Posterior interosseous free flap with extended pedicle for hand reconstruction

The anatomy of the posterior interosseous vessels makes them suitable as a donor area of free flap. The skin island can be designed on the perforating vessels of the distal third of the forearm, up to the dorsal wrist crease, to increase the pedicle length (7 to 9 cm). A series of nine flaps transferred to reconstruct hand defects is presented. All flaps were designed over the dorsal distal forearm, and dimensions permitted direct closure of the donor site (up to 4 to 5 cm wide). Apart from a linear scar, donor morbidity was negligible. All transfers were successful. Although its dissection is somewhat tedious, the anatomy of the vascular pedicle is suitable for microanastomosis and the skin island is thin, although hairy. The posterior interosseous free flap with extended pedicle may be a good choice when limited amounts of thin skin and a long vascular pedicle are needed.     

Sequential vascularized iliac bone graft and a superficial circumflex iliac artery perforator flap with a single source vessel for established mandibular defects

The major problems in dealing with established mandibular loss are severe soft-tissue contracture and a limited number of recipient vessels. The skin portion of the iliac osteocutaneous flap often necrotizes in cases without perforators of the deep circumflex iliac vessel. To overcome these problems, eight patients with established mandibular loss and no skin perforators of the deep circumflex iliac vessel were treated with a sequential vascularized iliac bone graft and a superficial circumflex iliac perforator flap with a single recipient vessel. Regarding the recipient vessels, the ipsilateral cervical vessels were used for four patients, and the contralateral facial and ipsilateral superficial temporal vessels were used for two cases each. The superficial circumflex iliac perforator flaps were 7 to 28 cm in length and 3 to 15 cm in width. The iliac bone grafts ranged from 7 to 13 cm in length, and three cases were repaired with the inner cortex of the iliac bone. There were no serious complications, such as flap necrosis or bone infection and resulting absorption. The advantages of this method are that both pedicles are very close to each other and of suitable diameter for anastomosis. Simultaneous flap elevation and preparation for the recipient site is possible. The skin flap and vascularized bone graft can be obtained from the same donor site. A single source vessel can nourish both the large skin area and bone sequentially. Longer dissection of the superficial circumflex iliac system to the proximal femoral division is unnecessary. A large flap can survive with a short segment of the superficial circumflex iliac system. Only the vascularized inner cortex of the iliac bone needs to be used, and the outer iliac cortex can be preserved, which results in less morbidity at the donor site.     

Late Maturation of Large Metaxylem Vessels in Soybean Roots: Significance for Water and Nutrient Supply to the Shoot

The large, late metaxylem (LMX) in the roots of soybean beginsdevelopment in the centre of the stele after lignification ofthe early metaxylem poles. Subsequent maturation of the firstappearing LMX elements is gradual. They were never mature inthe 8-d-old seedlings examined. In 10 to 15-d-old plants thefirst LMX matured to open vessels at a mean of 17 cm proximalto the root tip. Additional LMX vessels developed in more proximalregions of the roots and these also matured gradually. Based on calculations from relative vessel diameters, the potentialflow of xylem sap in a single central LMX vessel is 50 timesthat in the total of all the early metaxylem (EMX) vessels ofa typical primary root of soybean. There was a marked dependence of relative leaf area on the lengthof primary root with open LMX vessels. This may result fromthe predicted increased water and nutrient flow to the shoot,facilitated by the opening of the large vessels. It is suggestedthat, as in maize, the living LMX elements may function in ionaccumulation. Dicotyledonous roots, soybean, Glycine max, xylem vessels, xylem maturation, water conduction     

Vessel-diameter distribution in roots of grapevines (Vitis vinifera L. cv. Shiraz)

The distribution frequency patterns of diameter of xylem vessels and percentage of total predicted axial conductances were studied in 190-day and 212-day-old main roots of grapevine (Vitis vinifera L. cv. Shiraz) grown under well-watered and stressed conditions. The protoxylem were the first to mature and were responsible for most of the theoretical conductance in root segments between the tip and 2.5 cm from the tip. Some large xylem vessels retained cross walls and protoplasm up to 22.5 cm from the tip. Statistical tests using the Kolmogorov-Smirnov two sample test showed that the pattern of distribution frequency of xylem vessels classified in different diameter classes varied with distance from the root tip. The distribution frequency of xylem vessels was similar in both well-watered and stressed plants from the tip up to 15 cm from the tip. At distances further from the tip the distribution frequency of xylem vessels of well-watered plants was significantly different from that of stressed plants, with the former having more larger vessels than the latter. The pattern of vessel distribution frequency was different from that of percent total axial conductance (K_h) predicted with fewer large vessels carrying most of the axial flow.     

Persistent xylem cross-walls reduce the axial hydraulic conductivity in the apical 20 cm of barley seminal root axes: implications for the driving force for water movement

Abstract. Xylem vessels in the apical 25 cm of barley seminal axes were examined by scanning electron microscopy of fractured freeze dried or critical point dried specimens. In the apical 11 cm, there were three cross walls cm⁻¹ root in the central xylem vessel. The frequency then declined with distance but did not become less than 1.0 cm⁻¹ root until the 22–25-cm zone.
Suction was applied to the proximal end of segments of seminal axes whose surfaces had been sealed with wax to prevent radial entry of water. Perfusion of the xylem with solutions of Tinopal CBS-X revealed the conductive xylem vessels by fluorescent staining of their walls. In the apical 20 cm of the axis, only a variable number of smaller xylem vessels conduct water. Beyond this zone, the much larger central vessel becomes functional.
The flow of water (Jv) in the apical zone was very much less for a given presure (△P) than in the proximal zone > 25 cm from the tip, and could be predicted by the Poiseuille equation provided the correct number of functional vessels are known. This information, together with earlier results on water uptake along the root length are used to predict the attenuation of the hydrostatic driving force for water uptake along the root length.
Estimates of K⁺ concentrations in stelar parenchyma and xylem vessels were made by electron microproble X-ray analysis. These results show that [K⁺] in the xylem vessels may be two to three times greater in the zone 1–2 cm from the root tip than in the basal zone. Such a gradient of solute potential may, to some extent, offset the decreasing influence of the leaf water potential in apical zones where xylem is not fully conductive.     

Reduced release of nitric oxide to shear stress in mesenteric arteries of aged rats

We hypothesized that aging is characterized by a reduced release of nitric oxide (NO) in response to shear stress in resistance vessels. Mesenteric arterioles and arteries of young (6 mo) and aged (24 mo) male Fischer 344 rats were isolated and cannulated. Shear stress (15 dyn/cm(2))-induced dilation was significantly reduced and shear stress (1, 5, 10, and 15 dyn/cm(2))-induced increases in perfusate nitrite were significantly smaller at all shear stress levels in vessels of aged rats. Inhibition of NO synthesis abolished shear stress-induced release of nitrite. Furthermore, shear stress (15 dyn/cm(2))-induced release of nitrate was significantly higher and total nitrite (nitrite plus nitrate) was significantly lower in vessels of aged rats. Tiron or SOD significantly increased nitrite released from vessels of aged rats, but this was still significantly less than that in young rats. Superoxide production was increased and the activity of SOD was decreased in vessels of aged rats. There were no differences in endothelial NO synthase (eNOS) protein and basal activity or in Cu/Zn-SOD and Mn-SOD proteins in vessels of the two groups, but extracellular SOD was significantly reduced in vessels of aged rats. Maximal release of NO induced by shear stress plus ACh (10(-5) M) was comparable in the two groups, but phospho-eNOS in response to shear stress (15 dyn/cm(2)) was significantly reduced in vessels of aged rats. These data suggest that an increased production of superoxide, a reduced activity of SOD, and an impaired shear stress-induced activation of eNOS are the causes of the decreased shear stress-induced release of NO in vessels of aged rats.     

Radiation effect on the proliferating capillaries in rat transparent chambers.

The revascularization of the devascularized area in rat transparent chambers by the proliferating blood vessels was studied quantitatively on the changes of vascularity. On the vascularizing border, a hypervascular zone about 0-5 mm wide was formed. The border advanced constantly at 0-020 cm a day. Vascular density was fixed in the repaired area. The vascular length and repaired area increased on parabolic curves. The chambers were irradiated with single doses of 50, 100, 200, 400, 1000, 2000, and 4000 rad of 30Co gamma-rays, and the effects on the advance of the border were examined. With 200 rad and more, significant inhibition, greater with bigger doses, was seen in the advance of the borders. Regression of the borders also occurred. Irradiation with over 1000 rad destroyed the hypervascular zones.     

The thoracoacromial vessels as recipient vessels in microsurgery and supermicrosurgery: an anatomical and sonographic study

The purpose of this study was to investigate the presence and the precise course of the pectoral branch of the thoracoacromial vessels on the underside of the pectoralis major muscle by anatomical dissection and by color Doppler ultrasound. A further goal was to determine whether these vessels were suitable as recipient vessels in microsurgery and supermicrosurgery for breast reconstruction. In 18 cadavers, the pectoral branch of the thoracoacromial vessels was followed caudally until the diameter of the artery diminished to 1 mm. The same examination was carried out in 40 young female volunteers by tracing the vessel course with color Doppler ultrasound. The 1-mm cutoff point of the artery was measured with reference to the manubrium, the midsternal line, the clavicle, and the upper border of the closest rib. In addition, in the cadavers, the 2-mm cutoff point was determined. At both cutoff points, the diameter of the accompanying vein was measured. The pectoral branch of the thoracoacromial vessels with the artery and concomitant veins could be detected on all 100 undersides of the pectoralis major muscle, anatomically and sonographically. In their course from the acromial region downward, the arteries reached a diameter of 1 mm at an average of 9.9 cm from the manubrium, horizontally 9.4 cm from the midsternal line, and vertically 4.0 cm from the lower border of the clavicle. The 1-mm reference point was situated on the upper border of the third rib in 85 percent of cases. The average distance between the 1-mm and the 2-mm cutoff points was 3.5 cm. At the 1-mm cutoff point, the diameter of the vein was 0.9 mm, and at the 2-mm cutoff point, it was 1.7 mm. Because of their central position at the anterior hemithorax, these vessels are easily accessible from mastectomy incisions, even in skin-sparing mastectomies; the donor-site morbidity is negligible; and as the diameters of the vessels gradually decrease along their caudal course, the recipient site can be chosen precisely according to the length and the diameter of the donor vessels and major mismatch can be avoided. Thus, the pectoral branches of the thoracoacromial vessels are well suited as recipient vessels for (super)microsurgery and are a very promising addendum to the thoracodorsal and internal mammary vessels.     

Fusarium eumartii Growth in Resistant and Susceptible Oak Species

Fusarium eumartii is a fungus associated with declining Quercus robur , in which it is found in the vessels. The response of oak species to infection is known to vary: Q. robur is susceptible , but Quercus cerris and Quercus pubescens are resistant. An experiment was carried out in 1996 and repeated in 1997, to examine how F. eumartii colonization differed in oak species that were susceptible or resistant to the fungus by counting the number of vessels with mycelium at various distances from the inoculation site in infected seedlings and by determining the amount of viable fungus in infected tissue. Infected vessels with mycelium were counted on sections (10  μ m thick) cut at 0, 2, 4, 6, 8 and 10 cm from the inoculation site on 1-year-old inoculated seedlings as well as on sections cut every 2 cm to the seedling tip. The amount of viable fungus was determined by counting the colony forming units (CFUs) in stem segments from the same seedlings. Quercus robur seedlings had the greatest number of infected vessels and the greatest number of CFUs. Forty days after inoculation, the extent of vertical fungal spread was 28.12 cm in Q. robur , 3.15 cm in Q. cerris and 3.00 cm in Q. pubescens . The greatest number of CFUs was found in Q. robur at day 5 after inoculation. Analysis of variance confirmed the results.     

Clinical application of the free thin anterolateral thigh flap in 31 consecutive patients

In this retrospective study, 31 reconstructions using thin anterolateral thigh flaps and six cadaveric dissections of the thigh were investigated in consideration of the anatomic variations of the perforator vessels in the adipose layer, the safe area of flap circulation, and the clinical indications.Three variations of the perforator vessel course in the adipose layer were predicted correctly. The safe radius of a thin anterolateral thigh flap with a thickness of 3 to 4 mm was determined to be approximately 9 cm from the point where the perforator met the skin. The use of a thin anterolateral thigh flap for reconstruction of the neck, axilla, anterior tibial area, dorsum of the foot, circumference on the ankle, forearm, and dorsum of the hand was therefore recommended.     

Comparison of Heat-Pulse and Radioisotope Tracer Methods for Determining Sap-Flow Velocity in Stem Segments of Poplar

By applying a vacuum to stem segments of poplar, simultaneousdeterminations of the flow velocity were made using a convectedheat-pulse and a radioisotope (³²P). A regression equation v= 7.225 x 10^–2 u—4.329 x 10^–5u² (heat-pulsevelocity v on radioisotope velocity u) was fitted. This gavean average ratio u/v of c. 20 over the heat-pulse velocity range0—20 cm h^–1 with incremental ratios, du/dv, of 14and 49 for values of v of 0 and 600 cm h^–1. Using Marshall'stheoretical relationship between u and v, and taking into accountthe percentage of vessels involved in the flow, it was possibleto derive the value of the ratio u/v over the range 0–20cm h^–1 for v, and thus verify the theory. Increasing valuesof u/v over 20 cm h^–1 are attributed to lack of thermalhomogencity. Attention is drawn to the necessity to distinguishbetween the total lumen area and the percentage of vessels involvedin the flow.     

The blood supply of the reverse temporalis muscle flap: anatomic study and clinical implications

Although the reverse temporalis muscle flap has been used clinically, the exact vascular connection between the superficial and deep temporal vessels has not been clearly defined. The purpose of this study was to investigate the vascular territory of the reverse temporalis muscle supplied by the superficial temporal vessels. Six cadaver heads were studied using a colored lead oxide injection through the superficial temporal artery. The specimens were examined macroscopically and radiographically. The reverse temporalis muscle flap was then applied to a clinical case presenting with traumatic anterior skull base defect communicating with the nasal cavity. The cadaver specimens demonstrated that the superficial temporal artery formed an average 1.3 +/- 0.2 cm in width of dense vascular zone, which was located within 1.8 cm below the superior temporal line. The dense vascular network further perfused the anterior and posterior deep temporal arteries and the muscular branch of the middle temporal artery to supply the temporalis muscle. The mean perfused area of the temporalis muscle was 83 percent, ranging from 79 to 89 percent, in five cadaver heads. One cadaver revealed only 55 percent of perfused area in the absence of the muscular branch of the middle temporal artery. The consistent area without perfusion was located in the distal third of the posterior portion of the reverse temporalis muscle. In clinical cases, the reverse temporalis muscle flap was used successfully to obliterate the anterior skull base defect without evidence of muscle flap necrosis. The exact blood supply to the distal third of the posterior portion of the reverse temporalis muscle flap needs to be investigated further in vivo. Particular attention was paid to the inclusion of the muscular branch of the middle temporal artery in this flap to augment the blood supply to the temporalis muscle.     

Internal mammary vessels as a model for power Doppler imaging of recipient vessels in microsurgery.

The aim of this interdisciplinary study was to evaluate power Doppler imaging as a method of collecting reliable preoperative data concerning the diameters and topography of exemplary internal mammary vessels as recipient vessels in reconstructive microsurgery. Thirteen female patients (range, 37 to 58 years; mean, 45.6 years) were examined preoperatively with power Doppler imaging from the first to the fifth intercostal space parasternally and bilaterally. These data are compared with measurements obtained intraoperatively in each individual. Mean velocity in the artery in the second intercostal space on the right side is 47.11 cm/sec (range, 15 to 90 cm/sec) and on the left side is 42.25 cm/sec (range, 18 to 95 cm/sec). Mean velocity in the vein in the second intercostal space on the right side is 17.80 cm/sec (range, 10 to 30 cm/sec) and on the left side is 13.06 cm/sec (range, 5.3 to 32 cm/sec). The topographic results are in close agreement with intraoperative measurements and previous anatomical studies. Sonographic preoperative data of arteries (mean, 1.88 mm) show slightly smaller diameters than intraoperative measurements (mean, 2.08 mm), whereas veins show slightly larger diameters in sonography (mean, 2.33 mm) than intraoperatively (mean, 2.12 mm). Mean sonographic diameter of artery ranges from 2.14 mm (second intercostal space) to 1.46 mm (fifth intercostal space), of the vein from 2.76 (second intercostal space) to 1.25 mm (fifth intercostal space). In one case, a vein was not detectable. This noninvasive method leads to confirmation of the preoperative choice of the optimal recipient vessels for free tissue transfer and does not harm the patient.     

Moyamoya syndrome following growth hormone-secreting pituitary adenoma

We report a case of Moyamoya syndrome developing in association with growth hormone-secreting pituitary adenoma. A 31-year-old female presented with acromegalic features. Magnetic resonance imaging revealed a 1 × 2 cm tumor in the sella turcica and MR angiography demonstrated unremarkable findings. Blood growth hormone and insulin-like growth factor I levels were elevated to 74.1 ng/ml and over 1 575 ng/ml, respectively. The diagnosis was growth hormone-secreting pituitary adenoma, and the tumor was removed through a transsphenoidal approach. Four years after surgery, she visited the outpatient department due to left side weakness for 2 months. Magnetic resonance images showed acute and old infarcted lesions in the basal ganglia and subcortical area and residual small pituitary adenoma in the sellar area. MR angiography demonstrated stenosis of the bilateral distal internal carotid arteries with basal collateral vessels. Conventional cerebral angiography showed complete obstruction in the right internal carotid artery and severe stenosis of the left internal carotid artery, middle cerebral artery, and anterior cerebral artery with basal collateral vessels. Her blood growth hormone and insulin-like growth factor I levels were 15.3 ng/ml and 1 055 ng/ml, respectively. We believe that excess systemic exposures of growth hormone and insulin-like growth factor I may participate in the development of Moyamoya syndrome.     

陕北沙地3种典型灌木根木质部解剖结构及水力特性

比较了陕北沙地沙柳、柠条和沙棘3种典型灌木不同土壤深度(0～20和30～50 cm)根木质部解剖结构和水力特性.结果表明： 沙柳具有较高的叶水势,根木质部导管平均最大直径(d_max)、平均最小直径(d_min)、平均导管面积(A_lum)以及导管面积占木质部面积比例(A_ves/A_xyl)显著高于柠条和沙棘,根导管密度(VD)与沙棘相当但显著高于柠条;沙柳根的比导水率分别为柠条和沙棘的5.0和2.8倍;沙柳根栓塞脆弱性指数与柠条根相当,但显著高于沙棘根.表明沙柳属耗水型水分利用策略,而柠条和沙棘属节水型水分利用策略,且柠条更耐旱.3种灌木在2个土层深度的d_max、d_min和A_lum无显著差异,但30～50 cm土层根VD和A_ves/A_xyl显著高于表层;30～50 cm土层根比导水率显著高于表层根,但脆弱性指数小于表层根,深层根具有高的水分传输效率和低的水力脆弱性.     

Easy tissue expansion of prelaminated mucosa-lined flaps for cheek reconstruction in a canine model

In head and neck reconstruction, there is sometimes the need for a skin flap lined with mucosa. The object of this study was to determine whether small pieces of mucosa grafted onto the undersurface of a skin flap can be expanded in a reasonable time to provide the material required to reconstruct a full-thickness cheek defect as a free flap. The study consisted of two phases: prelamination and expansion of the flap, and vascularized free-tissue transfer of the flap. Six adult mongrel dogs were used. First, a 5 x 10-cm flap based on the saphenous vessels was elevated on the lower leg, and then four 1 x 2-cm pieces of mucosa harvested from the tongue were grafted onto the undersurface of the flap. A tissue expander (5 x 10 cm) was then placed under the flap, and the incision was closed primarily. The expanders were initially filled with just enough normal saline to obliterate dead space immediately after surgery. The expansion was continued twice weekly for 3 weeks until sufficient expansion was obtained. Two of six flaps were followed for an additional 6 weeks after the 3-week expansion period to observe whether additional mucosa could be obtained. After measurement of the mucosal area, each flap was transferred as free flap to reconstruct an iatrogenic cheek defect. The increase of mucosal surface area was compared with the original graft, and differences were analyzed using the paired t test. All flaps were successfully expanded without any complications. Histologic evaluation revealed that grafted mucosa took well without evidence of graft necrosis, and the intergraft area was covered with histiocytes. Angiography revealed well-defined vascular structures covering the entire area of the flap. The new mucosal area (23.5 +/- 2.4 cm2) was significantly larger than the original mucosal graft (8.7 +/- 0.9 cm2) (p < 0.001). The net increase of the mucosal area was 172.9 +/- 32.4 percent. The increase of mucosal area in two flaps, following a 6-week consolidation period after 3 weeks of expansion, was only slightly greater (25.9 +/- 1.3 cm2) than those without the consolidation period (22.3 +/- 1.8 cm2). This increase of the mucosal area appears to be related to the amount of expansion, and not to the length of the consolidation period. The flaps were successfully transferred as free flaps to reconstruct the full-thickness cheek defects without major complications. Although a staged operation to allow flaps to mature is needed, the present procedure has the advantages of providing a mucosa-lined flap and allowing primary closure of the donor site. The authors conclude that expansion of this flap has great potential in reconstructive surgery.     

The long head of the triceps brachii as a free functioning muscle transfer

This anatomic study investigates the possibility of using the long head of the triceps brachii muscle as a free functioning muscle transfer for the upper limb. It has been reported that the long head is not difficult to harvest and that its loss does not create significant donor-site morbidity. The muscle was studied in 23 fresh frozen upper limbs. The long head in all 23 specimens had a constant and proximal vascular pedicle from the profunda brachii artery and vein. The mean pedicle was long (4 cm) and had large-caliber vessels (diameter, 3-mm artery and 4-mm vein). Angiograms were carried out in five specimens and dye perfusion studies in six specimens. A single branch from the radial nerve of at least 7 cm in length innervated the muscle. Muscle architecture was studied in 12 specimens and revealed that the long head of the triceps is better suited for forearm reconstruction than either the gracilis or the latissimus dorsi muscles. The mean physiologic cross-sectional area (8.36 cm(2)) and fiber length (10.8 cm on the superficial surface and 8.2 cm on the deep surface) of the long head match more closely those of the flexor digitorum profundus and the extensor digitorum communis, the muscles most commonly replaced.     

Reconstruction of large sacral defects following total sacrectomy

Total sacrectomies for cancer ablation often result in extensive defects that are challenging to reconstruct. In an effort to elucidate the criteria to select the most effective reconstructive options, we reviewed our experience with the management of large sacral wound defects. All patients who had a sacral defect reconstruction after a total sacrectomy at our institution between January of 1993 and August of 1998 were reviewed. The size of the defect, the type of reconstruction, postoperative complications, and functional outcome in each patient were assessed. A total of 27 flaps were performed in 25 patients for sacral defect reconstruction after a total sacrectomy. Diagnoses consisted of chordoma (n = 13), giant cell carcinoma (n = 2), sarcoma (n = 5), rectal adenocarcinoma (n = 4), and radiation induced necrosis (n = 1). The size of sacral defects ranged from 18 to 450 cm2 (mean, 189.8 cm2). Ten patients, including five who had preoperative radiation therapy, underwent transpelvic vertical rectus abdominis myocutaneous (VRAM) flap reconstruction for sacral defects with a mean size of 203.3 cm2. Of these, five patients (50 percent) had complications (four minor wound dehiscences and one seroma). Eight patients, including one who had preoperative radiation therapy, underwent bilateral gluteal advancement flap reconstruction for sacral defects with a mean size of 198.0 cm2. They had no complications. Two patients, both of whom had preoperative radiation therapy, underwent gluteal rotation flap reconstruction for sacral defects of 120 cm2 and 144 cm2. Both patients had complications (one partial flap loss and one nonhealing wound requiring a free flap). Three patients, including one who had preoperative radiation therapy, underwent reconstruction with combined gluteal and posterior thigh flaps for sacral defects with a mean size of 246 cm2; two of these patients had partial necrosis of the posterior thigh flaps. Three patients, all of whom had preoperative radiation therapy, underwent free flap reconstruction for sacral defects with a mean size of 144.3 cm2. They had no complications. Our experience suggests that there are three reliable options for the reconstruction of large sacral wound defects: bilateral gluteal advancement flaps, transpelvic rectus myocutaneous flaps, and free flaps. In patients with no preoperative radiation therapy and intact gluteal vessels, the use of bilateral gluteal advancement flaps should be considered. In patients with a history of radiation to the sacral area and in patients whose gluteal vessels have been damaged, the use of the transpelvic VRAM flap should be considered. If the transpelvic VRAM flap cannot be used because of previous abdominal surgery, a free flap should be considered as a last option.     

Electrical resistance of muscle capillary endothelium.

A recently developed technique for in vivo determination of the electrical resistance of vascular endothelium in microvessels was applied to the vessels in a thin frog muscle, m. cutaneus pectoris. The technique consists of injection of current via a glass micropipette into a capillary and measurement of the resulting intra- and extravascular potential profiles with another micropipette placed at various distances from the current source. The theory of Peskoff and Eisenberg (1974) was used to handle the problems arising from distributed extravascular resistances and was experimentally shown to describe the external field satisfactorily. With this extension of one-dimensional cable theory the specific electrical resistance of arterial microvessels was 33 omega cm2 and of venous capillaries 23 omega cm2. The "length constants" were 135 and 112 micrometers, respectively. If results from arterial and venous vessels are taken together, the ionic permeabilities at 20 degrees C were PNa = 3.9 X 10(-5) cm X s-1, PK = 5.7 X 10(-5) cm X s-1, PCl = 5.9 X 10(-5) cm X s-1 and PHCO3 = 3.4 X 10(-5) cm X s-1. These figures agree with figures for capillary permeability obtained in tracer experiments on whole muscle. The study bridges a gap between single capillary and whole organ techniques with the conclusion that the two different approaches lead to similar results in muscle capillaries.     

Mechanical properties of rat middle cerebral arteries with and without myogenic tone

The inner diameter and wall thickness of rat middle cerebral arteries (MCAs) were measured in vitro in both a pressure-induced, myogenically-active state and a drug-induced, passive state to quantify active and passive mechanical behavior. Elasticity parameters from the literature (stiffness derived from an exponential pressure-diameter relationship, beta, and elasticity in response to an increment in pressure, Einc-p) and a novel elasticity parameter in response to smooth muscle cell (SMC) activation, Einc-a, were calculated. beta for all passive MCAs was 9.11 +/- 1.07 but could not be calculated for active vessels. The incremental stiffness increased significantly with pressure in passive vessels; Einc-p (10(6) dynes/cm2) increased from 5.6 +/- 0.5 at 75 mmHg to 14.7 +/- 2.4 at 125 mmHg, (p < 0.05). In active vessels, Einc-p (10(6) dynes/cm2) remained relatively constant (5.5 +/- 2.4 at 75 mmHg and 6.2 +/- 1.0 at 125 mmHg). Einc-a (10(6) dynes/cm2) increased significantly with pressure (from 15.1 +/- 2.3 at 75 mmHg to 49.4 +/- 12.6 at 125 mmHg, p < 0.001), indicating a greater contribution of SMC activity to vessel wall stiffness at higher pressures.