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).     

Characteristics of self-quenching of the fluorescence of lipid-conjugated rhodamine in membranes

Self- or concentration quenching of octadecylrhodamine B (C18-Rh) fluorescence increases linearly in egg phosphatidylcholine (PC) vesicles but exponentially in vesicles composed of egg PC:cholesterol, 1:1, as the probe concentration is raised to 10 mol%. Cholesterol-dependent enhancement of self-quenching also occurs when N-(lissamine-rhodamine-B-sulfonyl)dioleoylphosphatidylethanolamine is substituted for C18-Rh and resembles that in dipalmitoylphosphatidylcholine vesicles below, as opposed to above, the phase transition. These effects are not due to changes in dimer:monomer absorbance. Stern-Volmer plots indicate a dependence of quenching on nonfluorescent dimers both in the presence and absence of cholesterol. Decreases in fluorescence lifetimes with increasing probe concentration parallel decreases in residual fluorescence of C18-Rh with increasing probe concentration in PC and PC + cholesterol membranes, respectively. Decreases in the steady-state polarization of C18-Rh fluorescence as its concentration is raised to 10 mol% indicate energy transfer with emission between probe molecules in PC and to a lesser extent in PC + cholesterol membranes. The calculated R0 for 50% efficiency of energy transfer from excited state probe to monomer was 55-58 A and to dimer was 27 A. Since lateral diffusion of C18-Rh is probably too slow to permit collisional quenching during the lifetime of the probe, even if C18-Rh were concentrated in a separate phase, C18-Rh self-quenching appears to be due mainly to energy transfer without emission to nonfluorescent dimers.     

Effect of ionizing radiation of the antigenic composition of typhoid bacteria

Changes in the antigenic composition of typhoid bacteria occurring during the exposure of microbial suspension to different doses of gamma irradiation [Co60] ranging between 0.5 and 3.0 Mrad were studied. Immunoelectrophoresis in agar was used to determine the antigenic composition of different samples of irradiated bacteria. The antigenic composition of bacteria irradiated with doses up to 2.5 Mrad was found to be similar to that of non-irradiated bacteria. Antigens demonstrated by means of Vi, H and O ontisera are preserved in these bacteria. However, all irradiated bacteria in general slightly differ from non-irradiated bacteria; this is manifest in a different configuration and position of the precipitation lines in the cathodic part of the immunophoreograms. The content of the component migrating rapidly towards the cathode, evidently the O antigen in the R form, in the irradiated bacteria increases with the dose of radiation. No new serologically active substances, non-existent in non-irradiated bacteria, were found to appear in the process of irradiation.     

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.     

Development of mechanisms of recognition of fragmented images differing in the degree of fragmentation in children of preschool and primary school ages

Recognition of fragmented images with an increasing number of fragments was studied in children of three age groups (five to six, seven to eight, and nine to ten years of age) to compare the behavioral and neurophysiological parameters of recognition in these groups. The most pronounced changes in effectiveness of recognition were observed when the five- to six-year-old and seven- to eight-year-old children were compared. In the former, recognition was not accompanied by any significant changes in the event-related potentials of the prefrontal cortex or by an increase in N250?C400 (Ncl) in the extrastriate cortex (though it is an important characteristic of the process). However, the amplitude of the N170?C200 component, which reflects analysis and encoding of sensory features, did increase at the age of five to six years. Immaturity of the prefrontal cortex is manifested in a deficiency of the control: these children respond hastily and make numerous mistakes. In seven- to eight-year-old children, recognition is accompanied by an increase in the amplitude of the N100 and N250 components in the prefrontal cortex, whereas the amplitude of the Ncl component increases in the extrastriate cortex. The error rate and recognition threshold are significantly lower in these children than at the age of five to six years. The role of prefrontal cortex is the most pronounced at the age of nine to ten years, which is manifested in the Ncl amplitude and the later phases corresponding to the cognitive recognition. Our results demonstrate qualitative differences in the mechanisms of recognition in children of the preschool and primary school age. At the age of five to six years, recognition is a result of integration of the sensory signs. Beginning from the age of seven to eight years, the prefrontal cortex plays an important role in recognition of the fragmentary images; this brain region is responsible for a search of possible analogues in memory and identification of an object.     

Mechanism of alteration of the functional fraction of lipoprotein lipase in rat heart

Feeding glucose to fasted rats resulted in a decrease in the activity of heparin-releasable lipoprotein lipase in heart perfusates. Upon feeding fat to glucose-fed animals the level of heparin-releasable lipoprotein lipase increased 10–14 fold. An immunological titration was used to determine whether the changes in lipase activity following the various nutritional treatments were due to changes in the amount of enzyme present or to activation/inactivation processes. These data suggest that changes in the enzyme activity are due to alteration in the quantity of lipoprotein lipase protein.     

Mechanism of perception of changes in the magnetic field by ampullae of lorenzini of elasmobranchs

The mechanisms of reception of changes in the magnetic field by electroreceptor formations were investigated in experiments on Black Sea rays in which spike activity was recorded from single nerve fibers connected with the ampullae of Lorenzini. The responses of the ampullae of Lorenzini to magnetic stimulation were shown to be due to induced electric currents creating potential gradients in the body tissues of the fish and the sea water. On the basis of differences in responses of different ampullae to magnetic stimulation, it is possible to distinguish between magnetic stimuli and other stimuli acting on the electroreceptor system. Potentiation of the receptor response to magnetic stimulation was found as the fish came closer to the "shore." The mechanisms and biological importance of reception of changes in the magnetic field by the ampullae of Lorenzini are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 10, No. 1, 75–83, January–February, 1978.     

Regulation of frequency of luteinizing hormone pulses by magnitude of acute change in circulating concentration of progesterone of female cattle

The hypothesis was the greater the magnitude of acute increase in circulating concentration of progesterone of female cattle, the greater the acute inhibitory effect on frequency of pulsatile LH release. From Day 0 to 4 of the treatment period, females without functional corpora lutea were treated with varying doses of progesterone to result in varying concentrations of progesterone within the typical physiological range in blood. From Day 4 to 7, cattle were treated with a single dose of progesterone to achieve a similar circulating concentration of progesterone among all females in the study. Therefore, from Day 0 to 4 relative to Day 4 to 7 of the treatment period, females had a: (1) large (3.1 ng/ml), (2) moderate (2.5 ng/ml), or (3) small (0.5 ng/ml) increase in concentration of progesterone in blood. Frequency of LH pulses was greater (P <0.10) in females with the greatest magnitude of change in concentration of progesterone during the first 24 h following the change in concentration as compared with females with the moderate or small of change in concentration of progesterone suggesting our working hypothesis should be rejected. The greater the magnitude of acute change in concentration of progesterone, however, the longer time required for re-initiation of release of LH pulses of the amplitude of pulses that preceded the change in concentration of progesterone.     

Characterization of cells of amniotic fluids by immunological identification of intermediate-sized filaments: Presence of cells of different tissue origin

Summary Antibodies against intermediate-sized filaments, of the prekeratin or vimentin type, were used to investigate the presence of these filaments by indirect immunofluorescence microscopy in cultured and non-cultured amniotic fluid cells, in frozen sections of the placenta and in isolated cells of the amniotic epithelium. Two major classes of cells can be cultured from amniotic fluids, namely cells of epithelial origin containing filaments of the prekeratin type and cells of different origin which contain filaments of the vimentin type but are negative when tested with antibodies to epidermal prekeratin. The presence of prekeratin type filaments correlates with the morphology of colonies of amniotic fluid cell cultures in vitro as classified by Hoehn et al. (1974). Cells of E-type colonies are shown to be of epithelial origin. In contrast our data indicate a different origin of almost all cells of F-type colonies and of the large majority of cells of AF-type colonies. Cells of epithelial origin and positively stained with antibodies to epidermal prekeratin are occasionally scattered in F-type colonies and in variable percentages (up to 30%) in AF-type colonies. Surprisingly, cryostat sections of the amniotic epithelium and isolated groups of amniotic cells showed positive reactions with both antibodies to vimentin and prekeratin. The possibility that amniotic cells may be different from other epithelial cells in that they contain both types of filaments simultaneously already in situ is presently under investigation.Part of this work is included in the doctoral thesis of Irmgard Treiss to be submitted to the Faculty of Medicine of the University of Heidelberg     

Contractile properties of smooth muscles of bronchial tubes at formation of hyperreactance of airways

Contractile properties of smooth muscles of bronchial tubes of porpoises in formation of hyperreactance airways, were studied. Sensitization by ovalbumin results in formation of hyperresponsiveness of the airways as shown in increase in amplitude of contractile responses to histaminergic influences and oppression of adrenergic relaxations of segments. Respiratory epithelium oppresses contractile responses of airways in intact animals to histaminergic influences. Influence of epithelium on adrenergic responses depends on precontractile factor: they increase in prereduction by histamine. In formation of hyperresponse, the epithelium loses ability to modulate responses of smooth muscles of the airways. Incubation segments of smooth muscles of the airways in interleukin 5 increases contractile responses to histaminergic influences. Receptor of interleukin 5 (the soluble fraction) neutralizes the effect of exogenous interleukin 5, and incubation of receptor of sensitized animals oppresses histaminergic contractile responses.     

Mutagenicity of reactive derivatives of carcinogenic hydrocarbons: evidence of DNA repair

The ability of cellular DNA repair enzymes, which are active on ultraviolet light-induced lesions in DNA, to recognize and repair damage induced in DNA by exposure to carcinogenic polycylic hydrocarbons was investigated and the effect of such repair processes on the mutagenicity of the hydrocarbons determined. The carcinogenic hydrocarbos, 7-bromomethylbenz[a]anthracene (7-BrMeBA) and 7-bromomethyl-12-methylbenz[a]anthracene (7-BrMe-12-MeBA), chosen for this study because they form well characterized, stable products with DNA, were dissolved at various concentrations in acetone, added under mild conditions to biologically active DNA isolated from Bacillus subtilis, and the reaction stopped by ethanol precipitation. The hydrocarbons were determined by specific radioactivity to be covalently linked to DNA at a frequency of from 1–5 per 1000 nucleotides. An increased frequency of bound hydrocarbon molecules was directly correlated with a decrease in the buoyant density of the DNA as measured in analytical CsCl centrifugation studies. The samples of hydrocarbon-bound DNA were tested for survival of biological activity and for the frequency of induced forward mutations in two recipient strains (hcr⁺ and hcr^?) of Bacillus subtilis which differ in their ability to repair ultraviolet light-induced lesions in DNA. The survival of the biological activity was significantly higher in the repairing strain (hcr⁺). A higher frequency of mutations was detected in the repairing strain as well. The loss of transforming activity and the increase in the frequency of mutations (up to 20-fold) was directly proportional to the amount of hydrocarbon bound to the DNA samples. The majority of these mutations proved unable to revert spontaneously. Finally, the ability of highly purified rat liver endonuclease, shown to recognize lesions in UV-irradiated DNA, to recognize such hydrocarbon lesions was investigated. Tritiated 7-BrMeBA-treated DNAs exposed to the enzyme were found to sustain single-strand nicks in proportion to the amount of hydrocarbon bound while untreated DNA remained substantially intact. The action of the endonuclease appeared to result in an increase in the biological activity of DNA containing hydrocarbon residues when this was assayed in the hcr^? mutant.     

Age and features of the skeletotopy of the roots of the lungs of newborn infants and children

In 186 roentgenograms of frontal projections, obtained in children from birth up to 7 years of age, made according to the vital indications (but without any pathology in the thoracic organs), and in 63 isolated preparation of lungs, skeletotopy and size of the lung roots have been studied. The skeletopic difference between superior and inferior margins of the roots near the medial surface of the lung in the newborns during the first day of life has been stated to make in the projection to the frontal thoracic wall 2 ribs, or 2 vertebrae (to the posterior wall), and to the end of the first month of life-3 ribs, or 3 vertebrae, respectively; during the first year-2.5 ribs, or 2 vertebrae, in children of 1-7 years of age-2 ribs, or 2 vertebrae, respectively. The projection borders of the lung roots from birth up to 7 years of age are noted to change in time and with various intensity.     

Adaptation of siblings of female rats given ethanol effect of N-acetyl-L-cysteine

Summary Ethanol administration to female rats before and during pregnancy resulted in decreased number of litters and increased activities of serum GOT, GPT and ALP. The hepatotoxicity of ethanol was indicated by the histological alterations both in the mother and siblings. There was increased levels of tissue lipids in mother and litters born to alcoholic rats. The concentration of TBARS in the liver and kidney were significantly increased in alcohol treated rats and their litters. The activities of the anti-peroxidative enzymes SOD and CAT were decreased on alcohol treatment in female rats. The glutathione content in liver and kidney decreased significantly in litters born to alcoholic rats.We have observed that the treatment with N-acetylcysteine offers protection against the toxic effect of alcohol in female rats during pregnancy and litters born to them. In N-acetylcysteine treated rats the number of litters as well as the average birth weight were close to that of control animals. Nacetylcysteine decreases the activities of serum GOT, GPT and ALP in female rats. We have also observed decreased levels of tissue lipids in mother and litters born to alcoholic rats given N-acetylcysteine when compared to alcoholic rats. The levels of TBARS in liver, kidney were also decreased both in mother and litter born to alcohol + N-acetylcysteine, while the activities of SOD and CAT were increased in liver of alcoholic rats given N-acetylcysteine when compared to alcoholic rats. Histopathological studies also showed the protective effect of N-acetylcysteine in both mother and litter in liver and kidney against alcoholic induced toxicity.     

The medicalization of female fertility--points of significance for the study of menopause

This paper illustrates the need for human biologists to take into account the far-reaching influences of biomedicine in the study of reproductive aging. Data were drawn from western Massachusetts and Puebla, Mexico, to illustrate the effects of hysterectomy rates, tubal ligations and hormone replacement therapy (HRT) on studies of age and symptom experience at menopause. First, in examining age at natural menopause in relation to level of education, a country-specific, non-random pattern of participant exclusion due to hysterectomies was encountered. Second, in examining symptom frequency in relation to late childbearing, sample sizes were very small in part due to a high frequency of tubal ligations (43%) in Puebla, Mexico. Third, hot flash frequency during the two weeks prior to interview was, unexpectedly, not lower among women who used HRT. Human biologists who study the biological process of reproductive aging must also attend to the cultural influences of biomedicine.     

Effect of conditioning polarization of soma of giant neurons of mollusks on the mechanism of action-potential generation

To ascertain the properties of an excitable membrane of the soma of giant neurons of mollusks, experiments were carried out to study the effect of conditioning shift of the membrane potential on the mechanism of action-potential generation. The effect of conditioning was assessed from changes in the action-potential curve and its first derivative, as well as from the curve of transmembrane currents under voltage clamp conditions. It was found that a change in membrane potential evokes at least two reactions which have opposite effects on the mechanism of generation of action potentials. These reactions evidently have different time characteristics. One of these does not differ notably from the reaction recorded for other excitable structures, and is manifested in the activation (with hyperpolarization) or inactivation (with depolarization) of the mechanism generating action potentials. The other reaction contributes either to an increase (with depolarization) or a decrease (with hyperpolarization) in the efficiency of this mechanism. Conditioning polarization also has a marked effect on the system responsible for repolarization of the membrane during generation of action potentials. This effect is manifested in a change in the reaction of this system to tetraethylammonium ions. The specific membrane systems sustaining excitability and reacting to changes in the strength of the membrane's electrical field were found to be very inert. After a shift in the potential to a given stable level a rearrangement, lasting sometimes tens of seconds, takes place in the membrane.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 1, pp. 91–99, January–February, 1970.     

Ultrastructure of bovine blastocysts following cryopreservation: effect of method of blastocyst production

The objective of this study was to describe the ultrastructure of blastocysts derived by in vivo and in vitro methods and to investigate how the morphology is affected by exposure to cryoprotectant (10% glycerol) or cryopreservation by conventional slow freezing. In vivo derived blastocysts were characterized by a narrow perivitelline space (PvS), a continuous cover of numerous stacked microvilli (MV) on the plasma membrane, a well-defined system of cell-to-cell coupling and a large population of round or elongated mitochondria with numerous transverse cristae. Exposure of these blastocysts to cryoprotectant was manifested by shrinkage of the blastocysts and swelling of the mitochondria. Cryopreservation resulted in further shrinkage, damage to the MV, and accumulation of cellular debris. In comparison, the in vitro matured (IVM)/in vitro fertilized (IVF) in vivo cultured blastocysts displayed a wider PvS; they appeared to possess less MV and all blastocysts displayed some cellular debris in their PvS. There was also a decrease in the number of junctional contacts between the trophoblastic cells. The reaction of these blastocysts to exposure to cryoprotectant was similar to that of the in vivo derived blastocysts. However, they appeared to be more susceptible to cryopreservation. The totally in vitro produced (IVP) blastocysts displayed a wider PvS, no stacking of the MV, increased numbers of lipid droplets and a further reduction in the junctional contacts between trophoblastic cells. The IVP blastocysts sustained breakage of the zona pellucida on exposure to cryoprotectant and were extremely sensitive to cryopreservation, losing all cell structure and organization. The findings of the present study indicate that in vivo derived blastocysts possess certain structural characteristics that confer a greater tolerance on them to exposure to cryoprotectant and cryopreservation.     

Reaction of deamination of monoamines in the brain and heart of rats under the toxic action of hyperbaric oxygenation

Kinetic parameters of monoamine deamination processes in the rat brain and heart after hyperbaric oxygenation (HBO) in toxic conditions (6 ata) were studied. HBO was shown to cause a substantial reduction in MAO affinity to serotonin in the brain, but not in the heart. Contrastingly, MAO affinity to dopamine was found to decrease in the heart, but not in the brain in response to HBO. Differences of tyramine and 2-phenylethylamine deamination in the rat brain and heart were also reciprocal following toxic HBO. In the initial phase of seizure episode MAO activity in the brain and heart was also different. Distinct mechanisms of adaptation to toxic oxygen in the central nervous system and cardiovascular system are discussed.     

河南种子植物区系地理研究

河南省地处中原 ,属于我国南北过渡和东西过渡的重要区域 ,植物区系成分复杂多样并于周围地区联系广泛 ,对其植物区系研究对深入认识本省的自然环境特征及其在我国多种自然区划中的位置等有着重要意义。该文在最新资料的基础上 ,运用区系学原理对河南省种子植物区系的种类组成、地理成分 (属、种 2个层次上 )等进行了系统的分析 ,在此基础上概括出河南植物区系的基本特征为 :(1 )植物种类比较丰富 ,多样性较高 ;(2 )起源古老 ;(3 )地理成分复杂 ,温带成分略占优势 ,过渡性突出 ;(4 )中国特有植物比较丰富。     

Molecular dissection of alleles of the osmotic-1 locus of Neurospora crassa

Two-component histidine kinases of bacteria, plants, and fungi are involved in the regulation of intracellular events in response to changes in external environmental conditions. Fungal histidine kinases play important roles in osmoregulation, in vivo and in planta virulence, and sensitivity to certain classes of antifungals. The osmotic-1 (OS-1) locus of Neurospora crassa encodes a predicted protein with homology to histidine kinases and appears to be an osmosensor. Mutants of the OS-1 locus are hypersensitive to salt and are strongly resistant to dicarboximide antifungals. Molecular analysis of each of eight OS-1 mutants revealed that seven resulted from amino acid changes in a domain of the protein known as the linker region. These results indicate that the linker region of fungal two-component histidine kinases is essential for proper functioning of the kinase.     

A model of the mechanisms of formation of unit activity

Dependence of the temporal structure of the spike discharge of a neuron in a weakly interacting network on the characteristics of excitatory and inhibitory input flows and on cell parameters was analyzed by a mathematical model. The intensity of communication between individual neurons corresponded to the intensity of synaptic communication between real spinal neurons. The temporal course of trace and accommodation processes in the model was similar to that of these processes in real spinal neurons. Connection of inhibitory inputs and an increase in the intensity of their influences were shown to be equivalent to a decrease in the intensity of excitatory input flows. Changes in cell parameters had a significant effect on the spike discharge only in the case of weak input influences (the ratio of the amplitude of the combined ESP evoked by the input spike train to the threshold value of membrane potential at rest was about 1.2:1.0 to 1.4:1.0). An increase in the input flow intensity led to considerable reorganization of the firing pattern: Mean values of interspike intervals and their fluctuations were reduced, histograms of interspike intervals became more symmetrical, and periodic waves appeared on the autocorrelation histograms. It is concluded on the basis of these results and of data in the literature that the main factor determining reorganization of the temporal structure of unit activity in a network of weakly interacting cells is the intensity of the input flow.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 2, pp. 199–207, March–April, 1980.