Physiological neutrophil sequestration in the lung: visual evidence for localization in capillaries

Although the lung is known to be a major site of neutrophil margination, the anatomic location of these sequestered cells within the lung is controversial. To determine the site of margination and the kinetics of neutrophil transit through the pulmonary microvasculature, we infused fluorescein isothiocyanate-labeled canine neutrophils into the pulmonary arteries of 10 anesthetized normal dogs and made fluorescence videomicroscopic observations of the subpleural pulmonary microcirculation through a window inserted into the chest wall. The site of fluorescent neutrophil sequestration was exclusively in the pulmonary capillaries with a total of 951 labeled cells impeded in the capillary bed for a minimum of 2 s. No cells were delayed in the arterioles or venules. Transit times of individual neutrophils varied over a wide range from less than 2 s to greater than 20 min with an exponential distribution skewed toward rapid transit times. These observations indicate that neutrophil margination occurs in the pulmonary capillaries with neutrophils impeded for variable periods of time on each pass through the lung. The resulting wide distribution of transit times may determine the dynamic equilibrium between circulating and marginated neutrophils.     

Angiogenic factors and alveolar vasculature: development and alterations by injury in very premature baboons

Proper formation of the pulmonary microvasculature is essential for normal lung development and gas exchange. Lung microvascular development may be disrupted by chronic injury of developing lungs in clinical diseases such as bronchopulmonary dysplasia. We examined microvascular development, angiogenic growth factors, and endothelial cell receptors in a fetal baboon model of chronic lung disease (CLD). In the last third of gestation, the endothelial cell marker platelet endothelial cell adhesion molecule (PECAM)-1 increased 7.5-fold, and capillaries immunostained for PECAM-1 changed from a central location in airspace septa to a subepithelial location. In premature animals delivered at 67% of term and supported with oxygen and ventilation for 14 days, PECAM-1 protein and capillary density did not increase, suggesting failure to expand the capillary network. The capillaries of the CLD animals were dysmorphic and not subepithelial. The angiogenic growth factor vascular endothelial growth factor (VEGF) and its receptor fms-like tyrosine kinase receptor (Flt-1) were significantly decreased in CLD. Angiopoietin-1, another angiogenic growth factor, and its receptor tyrosine kinase with immunoglobulin and epidermal growth factor homology domains were not significantly changed. These data suggest that CLD impairs lung microvascular development and that a possible mechanism is disruption of VEGF and Flt-1 expression.     

Insulin binding to brain capillaries is reduced in genetically obese, hyperinsulinemic Zucker rats

In order to study the role of plasma insulin in regulating the binding of insulin to the endothelium of the blood-brain barrier (BBB), insulin binding to a purified preparation of brain capillaries was measured in both genetically obese Zucker rats and lean Zucker controls. We found a reduction of 65% in brain capillary insulin binding site number in the obese compared to lean rats with no change in receptor affinity. Furthermore, specific insulin binding to brain capillaries was negatively correlated (p less than 0.05) to the plasma insulin level, suggesting a role for plasma insulin in regulating insulin binding. A similar relationship was observed between insulin receptor number in liver membranes and the plasma insulin level. We conclude that obese, hyperinsulinemic Zucker rats exhibit a reduction in the number of BBB insulin receptors, which parallels the reduction seen in other peripheral tissues. Since insulin receptors have been hypothesized to participate in the transport of insulin across the BBB, the reduction observed in the obese rats may account for the decrease in cerebrospinal fluid insulin uptake previously demonstrated in these animals.     

Effect of oxygen consumption by measuring method on PO2 transients associated with the passage of erythrocytes in capillaries of rat mesentery

Mathematical models have predicted the existence of Po(2) gradients between erythrocytes in capillaries in the usual case where plasma contributes substantial resistance to oxygen diffusion. According to theoretical predictions, these gradients could be detected as rapid Po(2) fluctuations (erythrocyte-associated transients, EATs) along the capillary. However, verification of a model and correct choice of its parameters can be made only on the basis of direct experimental measurements. We used phosphorescence quenching microscopy to measure Po(2) in 52 capillaries of rat mesentery to obtain plasma Po(2) values 100 times/s at a given point along a capillary. A 532-nm laser generated 10-mus pulses of light, concentrated by a x100 objective, onto a spot 0.9 mum in diameter. The presence of erythrocytes in the excitation region was detected on the basis of phosphorescence amplitude (PA), proportional to the amount of plasma encountered by the laser beam, and on the basis of the intensity of transmitted laser light (LT), detected by a photodiode placed under the capillary. The data revealed correlated waveforms in PA, LT, and Po(2) in capillaries. The magnitude of the Po(2) gradients between erythrocytes and plasma was correlated with average capillary Po(2). EATs in Po(2) were more readily detected in capillaries with relatively low oxygenation. The correlation coefficients between PA and Po(2) for the half of the capillaries (n = 26) below the median Po(2) (mean Po(2) = 17 mmHg; R = -0.72) was higher than that for the other half (mean Po(2) = 39 mmHg; R = -0.38). These results support the theoretical predictions of EATs and plasma Po(2) gradients in capillaries.     

Effect of acute hypoxia on respiration and brain stem blood flow in the piglet

Changes in local brain stem perfusion that alter extracellular fluid Pco2 and/or [H+] near central chemoreceptors may contribute to the decrease in respiration observed during hypoxia after peripheral chemoreceptor denervation and to the delayed decrease observed during hypoxia in the newborn. In this study, we measured the changes in respiration and brain stem blood flow (BBF) during 2-4 min of hypoxic hypoxia in both intact and denervated piglets and calculated the changes in brain stem Pco2 and [H+] that would be expected to occur as a result of the changes in BBF. All animals were anesthetized, spontaneously breathing, and between 2 and 7 days of age. Respiratory and other variables were measured before and during hypoxia in all animals, and BBF (microspheres) was measured in a subgroup of intact and denervated animals at 0, 30, and 260 s and at 0 and 80 s, respectively. During hypoxia, minute ventilation increased and then decreased (biphasic response) in the intact animals but decreased only in the denervated animals. BBF increased in a near linear fashion, and calculated brain stem extracellular fluid Pco2 and [H+] decreased over the first 80 s both before and after denervation. We speculate that a rapid increase in BBF during acute hypoxia decreases brain stem extracellular fluid Pco2 and [H+], which, in turn, negatively modulate the increase in respiratory drive produced by peripheral chemoreceptor input to the central respiratory generator.     

Potential fields and barriers to diffusion in narrow cylindrical capillaries

In this paper, the wall potential along the center line of narrow solid capillaries has been derived. The potential barriers at the open end of such capillaries have been studied in detail. The influence of these potential barriers on the diffusion coefficients and their dependence on temperature and capillary radius have been evaluated. The implications of these energy barriers in the clarification of low pressure hysteresis phenomena have been pointed out.     

Cytoangioarchitectonics of the parasympathetic ganglion of the frog bladder according to findings from studies during life]

The form of neuronal bodies and their interarrangement with capillaries was studied in prevital parasympathetic ganglia in the bladder of the frog (Rana temporaria). The size of the neurons and the diameter of the capillaries were measured. Most of the neurons were stated to have oval form and they are oriented by their long axis along the capillaries, about 20% neurons have contacts with 2--3 capillaries; some neurons have no contacts and their distance from the nearest capillary is 32--26 mkm. Intermediate structure may be either a connective tissue or neuroglia, or (seldom) other neuronal cells. Unequal conditions of neuronal blood supply, as the author believes, demonstrate their different metabolism and various levels of their functional activity.     

眼科常用实验动物视网膜血管的比较

目的比较眼科常用实验动物视网膜血管尤其是视网膜毛细血管的情况,为实验时正确选择动物模型提供基础。方法取猕猴、家猪、新西兰大白兔、犬、猫、SD大鼠、C57小鼠以及豚鼠的正常眼球数个,完整剥离整个视网膜,用ADPase法进行血管染色,对视网膜血管进行形态学的比较。结果猕猴视网膜大血管从视盘穿出,分成四支分别供应视网膜四个象限,每条血管逐级分支最后成为毛细血管,其毛细血管呈网状分布,在赤道处分成两层,至周边变成一层,且有发育良好的黄斑区毛细血管拱环结构。家猪视网膜大血管由视盘发出后放射状走行,毛细血管也呈网状分布,无黄斑拱环结构。兔仅视盘两侧部分视网膜可见血管,毛细血管网状不明显。犬的视网膜血管也放射状走行,但迂曲明显,毛细血管不成网状。猫、大鼠、小鼠的视网膜大血管均由视盘发出,猫的分成上、鼻下、颞下三支,大鼠、小鼠的各方向均有,区域性不明显,三者的毛细血管网均发育良好,至周边部仍很密集,呈两层分布。豚鼠视网膜无可见的血管。结论用于研究人视网膜血管尤其是毛细血管时,可选用猕猴、家猪、猫、大鼠和小鼠作为动物模型;但要研究人黄斑区血管时,仅可选用猕猴等灵长类动物。     

Erythrocyte-associated transients in PO2 revealed in capillaries of rat mesentery

Mathematical models have predicted the existence of Po(2) gradients between erythrocytes in capillaries in the usual case where plasma contributes substantial resistance to oxygen diffusion. According to theoretical predictions, these gradients could be detected as rapid Po(2) fluctuations (erythrocyte-associated transients, EATs) along the capillary. However, verification of a model and correct choice of its parameters can be made only on the basis of direct experimental measurements. We used phosphorescence quenching microscopy to measure Po(2) in 52 capillaries of rat mesentery to obtain plasma Po(2) values 100 times/s at a given point along a capillary. A 532-nm laser generated 10-micros pulses of light, concentrated by a x100 objective, onto a spot 0.9 microm in diameter. The presence of erythrocytes in the excitation region was detected on the basis of phosphorescence amplitude (PA), proportional to the amount of plasma encountered by the laser beam, and on the basis of the intensity of transmitted laser light (LT), detected by a photodiode placed under the capillary. The data revealed correlated waveforms in PA, LT, and Po(2) in capillaries. The magnitude of the Po(2) gradients between erythrocytes and plasma was correlated with average capillary Po(2). EATs in Po(2) were more readily detected in capillaries with relatively low oxygenation. The correlation coefficients between PA and Po(2) for the half of the capillaries (n = 26) below the median Po(2) (mean Po(2) = 17 mmHg; R = -0.72) was higher than that for the other half (mean Po(2) = 39 mmHg; R = -0.38). These results support the theoretical predictions of EATs and plasma Po(2) gradients in capillaries.     

The distribution of capillaries in the somatic musculature of two vertebrate types with particular reference to teleost fish

The distribution of capillaries in teleost and rat striated muscles was investigated using a number of different methods. A new method for directly viewing capillaries was developed. Teleost white muscle has a capillary: fibre (C:F) ratio of between 0.2 and 0.3; and 0.6 to 1.0 peripheral capillaries per muscle fibre. 26-49% of fibres had no peripheral capillaries. Values for the rat gastrocnemius were 1.2, 2.6 and 4.8% respectively which compares well with literature values. Flathead red muscle had a C:F ratio of between 1.9 and 2.5; and between 5.3 and 6.6 peripheral capillaries per muscle fibre depending on the method used. Values for rat soleus were 1.8 and 4.1 respectively. Teleost pink fibres had an intermediate number of capillaries. Rat striated muscle, particularly the gastrocnemius, was found to be heterogeneous with respect to the distribution of capillaries. Flathead red muscle was homogeneous whilst teleost white muscle was only slightly variable. Flathead red muscle fibres are well suppled with subsarcolemmal mitochondria. These show a clumped distribution corresponding to the position of capillaries. In contrast teleost white fibres are almost totally devoid of these and all other mitochondria. No differences were observed in the vascularisation of either muscle type along the length of the fish. The results are discussed in relation to the division of labour between fibre types during swimming.     

Role of acid-base balance in the chemoreflex control of breathing.

This paper uses a steady-state modeling approach to describe the effects of changes in acid-base balance on the chemoreflex control of breathing. First, a mathematical model is presented, which describes the control of breathing by the respiratory chemoreflexes; equations express the dependence of pulmonary ventilation on Pco(2) and Po(2) at the central and peripheral chemoreceptors. These equations, with Pco(2) values as inputs to the chemoreceptors, are transformed to equations with hydrogen ion concentrations [H(+)] in brain interstitial fluid and arterial blood as inputs, using the Stewart approach to acid-base balance. Examples illustrate the use of the model to explain the regulation of breathing during acid-base disturbances. They include diet-induced changes in sodium and chloride, altitude acclimatization, and respiratory disturbances of acid-base balance due to chronic hyperventilation and carbon dioxide retention. The examples demonstrate that the relationship between Pco(2) and [H(+)] should not be neglected when modeling the chemoreflex control of breathing. Because pulmonary ventilation controls Pco(2) rather than the actual stimulus to the chemoreceptors, [H(+)], changes in their relationship will alter the ventilatory recruitment threshold Pco(2), and thereby the steady-state resting ventilation and Pco(2).     

Independent cerebral vasoconstrictive effects of hyperoxia and accompanying arterial hypocapnia at 1 ATA.

Breathing 100% O2 at 1 atmosphere absolute (ATA) is known to be associated with a decrease in cerebral blood flow (CBF). It is also accompanied by a fall in arterial Pco2 leading to uncertainty as to whether the cerebral vasoconstriction is totally or only in part caused by arterial hypocapnia. We tested the hypothesis that the increase in arterial Po2 while O2 was breathed at 1.0 ATA decreases CBF independently of a concurrent fall in arterial Pco2. CBF was measured in seven healthy men aged 21-62 yr by using noninvasive continuous arterial spin-labeled-perfusion MRI. The tracer in this technique, magnetically labeled protons in blood, has a half-life of seconds, allowing repetitive measurements over short time frames without contamination. CBF and arterial blood gases were measured while breathing air, 100% O2, and 4 and 6% CO2 in air and O2 backgrounds. Arterial Po2 increased from 91.7 +/- 6.8 Torr in air to 576.7 +/- 18.9 Torr in O2. Arterial Pco2 fell from 43.3 +/- 1.8 Torr in air to 40.2 +/- 3.3 Torr in O2. CBF-arterial Pco2 response curves for the air and hyperoxic runs were nearly parallel and separated by a distance representing a 28.7-32.6% decrement in CBF. Regression analysis confirmed the independent cerebral vasoconstrictive effect of increased arterial Po2. The present results also demonstrate that the magnitude of this effect at 1.0 ATA is greater than previously measured.     

Capillary distribution and metabolic histochemistry of the lateral propulsive musculature of pelagic teleost fish

Metabolic and vascular adaptation of teleost lateral propulsive musculature to an active mode of life was investigated in four pelagic teleosts (mackerel, yellowtail scad, pilchard and Australian salmon). Histochemical profiles and capillarisation data of the red and white muscle were compared to those of less active demersal species. Pelagic white muscle stained positively for the aerobic enzymes succinate dehydrogenase and NADH diaphorase, and had both subsarcolemmal and intermyofibrillar mitochondria which corresponded to the loci of the histochemical stain. Subsarcolemmal mitochondria tended to be localised close to capillaries. In contrast, white muscle from demersal species was unstained for the same enzymes and was devoid of mitochondria. Red muscle of all species had abundant mitochondria and stained intensely for aerobic enzymes. Capillarisation was quantified by determining the percentage of fibres surrounded by a given number of peripheral capillaries, mean fibre diameter, mean number of peripheral capillaries, capillary: fibre ratio and sharing factor where appropriate. Red muscle of mackerel, Australian salmon, pilchard and scad are better vascularised than red muscle of the flathead having 153, 200, 242, 291 and 309 microns 2 of cross-sectional fibre area per peripheral capillary, respectively. White muscle of mackerel, pilchard and scad are better vascularised than white muscle of the Australian salmon and flathead having 2040, 3367, 4992, 9893 and 10,469 microns 2 of cross-sectional fibre area per peripheral capillary, respectively. Red muscle of Australian salmon had distinct regional variation. Deep red muscle was found to be more highly vascularised (4.2 peripheral capillaries per muscle fibre) than lateral red muscle (1.9 peripheral capillaries per muscle fibre). Red muscle of the other species was less heterogeneous. White muscle capillarisation was slightly variable in all species. It is concluded that the white muscle of the pelagic species studied is functionally and structurally adapted for sustained aerobic activity with relatively abundant mitochondria being preferentially situated close to the source of gas and metabolite exchange.     

Microhemodynamics of blood flow in narrow glass capillaries of 9 to 20 micrometers; the Fahraeus effect

Velocities of the red blood cell (RBC) and the suspending medium in glass capillaries of 9 to 20 micron were measured under microscopic observation. The effects of physical factors such as driving pressure, capillary diameter, hematocrits and RBC deformability on flow velocities were studied using freshly drawn blood of the rat resuspended in phosphate buffered saline solution in the hematocrit range between 5 and 12.5%. These RBC suspensions were made to flow through the test glass capillaries under known negative driving pressures. Ratios of capillary hematocrit to feed hematocrit taken as measures of the Fahraeus effect showed almost constant value of about 0.74. While, ratios of capillary hematocrit to discharge hematocrit showed a characteristic dependence on capillary diameter, showing minimal values at about 13 micron in capillary diameter. The same hematocrit ratios were found to be well correlated with values of wall shear rates estimated from the relative RBC velocities.     

Vascular permeability to lanthanum in the rat incisor pulp

Summary Experiments were performed to compare the permeability of capillaries supplying the endoneurial environment, which is invested by perineurium, with vascular permeability in the pulp where perineurium is absent. Anaesthetised rats were perfused through the aorta with physiological solutions containing lanthanum nitrate at 37° C. Pieces of inferior alveolar nerve and segments of mandibular incisors were immersion-fixed and transverse sections were examined electron microscopically for the distribution of lanthanum. In the pulp the nerve fibres pass between lanthanum-impermeable arterioles and venules en route to the incisal end. In the peripheral pulp a few capillaries were permeable but the most permeable capillaries lay between the odontoblasts. Pulpal capillary permeability was attributed to the fenestrated endothelium and contrasted with the unfenestrated endoneurial capillaries which were impermeable to lanthanum. Whereas the tight junctions of endoneurial capillaries are known to prevent certain blood-borne substances from entering the endoneurium, it was not clear whether the permeability of the pulpal capillaries, which are distant from the nerve fibres, could affect the nerve fibre environment. No extravasated lanthanum reached the pulpal nerve fibres suggesting that they are not affected. Technically it was not possible to examine the incisal third of the tooth where the situation could be different because the volume of the pulp decreases and capillaries lie closer to the nerve fibres.     

Three-dimensional reconstruction of the human capillary network and the intramyocardial micronecrosis

Three-dimensional reconstruction of the human heart was performed to define the structure of the intramyocardial microvasculature. A total of 200 consecutive serial sections of 6 μm each were prepared from the left ventricular tissue of an autopsied human heart with normal coronary arteries. The corresponding arteriole, venule, and all capillaries were reconstructed using three-dimensional software. The capillary network extended right and left along the cardiomyocyte with major and minor axes of about 130 and 120 μm, respectively. The capillary length from an arteriole to an adjacent venule was about 350 μm. Two types of sack-like structures, the precapillary sinus and the capillary sinus, were present in the capillary network, and many capillaries diverged from these sinuses. The cardiomyocytes were covered with reticular capillaries. In contrast, the precapillary and capillary sinuses were surrounded by many cardiomyocytes. The arterial and venous capillaries were positioned alternately, forming a lattice pattern. Intramyocardial microcirculatory units forming a capillary network from an arteriole to adjacent venules on both sides were present. The sizes of myocardial micronecroses corresponded to that of the intramyocardial microcirculatory unit. These results show that the capillary network is an ordered and anatomically regulated structure and that the microcirculatory unit and the precapillary and capillary sinuses may play an important role in maintaining the intramyocardial microcirculation during contraction and relaxation.     

Pressure regulation in the microcirculation.

The results of direct pressure measurements are described which demonstrate that pressures in a certain fraction of mesenteric capillaries remain remarkably constant during large changes in systemic pressure. The results of isogravimetric studies, reported in the literature, are also described which indicate that this phenomenon may also occur in the intestine. The question is raised whether capillary pressures may therefore be regulated. Pressures recorded from mesenteric arterioles and capillaries are shown which indicate that maintenance of a constant capillary pressure is primarily the consequence of the vascular architecture peculiar to this tissue, and is merely a secondary reflection of mechanisms associated with flow regulation. The results of direct pressure measurements recorded in the microcirculation of intestinal muscle are also shown. These data indicate that capillary pressures in innervated, denervated, and xylocaine-treated intestinal muscle change in direct proportion to variations in arterial pressure. It is concluded that capillary pressures in the intestinal muscle layers are therefore not regulated, so that the observation that capillary pressures may be maintained is probably a phenomenon unique to the mesentery. Pressures recorded from capillaries in the mucosal villi are also shown and compared to capillary pressures measured in the microvasculature of mesentery and intestinal muscle. When systemic pressure was normal (107 +/- 10 mm Hg), capillary pressure in the mesentery averaged 30 to 33 mm Hg; capillary pressures in the intestinal muscle averaged 22 to 24 mm Hg; and capillary pressures in the mucosal villi averaged 13 to 15 mm Hg. These data suggest that mesenteric capillaries are primarily a filtering network; intestinal muscle capillaries are normally in fluid balance; whereas at rest mucosal capillaries are primarily absorptive. These pressures, recorded from the three major regions of the rat intestine, were used to calculate a weighted average for the whole organ. The calculated value, based on assumed values for relative capillary densities, was 17 mm Hg. This result compares favorably with data from whole organ, isogravimetric studies, and may clarify some of the apparent discrepancies between previous isogravimetric and servopressure studies.     

Calcium and avian intrapulmonary chemoreceptor response to CO2.

Intrapulmonary chemoreceptors (IPC) are highly responsive respiratory chemoreceptors that innervate the lungs of birds and diapsid reptiles. IPC are stimulated by low levels of lung Pco(2), inhibited by high levels of lung Pco(2), and their vagal afferents serve as a sensory limb for reflex adjustments of breathing depth and rate. Most IPC exhibit both phasic and tonic sensitivity to CO(2), and spike frequency adaptation (SFA) contributes to their phasic CO(2) responsiveness. To test whether CO(2) responsiveness and SFA in IPC is modulated by a Ca(2+)-linked mechanism, we quantified the role of transmembrane Ca(2+) fluxes and Ca(2+)-related channels on single-unit IPC function in response to phasic changes in inspired Pco(2). We found that 1) broad-spectrum blockade of Ca(2+) channels using cadmium or cobalt and blockade of L-type Ca(2+) channels using nifedipine increased IPC discharge; 2) activation of L-type Ca(2+) channels using BAY K 8644 reduced IPC discharge; 3) blockade of Ca(2+)-activated potassium channels using charybdotoxin (antagonist of large-conductance Ca(2+)-dependent K(+) channel) increased IPC discharge, but neither charybdotoxin nor apamin affected SFA; and 4) blockade of chloride channels, including Ca(2+)-activated chloride channels, with niflumic acid decreased IPC discharge at low Pco(2) and increased IPC discharge at high Pco(2), resulting in a net attenuation of the IPC CO(2) response. We conclude that Ca(2+) influx through L-type Ca(2+) channels has an inhibitory effect on IPC afferent discharge and CO(2) sensitivity, that spike frequency adaptation is not due to apamin- or charybdotoxin-sensitive Ca(2+)-activated K(+) channels in IPC, and that chloride channels blocked by niflumic acid help modulate IPC CO(2) responses.     

Pain pathways and transmission.

Pain has been a major concern of humankind since the ancient times, and it remains one of the most important subjects of all health care professionals. Despite the obvious overwhelming clinical importance, the major advances in its diagnosis and therapy have been made only recently. "How do the sensory apparatus of the body and system of signal transmission relate to pain of peripheral origin?" is the topic of discussion. To do this, it is important to understand what constitutes the total pain experience. It consists of: 1) signal transduction at the peripheral receptor site, 2) signal conduction along the peripheral nerve, 3) pain modulation at the level of the spinal cord, 4) pain perception at the supraspinal site, and 5) the associated sensations, emotional reactions, and effective state. The signal transmission related to pain may be modified by various analgesic agents. Specific analgesic agent has a specific site of action which may be at peripheral receptors, at peripheral nerves, at the level of the spinal cord, at supraspinal levels by activating descending inhibitory systems, or at more cephalad levels by reducing the affective component of pain.     

Scanning electron microscopy of vascular architecture in the gastric mucosa of the golden hamster

Summary The three-dimensional architectures and the regional differences of the vascular system in the mucosa of the hamster stomach were revealed by scanning electron microscopy of corrosion casts. In the forestomach, the vascular network spreads two-dimensionally in a thin lamina propria. In the corpus and the antrum, the capillaries in the thick lamina propria are well developed, extending three-dimensionally along the gastric pits and glands. In the corpus, the submucosal arteries enter the lamina propria to become ascending capillaries, which project toward the top of the lamina propria and anastomose to create a capillary network beneath the mucosal epithelium. A subepithelial capillary is much wider in diameter than an ascending capillary and is, therefore, a sinusoid capillary. Subepithelial capillaries join descending venules, which are less numerous than the ascending capillaries. Near the gastric lumen, the capillaries in the corpus can be classified into two types: arched type in the cephalic (upper) region and honeycomb type in the caudal (lower) region. In the antrum, the submucosal arterial plexus is less well developed than that in the corpus. The mucosal aspect of the corrosion cast shows many clumps, formed by a unit of capillary network. Functional significances of different vascular architectures in the gastric mucosa of the forestomach, corpus, and antrum are discussed.This study was supported in part by grants from the Research Fund of the Ministry of Education, Science, and Culture, Japan