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At least 973 records · Page 54Linked to original sources
PubMed1982

Suppressed immune response in infant monkeys associated with maternal separation.

The effect of maternal separation on an in vitro measure of the cellular immune response was studied in infant bonnet monkeys (Macaca radiata). Using a modified mixed-species separation paradigm, bonnet mother-infant pairs were each housed with a single adult female pigtailed monkey (Macaca nemestrina). Over a 14-day separation period, the infants showed a suppression of lymphocyte proliferation in response to mitogens relative to a 14-day baseline period which preceded separation. The lymphocyte response was restored following reunion. During separation, infants were initially agitated, and this was followed by observations of reduced activity and a slouched posture. Behaviors returned to baseline conditions following reunion. It was concluded that suppressed immunological functioning may be included among the pathophysiological consequences of maternal separation in infant monkeys.

Animals↗
PubMed2000

Separation vs. replication of inactive and active centromeres in neoplastic cells.

The inactive centromeres in neoplastic and transformed cells exhibit premature separation at prophase or pro-metaphase. The factor(s) that control this behavior are not known. Using a human breast cancer cell line, MDA 435, and a transformed mouse cell line (L929), we studied the relationship between the sequence of centromere separation and the replication of centromeric region associated with the active and inactive centromeres. Whereas the inactive centromeres in L929 cells replicate their pericentric heterochromatin earlier than that associated with the active centromeres, those in MDA 435 cells exhibited no strong correlation between early separation and replication. A comparison between the intragenomic patterns of separation with replication of only active centromeres showed that the former is not dependent upon the latter in either L929 cells or MDA 435 cells. These studies indicate that, whereas inactive centromeres in neoplastic cells separate prematurely in different species, there is no uniformity in the control for replication nor does the timing of separation depend upon the timing of replication of the centric region.

Animals↗
PubMed1997

Marital status effects on health: are there differences between never married women and divorced and separated women?

To test whether the effects of marital status on health differ between never married women and divorced and separated women, this study utilizes prospective panel data for a large national sample of non-institutionalized young women in the U.S. (the National Longitudinal Surveys of Young Women). The women were aged 24-34 at the beginning of two successive five-year follow-up intervals (1978-1983 and 1983-1988). The health effects of marital status were evaluated in regressions which assessed the relationships between initial marital status and subsequent health trends in each follow-up interval. In the first follow-up interval, never married women tended to have worse health trends than divorced and separated women for physical impairments and for overall health problems. However, there were no differences between never married women and divorced and separated women in health trends for psychosomatic symptoms in either follow-up interval or for any health measure in the second follow-up interval. Our analyses of cross-sectional data showed few significant differences in health between never married women and divorced and separated women. Taken together, the evidence from our study and previous studies suggests that differences between never married women and divorced and separated women may vary by age and/or cohort. Evidence for the 1970s and 1980s suggests that, among older women, divorced and separated women may have experienced more harmful health effects than never married women; however, among younger women, this difference may have been absent or possibly reversed.

Adult↗
PubMed2000

High-performance liquid chromatographic optimization study for the separation of natural and synthetic anabolic steroids. Application to urine and pharmaceutical samples.

An HPLC separation of a complex mixture containing 14 androgenic anabolic steroids (natural and synthetic) for screening purposes has been carried out. The applied optimization method involved the use of binary, ternary and quaternary mobile phases containing acetonitrile, methanol or tetrahydrofuran as organic modifiers. The effect of different reversed-phase packings and temperature on the separation using acetonitrile as organic modifier was studied. The optimum separation was achieved by using a water-acetonitrile (55:45, v:v) mobile phase and a Hypersil ODS (250 mm x 4.6 mm) 5 microm column (30 degrees C) in about 38 min, allowing the separation of 14 out of 14 compounds tested (when danazol is excluded, 13 out of 14 were separated in 23 min). Calibration graphs were obtained using bolasterone, methyltestosterone and canrenone as internal standards. Detection limits were in the range 0.012-0.11 microg ml(-1). The optimized separation was applied for monitoring the norethindrone acetate hydrolysis from tablets and to the analysis, after liquid-liquid extraction, of urine samples spiked with steroids.

Anabolic Agents↗
PubMed2000

Kinetics of phase separation under different process and design parameters in aqueous two-phase systems.

A practical study is presented of the effect of height/diameter (H/D) ratio of settlers on the kinetics of phase separation in aqueous two-phase systems (ATPSs). Poly(ethylene glycol) (PEG) 1000-phosphate systems with the presence of undiluted and diluted whey and disrupted yeast were used in batch studies. The influence of the biological suspensions on the rate of phase separation was investigated. It was observed that, phase separation time is much faster when disrupted suspension was used. The addition of undiluted suspensions to ATPSs slowed the process of phase separation. When the batch settler with a large cross section area (H/D ratio less than one) was used, the phases separated much faster than in a settler with a H/D ratio greater than one. Conclusions are drawn concerning the characterisation of the process and design parameters involved in the phase separation for the design of appropriate equipment.

Kinetics↗
PubMed1988

Free-flow electrophoretic apparatus for separation and concentration of proteins.

Protein separation in the free-flow electrophoretic apparatus with 48 channels at both the inlet and outlet using "artificial" pH gradients was investigated. The separation was carried out in borate-mannitol pH gradients and in pH gradients created by the concentration gradient of boric acid in the solutions of borax and mannitol. The separation pattern depended on the ratio of the rate of sample injection to the flow-rate of solutions in the separation chamber and did not change when the protein concentration in the sample was changed. The protein separation in the pH gradient was better than in case of conventional free-flow electrophoresis. The free-flow electrophoretic apparatus with multi-channel inlet of the separation chamber is suitable for concentration of biological materials, e.g. proteins and bacterial cells.

Alkaline Phosphatase↗
PubMed1984

Separation, isolation and identification of optical isomers of 1,4-benzodiazepine glucuronides from biological fluids by reversed-phase high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic (HPLC) method for the determination of four separate 1,4-benzodiazepine glucuronides in urine, plasma and bile is presented. We succeeded not only in determining the single glucuronides but also in separating the enantiomers (optical isomers) of the 1,4-benzodiazepine glucuronides. The optical isomers of the glucuronides of oxazepam and cinolazepam and of two other glucuronides of benzodiazepine metabolites could be well separated. The ratio of the isomers could be evaluated. An octadecyl reversed phase was used with a mobile phase of acetonitrile and 0.01 M orthophosphoric acid. After the initial separation, the isomers were fractionated by HPLC. After treatment with beta-glucuronidase to yield the aglycone, the separated fractions were hydrolysed to the corresponding benzophenones whose identity was confirmed by HPLC. Gas chromatography and gas chromatography-mass spectrometry demonstrated that the separated glucuronides corresponded to the enantiomeric benzodiazepines. Human urine and plasma as well as rabbit urine, plasma and bile were examined.

Benzodiazepines↗
PubMed1988

endo-1,4,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene-2-carboxylic acid, a superior resolving agent for the high-performance liquid chromatographic separation of enantiomers of hydroxylated derivatives of two azaaromatic hydrocarbons.

The high-performance liquid chromatographic (HPLC) separation of enantiomers of oxide and hydroxy derivatives of dibenz[a,j]acridine and 7-methylbenz[c]acridine was investigated on a chiral stationary phase chromatography column using commercially available columns. In most cases either poor or no separation of enantiomers was achieved. Normal-phase separation of diastereoisomeric ester derivatives of the hydroxy compounds, prepared from commercially available (-)-menthoxyacetic acid or (+)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetic acid, was investigated. No separation of the diastereoisomeric esters of trans-3,4-dihydroxy-3,4-dihydrodibenz[a,j]acridine was observed. However, diastereoisomeric esters prepared from (+)-endo-1,4,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene-2-carboxyl ic acid [(+)-HCA] were easily separated. Using the three chiral acids, diastereoisomers were prepared from sixteen hydroxy derivatives of dibenz[a,j]acridine and 7-methylbenz[c]acridine. (+)-HCA esters gave good to excellent HPLC separations which were superior to those achieved using other chiral acids in most cases. The enantiomeric composition of trans-3,4-dihydroxy-3,4-dihydrodibenz[a,j]acridine formed as a major rodent liver microsomal metabolite of dibenz[a,j]acridine was determined using (+)-HCA.

Acylation↗
PubMed1997

Unstable proteins: how to subject them to chromatographic separations for purification procedures.

The chromatographic separation of an unstable protein is often a challenge to the scientist working in the field of life sciences. Especially for the purification of sensitive enzymes, making use of conventional chromatographic techniques is difficult and frequently results in a complete loss of biological activity of the target protein. This report summarizes some general strategies that may help to keep unstable proteins in their native conformation during the rather harsh conditions of a purification procedure. In this context, a recently developed hollow fiber membrane module, suitable for performing on-line dialysis, is introduced and examples of its application to liquid column chromatography are given. Many innovative separation techniques, characterized by dramatic improvements in both performance and separation time, have recently been developed. Since the chromatographic separation of unstable proteins requires the use of modern state-of-the-art equipment and technology, emphasis is given to newly developed separation techniques such as expanded bed adsorption, perfusion chromatography, protein free flow electrophoresis and the use of tentacle gels. In addition, examples of recently published purifications of unstable proteins are discussed with respect to strategies ensuring the preservation of the native protein structure during chromatographic separation.

Adsorption↗
PubMed2002

Optimization of preparative electrophoretic chiral separation of ritalin enantiomers.

Continuous free flow electrophoresis (CFFE) was applied to the preparative chiral separation of ritalin enantiomers. Sulfated beta-cyclodextrin (sbeta-CD) was used as the chiral additive. Liquid chromatography-mass spectrometry (LC-MS) experiments were applied to study the time averaged concentration of sbeta-CD in the separation chamber. The distribution of sbeta-CD in the separation chamber greatly influenced resolution and the angle of deflection. To optimize the separation, several parameters (methanol, concentration of sbeta-CD in the cathodic wash and in the separation buffer, and the introduction of a low conductivity zone) were investigated. The dependence of the resolution and deflection angles of ritalin enantiomers on the concentration of sbeta-CD in both the separation buffer and in the cathode wash solution appeared to be non-linear. Under close to optimal conditions, resolution of ritalin enantiomers was about 0.8 with an average processing rate of 0.5 mg/h. Overall, the enantiomeric purity of the individual isomers was approximately 83%; however, of the 20 vials containing ritalin, the presence of both enantiomers was only detected in three vials.

Central Nervous System Stimulants↗
PubMed2002

Enantiomer separation by capillary electrophoresis utilizing carboxymethyl derivatives of polysaccharides as chiral selectors.

Enantiomer separations of various drugs by capillary electrophoresis (CE) were investigated utilizing carboxymethyl (CM) derivatives of some polysaccharides. Three types of CM-polysaccharides, namely CM-dextran, -amylose and -cellulose were employed as chiral selectors in the CE enantiomer separation. Capability of enantiomer separation by these CM-polysaccharides was compared with that by polysaccharides without CM residues (i.e. native or neutral polysaccharides). Among three selectors employed, CM-dextran and -cellulose showed a relatively wide capability of enantiomer separation. Modification of polysaccharides seems to lead to the enhancement of the capability of enantiomer separation. Degree of substitution greatly affected the capability of enantiomer separation of these polysaccharide derivatives as in the beta-cyclodextrins derivatives.

Amylose↗
PubMed2003

Fast separations on monolithic silica columns: method transfer, robustness and column ageing for some case studies.

Six separation methods, developed on conventional silica high performance liquid chromatography (HPLC) columns were transferred to monolithic silica columns of 5 and 10 cm length. The transferred methods include the separation of an alkylbenzene mixture, the separations of drugs from their impurities (nimesulide, tetracycline, phenoxymethylpenicillin and erythromycin) and the separation of a green tea extract. The transfer of the first three methods was successful while for the latter three it was not. Increasing the flow rate up to 9 ml/min (where possible) inversely decreased the analysis time of the successfully transferred methods to 48 s (alkylbenzene mixture) 1.8 min (nimesulide mixture) and 3 min (tetracycline mixture) while still reasonable well separated peaks were obtained. The robustness and repeatability of the transferred and accelerated separations was found to be acceptable. Despite the use of flow rates up to 9 ml/min and frequent mobile phase changes with pH values varying from 3.5 to 7, the column performance was found to be rather constant and the column ageing to be minimal.

Chromatography, High Pressure Liquid↗
PubMed1998

Optimization of mobile phase in the separation of beta-blockers by HPLC.

Beta-blockers are generally determined using high-performance liquid chromatography (HPLC). Previous HPLC separations of beta-blockers have often required a mobile phase containing three components; acetonitrile or methanol to control the retention; buffer to control the ionic strength and pH of the mobile phase; ion-pairing reagent to provide adequate retention of beta-blockers or organic amines as masking agent to reduce peak tailing. Due to the complexity of the mobile phases employed, development of these assays can be a laborious process. Additionally, alkyl sulphonates and organic amines dramatically reduces the life-time reduction of silica based C18 columns. The results of this study demonstrated that the addition of tested alkyl sulphonates and organic amines is not essential for an adequate separation of beta-blockers. In this study, we developed a simple HPLC method for the simultaneous separation of model beta-blockers, atenolol, practolol, metoprolol, oxprenolol and propranolol. Atenolol, practolol, metoprolol, oxprenolol and propranolol adequately separated with high peak symmetries using a mobile phase consisted of methanol/acetonitrile/phosphate buffer (10 mM, pH 3.0) (15:15:70, v/v/v). By altering only the fraction of methanol with respect to acetonitrile, method development becomes a more efficient separation. Furthermore, atenolol, practolol, metoprolol, oxprenolol and propranolol can be detected up to 0.25, 5, 10, 50 and 10 ng ml(-1). In this publication, we present the simultaneous separation of beta-blockers having a wide range of polarity. It is proposed that this new mobile phase, consisting only acetonitrile, methanol and phosphate buffer can be used for the analysis of the several beta-blockers presently in doping control analysis as well as others.

Acetonitriles↗
PubMed2004

Multidimensional separations in the pharmaceutical arena.

The introduction of novel, powerful and rapid multidimensional separation and characterization methods has produced revolutionary global changes at the genome, proteome and metabolome level, bringing about a radical transition in our views of living systems, at the molecular level. The age of proteomics and metabolomics demands high-resolution multidimensional separation techniques. Multidimensional gas and liquid chromatography techniques, in addition to capillary and microchip electrophoresis methods, offer increased resolution and sensitivity, while also affording adequate throughput and reproducibility to meet the demands of the modern pharmaceutical industry. Coupled with MS, these techniques provide not only separation but also reliable identification of the sample components. The resolving power of these methods has proved to be superior over individual one-dimensional approaches, enabling the comprehensive separation of complex biological mixtures, with excellent resolution and reproducibility. High capacity computer systems that are capable of rigorous qualitative and quantitative analysis of the separation profiles allow the establishment and mining of large databases. Examples of various modern multidimensional separation techniques, and their integration with MS, are reviewed, here, with respect to pharmaceutical analysis.

Chromatography, Gas↗
PubMed2002

Peak capacity of ion mobility mass spectrometry: separation of peptides in helium buffer gas.

Advances in the field of proteomics depend upon the development of high-throughput separation methods. Ion mobility-mass spectrometry is a fast separation method (separations on the millisecond time-scale), which has potential for peptide complex mixture analysis. Possible disadvantages of this technique center around the lack of orthogonality between separation based on ion mobility and separation based on mass. In order to examine the utility of ion mobility-mass spectrometry, the peak capacity (phi) of the technique was estimated by subjecting a large dataset of peptides to linear regression analysis to determine an average trend for tryptic peptides. This trend-line, along with the deviation from a linear relationship observed for this dataset, was used to define the separation space for ion mobility-mass spectrometry. Using the maximum deviation found in the dataset (+/-11%) the peak capacity of ion mobility-mass spectrometry is approximately 2600 peptides. These results are discussed in light of other factors that may increase the peak capacity of ion mobility-mass spectrometry (i.e. multiple trends in the data resulting from multiple classes of compounds present in a sample) and current liquid chromatography approaches to complex peptide mixture analysis.

Helium↗
PubMed1977

Some factors influencing the effects of temporary mother-infant separation: some experiments with rhesus monkeys.

Some experiments, reported in detail elsewhere, on the effects of mother-infant separation in rhesus monkeys are here reviewed and compared. They involved 4 groups--one in which mothers were removed for 13 days leaving the infant in the social group; one in which infants were removed; one in which mothers and infants were removed and separated; and one in which mothers and infants were removed but not separated. The nature of separation experience had a profound effect on the infant's response: infants left in a familiar environment while their mothers were removed showed marked but brief 'protest' and then profound 'despair', whilst infants removed to a strange cage showed more prolonged 'protest'. A major factor determining the effects of the separation experience in the weeks following reunion is the degree to which the mother-infant relationship has been disturbed by it. The multiplicity of factors affecting the outcome of a separation experience are discussed.

Animals↗
PubMed1997

The effects of divorce and separation on mental health in a national UK birth cohort.

BACKGROUND: Many studies have reported a negative impact of divorce and separation on health although it is still unclear to what extent this is due to early vulnerability, the material and social consequences of divorce or to its direct emotional effects. METHOD: Measures of anxiety and depression and potential alcohol abuse at age 43 were compared in 2085 participants from the MRC National Survey of Health and Development who were either married and never divorced or separated, or who had divorced or separated at least once. Analyses were adjusted for sociodemographic features, early vulnerability factors and current stressors. RESULTS: Divorce and separation were associated with increased anxiety and depression, and increased risk of alcohol abuse. This was the case after adjusting for educational attainment, age at first marriage, parental divorce, childhood aggression and neuroticism, and current financial hardship, lack of a confidante and frequency of social contact with friends or family. The association between divorce and risk of alcohol abuse became non-significant when the latter variable was controlled for. Associations between divorce and psychopathology were observed even though half of those separated or divorced were re-married or reunited with their spouses at the time of the analysis. There was, furthermore, no association between these mental health measures and time since first separation or divorce.

Adult↗
PubMed2003

Desipramine treatment reduces the long-term behavioural and neurochemical sequelae of early-life maternal separation.

Primate and rodent models of maternal separation have shown that repeated postnatal separation of young from the mother results in long-term changes to neurohormonal systems relevant to depression. To date, however, it remains unclear whether rodents that experience postnatal maternal separation display specific behavioural or biochemical features of depression in adulthood and whether these changes can be prevented by treatment with antidepressant drugs. We report here that maternally separated mice showed significantly shorter swim times on the forced swim test and significantly lower levels of brain-derived neurotrophic factor in dentate gyrus and CA3 regions of the hippocampus compared to control mice when assessed in adulthood. Neither of these differences was apparent in maternally separated mice that received chronic treatment with the antidepressant desipramine after maternal separation. These results suggest that intervention following early stress may eliminate the long-term vulnerability to behavioural and biochemical dysfunction that occurs following this early chronic stress.

Animals↗