Tuning Physical Properties of GelMA Hydrogels through Microarchitecture for Engineering Osteoid Tissue

Gelatin methacryloyl (GelMA) hydrogels have gained significant attention due to their biocompatibility and tunable properties. Here, a new approach to engineer GelMA-based matrices to mimic the osteoid matrix is provided. Two cross-linking methods were employed to mimic the tissue stiffness: standard cross-linking (SC) based on visible light exposure (VL) and dual cross-linking (DC) involving physical gelation, followed by VL. It was demonstrated that by reducing the GelMA concentration from 10% (G10) to 5% (G5), the dual-cross-linked G5 achieved a compressive modulus of ∼17 kPa and showed the ability to support bone formation, as evidenced by alkaline phosphatase detection over 3 weeks of incubation in osteogenic medium. Moreover, incorporating poly(ethylene) oxide (PEO) into the G5 and G10 samples was found to hinder the fabrication of highly porous hydrogels, leading to compromised cell survival and reduced osteogenic differentiation, as a consequence of incomplete PEO removal.

Thermoplastic PCL-b-PEG-b-PCL and HDI Polyurethanes for Extrusion-Based 3D-Printing of Tough Hydrogels

Novel tough hydrogel materials are required for 3D-printing applications. Here, a series of thermoplastic polyurethanes (TPUs) based on poly(ɛ-caprolactone)-b-poly(ethylene glycol)-b-poly(ɛ-caprolactone) (PCL-b-PEG-b-PCL) triblock copolymers and hexamethylene diisocyanate (HDI) were developed with PEG contents varying between 30 and 70 mol%. These showed excellent mechanical properties not only when dry, but also when hydrated: TPUs prepared from PCL-b-PEG-b-PCL with PEG of Mn 6 kg/mol (PCL₇-PEG₆-PCL₇) took up 122 wt.% upon hydration and had an E-modulus of 52 ± 10 MPa, a tensile strength of 17 ± 2 MPa, and a strain at break of 1553 ± 155% in the hydrated state. They had a fracture energy of 17976 ± 3011 N/mm² and a high tearing energy of 72 kJ/m². TPUs prepared using PEG with Mn of 10 kg/mol (PCL₅-PEG10-PCL₅) took up 534% water and were more flexible. When wet, they had an E-modulus of 7 ± 2 MPa, a tensile strength of 4 ± 1 MPa, and a strain at break of 147 ± 41%. These hydrogels had a fracture energy of 513 ± 267 N/mm² and a tearing energy of 16 kJ/m². The latter TPU was first extruded into filaments and then processed into designed porous hydrogel structures by 3D-printing. These hydrogels can be used in 3D printing of tissue engineering scaffolds with high fracture toughness.

Aiming for elimination: Outcomes of a consultation pathway supporting regional general practitioners to prescribe direct-acting antiviral therapy for hepatitis C

To increase access to treatment, the Australian government enabled general practitioners (GPs) to prescribe direct-acting antivirals (DAAs) to treat hepatitis C virus (HCV)-in consultation with a specialist if inexperienced in HCV management. This study describes the establishment and outcomes of a remote consultation pathway supporting GPs to treat HCV. Key stakeholders from primary and tertiary healthcare services in the Barwon South Western region developed and implemented an HCV remote consultation pathway. Pharmaceutical Benefits Schedule prescription data were used to evaluate GP DAA prescription 12 months pre-and post- pathway implementation. A retrospective review of patients referred for remote consultation for 12 months post- pathway inception was undertaken to determine the care cascade. HCV treatment initiation by GPs increased after implementation of the remote consultation pathway. In the 12-month study period, 74 GPs referred 169 people for remote consultation; 114 (67%) were approved for GP DAA treatment; 48 (28%) were referred for specialist assessment. In total, 119 (71%) patients commenced DAA; 69 were eligible for SVR12 assessment. Post-treatment HCV RNA data were available for 52 (75%) people; 37 achieved SVR12; 15 achieved SVR ranging from week 5 to 11 post-treatment. No treatment failure was detected. Collaborative development and implementation of a remote consultation pathway has engaged regional GPs in managing HCV. Follow-up post-treatment could be improved; however, no treatment failure has been documented. To eliminate HCV as a public health threat, it is vital that specialists support GPs to prescribe DAA.

Lack of nigral pathology in transgenic mice expressing human alpha-synuclein driven by the tyrosine hydroxylase promoter

alpha-Synuclein has been identified as a major component of Lewy body inclusions, which are one of the pathologic hallmarks of idiopathic Parkinson's disease. Mutations in alpha-synuclein have been found to be responsible for rare familial cases of Parkinsonism. To test whether overexpression of human alpha-synuclein leads to inclusion formation and neuronal loss of dopaminergic cells in the substantia nigra, we made transgenic mice in which the expression of wild-type or mutant (A30P and A53T) human alpha-synuclein protein was driven by the promoter from the tyrosine hydroxylase gene. Even though high levels of human alpha-synuclein accumulated in dopaminergic cell bodies, Lewy-type-positive inclusions did not develop in the nigrostriatal system. In addition, the number of nigral neurons and the levels of striatal dopamine were unchanged relative to non-transgenic littermates, in mice up to one year of age. These findings suggest that overexpression of alpha-synuclein within nigrostriatal dopaminergic neurons is not in itself sufficient to cause aggregation into Lewy body-like inclusions, nor does it trigger overt neurodegenerative changes.

Reversibly locking a protein fold in an active conformation with a disulfide bond: integrin alphaL I domains with high affinity and antagonist activity in vivo

The integrin alphaLbeta2 has three different domains in its headpiece that have been suggested to either bind ligand or to regulate ligand binding. One of these, the inserted or I domain, has a fold similar to that of small G proteins. The I domain of the alphaM and alpha2 subunits has been crystallized in both open and closed conformations; however, the alphaL I domain has been crystallized in only the closed conformation. We hypothesized that the alphaL domain also would have an open conformation, and that this would be the ligand binding conformation. Therefore, we introduced pairs of cysteine residues to form disulfides that would lock the alphaL I domain in either the open or closed conformation. Locking the I domain open resulted in a 9,000-fold increase in affinity to intercellular adhesion molecule-1 (ICAM-1), which was reversed by disulfide reduction. By contrast, the affinity of the locked closed conformer was similar to wild type. Binding completely depended on Mg(2+). Orders of affinity were ICAM-1 > ICAM-2 > ICAM-3. The k(on), k(off), and K(D) values for the locked open I domain were within 1.5-fold of values previously determined for the alphaLbeta2 complex, showing that the I domain is sufficient for full affinity binding to ICAM-1. The locked open I domain antagonized alphaLbeta2-dependent adhesion in vitro, lymphocyte homing in vivo, and firm adhesion but not rolling on high endothelial venules. The ability to reversibly lock a protein fold in an active conformation with dramatically increased affinity opens vistas in therapeutics and proteomics.

Relationship among nigrostriatal denervation, parkinsonism, and dyskinesias in the MPTP primate model

Presynaptic denervation is likely to play an important role in the pathophysiology of dyskinesias that develop after levodopa administration to patients with Parkinson's disease. In this study, the thresholds of nigrostriatal damage necessary for the occurrence of parkinsonism and levodopa-induced involuntary movements were compared in squirrel monkeys lesioned with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Animals treated with a regimen of MPTP that caused parkinsonism displayed > or =95% striatal dopamine depletion, 90% reduction of striatal dopamine uptake sites, and 70% nigral neuronal loss. Levodopa administration ameliorated the parkinsonian signs of these monkeys but also induced dyskinesias. A separate group of animals was treated with a milder MPTP regimen that caused 60%-70% striatal dopamine depletion, a 50% decrease in dopamine transporter, and 40% loss of dopaminergic nigral neurons. While these monkeys displayed no behavioral signs of parkinsonism, they all became dyskinetic after levodopa administration. The priming effect of levodopa, that is, the recurrence of dyskinesias in animals previously exposed to the drug, was compared in severely versus mildly lesioned monkeys. When severely injured parkinsonian animals underwent a second cycle of levodopa treatment, they immediately and consistently developed involuntary movements. In contrast, the recurrence of dyskinesias in primed monkeys with a partial nigrostriatal lesion required several levodopa administrations and remained relatively sporadic. The data indicate that moderate nigrostriatal damage which does not induce clinical parkinsonism predisposes to levodopa-induced dyskinesias. Once dyskinesias have been induced, the severity of denervation may enhance the sensitivity to subsequent levodopa exposures.

Identification of an essential gene encoding a class-V unconventional myosin in Drosophila melanogaster

Class-V myosins are a unique type of myosin motor with roles in intracellular transport. The mouse dilute gene was the first member of this class to be cloned, with mutations resulting in lightening of the coat colour or neurogenic defects leading to early death. Further examples of class-V myosins have been described in yeast, chicken and rat. Here, we report the cloning of the first class-V myosin from Drosophila. We show that expression of this myosin is predominantly in the adult germ line and early embryo and that the transcript is localised in the oocyte during oogenesis. Genetic and in situ hybridisation experiments have determined that this gene is located in the 43C region. We have evidence that it maps to a mutation in this region with an embryonic lethal phenotype.

The native form of alpha-synuclein is not found in the cerebrospinal fluid of patients with Parkinson's disease or normal controls

Alpha-synuclein has recently been shown to be a major constituent of Lewy bodies in Parkinson's disease (PD). This observation led us to investigate the possibility that its detection in the cerebrospinal fluid (CSF) could be used as a marker for Lewy bodies in the central nervous system. In this study we determined the pattern of expression of alpha-synuclein in patients with sporadic Parkinson's disease (PD) and normal controls, using western immunoblotting in conjunction with an antibody that recognizes the carboxyl terminal of alpha-synuclein protein. The native 19 kDa band normally seen in brain homogenates was not found in the CSF of either parkinsonian patients or control subjects. However, a novel band was observed, which migrated at a position in the range of 42 kDa in CSF from both patients and controls. We conclude that alpha-synuclein cannot be used as a biomarker for Lewy bodies during life. However, further characterization of the 42 kDa protein may be of interest.

Cloning and expression of az2, a putative zinc finger transcription factor from Drosophila melanogaster

A Drosophila gene (az2), mapping to a cluster of embryonic lethals at 43BC on the polytene chromosomes, has been sequenced and found to encode a predicted protein with six consecutive C2H2 zinc finger domains. The carboxy-terminus of az2 is related to a number of Drosophila and mammalian transcription factors. The 5' end of the gene is unrelated to genes in the databases. The gene is expressed in the adult female, in both the carcass and ovary, but is most abundant in the ovary. It is expressed in the nurse cells and transported to the oocyte.

MHC class II expression on human heart microvascular endothelial cells: exquisite sensitivity to interferon-gamma and natural killer cells

BACKGROUND

Immunocytochemical analysis of human organs in situ reveals differential expression of MHC class II antigens by microvascular endothelial cells (MVEC) and endothelial cells (EC) from large vessels. In view of the role of EC as initiators of allograft rejection, it is of interest to understand the regulation of MHC class II regulation by human MVEC. We have previously isolated, cultured, and characterized MVEC from the human heart, showing that although these cells were initially MHC class II positive, the antigens were lost after about 14 days in culture. These results suggest that basal expression in vivo is maintained by circulating factors.

METHODS

Here we have compared the sensitivity of human heart MVEC, human umbilical vein endothelial cells (HUVEC), and adult large vessel EC (aorta, coronary artery, and pulmonary artery) to interferon (IFN)-gamma and natural killer (NK) cell-mediated induction of MHC class II antigens. MVEC and HUVEC were cultured with 1, 5, 10, 50, 100, and 500 U/ml of IFN-gamma for 4 days, the cells were washed, and flow cytometry was used to examine HLA-DR expression at days 1, 2, 4, 7, 10, 14, and 21. EC were also cultured with purified NK cells in the presence and absence of neutralizing antibodies to IFN-gamma, and MHC class II expression was analyzed.

RESULTS

As little as 5 U/ml of IFN-gamma produced 98% positive cells in heart MVEC compared with 100-500 U/ml needed for the same effect in HUVEC or other large vessel EC (coronary, aorta, pulmonary). Class II expression was maintained longer by MVEC (for 17 days) compared with HUVEC (for 10 days). NK cells and supernatant from MVEC/NK cultures induced MHC class II antigens on MVEC and HUVEC in a dose-dependent fashion; the MVEC showed an enhanced sensitivity compared with the HUVEC. The NK effects were inhibited by neutralizing antibodies to IFN-gamma. The allostimulatory ability of MHC class II-positive EC was shown to be proportional to the amount of MHC class II on the cell surface.

CONCLUSIONS

The results suggest that basal expression of MHC class II on human MVEC is maintained by circulating IFN-gamma and NK cells. This conclusion has implications for therapeutic interventions.

Indium-111 labelled lymphocytes: isotope distribution and cell division

Since lymphocytes continue to proliferate and divide in vivo, it is important to determine the fate of a radionulide following lymphocyte labelling. Using the mixed lymphocyte reaction (MLR), we induced indium-111 labelled lymphocytes from a specific in-bred rat strain (AS) to divide and then observed the subsequent 111In distribution between cells and supernatant. L10 and L12.4 cells, which are allospecific CD4+ T lymphocytes from the AS rat, were stimulated in the MLR by antigen-presenting cells from the August rat, a different strain. We labelled L10 or L12.4 lymphocytes on day 0, the first day of the stimulation cycle, and continued to culture the lymphocytes in vitro. The proliferation of the cells was estimated according to their increase in number. The distribution of 111In between cell and supernatant fractions and between viable and dead (but intact) cells was measured in the cell suspension each day after labelling. The metabolic activity of 111In-labelled lymphocytes was compared with control cells by measuring their uptake of fluorine-18 fluorodeoxyglucose ([18F]FDG). 111In-labelled lymphocytes showed a poor proliferative response compared with control cells 24-48 h after labelling but increased in number after this time. From 24 to 72 h, about 70% of 111In was in the supernatant but only about 5%-10% was associated with intact dead cells. These dead cells tended to retain their 111In, losing less than 30% per day, suggesting that 111In in the supernatant was the result of active elimination from viable cells. Moreover, 24 h after culture, considerably more 111In was associated with viable than with dead lymphocytes, although over the next few days this distribution reversed. 111In-labelled lymphocytes took up more [18F]FDG than control cells at 24 h but not at 0 or 72-96 h; the maximum [18F]FDG uptake coincided with the greatest reduction in cell number. Furthermore, [18F]FDG uptake correlated with the initial 111In burden in lymphocytes labelled with 111In 24 h previously. The results are consistent with active elimination of 111In by 111In-labelled lymphocytes. The energy requirements for this are diverted away from cell division, thereby increasing the probability of cell death. As lymphocytes become 111In deplete, they recover their capacity to proliferate and their risk of death decreases. These findings have important implications for 111In-labelled lymphocyte scintigraphy, suggesting that cells remaining viable immediately after labelling will either subsequently die or alternatively eliminate the label.

Kinetics of folding of the IgG binding domain of peptostreptococcal protein L

The kinetics of folding of a tryptophan containing mutant of the IgG binding domain of protein L were characterized using stopped-flow circular dichroism, stopped-flow fluorescence, and HD exchange coupled with high-resolution mass spectrometry. Both the thermodynamics and kinetics of folding fit well to a simple two-state model: (1) Guanidine induced equilibrium denaturation transitions measured by fluorescence and circular dichroism were virtually superimposable. (2) The kinetics of folding/unfolding were single exponential under all conditions examined, and the rate constants obtained using all probes were similar. (3) Mass spectra from pulsed HD exchange refolding experiments showed that a species with very little protection from exchange is converted to a fully protected species (the native state) at a rate very similar to that of the overall change in tryptophan fluorescence; no intervening partially protected species were observed. (4) Rate constants (in H2O) and m values for folding and unfolding determined by fitting observed relaxation rates obtained over a broad range of denaturant concentrations to a two-state model were consistent with the equilibrium parameters deltaG and m: -RT ln(k(u)/k(f))/deltaG(U)H2O = 1.02; (m(u) + m(f))/m = 1.08. In contrast to results with a number of other proteins, there was no deviation from linearity in plots of ln k(obs) versus guanidine at low guanidine concentrations, both in the presence and absence of 0.4 M Na2SO4, suggesting that significantly stabilized intermediates do not accumulate during folding. Although all of the change in fluorescence signal during folding in phosphate buffer was accounted for by the simple exponential describing the overall folding reaction, fluorescence-quenching experiments using sodium iodide revealed a small reduction in the extent of quenching of the protein within the first two milliseconds after initiation of refolding in low concentrations of guanidine, suggesting a partial collapse of the unfolded chain may occur under these conditions. Comparison with results on the structurally and functionally similar IgG binding domain of streptococcal protein G show intriguing differences in the folding of the two proteins.

Supercritical fluid extraction of sulphamethazine and its metabolites from meat tissues

An investigation is reported of factors affecting the supercritical fluid extraction of sulphamethazine and five of its metabolites from spiked meat (swine liver and kidney). The addition of the polar modifier methanol to the carbon dioxide extracting fluid was found to generally enhance recoveries under subcritical and supercritical conditions. Recoveries of the ionic metabolites were increased by up to 72% when employing tetramethylammonium hydroxide for ion pairing in situ with the supercritical fluid extraction. Extraction efficiency is demonstrated to be dependent on the matrix. Extractions of the less polar compounds from the kidney are more successful than from the liver, which corresponds to their partitioning into the supercritical fluid and/or the greater fraction of highly extractable fatty materials. The kidney was more retentive than liver for the relatively more polar compounds, which suggests that the liver offers a less polar environment under the same extraction conditions.

The kinetics of MHC class I and class II expression in rat renal allografts

We have used in vivo localization of radiolabeled antibodies in a rat renal transplant model to compare the level of induction of major histocompatibility complex (MHC) class I and class II molecules in grafts undergoing rejection with grafts in which rejection was modified by cyclosporine (CsA). MHC class II expression increased in rejecting grafts, peaking on day 4, whereas a later rise in CsA-treated grafts was noted. The use of donor-specific antibodies demonstrated that this was due, in part, to a rise in class II of donor origin. No major differences in MHC class I levels were noted between the two groups until after day 4, when very little antibody localization was seen in the rejecting group. Our results suggest that therapeutic doses of CsA may not prevent the upregulation of class II that occurs during rejection, and that levels of class II are not of prognostic value in kidney transplantation.

Binding of sulphamethazine to pig plasma proteins and albumin

The interaction of sulphamethazine (SMZ) with pig plasma proteins and albumin was studied by ultrafiltration and equilibrium dialysis. Binding to pig plasma proteins was monophasic (affinity approximately 9.0 mol/L x 10(3)) and the main binding protein was albumin. At 37 degrees C and pH 7.4, the affinity of SMZ for albumin was about 8.0 mol/L x 10(3) and the number of binding sites was estimated as 1.4. Increasing the temperature from 4 to 45 degrees C resulted in a seven-fold decrease in affinity, and increasing pH from 6.0 to 8.0 enhanced affinity for pig albumin ten-fold. The free energy of binding (-delta G) and enthalpy change (-delta H) were around 5.5 and 5.1 Kcal/mol, respectively. The total entropy change (delta S) was small and positive, around 2 cal/mol/degree K. Studies with the fluorescent probes warfarin and dansylsarcosine, suggest that these bind to separate sites on porcine albumin. SMZ displaced both probes and inhibited the deacetylation of p-nitrophenyl acetate by pig albumin. We conclude that: (1) binding of SMZ to pig plasma proteins and albumin is weak; (2) the interaction with albumin is exothermic and enthalpy driven, and (3) pig albumin, like other mammalian albumins, appears to possess discrete binding sites for warfarin and dansylsarcosine. SMZ interacts with both these loci.

Affinity purification of rat cortical and chicken forebrain synaptosomes using a biotinylated derivative of omega-CgTx GVIA

We describe a magnetophoretic method for the affinity purification of synaptosomes expressing omega-CgTx GVIA-sensitive, N-type voltage-sensitive calcium channels (VSCCs). The method utilizes a biotinylated derivative of omega-CgTx GVIA which retains its ability to displace [125I] omega-CgTx GVIA from its binding sites on rat synaptic membranes. When coupled to streptavidin coated magnetizable beads, the hexanoyl spacer between omega-CgTx GVIA and the biotin:streptavidin bead complex is sufficiently long to allow flexibility of the toxin to bind to its receptor on synaptosomes. We have used this ligand successfully to isolate deaggregated synaptosomes from the parent fractions of chicken forebrain and rat cortex. In the chicken synaptosome parent fraction, omega-CgTx GVIA (1 nM-1 microM) produced a concentration-dependent block of the KCl-induced intracellular free Ca2+, [Ca2+]i, elevation with an IC50 of 28 nM. After affinity magnetophoresis no increase in [Ca2+]i elevation was observed in either the bound or unbound fractions. In the rat synaptosome parent fraction, the KCl-induced increase in free intracellular Ca2+ ([Ca2+]i) elevation was partially blocked by omega-CgTx GVIA (17 +/- 2% / 1 microM) and to a greater extent by omega-Aga IVA (55 +/- / 1 microM): a combination of the two toxins was additive (72 +/- 4% / 1 microM). The block obtained by omega-CgTx GVIA (1 microM) in the unbound fraction was reduced to 3 +/- 2%, whereas that by omega-Aga IVA (1 microM) increased to 82 +/- 3%. The block obtained by a combination of both toxins (83 +/- 2%) was the same as that with omega-Aga IVA alone (82 +/- 3%). No increase in free [Ca2+]i elevation was observed in the bound fraction although single synaptosome-like structures, displaying synaptophysin immunoreactivity, were detected on the beads. We conclude that omega-CgTx GVIA-sensitive N-type calcium channels are present on all chicken forebrain synaptosomes but only a subset of rat cortical synaptosomes.

pH-metric log P. 4. Comparison of partition coefficients determined by HPLC and potentiometric methods to literature values

The pKa and log P of 20 compounds, including six substituted phenols, two substituted quinolines, N-methylaniline, five barbiturate derivatives, two phenothiazines, and several other molecules of pharmaceutical interest, were determined by the potentiometric technique at 25 degrees C and ionic strength 0.1 M (KNO3). The log P values were determined also by partition HPLC. Three of the substances were of very low aqueous solubility, and for these the aqueous pKas were determined by extrapolation from methanol-water solutions using the Yasuda-Shedlovsky technique. Values of log P obtained both by potentiometry and by partition HPLC, which ranged from 0.3 to 5.4, were in very good acordance with literature values. The general applicability of the potentiometric technique to ionizable compounds of diversely varied structures was demonstrated by the study.

Absorption of N4-D-glucopyranosylsulphamethazine by rat everted intestinal sacs

Absorption of the N4-D-glucose conjugate of sulphamethazine (glucose-SMZ, 0.5 mM) by isolated everted sacs of the rat small intestine was studied at 37 degrees and pH 6.6. Phlorizin (0.5-2.0 mM) significantly reduced (P < 0.05) both mucosal and serosal transfer of glucose-SMZ and inhibition of mucosal transfer appeared to be concentration-dependent. Phloretin (0.5 mM) and removal of Na+ from the incubation medium also diminished absorption of glucose-SMZ. Furthermore, D-glucose (0.5 and 5.0 mM) inhibited mucosal and serosal transfer of the glycoside. The results suggest the D-glucose/Na+ cotransporter mediates absorption of glucose-SMZ from the small intestine of the rat. Thus, glucose-SMZ might be bioavailable from ingested tissues in which it is present.

Evidence for clonal anergy as a mechanism responsible for the maintenance of transplantation tolerance

The main stimulus triggering early acute allograft rejection is known to be delivered by the allogeneic "passenger" leukocytes present within the grafts. Once these cells have been replaced by cells of recipient origin, subsequent rejection episodes are generally less frequent and less acutely destructive. How this replacement affects the cell populations responsible for allograft rejection is not known. Here we report that rat alloreactive non-cytotoxic AS (RT1I) anti-August (RT1c) CD4+ T cells, that were shown to be specific for RT1.Bc+ August spleen stimulators, were able to cause acute rejection of normal August kidney allografts transplanted into sublethally irradiated AS recipients. These cells, however, failed to reject passenger cell-depleted (PCD) August kidneys, despite the substantial expression of RT1.Bc+ products on the graft tubular epithelium. In experiments in vitro, August kidney tubular epithelial cells expressing RT1.Bc+ antigens were found to be unable to stimulate the alloreactive T cells to proliferate. Moreover, preincubation with class II-positive August kidney epithelial cells specifically abrogated the alloreactivity of the T cells. Adding recombinant interleukin-2, however, restored the response to alloantigens. These results are consistent with the hypothesis that T cell populations capable of mediating early acute allograft rejection are different from those mediating late rejection, when donor passenger leukocytes are no longer present. They also suggest clonal anergy as one of the mechanisms responsible for maintaining long-term transplantation tolerance.

Mediation of acute but not chronic rejection of MHC-incompatible rat kidney grafts by alloreactive CD4 T cells activated by the direct pathway of sensitization

It has been previously postulated that there are two pathways of sensitization of MHC-incompatible kidney allografts: a direct pathway in which the host responder T cells are activated by MHC-incompatible passenger dendritic cells of the graft, and an indirect pathway, in which graft alloantigens are processed like "nominal" T cell antigens by host accessory cells, and presented as self-MHC restricted moieties. We show here that a rat AS anti-August alloreactive CD4+ T cell line, and a presumptive clone, activated through the direct pathway are capable in an adoptive transfer model of initiating rejection of normal August kidney grafts. However, neither the T cell line nor the presumptive clone initiates rejection of passenger cell-depleted August kidneys. The results support the hypothesis that direct pathway--sensitized T cells play a dominant role in early acute rejection, but not in chronic rejection.

Use of a murine T-cell hybridoma expressing human T-cell receptor alpha- and beta-gene products as a tool for the production of human T-cell receptor-specific monoclonal antibodies

We describe the production of mouse monoclonal antibodies specific for the human TcR using as the immunogen transfected murine T-cell hybridoma cells coexpressing mouse CD3 with human Jurkat TcR alpha and beta chains. The shortage of monoclonal antibodies (mAbs) specific for the human TcR-V alpha and V beta families reflects the difficulties in their production by conventional methods using whole human T cells or purified soluble receptors as immunogens. As an alternative strategy to circumvent these difficulties, we have generated a transfected mouse T-cell line expressing a human (Jurkat) TcR alpha beta dimer in a complex with mouse CD3. The parental mouse T-cell line, TG40, is a cell surface TcR-negative, cytoplasmic CD3-positive variant of the mouse T-cell hybridoma 2B4. The human-TcR alpha beta expressing mouse transfectant was used to immunize mice with the same genetic background as the parent mouse T-cell line, and a human TcR-specific response was successfully achieved. MAb-producing hybridomas were generated by fusing spleen cells from the immunized mice with the mouse myeloma cell line NSO. Of 124 hybridoma supernatants screens, 72 showed reactivity to the human T-cell line Jurkat. Twenty-four of the hybridomas producing human (Jurkat) TcR-specific antibodies were cloned and screened for reactivity to Jurkat TcR. Several IgG2b and IgM mAbs specific for the Jurkat T cell line were selected on the basis of their ability to modulate surface CD3 expression on Jurkat cells. Most of the antibodies do not stain other TcR-expressing human T cell leukemia cell lines, implying specificity for the variable domains of the Jurkat TcR.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of controlled local release of sodium fluoride on trabecular bone

Systemic sodium fluoride has been used in the treatment of osteoporosis. Recent studies have shown that it has a positive risk/benefit ratio for use in increasing spinal trabecular bone density. However, thinning of the cortices of the long bones with a resulting increase in fracture incidence has been observed. This study was designed to determine the response of bone to sodium fluoride released from a biodegradable polymer matrix, a technique which could potentially deliver it locally to a site of need in the skeleton which has a positive response to fluoride. In one group of mature New Zealand white rabbits, cylindrical poly(D,L-lactic acid) (PLA) implants, with or without impregnated sodium fluoride, were implanted into the contralateral femoral trochanters and tibial metaphyses. In a second group, similar implants were placed in adjacent vertebrae. Four weeks postimplantation, the femora, tibiae, and vertebrae were removed, sectioned, cleaned of all but mineralized tissue, and the surfaces of the sections stained. The stained surfaces were imaged and analyzed for morphometric properties of the trabeculae. Comparing contralateral vertebrae, those exposed to sodium fluoride had significantly thickened trabeculae, with decreased spacing between them and a greater bone fraction. A similar increase in trabecular width was found in the subchondral bone of the proximal tibiae exposed to local release fluoride. Femoral sections showed no difference, possibly due to the lack of extensive trabecular bone in the region chosen for study.

Abused to abuser: antecedents of socially deviant behaviors

The authors interviewed 34 young people who had been sexually abused as children 6 or 8 years after the abuse had occurred and compared them with 34 control subjects who had not been abused. They also compared subjects who had been abused for less than 1 year with those who had been abused for more than 1 year. The findings suggest a link between childhood sexual abuse and later drug abuse, juvenile delinquency, and criminal behavior. The authors explore the effects of pretrauma factors of previous childhood physical abuse and parental modeling of aggression and the postdisclosure factors of social and family blaming.

Pathways and cycles of runaways: a model for understanding repetitive runaway behavior

Based on information provided by 149 runaways staying in a Canadian shelter, the authors developed a model that explains repititious running away as the result of youths' cognitive confusion and unrealistic beliefs. The majority of the youths, who had run away an average of 8.9 times, felt that the events that led them to run away were unpredictable, yet 54 percent blamed only themselves for what happened. The paper describes the pathways, cycles, and outcomes of running away; analyzes the relationship between the youths' experiences with prostitution, delinquency, and sexual and physical abuse and the length of time they had been away from home; summarizes the youths' reasons for running away; compares the beliefs of runaways with and without a history of sexual abuse; and discusses interventions.

Risk for alcohol-related accidents in divorced and separated women

The relationship between marital status and risk for alcohol-related automobile accidents was examined in 10,544 subjects (12% women) who entered 28 driver alcohol education programs over a 6-month period in 1983. Women were more likely than men to be divorced or separated (28 vs 16%). In their marital category, women were younger than men and were more likely to be living alone with their children. The findings implicate the role of lifestyle factors in the development and maintenance of alcohol-related problems, and suggest that women in driver alcohol education programs may require more help than men because they have less social support.