Effects of rotating antibiotic and ionophore feed additives on volatile fatty acid production, potential for methane production, and microbial populations of steers consuming a moderate-forage diet.

Ionophores and antibiotics have been shown to decrease ruminal methanogenesis both in vitro and in vivo but have shown little evidence toward a sustainable means of mitigation. Feed additive rotation was proposed and investigated for methane, VFA, and microbial population response. In the present study, cannulated steers ( = 12) were fed a moderate-forage basal diet in a Calan gate facility for 13 wk. In addition to the basal diet, steers were randomly assigned to 1 of 6 treatments: 1) control, no additive; 2) bambermycin, 20 mg bambermycin/d; 3) monensin, 200 mg monensin/d; 4) the basal diet + weekly rotation of bambermycin and monensin treatments (B7M); 5) the basal diet + rotation of bambermycin and monensin treatments every 14 d (B14M); and 6) the basal diet + rotation of bambermycin and monensin treatments every 21 d (B21M). Steers were blocked by weight in a randomized complete block design where the week was the repeated measure. Rumen fluid was collected weekly for analysis ( = 13), and results were normalized according to individual OM intake (OMI; kg/d). Potential activity of methane production was not significantly different among treatments ( > 0.05). However, treatment tended to affect the CH-to-propionate ratio ( = 0.0565), which was highest in the control and lowest in the monensin, B21M, and B14M treatments (0.42 vs. 0.36, 0.36, and 0.33, respectively). The CH:propionate ratio was lowest in wk 2 and 3 ( < 0.05) but the ratio in wk 4 to 12 was not different from the ratio in wk 0. Week also affected total VFA, with total VFA peaking at wk 3 and plummeting at wk 4 (4.02 vs. 2.86 m/kg OMI; < 0.05). A significant treatment × week interaction was observed for the acetate-to-propionate (A:P) ratio, where bambermycin- and rotationally fed steers did not have a reduced A:P ratio compared with monensin-fed steers throughout the feeding period ( < 0.0001). Microbial analysis revealed significant shifts, but several predominant classes showed adaptation between 4 and 6 wk after additive initiation. There was no significant evidence to suggest that rotations of monensin and bambermycin provided additional benefits to steers consuming a moderate-forage diet at the microbial/animal and environmental level versus those continuously fed.

Liquid crystal over silicon device characteristics for holographic projection of high-definition television images.

We discuss some fundamental characteristics of a phase-modulating device suitable to holographically project a monochrome video frame with 1280 x 720 resolution. The phase-modulating device is expected to be a liquid crystal over silicon chip with silicon area similar to that of commercial devices. Its basic characteristics, such as number of pixels, bits per pixel, and pixel dimensions, are optimized in terms of image quality and optical efficiency. Estimates of the image quality are made from the noise levels and contrast, while efficiency is calculated by considering the beam apodization, device dead space, diffraction losses, and the sinc envelope.

Non-display applications and the next generation of liquid crystal over silicon technology.

The next generation of applications for liquid crystal (LC) over silicon technology will be non-display oriented systems such as adaptive optical interconnects, optical switches and optical image processors. These new non-display applications have a different set of material parameters, which means that existing display-based materials are not entirely optimal. This is particularly the case when the application is driven by phase modulation at high frame rates (more than 1 kHz). An example of such a non-display application is in adaptive optical interconnects. Optical data transmission between printed circuit boards is becoming more and more important as the data rate in electronic systems increases into the gigahertz region. One way of avoiding the data bottlenecks in board to board interconnects is to use optical links to transmit the data. Recent research into free-space optical links has shown that a high level of manufacturing tolerance must be used to maintain the link. However, one way of avoiding these limitations is to use a reconfigurable LC phase hologram as a beam-steering element to compensate for movement between the boards and maintain the optical data path.

Dynamic holography for optical interconnections. I. Noise floor of low-cross-talk holographic switches.

Reconfigurable optical interconnects constructed by recording dynamic holograms onto spatial light modulators may be crucial elements in all-optical networks. The extremely low cross-talk level of such free-space holographic switches was shown by an analytic approximation and verified experimentally. The fiber-to-fiber switch utilizes the spatial filtering properties of single-mode fibers, and its cross-talk noise is limited to the sidelobe power as a result of diffraction of the clipped Gaussian beam at the hologram aperture edges, provided that all higher orders are avoided. Greater than 45-dB cross-talk isolation has been measured at transverse-axis locations, and locating a fiber port at off-transverse-axis directions promises to double this level if aberrations are negligible.

Dynamic holography for optical interconnections. II. Routing holograms with predictable location and intensity of each diffraction order.

An analysis of dynamic phase-only holograms, described by fractional notation and recorded onto a pixelated spatial light modulator (SLM) in a reconfigurable optical beam-steering switch, is presented. The phase quantization and arrangement of the phase states and the SLM pixelation and dead-space effects are decoupled, expressed analytically, and simulated numerically. The phase analysis with a skip-rotate rule reveals the location and intensity of each diffraction order at the digital replay stage. The optical reconstruction of the holograms recorded onto SLM's with rectangular pixel apertures entails sinc-squared scaling, which further reduces the intensity of each diffraction order. With these two factors taken into account, the highest values of the nonuniform first-order diffraction efficiencies are expected to be 33%, 66%, and 77% for two-, four-, and and eight-level one-dimensional holograms with a 90% linear pixel fill factor. The variation of the first-order diffraction efficiency and the relative replay intensities were verified to within 1 dB by performing the optical reconstruction of binary phase-only holograms recorded onto a ferroelectric liquid crystal on a silicon SLM.

Quantitative assessment of localization and colocalization of glutamate, aspartate, glycine, and GABA immunoreactivity in the chick retina.

We examined the posthatch chick retina for the frequency of occurrence of localization and colocalization of four amino acid transmitter candidates: glutamate (Glu), aspartate (Asp), gamma aminobutyric acid (GABA), and glycine (Gly) using postembedding methods. We support previous studies of Glu, Asp, GABA, and Gly localization in the direct and indirect functional pathways of the chick retina and extend these studies with new qualitative and quantitative observations. We found that photoreceptors show distinct cellular immunoreactivity for both Glu (Glu+) and Asp+, but not for Gly (Gly-) or GABA. Moreover, there is compartmentalization of Glu and Asp staining within the photoreceptors. All horizontal cells react strongly with Asp and Glu, about three-fourths are GABA+ and three-fourths of these are Gly+. Bipolar cells are uniformly Glu+, heterogeneously Asp+, occasionally Gly+, but GABA-. A majority of amacrine cells stain heterogeneously with all antibodies: 90% are Gly+, slightly more than half colocalize Glu, GABA, and Gly. Furthermore, amacrine cells in the outer two or three rows of cells are more likely to be stained by Gly than Glu, Asp, or GABA. Confirming previous studies, ganglion cells were mostly immunoreactive for Glu and Asp with fewer reactive for GABA and Gly. Strong and distinctly cellular immunoreactivity was found in both central and peripheral retina. Our findings show: 1) there is extensive colocalization of Glu, Asp, GABA, and Gly among most retinal neurons, including some cells that contain all four; 2) cells of the direct functional pathway tend to be labeled by Glu and Asp generally to the exclusion of GABA and Gly, while those of the indirect pathway tend to be labeled by GABA+ and/or Gly+ in addition to Glu+ and Asp+; 3) different cell body layers have distinct patterns of colocalization; and 4) there is no qualitative difference in staining patterns between peripheral and central retina.

2'-Deoxyadenosine causes cell death in embryonic chicken sympathetic ganglia and brain.

Previous work has shown that nucleosides produce apoptosis in sympathetic ganglion (SG) cells in vitro. The present study examined the effects of nucleosides on the development of the chick embryo in vivo with special attention to the SG and the optic tectum of the central nervous system. In the presence of an adenosine deaminase inhibitor, adenosine and 2'-deoxyadenosine (2'-dAdo) produced different toxicity patterns: both adenosine and 2'-dAdo were toxic to E3 embryos, but only 2'-dAdo was toxic at later stages (E6 1/2, E11). Dosage experiments on E6 1/2 embryos showed that adenosine was less toxic than 2'-dAdo and that 2'-dAdo in sublethal doses was teratogenic. We also examined the effects of 2'-dAdo on embryonic chicken SG and optic tectum in vivo to determine whether sublethal doses of 2'-dAdo produced cell death in these centers on E6 1/2 and 10. In the E6 1/2 SG, 2'-dAdo produced significant neuron loss (83%) and a decrease in SG volume (65%); however, at E10, there was only minor cell loss (7%) and no significant change in SG volume. In the optic tectum at E6 1/2, cell loss was confined mainly to the tectal ventricular zone, but there was little sign of cell loss in this organ at E10. Since cell production is vigorous in the SG and optic tectum at E6 1/2 but relatively low at E10, 2'-dAdo appears to work by stopping cell proliferation. The ineffectiveness of 2'-dAdo at E10 may result from the lethality of 2'-dAdo to the embryo at low concentrations (30 microM) in vivo, well below the apoptosis-inducing concentrations employed in vitro (100-300 microM). These data extend previous findings showing that purine and pyrimidine metabolism plays an important role in development.

Effects of prenatal cocaine on hearing, vision, growth, and behavior.

The illicit use of cocaine has increased dramatically over the last 10-12 years. There has been a corresponding increase in cocaine abuse among obstetric patients and in the number of "cocaine babies." According to some estimates, these children make up more than half of the drug-associated births. This problem is therefore a major public health concern. Consequently, our laboratory investigated the effects of prenatal cocaine exposure on hearing, vision, growth, and exploratory/stress behavior. This chapter summarizes the literature on animals and humans on these topics and presents new observations from our laboratory. In terms of maternal toxicity, prenatal cocaine exposure causes hypertension, placental abruption, spontaneous abortion, poor pregnancy weight gain, and undernutrition secondary to appetite suppression. Some offspring effects include in utero growth retardation, cephalic hemorrhage, fetal edema, altered body composition, congenital malformations, and even pre- and postnatal death. The offspring can also exhibit a variety of behavioral, visual, hearing, and language disorders. Differential effects of animal strain and late gestational cocaine exposure are discussed. Comparisons are made between prenatal cocaine, the fetal alcohol syndrome, and the effects of prenatal undernutrition. Recommendations for clinical assessment and intervention are made.

Characterization of cocaine binding sites in the rat testes.

PURPOSE: An estimated 29 million individuals use cocaine in the United States. Studies have shown a high affinity for dose dependent binding of cocaine in the testes. Recent work done in our laboratory has shown that chronic administration of cocaine to male rats has an adverse effect on fertility and spermatogenesis by producing extensive morphological changes in the testes, leading to reduction in sperm production. As a first step toward understanding this process, we characterized and identified the pharmacological properties of [3H]cocaine binding sites in the testes. MATERIALS AND METHODS: Crude membranes from the testes were prepared from 35 days old male Sprague-Dawley rats. [3H]cocaine binding was measured by using the method of Madras et al. (1989) with modifications. The data from saturation binding assays were analyzed by Inplot (GraphPad Software, San Diego, CA) to determine the Kd and Bmax. RESULTS: Specific binding of [3H]cocaine was linearly dependent on membrane protein concentrations ranging from 0.2 to 8 mg./ml. The pooled data from three independent experiments revealed a mean affinity of 36 +/- 2.0 nM and Bmax of 1.84 +/- 0.13 pmol/mg. The present study demonstrates that testicular tissue has receptor protein that binds [3H]cocaine saturably and specifically. Competition displacement experiments revealed a shallow displacement curve for (-)cocaine and Win 35,428 with r2 = 0.96, indicative of multiple binding components. Computer analysis confirmed that a two component binding model was preferred statistically over a one component model in all three experiments (p < 0.001). CONCLUSION: The results from these studies suggest that the testicular tissue contains a protein that binds [3H]cocaine in a saturable and specific manner. It has a different sensitivity from the [3H]cocaine binding protein in the brain and placenta. Further clarification of the relationship between cocaine and its recognition site is necessary to understand the mechanism of testicular damage after cocaine exposure.

Digital-to-analog image conversion with an optically addressed spatial light modulator.

The possibility of using ferroelectric liquid-crystal optically addressed spatial light modulators to transfer images from silicon backplane devices is investigated. We propose a drive scheme for optically addressed spatial light modulators to perform digital-to-analog image conversion based on the speed performances of current and future silicon backplane devices and on temporal averaging. The validity of the drive scheme is experimentally demonstrated with a LED used to encode the gray levels, and we discuss the performance of the display system.

Effect of endoscopic white light on the developing rat retina.

OBJECTIVE: Our goal was determine the effect of endoscopic white light on the developing mammalian retina by quantitative histological analysis. STUDY DESIGN: Albino rats at postnatal days 10 (n = 16) and 16 (n = 20) were exposed to endoscopic white light for 1 h, while an equal number of littermate controls were not exposed, but otherwise treated identically. The thickness of the outer nuclear layer (ONL) and the total retinal thickness were measured light microscopically using a computer-assisted morphometry program. RESULTS: We found no statistically significant decrease in the thickness of the ONL or the total retinal thickness, nor were any significant decreases found in the ONL or the total retinal thickness for male or female groups. CONCLUSION: Endoscopic white light does not cause damage to the developing rodent neural retina detectable at the light microscopic level.

Resonant enhancement of low-contrast electro-optic effects.

Ferroelectric liquid crystals can be optimized for speed, but such materials tend to have small switching angles and consequently low contrast in the smectic A(*) phase. We describe a method whereby such a low-contrast but fast-switching effect can be enhanced, in theory giving the same contrast as a material with a switching angle of 22.5 degrees . This method therefore promises liquid-crystal modulators of high contrast and with speeds of the order of hundreds of nanoseconds. The theoretical basis of this method and initial results that support this analysis are presented.

Electron microscopic detection of glycoconjugates in the chicken lens.

The cytochemical localization of glycoconjugates in the 14-day old embryonic chick lens was analysed by lectin-gold labelling. Con A/HRP gold particles, specific for D-mannose labelled the interior of the rough endoplasmic reticulum, membranes of the Golgi complex, secretory vesicles and the plasma membranes of the lens epithelial cell. The lens capsule was heavily labelled. Lens fiber cell membranes were also labelled. In contrast LFA, specific for neuraminic acid, did not bind to the endoplasmic reticulum or nuclear membrane. Labelling of the Golgi complex, secretory vesicles and capsule was observed. The plasma membranes of epithelial and fiber cells were extensively labelled, and probably reflects the presence of glycolipids such as gangliosides.

Development of parvalbumin immunoreactivity in the chick Edinger Westphal nucleus.

To determine when the calcium-binding protein parvalbumin appears during development, neurons in the chick Edinger Westphal nucleus were examined for parvalbumin immunoreactivity at a variety of embryonic stages. Parvalbumin immunoreactivity appeared on embryonic day 14 (E14, Hamburger and Hamilton stage 40) in predominantly lateral Edinger Westphal neurons. Cytochrome oxidase activity within the nucleus was examined throughout development, as an indicator of physiological activity, and expression of cytochrome oxidase was compared with that of parvalbumin. Cytochrome oxidase activity was found to be uniformly high in all parts of the Edinger Westphal nucleus throughout development. Either the Edinger Westphal nucleus in physiologically active quite early in its development or other energy demands mask the correlation of cytochrome oxidase with electrical activity. Cytochrome oxidase was expressed well before parvalbumin immunoreactivity appeared. Voltage-activated calcium currents were characterized in E12 Edinger Westphal neurons. In both amplitude and composition, E12 calcium currents resemble those of E16 neurons, excluding the possibility that calcium currents appear de novo during or just prior to the appearance of parvalbumin. Both cytochrome oxidase activity and calcium currents are observed in Edinger Westphal neurons well before the appearance of parvalbumin during development. These findings do not exclude the possibility that physiological activity affects the expression of parvalbumin since other factors such as changing patterns of synaptic activity or the appearance of calcium conducting NMDA receptors have yet to be examined. However, they raise the possibility that additional factors such as an intrinsic developmental program or a change in the neuron's basal intracellular calcium requirements may also be involved.

Effect of endoscopic white light on the developing visual pathway: a histologic, histochemical, and behavioral study.

OBJECTIVE: We examined the potential teratogenic effect of endoscopic white light on the developing visual pathways. STUDY DESIGN: The right eye of chicken embryos (n = 22) was exposed to maximal endoscopic light intensity on day 10 of development. At day 17 of development the histologic characteristics of the light-exposed retinas were compared with those of the control embryos (n = 4). Normal functioning of the light-exposed eye was assessed by intravitreal injection of wheat germ agglutinin-horseradish peroxidase and observation of its axonal transport pattern to the diencephalic and mesencephalic visual centers. Axonal transport patterns were compared with those found in previous studies of normal embryos. Behavioral feeding patterns were compared between two groups of newly hatched chickens, one exposed to endoscopic light after hatching (n = 13) and the other, an unexposed control group (n = 12). RESULTS: No evidence of retinal damage, altered axonal transport or altered feeding patterns could be found between control and experimental animals. CONCLUSION: Endoscopic white light does not appear to be harmful to the developing retina and visual pathway.

Morphological study of the rostral interstitial nucleus of the medial longitudinal fasciculus in the monkey, Macaca mulatta, by Nissl, Golgi, and computer reconstruction and rotation methods.

We have studied the morphology of silver-impregnated neurons (rapid Golgi technique) in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), a center involved in the control of vertical and torsional saccadic eye movements. This morphological study of riMLF neurons in the rhesus monkey was undertaken to further our understanding of the functional circuitry of the oculomotor system. Our study employed Nissl, Golgi, and computer-assisted methods. The cytoarchitectonic boundaries of the riMLF and its relationships to neighboring structures were determined in both Nissl and Golgi preparations. Five (I-V) distinct morphological types of riMLF neurons were distinguished in the Golgi impregnations on the basis of soma size, dendritic size, numbers of primary dendrites, number of dendritic branch points, as well as form, number, and distribution of dendritic appendages. Type I neurons impregnated most frequently and had the most extensive and highly branched dendritic tree. Type II neurons displayed thick dendrites with complex dendritic appendages, but the dendritic tree was much more compact than that of type I cells. Type III and type V cells had fusiform somas and relatively unbranched dendritic trees but differed greatly in size as well as dendritic morphology. The type IV cell was the smallest neuron and had many characteristics of the local interneurons found in other thalamic, subthalamic, hypothalamic and midbrain centers. The type V was the largest neuron, least frequently impregnated, and found only at rostral riMLF levels. Digitized reconstructions of each type of neuron were rotated by the computer, which revealed that the dendritic trees of types I, III, and V occupy a disk-like compartment in the riMLF neuropil. In contrast, the tree of types II and IV occupy a roughly spherical compartment. We suggest that three of the cell types are well suited for specific purposes: type II cells for receiving topographically organized inputs that contain spatial information, type I cells for short-lead burst neuron output to the motor neurons or other premotor centers, and type IV cells for inhibitory inputs to type I cells.

Dynamic holographic interconnects that use ferroelectric liquid-crystal spatial light modulators.

Dynamic interconnect holograms are designed by the use of a simulated annealing algorithm and written to a 128 × 128 pixel ferroelectric spatial light modulator that is used in a binary-phase mode. Dynamic holograms are used to implement a 2 × 2 crossbar with single-mode fiber inputs and outputs, which function with as high as 27 dB of isolation between output ports. The principle is extended to two-dimensional interconnection holograms, and arbitrary fan-out to as high as 64 points is demonstrated with good performance.

Images of interconnection holograms are transferred from the spatial light modulator to an optically addressed spatial light modulator that is used in a binary-phase mode. The addition of a fixed array generator computer-generated hologram permits replication of the hologram image, thus creating a larger hologram with a high space-bandwidth product on the optically addressed spatial light modulator.

Results of a preliminary experiment are presented.

Retrograde transneuronal degeneration in a basal ganglia target, the lateral spiriform nucleus, induced by anterograde transneuronal degeneration following eye removal in the chicken.

The chicken lateral spiriform nucleus (Spl) receives its major input from the paleostriatum primitivum of the forebrain, projects almost exclusively upon the optic tectum, but receives no projections from the tectum. In the present study we show that not only do tectal ablations reduce the volume of the Spl, the cross-sectional area, and the number of Spl neurons, but eye removal also produces a statistically significant reduction in Spl volume, cross-sectional area, and neuron number. Because the retina does not project upon the Spl directly, and because both the retina and the Spl project upon the optic tectum, we propose that the retina produces its effects upon the Spl by an anterograde transneuronally induced retrograde transneuronal mechanism.

Bistability and nonlinearity in optically addressed ferroelectric liquid-crystal spatial light modulators: applications to neurocomputing.

We report the characteristics of a truly bistable optically addressed ferroelectric liquid-crystal spatial light modulator that is capable of storing binary images. We show that, in addition to this bistability, a nonlinear response and gray scales can be observed under certain operating conditions. We then report on how these capabilities can be used in implementing optical neurocomputing architectures.

GABA immunoreactive axons and growth cones in the developing chicken optic nerve and tract.

Immunohistochemical studies of the chicken embryo optic tract using an antibody to gamma-aminobutyric acid (GABA) reveal that the tract is initially free of GABA immunoreactive axons. During the second week of incubation, GABA+ axons appear in the tract, chiasm, and optic nerve. The number of GABA+ axons in the optic nerve increases through E18, although few are recognizable after hatching. Detailed staining of GABA+ growth cones confirmed that virtually all the GABA+ axons in the optic nerve were growing toward the retina. Taken together, the findings suggest that the GABA+ axons in the chiasm and nerve are largely a transient extension of the GABA+ optic tract cells, the tectogeniculate projection, or both.