Factors influencing activated clotting time following heparin administration for the initiation of cardiopulmonary bypass

OBJECTIVES

Initiation of cardiopulmonary bypass (CPB) for open-heart surgery requires that heparin be administered and reach an adequate value of activated clotting time (ACT). We previously introduced a new heparin formula that considered the preoperative ACT. In this study, we determined other factors affecting ACT.

METHODS

Adult patients who underwent cardiac surgery using CPB were divided into two groups according to their ACT value after the initial administration of heparin during surgery. ACT above 450 s was defined as "Reach", and this group was compared to the "Short" group with ACT below 450 s.

RESULTS

The Reach and Short groups included 334 (64.7%) and 182 (35.3%) cases, respectively. Univariate analysis indicated that preoperative heparin use, age ≥ 80 years, New York Heart Association classification 4, white blood cell counts above the higher limit, hematocrit below the lower limit, platelet cell counts below the lower limit, low albumin levels, moderate renal dysfunction, high C-reactive protein levels, high brain natriuretic peptide levels, and moderate deterioration of left ventricular ejection fraction were associated with the effects of heparin. Multivariate analysis revealed that age ≥ 80 years (odds ratio [OR] 2.53, 95% confidence interval [95%CI] 1.41-5.24), New York Heart Association classification 4 (OR = 4.44, 95%CI 1.59-15.35), and platelet count below the lower limit (OR 0.37, 95%CI 0.31-0.85) were associated with the effects of heparin.

CONCLUSION

Old age, heart failure, and lower platelet counts affected heparin activity. The dose of heparin should be considered in those patients to reach the target ACT.

Nano-scaled hydroxyapatite/polymer composite I. Coating of sintered hydroxyapatite particles on poly(gamma-methacryloxypropyl trimethoxysilane)grafted silk fibroin fibers through chemical bonding

The inorganic-organic composite consisting of nano-scaled hydroxyapatite (HAp) and silk fibroin (SF) fibers was prepared through covalent linkage to develop a novel biomaterial for a soft-tissue-compatible material. The preparation of the composite was conducted through the three-step procedure consisting of chemical modification using 2-methacryloxyethyl isocyanate (MOI) monomer to introduce vinyl groups on SF, poly(gamma-methacryloxypropyl trimethoxysilane) (MPTS) graft-polymerization on SF, and coupling process between the surface of polyMPTS-grafted SF and HAp nano-particles. The amount of the graft-polymerization of polyMPTS through vinyl groups was well controlled by the reaction time. The nano-crystals were subsequently coated on the grafted fibers by heating at 120 degrees C for 2 h in a vacuum. The crystalline structure of the SF substrate did not change in the procedure. In the SEM observation of the composite surface, it was found that the bonded nano-crystals were separated and partially aggregated with several crystals attached on the SF fiber surface. The HAp particles adhered more strongly on the SF surface with separation or aggregation of several crystals than on the surface of the original SF after ultrasonic treatment.

Hydroxyapatite and bFGF Coating of Detachable Coils for Endovascular Occlusion of Experimental Aneurysm

SUMMARY

The purpose of this study was to evaluate the effect of hydroxyapatite (HAp) and fibroblast growth factor-basic (bFGF) coating on Guglielmi detachable coils (GDCs) in an experimental aneurysm model. A total of 18 aneurysms were experimentally made in the common carotid arteries of swine. Embolization was done on these aneurysms using standard GDCs and coated GDCs with HAp (GDC-HAp) and with bFGF (GDC-HAp-bFGF). The animals were then killed 14 days after embolization. The development of tissue scarring and coverage the aneurysm's orifice were evaluated macroscopically. No significant difference of volume ratio of the coils exited in each groups. Macroscopically, covering ratio of fibrous membrane at the neck of aneurysms were 88.3 +/- 14.7% in a group with GDC-HAp-bFGF, while it were 26.7 +/- 15.3% in a group with standard GDC and it was 41.7 +/- 31.7% in a group with GDC-HAp. These results indicated that coating by hydroxyapatite and bFGF might facilitate a wound healing in an experimental aneurysm model.

HSP 47 and collagen mRNA expression in L929 cells adhered to lipid films

L929 cell adhesion on various lipid films prepared by Langmuir-Blodgett methods (LB method) were studied. L929 cells adhered to every lipid film similar to tissue culture poly(styrene) (TCPS). The mRNA expression of both collagen and HSP47 in adherent cells were evaluated by the RT-PCR method. mRNA expression of collagen was not altered during adhesion and proliferation duration, while HSP47 mRNA expression changed depending on culture time. L929 cells adhered to L-alpha-dipalmitoylphosphatidylcholine (DPPC)-films showed little HSP47 mRNA expression. It was suggested that DPPC films regulate L929 cell function via unique serum protein adsorption.

Hydroxyapatite coating of detachable coils for endovascular occlusion of experimental aneurysm

SUMMARY

The purpose of this study was to evaluate the effect of hydroxyapatite (HAp) coating on Guglielmi detachable coils (GDCs) in an experimental aneurysm model. A total of 12 aneurysms were experimentally made in the common carotid arteries of swine using a microsurgical technique. Embolization was done on these aneurysms using standard GDCs and GDCs coated with HAp (GDC-HAp). The animals were then killed 14 days after embolization. The physical properties of coated coils and the development of tissue scarring and coverage the aneurysm's orifice were evaluated macroscopically and microscopically. Macroscopically, a scar formation and coverage at the neck of aneurysms were observed in a group with GDC-HAp, while such findings were not seen in a group with GDC. With light microscope, fibroblasts were seen in the neck of the aneurysms in a group using GDC-HAp, whereas only a fibrin- like net was seen in a group using GDC. In a group with GDC-HAp, inflammatory response was more intense in the dome of the aneurysm with faster re-endothelial coverage of the neck of the aneurysm than the ones in a group with GDC. These results indicated that GDC-HAp might create a clinically beneficial biological surface in an experimental aneurysm model.

Moderate alcohol consumption reduces urinary 8-hydroxydeoxyguanosine by inducing of uric acid

Recent studies suggest that moderate alcohol consumption is associated with a low risk of cancer, coronary heart disease, and other diseases. Most of these diseases are considered to be related to the action of reactive oxygen species (ROS) at certain stages of disease progression. However, considerable evidence exists indicating that ethanol generates ROS in vivo. Thus, the reduced risk of disease as a result of alcohol consumption seems to contradict evidence suggesting the induction of ROS by ethanol. In the present study, we investigated whether oxidative stress was induced in moderate alcohol drinkers. We measured the total urinary biopyrrins and 8-hydroxydeoxyguanosine (8-OHdG) levels as a systemic oxidative stress marker and an oxidative DNA damage marker, respectively. Serum uric acid was also measured as an alcohol-induced antioxidant. We compared total urinary biopyrrins and 8-OHdG levels among groups with different alcohol habits. The results showed that total biopyrrins levels increased with the amount of alcohol consumed, but that the level of 8-OHdG significantly decreased with the amount of alcohol consumed. The decrease in 8-OHdG levels seemed to be associated with increasing levels of uric acid. Judging from the increasing level of total biopyrrins, alcohol may induce ROS. ROS may then cause cell damage in liver, as suggested by the positive correlation between the total biopyrrins levels and the serum GOT, GPT, and gammaGTP levels. However, since ROS may be more effectively counteracted by uric acid in organs other than the liver, DNA damage may be suppressed rather than induced. Accordingly, moderate alcohol consumption seems to have the overall effect of reducing DNA damage, as shown by the decrease in urinary 8-OHdG levels observed in our study.

Urinary 8-oxo-7, 8-dihydro-2'-deoxyguanosine and biopyrrins levels among construction workers with asbestos exposure history

It has been suggested that oxidative stress is associated with the cancers caused by asbestos. Since construction workers are sometimes exposed to low levels of asbestos, we investigated whether oxidative stress was elevated in construction workers who had been exposed to low levels of asbestos. The subjects were 48 Japanese construction workers. The defined asbestos-exposed group consisted of subjects who had the history of suspected exposure to asbestos and were diagnosed to have irregular opacities or pleural plaques. We measured the amount of 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG) and biopyyrins in the urine of the subjects. The results showed that 8-oxodG and biopyyrins levels in the defined asbestos-exposed group were higher, although they were not statistically significant, than those in the control group. In addition, the urinary 8-oxodG levels tended to correlate positively with the duration of suspected exposure to asbestos. These results suggest that even low-level asbestos exposure may induce oxidative stress and that the resulting's the oxidative stress might be related to lung cancer in construction workers.

Cellular distribution of thrombomodulin as an early marker for warm ischemic liver injury in porcine liver transplantation: protective effect of prostaglandin I2 analogue and tauroursodeoxycholic acid

BACKGROUND

Warm ischemia of the graft from non-heart-beating donors is considered a risk factor for posttransplant graft dysfunction. The early administration of cytoprotective agents may help improve graft dysfunction.

METHODS

Four groups of 10 pigs each underwent orthotopic liver transplantation. Prostaglandin I2 analogue, OP-41483, was administered intraportally 30 min before warm ischemic insult in donors and after reperfusion in recipients in one group. In the other study group, additional intravenous tauroursodeoxycholic acid (TUDC) was given before the warm ischemic insult in donors and after reperfusion, then maintained continuously until postoperative day (POD) 7.

RESULTS

Exposure of liver grafts to warm ischemia resulted in severe congestion with the disappearance of thrombomodulin (Tm) from the sinusoidal endothelial cells (SECs) and smooth muscle cells (SMCs) around biliary epithelial cells (BEpCs) 2 hr after reperfusion, followed by positive immunoreactivity of Tm in BEpCs with hyperbilirubinemia, which was related to high mortality. Combined administration of OP-41483 and TUDC had a protective effect, demonstrated by sustained immunoreactivity of Tm from SECs and SMCs until POD 7, without that reactivity in BEpCs. This was associated with reduced congestion and hyperbilirubinemia, similar to the control group not subjected to warm ischemia.

CONCLUSIONS

These findings suggest that negative immunoreactivity of Tm in SECs and SMCs surrounding BEpCs and positive in BEpCs may be an early marker for ischemic liver injury, and that OP-41483 and TUDC may protect against the microcirculatory and biliary derangement.

Techniques available for the management of massive sacrococcygeal teratomas

An infant born in the 34th week of gestation weighing 5,355 g with a massive sacrococcygeal (SC) tumor was delivered by elective cesarean section. An ultrasonographic examination showed solid and cystic components in the tumor. Resection was successfully undertaken with insertion of a Nélaton catheter into the rectum to avoid unnecessary impairment of the viscera. The tumor weighed 2,380 g, measured 25 x 14 x 11 cm, and was clinicopathologically diagnosed to be a SC teratoma. This experience and other publications show that several considerations including control of hemorrhage and coagulopathies, visceral protection, and avoidance of wound infection are necessary to facilitate the surgical management of massive SC tumors. Several suggestions are made concerning the pre- and intraoperative management of this rare tumor.

Study of cell-material interaction by estimating NF-kappaB activation in HeLa S3 cells adhered onto hydrophilic substrates

In order to interpret how cells recognize biomaterials, nucleic factor-kappa B (NF-kappaB) activation in the attached HeLa S3 cells on various substrates was evaluated. As substrates, materials of hydrophilic nature (cellulose, poly(acrylamide)-grafted poly(ethylene) (PAAm-g-PE), and lipids films) were used. The contemporary assay method for NF-kappaB was modified to fit our system. As a result, NF-kappaB activation varied depending on the substrates. The NF-kappaB outcome was induced significantly in the HeLa S3 cells that had adhered onto the lipid films in a short time. On the other hand, high levels of NF-kappaB induction were observed in the HeLa cells adhered to the celluose and PAAm-g-PE after a 24 h incubation period. The induction of NF-kappaB by cell-material interaction is discussed from the point of view of biocompatibility.

Study of cellular responses to polymeric biomaterials using the differential display method

In this study, we attempted to detect altered gene expressions in the cells that had adhered to various surfaces using the differential display method. Thioglycollate-elicited peritoneal exudate cells (PEC) and mouse fibroblast (L929) cells were cultured on the polymer films. After a predetermined time, the total RNA was isolated from cells and the differential mRNA expressions were evaluated by RT-PCR method. As a result, in the differential display of amplified cDNA from PEC, the different patterns of cDNA fragments among the samples were obtained. This indicates that there were many different mRNA expressions depending on the polymer surfaces. The use of differential method was proven to be useful for studying cell-polymer interaction.

Apatite coating on hydrophilic polymer-grafted poly(ethylene) films using an alternate soaking process

Previously, we developed a novel alternate soaking process and clarified that bone-like apatite was formed on/in organic polymer hydrogel matrices using this process. The present study focused on the apatite coating on hydrophilic polymer grafted poly(ethylene) (PE) films with various grafting densities and commonly used hydrophilic polymers, poly(acryl amide) (PAAm) and poly(acrylic acid) (PAAc) were employed. From X-ray diffraction analysis, hydroxyapatite was coated on PAAm- or PAAc- grafted PE films. The amount of apatite coated on PAAm-grafted PE (PAAm-g-PE) films increased with an increase in the reaction cycles and the grafting density of PAAm. Similar to PAAm-g-PE, the amount of apatite coated on PAAc-grafted PE (PAAc-g-PE) films increased linearly with an increase in the grafting density of the PAAc up to around 30 microg/cm2. While, no significant increase in the apatite coating on the PAAc-g-PE films was observed even after 50 reaction cycles when the grafting densities of PAAc were over 30 microg/cm2. Apatite coating was not observed on original PE films. Scanning electron microscopic images reveal that the aggregation of apatite crystals on all PAAm-g-PE films and PAAc-g-PE films with grafting density from 10 to 30 microg/cm2. On the other hand, a dense apatite layer with some cracks was coated when the grafting density of the PAAc chains was over 30 microg/cm2. These results indicated that it was possible to coat apatite on hydrophilic polymer grafted PE films by an alternate soaking process and that the apatite crystal morphology could be controlled as a function of polymer type and density.

Preparation and characterization of apatite deposited on silk fabric using an alternate soaking process

Apatite-deposited silk fabric composite materials were developed using a new alternate soaking process. The characteristics of deposited apatite were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR), and X-ray photoelectron spectroscopy (XPS). Apatite weight increased with alternating soaking in a calcium solution [200 mM aqueous calcium chloride solution buffered with tris(hydroxymethyl) aminomethane and HCl (pH 7.4)] and a phosphate solution (120 mM aqueous disodium hydrogenphosphate) changed every hour. SEM showed that apatite deposited after 21 or more repeated soakings was over 20 microm thick. XRD showed that with alternate soakings, the apatite crystals deposited on silk fabric elongated along the c axis. FTIR and XPS indicated the existence of carbonate, HPO(4)(2-), and Na(+) ions in addition to constituent ions of hydroxyapatite. A loss of HPO(4)(2-) and Na(+) ions in the deposit upon further soaking might be associated with an increasing apatite crystallinity. Apatite deposited on silk by the alternate soaking process was a deficient apatite containing carbonate, HPO(4)(2-), and Na(+) ions as in a natural bone tissue. Thus, this apatite-silk composite material might be potentially bioactive.

A novel hydroxyl radical scavenger, nicaraven, protects the liver from warm ischemia and reperfusion injury

BACKGROUND

Reactive oxygen species have been considered to be involved in liver injury at the procurement, preservation, and transplantation from donors without beating hearts. A novel hydroxyl radical scavenger, nicaraven with hydrophilic and lipophilic properties, infiltrates both intracellular and extracellular spaces where it effectively scavenges reactive oxygen species. Protection by nicaraven against ischemia and reperfusion damage of the brain, heart, and kidneys has been shown. The effect of this agent on the liver remains unclear.

METHODS

Two-hour total hepatic vascular exclusion was used. Eighteen beagle dogs were randomly assigned to 2 groups: 12 animals were not treated (group I) and 6 were treated with nicaraven (group II). Nicaraven was administered intravenously (2mg/kg/min) for 60 minutes before ischemia and for 3 hours, starting 30 minutes before reperfusion.

RESULTS

Two-week survival rates were 25% in group I and 100% in group II (P <.01). Nicaraven inhibited lipid peroxidation in the liver, improved hepatic and systemic hemodynamics and energy metabolism, and suppressed liver enzyme release, endothelin-1 elevation in hepatic venous blood, histologic damage, and neutrophil infiltration into the liver.

CONCLUSIONS

Nicaraven exerted hepatic protection against warm ischemia and reperfusion injury. This may indicate nicaraven as a potential candidate to attenuate liver injury from warm ischemia and preservation in transplantation from donors without beating hearts.

Polymyxin B binds to anandamide and inhibits its cytotoxic effect

Anandamide (ANA), an endogenous cannabinoid, can be generated by activated macrophages during endotoxin shock and is thought to be a paracrine contributor to hypotension. We discovered that ANA in saline/ethanol solution and in serum was efficiently adsorbed in a polymyxin B (PMB)-immobilized beads column and eluted with ethanol. We confirmed the direct binding of PMB to ANA by using surface plasmon resonance. The adsorption of ANA by PMB may abolish the diverse effects of ANA such as hypotension, immunosuppression, and cytotoxicity, and may suggest a new therapeutic strategy for endotoxin shock.

Handlebar hernia with intra-abdominal extraluminal air presenting as a novel form of traumatic abdominal wall hernia: report of a case

An 18-year-old male was admitted to our Emergency Department with a traumatic abdominal wall hernia (TAWH) of the left lower quadrant (LLQ) after suffering hypogastric blunt injury and urogenital lacerations in a motorcycle accident. Upright chest X-ray showed a small amount of right infradiaphragmatic free air, and a computed tomographic (CT) scan demonstrated an abdominal wall hernia. At surgery, no impairment was found in the digestive tract, and an abdominal herniorrhaphy was performed. It is suggested that the free air had passed through a connection between the scrotal laceration and the contralateral abdominal defect via the subcutaneous space and was palpated as emphysema. This is a new type of TAWH, which suggests that blunt abdominal trauma may result in negative pressure in the subcutaneous and peritoneal cavity, and this could reflect the pathophysiology of TAWH.

Evaluation of biological responses to polymeric biomaterials by RT-PCR analysis IV: study of c-myc, c-fos and p53 mRNA expression

In order to investigate how cells recognize biomaterials, mRNA that was expressed in attached human fibroblasts on various substrates was evaluated. The expressed oncogenes (c-fos and c-myc) and tumor suppressor gene (p53) mRNA were then isolated and detected using the RT-PCR method. As a result, c-fos and c-myc mRNA expression varied with respect to differences in the hydrophilicity-hydrophobicity of the substrates. Both c-fos and c-myc mRNA expression were low in the fibroblasts that had adhered to hydrophilic surfaces. The tendency of c-fos mRNA expression was similar to the adhesion curve of the cells. c-myc mRNA was largely induced in fibroblasts that had adhered to hydrophobic surfaces. p53 mRNA were largely induced in fibroblasts that had adhered to hydrophilic surfaces, while in the cells that had adhered to hydrophobic surfaces, p53 mRNA expression was low. We concluded that the expression of oncogenes and p53 mRNA is a powerful method for studying cell-polymer interactions or the evaluation of the carcinogenic activity of biomaterials.

Study on complex formation between recombinant human thrombomodulin fragment and thrombin using surface plasmon resonance

Human thrombomodulin (hTM) is a newly described endothelial cell associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant. The affinity constant of recombinant human soluble TM (rhs-TM) and a peptide containing active site of hTM fragment (f-hTM) with thrombin were determined using the surface plasmon resonance. The interaction of f-hTM with thrombin could be analyzed by a simple model, whereas the association and the dissociation steps of rhs-TM with thrombin consisted of at least two kinds of interaction phases. The dissociation constant for complex (K(D)) of f-hTM and thrombin was determined to be 205 nM, which was more than twice as high as that of rhs-TM (6.7 and 75 nM). The lower affinity of f-hTM was not due to the slow association rate but to the rapid dissociation rate. It comes clear that f-hTM interacts with thrombin rapidly.

Prolongation of canine liver allograft survival by a novel immunosuppressant, FTY720: effect of monotherapy and combined treatment with conventional drugs

BACKGROUND

The immunosuppressive effect and other properties of a novel immunosuppressant, FTY720, have been studied mostly in the experimental transplantation of various extrahepatic organs. In this experiment, we evaluated the antirejection potency and adverse effects of this agent on liver grafts using a canine liver transplantation model.

METHODS

Forty-eight orthotopic liver transplantations were performed by the standard technique under a veno-venous bypass. Liver recipients were divided into two studies: a single-dose study with FTY720 at various doses and a combined dose study with conventional immunosuppressants (cyclosporine or tacrolimus) alone and combined with FTY720. Survival, biochemical and hematological tests, blood levels of immunosuppressants, and postmortem histology were determined.

RESULTS

The median survival of untreated control animals was 9 days, whereas treatment with FTY720 at a dose of 0.1 mg/kg/day prolonged graft survival to 49.5 days. FTY720 at 1 mg/kg/day showed a slight but insignificant prolongation to 16 days, but when the dose was increased to 5 mg/kg/day, the graft was rejected at 10 days. The combination of FTY720, 0.1 mg/kg/day, with a subtherapeutic dose of cyclosporine, 5 mg/kg/ day, prolonged median animal survival from 40 days with cyclosporine alone to 74 days. A combination of FTY720 (0.1 mg/kg/day) with tacrolimus (0.5 mg/kg/ day) compromised animal survival, reducing survival from 83.5 days with tacrolimus alone to 30.5 days due to infectious complication and emaciation by overimmunosuppression. No evident drug-induced side effects were observed.

CONCLUSIONS

FTY720 has a potent immunosuppressive effect when used alone at 0.1 mg/kg/day in canine liver transplantation. FTY720 is a promising candidate for future clinical application in orthotopic liver transplantation.

Apatite formation on/in hydrogel matrices using an alternate soaking process (III): effect of physico-chemical factors on apatite formation on/in poly(vinyl alcohol) hydrogel matrices

The aim of this study is to clarify the physico-chemical factors which influence apatite formation on/in a hydrogel during a novel alternate soaking process. A poly(vinyl alcohol) (PVA) gel was used as a model matrix. The amount of apatite formed on/in PVA gels decreased with an increase in the reaction temperature during the same reaction cycles. This suggested that the equilibrium swelling ratios decreased with increasing reaction temperatures; that is, the diffusion of calcium and phosphate ions reduced at high reaction temperature. However, the crystallinity of apatite formed on/in PVA gels was greater at higher reaction temperatures. The amount of apatite formed on/in PVA gels increased with an increase in the calcium and phosphate solution concentrations, and increased by shaking at the first three reaction cycles. A few influences could be observed when the solution volume was changed, however, the soaking order was not effective in this study. These results indicate that the amount of apatite formation on/in PVA gels can be controlled by changing the reaction temperature and the Ca- and P-solution concentrations, and that the crystallinity of apatite can be also changed by controlling the reaction temperatures.

[Application of microvascular surgery in reconstructive digestive tract surgery]

In our institutes, microvascular surgery has been effectively used in reconstructive digestive tract surgery, including esophageal reconstruction and hepatic arterial reconstruction. Free jejunal transfer combined with a gastric pedicle or microvascularly augmented elongated gastric pedicle has been utilized for total esophageal reconstruction. A microvascularly augmented jejunal pedicle or colonic pedicle has been applied in thoracic esophageal reconstructive cases with gastrectomy. Moreover, microvascular surgery has been performed in the reconstruction of the hepatic arterial system in the surgical treatment of pancreatic or bile duct cancer and living related-donor liver transplantation. Some pitfalls in selection of the recipient vessels and handling the intraperitoneal vessels for microvascular anastomosis are also described. Although microvascular surgery has been carried out by plastic and reconstructive surgeons in a team surgical approach, revisions in the medical educational system to create a new-type of surgeon with practical skills and clinical experience in both digestive tract and microvascular surgery will be required in future.

Ca-adsorption and apatite deposition on silk fabrics modified with phosphate polymer chains

Silk fabric was modified with polymethacryloyloxyethylphosphate (pMOEP) by graft copolymerization. Ca-adsorption onto pMOEP-grafted silk fabric was significantly enhanced compared to that onto original silk fabric. SEM observation indicated that some crystallites were deposited on the pMOEP-grafted silk fabric after 1 week of immersion in simulated body fluid, whereas no change occurred on the surface of the original silk fabric. X-ray diffraction showed that this crystallite contained hydroxyapatite. These results indicate that pMOEP-grafted silk fabric induce hydroxyapatite formation more effectively than the original silk fabric.

Apatite formation on/in hydrogel matrices using an alternate soaking process: II. Effect of swelling ratios of poly(vinyl alcohol) hydrogel matrices on apatite formation

In our previous study, we reported a novel method of apatite formation on/in a three-dimensional hydrogel matrix. Using this method, bone-like apatite could be formed on/in the hydrogel matrix under normal conditions in vitro. A poly(vinyl alcohol) (PVA) gel was used as a model matrix. The method consists of two steps: first, water is transformed in a PVA gel with a CaCl2/Tris-HCl aqueous solution (pH 7.4) and second, the gel is soaked in a Na2HPO4 aqueous solution. In the present study, we report a detailed study of the effects of the swelling ratios of PVA gels on apatite formation. Cross-sectional observations and gravimetric measurements of PVA gels with various swelling ratios were done. The amount of apatite formed on/in PVA gels increased almost linearly with an increase in the reaction cycles. The rates of apatite formation on/in PVA gels largely depended on the swelling ratios, which were approximately 0.48, 0.61, 1.28, and 1.55 mg per cycle for swelling ratios of 4.1, 10.4, 16.8, and 30.1, respectively. The apatite content in PVA-apatite composites that was obtained by this method also increased with an increase of the reaction cycles. After six reaction cycles, a PVA gel with a high swelling ratio contains approximately 70 wt% of formed apatite in the composite. On the other hand, a gel with a low swelling ratio contains about 15 wt% of formed apatite in the composite. Cross-sectional views of the PVA gels after each cycle showed that apatite crystals were formed, not only on the surface of the gel but also within it after fifteen reaction cycles. The hydrogel-apatite composites that were obtained using an alternative soaking process will be useful as not only bone substitute materials but also as soft tissue adhesive materials.

A study on hydroxyapatite formation on/in the hydroxyl groups-bearing nonionic hydrogels

Using the biomimetic method, we formed a hydroxyapatite (HAp) layer on/in certain types of nonionic hydrogels that contain hydroxyl groups. The hydrogels used were poly(vinyl alcohol) (PVA), poly(2-hydroxyethyl methacrylate) (PHEMA), poly(glucosyloxyethyl methacrylate) (PGEMA), and agarose. Under an optical microscope, we observed a thin, continuous HAp layer on the top surface of the PVA, PHEMA, and PGEMA gels. On the other hand, we only observed an intermittent HAp layer on the surface of the agarose gel. The swelling ratio and the bound water content of these hydrogels were measured as an essential character in HAp formation. There was some relation among the HAp formation, the swelling ratios, and the bound water content.

Protective role of nitric oxide in ischemia and reperfusion injury of the liver

BACKGROUND

The suppressed production of nitric oxide (NO), associated with endothelial dysfunction, is thought to be a cause of ischemia and reperfusion injury of the liver. But findings of the salutary effects of NO enhancement on such injury have been conflicting. In this study, we tested our hypothesis that NO enhancement would attenuate ischemic liver injury. For this purpose, an NO precursor, L-arginine, and a novel NO donor, FK409, were applied to a 2-hour total hepatic vascular exclusion model in dogs.

STUDY DESIGN

L-arginine was administered IV at a dose of 100 mg/kg twice (n = 5), while 300 mg/kg twice of FK409 was infused continuously into the portal vein (n = 5). The drugs were given to the animals for 30 and 60 minutes before and after ischemia, respectively. Non-treated animals were used as the control (n = 10). Two-week survival, systemic and hepatic hemodynamics indices, liver function tests, energy metabolism, and histopathology were analyzed.

RESULTS

Both treatments comparably augmented hepatic tissue blood flow, decreased liver enzyme release, and increased high-energy phosphate restoration during the reperfusion period, all of which contributed to rescuing all of the treated animals from the 2-hour total hepatic ischemia. In contrast, ischemia caused 70% mortality in the control group. Histologically, structural abnormality and neutrophil infiltration were markedly attenuated by the treatments. Systemic hypotension was observed in the animals treated with FK409, however.

CONCLUSIONS

Our data demonstrate that NO enhancement alleviates the liver injury caused by ischemia and reperfusion. The supplementation of L-arginine, rather than FK409, is considered more applicable to clinical use because of the absence of systemic adverse effects.