Segmental volume distensibility of the canine thoracic aorta in vivo.

Segments of the canine ascending aorta, upper descending thoracic aorta, and middle descending thoracic aorta were instrumented with ultrasonic dimension gauges and a cathetertip manometer simultaneously to measure changes in segment diameter, length, and intravascular pressure. Volume distensibility (EV) was calculated as the sum of circumferential extensibility (EC), longitudinal extensibility (EL), and high order extensibilities (EK) for each segment. The EC and EL were linear expressions that represented percentage volume changes per mmHg pulse pressure due to circumferential and longitudinal dimensional changes. The high order extensibilities (second and third order) accounted for the percentage volume changes per mmHg pulse pressure due to the interactions between circumferential and longitudinal dimensional changes. Mean(SEM) EV values from six dogs were 1.62(0.31), 0.84(0.08), and 0.62(0.08)% delta V/mmHg delta P for the ascending aorta, upper descending thoracic aorta, and middle descending thoracic aorta segments respectively. The EV, EL, and EK of the ascending aorta segment were significantly greater than those of the upper descending thoracic aorta and middle descending thoracic aorta segments, whereas EC was significantly less in the ascending aorta than in both the upper descending thoracic aorta and middle descending thoracic aorta segments. It is concluded that there are regional differences in aortic distensibility and its components in vivo. Longitudinal wall motion is an important determinant of these aortic mechanical properties.

Labial adhesions presenting as urinary incontinence in postmenopausal women.

Most discussion on labial adhesions is about the pediatric group. A case is presented of a postmenopausal woman whose main complaint was urinary incontinence. Etiology, symptoms, signs, and diagnosis are discussed. Guidelines for treatment and prevention are proposed. Because the number of postmenopausal women is steadily increasing, it is important to draw attention to this condition.

Critique of conceptual basis of diffusing capacity estimates: a finite element analysis.

We present a simple geometric model of a pulmonary capillary segment containing a variable number of red blood cells. The pattern of CO transfer from alveolar air to capillary red blood cells in this model is accurately computed by a finite element method and used to explore conceptual flaws in the Roughton-Forster (RF) and morphometric methods of estimating pulmonary diffusing capacity for CO. The CO uptakes calculated by the finite element method at two alveolar O2 tensions are introduced into the RF model to determine whether the anatomically defined membrane component of diffusing capacity for CO (DmCO) and pulmonary capillary blood volume (Vc) are recovered. The same capillary model is also subjected to standard morphometric analysis. Results are compared at different levels of capillary hematocrit (Hct). The RF method accurately recovers DmCO and Vc at a low Hct but modestly overestimates DmCO and underestimates Vc at higher Hct; errors arise because conductance of the tissue-plasma membrane for CO varies with alveolar O2 tension. The morphometric method seriously overestimates DmCO because the true tissue-plasma resistance to diffusion is underestimated and the effective membrane utilized for diffusion is overestimated; these errors are accentuated by a low Hct.

Periovulatory beta-endorphin levels in premenstrual syndrome.

OBJECTIVE: To determine whether changes in peripheral beta-endorphin levels during the periovulatory phase are associated with symptoms of premenstrual syndrome (PMS). METHODS: Twenty-one PMS patients and ten controls were studied. All were in general good health and had no history of psychiatric disorders. They were between 21-44 years of age, had had regular menses for at least six previous cycles, and were carefully selected by charting the Visual Linear Analogue Scale and basal body temperature daily for 1 month. After an overnight fast, the subjects had blood drawn between 8:00 and 10:00 AM daily for 8 days, starting on the tenth day of the menstrual cycle, for one cycle. Beta-endorphin and LH were measured by radioimmunoassay. The day of the LH peak was defined as day LH 0. The beta-endorphin levels were expressed as the number of days before or after the LH surge. RESULTS: Beta-endorphin levels throughout the periovulatory phase were lower in PMS patients than in controls, and the differences were more remarkable on LH days 0 and 4. CONCLUSION: Our data suggest that an aberration of normal changes in beta-endorphin activity in PMS patients may occur around the time of ovulation.

A finite-element model of oxygen diffusion in the pulmonary capillaries.

We determined the overall pulmonary diffusing capacity (DL) and the diffusing capacities of the alveolar membrane (Dm) and the red blood cell (RBC) segments (De) of the diffusional pathway for O2 by using a two-dimensional finite-element model developed to represent the sheet-flow characteristics of pulmonary capillaries. An axisymmetric model was also considered to assess the effect of geometric configuration. Results showed the membrane segment contributing the major resistance, with the RBC segment resistance increasing as O2 saturation (SO2) rises during the RBC transit: RBC contributed 7% of the total resistance at the capillary inlet (SO2 = 75%) and 30% toward the capillary end (SO2 = 95%) for a 45% hematocrit (Hct). Both Dm and DL increased as the Hct increased but began approaching a plateau near an Hct of 35%, due to competition between RBCs for O2 influx. Both Dm and DL were found to be relatively insensitive (2-4%) to changes in plasma protein concentration (28-45%). Axisymmetric results showed similar trends for all Hct and protein concentrations but consistently overestimated the diffusing capacities (approximately 2.2 times), primarily because of an exaggerated air-tissue barrier surface area. The two-dimensional model correlated reasonably well with experimental data and can better represent the O2 uptake of the pulmonary capillary bed.

Regional deformation of the canine diaphragm.

To follow regional deformation of the diaphragm in dogs, radiopaque markers were implanted under surgical anesthesia into different anatomic regions of the muscle in triangular arrays (approximately 1 cm to a side). After recovery from surgery, changes in area and shape of the triangles were followed with biplane cinefluorography during quiet breathing and during inspiratory efforts against an occluded airway (Mueller maneuvers). From changes in shape of the triangles during contraction, area changes were decomposed into a major direction and magnitude of shortening (Eg1) and a minor length change (Eg2) perpendicular to Eg1, both expressed as a fraction of initial length at end expiration. With the use of these techniques, systematic differences in regional area change were observed in different parts of the diaphragm during inspiratory efforts at different lung volumes. Regional area always decreased during contraction in the crural and midcostal zones of apposition to the rib cage. Area decreased less and often increased during inspiratory efforts in the costal dome near the central tendon and in the costal region near its rib cage insertion. Differences in regional area change were not due to differences in the Eg1 in different parts of the diaphragm but were a consequence of differences in widening of the muscle along Eg2 perpendicular to the direction of Eg1. As lung volume was passively increased above functional residual capacity, regional area decreased in all parts of the diaphragm except in the costal regions near rib cage insertion, where area increased.

Red cell distortion and conceptual basis of diffusing capacity estimates: finite element analysis.

To understand the effects of dynamic shape distortion of red blood cells (RBCs) as it develops under high-flow conditions on the standard physiological and morphometric methods of estimating pulmonary diffusing capacity, we computed the uptake of CO across a two-dimensional geometric capillary model containing a variable number of equally spaced RBCs. RBCs are circular or parachute shaped, with the same perimeter length. Total CO diffusing capacity (DLCO) and membrane diffusing capacity (DMCO) were calculated by a finite element method. DLCO calculated at two levels of alveolar PO2 were used to estimate DMCO by the Roughton-Forster (RF) technique. The same capillary model was subjected to morphometric analysis by the random linear intercept method to obtain morphometric estimates of DMCO. Results show that shape distortion of RBCs significantly reduces capillary diffusive gas uptake. Shape distortion exaggerates the conceptual errors inherent in the RF technique (J. Appl. Physiol. 79: 1039-1047, 1995); errors are exaggerated at a high capillary hematocrit. Shape distortion also introduces additional error in morphometric estimates of DMCO caused by a biased sampling distribution of random linear intercepts; errors are exaggerated at a low capillary hematocrit.

Clinical trial of naltrexone in premenstrual syndrome.

Twenty women with the diagnosis of premenstrual syndrome (PMS) participated in a double-blind, placebo-controlled, crossover study to evaluate the efficacy of naltrexone, an oral opiate antagonist. This study was designed to test the hypothesis that inhibition of opiate withdrawal would aid in the treatment of PMS. The subjects received either placebo or naltrexone from days 9-18 of the cycle for three consecutive cycles. The mean scores of the three day-25 Menstrual Distress Questionnaires of 16 patients on naltrexone were compared with the mean scores of the same patients on placebo. Scores were at least ten points lower on naltrexone in 11 patients and at least ten points higher on naltrexone in two patients. Score changes of less than ten points were noted in the other three patients. The mean scores dropped 28 points on naltrexone (P = .016). The general acceptability of naltrexone was good, with side effects including nausea, decreased appetite, and dizziness. These results suggest that naltrexone alleviates many PMS symptoms and may be an effective treatment for this syndrome.

Effect of ovariectomy and estrogen replacement on hypothalamic, pituitary and peripheral blood beta-endorphin levels in the rat.

This study was initiated to detect possible changes in beta-endorphin (beta-EP) levels of the hypothalamus, anterior pituitary gland, and peripheral blood of rats after ovariectomy and estrogen administration. Attempts were also made to determine the correlation between peripheral and central levels of beta-EP. Twenty-six Sprague-Dawley rats were decapitated. Nine had intact ovaries (Gr. INT), and 17 were ovariectomized 3 weeks before they were killed. Nine of the ovariectomized rats received estradiol benzoate (EB) (Gr. EB) and the other 8 received peanut oil (Gr. OVX) prior to the decapitation. A beta-EP radioimmunoassay was used to analyze homogenates of the hypothalamus and anterior pituitary, and peripheral blood. In the hypothalamus, beta-EP levels were significantly lower in Gr. INT and Gr. EB than in Gr. OVX. In the pituitary gland and peripheral blood, beta-EP levels were significantly higher in Gr. INT than in Gr. OVX. Pituitary beta-EP levels did not vary between Gr. OVX and Gr. EB, although beta-EP levels in peripheral blood were significantly higher in Gr. EB than in Gr. OVX. No significant correlations were noted in beta-EP levels between the hypothalamus, pituitary gland, and peripheral blood in either Gr. INT, Gr. OVX, or Gr. EB. It appears that EB exerts different effects on beta-EP levels in the hypothalamus, anterior pituitary gland, and peripheral blood, and that beta-EP levels in these regions may be independent of one another.

Zinc and copper levels in premenstrual syndrome.

OBJECTIVE: To determine whether changes in peripheral zinc and copper levels are associated with symptoms of premenstrual syndrome (PMS). DESIGN: Ten PMS patients and 10 controls gave blood at 2- or 3-day intervals through three menstrual cycles. Serum zinc and copper were measured by flameless atomic absorption spectrophotometry. RESULTS: In the controls zinc values were not significantly different between the follicular and the luteal phases. In the patients, the values were significantly lower during the luteal phase than during the follicular phase. Lower levels of zinc during the luteal phase in PMS patients, compared with the controls, were noted. Copper levels were noted to be higher during the luteal phase in PMS patients compared with the controls. Because copper competes with zinc for intestinal absorption and serum protein binding sites, zinc:copper ratio can reflect the availability of zinc in the body. The computation of this ratio revealed that the ratio was significantly lower in the patients than those in the controls during the luteal phase. CONCLUSIONS: Our data suggest that zinc deficiency occurs in PMS patients during the luteal phase, and the availability of zinc in PMS patients during the luteal phase is further reduced by the elevated copper.

Effect of naloxone on luteinizing hormone secretion in premenstrual syndrome.

OBJECTIVES: To investigate the theory of brain opioid activity disregulation in premenstrual syndrome (PMS) and to discover the changes of central beta-endorphin activity during the menstrual cycle in PMS patients. DESIGN: Prospective study. SETTING: University-based PMS clinic. PATIENTS: All the patients and controls were between 20 and 45 years of age, with regular menses for at least six previous cycles. All the patients demonstrated at least 30% score increase in designated symptoms on the Visual Linear Analog Scale during the luteal phase compared with the follicular phase. In contrast, the score changes in the controls were < 30%. INTERVENTIONS: All subjects underwent LH-releasing hormone (LH-RH) stimulation test on days 2 to 3 of the cycle. Five naloxone infusions were administered on days 7 to 8 and 10 to 11, 1 day, 3 to 4 days, and 12 to 13 days after the LH surge as detected by the ovulation prediction kit. MAIN OUTCOME MEASURES: Luteinizing Hormone levels were recorded for 1 hour, followed by naloxone infusion at 2 mg/h for 4 hours. Blood samples were collected for LH tests every 15 minutes for 1 hour before, during, and for 1 hour after the infusion. RESULTS: All subjects had similar LH response to LH-RH. The integrated area of LH response to naloxone as expressed by percentage of the baseline on each of the 5 days did not show significant differences between the patients and the controls. CONCLUSIONS: The central beta-endorphin changes, if any, in PMS patients could not be demonstrated in our study.

Term pregnancy after fallopian tube transposition.

A 28-year-old woman suffered from pelvic pain and secondary infertility. She previously had right salpingo-oophorectomy because of ruptured right cornual EP. She was found to have a normal appearing left fallopian tube that entered into a noncommunicating residual horn of the uterus. Microsurgical transposition of the left tube and tubouterine implantation was performed successfully. For cases in which tubocornual anastomosis of the transposed tube is impossible because of previous cornual resection, our technique remains an option.

Vitamin A levels in premenstrual syndrome.

To determine whether changes in peripheral vitamin A levels are associated with symptoms of premenstrual syndrome (PMS), 10 PMS patients and 10 controls were studied. They gave blood at 2- or 3-day intervals through three menstrual cycles. The vitamin A was measured by fluorometry after cyclohexane extraction. In the controls, vitamin A values were 68.0 +/- 3.2 micrograms/dL (mean +/- SE) during the luteal phase and 69.8 +/- 4.2 micrograms/dL during the follicular phase. No significant changes were noted between the two values. In the patients, the values were 73.9 +/- 4.2 micrograms/dL during the luteal phase, which was not significantly different from 72.7 +/- 1.8 micrograms/dL during the follicular phase. No significant changes were noted between the controls and the patients in either the luteal or the follicular phase. Vitamin A deficiency in PMS patients was not demonstrated in our study.

Effects of misoprostol on lipoprotein (a) levels of ovariectomized rats.

OBJECTIVE: To determine the effects of misoprostol on plasma lipoprotein (a) concentrations of ovariectomized rats. DESIGN: Controlled prospective study. SETTING: Animal research laboratory. ANIMAL(S): Four-month-old female Sprague-Dawley rats. INTERVENTION(S): Blood samples were obtained before and 60 days after ovariectomy, and the rats were divided into three groups. Group I (five rats) was treated with vehicle (water); groups II and III (nine and eight rats, respectively) were treated with oral misoprostol at 100 and 200 microg/kg/d, respectively, for 60 days, after which blood was drawn again. MAIN OUTCOME MEASURE(S): Serum lipoprotein (a) levels. RESULT(S): The median lipoprotein (a) level before ovariectomy was 10.8 mg/dL (range, 10.6-46.5 mg/dL). Sixty days after ovariectomy, the level increased significantly to 15.9 mg/dL (range, 10.6-36.9 mg/dL). After treatment, there was no change in lipoprotein (a) levels in the vehicle-treated group (range, 16.3-21.1 mg/dL); however, the lipoprotein (a) levels decreased significantly in the group treated with 100 microg/kg/d of misoprostol, from 15.4 mg/dL to 10.8 mg/dL, and in the group treated with 200 microg/kg/d of misoprostol, from 17.1 mg/dL to 10.6 mg/dL. CONCLUSION(S): Misoprostol caused a significant decrease in lipoprotein (a) levels.

Pregnancy after metroplasty for uterine anomalies.

OBJECTIVE: To clarify the relation between metroplasty for correction of uterine anomalies and subsequent pregnancy, we reviewed the charts of all patients for whom a diagnosis of bicornuate, septate, or didelphic uterus had been made between 1972 and 1982 and analyzed their obstetric outcomes. DESIGN: Of the 146 patients evaluated, 23 received a metroplasty procedure, and 123 patients did not have surgical intervention. Fifteen of the nonsurgical patients could be matched with 15 of the surgical patients by age, chief complaint, gravidity, and type of anomaly and therefore served as matched controls. RESULTS: The percentage of patients with living children after the diagnosis of uterine anomaly was 67% for the matched nonsurgical group and 73% for the patients who underwent metroplasty. The difference was not statistically significant. Although marked improvement in fetal salvage rates was noted when reproductive outcomes before and after metroplasty were compared, the obstetric outcome was similar to that of the control groups after the diagnosis was made and surgery deferred. CONCLUSION: The efficacy of metroplasty in the treatment of multiple pregnancy losses is thus being questioned.

Neuropeptide levels in premenstrual syndrome.

To determine whether changes in circulating levels of neuropeptides are associated with symptoms of premenstrual syndrome (PMS), 20 women with the diagnosis of PMS and 20 asymptomatic subjects were studied. The premenstrual beta-endorphin levels were significantly lower in PMS patients (P = 0.0001). The decrease in beta-endorphin levels during the luteal phase, compared with the follicular phase, in PMS patients was also significant (P = 0.0002). Neurotensin, human pancreatic peptide, vasoactive intestinal polypeptide, gastrin, and bombesin-like immunoreactivity levels did not reveal significant changes between days 7 and 25 in patients with PMS.

Effects of misoprostol on bone loss in ovariectomized rats.

This study was performed to investigate whether misoprostol (prostaglandin E1 analogue) (Cytotec, Searle, England) is effective for restoration of bone loss. Four-month-old parous female Sprague-Dawley rats (n = 30) were subjected either to bilateral ovariectomy (OVX, 24 rats) or to sham surgery (sham, 6 rats). The OVX rats were divided into four groups 60 days after the surgery. Six of them were killed, and dual-energy X-ray absorption (Norland xr-36, Norland Corporation, Fort Atkinson, WI, USA) measurements were performed, called pretreatment OVX group. The remaining groups (each had 6 rats) treated orally with 0 (control), 100, 200 micrograms/kg/day misoprostol for 60 days. All rats were killed 60 days after having treatment, and bone loss of the lumbar spine was measured by dual-energy X-ray absorption. The bone mineral density was decreased by 25.4% in control group and 23.6% in pretreatment group compared to sham group, but restored by 86% and 96% in groups treated with 100 and 200 micrograms/kg/day misoprostol, respectively. These results suggest that misoprostol restores bone loss in the lumbar spine of OVX rats in a dose-dependent manner.

A constitutive relation for passive right-ventricular free wall myocardium.

We applied the pseudostrain energy function of Humphrey et al. [J. biomech. Engng 112, 333-346 (1990a, b)] to characterize the passive biaxial mechanical properties of the right ventricle free wall myocardium [Sacks and Chuong, J. biomech. Engng 115, 202-205 (1993)]. The myocardium was assumed to be incompressible, pseudoelastic, and transversely isotropic, with transmural variations in fiber orientation within test specimens accounted for by the strain energy function. Using nonlinear regression, material constants were determined for the right ventricle free wall myocardium from the sinus and conus regions. The pseudostrain energy function was found to model the biaxial mechanical data well (r2 > 0.99). Transmural variations in Cauchy stresses, as well as the magnitude of the in-plane shear stress, were found to be small. Although comparisons with the left ventricle midwall myocardium data [Humphrey et al., J. biomech. Engng 112, 340-346 (1990b)] show clear quantitative differences, there is an overall qualitative similarity in the mechanical behavior of ventricular myocardium.

Compressibility and constitutive equation of arterial wall in radial compression experiments.

A large number of papers treat the tensile properties of arterial wall, but few treat compressive properties. Almost everybody assumes incompressibility; few have measured the vessel wall fluid extrusion due to compressive loading. In this work, uniaxial compressive force is applied directly on rabbit thoracic artery in the radial direction to study its constitutive equation under compressive stresses. The resulting stress-strain curves show that the wall material becomes increasingly stiffer at larger compressive strain, quite similar to the behavior in tension. A pseudo-strain energy function of the exponential type which has been applied successfully on the tension side is used to identify the material constants on the compression side. The material constants are identified in two ways: with and without the assumption of incompressibility. To determine the compressibility of the wall, the fluid extrusion accompanying this type of loading is measured, and is found to be in the range of 0.50-1.26% of the undeformed tissue volume per 10 kPa compressive stress loading in the radial direction. At compressive stresses higher than 30 kPa, the percentage of fluid extrusion per unit compressive stress decreases. At this degree of fluid extrusion the tissue is only slightly compressible (or nearly incompressible). However, the use of incompressibility assumption in the stress-strain relationship results in a set of material constants which is very different from that derived without that assumption.

On the anisotropy of the canine diaphragmatic central tendon.

We studied the mechanical and anatomical anisotropy of the canine diaphragmatic central tendon (CT). Dumb-bell-shaped strips with effective dimensions of 10 x 2 mm (length x width) were cut from different regions of the canine diaphragmatic CT in two different orientations relative to the direction of neighboring muscle fibers. Specimens sampled with their long axial dimension oriented parallel to the neighboring muscle fibers were named Group-1 and those sampled with an orientation perpendicular to the neighboring muscle fibers were named Group-2. Results from one-dimensional stress-strain and tensile failure strength tests revealed that the CT is a nonlinear, inelastic, and anisotropic material. Group-1 specimens were found to have a higher stiffness, higher failure strength and higher strain energy density at failure than Group-2 specimens. Polarized microscopy showed that multiple sheets of collagen fiber bundles formed an orthogonal network in the tendon. Collagen fiber bundles along Group-1 direction formed parallel trajectory lines connecting the neighboring costal and crural muscles; bundles along Group-2 direction were observed to orient 90 degrees away. At the central apex region of the CT, collagen bundles of Group-1 formed a fan-like trajectory pattern. This collagen network architecture was compared favorably to the trajectories of an approximated principal stress field in the CT due to simulated contractile forces from its adjacent costal and crural muscles. These combined results suggest a structure-function relationship for the anatomical and mechanical anisotropy in the canine diaphragmatic CT.