Low-density Band Research Articles

Topographical organization of the projections from physiologically identified areas of the motor cortex to the striatum in the rat

The present study was undertaken to determine in the rat the topography of the neostriatal projections originating from the motor cortex. For that purpose, anterograde tracers (Phaseolus vulgaris leucoagglutinin: PHA-L; wheat germ agglutinin conjugated to horseradish peroxidase: WGA-HRP) were deposited in discrete cortical sites physiologically identified by microstimulation. Five major motor areas were considered in this study: the rostral (RFL) and caudal (CFL) forelimb areas, the hindlimb (HL) area, the vibrissae motor-frontal eye field (V-FEF) region and the jaw, lips and tongue (JLT) area (according to the nomenclature of Neafsey et al.). The results indicate that functionally different regions of the motor cortex project to different sectors of the caudate putamen (CPU). All 3 distinct limb areas RFL, CFL and HL project to the dorsolateral quarter of the CPU, V-FEF area projects to the dorsomedial quarter, whereas the JLT area projects to the ventrolateral quarter. The pattern of terminal labeling is relatively consistent, whatever the cortical area in which the tracer is deposited. This pattern is characterized by the presence of two or more labeled bands which are obliquely oriented along a ventrolateral-dorsomedial axis. Control experiments were also undertaken in which a retrograde tracer (WGA-HRP) was deposited in various neostriatal loci. The results are congruent with the findings of the anterograde study and further indicate that a given neostriatal sector receives projections from cytoarchitectonically different but functionally related regions of the neocortex. The somatotopic features of both motor and somatosensory corticostriatal projections appear to be in register. In addition, the striatal distribution of motor cortical fibers was compared in 6 experimental cases to the compartmental subdivision of the striatum in patches and matrix, following immunohistochemical localization of calbindin 28 kDa. The calbindin-immunoreactivity is extremely weak in the dorsolateral sector but is higher in the central and ventrolateral parts of the CPU. In these deep striatal regions receiving fibers from V-FEF, JLT and, to a lesser extent, from the limb areas, the cortical fibers are mostly directed to the matrix. The band-like organization of the projection from the motor cortex is correlated to the patch-matrix organization. The patches correspond to the bands of low density of terminal fibers and the matrix to the bands of high terminal density. The present results provide an anatomical basis to both electrophysiological and behavioral observations suggesting that functional distinctions can be established between subregions of the striatum.

Massive Subcapsular Fibrosis of the Liver

Massive and diffuse subcapsular fibrosis of the liver was detected in two patients with chronic liver disease. The subcapsular layer consisted of inflamed fibrous tissue containing rare portal tracts and myriads of bile ducts, indicating loss of subcapsular hepatocytes and their replacement by connective tissue. In the early evolutive phase, massive and diffuse subcapsular fibrosis of the liver appears on computed tomography (CT) scan as a low-density band, which merges with the hepatic parenchyma and is enhanced by contrast on dynamic imaging; it is undetectable by ultrasonography. In the advanced phase, it is easily recognizable by ultrasonography as a perihepatic sonolucent band and by CT scan as a low-density band, which is well demarcated from the hepatic parenchyma and is not enhanced with the dynamic technique.

The effect of prolonged ?bleaching? on skeletal banding and stable isotopic composition in Montastrea annularis

X-radiography and carbon and oxygen stable isotope analysis have been used to examine the effects of prolonged “bleaching” on the growth rate and chemical composition of the skeleton of the massive reef coral, Montastrea annularis. The post-bleaching linear growth of one colony that remained bleached for 10 to 12 months following the 1987 Caribbean-wide bleaching event was only 37% of mean annual growth from pre-bleaching years, and was manifest as a loss of the following year's low density band. Two colonies that did not bleach (normal) and two that bleached and regained their coloration (recovered) had linear growth rates over the same period that were 81 to 98% of mean pre-bleaching annual growth. Linear growth by a third recovered coral was 66% of pre-bleaching growth. No sub-annual stress bands were associated with the bleaching. The skeleton of the bleached colony had carbon and oxygen isotopic compositions that were reduced in range and enriched (increased) in both 13C and 18O in the post-bleaching year. The skeletons of two of the nine colonies, one bleached and one recovered, had depleted (reduced) δ18O values (-5.3 and -4.8%., respectively) during the bleaching episode that agree with the suggestion that positive temperature anomalies occurred during, and may have caused, the bleaching event. The range and values for all other normal and recovered corals, however, were not different between the post-bleaching year and previous years. Our data suggest that stress bands and isotopic analysis of coral skeletons may not always be reliable tools for examining the occurrence, cause or effects of certain discrete stress events that may interrupt skeletal growth.

Extension growth rates in two coral species from high-latitude reefs of Bermuda

Mean annual growth rates (skeletal linear extension) in the hermatypic coralsPorites astreoides Lamarck andDiploria labyrinthiformis (L.) were investigated mainly by X-radiography from a variety of localities at various depths on the high-latitude coral reefs of Bermuda. Growth rates of both species show an inverse curvilinear relationship with depth, with highest growth rates in the shallow inshore waters of Castle Harbour and lowest at the edge of the Bermuda platform and on the adjacent fore-reef slope. Annual density bands form seasonal couplets, with narrow, high density bands appearing to form in the spring-summer months and wider, low density bands over the rest of the year in both species. Comparison of the growth rates ofP. astreoides from Bermuda with those from lower latitude West Indian localities, particularly Jamaica, indicates an inverse relationship with latitude and a similar inverse curvilinear relationship with depth at both geographic locations. Growth rate-locality differences in Bermuda for both species are suggested to be controlled mainly by local differences in wave energy and food supply and possibly seasonal water temperature fluctuations; growth rate-depth differences by decreasing illumination with depth; and growth rate-latitudinal differences by reduction in winter water temperatures and light levels with increasing latitude.

Isolation and characterization of boar spermatozoa with and without a cytoplasmic droplet

1. 1. Boar semen was separated on a Percoll density gradient into three populations; a low-density band of immature sperm cells containing a cytoplasmic droplet and a high-density doublet band formed by spermatozoa without a cytoplasmic droplet. 2. 2. In these three cell populations four acid hydrolases were determined, viz. (1) α-glucosidase; (2) α-mannosidase; (3) β-galactosidase; (4) β-hexosaminidase. 3. 3. The release of the hydrolases (1), (2) and (3) from cytoplasmic droplet containing spermatozoa was stimulated whereas the release of β-hexosaminidase was inhibited by calcium ions. 4. 4. The results suggest that acid α-glucosidase, α-mannosidase and β-galactosidase are situated in the acrosome whereas acid β-hexosaminidase is localized predominantly in the cytoplasmic droplet of boar spermatozoa. 5. 5. We conclude that β-hexosaminidase should prove useful as a biochemical marker for cytoplasmic droplet containing spermatozoa and hence for the number of immature sperm cells in boar semen.

Molecular cloning and characterization of an rRNA operon in Streptomyces lividans TK21.

The number of rRNA genes in Streptomyces lividans was examined by Southern hybridization. Randomly labeled 23 and 16S rRNAs were hybridized with BamHI, BglII, PstI, SalI, or XhoI digests of S. lividans TK21 DNA. BamHi, BglII, SalI and XhoI digests yielded six radioactive bands each for the 23 and 16S rRNAs, whereas PstI digests gave one band for the 23S rRNA and one high-intensity band and six low-density bands for the 16S rRNA. The 7.4-kilobase-pair BamHI fragment containing one of the rRNA gene clusters was cloned into plasmid pBR322. The hybrid plasmid, pSLTK1, was characterized by physical mapping, Southern hybridization, and electron microscopic analysis of the R loops formed between pSLTK1 and the 23 and 16S rRNAs. There were at least six rRNA genes in S. lividans TK21. The 16 and 23S rRNA genes were estimated to be about 1.40 and 3.17 kilobase pairs, respectively. The genes for the rRNAs were aligned in the sequence 16S-23S-5S. tRNA genes were not found in the spacer region or in the context of the rRNA genes. The G + C content of the spacer region was calculated to be approximately 58%, in contrast to 73% for the chromosome as a whole.

Wood Anatomy of Martniaceae and Pedaliaceae

Quantitative and qualitative features are reported for one species of Martynia (Martyniaceae) and for seven species of six genera of Pedaliaceae. The inclusion of woody annuals as well as of shrubs provides a broader picture ofPedaliaceae than hitherto available. The wood features of Martyniaceae and Pedaliaceae (listed in the Systematic Conclusions) are compatible with placement of these families in Scrophulariales (Bignoniales). Ifindividual features of the two families are compared with those of other families of the order, however, no one family can be cited as more closely related to Martyniaceae and Pedaliaceae than any other. Martyniaceae is not necessarily the family closest to Pedaliaceae, but its wood is like that of herbaceous Pedaliaceae and may reflect not merely scrophularialean affinity but the similarity of its herbaceousness to that of Pedaliaceae as well. Wide vessels in Martyniaceae and Pedaliaceae very likely relate to high transpiration rates in the summer-wet areas where many of them grow. Low vessel density and apotracheal parenchyma bands that may store water and be related to semisucculence in Sesamothamnus. Thin-walled imperforate tracheary elements and predominance of upright ray cells in Martyniaceae and Pedaliaceae bear a relationship with the herbaceous nature of taxa.

Effects of monocular enucleation at different stages of development on the uncrossed retinocollicular projection in the opossum

Pouch young opossums aged from 5 to 34 days underwent unilateral eye enucleation and the projection from the remaining eye to the superior colliculus (SC) was explored at maturity by anatomical and physiological methods. The results were compared to data from normal or adult enucleated animals. Analysis of the experimental group showed that early enucleation resulted in an increased ipsilateral pathway which varied in terminal distribution with the timing of the lesion. When performed in the very young (first and second postnatal week) the uncrossed retinocollicular projection covered the entire area of the superficial layers of the superior colliculus but formed mediolateral bands of high and low label density at the rostral aspects of the SC. In the remainder of the early enucleated group the labeling also covered the entire area of the optic layers but the density of labeling was relatively homogeneous throughout the rostrocaudal extension of the SC. The distribution pattern of the uncrossed projection in adult enucleated opossums was similar to that described previously in normal animals. The electrophysiological results showed that, at all ages examined, early enucleation resulted in an orderly but expanded map in the SC restricted to the sector of the visual field seen by the temporal retina. The different anatomical patterns found in animals enucleated at these two early stages of development could not be distinguished by multiunit recordings.

An Indirect Computerized Tomography Sign of Chronic Subdural Hematoma demonstrated in the Posterior Fossa

In cases of chronic subdural hematoma (CSH), brain computerized.tomography (CT) scans frequently disclose a low density band in the posterior fossa (LDBP) between the lateral margin of the cerebellum and the adjacent petrous bone/tentorium cerebelli. Out of 121 cases of CSH, 56 (46%) showed the LDBP. The LDBP was mostly ipsilateral to the side of the CSH or bilateral. The frequency of the LDBP had no correlation with the severity of the cerebral midline shift or the thickness of the hematoma. As normal controls, CT scans of 257 cases in which no organic lesions were detected were used. Also 30 cases with dementing diseases, 2 cases with spinocerebellar degeneration and 428 cases of other neurological diseases such as head trauma other than CSH, brain tumor, cerebrovascular disease etc. were studied as disease controls. The incidence of the LDBP in both controls was significantly lower than in CSH. Therefore, the LDBP in cases of CSH was considered to be a significant associated finding of CT scans. The mechanism of the LDBP is discussed.

Environmental influences on skeletal banding in eastern Pacific (Panama) corals

The timing of skeletal band formation and concomitant changes in calcification rates and linear skeletal extension were investigated in Pavona corals growing under two distinct thermal regimes along the Pacific coast of Panama: fluctuating, marked by seasonal upwelling (Gulf of Panama) and stable, nonupwelling (Gulf of Chiriqui). The purpose of this study was to test the hypothesis that banding in corals is largely mediated by seasonal variations in temperature (Highsmith 1979). Our results indicate that the timing of band formation is synchronous at these two environmentally distinct locations. The low density (LD) portion of the annual band is accreted over a five month period (January–June) and represents an increase in linear skeletal extension (mm/mo.) as well as a marked increase in calcification rate (g CaCO3 · cm-2 · mo-1) relative to the high density portion which forms over the remaining seven month period (July through December). In contrast to the predictions of the Highsmith model these findings indicate that variations in light levels rather than fluctuation in temperature is a better correlate to changes in skeletal density. Qualitatively, banding patterns were similar at the two sites; however, higher growth rates (particularly with respect to the LD band) for Pavona clavus in the Gulf of Panama indicate that lower water temperatures and higher productivity, or both, may be responsible for quantitative differences in banding between sites. We found that formation of the HD band corresponds to lower light levels and the production of gametes. We propose that banding in corals is a complex phenomenon governed by endogenous processes (e.g. reallocation of energy from growth to reproduction) which may be mediated by exogenous factors (e.g light and productivity).

Separation of mouse lymphoblasts by discontinuous density centrifugation on percoll gradients

Mouse lymphoblasts generated in vivo by a topical application of the contact sensitiser oxazolone or by the contents of the gut lumen were separated by discontinuous density centrifugation on Percoll gradients. A 3-step gradient was used to divide the cells into two subpopulations. For cells from oxazolone stimulated lymph nodes, the low density band contained 20–30% of the initial cell number applied to the gradient; 25–40% of this population were in S phase and nearly all the large and pyroninophilic cells were confined to this layer. The high density step cells (70–80% of initial cell number) were predominantly small lymphocytes with <0.5% in S phase. Similar results were obtained using cells from picryl chloride stimulated lymph nodes or from mesenteric lymph nodes.

Optic fiber segregation in goldfish with two eyes innervating one tectal lobe

An ipsilateral retinotectal projection was induced by ablating one tectal lobe. Radioautography indicated that the ipsilateral that the ipsilateral projection initially spread out continuously over the remaining tectal lobe. With time, the continuous projection progressively changed into a rostrocaudally oriented banded projection that was comprised of high and low silver grain density bands. The undamaged native projection from the contralateral eye also became transformed into high and low density bands. The results indicate that foreign fibers displace portions of the native projection. Complete segregation of the two projections was not found at any time point examined. Low density bands did not represent spillover of label from a high density band since cobalt-filled optic fibers were found in low density bands. Quantitative analysis indicated that the contralateral projection occupied more tectal area than the ipsilateral projection. Area occupied by a projection, band width and band frequency showed appreciable between-fish variability. Correlations between band width and per cent of area occupied by a projection approached unity, indicating that large projections were isolated with wider bands. A model is proposed to account for induced banding in lower vertebrates.

Repair of O6-ethylguanine in DNA by a chromatin fraction from rat liver: transfer of the ethyl group to an acceptor protein.

Incubation of O6-[3H]ethylguanine-containing DNA with a rat liver chromatin fraction resulted in a decrease in the O6-ethylguanine content of the DNA. Analysis of the products of this reaction showed that the ethyl group had been transferred from the O6-ethylguanine to a protein acceptor. When the incubation mixture was separated on a cesium chloride gradient, the radioactivity removed from O6-ethylguanine appeared in a low-density band. This material has been isolated and subjected to trypsin digestion and high-pressure liquid chromatography analysis; it was sensitive to trypsin and the digest contained new high-pressure liquid chromatography peaks characteristic of oligopeptides. Radioactive peaks from the trypsin digestion have been digested further to the amino acid level and have been shown to contain S-[3H]ethylcysteine. Thus, we conclude that the repair activity in rat liver chromatin removes the ethyl group from O6-ethylguanine and transfers it to a cysteine moiety contained in an acceptor protein.

Kinetoplast DNA and RNA of Trypanosoma brucei.

Kinetoplast DNA (kDNA) and kinetoplast RNA (kRNA) were isolated from bloodstream and procyclic culture forms of two clonal strains of Trypanosoma brucei. No differences were observed in kDNA (maxicircle) restriction profiles between bloodstream or procyclic culture forms of the same strain. Some differences were observed in kDNA maxicircle restriction sites between the two strains. Buoyant density analysis of Pst I digested kDNA showed the release of a minor low density band representing unit length linearized maxicircle DNA. Pst I or Bam H1-linearized maxicircle DNA was isolated by the Hoechst 33258 dye--CsCl method and a restriction enzyme map of the maxicircle was constructed. Closed monomeric minicircles released from kDNA networks by sonication sedimented with a molecular size of around 1100 base pairs. A substantial minor length heterogeneity was evident in acrylamide gel electrophoresis of once cut minicircles. Several minicircle sequence classes and two Hind III maxicircle fragments representing approx. 50% of the maxicircle were cloned in the bacterial plasmid, pBR322, in Escherichia coli. A purified kinetoplast-mitochondrion fraction was isolated from procyclic culture forms by the Renografin flotation method. The major kRNA components were two small RNAs which comigrated with Leishmania tarentolae 9 and 12 S kRNAs in denaturing gels. These RNAs hybridized to the maxicircle component of the kDNA, specifically to the smaller cloned Hind III maxicircle fragment. This cloned fragment had substantial sequence homology with the cloned maxicircle fragment from L. tarentolae which contains the 9 and 12 S RNA genes, implying an evolutionary conservation of the 9 and 12 S gene sequences. Identical kRnAs were observed in cultured bloodstream forms of T. brucei.

Heterogeneity of chondrocyte mitochondria: A study of the Ca 2+ concentration and density banding characteristics of normal and rachitic cartilage

Previous morphological studies of the mineralizing epiphysis suggested that some mitochondria were concerned with Ca 2+ accumulation while others were associated with cellular energetics and metabolism. To determine if there was mitochondrial heterogeneity in chondrocytes of the epiphyseal growth plate, mitochondria were isolated from four different regions of the plate and subjected to continuous sucrose gradient centrifugation. Centrifugation of the organelles in a narrow density sucrose gradient (1.5–2.0 M) in the presence of inhibitors of Ca 2+ transport (ruthenium red and 5,5′-dithiobis-(2-nitrobenzoic acid)) revealed that considerable heterogeneity existed. In the least calcified zone 20% of the mitochondria formed a low density band of low Ca 2+ concentration (309 nmol/mg protein). Organelles isolated from more calcified tissue zones showed a concomitant increase in Ca 2+ concentration (up to 5700 nmol/mg protein) as well as an increase in the total percentage of mitochondria sedimenting in 2.0 M sucrose. The banding patterns of mitochondria isolated from rachitic and hypertrophic cartilage were similar. In addition, similarities were also noted in the Ca 2+ concentration and the cytochrome oxidase activities of mitochondria of these tissues. During recovery from the rachitic condition, there was a change in the density centrifugation characteristics of this tissue and a substantial increase was noted in the proportion of mitochondria sedimenting in 2.0 M sucrose. The Ca 2+ concentration of mitochondria of this rapidly calcifying tissue suggested that the critical Ca 2+ concentration necessary for initiation of the calcification mechanism was 4 μmol/mg protein.

Unique Enzymes of Purified Microsomes From Pig Fundic Mucosa: K+-stimulated adenosine triphosphatase and K+-stimulated pNPPase

Microsomal fractions from homogenates of pig gastric fundic mucosa showed high levels of K+-stimulated adenosine triphosphatase (ATPase) and K+-stimulated phosphatase. Similar preparations from antral mucosa showed virtually no such activity. Because of mitochondrial contamination the fundic microsomes were further separated by sucrose density gradient centrifugation. A low density band of membranes (peak 1.12 to 1.13 g per ml) possessed all of the K+-stimulated enzyme activities. Morphological features and the abundant glycoproteins of the low density microsomes suggested they might be derived from the tubulovesicles of oxyntic cells. Mitochondrial and ribosomal markers were associated with membranes with much higher densities (greater than 1.22). The K+-stimulated ATPase has a pH optimum of 7.5 and required Mg++, but neither Na+ nor ouabain had any appreciable effect on the activity. Stimulation of basal ATPase by K+ ranged from 1.5 to 3.0-fold with an apparent Ka for activation between 0.2 to 0.4 mM K+. Addition of various K+ ionophoretic substances (e.g., gramicidin) produced further stimulation of K+-ATPase up to 6 times the basal rate. The mean activities for seven separate preparations of purified low density pig fundic microsomes were as follows (micromoles of ATP hydrolyzed per mg protein per hr +/- SEM); basal ATPase, 15.8 +/- 2.8; plus 10 mM K+, 29.3 +/- 4.5; plus 10 mM K+ and 10(-5) M gramicidin, 45.2 +/- 5.2. Neither the basal ATPase nor the K+-stimulated rates were altered by HCO3- or Cl-. The occurrence of these active and unique enzyme activities in the oxyntic region of gastric mucosa suggest some relation with secretory activity. Possible functional roles are discussed.

Seasonal high and low density bands in reef coral skeletons

THE skeletal aragonite deposited by scleractinian reef corals is characterised by alternating bands of high and low density carbonate that are concordant with the growth surface of the colony. These density variations, which are readily observed by X-radiographic examination of 5–10 mm thick sections of the corallum cut parallel to the axis of growth, are annual in periodicity, such that one high density band plus one adjacent low density band represent the skeletal increment formed over one calendar year1–4. Skeletal X radiography is a powerful tool for studying both modern and fossil corals, for in addition to providing a wealth of growth rate data from specimens that grew undisturbed for many years in their natural habitat on the reef, valuable information about the coral itself and about the environment in which the coral lived can be obtained. As Buddemeier5 points out, density banding in reef corals can not only yield physiological and ecological information about these marine organisms, but also help to unlock the record of long term environmental conditions that is embodied in a coral skeleton. Reef corals, for example, are effective samplers of certain important radionuclides6.

Tissue dynamics in the periodontal ligament of the mandibular incisor of the mouse: A preliminary report

Grain distributions in autoradiographs of the lingual part of the periodontal ligament were studied 3, 7 and 14 days after [ 3H]-proline administration. The results suggest that the dental as well as the middle zones of the ligament move with the erupting incisor, while the alveolar zone remains static. Between the middle and alveolar zones, a narrow band of low cell-population density was commonly present; this might be a zone of tissue shear.

The buoyant density of bovine and rabbit spermatozoa.

A study of the buoyant density of intact spermatozoa from the bull and rabbit is presented. Sodium chloride sodium nitrate potassium tartrate potassium iodide caesium chloride glycerol sucrose Ficoll bovine serum albumin a colloidal silica solution and the methyl glucamine salt of umbradilic acid were used as gradient solutions for zonal isopycnic gradient centrifugation. The gradients were pre-formed with a gradient machine constructed entirely of plastic and were layered with the diluted semen sample as a lamella. 1 low-density band and 1 high-density band were observed in the centrifugation tubes. The low-density ban ranged from a buoyant density of 1.16 to 1.19 g/ml with all gradients used while the high-density band ranged from 1.25 to 1.32 g/ml depending upon the gradient used. Aging and physical or chemical treatment of the cells resulted in a higher number of cells in the high-density band. There were no evident differences in cell size or shape in the highdensity band although the cells did exhibit a lower motility and fertility and greater eosinophilia than cells in the lower-density band. Lower-density cells were not permeable as were higher density cells. The subdivision of high-density cells indicates that the relative composition of the solids in the cell is altered.