Fluctuations of grass pollen content in the atmosphere of East Perugia and meteorological correlations (year 1989)

Summary Gramineae pollination from a pollen monitoring station located in the eastern suburb of Perugia and meteorological correlations are reported. The data refers to the year 1989. Grass pollen peak pollination was from May to July; in this period the influence of relative humidity and of temperature on pollen concentration was very high. Phenological observations, to identify the time of maximum stamen extension in the most common genera in the area, are also reported. During the period of investigation the counts of pollen grains over four-hour periods showed a regular diurnal rhythm with peaks of concentration in the four-hour period 16.00–20.00. Aerosporological data and meteorological data related to four-hour periods were correlated following different criteria.     

Observing the Temperature Dependent Transition of the GP2 Peptide Using Terahertz Spectroscopy

The GP2 peptide is derived from the Human Epidermal growth factor Receptor 2 (HER2/nue), a marker protein for breast cancer present in saliva. In this paper we study the temperature dependent behavior of hydrated GP2 at terahertz frequencies and find that the peptide undergoes a dynamic transition between 200 and 220 K. By fitting suitable molecular models to the frequency response we determine the molecular processes involved above and below the transition temperature (T _D). In particular, we show that below T _D the dynamic transition is dominated by a simple harmonic vibration with a slow and temperature dependent relaxation time constant and that above T _D, the dynamic behavior is governed by two oscillators, one of which has a fast and temperature independent relaxation time constant and the other of which is a heavily damped oscillator with a slow and temperature dependent time constant. Furthermore a red shifting of the characteristic frequency of the damped oscillator was observed, confirming the presence of a non-harmonic vibration potential. Our measurements and modeling of GP2 highlight the unique capabilities of THz spectroscopy for protein characterization.     

The Nitrogen Use Efficiency of C(3) and C(4) Plants : III. Leaf Nitrogen Effects on the Activity of Carboxylating Enzymes in Chenopodium album (L.) and Amaranthus retroflexus (L.)

The relationships between leaf nitrogen content per unit area (N_a) and (a) the initial slope of the photosynthetic CO₂ response curve, (b) activity and amount of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC), and (c) chlorophyll content were studied in the ecologically similar weeds Chenopodium album (C₃) and Amaranthus retroflexus (C₄). In both species, all parameters were linearly dependent upon leaf N_a. The dependence of the initial slope of the CO₂ response of photosynthesis on N_a was four times greater in A. retroflexus than in C. album. At equivalent leaf N_a contents, C. album had 1.5 to 2.6 times more CO₂ saturated Rubisco activity than A. retroflexus. At equal assimilation capacities, C. album had four times the Rubisco activity as A. retroflexus. In A. retroflexus, a one to one ratio between Rubisco activity and photosynthesis was observed, whereas in C. album, the CO₂ saturated Rubisco activity was three to four times the corresponding photosynthetic rate. The ratio of PEPC to Rubisco activity in A. retroflexus ranged from four at low N_a to seven at high N_a. The fraction of organic N invested in carboxylation enzymes increased with increased N_a in both species. The fraction of N invested in Rubisco ranged from 10 to 27% in C. album. In A. retroflexus, the fraction of N_a invested in Rubisco ranged from 5 to 9% and the fraction invested in PEPC ranged from 2 to 5%.     

Stimulation of Ca efflux from fura-2-loaded platelets activated by thrombin or phorbol myristate acetate

We investigated the restoration of [Ca²⁺]_i in fura-2-loaded human platelets following discharge of internal Ca²⁺ stores in the absence of external Ca²⁺. After stimulation by thrombin [Ca²⁺]_i returned from a peak level of 0.6 μM to resting levels within 4 min. When ionomycin discharged the internal stores the recovery was slower with [Ca²⁺]_i still elevated at around 0.5 μM after 5 min. Thrombin added shortly after ionomycin could accelerate the recovery of [Ca²⁺]_i and restore resting levels within 5 min, an effect that was mimicked by phorbol-12-myristate-13-acetate (PMA). Since the continued presence of ionomycin precluded reuptake into the internal stores we conclude that thrombin and PMA stimulate Ca²⁺ efflux, perhaps via protein kinase C actions on a plasma membrane Ca²⁺ pump.     

A selective differential medium for the isolation of Listeria monocytogenes

A new medium has been developed for the isolation of Listeria monocytogenes from clinical specimens with a mixed flora. Almost complete inhibition of unwanted organisms was achieved and recognition of colonies of Listeria spp. was usually possible after 24 h using the aesculin-ferric ammonium citrate indicator system. Compared to McBride agar the new medium was more inhibitory to representative contaminating species in pure culture and more successful in isolating small numbers of L. monocytogenes from artificially seeded clinical specimens.     

Nucleotide sequence of the gene coding for a 130-kDa mosquitocidal protein of Bacillus thuringiensis israelensis

The nucleotide sequence of pVB131 containing the gene coding for a 130-kDa Bacillus thuringiensis israelensis (B.t.isr) mosquitocidal protein was determined. The pVB131 plasmid was constructed by Sekar and Carlton [Gene 33 (1985) 151-158]. Our sequencing revealed only one open reading frame large enough to code for a protein of 130 kDa. The translation start site was determined by sequencing the protein isolated from B.t.isr. The amino acid sequence of the protein was deduced from the nucleotide sequence, and its Mr was determined as 128,505. Immunological and biochemical analyses of B.t.isr mosquitocidal proteins indicated that the 130-kDa protein coded by pVB131 was indeed expressed in B.t.isr. Comparing the peptide sequence of the 130-kDa B.t.isr toxin with the sequences of other B.t. toxins having activities specific to lepidopteran species showed that several domains were highly homologous. This suggests that they are evolutionarily related to each other, and in the evolutionary process the sequences in the homologous domains that are important to the insecticidal activity have been conserved.     

The in-vivo response of the ribulose-1,5-bisphosphate carboxylase activation state and the pool sizes of photosynthetic metabolites to elevated CO2 inPhaseolus vulgaris L.

The short-term, in-vivo response to elevated CO₂ of ribulose-1,5-bisphosphate carboxylase (RuBPCase, EC 4.1.1.39) activity, and the pool sizes of ribulose 1,5-bisphosphate, 3-phosphoglyceric acid, triose phosphates, fructose 1,6-bisphosphate, glucose 6-phosphate and fructose 6-phosphate in bean were studied. Increasing CO₂ from an ambient partial pressure of 360–1600 bar induced a substantial deactivation of RuBPCase at both saturating and subsaturating photon flux densities. Activation of RuBPCase declined for 30 min following the CO₂ increase. However, the rate of photosynthesis re-equilibrated within 6 min of the switch to high CO₂, indicating that RuBPCase activity did not limit photosynthesis at high CO₂. Following a return to low CO₂, RuBPCase activation increased to control levels within 10 min. The photosynthetic rate fell immediately after the return to low CO₂, and then increased in parallel with the increase in RuBPCase activation to the initial rate observed prior to the CO₂ increase. This indicated that RuBPCase activity limited photosynthesis while RuBPCase activation increased. Metabolite pools were temporarily affected during the first 10 min after either a CO₂ increase or decrease. However, they returned to their original level as the change in the activation state of RuBPCase neared completion. This result indicates that one role for changes in the activation state of RuBPCase is to regulate the pool sizes of photosynthetic intermediates.Abbreviations and symbols A net CO₂ assimilation rate - C_a ambient CO₂ partial pressure - C_i intercellular CO₂ partial pressure - CABP 2-carboxyarabinitol 1,5-bisphosphate - k_cat catalytic turnover rate per RuBPCase molecule - PFD photon flux density (400 to 700 nm on an area basis) - PGA 3-phosphoglyceric acid - P_i orthophosphate - RuBP ribulose 1,5-bisphosphate - RuBPCase ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39)     

The role of air temperature in determining dormancy release and flowering ofCorylus avellana L.

Summary 7 years of airborne pollen monitoring in Perugia (central Italy) were used to determine the temperature requirements to break dormancy and to resume growth and bloom ofCorylus avellana L.,Corylus needs 1000 chill-units to complete its dormancy and this value, in the Perugian area, is met by the end of December or the first days of January. MoreoverCorylus trees require 220 growth degree hours before they are able to flower. If air temperature is high, this value can be achieved in only 10 days, but if the temperature remains too low, the heat accumulation can require up to 35 days. With these parameters it is possible to build a model to predict the date of the beginning ofCorylus avellana pollen season.