Shapes of curves of pH-dependence of reactions

A simple case is considered in which the rate of a two-step reaction depends on pH because the intermediate formed in the first step has to gain (or lose) a proton before it can react in the second step, and in which the rate-determining step therefore changes with pH. The curves of reaction rate against pH are shown to be symmetrical, and the sharpest peak possible has a width at half its height of 1.53pH units, i.e. of 2log(3+2 radical2). Any particular curve for this situation proves to be identical with a curve that could be generated for the pH-dependence of a single-step reaction in which the rate is proportional to the concentration of a particular ionic form of a reactant. Curves for the latter situation, however, can have forms impossible for the former case in which the rate-determining step changes, but only if the protonations that activate and deactivate the reactant are co-operative. The peak can then become even sharper, and its width at half its height can fall to 1.14pH units, i.e. to 2log(2+ radical3).     

Pathogenicity of two species of Fusarium on some cultivars of bean in greenhouse

Twenty isolates of Fusarium oxysporum and F. solani were isolated from the infected roots of bean in different farms of east Azarbaijan and Tehran Provinces and their pathogenicity determined. Most isolates of the fungi were identified as F. oxysporun. They caused root rot, yellowing and wilting of bean in the field. In this test, the roots of 6 cultivars of bean seedlings soaked in suspension of the 7 isolates of the fungi (a1, Gogan, a2, Bilverdi, a3, Savojbolagh-Hashtgerd, a4, field of Agr. Coll. a5, Khomein, a6, Ramjin of F. oxysporum and a7 of F. solani of Varamin, Iran) for 5 minute (106 spores/ml.) then transplanted into the sterilized soil in 4 pots (as replication). For control (a8) the roots soaked in distilled water. The results showed that percentage average of necrotic roots and crowns of isolates al, a2, a3, a5, a6, a7 was %20.31 in group a, a4 was %43.52 in group b and a8 was %2.77 in group c after 3 weeks. The isolate a4 (from the field of Agricultural College, Karaj) was more infectious than the other because it caused wilting, yellowing the leaves and decreased the growth very soon, followed by a5 with %25.32 rate was more pathogenic. Bean cultivar Goli-Red was more tolerant with %10.02 than the others of 16.29 (Naz Red) to 25.15 percent of necrotic the roots & stems.     

Comparison of models of insulin release

A model for insulin secretion with a storage and a labile compartment, as well as a provisionary factor, is combined with a signal model in which the signal can be the difference between an excitation and an inhibition, or the difference in concentrations inside and outside some cell components. The model, using a single set of values for the parameters, accounts in a semiquantitative manner for all of the regularly appearing features of the insulin secretion from thein vitro perfused pancreas to a wide range of patterns of glucose and tolbutamide stimulation. Among the features which can be accounted for are: early and late secretion of insulin as a function of glucose in terms of a single parameter; the apparent depletion and recovery during a pulsed pattern of stimulation by tolbutamide; the hypersecretion following a short period of rest during a prolonged stimulation by glucose; the negative spike which occurs when the concentration of glucose, which has been maintained for a period of time, is suddenly reduced to a lower level; and the appropriate responses to slow and fast ramp functions of glucose concentration.     

Spatial division of labour of Schoenoplectus americanus

If connected ramets are growing in heterogeneous environments, Division of Labour (DoL) among ramets potentially will result in more efficient sharing of resources and an overall benefit to the plants. As a result of DoL, connected ramets growing in a heterogeneous environment might achieve more biomass than ramets growing in a homogeneous environment. DoL has been demonstrated to occur in a few clonal plant species, although most studies simply focussed on biomass allocation, not on actual resource capturing such as water and nutrient consumption. The model system for our study is one in which two connected ramet groups of Schoenoplectus americanus were placed into contrasting environments. In one treatment, the connected ramets grew in heterogeneous environments and in the other treatment, the connected ramets grew in the same (i.e. homogeneous) environment. We manipulated two variables (light and salinity) in the experiment. We hypothesized that ramets growing in a shaded and fresh water condition in a heterogeneous environment would use more water than ramets growing in a similar condition but in a homogeneous environment. We further hypothesized that ramets growing in a light and saline condition in a heterogeneous environment would assimilate less water than ramets growing in a similar condition but in a homogeneous environment. These hypotheses are based on the assumption that ramets in a heterogeneous environment would translocate water from ramets growing in a shaded and fresh water condition to ramets growing in a light and saline water condition. We also hypothesized that ramets growing in heterogeneous environments achieve larger biomass than ramets in homogeneous environments. Ramets grown in light and saline conditions in heterogeneous environments allocated more biomass to aboveground parts, had taller shoots, larger Specific Green (leaf) Area and consumed less water than ramets grown in similar conditions but in a homogeneous environment. Results confirm the hypothesis that connected ramets in heterogeneous environments are specialised to capture locally abundant resources and share these with connected ramets growing in other habitats. The result of DoL is that the entire connected ramet system benefits and achieves higher biomass.     

Studies of the chemical composition of a healing skin wound in rats, and of the concentrations of some constituents of tissues distant from the healing wound

1. A skin lesion was made in rats by dorsal incision and the insertion of a polythene tube. 2. Over a period of 25 days after wounding, assays were performed for ascorbic acid, DNA, hydroxyproline, methionine, tryptophan, tyrosine and free amino acids in the lesion tissue. 3. The neutral-salt-soluble proteins of the lesion tissue were fractionated on DEAE-Sephadex, with the separation of fibrinogen and γ-globulin from a serum protein fraction. 4. Over a period of 20 days after wounding, in wounded rats and in controls, assays were conducted for: ascorbic acid in lens and liver, hydroxyproline, soluble protein, methionine and water in muscle and tendon, and free amino acids in muscle. 5. Relative to controls there was a decrease in lens and liver ascorbic acid, a rise in tendon hydroxyproline, a rise in muscle free amino acids, a fall in muscle protein and a rise in tendon and muscle water.     

The effect of a complex of meditation exercises on the psychophysiological state of young men

Using a simple motor response, a complex sensorimotor response, and a tapping test, the effect of a complex of meditation exercises on the neuromuscular coordination in healthy male students who were preliminarily trained in methods of self-regulation based on meditation techniques was studied. As a result of a 6-min session of self-regulation, a considerable decrease (by 30% or more) in the time of a simple motor response and a complex sensorimotor response (due to a decrease in the latent time at constant motor time) and a simultaneous decrease in the number of errors, as well as a considerable increase in the result of the tapping test, were recorded. A short-term effect expressed in an increase in the rate and accuracy of sensorimotor responses can be a result of a change in the functional state of the nervous system under the impact of transcendental meditation techniques.     

Analysis of the molecular interaction of the farnesyl moiety of transducin through the use of a photoreactive farnesyl analogue

Farnesylation of the gamma-subunit of the retinal G-protein, transducin (Talpha/Tbetagamma), is indispensable for light-initiated signaling in photoreceptor cells. However, the farnesyl-mediated molecular interactions important for signaling are not well understood. To explore this issue, we created a functional Tbetagamma analogue in which the farnesyl group was replaced with a (3-azidophenoxy)geranyl (POG) group, a novel farnesyl analogue with a distal photoreactive azido group. In the presence of lipid membranes and/or Talpha-GDP, UV irradiation of POG-modified Tbetagamma (POG-Tbetagamma) invariably yielded a cross-linked product Tgamma-Tbeta, reflecting a constitutive interaction of the Tgamma C-terminal lipid with Tbeta. In addition to the Tgamma-Tbeta adduct, a Tgamma-Talpha cross-link was detected in the aqueous fraction. Reconstitution of POG-Tbetagamma with Talpha and light-activated rhodopsin (Rh) in photoreceptor membranes resulted in cross-linking of Tgamma with a glycerophospholipid, indicating molecular interaction of the farnesyl group with cellular membranes. The Tgamma-phospholipid cross-link was observed only in the presence of both Talpha-GDP and Rh, and was abolished by the addition of GTPgammaS or by replacing Rh with opsin. These findings suggest a transient farnesyl-membrane interaction occurs only in a signaling state formed in a transducin-Rh ternary complex. On the other hand, UV irradiation of POG-Tbetagamma in a soluble complex with phosducin, a negative regulator of G-protein, yielded a Tgamma-phosducin adduct in addition to the Tgamma-Tbeta cross-link. These results illustrate that, rather than being a static membrane anchor, the farnesyl moiety plays an active role in the dynamics of protein-protein and protein-membrane interactions at defined steps in the signal transduction process.     

Findings of the importance of dietetic fiber in the regulation of cholesterolemia

We studied the variations of some lipid indexes in cholesterolemia, lipidemia and triglycerides in relation to a diet rich in bulk. Seven adult male subjects in good health were tested for cholesterol, lipid and triglycerides before and after a two week period of a dialy diet of 40 g of whole wheat bran containing about 10g of fiber. At the some time the lipid, cholesterol and triglycerides limits were measured in 3 groups of rabbits. The first groups was subjected to a normal diet, the second group was subjected to a diet of bleached flour and vitamins, and the third group had a diet similar to the second group but with the addition of 40 g whole wheat bran. The results of our investigation demonstrated a statistically significant decrease of cholesterol lipid and triglycerides levels the special diets at the some time we did not see in increase in the third group of rabbit. Our study seems to indicate that dietetic fibers exercise a vital role in regulating the concentration of plasma lipids even if the subject continues to consume a diet rich in fats. From this we see to importance of the dietetic fibers as a protective factor in the prevention of ateriosclerotic.     

Identification of secondary effects of hyperexcitability by proteomic profiling of myotonic mouse muscle

Myotonia is a symptom of various genetic and acquired skeletal muscular disorders and is characterized by hyperexcitability of the sarcolemma. Here, we have performed a comparative proteomic study of the genetic mouse models ADR, MTO and MTO*5J of human congenital myotonia in order to determine myotonia-specific changes in the global protein complement of gastrocnemius muscle. Proteomic analyses of myotonia in the mouse, which is caused by mutations in the gene encoding the muscular chloride channel Clc1, revealed a generally perturbed protein expression pattern in severely affected ADR and MTO muscle, but less pronounced alterations in mildly diseased MTO*5J mice. Alterations were found in major metabolic pathways, the contractile machinery, ion handling elements, the cellular stress response and cell signaling mechanisms, clearly confirming a glycolytic-to-oxidative transformation process in myotonic fast muscle. In the long-term, a detailed biomarker signature of myotonia will improve our understanding of the pathobiochemical processes underlying this disorder and be helpful in determining how a single mutation in a tissue-specific gene can trigger severe downstream effects on the expression levels of a very large number of genes in contractile tissues.     

Characterization of the yellow-pigment genes of Erwinia herbicola

A 6.7 kb DNA fragment containing the pigment genes of Erwinia herbicola Eho13 has been cloned into Escherichia coli. These genes were chromosomally encoded in E. herbicola. The entire DNA fragment could be divided into at least three regions. Deletions in Region I resulted in a non-pigmented phenotype, a deletion in Region II resulted in a pink/yellow phenotype, deletions in Region III resulted in either a pink or a non-pigmented phenotype. Tn1000 insertions in the same regions, however, gave different phenotypes. Insertions in Region II produced a pink phenotype. Insertions in Region III resulted in either a light-yellow or a non-pigmented phenotype. Minicell studies showed that the 6.7 kb DNA fragment encoded at least five proteins (50 kDa, 42 kDa, 36 kDa, 35 kDa and 34 kDa). A 2.7 kb HindIII deletion in Region I caused the disappearance of these proteins, suggesting that this 2.7 kb fragment may play a regulatory role in pigment synthesis. Our results also showed that a 4.1 kb EcoRV fragment consisted of Region I and a part of Region II complemented a pink/yellow clone of Eho10 (pHL545), suggesting that the pigments of Eho13 and Eho10 were probably similar or identical.     

Role of extralaryngeal muscles in phonation of subhuman primates

1. The electromyographic activity of eight external laryngeal and hyoid muscles was recorded during vocalization in the squirrel monkey (Saimiri sciureus). Calls of different types were elicited by electrical stimulation of the central grey of the midbrain in narcotized animals.
2. Peeping, a short, high-pitched call with minor frequency modulations, is associated with a marked activity in the cricothyroid, a moderate activity in the thyrohyoid, a weak activity in the sternohyoid and no activity in the sternothyroid, omohyoid, mylohyoid and anterior digastric muscles.
3. Chuck, a short, plosive call with a steep frequency descent over several kHz, is associated with a marked activity in the cricothyroid, a moderate activity in the thyrohyoid, sternothyroid and mylohyoid, a weak activity in the sternohyoid and omohyoid, and no or rare activity in the anterior digastric and inferior pharyngeal constrictor, respectively.
4. Cackling, a long and loud call consisting of alternating high- and low-pitched elements which follow each other repetitively in a 12–14 Hz rhythm, is associated with a similar muscular activity pattern as chuck except that the sternohyoid activity is relatively stronger.
5. Cawing, a short low-pitched call with a fundamental frequency of 200–700 Hz, shows a moderate activity in the sternothyroid, an occasional activity in the thyrohyoid and no activity in the cricothyroid, sternohyoid, omohyoid, anterior digastric and inferior pharyngeal constrictor.

     

Kinetics of enzymatic degradation of cyanide

CYANIDASE(@) is a new enzyme preparation capable of degrading cyanide in industrial wastewaters to ammonia and formate in an apparently one-step reaction, down to very low concentrations. This enzyme has both a high selectivity and affinity toward cyanide. A granular form of the biocatalyst was used in a recirculation fixed bed reactor in order to characterize the new biocatalyst with respect to pH, ionic strength, common ions normally present in wastewaters, mass transfer effects, and temperature. Long term stability was investigated. The kinetics of the enzymatic degradation of cyanide were studied in a batch reactor using the powdered immobilized enzyme preparation and modeled using a simple Michaelis-Menten equation.     

Mechanical control of the time-course of contraction of the frog heart

Changes in load during most phases of an isotonic contraction of the frog and turtle heart increased or decreased the duration of the twitch. It was abbreviated by a maintained increase or by a brief decrease in load. The relaxing effect of these procedures developed with a delay lasting more than a second under some conditions and will be called lengthening deactivation. The reverse procedures, a maintained diminution or a brief increase in load, increased the duration of the twitch. This effect will be called shortening activation. Although the termination of relaxation may be delayed or advanced by the mechanical interventions mentioned, the normal time- course of isotonic relaxation was always resumed later, regardless of the starting level of the load, making it possible to measure accurately changes in the duration of the twitch. The responses to changes in load produce positive feedback during the isotonic contraction and explain, at least in part, the difference in the time- course of isotonic and isometric contraction. The effects of changes in load were much smaller and briefer in the atrium than the ventricle.     

Certification of Probability of Sterilization of Liquid by Filtration

Four types of hydrosol filters, two reusable (diatomaceous cylinder and fritted-glass funnel) and two disposable (asbestos pad and membrane filter) were challenged with a heavy bacterial suspension to assess their ability to produce sterile filtrates. Two of the four diatomaceous earth filters, the four fritted-glass funnels, and all of the asbestos pads tested generally gave sterile filtrates. However, only one type of filter, one of the membranes in its manufacturer's own holder, consistently gave sterile filtrates. The two other types of membranes usually gave sterile filtrates if tested in one manufacturer's holder, but all types invariably gave contaminated filtrates when tested in another manufacturer's holder. Contaminated filtrates were generally attributed to a poor reusable filter or to a faulty holder used with a disposable filter. If a high degree of certainty is required for sterile heat-labile filtrate, it is suggested that the liquid be passed through two or more filters in a previously tested and proven system.     

Influence of ligands on the aggregation of the normal and mutant forms of phosphofructokinase 2 of Escherichia coli

The aggregation states of Escherichia coli phosphofructokinase 2 (Pfk-2) and of a mutant enzyme (Pfk-2*) altered in the inhibitory allosteric site for MgATP were measured in the presence and in the absence of substrates and products of the reaction. When sucrose gradient ultracentrifugation experiments were performed in the absence of added ligands, both enzymes sedimented as dimers. Likewise, at low concentrations of both substrates (0.1 mM) the aggregation state of Pfk-2 and Pfk-2* corresponded to a dimer. However, in the presence of 1 mM MgATP alone, Pfk-2 sedimented as a tetramer, whereas Pfk-2* sedimented as a dimer. At a low fructose 6-phosphate concentration (0.1 mM) and an inhibitory concentration of MgATP (4 mM), Pfk-2 sedimented as a tetramer. However, at the same MgATP concentration but at a higher fructose-6-P concentration (1 mM), a condition under which Pfk-2 is not inhibited by the Mg-nucleotide complex, the enzyme sedimented as a dimer. Pfk-2* is not inhibited under these conditions and sedimented as a dimer in each case. Thus, the effectiveness of MgATP in promoting the aggregation of Pfk-2 and Pfk-2* parallels the inhibitability of the enzymes by the nucleotide complex. However, ATP4-, a potent inhibitor of Pfk-2 and Pfk-2* that binds to the catalytic site of the enzymes, had no effect upon their aggregation states. Possibly Pfk-2* is not able to form a tetramer because of an alteration in the regulatory site for the Mg-nucleotide complex.     

Behavioural mode of action of deet: inhibition of lactic acid attraction

Using the mosquito Aedes aegypti in a novel olfactometer that measures movement towards and away from a stimulus, we could not confirm that 'deet' is a repellent of mosquitoes. In the absence of a host, deet was an attractant and in the presence of a host, it was an inhibitor of attraction. This inhibition occurred in the gaseous phase and was therefore not the result of the physical properties of deet. We determined that L-lactic acid, a component of human sweat that is an attractant to mosquitoes, is the target of this inhibition, implying that lactic acid may be a bottleneck in the behavioural cascade preceding blood-sucking.     

Consequences of postural changes and removal of vestibular inputs on the movement of air in and out of the lungs of conscious felines.

A variety of experimental approaches in human subjects and animal models established that the vestibular system contributes to regulation of respiration. In cats, the surgical elimination of labyrinthine signals produced changes in the spontaneous activity and posturally related responses of a number of respiratory muscles. However, these effects were complex and sometimes varied between muscle compartments, such that the physiological role of vestibulo-respiratory responses is unclear. The present study determined the functional significance of vestibulo-respiratory influences by examining the consequences of a bilateral labyrinthectomy on breathing rate and the pressure, volume, and flow rate of air exchanged during inspiration and expiration as body orientation with respect to gravity was altered. Data were collected from conscious adult cats acclimated to breathing through a facemask connected to a pneuomotach during 60 degrees head-up pitch and ear-down roll body rotations. Removal of vestibular inputs resulted in a 15% reduction in breathing rate, a 13% decrease in minute ventilation, a 16% decrease in maximal inspiratory airflow rate, and a 14% decrease in the maximal expiratory airflow rate measured when the animals were in the prone position. However, the lesions did not appreciably affect phasic changes in airflow parameters related to alterations in posture. These results suggest that the role of the vestibular system in the control of breathing is to modify baseline respiratory parameters in proportion to the general intensity of ongoing movements, and not to rapidly alter ventilation in accordance with body position.     

Isolation of domains of the plasma membrane of hepatocytes

Several recent studies have demonstrated the ability of techniques based on immunoadsorption to selectively isolate specialized subregions of membranes, termed domains, which are derived from a larger more complex parent membrane like the plasma membrane. The immunoadsorbent is directed against a specific antigen that resides exclusively or predominantly in the membrane domain to be isolated. Thus, a monospecific antibody to the domain-specific antigen is required. In the present study we developed a method employing a modified immunoblotting strategy which could utilize polyspecific antibodies to isolate membrane vesicles derived from a specific membrane domain of the hepatocyte plasma membrane. We also used specific cell surface labeling of the hepatocyte plasma membrane by lactoperoxidase-catalyzed iodination at 4 degrees C and preparation of different sized vesicles by sonication to facilitate isolation of the specific domain. For this study, polyspecific antisera were raised in goats against a membrane fraction, denoted N2u, which is enriched in bile canalicular proteins. This antiserum recognizes, among other antigens, a 110,000 Mr polypeptide previously shown to be localized in the bile canaliculus (J. Cook et al. (1983) J. Cell. Biol. 97, 1823-1833). A monospecific antiserum was raised in rabbits against the rat hepatocyte asialoglycoprotein receptor, a sinusoidal domain-specific set of glycoproteins whose major form has a Mr of 43,000. These antisera were each coupled indirectly to different pieces of nitrocellulose by the immunoblotting protocol and were used to isolate membrane vesicles from a crude extract of liver plasma membrane prepared by sonication. The ratio of iodinated asialoglycoprotein receptor to the 110,000 Mr polypeptide in vesicles isolated by the affinity nitrocellulose immunoadsorbent method indicate a 10- to 15-fold enrichment of sinusoidal-derived vesicles relative to bile canalicular-derived membrane vesicles. These results show that the affinity nitrocellulose immunoadsorbent method can be used to isolate domain-specific vesicles. Further, the affinity immunoadsorbent method described here for the isolation of domains of the plasma membrane is an integrative one allowing isolation of vesicles present in relatively small concentration in crude cell extracts and it requires minimal ultracentrifugation time.     

Continuity and prospects of development of researches in area system-integrativity of psychophysiology of functional state and cognitive activity

In the review one of actual problems of psychophysiology in studying a phenomenon of integration of mechanisms of regulation of state of a brain and features of the organization is discussed by a brain of cognitive activity. Basic value of results of long-term researches of academician N.P. Bechterevoj and of her school is opened in the field of neurophysiology of functional states as bases of the organization of mental activity in conditions of direct, long and sparing contact to a cortical and subcortical structures of a brain, with the help long-term intracerebral electrodes. Arguments about a commensurability and complementary value similar on amplitud-time parameters slow and superslow gradual changes of neurophysiological processes registered simultaneously in identified zones of subcortical structures of a brain and with removal from a surface of a head in cortical projections of basic integrativity of the centres are submitted. Representations about a brain as difficultly organized "swimming" many-contour, neurodinamic informational-controlling suprasystem with hierarchically, probability a principle of the organization different on speeds and intensity of processes of the ability to live participating in maintenance of a condition of rest, mental conditions and cognitive activity are formulated and argued. At the limited set universal neurodinamic "languages", the brain has the multiregister mechanism of regulation of conditions and selectivity of mechanisms of the integration providing the contribution differing on information maintenance gradual neurophysiological of processes of different levels of the structurally functional organization in formation of brain systems of maintenance of concrete kinds of cognitive activity.