The impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Singapore

The National University Hospital (NUH) Tissue Bank was established in October 1988. The National University of Singapore (NUS) was officially appointed by IAEA to be the IAEA/NUS Regional Training Centre (RTC) for RCA Member States for training of tissue bank operators on September 18, 1996. In the first five years since its establishment the National University Hospital Tissue Bank concentrated its work on the sterile procurement and production of deep frozen femoral heads and were used in patients for bone reconstruction. The cost of producing these tissues were about SGD$ 250 per femoral head although cost fees were initially charged at SGD$ 50 per femoral head. The most important activity carried out by Singapore within the IAEA was training. Between November 1997 and April 2007, a total of nine courses were conducted by RTC with a total of 180 tissue bank operators registered, 133 from Asia and the Pacific region (13 countries, including 2 from Iran), 14 from Africa (Zambia, Libya, Egypt, Algeria, and South Africa), 6 from Latin America (Brazil, Chile, Cuba, Peru, and Uruguay), 9 from Europe (Greece, Slovakia, Poland, and Ukraine), and 2 from Australia. The last batch (ninth batch) involved 20 students registered in April 2007 and will be due to sit for the terminal examination in April 2008.     

The impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Cuba

The first multi-tissue bank was founded at Havana in 1958. At that time, freeze-drying was used at the bank as a method of preserving, as well as Cobalt 60 irradiation to sterilise bone tissue, heart valves and others. The impact of the IAEA program in tissue banking activities in Cuba can be summarised as follows: (a) Increase in the production of sterilised tissues using ionising radiation (bone, pig skin and amnion) for medical treatment in the tissue bank of the Hospital Frank Pais; (b) increase of the quality of the productions of bone tissues, pig skin and amnion; (c) reduction in the import of tissues by increasing the local production of tissues; (d) sustainability in the number of donors through the implementation of a public and professional awareness campaign; (e) training of six persons in the Regional Training Centre of Buenos Aires; (f) qualification of one person in the administration of a tissue bank and in the implementation of a Quality System. The amount of tissues produced and sterilised using the ionising radiation techniques in the established banks was 25,510 units. The amount of patients treated with sterilised tissues produced by the established banks was 2,448.     

The impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Mexico

Tissue banking started in Mexico in 1948-1949, when two bone banks were established, one at the Infantile Hospital of Mexico and other at the Central Military Hospital. Mexico has benefited for the implementation of the IAEA program since through it has been able to settle down and to consolidate the Tissue Bank at the Instituto Nacional de Investigaciones Nucleares ININ (National Institute for Nuclear Research). This is the only bank in Latin America that has a Quality Management System in force, certified under ISO 9001:2000 since August 1, 2003. The first tissue processed was amnion. The main products of the BTR are amnion and pig skin. Both are biological tissues which their main use is as a wound dressing in patients with burns, scars, diabetic ulcers, epidermolysis bullosa, damaged ocular surface, etc. The General Health Law, published in 1984 and reformed in June 19, 2007, describes the procedure for the disposal of organs, tissues and human cadavers in its fourteenth title and in the Regulation for Sanitary Control. During the period 2001-2005, the ININ Tissue Bank produced 292 sterilised tissues (amnion, 86,668 cm², and frozen pig skin, 164,220 cm², at an estimated cost of 1,012,668 Mexican pesos. Until 2006, one hundred eighty five (185) patients have been treated with the use of sterilised tissues produced by the ININ Tissue Bank. The radiation source used for sterilisation of tissues is an industrial Cobalt-60 irradiator model JS-6500 AECL, which belongs to ININ. This equipment is located in other building, close to the BTR, in the Centro Nuclear de México “Dr. Nabor Carrillo Flores” (Nuclear Center of Mexico). Until 2006, six hospitals use in a routine way the sterilised tissues produced by the ININ Tissue Bank, for the treatment of burns originated by diverse agents like flame, electricity, liquids in boil, chemical reagents, as well as for the reconstruction of the ocular surface. Two of these hospitals treat patients of very low economic incomes, mainly needy individuals, who cannot afford to pay this type of treatments in other hospitals due to their high cost. The results obtained up to now are highly promising.     

The impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Thailand

Tissue banking started in Thailand in 1979. Five years after this, the Bangkok Biomaterial Centre (BBC) was established in the Faculty of Medicine, Siriraj Hospital, with the support of the IAEA program. The objective of the Centre was to provide sterile bones and tissues for clinical use. Through the passage of time, the Bangkok Biomaterial Centre has gained confidence from the end user and by 2007 has processed 33,872 allografts from 491 deceased donors and 4,035 live donors were used in medical treatment in 3,596 patients in more than 79 different hospitals. More than 305 surgeons from Thailand used the tissue produced in the BBC. At the beginning of its work the BBC concentrate its activities on the production of the following tissues: freeze dried bone, freeze dried dura mater and freeze dried fascia lata. All of these tissues were sterilised using ethylene oxide gas until the end of year 1984. Since 1985 the BBC sterilise tissue using ionising radiation. The BBC is now producing deep-frozen; bone tendon, cartilage, trachea and soft tissue; freeze-dried; bone, fascia lata, dura mater, amniotic membrane, bone hydroxyapatite, bone tablet and fresh preserved amniotic membrane Yongyudh Vajaradul is a Founder of Bangkok Biomaterial Centre and also a President of TATB, Bangkok, Thailand. Jorge Morales Pedraza is a former IAEA Interregional Project Manager, Vienna, Austria.     

Virus inactivation in bone tissue transplants (femoral heads) by moist heat with the 'Marburg bone bank system'

Several virus inactivation procedures like heat treatment, gamma irradiation and chemical sterilization are used to increase the safety of bone tissue transplants. In this study we present data on the virus-inactivating effect of heat disinfection on human femoral heads, using the Marburg bone bank system 'Lobator sd-2'. Three enveloped viruses (human immunodeficiency virus type 2 [HIV-2], bovine viral diarrhoea virus as a model for Hepatitis C virus [HCV], and the herpesvirus pseudorabies virus), and three non-enveloped viruses (hepatitis A virus, poliomyelitis virus, and bovine parvovirus) were investigated.In a model system the central part of human femoral heads was contaminated with the respective cell-free virus suspension, establishing a direct contact between virus and native bone tissue. The core temperature in the femoral heads during the sterilization process was determined in additional model experiments. A temperature of 82.5 degrees C, given by the manufacturer as the effective temperature for virus inactivation, was maintained for at least 15 min in decartilaged femoral heads with a diameter of < or = 56 mm. Heat treatment using the Lobator sd-2 inactivated all viruses in human femoral heads below the detection limit (at least by a factor of > or =4 log(10)).By combining a well-focussed anamnesis of the donors and serological testing for relevant infection markers (anti-HIV-1/2, HBsAg, anti-HBcore, anti-HCV, TPHA) with heat treatment of femoral heads in the Lobator sd-2 system, a high safety level is achieved. To further increase virus safety of cadaveric bone transplants, it is recommended that multi-organ donors are tested by nucleic acid testing (i.e. polymerase chain reaction) for HIV, HBV and HCV genome.     

The impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Indonesia

In 1986, the National Nuclear Energy Agency (Batan) in Jakarta started the research and development for the setting up of a tissue bank (Batan Research Tissue Bank/BRTB) by preserving fresh amnion or fetal membranes by lyophilisation and then sterilising by gamma irradiation. During the period of 1990 and 2000, three more tissue banks were set up, i.e., Biomaterial Centre in Surabaya, Jamil Tissue Bank in Padang, and Sitanala Tissue Bank in Tangerang. In 1994, BRTB produced bone allografts. The banks established under the IAEA program concentrated its work on the production of amnion, bone and soft tissues allografts, as well as bone xenografts. These tissues (allografts and xenografts) were sterilised using gamma irradiation (about 90%) and the rest were sterilized by ETO and those products have been used in the treatment of patients at more than 50 hospitals in Indonesia. In 2004, those tissue banks produced 8,500 grafts and 5,000 of them were amnion grafts for eye treatment and wound dressing. All of those grafts were used for patients as well as for research. In 2006, the production increased to 9,000 grafts. Although the capacity of those banks can produce more grafts, we are facing problems on getting raw materials from suitable donors. To fulfill the demand of bone grafts we also produced bone xenografts. The impact of the IAEA program in tissue banking activities in Indonesia can be summarised as follows: to support the national program on importing substitutes for medical devices. The price of imported tissues are between US$ 50 and US$ 6,000 per graft. Local tissue bank can produce tissues with the same quality with the price for about 10–30% of the imported tissues.     

Sufficient Penetration of Peracetic Acid into Drilled Human Femoral Heads

Chemical sterilisation methods for musculoskeletal transplants have the problem of penetration into all tissue strata. The present study examined if a peracetic acid/ethanol solution penetrated to a sufficient extent into specifically prepared femoral heads. To this effect, 10 femoral heads have been provided with drillings (diameter 2 mm, depth 10 mm) at a distance of 15 mm (series B) and placed in a diffusion chamber with sterilisation solution. From an additional central drilling at the femoral neck junction, the sample drawing was made after 30 min each over a period of 4 h for the iodometric determination of peracetic acid (PAA) concentration. Ten femoral heads, which did contain only the central drilling, served as controls (series A). In 9 of the examined femoral heads of series A the defined minimum concentration of PAA of 0.2% (inactivation of bacteria, spores, fungi) has been clearly exceeded over the complete period of measurement. About 0.8% PAA (inactivation of viruses) was achieved within 4 h only with six femoral heads. Nine out of the 10 examined femoral heads in series B show a clearly improved penetration behaviour which was expressed in smaller standard deviations, a faster increase in concentration, as well as in higher starting and final concentrations (approx. 0.9%) of PAA. Previous drying in air leads to a faster penetration into the centre of the bone. Standardised drilling of decartilaged femoral heads creates favourable conditions for the penetration of the PAA sterilisation solution into the whole tissue and guarantees a sufficient inactivation of microorganisms.     

A future vision of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking for Asia and the Pacific and Latin American regions

In order to solve some of the problems that are affecting tissue banking activities in the world, a new program/project proposal could be prepared by the IAEA and interested Member States in order to implement it in 2009. The main objective of the new program/project proposal could be the following: To consolidate tissue banks activities in a selected group of IAEA Member States by increasing the quality of the tissue processing and sterilization methods used. The specific objective to be reached by the new program/project proposal could be the following: To reach international standards in all activities carried out by a selected group of tissue banks, as well as the establishment of a limited regional tissue processing centres in specific regions. The following are the conditions to be met by the interested tissue banks, in order to participate in the new program/project proposal: To process different types of tissues for medical treatment using the ionizing radiation technique for tissue sterilization; To apply at least one of the current version of the IAEA Code of Practice, the IAEA Standards and the IAEA Public Awareness Strategies and to have the support of national health authorities for the use of the remaining IAEA documents in the near future; To have in force agreements with public and private hospitals for the use of the sterilized tissues processed by the bank for medical treatment; To have in place a donor referral system, or has the approval by the national health authorities to adopt such system in the near future; To receive the support from the national health authority to participate in the implementation of the new program/project proposal.     

The impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in India

The banking of tissues such bone and skin began in India in the 1980s and 1990s. Although eye banking started in 1945 there was little progress in this field for the next five decades. As part of the IAEA/RCA program to use ionising radiation for the sterilisation of biological tissues in Asia and the Pacific Region, the Tata Memorial Hospital (TMH) in 1986 decided to set up a tissue bank in Mumbai funded by the Government of India. The TMH Tissue Bank became operational in January 1988, and stands as a pioneering effort in the country to provide safe, clinically useful and cost-effective human allografts for transplantation. It uses the IAEA International Standards on Tissue Banking. All the grafts are sterilised terminally by exposure to a dose of 25 kGy of gamma radiation, which has been validated as recommended by the IAEA Code of Practice for the Radiation Sterilisation of Tissues Allografts: Requirements for Validation and Routine Control. The TMH Tissue Bank is registered with the Maharashtra State Health Authorities, and in May 2004, it became India’s first Tissue Bank to receive ISO 9001:2000 certification of its Quality Management System. From 1989 to September 2007, the TMH Tissue Bank has supplied 11,369 allografts to 310 surgeons operating in 69 hospitals in Mumbai and 56 hospitals in other parts of India. These numbers have been limited by difficulties with the retrieval of tissues from deceased donors due to inadequate resources and tissue donation policies of hospitals. As the Government of India representative in the IAEA program, the TMH Tissue Bank has promoted and co-coordinated these activities in the country and the development of tissue banks using radiation sterilisation of tissue grafts. Towards this end it has been engaged in training personnel, drawing up project proposals, and supporting the establishment of a Tissue Retrieval Centre in Mumbai. Currently it networks with the Zonal Transplant Co-ordination Centre of the Government of Maharashtra, and the newly instituted National Deceased Donor Transplantation Network, which will work with the Government of India to set up rules and regulations for organ and tissue donation and transplantation.     

The impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Brazil

Until 2000, efforts into organising tissue banks in Brazil had not progressed far beyond small “in house” tissue storage repositories, usually annexed to Orthopaedic Surgery Services. Despite the professional entrepreneurship of those working as part time tissue bankers in such operations, best practices in tissue banking were not always followed due to the lack of regulatory standards, specialised training, adequate facilities and dedicated personnel. The Skin Bank of the Plastic Surgery Department of the Hospital das Clinicas of Sao Paulo, the single skin bank in Brazil, was not an exception. Since 1956, restricted and unpredictable amounts of skin allografts were stored under refrigeration for short periods under very limited quality controls. As in most “tissue banks” at that time in Brazil, medical and nursing staff worked on a volunteer and informal basis undergoing no specific training. IAEA supported the implementation of the tissue banking program in Brazil through the regional project RLA/7/009 “Quality system for the production of irradiated sterilised grafts” (1998–2000) and through two interregional projects INT/6/049 “Interregional Centre of Excellence in Tissue Banking”, during the period 2002–2004 and INT/6/052 “Improving the Quality of Production and Uses of Radiation Sterilised Tissue Grafts”, during the period 2002–2004. In 2001–2002, the first two years of operation of the HC-Tissue Bank, 53 skin transplants were carried out instead of the previous 4–5 a year. During this period, 75 individuals donated skin tissue, generating approximately 90,000 cm² of skin graft. The IAEA program were of great benefit to Brazilian tissue banking which has evolved from scattered make shift small operations to a well-established, high quality tissue banking scenario.     

The impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Peru

The tissue bank “Rosa Guerzoni Chambergo” (RGCTB) located at the Child’s Health Institute was inaugurated in 1996, with the financial and technical support of the IAEA program on radiation and tissue banking. Since 1998, the biological bandage of fresh and lyophilised pigskin, amnion and bone tissue is processed routinely in this bank. In all cases, the tissue is sterilised with the use of Cobalt-60 radiation, process carried out at the Laboratories of Irradiation of the Peruvian Institute of Nuclear Energy (IPEN). The tissue bank in the Child’s Health Institute helped to save lives in an accident occurred in Lima, when a New Year’s fireworks celebration ran out of control in January 2002. Nearly 300 people died in the tragic blaze and hundreds more were seriously burned and injured. Eight Lima hospitals and clinics suddenly were faced with saving the lives of severely burned men, women and children. Fortunately, authorities were ready to respond to the emergency. More than 1,600 dressings were sterilised and supplied to Lima surgeons. The efforts helped save the lives of patients who otherwise might not have survived the Lima fire. Between 1998 and September 2007, 35,012 tissue grafts were produced and irradiated. Radiation sterilised tissues are used by 20 national medical institutions as well as 17 private health institutions. The tissue bank established in Peru with the support of the IAEA is now producing the following tissues: pigskin dressings, fresh and freeze-dried; bone allografts, chips, wedges and powdered, and amnion dressings air-dried. It is also now leading the elaboration of national standards, assignment being entrusted by ONDT (Organización Nacional de Donación y Transplantes; National Organisation on Donation and Transplant). This among other will permit the accreditation of the tissue bank. In this task is also participating IPEN.     

No influence of collagenous proteins of Achilles tendon, skin and cartilage on the virus-inactivating efficacy of peracetic acid–ethanol

The risk of transmitting human pathogenic viruses via allogeneic musculoskeletal tissue transplants is a problem requiring effective inactivation procedures. Virus safety of bone transplants was achieved using peracetic acid (PAA)-ethanol sterilisation. Proteins are known to have an adverse effect on the virus-inactivating capacity of PAA. Therefore we investigated virus inactivation by PAA in collagenous tissues. Achilles tendon, skin and cartilage were cut into small pieces, lyophilised and contaminated with pseudorabies virus (PRV) or porcine parvovirus (PPV). The inactivating capacity of PAA-ethanol was investigated by determining virus titres in the supernatant or the tissue pellet at different time-points. In all virus-contaminated tissue samples treatment for 10 min with PAA-ethanol resulted in titre reductions by a factor of >10(3). PRV was rapidly inactivated below the detection limit (< or =2.8 x 10(1) TCID(50)/ml). After 240 min a reduction by a factor of >10(4) was obtained for PPV in all samples, but a residual infectivity remained. Collagenous proteins of Achilles tendon, skin and cartilage had no adverse effect on the virus-inactivating capacity of PAA. PAA-ethanol used in the production process at the Charité tissue bank can therefore be recommended for treatment of non-osseous musculoskeletal tissues.     

Successful disinfection of femoral head bone graft using high hydrostatic pressure

The current standard for sterilization of potentially infected bone graft by gamma irradiation and thermal or chemical inactivation potentially deteriorates the biomechanical properties of the graft. We performed an in vitro experiment to evaluate the use of high hydrostatic pressure (HHP); which is widely used as a disinfection process in the food processing industry, to sterilize bone grafts. Four femoral heads were divided into five parts each, of which 16 were contaminated (in duplicate) with 10⁵–10⁷ CFU/ml of Staphylococcus epidermidis, Bacillus cereus, or Pseudomonas aeruginosa or Candida albicans, respectively. Of each duplicate, one sample was untreated and stored similarly as the treated sample. The remaining four parts were included as sterile control and non-infected control. The 16 parts underwent HHP at the high-pressure value of 600 MPa. After HHP, serial dilutions were made and cultured on selective media and into enrichment media to recover low amounts of microorganism and spores. Three additional complete femoral heads were treated with 0, 300 and 600 MPa HHP respectively for histological evaluation. None of the negative-control bone fragments contained microorganisms. The measured colony counts in the positive-control samples correlated excellent with the expected colony count. None of the HHP treated bone fragments grew on culture plates or enrichment media. Histological examination of three untreated femoral heads showed that the bone structure remained unchanged after HHP. Sterilizing bone grafts by high hydrostatic pressure was successful and is a promising technique with the possible advantage of retaining biomechanical properties of bone tissue.     

The evolution and impact of the International Atomic Energy Agency (IAEA) program on radiation and tissue banking in Asia and the Pacific region

The Asia and the Pacific region was within the IAEA program on radiation and tissue banking, the most active region. Most of the tissue banks in the Asia and the Pacific region were developed during the late 1980s and 1990s. The initial number of tissue banks established or supported by the IAEA program in the framework of the RCA Agreement for Asia and the Pacific region was 18. At the end of 2006, the number of tissue banks participating, in one way or another in the IAEA program was 59. Since the beginning of the implementation of the IAEA program in Asia and the Pacific region 63,537 amnion and 44,282 bone allografts were produced and 57,683 amnion and 36,388 bone allografts were used. The main impact of the IAEA program in the region was the following: the establishment or consolidation of at least 59 tissue banks in 15 countries in the region (the IAEA supported directly 16 of these banks); the improvement on the quality and safety of tissues procured and produced in the region reaching international standards; the implementation of eight national projects, two regional projects and two interregional projects; the elaboration of International Standards, a Code of Practice and a Public Awareness Strategies and, the application of quality control and quality assurances programs in all participating tissue banks.     

The International Atomic Energy Agency (IAEA) Program on Radiation and Tissue Banking: a Successful Program for Developing Countries

Since its inception the IAEA program in radiation and tissue banking supported the establishment of twenty five tissue banks in different countries. Now more than 103 tissue banks are now operating in these countries. The production of sterilized tissues has grown in an exponential mode within the IAEA program. From 1988 until the end of 2000 the production of sterilized tissues was 224,706 grafts, with an estimated value of at least $51,768,553 million dollars at the mean current charge rate in non-commercial banks in Europe and USA. During the period 1997–2002 several countries from Asia and the Pacific region produced more than 155,000 grafts, with an estimated value of about $36.7 million dollars. Training was considered to be one of the most important tasks to be supported. A total of 192 students were registered in the training program and 146 students graduated with a University Diploma. For many developing countries an additional benefit is not having to import expensive sterilized tissues from developed countries, but the exposure of orthopedic and plastic surgeons working, to new methods of using allografts in specific surgical treatments.     

Dermatan sulphate proteoglycan from human articular cartilage. Variation in its content with age and its structural comparison with a small chondroitin sulphate proteoglycan from pig laryngeal cartilage.

Low molecular mass proteoglycans (PG) were isolated from human articular cartilage and from pig laryngeal cartilage, which contained protein cores of similar size (Mr 40-44 kDa). However, the PG from human articular cartilage contained dermatan sulphate (DS) chains (50% chondroitinase AC resistant), whereas chains from pig laryngeal PG were longer and contained only chondroitin sulphate (CS). Disaccharide analysis after chondroitinase ABC digestion showed that the human DS-PG contained more 6-sulphated residues (34%) than the pig CS-PG (6%) and both contained fewer 6-sulphated residues than the corresponding high Mr aggregating CS-PGs from these tissues (86% and 20% from human and pig respectively). Cross-reaction of both proteoglycans with antibodies to bovine bone and skin DS-PG-II and human fibroblasts DS-PG suggested that the isolated proteoglycans were the humans DS-PG-II and pigs CS-PG-II homologues of the cloned and sequenced bovine proteoglycan. Polyclonal antibodies raised against the pig CS-PG-II were shown to cross-react with human DS-PG-II. SDS/polyacrylamide-gel analysis and immunoblotting of pig and human cartilage extracts showed that some free core protein was present in the tissues in addition to the intact proteoglycan. The antibodies were used in a competitive radioimmunoassay to determine the content of this low Mr proteoglycan in human cartilage extracts. Analysis of samples from 5-80 year-old humans showed highest content (approximately 4 mg/g wet wt.) in those from 15-25 year-olds and lower content (approximately 1 mg/g wet wt.) in older tissue (greater than 55 years). These changes in content may be related to the deposition and maintenance of the collagen fibre network with which this class of small proteoglycan has been shown to interact.     

Conductivities of pig dermis and subcutaneous fat measured with rectangular pulse electrical current

We examined experimentally the relationship between perpendicular and tangential electrical conductivities, σ, and peak current density J, in pig skin dermis and subcutaneous fat specimens by using a four-electrode measuring system with rectangular pulse electrical current (RPEC). We also investigated the relationship of the conductivity, σ, vs. pulse rate, f. The rates were selected at 8, 32, 64, and 128 pulses per second (pps), and the pulse width was fixed at 140 μs. These values are often used in vivo to enhance cutaneous regeneration with RPEC stimulation. It was found that the conductivities may be approximated to be for the skin dermis and for the subcutaneous fat in the conditions of this experiment. These findings implies that the conductivities of pig skin dermis and subcutaneous fat are anisotropic, i.e., σ_x = σ_y ≠ σ_z. It was also found that the conductivities are independent of current density and pulse rate in the current range from 20 μA/cm² to 120 mA/cm². © 1996 Wiley-Liss, Inc.     

Training tissue bank operators: the International Atomic Energy Agency (IAEA)/National University of Singapore (NUS) 10 years of experience

National University of Singapore (NUS) was appointed by IAEA to become IAEA/NUS Regional Training Centre (RTC) for Asia and the Pacific region in September 1996. The Government of Singapore (represented by the Ministry of Environment) with the National Science and Technology Board as the funding agency awarded a grant of S$225,500 to build a new purpose-built tissue bank to be the Regional Training Centre. National University Hospital provided a space of 2,000 square feet for this purpose. The first Diploma Course was launched on 3 November 1997 with 17 candidates with the first NUS Diploma Examination being held in October 1998. Between November 1997 and April 2007, a total of nine courses were conducted by RTC with a total of 180 tissue bank operators, 133 from Asia and the Pacific region (13 countries including 2 from Iran), 14 from Africa (Algeria, Egypt, Libya, Egypt, South Africa and Zambia), 6 from Latin America (Brazil, Chile, Cuba, Peru and Uruguay), 9 from Europe (Greece, Slovakia, Poland, Ukraine) and 2 from Australia. The last batch (ninth batch) involved twenty students registered in April 2007 and will be due to sit for the terminal examination only in April 2008.     

Book reviews

Summary

Work fulfilling actions and research specified in the Biodiversity Action Plan for SaxÍfraga hirculus is described. Two recovery sites have been set up in suitable mires situated within 3 km of lost sites.

Seeds from two of the three remaining N. Scottish sites germinated readily, and plants were successfully propagated in a garden. Transplanting to the first recovery site began in 1996 and to the second in 2000. Transplants survived well and increased in size, with some flowering. Direct sowing of seeds to the recovery sites was less successful, with poor survival and very slow growth of seedlings. Competition from resident mire plants is thought to control the performance of the transplants, growth being most checked in hummocks of Sphagnum warnstorfii. Ideally transplants should have c. 100 cm² basal area.     

Transdermal delivery of zidovudine (AZT): The effects of vehicles,enhancers, and polymer membranes on permeation across cadaver pig skin

The purpose of this study was to investigate the effects of vehicles, enhancers, and polymer membranes on 3-azido-3-deoxythymidine (AZT) permeation across cadaver pig skin. Four binary vehicles (ethanol/water, isopropyl alcohol/water, polyethylene glycol 400/water, and ethanol/isopropyl myristate [IPM] were tested for AZT solubility and permeability across pig skin; ethanol/IPM (50/50, vol/vol) demonstrated the highest AZT flux (185.23 μ/cm²/h). Next, the addition of various concentrations of different enhancers (N-methyl-2-pyrrolidone [NMP], oleic acid, and lauric acid) to different volume ratios of ethanol/IPM was investigated for their effect on AZT solubility and permeability across pig skin. The use of 2 conbinations (ethanol/IPM [20/80] plus 10% NMP and ethanol/IPM [30/70] plus 10% NMP) resulted in increased AZT solubility (42.6 and 56.27 mg/mL, respectively) and also high AZT flux values (284.92 and 460.34 μg/cm²/h, respectively) without appreciable changes in lag times (6.25 and 7.49 hours, respectively) when compared with formulations using only ethanol/IPM at 20/80 and 30/70 volume ratios without addition of the enhancer NMP. Finally, AZT permeation across pig skin covered with a microporous polyethylene (PE) membrane was investigated. The addition of the PE membrane to the pig skin reduced AZT flux values to ∼50% of that seen with pig skin alone. However, the AZT flux value attained with ethanol/IPM (30/70) plus 10% NMP was 215.30 μg/cm²/h, which was greater than the target flux (208 μg/cm²/h) needed to maintain the steady-state plasma concentration in humans. The results obtained from this study will be helpful in the development of an AZT transdermal drug delivery system.