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At least 181 records · Page 10Linked to original sources
PubMed2002

Liquid exclusion-adsorption chromatography: a new technique for isocratic separation of non-ionic surfactants. V. Two-dimensional separation of fatty acid polyglycol ethers.

Fatty acid polyglycol esters can be fully characterized using two-dimensional liquid chromatography with liquid chromatography under critical conditions (LCCC) as the first and liquid exclusion-adsorption chromatography (LEAC) as the second dimension. LEAC is run under isocratic conditions, which allows the use of the refractive index detector, and thus accurate quantitation. Fractions from LCCC are transferred to LEAC using the full adsorption-desorption technique, by which they are focussed and reconcentrated before injection into the second dimension. This is achieved by increasing the water content of the mobile phase behind the LCCC column. Monoester oligomers of up to 20 oxyethylene units can be resolved to the baseline. Diester oligomers are partially separated in the first dimension (LCCC).

Adsorption↗
PubMed1999

Separation of double-stranded DNA in conventional and isoelectric buffers: studies on stability and separation performance.

In the capillary electrophoresis of double-stranded DNA in isoelectric buffers, worsening of resolution was observed in electropherograms as a function of time passed from the preparation of the separation solution, which consisted of 0.7% hydroxypropylcellulose, HPC, Mr 10(6), diluted in 150 mM histidine buffer. The DNA standards used were: kilobase pair-ladder, Marker V and Marker VI. In order to understand what happens in the histidine-HPC solution with ageing, the absorbance spectrum (200-500 nm), the conductivity and the pH of the solutions as a function of time were monitored. Fresh His gave a distinct peak at 206 nm. For all the solutions a significant diminution in the maximum absorbance value at 206 nm was observed as a function of ageing, with the concomitant appearance of a peak at 278 nm as the solutions became older. Also the conductivity increases dramatically with the ageing of the solutions and seemed to reach a plateau after ca. 40 days. In concomitance with the conductivity increments with time, the pH of the His solution (isoelectric point, pI=7.6) grew slowly up to pH 7.9; these combined data indicated that a new species contributing to the conductivity and altering the pH was formed from the His molecule, suggesting that His degraded in time. When the dipeptide His-Gly was used instead, a similar ageing phenomenon was observed, but with much reduced kinetics. Mass spectrometry, coupled to RP-HPLC, detected, in aged His solutions, in addition to intact His, two main degradation products: a 110.1 u species and a 93.2 u compound. The mass of the former coincides with the protonated species derived from the formation of a Schiff base on the alpha-amino group of His and subsequent decarboxylation without transformation of the final Schiff base into a chetonic group (a histamine-like molecule terminating with an imino, rather than with an amino group).

Buffers↗
PubMed2005

Alteration of gene expression in intervertebral disc degeneration of passive cigarette- smoking rats: separate quantitation in separated nucleus pulposus and annulus fibrosus.

OBJECTIVE: We constructed a passive cigarette-smoking model with rats to investigate the molecular mechanism of intervertebral disc degeneration, and found by gene expression analysis that passive cigarette smoking stimulated the stress-responsive signal pathway and inhibited the apoptotic pathway. In this study, to clarify that these changes were derived from either nucleus pulposus (NP) or annulus fibrosus (AF), we separately collected NP and AF and quantitatively analyzed gene expression. METHODS: Total RNA was extracted from NP and AF of the lumbar intervertebral discs from rats which were kept in a smoking box for 4 and 8 weeks. Gene expression was measured by real-time PCR of cDNA synthesized from the total RNA. RESULTS: Stress-responsive protein, heat shock protein 70, was expressed similarly in NP and AF, and was upregulated to the same degree after 8 weeks of passive cigarette smoking. The protein tyrosine phosphatase gene was expressed more strongly in AF than in NP, and was upregulated after 8 weeks of smoking in both tissue parts. The type II collagen and aggrecan genes were predominantly expressed in AF and NP, respectively. CONCLUSION: These results indicate that passive cigarette smoking stimulates both NP and AF, and induces the stress-responsible genes such as heat shock protein 70 and protein tyrosine phosphatase in both.

Aggrecans↗
PubMed1982

Separation of subtypes of depression using discriminant analysis. I. Separation of unipolar endogenous depression from non-endogenous depression.

We derived a discriminant function based on clinical features to classify patients with endogenous depression ('melancholia') and non-endogenous ('neurotic') depression. The difference between the groups was not one of overall severity of illness alone. Bipolar melancholic patients were classified less well than were unipolars, supporting previous findings of clinical differences between these groups. The discriminant function (DF) was reduced to a discriminant index (DI) which classified a separate group of unipolar melancholic and non-endogenous patients with comparable accuracy. Approximately 80 per cent of all cases received a definite classification by the DI. The agreement between the 105 definite DI classifications and the clinical diagnoses was 90 per cent when results from the derivation and validation groups were combined. The DI classification was then validated against an objective biological marker, the dexamethasone suppression test (DST). The diagnostic discriminant index predicted the DST result with the same accuracy as the clinical diagnoses. The discriminant index can serve as an operational definition of the patients diagnosed as endogenous or nonendogenous unipolar depression in future studies by ourselves and other groups of investigators.

Adult↗
PubMed1972

Separation of HeLa cells by colloidal silica density gradient centrifugation. I. Separation and partial synchrony of mitotic cells.

Using a colloidal silica density gradient, HeLa cells in mitosis were found to have a density of 1.040-1.046 g/cc, lighter than the remaining interphase cells. The mitotic cells could be harvested and cultured after centrifugation, showing growth synchrony by measurement of a peak in mitotic index 21 hr after establishing the culture. By using Colcemid or vinblastine sulfate, HeLa cells were arrested in metaphase and centrifuged on the colloidal silica density gradient. The blocked metaphase cells were lighter in density than the interphase cells but somewhat more dense than untreated cells selected by the density gradient centrifugation. Near-equilibrium conditions were established during the centrifugation of cells so that cell density measurements could be made, and the gradient medium employed was not measurably toxic to those cells tested.

Cell Separation↗
PubMed1985

Stagewise separation to improve continuous centrifugal blood cell separators.

Staging is a technique used to improve blood cell collection efficiencies. In this paper, fractional cell recoveries are presented as functions of hematocrit as well as flow distribution. Material balances are presented, and the effect of increasing the number of stages studied in relation to increases in white blood cell collection efficiencies.

Blood Cells↗