bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ty3/gypsy‐like retrotransposons in Candida albicans and Candida dubliniensis: Tca3 and Tcd3
Authors: Goodwin Timothy J. D. , Dalle Nogare Damian E. , Butler Margaret I. , Poulter Russell T. M. 
Published: April 2003

AbstractTy3/gypsy retrotransposons are a widespread group of eukaryote mobile genetic elements. They are similar in structure to, and may be ancestors of, the vertebrate retroviruses. Here we describe the first Ty3/gypsy retrotransposons from the pathogenic yeasts Candida albicans and Candida dubliniensis, which we refer to as Tca3 and Tcd3, respectively. Tca3 was first identified in a variety of strains as an element lacking a large part of its coding region. Comparative analyses between C. albicans and C. dubliniensis allowed us to identify the closely related full‐length Tcd3 element, and, subsequently, the full‐length Tca3 elements. The full‐length versions of Tca3 and Tcd3 are broadly similar in structure to other Ty3/gypsy elements, but have several features of special interest, e.g. both elements appear to have a novel mechanism for priming minus‐strand DNA synthesis, probably involving conserved secondary structures adjacent to the 5′ LTRs. Also, while closely related to each other, the two elements appear to be fairly distantly related to other known Ty3/gypsy‐like elements. Finally, the occurrence of the internally deleted forms of Tca3 in many strains raises interesting questions concerning the evolution of these transposable elements in Candida and the evolution of Candida itself. The sequences reported in this paper have been assigned GenBank Accession Nos AF499463, AF499464 and AF510498. Copyright © 2003 John Wiley & Sons, Ltd.
Bringing judgment into combination forecasts
Authors: Sanders Nada R. , Ritzman Larry P. 
Published: April 2003

AbstractThis research investigates the benefits in forecast accuracy by combining judgmental forecasts with those generated by statistical models. Our study differs from prior research efforts in this area along two important dimensions. First, two different types of judgmental forecasts are evaluated for combination with statistical forecasts — one based on contextual knowledge and one based on technical knowledge. Contextual knowledge is information gained through experience on the job with the specific time series and products being forecasted. Technical knowledge is information gained from education on formal forecasting models and data analysis. Second, we investigate the conditions under which adding judgment to combination forecasts helps the most. Specifically, we test the improvement as a function of time series variability.Our results show that judgmental forecasts based on contextual knowledge, rather than technical knowledge, are the better input into combination forecasts. Bringing judgmental forecasts based on contextual knowledge into combination forecast improves forecast accuracy over the individual statistical and judgmental forecasts. However, the benefit attained from including contextual knowledge in the combination depends on the amount of inherent variability in the time series being forecast. More contextual knowledge is needed for combination forecasts if a time series has more data variability. If the amount of variability is low, less emphasis should be given to contextual knowledge when making combination forecasts. In general, our findings suggest a linear relationship between the amount of contextual knowledge needed and data variability.
Role of ornithine decarboxylase and the polyamines in nervous system development: Short‐term postnatal administration of α‐difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase
Authors: Slotkin T.A. , Whitmore W.L. , Lerea L. , Slepetis R.J. , Weigel S.J. , Trepanier P.A. , Seidler F.J. 
Published: April 2003

AbstractThe role of ornithine decarboxylase (ODC) and the polyamines in development of central and peripheral catecholaminergic neurons was examined through the use of α‐difluoromethylornithine (DFMO), a specific irreversible inhibitor of ODC. Short‐term postnatal administration of DFMO (500 mg/kg daily on days 1–6) to neonatal rats resulted in effective inhibition of ODC and depletion of both putrescine and spermidine in brain, heart and kidney; after cessation of DFMO administration, polyamine levels returned to normal by 10–13 days of age. There were no signs of generalized toxicity of short‐term DFMO treatment, as body weight gains were largely unaffected over the course of study (through weaning). However, development of peripheral sympathetic neurons was severely retarded by DFMO, with persistent and profound deficits of both cardiac and renal norepinephrine; the catecholamine deficiencies were unrelated to effects on end‐organ growth, as cardiac weights were essentially normal whereas kidney weights were adversely affected by DFMO. Development of the adrenal medulla, a peripheral catecholaminergic tissue which displays approximately the same developmental profile as do sympathetic neurons but which does not develop axonal projections, was not slowed by DFMO treatment; similarly, central noradrenergic and dopaminergic neurons, which undergo the majority of axonal outgrowth and synaptogenesis during the second to third postnatal week (just after the period in which polyamines returned to control levels), developed normally as assessed by measurements of transmitter levels, tyrosine hydroxylase activity and synaptosomal uptake of [3H]norepinephrine or [3H]dopamine. Extension of the period of DFMO treatment and consequent depletion of polyamines into the period in which central synaptogenesis occurs does, however, produce slowing of development of brain catecholamine neuronal projections. Thus, the ODC/polyamine system appears to play a critical postnatal role in catecholamine systems specifically undergoing active synaptogenesis.
A comparison of the regional ontogenesis of nicotine‐ and muscarine‐like binding sites in mouse brain
Authors: Falkeborn Y. , Larsson C. , Nordberg A. , Slanina P. 
Published: April 2003

AbstractThe postnatal development of the cholinergic neurotransmitter system was studied in the cortex, hippocampus, midbrain and cerebellum of 3‐, 7‐, 12‐, 17‐ and 30‐day‐old NMRI mice. The concentration of muscarine‐like binding sites determined with [3H]quinuclidinyl benzilate as a ligand increased progressively with age. A similar developmental pattern was found for the activity of a presynaptic marker, choline acetyltransferase (ChAT). When expressed as a percentage of the values for 30‐day‐old mice, however, the muscarine‐like receptors were parallel but preceding the development of ChAT in all the brain regions studied. The concentration of nicotine‐like binding sites studied with [3H]α‐bungaro‐toxin as a ligand gradually increased with age in the cortex, hippocampus and midbrain, with a peak between days 7 and 12, followed by a decrease towards day 30. With [3H]tubocurarine as a ligand, on the other hand, the concentration of nicotine‐like binding sites was in general high at 3 days and gradually decreased with age, suggesting that different subpopulations of nicotine‐like receptors might be determined when the two ligands are used.
The arachnoid granulations of the newborn human: An ultrastructural study
Authors: Gomez Daniel G. , Ehrmann Jorge E. , Potts D. Gordon , Pavese Albert M. , Gilanian Angela 
Published: April 2003

AbstractPortions of the superior sagittal sinus and lacunae laterales containing arachnoid villi and granulations from 8 full‐term newborn babies were studied by transmission electron microscopy. Arachnoid proliferations from 3 subjects were distended and fixed in vitro by applying a differential pressure of 8 cm H2O to the subarachnoid aspect of the tissues. The remaining cases were fixed in a collapsed state. Distended arachnoid proliferations showed morphologic characteristics associated with similar functional structures in experimental animals: shortened and enlarged interendothelial spaces; micropinocytotic activity and a system of endothelial‐lined tubules. All this is taken as evidence that arachnoid proliferations in newborn babies could already be engaged in cerebrospinal fluid absorption.
Ultrastructural cytochemistry of monoamines in cultured human fetal sympathetic neurons
Authors: Zeevalk Gail Duffy , Cederqvist Lars L. , Lyser Katherine M. 
Published: April 2003

AbstractThe presence and storage of adrenergic neurotransmitter (monoamines) in cultured human fetal sympathetic neurons was investigated by chromate‐dichromate cytochemistry, formaldehyde‐induced fluorescence and potassium permanganate fixation. Monoamines were specifically identified in the neurons by the presence of an electron dense precipitate following cytochemical treatment. Reaction product was found in cell somas and processes in all chromate—dichromate treated cultures. The size range and morphology of the precipitate indicated a vesicular storage site within large dense core vesicles. Neurons fluoresced after treatment with formaldehyde vapors, further confirming the presence of monoamines. When potassium permanganate was employed as the fixative, occasional positive dense core vesicles were found but their frequency was greatly reduced from that seen in the chromate‐dichromate treated cultures. These findings show that cultured human fetal sympathetic neurons retain an adrenergic phenotype during long‐term serum‐free culture. In addition, the storage site for the adrenergic neurotransmitter in the developing neuron is within large dense core vesicles. The lack of dense core vesicles in potassium permanganate fixed material is believed to be due to the depletion of monoamines during fixation.
A chick neural antigen identified by monoclonal antibodies
Authors: Leah John , Gynther Bruce , Kidson C. 
Published: April 2003

AbstractA monoclonal antibody technique has been used to locate a neural antigen which appears to be involved in developmental processes.Hybridomas were prepared using chick embryo sympathetic neurons as an immunogen and one clone, H3, was found to secrete antibodies which bound to neurons of the peripheral and central nervous system. The antibodies bound to both membrane and cytoplasmic sites of neurons but only to cytoplasmic sites of glial cells. When added to newly prepared cultures of embryonic sympathetic neurons the H3 antibodies impaired both neurite outgrowth and long‐term neuronal viability. No such effect was seen when the antibodies were added to established, differentiated neurons.
Factors influencing astrocyte growth and development in defined media
Authors: Michler‐Stuke Angelika , Wolff Joachim R. , Bottenstein Jane E. 
Published: April 2003

AbstractA previously described serum‐free, defined medium (G2 medium) containing transferrin, selenium, hydrocortisone, biotin, fibroblast growth factor (FGF) and fibronectin developed for the growth of human and rat derived glioma cells was investigated for its ability to support proliferation of astrocytes in primary cultures of neonatal rat cerebrum. These cells were able to grow in G2 medium. Enhanced proliferation and repeated subcultivation were obtained after adding insulin and/or epidermal growth factor (EGF) to the G2 medium at concentrations of 5 μg/ml and 10 ng/ml, respectively.In these modified media (called G4 and G5 medium) astrocytes showed a higher degree of morphological differentiation as compared to serum supplemented medium. Cell type specificity was determined by immunocytochemical staining of glial fibrillary acidic (GFA) protein, which could already be demonstrated 5 days after plating cells. G4 and G5 represent the first serum‐free defined media in which astrocytes proliferate and differentiate without preceding or intermediate contact to serum supplemented medium. Modification of the culture substratum by adding hyaluronic acid and chondroitin sulfate A to G4 medium (G2 medium + insulin) enhanced proliferation of astroglial cells by a factor of about 1.5. In the presence of epidermal growth factor no response to the altered culture dish surface was observed and the addition of fibronectin, otherwise a stringent plating requirement, was no longer necessary.
Reductions in the plating efficiency of the fetal neural precursor cells following maternal alcohol consumption
Authors: Kennedy L.A. , Elliot M.J. , Laverty W.H. 
Published: April 2003

AbstractMaternal alcohol abuse has been associated with reduced neural cell number and abnormal cell differentiation and organization in many regions of the developing mammalian brain. Experiments were conducted to determine whether changes in the neural precursor cells could be detected in primary culture following maternal alcohol consumption during the early proliferative period of the fetal brain growth spurt. Alcohol was administered to pregnant mice in the drinking water from days 11 to 19 of gestation. There was no alcohol‐related increase in the incidence of fetal mortality or malformation, but fetal body and brain weights were reduced. When disaggregated cells from the day 19 fetal neopallium were grown in culture, there was a reduction in the number of astroglial colonies yielded in 42% of alcohol‐exposed brains. This effect was expressed as a reduction in the absolute plating efficiency (APE) of the neural precursor cells. The APE was reduced as much as 80% in severely affected brains. There was no alcoholrelated difference in the in vitro morphogenesis of the astroglial colonies. Observations of the proliferative neural cells in situ suggest that there is an impaired recruitment of all neural cell types, but that the reduced APE reflects primarily a proportionate increase in the number of immature neurons among the cells obtained from the fetal neopallium. It appears that a prolongation of mitosis may be resulting in a general developmental delay in the fetal neocortex.
Tissue repair in the embryonic rat spinal cord following exposure to N‐ethyl‐N‐nitrosourea
Authors: Houle John D. , Das Gopal D. 
Published: April 2003

AbstractThe cytotoxic effects of N‐ethyl‐N‐nitrosourea (ENU) and the potential for recovery from this damage in the developing rat spinal cord was investigated. Emphasis was placed on determining the severity and location of initial cell necrosis and the subsequent reorganizational changes in the damaged tissues. Pregnant rats were injected i.v. with a single dose of ENU (60 mg/kg) on one of days 12–16 of gestation. At 6, 12, 24 and 48 h post‐injection one pregnant rat from each gestational stage was anesthetized, the embryos were removed, fixed and processed for embedding in paraplast or epon‐araldite. Transverse sections from embryos killed at 6 h revealed extensive necrosis throughout the neuroepithelium in accordance with the temporal‐spatial patterns of neurogenesis. At this dose level the post‐mitotic neuroblasts appeared unaffected. Regeneration of the damaged neural tissue as defined by the restoration of the neuroepithelial cell layer and removal of necrotic debris proceeded quickly, and within 48 h a near‐normal cytoarchitecture was observed. The embryonic age at time of ENU injection had no apparent influence on the actual sequence of tissue repair in the spinal cords although the events were slightly delayed within embryos exposed to ENU on days 12 or 13 of gestation.
A genetic taxonomy of hyperkinesis in the dog
Authors: Ginsburg Benson E. , Becker Robert E. , Trattner Alice , Bareggi Silvio R. 
Published: April 2003

AbstractAmong children who have difficulty inhibiting gross motor activity and focusing on learning tasks requiring them to do this, some are helped by central nervous system stimulants such as amphetamine, while others with identical symptoms are not. Similar variations in response to pharmacological agents are seen in other syndromes, suggesting that multiple biological mechanisms are involved and that these are selectively responsive to pharmacological manipulations. Diagnosis, therefore, involves not only the identification of the condition, but knowledge of the mechanisms by means of which it can be brought about, as well as some means of identifying these. Since such variations often have a genetic basis, their identification and characterization by genetic and pharmacogenetic approaches permit the investigator to avoid confounding biological variation with statistical error and, ultimately, to suit the treatment to the mechanism when there is no final common path permitting a single intervention specific to a given syndrome. Because such researches are difficult with human patients, we have been attempting to identify animal models with analogous symptoms to human conditions and homologous mechanisms underlying these. The present paper is one in a series describing a dog model for hyperkinesis.
Myelinogenic cycle and myelination status of the brain of the catfish, Heteropneustes fossilis
Authors: Yusuf Harun K.M. , Islam M. Sayedul 
Published: April 2003

AbstractThe lipid composition of the brain of the catfish, Heteropneustes fossilis (Bloch) was studied over the age period of 2–12 months, during which time the body weight increased from 2.5 to 33 g. The brain weight increased from 28 to 84 mg between 2 and 9 months of age, with a further increase of only 7 mg during the following three months. The concentration of cholesterol increased slowly up to 5 months of age, from which time the concentration began to increase rapidly and attained adult values at 8 months. The concentration of total lipid‐P increased steadily up to the age of 7 months and remained almost constant thereafter. In contrast, there was very little increase in the concentration of the galactolipids (cerebroside + sulphatide) until month 5, after which the concentration increased rapidly to reach the adult level at 8 months of age. The concentration of cholesterol esters decreased during development; however, there occurred a transient rise at 5 months of age, which continued up to 8 months. These data indicate that the period between months 5 and 8 is one of active myelination in the brain of this species. The mole ratio of cholesterol, phospholipids, and galactolipids in the adult fish brain was 31:53:1, much higher than that in adult mammalian brain. Moreover, within the phospholipids, ethanolamine phosphoglyceride comprised < 10%, as against the corresponding value in the mammals of about 40%. These data therefore suggest a low level of myelination in the brain of catfish, as compared to that in higher species.
Morphological maturation and survival of chicken and rat embryonic neurons on different culture substrata
Authors: Faltin J. , Lodin Z. , Hartman J. , Foucaud B. , Gombos G. , Sensenbrenner M. 
Published: April 2003

AbstractNeuronal cells from chicken and rat embryonic cerebral hemispheres were plated at a low cell concentration and cultured either on collagen or on a supporting continuous glial layer for periods of up to 21 days. The glial layer was either homologous or heterologous with regard to the animal species; the survival and maturation of the neuronal cells in these different conditions were investigated by light and electron microscopy.Neuronal cells cultured on collagen formed aggregates similar to those formed by neuronal cells plated at high cell density as described in a previous paper; a few aggregated neurons formed processes after 24 h and, only after 48 h of culture, more fibres had developed; the majority of the cells progressively degenerated between days 7 and 21 of culture. In contrast to this, neuronal cells cultured on a supporting glial layer, whether homologous or heterologous, progressively differentiated: neuronal perikarya remained well separated from each other and many processes were already formed after 24 h; later on, networks of fibres developed. At the electron microscopic level, microtubules and neurofilaments were present at a high density in the cells and fibres; immature synapses could be found, but infrequently. Differentiated cells were represented mostly by neurons; oligodendroglial cells were absent, and myelinated fibres could not be detected.The highest positive effect on the maturation and survival of neuronal cells was observed in the presence of a layer of glial cells from the same species. These results emphasize the essential role of glial cells for the neuronal maturation in the absence of contact between neuroblasts.
Delayed development of GFA immunoreactivity in the parietal cortex during thyroid hormone deficiency
Authors: Granholm A.‐Ch , Dahl D. , Siegel R. A. , Björklund H. , Seiger Å 
Published: April 2003

AbstractThe influence of neonatal hypothyroidism on the development of immunoreactivity to glial fibrillary acidic protein (GFA) was studied in parietal cortex of rats treated from birth with the antithyroid agent propylthiouracil (PTU) for 3 or 8 weeks. Density of GFA immunoreactivity was evaluated in cryostate sections reacted with an antiserum specific for GFA. Three weeks postnatally, the density of GFA‐immunoreactive structures in the cortical layers II‐V was 70% lower in PTU‐treated animals than in controls injected with the solvent. This marked difference between the groups was, however, not seen in either the molecular layer, layer VI or white matter. The inhibited development of GFA immunoreactivity was not persistent in animals treated with PTU for 8 weeks continuously. Plasma from animals treated with PTU for 1,2,3 and 8 weeks was collected and the TSH level in each group compared with samples from age‐matched controls and newborn pups. The treatment with PTU resulted in a more than 10‐fold increase in TSH level after 1 week of injections. In longterm groups of 8 weeks, the TSH level decreased in the PTU‐treated animals, but stayed considerably higher than control values throughout the experiments.The results described in the present paper indicate a thyroid hormone dependent development of the GFA immunoreactivity in cortex cerebri astrocytes.
The expression of concanavalin a binding glycoproteins during the development of cerebellar granule neurons in vitro
Authors: Webb Michael , Gallo Vittorio , Schneider Annerose , Balazs Robert 
Published: April 2003

AbstractWe present data on the expression of Concanavalin A (ConA) binding glycoproteins by granule cell enriched cultures derived from 8 day postnatal rat cerebellum. Time course studies were conducted over a 12 day culture period. ConA binding glycoproteins were localized on the cell bodies and fibres of the granule neurons using fluorescence microscopy. The fluorescence intensity increased between 4 and 12 days in vitro. Quantitative studies on the capacity of live cells to bind 125I‐iodinated ConA showed that there was a significant increase in the amount of lectin bound between 4 and 8 days in vitro. However, in contrast to previous results on the developing cerebellum in vivo [Zanetta et al. (1978) Brain Res.142, 301–319.], there was no decline in binding capacity after 8 days in culture. Glycoproteins expressed by these cells were analysed by staining SDS polyacrylamide gels with [125I]ConA. A large number of lectin binding proteins were observed which spread over a wide range of molecular weights. Only minor changes were detected in the profile of [125I]ConA binding glycoproteins with the maturation of the cells in culture. The comparison of the findings on granule cells developing in culture and in vivo suggested that an interaction between granule cell axons and their normal target neurons is involved in the regulation of the ConA binding protein content in the cerebellum.