Primordial GATA6 macrophages function as extravascular platelets in sterile injury.

Most multicellular organisms have a major body cavity that harbors immune cells. In primordial species such as purple sea urchins, these cells perform phagocytic functions but are also crucial in repairing injuries. In mammals, the peritoneal cavity contains large numbers of resident GATA6+ macrophages, which may function similarly. However, it is unclear how cavity macrophages suspended in the fluid phase (peritoneal fluid) identify and migrate toward injuries. In this study, we used intravital microscopy to show that cavity macrophages in fluid rapidly form thrombus-like structures in response to injury by means of primordial scavenger receptor cysteine-rich domains. Aggregates of cavity macrophages physically sealed injuries and promoted rapid repair of focal lesions. In iatrogenic surgical situations, these cavity macrophages formed extensive aggregates that promoted the growth of intra-abdominal scar tissue known as peritoneal adhesions.

Functional respiratory morphology in the newborn quokka wallaby (Setonix brachyurus).

A morphological and morphometric study of the lung of the newborn quokka wallaby (Setonix brachyurus) was undertaken to assess its morphofunctional status at birth. Additionally, skin structure and morphometry were investigated to assess the possibility of cutaneous gas exchange. The lung was at canalicular stage and comprised a few conducting airways and a parenchyma of thick-walled tubules lined by stretches of cuboidal pneumocytes alternating with squamous epithelium, with occasional portions of thin blood-gas barrier. The tubules were separated by abundant intertubular mesenchyme, aggregations of developing capillaries and mesenchymal cells. Conversion of the cuboidal pneumocytes to type I cells occurred through cell broadening and lamellar body extrusion. Superfluous cuboidal cells were lost through apoptosis and subsequent clearance by alveolar macrophages. The establishment of the thin blood-gas barrier was established through apposition of the incipient capillaries to the formative thin squamous epithelium. The absolute volume of the lung was 0.02 +/- 0.001 cm(3) with an air space surface area of 4.85 +/- 0.43 cm(2). Differentiated type I pneumocytes covered 78% of the tubular surface, the rest 22% going to long stretches of type II cells, their precursors or low cuboidal transitory cells with sparse lamellar bodies. The body weight-related diffusion capacity was 2.52 +/- 0.56 mL O(2) min(-1) kg(-1). The epidermis was poorly developed, and measured 29.97 +/- 4.88 microm in thickness, 13% of which was taken by a thin layer of stratum corneum, measuring 4.87 +/- 0.98 microm thick. Superficial capillaries were closely associated with the epidermis, showing the possibility that the skin also participated in some gaseous exchange. Qualitatively, the neonate quokka lung had the basic constituents for gas exchange but was quantitatively inadequate, implying the significance of percutaneous gas exchange.

Morphometry and allometry of the postnatal marsupial lung development: an ultrastructural study.

An utrastructural morphometric study of the postnatally remodelling lungs of the quokka wallaby (Setonix brachyurus) was undertaken. Allometric scaling of the volumes of the parenchymal components against body mass was performed. Most parameters showed a positive correlation with body mass in all the developmental stages, except the volume of type II pneumocytes during the alveolar stage. The interstitial tissue and type II cell volumes increased slightly faster than body mass in the saccular stage, their growth rates declining in the alveolar stage. Conversely, type I pneumocyte volumes increased markedly in both the saccular and alveolar stages. Both capillary and endothelial volumes as well as the capillary and airspace surface areas showed highest rates of increase during the alveolar stage, at which time the rate was notably higher than that of the body mass. The pulmonary diffusion capacity increased gradually, the rate being highest in the alveolar stage and the adult values attained were comparable to those of eutherians.

Morphometry and allometry of the postnatal lung development in the quokka wallaby (Setonix brachyurus): a light microscopic study.

The postnatally developing lungs of the quokka wallaby, Setonix brachyurus, were investigated macroscopically and by light microscopic morphometry. Lung, parenchymal and non-parenchymal volumes as well as the components of the latter two were analysed by regression analysis. The lungs comprised a single undivided left lung and a right lung with an adherent accessory lobe. Septal tissue growth was most remarkable in the canalicular and saccular stages. Between mid-canalicular stage and the saccular stage, the lung volume increased 2-fold, mainly due to airspace expansion, coupled with septal tissue thinning. The non-parenchymal vascular volume increase accelerated in the successive developmental stages while the airway and connective tissue volumes progressed in a decreasing order, being highest in the canalicular and saccular stages and lowest in the alveolar stage. Growth and remodelling of the alveolar septa occurred simultaneously with airspace subdivision. Airspace expansion accelerated during the stage of microvascular maturation, when most other parameters showed the least rate of increase.

Implementation of intussusceptive microvascular growth in the chicken chorioallantoic membrane (CAM).

Intussusceptive microvascular growth (IMG) is a new mechanism of capillary growth: The vascular network expands by insertion of newly formed columns of interstitial tissue (interstitial tissue structures) into the vascular lumen called tissue pillars or posts (diameter: 0.5-2.5 microm). IMG has so far been described during organ development and growth and in tumor angiogenesis. Different modes of its implementation could be demonstrated in the rat lung and the chicken chorioallantoic membrane (CAM). In the present investigation a further mechanism of IMG is reported in the chicken CAM: tissue pillars form by splitting of larger interstitial tissue structures and intercapillary walls located between neighboring capillary segments which will consecutively fuse. Splitting is dependent on the existence of a pillar's core composed of a bundle of collagen fibrils ensheathed by extensions of endothelial-like cells inside these structures. Pillar cores thus represent the smallest unit of interstitial tissue around which the vascular lumen might expand. This mode of IMG is obviously connected to physiological remodeling of the capillary network and appears to be dominant during later stages of CAM development.

Implementation of intussusceptive microvascular growth in the chicken chorioallantoic membrane (CAM): 1. pillar formation by folding of the capillary wall.

Intussusceptive microvascular growth is a new mode of capillary network growth originally described in the lungs of rabbits and rats. It constitutes an alternative to endothelial sprouting. The capillary network grows by insertion of new intercapillary meshes with dimensions around 1.5 microns called tissue pillars or posts. In a recent investigation, growth by intussusception was demonstrated in the chicken chorioallantoic membrane (CAM). In the present study the first of several modes of its implementation can now be presented in the CAM by in vivo video microscopy and analyses of light and electron microscopic serial sections: Cores of tissue pillars containing collagen fibrils ensheathed by extensions of endothelial-like cells will form within the tips of vertically running tissue folds that project into the capillary lumen. Due to retraction of tissue toward the intercapillary space the fold is thinning. Finally, the pillar's core is connected to its fold by a very slender extension of a single endothelial cell. Cell membrane fusion within that slender membrane-like structure causes subsequent separation of the pillar from its fold throughout an increasing vertical distance. This mechanism allows for expansion of the capillary network into the surrounding tissue, leaving behind tissue pillars as remnants of folds.

Evidence for intussusceptive capillary growth in the chicken chorio-allantoic membrane (CAM).

The aim of our investigations was to test whether the chicken chorio-allantoic membrane (CAM) could be an adequate in vivo model for a new mode of capillary growth, originally described in the rat lung and termed intussusceptive microvascular growth. According to that concept the capillary system does not grow by sprouting of vessels, but expands by insertion of transcapillary tissue pillars or posts which form new intercapillary meshes. In the present study, we observed slender transcapillary tissue pillars with diameters around 1 microns in the CAM by in vivo microscopy, and analyzed their ultrastructure by transmission electron microscopic investigation of serial sections. The pillars corresponded in size to those previously described in rat lung microvasculature. On day 7, the pillar core contained endothelial-, endothelial-like cells and collagen fibers, and on day 12 additionally chorionic epithelial cells. As a hypothesis we propose that slender cytoplasmic extensions of endothelial cells, heavily interdigitated in the post area and often projecting into the vascular lumen, could initiate the first step of pillar formation, i.e., interconnect opposite capillary walls. During both stages of development endothelial-like cells were observed in close relationship with the pillars. These cells seem to be relevant for tissue post completion and growth, as they were found to invade the core of the pillars. From the localization of the interendothelial junctions in the post region, a certain similarity to the concept proposed for the lung can be found. The observations confirm that the CAM is a very suitable material for the in vivo investigation of intussusceptive capillary growth.

Mammary epithelial differentiation in vitro: minimum requirements for a functional response to hormonal stimulation.

Mammary epithelial differentiation is the culmination of responses to a complex sequence of hormonal stimuli. An in vitro model for this process should retain the basic features of in vivo epithelial differentiation. The IM-2 mouse mammary cell line responds to lactogenic hormone stimulation by synthesizing the milk protein beta-casein. Epithelial and fibroblastic clones derived from IM-2 lack this ability, but cocultures of these clones regain responsiveness to lactogenic hormone stimulation. Studies of the epithelial cell clone 31E under various culture conditions reveal that the role of fibroblastic cells in supporting synthesis and secretion of beta-casein can be supplanted by culture in filter chambers without addition of exogenous extracellular matrix components. Electron microscopic and immunofluorescence studies show that, under these conditions, 31E epithelial cells exhibit the morphology and intercellular organization characteristic of mammary epithelium. Transepithelial electrical resistance measurements indicate that the cells are well polarized. Analysis of glucose metabolism is consistent with this polarization; glucose is utilized from the basal chamber, and lactate is excreted into the basal chamber. Immunoblot analysis demonstrates the vectorial protein secretion expected of polarized mammary epithelium: laminin is secreted into the basal chamber, whereas beta-casein is secreted into the apical chamber in response to lactogenic hormone stimulation from the lower chamber. Thus, the maintenance of a polarized intercellular organization that permits access of the basolateral cell surface to nutrients is sufficient for a pure culture of an established mammary epithelial cell clone to retain differentiated epithelial function in vitro.

Calcified left ventricular aneurysm in a 6-year-old boy. Case report.

The case of a calcified left ventricular aneurysm in a 6-year-old asymptomatic boy is presented. The anomaly was discovered on a routine chest X-ray. The etiology of this condition is discussed. A review of the literature reveals that this is a rare occurrence in children and that the origin is often unknown. Selective left coronary arteriography showed no arterial anomalies but early filling of the right coronary veins, apparently through small AV fistulas. This might have caused some peripheral myocardial underperfusion, followed by myocardial infarction and aneurysm formation. Aneurysmectomy was carried out uneventfully.

Myocardial metabolism in cyanotic congenital heart disease studied by arteriovenous differences of lactate, phosphate, and potassium at rest and during atrial pacing.

To study myocardial metabolism in chronic hypoxia due to cyanotic congenital heart disease, coronary arteriovenous differences of lactate (L), pyruvate (P), inorganic phosphate (Pi) and potassium (K) were measured in 14 cyanotic patients and seven controls, at rest and during atrial pacing. At rest, there was no difference in any parameter between cyanotic and noncyanotic patients. During atrial pacing (150-175/min) for 10 min, a moderate drop in L-extraction occurred in the control patients with some increase in L/P ratio in coronary venous blood. Cyanotic patients fell into two groups: in nine (group I), the arterial oxygen saturation (SaO2) dropped with pacing. Their L-extraction fell sharply, from 28.1 +/- 3.12 to --2.8 5.51 and L production occurred in five. There was a significance increase in coronary venous L/P ratio. Five cyanotic patients (group II) showed no drop in SaO2 with pacing, and L extraction as well as L/P ratio remained stable. Uptake of Pi was noted in all patients at rest, during pacing this disappeared in controls and group I cyanotics but not in group II. No K changes were seen in any patient. Thus, myocardial metabolism is normal at rest in patients with cyanotic CHD; during atrial pacing, a shift toward anaerobic metabolism occurs if SaO2 drops; cyanotic patients whose SaO2 remains stable appear to withstand pacing better than controls.

Tricuspid atresia, hypoplastic right ventricle, intact ventricular septum and congenital absence of the pulmonary valve.

A case of tricuspid atresia by sealing of the valves, associated with an intact ventricular septum, a hypoplastic right ventricle and the absence of the pulmonary valve, is described. The foramen ovale and the ductus arteriosus were widely patent but there was no interventricular communication. The pulmonary flow was assured by the ductus which had a saccular continuation in the pulmonary trunk. It is postulated that the lesions probably occurred during the period between the XIX and XXII horizons and that the malformed right coronary artery may have played an important role in producing the lesions of the right ventricle.