Adaptation of flow-induced dilation of arterioles to daily exercise

We aimed to test the hypothesis that daily exercise elicits an adaptation of blood flow/shear stress-induced dilation of arterioles. To this end we investigated the responses of isolated, pressurized arterioles of mesentery (MES) and plantaris (PL) skeletal muscle of sedentary (SED) and exercised (EX) rats to increases in perfusate flow (PF, range 0-30 microl/min). Rats were run on a treadmill, once daily for 3 to 4 weeks (with gradually increasing intensity up to 40 min at 28 m/min; a total of 15-19 sessions on the treadmill). The passive diameters of arterioles (obtained in Ca2+-free solution) were similar ( approximately 140 microm) but the pressure-induced active diameter (at 80 mmHg) of skeletal muscle arterioles was significantly smaller than that of mesenteric arterioles. The basal diameter of MES arterioles of SED and EX rats was: 83.5 +/- 3.6 and 83.9 +/- 2.9 microm, respectively; increases in PF increased the diameter of SED and EX arterioles to a similar degree by 33.2 +/- 4. 7 and 31.9 +/- 6.1 microm, respectively). The diameters of PL muscle arterioles of SED and EX rats were 62.1 +/- 6.2 and 68.0 +/- 5.5 microm. In contrast to arterioles of MES, the highest PF increased the diameters of arterioles of PL muscle from EX rats to a significantly greater extent than those from SED rats (52.4 +/- 7.8 vs 30.3 +/- 3.9 microm). Thus, there is a functional adaptation to exercise activity in arterioles of skeletal muscle but not in those of arterioles of mesentery. We speculate that the intermittent increase in blood flow/shear stress in arterioles of skeletal muscle during the periods of exercise activity may be the underlying mechanism responsible for this adaptation.

Early assessment of exercise induced skeletal muscle injury using plasma fatty acid binding protein

OBJECTIVE

To test whether fatty acid binding protein (FABP) is a useful plasma marker for the early detection of exercise induced skeletal muscle injury in healthy subjects.

METHODS

Plasma concentrations of FABP and myoglobin (Mb) were measured in six healthy physical education teacher trainees after 20 minutes of downhill running (16% incline; mean lactate 4 mmol/l; 70% (VO2MAX). Creatine kinase (CK) was measured for comparison.

RESULTS

Significant increases were found in plasma FABP (mean peak level 50 micrograms/l), Mb (823 micrograms/l), and CK (491 U/l). Mb and FABP concentrations were already significantly elevated (p < 0.05) at 30 minutes, but CK not until two hours after exercise. Whereas Mb and FABP decreased to normal levels within 24 hours, CK activity remained elevated until 48 hours. The Mb to FABP ratio in plasma after exercise induced muscle injury was 15.0 (1.3) (mean (SEM)) (range 7.4-31.1), which is within the range of ratios calculated for skeletal muscle tissue contents of Mb and FABP, but different from the reported plasma ratio after myocardial injury (4-6).

CONCLUSIONS

After eccentric exercise induced muscle injury, plasma FABP and Mb increase and decrease more rapidly than CK, indicating that both FABP and Mb are more useful than CK for the early detection of such injuries and the monitoring of injury during repeated exercise bouts. In addition, the Mb to FABP ratio in the plasma identifies the type of muscle injured.

Peroxisome degradation by microautophagy in Pichia pastoris: identification of specific steps and morphological intermediates

We used the dye N-(3-triethylammoniumpropyl)-4-(p-diethylaminophenylhexatrienyl ) pyridinium dibromide (FM4-64) and a fusion protein, consisting of the green fluorescent protein appended to the peroxisomal targeting signal, Ser-Lys-Leu (SKL), to label the vacuolar membrane and the peroxisomal matrix, respectively, in living Pichia pastoris cells and followed by fluorescence microscopy the morphological and kinetic intermediates in the vacuolar degradation of peroxisomes by microautophagy and macroautophagy. Structures corresponding to the intermediates were also identified by electron microscopy. The kinetics of appearance and disappearance of these intermediates is consistent with a precursor-product relationship between intermediates, which form the basis of a model for microautophagy. Inhibitors affecting different steps of microautophagy did not impair peroxisome delivery to the vacuole via macroautophagy, although inhibition of vacuolar proteases affected the final vacuolar degradation of green fluorescent protein (S65T mutant version [GFP])-SKL via both autophagic pathways. P. pastoris mutants defective in peroxisome microautophagy (pag mutants) were isolated and characterized for the presence or absence of the intermediates. These mutants, comprising 6 complementation groups, support the model for microautophagy. Our studies indicate that the microautophagic degradation of peroxisomes proceeds via specific intermediates, whose generation and/or processing is controlled by PAG gene products, and shed light on the poorly understood phenomenon of peroxisome homeostasis.

Regulation of the vasomotor activity of lymph microvessels by nitric oxide and prostaglandins

It was shown previously that the presence of endothelium modulates spontaneous vasomotion of small lymphatic vessels. In the present study, we aimed to elucidate the nature of endothelium-derived factors, produced in basal conditions and in response to agonists, that affect the smooth muscle tone of lymph microvessels in vitro. Afferent lymph microvessels were isolated from rat iliac lymph nodes, cannulated with glass micropipettes, and pressurized (6 cmH2O), and changes in their diameter were investigated with video microscopy. In resting conditions, isolated lymph vessels exhibited spontaneous constrictions and dilations. The maximum and minimum diameters (Dmax and Dmin) were 149.8 +/- 2.9 and 85.8 +/- 3.6 microns, respectively. Acetylcholine (ACh, 10(-7) to 10(-5) M) and sodium nitroprusside (SNP, 10(-8) to 10(-6) M) temporarily abolished diameter oscillations, increasing the diameter of lymphatics dose dependently. For example, 10(-5) M ACh and 10(-6) M SNP increased the diameter (Dmax) by 15.2 +/- 2.2 and 25.0 +/- 2.7 microns, respectively. Treatment of vessels with NG-nitro-L-arginine (10(-4) M) significantly reduced the amplitude of diameter oscillations and nearly completely eliminated ACh-induced dilation of lymph microvessels, whereas SNP (10(-6) M) elicited a significantly greater dilation (55.6 +/- 7.5 microns). Arachidonic acid (AA, 10(-8) to 10(-6) M) constricted (up to 50 microns), whereas prostaglandin E2 (PGE2, 10(-9) to 10(-7) M) dilated (up to 40 microns), lymphatic vessels. Indomethacin (10(-5) M) increased both Dmax and Dmin and completely inhibited AA-induced constrictions, but did not affect PGE2-induced dilations of lymph microvessels. AA-induced constrictions of lymphatics were converted into dilations after treatment with SQ-29,548, a selective PGH2-thromboxane A2 (PGH2-TxA2, 10(-6) M) receptor antagonist, whereas PGE2-induced dilations were not affected. We conclude that endothelial nitric oxide and prostaglandins are important modulators of lymphatic vasomotion, hence pumping activity of lymph microvessels in vivo.

Effects of prolonged strenuous endurance exercise on plasma myosin heavy chain fragments and other muscular proteins. Cycling vs running

BACKGROUND

This study evaluates creatine kinase, myosin heavy chain, and cardiac troponin blood levels following three types of exercise: 1) short-distance uphill or downhill running; 2) alpine ultramarathon; and 3) alpine long-distance cycling.

METHODS

EXPERIMENTAL DESIGN

Comparative field study; follow-up up to 10 days.

SETTING

Department of Sports Medicine. All biochemical markers were analysed at the Department of Medical Chemistry and Biochemistry.

PATIENTS OR PARTICIPANTS

Subjects included healthy, trained males (N = 53). All subjects were nonsmokers and free from medication prior to and during the study. Each volunteer was an experienced runner or cyclist, who had at least once successfully finished the Swiss Alpine Marathon of Davos or the Otztal-Radmarathon before.

INTERVENTIONS

Running or cycling.

MEASURES

Plasma concentrations of creatine kinase, myosin heavy chain fragments and cardiac troponins were measured to diagnose skeletal and cardiac muscle damage, respectively.

RESULTS

Skeletal muscle protein release is markedly different between uphill and downhill running, with very little evidence for muscle damage in the uphill runners. There is considerable muscle protein leakage in the ultramarathoners (67 km distance; 30 km downhill running). In contrast, only modest amounts of skeletal muscle damage are found after alpine long-distance cycling (230 km distance).

CONCLUSIONS

This study proves that there is slow-twitch skeletal muscle fiber damage after prolonged strenuous endurance exercise and short-distance downhill running. Exhaustive endurance exercise involving downhill running and short-distance downhill running lead to more pronounced injury than strenuous endurance exercise involving concentric actions. From our results there is no reason for suggesting that prolonged intense exercise may induce myocardial injury in symptom-less athletes without cardiac deseases.

[Heterogeneity of seminal vesicle amyloid. Immunohistochemical detection of lactoferrin and amyloid of the prealbumin-transthyretin type]

Localized depositions of amyloid in the seminal vesicles may occur in elderly men. Earlier immunohistochemical studies have failed to identify immunoreactivity of known amyloid material. In this autopsy study, all seminal vesicles of males older than 50 years were histologically examined to determine incidence and phenotype of seminal vesicle amyloidosis. Seven out of 50 patients (14%) showed depositions of amyloid in the seminal vesicles. These amyloid depositions as well as one additional case were characterized histochemically, immunohistochemically and electronmicroscopically. All but two of these patients (75%) showed simultaneously amyloid depositions in the heart. Lactoferrin immunoreactivity was found in 6 patients (75%). Lactoferrin is an iron-binding, bacteriostatic glycoprotein, which is produced in the seminal vesicles. Four patients with lactoferrin positive amyloid in seminal vesicle showed different amyloid depositions in the heart (immunoglobulin light chain amyloid AL-lambda). Two cases (25%) showed the same amyloid type in heart and seminal vesicles (prealbumin-transthyretin type amyloid). Our study shows that most amyloidoses of the seminal vesicles are organ-limited depositions of lactoferrin. These forms of localized amyloidosis have to be separated from senile systemic amyloidosis with seminal vesicle involvement.

Shear stress-induced dilation of arterioles

The following is the abstract of the article discussed in the subsequent letter:

McGahren, Eugene D., Kim A. Dora, David N. Damon, and Brian R. Duling. A test of the role of flow-dependent dilation in arteriolar responses to occlusion. Am. J. Physiol. 272 ( Heart Circ. Physiol. 41): H714–H721, 1997.—At an arteriolar bifurcation, occlusion of one of the branch arterioles has been reported to result in an increase in flow, shear stress, and vasodilation in the opposite unoccluded branch. This dilator response in the unoccluded branch, often referred to as the “parallel occlusion response,” has been cited as evidence that flow-dependent dilation is a primary regulator of arteriolar diameter in the microcirculation. It has not been previously noted that, during this maneuver, flow through the feed arteriole would be expected to decrease and logically should cause that vessel to constrict. We tested this prediction in vivo by measuring red blood cell (RBC) velocity and diameter changes in response to arteriolar occlusion in the microcirculatory beds of three preparations: the hamster cheek pouch, the hamster cremaster, and the rat cremaster. In all preparations, a vasodilation was observed in the feed arteriole, despite a decrease in both flow and calculated wall shear stress through this vessel. Unexpectedly, we found that dilation occurred in the unoccluded branch arterioles even in those cases in which RBC velocity and shear stress did not increase in the unoccluded branch arterioles. All values returned to the baseline level after the removal of occlusion. The magnitude of the dilation of the feed and branch arterioles varied between species and tissues, but feed and branch arterioles within a given preparation always responded in a similar way to each other. We conclude from our experiments that mechanisms other than flow-dependent dilation are involved in the vasodilation observed in the microcirculation during occlusion of an arteriolar branch.

Estrogen preserves regulation of shear stress by nitric oxide in arterioles of female hypertensive rats

Previously we found that flow-induced arteriolar dilation in male spontaneously hypertensive rats (SHR) is significantly impaired, due to the absence of the nitric oxide (NO)-mediated portion of the response, resulting in an elevation of maintained wall shear stress. Since estrogen has been shown to affect NO-mediated responses, we hypothesized that in female SHR (fSHR) the NO-mediated portion of flow-induced responses is preserved. Gracilis muscle arterioles (approximately 45 to 55 microm) from 12-week-old fSHR, ovariectomized fSHR (OV fSHR), or ovariectomized and supplemented with estrogen fSHR (OVE fSHR) were isolated, cannulated, and pressurized at 80 mm Hg of perfusion pressure. Arteriolar dilations elicited by step increases in perfusate flow from 0 to 25 microL/min were significantly less (by approximately 30%) in OV fSHR compared with fSHR and OVE fSHR (delta19.4+/-1.5 versus 26.0+/-0.9 and 26.8+/-2.0 microm, respectively at maximum flow rate). Inhibition of prostaglandin synthesis with indomethacin elicited a approximately 50% reduction in flow-dependent dilation in all three groups of rats. N(omega)-nitro-L-arginine (L-NNA) significantly inhibited flow-induced responses in arterioles of fSHR and OVE fSHR (by approximately 50%) but not in those of OV fSHR. Constrictions to norepinephrine (10(-7)-3 x 10(-7) mol/L) were significantly greater (up to approximately 40%) in arterioles of OV fSHR compared with those of fSHR and OVE fSHR; these differences, however, were abolished in the presence of L-NNA. In conclusion, estrogen seems to preserve the NO-mediated portion of flow/shear stress-induced dilation in female hypertensive rats resulting in a lower maintained wall shear stress in female than in male SHR. The lower wall shear stress may contribute to the mechanisms by which estrogen lowers systemic blood pressure and the incidence of cardiovascular diseases in women.

Muscular adaptation and strength during the early phase of eccentric training: influence of the training frequency

We investigated the effects of different training frequencies on maximum isometric voluntary contraction (MVC) force and plasma concentrations of muscle proteins during the early phase of eccentric training. MVC and plasma concentrations of creatine kinase (CK) and slow-twitch skeletal (cardiac beta-type) myosin heavy chain (MHC) fragments were measured before and 4 and 7 d after performing the first and last training task. Training tasks, which comprised 70 high-force eccentric contractions involving the thigh muscles (single leg), were performed under supervision in three groups (A, B, C) at the beginning and at the end of the study period (7 wk). In addition, groups A (N = 10) and B (N = 10) trained during the study period starting 1 wk after the first training task. Group A performed one training task once a week for 5 wk and group B (N = 10) twice a week for 2 wk and three times a week during the subsequent 3 wk. In all three groups the first training task resulted in delayed CK and MHC peaks and decrements in MVC, which were comparable (P > 0.05). Only training regimen B resulted in a significant increase in the MVC. Compared with the first training task training regimens, A and B significantly (P < 0.01) reduced the increase in serum muscle protein and muscle function impairment. The responses to the last training task did not differ significantly between groups A and B. In group C the responses after the second training task did not differ significantly from those observed after the first task. Our results suggest that, compared with group A, additional eccentric exercise in group B is the essential basis for the increase in muscle strength during the early phase of eccentric training without further benefits for muscular adaptation. In group C we found no muscular adaptation.

Myogenic responses of isolated lymphatics: modulation by endothelium

OBJECTIVE

To characterize the effect of increases of intraluminal pressure on the spontaneous diameter oscillations of isolated lymphatics and on the maximum and minimum diameter, in the presence and absence of endothelium.

METHODS

Afferent lymphatics were isolated from rat iliac lymph nodes. After cannulation of both ends, lymphatics were equilibrated for 60 minutes at a pressure of 6 cm H2O, and then changes in diameter oscillations to increases in perfusion pressure (from 2-10 cm H2O, were measured. The endothelium was removed by intraluminal infusion of air. Changes in diameter were expressed as a percentage of the corresponding passive diameter obtained in Ca(2+)-free solution.

RESULTS

Isolated lymphatics showed phasic spontaneous constriction and dilation (approximately 50 to approximately 150 microns). Removal of extracellular Ca2+ abolished spontaneous diameter oscillations, and the passive diameter increased from 183.0 +/- 5.3 to 205.1 +/- 8.8 microns as pressure increased from 2 to 10 cm H2O. In response to increases in pressure, the normalized minimum diameter (Dmin) increased (from 30.1% +/- 1.1% to 54.8% +/- 1.9% while the normalized maximum diameter (Dmax) of lymphatics did not change. With increasing pressure the amplitude of vasomotion (Dmax-Dmin) decreased, whereas the oscillation frequency increased. Removal of endothelium significantly reduced Dmax; hence, the oscillation amplitude decreased while the frequency increased. Also, endothelium removal elicited a significant change in the slope of the pressure-Dmax curve (from 0.01 +/- 0.4 to -1.43 +/- 0.34).

CONCLUSIONS

Increases in intraluminal pressure greatly affect the spontaneous vasomotion of lymphatics and activate the myogenic mechanism intrinsic to the smooth muscle. In addition, endothelial factors are important to maintain adequate lymphatic vasomotion. These findings suggest that intraluminal pressure and endothelial factors can be important contributors to the tone and pumping activity of lymphatics in vivo.

Endothelin and prostaglandin H2 enhance arteriolar myogenic tone in hypertension

We hypothesized that endothelin in addition to prostaglandin (PG)H2 may also contribute to the enhanced myogenic tone of skeletal muscle arterioles of spontaneously hypertensive (SH) rats. Changes in the diameter of isolated, cannulated arterioles (approximately 60 microm) from cremaster muscles of 30-week-old normotensive Wistar Kyoto (WKY) and SH rats were measured as a function of perfusion pressure (20 to 140 mm Hg). Pressure-induced constrictions were significantly enhanced between 60 to 140 mm Hg in arterioles of SH rats compared with those of WKY rats; at 80 and 140 mm Hg the normalized diameter of arterioles (expressed as a percentage of corresponding passive diameter) of SH rats was 11.0% and 15.4% less (P<.05) than that of WKY rats. After inhibition of thromboxane A2-PGH2 receptors by SQ 29,548 (10[-6] mol/L), the still enhanced myogenic response of SH arterioles was eliminated by the removal of endothelium or the administration of BQ-123 (10[-7] mol/L), an endothelin A (ET-A) receptor blocker, which also inhibited constrictions to exogenous ET-1 (10[-11] to 5x10[-10] mol/L). ET-1 elicited comparable responses in arterioles of SH and WKY rats. Thus, in SH rats the enhanced arteriolar constriction to increases in intravascular pressure seems to be due to the production of endothelium-derived constrictor factors PGH2 and endothelin.

Skeletal troponin I as a marker of exercise-induced muscle damage

The utility of skeletal troponin I (sTnI) as a plasma marker of skeletal muscle damage after exercise was compared against creatine kinase (CK), myoglobin (Mb), and myosin heavy chain (MHC) fragments. These markers were serially measured in normal physical education teacher trainees after four different exercise regimens: 20 min of level or downhill (16% decline) running (intensity: 70% maximal O2 uptake), high-force eccentric contractions (70 repetitions), or high-force isokinetic concentric contractions of the quadriceps group (40 repetitions). Eccentrically biased exercise (downhill running and eccentric contractions) promoted greater increases in all parameters. The highest plasma concentration were found after downhill running (median peaks: 309 U/l CK concentration (-CK-)), 466 microgram/l Mb concentration (-Mb-), 1,021 microU/l MHC concentration (-MHC-), and 27.3 microgram/l sTnI concentration ([sTnI]). Level running produced a moderate response (median peaks: 178 U/l -CK-, 98 microgram/l -Mb-, 501 microU/l -MHC-, and 6.6 microgram/l [sTnI]), whereas the concentric contraction protocol did not elicit significant changes in any of the markers assayed. sTnI increased and peaked in parallel to CK and stayed elevated (>2.2 microgram/l) for at least 1-2 days after exercise. In contrast to MHC, sTnI is an initial, specific marker of exercise-induced muscle injury, which may be partly explained by their different intracellular compartmentation with essentially no (MHC <0.1%) or a small soluble pool (sTnI: median 3.4%).

Estrogen maintains nitric oxide synthesis in arterioles of female hypertensive rats

We hypothesized that in female spontaneously hypertensive rats (SHR), estrogen moderates the dysfunction of arterioles by preserving nitric oxide synthesis. To this end, we conducted experiments on isolated gracilis muscle arterioles (approximately 55 microns in diameter) of 12-week-old (SHR divided into four groups: females (fSHR), ovariectomized females (fSHR-OV), ovariectomized females with estrogen replacement (fSHR-OV+ES, 50 micrograms/kg SC 17 beta-estradiol benzoate every 48 hours), and males (mSHR). Arteriolar diameter in the presence of perfusion pressures of 60, 80, 100, and 120 mm Hg were obtained, and diameter changes were measured (at 80 mm Hg) in response to various concentrations of substance P (10(-9) to 5 x 10(-8) mol/L), sodium nitroprusside (10(-8) to 10(-6) mol/L), and A23187 (5 x 10(-8) to 10(-6) mol/L). The pressure-induced diameter of mSHR and fSHR-OV arterioles was significantly less (by approximately 10%) than that of fSHR and fSHR-OV+ES arterioles. N omega-nitro-L-arginine (10(-4) mol/L), a nitric oxide synthase inhibitor, elicited a significant decrease in basal arteriolar diameter of fSHR (by approximately 19%) and fSHR-OV+ES (by approximately 17%), thereby eliminating the differences in tone among the various groups. Dilations of fSHR and fSHR-OV+ES arterioles to substance P were significantly greater (by 140% at a concentration of 5 x 10(-8) mol/L) than those of mSHR and fSHR-OV arterioles, whereas dilations to sodium nitroprusside were not different among the groups. A23187 (a nitric oxide releaser) elicited dilations in arterioles of fSHR (5.9 +/- 1.5%, 13.0 +/- 1.8%, and 19.2 +/- 2.1%) and fSHR-OV+ES (4.3 +/- 1.0%, 10.3 +/- 2.4%, and 15.0 +/- 4.0%) but constrictions in those of mSHR (-7.5 +/- 1.6%, -25.3 +/- 39%, and -36.9 +/- 4.1%) and fSHR-OV (-2.6 +/- 1.7%, 7.4 +/- 3.3%, and -11.5 +/- 6.1%). We conclude that estrogen in fSHR is responsible for the preservation of nitric oxide synthesis in skeletal muscle arterioles, resulting in a greater modulation of pressure-induced myogenic tone than in mSHR and maintenance of nitric oxide-mediated dilations.

Release of nitric oxide and prostaglandin H2 to acetylcholine in skeletal muscle venules

The role of endothelium in regulating venular resistance is not well characterized. Thus we aimed to elucidate the endothelium-derived factors involved in the mediation of responses of rat gracilis muscle venules to acetylcholine (ACh) and other vasoactive agents. Changes in diameter of perfusion pressure (7.5 mmHg)- and norepinephrine (10(-6) M)-constricted venules (approximately 225 microns in diam) to cumulative doses of ACh (10(-9) to 10(-4) M) and sodium nitroprusside (SNP, 10(-9) to 10(-4) M), before and after endothelium removal or application of various inhibitors, were measured. Lower doses of ACh elicited dilations (up to 42.1 +/- 4.7%), whereas higher doses of ACh resulted in smaller dilations or even constrictions. Endothelium removal abolished both ACh-induced dilation and constriction. In the presence of indomethacin (2.8 x 10(-5) M), a cyclooxygenase blocker, or SQ-29548 (10(-6) M), a thromboxane A2-prostaglandin H2 (PGH2) receptor antagonist, higher doses of ACh caused further dilation (up to 72.7 +/- 7%) instead of constriction. Similarly, lower doses of arachidonic acid (10(-9) to 10(-6) M) elicited dilations that were diminished at higher doses. These reduced responses were, however, reversed to substantial dilation by SQ-29548. The nitric oxide (NO) synthase blocker, N omega-nitro-L-arginine (L-NNA, 10(-4) M), significantly reduced the dilation to ACh (from 30.6 +/- 5.5 to 5.4 +/- 1.4% at 10(-6) M ACh). In contrast, L-NNA did not affect dilation to SNP. Thus ACh elicits the release of both NO and PGH2 from the venular endothelium.

Gender difference in myogenic tone of rat arterioles is due to estrogen-induced, enhanced release of NO

The characteristics of arteriolar myogenic responses of female rats have not been investigated. Thus experiments were conducted on isolated gracilis muscle arterioles (approximately 55 microm diameter) of four groups of 12-wk-old rats: male rats, female rats, ovariectomized female rats with no estrogen replacement (OV), and ovariectomized female rats with estrogen replacement (OV + E2, 50 microg/kg s.c. injection of 17beta-estradiol benzoate every 48 h). Diameter changes in response to increases in perfusion pressure from 20 to 140 mmHg and to various concentrations of substance P (SP, 10(-9)-5 x 10(-8) M) and sodium nitroprusside (SNP, 10(-8)-10(-6) M) were measured before and after administration of N(omega)-nitro-L-arginine (L-NNA, 10(-4) M), an inhibitor of NO synthase. Arteriolar diameters of male and OV female rats were significantly less at 60-140 mmHg pressure than those of normal female and OV + E2 female rats (at 80 mmHg, 45.4 +/- 1.8 and 43.1 +/- 2.2 vs. 58.4 +/- 1.6 and 57.3 +/- 1.3%). L-NNA elicited a significantly greater downward shift of pressure-diameter curves in arterioles of normal female and OV + E2 female rats than in arterioles of male and OV female rats (28.6 +/- 4.6 and 30.6 +/- 4.7 vs. 13.2 +/- 0.9 and 10.4 +/- 2.6%). Dilations of arterioles from normal female and OV +/- E2 female rats to SP were significantly greater (by 50-60%) than those from male and OV female rats (20.8 +/- 1.8 and 22.3 +/- 1.9 vs. 13.8 +/- 1.4 and 13.8 +/- 0.6% at 10(-8) M). L-NNA did not affect dilations to SNP but significantly reduced the dilation of arterioles in all groups to SP, more so in arterioles of male and OV female rats than in arterioles of the other two groups. We conclude that pressure-induced myogenic constriction of arterioles of female rats is less pronounced than that of male rats; this is, most likely, due to the enhanced release and/or activity of NO related to the presence of estrogen.

[Arthroscopic replacement of the anterior cruciate ligament with a double semitendinosus tendon]

At the university hospital of emergency surgery in Innsburck and at the emergency services department of the hospital in Schwaz, anterior cruciate ligament reconstruction was performed in 467 patients between January 1992 and September 1993. In 117 cases, a double semitendinous tendon was used as an autograft. A total of 60 of these patients were followed up at an average of 20 months (13-33) after reconstruction. The results were rated according to the OAK and the Tegner scores. Objective measurements of instability were carried out by a KT 1000 arthrometer. In addition, 21 patients underwent computer-interfaced dynamometer testing using a Cybex 6000. Standardized loading of the thigh muscles was performed at angular velocities of 60 degrees/s (3 repetitions) and 240 degrees/s (30 repetitions): peak torques and total work were analyzed. The mean age was 23.5 years (17-55): 48 were male, 21 female. The main reasons for the ACL ruptures were sports injuries (51 cases). The patients were classified into three groups according to the data of the repair (group 1 reconstruction up to 1 week after trauma-28 patients: group 2: reconstruction between the 2nd and 6th week after trauma-15 patients: group 3: reconstruction 6 and more weeks after trauma-26 patients). In group 1. additional ruptures of the menisci. lesions of the MCL. and chondromalacia were seen in 71.4%. in group 2 in 73.3% and in group 3 in 80.8%. The average rating in the OAK score was 90.16 points: 38 patients (55.70%) had excellent results. 18(26.09%) were good. 9(13.04%) were fair and 4(5.80%) were poor. The Tegner activity score showed a reduction of 0.36 points on average. The largest amount of anterior translation was performed with the KT 1000 manual drawer test (2.29 mm on average compared with the contralateral side). Dynamometer testing showed a statistically significant difference in flexor and extensor mechanism (compared with the non-involved side) in both peak torques and total work. A repeat arthroscopy became necessary in five cases: arthrofibrosis in three and incipient joint infection in two cases.

Regional bivalent-univalent pairing versus trivalent pairing of a trisomic chromosome in Saccharomyces cerevisiae

In meiosis I, homologous chromosomes pair, recombine and segregate to opposite poles. These events and subsequent meiosis II ensure that each of the four meiotic products has one complete set of chromosomes. In this study, the meiotic pairing and segregation of a trisomic chromosome in a diploid (2n + 1) yeast strain was examined. We find that trivalent pairing and segregation is the favored arrangement. However, insertions near the centromere in one of the trisomic chromosomes leads to preferential pairing and segregation of the "like" centromeres of the remaining two chromosomes, suggesting that bivalent-univalent pairing and segregation is favored for this region.

Both nitric oxide and prostaglandin-mediated responses are impaired in skeletal muscle arterioles of hypertensive rats

OBJECTIVE

To investigate the role played by endothelium-derived dilator factors in the regulation of peripheral vascular resistance by determining whether the dysfunction of the endothelium contributes to the reduced dilator responsiveness of skeletal muscle arterioles in hypertension.

METHODS

The endothelial function of isolated, cannulated, pressurized (at 80 mmHg) gracilis muscle arterioles (45-50 microns diameter) of normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) was compared by utilizing vasoactive agents of known action.

RESULTS

Acetylcholine (ACh, 10(-9), 10(-8) and 5 x 10(-8) mol/l) and sodium nitroprusside (SNP, 10(-8), 10(-7) and 10(-6) mol/l) elicited similar dilations in arterioles of WKY rats and SHR. Substance P (10(-9), 10(-8) and 5 x 10(-8) mol/l) caused significantly less dilation (by approximately 70%) of SHR arterioles compared with WKY rat arterioles. The calcium ionophore A23187 (5 x 10(-8), 5 x 10(-7) and 10(-6) mol/l) elicited dilations in WKY rat arterioles (9.1 +/- 1.1, 24.0 +/- 1.5, and 39.0 +/- 3.4%, respectively), whereas it evoked constrictions (6.5 +/- 1.1, 14.9 +/- 1.5, and 25.5 +/- 1.6%, respectively) in SHR arterioles. Removal of endothelium, inhibition of prostaglandin synthesis (indomethacin) or blockade of prostaglandin H2 (PGH2) receptors (by SQ 29548) eliminated A23187-induced constrictions of SHR arterioles. The nitric oxide synthase blocker, NG-nitro-L-arginine elicited a significantly greater inhibition of substance P-induced dilations and a greater reduction in basal diameter of WKY rat arterioles than it did in those from SHR.

CONCLUSIONS

These data suggest that, in SHR arterioles, the synthesis and/or action of nitric oxide is, or are, impaired and the metabolism of arachidonic acid is altered, resulting in an enhanced production of PGH2. The simultaneous dysfunction of these two dilator pathways of arteriolar endothelium could contribute significantly to the enhanced peripheral resistance observed in hypertension.

Myogenic responses of isolated rat skeletal muscle venules: modulation by norepinephrine and endothelium

The pressure-induced myogenic response of large venules of skeletal muscle and its possible interactions with adrenergic receptor activation and endothelial factors have not yet been elucidated. Therefore, first-order venules of rat gracilis muscle were isolated, cannulated, and placed in an organ chamber. Changes in internal diameter of the vessels as a function of perfusion pressure (PP) were obtained. In response to increases in PP (0.5-17.5 mmHg), the diameter of venules increased from 197.1 +/- 23.96 to 369 +/- 14.1 microns. In passive conditions (in Ca(2+)-free solution), the pressure-diameter curve of venules shifted significantly upward. In the presence of norepinephrine (NE; 10(-6) M) in the bath solution, the pressure-diameter curve of active venules shifted significantly downward, and in the pressure-normalized diameter curve, a negative slope developed (-6.1 +/- 4.6). In both the absence and presence of NE, removal of endothelium significantly reduced venular diameters in the pressure ranges of 3-5 and 2-5 mmHg, respectively, but did not change significantly the characteristics of the pressure-diameter curves. These findings indicate that the smooth muscle of venules actively responds to changes in intraluminal pressure. This response is greatly facilitated by NE and modulated by the endothelium. The myogenic response of skeletal muscle venules, especially in the presence of NE, could have a role in the regulation of the resistance and capacitance of venules and, consequently, blood flow and tissue exchange in skeletal muscle.

Successful twin pregnancy in homozygous beta-thalassemia after ovulation induction with growth hormone and gonadotropins

OBJECTIVE

To describe infertility treatment and pregnancy outcome in a patient with transfusion-dependent beta-thalassemia major and hypopituitarism.

DESIGN

Case report.

SETTING

University-affiliated infertility clinic.

PATIENT

Twenty-four-year-old infertile patient with homozygous beta-thalassemia.

INTERVENTION

Co-treatment with GH and gonadotropins.

RESULTS

Ovulation induction with clomiphene citrate or gonadotropins alone was unsuccessful. Combined treatment with hMG, hCG, and recombinant human GH followed by intrauterine insemination resulted in a viable twin pregnancy.

CONCLUSION

Human GH as an adjunct to hMG and hCG seems to be a sensible approach in the treatment of infertile homozygous beta-thalassemic patients among which very few pregnancies are reported.