Topographical depth reveals contact guidance mechanism distinct from focal adhesion confinement

Cellular response to the topography of their environment, known as contact guidance, is a crucial aspect to many biological processes yet remains poorly understood. A prevailing model to describe cellular contact guidance involves the lateral confinement of focal adhesions (FA) by topography as an underlying mechanism governing how cells can respond to topographical cues. However, it is not clear how this model is consistent with the well-documented depth-dependent contact guidance responses in the literature. To investigate this model, we fabricated a set of contact guidance chips with lateral dimensions capable of confining focal adhesions and relaxing that confinement at various depths. We find at the shallowest depth of 330 nm, the model of focal adhesion confinement is consistent with our observations. However, the cellular response at depths of 725 and 1000 nm is inadequately explained by this model. Instead, we observe a distinct reorganization of F-actin at greater depths in which topographically induced cell membrane deformation alters the structure of the cytoskeleton. These results are consistent with an alternative curvature-hypothesis to explain cellular response to topographical cues. Together, these results indicate a confluence of two molecular mechanisms operating at increased induced membrane curvature that govern how cells sense and respond to topography.

Automated cell segmentation for reproducibility in bioimage analysis

Live-cell imaging is extremely common in synthetic biology research, but its ability to be applied reproducibly across laboratories can be hindered by a lack of standardized image analysis. Here, we introduce a novel cell segmentation method developed as part of a broader Independent Verification & Validation (IV&V) program aimed at characterizing engineered Dictyostelium cells. Standardizing image analysis was found to be highly challenging: the amount of human judgment required for parameter optimization, algorithm tweaking, training and data pre-processing steps forms serious challenges for reproducibility. To bring automation and help remove bias from live-cell image analysis, we developed a self-supervised learning (SSL) method that recursively trains itself directly from motion in live-cell microscopy images without any end-user input, thus providing objective cell segmentation. Here, we highlight this SSL method applied to characterizing the engineered Dictyostelium cells of the original IV&V program. This approach is highly generalizable, accepting images from any cell type or optical modality without the need for manual training or parameter optimization. This method represents an important step toward automated bioimage analysis software and reflects broader efforts to design accessible measurement technologies to enhance reproducibility in synthetic biology research.

Interfacing Live Cells with Surfaces: A Concurrent Control Technique for Quantifying Surface Ligand Activity

Surface ligand activity is a key design parameter for successfully interfacing surfaces with cells─whether in the context of in vitro investigations for understanding cellular signaling pathways or more applied applications in drug delivery and medical implants. Unlike other crucial surface parameters, such as stiffness and roughness, surface ligand activity is typically based on a set of assumptions rather than directly measured, giving rise to interpretations of cell adhesion that can vary with the assumptions made. To fill this void, we have developed a concurrent control technique for directly characterizing in vitro ligand surface activity. Pairs of gold-coated glass chips were biofunctionalized with RGD ligand in a parallel workflow: one chip for in vitro applications and the other for surface plasmon resonance (SPR)-based RGD activity characterization. Recombinant α_Vβ₃ integrins were injected over the SPR chip surface as mimics of the cellular-membrane-bound receptors and the resulting binding kinetics parameterized to quantify surface ligand activity. These activity measurements were correlated with cell morphological features, measured by interfacing MDA-MB-231 cells with the in vitro chip surfaces on the live cell microscope. We demonstrate how the interpretation of a cell phenotype based on direct activity measurements can vary markedly from interpretations based on assumed activity. The SPR concurrent control approach has multiple advantages due to the fact that SPR is a standardized technique and has the sensitivity to measure ligand activity across the most relevant range of extracellular surface densities, while the in vitro chip design can be used with all commonly used light microscopy modalities (e.g., phase contrast, DIC, and fluorescence) so that a wide range of phenotypic and molecular markers can be correlated to the ligand surface activity.

Problem of Diminished cRGD Surface Activity and What Can Be Done about It

RGD peptides play a pivotal role in growing and diverse areas of biological research, ranging from in vitro experiments probing fundamental molecular mechanisms of cell adhesion to more applied in vivo strategies in medical imaging and cancer therapeutics. To better understand the outcomes of RGD-based approaches, we quantified the degree to which cyclic RGD (cRGD) activity is blocked by nonspecific binding of commonly used medium constituents. First, we show that recombinant α_Vβ₃ integrins can be used as a highly sensitive cell-free sensor to quantitatively and reliably characterize the activity of cRGD-functionalized surfaces via surface plasmon resonance (SPR). Next, SPR experiments were utilized to measure the extent of blocking of cRGD-functionalized surfaces by the commonly used agents BSA, PLL-g-PEG, and fetal calf serum (FCS)-supplemented media, using recombinant α_Vβ₃ integrin as a probe for cRGD binding activity in the presence of blocking agents. All three additives were highly efficient blockers of cRGD activity, as exemplified by cell culture media containing 1% FCS which reduced the cRGD activity by 33-fold. We then developed a strategy to combat these deleterious effects by employing the recombinant integrins as a protective cap. We show that the unblocked cRGD activity can be preserved in the presence of PLL-g-PEG by employing the α_Vβ₃ integrin as a removable protective cap, both in cell-free and in vitro experiments. In vitro studies with MDA-MB-231 cells cultured atop cRGD-functionalized surfaces found that cell adhesion and migration prevented by PLL-g-PEG were restored when this protective cap approach was used.

Nanoplasmonic pillars engineered for single exosome detection

Exosomes are secreted nanovesicles which incorporate proteins and nucleic acids, thereby enabling multifunctional pathways for intercellular communication. There is an increasing appreciation of the critical role they play in fundamental processes such as development, wound healing and disease progression, yet because of their heterogeneous molecular content and low concentrations in vivo, their detection and characterization remains a challenge. In this work we combine nano- and microfabrication techniques for the creation of nanosensing arrays tailored toward single exosome detection. Elliptically–shaped nanoplasmonic sensors are fabricated to accommodate at most one exosome and individually imaged in real time, enabling the label-free recording of digital responses in a highly multiplexed geometry. This approach results in a three orders of magnitude sensitivity improvement over previously reported real-time, multiplexed platforms. Each nanosensor is elevated atop a quartz nanopillar, minimizing unwanted nonspecific substrate binding contributions. The approach is validated with the detection of exosomes secreted by MCF7 breast adenocarcinoma cells. We demonstrate the increasingly digital and stochastic nature of the response as the number of subsampled nanosensors is reduced from four hundred to one.

Quantifying time-varying cellular secretions with local linear models

Extracellular protein concentrations and gradients initiate a wide range of cellular responses, such as cell motility, growth, proliferation and death. Understanding inter-cellular communication requires spatio-temporal knowledge of these secreted factors and their causal relationship with cell phenotype. Techniques which can detect cellular secretions in real time are becoming more common but generalizable data analysis methodologies which can quantify concentration from these measurements are still lacking. Here we introduce a probabilistic approach in which local-linear models and the law of mass action are applied to obtain time-varying secreted concentrations from affinity-based biosensor data. We first highlight the general features of this approach using simulated data which contains both static and time-varying concentration profiles. Next we apply the technique to determine concentration of secreted antibodies from 9E10 hybridoma cells as detected using nanoplasmonic biosensors. A broad range of time-dependent concentrations was observed: from steady-state secretions of 230 pM near the cell surface to large transients which reached as high as 56 nM over several minutes and then dissipated.

Dimension from covariance matrices

We describe a method to estimate embedding dimension from a time series. This method includes an estimate of the probability that the dimension estimate is valid. Such validity estimates are not common in algorithms for calculating the properties of dynamical systems. The algorithm described here compares the eigenvalues of covariance matrices created from an embedded signal to the eigenvalues for a covariance matrix of a Gaussian random process with the same dimension and number of points. A statistical test gives the probability that the eigenvalues for the embedded signal did not come from the Gaussian random process.

Grid-based partitioning for comparing attractors

Stationary dynamical systems have invariant measures (or densities) that are characteristic of the particular dynamical system. We develop a method to characterize this density by partitioning the attractor into the smallest regions in phase space that contain information about the structure of the attractor. To accomplish this, we develop a statistic that tells us if we get more information about our data by dividing a set of data points into partitions rather than just lumping all the points together. We use this method to show that not only can we detect small changes in an attractor from a circuit experiment, but we can also distinguish between a large set of numerically generated chaotic attractors designed by Sprott. These comparisons are not limited to chaotic attractors-they should work for signals from any finite-dimensional dynamical system.

A Label-free Technique for the Spatio-temporal Imaging of Single Cell Secretions

Inter-cellular communication is an integral part of a complex system that helps in maintaining basic cellular activities. As a result, the malfunctioning of such signaling can lead to many disorders. To understand cell-to-cell signaling, it is essential to study the spatial and temporal nature of the secreted molecules from the cell without disturbing the local environment. Various assays have been developed to study protein secretion, however, these methods are typically based on fluorescent probes which disrupt the relevant signaling pathways. To overcome this limitation, a label-free technique is required.

In this paper, we describe the fabrication and application of a label-free localized surface plasmon resonance imaging (LSPRi) technology capable of detecting protein secretions from a single cell. The plasmonic nanostructures are lithographically patterned onto a standard glass coverslip and can be excited using visible light on commercially available light microscopes. Only a small fraction of the coverslip is covered by the nanostructures and hence this technique is well suited for combining common techniques such as fluorescence and bright-field imaging.

A multidisciplinary approach is used in this protocol which incorporates sensor nanofabrication and subsequent biofunctionalization, binding kinetics characterization of ligand and analyte, the integration of the chip and live cells, and the analysis of the measured signal. As a whole, this technology enables a general label-free approach towards mapping cellular secretions and correlating them with the responses of nearby cells.

Optimizing Nanoplasmonic Biosensor Sensitivity with Orientated Single Domain Antibodies

Localized surface plasmon resonance (LSPR) spectroscopy and imaging are emerging biosensor technologies which tout label-free biomolecule detection at the nanoscale and ease of integration with standard microscopy setups. The applicability of these techniques can be limited by the restrictions that surface-conjugated ligands must be both sufficiently small and orientated to meet analyte sensitivity requirements. We demonstrate that orientated single domain antibodies (sdAb) can optimize nanoplasmonic sensitivity by comparing three anti-ricin sdAb constructs to biotin-neutravidin, a model system for small and highly orientated ligand studies. LSPR imaging of electrostatically orientated sdAb exhibited a ricin sensitivity equivalent to that of the biotinylated LSPR biosensors for neutravidin. These results, combined with the facts that sdAb are highly stable and readily produced in bacteria and yeast, build a compelling case for the increased utilization of sdAbs in nanoplasmonic applications.

Quantitative imaging of protein secretions from single cells in real time

Protein secretions from individual cells create spatially and temporally varying concentration profiles in the extracellular environment, which guide a wide range of biological processes such as wound healing and angiogenesis. Fluorescent and colorimetric probes for the detection of single cell secretions have time resolutions that range from hours to days, and as a result, little is known about how individual cells may alter their protein secretion rates on the timescale of minutes or seconds. Here, we present a label-free technique based upon nanoplasmonic imaging, which enabled the measurement of individual cell secretions in real time. When applied to the detection of antibody secretions from single hybridoma cells, the enhanced time resolution revealed two modes of secretion: one in which the cell secreted continuously and another in which antibodies were released in concentrated bursts that coincided with minute-long morphological contractions of the cell. From the continuous secretion measurements we determined the local concentration of antibodies at the sensing array closest to the cell and from the bursts we estimated the diffusion constant of the secreted antibodies through the extracellular media. The design also incorporates transmitted light and fluorescence microscopy capabilities for monitoring cellular morphological changes and intracellular fluorescent labels. We anticipate that this technique can be adapted as a general tool for the quantitative study of paracrine signaling in both adherent and nonadherent cell lines.

Quantitative LSPR imaging for biosensing with single nanostructure resolution

Localized surface plasmon resonance (LSPR) imaging has the potential to map complex spatio-temporal variations in analyte concentration, such as those produced by protein secretions from live cells. A fundamental roadblock to the realization of such applications is the challenge of calibrating a nanoscale sensor for quantitative analysis. Here, we introduce a new, to our knowledge, LSPR imaging and analysis technique that enables the calibration of hundreds of individual gold nanostructures in parallel. The calibration allowed us to map the fractional occupancy of surface-bound receptors at individual nanostructures with nanomolar sensitivity and a temporal resolution of 225 ms. As a demonstration of the technique's applicability to molecular and cell biology, the calibrated array was used for the quantitative LSPR imaging of anti-c-myc antibodies harvested from a cultured 9E10 hybridoma cell line without the need for further purification or processing.

Magnetic moment degradation of nanowires in biological media: real-time monitoring with SQUID magnetometry

Magnetic nanoparticles are used throughout biology for applications from targeted drug and gene delivery to the labeling of cells. These nanoparticles typically react with the biological medium to which they are introduced, resulting in a diminished magnetic moment. The rate at which their magnetic moment is diminished limits their utility for targeting and can signal the unintended release of surface-functionalized biomolecules. A foreknowledge of the time-dependent degradation of the magnetic moment in a given medium can aid in the selection of the optimal buffering solution and in the prediction of a reasonable experimental time frame. With this goal in mind, we have developed a SQUID magnetometer based methodology for measuring the saturation magnetic moment of nanoparticles in real time while immersed in a biological medium. Measurements on Co and Ni nanowires in a variety of commonly used buffered salines demonstrated that the technique has the dynamic range and sensitivity to detect the rapid reduction in moment due to active corrosion as well as much more subtle changes from the formation of a passivating surface oxide layer. In order to correlate the magnetic moment reductions to these specific chemical processes, samples were additionally characterized using x-ray photoelectron spectroscopy, inductively coupled plasma spectroscopy and scanning electron microscopy. The most reactive buffers studied were found to be phosphate and carbonate based, which caused active corrosion of the Co nanowires but only a comparatively slow passivation of the Ni nanowires by oxidation.

The use of DNA molecular beacons as nanoscale temperature probes for microchip-based biosensors

Today's biosensors and drug delivery devices are increasingly incorporating lithographically patterned circuitry that is placed within microns of the biological molecules to be detected or released. Elevated temperatures due to Joule heating from the underlying circuitry cannot only reduce device performance, but also alter the biological activity of such molecules (i.e. binding, enzymatic, folding). As a consequence, biochip design and characterization will increasingly require local measurements of the temperature and temperature gradients on the biofunctionalized surface. We have developed a technique to address this challenge based on the use of DNA molecular beacons as a nanoscale temperature probe. The surface of fused-silica chips with lithographically patterned, current-carrying gold rings have been functionalized with a layer of molecular beacons. We utilize the temperature dependence of the molecular beacons to calibrate the temperature at the center of the rings as a function of applied current from 25 to 50 degrees C. The fluorescent images of the rings reveal the extent of heating to the surrounding chip due to the applied current while resolving temperature gradients over length scales of less than 500nm. Finite element analysis and analytic calculations of the distribution of heat in the vicinity of the current-carrying rings agree well with the experimental results. Thus, molecular beacons are shown to be a viable tool for temperature calibration of micron-sized circuitry and the visualization of submicron temperature gradients.

Determination of the spin polarization of half-metallic CrO(2) by point contact Andreev reflection

Andreev reflection at a Pb/CrO(2) point contact has been used to determine the spin polarization of single-crystal CrO(2) films made by chemical vapor deposition. The spin polarization is found to be 0.96 +/- 0.01, which confirms that CrO(2) is a half-metallic ferromagnet, as theoretically predicted.

Spin diffusion in semiconductors

The behavior of spin diffusion in doped semiconductors is shown to be qualitatively different than in undoped (intrinsic) ones. Whereas a spin packet in an intrinsic semiconductor must be a multiple-band disturbance, involving inhomogeneous distributions of both electrons and holes, in a doped semiconductor a single-band disturbance is possible. For n-doped nonmagnetic semiconductors the enhancement of diffusion due to a degenerate electron sea in the conduction band is much larger for these single-band spin packets than for charge packets-this explains the anomalously large spin diffusion recently observed in n-doped GaAs at 1.6 K. In n-doped ferromagnetic and semimagnetic semiconductors the motion of spin packets polarized antiparallel to the equilibrium carrier spin polarization is predicted to be an order of magnitude faster than for parallel polarized spin packets. These results are reversed for p-doped semiconductors.

Measuring the spin polarization of a metal with a superconducting point contact

A superconducting point contact is used to determine the spin polarization at the Fermi energy of several metals. Because the process of supercurrent conversion at a superconductor-metal interface (Andreev reflection) is limited by the minority spin population near the Fermi surface, the differential conductance of the point contact can reveal the spin polarization of the metal. This technique has been applied to a variety of metals where the spin polarization ranges from 35 to 90 percent: Ni0.8Fe0.2, Ni, Co, Fe, NiMnSb, La0.7Sr0.3MnO3, and CrO2.

Effect of pulsed electromagnetic stimulation on facial nerve regeneration

OBJECTIVE

To determine if exposure to electromagnetic fields influences regeneration of the transected facial nerve in the rat.

DESIGN AND METHODS

The left facial nerve was transected in the tympanic section of the fallopian canal in 24 rats randomly assigned to 2 groups. The cut ends of the facial nerve were reapproximated without sutures within the fallopian canal to maximize the potential for regeneration. Rats in the experimental group (n= 12) were then exposed to pulsed electromagnetic stimulation (0.4 millitesla at 120 Hz) for 4 hours per day, 5 days per week, for 8 weeks. Rats in the control group (n=12) were handled in an identical manner without pulsed electromagnetic stimulation. Four other rats were given sham operations in which all surgical procedures were carried out except for the actual nerve transection. Two of these rats were placed in each group. Nerve regeneration was evaluated using electroneurography (compound action potentials), force of whisker and eyelid movements, and voluntary facial movements before and at 2-week intervals after transection. Histological evaluation was performed at 10 weeks after transection. Each dependent variable was analyzed using a 2-way analysis of variance with 1 between variable (groups) and 1 within repeated measures variable (days after transection).

RESULTS

Statistical analysis indicated that N1 (the negative deflection of depolarization phase of the muscle and/or nerve fibers) area, N1 amplitude, and N1 duration, as well as absolute amplitude of the compound action potentials, were all significantly greater 2 weeks after transection in the experimental than in the control group of rats. The force of eye and whisker movements after electrical stimulation was statistically greater in the experimental group of rats 4 weeks after transection. Voluntary eye movements in the experimental group were significantly better at 5 and 10 weeks, while whisker movements were better at 3 and 10 weeks. There was no statistical difference between the 2 groups for any histological variable.

CONCLUSION

Results of this study indicate that pulsed electromagnetic stimulation enhances early regeneration of the transected facial nerve in rats.

Changes in brainstem calcitonin gene-related peptide after VIIth and VIIIth cranial nerve lesions in guinea pig

The present study investigated the effect of seventh and eight cranial nerve lesions on the prominence of calcitonin gene-related peptide in the hypoglossal (XII), facial (VII), abducens (VI), and oculomotor (III) cranial nerve nuclei. Guinea pigs were anesthetized and subjected to unilateral cochlear removal, vestibular end organ ablation, and seventh nerve transection. After a survival period ranging from 4 h to 5 days, each animal was anesthetized and perfused intracardially. Frozen sections were collected through the brainstem and stained immunohistochemically for calcitonin gene-related peptide using a polyclonal antibody with the Vectastain ABC kit and protocol. Positive cells were counted in each nucleus bilaterally and analyzed for side to side differences. Nuclei XII and III showed no significant difference in the numbers of cells staining positively for calcitonin gene-related peptide between the ipsilateral and the contralateral sides to the lesion. However, nuclei VII and VI showed elevated numbers ipsilateral to the lesion on some days, but not all. For VII, there was no significant difference before 24 h, but there were significant differences 1-5 days after the lesion. Similarly, in VI, there was no difference before 24 h, but differences were significant beginning with day 1 and continuing through day 3, and finally disappearing by day 4. Changes in the numbers of CGRP positive cells in VII measurable 24 h after the lesion and continuing for at least 5 days afterward indicate a central nervous system retrograde response to peripheral motor nerve injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Paranasal sinus infection due to atypical mycobacteria in two patients with AIDS

Atypical mycobacteria, which are common opportunistic pathogens in patients with AIDS, have not been previously implicated in the pathogenesis of paranasal sinus infections; we describe two such patients. Clinical and radiographic evidence of bilateral maxillary and ethmoid sinusitis was observed for one patient; his infection proved resistant to therapy with conventional antimicrobials and decongestants. Endoscopic ethmoid sinus biopsy yielded a specimen containing acid-fast bacilli (AFB) that were later identified as Mycobacterium kansasii. Antimycobacterial therapy had not resulted in amelioration of the sinusitis > 2 months later, at which time he died of cerebral toxoplasmosis. The second patient presented with a tender right frontotemporal soft-tissue mass; a computed tomogram disclosed that it extended through the frontal bone to the frontal sinus. Inflamed tissue debrided from the sinus contained AFB; cultures first yielded M. kansasii and later Mycobacterium avium complex. Bacteremia due to both organisms was also demonstrated. Infection progressed despite therapy.

Repair of parastomal hernias using polypropylene mesh

Parastomal hernias are a common complication of ostomy construction. We have developed a method of repair that uses two strips of polypropylene prosthetic mesh through a midline incision. The medical records of 19 patients who underwent parastomal hernia repair were retrospectively reviewed. All nine patients operated on for this condition by the senior author (R.G.P.) (group 1) underwent repairs with this technique. All ten patients operated on by other surgeons in our center (group 2) underwent repairs in which the stoma was moved, the fascia was directly repaired through a parastomal incision, or the fascia was repaired via a midline incision. No patients in group 1 had recurrences while five patients in group 2 had recurrences. Neither group developed strictures or stomal prolapse. Our method of repair is technically easy and has excellent results. It is especially suitable in very large hernias in which incisional hernia is likely in the original stoma site if the stoma is moved.

Rudolf Virchow--father of cellular pathology

Rudolf Virchow, the famous German physician-scientist-statesman and social activist of nineteenth century Berlin, contributed greatly to the science of pathology by his teaching, research, and publishing. He consolidated the idea of cellular changes as the basis of disease and introduced many modern concepts and terms into medical science. He led in defining orderly, methodical procedures for the autopsy and emphasized its importance to medicine. Virchow's life and work fundamentally influenced and altered modern medical concepts of disease.

An analysis of toxic deaths, 1982 to 1985, Pima County, Arizona

Toxic deaths in Pima County, Arizona, were studied over a four-year period. The deaths were analyzed according to cause and manner of death, toxic substance, and demographic data. The age group 40 to 49 years had the highest rate of suicide from toxic substances. The accident death rate was highest for ages 20 to 29 years. Carbon monoxide was most often found to be the cause of deaths in this study. The most prevalent drugs were narcotics followed by antidepressants, cocaine, and barbiturates. Comparisons are made with similar studies.

Cocaine-related deaths in Pima County, Arizona, 1982-1984

A three-year review of toxicology data from medical examiner autopsies in Pima County, Arizona, has demonstrated that cocaine has rapidly become a leading substance of abuse, second only to alcohol in the frequency of drugs detected by toxicologic analysis of all suspicious deaths, motor vehicle accident fatalities, homicides, and suicides. Gastric contents and urine were analyzed by thin-layer chromatography, and nasal swabs, blood, and urine were tested for the combination of cocaine and its metabolite benzoylecgonine by quantitative radioimmunoassay. A total of seventy-two deaths in Pima County from 1982 to 1984 have involved cocaine. Seventy percent of these have occurred in the last fifteen months. Marked variation in the individual response to cocaine compared to the blood concentration of cocaine/metabolite was noted.

Lidocaine elimination: effects of metoprolol and of propranolol

The effects of administration of metoprolol and propranolol on lidocaine elimination were studied in six healthy young men who did not smoke. Each received three single intravenous doses of lidocaine (2.5 to 3.0 mg/kg injected over 10 min): one alone, one after 1 day pretreatment with propranolol (40 mg orally every 6 hr), and one after 1 day pretreatment with metoprolol (50 mg orally every 6 hr). Lidocaine clearance was 0.88 +/- 0.28 l X hr-1 X kg-1 before beta blockade, 0.61 +/- 0.20 l X hr-1 X kg-1 during metoprolol dosing, and 0.47 +/- 0.16 l X hr-1 X kg-1 during propranolol dosing. There was no correlation between the change in lidocaine elimination and the steady-state concentrations of metoprolol or propranolol, nor between the change in lidocaine clearance and the change in resting heart rate produced by either beta blocker. Metoprolol and propranolol reduce lidocaine elimination significantly.

A modified ion-selective electrode method for measurement of chloride in sweat

A modified method of analysis of sweat chloride concentration with an ion-selective electrode is presented. The original method of sweat chloride analysis proposed by the Orion Research Corporation (Cambridge, Massachusetts 02139) is inadequate because it produces erratic and misleading results. The modified method was compared with the reference quantitative method of Gibson and Cooke. In the modified method, individual electrode pads are cut and placed in the electrodes rather than using the pads supplied by the company; pilocarpine nitrate (2,000 mg/l) is used in place of pilocarpine HCl (640 mg/l); sodium bicarbonate as the weak electrolyte is used instead of K2SO4. A 10-minute period for sweat accumulation is employed rather than a zero-time collection as in the original Orion method. The modification has been studied for reproducibility in individuals, reproducibility between right and left arm in individuals; it has been compared extensively with the quantitative method of Gibson and Cooke, both in normal individuals and in patients with cystic fibrosis. There is excellent agreement between the modified method and the quantitative reference method. There appears to be a slight bias toward higher concentrations of chloride from the right arm compared with the left arm, but this difference is not medically significant.

Immunochemical determination of human immunoglobulins with a centrifugal analyzer

We used an unmodified centrifugal analyzer (Aminco "Roto-Chem II") to measure human immunoglobulins IgG, IgA, and IgM in diluted sera, with diluted commercial monospecific antisera. Turbidimetric endpoint readings at 340 nm were taken at 4 min for IgG and 12 min for IgA and IgM, although multiple timed-interval readings were printed so that the kinetics of the reaction could be observed. Polyethylene glycol was used to enhance the antigen--antibody reaction. A wide range of concentrations can be measured: for IgG, 0.1--24 g/liter; for IgA and IgM, 50--4000 mg/liter. Correlation with radial immunodiffusion and automated immunoprecipitin techniques was satisfactory. Precision, accuracy, linearity, and sensitivity were quite acceptable. Day-to-day precision ranged from 2.5% to 5.2%, depending on sample concentration. The technique is more precise than radial immunodiffusion, and is rapid, simple, and reliable.

Immunochemical determination of human immunoglobulins with a centrifugal analyzer

We used an unmodified centrifugal analyzer (Aminco "Roto-Chem II") to measure human immunoglobulins IgG, IgA, and IgM in diluted sera, with diluted commercial monospecific antisera. Turbidimetric endpoint readings at 340 nm were taken at 4 min for IgG and 12 min for IgA and IgM, although multiple timed-interval readings were printed so that the kinetics of the reaction could be observed. Polyethylene glycol was used to enhance the antigen--antibody reaction. A wide range of concentrations can be measured: for IgG, 0.1--24 g/liter; for IgA and IgM, 50--4000 mg/liter. Correlation with radial immunodiffusion and automated immunoprecipitin techniques was satisfactory. Precision, accuracy, linearity, and sensitivity were quite acceptable. Day-to-day precision ranged from 2.5% to 5.2%, depending on sample concentration. The technique is more precise than radial immunodiffusion, and is rapid, simple, and reliable.

Acute pulmonary alveolitis in narcotics abuse

Lungs of 17 narcotic abusers from medical-legal autopsies were studied to determine the pathological basis for regional alterations of ventilation and perfusion. Postmortem pulmonary angiographic and histological techniques demonstrated acute alveolar wall inflammation with exudation of fluid and cells into the alveoli in all eight abusers dying of narcotism and in six of nine dying of other causes. All abusers had extensive focal chronic intersititial inflammatory infiltrates. Vascular obstruction due to foreign material occurred only with intravenous use of oral pharmaceuticals, and then only in the microcirculation. Lungs of ten young adults dying suddenly with no history or evidence of narcotics abuse showed no acute alveolitis or intravascular foreign material. Intravenous narcotics injection produces transient acute alveolar inflammation that may account for respiratory manifestations and death. Permanent injury to the lung parenchyma or larger vessels with the usual forms of narcotic abuse is not common.

Pathologic changes in baboon lung allografts. Comparison of two immunosuppression regimes

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