Hydrodynamic perception in true seals (Phocidae) and eared seals (Otariidae)

Pinnipeds, that is true seals (Phocidae), eared seals (Otariidae), and walruses (Odobenidae), possess highly developed vibrissal systems for mechanoreception. They can use their vibrissae to detect and discriminate objects by direct touch. At least in Phocidae and Otariidae, the vibrissae can also be used to detect and analyse water movements. Here, we review what is known about this ability, known as hydrodynamic perception, in pinnipeds. Hydrodynamic perception in pinnipeds developed convergently to the hydrodynamic perception with the lateral line system in fish and the sensory hairs in crustaceans. So far two species of pinnipeds, the harbour seal (Phoca vitulina) representing the Phocidae and the California sea lion (Zalophus californianus) representing the Otariidae, have been studied for their ability to detect local water movements (dipole stimuli) and to follow hydrodynamic trails, that is the water movements left behind by objects that have passed by at an earlier point in time. Both species are highly sensitive to dipole stimuli and can follow hydrodynamic trails accurately. In the individuals tested, California sea lions were clearly more sensitive to dipole stimuli than harbour seals, and harbour seals showed a superior trail following ability as compared to California sea lions. Harbour seals have also been shown to derive additional information from hydrodynamic trails, such as motion direction, size and shape of the object that caused the trail (California sea lions have not yet been tested). The peculiar undulated shape of the harbour seals’ vibrissae appears to play a crucial role in trail following, as it suppresses self-generated noise while the animal is swimming.     

Organellar Na+/H+ exchangers: novel players in organelle pH regulation and their emerging functions

Mammalian Na+/H+ exchangers (NHEs) play a fundamental role in cellular ion homeostasis. NHEs exhibit an appreciable variation in expression, regulation, and physiological function, dictated by their dynamics in subcellular localization and/or interaction with regulatory proteins. In recent years, a subgroup of NHEs consisting of four isoforms has been identified, and its members predominantly localize to the membranes of the Golgi apparatus and endosomes. These organellar NHEs constitute a family of transporters with an emerging function in the regulation of luminal pH and in intracellular membrane trafficking as expressed, for example, in cell polarity development. Moreover, specific roles of a variety of cofactors, regulating the intracellular dynamics of these transporters, are also becoming apparent, thereby providing further insight into their mechanism of action and overall functioning. Interestingly, organellar NHEs have been related to mental disorders, implying a potential role in the brain, thus expanding the physiological significance of these transporters.     

Semi-rational engineering of an amino acid racemase that is stabilized in aqueous/organic solvent mixtures

Enzymes are industrially applied under increasingly diverse environmental conditions that are dictated by the efforts to optimize overall process efficiency. Engineering the operational stability of biocatalysts to enhance their half-lives under the desired process conditions is a widely applied strategy to reduce costs. Here, we present a simple method to enhance enzyme stability in the presence of monophasic aqueous/organic solvent mixtures based on the concept of strengthening the enzyme's surface hydrogen-bond network by exchanging surface-located amino acid residues for arginine. Suitable residues are identified from sequence comparisons with homologous enzymes from thermophilic organisms and combined using a shuffling approach to obtain an enzyme variant with increased stability in monophasic aqueous/organic solvent mixtures. With this approach, we increase the stability of the broad-spectrum amino acid racemase of Pseudomonas putida DSM 3263 eightfold in mixtures with 40% methanol and sixfold in mixtures with 30% acetonitrile.     

How do elevated levels of testosterone affect the function of the human fallopian tube and fertility?—New insights

Excess testosterone levels affect up to 20% of the female population worldwide and are a key component in the pathogenesis of polycystic ovary syndrome. However, little is known about how excess testosterone affects the function of the human fallopian tube—the site of gamete transport, fertilization, and early embryogenesis. Therefore, this study aimed to characterize alterations caused by long‐term exposure to male testosterone levels. For this purpose, the Fallopian tubes of nine female‐to‐male transsexuals, who had been undergoing testosterone treatment for 1–3 years, were compared with the tubes of 19 cycling patients. In the ampulla, testosterone treatment resulted in extensive luminal accumulations of secretions and cell debris which caused ciliary clumping and luminal blockage. Additionally, the percentage of ciliated cells in the ampulla was significantly increased. Transsexual patients, who had had sexual intercourse before surgery, showed spermatozoa trapped in mucus. Finally, in the isthmus complete luminal collapse occurred. Our results imply that fertility in women with elevated levels of testosterone is altered by tubal luminal obstruction resulting in impaired gamete transport and survival.     

Synthesis of ω-hydroxy dodecanoic acid based on an engineered CYP153A fusion construct

A bacterial P450 monooxygenase-based whole cell biocatalyst using Escherichia coli has been applied in the production of ω-hydroxy dodecanoic acid from dodecanoic acid (C12-FA) or the corresponding methyl ester. We have constructed and purified a chimeric protein where the fusion of the monooxygenase CYP153A from Marinobacter aquaeloei to the reductase domain of P450 BM3 from Bacillus megaterium ensures optimal protein expression and efficient electron coupling. The chimera was demonstrated to be functional and three times more efficient than other sets of redox components evaluated. The established fusion protein (CYP153A_{M. aq.}-CPR) was used for the hydroxylation of C12-FA in in vivo studies. These experiments yielded 1.2 g l^–1 ω-hydroxy dodecanoic from 10 g l^–1 C12-FA with high regioselectivity (> 95%) for the terminal position. As a second strategy, we utilized C12-FA methyl ester as substrate in a two-phase system (5:1 aqueous/organic phase) configuration to overcome low substrate solubility and product toxicity by continuous extraction. The biocatalytic system was further improved with the coexpression of an additional outer membrane transport system (AlkL) to increase the substrate transfer into the cell, resulting in the production of 4 g l^–1 ω-hydroxy dodecanoic acid. We further summarized the most important aspects of the whole-cell process and thereupon discuss the limits of the applied oxygenation reactions referring to hydrogen peroxide, acetate and P450 concentrations that impact the efficiency of the production host negatively.     

Care-Seeking and Management of Common Childhood Illnesses in Tanzania – Results from the 2010 Demographic and Health Survey

Background

Malaria, pneumonia and diarrhoea continue to kill millions of children in Africa despite the available and effective treatments. Correct diagnosis and prompt treatment with effective drugs at the first option consulted for child care is crucial for preventing severe disease and death from these illnesses. Using the 2010 Demographic and Health Survey data, the present study aims to assess care-seeking and management of suspected malaria, pneumonia and diarrhoea at various health care facilities in Tanzania.

Methods

We analyzed data for 8176 children born within a 5 years period preceding the survey.The information was collected by interviewing 5519 women aged 15–49 years in 10,300 households selected from 475 sample points throughout Tanzania.

Results

The most common first option for child care was PHC facilities (54.8%), followed by private pharmacies (23.4%). These were more commonly utilized in rural compared to urban areas: 61.2% versus 34.5% for PHC facilities, and 26.5% versus 17.7% for pharmacies. Women in urban areas and those with higher level of education more commonly utilized higher level hospitals and private facilities as their first option for child care. Only one in four children with fever had received a blood test during the illness with lowest proportion being reported among children solely attended at PHC facilities. Use of abandoned antimalarial drugs for the treatment of suspected malaria was also observed in public health facilities and antibiotics use for diarrhoea treatment was high (49.0%).

Conclusions

PHC facilities and pharmacies most commonly provided sub-optimal care. These facilities were more commonly utilized as the first option for child care in rural areas and among the poor and non-educated families. These are groups with the highest child mortality, which calls for interventions’ targeting improvement of care at these facilities to further reduce child mortality from treatable illnesses in Tanzania.     

TAP Mediates Import of Mycobacterium tuberculosis-Derived Peptides into Phagosomes and Facilitates Loading onto HLA-I

Processing and presentation of antigen on MHC-I class I molecules serves to present peptides derived from cytosolic proteins to CD8⁺ T cells. Infection with bacteria that remain in phagosomal compartments, such as Mycobacterium tuberculosis (Mtb), provides a challenge to this immune recognition as bacterial proteins are segregated from the cytosol. Previously we identified the Mtb phagosome itself as an organelle capable of loading MHC Class I molecules with Mtb antigens. Here, we find that the TAP transporter, responsible for importing peptides into the ER for loading in Class I molecules, is both present and functional in Mtb phagosomes. Furthermore, we describe a novel peptide reagent, representing the N-terminal domain of the bovine herpes virus UL49.5 protein, which is capable of specifically inhibiting the lumenal face of TAP. Together, these results provide insight into the mechanism by which peptides from intra-phagosomal pathogens are loaded onto Class I molecules.