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PubMed2000

Ontogeny of G-protein expression: control by beta-adrenoceptors.

Cardiac cell homeostasis is maintained in the face of excessive beta-adrenoceptor stimulation through the process of desensitization. Desensitization is not an inherent property of these cells but rather is acquired during development; neonates given beta-agonists actually show heterologous sensitization, involving changes in the expression and catalytic activity of adenylyl cyclase (AC) as well as an increased receptor/G-protein coupling. The current study examines the role of specific G-protein components, G(s)alpha and G(i)alpha, in the ontogeny of beta-adrenoceptor responses and in the transition from agonist-induced sensitization to desensitization. Between postnatal days (PN) 6 and 15 there was a significant decrease in the 52 kDa isoform of G(s)alpha with no accompanying change of the 45 kDa form; over the same period, G(i)alpha3 also declined substantially. In contrast, the 45 kDa isoform of G(s)alpha and G(i)alpha1,2 remained fairly constant over the same period and fluoride-stimulated AC activity increased. Treatment with isoproterenol on PN2-5 did not result in any significant changes in G(s)alpha expression but robustly decreased G(i)alpha1,2. These changes were accompanied by heterologous sensitization of AC activity at the level of AC itself, evidenced by equivalent increases in the enzymatic response to fluoride and forskolin-Mn2+. Isoproterenol given to older animals (PN11-14) also caused specific loss of G(i) protein, in this case targeting G(i)alpha3, whereas G(s)alpha again was unchanged; in contrast to the younger group, the older animals displayed heterologous desensitization of AC at the level of G-protein function (specific loss of the fluoride response). These results indicate that the normal ontogenetic increase of cardiac beta-adrenoceptor coupling to AC is not dependent on the absolute amount of G-proteins, nor on the relative balance of stimulatory (G(s)) and inhibitory (G(i)) subunits. However, the ability of receptor stimulation to downregulate G(i)alpha1,2, an event which is specific to immature cardiac cells, is likely to be an important component of the resistance of the fetal/neonatal heart to agonist-induced desensitization and hypertrophy. The maintenance of cardiac beta-adrenoceptor signaling in the face of intense stimulation is likely to play an important role in the physiologic adaptations necessary to the perinatal transition.

Adrenergic beta-Agonists↗
PubMed1992

Molecular insights into human immunodeficiency virus type 1 pathogenesis.

Infection with human immunodeficiency virus type 1 leads to a persistent but progressive cytopathic process that culminates in the near complete destruction of the CD4+ subset of T cells. The levels of human immunodeficiency virus type 1 replication and virus burden increase throughout the clinical course of disease reflecting a balance between the viral and cellular regulatory influences as well as the ability of the host immune system to eliminate infected T cells. Human immunodeficiency virus type 1 replication is dependent on the state of cellular activation and involves both inducible host cell derived transcription factors and at least three virus-derived gene products. Further study of the mechanism of action of these factors, particularly those encoded by the virus, may facilitate the future development of highly specific and effective therapies for human immunodeficiency virus type 1.

CD4-Positive T-Lymphocytes↗
PubMed1989

Taste reactivity analysis of 6-hydroxydopamine-induced aphagia: implications for arousal and anhedonia hypotheses of dopamine function.

The deficits in feeding and drinking that result from 6-hydroxydopamine (6-OHDA) lesions of the mesostriatal dopamine system are often explained using either sensorimotor arousal or anhedonia hypotheses. Sensorimotor arousal hypotheses posit that dopamine systems facilitate the capacity of sensory stimuli to activate any motor output. The anhedonia hypothesis suggests that dopamine systems amplify the hedonic impact of positive reinforcers. Natural palatability-dependent ingestive and aversive actions, which are emitted by rats to tastes, provide a sensitive test that can discriminate between these hypotheses: A reduction of sensorimotor arousal should diminish the ability of tastes to elicit any actions, whereas anhedonia should shift the balance between positive and aversive actions. To directly compare these two hypotheses, taste reactivity was examined in rats made aphagic by intranigral 6-OHDA injections. The results did not support either of these predictions: Taste reactivity was essentially unchanged. The persistence of normal taste reactivity argues against both an anhedonia and a global sensorimotor arousal interpretation and provides further evidence that the capacity for hedonics can be neurologically dissociated from motivated appetitive behavior. An incentive attribution hypothesis that can account for the results is discussed, along with its implications for a wide range of phenomena associated with dopamine depletion.

Animals↗
PubMed2002

The survivin:Fas ratio is predictive of recurrent disease in neuroblastoma.

BACKGROUND/PURPOSE: Several clinical and biologic features of neuroblastoma (NB) are used to predict the risk of recurrent disease. The balance between antiapoptotic and proapoptotic factors within a tumor may affect its ability to survive. Survivin is an antiapoptotic factor expressed in highly proliferative NB, whereas Fas is a proapoptotic factor that portends a favorable prognosis. The authors determined whether the ratio of survivin to Fas (S:F ratio) is predictive of recurrent disease in patients with NB. The authors previously have shown the S:F ratio is predictive of recurrent disease in pediatric renal tumors. METHODS: The authors quantified the levels of 9 different apoptotic mRNA species using Rnase Protection assay (RPA, Riboquant, PharMingen, San Diego, CA). Twenty-eight primary tumor specimens were evaluated from patients with ganglioneuroma (n = 3), ganglioneuroblastoma (n = 2), and neuroblastoma (n = 23) from tumors of all clinical stages obtained at the time of diagnosis. mRNA levels were calculated as a percentage of L32 for each specimen assayed, and positive expression was assumed to be greater than 10% of L32. RESULTS: Survivin was expressed in 90% of tumors that went on to recur and only in 27.7% of those that were cured. The S:F ratio was significantly greater in tumors that went on to recur (n = 10) compared with those from patients that were cured (n = 18) (median S:F ratio, 3.3 v 0.75; P =.0002, Wilcoxon rank-sum test). A cutoff ratio of 2.3 was highly predictive of tumor recurrence irrespective of clinical stage of disease (area under ROC curve = 0.906). Sensitivity was 80% (CI, 44.4% to 97.5%), specificity was 94.4% (CI, 72.7% to 99.9%), positive predictive value was 88.9% (CI, 51.8% to 99.7%), and negative predictive value was 89.5% (66.9% to 98.7%). Twenty-five of 28 (89.3%) tumor ratios were correct in predicting outcome. CONCLUSIONS: The survivin:Fas ratio in primary tumors may be used to predict the risk for recurrent disease in patients with NB. The S:F ratio appears to be a more sensitive predictor of recurrent disease than survivin expression alone. Determining this ratio may not only be helpful in guiding follow-up of patients with NB, but also may aid in stratifying patients for more aggressive therapeutic strategies.

Child↗
PubMedDate not supplied

[Long-term course of 6 boys with congenital nephrogenic diabetes insipidus].

From 1975-1986 6 boys with congenital nephrogenic diabetes insipidus were diagnosed at the age of 3 months to 10 years. Symptoms appeared within the first few weeks of life. The diagnosis was confirmed by polyuria, low urinary osmolality (97-225 mosm/kg H20), hypernatraemia (max. 171 mmol/l) and the missing response to vasopressin. The treatment was variable; 4 boys received only hydrochlorothiazide (2-2.5 mg/kg/d) which lead to a reduction of the daily urinary volume of 26-44%. Hyperelectrolytaemia disappeared and a normal thriving could be achieved. Later an additional treatment with indomethacin (2 mg/kg/d) was necessary in 3 boys because of an increase of polyuria; there was a further reduction of the daily urinary volume of 50-60%. The combination of hydrochlorothiazide and indomethacin in the treatment of the congenital nephrogenic diabetes insipidus was well tolerated and seems to be--especially during the first few years of life--a necessary and effective treatment which allows a normal thriving and psychointellectual development.

Adolescent↗
PubMed2001

Nicotine preconditioning antagonizes activity-dependent caspase proteolysis of a glutamate receptor.

Neuronal excitation is required for normal brain function including processes of learning and memory, yet if this process becomes dysregulated there is reduced neurotransmission and possibly death through excitotoxicity. Nicotine, through interaction with neuronal nicotinic acetylcholine receptors, possesses the ability to modulate neurotransmitter systems through numerous mechanisms that define this critical balance. We examined the modulatory role of nicotine in primary mixed cortical neuronal-glial cultures on activity-dependent caspase cleavage of a glutamate receptor, GluR1. We find that GluR1, but not GluR2 or GluR3, is a substrate for agonist (alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid)-initiated rapid proteolytic cleavage at aspartic acid 865 through the activation of caspase 8-like activity that is independent of membrane fusion and is not coincident with apoptosis. Dose-dependent nicotine preconditioning for 24 h antagonizes agonist-initiated caspase cleavage of GluR1 through a mechanism that is coincident with desensitization of both nAChRalpha4beta2 and nAChRalpha7 receptors and the delayed activation of a caspase 8-like activity. The modulation of GluR1 agonist-initiated caspase-mediated cleavage by nicotine preconditioning offers a novel insight into how this agent can impart its numerous effects on the nervous system.

Animals↗
PubMed2005

Nutritional status, cognition, and survival: a new role for leptin and AMP kinase.

Although adequate nutrition is essential for optimal neural activity and survival, mild energy restriction may improve cognition and prolong longevity. Energy status is monitored by the cellular AMP-activated protein kinase (AMPK) system, whereas leptin regulates total energy balance. We investigated the roles of AMPK and leptin in cognition and survival under diet restriction (DR). Hippocampal AMPK activity increases with energy restriction. Modest activation (DR to 60%) induces neurogenesis and improves cognition. However, DR to 40% augmented AMPK activity, reduced cognition and catecholamines, and increased neural apoptosis and mortality. Leptin signaling is preserved only in DR to 60%, countering the effects of AMPK "overactivation" by preventing neuroapoptosis, restoring noradrenergic activity and behavioral performance, and increasing longevity. The balance between leptin and AMPK is crucial in determining neuronal fate, cognitive ability, and survival. Should these findings extend to Man, then controlled activation of AMPK may improve neurodegenerative diseases, and leptin may have a new role in treating stress-associated malnutrition.

Adenylate Kinase↗
PubMed2001

Gene expression in the mammalian cochlea: a study of multiple vector systems.

Successful delivery of genes to the inner ear has been demonstrated using a variety of vectors and animal models. As our understanding of the molecular pathophysiology of hearing and balance disorders increases, the delivery of genes is becoming central to our ability to manipulate the function of the inner ear. This study evaluates the efficacy of gene transfer and the distribution of three different vector types within the inner ear. Adenovirus vectors, herpes virus vectors and liposomes carrying a plasmid with the green fluorescent protein or beta galactosidase marker genes and a CMV promoter were introduced into the inner ear of 3-month-old mice. The temporal bones and brain were then removed from the animals and examined for transgene expression. Distribution of staining in the treated ear was compared with distribution of staining in the contralateral inner ear. Staining for T cell markers was also carried out to determine inner ear immune response to gene transfer. Herpes virus vectors appear to target neurons most efficiently. Liposome vectors were least efficient in terms of gene transfer. Adenovirus vectors accomplished gene transfer to the widest variety of inner ear cells including auditory and vestibular hair cells. Newer generation adenovirus vectors promise less immune reaction and toxicity than traditional vectors and will be useful for both research and future clinical applications.

Animals↗
PubMed1978

The nephron in transport of sodium, amino acids, and glucose.

The ability of the kidney to maintain overall control of sodium and fluid balance appears greater than the sum of its parts, yet microperfusion and dissection studies that have assigned particular transport processes to individual segments of the nephron are helping to clarify a number of clinical states. Among those that can be so localized are certain congenital disorders accompanied by glycosuria and aminoaciduria.

Adenosine Triphosphate↗
PubMed1999

Ex vivo expansion of hematopoietic stem and progenitor cells: are we there yet?

Ex vivo expansion of hematopoietic stem and progenitor cells is a very ambitious idea that would have major implications in the areas of stem cell transplantation and somatic gene therapy. However, successful ex vivo expansion has evaded and frustrated scientists for a number of years. The goal of ex vivo expansion is to induce cell division and proliferation of stem cells while maintaining their primary functional characteristic, namely, their ability to engraft and sustain long-term hematopoiesis. Only when a balance between these two requirements is reached can ex vivo expansion of stem cells be considered successful. Establishing such a balance has not been easy. However, many lessons have been learned along the way, and today we have a more profound understanding of the potential obstacles facing ex vivo expansion than we did only a few years ago. In this review, we discuss these obstacles and evaluate the current status of ex vivo expansion of stem and progenitor cells both from the perspective of basic stem cell biology and from the viewpoint of clinical utility of these cells in transplantation.

Cell Culture Techniques↗
PubMed1999

Metabolic flux analysis: a powerful tool for monitoring tissue function.

In recent years, metabolic flux analysis has been widely used in bioprocess engineering to monitor cell viability and improve strain activity. Metabolic flux analysis refers to a methodology for investigating cellular metabolism whereby intracellular fluxes are calculated using a stoichiometric model for the major intracellular reactions and applying mass balances around intracellular metabolites. A powerful feature of this methodology is its ability to consider cellular biochemistry in terms of reaction networks. By considering the stoichiometry of biochemical reactions, it is possible to estimate the degree of engagement of each pathway participating in overall cellular activity, and hence obtain a comprehensive view of a cell s metabolic state. Given the potential impact of cellular energy metabolism on the function of engineered tissues, such comprehensive analysis of metabolic activity can be an extremely useful tool for tissue engineers. Estimates of intracellular fluxes under various environmental conditions could be used to optimize function in vivo as well as culture conditions in vitro. In this review, we provide a brief theoretical background of metabolic flux analysis and summarize the most widely used experimental approaches to obtain flux data. This review is intended as an overview of the field and as a starting point for tissue engineers wishing to learn about and eventually employ this methodology.

Animals↗
PubMed2003

Identity processing and self-consciousness in middle and later adulthood.

Identity process theory proposes that adjustment to aging can be conceptualized as involving the three processes of identity assimilation (maintaining self-consistency), identity accommodation (making changes in the self), and identity balance (maintaining a sense of self but changing when necessary). Measures of the identity processes and self-consciousness were administered to a community sample of 173 adults (108 women and 65 men) ranging in age from 42 to 85 years (M = 60.80; SD = 12.58). Consistent with theory, identity assimilation was positively associated with age and negatively related to self-reflection. Identity accommodation was negatively related to age and internal state awareness and positively related to self-reflection and public self-consciousness. Identity balance alone was positively related to internal state awareness, indicating that the ability to incorporate age-related changes within identity but at the same time maintain a consistent and positive view of the self is most conducive to successful aging.

Adaptation, Psychological↗
PubMed1998

Changing perspectives on aging and energy requirements: aging and digestive function in humans, dogs and cats.

When considering the question of energy balance, it is important to take into account energy provision and the ability of aging animals to digest macronutrients and thus obtain their maintenance energy requirement. A large number of studies have been conducted in humans in an effort to establish whether aging of the gastrointestinal tract has a significant effect on availability of dietary energy. The results of these studies have been conflicting, with indications that some aspects of gut functionality do decline with age, but little evidence overall to suggest that aging humans are at risk of energy deficit due to compromised digestive efficiency. A number of digestibility studies carried out with dogs confirm that there is no evidence of an age-related decline in digestive efficiency. This knowledge makes the determination of energy provision to senior dogs relatively straightforward to calculate. Many senior cats appear to exhibit quite a marked reduction in their ability to digest macronutrients, particularly fat, efficiently. Because this reduces the overall capacity to obtain energy from the diet, it is recommended that old cats should not routinely be offered reduced energy diets. For senior cats, the feeding regimen in later life should be to offer highly digestible diets that provide as much energy as adult maintenance rations.

Aged↗
PubMed1986

Early experience with continuous arteriovenous hemofiltration in critically ill pediatric patients.

The applicability of continuous arteriovenous hemofiltration (CAVH) for renal replacement therapy was evaluated in three infants and two young children with catastrophic medical and surgical illnesses. In the first four patients, CAVH was used in conjunction with either peritoneal or hemodialysis. In the fifth patient, CAVH was the sole renal replacement therapy employed; in this critically ill anuric infant, we were best able to evaluate the ability of CAVH to continuously control fluid, electrolyte, and acid-base balance, and allow the administration of adequate parenteral nutrition. The difficulties encountered were related to anticoagulation, establishment of adequate vascular access, and selection of an appropriate hemofilter for the performance of the technique. Despite the application of suction-assistance, we were unable to effectively employ a prototype pediatric hemofilter to attain a level of plasma ultrafiltration consistent with the objectives of therapy. However, we were able to effectively and safely employ an adult hemofilter for these purposes; modifications were made in the adult hemofilter system before its application in the smallest pediatric patients. Our experience suggests that, even in critically ill infants, CAVH can be successfully applied as an effective renal replacement therapy. However, further experience is required before its potential impact on patient survival can be assessed.

Acute Kidney Injury↗
PubMed2000

Altered plasma cytokines and total glutathione levels in parenterally fed critically ill trauma patients with adjuvant recombinant human growth hormone (rhGH) therapy.

OBJECTIVES: Glutathione (GSH) is a potent endogenous antioxidant that serves as one of the body's most important defenses against oxygen metabolites. Plasma levels of GSH are maintained primarily by a balance between secretion from the liver and degradation in the kidney. The ability to maintain and enhance tissue GSH may be of particular importance in controlling cytokine production in response to a stimulus like injury. The interaction after severe trauma between GSH and cytokines, tumor necrosis factor (TNF) -alpha, and interleukin (IL)-6, are not known. The purpose of the study was to investigate the levels of plasma GSH and cytokines TNF-alpha and IL-6 in adult patients admitted to the intensive care unit of our level I trauma center who were treated with recombinant human growth hormone (rhGH) for > or =7 days. DESIGN: Prospective, randomized, controlled trial. SETTING: Trauma intensive care unit. PATIENTS: Twenty-eight patients with multiple injuries and 14 normal postabsorptive controls. INTERVENTIONS: From 48-60 hrs after injury, when resuscitation was complete, a stable hemodynamic status was achieved and the patients were receiving maintenance fluid without nitrogen or calories, a blood sample was drawn for basal, plasma GSH, TNF-alpha, and IL-6 measurement. Intravenous feeding was then started and continued for 7 days. The patients were randomized to receive or not to receive daily intramuscular doses of recombinant human growth hormone (0.15 mg rhGH/kg/day). Daily morning plasma was obtained for analysis of GSH, TNF-alpha, and IL-6 levels. RESULTS: In the early catabolic "flow phase" of severe injury, the plasma levels of GSH were not altered but plasma TNF-alpha and IL-6 levels were increased significantly, compared with uninjured controls. Seven days of total parenteral nutrition alone enhanced plasma GSH levels (76%), but no change in TNF-alpha was observed. Supplementation with rhGH enhanced GSH (180%), and TNF (65%) with no changes in IL-6 levels. There is a significant linear relationship between plasma GSH and TNF-alpha levels in our rhGH-supplemented trauma patients. CONCLUSION: Modification of plasma GSH and TNF-alpha levels by adequate nutritional support with adjuvant rhGH during the postinjury period demonstrates the beneficial role of GSH in enhancing antioxidant defenses.

Adolescent↗
PubMed1994

Effects of S-dobutamine on ischemic myocardium caused by coronary artery narrowing.

Cardiovascular effects of S-dobutamine were compared with effects of vehicle and other catecholamines in dogs during and after 3 days of approximately 90% ligation of the left anterior descending coronary artery (LAD). Twenty-four hours after LAD ligation, dogs infused with S-dobutamine (2.5 micrograms/kg/min intravenously, i.v.) maintained systolic blood pressure (SBP 149 +/- 6 mm Hg), diastolic blood pressure (DBP 100 +/- 6 mm Hg), and aortic dP/dt60 (2.8 +/- 0.2 s-1), with no significant changes from preligation values. In comparison, saline-treated dogs showed decreases in arterial BP and contractility: SBP 121 +/- 4 mm Hg; DBP 85 +/- 3 mm Hg; and aortic dP/dt60 was 1.9 +/- 0.1 s-1. S-Dobutamine-infused dogs had a heart rate (HR) of 148 +/- 5 beats/min with 44 +/- 14 beats/min premature ventricular contractions (PVCs), whereas dogs infused with saline, R-dobutamine, dopamine, norepinephrine (NE), or isoproterenol (ISO) all displayed a significantly greater number of PVCs at 24 h. Myocardial necrosis was limited by S-dobutamine treatment (2.5 micrograms/kg/min i.v. for 54 h). As demonstrated by histologic examination, S-dobutamine ameliorated the effects of ischemia as compared with vehicle, R-dobutamine, dopamine, hexamethonium, NE, or ISO. Myocardial tissue electrolytes, quantified 72 h after LAD ligation, were maintained by S-dobutamine-infused dogs in all sections of left ventricle (LV); but in saline-treated dogs, Ca2+ increased eightfold, Na+ increased twofold, and both K+ and Mg2+ decreased 50% in tissue "at risk" as compared with tissues "not at risk." Coronary nutrient blood flow (CNBF) to myocardial capillary vessels was calculated by radiolabeled microspheres 2 h after LAD ligation. As compared with CNBF in untreated hearts, endocardial CNBF in hearts receiving S-dobutamine (5 micrograms/kg/min i.v.) increased from 26 +/- 8 to 49 +/- 15 ml/min/100 g in tissue at risk, from 102 +/- 26 to 217 +/- 50 in "border zone," and from 133 +/- 13 to 215 +/- 41 in tissue not at risk. CNBF values in animals receiving vehicle infusion were not significantly different from CNBF values measured after ligation only. The S-enantiomer of dobutamine, infused in dogs for 54 h after coronary artery ligation, maintained cardiac performance, electrolyte balance, and myocardial cellular viability and reduced incidences of arrhythmias through its ability to increase CNBF without increasing HR.

Animals↗