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PubMed2005

Comprehensive multi-dimensional chromatographic studies on the separation of saturated hydrocarbon ring structures in petrochemical samples.

Characterization of complex petrochemical samples has been a classical subject of comprehensive two-dimensional (2D) gas chromatography (GC x GC). Macroscopic properties of these samples can be described accurately by separation of compounds in classes of identical molecular functionality. Ring structures in the carbon backbone of these compounds, which can be divided in saturated and unsaturated, are amongst the foremost functionalities affecting samples properties. Unfortunately, GC x GC tuned for separation of both saturated and unsaturated ring structures is likely to result in convoluted chromatograms when a distribution of both molecular properties is present in the sample. An independent liquid chromatographic (LC) separation preceding GC x GC could be used to resolve the mixture based on unsaturated rings, allowing saturated rings to be resolved separately in the GC x GC separation. This three-dimensional separation (abbreviated LC-GC x GC) was performed after rigorous evaluation of LC as part of a multidimensional separation using LC x GC. Group-type separation was achieved using this separation for components with either saturated or unsaturated rings. Results of this separation were used to compare information obtained by GC x GC with LC-GC x GC.

Chromatography, Gas↗
PubMed2005

Mercury recovery in situ of four different dental amalgam separators.

Amalgam separators are used to physically remove dental amalgam from waste water in dental clinics. They are thereby supposed to reduce mercury (Hg) emissions to the municipal waste water system to acceptable levels. We here present results from a comparative study in situ of three amalgam separators available on the market, all with a claimed efficiency of 99% according to Danish and ISO protocols, and using sedimentation as the principle of separation. We also present corresponding data for an investigational prototype of an improved separator. The obtained efficiency of the three commercial separators is far below what is stated by the manufacturer and by authorities assumed to be the efficiency in clinical conditions. They reduced Hg emissions by 79 - 91%, leaving an average Hg content in outgoing waste water of 1.5 mg L(-1). However, the prototype separator participating in this study retained 99.9% of the waste water Hg emissions, leaving an average Hg content in outgoing waste water of 0.004 mg L(-1). Physical restrictions prohibit sedimentary type separators to recover the Hg fractions causing the largest damages in wastewater treatment plants. This fraction is not considered in the ISO protocol for testing amalgam separators, which therefore needs to be revised. Abolishing the use of dental amalgam and cleaning the tubing systems is the most efficient long-term solution to reduce Hg emissions from dental clinics. Until then, Hg emissions originating from placing, polishing or removing existing amalgam fillings, should be counteracted by the use of low-emission amalgam separators, already on the market or presently being developed for use alone or together with sedimentary type amalgam separators.

Dental Amalgam↗
PubMed1983

Separation of oestrogens in biological fluids and synthetic mixtures on Sephadex G-type gels.

The separations achieved when mixtures of both free and conjugated oestrogens from a variety of sources are chromatographed on columns of Sephadex gel are reviewed. The molecular identities of oestrogen conjugates which have been separated from human urine by these methods are listed in Table 1. Tables 2 and 3 contain the key experimental details for a total of 26 separations of oestrogen mixtures, abstracted from the total of 20 papers which were published during the period 1961-82. Table 4 details corresponding experimental data for the separation of free oestriol (in human blood) achieved by methods involving a combined Sephadex gel and immunochemical procedure abstracted from a further two papers. A careful analysis of the separation data given in the tables leads to the initial conclusion that the elution profile depends on the expected chromatographic variables for gel filtration chromatography, namely, type of Sephadex gel, length of column, nature and amount of sample applied and the sensitivity of detection methods. However, the separation achieved by the Sephadex columns is also shown to be critically dependent on the column temperature and the pH and chemical composition of the eluent and wash solvents. These latter effects, together with the realization that the molecular weights of the oestrogens being separated are very similar, leads to the conclusion that the separations summarized in Tables 2 and 3 are all being achieved by an absorption process. This being the case, it is suggested that the time-consuming methods of gel filtration chromatography need not be used. Confirmation of this proposal is afforded by a discussion of a recent paper in which the rapid separation of the oestrogens from other components in the biological matrix (urine) was achieved by an adsorption procedure. It is suggested that in the future, separations of oestrogens in biological materials may be most rapidly achieved in combining this type of adsorption procedure with HPLC.

Body Fluids↗
PubMed2001

High-performance liquid chromatographic separation of the enantiomers of organophosphorus pesticides on polysaccharide chiral stationary phases.

High-performance liquid chromatographic separation of the individual enantiomers of 12 organophosphorus pesticides (OPs) was obtained on polysaccharide enantioselective HPLC columns using alkane-alcohol mobile phase. The OP pesticides were crotoxyphos, dialifor, fonofos, fenamiphos, fensulfothion, isofenphos, malathion, methamidophos, profenofos, crufomate, prothiophos and trichloronate. The enantiomers of fenamiphos, fensulfothion, profenofos and crufomate were separated on CHIRALPAK AD; the enantiomers of fenamiphos were also separated on CHIRALPAK AS; the enantiomers of methamidophos, crufomate and trichloronate were separated on CHIRALCEL OD; the enantiomers of crotoxyphos, dialifor, fonofos, malathion, prothiophos and trichloronate were separated on CHIRALCEL OJ; and the enantiomers of isofenphos were separated on CHIRALCEL OG. Baseline or partial separation of the enantiomers of six of these OP pesticides was obtained on CHIRALCEL OJ. In continued method development, the separation of the enantiomers of the 12 OPs was investigated more extensively on CHIRALCEL OJ to determine whether the mobile phase composition, flow-rate and column temperature could be optimized to yield at least partial separation of the enantiomers. Chromatographic conditions were found that gave either baseline or near baseline separations of the enantiomers of the 12 OPs on the CHIRALCEL OJ column.

Chromatography, High Pressure Liquid↗
PubMed1998

Capillary electrophoretic separation of cationic porphyrins.

Cationic porphyrins have a wide variety of uses including those as nucleic acid binding and cleaving agents, as potential pharmacological agents, as electron donor/acceptors in intramolecular electron transfer processes and as analytical reagents. Herein, we report the separation of cationic porphyrins by capillary electrophoresis on fused silica in phosphate buffer at pH 2-5. The porphyrins studied in this work were synthesized from alkylation of the parent tetrapyridylporphyrin (TPyP) to give various pyridinium porphyrins. For example, methylation of TPyP gives a mixture of the mono-, cis-di-, trans-di-, tri- and tetramethylated porphyrins [e.g., 5,10,15,20-tetrakis(N-methyl-4-pyridiniumyl)-21H,23H-p orphyrin, TMPyP(4)]. Capillary electrophoresis on a synthetic mixture showed separation of four of these compounds. Mixtures after alkylation with iodopropionic acid and bromopropylamine were also separated. The cis-di- and trimethylated TMPyP derivatives were separated on a small preparative scale by centrifugal partition chromatography. Capillary electrophoresis was also used to separate metallo TMPyP(4) complexes including those of cobalt, copper, iron, manganese, palladium, tin, vanadium and zinc. The conformational isomers (atropisomers) of 5,10,15,20-tetrakis(N-methyl-2-pyridiniumyl)-21H,23H-p orphyrin, TMPyP(2), were also separated. Net charge, molecular mass and molecular shape all contribute to the differential retention of cationic porphyrins under capillary electrophoresis conditions. Additional factors affecting the separations, including aggregation and protonation of the porphyrins, were probed by evaluating the separation of TMPyP(4) and its butyl and octyl analogs as a function of solution conditions. Cationic porphyrins are difficult to separate using traditional chromatographic methods; capillary electrophoresis and centrifugal partition chromatography provide excellent new techniques for separation of this class of compounds.

Cations↗
PubMed1997

Neuroendocrine correlates of separation stress in the Siberian dwarf hamster (Phodopus sungorus).

Siberian dwarf hamsters form monogamous male-female pair bonds. Disruption of the pair bond results in increases in body mass and behavioral alterations similar to profiles seen in human atypical depression. We examined behavioral and neuroendocrine correlates associated with separation of the male from his mate. Animals were paired (n = 28 pairs) for 3 weeks, then 15 pairs were separated and 13 pairs remained as controls. Behaviors of the males were observed in a novel environment following 3 weeks of pairing and 4 weeks of separation. The 5-min behavioral test monitored exploratory, territorial behavior, and locomotor activity. Separated males showed a significant increase in body mass (p < 0.01). paralleled by an increase in food consumption (p < 0.01). Separated males had decreased seminal vesicle mass (p < 0.05) and testicular mass (p < 0.05). Behavioral analysis revealed that separated males showed no significant differences in grooming, scent-marking, alert on 2 feet, or escape behavior when compared to paired males. Separated males did show significant increases in inactivity (p < 0.05). Plasma cortisol levels were significantly increased in separated animals (p < 0.05), but there were no significant effects on testosterone. Resting levels of plasma norepinephrine and epinephrine were less in separated males, but this was significant only for norepinephrine (p < 0.05). In conclusion, separation stress was accompanied by increased hypothalamic-pituitary-adrenal axis function and decreased peripheral sympathetic nervous system activity and decreased reproductive profiles.

Animals↗
PubMed2000

Separate simultaneous processing of egocentric and relative positions.

It is well established that all kinds of visual attributes are processed separately within the brain. This separation is related to differences in the information that is relevant for the different attributes. When attributes differ greatly (such as colour and motion) it is obvious that they must rely on different information. However, separating the processing of different attributes could also allow highly related attributes to evolve independently, so that they end up being judged on the basis of different types of information. Here, we examine the case of egocentric and relative localisation. For judging egocentric positions, the orientation of the eyes has to be taken into account. This is not so for judging relative positions. We demonstrate that these two attributes can be processed separately by showing that simultaneous judgements of relative and egocentric position differ in their dependency on eye orientation. Subjects pursued a moving dot. We flashed either single targets, or pairs of targets with a 67 ms interval between them, directly below the subjects' gaze. As the eyes were moving during the 67 ms interval, the retinal separation between pairs of targets was different from their actual separation. Subjects indicated the position at which they saw the targets with reasonable reproducibility, with a consistent bias in the direction of the eye movement. However, when two targets were flashed, the indicated separation between them usually coincided with their retinal separation, rather than with their actual separation. We conclude that egocentric and relative spatial positions can be estimated separately and simultaneously, on the basis of different types of information.

Eye Movements↗
PubMed2003

Separation methods that are capable of revealing blood-brain barrier permeability.

The objective of this review is to emphasize the application of separation science in evaluating the blood-brain barrier (BBB) permeability to drugs and bioactive agents. Several techniques have been utilized to quantitate the BBB permeability. These methods can be classified into two major categories: in vitro or in vivo. The in vivo methods used include brain homogenization, cerebrospinal fluid (CSF) sampling, voltametry, autoradiography, nuclear magnetic resonance (NMR) spectroscopy, positron emission tomography (PET), intracerebral microdialysis, and brain uptake index (BUI) determination. The in vitro methods include tissue culture and immobilized artificial membrane (IAM) technology. Separation methods have always played an important role as adjunct methods to the methods outlined above for the quantitation of BBB permeability and have been utilized the most with brain homogenization, in situ brain perfusion, CSF sampling, intracerebral microdialysis, in vitro tissue culture and IAM chromatography. However, the literature published to date indicates that the separation method has been used the most in conjunction with intracerebral microdialysis and CSF sampling methods. The major advantages of microdialysis sampling in BBB permeability studies is the possibility of online separation and quantitation as well as the need for only a small sample volume for such an analysis. Separation methods are preferred over non-separation methods in BBB permeability evaluation for two main reasons. First, when the selectivity of a determination method is insufficient, interfering substances must be separated from the analyte of interest prior to determination. Secondly, when large number of analytes is to be detected and quantitated by a single analytical procedure, the mixture must be separated to each individual component prior to determination. Chiral separation in particular can be essential to evaluate the stereo-selective permeation and distribution of agents into the brain. In conclusion, the usefulness of separation methods during BBB permeability evaluation is immense and more application of these methods is foreseen in the future.

Blood-Brain Barrier↗
PubMed1984

Swedish early separated twins: identification and characterization.

A sample of twins separated early in life has been identified in the Swedish Twin Registry. When the registry was compiled in 1961 (old cohort) and 1973 (young cohort), one or both members of 961 pairs indicated that they were separated by the age of 10. In May 1979, both members of 698 pairs were alive and were sent a questionnaire concerning the circumstances of separation. Items included reasons and timing of separation, biological relatedness of rearing parents, degree of contact after separation (including whether they lived in the same area, attended the same school, or lived together again), rough measures of selective placement, and current frequency of contact. An attempt was then made to categorize the pairs based on degree of separation. A total of 257 pairs met the criteria: rearing parents of one twin biologically unrelated to rearing parents of the cotwin, twins not living together again after separation, and contact after separation a few times a year or less. As much as 50% were separated by their first birthday, and 80% by the age of five. Various data from the twin registry are presented describing the entire sample of early separated twins as compared to a matched sample of twins reared together.

Adolescent↗
PubMed2005

GCxMS of diesel: a two-dimensional separation approach.

Comprehensive two-dimensional gas chromatography can be viewed as a traditional gas chromatography with a sophisticated "elution-resolved" flame ionization detector (GC/FID) or a detector with separation capability. The concept of multidimensional chromatography can be extended to other detectors that also have separation capability, such as ultraviolet, infrared, and mass spectrometer. Mass spectrometry, combined with gas chromatography, GC/MS, has been a powerful separation/identification device for many years. However, if one applies the multidimensional separation concept to this combination with a nonfragmentation ionization method, GC/MS not only can be used as a separation/identification tool, but also a two (multiple) dimensional separation device, GCxMS. In this study, a two-dimensional separation (GCxMS) study of diesel composition is demonstrated and compared with the GCxGC technique. The major advantage of GCxMS is the compound class separation. The compound groups within a compound class are also well-separated on the basis of their parent masses. Because of the exact mass operation, the specific element containing compound distribution can also be generated through the extraction of specific mass groups. For qualitative analysis, GCxMS is a technique where one experiment can generate a wide range of information. GCxMS may also perform quantitative analysis when appropriate response factors for various compound groups are available. From GCxGC to GCxMS, the power of two (multiple) dimensional separation has just started exposing its advantages for complex mixture analysis. To achieve multiple dimensional separation in different forms, many improvements remain to be made. The challenge now is to combine/accommodate two or more different techniques to solve a specific complex separation problem. The GCxMS experience has pushed this effort one step ahead toward complete application of this new concept in the analysis of complex mixtures.

Journal Article↗
PubMed2002

Electrostatic separation of volatile organic compounds by ionization.

Removal technique of trace volatile organic compounds (VOCs) from air or other gases is of great concern in order to obtain contamination-free indoor air and various process gases for semiconductor manufacturing process. We propose a new technique for separating trace gas components. This technique utilizes preferential ionization and electrical migration of ions. Nitrogen and oxygen gas flow containing toluene vapor is divided into two flows, while the flow is irradiated with alpha-ray from 241Am under a DC electric field. The ionized toluene vapor in one flow electrically migrates into the other flow causing toluene rich and free flows. The separation efficiency of toluene is 50% when 0.5 L/min of inlet nitrogen stream contains 0.15 ppm of toluene at the applied voltage of 250 V. The separation efficiency of toluene increases with the mole fraction of oxygen in the carrier gas. The cation concentration flowing out from the separator is lower than the number of separated toluene molecules by 6 orders of magnitude, but the dependency of toluene separation efficiency on the applied voltage is the same as that of cation separation efficiency. The dependency of separation efficiency on the applied voltage and the gas flow velocity is qualitatively explained by the separation model which accounts for the generation and neutralization of VOC ions in the separator.

Air Pollutants↗
PubMed1994

Analytical chiral separation of the stereoisomers of a novel carbonic anhydrase inhibitor and its deethylated metabolite, and the assignment of absolute configuration of the human metabolite and chiral degradation products.

Several approaches to the separation of four stereoisomers, 1-4, of a novel, topically active, carbonic anhydrase inhibitor, 1, with two chiral centers in the molecule and four isomers, 5-8, of its chiral metabolite, 5, were evaluated. These methods include nonchiral derivatization followed by separation on chiral stationary phases (CSPs) and chiral derivatization and separation on nonchiral columns and on CSPs. Baseline separation of stereoisomers 1-4 was achieved in less than 15 min after chiral derivatization with (S)-(+)-1-(1-naphthyl)ethyl isocyanate (NEIC) and chiral chromatography on a (R)-N-(3,5-dinitrobenzoyl)phenyl glycine (DNBPG) column under normal phase (NP) conditions. Similarly, isomers 5-8 were baseline separated in less than 20 min after derivatization with NEIC and chromatography on nonchiral (nitrophenyl) and chiral [(S)-(3,5-dinitrobenzoyl)leucine; DNBL] columns in series under the same NP chromatographic conditions. Only partial separation of the diastereomeric derivatives was observed on a variety of nonchiral columns. In addition, all other direct and indirect chiral separation approaches gave only partial separation of at least two stereoisomers within the group of 1-4 or 5-8. The details of chiral separations using various methods and separation (alpha) and capacity factors (k') of the derivatized isomers 1-8 on a series of chiral and nonchiral columns are presented. Using these methods, the absolute configuration of the human metabolite of 1 was established as S1S2 (5), and the heat (HD) and light (LD) degradation products of 1 as R1S2 (3) and S1S2 (5), respectively.

Biotransformation↗
PubMed1989

Factors influencing cortisol and behavioral responses to maternal separation in guinea pigs.

Infant guinea pigs recently were found to respond to brief maternal separation with an increase in plasma cortisol levels. The present experiments were conducted to further characterize this response and compare it with the cortisol separation response previously observed in primates. In Experiment 1, separation of guinea pig pups from their mothers did not elevate the plasma cortisol levels of the pups at either 30 or 180 min when they remained alone in their home cages during the separation. Experiment 2 showed that cortisol levels of pups placed alone in a novel cage were greater at 30, 90, and 180 min than were those of pups placed in the cages together with their mothers. In contrast, the separated pups vocalized more than did pups tested with their mothers during the initial 30 min only. In Experiment 3, pups raised on inanimate surrogates responded less intensely to rearing-figure separation in terms of both cortisol and vocalizations than did mother-reared controls. Taken together, these results indicate both differences (response to home cage separation) and similarities (dissociation of cortisol and vocalization responses, effect of surrogate separation) in the separation responses of guinea pig and primate infants. The guinea pig model may provide a useful adjunct to primate studies for examining particular issues concerning physiological effects of brief separation from an attachment object.

Animals↗
PubMed1982

Sequence of centromere separation: role of centromeric heterochromatin.

The late metaphase-early anaphase cells from various tissues of male Mus musculus, M. poschiavinus, M. spretus, M. castaneus, female and male Bos taurus (cattle) and female Myopus schisticolor (wood lemming) were analyzed for centromeres that showed separation into two daughter centromeres and those that did not show such separation. In all strains and species of mouse the Y chromosome is the first one to separate, as is the X or Y in the cattle. These sex chromosomes are devoid of constitutive heterochromatin, whereas all autosomes in these species carry detectable quantities. In cattle, the late replicating X chromosome appears to separate later than the active X. In the wood lemming the three pairs of autosomes with the least amount of centromeric constitutive heterochromatin separate first. These are followed by the separation of seven pairs of autosomes carrying medium amounts of constitutive heterochromatin. Five pairs of autosomes with the largest amounts of constitutive heterochromatin are the last in the sequence of separation. The sex chromosomes with medium amounts of constitutive heterochromatin around the centromere, and a very large amount of distal heterochromatin, separate among the very late ones but are not the last. These observations assign a specific role to centromeric constitutive heterochromatin and also indicate that nonproximal heterochromatin does not exert control over the sequence in which the centromeres in the genome separate. It appears that qualitative differences among various types of constitutive heterochromatin are as important as quantitative differences in controlling the separation of centromeres.

Anaphase↗
PubMed1995

Comparative study of autoantigens for various bullous skin diseases by immunoblotting using different dermo-epidermal separation techniques.

We investigated the reactivity of pemphigus vulgaris (PV), pemphigus vegetans, pemphigus foliaceus (Pf), Brazilian Pf, bullous pemphigoid (BP), and epidermolysis bullosa acquisita (EBA) sera with an immunoblot analysis using human epidermal and dermal extracts as a source of antigen. To obtain epidermal and dermal extracts three different dermo-epidermal separation methods were used: namely, ethylenediaminetetraacetic acid (EDTA) separation, heat separation, and dispase separation. All the 15 PV and the seven pemphigus vegetans sera demonstrated a 130-kDa PV antigen in epidermal extracts obtained by all the three methods. Furthermore, three PV sera also showed a 160-kDa Pf antigen, desmoglein. Ten of 14 Pf sera and six of 15 Brazilian Pf sera reacted with desmoglein in the same pattern in all the three epidermal extracts. Fifteen of the 22 BP sera showed reactivity with 230-kDa BP antigen in the same pattern in all the three epidermal extracts, whereas 14 BP sera detected the 180-kDa BP antigen in extracts of EDTA- and heat-separated epidermis but not in dispase-separated epidermal extract. Dermal extracts were obtained by EDTA- and heat-separated dermis, and all six EBA sera labelled a 290-kDa EBA antigen in both samples. These results suggest that heat-separated skin is as useful as EDTA-separated skin for detecting various autoantigens, but heat separation is preferable because the preparation time is shorter.

Autoantigens↗
PubMed2002

Making up for lost time: the experience of separation and reunification among immigrant families.

In the United States today, one-fifth of the nation's children are growing up in immigrant homes. In the process of migration, families undergo profound transformations that are often complicated by extended periods of separation between loved ones--not only from extended family members, but also from the nuclear family. Though many families are involved in these transnational formulations, there has heretofore been little sense of the prevalence of these forms of family separations, nor of the effects on family relations. Further, such research has generally been conducted with clinical populations using Western theoretical frameworks and perspectives of families, limiting its applicability to immigrant families. The data presented in this article are derived from a bicoastal; interdisciplinary study of 385 early adolescents originating from China, Central America, the Dominican Republic, Haiti, and Mexico. Findings from this study indicate that fully 85% of the participants had been separated from one or both parents for extended periods. While family separations are common to all country-of-origin groups, there are clear differences between groups in lengths of separations as well as people from whom the youth are separated. Descriptive statistics of country-of-origin prevalence, patterns, and outcomes are presented. Results of analyses of variance indicate that children who were separated from their parents were more likely to report depressive symptoms than children who had not been separated. Further, qualitative data from youth, parent, and teacher perspectives of the experience of separation and reunification provide evidence that the circumstances and contexts of the separations lead to a variety of outcomes. We conclude with a discussion of attenuating and complicating factors family therapists should consider in the assessment and treatment of immigrant families.

Adolescent↗
PubMed2003

Fenceline contact of beef calves with their dams at weaning reduces the negative effects of separation on behavior and growth rate.

The purpose of this study was to examine the hypothesis that fenceline contact between beef calves and cows at weaning reduces indices of behavioral distress and associated temporary reductions in weight gain. One hundred Angus/Hereford-cross calves were randomly assigned to five treatments for 7 d in each of 3 yr to determine the effect of different weaning techniques on their behavior and subsequent growth. Treatments were 1) fenceline separation from dams on pasture (F-P), 2) total separation from dams on pasture (S-P), 3) total separation from dams in a drylot (corral) preconditioned to hay (S-D-P), 4) total separation from dams in a drylot not preconditioned to hay (S-D-NP), and 5) nonweaned controls on pasture (C-P). At the end of the 7-d postweaning period, all calves were placed on pasture in large groups. Calves were weighed weekly for 10 wk. In the days following weaning, F-P and C-P calves spent more time eating (grazing or eating hay) than S-P and S-D-NP calves (P < 0.05). The S-P calves spent more time walking (pacing) than calves in the other four treatments (P < 0.05), which did not differ. The S-P calves also spent less time lying down than C-P, F-P, and S-D-P calves (P < 0.05); S-P and S-D-NP calves did not differ in lying time. The F-P calves vocalized less than S-P and S-D-NP calves (P < 0.05). In general, treatment differences were greatest during the first 3 d following weaning with d 2 (20 to 30 h after weaning) showing the greatest disparity. The F-P calves spent approximately 60% of their time within 3 m of the fence separating them from their dams during the first 2 d following weaning, whereas F-P cows spent about 40% of their time within 3 m of the fence during this period. Postweaning cumulative body weight gains of the F-P calves were greater than the gains recorded for the calves in the three totally separated treatments (which did not differ). The F-P calves gained 95% more weight than the average calf in the three totally separated treatments in the first 2 wk and were still heavier at 10 wk (21.4 vs 11.0 kg, respectively, at 2 wk and 50.0 vs 38.2 kg, respectively, at 10 wk; P < 0.05). It was concluded that providing fenceline contact between beef calves and cows for 7 d following weaning reduces behavioral indices of distress seen in the totally separated calves. In addition, fenceline contact with dams at weaning minimizes losses in weight gain in the days following separation. Totally separated calves did not compensate for these early losses in weight gain even after 10 wk.

Animals↗
PubMed1998

Memory for spatial location: role of the hippocampus in mediating spatial pattern separation.

A paradigm based on measuring short-term memory for spatial location information as a function of spatial similarity between distal cues was developed to examine the role of pattern separation in the modulation of short-term memory for spatial information. A delayed-match-to-sample for spatial location task using a dryland version of the Morris water maze was used to assess spatial pattern separation in male Long-Evans rats. In the sample phase, animals were trained to displace an object that covered a baited food well in one of 15 spatial locations along a row of food wells perpendicular to a start box. In the ensuing choice phase, the animal was allowed to choose between two objects identical to the sample phase object. One covered the same baited food well as did the object in the study phase (correct choice), and another foil object (incorrect choice) covered a different unbaited food well along the row of wells. Five spatial separations were randomly used to separate the correct object from the foil object. After reaching a criterion before the operation, animals were given either hippocampal or cortical control lesions. In trials after the operation, control animals matched their performance before the operation across all spatial separations. In contrast, hippocampal-lesioned animals displayed impairments across all spatial separations with the exception of the longest (105 cm) spatial separation. The results suggest that the hippocampus may serve to separate incoming spatial information by temporarily storing one place separate from another. It is proposed that hippocampal lesions decrease efficiency in pattern separation, resulting in impairments in trials with increased spatial similarity among working-memory representations.

Animals↗