Modulation of the expression of interleukin 2 receptors of human thymocytes by recombinant interleukin 2

The effect of purified recombinant interleukin 2 on the expression of the receptors for interleukin 2 by human thymocytes was examined. Interleukin 2 augmented the expression of interleukin 2 receptors and interferon-gamma synthesis by thymocytes activated with concanavalin A, and it was required to maintain the growth of thymocytes in vitro and the expression of interleukin 2 receptors. The increase observed in the number of receptor bearing thymocytes and in the density of receptors due to interleukin 2 occurred within the first 2 days of culture. Dexamethasone inhibited the expression of interleukin 2 receptors, the synthesis of interferon-gamma, and the early proliferation and protein synthesis of lectin-activated thymocytes during the first 2 days of culture. The inhibitory effect of dexamethasone on the expression of interleukin 2 receptors and on the synthesis of interferon-gamma was reversed by interleukin 2, whereas its effect on proliferation and on protein synthesis during the first two days of culture was not reversed by interleukin 2. Interleukin 2 induced the proliferation of thymocytes in vitro, even in the absence of activation by lectin; however, the number of cells displaying receptors which could be detected with anti-Tac remained low throughout the first week of culture and interferon-gamma synthesis was not observed. Nonetheless, interleukin 2-induced proliferation was inhibited by anti-Tac on a dose dependent manner. The results of the study document that recombinant interleukin 2, like purified natural interleukin 2, is required for the expression of interleukin 2 receptors, for interferon-gamma synthesis, and for the growth of thymocytes in vitro.     

Use of autonomous audio recordings for the rapid inventory of birds in the white‐sand forests of the Peruvian Amazon

White‐sand forests are patchily distributed ecosystems covering just 5% of Amazonia that host many specialist species of birds not found elsewhere, and these forests are threatened due to their small size and human exploitation of sand for construction projects. As a result, many species of birds that are white‐sand specialists are at risk of extinction, and immediate conservation action is paramount for their survival. Our objective was to evaluate current survey methods and determine the relative effect of the size of patches of these forests on the presence or absence of white‐sand specialists. Using point counts and autonomous recorders, we surveyed avian assemblages occupying patches of white‐sand forest in the Peruvian Amazon in April 2018. Overall, we detected 126 species, including 21 white‐sand forest specialists. We detected significantly more species of birds per survey point with autonomous recorders than point counts. We also found a negative relationship between avian species richness and distance from the edge of patches of white‐sand forest, but a significant, positive relationship when only counting white‐sand specialists. Although we detected more species with autonomous recorders, point counts were more effective for detecting canopy‐dwelling passerines. Therefore, we recommend that investigators conducting surveys for rare and patchily distributed species in the tropics use a mixed‐method approach that incorporates both autonomous recorders and visual observation. Finally, our results suggest that conserving large, continuous patches of white‐sand forest may increase the likelihood of survival of species of birds that are white‐sand specialists.     

Stimulation of the hexose-monophosphate pentose pathway by delta 1-pyrroline-5-carboxylic acid in human fibroblasts.

L-pyrroline-5-carboxylic acid, an intermediate in the interconversions of glutamic acid, ornithine and proline, is a potent stimulator of the hexose-monophosphate pentose pathway in cultured human fibroblasts. These studies suggest that pyrroline-5-carboxylate reductase, which catalyzes the conversion of pyrroline-5-carboxylate to proline coupled with the oxidation of NADPH, provides the NADP for the observed activation of the hexose-monophosphate pentose pathway.     

Molecular Forms of Acetylcholinesterase and Butyrylcholinesterase in Human Plasma and Cerebrospinal Fluid

The measurement of cholinesterase activities in either plasma or cerebrospinal fluid (CSF) may ultimately prove to be relevant in the diagnosis of neurological and neuropsychiatric disorders. However, studies to date have examined only total enzyme activities. Therefore in the present study we have examined the distribution of the individual molecular forms of both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in plasma and CSF using sucrose density gradient centrifugation. Although the total activities of AChE were of the same order of magnitude in plasma and CSF, there was a considerable difference (120-500-fold) between total BChE activity in the CSF and the BChE-rich plasma. The analysis of the individual molecular forms revealed that the predominant molecular species of AChE and BChE in the CSF--both lumbar and ventricular--was the G4 form. The G4 form also constituted the majority of the plasma BChE activity and, on average, over half (56%) of the plasma AChE activity. The significance of the AChE and BChE molecular form compositions of both plasma and CSF and their possible relationship to pathological states are discussed.     

Copurification and characterization of deacetoxycephalosporin C synthetase/hydroxylase from Cephalosporium acremonium.

Deacetoxycephalosporin C synthetase (expandase), which catalyzes ring expansion of penicillin N to deacetoxycephalosporin C (DAOC), has been stabilized in vitro and purified to near homogeneity from the industrially important fungus Cephalosporium acremonium. Throughout the purification, the expandase activity remained physically associated with and in a constant ratio of 7:1 to DAOC hydroxylase activity. The latter activity mediates hydroxylation of DAOC to deacetylcephalosporin C (DAC). The copurified expandase/hydroxylase appeared to be monomeric, with a molecular weight of 41,000 +/- 2,000 and an isoelectric point of 6.3 +/- 0.3. Both catalytic activities required alpha-ketoglutarate, Fe2+, and O2 and were stimulated by ascorbate, dithiothreitol, and ATP. The Fe2+ requirement was specific, and sulfhydryl groups in the purified protein were apparently essential for both ring expansion and hydroxylation. The kinetics and stoichiometry of DAOC/DAC formation from the expandase/hydroxylase-catalyzed reactions suggested that ring expansion of penicillin N preceded hydroxylation of DAOC.     

Removal of sodium inactivation and block of sodium channels by chloramine-T in crayfish and squid giant axons.

Modification of sodium channels by chloramine-T was examined in voltage clamped internally perfused crayfish and squid giant axons using the double sucrose gap and axial wire technique, respectively. Freshly prepared chloramine-T solution exerted two major actions on sodium channels: (a) an irreversible removal of the fast Na inactivation, and (b) a reversible block of the Na current. Both effects were observed when chloramine-T was applied internally or externally (5-10 mM) to axons. The first effect was studied in crayfish axons. We found that the removal of the fast Na inactivation did not depend on the states of the channel since the channel could be modified by chloramine-T at holding potential (from -80 to -100 mV) or at depolarized potential of -30 mV. After removal of fast Na inactivation, the slow inactivation mechanism was still present, and more channels could undergo slow inactivation. This result indicates that in crayfish axons the transition through the fast inactivated state is not a prerequisite for the slow inactivation to occur. During chloramine-T treatment, a distinct blocking phase occurred, which recovered upon washing out the drug. This second effect of chloramine-T was studied in detail in squid axons. After 24 h, chloramine-T solution lost its ability to remove fast inactivation but retained its blocking action. After removal of the fast Na inactivation, both fresh and aged chloramine-T solutions blocked the Na currents with a similar potency and in a voltage-dependent manner, being more pronounced at lower depolarizing potentials.(ABSTRACT TRUNCATED AT 250 WORDS)