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P Ramm

Publications and source records attributed to P Ramm.

12 recordsLinked to original sources
PubMed1999

Imaging systems in assay screening.

High-throughput screening laboratories continuously seek higher throughput, lower cost and compound conservation. In an attempt to approach these goals, improvements in traditional detection instruments (e.g. scintillation counters, fluorescence plate readers, luminometers) are being made. A more radical alternative is the use of image-based detection methods, which have the advantage that large numbers of wells can be quantified in a single detection procedure (favouring miniaturization) and that faint luminescence or scintillation assays can be accomplished very rapidly. However, image-based screening is a very new technology and must prove itself before being broadly accepted. In this review, the technology of a commercial instrument for image-based screening (the LEADseeker from Amersham Pharmacia Biotech, Amersham, UK) is described, and its performance summarized with scintillation, luminescence, fluorescence and absorbance signals.

Journal Article↗
PubMed1994

Advanced image analysis systems in cell, molecular and neurobiology applications.

Many of today's image acquisition devices (scanners and cameras) yield high-resolution (1280 x 1024 pixels is typical) and/or high-precision (> 8 bits) image data. When coupled to a powerful image analyzer these image acquisition devices offer practical advantages in many bioscience applications. The benefits of high resolution include better contrast transfer (sharper images with more accurate density rendition) and an ability to work with large specimens at lower optical magnifications (larger field of view). High precision is useful if images contain subtle features (e.g., fluorescently labeled processes at densities close to background) and/or wide dynamic range. Examples are given, illustrating the use of a number of medium- and high-performance image acquisition devices with an advanced image analyzer. The examples include a comparison of intensified and integrating cameras in fluorescence microscopy, evaluation of the performance of a fast, cooled integrating camera in ratio fluorescence imaging, and a comparison of film and storage phosphor-plate performance in quantitative receptor autoradiography.

Animals↗
PubMed1990

Rates of cerebral protein synthesis are linked to slow wave sleep in the rat.

Using L-[1-14C]leucine autoradiography, rates of cerebral and local cerebral protein synthesis were studied during wakefulness, slow wave sleep (SWS) and REM sleep in the rat. In the cerebrum as a whole, the rate at which labelled leucine was incorporated into tissues was positively correlated with the occurrence of slow wave sleep. We failed to observe a significant correlation of protein synthesis rate with either wakefulness or REM sleep. As in the cerebrum as a whole, most discrete brain regions showed moderate positive correlations between the occurrence of SWS and rates of protein synthesis. There were no brain regions in which rates of protein synthesis showed striking correlations with sleep-wake states. Thus, the occurrence of SWS is associated with higher rates of protein synthesis throughout the brain. These data suggest that SWS sleep favors the restoration of cerebral proteins.

Animals↗
PubMed1987

Effects of extinction, pimozide, SCH 23390, and metoclopramide on food-rewarded operant responding of rats.

The similarity in the pattern of responding produced by extinction and dopamine (DA) receptor blockers has led to the suggestion that DA neurons may participate in the usual effects of reward on behaviour. The purpose of the present study was to evaluate the effect of receptor-subtype specific DA antagonists on food-rewarded operant responding. Rats were trained to lever press for food on a variable interval 30-s schedule. They then received one of the following treatments prior to testing on the next 5 days: saline, nonreinforcement, the DA receptor blocker pimozide (0.5 or 1.0 mg/kg), the D1 receptor blocker SCH 23390 (0.01, 0.05, 0.1 mg/kg), and the D2 receptor blocker metoclopramide (1.0, 5.0, 10.0 mg/kg). Nonreinforcement resulted in both intra- and intersession declines in responding. The drugs produced dose-dependent decreases in overall responding. Additionally, both doses of pimozide and the higher doses of SCH 23390 and metoclopramide altered intrasession patterns of responding when compared to saline, with their greatest effect being in the latter portion of the session. Intersession declines were seen with the highest doses of SCH 23390 and metoclopramide and control studies showed that these declines could not be attributed to a buildup of the drug with repeated dosing. It was concluded that both D1 and D2 receptors participate in the control of behaviour by reward.

Animals↗
PubMed1986

Cerebral and local cerebral metabolism in the cat during slow wave and REM sleep.

[14C]2-deoxyglucose autoradiography was used to show cerebral and regional cerebral metabolism during slow-wave sleep (SWS) and rapid-eye-movement sleep (REM) in the cat. Lower levels of mean cerebral metabolism, reflecting cerebral energy conservation, were associated with SWS. A clear link between REM and mean cerebral metabolism was not observed. At the regional level, SWS was associated with markedly low metabolism in thalamic sensory relays and in cortex. REM was associated with relatively low metabolism in the cerebellum, but with relatively high metabolism in the hippocampus, and in some 'motor' regions including the trigeminal and red nuclei. Thus, SWS was linked to cerebral energy conservation and to particularly low levels of functional activity in cortical and sub-cortical sensory regions. REM was unlike SWS in that: REM did not appear to be strongly linked to cerebral energy conservation; REM was linked to metabolism in fewer brain regions than was SWS; and most REM-linked regions exhibited relatively high levels of metabolism. In addition, while SWS was most clearly associated with functional activity in sensory regions, REM was linked to functional activity in a small number of limbic and motor regions. In sum, SWS and REM are associated with distinctive cerebral metabolic and functional states.

Animals↗
PubMed1984

Video and scanning microdensitometer-based imaging systems in autoradiographic densitometry.

The characteristics of computer-assisted imaging devices (CIDs) incorporating charge-coupled device cameras, vidicon cameras and scanning microdensitometers (SMDs) are compared. Advantages of vidicons include their low cost, the option of real-time imaging, continuously variable optical magnification and the wide choice of available vidicon elements. Disadvantages include densitometric non-linearities and, with some vidicons, lack of dynamic range. A CID comprising a laboratory minicomputer, image processing device, vidicon and SMD scanners and our 'PANDA' image analysis routines is described. Software corrections for vidicon errors are evaluated by comparing the densitometric accuracy of the CID receiving input from the vidicon camera and from the SMD. The scanners exhibit similar densitometric accuracy and linearity, and acceptable between-session repeatability. It is concluded that densitometric precision of a corrected vidicon scanner is not the limiting factor for quantitative autoradiographic densitometry.

Animals↗
PubMed1984

Functional activity in the lateral habenular and dorsal raphe nuclei following administration of several dopamine receptor antagonists.

2-[14C]deoxyglucose autoradiography was used to show regional functional activity in the rat brain following administration of the dopamine antagonists, cis-flupenthixol, metoclopramide, and pimozide. Elevation of functional activity was observed in the lateral habenula (LHb) following administration of all antagonists. The dorsal raphe nucleus (DR) exhibited decreased functional activity following cis-flupenthixol, which exerts effects at both the D1 and D2 receptors, but not following pimozide or metoclopramide, which primarily act at the D2 receptor. These results converge with previous reports suggesting that the functional status of the LHb is regulated by dopaminergic systems, and that LHb efferents may exert a major influence upon DR neurons. These data further suggest that an influence of the LHb upon DR neurons may be affected via the D1 receptor.

Animals↗
PubMed1983

Regional metabolic activity in the rat brain during sleep-wake activity.

[14C]2-Deoxyglucose autoradiography was used to demonstrate regional metabolic activity in the rat brain during wake, slow-wave sleep (SWS), and REM sleep. Data are expressed as values of relative metabolic activity (RMA, regional optic density/mean brain optic density), which show the level of metabolic activity in a region, relative to the mean level of the brain. Regions exhibiting obviously decreased RMA during SWS include the cerebellum, cortical layer IV, and most of the thalamus, including the massa intermedia and lateral geniculate nuclei. Low levels of RMA in sensory relay regions during SWS reflect functional deafference of the brain. In contrast, some limbic regions, including the hypothalamic core and hippocampal dentate fascia, exhibit increased RMA during SWS. Regions exhibiting increased RMA may have functions which are carried on at high levels during sleep. The metabolic appearance of the brain in REM is very different from that in SWS. The reticular core, substantia nigra, hippocampal dentate fascia, and stratum moleculare, and many regions associated with the extrapyramidal motor system, exhibit increased RMA. The cerebellum and ventral thalamic nucleus show decreased RMA, while the lateral thalamic nuclei and cortical layer IV show no metabolic state dependency. In sum, SWS is associated with a general decrease in RMA of sensory and motor areas, and with increased RMA in some limbic regions. RMA is similar in cerebellar and hippocampal regions during REM and SWS. In contrast, RMA in many sensory relay regions does not decrease during REM, and there is REM-specific increase of RMA in some pontomesencephalic regions associated with motor function.

Animals↗
PubMed1980

Enhancement of tyrosine hydroxylase activity by Oxotremorine does not affect sleep in the rat.

Marked enhancement of tyrosine hydroxylase (TH) activity was observed in the rostral pons of Wistar albino rats, 3 days after a single injection of Oxotremorine. TH activity in other brain areas, and regional levels of norepinephrine, dopamine, serotonin and 5-hydroxyindoleacetic acid were unaffected. Enhancement of TH activity did not affect length or number of REM episodes, or the amount of REM occurring in 24 hr. REM occurrence did not, thus, vary in accordance with activity of the rate-limiting enzyme for catecholamine synthesis. These data suggest that, although REM may reflect neuronal protein synthesis, REM is not part of a mechanism regulating the activity of enzymes in the pontine CA synthesis pathway.

Animals↗
PubMedDate not supplied

Recent trends in receptor analysis techniques and instrumentation.

Receptor autoradiography allows visualization of receptor binding sites at the regional or light microscopic level. Receptor autoradiography is a mature methodology, in widespread use. It is also a dynamic and expanding methodology, benefiting constantly from the introduction of new techniques and instrumentation. In particular, receptor autoradiography has taken advantage of image analysis instrumentation to provide efficient spatial mapping of receptor populations and their pharmacological characteristics. A major contribution to the understanding of receptors has come from the recent cloning of the genes coding for many of these receptors. This has allowed the use of in situ hybridization to demonstrate the cells expressing mRNA coding for specific receptor subtypes. The result is that many receptor populations, previously thought to be homogeneous, are shown to be composed of several subtypes. As a consequence, the distribution of many receptors requires re-examination, which is aided by the development of new and more selective ligands. With the incorporation of techniques from molecular biology into receptor autoradiography, the demands upon image analysis instruments have expanded. Over the past decade, densitometric image analysers have attained a high level of sophistication for classical receptor autoradiography. However, to serve the needs of today's receptor laboratory, an image analyser must be equally capable in regional densitometry, in counting and spatial mapping of grain and/or cell locations at the microscopic level, and in analysing electrophoresis gels. Advances in image analysis hardware and software are keeping pace with the requirements of receptor laboratories.

Animals↗
PubMedDate not supplied

Image analyzers for bioscience applications.

Image analysis systems are becoming more sophosticated, less costly, and very common in research laboratories. Therefore, the bioscience researcher is faced with a bewildering array of choices in establishing an image analysis facility. Critical components and characteristics of commercial image analyzers are discussed. State-of-the-art systems feature a graphical user interface, a powerful operating system (e.g., Microsoft OS/2), 1000 line image acquisition, processing and display, true color imaging, and very flexible scanner interfaces. Such systems are best suited to technically difficult applications, such as ratio fluorescence, or to automated analysis of anatomical features, particularly in stained material. Less powerful image analyzers offer medium resolution, and typically work with monochrome data acquired from video cameras. Such systems are suitable for many bioscience applications, including quantitative autoradiography and routine morphometry.

Analog-Digital Conversion↗