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At least 829 records · Page 46Linked to original sources

PubMed1993

Mechanism of lipid mobilization associated with cancer cachexia: interaction between the polyunsaturated fatty acid, eicosapentaenoic acid, and inhibitory guanine nucleotide-regulatory protein.

During a study of the mechanism of cancer cachexia, a debilitating condition in which catabolism of host muscle and adipose tissue occurs, it has been observed that the process can be effectively reversed in vivo by the polyunsaturated fatty acid, eicosapentaenoic acid (EPA), but not by other PUFA of either the n-3 or n-6 series. In vitro studies showed that EPA blocked the action of a tumour-produced catabolic factor at the level of the adipocyte, and that the effect of EPA also extended to beta-adrenergic stimuli and polypeptide hormones. Again the effect was specific to EPA and appeared to arise from an inhibition of the elevation of cyclic AMP levels in adipocytes in response to varied stimuli. Using isoprenaline stimulated lipolysis as a model system we have shown that EPA has a direct inhibitory effect on isoprenaline-stimulated adenylate cyclase in isolated plasma membrane fractions with half maximal inhibition at a concentration of 165 microM. The inhibitory effect was specific for EPA and was not shown by docosahexaenoic or arachidonic acids. The inhibitory effect of EPA on adenylate cyclase showed properties similar to hormonal inhibition of the enzyme in that it was (i) GTP-dependent, (ii) non-competitive with isoprenaline, (iii) eliminated following treatment of either adipocytes or plasma membrane fractions with pertussis toxin, which is known to ADP-ribosylate the alpha-subunit of an inhibitory guanine nucleotide-regulatory protein (Gi), thus leading to its inactivation. This suggests that inhibition of cyclic AMP formation by EPA was due, at least in part, to a Gi-mediated inhibition of adenylate cyclase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗

PubMedDate not supplied

Overexpression and purification of transcriptionally competent CREB from a recombinant baculovirus.

Signal transduction and viral stimulatory pathways converge ultimately at the level of transcriptional activation to influence the expression of a variety of cellular genes in response to environmental stimuli and developmental signals. Recent studies have implicated the cyclic AMP-responsive element-binding protein (CREB) to be involved in mediating transcriptional activation in response to multiple varied stimuli, including (1) stimulation of the protein kinase A signal transduction pathway; (2) membrane depolarization and increases in intracellular calcium; and (3) viral induced gene expression. In order to study the structure and functional mechanisms of CREB actions in these systems, full-length CREB-327 was expressed in Spodoptera frugiperda (Sf9) cells with the baculovirus expression vector system. The expressed CREB, which is phosphorylated and localized in the nucleus, is capable of enhancing the transcription of a reporter gene containing the CRE sequence in a cell-free transcription assay. Approximately 12.5 mg of purified CREB per liter of infected Sf9 cell culture can be obtained. These large amounts of purified protein will facilitate studies of the structure and functions of this important transcriptional regulatory protein.

Animals↗

PubMed2004

Control of motile and invasive cell phenotypes by focal adhesion kinase.

Cell motility is stimulated by extracellular stimuli and initiated by intracellular signaling proteins that localize to sites of cell contact with the extracellular matrix termed focal contacts. Focal adhesion kinase (FAK) is an intracellular protein-tyrosine kinase (PTK) that acts to regulate the cycle of focal contact formation and disassembly required for efficient cell movement. FAK is activated by a variety of cell surface receptors and transmits signals to a range of targets. Thus, FAK acts as an integrator of cell motility-associated signaling events. We will review the stimulatory and regulatory mechanisms of FAK activation, the different signaling connections of FAK that are mediated by a growing number of FAK-interacting proteins, and the modulation of FAK function by tyrosine and serine phosphorylation. We will also summarize findings with regard to FAK function in vertebrate and invertebrate development as well as recent insights into the mechanistic role(s) of FAK in promoting cell migration. As increased FAK expression and tyrosine phosphorylation have been correlated with the progression to an invasive cell phenotype, there is growing interest in elucidating the important FAK-related signaling connections promoting invasive tumor cell movement. To this end, we will discuss the effects of FAK inhibition via the dominant-negative expression of the FAK C-terminal domain termed FAK-related non-kinase (FRNK) and how these studies have uncovered a distinct role for FAK in promoting cell invasion that may differ from its role in promoting cell motility.

Amino Acid Sequence↗

PubMed2003

Creating biological membranes on the micron scale: forming patterned lipid bilayers using a polymer lift-off technique.

We present a new method for creating patches of fluid lipid bilayers with conjugated biotin and other compounds down to 1 microm resolution using a photolithographically patterned polymer lift-off technique. The patterns are realized as the polymer is mechanically peeled away in one contiguous piece in solution. The functionality of these surfaces is verified with binding of antibodies and avidin on these uniform micron-scale platforms. The biomaterial patches, measuring 1 micro m-76 microm on edge, provide a synthetic biological substrate for biochemical analysis that is approximately 100x smaller in width than commercial printing technologies. 100 nm unilamellar lipid vesicles spread to form a supported fluid lipid bilayer on oxidized silicon surface as confirmed by fluorescence photobleaching recovery. Fluorescence photobleaching recovery measurements of DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiIC(18)(3))) stained bilayer patches yielded an average diffusion coefficient of 7.54 +/- 1.25 microm(2) s(-1), equal to or slightly faster than typically found in DiI stained cells. This diffusion rate is approximately 3x faster than previous values for bilayers on glass. This method provides a new means to form functionalized fluid lipid bilayers as micron-scale platforms to immobilize biomaterials, capture antibodies and biotinylated reagents from solution, and form antigenic stimuli for cell stimulation.

Adsorption↗

PubMed2003

Effects of isoflurane on auditory middle latency (MLRs) and steady-state (SSRs) responses recorded from the temporal cortex of the rat.

Auditory steady-state responses (SSRs) are believed to result from superimposition of middle latency responses (MLRs) evoked by individual stimuli during repetitive stimulation. Our previous studies showed that besides linear addition of MLRs, other phenomena, mainly related to the adaptive properties of neural sources, interact in a complex way to generate the SSRs recorded from the temporal cortex of awake rats. The aim of this study was to evaluate the effects of the inhalational general anesthetic, isoflurane, on MLRs and SSRs at several repetition rates (30-60 Hz) recorded from the temporal cortex of rats. Auditory evoked potentials were obtained by means of epidural electrodes in the awake condition and during anesthesia at three isoflurane concentrations (0.38, 0.76 and 1.13 vol.% in oxygen). MLR latency significantly increased during anesthesia in a concentration-dependent manner, while MLR amplitude, even when significantly attenuated with respect to the mean awake baseline value, failed to correlate with isoflurane concentration. SSRs decreased in amplitude and increased in phase during anesthesia in a concentration-dependent manner and the anesthetic-induced decrease of SSR amplitude appeared to be higher than the corresponding MLR attenuation. SSR prediction curves synthesized by linear addition of MLRs failed to predict SSRs in both amplitude and phase. Moreover, phase discrepancies proved to be higher during anesthesia. Our results suggest that MLRs and SSRs recorded from the temporal cortex of the rat exhibit differential sensitivity to isoflurane and that isoflurane could enhance the role of rate-dependent effects in SSR generation.

Acoustic Stimulation↗

PubMed1999

Factors modulating the blood feeding behavior and the electrophysiological responses of labral apical chemoreceptors to adenine nucleotides in the mosquito Aedes aegypti (Culicidae).

The feeding of Aedes aegypti (L.) on blood is induced by the presence of phagostimulants: adenine nucleotides. Three chemoreceptive cells in the labral apical sensilla can distinguish the presence of adenine nucleotides depending on the other stimulus components. This work aims at correlating the sensory information arising from the labral apical sensilla with the feeding behavior in response to the same stimuli. The saline stimulating solution, containing adenine nucleotides, is modulated by changing one of the following components: salt concentration, buffer or pH. Cell 3 that responds to NaCl in a dose dependent manner seems to have another unique modality. The response of this cell is unaffected by ATP when the stimulating solution is NaCl buffered by NaHCO(3). It responds at a higher spike frequency to the presence of ATP in a NaCl solution without NaHCO(3). Thus in the presence of ATP Cell 3 detects whether the NaCl solution is buffered by NaHCO(3). Both the blood feeding response and the sensory information from Cell 2 (which responds at high spike frequencies to the presence of ATP) are modulated by pH in a similar way. Both responses present a bi-modal response, with a major peak at pH 4.0 and a moderate peak at the most alkaline pH value tested.

Journal Article↗

PubMed2002

Noradrenergic control of auditory information processing in female canaries.

An ethological procedure, based on the study of the sexual responsiveness of female canaries (Serinus canaria) to song playbacks was used to investigate the function of central noradrenergic inputs in the processing of auditory information. The effects of a noradrenergic denervation on sexual responses was analyzed in females exposed to playbacks of biological relevant auditory stimuli, i.e. sexually stimulating songs, presented alone or masked by auditory distractors. A decrease in behavioral responsiveness was observed as a function of the amount of masking distractors indicating that female canaries have the perceptual ability to discriminate and selectively attend to biologically relevant songs. After the systemic administration of DSP-4, a specific noradrenergic neurotoxin, females exhibited an overall decrease in sexual responsiveness to songs masked or not by distractors. No effect of DSP-4 were detected on the motor activity nor on reproductive behaviors. These results indicate that central noradrenergic inputs modulate the sexual behavior of female canaries by affecting the auditory processing of relevant information contained in sexually stimulating songs.

Acoustic Stimulation↗

PubMed2001

Spike timing, synchronization and information processing on the sensory side of the central nervous system.

To what extent is the variability of the neuronal responses compatible with the use of spike timing for sensory information processing by the central nervous system? In reviewing the state of the art of this question, I first analyze the characteristics of this variability with its three elements: synaptic noise, impact of ongoing activity and possible fluctuations in evoked responses. I then review the recent literature on the various sensory modalities: somato-sensory, olfactory, gustatory and visual and auditory processing. I emphasize that the conditions in which precise timing, at the millisecond level, is usually obtained, are conditions that usually require dynamic stimulation or sharp changes in the stimuli. By contrast, situations in which stimulation not belonging to the temporal domain is temporally encoded lead to much coarser temporal coding; although in both cases, neural networks transmit the signals with similarly high precision. Synchronization among neurons is an important tool in information processing in both cases but again seems to act either at millisecond or tens of millisecond levels. Information theory applied to both situations confirms that the average rate of information transmission is much higher in dynamic than in static situations. These facts suggest that channels of precise temporal encoding may exist in the brain but imply populations of neurons working in a yet to be discovered way.

Animals↗

PubMed2001

Effects of baseline skin temperature on pain ratings to suprathreshold temperature-controlled stimuli.

Variations in baseline skin temperature can be encountered in experimental and clinical pain states. Such variations have been shown to greatly alter the response to radiant heat stimuli when the temperature of the stimulus is not controlled. We carried out a psychophysical investigation to examine the influence of baseline skin temperature on pain ratings to temperature-controlled heat stimuli. A CO(2) laser thermal stimulator was used to deliver heat stimuli under radiometer feedback temperature control to the volar forearm. Each stimulus consisted of a 30 s controlled baseline interval (at 34 or 38 degrees C) followed by a stepped increase in temperature (to 46 or 47 degrees C for 1, 2 or 4 s). A run comprised one presentation of each of these12 different stimuli to different locations. Each experiment contained three runs. In runs 2 and 3, the stimulus intensity and duration at a given location were not changed, but the baseline temperature was alternated between 34 degrees C and 38 degrees C. The intensity of pain was rated using the technique of magnitude estimation. Mean normalized pain ratings for suprathreshold stimuli applied from the higher base temperature (1.03+/-0.03) were slightly greater than from the lower base temperature (0.96+/-0.03). In contrast, pain ratings to the 47 degrees C stimuli (1.11+/-0.03) were substantially greater than to the 46 degrees C stimuli (0.88+/-0.03). Thus a 4 degrees C change in baseline temperature has a smaller affect (about 8%) on pain ratings than a 1 degrees C change in stimulus temperature (about 27%). This suggests that variations in baseline skin temperature encountered in experimental and clinical pain states have only a minor impact on pain sensitivity to suprathreshold temperature-controlled stimuli.

Adult↗

PubMed1997

Localization of the messenger RNA for the c-Jun NH2-terminal kinase kinase in the adult and developing rat brain: an in situ hybridization study.

Stress-activated protein kinase/extracellular signal-regulated protein kinase-1/c-Jun NH2-terminal kinase kinase is a dual-specificity kinase which phosphorylates and activates stress-activated protein kinase/c-Jun NH2-terminal kinase, a recently discovered mitogen-activated protein kinase that is stimulated by stressful stimuli and that regulates cellular transcriptional activity. The distribution of the messenger RNA encoding for stress-activated protein kinase/extracellular signal-regulated protein kinase-1 was evaluated in the adult and developing rat central nervous system. In situ hybridization with a 35S-labelled 45mer oligodeoxynucleotide probe was used to map the distribution of the stress-activated protein kinase/extracellular signal-regulated protein kinase-1 messenger RNA in postnatal day 1, 3, 6, 9, 12, 15, 18, 21 and adult rat brains. Specific labelling was generally associated with neuronal profiles. In the adult central nervous system, high hybridization signals were observed in the hippocampus, the granular layer of the cerebellum, the medial habenula, the anterodorsal thalamic nucleus, the red nucleus, the pontine nuclei, the facial nucleus, the motor and mesencephalic nuclei of the trigeminal nerve, the hypoglossal nucleus, the vestibular nucleus and the nucleus ambiguus. Intermediate levels were present in diencephalic and mesencephalic regions and in the neocortex, while basal ganglia displayed a low hybridization signal. In the developing brain, the heterogeneous distribution of the hybridization signal observed in the adult brain was already present, but in the hippocampus and basal ganglia the stress-activated protein kinase/extracellular signal-regulated protein kinase-1 messenger RNA levels were significantly higher at postnatal day 3 and during the second postnatal week than in the adult. The results show that stress-activated protein kinase/extracellular signal-regulated protein kinase-1 is widely expressed in the rat central nervous system and co-localizes with its substrate stress-activated protein kinase. The observed changes in stress-activated protein kinase/extracellular signal-regulated protein kinase-1 messenger RNA levels during postnatal development suggest a role for this protein in the maturation of brain circuits.

Animals↗

PubMed1999

Trigeminal neuralgia: a diagnostic challenge.

A 38-year-old white woman came to the emergency department complaining of severe, unilateral jaw pain. She had consulted her primary care physician and dentist without achieving the correct diagnosis or significant relief of her symptoms. The emergency physician made the diagnosis of trigeminal neuralgia by obtaining a history of severe paroxysmal ipsilateral facial pain activated by numerous facial stimuli. A light stimulation of the trigger point precipitated the pain. Her pain relief from carbamazepine lent further credence to the diagnosis of trigeminal neuralgia and appropriate referral to a neurosurgeon. Pain relief was ultimately achieved for the last 8 months by a neurectomy of the right infraorbital nerve.

Adult↗

PubMed1995

[Consequences of surgery on nutritional status].

Trauma and surgery induce extensive physiological changes, commonly denominated the acute phase reaction (APR). This APR is activated by various kinds of stimuli, namely nociceptive stimulations, tissue injury, tissue ischaemia and reperfusion as well as by haemodynamic disturbances which occur commonly in such patients. APR is mainly characterised by the release of counter-regulatory hormones, complex metabolic changes and by the hepatic synthesis of numerous acute phase factors (C-reactive protein, haptoglobin, complement protein, etc). In addition, fever is typically present and there is a resistance to the nutritional support. The intensity of APR is variable, according to the extent of surgery, the subsequent course, occurrence of complications and to various factors related to the patient and its treatment. In patients with non complicated surgery and low or moderate severity trauma, the metabolic changes are minor and self-limited. In such a condition, there is no need for nutritional support. Conservely, in patients with complicated surgery or major trauma, there is an extensive APR, which can be very prolonged. This results in important and sustained metabolic changes, leading to extensive catabolism and progressive loss of body cell mass. The latter is amplified by the decreased body ability to adapt to starvation and by the resistance to the nutritional support that typically occur in complicated postoperative and trauma patients. Total parenteral nutrition does not prevent from metabolic changes occurring in surgical patients. By contrast, several experimental and human studies have shown that early enteral nutrition may alleviate both the endocrine and metabolic responses in such conditions. Regional anaesthesia, particularly by the epidural route, may also decrease but not abolish the extent of APR.

Acute-Phase Proteins↗

PubMedDate not supplied

Comparison between beta 3 and beta 2 adrenoceptor agonists as inhibitors of gastric acid secretion.

In order to investigate the role of beta 3 adrenoceptors in the regulation of gastric acid secretion we studied the effects of compound SR58611A (a selective agonist for atypical beta adrenoceptors), alone or in combination with beta-adrenoceptor antagonists, in the gastric fistula of a conscious cat. The effects of SR58611A were compared with those of clenbuterol, a selective agonist for beta 2 adrenoceptors. Intravenous infusion of SR58611A (0.3-3 mumol/kg/h) caused a dose-dependent, but partial, inhibition of the acid secretory response to 2-deoxy-D-glucose 100 mg/kg i.v., maximum effect not exceeding 40%. Clenbuterol (0.03-0.1 mumol/kg/h) caused a similar effect (maximum inhibition about 50%) at doses approximately 30 times lower. The acid secretion induced by the histamine H2-receptor agonist dimaprit (1 mumol/kg/h) was minimally affected by both beta adrenoceptor agonists. The inhibitory effect of SR58611A (3 mumol/kg/h) on 2-deoxy-D-glucose-induced acid secretion was not modified by pretreatment with the non-selective beta 1- and beta 2-adrenoceptor blocker propranolol, administered at doses (1.5 mumol/kg iv) that completely blocked the inhibitory effect of clenbuterol (0.1 mumol/kg/h). In contrast, bupranolol (10 mumol/kg i.v.) (a drug endowed with beta 3 antagonistic properties) prevented the inhibitory effects of both SR58611A and clenbuterol. The present data provide functional evidence that, besides beta 2-, also beta 3-adrenoceptors can have negative effects on gastric acid secretion, particularly when it is stimulated by indirect stimuli, like 2-deoxy-D-glucose. This gastric antisecretory activity may represent an additional mechanism for the physio-pharmacological control of gastric acid secretion.

Adrenergic beta-2 Receptor Agonists↗

PubMedDate not supplied

Studies of stimulus-evoked responses in single motoneurones in humans.

Surface electromyography (EMG) has been a powerful technique for studying reflex and other stimulus-evoked responses in the human nervous system. However, important additional insights can be gained into the operation of neural circuits by studying the responses of single motor units to various stimuli. In this paper, some of the advantages of single motor unit recording will be canvassed, and some examples of the application to this method to the study of reflex responses to sensory stimuli and brain stimulation will be presented.

Electric Stimulation↗

PubMed2000

Cytokine production by CAPAN-1 and CAPAN-2 cell lines.

Recently, there has been a great deal of interest in the role of cytokines in acute pancreatitis. Serum levels of IL-1, IL-6, and TNF-alpha have been demonstrated to be elevated in acute pancreatitis. We hypothesized that cytokines may be produced primarily by pancreatic parenchymal cells. Reasoning that ductal epithelium is the cell type most likely to be exposed to noxious stimuli in common causes of pancreatitis, such as ERCP and passage of a gallstone, we examined the response of well differentiated pancreatic ductal adenocarcinoma cell lines to stimuli known to stimulate cytokine production in other cells. CAPAN-1 and CAPAN-2 cells were incubated with endotoxin or TNF-alpha. The supernatant was assayed for production of IL-1, IL-6, and IL-8 by ELISA. The cells were assayed for activation of the transcription factor NF-kappaB by electrophoretic mobility shift assay. There was no detectable production of IL-1 by either cell line. CAPAN-1 cells had concentration-dependent production of IL-6 and IL-8 in response to both endotoxin and TNF-alpha. CAPAN-2 cells had concentration-dependent production of IL-6 and IL-8 in response to TNF-alpha. They had low level expression of IL-8 that was unaffected by any concentration of LPS, and no detectable production of IL-6 in response to LPS. These findings suggest that pancreatic duct cells may take an active part in the pathogenesis of acute pancreatitis through the production of cytokines.

Acute Disease↗

PubMed1991

Investigation of the afferent nerves of the lower urinary tract in patients with 'complete' and 'incomplete' spinal cord injury.

In 52 patients with a post-traumatic spinal cord lesion, both proprioception and exteroception in the lower urinary tract were investigated by determination of filling perception and with sensory threshold measurement towards electrical stimulation. Patients with incomplete lesions had one or both types of perception. Of the 42 patients, with a lesion diagnosed clinically as complete, 15 perceived bladder filling, electrical stimulation or both stimuli, indicating the existence of a nervous afferent pathway between the lower urinary tract and the cerebral cortex.

Afferent Pathways↗

PubMed2006

Effects of antidepressants on the brain/plasma distribution of corticosterone.

It is well established that hypothalamic-pituitary-adrenal (HPA) axis dysregulation, characterized by elevated circulating cortisol concentrations and impaired negative feedback inhibition, is associated with affective disorders. As normalization of the HPA axis function and mood-stabilizing effects occur simultaneously during antidepressant treatment, it is likely that these effects are either directly or indirectly dependent. Although data concerning the outward transport of glucocorticoids from the brain by P-glycoprotein (Pgp) are inconsistent, it has been hypothesized that antidepressants exert their clinical activity in parts by inhibiting Pgp, subsequently leading to enhanced brain glucocorticoid levels and the normalization of the HPA axis function. Here, we report on the effects of different antidepressants (amitriptyline, fluoxetine, mirtazapine, St John's wort extract) on the brain/plasma distribution of corticosterone in mice after acute and subchronic treatment. The four antidepressants exerted different effects on the corticosterone concentration in brain and plasma. Changes in corticosterone levels were highly correlated, suggesting passive diffusion between both tissues. St John's wort extract and fluoxetine elevated brain and plasma corticosterone concentrations after subchronic treatment. Mirtazapine and amitriptyline had no effect on corticosterone concentration after subchronic treatment, possibly because both are also potent antagonists at the 5-HT2 receptor, which mediates HPA axis stimulation by serotonergic stimuli. In addition, St John's wort is the only antidepressant tested which slightly elevated Pgp protein level in the brain.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2002

Mitochondrial dysfunction is an essential step for killing of non-small cell lung carcinomas resistant to conventional treatment.

Apoptosis, a tightly controlled multi-step mechanism of cell death, is important for anti-cancer therapy-based elimination of tumor cells. However, this process is not always efficient. Small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC) cells display different susceptibility to undergo apoptosis induced by anticancer treatment. In contrast to SCLC, NSCLC cells are cross-resistant to a broad spectrum of apoptotic stimuli, including receptor stimulation, cytotoxic drugs and gamma-radiation. Since resistance of tumor cells to treatment often accounts for the failure of traditional forms of cancer therapy, in the present study attempts to find a potent broad-range apoptosis inductor, which can kill therapy-resistant NSCLC cells were undertaken and the mechanism of apoptosis induction by this drug was investigated in detail. We found that staurosporine (STS) had cell killing effect on both types of lung carcinomas. Release of cytochrome c, activation of apical and effector caspases followed by cleavage of their nuclear substrates and morphological changes specific for apoptosis were observed in STS-treated cells. In contrast to treatment with radiation or chemotherapy drugs, STS induces mitochondrial dysfunction followed by translocation of AIF into the nuclei. These events preceded the activation of nuclear apoptosis. Thus, in lung carcinomas two cell death pathways, caspase-dependent and caspase-independent, coexist. In NSCLC cells, where the caspase-dependent pathway is less efficient, the triggering of an AIF-mediated caspase-independent mechanism circumvents the resistance of these cells to treatment.

Amino Acid Chloromethyl Ketones↗