A practical profile of integrated safety assessment of near-surface disposal of radwaste at PINSTECH.

Near-surface or shallow land disposal of radioactive waste has been the primary practice at the Pakistan Institute of Nuclear Science and Technology (PINSTECH). The adopted choice of this mode of disposal has been based on a study of the site and the quality and quantity of waste generated at the 5 MW reactor with HEU fuel. Specific measures regarding the radiation safety of the workers and environmental protection have been adopted. The waste disposal operations are conducted to meet local regulatory requirements, IAEA recommendations and internationally endorsed principles such as ALARA (as low as reasonably achievable - economic, social and other relevant factors being considered). The data obtained through the years of operational and management experience have manifested the robustness of the disposal system and reliability of the disposal criterion, and have also served to further refine the latter. Consequently, confidence in the current shallow-land-burial practices has increased. Radiological safety of these practices has been assessed by addressing different aspects of the safety and disposal system. These parameters, as indices of a non-exclusive and operational safety model, are presented.

The efficacy of nitrosonaphthol functionalized XAD-16 resin for the preconcentration/sorption of Ni(II) and Cu(II) ions.

Amberlite XAD-16 resin has been functionalized using nitrosonaphthol as a ligand and characterized employing elemental, thermogravimetric analysis and FT-IR spectroscopy. The sorption of Ni(II) and Cu(II) ions onto this functionalized resin is investigated and optimized with respect to the sorptive medium (pH), shaking speed and equilibration time between liquid and solid phases. The monitoring of the influence of diverse ions on the sorption of metal ions has revealed that phosphate, bicarbonate and citrate reduce the sorption up to 10-14%. The sorption data followed Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms. The Freundlich parameters computed are 1/n=0.56+/-0.03 and 0.49+/-0.05, A=9.54+/-1.5 and 6.0+/-0.5 mmol g(-1) for Ni(II) and Cu(II) ions, respectively. D-R isotherm yields the values of X(m)=0.87+/-0.07 and 0.35+/-0.05 mmol g(-1) and of E=9.5+/-0.23 and 12.3+/-0.6 kJ mol(-1) for Ni(II) and Cu(II) ions, respectively. Langmuir characteristic constants estimated are Q=0.082+/-0.005 and 0.063+/-0.003 mmol g(-1), b=(4.7+/-0.2)x10(4) and (7.31+/-0.11)x10(4)l mol(-1) for Ni(II) and Cu(II) ions, respectively. The variation of sorption with temperature gives thermodynamic quantities of DeltaH=-58.9+/-0.12 and -40.38+/-0.11 kJ mol(-1), DeltaS=-183+/-10 and -130+/-8 J mol(-1)K(-1) and DeltaG=-4.4+/-0.09 and -2.06+/-0.08 kJ mol(-1) at 298 K for Ni(II) and Cu(II) ions, respectively. Using kinetic equations, values of intraparticle transport and of first order rate constant have been computed for both the metal ions. The sorption procedure is utilized to preconcentrate these ions prior to their determination in tea, vegetable oil, hydrogenated oil (ghee) and palm oil by atomic absorption spectrometry using direct and standard addition methods.

Enrichment of Pb(II) ions using phthalic acid functionalized XAD-16 resin as a sorbent.

A simple and reliable method has been developed using polymeric material containing phthalic acid as a chelating agent to concentrate ultratrace amounts of lead ions in aqueous solutions. After characterization by CHN, IR, and thermal studies, the static and dynamic sorption behavior of Pb(II) ions onto new synthetic resin has been investigated. The sorption has been optimized with respect to pH, shaking speed, and contact time between the two phases. Maximum sorption is achieved from solution of pH 5-8 after 10 min agitation time. The lowest concentration for quantitative recovery is 5.8 ng cm(-3) with a preconcentration factor of approximately 850. The kinetics of sorption follows the first-order rate equation with the rate constant k=0.58+/-0.04 min(-1). The variation of the equilibrium constant K(c) with temperature between 10 and 50 degrees C yields values of DeltaH, 52.4+/-1.65 kJmol(-1), DeltaS, 186+/-5.21 Jmol(-1)K(-1), and DeltaG(303K), -4.15+/-0.002 kJmol(-1). The sorption data of Pb(II) ions in the concentration range from 2.41x10(-6) to 1.44x10(-4) molL(-1) follows the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms at all temperatures investigated. The sorption of Pb(II) ions onto synthesized resin in the presence of common anions and cations has also been measured. The possible sorption mechanism of Pb(II) ions onto phthalic acid modified XAD-16 is also discussed. The sorption procedure is utilized to preconcentrate Pb(II) ions prior to their determination in automobile exhaust particulates by atomic absorption spectrometry using direct and standard addition methods.

Optisol vs Dexsol as storage media for preservation of human corneal epithelium.

PURPOSE: To compare the efficacy of two storage media, Optisol GS and Dexsol, in preservation of donor corneal epithelium. METHODS: A total of 12 pairs of corneas not suitable for transplantation, all with intact epithelium, were used in this study, with one cornea of the pair stored in Optisol GS and its other counterpart in Dexsol. At each of three durations of storage--1, 2, and 4 days--four of these paired corneas were prepared for light microscopy and scanning and transmission electron microscopy. Another four pairs of control cornea were prepared in the same way and placed in universal fixative. MAIN OUTCOME MEASURES: Evaluation of the corneas was made by two observers masked as to the identity of the storage medium and length of storage. Loss of epithelial cells was evaluated by light microscopy. The attachment of the epithelium to the basement membrane,cellular integrity, intercellular junctions, and intracellular organelles were evaluated and compared by electron microscopy. RESULTS: The magnitude of epithelial loss correlated with the length of storage time. Control corneas maintained normal epithelium with preservation of all epithelial cell layers. Corneas stored for 1 day had minimal damage of the epithelium. Corneas stored for 2 days had a slight increase in epithelial damage, and corneas stored for up to 4 days showed a marked increase in epithelial damage. There were no significant differences between the two storage media. The basal cell layer was maintained in both the media at all time points, usually in good condition with mild-to-moderate damage in some cases. CONCLUSIONS: Loss of donor epithelium is related mainly to the length of storage and is similar in both Optisol GS and Dexsol. The storage time should be less than 4 days,especially when performing penetrating keratoplasty on patients with ocular surface disorders.

Sorption of traces of silver ions onto polyurethane foam from acidic solution.

The sorption of traces of silver ions onto polyurethane foam (PUF) has been investigated in detail. Maximum sorption of silver (K(d)=6109 cm(3) g(-1), %sorption>97.5%) has been achieved from 1 M nitric acid solution after equilibrating silver ions with approximately 29 mg PUF for 20 min. The kinetics and thermodynamics of the sorption of silver ions onto PUF have also been studied. The sorption of silver ions onto PUF follows a first-order rate equation, which results as 0.177 min(-1). The variation of sorption with temperature yields the values of DeltaH=-56.1+/-3.2 kJ mol(-1), DeltaS=-159.7+/-10.5 J mol(-1) K(-1) and DeltaG=-8.68+/-0.09 kJ mol(-1) at 298 K with a correlation factor gamma=0.9919. The sorption data were subjected to different sorption isotherms. The sorption follows Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The values of Langmuir isotherms Q=65.4+/-1.5 mumol g(-1) and b=(4.79+/-1.16)x10(4) dm(3) mol(-1) have been evaluated for Langmuir sorption constants, whereas the Freundlich sorption isotherm gives the value 1/n=0.12+/-0.02 and A=0.15+/-0.03 mmol g(-1). The D-R parameters computed were beta=-0.000817+/-0.000206 mol(2) kJ(-2), X(m)=76.8+/-8.7 mumol g(-1) and E=24.7+/-3.2 kJ mol(-1). The influence of common ions on the sorption was also examined. It is observed that Hg(II), thiourea, Al(III), thiocyanate and thiosulphate reduce the sorption, whereas Cu(II), citrate and acetate ions enhance the sorption significantly. It can be concluded that PUF may be used to remove traces of silver ions from its very dilute solutions or for its preconcentration from aqueous acidic solutions.

In-vitro comparative study of a locally prepared corneal storage medium and Optisol.

OBJECTIVE: To compare the in-vitro safety and efficacy of two corneal storage media, Optisol and H-Sol, a chondroitin-sulfate-based medium containing hydrocortisone prepared at the Eye Bank of Canada (Ontario Division). DESIGN: Twenty paired corneas from human donors (mean age 67.9 years) were randomly assigned for storage in corneal viewing chambers at 4 degrees C in Optisol (10 corneas) or H-Sol (10 corneas). The storage media were masked, and all measurements were done in a blinded fashion. OUTCOME MEASURES: Corneal clarity and thickness (measured at 0, 2, 4, 8 and 12 days), endothelial cell density and morphology (analysed at days 0 and 12). At day 12 cell viability was determined by staining with trypan blue and alizarin red S, and three randomly selected corneas from either medium were examined by scanning electron microscopy and transmission electron microscopy. RESULTS: Corneal thickness increased significantly from day 0 to day 12 in both Optisol and H-Sol, and corneal clarity decreased significantly in both media over this period (p < 0.05). At days 2, 4, 8 and 12 the corneas stored in Optisol were significantly thinner than those stored in H-Sol (p < 0.05). There were no significant differences between the media in any of the other indices studied. Endothelial cell density decreased significantly in both Optisol and H-Sol (p < 0.05). There were no within-group differences in percentage of cell loss, coefficient of variation of cell area, figure coefficient or percentage of hexagonal cells. CONCLUSIONS: The difference in corneal thickness between Optisol and H-Sol may have been due to the higher concentration of chondroitin sulfate in the former (2.5%, compared with 2% in H-Sol) or perhaps to the addition of other components to Optisol that are not present in H-Sol. Efforts continue to improve the formulation of H-Sol. Further studies are necessary to assess its safety and efficacy in vivo.

Changes in the corneal Na-K ATPase levels in eyes stored in moist chamber at 4 degrees C.

This report deals with a chronological measurement of Na-K ATPase enzyme activity in human and bovine corneas stored in a moist chamber at 4 degrees C. Paired human and bovine eyes were sterilized by the standard eye bank procedure and stored up to 6 days. At the desired time, the corneal endothelium was assayed for Na-K ATPase activity. The protein content of each tissue sample was also determined. In a parallel set of experiments, the viability of identical stored corneas was determined by trypan blue and alizarin red staining technique, and morphometric analysis was done to quantify the extent of the corneal endothelial damage. The human corneas showed that there was a significant progressive decrease in the Na-K ATPase activity as the storage time increased. The decrease was related to morphological endothelial damage.

Purpurogallin as a cytoprotector of cultured rabbit corneal endothelium.

We examined the protective properties of purpurogallin, a naturally occurring phenol, in delaying necrosis of cultured corneal endothelial cells caused by oxygen free radicals. Endothelial cell cultures were prepared from New Zealand white rabbits using microcarrier cell culture techniques. Corneal endothelial cells were treated with hypoxanthine (2 mM) and xanthine oxidase (67 IU/L) to generate free radicals. The criteria for cell necrosis were cytoplasmic shrinkage, dissolution of plasma membranes and presence of "haloes" around the cells on phase contrast microscopy, confirmed by transmission electron microscopy. More than 95% of second-generation cells exhibited morphologic evidence of necrosis within 4.62 +/- 0.82 minutes after exposure to oxyradicals. The addition of purpurogallin (0.25 or 1.0 mM) significantly increased time to cell necrosis to 8.18 +/- 0.83 and 11.59 +/- 1.71 minutes respectively (p < 0.05). Further studies are under way to determine whether purpurogallin may be useful in preventing endothelial cell damage in corneas preserved for corneal transplantation.

Toxicity and pharmacokinetics of intravitreally injected ciprofloxacin in rabbit eyes.

To assess the toxicity of intraocular injection of ciprofloxacin, 22 New Zealand white rabbits received midvitreal injections of 100, 200, 400, 800 or 3200 micrograms of ciprofloxacin in 0.1 mL of distilled water (39 eyes) or 0.1 mL of distilled water only (5 eyes). The ocular pharmacokinetics of intravitreally injected ciprofloxacin was determined by aqueous humour and vitreous sampling 1, 2, 4, 8, 12, 18 or 24 hours after midvitreal injection of 100 micrograms of the drug in one eye each of 25 New Zealand white rabbits. The samples were analysed by means of a disc diffusion bioassay. No ocular damage was noted on ophthalmoscopy at any of the concentrations tested. Histologic study showed mild, transient vacuolation of the nerve-fibre layer in all eyes, including the control eyes, 2 hours after injection; at 24 hours no vacuolation was evident except at concentrations of 800 and 3200 micrograms, at which plexiform layer damage was evident. Peak aqueous and vitreous levels of ciprofloxacin were obtained at 1 hour (0.59 and 27.26 micrograms/mL respectively); the vitreous level fell to below 1.0 micrograms/mL 12 hours after injection. We conclude that intravitreally injected ciprofloxacin may be a safe and useful antibiotic in the treatment of aminoglycoside-resistant bacterial endophthalmitis.

Quantitative analysis of collagen content and amino acids in trabecular meshwork.

The purpose of this study was to compare collagen content in the TM of normal and glaucomatous eyes, and to establish whether collagen levels change with age. Collagen content was measured in 30 normal and 27 age matched glaucoma trabeculectomy specimens by the sirius red dye binding technique, and in 14 normal and 15 age matched glaucoma specimens by amino acid analysis. Both dye binding data and amino acid analysis showed no statistical difference between normal and glaucoma samples. Age had no significant effect on mean optical densities or on the collagen-specific amino acids proline, hydroxyproline, and hydroxylysine. Amino acid variability, however, was statistically different between the two groups. These results indicate that mean collagen levels in the trabecular meshwork of glaucomatous eyes do not differ from those in normal eyes.

Phototoxic effects of 8-methoxypsoralen on rabbit corneal endothelium.

The phototoxic effects of 8-methoxypsoralen (8-MOP) were investigated using the rabbit corneal endothelium in organ culture. The corneas were divided into four groups: (a) irradiated with a mercury vapor lamp (emitting UVA and visible radiation) in the presence of 8-MOP (experimental), (b) irradiated without 8-MOP (control A), (c) incubated with 8-MOP (control B) and (d) incubated without 8-MOP (control C). Specular and light microscopic examination showed that the experimental corneas had greater cellular damage compared to the control corneas. The effects of 8-MOP were restricted to certain localized areas of the cornea. However there was no significant difference in the amounts of 51Cr released from the labelled experimental and control corneas. These results show phototoxic damage of the corneal endothelial cells.

Bio-effects of extremely low frequency electromagnetic fields (60 Hz.) on the healing of corneal epithelial wound: an in vitro study.

The organ cultures of standardized epithelial wound of rabbit cornea, were exposed to electric and magnetic fields components of the extremely low frequency (60 Hz) sinusoidal electromagnetic field, separately or in combination. The electric field was applied as a pure electric current via an agar-salt bridge, and the magnetic field component was applied as a pure polarized magnetic field by means of a pair of energized coils in a Helmholtz configuration. The two field components were at right angles to each other and in phase (phi = 0 degrees) when applied in combination. Their vectors or planes of polarization were parallel to the surface of the culture dish. The three exposure combinations used were: a) electric current density of 0.19 V/m (30 microA/cm2) and/or magnetic fields strength of 1.0 Gauss. (low intensity) b) electric current density of 0.31 V/m (50 microA/cm2) and/or magnetic fields strength of 1.5 Gauss. (medium intensity) c) electric current density of 0.57 V/m (90 microA/cm2) and/or magnetic fields strength of 2.5 Gauss. (high intensity). After 2 days of exposure the incorporation of radiolabelled thymidine into DNA of the regenerating epithelial cells was determined. Results showed thymidine incorporation (adjusted by regression for differences in the levels of DNA in corneal wound) (DNA*) depended upon the electromagnetic field strength. The only significant effect on this outcome, was an interaction effect between the electric (E) and magnetic (M) fields employed. The size and direction of this interaction depended strongly on the maximum field strengths. At the lowest level DNA* was significantly lower when both fields were present than would be expected from the effects of either field alone. At the highest level, DNA* was significantly higher. There were no significant effects for medium field strengths.

Cytotoxicity of gentamicin on corneal endothelium stored in vitro.

Since corneas are preserved in storage media containing gentamicin, the risk of gentamicin toxicity could increase with the increase in the storage time as well as with the increase in the concentration. We wished to determine the safety level of gentamicin on the corneal endothelium in terms of its concentration as a function of the storage time. One cornea (experimental) of a rabbit was stored in chondroitin sulfate medium (CSM) containing 0.5 mg/ml or 1 mg/ml of gentamicin, and the other cornea (control) was kept in CSM containing 0.1 mg/ml of gentamicin. Both corneas were stored up to 14 days at 4 degrees C. After storage, each corneal endothelium was studied by specular microscopy, light microscopy (following staining with trypan blue and alizarin red) and transmission electronmicroscopy. In comparison with the control corneas, the experimental corneas showed progressively greater amounts of endothelial cell damage, as the concentration of gentamicin or the storage time was increased. Our morphological study indicates that the presently recommended concentration of gentamicin (0.1 mg/ml) is not cytotoxic to the corneal endothelium provided the time of storage does not exceed 7 days.

A morphometric study of endothelial cells of human corneas stored in MK media and warmed at 37 degrees C.

No study has yet been done to investigate the changes in endothelial cell size, perimeter, and density that may result from the warming of corneas in MK (McCarey-Kaufman) medium for specular microscopy. In the present investigation eye bank eyes were stored in MK medium at 4 degrees C and rewarmed daily for six days at 37 degrees C before specular photography of the endothelium was performed. These photographs were compared with wet mount preparations stained with trypan blue and alizarin red made from the same corneas and those stored without rewarming for six days. In addition all corneas were qualitatively analysed with the scanning electron microscope (SEM). The data from serial specular photography were insufficient to allow significant conclusions to be drawn about day to day changes in cell morphology. However, analysis of wet mount preparations revealed that cell density and perimeter varied significantly between those corneas rewarmed daily and those held in cold storage for six days. SEM studies showed an intact cell monolayer with cell loss along the folds of corneal endothelium. We therefore concluded that repeated rewarming at 37 degrees C of corneas stored in MK medium at 4 degrees has a deleterious effect on cell morphology and that folds induced by swelling of corneal tissue result in endothelial cell damage with some loss.

Changes of MK medium during storage of human cornea.

By comparing the composition of McCarey-Kaufman (MK) medium before and after corneal storage we attempted to identify specific physiological changes in the medium as predictors of tissue damage. We also tried to determine if hydrocortisone (a lysosomal membrane stabiliser) added to the medium could reduce tissue damage during storage. Corneas (human and rabbit) were stored in the MK medium with and without hydrocortisone for 4 days at 4 degrees C. The water and nitrogen contents of the stored cornea were compared with those of the fresh cornea. The medium was analysed before and after corneal storage to determine the concentrations of glucose, protein, and amino acids as well as pH and osmolarity. Scanning electron microscopy (SEM) was used to estimate the degree of the corneal endothelial cell damage. The nitrogen contents and dry weights of the steroid treated and untreated stored corneas were similar to those of the fresh unstored cornea. The steroid treated cornea contained a lesser amount of water than the untreated cornea. The cornea stored in medium without steroid took up a greater amount of glucose from the medium than the cornea stored in medium with steroid. As compared with their concentrations in the fresh unused medium the concentrations of leucine, lysine, and glycine were lower and that of glutamic acid was higher in both the media used for corneal storage. However, the steroid treated storage medium as compared with the untreated storage medium had a greater reduction in the lowering of leucine, lysine, and glycine, and a lesser reduction in the increase of glutamic acid. Steroid treated medium also had a lesser amount of protein released from the stored cornea. Changes in the pH and osmolarity of the media before and after corneal storage were not remarkable. SEM showed that the endothelial cells of the cornea stored in the medium containing steroid were less damaged than those of the cornea stored in the medium without steroid.

Inhibition of vascular endothelial cell growth and trypsin activity by vitreous.

Vitreous from bovine, human and chick embryo has been found to contain a trypsin inhibitory activity. Chymotrypsin-inhibitory activity was also identified in bovine and chick embryo vitreous. Following either ultrafiltration or Bio Gel P-10 chromatography, these activities appear in fractions having a molecular weight greater than 10000 MW (ultrafiltration) or greater than 13000 MW (P-10 void volume), and are separable from low molecular weight aortic endothelial cell growth inhibitory activity present either in the ultrafiltrate or P-10 retarded volume. Treatment of the trypsin inhibitory fraction with hyaluronidase had no effect on trypsin inhibition, nor did addition of hyaluronic acid inhibit trypsin. Chick embryo vitreous and hyalocyte-conditioned medium were found to contain aortic endothelial cell growth inhibitory activity in both the void volume and retarded volume fractions following Bio Gel P-10 chromatography. Both the 6200 MW bovine vitreous endothelial cell growth inhibitor and the high molecular weight chick embryo vitreous endothelial cell growth inhibitor (greater than 13000 MW) were similar, in that most of the activity did not bind to heparin linked to Sepharose CL-6B.

Vascular endothelial cell growth inhibitor of normal and pathologic human vitreous.

Normal and pathologic human vitreous have been analyzed for the presence of a low-molecular weight inhibitor of aortic endothelial cell proliferation. Vitreous was subjected to gel chromatography and the material appearing in the retarded volume (less than 13,000 daltons) was tested for its ability to inhibit tritiated thymidine incorporation into DNA by calf aortic endothelial cells. Depending on the sample of vitreous analyzed, one or more fractions showing inhibitory activity were identified in each case.

Effects of acidic lake water on the eye.

The normal eyes of 6 men and 21 rabbits were exposed to samples of lake water, one eye to a sample of pH 4.6 and the other to a sample of pH 6.3. The men's eyes were exposed for 5 minutes on four occasions a week apart, whereas the rabbits' eyes were exposed for 15 minutes either on one occasion or once a day for 7 days. In the humans neither sample of water produced symptoms or signs of an adverse effect on the external eye tissues, apart from brief conjunctival congestion after every exposure. In the rabbits the two samples did not appear, in general, to have different effects on the ocular tissues, as judged from the osmolarity and cell count of the tears, conjunctival congestion, corneal staining with fluorescein, corneal permeability and histologic features of the cornea. In a few instances differences were observed, but their pathological significance was not apparent. These data suggest that lake water of a pH as low as 4.6 may not harm healthy eyes, however, larger and broader studies are essential.