Functioning of the electromechanical connection in the course of the contracture contraction

The effects of calcium release blocker dantrolene was tested on electrically evoked twitches and on contractures induced by potassium depolarization, by acetylcholine or caffeine. It was shown that the first: developmental, stage of potassium or acetylcholine contracture is inhibited by dantrolene and is not influenced by calcium free medium, therefore we may interpret it as based on a "voltage-dependent Ca release" (VDCR) mechanism of activation, whereas depolarization directly opens the rhyanodin receptor calcium channels. On the contrary, the next stage: the long-lasting plateau of contracture, is directly dependent on external Ca2+ and inhibited by dantrolene, and therefore can be described as "calcium induced Ca-release" (CICR) activation mechanism. In this case stored calcium is also released by rhyanodine receptors, although by means of entering the extracellular Ca2+. Finally, the last stage of low amplitude is not influenced by dantrolene nor by calcium-free medium. Therefore the activation of contraction on this stage is not based on the Ca2+ release through the rhyanodin receptor calcium channels.     

Remodeling the shape of the skeleton in the intact red cell.

The role of the membrane skeleton in determining the shape of the human red cell was probed by weakening it in situ with urea, a membrane-permeable perturbant of spectrin. Urea by itself did not alter the biconcave disk shape of the red cell; however, above threshold conditions (1.5 M, 37 degrees C, 10 min), it caused an 18% reduction in the membrane elastic shear modulus. It also potentiated the spiculation of cells by lysophosphatidylcholine. These findings suggest that the contour of the resting cell is not normally dependent on the elasticity of or tension in the membrane skeleton. Rather, the elasticity of the skeleton stabilizes membranes against deformation. Urea treatment also caused the projections induced both by micropipette aspiration and by lysophosphatidylcholine to become irreversible. Furthermore, urea converted the axisymmetric conical spicules induced by lysophosphatidylcholine into irregular, curved and knobby spicules; i.e., echinocytosis became acanthocytosis. Unlike controls, the ghosts and membrane skeletons obtained from urea-generated acanthocytes were imprinted with spicules. These data suggest that perturbing interprotein associations with urea in situ allowed the skeleton to evolve plastically to accommodate the contours imposed upon it by the overlying membrane.     

Regulation of the expression of the serine dehydratase gene in the kidney and liver of the rat

Serine dehydratase was induced in the kidneys of normal rats by the administration of either glucagon or dexamethasone. The increase in enzyme activity was associated with an increase in both enzyme protein and its mRNA, which were determined respectively by Western blot and RNA blot analysis. No apparent differences were observed between kidney and liver in the molecular weights of serine dehydratase proteins and the sizes of their mRNAs. Although kidney serine dehydratase was dramatically induced by either glucagon or dexamethasone, the liver enzyme was induced by glucagon but not by dexamethasone alone in the intact rat. On the other hand, liver serine dehydratase was induced in starvation, diabetes mellitus, and a high-protein diet. The kidney enzyme could not be induced under any of these conditions.     

Modulating the activity of the peptidyl transferase center of the ribosome

The peptidyl transferase (PT) center of the ribosome catalyzes two nucleophilic reactions, peptide bond formation between aminoacylated tRNA substrates and, together with release factor, peptide release. Structure and function of the PT center are modulated by binding of aminoacyl-tRNA or release factor, thus providing the basis for the specificity of catalysis. Another way by which the function of the PT center is controlled is signaling from the peptide exit tunnel. The SecM nascent peptide induces ribosome stalling, presumably by inhibition of peptide bond formation. Similarly, the release factor-induced hydrolytic activity of the PT center can be suppressed by the TnaC nascent peptide contained in the exit tunnel. Thus, local and long-range conformational rearrangements can lead to changes in the reaction specificity and catalytic activity of the PT center.     

Analysis of the mechanisms determining the varying relationship of the sperm from the marine and freshwater forms of the three-spined stickleback to the salinity of the medium]

The causes of differences in the reaction of spermatozoa of the fresh-water (morpha leiurus) and marine (m. trachurus) forms of three-spined stickleback Gasterosteus aculeatus to the high sea water salinity (the upper limit of spermatozoan motility being 18% and 52%, resp.) were investigated. The experiments with solutions of pure NaCl, CaCl2, MgCl2, KCl, LiCl (25 g/l) have shown that the movement of spermatozoa of m. leiurus is inhibited by NaCl only. The inhibition of chlorine channels of the plasma membrane by a specific inhibitor furosemide has shown that the activity of spermatozoa of m. leiurus is suppressed by the high Na+ concentrations. The experiments with ATP have revealed no differences in the activity of Na pump between the spermatozoa of mm. trachurus and leiurus. Amyloride, an inhibitor of Na channels, at a concentration of 1.10(-5) M relieved the inhibiting effect of the high Na+ concentrations on the activity of spermatozoa of m. leiurus. The differences in the reaction of spermatozoa of two forms of the stickleback appear, to be determined by differences in Na channels of the plasma membrane.     

Anatomy of the veins of the head in the domestic fowl

The anatomy of the cephalic venous system in the fowl was studied in 19 specimens by means of latex-injected preparations and by dissection. The brain sinuses converge dorsally upon the large cervical sinus and vertebral veins. Dorso-ventral communication is provided by the occipital veins posteriorly, while the ophthalmic system unites both dorsal and ventral sinuses and the temporal rete with the extracranial veins anteriorly. The jugular veins are formed from the superficial branches of the facial veins and serve mainly as outlets for extracranial blood. They are united at the base of the head by a prominent transverse anastomosis which slopes caudally towards the larger, right jugular. As in mammals, the carotid veins envelop the internal carotid arteries and anteriorly form a bulbous sinus cavernosus around the inter-carotid anastomosis.     

The effect of enzyme inhibitors on the resting potential and on the ion distribution of the sartorius muscle of the frog

Isolated frog sartorii were exposed for 30 minutes to HETP—an irreversible anti-cholinesterase, and were then soaked in Ringer's at 15°C. for 16 hours. At the end of the period of soaking the mean resting potential of the muscle fibers was only 29 mv. The decrease in the resting potential of the HETP-treated muscles was accompanied by a loss of potassium and a gain in sodium by the muscles. The effect of anticholinesterases on sodium extrusion was studied by incubating the muscles in a Ringer's containing half of the normal amount of sodium. The muscles respond by extruding sodium against a concentration gradient into the external medium. Sodium extrusion was blocked by prior exposure of the muscle to HETP, and reversibly blocked by exposure to physostigmine. The inhibition of sodium extrusion by physostigmine was correlated with the inhibition of the intracellular cholinesterase. Sodium extrusion was also blocked by high concentrations of 2-methyl-1,4-napthaquinone 8-sulfonic acid and by α-ketoglutarate, which are known to inhibit choline acetylase in vitro. But sodium extrusion was not affected by a third inhibitor of choline acetylase, phenobarbital. Sodium extrusion was unaffected by KCN and partially blocked by IAA. The IAA block was eliminated by the addition of pyruvate. It is concluded that either glycolysis or oxidative metabolism can furnish the energy needed for sodium extrusion.     

Studies on the relationship between the oxygen uptake and the release of amylase and sialic acid

The relationship between the oxygen uptake and the release of amylase and sialic acid induced by pilocarpine was investigated in dog submandibular glands. Pilocarpine dose-dependently stimulated the oxygen uptake. The dose required for the maximal response was 10 microM. The release of amylase and sialic acid induced by pilocarpine was inhibited by the addition of iodoacetic acid, malonic acid, 2, 4-dinitrophenol, antimycin A or sodium azide. The oxygen uptake induced by pilocarpine was significantly inhibited by iodoacetic acid, malonic acid, antimycin A or sodium azide. On the other hand, 2, 4-dinitrophenol further stimulated the oxygen uptake by pilocarpine. The increase in the oxygen uptake or the release of amylase and sialic acid induced by pilocarpine was significantly inhibited by ouabain. The Na+, K+-ATPase activity ratio in the microsomal fraction of dog submandibular glands was dose-dependently increased by pilocarpine. The Na+, K+-ATPase activity ratio induced by pilocarpine was significantly inhibited by ouabain, antimycin A, oligomycin or 2, 4-dinitrophenol. The pilocarpine-induced Na+, K+-ATPase activity ratio was significantly inhibited by the removal Ca2+ from the medium or the addition of 2 mM EGTA. These results suggest that the increase in the oxygen uptake by pilocarpine is profoundly involved in the energy supply for the process of amylase and sialic acid release. In particular, the energy supply demanded for the activation of Na+ pump may play a role in the mechanism by which pilocarpine induces the oxygen uptake.     

Dopamine and the chemoregulation of ventilation in the rat

In pentobarbitalized rats, exogenous dopamine inhibits ventilation by acting on peripheral chemoreceptors. This inhibition is suppressed by haloperidol and by domperidone. Almitrine bismesilate, a potent glomic stimulant, potentiates dopaminergic inhibitory responses by depletion of dopamine endogenous stores. After blockade by dopamine antagonists, as well as after dopamine depletion, ventilatory responses to NaCN i.v. is increased. This potentiation can be explained by the suppression of a negative feed-back control dependent on endogenous dopamine release during the glomic stimulation itself.     

Role of the temperature factor in determining the nature of the chronotropic response of the heart of cats in the simulation of increased venous inflow

The heart rate changes in response to the imitation of venous input to the heart by infusion of an additional blood volume to the right atria have been studied on anesthetized by chloralose cats. It has been discovered that patterns of the heart rate changes are determined by the infused blood temperature if it is equal to the blood temperature in heart, tachycardia appears, if it is below this temperature, bradycardia develops. These data explain, from our point of view, the contradictory results obtaining by different authors in experiments with the imitation of the increased venous input (Bainbridge reflex).     

The importance of glucose in the oxidative metabolism of the testis of the conscious ram and the role of the pentose cycle

1. [U-(14)C]Glucose was infused into one or both testicular arteries of ten conscious rams and the specific activity of the glucose taken up by the testis was compared with the specific activity of the carbon dioxide produced by the testis. 2. Equilibration had occurred after infusion for 3hr. when a mean of 68% of the carbon dioxide was being derived by the testis from blood glucose and 86% of the glucose taken up by the testis was being oxidized to carbon dioxide. After 5hr. infusion, these values were 71% and 83% respectively. 3. In four other conscious rams, [1-(14)C]glucose was infused into one testicular artery and [6-(14)C] glucose into the other and the ;specific yields' of carbon dioxide calculated for the two forms of glucose. 4. From these values, it was calculated that a mean of 9.3% of the glucose taken up by the testis was metabolized via the pentose cycle.     

Signalling the end of the line

Cellular senescence is a stable proliferation arrest induced by triggers such as short telomeres, activated oncogenes and genotoxic stress. Two studies show that cellular senescence induced by genotoxic stress depends on chronic DNA-damage signalling from irreparable damage to telomeres. Hence, dysfunctional or damaged telomeres are the initiators of multiple modes of senescence.     

Antibody-dendrimer conjugates: the number, not the size of the dendrimers, determines the immunoreactivity

Radioimmunotherapy using antibodies with favorable tumor targeting properties and high binding affinity is increasingly applied in cancer therapy. The potential of this valuable cancer treatment modality could be further improved by increasing the specific activity of the labeled proteins. This can be done either by coupling a large number of chelators which leads to a decreased immunoreactivity or by conjugating a small number of multimeric chelators. In order to systematically investigate the influence of conjugations on immunoreactivity with respect to size and number of the conjugates, the anti-EGFR antibody hMAb425 was reacted with PAMAM dendrimers of different size containing up to 128 chelating agents per conjugation site. An improved dendrimer synthesis protocol was established to obtain compounds of high homogeneity suitable for the formation of defined protein conjugates. The quantitative derivatization of the PAMAM dendrimers with DOTA moieties and the characterization of the products by isotopic dilution titration using (111)In/(nat)In are shown. The DOTA-containing dendrimers were conjugated with high efficiency to hMAb425 by applying Sulfo-SMCC as cross-linking agent and a 10- to 25-fold excess of the thiol-containing dendrimers. The determination of the immunoreactivities of the antibody-dendrimer conjugates by FACS analysis revealed a median retained immunoreactivity of 62.3% for 1.7 derivatization sites per antibody molecule, 55.4% for 2.8, 27.9% for 5.3, and 17.1% for 10.0 derivatization sites per antibody but no significant differences in immunoreactivity for different dendrimer sizes. These results show that the dendrimer size does not influence the immunoreactivity of the derivatized antibody significantly over a wide molecular weight range, whereas the number of derivatization sites has a crucial effect.     

糖基化、非糖基化、重组PAI－1功能和性质的比较

对从ＨｅｐＧ２细胞培养液中分离得到植基化和非糖基化ＰＡＩ－１（１型纤溶酶原激活物抑制剂）,以及从ｐＹＺＨＢＩ－６６表达菌中纯化的非糖基化重组ＰＡＩ－１的某些性质和功能进行比较,结果显示,糖基化ＰＡＩ－１对ｔＰＡ（组织型纤溶酶原激活物）有较强的抑制,能较显著地被蛋白质变性剂所激活,对热有较强的稳定性,糖基化与非糖基化ＰＡＩ－１在ｐＨ２．５－９．０的范围内都相当稳定。纤维蛋白原和肝素能明显提高两者对ｔＰＡ的抑制作用。     

Simultaneous Measurement of the Bioelectric Potential of the Cell Wall and the Vacuoles during the Oscillatory Response to the Nitella Cell

Simultaneous measurements of bioelectric potentials of the vacuole and cell wall in cells of Nitella mucronata were made by inserting glass microelectrodes into the vacuole and cell wall respeclively. During the oscillation of the bioelectric potential of the vacuole. induced by sudden changes of the external bathing solution or by the impalement of the cell with a microelectrode. the cell wall potential also exhibited fluctuations of variable intensities in phase and concomitant with spikes of the vacuolar potential oscillation. However, the polarity of the pulses of the cell wall potential was reverse to that of the spikes of the vacuolar potential. These results suggest that the same event is registered at both sides of the plasmalemma membrane across which these phenomena are occurring. The results also support the voltage clamp and tracer flux measurements on these cells which indicate that during the generation of single action potentials, induced by current, the plasma lemma transiently increases its permeability to Cl^? and K⁺ ions expelling them from the cell. The variable intensity of the transient hyperpolarizations of the cell wall potential is explained by the distance of the microelectrode in the cell wall from the plasmalemma.     

Electron microscopy of the oxynticopeptic cells of the gastric glands and the intestinal glands of the caecum of the guineapig.

Histomorphology of the gastric and intestinal glands was investigated in 19 sexually mature, adult guineapigs by light and transmission electron microscopy. Gastric glands exhibited the cytological characteristics of oxynticopeptic cells capable of both hydrochloric acid (HCl) and pepsinogen secretion. In the literature, occurrence of oxynticopeptic cells in the proventriculus of the domestic fowl (Toner, 1963; Bell & Freeman, 1971) and in the gastric glands of frogs has been reported (Sedar, 1961; Patt & Patt, 1969; Forte & Forte, 1970). It has been claimed by other investigators (Herriot et al., 1938; Long, 1967) that simultaneous secretion of HCl and pepsinogen by a single, not completely differentiated 'pure' cell type, was highly effective for rapid conversion of the zymogen to active enzyme. Under the light microscope with haematoxylin and eosin stain, the protein secreting activity of gastric glands in guineapigs was masked by the HCl secreting activity, thus morphologically resembling the oxyntic cells. Therefore, different cell types, for example protein-secreting peptic cells and the acid-secreting oxyntic cells, could not be distinguished on the basis of their morphology and staining affinity. For histochemical evaluation of the sections with stains-all method, most cells in the gastric glands responded by a positive reaction to protein. Further, protein containing cells were seen in the intestinal glands of the guineapig caecum. The function of this cell type was correlated with caecotrophic food habits of this species.     

Morphology and distribution of the synapses to the spinal motoneuron of the frog

Summary Neurosecretory axons and their dilatations in the pars nervosa of the human neurohypophysis were studied electron microscopically. The axons are of two different types based on their content of neurosecretory granules (NSGs): (i) NSGs of Type A are 100–300 nm, and (ii) NSGs of type B are 50–100 nm in diameter.While fibers (or axons) of type B were scarce, showing simple swellings and terminal formations, fibers of type A were ubiquitous in the human pars nervosa, exhibiting numerous dilatations with a diversity of internal structure, apparently representing the ultrastructural manifestation of intraaxonal turnover of neurohypophysial hormones. Based on the predominating aspect of their internal structure, dilatations of type A-fibers were classified into six different types, with various transitional forms: Type I is characterized by abundant NSGs; type II by prominent mitochondria; type III by abundant lysosomal bodies; type IV by an electron-lucent matrix with few organelles; type V by prominent tubuloreticular profiles; and type VI by numerous microvesicles. The functional significance of each type is discussed and a scheme of possible interrelationships between these dilatations is proposed.     

Studies on the manganese of the chloroplast

Manganese deficiency of green plants is known to affect preferentially the activity of the oxygen evolving system in the photosynthetic apparatus. Our studies showed that the time needed to reactivate photosynthesis in Mn-deficient algae varies with each culture, and is often very short when Mn is added not before illumination but during the light period. The recent finding by Cheniae and Martin that the reactivation requires light, is confirmed. The plain incorporation of ⁵⁴Mn into deficient algae as distinguished from reactivation was barely affected by light, yet was inhibited by uncouplers of phosphorylation. Higher plants responded to manganese deficiency either by adjusting the number of chloroplasts per cell to the limited Mn supply, or by forming disorganized chloroplasts with low chlorophyll content. These 2 types of responses produced chlorotic plants which had either a few photosynthetically active or many disabled chloroplasts. Photosystem I mediated photophosphorylation turned out to be much more sensitive to manganese deficiency than the system I dependent photoreduction of NADP⁺.     

Effect of reserpine on the differentiation of the external granular layer of the cerebellum in the chick embryo

In this work we analyse the effect produced by reserpine on the development of thickness and cell number in the external granular layer in the cerebellum of chick embryo. A striking 48-hour histogenetic delay is observed in the treated embryos relative to controls, as show by greater thickness and cell density of this layer in the former, as well as by retarded appearance of a typical radial morphological organization of the external granular layer.