on serine/threonine amino acid residues by inhibition of phosphatase type 1/2A inhibits the capacitative Ca2+ entry pathway in rat thymic lymphocytes. Importantly, the capacitative Ca2+ entry pathway in rat thymic lymphocytes is not modulated by activation of phorbol ester-sensitive protein kinase C.

A Ca2+ current activated by release of intracellular Ca2+ stores in rat basophilic leukemia cells (RBL-1)

We have characterized a Ca2+ current activated by depletion of intracellular Ca2+ stores (capacitative Ca2+ entry current) as a first step to investigate the mechanisms underlying communication between the intracellular Ca2+ stores and the plasma membrane Ca2+ permeability. Whole cell currents in response to voltage ramps from -125 to +60 mV from a holding potential of -40 mV were recorded in rat basophilic leukemia cells (RBL-1 cells) in solutions designed to optimize detection of a Ca2+ current. An inwardly rectifying current could be activated upon dialysis of the cell interior with pipette solutions devoid of Ca2+ and containing 20 mm BAPTA, a procedure expected to passively deplete intracellular Ca2+ stores. The current was maximally activated within 2 min, was sensitive to extracellular Ca2+ concentration and was abolished by removal of extracellular Ca2+. The current was markedly reduced in the presence of Ni2+ or La3+. The pathway activated by this protocol was permeant to Ba2+, displaying complex permeability characteristics at negative potentials. A small inward Mn2+ current consistent with a finite permeability of the pathway to Mn2+ was detected. In contrast Ni2+ displayed no detectable current carrying ability. Extracellular Na+ permeated the pathway in the absence of extracellular Ca2+. Under conditions designed to reduce passive depletion of intracellular Ca2+ stores, a Ca2+ current indistinguishable from that described above was activated by addition of ionomycin. This observation is consistent with the activation of the Ca2+ influx pathway occurring as a result of events associated with depletion of intracellular Ca2+ stores. Importantly, application of extracellular Ni2+ in the presence of ionomycin irreversibly inhibited the current. The presence of an inwardly rectifying K+ current in RBL cells could confound studies of the capacitative Ca2+ entry current when recorded using pipette solutions devoid of K+ since this current would be inward over the voltage range used to investigate the capacitative Ca2+ entry current. This study compares an inward rectifying K+ current and the capacitative Ca2+ entry current in RBL cells and highlights some similarities and differences between the two currents. The results demonstrate that caution should be exercised in interpreting recordings made using extracellular solutions containing even modest amounts of K+ when studying the capacitative Ca2+ entry current in RBL cells.

Extracellular ATP increases cytosolic calcium in cultured rat renal arterial smooth muscle cells

1. Experiments were conducted on cultured renal arterial smooth muscle cells to determine the ability of extracellular ATP to alter cytosolic calcium concentration and to determine the mechanisms by which this effect occurs. 2. ATP (100 mumol/L) caused the fluorescence ratio of fura-2 to increase from a control value of 1.06 +/- 0.05 to 2.06 +/- 0.13 (P < 0.01) before stabilizing at a sustained level of 1.35 +/- 0.04 (n = 8; P < 0.05). 3. Removal of extracellular calcium from the bathing medium resulted in an attenuation of the initial response to 100 mumol/L ATP with cell fluorescence increasing from 1.16 +/- 0.18 to 1.44 +/- 0.18 ratio units (n = 5). Furthermore, the initial increase in fluorescence ratio rapidly declined to 1.02 +/- 0.06, indicating that an influx of extracellular calcium is required to sustain the increase in fura-2 fluorescence. 4. Depletion of intracellular calcium pools with thapsigargin prevented the increase in fura-2 fluorescence evoked by ATP. 5. These data suggest that ATP-mediated increases in cytosolic calcium in cultured renal arterial smooth muscle cells involve calcium release from the thapsigargin-sensitive, intracellular pool in conjunction with calcium influx from the extracellular medium.

ATP depletion inhibits capacitative Ca2+ entry in rat thymic lymphocytes

The present study investigates the requirement for cellular ATP in the increase in plasma membrane Ca2+ permeability activated by the release of Ca2+ from intracellular stores in rat thymic lymphocytes (capacitative Ca2+ entry). The permeability state of this pathway following activation with thapsigargin was probed in control and ATP-depleted cells using fluorometric measurements of intracellular Ca2+, Mn2+ entry, and membrane potential, and unidirectional measurements of Ca2+ uptake using 45Ca2+. The capacitative Ca(2+)-entry pathway was markedly inhibited in cells depleted of ATP by incubation in glucose-free solution containing oligomycin, antimycin A, and 2-deoxy-D-glucose. These data cannot be explained on the basis of a loss of the transmembrane electrochemical gradient for Ca2+, alterations in intracellular pH or cellular Na+ content, a direct effect of the inhibitors of ATP production on the capacitative Ca(2+)-entry pathway, or the ability of thapsigargin to release Ca2+ from intracellular stores. Rather, these data are consistent with a requirement for ATP or a high-energy phosphate donor in the activation and/or maintained activation of capacitative Ca2+ entry.

Thapsigargin and cyclopiazonic acid initiate rapid and dramatic increases of IL-6 mRNA expression and IL-6 secretion in murine peritoneal macrophages

Two different inhibitors of endosomal calcium ATPase activity, cyclopiazonic acid and thapsigargin, were shown to release a common intracellular calcium pool in normal, murine macrophages. Furthermore, the release of this pool was accompanied by increased calcium uptake from the extracellular medium. The activity of these inhibitors was linked to an important biologic response, because both cyclopiazonic acid and thapsigargin induced rapid and dramatic increases in IL-6 mRNA expression and secretion. Compared with control cultures, macrophages treated with these inhibitors increased IL-6 mRNA expression approximately 10-fold by 15 min and approximately 20-fold by 2 h, as determined using quantitative competitive-reverse transcribed-PCRs. The increased mRNA expression was coupled to translation and secretion of this monokine since cyclopiazonic acid and thapsigargin induced significant increases in IL-6 secretion as early as 2 h, and up to approximately 70-fold increases by 20 h, when compared with control cultures. Taken together, these results demonstrate that both cyclopiazonic acid and thapsigargin generate potent intracellular signals that initiate rapid and dramatic production of IL-6. Both thapsigargin and cyclopiazonic acid increased IL-6 mRNA expression at 15 min in the absence of Ca2+ influx from the extracellular medium. These results suggest that events associated with endosomal Ca(2+)-ATPase inhibition contribute to the activation of normal macrophages as defined by increased monokine secretion.

Thapsigargin and cyclopiazonic acid initiate rapid and dramatic increases of IL-6 mRNA expression and IL-6 secretion in murine peritoneal macrophages

Two different inhibitors of endosomal calcium ATPase activity, cyclopiazonic acid and thapsigargin, were shown to release a common intracellular calcium pool in normal, murine macrophages. Furthermore, the release of this pool was accompanied by increased calcium uptake from the extracellular medium. The activity of these inhibitors was linked to an important biologic response, because both cyclopiazonic acid and thapsigargin induced rapid and dramatic increases in IL-6 mRNA expression and secretion. Compared with control cultures, macrophages treated with these inhibitors increased IL-6 mRNA expression approximately 10-fold by 15 min and approximately 20-fold by 2 h, as determined using quantitative competitive-reverse transcribed-PCRs. The increased mRNA expression was coupled to translation and secretion of this monokine since cyclopiazonic acid and thapsigargin induced significant increases in IL-6 secretion as early as 2 h, and up to approximately 70-fold increases by 20 h, when compared with control cultures. Taken together, these results demonstrate that both cyclopiazonic acid and thapsigargin generate potent intracellular signals that initiate rapid and dramatic production of IL-6. Both thapsigargin and cyclopiazonic acid increased IL-6 mRNA expression at 15 min in the absence of Ca2+ influx from the extracellular medium. These results suggest that events associated with endosomal Ca(2+)-ATPase inhibition contribute to the activation of normal macrophages as defined by increased monokine secretion.

Role of intracellular Ca2+ stores in the regulation of electrogenic plasma membrane Ca2+ uptake in a B-lymphocytic cell line

Experiments were undertaken to investigate the role of intracellular Ca2+ stores in the regulation of Ca2+ uptake in the cultured B-lymphocytic cell line CH12.LX.C4.5F5. Release of intracellular Ca2+ stores by addition of thapsigargin was accompanied by a biphasic increase in intracellular calcium concentration [Ca2+]i). The initial rise in [Ca2+]i was due to release of Ca2+ from intracellular stores as determined by its maintenance in the absence of extracellular Ca2+. The secondary phase was 1) dependent on the presence of extracellular Ca2+, 2) inhibited by 5 mM extracellular Ni2+, and 3) inhibited by high K+, consistent with electrogenic Ca2+ uptake from the extracellular medium. In order to more accurately investigate the electrogenic nature of this pathway we measured the membrane potential changes accompanying Ca2+ influx stimulated by release of Ca2+ from intracellular stores using bis(1,3-diethylthiobarbituric acid trimethine) oxonol in Bapta-loaded cells. Addition of 5 mM Ca2+ to cells pretreated with doses of thapsigargin or ionomycin shown to release intracellular Ca2+ stores induced a depolarization which was 1) dependent upon extracellular Ca2+, 2) abolished by 5 mM Ni2+, 3) independent of extracellular Na+, and 4) dependent upon Bapta loading. This depolarization was followed by a charybdotoxin-sensitive repolarization consistent with secondary activation of K+ channels. Changes in [Ca2+]i monitored under identical conditions were monitored fluorimetrically using indo-1 and were found to correlate with the changes in Em. On the basis of these data we conclude that an electrogenic Ca(2+)-permeable pathway exists in this B-lymphocytic cell line which is regulated by the degree of filling of an internal Ca(2+)-store.

Isolation and characterization of membrane potential changes associated with release of calcium from intracellular stores in rat thymic lymphocytes

Membrane potential changes accompanying Ca2+ influx stimulated by release of Ca2+ from intracellular stores (store-regulated Ca2+ uptake) were monitored in BAPTA-loaded rat thymic lymphocytes using the fluorescent indicator bis(1,3-diethylthiobarbituric acid)trimethine oxonol. Depletion of [Ca2+]i stores by the application of thapsigargin, ionomycin or cyclopiazonic acid induced a depolarization which was (i) dependent upon BAPTA-loading, (ii) dependent upon extracellular Ca2+, (iii) independent of extracellular Na+ and (iv) abolished by 5 mM extracellular Ni2+. This depolarization was followed by a charybdotoxin-sensitive repolarization and subsequent hyperpolarization to values approximating the K+ equilibrium potential, consistent with secondary activation of a K+ conductance. These membrane potential changes temporally correlated with Ca2+ influx from the extracellular medium as measured fluorimetrically with indo-1. The divalent cation permeability sequence was investigated by monitoring the magnitude of the depolarization observed following the addition of 4 mM Ca2+, Mn2+, Ba2+ or Sr2+ to cells pretreated with doses of thapsigargin or ionomycin known to activate the store-regulated calcium uptake pathway. On the basis of these experiments, we conclude that the store-regulated Ca2+ uptake pathway has the following permeability sequence: Ca2+ > Mn2+ >> Ba2+, Sr2+ with Mn2+ displaying significant permeability relative to Ca2+. This pathway is distinguishable from other divalent cation uptake pathways reported in other cells types on the basis of its activation by thapsigargin and its high Mn2+ permeability.

Ionomycin activates electrogenic Ca2+ influx in rat thymic lymphocytes

Increases in intracellular Ca2+ concentration ([Ca2+]i) after addition of the carboxylic Ca(2+)-transporting ionophore ionomycin have been reported to be inhibited by depolarization in mouse T- and B-lymphocytes, a result attributed to effects on the plasma-membrane Ca2+ pump. The present experiments were undertaken to test the hypothesis that activation of electrogenic Ca2+ uptake, due to release of Ca2+i from intracellular pools, underlies the membrane-potential (Em)-sensitivity of ionomycin-mediated Ca2+ uptake in T-lymphocytes. To address this proposal we have compared the characteristics of Ca2+ influx induced by ionomycin with those of Ca2+ influx activated by release of Ca2+ from intracellular stores (store-regulated Ca2+ uptake, SRCU). The endosomal Ca(2+)-ATPase inhibitor thapsigargin was used to bring about loss of Ca2+ from intracellular pools. In support of this hypothesis, we report that: (1) ionomycin releases Ca2+ from a thapsigargin-sensitive endosomal pool, a pool previously demonstrated to regulate electrogenic SRCU in rat thymic lymphocytes, (2) Ca2+ and Mn2+ uptake mediated by low doses of ionomycin are inhibited by compounds previously reported to inhibit SRCU, and (3) in the absence of SRCU, ionomycin-mediated Ca2+ uptake displays no sensitivity to Em. We conclude that activation of electrogenic SRCU can adequately account for the Em-sensitivity of Ca2+ flux previously attributed to alterations in Ca(2+)-pump activity. Such a mechanism of action may underlie previous reports of electrogenic Ca2+ transport mediated by ionomycin in other tissues.

Inhibition of Ca2+ transport pathways in thymic lymphocytes by econazole, miconazole, and SKF 96365

Cytochrome P-450 has been proposed to underlie the mechanism of regulation of the plasma membrane Ca2+ permeability by the Ca2+ content of the inositol 1,4,5-trisphosphate-sensitive Ca2+ pool. We have investigated the effects on divalent cation uptake in rat thymic lymphocytes of three structurally related imidazole reagents reported to inhibit redox mechanisms. Changes in intracellular Ca2+ concentration and intracellular Mn2+ concentration were measured fluorimetrically with indo-1 and/or quin-2. Econazole, miconazole, and SKF 96365 were found to be potent blockers of Ca2+ and Mn2+ uptake activated by release of Ca2+ from intracellular stores induced by thapsigargin. Additionally, we found that concentrations of these agents required to abolish divalent cation uptake also released Ca2+ from the thapsigargin-sensitive intracellular stores, consistent with inhibition of the endosomal Ca(2+)-ATPase. In agreement with this suggestion, we have found that all three of these agents are potent inhibitors of isolated sarcoplasmic reticulum Ca(2+)-ATPase. We conclude that econazole, miconazole, and SKF 96365 inhibit cytochrome P-450-independent filling of intracellular Ca2+ pools, as well as store-regulated Ca2+ entry, and caution against the use of these compounds as selective inhibitors of cytochrome P-450.

Coupling between intracellular Ca2+ stores and the Ca2+ permeability of the plasma membrane. Comparison of the effects of thapsigargin, 2,5-di-(tert-butyl)-1,4-hydroquinone, and cyclopiazonic acid in rat thymic lymphocytes

The regulation of Ca2+ uptake by receptors is incompletely understood. It has been proposed that the Ca2+ permeability of the plasma membrane increases in response to depletion of a critical intracellular Ca2+ storage compartment (Takemura, H., Hughes, A. R., Thastrup, O., and Putney, J. W. (1989) J. Biol. Chem. 264, 12266-12271). This hypothesis is based largely on the effect of thapsigargin, an inhibitor of endomembrane CA(2+)-ATPases. Due to the existence of an endogenous leak, inhibition of Ca2+ uptake by thapsigargin induces depletion of the stores. This is accompanied by increased plasmalemmal Ca2+ permeability, without change in the level of inositol phosphates. On the other hand, depletion of the intracellular stores by 2,5-di(tert-butyl)-1,4-hydroquinone (BHQ), a chemically unrelated inhibitor of the Ca(2+)-ATPases, fails to induce Ca2+ influx (Kass, G. E., Duddy, S. K., Moore, G. A., and Orrenius, S. (1989) J. Biol. Chem. 264, 15192-15198). In an attempt to reconcile these observations, we analyzed in lymphocytes the mode of action of thapsigargin and BHQ. In addition, we tested the effects of cyclopiazonic acid (CPA), a blocker of the skeletal muscle sarcoplasmic reticulum Ca(2+)-ATPase. All three compounds released Ca2+ from a common intracellular compartment. Thapsigargin and low concentrations of BHQ and CPA concomitantly elevated the plasmalemmal Ca2+ permeability. Higher concentrations of BHQ and CPA produced a secondary inhibition of the Ca2+ entry pathway, by a mechanism seemingly unrelated to their effects on the internal stores. This inhibitory side effect can account for the reported discrepancies between the effects of thapsigargin and BHQ. The data provide further support for the notion that endomembrane Ca2+ stores are functionally coupled to the plasma membrane Ca2+ permeability pathway.

Ca(2+)-activated K+ channels in rat thymic lymphocytes: activation by concanavalin A

1. The role of ion channels in the mitogenic response of rat thymic lymphocytes to concanavalin A (ConA) was studied using single-channel patch-clamp recordings and measurements of membrane potential with the fluorescent probe bis-oxonol. 2. ConA (20 micrograms ml-1) evoked a rapid membrane hyperpolarization; Indo-1 measurements indicated a concurrent increase in [Ca2+]i. The hyperpolarization was blocked by cytoplasmic loading with the Ca2+ buffer BAPTA (bis(O-amino-phenoxy)ethane-N,N,N',N'-tetraacetic acid), or charybdotoxin, a component of scorpion venom known to block K+ channels in lymphocytes. 3. Cell-attached patch-clamp recordings showed that both ConA and the Ca2+ ionophore ionomycin activated channels with high selectivity for K+. Two conductance levels were observed -6-7 pS and 17-18 pS-measured as inward chord conductance at 60 mV from reversal potential (Erev) with 140 mM-KCl in the pipette. The current-voltage relationship for the larger channel displayed inward rectification and channel open probability was weakly dependent upon membrane potential. 4. These experiments provide the first direct evidence for mitogen-activated Ca(2+)-gated K+ channels (IK(Ca)) in lymphocytes. This conductance is relatively inactive in unstimulated rat thymocytes but following the intracellular Ca2+ rises induced by ConA, IK(Ca) channels are activated and produce a significant hyperpolarization of the cell potential.

The role of intracellular Ca2+ in the regulation of the plasma membrane Ca2+ permeability of unstimulated rat lymphocytes

The mechanism responsible for the increase in cytosolic free Ca2+ concentration ([Ca2+]i) during mitogenic stimulation of lymphocytes has been widely investigated. By contrast, little is known about the processes underlying Ca2+i homeostasis in resting (unstimulated) cells. It has been suggested that [Ca2+]i is an important determinant of the rate of Ca2+ influx following mitogenic activation. Using rat thymic lymphocytes, we investigated whether the resting influx pathway is similarly controlled by [Ca2+]i. Otherwise untreated cells were Ca(2+)-depleted by loading with Ca2+ chelators while suspended in Ca(2+)-free solution. Ca2+ depletion induced an 8-fold increase in the rate of unidirectional Ca2+ uptake. The depletion-activated flux was voltage-sensitive and was blocked by La3+ and by compound SK&F 96365, a receptor-operated Ca2+ channel blocker. Upon reintroduction to Ca(2+)-containing solution, the increased influx brought about a rapid recovery of [Ca2+]i. Detailed analysis of the magnitude of the 45Ca2+ flux during this recovery indicated that [Ca2+]i is not the primary determinant of the plasmalemmal Ca2+ permeability. Instead, depletion of an internal thapsigargin-sensitive store correlates with and appears to be responsible for the increased permeability of the plasma membrane. Accordingly, the Ca2+ fluxes induced by intracellular Ca2+ depletion and by thapsigargin were pharmacologically indistinguishable. Mitogenic lectins also released Ca2+ from a thapsigargin-sensitive store and activated a plasmalemmal Ca2+ permeability displaying identical pharmacology. The data support the existence of a coupling process whereby the degree of filling of an internal Ca2+ store dictates the Ca2+ permeability of the plasma membrane. This coupling mechanism is important not only in mediating the effects of mitogens and other agonists, as suggested before, but seemingly also in the control of resting Ca2+i homeostasis in unstimulated cells.