Experimental data on methicillin tolerance and penetration into the eye media]

Tolerance of methicillin by the eye tissues was studied on its administration subconjunctively, into the front chamber and vitreous body of 20 rabbits. The studies showed that subconjunctival administration of the antibiotic was well tolerated in a dose of 50 mg, and its administration into the front chamber and vitreous body was well tolerated in doses of 1.0-2.5 mg. Penetration of methicillin into the fluids of the front chamber and vitreous body on its instillation into the conjunctive sac in a form of 2.5 per cent solution, its subconjunctival and retrobulbar injection in a dose of 50 mg and intramuscular administration in a dose of 40 mg/kg was studied. Animals with aseptic inflammation of the eyes due to burns of the cornea with 1 N hydrochloric acid were taken into the experiments. The method of agar diffusion with Staph. aureus 209P as the test-microbe was used. The studies showed that the highest methicillin concentrations in the eye media were observed an hour after the antibiotic subconjunctival administration. In the vitreous body they were 16 times lower than those in the front chamber fluid. The retrobulbar injections had no advantages over the subconjunctival administration for the antibiotic maximum concentrations in the vitreous body. The concentration of methicillin in the front chamber fluid on its local administration was many times higher than the minimum inhibitory concentration for staphylococci and may be considered as a therapeutic one.     

Sodium sulfapyridazine in new delayed-action bases for the treatment of bacterial conjunctivitis

Possible preparation of 10 per cent sodium sulfapyridazine ophthalmic drops containing aubazidan, a microbial polysaccharide, providing prolongation of the drops action and stability on the storage was studied. The pharmacokinetic studies showed that aubazidan which is a natural polymer provided high prolongation of the sulfapyridazine effect in the tissues of the anterior part of the eye in rabbits. The prolonged effect was similar to the previously observed effect of the solutions containing synthetic polymers such as 1 per cent polyacrylamide and polyvinyl . Satisfactory tolerance by the rabbit eye tissues of 6-fold daily instillations of the 10 per cent sodium sulfapyridazine solution with aubazidan for the observation period of 1 month was stated. When stored in vials the 10 per cent sodium sulfapyridazine ophthalmic drops with 0.5 per cent of aubazidan preserved the stability for 24 months with respect to the colour, transparency, viscosity, pH and drug content. It was demonstrated with using the agar diffusion method and Staphylococcus aureus, Proteus vulgaris, Escherichia coli and Pseudomonas aeruginosa as the test cultures that sodium sulfapyridazine completely preserved its antimicrobial activity in the presence of aubazidan. The data suggested that clinical trials of the 10 per cent sodium sulfapyridazine solution with 0.2-0.5 per cent of aubazidan were promising in prevention and therapy of bacterial conjunctivitis.     

Regulation of hydrogen peroxide in eye humors effect of 3-amino-1H-1,2,4-triazole on catalase and glutathione peroxidase of rabbit eye

Activities of catalase (H₂O₂ : H₂O₂ oxidoreductase, EC 1.11.1.6) and GSH peroxidase (GSH : H₂O₂ oxidoreductase, EC 1.11.1.9) have been measured in iris, ciliary body, retina, corneal epithelium, corneal endothelium, lens capsule-epithelium and decapsulated lens. 3-Amino-1H-1,2,4-triazole is a specific inhibitor of catalase and a potent cataractogenic agent. We observed marked inhibition of catalase activity in these tissues 1–6 h after the administration of a single intravenous dose of 1 g 3-aminotriazole per kg body weight in rabbit. This was associated with a 2–3-fold increase in the H₂O₂ concentrations of aqueous humor and vitreous humor. The increased peroxide concentrations were restored to the physiological levels as the catalase activity of eye tissues gradually returned to normal with time after injection. Under the conditions, GSH peroxidase activity of the afore-mentioned eye tissues was unaltered, GSH and protein sulfhydryl of lens were not changed, and ascorbic acid of aqueous humor and vitreous humor was not significantly altered. Based on these findings our conclusion is that catalase of eye tissues regulates the endogenous H₂O₂ in eye humors to the physiological level. We speculate that H₂O₂ may be the triggering factor in cataract induced by 3-aminotriazole.     

Mathematical model of flow in the vitreous humor induced by saccadic eye rotations: effect of geometry

Saccadic eye rotations induce a flow in the vitreous humor of the eye. Any such flow is likely to have a significant influence on the dispersion of drugs injected into the vitreous chamber. The shape of this chamber deviates from a perfect sphere by up to 10–20% of the radius, which is predominantly due to an indentation caused by the lens. In this paper we investigate theoretically the effect of the domain shape upon the flow field generated by saccades by considering an idealized model. The posterior chamber geometry is assumed to be a sphere with a small indentation, undergoing prescribed small-amplitude sinusoidal torsional oscillations, and, as an initial step towards understanding the problem, we treat the vitreous humor as a Newtonian fluid filling the chamber. The latter assumption applies best in the case of a liquefied vitreous or a tamponade fluid introduced in the vitreous chamber after vitrectomy. We find the flow field in terms of vector spherical harmonics, focusing on the deviation from the flow that would be obtained in a perfect sphere. The flow induced by the departure of the domain geometry from the spherical shape has an oscillating component at leading order and a smaller-amplitude steady streaming flow. The oscillating component includes a circulation cell formed every half-period, which migrates from the indentation towards the center of the domain where it disappears. The steady component has two counter-rotating circulations in the anterior part of the domain. These findings are in good qualitative agreement with the experimental results of Stocchino et al. (Phys Med Biol 52:2021–2034, 2007). Our results predict a significant reduction in the expected time for drug dispersal across the eye compared with the situation in which there is no fluid flow present.     

Pharmacokinetics of protegentin, a combined preparation

Protegentin is a combined preparation in the form of ointment containing 0.1 per cent of gentamicin, 0.25 per cent of erythromycin and 0.1 per cent of protease C. Pharmacokinetic studies on the preparation were conducted. Protegentin and gentamicin ointment, currently manufactured in this country, were applied to the surface of experimental pure cutaneous wounds in guinea pigs in a dose of 1 g. It was shown that inspite of the same contents of gentamicin in the ointments, the mean maximum concentration of the antibiotic in the underlying muscular tissue after the protegentin application was somewhat higher than that after the use of the gentamicin ointment. The differences in the drug concentration maintained during the whole observation period of 24 hours. However, they were not statistically significant. The gentamicin concentrations in serum after the use of protegentin were also somewhat higher than those after application of the gentamicin ointment (the differences were not statistically significant). Still, in no case the concentrations reached the potentially toxic ones. The erythromycin concentrations in the muscular tissue were much higher than those in the blood.     

Experimental study of a gentamicin aerosol]

The study of gentamicin aerosol showed its relative innocuousness: it did not inhibit the growth and development of young animals, did not induce pathological changes in the upper respiratory tract, kidneys, liver, heart and spleen on its prolonged use. Pathohistological examination revealed slight irritating effect of the gentamicin aerosol in the lungs after its use in a dose of 8 or 25 mg/kg for 6 weeks. A procedure for investigating the effect of the aerosol on the activity of the trachea ciliated epithelium of warm blooded animals was developed. The gentamicin aerosols prepared from solutions of different concentrations (1 to 50 mg/ml) induced ingibition of the ciliated epithelium function at average from 15 to 35 per cent which was associated with the solution acidity (pH 4.54 to 4.82). Such a decrease in the function of the ciliated epithelium due to the antibiotic aerosol use was a factor prolonging the antibiotic retention time in the respiratory organs. It was found that aqueous solutions of drugs used for inhalation, such as ephedrin, euphelin, dimedrol, N-acetyl-L-cystein and others had no effect on the activity of gentamicin and may be used with it in a form of aerosols.     

The natural histidine-containing dipeptide Nalpha-acetylcarnosine as an antioxidant for ophthalmic use

The naturally occurring compound Nalpha-acetylcarnosine is proposed as a prodrug of L-carnosine that is resistant to enzymatic hydrolysis by carnosinase. Eyes of rabbits were treated with 1% Nalpha-acetylcarnosine, L-carnosine, or placebo and extracts of the aqueous humor from the anterior eye chamber were analyzed for imidazole content by reverse-phase analytical high performance liquid chromatography (HPLC) and thin-layer (TLC) and ion-exchange chromatographic techniques. Topical administration of pure L-carnosine to the rabbit eye did not lead to accumulation of this compound in the aqueous humor over 30 min in concentration exceeding that in the placebo-treated matched eye. Nalpha-Acetylcarnosine showed dose-dependent hydrolysis in its passage from the cornea to the aqueous humor, releasing L-carnosine after l5-30 min of ocular administration of the prodrug in a series of therapeutic modalities: instillation < or = subconjunctival injection < or = ultrasound-induced phoresis. Different treatment techniques showed excellent toleration of 1%Nalpha-acetylcarnosine by the eye. Once in the aqueous humor, L-carnosine might act as an antioxidant and enter the lens tissue when present at effective concentrations (5-l5 mM). The advantage of the ophthalmic prodrug Nalpha-acetylcarnosine and its bioactivated principle L-carnosine as universal antioxidants relates to their ability to give efficient protection against oxidative stress both in the lipid phase of biological membranes and in aqueous environments. Nalpha-Acetylcarnosine is proposed for treatment of ocular disorders that have a component of oxidative stress in their genesis (cataracts, glaucoma, retinal degeneration, corneal disorders, ocular inflammation, complications of diabetes mellitus, and systemic diseases).     

The chemical composition and the osmotic pressure of the aqueous humor and plasma of the rabbit

Measurements were made of the osmotic pressure of plasma, and of aqueous humor taken from the anterior chamber of the right and left eyes and from the posterior chamber of unanesthetized rabbits. Aqueous humor from the anterior chamber was found to be hypertonic to the plasma by approximately 3 mM/liter equivalent of sodium chloride. The aqueous humor from the anterior and posterior chambers of the right and left eyes was isotonic. The concentration of chloride in the anterior and posterior chambers was the same. The concentration of all the major components of the aqueous humor and plasma has been determined by chemical analysis on fluid samples obtained from unanesthetized rabbits at approximately the same time. The calculated osmotic pressure of the total of these substances in terms of sodium chloride equivalent agrees to within better than 1 per cent of the total osmotic pressure as measured experimentally. The distribution of some individual anions and cations of the aqueous humor and plasma was determined. This distribution is widely different from that which would obtain at a state of equilibrium. The positive and negative charges carried by the ions in the aqueous humor were approximately equal. Sources of error in the experiments are discussed.     

Penetration of radioactive sodium and chloride into cerebrospinal fluid and aqueous humor

1. Experiments were performed on six dogs to determine the rate of penetration of Cl(33) and Na(24) across the blood-aqueous humor and blood-cerebrospinal fluid barriers after intravenous injection of the radioactive ions. The radioactivity measurements were made with an immersion type of Geiger-Müller counter. 2. The concentrations of the labelled ions in the anterior chamber and the cisterna magna increase slowly to approach that of plasma. The rate of penetration k is calculated from a simple exponential equation with the half-value interval t(0.5) or the time required for the labelled-ion concentration in the fluid to reach 50 per cent of that of plasma. The average t(0.5) for Cl(38) and Na(24) in aqueous humor are 34.3 +/- 9 and 27.3 +/- 9 minutes, respectively, while those for cerebrospinal fluid are 90 +/- 6 and 95 +/- 6 minutes, respectively. 3. A study of the radioactivity in plasma was made to determine the per cent remaining after a steady state was reached. By means of this determination the sodium and chloride space was calculated to be 33 +/- 5 per cent.     

Taenia crassiceps: experimental model of intraocular cysticercosis

An experimental model of Taenia crassiceps intraocular cysticercosis was developed in rabbits. The objectives of this study were to analyze the pathophysiology of this parasitic infection and to evaluate the humoral immune response. Cysticerci, inoculated in the anterior chamber of the eye, were able to grow; no inflammatory changes in the eye or anticysticercus antibodies in serum or in aqueous humor were detected during the 12-day period. In contrast, rabbits that had previously been either infected intraperitoneally with living T. crassiceps cysts or immunized intramuscularly with T. crassiceps antigenic extract developed an intense inflammatory reaction in the eye and high levels of antibodies were detected in serum and aqueous humor even before the intraocular inoculation of parasites. Furthermore, intraocular cysticerci showed minimal growth and some were eliminated. These findings support the concept that the eye is an immunologically privileged site in the nonimmunized host and the importance of the immune response in the elimination of this parasitic infection.     

Horseradish peroxidase: a reliable or a misleading tool for the investigations on the origin of the proteins of the aqueous humor?

The concept of the blood-aqueous barrier is largely based on the use of horseradish peroxidase (HRP). The present investigation was designed to check its reliability as a macromolecular tracer, especially with regard to the transport of plasma proteins. Rabbits were killed 5 min to 24 h after being intravenously injected with HRP. The tracer diffused rapidly, reaching the aqueous humor of the eye in 3 min or less and was detected at high concentration in the narrow space between the outer epithelial layer of the ciliary epithelium and the wall of the pervious capillaries in the stroma of the processes. HRP appeared to migrate from the blood to the posterior chamber, permeating the tight junctions, viz., the anatomical basis of the blood-aqueous barrier. It was detected at higher concentration at the anterior surface of the iris, at short time intervals; this was interpreted as penetration of the tracer from the aqueous humor of the anterior chamber. The choroid was also labeled in continuation with the reaction in the stroma of the pars plana of the ciliary body which, in turn, sometimes reached the iris root. Therefore, the pervious blood vessels of the choroid could be a source of macromolecules for the iris root. HRP also induced the formation of lysosomes in the ciliary epithelium. This can hardly be accepted as the way in which plasma proteins are physiologically transported to the aqueous humor. However, the pathway of HRP migration over short time intervals seems to be in agreement with previous research indicating that the entrance of serum albumin into the posterior chamber is the first step of its incorporation into the aqueous humor. Received: 7 June 1996 / Accepted: 15 January 1997     

Effect of a modified terrilytin on ampicillin pharmacokinetics in experimental peritonitis

The effect of modified terrilytin, a new enzyme of the microbial origin on the pharmacokinetics of ampicillin in experimental peritonitis was studied on 16 pubertal rabbits. Peritonitis was caused by laparotomy and administration of a 15 per cent fecal suspension into the abdominal cavity. The drugs were injected intramuscularly: the enzyme in a dose of 5 PU/kg and the antibiotic in a dose of 10 mg/kg. The ampicillin levels in the blood and peritoneal exudate were determined with the agar-diffusion method. The specimens were collected 30 minutes, 1, 1.5 and 2 hours after administration of the drugs. The animals were divided into 2 groups: control (not treated with the enzyme) and experimental. An increase in the antibiotic levels in the blood and peritoneal exudate by 50--54 per cent was observed. The maximum increase was recorded 30 minutes after simultaneous administration of the drugs.     

Experimental study of the pharmacokinetics of an amphotericin B derivative

Absorption, distribution and excretion of a new water soluble derivative of amphotericin B (NWSDA) were studied after its administration by different routes. After the antibiotic intravenous administration the therapeutic concentrations in blood, organs and urine were shown to remain for prolonged periods. The likely sites of NWSDA deposition were detected with microbiological and radionuclide methods. The most prolonged periods of antibiotic preservation were stated in the renal cortex, spleen and lungs. The ways of NWSDA excretion were studied in operated animals. Only 3.5 per cent of the antibiotic was excreted with urine and bile for 24 hours. The pharmacokinetic parameters of NWSDA after its intravenous administration were estimated. The bioavailability of the antibiotic after its intramuscular and oral administration was found to be low.     

Transport and steady-state concentration of plasma proteins in the vitreous humor of the chicken embryo: implications for the mechanism of eye growth during early development

The nature and origin of the proteins of the vitreous humor were examined in chickens during embryonic and early posthatching stages. The major proteins of the vitreous humor were similar in electrophoretic mobility to plasma proteins at all ages examined. Earlier studies from our laboratory and experiments described below showed that plasma proteins continuously entered and left the eye throughout its development. From these data it was concluded that the majority of vitreous-humor proteins were derived from the blood. The protein concentration of the vitreous humor was 13% of that of the plasma from embryonic Days 6 through 15 (E6 through E15). After E15, the relative protein concentration in the vitreous humor declined with respect to the plasma and reached 4% of the plasma protein concentration at hatching. Several possibilities were considered to account for how proteins can rapidly enter and leave the eye, yet maintain a steady-state concentration in the vitreous humor that is less than one-seventh of that in the blood.     

Gentamicin level in the prostate and its pharmacokinetics in patients with benign prostatic hypertrophy]

The study involved 15 male patients with periurethral prostatic adenoma without complete anuresis. The patients were given 80 mg of gentamicin intramuscularly one day before surgery and 80 mg in a one-hour infusion immediately before an operation. Gentamicin blood concentrations were measured. Pharmacokinetic parameters were calculated and dosage schemes for each patient basing on the antibiotic blood levels. Gentamicin levels in removed adenomas were also determined. Adenomas weighed between 18.0 and 45.8 grams while gentamicin concentration ranged from 1.31 to 3.8 micrograms/mL. It was found that gentamicin concentration in adenomas depend upon their weight. Moreover, pharmacokinetic parameters of this antibiotic exert negligible effect on its levels in adenoma.     

Intralymphatic administration of antibiotics in the complex treatment of suppurative complications in patients with neurosurgical pathology

The efficacy of endolymphatic route of gentamicin and ceporin administration was studied in 89 patients with neurosurgical pathological processes complicated by acute pneumonia (80 patients) and meningoencephalitis (9 patients) usually after ineffective antibiotic therapy according to the routine methods. The antibiotics were used in accordance with the antibiograms of the causative agents isolated from the bronchial tree or CSF. The endolymphatic use of gentamicin or ceporin once a day in doses of 80 mg or 1 g respectively provided rapid sanation and arresting of the inflammatory foci, lowering of the intoxication level, more rapid promotion of the positive time course of the clinico-roentgenological and laboratory indices and decreasing of the recovery periods by 1.5-2 times in 86 per cent of the patients with pneumonia. The endolymphatic administration of gentamicin in a dose of 80 mg twice a day or ceporin in a dose of 1 g twice a day allowed one to maintain the antibiotic therapeutic levels in the cerebrospinal fluid and to obtain satisfactory clinical results in the combined treatment of meningoencephalitis. The endolymphatic administration of the drugs was well tolerated by the patients and no adverse reactions were observed. This route of administration of antibiotics and in particular broad spectrum antibiotics may be recommended for urgent antibacterial therapy of especially severe neurosurgical patients with pyo-inflammatory complications and patients who did not respond to the routine antibiotic therapy.     

Vitreous Humor Rheology After Nd:YAG Laser Photo Disruption

This work aimed to consider the hazardous side effect of eye floaters treatment with Q-switched Nd:YAG laser on the protein and viscoelastic properties of the vitreous humor, and evaluate the protective role of vitamin C against laser photo disruption. Five groups of New Zealand rabbits were divided as follows: control group for (n = 3) without any treatment, the second group (n = 9) treated with Q-switched Nd:YAG laser energy of 5 mJ × 100 pulse delivered to the anterior, middle, and posterior vitreous, respectively (n = 3 for each). The third group (n = 9) received a daily dose of 25 mg/kg body weight vitamin C for 2 weeks, and then treated with laser as the previous group. The fourth group (n = 9) treated with 10 mJ × 50 pulse delivered to the anterior, middle, and posterior vitreous, respectively (n = 3 rabbits each). The fifth group (n = 9) received a daily dose of 25 mg/kg body weight vitamin C for 2 weeks, and then treated with laser as the previous group. After 2 weeks of laser treatment, the protein content, refractive index (RI), and the rheological properties of vitreous humor, such as consistency, shear stress, and viscosity, were determined. The results showed that, the anterior vitreous group exposed to of 5 mJ × 100 pulse and/or supplemented with vitamin C, showed no obvious change. Furthermore, all other treated groups especially for mid-vitreous and posterior vitreous humor showed increase in the protein content, RI and the viscosity of vitreous humor. The flow index remained below unity indicating the non-Newtonian behavior of the vitreous humor. Application of Q-switched Nd:YAG laser should be restricted to the anterior vitreous humor to prevent the deleterious effect of laser on the gel state of the vitreous humor.     

Pharmacokinetic study of implantable gentamycin preparations. I. Antibiotic pharmacokinetics in the implantation area and an evaluation of the prolonged effect of the preparations

Gentamicin pharmacokinetics was studied in the zone of subcutaneous implantation to rats of Septopal, a dosage form based on polymethylmethacrylate stable in vivo (4.5 mg of the antibiotic) and of preparations based on biodegradable polymers such as monocarboxycellulose, alginic acid, nonmodified and modified collagens (1 and 5 mg of the antibiotic). A three-phase pattern of gentamicin level changing in the implantation zone was observed: (1) rapid increasing and decreasing of the antibiotic concentration, (2) stabilization of the gentamicin content at a practically constant level and (3) slow lowering of the antibiotic level in the tissue. Comparison of the areas under the concentration/time curves showed that the modified collagen, alginic acid and monocarboxycellulose had the highest prolongation effect among the biodegradable polymers. Their use in the compositions provided during the first hours after the implantation the antibiotic concentrations in the administration site equal to tens micrograms per 1 g of the tissue. After that during 14 days the concentration of gentamicin in the implantation zone maintained at the level higher than its MIC for the main pathogens of wound infections.     

Developmental analysis of ocular morphogenesis in alpha A-crystallin/diphtheria toxin transgenic mice undergoing ablation of the lens.

The role of the lens in early eye development was examined in transgenic mice carrying the cytotoxic diphtheria toxin A gene driven by hamster alpha A-crystallin promoter sequences. Mice hemizygous for this construct are microphthalmic and contain a vacuolated and highly disorganized lens, whereas adult homozygous mice are completely ablated of the lens and lack a pupil, aqueous and posterior chamber, vitreous humor, iris, and ciliary body and show extensive convolution of the sensory retina. Developmental analysis of animals homozygous for the transgene revealed that the optic cup and lens vesicle form normally and that ablation of the lens occurs as a gradual degenerative process beginning between Days 12 and 13 of gestation. Degeneration of the lens vesicle coincides with retarded growth and development of the neuroretina, sclera, and cornea. The anterior lip of the optic cup fails to differentiate into the normal epithelium of the iris and ciliary body and the vitreous body does not develop. Although the retinal layers apparently form normally, retinal folding becomes prominent following lens degeneration. These results suggest that development of a functional lens from Embryonic Day 12.5 onward is critical for formation of the ciliary epithelium, iris, and vitreous body, as well as for appropriate growth, development, and maintenance of morphology of the retina, cornea, sclera, and optic nerve. Our results also provide information on the time course of DT-A-mediated cell destruction in vivo and are discussed in context with previous lens ablation studies and the importance of developmental analysis for interpretation of the extent to which morphogenetic aberrations are concurrent with or secondary to genetic ablation of the target tissue.     

Morphogenesis of the eye of Siberian sturgeon

The most relevant changes in Acipenser baeri eye organization were detected between hatching and 5 days post hatch. At this age, the eye had an anterior chamber, lens, iris, choroid gland, scleral cartilage, cornea and a vitreous chamber lined by the retina (with two photoreceptors: rods and single cones).