Cyclic guanosine monophosphate responses to atrial natriuretic factor, brain natriuretic peptide, but not C-type natriuretic peptide, and the characterization of their receptors in rat medullary thick ascending limb

The effects of atrial natriuretic factor (ANF), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) on renal medullary thick ascending limb (mTAL) have not been fully understood. The aim of this study is to examine the second-messenger responses of rat mTAL to ANF, BNP, and CNP. Characterizations of the ANF, BNP, and CNP receptors in mTAL were also performed by radioligand studies. Results showed that ANF and BNP were both capable of eliciting cyclic guanosine monophosphate (cGMP) responses in mTAL. Conversely, no cGMP response was observed upon stimulation by CNP in mTAL. The presence of ANF receptors was demonstrated by radioligand studies. One receptor site was found, and the Kd and maximum binding capacity were 4.0 +/- 0.45 nmol/L and 277.8 +/- 47.7 fmol/mg protein, respectively. BNP receptors were also found in mTAL, and ANF and BNP were sharing the same receptor. On the contrary, no CNP receptor could be shown by radioligand studies. These results suggest that guanylyl cyclase-coupled receptors (atrial natriuretic peptide receptor-A [ANPR-A]) specific for ANF and BNP are present in rat mTAL, while those for CNP (ANPR-B) are absent. ANF and BNP but not CNP act on mTAL to control water excretion.     

Genomic analysis reveals chromosomal variation in natural populations of the uncultured psychrophilic archaeon Cenarchaeum symbiosum

Molecular phylogenetic surveys have recently revealed an ecologically widespread crenarchaeal group that inhabits cold and temperate terrestrial and marine environments. To date these organisms have resisted isolation in pure culture, and so their phenotypic and genotypic characteristics remain largely unknown. To characterize these archaea, and to extend methodological approaches for characterizing uncultivated microorganisms, we initiated genomic analyses of the nonthermophilic crenarchaeote Cenarchaeum symbiosum found living in association with a marine sponge, Axinella mexicana. Complex DNA libraries derived from the host-symbiont population yielded several large clones containing the ribosomal operon from C. symbiosum. Unexpectedly, cloning and sequence analysis revealed the presence of two closely related variants that were consistently found in the majority of host individuals analyzed. Homologous regions from the two variants were sequenced and compared in detail. The variants exhibit >99.2% sequence identity in both small- and large-subunit rRNA genes and they contain homologous protein-encoding genes in identical order and orientation over a 28-kbp overlapping region. Our study not only indicates the potential for characterizing uncultivated prokaryotes by genome sequencing but also identifies the primary complication inherent in the approach: the widespread genomic microheterogeneity in naturally occurring prokaryotic populations.     

Detection of protein A produced by Staphylococcus aureus with a fiber-optic-based biosensor

Staphylococcus aureus is a pathogen important in causing human infections and intoxication. A sensitive fiber-optic that produces evanescent waves was developed for the detection of protein A, a product secreted only by S. aureus. In the immunosensor, a 40-mV argon-ion laser that generated laser light at 488 nm was used together with plastic optical fiber and antibodies to protein A were physically adsorbed onto the fiber. The principle of the detection involved a sandwich immunoassay with fluorescein isothiocyanate conjugated with anti-(protein A) immunoglobulin G to produce signals of the antigen-antibody reaction. The detection limit was 1 ng of protein A per milliliter. The fiber-optic immunosensor could be used for rapid and specific detection of S. aureus in clinical specimens and foods.     

Identification of race and sex from palate dimensions

Measurements of the width and depth of the palate were used to predict the race (American black or white) or sex or both of an individual. The sample consisted of 332 living subjects with permanent dentitions, and measurements were made between cusp tips, so palate size includes bony and dental components. Blacks, with a more square palate, were distinguished from whites primarily by greater interpremolar widths and P1-to-M2 depths. Simultaneous prediction of race and sex had a correct classification of 48%, which is about twice that expected from chance. Pooling the two sex increases correct classification of race to 83%. Formulas also are provided for each variable separately to accommodate fragmentary remains. Resilience of palatal structures to traumatic and natural forces makes this method practical in several forensic situations.     

Using learning communities to teach technical communication inaccounting

The paper describes the implementation of a learning community involving a technical communication course and an accounting course. Students are simultaneously registered in all the courses constituting the learning community. The learning community approach to writing instruction can be viewed as one way to implement writing across the curriculum with the following distinguishing features. First, students are registered simultaneously for both courses; the communication skills taught in one course are simultaneously reinforced in another course. Second, the faculty of the two courses interact extensively to deliver skills (e.g., communication skills) in a coherent manner across the two courses. We describe the development of a theoretical framework for connecting the two courses. This theoretical framework guided implementation decisions such as the choice of communication skills to be covered in the accounting course, the design of assignments, and the design of evaluation criteria. While we focus on the integration of an accounting course with a communication course, the learning community approach and the implementation steps are applicable to other disciplines     

Clinical predictors of HIV-1 infection among preschool children in Dar es Salaam, Tanzania

Seroprevalence of HIV-1 infection was determined in children aged between eighteen months and five years, attending maternal and child health (MCH) clinics in Dar es Salaam, Tanzania. A total of 889 children were eligible for the study, however seven children could not be enrolled because their mothers/guardians absconded and blood could not be drawn from 21 children due to refusal of mothers/guardians and from another 12 children due to technical reasons. Therefore, the participation rate was 95.5%. Of the 849 children screened, 14 (1.65%) were found to have IgG anti HIV-1 antibodies in their sera. The main clinical features found in children with symptomatic HIV-1 disease were weight loss, generalized lymphadenopathy, recurrent fevers, and prolonged diarrhoea. The utility of clinical features suggestive of HIV-1 infection (according to CDC classification) in identifying HIV-1 infection in children was evaluated and found to have high sensitivity (100%), specificity (96.9%) and negative predictive value (100%), but a low positive predictive value (35%). Marked variations in progression to symptomatic phase were noted, whereby some relatively young children had progressed to symptomatic phase (CDC class P-2A), while some older children were still in the asymptomatic stage (CDC class P-1 C). None of the symptomatic HIV-1 infected children presented with neurological disease, severe opportunistic infections, or malignancies. Although reduced mid-upper arm circumference and weight-for-age were associated with HIV seropositivity, these clinical parameters had low positive predictive values compared to the CDC classification.