Mechanical and biochemical characterization of the contraction elicited by a calcium-independent myosin light chain kinase in chemically skinned smooth muscle

Summary The contraction induced by a Ca²⁺-independent myosin light chain kinase (MLCK-) was characterized in terms of isometric force (F_o), immediate elastic recoil (SE), unloaded shortening velocity (V_us), shortening under a constant load and ATPase activity of chemically skinned smooth muscle preparations. These parameters were compared to those measured in a Ca²⁺-induced contraction to assess the nature of cross bridge interaction in the MLCK-induced contraction. F_o developed in chicken gizzard fibers as well as SE were similar in contractions elicited by either agent. V_us in the contraction induced by MLCK-(0.36 mg/ml) was similar though averaged 39.3±8.9% less than V_us induced by Ca²⁺ (1.6x10^–6M) in the control fibers. Addition of Ca²⁺ (1.6x10^–6M) to a contraction induced by MLCK-resulted in small increases in both F_o and V_us. Shortening under a constant load was similar for both types of contractions. The contraction induced by MLCK-was accompanied by an increased rate of ATP hydrolysis. The MLCK-induced contraction is thus kinetically similar though not identical to a contraction induced by Ca²⁺. We conclude that with respect to actin-myosin interaction, MLCK- and Ca²⁺-induced contractions are similar.     

Moderate cooling depresses the accumulation and the release of newly synthesized catecholamines in isolated canine saphenous veins

Moderate cooling (from 37 degrees to 24 degrees C) depressed the formation of 3H-dopamine and 3H-norepinephrine from 3H-tyrosine by isolated canine saphenous veins. Cooling reduced the evoked release of newly synthesized catecholamine to the same extent as that of stored norepinephrine. Hence the augmentation by cold of the contractile response to sympathetic nerve stimulation observed in earlier work is not accompanied by an augmented release of newly synthesized norepinephrine.     

Bicuculline and picrotoxin block gamma-aminobutyric acid-gated Cl- conductance by different mechanisms

Using isolated, internally perfused bullfrog dorsal root ganglion cells we have studied the dose-response curves for gamma-aminobutyric acid (GABA) in the presence of internally or externally applied GABA antagonists. With external application of antagonists the inhibition of the GABA current by bicuculline was competitive and that by picrotoxin was noncompetitive. Picrotoxin but not bicuculline blocked when internally perfused.     

Decompoisition of toxic and environmentally hazardous 2,3,7,8-tetra-chlorodibenzo-p-dioxin by gamma irradiation

Summary The decomposition of the toxic and environmentally hazardous 2378-TCDD by gamma irradiation was studied and successfully used to decontaminatge laboratory wastes containing small quantities of this chemically and biological stable compound. The method makes use of gamma irradiation from a commercial⁶⁰cobalt facility at high dose levels (100 kGy) to break down the compound into notoxic products. Irradiation also decomposed 2378-TCDD in contaminated soil from the Seveso accident.     

Normetanephrine and metanephrine oxidized by both types of monoamine oxidase

Summary Both normetanephrine and metanephrine were found to be oxidized by both types of monoamine oxidase in mouse liver mitochondria. Both K_m and V_max values of type B MAO for both substrates were higher than those of type A MAO, which caused the shift of inhibition curves with clorgyline and deprenyl according to the increase in substrate concentration.     

Dopamine and octopamine in whole body extracts of the bulb mite

Summary Using high performance liquid chromatography with electrochemical detection, whole body extracts of the bulb mite,Rhizoglyphus echinopus (Fumouze and Robin), were found to contain the biogenic amines dopamine and octopamine at concentrations of 4.3±0.6 and 2.3±1.4 ng g^–1 wet weight, respectively. Adrenaline, noradrenaline, tyramine,N-methyldopamine,N-acetyldopamine, and 5-hydroxytryptamine, if present, were below the limits of detectability. This is the initial demonstration of the presence of octopamine in a mite species.     

Aging alters resynchronization of the circadian system in rats after a shift of the light-dark cycle

Four days following an 8-h advance of the light-dark cycle, the circadian rhythms in the pineal N-acetyltransferase activity and melatonin content reappeared in 7-week-old rats, but were still abolished in 24-month-old animals.     

Starvation and penetration of bacteria in soils and rocks

Summary The soil and subsurface strata are low nutrient environments and their bacterial inhabitants must adopt starvation responses to survive. These responses include the formation of dormant, viable cells which, although reduced in cell size and volume, are able to respond to any improvement in nutrient availability. Starved bacteria are able to survive for extended periods without nutrients and their reduced size allows them to disperse deeply within rocks and soils greatly improving their penetration. These combined factors may increase opportunities for bacteria to reach a deep waste disposal site.     

Paternal allocation of sequestered plant pyrrolizidine alkaloid to eggs in the danaine butterfly, Danaus gilippus

Pyrrolizidine alkaloid sequestered by adult male Danaus gilippus from plants is transferred in large measure to the female at mating, and by the female to the eggs. The eggs, presumably, are protected as a result. The male's courtship pheromone, danaidone, derived from the sequestered alkaloid, may function to advertise the male's alkaloid-donating capacity.     

Secondary metabolites of the chemically rich ascoglossanCyerce nigricans

Summary Two new metabolites of an apparent propionate origin have been isolated from the organic extract of the ascoglossan molluscCyerce nigricans. The proposed structures for the new natural products are based on interpretation of their physical and spectral properties. The new compounds isolated lacked the potent ichthyodeterrent properties of the whole animal extract suggesting that other molecules are involved in the defense of this shell-less mollusc.