Development and utility of the FDA 'GutProbe' DNA microarray for identification, genotyping and metagenomic analysis of commercially available probiotics

AIM

Lactic acid bacteria are beneficial microbes added to many food products and dietary supplements for their purported health benefits. Proper identification of bacteria is important to assess safety as well as proper product labelling. A custom microarray (FDA GutProbe) was developed to verify accurate labelling in commercial dietary supplements.

METHODS AND RESULTS

Strain-specific attribution was achieved with GutProbe array which contains genes from the most commonly found species in probiotic supplements and food ingredients. Applied utility of the array was assessed with direct from product DNA hybridization to determine (i) if identification of multiple strains in one sample can be conducted and (ii) if any lot-to-lot variations exist with eight probiotics found on the US market.

CONCLUSIONS

GutProbe is a useful tool in identifying a mixture of microbials in probiotics and did reveal some product variations. In addition, the array is able to identify lot-to-lot differences in these products. These strain level attribution may be useful for routine monitoring of batch variation as part of a 'Good Manufacturing Practices' process.

SIGNIFICANCE AND IMPACT OF THE STUDY

The FDA GutProbe is an efficient and reliable platform to identify the presence of microbial ingredients and determining microbe differences in dietary supplements. The GutProbe is a fast, rapid method for direct community profiling or food matrix sampling.

Impact of five commercial baits containing chitin synthesis inhibitors on the protist community in Reticulitermes flavipes (Isoptera: Rhinotermitidae)

Eastern subterranean termite, Reticulitermes flavipes (Kollar), workers were continuously exposed to one of five chitin synthesis inhibiting (CSI) active ingredients and the protist community from the hindgut quantified biweekly for 21 d. The CSIs tested included commercially available formulations of diflubenzuron, hexaflumuron, lufenuron, noviflumuron, and novaluron. Results showed termites exposed to CSIs had a significant decrease (>or=30%) in the estimated total protist population after 3 d, regardless of treatment. Protist species impacted were Dinenympha fimbriata, D. gracilis, Microjoenia fallax, Pyrsonympha vertens, and Trichonympha agilis and could be indicative of weakened digestive homeostasis, but further studies are needed. We also provide evidence that lufenuron is highly toxic and discuss some of the implications this might have on termite management practices.

158. THE UNFOLDED PROTEIN RESPONSE MAY CONTRIBUTE TO GLUCOCORTICOID-INDUCED PLACENTAL GROWTH RESTRICTION IN THE RAT VIA INCREASED PLACENTAL EXPRESSION OF HEAT SHOCK PROTEIN 70

Perturbations of normal endoplasmic reticulum (ER) physiology occur in a number of pathological conditions, including diabetes and preeclampsia. These pathologies are associated with elevated levels of inappropriately folded proteins and induction of ER stress. Accumulation of misfolded proteins induces the unfolded protein response which increases ER protein folding capacity and promotes ER-associated degradation of unfolded proteins. Glucocorticoids are essential for maturation of fetal organs, however excess exposure during pregnancy retards fetal and placental growth. Glucocorticoids also induce ER stress within macrophages, which reside within the placenta, and activate immune responses which can lead to oxidative stress and subsequent placental dysfunction. We hypothesised that excess glucocorticoid exposure would induce ER stress within the placenta and contribute to restriction of fetal and placental growth. This study compared placentas (n = 6/group) for control (Con) and dexamethasone-exposed pregnancies (Dex; 0.75 μg/mL drinking water from day 13 of gestation) at days 16 and 22 of gestation in the rat (term = 23 days). Placentas were dissected into junctional (JZ) and labyrinth (LZ) zones for separate analysis. Quantitative PCR was used to determine expression of mRNA for markers of ER stress, including heat shock factors (HSF-1 and HSF-2), heat shock proteins (HSP-70 and HSP-90) and C/EBP homologous protein (CHOP10). HSF-1 expression increased 2- to 4-fold from day 16 to 22 in both placental zones, but was not increased by glucocorticoids. Dex-exposure increased HSP-70 expression 2- to 3-fold in the LZ at both days of gestation, indicative of an ER stress response. Similar patterns for JZ expression of HSP-70 were observed. JZ expression of HSP-90 was also upregulated by Dex at day 22 but not day 16. CHOP10 was not induced by Dex-administration in either zone at either gestational time, which suggests that rather than activation of the ATF6/PERK pathway, the activation of ER stress is likely to be via XBP1 induction.

Effect of dermatan sulfate on the indentation and tensile properties of articular cartilage

OBJECTIVE

This paper examines the hypothesis that the dermatan sulfate (DS) chain on decorin is a load carrying element in cartilage and that its damage or removal will alter the material properties.

METHODS

To test this hypothesis, indentation and tensile testing of cartilage from bovine patella were performed before and after digestion with chondroitinase B (cB). Removal of significant amounts of DS by cB digestion was verified by Western blot analysis of proteoglycans extracted from whole and sectioned specimens. Specimens (control and treated) were subjected to a series of step-hold displacements. Elastic modulus during the step rise (rapid modulus) and at equilibrium (equilibrium modulus), and the relaxation function during each step was measured for test (cB and buffer) and control (buffer alone) conditions.

RESULTS

cB had no effect on any of the viscoelastic mechanical properties measured, either in indentation or tension.

CONCLUSION

Removing or damaging approximately 50% of the DS had no effect on the mechanical properties, strongly suggesting that DS either carries very low load or no load.

Evaluation of fracture toughness of cartilage by micropenetration

Failure properties of cartilage are important in injury repair and disease, but few methods exist for measuring these properties, especially in small animals. To meet this need, a new indentation/penetration method for measuring fracture toughness of cartilage is proposed. During indentation, a conical tip is displaced into the surface of the cartilage, causing first a non-penetrating indentation, and then a penetration into the tissue. The method assumes that tissue penetration occurs during periods of "rapid work", which are identified from a curve of work rate vs. time. Total penetration depth is determined by summing the displacement during these periods. Fracture work is the work that occurs during "rapid work", or penetration, and fracture toughness defined as the fracture work divided by one-half the penetrated surface area of the indenting tip. The method was validated by indentation testing of bovine cartilage. Penetrating indentations with a conical tip were performed in bovine patellar cartilage and depth of penetration and fracture toughness predicted. For comparison with the indentation data, depth of penetration was measured in histological sections. These measurements agreed well with the predicted depth. Predicted fracture toughness also agreed with values measured via a macroscopic test. This newly described method has promise as a general method for measuring fracture toughness in cartilage, particularly in small animals, since penetrating tips with small tip radius can be manufactured and penetration may be accomplished in cartilage of minimal thickness.

Phosphatidylinositol-3 kinase inhibitors reproduce the selective antiproliferative effects of imatinib on chronic myeloid leukaemia progenitor cells

We investigated the role of the phosphatidylinositol-3 kinase (PI-3K) pathway in regulating the proliferation of primary chronic myeloid leukaemia (CML) progenitor cells by using imatinib to inhibit the activity of p210(Bcr-Abl). The effect of imatinib on the expression of PI-3K pathway proteins was investigated by kinase assays and Western blotting; PI-3K was inhibited by wortmannin or LY294002, Jak2 by AG490 and farnesylation by FTI II; progenitor cell proliferation (self-renewal) was measured by growing myeloid colonies in vitro, then replating them to observe secondary colony formation. Suppression of p210(Bcr-Abl) with imatinib indirectly suppressed the activity of PI-3K and its downstream targets (Erk, Akt and p70S6 kinase), thereby implicating the PI-3K pathway in p210(Bcr-Abl)-mediated signalling in primary CML progenitor cells. The PI-3K inhibitors, wortmannin and LY294002 reproduced the differential effects of imatinib on normal and CML progenitor cell proliferation in vitro by increasing normal cell (P = 0.001) and reducing CML cell proliferation (P = 0.0003). This differential effect was attributable to dysregulated signalling by granulocyte colony-stimulating factor in CML. The responses of individual patient's cells to wortmannin correlated with their responses to imatinib (P = 0.004) but not their responses to AG490 (Jak2 kinase inhibitor) or FTI II (farnesyltransferase inhibitor). Individual responses to wortmannin also correlated with responses to interferon alpha (IFNalpha) (P = 0.016). Imatinib-resistant K562 cells were sensitive to LY294002. Inhibition of the PI-3K pathway may be common to imatinib and IFNalpha and reflect dysregulated cytokine signalling. As imatinib-resistant cells remained sensitive to wortmannin and LY294002, targeting the PI-3K pathway may provide an alternative therapy for imatinib-resistant patients.

Effect of Specimen Thickness on Fracture Toughness of Bovine Patellar Cartilage

Fracture toughness and crack tip opening angle were measured for bovine patellar cartilage using modified single-edged notch specimens of two thicknesses. There was no difference in fracture toughness between thin (0.7 mm) versus relatively thick (2.7 mm) specimens, but the crack tip opening angle at initiation of crack propagation was larger for the thin specimens (106 deg) than for the thick specimens (70 deg). Fracture toughness of the bovine patellar cartilage 1.03kJ/m2 was not statistically different than that reported previously for canine patellar cartilage 1.07kJ/m2 employing the same methods. Large variation in measurements for both bovine and canine cartilage are in part attributable to variation between individual animals, and are consistent with variation in other mechanical property measurements for articular cartilage. The observed reduction in crack tip opening angle with increased specimen thickness is consistent with behavior of some engineering materials, and demonstrates that specimen thickness influences fracture behavior for bovine patellar cartilage.

Contact-mediated inhibition of human haematopoietic progenitor cell proliferation may be conferred by stem cell antigen, CD34

INTRODUCTION

The function of CD34, a transmembrane sialomucin expressed by human haematopoietic progenitor cells, is poorly understood. Its structure suggests it may act as a cell adhesion and signalling molecule.

MATERIALS AND METHODS

KGIa cells and primary CD34-positive marrow cells were tested for their ability to aggregate in the presence of the anti-CD34 antibody QBEND10; CFU-GM colonies were grown using standard methods and tested for their content of colony-forming cells by replating; 'haematons' were isolated from marrow by filtration; the phosphorylation of CD34 was investigated by immunoprecipitation and Western blotting

DISCUSSION

CD34-positive cells in human bone marrow, like KG1a cells, aggregate when incubated with QBEND10. Staining aggregates with anti-CD34-FITC revealed that aggregation involved co-localisation of CD34 at intercellular binding sites. We examined myeloid colonies (CFU-GM) grown from normal human bone marrow cells, and multicellular aggregates ('haematons') separated from freshly aspirated marrow by filtration, and found CD34-positive cells bound together with co-localisation of the CD34 at the binding sites. This finding shows that CD34-positive cell-cell adhesion occurs physiologically in vitro and in vivo. QBEND10-induced aggregation of KG1a and CD34-positive cells was enhanced by staurosporine (a protein kinase C inhibitor) and inhibited by genistein (a protein tyrosine kinase inhibitor). Moreover, aggregated cells had increased phosphorylation of tyrosine on CD34 and translocation of protein kinase C (PKC) to the cytoplasm, compared with non-aggregated cells. We used the ability of primary colonies to produce secondary colonies on replating as a functional parameter and found that the replating ability of the colonies was increased by treatment with genistein (P=0.003). In addition, the ability of individual samples of primary CD34-positive cells to undergo QBEND10-induced aggregation and the ability of CD34-positive cell-derived colonies to produce secondary clones on replating were inversely related (r=0.86).

CONCLUSION

Our results suggest that homotypic aggregation of haematopoietic progenitor cells may be an important mechanism for preventing inappropriate proliferation in vivo. Thus, regulation of expression of the CD34 molecule may play an important role in maintaining the normal level of haematopoietic activity by contact-mediated inhibition of progenitor cell proliferation.

The benefit of a special elective gynecologic oncology program for obstetrics and gynecology residents

OBJECTIVE

To assess the benefit of a special elective gynecologic oncology program for Obstetrics and Gynecology (Ob/Gyn) residents.

METHODS

We reviewed our housestaff records from July 1992 to June 1998 and the National Residency Matching Program (NRMP) subspeciality match results for gynecologic oncology from its inception in 1994 to 1999.

RESULTS

From July 1992 to June 1998, a total of 146 residents participated in our elective program. Of the 104 candidates who went through our program and subsequently participated in the NRMP, 55 (53%) obtained match positions. After completion of the elective, 42 of the 146 residents (29%) did not participate in the NRMP for gynecologic oncology and therefore were not eligible to obtain match appointments. During the study period, there were 255 other residents in the United States who applied for gynecologic oncology fellowship positions through the NRMP and did not participate in our program. Of these 255 candidates, 137 (54%) matched.

CONCLUSION

The percentage of residents who went through our program, participated in the NRMP, and obtained fellowships did not differ significantly from the percentage of residents who matched without participating in the program. However, almost one-third of the residents who went through our program did not participate in the NRMP. The reasons for their lack of participation were not formally evaluated, but are likely related to a personal decision to pursue another carrer pathway, a decision facilitiated by their experience in our program. Therefore, it appears that the main benefits of the program are to help potential candidates decide whether or not to pursue a career in gyencologic oncology and to aid fellowship programs in identifying exceptional candidates for subspecialty training.

Progenitor cells from patients with advanced phase chronic myeloid leukaemia respond to STI571 in vitro and in vivo

STI571 targets p210(BCR-ABL) in chronic myeloid leukaemia (CML). In vitro, STI571 reduces self-replication (replating ability) by chronic-phase CML CFU-GM. Here, we studied CFU-GM in advanced-phase (accelerated and blast crisis) CML. The numbers and self-replication of CFU-GM in advanced phase were greater than in the chronic phase. Self-replication by CFU-GM from advanced phase patients was reduced by STI571 or IFN alfa to the same extent as in the chronic phase. The reduced replating ability induced by STI571 correlated with that induced by IFN alpha (r=0.73). STI571 treatment in vivo also reduced replating ability and the numbers of CFU-GM/ml of blood.

Collagen architecture and failure processes in bovine patellar cartilage

Cartilage fails by fibrillation and wearing away. This study was designed to identify the microscopic failure processes in the collagen network of bovine cartilage using scanning electron microscopy. Cartilage samples from fibrillated cartilage from the bovine patella were removed from the bone, fixed, digested to remove proteoglycans, freeze-fractured, and processed for SEM. The architecture of the collagen network in the normal cartilage was first defined, and then the failure processes were identified by examining sites of fibrillation and at crack tips. The bovine patellar cartilage was organised with a superficial layer composed of 3-5 lamina, attached to a sub-superficial tissue by angled bridging fibrils. Collagen in the sub-superficial tissue was organised in lamina oriented in the radial direction up to the transition zone. Failure of the system occurred by cracks forming in superficial layer and lamina, creating flaps of lamina that rolled up into the larger 'fronds'. Larger cracks not following the laminar planes occurred in the transition, mid, and deep zones. Failure at the crack tips in the sub-superficial tissue appeared to be by peeling of collagen fibrils, as opposed to breaking of collagen fibrils, suggesting a 'glue' bonding the collagen fibrils in a parallel fashion. Cracks propagated by breaking these bonds. This bond could be a site of disease action, since weakening of the bond would accelerate crack propagation.

BCR-ABL and interleukin 3 promote haematopoietic cell proliferation and survival through modulation of cyclin D2 and p27Kip1 expression

Although it is evident that BCR-ABL can rescue cytokine-deprived hematopoietic progenitor cells from cell cycle arrest and apoptosis, the exact mechanism of action of BCR/ABL and interleukin (IL)-3 to promote proliferation and survival has not been established. Using the pro-B cell line BaF3 and a BaF3 cell line stably overexpressing BCR-ABL (BaF3-p210), we investigated the proliferative signals derived from BCR-ABL and IL-3. The results indicate that both IL-3 and BCR-ABL target the expression of cyclin Ds and down-regulation of p27(Kip1) to mediate pRB-related pocket protein phosphorylation, E2F activation, and thus S phase progression. These findings were further confirmed in a BaF3 cell line (TonB.210) where the BCR-ABL expression is inducible by doxycyclin and by using the drug STI571 to inactivate BCR-ABL activity in BaF3-p210. To establish the functional significance of cyclin D2 and p27(Kip1) expression in response to IL-3 and BCR-ABL expression, we studied the effects of ectopic expression of cyclin D2 and p27(Kip1) on cell proliferation and survival. Our results demonstrate that both cyclin D2 and p27(Kip1) have a role in BaF3 cell proliferation and survival, as ectopic expression of cyclin D2 is sufficient to abolish the cell cycle arrest and apoptosis induced by IL-3 withdrawal or by BCR-ABL inactivation, while overexpression of p27(Kip1) can cause cell cycle arrest and apoptosis in the BaF3 cells. Furthermore, our data also suggest that cyclin D2 functions upstream of p27(Kip1), cyclin E, and cyclin D3, and therefore, plays an essential part in integrating the signals from IL-3 and BCR-ABL with the pRB/E2F pathway.

Depression and blood types

A sample of 108 normal volunteers (grouped as blood Types O, A, and B/AB) were administered the Beck Depression Inventory. The results suggest that the association between depression and blood Type O that has been found for hospitalized patients can also be observed in normal patients.

The transmembrane domain of syntaxin 1A is critical for cytoplasmic domain protein-protein interactions

Assembly of the plasma membrane proteins syntaxin 1A and SNAP-25 with the vesicle protein synaptobrevin is a critical step in neuronal exocytosis. Syntaxin is anchored to the inner face of presynaptic plasma membrane via a single C-terminal membrane-spanning domain. Here we report that this transmembrane domain plays a critical role in a wide range of syntaxin protein-protein interactions. Truncations or deletions of the membrane-spanning domain reduce synaptotagmin, alpha/beta-SNAP, and synaptobrevin binding. In contrast, deletion of the transmembrane domain potentiates SNAP-25 and rbSec1A/nsec-1/munc18 binding. Normal partner protein binding activity of the isolated cytoplasmic domain could be "rescued" by fusion to the transmembrane segments of synaptobrevin and to a lesser extent, synaptotagmin. However, efficient rescue was not achieved by replacing deleted transmembrane segments with corresponding lengths of other hydrophobic amino acids. Mutations reported to diminish the dimerization of the transmembrane domain of syntaxin did not impair the interaction of full-length syntaxin with other proteins. Finally, we observed that membrane insertion and wild-type interactions with interacting proteins are not correlated. We conclude that the transmembrane domain, via a length-dependent and sequence-specific mechanism, affects the ability of the cytoplasmic domain to engage other proteins.

The influence of INK4 proteins on growth and self-renewal kinetics of hematopoietic progenitor cells

This study investigated the influence of expression of proteins of the INK4 family, particularly p16, on the growth and self-renewal kinetics of hematopoietic cells. First, retrovirus-mediated gene transfer (RMGT) was used to restore p16(INK4a) expression in the p16(INK4a)-deficient lymphoid and myeloid cell lines BV173 and K562, and it was confirmed that this inhibited their growth. Second, to sequester p16(INK4a) and related INK4 proteins, cyclin-dependent kinase 4 (CDK4) was retrovirally transduced into normal human CD34(+) bone marrow cells and then cultured in myeloid colony-forming cell (CFC) assays. The growth of CDK4-transduced colonies was more rapid; the cell-doubling time was reduced; and, upon replating, the colonies produced greater yields of secondary colonies than mock-untransduced controls. Third, colony formation was compared by marrow cells from p16(INK4a-/-) mice and wild-type mice. The results from p16(INK4a-/-) marrow were similar to those from CDK4-transduced human CFCs, in terms of growth rate and replating ability, and were partially reversed by RMGT of p16(INK4a). Lines of immature granulocytic cells were raised from 15 individual colonies grown from the marrow of p16(INK4a-/-) mice. These had a high colony-forming ability (15%) and replating efficiency (96.7%). The p16(INK4a-/-) cell lines readily became growth factor-independent upon cytokine deprivation. Taken together, these results demonstrate that loss of INK4 proteins, in particular p16(INK4a), increases the growth rate of myeloid colonies in vitro and, more importantly, confers an increased ability for clonal expansion on hematopoietic progenitor cells.

Neoadjuvant therapy for adenocarcinoma of the rectum: tumor response and acute toxicity

PURPOSE

This study was designed to evaluate the down-staging effect and acute toxicity of preoperative radiation and chemoradiation for primary adenocarcinoma of the rectum.

METHODS

The results of pretreatment staging with transrectal ultrasound and computed tomography were compared with final histologic stage in 260 consecutive patients who underwent neoadjuvant therapy and proctectomy for primary adenocarcinoma of the rectum. Patients underwent short-course radiation (2,000 cGy in five fractions), long-course radiation (4,500 cGy in 25 fractions), or chemoradiation (4,500 cGy in 25 fractions with concurrent chemotherapy).

RESULTS

Down-staging of one or more T stages occurred in 116 of 260 (45 percent) patients overall (short-course radiation 34/82 (42 percent), long-course radiation 55/122 (45 percent), chemoradiation 27/56 (48 percent), P = not significant). Down-staging of one or more N stages occurred in 85 of 178 (48 percent) patients overall (short-course radiation 12/45 (27 percent), long-course radiation 49/86 (57 percent), chemoradiation 24/47 (51 percent), P = 0.003). Complete pathologic response was observed in 16 of 260 (6 percent) patients overall (short-course radiation 4/82 (5 percent), long-course radiation 5/122 (4 percent), chemoradiation 7/56 (13 percent), P = 0.08). Resection with negative margins (distal, proximal, and radial) was achieved in 211 of 227 patients (93 percent) in whom complete radial margin data were available. Permanent stomas were created in 35 percent of patients; temporary stomas were created in 15 percent. Thirty-three Grade 3 or 4 toxicities occurred in 22 of 260 (8 percent) patients overall during neoadjuvant therapy. Toxicity was more frequent in patients receiving chemoradiation (14/56; 25 percent) and long-course radiation (8/122; 7 percent) than in those receiving short-course radiation (0/82; 0 percent), P < 0.0001. Perioperative complications occurred in 93 patients overall (36 percent). The postoperative mortality rate was 0.4 percent (1/260). There was no significant difference in the complication rate between patients treated with short-course radiation (26/82; 32 percent), long-course radiation (46/122; 36 percent), and chemoradiation (21/56; 38 percent).

CONCLUSION

Neoadjuvant therapy for adenocarcinoma of the rectum is well tolerated and can produce substantial down-staging and a high curative resection rate. Chemoradiation can achieve high complete pathologic response rates, although toxicity during neoadjuvant therapy is greater than for radiation alone. Short-course radiation can achieve down-staging of both T stage and N stage.

Peripheral blood progenitor cell mobilisation alters myeloid, but not erythroid, progenitor cell self-renewal kinetics

Transplantation of progenitor cells which have been mobilised into the bloodstream (PBPC) following the administration of G-CSF results in more rapid neutrophil recovery than transplantation of bone marrow (BM). The reasons for the accelerated neutrophil engraftment are not clear, but would be explained by increased self-replication of myeloid progenitor cells (CFU-GM). We have used a CFU-GM replating assay to investigate myeloid progenitor self-replication, and quantification of subcolony formation during erythroid burst formation to quantify erythroid progenitor self-renewal. Secondary colony formation by CFU-GM, grown from PBPC and then replated was increased compared with secondary colony formation by BM CFU-GM (P = 0.0001); erythroid subcolony formation was not altered. There was no difference between the replating abilities of PBPC CFU-GM derived from allogeneic donors (normal individuals) and autologous donors (patients with malignant disease) although differences were found between subgroups of autologous donors. The increased replication of PBPC could not be accounted for by a reduction in progenitor cell apoptosis; PBPC CFU-GM contained slightly fewer apoptotic CD34+ cells than BM CFU-GM. The increased replication by PBPC CFU-GM was reversible because it declined when CFU-GM colonies were passaged through three sequential CFU-GM replating cycles. This decline in self-replication was more rapid than the decline seen in replated BM CFU-GM. The self-replication of PBPC CFU-GM, and subcolony formation by BFU-E could be further enhanced by exposure to cytokines in vitro. We conclude that mobilisation alters the replication kinetics of myeloid, but not of erythroid, progenitor cells, that mobilisation-induced events are of limited duration and that in vitro exposure to cytokines may modify PBPC progenitor cell kinetics.

Olfactory bulb uptake and determination of biotransfer factors in the California ground squirrel (Spermophilus beecheyi) exposed to manganese and cadmium in environmental habitats

Manganese (Mn) and cadmium (Cd) profiles in olfactory bulbs of California ground squirrels (Spermophilus beecheyi) trapped at Lawrence Livermore National Laboratory's Site 300 facility in California were determined with proton induced X-ray emission (PIXE). As a reference, Mn profiles in olfactory bulbs from laboratory rats exposed via nose-only inhalation to 0.53 mg/m3 Mn in the form of MnCl2 were also determined with PIXE. Atomic absorption spectrophotometry was used to measure soil Mn and Cd contents from the trapping sites and Mn and Cd contents in ground squirrel liver and leg muscle tissues. The data from laboratory rats revealed that Mn uptake into the olfactory bulb occurs via inhalation exposure. Data from ground squirrels and knowledge of the collection sites indicate that although several routes of exposure may occur, fossorial rodent olfactory uptake affords a significant exposure route to Mn and Cd in soils. Measured biotransfer factors (ratio of leg muscle tissue metal content to soil metal content) for Cd in ground squirrels were 10(3)-fold greater than exposure modeling estimates based on oral Cd uptake data from livestock. The measurements for ground squirrel tissues show that when conducting ecological risk assessments for natural habitats considerable care should be taken in selecting transfer factors. Specifically, transfer factors derived from data pertaining to comparable exposure pathways and ecological setting should be used wherever possible.

Initial experience of a nephrologist-operated vascular access center

A nephrology practice in Alabama did not feel in control of vascular access management. Scheduling delays, as well as variable techniques and outcomes, leading to high morbidity and mortality, caused frustration with the existing care system for vascular access. Our objective was to develop an integrative system of vascular access care, involving nephrologists along with the other caregivers, and to demonstrate an improvement in outcomes. Nephrology Vascular Labs (NVL), a recent RMS-Lifeline acquisition, opened a vascular access center (VAC) as an extension of the nephrology practice. Both pre-ESRD and ESRD patients are evaluated and treated in the VAC. Treatment is rendered in a timely fashion, to the benefit of the patients. Nephrologists serve as the interventionists. More than 90% of vascular access problems detected at dialysis are treated at the VAC. More than 2000 procedures have been performed over 2 years. Procedures carried out include thrombolysis with angioplasty, fluoroscopy alone or with angioplasty, placement of cuffed and noncuffed catheters, removal of cuffed catheters, and minor surgeries. Success rates have been high. Minor and major complications have been relatively low. Referrals to both surgeons and radiologists are shown to emphasize the role of the VAC as part of an integrative system of vascular access care. Results of a patient satisfaction survey were excellent. The VAC has fulfilled the vision of creating a seamless integration of care for vascular access. Hospitalization rate has been reduced and it is suspected that the global cost of access care is markedly lower than prior to the VAC. Multiple nephrologists can rotate as the VAC's interventionist and jointly obtain good outcomes and have little variability among them. Several reasons for using a nephrologists as the interventionist are discussed.

Membrane-embedded synaptotagmin penetrates cis or trans target membranes and clusters via a novel mechanism

The synaptic vesicle protein synaptotagmin I has been proposed to serve as a Ca(2+) sensor for rapid exocytosis. Synaptotagmin spans the vesicle membrane once and possesses a cytoplasmic domain largely comprised of two C2 domains designated C2A and C2B. We have determined how deep the Ca(2+)-binding loops of Ca(2+).C2A penetrate into the lipid bilayer and report mutations in synaptotagmin that can uncouple membrane penetration from Ca(2+)-triggered interactions with the SNARE complex. To determine whether C2A penetrates into the vesicle ("cis") or plasma ("trans") membrane, we reconstituted a fragment of synaptotagmin that includes the membrane-spanning and C2A domain (C2A-TMR) into proteoliposomes. Kinetics experiments revealed that cis interactions are rapid (< or =500 micros). Binding in the trans mode was distinguished by the slow diffusion of trans target vesicles. Both modes of binding were observed, indicating that the linker between the membrane anchor and C2A domain functions as a flexible tether. C2A-TMR assembled into oligomers via a novel N-terminal oligomerization domain suggesting that synaptotagmin may form clusters on the surface of synaptic vesicles. This novel mode of clustering may allow for rapid Ca(2+)-triggered oligomerization of the protein via the membrane distal C2B domain.

A simple cryopreservation method for the maintenance of cell viability and mechanical integrity of a cultured cartilage analog

A method for cryopreserving a 100-microm-thick sheet of tissue produced by cultured rabbit chondrocytes has been developed. The method maintains cell viability and avoids tissue fracture and degradation of mechanical properties. A slow-freeze, fast-thaw procedure with 2 M Me(2)SO as the cryoprotectant resulted in no tissue fracture and approximately 90% viable cells after storage in culture flasks at -80 degrees C. The cells in the retrieved tissue remained responsive to IL-1beta, and tensile and fracture toughness properties of the tissue were not degraded by cryopreservation.

Noncontact anterior cruciate ligament injuries: risk factors and prevention strategies

An estimated 80,000 anterior cruciate ligament (ACL) tears occur annually in the United States. The highest incidence is in individuals 15 to 25 years old who participate in pivoting sports. With an estimated cost for these injuries of almost a billion dollars per year, the ability to identify risk factors and develop prevention strategies has widespread health and fiscal importance. Seventy percent of ACL injuries occur in noncontact situations. The risk factors for non-contact ACL injuries fall into four distinct categories: environmental, anatomic, hormonal, and biomechanical. Early data on existing neuromuscular training programs suggest that enhancing body control may decrease ACL injuries in women. Further investigation is needed prior to instituting prevention programs related to the other risk factors.

Distal radial metaphyseal forces in an extrinsic grip model: implications for postfracture rehabilitation

The purpose of this study was to establish the relationship between force at the distal radius and power grip force of the hand, a common functional and rehabilitation maneuver. This information will provide limits of allowable grip forces during postfixation rehabilitation and guide design requirements for fixation systems. By designing a model of power grip using the extrinsic hand musculotendinous units, we were able to compare grip force with force at the distal radius. Our results show that to obtain 10 N of grip force, approximately 26.3 N of force is transmitted through the distal radius, 52.4 N is transmitted through the radius and ulna combined, and 30.0 N needs to be applied to the flexor tendons. Fifty-one percent of the total forearm force was transmitted through the distal radius in this model. If all forearm forces were transmitted through the radius, 52 N of force would be transmitted through the distal radius to obtain 10 N of grip force. The clinical application of this model suggests that since failure forces of tested distal radius fixation systems range from 55 to 825 N, rehabilitation grip force should not exceed 10 to 159 N, depending on the type of fixation.

Kinetics of synaptotagmin responses to Ca2+ and assembly with the core SNARE complex onto membranes

The synaptic vesicle protein synaptotagmin I binds Ca2+ and is required for efficient neurotransmitter release. Here, we measure the response time of the C2 domains of synaptotagmin to determine whether synaptotagmin is fast enough to function as a Ca2+ sensor for rapid exocytosis. We report that synaptotagmin is "tuned" to sense Ca2+ concentrations that trigger neuronal exocytosis. The speed of response is unique to synaptotagmin I and readily satisfies the kinetic constraints of synaptic vesicle membrane fusion. We further demonstrate that Ca2+ triggers penetration of synaptotagmin into membranes and simultaneously drives assembly of synaptotagmin onto the base of the ternary SNARE (soluble N-ethylmaleimide-sensitive fusion protein [NSF] attachment receptor) complex, near the transmembrane anchor of syntaxin. These data support a molecular model in which synaptotagmin triggers exocytosis through its interactions with membranes and the SNARE complex.

The effects of grade III posterolateral knee complex injuries on anterior cruciate ligament graft force. A biomechanical analysis

To determine if untreated grade III injuries of the posterolateral structures contribute to increased force on an anterior cruciate ligament graft, we measured the force in the graft in cadaveric knees during joint loading after reconstruction with otherwise intact structures and in the same reconstructed knees after selected cutting of specific posterolateral knee structures. Tests were first performed on the knee with the posterolateral structures intact and then after sequential sectioning of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon. The graft force was significantly higher after fibular collateral ligament transection during varus loading at both 0 degree and 30 degrees of knee flexion than it was for the same loading of the joint with intact posterolateral structures. In addition, coupled loading of varus and internal rotation moments at 0 degree and 30 degrees of flexion further increased graft force beyond that with varus force alone. The increase in graft force remained significant with additional sequential cutting of the popliteofibular ligament and popliteus tendon. We believe this study supports the clinical observation that untreated grade III posterolateral structure injuries contribute to anterior cruciate ligament graft failure by allowing higher forces to stress the graft.

Quantitative particle-induced X-ray emission imaging of rat olfactory epithelium applied to the permeability of rat epithelium to inhaled aluminum

Neurotoxicity from chronic metal inhalation has been suggested as an underlying contributor to late-developing neurodegenerative diseases that have symptoms similar to Alzheimer's and Parkinson's syndromes. If inhaled metals contribute to pathogenesis of these diseases, identifying, localizing, and quantitating metal deposition(s) within specific target regions of the central nervous system will be critical to our understanding of the mechanisms. Standard analytical techniques used to date require exposure to extremely high concentrations of metals to meet analytical detection limits in small tissue areas. The relevance to lower-dose environmentally relevant exposures and potential protective barriers is therefore questionable. The feasibility of microbeam particle-induced X-ray emission is investigated as a method for rapidly scanning tissues to study the inhalation of metals, nasal permeability, and central nervous system deposition. The optimal beam spot and analysis time used to image the rat olfactory epithelium to facilitate the rapid detection of aluminum localizations were determined. Measurements of aluminum localizations in rat olfactory bulb and brain sections are also presented.

Evidence for a continuous decline in haemopoietic cell function from birth: application to evaluating bone marrow failure in children

There are considerable differences in haemopoietic activity between young children and adults on the one hand, and between adults and the elderly on the other. A fundamental unanswered question is whether these differences relate to discrete stages or are part of a continuous process. We have sought to define aspects of the haematological ageing process, and have found that results from children with bone marrow failure syndromes differ from age-matched reference values. Haemopoietic cells were obtained from umbilical cord blood, from blood and bone marrow of healthy individuals and from the blood of young patients with bone marrow failure syndromes. Clonogenic myeloid progenitors (CFU-GM) were grown in semi-solid medium to measure their frequency; the proliferative capacity of myeloid progenitors was measured by replating colonies and observing secondary colony formation. We found that the frequency of CFU-GM in normal marrow increased and their proliferative capacity decreased exponentially with age. The proliferative capacity of CFU-GM in normal blood also decreased exponentially with age. This relationship extrapolated back to the levels of proliferation measured for cord blood CFU-GM (age = 0). The proliferative capacities of CFU-GM from children with bone marrow failure syndromes were severely reduced compared with age-matched reference values. These results indicate that a decline in haemopoietic progenitor cell function begins at birth and continues throughout life. This decline may occur prematurely in childhood marrow failure syndromes with a predisposition to leukaemia.

Verbal imprecision as an index of knowledge in transition

Children can be verbally imprecise when they are learning, but this phenomenon is not well documented. Verbal imprecision, anecdotally referred to as "hemming and hawing," may be indexed by restatements, comments on one's lack of knowledge, deletions of sentence constituents, and pauses. The authors examined whether they could quantify indexes of verbal imprecision and use them to predict changes in problem-solving performance. Four types of verbal imprecision were found to predict improved performance. Results were used to make inferences about processes of knowledge change. In particular, evidence suggests that adopting a new approach and rejecting an old one may be independent, and ordered, processes. Although others have drawn similar conclusions, using verbal imprecision as the data source is a relatively unique and readily accessible method for lending support to this model of knowledge change.

A composites theory predicts the dependence of stiffness of cartilage culture tissues on collagen volume fraction

The tensile stiffness of tissue grown from chondrocyte culture was both measured experimentally and predicted using a composites model theory relating tissue microstructure to macroscopic material stiffness. The tissue was altered by several treatment protocols to provide a wide range of collagen fibril volume fraction (0.015-0.15). The rate of change of tissue modulus with change in collagen volume fraction predicted by the theory was within 14% of the slope of the linear fit through the experimental data, without the use of fitting parameters for the theoretical value of the slope. Use of the model to simulate cytokine mediated tissue digestion suggests that the action of IL-1beta and retinoic acid is mainly removal of proteoglycans and some removal of collagen. The model also indicates that the matrix and collagen remaining in the tissue has the same elastic properties as the untreated tissue, and is not damaged due to the alteration. Young's modulus of the collagen fibrils is predicted to be 120 MPa, a value in the range of previous studies. This value is dependent mainly on the matrix modulus and collagen fibril volume fraction and not on Poisson's ratio of either matrix or fibril. Poisson's ratio of the tissue depends primarily on the Poisson's ratio of the matrix.

Verbal imprecision as an index of knowledge in transition

Children can be verbally imprecise when they are learning, but this phenomenon is not well documented. Verbal imprecision, anecdotally referred to as "hemming and hawing," may be indexed by restatements, comments on one's lack of knowledge, deletions of sentence constituents, and pauses. The authors examined whether they could quantify indexes of verbal imprecision and use them to predict changes in problem-solving performance. Four types of verbal imprecision were found to predict improved performance. Results were used to make inferences about processes of knowledge change. In particular, evidence suggests that adopting a new approach and rejecting an old one may be independent, and ordered, processes. Although others have drawn similar conclusions, using verbal imprecision as the data source is a relatively unique and readily accessible method for lending support to this model of knowledge change.

Cell biology of CML cells

At the cellular level, expansion of haemopoiesis in chronic myeloid leukaemia (CML) must involve some imbalance in cell production along the myeloid maturation pathway. The relevant kinetic parameters are cell loss by apoptosis and differentiation and cell gain by proliferation (self-renewal). In spite of the predominance of the BCR-ABL-positive leukaemic cells, some BCR-ABL-negative, presumably normal, progenitor cells remain for long periods in chronic phase CML. Thus, understanding the kinetics of CML and normal progenitor cells may lead to therapeutic strategies capable of reducing malignant cell growth and reactivating normal haemopoiesis.

Renal arteriolar Na+/Ca2+ exchange in salt-sensitive hypertension

The present studies were performed to assess Na+/Ca2+ exchange activity in afferent and efferent arterioles from Dahl/Rapp salt-resistant (R) and salt-sensitive (S) rats. Renal arterioles were obtained by microdissection from S and R rats on either a low-salt (0.3% NaCl) or high-salt (8.0% NaCl) diet. On the high-salt diet, S rats become markedly hypertensive. Cytosolic calcium concentration ([Ca2+]i) was measured in fura 2-loaded arterioles bathed in a Ringer solution in which extracellular Na (Nae) was varied from 150 to 2 mM (Na was replaced with N-methyl-D-glucamine). Baseline [Ca2+]i was similar in afferent arterioles of R and S rats fed low- and high-salt diet. The change in [Ca2+]i (Delta[Ca2+]i) during reduction in Nae from 150 to 2 mM was 80 +/- 10 and 61 +/- 3 nM (not significant) in afferent arterioles from R rats fed the low- and high-salt diet, respectively. In afferent arterioles from S rats on a high-salt diet, Delta[Ca2+]i during reductions in Nae from 150 to 2 mM was attenuated (39 +/- 4 nM) relative to the Delta[Ca2+]i of 79 +/- 13 nM (P < 0.05) obtained in afferent arterioles from S rats on a low-salt diet. In efferent arterioles, baseline [Ca2+]i was similar in R and S rats fed low- and high-salt diets, and Delta[Ca2+]i in response to reduction in Nae was also not different in efferent arterioles from R and S rats fed low- or high-salt diets. Differences in regulation of the exchanger in afferent arterioles of S and R rats were assessed by determining the effects of protein kinase C (PKC) activation by phorbol 12-myristate 13-acetate (PMA, 100 nM) on Delta[Ca2+]i in response to reductions in Nae from 150 to 2 mM. PMA increased Delta[Ca2+]i in afferent arterioles from R rats but not from S rats. These results suggest that Na+/Ca2+ exchange activity is suppressed in afferent arterioles of S rats that are on a high-salt diet. In addition, there appears to be a defect in the PKC-Na+/Ca2+ exchange pathway that might contribute to altered [Ca2+]i regulation in this important renal vascular segment in salt-sensitive hypertension.

The effect of spinal instrumentation on lumbar intradiscal pressure

The purpose of this study was to investigate the effect of spinal instrumentation on the intradiscal pressure (IDP) within the fixed motion segment. In vitro biomechanical testing was performed in six single functional spinal units of fresh calf lumbar spines using a pressure needle transducer. Various loads were applied by a materials testing system device. In addition to intact spine (control), anterior spinal instrumentation (ASI) and pedicle screw fixation (PS) constructs, as well as destabilized spine were tested. Relative to the control, the destabilized spine tended to have an increased IDP; by 15% in axial compression and by 9-36% in flexion-extension. Compared to the control, PS decreased the IDP by 23% in axial loading and 51% in extension loading and increased it by 60% in flexion for each loading. ASI decreased the IDP by 32% in flexion and 1% in extension. Lateral bending produced symmetrical changes of IDP in the control and destabilized spine, but no change in the PS construct. The IDP of the ASI construct was decreased by 77% in ipsilateral bending and increased by 22% in contralateral bending. These results demonstrated that eccentric loading from the spinal instruments increased IDP and significant disc pressure may still exist despite an increase in motion segment stiffness after lumbar stabilization.

Lumbar intradiscal pressure after posterolateral fusion and pedicle screw fixation

In vitro biomechanical testing was performed in single-functional spinal units of fresh calf lumbar spines, using pressure needle transducers to investigate the effect of posterolateral fusion (PLF) and pedicle screw constructs (PS) on intradiscal pressure (IDP), in order to elucidate the mechanical factors concerned with residual low back pain after PLF. IDP of 6 calf lumbar spines consisting of L4 and L5 vertebrae and an intervening disc was measured under axial compression, flexion-extension and lateral bending in the intact spine, PS, PLF and the destabilized spine. Relative to the intact spines, the destabilized spines showed increased IDP in all of lordings and moments. IDP under PS and PLF were significantly decreased in axial compression, extension and lateral bending loads (p<0.05). In flexion, IDP under PS and PLF increased linearly proportional to the magnitude of flexion moment and reached as high as IDP of the intact spines. These results demonstrated that despite an increase in the stiffness of motion segments after PLF and PS, significant high disc pressure is still generated in flexion. Flexibility of PS and PLF may cause increased axial load sharing of the disc in flexion and increased IDP. This high IDP may explain patients' persisting pain following PS and PLF.

A two-color BCR-ABL probe that greatly reduces the false positive and false negative rates for fluorescence in situ hybridization in chronic myeloid leukemia

The t(9;22) translocation resulting in the fusion of BCR and ABL genes is pathognomonic in chronic myeloid leukemia (CML) and may be investigated at the molecular level using fluorescence in situ hybridization (FISH). Two-color BCR-ABL probes visualizing one fusion signal (1F FISH) have high false positive rates (FPR) and false negative rates (FNR). The FPR is a result of the random spatial association of probe signals within normal interphase cells so that some cells appear to contain the BCR-ABL fusion gene. The FNR of 1F FISH probes depends on the distance between the BCR and ABL probes hybridized to the BCR-ABL fusion gene (< or =368 kb); the "gap" between the signals causing the cell to be interpreted as normal. To overcome these difficulties, a two-color probe was used, employing four yeast artificial chromosome (YAC) sequences that span the breakpoint regions of the BCR and ABL genes and that visualize the two fusion signals BCR-ABL and ABL-BCR in CML cells (2F FISH). The FNR for the 2F FISH probes was assessed on clonal Ph+ granulocyte-macrophage-colony-forming cell (CFU-GM) derived colonies and was reduced to 0.4% (2/450), compared with an FNR of 13.5% (111/823) with 1F FISH. The FPR in normal mononuclear cells for the 2F FISH was 0. 19 +/- 0.12% (3/1,700), whereas the FPR using 1F FISH was 4.5 +/- 2.3% (63/1,294). The 2F FISH can thus be used to evaluate very small frequencies of BCR-ABL-positive and -negative interphase cells and may be of use in the clinical monitoring of CML.

Treatment with interferon-alpha preferentially reduces the capacity for amplification of granulocyte-macrophage progenitors (CFU-GM) from patients with chronic myeloid leukemia but spares normal CFU-GM

The biological target for interferon (IFN)-alpha in chronic myeloid leukemia (CML) is unknown, but one possibility is that amplification of granulocyte-macrophage colony-forming cells (CFU-GM) is reduced. Replating CFU-GM colonies and observing secondary colony formation provides a measure of CFU-GM amplification. Amplification of CML, but not normal, CFU-GM in vitro was significantly inhibited by IFN-alpha (P = 0.02). In 5 out of 15 CML cases studied by fluorescence in situ hybridization, in vitro treatment with IFN-alpha increased the proportion of CFU-GM, which lacked BCR-ABL. The ability of patients' CFU-GM to amplify, and suppression of this ability by IFN-alpha, predicted responsiveness to IFN-alpha therapy in 86% of cases. Investigation of patients on treatment with IFN-alpha showed a threefold reduction in CFU-GM amplification in responders (P = 0.03) but no significant change in nonresponders (P = 0.8). We conclude that IFN-alpha preferentially suppresses amplification of CML CFU-GM to varying degrees. The differing in vitro sensitivities to IFN-alpha and growth kinetics of individual patients' cells could help differentiate those who will or will not benefit from treatment with IFN-alpha.

Maximum unloaded length (MUL) and graft force as criteria for anterior cruciate ligament graft fixation

The biomechanical determinants of graft force after ACL reconstruction are reviewed. It is proposed that the two primary determinants are tunnel location and "maximum unloaded length" (MUL), defined as the distance between the origin and insertion tunnels when the graft just begins to carry load. MUL and graft stiffness determine graft force for a given flexion angle and external load. Although several variables can affect MUL, such as pretension level, flexion angle at pretension, and direction of tension, one variable is important, fixation position of the graft relative to the bone. It is proposed that a more rational basis for establishing graft fixation, rather than isometry, is graft force, reflecting the choice of MUL. Setting graft force with a device that adjusts MUL allows adjustment of the graft force to a chosen level of fixed pretension and joint laxity, while avoiding overstressing during passive range of motion due to poor tunnel placement.

A relevant dose of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone is extensively metabolized and rapidly absorbed in the canine tracheal mucosa

Lung cancer is largely a site-of-entry disease caused by inhaled carcinogenic agents, especially tobacco smoke. Two major groups of procarcinogens, tobacco-specific nitrosamines and polycyclic aromatic hydrocarbons, are putative agents, but their relative contributions are disputed. An important indicator of relative potency for these compounds is the dose to the target epithelial cells. Although we have reported the dose of polycyclic aromatic hydrocarbons to the canine tracheal epithelium [Gerde et al., Carcinogenesis (Lond.), 18: 1825-1832, 1997; Gerde et al., Carcinogenesis (Lond.), in press, 1998], the purpose of the current study was to characterize the absorption and metabolism of low levels of one tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in the canine trachea. One hundred ng of tritiated NNK were instilled in the distal trachea of the dog. Blood was repeatedly sampled from the azygous vein and both sides of the systemic circulation from 15 s to 30 min after instillation. Tissues were then removed and analyzed for the tritiated NNK and its metabolites. Autoradiography was used to determine the depth distribution of tritium in the tracheal mucosa. Most NNK appeared rapidly in the blood draining the airway mucosa, but there was also a slow clearance phase. During absorption, NNK was distributed within the entire depth of the mucosa to the tracheal cartilage; however, a portion was conspicuously bound to the mucin component of the mucous lining layer. Reversible binding to mucin may be largely responsible for the slow clearance phase. Despite the rapid absorption of most of the tritium, NNK was nonetheless extensively metabolized in the tracheal mucosa. Systemic metabolism was also rapid: within 18 min of instillation, the NNK parent compound had disappeared from the systemic circulation, and 45 min after instillation, no NNK was found in the trachea or any distal tissue. Although the rapid absorption and distribution of NNK and its metabolites ensured widespread and extensive distal binding in all tissues, first-pass metabolism and activation of NNK in the airway mucosa were sufficiently rapid to cause levels of binding at the site of absorption to be approximately 20-fold those of distal tissues. NNK may thus act as a site-of-entry carcinogen. This observation may be important in estimating the contribution of NNK to lung cancer relative to other carcinogens and for explaining increased incidences of oral cancers in users of snuff and chewing tobacco in which NNK is present in high concentrations.

Local metabolism in lung airways increases the uncertainty of pyrene as a biomarker of polycyclic aromatic hydrocarbon exposure

While inhaled polycyclic aromatic hydrocarbons have long been suspected to induce lung cancer in humans, their dosimetry has not been fully elucidated. A key question is whether the critical exposure occurs during absorption in the lungs, or if toxicants in the systemic circulation contribute significantly to lung cancer risk. In particular, data are needed to determine how the physical properties of inhalants affect local dosimetry in the respiratory tract. Pyrene, a tobacco smoke component, was selected for study because it has physical properties between those of highly lipophilic benzo[a]pyrene and water-soluble nitrosamines. Aliquots of 5 ng of pyrene dissolved in a phospholipid/ saline suspension were instilled as a single-spray bolus in the posterior trachea of the dog just anterior to the carina. For 3 h after instillation, blood was repeatedly sampled from the azygous vein, which drains the mucosa around the point of instillation, and from both sides of the systemic circulation. At 3 h post-instillation, tissue samples were taken. Autoradiography was used to determine the depth distribution of pyrene in the tracheal mucosa. The concentration of pyrene-equivalent radioactivity in the azygous vein peaked 9 min after the instillation. At approximately 30 min after instillation, a rapid early clearance phase shifted into a distinctly slower second clearance phase. Rates of rapid clearance were, however, sufficiently slow to indicate diffusion-limited absorption of pyrene in the trachea. This finding was corroborated by high concentrations of pyrene in the epithelium as determined by autoradiography. High epithelial concentration of pyrene combined with a slow penetration into the circulating blood allowed substantial first-pass metabolic conversion of pyrene in the tracheal mucosa. A total of 13% of the instilled pyrene was retained in the tracheal mucosa 3.2 h after instillation; of this, 29% was parent compound, 52% was organic-extractable metabolites, 14% was water-soluble metabolites and 6% (approximately 1% of the instilled amount) was covalently bound to tracheal tissues. Results support the inference that lipophilic protoxicants, because of slow, diffusion-limited absorption, are more likely than water-soluble protoxicants to be bioactivated in the lining epithelium and, in turn, induce first-pass toxicity at the site of entry. In addition, limitations were identified in the use of systemically distributed biomarkers of PAHs, such as urinary hydroxypyrene levels, as indicators of the biologically effective dose in airway target cells.

Chondrocytes in culture produce a mechanically functional tissue

A mechanically testable tissue was grown in vitro from rabbit chondrocytes that were initially plated at high density (approximately 80,000 cells/cm2). The DNA, collagen, and proteoglycan content, as well as the tissue thickness, tensile stiffness, and synthesis rates, were measured at 4, 6, and 8 weeks. The biochemical properties were similar to those for immature cartilage, with predominantly type-II collagen produced; this indicated that the cells retained their chondrocytic phenotype. The tissue formed a coherent mechanical layer with testable tensile stiffness as early as 4 weeks. The tensile elastic modulus reached 1.3 MPa at 8 weeks, which is in the range of values for native cartilage from the midzone. Collagen density was approximately 24 mg/ml at 8 weeks, which is about one-half the value for native cartilage, and the collagen fibril diameters were smaller. Chondrocytes in culture responded to culture conditions and were stimulated by cytokine interleukin-1beta. When culture conditions were varied to RPMI nutrient medium with lower fetal bovine serum and higher ascorbic acid concentrations, the thickness decreased and the modulus increased significantly. Interleukin-1beta, added to the 8-week culture for 2 weeks, caused a decrease of 60% in thickness, a decrease of 81% in proteoglycan content, and a decrease of 31% in collagen content; this is similar to the response of cartilage explants to interleukin-1beta. This cartilage analog may be useful as a model system to study structure-function relationships in cartilage or as cartilage-replacement tissue.

Fluoride supplement prescribing and dental referral patterns among academic pediatricians

OBJECTIVE

To determine how well the current fluoride supplementation schedule was known by academic pediatricians and to examine the fluoride supplement prescribing and dental referral practices among primary care faculty pediatricians at four medical centers.

SETTING

Four university medical centers in North Carolina.

SUBJECTS

Primary care faculty pediatricians.

METHOD

A questionnaire pretested for clarity was distributed to all identified full-time primary care pediatric faculty (42 members).

RESULTS

A total of 40 completed questionnaires were returned. Thirty-seven (93%) primary care faculty pediatricians reported that they routinely addressed the need for fluoride supplements for their patients, but only 28 (70%) determined the fluoride content of the drinking water before prescribing supplements. Thirty-five (87.5%) began supplements at the correct age, but fewer knew the correct doses for children of various ages. Only 23 (58%) referred their patients for oral examination and preventive care before the age of 36 months, contrary to American Academy of Pediatrics recommendations.

CONCLUSIONS

Pediatricians in an academic setting would be expected to be more knowledgeable of current recommendations than those in private practice. Failure to know and teach correct fluoride supplement recommendations and failure to recommend early professional dental involvement can result in less than optimum oral health.

Interleukin 3 (IL-3), but not stem cell factor (SCF) increases self-renewal by human erythroid burst-forming units (BFU-E) in vitro

Interleukin 3 (IL-3) and stem cell factor (SCF) are both important regulators of early haemopoietic cell development. Here, we have compared their effects or the kinetics of erythroid burst formation by BFU-E in normal adult bone marrow. We grew the BFU-E in the presence of erythropoietin (Epo) alone, Epo + IL-3 or Epo + SCF and scored the numbers of subcolonies in individual bursts after 14 days. The data were plotted as the cumulative distribution of the numbers of subcolonies per erythroid burst then linearised by logarithmic transformation. Analysis of the data revealed that IL-3 increases the numbers of subcolonies in BFU-E whilst SCF increases the size of the subcolonies themselves. Experiments involving combinations of Epo + IL-3 + SCF and the delayed addition of IL-3 or SCF indicated that the actions of IL-3 and SCF are largely independent of one another. We conclude that: (1) IL-3 acts at an earlier stage of erythroid differentiation than SCF, and (2) it may be possible to classify haemopoietic growth factors according to their effects on cell kinetics in vitro.

Local staging of prostate cancer with 0.2 T body coil MRI

This study was undertaken to evaluate the accuracy of low field strength body coil MRI in the staging of clinically localized prostate cancer. Fifty-three patients with prostate cancer were examined on a 0.2 T body coil system before undergoing radical prostatectomy. Of the 20 cases with unconfined stage T3 disease on histology, 12 were correctly staged, whilst three cases were overstaged by MRI. (Accuracy 79.2%, sensitivity 60%, and specificity 90.9%.) The accuracy, sensitivity and specificity for the detection of capsular penetration were 77.3%, 55% and 90.9%, respectively, whilst those for seminal vesical invasion were 94.3%, 83.3% and 95.7%, respectively. It is concluded that a high level of staging accuracy, comparable to that obtained in some published studies using high field strength endorectal coil MRI, can be obtained using 0.2 T body coil MRI.

Benzo[a]pyrene at an environmentally relevant dose is slowly absorbed by, and extensively metabolized in, tracheal epithelium

While tobacco smoke has been conclusively identified as a lung carcinogen, there is much debate over which smoke constituent(s) are primarily responsible for its carcinogenicity. Previous studies in our laboratory suggested that highly lipophilic carcinogens are slowly absorbed in the thicker epithelium of the conducting airways, potentially allowing for substantial local metabolism. The bioactivation of polycyclic aromatic hydrocarbons in airway epithelium may, hence, be important in tobacco smoke-induced carcinogenesis. In the present study, the hypothesis of slow absorption and substantial local metabolic activation of highly lipophilic carcinogen in airway epithelium was tested in dogs. A single dose of tritiated benzo[a]pyrene (BaP) dissolved in a saline/phospholipid suspension was instilled in the trachea, just anterior to the carina. At intervals of a few minutes up to 30 min over a 3-h period, blood samples were drawn from the azygous vein, which drains the area around the point of instillation, and from the systemic circulation. Tissue samples were taken at the end of the experiment. The concentration of BaP with depth into the tracheal mucosa was determined with autoradiography. BaP was slowly absorbed into the trachea with a half-time of approximately 73 min, which is consistent with diffusion-limited passage through the epithelium and lead to local doses in the tracheal epithelium that were more than a 1000-fold those of other tissues. The long retention of BaP in the epithelium provided the local metabolizing enzymes with high substrate levels over a long period, resulting in extensive metabolism. At 3 h after the exposure, 23% of the BaP-equivalent activity remained in the tracheal mucosa. Of this fraction, 13% was parent compound, 28% was organic extractable, 31% was water-soluble, and 28-7% of the instilled dose was bound to tracheal tissues. These results explain the tendency of highly lipophilic carcinogens, such as BaP, to induce tumors at the site of entry and, furthermore, indicate that the highly lipophilic components of tobacco smoke and polluted air may be the most important contributors to lung tumors of the conducting airways.