Patterns of sequence variation in the mitochondrial D-loop region of shrews

Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews (genus Sorex) for the region between the tRNA(Pro) and the conserved sequence block-F revealed variable numbers of 79-bp tandem repeats. These repeats were found in all 19 individuals sequenced, representing three subspecies and one closely related species of the masked shrew group (Sorex cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an adjacent 76-bp imperfect copy of the tandem repeats. One individual was heteroplasmic for length variants consisting of five and seven copies of the 79-bp tandem repeat. The sequence of the repeats is conducive to the formation of secondary structure. A termination-associated sequence is present in each of the repeats and in a unique sequence region 5' to the tandem array as well. Mean genetic distance between the masked shrew taxa and the pygmy shrew was calculated separately for the unique sequence region, one of the tandem repeats, the imperfect repeat, and these three regions combined. The unique sequence region evolved more rapidly than the tandem repeats or the imperfect repeat. The small genetic distance between pairs of tandem repeats within an individual is consistent with a model of concerted evolution. Repeats are apparently duplicated and lost at a high rate, which tends to homogenize the tandem array. The rate of D- loop sequence divergence between the masked and pygmy shrews is estimated to be 15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid sequence evolution in shrews may be due either to their high metabolic rate and short generation time or to the presence of variable numbers of tandem repeats.      

Comparison of gastric and intestinal antisecretory and protective effects of prostacyclin and its stable thia-amino-analogue (HOE 892) in consious rats

The effects of prostacyclin (PGI₂) and its stable thia-thimo-analogue (Hoe 892) on gastric and intestinal secretions and gastric mucosal lesions have been determined in conscious rats. Both PGI₂ and Hoe 892 given subcutaneously (s.c.) reduced dose-dependent gastric acid secretion, the ID₅₀ (dose producing 50% inhibition) being about 48.6 and 11.8 gmg/kg, respectively. In contrast, intragastric (i.g.) PGI₂ and Hoe 892 did not cause any change in gastric acid secretion at doses ranging from 1 to 100 gmg/kg. Both PGI₂ and Hoe 892 reduced significantly intestinal fluid secretion (antienteropooling activity). PGI₂ and Hoe 892 given i.g. or s.c. reduced dose-dependent gastric ulcer formation induced by acidified aspirin (ASA), Hoe 892 being somewhat less potent than PGI₂. Both PGI₂ and Hoe 892 were equally effective against mucosal necrosis induced by absolute ethanol and this effect was observed both after i.g. and s.c. administration of these agents. We conclude that stable thia-amino-PGI₂ analogue, Hoe 892, has similar gastric and intestinal antisecretory and protective activity as PGI₂ and may be useful in the prevention of gastric damage by various noxious agents.     

Clinical training in human immunodeficiency virus disease for community physicians. The Los Angeles experience.

In the past decade, the increased number of persons being treated for infection with the human immunodeficiency virus (HIV) has placed an enormous burden on specialty clinics. This is especially true in Los Angeles, where care of patients with the acquired immunodeficiency syndrome (AIDS) has been termed a "crisis" situation. Especially in its early stages, HIV disease can be appropriately managed by primary care physicians who provide patients with medical and psychological counseling and refer them to specialists when major AIDS-related complications develop. Physicians completing their training as recently as 5 years ago, however, received little systematic preparation in the care of HIV-infected patients and thus may lack important skills such as the ability to recognize opportunistic infections early in their course. By means of a 1-week intensive preceptorship in a high-volume AIDS clinic, we are preparing community physicians to assume a more active role in providing care for this growing patient population. In the preceptorship, participants receive one-on-one training from specialists in infectious diseases, pulmonary diseases, and hematology and oncology, as well as from internists and family physicians. Evaluation of the clinical experience demonstrated a greater level of confidence on the part of program participants in treating HIV-infected patients and showed that participants screen and test high-risk patients in their practices and devote a substantial proportion of their practices to caring for HIV-infected patients.     

Modeling interactions between voltage-gated Ca2+ channels and KCa1.1 channels

High voltage-activated (HVA) Cav channels form complexes with KCa1.1 channels, allowing reliable activation of KCa1.1 current through a nanodomain interaction. We recently found that low voltage-activated Cav3 calcium channels also create KCa1.1-Cav3 complexes. While coimmunoprecipitation studies again supported a nanodomain interaction, the sensitivity to calcium chelating agents was instead consistent with a microdomain interaction. A computational model of the KCa1.1-Cav3 complex suggested that multiple Cav3 channels were necessary to activate KCa1.1 channels, potentially causing the KCa1.1-Cav3 complex to be more susceptible to calcium chelators. Here, we expanded the model and compared it to a KCa1.1-Cav2.2 model to examine the role of Cav channel conductance and kinetics on KCa1.1 activation. As found for direct recordings, the voltage-dependent and kinetic properties of Cav3 channels were reflected in the activation of KCa1.1 current, including transient activation from lower voltages than other KCa1.1-Cav complexes. Substantial activation of KCa1.1 channels required the concerted activity of several Cav3.2 channels. Combined with the effect of EGTA, these results suggest that the Ca²⁺ domains of several KCa1.1-Cav3 complexes need to cooperate to generate sufficient [Ca²⁺]_i, despite the physical association between KCa1.1 and Cav3 channels. By comparison, Cav2.2 channels were twice as effective at activating KCa1.1 channels and a single KCa1.1-Cav2.2 complex would be self-sufficient. However, even though Cav3 channels generate small, transient currents, the regulation of KCa1.1 activity by Cav3 channels is possible if multiple complexes cooperate through microdomain interactions.     

Calcium dynamics during fertilization in C. elegans

Background

Of the animals typically used to study fertilization-induced calcium dynamics, none is as accessible to genetics and molecular biology as the model organism Caenorhabditis elegans. Motivated by the experimental possibilities inherent in using such a well-established model organism, we have characterized fertilization-induced calcium dynamics in C. elegans.

Results

Owing to the transparency of the nematode, we have been able to study the calcium signal in C. elegans fertilization in vivo by monitoring the fluorescence of calcium indicator dyes that we introduce into the cytosol of oocytes. In C. elegans, fertilization induces a single calcium transient that is initiated soon after oocyte entry into the spermatheca, the compartment that contains sperm. Therefore, it is likely that the calcium transient is initiated by contact with sperm. This calcium elevation spreads throughout the oocyte, and decays monotonically after which the cytosolic calcium concentration returns to that preceding fertilization. Only this single calcium transient is observed.

Conclusion

Development of a technique to study fertilization induced calcium transients opens several experimental possibilities, e.g., identification of the signaling events intervening sperm binding and calcium elevation, identifying the possible roles of the calcium elevation such as the completion of meiosis, the formation of the eggshell, and the establishing of the embryo's axis of symmetry.     

Novel voltammetric biosensor for determining acrylamide in food samples

Recent findings showing that acrylamide is formed in heat-treated foods rich in asparagine and reducing sugars such as glucose, have accelerated the needs for the development of new analytical methods to determine this potential human carcinogen. Acrylamide forms adduct with hemoglobin (Hb) as a result of the reaction with the alpha-NH2 group of N-terminal valine of Hb. This interaction is the basis of a new voltammetric biosensor to detect acrylamide. The biosensor was constructed using a carbon-paste electrode modified with hemoglobin (Hb), which contains four prosthetic groups of heme--Fe(III). Such an electrode displays a reversible reduction/oxidation process of Hb-Fe(III)/Hb-Fe(II). Interaction between Hb and acrylamide was observed through decreasing of the peak current of Hb-Fe(III) reduction. The electrodes presented a very low detection limit (1.2 x 10(-10)M). The validation made in the matrix obtained by water extraction of potato chips showed that the electrodes presented are suitable for the direct determination of acrylamide in food samples.     

Distribution of amiloride-sensitive sodium channels in the oral cavity of the hamster

The distribution of amiloride-sensitive sodium channels (ASSCs) in taste buds isolated from the oral cavity of hamsters was assessed by patch clamp recording. In contrast to the case for rats, taste cells from the fungiform, foliate and vallate papillae and from the soft palate all contain functional ASSCs. The differential distribution of ASSCs between the hamster and the rat may be important for understanding the physiology underlying the differing behavioral responses of these species to sodium salts.      

Synthesis, structure and electron-mediator properties of the mono- and difunctionalized macrobicyclic iron(II) tris-dioximates with thiol terminated ribbed spacer substituents

Nucleophilic substitution of the reactive chlorine atoms of mono- and dichlorine clathrochelate FeBd₂(HGmCl)(BF)₂ and FeBd₂(Cl₂Gm)(BF)₂ precursors (where Bd²⁻, HGmCl²⁻ and Cl₂Gm²⁻ are α-benzyldioxime, chloroglyoxime and dichloroglyoxine dianions, respectively) with HSCH₂CH₂SH and (HSCH₂CH₂)₂S in the presence of triethylamine afforded the FeBd₂(HGmSCH₂CH₂SH)(BF)₂ (1) and FeBd₂(HGm(SCH₂CH₂)₂SH)(BF)₂ clathrochelates with a sole thiol terminated spacer substituent and the FeBd₂((HS(CH₂CH₂S)₂)₂Gm)(BF)₂ clathrochelate with two longchain thiol-sulfide ribbed groups. The crystal and molecular structures of these complexes were obtained by X-ray crystallography. The clathrochelate molecules possess a geometry intermediate between a trigonal prism (TP) and a trigonal antiprism (TAP). The X-ray data are in a good agreement with the ⁵⁷Fe Mössbauer parameters for complexes studied. These parameters characterize them as the low-spin iron(II) complexes (the isomeric shift values) with TP-TAP geometry (the quadrupole splitting values). Application of clathrochelate self-assembled monolayer (SAM) as the redox mediators for the determination of hydrogen peroxide is discussed. The calibration curve for hydrogen peroxide concentrations was found to be in the range from 2.0 · 10⁻⁶ to 1.6 · 10⁻⁵ mol · L⁻¹ with limit of detection equal to 1.0 · 10⁻⁶ mol · L⁻¹. The clathrochelate SAM on gold electrode provides precise and sensitive amperometric determination of hydrogen peroxide.