Predictors of Lymph Node Metastasis in Western Early Gastric Cancer

BACKGROUND

The application of endoscopic and local resection for early gastric cancer (EGC) is limited by the risk of regional lymph node (LN) metastasis. We sought to determine the incidence and predictors of LN metastasis in a contemporary cohort of Western patients with early gastric cancer.

METHODS

Sixty-seven patients with pT1 gastric adenocarcinoma underwent radical surgery without neoadjuvant therapy at our institution between 1995 and 2011, and clinicopathologic factors predicting LN metastasis were analyzed.

RESULTS

LN metastases were present in 15/67 (22 %) pT1 tumors, including 1/23 (4 %) T1a tumors and 14/44 (32 %) T1b tumors. Tumor size, site, degree of differentiation, macroscopic tumor sub-classification, perineural invasion status, and depth of submucosal tumor penetration did not predict LN metastasis. The presence of lymphovascular invasion (LVI) and positive nodal status by endoscopic ultrasound (EUS) were the only factors that predicted LN metastasis on multivariate analysis. T1a tumors without LVI had a 0 % rate of positive LN, whereas T1b tumors with LVI had a 64.3 % rate of positive LN.

CONCLUSIONS

EGC limited to the mucosa, without evidence of LVI, and N0 on EUS, may be considered for limited resection. However, any EGC with submucosal invasion, LVI, or positive nodes on EUS should undergo radical resection with lymphadenectomy.

Factors influencing readmission after curative gastrectomy for gastric cancer

BACKGROUND

The incidence of, and associated risk factors for, readmission after potentially curative gastrectomy for patients with gastric cancer has not been well studied. We sought to determine the 30-day readmission rate as well as the potential risk factors for readmission at our institution in patients undergoing gastrectomy for gastric cancer with curative intent.

STUDY DESIGN

We performed a retrospective analysis of all patients undergoing potentially curative gastrectomy for gastric cancer from 1995 to 2011. The 30-day hospital readmission rate was determined, and potential clinicopathologic risk factors for readmission were examined.

RESULTS

Readmission to the hospital within 30 days occurred in 14.6% (61 of 418) of patients, including 6 patients who were readmitted more than once. The most common reasons for readmission included nutritional difficulties (n =12, 20%), intra-abdominal fluid collections (n = 11, 18%), and small bowel obstruction (n = 6, 10%). Factors associated with a higher 30-day readmission rate included type of resection (total gastrectomy, 23% vs subtotal gastrectomy, 13% vs esophagogastrectomy, 9%, p = 0.016), pre-existing cardiovascular disease (17%, p = 0.05), and history of a major postoperative complication (24%, p < 0.001). Factors not associated with a higher readmission rate included advanced age, pre-existing pulmonary disease, T or N stage, extent of lymph node dissection, receipt of neoadjuvant chemotherapy or radiotherapy, length of stay of the index hospitalization, and destination and level of support on discharge.

CONCLUSIONS

Readmission after potentially curative gastrectomy for gastric cancer is common. Patients with pre-existing cardiovascular disease, those who suffer major postoperative complications, and those undergoing total gastric resections are at especially high risk for readmission, and strategies designed to support these high-risk patients on discharge are warranted.

Effects of Butafosfan on salivary cortisol and behavioral response to social stress in piglets

We assessed the efficacy of Butafosfan, a component of Catosal, in the metaphylactic treatment of stress in pigs. Four 6-week-old female littermates were taken from 12 litters. They were confronted with a pig from a different litter for 2 h. There were 24 pairs, each consisting of confronting two unfamiliar pigs in a new pen. This housing of unfamiliar pigs provides a good, but simple, model of the psychosocial stress that pigs experience when housed in large groups on pig farms. Immediately before being housed with an unfamiliar pig, 12 pairs of pigs were injected subcutaneously with Catosal at a dose equivalent to 20 mg Butafosfan per kg body weight; the other 12 pairs received the control solution containing all ingredients of Catosal except Butafosfan. The frequency and duration of aggressive behavior and the salivary cortisol response were measured during the first 2 h of the encounter. No adverse effects associated with Catosal were observed. Subcutaneous injection of Catosal reduced the stress-induced salivary cortisol response and the frequency of aggressive behavior evoked by the social stress of housing two unfamiliar pigs together.

The pharmacological basis for metrifonate's favourable tolerability in the treatment of Alzheimer's disease

Metrifonate, through its pharmacologically active metabolite 2,2-dichlorovinyl dimethylphosphate (DDVP), is a long-acting cholinesterase inhibitor for the symptomatic treatment of mild-to-moderate Alzheimer's disease. Clinical studies with Alzheimer patients have demonstrated the favourable safety and tolerability profile of this drug. Metrifonate, at therapeutic doses for Alzheimer's disease, achieves high levels of cholinesterase inhibition, i.e. > or =70%, without the need for dose escalation. This is a consequence of the low rate of fluctuation of enzyme activity during therapy with metrifonate. This, in turn, is due to the protracted hydrolytic transformation of metrifonate into DDVP, the resulting smooth onset of cholinesterase inhibition, and the subsequent long duration of action which far outlasts the presence of the active drug in the body. Both metrifonate and DDVP are rapidly metabolized and eliminated from the body. Further, their metabolism does not involve the cytochrome P450 system and both compounds show low plasma protein binding. These pharmacokinetic features account, at least in part, for the favourable safety and tolerability profile of metrifonate as they suggest a minimal risk of drug-drug interactions with other likely co-medications in the long-term therapy of Alzheimer patients.

Sustained effect of metrifonate on cerebral glucose metabolism after immunolesion of basal forebrain cholinergic neurons in rats

To evaluate the influence of cholinergic projections from the basal forebrain on brain metabolism, we measured the cerebral metabolic rate of glucose (CMR(glu)) after unilateral lesioning of cholinergic basal forebrain neurons with the immunotoxin 192 IgG-saporin. CMR(glu) was determined in 24 cortical and 13 sub-cortical regions using the [14C]2-deoxy-D-glucose technique of Sokoloff. Average hemispheric CMR(glu) decreased by 7% (P<0.02) and 5% (P<0.05), 7 and 21 days after lesion, respectively. Regional effects were restricted to parietal and retrosplenial cortices, lateral habenula and the basal forebrain. We have previously shown that metrifonate increased CMR(glu) in intact rats. In lesioned rats, metrifonate (80 mg/kg, i. p.) was still active but the metabolic activation was reduced in terms of both the average hemispheric CMR(glu) and the number of regions significantly affected. Although it is reduced, the sustained effect of metrifonate in lesioned rats makes an argument for the use of this compound as treatment of cholinergic deficit in Alzheimer's disease.

Behavioral effects of apamin, a selective inhibitor of the SK(Ca)-channel, in mice and rats

Apamin, a highly selective and potent peptide that blocks the SK(Ca)-channels has been suggested to be a cognition enhancer. We tested apamin in the Morris water escape task, in shock motivated avoidance tasks, and in operant tasks in the Skinnerbox. We also used non-cognitive tests, such as the rat forced swimming test and cocaine-induced locomotor activity in the open field, and a test to assess the side effect profile. Mice and rats from different strains, and rats of different ages were used. The rat studies provided only weak support for the notion that apamin acts as a cognition enhancer. More convincing evidence was obtained from the mouse studies. Overt side effects of apamin were found at the dose of 0.3 mg kg(-1). This dose was close to, or even overlapped, the doses which improved cognition in mice. We conclude that apamin is a poor tool to assess the role of SK(Ca)-channels in learning and memory processes.

Metrifonate improves working but not reference memory performance in a spatial cone field task

The effects of metrifonate (3, 10 and 30 mg/kg, p.o.) on the working and reference memory performance of the rat were assessed in a spatial cone field task. The highest dose of metrifonate (30 mg/kg) improved the working memory performance, whereas none of the doses affected the reference memory performance. Other parameters of spatial discrimination performance were not affected by metrifonate treatment. The present results suggest that metrifonate has cognition-enhancing properties which are likely to be related to aspects of (spatial) working memory.

Kinetics of brain cholinesterase inhibition following metrifonate administration

In previous metrifonate (MTF) studies, there has been evidence for a preferential functional effect of the drug in cortical but not in striatal regions. In the present study we investigated the kinetics of brain cholinesterase (ChE) inhibition following an acute administration of MTF (100 mg/kg) in various brain regions of young and old Fischer 344 rats. The main objective was to test the hypothesis that the functional regional selectivity, observed in previous studies, was correlated with the extent of ChE inhibition. Using Karnovsky's method for histochemical staining, the highest staining intensity in control rats was found in the striatum and hippocampus, compared to a low basal activity in the frontal and frontoparietal cortices. In the striatum of drug treated old rats, enzyme inhibition was somewhat greater than that found in young rats. However, in the hippocampus, four to eight hours following MTF administration, the inhibition was greater in young compared to old rats. The differences in the sensitivity of various brain regions towards MTF induced ChE inhibition could not be correlated with the regional variation of MTF functional effects.

Characterization of learning and memory behaviors and the effects of metrifonate in the C57BL strain of mice

In the near future, a number of transgenic mouse models with neuropathological characteristics of Alzheimer's disease are expected to become widely available. It will be important to characterize their behavior in models for learning and memory. As a first step, we have characterized normal, medial septal-lesioned and hippocampal-lesioned C57BL mice, in different behavioral tests, i.e., water maze spatial navigation, Y-maze and passive avoidance behavior. These experiments were complemented by an investigation of the effects of acute treatment with an acetylcholinesterase inhibitor, metrifonate, in these behavioral tests. Normal C75BL mice perform very well in the water maze and the Y-maze, but suboptimally in the passive avoidance task. Lesioning of the medial septum or the dorsal hippocampus clearly impaired the performance of the mice. In medial septal-lesioned mice, metrifonate stimulated spatial navigation and alleviated the loss of activity in the Y-maze and passive avoidance. In hippocampal-lesioned mice, metrifonate had no effect on spatial navigation. It is concluded that C75BL mice are useful for testing in classical models for learning and memory, and that septohippocampal pathology is very likely to induce cognitive deficits in some of these models.

Effect of subchronic metrifonate treatment on cerebral glucose metabolism in young and aged rats

The effects of subchronic administration of metrifonate, a long-lasting cholinesterase inhibitor, on local cerebral glucose utilization were assessed in 3- and 27-month old Sprague-Dawley rats, using the autoradiographic [14C]2-deoxyglucose technique. Rats were treated twice daily with metrifonate (80 or 120 mg/kg) for 3 weeks. The [14C]2-deoxyglucose experiment was performed 18 h after the last metrifonate administration. In 3-month old rats, metrifonate 80 mg/kg increased the average hemispheric cerebral glucose utilization by 12% (P > 0.001). Significant effects were observed in 19 of the 54 regions studied, including cortical and limbic regions. The higher dose induced a larger effect (average increase 17%, 24 of the 54 regions affected). In 27-month old rats, very similar effects were obtained. These results show that repeated administration of metrifonate leads to a sustained metabolic activation in rat brain, at a level comparable to the activation observed previously after a single administration of the drug.

Animal models in the development of symptomatic and preventive drug therapies for Alzheimer's disease

Dementia of the Alzheimer type (AD) is clinically characterized by a progressive deterioration of intellect, memory, judgment, and abstract thinking. It is incurable, and causal therapy is not yet available. For the development of therapeutic drugs, valid animal models are needed that mimic the pathophysiological change in brain functions and the concomitant behavioural deterioration seen in AD patients. This article provides an overview of the animal models that are used most often to study the substrates and mechanisms of the pathological changes underlying AD and to identify, characterize and develop putative neuroprotective, antidegenerative, revalidation-supporting and/or cognition-enhancing compounds or treatments. The first generation of agents for the symptomatic treatment of the disease has been developed on the basis of results obtained with these models. These drugs are presently undergoing clinical testing or are already used therapeutically. There is, however, no single animal model that can mimic the full range of pathophysiological alterations and key symptoms of AD. New, genetically engineered mouse models that mimic at least some of the key pathological changes of AD are expected to provide tools that will facilitate the development of symptomatic and preventive drug therapies.

Effects of subchronic administration of metrifonate on cholinergic neurotransmission in rats

The effects of subchronic oral administration of metrifonate, a long-acting cholinesterase (ChE) inhibitor, on cholinergic neurotransmission were assessed in young adult male Wistar rats. Animals were treated twice daily with metrifonate. In a pilot study testing a 100 mg/kg dose of metrifonate for up to 14 days, ChE activity was found to steadily decrease to reach maximum inhibition levels of about 55%, 80% and 35% in brain, erythrocytes and plasma. Steady-state inhibition levels were attained by the 10th day of treatment. When metrifonate-treatment was discontinued, ChE activity in plasma returned to control levels within another day, while erythrocyte and brain ChE activity took more than 2 weeks to recover. In subsequent dose-response studies, metrifonate treatment was given for 3 and 4.5 weeks at doses of 0, 12.5, 25, 50, and 100 mg/kg, to different groups of animals, respectively. Correlation analysis indicted that brain ChE inhibition was more accurately reflected by erythrocyte than by plasma ChE inhibition, although all effects were highly correlated. The changes in ChE activity were not paralleled by changes in other parameters of the cholinergic neurotransmission, such as acetylcholine synthesis rate or acetylcholine receptor binding. It is therefore concluded that repeated administration of metrifonate to rats induces a long-lasting inhibition of ChE activity in a dose-related and predictable manner, which is neither subject to desensitization nor paralleled by counterregulatory downregulation of muscarinic or nicotinic receptor binding sites in brain.

Subchronic treatment increases the duration of the cognitive enhancement induced by metrifonate

The study compared the efficacy of acute versus chronic metrifonate treatment to improve initial and reversal learning of the water maze spatial navigation task in medial septal-lesioned rats. Acute oral administration of 30 mg/kg metrifonate at 30 min, but not at 150 or 360 min, before training improved the initial acquisition of the water maze task. In contrast, improvement of initial learning performance of medial septal-lesioned rats pretreated for 21 days with metrifonate was observed irrespective of the timing of metrifonate treatment relative to behavioral testing. Reversal learning was assessed after a four-day wash-out period. No drug treatment was administered during this part of the study. All the medial septal-lesioned rats that had received only acute treatment with metrifonate during the initial learning stage were now as impaired as vehicle treated medial septal-lesioned rats. However, the group subchronically pretreated with metrifonate performed better than the vehicle-treated medial septal-lesioned controls. These results indicate that both acute and subchronic treatment with metrifonate can facilitate spatial learning in medial septal-lesioned rats and the transient nature of this beneficial effect after single acute administration is transformed into a long-lasting improvement by subchronic treatment.

Effects of metrifonate, its transformation product dichlorvos, and other organophosphorus and reference cholinesterase inhibitors on Morris water escape behavior in young-adult rats

Metrifonate is currently under development as a putative cholinergic Alzheimer therapeutic, because it is a prodrug of the long-acting organophosphate cholinesterase (ChE) inhibitor dichlorvos. The aim of this study was to examine whether the transformation of metrifonate to dichlorvos and the resulting indirect inhibition of ChE are required for its previously documented cognition-enhancing properties in a standard Morris water escape task with intact rats. This was done by investigating whether the cognition-enhancing effects of metrifonate could be mimicked by dichlorvos, by the organophosphorus compounds diisopropylfluorophosphate and paraoxon or by structurally unrelated reference ChE inhibitors, such as tetrahydroaminoacridine, E2020, and physostigmine. Metrifonate, and to a lesser degree dichlorvos, and diisopropylfluorophosphate improved the acquisition of the water escape task, whereas paraoxon did not. The dose-response curves of the organophosphorus compounds were bell-shaped with apparent optimal doses of 10 to 30 mg/kg for metrifonate and 0.03 mg/kg for both dichlorvos and diisopropylfluorophosphate. The reference compounds E2020, physostigmine and tetrahydroaminoacridine did not affect learning and memory in the young-adult rat at doses that had previously been reported to mediate cognitive enhancement in deficiency models. Our results question whether the effect of metrifonate is mediated by inhibition of ChE alone and suggest the involvement of an additional, as yet unknown, mechanism of action.

Effects of nicotinamide on central cholinergic transmission and on spatial learning in rats

High-dose nicotinamide (1000 mg/kg) leads to a minor increase of plasma choline but to a major increase of the choline concentrations in the intra- and extracellular spaces of the brain. In the hippocampus, the nicotinamide-induced increase in choline was associated with an increase in the release of acetylcholine under stimulated conditions. In young rats, nicotinamide in doses between 10 and 1000 mg/kg did not influence spatial learning, as tested in the Morris water maze. In old rats, low doses of nicotinamide were ineffective whereas the high dose of 1000 mg/kg even impaired spatial learning. The combined administration of choline and nicotinamide had a synergistic effect on brain choline levels but had similar effects as nicotinamide given alone in the behavioral experiments. Additional tests for spontaneous behaviour and locomotion revealed procholinergic and sedative effects of the compound. We conclude that the ineffectiveness of the putative cognition enhancer nicotinamide in the learning task may be due to the observed sedative effect. Therefore, the development of nonsedative nicotinamide derivatives is recommended.

Species differences in [3H]linopirdine (DuP 996) binding to brain membranes

Binding of [3H]linopirdine was evaluated in membranes prepared from rat, mouse, calf, pig, and human brain tissue. Saturation and homologous competition experiments with freshly prepared and subsequently frozen brain membranes of young adult rats yielded biphasic binding curves. Analysing binding data with two-site models confirmed the existence of specific, high-affinity binding sites for [3H]linopirdine with a Kd value of 7.8 +/- 3.5 nM and revealed that another site with micromolar affinity for the radioligand may exist. Almost identical data were obtained with mouse brain membranes. However, high-affinity binding of [3H]linopirdine could not be detected in cerebral cortical membranes from calf, pig or an aged human subject, respectively. In these tissues [3H]linopirdine bound only with moderate affinity (Kd about 200 nM). In subsequent experiments using brain membranes either freshly prepared from aged (25-month-old) rats or prepared from young adult (3-month-old) rats after a post-mortem delay of up to 15 h, it could be excluded that the factors age or post-mortem delay were responsible for the lack of high-affinity [3H]linopirdine binding sites in calf, pig or human brain. It is concluded that [3H]linopirdine binding data obtained from rodent studies, and consequently physiological drug effects mediated by this drug target, cannot be readily extrapolated to other species including man.

Metrifonate induces cholinesterase inhibition exclusively via slow release of dichlorvos

Metrifonate, a long-acting cholinesterase (ChE) inhibitor with very low toxicity in warm-blooded animals, inhibits rat brain and serum cholinesterase (ChE) in vitro through its hydrolytic degradation product, dichlorvos. This conclusion is based on the finding that metrifonate-induced ChE inhibition showed the same pH dependence as its reported dehydrochlorination to dichlorvos. The ChE inhibition induced by dichlorvos was not pH dependent. It was mediated by a competitive drug interaction with the catalytic site of the enzyme, which led to irreversible inhibition within several minutes of incubation. After this time, addition of further substrate to the inhibited enzyme was not able to promote drug dissociation and hence enzyme reactivation. Similar characteristics of inhibition, i.e. interaction with the substrate binding site and time-dependent switch to non-competitive inhibition were observed with the reference compound, physostigmine. However, the physostigmine-induced inhibition of ChE could be readily reversed by further substrate addition. Another reference compound, tetrahydroaminoacridine (THA), also induced a reversible inhibition of rat brain and serum cholinesterase, but with a mechanism of action different from that of both dichlorvos and physostigmine in that enzyme inhibition occurred rapidly upon drug addition at an allosteric site on the enzyme surface. It is suggested that the unique slow release plus the slow inhibition of ChE by dichlorvos is responsible for the lower toxicity of metrifonate compared to that of directly acting ChE inhibitors.

Metrifonate and dichlorvos: effects of a single oral administration on cholinesterase activity in rat brain and blood

Cholinesterase activities in rat forebrain, erythrocytes, and plasma were assessed after a single oral administration of metrifonate or dichlorvos. In 3-month-old rats, the dichlorvos (10 mg/kg p.o.)induced inhibition of cholinesterase reached its peak in brain after l5-45 min and after 10-30 min in erythrocytes and plasma. Cholinesterase activity recovered rapidly after the peak of inhibition, but did not reach control values in brain and erythrocytes within 24 h after drug administration. The recovery of plasma cholinesterase activity, in contrast, was already complete 12 h after dichlorvos treatment. Metrifonate (100 mg/kg p.o.) had qualitatively similar inhibition kinetics as dichlorvos, albeit with a slightly delayed onset. Peak values were attained 45-60 min (brain) and 20-45 min (blood), after drug administration. Apparently complete recovery of cholinesterase activity was noted in both tissues 24 h after treatment. The dose-dependence of drug-induced inhibition of cholinesterase in rat blood and brain was determined at the time of maximal inhibition, i.e., 30 min after dichlorvos treatment and 45 min after metrifonate treatment. The oral ED(50) values obtained for dichlorvos were 8 mg/kg for brain and 6 mg/kg for both erythrocyte and plasma cholinesterase. The corresponding oral ED(50) values for metrifonate were 10 to 15 times higher, i.e., 90 mg/kg in brain and 80 mg/kg in erythrocytes and plasma. In rats deprived of food for 18 h before drug treatment, the corresponding ED(50) values for metrifonate were 60 and 45 mg/kg, respectively, indicating an about two-fold higher sensitivity of fasted rats to metrifonate-induced cholinesterase inhibition compared to non-fasted rats. Compared to 3-month-old rats, 19-month-old rats showed a higher sensitivity towards metrifonate and dichlorvos. At the time of maximal inhibition, there was a strong correlation between the degree of cholinesterase inhibition in brain and blood. These results demonstrate that single oral administration of metrifonate and dichlorvos induces an inhibition of blood and brain cholinesterase in the conscious rat in a dose-dependent and apparently fully reversible manner. While the efficiency of a given dose of inhibitor may vary with the satiety status or age of the animal, the extent of brain ChE inhibition can be estimated from the level of blood ChE activity.

Potent antagonism of calmodulin activity in vitro, but lack of antiproliferative effects on keratinocytes by the novel leukotriene biosynthesis inhibitor MK-886

MK-886, a leukotriene biosynthesis inhibitor, which prevents the translocation and activation of 5-lipoxygenase, has been proposed as an effective drug for the treatment of inflammatory disorders, including psoriasis. In the present study, we investigated the effects of MK-886 on calmodulin as a potential target protein of anti-inflammatory drug activity, and on the proliferation of cultured human keratinocytes, a calmodulin-dependent cellular response with indicative value for antipsoriatic drug activity. Despite potent calmodulin-antagonistic activity in vitro, MK-886 failed to block cell proliferation in a human keratinocyte line, whereas trifluoperazine, a well characterized calmodulin antagonist with similar effects on calmodulin activity in our in vitro assays, inhibited cell proliferation in a dose-dependent manner. Further investigations on the mechanism of action revealed that, in contrast with trifluoperazine, calmodulin antagonism by MK-886 in vitro is likely to be mediated at the level of the allosteric calmodulin-recognition site of phosphodiesterase, rather than by binding to calmodulin itself. Therefore, our data do not conflict with the proposed role of calmodulin in the regulation of cell proliferation, but demonstrate that drug-induced antagonism of calmodulin, detected by inhibition of calmodulin-dependent enzymes in vitro, is not necessarily linked to antiproliferative activity in human keratinocytes.

Chronic treatment with an anxiolytic dose of the 5-HT1A agonist ipsapirone does not alter ipsapirone acute neuroendocrine effects

We recently reported that chronic administration of the 5-HT1A receptor agonist, ipsapirone (0.5 milligrams in drinking water for 3 weeks), has anxiolytic activity in the rat. Herein, we investigated whether this treatment promotes tachyphylaxis to the acute neuroendocrine effects of ipsapirone. Rats chronically treated with ipsapirone displayed a 7% decrease in body weights, compared to vehicle-pretreated rats, thereby confirming previous observations. On the other hand, ipsapirone pretreatment did not affect basal plasma levels of adrenocorticotropin (ACTH), corticosterone, prolactin, aldosterone, and renin activity, nor did it affect their respective rises following an acute ipsapirone (50 mg/kg PO) challenge. Moreover, ipsapirone pretreatment did not affect the increase in plasma prolactin levels elicited by the dopaminergic receptor antagonist haloperidol. These results suggest that neither the 5-HT1A receptors nor the catecholamine receptors that mediate ipsapirone acute neuroendocrine effects develop tolerance to stimulation upon sustained ipsapirone treatment.

Radiolabelled calmodulin ligands: their low affinity and high lipophilicity may lead to artefacts in binding studies

In order to characterize the interaction site of a series of putative calmodulin antagonists of the diphenylalkylamine type with calmodulin (CaM), a representative member of this chemical class was radiolabelled. The binding of the selected compound, [3H]-VUF 4576, to calmodulin was studied according to a recently described technique using CaM agarose. However, some peculiar results were obtained: the tight binding of [3H]-VUF 4576 increased in presence of cold VUF 4576, resulting in a high non-specific binding. The unexpected results could readily be explained by a high binding capacity of the labelled compound and the cold ligands to the walls of the test tubes used. Such results were also found when [3H]-chlorpromazine ([3H]-CPZ) was applied. In literature comparable findings have been published. To explain such results the influence of positive cooperativity or irreversible binding has been suggested. We suppose that not only in our study, but also in other published investigations, binding to glass of the radioligand and/or the cold compounds may have had a strong influence. We suggest, therefore, that care should be taken in interpreting non-classical displacement data obtained with ligands which combine a rather low affinity and a high degree of lipophilicity, not only for binding to calmodulin, but for other systems as well.

Neuroendocrine effects of ipsapirone on the hypothalamic-pituitary adrenal axis: CRF, ACTH and cortisol in healthy volunteers

The neuroendocrine effects (changes in plasma CRF, ACTH and cortisol) of single and multiple (t.d.s. for 2 days) doses of ipsapirone (BAY Q 7821) 5 and 10 mg have been investigated in 6 healthy male volunteers. The study followed a balanced complete block, placebo-controlled and double blind design with two baseline phases (pre and post-treatment). Volunteers were investigated on identical days during 5 successive weeks. The results do not show a specific effect of ipsapirone on the hypothalamic-pituitary-adrenal axis when doses in the range of 5-30 mg per day were given.

Effects of tiflucarbine as a dual protein kinase C/calmodulin antagonist on proliferation of human keratinocytes and release of reactive oxygen species from human leukocytes

Various studies have suggested that calmodulin (CaM) is involved in the pathophysiology of psoriasis. Protein kinase C (PKC) is also accepted as playing a regulatory role in cell proliferation as well as in inflammatory processes. Therefore, we investigated the effects of the known CaM antagonist tiflucarbine (BAY/TVX P 4495) on two cellular systems related to the major clinical symptoms of psoriasis: proliferation of cultured human keratinocytes (HaCa T cell line) and release of reactive oxygen species (ROS) from human polymorphonuclear leukocytes (PMNL). Tiflucarbine inhibited both cellular responses in a dose dependent manner. Furthermore, tiflucarbine directly affected PKC, and may thus be considered to be a dual PKC/CaM antagonist with putative antipsoriatic activity. The effects of tiflucarbine on the different parameters were compared with those of the structurally unrelated dual PKC/CaM inhibitor W-7 and those of the potent PKC inhibitor staurosporine. The potencies of all three compounds were found to be in the same range as their PKC-inhibiting potency. Our data indicate that PKC, rather than CaM, may play a regulatory role in the release of ROS as well as in keratinocyte proliferation. Therefore, inhibition of PKC in general might have a therapeutic benefit in psoriasis.

Polymyxin B is a selective and potent antagonist of calmodulin

Polymyxin B, a cyclic peptide antibiotic, is considered to be a rather selective antagonist of protein kinase C. This drug is therefore widely used to evaluate the involvement of protein kinase C in cellular processes. In the present study, we investigated the effects of polymyxin B on the activity of calmodulin-dependent cyclic 3':5'-nucleotide phosphodiesterase in vitro. The drug potently inhibited this enzyme (IC50 80 nM in the presence of 500 microM Ca2+), while about 200-fold higher concentrations were required to inhibit protein kinase C to the same extent. Phosphodiesterase inhibition was competitive with respect to Ca2+ and calmodulin. Evidence for the formation of a complex between polymyxin B and calmodulin was obtained by polyacrylamide gel electrophoresis under non-denaturing conditions, and by affinity chromatography of calmodulin on polymyxin B-agarose. We therefore suggest that, at least in vitro, polymyxin B is a potent and selective inhibitor of calmodulin.

Cholinergic inositol phosphate formation in striatal neurons is mediated by distinct mechanisms

In murine striatal neurons devoid of functional synapses (6 days in vitro) the cholinergic agonists carbachol and arecoline evoked dose-dependent inositol phosphate (InsP) responses with mean log EC50s of -4.1 +/- 0.5 and -4.48 +/- 0.1, respectively. Carbachol (1 mM) and arecoline (1 mM) responses were insensitive to tetrodotoxin, a voltage-sensitive Na+ channel blocker, and were blocked by pirenzepine with relatively low affinity (logIC50 = -5.9 +/- 0.3 for the carbachol response and logIC50 = -5.8 +/- 0.3 for the arecoline response). After synaptogenesis (13 days in vitro) the maximal carbachol effect doubled whereas the arecoline response remained unchanged. This additional effect was sensitive to tetrodotoxin and the voltage-dependent Ca2+ channel blocker, omega-conotoxin. The tetrodotoxin-sensitive carbachol response was blocked by lower concentrations of pirenzepine than the tetrodotoxin-insensitive carbachol response. More than 75% of the InsP response evoked by low concentrations of muscarine (1 and 10 microM) was sensitive to tetrodotoxin whereas only 38% of the InsP response stimulated by 1 mM of muscarine could be blocked by tetrodotoxin. These results suggest that there are at least two different mechanisms (depending on the stage of development), activated most probably by two different muscarinic receptors responsible for the carbachol-induced InsP formation in striatal neurons.

Evidence for a specific recognition site for tiflucarbine on calmodulin

The putative antidepressant drug tiflucarbine (BAY P 4495) has previously been shown to inhibit calmodulin-dependent cyclic nucleotide phosphodiesterase competitively with respect to calmodulin. In order to determine whether this effect is mediated by a direct interaction with calmodulin, we measured the effects of radiolabelled triflucarbine in a direct ligand binding assay, using agarose-immobilized calmodulin. [3H]Tiflucarbine associated with low micromolar affinity with an apparently homogeneous class of recognition sites on calmodulin-agarose. No binding could be observed on calmodulin-deficient agarose. The effect was specific, saturable and reversible. Triflucarbine was the most potent calmodulin antagonist from a variety of structural analogues examined. The potencies of these derivatives to inhibit calmodulin-stimulated phosphodiesterase significantly correlated with their affinities towards the tiflucarbine binding site on calmodulin. No such correlation was evident when structurally unrelated reference compounds were tested. The association of tiflucarbine with calmodulin thus appears pharmacologically specific and selective and possibly contributes to the potent antidepressant activity of the drug.

Non classical, multiple-site interaction of [3H]-prazosin with the alpha 1-adrenoceptor of intact BC3H1 cells

1. In intact BC3H1 cells the EC50 of noradrenaline (NA) for the inositol phosphate response measured at 37 degrees C (EC50 = 193 nM) was much lower than its apparent dissociation constant (Ki37 degrees C = 83.211 microM) determined at this temperature by [3H]-prazosin binding. 2. After pretreatment of the cells with NA at 37 degrees C for 45 min, the time used in binding assays at this temperature, this difference between EC50 and Ki37 degrees C did not decrease significantly. An agonist-induced reduction in alpha 1-adrenoceptor affinity can therefore not explain the very high Ki37 degrees C value. 3. NA pretreatment at 37 degrees C decreased the number of [3H]-prazosin binding sites (assessed by whole cell binding at 2 degrees C) by only 49%; not by 100%, the value expected if agonist-induced receptor internalization were the origin of the very low Ki37 degrees C. 4. The EC50 of NA for the inositol phosphate response in the presence of 156 pM [3H]-prazosin was 1.841 microM but the IC50 of NA for the inhibition of [3H]-prazosin binding (126 pM) was 316 microM. As there is no alpha 1-adrenoceptor reserve in these cells we propose that at 37 degrees C [3H]-prazosin interacts, not only with the catecholamine recognition site (site 1) of the receptor, but also reacts weakly with another site from which it cannot be directly displaced by catecholamine-like substances (site 2).

Complex interactions of agonists with alpha 1-adrenoceptors in intact cells

1. The apparent Ki values of (-)-noradrenaline (NA), (+)- and (-)-adrenaline (Ad), phenylephrine and the mono-fluorinated NAs (in position 2, 5 or 6) for alpha 1-adrenoceptors of intact BC3H1 cells labelled with [3H]-prazosin were greatly dependent on the incubation temperature. 2. The EC50 values of these compounds for stimulation of the inositol phosphate (IP) accumulation at 37 degrees C were intermediate between their apparent dissociation constants at 2 degrees C (Ki2 degrees) and at 37 degrees C (Ki37 degrees). 3. The fact that an irreversible blockade of 46% +/- 6% (n = 3) of the [3H]-prazosin binding sites by phenoxybenzamine reduced the maximal IP-formation induced by NA by 57% +/- 5% (n = 3) shows that there is a direct coupling between alpha 1-adrenoceptors and phospholipase C in BC3H1 cells. 4. The Ki37 degrees s of all agonists tested were in the same range (0.1 to 1 mM) and showed no simple correlation with their EC50 values. 5. The Ki2 degrees values for all the agonist correlated linearly with their EC50 values but were about 20-100 times lower than the respective EC50 values (except for the partial agonist methoxamine). In order to explain this difference, we propose that the apparent high affinity in the cold could be due to an [3H]-prazosin-induced alteration of the active site of the alpha 1-adrenoceptor, increasing its apparent affinity for catecholamines.

New insights into maitotoxin action

Maitotoxin (3 ng/mol) induced a massive uptake of 45Ca2+ into BC3H1 cells. This effect exhibits a lag phase of 3 min. Inositol diphosphate formation occurred concomittantly with the 45Ca2+ uptake but inositol monophosphate formation was found only after a 5-min delay following toxin addition. Maitotoxin-induced 45Ca2+ influxes could not be blocked by either 1 microM verapamil, 1 microM nifedipine or 1 mM La3+ but was blocked by Zn2+ (IC50 = 41 microM). In addition to inositol phosphate formation and 45Ca2+ uptake, maitotoxin stimulated a large uptake of Na+ and a great loss of K+ in BC3H1 cells. In the absence of Ca2+ (1 mM EGTA) none of the four maitotoxin effects could be detected. After restoration of Ca2+, the maitotoxin effects reappeared even when the toxin itself was no longer present. The divalent cation, Co2+ (1 mM), inhibited ion movements induced by maitotoxin and also digitonin (8.1 microM). The toxin action showed a very pronounced pH dependence. At low pH, maitotoxin was inactive. The dose-response curves for H+ ion inhibition of maitotoxin-induced Ca2+ uptake showed a shift to the right when determined in the absence of HCO3- and HCO3-/Cl- ions. It was concluded that the primary action of maitotoxin in BC3H1 cells was a pore-forming or channel-forming activity of a non-classical type. Some properties of maitotoxin resemble those of alpha-latrotoxin, others those of pore-forming agents such as melittin or alpha-toxin of Staphylococcus aureus.

Neurotransmitter-induced inositol phosphate formation in neurons in primary culture

Inositol-1,4,5-trisphosphate, produced in cells as a breakdown product of phosphatidylinositol-4,5-bisphosphate, induces, in many cell types, release of calcium from intracellular stores. In murine striatal neurons, differentiated in primary culture, carbachol, norepinephrine, glutamate, and neurotensin stimulate 3H-labeled inositol phosphate (3H-IP) production. The glutamate response was recently characterized as being mediated primarily by receptors of the quisqualate subtype. In the present study, we found that major differences exist between glutamate-stimulated 3H-IP formation and those stimulated by the other neuromediators. The maximal response to glutamate occurred before and during synaptogenesis and declined thereafter, whereas the maximal response to either carbachol or norepinephrine required complete neuronal differentiation. Although the glutamate response appears to be mediated exclusively by direct interaction with the neurotransmitter receptors, responses to carbachol, norepinephrine, and neurotensin were partially or completely blocked by tetrodotoxin.

Dual action of excitatory amino acids on the metabolism of inositol phosphates in striatal neurons

Glutamate is able to stimulate inositol phosphate (IP) formation in striatal neurons in primary culture, mainly via an excitatory amino acid receptor of the quisqualate subtype. In the present study we show that carbachol (Carb)-(a cholinergic agonist), but not neurotensin or norepinephrine-induced IP production could be reduced by 40% when measured in the presence of Glu. The inhibition of the Carb response by Glu was dose dependent and reproduced by N-methyl-D-aspartate (NMDA). Quisqualate elicited an additive response with Carb. 2-Amino-5-phosphonovalerate (APV) completely reversed the NMDA-induced inhibition. APV had no significant effect on Glu- or kainate-induced inhibition. Therefore, striatal neurons contain at least three different excitatory amino acid receptors: a quisqualate receptor triggering the stimulation of IP metabolism, and an NMDA and a kainate receptor, both able to decrease the Carb-induced IP formation.

The potential antidepressant tiflucarbine down-regulates beta-adrenoceptors in rat brain

Subchronic treatment of rats with the potential antidepressant tiflucarbine down-regulated the noradrenaline (NA) responses of the cAMP system in cerebral cortex. A concomitant 25% decrease in dihydroalprenolol binding sites in cerebral cortical membranes was observed. The effect was dose-dependent (ED50 = 6 mg/kg), required a 9 days' treatment period, and was reversible 5 days after discontinuation of treatment. Tiflucarbine treatment increased the specific activity of soluble calmodulin (CaM)-dependent phosphodiesterase in rat brain. Tiflucarbine bound to CaM and inhibited its interaction with the phosphodiesterase. Adrenergic denervation by 6-hydroxydopamine (6-OHDA) injection prevented both the beta-adrenoceptor down-regulation and the increase in specific activity of the phosphodiesterase. We suggest that a synergistic interaction between a presynaptic phosphodiesterase inhibition and the NA reuptake blockade was responsible for the down-regulation induced by tiflucarbine. The data are compatible with the reported antidepressant properties of this drug.

Rolipram, a stereospecific inhibitor of calmodulin-independent phosphodiesterase, causes beta-adrenoceptor subsensitivity in rat cerebral cortex

Prolonged pretreatment of rats with the atypical antidepressant rolipram attenuates noradrenaline (NA) sensitivity of the cerebral cortical cAMP generating system. The development of this down-regulation is time (7 d treatment required) and dose dependent (EC50 = 0.35 mg/kg). Density of beta-adrenoceptor as measured by (-)-3H-dihydroalprenolol [(-)-3H-DHA] binding is also reduced by rolipram pretreatment. The effect of rolipram is absolutely stereospecific for the (-)-enantiomer (ED50 = 0.18 mg/kg). In addition, only with this isomer, a reduction in daily weight gain was found compared to sham treated controls. Presynaptic denervation using intracerebroventricular (i.c.v.) injections of 6-hydroxydopamine (6-OHDA) prior to or during rolipram treatment did not completely block the effect of a rolipram treatment on down-regulation of cerebral cortical beta-adrenoceptors. The data favor a pre- and postsynaptic action of rolipram different from all other antidepressants studied so far in this experimental setting. Rolipram is known as inhibitor of brain phosphodiesterase. Using partially purified calmodulin-independent phosphodiesterase from brain it is shown that exclusively the (-)-enantiomer of rolipram inhibits phosphodiesterase with an IC50 of 1.25 mumol/l whereas the (+)-isomer possesses little potency. Since a marked stereospecificity for the (-)-isomer of rolipram was displayed in all pharmacological parameters tested so far with (+)- and (-)-rolipram, it is suggested that stereospecific and isozyme specific inhibition of cAMP-phosphodiesterase is, at least in part, related to the mechanism of action of the potential antidepressant drug rolipram and possibly of other antidepressants as well.

Chronic thyroxine treatment of rats down-regulates the noradrenergic cyclic AMP generating system in cerebral cortex

Treatment of Sprague-Dawley rats for 9 days with 15 micrograms/kg of tri-iodo-thyronine, 50 micrograms/kg of thyroxine (T4) or 500 micrograms/kg of thyrotropin-releasing hormone decreased the number of beta receptors in cerebral cortex as measured by dihydroalprenolol binding. The dissociation constants of dihydroalprenolol (3.5 nM) were not altered by the treatment. Only tri-iodo-thyronine and T4 administration resulted in a concomitant reduction of norepinephrine (NE) elicited cyclic AMP formation in cerebral cortical slices. This process required at least a 7-day treatment period and was dose-dependent. Application of 1 microgram of T4 per kg for 9 days significantly diminished the NE responsivity of the cyclic AMP synthesizing system. Dose-response curves with NE indicate a reduction of the maximal response after T4 treatment with no change in ED50. An almost additive interaction between the effects of T4 and a low dose (3 mg/kg) of the tricyclic antidepressant imipramine was observed. Striking differences in the response of the adrenoceptor coupled adenylate cyclase to a 9-day T4 treatment were found when different rat strains, i.e., Fischer F-344, Long-Evans, Wistar and Sprague-Dawley were used. The hyperthyroid state of the animals was ascertained by measurements of plasma levels of tri-iodo-thyronine and T4. Down-regulation of NE sensitive adenylate cyclase by T4 treatment required intact synaptic structures because denervation by i.c.v. injection of 6-hydroxydopamine abolished the effect of T4 treatment. This is indicative of a postsynaptic localization of the down-regulated cyclic AMP generating system. The data stress the importance of the neuroendocrine system for adrenoceptor regulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapid Degradation of Isolated Lignins by Phanerochaete chrysosporium

Phanerochaete chrysosporium degraded purified Kraft lignin, alkali-extracted and dioxane-extracted straw lignin, and lignosulfonates at a similar rate, producing small-molecular-weight (∼1,000) soluble products which comprised 25 to 35% of the original lignins. At concentrations of 1 g of lignin liter −1 , 90 to 100% of the acid-insoluble Kraft, alkali straw, and dioxane straw lignins were degraded by 1 g of fungal mycelium liter −1 within an active ligninolytic period of 2 to 3 days. Cultures with biomass concentrations as low as 0.16 g liter −1 could also completely degrade 1 g of lignin liter −1 during an active period of 6 to 8 days. The absorbance at 280 nm of 2 g of lignosulfonate liter −1 increased during the first 3 days of incubation and decreased to 35% of the original value during the next 7 days. The capacity of 1 g of cells to degrade alkali-extracted straw lignin under optimized conditions was estimated to be as high as 1.0 g day −1 . This degradation occurred with a simultaneous glucose consumption rate of 1.0 g day −1 . When glucose or cellular energy resources were depleted, lignin degradation ceased. The ability of P. chrysosporium to degrade the various lignins in a similar manner and at very low biomass concentrations indicates that the enzymes responsible for lignin degradation are nonspecific.