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PubMed1996

Selection of appropriate recipient vessels in difficult, microsurgical head and neck reconstruction.

In a series of 327 cases of head and neck microsurgical reconstruction during 22 years beginning in 1974, the authors have reviewed 16 cases in which the first choice of recipient vessels was not available. The problems of selecting alternative and appropriate recipient vessels are discussed. Recipient vessels could be classified into three groups: adjacent small vessels that are usually considered to be the first choice; major vessels; and distant vessels. A correlation between the selection of substitute vessels and the region of reconstruction was found. Representative cases in each category are presented. In difficult cases in freeflap transfer, it is of prime importance to select healthy recipient vessels. Additionally, special precautions, including choice of anastomotic technique, are required.

Adult↗
PubMed1997

Wavelengths for port wine stain laser treatment: influence of vessel radius and skin anatomy.

Recent Monte Carlo computations in realistic port wine stain (PWS) models containing numerous uniformly distributed vessels suggest equal depth of vascular injury at wavelengths of 577 and 585 nm. This finding contradicts clinical experience and previous theory. From a skin model containing normal and PWS vessels in separate dermal layers, we estimate analytically the average volumetric heat production in the deepest targeted PWS vessel. The fluence rate distribution is approximated by Beer's law, which depends upon the tissue's effective attenuation coefficient, and includes a homogeneous fractional volumetric blood concentration corrected for finite-size blood vessels. The model predicts 585-587 nm wavelengths are optimal in adult PWSs containing at least one layer of small-radius blood vessels. In superficial PWSs, typically in young children with small-radius vessels, 577-580 nm wavelengths are optimal. Wavelength-independent results similar to those from Monte Carlo models are valid in single-layered PWSs of large-radius vessels. In conclusion, the volumetric heat production in the deepest targeted PWS blood vessel can be maximized on an individual patient basis. However, absorption of 585-587 nm wavelengths is sufficiently high in superficial lesions, so we hypothesize that these wavelengths may be considered adequate for the treatment of any PWS.

Adult↗
PubMed1999

Three-dimensional structure of the micro-blood vessels in thyroid tumors analyzed by immunohistochemistry coupled with image analysis.

The structure of micro-blood vessels, one of the most important factors influencing the tumor growth and tumor metastasis among histological types of thyroid malignancy, was analyzed immunochemically by staining tissues for platelet endothelial cell adhesion molecule-1 (PECAM-1). Human thyroid tumor tissue obtained at surgery, consisting of 18 cases of papillary carcinoma, 9 cases of follicular carcinoma, and 9 cases of anaplastic carcinoma were fixed in formalin solution, and paraffin sections were made. They were stained for PECAM-1 using the avidin-biotin complex (ABC) technique. The volume of the blood vessels and their three-dimensional (3D) structure were analyzed using an image analyzer. The volume ratios of blood vessels in thyroid tissues were: normal tissues, 1.10%; papillary carcinoma, 3.01%; follicular carcinoma, 8.13%; and anaplastic carcinoma, 0.91%. Ratios in malignant tumors were larger than in normal tissues, except for anaplastic carcinoma. The typical 3D structure of micro-blood vessels was histopathologically varied: branching tree-like blood vessels in papillary carcinomas; vessels of varied diameter surrounding follicle structure in follicular carcinomas; and simple and immature vessels in anaplastic carcinomas. The volume and 3D structure of micro-blood vessels in thyroid malignant tumors differed from those in normal tissues, and varied according to histological classification.

Adenocarcinoma, Follicular↗
PubMed1986

Neonatal sympathectomy of normotensive Wistar-Kyoto and spontaneously hypertensive rats with 6-hydroxydopamine: effects on resistance vessel structure and sensitivity to calcium.

6-Hydroxydopamine (6-OHDA) was injected on alternate days from birth to 3 weeks of age into spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) control rats. The effects of this neonatal treatment on cardiovascular structure and mesenteric resistance vessel calcium sensitivity was studied in young (6 week) and adult (5 month) rats. Mean arterial pressure of treated SHRs and WKYs was reduced by 10% compared with control rats, but the heart:body weight ratio was unaffected by treatment. Both pharmacological and histological studies suggested that at 6 weeks of age, mesenteric resistance vessels from treated WKYs were completely denervated, but that vessels from treated SHRs still had sparse innervation. At 5 months all vessels from the treated rats had some adrenergic innervation, but less than the control rats. In the WKYs, treatment was associated with reduced media:lumen ratio and reduced calcium sensitivity of the mesenteric resistance vessels, while no such changes were observed in the SHR vessels. The results indicate that the sympathetic nervous system in SHRs is more resistant to chemical denervation than the sympathetic nervous system of the WKYs. The results also suggest that sympathetic innervation of mesenteric resistance vessels may affect vessel structure and sensitivity.

Animals↗
PubMed1988

Resistance vessel structure and function in the etiology of hypertension studied in F2-generation hypertensive-normotensive rats.

The role of certain resistance vessel characteristics in the etiology of hypertension has been investigated using F2-generation hypertensive/normotensive rats. The F2 populations were bred from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) as well as from stroke-prone SHR (SHRSP) and outbred Wistar-Kyoto rats (WKYO), and are denoted SHR/WKY and SHRSP/WKYO, respectively. Mesenteric resistance vessels (lumen diameter ca 200 micron) were taken from rats in the highest and lowest blood pressure quartiles of 14-week SHR/WKY and 18-week SHRSP/WKYO, as well as from 15-week pure SHR and WKY and from 18-week pure SHRSP and WKYO. The vessels were mounted on a myograph for determination of their structural and contractile characteristics. The structure of the vessels, as expressed for example by their media : lumen ratio, was greatest in the vessels from the SHR and the SHRSP compared to those from the WKY and WKYO. Increased structure was seen in the vessels from the rats in the high blood pressure quartiles of each group of F2 populations, compared to the vessels from the rats in the low blood pressure quartiles, although in the SHR/WKY the difference was smaller than expected if structure were a major determinant of blood pressure. Vascular sensitivity to calcium and the effect of cocaine on noradrenaline sensitivity were increased in the vessels from the SHR and SHRSP, but were the same in the high and low blood pressure quartiles of the F2 populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Estimation of vessel flow and diameter during cerebral vasospasm using transcranial Doppler indices.

OBJECTIVE: An important limitation of transcranial Doppler (TCD) ultrasonography is its inability to directly measure blood flow or vessel diameter. To extend the ability of TCD ultrasonography, indices were derived from an intensity-weighted mean of the entire Doppler spectrum. The objective of this article is to test the behavior of these indices under conditions of diameter constancy (hyper- and hypoventilation) and when vessel diameter decreases (vasospasm). METHODS: A flow index (FI) was calculated by averaging several heartbeats of spectral data and calculating the first spectral moment. An area index (AI) was defined as the FI divided by the mean velocity, motivated by the knowledge that vessel flow is the product of vessel diameter and mean velocity. To test the FI and the AI under conditions of diameter constancy, middle cerebral artery Doppler signals were obtained from 20 patients during conditions of hypercarbia, hypocarbia, and normocarbia. To test the ability of these indices to evaluate a decrease in vessel diameter, signals from 41 sites on 23 arteries were obtained from patients who underwent both TCD and angiographic studies on two separate occasions after the occurrence of subarachnoid hemorrhage. The changes in the AI were compared with the arterial diameters measured from angiograms. RESULTS: The FI was proportional to the mean velocity in the cohort of healthy patients (r=0.97). The AI changed by less than 3% in the same cohort. The AI predicted the direction of the diameter change in all vessels showing angiographic changes in area. Changes in the AI and the measured angiographic changes in cross-sectional areas were correlated (overall, r=0.90; with two outlines removed, r=0.86). CONCLUSION: This variant of the intensity-weighted mean predicts changes in vessel cross-sectional area under conditions of changes in CO2 and cerebral vasospasm. This preliminary study suggests that careful use of this tool may provide accurate evaluation of cerebral blood flow through the large vessels and quantitative changes in diameter, which occur frequently after subarachnoid hemorrhage.

Adult↗
PubMed2000

Cutaneous blood vessels in scent pigs.

The purpose of this study was to systematically provide anatomic data for flap research in plastic surgery on the cutaneous blood vessels. Seven scent pigs used in this study were killed anesthetically, and their carotid vessels were intubated and injected with a black liquid rubber. Twenty-four hours later, the integument of the scent pig was removed, and the perforating points of the cutaneous vessels were recorded. The different-sized pieces of integument became transparent. Part of this transparent skin tissue was cut into cross-sectional strips. There were three types of the cutaneous vascular source, the same as in humans. Six division levels of vessels in the skin were identified, which formed five vascular plexuses and two systems (the perforating vessel system and the cutaneous vessel system). There were two sets of vein systems: the concomitant vein and the oscillating vein; the latter can be divided into regular and irregular types. The structures of the perforating vessel system and the cutaneous vessel system were the morphological basis for choosing flaps. Two anatomic points have been emphasized: the preserved vascular plexus in thin flaps (not the subcutaneous vascular network reported previously) and the dependency of vascular structure on its location. Otherwise, this study has also provided two new kinds of flaps used in experimental study: the arterial loop flap and the intermuscular septal perforator flap. Although there were differences as well as similarities in skin vasculature between humans and the scent pig, the scent pig is still suitable for flap research.

Animals↗
PubMed2005

Use of ultrasonography and positron emission tomography in the diagnosis and assessment of large-vessel vasculitis.

PURPOSE OF REVIEW: Ultrasonography and positron emission tomography have been increasingly studied and, in part, introduced in clinical practice to diagnose large-vessel vasculitides, such as temporal arteritis, Takayasu arteritis, large-vessel giant cell arteritis, and isolated aortitis. RECENT FINDINGS: Ultrasonography reveals characteristic homogenous, concentric wall thickening in vasculitis, often combined with stenoses and, less frequently, with acute occlusions. Thirteen studies describe sensitivities of 40 to 100% (median, 86%) for temporal artery vessel wall edema compared with histology, and of 35 to 86% (median, 70%) compared with clinical diagnosis. If wall edema, stenoses, and occlusions are included, sensitivities increase to 91 to 100% (median, 95%) compared with histology, and to 83 to 100% (median, 88%) compared with clinical diagnosis. Specificities for wall edema are 68 to 100% (median, 93%) compared with histology, and 78 to 100% (median, 97%) compared with clinical diagnosis. One should be aware of large-vessel giant cell arteritis in all patients with temporal arteritis and polymyalgia rheumatica. Ultrasonography reveals characteristic wall thickening, particularly of the distal subclavian, axillary, and proximal brachial arteries. Findings in Takayasu arteritis are similar, but the vessel wall swelling is usually brighter. Positron emission tomography reveals vasculitis in arteries with a diameter of more than 4 mm. Ultrasonography and positron emission tomography agreed completely in the anatomic distribution of changes in patients with large-vessel giant cell arteritis. It reveals asymptomatic large-vessel vasculitis in giant cell arteritis and Takayasu arteritis. Positron emission tomography is not suitable for the assessment of temporal arteries. SUMMARY: Ultrasonography and positron emission tomography are new, promising techniques to assess large-vessel vasculitides.

Aortitis↗
PubMed2003

Evaluation of a vessel sealing system, bipolar electrosurgery, harmonic scalpel, titanium clips, endoscopic gastrointestinal anastomosis vascular staples and sutures for arterial and venous ligation in a porcine model.

PURPOSE: We assessed the usefulness of the LigaSure (Valleylab, Boulder, Colorado) vessel sealing system for vascular control during laparoscopic surgery and compared it with other available hemostatic modalities. MATERIALS AND METHODS: A total of 31 domestic pigs were divided into 5 groups. In groups 1 and 2 the vessel sealing system was compared with titanium clips and Endo-GIA (United States Surgical, Stamford, Connecticut) staples. In group 3 the vessel sealing system was compared with standard Klepinger (Karl Storz, Culver City, California) bipolar forceps. In group 4 the harmonic scalpel and Trimax (United States Surgical) bipolar forceps were compared. In group 5 in vivo laparoscopic application of the vessel sealing system was evaluated. RESULTS: The 5 mm. laparoscopic vessel sealing system sealed arteries up to 6 mm. and veins up to 12 mm. in diameter at supraphysiological bursting pressure. We evaluated 13 arteries with a diameter of 6 mm. or less at a mean bursting pressure of 662 mm. Hg (range 363 to 1,985) and 11 veins with a diameter of 12 mm. or less with a mean bursting pressure of 233 mm. Hg (range 63 to 440). Collateral tissue damage extended 1 to 3 mm. from the application site. Standard bipolar energy with Klepinger and Trimax forceps was less reliable and in some cases vessel sealing could not be accurately assessed before vessel division. Collateral tissue injury was 1 to 6 mm. The harmonic scalpel did not reliably seal vessels larger than 3 mm. but resulted in the least acute collateral tissue injury of 0 to 1 mm. CONCLUSIONS: In the porcine model the LigaSure system is a viable option for laparoscopic management of arteries up to 6 mm. and veins up to 12 mm. in diameter.

Anastomosis, Surgical↗
PubMed2004

Calponin h1 expression in renal tumor vessels: correlations with multiple pathological factors of renal cell carcinoma.

PURPOSE: We determined whether the architecture of renal tumor vessels is immunohistochemically different from that of normal renal vessels and related to the various pathological factors that affect prognosis of renal cell carcinoma (RCC). MATERIALS AND METHODS: A total of 52 cases of primary RCC were selected. Tissues from radical nephrectomy specimens were stained with antibody to alpha-smooth muscle actin (alpha-SMA) and calponin h1. Immunostaining was evaluated semiqualitatively as 0-no staining to 3+-strong staining. Tumor cell proliferation was observed using proliferating marker Ki-67. Data were statistically compared with pathological factors, such as tumor size, histological pattern, growth pattern, cell type, nuclear grade, pathological stage and presence or absence of venous invasion. RESULTS: In normal renal tissues smooth muscle cells of the blood vessels showed strong immunoreactions with antibody to calponin h1 and alpha-SMA. Although alpha-SMA antibody showed similar strong immunoreactions in all types of renal tumor vessels, we observed qualitative alterations in the expression of calponin h1 in different types of RCCs. Strong to moderate immunoreactions with calponin h1 were observed in tumors with expansive growth and an alveolar pattern. Small tumors without venous invasion and chromophobe cell carcinomas also showed strong to moderate expression of calponin h1. Weak or absent expression of calponin h1 was observed significantly in infiltrating tumors, sarcomatous type, large, high grade and high stage tumors associated with significantly higher proliferating indexes. CONCLUSIONS: Our results strongly suggest that the renal tumor vessels are immunohistochemically different from normal renal vessels in respect to calponin h1 expression. We speculate that due to the decrease in or absence of calponin h1 tumor vessels do not develop adequate maturity to maintain vascular integrity. In addition, the distribution of calponin h1 significantly correlated with multiple pathological factors of RCC. Therefore, calponin h1 expression in renal tumor vessels could be a new, important pathological factor in RCC.

Adult↗
PubMed2002

Characteristics of tumors in lymph vessels play an important role in the tumor progression of invasive ductal carcinoma of the breast: a prospective study.

It is unknown whether the characteristics of tumor cells in lymph vessels play an important role in the tumor progression of invasive ductal carcinoma (IDC) of the breast. The purpose of this study was to investigate the significance of the characteristics of tumor cells in the lymph vessels in relation to the tumor progression in 393 IDC patients in comparison with well-known histological parameters. The dimensions of lymph vessel tumor emboli were measured, and their structural features, nuclear atypia, and numbers of mitotic and apoptotic figures were also assessed. Multiple regression analysis showed the dimension, the distance, the number of mitotic figures, the number of apoptotic figures, and papillary features of lymph vessel tumor emboli to be significantly associated with the increased number of cells invading the lymph vessels (P < .05). The Cox proportional hazard multivariate analyses showed that more than six apoptotic figures in lymph vessel tumor emboli significantly increased the hazard rates (HRs) of tumor recurrence and death in IDCs without nodal metastasis and that more than four mitotic figures in lymph vessel tumor emboli significantly increased the HRs of tumor recurrence and death in IDCs with nodal metastasis (P < .05). The present study showed that the histological characteristics of tumor cells in lymph vessels play a very important role in the tumor progression of IDCs.

Adult↗
PubMed2003

Alternative venous outflow vessels in microvascular breast reconstruction.

The lack of adequate recipient vessels often complicates microvascular breast reconstruction in patients who have previously undergone mastectomy and irradiation. In addition, significant size mismatch, particularly in the outflow veins, is an important contributor to vessel thrombosis and flap failure. The purpose of this study was to review the authors' experience with alternative venous outflow vessels for microvascular breast reconstruction. In a retrospective analysis of 1278 microvascular breast reconstructions performed over a 10-year period, the authors identified all patients in whom the external jugular or cephalic veins were used as the outflow vessels. Patient demographics, flap choice, the reasons for the use of alternative venous drainage vessels, and the incidence of microsurgical complications were analyzed. The external jugular was used in 23 flaps performed in procedures with 22 patients. The superior gluteal and transverse rectus abdominis musculocutaneous (TRAM) flaps were used in the majority of the cases in which the external jugular vein was used (72 percent gluteal, 20 percent TRAM flap). The need for alternative venous outflow vessels was usually due to a significant vessel size mismatch between the superior gluteal and internal mammary veins (74 percent). For three of the external jugular vein flaps (13 percent), the vein was used for salvage after the primary draining vein thrombosed, and two of three flaps in these cases were eventually salvaged. In three patients, the external jugular vein thrombosed, resulting in two flap losses, while the third was salvaged using the cephalic vein. A total of two flaps were lost in the external jugular vein group. The cephalic vein was used in 11 flaps (TRAM, 64.3 percent; superior gluteal, 35.7 percent) performed in 11 patients. In five patients (54.5 percent), the cephalic vein was used to salvage a flap after the primary draining vein thrombosed; the procedure was successful in four cases. In three patients, the cephalic vein thrombosed, resulting in two flap losses. One patient suffered a thrombosis after the cephalic vein was used to salvage a flap in which the external jugular vein was initially used, leading to flap loss, while a second patient experienced cephalic vein thrombosis on postoperative day 7 while carrying a heavy package. There was only one minor complication attributable to the harvest of the external jugular or cephalic vein (small neck hematoma that was aspirated), and the resultant scars were excellent. The external jugular and cephalic veins are important ancillary veins available for microvascular breast reconstruction. The dissection of these vessels is straightforward, and their use is well tolerated and highly successful.

Anastomosis, Surgical↗
PubMed2004

Sequential vascularized iliac bone graft and a superficial circumflex iliac artery perforator flap with a single source vessel for established mandibular defects.

The major problems in dealing with established mandibular loss are severe soft-tissue contracture and a limited number of recipient vessels. The skin portion of the iliac osteocutaneous flap often necrotizes in cases without perforators of the deep circumflex iliac vessel. To overcome these problems, eight patients with established mandibular loss and no skin perforators of the deep circumflex iliac vessel were treated with a sequential vascularized iliac bone graft and a superficial circumflex iliac perforator flap with a single recipient vessel. Regarding the recipient vessels, the ipsilateral cervical vessels were used for four patients, and the contralateral facial and ipsilateral superficial temporal vessels were used for two cases each. The superficial circumflex iliac perforator flaps were 7 to 28 cm in length and 3 to 15 cm in width. The iliac bone grafts ranged from 7 to 13 cm in length, and three cases were repaired with the inner cortex of the iliac bone. There were no serious complications, such as flap necrosis or bone infection and resulting absorption. The advantages of this method are that both pedicles are very close to each other and of suitable diameter for anastomosis. Simultaneous flap elevation and preparation for the recipient site is possible. The skin flap and vascularized bone graft can be obtained from the same donor site. A single source vessel can nourish both the large skin area and bone sequentially. Longer dissection of the superficial circumflex iliac system to the proximal femoral division is unnecessary. A large flap can survive with a short segment of the superficial circumflex iliac system. Only the vascularized inner cortex of the iliac bone needs to be used, and the outer iliac cortex can be preserved, which results in less morbidity at the donor site.

Adult↗
PubMed1979

Kinetics of l-Alanine Escape from Xylem Vessels.

Labeled ((3)H or (14)C) l-alanine was perfused through the xylem vessels of isolated tomato internodes (Lycopersicon esculentum cv. Moneymaker) at various concentrations (10(-6) molar to 10(-2) molar). At each concentration the escape of l-alanine from the xylem vessels was apparently a first order process, which is in agreement with Horwitz' (1958, Plant Physiology 33:81-93) model for irreversible escape from the xylem vessels. The escape constant (K) decreased at higher concentrations of l-alanine, which implies that Horwitz' model is inappropriate to describe the kinetics of l-alanine escape, and that the escape at least partly is a saturable process. To obtain data that relate the concentration of l-alanine in the xylem vessels and the escape rate of the amino acid, average escape rates per internode were measured and the corresponding concentrations were calculated from the integrated form of the Michaelis-Menten equation.AS THE CONCENTRATION DEPENDENCE OF THE ESCAPE RATE WAS BIPHASIC, THREE POSSIBLE MECHANISMS WERE CONSIDERED, ESCAPE BEING CAUSED BY: (a) saturable amino acid uptake of cells around the xylem vessels and diffusion into the free space; (b) saturable uptake of the cells around the xylem vessels, but at higher amino acid concentrations in the xylem vessels the number of cells, that participate in the uptake, increases; (c) two, simultaneously operating, saturable uptake systems in the cells around the xylem vessels.

Journal Article↗
PubMed2005

Vessel tree reconstruction in thoracic CT scans with application to nodule detection.

Vessel tree reconstruction in volumetric data is a necessary prerequisite in various medical imaging applications. Specifically, when considering the application of automated lung nodule detection in thoracic computed tomography (CT) scans, vessel trees can be used to resolve local ambiguities based on global considerations and so improve the performance of nodule detection algorithms. In this study, a novel approach to vessel tree reconstruction and its application to nodule detection in thoracic CT scans was developed by using correlation-based enhancement filters and a fuzzy shape representation of the data. The proposed correlation-based enhancement filters depend on first-order partial derivatives and so are less sensitive to noise compared with Hessian-based filters. Additionally, multiple sets of eigenvalues are used so that a distinction between nodules and vessel junctions becomes possible. The proposed fuzzy shape representation is based on regulated morphological operations that are less sensitive to noise. Consequently, the vessel tree reconstruction algorithm can accommodate vessel bifurcation and discontinuities. A quantitative performance evaluation of the enhancement filters and of the vessel tree reconstruction algorithm was performed. Moreover, the proposed vessel tree reconstruction algorithm reduced the number of false positives generated by an existing nodule detection algorithm by 38%.

Adult↗
PubMed2005

Morphometric assessment of collagen accumulation in germinal matrix vessels of premature human neonates.

Germinal matrix haemorrhage in premature neonates is commonly attributed to vascular immaturity, possibly related to an abbreviated process of angiogenesis. Terminal steps in the progression of angiogenesis are the formation of a subendothelial basal lamina containing collagen IV and an extracellular matrix containing collagens I and III. Immature vessels would predictably be deficient in these collagen subtypes. We analysed germinal matrix (GM), cortical, and white matter (WM) vessels with antibodies specific for collagens I, III and IV to test the hypothesis that GM vessels are immature. Brains were collected during post-mortem from prematurely born human neonates ranging in age from 17 weeks to 36 weeks postconception. All GM vessels were immunoreactive for collagen subtypes I, III and IV. Using digital image analysis, collagen IV immunoperoxidase-labelling was measured in vessels in GM, cortex and WM. Intensity values in GM and WM were normalized relative to cortical intensity within the same subject. At week 17 of gestation, GM vessels exhibited a higher concentration of collagen IV than did WM or cortical vessels. Regression analysis demonstrated that collagen intensity in GM was greater than that in cortex and WM at all stages. We conclude that GM vessels in even the youngest, prematurely born, viable neonates do not exhibit evidence of structural immaturity. The high incidence of GM haemorrhage in premature neonates may be related to factors other than a deficiency in accumulated collagen.

Brain↗
PubMedDate not supplied

Corneal vascularization in the Florida manatee (Trichechus manatus latirostris) and three-dimensional reconstruction of vessels.

The cornea of the Florida manatee is unique and unusual in its anatomy in that blood vessels have been found throughout. In all other animal species, this is considered a pathological condition impeding vision, and is usually caused by injury or trauma. The purpose of this study was to more clearly describe corneal vascularization by examining the architecture through three-dimensional reconstruction in order to find possible patterns in size, distribution, and location of blood vessels relative to gender, age, location, and season. Twenty-six eyes from 22 individuals were prepared for histologic examination and subsequent three-dimensional reconstruction. Every specimen examined had blood vessels in the cornea, comprising an average of 0.3% of total surface density (volume) of the cornea. No differences were found between individuals based on gender, age, and season. Environmental influences were not a significant factor either, which was not originally anticipated. The presence of vessels at the level of the anterior epithelium was surprising and it appeared that the vascularization was directed more anteriorly than was originally thought. The presence of blood vessels in a prenatal eye was also found. In all the eyes examined, no signs of injury or trauma could be observed. The presence of blood vessels appears to minimally impair vision based on their low density, size, and location. The association of vessels with the anterior epithelium and development of vessels within the fetus point to an evolutionary adaptation possibly due to the manatee's unique ability to move between water bodies.

Animals↗
PubMed1980

An increased calcium sensitivity of mesenteric resistance vessels in young and adult spontaneously hypertensive rats.

1. We have measured the calcium sensitivity in response to noradrenaline stimulation and potassium depolarization of isolated segments of 100 to 200 micrometer mesenteric resistance vessels from spontaneously hypertensive (SHR) and control Wistar-Kyoto rats. The rats were either young (4 wk) or adult (4 months), that is of ages before or after the SHRs had developed elevated blood pressure. Experiments were performed under conditions in which the effect of noradrenaline uptake by, and the potassium-induced noradrenaline release from, the nerve terminals in the vessel walls was eliminated. 2. The response of the SHR and WKY vessels to noradrenaline under conditions where only the extracellular calcium appeared to have been removed was similar. When subsequently stimulated maximally by noradrenaline, the calcium-sensitivity of the SHR vessels (Ca-ED50 approximately or equal to 0.1 mM) was greater than that of the WKY vessels (Ca-ED50 approximately or equal to 0.2 mM). When depolarized by potassium, all vessels were less sensitive to calcium and there was little difference in the calcium sensitivity of SHR and WKY vessels in either age group (Ca-ED50 approximately or equal to 0.8 mM). 3. The results suggest that whereas the potassium (potential)-dependent calcium permeability of the SHR smooth muscle cell membrane is normal, the noradrenaline-induced calcium permeability is abnormally high. The presence of this abnormality in the vessels from the young SHRs suggests that it may be a factor involved in the aetiology of hypertension in the SHR.

Aging↗