DNA exhibits multi-stranded binding recognition on glass microarrays

In the course of exploring the hybridization properties of glass DNA microarrays, multi-stranded DNA structures were observed that could not be accounted for by classical Watson-Crick base pairing. Non-denatured double-stranded DNA array elements were shown to hybridize to single-stranded (ss)DNA probes. Similarly, ssDNA array elements were shown to bind duplex DNA probes. This led to a series of experiments demonstrating the formation of multi-stranded DNA structures on the surface of microarrays. These structures were observed with a number of heterogeneous sequences, including both purine and pyrimidine bases, with shared sequence identity between the ssDNA and one of the duplex strands. Furthermore, we observed a strong binding preference near the ends of duplexes containing a 3'-homologous strand. We suggest that such binding interactions on cationic solid surfaces could serve as a model for a number of biological processes mediated through multi-stranded DNA.

Guided bone regeneration for dehiscence and fenestration defects on implants using an absorbable polymer barrier

BACKGROUND

Guided bone regeneration (GBR) using a non-absorbable barrier has provided clinicians the ability to place implants in sites compromised by insufficient bone, including immediate extraction sites. Recent evidence suggests that successful GBR outcomes may be possible using bioabsorbable polymer barriers.

METHODS

This report presents a case series of 9 patients with 8 fenestration and 3 dehiscence defects on implants consecutively treated with GBR. A bioabsorbable polymer barrier of poly(DL-lactide) was used in conjunction with a composite graft of freeze-dried bone allograft (FDBA)/demineralized freeze-dried bone allograft (DFDBA) mixed in a ratio of 1:1. Second-stage surgeries were performed at 4 to 8.5 months (5. 7 months average) post-placement. Biopsy material from 2 sites was obtained while exposing the implant for healing abutment connection.

RESULTS

Ten of the 11 defects (90.9%) achieved complete coverage of the osseous defects. Histologic evaluations revealed the formation of viable bone, frequently in close amalgamation with residual graft particles.

CONCLUSION

These case reports suggest that a poly(DL-lactide) polymer can be used as a physical barrier with a composite bone replacement graft to achieve successful GBR results of dehiscence/fenestration defects when placing implants.

Alveolar ridge and sinus augmentation utilizing platelet-rich plasma in combination with freeze-dried bone allograft: case series

BACKGROUND

Alveolar bone regeneration is frequently necessary prior to placement of implants. Efforts to improve wound healing have focused on factors that may enhance bone formation following guided bone regeneration (GBR) techniques alone or in combination with bone replacement graft materials. Recent reports suggest that platelet-rich plasma (PRP), presumably high in levels of peptide growth factors, may enhance the formation of new bone when used in combination with autogenous graft material.

METHODS

In this report, the clinical and radiographic results are presented on 15 consecutively treated patients using autologous PRP in combination with freeze-dried bone allograft (FDBA) for sinus elevation and/or ridge augmentation. FDBA and PRP (0.5 g/2cc PRP) were mixed and placed as a composite graft material. A gel formed by mixing autologous thrombin-rich plasma with PRP (1:4 ratio) was used to cover the graft material. Core biopsies of grafted areas were obtained in several patients as part of implant site preparation and were evaluated histologically to determine site maturation.

RESULTS

Of 36 implant fixtures, 32 (89%) were considered clinically successful demonstrating complete bone coverage of the implant, no mobility, and a normal radiographic appearance at the time of re-entry and 12 months post-implant exposure. Four implants were removed due to mobility at the time of surgical exposure. Histologic evaluation of biopsy specimens revealed numerous areas of osteoid and bone formation around FDBA particles, with no evidence of inflammatory cell infiltrate.

CONCLUSIONS

These clinical and histological findings suggest that ridge augmentation and sinus grafting with FDBA in combination with PRP provide a viable therapeutic alternative for implant placements. Future studies are necessary to determine whether PRP enhances new bone formation or maturation with bone replacement allografts.

Increase in expression of Hsp47 and collagen in hereditary gingival fibromatosis is modulated by stress and terminal procollagen N-propeptides

HGF is a rare oral condition characterized by a slow, progressive enlargement of the gingiva, involving both the maxilla and mandible. HGF provides a model for the study of regulatory features of conditions characterized by connective tissue hyperplasia. In this study, the culture characteristics of gingival fibroblasts derived from patients of the same family with HGF (n = 4) were similar with regard to cell cycle analysis. Flow cytometric DNA content analysis revealed uniform DNA diploidy for fibroblasts cultured from NG and HGF. NG cells showed a low S-phase fraction (19.8%) and G2/M fraction (5.8%) and a relatively high G1 phase fraction (74%). In contrast, HGF cells from all members of the tested kindred, exhibited diploid cells with a higher S-phase (40.9%) and G2/M (10.1%) fraction and a relatively low G1 phase fraction (40.9%). Furthermore, we demonstrated that the expression and production of Hsp47 parallels the increased levels of collagen secretion observed in HGF. In addition, we show that Hsp47 and collagen are coordinately regulated following stress via a feedback mechanism mediated by N-terminal procollagen propeptides. Utilizing confocal microscopy and antibodies directed against GST-fusion proteins encompassing the pro alpha1(I) N-propeptide globular domain (NP1) (residues 23-108), it was apparent that this regulatory mechanism does not involve significant interaction with Hsp47's chaperoning of procollagen.

Antitumor and antimetastatic activity of ribozymes targeting the messenger RNA of vascular endothelial growth factor receptors

Chemically stabilized hammerhead ribozymes are nuclease-resistant, RNA-based oligonucleotides that selectively bind and cleave specific target RNAs. Due to their potential for specifically inhibiting gene expression, ribozymes are being investigated for therapeutic applications as well as for the elucidation of gene function. In particular, we have investigated ribozymes that target the mRNA of the vascular endothelial growth factor (VEGF) receptors because VEGF signaling is an important mediator of tumor angiogenesis and metastasis. Here we report pharmacodynamic studies testing anti-Flt-1 (VEGFR-1) and anti-KDR (VEGFR-2) ribozymes in animal models of solid tumor growth and metastasis. Ribozymes targeting either Flt-1 or KDR significantly inhibited primary tumor growth in a highly metastatic variant of Lewis lung carcinoma. However, only treatment with the anti-Flt-1 ribozyme resulted in a statistically significant and dose-dependent inhibition of lung metastasis in this model. The anti-Flt-1 ribozyme was then tested in a xenograft model of human metastatic colorectal cancer in which significant inhibition of liver metastasis was observed. Taken together, these data represent the first demonstration that synthetic ribozymes targeting VEGF receptor mRNA reduced the growth and metastasis of solid tumors in vivo.

The treatment of intrabony defects with bone grafts

There is substantial clinical and histological evidence that support the concept that extraoral and intraoral autogenous bone grafts and demineralized freeze-dried bone allografts are effective regenerative materials in the treatment of intrabony defects. Moreover, long-term evaluations currently available suggest that the regenerative gains achieved remain clinically stable. Synthetic grafts may result in improved probing depths and clinical attachment levels but have yet to demonstrate the ability to initiate or enhance the formation of a new attachment apparatus.

Alteration in expression of MMP-1 and MMP-2 but not TIMP-1 and TIMP-2 in hereditary gingival fibromatosis is mediated by TGF-beta 1 autocrine stimulation

Hereditary gingival fibromatosis (HGF) is characterized by an excess accumulation of extracellular matrix (ECM) resulting in a generalized and fibrotic enlargement of the gingiva. To investigate some of the regulatory features of this condition, gingival fibroblasts from normal gingiva (NG) and HGF were examined for the expression and production of matrix metalloproteinases (MMPs) and their inhibitors, tissue matrix metalloproteinases inhibitor (TIMPs). Our results, obtained from 2 different assays, semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and enzymography, clearly demonstrated that the expression and production of MMP-1 and MMP-2 was significantly lower in fibroblasts from HGF than from NG. Interestingly, TIMP-1 and TIMP-2 expression from NG cells was shown to be slightly higher to those from HGF. Addition of antibodies against transforming growth factor-beta 1 (TGF-beta 1), which is produced in greater amounts by HGF fibroblasts, resulted in a slight increase in MMP-1 and a decrease in MMP-2 expression, whereas TIMP-1 and TIMP-2 expressions were unaffected. These patterns of expression and production suggest that enhanced TGF-beta 1 production reduce the proteolytic activities of HGF fibroblasts, which favor the accumulation of ECM.

Dynamic changes in plasma proinsulin/insulin ratio during insulin secretion influence correlation between radioimmunoassay (RIA) and IMX measurements of insulin

Because proinsulin and insulin have different circulatory half-lives, the ratio of proinsulin to insulin in plasma depends on the dynamics of insulin secretion. This variation can potentially influence comparison of IMX assays and radioimmunoassays (RIAs) for [insulin], given that the antibody used in the IMX assay has negligible cross-reactivity with proinsulin compared to the 40% cross-reactivity with proinsulin of the antibody used in the RIA. Simulation of a simple mass balance model for insulin and proinsulin concentrations during an oral glucose tolerance test predicts that the ratio (R) of RIA to IMX insulin measurements of [insulin] should transiently decrease, pass through a minimum, increase past the initial value, pass through a maximum and eventually return to the initial value. Using time course specimens from patients, this pattern of variation in R was observed in the majority (12/16) of cases studied. The variation in R for time course specimens (CV = 26%) was significantly greater than for other specimens (fasting, random or undesignated; P < 0.05). Thus, when comparing IMX and RIA measurements of [insulin], variation in R for samples from differing states of dynamic insulin secretion contains a component that is attributable to dynamic changes in the ratio of [proinsulin]/[insulin] in plasma.

Pharmacokinetics of an antiangiogenic ribozyme (ANGIOZYME) in the mouse

Vascular endothelial growth factor (VEGF) is a growth factor that contributes to the angiogenesis of developing tumors. To interfere with the action of VEGF, a nuclease-stabilized ribozyme, ANGIOZYME, has been developed against VEGF receptor subtype Flt-1 mRNA. To determine which routes of administration would be useful for systemic delivery of this ribozyme, a dose of 30 mg/kg [32P]ANGIOZYME was administered as an i.v., i.p., or s.c. bolus. Concentrations of ANGIOZYME in plasma, femur, kidney, liver, and lung were examined. ANGIOZYME was well absorbed after i.p. (90%) or s.c. administration (77%), with peak plasma concentrations occurring 30 minutes after dosing. Total body clearance after a single dose of 30 mg/kg ANGIOZYME was 20 ml/min/kg, and the elimination half-life was 33 minutes. The apparent volume of distribution at steady-state ranged from 0.5 to 1.3 L/kg. ANGIOZYME was detected in the four tissues examined through the 3 hour sampling period after i.v. or i.p. administration. After s.c. administration, ANGIOZYME was detected in femur, kidney, and lung but not in the liver. The highest concentrations of ANGIOZYME were found in kidney and femur with all three routes. Because of the rapid and extensive absorption after extravascular injections, either i.p. or s.c. administration could be considered for use in pharmacodynamic studies examining the effects of ANGIOZYME or other ribozymes with similar chemical modifications.

Polymer-assisted regenerative therapy: case reports of 22 consecutively treated periodontal defects with a novel combined surgical approach

This report describes the clinical application of an in situ formed barrier of poly(DL-lactide) used in combination with a composite graft of demineralized freeze-dried bone allograft (DFDBA) mixed with calcium sulfate and tetracycline in a ratio of 7:2:1 and citric acid root conditioning for the treatment of intrabony and furcation defects. The clinical outcome was assessed by changes in clinical attachment level (CAL) and probing depth (PD) in 18 consecutively treated patients with 17 intrabony and 5 furcation lesions. After patients demonstrated acceptable oral hygiene, the lesions were surgically treated with combination therapy using an in situ formed barrier over a DFDBA composite graft. Patients followed a stringent postoperative protocol and were evaluated at 6 months postsurgery. CAL improved for all sites from a presurgical average of 8.8+/-2.3 mm to 4.4+/-1.6 mm at 6 months postsurgery (4.4+/-1.5 mm gain), while PD was reduced from an average of 8.3+/-2.1 mm presurgery to 3.3+/-1.1 mm at 6 months postsurgery (5.0+/-1.8 mm reduction). Five furcations were treated, of which 4 were Class II and 1 was Class III. Of these furcation lesions, 3 had complete clinical closure, while 1 improved by 1 grade. The Class III furcation remained the same. Results suggest that DFDBA composite graft covered by an in situ formed barrier on root surfaces treated with citric acid can enhance the prognoses of teeth with periodontal lesions as measured by CAL gains and PD reductions. Further studies are warranted to compare this treatment to other more traditional forms of regenerative therapy to determine its comparative efficacy.

A technique report on the in situ application of Atrisorb as a barrier for combination therapy

This article describes a novel technique in which Atrisorb (Atrix Laboratories) is applied in situ as a barrier over a demineralized freeze-dried bone allograft on roots treated with citric acid. Follow-up reentry at 4.5 months demonstrated the effectiveness of this procedure. A rationale for in situ barrier application is presented.

Cellular uptake properties of a 2'-amino/2'-O-methyl-modified chimeric hammerhead ribozyme targeted to the epidermal growth factor receptor mRNA

Catalytic RNA or ribozymes have important potential applications as molecular biological tools in the study of gene expression and as therapeutic inhibitors of disease-causing genes. Very little is known, however, about the cellular uptake mechanisms of exogenously delivered synthetic ribozymes. In this study, we have characterized the uptake properties of a synthetic, 2'-O-methyl-modified ribozyme containing U4/U7 amino groups within the catalytic core of the hammerhead motif. The cellular uptake of the internally [32P]-radiolabeled hammerhead ribozyme in U87-MG glioma cells was temperature, energy, and pH dependent and involved an active process that could be competed with cold ribozyme of the same chemistry and sequence, an all 2'-O-methyl-modified ribozyme of the same sequence, antisense PS-ODNs, and a variety of other polyanions (salmon sperm DNA, spermidine, dextran sulfate, and heparin). Subcellular distribution studies of fluorescently labeled ribozymes confirmed an extranuclear, punctate localization similar to that observed for an endosomal marker, dextran. Our study highlights that hammerhead ribozymes, despite exhibiting a defined secondary structure, enter cells by an endocytic mechanism that appears to be similar to that reported for a variety of antisense ODNs. These observations should facilitate the development of more efficient delivery systems.

Arbitrarily primed polymerase chain reaction fingerprinting and clonal analysis of oral Fusobacterium nucleatum isolates

F. nucleatum is the most commonly isolated microorganism from subgingival plaque, but the role of this microorganism in periodontal diseases remains undefined. Arbitrarily primed polymerase chain reaction (AP-PCR) was evaluated as a method for fingerprinting F. nucleatum isolates and for use in clonal analysis. Pulsed field gel electrophoresis was used to further differentiate F. nucleatum isolates, with identical AP-PCR patterns. Extremely heterogeneous AP-PCR fingerprints were observed among the 98 F. nucleatum isolates, with 36 different genotypes observed with primer C1 and 30 different genotype detected with primer C2. Combining the results of the AP-PCR genotype analysis from C1 and C2 primer amplifications revealed that up to 7 different genotypes could be distinguished from isolates from the same oral cavity and that up to 4 different genotypes were observed within a single site. An intense amplicon at approximately 450 bp generated in AP-PCR amplification with primer C2 was associated with F. nucleatum subsp. nucleatum (ATCC 25586) and with 15 F. nucleatum isolates from diseased sites and 2 isolates from healthy sites. Pulsed field gel electrophoresis confirmed the AP-PCR genotypes and demonstrated increased discriminatory power over AP-PCR. The results indicated that AP-PCR and pulsed field gel electrophoresis provide a simple and sensitive means for differentiating oral F. nucleatum isolates and further demonstrate the heterogeneity of this species. These techniques may serve as useful tools in the clonal and epidemiological analysis of F. nucleatum isolates, which may help define the role of these microorganisms in periodontal diseases.

High-resolution NMR of an antisense DNA x RNA hybrid containing alternating chirally pure Rp methylphosphonates in the DNA backbone

A high-resolution proton NMR study has been performed on a hybrid duplex formed by a methylphosphonate (MP) oligodeoxyribonucleotide (MPO) and its target oligoribonucleotide, d(T(MP)CC(MP)-TT(MP)AG(MP)CT(MP)CC(MP)TG) x r(CAGGAGCUAAGGA), where MP corresponds to positions of methylphosphonate linkages in the pure R(p) stereoconfiguration. MP-containing analogs of DNA are reported to be effective antisense agents capable of specifically inhibiting protein synthesis with the R(p) chiral MPOs exhibiting greater affinity for the target mRNA than their S(p) counterparts. Nearly complete proton resonance assignments of the hybrid duplex have been made using two-dimensional nuclear Overhauser effect (2D NOE) spectra, at three different mixing times, and double quantum-filtered COSY (2QF-COSY) spectra. The 2QF-COSY cross-peak patterns which are resolved have been analyzed qualitatively to suggest sugar conformations. Distance restraints have been obtained from the 2D NOE spectra of the duplex in D(2)O. These interproton distance restraints were determined using a complete relaxation matrix method to improve accuracy. Specifically, a new approach termed RANDMARDI has been utilized to calculate these distance restraints, accounting for spectral noise and errors in 2D NOE peak volume integration. The calculated interproton distances and sugar puckers have been analyzed to assess the solution conformation of the hybrid. The hybrid duplex appears to have an overall solution structure which is distinct from standard B- and A-forms, but the RNA strand exhibits features of the A-form. The absence of H1'-H2' cross-peaks in the 2QF-COSY spectrum indicates a C3'-endo type of conformation for ribose sugars in the RNA strand. The deoxyriboses in the antisense DNA strand exhibit a mixed behavior with almost equal scalar coupling constant values for H1'-H2' and H1'-H2" and a strong H3'-H4' 2QF-COSY peak pattern. Variations in calculated values of interproton distances and sixth-root R factor analysis of experimental intensities indicate that the hybrid duplex may have a DNA strand with significant conformational plasticity.

Synthesis and thermodynamics of oligonucleotides containing chirally pure R(P) methylphosphonate linkages

Methylphosphonate (MP) oligodeoxynucleotides (MPOs) are metabolically stable analogs of conventional DNA containing a methyl group in place of one of the non-bonding phosphoryl oxygens. All 16 possible chiral R(P) MP dinucleotides were synthesized and derivatized for automated oligonucleotide synthesis. These dimer synthons can be used to prepare (i) all-MP linked oligonucleotides having defined R(P) chirality at every other position (R(P) chirally enriched MPOs) or (ii) alternating R(P) MP/phosphodiester backbone oligonucleotides, depending on the composition of the 3'-coupling group. Chirally pure dimer synthons were also prepared with 2'-O-methyl sugar modifications. Oligonucleotides prepared with these R(P) chiral methylphosphonate linkage synthons bind RNA with significantly higher affinity than racemic MPOs.

Influence of smoking on long-term clinical results of intrabony defects treated with regenerative therapy

This retrospective study compares the short-term (1 year) and long-term (2 to 5 year) clinical results of regenerative therapy in clinical private practice using a bone allograft for the treatment of intrabony defects in smokers and non-smokers. A total of 110 intrabony lesions were treated with demineralized freeze-dried bone allograft (DFDBA) following thorough defect debridement and root preparation in 53 patients (15 cigarette smokers and 38 non-smokers). Assessments of clinical attachment level (CAL) and probing depth (PD) were recorded at pre-treatment, 1 year post-treatment, and 2 to 5 years post-treatment. At 1 year post-treatment, significant gains in mean CAL were maintained for both smokers (2.7 mm) and non-smokers (3.4 mm). Similarly, significant reductions in mean PD were observed for smokers (3.0 mm) and non-smokers (3.8 mm) at the 1-year follow-up. However, when comparing relative improvements in clinical measures, smokers were found to exhibit significantly poorer treatment results (i.e., sites exhibited less CAL gain) at 1 year and 2 to 5 years follow-up. Relative to pre-treatment scores, differences in improvements observed for CAL at the 1-year evaluation (29.2% for smokers and 42.5% for non-smokers) were sustained in the subgroup of patients at 2 to 5 years follow-up (31.3% for smokers and 41.8% for non-smokers). Similar but non-significant trends were observed for relative reductions in probing depth for smokers and non-smokers at 1 year (41.9% for smokers and 49.3% for non-smokers) and 2 to 5 years follow-up (43.9% for smokers and 48.3% for non-smokers) for the subgroup of patients followed beyond 1 year. These results suggest that smoking adversely affects treatment outcome, as measured by gains in clinical attachment levels of intrabony defects treated by regenerative therapy using DFDBA.

Interstrand complex formation of purine oligonucleotides and their nonionic analogs: the model system of d(AG)8 and its complement, d(CT)8

We have investigated the role of purines in interstrand complex formation with regard to substitution of the negatively-charged, phosphodiester backbone by a nonionic, internucleoside linkage. Using the purine oligomer, d(AG)8, its methylphosphonate analog, d(AG)8, and the complementary pyrimidine oligomer, d(CT)8, as a model system, the stoichiometry, conformation, and stability of complexes formed at pH 8 were studied by spectroscopic and electrophoretic methods. When there is only one oligomer species in solution, d(AG)8 behaves as a single-stranded molecule. In contrast, the d(AG)8 oligomer readily forms an intermolecular self-complex, particularly in the presence of magnesium ion. Using either purine oligomer, duplexes can form with the d(CT)8 strand which differ in terms of their conformation and in the dependence of their thermal stability on sodium and magnesium ions. All studies show that a stable triplex forms with a 1:2 d(CT)8:d(AG)8 stoichiometry which does not require high concentrations of sodium or magnesium ions. Triplex formation between the d(CT)8 strand and two d(AG)8 strands was not observed. Native gel electrophoresis suggests that a 1:1:1 d(CT)8:d(AG)8:d(AG)8 complex may be formed. In regard to triplex formation, the advantage of the methylphosphonate backbone on the purine strand is clearly demonstrated.

Antisense oligonucleotide containing an internal, non-nucleotide-based linker promote site-specific cleavage of RNA

We have designed and synthesized a series of novel antisense methylphosphonate oligonucleotide (MPO) cleaving agents that promote site-specific cleavage on a complementary RNA target. These MPOs contain a non- nucleotide-based linking moiety near the middle of the sequence in place of one of the nucleotide bases. The region surrounding the unpaired base on the RNA strand (i.e. the one directly opposite the non-nucleotide-linker) is sensitive to hydrolytic cleavage catalyzed by ethylenediamine hydrochloride. Furthermore, the regions of the RNA comprising hydrogen bonded domains are resistant to cleavage compared with single-stranded RNA alone. Several catalytic moieties capable of supporting acid/base hydrolysis were coupled to the non-nucleotide-based linker via simple aqueous coupling chemistries. When tethered to the MPO in this manner these moieties are shown to catalyze site-specific cleavage on the RNA target without any additional catalyst.

Fate of demineralized freeze-dried bone allografts in human intrabony defects

Demineralized freeze-dried bone (DFDBA) is the most widely used allograft in periodontics. Little information exists, however, on the fate of DFDBA matrix or on the effects of residual particles within grafted defects. The purpose of this study was to histologically examine the fate of DFDBA used for regeneration in intrabony defects. A secondary objective was to compare the amount of new attachment apparatus formation, including component tissues, in relation to the presence or absence of residual graft material. Histologic data were obtained from earlier studies in which intrabony defects grafted with DFDBA were removed at 6 months en bloc and submitted for histologic examination. Histologic sections (1,120) from 12 patients with 32 grafted defects revealed that 72% of the grafted defects exhibited residual DFDBA particles. When present, DFDBA appeared amalgamated within the new viable bone. Data from 5 patients with 14 grafted sites permitted a within-subject comparison of the amount of regeneration in relation to the presence or absence of residual graft material. Defects harboring residual graft particles exhibited significantly greater amounts of new attachment apparatus formation (1.72 mm vs. 0.20 mm), including new bone (2.33 mm vs. 0.23 mm), cementum (1.74 mm vs. 0.23 mm), and associated periodontal ligament than sites without evidence of graft matrix (P < or = 0.05). No apparent differences were seen in the nature of the new attachment apparatus or component tissues, other than in amount of formation. Inflammation and graft containment appear to be important factors influencing the fate of DFDBA and the regenerative response.

Transpyloric passage of feeding tubes in patients with head injuries does not decrease complications

Early enteral nutrition is reported to improve outcome of patients with severe closed head injuries (CHI). The efficacy and safety of nasoenteric tube (NET) feeds, however, has been questioned; the risk of aspiration is the major concern. Our purpose was to determine the rate of transpyloric migration, the efficacy of adjunctive measures to promote passage, and the effect on pulmonary complications. Seventy-four consecutive patients with moderate to severe CHI received enteral nutrition. Glasgow Coma Scale (GSC) score was 5.2 on admission and 6.9 at 48 hours. NETs were placed an average of 5.6 days after admission; an average of three abdominal films per patient were used to assess tube position. No patients had endoscopic NET placement during this period. Ten patients required fluoroscopic placement after failure to pass spontaneously by 5 days. Overall, transpyloric passage was achieved in 32 patients (43%), whereas 42 (57%) remained intragastric. There were no differences between the postpyloric and intragastric groups in days to full feeding (5 vs. 7 days), ventilator days (11.9 vs. 12.5), intensive care unit length of stay (15.5 vs. 15.1), or incidence of pneumonia (81 vs. 69%) or aspiration (6 vs 7%). Sixty-two patients (83%) were transferred to extended care facilities and 50 (68%) were still receiving NET feedings. Spontaneous transpyloric passage of NET occurred in less than one-half of patients with severe CHI. The routine use of adjunctive measures to promote transpyloric passage was not particularly successful, had no obvious benefit, and therefore may not be necessary.

Is the timing of fracture fixation important for the patient with multiple trauma?

OBJECTIVE

The effect of timing of femur fracture fixation for patients with multiple trauma was studied to determine the effect of operative timing on eventual outcome.

METHODS

The relationship between timing of intramedullary rod (IMR) placement, degree of injury, and pulmonary complications was studied in 424 consecutive patients. The authors focused on 105 patients undergoing IMR placement with an Injury Severity score (ISS) of greater than or equal to 18. The effects of timing of IMR placement on various pulmonary complications, organ failure, intensive care unit (ICU) admission, and ventilatory assistance were studied for various time intervals.

RESULTS

Of the 424 patients, pulmonary complications increased slightly in the more seriously injured group (ISS > 18) but were not influenced by the timing of IMR placement. Of the 105 patients undergoing IMR placement with an ISS > or = 18, only 2 patients died. Both patients had an IMR placed in less than 24 hours and died later of head injury and delayed hemorrhage. The incidence of organ failure, number of ventilator days, and length of ICU stay did not differ between the groups based on timing of fracture fixation. The incidence of severe head injuries was higher in the group undergoing delayed IMR placement (> 48 hours).

CONCLUSIONS

Modest delays in IMR placement did not adversely affect patient outcome. Pulmonary complications were related to the severity of injury rather than to timing of fracture fixation. In a well-integrated trauma system, clinical judgment regarding the timing of IMR placement was the most important determinant of outcome. Delays that were made to stabilize the patient, treat associated injuries, and plan orthopedic reconstruction did not adversely affect patient outcome.

The role of bile acid secretion in the hepatic response to operation and infection

Hepatic function is altered in many surgery-related diseases. Bile acid secretion is the major determinant of bile formation and an important indicator of overall hepatic function. To investigate the cause of intrahepatic cholestasis, which is frequently associated with sepsis, we studied the effects of cecal ligation and puncture (CLP) and surgical stress on bile acid secretion and composition. CLP or a sham operation was performed on 20 male Sprague-Dawley rats. Bile was collected from each rat by cannulation of the common bile duct for 10-minute intervals, at 5 and 20 hours after the initial procedure. Bile acid analysis was then performed by high performance liquid chromatography (HPLC). In CLP rats, there was a significant (P < 0.05) cholestatic effect. Bile flow was reduced to 70 +/- 13 per cent at 5 hours, and to 55 +/- 16 per cent at 20 hours (per cent of the sham mean value). In the sham-operated rats, there was a significant choleresis at 20 hours. Bile flow was increased to 146 +/- 13 per cent; bile acid secretion to 245 +/- 24 per cent; and total bile acid concentration to 175 +/- 19 per cent of the sham 5-hour value (P < 0.05). This increased secretion was significantly greater in the metabolites of chenodeoxycholate. However, these surgical stress-associated changes in bile acid secretion and composition did not occur in CLP rats. These findings are consistent with surgical stress-induced induction of 7 alpha-hydroxylase, which was not found in the septic animals. These observations may provide useful insights into the early stages of the pathogenesis of sepsis-related hepatic dysfunction and failure.

Structure and dynamics of a DNA.RNA hybrid duplex with a chiral phosphorothioate moiety: NMR and molecular dynamics with conventional and time-averaged restraints

The three-dimensional structure of two thiophosphate-modified DNA.RNA hybrid duplexes d(GCTATAApsTGG).r(CCAUUAUAGC), one with R-thiophosphate chirality and one with S-thiophosphate chirality, have been determined by restrained molecular dynamics simulations (rMD). As the two yielded almost identical results, a description of results can be presented in the singular. The conformational flexibility of this hybrid has been investigated by employing time-averaged constraints during the molecular dynamics simulations (MD-tar). A set of structural restraints, comprising 322 precise interproton distance constraints obtained by a complete relaxation matrix analysis of the 2D NOE intensities as well as J coupling constants obtained from quantitative simulations of DQF-COSY cross-peaks in deoxyriboses, was reported in our previous paper [González, C., Stec, W., Kobylanska, A., Hogrefe, R. I., Reynolds, M., & James, T. L. (1994) Biochemistry 33, 11062-11072]. Multiple conformations of the deoxyribose moieties were evident from the scalar coupling constant analysis. Accurate distance constraints, obtained from complete relaxation matrix analysis, yielded a time-averaged solution structure via conventional restrained molecular dynamics which is not compatible with the experimental J coupling constants (root-mean-square deviation in J value approximately 2 Hz). However, vicinal coupling constant information can be reproduced when time-averaged constraints are used during the molecular dynamics calculations instead of the conventional restraints (Jrms approximately 0.6 Hz). MD-tar simulations also improve the NMR R factors. This improvement is more evident in the DNA than in the RNA strand, where no indication of conformational flexibility had been obtained. Analysis of the MD-tar trajectories confirms that deoxyriboses undergo pucker transitions between the S and N domain, with the major conformer in the S domain. The ribose moieties in the RNA strand, however, remain in the N domain during the entire simulation. Conformations of deoxyriboses in the intermediate domain near O4'-endo are obtained when the average structure is calculated with conventional NMR restraints. Since these conformations cannot account for the experimental J coupling information, and they only appear in a very low population in the MD-tar ensemble, we conclude that intermediate E sugar puckers are artifacts produced by the attempt to fit all the structural constraints simultaneously when in reality more than one conformer is present. Most structural features of the duplex remain the same in the average structure and in the MD-tar ensemble, e.g., the minor groove width, exhibiting an intermediate value compared with those of canonical A- and B-like structures.(ABSTRACT TRUNCATED AT 250 WORDS)