True Vessels Research Articles

Duplication Images in Vascular Sonography

The purpose of this study was to determine the characteristics and phenomena of duplication (or mirror) images in vascular sonography. We retrospectively reviewed 5 cases of vascular sonography that produced duplication images performed between June 30, 2009, and January 10, 2010. The 5 vascular studies included the subclavian artery (2), subclavian vein (1), carotid artery (1), and abdominal aorta (1). The characteristics of the color flow images and spectral Doppler waveforms in the artifactual vessels and in the true vessels were analyzed. Sources and mechanisms of producing duplication images were assessed. We were able to generate color flows in the artifactual vessels that were the same as in the true vessels in 2 cases. However, we were able to generate images in which the apparent flow directions in the artifactual vessels differed from the actual flow observed in the true vessels in all 5 cases by changing the orientation of the ultrasound beam relative to the true flow and the reflecting surface. Duplication images result from mirror reflections producing multipath artifacts. The appearance of the flow in an artifactual vessel on color Doppler imaging strongly depends on the angle of the incident sound beam and the surface structure of the strong reflector relative to the flow in the true vessel. Alternating the scanning plane and the angle of the incident sound beam to the reflector may help distinguish a duplication artifact from a true vessel in ambiguous cases.

Absence of lymphatic vessels in human dental pulp: a morphological study

Few and controversial data are available in the literature regarding the presence of lymphatic vessels in the human dental pulp. The present study was designed to examine morphologically the existence of a lymph drainage system in human dental pulp. Human dental pulp and skin sections were immunohistochemically stained with specific antibodies for lymphatic endothelium (D2-40, LYVE-1, VEGFR-3 [vascular endothelial growth factor receptor-3], and Prox-1), with the pan-endothelial markers CD31 and von Willebrand factor (vWF), and with the blood-specific marker CD34. Several blood vessels were identified in human pulps and skin. Lymphatic vessels were found in all human skin samples but in none of the pulps examined. Western blotting performed on human dermis and on pulps treated with collagenase (to remove odontoblasts) confirmed these results. Transmission electron microscopy indicated that vessels which, by light microscopy, appeared to be initial lymphatic vessels had no anchoring filaments or discontinuous basement membrane, both of which are typical ultrastructural characteristics of lymphatic vessels. These results suggest that under normal conditions human dental pulp does not contain true lymphatic vessels. The various theories about dental pulp interstitial fluid circulation should be revised accordingly.

Determining the Morphology of Polystyrene-block-poly(2-vinylpyridine) Micellar Reactors for ZnO Nanoparticle Synthesis

We report the use of reverse PS-b-P2VP diblock copolymer micelles as true nanoscale-sized reactor vessels to synthesize ZnO nanoparticles. The reverse micelles were formed in toluene and then sequentially loaded with zinc acetate dihydrate and tetramethylammonium hydroxide reactants. Moreover, high spatial resolution Z-contrast imaging and EDX spectroscopy techniques were used to confirm the segregation of the Zn cation to the core of the loaded micelles. Determining the chemical distribution with high nanoscale spatial resolution is shown to complement the less direct characterization by AFM, DLS and FTIR, thus demonstrating broader implications for the characterization of hybrid nanocomposite systems.

Evaluation of two different methods for vascular sampling by three‐dimensional power Doppler angiography in solid and cystic‐solid adnexal masses

To analyze two different methods for performing three-dimensional power Doppler angiography (3D-PDA) vascular sampling in solid and cystic-solid adnexal masses. Twenty-one 3D-PDA volumes from 18 consecutive and unselected solid or cystic-solid adnexal masses (13 malignant and five benign) were analyzed. A single examiner (J. L. A.) acquired all the volumes according to a predetermined scanning protocol. Two different observers (one inexperienced and the other experienced) calculated 3D-PDA vascular indices (vascularization index (VI), flow index (FI) and vascularization flow index (VFI)) from solid tumor areas. First, manual sampling (Plane A, 15 degrees rotation-step) was performed, and 1 week later 5-cm(3) sphere sampling from the most vascularized area was carried out. The observers made a record of any difficulty that they encountered in delineating the solid areas of tumors or in distinguishing true tumor vessels from pre-existing vessels, the time spent performing each analysis was recorded and inter- and intraobserver reproducibility was evaluated for each method using intraclass correlation coefficients (ICC). In four (19.0%) of the 21 volumes sphere sampling could not be performed because it was not possible to obtain a sphere smaller than 5.5 cm(3). This happened in cases in which image zooming was used when acquiring the 3D volume. The inexperienced observer encountered more difficulty, but not significantly more, than the experienced observer when analyzing 3D-PDA volumes both by manual sampling (29% vs. 14% of cases) and 5-cm(3) sphere sampling (35% vs. 18% of cases). The mean time spent by the inexperienced observer was significantly greater (P < 0.001) than that spent by the experienced observer both for manual sampling (6.11 min vs. 1.85 min) and 5-cm(3) sphere sampling (2.93 min vs. 2.15 min). Contrary to the findings for the experienced observer, the inexperienced observer required less time to perform sphere sampling than they did manual sampling. Interobserver agreement was high for both methods: ICC for manual volume, 0.993; manual VI, 0.908; manual FI, 0.913; manual VFI, 0.914; sphere volume, 0.949; sphere VI, 0.954; sphere FI 0.850; and sphere VFI, 0.953. Intraobserver reproducibility was also high, with all ICCs above 0.99. Manual and 5-cm(3) sphere sampling are reproducible methods for 3D-PDA vascular sampling. Caution is required when image zoom is used at the time of acquiring the volume because this may prevent sphere sampling. Difficulties found in performing both manual and sphere sampling do not seem to significantly affect the reproducibility of Doppler index calculations.

Hypertonie oculaire aiguë tardive compliquant une rétinopathie de la prématurité

We report the case of an acute rise in intraocular pressure occurring decades after the treatment for prematurity (ROP). A 54-year-old preterm woman presented an acute rise in intraocular pressure in her right amblyopic eye. Prominent dilatation of iridal vessels was noted. Fundus was not visible at that time because of corneal edema. Ocular echography was normal. The fellow eye showed temporal attraction of temporal vessels suggestive of retinopathy of prematurity at the cicatricial stage. Neovascular glaucoma was postulated and pressure control was obtained after cyclodestruction and transscleral cryoapplication. After resolution of corneal edema, fundus examination revealed extensive peripheral retinal photocoagulation scars. Iridocorneal angle presented extensive iridocorneal synechias without true new vessels. Visual acuity remained limited to hand motion. Prominent iris dilatation seen in some preterm patients can mimic rubeosis, and, in the present case, mislead to a diagnosis of neovascular glaucoma. Diagnosis can be difficult if the patient is not specifically asked for a history of prematurity. The case underlines the notion that ROP patients may present very late complications of the disease.

Tracheary Elements in Ferns: New Techniques, Observations, and Concepts

Longisections of xylem were studied with scanning electron microscopy (SEM) for roots of Angiopteris, upright axes of Psilotum, and rhizomes of eight species of leptosporangiate ferns of diverse habits and varied ecological preferences. In contrast to earlier studies using macerations, razor-blade sections of fixed material from living plants were prepared. All materials studied showed porose or reticulate pit membranes present on presumptive end walls of tracheids. Contrasting non-porose pits were observed on lateral walls of some tracheids. Tracheid to parenchyma pit pairs may have porose pit membranes on the tracheid side and nonporose pit membranes on the parenchyma side; thus degree of porosity in a section can represent the degree to which one primary wall or the other is pared away. Reticulate pit membranes on tracheary element end walls are evidently widespread in ferns. Such cells should not be considered vessel elements, although the reticulate pit membranes suggest a degree of transition toward the membrane-free perforations of typical vessels. True vessels (pit membranes absent in perforations) do occur in roots in a limited number of fern genera. The preparation methods of the present study produced results freer from artifacts than did macerations, and interpretations must be altered accordingly. Reports of lateral, multiple, and interrupted perforation plates in ferns are probably the result of loss of pit membranes due to the oxidative action of maceration and should be rejected. Likewise, ''pit dimorphism'' (alternately wide and narrow pits) and ''striate'' (corrugated) pit membranes in ferns represent artifacts. True vessel elements in ferns probably always have secondary wall architecture of end walls different from that of lateral walls. Progress in study of the nature of tracheary elements in ferns has been gradual, limited by techniques and technology. With light microscopy and macerations, vessels were early reported in Pteridium aquilinum (L.) Kuhn (Russow, 1873; Bliss, 1939) and Nephrodium filix-mas (L.) Schott (Russow, 1873). Gwynne-Vaughan's (1908) reports that vessels occurred in a number of other ferns have been discounted (Bancroft, 1911). Light microscope studies of macerations revealed distinctive perforation plates in roots of Marsilea (White, 1961; Loyal and Singh, 1978). White (1962) reported possible vessels in Astrolepis, Phlebodium, Polystichum ,a ndWoodsia. The report of possible vessels in these four genera by White (1962) was based on the presence of tracheary element end walls that were perceptibly different from lateral walls, an appearance which in turn is based on differences between end walls and lateral walls in secondary wall architecture. Because we had access to a scanning electron microscope (SEM), we endeavored to confirm White's (1962) reports. In our studies of xylem of Woodsia obtusa (Spr.) Torr. (Carlquist et al., 1997) and Phlebodium and Polystichum (Schneider and Carlquist, 1997), we obtained similar results. In the case of Woodsia obtusa, we used SEM study of sections prepared by paraffin sectioning techniques. Excessive fracturing of tracheid walls by

Electronic Clinical Challenges and Images in GI

Question: A 66-year-old man presented acutely with fresh and altered blood per rectum. This was preceded by the sudden onset of dull epigastric pain. The patient was a former smoker with a past history of peptic ulcer disease, but was otherwise fit and well. He denied any use of nonsteroidal anti-inflammatory drugs, but did admit to an alcohol intake of approximately 40 units per week. He was hemodynamically stable and, other than fresh red blood on digital rectal examination, there were no clinical findings of note. Laboratory tests on admission revealed a hemoglobin concentration of 11.5 g/dL (normal, 13–18 g/dL), with normal liver function tests. The level of serum amylase was mildly raised at 257 IU/L (normal, <110 IU/L). Urgent upper gastrointestinal (GI) endoscopy was undertaken as the first-line investigation. Although this showed a small amount of blood in the duodenum, it failed to identify an obvious source of bleeding. The patient had 3 further episodes of bleeding over the next month. No abnormality was detected at colonoscopy or on technetium Tc99m–pertechnetate scintography (Meckel’s scan). Dual-phase computed tomography (CT) of the abdomen showed coarse calcification of the pancreas, in keeping with a diagnosis of chronic pancreatitis (Image A, labeled 1). Endoscopic ultrasonography was reported as normal. Six weeks after the initial presentation, he presented again with hematochezia associated with a fall in hemoglobin concentration to 7.3 g/dL. Repeat upper GI endoscopy with a side-viewing endoscope demonstrated fresh blood in the distal duodenum with a blood clot at the ampulla of Vater (Image B). An urgent mesenteric angiogram was requested (Image C), and revealed a vascular malformation (labeled 2). What is the most likely diagnosis?View Large Image Figure ViewerDownload Hi-res image Download (PPT) Hemosuccus pancreaticus (HP), defined as the loss of blood into the GI tract via the main pancreatic duct, is an important, although rare, cause of upper GI hemorrhage.1Wagner W.H. Cossman D.V. Treiman R.L. et al.Hemosuccus pancreaticus from intraductal rupture of a primary splenic artery.J Vasc Surg. 1994; 19: 58-64Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar In this case, the source was a saccular aneurysm of the splenic artery, most probably a pseudoaneurysm secondary to previous acute pancreatitis (labeled 2 on Image C). First described by Lower and Farrell in 1931, HP, alternatively termed wirsungorrhea, is most commonly observed on a background of chronic calcific pancreatitis.2Camishion R.C. Pello M.J. Spence R.K. et al.Hemoductal pancreatitis.Surgery. 1992; 111: 86-89PubMed Google Scholar The principal presenting feature is epigastric pain, which immediately precedes the onset of overt GI bleeding. Intermittent bleeding is characteristic due to clot formation within the pancreatic duct.1Wagner W.H. Cossman D.V. Treiman R.L. et al.Hemosuccus pancreaticus from intraductal rupture of a primary splenic artery.J Vasc Surg. 1994; 19: 58-64Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar, 2Camishion R.C. Pello M.J. Spence R.K. et al.Hemoductal pancreatitis.Surgery. 1992; 111: 86-89PubMed Google Scholar In most cases, bleeding occurs secondary to rupture of an arterial pseudoaneurysm,3Negi S.S. Sachdev A.K. Bhojwani R. et al.Experience of surgical management of pseudo-aneurysms of branches of the coeliac axis in a North Indian Hospital.Trop Gastroenterol. 2002; 23: 97-100PubMed Google Scholar although it may also originate from true aneurysmal vessels or from hemorrhage within the pancreas itself.1Wagner W.H. Cossman D.V. Treiman R.L. et al.Hemosuccus pancreaticus from intraductal rupture of a primary splenic artery.J Vasc Surg. 1994; 19: 58-64Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar The diagnosis of HP usually requires several investigations, including endoscopic retrograde cholangiopancreatography, abdominal CT, and angiography.1Wagner W.H. Cossman D.V. Treiman R.L. et al.Hemosuccus pancreaticus from intraductal rupture of a primary splenic artery.J Vasc Surg. 1994; 19: 58-64Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar In this patient, mesenteric angiography (Image D) identified an eccentric aneurysm of the distal splenic artery with active bleeding into the pancreatic duct (labeled 3). The splenic artery saccular aneurysm was occluded by coil embolization of the splenic artery distal and proximal to the aneurysm (Image E).1Wagner W.H. Cossman D.V. Treiman R.L. et al.Hemosuccus pancreaticus from intraductal rupture of a primary splenic artery.J Vasc Surg. 1994; 19: 58-64Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar Coils in the proximal splenic artery alone would have been ineffective as the aneurysm would continue to fill via collaterals and retrograde flow. The same collaterals maintain splenic viability. The patient went on to make an uneventful recovery, and has not experienced any further episodes of acute upper GI bleeding.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Nodular pseudoangiomatous stromal hyperplasia of mammary stroma in a case showing rapid tumor growth

Pseudoangiomatous stromal hyperplasia (PASH) is an uncommon benign breast disease that presents as a localized breast mass. Breast tissue affected by PASH is characterized by a dense, collagenous proliferation of mammary stroma, forming interanastomosing capillary-like spaces. The importance of this benign lesion lies in distinguishing it from low grade angiosarcoma. We report a case of a 38-year-old woman who presented with a rapidly growing breast tumor. She visited our hospital with a complaint of a painless right breast mass. Physical examination revealed a 3.6 x 2.2 cm, oval, elastic-firm, well-defined and easily movable mass. Mammograms revealed no discrete mass or calcifications. Sonographic examination revealed a 3.5 x 2.5 x 2.2 cm, oval, well-defined and homogenous hypoechoic mass without a cyst. A fine-needle aspiration sample of the breast mass showed some clusters of epithelial cells with small papillary structures and many scattered stromal cells with naked nuclei. Based on these findings, a provisional diagnosis of fibroadenoma was made and the patient was followed up. One year after the first visit, the mass enlarged rapidly and a follow-up mammogram revealed an 8.2 x 5.5 cm circumscribed mass without calcifications. Given the history of rapid growth of the mass, tumor excision was performed. The excised tumor was well demarcated and had a smooth external surface. Histologic examination revealed normal breast ducts and lobules, and specific proliferative epithelial changes were not seen. The lobular and duct structure of the breast parenchyma were separated by an increased amount of stroma. The fibrous stroma contained numerous anastomosing slit-like spaces. Isolated spindle cells appeared intermittently at the margins of the spaces resembled endothelial cells. Immunohistochemical staining showed that endothelial cells lining true blood vessels were positive for Factor VIII-related antigen, but the spindle cells were negative for Factor VIII. Pseudoangiomatous stromal hyperplasia was diagnosed.

Spontaneous development of bilateral subdural hematomas in an infant with benign infantile hydrocephalus: color Doppler assessment of vessels traversing extra-axial spaces

We present an infant with macrocrania, who initially demonstrated prominent extra-axial fluid collections on sonography of the brain, compatible with benign infantile hydrocephalus (BIH). Because of increasing macrocrania, a follow-up sonogram of the brain was performed; it revealed progressive enlargement of the extra-axial spaces, which now had echogenic debris. Color Doppler US showed bridging veins traversing these extra-axial spaces, so it was initially thought that these spaces were subarachnoid in nature (positive cortical vein sign). However, an arachnoid membrane was identified superior to the cortex, and there was compression of true cortical vessels beneath this dural membrane. An MRI of the brain showed the extra-axial spaces to represent bilateral subdural hematomas. The pathogenesis of spontaneous development of the subdural hematomas, in the setting of BIH, is discussed. We also emphasize that visualizing traversing bridging veins through extra-axial spaces does not necessarily imply that these spaces are subarachnoid in origin.

Laparoscopic Excision of Symmetric Uterine Remnants in a Patient with Mayer-Rokitansky-Ku¨ster-Hauser Syndrome

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is an infrequent developmental defect characterized by congenital absence of the vagina and uterus. Various anomalies of the müllerian system have been operated on by laparoscopy. We performed operative laparoscopy to remove symmetric uterine remnants and right ovarian endometrioma in a woman with MRKH syndrome who suffered from intractable lower abdominal pain. Both anomalous structures, which had true uterine vessels, were located on their respective pelvic sidewalls close to the ureters. We suggest that operative laparoscopy can be performed safely to treat these patients, but careful identification and dissection of the main blood supply, if necessary, are of substantial importance in order to avoid ureteral injury.

Examining microcirculation improves the angiosome theory in explaining the delay phenomenon in a rabbit model.

Topographic and temporal changes in circulation were studied with laser Doppler flowmetry in rabbit dorsal skin flaps comprised of three vascular territories. The reduced caliber vessels along the dorsal median line, rather than the vessels interconnecting the thoracodorsal and deep circumflex iliac vascular trees, behaved as true choke vessels. The authors found an increased proximal circulation lasting for 48 to 72 hr. This coincided with the reported rapid phase of choke vessel dilatation. The increase in distal circulation began after postoperative day 3, coinciding with the resolution of proximal hyperemia but not with the earlier prominent vasodilatation. Secondary elevation of the flaps at 3 weeks did not disturb the homogeneous distribution of circulation and did not cause a hyperemic response at postoperative 24 hr. Based on these findings, the authors postulate that the same mechanisms may underlie the rapid choke vessel dilatation and microvascular dilatation observed at 48 to 72 hr postoperatively. Surgical delay may work not only by diminishing the resistance to blood flow along the flap, but also by diminishing the steal effect of increased proximal microcirculation, which characterizes this period, over the distal circulation.

Endoscopy databases and endoscopic research

Endoscopy databases and endoscopic research

Intestinal blood flow is controlled by both feed arteries and microcirculatory resistance vessels in freely moving rats.

1. In freely moving rats, intestinal blood flow, aortic blood pressure and blood pressure at the base of mesenteric arcades were measured simultaneously so as to determine the role of feed arteries and of the microcirculation in the control of intestinal vascular resistance. Segmental resistances of feed arteries (Rfeed) and of microcirculatory vessels (Rmicro) were calculated. 2. At rest, Rfeed and Rmicro were 32 and 68%, respectively, of the total intestinal vascular resistance. 3. Injection of noradrenaline (2 micrograms i.v,) increased Rfeed by 151% and Rmicro by 243%. Angiotensin II (400 ng i.v.) did not increase Rfeed significantly, but increased Rmicro by 239%. Conversely, serotonin (15 micrograms i.v.) increased Rfeed by 414% but did not affect Rmicro significantly. 4. Spontaneous physical activity increased Rfeed by 29% and Rmicro by 39%, while sudden environmental stress increased Rfeed by 116% and Rmicro by 129%. Infused noradrenaline (1 microgram min-1 i.v.) or adrenaline (0.8 microgram min-1 i.v.) reduced intestinal flow by 21 and 16% respectively, while noradrenaline, but not adrenaline, increased intestinal resistances. 5. alpha 1-Blockade with prazosin (0.1 mg i.v.) reduced Rfeed and Rmicro by 43 and 16%, respectively. Thereafter, environmental stress decreased Rfeed by 24% while Rmicro was unaffected. Intravenous noradrenaline and adrenaline responses were attenuated. 6. We conclude that in freely moving rats, mesenteric feed arteries, as well as microcirculatory vessels, are true resistance vessels, and that both participate in the control of intestinal blood flow.

Periarterial lymphoid sheath in the rat spleen: a light, transmission, and scanning electron microscopic study.

The periarterial lymphoid sheath (PALS) in the rat spleen was studied by light, transmission, and scanning electron microscopy. The PALS was divided into three regions: the central region, peripheral region, and marginal zone bridging channel. In the central region, lymphocytes were easily washed away by perfusion. Large spaces were found between flat reticular cells or in large meshworks of stellate reticular cells; these may be deep lymphatic vessels. True lymphatic vessels were found in the central region near the hilus. In the marginal zone bridging channel, flat reticular cells surrounded the central artery in a circumferential pattern and formed channel-like spaces between the flat reticular cells. These spaces were connected with the meshwork of the red pulp reticular cells and may be a route for lymphocytes between the deep lymphatic vessels and the red pulp. In the peripheral region of the PALS, it was usually difficult to wash away free cells by perfusion, and free cells were found among the reticular cells. In places in the peripheral region, however, free cells were washed away. It is suggested that the lymph flow may start from the region surrounding the PALS, and that the peripheral region of the PALS may also be another route for lymphocyte migration.

Microvascular ultrastructure in non-freezing cold injuries

The effects of repeated local exposure to cold on the integrity of the subcutaneous microcirculation were studied in a model using a transparent tissue chamber implanted into a dorsal skin fold of Syrian hamsters. A detailed study of the vascular ultrastructure within the chamber revealed the following features: Endothelial damage was prominent in true capillaries and venous vessels, while arterioles remained unaffected. The endothelial lining appeared extremely attenuated around the entire vascular perimeter causing the development of "gaps", some of which contained leukocytes or platelets. Smaller vessels were often completely filled with blood cells with leukocytes integrated into the endothelial wall. Fibrin was never observed within these occluded vessels. Finally, only veil-like remnants of the endothelium persisted, and compressed erythrocytes were still mimicking the original vascular outline. It is concluded that the ultrastructural changes observed after a repeated non-freezing cold injury closely resemble those observed during ischemia/reperfusion injury.

An immunohistochemical and ultrastructural study of the sinusoids of hepatocellular carcinoma

The sinusoids of 30 human hepatocellular carcinomas of various types were examined by electron microscopy and histochemically for binding to the Ulex europaeus lectin (UEA1). A population of sinusoidal macrophages was identified with an antibody to lysozyme (muramidase). The UEA1 binding was negative in normal sinusoids but positive in the tumor vessels. Macrophages resembling Kupffer cells were found within the tumor vessels but in smaller numbers than in either normal or cirrhotic liver tissue. Fibrolamellar and sclerosing carcinomas contained the smallest numbers. Ultrastructurally, endothelial cells of tumor vessels were thicker than normal, with fewer fenestrations. They contained bundles of microfilaments and showed basement membrane formation. Subendothelial myoid cells were found. These findings indicate that the sinusoidal vessels of hepatocellular carcinomas show features of true capillaries and precapillary blood vessels. The degree of this difference from normal hepatic sinusoids may reflect the relative immaturity of the cancer cells.

Perfused rat intestine for study of norepinephrine release.

Previous preparations for studying the neuronal release of norepinephrine (NE) employed relatively large vessels, nonsanguinous perfusates, and the preloading of [3H]NE. To study the stimulated release of endogenous NE and the responses of true resistance vessels, we developed a rat intestine preparation that is pump perfused with canine red blood cells suspended in bicarbonate buffer with 6% albumin. In a pentobarbital-anesthetized rat, the duodenum, colon, and cecum are extirpated to isolate the ileum vascularly. After the superior mesenteric artery and vein are cannulated, the perivascular nerves are isolated to stimulate the postganglionic sympathetic fibers. To evaluate the preparation, we stimulated the sympathetic fibers at 1-10 Hz with supramaximal pulses. Resistance changes were assessed by monitoring perfusion pressure, and the concentration of NE was assayed in the venous effluent by the single-isotope radioenzymatic method. During nerve stimulation, the increases in both resistance and NE release rate were frequency dependent. Repetitions of electrical stimulation yielded reproducible frequency-response curves. Pretreatment with phentolamine (10 microM) abolished the resistance response and enhanced stimulated NE release, which roughly tripled at 10 Hz. Phentolamine at smaller doses (1 microM) eliminated the resistance responses to stimulation but did not enhance NE release. Cocaine alone (30 microM) increased base-line resistance and unstimulated NE release. After cocaine pretreatment, phentolamine at 1 microM enhanced the stimulated NE release rate. We conclude that the isolated rat intestine contains postsynaptic alpha-adrenoceptors that mediate vasconstriction and prejunctional alpha 2-adrenoceptors that mediate the inhibition of NE release. Thus the rat intestine is a responsive preparation for studying the release of endogenous NE and noradrenergic neurotransmission.

Animal models to investigate drug effects on coronary physiology

AbstractCoronary blood flow is regulated by local intrinsic mechanisms according to the oxygen need of the myocardium, but the coronary circulation is also modulated by nervous, humoral, and extravascular influences. Therefore, any method used to study drug effects on the coronary circulation must take into account not only the direct effects of the drug but also any secondary drug effects that might indirectly influence the coronary vasculature. The simplest methods involve the use of isolated vessels. With these methods, the environment of the vessel can be precisely controlled, although usually only vessels larger than true resistance vessels can be studied. Isolated heart models have also been successfully employed, and in these models, effects of the drug on the myocardium must be considered. More complex models include in vivo anesthetized animal techniques with intracoronary drug administratiorl. With these models, drug effects on the coronary circulation as well as on other cardiac variables can be examined. The use of conscious, instrumented animals perhaps provides the most physiologic preparation and is very useful, particularly if intracoronary administration of drugs is employed.

The caudal heart of fish: not a lymph heart.

The caudal heart is traditionally regarded as part of the lymphatic vessel system in fish. Recently, however, a secondary blood vessel system has been demonstrated in this class of vertebrates, while the existence of lymphatics was questioned. In corrosion cats of the secondary system it is shown that the caudal heart functions as a venous pump in the secondary circulation. Contrary to current views fish do not have true lymphatic vessels. Theories on the phylogeny of lymphatics therefore should be revised accordingly.

Structural factors: the vascular wall. Consequences of treatment.

Like all tissues, blood vessels readily adapt their structure upon sustained functional changes. For example, pressure increases soon induce a largely proportional wall (w) thickening, where arteries, veins, and true resistance vessels respond alike. The latter also show a modest structural narrowing of average inner radius (ri), where the increased w/ri ratio results in a geometrically based vascular hyperreactivity. In primary hypertension, this type of precapillary resistance vessel adaptation implies an important "upward structural autoregulation" of systemic resistance, which is thereby kept increased also when vascular smooth muscle activity is entirely normal. Further, the systemic vascular hyperreactivity introduces a positive feedback interaction with functional pressor influences. By this mechanism, even marginal increases in "functional drive" may, if only sustained, steadily enhance the structural w/ri increase until it dominates hemodynamics. Similar alterations of the renal preglomerular vessels cause an early upward resetting of the renal barostat function, while wall thickening of large arteries helps to reset the baroreflexes. Also, the capacitance vessels show some structural adaptation that reduces venous compliance and contributes to blood volume centralization. Due to this overall structural resetting of hypertensive cardiovascular systems, the pharmacological problem of normalizing blood pressure is not one of merely damping an increased vascular smooth muscle activity. The task is more formidable, because effector cell activity must be kept even subnormal, despite counterregulatory mechanisms. These mechanisms almost all have been redesigned to maintain the high pressure state, with the long-range goal that true regression toward normality should ultimately ensue.