Accuracy of contacts calculated from 3D images of occlusal surfaces

OBJECTIVES

Compare occlusal contacts calculated from 3D virtual models created from clinical records to contacts identified clinically using shimstock and transillumination.

METHODS

Upper and lower full arch alginate impressions and vinyl polysiloxane centric interocclusal records were made of 12 subjects. Stone casts made from the alginate impressions and the interocclusal records were optically scanned. Three-dimensional virtual models of the dental arches and interocclusal records were constructed using the Virtual Dental Patient Software. Contacts calculated from the virtual interocclusal records and from the aligned upper and lower virtual arch models were compared to those identified clinically using 0.01mm shimstock and transillumination of the interocclusal record. Virtual contacts and transillumination contacts were compared by anatomical region and by contacting tooth pairs to shimstock contacts. Because there is no accepted standard for identifying occlusal contacts, methods were compared in pairs with one labeled "standard" and the second labeled "test". Accuracy was defined as the number of contacts and non-contacts of the "test" that were in agreement with the "standard" divided by the total number of contacts and non-contacts of the "standard".

RESULTS

Accuracy of occlusal contacts calculated from virtual interocclusal records and aligned virtual casts compared to transillumination were: 0.87+/-0.05 and 0.84+/-0.06 by region and 0.95+/-0.07 and 0.95+/-0.05 by tooth, respectively. Comparisons with shimstock were: 0.85+/-0.15 (record), 0.84+/-0.14 (casts), and 81+/-17 (transillumination).

CONCLUSIONS

The virtual record, aligned virtual arches, and transillumination methods of identifying contacts are equivalent, and show better agreement with each other than with the shimstock method.

Automated sample exchange and tracking system for neutron research at cryogenic temperatures

An automated system for sample exchange and tracking in a cryogenic environment and under remote computer control was developed. Up to 24 sample "cans" per cycle can be inserted and retrieved in a programed sequence. A video camera acquires a unique identification marked on the sample can to provide a record of the sequence. All operations are coordinated via a LABVIEW program that can be operated locally or over a network. The samples are contained in vanadium cans of 6-10 mm in diameter and equipped with a hermetically sealed lid that interfaces with the sample handler. The system uses a closed-cycle refrigerator (CCR) for cooling. The sample was delivered to a precooling location that was at a temperature of approximately 25 K, after several minutes, it was moved onto a "landing pad" at approximately 10 K that locates the sample in the probe beam. After the sample was released onto the landing pad, the sample handler was retracted. Reading the sample identification and the exchange operation takes approximately 2 min. The time to cool the sample from ambient temperature to approximately 10 K was approximately 7 min including precooling time. The cooling time increases to approximately 12 min if precooling is not used. Small differences in cooling rate were observed between sample materials and for different sample can sizes. Filling the sample well and the sample can with low pressure helium is essential to provide heat transfer and to achieve useful cooling rates. A resistive heating coil can be used to offset the refrigeration so that temperatures up to approximately 350 K can be accessed and controlled using a proportional-integral-derivative control loop. The time for the landing pad to cool to approximately 10 K after it has been heated to approximately 240 K was approximately 20 min.

Limits on the high-energy gamma and neutrino fluxes from the SGR 1806-20 giant flare of 27 December 2004 with the AMANDA-II detector

On 27 December 2004, a giant gamma flare from the Soft Gamma-Ray Repeater 1806-20 saturated many satellite gamma-ray detectors, being the brightest transient event ever observed in the Galaxy. AMANDA-II was used to search for down-going muons indicative of high-energy gammas and/or neutrinos from this object. The data revealed no significant signal, so upper limits (at 90% C.L.) on the normalization constant were set: 0.05(0.5) TeV-1 m;{-2} s;{-1} for gamma=-1.47 (-2) in the gamma flux and 0.4(6.1) TeV-1 m;{-2} s;{-1} for gamma=-1.47 (-2) in the high-energy neutrino flux.

Production scale-up and validation of packaging cell clearance of clinical-grade retroviral vector stocks produced in cell factories

The clinical implementation of gene therapy requires large-scale production of viral vector stocks (VS) derived from packaging cell lines. Upon scaling-up, maintenance of high viral titers and filtration of the VS become significantly challenging. Thus, production schemes amenable to straightforward validation must be developed. To this end, we have established a semi-closed process to manufacture batches of 7 l or more of clinical-grade oncoretroviral VS using 10-tray Cell Factories. Using a peristaltic pump, the VS are collected on 3 consecutive days, filtered, pooled and stored frozen. To ensure the absence of viable vector-producing cells (VPCs) from each VS unit-dose, we undertook an orthogonal log-removal validation study to demonstrate the ability of both the filtration system to remove viable cells and the VS freezing process to inactivate them. We demonstrate a total VPC-reduction of 11.6 log, thus insuring the absence of contaminating VPCs in transduced clinical samples. We also show that this production process generates stable VS that can be stored at -80 degrees C for more than 3 years. Importantly, this relatively simple and affordable process can be customized to generating large volume of VS for small animal or non-human primate studies. This methodology is not limited to the generation of cell-free clinical oncoretroviral VS, and can be applied to other types of vectors produced in packaging cell lines, such as lentiviral vectors.

Conservation of Genes and Culture: Historical and Contemporary Issues

The paper examines the reasons for and consequences of lost domestic animal biodiversity. The origin of domestic poultry and livestock diversity is reviewed from the first center of domestication in the Middle East during the Neolithic Revolution. Accompanied by domestic animals and birds, mankind spread worldwide over the last 12,000 yr, thereby increasing domestic animal biodiversity via adaptation to many environmental challenges, resulting in about 6,000 breeds within only a small number of species used for food. During the last 50 yr of the 20th century, about 20% of these livestock and poultry breeds have become extinct, and the remainder is at risk. This erosion of unique biodiversity is due to changes in farm practices developed in the West that involve mono-breed, intensive farming systems that are unsustainable. The close symbiotic relationship of Homo sapiens and domestic animals and birds over millennia is changing, resulting in a lost understanding of sustainability among urban communities. The single-minded focus on profit is resulting in the loss of the historic European and Western culture based on Judeo-Christian values. Respect for biological boundaries, community, and quality of life are disappearing in Western society. Concurrently, farming is now only a business. The principal decision makers are no longer farmers but business executives, who are remote from the farm. The emphasis on cheap food is the principal driver that leads to increased competition and unsustainable practices. Farmers as well as their breeds are disappearing. The advent of gene technology and transgenic livestock is reviewed with the prospect of extensive manipulation of animal form and function and abuse of genotypes as animals are redesigned, suffer, and lose all dignity. By handling its animals in this manner, high Western civilization is losing its culture and values and becoming simply the top animal species by using its power selfishly. The case is presented that the extinction of animals indicates an urgent need to conserve historic Western culture before it, too, is lost.

Livestock, ethics, and quality of life

Agricultural and animal scientists need to embrace a new vision beyond the single-minded existing pursuit of biological efficiency. The public in the West is no longer concerned solely with cheap food. Other paramount issues define quality of life, including: health and safety of foods; nutritional value; traditional, regional, locally produced, and organic foods; animal welfare; sustainable farming, environment, and rural resources. The paper provides examples of how the credibility of animal scientists has been lost due to some recent unethical behavior. Research, teaching and application of agricultural and animal science, especially of biotechnology, need to be reshaped into a new "Quality of Life Agricultural Era" to replace the "Era of Intensification." This new era will need fresh assumptions, beliefs and leadership to match the emerging social agenda of the 21st century. Animal scientists have a special role in implementing this new plausibility structure.

Elasticity of alveolar bone near dental implant-bone interfaces after one month's healing

Information is scarce about Young's modulus of healing bone surrounding an implant. The purpose of this preliminary study is to quantify elastic properties of pig alveolar bone that has healed for 1 month around titanium threaded dental implants, using the nanoindentation method. Two 2-year-old Sinclair miniswine were used for the study. Nanoindentation tests perpendicular to the bucco-lingual cross section were performed on harvested implant-bone blocks using the Hysitron TriboScope III. Nomarski differential interference contrast microscopy was used to identify pyramidal indentation measurements that were from bone. Reduced moduli, averaged for all anatomical regions, were found to start low (6.17 GPa) at the interface and gradually increase (slope=0.014) to a distance of 150 microm (7.89 GPa) from the implant surface, and then flatten to a slope of 0.001 from 150 to 1500 microm (10.13 GPa). Mean reduced modulus and its relationship to distance did not differ significantly by anatomic location (e.g., coronal, middle, and apical third; P>/=0.28 for all relevant tests) at 1 month after implantation.

Cognitive presentation of multiple sclerosis: evidence for a cortical variant

BACKGROUND

Although neuropsychiatric complications are well recognised, the presentation of multiple sclerosis with cognitive or neuropsychiatric symptoms has generally been considered a rare occurrence and to reflect subcortical pathology.

OBJECTIVES

To document the clinical, neuropsychological, and radiological features of six cases of cognitive presentation of multiple sclerosis, to review the relevant literature, and to propose a possible cortical basis for this clinical presentation.

SUBJECTS

Six patients (five women; age range 38 to 60 years) presented to the memory and cognitive disorders clinic in Cambridge with an initially undiagnosed cognitive/neuropsychiatric syndrome. All underwent neuropsychological evaluation, brain imaging, and ancillary investigations to establish a diagnosis of multiple sclerosis.

RESULTS

The six cases all had a progressive dementia syndrome with prominent amnesia, often accompanied by classic cortical features including dysphasia, dysgraphia, or dyslexia. Mood disturbance was ubiquitous and in three patients there was a long history of preceding severe depression. All six developed characteristic physical signs on follow up, with marked disabilities. A review of 17 previously reported cases highlighted the prominence of memory impairment and depression in the early stages.

CONCLUSIONS

On clinical, pathological, and radiological grounds, the neuropsychiatric presentation of multiple sclerosis may represent a clinicopathological entity of "cortical multiple sclerosis." Failure to recognise this will delay diagnosis and may expose patients to potentially dangerous and invasive investigation. Because the neuropsychiatric features of cortical multiple sclerosis are a major cause of handicap, their early recognition may be particularly important in view of emerging treatments.

The anterior cantilever in the implant-supported screw-retained mandibular prosthesis

STATEMENT OF PROBLEM

When implants are placed interforaminally in mandibular implant-supported screw-retained prostheses, the most anterior implant is usually positioned lingual to the incisors of the prosthesis. This creates an anterior cantilever with the entire prosthesis acting as a class I lever and possibly placing the anterior implant under alternating tension and compression during function.

PURPOSE

The purpose of this study was to measure the anterior cantilever of randomly chosen patients with restored mandibular implant-supported fixed prostheses, and to establish the proportions of anterior to posterior cantilever lengths relative to the anteroposterior spread.

MATERIAL AND METHODS

Thirteen edentulous patients were recruited from the University of Minnesota's dental implant program. Each patient had been restored with a maxillary complete denture and a mandibular implant-supported screw-retained prosthesis supported by 5 endosseous implants. Each patient had 1 mandibular impression made with irreversible hydrocolloid, which was poured in type III gypsum. A FaroArm precision 3D measuring stylus was used to make multiple-axis (X-Y-Z) measurements (mm) on the casts of the dental implants, of anteroposterior spread, and anterior and posterior cantilevers. Presence or absence of screw loosening was noted using a screwdriver with finger pressure. Data were analyzed using a 1-way analysis of variance to compare prostheses with loose screws to prostheses without loose screws, for each of 3 outcome measures: length of anterior cantilever, length of posterior cantilever, and anteroposterior spread (P<.05).

RESULTS

Mandibular anterior cantilever lengths ranged from 5.5 to 14.4 mm with a mean of 8.78 mm. Combined posterior cantilever lengths ranged from 9.2 to 20.9 mm with a mean of 16.2 mm. Anteroposterior spread ranged from 5.2 to 12.3 mm with a mean of 7.9 mm. From a total of 65 retaining screws, 7 were found to be completely loose. No apparent correlation was found between length of mandibular anterior cantilever and screw loosening (P=.45), although the ratio of posterior cantilever to anteroposterior spread (2:4) was significantly associated with screw loosening (P=.006).

CONCLUSION

Within the limitations of this study, anterior cantilevers in mandibular implant-supported screw-retained prostheses were frequent and appeared to depend on implant placement and prosthesis design. The ratio of anterior to posterior cantilever lengths was approximately 1:2.

Innate immune responses in viral encephalitis

The innate immune system is multifaceted, comprised of preformed factors, cells, and many proteins and lipid mediators produced by those cells. In the CNS these are critical in initiation and amplification of the inflammatory response and in the subsequent elicitation of the specific T cell response to viral encephalitis. Cells that are resident in brain parenchyma and peripheral cells that are recruited both play key roles in the hosts's responses. Unlike the peripheral compartments, in the CNS, non-cytolytic means of eliminating viral infections have been critical, since, in contrast to columnar epithelial cells, neurons are non-renewing. When the innate immune responses are inefficient or absent in viral encephalitis, pathology is more likely. Much more work remains to elucidate all of the critical cells and their mediators, as well as to develop new therapies for infections of the CNS.

71-year-old male with progressive dyspnoea and peripheral oedema: a case of cardiac amyloidosis

We present the case of a 71-year-old male with progressive dyspnoea. On physical examination there was evidence of congestive heart failure. The complete blood count was normal and twelve-lead ECG showed low voltage in the standard leads. Chest x-ray showed cardiomegaly, pulmonary congestion and left pleural effusion. Two-dimensional echocardiography and Doppler ultrasound studies revealed biatrial enlargement and a restrictive diastolic filling pattern. Serum protein electrophoresis was abnormal showing a monoclonal elevation of IgG. Amyloid heart disease was suspected. Fat pad biopsy showed findings consistent with amyloid heart disease. Melphalan and prednisone were initiated to help slow the progression of disease.

Composition and mass of the bacteriophage phi29 prohead and virion

The protein composition of the Bacillus subtilis bacteriophage phi29 prohead and virion was determined by combustion of gel bands of (3)H-labeled proteins. Copy numbers of individual proteins were calculated relative to the 12 copies of the head-tail connector protein. The mean numbers of copies of the major capsid protein in the prohead and virion were 241 and 218, respectively, approaching the 235 copies determined previously by cryoelectron microscopy. The mean numbers of copies of the dimeric head fiber on the prohead and virion were 24 and 31, respectively, demonstrating partial occupancy of the 55 fiber binding sites. Measured copies of neck and tail proteins in the virion included 11 of the lower collar, 58 of the appendage, and 9 of the tail; if the true copies of these proteins are 12, 60, and 9, respectively, the entire neck and tail of phi29 has quasi-sixfold symmetry. The mass of the fiberless prohead with pRNA was about 14.2 MDa, and the mass of the prohead determined by scanning transmission electron microscopy was consistent with the biochemical data. The mass of the fiberless virion containing the 12.8-MDa DNA genome was about 30.4 MDa. A full complement of dimeric fibers on the prohead or virion would increase the mass of the particle by about 3.2 MDa. The data complement studies relating the structure of phi29 components to dynamic functions in morphogenesis and infection.

Operator-induced compressive axial forces during implant gold screw fastening

STATEMENT OF PROBLEM

The gold screw of an implant is put under tension during fastening. An increase in operator-induced compressive axial force during fastening may diminish screw tension, lower the friction between the screw threads, and allow for increased tightening torque.

PURPOSE

This study was undertaken to assess and compare the compressive axial forces and torques placed simultaneously on implant gold screws by persons with varying degrees of expertise.

MATERIAL AND METHODS

A calibrated electric torque driver was used to fasten implant gold screws. Three groups of operators with various levels of implant experience (faculty [F; n = 4], prosthodontic residents [R; n = 4], and undergraduate dental students [S; n = 6]) were asked to repeatedly tighten and loosen a new gold abutment screw into a standard 3.75-mm diameter Branemark abutment. Compressive axial forces during torquing were assessed over the tightening time by means of a miniature load cell adapted to the electric torque driver. Each operator repeated the experiment 3 times after calibration. Within operator and between operator reliability were evaluated.

RESULTS

Loosening compressive axial forces were always higher than tightening compressive axial forces, and peak torque was less on loosening than tightening. Faculty placed a smaller range of forces on the screws (mean = 3.29 N, SD +/- 1.45 N) than did the residents (mean = 2.74 N, SD +/- 1.96) or the students (mean = 3.01 N, SD +/- 2.54).

CONCLUSION

The clinical experience of operators seems to influence their application of compressive axial force during gold screw tightening. Less torque during unfastening of gold screws seems to be related to increased axial loading.

Assessment of recovery in patients undergoing intravenous conscious sedation using bispectral analysis

PURPOSE

The Bispectral Index (BIS) has been recently shown to objectively predict the level of sedation in patients undergoing conscious sedation. It was the goal of this study to directly compare the recovery profile of patients where the BIS was used to monitor sedation with a control group where the monitor was not used.

PATIENTS AND METHODS

Forty patients undergoing third molar extractions under intravenous conscious sedation were randomly assigned to 2 groups. In both groups, induction of sedation was performed using a standard dose of fentanyl (1.5 microg/kg) and midazolam (0.05 mg/kg). Propofol was then given in 10 to 20 mg boluses until a clinically desirable sedation level was achieved. In 1 group, the BIS was then monitored continually during surgery using a microcomputer (Aspect-1050 Monitor, Aspect Co, Natick, MA) and recorded at 5-minute intervals. The anesthetist (N.A.S.) provided additional propofol boluses to maintain a BIS level of 70 to 80. In the other group, the BIS sensor was applied, but the monitor was not used. In this group, the sedation was modified, and additional propofol was given based solely on the anesthetist's subjective assessment of the desired level of sedation (Observer's Assessment of Alertness/Sedation [OAA/S] scale level 2 to 3). Additional boluses of 1 mg of midazolam were given during the procedure if patients required repeated boluses of propofol at less than 5-minute intervals to maintain the desired sedation level (BIS level of 70 to 80 or OAA/S level of 2 to 3). These additional midazolam boluses, as well as the time of the last sedative dose (propofol or midazolam) were recorded to study the effect of these factors on recovery.

RESULTS

Of the 40 patients initially included in the study, 1 subject in the BIS-monitored group was excluded due to the loss of intravenous access at initiation of the case. For the remaining 39 subjects, 19 were assessed objectively using the BIS monitor, whereas 20 were assessed subjectively using the OAA/S scale. The BIS cases were slightly longer in duration than the OAA/S cases, lasting an average of 26 minutes versus 22 minutes. This difference was statistically nonsignificant (P =.19). Less propofol was used in the BIS cases, with an average of 98 mg for BIS cases versus 106 mg for OAA/S cases (P =.59). The total dose in mg/kg/min was significantly less in the BIS group (0.054 mg/kg/min) than in the OAA/S group (0.074 mg/kg/min; P =.0082). There was no significant difference in the amount of midazolam administered after induction between the 2 groups (P =.60). The surgeon, who was blinded to whether the monitor was used, ranked the third molar extractions more difficult in the BIS group (P =.05). However, patients in the BIS group were on average more cooperative, with better maintenance of muscle tone. The difference in these parameters were nonsignificant (P =.15 and .092, respectively). A positive Romberg test was obtained earlier in BIS patients, although this difference was nonsignificant (P =.097). The straight-line test was completed significantly sooner in BIS patients (P =.013). There was no significant difference between the BIS and OAA/S groups in perceptual speed (P =.55) or computation (P =.32). There was essentially no difference between groups in patient-assessed comfort or recall of the procedure. There were also no notable differences in anesthesia complications, return to activities of daily life, or pain medication use between the 2 groups.

CONCLUSIONS

The BIS provides additional information for standard monitoring techniques that helps guide the administration of sedative-hypnotic agents. It appears that use of the BIS monitor can help to titrate the level of sedation so that less drugs are used to maintain the desired level. The trend toward an earlier return of motor function in BIS-monitored patients warrants further investigation.

Volumetric umbilical artery blood flow: comparison of the normal versus the single umbilical artery cord

OBJECTIVE

This was a study of the volumetric blood flow in single umbilical artery (SUA) cords as compared to three-vessel cords.

HYPOTHESIS

SUA flow will be twice that of an artery in a normal cord.

METHODS

We studied 276 patients (24 SUA, 252 normal cord) at 18-40 weeks' gestation utilizing gray-scale and color Doppler. Flow, flow/kg, velocity, artery diameter, Doppler velocimetry indices, estimated fetal weight (EFW) and amniotic fluid index (AFI) were compared. All fetuses were anatomically and cytogenetically normal.

RESULTS

Blood flow increased with advancing gestation and the SUA volume was twice that in the normal cord artery. Flow/kg decreased for both cords, with the SUA values twice those of normal cords. Arterial diameter and velocity increased, but to a greater degree in SUA. Velocimetry, although in the normal range, decreased progressively with the resistance indices always lower in the SUA cord. EFW and AFI were the same for both groups.

CONCLUSION

Volumetric blood and its components were measured indirectly with ultrasound. The SUA cord artery carried twice the blood volume of an artery in a three-vessel cord. Other flow parameters changed appropriately to explain the increased flow. For the anatomically normal fetus with SUA there was no increase in intrauterine growth restriction.

Non-Alzheimer dementias

The past decade has seen a considerable resurgence of interest in non-Alzheimer forms of neurodegenerative dementia. Advances in our understanding and classification of these conditions have taken place over a diverse range of disciplines: from genetics and immunohistochemistry to neuropsychology and psychiatry. The aim of this article is to review, from a clinician's perspective, our current understanding of the major degenerative dementias that fall into the differential diagnosis of Alzheimer's disease. The clinical variants of frontotemporal dementia (semantic dementia, progressive nonfluent aphasia, and dementia of a frontal type), amyotrophic lateral sclerosis associated dementia, corticobasal degeneration, and dementia with Lewy bodies are considered.

A randomized, controlled trial of transcutaneous carbon dioxide monitoring during ERCP

BACKGROUND

Pulse oximetry, used to monitor oxygen saturation during endoscopy, does not directly measure hypoventilation. Study goals were to determine whether transcutaneous carbon dioxide (PtcCO(2)) monitoring during endoscopic retrograde cholangiopancreatography (ERCP) prevents severe hypoventilation and to assess the accuracy of clinical observation and pulse oximetry in detecting hypoventilation.

METHODS

All patients received intensive clinical and electronic monitoring including pulse oximetry. Supplemental oxygen was administered for pulse oximetry < 90%. Patients were randomized to a treatment arm (group 1) where PtcCO(2) monitoring guided sedation or a control arm (group 2) where PtcCO(2) was recorded but unavailable for guiding sedation.

RESULTS

Group 1 had significantly fewer episodes of severe carbon dioxide retention (rise in PtcCO(2) >/=40 mm Hg above baseline) than group 2 (0 of 199 versus 5 of 196, respectively, p = 0.03), as well a shorter mean duration of procedure discomfort (8.3% of procedure duration rated as "uncomfortable" versus 11.5%, p = 0.04). Correlations between clinical observation and objective measures of ventilation were poor: level of sedation versus PtcCO(2) (R = 0.3) or pulse oximetry (R = 0.06); slowest respiratory rate versus PtcCO(2) (R = 0.4) or pulse oximetry (R = -0.4). PtcCO(2) rises of greater than 20 mm Hg occurred without oxygen desaturation in 10.7% of patients receiving supplemental oxygen.

CONCLUSIONS

Carbon dioxide retention during ERCP is not reliably detected by clinical observation or by pulse oximetry in patients receiving supplemental oxygen. The addition of PtcCO(2) monitoring prevents severe carbon dioxide retention more effectively than intensive clinical monitoring and pulse oximetry alone. The clinical relevancy of this observation needs to be determined in an appropriately designed outcome study.

The effects of cisplatinum and vincristine on peripheral nerve regeneration

Current treatment modalities for extremity sarcoma often include tumor extirpation plus neoadjuvant therapy. Limb-sparing surgery may require reconstruction of critical nerve defects. Neurotoxic side effects from adjuvant chemotherapy have been reported and raise concerns regarding the effects of chemotherapy on nerve regeneration. In an attempt to define the effects of adjuvant chemotherapy on peripheral nerve regeneration, cisplatin and vincristine were administered to rats following isografting of the posterior tibial nerve. Parameters used to assess peripheral nerve regeneration included walking track analysis and histomorphology. Sixty 250-g Sprague-Dawley rats were randomly allocated into one of three treatment groups. Each animal underwent a 15-mm reversed interposition nerve isograft from 30 donor rats into the right posterior tibial nerve. Ten animals served as control. The remaining animals were divided into two groups of 25 animals each. One group received cisplatin (75 mg/m2) and the other group received vincristine (1 mg/m2). Chemotherapy was administered at 4-week cycles for a total of six cycles (24 weeks). Walking track analysis was performed monthly. Nerve specimens were harvested from the grafted segment and the distal posterior tibial nerve for histomorphology. Walking track analysis demonstrated no statistical difference in print length between the control and chemotherapeutic groups at the conclusion of the study. The number of axons per square millimeter and nerve fiber density were not statistically different between control and chemotherapeutic groups. In the rodent posterior tibial nerve model, postoperative adjuvant therapy does not significantly alter functional outcome in peripheral nerve regeneration. The practice of immediate nerve grafting after tumor extirpation, despite planned postoperative chemotherapy, is supported.

Restructuring a competency-based orientation for registered nurses

A competency-based orientation is an orientation program that focuses on a new employee's ability to actually perform the expectations of his or her role in a particular setting. It differs from a traditional model in which the focus is on the cognitive knowledge necessary for the role. The authors will identify key elements educators may consider when evaluating such a program. The process used by the author's organization to evaluate and restructure the competency-based orientation program for registered nurses is also described.

In vivo evaluation of poly(L-lactic acid) porous conduits for peripheral nerve regeneration

The present study provides in vivo trials of poly(L-lactic acid) (PLLA) as a porous biodegradable nerve conduit using a 10 mm sciatic nerve defect model in rats. The PLLA conduits, fabricated by an extrusion technique, had an inner diameter of 1.6 mm, an outer diameter of 3.2 mm, and a length of 12 mm. They were highly porous with an interconnected pore structure (of 83.5% porosity and 12.1 microm mean pore size). The conduits were interposed into the right sciatic nerve defect of Sprague Dawley rats using microsurgical techniques; nerve isografts served as controls. Walking track analysis was performed after conduit placement monthly through 16 weeks. At the conclusion of 6 and 16 weeks, sections from the isograft/conduit and distal nerve were harvested for histomorphometric analysis. The right gastrocnemius muscle was also harvested and its weight was determined. All conduits remained intact without breakage. Moreover, no conduit elongated during the 16 weeks of placement. Walking track analysis and gastrocnemius muscle weight demonstrated increasing regeneration over the 16 weeks in both the conduit and isograft control groups, with control values significantly greater. The nerve fiber density in the distal sciatic nerve for the PLLA conduits (0.16+/-0.07) was similar to that for the control isografts (0.19+/-0.05) at 16 weeks. The number of axons/mm2 in the distal sciatic nerve for the PLLA conduits was lower than that for the isografts (13 800+/-2500 vs. 10700+/-4700) at 16 weeks. The results for PLLA were significantly improved over those for 75:25 poly(DL-lactic-co-glycolic acid) of a previous study and suggest that PLLA porous conduits may serve as a scaffold for peripheral nerve regeneration.

Risk factors for development of sexually abusive behaviour in sexually victimised adolescent boys: cross sectional study

OBJECTIVE

To identify factors that may increase the risk of a sexually victimised adolescent boy developing sexually abusive behaviour.

DESIGN

Sexually victimised boys who had sexually abused other children were compared with sexually victimised boys who had not done so.

SETTING

Social services departments in south east England were invited to refer sexually abused and sexually abusing boys to a London postgraduate teaching hospital.

SUBJECTS

25 adolescent boys aged between 11 years and 15 years and 11 months.

MAIN OUTCOME MEASURES

Adjusted odds ratios estimated from unconditional logistic regression.

RESULTS

Unadjusted odds rations for witnessing (8.1) as well as experiencing (18.0) intrafamilial violence and discontinuity of care (7.2) discriminated boys who had sexually abused from others who were solely victims of sexual abuse. Only the adjusted odds ratios for witnessing intrafamilial violence (39.7) discriminated the two groups.

CONCLUSIONS

The risk of adolescent boys who have been victims of sexual abuse engaging in sexually abusive behaviour towards other children is increased by life circumstances which may be unrelated directly to the original abusive experience, in particular exposure to a climate of intrafamilial violence. Our findings have implications for the management of boys found to have been sexually abused and raise important questions about the possibility of secondary prevention of subsequent abusive behaviour in those at greatest risk.