Evolution of the ATP-binding-cassette transmembrane transporters of vertebrates

The ATP-binding-cassette transmembrane transporters (ABC transporters) known from vertebrates belong to four major subfamilies: (1) the P- glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance regulators (CFTR); (3) the Tap proteins encoded with the major histocompatibility complex of mammals; and (4) the peroxisomal membrane proteins. Both Pgp and CFTR have a structure suggesting a past internal gene duplication; a phylogenetic analysis indicated that these duplications occurred independently, while an independent tandem gene duplication occurred in the case of the Tap family. Both the Pgp and Tap proteins show evidence of relationship to bacterial ABC transporters lacking internal duplication, and both are significantly more closely related to the HlyB and MsbA families of transporters from purple bacteria than they are to ABC transporters from nonpurple bacteria. The simplest hypothesis to explain this observation is that eukaryotic Pgp and Tap genes are descended from a mitochondrial gene or genes that were subsequently translocated to the nuclear genome. The Pgp genes of eukaryotes are characterized by a remarkable degree of convergent evolution between the ATP-binding cassettes of their N- terminal and C-terminal halves, whereas no such convergence is seen between the two halves of CFTR genes or between the duplicated Tap genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain not found in other ABC transporters apart from CFTR, showed high levels of both synonymous and nonsynonymous difference in comparisons among different mammalian species, suggesting that this region is a mutational hot spot.      

Evidence for the presence of β-lactamase inStreptomyces glaucescens and its inhibition by sodium clavulanate

Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis.     

Albumin-induced plasma volume expansion: diurnal and temperature effects

To develop a reliable procedure for the acute expansion of plasma volume (PV), 26 male volunteers were randomly assigned to either a thermoneutral (25 degrees C and 40% relative humidity) or hot-dry (37 degrees C and 25% relative humidity) environment; subsequently each subject was seated for at least 1 h and then infused intravenously with either 100 or 200 ml of a 25% albumin solution or 0.9% saline. On the day before each infusion, PV was estimated by dye dilution using indocyanine green. Net percent change in PV (using hematocrit and hemoglobin values) was calculated at 1, 3, 6, 9, 12, and 24 h postinfusion. The PV of subjects residing in the heat after a 100-ml saline infusion increased significantly over 1-h values at 6, 9, and 12 h postinfusion but not at 24 h. The same trend, although not significant, was apparent at room temperature. The data suggest a slow isooncotic circadian pattern of PV expansion and contraction. The infusion of hyperoncotic albumin produced rapid expansion of plasma volume. With the low dose (25 g) at 1 h postinfusion, the expansion was 379 +/- 102 ml in the heat and 301 +/- 160 ml at room temperature. With the high dose (50 g) at 1 h postinfusion, the expansion was 479 +/- 84 ml in the heat and 427 +/- 147 ml at room temperature. The high dose produced an expansion that persisted for at least 9 h in subjects in either environment. The data suggest a mechanism for the retention of fluid during heat acclimatization and a useful procedure for plasma volume expansion in humans.     

Normal acid-base status of arterial blood from the conscious, chair-restrained squirrel monkey.

Normal acid-base status of arterial blood (pHa =7.40, PaCO2=38.1 Torr) was demonstrated for conscious, restrained squirrel monkeys when environmental stimuli were minimized and monkeys are habituated to experimental procedures. These results indicate the potential for using squirrel monkeys in experiments in which normal acid-base status is a significant factor.     

Application and comparison of silver intensification methods for the diaminobenzidine and diaminobenzidine-nickel endproduct of the peroxidation reaction in immunohistochemistry and in situ hybridization.

Silver-intensification methods described in the literature for the diaminobenzidine (DAB) and diaminobenzidine-nickel (DAB/Ni) endproduct of the peroxidase reaction were compared in model systems after immunoperoxidase and in situ hybridization. First, these methods were compared in immunohistochemical model systems, using the demonstration of glial fibrillar acidic protein (GFAP) and prostate-specific antigen (PSA) in paraffin sections of human brain and prostate tissue, respectively. When DAB without Ni was used as substrate, tissue argyrophilia caused considerable background staining. Only when this tissue reactivity was quenched with, e.g., CuSO4 with H2O2 or thioglycolic acid, were the results acceptable. A considerable improvement in the signal-to-noise ratio could be obtained when nickel was included in the substrate mixture. The methods that proved to be best for demonstration of GFAP and PSA made use of acid developer solutions. Subsequently, these methods were compared with other sensitive immunostaining methods for demonstration of the gamma-delta T-cell receptor in frozen lymphoid tissue. In this model a considerable increase in the number of positive cells could be obtained using silver intensification. The different methods using DAB/Ni were also compared for use in DNA in situ hybridization (DISH). In this case two model systems were used: human papilloma virus type 11 (HPV-11) DNA in condyloma tissue (abundant target model) and Epstein-Barr virus (EBV) DNA in a mononucleosis lymph node (low target model). For demonstration of HPV-11, all methods gave more or less satisfactory results, which were best with the acid developer solutions. Moreover, for demonstration of EBV DNA, a signal could be obtained only with these developer solutions. Such a method also proved suitable in double immuno-hybrido stainings for the demonstration of EBV DNA in specific antigen-positive Reed-Sternberg cells in paraffin sections of Hodgkin lymph nodes.     

Three-Dimensional Trabecular Alignment Model

The Shear-slip Mesh Update Method (SSMUM) is being used in flow simulations involving large but regular displacements of one or more boundaries of the computational domain. We follow up the earlier discussion of the method with notes on practical implementation aspects. In order to establish a benchmark problem for this class of flow problems, we define and report results from a two-dimensional viscous flow around a rotating stirrer in a square chamber. The application potential of the method is demonstrated in the context of biomedical design problem, as we perform an analysis of blood flow in a centrifugal left ventricular assist device, or blood pump, which involves a rotating impeller in a non-axisymmetric housing.     

CURRICULUM GUIDE FOR RESEARCH ETHICS WORKSHOPS FOR COUNTRIES IN THE MIDDLE EAST

To help ensure the ethical conduct of research, many have recommended educational efforts in research ethics to investigators and members of research ethics committees (RECs). One type of education activity involves multi‐day workshops in research ethics. To be effective, such workshops should contain the appropriate content and teaching techniques geared towards the learning styles of the targeted audiences. To ensure consistency in content and quality, we describe the development of a curriculum guide, core competencies and associated learning objectives and activities to help educators organize research ethics workshops in their respective institutions. The curriculum guide is divided into modular units to enable planners to develop workshops of different lengths and choose content materials that match the needs, abilities, and prior experiences of the target audiences. The content material in the curriculum guide is relevant for audiences in the Middle East, because individuals from the Middle East who participated in a Certificate Program in research ethics selected and developed the training materials (e.g., articles, powerpoint slides, case studies, protocols). Also, many of the activities incorporate active‐learning methods, consisting of group work activities analyzing case studies and reviewing protocols. The development of such a workshop training curriculum guide represents a sustainable educational resource to enhance research ethics capacity in the Middle East.