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Results for “protocol optimization”

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PubMed2002

Kinetics and mechanism of intercellular ice propagation in a micropatterned tissue construct.

Understanding the effects of cell-cell interaction on intracellular ice formation (IIF) is required to design optimized protocols for cryopreservation of tissue. To determine the effects of cell-cell interactions during tissue freezing, without confounding effects from uncontrolled factors (such as time in culture, cell geometry, and cell-substrate interactions), HepG2 cells were cultured in pairs on glass coverslips micropatterned with polyethylene glycol disilane, such that each cell interacted with exactly one adjacent cell. Assuming the cell pair to be a finite state system, being either in an unfrozen state (no ice in either cell), a singlet state (IIF in one cell only), or a doublet state (IIF in both cells), the kinetics of state transitions were theoretically modeled and cryomicroscopically measured. The rate of intercellular ice propagation, estimated from the measured singlet state probability, increased in the first 24 h of culture and remained steady thereafter. In cell pairs cultured for 24 h and treated with the gap junction blocker 18beta-glycyrrhetinic acid before freezing, the intercellular ice propagation rate was lower than in untreated controls (p < 0.001), but significantly greater than zero (p < 0.0001). These results suggest that gap junctions mediate some, but not all, mechanisms of ice propagation in tissue.

Biophysical Phenomena↗

PubMed1996

Distinct local anesthetic affinities in Na+ channel subtypes.

Lidocaine is a widely used local anesthetic and antiarrhythmic drug that is believed to exert its clinically important action by blocking voltage-gated Na+ channels. Studies of Na+ channels from different species and tissues and the complexity of the drug-channel interaction create difficulty in understanding whether there are Na+ channel isoform specific differences in the affinity for lidocaine. Clinical usage suggests that lidocaine selectively targets cardiac Na+ channels because it is effective for the treatment of arrhythmias with few side effects on muscle or neuronal channels except at higher concentrations. One possibility for this selectivity is an intrinsically higher drug-binding affinity of the cardiac isoform. Alternatively, lidocaine may appear cardioselective because of preferential interactions with the inactivated state of the Na+ channel, which is occupied much longer in cardiac cells. Recombinant skeletal muscle (hSkM1) and cardiac sodium channels (hH1) were studied under identical conditions, with a whole-cell voltage clamp used to distinguish the mechanisms of lidocaine block. Tonic block at high concentrations of lidocaine (0.1 mM) was greater in hH1 than in hSkM1. This was also true for use-dependent block, for which 25-microM lidocaine produced an inhibition in hH1 equivalent to 0.1 mM in the skeletal muscle isoform. Pulse protocols optimized to explore inactivated-state block revealed that hSkM1 was five to eight times less sensitive to block by lidocaine than was hH1. The results also indicate that relatively more open-state block occurs in hSkM1. Thus, the cardiac sodium channel is intrinsically more sensitive to inhibition by lidocaine.

Anesthetics, Local↗

PubMed1998

Distribution of the endothelial constitutive nitric oxide synthase in the developing rat brain: an immunohistochemical study.

The present study deals with the distribution of endothelial constitutive nitric oxide synthase (ecNOS) in the developing rat brain using optimized protocols for preparation and fixation and the tyramide-signal-amplification technique. The immunostaining patterns of a monoclonal antibody against ecNOS are compared with results obtained with a rat pan-endothelial marker, the monoclonal RECA-1 antibody. It is shown that ecNOS is present in the endothelial lining of all types of blood vessels and the choroid plexuses of the rat brain from the beginning of vasculogenesis at embryonic day 11 until adulthood (75 weeks). The same is true for RECA-1 immunoreactivity, that was demonstrated in the developmental brain vasculature for the first time. Both antigens expressed identical immunostaining patterns. At all investigated stages of brain development neither ecNOS negative blood vessels nor ecNOS positive non-endothelial cells, e.g., neurons, were found. The data indicate that ecNOS is involved in the embryonic angiogenesis and the regulation of hemodynamic functions of brain vasculature throughout the individual life.

Animals↗

PubMed2001

Differentiating clinical profiles: predicting good responders, poor responders, and hyperresponders.

OBJECTIVE: To describe the different clinical and laboratory diagnostic methods (basal and dynamic tests) available to identify poor-, good-, and high-responder patients undergoing treatment with in vitro fertilization (IVF). DESIGN: Analytical review. SETTING: IVF program. PATIENTS: Women in different age groups undergoing IVF treatment. INTERVENTION(S): Assessment of clinical and laboratory parameters and correlation with outcomes. MAIN OUTCOME MEASURE(S): Response to ovarian stimulation and success of the assisted reproductive technologies (ART). RESULT(S): Age, basal follicle-stimulating hormone (FSH), estradiol and inhibin-B levels, and dynamic testing serve to predict individual response to ovarian stimulation for ART. CONCLUSION(S): Markers of ovarian reserve (day 3 FSH, inhibin B and E(2)) are particularly predictive and useful in guiding the choice of the optimal protocol for ART. However, no tests are absolutely predictive of a successful outcome. For the younger individual, and for the patient at risk of developing ovarian hyperstimulation syndrome (OHSS), assessment and identification of clinical and laboratory parameters predictive of a high response to ovarian stimulation should guide the clinician in choosing an appropriate stimulation protocol, thus attenuating the risk of OHSS.

Adult↗

PubMed1991

Comparison of silica-based cyanopropyl and octyl reversed-phase packings for the separation of peptides and proteins.

The performance of a silica-based C8 packing was compared with that of a less hydrophobic, silica-based cyanopropyl (CN) packing during their application to reversed-phase high-performance liquid chromatography (linear trifluoroacetic acid-water to trifluoroacetic acid-acetonitrile gradients) of peptides and proteins. It was found that: (1) the CN column showed excellent selectivity for peptides which varied widely in hydrophobicity and peptide chain length; (2) peptides which could not be resolved easily on the C8 column were widely separated on the CN column; (3) certain mixtures of peptides and small organic molecules which could not be resolved on the C8 column were completely separated on the CN column; (4) impurities arising from solid-phase peptide synthesis were resolved by a wide margin on the CN column, unlike on the C8 column, where these compounds were eluted very close to the peptide product of interest: and (5) specific protein mixtures exhibited superior resolution and peak shape on the CN column compared with the C8 column. The results clearly demonstrate the effectiveness of employing stationary phases of different selectivities (as opposed to the more common optimization protocol of manipulating the mobile phase) for specific peptide and protein applications, an approach underestimated in the past.

Amino Acid Sequence↗

PubMed2003

Temperature selectivity effects in reversed-phase liquid chromatography due to conformation differences between helical and non-helical peptides.

In order to characterize the effect of temperature on the retention behaviour and selectivity of separation of polypeptides and proteins in reversed-phase high-performance liquid chromatography (RP-HPLC), the chromatographic properties of four series of peptides, with different peptide conformations, have been studied as a function of temperature (5-80 degrees C). The secondary structure of model peptides was based on either the amphipathic alpha-helical peptide sequence Ac-EAEKAAKEX(D/L)EKAAKEAEK-amide, (position X being in the centre of the hydrophobic face of the alpha-helix), or the random coil peptide sequence Ac-X(D/L)LGAKGAGVG-amide, where position X is substituted by the 19 L- or D-amino acids and glycine. We have shown that the helical peptide analogues exhibited a greater effect of varying temperature on elution behaviour compared to the random coil peptide analogues, due to the unfolding of alpha-helical structure with the increase of temperature during RP-HPLC. In addition, temperature generally produced different effects on the separations of peptides with different L- or D-amino acid substitutions within the groups of helical or non-helical peptides. The results demonstrate that variations in temperature can be used to effect significant changes in selectivity among the peptide analogues despite their very high degree of sequence homology. Our results also suggest that a temperature-based approach to RP-HPLC can be used to distinguish varying amino acid substitutions at the same site of the peptide sequence. We believe that the peptide mixtures presented here provide a good model for studying temperature effects on selectivity due to conformational differences of peptides, both for the rational development of peptide separation optimization protocols and a probe to distinguish between peptide conformations.

Amino Acid Sequence↗

PubMed2001

Optimisation of an ELISA for the serodiagnosis of visceral leishmaniasis using in vitro derived promastigote antigens.

An antibody detection ELISA was developed for diagnosis of visceral leishmaniasis. Antigens released by Leishmania donovani promastigotes into a protein-free medium were used. SDS-PAGE analysis has indicated that Ld-ESM contain several protein antigens. Titration and chequer-board analyses were performed to optimise the assay protocol. Optimal results were obtained when antigen (50 microg/ml) was coated with PBS-methyl glyoxal buffer, and wells blocked with 0.5% casein. A serum dilution of 1:500 in antigen-coated wells, blocked with 0.5% casein, generated lowest absorbance with Ref-ve sera and higher absorbance with Ref+ve sera. All steps of the ELISA were performed at room temperature. The S/N ratio, the differential absorbance between the negative sample vs. the test or Ref+ve sample, was used to quantify the specific antigen and antibody reactions. An anti-human monoclonal antibody conjugated with HRP (MAb-conjugate) outperformed a commercially available anti-human polyclonal antibody conjugate (PAb-conjugate). The MAb-conjugate gave minimal background reactions with endemic sera. Optimised final assay steps mentioned below were used to evaluate sera samples from field trials. ELISA wells were coated with 50 microg/ml Ld-ESM mixed in PBS-methyl glyoxal overnight, and after removing the antigen, blocked with 0.5% casein for 1 h at RT. Patient sera along with control sera, diluted to 1:500 in PBS/T, were reacted for 1 h at RT. After washing the plate with PBS/T, wells were reacted with MAb-conjugate for 40 min at RT, and after washing, binding of antibodies was visualized by using TMB as a chromogen substrate. The relative specific binding was quantified by the S/N ratio. A batch of n=22 endemic sera from North Africa were evaluated and resulted with 100% specificity and sensitivity, 99.99% PPV and 95.45% NPV. The specificity and sensitivity of this assay will be further evaluated in planned retrospective and prospective multi-site trials.

Animals↗

PubMed1997

Optimization of the sulforhodamine B colorimetric assay.

Sulforhodamine B (SRB) protein staining has been widely used for cell proliferation and chemosensitivity testing, substituting for tetrazolium-based assays. However, the cell fixation step in the original assay is subject to error. We tested whether aspiration of medium with an automatic microplate multiwash device prior to fixation improves the method for adherent cells. A panel of adherent cell lines was used. Signal-to-noise ratios were significantly increased in the new assay. Coefficients of variation (CV) between replicate wells were significantly lower especially at lower cell densities. The linearity of the method improved, with absolute linearity over the whole range of cell densities. The aspiration procedure dislodged only negligible numbers of cells. Cytotoxicity testing using the cytotoxic agent paclitaxel showed no IC50 (50% inhibitory concentration) differences between the new and original methods but a better CV was associated with the optimized protocol. We conclude that aspiration of the growth medium prior to fixing comprises a safe and reliable practice which improves CV, linearity and the signal-to-noise ratio of the SRB assay.

Animals↗

PubMed1999

Reverse transcriptase in situ polymerase chain reaction for gene expression in rat mast cells and macrophages.

Direct reverse transcriptase in situ polymerase chain reaction (RT-in situ PCR) of selected mRNA expression in rat mast cells (MC) and alveolar macrophages (AM) was optimized. Rat peritoneal mast cells (PMC), rat cultured mast cells (RCMC), rat bronchoalveolar lavage cells (BALC) or rat cultured alveolar macrophages (NR8383) were studied for the detection of mRNA for beta-actin, TNF-alpha and/or CD8alpha. Each type of cell has unique optimal conditions for RT-in situ PCR. The following parameters were carefully evaluated for optimization: protease digestion, DNAse digestion, heparinase digestion, RT, PCR cycle number and signal development with chromagen. Heparinase digestion was required for PMC mRNA detection because they contain large amounts of heparin proteoglycan, which is a potent inhibitor of RT and Taq polymerase enzymes. Only a few PCR cycles were needed to produce a cytoplasmic signal for mRNA transcripts in RCMC, whereas other types of cells (PMC, BALC and NR8383) needed at least 20 cycles for mRNA detection. The mRNA signal in PMC was localized to the perinuclear region, whereas mRNA in other cell types (RCMC, BALC and NR8383) were detected throughout the cytoplasm. Furthermore, modified Southern blot analysis for TNF-alpha in RCMC treated with RT-in situ PCR demonstrated the specificity of amplification product. The modified and optimized protocols for this procedure were successfully applied to detect and localize several mRNA transcripts in rat MC and AM. The approach is valuable and can be used to further study selected gene expression in these and other cell types.

Animals↗

PubMed2000

Technical issues for MRI examination of the posterior fossa.

Examination of the posterior fossa by magnetic resonance imaging is discussed with respect to modern techniques and equipment, and including recent results of non-conventional studies in multiple sclerosis. Optimal protocol design will maximize resolution and signal strength while providing diagnostic contrast. Motion artifact from the sigmoid and transverse sinuses may appear as ghosting and can be mitigated with proper imaging parameter choices.

Artifacts↗

PubMed1985

Bacillus Calmette-Guerin immunotherapy for bladder cancer.

Bacillus Calmette-Guerin immunotherapy has been found by a number of investigators to be effective in the treatment and prevention of superficial bladder cancer. While the optimal protocol for bacillus Calmette-Guerin remains to be determined, experience with 92 randomized and 30 nonrandomized (high risk) patients followed for up to 5 years provides information that may improve future protocols. Side effects of bacillus Calmette-Guerin are observed to increase with increasing frequency and duration of treatment. The protection from tumor recurrence has persisted: only 6 of 30 patients (20 per cent) treated with bacillus Calmette-Guerin have had recurrent tumor compared to 14 of 27 controls (52 per cent, p equals 0.008, chi-square test), and mean time to recurrence increased from 24 to 48 months (p less than 0.005, Savage). Skin test reactivity to purified protein derivative is particularly useful in predicting response to bacillus Calmette-Guerin immunotherapy. Currently, 60 patients have been randomized to receive bacillus Calmette-Guerin immunotherapy and only 1 of 22 patients (4.5 per cent) in whom the purified protein derivative skin test results converted from negative to positive has had recurrent tumor, compared to 12 recurrences (32 per cent) in patients whose skin tests were positive before treatment or failed to convert following treatment (p equals 0.014, chi-square). Seven recurrences (33 per cent) developed in 21 patients whose skin tests remained negative (p equals 0.015) and 5 recurrences (29 per cent) developed in 17 patients whose tests previously were positive (p equals 0.068, Fisher's test, not significant). The benefit of percutaneous bacillus Calmette-Guerin is suggested by the observations that the recurrence rate in patients treated with intravesical bacillus Calmette-Guerin alone is 40 per cent, and all 7 patients whose purified protein derivative skin tests were negative continued to have negative results when percutaneous bacillus Calmette-Guerin was omitted (p equals 0.003). Among high risk patients a marked decrease in or complete prevention of recurrent tumor was observed in 82 per cent of 22 patients treated previously with chemotherapy and 11 of 14 (78 per cent) with carcinoma in situ have had a complete response.

Aged↗

PubMed1983

Simultaneous sonographic demonstration of tumor thrombus in the inferior vena cava and patient main renal vein in renal carcinoma.

With the introduction of new imaging modalities the optimal protocol for the evaluation of renal tumors is under close review. Angiographers frequently are faced with the question of whether to proceed to inferior venacavography following a selective renal angiogram that demonstrates a patent renal vein. We report a case of renal cell carcinoma in which the main renal vein was shown by ultrasound to be unequivocally patent but at the same time there was considerable tumor extension into the inferior vena cava. The necessity of full examination of the inferior vena cava, either by venacavography or ultrasound, in all cases of renal cell carcinoma is stressed.

Adenocarcinoma↗

PubMed2003

Angiogenic sprouting and capillary lumen formation modeled by human umbilical vein endothelial cells (HUVEC) in fibrin gels: the role of fibroblasts and Angiopoietin-1.

Angiogenesis is a multistep process of critical importance both in development and in physiological and pathophysiological processes in the adult. It involves endothelial cell (EC) sprouting from the parent vessel, followed by migration, proliferation, alignment, tube formation, and anastomosis to other vessels. Several in vitro models have attempted to recreate this complex sequence of events with varying degrees of success. We report an optimized protocol for human umbilical vein EC in which EC sprout from the surface of beads embedded in fibrin gels. Fibroblast-derived factors, other than Angiopoietin-1, promote sprouting, lumen formation, and long-term stability of neovessels. Analysis by time-lapse and still photomicroscopy demonstrates dynamic vessels guided by a "tip cell" that extends numerous processes into the gel. Behind this cell a lumen forms, surrounded by a single layer of polarized EC. The growing sprouts express notch 1, notch 4, and delta 4, as well as the downstream notch effector HESR-1. Importantly, cells can be infected with adenovirus to high efficiency without compromising sprout formation, thus allowing for manipulation of gene expression. This improved model recapitulates all the major steps of angiogenesis seen in vivo and provides a powerful model for analysis of this complex phenomenon.

Adenoviridae↗

PubMed1994

Towards a standard method to demonstrate adenylate cyclase activity at the electron microscopical level.

The ventral epidermis of the frog Rana fuscigula is a typical tight epithelium which acts as a functional syncytium in the active transepithelial transport of sodium ions. Transport across this epithelium is regulated by cyclic adenosine monophosphate (cAMP). This study was undertaken to formulate an optimal protocol for the localization, within this epithelium, of adenylate cyclase; the enzyme involved in cAMP synthesis. The ventral epithelium of R. fuscigula was collagenase treated and processed using five different fixation/incubation protocols. The components of a basal incubating medium were modified by changing the localizing agent, adding adenylate cyclase stimulators and inhibitors of other enzymes. Control incubations undertaken included a) leaving the substrate out, b) prior heat inactivation of the enzyme, c) specific blockers and d) incubation for alkaline phosphatase as an alternative enzyme. The samples were then processed for electron microscopy. Localization of adenylate cyclase was best obtained, when fixing the tissue after incubation for 30 min at 37 degrees C. The medium that gave the best and most consistent localization contained magnesium chloride; as a required ion, theophylline, dithiothreitol, ouabain, levamisole; as enzyme inhibitors, forskolin; as a stimulator of adenylate cyclase, lead nitrate; as the capture agent and column purified adenylyl imidodiphosphate; as the substrate.

Adenylyl Cyclase Inhibitors↗

PubMed1999

Modeling prostate cancer distributions.

OBJECTIVES: To use computer-assisted three-dimensional (3D) reconstruction to study cancer distribution in the prostate. The distributions have been determined using data from 81 prostates surgically removed because of cancer. METHODS: The pattern of distribution was determined by reshaping (morphing) all prostates in the same size category (small, medium, large) into the same shape and by overlayering the 3D distribution of all cancers into a "unit prostate." Also, the pattern of 3D distribution was defined for small, medium, and large volume cancers. RESULTS: The study yielded a clear, visual "scatter diagram" representation of the statistics of prostate cancer distribution. It confirmed previous general knowledge: small cancers are mainly found in the lower one third and principally in the dorsolateral part of the gland. CONCLUSIONS: This report is part of the investigations preliminary to establishing an optimal protocol for needle biopsy of prostate cancer.

Adult↗

PubMedDate not supplied

Group B streptococcus in the perinatal period. A review.

Prior to the 1960s, little was known about morbidity and mortality in humans due to group B streptococcus (GBS). Since that time, a thorough understanding of the organism's potential has been developed. Of pregnant women, 20-30% are prenatal carriers of GBS and 40-75% of these mothers will transmit GBS to their neonates. However, the actual incidence of GBS disease in infants is one to three cases per 1,000 live births. Several risk factors for transmission and development of early-onset GBS disease have been identified. The understanding of late-onset disease is less clear. Many strategies have been investigated to find an optimal protocol to reduce significantly the incidence of GBS disease in a cost-effective manner. The Centers for Disease Control and Prevention have recently made recommendations for prevention strategies against this disease.

Antibiotic Prophylaxis↗

PubMed2004

Intrahepatic arterial administration of low-dose methotrexate in patients with severe hepatic graft-versus-host disease: an open-label, uncontrolled trial.

BACKGROUND: Hepatic grafr-versus-host disease (GVHD) is associated with significant morbidity and mortality. Standard therapy includes systemically administered immunosuppressive drugs. More recent reports have described catheter-directed intrahepatic arterial (IHA) delivery of low-dose methotrexate (MTX) and methylprednisolone in the treatment of corticosteroid-resistant severe hepatic GVHD. OBJECTIVE: This article reports on MTX toxicity and the variability in plasma drug concentrations after IHA administration of low-dose MTX in patients with severe hepatic GVHD. METHODS: In this open-label, uncontrolled pilot study, MTX and methylprednisolone were administered via the hepatic artery in patients with corticosteroid-resistant grade III or IV GVHD of the liver. Patients also received standard therapy. MTX concentrations were measured in the hepatic artery 5 and 10 minutes after injection and in peripheral venous blood at 1, 2, and 24 hours. RESULTS: Six patients (5 males [83.3%], I female [16.7%]; median age, 32 years; range, 8-42 years) were enrolled in the study. No hepatotoxicity was observed after IHA administration of MTX. In 5 patients with normal renal function, plasma drug concentrations 24 hours after administration of MTX ranged from 0.01 to 0.12 micromol/L (mean [SD], 0.043 [0.042] micromol/L). In 1 patient with renal failure, plasma MTX concentrations were 1.0 micromol/L 24 hours after administration and 0.07 micromol/L 5 days after administration. The severe hematologic and renal toxicity observed in this patient may have contributed to his death. Adverse events in patients with GVHD and normal renal function, who had normal plasma MTX concentrations, were comparable to those that have been reported after administration of an intravenous infusion. CONCLUSIONS: In patients with GVHD and normal renal function, IHA administration of low-dose MTX was not associated with liver or bone marrow toxicity. Further study is needed to determine the optimal protocols for treating corticosteroid-resistant hepatic GVHD.

Adolescent↗

PubMed1999

Preparation of nuclear extracts from myelinating Schwann cells.

Myelination of peripheral nerve fibres is performed by Schwann cells and is associated with the coordinate upregulation of lipid synthesis and multiple genes encoding myelin-specific proteins. Both the decision to enter into a myelinating phenotype and subsequently, the quantity of myelin that each Schwann cell elaborates appear to be controlled by axonal signals. Understanding of the relevant signaling pathways and the downstream transcription factors and cis elements that confer myelin gene expression is notably limited. In large part, this has resulted directly from a lack of methods for obtaining nuclear extracts from myelinating Schwann cells thus precluding the application of numerous powerful molecular techniques. In this report, we describe a method that overcomes this limitation for the myelinating Schwann cells in the sciatic nerves of the mouse. During the evolution of the method, its effectiveness was monitored using an oligonucleotide containing the binding site for KROX-20, a transcription factor known to be present in myelinating Schwann cells. Following technical development, the optimized protocol has proven to be entirely reliable and thus novel experimental strategies now can be applied to the investigation of the molecular mechanisms controlling gene expression in peripheral nerves.

Animals↗