Technical note: Nitrogen isotopic fractionation can be used to predict nitrogen-use efficiency in dairy cows fed temperate pasture.

The objective of this study was to investigate the relationship between nitrogen isotopic fractionation (δ(15)N) and nitrogen-use efficiency (milk nitrogen/nitrogen intake; NUE) in pasture-fed dairy cows supplemented with increasing levels of urea to mimic high rumen degradable protein pastures in spring. Fifteen cows were randomly assigned to freshly cut pasture and either supplemented with 0, 250, or 336 g urea/d. Feed, milk, and plasma were analyzed for δ(15)N, milk and plasma for urea nitrogen concentration, and plasma for ammonia concentration. Treatment effects were tested using ANOVA and relationships between variables were established by linear regression. Lower dry matter intake (P = 0.002) and milk yield (P = 0.002) occurred with the highest urea supplementation (336 g urea/d) compared with the other two treatments. There was a strong linear relationship between milk δ(15)N - feed δ(15)N and NUE: [NUE (%) = 58.9 - 10.17 × milk δ(15)N - feed δ(15)N (‰) (r(2) = 0.83, P < 0.001, SE = 1.67)] and between plasma δ(15)N - feed δ(15)N and NUE: [NUE (%) = 52.4 - 8.61 × plasma δ(15)N - feed δ(15)N (‰) (r(2) = 0.85, P < 0.001, SE = 1.56)] . This study confirmed the potential use of δ(15)N to predict NUE in cows consuming different levels of rumen degradable protein.

Timing of supplementation alters grazing behavior and milk production response in dairy cows.

Offering feed supplements to grazing dairy cows results in substitution of pasture; however, previous data indicate that the time at which concentrate supplements are offered might affect the level of substitution. These data indicated that cows grazed more intensely presunset, regardless of the amount of supplement offered. It was, therefore, hypothesized that substitution rate would be less, and response to supplement greater if cows received their supplement at the p.m. rather than the a.m. milking. Forty-eight multiparous, nonpregnant, Holstein-Friesian cows, approximately 60 d in milk, were randomly allocated to 1 of 3 treatments in an incomplete crossover arrangement. Treatments were pasture only, pasture + 3 kg of concentrate supplement dry matter (DM) offered during the a.m. milking (AM-SUP), and pasture + 3 kg of concentrate supplement DM offered during the p.m. milking (PM-SUP). Time spent grazing and calculated pasture DM intake did not differ between the AM-SUP and PM-SUP cows. However, a tendency (0.18 kg of milk/kg of concentrate DM) was observed for an increased marginal milk response (kg of milk/kg of DM supplement) for the AM-SUP cows when compared with PM-SUP cows. Irrespective of when supplements were offered, supplementation reduced total grazing time by a similar amount, and the reduction in time spent grazing was evident throughout the day. Cows in the PM-SUP group ruminated for longer and cows in the AM-SUP group spent more time idle compared with the pasture only groups. Cows in the AM-SUP group grazed for less time during the major a.m. grazing bout following a.m. milking compared with PM-SUP cows; in comparison, the major p.m. grazing bout following p.m. milking was unaffected by supplementation. The results indicated possible improvements in marginal milk response to supplements from altering the timing of delivery.

Assessment of the production of analgesia induced by application of a rubber ring or local anaesthetic to the antler pedicle of yearling stags.

AIMS: To compare two methods of applying rubber rings to the pedicles of yearling stags to induce analgesia in the antler prior to removal. To compare the application of a rubber ring with that of a lignocaine ring block of the antler pedicle on the efficacy and time course of the analgesia produced in yearling stags. METHODS: Rubber rings were applied to the pedicles of 36 yearling stags that required velvet antler removal. The standard method, a doubled-over ring expanded and lowered down from the distal end of the antler and released midway down the pedicle, was compared with a cable-tie method on the other pedicle, where a ring was pulled around the pedicle by an electrical cable tie threaded through the ring. Brief electrical stimulation (train-of-four mode) was applied proximal and distal to the ring before, and at regular intervals for 1 hour after, application of the ring to a level that produced an auriculopalpebral reflex response. In a second experiment, each pair of antlers per yearling stag (n=36) was allocated to one of three pairs of treatments, viz no treatment (control) and the cable-tie method as described above, control and local anaesthesia (a ring block of 2 ml 2% lignocaine per cm pedicle circumference), or the cable-tie method and local anaesthesia. Electrical stimulation (tetanic mode) was applied to each antler approximately 25 mm distal to the pedicle/antler junction before, and at intervals up to 1 hour after, application of treatments at a level required to produce a head/neck avoidance behavioural response. In a third experiment, the two electrical stimulation protocols used above were directly compared by measuring the response of stags (n=8) to one protocol on each pedicle/antler prior to, and at intervals for 1 hour after, application of a rubber ring. At the end of each treatment in all three experiments, analgesia of the antler was established as a nil behavioural response of the stag to a saw cut to the antler (the 'nick test'). RESULTS: For both methods of application of a ring the minimum electrical stimulation required distal to the ring to elicit a reflex response increased from around 16 to 55 mA by 60 minutes. In contrast, the electrical stimulation required proximal to the ring remained low (approximately 17.0 mA) throughout. No stag subjected to either of the methods of application responded to the nick test 60 minutes after application of the ring. The electrical stimulation required to produce a behavioural response increased very rapidly in stags treated with local anaesthetic and at a slower rate in those treated with the cable-tie method but showed no significant increase in control stags. After 4 and 30 minutes, for local anaesthesia and the cable-tie method, respectively, 95% of stags were not responding to 80 mA. A significantly greater proportion of stags with antlers treated with local anaesthetic and the cable-tie method did not respond to the nick test than controls, and there was no significant difference in the frequency of the response between stags with treated antlers. The minimum current required to produce a response proximal to a rubber ring was slightly higher on average for train-of-four electrical stimulus (mean 18.1 (SD 2.6) mA) than for the tetanic mode (mean 11.9 (SD 2.5) mA). The increase in minimum current required to produce the respective response to stimulation distal to the ring was similar for both methods, although the maximum predicted value (67.4 mA) was lower for train-of-four than for the tetanic mode (84.5 mA). No stag responded to the nick test > or = 60 minutes after application of the ring. CONCLUSIONS: The cable-tie method was no different from the standard method as a procedure for producing analgesia in the antlers of yearling stags and should be accepted as an appropriate procedure for applying analgesic rings to yearling stags. The analgesia produced in the antlers of yearling stags by rubber rings applied by the cable-tie method to the pedicle was similar to that of a lignocaine ring block, but the time course for the development of analgesia was markedly different. Given that a lignocaine ring block is accepted as an adequate method of pain relief for antler removal, the application of rubber rings followed by a period of > or = 30 minutes after application can be advocated as a viable alternative for pain relief.

Neighbourhood deprivation and dental service use: a cross-sectional analysis of older people in England.

BACKGROUND: Appropriate dental care is an important part of maintaining good oral health. We examined the relationship between socioeconomic status, neighbourhood deprivation levels and older people's dental service use. METHODS: We used logistic regression analysis to assess the relationship between self-reported dental service use and neighbourhood deprivation, adjusting for individual socioeconomic and health factors, in individuals aged 65+ in the 2005 Health Survey for England (n = 4240). RESULTS: Among dentulous respondents, 69.9% reported attending for regular check-ups, 6.2% occasional check-ups, 18.4% only saw a dentist when in trouble and 5.6% never went to a dentist. In our adjusted model age, sex, region, education level, occupational social class, self-reported health and smoking status, but not degree of urbanization, were associated with use of dental services. Following adjustment for these other factors those living in the most deprived 20% of neighbourhoods, compared with those in the least deprived, had a relative risk ratio of 2.25 (95% confidence interval 1.59-3.17) of using dental services only when symptomatic, rather than going for regular or occasional check-ups. When alternative outcomes of reporting having recently seen a doctor or been a hospital inpatient were assessed these deprivation-related patterns in service use were not evident. CONCLUSION: Levels of neighbourhood deprivation are associated with the use of dental services by older people. Action is needed to ensure older people in deprived communities access appropriate and comprehensive dental services.

Rapid analysis of non-uniformly sampled pulsed field gradient data for velocity estimation.

Bretthorst's recent generalization of the Lomb-Scargle periodogram shows that a sufficient statistic for frequency estimation from non-uniformly, but simultaneously sampled quadrature data is equivalent to the FFT of those data with the missing samples replaced by zeros. We have applied this concept to the rapid analysis of pulsed field gradient MRI data which have been non-uniformly sampled in the velocity encoding wave vector q. For a small number of q samples, it is more computationally efficient to calculate the periodogram directly rather than using the FFT algorithm with a large number of zeros. The algorithm we have implemented for finding the peak of the generalized periodogram is simple and robust; it involves repeated apodization and grid searching of the periodogram until the desired velocity resolution is achieved. The final estimate is refined by quadratic interpolation. We have tested the method for fully developed Poiseuille flow of a Newtonian fluid and have demonstrated substantial improvement in the precision of velocity measurement achievable in a fixed acquisition time with non-uniform sampling. The method is readily extendible to multidimensional data. Analysis of a 256 by 256 pixel image with 8 q samples and an effective velocity resolution of better than 1/680 of the Nyquist range requires approximately 1 minute computation time on a 400 MHz SUN Ultrasparc II processor.

Effective dose equivalent and effective dose: comparison for common projections in oral and maxillofacial radiology.

OBJECTIVES: Effective dose equivalents (H(E)) and effective doses (E) for radiographic projections common in dentistry, calculated from the same organ dose distributions, are presented to determine whether the 2 quantities can be directly compared. STUDY DESIGN: Doses to all organs and tissues in the head, neck, trunk, and proximal extremities were determined for each projection (intraoral full-mouth radiographic survey, panoramic, cephalometric, temporomandibular tomograms, and submentovertex view) by computer simulation with Monte Carlo methods. H(E) and E were calculated from these complete distributions and by methods prescribed by the International Commission on Radiological Protection (ICRP). RESULTS: H(E) and E computed from complete dose distributions were found comparable within a few percentage points. However, those computed by strict application of ICRP methods were not. CONCLUSION: For radiographic projections with highly localized dose distributions, such as those common in dentistry, direct comparison of H(E) and E may not be meaningful, unless both computation algorithms are known.

Prospective study of modified condylotomy for treatment of nonreducing disk displacement.

OBJECTIVE: This study was performed to provide an objective assessment of the outcome of modified condylotomy for treatment of the painful temporomandibular joint with nonreducing disk displacement (Wilkes late stage III, IV, V). STUDY DESIGN: A prospective study of 31 consecutive patients (43 joints) was conducted. All patients had nonreducing disk displacement verified by means of disk imaging. Independent evaluations were performed to assess pain, dysfunction, and progression of disease. The examinations were performed before modified condylotomy and at intervals up to 1 year after the operation. Eighteen patients (26 joints) completed the required examinations. Patient-based assessments were completed for pain and diet on 15 of these 18 patients (23 joints) 3 years after the operation. RESULTS: Visual analog scale (VAS) scores (mean +/- SE) for pain improved from 7.4 +/- 0.4 before modified condylotomy to 2.4 +/- 0.5 1 year later (P <. 001). Joints with degenerative joint disease (Wilkes stage IV, V) had less satisfactory pain relief compared with stage III joints (3. 6 +/- 0.9 vs 1.1 +/- 0.4, P =.05) and an 11-fold higher risk (P <. 04) for serious residual pain (VAS score >4). Dietary restrictions improved from a mean VAS score of 5.3 +/- 0.7 before the operation to 7.7 +/- 0.5 1 year later (P =.02). Minor differences between mean VAS scores at 1 (2.1 +/- 0.5) and 3 (2.1 +/- 0.5) years for pain, and 1 (7.4 +/- 0.6) and 3 (8.1 +/- 0.6) years for diet, were not significant. Mean maximal interincisal opening was 36.7 +/- 2.0 mm before the operation, and this improved to 40.1 +/- 2.0 mm 1 year later (P <.02). Mean contralateral movement was 8.3 +/- 0.5 mm before the operation and 8.4 +/- 0.6 mm 1 year after the operation (P >.05). None of the 12 Wilkes late III joints progressed to Wilkes IV or V, and none of the 14 Wilkes IV, V joints showed evidence of further bone resorption. The rate for reoperation was 4%. Minor complications occurred in 5 patients and were resolved in all but 1 a year later. When these outcomes were judged by 7 American Association of Oral and Maxillofacial Surgeons assessment indices for internal derangement, the mean rate of favorable outcome was 87%. CONCLUSION: Modified condylotomy is a safe and effective operation for treating pain and diminished function of temporomandibular joints with nonreducing disk displacement. It also seems to be an effective treatment for slowing further progression of the internal derangement and associated pathologic conditions.

One- and three-year prospective outcome study of modified condylotomy for treatment of reducing disc displacement.

PURPOSE: This outcomes study was designed to provide a comprehensive evaluation of modified condylotomy for the treatment of the painful temporomandibular joint with reducing disc displacement (Wilkes stage II, early III). PATIENTS AND METHODS: A prospective study of 48 consecutive patients (79 joints) was conducted. All reducing disc displacements were verified by disc imaging. Independent evaluations were performed to assess pain, dysfunction, and progression of disease before modified condylotomy and at intervals up to 1 year after operation. Thirty-one patients (50 joints) completed the examination before the operation and 1 year later. Patient-based assessments were made for pain and diet in 22 patients (35 joints) 3 years after operation. RESULTS: The mean (+/- SE) visual analog scale (VAS) score for pain improved from 6.9+/-0.4 before modified condylotomy to 2.0+/-0.4 1 year later (P < .001). Serious pain (VAS score greater than 4) after operation was 7 times more likely (P < .04) when there was persistent disc displacement. The mean frequency of pain each day decreased from 14.6+/-1.4 hours to 4.8+/-1.3 hours (P < .001). Dietary restrictions improved from a mean VAS score of 6.1+/-0.5 before operation to 8.8+/-0.3 at 1 year (P < .001). Small differences between mean VAS scores for pain at 1 (2.0+/-0.5) and 3 (2.7+/-0.5) years and diet at 1 (8.6+/-0.4) and 3 (8.4+/-0.5) years after operation were not significant. Mean maximal incisal opening was 41.7+/-1.2 mm before operation and 43.5+/-1.1 mm 1 year later, but the difference was not statistically significant. Mean contralateral movement improved from 8.1+/-0.3 mm to 8.9+/-0.3 mm 1 year after operation (P < .05). Clicking was reduced from 64% of joints to 16% 1 year after operation (P < .001). The disc was reduced in 72% of joints, healing of an incipient degenerative lesion occurred in 1 joint, and there was no evidence of progression to nonreducing disc displacement (Wilkes late III, IV, V) or DJD (Wilkes IV, V) in any joint 1 year after modified condylotomy. The rate for reoperation was 4%. Complications occurred in 4 patients after operation and were resolved 1 year later. When these outcomes were judged by 7 AAOMS assessment indices for internal derangement, the mean rate of favorable outcome was 94%. CONCLUSION: Modified condylotomy is an effective operation for treating pain and diminished function of temporomandibular joints with reducing disc displacement. It is also an effective treatment for slowing and, in some cases, reversing the progression of internal derangement.

Transdermal water mobility in the presence of electrical fields using MR microscopy.

Magnetic resonance microscopy of skin from hairless rats under the influence of electrical fields was conducted for two cases: 1) low voltage constant electrical fields and 2) high-voltage short pulse, electrical fields. Under conditions of the low voltage and low current iontophoresis, i.e., 0 to 20 V, and 0 to 0.5 mA/cm2, it was found that the skin structure, as observed by magnetic resonance microscopy, did not significantly change until 20 Volts were applied across the 0.1 cm thick skin. Under these conditions, the viable epidermis appeared to swell, and this result corresponded to observations from scanning electron microscopy and other research from the literature. High voltage electrical fields, i.e., 220 V 1 ms pulses repeated once per second, appeared to hydrate the stratum corneum as is consistent with published literature on electroporation. In the case of iontophoresis, water self-diffusion coefficients in the epidermis and hair follicle regions at all voltages were affected by the electrical field. Statistical analysis at the 95% confidence level for the comparison of the average differences between diffusion coefficients with the electrical field on and with the electrical field off for pair matched pixels for the viable epidermis show that for 5 V (p = 0.00377), 10 V (p = 0.0108), 20 V (p = 0.0219) regimes there are statistically significant (p < or = 0.05) changes due to the applied electric field. The same analysis for the hair follicle region at 5 V (p = 6.89 x 10(-7)), 10 V (p = 1.42 x 10(-5)), 20 V (p = 3.23 x 10(-3)) also show statistically significant changes (p < or = 0.05). When the electroporation pulse was applied, the water diffusion coefficients increased by about 30% to 6.6 x 10(-6) cm2/s +/- 2.4 x 10(-7) cm2/s and 8.3 x 10(-6) cm2/s +/- 3.7 x 10(-7) cm2/s, for the epidermis and hair follicle regions, respectively. Significant differences were noted between diffusion coefficients in the viable epidermis and the hair follicles for all cases.

Xenon-131 surface sensitive imaging of aerogels in liquid xenon near the critical point.

In recent years, optically pumped xenon-129 has received a great deal of attention as a contrast agent in gas-phase imaging. This report is about the other NMR active xenon isotope (i.e., xenon-131, S = 32) which exhibits distinctive features for imaging applications in material sciences that are not obtainable from xenon-129 (S = (1/2)). The spin dynamics of xenon-131 in gas and liquid phases is largely determined by quadrupolar interactions which depend strongly on the surface of the surrounding materials. This leads to a surface dependent dispersion of relaxation rates, which can be substantial for this isotope. The dephasing of the coherence due to quadrupolar interactions may be used to yield surface specific contrast for imaging. Although optical pumping is not practical for this isotope because of its fast quadrupolar relaxation, a high spin density of liquid xenon close to the critical point (289 K) overcomes the sensitivity problems of xenon-131. We report the first xenon-131 magnetic resonance images and have tested this technique on various meso-porous aerogels as host structures. Aerogels of different densities and changing levels of hydration can clearly be distinguished from the images obtained.

Rapid MRI and velocimetry of cylindrical Couette flow.

A narrow-gap, temperature-controlled Couette flow rheometer has been developed to study fluid velocities within the annular gap between two concentric cylinders by nuclear magnetic resonance (NMR) imaging and velocimetry. Alternative pulsed-field-gradient-based nuclear magnetic resonance imaging strategies which may be used for measurement of velocity within the Couette flow device have been evaluated. These include two-dimensional (2-D) imaging techniques with acquisition times of several minutes and a one-dimensional (1-D) projection method which exploits the symmetry of the device to reduce overall measurement time to less than 1 min. Velocity measurements made using each technique are presented for a Newtonian fluid undergoing Couette flow at shear rates of approximately 20 and 60 s(-1).

A protocol for magnetic resonance imaging of the temporomandibular joints.

The complex concepts and procedures of magnetic resonance imaging (MRI) are unfamiliar to many dentists. Similarly, many radiologists lack understanding of the clinical requirements of the dentist for accurate assessment of TMJ abnormalities. Thus, TMJ imaging procedures may be inadequate or incomplete, may vary from facility to facility, and sometimes from patient to patient in a given facility. A protocol for TMJ imaging is presented which meets dental requirements and is rapidly performed in the MRI facility. The protocol may be copied and attached to the prescription to the imaging center. It may be modified or expanded to accommodate specific patient requirements or equipment performance.

Imaging of the temporomandibular joint: a position paper of the American Academy of Oral and Maxillofacial Radiology.

Various imaging techniques for the temporomandibular joint are discussed with respect to uses, strengths, and limitations. An imaging protocol is outlined for evaluating patients with a wide variety of temporomandibular joint related signs and symptoms.

Initial TMJ disk recapture with anterior repositioning appliances and relation to dental history.

Fifty-eight consecutive patients in a referral based practice seeking treatment for complex chronic painful temporomandibular joint (TMJ) disease were enrolled in a prospective study to assess the recapture of displaced disks by anterior repositioning appliances (ARA) and the improvement in disk position in those disks that did not fully recapture. After standard clinical workup, including assessment of pain, maxillary and mandibular ARAs were constructed which repositioned condyles to the Gelb 4/7 position as determined by cephalometrically-corrected linear tomograms. Multi-planar magnetic resonance imaging (MRI) was performed immediately before and after insertion of the mandibular ARA, showing three-dimensional recapture of disks in 85% and improved disk position in 6% of reducing displacements. Disk position was improved in 28% of nonreducing joints, but none were totally recaptured. Recapture or improvement was achieved in 91% of reducing, 28% of nonreducing, and 63% of all joints with internal derangements. Initial disk position, reduction on opening and recapture by ARA were statistically independent of patient age, number of teeth missing, number of third molars missing, malocclusion (Angle's class), overjet, overbite, prosthetic appliances, and previous orthodontic treatment. It was concluded that ARA therapy provided effective recapture of displaced TMJ disks that reduce upon mouth opening. In this population of patients with chronic TMJ pain, previous dental treatment had no statistically significant effect on the incidence of internal derangement or on disk recapture by ARA therapy. There was no evidence of adverse effect from orthodontics, prosthetics, or any other dental care.

Radiology: closing a century, opening a millennium.

As we close the file on the first century of radiology, we honor the pioneers and reflect on the progress they started. We also open a new file, not just a new century, but a new millennium of opportunity. The dramatic technologic advances in diagnostic imaging within recent decades have provided the foundation for expanding our activities in Oral and Maxillofacial Radiology. We are no longer just dental radiology; we can no longer rest on the teaching and practice of conventional dental radiography. We can summarize in one word the direction our efforts must take in opening the millennium: research. Only with research at the fundamental as well as clinical level we can continue to expand our service to the public, to our patients, and to our colleagues.

Long-term follow-up of modified condylotomy for internal derangement of the temporomandibular joint.

OBJECTIVES: The purpose of this study was to evaluate disk position and patient response 10 years after modified condylotomy for symptomatic reducing disk displacement. STUDY DESIGNS: Questionnaires and invitations to return for examination and temporomandibular joint magnetic resonance imaging were mailed to 39 consecutive patients 10 years after modified condylotomy. RESULTS: On a 10-point scale the mean pain experienced by the 17 respondents (27 joints) to the questionnaire was 2.0. Ninety percent of 20 joints (12 patients) examined were free of tenderness to palpation. Magnetic resonance imaging in 10 patients (17 joints) showed disk reduction in 59%, displacement with reduction in 29%, and displacement without reduction in 12%. Eighty-five percent of the joints met American Association of Oral and Maxillofacial surgeons criteria for a successful therapeutic outcome. CONCLUSIONS: The study suggests a role for modified condylotomy in the long-term management of symptoms associated with reducing disk displacement. Further, modified condylotomy can frequently reverse an internal derangement and seems to protect against the natural progression of osteoarthrosis.