Molecular structural basis of ligand selectivity for 5-HT2 versus 5-HT1C cortical receptors

A molecular structural criterion of ligand selectivity for the 5-HT2 versus 5-HT1C receptor was hypothesized on the basis of radioligand binding data. Despite the large number of compounds which have been tested at both receptors, analysis of published data led to the identification of only five agents which are greater than 10-fold selective for the 5-HT2 versus the 5-HT1C receptor. Comparison of the two-dimensional structures revealed that, although these five compounds represent three distinct structural classes, they share a common structural feature located in the region hypothesized to be involved in receptor binding: a carbonyl or carboxyl oxygen interposed spatially between an aromatic ring and nitrogen atom. This structural feature was used to predict the relative selectivity of compounds that had not previously been analyzed at both the 5-HT2 and 5-HT1C receptors. All six drugs tested which contain the identified reactive carbonyl or carboxyl group were found to be selective for the 5-HT2 versus the 5-HT1C receptor with selectivity ratios ranging from 26 to 380. By contrast, three agents which are structurally similar but do not contain the reactive carbonyl or carboxyl group displayed equally high affinity for both receptor binding sites. Since the physiological roles of the 5-HT2 and 5-HT1C receptor are markedly different, it would be of potential clinical and scientific value to utilize this molecular structural feature to further identify chemical compounds which would selectively interact with only one of the two receptors.     

Localization of ROMK channels in the rat kidney

Renal potassium secretion occurs in the distal segments of the nephron through apically located secretory potassium (SK) channels. SK may correspond to the ROMK channels cloned from rat kidney. In this study, the localization of ROMK at the cellular level in the rat kidney was examined using an affinity-purified polyclonal antibody raised against a C-terminal peptide of ROMK. The specificity of the antibody was demonstrated by immunoblots of membranes of Xenopus oocytes expressing ROMK2. Immunoblots of homogenates from rat renal outer medulla and cortex revealed predominant bands of 70 to 75 kD, which were ablated by preadsorption with an excess of peptide. These bands were specific for the rat kidney. Immunolocalization studies revealed that ROMK is expressed in specific nephron segments in both the cortex and medulla. In the cortex, ROMK was found in the apical domain of the thick ascending limb of Henle's loop, the connecting tubule, and in some, but not all, cells of cortical collecting tubules. In the medulla, expression in the apical membrane of the thick ascending limbs of Henle's loop was strong, whereas outer medullary collecting ducts were weakly stained. Expression in the thick ascending limb was also heterogeneous; some cells that expressed the Na-K-Cl cotransporter were weakly stained with the anti-ROMK antibody. No staining of glomeruli, proximal tubules, or inner medullary collecting ducts was found. The localization of ROMK agrees well with the findings of SK in patch-clamp studies and supports the view that ROMK is the SK channel of the distal segments of the nephron.     

Consensus heart failure. Centraal Begeleidingsorgaan voor de Intercollegiale Toetsing

Consensus heart failure--On June 17th, 1994, a consensus meeting was organised to establish guidelines for the diagnosis and treatment of heart failure. Reason to do this were controversies, especially among general practitioners, cardiologists, internists and gerontologists, which arise as a consequence of new diagnostic modalities (such as echocardiography) and altered aims of the treatment (besides relief of symptoms reduction of morbidity and mortality). A number of starting points were formulated by a preparatory committee: Heart failure constitutes a major health problem. It is defined by cardiac dysfunction with accompanying symptoms. Diagnosis and treatment should focus first on causes or contributing factors. The extent of diagnostic procedures depends on possible doubts with regard to diagnosis and aetiology and therapeutic consequences. Treatment should include non-medical measures. Apart from relief of symptoms, the choice of drugs is also determined by their potential to reduce morbidity and mortality. The pharmacotherapeutic approach has to be tailored to the needs of the patient with a central role for the ACE inhibitors. Patients with concomitant arrhythmias and (very) old patients form separate risk groups. Further attention should be paid to the prevention of heart failure.     

Position statement: single-dose activated charcoal. American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists

In preparing this Position Statement, all relevant scientific literature was identified and reviewed critically by acknowledged experts using agreed criteria. Well-conducted clinical and experimental studies were given precedence over anecdotal case reports and abstracts were not usually considered. A draft Position Statement was then produced and subjected to detailed peer review by an international group of clinical toxicologists chosen by the American Academy of Clinical Toxicology and the European Association of Poisons Centres and Clinical Toxicologists. The Position Statement went through multiple drafts before being approved by the boards of the two societies and being endorsed by other societies. The Position Statement includes a summary statement for ease of use and is supported by detailed documentation which describes the scientific evidence on which the Statement is based. Single-dose activated charcoal should not be administered routinely in the management of poisoned patients. Based on volunteer studies, the effectiveness of activated charcoal decreases with time; the greatest benefit is within 1 hour of ingestion. The administration of activated charcoal may be considered if a patient has ingested a potentially toxic amount of a poison (which is known to be adsorbed to charcoal) up to 1 hour previously; there are insufficient data to support or exclude its use after 1 hour of ingestion. There is no evidence that the administration of activated charcoal improves clinical outcome. Unless a patient has an intact or protected airway, the administration of charcoal is contraindicated.     

Analysis of lipidation of recombinant Lyme vaccine protein (rOspA) by electrospray mass spectroscopy

Lipidation at the N-terminal of recombinant outer surface protein A (rOspA) is an important determinant of its immunogenicity. Lipidation patterns of rOspA can be sensitive to processing environments and storage conditions. In order to assure product consistency and stability. it is essential to characterize and monitor lipidation patterns of rOspA through its life-cycle. Electrospray mass spectroscopy combined with maximum entropy calculation was employed to analyze the lipidation of rOspA. The results revealed that more than 90% of protein is a tri-lipidated rOspA and the remainder is di-lipidated. It was demonstrated that the method is both sensitive and quantitative and has the potential to be used for routine quality control and stability testing.     

Hepatitis G virus infection in hemodialysis patients and the effects of interferon treatment

OBJECTIVE: To characterize the nature of hepatitis G virus (HGV) infections in hemodialysis patients and to determine the responsiveness of HGV to antiviral therapy in these patients. METHODS: HGV, a recently identified flavivirus, is associated with non-A-E viral hepatitis infections. We studied HGV infections in hepatitis C virus (HCV)-infected hemodialysis patients over a 1-yr period, using two independent PCR assays and nucleic acid sequencing. Thirty-four of 63 study patients were treated with interferon. RESULTS: We observed a 27% prevalence (17/63 patients) and a 4% annual incidence of HGV infections in the study population. HGV was not detected in any of the 10 HGV-infected patients immediately after interferon therapy. Although seven of these 10 patients developed HGV relapses, three had long-term responses. The interferon responsiveness of HGV and HCV appeared to be unrelated. In contrast, all seven untreated HGV-infected patients remained viremic. Sequence analyses of the different HGV isolates revealed only very limited genetic variability in the polymerase chain reaction-amplified regions of HGV during 1 yr of observation. CONCLUSIONS: Our data suggest that HCV-infected hemodialysis patients are at substantial risk of acquiring HGV infection and that HGV infections are prevalent in this population. In addition, HGV infections become chronic but are responsive to interferon treatment.