Pd-Catalyzed Alkene Diamination Reactions of Nitrogen Electrophiles: Synthesis of Cyclic Guanidines and Ureas Bearing Dialkylaminomethyl Groups

The Pd-catalyzed coupling of N-allylguanidines or N-allylureas with O-benzoylhydroxylamine derivatives affords cyclic guanidines or cyclic ureas bearing dialkylaminomethyl groups. The desired products are obtained in good yield, and substrates bearing substituents at the allylic position are transformed with moderate diastereoselectivity. The mechanism of these reactions appears to involve anti-aminopalladation of the alkene, followed by a rare sp³C-sp³N bond-forming reductive elimination from an alkylpalladium complex that contains β-hydrogen atoms.

Synthesis of Cyclic Guanidines Bearing N-Arylsulfonyl and N-Cyano Protecting Groups via Pd-Catalyzed Alkene Carboamination Reactions

Palladium-catalyzed carboamination reactions of N-allylguanidines bearing cleavable N-cyano or N-arylsulfonyl protecting groups are described. The reactions afford cyclic guanidine products in good yield, and transformations of substrates bearing internal alkenes proceed with high diastereoselectivity. Deuterium labeling studies indicate these transformations proceed via anti-aminopalladation pathways.

Palladium-Catalyzed Alkene Carboamination Reactions of Electron-Poor Nitrogen Nucleophiles

Modified reaction conditions that facilitate Pd-catalyzed alkene carboamination reactions of electron-deficient nitrogen nucleophiles are reported. Pent-4-enylamine derivatives bearing N-tosyl or N-trifluoroacetyl groups are coupled with aryl triflates to afford substituted pyrrolidines in good yield. These reactions proceed via a mechanism involving anti-aminopalladation of the alkene, which differs from previously reported analogous reactions of N-aryl and N-boc pentenylamines. The application of these conditions to a formal synthesis of (±)-aphanorphine is also described.

Expanding the diversity of mycobacteriophages: insights into genome architecture and evolution

Mycobacteriophages are viruses that infect mycobacterial hosts such as Mycobacterium smegmatis and Mycobacterium tuberculosis. All mycobacteriophages characterized to date are dsDNA tailed phages, and have either siphoviral or myoviral morphotypes. However, their genetic diversity is considerable, and although sixty-two genomes have been sequenced and comparatively analyzed, these likely represent only a small portion of the diversity of the mycobacteriophage population at large. Here we report the isolation, sequencing and comparative genomic analysis of 18 new mycobacteriophages isolated from geographically distinct locations within the United States. Although no clear correlation between location and genome type can be discerned, these genomes expand our knowledge of mycobacteriophage diversity and enhance our understanding of the roles of mobile elements in viral evolution. Expansion of the number of mycobacteriophages grouped within Cluster A provides insights into the basis of immune specificity in these temperate phages, and we also describe a novel example of apparent immunity theft. The isolation and genomic analysis of bacteriophages by freshman college students provides an example of an authentic research experience for novice scientists.

Effect of prophylactic amoxicillin on endodontic flare-up in asymptomatic, necrotic teeth

The purpose of this prospective, randomized, double-blind, placebo-controlled study was to determine the effect of prophylactic amoxicillin on the occurrence of endodontic flare-up in asymptomatic, necrotic teeth. Seventy patients participated and had a clinical diagnosis of an asymptomatic, necrotic tooth with associated periapical radiolucency. One hour before endodontic treatment, patients randomly received either 3 g of amoxicillin or 3 g of a placebo control in a double-blind manner. After endodontic treatment, each patient received: ibuprofen; acetaminophen with codeine (30 mg); and a 5 1/2-day diary to record pain, swelling, percussion pain, and number and type of pain medication taken. The results demonstrated 10% of the 70 patients had a flare-up characterized by moderate-to-severe postoperative pain or swelling that began approximately 30 h after endodontic treatment and persisted for an average of 74 h. Of the seven patients who had flare-ups, 4 were in the amoxicillin group and 3 were not. Prophylactic amoxicillin did not significantly (p = 0.80) influence the endodontic flare-up. We concluded that a prophylactic dose of amoxicillin before endodontic treatment of asymptomatic, necrotic teeth had no effect on the endodontic flare-up.

Differential engraftment of genetically modified CD34(+) and CD34(-) hematopoietic cell subsets in lethally irradiated baboons

OBJECTIVE

To test gibbon ape leukemia virus (GALV) pseudotype vector transduction of marrow subpopulations that contribute to hematopoietic reconstitution in vivo.

MATERIALS AND METHODS

Autologous CD34(+) Lin(-), CD34(+) Lin(+), and CD34(-) Lin(-) marrow cells, transduced by coculture with PG13/LN, PG13/LNX, and PG13/LNY vector-producing cells, respectively, were transplanted in three female baboons. Two female baboons also were transplanted with fresh allogeneic CD34(-)Lin(-) marrow cells from MHC-matched male siblings and, to ensure survival, with autologous CD34(+)Lin(-) and CD34(+)Lin(+) marrow cells transduced with PG13/LN and PG13/LNX, respectively. The LN, LNX, and LNY vectors are identical except for different length sequences at the 3' end of the bacterial neomycin phosphotransferase (neo) gene.

RESULTS

LN(+) and LNX(+) cells from CD34(+)Lin(-) and CD34(+)Lin(+) cells, respectively, but no LNY(+) from CD34(-)Lin(-) cells were detectable in blood and marrow of all animals after transplant. LN(+), CD34(+)Lin(-) cells contributed to reconstitution of the T, B, and myeloid lineages. LNX(+), CD34(+)Lin(+) cells contributed only to B and myeloid lineages. Male cells, CD34(-)Lin(-), were detected by polymerase chain reaction in blood and marrow of the two allogeneic transplanted animals at estimated frequencies of </=0.001% 1 month after transplant in both animals. Male cells became undetectable in one animal and have remained detectable, with declining frequency, in the other for more than 15 months. In this animal, no male CD34(+) or colony-forming cells have been detected.

CONCLUSIONS

CD34(+)Lin(-) and CD34(+)Lin(+) marrow cells can serve as targets for GALV pseudotype retrovirus-mediated gene transfer. CD34(+)Lin(-) cells contribute to reconstitution of all hematopoietic lineages. Autologous CD34(-)Lin(-) cells were either not transduced by GALV pseudotype retrovirus vectors using current approaches or did not contribute significantly to reconstitution, as suggested by allogeneic transplants.

Practical methods for reducing radioactive contamination incidents in the nuclear cardiology laboratory

OBJECTIVE

The purpose of this study was to determine the extent and cause of radioactive contamination in our nuclear cardiology laboratory, and to develop possible solutions to minimize future occurrence.

METHODS

We conducted a retrospective review to determine the underlying causes of the 15 minor radioactive contamination events that have occurred in the exercise areas of our laboratory since 1986. Of the 15 documented events, 8 were caused by failure of intravenous apparatus and 7 were due to syringe mishandling. Based on a staff questionnaire, we determined the most prevalent causes of radioactive contamination. Other than problems associated with intravenous setup, the causes were lack of experience by the individual performing the injection, followed closely by radioactive syringe disposal problems, injection technique, and unclear designation of duties during the exercise procedure.

RESULTS

Based on these findings, we formulated a 4-part plan: a training program; a closely inspected intravenous apparatus; a mobile radioactive waste container; and a clear designation of duties for personnel to be included in the exercise procedure protocol.

CONCLUSION

We have implemented a sensible and practical plan for reducing radioactive contamination, which is currently being evaluated.

A prospective study of trephined bone grafts of the tibial shaft and iliac crest

Autogenous cancellous bone grafting is a common procedure in maxillofacial surgery. Open harvesting usually results in a long scar and considerable morbidity, but harvesting using a trephine can be done through a smaller scar with minimal morbidity. The commonly used anatomical areas for trephine harvesting are the iliac crest and the tibial shaft. A prospective study was carried out in 30 patients to compare the technique and the morbidity as perceived by patients using a visual analogue scale (VAS) and by an independent observer. The surgical anatomy and techniques are described. The results show no significant difference between the two groups, but the tibial trephine procedure is easier, quicker, and causes less blood loss. The total scores for pain and difficulty in walking were much less for tibial than that for the iliac grafts.

Severe combined immunodeficient mice engrafted with human splenocytes have functional human T cells and reject human allografts

Previous studies have shown that human hemopoietic cells can be adoptively transferred into immunodeficient C.B-17 scid/scid (SCID) mice that lack autologous T and B lymphocytes, to generate chimeric animals. The future development of novel immunomodulatory drugs in transplantation will depend increasingly on experimental animal models to investigate the properties of the agents on human cells before starting clinical trials. However, in previous models of SCID mice engrafted with human PBLs, human T cells have been found either to be in an unresponsive state, unable to respond to mitogenic stimulations in vitro, or to mediate skin graft rejection only when HLA-primed in vivo before their adoptive transfer into SCID mice. In addition, T cells and other leukocyte subsets engraft quite poorly in the lymphoid tissues of the animals. In an attempt to develop a useful model for transplantation research, we have inoculated SCID mice with fresh human splenocytes from cadaveric organ donors (hu-Spl-SCID mice). In this model, various leukocyte subsets engraft effectively in different lymphoid compartments. In addition, human T cells retain their proliferative responses to mitogens and to alloantigens when tested 3 wk after engraftment into SCID mice. Finally, mice engrafted with unprimed human spleen cells acutely reject human foreskin allografts. Treatment of hu-Spl-SCID mice with OKT3, an immunosuppressive mAb directed against the human CD3 complex associated with the TCR, prevents the rejection of most human skin allografts, indicating a major role for human T cells in this phenomenon. Thus, this hu-Spl-SCID model may be useful for the study of immunosuppressive therapies in a preclinical in vivo setting.

Severe combined immunodeficient mice engrafted with human splenocytes have functional human T cells and reject human allografts

Previous studies have shown that human hemopoietic cells can be adoptively transferred into immunodeficient C.B-17 scid/scid (SCID) mice that lack autologous T and B lymphocytes, to generate chimeric animals. The future development of novel immunomodulatory drugs in transplantation will depend increasingly on experimental animal models to investigate the properties of the agents on human cells before starting clinical trials. However, in previous models of SCID mice engrafted with human PBLs, human T cells have been found either to be in an unresponsive state, unable to respond to mitogenic stimulations in vitro, or to mediate skin graft rejection only when HLA-primed in vivo before their adoptive transfer into SCID mice. In addition, T cells and other leukocyte subsets engraft quite poorly in the lymphoid tissues of the animals. In an attempt to develop a useful model for transplantation research, we have inoculated SCID mice with fresh human splenocytes from cadaveric organ donors (hu-Spl-SCID mice). In this model, various leukocyte subsets engraft effectively in different lymphoid compartments. In addition, human T cells retain their proliferative responses to mitogens and to alloantigens when tested 3 wk after engraftment into SCID mice. Finally, mice engrafted with unprimed human spleen cells acutely reject human foreskin allografts. Treatment of hu-Spl-SCID mice with OKT3, an immunosuppressive mAb directed against the human CD3 complex associated with the TCR, prevents the rejection of most human skin allografts, indicating a major role for human T cells in this phenomenon. Thus, this hu-Spl-SCID model may be useful for the study of immunosuppressive therapies in a preclinical in vivo setting.

A non-activating "humanized" anti-CD3 monoclonal antibody retains immunosuppressive properties in vivo

OKT3, a mouse anti-human CD3 mAb, is a potent immunosuppressive agent used in clinical transplantation to prevent or treat allograft rejection. Associated with this therapy is the systemic release of several cytokines that result in a series of adverse side effects. This release of cytokines is dependent on the cross-linking mediated by OKT3 between T cells and the Fc gamma R-bearing cells. To generate an anti-human CD3 mAb with reduced activating properties as compared with OKT3, we have transferred the complementary determining regions of OKT3 onto human IgG frameworks and then performed point mutations that reduce the affinity of the "humanized" anti-CD3 mAbs for Fc gamma Rs. Initial, in vitro, studies showed that whereas OKT3 and the parental humanized anti-CD3 mAbs activated T cells similarly, a humanized Fc variant failed to do so. Both the Fc variant and the activating anti-CD3 mAbs induced comparable modulation of the TCR and suppression of cytolytic T cell activity, in vitro. In the current study, we exploited an experimental model in which human splenocytes from cadaveric organ donors were inoculated into severe combined immunodeficient mice (hu-SPL-SCID mice) to test the activating and immunosuppressive properties of these anti-human CD3 mAbs in vivo. Unlike injection of OKT3 or of the parental humanized mAb, administration of the Fc variant did not result in T cell activation in vivo, as evidenced by the lack of induction of surface markers of activation, and of systemic human cytokines, including IL-2. Importantly, similar prolongation of human allograft survival was achieved with all anti-CD3 mAbs, indicating that the nonactivating anti-CD3 mAbs retained significant immunosuppressive properties in vivo. Thus, the use of an Fc variant in clinical transplantation should result in fewer side effects than observed with OKT3, while maintaining its clinical efficacy.

Contemporary management of deep infections of the neck

Odontogenic infections rarely lead to involvement of the lateral and retropharyngeal spaces. When this does occur, the microbiology of the infection is similar to the typical odontogenic infection, ie, Streptococcus and oral anaerobes including Peptostreptococcus, Bacteroides, and Fusobacterium. There is an increased incidence of Fusobacterium seen in the more severe infections, as well as a higher incidence of Streptococcus milleri. Many patients who have deep cervical infections also have some compromise in their host defense mechanism, such as diabetes. The signs and symptoms of deep cervical space infections are similar to those of the severe submandibular space infection, but also includes sialorrhea, respiratory distress, odynophagia, and dysphagia. Lateral soft-tissue radiographs of the neck are useful in assisting with the diagnosis of retropharyngeal infections, and CT scans can provide definitive information regarding lateral pharyngeal space involvement. Treatment includes the use of high-dose intravenous bacteriocidal antibiotics. The recommended antibiotics are penicillin-metronidazole, ampicillin-sulbactam, or clindamycin. Certain cephalosporins may also be useful in selected patients. Early surgical intervention is also indicated. Aggressive incision and drainage of all of the involved spaces is necessary to assure early resolution of the infection. Continual airway monitoring and the establishment of surgical airways is the final portion of the treatment triad.

A systematic approach to management of high-flow vascular malformations of the mandible

High-flow vascular malformations of the mandible are associated with significant morbidity and mortality. As these lesions are rare, the experience that a clinician has with treatment may be limited. To facilitate understanding and treatment of such lesions in a controlled and efficient manner, a treatment protocol is presented that includes careful preoperative planning, embolization, and surgery.

Acid-base changes in the running greyhound: contributing variables

To determine the factors responsible for changes in [H+] during and after sprint exercise in the racing greyhound, Stewart's quantitative acid-base analysis was applied to arterial blood plasma samples taken at rest, at 8-s intervals during exercise, and at various intervals up to 30 min after a 402-m spring (approximately 30 s) on the track. [Na+], [K+], [Cl-], [total Ca], [lactate], [albumin], [Pi], PCO2, and pH were measured, and the [H+] was calculated from Stewart's equations. This short sprint caused all measured variables to change significantly. Maximal changes were strong ion difference decreased from 36.7 meq/l at rest to 16.1 meq/l; [albumin] increased from 3.1 g/dl at rest to 3.7 g/dl; PCO2, after decreasing from 39.6 Torr at rest to 27.9 Torr immediately prerace, increased during exercise to 42.8 Torr and then again decreased to near 20 Torr during most of recovery; and [H+] rose from 36.6 neq/l at rest to a peak of 76.6 neq/l. The [H+] calculated using Stewart's analysis was not significantly different from that directly measured. In addition to the increase in lactate and the change in PCO2, changes in [albumin], [Na+], and [Cl-] also influenced [H+] during and after sprint exercise in the running greyhound.

Rationale for removing impacted teeth: when to extract or not to extract

Age, crowding, disease and root resorption all influence the decision to remove impacted teeth. While not every impacted tooth causes a significant problem, each has that potential.

Physiological changes in the running greyhound (Canis domesticus): influence of race length

1. Racing greyhounds were allowed to run 402 m, 503 m, and 704 m to determine the influence of increased race length on physiological changes during and after exercise. 2. Plasma and whole blood variables that changed significantly with increased race length were [K+], [total protein], [lactate], hematocrit, and arterial pH. 3. Those variables that changed with increased race distance showed no indication of reaching a plateau; thus, the maximum changes that these variables might undergo with longer exercise duration remains unknown.

A comparison of the stress transfer characteristics of a dental implant with a rigid or a resilient internal element

It has been suggested that there is a unique set of problems associated with joining an implant and a natural tooth with a fixed partial denture. The manufacturer of the IMZ implant system claims that this procedure can be accomplished successfully because of the planned stress-distributing characteristics of their resin internal (intramobile) element. This study compared the difference in the stress patterns generated in photoelastic plastic by an IMZ implant with a resilient or a rigid internal element. Under a standardized cantilever load, the stress patterns were photographed in the field of a circular polariscope. The total stress areas were calculated and a statistical comparison performed. The static load conditions of the model demonstrated no statistical difference between the area of stress pattern generated by an IMZ implant with or without a resilient internal element. Moreover, a single load produced the same deflection of the cantilever beam regardless of which element was interposed.

Early soft tissue ingrowth into porous block hydroxyapatite

A dog model was used to determine the rate of soft tissue infiltration into porous block hydroxyapatite (PBHA) in order to provide a scientific basis for treatment of exposed implants. Ten mongrel dogs underwent alveolar ridge augmentation with PBHA and were killed at various times up to 21 days. Significant soft tissue ingrowth had occurred by 14 days and was complete by day 21. Bone formation was also seen as early as 14 days.

Use of cricothyroidostomy in oral and maxillofacial surgery

Surgical entry into the upper airway is not only important in emergency situations but also in the treatment of certain elective maxillofacial procedures. The procedure of choice by which surgical access is gained has traditionally been a tracheostomy. Although a cricothyroidostomy is easier and quicker to perform, with a higher degree of safety, it has generally been relegated to only emergency situations. The purpose of this paper is to present the anatomy, indications, and surgical technique of cricothyroidostomy. It is concluded that cricothyroidostomy, and not tracheostomy, is the preferred procedure for surgical establishment of an upper airway, either in elective maxillofacial surgical procedures, or in an emergency situation.

Clinical assessment of new I.V. sedation agents and techniques

The purpose of this paper has been to describe the information that must be gathered before a new drug can be used effectively and safely for I.V. sedation. A new drug, midazolam, has been used as an illustrative example.

Treatment of skin graft donor sites with a semipermeable polyurethane dressing

The use of a semipermeable dressing for skin graft donor sites has been described. It permits patients with healing donor sites to ambulate, shower, and wear clothing with no pain during the healing phase. Healing is easily monitored, and signs of infection can be detected early and treated promptly, preventing involvement of the full thickness of the wound. Patients can be discharged from the hospital while the donor site is still healing. The dressing can be removed painlessly at home or in the office. The SPD appears superior to any of the more conventional dressings currently in use for treating skin graft donor sites.