Estrogen suppresses activation but enhances formation phase of osteogenic response to mechanical stimulation in rat bone

We used a model whereby mechanical stimulation induces bone formation in rat caudal vertebrae, to test the effect of estrogen on this osteogenic response. Unexpectedly, estrogen administered daily throughout the experiments (8-11 d) suppressed, and ovariectomy enhanced, mechanically induced osteogenesis. Osteogenesis was unaffected by the resorption-inhibitor pamidronate, suggesting that the suppression of bone formation caused by estrogen was not due to suppression of resorption. We found that estrogen did not significantly reduce the proportion of osteocytes that were induced by mechanical stimulation to express c-fos and IGF-I mRNA; and estrogen suppressed mechanically induced osteogenesis whether administration was started 24 h before or 24 h after loading. This suggests that estrogen acts primarily not on the strain-sensing mechanism itself, but on the osteogenic response to signals generated by strain-sensitive cells. We also found that when estrogen administration was started 3 d after mechanical stimulation, by which time osteogenesis is established, estrogen augmented the osteogenic response. This data is consistent with in vitro evidence for estrogen responsiveness in two phenotypically distinct bone cell types: stromal cells, whose functional activities are suppressed, and osteoblasts, which are stimulated, by estrogen.     

Multilayer discrete-time neural-net controller with guaranteedperformance

A family of novel multilayer discrete-time neural-net (NN) controllers is presented for the control of a class of multi-input multi-output (MIMO) dynamical systems. The neural net controller includes modified delta rule weight tuning and exhibits a learning while-functioning-features. The structure of the NN controller is derived using a filtered error/passivity approach. Linearity in the parameters is not required and certainty equivalence is not used. This overcomes several limitations of standard adaptive control. The notion of persistency of excitation (PE) for multilayer NN is defined and explored. New online improved tuning algorithms for discrete-time systems are derived, which are similar to sigma or epsilon-modification for the case of continuous-time systems, that include a modification to the learning rate parameter plus a correction term. These algorithms guarantee tracking as well as bounded NN weights in nonideal situations so that PE is not needed. An extension of these novel weight tuning updates to NN with an arbitrary number of hidden layers is discussed. The notions of discrete-time passive NN, dissipative NN, and robust NN are introduced. The NN makes the closed-loop system passive.     

Effects of organophosphorus, carbamate, pyrethroid and organochlorine pesticides, and a heavy metal on survival and cholinesterase activity of Chironomus riparius Meigen

BACKGROUND & AIMS: The first therapeutic experiences with the conventional photosensitizer dihematoporphyrinester in the treatment of Barrett's esophagus show the curative potential of photodynamic therapy (PDT). The aim of this study was to test 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX, a photosensitizer with a high mucosa specificity without phototoxic side effects on the skin, as a new form of PDT. METHODS: Thirty-two patients (mean age, 68.5 years) with histologically proven high-grade dysplasia (n = 10) and mucosal cancer (n = 22) in Barrett's esophagus were treated. Four to 6 hours after oral ingestion of 5-ALA (dose, 60 mg/kg body wt), irradiation was conducted with a dye laser system (635 nm) with a light dose of 150 J/cm2. The patients received 20-80 mg omeprazole daily after PDT. RESULTS: High-grade dysplasia was eradicated in all patients (10 of 10), and mucosal cancer was eliminated in 17 of 22 patients (77%) at a mean follow-up of 9.9 months (range, 1-30 months). All tumors < or = 2 mm in thickness were completely ablated (17 of 17). The method-related mortality and morbidity was 0%. CONCLUSIONS: Severe dysplasia and thin (< or = 2 mm) mucosal cancer of Barrett's esophagus can be completely ablated. PDT might offer a minimally invasive treatment modality as an alternative to esophagectomy.     

Effect of radiographic positioning on interpretation of cubital joint congruity in dogs

OBJECTIVE: To ascertain effects of x-ray beam centering and limb position on apparent congruity of a normal cubital joint (elbow). ANIMALS: 6 skeletally mature male Treeing Walker Coonhounds without physical, radiographic, or gross evidence of elbow abnormalities. PROCEDURE: Relative movement among humerus, radius, and ulna and measured joint space width on mediolateral and craniocaudal radiographic views was compared, using various x-ray beam centering and limb positions. RESULTS: Highest agreement and greatest certainty on subjective determination of congruity was for the flexed 90 degrees mediolateral radiographic view with the x-ray beam centered on the elbow. Distortion artifact of the proximal ulnar measurements was significant when the x-ray beam was centered on the midpoint of the radius. On the mediolateral view, the humeroradial joint space became significantly wide when the elbow was flexed. On the craniocaudal view, maximal humeroradial joint space width was obtained when the x-ray beam bisected the angle of the joint or was angled +30 degrees toward the humerus. CONCLUSIONS: Artifact distortion of joint width affected objective and subjective assessment of elbow congruity when the limb was placed in extreme flexion or extension or when the x-ray beam was not centered over the area of interest. Optimal visualization of the humeroradial joint space on the craniocaudal view was achieved when the x-ray beam bisected the angle of the elbow or was slightly angled toward the humerus. CLINICAL RELEVANCE: Elbow congruity was best assessed on the flexed 90 degrees lateral radiographic view with the x-ray beam centered on the joint.     

Nutrition, physical activity, and bone health in women

Calcium and vitamin D can significantly impact bone mineral and fracture risk in women. Unfortunately, calcium intakes in women are low and many elderly have poor vitamin D status. Supplementation with calcium (approximately 1000 mg) can reduce bone loss in premenopausal and late postmenopausal women, especially at sites that have a high cortical bone composition. Vitamin D supplementation slows bone loss and reduces fracture rates in late postmenopausal women. While an excess of nutrients such as sodium and protein potentially affect bone mineral through increased calcium excretion, phytoestrogens in soy foods may attenuate bone loss through estrogenlike activity. Weight-bearing physical activity may reduce the risk of osteoporosis in women by augmenting bone mineral during the early adult years and reducing the loss of bone following menopause. High-load activities, such as resistance training, appear to provide the best stimulus for enhancing bone mineral; however, repetitive activities, such as walking, may have a positive impact on bone mineral when performed at higher intensities. Irrespective of changes in bone mineral, physical activities that improve muscular strength, endurance, and balance may reduce fracture risk by reducing the risk of falling. The combined effect of physical activity and calcium supplementation on bone mineral needs further investigation.     

Evolutionary variation in bacterial RNase P RNAs

Sequences encoding RNase P RNAs from representatives of the last remaining classical phyla of Bacteria have been determined, completing a general phylogenetic survey of RNase P RNA sequence and structure. This broad sampling of RNase P RNAs allows some refinement of the secondary structure, and reveals patterns in the evolutionary variation of sequences and secondary structures. Although the sequences range from 100 to <25% identical to one another, and although only 40 of the nucleotides are invariant, there is considerable conservation of the underlying core of the RNA sequence. RNase P RNAs, like group I intron RNAs but unlike ribosomal RNAs, transfer RNAs or other highly conserved RNAs, are quite variable in secondary structure outside of this conserved structural core. Conservative regions of the RNA evolve by substitution of apparently interchangeable alternative structures, rather than the insertion and deletion of helical elements that occurs in the more variable regions of the RNA. In a remarkable case of convergent molecular evolution, most of the unusual structural elements of type B RNase P RNAs of the low G+C Gram-positive Bacteria have evolved independently in Thermomicrobium roseum , a member of the green non-sulfur Bacteria.     

An ultrasonic approach to localization of fiducial markers forinteractive, image-guided neurosurgery. I. Principles

Fiducial markers are reference points used in the registration of image space(s) with physical (patient) space. As applied to interactive, image-guided surgery, the registration of image space with physical space allows the current location of a surgical tool to be indicated on a computer display of patient-specific preoperative images. This intrasurgical guidance information is particularly valuable in surgery within the brain, where visual feedback is limited. The accuracy of the mapping between physical and image space depends upon the accuracy with which the fiducial markers were located in each coordinate system. To effect accurate space registration for interactive, image-guided neurosurgery, the use of permanent fiducial markers implanted into the surface of the skull is proposed in this paper. These small cylindrical markers are composed of materials that make them visible in the image sets. The challenge lies in locating the subcutaneous markers in physical space. This paper presents an ultrasonic technique for transcutaneously detecting the location of these markers. The technique incorporates an algorithm based on detection of characteristic properties of the reflected A-mode ultrasonic waveform. The results demonstrate that ultrasound is an appropriate technique for accurate transcutaneous marker localization. The companion paper to this article describes an automatic, enhanced implementation of the marker-localization theory described in this article     

How many measurements are necessary in diagnosing mild to moderate hypertension?

Cowdria ruminantium is the etiologic agent of heartwater, a tick-transmitted foreign animal disease with considerable potential for entrance into the USA. A competitive enzyme-linked immunosorbent assay (cELISA) was developed to detect serologic responses to C. ruminantium infection. The cELISA utilized a recombinant form of the C. ruminantium major antigenic protein (MAP-1) as the antigen and an anti-MAP-1 monoclonal antibody as the competing indicator reagent. Experimental antisera to C. ruminantium and a wide variety of related ehrlichial organisms were used to evaluate cELISA reactivity. Only sera against C. ruminantium, Ehrlichia canis, E. chaffeensis, and a recently discovered cervine ehrlichia-like organism reacted positively in the cELISA. Specificity of the cELISA was > or = 99.5% in a survey of 1,774 southeastern US and Puerto Rican slaughter cattle sera but was only 85% in a group of 79 hunter-killed white-tailed deer (Odocoileus virginianus) from the southeastern USA. Reference true-positive and cELISA false-positive sera were further analyzed by end point titrations using the cELISA and by indirect fluorescent antibody (IFA) tests for reactivity with C. ruminantium, E. canis, and E. chaffeensis antigens. True heartwater-positive sera were significantly more reactive using the cELISA and C. ruminantium IFA procedures (P < 0.05), whereas false-positive sera were significantly more reactive with the antigens used in the E. chaffeensis IFA procedure (P < 0.05). A group of sera from 210 field-origin ruminants residing on known or potentially heartwater-endemic Caribbean islands revealed a substantial (12.4%) prevalence of cELISA-positive specimens. The cELISA is a relatively specific serodiagnostic test for heartwater in cattle and could be used to monitor for possible introduction of the disease into the USA. The cELISA may also be an excellent tool for monitoring the success of an ongoing Caribbean Amblyomma tick eradication program designed to eliminate the biological vector responsible for the perpetuation and spread of this dangerous foreign animal disease.