Cold hardiness of the green gemmules of Spongilla lacustris L. (Porifera: Spongillidae)

Most green gemmules of Spongilla lacustris survived enclosure in ice at –20 °C for up to 30 days; however, their rate of germination at 20 °C was less rapid than that of control gemmules. The length of time spent at low temperature had little effect on gemmule survival. In contrast, repeated cooling to –20 °C and warming to 4 °C led to a progressive decline in gemmule viability. These results indicate that cold injury occurs primarily during transitions between high and low temperatures.     

Cerebral Metabolic Effects of Monoamine Oxidase Inhibition in Normal and 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Acutely Treated Monkeys

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces dopaminergic cell death in the substantia nigra pars compacta (SNpc) and clinical parkinsonism in humans and experimental animals. Pretreatment with monoamine oxidase inhibitors prevents this cell death and associated parkinsonism by blocking the oxidation of MPTP to a toxic intermediate. The 2-deoxyglucose method was used to study the acute effects of MPTP in the monkey brain and the effects of monoamine oxidase inhibition on local cerebral glucose utilization in both normal and MPTP-treated monkeys. MPTP administration alone caused a major increase in glucose utilization in the SNpc and smaller increases in some subnuclei within the ventral tegmental area in which eventual dopaminergic cell loss also occurs. Pretreatment with pargyline abolished these metabolic increases, a finding suggesting both that the oxidized product of MPTP generates the metabolic increases and that the increased glucose consumption may contribute to cell toxicity. On the other hand, in most cortical, thalamic, striatal, brainstem, and cerebellar areas MPTP alone caused reductions in glucose utilization, and pargyline failed to prevent these effects. Pargyline alone depressed metabolism in the locus coeruleus and a few other monoaminergic structures.     

Superoxide Production by Respiring Membranes of Escherichia Coli

Of production by homogenates and isolated membranes of E. coli has been examined. Approximately one-fourth of the O₂-generated by extracts in the prescence of NAD (P) H is attributable to the membranes. The autoxidizable membrane component is a member of the respiratory chain, since O₂-production is NADH-specific, amplified by cyanide, and absent from membranes lacking the respiratory NADH dehyd-rogenase. Other respiratory substrates (succinate, I -phosphoglycerol, D-lactate. and L-lactate) supported Or production at efficiencies between 3 and 30 O₂-released per 10.000 electrons transferred, under conditions of substrate saturation.

Membranes from quinoneless mutants quantitatively retain the ability to evolve O₂-. indicating that the dehydrogenases are the sites of O₂-production. Relative O₂-production was greater at low substrate concentrations, probably reflecting the facilitation of unpairing of electrons that may occur when enzymes with multiple redox centers are only partially reduced.

Respiration rate, cell volume, rates of membraneous and cytosolic O₂-production, and SOD levels were used to calculate a steady-state concentration of O₂-between 10^--¹⁰ and 10^--⁹ M in well-fed, aerobic, SOD-proficient cells.     

Effects of Handling or Immobilization on Plasma Levels of 3,4-Dihydroxyphenylalanine, Catecholamines, and Metabolites in Rats

In conscious animals, handling and immobilization increase plasma levels of the catecholamines norepinephrine (NE) and epinephrine (EPI). This study examined plasma concentrations of endogenous compounds related to catecholamine synthesis and metabolism during and after exposure to these stressors in conscious rats. Plasma levels of 3,4-dihydroxyphenylalanine (DOPA), NE, EPI, and dopamine (DA), the deaminated catechol metabolites 3,4-dihydroxyphenylglycol (DHPG), and 3,4-dihydroxyphenylacetic acid (DOPAC), and their O-methylated derivatives methoxyhydroxyphenylglycol (MHPG) and homovanillic acid (HVA) were measured using liquid chromatography with electrochemical detection at 1, 3, 5, 20, 60, and 120 min of immobilization. By 1 min of immobilization, plasma NE and EPI levels had already reached peak values, and plasma levels of DOPA, DHPG, DOPAC, and MHPG were increased significantly from baseline, whereas plasma DA and HVA levels were unchanged. During the remainder of the immobilization period, the increased levels of DOPA, NE, and EPI were maintained, whereas levels of the metabolites progressively increased. In animals immobilized briefly (5 min), elevated concentrations of the metabolites persisted after release from the restraint, whereas DOPA and catecholamine levels returned to baseline. Gentle handling for 1 min also significantly increased plasma levels of DOPA, NE, EPI, and the NE metabolites DHPG and MHPG, without increasing levels of DA or HVA. The results show that in conscious rats, immobilization or even gentle handling rapidly increases plasma levels of catecholamines, the catecholamine precursor DOPA, and metabolites of NE and DA, indicating rapid increases in the synthesis, release, reuptake, and metabolism of catecholamines.     

Neuropeptide Y and natural killer cell activity: findings in depression and Alzheimer caregiver stress.

A reduction in immune function has been found in patients with a major depressive disorder and in persons undergoing severe life stress. This study investigated the association between increased sympathetic nervous system activity and reduced natural killer (NK) cytotoxicity in depression and Alzheimer caregiver stress. NK activity and plasma concentrations of epinephrine, norepinephrine, and neuropeptide Y were measured in depressed patients (n = 19) and age- and gender-matched controls (n = 19), and in Alzheimer spousal caregivers (n = 48) and matched noncaregiver controls (n = 17). Plasma levels of neuropeptide Y, but not circulating basal levels of catecholamines, were significantly (P less than 0.01) elevated in the depressed patients and in the caregivers compared with respective controls. NK activity was significantly (P less than 0.001) lower in the depressed patients than in their controls, but not different between the caregivers and the noncaregiver controls. Circulating concentrations of neuropeptide Y, but not catecholamines, were inversely correlated (r = -0.31, P less than 0.001) with NK activity. In addition, multiple regression analyses demonstrated that the significant (P less than 0.01) association between neuropeptide Y and natural cytotoxicity was independent of the relative contribution of age and basal and dynamic levels of epinephrine and norepinephrine. These findings suggest that increased sympathetic nervous system activity and the release of neuropeptide Y may be associated with the modulation of NK cytotoxicity.     

Culture and growth of Lessonia trabeculata (Phaeophyta,Laminariales) juvenile sporophytes in La Herradura de Guayacan Bay,northern Chile

Lessonia trabeculata is one of the major kelps found along the northern coast of Chile. In addition to its ecological and economic importance, L. trabeculata may be severely affected by environmental disturbances such as El Níño, which during 1982–1983 cleared wide areas along the coast of Peru and Chile. The main goal of this work was to mass culture L. trabeculata and to observe the growth of sporophytes obtained in the laboratory and cultured in the sea. Juvenile sporophytes obtained in the laboratory were attached between 1 and 6 m in depth. The linear growth rate, as blade elongation, was recorded weekly for seven months. No significant differences (p < 0.05) were found in sporophyte blade linear growth at different depths. The best elongation growth rate was 7.5 ± 1.6 mm d^–1 at 3 m during March. This preliminary work suggests that L. trabeculata follows an annual growth cycle similar to that of other Laminariales with a high rate of blade elongation during the summer and decreasing towards autumn. This species can be considered a potential candidate for aquaculture to increase the availability of raw material and aid in repopulation of overexploited areas.     

“Active” conformation of an inactive semi-synthetic ribonuclease-S

We have studied the integrity of folded structure of a fully active semi-synthetic ribonuclease-S which lacks amino acid residues 16 through 20, and an inactive one with the same residues deleted and 4-fluoro-l-histidine substituted for active site histidine 12. Using “Y” form crystals, we obtained X-ray structural data to a resolution of 2·6 Å and, incorporating phase information calculated from refined ribonuclease-S coordinates, prepared several types of electron density maps. These showed that the overall backbone structure and active site configuration of both analogues do not differ noticeably from those of the native protein. Structural homology extends to the catalytically relevant side-chain at position 12; 4-F-His² assumes the same position as does His in active ribonuclease-S. This supports the view that the 4-F-Hisl2 analogue is inactive due to a change in histidine 12 imidazole basicity, rather than to any significant conformational distortion within the active site.     

Synthesis of α- and β-glycosides containing spin labels,as probes for studies of carbohydrate-protein interaction

Nitroxide spin-labeled α-d-glycopyranosides were synthesized in good yield and in a highly stereoselective manner by reaction of per-O-benzyl-α-d-glycopyranosyl bromides with 2,2,6,6-tetramethyl-4-piperidinol under the bromide ion-catalyzed conditions devised by Lemieux etal. After hydrogenolysis, the deblocked intermidiates were oxidized to give the desired, spin-labeled α-d-glycopyranosides. Nitroxide spin-labeled α-d-glycopyranosides, as well as a β-maltoside, were synthesized by standard methods. The synthesis is also described of 2-amino-2-deoxy-d-glucose and -d-galactose derivatives having a spin label at C-2, and of the spin-labeled compound 1-[4-(β-d-galactopyranosyloxy)phenyl]-3-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl)-2-thiourea.     

Manganese and Defenses against Oxygen Toxicity in Lactobacillus plantarum

Lactobacillus plantarum is aerotolerant during log-phase growth on glucose, but is an obligate aerobe on polyols. Respiration was cyanide resistant and under certain conditions was associated with the accumulation of millimolar concentrations of H(2)O(2). On glucose, optimal growth was observed in the absence of O(2). Extracts of L. plantarum did not catalyze the reduction of paraquat by reduced nicotinamide adenine dinucleotide, but plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone) was readily reduced. Such extracts produced O(2) (-) in the presence of NADH plus plumbagin. Plumbagin caused a 10-fold increase in the rate of respiration of intact cells in the presence of glucose and also imposed a loss of viability which was dependent upon both glucose and O(2). Although extracts of L. plantarum were devoid of true superoxide dismutase activity, this organism was comparable to superoxide dismutase-containing species in its resistance toward hyperbaric O(2) and toward the oxygen-dependent lethality of plumbagin. L. plantarum required Mn-rich media and actively accumulated Mn(II). Soluble extracts were found to contain approximately 9 mug of Mn per mg of protein and 75 to 90% of this Mn was dialyzable. Such extracts exhibited a dialyzable and ethylenediaminetetraacetic acid-inhibitable ability to scavenge O(2) (-). This O(2) (-)-scavenging activity was due to the dialyzable Mn(II) present in these extracts and could be mimicked by MnCl(2). Cells grown in Mn-rich media were enriched in dialyzable Mn and were more resistant toward oxygen toxicity and toward the oxygen-dependent plumbagin toxicity than were cells grown in Mn-deficient media. L. plantarum exhibited no nutritional requirement for iron and little or no iron was present in these cells, even when they were grown in iron-rich media. L. plantarum thus appears to use millimolar levels of Mn(II) to scavenge O(2) (-), much as most other organisms use micromolar levels of superoxide dismutases.