The Stokes-Einstein relation in water/methanol solutions.

The hydrogen bonding ability of both water and methanol, together with the occurrence of hydrophobic interactions, makes their solutions nonideal. This nonideality is reflected in both dynamic and thermodynamic quantities at different extent depending on temperature and concentration. The thermal behavior in terms of transport quantities is investigated for different methanol molar fractions by using the concepts of the Stokes-Einstein relation. Starting from the pure compounds, we compare self-diffusion and viscosity data as a function of the temperature for methanol molar fractions XMeOH = 0.22, 0.5, and 0.7. The results are interpreted within the scenario of the mode coupling theory and show that the Stokes-Einstein relation is violated in a different way depending on the solution concentration.

ESR evidence of the dynamic crossover in the supercooled liquid states of a series of solid n-alkanes.

A study of the rotation dynamics of the spin probe TEMPO by electron spin resonance (ESR) spectroscopy in a series of six short- and medium-sized n-alkanes is presented. In addition to the usual crossover effects connected with solid-liquid phase transitions at temperature Tm and the solid-solid transition at Tss, we find a strong correlation between the change in reorientation at the characteristic ESR temperature TfastX1 < Tss and/or Tm with the ratio TfastX1/Tm = 0.76 ± 0.03 and the characteristic dynamic temperature, TX, obtained from the viscosity data. This indicates the presence of local disordered regions in the crystalline structure which is indeed sensitive to dynamic change at the crossover temperature TX ≅ TfastX1.

The role of the dynamic crossover temperature and the arrest in glass-forming fluids.

We discuss the role of the dynamic glass-forming fragile-to-strong crossover (FSC) in supercooled liquids. In the FSC, significant dynamic changes such as the decoupling (the violation of the Stokes-Einstein relation) of homologous transport parameters, e.g., the density relaxation time τ and the viscosity η, occur at a characteristic temperature T(c). We study the FSC using a scaling law approach. In particular, we use both forms of the mode-coupling theory (MCT): the original (ideal) and the extended form, which explicitly describes energy hopping processes. We demonstrate that T(c) plays the most important physical role in understanding dynamic arrest processes.

NMR evidence of a sharp change in a measure of local order in deeply supercooled confined water.

Using NMR, we measure the proton chemical shift delta, of supercooled nanoconfined water in the temperature range 195 K < T < 350 K. Because delta is directly connected to the magnetic shielding tensor, we discuss the data in terms of the local hydrogen bond geometry and order. We argue that the derivative -( partial differential ln delta/ partial differentialT)(P) should behave roughly as the constant pressure specific heat C(P)(T), and we confirm this argument by detailed comparisons with literature values of C(P)(T) in the range 290-370 K. We find that -( partial differential ln delta/ partial differentialT)(P) displays a pronounced maximum upon crossing the locus of maximum correlation length at approximately 240 K, consistent with the liquid-liquid critical point hypothesis for water, which predicts that C(P)(T) displays a maximum on crossing the Widom line.

Elastic neutron scattering study of water dynamics in ion-exchanged type-A zeolites.

With the aim to investigate, by means of elastic neutron scattering, the effects produced by the cation substitution on the dynamics of water in zeolites, we measured, using a neutron backscattering spectrometer, the temperature dependence of mean-square atomic displacements [u2] derived from window integrated quasielastic spectra of fully and partially hydrated Na-A and Mg50-A zeolites. The results, collected in the 20-273 K temperature range, reveal that, at low temperature, the [u2] shows a harmonic trend independent of hydration and cation substitution, and, at higher temperatures, the onset of a non-Gaussian dynamics of the elastic intensity. This latter takes place at T approximately 200 K and approximately 150 K for fully and partially hydrated samples, respectively. This behavior has been interpreted in terms of reorientational jumps of H atoms described by two-site processes within an asymmetric double-minimum potential. In spite of its simplicity, the model seems to reproduce the rearrangement of the hydrogen bond network of zeolitic water. The fit results indicate a reduced proton mobility by diminishing the water content and by the induced Na+-->Mg2+ ion exchange, in agreement with previous incoherent quasielastic neutron scattering results at higher temperatures.

In vitro scavenger activity of some flavonoids and melanins against O2-(.).

The scavenger activity against O2-. of some flavonoids and melanins (synthetic melanins and melanins isolated from animal tissues, vegetable seeds, and mushroom spores) has been studied by ESR spectrometry. All these substances, except flavon and flavanone, diminish the signal of O2-. generated in vitro by a system containing H2O2 and acetone in an alkaline medium. It is shown that the presence of hydroxyl groups in the B ring of flavonoids is essential for their scavenger activity. Moreover, the presence of a hydroxyl at C-3 enhances the scavenger ability of flavonoids. Generally, aglycons are more active than their glycosides. It seems plausible that the antioxidant property of these substances comes from their scavenger activity against O2-(.). It is also pointed out that the scavenger activity shown by melanins, is strictly correlated with their nature of stable free radical.

Study of a melanic pigment of Proteus mirabilis.

The present study sought to determine whether the pigment produced by Proteus mirabilis from the L-forms of various aromatic amino acids under aerobic conditions is melanic in nature. It is a black-brown pigment which behaves like a melanin in many respects, namely solubility features, bleaching by oxidizing agents and positive response to the Fontana-Masson assay. In the present study, for the first time, it was shown by electron spin resonance analysis that a bacterial melanin is able to act as a free radical trap, as was previously demonstrated for other melanins. Scanning electron microscopy studies showed a specific organized structure of the pigment as rounded aggregates of spherical bodies. DNA hybridization data did not reveal, in the P. mirabilis genome, any nucleotide sequence related to Shewanella colwelliana mel A, one of the two melanogenesis systems already defined at the molecular level in bacteria. Results obtained from experiments on pigment production inhibition suggest a possible role of tyrosinase in P. mirabilis melanogenesis. In conclusion, from the bulk of our results, it appears that the pigment produced by P. mirabilis is melanic in nature.

Computerized EEG profiles of haloperidol, chlorpromazine, clozapine and placebo in treatment resistant schizophrenia.

In this paper we have described early applications of computerized EEG techniques in psychopharmacology. Perhaps our most remarkable finding was there were practically no differences between very chronic drug free schizophrenic patients and normals, which contradicts much of the EEG imaging literature. To us, the most likely explanation is that most of the anterior slowing observed in other studies was due to contamination from orbital artifacts, which we took exceptional pains to remove. Lingering effects of neuroleptic medications may also have contributed. Alternatively, EEG deviations in schizophrenia may recede when the illness reaches a very chronic stage, although this hypothesis is less tenable. There were significant differences between placebo and the three neuroleptics in terms of increased amplitudes in the delta and theta frequency bands in the anterior head regions, which is compatible with data from other studies. These changes were most pronounced with clozapine and least prominent with haloperidol, with chlorpromazine occupying an intermediate position. This order happens to parallel their relative antiserotonergic, antihistaminic and anticholinergic properties. The latter may have been partially obscured by the addition of benztropine. In a subgroup of patients who were recorded under each of the treatment conditions, there were more fast frequencies with clozapine than with the other neuroleptics agreeing with Roubicek and Major. This could be a function of clozapine's increased adrenergic activity as reported by Ackenheil. An unexpected finding was that patients who responded to clozapine had higher amplitudes in the alpha spectrum, most pronounced in the left anterior quadrant, than did the nonresponders. These differences between responders and nonresponders obtained whether patients were on placebo, haloperidol or clozapine. Curiously, Buchsbaum et al. found that anxious patients who responded to benzodiazepines also had higher alpha amplitudes in the same brain regions, which differentiated them from nonresponders. These findings clearly warrant future scientific investigation. In this regard, the generalizability of our data is limited by the extremely chronic, treatment-resistant population studied. However, promising directions for further research in EEG and psychopharmacology have been identified.

The fragile-to-strong dynamic crossover transition in confined water: nuclear magnetic resonance results.

By means of a nuclear magnetic resonance experiment, we give evidence of the existence of a fragile-to-strong dynamic crossover transition (FST) in confined water at a temperature T(L)=223+/-2 K. We have studied the dynamics of water contained in 1D cylindrical nanoporous matrices (MCM-41-S) in the temperature range 190-280 K, where experiments on bulk water were so far hampered by crystallization. The FST is clearly inferred from the T dependence of the inverse of the self-diffusion coefficient of water (1D) as a crossover point from a non-Arrhenius to an Arrhenius behavior. The combination of the measured self-diffusion coefficient D and the average translational relaxation time tau(T), as measured by neutron scattering, shows the predicted breakdown of Stokes-Einstein relation in deeply supercooled water.

Gene expression in euploid human hybrid cells: ouabain resistance is codominant.

Single-step mutations to ouabain resistance have been induced in Lesch-Nyhan diploid fibroblasts carrying a variant G6PD isozyme (OuaR/HGPRT-/G6PDA). Two of these mutant strains, differing in the degree of ouabain resistance, were fused with wild-type human diploid fibroblasts (OuaS/HGPRT+/G6PDB) and hybrids isolated in doubly selective medium, ouabain + HAT (HOT). Four hybrids, identified by G6PD heteropolymers and stable tetraploid karyotypes, expressed ouabain resistance intermediate to that of the parents. The degree of ouabain resistance was influenced by the specific mutant allele of the OuaR parent, indicating both mutant and wild-type alleles are simultaneously expressed in hybrid cells. Intraspecific hybrids of this kind are especially suited to studies of gene regulation because all relevant genes present and the number of alleles at each locus is known.

Effect of intercellular communication on the selection of intraspecific human hybrids in HAT and ouabain.

Optimal conditions have been determined for selection of hybrids in HAT and ouabain (HOT) from the PEG-mediated fusion of OUAR/HGPRT-/G6PDA and OUAS/HGPRT+/G6PDB human diploid fibroblasts. In addition to the OUARHGPRT+G6PDAB tetraploid hybrids, several other types of HOT-resistant colonies were obtained from these fusions and identified by G6PD isozyme analysis and karyotyping as (1) hybrids contaminated with diploid parental cells, (2) symbiotic mixtures of the two types of parental cells, or (3) spontaneous OUAR mutants. The mechanism for parental cell growth in HOT is most likely the transfer of HAT resistance and/or ouabain resistance through gap junctions formed between resistant and sensitive cells.

Enhancing the efficiency of DNA-mediated gene transfer in mammalian cells.

We have investigated several of the experimental factors that affect calcium phosphate-DNA-mediated gene transfer of thymidine kinase (tk) into mouse LM tk- Cl 1D cells using unfractionated DNA from both Chinese hamster ovary cells and L6 rat myoblasts. Increases in the length of exposure to DNA (24 h) and the expression time (48 h) before selection result in a 20-fold enhancement in the efficiency of transformation. These modifications yield frequencies up to 35 HATR colonies/20 microgram tk"NA/10(6) recipient cells. Exposure to dimethyl sulfoxide enhances transformation efficiencies slightly for short DNA exposure times, but has no effect when optimal DNA exposure times are used. Several other variations in our standard transformation protocol were also examined: these include the concentration and size of the DNA and exposure to low concentrations of the nonionic detergent, Tween-80. We have also isolated and characterized a subclone of Cl 1D that is a high-efficiency recipient for the tk+ marker. Segregation analysis reveals that the majority of the TK+ transformants derived from this subclone are stable, in contrast to those derived from the DL 1D parent. The combination of improved methodology and the high-efficiency recipient subclone permits DNA-mediated transformation for tk at frequencies on the order of 10(-4) transformants per recipient cell.

Competence for DNA transfer of ouabain resistance and thymidine kinase: clonal variation in mouse L-cell recipients.

We have used the calcium phosphate precipitation technique to study the competence of mammalian cell recipients for transformation with genomic mammalian cell DNA. The transformation efficiency for thymidine kinase (tk) varies 10- to 20-fold (up to 10(-4) transformants/recipient) among different subclones of the LM tk- CL 1D mouse fibroblast cell line. Analysis of this phenotype among second-generation subclones indicates that subclones exhibiting high competence tend to breed true, whereas those with low competence do not. Isolation of Tk- revertants from TK+ transformants results in the selection of cells with a high-competence phenotype as measured by their subsequent transformation for tk. This phenotype appears to be a general characteristic of such cells because recipients more competent for transfer of a second marker, ouabain resistance (ouaR). This codominant marker coding for the Na K+-ATPase can be transferred at frequencies of 10(-5) in the high-competence recipients. These results indicate that competence for DNA-mediated gene transfer can be determined in part by genetic factors.

Comparison of contact-mediated communication in normal and transformed human cells in culture.

With an assay that quantitates the transfer of 6-thioguanylic acid from hypoxanthine phosphoribosyltransferase (IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8)-positive donor cells to negative recipient cells through gap junctions, differences in contact-mediated communication between normal and transformed human cells in culture have been detected. We have compared cells cultured from human tumors and simian virus 40-transformed cells with the normal human fibroblasts from which they were derived as well as with gap junction-deficient L cells. The communication, which is extensive in normal cells, is significantly reduced when transformed cells are used as either donors or recipients in the contact-feeding assay. Furthermore, the reduction in the transfer of nucleotides is enhanced when transformed cells are used as both donors and recipients, indicating a dosage effect or synergism, independent of enzyme activity. Fetal cells have a contact-feeding phenotype intermediate between that of normal and that of transformed cells. We suggest that the decrease in communication of nucleotides in transformed cells reflects quantitative or qualitative changes in membrane components responsible for gap junction formation.

[Application of the biotic index and the diversity index to the study of macro-benthons in a river]. / Applicazione dell'indice biotico e dell'indice di diversità allo studio di comunità macrobentoniche fluviali.

Using the Biotic Index and the Diversity Index the results are analysed of a study of the macrobenthic community sampled in the course of one year at three stations along he lowest-lying stretch of the River Simeto. The results obtained from applying the two different indices are not in perfect agreement one with the other. Whereas with the Biotic Index one could be led to consider the fluvial environment situation a good one, the Diversity Index shows the environment to be partially compromised by organic substances. On the basis of results of chemico-physico-microbiological analyses as well as data concerning the nutritive habits of the species found, we conclude that the Diversity Index is a more suitable instrument for measuring the biological reality of the Simeto.

Relationship of finite proliferative lifespan, senescence, and quiescence in human cells.

Cell hybrids were formed between human diploid fibroblasts (HDF) and carcinogen-transformed HDF to determine the relationship among: (1) finite proliferative lifespan, which we define as an age-related failure of a population to achieve one population doubling in 4 weeks; (2) arrest in a senescent state, which we define as cessation of DNA synthesis in a viable culture that is at the end of its lifespan by the above definition; and (3) arrest in a quiescent state, which we define as cessation of DNA synthesis in a young culture that is crowded or mitogen-deprived. HDF express all three of these phenotypes, which we have abbreviated FPL+, S+, and Q+, respectively. Carcinogen-transformed HDF are transformed to immortality (FPL-) and inability to achieve quiescence (Q-). They have no S phenotype because, by definition, this phenotype only exists in FPL+ cells. Fusion of FPL+, Q+, S+ HDF X FPL-, Q- carcinogen-transformed HDF produced hybrid clones that were FPL+, Q-, and S-, where the S- phenotype means that individual cells continued to synthesize DNA in cultures that had reached the end of their lifespan by our definition. These results are consistent with our hypothesis that senescent HDF and quiescent HDF may share a common mechanism for arrest in G1 phase. We have suggested that this could occur if the aging mechanism that is responsible for the FPL+ phenotype is a progressive decrease in the ability of cells to recognize or respond to mitogenic growth factors. If so, then cells would become physiologically mitogen-deprived at the end of their lifespan, which would cause them to arrest in the senescent state by the same mechanism that causes young cells to arrest in the quiescent state when they are mitogen-deprived. This hypothesis predicts that the FPL+ phenotype can be separated from the S+ phenotype--i.e., FPL+ cells can be S+ or S- --and that the Q and S phenotypes are linked--i.e., FPL+ cells are either Q+ and S+ or Q- and S-. Both these predictions are supported by the present data.

Circannual rhythm of the melanin content in frog liver (Rana esculenta L.).

The melanin content of Rana esculenta L. liver varies according to a circannual statistically significant rhythm, as shown by variance and single cosinor analysis. The maximum is found in autumn-winter, the minimum in spring-summer. The linear regression analysis shown a negative correlation between the amount of melanin and the environmental temperature.

[Study of factors influencing the changes in liver melanin content of amphibia. II. Effect of fasting]. / Studio dei fattori che influenzano le variazioni del contenuto melanico in fegato di anfibi.nota II--Azione del digiuno.

Statistical examination of the data from experiments conducted on groups of Amphibians induces us to retain as plausible the hypothesis which indicates in fasting one of the preminent factors that cause an increase in the melanic content of their liver. The temperature does not act directly, but indirectly, on the process of melanosynthesis, by inducing or otherwise the semilethargous state on which alimentation depends.

Isolation and analysis of somatic hybrids derived from two human diploid cells.

Lesch-Nyhan fibroblasts and normal human leukocytes with different glucose-6-phosphate dehydrogenase genotypes were fused by Sendai virus. Clones were isolated on the basis of their resistance to a medium containing hypoxanthine, amethopterin, and thymidine and ability to proliferate in monolayer culture. These mononuclear cells (1) incorporated [(3)H]hypoxanthine, (2) expressed the glucose-6-phosphate dehydrogenase heteropolymer, and (3) were polyploid. Therefore, hybrids can originate from the fusion of two diploid human cells. X chromosome inactivation did not occur in these hybrid cells of male origin. The hybrids expressed both parental genomes and exhibited the senescence and contact feeding characteristic of the human skin fibroblast.

The amphibian Kupffer cells build and demolish melanosomes: an ultrastructural point of view.

This ultrastructural research was carried out to investigate the nature of the liver pigment cells of anuran and caudate amphibians, the pattern of melanosome ontogenesis, and the demolition processes of old melanosomes. We demonstrate that these liver pigment cells are able to internalize zymosan particles and latex beads; therefore, being professional phagocytes, they, as liver resident macrophages, can be classified as Kupffer cells (KCs). They show "melanosomogenesis centers" in which several maturation stages of premelanosomes are visible; the premelanosomes are formed by two principal components: a filamentous structure that will constitute the "inner" area of the melanosome and a vesicular component, budding from the Trans Golgi Network and that carries enzymes, which will constitute the "cortical area" of the melanosome. Thus the KCs, thanks to the presence of the "melanosomogenesis centers," are also melanosome producing cells. They are also able to demolish melanosomes by heterophagocytosis and, probably, also by autophagocytosis. In conclusion, we propose a classification of vertebrate pigment cells.