Locating, quantifying and characterising radiation hazards in contaminated nuclear facilities using a novel passive non-electrical polymer based radiation imaging device.

This paper provides a summary of recent trials which took place at the US Department of Energy Oak Ridge National Laboratory (ORNL) during December 2010. The overall objective for the trials was to demonstrate that a newly developed technology could be used to locate, quantify and characterise the radiological hazards within two separate ORNL hot cells (B and C). The technology used, known as RadBall(®), is a novel, passive, non-electrical polymer based radiation detection device which provides a 3D visualisation of radiation from areas where effective measurements have not been previously possible due to lack of access. This is particularly useful in the nuclear industry prior to the decommissioning of facilities where the quantity, location and type of contamination are often unknown. For hot cell B, the primary objective of demonstrating that the technology could be used to locate, quantify and characterise three radiological sources was met with 100% success. Despite more challenging conditions in hot cell C, two sources were detected and accurately located. To summarise, the technology performed extremely well with regards to detecting and locating radiation sources and, despite the challenging conditions, moderately well when assessing the relative energy and intensity of those sources. Due to the technology's unique deployability, non-electrical nature and its directional awareness the technology shows significant promise for the future characterisation of radiation hazards prior to and during the decommissioning of contaminated nuclear facilities.

Electron probe analysis of calcium transport by small intestine.

Calcium transport in small intestine of rat and chick has been studied at the cellular level using the electron probe X-ray microanalyzer. Tissues were examined directly after removal as well as after incubation in a calcium solution. In both preparations, discrete calcium localizations were found associated with intracellular and extracellular goblet cell mucus. The in vitro preparations showed calcium in transit across the absorptive epithelium in discrete localizations. Although the primary path of transport was along lateral cell borders, some localizations were found in the cytoplasm in a supranuclear position. The effect of vitamin D depletion and repletion was to decrease and increase, respectively, the number of calcium localizations in transit across the epithelium. These results suggest that calcium is transported while in a sequestered form and indicate that goblet cell mucus plays a role in this transport process.

Analysis of muscle protein expression in polyethylene glycol-induced chicken: rat myoblast heterokaryons.

Heterokaryons derived from polyethylene glycol-mediated fusion of myoblasts at different stages of development were used to investigate the transition of cells in the skeletal muscle lineage from the determined to the differentiated state. Heterokaryons were analyzed by immunofluorescence, using rabbit antibodies against the skeletal muscle isoforms of chicken creatine kinase and myosin, and a mouse monoclonal antibody that cross-reacts with chicken and rat skeletal muscle myosin. When cytochalasin B-treated rat L8(E63) myocytes (Konieczny S.F., J. McKay, and J. R. Coleman, 1982, Dev. Biol., 91:11-26) served as the differentiated parental component and chicken limb myoblasts from stage 23-26 or 10-12-d embryos were used as the determined, undifferentiated parental cell, heterokaryons exhibited a progressive extinction of rat skeletal muscle myosin during a 4-6-d culture period, and no precocious expression of chicken differentiated gene products was detected. In the reciprocal experiment, 85-97% of rat myoblast X chicken myocyte heterokaryons ceased expression of chicken skeletal muscle myosin and the M subunit of chicken creatine kinase within 7 d of culture. Extinction was not observed in heterokaryons produced by fusion of differentiated chicken and differentiated rat myocytes and thus is not due to species incompatibility or to the polyethylene glycol treatment itself. The results suggest that, when confronted in a common cytoplasm, the regulatory factors that maintain myoblasts in a proliferating, undifferentiated state are dominant over those that govern expression of differentiated gene products.

Processing of endogenous pre-mRNAs in association with SC-35 domains is gene specific.

Analysis of six endogenous pre-mRNAs demonstrates that localization at the periphery or within splicing factor-rich (SC-35) domains is not restricted to a few unusually abundant pre-mRNAs, but is apparently a more common paradigm of many protein-coding genes. Different genes are preferentially transcribed and their RNAs processed in different compartments relative to SC-35 domains. These differences do not simply correlate with the complexity, nuclear abundance, or position within overall nuclear space. The distribution of spliceosome assembly factor SC-35 did not simply mirror the distribution of individual pre-mRNAs, but rather suggested that individual domains contain both specific pre-mRNA(s) as well as excess splicing factors. This is consistent with a multifunctional compartment, to which some gene loci and their RNAs have access and others do not. Despite similar molar abundance in muscle fiber nuclei, nascent transcript "trees" of highly complex dystrophin RNA are cotranscriptionally spliced outside of SC-35 domains, whereas posttranscriptional "tracks" of more mature myosin heavy chain transcripts overlap domains. Further analyses supported that endogenous pre-mRNAs exhibit distinct structural organization that may reflect not only the expression and complexity of the gene, but also constraints of its chromosomal context and kinetics of its RNA metabolism.

Transcription of the histone H5 gene is not S-phase regulated.

Levels of the tissue-specific linker histone H5 are elevated in mature erythroid cells as compared with levels in dividing cells of the same lineage. We examined levels of H5 mRNA in relation to the cell cycle in early erythroid cells transformed by avian erythroblastosis virus to determine whether the gene for this unusual histone is S-phase regulated. Northern blotting analyses revealed that during the cell cycle steady-state levels of H5 mRNA remained relatively constant in contrast to levels of the major core and H1 mRNAs which increased approximately 15-fold during S phase. In vitro pulse-labeling experiments involving nuclei isolated from synchronized cells at various stages of the cell cycle revealed that transcription of the H5 gene was not initiated at any particular stage of the cell cycle but was constitutive. In contrast, transcription of the H2A gene(s) initiated in early S phase, was present throughout the DNA replicative phase, and was essentially absent in G1 and G2 phases.

Genome-wide expression and response to exposure-based psychological therapy for anxiety disorders.

Exposure-based psychological treatments for anxiety have high efficacy. However, a substantial proportion of patients do not respond to therapy. Research examining the potential biological underpinnings of therapy response is still in its infancy, and most studies have focussed on candidate genes. To our knowledge, this study represents the first investigation of genome-wide expression profiles with respect to treatment outcome. Participants (n=102) with panic disorder or specific phobia received exposure-based cognitive behavioural therapy. Treatment outcome was defined as percentage reduction from baseline in clinician-rated severity of their primary anxiety diagnosis at post treatment and 6 month follow-up. Gene expression was determined from whole blood samples at three time points using the Illumina HT-12v4 BeadChip microarray. Linear regression models tested the association between treatment outcome and changes in gene expression from pre-treatment to post treatment, and pre-treatment to follow-up. Network analysis was conducted using weighted gene co-expression network analysis, and change in the detected modules from pre-treatment to post treatment and follow-up was tested for association with treatment outcome. No changes in gene expression were significantly associated with treatment outcomes when correcting for multiple testing (q<0.05), although a small number of genes showed a suggestive association with treatment outcome (q<0.5, n=20). Network analysis showed no association between treatment outcome and change in gene expression for any module. We report suggestive evidence for the role of a small number of genes in treatment outcome. Although preliminary, these findings contribute to a growing body of research suggesting that response to psychological therapies may be associated with changes at a biological level.

Effects of low atmospheric CO(2) on plants: more than a thing of the past.

In recent geological time, atmospheric CO(2) concentrations were 25-50% below the current level. Photosynthetic productivity of C(3) plants is substantially reduced at these low CO(2) levels, particularly at higher temperatures and during stress. Acclimation of photosynthesis to reduced CO(2) levels might compensate for some of this inhibition, but plants have a limited capacity to modulate Rubisco and other photosynthetic proteins following CO(2) reduction. Because of this, low CO(2) probably acted as a significant evolutionary agent, selecting plants adapted to CO(2) deficiency. Adaptations to low CO(2) might still exist in plants and might constrain responses to a rising CO(2) concentration.

Effect of CO2 Concentration on Carbonic Anhydrase and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Expression in Pea.

The effect of external CO2 concentration on the expression of carbonic anhydrase (CA) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was examined in pea (Pisum sativum cv Little Marvel) leaves. Enzyme activities and their transcript levels were reduced in plants grown at 1000 [mu]L/L CO2 compared with plants grown in ambient air. Growth at 160 [mu]L/L CO2 also appeared to reduce steady-state transcript levels for rbcS, the gene encoding the small subunit of Rubisco, and for ca, the gene encoding CA; however, rbcS transcripts were reduced to a greater extent at this concentration. Rubisco activity was slightly lower in plants grown at 160 [mu]L/L CO2, and CA activity was significantly higher than that observed in air-grown plants. Transfer of plants from 1000 [mu]L/L to air levels of CO2 resulted in a rapid increase in both ca and rbcS transcript abundance in fully expanded leaves, followed by an increase in enzyme activity. Plants transferred from air to high-CO2 concentrations appeared to modulate transcript abundance and enzyme activity less quickly. Foliar carbohydrate levels were also examined in plants grown continuously at high and ambient CO2, and following changes in growth conditions that rapidly altered ca and rbcS transcript abundance and enzyme activities.

Correlation of Carbonic Anhydrase and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Expression in Pea.

The enzyme carbonic anhydrase (carbonate dehydratase, EC 4.2.1.1) is an abundant soluble protein in the C3 plant chloroplast; however, its function in photosynthetic carbon assimilation is not well defined. In this study we have examined the relationship between carbonic anhydrase (CA) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) expression during pea (Pisum sativum) development as well as in various tissues and cultivars. Although absolute levels of activity and transcript abundance for the two proteins can vary considerably during development, a relatively constant ratio of CA to Rubisco transcript abundance and enzyme activity appears to be initiated during greening and maintained in mature and senescing photosynthetic tissue. Various pea cultivars, although exhibiting differing amounts of Rubisco and CA, also appear to maintain an invariant CA:Rubisco ratio. These data are discussed with respect to gene copy number, regulation of expression, and the proposed role of CA in photosynthetic carbon fixation.

Regulation of Periplasmic Carbonic Anhydrase Expression in Chlamydomonas reinhardtii by Acetate and pH.

The effects of mixotrophic growth with acetate and growth medium pH on expression of extracellular carbonic anhydrase (CA) in Chlamydomonas reinhardtii were evaluated. Addition of 10 mM acetate to the culture medium resulted in reduction of CA activity that was parallel to the reduction generated by growth of the algae in high external CO2 concentrations. This reduction in activity is a consequence of lower level of the CA protein as determined by western analysis. Transcript abundance of cah-1, the gene encoding the low CO2-induced CA, is also reduced by the addition of acetate as verified by northern analysis. Measurements of photosynthesis and respiration suggest that the acetate-induced reduction of CA expression is not a function of lowered photosynthetic capacity, but may be the result of increased internal CO2 concentration generated by high, acetate-stimulated respiratory rates. Growth medium pH can also influence extracellular CA expression. The induction of CA activity, protein abundance, and transcript levels by exposure to limiting inorganic carbon (Ci) concentrations is much more pronounced at higher than at lower pH values. The relationship between pH regulation of CA expression and its role in the Ci-concentrating mechanism are discussed.

Photosynthetic Gas Exchange and Discrimination against 13CO2 and C18O16O in Tobacco Plants Modified by an Antisense Construct to Have Low Chloroplastic Carbonic Anhydrase.

The physiological role of chloroplastic carbonic anhydrase (CA) was examined by antisense suppression of chloroplastic CA (on average 8% of wild type) in Nicotiana tabacum. Photosynthetic gas-exchange characteristics of low-CA and wild-type plants were measured concurrently with short-term, on-line stable isotope discrimination at varying vapor pressure deficit (VPD) and light intensity. Low-CA and wild-type plants were indistinguishable in the responses of assimilation, transpiration, stomatal conductance, and intercellular CO2 concentration to changing VPD or light intensity. At saturating light intensity, low-CA plants had lower discrimination against 13CO2 than wild-type plants by 1.2 to 1.8[per mille (thousand) sign]. Consequently, tissue of the low-CA plants was higher in 13C than the control plants. It was calculated that low-CA plants had chloroplast CO2 concentrations 13 to 22 [mu]mol mol-1 lower than wild-type plants. Discrimination against C18O16O in low-CA plants was 20% of that of the wild type, confirming a role of chloroplastic CA in the mechanism of discrimination against C18O16O ([delta]C18O16O). As VPD increased, stomatal closure caused a reduction in chloroplastic C02 concentration, and since VPD and chloroplastic CO2 concentration act in opposing directions on [delta]C18O16O, no effect of VPD was seen on [delta]C18O16O.

Developmental and genetic audiogenic seizure models: behavior and biological substrates.

Audiogenic seizure (AGS) models of developmental or genetic origin manifest characteristic indices of generalized seizures such as clonus or tonus in rodents. Studies of seizure-resistant strains in which AGS is induced by intense sound exposure during postnatal development provide models in which other neural abnormalities are not introduced along with AGS susceptibility. A critical feature of all AGS models is the reduction of neural activity in the auditory pathways from deafness during development. The initiation and propagation of AGS activity relies upon hyperexcitability in the auditory system, particularly the inferior colliculus (IC) where bilateral lesions abolish AGS. GABAergic and glutaminergic mechanisms play crucial roles in AGS, as in temporal lobe models of epilepsy, and participate in AGS modulatory and efferent systems including the superior colliculus, substantia nigra, basal ganglia and structures of the reticular formation. Catecholamine and indolamine systems also influence AGS severity. AGS models are useful for elucidating the underlying mechanisms for formation and expression of generalized epileptic behaviors, and evaluating the efficacy of modern treatment strategies such as anticonvulsant medication and neural grafting.

Resting and pure tone evoked metabolic responses in the inferior colliculus of young adult and senescent rats.

Metabolic responses from three sectors of the inferior colliculus (IC) divided according to frequency representation were examined bilaterally in young (YA) and aged adult (AA) rats using the 2-deoxyglucose method under quiescent or pure tone stimulus conditions. Resting IC metabolism in YA rats is characterized by elevated glucose uptake in the ventromedial (high frequency) relative to intermediate and dorsolateral sectors. AA resting incorporation is not reduced in any sector and is more uniform than YA uptake. Monaural high frequency stimulation (50 kHz) in YA animals evokes discrete contralateral banding along the ventromedial IC border, while stimulation in the optimal auditory sensitivity range of the rat at 8 kHz activates the intermediate sector of the contralateral IC. Although 50 kHz evoked ventromedial uptake is slightly reduced in AA rats contralaterally, the overall uptake within the three sectors does not differ significantly between ages under either of the monaural stimulus conditions; therefore senescent stability is exhibited. However, in AA rats the focus to 8 kHz stimulation has less clearly defined borders even though uptake within the intermediate sector is undiminished compared to YA animals, while 50 kHz elicited activity is typically reduced to a discontinuous band in the ventromedial sector of AA animals. These senescent changes may represent compensation in IC metabolism to changes in cochlear processing which are reflected in the activity of ascending auditory pathways.

Sources of projections to subdivisions of the inferior colliculus in the rat.

Brainstem and forebrain projections to major subdivisions of the rat inferior colliculus were studied by using retrograde and anterograde transport of horseradish peroxidase. Retrograde label from injection into the external cortex of the inferior colliculus appears bilaterally in cells of the inferior colliculus, as well as in other brainstem auditory groups including the ipsilateral dorsal nucleus of the lateral lemniscus and contralateral dorsal cochlear nucleus. The external cortex is the only collicular subdivision where an injection labels cells in the contralateral cuneate nucleus, gracile nucleus, and spinal trigeminal nucleus. Other projecting cells to the external cortex are found in the lateral nucleus of substantia nigra, the parabrachial region, the deep superior colliculus, the midbrain central gray, the periventricular nucleus, and area 39 of auditory cortex. Injection of the dorsal cortex of inferior colliculus heavily labels pyramidal cells of areas 41, 20, and 36 of the ipsilateral neocortex. Anterograde label from a large injection of auditory cortex is densely distributed in the dorsal cortex, lesser so in the external cortex, and only slightly in the central nucleus. Labelled cells appear in the central nucleus, dorsal cortex, and external cortex, primarily ipsilaterally, following dorsal cortex injection. Relatively few cells from other brainstem auditory groups show projections to the dorsal cortex. Injection of the central nucleus of the inferior colliculus results in robust labelling of nuclei of the ascending auditory pathway including the anteroventral, posteroventral, and dorsal cochlear nuclei (mainly contralaterally), and bilaterally the lateral superior olive, lateral nucleus of the trapezoid body, dorsal nucleus of the lateral lemniscus, and the central nucleus, dorsal cortex, and external cortex of the colliculus. The medial superior olive, superior paraolivary nucleus, and ventral nucleus of the trapezoid body essentially show ipsilateral projections to the central nucleus. The differential distribution of afferents to the inferior colliculus provides a substrate for functional parcellation of collicular subdivisions.

Postnatal cytoarchitecture of the rat medial geniculate body.

The medial geniculate body (MGB) is a thalamic structure that provides vital information flow to the forebrain for complex acoustic processing. The development of cytoarchitectural features of the MGB was examined in rat to identify age-related patterns of growth in major geniculate compartments that have been described previously (Clerici and Coleman [1990] J. Comp. Neurol. 297:14-31; Clerici et al. [1990] J. Comp. Neurol. 297:32-54): the ventral (MGv), dorsal (MGd), and medial (MGm) divisions. Results show that, on the day of parturition, all major nuclei of each division are characterized, including the ovoid (OV) and ventral (LV) nuclei of MGv; the dorsal, deep dorsal (DD), caudodorsal, limitans, and suprageniculate nuclei of MGd; and the MGm. The MGv and MGd, which display comparable areas at birth, show rapid growth to postnatal day 7 (PND7), which then slows until PND11, around the time of ear canal opening; subsequently, MGv accelerates growth to reach larger adult size. From PND11 to PND16, thionin facilitates parcellation by extensive staining of dendritic processes of MGd, MGm, and lateral posterior nucleus neurons but not neurons of the MGv or the dorsal lateral geniculate nucleus. Golgi stains after birth reveal restricted dendritic arborizations in MGv cells and dichotomous branching patterns of MGd neurons. Somal size in MGB increases dramatically subsequent to afferent innervation and again following onset of auditory function. Somal growth occurs between all postnatal age groups tested for OV, LV, and DD nuclei, although LV segments related to high and low frequencies do not differ. Cell packing density predicts the expanse of major MGB divisions better than somal size. These results demonstrate the integrity and growth patterns of MGB nuclei and divisions from nascence and provide a substrate for subsequent study of anatomical and physiological development of the MGB.

Anatomy of the rat medial geniculate body: I. Cytoarchitecture, myeloarchitecture, and neocortical connectivity.

The cytoarchitecture, myeloarchitecture, and neocortical connectivity of the rat medial geniculate body (MGB) were comprehensively studied in adult and immature rats to define major anatomical divisions and nuclei. The MGB is a highly intricate structure composed of the ventral (MGv), dorsal (MGd), and medial (MGm) divisions and component nuclei, each having reciprocal connections with auditory neocortex. The MGv lies inferior to the midgeniculate bundle and extends to the rostral, but not caudal MGB tip. The MGv is composed of ventral and ovoid nuclei bounded by a marginal zone, each region containing dark staining small and medium sized, densely packed neurons shown to have tufted dendritic morphology; in contrast to the MGd, but similar to the dorsal lateral geniculate nucleus, only the perikarya of MGv neurons stain for Nissl in early postnatal material. Ventral nucleus cells align with afferent brachial axons, which penetrate the nucleus in a dorsoventral direction, whereas rostrocaudal cellular arrays are retrogradely labeled after injections of horseradish peroxidase (HRP) into auditory cortex. The ovoid nucleus is a double spiraled structure encircled and penetrated by afferent fibers that determine the orientation of constituent perikarya. Neurons in the transition zone align with a spray of axons emanating from the juncture of the ovoid and midgeniculate bundles. Marginal zone neurons are oriented in parallel to the free geniculate wall. The MGd resides within and superior to the midgeniculate bundle, and is composed of several nuclei that stain palely for myelin. In immature material, both dendritic processes and somata in the MGd stain for Nissl with our protocol; many of these cells show a stellate arborization pattern that distinguishes this region from the MGv, but is similar to the staining pattern of immature neurons of the lateral posterior nucleus. The adult dorsal nucleus has medium-sized, loosely packed neurons. The deep dorsal nucleus is situated among the fibers of the midgeniculate bundle and contains loosely packed round and fusiform cells; the latter cell type constitutes a minor proportion of the adult neuronal population but the major cell type in immature animals. The caudodorsal nucleus, which occupies the caudal tip of the MGB and rostrally courses superior to the dorsal nucleus, contains small, dark staining multipolar cells; the ventrolateral nucleus courses inferior to the MGv. The suprageniculate and limitans nuclei are included in the auditory thalamus on the basis of connections with auditory neocortex; the former has medium to dark staining mixed-sized cells, and the latter has densely packed cells which form a vertical column.(ABSTRACT TRUNCATED AT 400 WORDS)

Anatomy of the rat medial geniculate body: II. Dendritic morphology.

The medial geniculate body (MGB) of the rat was studied with Golgi methods to determine the distribution of neurons identified by dendritic morphology. These findings were compared with major divisions and constituent nuclei established by somatic and fiber architectonics, and by connections with temporal neocortex (Clerici et al.: Society of Neuroscience Abstracts 12:1272, 1986; 13:325, 1987; Anatomical Record 218:23, 1987; Winer and Larue: Journal of Comparative Neurology 257:282-315, 1987; Clerici and Coleman: Journal of Comparative Neurology 297:14-31, 1990). It was found that an elaboration of the prototypical scheme proposed by Morest (Journal of Anatomy 98:611-630, 1964) for partitioning the mammalian MGB is valid for characterizing the rat MGB. Two predominant categories of principal neuron dendritic patterning were identified: a bushy cell having tufted dendritic fields and a stellate cell with a radiate dendritic domain. Tufted neurons have large caliber dendritic trunks that divide profusely into daughter branches close to the soma with intertwining higher order branches that maintain a relatively restricted dendritic field. Stellate neurons typically emit primary dendrites in all directions that then divide dichotomously at wide angles at subsequent orders of branching to produce a somewhat spheroidal dendritic field. In the present study, the rat MGB is found to be a tripartite structure composed of ventral (MGv), dorsal (MGd), and medial (MGm) divisions, each uniquely characterized by constituent dendritic morphology. The paramount neuronal class of the MGv is the tufted principal cell. In the ventral and ovoid nuclei of the MGv the neuronal orientation of highly oriented bitufted cells is in register with afferent brachial axons. In the ventral nucleus, this arrangement approximates vertical with a dorsomedial tilt most prominent rostrally; in the ovoid nucleus, tufted cells adhere to the double spiraled course of afferent axons. The transition zone between ventral and ovoid nuclei contains tufted neurons that align with radially oriented fibers issuing from the junction of the ovoid and midgeniculate bundles. Bitufted neurons of the marginal zone parallel fibers at the lateral margin of the geniculate. Within the MGd the dorsal and caudodorsal nuclei are characterized by stellate cells with extensive dendritic arbors and busy neurons with dendritic branches less tufted than those observed in the MGv. The deep dorsal nucleus contains bitufted neurons that polarize with the long axis of the midgeniculate bundle and intermingle with stellate neurons. The suprageniculate nucleus includes neurons with large somata and long, sparsely branched and dorsoventrally oriented dendrites orthagonal to corticothalamic axons, as well as smaller neurons and classical stellate cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Corticoamygdaloid and corticocortical projections of the rat temporal cortex: a Phaseolus vulgaris leucoagglutinin study.

The projections of the rat temporal cortex to the amygdala and cerebral cortex were studied using the sensitive anterograde tracer, Phaseolus vulgaris leucoagglutinin. These studies revealed that the core of temporal area 1 had no projections to the amygdala but did send efferents to several cortical fields that projected to the amygdala, including temporal area 2, temporal area 3, the lateral occipital area 2, and a cortical zone along the dorsal, rostral and caudal borders of temporal area 1 ("Tel fringe"). The temporal area 1 fringe cortex had light projections to the amygdala that were confined to the dorsolateral subdivision of the lateral amygdaloid nucleus. Temporal area 2 and the caudal portion of temporal area 3 had projections to both the dorsolateral and ventromedial subdivisions of the lateral nucleus; the projection from temporal area 2 targeted mainly the ventromedial subdivision, whereas the projection from the caudal portion of temporal area 3 terminated primarily in the dorsolateral subdivision. The rostral portion of temporal area 3 had projections to both subdivisions of the lateral nucleus and to the basal magnocellular nucleus. Temporal areas 2 and 3 also had light projections to the lateral capsular subdivision of the central amygdaloid nucleus. Temporal cortical areas exhibited extensive reciprocal connections with each other. Temporal areas with amygdaloid projections also had extensive projections to the perirhinal cortex. The results of the present investigation, in conjunction with other studies of temporal cortical connections, suggest that all temporal regions projecting to the amygdala are multimodal sensory areas. The core of temporal area 1, which is probably the primary auditory area, apparently has no direct projections to the amygdala. The differential projections of different temporal areas to the amygdala suggests the existence of several distinct multimodal pathways arranged in a parallel configuration.

Mithramycin- and 4'-6-diamidino-2-phenylindole (DAPI)-DNA staining for fluorescence microspectrophotometric measurement of DNA in nuclei, plastids, and virus particles.

The properties of two DNA-specific fluorochromes, 4'-6-diamidino-2-phenylindole (DAPI) and mithramycin, have been analyzed as reagents to quantitate cellular DNA by fluorescence microspectrophotometry. Optimal staining conditions and concentrations, and the effects of other cellular materials to which the dyes bind, have been evaluated in measurements of the DNA of rat, chick, and yeast nuclei, Gonyostomum chloroplasts, and T4 particles. Use of either fluorochrome permits a high degree of resolution of different DNA quantities in nuclei and in cell organelles, and the DAPI-DNA complex is sufficiently fluorescent to permit quantitation of the DNA content in genomes as small as those of individual T4 bacteriophage particles. Fluorescence of mithramycin- or DAPI-stained DNA is proportional to DNA quantity when DNA of the same has composition is compared. Quantitation does not appear to be affected discernably by the state of the DNA, whether in different stages of the cell cycle, in condensed chromosomes, or in noncycling, differentiated nuclei. The use of chicken red blood cells is recommended as an internal monitor for variations in staining conditions.

Differential sound-evoked metabolic activity in fetal tectum grafted into damaged adult rat inferior colliculus.

Long-Evans rats with unilateral lesions of the dorsal inferior colliculus (IC) received transplants of fetal tectal tissue to determine functional efficacy. Acoustic stimulation increases metabolic activity in both graft and host tissues relative to spontaneous activity in these regions. During periods of quiescence, graft tissue shows basal metabolic activity similar to that found in host IC. Coupled with previous anatomical findings, the results suggest that tectal grafts not only possess a neural structure resembling normal adult IC, but also contain cellular constituents which are responsive to sound. Given the apparent system-appropriate function of implanted fetal tectum, the graft tissue may be able to have a restorative effect within the damaged central auditory pathway.