The human beta 3-adrenergic receptor is resistant to short term agonist-promoted desensitization

The human beta 3-adrenergic receptor (beta 3AR) lacks most of the structural determinants that, in the beta 2AR, contribute to agonist-induced receptor desensitization. To evaluate the effect of these structural differences on the beta 3AR desensitization profile, the human beta 2- and beta 3AR were stably expressed in Chinese hamster fibroblasts (CHW) and murine Ltk- cells (L cells). Incubation of CHW-beta 2 or L-beta 2 cells with 10 microM isoproterenol for 30 min induced a decrease in the maximal agonist-stimulated adenylyl cyclase activity and a cAMP-dependent reduction in the potency of isoproterenol to stimulate the receptor. In addition, this pretreatment impaired the formation of the high affinity heterotrimeric agonist-receptor-guanine nucleotide-binding protein complex and induced the sequestration of approximately 30% of the beta 2AR away from the cell surface. In contrast, similar treatment of CHW-beta 3 and L-beta 3 cells did not affect the maximal receptor-stimulated adenylyl cyclase activity, nor did it induce any significant sequestration of the beta 3AR. In fact, only a modest cAMP-independent decrease in the potency of isoproterenol to stimulate the receptor could be observed after isoproterenol treatment. The rapid desensitization pattern of a chimeric beta 3AR, in which the third cytoplasmic loop and the carboxyl-terminal tail were exchanged with those of the beta 2AR (which include potential phosphorylation sites and other possible molecular determinants of desensitization), was found to be intermediate between those of the two original receptor subtypes. These results demonstrate that (i) the beta 3AR is less prone than the beta 2AR to undergo rapid agonist-promoted desensitization and, (ii) in addition to the phosphorylation sites located in the third cytoplasmic loop and the carboxyl-terminal tail of the beta 2AR, other molecular determinants contribute to short term desensitization.

[Aseptic osteomyelitis]

Based on a series of eight personal cases and a review of the literature, this study tries to define the diagnostic elements of aseptic osteomyelitis. Although sternocostoclavicular sites are immediately suggestive of the diagnosis, lesions of the pelvis and spine and long bones of the limbs are particularly difficult to diagnose. Inflammatory type pain occurred in episodesover a number of years and responded to NSAIs and possibly diphosphonates. Laboratory abnormalities were usually confined to a raised ESR, but alterations of the IgA levels, similar to those observed in ankylosing spondylitis were observed in four cases. Hyperostosis occurred late in the course, preceded by signs of osteomyelitis, periosteitis or enthesitis. Histology does not provide any formal conclusions. The most suggestive lesions are those of nonspecific aseptic osteomyelitis, followed by a Paget-like appearance. The interpretation of these findings may be complicated by the presence of eosinophils, giant cells or mast cells. Two elements are very valuable for establishing the diagnosis: the presence of infraradiological anterior thoracic increased uptake on bone scan and the presence of a skin disorder, either severe acne or, more especially, palmoplantar pustulosis.

Altered phosphorylation and desensitization patterns of a human beta 2-adrenergic receptor lacking the palmitoylated Cys341

Exposure of beta 2-adrenergic receptors to agonists causes a rapid desensitization of the receptor-stimulated adenylyl cyclase, associated with an increased phosphorylation of the receptor. Agonist-promoted phosphorylation of the beta 2-adrenergic receptor (beta 2AR) by protein kinase A and the beta-adrenergic receptor kinase (beta ARK) is believed to promote a functional uncoupling of the receptor from the guanyl nucleotide regulatory protein Gs. More recently, palmitoylation of Cys341 of the receptor has also been proposed to play an important role in the coupling of the beta 2-adrenergic receptor to Gs. Here we report that substitution of the palmitoylated cysteine by a glycine (Gly341 beta 2 AR) using site directed mutagenesis leads to a receptor being highly phosphorylated and largely uncoupled from Gs. In Chinese hamster fibroblasts (CHW), stably transfected with the human receptor cDNAs, the basal phosphorylation level of Gly341 beta 2AR was found to be approximately 4 times that of the wild type receptor. This elevated phosphorylation level was accompanied by a depressed ability of the receptor to stimulate the adenylyl cyclase and to form a guanyl nucleotide-sensitive high affinity state for agonists. Moreover, exposure of this unpalmitoylated receptor to an agonist did not promote any further phosphorylation or uncoupling. A modest desensitization of the receptor-stimulated adenylyl cyclase response was observed but resulted from the agonist-induced sequestration of the unpalmitoylated receptor and could be blocked by concanavalin A. This contrasts with the agonist-promoted phosphorylation and uncoupling of the wild type receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

[Primary bone lymphoma disclosed by osteolytic lesion of the femoral head]

A case of primary lymphoma of the bone is reported. The unusual site of the tumor in an epiphysis (head of femur) led to unconventional therapy by resection and hip replacement. Emphasis is put on the value of immunolabelling studies for the etiologic diagnosis.

The glial cell glutamate uptake carrier countertransports pH-changing anions

Uptake into glial cells helps to terminate glutamate's neurotransmitter action and to keep its extracellular concentration, [Glu]o, below neurotoxic levels. The accumulative power of the uptake carrier stems from its transport of inorganic ions such as sodium (into the cell) and potassium (out of the cell). There is controversy over whether the carrier also transports a proton (or pH-changing anion). Here we show that the carrier generates an alkalinization outside and an acidification inside glial cells, and transports anions out of the cells, suggesting that there is a carrier cycle in which two Na+ accompany each glutamate anion into the cell, while one K+ and one OH- (or HCO3-) are transported out. This stoichiometry predicts a minimum [Glu]o of 0.6 microM normally (tonically activating presynaptic autoreceptors and post-synaptic NMDA receptors), and 370 microM during brain anoxia (high enough to kill neurons). Transport of OH-/HCO3- on the uptake carrier generates significant pH changes, and may provide a mechanism for neuron-glial interaction.

Serum N terminal procollagen III fragment: a predictive marker of joint destruction in rheumatoid arthritis?

The level of the N terminal fragment of procollagen III (P3NP) levels of 100 consecutive patients affected by rheumatoid arthritis (RA) were evaluated in comparison with disease activity markers (erythrocytes sedimentation rate, C reactive protein), immunological status (rheumatoid factors, immune complexes) and joint destruction (assessed according to the Steinbrocker index). P3NP levels showed no significant relationship either to disease activity or to immunological status; however, a strong association was fond between X-ray grade and P3NP values. A two-year retrospective study of 32 patients belonging to the original 100 patient population allowed us to assign a predictive value for joint destruction to the P3NP level in the early stage of the disease.

Agonist-modulated palmitoylation of beta 2-adrenergic receptor in Sf9 cells

The palmitoylation of the human beta 2-adrenergic receptor (beta 2-AR) was studied in recombinant baculovirus-infected insect Sf9 cells. At 48 h post-infection, a high level expression of an epitope-tagged beta 2-AR (10-25 pmol/mg protein) was detected by [125I]iodocyanopindolol ([125I]CYP) binding assays. The identity of the receptor was confirmed both by photoaffinity labeling and immunoblotting. The fusion receptor displayed typical beta 2-AR pharmacological properties and conferred a beta-adrenergic sensitive adenylyl cyclase activity to the Sf9 cells. Moreover, exposure of the Sf9 cells to the beta-adrenergic agonist isoproterenol induced a rapid desensitization of the receptor-stimulated adenylyl cyclase activity. Purification of the epitope-tagged beta 2-AR by immunoprecipitation as well as by alprenolol-Sepharose affinity chromatography revealed that the receptor is covalently modified with palmitic acid in the insect cells as is observed in mammalian cells. In addition, short-term incubation of the cells with isoproterenol led to a specific increase in the incorporation of [3H]palmitate in the receptor, consistent with a rapid agonist-modulated turnover of the beta 2-AR-attached palmitic acid. These results suggest that agonist-mediated regulation of beta 2-AR post-translational palmitoylation could represent an other regulatory process for G protein-coupled receptors.

Clinical semiology of common cervicobrachial neuralgia. Data from 50 hospital cases

Common cervicobrachial neuralgia is less frequent than sciatica and its aetiological profile is more varied: men and women are equally affected, triggering factors or previous history are less often found and patients with anxiety or depression are relatively numerous. Clinically, signs of C7 lesion are present in half the patients. Acroparesthesias are frequent and may be the initial signs. Nocturnal pain is present in 50% of the cases. Signs of neurological deficit are rare, except for abolition of a reflex. The association of cervicobrachial neuralgia with tendinitis of the upper limb or algodystrophy of the shoulder is too frequent to be fortuitous. Left to itself, the syndrome usually lasts several months and sometimes one year. Recurrences are rare. The most frequent sequela is a painful neck.

[Rheumatoid metatarsals, original development of the first metatarsals]

Weight-bearing roentgenograms of 308 feet of rheumatoid arthritis patients were analyzed. Several angles were determined, including the metatarsus primus adductus angle (between the first and second metatarsals, > or = 10 degrees) and the forefoot spread angle (between the first and fifth metatarsals, > or = 30 degrees). Pes planus was diagnosed when the internal arch angle was equal to or greater than 130 degrees. Tarsal arthritis was defined as the presence of joint space narrowing. Varus of the first metatarsal was correlated with tarsal arthritis and pes planus but not with duration of the disease. Forefoot spread was correlated with duration of the disease and erosive metatarsal disease but not with involvement of the midfoot. These data demonstrate that orthopedic treatment should be initiated as soon as involvement of the first metatarsal is detected and should be directed at the hindfoot, midfoot, and first metatarsal whose deformations occur concomitantly.

Probing the functional conformation of neuropeptide Y through the design and study of cyclic analogues

The functional importance of the PP-fold conformation in neuropeptide Y (NPY) was investigated. NPY and N alpha-Ac-NPY(10-36), and corresponding cyclic analogues cyclo18,22-[Lys18,Asp22]-NPY and N alpha-Ac-cyclo18,22-[Lys18,Asp22]-NPY(10-36), were synthesized. Strategies for synthesis of the cyclic analogues included the use of the Kaiser oxime resin and a segment condensation approach. Circular dichroism studies in phosphate buffer, pH 5.0, indicated self-association of all four peptides at low micromolar concentrations. Monomeric N alpha-Ac-NPY(10-36) showed only 13% alpha-helix, compared to 32% alpha-helix for monomeric NPY, demonstrating a helix-stabilizing effect of residues 1-9 that is consistent with the PP fold. The [Lys18,Lys22] lactam bridge stabilized the helical conformation in N alpha-Ac-NPY(10-36)(51% alpha-helix), but was helix destabilizing in NPY (21% alpha-helix). In rat brain receptor binding assays, the cyclic and linear N alpha-Ac-NPY(10-36) analogues were equipotent (IC50 = 13 nM for 125I-BH-NPY displacement), although the cyclic analogue was twice as potent in rat vas deferens assays. NPY was more potent than its cyclic analogue in the brain receptor binding assays (IC50 = 0.07 and 0.25 nM, respectively), but these peptides were equipotent in the vas deferens assays. These results support a functional role for the PP fold in NPY and correlate with the solution conformations of the monomeric peptides.

Distinct regulation of beta 1- and beta 2-adrenergic receptors in Chinese hamster fibroblasts

The agonist-induced reduction of beta-adrenergic receptor (beta AR) cell surface density is a well documented phenomenon. The mechanisms responsible for this regulation have been well characterized for the beta 2AR. They include a rapid sequestration of the receptor away from the cell surface in a vesicular compartment and a longer term down-regulation of the total beta 2AR number. In contrast, very little is known about the cell surface regulation of the beta 1AR. In the present study, we have compared the agonist-mediated regulation of beta 1- and beta 2AR in Chinese hamster fibroblasts transfected with the cDNA encoding either beta AR subtype. Cells expressing similar numbers of the two beta AR subtypes were selected for the study. The expressed receptors exhibit typical beta 1- and beta 2AR selectivity for agonists and antagonists, as assessed by radioligand binding. Both receptors were found to be positively coupled to the adenylyl cyclase stimulatory pathway, but marked differences in the receptor regulation profiles were observed. Treatment of the cells expressing the beta 2AR with the agonist isoproterenol leads to a rapid sequestration of greater than 30% of the receptors away from the cell surface into a light vesicular fraction, where they are inaccessible to the hydrophilic ligand CGP-12177. In contrast, virtually no agonist-induced sequestration is observed in the cells expressing the beta 1AR. Longer exposure of the cells to isoproterenol leads to a time-dependent reduction in the total number of beta ARs in both beta 1- and beta 2AR-expressing cell lines. However, this down-regulation is significantly slower in the cells expressing the beta 1AR. In fact, no appreciable down-regulation of the beta 1ARs is detected in the first 4 hr of agonist treatment, compared with a down-regulation of greater than 50% of the beta 2ARs for the same period. After a 24-hr treatment with isoproterenol, less than 20% of the original number of beta 2ARs remain, whereas 60% of the beta 1ARs are still present after the same treatment. These results, therefore, suggest that, when expressed in an identical cell line, beta 1AR and beta 2AR follow distinct patterns of regulation. In fact, both agonist-induced sequestration and down-regulation are considerably blunted for the beta 1AR, compared with the beta 2AR.

Presence of low amounts of "neuronal" antigens in cultured human skin fibroblasts

To explore the utility of cultured skin fibroblasts in investigating diseases of the nervous system in which constituents characteristic of neurons are involved, sensitive immunochemical methods were used to test for the presence in skin fibroblasts of low amounts of proteins normally used as neuronal markers. The presence of each of the neurofilament triplet proteins and of neuron-specific enolase was demonstrated by immunoblotting and by immunocytochemistry, and of an 86-kDa synapsin-like material by immunoblotting. These observations agree with previous suggestions that readily available cultured fibroblasts may be useful in investigations of disorders in which molecules are involved which are typically associated with neurons in vivo, such as Alzheimer's disease.

Rheumatoid metatarsus. The original evolution of the first metatarsal

Three hundred and eight unselected rheumatoid feet underwent a weight-bearing X-ray examination. If the malformations of the forefoot studied here present a statistical association, the primus metatarsus adductus is closely connected with tarsal arthritis and flattened foot but does not depend on the duration of the disease. The spread forefoot is indeed related to the duration of the disease and the presence of a metatarsal erosion at the foot level, but is not affected by the lesions of the midfoot. It appears then that an early orthopaedic treatment should be prescribed, once the first signs of involvement of the first ray or pronounced pronation of the hindfoot are noticed; it must affect the hindfoot, the midfoot and the first ray which progress together.

Electrogenic uptake of sulphur-containing analogues of glutamate and aspartate by Müller cells from the salamander retina

1. The effect of sulphur-containing analogues of glutamate and aspartate on the membrane current of glial cells was studied by whole-cell clamping Müller cells isolated from the salamander retina. 2. L-Cysteic acid (CA), L-cysteinesulphinic acid (CSA), L-homocysteic acid (HCA), L-homocysteinesulphinic acid (HCSA) and S-sulpho-L-cysteine (SC) all evoked an inward membrane current that was large at negative potentials, and was smaller (but did not reverse) at more positive potentials up to +30 mV. 3. Removal of external sodium ions abolished the amino acid-evoked currents. Whole-cell clamping with pipettes containing no potassium led to a rapid suppression of the currents, that did not occur when potassium was included in the pipette. 4. The dependence of the currents on sulphur-containing amino acid concentration obeyed first-order Michaelis-Menten kinetics. The current evoked by co-application of L-glutamate and a sulphur-containing analogue was smaller than the sum of the currents produced by glutamate alone and by the sulphur analogue alone. 5. These data are consistent with the sulphur amino acid-evoked current being caused by uptake on the electrogenic glutamate uptake carrier, which co-transports an excess of Na+ ions into the cell, and counter-transports one K+ ion out of the cell. 6. The apparent Km (Michaelis-Menten constant) values for activation of uptake by CA (6 microM) and by CSA (60 microM) are low enough for uptake on the glutamate uptake carrier to be a plausible mechanism for terminating the postulated neurotransmitter action of these agents. However, the apparent Km values for uptake of HCA (2.95 mM), HCSA (1.65 mM) and SC (greater than 1 mM) are much higher than the EC50 (half-maximal effective concentration) concentrations for these agents' activation of NMDA (N-methyl-D-aspartate) channels. 7. Comparing the concentrations of sulphur amino acids needed to activate NMDA channels with their rate of uptake suggests that their potency for causing excitotoxic damage should follow the sequence HCA greater than SC greater than HCSA greater than Glu greater than CSA greater than Asp greater than CA.

[Physiology of fecal continence and defecation]

Defaecation is a complex function that requires interactions between the somatic and autonomic nervous systems. Moreover, social living standards lead to self-control of continence involving supraspinal nervous structures. After a brief description of the anatomy of the hind gut, the various reflex mechanisms underlying faecal continence and defaecation are exposed; the specificities of the nervous control of the smooth and striated muscles brought into play in these events are detailed. Then the main useful investigations allowing to localize the nervous structures at the origin of the anorectal disorders are reviewed.

Focal myositis: a pseudotumoral form of polymyositis

The authors report a case of pseudotumoral focal myositis found in a 55 year-old man, in the anteroexternal area of the right leg. The diagnosis was based on the pathological findings, the absence of any further clinical signs or laboratory findings, and no further development over time. They compare their patient's characteristics with cases found in the literature (24 cases during the past 20 years). Diagnostic certainty confirms the benign character of this pathology, which contrasts with the gravity of the classical form of polymyositis.

Serum IL-2 level in rheumatoid arthritis: correlation with joint destruction and disease progression

Understanding of T cell dysfunctions in rheumatoid arthritis (RA) may help to elucidate the pathophysiology of this disease. Cytokines determinations may be a promising approach and could represent a simple mean of quantifying RA immunological dysfunctions. In this study, interleukin-2 (IL-2) measurements were performed in sera of 74 RA patients to evaluate the potential use of this method to monitor "disease activity" and/or prognosis. Although the serum IL-2 levels of patients in active disease stage proved to be somewhat lower than those from patients with inactive disease, the difference was not significant. In our study, however, the serum IL-2 concentration was correlated with the circulating immune complexes level. In addition, patients with the highest serum IL-2 levels exhibited the poorest radiological stages and these same patients were often not receiving any disease modifying antirheumatic drugs (DMARD). Our results demonstrate that serum IL-2 level may be elevated in certain RA conditions. A better understanding of this phenomenon, especially the consequences of disease duration, could be of interest in the follow up and the prognosis of the disease.

Dysfunction of the beta- and alpha-adrenergic systems in a model of congestive heart failure. The pacing-overdrive dog

The functional integrity of the beta- and alpha-adrenergic stimulatory pathways in a rapid ventricular pacing model of congestive heart failure in dogs was investigated; normal dogs served as controls. Total beta-adrenergic receptor density was 35% lower (p less than 0.01) in the pacing-overdrive dogs, and the beta-adrenergic receptor-mediated stimulation of adenylate cyclase (Vmax) was found to be 68% and 72% lower (p less than 0.01) in the left and right ventricles of the paced dogs. In addition, the basal adenylate cyclase activity was found to be 56% and 68% lower (p less than 0.01) in the left and right ventricles of the failing heart. Similarly, the Vmax of 5'-guanylylimidodiphosphate (GppNHp) and forskolin stimulation of adenylate cyclase activity was significantly lower, 70% and 55%, respectively (p less than 0.01), in both ventricles of the paced dogs. However, although the concentration yielding half-maximal velocity for beta-agonist and GppNHp stimulation of adenylate cyclase was similar in both groups, that for forskolin stimulation of the enzyme was significantly increased (p less than 0.01). Pertussis toxin-mediated ADP-ribosylation of membranes from control and failing hearts revealed a significant decrease in the inhibitory guanine nucleotide binding protein content (48 +/- 9%, p less than 0.01) in the hearts of the paced dogs. Moreover, although the pertussis toxin treatment increased the basal and the forskolin-stimulated adenylate cyclase activity in both normal and failing heart membranes, the adenylate cyclase activity remained significantly depressed in the failing heart after pertussis toxin treatment (p less than 0.01). Consistent with the depressed adenylate cyclase activity, mechanical studies on isolated papillary muscles and trabeculae revealed a decrease in baseline total tension (from 7.0 +/- 0.7 to 3.8 +/- 0.4 g/mm2, p less than 0.01) and dT/dt (from 26 +/- 8 to 13 +/- 1 g/mm2/sec, p less than 0.01) in the pacing-overdrive model. Tension generation and dT/dt observed in the paced dogs in response to increasing concentrations of forskolin demonstrated a rightward shift in the dose-response curve and a decrease in maximal forskolin stimulation (p less than 0.01). Similarly, maximal tension and dT/dt in the presence of isoproterenol was significantly lower than in the normal dogs (p less than 0.01). The decrease in beta-adrenergic responsiveness was accompanied by a decrease and rightward shift in alpha 1-adrenergic responsiveness (increase in tension was 1.1 +/- 0.1 g/mm2 in paced dogs versus 2.1 +/- 0.1 g/mm2 in controls, p less than 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

Manometric and radiologic investigations and biofeedback treatment of chronic idiopathic anal pain

In 12 patients suffering from chronic idiopathic anal pain, the rectosphincteric function was studied using manometric and x-ray techniques. The results of manometric investigations were compared with those obtained in 12 healthy volunteers. In all patients, the resting pressure in the anal canal was significantly higher than in control subjects. In 10 patients, defecography revealed abnormalities of the pelvic muscles. We treated the patients by using biofeedback techniques, consisting of voluntary modifications of the state of contraction of the external sphincter. In all cases, pain disappeared after a mean of eight biofeedback training sessions. When noxious manifestations had disappeared, manometry showed a significant decrease in the anal canal resting pressure. Our results indicate 1) that chronic idiopathic anal pain is associated with abnormal anorectal manometric profiles, probably resulting from a dysfunctioning of the striated external anal sphincter, and 2) that biofeedback training is an effective treatment for chronic idiopathic anal pain.

Sternoclavicular pustulotic osteitis (SAPHO). 20-year interval between skin and bone lesions

In 2 cases of palmoplantar pustulosis, a 20-year interval was observed between the skin lesion and the bone involvement. In one case, the bone lesion came first. In the other a skin lesion was seen for 3 weeks without subsequent relapse. The 2 cases underline the multifaceted presentation of the condition for which we have coined the name synovitis acne pustulosis hyperostosis osteitis (SAPHO) syndrome.