Development of fibrinogen gamma-chain peptide-coated, adenosine diphosphate-encapsulated liposomes as a synthetic platelet substitute

BACKGROUND

The dodecapeptide HHLGGAKQAGDV (H12), corresponding to the fibrinogen gamma-chain carboxy-terminal sequence (gamma 400-411), is a specific binding site of the ligand for platelet GPIIb/IIIa complex. We have evaluated H12-coated nanoparticles (polymerized albumin or liposome) as platelet function-supporting synthetic products.

OBJECTIVES

To strengthen the hemostatic ability of H12-coated particles as a platelet substitute, we exploited installation of a drug delivery function by encapsulating adenosine diphosphate (ADP) into liposomes [H12-(ADP)-liposomes].

METHODS AND RESULTS

Via selective interaction with activated platelets through GPIIb/IIIa, H12-(ADP)-liposomes were capable of augmenting agonist-induced platelet aggregation by releasing ADP in an aggregation-dependent manner. When intravenously injected into rats, liposomes were readily targeted to sites of vascular injury as analyzed on computed tomography. In fact, comparable to fresh platelets, liposomes exhibited considerable hemostatic ability for correcting prolonged bleeding time in a busulphan-induced thrombocytopenic rabbit model. In addition, the liposomes showed no activating or aggregating effects on circulating platelets in normal rabbits.

CONCLUSION

H12-(ADP)-liposome may thus offer a promising platelet substitute, being made with only synthetic materials and exerting hemostatic functions in vivo via reinforcement of primary thrombus formation by residual platelets in thrombocytopenia at sites of vascular injury, but not in circulation.

Detailed comparison of expressed and native voltage-gated proton channel currents

Two years ago, genes coding for voltage-gated proton channels in humans, mice and Ciona intestinalis were discovered. Transfection of cDNA encoding the human HVCN1 (H(V)1) or mouse (mVSOP) ortholog of HVCN1 into mammalian cells results in currents that are extremely similar to native proton currents, with a subtle, but functionally important, difference. Expressed proton channels exhibit high H(+) selectivity, voltage-dependent gating, strong temperature sensitivity, inhibition by Zn(2+), and gating kinetics similar to native proton currents. Like native channels, expressed proton channels are regulated by pH, with the proton conductance-voltage (g(H)-V) relationship shifting toward more negative voltages when pH(o) is increased or pH(i) is decreased. However, in every (unstimulated) cell studied to date, endogenous proton channels open only positive to the Nernst potential for protons, E(H). Consequently, only outward H(+) currents exist in the steady state. In contrast, when the human or mouse proton channel genes are expressed in HEK-293 or COS-7 cells, sustained inward H(+) currents can be elicited, especially with an inward proton gradient (pH(o) < pH(i)). Inward current is the result of a negative shift in the absolute voltage dependence of gating. The voltage dependence at any given pH(o) and pH(i) is shifted by about -30 mV compared with native H(+) channels. Expressed H(V)1 voltage dependence was insensitive to interventions that promote phosphorylation or dephosphorylation of native phagocyte proton channels, suggesting distinct regulation of expressed channels. Finally, we present additional evidence that speaks against a number of possible mechanisms for the anomalous voltage dependence of expressed H(+) channels.

Development of biodegradable nanosheets as nanoadhesive plaster

Sheet-shaped carriers having both obverse and reverse surfaces (thus, a large contact area for targeting a site and adhesive properties without any chemical cross-linker onto tissue surface) have several advantages as surgical dressings. These advantages include active targeting over spherically shaped carriers, which thus have an extremely small contact area for targeting sites. Here, we propose a novel methodology for preparation of a free-standing, ultra-thin, and biocompatible polymer nanosheet having heterosurfaces, fabricated through macromolecular assembly. In the context of biomedical applications, the targeted properties include injectable sheet-shaped drug carriers having precisely controlled size by exploiting micropatterned substrate, and giant polymer nanosheets composed of biocompatible polysaccharides. A huge aspect ratio, in excess of 106, is particularly applicable for novel surgical dressings. These biocompatible polymer nanosheets having heterosurfaces can thus be regarded as new biomaterials for minimally invasive treatment.

[Histoculture drug response assay guided concurrent chemoradiotherapy for non-small cell lung cancer]

Retrospective analysis was done to evaluate concurrent chemoradiotherapy (CCRT) using chemotherapeutic agents judged to be sensitive by histoculture drug response assay (HDRA) for non-small cell lung cancer (NSCLC). We treated 21 NSCLC patients with CCRT using senstivie agents judged by HDRA from 1999 to 2004. Objective response was evaluated in 20 patients. They were consisted of 1 complete response (CR) case, 18 partial response (PR) cases, and 1 stable disease (SD) case. The response rate was 95%. Ten cancer related deaths were observed during 816 +/- 861 (60-2,780) days follow-up. Median survival time was 604 days. One- and 5-year survival rates were 73.9% and 40.3%, respectively. In conclusion, HDRA may improve efficacy of CCRT for NSCLC.

Lymphangiosarcoma in a cat

This report describes a 5-year-old female cat with lymphangiosarcoma arising within the dermis and subcutis of the caudal mammary region. The mass presented as a large, poorly demarcated and fluctuant swelling with bruising of the overlying skin. Histopathologically, the dermis and subcutis in the affected region were diffusely oedematous, haemorrhagic, and infiltrated by plump spindle cells that formed irregular vascular clefts and cavernous channels. Neoplastic cells were aligned in one or more layers along oedematous collagenous trabeculae. The vascular clefts and channels contained only a few or no erythrocytes. The neoplastic cells had moderate to marked nuclear pleomorphism and prominent nucleoli. Lymphocytes and plasma cells were scattered throughout the neoplasm and the adjacent soft tissues. Immunohistochemical labelling revealed the neoplastic cells to express vimentin, factor VIII-related antigen and the lymphatic endothelial cell marker PROX-1, but the cells did not express cytokeratin. The nuclei of many neoplastic cells expressed the proliferation marker Ki67. These histopathological and immunohistochemical findings confirmed the diagnosis of lymphangiosarcoma. This is the first report describing the usefulness of expression of PROX-1 for differentiating between angiosarcoma of lymphatic and vascular origin in cats.

Prolonged hemostatic ability of polyethylene glycol?modified polymerized albumin particles carrying fibrinogen ?-chain dodecapeptide

BACKGROUND

Second-generation platelet (PLT) substitutes for treatment of bleeding were studied and the focus was on a dodecapeptide, HHLGGAKQAGDV (H12), which is a fibrinogen gamma-chain carboxy-terminal sequence (gamma 400-411) and exists only in a fibrinogen domain.

STUDY DESIGN AND METHODS

H12 was conjugated to the surface of polymerized albumin particles (polyAlb) modified with polyethylene glycol (PEG) chains to produce biocompatible particles (H12-PEG-polyAlb) that had prolonged blood circulation t((1/2)) and were more stable in vitro and in vivo compared with H12-polyAlb (not modified with PEG). H12-PEG-polyAlb was administered intravenously into thrombocytopenic rats and the t((1/2)) of the particles and the tail bleeding time were measured to evaluate the prolongation in the hemostatic effect.

RESULTS

H12-PEG-polyAlb particles modified with PEG prolonged the t((1/2)) and maintained specific binding ability to activated PLTs. The particles dose dependently shortened the tail bleeding time of thrombocytopenic rats 6 hours after injection.

CONCLUSION

H12-PEG-polyAlb may be a suitable candidate for treatment of bleeding into thrombocytopenic patients as an alternative to PLT concentrate transfusion.

New strategy of platelet substitutes for enhancing platelet aggregation at high shear rates: cooperative effects of a mixed system of fibrinogen γ-chain dodecapeptide- or glycoprotein Ibα-conjugated latex beads under flow conditions

To construct platelet substitutes that have hemostatic properties over a wide range of shear rates, we used fibrinogen gamma-chain carboxy-terminal sequence HHLGGAKQAGDV (H12), which recognizes activated platelets at low shear rates, and a recombinant water-soluble moiety of the platelet glycoprotein (rGPIbalpha), which recognizes von Willebrand factor at high shear rates. Three kinds of samples were prepared for this purpose: H12-conjugated latex beads (H12-latex beads), rGPIbalpha-latex beads, and H12/rGPIbalpha-latex beads. These samples were evaluated in thrombocytopenia-imitation blood at various flow conditions. Based on ADP-induced platelet aggregation studies, the H12-latex beads significantly enhanced platelet aggregation via H12 binding with GPIIb/IIIa activated on the surface of activated platelets, whereas the rGPIbalpha-latex beads did not support platelet aggregation. In the case of the H12/rGPIbalpha-latex beads, the function of H12 was suppressed by steric hindrance from the larger rGPIbalpha bound to the latex bead. A mixture of the H12-latex beads and the rGPIbalpha-latex beads adhered to a collagen surface over a wide range of shear rates. In particular, at high shear rates, a cooperative effect was observed in the enhancement of platelet thrombus formation compared with H12-latex beads or rGPIbalpha-latex beads alone. We propose that a mixed system of H12- and rGPIbalpha-conjugated nanoparticles is a more effective platelet substitute than each of the beads used alone and has enhanced platelet aggregation properties.

[Surgical stabilization of multiple rib fracture and flail chest]

The experience of 14 cases with surgical stabilization of multiple rib fracture and flail chest was reported. They were 11 men and 3 women of 31 to 87 years of age. Paradoxical chest movement was noted in 10 patients. Thirteen of 14 patients successfully weaned from the ventilator less than 7 days after surgery. Of 14, 4 cases were treated with internal fixation and the others were with acetabular reconstruction plates with or without rib stapler. No case of death was experienced. Ten patients who were performed fixation with acetabular reconstruction plate weaned from the ventilator earlier than cases treated by internal fixation, suggesting the superiority of the acetabular reconstruction plate. Improvement of rib stapler and the development of a titanium plate of specific use for rib is expected in the future.

[Effects of octreotide acetate on intractable chylothorax after surgery for congenital heart diseases]

We experienced 2 infants in whom octreotide acetate was effective on intractable chylothorax after surgery for congenital heart diseases. They were 8- and 5-month-old. They were diagnosed as having corrected transposition of the great arteries (TGA) and tetralogy of Fallot respectively, and underwent bidirectional Glenn anastomosis and right modified Blalock Taussig shunt. Chylothorax was revealed on the 11th and the 1st postoperative day, and was not improved by any conventional therapy in either case. Then octreotide acetate was infused continuously with 0.1-0.6 micorg/kg/hour for 24 and 7 days. Chylothorax disappeared completely without any complications such as disturbance of blood sugar level or growth retardation. Octreotide acetate was effective and safe even in infants in intractable chylothorax after surgery for congenital heart diseases, as long as used for short period.

[Effects of additional pulmonary blood flow after bidirectional Glenn procedure]

Thirteen cases of functional single ventricle who had undergone bidirectional Glenn procedure were divided into 2 groups according to presence (5) or absence (8) of additional pulmonary blood flow. Additional flow was preserved in cases with relatively small pulmonary artery index (PA index), and their sources were antegrade pulmonary blood flow (2), and Blalock-Taussig (BT) shunt (3). In the control group, PA index was reduced to about 70% of the preoperative value, while in the additional group, pulmonary artery growth was recognized without significant elevation of mean pulmonary artery pressure. However, atrioventricular valve regurgitation progressed and systemic ventricular volume did not decrease after Glenn in the additional group. Therefore special consideration for the timing of Fontan procedure is mandatory.

[Evaluation of aortic valve replacement involving small severely calcified aortic annulus in elderly patients]

We performed aortic valve replacement in 24 patients aged over 70 with small calcified valves. The surgical management of such patients remains controversial as the extensive calcification compromises implantation. Hence, we used an ultrasonic debridement instrument to remove calcium and selected a small prosthesis with the largest possible orifice without enlargement of the aortic annulus. Echocardiography showed significant reductions in left ventricular mass index compared with preoperative values. Early and mid-term prognosis has been relatively good.

GABAergic synaptic transmission modulates swimming in the ascidian larva

To examine the role of the amino acid GABA in the locomotion of basal chordates, we investigated the pharmacology of swimming and the morphology of GABA-immunopositive neurones in tadpole larvae of the ascidians Ciona intestinalis and Ciona savignyi. We verified that electrical recording from the tail reflects alternating muscle activity during swimming by correlating electrical signals with tail beats using high-speed video recording. GABA reversibly reduced swimming periods to single tail twitches, while picrotoxin increased the frequency and duration of electrical activity associated with spontaneous swimming periods. Immunocytochemistry for GABA revealed extensive labelling throughout the larval central nervous system. Two strongly labelled regions on either side of the sensory vesicle were connected by an arc of labelled fibres, from which fibre tracts extended caudally into the visceral ganglion. Fibre tracts extended ventrally from a third, more medial region in the posterior sensory vesicle. Two rows of immunoreactive cell bodies in the visceral ganglion extended neurites into the nerve cord, where varicosities were seen. Thus, presumed GABAergic neurones form a network that could release GABA during swimming that is involved in modulating the time course and frequency of periods of spontaneous swimming. GABAergic and motor neurones in the visceral ganglion could interact at the level of their cell bodies and/or through the presumed GABAergic fibres that enter the nerve cord. The larval swimming network appears to possess some of the properties of spinal networks in vertebrates, while at the same time possibly showing a type of peripheral innervation resembling that in some protostomes.

Opposing effects of oestradiol and progesterone on intracellular pathways and activation processes in the oxidative stress induced activation of cultured rat hepatic stellate cells

BACKGROUND

Oxidative stress, including the generation of reactive oxygen species (ROS), is involved in hepatofibrogenesis. The authors' previous studies have shown that oestradiol suppresses hepatic fibrosis in animal models and attenuates the activation of cultured rat hepatic stellate cells (HSCs), which possess oestrogen receptor subtype beta and are also activated by ROS.

AIMS

To define the mechanisms by which female sex hormones play an antifibrogenic role in activated HSCs, the effects of oestradiol and progesterone on ROS generation processes and intracellular pathways, leading to the activation of HSCs undergoing oxidative stress, was examined.

METHODS

HSCs, isolated from rats, were cultured for 7 days with oestradiol or progesterone for 24 hours as pretreatment, and oxidative stress was then induced by exposure to low doses of hydrogen peroxide for another 24 hours.

RESULTS

Oestradiol inhibited ROS generation and antioxidant enzyme loss via the suppression of NADH/NADPH oxidase activity, and attenuated hydrogen peroxide induced transforming growth factor-beta1 (TGF-beta1) expression, HSC proliferation and transformation, and the activation of mitogen activated protein kinase (MAPK) pathways and transcription factors. Progesterone exerted a stimulatory effect through the progesterone receptor on the induction of ROS generation processes and intracellular pathways, resulting in TGF-beta1 expression and HSC activation, and fibrogenic effects were inhibited by oestradiol.

CONCLUSION

These findings show for the first time that oestradiol inhibits the activation of transcription factors by suppressing ROS generation processes and the MAPK pathways, and inactivates the downstream transcription processes involved in TGF-beta1 expression and HSC activation, whereas progesterone acts in opposition to the favourable effects of oestradiol and its effects are blocked by oestradiol.

[Jatene procedure with arch repair; usefulness of rapid two-stage repair]

Four cases of Jatene procedure with arch repair were performed since 2000 in our department. Two-stage repair was used in all cases and the extended end-to-end anastomosis and pulmonary artery banding (PAB) were performed in 3 cases as the initial repair. In a recent case of TGA type I with coarctation of the aorta (CoA), only subclavian flap aortoplasty was performed when he was 6-day-old and patent ductus arteriosus (PDA) was preserved and rapid two-stage Jatene procedure was performed when he was 8-day-old. There was no hospital or late death, or reoperation. The results of the two-stage Jatene procedure with arch repair was good and safe. Rapid two-stage repair was thought to be a useful choice especially for TGA type I with arch anomaly.

Opposing effects of oestradiol and progesterone on intracellular pathways and activation processes in the oxidative stress induced activation of cultured rat hepatic stellate cells

BACKGROUND

Oxidative stress, including the generation of reactive oxygen species (ROS), is involved in hepatofibrogenesis. The authors' previous studies have shown that oestradiol suppresses hepatic fibrosis in animal models and attenuates the activation of cultured rat hepatic stellate cells (HSCs), which possess oestrogen receptor subtype beta and are also activated by ROS.

AIMS

To define the mechanisms by which female sex hormones play an antifibrogenic role in activated HSCs, the effects of oestradiol and progesterone on ROS generation processes and intracellular pathways, leading to the activation of HSCs undergoing oxidative stress, was examined.

METHODS

HSCs, isolated from rats, were cultured for 7 days with oestradiol or progesterone for 24 hours as pretreatment, and oxidative stress was then induced by exposure to low doses of hydrogen peroxide for another 24 hours.

RESULTS

Oestradiol inhibited ROS generation and antioxidant enzyme loss via the suppression of NADH/NADPH oxidase activity, and attenuated hydrogen peroxide induced transforming growth factor-beta1 (TGF-beta1) expression, HSC proliferation and transformation, and the activation of mitogen activated protein kinase (MAPK) pathways and transcription factors. Progesterone exerted a stimulatory effect through the progesterone receptor on the induction of ROS generation processes and intracellular pathways, resulting in TGF-beta1 expression and HSC activation, and fibrogenic effects were inhibited by oestradiol.

CONCLUSION

These findings show for the first time that oestradiol inhibits the activation of transcription factors by suppressing ROS generation processes and the MAPK pathways, and inactivates the downstream transcription processes involved in TGF-beta1 expression and HSC activation, whereas progesterone acts in opposition to the favourable effects of oestradiol and its effects are blocked by oestradiol.