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PubMedDate not supplied

Bilateral femoral angiography: a step-by-step approach.

A "stepping table top" is utilized for angiography that visualizes pelvic and peripheral vessels from the aortic bifurcation to the pedal arch. The stepping table moves the distance of a film (12 in) coincidentally with a bolus column of contrast media down the lower extremities. By timing a bolus of contrast media accurately, a program can be created to ensure table movements that match peak opacification of the blood vessels at each station.

Angiography↗
PubMed1987

Effects of step-up and step-down heating combined with radiation on murine tumor and normal tissues.

Radiosensitizing effects of step-up heating (SUH) and step-down heating (SDH) on the tumor and skin were studied by using mammary adenocarcinoma transplanted to the foot of the C3H/He mouse. The tumor and skin responses were assessed by the tumor growth delay method and the skin reaction scoring method, respectively. Neither SDH (44 degrees, 10 min----42 degrees, 30 min) nor SUH (42 degrees, 30 min----44 degrees, 10 min) alone caused a substantial tumor or skin response. When the heat treatment was given immediately after irradiation, the thermal enhancement ratio (TER) was higher in SDH than in SUH for tumors as well as the skin. A therapeutic gain factor (TGF) of 1.2 was obtained in SUH, while no therapeutic benefit was found in SDH. SDH was applied at various times (0 to 3 hr) before or after irradiation. When SDH was given before irradiation, the TER was consistently high to almost the same degree for tumors and the skin regardless of the time interval, resulting in minimal or no therapeutic gain. With SDH after irradiation, the TER for the skin decreased with increase in the time interval, while the TER for the tumor was moderately enhanced. Therefore, the TGF increased with increase in the time interval and reached 2.2 when SDH was given 3 hr after radiation. SUH is slightly advantageous over SDH in terms of the TGF, and SDH should be given 3 hr after irradiation when selective tumor heating is not possible.

Animals↗
PubMed1978

Step-by-step management of female victims of sexual assault.

Various authors have published advice on the management of victims of sexual assault--male and female. Most published accounts provide general advice, ordered according to theoretical considerations rather than to the chronological sequence of tasks to be performed. Our experience has been that a task list sequenced in chronological fashion is very useful in helping the attending doctor to remember what to do and how to do it. The step-by-step list used for women seen at Perth's Sexual Assault Referral Centre (SARC) is presented here.

Australia↗
PubMed1996

Comparison of continuous step-and-shoot versus step-and-shoot acquisition SPECT.

UNLABELLED: This study compared the quality of SPECT images obtained with step-and-shoot mode (SSM) and continuous step-and-shoot mode (CSSM). METHODS: Computer simulations of SSM and CSSM were performed with a two-dimensional Shepp-Logan head phantom and a high-resolution parallel-hole collimator. The effects of noise and photon attenuation were examined. RESULTS: Without noise and without attenuation, small structures in reconstructed images obtained using fast CSSM (less than 4 sec per view plus the moving time from one view to the next) were slightly blurred and rotated in the opposite direction of detector motion. With both noise and attenuation, these artifacts were not visible, and the image quality obtained from CSSM, especially from fast CSSM, was improved as compared to that resulting from the corresponding SSM due to the increasing number of counts. The improvement of image quality became less significant with increasing acquisition time and in the presence of attenuation. CONCLUSION: For fast SPECT, CSSM provided better image quality than the corresponding SSM, especially when attenuation effects were not present. For relatively long time SPECT without attenuation compensation that is typical for clinical studies, the image quality of CSSM was similar to that of SSM.

Computer Simulation↗
PubMed1996

Monobloc and facial bipartition osteotomies: a step-by-step description of the surgical technique.

The surgical management of upper and midface deformities in the craniofacial dysostosis syndromes has evolved gradually. Staged surgical procedures performed at intervals to coincide with facial growth, visceral function, and psychosocial development represent the current approach. The lack of consensus on timing and techniques for the management of the complex upper and midface deformities reflects not only uncertainty about the results achieved with any one approach to treatment but also confusion about how to perform the intricate and technically sensitive procedures. The purpose of this article is to provide the surgeon with a step-by-step technical description of the monobloc and facial bipartition osteotomies as I routinely perform them. By understanding the details for their safe execution, craniofacial surgeons are able to maintain these reconstructive options as active components in their armamentarium.

Acrocephalosyndactylia↗
PubMed1997

[A system of step-by-step differentiation of methicillin-resistant Staphylococcus aureus].

One hundred and eighty four strains of methicillin resistant Staphylococcus aureus (MRSA) isolated in pyosurgical and burn departments of Moscow, Minsk, Omsk, Tbilisi, Vologda, Smolensk and Dushanbe were differentiated with using phages of the International Set (BIS), two collections of experimental phages and two-probe fingerprinting. More than 50 per cent of the isolates could not be typed by the BIS phages. The Experimental Collection of the N.F. Gamaleya Research Institute of Epidemiology and Microbiology (Moscow) was more useful in the differentiation in comparison to the Experimental Collection of the London Health Centre. A new approach applied by us to the establishment of our collection i.e. screening of cultures with a definite specificity of the system of the restriction-modification (by a modified phage 85) followed by their differentiation with respect to the specificity of the prophages (by the induced phages with the respective modification specificity) provided reliable and reproducible results. Our collection made it possible to classify the phage type 85 strains which as was confirmed by the fingerprinting data belonged to 3 different genotype variants. The fingerprinting had no advantages over the typing by the phages of the more extended phage set and was recommended for differentiation of the strains (14 per cent) not sensitive to the phages used. A step-by-step scheme for typing MRSA easy for use in clinical and epidemiological laboratories is described.

Bacteriophage Typing↗
PubMed1998

Primary care guide to managing a breast mass: step-by-step workup.

Missed breast cancer is the most common malpractice suit filed in the US. But even without a biopsy of every mass, clinicians can reduce the risk of failed diagnosis to 1% by using a triple-diagnosis method to working up a breast mass, according to these experts, who offer a step-by-step guide. Includes QuickTimeTM video of breast exam. Failure to diagnose breast cancer in a timely manner is the most common reason for malpractice litigation in the US. Unless the potential for false-negative results of physical examination, mammography, ultrasound, and fine-needle aspiration biopsy (FNAB) is recognized, delay in the diagnosis of breast cancer will continue to occur. A systematic, thorough approach to the workup of any breast mass-- including a careful history, clinical breast examination, and documentation--is crucial. Upon detection of a mass, distinguishing the cyst from the solid mass (often by fine-needle aspiration or FNAB) is one of the most important tasks facing the clinician. Although most cysts resolve upon aspiration, solid masses require further workup to rule out cancer. Because of the false-negatives associated with individual methods of diagnosis, the authors recommend the triple-diagnosis method of detection. Simultaneous evaluation of a breast mass using clinical breast examination, radiography, and FNAB can lower the risk of missing cancer to only 1%, effectively reducing the rate of diagnostic failure and increasing the quality of patient care.

Breast↗
PubMed2001

Step-by-step uncoordination of the pyrazolyl rings of hydrotris(pyrazolyl)borate ligands in comlexes of Rh and RhIII.

Compounds of rhodium(I) and rhodium(III) that contain ancillary hydrotris(pyrazolyl)borate ligands (Tp') react with monodentate and bidentate tertiary phosphanes in a step-wise manner, with incorporation of P-donor atoms and concomitant replacement of the Tp' pyrazolyl rings. Accordingly, [Rh(kappa3-TpMe2)(C2H4)(PMe3)] (1b), converts initially into [Rh(kappa2-TpMe2)-(PMe3)2] (3), and then into [Rh(kappa1-TpMe2)-(PMe3)3] (2) upon interaction with PMe3 at room temperature, in a process which can be readily reversed under appropriate experimental conditions. Full disengagement of the Tp' ligand is feasible to give Tp' salts of rhodium(I) complex cations, for example, [Rh(CO)(dppp)2]-[TpMe2,4-Cl] (5; dppp = Ph2P(CH2)3PPh2), or [Rh(dppp)2][TpMe2,4-Cl] (6). Bis(hydride) derivatives of rhodium(III) exhibit similar substitution chemistry, for instance, the neutral complex [Rh(Tp)-(H)2(PMe3)] reacts at 20 degrees C with an excess of PMe3 to give [Rh(H)2-(PMe3)4][Tp] (9b). Single-crystal X-ray studies of 9b, conducted at 143 K, demonstrate the absence of bonding interactions between the [Rh(H)2(PMe3)4]+ and Tp ions, the closest Rh...N contact being at 4.627 A.

Journal Article↗
PubMed2006

The alpha-to-beta conformational transition of Alzheimer's Abeta-(1-42) peptide in aqueous media is reversible: a step by step conformational analysis suggests the location of beta conformation seeding.

Current views of the role of beta-amyloid (Abeta) peptide fibrils range from regarding them as the cause of Alzheimer's pathology to having a protective function. In the last few years, it has also been suggested that soluble oligomers might be the most important toxic species. In all cases, the study of the conformational properties of Abeta peptides in soluble form constitutes a basic approach to the design of molecules with "antiamyloid" activity. We have experimentally investigated the conformational path that can lead the Abeta-(1-42) peptide from the native state, which is represented by an alpha helix embedded in the membrane, to the final state in the amyloid fibrils, which is characterized by beta-sheet structures. The conformational steps were monitored by using CD and NMR spectroscopy in media of varying polarities. This was achieved by changing the composition of water and hexafluoroisopropanol (HFIP). In the presence of HFIP, beta conformations can be observed in solutions that have very high water content (up to 99 % water; v/v). These can be turned back to alpha helices simply by adding the appropriate amount of HFIP. The transition of Abeta-(1-42) from alpha to beta conformations occurs when the amount of water is higher than 80 % (v/v). The NMR structure solved in HFIP/H2O with high water content showed that, on going from very apolar to polar environments, the long N-terminal helix is essentially retained, whereas the shorter C-terminal helix is lost. The complete conformational path was investigated in detail with the aid of molecular-dynamics simulations in explicit solvent, which led to the localization of residues that might seed beta conformations. The structures obtained might help to find regions that are more affected by environmental conditions in vivo. This could in turn aid the design of molecules able to inhibit fibril deposition or revert oligomerization processes.

Algorithms↗
PubMed2006

Step-by-step progress toward understanding the hepatitis C virus RNA helicase.

Helicases are a ubiquitous class of enzymes involved in nearly all aspects of DNA and RNA metabolism. Despite recent progress in understanding their mechanism of action, limited resolution has left inaccessible the detailed mechanisms by which these enzymes couple the rearrangement of nucleic acid structures to the binding and hydrolysis of ATP. Observing individual mechanistic cycles of these motor proteins is central to understanding their cellular functions. Here we follow in real time, at a resolution of two base pairs and 20 ms, the RNA translocation and unwinding cycles of a hepatitis C virus helicase (NS3) monomer. NS3 is a representative superfamily-2 helicase essential for viral replication, and therefore a potentially important drug target. We show that the cyclic movement of NS3 is coordinated by ATP in discrete steps of 11 +/- 3 base pairs, and that actual unwinding occurs in rapid smaller substeps of 3.6 +/- 1.3 base pairs, also triggered by ATP binding, indicating that NS3 might move like an inchworm. This ATP-coupling mechanism is likely to be applicable to other non-hexameric helicases involved in many essential cellular functions. The assay developed here should be useful in investigating a broad range of nucleic acid translocation motors.

Antiviral Agents↗
PubMed1988

Evidence of intracellular and trans-acting differentiation-inducing activity in human promyelocytic leukemia HL-60 cells: its possible involvement in process of cell differentiation from a commitment step to a phenotype-expression step.

We previously reported that human promyelocytic leukemia HL-60 cells, when treated with various inducers in magnesium-deficient medium, became committed to differentiate but did not express the differentiation-related phenotypes (Okazaki et al., J. Cell. Physiol., 131:50-57, 1987). In the present study we demonstrated the existence of an intracellular differentiation-inducing activity (int-DIA) in differentiation-committed phenotype-nonexpressing HL-60 cells by using cybrid formation between untreated HL-60 cells and cytoplasts from HL-60 cells treated in magnesium-deficient medium with 100 nM 1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3). Cell extracts from similarly treated HL-60 cells also showed int-DIA, which when added (10 mg total protein/ml) to culture of untreated HL-60 cells, could increase the percentages of nitroblue tetrazolium (NBT)- and nonspecific esterase (NSE)-positive cells from 1% to 53%, and from 0 to 32%, respectively. They also induced differentiation of human monoblastic leukemia U-937 cells and of human myeloblastic leukemia KG-1 cells but not of erythroleukemia K-562 cells. These results suggested that the int-DIA had a common effect on differentiation induction in several human myeloid cell lines and may be involved in inducing cells to proceed from a commitment to a phenotype-expression step during human myeloid cell differentiation.

Calcitriol↗
PubMed1985

The reactivity of frozen B lymphocytes to B cell mitogens and human B cell growth factor: a study of step 1 and step 2 activators.

Human B lymphocytes, purified from the peripheral blood of several different donors can be pooled, frozen, and stored in liquid nitrogen to provide an easy and reproducible source of cells for mitogenic assays. These B cell preparations did not show any reactivity to T cell mitogens, but responded to Staphylococcus aureus Cowan strain 1 (SAC) and anti-IgM antibodies to the same extent as freshly purified B cells. When stimulated with either anti-IgM antibodies or SAC, these B cells became responsive to B cell growth factor (BCGF), allowing a quantitative measurement of this important lymphokine activity. In addition, we have studied the reactivity of frozen B lymphocytes to various combinations of activators. We have confirmed that phorbol myristate acetate (PMA) was a very potent mitogenic agent for preactivated human B cells and shown that bacterial lipopolysaccharide (LPS), although not mitogenic by itself, could synergize with anti-IgM antibodies to yield increased levels of stimulation. Furthermore experiments using the lysosomotropic agent leucine methyl ester showed that the action of LPS on anti-IgM-stimulated B cells did not require the presence of functional monocytes. Neither PMA nor LPS could induce BCGF responsiveness and thus these two compounds can be considered exclusive step 2 activators for human peripheral blood B cells.

Antibodies, Anti-Idiotypic↗
PubMed1989

Clinical relevance of step-by-step mandibular advancement in the treatment of mandibular retrusion using the Fränkel appliance.

The effect of the Fränkel appliance was evaluated in patients with mandibular retrusion who were monitored during an active treatment phase of approximately 14 months in the early mixed dentition. The sample treated with the Fränkel appliance consisted of 120 subjects. In 60, the initial construction bite was taken with the incisors in an end-to-end relationship (Fränkel group A). In 60 patients (Fränkel group B), mandibular position was advanced sequentially in small steps. Fifty untreated subjects of approximately the same age and with almost identical characteristics of skeletal Class II malocclusion served as a comparison group. Permanent teeth were not extracted during the period studied in any of the subjects. For statistical analysis of the difference between the variables used in this study, analysis of variance and the t test were used. The results of this study indicate that the distances between pogonion and condylion or articulare increased in both Fränkel groups A and B significantly more than in the untreated sample. However, the anteroposterior position of pogonion relative to the maxillary landmarks remained unchanged in Fränkel group A. The increase in the distance between pogonion and articulare or condylion primarily resulted from a positional change of pogonion inferiorly, which was accompanied by a significant increase of the mandibular plane angle and the gonial angle. In contrast, pogonion moved anteriorly in Fränkel group B significantly more than in the untreated group, that is, the sagittal discrepancy between maxilla and mandible significantly improved in Fränkel group B, whereas it remained unchanged in Fränkel group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Activator Appliances↗
PubMed2005

Production of soybean phosphatidylcholine-chitosan nanovesicles by reverse phase evaporation: a step by step study.

In the present work, we describe the preparation of composite nanovesicles containing soybean phosphatidylcholine and polysaccharide chitosan by the reverse phase evaporation method. Nanovesicles free from chitosan prepared in the same way were studied as reference. The production method involves the preparation of reverse micelles followed by the formation of an organogel, which is dispersed in water to yield the final liposomal structures. Structural changes in each step of the nanovesicles preparation were studied by means of static and dynamic light scattering as well as small angle X-ray scattering. Chitosan was also fully characterized in solution. The hydrodynamic radius of the composite nanovesicles is in the range of 174-286 nm, depending on the chitosan contents. A comparison with nanovesicles free from chitosan indicates the existence of higher contents of multilamellae structures in the composites, as well as improved stability in water.

Acetates↗
PubMed2003

A protocol for 'enhanced pepsin digestion': a step by step method for obtaining pure antibody fragments in high yield from serum.

The digestion of ovine antiserum under acidic conditions (pH 3.5) by pepsin is highly effective at reducing all unwanted serum components to low molecular weight (< or =13 kDa) fragments while leaving the approximately 100-kDa F(ab')(2) intact. The pH is then raised to 6 to stop further digestion and the reaction mixture centrifuged or filtered to remove any insoluble contaminants. Next, unwanted low molecular weight fragments are removed by diafiltration with a 30-kDa nominal molecular weight cut-off membrane leaving an F(ab')(2) solution contaminated only with some pepsin and a small amount of the aggregated low molecular weight fragments. Material of this purity is suitable for many applications but, since all the contaminants are highly acidic, they can be easily removed by passage down an anion-exchange column to yield F(ab')(2) that is essentially free from pepsin and aggregates with a typical purity of over 96% and yields of 16-19 g/l serum. When an antivenom was processed, approximately 78% of the original serum's toxin neutralising capacity was recovered. This simple, high yield protocol for processing serum to highly purified F(ab')(2) avoids the need for an initial or any subsequent salt precipitation step and can be utilised for either bench or large scale production. If required, a mild reducing agent may be used finally to create Fab fragments.

Animals↗
PubMed1991

Determining rate constants for irreversible polymerization where the initial step and propagation steps have different rate constants: consideration of polyadenylate polymerase.

A new relationship is derived between the amount of monomer incorporated and the amount of initiated primer in an irreversible polymerization where the first step, initiation, has a rate constant differing from the elongation rate constants. It is valid for template directed and template independent polymerization. This relationship can be used in kinetic simulation. It suggests a simpler curve fitting technique to attain rate constants from a relatively small data set. Our analysis reveals some limitations of the model of irreversible polymerization; these limitations have not been obvious previously. For example, the initiation rate constant is not attainable from simple monomer incorporation data. Reliable rate constants can be obtained with minimal time course studies.

Kinetics↗
PubMed2003

Structure-based description of a step-by-step synthesis of homo- and heterodinuclear (4f, 4f ') lanthanide complexes.

The stepwise course of the synthesis of homo- (4f, 4f) and heterodilanthanide (4f, 4f ') complexes has been investigated through structural determination of the intermediate and final products occurring in the process. In the first step, the tripodal ligand H(3)L is reacted with Ln(NO(3))(3) x 5H(2)O to give a complex (H(3)L)Ln(NO(3))(3) in which the ligand does exist in a zwitterionic form. This unexpected feature has been definitely supported by a structural determination performed on a closely related complex (HL')(3)Ln(NO(3))(3) (1). These species are fairly stable and may be isolated. In basic medium, (H(3)L)Ln(NO(3))(3) is deprotonated to yield a neutral LLn complex crystallized as LLnNaClO(4) (2), the lanthanide ion being linked to the inner N(4)O(3) coordination site of the ligand. Finally, addition of Ln'(NO(3))(3) x 5H(2)O (Ln' being similar or different from Ln) to the LLn complex yields the desired homo- or heterodinuclear LLnLn'(NO(3))(3) complex 3, where the Ln' ion is coordinated to the outer O(3)O(3) coordination site of the tripodal ligand. Complex 1 (Ln = La) crystallizes in the triclinic space group P1 (No. 2): a = 11.1883(7) A, b = 11.8993(9) A, c = 16.4197(10) A, alpha = 81.900 (6) degrees, beta = 79.406(5) degrees, gamma = 79.470(6) degrees, V = 2099.5(2) A(3), Z = 2. Complex 2 (Ln = Eu) crystallizes in the monoclinic space group P2(1)/n (No. 14): a = 13.6333(13) A, b = 15.3799(12) A, c = 17.1473(13) A, beta = 111.283(10) degrees, V = 3350.2(5) A(3), Z = 4. Complex 3 (Ln = Ln' = Dy) crystallizes in the trigonal space group R3 (No. 148) with a = b = 23.847(3) A, c = 42.982(2) A, V = 21168(4) A(3), Z = 18. Complex 3 possesses a Dy(O(phenoxo))(3)Dy core, and a nitrato anion has been replaced by a eta(2)-chelated o-vanillin anion. We did not succeed in obtaining crystals of any of the heterodinuclear LLnLn'(NO(3))(3) entities, but their existence was unambiguously confirmed by positive fast atom bombardment mass spectrometry experiments.

Journal Article↗
PubMed2003

A step-by-step model of phototransduction cascade shows that Ca2+ regulation of guanylate cyclase accounts only for short-term changes of photoresponse.

A mathematical model of the vertebrate phototransduction mechanism was designed in a modular fashion, in that increasingly complex behaviors can be turned on and off to evaluate the relative involvement of all elements of the phototransduction cascade. The problem was approached by starting with a minimum model in which the intracellular cGMP concentration ([cGMP]i) was determined by guanylate cyclase (GC), whose activity was assumed not to be regulated by any factor (such as Ca2+) and by phosphodiesterase (PDE), whose activity was assumed to be proportional to the light intensity. All dependences were subsequently introduced, i.e. the equations describing PDE activation in detail, the Ca2+ regulation of GC and the action of intracellular Ca2+ buffers. The simulations and fits show that a high-gain, smooth time- and light-dependent PDE activation, a Ca2+-dependent GC, and a Ca2+-dependent buffer mechanism are required to account for the flash response kinetics in the dark and on dim backgrounds of light, and the effect of exogenous Ca2+ buffers to produce responses characterized by slow and damped oscillations and to enhance the low-frequency noise. However, it was not possible to find any set of parameters able to simultaneously interpolate the waveform of the flash responses (in the dark and on a background of light) and the responses to steps of light. It is therefore concluded that at least one more shut-off mechanism (possibly not Ca-dependent) is necessary to fully account for the phenomenology of the light response in rod photoreceptors.

Animals↗