Binding of opiates and endogenous opioid peptides to neuroleptic receptor sites in the corpus striatum.

Some opiates with morphinan- and benzomorphan-structures possess affinities for neuroleptic receptors as revealed by their abilities to compete with ³H-spiroperidol for common binding sites in rat striatum $\text{in vitro}$ (IC₅₀ in the range between 10^?6 and 10^?5M). The binding of these opiates to neuroleptic receptors appears to be of pharmacological significance, since $\text{in vivo}$ studies in mice revealed a small but significant displacement of spiroperidol by high doses of the opiate antagonist levallorphan from specific binding sites in the striatum. In addition, there exists some correlation between the ability of opiates to bind to neuroleptic receptor sites $\text{in vitro}$ and their potency to evoke “bizarre behavior” in rats $\text{in vivo}$. In contrast, a wide variety of other opiates having morphine-, morphinone- or oripavine-structure showed no affinity for neuroleptic binding sites $\text{in vitro}$ (IC₅₀ greater than 10^?4 M). Of the opioid peptides (methionine-enkephalin, leucine-enkephalin and β-endorphin) none has an affinity for neuroleptic binding sites. A variety of other peptides were also investigated but did not interfere with spiroperidol binding. Only ACTH showed a moderate affinity for neuroleptic binding sites.     

Adenosylhomocysteinase and adenosine nucleosidase activities in Lupinus luteus cotyledons during seed formation and germination

The activities of adenosylhomocysteinase (EC 3.3.1.1) and adenosine nucleosidase (EC 3.2.2.7) were assayed in extracts from yellow lupin (Lupinus luteus L.) cotyledons at different stages of seed formation and seedling development. Adenosylhomocysteinase activity was demonstrated in all the cotyledon extracts examined. Its lowest level was found in the dry seeds and the highest, in 4-day-old seedling cotyledons. Extracts from the cotyledons of maturating seeds, dry seeds, and seedlings up to the second day of growth exhibited no adenosine nucleosidase activity. Adenosine nucleosidase activity appeared in the cotyledons of 2-day-old seedlings and its highest level was reached in 4-to 5-day-old seedlings. There is no inhibitor of adenosine nucleosidase in the maturating and dry yellow lupin seeds. No activator of a possible zymogen form of adenosine nucleosidase from maturating or dry seeds occurs in the growing seedlings.     

Effects of oleate,palmitate, and octanoate on gluconeogenesis in isolated rabbit liver cells

The effect of oleate, palmitate, and octanoate on glucose formation was studied with lactate or pyruvate as substrate. Octanoate was much more quickly oxidized and utilized for ketone body production than were oleate and palmitate. Among fatty acids studied, only octanoate resulted in a marked increase of the 3-hydroxybutyrate/acetoacetate (3-$\text{OHB}\text{AcAc}$) ratio. Each of the fatty acids studied stimulated glucose synthesis from pyruvate. The enhancement of gluconeogenesis by long-chain fatty acids was abolished after the addition of ammonia. As concluded from the “crossover” plot, the stimulatory effect of fatty acids was due to: (i) a stimulation of pyruvate carboxylation, (ii) a provision of reducing equivalents for glyceraldehyde phosphate dehydrogenase, and (iii) an acceleration of flux through hexose diphosphatase. Moreover, palmitate and oleate resulted in an increased generation of mitochondrial phosphpenolpyruvate, while in the presence of octanoate, the activity of mitochondrial phosphoenolpyruvate carboxykinase was diminished. When lactate was used as the glucose precursor, palmitate and oleate increased glucose production by about 50% but did not affect the contribution of mitochondrial phosphoenolpyruvate carboxykinase to gluconeogenesis. In contrast, in spite of the stimulation of both pyruvate carboxylase and hexose diphosphatase, as judged from the crossover plot, the addition of octanoate resulted in a marked inhibition of both glucose formation and mitochondrial generation of phosphoenolpyruvate. The inhibitory effect of octanoate was reversed by ammonia. Results indicate that fatty acids and ammonia are potent regulatory factors of both the rate of glucose formation and the contribution of mitochondrial phosphoenolpyruvate carboxykinase to gluconeogenesis in hepatocytes of the fasted rabbit.     

Replication variants of the human inactive X chromosome

The sequence of DNA replication was studied within the inactive X chromosome in human lymphocytes, by means of the FPG method. Several variants of the replication sequence were found. The number of variants in the cells of a single donor exceeded 2 in each of the 4 normal individuals studied. The phenomenon is discussed with respect to the regulation of DNA synthesis and to the cell differentiation process.     

Dipole moments of random coil polypeptides

The Rotational Isomeric States model is applied to calculate dipole moments of polypeptides of the twenty natural α-amino acids in the random coil state. Dipole moments of each repeat unit (μ_i), are evaluated using a quantum mechanics procedure. Dipole moment ratios ($\text{D}{}_{\mathrm{x}}\text{=}\text{〈μ}{}^2\text{〉}\text{x}\text{μ}{}_{\mathrm{i}}{}^2\text{,}\text{x = number of repeat units}$) of homopolypeptides are calculated and extrapolated to x →?. With a few exceptions, D_? = 0.36 ± 0.1. Ten actual proteins and three enzymes are also studied; their dipole ratios (D_x′ =〈μ〉/x) range from 7.34 to 10.57 in 10^?59 C² m² (6.6–9.5 D²). Diffferences in the values of D_x′ are due mainly to the different contributions, μ_i, of the amino acid residues contained in each polymer, whereas the sequence of amino acids has a very minor effect.     

Stabilization of a miniderivative of the broad-host-range IncW plasmid pSa by insertion of plasmid R1parB region

The plasmid vector pEM100 (13.5 kb) constructed from pGV1106, a miniderivative of the broad-host-range IncW pSa plasmid, and the pAM330 plasmid ofBrevibacterium lactofermentum is not stably maintained inEscherichia coli host cells under nonselective growth conditions. By insertion of a 0.9 kb DNA fragment containing theparB locus (responsible for the maintenance of plasmid R1 inE. coli cells) to plasmid pEM100, plasmid pEM110 was prepared which is maintained in a population ofE. coli cells growing without a selection pressure very stably. Translated by Č. Novotny     

Heterotropic interactions in Escherichia coli aspartate transcarbamylase. Subunit interfaces involved in CTP inhibition and ATP activation

In Escherichia coli aspartate transcarbamylase, each regulatory chain is involved in two kinds of interfaces with the catalytic chains, one with the neighbour catalytic chain which belongs to the same half of the molecule (R1-C1 type of interaction), the other one with a catalytic chain belonging to the other half of the molecule (R1-C4 type of interaction). In the present work, site-directed mutagenesis was used to investigate the involvement of the C-terminal region of the regulatory chain in the process of feed-back inhibition by CTP. Removal of the two last C-terminal residues of the regulatory chains is sufficient to abolish entirely the sensitivity of the enzyme to CTP. Thus, it appears that the contact between this region and the 240s loop of the catalytic chain (R1-C4 type of interaction) is essential for the transmission of the regulatory signal which results from CTP binding to the regulatory site. None of the modifications made in the R1-C4 interface altered the sensitivity of the enzyme to the activator ATP, suggesting that the effect of this nucleotide rather involves the R1-C1 type of interface. These results are in agreement with the previously proposed interpretation that CTP and ATP do not simply act in inverse ways on the same equilibrium.