Feeding rumen-protected lysine altered immune and metabolic biomarkers in dairy cows during the transition period

This experiment was conducted to determine the effects of feeding rumen-protected lysine (RPL; AjiPro-L Generation 3, Ajinomoto Health and Nutrition North America Inc.) from -26 ± 4.6 d prepartum (0.54% RPL of dietary dry matter intake) to 28 d postpartum (0.39% RPL of dietary dry matter intake) on immunometabolic status and liver composition in dairy cows. Seventy-five multiparous Holstein cows, blocked by parity, previous 305-d mature-equivalent milk production, expected calving date, and body condition score during the far-off dry period were assigned to 1 of 4 dietary treatments in a randomized, complete block design with a 2 × 2 factorial arrangement of treatments. Treatments prepartum consisted of total mixed ration top dressed with RPL (PRE-L) or without RPL (PRE-C), and postpartum treatments consisted of total mixed ration top dressed PRE-L prepartum and postpartum, PRE-L prepartum and PRE-C postpartum, PRE-C prepartum and PRE-L postpartum, and PRE-C prepartum and postpartum in 300 g of molasses. Blood samples were taken on -7 ± 0.5, 0 ± 0.5, 7 ± 0.9, 14 ± 0.9, and 28 ± 0.5 d relative to calving. Whole blood samples were taken on -14 ± 0.5, -7 ± 0.5, 7 ± 0.9, and 14 ± 0.9 d relative to calving for oxidative burst and phagocytic capacity of monocytes and neutrophils. Liver samples were collected via a biopsy on -12 ± 4.95 and 13 ± 2.62 d relative to calving and analyzed for liver composition (triacylglyceride and carnitine concentrations), mRNA expression of hepatic genes, and protein abundance. Protein abundance was calculated by normalizing intensity bands for a specific protein with glyceraldehyde-3-phosphate dehydrogenase. Concentrations of haptoglobin and glutathione peroxidase activity in plasma were lower at d 0 for cows in PRE-L (102 µg/mL and 339 nmol/min per mL, respectively) compared with cows in PRE-C (165 µg/mL and 405 nmol/min per mL, respectively). Oxidative burst capacity in monocytes tended to be greater on d 7 postpartum for cows in PRE-L (65.6%) than cows in PRE-C (57.5%). Additionally, feeding RPL altered the mRNA expression in liver tissue prepartum [decreased INSR (insulin receptor), CPT1A (carnitine palmitoyltransferase 1A), and IL1B (interleukin 1 β)] and postpartum [increased IL8 (interleukin 8), EHMT2 (euchromatic histone lysine methyltransferase 2), TSPO (translocator protein), and SLC3A2 (solute carrier family 3 member 2); and decreased SLC7A1 (solute carrier family 7 member 1), SOD1 (superoxide dismutase 1), and SAA3 (serum amyloid A 3)] compared with cows not consuming RPL]. Additionally, cows in the PRE-C prepartum and PRE-L postpartum treatment tended to have greater protein abundance of mTOR postpartum compared with the PRE-C prepartum and postpartum treatment. Protein abundance of SLC7A7 (solute carrier family 7 member 7) pre- and postpartum tended to be greater and BBOX1 (gamma-butyrobetaine dioxygenase 1) tended to be less when RPL was consumed prepartum. In conclusion, cows that consumed RPL during the transition period had molecular changes related to liver composition, enhanced liver function indicated by greater total protein and albumin concentrations in plasma, and improved immune status indicated by decreased haptoglobin, glutathione peroxidase activity, and immune related mRNA expression.

Disease modification and symptom relief in osteoarthritis using a mutated GCP-2/CXCL6 chemokine

We showed that the chemokine receptor C-X-C Motif Chemokine Receptor 2 (CXCR2) is essential for cartilage homeostasis. Here, we reveal that the CXCR2 ligand granulocyte chemotactic protein 2 (GCP-2) was expressed, during embryonic development, within the prospective permanent articular cartilage, but not in the epiphyseal cartilage destined to be replaced by bone. GCP-2 expression was retained in adult articular cartilage. GCP-2 loss-of-function inhibited extracellular matrix production. GCP-2 treatment promoted chondrogenesis in vitro and in human cartilage organoids implanted in nude mice in vivo. To exploit the chondrogenic activity of GCP-2, we disrupted its chemotactic activity, by mutagenizing a glycosaminoglycan binding sequence, which we hypothesized to be required for the formation of a GCP-2 haptotactic gradient on endothelia. This mutated version (GCP-2-T) had reduced capacity to induce transendothelial migration in vitro and in vivo, without affecting downstream receptor signaling through AKT, and chondrogenic activity. Intra-articular adenoviral overexpression of GCP-2-T, but not wild-type GCP-2, reduced pain and cartilage loss in instability-induced osteoarthritis in mice. We suggest that GCP-2-T may be used for disease modification in osteoarthritis.

In vivo potency assay for the screening of bioactive molecules on cartilage formation

Cartilage regeneration is a priority in medicine for the treatment of osteoarthritis and isolated cartilage defects. Several molecules with potential for cartilage regeneration are under investigation. Unfortunately, in vitro chondrogenesis assays do not always predict the stability of the newly formed cartilage in vivo. Therefore, there is a need for a stringent, quantifiable assay to assess in vivo the capacity of molecules to promote the stable formation of cartilage that is resistant to calcification and endochondral bone formation. We developed an ectopic cartilage formation assay (ECFA) that enables one to assess the capacity of bioactive molecules to support cartilage formation in vivo using cartilage organoids. The ECFA predicted good clinical outcomes when used as a quality control for efficacy of chondrocyte preparations before implantation in patients with cartilage defects. In this assay, articular chondrocytes from human donors or animals are injected either intramuscularly or subcutaneously in nude mice. As early as 2 weeks later, cartilage organoids can be retrieved. The size of the implants and their degree of differentiation can be assessed by histomorphometry, immunostainings of molecular markers and real-time PCR. Mineralization can be assessed by micro-computed tomography or by staining. The effects of molecules on cartilage formation can be tested following the systemic administration of the molecule in mice previously injected with chondrocytes, or after co-injection of chondrocytes with cell lines overexpressing and secreting the protein of interest. Here we describe the ECFA procedure, including steps for harvesting human and bovine articular cartilage, isolating primary chondrocytes, preparing overexpression cell lines, injecting the cells intramuscularly and retrieving the implants. This assay can be performed by technicians and researchers with appropriate animal training within 3 weeks.

Feeding rumen-protected lysine to dairy cows prepartum improves performance and health of their calves

Providing adequate concentrations of AA in the prepartum diet is pivotal for the cow's health and performance. However, less is known about the potential in utero effects of particular AA on early-life performance of calves. This experiment was conducted to determine the effects on dairy calves when their dams were fed rumen-protected lysine (RPL; AjiPro-L Generation 3, Ajinomoto Heartland Inc.; 0.54% dry matter of total mixed ration as top dress) from 26 ± 4.6 d (mean ± standard deviation) before calving until calving. Seventy-eight male (M) and female (F) Holstein calves were assigned to 2 treatments based on their dams' prepartum treatment, RPL supplementation (PRE-L) or without RPL (CON). At the time of birth (0.5-2 h after calving), before colostrum was fed, blood samples were collected. An initial body weight was obtained at 1 to 3 h after birth. Calves were fed 470 g of colostrum replacer (Land O'Lakes Bovine IgG Colostrum Replacer, Land O'Lakes, Inc.) diluted in 3.8 L of water. Calves were provided water ad libitum and fed milk replacer (Advance Excelerate, Milk Specialties Global Animal Nutrition; 28.5% crude protein, 15% fat) at 0600 h and 1700 h until 42 d of age. Calves were measured weekly, at weaning (d 42), and at the end of the experimental period (d 56). Plasma concentrations of AA were measured on d 0, 7, and 14 d using ultra-performance liquid chromatography-mass spectrometry (Waters) with a derivatization method (AccQ-Tag Derivatization). Final body weight was greater for M (87 ± 11 kg) than F (79 ± 7 kg). Calves in PRE-L tended to have greater dry matter (814 ± 3 g/d) and crude protein (234 ± 6 g/d) intakes than those in CON (793 ± 9 g/d and 228 ± 11 g/d, respectively). Calves in PRE-L had greater average daily gain (0.96 ± 0.04 kg/d) than calves in CON (0.85 ± 0.03 kg/d) during wk 6 to 8. Calves in PRE-L tended to be medicated fewer days than CON (4.7 ± 1.2 d vs. 6.2 ± 3.4 d, respectively). Calves in PRE-L-M and CON-F (2,916 ± 112 µM and 2,848 ± 112 µM, respectively) had greater total AA concentration in plasma than calves in PRE-L-F and CON-M (2,684 ± 112 µM and 2,582 ± 112 µM, respectively). Calves in PRE-L-F and CON-M (4.09 ± 0.11% and 4.16 ± 0.11%, respectively) had greater concentration of Lys as a percentage of total AA compared with calves in CON-F and PRE-L-M (3.91 ± 0.11% and 3.90 ± 0.11%, respectively). Calves in PRE-L tended to have greater percentage of phagocytic neutrophils (39.6 ± 1.59%) than calves in CON (35.9 ± 1.59%). In conclusion, increasing the metabolizable lysine provided to prepartum dairy cows had modest effect over offspring performance, with the major result being a greater average daily gain for calves in PRE-L during the preweaning phase (wk 6-8).

ROR2 blockade as a therapy for osteoarthritis

Osteoarthritis is characterized by the loss of the articular cartilage, bone remodeling, pain, and disability. No pharmacological intervention can currently halt progression of osteoarthritis. Here, we show that blocking receptor tyrosine kinase-like orphan receptor 2 (ROR2) improves cartilage integrity and pain in osteoarthritis models by inhibiting yes-associated protein (YAP) signaling. ROR2 was up-regulated in the cartilage in response to inflammatory cytokines and mechanical stress. The main ligand for ROR2, WNT5A, and the targets YAP and connective tissue growth factor were up-regulated in osteoarthritis in humans. In vitro, ROR2 overexpression inhibited chondrocytic differentiation. Conversely, ROR2 blockade triggered chondrogenic differentiation of C3H10T¹/₂ cells and suppressed the expression of the cartilage-degrading enzymes a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5. The chondrogenic effect of ROR2 blockade in the cartilage was independent of WNT signaling and was mediated by down-regulation of YAP signaling. ROR2 signaling induced G protein and Rho-dependent nuclear accumulation of YAP, and YAP inhibition was required but not sufficient for ROR2 blockade-induced chondrogenesis. ROR2 silencing protected mice from instability-induced osteoarthritis with improved structural outcomes, sustained pain relief, and without apparent side effects or organ toxicity. Last, ROR2 silencing in human articular chondrocytes transplanted in nude mice led to the formation of cartilage organoids with more and better differentiated extracellular matrix, suggesting that the anabolic effect of ROR2 blockade is conserved in humans. Thus, ROR2 blockade is efficacious and well tolerated in preclinical animal models of osteoarthritis.

WNT3A-loaded exosomes enable cartilage repair

Cartilage defects repair poorly. Recent genetic studies suggest that WNT3a may contribute to cartilage regeneration, however the dense, avascular cartilage extracellular matrix limits its penetration and signalling to chondrocytes. Extracellular vesicles actively penetrate intact cartilage. This study investigates the effect of delivering WNT3a into large cartilage defects in vivo using exosomes as a delivery vehicle. Exosomes were purified by ultracentrifugation from conditioned medium of either L-cells overexpressing WNT3a or control un-transduced L-cells, and characterized by electron microscopy, nanoparticle tracking analysis and marker profiling. WNT3a loaded on exosomes was quantified by western blotting and functionally characterized in vitro using the SUPER8TOPFlash reporter assay and other established readouts including proliferation and proteoglycan content. In vivo pathway activation was assessed using TCF/Lef:H2B-GFP reporter mice. Wnt3a loaded exosomes were injected into the knees of mice, in which large osteochondral defects were surgically generated. The degree of repair was histologically scored after 8 weeks. WNT3a was successfully loaded on exosomes and resulted in activation of WNT signalling in vitro. In vivo, recombinant WNT3a failed to activate WNT signalling in cartilage, whereas a single administration of WNT3a loaded exosomes activated canonical WNT signalling for at least one week, and eight weeks later, improved the repair of osteochondral defects. WNT3a assembled on exosomes, is efficiently delivered into cartilage and contributes to the healing of osteochondral defects.

Feeding rumen-protected lysine prepartum increases energy-corrected milk and milk component yields in Holstein cows during early lactation

Feeding rumen-protected Lys (RPL) may be used to increase lactation performance in dairy cows; however, the effect of feeding RPL during the prepartum period and subsequent effect on postpartum performance is not well explored. Therefore, this experiment was conducted to determine the effects of feeding RPL (AjiPro-L Generation 3, Ajinomoto Heartland Inc., Chicago, IL) prepartum, postpartum, or both on performance, health, and blood metabolites. Seventy-five multiparous Holstein cows, blocked by parity, previous 305-d mature-equivalent milk production, expected calving date, and body condition score during the far-off dry period were assigned to 1 of 2 dietary treatments: total mixed ration with or without RPL in a randomized, complete block design. A 2 × 2 factorial arrangement of treatments was used. Prepartum (-28 d to calving), animals were fed a diet (forage, 68% of dietary DM) with RPL [PRE-L; 0.54% RPL of dietary dry matter intake (DMI)] or without RPL (control; PRE-C). After calving, half of the cows from each prepartum treatment group were assigned to a diet (forage, 55.5% of dietary DM) with RPL (PRE-L POST-L; PRE-C POST-L; 0.40% RPL of dietary DMI) or without RPL (PRE-C POST-C; PRE-L POST-C) until d 28 postpartum. Cows were milked twice a day and milk samples were taken on 7 ± 1.3, 14 ± 1.4, and 28 ± 1.1 d relative to calving (DRC). Milk yield and DMI were recorded daily. Blood samples were taken for plasma AA analysis on -7 ± 0.5, 0 ± 0.5, 7 ± 0.9, and 14 ± 0.9 DRC. Cows in PRE-L had greater body weight at -2 and -1 wk before calving compared with those in PRE-C, though body weight change from wk -4 to -1 was not different. Body weight (717 ± 6 kg) was greater and DMI (18.1 ± 0.7 kg) tended to be greater for cows in PRE-L POST-L and PRE-L POST-C compared with those that were in PRE-C POST-L and PRE-C POST-C (707 ± 6 and 16.8 ± 0.7 kg, respectively). Energy-corrected milk (48.8 ± 1.9 kg/d), milk fat (1.9 ± 0.1 kg/d), milk true protein (1.4 ± 0.1 kg/d), milk casein (0.6 ± 0.04 kg/d), and milk lactose yields (2.1 ± 0.1 kg/d) were greater for cows in PRE-L POST-L and PRE-L POST-C compared with those that were in PRE-C POST-L and PRE-C POST-C (44.2 ± 1.9, 1.7 ± 0.1, 1.3 ± 0.1, 0.5 ± 0.04, 1.9 ± 0.1 kg/d, respectively). Plasma concentrations of Lys prepartum (69.8 ± 1.8 µM) increased for cows in PRE-L compared with those in PRE-C (62.5 ± 1.3 µM). In conclusion, RPL consumed prepartum tended to increase postpartum DMI and increased energy-corrected milk and milk component yields. This indicates that prepartum supply of intestinally available Lys is pertinent to postpartum performance. However, postpartum supply of intestinally available Lys had no effect on cows' performance.

Agrin induces long-term osteochondral regeneration by supporting repair morphogenesis

Cartilage loss leads to osteoarthritis, the most common cause of disability for which there is no cure. Cartilage regeneration, therefore, is a priority in medicine. We report that agrin is a potent chondrogenic factor and that a single intraarticular administration of agrin induced long-lasting regeneration of critical-size osteochondral defects in mice, with restoration of tissue architecture and bone-cartilage interface. Agrin attracted joint resident progenitor cells to the site of injury and, through simultaneous activation of CREB and suppression of canonical WNT signaling downstream of β-catenin, induced expression of the chondrogenic stem cell marker GDF5 and differentiation into stable articular chondrocytes, forming stable articular cartilage. In sheep, an agrin-containing collagen gel resulted in long-lasting regeneration of bone and cartilage, which promoted increased ambulatory activity. Our findings support the therapeutic use of agrin for joint surface regeneration.

Targeting Extracellular Vesicles to the Arthritic Joint Using a Damaged Cartilage-Specific Antibody

The targeted delivery of therapies to diseased tissues offers a safe opportunity to achieve optimal efficacy while limiting systemic exposure. These considerations apply to many disease indications but are especially relevant for rheumatoid arthritis (RA), as RA is a systemic autoimmune disease which affects multiple joints. We have identified an antibody that is specific to damaged arthritic cartilage (anti-ROS-CII) that can be used to deliver treatments specifically to arthritic joints, yielding augmented efficacy in experimental arthritis. In the current study, we demonstrate that scaffolds enriched with bioactive payloads can be delivered precisely to an inflamed joint and achieve superior efficacy outcomes consistent with the pharmacological properties of these payloads. As a scaffold, we have used extracellular vesicles (EVs) prepared from human neutrophils (PMNs), which possess intrinsic anti-inflammatory properties and the ability to penetrate inflamed arthritic cartilage. EV fortified with anti-ROS-CII (EV/anti-ROS-CII) retained anti-ROS-CII specificity and bound exclusively to the damaged cartilage. Following systemic administration, EV/anti-ROS-CII (a) exhibited the ability to localize specifically in the arthritic joint in vivo and (b) was able to specifically target single (viral IL-10 or anti-TNF) or combined (viral IL-10 and anti-TNF) anti-inflammatory treatments to the arthritic joint, which accelerated attenuation of clinical and synovial inflammation. Overall, this study demonstrates the attainability of targeting a pro-resolving biological scaffold to the arthritic joint. The potential of targeting scaffolds such as EV, nanoparticles, or a combination thereof alongside combined therapeutics is paramount for designing systemically administered broad-spectrum of anti-inflammatory treatments.

Shall I go digital?

Dental radiographic imaging is slowly transferring to digital format. The decision to invest in this new technology should be based on a good understanding of the different types of digital imaging available within the dental field. This article outlines its use in general dental practice, highlighting the pros and cons of the various systems both for intra-oral and extra-oral radiography.

CLINICAL RELEVANCE

An understanding of the mechanisms of digital imaging and their associated potential problems are required by any clinician moving to film-less imaging.

In vitro and in vivo analysis of the inability of fetal rabbit wounds to contract

Fetal rabbit wounds that are sutured show excellent repair without obvious scarring. In contrast, an unsutured wound in a rabbit fetus does not close, and it appears that the process of wound contraction does not occur. Experiments were carried out to illustrate the mechanisms responsible for the noncontraction of open fetal rabbit wounds. Results showed that the lack of wound contraction was not an artifact caused by rapid fetal growth. With regard to the ability of cultured fetal fibroblasts to show cytoplasmic muscle-induced cell contraction, we found that, in cultured fetal fibroblasts, cell contraction was induced by adenosine triphosphate. Contractile abilities of fetal-derived fibroblasts were equivalent to those of adult-derived fibroblasts. The fetal fibroblasts also demonstrated the generation of superior contractile activity when examined in a fibroblast-populated collagen lattice model. Finally, the ability of amniotic fluid to alter wound contraction was addressed by means of the fibroblast-populated collagen lattice in vitro model. Increasing concentrations of amniotic fluid inhibited fetal fibroblast lattice contraction. Therefore, rabbit amniotic fluid contains an inhibitor that may be partially responsible for the noncontraction of fetal rabbit wounds in utero.

Dlx homeobox gene family expression in osteoclasts

Skeletal growth and homeostasis require the finely orchestrated secretion of mineralized tissue matrices by highly specialized cells, balanced with their degradation by osteoclasts. Time- and site-specific expression of Dlx and Msx homeobox genes in the cells secreting these matrices have been identified as important elements in the regulation of skeletal morphology. Such specific expression patterns have also been reported in osteoclasts for Msx genes. The aim of the present study was to establish the expression patterns of Dlx genes in osteoclasts and identify their function in regulating skeletal morphology. The expression patterns of all Dlx genes were examined during the whole osteoclastogenesis using different in vitro models. The results revealed that Dlx1 and Dlx2 are the only Dlx family members with a possible function in osteoclastogenesis as well as in mature osteoclasts. Dlx5 and Dlx6 were detected in the cultures but appear to be markers of monocytes and their derivatives. In vivo, Dlx2 expression in osteoclasts was examined using a Dlx2/LacZ transgenic mouse. Dlx2 is expressed in a subpopulation of osteoclasts in association with tooth, brain, nerve, and bone marrow volumetric growths. Altogether the present data suggest a role for Dlx2 in regulation of skeletal morphogenesis via functions within osteoclasts.

Salivary gland disease

Salivary gland disease covers a wide range of pathological entities, including salivary gland-specific disease, as well as manifestations of systemic diseases. This chapter discusses the recent advances in managing obstructive salivary gland disease, the move from gland excision to gland preservation, the dilemmas in diagnosing and managing tumours of the salivary glands, and the international data collection to understand the aetiology and progression of Sjögren's disease.

Satb2 haploinsufficiency phenocopies 2q32-q33 deletions, whereas loss suggests a fundamental role in the coordination of jaw development

The recent identification of SATB2 as a candidate gene responsible for the craniofacial dysmorphologies associated with deletions and translocations at 2q32-q33, one of only three regions of the genome for which haploinsufficiency has been significantly associated with isolated cleft palate, led us to investigate the in vivo functions of murine Satb2. We find that, similar to the way in which SATB2 is perceived to act in humans, craniofacial defects due to haploinsufficiency of Satb2, including cleft palate (in approximately 25% of cases), phenocopy those seen with 2q32-q33 deletions and translocations in humans. Full functional loss of Satb2 results in amplification of these defects and leads both to increased apoptosis in the craniofacial mesenchyme where Satb2 is usually expressed and to changes in the pattern of expression of three genes implicated in the regulation of craniofacial development in humans and mice: Pax9, Alx4, and Msx1. The Satb2-dosage sensitivity in craniofacial development is conspicuous--along with its control of cell survival, pattern of expression, and reversible functional modification by SUMOylation, it suggests that Satb2/SATB2 function in craniofacial development may prove to be more profound than has been anticipated previously. Because jaw development is Satb2-dosage sensitive, the regulators of Satb2 expression and posttranslational modification become of critical importance both ontogenetically and evolutionarily, especially since such regulators plausibly play undetected roles in jaw and palate development and in the etiology of craniofacial malformations.

A Revolution in the Management of Obstructive Salivary Gland Disease

Salivary gland obstruction is the commonest cause of salivary gland disease presenting to the general dental practitioner. To date, with the exception of the most surgically accessible stones found within the anterior ducts, there has been little treatment to offer patients except surgical removal of the gland, with the associated risks to the facial and trigeminal nerves. In the last 10 years, more conservative treatment modalities have been developed, opening up a range of treatment options which combine to provide an alternative management of these cases. This paper presents data from one unit in which lithotripsy, which is the destruction of stones (calculi) using shock waves, basket retrieval, a modified minor surgical technique, and balloon dilatation have been used to treat salivary gland obstruction successfully. Over 70% of stones can now be retrieved leaving a functioning gland.

CLINICAL RELEVANCE

Salivary gland obstruction is a clinical problem presenting to the general dental practitioner, and requires an understanding of the range of treatment options available.

Expression and regulation of the Msx1 natural antisense transcript during development

Bidirectional transcription, leading to the expression of an antisense (AS) RNA partially complementary to the protein coding sense (S) RNA, is an emerging subject in mammals and has been associated with various processes such as RNA interference, imprinting and transcription inhibition. Homeobox genes do not escape this bidirectional transcription, raising the possibility that such AS transcription occurs during embryonic development and may be involved in the complexity of regulation of homeobox gene expression. According to the importance of the Msx1 homeobox gene function in craniofacial development, especially in tooth development, the expression and regulation of its recently identified AS transcripts were investigated in vivo in mouse from E9.5 embryo to newborn, and compared with the S transcript and the encoded protein expression pattern and regulation. The spatial and temporal expression patterns of S, AS transcripts and protein are consistent with a role of AS RNA in the regulation of Msx1 expression in timely controlled developmental sites. Epithelial–mesenchymal interactions were shown to control the spatial organization of S and also AS RNA expression during early patterning of incisors and molars in the odontogenic mesenchyme. To conclude, this study clearly identifies the Msx1 AS RNA involvement during tooth development and evidences a new degree of complexity in craniofacial developmental biology: the implication of endogenous AS RNAs.

Intergenic enhancers with distinct activities regulate Dlx gene expression in the mesenchyme of the branchial arches

The vertebrate Dlx genes, generally organized as tail-to-tail bigene clusters, are expressed in the branchial arch epithelium and mesenchyme with nested proximodistal expression implicating a code that underlies the fates of jaws. Little is known of the regulatory architecture that is responsible for Dlx gene expression in developing arches. We have identified two distinct cis-acting regulatory sequences, I12a and I56i, in the intergenic regions of the Dlx1/2 and Dlx5/6 clusters that act as enhancers in the arch mesenchyme. LacZ transgene expression containing I12a is restricted to a subset of Dlx-expressing ectomesenchyme in the first arch. The I56i enhancer is active in a broader domain in the first arch mesenchyme. Expression of transgenes containing either the I12a or the I56i enhancers is dependent on the presence of epithelium between the onset of their expression at E9-10 until independence at E11. Both enhancers positively respond to FGF8 and FGF9; however, the responses of the reporter transgenes were limited to their normal domain of expression. BMP4 had a negative effect on expression of both transgenes and counteracted the effects of FGF8. Furthermore, bosentan, a pharmacological inhibitor of Endothelin-1 signaling caused a loss of I56i-lacZ expression in the most distal aspects of the expression domain, corresponding to the area of Dlx-6 expression previously shown to be under the control of Endothelin-1. Thus, the combinatorial branchial arch expression of Dlx genes is achieved through interactions between signaling pathways and intrinsic cellular factors. I56i drives the entire expression of Dlx5/6 in the first arch and contains necessary sequences for regulation by at least three separate pathways, whereas I12a only replicates a small domain of endogenous expression, regulated in part by BMP-4 and FGF-8.

Extracapsular dissection for clinically benign parotid lumps: reduced morbidity without oncological compromise

Previous studies have shown that extracapsular dissection (ECD) is an alternative approach to superficial parotidectomy (SP) for pleomorphic adenoma parotid tumours, associated with low recurrence rates equal to those following SP, but with significantly reduced morbidity. However, if a malignant tumour masquerades as a clinically benign lump, this approach may be inappropriate. This study addressed this question by analysing the outcome of 821 consecutive patients with parotid tumours treated at one centre over 40 years and with a median 12 (range 5–30) years follow-up. Tumours were classified as ‘simple’ (discrete, mobile, < 4 cm: n=662) and ‘complex’ (deep, fixed, facial nerve palsy, ⩾4 cm: n=159). Among the ‘simple’ or clinically benign tumours, 503 patients underwent ECD; 159 patients underwent SP. In all, 32 (5%) clinically benign cases were subsequently revealed as malignant histologies (ECD, 12; SP, 20). For each group, 5- and 10-year cancer-specific survival rates were 100 and 98%, respectively. There were no differences in recurrence rates when subanalysed by surgical groups, but ECD was associated with significantly reduced morbidity (P < 0.001). This study demonstrates that ECD is a viable alternative to superficial parotidectomy for the majority of parotid tumours, associated with reduced morbidity without oncological compromise.

Adsorptive membrane chromatography for purification of plasmid DNA

Adsorptive membranes were investigated for the downstream processing of plasmid DNA by quantifying both separation efficiencies and adsorption uptake with the anion-exchange membranes. Separation efficiencies of the 10-ml Mustang-Q were measured using pulses of 6.1-kilo base pair plasmid DNA and lysozyme tracers, and comparing the responses for both conventional and reverse-flow operation. The plasmid exhibited nearly 200 plates/cm, almost as high efficiency as the protein despite the large difference in size. This behavior contrasts strongly with typical behavior for spherical porous particle packings, which predicted large decreases in efficiency with increases in tracer size. Batch adsorption isotherms for the 6.1-kilo base pair plasmid on small sheets of anion-exchange membranes at various ionic strengths showed high capacities for very large biomolecules. The maximum binding capacity for the membrane unit was calculated as 10 mg plasmid/ml, an order of magnitude greater than typical values reported for porous beads.

Treatments that weaken Pavlovian conditioned fear and thwart its renewal in rats: implications for treating human phobias

In experiments using a total of 144 albino rat subjects, the authors assessed the ability of fear-weakening treatments to prevent fear renewal (relapse). Conditioned suppression of operant behavior served as the measure of fear in an A-B-A (acquisition-treatment-test) renewal paradigm. In Experiment 1, 100 nonreinforced exposures to a feared cue during treatment (extinction) did not reduce fear renewal relative to 20 exposures. In Experiment 2, explicitly unpaired (EU) treatments thwarted both renewal and reacquisition. In Experiment 3, conditioned inhibition (CI) and differential conditioning (DC) treatments weakened renewal and resisted both reacquisition and a form of reinstatement. In Experiment 4, EU, DC, and CI treatments all thwarted renewal. Evidence suggested that the ability of the treatments to do so reflected the combined effects of transfer of extinction across treatment and test contexts and habituation to the unconditioned stimulus.

Effect of locally applied GM-CSF on oral mucositis after stem cell transplantation: a prospective placebo-controlled double-blind study

Oral mucositis is a frequent side effect of myeloablative chemo- and radiotherapy preceding stem cell transplantation. It causes pain, poor food intake, and is a port of entry for infection. We studied whether GM-CSF applied topically in the oral cavity can prevent or ameliorate this mucositis. In 36 consecutive patients undergoing a stem cell transplantation, we performed a double-blind placebo-controlled study of 300 micrograms GM-CSF in a 2% methylcellulose gel daily versus a 2% methylcellulose gel alone. Both were locally applied in the oral cavity. The primary end-point was mucositis as measured by the WHO toxicity scale for mucositis, oral assessment scale, and a subjective pain scale, all scored daily. The secondary end-points were need to give parenteral nutrition and morphine, incidence of fever and infections, and duration of neutropenia and hospitalization. No differences were found in the median subjective pain scores, WHO scores, and oral assessment scores between the placebo and the GM-CSF groups. In both groups, nine patients required morphine for pain control. Ten patients in the placebo group and 11 in the GM-CSF group received parenteral nutrition. Documented infections, use of broad-spectrum antibiotics, and number of days with fever were similar in the placebo and the GM-CSF groups. The duration of neutropenia below 0.5 x 10(9)/l (median 14.5 days in the placebo group versus 17 days in the GM-CSF group) and the duration of hospitalization (28.5 versus 29 days) was also not significantly different. We found no beneficial effect of 300 micrograms GM-CSF dissolved in a 2% methylcellulose gel applied locally for chemo- and radiotherapy-induced mucositis in patients undergoing a stem cell transplantation.

Adrenalectomy eliminates the extinction spike in autoshaping with rats

Experiment 1, using rats, investigated the effect of adrenalectomy (ADX) on the invigoration of lever-contact performance that occurs in the autoshaping situation after a shift from acquisition to extinction (called the extinction spike). Groups of rats with ADX or sham operations were trained under spaced and massed conditions [average intertrial intervals (ITI) of either 15 or 90 s] for 10 sessions and then shifted to extinction. ADX did not affect acquisition training but it eliminated the extinction spike. Plasma corticosterone levels during acquisition were shown in Experiment 2 to be similar in rats trained under spaced or massed conditions. Adrenal participation in the emotional arousal induced by conditions of surprising nonreward (e.g., extinction) is discussed.

Antagonistic regulation of Dlx2 expression by PITX2 and Msx2: implications for tooth development

The transcriptional mechanisms underlying tooth development are only beginning to be understood. Pitx2, a bicoid-like homeodomain transcription factor, is the first transcriptional marker observed during tooth development. Because Pitx2, Msx2, and Dlx2 are expressed in the dental epithelium, we examined the transcriptional activity of PITX2 in concert with Msx2 and the Dlx2 promoter. PITX2 activated while Msx2 unexpectedly repressed transcription of a TK-Bicoid luciferase reporter in a tooth epithelial cell line (LS-8) and CHO cell line. Surprisingly, Msx2 binds to the bicoid element (5'-TAATCC-3') with a high specificity and competes with PITX2 for binding to this element. PITX2 binds to bicoid and bicoid-like elements in the Dlx2 promoter and activates this promoter 45-fold in CHO cells. However, it is only modestly activated in the LS-8 tooth epithelial cell line that endogenously expresses Msx2 and Pitx2. RT-PCR and Western blot assays reveal that two Pitx2 isoforms are expressed in the LS-8 cells. We further demonstrate that PITX2 dimerization can occur through the C-terminus of PITX2. Msx2 represses the Dlx2 promoter in CHO cells and coexpression of both PITX2 and Msx2 resulted in transcriptional antagonism of the Dlx2 promoter. Electrophoretic mobility shift assays demonstrate that factors in the LS-8 cell line specifically interact with PITX2. Thus, Dlx2 gene transcription is regulated by antagonistic effects between PITX2, Msx2, and factors expressed in the tooth epithelia.

Independent regulation of Dlx2 expression in the epithelium and mesenchyme of the first branchial arch

Dlx2, a member of the distal-less gene family, is expressed in the first branchial arch, prior to the initiation of tooth development, in distinct, non-overlapping domains in the mesenchyme and the epithelium. In the mesenchyme Dlx2 is expressed proximally, whereas in oral epithelium it is expressed distally. Dlx2 has been shown to be involved in the patterning of the murine dentition, since loss of function of Dlx1 and Dlx2 results in early failure of development of upper molar teeth. We have investigated the regulation of Dlx2 expression to determine how the early epithelial and mesenchymal expression boundaries are maintained, to help to understand the role of these distinct expression domains in patterning of the dentition. Transgenic mice produced with a lacZ reporter construct, containing 3.8 kb upstream sequence of Dlx2, led to the mapping of regulatory regions driving epithelial but not mesenchymal expression in the first branchial arch. We show that the epithelial expression of Dlx2 is regulated by planar signalling by BMP4, which is coexpressed in distal oral epithelium. Mesenchymal expression is regulated by a different mechanism involving FGF8, which is expressed in the overlying epithelium. FGF8 also inhibits expression of Dlx2 in the epithelium by a signalling pathway that requires the mesenchyme. Thus, the signalling molecules BMP4 and FGF8 provide the mechanism for maintaining the strict epithelial and mesenchymal expression domains of Dlx2 in the first arch.

Postoperative pulmonary edema

BACKGROUND

Noncardiogenic pulmonary edema may be caused by upper airway obstruction due to laryngospasm after general anesthesia. This syndrome of "negative pressure pulmonary edema" is apparently well known among anesthesiologists but not by other medical specialists.

METHODS

We reviewed the cases of seven patients who had acute pulmonary edema postoperatively.

RESULTS

There was no evidence of fluid overload or occult cardiac disease, but upper airway obstruction was the most common etiology. Each patient responded quickly to therapy without complications.

CONCLUSIONS

Of the seven patients with noncardiogenic postoperative pulmonary edema, at least three cases were associated with documented laryngospasm causing upper airway obstruction. This phenomenon has been reported infrequently in the medical literature and may be underdiagnosed. Immediate recognition and treatment of this syndrome are important. The prognosis for complete recovery is excellent.

Molecular control of odontogenic patterning: positional dependent initiation and morphogenesis

We have previously proposed that the patterning of the mammalian dentition is determined by an odontogenic homeobox code, whereby positional specification of odontogenic ectomesenchymal cell populations in a given region of the first branchial arch are determined by the combination of different homeobox genes expressed, described in detail in (1). Here we describe the first functional evidence for such a mechanism, and show that development of different types of teeth is controlled by independent genetic pathways. We suggest a mechanism whereby patterning is determined by position dependent control of tooth germ initiation, and propose that the pathway of morphogenesis is directly linked to the early mesenchymal expression of homeobox genes.

Patterning of the murine dentition by homeobox genes

Homeobox genes have been shown to be important for the regulation of pattern formation of many systems during embryogenesis. Overlapping domains of Hox gene expression in the paraxial mesoderm have been suggested to create a combinatorial code of expression (Hox code) specifying the structures of individual segments such as the vertebrae. Hox genes are not expressed in the neural crest cells contributing to tooth formation, and so a Hox code can not be involved in patterning the dentition. It has previously been proposed that other, non-Hox homeobox genes may pattern the dentition. Expression data in this paper shows that there is a pattern of overlapping domains of homeobox gene expression in facial mesenchyme prior to the initiation of tooth development. We propose that expression of these genes constitutes an odontogenic homeobox code which patterns the dentition.

Role of Dlx-1 and Dlx-2 genes in patterning of the murine dentition

The molecular events of odontogenic induction are beginning to be elucidated, but until now nothing was known about the molecular basis of the patterning of the dentition. A role for Dlx-1 and Dlx-2 genes in patterning of the dentition has been proposed with the genes envisaged as participating in an ‘odontogenic homeobox gene code’ by specifying molar development. This proposal was based on the restricted expression of the genes in molar ectomesenchyme derived from cranial neural crest cells prior to tooth initiation. Mice with targeted null mutations of both Dlx-1 and Dlx-2 homeobox genes do not develop maxillary molar teeth but incisors and mandibular molars are normal. We have carried out heterologous recombinations between mutant and wild-type maxillary epithelium and mesenchyme and show that the ectomesenchyme underlying the maxillary molar epithelium has lost its odontogenic potential. Using molecular markers of branchial arch neural crest (Barx1) and commitment to chondrogenic differentiation (Sox9), we show that this population alters its fate from odontogenic to become chondrogenic. These results provide evidence that a subpopulation of cranial neural crest is specified as odontogenic by Dlx-1 and Dlx-2 genes. Loss of function of these genes results in reprogramming of this population of ectomesenchyme cells into chondrocytes. This is the first indication that the development of different shaped teeth at different positions in the jaws is determined by independent genetic pathways.

Acute hyperglycemia following intraperitoneal irrigation with 10% dextrose in a patient with pseudomyxoma peritonei

Pseudomyxoma peritonei is a condition characterized by the production of large amounts of mucopolysaccharide by a neoplastic epithelium. Although surgical debulking and removal of the mucinous ascites may be attempted, complete removal of the material is often impossible. Intraperitoneal lavage with 10% dextrose in water (D10W) has been advocated to prevent reaccumulation of the mucus and complications such as bowel obstruction requiring repeat laparotomy. We describe a patient undergoing operation for a large abdominopelvic mass. At laparotomy, a mucinous cystadenocarcinoma of the ovary was found with a great deal of tenacious, mucinous ascites and peritoneal implants. In an effort to more efficiently remove the mucus and prevent subsequent reaccumulation, intraperitoneal irrigation with 10% dextrose in water (D10W) was performed. The patient, who gave no history of prior glucose intolerance, was soon thereafter found to be profoundly hyperglycemic (serum glucose >500 mg/dl). She was treated with insulin and recovered without evident sequelae. Practitioners should be aware of this potentially dangerous complication associated with intraperitoneal dextrose instillation.

Administration of PRN medication by mental health nurses

The administration of PRN medication by mental health nurses is an important, yet poorly explored aspect of psychiatric inpatient care. An examination of nurses' reasons for administering PRN medication is essential in ensuring its appropriate and effective use. Data were gathered from the drug charts of 44 inpatients on two acute psychiatric wards. Most PRN medication was given orally and the most frequently administered drugs were procyclidine, lorazepam, ibuprofen, diazepam and droperidol. The main reason for administering PRN medication was because patients had 'requested' it. Results were broadly consistent with previous research. It is recommended that nurses should give clear and specific reasons for administering PRN medication based on a valid assessment. Implications for clinical practice and further research are also discussed.

Hemolytic uremic syndrome after high dose chemotherapy with autologous stem cell support

BACKGROUND

Chemotherapy intensification may lead to new forms of toxicity such as hemolytic uremic syndrome.

METHODS

Three patients are described who developed this complication 4 to 6 months after high dose chemotherapy followed by autologous stem cell support. The literature on this subject is reviewed.

RESULTS

One patient was conditioned with BEAC (carmustine, etoposide, cytosine arabinoside, and cyclophosphamide) and received autologous bone marrow. The other two underwent triple peripheral stem cell transplantation after conditioning with CTC (carboplatin, cyclophosphamide, and thiotepa). Symptoms were hypertension, microangiopathic hemolytic anemia, thrombocytopenia, and renal insufficiency. One patient had a retinal vein thrombosis. One patient died of a cardiac arrest shortly after the diagnosis was made. The remaining two achieved a partial remission: one with fresh frozen plasma without plasmapheresis and fresh frozen plasma, but improved on high dose intravenous immunoglobulin and vincristine.

CONCLUSIONS

Hemolytic uremic syndrome is a serious complication of the more intensive chemotherapy made possible by stem cell support. Because of the rapidly growing indications for this approach, an increase in this type of vascular complication is expected.

Corynebacterium CDC group JK (Corynebacterium jeikeium) sepsis in haematological patients: a report of three cases and a systematic literature review

We describe 3 patients with Corynebacterium jeikeium sepsis in neutropenic phase during treatment for acute myeloid leukaemia. Fever was the first symptom. All had a central venous catheter which was removed. Two patients developed subcutaneous nodules containing pus when the neutrophil count recovered; 1 had intracutaneous and pulmonary lesions. They were treated with vancomycin and recovered when the neutrophil count started to rise. A review of 80 neutropenic patients with C. jeikeium sepsis reported in the literature, together with our 3 cases indicates that risk factors for infection are the presence of a central venous catheter, being an adult male or postmenopausal female, profound and prolonged neutropenia and exposure to multiple antibiotics. Skin lesions are reported in 48% and pulmonary lesions in 36% of the patients. The overall mortality is 34% but in patients with recovery of the bone marrow only 5%. Therefore haematopoietic growth factors should be considered in neutropenic patients with C. jeikeium infection.

The spatial localization of Dlx-2 during tooth development

The spatial distribution of Dlx-2 protein during murine tooth development has been investigated using immunohistochemistry with Dlx-2 antibodies. In common with several other homeobox genes expressed in toothgerms, Dlx-2 shows a multiphasic distribution in both epithelially and mesenchymally derived structures. This localization shows a number of similarities with the expression of Msx-2 and suggests a role for Dlx-2 in tooth initiation and tissue patterning.

Research considerations: guardianship and the vulnerable elderly

1. The use of legal guardianship for the elderly is increasing due to the increase in numbers of vulnerable elders and the subsequent dynamic effect on their families and communities. 2. Although the guardianship system provides a necessary service, the effects on "wards of the court" can lead to further physical and psychological deterioration due to their loss of all major decision making powers. 3. There is an assumption that the closest living relative would be the best guardian. There also is an assumption that elders who are confused or disoriented in dealing with money or business affairs require full guardianship. The validity of these assumptions, without assessment and intervention of geriatric specialists, is questionable.

Differential expression of insulin-like growth factors I and II (IGF I and II), mRNA, peptide and binding protein 1 during mouse palate development: comparison with TGF beta peptide distribution

Development of the mammalian secondary palate involves a series of epithelial mesenchymal interactions: during one of these, a mesenchymal signal specifies regionally distinct palatal epithelial differentiation. Extracellular matrix molecules and soluble growth factors may be involved in this signalling process. In this study, we have mapped the expression of the genes for insulin-like growth factors (IGF I and II), the peptides they encode, and the IGF binding protein 1 (IGF BP-1) during murine palatogenesis (embryonic days (E) 12-15). IGF-I gene expression was below detectable levels in the craniofacial region at all ages. IGF-I peptide was at the threshold of immunocytochemical detection and widely distributed in the palatal mesenchyme, decreasing in staining intensity from E12 to E14. By contrast, IGF-II mRNA was intensely localised in several tissues. IGF-II gene expression within the forming palate was developmentally regulated. In the vertical palatal shelves (E12 to E13) IGF-II gene expression was absent. On early E14, in the horizontal prefusion palate, significant expression was present in the palatal mesenchyme, but not the epithelium. Once palatal fusion had occurred, mesenchymal expression fell rapidly to undetectable levels. IGF-II mRNA was next detectable in the secondary palate on late E15 at sites of membranous bone formation. By contrast to the mRNA distribution, IGF-II peptide was localised predominantly in the palatal epithelia (particularly the nasal and medial edge epithelia) but also in the mesenchyme of the E14 prefusion palate. Significantly, the IGF binding protein had a similar distribution pattern to the IGF-II peptide. At all ages, the developing tongue myotubes labelled heavily for IGF-II mRNA, protein and binding protein. These data suggest that IGF-II may play a localised paracrine role during murine palatogenesis, perhaps in the mesenchymal signalling of epithelial differentiation. IGF-II may also serve to coordinate the development of the tongue and palate. The distribution of IGF-II peptide was very similar to that of TGF-beta, suggesting a possible interactive role of these growth factors during palate development. Finally, evidence that the IGF-II gene is imprinted (Ferguson-Smith et al. 1991) and may be the target for uniparental disomy in the human Beckwith Wiedemann syndrome (Henry et al. 1991), which is characterised by the overgrowth of tissues (especially the tongue) expressing IGF II in the embryo, indicates the necessity of reanalysing human cleft palate families for disruption (including uniparental disomy) of the genes encoding IGFs, their receptors and binding proteins.

Incidence and clinical epidemiology of streptococcal septicemia during treatment of acute myeloid leukemia

The incidence and outcome of streptococcal septicemia was analyzed in 76 consecutive patients with newly diagnosed and relapsed acute myeloid leukemia. They received 215 courses of remission induction or intensive consolidation treatment. There were 31 different episodes of streptococcal septicemia in 27 patients, making these microorganisms the most frequently encountered bacteria in blood cultures. This high incidence coincided with the introduction of selective intestinal decontamination. In 24 episodes (20 patients) there was a fast recovery, but 7 patients developed pulmonary symptoms resulting in death due to respiratory failure in 5 of them. The infections all occurred in the phase of maximum bone marrow suppression 1-3 weeks after the start of the chemotherapy. Streptococcal septicemia was not limited to patients treated with cytosine arabinoside but also occurred in patients treated with other regimens of intensive chemotherapy. In 28 episodes there were no focal signs of infection, but in half there were symptoms of treatment induced gastrointestinal toxicity. The streptococci probably invade through oral and gastrointestinal mucosa damaged by the chemotherapy. Selective decontamination may play a promoting role.

Analysis of skin grafting techniques in the fetal rabbit

The experimental model reported here was developed initially to examine the possibility of in utero coverage of congenital soft tissue defects using several types of reconstructive techniques. To pursue this, full-thickness skin grafts, pedicle flaps, and skin "islands" were fashioned on the backs of fetal rabbits; equivalent adult control wounds were also created. While all pedicle flaps and skin islands remained viable, none of the full-thickness grafts survived in the fetus. All adult control flaps, skin islands, and skin grafts were viable. Angiogenesis is crucial to full-thickness skin graft survival. These observations suggest that the death of full-thickness fetal skin grafts may be related to a failure of neovascularization in the graft bed. Further analysis using this model may help elucidate the factors involved in fetal angiogenesis. Additionally, this model may permit testing of putative angiogenic factors applied under a full-thickness skin graft; graft survival offers an easy, objective, and quantifiable means of data analysis.

Analysis of transforming growth factor beta receptor binding in embryonic, fetal, and adult rabbit fibroblasts

Adult wound repair traits including inflammation, fibroplasia, and collagen deposition are not seen at fetal wound sites. This observation raised questions about regulatory mechanisms extant in fetal healing. Transforming growth factor beta (TGF-beta) is an important regulatory polypeptide known to orchestrate fibroplasia and collagen synthesis during adult wound repair. Previous studies have suggested that the wounded rabbit fetus is capable of responding with these adult characteristics if provided with exogenous TGF-beta. In order to test whether the observed in vivo effects of TGF-beta in the rabbit fetus might be due to a direct effect on the fibroblast, TGF-beta receptor binding characteristics of early passage cultured embryonic (14 days' gestation), fetal (24 days' gestation), and adult rabbit fibroblasts were studied by flow cytometry. Experiments were carried out using fluorescein-conjugated TGF-beta (F-TGF-beta) with analysis on an EPICS V flow cytometer. F-TGF-beta was incubated with each of the three fibroblast types at 37 degrees C after which time the cells were washed twice and analyzed with a minimum of 10(5) cells for each data point. F-TGF-beta bound rapidly and reversibly to the embryonic, fetal, and adult fibroblasts with saturation being achieved at 1 nmol/L for fetal and adult cells, and 8 nmol/L in the embryonic fibroblasts. Saturating concentrations of F-TGF-beta yielded mean channel numbers (a function of relative amounts of F-TGF-beta-bound) of 172, 114, and 97 for embryonic, fetal, and adult cells, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of intraoperative ultrasound during hepatic resection in pediatric patients

Five pediatric patients with primary liver tumors were evaluated preoperatively with ultrasound (US), computerized tomography (CT), and angiography, and tentative operative plans were formulated. Intraoperative US was subsequently used to examine these children, resulting in changes in operative strategy of all five patients despite their extensive preoperative evaluations. Intraoperative ultrasound appears to provide the most accurate assessment of both the extent of tumor and its vascular relationships. Thus, operative strategies may be precisely tailored on the basis of such information, allowing rational resection where appropriate, while futile attempts at removal of inoperable lesions may be averted.

Characterization and quantitation of wound matrix in the fetal rabbit

Fetal response to injury has been characterized by the deposition of a matrix that is not primarily collagen. This study was designed to identify this matrix, in order to better understand the fetal mechanism of tissue repair. Silastic/polyvinyl alcohol sponge (PVA) wound implants were placed paravertebrally in 24-day gestation (31 days = term) fetal (n = 65) and adult (n = 43) rabbits and then harvested from one hour to 6 days post-wounding. Histologic analysis of the fetal wound matrix deposited in the PVA implants suggested the presence of glycosaminoglycans (GAG) rather than the collagen found in adult wound implants. To further analyze the fetal wound matrix, the GAG content was quantitated using an Alcian Blue dye-binding assay. Results showed significantly increased (p less than 0.05) GAG deposition on days 2-6 in the fetal wound compared to the adult wound. Fetal GAG levels were approximately three times those of the adult during this period. Separation of individual GAG species by cellulose acetate electrophoresis demonstrated that the GAG matrix of the fetal wound was composed predominantly of hyaluronic acid. This finding was confirmed by selective enzymatic digestion of separated GAG species using highly specific polysaccharidases. These observations of hyaluronic acid deposition in the fetal wound may be ascribed an important physiologic role by providing a more fluid and malleable matrix rather than a restrictive matrix composed of collagen. This new evidence coupled with earlier findings of the lack of an acute inflammatory response in the fetus further supports the hypothesis that the fetal response to injury is significantly different from the adult response.

Preparation of microgram quantities of BaP-DNA adducts using isolated rat hepatocytes in vitro

The analysis of carcinogen-DNA adducts generally requires the preparation (by chemical or biological means) of DNA adduct standards, in amounts sufficient for chemical characterization. We have established conditions for the in vitro biological preparation of microgram quantities of DNA adducts derived from benzo[a]pyrene (BaP), fluoranthene and 7,12-dimethylbenzanthracene, using isolated rat hepatocytes. The metabolic activation of 180 microM BaP by isolated rat hepatocytes in a calf-thymus-DNA (CT-DNA)-supplemented medium resulted in the formation of 2.9 micrograms of BaP adducted to 56.7 mg of DNA. The average level of binding in this experiment was 148 +/- 8 pmol BaP bound/1 mg DNA, which compares favorably to the 10-30 pmol BAP/1 mg DNA which is typical of mouse skin adducts in vivo. In another experiment, BaP-DNA adduct formation in calf-thymus DNA added to hepatocyte incubations was further increased to 327 +/- 27 pmol/mg DNA, by physical shearing of the DNA prior to the incubation. The HPLC profile of the BaP adducts produced using hepatocytes plus CT-DNA is virtually indistinguishable from that produced by tumor-initiating doses of BaP applied to mouse skin in vivo, and the major DNA adduct formed by the hepatocytes co-elutes with the (+)-anti-diol-epoxide adduct of deoxyguanosine. Similar experiments using fluoranthene and 7,12-dimethylbenzanthracene also resulted in substantial DNA adduct formation; however, incubations using dibenz[a,h]anthracene did not. These results indicate that isolated rat hepatocytes in vitro can be useful for the preparation of DNA adducts of a number of polycyclic aromatic hydrocarbons, in quantities sufficient for chemical characterization.