Tridimensional study of the deep cortex of the rat lymph node. V: Postnatal development of the deep cortex units

ABSTRACT Recently, the deep cortex of the adult rat lymph node was shown to be made up of semirounded lymphocytic “units.” Each unit is contiguous to the peripheral cortex, bulges into the medulla, and is centered on the opening(s) of an afferent lymphatic vessel of a node. Furthermore, each unit comprises a “center” and a “periphery,” bearing distinct morphological features. The present study investigated the postnatal development of the units in rats of various ages. One minute after birth, no lymphocytic structures were detected in the nodes. One day after birth, tiny rounded lymphocytic areas were detected in the developing cortex. These areas were topographically related to the openings of afferent lymphatic vessels. One week after birth, small semirounded lymphocytic areas with some morphological features of the adult deep cortex units were observed. Two weeks after birth, typical units were present in the nodes. The observations indicated that the rounded lymphocytic areas observed in nodes of rats aged 1 week or less were actually developing deep cortex units. The overall findings further provided information on the morphological processes involved during the postnatal development of the deep cortex units. Key words: lymph node, deep cortex, development of deep cortex, rat.     

Tridimensional study of the deep cortex of the rat lymph node. VI. The deep cortex units of the germ-free rat

The deep cortex of the normal rat lymph node consists of semirounded lymphocytic structures, termed deep cortex "units," each being centered on the opening of an afferent lymphatic. The aim of the present work was to investigate the morphologic features of the units in germ-free animals, in an attempt to evaluate the influence on natural exogenous antigenic stimulation on the development of the units. For this, the lymph nodes from various anatomic locations from 8-week-old Sprague-Dawley germ-free rats were analysed tridimensionally. The observations revealed that, in comparison with the lymph nodes of normal rats, the units of the cervical and mesenteric lymph nodes of the germ-free animals were underdeveloped, while those of the brachial, inguinal, and popliteal lymph nodes were unchanged. Moreover, the germ-free state modified the units of the mesenteric lymph nodes in a manner not encountered in the remaining lymph nodes. Other morphologic features of the peripheral cortex of the lymph nodes of germ-free rats also differed from those of normal ones. The significance of these differences is discussed with respect to immune responses and the process of lymphocyte recirculation. They are of interest because they support previous proposals regarding some aspects of the functioning of the normal lymph node, accounting for the features of the structures and overall architecture of the organ.     

Tridimensional study of the deep cortex of the rat lymph node. II: Relation of deep cortex units to afferent lymphatic vessels

Recently, we reported that the deep cortex of the rat lymph node is formed of semi-rounded structures, the “deep cortex units,” contiguous to the peripheral cortex and bulging into the medulla. It was suggested that a unit represents an accumulation of lymphocytes centered on the opening of an afferent lymphatic vessel. To verify the proposal, we carried out a tridimensional analysis of serially sectioned rat nodes, fixed by perfusion and trimmed in such a way as to preserve their lymphatics. The tridimensional analysis revealed that a constant topographical relationship exists between the units and the openings of the afferent lymphatics. The results demonstrated that the topographical organization of the deep cortex of a rat node correlates with the distribution pattern of the opening(s) of its afferent lymphatic(s). The overall observations suggested the following explanation for the shape and topography of the units: factor(s) present in the lymph would spread in a radial manner from the opening(s) of an afferent lymphatic through the underlying cortex. The factor(s) would induce morphological modifications in the stimulated semi-rounded area which, in turn, would provoke a local accumulation of circulating lymphocytes.     

Topography of the deep cortex of the lymph nodes of various mammalian species

In preceeding studies, we clarified the histology of the deep cortex of the rat lymph node. It was shown that the deep cortex is made up of basic elements termed “deep cortex units,” some of which are fused to one another into “deep cortex complexes.” Each unit is a semirounded lymphocytic structure, centered on the opening of an afferent lymphatic, contiguous to the peripheral cortex, and bulging into the medulla of a node. Moreover, each unit comprises a “center” and a “periphery,” bearing distinct morphological features. The present work was undertaken to verify whether the histology of the deep cortex of nodes from various species of mammals, currently used for experimental immunology, is comparable to that of the rate. The observations yielded a positive answer to the question.     

Modifications of the structures of the rat lymph nodes by neonatal thymectomy

Until recently, the deep cortex of the lymph node was thought to exist as a layer completely underlying the peripheral cortex. It was known, moreover, that through neonatal thymectomy, the lymphocyte population of the deep cortex could be depleted. Through our current research, however, we have demonstrated that the deep cortex actually consists of hemispherical 'units'. Each unit is centered under an opening of an afferent lymphatic and comprises a center and a periphery with different morphological features and functions. In the light of this new knowledge, we felt it appropriate to reexamine the influence of neonatal thymectomy on node histology. Rats were thymectomized 5 h after birth. When they were 8 weeks old, nodes from various anatomical sites were submitted for morphological analysis. The resulting observations were compared to those made with nodes of nude as well as normal rats. It was found that the histological changes induced by neonatal thymectomy were comparable to those resulting from the congenital athymic state, but with marked differences. Differences were also observed in the nodes of thymectomized and semi-thymectomized rats. The discussion deals with these differences and presents new observations.     

Blood vascular network of the rat lymph node: Tridimensional studies by light and scanning electron microscopy

Many aspects of the blood vascular network of the lymph node are unknown, and others need confirmation. We have studied the blood vasculature of rat peripheral lymph nodes by means of carbon perfusion and vascular cast corrosion techniques. At the hilus of the node, an artery gives off arterioles running in medullary cords towards the cortex. Some reach the peripheral cortex directly, branching there into slender cortical vessels. Other arterioles enter the periphery of the deep cortex units, and then head towards the peripheral cortex. Upon reaching it, they curve part way above the center of the deep cortex units and provide slender branches to the overlying peripheral cortex. Dense plexuses of capillaries arise from arterioles in the medullary cords, in the periphery of the deep cortex units, and in the outermost stratum of the extrafollicular zone of the peripheral cortex. In the cortex, the draining high endothelial venules are restricted to the extrafollicular zone and to the periphery of the deep cortex units. At the cortico-medullary junction, these peculiar venules transform into regular medullary venules which form the hilar veins. In contrast, the folliculo-nodules and center of the deep cortex units are little vascularized by a loose capillary network, while no vessels occur in the subsinus layer. These features of the node vascular network are of interest in relation to the node architecture.     

The influence of the lymph node on the protein concentration of efferent lymph leaving the node.

1. Experiments have been performed in sheep to determine the contribution of lymph formed within a lymph node to the total protein output in lymph leaving the node. 2. The lymphatic duct leaving the popliteal lymph node was cannulated and the protein and lymphocyte output in efferent lymph determined. The afferent lymph flow to the popliteal node was then diverted and lymph formed only within the lymph node collected from the efferent cannula. It appeared from the results that the popliteal lymph node forms lymph at the rate of approximately 1 ml. per hour and may contribute 30-50% of the protein output observed in efferent lymph. 3. The importance of lymph formation within the lymph node varied between nodes found in different regions of the body. This was due in part to the different protein concentrations in the afferent lymph to the different nodes. 4. A positive correlation was found between the protein and lymphocyte concentrations in efferent lymph from the popliteal lymph node in seven out of eleven sheep and in lymph formed within the popliteal lymph node in two out of three sheep. It is suggested that this relationship may be due to an increased transfer of plasma proteins through the post-capillary venules in the lymph node accompanying the continual traffic of lymphocytes across the wall of these vessels. The results indicated that the protein transfer across the post-capillary venules was not an indiscriminate transfer of plasma per se but a selective transport from the blood plasma compartment based on molecular size.     

The histogenesis of lymph nodes in rat and rabbit

The histogenesis of the popliteal lymph node in the rat and the popliteal and inguinal lymph nodes in the rabbit was examined by light microscopy. Special emphasis has been laid on the initial lymphocyte population in the lymph node anlage. In the rat on the seventeenth day of gestation lymphoid cells populate a limited mesenchymal area along the vein wall. The next day the mesenchyme shows a bulb-shaped outgrowth causing an indentation in the wall of a lymph vessel, running parallel to the vein and having a saccular widening at this place. The bulb-shaped lymphoid outgrowth fills up the widened lymph vessel; the subcapsular sinus originates from the remaining parts of the lymph vessel. At birth the lymph node can be divided into a primitive cortex consisting of an area with evenly scattered lymphocytes among the basic network of reticular cells and a medulla. About three days after birth an ovoid area containing a dense concentration of lymphocytes is observed in the inner cortex. In the next days it expands in both lateral and medullary direction but not into the outer cortex. Primary follicles appear in the outer cortex 18 days after birth. The development of the inguinal and popliteal lymph nodes in the rabbit shows the same characteristics as the histogenesis of the popliteal lymph node in the rat. The morphogenesis of the lymph node is summarized in a schematic diagram.     

Tridimensional study of the deep cortex of the rat lymph node: VIII. The deep cortex units of the athymic nude rat

The deep cortex of the lymph node of various species actually consists of hemispherical structures, termed deep cortex "units." Each unit is centered under an opening of an afferent lymphatic and comprises a center and a periphery. In a recent work on the nude mouse, we found that the congenital athymic state inhibits the development of the lymphocyte population in the center of the units as well as in a related area of peripheral cortex, and that it also modifies other nodal components. In the present work, we wanted to compare the effects of the athymic state on the rat nodes. Therefore, nodes from various anatomical locations in 8-week-old nude rats were submitted to a tridimensional analysis. The overall effects of the congenital athymic state were found to be comparable in rats and mice. However, marked differences were noticed in the modifications of the node histology, in both species of nude animals. Their significance is discussed together with new findings.     

A histological and experimental study on the fate of an increased number of lymph follicles produced in the mouse popliteal lymph node by exogenous antigen stimulation

Eight-week-old female C57B1/6 mice were injected with endotoxin LPS and/or other antigens into the left hind footpad, and then the number of lymph follicles in the draining popliteal lymph nodes was examined. In untreated mice each popliteal node contained 10-12 lymph follicles at both 8 and 15 weeks of age. Animals given 50 micrograms of LPS at 8 weeks of age showed an increase in the number of lymph follicles 3 weeks later, but this number returned to normal levels by 15 weeks after the LPS injection. After a 2-micrograms-LPS injection at 23 weeks of age, the number of lymph follicles in the draining lymph node was unchanged, but that in animals given the 2-micrograms-injection 15 weeks after the 50-micrograms-LPS injection was significantly increased. In animals receiving 2 Lf of diphtheria toxoid, instead of the 2-micrograms-LPS, at 15 weeks after a 50-micrograms-LPS injection, the number of lymph follicles per draining node was within the normal range. In one group of mice, the initial injection of 50-micrograms-LPS at 8 weeks of age was followed by injections every third week of several kinds of antigens which had been shown to be ineffective in inducing follicle formation. Here, the number of lymph follicles in the draining popliteal node was kept to significantly increased levels at 25 weeks of age. The present results suggest that, while most lymph follicles normally developing in the lymph node are maintained for a long time under normal conditions, many lymph follicles induced by antigenic challenge have a limited life span and undergo atrophy unless they are periodically activated by additional antigenic stimuli, and that atrophied follicles finally become unable to respond to antigenic stimulation. It is also suggested that antigenic materials which trigger the formation of lymph follicles in the primary challenge can evoke follicle formation more efficiently in the secondary challenge.     

Fate of Autogenous Canine Lymphocytes after Injection into an Afferent Lymphatic of the Popliteal Lymph Node

Dog thoracic duct lymphocytes were labeled in vitro with ³H-uridine and infused into an afferent lymphatic of the popliteal lymph node of the same dog. Ten minutes after infusion nearly all the injected radioactivity was recovered from the lymph node. An effect of infusion flow rate on the percentage of cells retained by the lymph node was observed ½ to 3½ hours after infusion, and was probably mediated by the tendency of the node to become edematous after infusions at a rate exceeding 0.045 ml/min. Edematous nodes retained 83.7% of the cells, as compared to 47.5% for nonedematous nodes. As early as 30 minutes after infusion a small amount of ³H-radioactivity was found in the spleen and thoracic duct lymph. The deep iliac and paraaortic nodes on the side of the infusion contained significant amounts of ³H-radioactivity, while negligible amounts were detected in the contralateral popliteal node at any time. The intranodal localization of the ³H-labeled cells was studied by radioautography. All labeled cells remained intrasinusoidal during the first 4 hours after infusion. At 9 and 21 hours some labeled cells were located in the extrasinusoidal parenchymal lymphoid tissue of the cortex and the medulla, but the majority still remained intrasinusoidal.     

Macrophages and the activity of high endothelial venules. The effect of interferon-gamma

Interruption of the afferent lymphatic vessels of rat popliteal lymph nodes led to the disappearance of the monoclonal antibody ED3-reactive subcapsular sinus macrophages within 3 weeks, but had no effect on the ED1+ macrophages in the paracortical area. This disconnection of the afferent lymph flow to the popliteal lymph node also reduced the capacity of high endothelial venules (HEV) to bind lymphocytes and led to a flattening of the HEV. Activating factors or cells in the incoming lymph might be responsible for the maintenance and function of several different cell populations and we therefore wished to determine if the effects of interruption could be restored by injection of recombinant rat interferon-gamma (rIFN-gamma). Injection of rIFN-gamma directly into operated lymph nodes could mediate an apparent increase of ED1+ cells within 24 h but rIFN-gamma could not restore the macrophage subpopulation in the subcapsular sinus, as recognized by monoclonal antibody ED3. Restoration of the decreased binding capacity of HEV could not be observed with the doses and time points tested, suggesting that HEV are a distinct type of endothelium.     

Patterns of age-dependent changes in the numbers of lymph follicles and germinal centres in somatic and mesenteric lymph nodes in growing C57Bl/6 mice

The timing of the first appearance of lymph follicles and germinal centres in various lymph nodes, and the ways in which numbers of these and IgM-synthesising cells increase within the nodes, were investigated in male and female C57Bl/6N mice aged from 4 d to 16 wk. The lymphoid organs examined were the Peyer's patches, spleen, somatic (submandibular, deep cervical, brachial, axillary, inguinal and popliteal) and visceral (mesenteric and lumbar) lymph nodes. Primary follicles appeared in most somatic lymph nodes 6 d after birth. The number of follicles per node then increased rather sharply in larger lymph nodes and slowly in smaller nodes, up to 28 d of age, reaching a level which varied according to the location of the node. Thereafter, the number of follicles in the somatic lymph nodes increased only slightly to moderately, reaching a peak or plateau at 8–12 wk. In the mesenteric (ileocaecal) nodes, primary follicles first appeared at 12 d, then increased linearly during the suckling period and after weaning to reach a plateau at 8 wk of age. Germinal centres appeared in the submandibular and mesenteric nodes at 28 d and their numbers increased consistently in the latter, while remaining low in the former. The impact of possible 'natural' exogenous antigen stimulation of the various lymph nodes was estimated from the presence of IgM-synthesising cells and germinal centres. Differences between the patterns of age-dependent changes in the numbers of lymph follicles observed in the somatic and mesenteric lymph nodes during their ontogeny are discussed in relation to differences in the magnitude of the exogenous antigen stimulatory effect. We also found that the variations in the numbers of lymph follicles produced in somatic lymph nodes at different locations during the first 28 d after birth reflected differences in the dimensions of the body regions drained by a particular somatic lymph node at this stage of development.     

Tridimensional study of the deep cortex of the rat lymph node. III. Morphology of the deep cortex units

Recently we reported that the deep cortex of the rat lymph node is made up of semi-rounded “units,” some of which are partially fused into “complexes”. We further found that each unit is centered on the opening(s) of an afferent lymphatic vessel, the topographical organization of the deep cortex of a node correlating with the distribution pattern of the opening(s) of its afferent lymphatic(s). The present study aims to clarify the morphology of the deep cortex unit, particularly with regard to its reticular framework, its lymphatic sinuses, as well as its network of postcapillay venules. For that purpose, we analyzed rat nodes from various locations by way of tridimensional reconstruction. The observations revealed that each unit is formed of a “center” and a “periphery,” distinguishable from one another on the basis of their morphological features. The center is nearly devoid of reticular fibers, whereas the periphery exhibits a dense framework of fibers. Moreover, the periphery is the site of concentration of most postcapillary venules of a unit and contains lymphatic sinuses which, peculiarly, are often loaded with small lymphocytes. While both regions are populated mainly by small lymphocytes, the periphery usually contains a lower concentration of these cells than the center. The overall findings support the view that the center is a site of cellular retention and proliferation, whereas the periphery is a site of rapid lymphocyte migration in and out of the unit.     

Overall architecture and pattern of lymph flow in the rat lymph node

The immunogenic content of the afferent lymph stimulates structures in the lymph node. Thus, a better knowledge of the processes of lymph flow and filtration in the organ should help us better understand various aspects of the node's function. To gain this understanding, we analyzed the distribution of flow in rat node draining areas locally injected with a small dose of China ink. Because the lymph-flow pattern is likely related to the overall architecture of the node, we simultaneously studied its morphology. Indeed, while the different structures of the node are known, some aspects of its overall architecture need to be resolved. The present work aimed to accomplish this by an analysis of semiserial sections of nodes from various anatomical locations in normal rats; the sections were stained by the Dominici technique or silver-impregnated. With respect to their architecture, the nodes could be distinguished into those with either a discontinuous or a continuous subcapsular sinus and peripheral cortex. These are referred to here, respectively, as segmented and nonsegmented nodes. In the segmented nodes, the subcapsular sinus with the peripheral cortex is separated by “gaps,” in which medullary sinuses reached the capsule. Further, a node appears to be divided into one or more “physiological compartments,” each one representing a nodal area related to an opening of an afferent lymphatic. The findings on China-ink distribution indicate that the lymph-flow pattern varies in different nodes and is determined by the particular architecture of a node, i.e., the lymph flow in a given node aligns itself along the pattern of segmentation of the organ. The findings suggest that the lymph content is first held by the endothelium lining the inner wall of a restricted area of the subcapsular sinus in a concentration which decreases with the distance from the related afferent lymphatic opening. Part of the content, possibly its nonimmunogenic fraction, would later be released to flow further along the sinus. It would then be phagocytosed by the macrophage accumulation located in the portions of medullary sinuses into which the lymph enters from the subcapsular sinus. The lymph thus filtered then flows along the medullary sinuses and leaves the organ. The latter findings also indicate that a node is divided into physiological compartments, each one being stimulated by the lymph from a given afferent lymphatic opening. As the immunogenic content of the lymph can differ from one lymphatic to another, this explains the frequent variations in similar structures located in different areas of a given node. Hence, the pattern of distribution of the openings of the afferent lymphatics of a node can account for the particularities of its overall architecture and its division into physiological compartments.     

Effect of interferon-alpha-2a on the output of recirculating lymphocytes from single lymph nodes.

The output of recirculating lymphocytes from cannulated popliteal lymph nodes in sheep was measured after administration of human recombinant interferon (rIFN)-alpha-2a. Interferon (IFN) injection caused a dramatic decrease in lymphocyte output from lymph nodes. Following a single s.c. or i.d. injection of 2 x 10(7) U IFN into the drainage area of the popliteal lymph node, lymphocyte output fell to below 1% of the pre-treatment level and remained depressed for up to 35 hr. A substantial decrease in lymphocyte output from cannulated nodes also occurred after IFN was injected either i.v., into the skin of the opposite non-cannulated hind leg or into an afferent lymphatic vessel leading to the popliteal lymph node. After the period of depressed lymphocyte output, a seemingly compensatory surge of cell traffic occurred that lasted 2-3 days. During this phase there was a relative increase in the proportion of CD4+ T cells in lymph. Similar changes occurred after each treatment in animals given multiple doses of IFN. These effects are unlikely to be antigen-induced since there was no blast cell response in any treated animal. The analysis of blood and lymph plasma samples showed that the most severe depression of lymphocyte output was associated with high levels of IFN, while there was no apparent correlation between the reduction in lymphocyte traffic and concentrations of cortisol in plasma. These results suggest that IFN-alpha-2a is involved directly in the regulation of lymphocyte output from lymph nodes.     

Gaps and fragmentation of the superficial cortex in the abdominal and pelvic lymph nodes of elderly Japanese

Gaps and fragmentation of the superficial lymph node cortex are considered to provide intranodal shunt flow between the afferent and efferent vessels. Using serial sections of 205 nodes obtained from 27 donated cadavers more than 70 years of age, we examined the histological architecture of the abdominal and pelvic nodes in elderly Japanese. Secondary follicles were rare in the specimens. Cortex gaps were, to a greater or lesser degree, found in all nodes. We classified these nodes into three types according to how often the gap occurred. Type 1 nodes, with a relatively complete shield for the afferent lymph, were most frequently found in gastric nodes, whereas type 3 nodes, with numerous gaps, were often observed in the colic, para-aortic and pelvic nodes. The type 3 nodes showed a specific architecture characterized by a fragmented superficial cortex, three-dimensionally assembled cords and a common sinus between them. Primary follicles were located in the assembled cord structures as well as at the superficial cortex. Irrespective of the type, B and T lymphocyte areas were intermingled in the cortex-like areas. The present results reveal region-specific histological heterogeneity in aged human visceral nodes. Due to increased surface areas, the type 3 architecture seemed to accelerate systemic immunity rather than act as a local barrier in the para-aortic and pelvic nodes, which are located centrally along the lymphatic drainage routes. However, thick trabeculae often seemed to develop in the type 3 sinus to decrease nodal function with aging.     

Disappearance and reappearance of high endothelial venules and immigrating lymphocytes in lymph nodes deprived of afferent lymphatic vessels: a possible regulatory role of macrophages in lymphocyte migration

Interruption of the afferent lymphatic vessels of the popliteal lymph node resulted in the disappearance of high endothelial venules (HEV) and immigrating lymphocytes within 3 weeks. HEV showed several characteristic morphological changes: the endothelial cells became flattened and less pyroninophilic, the chromatine became condensed and protein synthetizing and secretory cell organelles became scarce. At the same time the number of macrophages in the lymph node was severely reduced. Injection of sheep red blood cells into such lymph nodes, 6 weeks after operation, resulted in reappearance of HEV and immigrating lymphocytes, and development of many plasma cells and some germinal centres. Injection of lipopolysaccharide into the operated lymph nodes resulted in the appearance of many plasma cells and a few poorly developed germinal centres; HEV and immigrating lymphocytes, however, remained almost absent. The results show a relationship between the immigration of lymphocytes and the activity of the endothelial cells in the HEV. The activation of the latter may occur by mediators released by antigen-stimulated macrophages and T cells. Moreover, the morphological features of the HEV are independent of the presence of recirculating lymphocytes.     

Effect of the fever reaction on lymph cytologic composition and lymph node structure]

The authors studied the cytologic composition of afferent and efferent lymph and the morphology of the popliteal lymph node during a fever reaction of various duration. The fever reaction was attended by quantitative and qualitative in the cytologic composition of both lymph types. Reduction of the leukocyte count in the first hours of fever was replaced by its increase: the percentage of small- and moderate-size lymphocytes reduced, while that of poorly-differentiated cells--blasts and prolymphocytes--increased. The number of neutrophils and monocytes in the afferent lymph grew and its toxicity increased. Phenomena of dynamic stereotypy were noted during the development of the fever reaction: hyperplasia of the lymphatic substance with an increase of the number of lymphocytes and poorly-differentiated cells in the follicles and paracortical zone of the lymph nodes, hyperplasia of the pulpar bands, and signs of a macrophageal reaction.     

右旋糖酐-二乙烯三胺五乙酸-钆离子螯合物与马根维显在间质磁共振淋巴造影中的对比

目的 比较右旋糖酐-二乙烯三胺五乙酸 钆离子螯合物(dextran-DTPA-Gd)和马根维显两种对比剂在间质MRI淋巴造影中淋巴显影的价值。方法 选择健康成年新西兰兔12只,体重为2.7～3.7kg。仰卧位固定兔,经3D TOF CE-MRA序列扫描,平扫后右侧后肢第1、2、3趾蹼间隙注
射dextran-DTPA-Gd 各0.4ml(3.96×10^-3mol/L),共1.2ml;30min后左侧后肢第1、2、3趾蹼间隙注射马根维显各0.4ml(0.4998mol/L),共1.2ml,行MR增强扫描,扫描间隔分别为10、15、20、25、30、35、40、45、50、55、60min、2h、4h、24h。平扫和增强扫描的相关参数相同。分析不同
时间段淋巴显影强化程度,测量并计算腘窝淋巴结增强前后的信号强度(E%),绘制其信号强度-时间曲线,比较两种显影剂对淋巴显影的区别。结果 平扫时双侧腘窝淋巴结均呈等信号。右侧dextran-DTPA-Gd注射后10min,引流区后肢淋巴管及腘窝淋巴结信号强化明显、显示清晰,腘窝
淋巴结E%为212.7%,35min左右达到峰值,E%值为314.1%,4h后为208.2%,24h后扩清。左侧马根维显注射10min时,引流区域后肢血管强化明显,造影剂大部分吸收入血管进入膀胱,后肢淋巴管及腘窝淋巴结信号弱,腘窝淋巴结E%为78.8%,20min左右达到峰值,E%值为98.3%,4h后减至
29.0%,24h后扩清。淋巴结E%经统计学分析差异有统计学意义(P<0.05)。实验前后动物的生化检查等数据未见异常变化,其差异无统计学意义(P>0.05),送检的内脏器官组织学检查未见明显的病理学改变。结论 相比马根维显小分子造影剂,dextran-DTPA-Gd是一种有效的淋巴造影剂,
能够特异性靶向强化淋巴结及淋巴管。