In Vitro and in Vivo Hemocompatibility Evaluation of Graphite Coated Polyester Vascular Grafts

Attempts have been made in this study to prepare a homogeneous and stable coating of graphite on polyester vascular grafts (GPVG) using an electrophoresis method to evaluate thromboresistant and blood compatibility of GPVG in comparison to non-coated PVG and InterGard (collagen sealed PVG) as control.

Lactate dehydrogenase (LDH) activity measurement was carried out on all PVG types to evaluate platelet adhesion. To examine tissue reaction GPVG and non-coated sheets of knitted polyester fabric were implanted simultaneously in the dorsal flank of rats subcutaneously. The GPVG, non-coated and control were implanted in descending aorta as end-to-end or end-to-side implantation substitution in 25 sheep for 4–60 weeks.

Results showed that the graphite coating on polyester vascular grafts reduced the number of adherent platelets and prevent platelet activation and spreading on the surface in comparison with non-coated and control. Pathological investigation showed inflammatory reactions were totally resolved after 12 weeks and there was no difference in the tissue reaction between graphite coated, non-coated and control patches. All grafts remained patent and there was no significant difference in patency rate between these three types of PVG. We found that GPVG has no need for pre-clotting and it showed lower platelet aggregation, thinner capsule formation and lower calcification after 15 months. However, suturing of GPVG was more difficult in comparison with the other types.

Secondary polycythaemia associated with unilateral renal cystic disease

Unilateral renal cystic disease (URCD) is a rare condition, with pathological features indistinguishable from autosomal dominant polycystic kidney disease (ADPKD). In contrast to this condition, however, URCD is not inherited, is not associated with progressive deterioration in renal function, and is unilateral. We present a case of URCD associated with polycythaemia, which showed resolution following nephrectomy. Secondary polycythaemia has not previously been reported in cases of URCD, but may be hypothesised to be a result of excess erythropoietin production.

Preconditioning of the rat random-pattern skin flap: modulation by opioids

Opioid receptors have been implicated in protecting several organ systems from ischaemic events. The authors have studied the effects of opioid receptors on random-pattern skin flap survival. Sixty-nine male Sprague-Dawley rats were used. Bipedicled dorsal skin flaps (2 x 8 cm) were elevated at the midline. Different doses of morphine (0.01, 0.1, 1 and 5 mg/flap) were administered locally in the cranial half of the flap and systemically through intraperitoneal injections (5 and 10 mg/kg). In another experiment, 0.4 mg/flap of naloxone was injected followed by 5 mg/flap injection of morphine to determine whether the effect of morphine is receptor mediated. The role of the opioid receptors in the ischaemic preconditioning (IPC) phenomenon was investigated by administration of naloxone (0.4 mg/flap) 1 h before clamping the cranial pedicle for 20 min followed by 40 min of reperfusion. Appropriate control groups were included. The cranial pedicle was cut 2 h after saline or drug administration in all groups and flap survival area was evaluated on the seventh postoperative day. Local administration of morphine in higher doses (1 and 5 mg/flap) significantly reduced the amount of flap necrosis when compared to that of the control cohort (P < 0.05). Naloxone abolished this protective effect of morphine. Furthermore naloxone significantly decreased the anti-ischaemic effect of the IPC. Systemic administrations of morphine had no significant effect on flap survival area in compare with the control group.

In vitro and in vivo hemocompatibility evaluation of graphite coated polyester vascular grafts

Attempts have been made in this study to prepare a homogeneous and stable coating of graphite on polyester vascular grafts (GPVG) using an electrophoresis method to evaluate thromboresistant and blood compatibility of GPVG in comparison to non-coated PVG and InterGard (collagen sealed PVG) as control.

Lactate dehydrogenase (LDH) activity measurement was carried out on all PVG types to evaluate platelet adhesion. To examine tissue reaction GPVG and non-coated sheets of knitted polyester fabric were implanted simultaneously in the dorsal flank of rats subcutaneously. The GPVG, non-coated and control were implanted in descending aorta as end-to-end or end-to-side implantation substitution in 25 sheep for 4–60 weeks.

Results showed that the graphite coating on polyester vascular grafts reduced the number of adherent platelets and prevent platelet activation and spreading on the surface in comparison with non-coated and control. Pathological investigation showed inflammatory reactions were totally resolved after 12 weeks and there was no difference in the tissue reaction between graphite coated, non-coated and control patches. All grafts remained patent and there was no significant difference in patency rate between these three types of PVG. We found that GPVG has no need for pre-clotting and it showed lower platelet aggregation, thinner capsule formation and lower calcification after 15 months. However, suturing of GPVG was more difficult in comparison with the other types.

Mechanisms of tumor metastasis to bone

Bone metastases occur in approximately 80% of patients with advanced cancer. They are characterized by cancer cell growth and bone destruction that cause pain, fractures, anemia, and hypercalcemia. At diagnosis, bone metastases are usually incurable owing to their advanced development. However, the early stages in their formation are asymptomatic and begin as single micrometastatic cells from the blood stream. These cells can be detected by molecular analysis of bone marrow in approximately 30% of patients at the time of cancer diagnosis, but not all single micrometastatic cells develop into clinically significant bone metastases. A synergistic relationship exists between the micometastasis and the bone environment creating favorable conditions for the development and growth of disseminated tumor cells. Such bone metastases induce osteolysis or new bone formation, releasing growth factors and cytokines, which in turn amplify this pathological mechanism. The underling hypothesis, first proposed by Paget in 1889, is that the growth of disseminated tumor cells in bone is dependent on the fertility of the soil or bone itself. This article explores the most current opinions in this area of study and presents a comprehensive summary of the major factors involved.

Induced beta-carotene synthesis driven by triacylglycerol deposition in the unicellular alga dunaliella bardawil

Under stress conditions such as high light intensity or nutrient starvation, cells of the unicellular alga Dunaliella bardawil overproduce beta-carotene, which is accumulated in the plastids in newly formed triacylglycerol droplets. We report here that the formation of these sequestering structures and beta-carotene are interdependent. When the synthesis of triacylglycerol is blocked, the overproduction of beta-carotene is also inhibited. During overproduction of beta-carotene no up-regulation of phytoene synthase or phytoene desaturase is observed on the transcriptional or translational level, whereas at the same time acetyl-CoA carboxylase, the key regulatory enzyme of acyl lipid biosynthesis, is increased, at least in its enzymatic activity. We conclude that under normal conditions the carotenogenic pathway is not maximally active and may be appreciably stimulated in the presence of sequestering structures, creating a plastid-localized sink for the end product of the carotenoid biosynthetic pathway.

Phytoene synthase from Narcissus pseudonarcissus: functional expression, galactolipid requirement, topological distribution in chromoplasts and induction during flowering

A cDNA coding for the carotenoid biosynthetic enzyme phytoene synthase was cloned from a Narcissus pseudonarcissus flower cDNA library, and the corresponding protein was overexpressed in insect cells using the baculovirus lipofection system. The full-length overexpressed enzyme exhibited very reduced catalytic activity compared with an overexpressed N-truncated form, with its transit sequence removed by site-directed mutagenesis. The shortened form readily bound quantitatively to lipid bilayers. Although it was active with liposomes prepared from plastid lipids, with phospholipid liposomes it was not, even though association took place. In this latter case, free galactose was capable of substituting for galactolipids, resulting in enzymatic activity. It is concluded that galactolipids are involved in catalytic activity, but do not serve as a membrane anchor. Antibodies raised against the recombinant enzyme made it possible to distinguish between a membrane-bound and a soluble, protein-complexed inactive form of phytoene synthase, present in the chromoplast stroma. These findings and data on phytoene synthase mRNA and protein expression presented here are discussed in terms of a possible regulatory role in color formation during chromoplast (flower) development.

Inferior and superior vena caval blood flows during cross-clamping of the thoracic aorta in pigs

Changes in blood flow through the inferior and superior venae cavae during cross-clamping of the thoracic aorta just above the diaphragm were studied in 28 miniature pigs anesthetized with enflurane titrated to maintain systemic arterial blood pressure close to normal values. Surgical preparation included sternotomy with subsequent placement of a noncannulating electromagnetic probe around the ascending aorta and a cannulating electromagnetic probe in the transected inferior vena cava. Superior vena caval flow was calculated as the difference between aortic flow and inferior vena caval flow. Clamping of the thoracic aorta alone (n = 10) was accompanied by severe arterial hypertension, a dramatic decrease in inferior vena caval flow, and an increase in superior vena caval flow, which resulted in a moderate increase in aortic flow. Simultaneous clamping of the thoracic aorta and inferior vena cava (n = 13) was accompanied by no significant change in arterial pressure or superior vena caval flow. The oxygen content in mixed venous blood significantly (p less than 0.05) increased from 9.5 +/- 1.1 to 13.4 +/- 1.8 ml.dl-1 in animals undergoing clamping of the thoracic aorta only, but did not change significantly in animals subjected to simultaneous clamping of the aorta and inferior vena cava. The study demonstrates a substantial increase in superior vena caval flow during cross-clamping of the thoracic aorta. Further studies elucidating the mechanism of the observed changes are required.