The Effect of MHC Antigen Matching Between Donors and Recipients on Skin Tolerance of Vascularized Composite Allografts

The emergence of skin-containing vascularized composite allografts (VCAs) has provided impetus to understand factors affecting rejection and tolerance of skin. VCA tolerance can be established in miniature swine across haploidentical MHC barriers using mixed chimerism. Because the deceased donor pool for VCAs does not permit MHC antigen matching, clinical VCAs are transplanted across varying MHC disparities. We investigated whether sharing of MHC class I or II antigens between donors and recipients influences VCA skin tolerance. Miniature swine were conditioned nonmyeloablatively and received hematopoietic stem cell transplants and VCAs across MHC class I (n = 3) or class II (n = 3) barriers. In vitro immune responsiveness was assessed, and VCA skin-resident leukocytes were characterized by flow cytometry. Stable mixed chimerism was established in all animals. MHC class II-mismatched chimeras were tolerant of VCAs. MHC class I-mismatched animals, however, rejected VCA skin, characterized by infiltration of recipient-type CD8⁺ lymphocytes. Systemic donor-specific nonresponsiveness was maintained, including after VCA rejection. This study shows that MHC antigen matching influences VCA skin rejection and suggests that local regulation of immune tolerance is critical in long-term acceptance of all VCA components. These results help elucidate novel mechanisms underlying skin tolerance and identify clinically relevant VCA tolerance strategies.

Skin grafts from genetically modified α-1,3-galactosyltransferase knockout miniature swine: A functional equivalent to allografts

Burn is associated with a considerable burden of morbidity worldwide. Early excision of burned tissue and skin grafting of the resultant wound has been established as a mainstay of modern burn therapy. However, in large burns, donor sites for autologous skin may be limited. Numerous alternatives, from cadaver skin to synthetic substitutes have been described, each with varying benefits and limitations. We previously proposed the use of genetically modified (alpha-1,3-galactosyl transferase knockout, GalT-KO) porcine skin as a viable skin alternative. In contrast to wild type porcine skin, which has been used as a biologic dressing following glutaraldehyde fixation, GalT-KO porcine skin is a viable graft, which is not susceptible to loss by hyperacute rejection, and undergoes graft take and healing, prior to eventual rejection, comparable to cadaver allogeneic skin. In the current study we aimed to perform a detailed functional analysis of GalT-KO skin grafts in comparison to allogeneic grafts for temporary closure of full thickness wounds using our baboon dorsum wound model. Grafts were assessed by measurement of fluid loss, wound infection rate, and take, and healed appearance, of secondary autologous grafts following xenograft rejection. Comparison was also made between fresh and cryopreserved grafts. No statistically significant difference was identified between GalT-KO and allogeneic skin grafts in any of the assessed parameters, and graft take and function was not adversely effected by the freeze-thaw process. These data demonstrate that GalT-KO porcine grafts are functionally comparable to allogeneic skin grafts for temporary closure of full thickness wounds, and support their consideration as an alternative to cadaver allogeneic skin in the emergency management of large burns.

Bestrophin-3 is differently expressed in normal and injured mouse glomerular podocytes

AIM

Bestrophins are putative calcium-activated chloride channels. Recently, cell-protective functions for Bestrophin-3 (Best3) were proposed. Best3 exists in different splice variants. We have here examined expression, alternative splicing and localization of Best3 in mouse podocytes under normal conditions and during endoplasmic reticulum (ER) stress.

METHODS

Best3 expression was determined on the mRNA level using quantitative PCR and on the protein level by immunohistochemistry and Western blotting.

RESULTS

Staining for Best3 was pronounced in glomeruli and was detected in cultured mouse podocytes. Best3 did not co-localize with markers for endothelial cells (CD31), podocyte foot processes (synaptopodin) or microtubules (actin). However, immunogold-based electron microscopy and co-localization with nestin showed Best3 presence in podocyte primary processes and cell bodies. Only two splice variants of Best3 mRNA (both lacking exons 2 and 3, and one also lacking exon 6), but no full-length variant, were detected. ER stress induced by lipopolysaccharides in vivo transiently elevated mRNA levels of total Best3 and its two splice variants with different time courses. In cultured podocytes under ER stress induced by thapsigargin, the expression of total Best3, its splice variants and nestin transiently increased with similar time courses. The ER stress marker C/EBP homologous protein (CHOP) and nestin mRNA increased during ER stress in vivo and in vitro.

CONCLUSIONS

Best3 is localized intracellularly in cell bodies and primary processes of mouse podocytes and is co-localized with nestin. Two splice variants of Best3 are expressed in glomeruli and in cultured podocytes, and their expression is differentially regulated in ER stress.

Transgenic expression of human CD47 markedly increases engraftment in a murine model of pig-to-human hematopoietic cell transplantation

Mixed chimerism approaches for induction of tolerance of solid organ transplants have been applied successfully in animal models and in the clinic. However, in xenogeneic models (pig-to-primate), host macrophages participate in the rapid clearance of porcine hematopoietic progenitor cells, hindering the ability to achieve mixed chimerism. CD47 is a cell-surface molecule that interacts in a species-specific manner with SIRPα receptors on macrophages to inhibit phagocytosis and expression of human CD47 (hCD47) on porcine cells has been shown to inhibit phagocytosis by primate macrophages. We report here the generation of hCD47 transgenic GalT-KO miniature swine that express hCD47 in all blood cell lineages. The effect of hCD47 expression on xenogeneic hematopoietic engraftment was tested in an in vivo mouse model of human hematopoietic cell engraftment. High-level porcine chimerism was observed in the bone marrow of hCD47 progenitor cell recipients and smaller but readily measurable chimerism levels were observed in the peripheral blood of these recipients. In contrast, transplantation of WT progenitor cells resulted in little or no bone marrow engraftment and no detectable peripheral chimerism. These results demonstrate a substantial protective effect of hCD47 expression on engraftment and persistence of porcine cells in this model, presumably by modulation of macrophage phagocytosis.

Genetically modified porcine split-thickness skin grafts as an alternative to allograft for provision of temporary wound coverage: preliminary characterization

Temporary coverage of severely burned patients with cadaver allograft skin represents an important component of burn care, but is limited by availability and cost. Porcine skin shares many physical properties with human skin, but is susceptible to hyperacute rejection due to preformed antibodies to α-1,3-galactose (Gal), a carbohydrate on all porcine cells. Our preliminary studies have suggested that skin grafts from α-1,3-galactosyltransferase knock out (GalT-KO) miniature swine might provide temporary wound coverage comparable to allografts, since GalT-KO swine lack this carbohydrate. To further evaluate this possibility, eight non-human primates received primary autologous, allogeneic, GalT-KO, and GalT+xenogeneic skin grafts. Additionally, secondary grafts were placed to assess whether sensitization would affect the rejection time course of identical-type grafts. We demonstrate that both GalT-KO xenografts and allografts provide temporary coverage of partial- and full-thickness wounds for up to 11 days. In contrast, GalT+xenografts displayed hyperacute rejection, with no signs of vascularization and rapid avulsion from wounds. Furthermore, secondary GalT-KO transplants failed to vascularize, demonstrating that primary graft rejection sensitizes the recipient. We conclude that GalT-KO xenografts may provide temporary coverage of wounds for a duration equivalent to allografts, and thus, could serve as a readily available alternative treatment of severe burns.

Vascularized composite allograft tolerance across MHC barriers in a large animal model

Vascularized composite allograft (VCA) transplantation can restore form and function following severe craniofacial injuries, extremity amputations or massive tissue loss. The induction of transplant tolerance would eliminate the need for long-term immunosuppression, realigning the risk-benefit ratio for these life-enhancing procedures. Skin, a critical component of VCA, has consistently presented the most stringent challenge to transplant tolerance. Here, we demonstrate, in a clinically relevant miniature swine model, induction of immunologic tolerance of VCAs across MHC barriers by induction of stable hematopoietic mixed chimerism. Recipient conditioning consisted of T cell depletion with CD3-immunotoxin, and 100 cGy total body irradiation prior to hematopoietic cell transplantation (HCT) and a 45-day course of cyclosporine A. VCA transplantation was performed either simultaneously to induction of mixed chimerism or into established mixed chimeras 85-150 days later. Following withdrawal of immunosuppression both VCAs transplanted into stable chimeras (n=4), and those transplanted at the time of HCT (n=2) accepted all components, including skin, without evidence of rejection to the experimental end point 115-504 days posttransplant. These data demonstrate that tolerance across MHC mismatches can be induced in a clinically relevant VCA model, providing proof of concept for long-term immunosuppression-free survival.

Decreased survival of newborn neurons in the dorsal hippocampus after neonatal LPS exposure in mice

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Neonatal inflammation reduces the survival of dividing neurons and astrocytes.

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Neonatal inflammation does not affect the survival of post-mitotic cells.

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Decrease in cell survival was specific for the granule cells of the dorsal blade of the hippocampus.

Experimental studies show that inflammation reduces the regenerative capacity in the adult brain. Less is known about how early postnatal inflammation affects neurogenesis, stem cell proliferation, cell survival and learning and memory in young adulthood. In this study we examined if an early-life inflammatory challenge alters cell proliferation and survival in distinct anatomical regions of the hippocampus and whether learning and memory were affected. Lipopolysaccharide (LPS, 1 mg/kg) was administered to mice on postnatal day (P) 9 and proliferation and survival of hippocampal cells born either prior to (24 h before LPS), or during the inflammatory insult (48 h after LPS) was evaluated. Long-term cell survival of neurons and astrocytes was determined on P 41 and P 60 in the dorsal and ventral horns of the hippocampus. On day 50 the mice were tested in the trace fear conditioning (TFC) paradigm. There was no effect on the survival of neurons and astrocytes that were born before LPS injection. In contrast, the number of neurons and astrocytes that were born after LPS injection were reduced on P 41. The LPS-induced reduction in cell numbers was specific for the dorsal hippocampus. Neither early (48 h after LPS) or late (33 days after LPS) proliferation of cells was affected by neonatal inflammation and neonatal LPS did not alter the behavior of young adult mice in the TFC test. These data highlight that neonatal inflammation specifically affects survival of dividing neurons and astrocytes, but not post-mitotic cells. The reduction in cell survival could be attributed to less cell survival in the dorsal hippocampus, but had no effect on learning and memory in the young adult.

Toll-like receptor 3 expression in glia and neurons alters in response to white matter injury in preterm infants

Toll-like receptors (TLRs) are members of the pattern recognition receptor family that detect components of foreign pathogens or endogenous molecules released in response to injury. Recent studies demonstrate that TLRs also have a functional role in regulating neuronal proliferation in the developing brain. This study investigated cellular expression of TLR3 using immunohistochemistry on human brain tissue. The tissue sections analysed contained anterior and lateral periventricular white matter from the frontal and parietal lobes in post-mortem neonatal cases with a postmenstrual age range of 23.6-31.4 weeks. In addition to preterm brains without overt pathology (control), preterm pathology cases with evidence of white matter injuries (WMI) were also examined. In order to identify TLR-positive cells, we utilized standard double-labelling immunofluorescence co-labelling techniques and confocal microscopy to compare co-expression of TLR3 with a neuronal marker (NeuN) or with glial markers (GFAP for astrocytes, Iba-1 for microglia and Olig2 for oligodendrocytes). We observed an increase in the neuronal (28 vs. 17%) and astroglial (38 vs. 21%) populations in the WMI group compared to controls in the anterior regions of the periventricular white matter in the frontal lobe. The increase in neurons and astrocytes in the WMI cases was associated with an increase in TLR3 immunoreactivity. This expression was significantly increased in the astroglia. The morphology of the TLR3 signal in the control cases was globular and restricted to the perinuclear region of the neurons and astrocytes, whilst in the cases of WMI, both neuronal, axonal and astroglial TLR3 expression was more diffuse (i.e., a different intracellular distribution) and could be detected along the extensions of the processes. This study demonstrates for the first time that neurons and glial cells in human neonatal periventricular white matter express TLR3 during development. The patterns of TLR3 expression were altered in the presence of WMI, which might influence normal developmental processes within the immature brain. Identifying changes in TLR3 expression during fetal development may be key to understanding the reduced volumes of grey matter and impaired cortical development seen in preterm infants.

The gracilis myocutaneous free flap in swine: an advantageous preclinical model for vascularized composite allograft transplantation research

Vascularized composite allotransplantation (VCA) has become a clinical reality, prompting research aimed at improving the risk-benefit ratio of such transplants. Here, we report our experience with a gracilis myocutaneous free flap in Massachusetts General Hospital miniature swine as a preclinical VCA model. Fourteen animals underwent free transfer of a gracilis myocutaneous flap comprised of the gracilis muscle and overlying skin, each tissue supplied by independent branches of the femoral vessels. End-to-end anastomoses were performed to the common carotid artery and internal jugular vein, or to the femoral vessels of the recipients. Thirteen of fourteen flaps were successful. A single flap was lost due to compromise of venous outflow. This model allows transplantation of a substantial volume of skin, subcutaneous tissue, and muscle. The anatomy is reliable and easily identified and harvest incurs minimal donor morbidity. We find this gracilis myocutaneous flap an excellent pre-clinical model for the study of vascularized composite allotransplantation.

Expression and Subcellular Localization of TLR-4 in Term and First Trimester Human Placenta

Toll-like receptor 4 (TLR-4) mediates Gram-negative bacterial-induced inflammatory responses, including production of pro-inflammatory cytokines. Maternal infection and inflammation play an important role in preterm birth and neonatal brain damage. The localization of placental TLR-4 as well as changes during normal gestation are critical issues in understanding the role of toll-like receptors in defending the placento-fetal unit from maternal infection. We therefore investigated, by immunohistochemistry (IHC) and Western blot, the subcellular localization of TLR-4 in first trimester and term human placenta. In both term placenta (n=4) and first trimester placenta villous samples (n=5), immunoreactivity for TLR-4 was found in the cytoplasm of the syncytiotrophoblast, with darker staining in some areas of the maternal facing plasma membrane (MVM). In addition, TLR-4 was found to be expressed in the first trimester cytotrophoblast cells. Using Western blot analysis, TLR-4 was identified in both placental homogenates and isolated MVM and the fetal facing basal membrane (BM). TLR-4 expression in MVM was significantly higher in term (n=9) as compared to first trimester (n=2) samples. We have shown for the first time that the subcellular localization of TLR-4 in term placenta is preferentially in the MVM compared to BM. The MVM is continuously bathed in maternal blood, suggesting that from this vantage point TLR-4 can initiate a rapid response to maternal bacterial infection.

Expression of the p75 neurotrophin receptor by striatal cholinergic neurons following global ischemia in rats is associated with neuronal degeneration

The induction of the p75 neurotrophin receptor (p75NTR) on striatal cholinergic neurons by global hypoxic-ischemia has been reported to promote neuron survival. We have found, however, while the p75NTR-expressing neurons survive the insult for the first 5 days, subsequently they undergo shrinkage, loss of choline acetyl transferase (ChAT) expression, and more than 96% are eventually lost by 8 days. In contrast ChAT-expressing cells in the surrounding region of the infarction, do not express p75NTR and there is no evidence of neuronal loss. These results suggest the expression of p75NTR on cholinergic interneurons of the rat striatum is associated with delayed neuronal degeneration.

Synergistic activation of caspase-3 by m-calpain after neonatal hypoxia-ischemia: a mechanism of "pathological apoptosis"?

The relative contributions of apoptosis and necrosis in brain injury have been a matter of much debate. Caspase-3 has been identified as a key protease in the execution of apoptosis, whereas calpains have mainly been implicated in excitotoxic neuronal injury. In a model of unilateral hypoxia-ischemia in 7-day-old rats, caspase-3-like activity increased 16-fold 24 h postinsult, coinciding with cleavage of the caspase-3 proenzyme and endogenous caspase-3 substrates. This activation was significantly decreased by pharmacological calpain inhibition, using CX295, a calpain inhibitor that did not inhibit purified caspase-3 in vitro. Activation of caspase-3 by m-calpain, but not mu-calpain, was facilitated in a dose-dependent manner in vitro by incubating cytosolic fractions, containing caspase-3 proform, with calpains. This facilitation required the presence of some active caspase-3 and could be abolished by including the specific calpain inhibitor calpastatin. This indicates that initial cleavage of caspase-3 by m-calpain, producing a 29-kDa fragment, facilitates the subsequent cleavage into active forms. This is the first report to our knowledge suggesting a direct link between the early, excitotoxic, calcium-mediated activation of calpain after cerebral hypoxia-ischemia and the subsequent activation of caspase-3, thus representing a tentative pathway of "pathological apoptosis."

Bacterial endotoxin sensitizes the immature brain to hypoxic--ischaemic injury

Epidemiological studies show a markedly increased risk of cerebral palsy following the combined exposure of infection and birth asphyxia. However, the underlying mechanisms of this increased vulnerability remain unclear. We have examined the effects of a low dose of bacterial endotoxin on hypoxic--ischaemic injury in the immature brain of rats. Bacterial endotoxin (lipopolysaccharide 0.3 mg/kg) was administered to 7-day-old rats 4 h prior to unilateral hypoxia--ischaemia and the neurological outcome was determined 3 days later. Rectal temperature and cerebral blood flow was measured during the study and the expression of CD14 and toll-like receptor-4 mRNA in the brain was examined. We found that a low dose of endotoxin dramatically sensitizes the immature brain to injury and induces cerebral infarction in response to short periods of hypoxia--ischaemia that by themselves caused no or little injury. This effect could not be explained by a reduction in cerebral blood flow or hyperthermia. In association with the sensitization of injury we found an altered expression of CD14 mRNA and toll-like receptor-4 mRNA in the brain. These results suggest that the innate immune system may be involved in the vulnerability of the immature brain following the combination of infection and hypoxia--ischaemia.

Reduced number of neurons in the hippocampus and the cerebellum in the postnatal guinea-pig following intrauterine growth-restriction

Intrauterine growth restriction is a risk factor for neurological and behavioural deficits in children although the precise underlying biological correlate for this is unclear. The present study shows that animals with intrauterine growth restriction, induced by a period of reduced placental blood flow during the second half of pregnancy, demonstrate reduced numbers of neurons in the hippocampus and the cerebellum in conjunction with retarded dendritic and axonal growth within these structures. Intrauterine growth restriction was induced at 30 days gestational age by unilateral uterine artery ligation in pregnant guinea-pigs. At one week of age, the total number of CA1 pyramidal neurons in the hippocampus and the Purkinje neurons in the cerebellum were determined using the combined fractionator/optical disector technique. The Cavalieri Principle was used to determine the volume of specific regions within the hippocampus and cerebellum. The body weight of animals that were classified as intrauterine growth-restricted was reduced by 42% (n=8) compared with control animals (n=8, P<0.001), while there was a smaller effect on brain weight (16% reduction, P<0.01). Estimates of the total number of neurons showed a reduction in CA1 pyramidal neurons in growth-restricted animals (4.19+/-0.43x10(5)) compared with control (5.20+/-0.44x10(5), P<0.01), and the volume of the stratum oriens layer above the CA1 region, which contains the apical dendrites of the CA1 pyramidal neurons, was reduced by 21% (P<0.01) in growth-restricted animals. In the cerebellum there was a reduction in the number of Purkinje neurons in growth-restricted animals (3.97+/-0.50x10(5)) compared with control (5.13+/-0.52x10(5), P<0.01), and in the volume of the molecular layer (17%, P<0.05), the internal granular layer (22%, P<0.01) and in the volume of the cerebellar white matter (23%, P<0.01). These results show that a period of placental insufficiency during the second half of pregnancy can effect brain development in a way which could lead to neurological and behavioural deficits in the postnatal animal.

Exposure to prenatal carbon monoxide and postnatal hyperthermia: short and long-term effects on neurochemicals and neuroglia in the developing brain

The effects of prenatal exposure to carbon monoxide (CO), a major component of cigarette smoke, was studied alone or in combination with postnatal hyperthermia, on the structural and neurochemical development of the postnatal brain at 1 and 8 weeks. Pregnant guinea pigs (n = 11) were exposed to 200 p.p.m CO for 10 h/day from midgestation until term (68 days), whereas control mothers (n = 10) breathed room air. On postnatal day 4, neonates from the control and CO-exposed pregnancies were exposed to hyperthermia (35 degrees C) for 75 min or remained at ambient (23 degrees C) temperature. Using semiquantitative immunohistochemical techniques the following neurotransmitter alterations were found in the medulla at 1 week: a decrease in met-enkephalin-immunoreactivity (IR) following postnatal hyperthermia and an increase in 5-hydroxytryptamine-IR following a combination of CO and hyperthermia. No alterations were observed in substance P- or tyrosine-hydroxylase-IR in any paradigm. At 8 weeks of age the combination of prenatal CO exposure followed by a brief hyperthermic stress postnatally resulted in lesions throughout the brain and an increase in glial fibrillary acidic protein-IR in the medulla. Such effects on brain development could be of relevance in cardiorespiratory control in the neonate and could have implications for the etiology of Sudden Infant Death Syndrome, where smoking and hyperthermia are major risk factors.

Antenatal brain injury: aetiology and possibilities of prevention

Although the aetiology of antenatal brain injury is often unclear, procedures can be employed to prevent or reduce the risk of injury. Defective neuropore closure can be prevented by periconceptional administration of folic acid, and the incidence of other severe malformations and genetic disorders can be reduced by early identification and termination of pregnancy. Antenatal identification of IUGR, administration of corticosteroids to cases with pending preterm birth, and treatment of maternal/fetal infections would also reduce the incidence of injury. Mothers can decrease the risk of injury by maintaining a good diet, avoiding smoking, alcohol intake and exposure to TORCH infections during pregnancy.

The use of additives to modulate the release of a sparingly water soluble drug entrapped in PLA50 microparticles: in vivo investigation

Sustained and total release of the sparingly water soluble compound, namely 1-[2-(4-fluorobenzoyl)aminoethyl]-4-(7-methoxynaphthyl) piperazine hydrochloride (FAM), from poly (DL-lactic acid) (PLA50) microparticles was previously shown to be feasible if the particles are obtained by grinding a solid mixture composed of the polymer and a percolating array of the compound mixed with an additive. Such microparticles, where the additive was poly (ethylene glycol) (PEG), dimyristoylphosphatidylcholine (DMPC), or Poloxamer 6800, were administrated subcutaneously to rats either as depot or using a liquid vehicle. The variations of the plasma concentration vs time determined by high pressure liquid chromatography and fluorometric detection, were plotted for the various microparticle systems, blood being taken twice from each animal and each measurement being triplicated. Data were analysed by non-compartmental analysis, in order to evaluate the elimination constant, the half-life, the area under the curve and the bioavailability for each system. Kinetics experiments were performed over 24h and also for 7 days. It was found that, for the selected formulations, the release of the sparingly water soluble compound depends on the dissolution rate in vivo and on the physicochemical characteristics of the additive, including solubility and micelle formation. Data correlated well with the results of previous in vitro investigation.

The use of additives to modulate the release of a sparingly water soluble drug entrapped in PLA50 microparticles

One of the major problems raised by the microencapsulation of drugs which are sparingly soluble in water is the difficulty to achieve a controlled and total release of the drug. It was previously shown that the microencapsulation of a model water insoluble drug, namely 1-[2-(4-fluorobenzoyl)aminoethyl]-4-(7-methoxynaphthyl) piperazine hydrochloride (FAMP) with a hydrophilic additive like low molar mass poly(ethylene glycol)s (PEG) can fulfil these requirements, provided all the drug + additive matter is in contact with the surrounding liquid medium via open pores and percolating channels. In this paper, PEG was replaced by other additives, selected because of their potential ability to increase the solubility of FAMP in pH = 7.4 isosomolar phosphate buffer (PBS). The idea was that increasing the solubility locally in microparticles could allow the drug to be released, despite its poor solubility in aqueous media like body fluids, and be absorbed before recrystallization. The solubility in PBS of FAMP mixed with additive, in the form of solid dispersions, was determined for various additives, namely citric acid, dimyristoyl DL-alpha-phosphatidyl choline (DMPC), poloxamer copolymers of different compositions and poly(dodecyl L-lysine citramidate) (PLCAC12(100)), an aggregate-forming hydrophilic polyelectrolyte containing 100%, hydrophobizing ester groups which can accommodate lipophilic compounds in hydrophobic pockets present in the aggregates. PEG was taken as a reference. It was found that DMPC, some poloxamers and the hydrophobized polyelectrolyte do increase the solubility of FAMP in PBS. Investigation was made of the release of FAMP from ground microparticles, whose loads were composed of FAMP combined with these solubilization-promoting additives. It was found that the release rate of FAMP from such systems can be increased and modulated to achieve an in vitro sustained release over a 20-30 day period and secure exhaustion of the particles at the end of this period.

In vitro delivery of a sparingly water soluble compound from PLA50 microparticles

The administration of a sparingly soluble drug is always problematic, especially when the drug has to be released from the degradable matrix of a polymeric drug delivery system. Attempts were made to achieve the complete release of 1-[2-(fluorobenzoyl) aminoethyl]-4-(7-methoxynaphtyl)piperazine (FAMP), a potential anxiolytic and antidepressor hydrophobic compound, from racemic poly(lactic acid) (PLA50)-based microparticles, 100% release was required at a low rate in order to allow monthly repeated S.C. or I.M. injections of this potent compound. FAMP-polymer combinations were made in the form of microspheres by the solvent evaporation technique. Release profiles were investigated under dynamic conditions by using a constant flow rate of pH 7.4 0.15 M phosphate buffer, used as a model of body fluids. Under these conditions, none of the microsphere compositions led to total release within a month, even when hydrophilic excipients, namely fructose and PEG were added. PLA50-FAMP microparticles with compositions and sizes similar to those of the microspheres, were then made by direct blending in dichloromethane, evaporation of the solvent, grinding and sieving. These formulations also failed in providing total drug release within 30 days, even at a high drug load. FAMP/PLA50/water-soluble additive, ternary grounded particles were finally prepared with fructose, PLA50 oligomers or poly(ethylene glycol) (PEG) as the additive. Only PLA50 grounded particles with percolating FAMP-PEG microdomains allowed 100% release of FAMP over a 30 day period, at a quasi constant rate which depended primarily on solubility and channelling provided the flow was slow enough. Data are discussed in terms of the accessibility of the entrapped drug to the aqueous medium.

Reduction in choline acetyltransferase immunoreactivity but not muscarinic-m2 receptor immunoreactivity in the brainstem of SIDS infants

The cholinergic neurotransmitter system is vital for several brainstem functions including cardiorespiratory control and central chemosensitivity. This study has examined aspects of the cholinergic neurotransmitter system in the brainstem of sudden infant death syndrome (SIDS) and control infants. The cellular localisation and the optical density of the immunoreactivity of the cholinergic enzyme choline acetyltransferase (CHAT-IR) and the muscarinic acetylcholine receptor m2 (m2-IR) in the medulla was described in 14 SIDS and 9 control cases. There was a reduction in the number of CHAT-IR neurons in the hypoglossal nucleus (control: 71.2+/-8.3% vs SIDS: 46.1+/-5.3%) and the dorsal motor nucleus of the vagus (DMV) (control: 77.2+/-5.0% vs SIDS: 52.5+/-7.4%) and reduced optical density of CHAT-IR in the hypoglossal nucleus (control: 0.20+/-0.01 vs SIDS; 0.14+/-0.02) in SIDS infants. In contrast there were no changes in the optical density of m2-IR in the hypoglossal nucleus, the DMV, or the arcuate nucleus. Hypoplasia of the arcuate nucleus was observed in one SIDS infant. These results suggest that there is a specific defect in some cholinergic motor neurons in the medulla of SIDS infants. This could lead to abnormal control of cardiovascular and respiratory function and airway patency and may be one of the contributing factors in the etiology of SIDS.

Maturational change in the cortical response to hypoperfusion injury in the fetal sheep

A characteristic of perinatal encephalopathies are the distinct patterns of neuronal and glial cell loss. Cerebral hypoperfusion is thought to be a major cause of these lesions. Gestational age is likely to influence outcome. This study compares the cortical electrophysiologic and histopathologic responses to hypoperfusion injury between preterm and near term fetuses. Chronically instrumented 0.65 (93-99-d, n = 9) and 0.9 (119-133-d, n = 6) gestation fetal sheep underwent 30 min of cerebral hypoperfusion injury. The parasagittal cortical EEG and impedance (measure of cytotoxic edema) responses plus histologic outcome (3 d) were compared. The acute rise in impedance was similar in amplitude, but the onset was delayed (5.0 +/- 0.7 versus 9.1 +/- 1.1 min, p < 0.05) in the preterm fetuses relative to those near term. In contrast the extent of the secondary rise was reduced (p < 0.01) and peaked earlier in the preterm fetuses (19.8 +/- 1.0 versus 40.5 +/- 3.5 h, p < 0.01). Both groups had a similar fall in EEG spectral edge frequency. The preterm fetuses had a milder loss of EEG intensity at 72 h (-7.7 +/- 1.5 versus -12.8 +/- 0.9 dB, p < 0.05). At both ages there was a predominantly parasagittal cortical distribution of damage with a similar pattern of neuronal loss in the thalamus and striatum. There was extensive selective neuronal loss within the upper layers of the cortex in those near term. In contrast the preterm fetuses developed subcortical infarcts (p < 0.05). The cortical response to injury altered during the last trimester. The results suggest the severity of the delayed phase of cortical neuronal injury and selective neuronal loss increased near term. In contrast, the preterm fetuses had a more rapidly evolving injury leading to necrosis of the subcortical white matter.

Fetal brain injury following prolonged hypoxemia and placental insufficiency: a review

It is well-established that severe, acute episodes of hypoxemia can damage the brain before birth, but the effects of more sustained hypoxemia are less well understood. We have used fetal fetal sheep in a series of studies aimed at determining the effects of prolonged hypoxemia, induced by placental insufficiency of differing severity and duration, on fetal brain structure. Restriction of placental, and hence fetal, growth by carunclectomy caused impaired development of neural processes and connections in the hippocampus, cerebellum, and visual cortex; neuronal migration and neuronal numbers did not appear to be affected. Twenty days of placental insufficiency during late gestation induced by umbilicoplacental embolisation also caused abnormalities in brain structure; the cerebellum, which develops late in gestation, was particularly affected. In the cortex, there was evidence of white matter lesions, an increase in the size of capillaries and a proliferation of astroglia. We also examined the effects of shorter periods of hypoxemia (6-12 hr) near mid-gestation on brain structure; fetuses were allowed to recover for 7 or 35 days after the hypoxemic challenge. The major changes were mild focal damage in the cortical white matter, a reduction in the number of Purkinje cells, a delay in the growth of neural processes in the cerebellum and proliferation of blood vessels. The hippocampus was also affected, in particular the areal density of pyramidal cells was reduced. The use of several classes of pharmacological agents with the potential to protect neurons from hypoxemic injury is discussed in relation to the developing brain.

The application of pen-based computer technology to home health care

The purpose of this project was to study the applicability of pen-based computer technology to home health care through the development of a pen-based computer system for a Hospital/Community-Patient Review Instrument (H/C-PRI) used for nursing home placement. The sample included nurses (n = 12) from the four regional Visiting Nurse Service of New York offices, as well as all patients on whom a H/C-PRI was completed during the pre-period (n = 238) and patients on whom a H/C-PRI was completed during the post-period (n = 238). The quality of documentation was higher for patients whose H/C-PRI was performed using the pen-based computer (0% calculation errors) than for those patients whose H/C-PRI was documented in the usual manner (11% calculation errors).

The effects of IGF-1 treatment after hypoxic-ischemic brain injury in adult rats

Intraventricular injection of insulin-like growth factor 1 (IGF-1) 2 h after hypoxic-ischemic injury reduces neuronal loss. To clarify the mode of action, we compared histological outcome between treatment groups in the following three studies: 0, 0.5, 5, and 50 micrograms IGF-1 given 2 h after injury; 0 and 20 micrograms IGF-1 given 1 h before; and 20 micrograms IGF-1 and insulin or vehicle alone given 2 h after. Unilateral hypoxic-ischemic injury was induced in adult rats by ligation of the right carotid and exposure to 6% O2 for 10 min. Histological outcome was evaluated in the cortex, striatum, and hippocampus 5 days later. Five to 50 micrograms IGF-1 reduced the incidence of infarction and neuronal loss in a dose-dependent manner in all regions (p < 0.05), and 50 micrograms reduced the infarction rate from 87 to 26% (p < 0.01). Pretreatment did not alter outcome. IGF-1 improved outcome compared with equimolar doses of insulin (p < 0.05) and did not affect systemic glucose concentrations or cortical temperature. The results indicate that the neuronal protective effects of IGF-1 are specific and are not mediated via insulin receptors, hypothermia, or hypoglycemic mechanisms. Centrally administered IGF-1 appears to provide worthwhile trophic support to cells within most cerebral structures after transient hypoxic-ischemic injury.

Pathophysiology of perinatal asphyxia

Following a severe asphyxial episode many cells can recover metabolically, and a cascade of processes are triggered in which intervention, even some hours later, can allow rescue of some cells that would otherwise die. A number of principles, however, needs to be carefully considered before extrapolating from animal to human trials. In particular, the effects on long-term outcome and on those who are compromised by intrauterine growth retardation need to be determined. It is critical to be able to identify rapidly those infants in terms of nature and severity of injury who are most likely to benefit from treatment. The dimension of time and phase of injury or recovery are key factors to effective intervention. Novel continuous cerebral function monitoring techniques such as those based on real-time spectral analysis of the EEG activity, cortical impedance monitoring, and near-infrared spectroscopy have considerable potential for determining the severity and pathophysiologic phase of injury on line.

Outcome after ischemia in the developing sheep brain: an electroencephalographic and histological study

The role of seizures occurring with perinatal hypoxic-ischemic encephalopathies is unclear. We examined the relationships between the time course of parasagittal electroencephalographic (EEG) activity and pathological outcome following transient cerebral ischemia, which was induced in 33 chronically instrumented fetal sheep by occluding the carotid arteries after ligation of the vertebral-carotid anastomoses. The EEG was quantified with real-time spectral analysis. Histological outcome was assessed 72 hours later. After 10 or 20 minutes of ischemia, EEG activity was depressed and then progressively recovered and mild selective neuronal loss was seen. The length of this depression correlated with the duration of ischemia (r = 0.88). After 30 or 40 minutes of ischemia, EEG activity remained depressed for 8 +/- 2 hours, followed by a rapid transition to low-frequency epileptiform activity that reached maximum intensity at 10 +/- 3 hours. By 72 hours, EEG intensity had fallen below control levels. This sequence of prolonged depression, epileptiform activity, and then loss of intensity was associated with the development of laminar necrosis of the underlying cortex. These electrophysiological sequelae may have prognostic value. The results indicate that after a severe hypoxic-ischemic insult, the parasagittal cortex becomes hyperexcitable before the final loss of activity. Secondary neuronal death may occur in this phase.

A role for IGF-1 in the rescue of CNS neurons following hypoxic-ischemic injury

Three days after unilateral hypoxic-ischemic injury in infant rats insulin-like growth factor 1 (IGF-1) production by astrocytes was enhanced in the injured region. This was associated with increased expression of mRNA for IGF binding protein-3 but not for binding protein-1. In adult rats a single lateral cerebroventricular injection of IGF-1 two hours following a similar injury markedly reduced neuronal loss. It is suggested that endogenous IGF-1 is neurotrophic and that centrally administered IGF-1 may have therapeutic potential for brain injury.

The effect of hypothalamic lesions on the length of gestation in fetal sheep

Twenty-nine sheep fetuses were subject to stereotaxic surgery at 106 to 110 days of gestation. Electrolytic lesions were placed bilaterally in the anterior hypothalamus. Sham-operated controls (n = 4) were delivered at 146.3 +/- 4.3 days. Of the fetuses with lesions, two were excluded because histologic confirmation of the lesion was not possible. Those fetuses with bilateral lesions of the suprachiasmatic nuclei (n = 4) were delivered at 148 +/- 10 days. In 10 animals with bilateral lesions of the paraventricular nuclei, delivery was significantly (p less than 0.0001) prolonged to at least 165.6 +/- 5.1 days. In nine animals with lesions not involving the endocrine hypothalamus, delivery was at 148.1 +/- 4.3 days. All animals that were delivered after 157 days (n = 9) had lesions including the paraventricular nuclei bilaterally (p less than 0.01). The adrenal glands of fetuses with prolonged gestation were normal in weight and light microscopic appearance. These observations demonstrate that fetal neural pathways involving the paraventricular nuclei are essential for parturition in the sheep. However, fetal adrenal growth can continue without such influences.

Culture conditions for induction of green plants from barley microspores by anther culture methods

With barley a large variation in frequency of plant formation from microspores of spikes from the same plant has been observed. The highest frequency of plant formation was obtained when culturing anthers in the dark on a high Ficoll medium containing 2,4-D and kinetin to induce proembryo (or callus) formation. Subsequently the proembryos or calli were cultured in dim light on a high Ficoll-high sugar medium containing IBA and kinetin. Finally the embryos were transferred to a starch agar medium. A maximum of 13 green plants were obtained from microspores of a single anther.The ratios of green to albino microspore derived plants varied from 9∶1 to 1∶9 depending on culture conditions. Under anaerobic conditions, lactic acid and other organic acids may have damaged the organelles in the cells resulting in the formation of albino plants. Thus, direct embryogenesis by using a well-buffered, high Ficoll-high sugar medium and proper aeration are essential for obtaining high frequency of green plants from microspores.

Continuous non-destructive determination of nitrogenase activity in microbiol cultures

The dinitrogen fixing enzyme nitrogenase (nitrogen:(acceptor) oxidoreductase)(EC 1.7.99.2) is monitored by its ability to reduce acetylene to ethylene. Low, non-inhibitory concentrations of acetylene (approximately 10(-7)mol/litre) are mixed with the gas flow aerating microbiol cultures, and acetylene and ethylene in the effluent gas are determined by gas chromatography. The procedure is safe, simple and carried out in situ without disturbing the growing culture. Transient changes in nitrogenase activity are easily detected. The technique may be automated.