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Biomedical subjects

C Gentry

Publications and source records attributed to C Gentry.

At least 19 recordsLinked to original sources

Regulation and function of spinal and peripheral neuronal B1 bradykinin receptors in inflammatory mechanical hyperalgesia.

Activation of either B1 or B2 bradykinin receptors by kinins released from damaged tissues contributes to the development and maintenance of inflammatory hyperalgesia. Whereas B2 agonists activate sensory neurones directly, B1 agonists were thought only to have indirect actions on sensory neurones. The recent discovery of constitutive B1 receptor expression in the rat nervous system lead us to re-investigate the role of neuronal B1 receptors in inflammatory hyperalgesia. Therefore we have examined B1 bradykinin receptor regulation in rat dorsal root ganglia in a model of inflammatory hyperalgesia, and correlated it with hyperalgesic behaviour. Twenty-four hours after injection of Freund's complete adjuvant into one hindpaw, there was a significant increase in B1 protein expression (measured by immunohistochemistry) in both ipsilateral and contralateral dorsal root ganglion neurones, whereas axotomy resulted in reduction of B1 protein in ipsilateral dorsal root ganglia. In behavioural experiments, the B1 antagonist desArg10HOE140, administered by either intrathecal or systemic routes, attenuated Freund's complete adjuvant-induced mechanical hyperalgesia in the inflamed paw, but did not affect mechanical allodynia. The B1 agonist, desArg9BK, did not affect paw withdrawal thresholds in nai;ve rats following intraplantar administration into the paw, whilst intrathecal administration elicited mechanical hyperalgesia. However, after Freund's complete adjuvant-induced inflammation, desArg9BK caused a marked mechanical hyperalgesia, by either route, of the contralateral, uninflamed hindpaw, correlating with the observed contralateral and ipsilateral increases in receptor levels. Our results suggest a functional role for B1 receptors expressed both in the periphery and in the spinal cord, in mechanical hyperalgesia during inflammation.

Animals↗

Epilepsy, hyperalgesia, impaired memory, and loss of pre- and postsynaptic GABA(B) responses in mice lacking GABA(B(1)).

GABA(B) (gamma-aminobutyric acid type B) receptors are important for keeping neuronal excitability under control. Cloned GABA(B) receptors do not show the expected pharmacological diversity of native receptors and it is unknown whether they contribute to pre- as well as postsynaptic functions. Here, we demonstrate that Balb/c mice lacking the GABA(B(1)) subunit are viable, exhibit spontaneous seizures, hyperalgesia, hyperlocomotor activity, and memory impairment. Upon GABA(B) agonist application, null mutant mice show neither the typical muscle relaxation, hypothermia, or delta EEG waves. These behavioral findings are paralleled by a loss of all biochemical and electrophysiological GABA(B) responses in null mutant mice. This demonstrates that GABA(B(1)) is an essential component of pre- and postsynaptic GABA(B) receptors and casts doubt on the existence of proposed receptor subtypes.

Animals↗

Metabotropic glutamate receptor subtype 5 (mGlu5) and nociceptive function. I. Selective blockade of mGlu5 receptors in models of acute, persistent and chronic pain.

The excitatory neurotransmitter, glutamate, is particularly important in the transmission of pain information in the nervous system through the activation of ionotropic and metabotropic glutamate receptors. A potent, subtype-selective antagonist of the metabotropic glutamate-5 (mGlu5) receptor, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), has now been discovered that has effective anti-hyperalgesic effects in models of inflammatory pain. MPEP did not affect rotarod locomotor performance, or normal responses to noxious mechanical or thermal stimulation in naïve rats. However, in models of inflammatory pain, systemic administration of MPEP produced effective reversal of mechanical hyperalgesia without affecting inflammatory oedema. In contrast to the non-steroidal anti-inflammatory drugs, indomethacin and diclofenac, the maximal anti-hyperalgesic effects of orally administered MPEP were observed without acute erosion of the gastric mucosa. In contrast to its effects in models of inflammatory pain, MPEP did not produce significant reversal of mechanical hyperalgesia in a rat model of neuropathic pain.

Animals↗

The role of central and peripheral Cannabinoid1 receptors in the antihyperalgesic activity of cannabinoids in a model of neuropathic pain.

We have examined the effects of cannabinoid agonists on hyperalgesia in a model of neuropathic pain in the rat and investigated the possible sites of action. The antihyperalgesic activity of the cannabinoids was compared with their ability to elicit behavioural effects characteristic of central cannabinoid activity. WIN55,212-2 (0.3-10 mg kg(-1)), CP-55,940 (0.03-1 mg kg(-1)) and HU-210 (0.001-0.03 mg kg(-1)) were all active in a 'tetrad' of tests consisting of tail-flick, catalepsy, rotarod and hypothermia following subcutaneous administration, with a rank order of potency in each of HU-210 > CP-55,940 > WIN55,212-2. The effects of WIN55,212-2 in each assay were blocked by the Cannabinoid1 (CB1) antagonist SR141716A. In the partial sciatic ligation model of neuropathic pain WIN55,212-2, CP-55,940 and HU-210 produced complete reversal of mechanical hyperalgesia within 3 h of subcutaneous administration with D50 values of 0.52, 0.08 and 0.005 mg kg(-1), respectively. In this model WIN55,212-2 was also effective against thermal hyperalgesia and mechanical allodynia. WIN55,212-2 produced pronounced reversal of mechanical hyperalgesia following intrathecal administration that was blocked by the CB1 antagonist SR141716A. Following intraplantar administration into the ipsilateral hindpaw, WIN55,212-2 produced up to 70% reversal of mechanical hyperalgesia, although activity was also observed at high doses following injection into the contralateral paw. The antihyperalgesic effect of WIN55,212-2 injected into the ipsilateral paw was blocked by subcutaneously administered SR141716A, but was not affected by intrathecally administered SR141716A. These data show that cannabinoids are highly potent and efficacious antihyperalgesic agents in a model of neuropathic pain. This activity is likely to be mediated via an action in both the CNS and in the periphery.

Analgesics↗

VR1 protein expression increases in undamaged DRG neurons after partial nerve injury.

Changes in phenotype or connectivity of primary afferent neurons following peripheral nerve injury may contribute to the hyperalgesia and allodynia associated with neuropathic pain conditions. Although earlier studies using partial nerve injury models have focused on the role of damaged fibres in the generation of ectopic discharges and pain, it is now thought that remaining undamaged fibres may be equally important. We have examined the expression of the sensory neuron-specific cation channel Vanilloid Receptor 1 (VR1), an important transducer of noxious stimuli, in three models of nerve injury in the rat, using anatomical separation or fluorescent retrograde tracers to identify damaged or undamaged sensory neurons. After total or partial sciatic nerve transection, or spinal nerve ligation, VR1-immunoreactivity (IR) was significantly reduced in the somata of all damaged dorsal root ganglion (DRG) neuronal profiles, compared to controls. However, after partial transection or spinal nerve ligation, VR1 expression was greater in the undamaged DRG somata than in controls. Unexpectedly, after L5 spinal nerve ligation, VR1-IR of the A-fibre somata increased approximately 3-fold in the uninjured L4 DRG compared to controls; a much greater increase than seen in the somata with C-fibres. Furthermore, we found that VR1-IR persisted in the transected sciatic nerve proximal to the lesion, despite its down-regulation in the damaged neuronal somata. This persistence in the nerve proximal to the lesion after nerve section, together with increased VR1 in DRG neurons left undamaged after partial nerve injury, may be crucial to the development or maintenance of neuropathic pain.

Animals↗

Complementary and alternative medicine: applications and implications for cognitive functioning in elderly populations.

OBJECTIVE: Aged populations in the United States are growing in numbers, and stand to be affected most by the changing shape of healthcare delivery. Within these elderly populations, the problem of decreased cognitive functioning due to dementing disorders is rising. Recent compelling research on complementary and alternative medicine interventions targeted at cognitive deficits in the elderly is reviewed in this survey. DATA SOURCES: A literature review was undertaken to identify original clinical research studies, review articles, chapters, and books on treating cognitive deficits in the elderly. Contact with complementary and alternative medicine researchers provided additional information concerning developments in this field. STUDY SELECTION: Research studies that were methodologically sound were selected for review. More purely clinical studies also were included to provide a thorough overview of the limited amount of accumulated knowledge in this field. DATA SYNTHESIS: A qualitative synthesis of the above data was used to comprehensively present all information accumulated to date in this field. CONCLUSIONS: Although still in the preliminary stages of development, clinical research exploring the benefits of complementary and alternative therapies for cognitive deficits among the elderly shows a significant level of promise that warrants a further investment of resources.

Aged↗

Targetable HPMA copolymer-adriamycin conjugates. Recognition, internalization, and subcellular fate.

Recognition, internalization, and subcellular trafficking of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugates containing N-acylated galactosamine (GalN) or monoclonal OV-TL16 antibodies (Ab) have been investigated in human hepatocarcinoma HepG2 and ovarian carcinoma OVCAR-3 cells, respectively. The intrinsic fluorescence of fluorescein or adriamycin (ADR) attached to HPMA copolymers permitted us to follow the subcellular fate of HPMA copolymer conjugates by confocal fluorescence microscopy and fluorescence spectroscopy. The pattern of fluorescence during incubation of HPMA copolymer-ADR-GalN conjugate containing lysosomally degradable tetrapeptide (GFLG) side-chains with HepG2 cells was consistent with conjugate recognition, internalization, localization in lysosomes, followed by the release of ADR from the polymer chains and ultimately diffusion via the cytoplasm into the cell nuclei. A similar pattern was observed in OVCAR-3 cells for Ab targeted HPMA copolymer conjugates. To test our hypothesis that HPMA-copolymer-bound anticancer drugs will be inaccessible to the energy-driven P-glycoprotein efflux pump in multidrug resistant (MDR) cells, we have compared the internalization of the HPMA copolymer-ADR conjugates by sensitive (A2780) and ADR-resistant (A2780/AD) ovarian carcinoma cell lines. Preliminary data on relative retention of ADR in MDR (A2780/AD) cells indicate a higher intracellular ADR concentration after incubation with HPMA copolymer-ADR conjugate when compared to incubation with free (unbound) ADR.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

HPMA copolymer-anticancer drug-OV-TL16 antibody conjugates. II. Processing in epithelial ovarian carcinoma cells in vitro.

The binding, internalization, subcellular trafficking and in vitro cytotoxicity of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-anti-cancer drug-OV-TL16 antibody (Ab) conjugates in the ovarian carcinoma OVCAR-3 cell line have been investigated. Adriamycin (ADR) and meso chlorin e6 mono(N-2-aminoethylamide) (Mce6) photosensitizer were used as anti-cancer drugs. Targeted (Ab-containing) conjugates were compared with non-targeted HPMA copolymer-drug conjugates and with free drugs. Targeted conjugates were taken up rapidly by cells and detected within lysosomes by confocal fluorescence microscopy. The ADR attached to polymer chains via a degradable GFLG spacer was released from the conjugate, diffused via the lysosomal membrane into the cytoplasm and ultimately accumulated in the cell nuclei. In contrast, conjugates containing ADR bound via the GG spacer accumulated in the lysosomes, but no fluorescence could be detected in the cell nuclei. Binding the drugs to a non-targeted HPMA copolymer decreased their cytotoxicity in vitro. The IC50 dose increased from 2 microM for free ADR to 150 microM for P(GFLG)-ADR (P is the HPMA copolymer backbone) and from 0.34 microM for free Mce6 (with light) to 290 microM for P-(GG)-Mce6. However, attachment of OV-TL16 Abs rendered HPMA copolymer-drug conjugates biorecognizable by OVCAR-3 cells and markedly increased their cytotoxicity. The IC50 doses were 4.4 and 0.38 microM for the targeted conjugates P(GFLG)-ADR-Ab and P(GG)-Mce6-Ab (with light), respectively. Biorecognition was shown to be specific by inhibition experiments with free Ab. The findings indicate the potential of these conjugates as effective agents in the treatment of ovarian cancer.

Antibodies, Monoclonal↗

HPMA copolymer-anticancer drug-OV-TL16 antibody conjugates. 1. influence of the method of synthesis on the binding affinity to OVCAR-3 ovarian carcinoma cells in vitro.

The influence of different methods of binding the OV-TL16 antibody and its Fab' fragment to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer--drug (adriamycin [ADR] or meso chlorin e6 mono(N-2-aminoethylamide) (Mce6)) conjugates on the affinity of conjugates to an ovarian carcinoma (OVCAR-3) cell associated antigen was investigated. The binding of the antibody to HPMA copolymer--drug (ADR or Mce6) conjugates via amino groups resulted in conjugates which were heterogeneous in their antigen binding. Coupling, the HPMA copolymer--Mce6 conjugate to the carbohydrate region of the antibody resulted in conjugates with a more homogeneous distribution of affinity constants than conjugates prepared by linking the antibody to the polymer via amino groups. However, both methods resulted in a decrease in the affinity constant compared to the native antibody. Conjugates prepared with the Fab' frgment of the OV-TL16 antibody demonstrated a more homogenous affinity than either conjugate prepared with the whole antibody. To verify the hypothesis that the changes in the binding affinity and homogeneity are a consequence of conformational changes in the antibody structure, a series of physiocochemical methods were employed to characterize the conjugates. The excitation energy transfer between OV-TL16 antibody and drugs (ADR and Mce6) and the spectral properties of Mce6 were used to monitor the interactions between the antibody and drugs. The quenching of the intrinsic fluorescence of the antibody was also employed to study its conformational changes. An attempt has been made to correlate the biorecognition at the cellular surface with the interactions of drug with the antibody molecule and with the changes in antibody conformation.

Antibody Specificity↗

Neutropenia does not prevent etodolac- or indomethacin-induced gastrointestinal damage in the rat.

Neutrophils have been implicated in the acute formation of gastric mucosal erosions induced by nonsteroidal antiinflammatory drugs. The aims of the present study were to determine, in rats, the role of neutrophils in the pathogenesis of etodolac- and indomethacin-induced gastrointestinal ulceration and blood loss. Both drugs caused gastrointestinal ulceration, which was associated with increased blood loss, a rise in plasma haptoglobin concentration, and a rise in the number of circulating neutrophils. A marked infiltration of neutrophils occurred only in ileal tissue. Pretreatment with a selective antineutrophil serum induced a significant neutropenia, which failed to inhibit either etodolac- or indomethacin-induced gastrointestinal ulceration and blood loss. A further study demonstrated that the antineutrophil serum did not prevent gastric erosions induced by indomethacin, but it inhibited carrageenan paw edema, which is dependent, in part, on neutrophil infiltration and activation. It is concluded that neutrophils do not contribute to gastrointestinal ulceration and blood loss induced by nonsteroidal antiinflammatory drugs. Furthermore, in contrast with previous studies, our results provide no evidence that neutrophils contribute to indomethacin-induced acute gastric erosion formation.

Animals↗

Gastrointestinal irritancy, antiinflammatory activity, and prostanoid inhibition in the rat. Differentiation of effects between nabumetone and etodolac.

Many nonsteroidal antiinflammatory drugs have the ability to cause gastrointestinal damage in both animals and man. The aim of the present study was to compare nabumetone, a nonacidic drug, with etodolac on rat gastric mucosal damage and prostanoid synthesis, while concurrently measuring prostanoid production during edema formation in a carrageenan model of paw inflammation. The results showed that both drugs inhibited paw exudate prostaglandin E2 and edema significantly, but they did not inhibit gastric prostanoid production 4 hr after dosing. Gastric damage, however, was observed with etodolac. Additional time-course studies showed that over a 4-hr period, etodolac, unlike nabumetone, markedly inhibited gastric mucosal prostaglandin E2 production, which was associated with gastric erosion formation. Further studies demonstrated that nabumetone did not induce gastrointestinal damage or blood loss when administered to rats in a high antiinflammatory oral dose. In contrast, etodolac produced marked gastrointestinal damage and bleeding, which was evident for up to 48 hr after the dose. It is suggested that nabumetone's favorable gastrointestinal irritancy profile may relate, in part, to its nonacidic nature and to its differential effects on prostanoid production.

6-Ketoprostaglandin F1 alpha↗

Nabumetone, an effective anti-inflammatory agent, lacks gastrointestinal irritancy in the rat when dosed orally for one month: comparison with tiaprofenic acid and etodolac.

OBJECTIVE: To determine the effects of nabumetone, compared with tiaprofenic acid and etodolac, on anti-inflammatory efficacy and gastrointestinal irritancy in the rat when dosed orally for one month at a high anti-inflammatory dose. METHODS: Carrageenan paw edema was used as a model of inflammation. Gastrointestinal mucosal integrity was assessed by concurrently measuring ulcer formation. mucosal and tissue prostanoid production and plasma haptoglobin. Haemoglobin, present in the cecal contents, was used as a measure of blood loss. RESULTS: Nabumetone, tiaprofenic acid and etodolac inhibited inflammation. Etodolac induced marked gastrointestinal damage and blood loss whereas tiaprofenic acid caused only gastric damage. Nabumetone was found not to alter mucosal integrity. CONCLUSION: Nabumetone proved to be an effective anti-inflammatory agent that was devoid of gastrointestinal irritancy.

Administration, Oral↗

Antiinflammatory and gastrointestinal effects of nabumetone or its active metabolite, 6-methoxy-2-naphthylacetic acid (6MNA). Comparative studies with indomethacin.

6MNA, the active metabolite of the nonacidic antiinflammatory drug nabumetone, was investigated using intravenous administration for effects on (1) carrageenan paw edema and gastric irritancy compared with either oral nabumetone or both oral and intravenous indomethacin when given acutely and (2) gastrointestinal irritancy when given in repeat dosing studies. Oral doses of nabumetone or intravenous 6MNA produced effective antiinflammatory activity together with significant inhibition of paw exudate PGE2. Antiinflammatory oral doses of nabumetone or intravenous 6MNA produced minimal effects on gastric 6-keto PGF1 alpha production with an absence of gastric damage, in contrast with indomethacin. In repeat dose studies, 6MNA failed to induce gastrointestinal damage even at doses where general toxicity was evident. These results show that in the rat, 6MNA is an effective antiinflammatory drug but even in very high intravenous doses does not have the propensity to induce gastrointestinal damage.

Administration, Oral↗

A radiation-induced inhibitor of chromosome condensation and nuclear envelope breakdown in HeLa cells.

An in vitro microscopic assay for mitosis-inducing activity in mitotic HeLa cells was developed and used to demonstrate that cells irradiated and arrested in G2 phase of the cell cycle contain an inhibitor of mitosis. This assay system has a number of advantages over other assays including the use of autologous components (HeLa nuclei and mitotic cell extracts) in contrast to the microinjection method with Xenopus oocytes and without the requirements for microinjection expertise and Xenopus oocytes. The radiation-inducible inhibitor was detected at the lowest radiation dose tested (2 Gy) with maximal activity achieved within 30 min after radiation. Inhibitor activity decayed with time after radiation (2 Gy) with no activity detected at 6 h even though the cells remained in G2 phase, suggesting that either synthesis or activation of additional components is necessary for recovery from G2 arrest. The inhibitor activity was not detected in irradiated cells treated with caffeine to induce premature recovery from G2 arrest.

Animals↗

Anti-inflammatory and gastrointestinal effects of nabumetone or its active metabolite, 6MNA (6-methoxy-2-naphthylacetic acid): comparison with indomethacin.

6MNA, the active metabolite of the non-acidic anti-inflammatory drug nabumetone, was investigated using intravenous administration for effects on (a) carrageenan paw oedema and gastric irritancy compared to either oral nabumetone or both oral and intravenous indomethacin when given acutely and (b) gastrointestinal irritancy when given in repeat dosing studies. An oral dose of nabumetone or intravenous 6MNA produced effective anti-inflammatory activity together with significant inhibition of paw exudate PGE2. An anti-inflammatory oral dose of nabumetone or intravenous 6MNA produced minimal effects on gastric 6-keto-PGF1 alpha production, with an absence of gastric damage, in contrast to indomethacin. In repeat dose studies, 6MNA failed to induce gastrointestinal damage even at doses where general toxicity was evident. These results show that in the rat 6MNA, the active metabolite of nabumetone, is an effective anti-inflammatory drug but, even in very high intravenous doses, does not have the propensity to induce gastrointestinal damage.

6-Ketoprostaglandin F1 alpha↗

Anti-inflammatory efficacy and gastrointestinal irritancy: comparative 1 month repeat oral dose studies in the rat with nabumetone, ibuprofen and diclofenac.

Repeat oral dosing of nabumetone for 1 month maintains anti-inflammatory efficacy in a carrageenan model of paw oedema yet does not cause gastrointestinal damage. In contrast, ibuprofen or diclofenac, while also retaining anti-inflammatory activity, produced marked gastrointestinal irritancy as evidenced by mucosal damage and blood loss.

Animals↗

Fate of the hippocampal mossy fiber projection after destruction of its postsynaptic targets with intraventricular kainic acid.

Intraventricular injections of kainic acid were used to create a model of selective cell death in order to study the fate of afferent projections that are deprived of their postsynaptic targets. This treatment rapidly destroyed hippocampal CA3 pyramidal cells, but not those neurons that give rise to their mossy fiber and entorhinal afferents. Light microscopic studies with the Timm's sulfide silver stain indicated that half or more of the mossy fiber boutons in area CA3b were lost within the first 1-3 days after kainic acid administration. This finding was confirmed by electron microscopy. Electron-dense, usually vacuolated mossy fiber boutons accounted for about 10-20% of the total population present at a 4-hour survival time, but were not encountered in control rats nor at survival times longer than 1 day. Other mossy fiber boutons remained electron lucent, but enlarged, became more rounded in shape, and suffered an apparent loss of synaptic vesicles. It is suggested that degeneration of some mossy fiber boutons and resorption of others into the axon may have accounted for the precipitous decline in their number. The dendritic excrescences contacted by these boutons were nearly all undergoing electron-dense degeneration 4 hours after kainic acid administration. In rats that survived 6-8 weeks mossy fiber boutons remained somewhat scarce, individual boutons appeared relatively small, and only one-third the normal percentage were observed to be engaged in more than one synaptic contact within a single cross section. A qualitative electron microscopic study of the entorhinal projection to area CA3 suggested a response to kainic acid treatment similar to that of the mossy fiber projection, except that no entorhinal boutons were seen to become electron dense. These findings suggest that presynaptic fibers in the mature hippocampus adjust the size of their terminal arborizations and number of synaptic contacts to accommodate a reduction in the target cell population. The rapid loss of mossy fiber boutons may be attributable to an unusual fragility of these structures when they are deprived of the mechanical support normally provided by the pyramidal cell. Finally, the ability of kainic acid administration to alter the number and distribution of presynaptic elements must be taken into account whenever this toxin is used to make selective lesions of postsynaptic cells.

Afferent Pathways↗

Degeneration of hippocampal CA3 pyramidal cells induced by intraventricular kainic acid.

Degeneration of hippocampal CA3 pyramidal cells was investigated by light and electron microscopy after intraventricular injection of the potent convulsant, kainic acid. Electron microscopy revealed evidence of pyramidal cell degeneration within one hour. The earliest degenerative changes were confined to the cell body and proximal dendritic shafts. These included an increased incidence of lysosomal structures, deformation of the perikaryal and nuclear outlines, some increase in background electron density, and dilation of the cisternae of the endoplasmic reticulum accompanied by detachment of polyribosomes. Within the next few hours the pyramidal cells atrophied and became electron dense. Then these cells became electron lucent once more as ribosomes disappeared and their membranes and organelles broke up and disintegrated. Light microscopic changes correlated with these ultrastructural observations. The dendritic spines and the initial portion of the dendritic shaft became electron dense within four hours and degenerated rapidly, whereas the intermediate segment of the dendrites swelled moderately and became more electron lucent. No degenerative changes were evident in pyramidal cell axons and boutons until one day after kainic acid treatment. Less than one hour after kainic acid administration, astrocytes in the CA3 area swelled, initially in the vicinity of the cell body and mossy fiber layers. It is suggested that the paroxysmal discharges initiated in CA3 pyramidal cells by kainic acid served as the stimulus for this response. Phagocytosis commenced between one and three days after kainic acid administration, but remained incomplete at survival times of 6-8 weeks. Astrocytes, microglia, and probably oligodendroglia phagocytized the degenerating material. These results point to the pyramidal cell body and possibly also the dendritic spines as primary targets of kainic acid neurotoxicity. In conjunction with other data, they support the view that lesions made by intraventricular kainic acid can serve as models of epileptic brain damage.

Animals↗