Experimental parkinsonism modulates multiple genes involved in the transduction of dopaminergic signals in the striatum

The irreversible loss of the dopamine-mediated control of striatal function is considered the functional substrate of the motor symptoms of Parkinson's disease. This pathological event causes a complex rearrangement of neuronal activity which involves specific dopamine-regulated cellular functions and, secondarily, several other cellular properties and transmitter systems. In the present study, we applied recently developed cDNA microarray technology to investigate the genetic correlates of the alterations produced by 6-hydroxydopamine-induced dopamine denervation in the nucleus striatum. We found that chronic dopamine denervation caused the modulation of 50 different genes involved in several cellular functions. In particular, products of the genes modulated by this experimental manipulation are involved both in the intracellular transduction of dopamine signal and in the regulation of glutamate transmission in striatal neurons, providing some information on the possible neuronal events which lead to the reorganization of glutamate transmission in the striatum of parkinsonian rats.     

Activation of dopamine D1-like receptors excites LTS interneurons of the striatum

Dopamine (DA) has a crucial role in the modulation of striatal neuron activity. Along with projection cells, striatal interneurons receive dense dopaminergic innervation from midbrain neurons, thus, also suggesting that these intrinsic cells represent a synaptic target for DA action in the striatum. In the present study, we investigated the effects of DA on low-threshold spike (LTS) interneurons of the rat striatum, by means of in vitro whole-cell patch-clamp electrophysiological recordings. Dopamine depolarized LTS cells, a pharmacological effect prevented by D1- but not D2-like DA receptor antagonists. The membrane depolarization produced by DA was sufficient to trigger action potential discharge in the recorded cells and was insensitive to tetrodotoxin and glutamate receptor antagonists. In addition, this pharmacological effect was mimicked by D1- but not D2-like DA receptor agonists, implying the selective involvement of D1-like receptors in this action.     

A role for MAP kinase in the antitumor activity of a nucleoside analog

Nucleoside analogs (NAs) have been used extensively in both antitumor and antiviral therapies. Their general mechanism of action has been postulated to result from incorporation into DNA, leading to disruption of DNA synthesis and DNA polymerase inhibition. To further explore the antitumor mechanisms of NAs we have evaluated ganciclovir (GCV), an NA antiviral agent, in herpes simplex virus thymidine kinase (HSV-TK) gene-modified tumor cells. This system allows specific evaluation of the antitumor effects of NAs because the antitumor effect is directly related to the phosphorylation of the prodrug GCV by the HSV-TK enzyme in the gene-modified tumor cells. We demonstrated that GCV incorporates into DNA and inhibits DNA polymerase, as has been observed in HSV-infected cells and with other antitumor NAs in tumor cells. A novel observation is that GCV activates MAP kinase within 1 hour of GCV exposure. This activation directly correlates with cytotoxicity, because inhibition of the MAP kinase extracellular regulated kinase (Erk) by PD98059, reversed GCV-mediated cytotoxicity. This effect appears to be specific to the Erk pathway, because inhibition of the p38 kinase with SB203580 had no effect on cytotoxicity. Further, GCV does not act as a DNA-damaging agent or activate general DNA-repair mechanisms, but does produce a number of metabolic disruptions, including a reversible decrease in NAD levels. These effects appear to be downstream of the earlier activation of Erk in this system, which may be a novel mechanism of action for GCV cytotoxicity in HSV-TK gene-modified tumor cells, and thus, needs to be further evaluated as the mechanism of tumor cell killing by other antitumor NAs.     

Acetylcholine-mediated modulation of striatal function

Striatal spiny neurones serve as a major anatomical locus for the relay of cortical information flow through the basal ganglia. these projection neurones also represent the main synaptic target of cholinergic interneurones, whose physiological role in striatal activity still remains largely enigmatic. The striatal cholinergic system has been implicated in the pathophysiology of movement disorders such as Parkinson's disease, but the cellular mechanisms underlying cholinergic-neurone function are still unknown. On the basis of in vitro electrophysiological evidence, obtained from a rat corticostriatal-slice preparation, we propose that endogenous ACh exerts a complex modulation of striatal synaptic transmission, which produces both short-term and long-term effects. ACh-mediated mechanisms might be of crucial importance in processing the cortical inputs to the striatum.     

Impaired Excitatory Transmission in the Striatum of Rats Chronically Intoxicated with Manganese

Chronic exposure to manganese (Mn) is known to produce a parkinsonian or dystonic state in humans caused by a rather selective involvement of the basal ganglia. Experimental observations suggest that secondary excitotoxic mechanisms play a crucial role in the development of Mn-induced neurodegeneration in the striatum, although the site of interference of Mn with glutamatergic transmission in this brain area is still unknown. To answer this question, in the present in vitro study, we investigated the physiological characteristics of striatal excitatory synaptic transmission in a rat model of Mn intoxication. We found that chronic Mn greatly increased both frequency and amplitude of spontaneous excitatory postsynaptic potentials, in the absence of appreciable changes of intrinsic membrane properties of striatal cells. The sensitivity of striatal neurons to glutamate AMPA and NMDA receptor stimulation was unaffected by Mn poisoning, as demonstrated by comparing the membrane responses produced in control and treated rats to the application of selective agonists of these receptors and to the direct activation of corticostriatal glutamatergic fibers. In addition, also paired-pulse facilitation was unaltered by Mn treatment, indicating that this toxin does not affect the pre- and postsynaptic mechanisms responsible for the appearance of this short-term form of synaptic plasticity at corticostriatal synapses. It is concluded, therefore, that hyperactivity of corticostriatal neurons, rather than increased postsynaptic sensitivity to glutamate, accounts for the abnormal excitation of striatal neurons in the course of Mn intoxication.     

Carboplatin and 5-fluorouracil in poor performance status patients with advanced urothelial cancer

BACKGROUND: In view of the difficulties in administering aggressive treatmentto elderly patients, frequently with concomitant medical problems,a treatment program with the combination of carboplatin and5-FU for advanced urothelial tumors was designed. The aim wasto maintain an efficacious therapeutic schedule while minimizingtoxicity. PATIENTS AND METHODS: Twenty-three patients with advanced bidimensionally measurableurothelial carcinoma were given carboplatin 100 mg/m² and 5-fluorouracil500 mg/m² days 1–3 which was escalated to carboplatin125 mg/m² and 5-fluorouracil 625 mg/m². 5 patients were >70 years, the ECOG performance status was 2–3 in 10 patients(43%), and the creatinine was > 2.0 mg/dl in 3 patients (13%).Five patients (22%) had pre-existing cardiac disease, and Ihad hepatopathy. Nine patients (39%) had prior cisplatin. RESULTS: Ten patients remained at level 1, and 12 others had the dosageescalated to level 2. Twenty-one patients are evaluable forresponse. Response was observed in 5 of 21 (24%) evaluable patients(95% confidence limits 15%–33%), only at dose level 2.There was 1 CR (5%) and 4 PR (19%). There were no responsesin patients who had prior DDP versus 5 of 13 (38%) responsesin patients who had not had prior DDP. The median time to responsewas 2 months. The median duration of response was 8 months.At level 2 myelotoxicity was significant, and led to a returnto level 1 in 2 patients. Nine of 12 patients (75%) treatedat level 2 had grade 3 leukopenia, and 1 patient had nadir sepsis.4 patients (33%) had grade 4 thrombocytopenia. CONCLUSIONS: Moderate activity was shown with this regimen in untreated patientsat level 2. This regimen presents a feasible outpatient alternativefor patients who are unable to undergo more aggressive chemotherapy. carboplatin, chemotherapy, poor performance status, transitional cell carcinoma, urothelium     

Platelet-derived growth factor indirectly stimulates angiogenesis in vitro.

We evaluated the effect of platelet-derived growth factor (PDGF) on capillary formation using an in vitro angiogenesis model system in which microvascular fragments and myofibroblasts (Mfs) isolated from rat epididymal lipid tissues were grown in co-culture. In this system Mfs induce capillary formation by producing an endothelial cell growth factor and by secreting extracellular matrix components that cause endothelial cells to form cordlike structures. Addition of PDGF enhances in vitro capillary growth. Although some recently described microvascular endothelial cells display PDGF receptors and respond to PDGF, we found no evidence for direct PDGF action on the rat epididymal microvascular endothelial cells. Rather, we found that PDGF increased the proliferation of Mfs, as well as the production of Mf-derived endothelial cell growth factor and matrix collagen type I. Our results suggest that even in cases where the microvasculature lacks PDGF receptors, PDGF may accelerate capillary formation by activating connective tissue cells in the vicinity of endothelial cells.     

IL-6 induces regionally selective spinal cord injury in patients with the neuroinflammatory disorder transverse myelitis

Transverse myelitis (TM) is an immune-mediated spinal cord disorder associated with inflammation, demyelination, and axonal damage. We investigated the soluble immune derangements present in TM patients and found that IL-6 levels were selectively and dramatically elevated in the cerebrospinal fluid and directly correlated with markers of tissue injury and sustained clinical disability. IL-6 was necessary and sufficient to mediate cellular injury in spinal cord organotypic tissue culture sections through activation of the JAK/STAT pathway, resulting in increased activity of iNOS and poly(ADP-ribose) polymerase (PARP). Rats intrathecally infused with IL-6 developed progressive weakness and spinal cord inflammation, demyelination, and axonal damage, which were blocked by PARP inhibition. Addition of IL-6 to brain organotypic cultures or into the cerebral ventricles of adult rats did not activate the JAK/STAT pathway, which is potentially due to increased expression of soluble IL-6 receptor in the brain relative to the spinal cord that may antagonize IL-6 signaling in this context. The spatially distinct responses to IL-6 may underlie regional vulnerability of different parts of the CNS to inflammatory injury. The elucidation of this pathway identifies specific therapeutic targets in the management of CNS autoimmune conditions.     

Chronic dialysis and forcing of the ability to fantasize. Evaluation of the alexithymic phenomenon in a group of dialyzed patients

In order to evaluate personality modifications toward greater concreteness and a consequent reduction of fantasizing in subjects undergoing chronic haemodialytic treatment, the Shalling Sifneos Personality Scale (S.S.P.S.) was administered to a group of patients undergoing dialysis and to two control groups: one consisting of patients with chronic hepatitis and the other of healthy subjects. The S.S.P.S. measures the alexithymic traits of the personality. Subjects undergoing dialysis scored significantly higher than chronic hepatitis patients and healthy subjects; the latter group had the lowest scores. The alexithymic score, moreover, appears to be directly correlated with the duration of dialysis. It is suggested that the prominence of the alexithymic phenomenon may be related to defense mechanisms against recurrent anguish about dying and to the tendency to assume certain characteristics of the particular therapeutic regimen, such as concreteness and rationality, so as to be able to tolerate the aggressive aspects of the treatment.