Weak acid accumulation in the serosal extracellular compartment of the frog gastric mucosa

The dimethyloxazolidine dione distribution in the extracellular compartments of the frog gastric mucosa was analyzed by washout kinetics. The volumes of the two extracellular compartments, serosal and mucosal, were estimated by inulin washout as $\text{0.435 ± 0.019}$ and $\text{0.176 ± 0.018 μl/μl}$ tissue water, respectively. In the serosal extracellular space, significant dimethyloxazolidine dione accumulations of $\text{2.63 ± 0.25}$, $\text{2.28 ± 0.16}$, and $\text{1.86 ± 0.08}$ times that of the bathing media were found for bathing solutions with pH values of 6.9, 7.4, and 7.9 respectively. A high pH of the serosal extracellular fluid by itself could not account for the high values of dimethyloxazolidine dione accumulation. A difference in the total dimethyloxazolidine dione accumulation requires: (a) the existence of differences in the pH values and also the existence of a difference in the diffusion coefficient of the two forms of dimethyloxazolidine dione; or (b), a binding of one of the two forms, i.e., binding of dimethyloxazolidine dione form by fixed charges.     

Exchange between inorganic phosphate and adenosine triphosphate in (Na+,K+)-ATPase

(Na⁺,K⁺)-ATPase is able to catalyze a continuous ATP?P_i exchange in the presence of Na⁺ and in the absence of a transmembrane ionic gradient. At pH 7.6 the Na⁺ concentration required for half-maximal activity is 85 mM and at pH 5.1 it is 340 mM. In the presence of optimal Na⁺ concentration, the rate of exchange is maximal at pH 6.0 and varies with ADP and P_i concentration in the assay medium. ATP?P_i exchange is inhibited by K⁺ and by ouabain.     

Flowering process in soybean under water deficit conditions: A review on genetic aspects

Soybean is a key crop in many countries, being used from human food to the animal industry due to its nutritional properties. Financially, the grain chain moves large sums of money into the economy of producing countries. However, like other agricultural commodities around the world, it can have its final yield seriously compromised by abiotic environmental stressors, like drought. As flowers imply in pods and in grains inside it to minimize damages caused by water restriction, researchers have focused on understanding flowering-process related genes and their interactions. Here a review dedicated to the soybean flowering process and gene network involved in it is presented, describing gene interactions and how genes act in this complex mechanism, also ruled by environmental triggers such as day-light and circadian cycle. The objective was to gather information and insights on the soybean flowering process, aiming to provide knowledge useful to assist in the development of drought-tolerant soybean lines, minimizing losses due to delays or anticipation of flowering and, consequently, restraining financial and productivity losses.     

Comparison of the human with the sheep genomes by use of human chromosome-specific painting probes

Human chromosome specific painting probes were hybridized on sheep (Ovis aries, 2n = 54) chromosomes by FISH. The painting results on sequentially stained RBA-banded preparations demonstrated high degree of conserved regions between human and sheep genomes. A total of 48 human chromosome segments were detected in sheep chromosomes. Comparisons with sheep gene mapping data available and previous Zoo-FISH data obtained in sheep, cattle, and river buffalo were performed. Received: 13 October 1998 / Accepted: 18 February 1999     

A procolophonoid reptile with temporal fenestration from the Middle Triassic of Brazil

The small tetrapod Candelaria barbouri, from the Middle Triassic of southern Brazil, is the first example of an owenettid procolophonoid outside Africa and Madagascar. Candelaria barbouri was originally described as a primitive procolophonid; however, a re-examination of the holotype, as well as new material, reveals that C. barbouri is in fact the youngest member of the Owenettidae, extending the chronological range of the group by more than 10 million years. The recognition of C. barbouri as an owenettid points to a broader diversity and distribution for owenettids than hitherto thought. In addition, C. barbouri is the first member of the Owenettidae to exhibit temporal fenestrae, a discovery that draws attention to the significance of this feature in 'anapsid' reptiles.     

Heat of PPi hydrolysis varies depending on the enzyme used. Yeast and corn vacuolar pyrophosphatase

With yeast-soluble inorganic pyrophosphatase, the heat released during PP(i) hydrolysis was -6.3 kcal/mol regardless of the KCl concentration in the medium. With the membrane-bound pyrophosphatase of corn vacuoles, the heat released varies between -23.5 and -7.5 kcal/mol depending on the KCl concentration in the medium and whether or not a H(+) gradient is formed across the vacuole membranes. The data support the proposal that enzymes are able to handle the energy derived from phosphate compound hydrolysis in such a way as to determine the parcel that is used for work and the fraction that is converted into heat.     

Comparison between the surface plasmon resonance (SPR) and the quartz crystal microbalance (QCM) method in a structural analysis of human endothelin-1

In this study, an automated surface plasmon resonance (SPR)-based biosensor was compared with a quartz crystal microbalance (QCM) biosensor. The two biosensor systems were used for characterizing a site-directed monoclonal antibody (mAb), raised against the C-terminal heptapeptide ET-1_15–21 of the human endothelin (ET-1). The mAb was characterized by its capacity for binding to ET-1, ET-3, Big.ET-1_22–38, the C-terminal (ET-1_15–21, ET-1_16–21, ET-1_17–21), and six derivates of ET-1_16–21, each containing a substitution with alanine (Ala) of a single aminoacid from position 16–21, respectively. The mAb reacted well with ET-1 and its fragments ET-1_15–21, ET-1_16–21, ET-1_17–21, but showed only a partial cross-reaction with ET-3, and did not bind human Big.ET-1_22–38. The Ala substitution on position 16,17, or 19 of ET-1_16–21 did not affect the antibody binding capacity of the hexapaptide ET-1_16–21. On the contrary, Ala substitution or Asp¹⁸, Ile²⁰ and particularly Trp²¹, inhibited its immunoreactivity. Thus the C-terminal represents an immunodominant epitope in ET-1 and is important for antibody binding. The SPR and QCM response signals were similar in shape but differing in time scales, reflecting differences in detection mechanisms. With regard to the fundamental problem of comparing different measurement principles, we found a good correlation between results obtained using the BIA technology and the QCM.     

Thyroid hormones differentially regulate the distribution of rabbit skeletal muscle Ca(2+)-ATPase (SERCA) isoforms in light and heavy sarcoplasmic reticulum

The sarcoplasmic reticulum (SR) is composed of two fractions, the heavy fraction that contains proteins involved in Ca2+ release, and the light fraction enriched in Ca(2+)-ATPase (SERCA), an enzyme responsible for Ca2+ transport from the cytosol to the lumen of SR. It is known that in red muscle thyroid hormones regulate the expression of SERCA 1 and SERCA 2 isoforms. Here we show the effects of thyroid hormone on SERCA expression and distribution in light and heavy SR fractions from rabbit white and red muscles. In hyperthyroid red muscle there is an increase of SERCA 1 and a decrease of SERCA 2 expression. This is far more pronounced in the heavy than in the light SR fraction. As a result, the rates of Ca(2+)- ATPase activity and Ca(2+)-uptake by the heavy vesicles are increased. In hypothyroidism we observed a decrease in SERCA 1 and no changes in the amount of SERCA 2 expressed. This promoted a decrease of both Ca(2+)-uptake and Ca(2+)-ATPase activity. While the major differences in hyperthyroidism were found in the heavy SR fraction, the effects of hypothyroidism were restricted to light SR fraction. In white muscle we did not observe any significant changes in either hypo- or hyperthyroidism in both SR fractions. Thus, the regulation of SERCA isoforms by thyroid hormones is not only muscle specific but also varies depending on the subcellular compartment analyzed. These changes might correspond to the molecular basis of the altered contraction and relaxation rates detected in thyroid dysfunction.     

Use of meta-analysis to combine candidate gene association studies: application to study the relationship between the ESR PvuII polymorphism and sow litter size

This article investigates the application of meta-analysis on livestock candidate gene effects. The PvuII polymorphism of the ESR gene is used as an example. The association among ESR PvuII alleles with the number of piglets born alive and total born in the first (NBA1, TNB1) and later parities (NBA, TNB) is reviewed by conducting a meta-analysis of 15 published studies including 9329 sows. Under a fixed effects model, litter size values were significantly lower in the "AA" genotype groups when compared with "AB" and "BB" homozygotes. Under the random effects model, the results were similar although differences between "AA" and "AB" genotype groups were not clearly significant for NBA and TNB. Nevertheless, the most noticeable result was the high and significant heterogeneity estimated among studies. This heterogeneity could be assigned to error sampling, genotype by environment interaction, linkage or epistasis, as referred to in the literature, but also to the hypothesis of population admixture/stratification. It is concluded that meta-analysis can be considered as a helpful analytical tool to synthesise and discuss livestock candidate gene effects. The main difficulty found was the insufficient information on the standard errors of the estimated genotype effects in several publications. Consequently, the convenience of publishing the standard errors or the concrete P-values instead of the test significance level should be recommended to guarantee the quality of candidate gene effect meta-analyses.