Characterisation of functional deficits induced by AAV overexpression of alpha-synuclein in rats

Background

In the last decades different preclinical animal models of Parkinson's disease (PD) have been generated, aiming to mimic the progressive neuronal loss of midbrain dopaminergic (DA) cells as well as motor and non-motor impairment. Among all the available models, AAV-based models of human alpha-synuclein (h-aSYN) overexpression are promising tools for investigation of disease progression and therapeutic interventions.

Objectives

The goal with this work was to characterise the impairment in motor and non-motor domains following nigrostriatal overexpression of h-aSYN and correlate the behavioural deficits with histological assessment of associated pathology.

Methods

Intranigral injection of an AAV9 expressing h-aSYN was compared with untreated animals, 6-OHDA and AAV9 expressing either no transgene or GFP. The animals were assessed on a series of simple and complex behavioural tasks probing motor and non-motor domains. Post-mortem neuropathology was analysed using immunohistochemical methods.

Results

Overexpression of h-aSYN led to progressive degeneration of DA neurons of the SN and axonal terminals in the striatum (STR). We observed extensive nigral and striatal pathology, resembling that of human PD brain, as well as the development of stable progressive deficit in simple motor tasks and in non-motor domains such as deficits in motivation and lateralised neglect.

Conclusions

In the present work we characterized a rat model of PD that closely resembles human PD pathology at the histological and behavioural level. The correlation of cell loss with behavioural performance enables the selection of rats which can be used in neuroprotective or neurorestorative therapies.

Effect of MN (III) tetrakis (4-benzoic acid) porphyrin by photodynamically generated free radicals on SODs keratinocytes

Superoxide, a reactive form of oxygen, can be produced in vivo either in normal and under pathophysiologic conditions or by photosensitizing chemicals, as during photodynamic treatment. Photodynamic therapies (PDT), widely adopted in Dermatology and Oncology, are known to generate reactive oxygen species (ROS) and may contribute to structural alterations and oxidatively generated modifications of cellular antioxidants. We hypothesized that over-production of free radicals would decrease the enzymatic activities of endogenous cellular antioxidants. To test this hypothesis, keratinocytes were treated with the photosensitizer Photofrin plus visible light to produce free radicals and CuZnSOD and MnSOD activities were measured. Photodynamic treatment of keratinocytes increases malonylaldehyde production, nitrotyrosine staining and superoxide production. The enzymatic activities of CuZnSOD and MnSOD were significantly decreased after Photofrin plus visible light treatment. Our results suggest that the main cellular antioxidant system can be inactivated by photodynamically generated ROS. Pretreatment of keratinocytes with free radicals scavenger such as Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP) was able to restore the endogenous antioxidant system activities, inhibiting the MDA formation, nitrotyrosine staining and superoxide formation. Antioxidant therapy could therefore be a useful tool in protecting healthy epidermal cells against common side effects induced by antitumor targeted therapies.

Tetralogy of Fallot variant with pulmonary atresia (pseudotruncus arteriosus) in a case of maternal PKU syndrome

The authors report on a child with a rare variant of the Tetralogy of Fallot with pulmonary atresia also known as Pseudotruncus arteriosus, who was born by a mother affected by classic phenylketonuria (PKU), diet free of phenylalanine until the age of seven years. According to the authors, this is the first example of such rare variant in an offspring of maternal PKU syndrome.

Bilateral Congenital Absence of Internal Carotid Arteries in a Woman with Dementia

Dysgenesis of THE internal carotid artery is considered a rare condition, present in about 0.01% of subjects. This anomaly is generally asymptomatic and often represents an incidental finding in radiological examinations of the head performed for other reasons. A 75-year-old woman with symptoms of dementia was admitted to our hospital. Computed tomography and magnetic resonance examinations were performed. They showed the absence of both internal carotid arteries and the congenital nature of this abnormality. The usefulness of CT and MRI examinations in patients with this vascular abnormality is discussed.

Trazodone therapy of the post-stroke depression

The incidence of depression following a hemispheric stroke ranges from 25 to 60%. The benefit of antidepressant therapy on the outcome of rehabilitation in the subacute post-stroke phase is well known. We studied subjects both with and without evidence of depression, as indicated by any one of three criteria: (i) Clinical diagnosis of depression, (ii) Abnormal Zung-depression score. (iii) Abnormal dexamethasone suppression test (DST). Patients in a stroke rehabilitation program (22) were randomized to receive either placebo or 300 mg/day trazodone-HCl, beginning 30 days after the stroke. Patients with either a clinical diagnosis of depression or abnormal Zung depression scores showed a consistent trend towards greater improvement in Barthel activities of daily living (ADL) scores, with antidepressant therapy, as compared to patients receiving placebo. An abnormal DST was associated with significant improvement in the ADL scores in subjects receiving trazodone, i.e., in post-stroke depression such a treatment seems to be beneficial.

Psychotic complications of long term levodopa treatment of Parkinson's disease

Psychotic symptoms such as hallucinations, delusions and confusion are well known side-effects of levodopa (LD) therapy of Parkinson's disease (PD), even if there is much confusion regarding the variability of the psychotic manifestations. We studied 18 patients clinically treated with LD associated with an inhibitor of peripheral aminoacid decarboxylase (DI). Daily dosage of LD ranged between 250 and 1750 mg; the mean age of patients was 72.7 years; the age at the onset of the disease was 63.3 and duration of the disease 8.4 years. In all patients any possible etiology of Parkinsonism were excluded. Brain CT scan excluded focal lesions in all cases. Psychotic complications were seen in 8 patients: using DSM-III-R-criteria, the various LD-induced psychotic states can be classified in two groups: simple (including or hallucinations with preserved insight) and complex ones (including chronic confusion without preserved insight). Patients with complex symptoms were younger at the onset of the disease and they developed these symptoms later, and these patients were also more susceptible to dyskinesias developed before psychotic complications.

Molecular modelling and enzymatic studies of acetylcholinesterase and butyrylcholinesterase recognition with paraquat and related compounds

The potent herbicide paraquat and three other analogues MPP+, MPDP+ and MPTP have a known toxicological profile linked to the ability to damage dopaminergic neurons. Other biological effects were recently addressed to this class of compounds, including the ability to interact with enzymatic targets involved in the Central Nervous System, such as the acetylcholinesterase (AChE) and the butyrylcholinesterase (BuChE). A combined molecular modelling and enzymatic study focusing onto their interaction against the AChE and BuChE is reported. The former study was performed by docking techniques using target known co-crystallographic models. The latter study was carried out by the widely adopted Ellman's method. In both studies the anti-Alzheimer FDA approved drug tacrine was used as reference inhibitor. Our results indicate that paraquat, MPTP, MPDP+ and MPP+ recognize both enzymatic cleft in a similar fashion compared to the reference inhibitor. A structure-activity correlation was found with the net charge of the ligands, indicating a major role of the electrostatic term in the recognition and inhibition of these compounds. Our data completed their enzymatic profile, added new information on the molecular mechanisms underlying their neurotoxicity useful for the rational design of new cholinesterase inhibitors.

Blink reflex abnormalities in children with Tourette syndrome

Tourette syndrome (TS) is a common disorder which typically occurs during childhood or early adolescence. There is no definitive diagnostic test for TS. The objective of this study was to demonstrate whether neurophysiological abnormalities of the blink reflex can be observed in children with TS. We enrolled 15 children with TS, diagnosed according to DSM IV Diagnostic Criteria, and 15 controls. The blink reflex was elicited by stimulating the supraorbital nerve in order to measure the early response (R1), homolateral and contralateral R2 (late) responses, amplitude of R1 and duration of R2. The mean duration of R2 was significantly longer in TS patients than in the controls (P < 0.001, Student's t-test). An abnormal pattern of the blink reflex can be, even in childhood, an early neurophysiologic marker of TS, which is not related to the duration of TS or to the age of onset.

Progressive supranuclear palsy: A systematic review

The progressive supranuclear palsy (PSP) is a rapidly progressing degenerative disease belonging to the family of tauophaties, characterized by the involvement of both cortical and subcortical structures. Although the pathogenesis of PSP is still uncertain, genetic, biochemical, and immunohistochemical studies have been performed and are reviewed here. Genetic factors, oxidative damage, neurotoxins, and environmental factors contribute to tau deposition in the cerebral areas involved in PSP. Symptoms originate from the ensuing dysfunction of dopaminergic, GABAergic, cholinergic, and noradrenergic pathways. Recent advances in neuroradiological and instrumental examinations facilitate the diagnosis and have gained new insights into the pathophysiology of PSP, although the primary cause of the disease is unknown and disease-modifying drugs are not yet available.

Different clinical and evolutional patterns in late idiopathic and vascular parkinsonism

OBJECTIVE

The aim of this study was to examine the clinical picture of Parkinson's disease (PD) and vascular parkinsonism (VP) in the elderly, in an attempt to differentiate the clinical history, symptoms, signs and response to therapy.

MATERIAL AND METHODS

Thirty-two elderly patients with late onset PD and 45 with VP were enrolled and the clinical features of two groups were compared. All patients underwent brain MRI and were scored using the Unified Parkinson's Disease Rating Scales (UPDRS) -II, -III.

RESULTS

Patients with PD had a younger age at onset and a longer duration of the disease as compared to patients with VP. Nearly all PD patients showed a good response to levodopa therapy, while only 29% of patients with VP were responsive to levodopa treatment. Vascular risk factors as well as postural tremor, gait disorders and pyramidal signs with lower body predominance, were more frequent in patients with VP. Ninety-three % of PD patients had normal MRI, whereas all patients with VP had cerebral vascular lesions. UPDRS-II, -III scores at baseline were higher in VP than in PD patients and their increases throughout the follow-up period were more marked in VP than in PD patients.

CONCLUSIONS

Clinical history, symptoms, signs, response to therapy, and brain imaging help to differentiate PD and VP as two clinical entities with different clinical, prognostic and therapeutic implications, even if the coexistence of PD and a cerebral vascular disease in elderly patients is not infrequent and can make the diagnosis difficult.

[Gilles de la Tourette's syndrome: a systematic review]

Gilles de la Tourette's syndrome is more frequent than once believed. This syndrome is a chronic disorder whose long term outcome is generally favourable, characterized by a fluctuating course. The etiopathogenesis of Gilles de la Tourette's syndrome has not been ascertained, although the frontal-subcortical neural pathways seem to be involved. This extrapyramidal syndrome is frequently associated with attention-deficit/hyperactivity disorder, obsessive-compulsive disorder, and behaviour problems. A correct diagnosis is the first step for a proper management of this disorder, which makes use of behavioural and pharmacological interventions.

Dementia with Lewy bodies: a review

The dementia with Lewy bodies (DLB) is the second major type of senile, degenerative dementia, after the Alzheimer disease (AD). It is characterized by the presence of cytoplasmic inclusions of alpha-synuclein in the cerebral cortex and in the nuclei of the brain stem. DLB patients frequently have complex visual hallucinations, depressive symptoms, Parkinsonian manifestations and cognitive deficits, showing important associations with the Parkinson disease and the AD. The DLB should be differentiated from atypical Parkinsonisms, but the differential diagnosis often remains difficult and unsafe. Clinical and neuropathological findings, as well as neuroimaging are valuable tools in establishing specific diagnosis of DLB. Acetylcholinesterase inhibitors, dopamine-agonists, benzodiazepines of short or medium half-life, and antidepressants may be useful in the treatment of DLB, depending on the dominant symptoms of the given patients.

Efficacy and safety of fixed-dose oral sildenafil in the treatment of sexual dysfunction in depressed patients with idiopathic Parkinson's disease

OBJECTIVE AND METHODS

The efficacy and safety of oral Sildenafil, a potent inhibitor of phosphodiesterase type 5, were evaluated in depressed men with idiopathic Parkinson's disease and erectile dysfunction. Thirty-three men were enrolled in a 4-month prospective, open-label, fixed-dose study, and received 50mg of Sildenafil in the home setting approximately 1 hour before sexual activity, not more than once daily. Efficacy was determined by responses to question 3 (ability to achieve an erection) and question 4 (ability to maintain an erection) of the 15-item International Index of Erectile Function (IIEF). Other measures of efficacy included the five sexual function domains of IIEF, a global efficacy question, the Beck Depression Inventory (BDI) and the Hamilton Depression Rating Scale-21 (HDRS-21).

RESULTS

At the end of the study, improved erections were reported by 84.8% of patients. Sildenafil significantly increased patients' ability to achieve and maintain erections. Significant improvements were also observed in the IIEF domains for erectile function, orgasmic function, intercourse satisfaction and overall sexual satisfaction. BDI and HDRS scores improved from baseline to the end of the study. A clear improvement of depressive symptoms was observed in 75% of patients. Sildenafil was well tolerated in all the patients.

CONCLUSIONS

Treatment with oral Sildenafil improves erectile function and, indirectly, depressive symptoms in patients with idiopathic Parkinson's disease stages 1-3, and is well tolerated.

Autoimmune thyroiditis and acquired demyelinating polyradiculoneuropathy

Guillain-Barrè syndrome (GBS) and Miller-Fisher syndrome (MFS) are variant forms of acquired demyelinating polyradiculoneuropathy. Their concurrence with immune disorders of the thyroid is infrequent. We report on a 7.5-year-old girl in whom a subclinical thyroiditis was concurrently detected to GBS and a 70-year-old woman with Hashimoto's thyroiditis (HT) who had recurrent MFS. Even though autoimmune thyroiditis is associated with many autoimmune disorders more often than would be expected by chance alone, its concurrence with immune disorders of the peripheral nerve is less frequently reported. The calculated coincidental concurrence of acquired demyelinating polyradiculoneuropathy (in both variants, MFS and GBS) and autoimmune thyroiditis (as in the present cases) was extremely low (0.0004%), thus suggesting common pathogenic mediators.

Modulatory action of noradrenergic system on spinal motoneurons in humans

Previous findings in animals demonstrated that the noradrenergic coeruleospinal system exerts a tonic facilitation on spinal reflexes and that activation of alpha2-autoinhibitory receptors can be responsible for a disfacilitation of the spinal activity. To investigate this issue further, we examined whether this system is also involved in descending facilitatory control of spinal motoneurons in healthy humans. The H-reflex technique was utilized to assay the motoneuronal excitability. The ratio between the maximal reflex response (H) and maximal direct response (M) was determined in each subject and was calculated at 10 min intervals before and after i.v. administration of the alpha2-agonist clonidine (0.5 microg/kg). In all subjects a marked decrease of the H/M ratio, due to depression of the H response, occurred 10 min following the clonidine injection and reached its maximum within 30 min. No significant changes of blood pressure values were provoked by drug injections. These results suggest that an autoinhibitory action may be induced by alpha2-receptor activation of locus coeruleus neurons in humans, and that this device may serve as a mechanism for a myotonolytic action on spinal motoneurons.

Neurobehavioral syndrome induced by H2-receptor blocker withdrawal: possible role of prolactin

Cimetidine and ranitine are histamine H2-receptor blockers widely used for the treatment of gastric hypersecretion and duodenal pathologies. They are known to induce hyperprolactinemia in humans. Forty-six patients treated with cimetidine or ranitidine who were exhibiting a neurobehavioral syndrome after withdrawal of the drugs were selected. This syndrome was associated with a drop in plasma prolactin levels. The symptoms of this syndrome were greatly improved by restoration of treatment with the same drugs and reappeared when the treatment was again suspended. This syndrome was inhibited in 36 patients by administration of domperidone (30 mg/day), a drug inducing hyperprolactinemia without crossing the blood-brain barrier, as compared with 10 control patients treated with placebo. These results suggest that the drop in prolactin levels occurring when cimetidine and ranitidine are suspended may contribute to the development of this syndrome. Also, the withdrawal of H2-receptor blockers could be included among the possible causes of some neurotic syndromes.

Transient global amnesia and cerebral infarct: a case report

Transient global amnesia refers to a sudden and isolated dysfunction of memory for recent events, lasting a few hours. The pathogenesis of this neurological disorder is still uncertain. The most accepted hypotheses concern ischaemic, epileptic and migraine causes. We now report a case of transient global amnesia associated with computed tomography evidence for a hypodense area in the left thalamus 10 days after the transient memory dysfunctions.

Nitric oxide modulates agonist-evoked Ca2+ release and influx responses in PC12-64 cells

Nitric oxide (NO) is a signalling molecule involved in events crucial to neuronal cell function such as neurotransmitter release, gene transcription, and neurotoxicity. In these, as well as in many other neuronal processes, a key role may be played by the increases of the intracellular Ca2+ concentration ([Ca2+]i) occurring in response to activation of plasma membrane receptors coupled to phosphatidylinositol 4,5-bisphosphate hydrolysis. Such a [Ca2+]i increases are sustained by release of the cation from intracellular stores and stimulation of influx through specific Ca2+ channels. We have investigated the role of NO in modulating the two above Ca2+ processes occurring subsequently to muscarinic receptor activation in a selected clone (PC12-64) of PC12 cells, a neurosecretory/neuronal cell model. Analysis of [Ca2+]i variations in fura-2-loaded cells, exposed to different NO synthase inhibitors or NO donors, showed that Ca2+ release from intracellular stores was moderately inhibited and stimulated by these two groups of drugs, respectively, while Ca2+ influx through the channels directly coupled to muscarinic receptors was found to be insensitive to NO action. In contrast, Ca2+ influx activated by muscarinic receptor-induced store depletion (investigated also by Mn2+ quenching of the fura-2 signal) was increased by NO generation and inhibited by NO synthase blockade. Incubation of the cells with 8-bromo cGMP did not mimick the action of NO, suggesting that the effect of the messenger on Ca2+ influx is exerted through a signalling pathway different from cGMP generation.

Nitric oxide modulation of agonist-evoked intracellular Ca2+ release in neurosecretory PC-12 cells: inhibition of phospholipase C activity via cyclic GMP-dependent protein kinase I

Nitric oxide is a signaling molecule involved in events crucial to neuronal cell function, such as neurotransmitter release, gene transcription, and neurotoxicity, i.e., a number of processes in which a key role appears to be played by increases in intracellular Ca2+ concentration. In the neurosecretory/neuronal cell line PC-12, we have investigated the role of nitric oxide in the modulation of Ca2+ release from intracellular stores elicited by activation of three different receptors coupled to phosphatidyl-inositol-4,5-bisphosphate hydrolysis, i.e., the purinergic P2U, muscarinic M3, and bradykinin B2 receptors. The results obtained show that nitric oxide donors have an inhibitory effect on agonist-evoked Ca2+ release. This effect is not due to nitric oxide-induced modifications of Ca2+ storage, because the total releasable Ca2+ pool, measured as the radioactivity released by thapsigargin and ionomycin in cells loaded at equilibrium with 45Ca2+, was unchanged. In contrast, nitric oxide donors decreased agonist-evoked inositol-1,4,5-trisphosphate generation and total inositol phosphate accumulation. Similarly, nitric oxide inhibited total inositol phosphate accumulation stimulated by either aluminium fluoride or Ca2+. All of these effects were mimicked by the cGMP analogue 8-bromo-cGMP. When cells were incubated with nitric oxide synthase inhibitors, the results observed were opposite those produced by nitric oxide donors. All of the effects of nitric oxide were abolished when cells were treated with the cGMP-dependent protein kinase I inhibitor KT5823. Furthermore, KT5823 mimicked the effects of nitric oxide synthase inhibitors. We conclude that nitric oxide and Ca2+ signaling pathways are interconnected in PC-12 cells. Modulation of inositol phosphate generation and Ca2+ release by nitric oxide appears to be exerted primarily at the level of phospholipase C functioning and to be mediated by the activation of cGMP-dependent protein kinase I.

Neurodegeneration produced by intrahippocampal injection of paraquat is reduced by systemic administration of the 21-aminosteroid U74389F in rats

The behavioural, electrocortical (ECoG) and neurodegenerative effects of intrahippocampal injection of paraquat, a well-known free radical producing agent, were studied in rats. Injection of paraquat (100 nmol) into one dorsal hippocampus produced limbic motor and ECoG seizures. These effects were accompanied at 24 h by severe damage to CA1, CA3 and CA4 hippocampal pyramidal neurones and dentate gyrus granule cells. In comparison to the cell number counted in control, untreated, side of the hippocampus, significant (P < 0.05) neuronal loss was observed in the CA1 and CA3 pyramidal cell layers of the treated hippocampus. A lower dose of the herbicide (10 nmol) did not produce consistent motor and ECoG effects and in no instance was significant neuronal loss observed. A pretreatment with U74389F [21-4-(2,6-di-l-pyrrodinyl-4-pyridinyl)-1-piperazinyl-pregna-1,4,9 (11)triene-3,20-dione monomethansulfonate] (30 mg/kg i.p., 15 min before paraquat) completely protected rats from motor and ECoG epileptogenic effects induced by intrahippocampal paraquat (100 nmol). This dose of U74389F also reduced the hippocampal damage typically produced by paraquat and no significant neuronal loss was reported in the CA1 and CA3 pyramidal cell layers. A lower dose of U74389F (10 mg/kg i.p.) did not afford any protection against the epileptogenic effects produced by paraquat (100 nmol); in these animals hippocampal damage was still evident though neuronal loss did not reach statistical significance. In conclusion, the present data show that systemic administration of U74389F possesses neuroprotective effects against seizures and neurodegeneration typically elicited by intrahippocampal injection of paraquat.

Phorbol 12-myristate 13-acetate induces resistance of human melanoma cells to natural-killer- and lymphokine-activated-killer-mediated cytotoxicity

Human melanoma cells are sensitive to the lytic activity of natural killer (NK) and lymphokine-activated killer (LAK) cells in vitro. The events resulting in tumour cell killing by lymphocytic effectors have not been completely clarified, and the same target cell determinants regulating responsiveness to immune cytolysis have not yet been identified. Indeed, changes in the differentiative status of leukemia cells as well as in the expression of major histocompatibility complex (MHC) antigens have been described to modulate sensitivity to cytotoxic effectors; moreover surface expression of adhesion factors or extracellular matrix proteins by the cancer cells can promote the activation of the cytolytic effectors and has been described to correlate with tumour cell sensitivity to cytolytic cells. We reasoned that treatment with differentiation inducers could modulate melanoma cell sensitivity to NK and LAK cells. The present study demonstrates that human melanoma GLL-19 cells, when treated with the phorbol diester phorbol 12-myristate 13-acetate (PMA) in vitro, undergo growth inhibition and neuron-like differentiation. Moreover, PMA treatment induces an evident inhibition of GLL-19 cell sensitivity to NK- and LAK-mediated cytotoxicity. GLL-19 cells express constitutively MHC class I antigens. PMA treatment, however, does not modify the expression of MHC class I and class II DR antigens in human melanoma GLL-19 cells. We have finally evaluated the effects of PMA on the expression at the cell surface of adhesion factors such as ICAM-1, and extracellular matrix proteins such as collagen IV, laminin and fibronectin; we have also studied the expression of the integrin vitronectin receptor, a membrane receptor for adhesive proteins. While adhesion factors and extracellular matrix proteins appear to play an important role in the interaction between immune effector and tumour target, it can be supposed that the modulation of such membrane-associated proteins or glycoproteins induces NK and LAK resistance in cancer cells. We indeed found that PMA treatment induced in GLL-19 a marked reduction of membrane expression of collagen IV and ICAM-1; moreover PMA reduced the cell membrane expression of the integrin vitronectin receptor. On the other hand, membrane expression of fibronectin and laminin was not affected by PMA. These data indicate that the acquisition of a NK- and LAK-resistant phenotype by GLL-19 cells occurs together with cell differentiation, down-regulation of membrane expression of collagen IV, ICAM-1 and vitronectin receptor, but in the absence of changes in MHC antigens.

GTP-binding proteins transduce signals generated via human FC gamma receptor IIIA (CD16)

This study demonstrates that GTP-binding proteins regulate Fc gamma RIII-mediated signal transduction and inositol phosphate (IPn) generation in human NK cells. In addition the cross-linking of CD16 by mAb, guanosine 5'-o-3-thiophosphate induced 1,4,5 inositol trisphosphate (IP3) release in permeabilized NK cells and their membranes. By contrast, guanosine 5'-o-2-thiophosphate, almost completely inhibited IP3 generation induced by cross-linking with anti-CD16 mAb. Pretreatment of NK cells with 10 to 100 ng/ml Vibrio cholerae toxin (Ctx) almost completely inhibited the generation of IP3 and of other Ipn as well as Fc gamma RIII-operated cell functions such as antibody-dependent cell-mediated cytotoxicity against antibody-coated P815 mastocytoma cells. Isolated B subunit of Ctx was inactive. Bordetella pertussis toxin (0.1 to 1 microgram/ml) only marginally affected IP3 release and antibody-dependent cell-mediated cytotoxicity. Ctx increased cAMP levels in NK cells. However, inhibition of IP3 release preceded the rise of cAMP. Moreover, cAMP analogues (8-chlor-cAMP, 8-bromo-cAMP, dibutiryl-cAMP), as well as intracellular cAMP-enhancing agents (PGE1, PGE2, and forskolin) did not mimicked the effects of Ctx on IP3 generation, suggesting that the adenylate cyclase pathway is not responsible for the early effects of Ctx on Fc gamma RIII-mediated signalling. Overall these results demonstrate that signal transduction via Fc gamma RIII is mediated by Ctx-sensitive cellular membrane GTP-binding protein.

GTP-binding proteins transduce signals generated via human FC gamma receptor IIIA (CD16)

This study demonstrates that GTP-binding proteins regulate Fc gamma RIII-mediated signal transduction and inositol phosphate (IPn) generation in human NK cells. In addition the cross-linking of CD16 by mAb, guanosine 5'-o-3-thiophosphate induced 1,4,5 inositol trisphosphate (IP3) release in permeabilized NK cells and their membranes. By contrast, guanosine 5'-o-2-thiophosphate, almost completely inhibited IP3 generation induced by cross-linking with anti-CD16 mAb. Pretreatment of NK cells with 10 to 100 ng/ml Vibrio cholerae toxin (Ctx) almost completely inhibited the generation of IP3 and of other Ipn as well as Fc gamma RIII-operated cell functions such as antibody-dependent cell-mediated cytotoxicity against antibody-coated P815 mastocytoma cells. Isolated B subunit of Ctx was inactive. Bordetella pertussis toxin (0.1 to 1 microgram/ml) only marginally affected IP3 release and antibody-dependent cell-mediated cytotoxicity. Ctx increased cAMP levels in NK cells. However, inhibition of IP3 release preceded the rise of cAMP. Moreover, cAMP analogues (8-chlor-cAMP, 8-bromo-cAMP, dibutiryl-cAMP), as well as intracellular cAMP-enhancing agents (PGE1, PGE2, and forskolin) did not mimicked the effects of Ctx on IP3 generation, suggesting that the adenylate cyclase pathway is not responsible for the early effects of Ctx on Fc gamma RIII-mediated signalling. Overall these results demonstrate that signal transduction via Fc gamma RIII is mediated by Ctx-sensitive cellular membrane GTP-binding protein.

Trends of organochlorine residues in eggs of birds from Italy, 1977 to 1985

All the eggs, collected in Italy in 1982 and 1983, of two species of passerine birds, three gulls, four terns and the night heron, contained DDE and, with lower frequencies, other organochlorine contaminants. Organochlorines were more concentrated in the species of higher trophic level. DDE contamination showed a decreasing trend from 1978 to 1985 in one passerine, two terns and in the heron. After 1980-1982, the level of contamination was below the critical threshold beyond which reproduction is affected, eggshell thickness was only slightly or not reduced; therefore, the current impact of organochlorines on these birds is probably negligible. Detrimental effects may have occurred during the 1970s, when some of the eggs were contaminated beyond the critical threshold.