The Brain Network of Naming: A Lesson from Primary Progressive Aphasia

Objective

Word finding depends on the processing of semantic and lexical information, and it involves an intermediate level for mapping semantic-to-lexical information which also subserves lexical-to-semantic mapping during word comprehension. However, the brain regions implementing these components are still controversial and have not been clarified via a comprehensive lesion model encompassing the whole range of language-related cortices. Primary progressive aphasia (PPA), for which anomia is thought to be the most common sign, provides such a model, but the exploration of cortical areas impacting naming in its three main variants and the underlying processing mechanisms is still lacking.

Methods

We addressed this double issue, related to language structure and PPA, with thirty patients (11 semantic, 12 logopenic, 7 agrammatic variant) using a picture-naming task and voxel-based morphometry for anatomo-functional correlation. First, we analyzed correlations for each of the three variants to identify the regions impacting naming in PPA and to disentangle the core regions of word finding. We then combined the three variants and correlation analyses for naming (semantic-to-lexical mapping) and single-word comprehension (lexical-to-semantic mapping), predicting an overlap zone corresponding to a bidirectional lexical-semantic hub.

Results and Conclusions

Our results showed that superior portions of the left temporal pole and left posterior temporal cortices impact semantic and lexical naming mechanisms in semantic and logopenic PPA, respectively. In agrammatic PPA naming deficits were rare, and did not correlate with any cortical region. Combined analyses revealed a cortical overlap zone in superior/middle mid-temporal cortices, distinct from the two former regions, impacting bidirectional binding of lexical and semantic information. Altogether, our findings indicate that lexical/semantic word processing depends on an anterior-posterior axis within lateral-temporal cortices, including an anatomically intermediate hub dedicated to lexical-semantic integration. Within this axis our data reveal the underpinnings of anomia in the PPA variants, which is of relevance for both diagnosis and future therapy strategies.     

Production of Polyclonal Antibody to the Bovine Adrenal Atrial Natriuretic Factor-R1 Receptor

Abstract

A polyclonal antibody monospecific for an intracellular epitope of the atrial natriuretic factor (ANF)-R₁ receptor was produced. The receptor protein (200 pmoles) was purified to homogeneity from bovine adrenal zona glomerulosa (BAZG), reduced, alkylated and digested with trypsin. The tryptic fragments were purified by reverse-phase h.p.l.c. on a C18 column. Based on the sequence of one of these fragments, a peptide was chemically synthesized, coupled to thyroglobulin and injected into rabbits. The antibody obtained was shown to be specific for the R₁-type as no receptor was detected in bovine red blood cells (RBC) (which are devoid of ANF receptors) and in NIH-3T3 cell membranes (where only the R₂-type is expressed). Several other tissues were screened and comparison of the immunoreactive receptor density estimates with those obtained by ANF binding yielded a correlation coefficient (r²) of 0.965. The minimal detectable dose was typically 3 fmoles/tube and the ED⁵⁰ of the RIA was 30 fmoles/tube. Cyanogen bromide digestion of the receptor was essential for antigenic detection, indicating that the epitope is probably hindered due to the tertiary structure of the native protein. Moreover, location of the epitope in the kinase homology domain of the receptor, combined with partial tryptic digestion, suggests that the proteolysis-sensitive region of the receptor is located between the transmembrane- spanning domain and the amino acid 586. This method of production of antibodies should be useful to precisely map the amino acids involved in various functions of the receptor.     

Classification of weevils as a data-driven science: leaving opinion behind

Data and explicit taxonomic ranking criteria, which minimize taxonomic change, provide a scientific approach to modern taxonomy and classification. However, traditional practices of opinion-based taxonomy (i.e., mid-20^th century evolutionary systematics), which lack explicit ranking and naming criteria, are still in practice despite phylogenetic evidence. This paper discusses a recent proposed reclassification of weevils that elevates bark and ambrosia beetles (Scolytinae and Platypodinae) to the ranks of Family. We demonstrate that the proposed reclassification 1) is not supported by an evolutionary systematic justification because the apparently unique morphology of bark and ambrosia beetles is shared with other unrelated wood-boring weevil taxa; 2) introduces obvious paraphyly in weevil classification and hence violates good practices on maintaining an economy of taxonomic change; 3) is not supported by other taxonomic naming criteria, such as time banding. We recommend the abandonment of traditional practices of an opinion-based taxonomy, especially in light of available data and resulting phylogenies.     

DOCKING LIGANDS TO VASOPRESSIN AND OXYTOCIN RECEPTORS VIA GENETIC ALGORITHM

ABSTRACT

The aim of the study was to computer-dock selected ligands to neurophyseal receptors in order to identify amino acid residues responsible for ligand–receptor interactions. To this aim, reliable oxytocin receptor (OTR) and arginine-vasopressin receptor (V1aR/V2R) models were built. The OTR-selective agonist [Thr⁴,Gly⁷]OT, the OTR-selective cyclohexapeptide antagonist L-366,948 and OT itself were docked via genetic algorithm to OTR, V1aR, and V2R and relaxed using a constrained simulated annealing protocol. For the analysis of receptor/ligand interactions a subset of initial conformations was chosen using energetic and steric criteria. All three ligands seem to prefer similar modes of binding to the receptors, manifested by repetitive residues of the receptors which directly interact with the ligands. Taking into account that many aspects of mechanisms of G protein-coupled receptor (GPCR) action are still unsolved, the results obtained with the docking simulations may propose future experimental research, especially in site-directed mutagenesis analysis and searching for key amino acid residues responsible for drug activities.     

Association Between Prolactinoma and Body Mass Index

ObjectiveObesity is increasing worldwide, and certain endocrine disorders may contribute to weight gain. While several studies have examined the association between weight gain and prolactinomas, the results are conflicting. Therefore, this study aimed to determine if body mass index (BMI) is higher among those with prolactinomas than those without.MethodsWe identified patients ≥18 years of age referred to an endocrine clinic between 2008 and 2018 with newly diagnosed prolactinomas. We extracted the relevant information, and comparative data was obtained from the 2015-2016 National Health and Nutrition Examination Survey.ResultsIn total, 34 cases met the inclusion criteria. One third of the patients described weight gain at presentation. Those with prolactinomas had a significantly higher BMI than the National Health and Nutrition Examination Survey population (median BMI, 29.8 kg/m² vs 28.3 kg/m², P = .0048). When stratified by sex, only men with prolactinomas had an increased BMI compared with the controls. Moreover, those with prolactinomas had a higher prevalence of class II obesity (BMI ≥ 35 kg/m²) than the survey population (35% vs 18%, P = .01). Among the prolactinoma patients, a correlation was observed between BMI and log-transformed prolactin levels (R² = 0.4, P = .0002).ConclusionWeight gain can be a presenting symptom for patients with newly diagnosed prolactinomas. Those with prolactinomas have a higher BMI and an increased prevalence of class II obesity. These findings suggest that patients should be counseled regarding weight issues related to prolactinomas at presentation and should be a consideration in the investigative and treatment algorithm of prolactinomas.     

Intérêt diagnostique de la TEP-TDM au 18F-FDG dans le diagnostic d’endocardite infectieuse sur valve native

BackgroundNative valve endocarditis (NVE) is a rare but serious disease. The prognosis depends on the rapidity of diagnosis, and is currently based on modified Duke criteria, where echocardiography has a key role but may lack sensitivity if valves are calcified. For prosthetic valves, the European Society of Cardiology 2015 recommendations added ¹⁸F-FDG PET/CT as a major imaging criterion as well as for extension assessment. This study evaluated the diagnostic accuracy of ¹⁸F-FDG PET/CT in NVE and in extension assessment.MethodsThis retrospective study involved 59 patients suspected of NVE at Bordeaux university hospital between 2011 and 2019 and received ¹⁸F-FDG PET/CT. The final diagnosis was established according to Duke criteria after 3 months of management. Infective endocarditis (IE) was assessed in the initial phase according to the Duke criteria. All PET/CTs were blindly reviewed jointly by a junior and senior nuclear-medicine physician.ResultsIn total, 59 patients were included. At 3 months, 26 patients had definite IE, 22 had rejected IE, and 11 possible IE. Twelve patients had positive PET/CT results. The sensitivity of the modified Duke criteria in the initial phase was 77% and the specificity was 81%. When combined with ¹⁸F-FDG PET/CT, the sensitivity of the Duke criteria increased to 96% and the specificity was 81%. The sensitivity of ¹⁸F-FDG PET/CT alone was 46%. All three patients with perivalvular abscess had positive PET/CT results. Of the 22 patients with NVE definite at 3 months, fourteen (54%) had at least one septic embolism diagnosed on PET/CT.ConclusionsThe implementation of ¹⁸F-FDG PET/CT with modified Duke criteria increased the sensitivity for NVE diagnosis in the initial phase and contributed to IE extension assessment. It may contribute to making the diagnosis of a local cardiac complication.     

AN 18-Month Open-Label Trial of Teriparatide in Patients with Previous Parathyroidectomy at Continued Risk for Osteoporotic Fractures: An Exploratory Study

ObjectiveTo determine whether teriparatide increases lumbar spine bone mineral density (BMD) in patients who have undergone parathyroidectomy for primary hyperparathyroidism (PHPT) and are at continued risk for fracture.MethodsThis open-label, nonrandomized, uncontrolled exploratory design study included patients who had undergone parathyroidectomy for PHPT and were judged to be at continued risk for fracture according to National Osteoporosis Foundation criteria. Patients were administered teriparatide subcutaneously, 20 mcg daily, for 18 months after they satisfactorily completed the screening period to ensure their eligibility for study participation. BMD was assessed by dual-energy x-ray absorptiometry at baseline, 6 months, 12 months, and 18 months. Secondary objectives included efficacy of teriparatide on increasing hip BMD, incidence of fractures, and safety measurements.ResultsSeven women and 3 men were included. Change in mean lumbar spine BMD was 0.059 gm/cm², which is a 7.1% increase (P = .005). Change in mean femoral neck BMD was 0.019 gm/cm², which is a nonsignificant increase of 3.3% (P = .49). There was no incidence of fractures. There were no significant changes in the safety measurements.ConclusionsThe use of teriparatide in patients with PHPT who have undergone parathyroidectomy and are still at risk for fracture is effective in improving lumbar spine BMD without deleterious effects on safety. Teriparatide should therefore be considered as a viable alternative for the treatment of these patients, as it may help in the prevention of fractures and their complications. (Endocr Pract. 2011;17:377-383)     

Mutational and Cysteine Scanning Analysis of the Glucagon Receptor N-terminal Domain

The glucagon receptor belongs to the B family of G-protein coupled receptors. Little structural information is available about this receptor and its association with glucagon. We used the substituted cysteine accessibility method and three-dimensional molecular modeling based on the gastrointestinal insulinotropic peptide and glucagon-like peptide 1 receptor structures to study the N-terminal domain of this receptor, a central element for ligand binding and specificity. Our results showed that Asp⁶³, Arg¹¹⁶, and Lys⁹⁸ are essential for the receptor structure and/or ligand binding because mutations of these three residues completely disrupted or markedly impaired the receptor function. In agreement with these data, our models revealed that Asp⁶³ and Arg¹¹⁶ form a salt bridge, whereas Lys⁹⁸ is engaged in cation-π interactions with the conserved tryptophans 68 and 106. The native receptor could not be labeled by hydrophilic cysteine biotinylation reagents, but treatment of intact cells with [2-(trimethylammonium)ethyl]methanethiosulfonate increased the glucagon binding site density. This result suggested that an unidentified protein with at least one free cysteine associated with the receptor prevented glucagon recognition and that [2-(trimethylammonium)ethyl]methanethiosulfonate treatment relieved this inhibition. The substituted cysteine accessibility method was also performed on 15 residues selected using the three-dimensional models. Several receptor mutants, despite a relatively high predicted cysteine accessibility, could not be labeled by specific reagents. The three-dimensional models show that these mutated residues are located on one face of the protein. This could be part of the interface between the receptor and the unidentified inhibitory protein, making these residues inaccessible to biotinylation compounds.     

Minireview: Factors to Consider in the Naming of a G Protein-Coupled Receptor Subtype

Abstract

Receptors that mediate their effects through G proteins are predicted to have a seven transmembrane domain architecture. The last few years have seen a remarkable increase in the cloning of members of this superfamily leading to the identification of many more receptors than previously thought to exist on the basis of differences in agonist and antagonist specificities. This has important implications for nomenclature and classification, especially in view of the difficulty in relating receptors identified through cloning techniques to endogenously expressed receptors. Receptor cloning has also identified important differences in receptors between species raising the question as to whether these should be considered as species homologues or distinct subtypes. It is also becoming increasingly apparent that the pharmacology of this superfamily of receptors is influenced by the nature of the G protein present in the host cell and by alternative splicing of the receptor. The rapid pace of developments in this area necessitate the need for a regular publication summarizing recent developments. In the future, the cloning of G protein-coupled receptors will enable rationalization of the naming of individual receptor subtypes and identification of their inter-relationships.     

Clinical Use of Aromatase Inhibitors: Current Data and Future Perspectives

Abstract

A systematic procedure for the kinetic study of irreversible inhibition when the enzyme is consumed in the reaction which it catalyses, has been developed and analysed. Whereas in most reactions the enzymes are regenerated after each catalytic event and serve as reusable transacting effectors, in the consumed enzymes each catalytic center participates only once and there is no enzyme turnover. A systematic kinetic analysis of irreversible inhibition of these enzyme reactions is presented. Based on the algebraic criteria proposed in this work, it should be possible to evaluate either the mechanism of inhibition (complexing or non-complexing), or the type of inhibition (competitive, non-competitive, uncompetitive, mixed non-competitive). In addition, all kinetic constants involved in each case could be calculated. An experimental application of this analysis is also presented, concerning peptide bond formation in vitro. Using the puromycin reaction, which is a model reaction for the study of peptide bond formation in vitro and which follows the same kinetic law as the enzymes under study, we have found that: (i) the antibiotic spiramycin inhibits the puromycin reaction as a competitive irreversible inhibitor in a one step mechanism with an association rate constant equal to 1.3 × 10⁴M^-1s^-1 and, (ii) hydroxylamine inhibits the same reaction as an irreversible non-competitive inhibitor also in a one step mechanism with a rate constant equal to 1.6 × 10^-3 M^-1s^-1.     

Simplified patient-specific renal dosimetry in 177Lu therapy: a proof of concept

PurposeThe aim of this proof-of-concept study is to propose a simplified personalized kidney dosimetry procedure in ¹⁷⁷Lu peptide receptor radionuclide therapy (PRRT) for neuroendocrine tumors and metastatic prostate cancer. It relies on a single quantitative SPECT/CT acquisition and multiple radiometric measurements executed with a collimated external probe, properly directed on kidneys.MethodsWe conducted a phantom study involving external count-rate measurements in an abdominal phantom setup filled with activity concentrations of ^99mTc, reproducing patient-relevant organ effective half-lives occurring in ¹⁷⁷Lu PRRT. GATE Monte Carlo (MC) simulations of the experiment, using ^99mTc and ¹⁷⁷Lu as sources, were performed. Furthermore, we tested this method via MC on a clinical case of ¹⁷⁷Lu-DOTATATE PRRT with SPECT/CT images at three time points (2, 20 and 70 hrs), comparing a simplified kidney dosimetry, employing a single SPECT/CT and probe measurements at three time points, with the complete MC dosimetry.ResultsThe experimentally estimated kidney half-life with background subtraction applied was compatible within 3% with the expected value. The MC simulations of the phantom study, both with ^99mTc and ¹⁷⁷Lu, confirmed a similar level of accuracy. Concerning the clinical case, the simplified dosimetric method led to a kidney dose estimation compatible with the complete MC dosimetry within 6%, 12% and 2%, using respectively the SPECT/CT at 2, 20 and 70 hrs.ConclusionsThe proposed simplified procedure provided a satisfactory accuracy and would reduce the imaging required to derive the kidney absorbed dose to a unique quantitative SPECT/CT, with consequent benefits in terms of clinic workflows and patient comfort.     

Quality of web based information on treatment of depression: cross sectional survey

ObjectivesTo evaluate quality of web based information on treatment of depression, to identify potential indicators of content quality, and to establish if accountability criteria are indicators of quality.DesignCross sectional survey.ResultsAlthough the sites contained useful information, their overall quality was poor: the mean guideline, issues, and global scores were only 4.7 (range 0-13) out of 43, 9.8 (6-14) out of 17, and 3 (0.5-7.5) out of 10 respectively. Sites typically did not cite scientific evidence in support of their conclusions. The guideline score correlated with the two other quality of content measures, but none of the content measures correlated with the Silberg accountability score. Content quality was superior for sites owned by organisations and sites with an editorial board.ConclusionsThere is a need for better evidence based information about depression on the web, and a need to reconsider the role of accountability criteria as indicators of site quality and to develop simple valid indicators of quality. Ownership by an organisation and the involvement of a professional editorial board may be useful indicators. The study methodology may be useful for exploring these issues in other health related subjects.     

Y a t-il encore de la place pour la scintigraphie conventionnelle aux récepteurs de la somatostatine dans les tumeurs carcinoïdes à l’ère de la TEP ?

Our aim is to discuss, based on literature data, whether or not there is still a place for conventional somatostatin receptor scintigraphy (C-SRS) in the exploration of carcinoid tumours (CT) in the era of PET.MethodsBibliography was obtained by an interrogation of database: PubMed and Cochrane for the last 10 years. Keywords used were “neuroendocrine tumors”, “carcinoid tumors”, “pentetreotide”, “somatostatin”, “gallium-68” and “indium-111”.ResultsC-SRS visualized local or distant metastasis, with a sensitivity reaching 90% when size lesion is greater than 1 cm. It was more sensitive than morphologic exams in the detection of the primary lesion as well as the metastases and recurrent lesions. C-SRS had modified the therapeutic strategy in 21 to 53% of patients. It had determined resecability criteria and had predicted somatostatin analogue treatment efficiency. Furthermore, C-SRS was very useful in the follow-up of these tumours, mainly in the early detection of postoperative residues and recurrence. Recently, ⁶⁸Ga-DOTA-TOC PET had been used in some centers. According to many authors, it was superior to C-SRS for the detection of CT localization in the lung and skeleton and was similar for the detection of CT localization in liver and brain. According to these authors, ⁶⁸Ga-DOTA-TOC PET had evidenced lesions than C-SRS; nevertheless, there is always a global similar sensitivity in carcinoid tumours.Conclusion⁶⁸Ga-DOTA-TOC PET is surely more advantageous in guiding clinical management and follow-up, yet this imaging modality is expensive and not widespread. Nevertheless, C-SRS, which is cheaper, is an accurate technique in carcinoid tumours. Furthermore, if C-SRS proves negative, ⁶⁸Ga-DOTA-TOC PET should be indicated.     

A lysine-free mutant of epidermal growth factor as targeting moiety of a targeted toxin

AimsElevated levels of epidermal growth factor (EGF) receptor are observed on several human tumors, e.g. cervical carcinoma and mamma carcinomas. The natural ligand EGF is an alternative to established antibodies and tyrosine kinase inhibitors for targeting EGF receptor-overexpressing tumor cells for therapy. Conjugations of compounds to EGF lack the necessary homogeneity for an intended application, since several amino acids may react with the chemical linker.Main methodsWe designed an EGF variant (EGF^RR) in which the two lysines were substituted with arginine (K28R and K48R). EGF^RR was fused to the protein toxin saporin to obtain a model protein for detailed analyses on EGF receptor binding and on both the enzymatic activity of saporin and the cytotoxicity of the fusion protein.Key findingsThe mutation decreased the enzymatic activity of saporin 2.3-fold and the binding of EGF^RR retained its specificity for EGF receptor while increasing the Kd 5.5-fold. In spite of these differences the cytotoxicity of the fusion protein was unchanged in comparison to a fusion protein with EGF both when applied alone and in combination with cytotoxicity augmenting saponin.SignificanceWe conclude that EGF^RR retained its ability to bind with high specificity to EGF receptor and is thus suitable for a number of chemical linkage applications such as targeting drugs or dyes to EGF receptor-expressing cells.     

Impact of polyphenols on receptor–ligand interactions by NMR: the case of neurotensin (NT)–neurotensin receptor fragment (NTS1) complex

Abstract

Ligand–receptor interactions can be implicated in many pathological events such as chronic neurodegenerative diseases. Thus, the discovery of molecules disrupting this type of interactions could be an interesting therapeutic approach. Polyphenols are well known for their affinity for proteins and several studies have characterized these direct interactions. But studying the direct influence of multi-therapeutic drugs on a ligand–receptor complex relevant to a neurodegenerative disorder is a challenging issue. Solution NMR, molecular modeling and iterative calculations were used to obtain information about the interaction between a phenolic compound, α-glucogallin (α-2) and a ligand/fragment receptor complex neurotensin (NT) and its receptor NTS1. The α-2 was shown to bind to NT and a peptidic fragment of its NTS1 receptor, independently. Although the formation of the corresponding ligand–receptor complex did not seem to be affected, this experimental modeling protocol will enable the evaluation of other anti-amyloidogenic compounds such as blockers of NT–NTS1 binding. These types of studies help in understanding the specificity and influence in binding and can provide information to develop new molecules with a putative pharmacological interest.

Communicated by Ramaswamy H. Sarma     

A combination of Olea europaea leaf extract and Spirodela polyrhiza extract alleviates atopic dermatitis by modulating immune balance and skin barrier function in a 1-chloro-2,4-dinitrobenzene-induced murine model

BackgroundAtopic dermatitis is a chronic inflammatory skin disease in humans. Although Olea europaea leaf extract (OLE) and Spirodela polyrhiza extract (SPE) have been used to protect against skin damage, the effects of their combined administration on atopic dermatitis have yet to studied.PurposeIn this study, we evaluated the potential therapeutic effects of an OLE and SPE combination on the progression of atopic dermatitis and the possible mechanisms underlying these effects in 1-chloro-2,4-dinitrobenzene (DNCB)-treated NC/Nga mice.MethodsAtopic dermatitis was induced by topical application of 0.2% w/v DNCB prepared in an olive oil:acetone solution (1:3), and thereafter OLE, SPE and OLE + SPE were administered orally for 5 weeks. We determined atopic dermatitis symptoms, serum IgE levels, and levels of cytokine- and gene expression in the dorsal skin and splenocytes, and performed histological and immune cell subtype analyses. The expression of skin barrier-related proteins (filaggrin, sirtuin 1, and claudin 1) was also evaluated.ResultsThe OLE + SPE combination significantly ameliorated atopic dermatitis symptoms, including dermatitis scores, and reduced epidermal thickness and infiltration of different inflammatory cells in mice with DNCB-induced atopic dermatitis. It also significantly reduced the number of CD4⁺, CD8⁺, and CD4⁺/CD69⁺ T cells; immunoglobulin E-producing B cells (CD23⁺/B220⁺) in the axillary lymph nodes; CD3⁺ T-cell eosinophils (chemokine–chemokine receptor 3⁺/CD11b⁺) in the skin; and CD3⁺ T cells, immunoglobulin E-producing B cells (CD23⁺/B220⁺), and eosinophils in peripheral blood mononuclear cells. Additionally, the experimental combination lowered levels of serum immunoglobulin E and histamine, as well as Th2-mediated cytokines, and interleukin-4, -5, and -13, whereas it increased the levels of Th1-mediated cytokine interferon-γ in splenocytes. Furthermore, the preparation significantly restored expression of the skin barrier-related proteins filaggrin, sirtuin 1, and claudin 1, and also reduced the expression of the inflammatory cytokine interleukin-6 and chemokine–chemokine receptor 3, as well as the pruritus-related cytokine interleukin-31 and interleukin-31 receptor, in atopic dermatitis skin lesions.ConclusionTaken together, our findings indicate that administration of a combination of OLE and SPE can alleviate atopic dermatitis symptoms by regulating immune balance and skin barrier function and may be an effective therapeutic option for the treatment of atopic dermatitis.     

Molecular Cloning,Stable Expression and Desensitization of the Human Dopamine D1B / D5 Receptor

Abstract

The sub-family of dopamine D1-like receptors is now known to be comprised of at least two members: the originally cloned D1 receptor (herein referred to as the D1a receptor) and a related receptor referred to as the D1b, D1β or D5 dopamine receptor (herein referred to as the D1b/D5 receptor). Here, we characterize the D1b/D5 receptor expressed transiently in COS-7 cells and permanently in Ltk^? cells.

Transiently expressed human D1b/D5 receptors bind the D1 specific ligand [¹²⁵I]SCH 23982 saturably and with high affinity (K_D = 500 _pM). Competition for [¹²⁵I]SCH 23982 binding to rat D1b/D5 and human D1a and D1b/D5 receptors supports the contention that the two D1b/D5 receptors are species homologues. Furthermore, in COS-7 cells, as previously observed, dopamine competes for the binding of [¹²⁵I]SCH 23982 to human D1b/D5 receptors with a higher affinity than that seen at the human D1a receptor. These results are similar to those seen in Ltk^? cells permanently transfected with the human D1b/D5 receptor. In these cells, dopamine competition for [¹²⁵I]SCH 23982 binding is complex, sensitive to guanine nucleotides and of a higher affinity than that observed for dopamine binding to the human D1a receptor expressed in these same cells. In both D1a and D1b/D5 expressing Ltk^? cells, dopamine stimulates adenylyl cyclase with an EC₅₀ of = 200 nM. Furthermore, preincubation of Ltk^? cells expressing the D1a and D1b/D5 receptors with dopamine results in desensitization of the response of adenylyl cyclase to subsequent agonist stimulation.     

Expression - Level Dependent Activation of Recombinant Human Parathyroid Hormone/Parathyroid Hormone-Related Peptide Receptor: Effect of Human Parathyroid Hormone (1-34), (1-31), and (28-48)

Abstract

A stable recombinant Chinese hamster ovary (CHO) cell model system expressing the human type-1 receptor for parathyroid hormone and parathyroid hormone-related peptide (hPTH-R) was established for the analysis of human PTH (hPTH) variants. The cell lines showed receptor expression in the range from 10⁵ to 1.9xl0⁶ receptors per cell. The affinity of the receptors for hPTH-(l-34) was independent of the receptor number per cell (K<j = 8 nmol/1). The induction of cAMP by hPTH-(l-34) is maximal in clones expressing >2xl0⁵ receptors per cell and Ca⁺⁺ signals were maximal in cell lines expressing >1.4xl0⁶ receptors per cell. Second messenger specific inhibitors demonstrated that PTH-induced increases in intracellular cAMP and Ca⁺⁺ are independent and Ca⁺⁺ ions are derived from intracellular stores. The cAMP-specific receptor activator hPTH-(l-31) showed also an increase in intracellular Ca⁺⁺. Even in cell lines expressing more than 10 receptors per cell the Ca⁺⁺/PKC specific activator hPTH-(28-48) did not activate hPTH-Rs. Based on these results, synthesis of further derivatives of PTH is required to identify pathway-specific ligands for the type-1 hPTH-R.     

The biomimetic [Cr3O(O2CCH2CH3)6(H2O)3]+ decreases plasma cholesterol and triglycerides in rats: towards chromium-containing therapeutics

3 O(O₂CCH₂CH₃)₆ (H₂O)₃]⁺ 1 and a naturally occurring, biologically active form of chromium, low-molecular-weight chromium-binding substance (LMWCr), to rats are described. Given that the complexes are proposed to function by interacting with insulin receptor, trapping it in its active conformation, in contrast to current chromium-containing nutrition supplements, which only serve as sources of absorbable chromium, changes in lipid and carbohydrate metabolism would be expected. After 12 weeks administration (20 μg/kg body mass), compound 1 results in 40% lower levels of blood plasma LDL cholesterol, 33% lower levels of total cholesterol, and significantly lower HDL cholesterol and triglyceride; these results are in stark contrast to those of administration of other forms of Cr(III) to rats, which have no effect on these parameters. LMWCr, in contrast to 1, has no effect as it probably is degraded in vivoor excreted. These results are interpreted in terms of the mechanism of chromium action in response to insulin and the activation of insulin receptor, and the potential for the rational design of chromium-containing therapeutics is discussed. Received: 27 May 1999 / Accepted: 4 October 1999