Interaction of reticular structures in the brain of the cat

In acute and chronic experiments on 35 cats an inhibitory influence was found of the caudal reticular nucleus of pons Varolii on unit activity of the sensorimotor cortex and dorsal part of the midbrain reticular formation. The influence of this structure on unit activity of the ventral part of the midbrain reticular formation was mainly of a facilitatory character. Activation of the ventral part inhibited the unit activity of the dorsal part of the same structure. Consequently, the caudal reticular nucleus of pons Varolii elicits inhibition at the level not only of the cerebral cortex but also of the midbrain reticular formation (of its dorsal part). The character of these influences coincides with that of unit activity changes of these two areas of the midbrain reticular formation during the development of the paradoxical phase of sleep. The obtained facts must underlie the stopping of convulsive activity in this phase of sleep.     

Role of the reticular formation of the midbrain in the process of formation of background activity of cortex neurons

In strict experimental conditions the basic activity of optic-cortex neurons in the rabbit was depressed after transverse section at the level of the rostral part of the reticular formation of the midbrain. Electrolytic destruction or functional blockage of the midbrain reticular formation (nucleus reticularis tegmenti) produces a decrease in frequency and magnitude in the grouping indexes of the cortex-neuron pulses that manifest the activity in these conditions. Destruction of specific nuclei in the optic pathway (those of the lateral geniculate body and the corpora bigemina) made no substantial change in the nature of the cortex-neuron pulses. Comparison of the parameters of pulsation activity of the same cortex neurons, as recorded before and after functional exclusion of the midbrain reticular formation, revealed that the increase in grouping of these pulses after the reticular formation was blocked induced changes in the intervals between groups of pulses, while the frequency of pulses within the groups remained constant. On the basis of the data obtained we may assume that the midbrain reticular formation plays an important role in generation of the background activity of cortex neurons, being a triggering mechanism that sets off a group of pulses. Distribution of pulses within the group is apparently due to the activity of cortex mechanisms only.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 1, pp. 43–51, January–February, 1970.     

Age-dependent decline in bone nodule formation stimulating activity in rat serum is mainly due to the change in the corticosterone level

The replacement of fetal bovine serum with rat serum in a culture medium brought about a marked increase in the formation of mineralized bone nodules (BN) in primary cultures of rat calvarial cells. These effects of rat serum were most prominent when added during the early phase of the culture, indicating that the serum factor mainly acts on the cells during the growing phase. A significant increase in BN formation was observable at final rat serum concentration as low as 1%, and the effect was dependent on serum concentration, at least up to 10%. The addition of rat serum also increased alkaline phosphatase (ALP) activity, collagen synthesis, and DNA synthesis in calvarial cells. BN formation stimulating activity was extractable with ethyl acetate. The ethyl acetate extract was purified by TSK-GEL OH-120 column chromatography by monitoring the stimulation of ALP activity in ROS 17/2.8 cells. The chromatographic behavior of the ALP activity was found to be identical to that of corticosterone, the major glucocorticoid in rodents and the preincubation of the purified fraction with anticorticosterone antibody abolished the ALP stimulating activity. These results suggest that BN formation stimulating activity in rat serum is mainly attributable to corticosterone. The concentration of serum corticosterone decreased with age in parallel with BN formation stimulating activity, which suggests that the physiological level of corticosterone may have a regulatory role in the maintenance of osteoblast function.     

Role of the FGF and MEK signaling pathway in the ascidian embryo

In the ascidian embryo, a fibroblast growth factor (FGF)-like signal from presumptive endoderm blastomeres between the 32-cell and early 64-cell stages induces the formation of notochord and mesenchyme cells. However, it has not been known whether endogenous FGF signaling is involved in the process. Here it is shown that 64-cell embryos exhibit a marked increase in endogenous extracellular signal-regulated kinase (ERK/MAPK) activity. The increase in ERK activity was reduced by treatment with an FGF receptor 1 inhibitor, SU5402, and a MEK (ERK kinase/MAPKK) inhibitor, U0126. Both drugs blocked the formation of notochord and mesenchyme when embryos were treated at the 32-cell stage, but not at the 2- or 110-cell stages. The dominant-negative form of Ras also suppressed notochord and mesenchyme formation. Both inhibitors suppressed induction by exogenous basic FGF. These results suggest that the FGF signaling cascade is indeed necessary for the formation of notochord and mesenchyme cells during ascidian embryogenesis. It is also shown that FGF signaling is required for formation of the secondary notochord, secondary muscle and neural tissues, and at least ERK activity is necessary for the formation of trunk lateral cells and posterior endoderm. Therefore, FGF and MEK signaling are required for the formation of various tissues in the ascidian embryo.     

Lateral clustering of cadherin-4 without homophilic interaction: possible involvement in the concentration process at cell-cell adhesion sites as well as in the cell adhesion activity

It is thought that the concentration of classic cadherins at cell-cell adhesion sites is essential for generating strong cell-cell adhesion activity, but the mechanism is not well understood. To clarify the structural basis of the concentration process and the cell adhesion activity, we constructed various mutants of cadherin-4 and examined the adhesion properties of the transfectants. A deletion mutant lacking the entire cytoplasmic domain had weak, but significant Ca(2+)-dependent cell adhesion activity. Interestingly, the deletion mutant showed intrinsic cluster formation in the absence of cell-cell adhesion, possible lateral cluster formation. The cytoplasmic domain-deleted cadherin-4 containing the mutation of Trp-2 to Ala, which is known to inhibit the strand dimer formation required for the cell-cell adhesion, retained the possible activity of lateral cluster formation, supporting this notion. These results suggest that the extracellular domain has intrinsic activity of lateral cluster formation. Indeed, deletion of a cadherin repeat in the extracellular domain significantly reduced or abolished the lateral cluster formation as well as the concentration of cadherin-4 at cell-cell contact sites and cell adhesion activity. When transfectants of the cytoplasmic domain-deleted cadherin-4 made cell-cell contact and formed intimate cell-cell adhesion, the lateral clusters of cadherin-4 initially gathered at cell-cell contact sites, and a smooth linear concentration was gradually formed along the cell-cell adhesion interface. The results suggest that the lateral cluster formation is involved in the concentration process of cadherin-4 at cell-cell adhesion sites, hence in the strong cell adhesion activity of cadherin-4 as well.     

Increased CDK1 activity determines the timing of kinetochore-microtubule attachments in meiosis I

Chromosome segregation during cell division depends on stable attachment of kinetochores to spindle microtubules. Mitotic spindle formation and kinetochore–microtubule (K-MT) capture typically occur within minutes of nuclear envelope breakdown. In contrast, during meiosis I in mouse oocytes, formation of the acentrosomal bipolar spindle takes 3–4 h, and stabilization of K-MT attachments is delayed an additional 3–4 h. The mechanism responsible for this delay, which likely prevents stabilization of erroneous attachments during spindle formation, is unknown. Here we show that during meiosis I, attachments are regulated by CDK1 activity, which gradually increases through prometaphase and metaphase I. Partial reduction of CDK1 activity delayed formation of stable attachments, whereas a premature increase in CDK1 activity led to precocious formation of stable attachments and eventually lagging chromosomes at anaphase I. These results indicate that the slow increase in CDK1 activity in meiosis I acts as a timing mechanism to allow stable K-MT attachments only after bipolar spindle formation, thus preventing attachment errors.     

The behaviour of acetylcholinesterase activity in neurons of the bulbous part of the reticular formation in albino rats after bilateral vagotomy.

The influence of a bilateral vagotomy on the acetylcholinesterase activity (AChE) in the neurons of the bulbous part of the reticular formation of albino rats was investigated. An increase in the reaction to acetylcholinesterase (AChE) was ascertained in the large as well as the small neurons 8 h after the transection of the vagus nerves, which indicates their decreased activity. It may be assumed that a bilateral vagotomy causes a decrease in the activity of cholinergic mechanisms within the periphery of the reticular formation neurons.     

A spectral-correlational analysis of the EEG of the neocortex in the rabbit in a state of thirst

Summate electrical activity of the rabbit neocortex during formation of drinking excitation was studied by means of mathematical analysis. It is shown that the change of the electrical activity depends on the level of drinking excitability created by various duration of water deprivation (24-48 h) and is expressed in a generalized lowering of potentials amplitude without frequency change. Spectro-correlative EEG analysis showed that lowering of spectrum power took place within the whole analyzed frequencies range. Besides, an increase took place of interconnections of the cortical electrical processes, estimated by coherence function. It may by suggested that the manifested reconstruction of spectro-correlative characteristics of the neocortical biopotentials reflects a formation of motivational excitation establishing optimal level of cortex functioning.     

Porcupine-mediated lipid-modification regulates the activity and distribution of Wnt proteins in the chick neural tube

A long-term goal of developmental biology is to understand how morphogens establish gradients that promote proper tissue patterning. A number of reports describe the formation of the Wg (Wnt1) gradient in Drosophila and have shown that Porcupine, a predicted membrane-bound O-acyl transferase, is required for the correct distribution of Wg protein. The discovery that Wnts are palmitoylated on a conserved cysteine residue suggests that porcupine activity and Wnt palmitoylation are important for the generation of Wnt gradients. To establish the role of porcupine in Wnt gradient formation in vertebrates, we tested the role of porcupine/Wnt palmitoylation in human embryonic kidney 293T cells and in the chick neural tube. Our results lead us to conclude that: (1) vertebrate Wnt1 and Wnt3a possess at least one additional site for porcupine-mediated lipid-modification; (2) porcupine-mediated lipid-modification of Wnt proteins promotes their activity in 293T cells and in the chick neural tube; and (3) porcupine-mediated lipid-modification reduces the range of activity of Wnt1 and Wnt3a in the chick neural tube. These findings highlight the importance of porcupine-mediated lipid modifications in the formation of vertebrate Wnt activity gradients.     

Function of the superior colliculi of the corpora quadrigemina during creation of a local focus of increased excitability in the mesencephalic reticular formation and sensomotor cortex

In chronic experiments on waking rabbits, the foci of heightened excitability in the sensorimotor cortex and mesencephalic reticular formation affected in a similar way the background neuronal activity in the superior colliculi and that evoked by light stimuli. The effect was manifested in elimination of inhibitory pauses in the neuronal response to light stimulus and in a general increase of discharge frequency. Similarity of the cortical and reticular influences is due to their possible mediation by the same collicular interneurones participating in inhibitory pauses formation in the process of backward inhibition. Increased neuronal activity in the superior colliculi under the action of local foci in the sensorimotor cortex and mesencephalic reticular formation correlated with appearance of forelimb motor reaction to isolated light stimulus testifying to a formation of a functional connection between the visual and motor analyzers. Possible role of the superior colliculi in this process and their participation in the formation of a visually controlled reaction is discussed.     

Formation of slow background activity in different parts of the visual analyzer following section of half the tectum mesencephali

Significant changes in the formation of electrical activity rhythms have been revealed in the lateral geniculate body, superior colliculus and visual cortex during section of one half of midbrain operculum in cats anesthetized with nembutal. It was determined that all changes in slow activity generation in the lateral geniculate body, superior colliculus are reflected in changes in the formation of electrical activity of the visual cortex. It is suggested that lateral geniculate body and superior colliculus may be involved in the generation of some electrical activity rhythms of the visual cortex.     

Is lipoxygenase involved in the formation of ethylene from ACC?

Freezing or desiccation of winter rape leaves ( Brassica napus L. var. oleifera (cv. Górczanski) stimulated both lipoxygenase (EC 1.13.11.12) activity and ethylene formation during the post-stress period. The effect depended on the degree of membrane injury. In tissues showing injury less than 50% (as checked with the electrical conductivity method) both activities increased according to the degree of stress-induced damage. In leaves injured to a higher degree both activities decreased. Light and low temperature (5°C) inhibited the development of both lipoxygenase activity and ethylene formation in leaf disks stored for 20 h. Ethylene formation was also observed in a model system where soybean lipoxygenase was added to a mixture containing 1-aminocyclopropane-1-carboxylic acid and linoleic or linolenic acid as substrate for lipoperoxide formation. Changes in pH and temperature conditions of the incubation mixture caused similar differences in the lipoxygenase activity and ethylene formation. We propose that the stimulation of lipoxygenase-catalysed oxidation of polyunsaturated fatty acids (increasing free radical formation) leads to an increased ethylene production from ACC.     

Molecular interactions in the phenomenology of the onset of mental illness

The requirements for a normal functioning of the central nervous system (CNS) are discussed with particular reference to the rigorous separation among central neurotransmitters. Any leak of a transmitter into synapses of different central pathways constitutes a sort of “short circuit”. This evenience might lead to the formation of endogenous psychotogenic agents such as the adrenochrome-acetylcholine (ADAC) which upset the normal functioning of the synapses by activating monoamineoxidase (MAO) and inhibiting acetylcholinesterase (AcChE) and catechol-O-methyl transferase (COMT). The formation of ADAC can be non-enzymatic, but the involvement of enzyme systems such as catecholamine-cyclase and catalase-peroxidase is very likely in either its formation or deactivation. A new colorimetric method for measuring cyclase activity in serum, in concomitance with a reduced peroxidase activity, was applied to analyse the serum of a number of mental patients. The cyclase-peroxidase activity in the serum of these patients was significantly higher than the activity of normal serum. Among the different possible explanations of the fact, its meaning in connection with the protectiveeffects of melanin formation or with the lowering of the pool of physiological reducing agents is pointed out. The short circuit and ADAC formation hypothesis can reasonably account for the onset of mental illness and is not in contrast with other biochemical theories proposed so far.     

Histochemical study of monoamine oxidase latency in the liver of the rat.

In a histochemical test system with adrenaline as substrate and nitroblue tetrazolium (NBT) as electron acceptor, an increase of NBT reduction in rat liver sections was found microspectrophotometrically following short hypotonic treatment. Investigations with iproniazide, a monoamine oxidase inhibitor, and non-enzymatic NBT reduction showed that the increased formazan formation was related to the presence of monoamine oxidase. It is suggested that the reason for the observed increase of formazan formation is due to increased permeability of the inner mitochondrial membrane to NBT. Consequently, the increase of monoamine oxidase observed in the histochemical test system does not represent mobilization of a latent activity, but rather complete assessment of activity that is normally present.     

Inhibitor factors in the serum of patients with the AIDS-related complex

The data on the presence of factors blocking the reaction of E-rosette formation and leukocyte chemotaxis in the blood sera of patients with AIDS-related complex (ARC) and HIV-positive donors are presented. Most frequently the blocking of E-rosette formation coincided with the presence of a inhibiting effect on the migration capacity of leukocytes. This blocking activity was not linked with the presence of C-reactive protein in the circulation stream. The treatment of ARC patients with plasmapheresis and/or travolol was accompanied either by the disappearance of blocking activity or by the appearance of activity stimulating E-rosette formation.     

Some Factors Affecting the Anthocyanin Formation by Populus Cells in Suspension Culture

In order to elucidate the mechanism of anthocyanin formation by Populus cells in suspension culture, the favourable conditions for anthocyanin formation were investigated. The influence of some factors affecting the anthocyanin formation, i.e. light, sucrose and riboflavin etc. were also examined. Light irradiation and high sucrose concentrations brought about a marked increase of PAL activity, which increased rapidly at the lag phase preceding the anthocyanin formation. The effect of blue light on anthocyanin formation was markedly superior to other kinds of monochromatic light (green and red) or white light. Riboflavin was effective only under light exposure. It was inferred that light, sucrose, riboflavin and PAL activity etc. were closely related with the anthocyanin formation. Especially, light and sucrose cooperated in the increase of PAL activity which was a key enzyme in the biosynthesis of anthocyanin.     

Involvement of calmodulin in the regulation of adenylate cyclase activity in guinea-pig enterocytes

The involvement of calmodulin as an activator of adenylate cyclase activity was examined in isolated guinea-pig enterocytes and in a membrane preparation. In enterocytes, which responded to prostaglandin E1, vasoactive intestinal peptide and cholera toxin with a significant increase in the rate of cAMP formation trifluoperazine, a calmodulin antagonist, completely inhibited cAMP formation. In a membrane preparation adenylate cyclase activity was stimulated 10-20-fold by the GTP analog, guanosine 5'-[beta-imido]5'-triphosphate (Gpp[NH]p). Prostaglandin E1 and vasoactive intestinal peptide enhanced cAMP formation in this system by 2-3- and 1.2-1.6-fold. respectively. Addition of 200 nM calmodulin to membranes, in which endogenous calmodulin was decreased from 1.4 microgram/mg protein to 0.5 microgram/mg protein by washing with buffer containing EGTA and EDTA, resulted in a 3-4-fold increase of adenylate cyclase activity. The absolute increment in adenylate cyclase activity caused by calmodulin (10-15 pmol cAMP/min per mg protein) was approximately the same in the absence or presence of Gpp[NH]p. The apparent Ka for Gpp[NH]p (6 . 10-7 M) was not significantly changed by the addition of calmodulin. Although endogenous calcium (approx. 10 microM) in the enzyme assay was adequate to affect stimulation by calmodulin, a maximal effect was observed at a calcium concentration of 100 microM. These findings indicate that a calmodulin-sensitive form of adenylate cyclase is present in guinea-pig enterocytes, and that stimulation of cAMP formation in the intestinal mucosa may involve a calmodulin-mediated mechanism.     

Tyrosyltubulin ligase activity in brain,skeletal muscle,and liver of the developing chick

The developmental course of tyrosyltubulin ligase activity has been measured in three tissues of the embryonic chick: skeletal muscle; whole brain; and liver. There is a sharp peak in enzyme activity in muscle at day 13 when myotube formation is proceeding rapidly. In brain, high activities are maintained over a prolonged period. Liver has relatively little activity which decreases steadily over the entire developmental period that was examined. The possible relationship between high levels of tyrosyltubulin ligase activity and morphological changes dependent upon microtubule formation is discussed.     

Further evidence for a separate enzymic entity for the synthesis of homocitrulline, distinct from the regular ornithine transcarbamylase

Differential digitonin extraction of rat liver mitochondria and of mitochondria of livers of affected and unaffected male sparse fur mice released a lysine transcarbamylase activity from the mitochondria at a digitonin to protein ratio in between that for myokinase and glutamate dehydrogenase, but at a slightly lower ratio than the ornithine transcarbamylase activity. Homocitrulline formation by isolated rat liver mitochondria is independent of the uptake of lysine by mitochondria as evidenced by the insensitivity of homocitrulline formation to changes in the matrix pH, in contrast to citrulline formation from ornithine. High-performance liquid chromatography separates the lysine transcarbamylase activity from the ornithine transcarbamylase activity. It is concluded that the lysine transcarbamylase activity is localized outside the inner mitochondrial membrane.