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Biomedical subjects

J D Lindsey

Publications and source records attributed to J D Lindsey.

At least 19 recordsLinked to original sources
PubMed1992

Propagation of ciliary smooth muscle cells in vitro and effects of prostaglandin F2 alpha on calcium efflux.

The effect of prostaglandin F2 alpha (PGF2 alpha) on calcium efflux from ciliary smooth muscle cells was studied. Ciliary smooth muscle cells, cultured from human ciliary muscle explants, retained the morphologic and immunologic characteristics of smooth muscle cells. High concentrations (to 10(-6) mol/l) of PGF2 alpha were associated with a dose-dependent increase of calcium (45Ca) efflux, whereas at concentrations lower than 10(-8) mol/l there was little or no 45Ca efflux. Our in vitro data are inconsistent with the experimental hypothesis that PGF2 alpha at pharmacologic concentrations relaxes ciliary muscle with a consequent increase in uveoscleral outflow.

Actins↗
PubMed1990

Photoreceptor survival-promoting activity in interphotoreceptor matrix preparations: characterization and partial purification.

It is well established that many types of cells are dependent on trophic factors for their survival. We are investigating whether photoreceptor survival may also be dependent upon such a factor, as well as the possibility that the interphotoreceptor matrix (IPM), which lies between the outer retina and the RPE, may be a source of photoreceptor survival-promoting activities. Well-characterized cultures of embryonic chick retinal neurons and photoreceptors, in which the photoreceptors spontaneously degenerate between 7 and 10 days in culture, were used to test this hypothesis. Crude extracts of IPM were found to support three- to fourfold increases in photoreceptor survival in 10-day cultures. This response was dose-dependent, saturable, and specific for photoreceptors, since there was no difference in the number of non-photoreceptor neurons between treated and control cultures. This photoreceptor survival-promoting activity (PSPA) may function when present either as a substratum-bound molecule or as a medium supplement. PSPA is heat labile, sensitive to freeze-thawing, and stable only within a very narrow pH range. The activity binds to heparin affinity columns but, in contrast to the behavior of growth factors such as FGF, it can be eluted from the columns at low salt concentrations (0.5 M NaCl). PSPA is eluted from a Sephacryl S-200 gel filtration column in two regions with Mr = 400-450 kDa and 33 kDa, respectively. SDS-gel electrophoresis suggests that the high molecular weight activity is composed of aggregates of lower molecular weight molecules. While this factor has not been purified to homogeneity, the combination of heparin-agarose affinity chromatography and hydrophobic interaction chromatography on phenyl-Sepharose columns results in 720-fold purification of the activity, with one unit of PSPA activity corresponding to 40 ng protein. This partial purification is accompanied by substantial reduction in the complexity of protein patterns in silver-stained SDS-gels. These findings are potentially important since a macromolecular factor promoting photoreceptor survival could play a role in the normal development of the retina, and could also further our understanding of retinal degenerations such as retinitis pigmentosa.

Animals↗
PubMed1985

The neuronal endomembrane system. I. Direct links between rough endoplasmic reticulum and the cis element of the Golgi apparatus.

This is the first of three papers describing new components and structural relationships within the neuronal endomembrane system. This system includes: the nuclear envelope, rough endoplasmic reticulum, the Golgi apparatus, lysosomes, axoplasmic reticulum, and discrete cytoplasmic compartments such as vesicles, multivesicular bodies, and so on. Previous high voltage electron microscope studies of osmium-impregnated Golgi apparatus have shown that small varicose tubules often arise from the cis element. In bullfrog spinal ganglia, these tubules have been seen to extend into cytoplasmic domains occupied by rough endoplasmic reticulum (RER). This study was undertaken to determine whether varicose tubules form direct connections with RER and to measure cytoplasmic density of varicose tubules. Spinal ganglia from Rana catesbeiana were fixed by osmium impregnation and, in some cases, were then stained en bloc with lead aspartate. Sixty- to 3000-nm-thick sections of this tissue, as well as of ganglia prepared by conventional protocol, were studied using standard and high voltage electron microscopy. Quantitative analysis revealed that 9% of the varicose tubules connected with the Golgi cis element. To determine whether continuities existed between RER and any of these tubules, more than 50 tubules were fully reconstructed from images of serial sections. The "ends" of these reconstructed tubules were then studied by high magnification stereoscopy. This was facilitated by the en bloc lead staining which allowed visualization of unimpregnated RER elements along with the impregnated tubules. Small varicose tubules as well as larger smooth tubules were found to have formed confluent bridges between the cis element and RER. In addition, the varicose tubules were found to bridge widely separated elements of RER. Finally, numerous examples of varicose and smooth tubules were seen to extend from RER and from cis elements to eventually form blind endings. These findings raise the possibility that the tubules form highly dynamic transitory connections between RER and the Golgi apparatus as well as between separated elements of RER. Those between RER and Golgi apparatus are ideally positioned to play a major role in the transfer of protein or lipid components first assembled in RER to the Golgi apparatus for terminal synthetic modification.

Animals↗
PubMed1985

The neuronal endomembrane system. III. The origins of the axoplasmic reticulum and discrete axonal cisternae at the axon hillock.

The axoplasmic reticulum (AR) and the discrete element (e.g., vesicles, vesiculotubular bodies, multivesicular bodies, etc.) constitute the endomembrane system of the axon. It is reported here that the AR of bullfrog sciatic nerve readily fills with osmium deposits during osmium impregnation. In contrast, the discrete elements and mitochondria are highly resistant to impregnation. Hence this preparation is well suited to address the nature of possible interactions between AR and rough endoplasmic reticulum (RER) in the axon hillock. It is also ideal to study the origin of the axonal discrete elements within the cell body as well as their interaction with other somal endomembrane system components. Tissues used in the present study were spinal ganglia, sciatic nerve, and spinal roots from Rana catesbeiana. Thick sections (1 to 2 microm) of this material were studied by high voltage electron microscopy. In some cases, osmium impregnation was followed by en bloc staining with lead aspartate. This made visible membranous structures that had not filled with osmium deposits during impregnation. Serial 170-nm-thick sections of this latter material were prepared and serial stereo pair electron micrographs of axon hillocks were collected. These were used to reconstruct three-dimensionally the AR and to study its relationship with RER and with discrete elements. The impregnated AR within the axon hillock was found to terminate as many proximally pointing finger-like projections. A large portion of these projections were found to form connections with RER. Some, however, terminated as true blind endings. Single unimpregnated discrete cisternae were found throughout the cytoplasm of the cell body, axon hillock, and axon. Large clusters of unimpregnated vesicles were usually found in close association with the trans face of the Golgi apparatus. These results indirectly support the hypothesis that vectors of fast axonal transport, namely the discrete elements, form directly at the trans face of the Golgi apparatus. From here they move toward and subsequently down the axon without any membrane fission-fusion events with either RER or AR. AR, although it forms continuities with RER, retains a distinctly different chemical composition from RER as evidenced by its much higher affinity for osmium. Thus, it should be considered as an endomembrane component separate from, although intimately related to the RER.

Animals↗
PubMed1985

The neuronal endomembrane system. II. The multiple forms of the Golgi apparatus cis element.

The cis element and its associated tubules and vesicles are ideally positioned to play a major role in the sorting of rough endoplasmic reticulum components destined for processing in the Golgi apparatus. Its position is also ideal for playing a major role in the assembly of the saccules which constitute the Golgi apparatus. The present study was undertaken to critically analyze the normal morphology of this Golgi apparatus component. Seventy- to 2000-nm-thick sections of bullfrog spinal ganglia, fixed by osmium impregnation as well as by conventional protocols, were studied using standard and high voltage electron microscopy. Impregnated cis elements were also reconstructed from 170-nm serial sections. These studies found that adjacent neurons within the given ganglion contain cis elements of widely different morphology. In larger neurons, a different cis element organization was also found in different regions of the same cells. Based on structural comparisons, all of the different cis element forms observed could be systematically assembled into a gradual continuum of morphological variation. This continuum was circular in a manner analogous to chromosomal variations seen in highly mitotic tissues. For the sake of discussion, five distinctly different form categories were established. Some forms contained structures that are described herein for the first time. Most notable among these is the cis tubular network, an extensive system of parallel tubules that closely apposed the regularly perforated cis saccule. Osmiophilic vesicles were found to collect in tight clusters that closely apposed certain forms of the cis element. These findings raise the possibility that the cis element and its associated structures may undergo morphological transformations as part of their normal function.

Animals↗
PubMed1984

The effects of test difficulty on undergraduates' state anxiety and perception of test difficulty.

The finding of a previous study that student perception of difficulty level may be just as important as the actual difficulty levels was reinterpreted. A specially developed Educational Psychology Recognition Test and Test Perception Inventory assessed task difficulty and perception of exam difficulty, respectively, in 30 American undergraduates. A modified version of the State-Trait Anxiety Inventory assessed state anxiety. Results indicated, that 1) test difficulty did not significantly affect state anxiety but did significantly affect perception of exam difficulty, 2) students administered the high-difficulty test exhibited a perception of higher exam difficulty than those taking the medium- and low-difficulty tests, and 3) there was no significant difference for the perception of exam difficulty between students taking the medium- and low-difficulty tests.

Achievement↗
PubMed1984

Expression of cone-like properties by chick embryo neural retina cells in glial-free monolayer cultures.

We report here that cells present in embryonic chick retinal monolayer cultures express differentiated properties characteristic of chick cones developing in vivo. Cell suspensions from 8-d chick embryo retina (a stage when photoreceptor differentiation has not yet started) were cultured for up to 7 d in low density, glial-free monolayers. Under these conditions, monopolar cells represent approximately 40% of the total number of process-bearing neurons. After 6 d in vitro, most of these monopolar cells showed morphological features reminiscent of developing chick cones. These features could be detected with phase-contrast microscopy, lectin cytochemistry, and transmission and scanning electron microscopy. Characteristic cone traits expressed by cultured monopolar cells included the following: (a) a highly polarized organization; (b) a single, short, usually unbranched neurite; (c) the polarized position of the nucleus close to the origin of the neurite; (d) characteristic cone inner segment features such as abundant free ribosomes, a polarized Golgi apparatus, a cluster of mitochondria distal to the nucleus, a big, membrane-bound, pigment-containing vacuole reminiscent of the "lipid droplet" characteristic of chick cones, and at least in some cases, a well-developed paraboloid; (e) the presence of a complex of apical differentiations including abundant microvilli and in some cases also a cilium-like process; and (f) the staining of the apical region of the cell with peanut lectin, which has been shown to be selective for chick embryo cones (Blanks, J.C., and L.V. Johnson, 1983, J. Comp. Neurol., 221:31-41; and Blanks, J.C., and L.V. Johnson, 1984, Invest. Ophthalmol. Visual Sci., 25:546-557). This pattern of differentiation achieved by 8-d chick retina cells after 6 d in vitro is similar to that shown by 14-d-old chick embryo cones in vivo. Outer segments are not present at this stage of development either in vivo or in vitro. This experimental system is now being used to search for cellular and molecular signals controlling survival and differentiation of cone cells.

Animals↗
PubMed1984

Performance of EMR and learning-disabled students on the brigance, peabody, and wide range achievement tests.

Achievement test results are commonly used for making educational decisions for students labeled mildly mentally retarded, educationally retarded, and learning disabled. Teachers frequently assume that individual achievement tests are comparable. High correlations between achievement tests are typically reported and drawn from scores obtained primarily from regular student populations. When these tests are given to special populations, in this case mildly mentally retarded and learning-disabled students, the specific abilities of the pupils interact with aspects of the test items. In the present study, significant differences were found on the subtests of three tests that were designed to measure the same area of achievement.

Achievement↗
PubMed1983

The axoplasmic reticulum within myelinated axons is not transported rapidly.

The axoplasmic reticulum in myelinated axons is an extensive system of branched smooth membranous tubules which is found throughout the length of large axons. To investigate its motility and possible role in fast axonal transport, a focal chilling method was used to arrest transport at two sites separated by a 3 mm wide warm region along the saphenous nerve of mice. The experiments ran for 3-4 h since axoplasmic material travelling faster than 25 mm/day would clear from the central warm region. The nerve was subsequently fixed and processed by a technique that enhances the electron density of the axoplasmic reticulum. Thin and thick sections from several regions along the nerve were then systematically studied using conventional and high voltage electron microscopy. In these studies we found that: 1. the axoplasmic reticulum does not accumulate against the proximal sides of the cold blocks; 2. although often closely associated, there is no evidence of continuity between the axoplasmic reticulum and the discrete membranous compartments that do accumulate proximal to the chilled regions; 3. the axoplasmic reticulum remains in the central 3 mm wide warm region; 4. the axoplasmic reticulum does not accumulate against the distal sides of the cold blocks; 5. retrogradely moving elements that do accumulate distal to the cold blocks do not fuse with the axoplasmic reticulum and are not contained in it; and 6. both retrograde and anterograde vector types are often closely associated with elements of axoplasmic reticulum. These results were supported by quantitative morphometric analysis. We conclude that the axoplasmic reticulum represents a discrete membrane system, separate from either anterogradely or retrogradely moving rapid transport vectors, and that this interconnected cisternal system itself is not rapidly transported.

Animals↗
PubMed1983

The effects of trait anxiety and test difficulty on undergraduates' state anxiety.

The purpose of this study was to determine the effects of trait anxiety (stable anxiety resulting from personality characteristics which predisposes an individual to anxiety) and test difficulty on state anxiety (transitory anxiety that results from particular situations which are regarded as difficult or dangerous) of 32 undergraduates. The Test Anxiety Inventory assessed trait anxiety, a modified version of the State-Trait Anxiety Inventory assessed state anxiety, and a specially developed Educational Psychology Recall Test assessed task difficulty. Results indicated that trait anxiety and test difficulty level affected state anxiety. Trait anxiety and test difficulty level did not interact to affect state anxiety.

Anxiety↗
PubMed1982

Evidence that all newly synthesized proteins destined for fast axonal transport pass through the Golgi apparatus.

Effects of the sodium ionophore, monensin, were examined on the passage from neuronal cell body to axon of materials undergoing fast intracellular transport. In vitro exposure of bullfrog dorsal root ganglia to concentrations of drug less than 1.0 micron led to a dose-dependent depression in the amount of fast-transported [3H]leucine- or [3H]glycerol-labeled material appearing in the nerve trunk. Incorporation of either precursor was unaffected. Exposure of a desheathed nerve trunk to similar concentrations of monensin, while ganglia were incubated in drug-free medium, had no effect on transport. With [3H]fucose as precursor, fast transport of labeled glycoproteins was depressed to the same extent as with [3H]leucine; synthesis, again, was unaffected. By contrast, with [3H]galactose as precursor, an apparent reduction in transport of labeled glycoproteins was accounted for by a marked depression in incorporation. The inference from these findings, that monensin acts to block fast transport at the level of the Golgi apparatus, was supported by ultrastructural examination of the drug-treated neurons. An extensive and selective disruption of Golgi saccules was observed, accompanied by an accumulation of clumped smooth membranous cisternae. Quantitative analyses of 48 individual fast-transported protein species, after separation by two-dimensional gel electrophoresis, revealed that monensin depresses all proteins to a similar extent. These results indicate that passage through the Golgi apparatus is an obligatory step in the intracellular routing of materials destined for fast axonal transport.

Animals↗
PubMed1981

An increase in smooth endoplasmic reticulum and a decrease in Golgi apparatus occur with ionic conditions that block initiation of fast axonal transport.

The ultrastructure of bullfrog spinal ganglia was analyzed after incubation in media containing concentrations of calcium and cobalt known to inhibit export of proteins from the soma to the axon. Although most somal organelles were morphologically unchanged by the various incubation media, striking changes were seen in the smooth endoplasmic reticulum (SER) and the Golgi apparatus (GA). In order of effect, calcium-free medium (CFM), normal medium supplemented with cobalt (NM--Co), and CFM supplemented with cobalt (CFM--Co) produced increasing amounts of SER coupled with decreasing densities of GA stacks. In the extreme case, CFM--Co incubation resulted in a nearly 10-fold increase in SER volume as well as in a virtually complete depletion of GA stacks. Axons originating within the ganglion were also examined and showed little change after the various incubations. The rank order of the altered incubation media in producing morphological changes was the same as the relative effectiveness of the media in depressing the fast axonal transport of [3H]protein within the dorsal root ganglion neurons. The morphological and biochemical results are discussed with respect to establishing the localization of the calcium-dependent step(s) that has been proposed to occur in the neuronal soma during the initiation of axonal transport.

Animals↗
PubMed1981

Effects of exceptionality status and art instruction on Goodenough--Harris standard IQs.

The effects of exceptionality, art instruction, and time elapsing between test administrations on Goodenough--Harris Drawing Test composite standard IQs was investigated. Twenty-four nonexceptional, 24 learning-disabled, and 24 EMR students participated. Half the students received 90 minutes of instruction (over 2 days) in drawing the human figure. The Goodenough--Harris Drawing Test was administered to all students the day after the final art lesson and 3 weeks after the first administration. Using a repeated measures analysis of variance, we found that exceptionality, art instruction, and time elapsing between test administrations affected composite standard IQs.

Adolescent↗
PubMed1979

Early onset and topographical distribution of hypertrophied astrocytes in hippocampus of aging rats: a quantitative study.

Our results indicate that the density of astrocytes exhibiting hypertrophy in the hippocampus increases dramatically and progressively with age, being significantly elevated even in mid-life (13 month) animals. However, the total population of astrocytic cells (hypertrophied and nonhypertrophied) in the quantified region is not significantly elevated. Further, the relative distributions of both hypertrophied and total glial cells remained remarkably constant at the three ages measured. Reactive hypertrophy of astrocytes therefore appears to occur "in place" and migration of astrocytes does not appear to be a major factor in the hippocampus during aging. Of particular note was the finding that astrocyte hypertrophy is far more prominent in synaptic terminal fields than in myelinated fibers of the same system.

Aging↗