Polyacrylonitrile Hemofiltration for the Adsorption Myoglobin in Tardy Revascularization Syndrome: In Vitro Assessment

The Authors examine the behavior of P.A.N. membranes hemoperfusion combined with district hemodialysis in the prevention of tardy revascularization syndrome. Their experience “in vitro” seems to confirm the use of P.A.N. membrane is advisable whenever an increase of the myoglobin concentration occurs and they also envisage the use of the P.A.N. membrane in the prevention of T.R.S.

Psychiatric Manifestations as a Primary Symptom in Antiphospholipid Syndrome

Antiphospholipid syndrome is a disorder characterised by recurrent venous or arterial thrombosis and/or foetal losses associated with typical laboratory abnormalities. The initial manifestation of anthiphospholipid syndrome can involve many organ systems either singly or in combination. We describe the case of a 62 year old female showing schizophrenia-like symptoms in which further evaluations allowed us to diagnose the antiphospolipid syndrome.

Alois Alzheimer and Gaetano Perusini: should man divide what fate united?

Three points of interest lie in considering how Alzheimer, and more significantly Perusini, struggled to throw light on the cause of this devastating disease. There is a stimulating possibility that Perusini believed presenile forms of Alzheimer's disease described the same disease as senile forms. If so this would anticipate current opinion, and reveal Perusini to dissent from Kraepelin. In addition, Perusini may have understood the pathological relationship between neuritic plaques and vascular changes, once more foreseeing the modern view of Alzheimer's disease. Finally, Perusini and Alzheimer disagreed with Jung's view concerning the relationship between neuropathology and clinical psychiatry. This point highlights the major change occurring at that time from classical neurology to the psychoanalytic era. In his last work (1911) Alzheimer quoted his Italian disciple many times, even speaking of 'Perusini's cases' (Perusinischen Fälle). This article is an attempt to change the eponym of Alzheimer's disease into the Alzheimer-Perusini disease. This is a brief history of a master and his disciple, whose scientific lives were, by events, divided.

Trend of healthcare-associated infections in children: annual prevalence surveys in a research hospital in Italy, 2007-2010

BACKGROUND

Annual prevalence surveys of healthcare-associated infections (HAIs) between 2007 and 2010 were conducted in the largest tertiary care children's hospital in Italy. During this period, actions to improve HAI prevention were implemented, including strengthened isolation measures; adoption of care bundles for invasive procedures; hand hygiene promotion using the World Health Organization multimodal strategy; and promotion of appropriate antimicrobial use.

AIM

To determine the impact of these measures on HAI rates.

METHODS

A total of 1506 patients were surveyed. Information on patient demographics, mechanical ventilation, central line and urinary catheterization in the preceding 48 h, and surgery in the previous 30 days were abstracted from medical charts. The type and date of onset of HAIs, and microbiological data were recorded. Univariate and multivariate logistic analysis were used to evaluate changes in HAI rates over time, and the influence of ward type and patient characteristics.

FINDINGS

There were significant (P < 0.001) reductions in the prevalence of patients developing HAI (from 7.6% to 4.3%) and in the prevalence of total HAIs (from 8.6 to 4.3 per 100 patients). Factors independently associated with increased HAI risk were hospitalization in intensive care ward, length of stay >30 days, presence of invasive device, and age 6-11 years.

CONCLUSION

This HAI prevention strategy was influential in decreasing infections among hospitalized children. Repeated prevalence surveys are an effective tool for monitoring HAI frequency, increasing awareness among the healthcare personnel, and contributing to the establishment of effective infection control.

Antidepressant treatment restores brain-derived neurotrophic factor (BDNF) serum levels and ameliorates motor function in parkinson's disease patients

Introduction

Depression is a common psychiatric disorder in Parkinson's disease (PD). It has been proposed that antidepressant drugs may bust brain production of trophic factors, such as brain-derived neurotrophic factor (BDNF) and glial cell derived neurotrophic factor (GDNF), an effect associated with improvement of clinical symptoms. However, BDNF and GDNF play also a role in the maintenance of dopaminergic neurons, which undergo to neuronal death during PD course.

Aims

Based on these findings we explored the hypothesis that PD depressed patients may have altered BDNF or GDNF serum levels and that antidepressant drugs may restore them and potentially have beneficial effects not only for depressive but also parkinsonian symptoms.

Methods

We measured by enzyme linked immunosorbent assay (ELISA) the serum levels of BDNF and GDNF in depressed PD patients, non depressed PD patients and healthy subjects and correlated them with clinical observations.

Results

We found:

(1)

Conclusion

Our data suggest that PD patients are characterized by a reduction of BDNF serum levels and that depression may exacerbate this effect and worse PD symptoms. It is proposed that association between anti-parkinsonian treatment and SSRI could be a good therapeutic chance not only for treating depression in PD but also for improving PD symptoms.

Pregabalin versus naltrexone in alcohol dependence: a randomised, double-blind, comparison trial

Pregabalin (PRE) acts as a presynaptic inhibitor of the release of excessive levels of excitatory neurotransmitters by selectively binding to the alpha(2)-delta subunit of voltage-gated calcium channels. In this randomised, double-blind comparison trial with naltrexone (NAL), we aimed to investigate the efficacy of PRE on alcohol drinking indices. Craving reduction and improvement of psychiatric symptoms were the secondary endpoints. Seventy-one alcohol-dependent subjects were detoxified and subsequently randomised into two groups, receiving 50 mg of NAL or 150-450 mg of PRE. Craving (VAS; OCDS), withdrawal (CIWA-Ar) and psychiatric symptoms (SCL-90-R) rating scales were applied. Alcohol drinking indices and craving scores were not significantly different between groups. Compared with NAL, PRE resulted in greater improvement of specific symptoms in the areas of anxiety, hostility and psychoticism, and survival function (duration of abstinence from alcohol). PRE also resulted in better outcome in patients reporting a comorbid psychiatric disorder. Results from this study globally place PRE within the same range of efficacy as that of NAL. The mechanism involved in the efficacy of PRE in relapse prevention could be less related to alcohol craving and more associated with the treatment of the comorbid psychiatric symptomatology.

Inhibition of AChE: structure-activity relationship among conformational transition of Trp84 and biomolecular rate constant

In this study the authors attempt to correlate kinetic constants for carbamylation of AChE, by a series of carbamate inhibitors, with the conformational positioning of Trp84 in transition state complexes of the same carbamates with Torpedo AChE, as obtained by computerized molecular modelling. They present evidence for changes in the distance of the carbamates from the center of the indole ring which can be correlated with the bimolecular rate constants for inhibition. As a result the greater the distance from Trp84, the smaller the bimolecular inhibition constant value, ki (= k2/Ka), becomes. In conclusion, the value of the bimolecular rate constant for selected AChE inhibitors (structural changes that have been hypothesised or natural alkaloids of unknown activity) which possess similar size and rigidity, can be obtained. Under these conditions energy minimization alone seems to be sufficient even to accurately predict protein-substrate interactions that actually occur. Modelling studies also suggest that conformational re-orientation of Trp84 in the transition state could produce an overall movement of the Cys67-Cys94 loop.

2,3-DPG-Hb complex: a hypothesis for an asymmetric binding

This study was undertaken to test the symmetry of 2,3-diphosphoglycerate (2,3-DPG) binding site in hemoglobin (Hb). From Arnone's study [A. Arnone, Nature (London) 237 (1972) 146] the 2,3-DPG binding site is located at the top of the cavity, that runs through the center of the deoxy-Hb molecule. However, it is possible that this symmetry reported by Arnone, for crystals of 2,3-DPG-Hb complex, might not be conserved in solution. In this paper, we report the 31P nuclear magnetic resonances of the 2,3-DPG interaction with Hb. The 2,3-DPG chemical shifts of the P2 and P3 resonance are both pH- and hemoglobin-dependent [protein from man, polar bear (Ursus maritimus), Arctic fox (Alopex lagopus) and bovine]. 2,3-DPG binds tightly to deoxyhemoglobin and weakly, nevertheless significantly, to oxyhemoglobin. In particular, our results suggest similar spatial position of the binding site of 2,3-DPG in both forms of Hb in solutions. However, the most unexpected result was the apparent loss of symmetry in the binding site, which might correlate with the ability of the hemoglobin to modulate its functional behavior. The different interactions of the phosphate groups indicate small differences in the quaternary structure of the different deoxy forms of hemoglobin. Given the above structural perturbation an asymmetric binding in the complex could justify, at least in part, different physiological properties of Hb. Regardless, functionally relevant effects of 2,3-DPG seem to be measured and best elucidated through solution studies.

Effects of cholinergic drugs on neocortical EEG and flash-visual evoked potentials in the mouse

The effects of single intraperitoneal injection of two cholinesterase inhibitors, physostigmine (PHY; 0.01, 0.025, 0.05, 0. 1, 0.2 mg/kg) and heptylphysostigmine (HEP; 0.5, 2, 6 mg/kg) on electroencephalographic (EEG) activity and flash visual evoked potentials (f-VEP) in the occipital cortex were compared in DBA/2 mice. EEG spectral analysis of awake periods showed that PHY at all doses and HEP at 2 mg/kg induced an increase of power in the 4.25- to 7-Hz frequency band. Furthermore, PHY at the higher doses and HEP at all doses induced a decrease of power in the 7.25- to 12-Hz frequency band, while the lower doses of PHY (0.01, 0.025 mg/kg) produced an increase of this band. EEG effects elicited by the two drugs were similar, when doses displaying analogous biochemical effects (acetylcholinesterase inhibition) were used (i.e. 0.01 and 0. 025 mg/kg of PHY versus 0.5 and 2 mg/kg of HEP). PHY and HEP induced similar changes in f-VEPs. Amplitudes of early and late components (P1N1, N1P2, P4N4 and particularly N1P3) were enhanced, while amplitudes of middle components were depressed after all doses. The peak latency measures were generally delayed, even though, after the lower doses, a trend to a latency reduction was evident in late components. This finding might indicate a possible effect on stimulus speed diffusion by 'low therapeutic' doses, analogous to the ones used in men. Our data show that both drugs are effective in modifying EEG and f-VEP parameters connected with brain cholinergic function, although in a very narrow dose range.

Effects of the novel acetylcholinesterase inhibitor N-octyl-1,2,3, 4-tetrahydro-9-aminoacridine on locomotor activity and avoidance learning in mice

The acetylcholinesterase reversible inhibitor N-octyl-1,2,3, 4-tetrahydro-9-aminoacridine (THA-C8) is a new synthesized derivative of tacrine (THA) characterized by an alkyl chain in the molecular structure which ameliorates the penetrability of the compound into the central nervous system. THA-C8 (0.1-5 mg/kg) significantly reduced spontaneous locomotor activity in CD1 mice at a dose of 3 mg/kg. Moreover, THA-C8 (0.2-2 mg/kg) significantly improved shuttle-box avoidance acquisition at doses (0.25, 0.3, 1 mg/kg) not affecting locomotion and that are much lower than the doses reported to be effective for THA in animal models. From the data reported it seems that the new compound could be interesting for therapeutic purposes.

Anionic binding site and 2,3-DPG effect in bovine hemoglobin

It is generally believed that bovine hemoglobin (BvHb) interacts weakly with 2,3-diphosphoglycerate (2,3-DPG) in a chloride-free media and not at all in the presence of physiological concentrations of chloride (100 mM). This lack of interaction has raised several questions at both structural and evolutionary levels. Results obtained in this study via 31P nuclear magnetic resonance (NMR) show that, even in the presence of 100 mM chloride ions, 2,3-DPG does, in fact, interact with bovine deoxy-Hb. This spectroscopic observation has been confirmed by oxygen binding experiments, which have also shown that, under certain conditions, chloride and 2,3-DPG may display a synergistic effect in modifying the oxygen affinity of bovine hemoglobin. It could be that this synergistic effect has its structural basis in a conformational modification induced by 2,3-DPG, possibly causing extra chloride anions to approach the positive charges which constitute the anion binding site. Another possibility, not necessarily an alternative, is the additional chloride binding site recently identified [Fronticelli, C., Sanna, M. T., Perez-Alvarado, G. C., Karavitis, M., Lu, A.-L., and Brinnigar, W. S. (1995) J. Biol. Chem 270, 30588-30592] involving lysine beta76 that in bovine Hb substitutes for the alanine residue present in human hemoglobin. All of these findings are in agreement with the very low enthalpy of oxygenation that characterizes bovine Hb when both chloride and 2,3-DPG are present in concomitance. The results reported here clearly show that bovine hemoglobin does react with 2, 3-DPG and is functionally affected by this organic phosphate. Hence, the very low intraerythrocytic concentration of 2,3-DPG (0.5 mM) in adult bovine red blood cells is the result of metabolic adaptation which cannot be explained solely by the different amino acid sequence at the level of the 2,3-DPG binding site.

The role of TRP84 in catalytic power and the specificity of AChE

The structure-function relationship between the alkaloids physostigmine, physovenine and the three structurally related compounds were investigated by employing kinetic studies and molecular modeling. Crystallographic data from the X-ray conformation of the Torpedo californica acetylcholinesterase complex together with the transition state analog inhibitor m-(N,N,N,-Trimethylammonio) trifluoroacetophenone (TMTFA) was used as template onto which inhibitors were superimposed. Among the structural elements of the active site, TRP84 residue shows a versatile role. In fact, its aromatic electrons not only can be employed in pi-cation interactions, as is the case for ACh, but they can also provide a polarizable surface for van der Waals and London interactions.

Studies on a new series of THA analogues: effects of the aromatic residues that line the gorge of AChE

A series of N-monoalkylsubstituted 1,2,3,4-tetrahydro-9-aminoacridines have been prepared after modelling simulation of the AChE-inhibitor complex. Molecular modelling has predicted a number of hydrophobic residues to be involved in the catalytic mechanism of this interaction between the binding sites of AChE and this series of aminoacridines. In these compounds the acridine moiety becomes sandwiched between the rings of PHE330 and TRP84. In particular, the alkyl chain shows the important role of aromatic groups as binding sites. Their in vitro inhibitory properties (enzyme from Electrophorus electricus) confirm the aromatic groups as a general and significant characteristic of the mechanism of AChE inhibition.

Bovine hemoglobin cross-linked through the beta chains: functional and structural aspects

2-Nor-2-formylpyridoxal (NFPLP) has been synthesized and coupled to bovine Hb according to the procedure developed by Benesch and Benesch. The reaction of bovine Hb with NFPLP leads to a cross-linkage between the beta subunits, which greatly stabilizes the low affinity T state of the molecule and simultaneously abolishes the tendency of the tetramer to dissociate into alpha beta dimers. The functional properties, examined from both the equilibrium and kinetic points of view, indicate that the chemical modification affects the O2 affinity, abolishes cooperativity, and induces a slight decrease of the Bohr effect. From modeling studies we are confronted with two different structural alternatives; the cross-link of beta chains may be formed between lysine 82 of beta2 and the N terminus of methionine 2 of beta1 or between the two lysine 82 residues of both beta2 chains. Digestion of modified beta globin chains and isolation of the cross-linked peptide have showed that NFPLP cross-links Met-beta2 and Lys-beta82. This allowed discussion in some detail of the molecular basis of the Bohr effect of the modified bovine hemoglobin. On the whole, NFPLP-modified bovine Hb could be considered as a first step toward the synthesis of a potential blood substitute.

"On the suggestion of Dr. Alzheimer I examined the following four cases." Dedicated to Gaetano Perusini

Gaetano Perusini merits a great deal more credit for his work on the elaboration of the concepts regarding what is now called Alzheimer's disease (AD). Perusini's work in Alzheimer's laboratory and his subsequent studies have been, if not neglected, largely unmentioned. This article is an attempt to report a fascinating piece of medical history in order to redress the balance. Surely, Perusini's work deserves to be reexamined. The same applies to Fischer's investigation. Some of the puzzles discussed by Perusini are still unresolved.

Synthesis of phenothiazine derivatives as potential inhibitors of phospholipase C

In order to study the structure-activity relationships of phenothiazine derivatives inhibiting phosphatidylinositol-specific phospholipase C (PI-PLC), the synthesis of some phenothiazine amide, amine and ester derivatives was performed mainly by reacting 10H-phenothiazine-10-propanoyl chloride with some amines and alcohols; the resulting amides were reduced with borane to yield the corresponding amines. Starting from 2-chloro and 2-trifluoromethyl-10H-phenothiazine-10-propanoyl chloride two amides were synthesized. The inhibiting activity on PI-PLC from human platelets is reported.

Physostigmine analogs anticholinesterases: effects of the lengthening of the N-carbamic chain on the inhibition kinetics

Data are presented about the inhibitor power of new carbamates against acetylcholinesterase. The study was carried out on two series of physostigmine analogs, N-alkyl and N-methyl,N-alkylphysostigmines. For these inhibitors, the second-order rate constants for inhibition, ki, and the first-order rate constants of reactivation, k3, have been determined. From the reported results, electronic, hydrophobic and steric effects, due to the enhancement of the alkyl chain, may have influenced all kinetics parameters discussed. In comparison to physostigmine, both the new N-methyl,N-alkylphysostigmines and the N-alkylphysostigmines showed a non-linear decrease in the values of ki and k3. This study presents the hydrophobic interactions as an important factor not only in determining carbamylation but also decarbamylation rates constants.

Different promoter regions control level and tissue specificity of expression of Agrobacterium rhizogenes rolB gene in plants

Expression of the rolB gene of A. rhizogenes T-DNA triggers root differentiation in transformed plant cells. In order to study the regulation of this morphogenetic gene, the GUS reporter gene was placed under the control of several deleted fragments of the rolB 5' non-coding region: carrot disc transformations and the analysis of transgenic tobacco plants containing these constructions identified the presence of distinct regulatory domains in the rolB promoter. Two regions (located from positions -623 to -471 and from -471 to -341, from the translation start codon) control the level but not the tissue specificity of rolB expression: progressive deletions of the rolB promoter starting from position -1185 to -341, although at different levels, maintained the same pattern of GUS expression-maximal in root meristems and less pronounced in the vascular tissue of aerial organs. Further deletion of 35 bp, from -341 to -306, drastically affected tissue specificity: GUS activity was still clearly detectable in the vascular tissue of the aerial organs while expression in the root meristem was totally suppressed. Analysis of transgenic embryos and seedlings confirmed that distinct promoter domains are responsible for meristematic (root) and differentiated (vascular) expression of rolB. Finally, we present data concerning the effects of plant hormones on the expression of rolB-GUS constructions.

The effect of heptyl-physostigmine, a new cholinesterase inhibitor, on the central cholinergic system of the rat

Heptyl-physostigmine (Heptyl-Phy; MF-201) is a new carbamate derivative of physostigmine (Phy) with greater lipophilicity and longer inhibitory action on cholinesterase (ChE) activity than the parent compound. Following single dose administration of 5 mg/kg heptyl-Phy i.m., maximal whole brain acetylcholinesterase (AChE) inhibition (82%) if reached at 60 min. Inhibition of plasma BuChE butyrylcholinesterase (BuChE) remains close to the steady state level (60%) between 120 and 360 min. At 360 min, whole brain AChE activity is still 67% inhibited compared to controls. Inhibition of AChE activity displays brain regional differences which are more significant at 360 min. At this time point, AChe activity in cerebellum is only 40% inhibited while frontal cortex and medial septum are still 80% inhibited. Increases in acetylcholine (ACh) levels also show regional differences, however, there is no direct relationship between AChE inhibition and ACh increase. The electrically evoked [3H]ACh release in cortical slices was inhibited only by the highest concentration of heptyl-Phy tested (10(-4) M). At this concentration ChE activity was 97% inhibited in vitro. In conclusion, our results demonstrate that heptyl-Phy compares favorably to other reversible cholinesterase inhibitors (ChEI), particularly to Phy as far as producing a more long-lasting inhibition of AChE and a more prolonged increase of ACh in brain with less severe side effects. Therefore, it represents an interesting candidate for cholinomimetic therapy of Alzheimer disease (AD).

New analogs of physostigmine: alternative drugs for Alzheimer's disease?

The synthesis of a series of physostigmine analogs, in which the methylcarbamyl group has been substituted with monoalkylcarbamyl, dimethyl- and diethylcarbamyl groups, is reported. These compounds were prepared with the aim of investigating their possible therapeutic effects in the treatment of Alzheimer's type dementia. The new analogs of physostigmine are inhibitors of acetylcholinesterase from Electroforus electricus, with a value of the reactivation constant, k3 smaller than the one of physostigmine. The percentage of anticholinesterase activity in vitro and in vivo, the acute toxicity and some behavioural effects were also evaluated for selected derivatives. The reactivation constant, in vitro, supports the view that the derivatives described would be more suitable for therapeutic use than physostigmine.

Agrobacterium rhizogenes T-DNA genes capable of inducing hairy root phenotype

Segments of the TL-DNA of the agropine type Ri plasmid pRi 1855 encompassing single and groups of open-reading frames were cloned in the Ti plasmid-derived binary vector system Bin 19. Leaf disc infections on Nicotiana tabacum led to transformed plants, some of which showed typical hairy root phenotypes, such as the wrinkled leaf morphology, excessive and partially non geotropic root systems and the ability of leaf explants to differentiate roots in a hormone-free culture medium. Particularly interestingly, most of these traits were shown by plants transformed with a TL-DNA segment encompassing the single ORF 11, corresponding to the rolB locus. Hairy root can be induced by this latter T-DNA segment on wounded stems of tobacco plants; hairy root induction on carrot discs requires, on the contrary, a more complex complement of TL-DNA genes.

A long-lasting cholinesterase inhibitor affecting neural and behavioral processes

A series of analogues of physostigmine were prepared with the aim of investigating their inhibitory effects on acetylcholinesterase in the treatment of Alzheimer's disease. One of the isomers prepared was evaluated for its anticholinesterase activity in vivo, acute toxicity, and some behavioral effects. This compound was a competitive inhibitor of the enzyme and was found to antagonize the stimulating effect produced by scopolamine on locomotor activity and to facilitate memory consolidation.

Anticholinesterase activity of a new carbamate, heptylphysostigmine, in view of its use in patients with Alzheimer-type dementia

The anticholinesterase activity of a new carbamate, heptylphysostigmine, was studied in vitro. This compound is a competitive inhibitor of acetylcholinesterase (or true cholinesterase) having Ki = (1 +/- 0.5) X 10(-7) M. The inhibition was instantaneous at the onset and did not diminish with prolonged incubation of the drug and enzyme.

Acetylcholinesterase inhibition by eserine: rate constants of reaction. Part II

The inhibition of eel acetylcholinesterase by physostigmine at 20 degrees and 25 degrees C have been investigated. In our evaluation the unimolecular reactivation rate constant, k3, the carbamylation rate constant, k2, and the binding constant, Ka, are the first simultaneously determined. The mechanism of this reaction is discussed.

Localization of agropine-synthesizing functions in the TR region of the root-inducing plasmid of Agrobacterium rhizogenes 1855

The region of the Ri plasmid pRi 1855 that encodes agropine synthesis has been identified through its sequence homology with the equivalent genes of the octopine Ti plasmid pTi ACH5. Interestingly the agropine genes lie outside the so-far identified T-DNA of pRi 1855, and are separated from this latter by a long sequence of non integrated plasmid DNA. The presence of this additional T-DNA (TRight DNA) in hairy roots was demonstrated by Southern blot analysis and by the presence of specific transcripts. The genes for agropine synthesis are arranged in the Ri plasmid in a reversed order as compared to their orientation in the Ti plasmid pTi ACH5.

A new simple method for determining the kinetic constants of inhibited acetylcholinesterase

The authors, with a spectrophotometric procedure, have evaluated the kinetic constants of physostigmine, a cholinesterase inhibitor which assumes an important function when the degeneration of cholinergic projections is observed. This approach overcomes some of the difficulties encountered in measuring the binding and the carbamylation rate constants. A kinetic treatment, consistent with the experimental results observed in the enzyme-inhibitor system in the presence of substrate, is developed.

Polyacrylonitrile hemofiltration for the adsorption myoglobin in tardy revascularization syndrome: in vitro assessment

The Authors examine the behavior of P.A.N. membranes hemoperfusion combined with district hemodialysis in the prevention of tardy revascularization syndrome. Their experience "in vitro" seems to confirm the use of P.A.N. membrane is advisable whenever an increase of the myoglobin concentration occurs and they also envisage the use of the P.A.N. membrane in the prevention of T.R.S.

Restriction endonuclease mapping of the root-inducing plasmid of Agrobacterium rhizogenes 1855

The root-inducing plasmid of the agropine type Agrobacterium rhizogenes 1855 was mapped by means of the restriction endonuclease EcoRI. The circular arrangement of the more than 60 fragments generated by this enzyme was established by electrophoretic analysis of pBR322 clones harboring overlapping segments of pRi1855 derived by partial digestion with EcoRI. A large region of the plasmid comprising the T-DNA was mapped with two additional enzymes, BamHI and HindIII, by means of Southern blot hybridizations between the fragments generated by the three enzymes.

Identification of T-DNA in the root-inducing plasmid of the agropine type Agrobacterium rhizogenes 1855

The region of the virulence plasmid of the agropine type Agrobacterium rhizogenes 1855 (pRi-1855) which is transferred to plant cells upon infection (T-DNA) has been identified by means of Southern blot hybridizations with the T-DNA of the mannopine type A. rhizogenes 8196. The presence in the plant genome of the pRi-1855 sequences thus identified is demonstrated in carrot roots derived from infection with strain 1855. The T-DNA of pRi-1855 has been mapped by means of cloned Eco RI partial digests. Although strongly homologous with each other, the cores of the T-regions of the mannopine and agropine Ri plasmids are not colinear since the latter contains a central segment of DNA which is absent from the T-region of pRi-8196. Unexpected homologies between the T-region of pRi-1855 and normal carrot DNA have been observed and are discussed here.

Agrobacterium tumefaciens RNA polymerase: a new purification procedure and a study of the stable binding sites on homologous deoxyribonucleic acid

RNA polymerase (RNA nucleotidyltransferase, EC 2.7.7.6) of Agrobacterium tumefaciens has been purified according to a fast and efficient procedure. The method involves only two chromatographic steps and yields a highly active enzyme. The RNA polymerase was studied with respect to the ability to bind its homologous genome. A. tumefaciens deoxyribonucleic acid (DNA) binds the enzyme even when fragmented at undergenic size (300 base pairs). The general binding is unspecific and very labile at low concentrations of heparin (0.66 micrograms/mL). The number and distribution of the stable binding sites, class A sites [Hinkle, D., & Chamberlin, M. J. (1972) J. Mol. Biol. 70, 157-185], have been calculated from the heparin-induced dissociation kinetics of binary complexes formed between the enzyme and DNA fragments of various sizes. A total of 3.5 x 10(3) class A sites (forming binary complexes with a half-life of 16.6 min) are present on A. tumefaciens genome, a large number of which show a distribution of 800-1000 base pairs. The rest have a more widely spaced distribution. The interactions between Escherichia coli RNA polymerase and the A. tumefaciens template have also been examined, and it has been observed that E. coli holoenzyme forms stable complexes with a shorter half-life and recognizes a lower number of class A sites on A. tumefaciens genome.

Effect of non-histone chromosomal proteins on transcription in vitro in sea-urchin

Non-histone chromosomal proteins prepared from chromosomal material of the sea-urchin Paracentrotus lividus affect RNA synthesis in vitro. 1. The extent of transcription can be radically changed from inhibition to stimulation, depending on the DNA/non-histone chromosomal proteins ratio. 2. A correlation exists between stage of development and influence on transcription. 3. Non-histone chromosomal proteins exert their action by intervening directly on some initiation step of RNA synthesis, as shown by the numbers of initiation events that take place in their presence or absence. 4. Stimulatory activity is observed only in restrictive conditions of ionic strength and temperature. These observations are in agreement with models that predict for non-histone chromosomal proteins a regulatory role on the transcription process exerted through a modulation of promoter availability.