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PubMed2004

Path integral approach to Brownian motion driven with an ac force.

Brownian motion in a periodic potential driven by an ac (oscillatory) force is investigated for the full range of damping constant from the overdamped limit to the underdamped limit. The path (functional) integral approach is advanced to produce formulas for the probability distribution function and for the current of the Brownian particle in response to an ac driving force. The negative friction Langevin dynamics technique is employed to evaluate the dc current for various parameters without invoking the overdamped or the underdamped approximation. The dc current is found to have nonlinear dependence upon the damping constant, the potential parameter, and the ac force magnitude and frequency.

Journal Article↗

PubMed1995

Cloning and functional expression of a rat kidney extracellular calcium/polyvalent cation-sensing receptor.

The maintenance of a stable extracellular concentration of ionized calcium depends on the integrated function of a number of specialized cells (e.g., parathyroid and certain kidney epithelial cells). We recently identified another G protein-coupled receptor (BoPCaRI) from bovine parathyroid that responds to changes in extracellular Ca2+ within the millimolar range and provides a key mechanism for regulating the secretion of parathyroid hormone. Using an homology-based strategy, we now report the isolation of a cDNA encoding an extracellular Ca2+/polyvalent cation-sensing receptor (RaKCaR) from rat kidney. The predicted RaKCaR protein shares 92% identity with BoPCaR1 receptor and features a seven membrane-spanning domain, characteristic of the G protein-coupled receptors, which is preceded by a large hydrophilic extracellular NH2 terminus believed to be involved in cation binding. RaKCaR cRNA-injected Xenopus oocytes responded to extracellular Ca2+, Mg2+, Gd3+, and neomycin with characteristic activation of inositol phospholipid-dependent, intracellular Ca(2+)-induced Cl- currents. In rat kidney, Northern analysis revealed RaKCaR transcripts of 4 and 7 kb, and in situ hybridization showed localization primarily in outer medulla and cortical medullary rays. Our results provide important insights into the molecular structure of an extracellular Ca2+/polyvalent cation-sensing receptor in rat kidney and provide another basis on which to understand the role of extracellular divalent cations in regulating kidney function in mineral metabolism.

Amino Acid Sequence↗

PubMed2005

[Implementation of integrated hospital information system in the existing hospital organization--experience at Dubrava Clinical Hospital in Zagreb].

In the modern hospital information systems govern extremely important functions such as patient management, control of work flows, administration, etc., with a great variety of recommended standards used in functional integration of healthcare information systems. The main parts of the original idea of the integrated Hospital Information System have been implemented at Dubrava University Hospital in Zagreb through several phases, resulting in data production covering distinct areas of hospital administration. This paper describes the basic idea of information, organization problems and steps taken in the implementation. International standards in communication have been implemented in the system.

Computer Communication Networks↗

PubMed1995

Assessment of blood-retinal barrier integrity.

The blood-retinal barrier consists of two components which are comprised of the retinal vascular endothelium and the retinal pigment epithelium, respectively. Its functional integrity can be recognized by tight junctions between these cells with a paucity of endocytic vesicles within them and the presence of the molecules that regulate the ionic and metabolic gradients that constitute the barrier. The barrier is compromised in several disease processes and by a variety of agents, but in most cases the location and mechanism for barrier failure is not understood. Perfusion with a variety of radiolabeled tracer molecules, vitreous fluorophotometry, or magnetic resonance imaging can be used to quantitate blood-retinal barrier leakage. Fluorescein angiography or magnetic resonance imaging can localize sites of leakage in vivo with limited resolution. Evans blue dye can be used to visualize blood-retinal barrier failure in gross pathological specimens and immuno-histochemical labeling of serum proteins such as albumin or fibrinogen can be used to localize sites of blood-retinal barrier breakdown by light microscopy. Tracers such as horseradish peroxidase, microperoxidase, or lanthanum, or the immunocytochemical demonstration of albumin can be used to reveal blood-retinal barrier breakdown at the ultrastructural level and provide insights into the mechanisms involved. This review discusses the advantages and limitations of each of these methods to aid in selection of the appropriate techniques to derive the desired information.

Animals↗

PubMed2005

Adult neurogenesis: from precursors to network and physiology.

The discovery that the adult mammalian brain creates new neurons from pools of stemlike cells was a breakthrough in neuroscience. Interestingly, this particular new form of structural brain plasticity seems specific to discrete brain regions, and most investigations concern the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampal formation (HF). Overall, two main lines of research have emerged over the last two decades: the first aims to understand the fundamental biological properties of neural stemlike cells (and their progeny) and the integration of the newly born neurons into preexisting networks, while the second focuses on understanding its relevance in brain functioning, which has been more extensively approached in the DG. Here, we propose an overview of the current knowledge on adult neurogenesis and its functional relevance for the adult brain. We first present an analysis of the methodological issues that have hampered progress in this field and describe the main neurogenic sites with their specificities. We will see that despite considerable progress, the levels of anatomic and functional integration of the newly born neurons within the host circuitry have yet to be elucidated. Then the intracellular mechanisms controlling neuronal fate are presented briefly, along with the extrinsic factors that regulate adult neurogenesis. We will see that a growing list of epigenetic factors that display a specificity of action depending on the neurogenic site under consideration has been identified. Finally, we review the progress accomplished in implicating neurogenesis in hippocampal functioning under physiological conditions and in the development of hippocampal-related pathologies such as epilepsy, mood disorders, and addiction. This constitutes a necessary step in promoting the development of therapeutic strategies.

Aging↗

PubMed2001

Strategies for integrating primary health services in middle- and low-income countries: effects on performance, costs and patient outcomes.

BACKGROUND: Integration of primary health care is change to bring together inputs, organisation, management and delivery of particular service functions. Integration has been promoted in the health sector to improve the efficiency of health care delivery. The need for integration arose from perceptions that services were fragmented when delivered through separate vertical programmes. Integration is relevant to the health system at various levels, and this review is concerned with integration at the point of delivery. OBJECTIVES: To assess the effects of strategies to integrate primary health care services on producing a more coherent product and improving health care delivery and health status, in relation to service cost, outputs, impact and user acceptability. SEARCH STRATEGY: We searched the Cochrane Effective Practice and Organisation of Care Group specialised register (August 2000), MEDLINE (1966 to September 2000), EMBASE (1988 to September 2000), Socio Files (1974 to September 2000), Popline (1970 to September 2000), HealthStar (1975 to September 2000), Cinahl (1982 to September 2000); Cab Health (1972 to 1999), International Bibliography of the Social Sciences (1970 to 1999), and reference lists of articles. We also searched the Internet and World Health Organization (WHO) library database, hand searched relevant WHO publications and contacted experts in the field. SELECTION CRITERIA: Randomised trials, controlled before and after studies, and interrupted time series analyses of integration strategies in primary health care services. Health services in high-income countries were excluded. The primary outcomes were service outputs: productivity and coverage, impact, user acceptability and unit cost. DATA COLLECTION AND ANALYSIS: Two reviewers independently extracted data and assessed study quality. MAIN RESULTS: Four studies were included. There was no consistent pattern of benefit. Integration had a clear positive effect on the outputs in only one study; in another it had similar effects to vertical programme delivery but greater effect than the control group. In the other two studies integration resulted in negative outputs in comparison with vertical programmes, although in one of these integration performed better than the control group. REVIEWER'S CONCLUSIONS: Few studies of good quality, large and with rigorous study design have been carried out to investigate the evidence to support integration as a style of service delivery. In fact, some studies found greater effects for vertical health care delivery. Policy makers and planners considering integration could introduce strategies, using rigorous study design, to allow further evaluation and increase the base of studies from which to draw evidence.

Clinical Trials as Topic↗

PubMed2006

Sample pretreatment on a microchip with an integrated electrospray emitter.

This study presents a microbead-packed PDMS microchip with an integrated electrospray emitter for sample pretreatment prior to sheathless ESI-MS. We prove the concept of analytical functions integrated onto a cm-sized area of a single bulk material. The microchip consists of two PDMS substrates replicated from SU-8 fabricated silicon wafer masters, bonded together after oxidation by corona discharge treatment. The channel within the microchip contains a grid structure that was used to trap 5 microm hypercross-linked polystyrene beads. The beads acted as a medium for sample desalting and enrichment. Electrical contact for the sheathless ESI process was achieved by coating the integrated emitter with conductive graphite powder after applying a thin layer of PDMS as glue. The coating as well as the bond of the PDMS structures showed excellent durability. A continuous spray was obtained from the microchip for over 800 h in a long-term electrospray stability experiment. Desalting and enrichment of neuropeptides from a physiological salt solution was successful by loading the sample onto the packed beads, followed by a washing and an eluting step. The results were obtained and evaluated using a TOF MS. An LOD of approximately 20 fmol (loaded onto the beads) for angiotensin II was obtained from a sample of neuropeptides dissolved in physiological salt solution.

Dimethylpolysiloxanes↗

PubMed2006

Erythropoietin in thyroid cancer.

Erythropoietin (Epo) and the epo-receptor (EpoR) have been implicated in tumor growth, invasion and metastasis. We previously demonstrated Epo and EpoR expression in a small group of archived papillary thyroid cancers (PTC), but were unable to examine functional integrity using formalin-fixed tissues. In the present study, we examined the in vitro expression, induction and function of Epo and EpoR in papillary (NPA), follicular (WRO) and anaplastic (ARO-81) thyroid cancer cells. We found that all three cell lines expressed Epo and EpoR mRNA and that the hypoxia-mimetic cobalt induced Epo expression in all cell lines. None of the growth factors we examined (thyrotropin, vascular endothelial growth factor, IGF-I, or human Epo) altered Epo or EpoR gene expression. Importantly, however, administration of Epo to NPA but not WRO cells resulted in significant alterations in the expression of several mitogenic genes including cyclooxygenase-2 (COX-2), beta-casein (CSN2), wild type p53-induced gene-1 (WIG1) and cathepsin D (CTSD). Epo treated ARO-81 cells only had an increase in CSN2 expression. We conclude that Epo and EpoR are expressed by thyroid cancers and that stimulation of the Epo/EpoR signal pathway results in changes that could impact on the clinical behavior of thyroid cancers.

Carrier Proteins↗

PubMed1989

Steroidogenic properties of isolated turkey adrenocortical cells.

Some functional properties of highly enriched turkey poult adrenocortical cells were characterized. Cells were incubated with various mammalian and avian ACTH analogues, 8-Br-cAMP, and 25-hydroxycholesterol for 2 hr. Corticosterone production and, where appropriate, cyclic AMP (cAMP) production were measured by radioimmunoassay. Human ACTH-(1-24) was the most efficacious and potent ACTH analogue for stimulating corticosterone and cAMP production, whereas turkey ACTH-(1-39) was among the least efficacious and least potent analogues. Maximal corticosterone production induced by 8-Br-cAMP and supported by 25-hydroxycholesterol was 67-109% greater than that induced by ACTH analogues. The data suggest that intracellular concentrations of cAMP-dependent factors and steroidogenic enzymes exceed those which are accessible to ACTH-activated cellular processes. In addition, there were sex-dependent contrasts in some functional parameters, despite the immature status of the birds. Basal corticosterone production of female cells was 19% greater than that of male cells, albeit maximal ACTH analogue-induced corticosterone production was not different between male and female cells. In contrast, maximal 8-Br-cAMP-induced and 25-hydroxycholesterol-supported corticosterone production of male cells were, respectively, 72 and 45% greater than that of female cells, thus suggesting greater intracellular concentrations of protein kinase A-dependent factors and steroidogenic enzymes in male cells compared to female cells. However, maximal ACTH-induced cAMP production of female cells was 21% greater than those of male cells, thus suggesting a compensatory mechanism in female cells. In addition, there were sex-dependent differences in sensitivity to ACTH as indicated by corticosterone and cAMP responses to ACTH analogues: sensitivity to ACTH as indicated by corticosterone and cAMP responses to ACTH analogues: sensitivity of male cells was 1.2-3.2 times that of female cells. A sex-dependent difference in ACTH-cell interaction, possibly including ACTH receptors, is implicated since there were no sex differences in cellular sensitivities to 8-Br-cAMP and 25-hydroxycholesterol. These data indicate that the turkey adrenal gland is amenable for the preparation of isolated adrenocortical cells that have functional integrity. Thus, turkey adrenocortical cells expand the in vitro repertoire for elucidating the regulatory mechanisms of avian adrenocortical function.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2001

p53 cellular localization and function in neuroblastoma: evidence for defective G(1) arrest despite WAF1 induction in MYCN-amplified cells.

This study investigated the hypothesis that p53 accumulation in neuroblastoma, in the absence of mutation, is associated with functional inactivation, which interferes with downstream mediators of p53 function. To test this hypothesis, p53 expression, location, and functional integrity was examined in neuroblastoma by irradiating 6 neuroblastoma cell lines and studying the effects on p53 transcriptional function, cell cycle arrest, and induction of apoptosis, together with the transcriptional function of p53 after irradiation in three ex vivo primary, untreated neuroblastoma tumors. p53 sequencing showed five neuroblastoma cell lines, two of which were MYCN-amplified, and that all of the tumors were wild-type for p53. p53 was found to be predominantly nuclear before and after irradiation and to up-regulate the p53 responsive genes WAF1 and MDM2 in wild-type p53 cell lines and a poorly-differentiated neuroblastoma, but not a differentiating neuroblastoma or the ganglioneuroblastoma part of a nodular ganglioneuroblastoma in short term culture. This suggests intact p53 transcriptional activity in proliferating neuroblastoma. Irradiation of wild-type p53 neuroblastoma cell lines led to G(1) cell cycle arrest in cell lines without MYCN amplification, but not in those with MYCN amplification, despite induction of WAF1. This suggests MYCN amplification may alter downstream mediators of p53 function in neuroblastoma.

Apoptosis↗

PubMed1998

Calcium: outside/inside homeostasis and signalling.

More and more data accumulate concerning calcium dependent effects in all compartments of cells. The higher the organism in evolution the more calcium becomes involved. Inspection of the data while looking for an explanation of the involvement of calcium in metabolism, nuclear functions, control over pumps, external activities, mineralisation and so on leads one to suppose that calcium has an integrating function. The implication is that calcium flow is a large network connecting the environment, the cytoplasm, vesicles, organelles, the nucleus and in higher species, organs. There is the possibility then that calcium ion functions are being analysed, often in vitro, in a bit by bit reductionist manner while in vivo calcium is the equivalent of an electron in complicated electrical circuits. We then should look for its connections to energy, to effects where conformational switching by calcium pulses is equivalent to magnetic triggering by electron flow and where storage in vesicles is equivalent to condenser-like devices and so on. The appearance of pulsing, of time delays in parts of circuits, and other properties of electronic circuits seen in calcium triggering are then explicable as part of calcium circuit design. No other ion can operate in the same way due to the peculiarities of the calcium ion, its size, charge, ionisation potential and its availability which allow it both to flow rapidly yet to bind considerably.

Adenosine Triphosphate↗

PubMed2001

Galactolipids not associated with the photosynthetic apparatus in phosphate-deprived plants.

The galactolipid digalactosyldiacylglycerol (DGGD) is one of the major constituents of thylakoids, accounting for about 25% of polar lipids found in these membranes. Although the presence of DGDG has frequently been correlated with the structural and functional integrity of the photosynthetic apparatus, it is still a matter of debate of what the in-vivo function of DGDG actually might be. To further the understanding of the role of DGDG within the photosynthetic apparatus, experiments were conducted on different Arabidopsis thaliana lines with altered DGDG content. The dgd1 mutant is characterized by a 90% reduction in the DGDG content, resulting in a severe dwarfism during growth. Complementation of the dgd1 mutant with a DGD1 cDNA completely restored the wild-type characteristics, while photosynthesis-related parameters were intermediate in transgenic plants with a partial reduction in DGD1 activity caused by post-transcription gene silencing due to over-expression of a DGD1 cDNA in wild-type plants. These data provide clear evidence for a causal relationship between the DGDG content, and the structure and function of the photosynthetic apparatus. However, a significant DGDG accumulation in the dgd1/pho1 double mutant was without any detectable effect on photosynthetic activity, indicating that the molecular DGDG species synthesized upon phosphate deprivation in leaves cannot substitute for the DGDG species present under normal nutrient supply of plants. It is suggested that depending on the environmental growth conditions different pools of DGDG species exist in plants of which one is not associated with the photosynthetic apparatus.

Arabidopsis↗

PubMed1987

The role of perfusion washout in limb revascularization procedures.

Amputated rat hindlimbs were subjected to either normothermic (26 degrees C) or hypothermic (4 degrees C) ischemia. Experimental limbs had their microcirculation washed out (either before or after the ischemic insult) with a physiologic acellular plasma substitute previously reported to enhance flap survival following extended periods of warm ischemia. Control limbs were not washed out; i.e., stagnant blood remained in these limbs. Following the ischemic interval, amputated limbs were replanted. Monastral blue B, a colloidal pigment capable of labeling leaky blood vessels, was administered systemically to all rats just prior to vascular declamping. Limb biopsies of skin and muscle were harvested 30 minutes following revascularization in order to assess Monastral labeling and, therefore, the functional integrity of the microcirculation. Results confirm that stagnant blood under conditions of warm ischemia is detrimental to the functionality of the microcirculation in both skin (p less than 0.03) and muscle (p less than 0.007). Accordingly, perfusion washout, when performed prior to the ischemic period, enhances limb survival following 6 hours of warm ischemia (p less than 0.01). Hypothermia protects against the detrimental effects of stagnant blood; perfusion offers no benefit if hypothermic conditions prevail. Physiologic mechanisms responsible for these findings are discussed.

Animals↗

PubMed2006

Merging fields: stem cells in neurogenesis, transplantation, and disease modeling.

Traditionally, applied stem cell research has been segregating into strategies aiming at endogenous repair and cell transplantation. Recent advances in both fields have unraveled unexpected potential for synergy between these disparate fields. The increasing dissection of the step-wise integration of adult-born neurons into an established brain circuitry provides a highly informative blueprint for the functional incorporation of grafted neurons into a host brain. On the other hand, in vitro recapitulation of developmental differentiation cascades permits the de novo generation of various neural cell types from pluripotent embryonic stem (ES) cells. Advanced tools in stem cell engineering enable not only genetic selection and instruction of disease-specific donor cells for neural replacement but also the exploitation of stem cells as transgenic cellular model systems for human diseases. In a comparative approach we here illuminate the functional integration of neurons derived from endogenous and transplanted stem cells, the evolving technologies for advanced stem cell engineering and the impact of cloned and mutated stem cells on disease modeling.

Adult↗

PubMed1986

Phenylalanine alters the mean power frequency of electroencephalograms and plasma L-dopa in treated patients with phenylketonuria.

Phenylketonuria is a human model for the study of the effects of phenylalanine on brain function. We found previously a correlation between high blood phenylalanine, prolonged performance times on neuropsychological tests of higher integrative function, and decreased urinary dopamine in 10 patients. In this protocol we examine changes in triplicate of plasma dihydroxyphenylalanine (L-DOPA) and the mean power frequency of the electroencephalogram in eight additional older patients with phenylketonuria using longer intervals in a blinded, cross-over design. Mean power frequency was obtained by Fourier transform of the power spectrum from traditional eight channel electroencephalograms. Plasma L-DOPA was quantitated by radioenzymatic methods. In all patients statistically significant decreases were found in the mean power frequency of the electroencephalogram and in plasma L-DOPA when plasma L-phenylalanine increased. These findings were reversible and correlated in the reverse direction when plasma L-phenylalanine was reduced. Thus changes in the mean power frequency of electroencephalograms and circulating L-DOPA offer sensitive parameters of human brain function in vivo. These findings indicate reversible effects of elevated plasma phenylalanine on electrical function of the brain which may be mediated in part through inhibition of catecholamine synthesis.

Adolescent↗

PubMed2000

Validation of an analytic method of calculating cerebral glucose metabolism using PET.

UNLABELLED: Quantitative modeling of cerebral metabolic rate for glucose (CMRglc) using PET with the FDG method requires calculation of the integral of the time course of radioactivity in arterial plasma. Numeric integration has typically been used but requires 30 or more blood samples taken between 15 s and 100 min after injection of the radiotracer. Our laboratory has developed an alternative integration method that fits the values of the plasma samples to an analytically integrable function using only 4-6 samples taken between 40 and 110 min after radiotracer injection. METHODS: The plasma integrals were calculated by both the analytic and the numeric methods with data from FDG PET studies that were not used in the development of the analytic method. In 39 PET studies from 22 healthy volunteers, 30 plasma samples were taken over 110 min. RESULTS: The plasma integrals determined by the analytic and numeric methods yielded a within-subject correlation coefficient of >0.95 and differences of <10%. CONCLUSION: Because the analytic method requires less blood sampling and does not require sampling immediately after radiotracer injection, the experimental procedure is simplified without loss of accuracy in CMRglc computation, and the effect of missing or incorrect samples is reduced.

Adult↗

PubMed2005

Wrist ligaments: their significance in carpal instability.

BACKGROUND: Understanding the exact contribution of the supporting ligaments to the functional integrity of the wrist is crucial for the diagnosis and treatment of carpal instabilities. The present study evaluates functional significance of the wrist ligaments with respect to carpal instabilities. MATERIALS AND METHODS: Sixteen fresh cadaver wrists were dissected. Extrinsic and intrinsic ligaments of the wrists (ligamentum radioscaphocapitatum, ligamentum radiolunotriquetrum and ligamentum triquetrohamatocapitatum) were sectioned sequentially. After sectioning of each ligament, the wrist was examined for clinical signs of instability such as misalignement of carpal bones, limited range of motion and dorsal translation. When instability was suspected, radiographs were taken and if instability was confirmed, then the ligament was repaired. RESULTS: Although none of the dorsal ligaments sectioning resulted in instability, sectioning of ligamentum scaphotrapeziotrapezoideum, ligamentum radioscaphocapitatum, ligamentum radiolunotriquetrum and ligamentum triquetrohamatocapitatum displayed scaphotrapeziotrapezoidal, dorsal intercalated segment, lunotriquetral and capitohamate instability respectively. In two wrists with arthrosis, sectioning of all ligaments didn't lead to any instability. CONCLUSION: Instability of the wrist can be classified on anatomical basis after the name of these four ligaments involved i.e. l. scaphotrapeziotrapezoideum, l. radioscaphocapitatum, l. radiolunotriquetrum and l. triquetrohamatocapitatum respectively . This approach clarifies the etiology and treatment of carpal instabilities.

Cadaver↗

PubMed1998

[A new formulation of death: definition, criteria and diagnostic tests].

OBJECTIVE: To present a new formulation of human death based on neurological considerations. DEVELOPMENT: One of the reasons there is still controversy over a new formulation of human death which is acceptable to society, is that many authors do not suitably integrate three fundamental aspects which should be included in such a formulation: definition, criteria and diagnostic tests. We review the physiopathological mechanisms for generation of consciousness and discuss the three fundamental criteria presented by different authors in recent decades: the whole encephalum, brainstem death and neocortical criteria. We conclude that there are major contradictions in the three criteria with regard to satisfactory integration of the elements, definition, criteria and diagnostic tests. We therefore present a new formulation of human death. DEFINITION: irreversible loss of consciousness, since this gives the essential human attributes, and is the most integrating function of the organism. CRITERIA: cortico-subcortical connections for the generation of both components of consciousness (capacity and content). DIAGNOSTIC TESTS: no waking response to stimuli (capacity), no cognitive nor affective functions (content). CONCLUSIONS: We present a new formulation of human death on a neurological basis which permits satisfactory integration of the three fundamental elements, definition, criteria and diagnostic tests, and so offers a suitable starting point from which man may start to understand death.

Brain↗