After the Randomized Trial: Implementation of Community-Based Continence Promotion in the Real World

BACKGROUND/OBJECTIVES

Most women aged 65 and older have incontinence, associated with high healthcare costs, institutionalization, and negative quality of life, but few seek care. Mind over Matter: Healthy Bowels, Healthy Bladder (MOM) is a small-group self-management workshop, led by a trained facilitator in a community setting, proven to improve incontinence in older women.

DESIGN

We used mixed methods to gather information on the real-world adoption, maintenance, and implementation of MOM by community agencies following a randomized controlled trial (RCT) that tested intervention effects on incontinence.

SETTING

Community agencies serving older adults in six Wisconsin communities.

PARTICIPANTS

Community agency administrators and facilitators trained to offer MOM for the RCT.

MEASUREMENTS

Investigators tracked rates of adoption (offering MOM in the 12 months following the RCT) and maintenance (offering MOM more than once in the next 18 months) in six communities. Individual interviews and focus groups (N = 17) generated qualitative data about barriers and facilitators related to adoption and maintenance. Trained observers assessed implementation fidelity (alignment with program protocol) at 42 MOM sessions.

RESULTS

A total of 67% of communities (four of six) adopted MOM, and 50% (three of six) maintained MOM. No implementation fidelity lapses occurred. Facilitators of adoption and maintenance included MOM's well-organized protocol and lean time commitment, sharing of implementation efforts between partner organizations, staff specifically assigned to health promotion activities, and high community interest in continence promotion. Other than stigma associated with incontinence, barriers were similar to those seen with other community-based programs for older adults: limited funding/staffing, competing organizational priorities, challenges identifying/training facilitators, and difficulty engaging community partners/participants.

CONCLUSION

Using design for dissemination and community engagement, assessment of implementation outcomes is feasible in conjunction with a clinical RCT. Partner-centered implementation packages can address barriers to adoption and maintenance.

Small-Group, Community-Member Intervention for Urinary and Bowel Incontinence: A Randomized Controlled Trial

OBJECTIVE

To evaluate the effects of Mind Over Matter: Healthy Bowels, Healthy Bladder, a small-group intervention, on urinary and bowel incontinence symptoms among older women with incontinence.

METHODS

In this individually randomized group treatment trial, women aged 50 years and older with urinary, bowel incontinence, or both, were randomly allocated at baseline to participate in Mind Over Matter: Healthy Bowels, Healthy Bladder immediately (treatment group) or after final data collection (waitlist control group). The primary outcome was urinary incontinence (UI) improvement on the Patient Global Impression of Improvement at 4 months. Validated instruments assessed incontinence, self-efficacy, depression, and barriers to care-seeking. Intent-to-treat analyses compared differences between groups. Target sample size, based on an anticipated improvement rate of 45% in treated women vs 11% in the control group, 90% power, type I error of 0.05, with anticipated attrition of 25%, was 110.

RESULTS

Among 121 women randomized (62 treatment group; 59 control group), 116 (95%) completed the 4-month assessment. Most participants were non-Hispanic white (97%), with a mean age of 75 years (SD 9.2, range 51-98); 66% had attended some college. There were no significant between-group differences at baseline. At 4 months, 71% of treated women vs 23% of women in the control group reported improved UI on Patient Global Impression of Improvement (P<.001); 39% vs 5% were much improved (P<.001). Regarding bowel incontinence, 55% of treated women vs 27% of women in the control group improved on Patient Global Impression of Improvement (P<.005), with 35% vs 11% reporting much improvement (P<.005). Treated women improved significantly more than women in the control group on all validated instruments of incontinence severity, quality of life, and self-efficacy. Care-seeking rates were similar between groups.

CONCLUSION

Participation in a small-group intervention improves symptoms of both urinary and bowel incontinence in older women. Mind Over Matter is a feasible model with potential to bring effective behavioral solutions to the community.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT03140852.

Comparing Visual and Digital Counting Methods to Estimate Horn Fly (Diptera: Muscidae) Populations on Cattle

Horn fly, Haematobia irritans (L.), population estimates often serve as a diagnostic tool prior to implementing managerial control options available to researchers and producers. Digital photographs taken of cattle infested with horn flies have been suggested to provide similarly accurate population estimates as compared with traditional visual assessments. The objective of this study was to compare visual and digital techniques used to estimate horn fly populations. Sixteen Angus × Hereford yearling heifers artificially infested with four levels of horn flies (Low = 0 flies; Medium = 250 flies; High = 500 flies; Extreme = 1,000 flies) were evaluated. Population estimates were taken visually by experienced (VE1) and inexperienced (VE2) technicians, as well as digitally, with photographs taken on both lateral sides of the south-facing animal. Horn flies were counted in both photographs and combined (CDC) for full body estimates. In addition, the highest photographed side population times two (DDC) was used for comparison. Estimations were made at 0700, 1200, and 1900 h the day following infestation. A time of observation × infestation level interaction (P < 0.01) was detected. On average, VE1 population estimates were greater (P < 0.01) than any other counting method observed. Morning estimates were greater (P < 0.05) than those taken at noon or in the early evening regardless of counting method. Further research regarding the standardization of these techniques to ensure more accurate population estimates is needed before these methods can be incorporated into integrated pest management programs.

Validation of an instrument to assess barriers to care-seeking for accidental bowel leakage in women: the BCABL questionnaire

INTRODUCTION AND HYPOTHESIS

Fewer than 30% of women with accidental bowel leakage (ABL) seek care, despite the existence of effective, minimally invasive therapies. We developed and validated a condition-specific instrument to assess barriers to care-seeking for ABL in women.

METHODS

Adult women with ABL completed an electronic survey about condition severity, patient activation, previous care-seeking, and demographics. The Barriers to Care-seeking for Accidental Bowel Leakage (BCABL) instrument contained 42 potential items completed at baseline and again 2 weeks later. Paired t tests evaluated test-retest reliability. Factor analysis evaluated factor structure and guided item retention. Cronbach's alpha evaluated internal consistency. Within and across factor item means generated a summary BCABL score used to evaluate scale validity with six external criterion measures.

RESULTS

Among 1,677 click-throughs, 736 (44%) entered the survey; 95% of eligible female respondents (427 out of 458) provided complete data. Fifty-three percent of respondents had previously sought care for their ABL; median age was 62 years (range 27-89); mean Vaizey score was 12.8 (SD = 5.0), indicating moderate to severe ABL. Test-retest reliability was excellent for all items. Factor extraction via oblique rotation resulted in the final structure of 16 items in six domains, within which internal consistency was high. All six external criterion measures correlated significantly with BCABL score.

CONCLUSIONS

The BCABL questionnaire, with 16 items mapping to six domains, has excellent criterion validity and test-retest reliability when administered electronically in women with ABL. The BCABL can be used to identify care-seeking barriers for ABL in different populations, inform targeted interventions, and measure their effectiveness.

Barriers to seeking care for accidental bowel leakage: a qualitative study

INTRODUCTION AND HYPOTHESIS

Fewer than 50 % of women with urinary incontinence (UI) and 30 % of women with accidental bowel leakage (ABL) seek care. We sought to describe barriers to care seeking for ABL to inform development of an instrument to measure these barriers.

METHODS

We recruited women with ABL with varied prior care-seeking experiences to participate in focus groups and cognitive interviews so we could understand factors that may have prevented or delayed care seeking. Focus groups continued until thematic saturation was reached using conventional content analysis. Final themes were established and characterized by comparing within and across the focus groups and with previously described UI and ABL care-seeking barriers. Cognitive interviews were confirmatory.

RESULTS

Thirty-nine women (aged 46-85) participated in six focus groups and ten cognitive interviews; 89 % were white, 8 % African American, and 3 % Latina. We identified 12 barriers to seeking care for ABL: (1) Lack of knowledge about the condition; (2) Lack of knowledge about treatment; (3) Fear of testing/treatment; (4) Normative thinking; (5) Avoidance/denial; (6) Life impact; (7) Embarrassment/shame; (8) Self-blame; (9) Stigma; (10) Isolation; (11) Provider barriers; (12) Access limitations. These 12 barriers encompassed three overarching themes: the internalized self in relation to ABL; perceptions about ABL and its treatments; and interaction with the healthcare system.

CONCLUSIONS

ABL care-seeking barriers are similar to those described for UI, with the notable addition of lack of knowledge that ABL is a medical condition experienced by others. Interventions to promote access to effective treatments for ABL should include information about prevalence and treatability.

Adaptation of the Grasha Riechman Student Learning Style Survey and Teaching Style Inventory to assess individual teaching and learning styles in a quality improvement collaborative

BACKGROUND

NIATx200, a quality improvement collaborative, involved 201 substance abuse clinics. Each clinic was randomized to one of four implementation strategies: (a) interest circle calls, (b) learning sessions, (c) coach only or (d) a combination of all three. Each strategy was led by NIATx200 coaches who provided direct coaching or facilitated the interest circle and learning session interventions.

METHODS

Eligibility was limited to NIATx200 coaches (N = 18), and the executive sponsor/change leader of participating clinics (N = 389). Participants were invited to complete a modified Grasha Riechmann Student Learning Style Survey and Teaching Style Inventory. Principal components analysis determined participants' preferred learning and teaching styles.

RESULTS

Responses were received from 17 (94.4 %) of the coaches. Seventy-two individuals were excluded from the initial sample of change leaders and executive sponsors (N = 389). Responses were received from 80 persons (25.2 %) of the contactable individuals. Six learning profiles for the executive sponsors and change leaders were identified: Collaborative/Competitive (N = 28, 36.4 %); Collaborative/Participatory (N = 19, 24.7 %); Collaborative only (N = 17, 22.1 %); Collaborative/Dependent (N = 6, 7.8 %); Independent (N = 3, 5.2 %); and Avoidant/Dependent (N = 3, 3.9 %). NIATx200 coaches relied primarily on one of four coaching profiles: Facilitator (N = 7, 41.2 %), Facilitator/Delegator (N = 6, 35.3 %), Facilitator/Personal Model (N = 3, 17.6 %) and Delegator (N = 1, 5.9 %). Coaches also supported their primary coaching profiles with one of eight different secondary coaching profiles.

CONCLUSIONS

The study is one of the first to assess teaching and learning styles within a QIC. Results indicate that individual learners (change leaders and executive sponsors) and coaches utilize multiple approaches in the teaching and practice-based learning of quality improvement (QI) processes. Identification teaching profiles could be used to tailor the collaborative structure and content delivery. Efforts to accommodate learning styles would facilitate knowledge acquisition enhancing the effectiveness of a QI collaborative to improve organizational processes and outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00934141 Registered July 6, 2009. Retrospectively registered.

Narrative communication in cancer prevention and control: a framework to guide research and application

Narrative forms of communication-including entertainment education, journalism, literature, testimonials, and storytelling-are emerging as important tools for cancer prevention and control. To stimulate critical thinking about the role of narrative in cancer communication and promote a more focused and systematic program of research to understand its effects, we propose a typology of narrative application in cancer control. We assert that narrative has four distinctive capabilities: overcoming resistance, facilitating information processing, providing surrogate social connections, and addressing emotional and existential issues. We further assert that different capabilities are applicable to different outcomes across the cancer control continuum (e.g., prevention, detection, diagnosis, treatment, survivorship). This article describes the empirical evidence and theoretical rationale supporting propositions in the typology, identifies variables likely to moderate narrative effects, raises ethical issues to be addressed when using narrative communication in cancer prevention and control efforts, and discusses potential limitations of using narrative in this way. Future research needs based on these propositions are outlined and encouraged.

Ozonolysis of Mixed Oleic-Acid/Stearic-Acid Particles: Reaction Kinetics and Chemical Morphology

The ozonolysis of mixed oleic-acid/stearic-acid (OL/SA) aerosol particles from 0/100 to 100/0 wt % composition is studied. The magnitude of the divergence of the particle beam inside an aerosol mass spectrometer shows that, in the concentration range 100/0 to 60/40, the mixed OL/SA particles are liquid prior to reaction. Upon ozonolysis, particles having compositions of 75/25 and 60/40 change shape, indicating that they have solidified during reaction. Transmission electron micrographs show that SA(s) forms needles. For particles having compositions of 75/25, 60/40, and greater SA content, the reaction kinetics exhibit an initial fast decay of OL for low O(3) exposure with no further loss of OL at higher O(3) exposures. For compositions from 50/50 to 10/90, the residual OL concentration remains at 28 +/- 2% of its initial value. The initial reactive uptake coefficient for O(3), as determined by OL loss, decreases linearly from 1.25 (+/-0.2) x 10(-3) to 0.60 (+/-0.15) x 10(-3) for composition changes of 100/0 to 60/40. At 50/50 composition, the uptake coefficient drops abruptly to 0.15 (+/-0.1) x 10(-3), and there are no further changes with increased SA content. These observations can be explained with a combination of three postulates: (1) Unreacted mixed particles remain as supersaturated liquids up to 60/40 composition, and the OL in this form rapidly reacts with O(3). (2) SA, as it solidifies, locks into its crystal structure a significant amount of OL, and this OL is completely inaccessible to O(3). (3) Accompanying crystallization, some stearic acid molecules connect as a filamentous network to form a semipermeable gel containing liquid OL but with a reduced uptake coefficient because of the decrease in molecular diffusivity in the gel. An individual particle of 50/50 to 90/10 is hypothesized as a combination of SA crystals having OL impurities (postulate 2) that are partially enveloped by an SA/OL gel (postulate 3) to explain (a) the abrupt drop in the uptake coefficient from 60/40 to 50/50 and (b) the residual OL content even after high ozone exposure. The results of this study, pointing out the important effects of particle phase, composition, and morphology on chemical reactivity, contribute to an improved understanding of the aging processes of atmospheric aerosol particles.

Inhibition of hypothalamic GnRH secretion in the ewe by antigonadotropic decapeptide during the estrous cycle and nonbreeding season

Previous experiments from our laboratory and others have shown that the peptide antigonadotropic decapeptide (AGD) has marked inhibitory effects on luteinizing hormone (LH) secretion in rats and ewes. The first objective of this study was to determine whether AGD inhibits LH secretion by regulating hypothalamic release of gonadotropin hormone (GnRH). AGD (200 microg in 200 microL of 0.3% bovine serum albumin [BSA] saline) or vehicle was infused into the lateral ventricle of ovariectomized (OVX) ewes with hypophyseal-portal cannulae, and GnRH secretion was monitored. The frequency of GnRH and LH pulses in AGD-treated ewes was significantly decreased (p < 0.05) but did not change in the control ewes. The second objective of this investigation was to evaluate changes in hypothalamic sensitivity to AGD in the ewe during the estrous cycle and nonbreeding season. During the estrous cycle, the effects of AGD on LH secretion were assessed following ovariectomy, during the metestrous, diestrous, and proestrous phases of the estrous cycle. The response to AGD during the estrous cycle was compared to its effect during the anestrous season. LH, cortisol, and prolactin (PRL) concentrations were assayed in peripheral blood samples obtained at 10-min intervals over a 6-h period prior to injection of either vehicle (200 microL of 0.3% BSA in 0.9% saline) or AGD (200 microg in 200 microL of vehicle), and for an additional 10 h following treatment. LH pulse frequency decreased after treatment with AGD (p < 0.05) at all times in OVX and intact ewes compared to vehicle-treated controls. During the anestrous season, AGD treatment was more effective in inhibiting LH pulse frequency than during the breeding season (p < 0.05). Furthermore, there was a significant increase (p < 0.05) in mean cortisol concentrations after AGD infusion in all AGD-treated groups compared to controls independent of season or reproductive status. PRL concentrations were also increased (p < 0.05) following treatment with AGD. These results suggest that inhibition of pulsatile LH release induced by AGD is modulated by alterations in frequency of hypothalamic discharges of GnRH. Furthermore, changes in the inhibitory actions of AGD may contribute to the seasonal regulation of hypothalamic GnRH secretion in the ewe.

Ovine prostaglandin F2alpha receptor: steroid influence on steady-state levels of luteal mRNA

Expression of the receptor for prostaglandin F2alpha (PGF2alpha) is decreased in the ovine corpus luteum during regression and increased in early pregnancy. This study was designed to evaluate the influence of progesterone and/or 17beta-estradiol (E2) on this regulation. Circulating progesterone (functional regression) and luteal PGF receptor mRNA decreased (p < 0.05) within 8 h of PGF2alpha-induced luteal regression in midluteal phase (day 10; d 10) ewes; however, internucleosomal DNA fragmentation (structural regression) was not yet increased. Additionally, luteal PGF receptor mRNA and circulating progesterone were greater (p < 0.05) in pregnant than in nonpregnant ewes on d 14, but not on d 12. Twelve hours following injection of d 10 ewes with E2, steady-state levels of mRNA for PGF receptor were decreased (p < 0.05), although circulating progesterone and DNA laddering were unchanged. Conversely, luteal mRNA for PGF receptor was increased (p < 0.05) by E2 treatment in hysterectomized ewes. These results provide evidence that (1) luteal PGF receptor expression parallels circulating progesterone levels during functional regression and in early pregnancy, but (2) expression of PGF receptor can be dissociated from alterations in circulating progesterone by injection with E2. Additionally, decreased PGF receptor expression initiated by E2 is uterine-dependent, whereas the direct luteal effect (hysterectomized ewes) of E2 is a stimulation of PGF receptor expression. These results collectively support the belief that the apparent downregulation of PGF receptor during luteal regression is associated with uterine-derived PGF2alpha and its intracellular effects rather than with alterations in ovarian steroid production.

Direct effects of luteal regression on anterior pituitary response to GNRH

The preovulatory period of the ewe is marked by a dramatic decrease in concentrations of progesterone in serum during the late luteal phase, followed by elevated luteinizing hormone (LH) secretion, final follicular maturation and ovulation. This experiment was designed to ascertain the extent to which removal of endogenous progesterone negative feedback at the anterior pituitary gland, independent of effects at the hypothalamus, promotes increased secretion of LH in the hours immediately after induction of luteolysis. Estrus was synchronized in ovary-intact ewes with two injections of prostaglandin F2 alpha (PGF2 alpha) analog given 10 d apart (Day 0 = second day after the second PGF2 alpha injection). Ewes were subjected to hypothalamic-pituitary disconnection (HPD; n = 6) on Day 3 and were pulsed with gonadotropin-releasing hormone (GnRH). Ewes were used during the estrous cycle or received approximately 400 IU pregnant mare serum gonadotropin (PMSG) on Day 2 to stimulate ovulation; there was no difference (P < 0.10) in ovulation rate or progesterone production between these two groups. Luteal regression was induced by injection of PGF2 alpha analog on approximately Day 10 of the estrous cycle. Blood samples were collected around exogenous GnRH pulses before and at 2- or 4-hr intervals after PGF2 alpha administration and concentrations of LH and progesterone determined. At 4, 12, and 24 hr after PGF2 alpha administration, mean serum progesterone levels in all ewes had decreased by 54.7%, 66.2% and 89.4%, respectively (P < 0.05) from pre-injection levels. The decrease in progesterone was associated with an increase (P < 0.01) in LH pulse amplitude with means at 4-hr post-PGF2 alpha ranging from 190% to 288% of pre PGF2 alpha values. Mean serum LH levels were also increased (P < 0.01) within 4 hr of PGF2 alpha administration and remained elevated at all but the 24-hr time point. The timing of this increase (within 4 hr) indicates that it is independent of changes in serum estradiol concentrations, which do not increase for at least 16 hr after induction of luteolysis. Thus, removal of endogenous progesterone negative feedback at the anterior pituitary gland in the hours immediately after induction of luteolysis seems to play a role in facilitating LH release independently of hypothalamic action.

Estradiol and gonadotropin-releasing hormone (GnRH) interact to increase GnRH receptor expression in ovariectomized ewes after hypothalamic-pituitary disconnection

Gonadotropin-releasing hormone (GnRH) receptor expression is regulated by estradiol and GnRH itself. The objective of this experiment was to determine the extent to which low levels of estradiol, similar to those observed during the transition from the luteal to the follicular phase of the estrous cycle, and GnRH interact to regulate expression of GnRH receptors and GnRH receptor mRNA. Ewes were ovariectomized (OVX) at least 2 wk prior to initiation of the experiment, and the pituitary gland was surgically disconnected from the hypothalamus to remove ovarian and hypothalamic inputs to the pituitary. Within 24 h after hypothalamic-pituitary disconnection, ewes received pulses of GnRH (250 ng/pulse) every 2 h for 6 d. At the end of 6 d, ewes were randomly assigned to treatments in a 2 x 2 factorial arrangement as follows: half of the animals received a single estradiol implant and half received an empty implant (placebo). At the same time, animals also received one of the following treatments: (1) saline or (2) GnRH (100 ng/pulse/2 h). Additionally, one group of ewes was ovariectomized, but not subjected to hypothalamic-pituitary disconnection (OVX controls). Blood samples were collected 15 min prior to each pulse of GnRH or saline and at 15-min intervals for 1 h after each pulse until tissues were collected and concentrations of luteinizing hormone (LH) were determined. Anterior pituitaries were collected 24 h after implant insertion to quantitate steady-state amounts of GnRH receptor mRNA and numbers of GnRH receptors. Mean LH was greatest in ovariectomized control ewes compared to all other treatments (p < 0.05). Mean LH and LH pulse amplitude in the placebo and GnRH-treated group most closely mimicked LH secretion in ovariectomized control animals. Mean LH and LH pulse amplitude were similar between both GnRH-treated groups (p < 0.05). Mean LH and LH pulse amplitude were significantly lower in all animals treated with saline compared to OVX controls (p < 0.05). Treatment with an estradiol implant and pulsatile GnRH increased (p < 0.05) relative amounts of GnRH receptor mRNA and the number of GnRH receptors compared to all other treatments. There were no differences in GnRH receptor expression between the remaining treatment groups (p > 0.05). Therefore, in OVX ewes after hypothalamic-pituitary disconnection, low levels of estradiol and GnRH are required to increase GnRH receptor mRNA and GnRH receptor numbers. Since we only observed an increase in GnRH receptor expression in the presence of both estradiol and GnRH, we conclude that there is a synergistic interaction between these two hormones in the regulation of GnRH receptor expression.

Regulation of amounts of mRNA for GnRH receptors by estradiol and progesterone in sheep

Expression of GnRH receptors increases prior to the onset of the preovulatory surge of LH in sheep. Two experiments were conducted to investigate the interactions of progesterone (P) and estradiol (E) on amounts of mRNA for GnRH receptors and the number of receptors for GnRH. The first study was designed as a 2 x 2 factorial arrangement of treatments to investigate effects of removal of P and the presence of E. Ewes that had been ovariectomized (OVX) for at least 4 wk received one silastic implant containing E and two silastic implants containing P for 6 d to mimic concentrations of these steroids during the luteal phase of the estrous cycle. Anterior pituitary glands were collected (n = 4 animals/group): 1. Prior to implant removal and 12 h after removal of: 2. P only. 3. E only. 4. P and E. Regardless of whether or not E was present, amounts of mRNA for GnRH receptors (P = 0.87) and number of GnRH receptors (P = 0.43) were not different within 12 h after removal of P. In the second experiment, ewes were OVX on d10-12 of the estrous cycle (d0 = estrus), and immediately received silastic implants containing E and P as described above. Anterior pituitary glands were collected on d12 of the estrous cycle (n = 5), prior to implant removal (n = 5), and from the remaining ewes 24 h after removal of P only (n = 7) or removal of P and E (n = 6). Relative amounts of mRNA for GnRH receptors and the number of GnRH receptors were similar (P > 0.05) on d12 of the estrous cycle and prior to implant removal. Removal of both P and E did not affect (P > 0.05) amounts of GnRH receptor mRNA or number of GnRH receptors. However, the removal of P and the presence of E increased (P < 0.05) amounts of mRNA for GnRH receptors, but did not affect (P > 0.05) the number of GnRH receptors. We conclude that increased amounts of GnRH receptor mRNA require the removal of P and the presence of E.

The estradiol-induced luteinizing hormone surge in the ewe is not associated with increased gonadotropin-releasing hormone messenger ribonucleic acid levels

This experiment was undertaken to determine whether the estrogen-induced LH and GnRH surge in the ewe is associated with activation of a specific subpopulation of neurons in the mid-brain of the ewe as indicated by a change in GnRH mRNA levels. Fifteen ovariectomized ewes were assigned to treatment groups 3-4 wk after ovariectomy. One group of ewes served as controls (n = 2); 50 microg estradiol-17beta (E2) was administered to the remaining ewes. Blood samples were collected from all ewes before treatment (2-h period at 10-min intervals) and continued at 30-min intervals until tissue was collected. At 6, 12, 18, and 24 h after E2 (n = 3 for each time point), brains were collected and processed for localization and measurement of GnRH mRNA by in situ hybridization histochemistry. Serum was analyzed for LH concentrations. Serum LH was pulsatile in controls and decreased at 6 h after E2, and by 12 h the LH surge was initiated. LH levels peaked at 18 h after E2 and returned to basal levels 24 h after E2 treatment. A cRNA probe corresponding to the GnRH-associated peptide region of ovine GnRH prepropeptide mRNA was used to identify GnRH mRNA. Associated with the onset and peak of the LH surge were decreased levels (p < 0.1) of GnRH mRNA in neurons of the preoptic area (POA). Neither the number nor mRNA content of GnRH neurons in the diagonal band of Broca, septal area, or medial basal hypothalamus (MBH) changed during the LH surge. In contrast to E2-induced increases in GnRH secretion during the LH surge, our data indicate that E2 decreases steady-state amounts of GnRH mRNA and that GnRH neurons in the POA are influenced to the greatest extent during the E2-induced GnRH surge.

Chronic lateral ventricle infusion of a pineal gland-derived decapeptide alters pulsatile secretion of LH in rats

The object of this investigation was to determine whether chronic lateral ventricle infusion of a pineal gland-derived antigonadotropic decapeptide (AGD) would affect pulsatile luteinizing hormone (LH) release in conscious, unrestrained male rats. Adult male Harlan SD rats were bilaterally orchiectomized and maintained under conditions of controlled photoperiods and temperature. After three (Experiment one) or four (Experiment two) weeks each was fitted stereotaxically with a stainless steel cannula for infusion into the right lateral ventricle. Each cannula was attached to a subcutaneous osmotic minipump filled either with artificial cerebrospinal fluid (CSF) or AGD in CSF (0.5 microgram/microliter). CSF (1.0 microliter/hr) or the AGD (0.5 microgram/microliter hr) was infused over a period of four days. Blood samples for determined of LH by radioimmunoassay were obtained at five minute intervals from a Tygon microbore cannula inserted via a femoral artery into the abdominal aorta. LH pulses were defined and identified with a computerized deconvolution algorithm designed to determine spontaneous LH secretory events. Although mean LH levels were not significantly reduced, LH secretory pulse frequency and nadirs were significantly decreased by ADG infusion (p<0.01). Additionally, LH secretory pulse amplitude and LH secretory response to LHRL administration were significantly increased (p<0.01) by AGD treatment. These results confirm initial reports of depressive effects of the AGD on LH secretion and support its hypothesized central site of action.

Estradiol up-regulation of pituitary progesterone binding is required for progesterone inhibition of luteinizing hormone release

This study examines the regulation of progesterone receptor (PR) in the inhibition of pituitary luteinizing hormone (LH) secretion. Ovariectomized ewes underwent hypothalamic-pituitary disconnection, were pulsed with gonadotropin-releasing hormone (GnRH) and received 1 of 4 treatments: estradiol alone (E), estradiol priming before progesterone (E+P), E removed and replaced with P (E-P), or no steroids (C). P treatment for 24 h, with E or following E-priming, reduced LH pulse amplitude by 55% (p<0.05). E alone did not affect LH release. E increased pituitary cytosolic P binding capacity fourfold over controls (p<0.01) and P further increased binding to eight times controls (p<0.01). Pituitary PR mRNA increased to 149 and 171% of C in E and E+P groups, respectively (p<0.05), but E removal resulted in PR mRNA levels not different from controls. Pituitary receptors for GnRH were tripled by E alone compared to C (p<0.01), whereas P alone or with E had no effect. These data suggest an E-induced, direct pituitary inhibition of LH secretion by P and that this effect of P is associated with E-enhanced binding of P in the pituitary. Additionally, the direct pituitary effects of P on LH secretion cannot be accounted for by influences on GnRH receptor numbers.

Serum progesterone and luteinizing hormone in ewes treated with PGF 2 alpha during mid-gestation and gonadotropin releasing hormone after parturition

Two studies were conducted to determine if postpartum (PP) reproductive function could be enhanced in ewes by PGF2 alpha during mid-gestation (Trial 1) and GnRH within 10 days PP (Trial 2). Trial 1 utilized 31 ewes (mean body weight = 84 kg) assigned to two treatment groups to receive (I.M.) either saline (control, n = 17) or PGF2 alpha (0.14 mg/kg body weight, n = 14) on day 74 of gestation. Results from the first study indicated success in regressing the corpus luteum (CL) of pregnancy as indicated by decreased serum progesterone (P4, P < 0.05) by 24 hours after treatment. In addition, by 20 days after treatment, serum luteinizing hormone (LH) concentrations in treated ewes were higher (P < 0.01) than in controls. However, ovarian activity was not re-established by 30 days PP in this study. In Trial 2, 35 ewes (mean body weight = 79 kg) were randomly assigned to one of four groups: no treatment (controls, n = 9), PGF2 alpha (no GnRH, n = 9), GnRH (no PGF2 alpha n = 9) or both PGF2 alpha and GnRH (n = 9). The PGF2 alpha-treated animals received 0.14 mg PGF2 alpha/kg body weight (I.M.) on day 73 of gestation and GnRH-treated ewes received 50 micrograms GnRH (I.M.) on days 2, 6, and 10 PP. As in Trial 1, P4 concentrations in PGF2 alpha-treated ewes were lower (P < 0.02) than in control ewes by 24 hours after treatment. Progesterone remained lower in PGF2 alpha-treated animals through day 116 of gestation. However, no differences were detected (P > 0.65) in LH concentrations between the two groups in this same period. Likewise, no differences were observed (P > 0.32) in LH concentrations between the PGF2 alpha-treated and control ewes on days 2, 6, and 10 PP. However, elevated (P < 0.07) LH concentrations were noted in ewes receiving 50 micrograms GnRH compared with ewes not receiving GnRH. In addition, area under the LH curve (AUC) was greater (P < 0.01) for GnRH-treated animals on days 2, 6, and 10 PP and LH AUC increased over the PP period in GnRH-treated ewes. Three of eight ewes receiving both PGF2 alpha and GnRH treatments had ovarian activity within 30 days PP as indicated by P4 concentrations above 1 ng/ml while no other ewes had ovarian activity during this time period.

Age-related changes in biogenic amines, opiate, and steroid receptors in the prepubertal bull calf

Events leading to the increase in pulsatile LH secretion during prepubertal development in the bull calf may include removal of inhibitory or the development of stimulatory mechanisms affecting the hypothalamic release of GnRH. To examine possible contributing systems, serial blood samples were collected from Holstein bull calves at 2, 5, and 10 wk of age one day prior to receiving either no treatment (controls) or two injections of alpha-methyl-p-tyrosine (alpha-MPT), an inhibitor of catecholamine synthesis. Blood was sampled every 10 min for 5 h and serum was analyzed for LH by RIA. Following treatment, animals were killed and hypothalamic and pituitary tissues were removed for analysis of total opiate receptors, mu-opiate receptors, estrogen and androgen receptors and concentrations of monoamines: dopamine, the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DO-PAC), norepinephrine, serotonin, and its metabolite 5-hydroxyindole-3-acetic acid (5-HIAA). Pulses of LH increased from non-detectable at 2 wk to nearly 1.5 pulses per sampling period at 10 wk. Pulse height rose to 0.95 +/- 0.16 ng/ml at 10 wk. Total opiate receptor number as determined by binding to naloxone was unchanged in all tissues between 2 and 10 wk. In contrast, mu-opiate receptors (DAGO binding) increased 2-fold in the preoptic-anterior hypothalamic area between 5 and 10 wk. No age-related changes in estrogen receptor concentrations were observed in any tissue except the anterior pituitary in which binding increased 3.2-fold between 2 and 10 wk. A similar increase was not noted for androgen receptors in the pituitary; however, testosterone binding in the preoptic-anterior hypothalamic area was 4.6-fold higher at 5 wk compared to levels at 2 and 10 wk.(ABSTRACT TRUNCATED AT 250 WORDS)

Progesterone directly inhibits pituitary luteinizing hormone secretion in an estradiol-dependent manner

We recently demonstrated that progesterone and estradiol inhibit pituitary LH secretion in a synergistic fashion. This study examines the direct feedback of progesterone on the estradiol-primed pituitary. Nine ovariectomized (OVX) ewes underwent hypothalamic-pituitary disconnection (HPD) and were infused with 400 ng GnRH every 2 h throughout the experiment. After 7 days of infusion, estradiol was implanted s.c. Four days later, estradiol implants were exchanged for blank implants in 4 ewes and for progesterone implants in 5 ewes. These implants remained in place for another 4 days. Blood samples were collected around exogenous GnRH pulses before and 0.5 to 96 h after implant insertion and exchange. Serum LH and progesterone concentrations were determined through RIA. One month later, 4 of the HPD-OVX ewes previously implanted with steroids were reinfused with GnRH and the implantation protocol was repeated using blank implants only. In estradiol-primed ewes, progesterone significantly lowered LH secretion after 12 h of implantation and LH secretion remained inhibited while progesterone implants were in place (p less than 0.05). Removing estradiol transiently lowered LH secretion, and this effect was significant only 24 h after estradiol withdrawal (p less than 0.05). These data suggest that progesterone has a direct, estradiol-dependent inhibitory effect on pituitary LH release and that estradiol may sustain pituitary gonadotrope response to GnRH.

Pineal melatonin inhibition of tumor promotion in the N-nitroso-N-methylurea model of mammary carcinogenesis: potential involvement of antiestrogenic mechanisms in vivo

The N-methyl-N-nitrosourea (NMU) model of hormone-responsive rat mammary carcinogenesis was used to address the hypothesis that melatonin (Mel), the principle hormone of the pineal gland, inhibits tumorigenesis by acting as an anti-promoting rather than an anti-initiating agent. Daily late-afternoon injections of Mel (500 micrograms/day), restricted to the initiation phase of NMU mammary tumorigenesis, were ineffective in altering tumor growth over a 20-week period. When Mel treatment was delayed for 4 weeks after NMU and then continued through the remainder of the promotion phase, only tumor number was significantly lower than in controls. However, when Mel injections encompassed the entire promotion phase, both tumor incidence and number were significantly lower than in the controls. Although elimination of the endogenous Mel signal via pinealectomy promoted tumor growth, the effect was not statistically significant. Serum levels of estradiol and tumor estrogen receptor content were unaltered by either Mel or pinealectomy. While Mel treatment failed to affect circulating prolactin levels, pinealectomy caused a two-fold increase in serum prolactin. The estradiol-stimulated recrudescence of tumors following ovariectomy was completely blocked by either 20, 100 or 500 micrograms Mel/day or tamoxifen (20 micrograms/day). Thus, Mel appears to be an anti-promoting hormone that may antagonize the tumor-promoting actions of estradiol in this model of mammary tumorigenesis.

Direct pituitary effects of estradiol and progesterone on luteinizing hormone release, stores, and subunit messenger ribonucleic acids

To determine the direct, chronic actions of progesterone (P4) and estrogen (estradiol, E2) on anterior pituitary synthesis and release of LH, 24 western range ewes underwent hypothalamic-pituitary disconnection (HPD) and ovariectomy (OVX) during the breeding season and were pulsed with exogenous GnRH with or without steroid replacement. Sequential blood samples were collected before infusion of GnRH and on Days 7 and 14 of GnRH infusion. Silastic capsules of P4 and/or E2 were implanted s.c. on Day 7 and remained in place throughout the experiment. Control ewes received only GnRH infusion. Blood sampling was centered around three exogenous GnRH pulses. After the final blood sampling, pituitaries were collected and stored at -70 degrees C. Concentrations of LH in serum and pituitaries were determined by RIA. Relative concentrations of LH subunit mRNAs were determined by Fast Blot analysis. Simultaneous implantation of P4 and E2 lowered LH pulse amplitude 70% and mean serum levels 30% compared with controls. Neither steroid alone affected LH release. E2 alone or in combination with P4 lowered LH-beta subunit mRNA concentrations 40% compared with controls while alpha-subunit levels were unchanged. Only E2 alone altered the pituitary content of LH, causing a 60% decrease. We conclude that the combination of P4 and E2 is necessary for inhibition of GnRH-stimulated LH secretion. E2 inhibits GnRH-stimulated LH-beta subunit mRNA concentrations but does not affect alpha-subunit mRNA concentrations. The control of pituitary LH content by P4 and E2 is the result of changes in both LH-beta subunit mRNA concentrations and LH secretion.

Advancement of postnatal pulsatile luteinizing hormone secretion in the bull calf by pulsatile administration of gonadotropin-releasing hormone during infantile development

The transition from infantile to prepubertal development in bull calves coincides with the onset of postnatal LH secretion following differentiation of pituitary gonadotropes. Increased pulsatile secretion of hypothalamic GnRH may contribute to maturational development of the hypothalamic-pituitary axis. To evaluate the role of GnRH pulse frequency in mediating changes in pituitary response that may lead to altered LH release, serum LH concentrations in Holstein bull calves treated with exogenous GnRH were examined. Nine calves received 200 ng GnRH for 5 min every hour from 1-6 wk of age (GnRH-T), while 5 animals served as controls. Weekly through 6 wk of age, jugular venous blood was collected every 10 min for 8 h. Blood samples from GnRH-T animals were taken during 2 exogenous GnRH pulses followed by 6 h of sampling without exogenous GnRH. Mean serum LH concentrations were greater (p less than or equal to 0.01) in GnRH-T calves than in controls at 2 through 6 wk of age. LH pulse height did not change in either group during the study period. However, LH pulse frequency in GnRH-T calves increased with age (P less than or equal to 0.01), and at 4-6 wk of age, the rate of pulsatile LH secretion was greater (p less than or equal to 0.01) in GnRH-T calves than in controls. Pituitary LH content increased 2.4-fold after GnRH infusion (p less than or equal to 0.01); this increase was associated with a doubling of the pituitary LH-beta mRNA concentration found in controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin F2 alpha-induced calcium transient in ovine large luteal cells: I. Alterations in cytosolic-free calcium levels and calcium flux

The effect of prostaglandin F2 alpha (PGF2 alpha) on cytosolic calcium homeostasis was studied in suspensions of ovine large or small luteal cells from superovulated ewes. In large cells loaded with fura-2 (AM), resting cytosolic-free calcium ([Ca2+]i) was 62 +/- 5 nM (Hanks' medium, pH 7.15), and PGF2 alpha (0.5 microM) induced a rapid transient increase in [Ca2+]i to 152 +/- 6 nM, which then decreased to 97 +/- 6 nM within 3 min and remained at this level for the remainder of the treatment period (10-20 min). PGF2 alpha did not alter intracellular pH (pHi) in cells loaded with snarf-1 (AM) (pHi indicator). The transient nature of the [Ca2+]i increase was due, at least in part, to the ability of PGF2 alpha to stimulate (P less than 0.05) 45Ca2+ efflux. In small cells, resting [Ca2+]i was 57 +/- 5 nM, and no change in [Ca2+]i levels or pHi occurred with the addition of PGF2 alpha. PGF2 alpha also did not affect 45Ca2+ efflux in small cells. Calcium uptake was not significantly altered by PGF2 alpha in large or small cells. Data from kinetic analysis of the calcium transient was best fit to a two-compartment model consisting of a rapidly effluxing compartment and a slowly effluxing compartment. The size and rate constants were 62 +/- 10 nM and 3.6 +/- 1 min-1, respectively, for the rapidly effluxing compartment and 140 +/- 9 nM and 0.02 +/- 0.002 min-1, respectively, for the slowly effluxing compartment. These results provide evidence for a direct effect of PGF2 alpha specifically on the ovine large luteal cell that involves alterations in [Ca2+]i and calcium flux. This effect is likely to be involved in intracellular mediation of the signal for luteal regression.

Gonadotropin-releasing hormone secretion during the postpartum anestrous period of the ewe

An increase in episodic release of LH is putatively the initial event leading to the onset of postpartum ovarian cyclicity in ewes. This experiment was conducted to determine the relationship between hypothalamic release of GnRH and onset of pulsatile secretion of LH during postpartum anestrus. Control ewes (n = 7) were monitored during the postpartum period to determine when normal estrous cycles resumed. In controls, the mean interval from parturition to the first postpartum estrus as indicated by a rise in serum progesterone greater than 1 ng/mg was 25.8 +/- 0.6 days. Additional ewes (n = 4-5) at 3, 7, 14, and 21 days postpartum (+/- 1 day) were surgically fitted with cannula for collection of hypophyseal-portal blood. Hypophyseal-portal and jugular blood samples were collected over a 6- to 7-h period at 10-min intervals. The number of GnRH pulses/6 h increased (p less than 0.05) from Day 3 postpartum (2.2 +/- 0.5) to Days 7 and 14 (3.6 +/- 0.2 and 3.9 +/- 0.4, respectively). A further increase (p less than 0.05) in GnRH pulse frequency was observed at Day 21 postpartum (6.4 +/- 0.4 pulses/6 h). Changes in pulsatile LH release paralleled changes observed in pulsatile GnRH release over Days 3, 7, 14, and 21 postpartum (0.83 +/- 0.3, 2.8 +/- 0.4, 2.9 +/- 0.6, and 4.0 +/- 1.1 pulses/6 h, respectively). GnRH pulse amplitude was higher at Day 21 than at Days 3, 7, or 14 postpartum. These findings suggest that an increase in the frequency of GnRH release promotes the onset of pulsatile LH release during postpartum anestrus in ewes.

Two exceptional sets of physiological clearance curves and their mathematical form: test cases?

Amiodarone concentrations y(t) have been measured from 1 min to more than 50 days following 10 min of infusion, with about 40 observations on each of six normal subjects (Tucker et al., 1984, Eur. J. clin. Pharmacol. 26, 655-656). The form of the log-log plots-ln(y) vs ln(t)--is investigated. These appear to show three phases. First there is a rapid decrease of y(t), then a straight line corresponding to a small negative power of t, ca -0.3, and this line changes continuously but quickly at about 0.5 day into a steeper line that is almost straight. For the curve fitting a simple "spline-type" device was successful. Two continuity conditions were imposed at the time of changeover, which was one of the unknown parameters. The results are compared in detail with those from a set of 15 radiocalcium curves obtained during 2 weeks or more from a single injection of 47Ca (Neer et al., 1967, J. clin. Invest. 46, 1364-1379). Again two power functions of time can be seen. The changeover is much more gradual than with amiodarone, and the fits are still better. Both sets of curves are fitted with fewer adjustable parameters than with the usual multiexponentials that are interpreted in terms of homogeneous compartments. Theoretical and practical implications are mentioned. There is much indirect evidence that hundreds of other clearance curves may consist largely of one or two of such power functions of time.

Ontogeny of pulsatile secretion of gonadotropin-releasing hormone in the bull calf during infantile and pubertal development

During the infantile period of development in the bull calf (birth to 6 weeks of age), there is a virtual absence of episodic secretion of LH. Transition from infancy to the prepubertal period (6-10 weeks of age) is characterized by the onset of episodic LH release. This study was conducted to characterize the ontogeny of episodic GnRH release during these developmental periods. During the primary experiment, calves at 2, 5, 8, and 12 weeks of age (n = 4/age) were surgically fitted with cannulae for the collection of mixed hypophyseal portal and cavernous sinus blood. Hypophyseal portal and cavernous sinus and jugular blood samples were collected over a 9- to 12-h period at 10 min intervals. No pulses of LH were observed in calves at 2 or 5 weeks of age. At 8 and 12 weeks of age, pulsatile LH release became evident with a mean of 1.0 +/- 0.3 and 2.20 +/- 0.7 pulses/10 h, respectively. Unlike LH secretion, calves at both 2 and 5 weeks of age released GnRH in a pulsatile manner (3.5 +/- 0.2 and 5.0 +/- 0.6 pulses/10 h, respectively). The frequency of pulsatile GnRH release increased from 7.9 +/- 0.4 pulses/10 h at 8 weeks of age to 8.9 +/- 0.7 pulses/10 h at 12 weeks of age. These findings demonstrate the presence of pulsatile secretion of GnRH during the infantile period of development. Furthermore, the postnatal ontogeny of pulsatile LH release in this species is associated with an increase in the frequency of pulsatile GnRH secretion.

In-vitro and in-vivo responsiveness of the corpus luteum of the mare to gonadotrophin stimulation

Dispersed horse luteal cells were used to evaluate the ability of horse LH, hCG and PMSG to stimulate progesterone secretion in vitro. Morphological characterization of these cells before gonadotrophin stimulation indicated the presence of two populations of cells based on cell diameters. In luteal cells incubated as suspended cells, horse LH and hCG stimulated (P less than or equal to 0.05) progesterone production at all levels of treatment. Stimulation of progesterone secretion by hCG was greater (P less than or equal to 0.05) than by horse LH over the range of concentrations utilized. When mares (N = 7) received an intramuscular injection of 1000 i.u. hCG on Days 3, 4 and 5 after the end of oestrus, there was an increase (P less than or equal to 0.05), in peripheral progesterone concentrations beginning on Day 7 and continuing until Day 14 compared with controls (N = 7). Peripheral progesterone concentrations continued to be elevated in hCG-treated mares for Days 15-30 after oestrus in those mares that conceived. Although treatment with hCG increased progesterone concentrations, it had no influence on anterior pituitary release of LH as measured by frequency and amplitude of LH discharge. We conclude that the mare corpus luteum is responsive to gonadotrophins in vitro and that exogenous hCG can enhance serum progesterone concentrations throughout the oestrous cycle and early pregnancy.

Hormonal alterations in the lactating dairy cow in response to thermal stress

The influence of acute exposure to thermal stress on the secretion of progesterone, estradiol, cortisol, and LH was monitored in 14 lactating Holstein cows. Eight cows were maintained throughout the summer in a refrigerated air-conditioned tie stall barn. An additional eight cows were maintained in outdoor corrals with access only to shade. Rectal temperatures and respiration rates of cows under heat stress conditions were elevated above the cows maintained under air conditioning. Cows in both environments exhibited similar serum concentrations of progesterone and estradiol throughout the estrous cycle. Serum cortisol concentrations were higher in heat-stressed cows compared to cows maintained under cooling. The number of LH pulses on d 5 of the estrous cycle was greatly reduced in the heat-stressed cows compared to the cows under cooling. No differences in the number of pulses of LH were observed on d 12 of the estrous cycle between cows in the two environments. Data suggest that heat stress can suppress anterior pituitary release of LH without having a measurable influence on ovarian steroid hormone secretion.

Fertility and hormonal responses to temporary relief of heat stress in lactating dairy cows

The influence of temporary cooling on pregnancy rate and ovarian secretion of cortisol, estradiol and progesterone in Holstein cows was evaluated during the months of June to September. Cows were randomly assigned to one of five treatment groups: 1) evaporative cooling, 8 d; 2) evaporative cooling, 16 d; 3) refrigerated air conditioning, 8 d; 4) refrigerated air conditioning, 16 d and 5) controls maintained outdoors with access to shade. Estrus was synchronized by giving two injections of prostaglandin (25 mg). Cows in the cooled groups were placed in box stalls at the time of the second prostaglandin injection, allowing them to be cooled for approximately 3 d prior to breeding. Blood samples were taken on days 0, 5, 10, 15, 20 and 25 postbreeding and serum was analyzed for estradiol, cortisol, progesterone and a pregnancy-specific protein. Pregnancy rates as determined by palpation per rectum at 40 to 60 d post breeding were not different between cows in cooled treatments, regardless of duration or type of cooling. Pregnancy rate was higher (P<0.05) in cooled as compared to control cows. Serum progesterone concentrations were higher on Day 15 in cooled cows as compared to control cows. No differences in serum estradiol or cortisol concentrations were observed between cooled and control cows. Pregnancy-specific protein determinations indicated that 50% of both cooled and control cows conceived. Results indicate that temporary cooling increased pregnancy rates by increasing embryonic survival rates.

Gonadal regulation of LH secretion in prepubertal bull calves

In the present study we examined the influence of castration and exogenous estradiol on pulsatile LH release during the transition from infancy to the prepubertal period of development. Bull calves were assigned to treatments (N = 5 treatment) at 6 weeks of age. Treatments consisted of intact controls, castrates and castrates receiving estradiol implants. Plasma LH response was monitored over 8 hr periods at 7, 8, 9, 10, 11 and 13 weeks of age. Castration alone did not alter LH concentrations, compared to controls until 10 weeks of age. At 10, 11 and 13 weeks, mean LH concentration and the number of LH pulses/8 hr period were greater (P less than .05) in castrates than in controls. In castrates with estradiol implants, mean LH concentration and the number of LH pulses/8 hr period were suppressed at all ages compared to controls and castrate treatments. These results indicate that LH release is not inhibited by gonadal factors from 6 to 9 weeks of age in the bull calf. However, estradiol negative feedback on LH secretion is evident during this same developmental period.

Random walk type models for indicator-dilution studies: comparison of a local density random walk and a first passage times distribution

The relative merits of the local density random walk and the first passage times distributions were compared with respect to their practical applicability in cardiovascular research and clinical practice. Open indicator-dilution curves of varying shape were used, and reference values for area and mean transit times were calculated numerically. Curves not perturbed by recirculation were obtained in two different ways. Thermodilution curves were obtained in an animal model at the left and the right side of the heart respectively and conductivity curves with 0.5% NaCl solution as indicator were obtained in a hydrodynamic circulation model. The fits of the two types of distribution were equally accurate for the more symmetrical curves; for very skewed curves the local density random walk fit proved to be more accurate. This result could be related to the greater difference in shape between the first passage times and local density random walk distribution for a large degree of asymmetry. For this reason the local density random walk distribution for fitting indicator-dilution curves was used in a variety of other experimental conditions.

Changing relationships between stature and lung volumes during puberty

In a follow-up study the relationship between growth in body dimensions and in lung volumes during the adolescent growth spurt was studied in 149 girls and 477 boys, aged 11.5-14.0 years at the start of the study. Total lung capacity (TLC), residual volume, vital capacity (VC) and series dead space were measured twice a year for 6 years. When analyzed cross-sectionally lung volumes can be described by a power function of stature, both for each set of half-yearly measurements and when all data are pooled. The powers were close to 3, increasing at each time of measurement in boys and decreasing in girls. These trends reflect that in each subject the growth spurt does not start at the same age, and that individual growth occurs non-linearly along a steeper line than found in the cross-section. Using simple allometric relationships between stature and lung volumes, volume predictions are too high in the youngest age group, and too low in the oldest adolescents. Including age in the regression equation removes this trend in the cross-sectional data, and for VC and TLC also in the longitudinal data.

Changes in the concentration of hypothalamic and hypophyseal receptors for estradiol in pregnant and postpartum ewes

The sensitivity of the hypothalamic-pituitary axis to estradiol was evaluated by monitoring changes in the concentration of receptors for estradiol during gestation and the postpartum period of the ewe. Ewes that had been bred during anestrus so that lambing would occur during the breeding season were killed on d 50 and 140 of gestation or on d 2, 13, 22 and 35 postpartum. Total cytosolic receptors for estradiol were quantified in the anterior and posterior hypothalamus, median eminence, anterior pituitary and cerebral cortex. Concentration and total number of receptors for estradiol in the anterior and posterior hypothalamus and anterior pituitary gland during gestation through d 13 postpartum were similar but increased (P less than .05) by d 22 and 35 postpartum. Changes in the concentration of receptors for estradiol were tissue-specific because stage of reproduction did not influence the number of receptors for estradiol in the median eminence or cerebral cortex. Increases in the concentration of receptors for estradiol in hypothalamic and pituitary tissues on d 22 postpartum immediately preceded the onset of normal ovarian cyclicity in ewes. From these data we conclude that resumption of reproductive cycles in postpartum ewes occurs about the time concentrations of receptors for estradiol in the anterior pituitary gland and hypothalamus increase.

Functional changes in luteinizing hormone-secreting cells from pre- and postpartum ewes

Luteinizing hormone (LH)-containing cells from ovine pituitaries obtained during gestation and at various times after parturition were examined to determine whether the ability to store and secrete LH in vitro was correlated with morphological changes. Pituitaries collected on days 50 and 140 of gestation and on days 2, 13, 22, and 35 after parturition were enzymatically dissociated and the resulting cells cultured in media containing estradiol (12 pg/ml), cortisol (12 ng/ml), or no steroid. After 4, 7, or 10 days of culture, cells were washed and basal LH, gonadotropin-releasing hormone (GnRH)-stimulated release of LH, and cellular content of LH were determined. The content of LH (ng/10(6) cells) was lowest on day 140 of gestation (2.7 +/- 0.3) and day 2 postpartum (2.2 +/- 0.6) and then increased (P less than 0.05) on days 13 (36.6 +/- 8.3), 22 (59.9 +/- 14.4), and 35 (54.6 +/- 19.3) postpartum. The percentage of pituitary cells containing immunoreactive LH nearly doubled (P less than 0.05) between days 2 (5.6 +/- 0.2%) and 35 (10.6 +/- 1.1%) postpartum. Moreover, LH-containing cells were smaller, and the percent total cellular volume occupied by secretory granules was less on day 2 than on days 22 and 35 after parturition. Secretion of LH after 4, 7, or 10 days of culture reflected the cellular content of LH and was not influenced by the presence of steroids in the media. These data indicate that decreased synthesis of LH during gestation is associated with hypoplasia of the LH-secreting cells. These cells are reactivated during the postpartum period and their capacity to synthesize LH gradually returns to normal.

Prepubertal changes in the hypothalamic-pituitary axis of Holstein bulls

We investigated the nature and sites of changes in the hypothalamic-pituitary axis associated with the onset of high-frequency, high-amplitude discharges of luteinizing hormone (LH) in young bulls during the transition from the infantile to the prepubertal phase of development. Blood serum and neuroendocrine tissues from bulls killed at 1, 6, 10, 14, or 18 wk of age were evaluated. Concentrations of LH in serum from bulls 1 or 6 wk old averaged less than 0.25 ng/ml and only one episodic discharge of LH was detected for 10 bulls. At 10, 14, or 18 wk, 14 of 15 bulls had episodic discharges of LH. Concentrations of testosterone in serum were progressively higher at 10, 14, and 18 wk, but the concentration of estradiol was maximal at 6 wk. The concentrations of gonadotropin-releasing hormone (GnRH) in the anterior hypothalamus, posterior hypothalamus, or median eminence were not influenced by age. However, concentration of GnRH receptors in the anterior pituitary gland increased 314% between 6 and 10 wk and the concentration of LH increased 67%. Between 6 and 10 wk, concentrations of estradiol receptors in the anterior and posterior hypothalamus declined by 68% and 46%, but the concentration of estradiol receptors in the anterior pituitary gland increased by 103%. For most characteristics, there was no major change between 10 and 18 wk. We postulate that between 6 and 10 wk of age, there is 1) removal of an estradiol-mediated block of GnRH secretion and 2) an estradiol-mediated, and possibly GnRH-mediated, increase in pituitary GnRH receptors. Together, these changes result in greatly increased stimulation of the anterior pituitary gland by GnRH between 6 and 10 wk of age and stimulation of the discharges of LH characteristic of bulls in the early prepubertal phase of development.

Measurement of messenger RNA for luteinizing hormone beta-subunit and alpha-subunit during gestation and the postpartum period in ewes

Pituitary content of luteinizing hormone (LH) and mRNAs for LH beta-subunit (LH beta), alpha-subunit, prolactin, and growth hormone were measured in ewes on Days 50 and 140 of gestation and on Days 2, 13, 22, and 35 postpartum. Content of LH in dissociated anterior pituitary cells declined (P less than 0.05) between Days 50 and 140 of gestation and remained low at 2 days postpartum. By 22 days postpartum, pituitary concentrations of LH were comparable to concentrations in normally cycling ewes. During gestation concentrations of mRNA for LH beta and alpha-subunit paralleled changes in cellular content of LH, reaching minimal levels on Day 140. By Day 2 postpartum, pituitary concentrations of mRNAs for LH beta and alpha-subunit began to increase; they reached maximum levels by Day 13 postpartum. There appeared to be a gradual linear increase in mRNA for prolactin through gestation and the postpartum period. No changes in mRNA for growth hormone were noted during the prepartum or postpartum periods. These data suggest that the decline in pituitary concentrations of LH during gestation is due to a decrease in cellular mRNA for LH beta and alpha-subunit. The increase in mRNA for LH beta and alpha-subunit appears to precede an increase in cellular content of LH in the postpartum ewe by several days.

Negative power functions of time in pharmacokinetics and their implications

When a clearance curve in pharmacokinetic studies--and in tracer kinetics in general--is well fitted by a sum of negative exponentials of time, in very many cases the data would also be well fitted over much or all of the same period by a function of time consisting mainly of a negative power or by a gamma function. There are also instances where two such power functions can be observed in the same clearance curve. Examples are given from numerous reanalyses of published results. These facts have not been explained, except as being fortuitous, by any existing theory or model based on two or more homogeneous compartments. Theoretical and practical implications are outlined and some general recipes are put forward with a view to replacing multicompartmental analysis.

Effect of number of receptors for gonadotropin-releasing hormone on the release of luteinizing hormone

The relationship between number of receptors for gonadotropin-releasing hormone (GnRH) and the ability of the anterior pituitary gland to release luteinizing hormone (LH) was examined in ovariectomized ewes. A GnRH antagonist was used to regulate the number of available receptors. The dose of GnRH antagonist required to saturate approximately 50 and 90% of GnRH receptors in ovariectomized ewes was determined. Thirty min after intracarotid infusion of GnRH antagonist, ewes were killed and the number of unsaturated (i.e., those available for binding) pituitary GnRH receptors was quantified. Infusion of 10 and 150 micrograms GnRH antagonist over a 5-min period reduced binding of the labeled ligand to approximately 50 and 12% of controls, respectively. The effect of reducing the number of GnRH receptors on release of LH after varying doses of the GnRH agonist, D-Ala6-GnRH-Pro9-ethylamide (D-Ala6-GnRH) was then evaluated. One of four doses of D-Ala6-GnRH (0.125, 2.5, 50 and 400 micrograms) was given i.v. to 48 ovariectomized ewes whose GnRH receptors had not been changed or were reduced to approximately 50 or 12% of control ewes. In ewes with a 50% reduction in GnRH receptors, total release of LH (area under response curve) was lower than that obtained for controls (P less than 0.01) at the 0.125-micrograms dose of D-Ala (6.1 +/- 0.7 cm2 vs. 13.5 +/- 0.7 cm2) but was not different at the 2.5-, 50- or 400-micrograms doses of D-Ala6-GnRH.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the FEV1-height relationship during pubertal growth

In two cohorts of boys (n = 167) and two cohorts of girls (n = 131), FEV1, stature, body weight and two thoracic dimensions were measured eight times at intervals of about six months; the mean ages of each cohort at the start of the study were 12.5 and 13.5 years respectively. In each of the repeated cross-sections, FEV1 could be described as a power function of stature (FEV1 = aHk). In boys, the power (derived from regression of In FEV1 on ln H) increased from 2.60 to 3.04 and declined to 2.40; in girls, it decreased steadily from 2.87 to 1.94, attaining adult values at about age 15. A similar but less pronounced trend was observed for ln FEV1 against ln body mass. The adolescent growth spurt could be best studied in the boys. The individual (longitudinal) log-log plots of FEV1 versus stature or thoracic height were obviously non-linear in 52% and 33% of the boys respectively, with the greatest increase in FEV1 towards the end of the curve. In 78 boys with an apparently straight ln FEV1-ln H plot, the slopes of individual curves varied between 1.86 and 7.53; the mean value (3.99) was larger than in any of the repeated cross-sections. Applying allometric principles of similarity, FEV1 was about isometrically related to body mass but varied as about the 3.5th power of stature, with age-related trends in boys and girls. These findings reflect changes in bodily proportions and shape during the adolescent growth spurt, with growth in lung volume lagging behind growth in standing height.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological interpretation of the skewness of indicator-dilution curves; theoretical considerations and a practical application

Indicator-dilution curves can be interpreted and analysed by describing the system between injection- and sampling site with a physical model. Till now mainly compartmental and distributed models have been investigated. One feature of distributed models is the possibility to interpret skewness or asymmetry of the curve in terms of a parameter, proportional with the Peclet number, which is a measure of the relative contribution between convection and diffusion in indicator transport. In patients with and without pulmonary edema, we analyzed a number of curves obtained with an intravascular indicator (131I radioiodinated serum albumin, RISA) and a diffusing indicator (tritiated water, THO) over the pulmonary vascular bed. Edema was measured by indexed extravascular lung water and by critical pressure, defined as the difference between pulmonary capillary wedge pressure and plasma colloid osmotic pressure. The significant decrease of the symmetry of the RISA curves with increasing cardiac output we explained by an increasing labyrinth dispersion and increasing turbulence at higher flows. For normals we found all THO curves to be less skew than albumin curves. This difference diminished and even reversed when the degree of pulmonary edema increased. We suggest a hypothesis for this phenomenon by considering various mechanisms responsible for dispersion and capillary exchange of the indicator during transport from injection to sampling site. In normals the contribution of Taylor diffusion during laminar flow in parts of the circulatory system may be responsible for the greater symmetry of THO curves; with increasing pulmonary edema, transcapillary diffusion of THO causes THO curves to become more skew and even more asymmetric when compared with albumin curves.

Role of estradiol in inducing an ovulatory-like surge of luteinizing hormone in sheep

Two experiments were performed to examine the effect of estradiol on secretion of luteinizing hormone (LH) and on the number of receptors for gonadotropin-releasing hormone (GnRH) after down regulation of GnRH receptors in ovariectomized ewes. In the first experiment, ovariectomized ewes were administered one of four treatments: Group 1) infusion of GnRH i.v. for 40 h; Group 2) injection of 100 micrograms estradiol i.m.; Group 3) infusion of GnRH i.v. for 16 h followed immediately by an injection of 100 micrograms estradiol i.m.; and Group 4) infusion of GnRH i.v. for 40 h plus injection of 100 micrograms estradiol i.m. after the 16th h of infusion. Ewes in Groups 1, 3 and 4 responded to the infusion of GnRH with an immediate increase in serum concentrations of LH, with maximum values occurring between 2 and 4 h after the start of infusion; serum concentrations of LH then began to decline and were approaching the pretreatment baseline within 16 h. Administration of estradiol resulted in a surge of LH regardless of whether the pituitary had been desensitized by infusion of GnRH or not. In all cases the magnitude of the surge was similar to that induced by the initial infusion of GnRH. In Groups 2 and 3 the surge of LH began at 12.3 +/- 0.1 and 11.9 +/- 0.1 h after administration of estradiol. In contrast, the ewes in Group 4 had a surge of LH beginning 3.7 +/- 0.1 h after administration of estradiol.(ABSTRACT TRUNCATED AT 250 WORDS)

Short and long term variability of indices from the single and multiple breath nitrogen test

We have studied the short and long term variabilities of indices derived from the single and multiple breath nitrogen tests in adolescents aged 12-18 years. In 333 boys and girls, up to 10 measurements were performed at half-year intervals; in 39 of them four measurements were also made at 10 min intervals. The standard deviations of the residual volume and the height of phase IV were roughly proportional to the magnitude of these indices, and so were best expressed by coefficients of variation, of which the means were 8% and 37% respectively. The measurement error in residual volume (RV) was small (1.4 to 1.9%) when compared to 'real' biological variability (8.9%). The variabilities of other tests were not correlated with their magnitude. Using autocorrelation coefficients, short term variability could be approximated from longitudinal data for the vital capacity (VC) and RV, but less well for other indices. The between-to-within variance ratios were rather low in the 39 healthy pupils. Based on these findings, RV and VC appear to be indices with a potentially good predictive value for lung volume assessment or for detecting abnormal lung growth in longitudinal studies of adolescents.

Functional development of the parasympathetic innervation of the sino-auricular node in newborn rabbits, cats and guinea pigs

The effects of supramaximal vagus nerve stimulation on heart rate were studied in newborn rabbits, cats and guinea pigs. The analysis of the stimulus-effect curve revealed that the earlier proposed relationship: log If/IO = H.f (IO is the steady state PP-interval before and If during stimulation, f is the stimulus frequency, and H the slope of the line) accurately summarizes the relation in rabbits, while with minor deviations it also holds for newborn cats and guinea pigs. Thus, the vagus effect for each nerve and animal is characterized by the slope of the line, H. In rabbits and cats the vagus effect decreased during the first postnatal week to about 1/3 and 1/5 of the initial value at birth. Guinea pigs, however, did not show such a postnatal change of the vagus effect. In comparison with rabbits and cats these animals are born at a relatively late ontogenetic stage. Therefore, we hypothesized that the decrease in vagus effect is related to the stage of development and occurs mainly before birth in this species.

Influence of external resistance and minor flow variations on single breath nitrogen test and residual volume

Inspiratory and expiratory flow are known to influence parameters obtained from the single breath nitrogen test. We assessed the influence of two different flow rates (0.3 and 0.5 1.s-1) with and without the use of an external resistor during inspiration and/or expiration on the indices of the single breath nitrogen test in eight healthy subjects. We found that when an external resistance was used during expiration residual volume was larger and the height of phase IV smaller, because the resistance interferes with complete lung emptying. When applied only during inspiration the resistance did not affect any of the measurements. The height of phase IV was greater at a flow of 0.3 1.s-1 than at 0.5 1.s-1; also residual volume was greater at the lower flow rate. The effect of flow rate can be accounted for by continuous gas exchange during the manoeuvers. The slope of the alveolar plateau and closing volume are not influenced by the resistance or by minor changes in flow rate. We conclude that for commonly used indices (slope of phase III, closing volume) the use of a resistance does not affect the results and is helpful for the subject; residual volumes are affected by both the resistance and the flow rate, but these effects are small.

Selection of variables from maximum expiratory flow-volume curves

Various methods are in use for estimating physiological variables from maximum expiratory flow-volume curves, and some of these are recommended by international bodies for use on adults. We have compared eight such methods in 433 adolescents aged 12-16 years. The mean values of expiratory flows, FVC and FEV1 by each method differed less than 6% from those obtained by the method recommended by the ATS, except for MEF25, where differences between methods were substantially larger. The mean within-individual coefficients of variation of FVC and FEV1 did not differ between methods and improved from about 3.1 to 2.6% and 2.7 to 2.3% respectively when using 5 instead of 3 acceptable curves. For expiratory flows, the coefficients of variation ranged between 4.2 and 9.4% and improved slightly but not consistently when using more than 3 acceptable curves. Reproducibilities were systematically poorer when flows were derived from one "best" FVC manoeuvre. It is concluded that taking more than 3 acceptable blows is not cost-effective, even in inexperienced adolescents. An envelope method and maximum composite curve from FVC reproducible within 5% from the largest one are recommended for use with teenagers.