Somatostatin mydriasis in mice

Administration of somatostatin intracerebroventricularly to mice produced a dose-dependent mydriasis, whereas intravenous injections were ineffective. Naloxone could prevent or abolish this effect. It is suggested that somatostatin either directly excites opiate receptors or activates endopioid pathways involved in the regulation of pupillary size.     

Heterogeneity of Benzodiazepine Receptors: Experimental Differences Between [3H]Flunitrazepam and [3H]Ethyl-β-carboline-3-carboxylate Binding Sites in Rat Brain Membranes

Abstract: This study was designed to analyze possible differences in the binding of [³H]flunitrazepam ([³H]FNZP) and [³H]ethyl - β - carboline - 3 - carboxylate ([³H]β-CCE), to rat brain membranes, in various experimental conditions. In cerebral cortex, hippocampus, cerebellum, and orain stem the number of binding sites for [³H]β-CCE was higher than for [³H]FNZP; both were displaced by clonazepam. Until the 7th day of postnatal brain development the numbers of [³H]FNZP and [³H]β-CCE sites were equivalent; but later on, the β-carboline sites increased to a higher level. Noradrenergic denervation by 6-hydroxydopamine was followed in the hippocampal formation. Already after 2 days, there was a decrease in [³H]FNZP sites, which reached 70% of control after 14 days. Similar results were obtained with DSP-4 denervation. This change was only in B_max and not in K_D, In contrast, the [³H]β-CCE sites did not change with denervation. Neonatal injection of l - 2,4,5 - trihydroxyphenylalamine or DSP-4 produced in the adult a decrease in [³H]FNZP sites in the cerebral cortex, in parallel with the noradrenergic denervation. On the other hand, there was an increase in the cerebellum and brain stem, in correspondence with the hyperinnervation by sprouting. In these rats, the number of sites for [³H]β-CCE did not change in the different brain regions. With 0.1% Triton X-100, applied to synaptosomal membranes, [³H]FNZP binding was reduced by 35%, while that of [³H]β-CCE was not significantly changed. These results suggest that there is heterogeneity of binding sites for benzodiazepine receptors in rat brain. A tentative interpretation of the experiments involving noradrenergic denervation and hyperinnervation, as well as those with Triton X-100, is that [³H]FNZP binds to pre- and postsynaptic receptors, while [³H]β-CCE binds mainly to postsynaptic benzodiazepine receptors.     

Effect of alpha-fluoromethylhistidine on the histamine content of the brain of W/Wv mice devoid of mast cells: turnover of brain histamine

In the brains of W/Wv mutant mice that have no mast cells, the histidine decarboxylase (HDC) level is as high as in the brain of congenic normal mice (+/+), but the histamine content is 53% of that of +/+ mice. The effects of alpha-fluoromethylhistidine (alpha-FMH) on the HDC activity and histamine content of the brain of W/Wv and +/+ mice were examined. In both strains, 30 min after i.p. injection of alpha-FMH the HDC activity of the brain had decreased to 10% of that in untreated mice. The histamine content decreased more gradually, and after 6 h about half of the control level remained in +/+ mice, whereas histamine had disappeared almost completely in W/Wv mice. It is concluded that the portion of the histamine content that was depleted by HDC inhibitor in a short time is derived from non-mast cells, probably neural cells. The half-life of histamine in the brain of W/Wv mice was estimated from the time-dependent decrease in the histamine content of the brain after administration of alpha-FMH: 48 min in the forebrain, 103 min in the midbrain, and 66 min in the hindbrain.     

Influence of auxin and mycorrhizal fungi on thein vitro formation and growth ofPinus pinaster roots

Summary Experiments, performed withPinus pinaster cloned shoots submitted to an auxin treatment (NAA 10^–6 M, 18 days), demonstrated that rooting abilityin vitro persists over 5 successive induction cycles (through out a 9-month period). Rooting ability needs a permanent synthesis of auxin synergists which activate the metabolism of cell dedifferentiation and root primordium initiation. Agar culture permitted intense meristem initiation, but prevented active root elongation. In the presence of a mycorrhizal fungus,Pisolithus tinctorius orHebeloma cylindrosporum, roots resumed growth and short lateral root formation was stimulated. These two phenomena induced by fungal association improve the quality of the root systems required to facilitate successful transplantation from test-tubes to field conditions.     

Specific photoperiodic stimulation of dry matter production in a high-latitude cultivar of Poa pratensis

Vegetative plants of Poa pratensis L. cv. Holt (origin 69°N) raised in short days gave large and significant increases in plant dry weight, plant height and leaf area upon exposure to continuous light, compared with 8-h short days, at essentially identical daily inputs of radiant energy (8-h summer daylight ± low intensity extension). For example, by the fourth harvest (after 26, 34 and 46 days at 21, 15 and 9°C, respectively), the dry weights of plants in long days were 81, 163 and 195% greater than those of the corresponding short-day controls at the respective temperatures. Plant leaf areas in long days were between two and four times as large as control values by the end of the experiment. This was mainly due to increased leaf length caused by long-day stimulation of cell extension and division. However, the photoperiod did not affect the partitioning of assimilates amongst leaves, culms and stolons. Most of these effects could also be brought about by exogenous gibberellin application to plants in short days. However, in contrast to the effect of long days, gibberellin treatment also induced stem internode elongation even in these vegetative plants. Examination by standard growth analysis procedures revealed that the observed increases in relative growth rate were due primarily to increased net assimilation rate followed, several days later, by increases in leaf area ratio when newly-emerged leaves began to constitute a significant proportion of the leaf area. It is concluded that these reactions are of great adaptive significance for growth at the marginal temperatures prevailing at high latitudes.     

Nutrition of winter wheat during the life cycle. I. Yield and accumulation of dry matter and minerals

Mineral uptake by winter wheat (Trilicum aestivum L. cv. Martonvasari 8) was studied throughout the life cycle. Accumulation of macronutrients (i.e. total nitrogen, phosphorus, potassium, sodium, magnesium and calcium) and the water content of roots and shoots of plants grown in complete nutrient solution were higher than those of plants grown in two types of soils. The supply of macronutrients was in some cases limiting for soil-grown plants as revealed by a comparison of available and accumulated amounts of these nutrients. Their supply was abundant, however, for solution-grown plants. This led to a doubling of grain yield for the latter plants with a three fold increase in accumulation of dry matter and a five-fold increase in fresh weight. The efficiency ratios of solution-grown plants to soil-grown plants were approximately 1 for N and Na, 0.5 for Mg and Ca, and 0.3 for P and K.     

The effects of time of seed production on the germination response of Spergularia marina

Germination studies were carried out with seeds of Spergularia marina L. Griseb produced over an interval of six months (June-November). The response of the seeds to light and dark, various constant and alternating temperature regimes, and salinity were determined. In addition, the effects of soil moisture status at the time of seed production on the subsequent germination response of seeds were also determined. Light was an absolute requirement for germination. While a constant temperature regime did not generally favour germination of seed of any month, alternating temperature greatly enhanced germination with an optimum at 5/15°C in all seeds. When imbibed in solutions of different salinities, seeds collected in July and October behaved like true halophyte seeds whereas those collected in June. August, September and November behaved like glycophyte seeds.
High concentration of gibberellic acid (3 000 μ M ) stimulated dark germination in the June and November seed lots, but in light, low GA3 concentration (300 μ M ) stimulated germination most. The addition of kinetin (30 μ M ) plus gibberellic acid enhanced germination in the dark in contrast to GA3 alone; kinetin alone stimulated a very low percentage germination.
The moisture status of the soil at the time seeds were produced did not affect the germination response of an early seed crop (July) but affected that of the later seeds (August).
Judging from the different germination responses, it appears that the seeds belong to at least two physiological groups, one which appears to need either a dark-wet or cold-wet pretreatmem for high germination to occur; and the other group which does not need pretreatmem. The ecological significance of these varied responses is discussed in relation to the survival of the species in its habitat.     

Factors affecting invertase activity in soils

Summary The rate of reducing sugars released through invertase activity exhibited a buffer pH optimum of 5.0. Generally, the decline in invertase activity in its pH-profile near the optimal pH range was due to a reversible reaction that involved ionization or deionization of the functional groups in the active centre of the protein, but under highly acidic or alkaline conditions (pH<4 to >9) the reduced activity appears to be due to irreversible inactivation of the enzyme. The dependence of the reaction on the amount of enzyme present was linear up to 3 g of soil. By varying the substrate concentration, it was found that the reaction rate of this enzyme approached zero-order kinetics when 145mM of sucrose solution was added to soils. Application of three linear transformations of the Michaelis-Menten equation indicated that the apparent K_m constants varied among the soils studied, but the results obtained by the three plots were similar. By using the Lineweaver-Burk plot, the K_m values in five soils ranged from 16.3 to 42.1 (avg.=24.5) mM and V_max values ranged from 1.98 to 7.37 mg of reducing sugars released/g of soil/24 h. The optimum temperature for invertase activity in soils was observed at 50°C and denaturation of the enzyme began at 55°C. The activation energy (E_a) and enthalpy of activation (H^*) values for invertase activity, expressed in kJ/mole, ranged from 6.1 to 43.1 and 3.5 to 40.5, respectively. The Q₁₀ values for the invertase reaction in soils with a temperature range to 10 to 50°C ranged from 1.08 to 1.96. Under standerd conditions, the accumulation of reducing sugars was linear with time up to 48 h. Among the various pretreatments that affected invertase activity in soils, toluene, TCA, and PMA inhibited the enzyme by an average of 19, 54, and 11%, respectively. Steam-sterilization essentially destroyed soil invertase.     

Physical conditions of propagation media and their influence on the rooting of cuttings

Summary The formation and subsequent growth of roots by cuttings of poinsettia, hydrangea, rose and azalea in various propagation media, Jiffy-7, Jiffy-9 and Grodan under different conditions of aeration was investigated. The interrelationships of the effects of air content of the media, temperature and light intensity on the rooting of poinsettia cuttings was also studied.With low air contents (0 cm moisture tension) in the propagation media the formation and growth of roots was strongly inhibited. The rooting performance of rose appeared to be less affected by the poor aeration. Increasing air content improved rooting but best results were obtained at moisture tensions of 4 to 8 cm. Rooting seems to be better correlated with oxygen diffusion rate (ODR) than with air content.For poinsettia cuttings the optimum temperature for rooting was 24 to 28°C. At low temperatures rooting was delayed while at higher temperatures it was almost completely inhibited. Callus formation increased with temperature but decreased with increasing moisture tension. Conditions which induced large callus formation inhibited root formation.High light intensity during rooting reduced overall rooting performance and the inhibition was most pronounced in conjunction with high moisture tensions.Report No. 255.     

Studies on the prolonged storage of Metarhizium anisopliae conidia: effect of growth substrate on conidial survival and virulence against mosquitoes

Metarhizium anisopliae was grown on six complex mycological media and on three types of rice at three moisture levels to determine the effect of growth substrate on conidial yield, viability, and virulence against mosquitoes immediately after spore maturation and after the storage of conidia at four different temperature-relative humidity (RH) combinations over a 1-year period. Conidial yields varied with the mycological media, but the viability and virulence of conidia against mosquitoes produced on all substrates were similar when spores were stored under the same conditions. The storage conditions were more critical to spore survival and virulence than the substrate upon which conidia were produced. The comparison of rice types for conidial production indicated that conidial yield, viability, and virulence to mosquitoes were more dependent upon the moisture level during growth and on the storage conditions that upon the rice used. The best storage conditions among those tested for the retention of both spore viability and virulence against mosquitoes were 19°C–97% RH and 4°C–0% RH.