Assembly of an SAP97-AKAP79-cAMP-dependent protein kinase scaffold at the type 1 PSD-95/DLG/ZO1 motif of the human beta(1)-adrenergic receptor generates a receptosome involved in receptor recycling and networking

Appropriate trafficking of the beta(1)-adrenergic receptor (beta(1)-AR) after agonist-promoted internalization is crucial for the resensitization of its signaling pathway. Efficient recycling of the beta(1)-AR required the binding of the protein kinase A anchoring protein-79 (AKAP79) to the carboxyl terminus of the beta(1)-AR (Gardner, L. A., Tavalin, S. A., Goehring, A., Scott, J. D., and Bahouth, S. W. (2006) J. Biol. Chem. 281, 33537-33553). In this study we show that AKAP79 forms a complex with the type 1 PDZ-binding sequence (ESKV) at the extreme carboxyl terminus of the beta(1)-AR, which is mediated by the membrane-associated guanylate kinase (MAGUK) protein SAP97. Thus, the PDZ and its associated SAP97-AKAP79 complex are involved in targeting the cyclic AMP-dependent protein kinase (PKA) to the beta(1)-AR. The PDZ and its scaffold were required for efficient recycling of the beta(1)-AR and for PKA-mediated phosphorylation of the beta(1)-AR at Ser(312). Overexpression of the catalytic subunit of PKA or mutagenesis of Ser(312) to the phosphoserine mimic aspartic acid both rescued the recycling of the trafficking-defective beta(1)-ARDelta PDZ mutant. Thus, trafficking signals transmitted from the PDZ-associated scaffold in the carboxyl terminus of the beta(1)-AR to Ser(312) in the 3rd intracellular loop (3rd IC) were paramount in setting the trafficking itinerary of the beta(1)-AR. The data presented here show that a novel beta(1)-adrenergic receptosome is organized at the beta(1)-AR PDZ to generate a scaffold essential for trafficking and networking of the beta(1)-AR.     

Depression comorbidity among patients with tuberculosis in a university teaching hospital outpatient clinic in Nigeria

Background Tuberculosis (TB) remains a leading infectious cause of morbidity and mortality throughout the world. Medication non-compliance has been recognised as one of the drawbacks in the successful management of this disease. Hence, different approaches for ensuring medication compliance have been adopted; these include the Directly Observed Therapy Short course (DOTS). TB is associated with psychiatric morbidity, particularly depressive disorder, and this has been recognised as a cause of poor compliance and a cause of increased morbidity and mortality from the disease. Despite this recognition, little attention is paid to the identification of depression among TB patients, particularly in the DOTS clinics that most of these patients attend. This study was designed to determine the prevalence of depression in patients with TB attending the DOTS outpatient clinic in a university teaching hospital in Nigeria, and to find out the factors that may be associated with this.Method All consenting TB patients attending the clinic completed a socio-demographic questionnaire and nine-item Patient Health Questionnaire (PHQ-9) designed to screen for depression, especially in outpatient and primary care settings.Results Sixty-five patients participated in the study of whom 41 (63.1%) were males. The mean age of the respondents was 35.1 ± 14.4 (range 15-70 years). Eighteen (27.7%) of the patients had depression, comprising 14 (21.5%) with mild depression and four (6.2%) with moderate depression. Socio-demographic factors (age groups, P=0.024; and financial status, P=0.02) and a clinical factor (persistent cough, P=0.04) were significantly associated with depression.Conclusion Measures to reduce depression among patients with TB should include effective symptom control, particularly of coughing, and measures to improve the financial status of this group of patients. Financial empowerment of patients may reduce depression in them, improve the compliance rate to anti-TB medication, and could furthermore bring an improvement to their quality of life.     

The influence of harmaline on the movements of sodium ions in smooth muscle of the guinea pig ileum

Summary The effect of changing the extracellular concentration of both Na⁺ and K⁺ on the longitudinal muscle of the guinea-pig ileum was studied in the presence and absence of harmaline. A decrease in extracellular Na⁺ concentration was found to produce a dose-dependent contractile response, which may suggest the existence of a Na...Ca exchange mechanism in this muscle. Harmaline (2 × 10⁻⁴ M) was found to reversibly inhibit this contraction and was also found to selectively block the tonic component of high-K induced contradictions. In view of the fact that harmaline is a non-competitive inhibitor of Ca-induced contractions (Hider et al., Europ. J. Pharmacol., 71, 87, 1981), the action of harmaline was interpreted as being a specific inhibitor of the Na... exchange mechanism, binding specifically to Na⁺ coordination sites.     

In vivo secretory responses of submandibular glands in streptozotocin-diabetic rats to sympathetic and parasympathetic nerve stimulation

Submandibular gland responses to sympathetic and parasympathetic nerve stimulation were studied in streptozotocin-diabetic rats. Morphologically, the acinar cells in control glands were relatively uniform in size and contained electron-lucent granules. The granular ducts were distinguished by the presence of electron-dense granules. With the exception of intracellular lipid droplets and the presence of a few autophagosomes in diabetic glands, no consistent differences in acinar cell structure were observed. In contrast, the diameter of the granular ducts and the granule content of their cells were less in diabetic glands. At 3 weeks sympathetic flow rate, salivary protein concentration, and total protein output were unaffected by diabetes. Sympathetic flow rate was greater at 3 months, and the concentration of protein in the saliva was lower. In 6-month diabetic rats flow rate remained increased, but protein concentration and total protein output were reduced. The decrease in salivary protein concentration at 3 and 6 months was accompanied by a reduction in secretory granule release from acinar and granular duct cells. No consistent differences in flow rate, protein concentration, protein output, or secretory granule release were observed following parasympathetic stimulation. We conclude that the effects of diabetes on nerve-stimulated flow rate and protein release depend on the duration of diabetes and the type of stimulation, and are independent of one another.     

Piezoelectric crystal biosensors

The recent development of piezoelectric devices as biosensors is reviewed. Biological materials, like enzymes, lipids, antibodies and antigens, have been used as specific coatings and were utilized for the determination of different substrates. Methods of protein coating and several applications are reported including microgravimetric immunoassays, microbial assays, DNA hybridization, enzyme detections and gas phase biosensors. Although the piezoelectric immunochemical sensor is convenient to use and very promising, a thorough understanding of the different phenomena associated with crystals frequency measurement in biological reactions is still lacking and deserves further investigation.     

A fluorescence-based fiber optic biosensor for the flow-injection analysis of penicillin

A penicillin fiber optic sensor is described. The sensor is based on co-immobilization of a pH indicator, fluorescein isothiocyanate (FITC), and penicillinase on a preactivated biodyne B membrane attached to the end of a bifurcated optical fiber. The characteristics of the sensor are investigated in conjunction with a flow injection analysis system. The proposed sensor is reversible and responds to penicillin in the concentration range of 1 x 10(-4) to 5 x 10(-2) mol/L. The application of this sensor to penicillin analysis in some pharmaceutical samples is demonstrated.     

Can MTT be used to quantify the antioxidant activity of plant extracts?

Antioxidant properties of three different medicinal plant extracts from northern Nigeria were evaluated using the traditional qualitative 2,2, diphenyl-picrylhydrazyl (DPPH) method and a new 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) microdilution method described here. The results were in agreement. It is a simple, rapid and inexpensive method compared with many other methods for determining quantitative antioxidant activity of plant extracts.     

Isolation and characteristics of 10 microsatellite markers from the endangered coconut crab (Birgus latro)

The coconut crab (Birgus latro), an endangered marine-dispersed crustacean, is facing severe and probably accelerating population extinction worldwide, but biological information on its conservation remains deficient. In order to reveal the genetic structure of B. latro, 10 microsatellite loci were developed. A high degree of polymorphism was observed with a mean number of alleles per locus of 16.9. The mean expected heterozygosities were also high, ranging from 0.742 to 0.965. The observed heterozygosities ranged from 0.210 to 0.925. Departures from Hardy-Weinberg equilibrium were observed at five loci after the Bonferroni correction. These hypervariable markers will be utilized to study the genetic diversity and conservation of B. latro throughout its distribution range in the Pacific and Indian Oceans.     

The positive charge at Lys-288 of the glucagon-like peptide-1 (GLP-1) receptor is important for binding the N-terminus of peptide agonists

Lysine-288 in the glucagon-like peptide-1 receptor was predicted to be ideally positioned to play a role in hormone binding. Subsequent mutation of Lys-288 to Ala or Leu greatly reduced hormone affinity, while substitution with Arg had minimal effect. Compared to wild type, the Lys288-Ala receptor had a reduced affinity for three peptide ligands with complete N-terminal sequences but not for their N-truncated analogues. Hence, the role of this positively charged residue, which is conserved at the equivalent position in all other Family B receptors, was determined to be important for receptor interaction with the N-terminal eight residues of peptide agonists.