SR33805, a Ca2+ antagonist with length-dependent Ca2+ -sensitizing properties in cardiac myocytes

1. This study examined the effects of SR33805, a fantofarone derivative with reported strong Ca(2+) -antagonistic properties, on the contractile properties of intact and skinned rat ventricular myocytes. 2. On intact cells loaded with the Ca(2+)-fluorescent indicator Indo-1, the application of low concentrations of SR33805 enhanced the amplitude of unloaded cell shortening and decreased the duration of cell shortening. Amplitude of the Ca(2+) transient was also decreased. 3. These effects were accompanied with a shortening of the action potential and a dose-dependent blockade of L-type calcium current (IC(50)=2.4 x 10(-8) M). 4. On skinned cardiac cells, the application of a low SR33805 concentration (10(-8) M) induced a significant increase in maximal Ca(2+)-activated force at the two-tested sarcomere lengths (SLs), 1.9 and 2.3 microm. 5. The application of a larger dose of SR33805 (10(-6)-10(-5) M) induced a significant leftward shift of the tension-pCa relation that accounts for Ca(2+)-sensitization of the myofilaments, particularly at 2.3 microm SL. 6. In conclusion, despite its strong Ca(2+)-antagonistic properties SR33805 increases cardiac cell contractile activity as a consequence of its Ca(2+)-sensitizing effects. These effects are attributable to both an increase in the maximal Ca(2+)-activated force and a length-dependent Ca(2+)-sensitization.     

Serotonin and drug reward: focus on 5-HT2C receptors

Pharmacological manipulation of the 5-hydroxytryptamine (5-HT; serotonin) system has long been associated with a regulation of feeding behaviour, however, the initial part of this article reviews evidence that central 5-HT systems similarly modulate reward-related behaviours, particularly drug reward. The second part of this article considers what we believe to be strong emerging pharmacological and genetic evidence that many of these effects are mediated through 5-HT_2C receptor signalling mechanisms. Finally, we consider the potential for selective 5-HT_2C agonists as therapies for substance abuse disorders and the medical implications for different 5-HT_2C receptor isoforms generated by RNA editing.     

Neurofibrillary degeneration of the Alzheimer-type: an alternate pathway to neuronal apoptosis?

Neuronal death is a process which may be either physiological or pathological. Apoptosis and necrosis are two of these processes which are particularly studied. However, in neurodegenerative disorders, some neurons escape to these types of death and "agonize" in a process referred to as neurofibrillary degeneration. Neurofibrillary degeneration is characterized by the intraneuronal aggregation of abnormally phosphorylated microtubule-associated Tau proteins. A number of studies have reported a reactivation of the cell cycle in the neurofibrillary degeneration process. This reactivation of the cell cycle is reminiscent of the initiation of apoptosis in post-mitotic cells where G1/S markers including cyclin D1 and cdk4/6, are commonly found. However, in neurons exhibiting neurofibrillary degeneration, both G1/S and G2/M markers are found suggesting that they do not follow the classical apoptosis and an aberrant cell cycle occurs. This aberrant response leading to neurofibrillary degeneration may be triggered by the sequential combination of three partners: the complex Cdk5/p25 induces both apoptosis and the "abnormal mitotic Tau phosphorylation". These mitotic epitopes may allow for the nuclear depletion of Pin1. This latter may be responsible for escaping classical apoptosis in a subset of neurons. Since neurofibrillary degeneration is likely to be a third way to die, molecular mechanisms leading to changes in Tau phosphorylation including activation of kinases such as cdk5 or other regulators such as Pin1 could be important drug targets as they are possibly involved in early stages of neurodegeneration.     

Expression of the murine CB2 cannabinoid receptor using a recombinant Semliki Forest virus

A recombinant Semliki Forest virus (SFV) RNA construct, SFV1-mCB(2) RNA, was employed for the high-level expression of the murine CB(2) (mCB(2)) cannabinoid receptor in baby hamster kidney cells. Biosynthetic radiolabel incorporation studies in concert with urea-sodium dodecylsulfate-polyacrylamide gel electrophoresis (urea-SDS-PAGE) and western immunoblotting revealed that two major proteins of approximately 26 and 40kDa were produced by the construct. The 40kDa product, but not the 26kDa product, was glycosylated as determined by 2-deoxy-D-glucose incorporation and peptide-N-glycosidase F digestion analysis. Assessment of [3H]CP55940 ([3H]-(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol) binding data for membranes of cells transfected with SFV1-mCB(2) RNA indicated a K(d) of 0.35+/-0.04nM and a B(max) of 24.4+/-2.7pmol/mg. A rank order of binding affinities for cannabinoids, which paralleled that reported for native mCB(2) receptors, was observed. The CB(2) receptor-specific antagonist SR144528 (N-[(1S)-endo-1,3,3-trimethyl bicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide) blocked binding of [3H]CP55940, while the CB(1) receptor-specific antagonist SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride] had a minimal effect. These results indicate that the recombinant receptor expressed from SFV1-mCB(2) RNA exhibits properties, including ligand binding features, that are consistent with those for the native mCB(2) receptor. However, the presence of both 26 and 40kDa receptor species is consistent with alternative translation from two AUG start sites using the SFV1-mCB(2) RNA expression system.     

Adrenomedullin receptor binding sites in rat brain and peripheral tissues

The existence of specific adrenomedullin receptor binding sites was investigated using the agonist peptide fragment [125I]human adrenomedullin-(13-52) in rat brain, lung and vas deferens homogenates. Saturation-binding experiments suggest that [125I]human adrenomedullin-(13-52) binds to an apparent single population of sites with similar affinities (K(D) of 0.3 to 0.6 nM) but with different maximal binding capacity in the rat brain, lung and vas deferens homogenates (B(max) of 73, 1760 and 144 fmol/mg protein, respectively). Competition-binding experiments using various analogues and fragments of calcitonin gene-related peptide (CGRP) and adrenomedullin were also performed using this radioligand. Competition-binding profiles suggest the possible existence of heterogeneous populations of adrenomedullin receptor binding sites. For example, in rat brain, human adrenomedullin-(1-52) and human adrenomedullin-(13-52) competed against specific [125I]human adrenomedullin-(13-52) sites with competition curves best fitted to a two-site model. Additionally, human calcitonin gene-related peptide alpha (hCGRPalpha), [Cys(Et)(2,7)]hCGRPalpha and [[R-(R,(R*,S*)]-N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl]carbonyl]pentyl]amino]-1-[(3,5-dibromo-4-hydroxyphenyl)methyl]-2-oxoethyl]-4-(1,4-dihydro-2-oxo-3(2H)-quinazolinyl)-,1-Piperidinecarboxamide] (BIBN4096BS) competed against specific [125I]human adrenomedullin-(13-52) binding with profiles that were also best fitted to a two-site model. Furthermore, binding assays performed in the presence of GTPgammaS (100 microM) revealed that this compound inhibited 20% of specific [125I]human adrenomedullin-(13-52) sites in rat brain homogenates and competition curves of human adrenomedullin-(1-52) and [Cys(Et)(2,7)]hCGRPalpha against specific [125I]human adrenomedullin-(13-52) sites remained best fitted to a two-site model. Moreover, the existence of specific [125I]human adrenomedullin-(13-52) binding sites that are resistant to human adrenomedullin-(22-52) and human CGRP-(8-37) is suggested in the rat brain and vas deferens. Taken together, these data provide evidence for the possible existence of heterogeneous populations of adrenomedullin binding sites in rat brain and peripheral tissues.     

Hidden from view: violent deaths among pregnant women in the District of Columbia, 1988-1996

OBJECTIVE: Maternal mortality is underreported in the United States in part because traumatic deaths are not included in nationally reported maternal mortality ratios. The overall study goal was to compare women whose deaths had been reported to and investigated by a medical examiner and who had evidence of pregnancy to women without evidence of pregnancy in terms of socio-demographic information, toxicology results, and manner and cause of death. A secondary goal was to compare the pregnancy status and gestational age of women with evidence of pregnancy at the time of death in relation to the manner of death, with particular focus on women who died as a result of violent death. METHODOLOGY: Autopsy charts from 1988-1996 for 651 women aged 15 to 50 from the District of Columbia Office of the Chief Medical Examiner whose autopsies included examination of the uterus were reviewed. Medical examiners' classification of manner and specific causes of death were used as the main outcome measures. Overall, the sample reflected demographic characteristics of women of childbearing age in the District of Columbia, with 82% black, 74.6% unmarried, and 46.5% aged 20 to 34. RESULTS: Among the 651 autopsy charts evaluated, 30 (4.6%) documented evidence of pregnancy; 43.3% of the women who died due to homicide with evidence of pregnancy were not included in the 21 pregnancy-related deaths officially reported by the District of Columbia State Center for Health Statistics during the study period, and therefore, were also not included in national maternal mortality ratios. Although not statistically significant, 11% more homicides occurred among women with evidence of pregnancy as compared to non-pregnant women. Pregnant women who died a violent death were significantly more likely than non-pregnant women to have died due to gunshot trauma. A significant proportion of pregnant women were < 21 weeks gestation at the time of their death. Additionally, women in this sample with evidence of pregnancy were over 3 times more likely to have been teenagers compared to non-pregnant women. CONCLUSION: Medical examiner autopsy records identify violent pregnancy-associated deaths, many of which occur early in pregnancy and are missed by other enhanced case-finding techniques that require a record of a birth or fetal death. These deaths are usually excluded from reported maternal mortality ratios. Few studies have evaluated the prevalence of homicide in women of childbearing age, yet understanding the extent of less commonly associated causes of death during pregnancy such as homicide, may lead to improved identification of preventable problems that contribute to maternal morbidity and mortality. This study, which sheds new light on the identifying and reporting of maternal mortality, and specifically on homicide as a form of violence toward pregnant women, should be of particular interest for all women's health providers, as well as public health professionals, researchers, and advocates who are interested in the design, development, and evaluation of prevention programs, especially those directed toward preventable problems such as domestic violence.     

A systematic review of the diagnostic accuracy of physical examination for the detection of cirrhosis

Background  

We conducted a review of the diagnostic accuracy of clinical examination for the diagnosis of cirrhosis. The objectives were: to identify studies assessing the accuracy of clinical examination in the detection of cirrhosis; to summarize the diagnostic accuracy of reported physical examination findings; and to define the effects of study characteristics on estimates of diagnostic accuracy.     

Adverse effects of Disulone; results of the France pharmacovigilance inquiry. Regional Centers of Pharmacovigilance

Disulone (dapsone + ferrous oxalate) is a sulphone marketed in France since 1958 and authorized in P. Carinii prophylaxis in HIV+ cotrimoxazole intolerant patients, bullous dermatosis, leprosy and polychondritis. Between 1983 and 1998, 249 adverse reactions were reported to French pharmacovigilance centres and Aventis, the manufacturer. Every side-effect was reviewed and the causal relationship was assessed on the basis of the French method for causality assessment. Main side-effects were divided as follows: 117 blood dyscrasias (generally neutropenia and agranulocytosis, rarely methaemoglobinaemia, haemolysis, macrocytosis, anaemia, aplastic anaemia, haemochromatosis and sulphaemoglobinaemia); 29 hypersensitivity syndrome; 39 cutaneous reactions, generally rash; 27 liver injuries (cholestatic, cytolytic and mixed hepatitis); 27 neurological and psychiatric side-effects including 7 axonal neuropathy; 10 gastrointestinal effects, generally nausea and vomiting. Five deaths were reported (4 septicaemia including one case not due to dapsone and 1 digestive bleeding due to underlying disease). In the other cases the outcome was favourable. The results were compared with the published references. It would seem to be important to reinforce information to prescribers about the possible serious adverse reactions with dapsone, particularly hypersensitivity syndrome and agranulocytosis, that can cause death if the drug is not stopped in time.     

Risk factors for chronic constipation based on a general practice sample

OBJECTIVES: Many factors have been associated with the occurrence of constipation, particularly poor diet and lack of exercise. However, the importance of medications and general medical illnesses in constipation remains more uncertain. We aimed to identify risk factors for constipation from among patient clinical, therapeutic, and demographic characteristics. METHODS: The sample was composed of patients explicitly diagnosed with chronic constipation (n = 7251), those diagnosed with constipation of unspecified chronicity (n = 6441), and a sample of controls (n = 7103). All were drawn from a general practice research database representing more than 10 yr of data collection. RESULTS: A large number of clinical and therapeutic factors were independently associated with chronic constipation over and above age and gender. Primary neurological diseases were strongly associated with constipation but accounted for few cases. Opioids (OR = 1.6, population attributable risk [PAR] = 2.6%), diuretics (OR = 1.7, PAR = 5.6%), antidepressants (OR = 1.9, PAR = 8.2%), antihistamines (OR = 1.8, PAR = 9.2%), antispasmodics (OR = 3.3, PAR = 11.6%), anticonvulsants (OR = 2.8, PAR = 2.5%) and aluminum antacids (OR = 1.7, PAR = 3.0%) were associated with the highest risk among medications. CONCLUSIONS: Constipation is common in primary care, and multiple medications seem to be an important contributing factor. Concurrent diseases are also associated but at most are only contributing to a minority of cases.     

History dependence of rate covariation between neurons during persistent activity in an oculomotor integrator

Persistent firing in response to a brief stimulus is a neural correlate of short-term memory in a variety of systems. In the oculomotor neural integrator, persistent firing that encodes eye position is maintained in response to transient saccadic eye-velocity commands. To a first approximation, firing rates in the integrator vary linearly with eye position. Thus, viewed across many cells, the pattern of persistent firing in the integrator may be constrained to a unique line of stable states. Here this idea was tested by examining the relationship between firing rates of simultaneously recorded neurons. Paired recordings were obtained in awake goldfish from neurons in hindbrain area I, an essential part of the horizontal eye-position integrator. During spontaneous eye movements consisting of sequential fixations at different horizontal positions, the pair relationship between the majority of cells on the same side of the integrator was not unique: for a given rate of one cell, the rate of the paired cell assumed different values that depended systematically on the preceding saccade history. This finding suggests that the set of persistent firing states that encode eye position is not constrained to a unique line, and that models with stable states restricted to a such a line need to be modified accordingly.