Boris Pirkić

A Nonionic Surfactant/Chitosan Micelle System in an Innovative Eye Drop Formulation

Micelle systems composed of the polyoxyethylated nonionic surfactant Pluronic F127 (F127) and cationic polyelectrolyte chitosan (CH) were prepared with dexamethasone (DEX) as a hydrophobic model drug. The F127/CH micelles were characterised by their hydrodynamic diameter and a zeta-potential ranging between 25.4 and 28.9 nm and +9.3 and +17.6 mV, respectively. The DEX loading was between 0.48% and 0.56%, and no significant influence of CH on DEX loading was observed. All micelle systems were characterised by prolonged release profiles. The addition of CH significantly enhanced the in vitro DEX release rate and transport across Caco-2 cell monolayers, as compared to the CH-free F127 micelle system. This colloidal carrier was well tolerated in rabbit eyes, and no clinically abnormal signs in various ocular structures were observed. The increase in intraocular pressure (IOP) in rabbits was used to evaluate DEX ocular bioavailability. The AUC values showed a 1.7- and 2.4-fold increase in bioavailability with F127 and F127/0.015 (w/v) % CH micelle systems, respectively, as compared to a standard DEX suspension. These data indicate improved intraocular DEX absorption from the micelle systems, which can be ascribed to both F127 and CH corneal permeability enhancement.

Feline high-rise syndrome: 119 cases (1998-2001)

High-rise syndrome was diagnosed in 119 cats over a 4-year period. 59.6% of cats were younger than one year, and the average height of the fall was four stories. High-rise syndrome was more frequent during the warmer period of the year. 96.5% of the presented cats, survived after the fall. 46.2% of cats had fractured limbs; 38.5% of fractures were of the forelimb, 61.5% of the hindlimb. The tibia was fractured most often (36.4%), followed by the femur (23.6%). 78.6% of femoral fractures were distal. The mean age of patients with femoral fractures was 9.1 months, and with tibial fractures 29.2 months. Thoracic trauma was diagnosed in 33.6% of cats. Pneumothorax was diagnosed in 20% of cats, and pulmonary contusions in 13.4%. Falls from the seventh or higher stories, are associated with more severe injuries and with a higher incidence of thoracic trauma.

Biological repair of thyroid cartilage defects by osteogenic protein-1 (bone morphogenetic protein-7) in dog.

The efficacy of human recombinant osteogenic protein-1 (OP-1; bone morphogenetic protein-7) in regeneration of dog larynx was examined by treating thyroid cartilage defects (1.5 cm2) in dogs with thyroid allografts covered with host perichondrium or fascia. Prior to implantation allografts were frozen, thawed and demineralized. The treatment groups were as follows: I - Allograft control implant (n = 3); II - Implants coated with 500 μg OP-1 (n = 4); III - Implants coated with 100 μg OP-1 (n = 3); IV - Implants coated with 500 μg OP-1 and covered with neck fascia (n = 3); and V - Implants extracted with 1M NaCl and guanidine hydrochloride, and coated with 500 μg OP-1 (n = 4). Dogs were sacrificed four months following surgery. Each larynx was removed, carefully dissected and a three-dimensional reconstruction of the defect area was performed on serial sections. The results revealed that the implants of control dogs remained intact with no apparent reduction in size and new tissue formation. OP-1 enriched thyroid allografts, dose dependently induced bone, cartilage and ligament-like structures comprising up to 80% of the total regenerated defect area. Boundaries of the defects healed by formation of new bone when bone resided within the old thyroid cartilage layers. Old cartilage not containing bone within its layers healed by complete integration with newly formed cartilage. Both new bone and cartilage were embedded into layers of new ligament-like tissue which expressed specific morphologic and molecular markers. The three newly formed tissues were tightly connected into a “bone-cartilage-ligament continuum” of tissues, suggesting that OP-1 served as a multiple tissue morphogen in this specific microenvironment.

Application of a semitendinosus muscle flap in the treatment of perineal hernia in a cat

The article described one case of perineal hernia in a cat treated by method of application of a semitendinosus muscle flap.

IN VITRO CULTIVATION OF CANINE LIMBAL TRANSPLANT

Limbal epithelial stem cells are the ultimate source of regeneration of the entire corneal epithelium under both normal and injured conditions. The corneal epithelium plays a crucial role in homeostasis and integrity of the eye. To maintain the integrity of the ocular surface, corneal epithelial cells must be balanced by stem cells, located at the limbus. The limbus is the crossing area between the cornea and sclera, 1 mm in width, and together with conjunctival epithelium plays an important role in regenerating the cornea after traumatic injuries. The aim of this study was to evaluate the culturing patterns of canine limbal stem cells and to optimize growing conditions of these cell cultures in order to develop a reliable biomedical model intended for studying the potentials of allografts/xenografts originated from canine tissues. Canine stem cell equivalents have potentials in reparative/regenerative veterinary medicine.

In vitro cultivation of porcine limbal stem cells

Abstract Similarly as in other organ structures stem cells are present in cornea residing basal epithelial layer termed palisade of Voight. A growing interest in allografts and xenografts implies a thorough study of regenerative potentials of these cells, as well as a clear description of their patterns in in vitro tissue cultures to be grafted. Recently we have developed a simple method for cultivation of porcine corneal epithelial stem cells obtained by biopsy from the limbal region. Eight enucleated eyes were obtained from four slaughtered pigs. 5 mm2 samples of limbal epithelium were taken by keratotomy method. The primary cultures of these cells showed phenotypic and morphometric characteristics of porcine corneal epithelial cells following May-Grunwald-Giemsa staining. After 5d of sowing they reached 80% of confluence. With the «Night & Day» lenses a total confluence was achieved 5d earlier in comparison to the cells that were grown in the secondary cultures. Accordingly, the use of porcine limbal stem cells has potentials in veterinary medicine (as novel approach in reparative/regenerative medicine of pets, horses and selected breeds), but also are in accordance with the extensive studies on the potential use of xenografts, mainly swine tissues/organs, in humans.

The effect of preanesthetic administration of lactated ringer solution on blood pressure in isoflurane-anesthetized horses.

Hypotension induced by volatile agents is particularly notorious in horses and it is probably one of the major causes of the high anaesthetic risk in this species. In the present study we investigated the influence of 10 mL/kg lactated Ringer solution on the values of arterial blood pressure during the elective surgical procedure, administered right before the induction of anaesthesia. The goal was to establish if it was possible to lower the risk of hypotension development with this type of therapy. Nine horses divided in two groups were used in this study. All the horses were submitted to the same anesthetic regimen. The second group of horses received 10 mL/kg i.v. lactated Ringer solution in the 15 minutes time before the induction of anesthesia. The effect of lactated Ringer solution was noted at the beginning of anesthesia. Statistically significant differences among groups were noticed during the first measurement. The results indicate that the suggested method may provide a very simple way of supporting the cardiovascular system at least at the beginning of the surgical procedure.