Carbon footprint assessment of recycling technologies for rare earth elements: A case study of recycling yttrium and europium from phosphor.

Rare earth elements are key raw materials in high-technology industries. Mining activities and manufacturing processes of such industries have caused considerable environmental impacts, such as soil erosion, vegetation destruction, and various forms of pollution. Sustaining the long-term supply of rare earth elements is difficult because of the global shortage of rare earth resources. The diminishing supply of rare earth elements has attracted considerable concern because many industrialized countries regarded such elements as important strategic resources for economic growth. This study aims to explore the carbon footprints of yttrium and europium recovery techniques from phosphor. Two extraction recovery methods, namely, acid extraction and solvent extraction, were selected for the analysis and comparison of carbon footprints. The two following functional units were used: (1) the same phosphor amounts for specific Y and Eu recovery concentrations, and (2) the same phosphor amounts for extraction. For acid extraction method, two acidic solutions (H2SO4 and HCl) were used at two different temperatures (60 and 90°C). For solvent extraction method, acid leaching was performed followed by ionic liquid extraction. Carbon footprints from acid and solvent extraction methods were estimated to be 10.1 and 10.6kgCO2eq, respectively. Comparison of the carbon emissions of the two extraction methods shows that the solvent extraction method has significantly higher extraction efficiency, even though acid extraction method has a lower carbon footprint. These results may be used to develop strategies for life cycle management of rare earth resources to realize sustainable usage.

3-D Imaging Reveals Participation of Donor Islet Schwann Cells and Pericytes in Islet Transplantation and Graft Neurovascular Regeneration.

The primary cells that participate in islet transplantation are the endocrine cells. However, in the islet microenvironment, the endocrine cells are closely associated with the neurovascular tissues consisting of the Schwann cells and pericytes, which form sheaths/barriers at the islet exterior and interior borders. The two cell types have shown their plasticity in islet injury, but their roles in transplantation remain unclear. In this research, we applied 3-dimensional neurovascular histology with cell tracing to reveal the participation of Schwann cells and pericytes in mouse islet transplantation. Longitudinal studies of the grafts under the kidney capsule identify that the donor Schwann cells and pericytes re-associate with the engrafted islets at the peri-graft and perivascular domains, respectively, indicating their adaptability in transplantation. Based on the morphological proximity and cellular reactivity, we propose that the new islet microenvironment should include the peri-graft Schwann cell sheath and perivascular pericytes as an integral part of the new tissue.

Effects of Dipeptidyl Peptidase-4 Inhibition with MK-0431 on Syngeneic Mouse Islet Transplantation.

Dipeptidyl peptidase (DPP)-4 inhibitors increase circulating levels of glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide which may promote ß-cell proliferation and survival. This study tested if DPP-4 inhibition with MK-0431 is beneficial for diabetic mice syngeneically transplanted with a marginal number of islets. We syngeneically transplanted 150 C57BL/6 mouse islets under the kidney capsule of each streptozotocin-diabetic mouse and then treated recipients with (n = 21) or without (n = 17) MK-0431 (30 mg/kg/day, po) for 6 weeks. After islet transplantation, blood glucose levels decreased in both MK-0431-treated and control groups. However, the blood glucose and area under the curve of the intraperitoneal glucose tolerance test at 2, 4, and 6 weeks were not significantly different between MK-0431-treated mice and controls. During 6 weeks, both groups exhibited increased body weights over time. However, the weight between two groups did not differ throughout the study period. At 6 weeks after transplantation, the graft beta-cell mass (0.024 ± 0.005 versus 0.023 ± 0.007 mg, P = 0.8793) and insulin content (140 ± 48 versus 231 ± 63 ng, P = 0.2939) were comparable in the MK-0431-treated group and controls. Our results indicate posttransplant DPP-4 inhibition with MK-0431 in the diabetic recipient with a marginal number of islets is not beneficial to transplantation outcome or islet grafts.

Prevention and Reversal of Diabetes by All-Trans Retinoid Acid and Exendin-4 in NOD Mice.

It has been shown that all-trans retinoid acid (ATRA) hinders the development of autoimmune diabetes by inducing immune tolerance status. Meanwhile, exendin-4 increases beta-cell function and mass. Thus, we hypothesized that ATRA and exendin-4 combination therapy would prevent and reverse autoimmune diabetes. NOD/scid mice were intravenously transferred with splenocytes isolated from 12-week-old female NOD mice. After adoptive transfer, mice were treated with vehicle, ATRA (0.5 mg/mouse intraperitoneally every other day), exendin-4 (3 µ g/kg subcutaneously twice daily), or combination for 6 weeks. Compared with vehicle, ATRA (P = 0.022) and ATRA plus exendin-4 (P = 0.013) treatment delayed the onset of diabetes. The pancreatic insulin content in mice treated with ATRA (P = 0.013) and exendin-4 (P < 0.02) was significantly higher than that of control mice. All but one spontaneous diabetic NOD mouse treated with ATRA and/or exendin-4 remained persistent hyperglycemic. ATRA and/or exendin-4 treatment did not alter their blood glucose levels and survival. Our results indicate that, before the onset of autoimmune diabetes, ATRA and exendin-4 treatment alone preserves pancreatic beta cells; ATRA and ATRA plus exendin-4 treatment delays the onset of autoimmune diabetes. However, after the onset of autoimmune diabetes, ATRA and/or exendin-4 treatment is unable to reverse hyperglycemia or improve survival.

Three-dimensional islet graft histology: panoramic imaging of neural plasticity in sympathetic reinnervation of transplanted islets under the kidney capsule.

Microscopic examination of transplanted islets in an ectopic environment provides information to evaluate islet engraftment, including revascularization and reinnervation. However, because of the dispersed nature of blood vessels and nerves, global visualization of the graft neurovascular network has been difficult. In this research we revealed the neurovascular network by preparing transparent mouse islet grafts under the kidney capsule with optical clearing to investigate the sympathetic reinnervation via three-dimensional confocal microscopy. Normoglycemic and streptozotocin-induced diabetic mice were used in syngeneic islet transplantation, with both groups maintaining euglycemia after transplantation. Triple staining of insulin/glucagon, blood vessels, and tyrosine hydroxylase (sympathetic marker) was used to reveal the graft microstructure, vasculature, and sympathetic innervation. Three weeks after transplantation, we observed perigraft sympathetic innervation similar to the peri-islet sympathetic innervation in the pancreas. Six weeks after transplantation, prominent intragraft, perivascular sympathetic innervation was achieved, resembling the pancreatic intraislet, perivascular sympathetic innervation in situ. Meanwhile, in diabetic recipients, a higher graft sympathetic nerve density was found compared with grafts in normoglycemic recipients, indicating the graft neural plasticity in response to the physiological difference of the recipients and the resolving power of this imaging approach. Overall, this new graft imaging method provides a useful tool to identify the islet neurovascular complex in an ectopic environment to study islet engraftment.

Magnetic resonance imaging of mouse islet grafts labeled with novel chitosan-coated superparamagnetic iron oxide nanoparticles.

OBJECT: To better understand the fate of islet isografts and allografts, we utilized a magnetic resonance (MR) imaging technique to monitor mouse islets labeled with a novel MR contrast agent, chitosan-coated superparamagnetic iron oxide (CSPIO) nanoparticles. MATERIALS AND METHODS: After being incubated with and without CSPIO (10 µg/ml), C57BL/6 mouse islets were examined under transmission electron microscope (TEM) and their insulin secretion was measured. Cytotoxicity was examined in α (αTC1) and ß (NIT-1 and ßTC) cell lines as well as islets. C57BL/6 mice were used as donors and inbred C57BL/6 and Balb/c mice were used as recipients of islet transplantation. Three hundred islets were transplanted under the left kidney capsule of each mouse and then MR was performed in the recipients periodically. At the end of study, the islet graft was removed for histology and TEM studies. RESULTS: After incubation of mouse islets with CSPIO (10 µg/mL), TEM showed CSPIO in endocytotic vesicles of α- and ß-cells at 8 h. Incubation with CSPIO did not affect insulin secretion from islets and death rates of αTC1, NIT-1 and ßTC cell lines as well as islets. After syngeneic and allogeneic transplantation, grafts of CSPIO-labeled islets were visualized on MR scans as persistent hypointense areas. At 8 weeks after syngeneic transplantation and 31 days after allogeneic transplantation, histology of CSPIO-labeled islet grafts showed colocalized insulin and iron staining in the same areas but the size of allografts decreased with time. TEM with elementary iron mapping demonstrated CSPIO distributed in the cytoplasm of islet cells, which maintained intact ultrastructure. CONCLUSION: Our results indicate that after syngeneic and allogeneic transplantation, islets labeled with CSPIO nanoparticles can be effectively and safely imaged by MR.

An interactive method for achieving ergonomically optimum conditions during laparoscopic surgery.

Laparoscopy is widely used during living kidney donation, nephrectomy, bariatric surgery, and surgery for gastrointestinal tumors and colorectal cancer. However, laparoscopic surgery requires prolonged use of instruments and has low mechanical efficiency. In addition, to meet specific surgical demands while visualizing the surgical area on the screen, surgical personnel frequently violate the postures proposed by human factor engineering; this naturally results in a physical burden on the personnel. In this study, using laparoscopic nephrectomy as an example, an auxiliary hoisting device for surgery was designed, and pedals from a variety of equipment were integrated into the auxiliary plant. Both entity testing conducted in the hospital and 3D surgical simulation of the auxiliary plant showed that this device could improve compliance with human factor engineering recommendations during laparoscopic surgery and could also promote interaction and tacit understanding between surgical personnel, thereby providing ergonomically optimum conditions during laparoscopy.

Tailored nanoparticles for tumour therapy.

Gd doped iron-oxide nanoparticles were developed for use in tumour therapy via magnetic fluid hyperthermia (MFH). The effect of the Gd3+ dopant on the particle size and magnetic properties was investigated. The final particle composition varied from Gd0.01Fe2.99O4 to Gd0.04Fe2.96O4 as determined by Inductively coupled plasma atomic emission spectroscopy (ICP-AES). TEM image analysis showed the average magnetic core diameters to be 12 nm and 33 nm for the lowest and highest Gd levels respectively. The specific power adsorption rate (SAR) determined with a field strength of 246 Oe and 52 kHz had a maximum of 38Wg(-1) [Fe] for the Gd0.03Fe2.97O4 sample. This value is about 4 times higher than the reported SAR values for Fe3O4. The potential for in vivo tumour therapy was investigated using a mouse model. The mouse models treated with Gd0.02Fe2.98O4 displayed much slower tumour growth after the first treatment cycle, the tumour had increased its mass by 25% after 7 days post treatment compared to a 79% mass increase over the same period for those models treated with standard iron-oxide or saline solution. After a second treatment cycle the mouse treated with Gd0.02Fe2.98O4 showed complete tumour regression with no tumour found for at least 5 days post treatment.

A multi-band fast-locking delay-locked loop with jitter-bounded feature.

In this paper, a fast-locking delay-locked loop (DLL) with jitter-bounded feature is presented. In the proposed fast-locking mechanism, a frequency estimator and a programmable voltage circuit are developed to rapidly switch the control node of voltage-controlled delay line to a voltage level near the final required value. After that, the DLL output will be quickly locked by the following charge pumping on the loop filter. In the jitter-bounded approach, two phase-frequency detectors and a tunable delay are employed to hold the output clock jitter between two reference inputs after the DLL is locked. Furthermore, to enhance the flexibility of the presented DLL, a frequency multiplier with fewer active devices is also developed to provide high-frequency clock output for wideband applications. The presented DLL is implemented in a 0.18-µm 1P6M CMOS technology. The active area without contact pads is 0.34 × 0.41 mm(2). A minimum lock time of six clock cycles is measured from no reference input to locked state. The output frequency ranges of the DLL and the frequency multiplier can be measured from 200 to 400 MHz and from 1 to 2 GHz, respectively. The power dissipation of the presented DLL is 31.5 mW at a 1.8 V supply voltage.

Gene knockdown of the N-methyl-D-aspartate receptor NR1 subunit with subcutaneous small interfering RNA reduces inflammation-induced nociception in rats.

BACKGROUND: Spinal N-methyl-D-aspartate receptors have been demonstrated to play an important role in the facilitation and maintenance of nociception. To avoid adverse effects of blocking N-methyl-D-aspartate receptors in the central nervous system, blocking N-methyl-D-aspartate receptor in peripheral nervous system is an ideal alternative. Transfection of small interfering RNAs (siRNAs) into cells has been revealed to provide potent silencing of specific genes. In this study, the authors examined the effect of subcutaneous injection of siRNA targeting the NR1 subunit of the N-methyl-D-aspartate receptor on silencing NR1 gene expression and subsequently abolishing inflammatory nociception in rats. METHODS: Male Sprague-Dawley rats received intradermal injection of NR1 siRNA and underwent injection of formalin or complete Freund's adjuvant. The flinch response and mechanical hypersensitivity by von Frey filaments were assessed. Then the messenger RNA and protein of NR1 in skin and dorsal root ganglion were analyzed. RESULTS: The results revealed that subcutaneous injection of 1 nmol NR1 siRNA effectively diminished the nociception induced by formalin and complete Freund's adjuvant stimuli and attenuated the level of NR1 messenger RNA and protein in skin and ipsilateral dorsal root ganglion. The antinociception effect and the inhibition of NR1 expression persisted for about 7 days after administration of NR1 siRNA. CONCLUSIONS: The data of this study suggest that NR1 siRNA has potential therapeutic value in the treatment of inflammatory pain induced or maintained by peripheral nociceptor activity and support the potential application of this method to the study of nociceptive processes and target the validation of pain-associated genes.

Exendin-4 treatment expands graft beta-cell mass in diabetic mice transplanted with a marginal number of fresh islets.

Exendin-4 stimulates insulin secretion, suppresses glucagons secretion, increases beta-cell replication and neogenesis, and reduces beta-cell apoptosis. However, it has been shown that posttransplant exendin-4 treatment did not improve glucose homeostasis in diabetic mice transplanted with a large number of freshly isolated islets. The aim of this study was to test if exendin-4 is beneficial for hyperglycemic recipients with a marginal number of fresh islets. We transplanted 150 C57BL/6 mouse islets under the kidney capsule of inbred streptozotocin-diabetic mice, and then treated the recipients with and without exendin-4 for 6 weeks. Before and after transplantation, recipients' blood glucose, body weight, and intraperitoneal glucose tolerance test were measured. At 6 weeks, the grafts were removed to determine beta-cell mass. Blood glucose levels in both groups decreased progressively after transplantation, and the exendin-4-treated group had had lower blood glucose than controls since day 3. By 6 weeks, euglycemia was achieved more in mice treated with exendin-4 than in controls (100% vs. 62.5%, p = 0.018). The time to obtain normoglycemia was shorter in the exendin-4-treated group than in controls (12 +/- 8 vs. 29 +/- 13 days, p < 0.001). Blood glucose at 6 weeks was 123 +/- 18 and 170 +/- 62 mg/dl in the exendin-4-treated group and controls, respectively (p = 0.008). Additionally, the exendin-4-treated group had better glucose tolerance than controls at 2 and 4 weeks (p <0.02). However, both groups exhibited increased body weight over time, and weight changes did not significantly differ between the two groups throughout the study period. At 6 weeks after transplantation, grafts in the exendin-4-treated group were more prominent and contained more insulin-stained cells than those of controls. They had 2.3-fold beta-cell mass of the graft compared with controls (0.30 +/- 0.11 vs. 0.13 +/- 0.03 mg, p = 0.012). These results indicate posttransplant exendin-4 treatment in the diabetic recipient with a marginal number of fresh islets expands graft beta-cell mass and improves transplantation outcome.

Applications of flexible bronchoscopy in infants with congenital vocal cord paralysis: a 12-year experience.

BACKGROUND: Congenital vocal cord paralysis (VCP) is a common cause of congenital stridor. Before the widespread application of flexible bronchoscopy (FB) by pediatricians, congenital stridor in infants was usually attributed to laryngomalacia. Prompt recognition and careful follow-up is crucial for the management of congenital VCP. METHODS: We performed a retrospective chart review of newborn infants with congenital VCP diagnosed by FB over a 12-year period. RESULTS: During the 12-year period, FB was performed on a total of 356 infants. Fifteen (4%) infants were diagnosed with congenital VCP. There were eight males and seven females and the mean age at diagnosis was 76.6 days. Stridor with respiratory distress was the most prominent presenting symptom. The majority (93%, 14/15) demonstrated bilateral VCP, while one patient (7%) had unilateral VCP. Seven of the 15 (46%) patients had idiopathic VCP, while eight (54%) had VCP associated with neuromuscular disorders. Tracheotomy was necessary in four patients (26%). None of them underwent further surgical interventions. Spontaneous recovery occurred in 10 patients (71%), and of these, 90% (9/10) were treated without tracheotomy. CONCLUSION: In order to allow prompt diagnosis of congenital VCP, FB should be performed in every newborn infant with stridor. Patients with congenital VCP should undergo additional imaging studies to detect any associated neurological abnormalities and intrathoracic comorbidities. The majority of patients can be managed conservatively and monitored carefully using serial FB. Corrective surgery should be reserved for those with a lack of resolution at prolonged follow-up, and those with significant comorbidities.

Preincisional subcutaneous infiltration of ketamine suppresses postoperative pain after circumcision surgery.

OBJECTIVE: N-methyl-D-aspartate and other glutamate receptors have been shown to present on the peripheral axons of primary afferents, and peripheral injection of N-methyl-D-aspartate-receptor antagonists can suppress hyperalgesia and allodynia. Thus, this study examined postoperative analgesic and adverse effects of local ketamine administered postoperatively. METHODS: Ketamine (0.3%, 3 mL) or saline was subcutaneously infiltrated before incision in a double-blind manner using a sample population of 40 patients undergoing circumcision surgery, equally and randomly assigned to 2 groups based on the treatment. The saline-infiltrated patients also received 9-mg intramuscular ketamine into the upper arm to control for any related systemic analgesic effects. The patients were followed up for 24 hours to determine postoperative analgesia and identify adverse effects. RESULTS: In the ketamine-infiltrated patients, the time interval until first analgesic demand (166 vs. 80 min) was longer and the incidence of pain-free status (pain score=0) during movement (45% vs. 10%) and erection (40% vs. 0%) was significantly higher than for the saline-treated analogs (P<0.05). The dose of ketorolac use and pain score during erection were significant lower in group ketamine patients. No significant differences were noted with respect to the incidence of adverse effects comparing the 2 groups. DISCUSSION: We conclude that preincisional subcutaneous ketamine infiltration can suppress postoperative pain after the circumcision surgery.

Cardiac arrest during spinal anesthesia: a report of two cases.

Spinal anesthesia is a widely practiced technique for both elective and emergency procedures. It is so recommended because of its efficacy and safety. Cardiac arrest during spinal anesthesia is considered as a "very rare", "unusual", and "unexpected" event. We report here two instances of cardiac arrest during spinal anesthesia in young healthy people. Discussions on the causes, management, and prevention of cardiac arrest following spinal anesthesia are also brought forward in the text.

Acute airway obstruction associated with granulation tissue of tracheostoma--a case report.

We report an 85-year-old tracheostomized male patient who underwent ventriculoperitoneal shunt because of hydrocephalus. Postoperative acute airway obstruction and tension pneumothorax developed due to the granulation tissue of tracheostoma which scraped off from the tracheostoma in the act of endotracheal intubation for operation and it lay dormant around until it was drawn into the endotracheal tube (ETT) by negative pressure during suction of trachea in intensive care unit. Persistent hypoxemia in consequence of airway obstruction resulted in cardiac arrest and expiratory seal of trachea eventuated in tension pneumothorax. Flexible fiberoptic bronchoscopy performed during resuscitation disclosed that the obstruction was due to granulation tissue which blocked the ETT lumen. Immediate exchange of endotracheal tube and placement of chest tube made the patient tide over this crisis. No sequela resulted from this crisis and the patient was discharged one week later.

Transgenic expression of decoy receptor 3 protects islets from spontaneous and chemical-induced autoimmune destruction in nonobese diabetic mice.

Decoy receptor 3 (DCR3) halts both Fas ligand- and LIGHT-induced cell deaths, which are required for pancreatic beta cell damage in autoimmune diabetes. To directly investigate the therapeutic potential of DCR3 in preventing this disease, we generated transgenic nonobese diabetic mice, which overexpressed DCR3 in beta cells. Transgenic DCR3 protected mice from autoimmune and cyclophosphamide-induced diabetes in a dose-dependent manner and significantly reduced the severity of insulitis. Local expression of the transgene did not alter the diabetogenic properties of systemic lymphocytes or the development of T helper 1 or T regulatory cells. The transgenic islets had a higher transplantation success rate and survived for longer than wild-type islets. We have demonstrated for the first time that the immune-evasion function of DCR3 inhibits autoimmunity and that genetic manipulation of grafts may improve the success and survival of islet transplants.

Canine islet isolation, cryopreservation, and transplantation to nude mice.

BACKGROUND: Successful human islet transplantation has led to insulin independence in type 1 diabetes. Dogs constitute an animal model for preclinical studies. We present our recent experience in canine islet isolation, cryopreservation and transplantation. METHODS: Twenty-seven pancreases from mongrel dogs, weighing 9-31 kg, were removed. Each pancreas was digested with collagenase, and then purified by density gradients. Islet number and purity were counted, and the viability of isolated islets was assessed in vitro by static incubation, perifusion study and in vivo transplantation into nondiabetic or diabetic nude mice. Additionally. freshly isolated islets were cryopreserved for 1 week, and then studied in vitro. RESULTS: The islet yield and purity were 121,000 +/- 135,000 IEQ per pancreas and 81.4 +/- 1.2%, respectively. The stimulation index (insulin release in 300 mg/dl glucose/insulin release in 100 mg/dl glucose) of the isolated islets was 6.6 +/- 1.9 (N = 7), and first and second phases of insulin secretion were demonstrated during perifusion study. After 1-week cryopreservation, the islet number decreased from 1,000 to 540 (N = 1) and insulin content decreased from 50.95 to 39.23 microg/150 islets (N = 1). These islets maintained their insulin response to high glucose. Four weeks after transplantation, the grafts showed abundant beta-cells and significant insulin content. Normoglycemia was achieved in 14 of 23 diabetic recipients after transplantation with 2,000 freshly isolated islets. CONCLUSION: Canine islets isolated at our laboratory were viable and maintained their physiological function both in vitro and in vivo.

Beneficial effects of hyperbaric oxygen therapy on islet transplantation.

We envisage that hyperbaric oxygen (HBO) would ameliorate islet anoxia, preventing early graft failure. Thus, treatment of HBO to diabetic recipients should improve the outcome of islet transplantation. We tested this hypothesis by syngeneically transplanting insufficient number of islets (150 islets) into streptozotocin-diabetic C57BL/6 mice, each followed by HBO (2.4 ATA, 100% O2) therapy for 1.5 h from day 0 to 28, once daily (group A) or twice daily (group B), or from day 5 to 28, once daily (group C) or twice daily (group D), 6 days/week. Recipients without HBO treatment served as controls. At day 28 after transplantation, groups B, C, and D gained weight and had lower blood glucose compared with their baseline values. In addition, groups B and D had higher insulin content of the graft than the controls. To determine the optimal timing of HBO therapy, groups B and D were compared with recipients treated with HBO twice daily, 6 days/week, from day -14 to 0 (group E) and from day -14 to 28 (group F). At day 28 after transplantation, groups B, D, E, and F had significantly lower blood glucose than their individual baseline values and higher insulin content of the graft than controls. But only group F had more beta-cell mass of the graft than controls. These findings lend credence to the expectation that peritransplant application of adequate frequency of HBO to diabetic recipients would enhance the performance and growth of the islet graft, resulting in an improvement of the outcome of the transplantation.

Beneficial Effects of Hyperbaric Oxygen Therapy on Islet Transplantation.

We envisage that hyperbaric oxygen (HBO) would ameliorate islet anoxia, preventing early graft failure. Thus, treatment of HBO to diabetic recipients should improve the outcome of islet transplantation. We tested this hypothesis by syngeneically transplanting insufficient number of islets (150 islets) into streptozotocin-diabetic C57BL/6 mice, each followed by HBO (2.4 ATA, 100% O2) therapy for 1.5 h from day 0 to 28, once daily (group A) or twice daily (group B), or from day 5 to 28, once daily (group C) or twice daily (group D), 6 days/week. Recipients without HBO treatment served as controls. At day 28 after transplantation, groups B, C, and D gained weight and had lower blood glucose compared with their baseline values. In addition, groups B and D had higher insulin content of the graft than the controls. To determine the optimal timing of HBO therapy, groups B and D were compared with recipients treated with HBO twice daily, 6 days/week, from day -14 to 0 (group E) and from day -14 to 28 (group F). At day 28 after transplantation, groups B, D, E, and F had significantly lower blood glucose than their individual baseline values and higher insulin content of the graft than controls. But only group F had more ß-cell mass of the graft than controls. These findings lend credence to the expectation that peritransplant application of adequate frequency of HBO to diabetic recipients would enhance the performance and growth of the islet graft, resulting in an improvement of the outcome of the transplantation.

Influence of Donor Age on Mouse Islet Characteristics and Transplantation.

Old donor age has been considered as a risk factor and relative contraindication for transplantation. This study was designed to investigate the influence of donor age on islet characteristics and transplantation. Islets isolated from 8 (I-A)-, 32 (I-B)-, or 64 (I-C)-week-old C57BL/6 mice were studied for number, size, insulin content, and secretion. After syngeneically transplanting 300 islets under the kidney capsule of strep-tozotocin-diabetic mice (R-A, R-B, and R-C, respectively), we measured recipients' metabolic parameters as well as the ß-cell mass and insulin content of the graft. Eight-week-old donors had better glucose tolerance than 32- and 64-week-old donors. However, 64-week-old donors had more pancreatic insulin content than 8- and 32-week-old donors. I-B and I-C were greater in number, larger in size, and higher in insulin content than I-A. But perifusion study showed I-C secreted less insulin, albeit with a similar stimulation index compared with that of I-A and I-B. After transplantation, the fall of blood glucose in R-C was faster than that in R-A and R-B. At 12 weeks, the recipients' blood glucose, body weight, HbA1c, and the ß-cell mass and insulin content of the graft were comparable in all groups. However, R-C had better glucose tolerance than R-A. During follow-up, R-A and R-B maintained lifelong normoglycemia and their glucose tolerance did not deteriorate. These data indicate that islets isolated from donors with different ages have different characteristics and effects on transplantation. The islets isolated from aged donors are functioning well and can be a potential source for transplantation; however, because we transplanted a large islet mass from the aged donors, the role of the islet dose needs to be further clarified.