Effects of executive load on crashes and near-crashes for young versus older drivers

With the increasing use of infotainment systems in vehicles, secondary tasks requiring executive demand may increase crash risk, especially for young drivers. Naturalistic driving data were examined to determine if secondary tasks with increasing executive demand would result in increasing crash risk. Data were extracted from the Second Strategic Highway Research Program Naturalistic Driving Study, where vehicles were instrumented to record driving behavior and crash/near-crash data. executive and visual-manual tasks paired with a second executive task (also referred to as dual executive tasks) were compared to the executive and visual-manual tasks performed alone. Crash/near-crash odds ratios were computed by comparing each task condition to driving without the presence of any secondary task. Dual executive tasks resulted in greater odds ratios than those for single executive tasks. The dual visual-manual task odds ratios did not increase from single task odds ratios. These effects were only found in young drivers. The study shows that dual executive secondary task load increases crash/near-crash risk in dual task situations for young drivers. Future research should be conducted to minimize task load associated with vehicle infotainment systems that use such technologies as voice commands.

Impacts of dance on cognition, psychological symptoms and quality of life in Parkinson's disease

BACKGROUND

While dance may improve motor features in Parkinson's disease (PD), it is not yet clear if the benefits extend to non-motor features.

OBJECTIVE

To determine whether dance classes based on Dance for PD®, improve cognition, psychological symptoms and Quality of Life (QoL) in PD.

METHODS

Participants were allocated to a Dance Group (DG; n = 17) or Control Group (CG: n = 16). Participants had early-stage PD (Hoehn & Yahr: DG = 1.6±0.7, CG = 1.5±0.8) with no cognitive impairment (Addenbrooke's score: DG = 93.2±3.6, CG = 92.6±4.3). The DG undertook a one-hour class, twice weekly for 12 weeks, while the CG had treatment as usual. Both groups were assessed for disease severity (MDS-UPDRS), cognition (NIH Toolbox® cognition battery, Trail Making Test), psychological symptoms (Hospital Anxiety and Depression Scale, MDS-UPDRS-I) and QoL (PDQ-39, MDS-UPDRS-II).

RESULTS

Group comparison of pre-post change scores showed that selected cognitive skills (executive function and episodic memory), psychological symptoms (anxiety and depression) as well as QoL (PDQ-39 summary index) were significantly improved by the intervention (DG > CG, p's < 0.05, Cohen's d > 0.8).

DISCUSSIONS AND CONCLUSION

Dance classes had a clear benefit on psychological symptoms, QoL and a limited cognitive benefit. Follow-up assessment is required to confirm the durability of these effects.

Implementation of the North Carolina HIV Bridge Counseling Program to Facilitate Linkage and Reengagement in Care for Individuals Infected with HIV/AIDS

BACKGROUND Statewide interventions are critical to meeting the goals of the National HIV/AIDS Strategy in this country. In 2012, the North Carolina Division of Public Health developed the North Carolina State Bridge Counselor program to improve linkage to and reengagement in care for newly diagnosed persons and persons living with HIV who were out-of-care.METHODS We reviewed the planning process for the North Carolina State Bridge Counselor program, which involved a review of existing strengths-based counseling models for persons living with HIV, implementation of these models, and communication strategies with other providers. State bridge counselor responsibilities were delineated from the role of disease intervention specialists while retaining the fieldwork capability of disease intervention specialists to conduct outreach and provide services for persons living with HIV throughout the state.RESULTS Program implementation required extensive planning with stakeholders, incorporation of strengths-based counseling models, development of performance standards, and utilization of CAREWare, an HIV care software program to document referrals and data-sharing between state bridge counselors and clinics. By the end of 2014, state bridge counselor services were provided to approximately 60 of the 400 persons living with HIV (15%) who are diagnosed each quarter in North Carolina, with increasing utilization of the program.LIMITATIONS We assessed the development of this intervention specific to the North Carolina Division of Public Health, which may limit its generalizability. However, the State Bridge Counselor program was implemented in both urban and rural areas throughout the state, which increases its applicability to different public health programs throughout the country.CONCLUSION We demonstrated that a statewide State Bridge Counselor program for linkage and reengagement activities can be implemented by leveraging existing infrastructures, electronic medical records, HIV care networks, and fieldwork activities.

Neurodegeneration and early lethality in superoxide dismutase 2-deficient mice: a comprehensive analysis of the central and peripheral nervous systems

The contribution of oxidative stress to diabetic complications including neuropathy is widely known. Mitochondrial and cellular damage are associated with the overproduction of reactive oxygen species and decreased levels or function of the cellular antioxidant mitochondrial manganese superoxide dismutase (SOD2). We hypothesized that targeted SOD2 deletion in the peripheral nervous system using cre-lox technology under control of the nestin promoter would accelerate neuropathy in a type 2 model of diabetes, the BKS.db/db mouse. SOD2-deficient mice, however, demonstrated severe gait deformities and seizures and died by 20 days of age. Examination of SOD2 expression levels revealed that SOD2 was lost in brain and reduced in the spinal cord, but appeared normal in dorsal root ganglia and peripheral nerves in SOD2-deficient mice. These findings indicate incomplete targeted knockout of SOD2. Morphological examination revealed cortical lesions similar to spongiform encephalopathy in the brain of SOD2-deficient mice. No lesions were evident in the spinal cord, but changes in myelin within the sciatic and sural nerves including a lack of cohesion between layers of compact myelin were observed. Together, these results indicate that targeted neuronal SOD2 knockout using the nestin promoter results in severe central nervous system degeneration and perinatal lethality in mice. A specific peripheral nervous system-targeting construct is required to examine the consequences of SOD2 knockout in diabetic neuropathy.

Unaltered graft survival and intragraft lymphocytes infiltration in the cardiac allograft of Cxcr3-/- mouse recipients

Previous studies showed that absence of chemokine receptor Cxcr3 or its blockade prolong mouse cardiac allograft survival. We evaluated the effect of the CXCR3 receptor antagonist MRL-957 on cardiac allograft survival, and also examined the impact of anti-CXCR3 mAb in human CXCR3 knock-in mice. We found only a moderate increase in graft survival (10.5 and 16.6 days, p < 0.05) using either the antagonist or the antibody, respectively, compared to control (8.7 days). We re-evaluated cardiac allograft survival with two different lines of Cxcr3(-/-) mice. Interestingly, in our hands, neither of the independently derived Cxcr3(-/-) lines showed remarkable prolongation, with mean graft survival of 9.5 and 10.8 days, respectively. There was no difference in the number of infiltrating mononuclear cells, expansion of splenic T cells or IFN-gamma production of alloreactive T cells. Mechanistically, an increased other chemokine receptor fraction in the graft infiltrating CD8 T cells in Cxcr3(-/-) recipients compared to wild-type recipients suggested compensatory T-cell trafficking in the absence of Cxcr3. We conclude Cxcr3 may contribute to, but does not govern, leukocyte trafficking in this transplant model.

Differences between collagen morphologies, properties and distribution in diabetic and normal biobreeding and Sprague–Dawley rat sciatic nerves

Both structural and functional differences between normal and diabetic nerve have been observed, in human patients and animal models. We hypothesize that these structural differences are quantifiable, morphologically and mechanically, with the ultimate aim of understanding the contribution of these differences to permanent nerve damage. The outer collagenous epineurial and perineurial tissues of mammalian peripheral nerves mechanically and chemically shield the conducting axons. We have quantified differences in these collagens, using whole-nerve uniaxial testing, and immunohistochemistry of collagens type I, III, and IV in diabetic and normal nerves. We present results of two studies, on normal and diabetic BioBreeding (BB), and normal, diabetic and weight-controlled Sprague-Dawley (SD) rats, respectively. Overall, we measured slightly higher uniaxial moduli (e.g. 5.9 MPa vs. 3.5 MPa, BB; 10.7 MPa vs. 10.0 MPa, SD at 40% strain) in whole nerves as well as higher peak stresses (e.g. 0.99 MPa vs. 0.74 MPa, BB; 2.16 MPa vs. 1.94 MPa, SD at 40% strain) in the diabetics of both animal models. We measured increased concentrations of types III and IV collagens in the diabetics of both models and mixed upregulation results were observed in type I protein levels. We detected small differences in mechanical properties at the tissue scale, though we found significant structural and morphometric differences at the fibril scale. These findings suggest that whole-tissue mechanical testing is not a sufficient assay for collagen glycation, and that fibrillar and molecular scale assays are needed to detect the earliest stages of diabetic protein glycation.

Digital electron microscopic examination of human sural nerve biopsies

Diabetic peripheral polyneuropathy is characterized by axonal degeneration and regeneration as well as by Schwann cell and microvascular changes. These changes have been described at both the light (LM) and the electron microscopic (EM) levels; however, EM has not been applied to large clinical trials. Our goal was to adapt the rigorous techniques used for quantifying human biopsies with LM image analysis to accommodate ultrastructural analyses. We applied digital image capture and analysis to the ultrastructural examination of axons in sural nerve biopsies from diabetic patients enrolled in a multicenter clinical trial. The selection of sural nerve biopsies was based on the quality of specimen fixation, absence of physical distortion, and nerve fascicle size (> or =100,000; < or =425,000 microm2). Thin sections were collected on formvar-coated slot grids, stabilized with carbon and scanned on a Phillips CM100 transmission electron microscope. Digital images were captured with a Kodak Megaplus 1.6 camera. A montage was constructed using software derived from aerial mapping applications, and this virtual image was viewed by EM readers. Computer-assisted analyses included identification and labeling of individual axons and axons within regenerating clusters. The average density of regenerating myelinated axon clusters per mm2 was 65.8 +/- 5.1, range of 0-412 (n = 193). These techniques increase the number of samples that may be analyzed by EM and extend the use of this technique to clinical trials using tissue biopsies as a primary endpoint.

A preliminary investigation of the effectiveness of a sleep apnea education program

OBJECTIVES

This study aimed to evaluate a standardised sleep apnea patient education program and develop a study design that may be used to evaluate other such education programs.

METHOD

Thirty-four adults diagnosed with obstructive sleep apnea hypopnea syndrome (OSAHS) underwent a standard sleep apnea education program and completed measures of knowledge of and beliefs about sleep apnea before, after, and 3 months following education. Two outcome measures were used: the Apnea Knowledge Test (AKT) and the Apnea Beliefs Scale (ABS).

RESULTS

AKT results showed significant knowledge gains posteducation, which were maintained at follow-up. Patients also reported more positive beliefs about their ability to change their behaviour and comply with continuous positive airway pressure (CPAP) treatment recommendations after education.

DISCUSSION

Findings from this preliminary investigation suggest that the education program used in this study may improve patients' knowledge of CPAP and promote functional beliefs about OSAHS treatment. This program clearly warrants further research, and ultimately such programs may prove important in improving CPAP compliance.

Treatment of tardive dyskinesia with donepezil: a pilot study

BACKGROUND

Tardive dyskinesia (TD) remains a significant clinical problem for which there is no uniformly effective treatment. Earlier trials with acetylcholine precursors may have been disappointing because of underlying damage to striatal cholinergic neurons in patients with TD. In contrast, new cholinesterase inhibitors, developed for the treatment of dementia, may improve TD by directly increasing cholinergic synaptic transmission.

METHOD

We conducted an 8-week open-label trial of donepezil in the treatment of TD. Ten patients with schizophrenia or schizoaffective disorder who received stable doses of antipsychotics and met DSM-IV criteria for TD were treated with donepezil, 5 to 10 mg/day, for 6 weeks after a 2-week baseline period. Changes in total Abnormal Involuntary Movement Scale (AIMS) scores measured every 2 weeks were assessed for significance. Patients were also assessed using the Brief Psychiatric Rating Scale, the Mini-Mental State Examination, the Barnes Akathisia Scale, and the Simpson-Angus Scale.

RESULTS

Total AIMS scores decreased significantly (p = .0009), with no changes in other measures. Nine patients showed a positive response. Improvement was greatest in orofacial and upper extremity movements. No significant interactions were noted between the total AIMS scores and age (p > .29), duration of TD (p > .38), or duration of antipsychotic treatment (p > .14).

CONCLUSION

Donepezil appeared to be effective in suppressing TD in this pilot study. However, placebo-controlled, double-blind studies are necessary before donepezil can be recommended as a treatment for TD.

Synthesis of novel retinoid X receptor-selective retinoids

Retinoids 1-5 have been identified as potent RXR agonists for evaluation in the treatment of non-insulin-dependent (type II) diabetes mellitus (NIDDM). Highly convergent syntheses of 1-5 have been developed. The core tetrahydronaphthalene 7, employed in the synthesis of 1 and 2, was prepared in 98% yield using an AlCl(3)-catalyzed (0.03 equiv) Friedel-Crafts alkylation of toluene with 2,5-dichloro-2,5-dimethylhexane 6. A nitromethane-mediated Fridel-Crafts acylation of 7 with chloromethylnicotinate 9 was developed to prepare ketone 10 in 68% yield. Chelate-controlled addition of MeMgCl to 10 followed by dehydration afforded olefin 11 in 65% yield. Cyclopropanation of 11 with trimethylsulfoxonium ylide, followed by saponification, completed a five-step synthesis of 1 in 33% yield. FeCl(3)-catalyzed (0.05 equiv) Friedel-Crafts acylation of 7 with chloromethylterephthalate 14 afforded ketone 15 in 81% yield. Saponification of 15 and reaction with 50% aqueous NH(2)OH in AcOH afforded a 9:1 mixture of cis and trans oximes, from which the desired cis-oxime 2 was isolated in 43% yield. The core bromo-dihydronaphthalene 29 required for the synthesis of 3-5 was prepared by a Shapiro reaction. Transmetalation of 29 and reaction with Weinreb amides 30b or 36 afforded ketones 32 and 37, which were converted into 3-5 using chemistry comparable to the tetrahydronaphthylene series. Suzuki coupling of boronic acids 41 and 42 with vinyl triflate 43 provided an alternative approach to the synthesis of this class of compounds.

Depletion of taurine in experimental diabetic neuropathy: implications for nerve metabolic, vascular, and functional deficits

In diabetes, increased oxidative stress, disruption of signal transduction pathways, and endothelial dysfunction have been critically implicated in the pathogenesis of experimental diabetic neuropathy (EDN). The development of nerve conduction slowing in diabetes is accompanied by depletion of the beta-amino acid taurine. Since taurine functions as an antioxidant, calcium modulator, and vasodilator, taurine depletion may provide a pathogenetic link between nerve metabolic, vascular, and functional deficits complicating diabetes. The mechanism(s) of nerve taurine depletion, the localization of critical taurine deficits, and its pathophysiological significance in EDN are however unknown. This study explored the pathophysiological effects of selective nerve taurine replacement in streptozotocin-diabetic (STZ-D) rats. A polyclonal human taurine transporter (TT) antibody was also generated in order to determine potential loci of critical taurine depletion. Two weeks of STZ-D reduced sciatic motor nerve conduction velocity (NCV) by 23% (P < 0.01), decreased composite nerve blood flow by 38% (P < 0.01), and reduced nerve taurine content by 29% (P < 0.05). In STZ-D rats, a 1% taurine diet corrected nerve taurine depletion, prevented motor NCV slowing, and partially attenuated composite nerve blood flow deficits. After 6 weeks of STZ-D, a 1% taurine diet ameliorated motor NCV slowing and endoneurial nutritive blood flow deficits, prevented digital sensory NCV slowing, and reduced ouabain-sensitive nerve (Na,K)-ATPase activity. Immunohistochemical studies localized taurine and the TT to the vascular endothelium and Schwann cells of the sciatic nerve. In conclusion, taurine depletion in the vascular endothelium and Schwann cells of the sciatic nerve may contribute to the neurovascular and metabolic deficits in EDN.

The CXCR4 agonist ligand stromal derived factor-1 maintains high affinity for receptors in both Galpha(i)-coupled and uncoupled states

The alpha chemokine receptor CXCR4 and its only characterized chemokine ligand, stromal cell-derived factor-1 (SDF-1), are postulated to be important in the development of the B-cell arm of the immune system. In addition, CXCR4 is a critical coreceptor in support of viral entry by T-cell line tropic strains (X4) of the Human Immunodeficiency Virus Type 1 (HIV-1), viral variants which predominate in some infected individuals in end stage disease. SDF-1 can block X4-tropic HIV-1 infection of CD4+ target cells in vitro, and allelic variants of the human gene encoding SDF-1 in vivo correlate with delayed disease progression. Therefore, CXCR4 may be an appropriate target for therapeutic intervention in acquired immunodeficiency syndrome (AIDS), and knowledge of the pharmacology of SDF-1 binding to its cognate receptor will be important in the interpretation of these experiments. We report here a Kd derived using a competition binding assay of 4.5 nM for CXCR4 endogenously expressed on peripheral blood monocytes and T-cells. This affinity is similar to that which SDF-1 exhibits when binding to endogenous CXCR4 on an established immortal Jurkat T-cell line as well as recombinant CXCR4 transfected into Chinese Hamster Ovary (CHO) cells. We also demonstrate that the determined affinity of SDF-1 for CXCR4 is reflective of its ability to induce a CXCR4-mediated signal transduction in these different cell types. Furthermore, using Bordetella pertussis toxin, we observe that high affinity binding of SDF-1 to CXCR4 is independent of the G-protein coupled state of the receptor, as uncoupling of G-protein did not lead to the appearance of measurable low affinity SDF-1 binding sites. Moreover, binding affinity and receptor number were unaffected by uncoupling for both recombinant and endogenously expressed CXCR4. Thus, SDF-1 is novel among agonist ligands of G protein-coupled receptors in that it appears to have equal affinity for both the G protein-coupled and uncoupled states of CXCR4.

Treatment of antibody-mediated accelerated rejection using plasmapheresis

Accelerated antibody-mediated rejection is believed to be due to an anamnestic response of an allograft recipient to donor antigens. Few reports have demonstrated successful reversal of this type of rejection, and no consensus exists for either diagnosis or treatment. Accelerated antibody-mediated rejection was suspected on the basis of clinical findings and confirmed by cytotoxic and flow crossmatches, and leukocyte antibody screens. Serial crossmatches and antibody screens were performed through post-transplant day 112. Plasmapheresis was performed on post-transplant days 1, 2, 4, 6, 12, 14, 20, and 28. The duration of treatment was determined by the cytotoxic crossmatch results. We present a case of successfully treated accelerated antibody-mediated rejection using plasmapheresis and aggressive immunosuppression. Serial crossmatch and leukocyte antibody screen results are presented that confirm the production of anti-donor antibody and demonstrate the effectiveness of the treatment protocol in eliminating detectable levels of the anti-donor antibody. At 6 months post-transplant, the patient has a serum creatinine of 1.1 and has not had any additional rejection episodes or infectious complications. The protocol suggested in this paper allows for rapid diagnosis, institution of treatment, and monitoring the efficacy of treatment, providing the basis for follow-up clinical trials.

Acute and chronic effects of an aromatase inhibitor on territorial aggression in breeding and nonbreeding male song sparrows

Many studies have demonstrated that male aggression is regulated by testosterone. The conversion of testosterone to estradiol by brain aromatase is also known to regulate male aggression in the breeding season. Male song sparrows (Melospiza melodia morphna) are territorial not only in the breeding season, but also in the nonbreeding season, when plasma testosterone and estradiol levels are basal. Castration has no effect on nonbreeding aggression. In contrast, chronic (10 day) aromatase inhibitor (fadrozole) treatment decreases nonbreeding aggression, indicating a role for estrogens. Here, we show that acute (1 day) fadrozole treatment decreases nonbreeding territoriality, suggesting relatively rapid estrogen effects. In spring, fadrozole decreases brain aromatase activity, but acute and chronic fadrozole treatments do not significantly decrease aggression, although trends for some behaviors approach significance. In gonadally intact birds, fadrozole may be less effective at reducing aggression in the spring. This might occur because fadrozole causes a large increase in plasma testosterone in intact breeding males. Alternatively, estradiol may be more important for territoriality in winter than spring. We hypothesize that sex steroids regulate male aggression in spring and winter, but the endocrine mechanisms vary seasonally.

Neurons undergo apoptosis in animal and cell culture models of diabetes

Recent clinical trials indicate that the severity of diabetic neuropathy is correlated with the level of patient glycemic control. In the current study, hyperglycemia induces apoptotic changes in dorsal root ganglion neurons and Schwann cells in vivo both in streptozotocin-treated diabetic rats and in rats made acutely hyperglycemic with infused glucose. Typical apoptotic nuclear and cytoplasmic changes are observed. In addition mitochondrial changes recently reported to occur as part of the apoptotic cascade, such as ballooning of mitochondria and disruption of the internal cristae, are seen in diabetic dorsal root ganglion neurons and Schwann cells. Similar changes have been reported in neurons in the presence of oxidative stress. In order to study the neurotoxic effects of high glucose we developed an in vitro model using rat dorsal root ganglion neurons. In dorsal root ganglion cultured in defined medium, addition of moderate glucose levels results in neurite degeneration and apoptosis. These changes are coupled with activation of caspase-3, dependent on the concentration of glucose. The apoptotic changes observed in vitro are similar to those observed in vivo. In contrast, addition of IGF-I, even at physiological concentrations, prevents activation of caspase-3 and neuronal apoptosis in vitro. We suggest that oxidative stress may promote the mitochondrial changes in diabetic animals and lead to activation of programmed cell death caspase pathways. These results imply a new pathogenetic mechanism for diabetic sensory neuropathy.

Generation of mice expressing the human glucagon receptor with a direct replacement vector

The process of evaluating the in vivo efficacy of non-peptidyl receptor antagonists in animal models is frequently complicated by failure of compounds displaying high affinity against the human receptors to show measurable affinity at the corresponding rodent receptors. In order to generate a suitable animal model in which to evaluate the in vivo activity of non-peptidyl glucagon receptor antagonists, we have utilized a direct targeting approach to replace the murine glucagon receptor with the human glucagon receptor gene by homologous recombination. Specific expression of the human glucagon receptor (GR) in the livers of transgenic mice was confirmed with an RNase protection assay, and the pharmacology of the human GRs expressed in the livers of these mice parallels that of human GR in a recombinant CHO cell line with respect to both binding of 125I-glucagon and the ability of glucagon to stimulate cAMP production. L-168,049, a non-peptidyl GR antagonist selective for the human GR shows a 3.5 fold higher affinity for liver membrane preparations of human GR expressing mice (IC50 = 172 +/- 98 nM) in the presence of MgCl2 in marked contrast to the measured affinity of the murine receptor (IC50 = 611 +/- 197 nM) for this non-peptidyl antagonist. The human receptors expressed are functional as measured by the ability of glucagon to stimulate cAMP production and the selectivity of this antagonist for the human receptor is further verified by its ability to block glucagon-stimulated cyclase activity with 5 fold higher potency (IC50 = 97.2 +/- 13.9 nM) than for the murine receptor (IC50 = 504 +/- 247 nM). Thus we have developed a novel animal model for evaluating GR antagonists in vivo. These mice offer the advantage that the regulatory sequences which direct tissue specific and temporal expression of the GR have been unaltered and thus expression of the human gene in these mice remains in the normal chromosomal context.

Insulin-like growth factor-I and central nervous system development

Insulin-like growth factor-I (IGF-I), a 70-amino acid-protein structurally similar to insulin, promotes cell proliferation and differentiation in multiple tissues. Most of its effects are mediated by the Type I IGF receptor (IGF-IR), a heterotetramer that has tyrosine kinase activity and phosphorylates insulin receptor substrates (IRS-1 and 2) which leads to the activation of two downstream signaling cascades: the MAP kinase and the phosphatidylinositol 3-kinase (P3K) cascades. The growth-promoting effects of IGF-I are prominent in the nervous system, qualifying this molecule as a neurotrophin. Although the primary regulator of IGF-I expression is growth hormone (GH), the developmental expression of IGF-I in various tissues precedes that of GH, supporting an independent role of IGF-I in embryonic and fetal life [1]. This review will examine the effect of IGF-I on central nervous system (CNS) development. The specialized structure of the CNS is the product of a complex series of biological events which result from the interaction between the cells' genetic program and environmental influences. CNS development begins in the embryo with dorsal ectodermal cell proliferation to form the neural plate, and, with its closure, the neural tube, followed by the rapid division of pluripotential cells, their migration to the periphery of the neural tube, and differentiation into neural or glial cells. During the latter stages, cells form special structures such as nuclei, ganglia, cerebral cortical layers, and they also develop a network with their cytoplasmic extensions, neurites. Many more cells and connections are generated in fetal life than are found in the mature organism. This excessive production of some cell groups and neurites may compensate for tissue loss due to various injuries, and their selective elimination also constitutes an efficient way to organize the architecture of the CNS. This elimination is believed to be accomplished by apoptosis. The cells' intrinsic program for development includes the expression of various genes at different times. Environmental influences, such as extracellular matrix (ECM) molecules that attract or repel cells, afferent inputs, and target-derived diffusible molecules modify and modulate cellular behavior. IGF-I is among the molecules which affect several steps involved in development.

Molecular characterization and expression of cloned human galanin receptors GALR2 and GALR3

Galanin is a 29- or 30-amino acid peptide with wide-ranging effects on hormone release, feeding behavior, smooth muscle contractility, and somatosensory neuronal function. Three distinct galanin receptor (GALR) subtypes, designated GALR1, 2, and 3, have been cloned from the rat. We report here the cloning of the human GALR2 and GALR3 genes, an initial characterization of their pharmacology with respect to radioligand binding and signal transduction pathways, and a profile of their expression in brain and peripheral tissues. Human GALR2 and GALR3 show, respectively, 92 and 89% amino acid sequence identity with their rat homologues. Radioligand binding studies with 125I-galanin show that recombinant human GALR2 binds with high affinity to human galanin (K(D) = 0.3 nM). Human GALR3 binds galanin with less affinity (IC50 of 12 nM for porcine galanin and 75 nM for human galanin). Human GALR2 was shown to couple to phospholipase C and elevation of intracellular calcium levels as assessed by aequorin luminescence in HEK-293 cells and by Xenopus melanophore pigment aggregation and dispersion assays, in contrast to human GALR1 and human GALR3, which signal predominantly through inhibition of adenylate cyclase. GALR2 mRNA shows a wide distribution in the brain (mammillary nuclei, dentate gyrus, cingulate gyrus, and posterior hypothalamic, supraoptic, and arcuate nuclei), and restricted peripheral tissue distribution with highest mRNA levels detected in human small intestine. In comparison, whereas GALR3 mRNA was expressed in many areas of the rat brain, there was abundant expression in the primary olfactory cortex, olfactory tubercle, the islands of Calleja, the hippocampal CA regions of Ammon's horn, and the dentate gyrus. GALR3 mRNA was highly expressed in human testis and was detectable in adrenal gland and pancreas. The genes for human GALR2 and 3 were localized to chromosomes 17q25 and 22q12.2-13.1, respectively.

Insulin-like growth factors regulate neuronal differentiation and survival

Insulin-like growth factor I (IGF-I) and IGF-II are potent trophic factors for motor and sensory neurons and glial cells. The actions of IGF-I and IGF-II are mediated via the IGF-I receptor (IGF-IR). IGF:IGF-IR binding activates distinct signaling cascades, which in turn mediate the trophic effects of the IGFs. We discuss three main IGF coupled events: growth cone motility, long-term neurite outgrowth, and neuroprotection. Our data suggest that IGF-I enhances growth cone motility by promoting reorganization of actin and activation of focal adhesion proteins via the phosphatidylinositol-3 kinase (Pl-3K) pathway. Long-term treatment with IGF-I activates the mitogen-activated protein (MAP) kinase cascade and promotes neurite outgrowth. A separable, but likely linked, action of the IGFs via Pl-3K is protection of neurons from apoptosis. These pleotrophic effects of IGFs suggest that this family of growth factors may have potential clinical utility in the treatment of neurological disorders.

First report of recombination between the HLA-DR and HLA-DQ loci within a family

Although unusual associations of HLA-DR and HLA-DQ alleles seen in ancestral haplotypes have indicated that recombination between these genes occurred in the past, an actual crossover event between DR and DQ has never been shown within a family. In a study of families with Graves' disease we have identified an individual from a three generation family who inherited a maternal haplotype that is the result of a recombinational event between the HLA-DR and the HLA-DQ loci on her chromosomes. Family members were typed for HLA class I by the lymphocyte microcytotoxicity test and for HLA class II by polymerase chain reaction (PCR) with sequence-specific primers or with sequence-specific oligonucleotide probes after PCR. Based on linkage disequilibrium it is likely that the recombinant haplotype is present in the proband rather than his brother. This haplotype was subsequently inherited by one of the proband's sons. The data presented support the conclusion that the recombinant haplotype resulted from a crossover event between the mother's DRB1 and DQA1 genes. Thus, recombination between the HLA-DR and HLA-DQ genes has been demonstrated within this family; a recombination event not previously described.

Pharmacological characterization and tissue distribution of the human and rat GALR1 receptors

The diverse biological functions of galanin are mediated via membrane bound high-affinity receptors. In order to identify and characterize potential galanin receptor subtypes, we have examined the specific 125I-galanin binding to the CHP-212 human neuroblastoma cell line. The galanin receptors expressed in CHP-212 cells, like GALR1 have high affinity for galanin (Kd = 0.07 nM) and the potency for inhibition of 125I-galanin binding by galanin peptides parallels that of hGALR1 expressed in a stable CHO cell line. We confirmed that GALR1 is expressed in these cells by RT-PCR. We further determined the tissue expression patterns of hGALR1 which is expressed in a variety of human tissues at a very low level, with the highest levels seen in heart, small intestine and prostate. A species of approximately 70 kDa is recognized by antisera specific for hGALR1 by Western blot analysis and should allow future measurements of receptor protein expression.

Molecular cloning and characterization of a new receptor for galanin

Galanin (GAL) is a widely distributed neuropeptide with diverse biological effects including modulation of hormone release, antinociception and modification of feeding behavior. Its effects are mediated through G-protein-coupled receptors (GPCR) for which only a single type has been cloned, GAL receptor 1 (GALR1). We describe the cloning of a second galanin receptor type, GALR2, from rat hypothalamus. The GALR2 amino acid sequence is 38% identical to GALR1 and is pharmacologically similar to GALR1 when expressed in COS-7 cells. GALR2 is encoded by a single gene containing at least one intron and expressed in a diverse range of tissues.

Suramin disrupts insulin-like growth factor-II (IGF-II) mediated autocrine growth in human SH-SY5Y neuroblastoma cells

Suramin, traditionally used in the treatment of trypanosomiasis, is under investigation in the treatment of cancer. One side effect that limits its use is the onset of a sensorimotor polyneuropathy. In order to investigate the mechanism by which suramin induces polyneuropathy, we examined its effects on SH-SY5Y human neuroblastoma cells, an in vitro model of neuronal growth and differentiation. Addition of 50-400 micrograms/ml suramin to SH-SY5Y cells grown in 0.6% CS inhibited [3H]thymidine ([3H]TdR) incorporation and cell growth. Upon removal of suramin, [3H]TdR incorporation increased, demonstrating that levels of suramin used were cytostatic and not cytotoxic. Analysis of suramin-treated SH-SY5Y cells by flow cytometry revealed growth arrest in the G1/G0 phase of the cell cycle. IGF-II-induced SH-SY5Y growth is mediated by the type I IGF receptor (IGF-IR). Therefore, we examined its effect on IGF-IR tyrosine phosphorylation. Suramin prevented IGF-II-stimulated IGF-IR tyrosine phosphorylation. These results indicate that in SH-SY5Y cells, suramin acts as a cytostatic agent and can block IGF-II-dependent cell growth by preventing IGF-IR activation. Thus, suramin toxicity in the peripheral nervous system may be due, in part, to preventing IGF and other growth factors from activating their receptors.

Immunohistochemical localization of insulin-like growth factor binding protein-5 in the developing rat nervous system

The insulin-like growth factors (IGF-I and IGF-II) are peptides with both growth-promoting and insulin-like metabolic effects. The IGFs interact with and are modulated by a group of six IGF-binding proteins (IGFBP-1 through IGFBP-6). Previous studies have characterized IGFBP-5 and IGF-I gene expression in the developing nervous system. In the current study, cellular and tissue-specific distribution of IGFBP-5 protein was examined in the developing rodent nervous system using immunohistochemistry. Beginning with embryonic stage E12, IGFBP-5 immunoreactivity was observed in peripheral nerves. This pattern persisted through adulthood and was detected within Schwann cells and axons after postnatal day 16 (P16). IGFBP-5 immunoreactivity first appeared in the CNS at P16. Purkinje cells of the cerebellum were immunostained at P16, P32 and in the adult. IGFBP-5 immunoreactivity was also detected in several brain stem nuclei and their corresponding tracts as well as neuroglia. Nerve tracts and glia in the postnatal spinal cord were also immunopositive, however, spinal cord neurons were not stained. The current results, coupled with the known profile of IGF-I expression during nervous system development demonstrates the colocalization of IGF-I and IGFBP-5 in PNS, cerebellum, and brain stem.

Insulin-like growth factor II in the pathogenesis of human neuroblastoma

Insulin-like growth factor II (IGF-II) acts as an autocrine growth factor for many in vitro tumor cell lines including neuroblastoma. To examine the role of IGF-II in tumor biology we have analyzed a total of 56 primary neuroblastoma tumor samples for the presence of IGF-II using a combination of mRNA and protein analysis. A group of 21 samples was examined for the presence of IGF-II mRNA by slot blot and a separate group of 37 samples was examined for IGF-II immunoreactivity. IGF-II was detected in 48% of the total tumor specimens analyzed. IGF-II immunoreactivity was observed in cells resembling developing neuroblasts and was confined to the cytoplasm and proximal neurites. The appearance of IGF-II mRNA and protein did not correlate with tumor prognostic features including stage, histology, or N-myc amplification. These data suggest that the expression of IGF-II is not confined to a specific stage of the disease but may have a broader role in the pathogenesis of neuroblastoma.

Gonadotropin-releasing hormone neurons in the rhesus macaque are not immunoreactive for the estrogen receptor

The issue of whether gonadotropin-releasing hormone (GnRH) neurons in the primate contain the estrogen receptor was examined by immunocytochemistry using prepubertal and adult (intact and ovariectomized) female rhesus macaques. No GnRH neurons were found to contain nuclei that were immunoreactive for the estrogen receptor. These results confirm in primates what has been reported in other species and leave open the question of how the effects of gonadal steroids on GnRH neurons are mediated.

Antimicrobial characterization and interrelationships of dirithromycin and epidirithromycin

Dirithromycin is the 9-N,11-O-oxazine adduct formed from 9(S)-erythromycylamine and 2-(2-methoxyethoxy)acetaldehyde in which the methoxyethoxymethyl substituent on the oxazine ring possesses the R configuration. Epidirithromycin is its isomer in which the methoxyethoxymethyl substituent has the opposite (S) configuration. Both compounds readily epimerize in solution, reaching an equilibrium ratio of 85:15 in favor of dirithromycin, given sufficient time. The rate of interconversion is dependent upon pH, temperature, and solvent. An enriched sample of epidirithromycin (95% purity) was synthesized by condensing erythromycylamine and 2-(2-methoxyethoxy)acetaldehyde in diethyl ether as the reaction solvent, and the product was fully characterized by nuclear magnetic resonance spectroscopy and high-pressure liquid chromatographic (HPLC) analysis. Both oxazine derivatives readily hydrolyze to erythromycylamine, so all three compounds exhibit the same antibiotic activity in vitro. In order to determine whether dirithromycin itself possesses significant antimicrobial activity without initial hydrolysis to erythromycylmine, inhibition of cell-free ribosomal protein synthesis was measured under conditions which were adapted to minimize hydrolysis, as measured by analytical HPLC in parallel experiments. Under these particular conditions, inhibition of ribosomal protein synthesis by dirithromycin was < 10% of the value measured for erythromycylamine.

Purification and characterization of a naturally occurring vascular endothelial growth factor.placenta growth factor heterodimer

Vascular endothelial growth factor (VEGF) is a potent and selective mitogen for endothelial cells that is angiogenic in vivo and induced by hypoxia. A homologous protein, placenta growth factor (PlGF), is also reported to be mitogenic for endothelial cells in culture. The rat GS-9L glioma cell line produces not only VEGF homodimers but also PlGF homodimers and a novel heterodimer composed of VEGF and PlGF subunits. All three dimeric forms were purified to apparent homogeneity, and their structures and mitogenic activities were compared. VEGF.PlGF heterodimers are vascular endothelial cell mitogens nearly as potent as VEGF homodimers. Therefore, some of the biological activities attributed to VEGF homodimers might be mediated by VEGF.PlGF heterodimers. In contrast, pure PlGF homodimers are mitogenic for endothelial cells only at high, possibly non-physiologic concentrations; thus the biological relevance of their mitogenic activity for these cells is not obvious. However, the existence of not only homodimers but also heterodimers clearly extends the similarity between the VEGF/PlGF and the homologous platelet-derived growth factor systems.

Ontogeny of neurotransmitter systems in the paracervical ganglion and uterine cervix of the rat

BACKGROUND

The paracervical ganglia (PG) are components of the pelvic plexus that provides sensory and motor innervation to the reproductive system of the female rat. Several neurotransmitters including norepinephrine (NE), acetylcholine (ACh), neuropeptide Y (NPY), and vasoactive intestinal polypeptide (VIP) are present in neurons of the adult PG and in axons innervating the adult uterus and uterine cervix. The current study was undertaken to describe the onset of immunoreactivity of these neurotransmitters and neuropeptides during development.

METHODS

Female rats, ages E18 to P36, were prepared for immunohistochemistry for TH (tyrosine hydroxylase, a marker of noradrenergic neurons), NPY, or VIP as well as the histochemical demonstration of acetylcholinesterase (AChE).

RESULTS

All four markers were detected in neurons of the PG at E18. Changes in the appearance of these markers from E18 to P36 reflected previously described growth changes in the PG. Axons containing AChE, TH, NPY, or VIP were first detected within the cervix at E20. Immunopositive axons first appeared as thick, unbranched structures at the outermost portion of the cervical myometrium. Over time, these axon bundles ramified to form discrete varicose axons. The ingrowth was similar for axons containing each of the four markers.

CONCLUSIONS

The relative density of each neuronal type in the PG was reflected in the density of axons containing the same marker in the cervix. Changes in neurotransmitter/neuropeptide staining of PG neurons or axons in the cervix were not observed as the animals approached puberty.

Immunohistochemical localization of insulin-like growth factor-II (IGF-II) and IGF-binding protein-2 during development in the rat brain

The insulin-like growth factors (IGF-I and IGF-II) are peptide growth factors with both growth-promoting and insulin-like activities. In the nervous system, the expression of both IGF-I and IGF-II messenger RNAs (mRNAs) is developmentally regulated, with IGF-I expression highest during puberty, and IGF-II levels peaking during the perinatal period. The IGFs interact with and are modulated by a group of six binding proteins, the IGF-binding proteins (IGFBP-1 to IGFBP-6). IGFBP-2 mRNA is most prevalent in the nervous system, where, like IGF-II, its expression correlates with a period of brain growth. In the current study, cells containing IGF-II and IGFBP-2 were identified within the developing nervous system of the rat on embryonic day 12 (E12), E14, E18, and postnatal day 1 and in the adult. IGF-II immunoreactivity was detected within the mesenchymal core of the choroid plexus at all ages examined and was also observed in the developing leptomeninges. IGF-II appeared transiently in the central nervous system in presumptive glia of the hippocampus and medial basal hypothalamus and in a small population of neurons in the brain stem. IGFBP-2 was consistently observed in the epithelium of the choroid plexus as well as in the epithelia of the developing otic and olfactory placodes. While these results confirm the developmental expression of IGF-II and IGFBP-2 mRNA in the central nervous system, discrepancies exist between these data and those using molecular techniques. This may be due in part to differential sites of IGF-II and IGFBP-2 production compared to sites of action.

Induction of vascular endothelial growth factor expression by prostaglandin E2 and E1 in osteoblasts

PGE1 and PGE2 are potent stimulators of bone formation. Osteogenesis is strongly dependent on angiogenesis. Vascular endothelial growth factor (VEFG), a secreted endothelial cell-specific mitogen, has been implicated in physiological and pathological angiogenesis. The aim of this study was to examine the possible role of VEGF in PG stimulation of bone formation. We found that in rat calvaria-derived osteoblast-enriched cells and in the osteoblastic RCT-3 cell line PGE2 and E1 increased VEGF mRNA and protein levels. The increased expression of VEGF mRNA produced by PGE2 was rapid (maximal at 1 h), transient (declined by 3 h), potentiated by cycloheximide, and abolished by actinomycin D. PGE2 had no effect on VEGF mRNA stability, suggesting transcriptional regulation of VEGF expression by PGF2. Rp-cAMP, a cAMP antagonist, suppressed VEGF mRNA induced by PGE2, indicating cAMP mediation. The upregulation of VEGF expression by PGE2 in the preosteoblastic RCT-1 cells was potentiated by treatment with retinoic acid, which induces the differentiation of these cells. The upregulation of VEGF mRNA by PGE2 was inhibited by dexamethasone treatment. In addition, Northern blot analysis showed that VEGF mRNA is expressed in adult rat tibia. In summary, we documented, for the first time, the expression of VEGF in osteoblasts and in bone tissue. Stimulation of VEGF expression by PGs and its suppression by glucocorticoids, which, respectively, stimulate and suppress bone formation, strongly implicate the involvement of VEGF in bone metabolism.

Progression of symptoms in neuroleptic malignant syndrome

The neuroleptic malignant syndrome (NMS) is a rare but potentially fatal disorder characterized by mental-status changes, muscle rigidity, hyperthermia, and autonomic dysfunction. Systematic examination of early signs and the progression of symptoms in NMS may be worthwhile to facilitate prompt recognition and interventions to abort the syndrome in its incipient stage. The authors present the results of a preliminary review of the temporal sequence of the four predominant signs of NMS as described in 340 clinical reports of NMS in the literature. Of all order implications, 70.5% were consistent with the sequence of mental-status changes, rigidity, hyperthermia, and autonomic dysfunction. Changes in either mental status or rigidity were the initial manifestations of NMS in 82.3% of cases with a single presenting sign and were significantly more likely to be observed before hyperthermia and autonomic dysfunction. Methodological limitations of these data and clinical implications are discussed.

The ontogeny of gonadotropin-releasing hormone neurons in the chick

The origin of gonadotropin-releasing hormone (GnRH) neurons in the olfactory placode and their subsequent migration into the central nervous system (CNS) has been described in several species. The current study was undertaken to delineate the time course and route of GnRH neuronal migration in the chick using antisera generated against both the mammalian form of GnRH (LR1) and a specific chicken GnRH (cGnRH I). Chicks aged E4.5 through day of hatching were processed for GnRH immunocytochemistry. Under the incubation conditions employed in this study, GnRH neurons first appeared on E4.5 in the olfactory epithelium. GnRH neurons exit from the olfactory epithelium and follow the extracranial course of the olfactory nerve to the anterior pole of the developing forebrain. Within the nerve, cells are in close apposition to each other. By E5, cells had reached the surface of the telencephalon. Upon entering the CNS, the GnRH neurons dispersed within the neuropil and continued their migration as individuals. As development progressed, GnRH neurons migrated dorsally and caudally within the brain and reached their adult positions by E12. GnRH axons were detected in the vicinity of GnRH cell bodies with the cGnRH I antiserum as early as E4.5; however, GnRH axons did not reach the median eminence until E14. These results extend earlier reports in mammal and chick on the extracranial origin of GnRH neurons and their path of entry into and dispersion within the CNS.

Synthesis and structure-activity relationships of new 9-N-alkyl derivatives of 9(S)-erythromycylamine

A series of new 9-N-alkyl derivatives of 9(S)-erythromycylamine has been synthesized by reductive alkylation of erythromycylamine with aliphatic aldehydes and sodium cyanoborohydride. Alternative syntheses employing hydrogenation methods have also been developed. These new 9-N-alkyl derivatives possess excellent antimicrobial activity in vitro and in vivo, especially when administered orally to treat experimental infections in mice. From structure-activity studies, 9-N-(1-propyl)erythromycylamine (LY281389) was selected as the most efficacious derivative. These methods have also been extended to the synthesis of some 9-N,N-dialkyl derivatives of erythromycylamine.

Amino acid and cDNA sequences of a vascular endothelial cell mitogen that is homologous to platelet-derived growth factor

Glioma-derived vascular endothelial cell growth factor (GD-VEGF) is a 46-kDa dimeric glycoprotein mitogen with apparently greater specificity for vascular endothelial cells than the well-characterized fibroblast growth factors. The GD-VEGF cDNA sequence encodes a 190-amino acid residue subunit that is converted, by removal of an amino-terminal hydrophobic secretory leader sequence, to the mature 164-residue subunit characterized by direct amino acid sequencing. The GD-VEGF homodimeric subunit is homologous to the platelet-derived growth factor A and B chains and its oncogene homologue v-sis.

Sleep disturbance as the hallmark of posttraumatic stress disorder

The reexperiencing of a traumatic event in the form of repetitive dreams, memories, or flashbacks is one of the cardinal manifestations of posttraumatic stress disorder (PTSD). The dream disturbance associated with PTSD may be relatively specific for this disorder, and dysfunctional REM sleep mechanisms may be involved in the pathogenesis of the posttraumatic anxiety dream. Furthermore, the results of neurophysiological studies in animals suggest that CNS processes generating REM sleep may participate in the control of the classical startle response, which may be akin to the startle behavior commonly described in PTSD patients. Speculating that PTSD may be fundamentally a disorder of REM sleep mechanisms, the authors suggest several strategies for future research.

A mutation that prevents GTP-dependent activation of the alpha chain of Gs

Membrane-bound G proteins carry information from receptors on the outside of cells to effector proteins inside cells. The alpha subunits of these heterotrimeric proteins bind and hydrolyse GTP and control the specificity of interactions with receptor and effector elements. Signalling by G proteins involves a cycle in which the inactive alpha beta gamma-GDP complex dissociates to produce alpha*-GTP, which is capable of activating the effector enzyme or ion channel; the alpha*-GTP complex hydrolyses bound GTP and reassociates with beta gamma to form the inactive complex. We have characterized a mutation that interrupts this GTP-driven cycle in alpha s, the alpha-chain of Gs, the G protein that stimulates adenylyl cyclase. The mutation converts a glycine to an alanine residue in the presumed GDP-binding domain of alpha s. The location and biochemical consequences of this mutation suggest a common mechanism by which binding of GTP or ATP may induce changes in the conformation of a number of nucleoside triphosphate binding proteins.

Carboxyl terminal domain of Gs alpha specifies coupling of receptors to stimulation of adenylyl cyclase

The alpha subunits of Gs and Gi link different sets of hormone receptors to stimulation and inhibition, respectively, of adenylyl cyclase. A chimeric alpha i/alpha s cDNA was constructed that encodes a polypeptide composed of the amino terminal 60% of an alpha i chain and the carboxyl terminal 40% of alpha s. The cDNA was introduced via a retroviral vector into S49 cyc- cells, which lack endogenous alpha s. Although less than half of the hybrid alpha chain is derived from alpha s, its ability to mediate beta-adrenoceptor stimulation of adenylyl cyclase matched that of the normal alpha s polypeptide expressed from the same retroviral vector in cyc- cells. This result indicates that carboxyl terminal amino acid sequences of alpha s contain the structural features that are required for specificity of interactions with the effector enzyme, adenylyl cyclase, as well as with the hormone receptor.

Mutations probe structure and function of G-protein alpha chains

The molecular genetic approach has just begun to provide hints of answers to some of the questions posed at the outset of this paper. We have some idea of which portions of the alpha chain of Gs interact with receptors and effectors, and we guess that the same is true of corresponding regions of other alpha chains. We have a tantalizing hint that points to a key region of alpha s that is necessary for the conformational change induced by binding GTP, and the vague outline of a hypothesis regarding the mechanism by which receptors release GDP from its binding site on the alpha chain. The alpha chain region (domain) that interacts with beta gamma remains unknown. The tenuous quality of all these hints and hypotheses is obvious, and at least in the short term, frustrating. Even the present level of our understanding, however, is impressive in comparison with what was known of G-protein function only 5 years ago. Now we can pose much more precise questions and hope that a combination of the molecular genetic approach with biophysical probes of structure will provide satisfying answers.

Genetic deficiency of the alpha subunit of the guanine nucleotide-binding protein Gs as the molecular basis for Albright hereditary osteodystrophy

Patients who have pseudohypoparathyroidism type I associated with Albright hereditary osteodystrophy commonly have a genetic deficiency of the alpha subunit of the G protein that stimulates adenylyl cyclase (alpha Gs) (ATP pyrophosphate-lyase, EC 4.6.1.1). To discover the molecular mechanism that causes alpha Gs deficiency in these patients, we examined eight kindreds with one or more members affected with Albright hereditary osteodystrophy or pseudohypoparathyroidism and alpha Gs deficiency. In these families, alpha Gs deficiency and the Albright hereditary osteodystrophy phenotype were transmitted together in a dominant inheritance pattern. Using a cDNA hybridization probe for alpha Gs, restriction analysis with several endonucleases showed no abnormalities of restriction fragments or gene dosage. RNA blot and dot blot analysis of total RNA from cultured fibroblasts obtained from the patients revealed approximately equal to 50% reduced mRNA levels for alpha Gs in affected members of six of the pedigrees but normal levels in affected members of the two other pedigrees, compared to mRNA levels in fibroblasts from unaffected individuals. By contrast, mRNA levels encoding the alpha subunit of the G protein that inhibits adenylyl cyclase were not altered. Our findings suggest that several molecular mechanisms produce alpha Gs deficiency in patients with pseudohypoparathyroidism type Ia and that major gene rearrangements or deletions are not a common cause for alpha Gs deficiency in pseudohypoparathyroidism type I.

Identification of receptor contact site involved in receptor-G protein coupling

The mammalian G proteins transduce information from extracellular signals, including neurotransmitters, hormones and sensory stimuli, into regulation of effector enzymes or ion channels within cells. Triggered by appropriate extracellular signals, receptor proteins specifically activate members of the G protein family by catalysing replacement of GDP by GTP at the guanine nucleotide binding site. Like the receptor proteins, the heterotrimeric G proteins exhibit impressive structural similarities, suggesting that all receptor-G protein interactions use homologous structural elements and a single molecular mechanism. Topologically equivalent portions of each G protein may therefore interact with the appropriate receptor. We recently predicted the secondary structure of a composite G protein alpha-chain and proposed that a predicted amphipathic alpha-helix at the extreme carboxy-terminus of the polypeptide directly contacts receptors. This proposal has now been confirmed by sequencing complementary DNAs of the gene that encodes the alpha-chain (alpha s) of the stimulatory regulator (Gs) of adenylyl cyclase in wild-type cells and in a mutant mouse S49 lymphoma cell line, unc, in which Gs cannot be activated by hormone receptors. The sequences reveal a point mutation in the unc gene that substitutes a proline residue for an arginine near the carboxy-terminus of the alpha s-polypeptide. Expression of recombinant alpha s-unc in genetically alpha s-deficient S49 cells reproduces the unc phenotype.

Chromosomal assignment of the murine Gi alpha and Gs alpha genes. Implications for the obese mouse

The G protein family of transmembrane signaling molecules includes Gs and Gi, the stimulatory and inhibitory regulators of adenylate cyclase. These and other characterized G proteins are comprised of beta, gamma, and alpha chains, the latter being the most variable among the proteins and thus serving to distinguish them. Previous results (Begin-Heick, N. (1985) J. Biol. Chem. 260, 6187-6193) suggested that the autosomal recessive mouse mutation obese (ob), which results in an abnormal response of adipose tissue to lipolytic hormones, is due to a defect in the gene coding for the alpha chain of Gi. In order to test this hypothesis we used a cloned cDNA probe representing murine Gi alpha mRNA in conjunction with a panel of Chinese hamster-mouse somatic cell hybrids segregating mouse chromosomes to map the Gi alpha gene in the mouse. In addition, we used a cDNA probe representing the murine Gs alpha gene to a specific mouse chromosome. Our results indicate that the Gi alpha locus maps to mouse chromosome 9, while Gs alpha is localized to region 2E1-2H3 of mouse chromosome 2. Localization of the Gi alpha gene to chromosome 9 excludes this gene as a site of the ob mutation, since the ob locus maps to chromosome 6. Furthermore, our findings indicate that certain members of the murine G protein alpha gene family have dispersed to different chromosomes since diverging from a common ancestral gene.