New substrates for the dicarboxylate transport system of Sinorhizobium meliloti

The dicarboxylate transport (Dct) system of Sinorhizobium meliloti, which is essential for a functional nitrogen-fixing symbiosis, has been thought to transport only dicarboxylic acids. We show here that the permease component of the Dct system, DctA, can transport orotate, a monocarboxylic acid, with an apparent K(m) of 1.7 mM and a V(max) of 163 nmol min(-1) per mg of protein in induced cells. DctA was not induced by the presence of orotate. The transport of orotate was inhibited by several compounds, including succinamic acid and succinamide, which are not dicarboxylic acids. The dicarboxylic acid maleate (cis-butenedioic acid) was not an inhibitor of orotate transport, which suggests that it was not recognized by DctA. However, maleate was an excellent inducer of DctA expression. Our evaluation of 17 compounds as inducers and inhibitors of transport suggests that substrates recognized by S. meliloti DctA must have appropriately spaced carbonyl groups and an extended conformation, while good inducers are more likely to have a curved conformation.     

Thyrotoxicosis: relations between clinical state and biochemical changes during carbimazole treatment.

The relation between clinical and biochemical changes in thyrotoxicosis were studied in 12 patients with Graves''s disease who were being treated with carbimazole. Clinical assessment (using the Crooks-Wayne index) was combined with the measurement of free thyroxine and triiodothyronine indices (FT4I and FT3I) and the assessment of two tissue markers of thyroid hormone action--sex-hormone-binding globulin (SHBG) levels and the thyrotrophin responses to TRH. In general the FT4I and FT3I fell rapidly once treatment was started, and returned to normal in one to four weeks, followed shortly by SHBG levels. The thyrotrophin response returned at this time in two patients, who still had borderline high levels of FT3I and SHBG. The clinical score fell more slowly and variably and was less closely related to any of the biochemical indices than these were to each other. During the early phase of treatment with antithyroid drug the clinical evaluation may be an unreliable indicator of persisting thyroid hormone excess, and when the patient seems clinically but not biochemically thyrotoxic the symptoms should be treated on their own merits with beta-blocking drugs and not with increased doses of antithyroid drugs.     

Structure and growth rates of the high-latitude coral: <Emphasis Type="Italic">Plesiastrea versipora</Emphasis>

The high-latitude coral species Plesiastrea versipora was investigated to identify growth rates in colonies over 1 m in diameter. Six colonies from two temperate gulfs (latitudes of 33°–35°S) in Southern Australia were examined using X-ray, luminescence and ²³⁸U/²³⁰Th dating techniques. Annual density bands were present in each coral but varied in width and definition, suggesting different linear extension and calcification rates. Differences in density band width were observed at the local scale (amongst colonies on the same reef) and regional scales (between the two gulfs). Extension rates of the P. versipora colonies examined in this study varied between 1.2 and 7 mm per year, which are amongst the slowest growth rates reported for hermatypic corals. As only one of the six P. versipora colonies had obvious luminescent banding, we conclude that luminescent banding is not an accurate chronological marker in this species of temperate water coral. Coral age estimates derived from counting density bands in X-radiographs ranged from 90 to 320 years for the six colonies studied. U-Th ages from the same colonies determined by high-precision multi-collector inductively coupled plasma mass spectrometer established radiometric ages between 105 and 381 years. The chronological variation in absolute ages between the two techniques varied between 2 and 19% in different colonies, with the lowest growth rates (~1 mm) displaying the greatest variation between density band age and radiometric U-Th age. This result implies that the age of P. versipora and other slow-growing corals cannot be determined accurately from density bands alone. The outcome of this research demonstrates that P. versipora may be useful as a paleoclimate archive, recording several centuries in a single colony in high-latitude environments (corals found in latitudes greater than 30° in either hemisphere), where other well-established coral climate archives, such as Porites, do not occur.     

Genetic Transfer of Episomic Elements Among Erwinia Species and Other Enterobacteria: F′lac+

The episomic element F'lac(+) was transferred, probably by conjugation, from Escherichia coli to Lac(-) strains of Erwinia herbicola, Erwinia amylovora, and Erwinia chrysanthemi (but not to several other Erwinia spp. In preliminary trials). The lac genes in the exconjugants of the Erwinia spp. showed varying degrees of stability depending on the strain (stable in E. herbicola strains Y46 and Y74 and E. amylovora strain EA178, but markedly unstable in E. chrysanthemi strain EC16). The lac genes and the sex factor (F) were eliminated from the exconjugants by treatment with acridine orange, thus suggesting that both lac and F are not integrated in the Erwinia exconjugants. All of the tested Lac(+) exconjugants of E. herbicola strains Y46 and Y74 and E. amylovora strain EA178, but not of E. chrysanthemi strain EC 16, were sensitive to the F-specific phage M13. The heterogenotes (which harbored F'lac(+)) of E. herbicola strains Y46 and Y74, E. amylovora strain EA178, and E. chrysanthemi strain EC16 were able to transfer lac genes by conjugation to strains of E. herbicola, E. amylovora, E. chrysanthemi, Escherichia coli, and Shigella dysenteriae. The frequency of such transfer from Lac(+) exconjugants of Erwinia spp. was comparable to that achieved by using E. coli F'lac(+) as donors, thus indicating the stability, expression, and restriction-and-modification properties of the sex factor (F) in Erwinia spp.     

Microprobe study of toad urinary bladder in absence of serosal K+

Summary The bulk of the intracellular potassium in mucosal epithelial cells from toad urinary bladder has been previously reported to exchange very slowly with the serosal medium, with a half-time of some 9 hr. This observation, based on chemical analyses of mucosal cell scrapings, has been reexamined with simultaneous diffractive and energy dispersive electron probe X-ray microanalysis. Fifty-three intracellular sites in hydrated sections and 286 sites in dehydrated sections were studied in bladders from eight toads under baseline conditions and after removal of serosal K⁺ for 83–133 min, with or without 10^–2 m ouabain. The baseline data confirm and extend previous examinations of the intracellular ionic composition, and provide the most direct measure of intracellular water thus far available for this tissue. Removal of serosal K⁺ reduced the intracellular K⁺ content by 20%, increased intracellular Na⁺ content threefold, and slightly reduced the intracellular Cl^– and water contents, qualitatively consistent with published chemical analyses. The intracellular Na⁺ content of mucosal origin, measured by radioactive tracers and chemical analyses of cell scrapings, has been reported to be unchanged under these conditions Simultaneous addition of ouabain and removal of external K⁺ produced a dramatic fall in intracellular K⁺ of more than 80% in a third of the cells and reduced the mean intracellular K⁺ content by 60%; 20% of the cells appeared to retain K⁺ more effectively than the bulk of the epithelial cell population. We conclude that: (i) the low rate of net exchange of intracellular K⁺ with the serosal bulk solution primarily reflects recycling of K⁺ across the basolateral membranes, (ii) radioactive tracer and chemical measurements of the intracellular Na⁺ pool of mucosal origin substantially underestimate the total intracellular Na⁺ content under certain experimental conditions, and (iii) the epithelial cells display a functional heterogeneity of response to the effects of adding ouabain and withdrawing external K⁺.     

Tyrosine phosphorylation of the herpes simplex virus type 1 regulatory protein ICP22 and a cellular protein which shares antigenic determinants with ICP22.

At least eight herpes simplex virus type 1 (HSV-1) and five HSV-2 proteins were tyrosine phosphorylated in infected cells. The first viral tyrosine phosphoprotein identified was the HSV-1 regulatory protein ICP22. Also, two novel phosphotyrosine proteins were bound by anti-ICP22 antibodies. H(R22) is a cellular protein, while the F(R10) protein is observed only in HSV-1-infected cells.     

Serum progesterone concentration in pyometritic and normal postpartum dairy cows

Two studies were conducted to evaluate the concentration of serum progesterone in pyometritic cows and relate it to palpation of ovarian structures per rectum . In Trial 1, serum samples from 34 pyometritic cows were assayed for progesterone. Mean serum progesterone concentrations were 6.8 +/- 0.7 ng/ml. In Trial 2, each of 54 pyometritic cows was paired with a control cow on the basis of days post partum (18-50 days). Mean concentration of progesterone was 9.7 +/- 1.0 ng/ml for the pyometritic cows and 5.7 +/- 0.8 ng/ml in control cows (P<0.005). Progesterone concentration was greater (P<0.005) in both groups of cows with palpable corpora lutea (CLs). Ninety-six percent of the pyometritic cows had palpable CLs compared to 57% of the control group. Comparing serum progesterone only in cows with a palpable CL, the mean concentration was still greater (P<0.005) in the pyometritic group (10.6 +/- 1.0 ng/ml) than the control group (6.6 +/- 1.0 ng/ml). Compatability of rectal palpation findings and concentrations of serum progesterone were 92.6% for the pyometritic group and 72.2% for the control group. Progesterone concentration increased (P<0.05) by increased days post partum in Trial 2 (n=54) but not in Trial 1 (n=23). In both Trials 1 and 2, uterine size due to pyometra increased (P<0.05) with increased days post partum. No other associations were found.