[Recommendations for the suspected diagnosis and management of Multisystemic Inflammatory Syndrome (MIS-C) in the context of a SARS-CoV-2 pandemic. April 2021]

Multisystem inflammatory syndrome temporally associated with COVID-19 (MIS-C) is a post-infectious complication described in children and adolescents with previous exposure to SARS-CoV-2. Because of its potential to evolve to severe disease -including cardiovascular impairment and multiple organ failure it requires a prompt diagnosis and appropriate management, including intensive care for most cases. These guidelines compile recent information from scientific literature, from our local clinical experiences during the past pandemic year, and have been discussed by experts. The recommendations provided are meant to help the clinical work of health teams attending the pediatric population.

Hematologic parameters and biomarkers predictors of severity in Multisystem Inflammatory Syndrome in children associated with SARS-CoV-2

INTRODUCTION

The multisystem inflammatory syndrome in children associated with SARS-CoV-2 (MIS-C) is cha racterized by a hyperinflammatory state resulting from a cytokine storm, evidenced by alterations in laboratory blood testing and acute-phase proteins.

OBJECTIVE

to describe the clinical and labora tory characteristics of patients hospitalized due to MIS-C and identify predictive markers of severity.

PATIENTS AND METHOD

Retrospective study of 32 patients. The group was divided into critical and non-critical according to clinical presentation and therapy used. Clinical and laboratory aspects were studied, including complete blood count, coagulation tests, and biomarkers.

RESULTS

18/32 were males, with a median age of 6.8 years. The most frequent manifestations were cardiovascular (84.3%), digestive (84%), and mucocutaneous (59%). The group of critical patients included 15 patients, 12 were males with a median age of 8.9 years, and the non-critical group included 17 patients, 6 were males with a median age of 5.4 years. The laboratory parameters at the admission in the global group showed increased C-reactive protein, D-dimer, leukocytes, neutrophils, ferritin, and fibrinogen. In contrast, albumin and blood sodium levels were decreased. At admission, the critical group was cha racterized by presenting thrombocytopenia, hypoalbuminemia, prolonged prothrombin time, and elevated ferritin. At the time of deterioration, there was an intensification of thrombocytopenia, in creased C-reactive protein together with increased neutrophils level.

CONCLUSION

The blood count, C-reactive protein, and albuminemia at admission proved to be significantly important in the identi fication of patients at risk of clinical deterioration.

[Clinical manifestations of SARS-CoV-2 infection in children in the middle of pandemic season in a pediatric tertiary center. Report of local COVID Clinical Committee, Hospital de Niños Roberto del Río, Santiago Chile]

BACKGROUND

SARS-CoV-2 virus infection responsible for de pandemic in course, is a new clinical and physiopathological entity, whose control is still uncertain till we can provide an effective and universal vaccine. In the beginning it was described as a respiratory disease which affects mainly adults, children can have the disease too and in this group the disease can be different than the adult disease. Acute infection in children is mostly mild and when it requires hospital assistance it resolves with support therapy and without complications most of the time. However, in the Pediatric Inflammatory Multisystemic Syndrome is vital the early clinical suspect and refers to a tertiary center to bring support and properly treatment.

AIM

To describe the clinical spectrum of SARS-CoV-2 virus disease in a pediatric referral center with the pandemic still in development.

METHOD

A case series of 537 patients with SARS-CoV-2 infection treated between March 1 and July 15, 2020 is presented with a description of those who were hospitalized.

RESULTS

127 (23%) of them were hospitalized and of these 69% were symptomatic. Twenty-six patients (20%) of those hospitalized presented PIMS, only one died for complications of his chronic diseases.

[Helicobacter pylori infection in symptomatic patients with benign gastroduodenal diseases: analysis of 5.664 cases]

Infection with Helicobacter pylori (H. pylori) is highly prevalent in Chile, but there are no systematic studies in patients with upper gastrointestinal symptoms.

AIM

To determine the prevalence of H. pylori infection, according to age, gender and endoscopic pathology in a large sample of patients.

METHODS

We studied 7,893 symptomatic patients submitted to upper gastrointestinal endoscopy between July 1996 and December 2003 in the context of a screening program of gastric cancer in a high risk population. H. pylori infection was determined by rapid urease test (RUT) in antral mucosa. We excluded 158 patients with gastric cancer (2%) and 2,071 patients without RUT.

RESULTS

We included 5,664 patients, mean age 50.7 +/- 13.9 years, women 72.1%. Endoscopic diagnoses were normal in 59.3%, erosive esophagitis in 20%, gastric ulcer (GU) in 8.1%, duodenal ulcer (DU) in 6.4%, and erosive gastropathy in 6.2%. RUT was positive in 78% of patients. After adjusting for age and sex and with respect to patients with normal endoscopy, frequency of H. pylori infection was 86.6% in DU (OR 2.1, 95% CI 1.5-2.8, p < 0.001); 81.4% in GU (OR 1.8, 95% CI 1.4-2.4; p < 0.001 ); 79.9% in erosive gastropathy (OR 1.4, 95% CI 1.03-1.8; p = 0.03) and 77.4% in erosive esophagitis (OR 1.1, 95% CI: 0.9-1.3; p = NS). The probability of H. pylori infection decreased significantly with age, more markedly in men with normal endoscopy.

CONCLUSIONS

Prevalence of H. pylori infection is very high in symptomatic Chilean patients and even higher in those with gastroduodenal ulcer or erosions, while in patients with erosive esophagitis is similar to those with normal endoscopy. The frequency of infection decreases with age, probably as a consequence of rising frequency of gastric mucosal atrophy.

[Populational research of gastric cancer in digestive symptomatic patients, from 1996 to 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]

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.

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)

Development of an in vitro model of primate cervical goblet cells

Mucins, are densely packed in secretory granules of goblet cells. Upon exocytosis they undergo massive hydration that results in the formation of the mucus gel. Because the mucin polymer network is held together by tangles and low energy bonds, the rheological properties of this gel are mainly determined by the degree of postexocytotic hydration. Hydration in mucus is governed by a Donnan equilibrium as it is driven by electrostatic interaction among the polyionic charges of the mucins and other fixed polyions. Although, variations of charge density of the mucin polymer could be an efficient physiologic mechanism to control the rate of mucus hydration and rheology, this subject has not been investigated. In here we describe a primary tissue culture system of cervical goblet cells of the monkey uterus. This preparation allows to measure directly the kinetic of hydration of exocytosed mucins. Because the physicochemical parameters of the bathing medium can be effectively controlled, variations in the kinetic of mucins swelling upon exocytosis, can be used as a convenient indicator of fluctuations of charge density in secretory products. Since the cervical mucosa readily respond to endocrine influences, this preparation can provide a useful model to study the effect of hormones or other transmitters on polyionic charge density of secretory product.

Stimulus-response coupling in mammalian ciliated cells. Demonstration of two mechanisms of control for cytosolic [Ca2+]

Changes of cytosolic [Ca2+] have been proposed to couple stimulation of ciliary movement, however, quantitative measurements of fluctuations of intracellular free [Ca2+] associated with stimulation of ciliated cells have not been investigated. In primary cultures of rabbit oviductal ciliated cells, the stimulation of ciliary activity produced by micromolar concentrations of adenosine triphosphate (ATP) and prostaglandin F2 alpha (PGF2 alpha) was associated with a transient increase of intracellular [Ca2+]. Whereas the increase of cytosolic [Ca2+] and beat frequency produced by ATP were inhibited by the Ca-channel blocker LaCl3, the rise of cytosolic [Ca2+] and frequency of ciliary beat produced by PGF2 alpha was not affected by LaCl3. These results are the first direct demonstration that fluctuations of cytosolic [Ca2+] are associated with increased ciliary beat frequency in mammalian epithelial cells. The present findings suggest two different calcium-dependent mechanisms for stimulus-coupling in ciliary epithelium: ATP acting via purinergic receptor coupled to transmembrane influx of Ca2+, and PGF2 alpha acting via receptor-mediated release of intracellular sequestered Ca.

Molecular mechanism of product storage and release in mucin secretion. II. The role of extracellular Ca++

Mucin-containing granules, produced by mammalian goblet cells in vitro, undergo massive post-exocytotic swelling (23). Their swelling kinetics are similar to the swelling of condensed artificial polymer gels (22). Earlier, we proposed that mucins are condensed in the secretory granule and expand by swelling during or after exocytosis (21). The swelling of mucus is affected by ionic influences, as it is governed by a Donnan equilibrium process (21). However, the effect of cations on the swelling of newly released mucins had not yet been investigated. Calcium has been found in high concentration inside secretory granules of mucin-secreting cells (18, 9, 25), and is also elevated in the mucus of cystic fibrosis patients (17). The present experiments were designed to study the effect of extracellular Ca++ concentration on the swelling kinetics of the newly released secretory product of respiratory goblet cells in vitro. The data show that extracellular Ca++, in concentrations similar to those found in the mucus of cystic fibrosis patients (2 to 4 mM) can produce a four-fold decrease in the diffusivity of the newly released mucin polymer network, resulting in a slow rate of swelling, and a mucus that remains thick for long periods of time. The present findings are in agreement with the Donnan equilibrium hypothesis for the regulation of mucus swelling and rheology (21), and bear important implications for the pathophysiology of cystic fibrosis.

Molecular mechanism of mucin secretion: I. The role of intragranular charge shielding

Mucus is an ubiquitous polymer hydrogel that functions as a protective coat on the surface of integument and mucosa of species ranging from simple animals (such as coelenterates) to mammals. The polymer matrix of mucus is made out of long-chain glycoproteins called mucins that are tangled together, forming a randomly woven, highly polyionic network (Lee et al., 1977; Verdugo et al., 1983). Mucin-containing granules, produced by mammalian goblet cells in vitro, undergo massive post-exocytotic swelling. Their swelling kinetics is similar to the swelling of condensed artificial polymer gels (Verdugo, 1984; Tanaka and Fillmore, 1979). We had proposed that mucins must be condensed in the secretory granule and expand by hydration during or after exocytosis (Verdugo, 1984; Tam and Verdugo, 1981). However, the polyionic charges of mucins prevents condensation unless they (the mucins) are appropriately shielded. The present experiments were designed to assert the presence of an intragranular shielding cation and its role in secretion. Giant mucin granules of the slug (Ariolimax columbianus) are released intact from mucus-secreting cells of the slug's skin. They burst spontaneously outside the cell, forming, upon hydration, the typical slug mucus (Deyrup-Olsen et al., 1983). We report here that these granules contain from 2.5 to 3.6 moles calcium/kg dry material, and that calcium is released from the granules immediately before the burst that discharges their secretory product. Therefore, we propose that calcium functions as a shielding cation of polyionic mucins, and that the bursting discharge of mucins from secretory granules must result from the release of calcium from the intragranular compartment.(ABSTRACT TRUNCATED AT 250 WORDS)

The oviductal cilia and Kartagener's syndrome

Women who have Kartagener's syndrome (primary ciliary dyskinesia) may or may not be fertile. The bronchial mucociliary clearance is reduced markedly in most of these women; this has led investigators to the conclusion that the cilia in the respiratory tract are immotile, and that "beating cilia may have no indispensable role in the female reproductive tract." Yet motile cilia are considered by many workers to be essential for normal ovum transport. More recently, bizarre ciliary motion has been described in the respiratory cilia of Kartagener's women. Our hypothesis was that the dyskinetic ciliary activity (or immotility) would be the same in both the respiratory and reproductive tracts and thus explain the fertility (or lack of it) in Kartagener's women. This report shows an identical ultrastructure and absolute immotility of cilia in both the respiratory tract and reproductive tract of a woman with Kartagener's syndrome who has never conceived. From this concordance, we suggest that the fertility of Kartagener's women is explained by the dyskinetic motion of oviductal cilia, and that the ciliated endosalpinx is essential for human reproduction.

Hydration kinetics of exocytosed mucins in cultured secretory cells of the rabbit trachea: a new model

Experiments have been done to test the idea that mucins undergo postexocytotic swelling. Previous work led to the hypothesis that the glycoprotein network of the mucus gel is probably held together by entanglements and low energy bonds, rather than by interchain covalent bonding. Since glycoproteins and other proteins in the mucus are polyions, it was further proposed that mucus must be capable of swelling, with its swelling properties depending on the pH and ionic strength of the medium hydrating the mucus. Experiments using oestrous cervical mucus from cows as a model confirmed this prediction. Observations on tissue cultures of respiratory secretory cells reported here show that freshly secreted mucins also undergo swelling during and after exocytosis. This evidence supports the hypothesis that the rheological properties of mucus may be physiologically regulated by hydration via control of the transepithelial movement of water, ions and soluble proteins, rather than by variations in the degree of covalent cross-linking between glycoprotein chains as proposed earlier.

Conformational structure of respiratory mucus studied by laser correlation spectroscopy

Samples of respiratory mucus were obtained from the trachea of dogs and patients undergoing bronchoscopy. The samples were studied by laser correlation spectroscopy. The autocorrelation function of laser light scattered by both human and canine respiratory mucus was a single exponential in thick mucus or a double exponential in thin watery mucus. This finding suggests that, as in the case of uterine cervical mucus, the molecular structure of respiratory mucus is an ensemble of entangled, randomly-coiled glycoproteins forming a loose network of variable density rather than a covalently cross-linked molecular network as proposed in earlier studies.

beta-Adrenergic stimulation of respiratory ciliary activity

We investigated the effect of isoproterenol on ciliary activity using a mucus-free preparation of cultured ciliated cells of the rabbit trachea. The frequency of ciliary beating was monitored by dynamic laser-scattering spectroscopy. The results demonstrated that isoproterenol directly stimulates the activity of ciliated cells of the respiratory epithelium and that this effect is beta-adrenergic specific inasmuch as the observed stimulation can be blocked by propranolol.

Ca2+-dependent hormonal stimulation of ciliary activity

It has been demonstrated that calcium modulates ciliary activity in protozoa and also in epithelial cilia of the mussel gill. Changes in the frequency of ciliary beat in the oviduct of the salamander have also been associated with movement of Ca2 across the cell membrane. However, the control of ciliary activity in mammals is poorly understood and the function of calcium in mammalian cilia and its role in coupling hormonal effects to changes in ciliary activity have been only preliminarily investigated. The evidence presented here suggests that the stimulus-response coupling of the stimulating effect of prostaglandin E2 (PGE2) on ciliary activity of the rabbit oviduct is carried out by release of intracellular Ca2+.

Hormonal control of oviductal ciliary activity: effect of prostaglandins

Prostaglandins have been shown to exist in the walls of the oviduct and to effect strongly oviductal muscle contractions and egg transport. Our observations, using laser light-scattering spectroscopy, indicate that the "natural" prostaglandins F2 alpha, E1, and E2 can stimulate ciliary activity in cultures of ciliated epithelium of the rabbit oviduct. These findings suggest a new alternative to explain the effect of prostaglandins on oviductal egg transport.

A stochastic model for oviductal egg transport

A mathematical description of ovum transport based on Langevin's diffusion equation is presented. The proposed model is deduced from qualitative features of this phenomenon, not induced from numerical fitting of experimental data. We demonstrate that egg transport in the ampulla of the rabbit oviduct can be represented as a one-dimensional random walk in a field of external force. The application of the model to describe isthmic ovum and sperm transport on the basis of simple random walk process is also discussed. The present formulation identifies and characterizes the forces involved in the motions of the ovum and predicts specific alternatives for physiological regulation of egg transport in the oviduct.

Laser light-scattering spectroscopy: preliminary results on bioassay of cystic fibrosis factor(s)

The effect of 7 cystic fibrosis sera and 4 normal sera was investigated in 37 cultures of ciliated epithelium of the rabbit trachea. Serum was introduced in the Rose culture chambers in a concentration of 10% by volume. The frequency of ciliary beat was monitored by laser light-scattering spectroscopy. The results show that the response of cilia to sera can be well characterized by laser light scattering. Our preliminary evidence suggests that an early increase in the frequency of ciliary beat, followed by rapid arrest of ciliary activity, is a sensitive and characteristic response produced by cystic fibrosis serum, and not by normal serum.

Laser light-scattering spectroscopy: a new application in the study of ciliary activity

A uniquely precise and simple method to study ciliary activity by laser light-scattering spectroscopy has been developed and validated. A concurrent study of the effect of Ca2+ on ciliary activity in vitro by laser scattering spectroscopy and high speed cinematography has demonstrated that this new method is simpler and as accurate and reproducible as the high speed film technique.

Kinetic characteristics of the excitability-inducing material channel in oxidized cholesterol and brain lipid bilayer membranes

The kinetic characteristics of the opening and closing of the excitability-inducing material (EIM) channel in oxidized cholesterol and in brain lipid bilayers are compared. The kinetics of the opening and closing of individual ion-conducting channels in bilayers doped with small amounts of EIM are determined from discrete fluctuations in ionic current. The kinetics for approach to steady-state conductance are determined for lipid bilayers containing many channels. Steady-state and kinetic characteristics for the EIM channel incorporated in brain lipid bilayers can be accounted for by the model developed for the EIM channel incorporated in oxidized cholesterol membranes. Relaxation time, calculated from rate constants of single-channel membranes or directly measured in many-channel membranes is strongly temperature dependent, and is always shorter in brain lipid membranes. Changes in temperature do not affect the interaction of the electric field and the open channel, but the open configuration of the EIM channel in brain lipid bilayers is stablized with increasing temperature. The configurational energy difference between the open and closed channel, calculated from temperature studies, is larger in brain lipid bilayers. The energy barrier which separates the two configurations of the channel is larger in oxidized cholesterol bilayers.

Methods for studying oviductal physiology

In studying oviductal physiology, it is important to sort out the complex interrelationships between muscle, cilia, nerves and secretory processes as they each of themselves, or in concert, effect gamete transport. In this review, a variety of physiological techniques and bioengineering approaches which have been used to monitor contractile and ciliary activity, are described and critically evaluated.

Cardiac muscle models. An overextension of series elasticity?

Quick-stretch and quick-release experiments were performed on right ventricular cat papillary muscles to test the applicability of the Hill model to cardiac mechanics. Series elastic component (SEC) force-length curves were calculated from stretches and releases carried out at various times during the contractile cycle. At any SEC force, the SEC elastic modulus depended on the time during the contractile cycle at which it was measured. When measured at the same time and at the same SEC force, elastic moduli obtained by releases of less than 1% of muscle length differed from those obtained by corresponding stretches. Larger stretches, in fact, appeared to yield negative elastic moduli. Thus, a unique SEC modulus could not be identified at any level of SEC force. It is concluded that the concept of the SEC as a passive elasticity appears unsatisfactory and, as a consequence, that the quantitative validity of the Hill model for cardiac muscle is questionable. Moreover, since an anatomical counterpart of the SEC has not been identified, the Hill model also appears unsatisfactory from a structural point of view.