Modification of the action of ionizing radiation on cells of transplantable tumors by administering xanthobine

In experiments on mice it was established that the radiosensitizing effect of xanthobin was manifested by the enhancement of the inhibiting action of ionizing radiation on the growth of adenocarcinoma RL-67, diminution of the "shoulder" of the survival curve of Ehrlich ascites tumor cells, and increase in the average life of tumor-bearing animals.     

Application of the “-Omic-” technologies in phytomedicine

The proof of efficacy of phytopreparations and the determination of their mode of action are permanent challenges for an evidence-based phytotherapy. The technology platform of genomics, proteomics and metabolomics ("-omic-" technologies) are high-throughput technologies. They increase substantially the number of proteins/genes that can be detected simultaneously and have the potential to relate complex mixtures to complex effects in the form of gene/protein expression profiles. Provided that phytopreparation-specific signatures in the form of gene/protein expression profiles can be developed, these technologies will be useful for the chemical and pharmacological standardization and the proof of the toxicological potential of a plant extract. Over a long-term perspective they may economize the proof of efficacy, the determination of the mode of action of phytomedicines and allow to investigate herbal extracts without prominent active principle(s). The application of this genomics revealed already that gene expression profiles induced by single drugs and the ones induced by the combination of the same drugs can be entirely different. These results make the information of the mode of action of isolated "active principles/lead substances" of phytopreparations questionable. The application of the "-omic-" technologies may lead to a change of paradigms towards the application of complex mixtures in medicine and open the new field of phytogenomics, -proteomics and -metabolomics.     

"Action potentials" in Neurospora crassa, a mycelial fungus.

Occasional spontaneous "action potentials" are found in mature hyphae of the fungus Neurospora crassa. They can arise either from low-level sinusoidal oscillations of the membrane potential or from a linear slow depolarization which accelerates into a rapid upstroke at a voltage 5-20 mV depolarized from the normal resting potential (near-180 mV). The "action potentials" are long-lasting, 1-2 min and at the peak reach a membrane potential near-40 mV. A 2-to 8-fold increase of membrane conductance accompanies the main depolarization, but a slight decrease of membrane conductance occurs during the slow depolarization. Two plausible mechanisms for the phenomenon are (a) periodic increases of membrane permeability to inorganic ions, particularly H+ or Cl- and (b) periodic decreases in activity of the major electrogenic pump (H+) or the Neurospora membrane, coupled with a nonlinear (inverse signoid) current-boltage relationship. Identification of action potential-like disturbances in fungi means that such behavior has now been found in all major biologic taxa which have been probed with suitable electrodes. As yet there is no obvious function for the events in fungi.     

Morphometric evaluation of the effect of opioid peptides on cysteamine-induced ulcer in rats

Morphometry was used to study the action of an enkephalin analog and beta-endorphine on the duodenal mucosa in rats with an experimental ulcer induced by cysteamine. Enkephalin produced a more powerful protective action than endorphine. The antiulcerous action was manifested in the diminution of dystrophic changes, redistribution of inflamed cells with an increase in the lymphocyte and monocyte counts, and in the reduction of the number of tissue macrophages and histocytes. Administration of opioids provoked a particularly marked increase in the eosinophil count in the duodenal mucosa. All these effects were abolished by naloxone. It is concluded that the tissue effects of opioids are mediated by specific opiate receptors.     

Effect of a new beta-blocker (CM 6805) on the action potential of guinea pig atrial fiber

CM6804 effect has been studied about some parameters of the intracellular action potential (AP) of guinea pig autorythmic auricle. Auricle was preserved alive under Tyrode oxygenated solution at 37 degrees C. AP is measured by a fluctuating intracellular glass microelectrode. At a concentration of 5 . 10(-5) M, CM doesn't alter the resting membrane potential, it causes a small overshoot reduction, it decreases the maximum depolarization rate and the heart rate, it increases the action potential duration. Overshoot and maximum depolarization rate decrease prove that CM modifies the membrane permeability probably by a diminution of the sodium rapid inward current. CM action is similar to others aryl-oxy-propyl propanolamine like propranolol.     

Ultrastructural changes in nucleoli and fibrillar centers under the effect of local ultraviolet microbeam irradiation of interphase culture cells

As shown previously, ultraviolet (uv) microbeam irradiation of one of the two mature nucleoli within an interphase cell nucleus causes significant diminution and inactivation of the irradiated nucleolus and compensatory growth and activation of the nonirradiated one. In the present work we describe the results of an ultrastructural study of this phenomenon. The changes in the nucleoli were examined by means of complete series of ultrathin sections obtained from seven irradiated pig kidney cells. The compensatory hypertrophy of the nonirradiated nucleoli is shown to be accompanied by a nearly twofold increase in the number of fibrillar centers (FCs) and by a decrease in their linear dimensions compared with the control cells of the same ploidy. In the degraded nucleoli the number of FCs decreases, but their dimensions increase. Ultraviolet microbeam irradiation causes dramatic diminution of the dense fibrillar component within the irradiated nucleoli as well. The nucleolar capacity for compensatory hypertrophy indicates that in addition to active ribosomal genes, mature nucleoli also contain "silent" genes capable of being activated under extreme conditions to sustain the required level of rRNA synthesis. It is assumed that activation of latent ribosomal genes is accompanied by FC "fragmentation" without a considerable increase in their total volume per cell.     

An electrogenic sodium pump in Limulus ventral photoreceptor cells

A hyperpolarization can be recorded intracellularly following either a single bright light stimulus or the intracellular injection of Na⁺. This after-hyperpolarization is abolished by bathing in 5 x 10^-6 M strophanthidin or removal of extracellular K⁺. Both treatments also lead to a small, rapid depolarization of the dark-adapted cell. When either treatment is prolonged, light responses can still be elicited, although with repetitive stimuli the responses are slowly and progressively diminished in size. The rate of diminution is greater for higher values of [Ca⁺⁺]_out; with [Ca⁺⁺]_out = 0.1 mM, there is almost no progressive diminution of repetitive responses produced by either K⁺-free seawater or strophanthidin. We propose that an electrogenic Na⁺ pump contributes directly to dark-adapted membrane voltage and also generates the after-hyperpolarizations, but does not directly generate the receptor potential. Inhibition of this pump leads to intracellular accumulation of sodium ions, which in turn leads to an increase in intracellular Ca⁺⁺ (provided there is sufficient extracellular Ca⁺⁺). This increase in intracellular calcium probably accounts for the progressive decrease in the size of the receptor potential seen when the pump is inhibited.     

Conformational changes in the active site of tryptophanase revealed by the circular dichroism method

Tryptophanase from E. coli displays positive CD in the coenzyme absorption bands at 337 and 420 nm. Breaking of the internal coenzyme-lysine imine bond upon reaction with hydroxylamine or amino-oxyacetate is accompanied by a strong diminution of the positive CD. Interaction of tryptophanase with L-threonine and beta-phenyl-DL-serine(threo form) leads to a decrease in absorbance at 337 nm and to an increase at 425 nm. This is associated with inversion of the CD sign, i.e. with disappearance of the positive CD in the 420-nm band and its replacement by a negative CD. L-Phenylalanine, alpha-methyl-DL-serine and D-alanine cause an increase in absorbance at 425-430 nm and a diminution of the positive CD in this band. In the presence of D-alanine and indole a negative CD appears in the 400-450 nm region. It is inferred that an external coenzyme-quasisubstrate aldimine is formed on interaction of the above amino acids with the enzyme. L-Alanine and oxindolyl-L-alanine evoke an intense narrow absorption band at 500 nm ascribed to a quinonoid intermediate; a positive CD is observed in this band. The dissymmetry factor delta A/A in the 500-nm band is much smaller than that in the absorption bands of the unliganded enzyme. Inversion of the CD sign on formation of the external aldimine and diminution of the dissymmetry factor in the quinonoid band indicate that reorientations of the coenzyme occur in the course of the catalytic action of tryptophanase.     

Partial contribution of the ATP-sensitive K+ current to the effects of mild metabolic depression in rabbit myocardium

The object of the study was to compare the capability of glibenclamide to block the effects of K⁺-ATP channel activators on action potential duration and steady state whole cell current to its efficiency in counteracting the effects of hypoxia or metabolic poisons in the presence of glycolytic substrate. The modulation of action potential duration by 30 M glibenclamide was tested in perfused hearts subjected to hypoxia or to the K⁺-ATP channel opener pinacidil. Similar protocols were used to study the modifications of the steady state whole cell current in isolated ventricular myocytes. It was found that glibenclamide did not prevent early action potential shortening induced by hypoxia but produced a partial recovery after 15 min of exposure. At the steady state the action potential duration had lengthened by 53±6% at plateau level and 42±3% at 95% repolarization. In contrast, action potential shortening induced by 100 M pinacidil was fully reversed by glibenclamide within 2 min. Freshly dispersed ventricular myocytes were characterized in control conditions as for the properties of the steady state current. This current, measured at the end of 450 ms long pulses showed typical inward rectification that was abolished by 50 M Ba²⁺. Cyanide (2 mM), carbonyl-cyanide m-chlorophenylhydrazone (CCCP, 200 nM) and BRL 38227 (30 M) produced characteristic increases in time independent outward currents. Glibenclamide abolished the outward current induced by BRL 38227 and the concomitant action potential shortening. Addition of cyanide in the presence of glibenclamide and BRL 38227 produced a new increase in outward current accompanied by action potential shortening. In the absence of K⁺-ATP channel activators, glibenclamide partly inhibited the CCCP induced current. Our data suggested that the delayed onset of glibenclamide action in hypoxic hearts is not due to diffusion barriers. They rather support the view that mechanisms other than K⁺-ATP channel activation could determine the early action potential shortening in whole hearts. The partial recovery observed under glibenclamide may be due, in part, to channel desensitization but also reflect the contribution of more than one current system to the action potential shortening because the glibenclamide insensitive fraction of the CCCP induced current is partly blocked by low concentrations of Ba²⁺. Differences with other data in the literature are attributed to the degree to metabolic blockade, to species differences, and to the inherent heterogeneities of the whole heart model where non-muscle cells may modulate the response to hypoxia.     

Differences between dose-effect curves for ethanol on locomotion and rearings in mice of various strains]

Ethanol (1--5 g/kg, per os) dose-response curve for locomotion in male mice of 4 strains (SHR, BALB/c, C3HA and C57BL/6) is characterized by a gradual rise up to the top (at 3 g/kg for all strains except C3HA, in which it was attained at 5 g/kg) and by subsequent decline. The dose-response curve for rearings gradually and gently slopes down to zero. The stimulant effect of ethanol (1.5--3 g/kg) can therefore be measured by an increase in lovomoyion. However, the action of various drugs (or other factors) on this effect has to be evaluated simultaneously from locomotion and rearings since a decrease in locomotion as a result of the curve fracture may indicate both diminution and enhancement of the stimulant effect of ethanol. Simultaneous decrease or increase in the rate of rearings suggests potentiation or diminution of the effect of ethanol, respectively.     

Permeability Changes Associated with the Action Potential in Procaine-Treated Crayfish Abdominal Muscle Fibers

Permeability changes associated with prolonged action potentials have been analyzed in procaine-treated crayfish abdominal muscle fibers. The effect of external Ca indicates that the increase in membrane conductance observed during the rising phase of the action potential is primarily due to a permeability increase for Ca. A remnant of the permeability increase may cause the succeeding plateau as shown by its high conductance and by the effect of low Mn. A delayed increase in conductance precedes the termination of the plateau phase. This is due to a delayed increase in permeability, probably for K, that is observed when depolarizing electrogenesis is eliminated. High external Ca reduces the action potential duration, the falling phase starting at a higher depolarization. These changes may be related to an earlier onset of the delayed increase in permeability, induced by a larger inside positivity in the presence of higher Ca. No "anomalous rectification" is seen in early or late I-V curves for small depolarizations. Ba may replace Ca in its role in depolarizing electrogenesis, and the first action potential induced in Ba saline has a large overshoot and a long duration. In higher Ba salines, action potentials are greatly prolonged. Long term soaking in Rb-containing or K-free saline also augments and prolongs the action potential. These changes are assumed to be related to depression of the K permeability of the membrane.     

Action of middle molecules from chronic renal insufficiency treated by hemodialysis on mitochondrial respiration

"Middle molecules" are isolated both from the urine of normal subjects and from the blood of patients suffering from chronic renal insufficiency treated by hemodialysis. Their action is tested on mitochondrial respiratory activity. Some of these molecular species (fraction 7 f and 7 g) are without any effect. On the other hand the 7 c middle molecules fraction gives a loss of respiratory control due to a decrease of respiratory activity in state 3. A diminution of the P/O ratio is noted and so the available ATP pool is decreased. This action can be compared to the fact that 7 c plasmatic fraction concentration seems to be connected with the patients clinical condition.     

Electrophysiology of a myoid epithelium inChelophyes (Coelenterata: Siphonophora)

Summary The passive electrical properties, and the ionic basis of the action potential have been examined in the subumbrella myoid epithelium of the siphonophoreChelophyes. The myoepithelial cells are electrically coupled, and are 20 m wide, some 1 mm long, and only 5 m thick. Membrane constants determined by a 2-electrode study were: = 280 m; R_m = 0.11 kOhm/cm²; R_i = 24 Ohm/cm. Mean resting potential was – 85 mV. The first action potential of a series (whether evoked by repetitive stimulation, or occurring in a natural unstimulated swimming burst) shows a rapid rise and fall with no afterpotential. The overshoot is small, but successive action potentials show a remarkable facilitation, overshooting by as much as 70 mV. They also show a plateau phase after the initial rapid rise, which is terminated by a rapid fall. Conduction velocity was 27 cm/s.Changes in the external milieu, and the effects of Ca²⁺ blocking agents indicated that the action potentials are complex events. Although insensitive to TTX, the action potential is dependent on external sodium concentration, and is not abolished by Ca²⁺ blocking agents: in this respect it resembles the sodium-dependent action potentials of other siphonophore tissues.The ionic basis of the facilitated action potentials is not yet clear, but it seems probable that a fast potassium conductance terminating the unfacilitated action potential is progressively inactivated during repetitive activity, and that the plateau phase of the facilitated action potential is maintained by a sodium conductance mechanism, to be terminated by a calcium-activated potassium conductance.Abbreviations EGTA 1,2-bis-[2-di(carboxymethyl)-amino-ethoxyl]-ethane - TEA tetraethyl ammonium chloride - TTX tetrodotoxin This work was carried out during a visit to the Station Zoologique, Villefranche-sur-Mer in the spring of 1979; it is a pleasure to express our thanks to Prof. P. Bougis and his staff for their kind hospitality. Q.B. and P.A.V.A. were supported by a grant from the British Council which is gratefully acknowledged.     

Sodium flux through the sodium channels of axon membrane fragments isolated from lobster nerves

The efflux of 22Na from vesicles formed by axolemma fragments isolated from lobster nerves was studied in the presence and in the absence of drugs having well-known action on the sodium channels. The vesicles were equilibrated 12-14 h at 4 degrees C with 22Na in lobster solution containing 1 mM ouabain. Afterwards the suspension was divided: one portion was used as control and the others were treated with veratrine (0.025-0.50 mg/ml), tetrodotoxin (1-2,000 nM) in the presence of veratrine, or tetrodotoxin alone. After 3 h at 20-22 degrees C, the suspensions were diluted into nonradioactive solutions and the 22Na efflux followed by a rapid filtration technique. The results revealed that veratrine increases the efflux rate and the additional application of tetrodotoxin abolishes it, e.g., 0.50 mg of veratrine/ml increases the rate, expressed in 10(-2) min(-1), from 0.59 +/- 0.04 (mean +/- SEM; n = 13) to 0.86 +/- 0.05 (n = 13), and the addition of 100 nM tetrodotoxin diminishes it to 0.48 +/- 0.07 (n = 4). This increase and diminution are statistically significant (P less than 0.005), but this is not the case between the control and the veratrine plus tetrodotoxin values (P greater than 0.05). 50% of the diminution is produced by 11.9 +/- 2.4 nM tetrodotoxin. Tetrodotoxin alone produces a slight diminution of the 22Na efflux. Batrachotoxin (0.50 muM) has an action similar to veratrine's. These findings are considered evidence of the presence of functioning sodium channels in the isolated axolemma fragments.     

Chromatin diminution and early cleavage in Parascaris univalens (Nematoda)

Summary In Parascaris developmental commitment to the germ line and somatic lineages is indicated by the orientation of the mitotic spindle in blastomeres, the topology of cells in the embryo, and chromatin diminution in presomatic blastomeres. Using three different experimental techniques: transient pressure treatment, application of cytochalasin B, and isolation of blastomeres, we have succeeded in uncoupling several developmental processes during cleavage of P. univalens. The following results were obtained: (1) Following mitotic nondisjunction we observed identical behavior of all chromatids in each blastomere. Thus chromosome differentiation by differential replication does not occur. (2) Chromosome fragments obtained by pressure treatment of egg cells underwent chromatin diminution. Thus this process does not require an intact germ-line chromosome. However, chromosomes immobilized on a monopolar spindle did not undergo chromatin diminution. Thus diminution appears to require segregation of chromatids. (3) Blastomeres that completely lacked chromosomes as a result of mitotic nondisjunction underwent normal early cleavage divisions. (4) Pressure treatment or prolonged treatment with cytochalasin B caused egg cells or germ line blastomeres to lose their germ line quality, as deduced from the coincident occurrence of symmetrical (presomatic-like) cleavage and chromatin diminution. (5) Isolated blastomeres from 2-cell embryos, i.e. 1/2 blastomeres, usually cleaved according to their prospective fates in the whole embryo. However, in some partial embryos derived from such blastomeres, chromatin diminution was delayed for either one or two cleavage mitoses. An activation model as an alternative to a prelocalization model is presented, which can account for early blastomere topogenesis and chromatin diminution.     

Effect of formaldehyde and glutaraldehyde on electrical properties of cardiac Purkinje fibers

The effects of formaldehyde, glutaraldehyde, 1-fluoro-2,4-dinitrobenzene, and 1,5-difluoro-2,4-dinitrobenzene on the electrophysiological properties of cardiac Purkinje fibers were studied. At concentrations of 2.5 mM the aldehydes produced a transient hyperpolarization, lengthening of the plateau of the action potential, and an increase in action potential overshoot and upstroke velocity. If exposure to aldehyde was continued, the fiber failed to repolarize after an action potential and the membrane potential stabilized at about -30 mv. If exposure was terminated before this, recovery was usually complete. At the time the fibers were hyperpolarized the input resistance was increased without much change in length constant, leading to an increase in both calculated membrane resistance and calculated core resistance. Although it was anticipated that an effect of the aldehydes on the membrane was to increase fixed negative charge, it was difficult to explain all the electrophysiological changes on this basis. The major effects of the fluorobenzene compounds were not the same; they produced a shortening of the action potential and a rapid loss of excitability.     

Differences in Na and Ca Spikes As Examined by Application of Tetrodotoxin, Procaine, and Manganese Ions

The effects of tetrodotoxin, procaine, and manganese ions were examined on the Ca spike of the barnacle muscle fiber injected with Ca-binding agent as well as on the action potential of the ventricular muscle fiber of the frog heart. Although tetrodotoxin and procaine very effectively suppress the "Na spike" of other tissues, no suppressing effects are found on "Ca spike" of the barnacle fiber, while the initiation of the Ca spike is competitively inhibited by manganese ions. The initial rate of rise of the ventricular action potential is suppressed by tetrodotoxin and procaine but the plateau phase of the action potential is little affected. In contrast the suppressing effect of manganese ions is mainly on the plateau phase. The results suggest that the plateau phase of the ventricular action potential is related to the conductance increase in the membrane to Ca ions even though Na conductance change may also contribute to the plateau.     

Light-Induced Changes in Photoreceptor Membrane Resistance and Potential in Gecko Retinas : II. Preparations with Active Lateral Interactions

The time-course of light-induced changes in membrane voltage and resistance were measured in single photoreceptors in eyecup preparations of Gekko gekko. A small circular stimulus directed toward the impaled receptor produced membrane hyperpolarization. Application of a steady annular light to the receptor periphery resulted in diminution of the receptor's response to the stimulus. The effects of illumination of the surrounding receptors were isolated by directing a small, steady desensitizing light to the impaled receptor and then applying a peripheral stimulus. Brief stimuli produced a transient decrease in resistance with rapid onset and offset, a time-course similar to that of the response diminution. For some cells a depolarization that coincided with the resistance decrease was seen. During illumination with prolonged stimuli the resistance decrease was followed by a slow increase. After offset resistance rose transiently above the original value and then returned slowly to its original value. The slow resistance changes were not accompanied by changes in membrane voltage. The response diminution, resistance decrease, and depolarization were not observed in retinas treated with aspartate or hypoxia. It is therefore concluded that these effects are mediated by horizontal cells. The diminution is achieved by shunting the receptor potential and may play a role in field adaptation.     

Singlet oxygen and plants

The generation, occurrence and action of singlet oxygen in plant tissue is reviewed. Particular emphasis is placed upon its formation from triplet sensitizers and its reactivity with molecules of biological importance such as lipids and amino acids. The possibility of singlet oxygen generation in chloroplasts is discussed in relation to potential quenching systems such as carotenoid pigments, ascorbate and α-tocopherol. The problems associated with carotenoid diminution and some stress and herbicide treatment conditions are related to the possibility of damage by singlet oxygen. The action of a number of secondary plant substances, including quinones, furanocoumarins, polyacetylenes and thiophenes, as plant defence agents is discussed in relation to the photodynamic generation of singlet oxygen.     

Sertoli cell function in albino rats treated with etoposide during prepubertal phase

Sertoli cell plays a key role in spermatogenesis. Many studies refer that this cell is not harmed by the majority of anticancer treatments known to cause damage to the testis. However, in the previous study we observed that etoposide, an efficient chemotherapeutic drug, provokes an increase in numerical density of the Sertoli cells. This phenomenon suggests that this cell was harmed by etoposide. Thus, we decided to investigate a possible direct action of etoposide on Sertoli cells analyzing the function of this cell and relating it with the integrity and damage of the seminiferous epithelium. Prepubertal albino rats received 5 mg/kg of etoposide for eight consecutive days and were sacrificed in different ages. The control groups received 0.9% saline solution. The testes were fixed in Bouin’s liquid for transferrin immunolabeling and testicular labeled tissue volume density measurement. Except for the younger rats, all the etoposide-treated rats showed diminution of transferrin immunolabeling in the seminiferous epithelium, and consequently, of total labeled testicular tissue volume density. We concluded that the diminution of transferrin labeling in the seminiferous epithelium was not associated with germ cell absence such as commonly reported. The results suggest etoposide impairs Sertoli cell function.