Early effects of arterial hemodynamic conditions on human saphenous veins perfused ex vivo

Exposure to the arterial hemodynamic environment is thought to be a potential trigger for the pathological remodeling of saphenous vein grafts. Using matched pairs of freshly isolated human saphenous vein, we analyzed the early effects of ex vivo hemodynamic conditions mimicking the venous (native) compared with arterial (graft) environment on the key components of vascular remodeling, ie, matrix metalloproteinase (MMP)-9 and MMP-2 and cell proliferation. Interestingly, we found that arterial conditions halved latent MMP-9 (50+/-11%, P=0.01) and MMP-2 (44+/-6%, P=0.005) levels relative to matched vein pairs maintained ex vivo under venous perfusion for up to 3 days. Immunostaining supported decreased MMP levels in the innermost area of arterially perfused veins. Either decreased synthesis or increased posttranslational processing may decrease MMP zymogen levels. Biosynthetic radiolabeling showed that arterial perfusion actually increased MMP-9 and MMP-2 production. When we then examined potential pathways for MMP zymogen processing, we found that arterial conditions did not affect the expression of MT-MMP-1, a cell-associated MMP activator, but that they significantly increased the levels of superoxide, another MMP activator, suggesting redox-dependent MMP processing. Additional experiments indicated that increased superoxide under arterial conditions was due to diminished scavenging by decreased extracellular superoxide dismutase. Arterial perfusion also stimulated cell proliferation (by 220% to 750%) in the majority of vein segments investigated. Our observations support the hypothesis that arterial hemodynamic conditions stimulate early vein graft remodeling. Furthermore, physiological arterial flow may work to prevent pathological remodeling, particularly the formation of intimal hyperplasia, through rapid inactivation of secreted MMPs and, possibly, through preferential stimulation of cell proliferation in the outer layers of the vein wall.     

Effect of increased glucose load on maternal-fetal transport of alpha-aminoisobutyric acid in the perfused human placenta: in vitro study

The role of hyperglycemia on modulation of maternal-fetanl transport of amino acids in humans is little understood. Hence, we have explored the effect of increased glucose load on transport kinetics of a model non-metabolizable amino acid, alpha-aminoisobutyric acid (AIB), in the human placenta in vitro. Transport kinetics of AIB in maternal-fetal direction was studied using perfusion of isolated human placental lobules. NCTC (National Culture and Tissue Collection)-135 medium, diluted with Earle's buffered salt solution was used as the perfusate and tritiated water was used as the reference marker. Effect of increased glucose load on transport kinetics of study and reference substances was studied in normal term placentae (n=5; gestational age, 38.5±0.5 weeks) in succeeding experimental phases, after a control perfusion phase with physiological glucose concentration. AIB transport fraction (TF), relative to tritiated water TF, averaged 54.8% in control euglycemic phase while in hyperglycemic concentration phases of 27.8 and 55.6 mM, the AIB TF index averaged 42.4% and 38.2%, respectively. Analysis of variance revealed that the difference was statistically significant. Similarly, absorption rate index of the amino acid was also significantly lower in the hyperglycemic perfusion phases compared t control euglycemic phase. We conclude that hyperglycemia may play a deleterious role in limiting maternal-fetal transport of A-type amino acids in the in vivo state. Received: 5 July 2001 / Accepted in revised form: 3 December 2001     

Macromolecular transport in rabbit blastocysts: evidence for a specific uteroglobin transport system

Though uterine proteins are found within the blastocoel of the rabbit blastocyst, the mechanisms involved in protein entry into the blastocoel have not been studied. To investigate potential avenues of protein entry into the blastocoel, we have monitored uptake of a fluorescent, fluid-phase marker (lucifer yellow) into the rabbit blastocyst trophectodermal cell. In addition, we have measured the transtrophectodermal permeabilities of several uterine proteins (uteroglobin (UTG), rabbit serum albumin, rabbit IgG), and radiolabeled fluid-phase markers (sucrose, polyethylene glycol, dextran) in the 6- and 7-day post-coitus rabbit blastocyst. Extrablastocoelic lucifer yellow (LY) was rapidly endocytosed by the trophectodermal cell and was subsequently trapped in a perinuclear compartment for at least 30 min after removal of the extracellular dye. The slow rate of LY turnover within the endocytic compartments implies that the rate of fluid-phase transcytosis was negligible. Permeability coefficients of the fluid-phase markers and proteins, with the exception of UTG, decreased with increasing molecular weight of each compound tested. These data are consistent with the conclusion that these compounds traverse the trophectoderm via a 'leak' pathway, as opposed to a transcytotic pathway. In contrast, permeability of 125I-UTG when compared to the other compounds, was 10-fold greater than would be predicted based on its molecular weight. Furthermore, the flux of radioiodinated UTG displayed saturation kinetics with a Km of 19.5 micrograms/ml and a Vmax of 132 ng.cm-2.h-1. Sodium dodecylsulfate-polyacrylamide gel electrophoresis demonstrated that the radioiodinated protein recovered from the blastocoel was of a lower molecular weight than native UTG and was not immunoreactive with goat anti-UTG antibody. Our data are consistent with the idea that UTG is transported across the trophectoderm by a receptor-mediated system, and UTG is modified intracellularly during transport to a protein of a lower molecular weight.     

Studies on the transport of insulin antibodies across the placenta to the fetus and their effect on the fetal pancreatic islet system

Summary This paper continues the preliminary communications on the insulin resistance of the offspring of insulin-resistant mothers. The investigations were carried out in guinea pigs and humans. It was shown that insulin antibodies pass into the fetal circulation which results in the appearance of passive insulin-resistance. This resistance disappears in the first weeks of life. Antibodies to bovine insulin bind in part endogenous insulin of guinea pigs, as demonstrated by marked hyperglycemia in the offspring of insulin-resistant mothers. Insulin antibodies have no noticeable effect on the architecture of the pancreas in guinea pigs in the perinatal period.This work was subsidized in part by the Polish Academy of Science.     

Establishment of a parathyroid hormone-responsive phosphate transport system in vitro using cultured renal cells

A new system was established using primary cultured mouse kidney epithelial cells to study the effect of PTH on renal tubular phosphate transport. The cells used in our study had alkaline phosphatase activity. They showed increased cAMP content in response to PTH, calcitonin, and vasopressin. Thus, these cells were thought to be a mixture of cells originating from the proximal and distal renal tubules. To explore the mechanism of phosphate handling in these cells, the accumulation of radioactive phosphate from the medium into the cells and the spaces between the cell layer and culture plate (submonolayer spaces) was measured. The accumulation of phosphate by the cells was a sodium-dependent, energy-dependent process, which was demonstrated by inhibition both in the absence of sodium and in the presence of ouabain or 2,4-dinitrophenol. Furthermore, phosphate accumulation was decreased significantly by PTH presumably acting through cAMP. PTH inhibited phosphate accumulation not by affecting the efflux process, but by affecting the uptake process through the apical membrane of the cultured cells without altering the compartmental mental distribution of the accumulated phosphate. These characteristics of phosphate accumulation resemble those of renal tubular phosphate transport.     

Direct visualization of lipid deposition and reverse lipid transport in a perfused artery : roles of VLDL and HDL

The major goal of this study was to determine the interactions of VLDL surface and core lipids with the artery wall. We first demonstrated in vitro that surface lipid in VLDL could be traced using the phospholipid-like fluorescent probe 1,1'-dioctadecyl-3,3, 3',3'-tetramethyl-indocarbocyanine (DiI). The core of VLDL particles was traced by fluorescently labeling apolipoprotein B with TRITC. The labeled VLDLs were perfused through rat carotid arteries, and accumulation of the fluorescently labeled VLDL components in the arterial walls was determined by quantitative fluorescence microscopy. Addition of lipoprotein lipase increased the accumulation of both DiI and TRITC by >2.3-fold. Histological examination showed that DiI and TRITC were primarily localized to the endothelial layer; however, DiI also accumulated as small "lakes" deeper in the artery, in a subendothelial position. Addition of HDL to the perfusion decreased the accumulation of surface lipid and apolipoprotein B-containing particles and eliminated the DiI lakes. Moreover, the increase in endothelial layer permeability associated with lipolysis was attenuated 21% by HDL. If VLDL surface lipid first was allowed to accumulate in the arterial wall, its subsequent rate of loss was more than twice as fast if HDL was included in the perfusate. These studies directly demonstrate atherogenic effects of VLDL lipolysis and their inhibition by HDL.     

Monensin action on the Golgi complex in perfused rat liver: evidence against bile salt vesicular transport.

Several studies suggest that bile salts are transported from the basolateral to the canalicular membrane of hepatocytes by a vesicular pathway, possibly in part via the Golgi complex. To test this hypothesis, the present study examined, in the perfused rat liver, the influence of the Na+ ionophore monensin on the biliary secretion of taurocholate and biliary lipids. The effects of the drug have been checked by the study of the ultrastructural modifications of the Golgi complex, secretion of horseradish peroxidase, and bile salt uptake. An infusion of monensin (1, 3, or 5 mumol/L) into the liver induced considerable swelling of the Golgi complex within 5 minutes. After a bolus injection of horseradish peroxidase during monensin infusion, the biliary secretion of the protein was delayed (1 mumol/L monensin) and markedly reduced (5 mumol/L monensin). Bile salt uptake was virtually unchanged except with 5 mumol/L monensin. This suggests that monensin has the same effects on the subcellular traffic in the perfused liver as in cultured cells. After a bolus injection of taurocholate (0.25, 5.0, or 8.5 mumol/100 g body wt) during monensin infusion, the pattern of biliary secretion of the bile salt was identical to that of controls. During continuous infusion of taurocholate, a 10-minute monensin infusion (1 or 3 mumol/L) had no effect on the biliary secretion of taurocholate and on the secretion of lecithin and cholesterol induced by taurocholate. High concentrations (5 mumol/L) or prolonged infusions (20 minutes) of monensin decreased the biliary secretion of bile salts but corresponded to a marked decrease of taurocholate uptake. In summary, the Na+ ionophore monensin altered the Golgi complex and the vesicular transport of horseradish peroxidase, whereas taurocholate biliary secretion was not influenced unless taurocholate biliary secretion was not influenced unless taurocholate uptake by the liver was markedly decreased. It may be concluded that taurocholate and biliary lipid secretion, under these conditions, does not depend essentially on pathways involving acidic transporting vesicles and particularly the trans-Golgi complex.     

Simultaneous assessment of prohormone transport and processing in four separate islet cell types: a combined autoradiographic and biochemical study

This study was performed to assess the relationships between prohormone transport and processing in separate cell types in pancreatic islet tissue. Anglerfish islets were subjected to pulse-chase incubation with [3H]tryptophan and/or [35S]cysteine. Tissue and media were removed at specific time points during the incubation and prepared for electron microscopic examination or biochemical analysis. Specific islet cell types were identified ultrastructurally using protein A gold immunocytochemistry. Transport of newly synthesized peptides through specific subcellular compartments was monitored using electron microscopic autoradiography. Prohormone-product ratios were established by gel filtration and high-performance liquid chromatography analyses of tissue extracts. Complete analyses were performed on A-cells (source of proglucagon-II, glucagon-II, and glucagon-like peptide-II), B-cells (proinsulin and insulin), D-cells (prosomatostatin-II and somatostatin-28), and S-cells (prosomatostatin-I and somatostatin-14). Transport of newly synthesized peptides proceeded from rough endoplasmic reticulum (RER) to Golgi complex and then to mature secretory granules in all cell types. The transport rate was most rapid in A- and B-cells, slower in S-cells, and slowest in D-cells. The T1/2 for conversion of prohormone to product(s) was shortest in S-cells (150 min), slightly longer in B-cells (155 min), much longer in D-cells (259 min), and greater than 300 min in A-cells. These results demonstrate that the transport/prohormone conversion relationships are unique in each of the islet cell types monitored.     

Automated 2D IR spectroscopy using a mid-IR pulse shaper and application of this technology to the human islet amyloid polypeptide

The capability of 2D IR spectroscopy to elucidate time-evolving structures is enhanced by a programmable mid-IR pulse shaper that greatly improves the ease, speed, and accuracy of data collection. Traditional ways of collecting 2D IR spectra are difficult to implement, cause distorted peak shapes, and result in poor time resolution and/or phase problems. We report on several methods for collecting 2D IR spectra by using a computer-controlled germanium acoustooptic modulator that overcomes the above problems. The accuracy and resolution of each method is evaluated by using model metal carbonyl compounds that have well defined lineshapes. Furthermore, phase cycling can now be employed to largely alleviate background scatter from heterogeneous samples. With these methods in hand, we apply 2D IR spectroscopy to study the structural diversity in amyloid fibers of aggregated human islet amyloid polypeptide (hIAPP), which is involved with type 2 diabetes. The 2D IR spectra reveal that the beta-sheet fibers have a large structural distribution, as evidenced by an inhomogeneously broadened beta-sheet peak and strong coupling to random coil conformations. Structural diversity is an important characteristic of hIAPP because it may be that partly folded peptides cause the disease. This experiment on hIAPP is an example of how computer generation of 2D IR pulse sequences is a key step toward automating 2D IR spectroscopy, so that new pulse sequences can be implemented quickly and a diverse range of systems can be studied more easily.     

Hepatic metabolism during acute ethanol administration: a phosphorus-31 nuclear magnetic resonance study on the perfused rat liver under normoxic or hypoxic conditions

The effect of ethanol metabolism on the energetic parameters and intracellular pH of the isolated perfused rat liver from fed rats was studied by phosphorus-31 nuclear magnetic resonance spectroscopy. This technique allowed us to analyze nondestructively and in real time the role of low oxygen tension on the possible injurious effect of ethanol on the liver cells. A quantitative analysis of nuclear magnetic resonance data recorded on a perfused rat liver within a 30 mm diameter probe has been performed at 80.9 MHz. Under normoxic and normothermic conditions, the levels of phosphorylated metabolites detected by nuclear magnetic resonance were 2.8, 0.3 and 2 mumoles per gm liver wet weight for ATP, ADP and inorganic orthophosphate, respectively. The cytosolic pH was 7.25 +/- 0.05. During a period of 4 min of hypoxia induced by reducing the perfusion flow rate to 25% of its initial value (i.e., from 12 ml to 3 ml per min per 100 gm body weight), the level of ATP dropped to 2.2 mumoles per gm liver wet weight. Concomitantly, ADP and inorganic orthophosphate increased to 0.6 and 3.3 mumoles per gm liver wet weight. Cytosolic pH fell to 7.02 +/- 0.05. Perfusion of the liver with a Krebs medium containing 70 mM (0.4%) ethanol induced a sharp decrease in intracellular inorganic orthophosphate to reach 1.3 mumole per gm liver wet weight and after a lag time of 4 to 6 min, a decrease in ATP level (2.15 mumoles per gm liver wet weight). A large increase in phosphomonoesters (mainly sn-glycerol 3-phosphate) up to 6 mumoles per gm liver wet weight was also observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Monoclonal antibodies to a human islet cell surface glycoprotein: 4F2 and LC7-2

Monoclonal antibodies 4F2 and LC7-2 react with a cell surface differentiation antigen expressed by the endocrine cells of the human pancreatic islet, but not by the acinar pancreatic, ductular, vascular, or stromal connective tissue cells. Western immunoblotting procedures demonstrate the reactivity of the monoclonal antibody 4F2 with a 120 kilodalton islet cell protein in detergent-solubilized cell extracts. These two monoclonal antibodies have potential for application in many aspects of islet cell research and diabetes in general.     

Laparoscopic microwave ablation of human liver tumours using a novel three-dimensional magnetic guidance system

Background

Accurate antenna placement is essential for effective microwave ablation (MWA) of lesions. Laparoscopic targeting is made particularly challenging in liver tumours by the needle''s trajectory as it passes through the abdominal wall into the liver. Previous optical three-dimensional guidance systems employing infrared technology have been limited by interference with the line of sight during procedures.

Objective

The aim of this study was to evaluate a newly developed magnetic guidance system for laparoscopic MWA of liver tumours in a pilot study.

Methods

Thirteen patients undergoing laparoscopic MWA of liver tumours gave consent to their participation in the study and were enrolled. Lesion targeting was performed using the InnerOptic AIM™ 3-D guidance system to track the real-time position and orientation of the antenna and ultrasound probe.

Results

A total of 45 ablations were performed on 34 lesions. The median number of lesions per patient was two. The mean ± standard deviation lesion diameter was 18.0 ± 9.2 mm and the mean time to target acquisition was 3.5 min. The first-attempt success rate was 93%. There were no intraoperative or immediate postoperative complications. Over an average follow-up of 7.8 months, one patient was noted to have had an incomplete ablation, seven suffered regional recurrences, and five patients remained disease-free.

Conclusions

The AIM™ guidance system is an effective adjunct for laparoscopic ablation. It facilitates a high degree of accuracy and a good first-attempt success rate, and avoids the line of site interference associated with infrared systems.     

Organ donor pancreases for the study of human islet cell histology and pathophysiology: a precious and valuable resource

Direct in vivo assessment of pancreatic islet-cells for the study of the pathophysiology of diabetes in humans is hampered by anatomical and technological hurdles. To date, most of the information that has been generated is derived from histological studies performed on pancreatic tissue from autopsy, surgery, in vivo biopsy or organ donation. Each approach has its advantages and disadvantages (as summarised in this commentary); however, in this edition of Diabetologia, Kusmartseva et al ( https://doi.org/10.1007/s00125-017-4494-x) provide further evidence to support the use of organ donor pancreases for the study of human diabetes. They show that length of terminal hospitalisation of organ donors prior to death does not seem to influence the frequency of inflammatory cells infiltrating the pancreas and the replication of beta cells. These findings are reassuring, demonstrating the reliability of this precious and valuable resource for human islet cells research.