Tendinopatía cálcica: etiopatogenia y evaluación por imágenes / Calcific tendinitis: aetiopathogenesis and imaging evaluation

Resumen: La tendinopatía cálcica es causada por el depósito patológico de cristales de hidroxiapatita de calcio en los tendones y es una causa común de dolor en las articulaciones. Afecta más frecuentemente al hombro y la cadera, con hallazgos característicos en imágenes; sin embargo, cualquier tendón puede estar involucrado. Ocasionalmente, la tendinopatía cálcica puede simular patología agresiva, como infección o neoplasia, especialmente en RM. Fisiotpatológicamente, las calcificaciones provendrían de una diferenciación anormal de las células madre del tendón, que comienzan a producir calcio, aunque todavía no es del todo claro. Los radiólogos deben estar familiarizados con los hallazgos de las imágenes para distinguir la tendinopatía cálcica de procesos más agresivos. La aspiración y lavado guiado bajo ecografía es una técnica útil realizada por el radiólogo para el tratamiento de casos sintomáticos. La familiaridad con estos procedimientos y su apariencia en imágenes es un aspecto importante en el manejo de esta enfermedad. El propósito de esta revisión es analizar la etiopatogenia de la tendinopatía cálcica, la evaluación con imágenes en los sitios de presentación más comunes y también en los menos frecuentes, así como el papel que desempeña la ecografía en el tratamiento de la patología.

Abstract: Calcific tendinitis is caused by abnormal deposition of calcium hydroxyapatite crystals in tendons and is a common cause of joint pain. The disease typically affects the shoulder and hip, with characteristic imaging findings; however, any tendon can be involved. Occasionally, calcific tendinitis can mimic aggressive disorders, such as infection and neoplasm, especially on MRI. Apparently, the calcifications come from an abnormal differentiation of the tendon stem cells, which begin to produce calcium. Radiologists should be familiar with the imaging findings to distinguish calcific tendinitis from more aggressive processes. Image-guided percutaneous needle aspiration is a useful technique performed by the radiologist for the treatment of symptomatic cases. Being familiar with these processes and their imaging appearance is an important aspect in the management of this common disease. The purpose of this review is to analyze the pathogenesis of calcium tendinopathy, the evaluation of images in both the most common and less frequent presentation sites, as well as the role played by ultrasound in the treatment of pathology.

Procedimientos intervencionales guiados por ultrasonido en radiología musculoesquelética / Ultrasound guided interventional procedures in musculoskeletal radiology

Ultrasound is a useful diagnostic modality to study many structures such as subcutaneous tissue, tendons, muscles, joints, and nerves. It has low cost, wide availability and high resolution. These advantages make ultrasound a good modality in interventional procedures like soft tissue tumors biopsy, aspiration of cysts and other collections, and also in treating symptomatic calcifications like deposition of hidroxiapatite crystals in the rotator cuff, among other indications. Our objetive is to present the experience of the authors in performing musculoskeletal interventional procedures by ultrasound.

El ultrasonido es una modalidad imaginológica útil para el estudio de múltiples estructuras, tales como tejidos subcutáneos, tendones, músculos, articulaciones y nervios. Tiene un bajo costo, amplia disponibilidad y alta resolución. Estas ventajas hacen del ultrasonido una excelente modalidad en procedimientos intervencionales tales como biopsias de tejidos de partes blandas, aspiración de quistes y otras colecciones y también en el tratamiento de calcificaciones sintomáticas, tales como depósitos de cristales de hidroxiapatita de calcio en el manguito rotador. Este artículo desea mostrar la experiencia de los autores en la realización de procedimientos intervencionales musculoesqueléticos guiados por ultrasonido.

Patrón de maduración imagenológica del injerto semitendinoso gráciles en reconstrucción de ligamento cruzado anterior / Post operative magnetic resonance maturation pattern in ACL reconstruction

Introduction: Anterior Cruciate Ligament (ACL) reconstruction is frequently evaluated using Magnetic Resonance Imaging (MRI). In order to do this, it becomes very important to recognize the changes of the graft along the first postoperative months. Objective and Hypothesis: Establish the maturation pattern of the ST-G graft after reconstruction of the ACL on the third and sixth month after surgery by means of MRI. Materials and Methods: 32 ACL reconstructions were evaluated by MRI on the 3rd and 6th month after surgery. The graft was analyzed at the level of the femoral tunnel and the articular segment. The maturation criteria used in this study were a low and homogeneous intrasubstance signal and the absence of ligament-to-bone interface. Results: At the 31d month after surgery, 44 percent of the patients had a low intensity signal in the femoral tunnel and 63 percent articular. The signal was homogeneously low in 6 percent of the patients at the femoral tunnel and in 53 percent of the patients at the articular segment. The absence of a ligament-to-bone interface was found in 44 percent of the patients. Six months after surgery, we found low intensity signals in 78 percent of the patients at the femoral tunnel and in 94 percent of the patients at the articular segment. The signal was homogeneously low in 41 percent of the patients in the femoral tunnel and in 78 percent of the patients within the articular segment. The absence of a ligament-to-bone interface was found in 66 percent of the patients. Conclusions: The graft matured during the period of observation and the number of homogeneous low-intensity signals increased between the third and sixth month, thus our hypothesis is confirmed. According to all the criteria employed in this study, the intrarticular segment matures earlier than the intra-tunnel segment.

Introducción: La evaluación de la reconstrucción de ligamento cruzado anterior (LCA) por medio de la resonancia magnética (RM) es un método frecuentemente utilizado. Resulta por tanto fundamental conocer los cambios evolutivos del injerto en los primeros meses del postoperatorio. Objetivo e Hipótesis: Determinar un patrón de maduración mediante RIVI del injerto semitendinoso-gracilis (ST-G) en la reconstrucción de LCA at tercer y sexto mes postcirugía. Pacientes y Métodos: 32 pacientes sometidos a reconstrucción de LCA, fueron estudiados mediante RM a los 3 y 6 meses postcirugía. Se evaluaron las características del injerto, a nivel del túnel femoral y segmento articular, definiendo como criterios de maduración la obtención de una baja intensidad de señal intra sustancia, de aspecto homogéneo y con ausencia de interfase osteoligamentosa. Resultados: Al tercer mes de la cirugía, encontramos 44 por ciento de señal de baja intensidad a nivel del túnel femoral y 63 por ciento articular. La señal fue homogénea en 6 por ciento de los pacientes a nivel del túnel femoral y 53 por ciento articular. La ausencia de interfase osteoligamentosa se pesquisó en 44 por ciento de los pacientes. Al sexto mes, encontramos 78 por ciento de señal de baja intensidad a nivel del túnel femoral y 94 por ciento articular. La señal fue homogénea en 41 por ciento de los pacientes a nivel del túnel femoral y 78 por ciento articular. La ausencia de interfase osteoligamentosa se pesquisó en 66 por ciento de los pacientes. Conclusiones: Se observa que el injerto evoluciona, madurando entre el tercer y sexto mes de acuerdo a los criterios utilizados, confirmando así la hipótesis de que existe un patrón de maduración definido. El segmento intrarticular, madura más precozmente que el segmento intra-túnel.

Ultrasonido en el estudio de tumores de las partes blandas: [revisión] / Ultrasound in the study of soft-tissue tumors: [review]

Ultrasound (US) has become a method of multiple applications in clinical and radiological practice. Over the last years, however, US has developed as a reliable and useful diagnostic method in muscle-skeletal system diseases as well as in rheumatological and traumatologic pathologies, being the sports medicine setting where it reaches an ever-increasing acceptance among clinicians. Soft-tissue tumors constitutes an area where US plays a relatively secondary role if compared with Magnetic Resonance Imaging, a more expensive technique that, when dealing with certain specific entities, may offer less accuracy in sensitivity and specificity results than those provided by US. This study was conducted to demonstrate Ultrasound abilities in the diagnosis and characterization of most frequent soft-tissue tumors.

El ultrasonido se ha constituido en un método de múltiples aplicaciones en nuestro medio. En los últimos años se ha difundido su utilización como método diagnóstico en la patología del sistema musculoesquelético, especialmente en enfermedades reumatológicas, traumatológicas en general y en la esfera de la medicina deportiva, donde goza de creciente aceptación por parte de los clínicos. El área de los tumores de partes blandas constituye un segmento de la patología en que el ultrasonido juega un rol relativamente secundario en relación a la resonancia magnética, método más oneroso, que en algunas entidades específicas puede tener un rendimiento inferior al ultrasonido. El presente artículo pretende revisar las capacidades del ultrasonido en el estudio de los tumores de partes blandas más frecuentes.

Clasificación ultrasonografica de los desgarros musculares / Ultrasonographic classification of the muscle tears

Los desgarros musculares son lesiones frecuentes en la práctica deportiva y conllevan especial importancia cuando se trata de deportistas profesionales. El ultrasonido ha demostrado ser una herramienta de diagnóstico muy eficaz en el diagnóstico y caracterización de estas lesiones, en base a patrones más o menos característicos que hemos observado en nuestra experiencia. La clasificación anglosajona en grado 1,2 y 3, no tiene mayor utilidad práctica, al menos en nuestro país. Se propone, una clasificación basada en el tipo y ubicación de estas lesiones (aspecto cualitativo), sumado a la medición (aspecto cuantitativo), que ha demostrado utilidad para el manejo terapéutico.

[Populational research of gastric cancer in digestive symptomatic patients, from 1996 to 2000]. / Pesquisa poblacional de cáncer gástrico en pacientes sintomáticos digestivos, período 1996-2000.

BACKGROUND: Gastric cancer is the first cause of death due to malignant tumors in Chile. Its mortality rates have stabilized in the last two decades and its prognosis is closely associated to the degree of tumor invasion at the moment of surgery. AIM: To study the frequency of gastric cancer among symptomatic patients subjected to an upper gastrointestinal endoscopy at a secondary care health center. PATIENTS AND METHODS: All upper gastrointestinal endoscopies performed to patients derived from public primary care clinics were recorded. RESULTS: In the study period, 4,145 endoscopies were done to 818 men and 2,128 women. Seventy one percent of patients were aged over 40 years of age. Fifty one carcinomas and one lymphoma were detected. Of these, 10 tumors were incipient. Thirty one patients were operated on and in 22 a total gastrectomy was performed. One patient, that required an esophageal resection, died. CONCLUSIONS: Gastric cancer was detected in 1.2% of symptomatic adult patients subjected to an upper gastrointestinal endoscopy.

Mouse mast cell secretory granules can function as intracellular ionic oscillators.

Fluorescent Ca2+ probes and digital photo-sectioning techniques were used to directly study the dynamics of Ca2+ in isolated mast cell granules of normal (CB/J) and beige (Bg(j)/Bg(j)) mice. The resting intraluminal free Ca2+ concentration ([Ca2+]L) is 25 +/- 4.2 microM (mean +/- SD, n = 68). Exposure to 3 microM inositol 1,4,5-trisphosphate (InsP3) induced periodic oscillations of luminal Ca2+ ([Ca2+]L) of approximately 10 microM amplitude and a period around 8-10 s. The [Ca2+]L oscillations were accompanied by a corresponding oscillatory release of [Ca2+]L to the extraluminal space. Control experiments using ruthenium red (2 microM) and thapsigargin (100 nM) ruled out artifacts derived from the eventual presence of mitochondria or endoplasmic reticulum in the isolated granule preparation. Oscillations of [Ca2+]L and Ca2+ release result from a Ca2+/K+ exchange process whereby bound Ca is displaced from the heparin polyanionic matrix by inflow of K+ into the granular lumen via an apamin-sensitive Ca2+-sensitive K+ channel (ASK(Ca)), whereas Ca2+ release takes place via an InsP3-receptor-Ca2+ (InsP3-R) channel. These results are consistent with previous observations of [Ca2+]L oscillations and release in/from the endoplasmic reticulum and mucin granules, and suggest that a highly conserved common mechanism might be responsible for [Ca2+]L oscillations and quantal periodic Ca2+ release in/from intracellular Ca2+ storage compartments.

Intracellular pathways regulating ciliary beating of rat brain ependymal cells.

1. The mammalian brain ventricles are lined with ciliated ependymal cells. As yet little is known about the mechanisms by which neurotransmitters regulate cilia beat frequency (CBF). 2. Application of 5-HT to ependymal cells in cultured rat brainstem slices caused CBF to increase. 5-HT had an EC50 of 30 microM and at 100 microM attained a near-maximal CBF increase of 52.7 +/- 4.1 % (mean +/- s.d.) (n = 8). 3. Bathing slices in Ca2+-free solution markedly reduced the 5-HT-mediated increase in CBF. Fluorescence measurements revealed that 5-HT caused a marked transient elevation in cytosolic Ca2+ ([Ca2+]c) that then slowly decreased to a plateau level. Analysis showed that the [Ca2+]c transient was due to release of Ca2+ from inositol 1,4,5-trisphosphate (IP3)-sensitive stores; the plateau was probably due to extracellular Ca2+ influx through Ca2+ release-activated Ca2+ (CRAC) channels. 4. Application of ATP caused a sustained decrease in CBF. ATP had an EC50 of about 50 microM and 100 microM ATP resulted in a maximal 57.5 +/- 6.5 % (n = 12) decrease in CBF. The ATP-induced decrease in CBF was unaffected by lowering extracellular [Ca2+], and no changes in [Ca2+]c were observed. Exposure of ependymal cells to forskolin caused a decrease in CBF. Ciliated ependymal cells loaded with caged cAMP exhibited a 54.3 +/- 7.5 % (n = 9) decrease in CBF following uncaging. These results suggest that ATP reduces CBF by a Ca2+-independent cAMP-mediated pathway. 5. Application of 5-HT and adenosine-5'-O-3-thiotriphosphate (ATP-gamma-S) to acutely isolated ciliated ependymal cells resulted in CBF responses similar to those of ependymal cells in cultured slices suggesting that these neurotransmitters act directly on these cells. 6. The opposite response of ciliated ependymal cells to 5-HT and ATP provides a novel mechanism for their active involvement in central nervous system signalling.

Role of Ca2+/K+ ion exchange in intracellular storage and release of Ca2+.

Although fluctuations in cytosolic Ca2+ concentration have a crucial role in relaying intracellular messages in the cell, the dynamics of Ca2+ storage in and release from intracellular sequestering compartments remains poorly understood. The rapid release of stored Ca2+ requires large concentration gradients that had been thought to result from low-affinity buffering of Ca2+ by the polyanionic matrices within Ca2+-sequestering organelles. However, our results here show that resting luminal free Ca2+ concentration inside the endoplasmic reticulum and in the mucin granules remains at low levels (20-35 microM). But after stimulation, the free luminal [Ca2+] increases, undergoing large oscillations, leading to corresponding oscillations of Ca2+ release to the cytosol. These remarkable dynamics of luminal [Ca2+] result from a fast and highly cooperative Ca2+/K+ ion-exchange process rather than from Ca2+ transport into the lumen. This common paradigm for Ca2+ storage and release, found in two different Ca2+-sequestering organelles, requires the functional interaction of three molecular components: a polyanionic matrix that functions as a Ca2+/K+ ion exchanger, and two Ca2+-sensitive channels, one to import K+ into the Ca2+-sequestering compartments, the other to release Ca2+ to the cytosol.

Kinetics of release of serotonin from isolated secretory granules. I. Amperometric detection of serotonin from electroporated granules.

We developed a method for measuring the efflux of 5-hydroxytryptamine (5-HT, serotonin) from isolated intact granules of the mast cell of the beige mouse. This method combines electroporation of the vesicle membrane with amperometric detection of 5-HT. A single secretory granule is placed between two platinum electrodes (distance approximately 100 microm) and positioned adjacent (<1 microm) to a carbon fiber microelectrode. A short (approximately 30 micros) high-intensity voltage pulse (electric field of approximately 5 kV/cm) is delivered to the electrodes to trigger the mechanical breakdown of the granule membrane, which activates the release of 5-HT. We observed concurrent swelling of the granule matrix with the oxidation of 5-HT at the carbon fiber electrode (overpotential + 650 mV). Similar to the release of secretory products during exocytosis, the oxidation current exhibits a spike-like time course with a noninstantaneous rising phase (time between onset of current and maximum flux, t(max)) with approximately 25% of the molecules released during this period. When the current reaches its maximum, the granule matrix attains its maximum swollen state. We found that the rising phase depends on the initial cross-sectional area of the granule (t(max) approximately 21r2) and reflects the time required for membrane rupture. The average t(1/2)spike of the amperometric spikes was found to be approximately 150 ms, which is 3-7 times faster than the t(1/2) measured during cellular exocytosis.

Kinetics of release of serotonin from isolated secretory granules. II. Ion exchange determines the diffusivity of serotonin.

We measured the efflux of 5-hydroxytryptamine (5-HT, serotonin) from an intact secretory granule extracted from the mast cell of the beige mouse. The efflux was measured with amperometry after rupture of the granule membrane was triggered by electroporation. We determined the diffusivity of 5-HT within the secretory granule to be 2.0 x 10(-8) cm2 s(-1) when the granule is in contact with a physiological saline and found that this diffusivity depends on the valence of the cation in the external electrolyte. There is a fivefold increase in the diffusion coefficient of 5-HT determined in CsCl (150 mM, pH 7.2) at 3.7 x 10(-8) cm2 s(-1) compared to that determined in histamine dihydrochloride (Hi, 100 mM at pH 4.5) at 0.7 x 10(-8) cm2 s(-1). We found that the rate of expansion of the granule matrix observed in physiological medium correlates with the efflux of 5-HT, and that the rate of swelling of the matrix and the efflux depend on the microviscosity within the granule matrix and not the bulk viscosity of the external solution. The low diffusivity of 5-HT (approximately 500-fold less than in the bulk), the observation that the valence of the counterion affects this diffusivity, and the relationship between the volume changes of the matrix and the efflux suggest that 5-HT is released from the granule by ion exchange. We discuss the implications of this result for exocytotic release in mast cells and propose that an ion exchange mechanism could control the rate of release in other secretory systems.

[Skin and mucous membrane hemorrhages: clinical assessment, study sequence and relative frequency of hereditary diseases of the hemostasis in a Chilean population]. / Hemorragias mucocutáneas: evaluación clínica, secuencia de estudio y frecuencia relativa de enfermedades hereditarias de la hemostasia en población Chilena.

BACKGROUND: Skin and mucous membrane hemorrhages are distinctive manifestations of hereditary diseases of primary hemostasis and, among them, the different types of von Willebrand disease and of platelet function disorders are the most prevalent. AIM: To know the relative frequency of these disorders and to know the clinical features of patients with mucocutaneous hemorrhages. PATIENTS AND METHODS: Five hundred eighty nine patients whose main symptom was the presence of mucocutaneous hemorrhages were studied. Bleeding time, platelet count, coagulant activity of factor VIII (FVIII:C), FvW: Ag and FvW: CoRis and ABO blood group were measured in all patients in a first stage. According to the results of these tests, further studies were decided. RESULTS: In patients younger than 13 years old, male predominated and, in older patients, females consulted with higher frequency. There was a higher proportion of individuals with O blood type than in the normal population. Bleeding time was abnormal in 330 patients (56%). One hundred ten patients (19%) had won Willebrand disease and, among them, one third had a normal bleeding time. Isolated reduction of factor WII activity was found in 66 patients (11%, 51 males) and 32 of these had normal bleeding time. Eighty one patients (14%) were considered to have an hereditary platelet function defect. A precise diagnosis was not achieved in 332 patients (56%). CONCLUSIONS: Among patients consulting for mucocutaneous hemorrhages, 19% had von Willebrand disease, 11 had an isolated reduction of factor VIII activity, 14% had platelet function defects and in 56%, a precise diagnosis was not reached.

Characterization of a marker for tracheal basal cells.

An IgM monoclonal antibody (1D9/B3) is characterized, which specifically recognizes basal cells of the upper airway epithelium. Although morphological features have been used to follow cell lineage and differentiation, an objective assessment of differentiation can be enhanced by characterizing the expression of specific antigens that form the phenotypic profile of specialized cells. Mice were immunized with rabbit tracheal basal cells that had been obtained by pronase digestion and purified into a subpopulation of basal cells by flow cytometry. Six immunization experiments produced five hybridomas specific to epithelial cells. A hybridoma whose supernatant immunocytochemically stained the basal cell subpopulation of rabbit tracheal cells was selected. The antibody reacted with tracheal basal cells in rabbit, rat, sheep, pig, and human tracheal sections, and in cultured monolayers of tracheal epithelial cells of the same species. The antibody did not react with the basal cells of other rabbit tissue, including the skin, or other rabbit epithelia. Confocal microscopy and exposure of tracheal epithelial cells to fluorescent-tagged monoclonal antibody 1D9/B3 prior to loading on to flow cytometry showed that the basal cell antibody recognized an intracellular epitope. The epitope for the 1D9/B3 antibody was characterized by Western blotting. The 1D9/B3 antibody appears to be a distinct and specific marker to the airway epithelial basal cell and will be useful in studies of airway epithelial differentiation, injury, and regeneration.

Characterization of a marker of differentiation for tracheal ciliated cells independent of ciliation.

Although morphologic features have been used to follow cell lineage and differentiation, an objective assessment of differentiation can be best established by characterizing the expression of specific proteins that form the phenotypic profile of differentiated cells. Thus, specific markers or probes are required to unequivocally identify the various types of cells resulting from differentiation in a cell lineage. We report characterization of an IgM monoclonal antibody (5B4/H3), which recognized a surface antigen of approximately 130 kD unique to ciliated cells. The antibody reacted with the lumenal surface of the ciliated cells in transmission electron micrographs, in immunohistochemical staining of tracheal sections, and in cultured monolayers of tracheal epithelial cells. Flow cytometry, performed on enzymatically dispersed tracheal epithelial cells tagged with 5B4/H3 and fluorescent-labeled goat anti-mouse IgA/IgG/IgM, produced a population of fluorescent ciliated cells and a mixed nonfluorescent, nonciliated cell population. Ciliated cells were followed in vitro by time-lapse video microscopy for 48 to 72 h. Some of the ciliated cells lost their cilia under these culture conditions, but these cells were still found to react with the 5B4/H3 antibody. The antigen detected by this antibody remained on the surface of the cells after they lost their cilia. These results indicate that 5B4/H3 recognized a cell surface antigen that is specific to the ciliated cells and is independent of cell morphology. This marker will be useful in tissue culture studies of airway epithelial lineage, or differentiation, in which cell morphology is variable and cannot be used as a reliable marker of differentiation.

Liquid crystalline order in mucus.

NASA: Mucus plays an exceptionally wide range of important biological roles. It operates as a protective, exchange, and transport medium in the digestive, respiratory, and reproductive systems of humans and other vertebrates. Mucus is a polymer hydrogel. It is secreted as discrete packages (secretory granules) by specialized secretory cells. Mucus hydrogel is stored in a condensed state inside the secretory granules. Depending upon the architecture of their constituent macromolecules and on the composition of the solvent, polymer gels can form liquid crystalline microstructures, with orientational order being exhibited over optically resolvable distances. Individual mucin molecules consist of alternating rigid segments (heavily glycosylated; hydrophilic) and flexible segments (nonglycosylated; hydrophobic). Polymer molecules consisting of rigid units linked by flexible spacers are frequently associated with liquid crystalline behavior, which again raises the possibility that mucus could form anisotropic fluid phases. Suggestions that mucins may be self-associating in dilute solution have previously been challenged on the basis of sedimentation-equilibrium studies performed on mucus in which potential sites of association were competitively blocked with inhibitors. However, the formation of stable liquid crystalline phases does not depend on the existence of inter- or intramolecular associations; these phases can form on the basis of steric considerations alone.^ieng

Autoregulation of beat frequency in respiratory ciliated cells. Demonstration by viscous loading.

As opposed to the virtually constant load exerted by water on the cilia of ciliated protozoa, the hydrodynamic load on respiratory cilia can undergo broad variations because of changes in the rheologic properties of mucus. When water-rowing ciliated cells are exposed to increased viscosity (1 to 50 cP), their beat frequency decreases exponentially. According to Newton's fluid dynamic theory, this outcome is expected for an engine that generates constant force. However, the findings reported here indicate that when mucus-propelling respiratory ciliated cells are exposed to high viscous loads, ranging from 12 to 150 cP, the frequency of ciliary beat decreases only slightly, whereas the beat amplitude remains virtually constant. These observations suggest that ciliated cells of the respiratory tract have a functional reserve that allows them to autoregulate their mechanical output in response to the changes in viscosity to which they are normally exposed in the airway.

Mucin exocytosis.

Mucins produced by goblet cells of the respiratory mucosa are condensed while stored in secretory granules. Mucin condensation and its decondensation upon exocytosis can be explained by the theory of polymer gel phase transition. After the opening of a secretory pore, Ca2+ inside the granule is exchanged for extracellular Na+. Na/Ca exchange triggers a polymer gel phase transition whereby the mucin polymer matrix undergoes massive swelling and thereby changes from a condensed to a hydrated phase. Swelling of the granular content is driven by a Donnan potential and results in the release of secretory product and the formation of small mucin gels, which later anneal to each other to form the respiratory mucus. Because of the tangled rather than cross-linked topology of the mucin network, the rheologic properties of the respiratory mucus depend primarily on hydration. As mucins are polyionic, the hydration of mucus is controlled by a Donnan equilibrium. Hence, mucus hydration and rheology are determined by two factors: the quantity, chain length, and charge density of the secreted mucins, and the amount and the ionic and polyionic composition of the water transported across the respiratory mucosa.

Reversible condensation of mast cell secretory products in vitro.

We have investigated the mechanisms responsible for the condensation and decondensation of secretory products that occur in mast cell secretion. We show here that the hydrated matrix of an exocytosed secretory granule can be recondensed to its original volume by exposure to acidic solutions containing histamine at concentrations that mimic those found in vivo. Recondensation by acidic histamine began in the range of 1-10 mM with a dose response curve that was accurately predicted by a Hill type equation with four highly cooperative binding sites and a half maximum concentration of [Hi++] = 3.9 mM. Recondensation by histamine showed a sigmoidal dependency on pH (critical range pH 5.5-6.5) and was fully reversible. These experiments suggest that histamine, possibly by binding to anionic sites in the protein-heparin complex of the granule matrix, triggers a change in the polymeric structures of the granule matrix from an extended coil to a collapsed globular state. This may be a useful model for understanding the condensation of secretory products into dense core granules and their subsequent decondensation upon exocytosis.

Enrichment of subpopulations of respiratory epithelial cells using flow cytometry.

The application of flow cytometry to enrich airway epithelial cell subpopulations is described. A complementary epithelial cell preparative technique is also outlined. The ability of the airway epithelium to protect the lung from environmental insults results from a complex interaction among the different cells that form its matrix. The separation of the different epithelial cell types is an essential step in the studies of mechanisms of the controlling factors of cell repair, cell differentiation, and neoplastic transformation. Epithelial cells of the New Zealand white rabbit trachea are prepared using enzymatic digestion and microdissection. Small sections of tracheal wall are dissected into pieces approximately 10 mm2. The mucosa is dissected and placed in 0.15% hyaluronidase for 40 min at 22 degrees C. Mucus is removed, and the mucosa is then placed in 0.1% pronase at 37 degrees C for 30 min. With careful dissection, the epithelium can be dissected from the mucosa in 10-mm2 sheets. Sheets of epithelial cells are placed in 6 ml of an enzymatic solution containing collagenase, 0.2% bovine serum albumin, 0.04% soya bean trypsin inhibitor, 0.06 ml of 1 M Hepes buffer for 3 h at 37 degrees C. The cells are gently pipetted during the 3-h period, yielding a suspension of viable cells. Subpopulations of these different cell types are enriched using an Orthocytofluorograph 50111. A krypton ion laser was used for excitation of cells at 488 nm. Forward-angle and 90 degrees scatter were gated on the histogram. The purification of the ciliated, basal, and secretory cells was 90%, 97%, and 94%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)