Physical and chemical scavenging of singlet molecular oxygen by tocopherols

Singlet molecular oxygen (1O2) arising from the thermal decomposition of the endoperoxide of 3,3'-(1,4-naphthylidene) dipropionate was used to assess the effectiveness of alpha-, beta-, gamma-, and delta-tocopherol in the physical quenching as well as the chemical reaction of 1O2. The relative physical quenching efficiencies of the tocopherol homologs were found to decrease in the order of alpha greater than or equal to beta greater than gamma greater than delta-tocopherol. The ability of physical quenching depends on a free hydroxyl group in position 6 of the chromane ring. Chemical reactivity of the tocopherol homologs with 1O2 was low, accounting for 0.1-1.5% of physical quenching with beta-tocopherol showing particularly low reactivity, resulting in the sequence alpha greater than gamma greater than delta greater than beta-tocopherol. Tocopheryl quinones were products of all tocopherol homologs, and in addition a quinone epoxide was a major product from gamma-tocopherol. This quinone epoxide was not cleaved by rat liver microsomal epoxide hydrolase; however, it reacted further with 1O2. It is concluded that methylation in position 5 of the chromane ring enhances physical quenching of 1O2, whereas chemical reactivity is favored by a methylated position 7. In view of the fact that beta-tocopherol is as effective as alpha-tocopherol in physical quenching of 1O2 but shows very low chemical reactivity, this tocopherol homolog might be particularly suitable for biological conditions in which an accumulation of oxidation products might weaken the antioxidant defense.     

A truncation mutation in the avian beta-adrenergic receptor causes agonist-induced internalization and GTP-sensitive agonist binding characteristic of mammalian receptors

Recombinant turkey erythrocyte beta-adrenergic receptors expressed in murine L cells exhibited characteristic avian subtype selectivity for agonists and antagonists. In 10 of the 11 clones studied, no agonist-induced internalization of receptor was observed, although agonist-induced uncoupling of receptor and adenylyl cyclase occurred rapidly. GTP caused little or no decrease in affinity for beta-adrenergic agonists. Such behavior is commonly observed in avian erythrocytes. In contrast, one clone was susceptible to agonist-induced receptor internalization and down-regulation even though it exhibited characteristic avian beta-adrenergic ligand-binding properties. The affinity of this variant receptor for agonists was also notably reduced by GTP. Electrophoresis of affinity-labeled receptor from this clone indicated an apparent size of about 33 kDa, about 12 kDa less than that of the native or recombinant turkey beta-adrenergic receptor. Genomic DNA from this cell line that encodes the receptor was cloned and partially sequenced. The coding region of the original receptor cDNA was interrupted after codon 412 (out of 483) and was followed by 36 base pairs of novel sequence prior to the first in-frame stop codon. These results suggest that the lack of both hormone-induced internalization and GTP-sensitive, high affinity binding of agonists that is characteristic of the beta-adrenergic receptor in avian erythrocytes is due to intrinsic properties of the receptor. The restoration of these phenomena in a C-terminally truncated mutant receptor suggests the importance of the C-terminal domain in determining these processes.     

An analog of ACTH/MSH (4–9), ORG-2766, reduces cerebral uptake of morphine

The uptake of morphine was significantly reduced in most regions of the brains of conscious, unrestrained rats within 10 minutes after treatment with an analog of ACTH/MSH (4–9), ORG-2766. The effect was most obvious in regions with significant densities of enkephalin receptors, namely basal ganglia, hippocampus and cortex. The results explain, in part, how some fragments and analogs of ACTH/MSH may antagonize behavioral actions of morphine, even though some of these peptides lack significant opiate receptor binding properties. We believe that this effect of ORG-2766 is related to an action on the permeability characteristics of the brain microvasculature. The underlying mechanism is unknown.     

Effect of membrane dialysis and filtration-sterilization on erythropoietin activity.

Most erythropoietin (Ep) preparations contain non-erythropoietin contaminants. The use of such hormone concentrates raises important questions regarding interpretations of results derived from in vivo and especially from in vitro studies. By sterilizing various Ep preparations with Nalgene, Millipore, or Selas silver filtration, or even after conventional membrane dialysis, variable responses were noted when the Ep was assayed with mouse bone marrow cells in vitro (i.e. by stimulating the production of erythroid colonies from CFU-e and BFU-e) and in vivo (i.e., by using the exhypoxic, polycythemic mouse bioassay for Ep). The utility and limitations of such preparative procedures are discussed.     

The effect of methallibure and cyproterone acetate on the gonadotrophic cells, plasma androgen levels and testes of precocious 1+ male Atlantic salmon parr Salmo salar L.

Developing 1+ male Atlantic salmon parr were treated with methallibure and cyproterone acetate. Both these drugs failed to prevent gonad maturation but they did decrease the gonadotrophic cell size and lower plasma androgen levels. These results are discussed in relation to previous studies. It is concluded that gonadotrophic cells control gonadal androgen production, that cyproterone acetate is a central inhibitor of gonadotrophin production and that these two chemical agents could be effective as chemosterilants if administered early in gonad maturation cycle.     

Patterns of early and late discharges in somatotopically identified precentral neurons in awake monkeys in response to somatic inputs.

Extracellular recordings were made of single neurons in precentral cortex of awake monkeys. These neurons were somatotopically identified with respect to their responses to inputs from single joints or their somatic surround. Many of these neurons exhibited early (less than 50 ms) and late (greater than 50 ms) discharges in response to flexion or extension torques delivered about the wrist. With the monkey in a mode requiring opposition to the injected torque, all responsive neurons showed a parallel excitatory or inhibitory modification in the early and late discharges. This was true both for cells identified as wrist (flexion-extension) neurons and those identified as nonwrist (flexion-extension) neurons. These findings indicate that the reflex and voluntary components of percentral discharge invariably show a congruent functional response to a torque disturbance, for this particular instruction set.     

Stability of a reference panel of lyophilized hepatitis B antigens and antibodies

A lyophilized hepatitis B working/reference panel has been prepared for use in standardization tests. This panel includes HBsAg, anti-HBs, HBeAg/anti-HBe and subtype reagents. Quantitative analysis of the HBsAg reagents indicates that at a storage temperature of -20 degrees C, only 1 log at maximum of RIA counts per minute would be lost in 95 years. After storage at -20 degrees C for 1 year, there has been no loss of reactivity in any of the tests used to detect HBsAg, anti-HBs, HBeAg/anti-HBe or subtypes.     

Comparison of fatty acid oxidation in mitochondria and peroxisomes from rat liver

Oxygen uptake with succinate or palmitoyl-CoA as substrates can be measured in rat liver mitochondria that have been isolated by sucrose density gradient centrifugation providing the fractions are diluted with a 30 mM phosphate buffer rather than with an isotonic medium. Separate assay procedures were used to measure peroxisomal and mitochondrial β-oxidation of palmitoyl-CoA in the fractions of a sucrose gradient used to separate these organelles. A preliminary estimate of the ratio of palmitoyl-CoA oxidation by the mitochondrial fraction relative to the surviving peroxisomes from livers of male rats was 3.2.