Spatial distribution of tissue level properties in a human femoral cortical bone

The mechanical properties of cortical bone are determined by a combination bone tissue composition, and structure at several hierarchical length scales. In this study the spatial distribution of tissue level properties within a human femoral shaft has been investigated. Cylindrically shaped samples (diameter: 4.4mm, N=56) were prepared from cortical regions along the entire length (20-85% of the total femur length), and around the periphery (anterior, medial, posterior and lateral quadrants). The samples were analyzed using scanning acoustic microscopy (SAM) at 50MHz and synchrotron radiation micro computed tomography (SRμCT). For all samples the average cortical porosity (Ct.Po), tissue elastic coefficients (c(ij)) and the average tissue degree of mineralization (DMB) were determined. The smallest coefficient of variation was observed for DMB (1.8%), followed by BV/TV (5.4%), c(ij) (8.2-45.5%), and Ct.Po (47.5%). Different variations with respect to the anatomical position were found for DMB, Ct.Po and c(ij). These data address the anatomical variations in anisotropic elastic properties and link them to tissue mineralization and porosity, which are important input parameters for numerical multi-scale bone models.     

Muscle activity at the ilio-sacral articulation of frogs

Electromyographic recording indicates that the sequence of muscle firing around the ilio-sacral joint is similar for three species of frogs during locomotion, despite differences in gross morphology at the articulation. The ilio-sacral musculature is most active during the take-off phase of a jump, and there is a correlation between the degree of muscle activity and height of jump. This muscle activity is involved in aligning the center of mass of the frog with the direction of the propulsive force of the jump. The firing pattern of the ilio-sacral musculature is essentially similar during swimming and jumping, and suggests that differences in medium (water vs. air) are responsible for differences in propulsive thrust in the two types of locomotion.     

Topographic distribution of taste responsiveness in the hamster medulla

The purpose of the present investigation was to map the multiunitresponsiveness of the gustatory portion of the nucleus of thesolitary tract (NTS) in the hamster, elicited by chemical stimulationof oral taste receptors. Neural responsiveness to four stimuli(0.1 M sucrose, 0.03 M NaCl, 0.003 M HCl, 0.001 M QHCl) deliveredto either the anterior tongue or other parts of the oral cavitywas examined at 37 NTS recording sites. Gustatory responseswere shown-to depend collectively upon the stimulus, the receptivearea being stimulated, and the location of the recording sitewithin the NTS. By comparing the proportional magnitudes ofintegrated responses across recording sites, unique topographicpatterns of responsiveness were demonstrated for sucrose, NaCIand QHCl. Responses to HCl and NaCl generated similar patterns.Further, the response patterns for each stimulus differed followingstimulation of the anterior tongue or posterior oral cavity.Spatial differences in NTS responsiveness arise as a resultof differences in peripheral gustatory nerve sensitivities andprovide a possible substrate for the coding of taste quality.     

Functional assessment of human femoral arteries after cryopreservation

An established method for the cryopreservation of human femoral arteries for subsequent transplantation as allografts has been studied with particular attention to preservation of smooth muscle and endothelium. Human femoral arteries (HFAs) were harvested from multi-organ donors. Two groups were established; a control group of unfrozen HFAs and a group of cryopreserved HFAs. Cryopreservation was performed using RPMI solution containing dimethyl sulfoxide and the rate of cooling was 1 degrees C/min to -40 degrees C and faster thereafter until -150 degrees C was reached. The contraction and relaxation responses of unfrozen and frozen/thawed arteries were assessed by measurement of the isometric force generated by the HFAs in an organ bath. After thawing (warming was at 15 degrees C/min) the maximal contractile response to noradrenaline was 43% of the response of unfrozen HFAs. The endothelium-independent response to sodium nitroprusside was not altered, whereas the endothelium-dependent relaxation response to acetylcholine was slightly altered. The cryopreservation method used provided limited preservation of the contractility of human femoral arteries, and good preservation of both endothelium-independent and endothelium-dependent relaxation responses.     

Topographic distribution of mitoses in the adrenal cortex of the rat

The situation of mitoses in the adrenal glands of the rat has been studied by measuring the distance between each of them (3,061 in the whole) at the surface. The curve of their distribution, logarithmic-normal type, shows that they are the most numerous in germinative zone classically described, but that they appear down to the depth of inner fascicula.     

Topographic mapping of the axons of the femoral chordotonal organ neurons in the cricket Gryllus bimaculatus

Central projections of the femoral chordotonal organ (FCO) neurons in the cricket Gryllus bimaculatus were investigated by selectively staining small numbers of axons. The FCOs in all legs consist of partly fused ventral and dorsal scoloparia in the proximal femur. The ventral scoloparium neurons can be reliably divided into two groups: the ventral group neurons (VG), which are arranged in a sequentially smaller manner distally, and dorsal group neurons (DG), which simply aggregate in the proximal region near the dorsal scoloparium. All axons of the FCO projected to the ipsilateral half of the respective thoracic ganglion. The VG axons possessed dorso-lateral branches in the motor association neuropile and antero-ventral branches dorso-lateral to the anterior ventral association centre. However, the more proximally the somata were situated, the more medially the main neurites terminated. The DG axons showed some variations: some axons of the distally located neurons possessed dorso-lateral branches and terminated on the boundary region of the mVAC, while the other axons terminated exclusively in the medical ventral association centre (mVAC), including the ventral part, which receives auditory sensory neuron projections. All axons of the dorsal scoloparium neurons projected exclusively into the dorsal part of the mVAC; however, the ventrally located neurons projected more ventrally than did the dorsally located neurons. The above characteristics were nearly identical in the pro- and metathoracic FCOs. These results suggest that the cricket FCO axons are roughly organized in a somatotopic map and are broadly differentiated in their function.     

Contractile and relaxant responses of diabetic dog femoral arteries

Strips of femoral arteries of normal and alloxan-treated dogs were set up for isometric recording. The contractile response to phenylephrine and the relaxant response to acetylcholine were determined. Neither alloxan treatment nor mechanical removal of endothelium altered the EC50 value for phenylephrine. The slope of phenylephrine dose-response curves of diabetic and healthy vessels with intact endothelium was similar, whereas the slope of phenylephrine dose-response curves of endothelium-denuded diabetic arteries was significantly greater than that of the denuded healthy arteries. Removal of the endothelium completely abolished the relaxant effect of acetylcholine. The relaxant potency (IC50) of acetylcholine was not affected by alloxan treatment. The results suggest that in canine femoral arteries the relaxant activity of acetylcholine is unaffected in experimental diabetes and the damage of the arterial endothelium may play a role in the increased responsiveness of diabetic vessels to adrenergic agonists.     

EDHF mediates the relaxation of stretched canine femoral arteries to acetylcholine.

To test the hypothesis that mechanically stretched arteries relax to endothelium-derived vasodilators, we challenged endothelium-intact dog femoral artery rings stretched from 1 to 16 g total initial tension (active force and passive elastic) with 10(-6) M acetylcholine (ACh), an endothelium-dependent dilator. The relaxation to 10(-6) M sodium nitroprusside (SNP), an endothelium-independent dilator, increased with the total initial tension. The relaxation to ACh averaged approximately 65% of the relaxation to SNP at total initial tensions of 4 to 16 g. To determine the nature of the endothelial-derived products involved, we compared the ACh-induced relaxation of stretched rings (6.5 +/- 0.2 g total initial tension) with rings chemically contracted with phenylephrine (Phe, 10(-7) to 10(-5) M) (6.5 +/- 0.3 g total initial tension). ACh-induced relaxation was evaluated before and after the inhibition of the synthesis of eicosanoids [cyclooxygenase (10(-5) M indomethacin) and lipoxygenase (10(-5) M nordihydroguariaretic acid)] and nitric oxide [nitric oxide synthase (10(-5) M Nw-nitro-L-arginine)]. The contribution of endothelium-derived hyperpolarizing factor (EDHF) was identified by blocking calcium-activated potassium channels (10(-8) M iberiotoxin). SNP (10(-6) M) relaxed stretched rings by 1.7 +/- 0.1 g and chemically-activated rings by 4.8 +/- 0.2 g. ACh relaxed stretched rings to 73 +/- 3% of the SNP relaxation and this was only attenuated in the presence of iberiotoxin. ACh relaxed Phe-activated rings to 60 +/- 3% of the SNP relaxation. This relaxation was attenuated by inhibition of the synthesis of nitric oxide and (or) eicosanoids. Therefore, ACh relaxed stretched rings through the release of EDHF whereas the relaxation of chemically activated rings to ACh involved multiple endothelium-derived vasodilators.     

Functional assessment of cryopreserved human femoral arteries for pharmaceutical research

An established method for cryopreservation that might preserve the vascular and endothelial responses of human femoral arteries (HFAs) to be transplanted as allografts was studied. HFAs were harvested from multiorgan donors and stored at 4 degrees C in saline solution before cryostorage. Thirty HFA rings were isolated and randomly assigned to one control group of unfrozen HFAs (eight rings) and one group of cryopreserved HFAs (22 rings).Cryopreservation was performed in RPMI solution containing dimethylsulfoxide (DMSO) and the rate of cooling was -1 degrees C/min until -40 degrees C and faster rates until -150 degrees C was reached. The contractile and relaxant responses of unfrozen and frozen/thawed arteries were assessed in organ bath by measurement of isometric force generated by the HFAs.After thawing, the maximal contractile responses to the contracting agonist tested (noradrenaline) were in the range of 43% of the responses in unfrozen HFAs. The endothelium-independent responses to sodium nitroprusside were not altered whereas the endothelium-dependent relaxant responses to acetylcholine were weakly altered.The cryopreservation method used provided a limited preservation of contractility of HFAs, a good preservation of the endothelium-independent relaxant responses, and a good preservation of endothelium-dependent relaxation. It is possible that further refinements of the cryopreservation protocol, such as a slower rate of cooling and a more controlled stepwise addition of DMSO, might allow better post-thaw functional recovery.     

Laser angioplasty of peripheral arteries after unsuccessful recanalization of the superficial femoral artery

AIM: To demonstrate the range of applying laser angioplasty after unsuccessful recanalization of the superficial femoral artery (SFA) with conventional interventional techniques. MATERIALS AND METHODS: In a prospective trial in 94 cases with occlusion of the SFA and formerly unsuccessful conventional percutaneous transluminal angioplasty, laser angioplasty for recanalization was applied. The average occlusion length of the SFA was 17.5 cm (range 4-36 cm). The recanalization attempt was made using the crossover technique in 78 patients, in eight patients with the antegrade technique and in another eight patients using the transpopliteal technique. The primary recanalization attempt was performed with Terumo wires (curved and straight) as well as different catheters (Multipurpose/Vertebralis/Cobra). After the unsuccessful recanalization attempt the laser catheter was applied. RESULTS: The application of laser angioplasty demonstrated a successful recanalization of the SFA in 76/94 patients (80.9%). In 18 patients (19.1%) the recanalization was not possible even with percutaneous transluminal laser angioplasty (PTLA). The reason for the unsuccessful PTLA was in 10 cases due to obstructing calcified material, which was resistant to PTLA application. In four cases obstructing calcifications caused the laser catheter to be positioned in subintimal tissue, resulting in perforation of the SFA. In another four patients there was an aberrant anatomy of the SFA which resulted in a direct vessel injury after advancing the laser catheter. After a follow-up period of 12 months primary, primary-assisted and secondary patency rates were 50.0%, 65.8% and 73.7%, respectively. DISCUSSION: In primarily unsuccessful recanalization of the SFA, PTLA allows in 80% of cases a successful recanalization of the SFA. The technical success rate and the patency rate support the application of PTLA.