Three-dimensional CT angiography: renal applications

CT angiography has become an effective noninvasive imaging modality for evaluating the renal vasculature. The current clinical applications for CT angiography and three-dimensional (3D) imaging related to the kidneys and renal vasculature include evaluation of renal artery stenosis, renal diseases related to aortic diseases, living-related renal donor candidates, and preoperative evaluation of renal masses for possible nephron sparing surgeries. Imaging parameters need to be individually prescribed for renal CT angiography depending on the diagnostic goal of the examination. Methods for optimizing spiral CT protocols including patient preparation, contrast administration, image acquisition parameters, and image reconstruction will be covered.

Involvement of Ras/MAP kinase in the regulation of Ca2+ channels in adult bullfrog sympathetic neurons by nerve growth factor

The cellular mechanisms that underlie nerve growth factor (NGF) induced increase in Ca(2+)-channel current in adult bullfrog sympathetic B-neurons were examined by whole cell recording techniques. Cells were maintained at low density in neuron-enriched, defined-medium, serum-free tissue culture for 6 days in the presence or absence of NGF (200 ng/ml). The increase in Ba2+ current (IBa) density induced by NGF was attenuated by the RNA synthesis inhibitor cordycepin (20 microM), by the DNA transcription inhibitor actinomycin D (0.01 microgram/ml), by inhibitors of Ras isoprenylation (perillic acid 0.1-1.0 mM or alpha-hydroxyfarnesylphosphonic acid 10-100 microM), by tyrosine kinase inhibitors genistein (20 microM) or lavendustin A (1 microM), and by PD98059 (10-100 microM), an inhibitor of mitogen-activated protein kinase kinase. Inhibitors of the phosphatidylinositol 3-kinase (PI3K) pathway (wortmannin, 100 nM, or LY29400, 100 microM) were ineffective as were inhibitors of phospholipase C gamma (U73122 or neomycin, both 100 microM). The effect of NGF persisted in Ca(2+)-free medium that contained 1.8 mM Mg2+ and 2 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. It was mimicked by a Trk antibody that was capable of inducing neurite outgrowth in explant cultures of bullfrog sympathetic ganglion. Antibodies raised against the low-affinity p75 neurotrophin receptor were ineffective in blocking the effect of NGF on IBa. These results suggest that NGF-induced increase in Ca2+ channel current in adult sympathetic neurons results, at least in part, from new channel synthesis after Trk activation of Ras and mitogen activated protein kinase by a mechanism that is independent of extracellular Ca2+.

Gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral arteries: evaluation of a multistation examination using two gadopentetate dimeglumine infusions

OBJECTIVE

Three-dimensional gadolinium-enhanced MR angiography is a rapid and accurate method that can at times image only a limited amount of anatomy during an examination. We evaluated a technique that doubled the anatomy imaged by obtaining two separate gadolinium-enhanced MR angiograms during a single examination.

MATERIALS AND METHODS

Twenty-three patients referred for MR evaluation of aortic or peripheral vascular disease underwent two successive gadolinium-enhanced three-dimensional MR angiographic examinations during a single MR examination. An injection of 15 ml of gadopentetate dimeglumine was used for the first MR angiogram, and 25 ml was used for the second MR angiogram. The angiograms were quantitatively and qualitatively evaluated to determine the effect of residual gadolinium from the initial MR angiogram on the second angiogram.

RESULTS

The two studies depicted either the entire aorta to the femoral arteries (n = 10) or the distal aorta to the popliteal arteries (n = 13). The total mean gadolinium dose was 0.245 mmol/kg per patient. An average of 15 min elapsed between injections. The value of arterial signal-to-noise ratio (mean, 48.8 versus 56.4) and artery-to-vein contrast-to-noise ratio (mean, 45.5 versus 49.0) increased between the first and second angiograms, respectively. Residual gadolinium elevated the values for venous signal-to-noise ratio (mean, 2.3 versus 7.2) and background-to-muscle signal-to-noise ratio (mean, 5.5 versus 10.1) on the second MR angiogram. Qualitative evaluation by three observers showed no significant differences in diagnostic usefulness or overall image quality between the first and second MR angiograms.

CONCLUSION

The use of two low-dose gadolinium-enhanced three-dimensional MR angiograms during a single examination is a feasible approach to increase anatomic coverage when performing gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral vessels. Although background enhancement is slightly elevated on the second angiogram, such enhancement does not significantly change diagnostic usefulness or overall image quality.

Alloreactive T cells that do not require TCR and CD8 coengagement are present in naive mice and contribute to graft rejection

Class I alloreactive CTL populations have been defined as either CD8 dependent or CD8 independent, based upon their ability to kill target cells in the presence of Ab to CD8. The CD8-dependent population uses CD8 in a coreceptor role with the TCR, and mutations in the class I molecule that destroy the CD8 binding site abrogate CTL killing, even if the target cell expresses other allelic forms of class I molecules with an intact binding site for CD8. The CD8-independent population apparently does not require CD8, as Ab to CD8 has no effect on the ability of these cells to kill appropriate target cells. We have isolated a third population of CTL that is inhibited by the addition of CD8 Ab yet can kill target cells that express the alloantigenic molecule incapable of binding CD8, provided that the target cells also express non antigenic class I molecules that contain an intact binding site for CD8. We refer to these cells as CD8 bystander-dependent CTL. Many (10 of 12) of these CTL were able to kill H-2Kb-expressing transfectants of T2 cells, consistent with the idea that they recognize a peptide-independent determinant that may be expressed at a high density on the cell surface. These CD8 bystander-dependent CTL are only readily detectable in vitro when spleen cells from mice primed in vivo with a skin graft are used.

Inhibition of the ATP-sensitive potassium channel from mouse pancreatic beta-cells by surfactants

1. We have used patch-clamp methods to study the effects of the detergents, Cremophor, Tween 80 and Triton X100 on the K(ATP) channel in the pancreatic beta-cell from mouse. 2. All three detergents blocked K(ATP) channel activity with the following order of potency: Tween 80 (Ki< approximately 83 nM)>Triton X100 (Ki=350 nM)>Cremophor. In all cases the block was poorly reversible. 3. Single-channel studies suggested that at low doses, the detergents act as slow blockers of the K(ATP) channel. 4. Unlike the block produced by tolbutamide, that produced by detergent was not affected by intracellular Mg2+-nucleotide, diazoxide or trypsin treatment, nor did it involve an acceleration of rundown or increase in ATP sensitivity of the chanel. 5. The detergents could block the pore-forming subunit, Kir6.2deltaC26, which can be expressed independently of SUR1 (the regulatory subunit of the K(ATP) channel). These data suggest that the detergents act on Kir6.2 and not SUR1. 6. The detergents had no effect on another member of the inward rectifier family: Kir1.1a (ROMK1). 7. Voltage-dependent K-currents in the beta-cell were reversibly blocked by the detergents with a far lower potency than that found for the K(ATP) channel. 8. Like other insulin secretagogues that act by blocking the K(ATP) channel, Cremophor elevated intracellular Ca2+ in single beta-cells to levels that would be expected to elicit insulin secretion. 9. Given the role of the K(ATP) channel in many physiological processes, we conclude that plasma borne detergent may have pharmacological actions mediated through blockage of the K(ATP) channel.

Role of CT angiography in the preoperative evaluation for laparoscopic nephrectomy

Laparoscopic nephrectomy (LN) was recently introduced as a minimally invasive alternative to open nephrectomy in living related renal donation. Because of the limited field of view available with laparoscopic techniques, the role of preoperative radiologic evaluation in LN has expanded to include anatomic definition of the renal arteries, collecting system, renal parenchyma, and renal venous anatomy. Computed tomographic (CT) angiography has proved to be a minimally invasive alternative to conventional angiography in the preoperative evaluation of living related renal donors. CT angiography has been shown to have an accuracy comparable to that of conventional angiography in predicting renal arterial anatomy. In addition, CT angiography provides comprehensive definition of the renal vascular anatomy including the location, size, and length of the renal, adrenal, gonadal, and lumbar veins. Dual-phase spiral CT combined with three-dimensional CT angiography constitute a single, minimally invasive procedure that can provide a complete preoperative evaluation of potential living related renal donors prior to LN. Comprehensive anatomic depiction of the renal arterial and venous supplies aids in surgical planning and helps avoid potential complications.

A plasmid expression system for quantitative in vivo biotinylation of thioredoxin fusion proteins in Escherichia coli

The high affinity binding interaction of biotin to avidin or streptavidin has been used widely in biochemistry and molecular biology, often in sensitive protein detection or protein capture applications. However, in vitro chemical techniques for protein biotinylation are not always successful, with some common problems being a lack of reaction specificity, inactivation of amino acid residues critical for protein function and low levels of biotin incorporation. This report describes an improved expression system for the highly specific and quantitative in vivo biotinylation of fusion proteins. A short 'biotinylation peptide', described previously by Schatz, is linked to the N-terminus of Escherichia coli thioredoxin (TrxA) to form a new protein, called BIOTRX. The 'biotinylation peptide' serves as an in vivo substrate mimic for E. coli biotin holoenzyme synthetase (BirA), an enzyme which usually performs highly selective biotinylation of E.coli biotin carboxyl carrier protein (BCCP). A plasmid expression vector carrying the BIOTRX and birA genes arranged as a bacterial operon can be used to obtain high level production of soluble BIOTRX and BirA proteins and, under appropriate culture conditions, BIOTRX protein produced by this system is completely biotinylated. Fusions of BIOTRX to other proteins or peptides, whether these polypeptides are linked to the C-terminus or inserted into the BIOTRX active site loop, are also quantitatively biotinylated. Both types of BIOTRX fusion can be captured efficiently on avidin/streptavidin media for purification purposes or to facilitate interaction assays. We illustrate the utility of the system by measurements of antibody and soluble receptor protein binding to BIOTRX fusions immobilized on streptavidin-conjugated BIAcore chips.

Virtual angioscopy using spiral CT and real-time interactive volume-rendering techniques

Our purpose was to describe a technique for visualizing the inner contours of the vasculature using contrast enhanced spiral CT and volume rendering techniques. Because the technique is similar to using a camera to look inside vessels, we call this technique "virtual angioscopy." Preliminary results suggest virtual angioscopy using volumetric 3D rendering techniques as a potentially useful technique for the noninvasive evaluation of vascular pathology.

Guidelines for anal cytology--to make cytological diagnosis and follow up much more reliable

Anal intraepithelial neoplasia is a difficult diagnostic and management problem, particularly when it occurs in women with synchronous or metachronous genital intraepithelial neoplasia. Diagnosis and follow up by colposcopy is too specialized for widespread use, and although anal cytology has been used before it has been thought of as too inconsistent for practical application. This study standardized collection of specimens and investigated interobserver variation. The aim of the study was to determine whether observers could reliably distinguish high grade anal intraepithelial neoplasia from other conditions. Standardized collection of anal preparations was achieved in the host centre. A meeting of experienced cytopathologists was convened to agree guidelines for anal cytology. These guidelines were sent to the panel of six observers who were subsequently circulated with 30 cytopathological preparations in random order and asked to report them all. The results were collected and processed centrally. Four individuals were in complete agreement about those preparations which were inadequate for reporting, but two others had a lower threshold for rejecting preparations as inadequate. There was agreement between the observers in over 95% of cases in distinguishing high grade intraepithelial neoplasia from other cytological conditions. Kappa values range from 0.66 to 1.00. This study demonstrates that the provision of guidelines for the interpretation of anal cytopathological preparations can result in a high degree of interobserver agreement about the clinically important distinction between high grade anal intraepithelial neoplasia and other conditions. Anal cytology is a more useful technique for diagnosis and follow up of 'at risk' individuals than has previously been suggested, and should be utilized more widely in this group of patients.

A longitudinal study of the dental care of adults in the general dental service in Scotland: the first 6 years, 1988-1994

OBJECTIVE

To provide an overview of routine dental care for adults attending the general dental service in Scotland, in a more detailed manner than is currently possible from national data sets.

DESIGN AND SETTING

Cohort study in the general dental service.

SUBJECTS AND METHODS

The cohort consisted of 992 Scottish dentate adults who participated in the adult dental health survey of 1988, conducted by the Office of Population Censuses and Surveys. Details of subsequent treatment undertaken in the general dental service were provided by Dental Practice Division, Edinburgh.

MAIN OUTCOME MEASURES

Production of patient-specific and tooth-specific data on dental attendance and treatment.

RESULTS

71% of the cohort attended at least once in the 6 years. Registration levels, following the introduction of the continuing care contract, reached 42-44%. Observed lapses in registration illustrate the changing membership of the relatively static level of registration year-on-year. Vulnerability to treatment of different tooth sites is illustrated graphically.

CONCLUSIONS

Cohort studies provide valuable information on patterns of attendance and treatment needed for planning of dental health services. Growing computer power and increasing demands for management data may mean that future work of this nature can be more appropriately undertaken at the population level.

Electrophysiological and metabolic characterization of single beta-cells and islets from diabetic GK rats

We have used the whole-cell recording technique to determine whether ATP-sensitive potassium (K[ATP]) currents, voltage-dependent Ca2+ currents, and exocytosis are different in single beta-cells from pancreatic islets of Goto-Kakizaki (GK) rats, a novel model of NIDDM, and normal rats. In addition, we have also measured the insulin secretory responses, ATP content, and the rate of glucose metabolism in intact islets. Although the glucose sensitivity of the K(ATP) current was similar between GK rats and controls, in the absence of glucose, K(ATP) current density was larger in GK rats, which resulted in a more hyperpolarized membrane potential. Whole-cell Ca2+ currents were similar. By monitoring the cell capacitance with a fixed intracellular solution, no difference was detected in the exocytotic responses of beta-cells from normal and GK rats. In islets from GK rats, the rates of glucose utilization ([3H]H2O production from 5-[3H]glucose) and oxidation ([14C]CO2 production from U-[14C]glucose) were not significantly different from controls. Insulin secretion, however, was impaired (by 50%), and this was paralleled by a smaller increase in ATP content in response to stimulation by 10 mmol/l glucose in islets from GK rats when compared with controls. Under conditions in which K(ATP) channels were held open and the effects of glucose were independent of membrane potential, insulin release was still significantly lower in GK rat islets than in controls. These findings suggest that the impaired insulin secretion in islets from GK rats does not simply result from a failure to close K(ATP) channels, nor does it result from an impairment in calcium secretion coupling.

Portal venous system thrombosis: helical CT angiography before transjugular intrahepatic portosystemic shunt creation

PURPOSE

To evaluate the utility of helical computed tomographic (CT) angiography for depiction of thrombi in the portal venous system in patients under consideration for transjugular intrahepatic portosystemic shunt (TIPS) creation.

MATERIALS AND METHODS

Contrast material-enhanced helical CT was performed before TIPS creation in 25 patients. Axial, multiplanar, and three-dimensional images were evaluated to determine whether thrombus was present in the portal system and whether TIPS creation was contraindicated. CT findings were confirmed at visceral angiography (n = 3), direct portography (n = 20), or duplex ultrasonography (n = 2).

RESULTS

Ten (40%) of 25 patients, including 10 (56%) of 18 patients with refractory variceal hemorrhage, had thrombus in the portal venous system. Helical CT scans depicted thrombus in nine (90%) of 10 patients (95% confidence interval = 0.71, 1.00) and in 16 (94%) of 17 vessels (95% confidence interval = 0.83, 1.00), including the portal vein (eight of eight patients), splenic vein (three of four patients), and superior mesenteric vein (five of five patients). TIPS creation was canceled in four (16%) patients on the basis of CT findings.

CONCLUSION

Thrombi in the portal venous system are common in patients with refractory variceal hemorrhage. Helical CT angiography is sensitive and specific for portal venous system thrombosis and can provide information that alters treatment in these patients.

Low concentrations of muscarine potentiate M-current in bullfrog sympathetic B-neurones

The concentration-dependence of the effect of muscarine on M-current (IM) and the underlying M-conductance (gM) in B-cells of bullfrog sympathetic ganglion was examined using whole-cell recording techniques. High concentrations of muscarine (> or = 200 nM) produced the classical suppression and over-recovery of steady-state IM at -30 mV. By contrast, low concentrations of muscarine (< or = 30 nM) shifted the gM activation curve to more negative potentials, increased the activation time constant (tau a) and increased steady-state IM. This effect may reflect muscarine-induced changes in submembrane Ca2+ concentration.

Detection of resin acid compounds in airborne particulate generated from rosin used as a soldering flux

Various uses of rosin and exposure to its resin acid constituents have been associated with dermal and pulmonary sensitization. Methodology is presented to detect resin acids common to rosin (such as abietic and dehydroabietic acid) found in aerosol from heated rosin flux. Air filtration, solvent filter extraction, and gas chromatography/mass spectrometry were used to provide qualitative and quantitative information on the resin acid content of aerosol produced during soldering with rosin flux. Abietic acid and dehydroabietic acid were identified and quantified in aerosol derived from heated rosin flux, in samples collected in the field and in laboratory generated samples. Other resin acids (including several apparently oxidized resin acids) were detected, but not quantified. Laboratory mass balance experiments using soldering temperatures and liquid rosin flux showed that much of the nonvolatile material originally present in unheated flux may be captured on a sampling filter following heating and aerosolization. The data presented suggest that resin acids are a major component (with regard to mass) of the airborne contaminants produced during soldering with rosin flux. Abietic acid was shown to be unstable on sampling filters held for a period of weeks, while dehydroabietic acid and total solvent-soluble material were not found to degrade under the same conditions. Rosin aerosol produced in the laboratory using a soldering iron and liquid rosin flux produced particles shown to be of respirable size using scanning electron microscopy.

Regulation of N- and L-type Ca2+ channels in adult frog sympathetic ganglion B cells by nerve growth factor in vitro and in vivo

To examine mechanisms responsible for the long-term regulation of Ca2+-channels in an adult neuron, changes in whole cell Ba2+ current (IBa) were examined in adult bullfrog sympathetic ganglion B cells in vitro. Cells were cultured at low density in defined, serum free medium. After 15 days, total IBa was similar to the initial value, whereas IBa density was reduced by approximately 36%, presumably due to an increase in neuronal surface area. By contrast, IBa density remained constant after 6-15 days in the presence of murine beta-NGF (200 ng/ml), and total IBa was almost doubled. Inclusion of cytosine arabinoside (Ara-C; 10 microM) to inhibit proliferation of nonneuronal cells, did not affect the survival of neurons in the absence of nerve growth factor (NGF) nor did it attenuate IBa. Ara-C did not prevent the effect of NGF on IBa. There were three independent components to the action of NGF; during 6-9 days, it increased omega-conotoxin-GVIA-sensitive N-type IBa (IBa,N); increased nifedipine-sensitive L-type IBa (IBa,L) and decreased inactivation of the total Ba2+ conductance (gBa). The latter effect involved a selective decrease in the amplitude of one of the four kinetic components that describe the inactivation process. Total IBa was also 55.8% larger than control in the somata of B cells acutely dissociated from leopard frogs that had received prior subcutaneous injections of NGF. By contrast, injection of NGF antiserum decreased total IBa by 29.4%. There was less inactivation of gBa in B cells from NGF-injected animals than in cells from animals injected with NGF antiserum (P < 0.001). These data suggest that NGF-like molecule(s) play(s) a role in the maintenance of IBa in an adult amphibian sympathetic neuron; the presence of NGF may allow the neuron to maintain a constant relationship between cell size and current density. They also show that IBa inactivation in an adult neuron can be modulated in a physiologically relevant way by an extracellular ligand.

Inability of the activated partial thromboplastin time to predict heparin levels. Time to reassess guidelines for heparin assays

BACKGROUND

In treating venous thromboembolic disorders, patient outcomes appear to correlate with heparin levels. Due to pharmacokinetic and pharmacodynamic variations, a relationship between heparin dose and level cannot be reliably predicted in individual patients. Some patients have low heparin levels despite therapeutic activated partial thromboplastin times (aPTTs), which may increase their risk for recurrent thromboembolism. Patients with high heparin requirements appear to have fewer bleeding episodes with heparin level-guided therapy. The aPTT does not reliably correlate with heparin blood concentrations or antithrombotic effects. Consequently, heparin therapy monitored with heparin levels may be more effective and safer.

OBJECTIVES

To prospectively determine whether (1) the aPTT therapeutic range adequately predicts heparin levels in 38 patients used to establish the therapeutic aPTT range as is currently recommended and (2) whether 3 paired sets of aPTT-antifactor Xa levels provide the basis for using aPTTs to predict subsequent heparin levels in individual patients (n = 27) receiving intravenous heparin for coronary artery disease or venous thromboembolic disease.

RESULTS

In the therapeutic aPTT range established, the R2 value for the relationship was 0.4. Prediction intervals were wide. For an aPTT of 60 seconds, the 95% prediction interval estimates were heparin levels of 0.05 to 1.0 U/mL. In individual patients, the aPTT-antifactor Xa relationship had an average R2 value of 0.75. There was no consistent relationship between the aPTT and anti-factor Xa level in a significant number of patients.

CONCLUSIONS

The aPTT does not appear to be a useful surrogate for heparin levels. These findings suggest that the current recommendations on the use of heparin levels should be expanded.

Nociceptin inhibits T-type Ca2+ channel current in rat sensory neurons by a G-protein-independent mechanism

Nociceptin (orphanin FQ) is a novel, opioid-like, heptadecapeptide that is an endogenous ligand for the opioid receptor-like (ORL1) receptor. Unlike classical opioids, nociceptin can produce hyperalgesia when injected intracerebroventricularly into mice. Despite this, nociceptin has been reported to decrease transmitter release, activate an inwardly rectifying K+ conductance, and suppress high-voltage-activated Ca2+ channel conductances (HVA gCa) in much the same way as micro-, delta-, and kappa-opioids. We report an action of nociceptin that is not shared by morphine: the suppression of low-voltage-activated, transient calcium (barium) current (IBa,T) in acutely dissociated rat dorsal root ganglion (DRG) neurons (EC50 = 100 nM). This effect was reflected as inhibition of bursts of action potentials that can be evoked in "medium-sized" DRG neurons. Experiments with GTP-gamma-S (100 microM), GDP-beta-S (2 mM), or aluminum fluoride (AlF3) (100 microM) in the patch pipette failed to provide evidence for G-protein involvement in nociceptin-induced IBa,T suppression. By contrast, both morphine and nociceptin suppressed HVA gCa, and the latter response was affected by intracellular GTP-gamma-S, GDP-beta-S, and AlF3 in ways that confirmed G-protein involvement. The selective effect of nociceptin on IBa,T may therefore be relevant to understanding why its behavioral actions differ from those of other opioids. This G-protein-independent effect of the action of nociceptin may reflect a new general mechanism of action for opioid peptides within the nervous system.

Three-dimensional CT stereoscopic visualization of renal masses: impact on diagnosis and patient treatment

OBJECTIVE

The objective of this study was to determine whether three-dimensional reconstruction with stereoscopic display of helical CT data sets and CT angiography are useful in the examination of patients with known or suspected renal masses.

CONCLUSION

Volume-rendering techniques applied to helical CT data sets coupled with three-dimensional stereoscopic imaging provide a complete examination of patients with known or suspected renal masses. Such information can help guide patient treatment and provide a single preoperative study when nephron-sparing surgery or total nephrectomy is considered.

Audiometer calibration: two neglected areas

British and International Standards for pure tone audiometry require that the static force exerted by the earphone/bone vibrator headband is within certain limits. However, no recommended procedure is given for making force measurements. In addition, standards for audiometers require that linearity of output level is within certain limits. Only a brief outline of a procedure is available for measuring linearity at low intensity levels. Both these areas of audiometer calibration tend to be neglected according to our survey of organizations offering calibration services. Equipment and protocols for measuring both have been developed at the MRC Institute of Hearing Research, and are described. A convenience sample of audiometers gave a wide range of headband forces, many of which do not comply with the relevant standard. Linearity of output at low levels did comply with the relevant standard for all audiometers measured. We recommend the use of simple devices, such as those described, for routine calibration. They are quick and easy to use, give reliable results, and are inexpensive.

Rheological and Solid-Liquid Separation Properties of Bimodal Suspensions of Colloidal Gibbsite and Boehmite

Bimodal suspensions of nanometer-sized boehmite particles and micron-sized gibbsite particles in 0.10 M NaNO3 are used as models to gain insight into the physical properties of agglomerating colloidal suspensions containing bimodal distributions of primary particles. Results on the gibbsite-boehmite mixtures show that the presences of small particles in a suspension can have a dramatic impact on the rheological, sedimentation, and filtration characteristics of suspensions of larger particles. Transmission electron micrographs show that boehmite forms a coating on the larger gibbsite particles. The coating provides steric repulsion and reduces the attractive interactions between the larger particles, leading to viscosity decreases and greater densification of sediments and filter cakes. A model has been developed to rationalize observed property changes based on the range of agglomerate structures that can form in mixtures of large and small particles. Results are discussed in the content of the processing of nuclear waste sludges, but are applicable to a wide range of bimodal suspensions.

Interventions used by staff nurses to manage "difficult" patients

Interventions utilized by nurses to manage "difficult" patients and outcomes indicating successful interventions were investigated. Themes included getting the difficult patient label, difficult patient behaviors, reflecting on the label and passing it on, coping with a difficult patient, interventions that worked, and interventions that did not work. Clues indicating that patient behavior was changing were also identified.

Distribution of Ly-6C on lymphocyte subsets: I. Influence of allotype on T lymphocyte expression

The expression patterns of the Ly-6C Ag were examined on splenic and thymic lymphocyte subsets of Ly-6.1 and Ly-6.2 strains of mice using the rat mAb 15.1. Ly-6C is expressed on subsets of CD4+ and CD8+ splenocytes, and a portion of NK cells. Within the splenic and lymph node CD4+ T cell compartment, Ly-6C expression is restricted to Ly-6.2 strains of mice, and is present on a subset of naive cells. Ly-6C is expressed on the majority of peripheral CD8+ T cells in both Ly-6.1 and Ly-6.2 strains, and is found primarily on the Ag-experienced subset. In the thymus, Ly-6C is present on subpopulations of CD4- CD8+, CD4- CD8-, and CD4+ CD8- cells. Ly-6C+ CD4- CD8+ thymocytes show a mature phenotype, while Ly-6C+ CD4- CD8- and Ly-6C+ CD4+ CD8- thymocytes appear to be part of the recently described NK1.1+ alphabeta TCR+ population. On account of the marked differences in Ly-6C expression on peripheral CD4+ T cells from Ly-6.1 and Ly-6.2 strains of mice, additional experiments were undertaken to assess Ly-6C expression in parental and Ly-6.1 x Ly-6.2 F1 mice. Neither phenotype dominated in the F1 offspring, with frequencies of Ly-6C+ CD4+ splenocytes falling in the intermediate range. Further experiments compared the staining patterns of the rat anti-pan Ly-6C (Ly-6.1 and Ly-6.2) Ab with a mouse anti-Ly-6.2 allotype specific Ab, with emphasis on both Ly-6.2 and Ly-6.1 x Ly-6.2 F1 mice. The results demonstrate the presence of lymphocytes that express the pan form of Ly-6C but not the form recognized by the alloantibody. This latter finding suggests the presence of more than one form of the Ly-6C Ag.