Effect of chronic treatment with NNC 756, a new D-1 receptor antagonist, or raclopride, a D-2 receptor antagonist, in drug-naive Cebus monkeys: dystonia, dyskinesia and D-1/D-2 supersensitivity

When given subcutaneously in gradually increasing doses, up to 1 mg/kg, NNC 756, a dopamine (DA) D-1 antagonist, failed to produce dystonia in eight drug-naive Cebus monkeys. In contrast, raclopride, a DA D-2 antagonist, produced dystonia at low doses (0.010-0.015 mg/kg). Following pre-treatment with raclopride, NNC 756 also induced dystonia at low doses (0.015-0.025 mg/kg), but continued treatment caused tolerance, and increasing doses of NNC 756 could be administered without induction of dystonia. NNC 756 induced a dose-dependent parkinsonism (slow, stiff movements and tremor), and more sedation than raclopride. After treatment for 14 weeks, withdrawal of raclopride (0.01 mg/kg) led to mild oral dyskinesia (tardive dyskinesia), while withdrawal of NNC 756 (1.0 mg/kg) led to a special grooming syndrome, but no dyskinesia. Withdrawal of raclopride as well as NNC 756 led to behavioural D-1 and D-2 dopamine supersensitivity in the form of increased dyskinesia (including grooming after NNC 756) induced by D-1 agonist (SKF 81297) and increased arousal induced by D-2 agonist (quinpirole). These results indicate that D-1 antagonists such as NNC 756 elicit fewer extrapyramidal symptoms (both acute and tardive) than D-2 antagonists such as raclopride, although extremely high doses may cause a special grooming withdrawal syndrome.     

Topoisomerase II levels and drug response in small cell lung cancer

Acquired resistance to chemotherapy is the major obstacle to cure of small cell lung cancer (SCLC). Some of the most active drugs in the treatment of this tumor exert their cytotoxicity by interacting with the nuclear enzyme topoisomerase II (topo II), which in mammalian cells occurs in two isoforms, alpha and beta. We examined the relationship between levels of topo II alpha and beta and drug response in a panel of 25 unselected SCLC cell lines. Chemosensitivity to several topo II-interactive drugs, as well as other chemotherapeutic agents, was quantitated previously using a modified MTT assay. Topo II levels were determined by immunoblot analysis of whole cell lysates, with topo II alpha and beta isoform-specific antibodies, and results were expressed relative to levels found in NCI-H209 cells which had the highest topo II alpha in this series of cell lines. Levels of topo II alpha and beta mRNA were determined by Northern blotting. Pearson correlation analysis was used to determine the significance of the relationship between topo II alpha and beta levels and response to the various chemotherapeutic drugs, as well as the treatment history of the patients from whom the cell lines were derived. These analyses revealed an inverse correlation between topo II alpha levels and resistance to all of the tested drugs, including several drugs which are not known to interact with topo II. This correlation was statistically significant for doxorubicin, cisplatin, epirubicin, melphalan, nitrogen mustard, and vinblastine. With one exception (cisplatin), there were no significant correlations between topo II beta levels and drug response. There was no significant correlation between topo II alpha and beta levels and treatment history. Taken together, our results are consistent with the hypothesis that levels of topo II alpha are important determinants of drug response in SCLC.     

New and old antipsychotics versus clozapine in a monkey model: adverse effects and antiamphetamine effects

Rationale: Neuroleptic primed Cebus apella monkeys have proven reliable in screening antipsychotics for extrapyramidal side effect (EPS) potential in humans, and the ratio EPS liability/antiamphetamine efficacy [“therapeutic index” (TI)] has fit well with clinical results. Objectives: 1) To find the TIs of one new (quetiapine), three potential [NNC 756 (dopamine (DA) D₁ antagonist), NNC 22-0031 (alpha-1 adrenergic/5-HT₂ serotonergic/DA D₁ and D₂ antagonist) and DOD 647 (DA D₁ and D₂ antagonist)] and three old antipsychotics (haloperidol, melperone and clozapine), 2) to test the model further and 3) to gain more insight as to clozapine’s neuropharmacology. Methods: Seven monkeys received haloperidol daily for 2 years; all were sensitized to dystonia. All drugs were given SC, in increasing doses until two animals had dystonia/other adverse effects (AE), and in decreasing doses with a fixed dose of dextroamphetamine producing motor unrest and stereotypies, to find the minimum significant antiamphetamine dose (AA). The ratio AE/AA = TI. Results: Excepting clozapine and DOD 647, all drugs induced dystonia. At 2–4 mg/kg, clozapine caused uncoordinated movements, myoclonic jerks and rough tremor; unlike dystonia, the syndrome was not alleviated but worsened by the anticholinergic, biperiden. DOD 647 up to 2 mg/kg had no adverse effects. The TIs of the new and potential antipsychotics were 3–5 versus 4 for clozapine and 1 for haloperidol and melperone, suggesting that like clozapine, these new drugs will not produce EPS at antipsychotic doses. Received: 31 October 1997/Final version: 9 November 1998     

Animal models of Parkinson's disease: An empirical comparison with the phenomenology of the disease in man

Summary Animal models are an important aid in experimental medical science because they enable one to study the pathogenetic mechanisms and the therapeutic principles of treating the functional disturbances (symptoms) of human diseases. Once the causative mechanism is understood, animal models are also helpful in the development of therapeutic approaches exploiting this understanding. On the basis of experimental and clinical findings. Parkinson's disease (PD) became the first neurological disease to be treated palliatively by neurotransmitter replacement therapy.The pathological hallmark of PD is a specific degeneration of nigral and other pigmented brainstem nuclei, with a characteristic inclusion, the Lewy body, in remaining nerve cells. There is now a lot of evidence that degeneration of the dopaminergic nigral neurones and the resulting striatal dopamine-deficiency syndrome are responsible for its classic motor symptoms akinesia and bradykinesia. PD is one of many human diseases which do not appear to have spontaneously arisen in animals. The characteristic features of the disease can however be more or less faithfully imitated in animals through the administration of various neurotoxic agents and drugs disturbing the dopaminergic neurotransmission.The cause of chronic nigral cell death in PD and the underlying mechanisms remain elusive. The partial elucidation of the processes underlie the selective action of neurotoxic substances such as 6-hydroxydopamine (6-OHDA) or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), has however revealed possible molecular mechanisms that give rise to neuronal death. Accordingly, hypotheses concerning the mechanisms of these neurotoxines have been related to the pathogenesis of nigral cell death in PD.The present contribution starts out by describing some of the clinical, pathological and neurochemical phenomena of PD. The currently most important animal models (e.g. the reserpine model, neuroleptic-induced catalepsy, tremor models, experimentally-induced degeneration of nigro-striatal dopaminergic neurons with 6-OHDA, methamphetamine, MPTP, MPP⁺, tetrahydroisoquinolines, -carbolines, and iron) critically reviewed next, and are compared with the characteristic features of the disease in man.     

Systemic liberation of interleukin-1β and interleukin-1 receptor antagonist in the perioperative phase of liver transplantation

We measured systemic serum levels of interleukin-1 receptor antagonist (IL-1ra), interleukin-1 (IL-1), tumor necrosis factor (TNF-), and interleukin-6 (IL-6) during the preoperative, anhepatic, and postreperfusional phases up to the 7th postoperative day in 60 patients undergoing orthotopic liver transplantation (LTx). In contrast to IL-1, IL-1ra, TNF-, and IL-6 showed a significant elevation in relation to the early phase after reperfusion, while TNF- displayed a high grade of scatter. In addition, IL-1ra levels were significantly elevated during the anhepatic phase. Maximum serum levels were found at 15 min after reperfusion, 120 min after reperfusion, and on the 1st postoperative day, respectively. Serum levels decreased considerably at 24 h and 7 days after reperfusion. The comparative monitoring of systemic cytokine and cytokine antagonist levels, in particular the liberation of IL-1ra and IL-6 may provide useful parameters for the development of new liver preservation theories for LTx.     

Ampicillin-sulbactam susceptibility testing criteria

In vitro studies in five different medical centers documented the susceptibility of 2,440 consecutive isolates of theEnterobacteriaceae against ampicillin-sulbactam disks of different potencies. For determination of MICs, both 2:1 or 1:1 ratios were used as long as the concentrations of sulbactam at the breakpoints remained the same, i.e. MIC 16/8.0 µg/ml or 8.0/8.0 µg/ml for the susceptible category. Disks containing 10 µg of ampicillin and 10 µg of sulbactam are still to be preferred with interpretive criteria of 15 mm for susceptible and 11 mm for resistant (MIC 64/32 µg/ml or 32/32 µg/ml). The reliability of the disk test actually diminished when the amount of sulbactam in the disk was increased.     

The muscarinic M1/M4 receptor agonist xanomeline exhibits antipsychotic-like activity in Cebus apella monkeys.

Xanomeline is a muscarinic M(1)/M(4) preferring receptor agonist with little or no affinity for dopamine receptors. The compound reduces psychotic-like symptoms in patients with Alzheimer's disease and exhibits an antipsychotic-like profile in rodents without inducing extrapyramidal side effects (EPS) at therapeutically relevant doses. In the present study, we examined whether the xanomeline-induced functional dopamine antagonism found in rodent studies could also be observed in nonhuman primates. In addition, we studied whether the lack of EPS observed in rodents also applies to primates. To this end, we investigated the effects of xanomeline on the behavior induced by D-amphetamine and (-)-apomorphine in drug-naive Cebus apella monkeys. Antipsychotic compounds antagonize amphetamine-induced motor unrest and stereotypies in this species. Xanomeline inhibited D-amphetamine-induced motor unrest, stereotypies and arousal as well as apomorphine-induced stereotypies and arousal in drug-naive Cebus apella monkeys. Xanomeline did not induce EPS but vomiting occurred in some monkeys at high doses, in accordance with emetic events observed in Alzheimer patients following xanomeline administration. Even when xanomeline was tested in EPS-sensitized Cebus apella monkeys, EPS were not observed at the dose range of xanomeline used in the D-amphetamine-apomorphine combination study (0.5-3 mg/kg). However, when xanomeline was tested at 4 mg/kg, moderate dystonia was seen in two out of three monkeys. It is concluded that xanomeline inhibits D-amphetamine- and (-)-apomorphine-induced behavior in Cebus apella monkeys at doses that do not cause EPS. These data further substantiate that muscarinic receptor agonists may be useful in the pharmacological treatment of psychosis.     

Immune deficiencies in chronic intestinal pseudo-obstruction

Aim: Chronic intestinal pseudo-obstruction has been associated with urinary disorders, myopathy, and ophthalmoplegia in adults and cholelithiasis in children. We observed a high percentage of total-parenteral-nutrition-dependent patients with pseudo-obstruction and recurrent infections requiring gammaglobulin infusions. Methods: AH records for 23 children with chronic intestinal pseudo-obstruction (10 females and 13 males, mean age 9.8 y ± 4.9 y, range 4–24 y) referred for a nutritional evaluation from 1992 to 1995 were reviewed. Chronic intestinal pseudo-obstruction was diagnosed by clinical, radiographic findings and antroduodenal manometry. Intestinal full-thickness biopsies were performed in seven children. Results: Hypogammaglobulinemia was diagnosed in 18 patients (78%): 16 patients had various immunoglobulin deficiencies and 2 had selective antibody deficiency. Intravenous gammaglobulin was administered in 14 patients. Other medical conditions affecting the children are summarized as follows: autonomic dysfunction in 10 patients (43%), recurrent hypoglycemia in 9 (39%), asthma in 9 (39%), cholecystitis in 7 (30%), low serum carnitine level in 6 (26%), urinary dysfunction in 6 (26%), pancreatitis in 5 (22%), behavioral problems in 5 (22%), myopathy in 2 (9%), idiopathic thrombocytopenia in 2 (8%), velopharyngeal insufficiency in 1 (4%), oculocutaneous albinism in 1 (4%), Pierre-Robin syndrome in 1 (4%), and protein C deficiency in 1 (4%). Munchausen syndrome was suspected in two patients. Conclusions: Chronic intestinal pseudo-obstruction appears to be associated with immune deficiencies. It is unclear if the immune deficiencies, intestinal pseudo-obstruction, and the other medical conditions have a common underlying etiology. Repeated infections may be due to impaired immune function in children with chronic intestinal pseudo-obstruction. We recommend screening for immune deficiencies in children with chronic intestinal pseudo-obstruction.     

Impaired iron homeostasis in Parkinson's disease

Despite physiological systems designed to achieve iron homeostasis, increased concentrations of brain iron have been demonstrated in a range of neurodegenerative diseases. These including the parkinsonian syndromes, the trinucleotide repeat disorders and the dementia syndromes. The increased brain iron is confined to those brain regions most affected by the degeneration characteristic of the particular disorder and is suggested to stimulate cell damage via oxidative mechanisms. Changes in central iron homeostasis have been most closely investigated in PD, as this disorder is well characterised both clinically and pathologically. PD is associated with a significant increase in iron in the degenerating substantia nigra (SN) and is measureable in living PD patients and in post-mortem brain. This increase, however, occurs only in the advanced stages of the disease, suggesting that this phenonoma may be a secondary, rather than a primary initiating event, a hypothesis also supported by evidence from animal experiments. The source of the increased iron is unknown but a variety of changes in iron homeostasis have been identified in PD, both in the brain and in the periphery. The possibility that an increased amount of iron may be transported into the SN is supported by data demonstrating that one form of the iron-binding glycoprotein transferrin family, lactotransferrin, is increased in surviving neurons in the SN in the PD brain and that this change is associated with increased numbers of lactotransferrin receptors on neurons and microvessels in the parkinsonian SN. These changes could represent one mechanism by which iron might concentrate within the PD SN. Alternatively, the measured increased in iron might result from a redistribution of ferritin iron stores. Ferritin is located in glial cells while the degenerating neurons do not stain positive for ferritin. As free radicals are highly reactive, it is unlikely that glial-derived free radicals diffuse across the intracellular space in sufficent quantities to damage neuronal constituents. If intracellular iron release contributes to neuronal damage it seems more probable that an intraneuronal iron source is responsible for oxidant-mediated damage. Such a iron source is neuromelanin (NM), a dark-coloured pigment found in the dopaminergic neurons of the human SN. In the normal brain, NM has the ability to bind a variety of metals, including iron, and increased NM-bound iron is reported in the parkinsonian SN. The consequences of these phenomena for the cell have not yet been clarified. In the absence of significant quantities of iron NM can act as an antioxidant, in that it can interact with and inactivate free radicals. On the other hand, in the presence of iron NM appears to act as a proxidant, increasing the rate of free radical production and thus the oxidative load within the vulnerable neurons. Given that increased iron is only apparent in the advanced stages of the disease it is unlikely that NM is of importance for the primary aetiology of PD. A localised increase in tissue iron and its interaction with NM may be, however, important as a secondary mechanism by increasing the oxidative load on the cell, thereby driving neurodegeneration.