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Biomedical subjects

M Beer

Publications and source records attributed to M Beer.

At least 19 recordsLinked to original sources
PubMed1992

Novel 5-HT3 antagonists: indol-3-ylspiro(azabicycloalkane-3,5'(4'H)-oxazoles).

The synthesis and biochemical evaluation of a series of spirofused indole oxazoline 5-HT3 antagonists is described in which the oxazoline ring acts as a bioisosteric replacement for esters and amides. The effect of substitution about the indole ring has shown the steric limitations of the aromatic binding site. Incorporation of a variety of azabicyclic systems within the rigid spirofused framework has allowed the definition of a binding model which incorporates a number of known antagonists and agonists. In this model steric constraints limit substitution around the indole ring although there is some bulk tolerance at the 1- and 2-positions. The importance of constraining the basic nitrogen within an azabicyclic system is underlined by comparison with the monocyclic piperidine. The highest affinity was observed for those compounds in which the basic nitrogen occupies a bridgehead position, the most potent analogue in this group being the azabicyclic [3.3.1] system (pIC50 = 8.95), suggesting lipophilic interactions may play a role in increasing affinity. A suggested model for agonist binding is included in which the basic nitrogens are superimposed and the 5-hydroxyl group of 5-HT is superimposed on the H-bond-accepting atom of the heterocyclic linking group.

Animals↗
PubMed1992

A randomized prospective study of cisplatin and vinblastine versus cisplatin, vinblastine and mitomycin in advanced non-small cell lung cancer.

From June 1986 to February 1989, 103 patients with advanced non-small cell lung cancer, with no previous chemotherapy, were randomized to receive either a combination of cisplatin and vinblastine (group A) or the same combination with the addition of mitomycin (group B). In group A, 15/48 evaluable patients had objective responses, as did 8/45 in group B. The median survivals were 35 and 32 weeks, respectively. The median survival of patients with response or stable disease was 43 weeks. Response and survival did not differ significantly between treatment groups. The addition of mitomycin to the two-drug combination showed no major therapeutic benefit, while bone marrow toxicity was increased. Three patients in group B died of sepsis. Among the different patient characteristics, disease stage, performance status and response had influence on survival.

Adult↗
PubMed1992

Factors influencing complete response and survival in patients with head and neck cancer treated with platinum-based induction chemotherapy. A Hellenic Co-operative Oncology Group Study.

One hundred fifteen consecutive patients with locally advanced carcinoma of the head and neck were treated between August 1984 and August 1989 with three cycles of either of two platinum-based induction chemotherapies, followed by local treatment. After the completion of chemotherapy 26 (23%) patients had complete responses (CR). Several pre-treatment characteristics were analyzed for a possible correlation to CR to induction chemotherapy and to survival. The following variables were closely interrelated: sex, history of smoking, alcohol abuse, histologic type, tumor site and grade. Tumor stage and negative history of smoking were correlated with CR. The variables which were individually correlated with survival were keratinization, CR to chemotherapy, alcohol abuse, histologic type, site and grade of the primary tumor, serum albumin level and tumor stage. A regression analysis after Cox's model to identify a limited set of predictors selected CR, serum albumin, tumor grade, performance status and nodal status as the most significant; when analyzing the data without the time-dependent variable CR, the factors selected by the model were serum albumin, tumor grade, performance status and tumor stage. In conclusion, serum albumin level, tumor grade, performance status and tumor stage prior to treatment can be used to define risk classes in our patient population.

Adolescent↗
PubMed1992

Subsets of tumors responsive to cisplatin or carboplatin combinations in patients with carcinoma of unknown primary site. A Hellenic Cooperative Oncology Group Study.

In this retrospective analysis 48 patients with metastatic undifferentiated carcinoma, adenocarcinoma and epidermoid carcinoma of unknown origin were studied. The purpose of this analysis was to evaluate both the response rate and the toxicity of combination chemotherapy containing cisplatin or carboplatin, and to attempt to identify certain clinical subsets of patients sensitive to these drugs. Four patients were not evaluable and 13 (29.5%), eight of the 34 treated with regimens containing cisplatin and 5/14 with carboplatin-based chemotherapy, responded to treatment. Six of the 23 with undifferentiated tumours, 4/17 with adenocarcinomas and 3/8 with epidermoid cancers responded to chemotherapy. Four of 6 women with adenocarcinoma of the peritoneal cavity, 5/11 with undifferentiated carcinomas with midline distribution and 3/5 with epidermoid carcinomas of the cervical nodes responded. Seven patients achieved complete and six partial remissions. The mean duration of response was nine months; a number of patients enjoyed prolonged and/or durable remissions. Toxicity was tolerable. We conclude that: (a) both cisplatin and carboplatin are active agents in this syndrome with one-third of the evaluable patients responding, and (b) there may be chemosensitive subgroups, such as patients with peritoneal adenocarcinomatosis, undifferentiated carcinoma with midline distribution and metastatic epidermoid carcinoma of the neck nodes. The effectiveness of carboplatin in these patients and the responsiveness of metastatic epidermoid carcinoma of unknown origin have not been adequately dealt with in the literature.

Adenocarcinoma↗
PubMed1991

Carboplatin, continuous infusion fluorouracil and mid-cycle high-dose methotrexate as initial treatment in patients with locally advanced head and neck cancer. Hellenic Co-operative Oncology Group Study.

Forty-nine patients with locally advanced squamous cell carcinoma of the head and neck (SCCHN) were treated with 3 cycles of induction chemotherapy prior to definitive local treatment (surgery and/or radiation therapy). Chemotherapy consisted of carboplatin 300 mg/m2 on day 1, fluorouracil 1000 mg/m2 daily as a continuous infusion on days 1 to 5 and high-dose methotrexate 1.2 g/m2 with leucovorin rescue on day 14. After completing the induction chemotherapy, 9 patients (18%) achieved a complete remission (CR), 26 (54%) a partial remission (PR), 7 had stable disease and 7 a progression. The response rates increased to 53% CR and 18% PR following locoregional treatment. Survival at 12 months was 61% and its actuarial probability at 24 months 31%. Median time to progression was 14 months. Toxicity from chemotherapy was generally mild. Nausea was observed in 35%, vomiting in 26%, stomatitis in 57%, anemia in 22%, leukopenia in 36%, thrombocytopenia in 26% and diarrhea in 6% of the patients. In conclusion, the combination of carboplatin, 5-day continuous-infusion fluorouracil and mid-cycle high-dose methotrexate is a moderately effective, well tolerated regimen in patients with SCCHN but does not seem superior to the combination of carboplatin and fluorouracil only.

Aged↗
PubMed1991

Behavioural and biochemical evidence of the interaction of the putative antipsychotic agent, BMY 14802 with the 5-HT1A receptor.

The behavioural and biochemical profile of the sigma ligand and putative antipsychotic agent, BMY 14802 (alpha-(4-fluorophenyl)-4-(5-fluoro-2- pyrimidinyl)-1-piperazine butanol) has been determined in the mouse and rat. In mice, pretreatment with BMY 14802 attenuated both amphetamine-induced hyperactivity and conditioned avoidance responding, consistent with its previously reported antipsychotic potential. In common with 5-HT1A receptor agonists or partial agonists, BMY 14802 induced (a) a dose-dependent hypothermia in mice; (b) aspects of the 5-HT behavioural syndrome in rats, (c) antagonised mescaline-induced head twitches in mice and (d) generalised to the 8-hydroxy-2-(di-n-propylamino)tetralin discriminative stimulus over the dose range of 3-15 mg/kg. BMY 14802 had appreciable affinity for the 5-HT1A receptor (pIC50 = 6.7 compared to 7.3 for sigma binding) and antagonised forskolin-stimulated adenylate cyclase activity with a pEC50 of 6.2, consistent with an agonist action at this receptor. The results support the involvement of 5-HT1A receptors, but not the sigma binding site, in the behavioural profile of BMY 14802.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1991

High-dose epirubicin as a single agent in the treatment of patients with advanced breast cancer. A Hellenic Co-operative Oncology Group study.

Fifty-two women with advanced breast cancer were treated with 6 cycles of epirubicin. Even though the study was started with a dose schedule of 110 mg/m2 every 3 weeks, the average treatment interval was 26 days and the median weekly dose 78% of the protocol requirement. Forty-eight patients were evaluable for response; 3 achieved a complete remission which lasted for 17, 24 and 65 weeks, respectively, and 14 a partial remission. Median survival was 32 weeks. Toxicity included nausea/vomiting (68%), anemia (24%), leukopenia (37%), thrombocytopenia (8%), alopecia (81%), stomatitis (24%), diarrhea (14%), fever (19%) and fatigue (14%). Also 1 treatment-related death occurred and 2 cases of arrhythmia. Monotherapy with high doses of epirubicin has definite activity in advanced breast cancer and deserves further study in combination with hematopoietic growth factors which might allow a higher dose intensity.

Adult↗
PubMed1991

Novel 5-HT3 antagonists. Indole oxadiazoles.

The synthesis and biochemical evaluation of a series of indole oxadiazole 5-HT3 antagonists are described. The key pharmacophoric elements have been defined as a basic nitrogen, a linking group capable of H-bonding interactions, and an aromatic moiety. The steric limitations of the aromatic binding site have been determined by substitution about the indole ring. Variation of the heterocyclic linking group has shown that while two hydrogen-bonding interactions are possible, only one is essential for high affinity. The environment of the basic nitrogen has been investigated and shown to be optimal when constrained within an azabicyclic system. These results have been incorporated into a proposed binding model for the 5-HT3 antagonist binding site, in which the optimum distance between the aromatic binding site and the basic amine is 8.4-8.9 A and the steric limitations are defined by van der Waals difference mapping.

Animals↗
PubMed1991

Acetylation of serotonin in the rabbit pineal gland: an N-acetyltransferase with properties distinct from NAT1 and NAT2 is responsible.

Two rabbit arylamine N-acetyltransferases (NAT1 and NAT2, EC 2.3.1.5) have been cloned and characterized recently in this laboratory. They catalyze the acetylation of primary arylamine and hydrazine drugs and other substrates in the liver, including sulfamethazine, p-aminosalicylic acid, and p-aminobenzoic acid. In the pineal gland, serotonin is metabolized to N-acetylserotonin by an unknown N-acetyl-transferase. Similarity of the liver enzymes and the pineal gland arylalkylamine N-acetyltransferase (AA-NAT) has been suggested, because pineal gland homogenates were shown to metabolize arylamine substrates as p-phenetidine, aniline, or phenylethylamine, and liver homogenates or partially purified liver enzyme preparations catalyzed the N-acetylation of serotonin. The present study was undertaken to elucidate the possible role of NAT1 or NAT2 in serotonin acetylation in the pineal gland. We transiently expressed rNAT1 and rNAT2 genes in COS cells, studied the kinetics of the enzymes produced with various substrates, and compared these data with activities of rabbit pineal glands and livers. These enzymatic studies were complemented with western blot analysis with antibodies against NAT1 and NAT2. Cross-hybridization of rNAT1 or rNAT2 to the gene for the pineal gland AA-NAT was tested by Southern blot studies of genomic rabbit DNA. Our results indicate that although NAT1 is expressed in the pineal gland, it is not involved in the physiologically important step of N-acetylation of serotonin.

Acetylation↗
PubMed1991

[Laparoscopic pelvic lymphadenectomy. Indications, technique, initial results].

The therapeutic management of carcinoma of the prostate and the bladder depends on the tumor involvement of the hypogastric and obturatoric lymph nodes. Pelvic lymphadenectomy reveals the most accurate information about metastatic spread to the lymph nodes in patients with prostatic carcinoma. The pathologic information it offers cannot be acquired by any other diagnostic procedure. In cadaver studies and animal experiments in dogs we developed a technique for laparoscopic pelvic lymphadenectomy. Since 1990 six patients underwent a transperitoneal laparoscopic lymphadenectomy. First results show the feasibility of our operative technique. Currently the future role of laparoscopic pelvic lymphadenectomy in clinical management of prostatic carcinoma cannot be estimated.

Electrocoagulation↗
PubMed1991

Monomorphic and polymorphic human arylamine N-acetyltransferases: a comparison of liver isozymes and expressed products of two cloned genes.

A genetic polymorphism of human liver arylamine N-acetyltransferase (NAT; EC 2.3.1.5) enzyme activity divides populations into distinguishable "slow acetylator" and "rapid acetylator" phenotypes. Two human genes, NAT1 and NAT2, encoding NAT proteins [DNA Cell Biol. 9:193-203 (1990)] were transiently expressed in cultured monkey kidney COS-1 cells, and the resulting recombinant NAT1 and NAT2 proteins were compared with N-acetyltransferase activities in human liver cytosol with respect to their stability, chromatographic behavior on anion exchange columns, electrophoretic mobility, and arylamine acceptor substrate specificity. NAT1 was far less stable in vitro than NAT2. Under conditions designed to optimize enzyme stability, anion exchange chromatography experiments revealed that enzymes corresponding to both recombinant NAT1 and NAT2 were expressed in human liver. Recombinant and human liver NAT1 enzymes showed the same characteristic selectivity (low apparent Km, high Vmax) for the "monomorphic" substrates p-aminosalicylic acid and p-aminobenzoic acid. Such substrates fail to discriminate between the acetylator phenotypes in vivo. The same criteria established that recombinant NAT2 was indistinguishable from one of two previously observed N-acetyltransferases (NAT2A and NAT2B) whose liver contents correlate with acetylator phenotype in human populations. Recombinant NAT2 and the liver NAT2 isoforms NAT2A and NAT2B selectivity N-acetylated the "polymorphic" substrates sulfamethazine and procainamide, whose disposition in vivo is affected by the acetylation polymorphism. Interestingly, the carcinogen 2-aminofluorene was very efficiently metabolized by both NAT1 and NAT2. Independent regulation of NAT1 and NAT2 genes was suggested by a lack of correlation of NAT1 and NAT2 enzyme activities in cytosols from 39 human livers. The results provide strong evidence that the NAT2 locus is the site of the human acetylation polymorphism. In addition, the use of recombinant NAT1 and NAT2 will allow us to predict whether any given arylamine will be polymorphically acetylated in humans.

Acetylation↗
PubMed1990

A single dose of 8-OH-DPAT reduces raphe binding of [3H]8-OH-DPAT and increases the effect of raphe stimulation on 5-HT metabolism.

8-Hydroxy-(di-n-propylamino)tetralin (8-OH-DPAT) has antidepressant-like effects in rats and selectively reduces presynaptic 5-HT1A function a day after administration. In the present study, the effect of 8-OH-DPAT (1 mg/kg s.c.) pretreatment on presynaptic (raphe nuclei) and postsynaptic (frontal cortex and hippocampus) [3H]8-OH-DPAT binding was studied. Bmax values were markedly reduced in the raphe, but not in the hippocampus and frontal cortex. Kd values were unchanged. Electrical stimulation of the dorsal raphe (300 microA, 1 ms, 20 Hz, 30 min) significantly increased 5-hydroxyindoleacetic acid in the frontal cortex, but not in the amygdala or the nucleus accumbens and caused smaller increases in the rest of the brain. The increase in the frontal cortex was significantly potentiated one day after giving 8-OH-DPAT. These results confirm the ability of 8-OH-DPAT to desensitise presynaptic 5-HT1A receptors and suggest that this may lead to a loss of feedback control so that, on neuronal stimulation, the increase of 5-HT function is enhanced. This effect may underlie the antidepressant-like action of 8-OH-DPAT pretreatment, i.e. its ability to oppose restraint-induced defects in locomotion on placement in an open field one day later. A requirement of presynaptic 5-HT for this behavioural effect is consistent with its prevention by the 5-HT synthesis inhibitor parachlorophenylalanine.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1990

Dimethylthiourea reduces ischemic brain edema without affecting cerebral blood flow.

Oxygen free radicals have been implicated as mediators of tissue damage in ischemic brain. We previously demonstrated that the hydroxyl radical scavenger 1,3-dimethyl-2-thiourea (DMTU) reduces infarct size after middle cerebral artery occlusion (MCAO) in rats. The present study was undertaken to determine whether this protection results from a preservation of the CBF. Adult male Sprague-Dawley rats were treated with DMTU (750 mg/kg i.p.) or saline vehicle 1 h before right MCAO. One-half 4, or 24 h after MCAO, animals were killed and samples were taken from the central, intermediate, and outer zones of the MCA distribution of each cortical mantle. Separate groups of animals were used to analyze these samples for water content (wet and dry weight), CBF [( 14C]butanol), or blood-brain barrier permeability [( 3H]alpha-aminoisobutyric acid). CBF was reduced in a graded fashion in the ischemic cortex: 0.169 +/- 0.020, 0.261 +/- 0.017, and 0.435 +/- 0.023 ml/g/min (mean +/- SEM, n = 8) after 4 h in the central, intermediate, and outer zones, respectively. Brain edema was present in a similar pattern, while blood-brain barrier permeability remained normal. Treatment with DMTU significantly reduced brain edema in the central and intermediate zones at both 4 and 24 h. However, CBF in the DMTU-treated animals was identical to that of the vehicle-treated animals. These results suggest that hydroxyl radicals play a role in the development of ischemic brain edema, but the mechanism does not appear to involve a direct effect on CBF.

Animals↗
PubMed1990

The six-minute walk--an adequate exercise test for pacemaker patients?

In many pacemaker patients bicycle and treadmill ergometry are not practicable. As an alternative, we performed a 6-minute walk on a 20-m corridor in 97 pacemaker patients, who were asked to walk as far as possible determining their speed by themselves. Results were compared with those of bicycle ergometry in 42 of these patients and with treadmill exercise of a group of 92 other pacemaker patients. In the 6-minute walk, performance and maximal heart rate were slightly lower (49 +/- 18 W; 96 +/- 23 beats/min) than in bicycle (57 +/- 16 W; 110 +/- 26 beats/min) and treadmill ergometry (50 +/- 37 W; 102 +/- 35 beats/min). A good correlation was found between walking and bicycling (r = 0.74) and in subgroups of patients with different pacemaker indications. All patients preferred the walk to bicycle ergometry considering it to be more related to daily physical activity. In conclusion, a 6-minute walk is a simple and physiological exercise test for nearly all pacemaker patients with good correlation to other types of exercise. It seems to be preferable to other tests because of its better acceptance and practicability.

Aged↗