Volume therapy with colloid solutions preserves intestinal microvascular perfusion in endotoxaemia

Colloid solutions have been suggested to improve microvascular perfusion due to their anti-inflammatory properties. Whether this also applies for the gut, an important immunological organ vulnerable to hypoperfusion is unknown. This study investigated intestinal microcirculation of endotoxaemic rats after volume therapy with colloid solutions such as hydroxyethyl starch (HES) and gelatin or isotonic saline (NaCl). In addition intestinal oxygenation and morphology as well as mesenteric leukocyte-endothelium interaction were quantified. Rats were anaesthetised with urethane and ketamine, mechanically ventilated, and monitored haemodynamically. Normotensive endotoxaemia was induced by a continuous intravenous infusion of Escherichia coli lipopolysaccharide (LPS, 1.5 mg kg(-1) h(-1)). After 1 h of LPS infusion either 6% HES (16 ml kg(-1)), 4% gelatin (16 ml kg(-1)) or 0.9% NaCl (64 ml kg(-1)) were infused for 1 h. Using intravital microscopy, functional capillary density (FCD) and red blood cell velocity (RBCV) were measured in the mucosa of the terminal ileum at baseline and 3 h after volume therapy. In another set of animals, mesenteric leukocyte-endothelium interaction was determined 3 h after volume therapy. In all animals intestinal lactate/pyruvate ratio and intestinal morphology were assessed. Three hours after volume therapy, FCD decreased in NaCl (808 [749/843] cm(-1); median [quartiles] P<0.05 versus baseline) but not in HES (995 [945/1036] cm(-1)) and gelatin (988 [867/1193] cm(-1)) groups. RBCV, lactate/pyruvate ratio and intestinal morphology did not differ among groups. Also mesenteric leukocyte-endothelium interaction was not significantly influenced by either treatment. In conclusion, early volume therapy with HES or gelatin, but not with NaCl, preserved gut microvascular perfusion during endotoxaemia but did not have a significant effect on tissue oxygenation nor morphological appearance in this experimental model. An anti-inflammatory effect of colloid solutions was not seen and fails to explain the changes in intestinal microcirculation.

The effect of carbodiimide-derivatized hyaluronic acid and gelatin surface modification on peroneus longus tendon graft in a short-term canine model in vivo

PURPOSE

We have recently reported that application of carbodiimide-derivatized hyaluronic acid and gelatin (cd-HA gelatin) to a peroneus longus tendon graft increased tendon graft gliding ability and decreased work of flexion compared with untreated grafts in a canine model in vivo. In this study, we investigated the effect of this modification on adhesions, stiffness, strength of the distal attachment, and fibroblast count.

METHODS

A total of 24 dogs were used for this study. The peroneus longus tendons of each hind leg were grafted into the 2nd and 5th digits of one forepaw in each dog. One peroneus longus tendon was treated with cd-HA gelatin prior to grafting, and the other one was immersed in 0.9% saline solution as a control. Animals were killed 1, 3, or 6 weeks postoperatively.

RESULTS

The adhesion score of cd-HA gelatin-treated tendons was significantly less than that in the saline-treated tendons at all time points. There was no significant difference in the indentation stiffness between HA- and saline-treated grafts at any time point. For the ultimate force at the distal attachment, there was a significant difference among the time points, with a steady increase over time, but no significant difference between treated and control tendons at any time point. There was no significant difference in fibroblast count between treated and control tendons at any time point.

CONCLUSIONS

Although gross adhesion formation was less, there was no significant difference in strength at the distal tendon-bone interface, cellularity, or tendon graft stiffness when comparing saline-treated and cd-HA gelatin-treated tendon grafts in vivo.

Mechanical and biocompatible influences of chitosan fiber and gelatin on calcium phosphate cement

Calcium phosphate cement (CPC) is a widely used bone substitute in the clinic; however, the low strength of CPC limits its utilization. In this study, we investigated mechanical influences of chitosan fiber combined with gelatin on CPC, and examined the biocompatibility of the new composite with rat bone marrow stromal cells. Compared to the fiber impregnated in phosphate buffered saline (80.5 MPa), our study showed that tensile strength of chitosan fiber increased 106 and 114% with the impregnation of gelatin at the mass fraction 5 and 10%, although this increase was not statistically significant. It was demonstrated by Fourier transform infrared spectroscopy that the characteristic absorption bands of chitosan were changed with the addition of gelatin. The optimal flexural strength enhancement was obtained when CPC was reinforced with fiber at volume fraction of 30% and gelatin at mass fraction of 5% (maximum: 12.31 MPa). The fiber morphology was more compact when the chitosan fibers impregnated with gelatin at mass fraction of 5 or 10% than chitosan alone. The fracture analysis showed that the new CPC-chitosan fiber-gelatin composite presented many remnants of CPC adhered to fibers. Short minimum essential medium extract test showed no cell growth inhibition after the addition of the new composite. Rat bone marrow stromal cells retain the ability to spread and grow on the composite. Our studies demonstrated that the flexural strength is greatly increased by using CPC incorporated with proper ratio of CF and gelatin. More over, the new composite demonstrated biocompatibility in vitro.

[Effect of proteins pre-coating on bone marrow mesenchymal cells retention and proliferation on decellular bovine pericardium]

To observe the growth of rat bone marrow mesenchymal cells (BMMCs) on decellular bovine pericardia in vitro and to investigate the effect of proteins pre-coating on cells retention and proliferation, bovine pericardia were decellularized using trypsin, DNase and Triton X-100 respectively. Then three proteins (fibronetin (FN), gelatin, collagen I) were coated on the surfaces of the bovine pericardia separately. BMMCs were harvested from rat thighbone marrow , then expanded and seeded onto decellular bovine pericardia with the proteins pre-coated . Decelluar bovine pericardia without coating were used as controls. The retention and growth of BMMSCs were observed by Hochest staining and analyzed by MTT method. It was shown that the retention and proliferation of BMMCs on FN group and gelatin group were significantly enhanced comparing with those on collagen I group and control group (P < 0.001). There was no significant difference between FN group and gelatin group (P > 0.05), nor between collagen I group and control group (P > 0.05). We conclude that the retention and proliferation of seeding cells on FN and gelatin could be significantly improved on decellular bovine pericardia (DBP) but not on collagen I.

Influence of sex and estrous cycle on the effects of acute tryptophan depletion induced by a gelatin-based mixture in adult Wistar rats

Women are more vulnerable to develop depression and anxiety disorders than men. This may be related to higher serotonergic vulnerability in women. Serotonergic vulnerability entails that differences between people in the regulation of serotonin (5-HT) determine the vulnerability of an individual to develop depression or other 5-HT-related disorders. The aim of the present experiment was to evaluate whether male and female Wistar rats differ in serotonergic vulnerability. Here, a stronger behavioral response to acute tryptophan (TRP) depletion was assumed to reflect serotonergic vulnerability. Twenty-four male and 48 female rats were repeatedly subjected to treatment with a gelatin-based protein-carbohydrate mixture, either with or without L-tryptophan. Female estrous cycle phase was determined by means of vaginal smears and the females were divided into two groups based on their estrous cycle phase: pro-estrus/estrus and met-estrus/di-estrus. Blood samples showed stronger TRP depletion in males than females. There was no effect of estrous cycle on plasma TRP concentrations. In contrast, treatment effects on some brain TRP concentrations were influenced by estrous cycle phase, females in pro-estrus/estrus showed the strongest response to TRP depletion. In the open field test and home cage emergence test, females in pro-estrus/estrus also showed the strongest behavioral response to acute TRP depletion. In general, females showed more activity than males in anxiety-related situations and this effect appeared to be enhanced by TRP depletion. In the social interaction test, passive body contact in males and females in pro-estrus/estrus was decreased after TRP depletion whereas it was increased in females in the met-estrus/di-estrus phase. Acute TRP depletion affected object recognition, but did not affect behavior in the forced swimming test and a reaction time task. It is concluded that sex and estrous cycle phase can influence the behavioral response to TRP depletion, and that females in pro-estrus/estrus show the strongest behavioral response to acute TRP depletion.

FLUID RESUSCITATION IN SEVERE SEPSIS AND SEPTIC SHOCK

The aim of this study was to investigate whether the type of i.v. fluid administered has an impact on outcome in an animal model of septic shock. The study included 28 anesthetized, invasively monitored, mechanically ventilated female sheep (29.5 +/- 4.0 kg), which received 0.5 g/kg body weight of feces into the abdominal cavity to induce peritonitis. During the surgical operation and 4 h after feces spillage, only Ringer's lactate (RL) was administered in all animals. Thereafter, animals were randomized to receive continuous infusions of RL (n = 7) alone or combined with either 20% albumin (n = 7, volume ratio to RL 1:10) or 6% hydroxyethyl starch (HES) (n = 7, volume ratio to RL 1:1), or gelatin alone (n= 7, no volume limitation). Fluid resuscitation was titrated to maintain pulmonary artery occlusion pressure at baseline levels throughout the experiment. No antibiotics or vasoactive drugs were administered, and animals were monitored until their spontaneous death. Hemodynamic variables were better with HES and albumin than with the other fluids, as reflected by higher stroke volume, cardiac index, and oxygen delivery (all P < 0.05). Hydroxyethyl-starch-treated animals also had lower arterial lactate concentrations (P < 0.01). However, times to develop hypotension and oliguria were similar in all groups. Blood interleukin (IL) 6 concentrations were significantly increased in all groups. The mean survival time was similar in all groups. In this clinically relevant model of prolonged septic shock, albumin and HES solution resulted in higher cardiac output, oxygen delivery, and lower blood lactate levels than gelatin and RL; however, the choice of i.v. fluid did not affect outcome.

Randomized clinical trial comparing the effects on renal function of hydroxyethyl starch or gelatine during aortic aneurysm surgery

Background

The optimal colloid for renal protection during abdominal aortic aneurysm (AAA) surgery is not known. This study compared the effects of two hydroxyethyl starch (HES) solutions and gelatine on perioperative renal function.

Methods

Sixty-two patients undergoing AAA surgery were randomized to 6 per cent HES of molecular weight 200/0·62 kDa or 130/0·4 kDa, or 4 per cent gelatine for plasma expansion. Measurements were taken of serum urea and creatinine to mark glomerular filtration, urinary immunoglobulin G : creatinine ratio to mark glomerular membrane function and α1-microglobulin : creatinine ratio to mark tubular dysfunction before, and for 5 days after, surgery.

Results

Serum urea was lower in both HES groups than the gelatine group. Serum creatinine was lower with HES 130/0·4 compared with gelatine at days 1, 2 and 5 after surgery (P = 0·020, P = 0·045 and P = 0·045 respectively). Urinary α1-microglobulin : creatinine ratio was lower with HES 200/0·62 compared with gelatine at 4 and 8 h (P &lt; 0·050) and lower with HES 130/0·4 compared with gelatine at 4 to 24 h, and on days 4 and 5 (P &lt; 0·050). Urinary immunoglobulin G : creatinine was lower in both HES groups compared with gelatine. There was no difference between the two starch groups.

Conclusion

Compared with gelatine, volume expansion with both types of HES during AAA surgery improved renal function and reduced renal injury.

Physical properties of nisin-incorporated gelatin and corn zein films and antimicrobial activity against Listeria monocytogenes

Edible films of gelatin and corn zein were prepared by incorporating nisin to the film-forming solutions. Corn zein film with nisin of 12,000 IU/ml had an increase of 11.6 MPa in tensile strength compared with the control, whereas gelatin film had a slight increase with the increase of nisin concentration added. Water vapor permeability for both corn zein and gelatin films decreased with the increase of nisin concentration, thus providing a better barrier against water. Antimicrobial activity against Listeria monocytogenes increased with the increase of nisin concentration, resulting in 1.4 log cycle reduction for corn zein film and 0.6 log cycle reduction for gelatin film at 12,000 IU/ml. These results suggest that incorporation of nisin into corn zein and gelatin films improve the physical properties of the films as well as antimicrobial activity against pathogenic bacteria during storage, resulting in extension of the shelf life of food products by providing with antimicrobial edible packaging films.

Hydroxyethyl Starch, but Not Modified Fluid Gelatin, Affects Inflammatory Response in a Rat Model of Polymicrobial Sepsis with Capillary Leakage

BACKGROUND

Intravascular volume therapy is crucial in septic patients to improve tissue perfusion and maintain stable hemodynamics. Modified fluid gelatins (MFG) and medium weight hydroxyethyl starches (HES) are the most widely used synthetic colloids. Our aim in this study, performed in septic rats challenged by cecal ligation and puncture (CLP), was to investigate the effects of HES and MFG on pulmonary capillary leakage and to determine whether an antiinflammatory mechanism was involved.

METHODS

Animals were randomly allocated to eight groups: saline control; CLP and saline; CLP and HES (7.5, 15, and 30 mL/kg); CLP and MFG (7.5, 15, and 30 mL/kg). Each group had 20 rats, 10 of which were used for pulmonary capillary leakage and 10 for other measurements. Four hours after CLP, the specified doses of HES or MFG were infused. Six hours after surgery, pulmonary capillary leakage, levels of tumor necrosis factor-alpha, interleukin-1beta, and macrophage inflammatory protein-2, intercellular adhesion molecule-1 mRNA expression, myeloperoxidase activity, lung histological changes, and nuclear factor-kappaB activation were measured.

RESULTS

HES and MFG significantly attenuated the increase in capillary leakage in a dose-dependent manner. In addition, HES could decrease tumor necrosis factor-alpha, interleukin-1beta, and macrophage inflammatory protein-2 expression, intercellular adhesion molecule-1 mRNA expression, myeloperoxidase activity, neutrophil infiltration, and nuclear factor-kappaB activation, whereas MFG could not.

CONCLUSIONS

HES may attenuate capillary leakage by modulating an inflammatory response, whereas an antiinflammatory mechanism was not involved in the effects of MFG on capillary leakage.

Long-Term Culturing of Undifferentiated Embryonic Stem Cells in Conditioned Media and Three-Dimensional Fibrous Matrices Without Extracellular Matrix Coating

ESCs have unlimited proliferation potential and capability to differentiate into all tissue types. They are ideal cell sources for tissue engineering and cell therapy, but their supplies are limited. Current in vitro ESC cultures are carried out in tissue flasks with the surface precoated with extracellular matrix (ECM) proteins. T-flask cultures also require frequent subculturing because their limited surface area cannot support long-term growth of ESCs. In this work, ECM coating and frequent subculturing required in two-dimensional (2D) cultures were circumvented by culturing murine ESCs in three-dimensional (3D) polyethylene terephthalate (PET) fibrous matrices. Also, media conditioned with STO fibroblast cells were used to replace leukemia inhibitory factor and to effectively maintain the pluripotency of murine ESCs in a long-term static culture. However, the lactic acid present in the conditioned medium could inhibit ESC growth and induce spontaneous differentiation when its concentration exceeded 1.5 g/l. In addition, the 3D static culture could be limited by oxygen, which was depleted in the long-term culture when cell density in the matrix was high. However, these problems can be alleviated in dynamic culture with improved oxygen transfer and continuous media perfusion. The matrix pore size also had profound effects on ESCs. The smaller-pore (30-60 mum) matrix gave a higher proliferation rate and Oct-4 and stage specific embryonic antigen-1 expressions. Overall, the 3D culturing method is superior to the 2D culture method and can provide an economical way to mass-produce undifferentiated ESCs in uncoated matrices and conditioned media.

Synthesis and evaluation of injectable, in situ crosslinkable synthetic extracellular matrices for tissue engineering

Simple and effective biocompatible materials that mimic the natural extracellular matrix (ECM) were developed for a variety of uses in regenerative medicine. These synthetic ECMs (sECMs) were designed to recapitulate the minimal composition required to obtain functional ECMs. The sECM components are crosslinkable in situ, and may be seeded with cells prior to injection in vivo, without compromising either the cells or the recipient tissues. Several sECM compositions were evaluated to establish which formulation would be most beneficial for cell growth and tissue remodeling. Three natural ECM macromonomeric building blocks were employed: hyaluronan (HA), chondroitin sulfate (CS), and gelatin (Gtn). The carboxyl-rich glycosaminoglycans and Gtn were each chemically modified to give the corresponding thiolated dithiopropionylhydrazide (DTPH) derivatives (CS-DTPH, HA-DTPH, and Gtn-DTPH). Different compositions of CS-Gtn and HA-Gtn hydrogels were fabricated by crosslinking the thiolated biomacromonomers with polyethylene glycol diacrylate. Each sECM had high water content (>96%), biologically suitable mechanical properties, and a useful gelation time ( approximately 2-6 min). The bioerosion rates for the sECMs were determined, and a given composition could be selected to meet the requirements of a given clinical application. Both the HA-Gtn and CS-Gtn sECM hydrogels supported cell growth and proliferation with cultured murine fibroblasts in vitro. Moreover, subcutaneous injection of a suspension of murine fibroblasts in each of the two sECM hydrogels into nude mice in vivo resulted in the formation of viable and uniform soft tissue in vivo.

Experimental Evaluation of Early and Long-Term Effects of Microparticle Embolization in Two Different Mini-Pig Models. Part I: Kidney

PURPOSE

Using a pig model: (1) to evaluate the vascular distribution pattern, including the homogeneity and completeness of the intra-arterial microsphere distribution, of 40-120-microm trisacryl-gelatin microspheres (Embospheres) in acute whole-kidney embolization; (2) to evaluate the durability and biocompatibility of 40-120-microm trisacryl-gelatin microspheres (Embospheres) in chronic partial kidney embolization.

METHODS

Twenty-two animals were divided into four groups: group 1 (n = 4) underwent total arterial renal occlusion with immediate euthanasia. Groups 2-4 had chronic superselective and partial renal embolization with increasing follow-up times: group 2 (n = 2), 1 week; group 3 (n = 7), 4 weeks; and group 4 (n = 9), 14 weeks. Key endpoints in group 1 were homogeneity and completeness of acute embolizations. In groups 2-4 the key endpoints were durability of embolization and particle-related inflammation in chronic partial embolizations as assessed by quantitative angiography or histomorphometry. A numerical angiographic occlusion score (0.0 to 4.0, where 3.0 is optimal) was developed to assess and quantify the angiographic durability of superselective embolizations (groups 2-4).

RESULTS

In group 1, a relatively homogeneous distribution of the particles from segmental arteries to the precapillary level was shown by histomorphometry. Some particles reached the glomerular vas afferens (10 microm diameter). In groups 2-4, a mild recanalization appeared during follow-up. The immediate average postembolization occlusion score of 3.18 +/- 0.73 was reduced to 1.44 +/- 0.73 (statistically significant). Microscopy revealed subtotal necrosis but no foreign body granuloma formation. The intra-arterial appearance of giant cells closely attaching to the surface of the embolic spheres inside the vessel lumen was noted. Vessel walls showed major ischemic reactions.

CONCLUSION

Microspheres 40-120 microm in diameter might achieve total occlusion of the arterial kidney vasculature when injected centrally as a result of their fairly homogeneous distribution. Segmental renal infarction occurs after chronic partial embolization despite recanalizations during follow-up. Only mild specific intra-arterial foreign body reactions were found.

Evaluation and biological characterization of bilayer gelatin/chondroitin-6-sulphate/hyaluronic acid membrane

A biodegradable polymer scaffold was developed using gelatin, chondroitin-6-sulphate, and hyaluronic acid in the form of bilayer network. The bilayer porous structure of gelatin-chondroitin-6-sulphate-hyaluronic acid (G-C6S-HA) membrane was fabricated using different freezing temperatures followed by lyophilization. 1-Ethyl-3(3-dimethylaminopropyl) carbodiimide was used as crosslinking agent to improve the biological stability of the scaffold. The morphology, physical-chemical properties, and biocompatibility of bilayer G-C6S-HA membrane were evaluated in this study. The functional groups change in crosslinked G-C6S-HA scaffold was characterized by fourier transform infrared spectroscopy. The retention of glycosaminoglycan contents and matrix degradation rate were also examined by p-dimethylamino benzaldehyde and 2,4,6-trinitrobenzene sulphonic acid, respectively. Water absorption capacity was carried out to study G-C6S-HA membrane water containing characteristics. The morphology of the bilayer G-C6S-HA membrane was investigated under scanning electron microscope and light microscopy. In vitro biocompatibility was conducted with MTT test, LDH assay, as well as histological analysis. The results showed that the morphology of bilayer G-C6S-HA membrane was well reserved. The physical-chemical properties were also adequate. With good biocompatibility, this bilayer G-C6S-HA membrane would be suitable as a matrix in the application of tissue engineering.

Plasma volume expansion of 5% albumin, 4% gelatin, 6% HES 130/0.4, and normal saline under increased microvascular permeability in the rat

OBJECTIVE

To compare the colloids 5% albumin, 4% gelatin, and 6% HES 130/0.4 with one another and with normal saline regarding their plasma expanding effects at increased permeability and to compare the results with those from a previous study at normal permeability.

DESIGN AND SETTING

Prospective controlled randomized laboratory study in a university research laboratory.

SUBJECTS

48 adult male Sprague-Dawley rats.

INTERVENTIONS

Permeability was increased by an injection of 0.5 ml dextran 70 using the fact that dextran causes anaphylactic reaction in the rat. Plasma volume was determined ((125)I albumin tracer technique) after anesthesia, 1 h after dextran injection (before infusion for 10-15 min of 20 ml/kg bw of each of the colloids or 80 ml/kg saline), and 3 h later. Blood pressure, hematocrit, blood gases, and electrolytes were measured. CVP was measured in four rats.

MEASUREMENTS AND RESULTS

Plasma volume was 41.1+/-1.9 ml/kg at baseline (n=9), and 29.1+/-4.1 ml/kg (n=35) 1 h after the dextran injection. Three hours after infusion of the plasma expander plasma volume had increased by 17.1+/-3.4 ml/kg in the albumin group, 7.9+/-3.6 ml/kg in the gelatin group, 7.4+/-4.4 ml/kg in the HES group, and 12.2+/-3.1 ml/kg in the saline group. It was unchanged in a control group given no solution (n=7 for all groups).

CONCLUSION

Albumin was a more effective plasma volume expander than gelatin or HES or saline (saline in 4 times larger volume). Gelatin and HES were equally effective. All solutions showed a smaller plasma expanding effect than observed in a previous study with normal permeability.

Effects of a new perfluorocarbon emulsion on human plasma and whole-blood viscosity in the presence of albumin, hydroxyethyl starch, or modified fluid gelatin: an in vitro rheologic approach

BACKGROUND

Artificial oxygen carriers such as perfluorocarbon (PFC) emulsions have reached Phase III clinical trials as alternatives to homologous blood, but their rheologic effects have not been characterized. In this study, the rheologic effects of PFC emulsion in the presence of clinically used volume expanders were investigated.

STUDY DESIGN AND METHODS

The effects of a new PFC emulsion (small droplet size with narrow size distribution) at two PFC concentrations (4 and 8 g/dL) on plasma and whole-blood viscosity in the presence of human albumin solution (HAS), hydroxyethyl starch (HES), or modified fluid gelatin (MFG) were investigated. Three hematocrit (Hct) levels were investigated: 30, 20, and 13 percent. Plasma, PFC emulsions, and whole-blood viscosity, with a Couette viscometer, and RBC elongation, with an ektacytometer, were measured for shear rates of 0.2 to 128 per second.

RESULTS

The two PFC concentrations increased plasma and whole-blood viscosities. Viscosity values similar to physiologic ones (Hct level, 40%) were observed at: 1) Hct level of 13 percent, with 4 or 8 g per dL MFG-PFC; 2) Hct level of 20 percent, with 4 g per dL MFG-PFC; and 3) Hct level of 30 percent, with 4 g per dL HES-PFC and 4 and 8 g per dL HAS-PFC. RBC deformability was unchanged.

CONCLUSION

It is concluded that this new PFC emulsion increases plasma and blood viscosity and that among the three studied volume expanders, the interaction with MFG can result in viscosity values above the physiologic one even at low Hct values. The possible consequences of the increased viscosity at low Hct values are discussed.

Efficacy of a skin-protection powder for use as a dressing for intractable ulcers

OBJECTIVE

Stomahesive skin-protection powder has been reported to be useful as a skin-care and skin-barrier product for the management of stomas. This study aimed to evaluate its efficacy, in terms of wound healing, moisture retention and pain management, as an alternative to conventional dressing materials. Both clinical and animal studies were undertaken.

METHOD

The efficacy of the Stomahesive powder was tested by measuring the thickness of granulation tissue formed in a total skin defect in a db/db mouse model. We then compared the healing process using either the skin-protection powder or a conventional film dressing material. In the clinical study 17 patients with various intractable ulcers were treated with Stomahesive powder, and healing was evaluated.

RESULTS

In the mouse model, granulation tissue in the wounds treated with the powder was 2.86 times thicker than that of the wounds treated with the film dressing. In the clinical study, 16 out of 17 wounds healed completely.

CONCLUSION

The Stomahesive powder could be an effective treatment modality for contact ulceration, superficial ulcers with complex contours and morphology, and superficial ulcers contaminated by liquid faeces or vaginal discharge that have not responded to conventional dressings.

DECLARATION OF INTEREST

None.

Effect of synthetic colloids on major histocompatibility complex class II expression

STUDY OBJECTIVE

Synthetic colloids are used for perioperative fluid management. We hypothesized that their use may be associated with changes in major histocompatibility complex (MHC) class II expression. This could affect patients' morbidity and mortality during clinical intervention.

SETTING

University research laboratory.

SUBJECTS

Whole blood samples from healthy volunteers.

INTERVENTIONS

Whole blood samples from healthy volunteers (n = 6) were incubated with different concentrations of hydroxyethyl starch (HES) from maize and potato (pHES), dextran, and polygelin (gelatine) for 24 hours with or without 100 U/mL human interferon gamma (IFN-gamma; stimulus for MHC class II expression). The expression of human leukocyte antigen (HLA): HLA-DR, HLA-DQ, and HLA-DP was detected simultaneously by a fluoresceinisothiocyanate (FITC)-labeled antibody and analyzed by flow cytometry on lymphocytes and monocytes.

MEASUREMENTS AND MAIN RESULTS

Hydroxyethyl starch, pHES, and dextran induced a significant increase in HLA expression. The induction of MHC class II was independent of the structure (50 mg/mL: control, 8.7+/-1.4%; HES, 28 +/- 9.7%; pHES, 29.8 +/- 11.7%; and dextran, 50.2 +/- 8.1%). In contrast, polygelin increased HLA expression only at the highest concentration of gelatine (5 mg/mL, 7.8 +/- 1%; 50 mg/mL, 7.6 +/- 0.8%; 100 mg/mL, 7.3 +/- 1%; 200 mg/mL,16.2 +/- 2.3%). The addition of IFN-gamma decreased HLA expression in presence of highest concentration of HES and dextran.

CONCLUSION

In an ex vivo laboratory setting, we demonstrate that high concentrations of plasma expanders are associated with increased HLA expression on lymphocytes and monocytes. However, further in vivo studies are necessary to demonstrate the clinical significance of this observation.

Plasma volume expansion and transcapillary fluid exchange in skeletal muscle of albumin, dextran, gelatin, hydroxyethyl starch, and saline after trauma in the cat*

OBJECTIVE

To compare 5% albumin, 6% dextran 70, 3.5% gelatin, 6% hydroxyethyl starch 130/0.4, and saline regarding their plasma volume expanding effect after a surgical skeletal muscle trauma and their simultaneous effects on transvascular fluid exchange in skeletal muscle.

DESIGN

Controlled, prospective, randomized laboratory study.

SETTING

University research laboratory.

SUBJECTS

Thirty-six adult cats.

INTERVENTIONS

Systemic arterial pressure and tissue volume variations of and blood flow to a surgically isolated and autoperfused calf muscle placed in a plethysmograph were recorded. Arterial and venous pressures to the muscle were kept constant. After preparation, plasma volumes were determined by a I albumin tracer technique just before and 3 hrs after a bolus infusion of the plasma expander (25 mL/kg).

MEASUREMENTS AND MAIN RESULTS

Plasma volume was 20.9 +/- 2.9 mL/kg (n = 36) just before infusion of the plasma expander (normal plasma volume for the cat is 34-37 mL/kg). The remaining volume expansion of the infusion after 3 hrs was 6.8 mL/kg for albumin, 11.2 mL/kg for dextran, 1.8 mL/kg for gelatin, 2.2 mL/kg for hydroxyethyl starch, and 0.9 mL/kg for saline. Plasma volume decreased by 1.1 mL/kg when no solution was given (n = 6 per group). Colloid osmotic pressure was better preserved with dextran and albumin than with the other solutions. Albumin and dextran reduced muscle volume by absorption after 3 hrs, whereas the initial absorption turned to net filtration in the gelatin and hydroxyethyl starch groups. Saline infusion increased muscle volume by filtration for about 20 mins, followed by an approximately constant volume.

CONCLUSION

The relatively poor plasma expansion for all solutions analyzed can most likely be explained by increased transcapillary leakage due to increased microvascular permeability following trauma. Under such circumstances, for equal volumes, plasma expansion was better preserved with 6% dextran 70 than with 5% albumin, which was better than 3.5% gelatin, 6% hydroxyethyl starch 130/0.4, and saline.

Biomimetic bilayered gelatin-chondroitin 6 sulfate-hyaluronic acid biopolymer as a scaffold for skin equivalent tissue engineering

In order to develop an adequate scaffold for skin tissue engineering, a bilayered gelatin-chondroitin 6 sulfate-hyaluronic acid membrane with a different pore size on either side was prepared. A rete ridges-like topographic microporous structure, which provided the paracrine crosstalk in the epithelial-mesenchymal interactions, was formed. Chondroitin-6-sulfate and hyaluronic acid were incorporated within the gelatin membrane to mimic skin composition and create an appropriate microenvironment for cell proliferation, differentiation, and migration. In the study, the lower layer of the membrane (pore size: 150 microm) was seeded with dermal fibroblasts and acted as the feeder layer for keratinocyte inoculation. Meanwhile, the upper layer (pore size: 20-50 microm) was seeded with keratinocytes for epidermalization. The dermal fibroblasts were dynamically seeded in a self-designed spinner flask for more even cell distribution. The keratinocytes were cultured in submerged conditions for 5 days and then in an air-liquid interface condition for further differentiation. After being cultured for 21 days, the upper layer, seeded with keratinocytes, developed into an epidermis-like structure while the lower part, which was seeded with dermal fibroblasts developed into a dermis-like structure. A histological examination and immunostain were used to prove that keratinocytes maintain their phenotype and stratified epidermis layers were formed within 21 days. In brief, the bilayered skin substitute with biological dermal analog and epidermal structure was successfully fabricated. From this study, we can suggest that the culture model is suitable for autologous skin equivalent preparation.

Respiratory burst activity of Atlantic cod (Gadus morhua L.) blood phagocytes differs markedly from that of rainbow trout

In the present study we investigated the respiratory burst (RB) activity of Atlantic cod (Gadus morhua L.) blood phagocytes and we evaluated how the RB activity of cod blood cells differ from that of trout. The RB activities were measured directly from highly diluted whole blood as luminol-amplified chemiluminescence (CL) under various conditions. Studies regarding the blood dilutions for cod whole blood chemiluminescence measurements (WBCL) revealed that at a final blood dilution of 1.5 microl ml(-1) or less the CL response was strictly proportional to the number of phagocytes. This range of blood dilution did not markedly differ from that of trout. However, the opsonisation capacity of cod plasma was markedly poorer. The RB activity of phagocytes was most active at 15 degrees C when heterologous cod serum was used as a source of opsonin, whereas at final blood dilution of 8.0 microl ml(-1) (when homologous cod plasma was at a higher concentration) the highest RB activity was observed at 10 degrees C. Aeromonas salmonicida strain MT004 (As MT004) induced higher RB activity than the two known pathogens for cod, atypical A. salmonicida and Vibrio anguillarum. Cod blood phagocytes were more responsive to plastic surfaces and the adhesion response of phagocytes was partly inhibited but did not totally vanish even at a final gelatin concentration of 0.4%. Moreover, cod serum enhanced the adherence of phagocytes and cod blood phagocytes also showed slow spontaneous degranulation. Finally, within the tested anticoagulants (heparin, Na-citrate, EDTA) heparin treated blood phagocytes generated the highest RB activity.

Effect of cationized gelatins on the paracellular transport of drugs through caco-2 cell monolayers

Cationized gelatins, candidate absorption enhancers, were prepared by addition of ethylenediamine or spermine to gelatin and the effects of the resulting ethylenediaminated gelatin (EG) and sperminated gelatin (SG) on the paracellular transport of 5(6)-carboxyfluorescein (CF), FITC-dextran-4 (FD4), and insulin through caco-2 cell monolayers were examined. The Renkin function was used for characterization of the paracellular pathway and changes in the pore radius (R) and pore occupancy/length ratio (epsilon/L) calculated from the apparent permeability coefficients (P(app)) of CF and FD4 are discussed. Ethylenediaminetetraacetic acid (EDTA) increased the R of the caco-2 cell monolayer and the P(app) of all compounds examined was markedly increased by the addition of EDTA. On the other hand, EG and SG did not increase R and their enhancing effects were not as strong as those of EDTA. The increase in epsilon/L could be the enhancing mechanism for the cationized gelatins. The number of pathways for water-soluble drugs, such as CF and FD4, in the caco-2 monolayers could be increased by the addition of the cationized gelatins. The ratios of the permeability coefficients of insulin (observed/calculated based on the Renkin function) suggest that insulin undergoes enzymatic degradation during transport which is not inhibited by enhancers.

Accelerated repair of cortical bone defects using a synthetic extracellular matrix to deliver human demineralized bone matrix

Injectable hydrogel and porous sponge formulations of Carbylan-GSX, a crosslinked synthetic extracellular matrix (ECM), were used to deliver human demineralized bone matrix (DBM) in a rat femoral defect model. A cortical, full-thickness 5-mm defect was created in two femurs of each rat. Six rats were assigned to each of five experimental groups (thus, 12 defects per group). The defects were either untreated or filled with Carbylan-GSX hydrogel or sponges with or without 20% (w/v) DBM. Radiographs were obtained on day 1 and at weeks 2, 4, 6, and 8 postsurgery of each femur. Animals were sacrificed at week 8 postsurgery and each femur was fixed, embedded, sectioned, and processed for Masson's Trichrome staining. The bone defects were measured from radiographs and the fraction of bone healing was calculated. The average fractions of bone healing for each group were statistically different among all groups, and all treatment groups were significantly better than the control group. The Carbylan-GSX sponge with DBM was superior to the sponge without DBM and to the hydrogel with DBM. Histology showed that defects treated with the Carbylan-GSX sponge plus DBM were completely filled with newly generated bone tissue with a thickness comparable to native bone. Carbylan-GSX sponge was an optimal delivery vehicle for human DBM to accelerate bone healing.

Effect of Charge and Molecular Weight on the Functionality of Gelatin Carriers for Corneal Endothelial Cell Therapy

Cell transplantation strategies usually involve the use of supporting carrier materials because of the soft and fragile nature of these grafts. In this work, a cell-adhesive gelatin hydrogel carrier was fabricated to deliver cultivated human corneal endothelial cell (HCEC) sheets, which were harvested from thermo-responsive poly(N-isopropylacrylamide) (PNIPAAm)-grafted culture surfaces. The carrier disks, consisting of gelatins with a different isoelectric point (IEP = 5.0 and 9.0) and a molecular weight (MW) ranging from 3 to 100 kDa, were subjected to 16.6 kGy gamma irradiation for sterilization. The effect of IEP and MW of the raw gelatins (i.e., before irradiation) on the functionality of sterilized disks was studied by determinations of mechanical property, water content, dissolution degree, and cytocompatibility. Irrespective of the IEP of raw gelatin, hydrogel disks prepared with high MW (100 kDa) exhibited a greater tensile strength, lower water content, and slower dissolution rate than those made of low MW gelatin (8 and 3 kDa). From the investigation of cellular responses to the disks, the negatively charged gelatin (IEP = 5.0) groups were more cytocompatible when compared with their positively charged counterparts (IEP = 9.0) at the same MW (100 kDa). Additionally, in the negatively charged gelatin groups, only a slight increase in pro-inflammatory cytokine expression was observed with increasing MW of gelatin from 3 to 100 kDa. It is concluded that the gamma-sterilized hydrogel disks made from raw gelatins (IEP = 5.0, MW = 100 kDa) with appropriate dissolution degree and acceptable cytocompatibility are capable of providing stable mechanical support, making these carriers promising candidates for intraocular delivery of cultivated HCEC sheets.