bluuebunny/crossref_metadata_2025 huggingface dataset:
Early Neural Correlates of Conscious Somatosensory Perception
Authors: Palva Satu , Linkenkaer-Hansen Klaus , Näätänen Risto , Palva J. Matias
Published: May 2005

The cortical processing of consciously perceived and unperceived somatosensory stimuli is thought to be identical during the first 100-120 ms after stimulus onset. Thereafter, the electrophysiological correlates of conscious perception have been shown to be reflected in the N1 component of the evoked response as well as in later (>200 ms) nonstimulus-locked γ-band (28-50 Hz) oscillatory activity. To evaluate more specifically the time course and correlation of neuronal oscillations with conscious perception, we recorded neuromagnetic responses to threshold-intensity somatosensory stimuli. We show here that cortical broadband activities phase locked to the subsequently perceived stimuli in somatosensory, frontal, and parietal regions as early as 30-70 ms from stimulus onset, whereas the phase locking to the unperceived stimuli was weak and primarily restricted to somatosensory regions. Such stimulus locking also preceded the perceived stimuli, indicating that the phase of ongoing cortical activities biases subsequent perception. Furthermore, the data show that the stimulus locking was present in the θ- (4-8 Hz), α- (8-14 Hz), β- (14-28 Hz), and γ- (28-40 Hz) frequency bands, of which the widespread α-band component was dominant for the consciously perceived stimuli but virtually unobservable for the unperceived stimuli. Our results show that the neural correlates of conscious perception are already found during the earliest stages of cortical processing from 30 to 150 ms after stimulus onset and suggest that α-frequency-band oscillations have a role in the neural mechanisms of sensory awareness.
Emx2andPax6Function in Cooperation withOtx2andOtx1to Develop Caudal Forebrain Primordium That Includes Future Archipallium
Authors: Kimura Jun , Suda Yoko , Kurokawa Daisuke , Hossain Zakir M. , Nakamura Miwa , Takahashi Maiko , Hara Akemi , Aizawa Shinichi
Published: May 2005

One of the central issues in developmental neurobiology is how the forebrain is organized ontogenetically. The traditional view is that the anterior neuroectoderm first develops into mesencephalic and prosencephalic vesicles; the latter vesicle subsequently develops into the diencephalon and secondary prosencephalon, of which dorsal parts protrude to generate the telencephalon. The diencephalon yields the pretectum, thalamus, and prethalamus, and the telencephalon produces the archipallium, neopallium, and ganglionic eminences. By identifying cell descendants that once expressedEmx2with use of theCreknock-in mutant into theEmx2locus and analyzing phenotypes of double mutants betweenEmx2andOtx2/Otx1and betweenEmx2andPax6, we propose that at the 3-6 somite stage, the anterior neuroectoderm develops into three primordia: midbrain, caudal forebrain, and rostral forebrain. The caudal forebrain primordium generates not only the pretectum, thalamus, and prethalamus but also the archipallium, cortical hem, choroid plexus, choroidal roof, and eminentia thalami. The primordium corresponds to theEmx2- orPax6-positive region at the 3-6 somite stage that most probably does not include the future neopallium or commissural plate.Otx2andOtx1that are expressed in the entire future forebrain and midbrain cooperate with thisEmx2andPax6expression in the development of the caudal forebrain primordium;Emx2andPax6functions are redundant. In the embryonic day 9.5Emx2-/-Pax6-/-double mutant, the caudal forebrain remained unspecified and subsequently transformed into tectum in a mirror image of the endogenous one.
Distinct Cortical Pathways for Processing Tool versus Animal Sounds
Authors: Lewis James W. , Brefczynski Julie A. , Phinney Raymond E. , Janik John J. , DeYoe Edgar A.
Published: May 2005

Human listeners can effortlessly categorize a wide range of environmental sounds. Whereas categorizing visual object classes (e.g., faces, tools, houses, etc.) preferentially activates different regions of visually sensitive cortex, it is not known whether the auditory system exhibits a similar organization for different types or categories of complex sounds outside of human speech. Using functional magnetic resonance imaging, we show that hearing and correctly or incorrectly categorizing animal vocalizations (as opposed to hand-manipulated tool sounds) preferentially activated middle portions of the left and right superior temporal gyri (mSTG). On average, the vocalization sounds had much greater harmonic and phase-coupling content (acoustically similar to human speech sounds), which may represent some of the signal attributes that preferentially activate the mSTG regions. In contrast, correctly categorized tool sounds (and even animal sounds that were miscategorized as being tool-related sounds) preferentially activated a widespread, predominantly left hemisphere cortical “mirror network.” This network directly overlapped substantial portions of motor-related cortices that were independently activated when participants pantomimed tool manipulations with their right (dominant) hand. These data suggest that the recognition processing for some sounds involves a causal reasoning mechanism (a high-level auditory “how” pathway), automatically evoked when attending to hand-manipulated tool sounds, that effectively associates the dynamic motor actions likely to have produced the sound(s).
Hypocretin and Nicotine Excite the Same Thalamocortical Synapses in Prefrontal Cortex: Correlation with Improved Attention in Rat
Authors: Lambe Evelyn K. , Olausson Peter , Horst Nicole K. , Taylor Jane R. , Aghajanian George K.
Published: May 2005

Thalamic projections to prefrontal cortex are important for executive aspects of attention. Using two-photon imaging in prefrontal brain slices, we show that nicotine and the wakefulness neuropeptide hypocretin (orexin) excite the same identified synapses of the thalamocortical arousal pathway within the prefrontal cortex. Although it is known that attention can be improved when nicotine is infused directly into the midlayer of the prefrontal cortex in the rat, the effects of hypocretin on attention are not known. The overlap in thalamocortical synapses excited by hypocretin and nicotine and the lack of direct postsynaptic effects prompted us to compare their effects on a sustained and divided attention task in the rat. Similar to nicotine, infusions of hypocretin-2 peptide into the prefrontal cortex significantly improved accuracy under high attentional demand without effects on other performance measures. We show for the first time that hypocretin can improve attentional processes relevant to executive functions of the prefrontal cortex.
Specific Functions of Synaptically Localized Potassium Channels in Synaptic Transmission at the Neocortical GABAergic Fast-Spiking Cell Synapse
Authors: Goldberg Ethan M. , Watanabe Shigeo , Chang Su Ying , Joho Rolf H. , Huang Z. Josh , Leonard Christopher S. , Rudy Bernardo
Published: May 2005

Potassium (K+) channel subunits of the Kv3 subfamily (Kv3.1-Kv3.4) display a positively shifted voltage dependence of activation and fast activation/deactivation kinetics when compared with other voltage-gated K+channels, features that confer on Kv3 channels the ability to accelerate the repolarization of the action potential (AP) efficiently and specifically. In the cortex, the Kv3.1 and Kv3.2 proteins are expressed prominently in a subset of GABAergic interneurons known as fast-spiking (FS) cells and in fact are a significant determinant of the fast-spiking discharge pattern. However, in addition to expression at FS cell somata, Kv3.1 and Kv3.2 proteins also are expressed prominently at FS cell terminals, suggesting roles for Kv3 channels in neurotransmitter release. We investigated the effect of 1.0 mmtetraethylammonium (TEA; which blocks Kv3 channels) on inhibitory synaptic currents recorded in layer II/III neocortical pyramidal cells. Spike-evoked GABA release by FS cells was enhanced nearly twofold by 1.0 mmTEA, with a decrease in the paired pulse ratio (PPR), effects not reproduced by blockade of the non-Kv3 subfamily K+channels also blocked by low concentrations of TEA. Moreover, in Kv3.1/Kv3.2 double knock-out (DKO) mice, the large effects of TEA were absent, spike-evoked GABA release was larger, and the PPR was lower than in wild-type mice. Together, these results suggest specific roles for Kv3 channels at FS cell terminals that are distinct from those of Kv1 and large-conductance Ca2+-activated K+channels (also present at the FS cell synapse). We propose that at FS cell terminals synaptically localized Kv3 channels keep APs brief, limiting Ca2+influx and hence release probability, thereby influencing synaptic depression at a synapse designed for sustained high-frequency synaptic transmission.
Developmental Changes in AMPA and Kainate Receptor-Mediated Quantal Transmission at Thalamocortical Synapses in the Barrel Cortex
Authors: Bannister Neil J. , Benke Timothy A. , Mellor Jack , Scott Helen , Gürdal Esra , Crabtree John W. , Isaac John T. R.
Published: May 2005

During the first week of life, there is a shift from kainate to AMPA receptor-mediated thalamocortical transmission in layer IV barrel cortex. However, the mechanisms underlying this change and the differential properties of AMPA and kainate receptor-mediated transmission remain essentially unexplored. To investigate this, we studied the quantal properties of AMPA and kainate receptor-mediated transmission using strontium-evoked miniature EPSCs. AMPA and kainate receptor-mediated transmission exhibited very different quantal properties but were never coactivated by a single quantum of transmitter, indicating complete segregation to different synapses within the thalamocortical input. Nonstationary fluctuation analysis showed that synaptic AMPA receptors exhibited a range of single-channel conductance (γ) and a strong negative correlation between γ and functional channel number, indicating that these two parameters are reciprocally regulated at thalamocortical synapses. We obtained the first estimate of γ for synaptic kainate receptors (<2 pS), and this primarily accounted for the small quantal size of kainate receptor-mediated transmission. Developmentally, the quantal contribution to transmission of AMPA receptors increased and that of kainate receptors decreased. No changes in AMPA or kainate quantal amplitude or in AMPA receptor γ were observed, demonstrating that the developmental change was attributable to a decrease in the number of kainate synapses and an increase in the number of AMPA synapses contributing to transmission. Therefore, we demonstrate fundamental differences in the quantal properties for these two types of synapse. Thus, the developmental switch in transmission will dramatically alter information transfer at thalamocortical inputs to layer IV.
Rhodopsin Formation inDrosophilaIs Dependent on the PINTA Retinoid-Binding Protein
Authors: Wang Tao , Montell Craig
Published: May 2005

Retinoids participate in many essential processes including the initial event in photoreception. 11-cis-retinal binds to opsin and undergoes a light-driven isomerization to all-trans-retinal. In mammals, the all-trans-retinal is converted to vitamin A (all-trans-retinol) and is transported to the retinal pigment epithelium (RPE), where along with dietary vitamin A, it is converted into 11-cis-retinal. Although this cycle has been studied extensively in mammals, many questions remain, including the specific roles of retinoid-binding proteins. Here, we establish theDrosophilavisual system as a genetic model for characterizing retinoid-binding proteins. In a genetic screen for mutations that affect the biosynthesis of rhodopsin, we identified a novel CRAL-TRIO domain protein, prolonged depolarization afterpotential is not apparent (PINTA), which binds to all-trans-retinol. We demonstrate that PINTA functions subsequent to the production of vitamin A and is expressed and required in the retinal pigment cells. These results represent the first genetic evidence for a role for the retinal pigment cells in the visual response. Moreover, our data implicateDrosophilaretinal pigment cells as functioning in the conversion of dietary all-trans-retinol to 11-cis-retinal and suggest that these cells are the closest invertebrate equivalent to the RPE.
Presynaptic Ca2+Requirements and Developmental Regulation of Posttetanic Potentiation at the Calyx of Held
Authors: Korogod Natalya , Lou Xuelin , Schneggenburger Ralf
Published: May 2005

Large excitatory synapses in the auditory system, such as the calyx of Held, faithfully transmit trains of action potentials up to a frequency of a few hundred hertz, and these synapses are thought to display a limited repertoire of synaptic plasticity. Here, we show that brief trains of 100 Hz stimulation induce posttetanic potentiation (PTP) of transmitter release at the calyx of Held. In young rats [postnatal day 4 (P4) to P6], PTP could be induced with shorter 100 Hz trains compared with older age groups (P8-P10 and P12-P14), but the maximal amount of PTP was similar, with ∼200% of control EPSC amplitude. The size of the readily releasable pool of vesicles was not increased significantly during PTP. Bath application of the membrane-permeable Ca2+chelator EGTA-AM suppressed PTP, indicating a role for presynaptic Ca2+in PTP at the calyx of Held. Presynaptic Ca2+imaging showed that the intracellular Ca2+concentration, [Ca2+]i, was increased by 40-120 nmat the peak of PTP, and this “residual” [Ca2+]idecayed in parallel with PTP, with time constants in the range of 10-60 s. During whole-cell recording of the presynaptic calyx of Held, PTP was absent, and the decay of residual [Ca2+]iwas strongly accelerated. The data show that the calyx of Held expresses a mechanism of transmitter release potentiation in which a small, sustained elevation of basal [Ca2+]iincreases the transmitter release probability after trains of high-frequency stimulation.
Sodium Currents in Medullary Neurons Isolated from the Pre-Bötzinger Complex Region
Authors: Ptak Krzysztof , Zummo Greer G. , Alheid George F. , Tkatch Tatiana , Surmeier D. James , McCrimmon Donald R.
Published: May 2005

The pre-Bötzinger complex (preBötC) in the ventrolateral medulla contains interneurons important for respiratory rhythm generation. Voltage-dependent sodium channels mediate transient current (INaT), underlying action potentials, and persistent current (INaP), contributing to repetitive firing, pacemaker properties, and the amplification of synaptic inputs. Voltage-clamp studies of the biophysical properties of these sodium currents were conducted on acutely dissociated preBötC region neurons. Reverse transcription-PCR demonstrated the presence of mRNA for Nav1.1, Nav1.2, and Nav1.6 α-subunits in individual neurons. A TTX-sensitiveINaPwas evoked in all tested neurons by ramp depolarization from -80 to 0 mV. Including a constant in the Boltzmann equation for inactivation by estimating the steady-state fraction of Na+channels available for inactivation allowed prediction of a window current that did not decay to 0 at voltages positive to -20 mV and closely matched the measuredINaP. Riluzole (3 μm), a putativeINaPantagonist, reduced bothINaPandINaTand produced a hyperpolarizing shift in the voltage dependence of steady-state inactivation. The latter decreased the predicted window current by an amount equivalent to the decrease inINaP. Riluzole also decreased the inactivation time constant at potentials in which the peak window/persistent currents are generated. Together, these findings imply thatINaPandINaTarise from the same channels and that a simple modification of the Hodgkin-Huxley model can satisfactorily account for both currents. In the rostral ventral respiratory group (immediately caudal to preBötC),INaPwas also detected, but peak conductance, current density, and input resistance were smaller than in preBötC region cells.
Environmental Enrichment Mitigates Cognitive Deficits in a Mouse Model of Alzheimer's Disease
Authors: Jankowsky Joanna L. , Melnikova Tatiana , Fadale Daniel J. , Xu Guilian M. , Slunt Hilda H. , Gonzales Victoria , Younkin Linda H. , Younkin Steven G. , Borchelt David R. , Savonenko Alena V.
Published: May 2005

Epidemiological studies suggest that individuals with greater education or more cognitively demanding occupations have diminished risk of developing dementia. We wanted to test whether this effect could be recapitulated in rodents using environmental enrichment, a paradigm well documented to attenuate behavioral deficits induced by various pathological insults. Here, we demonstrate that learning and memory deficits observed in a transgenic mouse model of Alzheimer's disease can be ameliorated by enrichment. Female transgenic mice overexpressing amyloid precursor protein and/or presenilin-1 and nontransgenic controls were placed into enriched or standard cages at 2 months of age and tested for cognitive behavior after 6 months of differential housing. Enrichment significantly improved performance of all genotypes in the radial water maze and in the classic and repeated-reversal versions of the Morris water maze. However, enrichment did not benefit all genotypes equally. Mice overproducing amyloid-β (Aβ), particularly those with amyloid deposits, showed weaker memory for the platform location in the classic Morris water maze and learned new platform positions in the repeated-reversals task less quickly than their nontransgenic cagemates. Nonetheless, enrichment normalized the performance of Aβ-overproducing mice to the level of standard-housed nontransgenic mice. Moreover, this functional preservation occurred despite increased neuritic plaque burden in the hippocampus of double-transgenic animals and elevated steady-state Aβ levels, because both endogenous and transgene-derived Aβ are increased in enriched animals. These results demonstrate that the generation of Aβin vivoand its impact on the function of the nervous system can be strongly modulated by environmental factors.
Pincher-Mediated Macroendocytosis Underlies Retrograde Signaling by Neurotrophin Receptors
Authors: Valdez Gregorio , Akmentin Wendy , Philippidou Polyxeni , Kuruvilla Rejji , Ginty David D. , Halegoua Simon
Published: May 2005

Retrograde signaling by neurotrophins is crucial for regulating neuronal phenotype and survival. The mechanism responsible for retrograde signaling has been elusive, because the molecular entities that propagate Trk receptor tyrosine kinase signals from the nerve terminal to the soma have not been defined. Here, we show that the membrane trafficking protein Pincher defines the primary pathway responsible for neurotrophin retrograde signaling in neurons. By both immunofluorescence confocal and immunoelectron microscopy, we find that Pincher mediates the formation of newly identified clathrin-independent macroendosomes for Trk receptors in soma, axons, and dendrites. Trk macroendosomes are derived from plasma membrane ruffles and subsequently processed to multivesicular bodies. Pincher similarly mediates macroendocytosis for NGF (TrkA) and BDNF (TrkB) in both peripheral (sympathetic) and central (hippocampal) neurons. A unique feature of Pincher-Trk endosomes is refractoriness to lysosomal degradation, which ensures persistent signaling through a critical effector of retrograde survival signaling, Erk5 (extracellular signal-regulated kinase 5). Using sympathetic neurons grown in chamber cultures, we find that block of Pincher function, which prevents Trk macroendosome formation, eliminates retrogradely signaled neuronal survival. Pincher is the first distinguishing molecular component of a novel mechanistic pathway for endosomal signaling in neurons.
Antioxidants: Science, Technology, and Applications
Authors: Wanasundara P. K. J. P. D. , Shahidi F.
Published: May 2005

Antioxidants are compounds that are employed to enhance shelf life and preserve the quality of fats and oils and lipid‐containing foods by suppressing oxidation reactions of their unsaturated components. These compounds could be naturally present, deliberately added, or generated during processing. Antioxidants are needed in small quantities to participate or interfere in the lipid autoxidation reaction cascade via various mechanisms. They should not impart any undesirable characters to the food, they should be stable, and they should be nontoxic. Application of these antioxidation differs depending on the nature of the food, conditions of intended processing, and storage. However, antioxidants that are deliberately added to foods are thoroughly scrutinized for their safety and toxicology aspects. Their usage in food is regulated under different legislatures in various countries. This chapter examines the purpose of antioxidant use, chemistry of antioxidant activity, and natural synthetic compounds that exert antioxidative activity in foods, as well as the relevant technological, toxicological, and regulatory considerations.
Peanut Oil
Authors: Pattee Harold E.
Published: May 2005

This chapter provides a background on the origin of the peanut, spreading of the peanut from its source of origin, and evolution of the peanut oil industry. A 30‐year summation of world peanut production, peanut oil and meal production, and utilization of these products provides an overview of the changes in sources of production and consumption that has occurred within this time period across the 11 major peanut producing countries. Over the last 30 years (1972–2002), there has been a 22% increase in the area harvested, a 51% increase in yield, and a 92% increase in total peanut oil consumption. Advances in oil extraction procedures are presented, as are advances in the development of the high oleic peanut oil sources. Compositional aspects of peanut oil are reviewed. Other subject areas are the use of peanut oil as a seed protectant, dietary aspects, and allergenicity.
Urokinase activity in the developing avian heart: A spatial and temporal analysis
Authors: McGuire Paul G. , Orkin Roslyn W.
Published: May 2005

Early events in cardiac morphogenesis are characterized by cell migrations and extensive tissue remodeling. This study was undertaken to determine the levels of urokinase in specific regions of the avian heart during early stages of development. Urokinase has previously been shown to be involved in both cell migration and matrix turnover. Elevated urokinase activity and mRNA levels were assocated with the onset of ventricular trabeculation and mesenchymal cell migration in the endocardial cushion tissues. Urokinase was localized by immunostaining to the endocardial and mesenchymal cells of the developing atrioventricular canal (AVC) and outflow tract (OFT) as well as with evaginating ventricular endocardium. No immunoreactivity was seen associated directly with the martix, suggesting that the enzyme remained mostly cell associated, a finding which was confirmed in isolated endocardial cells. Results from this study suggest a role for urokinase in the tissue remodeling and cell migration that occurs during the early stages of cardiac morphogenesis.
Family resemblance for cranio‐facial measurements in Velanti Brahmins from Andhra Pradesh, India
Authors: Poosha D. V. R. , Byard P. J. , Satyanarayana M. , Rice J. P. , Rao D. C.
Published: May 2005

Maximum likelihood estimates of familial correlations are presented for 12 cranio‐facial measurements taken on 399 nuclear families from Southern India. Marital resemblance is significantly different from zero for head circumference, head breadth, minimum frontal breadth, bizygomatic breadth, total facial height, and nasal height, but not for bigonial breadth, nose breadth, nose depth, or ear dimensions. All other familial correlations are significantly greater than zero except for the father‐daughter correlation for nasal depth. Path analysis with a TAU transmission model with sex effects reveals that family resemblance for head circumference, head length, bigonial breadth, total facial height, and nasal height, but not for bigonial breadth, nose breadth, nose depth, or ear dimensions. All other familial correlations are significantly greater than zero except for the father‐daughter correlation for nasal depth. Path analysis with a TAU transmission model with sex effects breadth, and sex effects in transmission were found for head breadth and nose dimensions. Sex effects in this sample may be due to the fact that different anthropometrists were used for male and female subjects.
The time and energy expenditure of indigenous women horticulturalists in the Northwest Amazon
Authors: Dufour Darna L.
Published: May 2005

The energy cost of subsistence activities and the daily time and energy budgets of Tatuyo women were assessed as part of a village energy flow study. The Tatuyo are swidden horticulturalists relying on bitter manioc (Manihot esculenta) as a staple crop. Except for the actual felling of new gardens, women are responsible for most of the horticultural work and food preparation. Time budgets were assessed using 24‐hour activity diaries. Rates of energy expenditure in typical activities were measured by indirect calorimetry using a Max‐Planck respirometer. Daily energy expenditure was calculated using these rates in conjunction with the activity diaries. Rates of energy expenditure in standard activities were moderate and broadly comparable to published values for other populations living in tropical environments. The mean daily energy expenditure was 2,133 kcal (8.9 MJ). This value is similar to that reported for other subsistence horticulturalists and close to the FAO recommendation for energy intake for moderately active individuals.
Population structure in the Connecticut Valley. I. Marital migration
Authors: Swedlund A. C. , Jorde L. B. , Mielke J. H.
Published: May 2005

This study reports on an analysis of marital migration among 12 communities in the Connecticut River Valley of Massachusetts during the years 1790–1849. Genetic inferences are drawn, and the requisite assumptions considered. The effect of geographic distance on genetic kinship is predicted using Malécot's isolation‐by‐distance model. The resulting estimates are discussed in terms of geographic and historical factors. The configuration of communities as predicted by kinship values approximates closely their actual geographic locations. Estimated genetic heterogeneity was low for the historical Connecticut Valley population, and community isolation breaks down rapidly over time. The region thus assumes its place among a number of sedentary, agricultural populations for which the isolation‐by‐distance model provides an adequate representation. A regression analysis which includes variables in addition to distance indicates that historical and economic factors contribute some additional explanatory power to the distribution of mating frequencies.
Dental microwear and mechanisms in early hominids from Laetoli and Hadar
Authors: Puech Pierre‐FrançOis , Albertini Henri
Published: May 2005

The dentition of early hominids from Laetoli and Hadar provide evidence of “incisal stripping” and a shear‐grinding action for C/P3 complex through microscopic examination of wear facets on dental crowns. This masticatory pattern of dental wear resembles that of Papio papio and suggests behavioral analogies between early hominids and Papio.
Multinucleate ameloblasts in the rat incisor
Authors: Smith C. E. , Warshawsky H.
Published: May 2005

Cytological examination of the rat incisor enamel organ with the light and electron microscope revealed a small number of ameloblasts which contained two and sometimes three or more nuclei per cell. A multinucleate ameloblast usually contained two vertically apposed nuclei situated near the base of the cell. A narrow cytoplasmic band was interposed between adjacent nuclear envelopes. The apical nucleus was often the more elongated of the two nuclei and it fitted a convexity or a concavity within the more basally positioned nucleus. In serial sections examined with the electron microscope no connections were observed between the nuclei. In animals injected with 3H‐thymidine instances of multinucleate ameloblasts were found within the advancing front of labeling where only one of the nuclei contained label. Finally, quantitative analysis by nuclear counting established that multinucleate ameloblasts were 60 times more frequent within the maturation zone as in the secretory zone of amelogenesis. As well, the numbers of multinucleate ameloblasts increased progressively in the course of the maturation stage. It was concluded that multinucleate ameloblasts increase with cell age and likely arise by the process of cell fusion.
The free autografting of entire limb muscles in the cat: Morphology
Authors: Mufti Shahzad A. , Carlson Bruce M. , Maxwell Leo C. , Faulkner John A.
Published: May 2005

Normal or pre‐denervated extensor digitorum longus (EDL) muscles were successfully grafted in place of the contralateral EDL muscles in cats. Histological preparations of 57 grafts were examined at intervals from 4 to 170 days after transplantation. The morphological sequence of events in a cat muscle graft is similar to that in the rat except that the time course of regeneration is considerably slower. Surviving original muscle fibers form a thin rim at the periphery of the graft. Beneath this rim, the original muscle fibers undergo fragmentation, starting near the periphery and progressing toward the center. Regenerating muscle fibers take the place of the degenerated muscle fibers. In pre‐denervated grafts, the last of the original muscle fibers in the center of the graft have broken down by 41 days whereas in normal muscle grafts the original muscle fibers in the central region persist until 50 days. The main difference between grafts of normal and pre‐denervated muscles is the rate of breakdown of the original muscle fibers. Long term grafts of both groups are morphologically very similar.
In vitro activation of adenylate cyclase by parathyroid hormone and calcitonin during normal and hydrocortisoneinduced cleft palate development in the golden hamster
Authors: Waterman Robert Earle , Palmer Gene C. , Palmer S. Jo , Palmer Susan M.
Published: May 2005

An adenylate cyclase highly responsive to stimulation by parathyroid hormone (PTH) and calcitonin (CT) in vitro was observed at certain times during normal prenatal development of the maxillary‐palatal process complex in the golden hamster. Responses of the enzyme to these hormones were barely detectible at the earliest stage examined (day 10/20). The enzyme became extremely sensitive to activation by either hormone during the time of rapid growth of the palatal processes (day 11/20) and during fusion between the palatal processes (day 12/20). Thereafter, responses were greatly diminished and little or no activation of adenylate cyclase was observed until birth. Adenylate cyclase from fetuses in which clefts of the secondary palate were induced by maternal treatment with hydrocortisone (50 mg) on day 11/3 also displayed an enhanced sensitivity to PTH and CT on day 11/20, but the sensitivity of the enzyme was greatly decreased from that in normal animals during the normal time of palatal fusion (day 12/20) and was barely detectible or absent at the remaining time periods studied (days 13/20 and 14/20). Addition of hydrocortisone to the incubation mixture, either separately or in combination with PTH or CT, did not remarkably affect the response of adenylate cyclase to these hormones. Moreover, the appearance of the adenylate cyclase sensitive to hormonal activation did not result from changes in phosphodiesterase activity during palatal maturation.
Putative steroidogenic cells associated with the ductuli efferentes of the ground squirrel (Citellus lateralis)
Authors: Pudney Jeffrey , Fawcett Don W.
Published: May 2005

During a study on the fine structure of different regions of the reproductive tract of the ground squirrel, Citellus lateralis, cells possessing cytological features associated with steroid production were observed among the ductuli efferentes. Comparison of the morphology of these cells with that of Leydig and adrenocortical cells, demonstrated that they resembled Leydig cells in many anatomical details. Further evidence for the similarity of the cells associated with the ductuli efferentes to Leydig cells emerged during sexual regression, when both types of cells underwent the same regressive changes in organization and morphology. This suggests that the cells present among the ductuli efferentes are active in the synthesis of androgenic hormones, and possibly play a role in the endocrine control of reproduction in this species of ground squirrel.
Glycoprotein containing vesicles in the surface epithelial cells of the ascending colon of the rat
Authors: Michaels John E.
Published: May 2005

Recently, radioautographic studies have shown that cell coat glycoproteins are transported to the cell surface by vesicles both in the amoeba (Flickinger, '75) and in the epithelial cells of the ascending colon of the mouse (Michaels and Leblond, 1976). In the current morphological and cytochemical study of the surface epithelial cells of the rat ascending colon, it is shown that filamentous material, resembling the cell coat, is contained in saccules toward the mature face of the Golgi apparatus and in vesicles close to the apparatus and near the terminal web. The vesicles are limited by a unit membrane composed of asymmetric osmiophilic leaflets and similar to the plasma membrane. When stained by the periodic acid‐chromic acid‐silver methenamine technique, silver was precipitated on the cell components containing the filamentous material indicating the presence of glycoproteins. Narrow invaginations from the cell surface that may correspond to vesicles undergoing exocytosis were also positive for glycoproteins. The distribution of the filamentous material that was glycoprotein positive parallels the pathway followed by material that had been found to be labeled with a tritiated glycoprotein precursor (3H‐fucose) in the epithelial cells of the ascending colon of the mouse. It is suggested that the system of vesicles in the rat colon cells is acting in a manner similar to the vesicles in the mouse cells to transport cell coat glycoproteins from the Golgi apparatus to the cell surface.
Interactions between rat epididymal epithelium and spermatozoa
Authors: Fornés Miguel W. , De Rosas Juan C.
Published: May 2005

We studied in the rat epididymis the presence of membrane‐bounded vesicles in the stereociliar areas of the epithelial cells. The intimate contact between principal cell stereocilia and luminal spermatozoa was also explored.

The epididymidis of adult male albino rats were fixed with Mollenhauer's fixative via the thoracic aorta; they were removed and the caput and the cauda were separated and fixed for 4 additional hours at 4°C. After fixation, the samples were processed with routine techniques for transmission and scanning electron microscopy.

The study showed membrane‐bounded vesicles in the lumen of the caput and cauda epididymidis. They are present between stereocilia, in the most peripheral regions of the epididymal lumen, and in a stereocilia‐free zone in the apical plasma membrane of the principal cells. The smaller vesicles are located near the apical surface of the latter, and the larger ones are located near the tips of the stereocilia. Their contents are electron lucent in some images and electron dense in others. In several thin sections some of the vesicles are observed to have a stalk. This suggests that the possible mode of production may be an exocytotic process. Some membrane‐bounded vesicles were found to be in contact with the head or the tail of maturating spermatozoa.

Moreover, an intimate contact was found to exist in the epididymidis between the plasma membranes of the spermatozoa and the stereocilia.

These observations seem to suggest two possible mechanisms for sperm‐epididymal cell relations: 1) release of a secretion product via the membrane‐bounded vesicles and 2) direct contact between stereocilia and spermatozoa.
Sectional anatomy of the pelvis in the male rat with ultrasound correlations
Authors: Suzuki Takanori , Takezawa Yutaka , Tamura Yoshimi , Mashimo Tooru , Imai Kyoichi , Yamanaka Hidetoshi , Suzuki Keiji
Published: May 2005

Ten‐week‐old male Wistar rats were used for sectional anatomy and ultrasonic diagnosis of the pelvis. The prostate and the urinary bladder were identified easily on longitudinal section by ultrasound examination. The prostate (ventral, lateral, and dorsal lobes) was located in the midline of the pelvis cavity on transverse sections and the caudal side of the urinary bladder on longitudinal sections. The urinary bladder was positioned at the cranial side of the prostate on longitudinal sections and in the midline of the pelvis cavity on transverse sections. The seminal vesicles were located at right and left positions of the urinary bladder.

Ultrasonic diagnosis was estimated to be useful for experimental studies and we hope that ultrasound techniques may reduce the number of rats used for the treatment of prostate and urinary bladder cancers.
Inflated, dried whole lung specimens
Authors: Oldham Michael J. , Phalen Robert F.
Published: May 2005

A method is described for preparing fully‐inflated whole lung specimens that are suitable for instruction or research purposes. Undamaged lungs are removed from the body and then tracheally cannulated and lavaged with tap water more than 250 times. The treatment also includes rinsing blood from vessels with water. A final filling of the lung with alcohol is optional. The multiply rinsed lung is drained and inflated to 30 cm of H2O pressure with dehumidified air and held at that pressure until the tissue is completely dry. The resulting specimens are light in color and appear to be permanent if stored properly.
Quantitative morphology of the nervous system: Expanding horizons
Authors: Bolender R. P. , Charleston J. , Mottet K. , McCabe J. T.
Published: May 2005

In this review, we show how some of the recent developments in quantitative morphology (QM) are creating exciting new opportunities for studying the structure of the nervous system. We begin with a brief overview of QM, focusing on the problems neurobiologists are likely to encounter when collecting and interpreting data from tissue sections. Many of these problems, which range from selecting a sampling method to learning the latest methods, are being solved by creating a new generation of research tools. We describe several of these new tools and show how they can be used to assemble new quantitative methods for in situ hybridization, immunocytochemistry, and camera lucida drawings. The review includes examples of how QM is being used to study the brain and concludes with a brief discussion of diagnostic pathology and its need for new quantitative approaches.
A morphometric and computer‐assisted three‐dimensional reconstruction study of neural tube formation in chick embryos
Authors: Nagele Robert G. , Bush Kevin T. , Lynch Francis J. , Lee Hsin‐Yi
Published: May 2005

The origin of the driving forces for neural tube formation remains uncertain but is currently thought to involve the participation of microfilament bundles situated in the apical ends of neuroepithelial cells. In the work presented here, we show how morphometric measurements that map local variations in the apical geometry of neuroepithelial cells (especially apical constriction) can provide information on the distribution of motive forces within the neuroepithelium during neural tube formation. When used in combination with computer‐assisted, three‐dimensional reconstruction, it becomes possible to analyze the morphometric data from a dynamic, three‐dimensional perspective. As an example application of this method, we have used morphometry to evaluate the effects of ionomycin on the developing neuroepithelium. Treatment of early (stages 6‐8) chick embryos with 5 μM ionomycin was found to cause rapid bending of the neuroepithelium within 1 min of exposure and a dramatic acceleration of the normal sequence of neural tube formation. Electron microscopy and morphometry revealed that this acceleration was coincident with a marked increase in the local degree of apical constriction of neuroepithelial cells, presumably a consequence of enhanced contractile activity of apical microfilament bundles. This work shows that transient elevation of free calcium levels can accelerate the usualal sequential phases of NT formation. The rapidity of the response (hours of normal development reduced to minutes), increased prominence of apical microfilament bundles, and the enhanced degree of apical constriction strongly support a direct causal role for apical microfilament bundles and apical constriction of neuroepithelial cells in bending of the neuroepithelium.
Hypothalamic dopaminergic neurons in transgenic dwarf mice: Histofluorescence, immunocytochemical, and in situ hybridization studies
Authors: Phelps Carol J. , Carlson Susan , Hurley David L.
Published: May 2005

Spontaneous dwarf mice, in which both growth hormone (GH) and prolactin (PRL) are undetectable, are severely deficient in the PRL‐inhibiting catecholamine dopamine (DA), as well as its synthetic enzyme, tyrosine hydroxy‐lase (TH), in the basal hypothalamus (Phelps et al., Cell Tissue Res., 240:19–25, 1985; Phelps, Brain Res., 416:354–358, 1987). In contrast, transgenically constructed dwarf mice (Behringer et al., Genes Dev., 2:453–461, 1988) show complete ablation of pituitary GH cells, but PRL cells are retained at a level of ≈ 10% of normal. In order to determine the feedback effect of this reduced, rather than absent, PRL on hypothalamic DA neurons, brains of transgenic dwarf mice were examined for catecholamine transmitters by histofluorescence, for the synthetic enzyme TH by immunocytochemistry, and for TH mRNA expression by in situ hybridization. DA histofluorescence in transgenic dwarfs was comparable to that of normal littermate mice in nonpituitary regulating areas (perikarya of zona incerta [A13] of hypothalamus and in midbrain substantia nigra areas [A9]). Arcuate nucleus (A12) DA neurons that inhibit PRL secretion, however, showed dim to absent fluorescence in perikarya and in external median eminence terminals in dwarfs. There were reduced (P < 0.05) numbers of A12 TH‐immunoreactive neurons in transgenic dwarfs, to approximately 60% of those in normal mice. In contrast, TH‐positive neurons in other hypothalamic areas (A13, A14) had average populations equivalent to those in normal mice. Quantification of TH mRNA abundance by in situ hybridization using both image analysis of hybridization over the arcuate nucleus, and grain counts per individual A12 cell in this nucleus, indicated that relative mRNA levels were the same in normal and transgenic dwarfs. The observations indicate that reduction in pituitary PRL is accompanied by defective expression in hypothalamic tuberoinfundibular neurons, which is severe at the DA neurotransmitter level, significant regarding observable TH immunoreactivity, and undetectable with regard to TH mRNA expression. Collectively, the findings suggest that posttranscriptional processes are involved with the mediation of PRL feedback upon hypothalamic neurons. Technically and quantitatively, the report presents the feasibility of simultaneous evaluation of transmitter histofluorescence, synthetic enzyme immunocytochemistry, and mRNA expression in individual animals.
Application of confocal laser scanning microscopy to the deep pineal gland and other neural tissues
Authors: Welsh Marcia G. , Ding Jian Ming , Buggy James , Terracio Louis
Published: May 2005

The study of the deep pineal gland of the Mongolian gerbil and other neuronal tissue from the rat by means of confocal laser scanning microscopy (CLSM) is described. Opical serial sectioning was performed on thick (100–200 μm) sections of the deep pineal gland of the Mongolian gerbil stained immunohis‐tochemically using antisera to S‐antigen and tyrosine hydroxylase (TH). Both dual‐stained and single‐stained material was examined using the fluorochromes fluorescein isothiocyanate (FITC) and Texas Red. High resolution images were obtained showing that pinealocytes have 1–3 processes that extend primarily to other pinealocytes or presumptive pinealocytes. Pinealocytes are located within the deep pineal gland as well as adjacent to the posterior aspect of the medial habenular nuclei. Pinealocyte processes were not seen extending into the habenular nuclei, but rather ended within the deep pineal gland a significant distance from their perikarya. The TH‐immunopositive fibers were distributed throughout the deep pineal gland, often forming “baskets” of fibers around pinealocytes rather than being associated primarily with blood vessels. Other uses of the confocal microscope are demonstrated on rat neural tissue reacted with peroxidase/diaminobenzidine (DAB) immunohistochemistry and FITC fluorescence immunohistochemistry (paraventricular nucleus) as well as Golgi‐stained neuronal tissue (cerebral cortex). The HRP/DAB and Golgi‐stained images were visualized using the reflected image mode of the confocal system. A summary of the advantages of CLSM include the following: (1) the optical sectioning capabilities allow for true three‐dimensional imaging thus aiding in the determination of the three‐dimensional structure of a cell plus cell‐cell associations, (2) intact tissue as well as thick sections can be used without mechanical sectioning artifacts, (3) higher resolution can be obtained due to elimination of out‐of‐focus fluorescence, (4) CLSM requires significantly less time than other three‐dimensional reconstruction techniques, and (5) once computerized, the data can be analyzed or processed in a variety of ways.
Unbiased stereological estimation of the total number of neurons in the subdivisions of the rat hippocampus using the optical fractionator
Authors: West M. J. , Slomianka L. , Gundersen H. J. G.
Published: May 2005

A stereological method for obtaining estimates of the total number of neurons in five major subdivisions of the rat hippocampus is described. The new method, the optical fractionator, combines two recent developments in stereology: a three‐dimensional probe for counting neuronal nuclei, the optical disector, and a systematic uniform sampling scheme, the fractionator. The optical disector results in unbiased estimates of neuron number, i.e., estimates that are free of assumptions about neuron size and shape, are unaffected by lost caps and over‐projection, and approach the true number of neurons in an unlimited manner as the number of samples is increased. The fractionator involves sampling a known fraction of a structural component. In the case of neuron number, a zero dimensional quantity, it provides estimates that are unaffected by shrinkage before, during, and after processing of the tissue. Because the fractionator involves systematic sampling, it also results in highly efficient estimates. Typically only 100–200 neurons must be counted in an animal to obtain a precision that is compatible with experimental studies. The methodology is compared with those used in earlier works involving estimates of neuron number in the rat hippocampus and a number of new stereological methods that have particular relevance to the quantitative study of the structure of the nervous system are briefly described in an appendix.
Ipsilaterally projecting rubrospinal neurons in adult and developing opossums
Authors: Xu Xiao Ming , Martin G. F.
Published: May 2005

We have combined injections of Fast Blue with lesions of the rubrospinal tract rostral and contralateral to them to determine if an ipsilateral rubrospinal projection exists in adult or developing opossums and, if so, to characterize the neurons giving rise to it. Although the results indicate that some rubral neurons project ipsilaterally, they are very few in number. Using quantitative and image analysis techniques, we have shown that 0.6% of the rubral neurons that project to the lumbar cord in adult opossums do so ipsilaterally and that such neurons are comparable in location and size to those that project contralaterally. Similar results were obtained in developing opossums. Our results are discussed in light of rubrospinal development and ongoing experiments related to rubrospinal plasticity.