Intraorganic lymphatic bed of the cattle heart

Lymphomicrocirculatory networks of endocardium, myocardium and epicardium, as well as lymphatic vessels of four orders represent the intraorganic lymphatic bed of the cattle heart. In the endocardium there is a lymphatic network with close loops and a small amount of blindly beginning capillaries. The capillary lymphatic bed of the endocardial trabeculae carneae is much more dense than that in the other part of the endocardial surface. The spatial lymphatic network of the myocardium is joined with the lymphomicrocirculatory networks of the endocardium and epicardium by means of a large amount of connections. The epicardial lymphatic bed is formed by blindly beginning lymphatic capillaries, which situate in close and nonclose loops of the lymphatic network. In the epicardium there is only one lymphatic network. The size of the loops and the diameter of the lymphatic capillaries is directly proportional to the age of the animals.     

The intraorganic lymphatic bed of the mucous membrane of the tongue

The intraorganic lymphatic bed of the canine tongue mucous membrane is presented by the superficial and deep capillary networks and by the plexuses of the intraorganic lymphatic vessels. The capillaries of the superficial network in the thickness of the mucous membrane of the dorsal surface of the lingual tip, body and root form the lymphatic bed of the mechanical and gustatory papillas. The diameter of the capillaries in the both networks and in the intraorganic lymphatic vessels is greater in the mucous membrane of the ventral surface of the tip and of the lateral surfaces of the lingual body, and density of their arrangement is higher in the mucous membrane on the dorsal surface of the lingual tip, body and root. The capillaries of the superficial network in all areas of the lingual mucous membrane are thinner than those of the deep network, and the loops formed by the capillaries of the superficial network are less than the loops of the deep network.     

Lymphatic bed of the heart in the post-resuscitation period

In the experiment performed on 96 rabbits, by means of silver nitrate impregnation and Gerota mass injection methods, changes in the epicardial lymphatic bed have been investigated after 5-minutes' clinical death caused by hemorrhage. During first hours after resuscitation certain signs of the lymphatic drenage activation are revealed. In most of the animals the specific density of the lymphatic bed increases, capillaries and postcapillaries dilate, hyperargirophilia of cytoplasm and nuclei of endotheliocytes appears. In the animals sacrificed against the background of a severe state (with certain, signs of a pronounced hypoxia), there are dystrophically and degeneratively altered endotheliocytes. This is accompanied with hyper- hypoargyrophilia of endothelium, fragmentation of its cell borders, with deterioration of injection ability of the lymph outflow pathways. In the rabbits survived, by the 7th-14th days a gradual normalization of the parameters studied takes place.     

Lymphatic bed of the muscular sheath of the small intestine in animals and man during ontogenesis]

In the anatomy of the lymphatic bed of the small intestine muscle layer still there are obscure questions on the phylo- and ontogenesis of man and animals. Under study were 92 corpses (35 men, 27 cats and 30 dogs) of different age, beginning from the intrauterine period to old age. Different methods were used: polychromatic injection; macro- and microscopic dissection; staining after van Gieson and with haematoxilineeosin; impregnation with 0,25-1% solution of silver nitrate; dehydration and clearing; counting of the density of loops per a mm2 and the depth of their disposition in the intestinal wall with an ocular-micrometer. It was shown that formation of the lymph capillaries and their network in cats, dogs and man began from the end of the intrauterine period, was completed in new-borns and became sufficiently developed in young age. The structure of the lymph capillary networks is closely connected with the development of the muscle layer of the small intestine. Formation of the lymph lacunas begins after birth. With age the lymph capillary network becomes looser, the loops break and their size enlarges.     

Morphology of lymphatics of the mammalian heart with special reference to the architecture and distribution of the subepicardial lymphatic system

The subepicardial lymphatic system in the rat and dog heart has been investigated by means of scanning electron microscopy. Following application of hydrogen peroxide, the epicardium was removed with a forceps under a dissecting microscope. The subepicardial region contained a well-developed lymphatic system which consisted of the main lymphatic trunks and lymphatic capillaries. The lymphatic trunks of large diameters ran from the apex of the heart to its base. The subepicardial lymphatic capillaries were ramified and anastomosed with each other to form a relatively dense network which extended over the entire surface of both ventricles. These networks joined the main lymphatic trunks. Further, some similar networks were connected with the underlying myocardial lymphatic capillaries.     

Activation and repolarization patterns in the ventricular epicardium under sinus rhythm in frog and rabbit hearts

Our study compared the contributions of activation sequence and local repolarization durations distribution in the organization of epicardial repolarization in animals with fast (rabbit) and slow (frog) myocardial activation under sinus rhythm. Activation times, repolarization times and activation-recovery intervals (ARI) were obtained from ventricular epicardial unipolar electrograms recorded in 13 Chinchilla rabbits (Oryctolagus cuniculus) and 10 frogs (Rana temporaria). In frogs, depolarization travels from the atrioventricular ring radially. ARIs increased progressively from the apex to the middle portion and finally to the base (502+/-75, 557+/-73, 606+/-79 ms, respectively; P<0.01). In rabbits, depolarization spread from two epicardial breakthroughs with the duration of epicardial activation being lower than that in frogs (17+/-3 vs. 44+/-18 ms; P<0.001). ARI durations were 120+/-37, 143+/-45, and 163+/-40 ms in the left ventricular apex, left, and right ventricular bases, respectively (P<0.05). In both species, repolarization sequence was directed from apex to base according to the ARI distribution with dispersion of repolarization being higher than that of activation (P<0.001). Thus, excitation spread sequence and velocity per se do not play a crucial role in the formation of ventricular epicardial repolarization pattern, but the chief factor governing repolarization sequences is the distribution of local repolarization durations.     

Cardiac electric field on the epicardial and body surfaces during the period of depolarization and repolarization of ventricular myocardium in pikes

Body surface and ventricular epicardial potential distributions during the electrocardiographic QRST interval were studied in pikes with the aid of potential mapping. The earliest epicardial activation was observed at the posterior base near the atrioventricular orifice. The areas of the earliest repolarization were found at the apex and the posterior base, whereas the area of the latest repolarization was detected at the anterior base. In the initial period of the QRS, the minimum was developed in the middle third of the right lateral body surface, and the maximum in the middle third of the ventral body surface. The body surface potential distribution during the ST-Twas characterized by the clear-cut negative potential zone in the cranial ventral area with the rest of the body surface having positive potentials, a pattern being largely unchanged throughout the period of the T-wave. The ventricular epicardial repolarization sequence differed from the activation sequence. The ventricular epicardial depolarization and repolarization sequences as well as epicardial potential distributions are expressed in the cardiac electric field on the body surface during the QRS and ST-T complexes.     

Vasculogenesis of the bursa cloacalis (bursa of Fabricius) of the chick embryo

Vasculogenesis of the bursa cloacalis (bursa of Fabricius) was examined in 10- to 21-day chick embryos and in chicks during the first 5 days post-hatching. The entire circulatory system was injected with India ink, and the bursae were then removed and either cleared for examination in toto or sectioned serially. The bursa was supplied by three pairs of extrinsic blood vessels. At 10 and 11 days of incubation, most intrinsic vessels were arranged in a superficial, hexagonal network. In regions of developing plicae, the hexagonal plexus extended into the core of each plica, forming middle plical vessels. The latter were interconnected across interplical areas by cross-connecting vessels. The middle plical vessels gave rise to small capillary offshoots, which soon increased in complexity, forming delicate loops. Branches extended from these loops through the subepithelial lamina propria to incipient epithelial buds by 12 days of incubation. All epithelial buds were supplied by at least one such branch, and similar branches extended to the basal aspect of the epithelium in areas where epithelial buds had not yet formed. This observation is consistent with the hypothesis that blood vessels induce formation of epithelial buds. At about 15 days of incubation, the cortex and medulla of each developing lymphatic follicle were defined clearly, and an intricate, web-like, capillary network coursed throughout the follicular cortex. The medulla appeared to be devoid of capillaries. The diameters of all intrinsic and extrinsic bursal blood vessels gradually increased throughout development. During post-hatching stages, the diameters of the extrinsic vessels continued to increase, whereas those of the intrinsic vessels were markedly decreased from late pre-hatching stages.     

Main principles of the organization of the microcirculatory bed of the human greater omentum in early ontogenesis

The formation process of the terminal blood bed of the greater omentum has been studied in 42 human fetuses 14--28-week-old. The main peculiarities of the greater omentum blood bed by the 14th week of development are: paired arrangement of the afferent and deferent blood vessels and loop-shaped type of capillary growth, that joining the arteriole and venule, lend the blood stream a maximally centralized character. In 15--16 weeks of the fetal development in the omentum another type of the vascular growth occurs, characterized with appearance of single angioblastic processes that branch off the apex of the capillary loops. As a result new capillaries form; they connect apices of the capillary loops, that in their turn make bases for developing a true capillary network. Together with this, presence in ontogenesis of an autochthonous way of capillary appearance is proved, their connection with the closed blood stream is followed. Distinguishing of the loop-shaped stage in the capillary growth determines certain difference between vasculogenesis in ontogenesis and the vascular growth at reparative regeneration, since the base for the latter is only the capillary growth by means of single angioblastic processes.     

Ectopia cordis thoracalis with craniofacial defects resulting from early amnion rupture

A 33-week-gestation fetus was evaluated as having ectopia cordis thoracalis, midline sternal cleft, frontonasal dysgenesis, a midfacial cleft, and amniotic bands. Fibrous bands were attached to the apex of the heart, face, and the brain. There were no associated limb defects or scoliosis. The findings in this fetus and those in the literature suggest that acute amnion rupture in the third week of gestation may be the cause of these defects. Mechanical teratogenesis by tissue bands adherent to the heart may lead to ectopia cordis. The changes seen in the thorax, face, and brain suggest pressure necrosis, incomplete morphogenesis, tearing and tethering by amnion, and compression as a cause for these defects. A spectrum of defects is found following amnion rupture with the abnormalities being dependent upon the timing of the event. Ectopia cordis with amniotic bands appears to have an etiology distinct from isolated ectopia cordis. This suggests several different etiologies for ectopia cordis.     

Functional morphology of the avian medullary cone

The organization of the renal medulla of the Gambel's quail, Callipepla gambelii, kidney was examined to determine the number of loops of Henle and collecting ducts and the surface area occupied by the different nephron segments as a function of distance down the medullary cones. Eleven medullary cones were dissected from the kidneys of four birds, and the tissue was processed and sectioned for light microscopy. In addition, individual nephrons were isolated on which total loop thin descending segment and thick prebend segment lengths were measured. The results show no correlation between the absolute number of loops of Henle and the length of the medullary cones. The number of thick and thin limbs of Henle and collecting ducts decrease exponentially with distance toward the apex of the cones and the rate of decrease is similar for cones of different lengths. Initially there is a rapid decrease in the number of thin limbs of Henle, indicating that most nephrons do not penetrate the cones a great distance. Thick descending limbs of Henle (prebend segment) ranged in length from 50 to 770 microm, and there was little correlation with the total length of the loop of Henle. However, the length of the thin limb of Henle correlated well with total loop length. The cell surface areas of the limbs of the loop of Henle and the collecting ducts decreased toward the apex of the cones.     

Localization and proliferation of lymphatic vessels in the tympanic membrane in normal state and regeneration

We clarified the localization of lymphatic vessels in the tympanic membrane and proliferation of lymphatic vessels during regeneration after perforation of the tympanic membrane by using whole-mount imaging of the tympanic membrane of Prox1 GFP mice. In the pars tensa, lymphatic vessel loops surrounded the malleus handle and annulus tympanicus. Apart from these locations, lymphatic vessel loops were not observed in the pars tensa in the normal tympanic membrane. Lymphatic vessel loops surrounding the malleus handle were connected to the lymphatic vessel loops in the pars flaccida and around the tensor tympani muscle. Many lymphatic vessel loops were detected in the pars flaccida. After perforation of the tympanic membrane, abundant lymphatic regeneration was observed in the pars tensa, and these regenerated lymphatic vessels extended from the lymphatic vessels surrounding the malleus at day 7. These results suggest that site-specific lymphatic vessels play an important role in the tympanic membrane.     

Development of the thoracic duct in the prenatal period of human ontogeny

In 40 series of histological sections performed in human embryos and prefetuses from 4 up to 20 weeks of development, as well as in 20 corpses of fetuses and stillborns, it has been stated that the anlage of the thoracic duct appear in 6-7-week-old fetuses as lymphatic clefts surrounded with mesenchymal cells that are situated near large veins in the areas of the most active morphogenesis. Connecting with each other, the clefts form the jugular and retroperitoneal lymph sacs and a well branching network of canals. From the latter, on the 7th-8th week of development a plexus of lymph vessels appear, and later on (on the 8th-9th week)--bilaterally situating trunks of the thoracic duct. Further development of the thoracic duct is connected with the lymph nodes formation, their germs appear on the 9th-10th week along the course of the left trunk, as well as along the ductal branches and anastomoses. The formation of the lymph nodes results in reduction of some trunks and plexuses of the thoracic duct. Owing to this, its form in 14-15-week-old prefetuses resembles the one in newborns. Disturbances in the formation processes of the lymph nodes along the course of the reducing ductal areas, as well as their formation along the course of its main trunk can result in various structural variants of the thoracic duct in children and grown-up persons. Histogenesis of the thoracic duct wall and formation of the lymph nodes are not completed by birth.     

Lymphangiogenesis in post-natal tissue remodeling: lymphatic endothelial cell connection with its environment

The main physiological function of the lymphatic vasculature is to maintain tissue fluid homeostasis. Lymphangiogenesis or de novo lymphatic formation is closely associated with tissue inflammation in adults (i.e. wound healing, allograft rejection, tumor metastasis). Until recently, research on lymphangiogenesis focused mainly on growth factor/growth factor-receptor pathways governing this process. One of the lymphatic vessel features is the incomplete or absence of basement membrane. This close association of endothelial cells with the underlying interstitial matrix suggests that cell–matrix interactions play an important role in lymphangiogenesis and lymphatic functions. However, the exploration of interaction between extracellular matrix (ECM) components and lymphatic endothelial cells is in its infancy. Herein, we describe ECM–cell and cell–cell interactions on lymphatic system function and their modification occurring in pathologies including cancer metastasis.     

Development of neuron-capillary interrelationships in the nuclei of the anterior portion of the human hypothalamus during ontogenesis

Three periods in the formation of the spatial arrangement of the neuronal nuclei have been stated: 1) from the prenatal period, infancy including--pronounced decrease in the density of the neuronal cells arrangement; 2) from the childhood up to adolescence--relative stabilization in the hypothalamic cellular composition; 3) mature and old age--secondary decrease in the dencity of the neuronal cells arrangement. Certain peculiarities in the nuclear capillary composition and in their neuronal-capillary relationships have been revealed: during the prenatal ontogenesis, the dencity of the neuronal cells arrangement decreases and their size increases that is followed by decrease in their capillary loops. In postnatal ontogenesis no proportional relationship between the dencity of neuronal cells arrangement and that of capillary network in the nuclei of the anterior hypothalamus was noted.     

Structure and function of lymphatic postcapillaries (coordinating mechanism of the processes of interstitial transport and lymphatic resorption

Investigation performed on topography, structure and resorptive function of lymphatic microvessels in the serous membranes gives possibilities to work out a model on formation and transport of lymph. Lymphatic postcapillaries (LP) - thin-walled endothelial channels with valves make an important link of the lymphatic system. The LP structure is similar to that of capillaries. These microvessels are situated in the interstitial space area, that are characterized with their high content of plasma proteins and water. Interrelation in concentrations of protein in the LP lumen and in the tissue ensures the existence of the osmotic gradient pressure through the wall and contributes liquor resorption into the lumen of microvessels. Peritoneal lymphatic capillaries are situated in the areas of a higher hydrotation level of the interstitial space. They can control the rate of the liquor filtration from plasma into tissue and regulate the resorption level in the whole lymphatic network. The model provides a differentiated participation of the LP and capillaries in performing resorption of proteins and liquor from the interstitium. The resorption mechanisms are closely connected with processes of the lymph movement along the vessels.     

Epicardial and intramural excitation during ventricular pacing: effect of myocardial structure

Published studies show that ventricular pacing in canine hearts produces three distinct patterns of epicardial excitation: elliptical isochrones near an epicardial pacing site, with asymmetric bulges; areas with high propagation velocity, up to 2 or 3 m/s and numerous breakthrough sites; and lower velocity areas (<1 m/s), where excitation moves across the epicardial projection of the septum. With increasing pacing depth, the magnitude of epicardial potential maxima becomes asymmetric. The electrophysiological mechanisms that generate the distinct patterns have not been fully elucidated. In this study, we investigated those mechanisms experimentally. Under pentobarbital anesthesia, epicardial and intramural excitation isochrone and potential maps have been recorded from 22 exposed or isolated dog hearts, by means of epicardial electrode arrays and transmural plunge electrodes. In five experiments, a ventricular cavity was perfused with diluted Lugol solution. The epicardial bulges result from electrotonic attraction from the helically shaped subepicardial portions of the wave front. The high-velocity patterns and the associated multiple breakthroughs are due to involvement of the Purkinje network. The low velocity at the septum crossing is due to the missing Purkinje involvement in that area. The asymmetric magnitude of the epicardial potential maxima and the shift of the breakthrough sites provoked by deep stimulation are a consequence of the epi-endocardial obliqueness of the intramural fibers. These results improve our understanding of intramural and epicardial propagation during premature ventricular contractions and paced beats. This can be useful for interpreting epicardial maps recorded at surgery or inversely computed from body surface ECGs.     

Meristems: start your signaling

All of the cells of the shoot apex are derived from a small number of stem cells in the center of the shoot meristem. Hence, cell lineage plays no role in establishing pattern formation or cell fate at the shoot apex. Growing evidence has implicated a number of cell signaling pathways in regulating shoot meristem development and organ formation. These signaling pathways include receptor-mediated signaling, protein movement via plasmodesmata, and potential feedback loops.     

MRI-determined left ventricular "crescent effect": a consequence of the slight deviation of contents of the pericardial sack from the constant-volume state

During one cardiac cycle, the volume encompassed by the pericardial sack in healthy subjects remains nearly constant, with a transient +/-5% decrease in volume at end systole. This "constant-volume" attribute defines a constraint that the longitudinal versus radial pericardial contour dimension relationship must obey. Using cardiac MRI, we determined the extent to which the constant-volume attribute is valid from four-chamber slices (two-dimensional) compared with three-dimensional volumetric data. We also compared the relative percentage of longitudinal versus radial (short-axis) change in cross-sectional area (dimension) of the pericardial contour, thereby assessing the fate of the +/-5% end-systolic volume decrease. We analyzed images from 10 normal volunteers and 1 subject with congenital absence of the pericardium, obtained using a 1.5-T MR scanner. Short-axis cine loop stacks covering the entire heart were acquired, as were single four-chamber cine loops. In the short-axis and four-chamber slices, relative to midventricular end-diastolic location, end-systolic pericardial (left ventricular epicardial) displacement was observed to be radial and maximized at end systole. Longitudinal (apex to mediastinum) pericardial contour dimension change and pericardial area change on the four-chamber slice were negligible throughout the cardiac cycle. We conclude that the +/-5% end-systolic decrease in the volume encompassed by the pericardial sack is primarily accounted for by a "crescent effect" on short-axis views, manifesting as a nonisotropic radial diminution of the pericardial/epicardial contour of the left ventricle. This systolic drop in cardiac volume occurs primarily at the ventricular level and is made up during the subsequent diastole when blood crosses the pericardium in the pulmonary venous Doppler D wave during early rapid left ventricular filling.     

Roentgenologic investigation of collateral lymphatic pathways after ligation of the thoracic duct

In 80 Wistar rats by means of electroroentgenolymphography lymphatic pathways and thoracic duct have been studied, normal and after ligation of the latter in 1-3 days, 1 and 2-3 months. Contrasting of the thoracic duct in the control animals reveals its additional ducts, that run in parallel to the main collector and they get into it after a certain distance, as well as different time phases of filling the duct are noted. When the thoracic duct is ligated, in 1-3 days dilatation of the ductal cistern, contrasting of lymphatic vessels and nodes in other regions are observed. In 1 month of the experiment the thoracic duct cistern is poorly expressed in comparison with the early time. The contrast substance continues to get into the group of the lymph nodes in other regions. A network of anastomoses of lymphatic vessels is formed in the area of ligation. In 2-3 months, when the contrast substance continues to get retrogradely into other groups and regions of the lymph nodes, final restoration of the lymph-flow takes place at the expense of formation of collateral pathways.