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PubMed2006

Immunodetection of pectin and arabinogalactan protein epitopes during pollen exine formation of Beta vulgaris L.

We present the results of ultrastructural and immunocytochemical studies of sugar beet microsporocytes during the developmental phase that begins with the first meiotic metaphase and ends with the formation of young tetrads. The most prominent feature noted during this period of microsporogenesis was the presence of numerous cisternae of endoplasmic reticulum which frequently lie perpendicular to the surface of the plasma membrane and eventually fuse to it. Microscopic observations have been combined with the detection of several carbohydrate epitopes representing pectins and arabinogalactan proteins in the primexine and incipient exine. Pectin domains that possess both low and highly methylesterified epitopes, as well as pectin side chains enriched in (1-->4)-beta-D-galactose residues, are deposited in this young microspore wall. The epitopes of arabinogalactan protein that bind to JIM13, JIM8, and LM2 antibodies are localised within the callose wall surrounding posttelophase tetrads. The possibility of endoplasmic-reticulum involvement in the synthesis, transport, or metabolism of several microspore wall compounds is discussed.

Beta vulgaris↗
PubMed2006

Effects of simulated microgravity on male gametophyte of Prunus, Pyrus, and Brassica species.

In this study we evaluated the effect of simulated microgravity on pollen germination of both herbaceous and woody species in order to investigate the possibility of applying gametophytic selection for plant growth in the space environment. The behaviour of gametophytes exposed to the stress of clinostat rotation could be used to screen the degree of tolerance of the sporophyte to simulated microgravity. The use of male gametophyte selection overcomes the problems generally encountered by sporophytic selection in space especially for woody plants: the large size of plants and their long juvenile phase. In this experiment, pollen collected from just bloomed flowers of Prunus persica, P. avium, P. domestica, Pyrus communis, and Brassica rapa was subjected to tests assessing its viability by techniques such as fluorochromatic reaction. Once pollen viability was ascertained by fluorescence microscopy, pollen was placed on the growth medium in petri dishes both at 1 g and on the clinostat. After incubating for 1 day at room temperature, pollen was observed under a light microscope in order to detect parameters such as the percentage of germination and the growth direction. Then histochemical analyses were performed in order to verify the presence and distribution of nuclei, cytoplasm, and storage substances. Moreover, the presence, size, and morphology of callose plugs were observed. Results showed that the response of gametophytes to simulated microgravity is dependent on the species, some showing altered metabolism, others being unaffected.

Brassica↗
PubMed2006

Links between early pollen development and aperture pattern in monocots.

Although the pollen grains produced in monocots are predominantly monosulcate (or monoporate), other aperture types are also found within this taxonomic group, such as the trichotomosulcate, inaperturate, zonaperturate, di-, or triaperturate types. The aperture pattern is determined during the young-tetrad stage of pollen development and it is known that some features of microsporogenesis can constrain the aperture type. For example, trichotomosulcate pollen is always associated with simultaneous cytokinesis, a condition considered as derived in the monocots. Our observations of the microsporogenesis pathway in a range of monocot species show that this pathway is surprisingly variable. Our results, however preliminary, reveal that variation in microsporogenesis concerns not only cytokinesis but also callose deposition among the microspores and shape of the tetrads. The role played by these features in aperture pattern determination is discussed.

Cytokinesis↗
PubMed2006

Comparative exine ontogeny in some members of the family Zygophyllaceae sensu lato.

Exine ontogeny is studied in five taxa of the family Zygophyllaceae sensu lato (Peganum harmala L., Zygophyllum album L., Fagonia cretica L., Tribulus terrestris L., and Nitraria retusa [Forsk.] Asch.). In the beginning of the tetrad stage, the plasmalemma is attached to the callose wall, except in T. terrestris, where it describes crests and hollows. The primexine matrix is fibrillar, bilayered in T. terrestris and unilayered in the other taxa. In all species except P. harmala, the procolumellae are heterogeneous with clear zones and they become compact later. In T. terrestris, they are built on the crests. In Z. album and T. terrestris, a primordial nexinic lamella is set up. It is tripartite with a white line seen at some levels; on its external leaflet, the foot layer is observed, and on its internal leaflet, there is the endexine with numerous lamellae. This white line disappears often in the mature exine. In T. terrestris, there is a thick nexine that is coarsely lamellate inside. In the aperture zone, the columellae are lacking, the tectum and the foot layer get thinner; they unite and form the apertural membrane with the external part of the endexine. There is a granulolamellar endexinic zone well developed in P. harmala, whereas it is threelayered and weakly developed in T. terrestris.

Pollen↗
PubMed2002

Immunocytochemical evidence of calreticulin-like protein in pollen tubes and styles of Petunia hybrida Hort.

With a polyclonal antibody raised against calreticulin (CRT) the locations where the protein occurs in unpollinated and pollinated styles of Petunia hybrida were localized. The epitopes binding the CRT antibody were immunolocalized preferentially in pollen tubes. In transmitting tract cells, both before and after pollination, the level of CRT was low. The protein was mainly localized in the cytosol and around dictyosomes of transmitting-tract cells. In pollen tubes, a high level of CRT was found at their tips rich in endoplasmatic reticulum, cisternae piles of reticular and/or dictyosomal origin, and vesicles. Binding sites of the CRT antibody were also found in the internal callosic cell wall of the pollen tube. These results indicate a role of CRT in cells directly participating in pollen-pistil interaction.

Antibodies↗
PubMed2003

The alien hand syndrome: classification of forms reported and discussion of a new condition.

The term "alien hand" refers to a variety of clinical conditions whose common characteristic is the uncontrolled behavior or the feeling of strangeness of one extremity, most commonly the left hand. A common classification distinguishes between the posterior or sensory form of the alien hand, and the anterior or motor form of this condition. However, there are inconsistencies, such as the phenomenon of diagonistic dyspraxia, which is largely a motor syndrome despite being more frequently associated with posterior callosal lesions. We discuss critically the existing nomenclature and we also describe a case recently reported by us which does not fit any previously reported condition, termed agonistic dyspraxia. We propose that the cases of alien hand described in the literature can be classified into at least five broad categories: (i) diagonistic dyspraxia and related syndromes, (ii) alien hand, (iii) way-ward hand and related syndromes, (iv) supernumerary hands and (v) agonistic dyspraxia.

Apraxias↗
PubMed2005

Neuronal connection of the cortex and reconstruction of the visual space.

The distributions of retrograde labeled cells in fields 17 and 18 and the fields 17/18 transitional zone were studied in both hemispheres of cats after microiontophoretic administration of horseradish peroxidase into individual cortical columns in fields 17, 18, 19, and 21a. The clustered organization of the internal connections of the cortical fields, the asymmetrical locations of labeled callosal cells relative to the injected columns, and the defined distribution of labeled cells in layers A of the lateral geniculate body suggested that eye-specific neuronal connections support "binding" of the visual hemifields separately for each eye. Application of marker to columns in fields 19 or 21a demonstrated disparate inputs from fields 17 and 18 and the fields 17/18 transitional zone. It is suggested that these connections may support the extraction of loci and stereoscopic boundaries located in the central sectors of the visual space.

Animals↗
PubMed2006

Cytophysiology of spiny stellate cells in the striate cortex and their role in the excitatory mechanisms of intracortical synaptic circulation.

Spiny stellate cells (SS) are an exclusive category of cortical interneurons and are the major component of intracolumnar, lateral, and callosal excitation of pyramidal and non-pyramidal neurons in the neocortex. The axons of SS make contact with the apical dendrites of pyramidal neurons, forming cartridge-type en passant synapses with them. SS establish recurrent connections with inhibitory interneurons and other SS, and also form autapses contacts. SS subtypes were identified and descriptions of their structure, neurochemical specialization, and spatial organization in the human and animal neocortex are provided. The results of our own studies, along with published data, are used to form a critical analysis of current concepts of the histophysiology of recurrent excitatory and inhibitory neurocirculation in cortical modules.

Afferent Pathways↗
PubMed2006

Interhemisphere connections of the visual cortex in cats with bilateral strabismus.

The distribution of retrograde labeled callosal cells after microiontophoretic application of horseradish peroxidase into individual cortical columns in fields 17 and 18 was studied in cats reared with bilateral strabismus (with an angle of eye deviation of 10-35 degrees ). The area containing labeled cells was located asymmetrically in relation to the position of the injected column in the opposite hemisphere. Some of the cells were located in those parts of the transitional zone between fields 17 and 18 whose retinotopic coordinates corresponded to the column coordinates (as in intact cats). Other labeled cells were located in fields 17 and 18 and were grouped into clusters located at distances of about 1000 microm from the marginal clusters of the transitional zone. The locations of labeled cells in the lateral geniculate body showed that most columns receive inputs from the ipsilateral eye. Evidence for eye specificity of these monosynaptic interhemisphere connections is presented. The functional significance of changes in these connections in bilateral strabismus is discussed.

Animals↗
PubMed2005

The role of the corpus callosum in interhemispheric transfer of information: excitation or inhibition?

The corpus callosum is the major neural pathway that connects homologous cortical areas of the two cerebral hemispheres. The nature of how that interhemispheric connection is manifested is the topic of this review; specifically, does the corpus callosum serve to communicate an inhibitory or excitatory influence on the contralateral hemisphere? Several studies take the position that the corpus callosum provides the pathway through which a hemisphere or cortical area can inhibit the other hemisphere or homologous cortical area in order to facilitate optimal functional capacity. Other studies suggest that the corpus callosum integrates information across cerebral hemispheres and thus serves an excitatory function in interhemispheric communication. This review examines these two contrasting theories of interhemispheric communication. Studies of callosotomies, callosal agenesis, language disorders, theories of lateralization and hemispheric asymmetry, and comparative research are critically considered. The available research, no matter how limited, primarily supports the notion that the corpus callosum serves a predominantly excitatory function. There is evidence, however, to support both theories and the possibility remains that the corpus callosum can serve both an inhibitory and excitatory influence on the contralateral hemisphere.

Arousal↗
PubMed2006

Loss of Necrotic Spotted Lesions 1 associates with cell death and defense responses in Arabidopsis thaliana.

We isolated a lesion mimic mutant, necrotic spotted lesions 1 (nsl1), from Ds-tagged Arabidopsis thaliana accession No-0. The nsl1 mutant exhibits a growth retardation phenotype and develops spotted necrotic lesions on its rosette and cauline leaves. These phenotypes occur in the absence of pathogens indicating that nsl1 mutants may constitutively express defense responses. Consistent with this idea, nsl1 accumulates high levels of callose and autofluorescent phenolic compounds localized to the necrotic lesions. Furthermore RNA gel blot analysis revealed that genes associated with disease resistance activation are upregulated in the nsl1 mutants and these plants contain elevated levels of salicylic acid (SA). Crossing nsl1 with an SA deficient mutant, eds16-1, revealed that the nsl1 lesions and growth retardation are dependent upon SA. The nsl1 phenotypes are not suppressed under either the rar1-10 or sgt1b-1 genetic background. NSL1 encodes a novel 612aa protein which contains a membrane-attack complex/perforin (MACPF) domain, which is conserved in bacteria, fungi, mammals and plants. The possible modes of action of NSL1 protein in negative regulation of cell death programs and defense responses are discussed.

Amino Acid Sequence↗
PubMed1975

Submicroscopic changes of cortex nerve cells in chronic mirror epileptic focus in rats.

Submicroscopic changes of neurons, synapses, glial cells and some elements of capillaries were established by studying chronic mirror foci which appeared in the rat cerebral cortex after implantation of cobalt-gelatinous rods into the contralateral hemisphere. The results were compared with normal control cortex and with changes after thermocoagulation of the symmetrical contralateral cortex. It is shown that epileptogenic lesions produce a significant reduction of RNA-components, edema and vacuolization of neuronal cytoplasm, hypertrophy and proliferation of glial cells. The revealed pathological changes of the synapses were manifested by dilatation of some vesicles and the appearance of heterogenic inclusions. The characteristic features of Wallerian degeneration of callosal synapses and the reversible retrograde changes of the neurons which send their axons into the traumatized zone of the contralateral hemisphere were observed to be similar after both experimental lesions.

Animals↗
PubMed1978

Cortical projections of the thalamic mediodorsal nucleus in the rabbit.

The cortical projection of the thalamic mediodorsal nuclear complex (MD) in the rabbit was mapped retrograde horseradish peroxidase and anterograde tritiated proline techniques. The projection field occupied the entire medial wall rostral to a mid corpus callosal level, wrapped around the frontal pole onto the lateral convexity and tailed off caudally on the dorsal bank of the rhinal sulcus. The projection of the lateral approximately one-half of MD, the half which does not receive olfactory input, was confined to medial cortex supply all but the most rostral region. This projection field of lateral MD was precisely organized in two dimensions with the most lateral part projecting most caudally and the most dorsal part projecting most ventrally. A representation for the third, anterior-posterior (A-P), dimension was not evident since any cortical point within the field was supplied by a cylinder of cells extending the entire A-P extent of lateral MD. The medial half of MD, which does receive olfactory input, projected to the remaining rostral medical cortex, the lateral convexity and rhinal sulcal region. The inverse dorsoventral relationship was partially preserved and on overlapping A-P gradient was present with sulcal projections originating more caudally in medial MD and the rostral medial projection originating more rostrally.

Animals↗
PubMed1981

Structure of human auditory cortex. II. Axon distributions and morphological correlates of speech perception.

In Golgi-impregnated specimens of human auditory cortex banding patterns of cortical afferents have been found. Viewed sagitally they are vertical columns with components in layers III, IV, VI and sometimes V. Viewed tangentially they are winding stripes roughly parallel to the gyral axis and of variable width (usually a few hundred micrometers). Although it is not possible to determine it in such sections, they are probably - by analogy with animal experiments - of callosal and/or thalamic origin. Also found were narrow radial bundles, also of indefinite origin. Relative densities of impregnated axons were higher in the columns than between them; also, the tangential orientation component was accentuated within the columns. These findings, together with those of the previous paper, are related to neurolinguistic discoveries. Possible morphological correlates are discussed for neurolinguistic phenomena such as parallel processing of phonemes and words and unilateral, categorical perception of consonants compared with bilateral recognition of vowels and continuous transitions between them.

Aged↗
PubMed1982

The hemispheric dominance of cortical cells in the absence of direct visual pathways.

Unit recording was carried out in the visual cortex of split chiasm and optic tract-sectioned adult cats. From the proportions of the visually responsive and unresponsive cells found in each hemisphere of the operated cats it was concluded that the indirect pathway via the corpus callosum becomes visually inactive under these conditions. However, the direct geniculocortical pathway remains visually active. Thus, it was assumed that unilateral or bilateral elimination of the decussating pathway has a crucial effect on the amount of interhemispheric callosal transfer of basic visual functions.

Animals↗
PubMed1982

Cortical lesion effects and vocalization in the squirrel monkey.

The effects of bilateral destruction of the cortical face area, anterior and posterior supplementary motor area and anterior cingular cortex on spontaneous vocalization were studied in 16 squirrel monkeys (Saimiri sciureus). Each type of lesion was made in two groups of two animals each. Both animals of a group received the same type of lesion at the same day. Each group was recorded for 10 sessions of one hour before operation and 10 sessions after operation. Pre- and post-operative vocalizations were compared in respect to total number and acoustic structure. It was found that none of the lesions affected acoustic structure as judged by a sonagraphic analysis. However, lesions in the anterior supplementary motor area (at the level of the callosal genu) reduced the total vocalization number significantly. This decrease was essentially due to a drastic reduction of the so-called isolation peep, a long-distance contact call. The results suggest: (i) that the cortical face area is only involved in the control of learnt vocal utterances (such as human speech and song) but not in the production of genetically preprogrammed utterances (such as monkey calls and human pain groans); (ii) that the anterior cingulate cortex is necessary for the volitional initiation of vocalization but not for the initiation of calls in an emotional situation; (iii) that the posterior supplementary motor area does not play any role in vocal behaviour of monkeys; and (iv) that the anterior supplementary motor area is involved in the production of vocalization which are not triggered directly by external events.

Animals↗
PubMed1983

Binocular properties of lateral suprasylvian cortex are not affected by neonatal corpus callosum section.

The lateral suprasylvian cortex (LS) was physiologically examined in cats with neonatal section of the posterior corpus callosum (CC) at 2 or 3 weeks after birth. All receptive field properties of the LS cells, including ocular dominance, were found to be normal, despite a reduction in binocular activation in area 17 in the 2 week CC cats. Therefore, binocular activation of LS cells is not dependent on callosal input at any age, nor is it dependent on normal levels of binocular activation of striate cortex.

Animals↗
PubMed1985

Hypertrophy of cholinergic neurones of the rat basal nucleus following section of the corpus callosum.

The effect of division of the corpus callosum on immunohistochemically identified cholinergic neurones of the basal nucleus has been examined in rats. Following callosal section the cholinergic cell bodies on both sides are significantly larger (25%) than those in normal animals. This hypertrophy persists for at least 62 days after operation, the longest survival time examined. It is greatest when the animal is operated on in infancy, but it occurs at all ages examined. The enlargement is similar to that seen in the cells of the same nucleus on one side following contralateral cortical damage.

Animals↗