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PubMed1989

Receptor-operated calcium-permeable channels in vascular smooth muscle.

The extracellular Ca2+ dependence of agonist stimulation of vascular smooth muscle (VSM) has been investigated in rat cultured aortic smooth muscle cells (SMCs) and isolated mesenteric resistance vessels (MRVs). Agonists such as [Arg8]vasopressin (AVP), angiotensin II (Ang II), and adenosine-5'-triphosphate (ATP) stimulated 45Ca2+ entry into the SMCs that was (a) independent of the extent to which the membranes were polarized, and (b) was not inhibited by organic Ca2+ channel antagonists. Measuring the intracellular Ca2+ concentration [( Ca2+]i) after stimulation with agonists revealed a rapid increase of [Ca2+]i, which was followed by a sustained rise that was insensitive to Ca2+ antagonists. In Ca2+-free medium, only the initial peak of [Ca2+]i was still observed, but the sustained response to the agonists disappeared completely. This observation indicates that the sustained elevation seen in Ca2+-containing medium was the consequence of agonist-induced Ca2+ entry. In MRVs, a corresponding Ca2+-antagonist-insensitive, agonist (norepinephrine and AVP)-induced tonic tension was also identified. Moreover, agonists were able to induce sustained tension in the MRVs regardless of whether the membrane was normally polarized or was previously depolarized (80 mM K+) upon their administration. The agonist-stimulated 45Ca2+ entry in the SMCs could be blocked by the multivalent cations La3+, Cd2+, Mn2+, Co2+, Ni2+, and Mg2+ (in this order of potency). Depolarization-induced 45Ca2+ influx was inhibited by these cations in the same order of potency, but was significantly more sensitive to Cd2+ and significantly less sensitive to La3+ than that stimulated by agonists. Treatment with 2-nitro-4-carboxyphenyl-N,N-diphenyl-carbamate (NCDC, a proposed inhibitor of phospholipase C) reduced both the agonist-induced 45Ca2+ influx and the sustained elevation of [Ca2+]i in the SMCs. NCDC also abolished both contraction and depolarization induced by agonists in the MRVs. The kinase C stimulator phorbol-12-myristate-13-acetate (PMA) inhibited the agonist-induced 45Ca2+ influx and sustained increase in [Ca2+]i in the SMCs, whereas the kinase C inhibitor staurosporine had no effect. In the MRVs, in contrast, PMA had no influence on agonist-induced contractions. Staurosporine (1 microM), however, completely prevented these contractions, as did NCDC, but, unlike NCDC, it did so without affecting the agonist-induced depolarization. These data support an important role of receptor-operated Ca2+-permeable channels in VSM activation by agonists and suggest that these channels may be controlled by intracellular enzymic pathways and second messenger systems.

Animals↗
PubMed1999

Technical experiences with a microsurgical model of lymphatic reconstruction after intestinal transplantation in rats.

The surgical procedure of intestinal transplantation disrupts the graft's lymphatic drainage. Despite morphological regeneration, the functional impairment of the lymphatic system may contribute to many pathophysiological changes after transplant. We describe the technical details and results of a microsurgical model of lymphatic reconstruction (LR), which immediately reconstitutes lymphatic drainage of the intestinal graft in rats. A total of 42 orthotopic intestinal transplants with LR was performed. The patency of the LR was assessed between postoperative days 2 and 100 using either methylene-blue staining of the lymphatic vessels or mesenteric lymphoradiography. A total patency rate of 88% was achieved. Genetic background, occurrence of rejection, and immunosuppressive treatment with cyclosporine did not affect the patency rate. Technical aspects and potential applications of this model are discussed.

Anastomosis, Surgical↗
PubMed1995

Multiple types of ryanodine receptor/Ca2+ release channels are expressed in vascular smooth muscle.

Functional studies on vascular smooth muscle suggest the presence of ryanodine receptors (RyRs) with differing properties. In an attempt to understand such differences we investigated, using reverse transcription-polymerase chain reaction (RT-PCR), the possibility that smooth muscle cells express multiple types of RyRs. RNA was extracted from rat aorta, superior and small mesenteric arterial vessels, purified aortic smooth muscle media, or cultured aortic smooth muscle cells for cDNA synthesis. The cDNAs encoding RyR1, RyR2, and RyR3 were amplified using PCR primers based on sequences close to the 3' coding region of the RyR genes and PCR products verified by restriction endonuclease analysis. All three members of the RyR gene family were found to be present in vascular smooth muscle. This finding of multiple types of RyRs expressed in the same cell type indicates a complex mechanism of RyR Ca2+ channel regulation involving the formation of homo- and/or heterotetrameric complexes.

Animals↗
PubMed1995

Importance of valves and lymphangion contractions in determining pressure gradients in isolated lymphatics exposed to elevations in outflow pressure.

Lymphatic pressures were measured at several locations along an isolated lymphatic system exposed to elevations in outflow pressure. The objective of this study was to determine the contributions of lymphangion contractions and valve function to the observed pressure gradients. In each experiment, five bovine mesenteric lymphatic vessels (each with four to nine lymphangions) were joined in series by t-pieces connected to pressure transducers. The vessels were placed in an organ bath with input provided by a reservoir filled with Krebs solution. With a constant inflow pressure of 4 cm H2O, outflow pressures were elevated in 2- or 5-cm H2O increments. Except for inflow and outflow pressures which were fixed, the pressures measured at four other locations along the system were pulsatile due to lymphatic contractions. The mean pressures increased as outflow pressures were raised. While mean pressures were highest at the outflow end, estimates of the net pressure generated by each segment suggested that all segments, including those at the most upstream locations, increased their contractile activity. In addition, diastolic pressure gradients formed across the system. These did not appear to be due to valve failure (endurance limit of valves was 168 +/- 32 cm H2O) but rather, appeared to relate to the progressive inability of lymphangions to empty which, for a given lymphangion, began to occur at a mean outflow pressure of 9.8 +/- 1.1 cm H2O.

Animals↗
PubMed1997

Inhibitory effects of fluorescein isothiocyanate photoactivation on lymphatic pump activity.

The effects of photoactivation of fluorescein 5'-isothiocyanate (FITC)-dextran on lymphatic pump activity of rat mesenteric collecting vessel were studied in vivo. Rats were anesthetized with intraperitoneal alpha-chloralose and urethane, and the mesenteries were studied by using intravital videomicroscopic techniques. The diameter of the collecting lymph vessels were continuously monitored and lymphatic pump parameters (end diastolic diameter, end systolic diameter, stroke volume index, ejection fraction, contraction frequency, and pump flow index) were calculated. FITC-dextran (42 nmol/100 g body wt) without illumination caused no disturbance of lymphatic pump activity. Photoactivated FITC-dextran significantly increased end systolic diameter and decreased stroke volume index, ejection fraction, contraction frequency, and pump flow index. End diastolic diameter was not changed throughout the experiment. Superoxide dismutase (120 U/ml) and catalase (5000 U/ml) had no protective effect on photoactivated FITC-induced pump dysfunction, while histidine (singlet oxygen quencher, 10 mM) significantly prevented the disturbance of pump parameters. These results indicate that photoactivation of FITC induces negative chronotropic and negative inotropic effects in lymphatic pump activity through generation of singlet oxygen in the mesentery.

Animals↗
PubMed1987

Culture and characterization of bovine mesenteric lymphatic endothelium.

Lymphatic endothelial cells isolated from bovine mesenteric lymphatic vessels were cultured and characterized. Lymphatic endothelial cells grew as a monolayer displaying an elongated morphology in preconfluent primary cultures. When confluent, the cells exhibited a polygonal morphology to form a "cobblestone" pattern previously described for cultured vascular endothelium. All culture lymphatic endothelial cells expressed Factor VIII-related antigen and bound Ulex europaeus I lectin. Ultrastructurally, cultured lymphatic endothelium was characterized by the presence of Weibel-Palade bodies as well as the usual cytoplasmic organelles.

Animals↗
PubMed1998

Bradykinin release from high molecular weight kininogen and increase in plasma kallikrein-like activity following sensory stimulation by food in the rat.

Cephalic stimulation by food elicits, among other responses, dilatation of mesenteric blood vessels preparatory for digestion. The possible participation of bradykinin (BK), a powerful endogenous vasodilator, in this response was studied in fasted rats prior and following stimulation by sight and scent of food (sensory stimulation, SS), actual ingestion being denied to the animals. BK content of plasma high (HK) and low molecular weight kininogen (LK) was determined by bioassay on the atropinized, antihistamine-treated isolated guinea-pig ileum following release by trypsin from heat/acid denatured plasma. BK corresponding to LK was estimated in plasma which prior to denaturation had been incubated with kaolin, a process which leads to quantitative release and inactivation of BK from HK, but does not affect LK. BK corresponding to (HK + LK) was determined in plasma not exposed to kaolin. BK contained in HK was the difference between BK of (HK + LK) and of BK of LK. Plasma and glandular kallikreins were estimated by fluorimetry, using specific synthetic substrates. A 40.6+/-4.0% decrease (P<0.001) of BK in HK occurred in rats after 90 s of SS; LK remained unaffected. Ten minutes of SS did not result in further change. Atropine inhibited the effect of SS. Return of HK to pretreatment levels occurred when, following 90s of SS, rats were allowed to rest for 60 min in the absence of food. Renewed capacity to respond to SS was then observed. Plasma kallikrein, but not glandular kallikrein, increased in plasma of rats after SS. Increased free BK was detected in the circulation of Enalapril-protected rats after SS. Electrical stimulation of the distal sector of the sectioned left abdominal vagus nerve of Nembutal-anesthetized fasted rats reproduced the effect of SS on HK. It is concluded that visuo-olfactory stimulation by food generates nerve impulses, possibly carried by the vagus nerve, which by activating plasma kallikrein lead to cleavage of circulatory HK and release of BK in the rat.

Animals↗
PubMed2001

Liver metastasis in gastric cancer with particular reference to lymphatic advancement.

BACKGROUND: We have previously reported that, in models of mesenteric lymph vessel obstruction in rats, we observed lymphaticovenous communication. This suggested that cancer cells metastasized to the liver by a lymphatic route. In the present study, we investigated the relationship between liver metastasis and lymphatic involvement in gastric carcinoma by examining resected specimens. METHODS: Twenty gastric cancer patients who had synchronous liver metastasis and 17 who developed metachronous liver metastasis after gastrectomy, performed between 1985 and 1997, were included in this study. They were compared with 44 advanced gastric cancer patients who had neither synchronous nor subsequent liver metastasis, and who survived with a disease-free course for more than 5 years. We compared the patients' clinicopathological features; in particular, we investigated extranodal invasion in the resected lymph nodes. This invasion was classified according to the pattern of extranodal cancer invasion, with or without rupture of the lymph node capsule. RESULTS: Liver metastasis was more frequent in patients with extranodal invasion than in those without extranodal invasion (P < 0.002). Multivariate analysis revealed that the correlation between extranodal invasion and liver metastasis was significant (P < 0.024); the odds ratio was 4.412. Metastasis to the lymph nodes was the next most significant risk for liver metastasis. CONCLUSION: We consider that the lymphatic system is closely related to the establishment of liver metastasis; in particular, extranodal invasion is a significant risk factor for liver metastasis in patients with gastric cancer.

Aged↗
PubMed1981

Specific cerebrovascular localization of glutamate decarboxylase activity.

Glutamate decarboxylase (GAD) activity and GABA levels, determined with a [3H]muscimol radioreceptor assay, were found to be significantly higher in cerebral blood vessels from the piaarachnoid membrane as compared to extracranial vessels (aorta, mesenteric and femoral arteries, and vena cava). A cerebrovascular localization for GABA and GAD is consistent with earlier studies suggesting that an indigenous GABA system is involved in cerebral vascular function.

Animals↗
PubMed1995

Histopathology of cultured sea bass (Lates calcarifer) (Centropomidae) infected with Cruoricola lates (Trematoda: Sanguinicolidae) from Pulau Ketam, Malaysia.

Cruoricola lates are found throughout sea bass (Lates calcarifer), most commonly in the mesenteric blood vessels, kidney, pericardial vessels, and eye. Eggs of C. lates were predominantly found in the gills, ventricle, hepatopancreas, and kidneys, but only develop to miracidia regularly in the gills and heart. Single miracidia escaping appear to cause little damage, but groups induce an inflammatory response and haemorrhage. Endocardial macrophages encapsulate eggs trapped between trabeculae in the heart. The reaction to eggs in the kidneys, hepatopancreas and spleen consists of fibrocytic encapsulation. Infection at the levels observed in this study were insufficient to cause lethal pathological changes, but could result in reduced food conversion ratios or impaired immunological capacity.

Animal Husbandry↗
PubMed1990

Intussusception-type antireflux valve in the Roux-en-Y loop to prevent ascending cholangitis after hepatic portojejunostomy.

An intussusception-type antireflux valve was created in the Roux-en-Y loop in 23 infants with biliary atresia (17 new cases, and six others after episodes of ascending cholangitis) and 10 patients with congenital bile duct dilatation, in order to prevent ascending cholangitis after hepatic portojejunostomy. Mesenteric blood vessels were divided in a 4 cm length of the Roux-en-Y loop, and the distal 1.5 cm of this portion was further denuded of the seromuscular layer; an antireflux valve was thus established by invaginating the proximal portion into the denuded jejunum. No case, in which this technique was used, was associated with any surgical complications, and ascending cholangitis never developed in any of the 17 new cases with biliary atresia, during an average follow-up of 32 months.

Anastomosis, Roux-en-Y↗
PubMed1990

Twenty-five years' experience with Hirschsprung's disease.

Sixty-three patients with biopsy-proven Hirschsprung's disease were diagnosed at LeBonheur Children's Medical Center, Memphis, TN between 1955 and 1980. Fifty-eight of these patients had pull-through procedures performed by three similarly trained pediatric surgeons. The follow-up was 100 percent, averaging 8 years from initial diagnosis. Demographics, surgical procedures performed, and complications are reviewed. Significant findings are (1) anastomotic strictures occurred most frequently when the level of aganglionosis was at the sigmoid colon; (2) postoperative encopresis was most likely when the endorectal pull-through procedures were performed before the age of 10 months; and (3) with selective use of colostomies or enterostomies performed prior to the pull-through procedure, the incidence of enterocolitis was low, with 0% mortality. On the basis of these findings, we recommend that, when the most proximal level of aganglionosis is the sigmoid colon, it is important to critically inspect the angulation of mesenteric blood vessels and viability of the splenic flexure pull-through colon segment to prevent ischemia and therefore anastomotic strictures. The endorectal pull-through procedure should be delayed until after 10 months of age. Infants with Hirschsprung's disease should have a colostomy or enterostomy prior to a pull-through procedure. Patients diagnosed at 10 months of age or more, who have not had earlier bouts of enterocolitis, are not low percentile weight, and are without signs of severe obstruction, are candidates for pull-through without a prior fecal diversion procedure.

Adolescent↗
PubMed1991

Nuclear magnetic resonance as a noninvasive method of diagnosing intestinal ischemia: technique and preliminary results.

Despite the long-standing effort to identify a noninvasive method of diagnosing intestinal ischemia, no reliable biochemical or radiographic technique has evolved. We explored the use of phosphorus nuclear magnetic resonance (PNMR) as a method of detecting surgically induced intestinal ischemia. Using Lewis strain rats (250 to 300 g), small intestine ischemia was produced by ligation in succession from the ligament of Treitz to the ileocecal valve 1 of 2 (group I), 2 of 3 (group II), 3 of 4 (group III), and 4 of 5 (group IV) mesenteric terminal vessels. A sham-operated group was used as a control. Following the surgical procedure, the abdomen was closed and the rat positioned under the PNMR apparatus. Using phosphorus spectroscopy, data were analyzed using a computer program and plotted on a graph indicating relative peaks for the phosphate-based compounds. As a means of comparing groups, we devised an inorganic phosphate to phosphocreatine ratio ("ischemia index"), a qualitative measurement indicating trends used to evaluate ischemia. At the completion of the PNMR study, the abdomen was reopened and proximal, mid, and distal small intestine segments were harvested for histological evaluation using a previously established grading system for intestinal ischemia. Preoperatively, immediately postoperatively, and approximately 2 hours postoperatively, blood samples were obtained for hexosaminidase levels. With increasing vascular ligation, there was an upward trend in both the histological appearance of ischemia and the PNMR ischemia index indicative of increasing tissue ischemia. A similar trend was identified when the histological ischemia grade was directly correlated with the PNMR ischemia index. Hexosaminidase levels did not correlate with ischemia in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Lymphatic smooth muscle responses to leukotrienes, histamine and platelet activating factor.

Regional lymphatics regulate the accumulation of edema resulting from inflammation. The effects of mediators of inflammation on lymphatic smooth muscle, the primary determinant of lymph flow, are poorly understood. We studied mesenteric lymphatic vessels in 22 anesthetized rats with in vivo videomicroscopy following topical applications of histamine, leukotriene C4 or D4, or platelet-activating factor (PAF). Diameter, contractility, and contraction frequency were measured, and flow was calculated. Histamine caused increases in vessel diameter and contractility (174 and 218% of control, respectively; P less than 0.05), while contraction frequency was unaffected. Leukotrienes C4 and D4 caused an increase in frequency of contraction (348 and 392% of control, respectively; P less than 0.05), while having no significant influence on diameter or contractility. PAF caused smooth muscle relaxation, resulting in vasodilation and a decrease in contraction frequency (202 and 5% of control, respectively; P less than 0.05). Topical application of histamine and leukotrienes caused significant increases in calculated flow, while PAF decreased calculated flow. Mediators of inflammation have striking and diverse effects on lymphatic smooth muscle activity.

Administration, Topical↗
PubMed1987

Dextrorphan: an antagonist for phencyclidine receptors.

Radio-binding assay, bioassay and HPLC detection were used to observe the antagonistic effects of dextrorphan on PCP's actions. Dextrorphan displayed high affinity to PCP receptor in the rabbit mesenteric blood vessels. It had weak PCP-like bioactivity, but could antagonize PCP's action dose-dependently in vitro study with the rabbit ear artery preparation and shifted the dose-response curve of PCP to the right. After PCP administration, the content of norepinephrine in the vascular bath medium was increased, which was reversed by dextrorphan. Thus suggests that dextrorphan is an antagonist with very mild agonistic action for PCP receptors.

Animals↗