Showing papers by "Jagiellonian University published in 1996"

Broad-band γ-ray and X-ray spectra of NGC 4151 and their implications for physical processes and geometry

Abstract: We study y-ray observations of NGC 4151 by the Gamma Ray ObselVatory (GRO)/ OSSE contemporaneous with X-ray observations by ROSAT and Ginga in 1991 June andASCA in 1993 May. The spectra are well modelled by thermal Comptonization and a dual neutral absorber. We also find, for the first time for NGC 4151, a Compton~reflecti on spectral component in the Ginga/OSSE data. When reflection is taken into account, the intrinsic X-ray energy spectral index is 0(",0.8 and the plasma temperature is '" 60 ke V for both observations, conditions which imply an optical depth of '" 1. The X-ray spectral index is within the range, 0(~0.95 ±0.15, observed from other Seyfert Is. Also, the OSSE spectra of those and other observations of NGC 4151 are statistically indistinguishable from the average OSSE spectrum of radio-quiet Seyfert Is. Thus, NGC 4151 observed in 1991 and 1993 has the intrinsic X-ray/y-ray spectrum typical for Seyfert Is, and the main property distinguishing it from other Seyfert Is is a large absorbing column of '" 1023 cm -2. We find no evidence for a strong, broad and redshifted Fe KO( line component in the ASCA spectrum of 1993 May. Also, the Compton-reflection component in the Ginga/OSSE spectrum is a few times too small to account for the strength of the broad/redshifted line reported elsewhere to be found in this and other ASCA spectra ofNGC 4151. On the other hand, we confirm previous studies in that archival X-ray data do imply strong intrinsic X-ray variability and hardness of the intrinsic spectrum in low X-ray states. An observed softening of the intrinsic X-ray spectrum with the increasing flux implies that variability in y-rays is weaker than in X-rays, which agrees with the 100-ke V flux changing only within a factor of 2 in archival OSSE and GRANAT/SIGMA observations. The relative hardness of the intrinsic X-ray spectrum rules out the homogeneous hot corona/cold disc model for this source. Instead, the hot plasma has to subtend a small solid angle as seen from the source of UV radiation. If the hot plasma is purely thermal, it consists of electrons rather than e± pairs. On the other hand, the plasma can be pair-dominated if a small fraction of the power is non-thermal.

Bioactivity of flavonoids.

Abstract: Flavonoids are benzo-gamma-pyrone derivatives of plant origin. They possess wide spectrum of biological activity. From the therapeutical point of view the most important are their antioxidant properties. These are the result of high propensity to electron transfer, ferrous ions chelating activity and direct scavenging of reactive oxygen species. Flavonoids inhibit enormous number of enzymes. From the pharmacological point of view inhibition of cyclooxygenase and lipoxygenases as well as scavenging of superoxide anions seem to be essential. Flavonoids are antiinflammatory agents as the result of diminished formation of proinflammatory mediators (prostaglandins, leukotrienes, reactive oxygen species, nitric oxide). They are also antithrombotic owing to their ability to scavenge superoxide anions. These anions are strong inhibitors of prostacyclin production. Removal of superoxide anions by flavonoids facilitates antiaggregatory PGI2 formation. Superoxide anions generate proagregatory isoprostanes. The antiaggregatory effect of flavonoids may be due to the limitation of formation of isoprostanes. Empirical use of flavonoids as drugs acquired recently scientific confirmation.

Bronchial aspirin challenge causes specific eicosanoid response in aspirin-sensitive asthmatics.

Abstract: We have shown that inhalation of lysine aspirin enhances leukotriene production in the lungs of patients with aspirin-induced asthma (AIA). To assess the specificity of this reaction, we compared two well-matched groups of patients: eleven with AIA versus 14 asthmatics tolerant to aspirin (ATA). All subjects underwent bronchoalveolar lavage (BAL) with saline followed immediately by instillation of 10 mg of lysine aspirin, into a right middle lobe segmental bronchus, which was lavaged 15 min later. At baseline the two groups did not differ with respect to BAL fluid concentrations of cyclooxygenase products, peptido-leukotrienes, histamine, tryptase, interleukin-5 (IL-5), eosinophil cationic protein (ECP), or eosinophil number. Fifteen minutes after aspirin instillation, there was a statistically significant rise in peptido-leukotrienes, IL-5, and eosinophil number in AIA, but not in ATA, but not in ATA patients. In the former, but not in the latter group, mean histamine concentrations rose in response to aspirin, approaching the level of statistical significance. Tryptase and ECP levels showed no significant change. Aspirin significantly depressed PGE2 and thromboxane B2 (TXB2) in both groups, however PGD2, PGF2 alpha, and 9 alpha, 11 beta-PGF2 decreased only in ATA patients. A characteristic disturbance in eicosanoid balance, produced by aspirin in patients intolerant to this drug, might explain precipitation of asthma attacks.

Long-term depression of horizontal connections in rat motor cortex.

Abstract: The possibility for long-term depression (LTD) of synaptic transmission in layer II/III horizontal connections within motor cortex was investigated using field potentials and intracellular recordings in rat brain slices. The LTD was induced by low-frequency stimulation at 2 Hz for 10 min in sites displaced horizontally by 0.5 mm from the stimulating electrode. Response amplitude measured 25-30 min after 2 Hz stimulation ended was 79% of baseline values (n = 13) at half maximal stimulation and 59% when 2 Hz stimulus intensity was doubled (n = 10). In 13/15 tested cases LTD in horizontal connections was specific to the activated pathway. Intracellular recordings from six neurons confirmed synaptic character of response depression. Horizontal connections in which LTD was induced retained the capability of increasing synaptic strength. Long-term potentiation could be induced in previously depressed pathways by simultaneous theta burst stimulation of two converging horizontal inputs combined with transient local application of GABA(A) receptor antagonist bicuculline methiodide (mean increase: 45 +/- 8% n = 6) or by simultaneous theta burst stimulation of converging horizontal and vertical inputs (mean change: 26 +/- 6%, n = 5). These data demonstrate that activity-dependent mechanisms may regulate bidirectionally the effectiveness of horizontal synaptic coupling between cortical neurons, thus forming a potential mechanism for plasticity of cortical connections and the representation patterns they support.

Trust and Emerging Democracy: Lessons from Poland

Abstract: The former communist societies of Eastern Central Europe (e.g. Poland) repeatedly experience barriers and blockades on the road toward an open, democratic, market society of the Western type. The author claims that most of the problems are due to the deficiency of cultural resources, the central of which is trust. A theory of trust is proposed, informed by the author's earlier work on `social becoming'. The `culture of distrust' is found to pervade Polish society at all levels of social life. Part of that syndrome derives from the legacy of real socialism, but more attention should be focused on current conditions: the new `risk environments', widespread anomie, inefficiency of political elites, and an enhanced feeling of relative deprivation after revolutionary elation and unrealistic hopes. To restore trust, an indispensable component of robust social tissue, the consistency of reforms must be safeguarded, the rule of law meticulously observed, integration with Western democracies speeded up and trust i...

Optimal Allocation of Resources Explains Interspecific Life-History Patterns in Animals with Indeterminate Growth

Abstract: In a previous paper it was suggested that interspecific allometries of physiological (respiration, assimilation and production rates) as well as life-history (age and size at maturity, life expectancy) parameters are by-products of body-size optimization in animals with determinate growth. Here the analysis is extended to animals with indeterminate growth, such as fish or reptiles. In a seasonal environment it is optimal to grow after maturation, and increasingly more resources should be devoted to reproduction year after year. This leads to growth curves that closely resemble Bertalanffy's curves characterized by growth constant k and asymptotic length l$\_{\infty}$. Sets of parameters describing mortality and productivity were generated with a random number generator. Then the schedule of growth was calculated for each `species' obtained, under the assumption of optimal allocation of resources. Interspecific comparisons in a set of such species resemble the empirical patterns discovered by Beverton & Holt and discussed extensively by Charnov: mortality rate and growth constant k are positively related, length at maturity and asymptotic length l$\_{\infty}$ are positively correlated, and k and l$_{\infty}$ are negatively correlated. Data for fish and reptiles match these predictions.

Optimization of the Lennard‐Jones parameters for a combined ab initio quantum mechanical and molecular mechanical potential using the 3‐21G basis set

Abstract: A combined ab initio quantum mechanical and molecular mechanical (AI-QM/MM) potential for use in molecular modeling and simulation has been described. In this article, we summarize a procedure for deriving the empirical parameters embedded in a combined QM/MM model and suggest a set of Lennard-Jones parameters for the combined ab initio 3-21G and MM OPLS-TIP3P (AI-3/MM) potential. Interaction energies and geometrical parameters predicted with the AI-3/MM model for over 80 hydrogen-bonded complexes of organic compounds with water were found to be in good accord with ab initio 6-31G(d) results. We anticipate that the AI-3/MM potential should be reasonable for use in condensed phase simulations. © 1996 by John Wiley & Sons, Inc.

Permeability of Nitric Oxide through Lipid Bilayer Membranes

Abstract: Profiles of the local nitric oxide (.NO) diffusion-concentration product across the egg yolk phosphatidylcholine membrane in the absence and presence of 30 mol% cholesterol were obtained using line-broadening electron paramagnetic resonance (EPR) and lipid-soluble nitroxide spin labels. Membrane .NO permeability coefficients were calculated from these profiles. At 20 degrees C, values of 93 and 77 cm/s for membranes in the absence and presence of cholesterol were obtained, compared with 73 and 66 cm/s for water layers of the same thickness as the membranes. Fluid-phase membranes are not barriers to .NO transport. Cholesterol significantly increases .NO transport in the center of the lipid bilayer.

Looking back: The year 1989 as a cultural and civilizational break

Abstract: The transformations in East-Central Europe after 1989 proceed at two distinct levels: institutional and cultural. The complete transition to democratic polity and market economy can be effected only if appropriate cultural “habits of the heart” emerge and become fully established. The period of real-socialism has left a vicious legacy of “civilizational incompetence”, due to the impact of “bloc culture”. But the traditions of indigenous, national cultures as well as globalized Western culture may serve as an antidote, slowly eradicating the vestiges of communism. The major role in this process is performed by the young generation, who was able to escape the indoctrination and habituation by the communist system.

Long-term potentiation and long-term depression of horizontal connections in rat motor cortex.

Abstract: This paper reviews studies that investigate conditions resulting in long-lasting modifications of synaptic efficacy in horizontal connections within layers II/III of adult rat motor cortex using the in vitro slice preparation. Long-term potentiation (LTP) was induced by high frequency theta burst stimulation (TBS) when local synaptic inhibition was transiently suppressed by bicuculline methiodide application at the recording site immediately prior to TBS of the horizontal pathway. Without bicuculline, TBS failed to produce LTP. LTP could also be induced without Bic application by conjoint TBS of horizontal and vertical (ascending) inputs. By contrast, long-term depression (LTD) of horizontal transmission was induced by 10 min of 2 Hz stimulation. Depressed horizontal connections nevertheless retained the capability for synaptic strength increases. These studies indicate that synaptic modification across horizontally connected neurones is regulated both by the arrangement of their intrinsic circuits and by the availability of mechanisms for modification at individual synapses. Activity dependent forms of synaptic plasticity operating within horizontal connections may form a spatial substrate and mechanism for experience-dependent regulation of cortical representations.

Limits to the Energy Budget in a Rodent, Peromyscus maniculatus: Does Gut Capacity Set the Limit?

Abstract: Nonreproducing Peromyscus maniculatus acclimated to 23° C and a standard mouse food can maintain a positive energy balance at-10° C. Their maximum cold-induced rate of energy assimilation is about 90 kJ/d, which is twice the energy expenditure at 23°C and five times their basal metabolic rate. Cold-acclimated individuals have an enlarged alimentary tract and at-18° C achieve a maximum cold-induced rate of energy assimilation of 113 kJ/d. The pattern of energy budget limitations depends on sex: males adopt a more frugal strategy of energy use. In females acclimated to afiber-diluted diet, the size of the alimentary tract and the maximum cold-induced rate of energy assimilation are increased. In males the effect is opposite. There is a strong correlation between an individual's maximum cold-induced rate of energy assimilation and the size of the alimentary tract, liver, and kidney; the correlation is strongest for the mass of the small intestine. These results are consistent with the hypothesis that energy ...

Chloroplast Distribution in Arabidopsis thaliana (L.) Depends on Light Conditions during Growth.

Abstract: Chloroplasts of Arabidopsis thaliana move in response to blue light. Sensitivity to light and the range of fluence rates to which the chloroplasts respond were found to be comparable to those of other higher plants studied. We investigated typical chloroplast distributions in Arabidopsis grown under three different light conditions:standard-light conditions, similar to natural light intensities; weak-light intensities, close to the compensation point of photosynthesis; and strong-light intensities, close to the saturation of the light-response curve of photosynthesis. We observed a striking difference in chloroplast arrangement in darkness between plants grown under weak- and strong-light conditions. There was a slight difference after weak-light pretreatment, and the arrangements of chloroplasts after strong-light pretreatment in both plant groups were very similar. These results support the ecological significance of chloroplast movements.

Critical Behavior in Gravitational Collapse of a Yang-Mills Field.

Abstract: We present results from a numerical study of spherically symmetric collapse of a self-gravitating, SU(2) gauge field. Two distinct critical solutions are observed at the threshold of black hole formation. In one case, the critical solution is discretely self-similar, and black holes of arbitrarily small mass can form. However, in the other instance, the critical solution is the $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ static Bartnik-Mckinnon sphaleron, and black hole formation turns on at finite mass. The transition between these two scenarios is characterized by the superposition of both types of critical behavior.

Apoptosis of monocytes and prolonged survival of granulocytes as a result of phagocytosis of bacteria.

Abstract: Monocytes and granulocytes were incubated with suspensions of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, or Salmonella enteritidis and, after being washed free of bacteria, cultured for up to 48 h. Every few hours, samples of cultured cells were taken for DNA isolation. Monocytes which phagocytosed bacteria showed features of apoptotic cells, as determined by light microscopy and DNA fragmentation detected by gel electrophoresis. The phenomenon was observed 2 to 4 h after phagocytosis, in contrast, control monocytes did not show signs of apoptosis until 48 h of culture. Intact control granulocytes spontaneously became apoptotic after 12 h of culture. In contrast, degradation of DNA in cells exposed to bacteria was delayed by 12 to 24 h. In conclusion, our observation suggests that granulocytes and monocytes react differently to phagocytosis of bacteria.

The atopy trait in hypersensitivity to nonsteroidal anti-inflammatory drugs.

Abstract: The prevalence of atopy was evaluated in two groups of subjects with hypersensitivity to nonsteroidal anti-inflammatory drugs (NSAID): 1) 78 patients with aspirin-induced asthma (AIA) confirmed by oral or bronchial provocation challenges 2) 42 subjects with hypersensitivity to pyrazolone drugs (case history and positive skin tests to noramidopyrine/aminophenazone) who tolerated aspirin well Fifty sex- and age-matched persons from an unselected general population, with no hypersensitivity to NSAID, formed the control group Atopy was estimated from the results of the following clinical and biologic parameters: 1) 1) personal and family history of atopic diseases 2) 2) skin prick tests with 16 aeroallergens 3) 3) serum levels of specific IgE to five aeroallergens 4) 4) total serum IgE level Different definitions of atopy were used, consisting of constellations of two or three of the above-mentioned features The results of the study revealed that the prevalence of atopy varied according to the criteria used for its definition Irrespective of the definition used, a similar distribution of atopy was observed in both groups of patients with hypersensitivity to NSAID Atopy was more frequent in either group of patients with intolerance of NSAID than in the control group Thus, atopy is related to adverse drug reactions to NSAID

Health, well-being and burnout of ICU nurses on 12- and 8-h shifts

Abstract: It is generally agreed that some features of shift systems can influence the extent of well-being and health problems experienced by the workers involved. Extended working days (9-12 h) have been found to aggravate some problems associated with shiftwork, especially when the work is mentally and emotionally demanding. The aim of the study was to compare measures of health, sleep, psychological and social well-being, job satisfaction and burnout of ICU nurses on 12- and 8-h shifts. The groups of subjects were matced for age, length of shiftwork experience, marital status and number of hours worked. the 12-h shift nurses, when compared to their 8-h shift colleagues, experienced more chronic fatigue, cognitive anxiety, sleep disturbance and emotional exhaustion. Job satisfaction seems to be independent of the shift duration. The nurses on 12-h shifts reported less social and domestic disruption than those on 8-h shifts. The 12-h shift nurses showed worse indices of health, well-being and burnout tan...

Protective and bronchodilator effects of prostaglandin E and salbutamol in aspirin-induced asthma.

Abstract: We performed a double-blind, two-phase study on protective and bronchodilator effects of prostaglandins E2 and E1 (PGE2, PGE1) and salbutamol in patients with aspirin-induced asthma (AIA). In phase 1 we assessed the effects of pretreatment with PGE2, salbutamol, or the PGE1-analogue, misoprostol, on bronchoconstriction precipitated by inhalation of L-lysine aspirin in 11 patients with AIA. PGE2 and salbutamol were inhaled at equimolar concentrations of 0.25 mumol, 5 min before the aspirin challenge, while 400 micrograms misoprostol was administered orally 1 h before challenge. PGE2 attenuated the bronchoconstrictive reactions in 10 patients, salbutamol in eight, and misoprostol in seven. The mean provocative dose of aspirin causing a 20% fall in FEV1 (PD20) decreased after PGE2 (p = 0.04) and salbutamol (p = 0.06), but only marginally after misoprostol (p = 0.25). There was a positive correlation between magnitude of the protection offered by the three compounds in individual subjects. In phase 2, we examined bronchial response to inhaled PGE2, PGE1, salbutamol, and 2% ethanol in 12 AIA patients compared with 10 aspirin-tolerant patients with asthma. AIA subjects were characterized by less pronounced and shorter bronchodilator responses. There was no correlation between the protective and bronchodilator actions of the compounds used in individual patients. Thus, inhaled PGE2 and salbutamol protect against aspirin-induced attacks of asthma through mechanisms unrelated to their bronchodilator properties. Airways of aspirin-sensitive patients with asthma demonstrate distinct bronchial reactivity.

The average X-ray/gamma-ray spectrum of radio-quiet Seyfert 1s

Abstract: We have obtained the average 1--500 keV spectrum of radio-quiet Seyfert 1s using data from EXOSAT, Ginga, HEAO, and GRO/OSSE The spectral fit to the combined average EXOSAT and OSSE data is fully consistent with that for Ginga and OSSE, confirming results from an earlier Ginga/OSSE sample The average spectrum is well-fitted by a power-law X-ray continuum with an energy spectral index of $\alpha \simeq 09$ moderately absorbed by an ionized medium and with a Compton reflection component A high-energy cutoff (or a break) in the the power-law component at a few hundred keV or more is required by the data We also show that the corresponding average spectrum from HEAO A1 and A4 is fully compatible with that obtained from EXOSAT, Ginga and OSSE These results confirm that the apparent discrepancy between the results of Ginga (with $\alpha \simeq 09$) and the previous results of EXOSAT and HEAO (with $\alpha \simeq 07$) is indeed due to ionized absorption and Compton reflection first taken into account for Ginga but not for the previous missions Also, our results confirm that the Seyfert-1 spectra are on average cut off in gamma-rays at energies of at least a few hundred keV, not at $\sim 40$ keV (as suggested earlier by OSSE data alone) The average spectrum is compatible with emission from either an optically-thin relativistic thermal plasma in a disk corona, or with a nonthermal plasma with a power-law injection of relativistic electrons

Non-commutative geometry of finite groups

Abstract: A finite set can be supplied with a group structure which can then be used to select (classes of) differential calculi on it via the notions of left-, right- and bicovariance. A corresponding framework has been developed by Woronowicz, more generally for Hopf algebras including quantum groups. A differential calculus is regarded as the most basic structure needed for the introduction of further geometric notions like linear connections and, moreover, for the formulation of field theories and dynamics on finite sets. Associated with each bicovariant first-order differential calculus on a finite group is a braid operator which plays an important role for the construction of distinguished geometric structures. For a covariant calculus, there are notions of invariance for linear connections and tensors. All these concepts are explored for finite groups and illustrated with examples. Some results are formulated more generally for arbitrary associative (Hopf) algebras. In particular, the problem of extension of a connection on a bimodule (over an associative algebra) to tensor products is investigated, leading to the class of `extensible connections'. It is shown that invariance properties of an extensible connection on a bimodule over a Hopf algebra are carried over to the extension. Furthermore, an invariance property of a connection is also shared by a `dual connection' which exists on the dual bimodule (as defined in this work).

Oral cavity as permanent reservoir of Helicobacter pylori and potential source of reinfection.

Abstract: Recent studies in developed countries showed that neither dental plaques nor dentures are important reservoir for Helicobacter pylori (Hp), whereas studies in developing countries revealed a high prevalence of Hp in dental plaques, though elsewhere the culture of bacterium or its DNA analysis by polymerase chain reaction in the material obtained from oral cavity were not successful. This study was designed to compare the incidence of Hp in oral cavity (saliva, dental plaques and gingival pockets) using Campylobacter-like organism (CLO) test and culture and in the presence of Hp in the stomach using 14C-urea breath test (UBT), CLO-test and culture (antral biopsy specimens). Hundred dyspeptic subjects with endoscopically normal gastro-duodenal mucosa and 55 symptomatic patients with active duodenal peptic ulcer (DU) were tested for the presence of Hp. Thirty of these DU patients were also examined for presence of Hp in oral cavity and the stomach just before the start and 4 weeks after the termination of one week triple therapy (Omeprazole 20 mg bd, Clarithromycin 500 mg bd and Tinidazole 500 mg bd) when the DU was found endoscopically healed. In the group of 100 dyspeptic subjects, the Hp was detected by CLO-test in saliva, dental plaques and gingival pockets in 84%, 100% and 100% of cases and by the culture in 55%, 88% and 100%, respectively. The presence of Hp, as determined by UBT in the stomach in these subjects was 60%. Using CLO-test and culture, all (100%) out of 55 DU patients, were found to be Hp positive in the oral cavity and in 95% in the stomach. Following one week triple therapy in 30 DU patients, the Hp was still detected in oral cavity by CLO-test in all patients (100%) and by culture in 27 patients (90%), whereas in the stomach, the Hp was found by UTB and culture only in one of these patients (97% Hp eradicated). We conclude that the Polish population including dyspeptic and DU patients, the mouth is permanent reservoir of Hp and that the successful Hp eradication from the stomach by systemic therapy fails the Hp status in the oral cavity that might be a potential source of gastric reinfection in these patients.

New approach to 13C-urea breath test: capsule-based modification with low-dose of 13C-urea in the diagnosis of Helicobacter pylori infection.

Abstract: This study was designed to evaluate a novel modification of the non-invasive capsule-based 13C-urea breath test (13C-UBT). 114 patients were tested for Helicobacter pylori (HP) infection with the use of only 38 mg 13C-urea administrated in solid capsulated form. Obtained results were compared with tissue based methods: histology and rapid urease test (CLOtest). Results of histology and/or CLOtest were considered as the gold standard for each patient. In addition, also capsule-based, micro-dose (37kBq) 14C-urea breath test (14C-UBT) was performed. With a cut-off for delta-over-base values of 5/1000 (i.e., 5 per mil), 13C-UBT results (measured by non-dispersive infrared spectroscopy, NDIRS) correlated highly significant with combined results for invasive methods i.e., CLOtest + histology score. Compared with histology, CLOtest, and the gold standard, the diagnostic values of the test were: sensitivity 97%, specificity 95%, with positive and negative predictive values about 90% and 98% respectively. The modified 13C-UBT test was found to be in full concordance with 14C-UBT; there was 100% agreement in the diagnostic classification of all positive (89) and negative (25) patients. Described modification of 13C-UBT showed that presented modification of 13C-UBT is an excellent, simple, low cost, non invasive, and safe diagnostic tool in HP detection and should be recommended particularly in cases when the use of radioactive urea is contraindicated.

Secular determinants of random unitary matrices

Abstract: We consider the characteristic polynomials of random unitary matrices U drawn from various circular ensembles. In particular, the statistics of the coefficients of these polynomials are studied. The variances of these `secular coefficients' are given explicitly for arbitrary dimension and continued analytically to arbitrary values of the level repulsion exponent . The latter secular coefficients are related to the traces of powers of U by Newton's well known formulae. While the traces tend to have Gaussian distributions and to be statistically independent among one another in the limit as the matrix dimension grows large, the secular coefficients exhibit strong mutual correlations due to Newton's mixing of traces to coefficients. These results might become relevant for current efforts at combining semiclassics and random-matrix theory in quantum treatments of classically chaotic dynamics.

Theoretical calculation of the electroabsorption spectra of polyacene crystals

Abstract: A two‐dimensional analog of the Merrifield model of the coupling between the Frenkel and charge transfer (CT) excitations of a molecular crystal is applied for the calculation of the electroabsorption (EA) spectra of polyacene crystals. The approach is essentially nonempirical, with most of the necessary input data estimated either from theoretical calculations or from independent experiments. Good quantitative reproduction of the experimental EA spectra is achieved, both in their absolute amplitude and intensity pattern. The large amplitude of the Frenkel exciton part of the spectra is successfully accounted for without the necessity to invoke anomalously large molecular polarizabilities. Some basic assumptions of previous analyses are shown to be invalid and future prospects of the new approach are discussed.

Role of capsaicin-sensitive sensory nerves in gastroprotection against acid-independent and acid-dependent ulcerogens.

Abstract: Treatment with small doses of topical capsaicin protects the gastric mucosa from the damage by strong irritants but functional ablation of sensory nerves by pretreatment with larger dose of parenteral capsaicin augments the formation of gastric lesions via unknown mechanism. This study was designed to determine the role of gastric acid secretion, mucosal blood flow (GBF) and prostaglandins (PG) generation in the gastroprotection induced by small doses of topical or parenteral capsaicin in rats with intact or capsaicin-deactivated sensory nerves. Gastric lesions were produced in rats with intact sensory nerves (series A) or capsaicin-deactivated nerves (series B) using intragastric (i.g.) application of 100% ethanol, acidified aspirin (ASA) or water immersion and restraint stress (WRS). Pretreatment with i.g. capsaicin (0.12-1.0 mg/kg) in rats with intact sensory nerves (series A) reduced dose-dependently the mucosal damage caused by ethanol, ASA or WRS, the dose inhibiting the lesion area by 50% (ID5o) being 0.3, 0.5 and 0.7 mg/kg, respectively. This protection was accompanied by a significant rise in gastric mucosal blood flow (GBF). Parenteral application of capsaicin (1.2-10 mg/kg s.c.) that in intact rats dose-dependently increased GBF, also dose-dependently reduced gastric damage induced by ASA or WRS (but not by ethanol), the ID50 being 5 and 3 mg/kg, respectively. The reduction by i.g. capsaicin of ethanol- or WRS-induced mucosal lesions was accompanied by a rise in GBF and this effect was reversed by indomethacin at a dose that suppressed endogenous PG biosynthesis by about 90%, indicating that PG are involved in the protective activities of topical capsaicin. Furthermore, topical and to a lesser extent parenteral capsaicin given to rats with intact or deactivated sensory nerves inhibited gastric acid and pepsin outputs, suggesting that this inhibition could contribute to the capsaicin-induced gastroprotection against acid-dependent mucosal lesions (ASA or WRS). Capsaicin deactiva-tion of sensory nerves aggravated mucosal lesions induced by all three ulcerogens and this effect was accompanied by a marked decrease in GBF. In such capsaicin-deactivated rats, topical capsaicin also reduced ethanol-, ASA- or WRS-induced lesions, while parenteral capsaicin was effective only in the protection against the damage induced by acidified ASA and WRS but not by ethanol. The protection against WRS lesions and accompanying rise in GBF by parenteral capsaicin were also reversed by the pretreatment with indomethacin applied in a dose suppressing the generation of PG. We conclude that capsaicin is capable of protecting gastric mucosa in rats with both intact and capsaicin-deactivated rats and that this protective activity depends, at least in part, upon its hyperemic and antisecretory effects that may be mediated, at least in part, by endogenous release of PG.

Gamma delta T cells from tolerized alpha beta T cell receptor (TCR)-deficient mice inhibit contact sensitivity-effector T cells in vivo, and their interferon-gamma production in vitro.

Abstract: Contact sensitivity (CS) responses to reactive hapten Ag, such as picryl chloride (PCl) or oxazolone (OX), are classical examples of T cell–mediated immune responses in vivo that are clearly subject to multifaceted regulation. There is abundant evidence that downregulation of CS may be mediated by T cells exposed to high doses of Ag. This is termed high dose Ag tolerance. To clarify the T cell types that effect CS responses and mediate their downregulation, we have undertaken studies of CS in mice congenitally deficient in specific subsets of lymphocytes. The first such studies, using αβ T cell–deficient (TCRα−/−) mice, are presented here. The results clearly show that TCRα−/− mice cannot mount CS, implicating αβ T cells as the critical CS-effector cells. However, TCRα−/− mice can, after high dose tolerance, downregulate α+/+ CS-effector T cells adoptively transferred into them. By mixing ex vivo and then adoptive cell transfers in vivo, the active downregulatory cells in tolerized α−/− mice are shown to include γδ TCR+ cells that also can downregulate interferon-γ production by the targeted CS-effector cells in vitro. Downregulation by γδ cells showed specificity for hapten, but was not restricted by the MHC. Together, these findings establish that γδ T cells cannot fulfill CS-effector functions performed by αβ T cells, but may fulfill an Ag-specific downregulatory role that may be directly comparable to reports of Ag-specific downregulation of IgE antibody responses by γδ T cells. Comparisons are likewise considered with downregulation by γδ T cells occurring in immune responses to pathogens, tumors, and allografts, and in systemic autoimmunity.