Plasma catecholamines: effects of footshock level and hormonal modulators of memory storage

Plasma levels of norepinephrine (NE) and epinephrine (EPI) were measured in male Sprague-Dawley rats before and at several times after training injections of agents known to enhance or to impair later retention performance for a one-trial inhibitory (passive) avoidance task. Two days before testing, each animal was surgically prepared with a chronic tail artery catheter that allows for repeated blood sampling in unhandled rats. Exposure to a single, intense training footshock (3.0 mA, 2.0 sec duration) resulted in an immediate but transient increase in plasma levels of EPI and to a lesser extent NE. Plasma levels of both catecholamines did not differ between unshocked controls and animals that received a weak training footshock (0.6 mA, 0.5 sec duration). An injection of EPI at a dose that enhances retention performance (0.1 mg/kg, sc) resulted in increments in plasma EPI levels of 0.8-1.9 ng/ml from 5 to 40 min after injection. An injection of EPI (0.5 mg/kg, sc) at a dose that produces retrograde amnesia resulted in increments in plasma EPI ranging from 3.7 to 4.5 ng/ml during the 40 min after injection. Plasma NE levels were not significantly altered following an EPI injection. A single injection of adrenocorticotropin (ACTH, 0.3 or 3.0 IU per rat) did not alter the plasma catecholamine responses to training with a weak footshock. Similarly, the synthetic ACTH analog, Organon 2766 (125 or 250 mg/Kg) did not affect plasma catecholamines in untrained (unshocked) rats.These results demonstrate that significant increments in plasma levels of NE and EPI occur shortly after inhibitory avoidance training. Furthermore, an injection of EPI that enhances retention of an inhibitory avoidance task mimics the magnitude, though not the temporal characteristics, of the endogenous adrenal medullary response to a training footshock. Other hormonal treatments (ACTH and Organon 2766) which enhance memory storage do not affect plasma levels of NE and EPI.     

Energy-dependent changes in the conformation of the epsilon subunit of the chloroplast ATP synthase

Rabbit antiserum raised against the isolated native epsilon subunit of the chloroplast coupling factor 1 activated the ATPase activity of coupling factor 1 in solution by removing the epsilon subunit. Incubation of thylakoid membranes with the antiserum in the dark had no effect on photophosphorylation or on the dithiothreitol-induced Mg2+-ATPase activity. Incubation with the antiserum during illumination, however, strongly inhibited both activities and caused the membranes to become leaky to protons. The results indicate that the formation of a proton gradient across the thylakoid membrane induces a change in conformation of the epsilon subunit of the ATP synthase such that it becomes susceptible to attack and removal by the antibodies. This change may be a part of the mechanism that results in energy-dependent activation of the ATP synthase.     

Transposable element-induced mutations of the viviparous-1 gene in maize

The viviparous-1 (vp1) locus in maize is a developmental gene that controls diverse aspects of the maturation phase of seed development. Mutations of vp1 alter embryo sensitivity to the hormone abscisic acid and block formation of anthocyanin pigment. Molecular cloning of a Robertson Mutator-induced mutant allele, vp1-mum-1, by transposable element tagging has allowed analysis of several transposon-induced vp1 mutants. In the vp1-Mc mutation, the gene is disrupted by 4.0 kbp insertion, which results in expression of a 3′ truncated mRNA. Phenotypically, this allele is at least partially functional in causing embryo dormancy, but is ineffective in controlling anthocyanin expression. This result suggests that disruption of the C-terminal domain of the Vp1 protein specifically affects regulation of the anthocyanin pathway. A second Mutator- derived allele, vp1-mum2, exhibits an unusual form of somatic mutability in which endosperm cells revert from wild-type vp1 expression to a mutant condition. The vp1-mum2 allele contains a 1.5 kbp Insertion that has no detectable homology to known Mu elements. This element is retained In wild-type germinal revertants derived from vp1-mum2 An apparent DNA modification affecting cleavage at an internal Sstl restriction site in the element correlates with vp1-mum2 states that exhibit wild-type Vp1 expression. A model involving mitotic assortment of modified and unmodified DNA strands during development is proposed for vp1-mum2 somatic mutation.     

Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications

Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of individuals representing 54 species of frogs, two species of salamanders, a caecilian, and a lungfish. Eight of these sites were present in all species examined, and two were found in all but one species. Alignment of these conserved restriction sites revealed, among anuran 28S rRNA genes, five regions of major length variation that correspond to four of 12 previously identified divergent domains of this gene. One of the divergent domains (DD8) consists of two regions of length variation separated by a short segment that is conserved at least throughout tetrapods. Most of the insertions, deletions, and restriction-site variations identified in the 28S gene will require sequence-level analysis for a detailed reconstruction of their history. However, an insertion in DD9 that is coextensive with frogs in the suborder Neobatrachia, a BstEII site that is limited to representatives of two leptodactylid subfamilies, and a deletion in DD10 that is found only in three ranoid genera are probably synapomorphies.      

Energetic and rate effects on methanogenesis of ethanol and propionate in perturbed CSTRs

Energetic and reaction-rate interactions between hydrogenic (hydrogen-producing) and hydrogenotrophic (hydrogen-consuming) bacteria were investigated in five perturbation experiments performed on steady-state, mixed-culture methanogenic CSTRs receiving ethanol, propionate, or both hydrogenic substrates. When a large quantity of propionate was suddenly added to a propionatefed CSTR, P(H(2) ) increased to 10(-4) atm and propionate oxidation remained energetically favorable. When ethanol was added to a CSTR receiving ethanol, P(H(2) ) rose to 6.3 x 10(-3) atm within 5 h. In both perturbations, P(H(2) ) remained at levels such that oxidation of the hydrogenic substrate remained energetically favorable throughout the transient. Sudden increase in ethanol concentration in the ethanol- and propionate-fed CSTR resulted in an increase in P(H(2) ) such that propionate oxidation became energetically unfavorable and was blocked. Propionate utilization resumed when the added ethanol was depleted and P(H(2) ) returned to its previous steady-state levels. Ethanol perturbation of ethanol- and propionate-fed CSTRs led to the formation of reduced products, including n-propanol and four-through seven-carbon n-carboxylic acids, when P(H(2) ) was elevated; these products disappeared after P(H(2) ) returned to previous, steady-state levels. The transformations were consistent with reaction energetics. Reduced product formation may have been a sink for reducing equivalents, as an alternative to oxidation for propionate utilization, as indicated by an electron equivalents balance over the time course of experiments.     

Effects of phenolic acids on ammonia oxidation by terrestrial autotrophic nitrifying microorganisms

Abstract It has been hypothesized that vegetation in certain ecosystems inhibits nitrification in soil by producing phenolic compounds that inhibit oxidation of ammonia by nitrifying microorganisms. This hypothesis is based largely on a report that very low concentrations (10⁻⁶ M–10⁻⁸ M) of several phenolic acids (notably ferulic acid) completely inhibited NO₂⁻ production in an aqueous suspension of soil treated with (NH₄)₂SO₄ and a nutrient solution suitable for growth of Nitrosomonas and other autotrophic nitrifying microorganisms. To evaluate this hypothesis, we determined the effects of three ohenolic acids (ferulic acid, caffeic acid, and p -coumaric on nitrite production by representatives of three genera of terrestrial autotrophic nitrifying microorganisms ( Nitrosospira, Nitrosomonas , or Nitrosolubos ) grown on a defined medium containing NH₄⁺. We found that nitrite production by the Nitrososspira was not inhibited by ferulic acid, caffeic acid, or p -coumaric acid at concentrations of 10⁻⁶ or 10⁻⁵ M and was only slightly inhibited when these acids were at a concentration of 10⁻⁴ M. We also found that ferulic acid did not markedly inhibit nitrite production by the three genera of nitrifying microorganisms studied, even when its concentration was as high as 10⁻³ M. These observations invalidate the hypothesis tested because the phenolic acids studied did not significantly retard ammonia oxidation by autotrophic microorganisms even when their concentration in cultures of these microorganisms greatly exceeded their concentrations in soils.     

Utilization rates of trace halogenated organic compounds in acetate-grown biofilms

Trace concentrations of chlorinated benzenes and chlorinated aliphatics were biotransformed by acetate-supported biofilms, the former under aerobic conditions and the latter under methanogenic conditions. The rates of transformation of the halogenated organic compounds (secondary substrates) differed from that of acetate, the primary substrate; some were higher, some were lower, and some were similar. Factors affecting the relative rates of utilization in multisubstrate systems are not known.     

Association between cutaneous occlusive vascular disease, cigarette smoking, and skin slough after rhytidectomy

This prospective study attempted to determine if nonreversible occlusive vascular changes in the skin contribute to skin slough after rhytidectomy. The dermal microvasculature from 83 consecutive rhytidectomies was evaluated for intimal proliferation and/or hyalin sclerosis. Occlusive vascular disease increased progressively with age in all patients, but smokers and ex-smokers had significantly greater involvement than nonsmokers at any given age (p = 0.03). Severe occlusive vascular disease and skin slough were associated (p = 0.02), and there was a strong trend toward an association between active smoking and skin slough (p = 0.06). Among smokers, there was a significant relationship between skin slough and failure to abstain from smoking postoperatively (p = 0.006). We conclude that with aging, nonreversible occlusive changes develop in the dermal microvasculature. These changes appear to be accelerated by cigarette smoking. Our data, however, show that these nonreversible occlusive vascular changes by themselves do not completely account for the occurrence of skin slough after rhytidectomy.     

Transformations of 1- and 2-carbon halogenated aliphatic organic compounds under methanogenic conditions.

Several 1- and 2-carbon halogenated aliphatic organic compounds present at low concentrations (less than 100 micrograms/liter) were degraded under methanogenic conditions in batch bacterial cultures and in a continuous-flow methanogenic fixed-film laboratory-scale column. Greater than 90% degradation was observed within a 2-day detention time under continuous-flow methanogenic conditions with acetate as a primary substrate. Carbon-14 measurements indicated that chloroform, carbon tetrachloride, and 1,2-dichloroethane were almost completely oxidized to carbon dioxide, confirming removal by biooxidation. The initial step in the transformations of tetrachloroethylene and 1,1,2,2-tetrachloroethane to nonchlorinated end products appeared to be reductive dechlorination to trichloroethylene and 1,1,2-trichloroethane, respectively. Transformations of the brominated aliphatic compounds appear to be the result of both biological and chemical processes. The data suggest that transformations of halogenated aliphatic compounds can occur under methanogenic conditions in the environment.     

Selective modification of coupling factor 1 in spinach chloroplast thylakoids by a fluorescent maleimide

N-(1-Anilinonaphthyl-4)maleimide (ANM) has been used to modify coupling factor 1 (CF1), the terminal coupling factor of photophosphorylation in chloroplasts. As with other monofunctional maleimides, incubation of thylakoids with ANM in the light, but not in the dark, causes energy transfer inhibition of photophosphorylation. In the dark, sites on both the gamma and epsilon subunits of CF1 are modified. The light-accessible site is also on the gamma subunit. Trypsin digestion of the enzyme after dithiothreitol activation reveals that the dark-and light-accessible sites on the gamma subunit are different amino acid residues. Fluorescence of ANM bound at the dark-and light-accessible sites has been measured after isolation of CF1 from thylakoids. The fluorescence emission maximum of ANM at the light-accessible site is blue-shifted and the quantum yield is increased 2-fold relative to ANM bound at dark-accessible sites. On the soluble enzyme, fluorescence polarization is high and equivalent for ANM bound at both dark-and light-accessible sites. Fluorescence energy transfer from a tryptophan in a hydrophilic region of the epsilon subunit to ANM bound to the epsilon subunit but not to the gamma subunit has been observed. The significance of these observations is discussed with respect to the structure of the gamma subunit and its role in conformational transitions within CF1 that occur during energization of the membrane.