Risky self-management behaviors in adolescents with type 1 diabetes: Measurement validation for the Diabetes-Specific Risk-Taking Inventory

OBJECTIVE

Among persons with type 1 diabetes (T1D), adolescents often experience the greatest challenge achieving optimal treatment engagement and glycemic targets. Risk-taking behaviors often increase during adolescence and may interfere with engagement in T1D care. We developed the Diabetes-Specific Risk-Taking Inventory (DSRI) to assess risky T1D self-management behaviors in adolescents with T1D. In the current study, we aimed to examine the DSRI's psychometric properties.

RESEARCH DESIGN AND METHODS

We surveyed a national sample of 224 adolescents from the T1D Exchange registry (M age = 16.9 ± 1.1, 49% female, M A1c = 8.5% ± 1.3, 76.8% on insulin pumps) in a cross-sectional design. Participants completed the DSRI and measures of engagement, general risk-taking, and executive functioning and reported on incidence of severe hypoglycemia and diabetic ketoacidosis over the past year.

RESULTS

The DSRI demonstrated reliability (internal consistency: α = 0.89; test-retest reliability: r = 0.86, p < 0.01). Concurrent validity was demonstrated through significant associations between the DSRI and T1D engagement (r = -0.75), general risk-taking (r = 0.57), executive dysfunction (r = 0.34), and report of severe hypoglycemia over the past year (r = 0.22). The DSRI accounted for unique variance in adolescents' most recent glycated hemoglobin, above and beyond other variables, indicating its incremental validity.

CONCLUSIONS

Overall, initial psychometrics suggest the DSRI is a reliable and valid measure of risks that adolescents may take with their T1D care. This innovative self-report measure has potential to be an actionable clinical tool to screen for high-risk behaviors not routinely assessed in T1D clinical care.

"Why We Keep Coming Back": Family and Provider Perspectives on Factors Influencing Long-term Follow-up for Pediatric Cancer Survivorship Care

PURPOSE

The majority of childhood cancer survivors do not follow-up for long-term risk-based screening for recurrent illness and treatment late effects, despite a high prevalence of secondary morbidities. The primary aim of this study was to investigate factors that influence long-term follow-up for survivorship care, from the perspectives of providers, patients, and caregivers.

MATERIALS AND METHODS

A semistructured interview was designed to elicit stakeholder perspectives on factors that facilitate or impede routine clinic visits after completion of cancer therapy. Results were analyzed using a qualitative framework method.

RESULTS

Providers, patients, and caregivers identified a wide range of factors that might influence long-term follow-up for care. All respondents noted the importance of efficient clinical operations, resources such as parking, provider behaviors, rapport/attachment, and patient/family logistics. Compared with patients/caregivers, providers more frequently mentioned institutional operations, their own education and skills, patient/family understanding and motivation, and interpersonal processes such as communication style. Families more frequently mentioned clinic environment, and patients more frequently noted the importance of having a family member present, something neither providers nor caregivers reported.

CONCLUSIONS

Providers, patients, and patient caregivers have different perspectives regarding factors that may influence follow-up for long-term survivorship care. Understanding these differences can help inform efforts to improve follow-up.

An Automated Risk Index for Diabetic Ketoacidosis in Pediatric Patients With Type 1 Diabetes: The RI-DKA

Identifying patients at high risk for diabetic ketoacidosis (DKA) is crucial for informing efforts at preventive intervention. This study sought to develop and validate an electronic medical record (EMR)-based tool for predicting DKA risk in pediatric patients with type 1 diabetes. Based on analysis of data from 1,864 patients with type 1 diabetes, three factors emerged as significant predictors of DKA: most recent A1C, type of health insurance (public vs. private), and prior DKA. A prediction model was developed based on these factors and tested to identify and categorize patients at low, moderate, and high risk for experiencing DKA within the next year. This work demonstrates that risk for DKA can be predicted using a simple model that can be automatically derived from variables in the EMR.

A Comprehensive System for Identifying Patients With Type 1 Diabetes at Increased Risk for Diabetic Ketoacidosis at Texas Children's Hospital

Quality Improvement Success Stories are published by the American Diabetes Association in collaboration with the American College of Physicians and the National Diabetes Education Program. This series is intended to highlight best practices and strategies from programs and clinics that have successfully improved the quality of care for people with diabetes or related conditions. Each article in the series is reviewed and follows a standard format developed by the editors of Clinical Diabetes. The following article describes a project at Texas Children's Hospital aimed at improving identification of patients with type 1 diabetes at high risk for diabetic ketoacidosis.

The Diabetes-Specific Risk-Taking Inventory: Piloting a New Measure for Adolescents With Type 1 Diabetes

OBJECTIVE

We sought to develop and pilot a new measure, the Diabetes-Specific Risk-Taking Inventory (DSRI), to assess unhealthy risk-taking behaviors among adolescents with type 1 diabetes.

METHODS

Thirteen diabetes health care providers, 30 adolescents with type 1 diabetes (aged 15-19 years, 60% female, mean A1C 8.7% [72 mmol/mol], and 33% on insulin pumps), and the adolescents' caregivers rated the perceived riskiness of each item on the DSRI. Adolescents completed the DSRI, for which they reported how often they engaged in 34 behaviors that could place them at risk for acute complications of type 1 diabetes or out-of-range blood glucose levels. Adolescents also completed the risk-taking subscale from the Risk-Taking and Self-Harm Inventory for Adolescents, and parents completed the parent-proxy Diabetes Management Questionnaire. Mean A1C during the previous year was obtained via medical chart review.

RESULTS

Results indicated good content validity and feasibility for using the DSRI in a research context, as 100% of adolescents who consented to the study completed the measure. The DSRI was positively correlated with general risk-taking and negatively correlated with diabetes management, indicating preliminary evidence of convergent validity. The DSRI also correlated with A1C.

CONCLUSION

This pilot study extends our previous work in developing a conceptual model for illness-specific risk-taking. The DSRI is a promising new measure to assess illness-specific risk-taking, including unhealthy risk-taking behaviors, for adolescents with type 1 diabetes.

Neurocognitive, adaptive, and psychosocial functioning in individuals with Robinow syndrome

It has been estimated that 10-15% of people with Robinow syndrome (RS) show delayed development, but no studies have formally assessed developmental domains. The objective of this study is to provide the first description of cognitive, adaptive, and psychological functioning in RS. Thirteen participants (10 males) aged 4-51 years were seen for neuropsychological screening. Eight had autosomal-dominant RS (DVL1, n = 5; WNT5A, n = 3), four had autosomal-recessive RS (NXN, n = 2; ROR2, n = 2), and one had a mutation on an RS candidate gene (GPC4). Participants completed measures of intellectual, fine-motor, adaptive, executive, and psychological functioning. Findings indicated generally average intellectual functioning and low-average visuomotor skills. Adaptive functioning was average in autosomal-recessive RS (RRS) but low average in autosomal-dominant RS (DRS). Parent-report indicated executive dysfunction and attention problems in 4/8 children, 3/4 of whom had a DVL1 variant; adult self-report did not indicate similar difficulties. Learning disabilities were also reported in 4/8 individuals with DRS, 3/4 of whom had a DVL1 variant. Peer problems were reported for a majority of participants, many of whom also reported emotional concerns. Altogether, the findings indicate average neurocognitive functioning in RRS. In contrast, DRS, especially DVL1 pathogenic alleles, may confer specific risk for neurodevelopmental disability.

Costello syndrome: Clinical phenotype, genotype, and management guidelines

Costello syndrome (CS) is a RASopathy caused by activating germline mutations in HRAS. Due to ubiquitous HRAS gene expression, CS affects multiple organ systems and individuals are predisposed to cancer. Individuals with CS may have distinctive craniofacial features, cardiac anomalies, growth and developmental delays, as well as dermatological, orthopedic, ocular, and neurological issues; however, considerable overlap with other RASopathies exists. Medical evaluation requires an understanding of the multifaceted phenotype. Subspecialists may have limited experience in caring for these individuals because of the rarity of CS. Furthermore, the phenotypic presentation may vary with the underlying genotype. These guidelines were developed by an interdisciplinary team of experts in order to encourage timely health care practices and provide medical management guidelines for the primary and specialty care provider, as well as for the families and affected individuals across their lifespan. These guidelines are based on expert opinion and do not represent evidence-based guidelines due to the lack of data for this rare condition.

Age-related differences in prevalence of autism spectrum disorder symptoms in children and adolescents with Costello syndrome

Dysregulation of the mitogen activated protein kinase (MAPK) pathway in Costello syndrome (CS) may contribute to increased risk for autism-spectrum disorder (ASD). We examined prevalence of ASD symptoms in 14 individuals (six females) age 1-18 years with molecularly confirmed CS. Caregivers completed the Modified Checklist for Autism in Toddlers (M-CHAT) for ages 0-4 years (n = 7), and the Social Communication Questionnaire (SCQ) for ages 4 and older (n = 7). Age was associated with meeting ASD criteria: 5/7 (71.4%) younger children met the ASD cut-off on the MCHAT, compared to 0/7 older children on the SCQ. The following medical and developmental factors were strongly associated with ASD criteria on the M-CHAT: having a gastrostomy tube at time of assessment, not eating solid food, not walking, and not being toilet trained. Two children who met stricter ASD criteria had significantly lower adaptive functioning and were physically much more impaired. Among older participants, SCQ subscale scores in communication, socialization, and repetitive behavior domains were comparable to the typically-developing normative sample. ASD symptoms were highly elevated in younger CS individuals. Older children did not differ from typically developing samples in prevalence of ASD symptoms. CS individuals may appear to fall on the autism spectrum in early childhood due to severe feeding and orthopedic problems that improve by age four, suggesting many of these children may eventually emerge out of an ASD presentation.

Illness-Specific Risk-Taking in Adolescence: A Missing Piece of the Nonadherence Puzzle for Youth With Type 1 Diabetes?

Risky behavior is often at its lifetime peak in adolescence. Chronic illness creates additional opportunities for risk because nonadherence behaviors can jeopardize adolescents' health. Adolescents with type 1 diabetes could engage in risky behavior around insulin administration that would put them in danger of severe health consequences. It is possible that some nonadherence behaviors observed in adolescents with type 1 diabetes may result from youth taking risks with their medical treatment. Illness-specific risk-taking behaviors are not captured in most assessments of adherence, which primarily focus on frequency of adherence behaviors. This article reviews current models of general risk-taking and their implications for diabetes management. The authors argue that illness-specific risk-taking may be an important, understudied aspect of illness management that can inform future studies and treatment of nonadherence in adolescents with type 1 diabetes.

Seeing the Person, Not the Illness: Promoting Diabetes Medication Adherence Through Patient-Centered Collaboration

IN BRIEF Nonadherence to diabetes medications is a primary contributor to health complications and avoidable hospitalizations. This article discusses the evidence for taking a person-centered (as opposed to illness-centered) approach to promoting medication adherence among diabetes patients, provides suggestions for ways in which diabetes clinicians can best promote medication adherence, and argues for needed changes in how health care systems support providers in their efforts at adherence promotion.

Practical strategies to enhance executive functioning and strengthen diabetes management across the lifespan

The complex type 1 diabetes (T1D) management regimen places extra demands on one's ability to plan, organize, and problem-solve, a set of skills described as executive functioning (EF). Research on the relation between EF and T1D management has been mounting and suggest that deficits in EF skills likely interfere with optimal management. However, given the substantial EF demands of T1D management, any person with T1D, including those without clinically significant deficits, could likely benefit from strategies to improve diabetes-related EF skills. The current review outlines typical EF development across the lifespan and suggests behavioral strategies (e.g., environmental modifications) from the EF literature and clinical experience to enhance EF skills at each period of development. When executive dysfunction is suspected, formal neuropsychological assessment is recommended as EF concerns can be a significant problem of their own, or they could be an indicator of another psychological disorder, such as depression or dementia.

Neurocognitive profile of a young adolescent with DK phocomelia/von Voss phocomelia/von Voss Cherstvoy syndrome

DK phocomelia/von Voss Cherstvoy syndrome is a rare condition characterized by upper limb and urogenital abnormalities and various brain anomalies. Previously reported cases have noted significant developmental delays, although no formal testing of cognitive abilities has been reported. In this paper we describe results from a comprehensive neuropsychological evaluation of a 12-year-old male with DK phocomelia syndrome. Test findings indicated mild impairment in intellectual functioning, with more significant impairment in adaptive skills and academic achievement. The neuropsychological profile converged with neurological findings, showing a distinct pattern of strengths and weaknesses that suggests functional compromise of posterior brain regions with relatively well-preserved functioning of more anterior regions. Specifically, impairments were evident in perceptual reasoning, visual perception, and visuomotor integration, whereas normal or near normal functioning was evident in memory, receptive language, social cognition, attention, and most aspects of executive functioning. To our knowledge this is the first report to describe the neurocognitive profile of an individual with DK phocomelia syndrome.

Diabetes in ethnically diverse youth: disparate burden and intervention approaches

There is a rising prevalence of diabetes in youth and children, and the burden of this epidemic has shifted from primarily one affecting white youth to now affecting multiple ethnicities. As the incidence and prevalence of diabetes rise in ethnically diverse youth, indices of health and care in these populations are important to examine to understand the state of disparities and address them. Research reviewed indicates that there is evidence of disparities in glycemic control, as well as shortand long-term complications. Multisystemic factors contributing to these disparities include: 1) individual risk factors, 2) contextual risk factors, and 3) systemic risk factors. Interventions developed specifically to address these disparities, those that are tailored for these groups, and those that simply include ethnically diverse youth in their analyses are discussed below. Implications for future research and clinical practice are discussed.

Neurocognitive outcomes in pediatric diabetes: a developmental perspective

The impact of diabetes on the developing brain is well-accepted. Effects on neurocognitive functioning are moderate but have larger functional implications, especially when considered through a developmental lens. Pathophysiological factors such as severe hypoglycemia and chronic hyperglycemia can alter developmental trajectories in early childhood and perhaps at later periods. In this paper, we selectively review neurocognitive outcomes in pediatric diabetes (largely type 1), integrating recent research from developmental neuroscience and neuroimaging. We examine the effects of diabetes at different stages and place findings within a neurodevelopmental diathesis/stress framework. Early-onset diabetes is associated with specific effects on memory and more global cognitive late-effects, but less is known about cognitive outcomes of diabetes in later childhood and in adolescence, a time of increased neurobehavioral vulnerability that has received relatively limited empirical attention. Studies are also needed to better elucidate risk and protective factors that may moderate neurodevelopmental outcomes in youth with diabetes.

Neurocognitive functioning in children and adolescents at the time of type 1 diabetes diagnosis: associations with glycemic control 1 year after diagnosis

OBJECTIVE

To determine whether impairments in neurocognitive functioning are detectable at type 1 diabetes diagnosis and associated with subsequent glycemic control.

RESEARCH DESIGN AND METHODS

Children/adolescents (N = 147) aged 5-18 years completed neuropsychological testing during their inpatient hospitalization for new-onset type 1 diabetes. Test scores were compared with normative data using one-sample Student t tests. Children with onset before 8 years of age were compared with children aged 9-18 years using ANOVA, and associations between neurocognitive performance at diagnosis and glycemic control 1 year postdiagnosis were examined using regression analyses.

RESULTS

Children with type 1 diabetes performed significantly below expectations on most neurocognitive measures (P values <0.0001), with large decrements from the normative mean evident in psychomotor speed (>1 SD), visuomotor integration (0.7 SD), and phonemic fluency (0.8 SD). High incidence of impairment (scores less than second percentile) was evident on all tasks except digit span. Dominant-hand psychomotor speed was significantly associated with poor glycemic control (A1C ≥9.5% [80 mmol/mol]; P = 0.032) 1 year postdiagnosis, controlling for race/ethnicity, sex, and reading ability. Impaired psychomotor speed was associated with a 0.77% increase in mean A1C (8.4 mmol/mol).

CONCLUSIONS

Deficits were evident in neurocognitive functioning within days of diabetes diagnosis that were associated with diabetes outcomes over 1 year postdiagnosis. Impairment was most apparent in psychomotor speed, consistent with research implicating damage to posterior white matter tracts and associated gray matter regions in type 1 diabetes. Psychomotor impairment may be an early marker for a broader neurobehavioral vulnerability that has implications for long-term diabetes management.

Vasorelaxation responses to insulin in laminar vessel rings from healthy, lean horses

Hyperinsulinemia causes laminitis experimentally and is a risk factor for naturally occurring laminitis. The aim of this study was to investigate the effects of insulin on laminar vascular relaxation and to induce insulin-associated vascular dysfunction in vitro. Relaxation responses of isolated laminar arterial and venous rings to acetylcholine and insulin were evaluated. To alter vascular function in response to insulin, all vessel rings were incubated with insulin or vehicle, submaximally contracted, administered insulin again and relaxation responses recorded. Laminar arteries were also incubated with the mitogen-activated protein kinase (MAPK) inhibitor, PD-98059. Relaxation in response to acetylcholine was not different between arteries and veins, but veins relaxed less in response to insulin than arteries. In arteries incubated with insulin, the subsequent relaxation response to insulin was blunted. Veins had minimal relaxation to insulin regardless of incubation. Arteries incubated with PD-98059 relaxed more in response to insulin than arteries not exposed to PD-98059, indicating that MAPK plays a role in maintenance of basal tone in laminar arteries. A differing response of laminar veins and arteries to insulin-induced relaxation may be important in understanding the link between hyperinsulinemia and laminitis. In vitro induction of vascular dysfunction in response to insulin in laminar arteries may be useful for testing therapeutic interventions and for understanding the pathophysiology of laminitis.

A psychosocial risk index for poor glycemic control in children and adolescents with type 1 diabetes

OBJECTIVE

The aim of this study was to develop and validate a psychosocial screening tool to predict risk for poor glycemic control in children with type 1 diabetes.

METHODS

Participants seen for psychological screening were 196 children aged 3-18 yr at diabetes diagnosis. A psychosocial risk index was developed to predict poor glycemic control [mean hemoglobin A1c (HbA1c) ≥ 9.5%; 80 mmol/mol] 1-4 yr post diagnosis. Cutoff scores were derived for multiple levels of risk from receiver operating characteristic (ROC) curves and likelihood ratios (LRs). Discrimination and calibration were examined in the sample, and validated in 1000 bootstrap samples. Ability to predict diabetes-related emergency-room (ER) visits and diabetic ketoacidosis (DKA) was also tested.

RESULTS

The risk index accounted for 16.2% of variance in mean HbA1c, discriminated between children with and without poor glycemic control [area under the receiver operating characteristic curve (AUC) = 0.814, 0.713-0.915; p < 0.001], ER visits (AUC = 0.655, 0.561-0.748; p = 0.001), and DKA(AUC = 0.709, 0.588-0.830; p = 0.001), and was well-calibrated. Every one-point increase in score was associated with an absolute increase in risk for poor glycemic control of approximately 10% (LRs = 1.7, 3.2, 5.8, and 9.3). Sensitivity and specificity were 0.68 (0.43-0.86) and 0.79 (0.72-0.84) for detecting patients at moderate risk, and 0.53 (0.29-0.75) and 0.91 (0.85-0.95) for detecting high-risk patients. The index performed equally well in validation samples.

CONCLUSIONS

This paper presents the first psychosocial risk index for poor glycemic control in children newly diagnosed with type 1 diabetes. It is brief, easily administered, and provides a single score that translates directly into an estimate of risk that can help guide routine diabetes care.

Verbal memory functioning in adolescents and young adults with Costello syndrome: evidence for relative preservation in recognition memory

Costello syndrome (CS) is a rare genetic disorder caused by germline mutations in the HRAS proto-oncogene which belongs to the family of syndromes called rasopathies. HRAS plays a key role in synaptic long-term potentiation (LTP) and memory formation. Prior research has found impaired recall memory in CS despite enhancement in LTP that would predict memory preservation. Based on findings in other rasopathies, we hypothesized that the memory deficit in CS would be specific to recall, and that recognition memory would show relative preservation. Memory was tested using word-list learning and story memory tasks with both recall and recognition trials, a design that allowed us to examine these processes separately. Participants were 11 adolescents and young adults with molecularly confirmed CS, all of whom fell in the mild to moderate range of intellectual disability. Results indicated a clear dissociation between verbal recall, which was impaired (M = 69 ± 14), and recognition memory, which was relatively intact (M = 86 ± 14). Story recognition was highly correlated with listening comprehension (r = 0.986), which also fell in the low-average range (M = 80 ± 12.9). Performance on other measures of linguistic ability and academic skills was impaired. The findings suggest relatively preserved recognition memory that also provides some support for verbal comprehension. This is the first report of relatively normal performance in a cognitive domain in CS. Further research is needed to better understand the mechanisms by which altered RAS-MAPK signaling affects neuronal plasticity and memory processes in the brain.

Paternal involvement in pediatric Type 1 diabetes: fathers' and mothers' psychological functioning and disease management

Psychological functioning in fathers of children with Type 1 diabetes has received relatively little attention compared to mothers. This study examined fathers' perceived involvement in their children's diabetes care as it related to mothers' and fathers' pediatric parenting stress, depression, anxiety, marital satisfaction, and sleep, and to their children's diabetes regimen adherence and glycemic control. Eighty-two mothers and 43 fathers completed questionnaires. Multivariate linear regressions were conducted separately for mothers and fathers to determine the relationships between the perceived amount and the perceived helpfulness of father involvement in child diabetes care on parental psychosocial functioning and child diabetes control. Maternal perceptions of father helpfulness and amount of involvement in illness care were related to improved marital satisfaction and fewer depressive symptoms in mothers. In fathers, perception of their own amount of involvement was related to increased pediatric parenting stress and anxiety. Better child regimen adherence was associated with maternal perceptions of father helpfulness but not the amount of their involvement, while paternal perceptions of their own helpfulness were related to poorer glycemic control. These findings suggest that fathers and mothers may react differently to their roles in childhood illness and that perceptions of their involvement may be differently associated with children's glycemic control and regimen adherence.

Neurocognitive, adaptive, and behavioral functioning of individuals with Costello syndrome: a review

Costello syndrome is a rare rasopathy resulting from germline mutations of the proto-oncogene HRAS. Its phenotype includes severe failure-to-thrive, cardiac abnormalities, a predisposition to benign and malignant tumors, hypotonia, and developmental delay. Costello syndrome is associated with cognitive impairment, including intellectual functioning generally in the mild to moderate range of disability, commensurate adaptive functioning, and increased anxiety. Relative strengths have been found for nonverbal fluid reasoning (FR). Gender effects have been reported, with females showing better adaptive functioning across domains. Developmentally, nonverbal skills plateau in late childhood/early adolescence, whereas the rate of vocabulary acquisition may increase in adolescence into early adulthood. Here we review the literature assessing cognitive, adaptive, and behavioral functioning in Costello syndrome, and we provide data from an ongoing longitudinal study. Severity of cognitive impairment may depend upon the specific HRAS mutation, as three individuals with the p.G13C change showed average nonverbal FR skills and borderline-to-low average overall nonverbal IQ. Further, separation anxiety is more common in Costello syndrome than in the general population, affecting 39% of this cohort, and males are more often overly anxious than females. Interrelations between anxiety and cognitive and adaptive functioning were found, pointing to functional difficulties as a likely source of stress and anxiety. Taking into account data from animal models, cognitive and behavioral changes likely originate from abnormal differentiation of neuronal precursor cells, which result in structural and functional brain differences.

Feasibility, acceptability, and predictive validity of a psychosocial screening program for children and youth newly diagnosed with type 1 diabetes

OBJECTIVE

Psychosocial screening has been recommended for pediatric patients with newly diagnosed type 1 diabetes and their families. Our objective was to assess a psychosocial screening protocol in its feasibility, acceptability to families, and ability to predict early emerging complications, nonadherent family behavior, and use of preventive psychology services.

RESEARCH DESIGN AND METHODS

A total of 125 patients and their caregivers were asked to participate in a standardized screening interview after admission at a large urban children's hospital with a new diagnosis of type 1 diabetes. Medical records were reviewed for subsequent diabetes-related emergency department (ED) admissions, missed diabetes clinic appointments, and psychology follow-up within 9 months of diagnosis.

RESULTS

Of 125 families, 121 (96.8%) agreed to participate in the screening, and a subsample of 30 surveyed caregivers indicated high levels of satisfaction. Risk factors at diagnosis predicted subsequent ED admissions with a sensitivity of 100% and a specificity of 98.6%. Children from single-parent households with a history of behavior problems were nearly six times more likely to be seen in the ED after diagnosis. Missed appointments were likeliest among African Americans, 65% of whom missed at least one diabetes-related appointment. Psychology services for preventive intervention were underutilized, despite the high acceptability of the psychosocial screening.

CONCLUSIONS

Psychosocial screening of newly diagnosed patients with type 1 diabetes is feasible, acceptable to families, and able to identify families at risk for early emerging complications and nonadherence. Challenges remain with regards to reimbursement and fostering follow-up for preventive care.

Early risk factors for nonadherence in pediatric type 1 diabetes: a review of the recent literature

Nonadherence to different aspects of the diabetes regimen is common. Problems early in the course of illness predict later difficulties with nonadherence; conversely, good management early on protects against later complications. Screening for early risk factors at the time of diabetes diagnosis is therefore critical for promoting the health of children with type 1 diabetes. The purpose of this paper is to review and synthesize the recent empirical literature on early risk factors for nonadherence in type 1 diabetes, with a focus on three specific adherence behaviors: insulin administration, blood glucose monitoring, and clinic attendance. Risk factors are considered within several broad categories: sociodemographic barriers that limit access to care; child and parent factors that affect adherence both directly and indirectly via their impact on the development of family teamwork; and family interactions with their health-care providers. We integrate the different findings into a "simple model" that can be used to develop efficient screening protocols that can in turn guide efforts at preventive intervention.

Longitudinal course of cognitive, adaptive, and behavioral characteristics in Costello syndrome

Costello syndrome is a rare rasopathy caused by germline mutations in the oncogene HRAS resulting in increased signal transduction through the Ras/mitogen-activated protein kinase pathway. In contrast to the more common rasopathies, such as neurofibromatosis type 1 and Noonan syndrome, limited information is available on standardized cognitive testing in this cohort. Past research indicated a mean average IQ in the mild mental retardation range, with strengths in fluid reasoning (FR) and weakness in expressive language, as well as static skills over time. Here we report on standardized IQ and adaptive functioning in 18 individuals with Costello syndrome, nine males and nine females, and longitudinal development for 11 who had previous testing. The overall IQ, ranging from severe mental retardation to the average range, with a mean in the mildly mentally retarded range, was again found to be stable, but an interesting pattern in the development of nonverbal FR was identified. Participants showed an improvement in nonverbal FR, followed by stable skills thereafter, suggesting a "late bloomer" effect in late childhood/early adolescence. Overall adaptive functioning fell into the range of Intellectual Disability for 70% of subjects, with Socialization as a relative strength and Daily Living Skills an area of relative difficulty. Interestingly, females were found to be higher functioning than males in all domains, including Communication, Daily Living Skills and Socialization. Caregivers reported significantly more behavioral concerns in males, including internalizing, externalizing, and other maladaptive behaviors. In contrast, no gender differences were found in cognitive or visuomotor functioning.

Comparison of single-level cervical fusion and a metal-on-metal cervical disc replacement device

Cervical fusion is the common treatment for cervical disc disease but can cause secondary disorders. The Prestige ST cervical disc prosthesis (Medtronic Sofamor Danek, Memphis, TN) was designed to preserve spinal motion to potentially limit the secondary disorders. In this article, we report 2-year results from a single-center study comparing use of this device with use of anterior cervical discectomy and fusion (ACDF). Nineteen patients were prospectively randomized to receive the device or to undergo ACDF. Twenty-four months after surgery, patients who received the device demonstrated improvement in neck pain, arm pain, and neurologic function. In our cohort, patients who underwent arthroplasty demonstrated greater improvement in neurologic function and neck pain than patients who underwent cervical discectomy and fusion.

Pharmacologic identification of putative D1 dopamine receptors in feline kidneys

The presence of dopamine (DA) receptors in feline kidneys is a matter of contention. Radioligand binding and Western blotting studies were employed to determine whether DA receptors are present in feline kidneys. The pharmacologic profile of the selective D1-receptor antagonist [3H]-SCH 23390 was studied in renal cortical membrane preparations from cats by conducting saturation binding isotherm and competitive binding experiments. [3H]-SCH 23390 bound to feline renal cortical membranes in a manner consistent with labeling of a D1-like receptor. The binding profile revealed a single site D1-like or D1 receptor in the feline renal cortex with a Kd = 7.8 +/- 1.0 nmol/L and Bmax = 76.5 +/- 19.5 fmol/mg. Competitive binding studies for [3H]-SCH 23390 against unlabeled agonists yielded the following Ki values and rank order of competition: SKF38393 (Ki = 0.47 +/- 0.26 micro m) > fenoldopam (Ki = 3.12 +/- 1.1 micro m) > DA (Ki = 933.1 +/- 1.6 micro m). Competitive binding studies for [3H]-SCH-23390 against unlabeled antagonists yielded the following rank order of competition: SCH 23390 (Ki = 1.97 +/- 0.81 micro m) > spiperone (Ki = 3.79 +/- 0.79) > metoclopramide (Ki = 4.26 +/- 2.4 micro m). Western blot analysis with anti-DA D1 receptor antibodies detected a single band with Mr of 74 kDa corresponding to a D1 DA receptor. These results suggest that a putative D1-like or D1 receptor exists in feline kidneys different from those previously identified in rat, dog or human kidneys.

Estradiol plus progesterone treatment modulates select elements of the proinflammatory cytokine cascade in steers: attenuated nitric oxide and thromboxane B2 production in endotoxemia

Estradiol plus progesterone (EP) implants have been shown to favorably alter the time course or decrease the severity of many of the clinical manifestations associated with coccidiosis and endotoxemia in calves. This study evaluated the effect of EP treatment on plasma tumor necrosis factor-alpha (TNF), thromboxane (TXB), prostacyclin (PRC), nitrite and nitrate (NO[x]), and cortisol. Holstein steer calves were divided into four groups: control, EP, endotoxin (LPS), and EP + LPS (n = five/group). Estradiol/progesterone pellets (Synovex-S) were implanted subcutaneously when calves reached 20 wk of age. One week after implantation, calves were injected i.v. with endotoxin (i.e., lipopolysaccharide; LPS, 0.6 microgram/kg of BW) or nonpyrogenic saline placebo. Body temperature was measured and blood was collected before injection and at 1, 2, 3, 4, 6, and 8 h thereafter. Plasma concentrations of TNF, cortisol, TXB, PRC, NO[x], were measured. Body temperature increased in both LPS and LPS-EP calves, but had returned to normal by 6 h in the LPS-EP group (P < 0.05). Plasma TNF and cortisol increased after LPS (P < 0.01), but were not differentially affected by EP treatment. Likewise, EP did not affect the magnitude of increase in LPS-induced PRC, but EP decreased the magnitude of increase in TXB (P < 0.05). Plasma NO[x]) levels were increased (P < 0.01) in calves after LPS; treatment with EP attenuated the LPS-associated increase in plasma NO[x] levels. These results suggest that EP exerts specific effects on different components of the proinflammatory cytokine cascade. Although the initiation of responses mediated by TNF, cortisol, and PRC do not seem to be differentially affected by EP, components of the nitric oxide- and TXB-axis responses to LPS are decreased in calves pretreated with EP.

Reduced growth of calves and its reversal by use of anabolic agents

Disease has profound effects on the immune system, endocrine system, and on the growth process. Since diseases are catabolic to the animal, there is current interest in the possible role of anabolic hormones to counter the effects of disease in general and minimize the effects of a disease process on growth and development. A number of anabolic hormones, such as growth hormone (GH) and estradiol + progesterone (EP), have been studied for their role in enhancing growth and stimulating immune function and are thus candidates for hormonal intervention in disease processes. GH has been shown to be effective in countering some of the deleterious effects of endotoxemia but was ineffective in a parasitic disease model. Studies with EP have shown similar success with both endotoxemia and a parasitic disease model. Moreover, GH and EP do not share a common mechanism of action, suggesting that the effects are not simply due to anabolic actions. While the mechanism of action of GH in endotoxemia has been examined, the effects of EP are via an unknown mechanism, possibly by inhibition of IL-I action or inhibition of nitric oxide overproduction.

Molecular and pharmacological characterization of the canine brainstem alpha-2A adrenergic receptor

This study characterizes the alpha2-adrenergic receptors present in canine brainstem. Radioligand binding and reverse transcriptase-polymerase chain reaction (RT-PCR) experiments were performed in canine brainstem to identify the receptors present and determine the pharmacological properties of these receptors. The pKi values derived from radioligand competition curves for a number of adrenergic receptor agents at the four alpha2-adrenergic receptor subtypes were compared to the canine brainstem. The pKi values at the canine brainstem alpha2-adrenergic receptor were consistent with the presence of the alpha2A-adrenergic receptor. To determine whether the canine brainstem expressed the message for the alpha2A-adrenergic receptor, RT-PCR was performed with specific primers for the four subtypes of alpha2-adrenergic receptors. In the canine brainstem, only the primers corresponding to a region in the human alpha2A-adrenergic receptor produced a PCR product. No bands were detected in the canine brainstem lanes with the alpha2B-, alpha2C-, or alpha2D-receptor primers. These data suggest that the canine brainstem contains the alpha2A-adrenergic receptor.

Selectivity of atipamezole, yohimbine and tolazoline for alpha-2 adrenergic receptor subtypes: implications for clinical reversal of alpha-2 adrenergic receptor mediated sedation in sheep

The alpha2-adrenergic receptor antagonists, yohimbine, atipamezole and tolazoline, are used in veterinary medicine as reversal agents for the sedative/hypnotic effects of alpha2-agonists. Ruminants have increased sensitivity to the sedative/hypnotic effects of alpha2-agonists compared to other species. The receptors mediating the sedative effects of alpha2-agonists are located primarily on locus coeruleus neurons in the pons of the lower brainstem. Four pharmacological subtypes of the alpha2-adrenergic receptor (A,B, C and D) have been identified based on differences in ligand affinity. The aim of this study was to: 1) determine the pharmacological profile of atipamezole, yohimbine and tolazoline at the four alpha2-adrenergic receptor subtypes and; 2) determine whether these agents differ in their affinities at the alpha2-adrenergic receptor present in the sheep brainstem. In inhibition binding studies against the selective alpha2-adrenergic receptor ligand [3H]-MK-912, tolazoline showed the lowest affinity for all four alpha2-adrenergic receptor subtypes compared to yohimbine and atipamezole. The affinities of yohimbine and atipamezole were similar at the alpha2A-, alpha2B- and alpha2C-adrenergic receptors but differed by approximately 100 fold at the alpha2D-adrenergic receptor. Atipamezole had a 100 fold higher affinity at the alpha2D-adrenergic receptor when compared to yohimbine. To determine the ligand binding characteristics of these agents at the alpha2-adrenergic receptor in sheep brainstem, membranes were labelled with [3H]-MK-912 and inhibition competition curves were performed. Atipamezole showed approximately a 100 fold higher affinity for the sheep brainstem alpha2-adrenergic receptor compared to yohimbine which was similar to what was observed for the alpha2D-adrenergic receptor in PC12 cells transfected with RG-20. The results from these studies suggest that atipamezole has a high affinity for the alpha2D-adrenergic receptor that appears to be the receptor subtype in sheep brainstem.

ANG II-related myocardial damage: role of cardiac sympathetic catecholamines and beta-receptor regulation

The objectives of this study were 1) to determine whether ANG II-induced myocardial damage (ANG Dam) is mediated via the beta1-adrenergic receptor, 2) to elucidate whether adrenal medulla or cardiac sympathetic neuron catecholamines are responsible for ANG Dam, and 3) to determine whether the lack of damage after 3 days of elevated ANG II levels is due to beta1-receptor downregulation. To this end, ANG II was administered to rats 1) that were treated with a beta-receptor blocker, 2) after adrenal medullectomy and/or cardiac sympathectomy, and 3) for 3 or 8 days. ANG II caused both myocyte necrosis and coronary vascular damage after adrenal medullectomy but not after cardiac sympathectomy. There was a 38 and 55% decrease in beta-receptor density after 3 and 8 days, respectively, of ANG II infusion, and an upregulation to control levels 5 days after a 3-day ANG II infusion was stopped. We conclude that cardiac sympathetic neuron catecholamines are responsible for ANG Dam and that the acute nature of this damage is associated with a downregulation of beta1-adrenergic receptors.

Affinity of detomidine, medetomidine and xylazine for alpha-2 adrenergic receptor subtypes

alpha 2-Adrenergic receptor agonists are widely used in veterinary medicine as sedative/hypnotic agents. Four pharmacological subtypes of the alpha 2-adrenergic receptor (A, B, C and D) have been identified based primarily on differences in affinity for several drugs. The purpose of this study was to examine the affinities of the sedative agents, xylazine, detomidine and medetomidine at the four alpha 2-adrenergic receptor subtypes. Saturation and inhibition binding curves were performed in membranes of tissues containing only one subtype of alpha 2-adrenergic receptor. The KD for the alpha 2-adrenergic receptor radioligand, [3H]-MK-912, in HT29 cells (alpha 2A-), neonatal rat lung (alpha 2B-), OK cells (alpha 2C-) and PC12 cells transfected with RG20 (alpha 2D-) were 0.38 +/- 0.08 nM, 0.70 +/- 0.5 nM. 0.07 +/- 0.02 nM and 0.87 +/- 0.03 nM, respectively. Detomidine and medetomidine had approximately a 100 fold higher affinity for all the alpha 2-adrenergic receptors compared to xylazine but neither agonist displayed selectivity for the alpha 2-adrenergic receptor subtypes. These data suggest that available sedative/hypnotic alpha 2-adrenergic receptor agonists can not discriminate between the four known alpha 2-adrenergic receptor subtypes.

Activation of alpha-2 adrenergic receptors inhibits norepinephrine release by a pertussis toxin-insensitive pathway independent of changes in cytosolic calcium in cultured rat sympathetic neurons

Whole-cell electrophysiological studies suggest that sympathetic nerve alpha-2 adrenergic receptors are coupled to voltage-dependent N-type calcium channels through the Gi family of proteins to inhibit neurotransmitter release. Because most nerve terminals are too small for direct electrophysiological recordings, the aim of this study was to examine the relationship between alpha-2 adrenergic receptor-mediated inhibition of norepinephrine release and the rise in cytosolic calcium in neurites from cultured sympathetic neurons. In cultured rat superior cervical ganglion neurons, the alpha-2 adrenergic receptor agonists, UK-14304 (0.01-10 microM) and oxymetazoline (0.1-10 microM), and the N-type calcium channel blocker, omega-conotoxin GVIA (0.1-10 nM), inhibited the release of tritiated norepinephrine in response to electrical stimulation (1 Hz, 30 pulses, 0.1 ms, 70 V). The inhibitory effect of the alpha-2 adrenergic receptor agonists was not altered by pretreatment with pertussis toxin (200 ng/ml, 18 h), although pertussis toxin blocked the inhibition of forskolin-stimulated cAMP accumulation by UK-14304. In fura-2 loaded cells, electrical stimulation (1 Hz, 30 pulses, 0.1 ms, 70 V) increased cytosolic calcium in sympathetic neuronal processes. Blockade of N-type calcium channels with omega-conotoxin (1 and 10 nM) reduced the rise in cytosolic calcium by 25 +/- 3% and 52 +/- 6%, respectively, whereas UK-14304 and oxymetazoline did not alter the electrically stimulated rise in cytosolic calcium. These data suggest that blockade of N-type calcium channels with omega-conotoxin GVIA inhibits stimulated norepinephrine release and cytosolic calcium measured with fura-2 at similar concentrations, whereas activation of alpha-2 adrenergic receptor inhibits norepinephrine release by a pathway that is insensitive to pertussis toxin and changes in cytosolic calcium in neurites from cultured rat superior cervical ganglion cells.

Activation of protein kinase C by angiotensin II decreases beta 1-adrenergic receptor responsiveness in the rat heart

Cardiac beta-adrenergic receptors are the primary driving force for the enhancement of contractility in response to sympathetic stimulation. Angiotensin II influences cardiac function by modulating sympathetic activity and by activating cardiac angiotensin II receptors. The aim of this study was to determine whether activation of cardiac angiotensin II receptors modulates the responsiveness of the heart to beta-adrenergic receptor activation. Male Sprague-Dawley rats were anesthetized and the hearts isolated and perfused with oxygenated Krebs-Henseleit buffer (KHB). Coronary artery perfusion pressure, left ventricular pressure (LVP), left ventricular dP/dtmax, and heart rate (HR) were measured. Bolus administration of the beta-adrenergic receptor agonists, isoproterenol, dobutamine, and salbutamol, produced dose-related increases in LVP, LV dP/dt(max), and HR. Addition of angiotensin-II (10-100 nM) to the KHB slightly increased coronary perfusion pressure but did not alter baseline LVP, LV dP/dt(max), or HR. Angiotensin II reduced the increase in LVP, LV dP/dt(max), and HR elicited by isoproterenol and dobutamine but did not affect responses to salbutamol. The inhibitory effect of angiotensin II was blocked by the AT1-receptor antagonist, losartan, and the protein kinase C inhibitor, calphostin C (50 nM). Activation of protein kinase C with phorbol-12, 13-dibutyrate (PDBu; 10 nM) reduced cardiac responses to all three agonists, although the effects were less on responses elicited by salbutamol. These data suggest that activation of protein kinase C by angiotensin II decreases the responsiveness of the rat heart to beta 1-adrenergic stimulation and that angiotensin II-mediated protein kinase C activation may differ from that activated by phorbol esters.

Neuropeptide Y inhibits adrenergic transmitter release in cultured rat superior cervical ganglion cells by restricting the availability of calcium through a pertussis toxin-sensitive mechanism

Neuropeptide Y has been reported to inhibit the release of the adrenergic transmitter from sympathetic nerves in many tissues. The purpose of this study was to determine the mechanism of the inhibitory effect of neuropeptide Y on the release of the adrenergic transmitter in cultured superior cervical ganglion cells prelabeled with tritiated norepinephrine. In cultured superior cervical ganglion cells superfused with a HEPES-buffered saline, electrical field stimulation (1 Hz, 30 pulses, 1 ms, 60 V) increased the fractional overflow of tritium. Neuropeptide Y (50 nM) attenuated this depolarization-induced increase in transmitter release. The nonhydrolyzable cAMP analog, 8-(4-chlorophenylthio)cyclic AMP (100 microM) and the potassium channel blockers, tetraethylammonium chloride (1 mM) and 4-aminopyridine (300 microM) potentiated the electrically stimulated increase in fractional tritium overflow but failed to alter the inhibitory effect of neuropeptide Y on fractional tritium overflow. Increasing the calcium concentration in the superfusion fluid from 1.8 to 5.4 mM potentiated the electrically stimulated increase in fractional tritium overflow and attenuated the inhibitory effect of neuropeptide Y. Reduction of superfusion fluid calcium concentration to 0.5 mM decreased electrically stimulated fractional tritium overflow and augmented the inhibitory effect of NPY on release of tritium. The fractional release of tritium in response to the calcium ionophore, ionomycin, was not significantly altered by neuropeptide Y. In Fura-2-loaded isolated sympathetic neurites obtained from superior cervical ganglia explants, the depolarization-induced (54 mM KCl) increase in cytosolic calcium was attenuated by neuropeptide Y (50 nM).(ABSTRACT TRUNCATED AT 250 WORDS)

Contribution of calcium to isoproterenol-stimulated lipolysis in the isolated perfused rabbit heart

The present study was performed to investigate the contribution of adenosine 3',5'-cyclic monophosphate (cAMP) and calcium to isoproterenol-stimulated lipolysis in the isolated rabbit heart perfused with Krebs-Henseleit buffer according to the method of Langendorff. Isoproterenol (0.05-1.5 nmol) increased glycerol output, left ventricular dP/dtmax, and heart rate but decreased coronary perfusion pressure. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (50 microM) failed to alter the basal or isoproterenol-induced increase in glycerol output, whereas cilostamide (5 microM) enhanced basal and inhibited isoproterenol-stimulated glycerol output. Inhibition of adenylyl cyclase with (phenylisopropyl)adenosine reduced isoproterenol-stimulated mechanical parameters but had no effect on basal or isoproterenol-stimulated glycerol output, whereas the cAMP analogue 8-(4-chlorophenylthio)-cAMP did not increase glycerol output but produced changes in mechanical parameters similar to isoproterenol. Decreasing perfusion fluid calcium concentration from 1.2 to 0.5 mM or infusion of the calcium channel antagonist diltiazem (23 microM) abolished the increase in glycerol output in response to isoproterenol. Activation of adenylyl cyclase with forskolin increased glycerol output, but the increase was abolished by reducing perfusion fluid calcium concentration or by diltiazem. These data suggest that, in the rabbit heart, isoproterenol-stimulated lipolysis appears to be mediated predominantly by calcium as a secondary metabolic response provided by the increase in mechanical activity.

Cyclic AMP modulates but does not mediate the inhibition of [3H]norepinephrine release by activation of alpha-2 adrenergic receptors in cultured rat ganglion cells

The purpose of this study was to determine whether a decrease in cyclic AMP accumulation mediates the inhibition of norepinephrine release in response to alpha-2 adrenergic receptor activation in cultured rat superior cervical ganglion cells. Superior cervical ganglia from neonatal rats were dissociated and cultured on collagen-coated plastic strips. Neurotransmitter release was assessed by measuring the fractional overflow of tritium in superfused cells prelabeled with [3H]norepinephrine. Intracellular cyclic AMP accumulation was measured using radioimmunoassay. Electrical field stimulation at 1 Hz, 30 pulses, 1 ms duration at 20 min intervals produced an increase in the fractional overflow of tritium that was composed predominantly of intact [3H]norepinephrine. The alpha-2 adrenergic receptor agonist UK-14,304 dose-dependently attenuated the increase in fractional tritium overflow elicited by electrical field stimulation. The adenylyl cyclase activator, forskolin, increased cyclic AMP accumulation in superior cervical ganglion cells and UK-14,304 dose-dependently inhibited forskolin-stimulated cyclic AMP accumulation. UK-14,304 had no effect on basal cyclic AMP accumulation or cyclic AMP accumulation during electrical field stimulation. Forskolin (1-10 microM) or the non-hydrolysable cAMP analog, 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (1-100 microM), slightly increased basal and dose-dependently potentiated the increase in fractional tritium overflow in response to electrical stimulation. Despite enhancement by forskolin and 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate of fractional tritium overflow caused by electrical field stimulation, UK-14304 (1-10 microM) reduced release to a similar degree as that observed in the absence of forskolin or 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of prejunctional alpha-2 adrenergic receptors involved in modulation of adrenergic transmitter release in the isolated perfused rat kidney

The subclassification of alpha-2 adrenergic receptors into A and B subtypes is based on radioligand binding and functional studies. Radioligand binding studies also have suggested the existence of C and D subtypes, which have only been described as binding sites. This study was designed to determine the subtype of prejunctional alpha-2 adrenergic receptor involved in inhibition of norepinephrine release from sympathetic nerves in the rat kidney. Electrically induced (0.25 Hz, 50 V, 0.5 msec, 10 pulses) fractional tritium overflow was measured in kidneys isolated from male Sprague-Dawley rats and prelabeled with [3H]norepinephrine. The alpha-2 receptor antagonists rauwolscine and yohimbine did not enhance fractional tritium overflow, suggesting the lack of autoinhibition at this frequency of stimulation. The alpha-2 receptor agonist, UK-14,304, inhibited electrically stimulated fractional tritium overflow with an ED50 of 4.85 +/- 0.35 nM. pA2 values for various alpha receptor antagonists against UK-14,304-induced inhibition of fractional tritium overflow were: rauwolscine, 8.8; yohimbine, 8.1; prazosin, 7.4; BAM 1303, 7.5; SKF 104078, 6.4; phentolamine, 8.7; WB 4101, 8.1; corynanthine, 6.1; and ARC-239, 7.2. The correlation coefficients and slopes of the regression lines between pA2 values of alpha receptor antagonists at the prejunctional alpha-2 adrenergic receptor and the reported pKi values obtained from radioligand binding studies were: 0.48 and 0.82; 0.61 and 0.58; 0.53 and 0.85; and 0.89 and 1.05 for the alpha-2A, B, C and D adrenergic receptors, respectively. These data suggest that the prejunctional alpha-2 adrenergic receptor modulating [3H]norepinephrine release in the rat kidney most closely resembles the alpha-2D adrenergic receptor characterized by radioligand binding studies.

Mechanism of neurotransmitter release elicited by the preferential alpha 1-adrenergic receptor agonist phenylephrine in superfused superior cervical ganglion cells in culture

Phenylephrine increased [3H]norepinephrine efflux and accumulation of cyclic AMP in cultured rat superior cervical ganglion cells superfused with Tyrode's solution. The purpose of this study was to determine the mechanism and relationship between these two events. Electrical stimulation (1-2 Hz), potassium chloride (50 mM), and the preferential alpha 1-adrenergic receptor agonist phenylephrine (1-100 microM) increased fractional tritium efflux, whereas methoxamine, cirazoline, and amidephrine were relatively ineffective. Phenylephrine, but not methoxamine and cirazoline, also increased cyclic AMP accumulation. Phenylephrine-induced tritium efflux was not altered by alpha- and beta-adrenergic receptor antagonists or by removal of extracellular calcium. Phenylephrine-induced cyclic AMP accumulation was blocked by the beta-adrenergic receptor antagonists propranolol and atenolol. Forskolin (10 microM) and the nonhydrolyzable cyclic AMP analogue 8-(4-chlorophenylthio)cyclic AMP (100 microM) had minimal effect on tritium efflux. However, phenylephrine-evoked increase in tritium efflux was dose dependently attenuated by the neuronal uptake blocker cocaine, and phenylephrine dose-dependently inhibited the incorporation of [3H]norepinephrine into neuronal stores. We conclude that the increase in tritium efflux induced by phenylephrine is independent of cyclic AMP accumulation and appears to be mediated by uptake of phenylephrine via the neuronal carrier-mediated amine transport process, which in turn promotes efflux of the adrenergic transmitter from its storage sites.

Effects of synthetic ANF (rANF(3-28)) on sympathetic neurotransmission in the isolated perfused rat kidney

The effects of synthetic atrial natriuretic factor (rANF(3-28)) on sympathetic neurotransmission in the isolated perfused rat kidney was examined. ANF (10(-10)-10(-7) M) had no significant effect on stimulus-induced (1 Hz, 2 min) overflow of endogenous norepinephrine (NE) from the rat kidney. ANF also failed to affect stimulus-induced overflow which was markedly enhanced as a result of prejunctional beta-adrenoceptor activation with isoproterenol (10(-6)M). However, over the same concentration range ANF markedly attenuated the vasoconstrictor response to nerve stimulation. In addition, ANF significantly reduced the renal vasoconstrictor responses to intra-arterial injections of NE and angiotensin II. These results suggest that, while ANF potently inhibits renal sympathetic neurotransmission by inhibition of vascular responsiveness to vasoconstrictor stimuli, ANF does not appear to have a prejunctional effect to alter NE release from renal sympathetic nerves.

Renal periarterial nerve stimulation-induced vasoconstriction at low frequencies is primarily due to release of a purinergic transmitter in the rat

In the isolated rat kidney, the vasoconstrictor response elicited by periarterial nerve stimulation at low frequencies (2 Hz) is resistant to alpha adrenergic receptor blockade. It has been proposed that in some blood vessels ATP is coreleased with norepinephrine during nerve stimulation to activate P2-purinergic receptors and is responsible for the component of the vasoconstrictor response that is resistant to alpha adrenergic receptor blockade. To assess the contribution of a purinergic transmitter in the vasoconstriction elicited by periarterial nerve stimulation in the isolated Tyrodes-perfused rat kidney, fractional overflow of [3H]norepinephrine and vasoconstrictor responses to renal nerve stimulation were examined after alpha adrenergic receptor blockade and/or P2-purinergic receptor desensitization. The alpha-1 adrenergic receptor antagonists prazosin (0.1-1.0 microM) and corynanthine (0.1-1.0 microM) and the nonselective alpha adrenergic receptor antagonist phentolamine (0.1-1.0 microM) did not significantly reduce vasoconstrictor responses elicited by low frequency (0.5-4 Hz) but attenuated the responses to high-frequency (6-10 Hz) periarterial nerve stimulation. At low-frequency renal nerve stimulation, selective P2-purinergic receptor desensitization abolished the vasoconstriction at 0.5 Hz and dramatically attenuated the responses up to 4 Hz. In the presence of prazosin, the component of the vasoconstrictor response that was resistant to alpha adrenergic receptor blockade at all frequencies of renal nerve stimulation was abolished after treatment with alpha, beta-methylene ATP. On the other hand, in the isolated perfused rabbit kidney, prazosin (1.0 microM) alone reduced dramatically the vasoconstrictor responses to periarterial nerve stimulation over the same frequencies used in the rat.(ABSTRACT TRUNCATED AT 250 WORDS)