Synergic effect of vicinal stereocenters in [3 + 2] cycloadditions of carbohydrate azadipolarophiles and mesoionic dipoles: origin of diastereofacial selectivity.

The intermolecular [3 + 2] cycloaddition of carbohydrate-derived 1,2-diaza-1,3-butadienes and 1,3-thiazolium-4-olates provides a conceptual basis for the problem of diastereofacial preference in the acyclic series of unsaturated sugars. Experimental results employing a side chain of D-arabino configuration have shown the stereodifferentiation exerted by the first stereogenic center that renders the Re,Re face of the acyclic sugar-chain azadiene eligible for cycloaddition (J. Org. Chem. 2000, 65, 5089). The results of the present work, now utilizing an alternative framework of D-lyxo configuration, evidence the discriminating power of the second stereogenic carbon, which induces the preferential approach to the Re,Si face of the heterocyclic dipole. This scheme of face selectivity is also grounded in theoretical calculations at a semiempirical level. In addition to dihydrothiophenes, which are the expected products of the [3 + 2] cycloaddition, bicyclic systems based on dihydrothieno[2,3-c]piperidine skeleton can also be obtained.

High-frequency transcutaneous electrical nerve stimulation alters thermal but not mechanical allodynia following chronic constriction injury of the rat sciatic nerve.

OBJECTIVE: To determine if daily transcutaneous electrical nerve stimulation (TENS) can alter the thermal and mechanical allodynia that develops after chronic constriction injury (CCI) to the right sciatic nerve of rats. DESIGN: A completely randomized experimental design was used. Four groups of rats underwent CCI surgery to the right sciatic nerve and either were not treated with TENS or received TENS starting at different times after the CCI surgery. INTERVENTIONS: TENS was delivered daily for 1 hour to CCI rats through self-adhesive electrodes applied to skin innervated by the right dorsal rami of lumbar spinal nerves L1-6. Rats of different groups received daily TENS starting immediately, 20 to 30 hours, or 3 days after the CCI surgery. MAIN OUTCOME MEASURE: Thermal and mechanical pain thresholds of hind paws were assessed bilaterally in all rats twice before the CCI surgery (baseline) and then 2, 7, 12, and 14 days after surgery. Thermal and mechanical allodynia were expressed as difference scores between the pain thresholds of right and left hind paws. These values were normalized to differences that existed between the two paws at baseline. RESULTS: Daily TENS beginning immediately after CCI surgery prevented the development of thermal allodynia at all assessment times (p < .05). Daily TENS starting 1 day after surgery reduced thermal allodynia, but only on days 2 and 14 (p < .05). Daily TENS beginning 3 days after surgery had no effect on the development of thermal allodynia. Regardless of when it was started, daily TENS did not consistently alter mechanical allodynia in CCI rats. CONCLUSION: It appears that daily TENS can prevent thermal but not mechanical allodynia in this model. However, early intervention with the treatment is critical if it is to be effective at all.

Searching for the vomeronasal organ of adult humans: preliminary findings on location, structure, and size.

The adult human vomeronasal organ (VNO) has been the focus of numerous recent investigations, yet its developmental continuity from the human fetal VNO is poorly understood. The present study compared new data on the adult human "VNO" with previous findings on the fetal human VNO. Nasal septa were removed from twelve adult human cadavers and each specimen was histologically sectioned. Coronal sections were stained with hematoxylin-eosin and periodic acid-Schiff-hematoxylin. The sections were examined by light microscopy for the presence of VNOs and the anterior paraseptal cartilages (PC). VNOs were quantified using a computer reconstruction technique to obtain VNO length, volume, and vomeronasal epithelium (VNE) volume. Histologically, VNOs and PCs were identified in eleven specimens. VNOs had ciliated, pseudostratified columnar epithelium with goblet cells. Variations (e.g., multiple communications to the nasal cavity) were observed in several specimens. Quantification was possible for 16 right or left VNOs. Right or left VNOs ranged from 3.5 to 11.8 mm in length, from 1.8 to 33.8 x 10(-4)cc in volume, and from 2.7 to 18.1 x 10(-4)cc in VNE volume. Results indicated that the adult human VNO was similar in VNE morphology, lumen shape, and spatial relationships when compared to human fetal VNOs. By comparison with previous fetal VNO measures, mean VNO length, volume, and VNE volume were larger in adult humans. These results support previous suggestions that postnatal VNO growth occurs. Findings on location and spatial relationships of the adult VNO were similar to those seen in human fetuses, but critical questions remain regarding the ontogeny of the vomeronasal nerves and VNE.

Approach to dissection of the anterior thoracic wall and the entrance to the thoracic cavity.

Dissection of the anterior chest wall typically precedes the opening of the thoracic cavity. The techniques for exposing and subsequently reflecting or removing the structures of the anterior chest wall have been well described. However, these approaches that involve the systematic dissection of the layers of tissue overlying the anterior thoracic wall prior to the removal of the anterior thoracic wall render the pectoral regions and axillas unfit for continued study. The authors offer an alternative dissection that allows continued access to the thoracic cavity while maintaining the integrity of the pectoral and axillary regions. This new technique may facilitate more efficient use and complete study of each specimen.

Variation in the triceps brachii muscle: a fourth muscular head.

Routine cadaver dissection has resulted in the identification of a fourth head of the triceps brachii muscle on the left side in one specimen. This novel arrangement demonstrated a single tendon arising from the proximal posteromedial aspect of the humeral shaft, distal to the shoulder capsule. The tendon of this fourth head passed along the medial aspect of the humerus and gave way to a muscle belly on the medial surface of the distal one-third of the humerus. The tendon of the fourth head passed directly over the neurovascular bundle containing the radial nerve and deep brachial artery at approximately the point where the neurovascular bundle entered the radial sulcus. This close positional relationship between the tendon of the fourth head, the radial nerve, and the deep brachial artery has prompted us to speculate on the possible clinical significance of this finding in relation to radial nerve palsy and arterial compression. Additionally, the position of the muscle belly, lying in close proximity to the ulnar groove, invites speculation on the role of the fourth head in cases of snapping elbow. To the authors' knowledge, a description of the muscular fourth head of the triceps as seen in the present work has not been noted in previous literature.

Acute effects of therapeutic ultrasound delivered at varying parameters on the blood flow velocity in a muscular distribution artery.

Therapeutic modalities that alter hemodynamic parameters may have a dramatic impact on the viability of living tissues. The purpose of the current study was to investigate the response of blood flow velocity to various treatment parameters of therapeutic ultrasound. Twenty healthy volunteers attended six randomly selected, 15-minute treatment sessions of the following parameters: Tx-1 = 1.0 MHz at 1.5 W/cm2, Tx-2 = 1.0 MHz at 1.0 W/cm2; Tx-3 = 3.0 MHz at 1.2 W/cm2; Tx-4 = 3.0 MHz at 1.0 W/cm2, Tx-5 = sham; and Tx-6 = control. Ultrasound was applied to a circular area over the triceps surae muscle mass. Blood flow velocity in the popliteal artery was assessed after 5, 10, and 15 minutes of ultrasound and at two posttreatment intervals via a dual frequency, bidirectional ultrasound Doppler. A two-factor analysis of variance (p < or = 0.05) with repeated measures for treatment and time was performed on the data. Groups Tx-1 and Tx-2 showed significant increases in blood flow velocity when compared with the control and all other groups. The sham group showed significant increases in blood flow velocity when compared with the control group. Group Tx-3 and Tx-4 showed no significant change when compared with the sham condition. The results of the current study indicate that 1.0 MHz ultrasound delivered at 1.0 and 1.5 W/cm2 to the triceps surae musculature as described in the present study can increase the blood flow velocity in the popliteal artery.

Transcutaneous neuromuscular electrical stimulation effect on the degree of microvascular perfusion in autonomically denervated rat skeletal muscle.

OBJECTIVE: To determine the effect of transcutaneous neuromuscular electrical stimulation (TNMES) on the degree of microvascular perfusion in autonomically denervated skeletal muscle. DESIGN: A completely randomized experimental design was used to compare the effects of TNMES on the degree of microvascular perfusion in the tibialis anterior (TA) and extensor digitorum longus (EDL) muscles from autonomically denervated rats (Ch-TES) to the degree of microvascular perfusion in the same muscles of untreated controls, rats receiving only TNMES (TES), and rats receiving only autonomic denervation (shams). INTERVENTION: All electrical stimulation treatments were delivered via carbon silicone surface electrodes, and evoked sustained tetanic contraction of the TA and EDL muscles. Autonomic denervation was achieved by the application of chlorisondamine. MAIN OUTCOME MEASURES: The degree of microvascular perfusion was determined for the deep (DTA) and superficial (STA) region of the TA muscle and the EDL muscle by calculating their perfused microvessel/muscle fiber (PV/F) ratio. RESULTS: The PV/F ratio in the DTA from Ch-TES animals was greater (p < or = .05) than that in the same muscle from control and sham animals. The PV/F ratios in the STA and EDL from Ch-TES animals were not significantly (p > .05) different from the PV/F ratio in the respective muscles of shams. CONCLUSIONS: The response of the microvasculature in autonomically denervated skeletal muscle to TNMES that evokes muscle contraction is variable, and (2) mechanisms other than autonomic regulation may be involved in this hyperemic response.

A variation in the organization of abductor pollicis longus.

The abductor pollicis longus (APL) muscle has been studied bilaterally in 50 cadavers. A variation in the organization of the muscle was found bilaterally in 15 of the 50 specimens. The novel muscular arrangement gives the appearance of being an additional muscle belly arising from the lateral aspect of the distal portion of the typical abductor pollicis longus muscle belly. This variation in the arrangement also creates a retinacular-like tunnel which encases the tendons of the extensor carpi radialis longus and the extensor carpi radialis brevis muscles. To the authors' knowledge, this arrangement has not been cited in the recent medical literature. An understanding of this unusual finding may be clinically relevant in describing the dorso-lateral compartment of the distal forearm.

The influence of muscle contraction on the degree of microvascular perfusion in rat skeletal muscle following transcutaneous neuromuscular electrical stimulation.

Electrotherapy is used clinically according to a variety of protocols and at various intensities with the intent of effecting any number of physiological changes. The purpose of this study was to determine if the increased degree of microvascular perfusion observed following 2,500 Hz transcutaneous neuromuscular electrical stimulation (TNMES) is dependent on evoked muscle contractions. The tibialis anterior (TA) and extensor digitorum longus (EDL) muscles from 30 male rats were analyzed. Six animals were untreated and served as controls, while the TA and EDL muscles of six animals were treated with TNMES at current intensities three times that needed to evoke a minimum visible contraction in the TA (M-TNMES). The remaining animals were treated with gallamine, which effectively blocked neurally mediated muscle contraction. The TA and EDL muscles of six gallamine-treated rats received no TNMES and served as shams (G-Sham), six received M-TNMES (GM-TNMES), and six received TNMES at intensities sufficient to produce sustained muscle contraction with a neuromuscular blockade in place (G-HIS). Perfused microvessels were labeled with fluorescein isothiocyanate-bovine serum albumin. The degree of microvascular perfusion was determined by calculating perfused microvessel/muscle fiber ratios (PV/F). The mean PV/F ratios of all groups were compared using Fisher's LSD (alpha = 0.05). When compared to controls, the PV/F ratios of the TA and EDL muscles in M-TNMES and G-HIS groups showed a significant (p < or = 0.05) increase while the G-Sham and GM-TNMES groups were similar to controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of motor neuromuscular electrical stimulation on microvascular perfusion of stimulated rat skeletal muscle.

The purpose of this study was to determine the effect of neuromuscular electrical stimulation (NMES) (2,500-pps sine wave interrupted at 50 bps) on the degree of microvascular perfusion in stimulated skeletal muscle. The tibialis anterior (TA) and extensor digitorum longus (EDL) muscles of 36 male rats were treated with NMES for 30 minutes at current amplitudes sufficient to produce a sustained muscle contraction (motor NMES). Muscle tissue was removed at 0, 5, 10, 15, and 30 minutes after NMES. The perfused vessel/muscle fiber ratio (PV/F) of the stimulated animals at time 0 minutes was greater than that of the unstimulated control animals. A gradual decrease in the magnitude of the PV/F increase was noted over time. Depending on the muscle's fiber-type composition, the PV/F values returned to control levels by 10 to 30 minutes after motor NMES. The results indicate (1) that motor NMES significantly increases the degree of microvascular perfusion in stimulated rat skeletal muscle and (2) that the increased degree of perfusion persists for various lengths of time, depending on the fiber-type composition of the muscle. Thus, if responses in an animal model can be used as indicators of similar human responses, then the results of this study suggest that NMES can be used to increase the degree of microvascular perfusion in human skeletal muscle.