Nucleotide sequence of the glnA-glnL intercistronic region of Escherichia coli

The nucleotide (nt) sequence of a 682-bp fragment containing the 3' end of the glnA gene, the region between the glnA and glnL genes, and the 5' end of the glnL gene from Escherichia coli was determined. This segment contains the region coding for the last 107 amino acids (aa) of glutamine synthetase, including the adenylylation site of this enzyme. The analysis of this sequence revealed two REP sequences, a Rho-independent terminator, the putative glnL promoter and the possible binding site for the glnG product, NRI.     

Biomass and production of Argyrodiaptomus furcatus,a tropical calanoid copepod in Broa Reservoir,southern Brazil

The biomass and the production of Argyrodiaptomus furcatus (Sars), the most abundant copepod in Broa Reservoir (São Carlos, São Paulo State), were estimated, determining in the laboratory the development time and the quantity of organic carbon and establishing the relationship between these two parameters. The daily production was calculated from P = B(1- e^gt) and the annual production was obtained by integrating daily production against time. The maximum production of Argyrodiaptomus furcatus in the reservoir depends on the region considered and on the period of the year. The maximum production was 45.15 mg C m^–3d^–1 in March, 1976 at station II, region of macrophytes and 6.74 mg C m^–3d^–1 at station IV, near the dam. The mean production for the year is 6.26 mg C m^–3d^–1 at station II and 1.43 mg C m^–3d^–1 at station IV.     

Identifiability from parameter bounds. Structural and numerical aspects

Some a priori and a posteriori aspects of the identifiability problem for unidentifiable models are discussed. It is argued that the nation of identifiability from parameter bounds has a minor a priori structural relevance. The parameter bounds rationale may prove a useful a posteriori numerical notion. However, its practical potentiality needs careful evaluation, as the use of point estimates automatically builds into the model some hidden structural constraints. Examples are given.     

Differential salt fractionation of active and inactive genomic domains in chicken erythrocyte

We have utilized the Sanders salt fractionation technique (Sanders, M. M. (1978) J. Cell Biol. 79, 97-109) to analyze the products of micrococcal nuclease digestion of adult chicken erythrocyte nuclei. By dot-blot hybridization with specific gene probes, it is found that nucleosomes from the globin gene domain, including a region extending to about 10 kilobase pairs 5' to the beta p gene are selectively enriched in the fractions eluted at low salt. In contrast, a single copy sequence located at about 10 kilobase pairs 5' to the beta p gene was concentrated in the less salt-soluble fractions. The vitellogenin and ovalbumin genes, which are never expressed in erythroid tissues, are also concentrated in the less salt-soluble fractions. Some more generally expressed genes (histone H4, thymidine kinase) appear to be more uniformly distributed. The low salt fractions are depleted in H1/H5, enriched in high mobility group 14 and 17, and contain somewhat more highly acetylated histones.     

NADPH-generating system: Influence on microsomal mono-oxygenase stability during incubation for the liver-microsomal assay with rat and mouse S9 fractions

Activity levels of 7-ethoxycoumarin O-deethylase (ED), aminopyrine N-demethylase (APD), p-nitroanisoleO-demethylase (p-NAD) and glucose-6-phosphate dehydrogenase (G-6-PDH) were determined in incubation mixtures for the liver-microsomal assay (LMA) at time 0 and after 1 and 2 h incubation under conditions for mutagenic assay. The experiments were performed with S9 liver fractions from mice (induced with Na-phenobarbital and β-naphthoflavone) and rats (induced with Aroclor 1254) with and without G-6-PDH in the incubation mixtures.

In the absence of G-6-PDH the activities were significantly lower at time 0 in the mouse. The pattern of stability, however, was similar for the activities, with an increase of stability after 1 and 2 h of pre-incubation (an exception for p-NAD).

Only ED activity showed a similar behaviour in the rat. No differences were present for APD and p-NAD activities at time 0 in the rat, but the enzyme stabilities were significantly decreased after 2 h of incubation (about 15% and 10% for APD and p-NAD respectively) in the absence of G-6-PDH.

At time 0, the amounts of G-6-PDH differed between mouse and rat fractions; however, during the incubations for LMA they decreased by about 57% and 53% for the two species, respectively. In addition to the above biochemical results, the presence of exogenous G-6-PDH in the incubations for the mutagenic assay, significantly increased the mitotic gene conversion and mitotic crossing-over of dimethylnitrosamine (DMN) and AR2MNFN (a nitroimidazo[2,1-b]thiazole) in the D₇ strain of Saccharomyces cerevisiae.     

Origin of the Thymidine Kinase Induced by Polyoma Virus in Productively Infected Cells

Cells of the 3T3 mouse line efficiently supported the multiplication of polyoma virus, and the infectious process was accompanied by a marked increase in thymidine kinase (TK) activity. Two lines of 5-bromodeoxyuridine-resistant 3T3 cells have been isolated. As expected, these cells incorporated practically no exogenous thymidine into their deoxyribonucleic acid (DNA) and contained negligible TK activity. Like the parental 3T3 cells, TK(-) lines were susceptible to productive infection by polyoma virus, but infection did not lead to an increase in TK activity. Since kinase activity did appear after infection with another virus (vaccinia) known to contain the gene(s) for that enzyme, it is concluded that TK is not one of the gene products of polyoma virus. As induction of cellular DNA synthesis by polyoma virus occurs normally when the TK(-) cells are infected in the stationary phase, TK cannot play a role in the determination of this phenomenon.     

The ATP-bioluminescence method for a rapid evaluation of the microbial activity in the stone materials of monuments

The examination of the state of conservation of works of art in stone includes the assessment of the presence of microbiological agents on the surface of the decayed monuments. These microorganisms can accelerate, via their metabolic activity, the decay process of the stone surface. At present this assessment is made with the traditional techniques for the microbiological examination of the soil, provides results only after a delay of 30 days. A bioluminescent ATP assay should provide rapid quantitation of actively growing organisms on the surface of a stone monument, and the applicability of this technique was verified on some samples of sandstone (Pietraforte) collected from a historic building (the Strozzi Palace) in Florence. These samples were evaluated for the amount of the ATP and the total number of microorganisms. The results obtained suggest that the bioluminescent assay could be suitable for detecting and quantitating the presence of microorganisms in a sample of stone.     

Benzyladenine induces the appearance of LHCP-mRNA and of the relevant protein in dark-grown excised watermelon cotyledons

Cotyledons were excised from imbibed watermelon seeds, grown for 4 days in darkness on water or 10 M benzyladenine (BA) and then tested for the presence of the light-harvesting chlorophyll a/b protein (LHCP) and its mRNA. LHCP was assayed immunologically by western blotting of SDS gels: the protein was present in plastids, but it was not recovered with the thylakoid fraction. Antibodies directed against LHCP precipitated a 32 kDa polypeptide from translation products of poly(A) RNA of cotyledons only if these had been grown on BA. Taken together the data suggest that in absence of light cytokinins are necessary for the maintenance of a detectable level of LHCP-mRNA as well as for synthesis of the protein.     

A neural model for generating and learning a rapid movement sequence

 In this article, a neural model for generating and learning a rapid ballistic movement sequence in two-dimensional (2D) space is presented and evaluated in the light of some considerations about handwriting generation. The model is based on a central nucleus (called a planning space) consisting of a fully connected grid of leaky integrators simulating neurons, and reading an input vector Ξ (t) which represents the external movement of the end effector. The movement sequencing results in a succession of motor strokes whose instantiation is controlled by the global activation of the planning space as defined by a competitive interaction between the neurons of the grid. Constraints such as spatial accuracy and movement time are exploited for the correct synchronization of the impulse commands. These commands are then fed into a neuromuscular synergy whose output is governed by a delta lognormal equation. Each movement sequence is memorized originally as a symbolic engram representing the sequence of the principal reference points of the 2D movement. These points, called virtual targets, correspond to the targets of each single rapid motor stroke composing the movement sequence. The task during the learning phase is to detect the engram corresponding to a new observed movement; the process is controlled by the dynamics of the neural grid. Received: 16 March 1995/Accepted in revised form: 25 July 1995