Functional differentiation of the theta-rhythm of the hippocampus in the cat

On the model of discriminating alimentary conditioned reflex with spatial separation of the sources of conditioned (CR, light flashes) and unconditioned (feeding trough) stimuli the theta-rhythm of the dorsal hippocampus was evaluated in cats. Two types of the theta-rhythm were observed in the spectrum of the hippocampal electrical activity: low-amplitude, consisting of a slow growing theta-waves (type I) and high-amplitude consisting of rapidly increasing theta-waves (type II). The type I theta-rhythm is sensitive to noradrenaline and correlates with behavioural forms directed immediately to the realization of alimentary motivation, while the type II is sensitive to serotonin and correlates with behavioural forms directed to the source of the conditioned stimulus. Enhancement of the type II theta-rhythm takes place during a delay of the expected conditioned stimulus. It is suggested that type I theta-rhythm reflects a level of activity of the brain structures connected with unconditioned mechanisms, with realization of biological motivations, while type II theta-rhythm is connected with conditioned reinforcing stimuli; it correlates with various forms of conditioned orienting reflexes and reflects the work of the "nervous model of reinforcing stimulus".     

On the origin of the Hirudinea and the demise of the Oligochaeta

The phylogenetic relationships of the Clitellata were investigated with a data set of published and new complete 18S rRNA gene sequences of 51 species representing 41 families. Sequences were aligned on the basis of a secondary structure model and analysed with maximum parsimony and maximum likelihood. In contrast to the latter method, parsimony did not recover the monophyly of Clitellata. However, a close scrutiny of the data suggested a spurious attraction between some polychaetes and clitellates. As a rule, molecular trees are closely aligned with morphology-based phylogenies. Acanthobdellida and Euhirudinea were reconciled in their traditional Hirudinea clade and were included in the Oligochaeta with the Branchiobdellida via the Lumbriculidae as a possible link between the two assemblages. While the 18S gene yielded a meaningful historical signal for determining relationships within clitellates, the exact position of Hirudinea and Branchiobdellida within oligochaetes remained unresolved. The lack of phylogenetic signal is interpreted as evidence for a rapid radiation of these taxa. The placement of Clitellata within the Polychaeta remained unresolved. The biological reality of polytomies within annelids is suggested and supports the hypothesis of an extremely ancient radiation of polychaetes and emergence of clitellates.     

Reversal of the effect of the allosteric ligands of dCMP-aminohydrolase and stabilization of the enzyme in the T form

The 5-mercury derivative of dCMP is a substrate of deoxycytidylate aminohydrolase in the presence of mercaptoethanol. With this substrate a reversal of the effect of the allosteric ligands of the enzyme is observed. dCTP, which is an allosteric activator for aminohydrolysis of dCMP, becomes an inhibitor for the mercury substrate, whilst dTTP, an allosteric inhibitor for dCMP, becomes an activator for the mercury substrate.This observation has been interpreted by assuming that dCMP-Hg-S-CH₂-CH₂-OH is a substrate of the T form of the enzyme. By reacting dCMP-aminohydrolase in the T form (in the presence of dTTP) with glutaraldehyde, an enzyme has been isolated that is no longer active with dCMP, while it is fully active with the mercurated analog. Gel electrophoresis demonstrated that glutaraldehyde does not produce intermolecular crosslinks, but fixes 95% of the enzyme in a stable hexameric form by intramolecular crosslinks. The data are explained by assuming that glutaraldehyde stabilizes the enzyme in the T conformation.     

Study on the morphology of the gall-bladder of the goat

200 gall-bladders of goat were studied for histology and histochemistry. The lining epithelium is tall columnar with striated border. The glands are mucous and serous, and the secretion of both surface and glands is a polyssaccharide-protein complex. The regional differences at neck, body and fundus of the gall-bladder are described. Few enterochromaffin cells with granules, which are PAS-positive and contain 5-hydroxytryptamine, are encountered at the wedge between the granular epithelial cells and the cells lining the crypts. The relationship between these cells and lymphocytic infiltration is discussed. The thick circular muscle layer at the neck region is considered a sphincter of the gall-bladder.     

Morphology of the gynoecium and systematic position of the Ochnaceae

The gynoecium is syncarpous in all Ochnaceae. In the Ochnoideae carpels are peltate with a conventional cross-zone bearing one ovule, or, in Lophira , a very broad cross-zone with an horizontal ovular row. In Ochna and Brackenridgea , the style is gynobasic, each carpel develops transmitting tissue on its morphologically dorsal surface, and this tissue lines a canal or originates a solid inner strand in each carpel at style level. The style is tubular, with an inner cuticle, and compound, each component with its own transmitting tissue. In Ouratea the style is solid with a single compound transmitting strand. In Lophira and Elvasia the transmitting tissue seems to be developed by the morphologically ventral carpellary surfaces. Ovules are unitegmic with a bivalent integument.
In the Sauvagesioideae carpels are peltate, but with ovules above the cross-zones, on margins of the symplicate zone. In Euthemis , there is one ovule on each side of, and close to, each cross-zone. The single stylar canal is bounded by the morphologically dorsal carpellary surfaces. In Sauvagesia ovules occur on both sides of the cross-zones but most of them are above on carpel margins, as are all ovules of Cespedesia. The stylar canal of Sauvagesia is bounded by the ventral carpel surfaces, three strips of the outer surface passing inside at the sutures and developing into transmitting tissue. The stylar canal of Cespedesia is bounded by the dorsal carpel surfaces. The gynoecium of Wallacea has two epeltate carpels with a laminar placentation, the carpel margins being displaced on to the topographically ventral carpel surfaces with a row of ovules along each margin. Ovules are bitegmic.
The Ochnoideae, which shows relationships with the Rutaceae, Meliaceae, Simaroubaceae and Hippocastanaceae, is more advanced than the Sauvagesioideae, which clearly belongs in the Violales. The Ochnaceae is to be placed in the Violales.     

Theoretical study of the optimal shape of the front profile of the lens in the eye of the scallop,Pecten

The optimal shape of the front profile of the thick lens in the eye of the scallop,Pecten is theoretically, geometric optically investigated as a function of the refractive index of the lens and the retina, as well as of the geometrical parameters of the eye. The shape of the theoretical front surfaces is compared with that of the real, experimentally determined front face of the lens. The degree of correction of the lens for spherical aberration of the reflecting spherical mirror in thePecten eye is examined. The optimal shape of the front profile of the lens depends strongly on a set of parameters, such that a certain fine tuning is required among them to assure a full correction for spherical aberration. The extreme variability of the eye parameters and the shape of the front face of the lens in the scallop is inconsistent with this fine tuning requirement. The degree of correction of thePecten lens for spherical aberration might not be as good as it could be, a possible biooptical reason for which is discussed.     

Arterial component of the angioarchitecture of the canine ovary

In order to study and possibly identify a vascular pattern in the canine ovary, 30 ovarian specimens received arterial injections of a mixture of 'Micropaque' with hydrosoluble red pigment, followed by clearing. The aorta or the femoral artery was catheterized and the injection was performed under a constant pressure of 120 mm Hg. The blood supply of the ovary is provided by the ovarian and the uterine artery. The former appears to be the most important of the two arteries since it is the largest and is the origin of a very rich vascular net in the ovarian stroma. It follows a helicine course within the broad ligament and enters into the ovarian stroma either by a single trunk or by two divergent branches, each supplying the anterior and the posterior half. When there is only a single trunk, one can see a vascular tuft totally occupying the stroma, with tortuosities running in the same direction as the longitudinal axis of the ovary. When there are two branches, the distribution is similar but with two tufts instead of one. From the ovarian artery several branches arise, the largest and most frequent being the lateral tubal artery and a branch which anastomoses with the uterine artery in the mesovarium. Other branches anastomose with one another or with branches of the uterine artery, forming a rich vascular net along the mesovarium. The uterine artery is situated within the broad ligament and runs along the lateral border of the uterus and up to the superior extremity of the uterus where it ends.(ABSTRACT TRUNCATED AT 250 WORDS)     

On the nature of the horny scales of the pangolin

The pangolin scale is a horny derivative of the epidermis. It is complex in structure and is divisible into three distinct regions. The dorsal plate forms approximately one-sixth of the scale thickness. It is composed of flattened solid keratinized cells without basophilic nuclear remnants. This region tends to fray easily. The dorsal plate contains bound phospholipids and sulphydryl groups but is weak in disulphide bonds.
The bulk of the scale is made up of the intermediate plate formed of less flattened cells without basophilic nuclei. This region is rich in disulphide bonds but contains no appreciable bound phospholipids or sulphydryl groups.
The ventral plate is only a few cells thick and is rich in bound phospholipids, which also occur in the underlying scale bed epidermis.
These three regions of the scale are formed from separate epidermal germinal areas which do not develop a granular layer. Keratohyalin granules are, however, formed in the epidermis between the scales.
It is suggested on the basis of histological structure and dishribution of chemical constituents that pangolin scales are probably homologous with primate nails.
Evidence against the views that they are homologous with reptilian scales or are derived from compressed hairs is presented.     

On the neurodynamics of the creation of consciousness

Consciousness is expected to have a specific temporal dynamics. The COrollary Discharge of Attention Movement (CODAM) model of consciousness is deduced from an engineering approach to attention and motor attention. This model is briefly described, as is support arising from brain dynamics, especially that for the attentional blink. The understanding of known temporal dynamics in the brain associated with the emergence of consciousness is then developed from CODAM, and specifically related to the N2 ERP brain signal. How the pre-reflective self, as content-free, interacts with the content of experience is discussed in terms of the possibility that such experience arises from some proto-self generated by body signals; experiments are described which indicate that no pre-reflective self based on body signals is observable. Only a content-free pre-reflective self is consistent with this data, as CODAM suggests. How such a pre-reflective self can be further fused to give temporal continuity of a sense of self is considered in terms of various mechanisms which could be present for preserving the sense of self. The observation of the N2 signal in hippocampal encoding is proposed as providing a justification for the encoding of the N2–P3 sequence of brain signals. This would correspond to episodic encoding of the sequence of experiences of the pre-reflective self; this will thereby provide the necessary control signals in time so that ‘I’ is experienced as part of the retrieval of such memories.     

Characterization of the exchangeable protons in the immediate vicinity of the semiquinone radical at the QH site of the cytochrome bo3 from Escherichia coli

The cytochrome bo3 ubiquinol oxidase from Escherichia coli resides in the bacterial cytoplasmic membrane and catalyzes the two-electron oxidation of ubiquinol-8 and four-electron reduction of O2 to water. The one-electron reduced semiquinone forms transiently during the reaction, and the enzyme has been demonstrated to stabilize the semiquinone. Two-dimensional electron spin echo envelope modulation has been applied to explore the exchangeable protons involved in hydrogen bonding to the semiquinone by substitution of 1H2O by 2H2O. Three exchangeable protons possessing different isotropic and anisotropic hyperfine couplings were identified. The strength of the hyperfine interaction with one proton suggests a significant covalent O-H binding of carbonyl oxygen O1 that is a characteristic of a neutral radical, an assignment that is also supported by the unusually large hyperfine coupling to the methyl protons. The second proton with a large anisotropic coupling also forms a strong hydrogen bond with a carbonyl oxygen. This second hydrogen bond, which has a significant out-of-plane character, is from an NH2 or NH nitrogen, probably from an arginine (Arg-71) known to be in the quinone binding site. Assignment of the third exchangeable proton with smaller anisotropic coupling is more ambiguous, but it is clearly not involved in a direct hydrogen bond with either of the carbonyl oxygens. The results support a model that the semiquinone is bound to the protein in a very asymmetric manner by two strong hydrogen bonds from Asp-75 and Arg-71 to the O1 carbonyl, while the O4 carbonyl is not hydrogen-bonded to the protein.     

Histogenesis of the taste buds of the vallate papilla in the in the rat in the postnatal stages of development

The developing taste buds of vallate papillae were studied with electron microscope in rats during the first 7 days after birth. Two types of cells--light and dark--are identified in the taste buds of a one day old animal. The apical parts of dark cells are characterized by numerous dark granules. A distinguishing feature of light cells is the presence of synaptic contacts with afferent intragemmal nerves. On the 4th day of development on the top of the apical parts of the cell, a microvillar apparatus is seen to form, which does not yet communicate with the oral cavity. On the 7th day, basal cells appear in the taste buds. Some of these cells are seen mitotically dividing. The differentiated microvillar apparatus now communicates with oral cavity. The structure of the taste buds is getting similar to that in the adults. The structural and functional peculiarities of the developing taste buds are discussed in association with the period of ontogenesis under consideration.     

Ultrastructure of the copper-accumulating region of the Drosophila larval midgut

The copper-accumulating region of the midgut is a mosaic of interstitial and cup-shaped, copper-accumulating cells. The cup of each cuprophilic cell is lined with a highly refractile border of long microvilli except in one strain where it is predominantly lamellar. The nucleus lies basally; the basal plasma membrane is fairly extensively infolded. Cytolysomes are abundant and increase in number with increasing copper content of the diet. The interstitial cells bear short, less regular microvilli and have a less electron-dense cytoplasm. The nucleus is apical, the mitochondria-associated basal membrane is very extensively infolded and cytolysomes are less abundant. Virus-like particles present in nuclei of both cell types increase in number with increasing copper concentration.     

Ultrastructure of the vitreous body of the rabbit

Examination in the scanning and the transmission electron microscope showed three morphologically and structurally different types of cells in the vitreous body of the healthy rabbit eye: 1. cells with numerous cytoplasm processes, whose high metabolic activity is represented by the presence of a large number of organelles and which are capable of synthesizing fibrillar material; 2. elongate cells with a flattened nucleus, with long, narrow cytoplasm processes arising from both their poles and with only a few organelles in their cytoplasm; 3. large spherical cells with structureless contents, whose nucleus and few organelles are situated below the cell membrane. The organized component of the intercellular matter of the rabbit vitreous body is composed of collagen fibrils with a very variable diameter (24-180 nm), The collagen fibrils form the basis of the three-dimensional skeleton of the intercellular matter of the vitreous body.     

Application of the mathematics of coupled oscillator systems to the analysis of the neural control of locomotion.

In many animals, the activities of limb motor neurons are rhythmic during locomotion. In some animals it is known that each limb is innervated by a local control center that resides in a discrete portion of the central nervous system. Each local control center is a biological oscillator. Since each limb moves with the same frequency as each other limb and with regulated phase delay with respect to each other limb, then it follows that the local control centers are coupled to one another. The locomotory pattern generator within the central nervous system is therefore a coupled oscillator system. The mathematics of coupled oscillator systems can assist in the construction of a model of the neural pattern generator. This model can be utilized to formulate testable predictions concerning the neural control of locomotion. Experimental data gathered from organisms in several phylums are consistent with the predictions of the model.     

Morphological characteristics of the structures delimiting the residual cavity of the hypophysis in rats after electrocoagulation of the median eminence of the hypothalamus]

By means of light and electron microscopy it has been shown that the remnant cavity of the hypophysis of intact and sham-operated rats on the side of the intermedial lobe is restricted with a continuous layer of epithelial cells with a well pronounced basal membrane. On the side of the frontal lobe the covering epithelium has peculiar "fenestra" through which adenocytes have free contacts with the remnant cavity. After electrocoagulation of the rostral area of the medial eminence, especially in remote postoperative terms, the remnant cavity enlarges up to gigantic size, contains a great amount of colloid, erythrocytes, fragments of cells of the anterior lobe of the hypophysis and secretory granules. The anterior epithelium is lacking on considerable areas and hence adenocytes are disposed in the cavity directly. All their organoids are preserved though a little changed, the cytomembrane is absent. On the apical surface of the posterior epithelium there appear large cytoplasmic protrusions which having separated enter the remnant cavity. The main provider of the "raw material" for colloid is likely to be the anterior lobe of hypophysis.     

Observations on the Fine Structure of the Gastric Parietal Cell of the Rat

The structure of the rat parietal cell was examined by electron microscopy. The intercellular and intracellular canalculi are lined by microvilli which are more numerous and larger than those of other gastric cells. The numerous mitochondria have closely packed cristae and a dense matrix containing opaque particles. The cytoplasmic vacuoles typical of parietal cells are part of a network of smooth surfaced tubules and vacuoles (the endoplasmic reticulum) which is intimately associated with the mitochondria and probably connected with the lumen of the canaliculi. Only a few dense particles are found attached to the surface of these tubules. The structure of the parietal cell is compared with that of other cells whose function also is transport of inorganic ions and water. Evidence is presented supporting the hypothesis that parietal cells differentiate from a less structurally specialized cell in the neck region of the gastric gland.     

Innovative surgical approach for the Pierre Robin anomalad: subperiosteal release of the floor of the mouth musculature

The Pierre Robin anomalad presenting with severe respiratory distress is a difficult situation still associated with a significant mortality rate. A surgical approach based on a new idea is described. The concept is that the musculature of the floor of the mouth is under increased tension and pushes the tongue upward and backward with secondary respiratory obstruction. The surgical approach consists of a subperiosteal release of the musculature of the floor of the mouth through a 2-cm submental incision. So far this procedure has been used in four patients with severe obstruction, and marked improvement has occurred postoperatively in all cases. This surgical technique is simple and is associated with little morbidity. It should lessen the need for tracheostomy, which carries a greater morbidity, especially in newborns. We think that this new surgical approach can significantly improve the outcome of the severe form of Pierre Robin anomalad.     

A population analysis of the variability of the hooklets in the cestode Triaenophorus crassus

The paper presents data on the variability of attachment organs in the cestode Triaenophorus crassus, a parasite of freshwater fishes. The greatest range of variability of all the characters is typical of whitefish, a fish with a long life cycle, while the shortest one is characteristic of vendace and young of trout. It is suggested that the stay of the parasite in fishes, associated with host age, is accompanied by the increase in average sizes of hooks and variability range. Such an approach together with the analysis of hooks variability gives the possibility to estimate the participation of secondary intermediate hosts in the circulation of the parasite in the water body.     

Rhythmic fluctuations in the synthetic activities of the nodulated root of the legume

Summary If a nodulated legume is decapitated immediately after a brief period of photosynthesis in C¹⁴O₂ a highly reproducible pattern of labelling is detected among the amino compounds of the root bleeding sap. The sequences of this pattern apparently reflect the consequences of the exchange of labelled carbohydrate with various morphological and metabolic compartments of the root. The progress of the exchange is greatly influenced by diurnal variations in root metabolism.An endogenous component is described for the rhythmic discharge of amino compounds into the bleeding sap. At 24°C the period of the rhythm is slightly greater than 24 hours.Plants with branched shoots are used to study environmental influences on the translocation of labelled assimilates from a shoot, and the utilisation of these materials in synthesis of organic compounds of nitrogen in the nodulated root. One half of the branched shoot is fed with C¹⁴O₂ and its unlabelled partner removed for collection of bleeding sap. A progressive enrichment of bleeding sap with radiocarbon occurs only if the plants are exposed to normal photoperiods and ambient temperatures. Similar plants retained in darkness in constant temperature exhibit a rapid decline in the specific activity of the amino fraction of the bleeding sap, suggesting that translocation from the pool of labelled carbohydrate in the shoot has failed to keep pace with root synthesis.     

The structure of the middle ear epithelium of the rat and the effect of Eustachian tube obstruction

Summary The middle ear cavity of the rat is lined with ciliated and squamous epithelium. The arrangement of the ciliated cells, interspersed with secretory cells, in distinct tracts and their continuity with the ciliated epithelium of the Eustachian tube, suggests the existence of a mucociliary transport system for cleaning the middle ear cleft. The secretory cells produce either neutral or sulphated glycoproteins, dependent on their location. In addition to these secretions, the epithelium of the lower part of the Eustachian tube is bathed with secretory products of seromucous glands.Also in the areas with squamous epithelium, numerous small secretory cells, the character of which is only identifiable with the electronmicroscope, are present. It is concluded that the middle ear lining can be considered as a locally modified respiratory epithelium.Blockade of the mucociliary transport system, supposedly a crucial aetiological factor in secretory otitis media, by obstruction of the Eustachian tube, induces pathogenic behaviour of microorganisms normally present in the middle ear. This results in either a transient or a longstanding infective middle ear disease, associated with a large variety of changes of the mucosa, especially with respect to the secretory activity.The data obtained indicate that the increased secretory activity encountered in secretory otitis media cannot be attributed to the isolated effect of tubal occlusion, but rather to an infective process.