Reduction of central nervous system reperfusion injury in rabbits using doxycycline treatment

BACKGROUND AND PURPOSE: Activated leukocytes appear to potentiate central nervous system reperfusion injury, and agents that block leukocyte adhesion have shown neuroprotective efficacy in experimental models. Doxycycline, a tetracycline antibiotic, inhibits leukocyte function in vitro, presumably through divalent cation binding. We used a model of focal central nervous system reperfusion injury to determine the efficacy of doxycycline treatment in preserving neurological function. METHODS: Rabbits randomly received 10 mg/kg i.v. doxycycline 30 minutes before ischemia (pretreatment group) or 45 minutes after ischemia (posttreatment group) or received phosphate-buffered saline vehicle (control group) followed by 10 mg/kg q 8 hours times two. The average length of reversible spinal cord ischemia required to produce paraplegia (P50) at 18 hours was calculated for each group. RESULTS: For the control group (n = 13), the P50 was 22.8 +/- 2.2 minutes; for the pretreatment group (n = 14), 35.5 +/- 2.4 minutes (P < .01; t = 3.8); and for the posttreatment group (n = 13), 31.4 +/- 4.2 minutes (not significant; t = 1.6). Doxycycline also attenuated postischemic decreases in vivo leukocyte counts and inhibited in vitro leukocyte adhesion. Therapeutic doxycycline levels at 24 hours were confirmed in the plasma and spinal cord. CONCLUSIONS: This significant protective effect suggests that doxycycline, a safe and readily available agent, may play a role in reducing clinical central nervous system reperfusion injury.     

S-phase fractions of breast carcinomas. Relationships to morphology, estrogen and progesterone receptors, and early recurrence

Analysis of the S-phase fractions (SPF) measured by in vitro thymidine labeling, morphological appearances, and estrogen receptor (ER) assays of primary invasive breast carcinomas demonstrated several interrelationships. Lobular, mucinous, tubular, and adenocystic carcinomas consistently had low SPF and were usually positive for ER. The same was true for the carcinomas of no special histologic type [the not otherwise specified (NOS) group of E. R. Fisher including "infiltrating ductal" and undifferentiated carcinomas] with minimal anaplasia. Medullary, atypical medullary, and morphologically unclassifiable carcinomas with marked nuclear anaplasia nearly always had high SPF and were usually negative for ER. High SPF was associated with advanced stages of carcinoma initially or with early recurrence following mastectomy.     

In vivo bone strain patterns in the zygomatic arch of macaques and the significance of these patterns for functional interpretations of craniofacial form

It has been proposed that the mammalian facial skeleton is optimized for countering or dissipating masticatory stress. As optimized load-bearing structures by definition exhibit maximum strength with a minimum amount of material, this hypothesis predicts that during chewing and biting there should be relatively high and near uniform amounts of strain throughout the facial skeleton. If levels of strain in certain areas of the facial skeleton are relatively low during these behaviors, this indicates that the amount of bone mass in these areas could be significantly reduced without resulting in the danger of structural failure due to repeated masticatory loads. Furthermore, and by definition, this indicates that these areas are not optimized for countering masticatory stress, and instead their overall morphology and concentration of bone mass has most likely been selected or influenced mainly by factors unrelated to the dissipation or countering of chewing and biting forces. An analysis of in vivo bone strain along the lateral aspect of the zygomatic arch of macaques indicates the clear absence of a high and near uniform strain environment throughout its extent. Instead, there is a steep strain gradient along the zygomatic arch, with the highest strains along its anterior portion, intermediate strains along its middle portion, and the lowest strains along its posterior portion. These data, in combination with earlier published data (Hylander et al., 1991), indicate that levels of functional strains during chewing and biting are highly variable from one region of the face to the next, and therefore it is unlikely that all facial bones are especially designed so as to minimize bone tissue and maximize strength for countering masticatory loads. Thus, the functional significance of the morphology of certain facial bones need not necessarily bear any important or special relationship to routine and habitual cyclical mechanical loads associated with chewing or biting. Furthermore, the presence of these steep strain gradients within the facial skeleton suggests that the amount of bone mass in the low-strain areas may be largely determined by factors unrelated to processes frequently referred to as "functional adaptation," or conversely, that the "optimal strain environment" of bone varies enormously throughout the facial skeleton (cf., Rubin et al., 1994). Based solely on anatomical considerations, it is likely that the zygomatic arch is bent in both the parasagittal and transverse planes and twisted about its long axis. Due to constraints on rosette position, the strain data are incapable of determining if one or more of these loading conditions predominate. Instead, the strain data simply provide limited support for the possible presence of all of these loading regimes. Finally, as the masseter muscle is concentrated along the anterior portion of the zygomatic arch and as the arch has fixed ends, the largest shearing forces and the largest bending and twisting moments are located along its anterior portion. This in turn explains why the largest strains are found along the anterior portion of the zygomatic arch.     

An Improved Extended Active Observer for Adaptive Control of A <Emphasis Type="Italic">n</Emphasis><Emphasis Type="Italic">−</Emphasis>DOF Robot Manipulator

A novel algorithm for simultaneous force estimation and friction compensation of constrained motion of robot manipulators is presented. This represents an extension of the improved extended active observer (IEAOB) algorithm reported earlier and proposes a higher order IEAOB or N?th order IEAOB (IEAOB ?N) for a n?DOF robot manipulator. Central to this observer is the use of extra system states modeled as a Gauss-Markov (GM) formulation to estimate the force and disturbances including robot inertial parameters and friction. The stability of IEAOB ?N is verified through stability analysis. The IEAOB-1 is validated by applying it to a Phantom Omni haptic device against a Nicosia observer, disturbance observer (DOB)/reaction torque observer (RTOB), and nonlinear disturbance observer (NDO), respectively. The results show that the proposed IEAOB-1 is superior to the compared observers in terms of force estimation. Then, the performance of the IEAOB ? N is experimentally studied and compared to the IEAOB-1. Results demonstrate that the IEAOB ? N has an improved capability in tracking nonlinear external forces.     

Reactions and Reactivity in Self‐Assembled Monolayers

Self‐assembled monolayers (SAMs) are excellent models for studying interfacial reactions. Here monolayer chemistry is reviewed, focusing on the features that have no analogues in solution chemistry. The growth of surface‐attached polymers, intrafilm reactions, chemistry, photochemistry and reactivity issues are all discussed.