Trabecular

Most bones of the human skeleton are composed of two structurally distinct types of tissue compact (dense) and trabecular (cancellous, spongy) bone. Both types contain the same elements cells ( osteocytes) embedded in a mineralised matrix and connected by small canals ( canaliculi ). In compact bone, which makes up 85% of the skeleton, these components form elongated cylinders of concentric lamellae surrounding a central blood vessel (called osteon or Haversian system). Cancellous bone, in contrast, forms thin,... 

FIGURE 24-1. In the normal eye, aqueous humor flows through the ciliary body into the posterior chamber, through the pupil into the anterior chamber, and out through the trabecular meshwork to the canal of Schlemm into the venous drculation. 

Dicarboxymethyl chitosan and 6-oxychitin sodium salt, applied to femoral surgical defects for 3 weeks produced a good histoarchitectural order in the newly formed bone tissue. The spongious trabecular architecture was restored in the defect site. The association of the chitin derivatives with the osteoblasts seemed to be the best biomaterial in terms of bone tissue recovery [128]. 

It is estimated that approximately 4% of compact bone is renewed annually in the typical healthy adult, whereas approximately 20% of trabecular bone is replaced. 

Figure 7.1. Early diagrams showing the relationship between stresses created by forces on bones and the internal architecture of the skeleton (a) Culmann s calculation of the stress trajectories in a crane, (b) Wolff s drawing of the trabecular orientation in the upper part of the femur, and (c) a photograph of the cross-section of the upper part of the femur.

Picherit et al., 2000 1 yr old OVX rats oral administration, 90 d genistein or daidzein at 10 mg/kg body weight Overall daidzein > genistein in this study. Total femoral BMD losses and vertebral trabecular bone were protected by estradiol and daidzein, but genistein was not efficient. Bone strength (femoral failure stress) protected by estradiol, daidzein and genistein... 

As noted above, the presence of Met(O) in proteins would go undetected after acid hydrolysis and subsequent amino acid analysis. Thus, since this method of hydrolysis is most commonly used, it is impossible to ascertain from the literature the abundance of Met(O) residues normally present in proteins. However, a number of studies have reported the presence of Met(O) residues in various proteins using one of the appropriate procedures described above. It has been found that Met(O) residues comprise 30% of the total Met in proteins isolated from bovine glomerular basement membranes and anterior lens . Other investigators have reported that the levels of Met(O) in proteins of the trabecular meshwork of human eyes increased with the age of the donor . The amount of Met(O) detected ranged from 15% (10 years old) to 55% (79 years old) of the total methionine content found in the tissue samples. Other studies have shown that in certain species of clams the proteins of the hinge ligament contain only Met(0) residues and no Met . In addition, it has also been reported that as much as 18% of the Met residues in pea seed proteins is in the form of Met(O) . Lastly, Met(O) residues have been found in... 

Fig. 2.1.16 Trabecular bone structure, muscle after removal of the soft tissue (right). Image and tendon of a mouse tail in vitro at 21.14T, parameters multi-slice spin-echo method,...

MHz (left). The trabecular structure and 512 x 256 pixels, FOV 6x3 mm, resolution the muscle tissue are clearly resolved, the 11.7 pm per pixel, slice thickness 64 pm, TR... 

K. Kose, Y. Matsuda, T. Kurimoto, S. Hashimoto, Y. Yamazaki, T. Haishi, S. Utsuzawa, H. Yoshioka, S. Okada, M. Add, T. Tsuzaki 2004, (Development of a compact MRI system for trabecular bone volume fraction measurements), Magn. Reson. Med. 52, 440—444. 

Osteopenia (80%) and osteoporosis, usually affecting trabecular bone... 

The penis consists of three components, two dorsolateral corpora cavernosa and a ventral corpus spongiosum that surrounds the penile urethra and distally forms the glans penis. The corpora cavernosa consist of blood-filled sinusoidal or lacunar spaces, which are lined with endothelial cells, supported by trabecular smooth muscle, and surrounded by a thick fibrous sheath called the tunica albuginea. The caver-nosal arteries, which are branches of the penile artery, penetrate the tunica albuginea and supply blood flow to the penis. 

The human skeleton consists of both cortical and trabecular bone. Cortical bone is dense and compact and is responsible for much of bone strength. It is the most common type of... 

Under normal circumstances, the skeleton undergoes a dynamic process of bone remodeling. Bone tissue responds to stress and injury through continuous replacement and repair. This process is completed by the basic multicellular unit, which includes both osteoblasts and osteoclasts. Osteoclasts are involved with resorption or breakdown of bone and continuously create microscopic cavities in bone tissue. Osteoblasts are involved in bone formation and continuously mineralize new bone in the cavities created by osteoclasts. Until peak bone mass is achieved between the ages of 25 and 35, bone formation exceeds bone resorption for an overall increase in bone mass. Trabecular bone is more susceptible to bone remodeling in part owing to its larger surface area. 

After the transport of aqueous humor into the posterior chamber, it flows through the pupil into the anterior chamber where it provides oxygen and nutrition to the avascular lens and cornea. Aqueous humor then exits the anterior chamber through the trabecular meshwork and drains into Schlemm s canal which drains aqueous humor into the episcleral venous system. 

Eighty percent of aqueous humor drains through the trabecular meshwork, which is a lattice of connective tissue that surrounds the anterior chamber. The size of the trabecular meshwork can be altered by the contraction or the relaxation of the ciliary muscle. Stimulation of muscarinic receptors on the ciliary muscle causes contraction, which in turn causes the pores of the trabecular meshwork to open, increasing aqueous humor outflow. 

F2o, analog uveoscleral outflow and to a lesser extent trabecular outflow... 

Laser trabeculoplasty uses laser energy aimed at the trabecular meshwork to improve the outflow of aqueous humor and can be used as first-line therapy, especially in patients unable or unwilling to adhere to medical therapy. Laser trabeculoplasty may be used as bridge therapy between medical and surgical intervention, and approximately 50% of laser trabeculoplasty procedures will fail at 10 years. Trabeculectomy is the removal of a portion of the trabecular meshwork to improve aqueous... 

Pilocarpine directly stimulates the muscarinic (M3) receptors of the ciliary body which causes contraction of the ciliary muscle. This results in widening of the spaces in the trabecular meshwork, which causes an increase in aqueous humor outflow and reduces IOP by 20% to 30%. 

Synechia Adhesions or the abnormal attachment of the iris to another structure. Peripheral anterior synechia refers to occurrence of synechia with the trabecular meshwork. 

Skeletal deposition is assumed to distribute into two pools 50% goes to the trabecular bone surface and 50% to the cortical bone surface. A first order rate coefficient for elimination of americium from liver to plasma is assumed to be 0.0019 day 1 (half-time, 365 days). 

Bone is divided into trabecular and cortical components, with each further divided into surface bone, bone volume, and bone cavity (marrow compartment). Deposition of americium is assumed to occur from plasma directly to bone surfaces, whereas elimination from bone occurs by transfer from the bone surface or volume to the marrow cavity, and then from the marrow cavity to plasma (Figure 3-6). Transfers of americium within the cortical or trabecular bone compartments are modeled based on assumptions about rates of bone formation and resorption, which are assumed to be vary with age, but are equal within a given age group (Leggett et al. 1982). Movement of americium to the marrow compartment is determined by the bone resorption rate, whereas, movement from the bone surface to the bone volume is assumed to occur by burial of surface deposits with new bone and is determined by the bone formation rate. During growth, bone formation and resorption are assumed to occur at different sites within bone therefore, the rate of removal of americium from the bone surface is approximated by the sum of the bone resorption rate (represented in the model by the movement of americium to the marrow compartment) and the rate of bone... 

Durbin and Schmidt (1985) proposed a model for tissue distribution and excretion of absorbed americium in humans. A unique feature of this model is that transfers from plasma to tissues are assumed to be instantaneous therefore, a central plasma (and blood) compartment is not included in the model (see Figure 3-10). Tissue compartments included in the model are slow and fast turnover bone compartments, representing cortical and trabecular bone, respectively liver and slow and fast turnover for other soft tissue compartments. Excretion pathways include urine and feces. Urinary excretion is represented as a sum of the contributions from bone, liver, and other soft tissues. Fecal americium is assumed to be excreted from the liver. 

DC, dendritic cell EC, endothelial cell EpC, epithelial cell FDC, follicular dendritic cell FDL, foot draining lymph FLS, fibroblast-like synoviocyte MC, mast cell MDDC, monocyte-derived dendritic cell MLS, macrophage-like synoviocyte MNC, mononuclear cell Mo, monocyte M0, macrophage OB, osteoblast pDC, plasmacytoid dendritic cell PMNs, polymorphonuclear neutrophils SC, stromal cell STC, synovium tissue cell TB, trabecular bone. 

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