CPCCOEt, a noncompetitive metabotropic glutamate receptor 1 antagonist, inhibits receptor signaling without affecting glutamate binding

Metabotropic glutamate receptors (mGluRs) are a family of G protein-coupled receptors characterized by a large, extracellular N-terminal domain comprising the glutamate-binding site. In the current study, we examined the pharmacological profile and site of action of the non-amino-acid antagonist 7-hydroxyiminocyclopropan[b]chromen-1a-carboxylic acid ethyl ester (CPCCOEt). CPCCOEt selectively inhibited glutamate-induced increases in intracellular calcium at human mGluR1b (hmGluR1b) with an apparent IC50 of 6.5 microM while having no agonist or antagonist activity at hmGluR2, -4a, -5a, -7b, and -8a up to 100 microM. Schild analysis indicated that CPCCOEt acts in a noncompetitive manner by decreasing the efficacy of glutamate-stimulated phosphoinositide hydrolysis without affecting the EC50 value or Hill coefficient of glutamate. Similarly, CPCCOEt did not displace [3H]glutamate binding to membranes prepared from mGluR1a-expressing cells. To elucidate the site of action, we systematically exchanged segments and single amino acids between hmGluR1b and the related subtype, hmGluR5a. Substitution of Thr815 and Ala818, located at the extracellular surface of transmembrane segment VII, with the homologous amino acids of hmGluR5a eliminated CPCCOEt inhibition of hmGluR1b. In contrast, introduction of Thr815 and Ala818 at the homologous positions of hmGluR5a conferred complete inhibition by CPCCOEt (IC50 = 6.6 microM), i.e., a gain of function. These data suggest that CPCCOEt represents a novel class of G protein-coupled receptor antagonists inhibiting receptor signaling without affecting ligand binding. We propose that the interaction of CPCCOEt with Thr815 and Ala818 of mGluR1 disrupts receptor activation by inhibiting an intramolecular interaction between the agonist-bound extracellular domain and the transmembrane domain.     

The effect of long term and high dose interferon treatment in Chronic hepatitis C

The results of 43 interferon treatments of 35 patients (23 male, 12 female) are reported. The duration of the treatment was 6–18 months, the dose of interferon was 3x3-5 MU weekly. Complete response (HCV RNA became negative) was found in 11, relapse was observed in 3 patients. Partial response (transaminase levels became normal, or less than twice normal value, but patients remained HCV RNA positive) occurred in 23 cases, relapse was obeserved in 16. The therapy had no effect in 9 cases. The higher dose and longer term interferon therapy resulted in a higher rate of response to the treatment and a reduction in the number of relapses. This work was supported by the Hungarian Ministry of Welfare (No. T-10 064/93).     

Pharmacokinetics of sulfadiazine and trimethoprim in man

Summary Sulfadiazine (SDZ) 800 mg and trimethoprim (TMP) 160 mg were given orally to 10 normal subjects and the concentration of SDZ and TMP in serum and urine was followed for 24 h. Both drugs showed a significant negative correlation between individual peak concentrations in serum and the body weight of the subject. Twelve hours after dosing the serum concentration was 12 to 25 µg/ml for SDZ and 0.3 to 1.1 µg/ml for TMP. Individual concentration ratios between SDZ and TMP in serum were 4.8 (1 h) – 145 (24 h), and in the urine the ratio was close to 6 throughout the 24 h collection period. The range of urinary concentrations was from 65 to 400 µg/ml for SDZ and from 13.8 to 93.4 µg/ml for TMP. The fraction acetylated SDZ/acetylated SDZ + SDZ was 21% during the 0–8 h period, 33% during the 8–15 h period and 41% during the 15–24 period. The average values for the notional volume of distribution, V_d, were 0.36±0.13 1/kg for SDZ and 1.39±0.25 1/kg for TMP. The average t_1/2 was 15.2±7.4 h for SDZ and 7.4±1.9 h for TMP. Individual subjects showed a significant correlation between the serum clearance of TMP and SDZ (p<0.01) and also between the renal clearance of the two drugs (p<0.05). The serum clearance was significantly correlated with the renal clearance for TMP but not for SDZ. For SDZ V_d was significantly negatively correlated with the elimination constant; for TMP no such correlation was found. The serum clearance of SDZ was significantly correlated with the percentage of SDZ which was excreted as the (presumably) acetylated compound. The renal clearance of SDZ was independent of the serum concentration of SDZ. There was a highly significant negative correlation between the renal clearance and serum concentration of TMP, as well as for acetylated SDZ. The renal clearance of acetylated SDZ averaged more than six times that of unconjugated SDZ. With increased urine flow the renal clearances of TMP and SDZ were significantly increased.     

Computer tomography of cerebellopontine angle lesions.

Computer tomography (CT) was used in 53 consecutive patients with a working diagnosis of cerebellopontine angle tumor. The CT was performed with the 160 X 160 matrix scanner, height of sections was 13 mm. Metrizoate sodium (1.5 ml/kg of body weight) was used for tumor enhancement. Seventeen CT scans revealed tumors; one patient proved at operation to be false-positive. Thirty-six CT scans revealed no tumors; two examinations may prove to be false-negative, but surgical verification has so far not been obtained. The smallest tumor demonstrated by CT extended 7 mm into the angle, while one of the possible false-negative CT scans after iophendylate injection cisternography showed a tumor extending 5 mm into the angle. It is concluded that CT is a harmless, noninvasive neuroradiological procedure, and should precede invasive procedures. It can be used safely in patients with increased intracranial pressure.     

Clinical experience with vestibular schwannomas: epidemiology, symptomatology, diagnosis, and surgical results

The Danish model for vestibular schwannoma (VS) surgery has been influenced by some historical otological events, taking its origin in the fact that the first attempt to remove CPA tumors was performed by an otologist in 1916. In approximately 50 years VS surgery was performed by neurosurgeons in a decentralized model. Highly specialized neuro- and otosurgeons have been included in our team since the early beginning of the centralized Danish model of VS surgery in 1976. Our surgical practice has always been performed on the basis of known and proven knowledge, but we spared no effort to search for innovative procedures. The present paper reflects the experience we have gained in two decades of VS surgery. Our studies on the incidence, symptomatology, diagnosis, expectancy and surgical results are presented. Received: 26 February 1997 / Accepted: 7 July 1997     

Persistent induction of nitric oxide synthase in tumours from mice treated with the anti-tumour agent 5,6-dimethylxanthenone-4-acetic acid.

An anti-tumour agent 5,6-dimethylxanthenone-4-acetic acid (5,6-MeXAA) induced nitric oxide synthase (NOS) in the tumour, spleen, thymus and small intestine, but not in the lung, liver, kidney, heart or skeletal muscle in B6D2F1 mice bearing subcutaneous colon 38 tumours. This pattern of induction is distinct from that caused by agents such as endotoxin, muramyl dipeptide or Corynebacterium parvum. The induction of NOS (iNOS) in the tumour was more persistent (maximal at 3 days) than in other tissues (maximal at 12 h). Immunohistochemical staining suggested that iNOS was located in macrophages and endothelial cells within and around the tumour. Treatment with 5,6-MeXAA also caused substantial increases in plasma nitrite and nitrate (NOx) concentrations that peaked at 8-12 h after 5,6-MeXAA. The increase in plasma NOx was prevented by a NOS inhibitor N-iminoethyl-L-ornithine (L-NIO), indicating that it was due to enhanced production of NO. Tumour-bearing mice were more responsive than controls to 5,6-MeXAA both in their plasma NOx increase and in their lower maximally tolerated dose. L-NIO was unable to prevent the complete tumour necrosis and regression caused by 5,6-MeXAA at a dose that substantially inhibited the increase of plasma NOx. In conclusion, the experimental anti-tumour agent 5,6-MeXAA induced NO synthesis in tumour-associated macrophages and in immunologically active tissues in parallel with its effects on tumour growth. The experiments with a non-selective NOS inhibitor L-NIO, however, suggest that NO is not a significant component in the mechanism of the anti-tumour action of 5,6-MeXAA in this particular model.     

Teniposide or carboplatin in patients with recurrent or advanced cervical carcinoma: A randomized phase II trial

Thomsen TK, Pfeiffer P, Bertelsen K. Teniposide or carboplatin in patients with recurrent or advanced cervical carcinoma: A randomized phase II trial. Int J Gynecol Cancer 1998; 8 : 310–314.
The aim of the present study was to investigate response rates, time to progression, and survival with teniposide or carboplatin in patients with advanced or recurrent cervical cancer and to estimate the toxicity of each drug regimen.
Twenty-eight patients with recurrent or advanced cervical cancer entered the study. Two patients were ineligible (severe renal impairment, n = 1; performance status 3, n = 1) and were excluded from the analysis. The remaining 26 patients were randomized to either carboplatin (400 mg/m² on day 1, intravenously every four weeks) or teniposide (125 mg/m² on days 1, 2 and 3, intravenously every four weeks). Twelve patients were randomized to the carboplatin arm and 14 patients to the teniposide arm. They were all comparable with respect to age, performance status, histology, primary FIGO stage, and prior therapy.
Response was seen in four patients in each group (33% and 29%, respectively), all but one being partial. (One patient in the teniposide group had complete response). Time to progression and median survival were similar in the two groups (median time to progression 20/17 weeks and median survival 40/41 weeks, respectively.)
In general, toxicity was moderate. Leukopenia (WHO grade 3 or 4) was seen in one patient treated with teniposide, and thrombocytopenia (WHO grade 3 or 4) in one patient treated with carboplatin. Eleven patients (79%) in the teniposide group had alopecia requiring a wig. The study implies that both drugs have some activity in cervical cancer. Carboplatin has the advantage that it can be administered on an out-patient basis.     

Gestational age, birth weight, and the risk of hyperkinetic disorder.

AIMS: To study the association between gestational age and birth weight and the risk of clinically verified hyperkinetic disorder. METHODS: Nested case-control study of 834 cases and 20 100 controls with incidence density sampling. RESULTS: Compared with children born at term, children born with gestational ages of 34-36 completed weeks had a 70% increased risk of hyperkinetic disorder (rate ratio (RR) 1.7, 95% confidence interval (CI) 1.2 to 2.5). Children with gestational ages below 34 completed weeks had an almost threefold increased risk (RR 2.7, 95% CI 1.8 to 4.1). Children born at term with birth weights of 1500-2499 g had a 90% increased risk of hyperkinetic disorder (RR 1.9, 95% CI 1.2 to 2.9), and children with birth weights of 2500-2999 g had a 50% increased risk (RR 1.5, 95% CI 1.2 to 1.8) compared with children born at term with birth weights above 2999 g. The results were adjusted for socioeconomic status of the parents, family history of psychiatric disorders, conduct disorders, comorbidity, and maternal smoking during pregnancy. Results related to birth weight were unchanged after adjusting for differences in gestational age. CONCLUSIONS: Children born preterm, also close to term, and children born at term with low birth weights (1500-2499 g) have an increased risk of clinically verified hyperkinetic disorder. These findings have important public health perspectives because the majority of preterm babies are born close to term.