Development and internal validation of clinical prediction models for outcomes of complicated intra-abdominal infection.

BACKGROUND: Complicated intra-abdominal infections (cIAIs) are associated with significant morbidity and mortality. The aim of this study was to describe the clinical characteristics of patients with cIAI in a multicentre study and to develop clinical prediction models (CPMs) to help identify patients at risk of mortality or relapse. METHODS: A multicentre observational study was conducted from August 2016 to February 2017 in the UK. Adult patients diagnosed with cIAI were included. Multivariable logistic regression was performed to develop CPMs for mortality and cIAI relapse. The c-statistic was used to test model discrimination. Model calibration was tested using calibration slopes and calibration in the large (CITL). The CPMs were then presented as point scoring systems and validated further. RESULTS: Overall, 417 patients from 31 surgical centres were included in the analysis. At 90 days after diagnosis, 17.3 per cent had a cIAI relapse and the mortality rate was 11.3 per cent. Predictors in the mortality model were age, cIAI aetiology, presence of a perforated viscus and source control procedure. Predictors of cIAI relapse included the presence of collections, outcome of initial management, and duration of antibiotic treatment. The c-statistic adjusted for model optimism was 0.79 (95 per cent c.i. 0.75 to 0.87) and 0.74 (0.73 to 0.85) for mortality and cIAI relapse CPMs. Adjusted calibration slopes were 0.88 (95 per cent c.i. 0.76 to 0.90) for the mortality model and 0.91 (0.88 to 0.94) for the relapse model; CITL was -0.19 (95 per cent c.i. -0.39 to -0.12) and - 0.01 (- 0.17 to -0.03) respectively. CONCLUSION: Relapse of infection and death after complicated intra-abdominal infections are common. Clinical prediction models were developed to identify patients at increased risk of relapse or death after treatment, these now require external validation.

A Screen for Antibiotic Resistance Determinants Reveals a Fitness Cost of the Flagellum in Pseudomonas aeruginosa.

The intrinsic resistance of Pseudomonas aeruginosa to many antibiotics limits treatment options for pseudomonal infections. P. aeruginosa's outer membrane is highly impermeable and decreases antibiotic entry into the cell. We used an unbiased high-throughput approach to examine mechanisms underlying outer membrane-mediated antibiotic exclusion. Insertion sequencing (INSeq) identified genes that altered fitness in the presence of linezolid, rifampin, and vancomycin, antibiotics to which P. aeruginosa is intrinsically resistant. We reasoned that resistance to at least one of these antibiotics would depend on outer membrane barrier function, as previously demonstrated in Escherichia coli and Vibrio cholerae This approach demonstrated a critical role of the outer membrane barrier in vancomycin fitness, while efflux pumps were primary contributors to fitness in the presence of linezolid and rifampin. Disruption of flagellar assembly or function was sufficient to confer a fitness advantage to bacteria exposed to vancomycin. These findings clearly show that loss of flagellar function alone can confer a fitness advantage in the presence of an antibiotic.IMPORTANCE The cell envelopes of Gram-negative bacteria render them intrinsically resistant to many classes of antibiotics. We used insertion sequencing to identify genes whose disruption altered the fitness of a highly antibiotic-resistant pathogen, Pseudomonas aeruginosa, in the presence of antibiotics usually excluded by the cell envelope. This screen identified gene products involved in outer membrane biogenesis and homeostasis, respiration, and efflux as important contributors to fitness. An unanticipated fitness cost of flagellar assembly and function in the presence of the glycopeptide antibiotic vancomycin was further characterized. These findings have clinical relevance for individuals with cystic fibrosis who are infected with P. aeruginosa and undergo treatment with vancomycin for a concurrent Staphylococcus aureus infection.

Does gender or mode of HIV acquisition affect virological response to modern antiretroviral therapy (ART)?

OBJECTIVES: Previous UK studies have reported disparities in HIV treatment outcomes for women. We investigated whether these differences persist in the modern antiretroviral treatment (ART) era. METHODS: A single-centre cohort analysis was carried out. We included in the study all previously ART-naïve individuals at our clinic starting triple ART from 1 January 2006 onwards with at least one follow-up viral load (VL). Time to viral suppression (VS; first viral load < 50 HIV-1 RNA copies/mL), virological failure (VF; first of two consecutive VLs > 200 copies/mL more than 6 months post-ART) and treatment modification were estimated using standard survival methods. RESULTS: Of 1086 individuals, 563 (52%) were men whose risk for HIV acquisition was sex with other men (MSM), 207 (19%) were men whose risk for HIV acquisition was sex with women (MSW) and 316 (29%) were women. Median pre-ART CD4 count and time since HIV diagnosis in these groups were 298, 215 and 219 cells/µL, and 2.3, 0.3 and 0.3 years, respectively. Time to VS was comparable between groups, but women [adjusted hazard ratio (aHR) 2.32; 95% confidence interval (CI) 1.28-4.22] and MSW (aHR 3.28; 95% CI 1.91-5.64) were at considerably higher risk of VF than MSM. Treatment switches and complete discontinuation were also more common among MSW [aHR 1.38 (95% CI 1.04-1.81) and aHR 1.73 (95% CI 0.97-3.16), respectively] and women [aHR 1.87 (95% CI 1.43-2.46) and aHR 3.20 (95% CI 2.03-5.03), respectively] than MSM. CONCLUSIONS: Although response rates were good in all groups, poorer virological outcomes for women and MSW have persisted into the modern ART era. Factors that might influence the differences include socioeconomic status and mental health disorders. Further interventions to ensure excellent response rates in women and MSW are required.

CMV in the gut: a critical review of CMV detection in the immunocompetent host with colitis.

As scientific techniques for the detection of cytomegalovirus (CMV) improve, we are able to detect small amounts of CMV in the mucosal wall. As clinicians, we are unsure how to interpret the results of this novel test. There is controversy in the literature as to the significance of the detection of CMV in the gut. Whilst the importance of CMV and reactivation of the virus is clear in those patients such as allograft recipients with established immune compromise, the role is less clear in patients with less damaged immune systems. We explore whether the detection of CMV in such cases influences outcome and how it should be optimally managed. We discuss the optimal management of such cases, according to current guidelines, with a review of the literature.

Staphylococcus aureus bacteriuria: implications and management.

Background: Staphylococcus aureus is isolated in around 0.2%-4% of positive urinary cultures, more commonly in the contexts of long-term care, urological abnormalities and procedures, male sex, older age and comorbidities. Isolation may represent contamination, colonization, urinary tract infection or bacteraemic seeding from another site, and may be linked to S. aureus bacteraemia. However, there is little guidance on investigation and management of S. aureus bacteriuria. We performed a retrospective analysis of cases in our service, including clinical characteristics, investigations and treatment. Methods: Data were collected on all urine samples taken from adult patients over a 5-year period from which S. aureus was isolated. Detailed analysis including investigations and management was conducted in those collected over a 1-year period. Results: From 511 patients, 668 urine cultures positive for S. aureus were identified; 6.5% of cases were positive for MRSA. Of 93 patients who had blood cultures taken, there were 6 cases of S. aureus bacteraemia, 4 of which were associated with urological instrumentation. Of 94 cases analysed in detail, 57% were treated with antibiotics, and 49% had repeat urine cultures. Factors associated with recurrence were urinary catheterization, urological abnormality, diabetes and inpatient status. Conclusions: Our experience does not support the routine taking of blood cultures or treatment of asymptomatic bacteriuria in well patients with S. aureus bacteriuria in this setting. However, repeat urine culture, and investigation and treatment of higher risk patients, for example, prior to bladder instrumentation, may be warranted. We propose a simple algorithm to guide clinicians.

Gut Commensal Bacteroidetes Encode a Novel Class of Vitamin B12-Binding Proteins.

Human gut commensal Bacteroidetes rely on multiple transport systems to acquire vitamin B12 and related cobamides for fitness in the gut. In addition to a set of conserved transport proteins, these systems also include a diverse repertoire of additional proteins with unknown function. Here, we report the function and structural characterization of one of these proteins, BtuH, which binds vitamin B12 directly via a C-terminal globular domain that has no known structural homologs. This protein is required for efficient B12 transport and competitive fitness in the gut, demonstrating that members of the heterogeneous suite of accessory proteins encoded in Bacteroides cobamide transport system loci can play key roles in vitamin acquisition. IMPORTANCE The gut microbiome is a complex microbial community with important impacts on human health. One of the major groups within the gut microbiome, the Bacteroidetes, rely on their ability to capture vitamin B12 and related molecules for fitness in the gut. Unlike well-studied model organisms, gut Bacteroidetes genomes often include multiple vitamin B12 transport systems with a heterogeneous set of components. The role, if any, of these components was unknown. Here, we identify new proteins that play key roles in vitamin B12 capture in these organisms. Notably, these proteins are associated with some B12 transport systems and not others (even in the same bacterial strain), suggesting that these systems may assemble into functionally distinct machines to capture vitamin B12 and related molecules.

Blood-stage malaria vaccines - recent progress and future challenges.

Plasmodium falciparum malaria is a major global health problem, responsible for up to 1 million deaths each year. Major efforts have been made to develop an effective vaccine against this disease, to reduce the associated morbidity and mortality. There has already been considerable progress, with the first vaccine against the pre-erythrocytic stages of P. falciparum now en route to licensure. There remains, however, a strong scientific rationale for the development of a highly effective additional vaccine component against the blood stages of the parasite, which could be deployed in conjunction with partially effective control measures against the pre-erythrocytic stages. Here, recent progress in the clinical development of blood-stage vaccines is reviewed, including methods of antigen selection, the limitations of in-vitro assays for selecting vaccines for clinical development, and the results of recently published clinical trials. This review seeks to summarize recent developments in our understanding of immunity to blood-stage parasites, as well as the relevant key advances made in vaccine technologies over the last decade. The future challenges that face this field of vaccine research are also described.

Imaging in the investigation and management of Staphylococcus aureus bacteraemia: a role for advanced imaging techniques.

Staphylococcus aureus bacteraemia (SAB) continues to affect ∼25,000 patients in the UK per year with a high crude mortality of 30% at 90 days. Prompt source control improves outcomes in sepsis and SAB and is included in sepsis guidelines. A recent clinical trial of adjunctive antibiotic treatment in SAB found that the majority of recurrences of SAB were associated with a failure of source management. In this condition, the ability to control the source of infection may be limited by the ability to detect a focus of infection. Echocardiogram is now a routinely used tool to detect such unknown foci in the form of unexpected infectious vegetations. We review the literature to explore the utility of advanced imaging techniques, such as [18F]fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and magnetic resonance imaging (including whole-body MRI), to detect foci which may otherwise be missed. As unknown foci are associated with increased mortality, we propose that increasing the detection of foci could enable improved source control and result in improved outcomes in SAB.

Translocation of a gut pathobiont drives autoimmunity in mice and humans.

Despite multiple associations between the microbiota and immune diseases, their role in autoimmunity is poorly understood. We found that translocation of a gut pathobiont, Enterococcus gallinarum, to the liver and other systemic tissues triggers autoimmune responses in a genetic background predisposing to autoimmunity. Antibiotic treatment prevented mortality in this model, suppressed growth of E. gallinarum in tissues, and eliminated pathogenic autoantibodies and T cells. Hepatocyte-E. gallinarum cocultures induced autoimmune-promoting factors. Pathobiont translocation in monocolonized and autoimmune-prone mice induced autoantibodies and caused mortality, which could be prevented by an intramuscular vaccine targeting the pathobiont. E. gallinarum-specific DNA was recovered from liver biopsies of autoimmune patients, and cocultures with human hepatocytes replicated the murine findings; hence, similar processes apparently occur in susceptible humans. These discoveries show that a gut pathobiont can translocate and promote autoimmunity in genetically predisposed hosts.

Gut microbiota. Antimicrobial peptide resistance mediates resilience of prominent gut commensals during inflammation.

Resilience to host inflammation and other perturbations is a fundamental property of gut microbial communities, yet the underlying mechanisms are not well understood. We have found that human gut microbes from all dominant phyla are resistant to high levels of inflammation-associated antimicrobial peptides (AMPs) and have identified a mechanism for lipopolysaccharide (LPS) modification in the phylum Bacteroidetes that increases AMP resistance by four orders of magnitude. Bacteroides thetaiotaomicron mutants that fail to remove a single phosphate group from their LPS were displaced from the microbiota during inflammation triggered by pathogen infection. These findings establish a mechanism that determines the stability of prominent members of a healthy microbiota during perturbation.

Comparative assessment of transmission-blocking vaccine candidates against Plasmodium falciparum.

Malaria transmission-blocking vaccines (TBVs) target the development of Plasmodium parasites within the mosquito, with the aim of preventing malaria transmission from one infected individual to another. Different vaccine platforms, mainly protein-in-adjuvant formulations delivering the leading candidate antigens, have been developed independently and have reported varied transmission-blocking activities (TBA). Here, recombinant chimpanzee adenovirus 63, ChAd63, and modified vaccinia virus Ankara, MVA, expressing AgAPN1, Pfs230-C, Pfs25, and Pfs48/45 were generated. Antibody responses primed individually against all antigens by ChAd63 immunization in BALB/c mice were boosted by the administration of MVA expressing the same antigen. These antibodies exhibited a hierarchy of inhibitory activity against the NF54 laboratory strain of P. falciparum in Anopheles stephensi mosquitoes using the standard membrane feeding assay (SMFA), with anti-Pfs230-C and anti-Pfs25 antibodies giving complete blockade. The observed rank order of inhibition was replicated against P. falciparum African field isolates in A. gambiae in direct membrane feeding assays (DMFA). TBA achieved was IgG concentration dependent. This study provides the first head-to-head comparative analysis of leading antigens using two different parasite sources in two different vector species, and can be used to guide selection of TBVs for future clinical development using the viral-vectored delivery platform.

Ovarian regulation of postcoital gonadotropin release in the rabbit: reexamination of a functional role for 20 alphadihydroprogesterone.

In the rabbit, it has proposed that an ovarian progestin, 20 alpha-dihydroprogesterone (20alphaP), released at mating, is essential for a normal postcoital LH surge. However, we measured plasma levels of LH and 20alphaP after mating in rabbits and observed that the frequency, magnitude and time-course of changes in circulating levels of 20alphaP seemed inappropiate to account for the rapid and major surge of LH secretion. This prompted us to re-evalute the role of the ovary in regulating postcoital LH secretion. In chronically ovariectomized (greater than 30 days) does pretreated with estrogen, mating induced a normal LH surge in only 1 of 10 animals, indicating that an ovarian product in addition to estrogen is required for a normal postcoital LH surge. However, when 20alphaP was injected soon after mating in chronically ovariectomized does pretreated with estrogen, only 2 of 9 displayed normal LH surges; this proportion is not different from that (1/10) observed with estrogen treatment alone. To demonstrate that the estrogen treatment, which produced supraphysiologic plasma estradiol levels, did not itself block LH release, 6 intact anestrus females were treated with the same estrogen regimen. Estrus was induced in 5 and each displayed a large post-coital LH surge and ovulated. As a final test of the 20alphaP hypothesis, 5 spontaneously estrous does were ovariectomized within 15 min post coitum to abolish acute increases in circulating ovarian hormones. Three animals released LH in amounts and temporal pattern indistinguishable from intact estrous does. A fourth released smaller amounts of LH. Two of 4 sham-operated does also had normal LH surges. These findings indicate that ovarian hormones are required before mating to support the capacity of the LH secretory mechanism to respond to coitus. Chronic alteration in the hormonal milieu by ovariectomy appears to produce a change in the hypothalamo-hypophysial complex that is not reversed by estrogen, alone. More importantly, these results demonstrate clearly that neither 20alphaP nor any other ovarian hormone is required post coitum, at least after 15 min, for normal LH release.

Thyroid angiogenesis: endotheliotropic chemoattractant activity from rat thyroid cells in culture.

Thyroid enlargement in response to chronic hypersecretion of TSH reflects the coordinated growth of both parenchyma and stroma. Because Wollman et al. observed in propylthiouracil-fed rats that enlargement and remodeling of thyroid capillaries were strictly localized around follicles, they hypothesized that growth of perifollicular blood vessels is stimulated by angiogenic factors secreted by neighboring follicular epithelial cells. In support of this hypothesis, we report that media conditioned by rat thyroid cells were very active in an in vitro angiogenesis bioassay that measures stimulation of endothelial cell migration through chemotaxis membranes in microwell Boyden chamber assemblies. Primary cultures of thyroid cells from collagenase-dispersed glands from male or female Holtzman rats fed 0.01% propylthiouracil in the drinking water released activity that produced up to 5-fold increases in endothelial cell migration rates relative to those in identical unconditioned medium. Thyroid-derived activity was primarily chemotactic (i.e. only weakly chemokinetic) to both rabbit aortic and microvascular endothelial cells. That endotheliotropic activity is derived from thyroid parenchyma is indicated by the finding that media conditioned by FRTL cells, a clonally derived thyroid follicular epithelial cell line, produced parallel chemoattractant responses. Thyroid-conditioned media were also chemoattractant to mouse BALB/c-3T3 cells, which have endothelial cell characteristics. In contrast, thyroid-conditioned media did not increase the high spontaneous migration rate of Walker rat sarcoma (WR256) cells. T4, T3, thyroglobulin, bovine fibroblast growth factor (alpha and beta), and media conditioned by rabbit endothelial cells were inactive. Chemoattractant activity in serum containing conditioned media was retained by both 10,000 and 30,000 mol wt cut-off (MWCO) ultrafilters. Activity in serum-free thyroid-conditioned media was largely retained by 10,000 MWCO filters, but only partially retained by 30,000 MWCO filters; activity in the 30,000 filtrate was recoverable in a 10,000 MWCO retentate. These findings support the hypothesis that capillary growth during thyroid enlargement occurs, at least in part, as a result of a parenchymal-stromal (epithelial-mesenchymal) paracrine interaction mediated by specific endotheliotropic (angiogenic) factors released by follicular epithelial cells and distinct from T3, T4, and thyroglobulin.

Preliminary characterization of angiogenic activity in media conditioned by cells from luteinized rat ovaries.

Angiogenic activity was detected in media conditioned by ovarian cells from superovulated, pseudopregnant (PMSG/human CG treated) immature Holtzman rats. Media conditioned by cells from luteinized rat ovaries stimulated the directed migration of rabbit endothelial cells or mouse Balb/c3T3 cells, but was not mitogenic to either cell type. That endotheliotropic activity was not associated with a steroid was indicated by the finding that chemoattractant activity was detected in fractions after reversed-phase C18 chromatography, which removes more than 95% of steroids present in the media, and that chemoattractant activity was precipitated by ammonium sulfate and by ethanol. Full chemoattractant activity was recovered after boiling (95 C for 30 min), lyophilization, dialysis, Sephadex G-25 desalting columns, and pH changes from 3-10. After Sephadex G-200 chromatography, chemoattractant activity emerged at elution volumes corresponding to 20,000-30,000 mol wt. Chemoattractant activity was not retained by Concanavalin A-Sepharose or gelatin-Sepharose, and was only partially retained by heparin-agarose. Chemoattractant activity was also partially retained on both cation and anion exchange columns. Our collective findings indicate the presence of a nonsteroidal, heat-stable, pronase-sensitive factor, nominal mol wt of 20,000-30,000, in media conditioned by cells from luteinized rat ovaries; this factor is chemoattractive but not mitogenic to endothelial cells. Ovarian-derived chemoattractant activity appears to be distinct from fibroblast growth factor because it lacked detectable mitogenic activity, and because fibroblast growth factor was not active in our cell migration bioassay. Because stimulation of endothelial cell migration is a key event during angiogenesis, demonstration of an ovarian endotheliotropic chemoattractant is consistent with our hypothesis that angiogenesis factors play a role in the paracrine regulation of ovarian function.

Between-ovary interaction in the regulation of follicle growth, corpus luteum function, and gonadotropin secretion in the primate ovarian cycle. III. Temporal and spatial dissociation of folliculogenesis and negative feedback regulation of tonic gonadotropin release after luteectomy in rhesus monkeys.

This study was designed to examine effects of previous ovarian status on subsequent follicle growth and the role of between-ovary communication in the regulation of folliculogenesis and gonadotropin secretion during the primate ovarian cycle. Responses to luteectomy were compared in two groups of rhesus monkeys. In the first, follicle growth and corpus luteum function had been constrained chronically to a single ovary by hemiovariectomy performed 66--258 days earlier; the second group was composed of intact monkeys that underwent contralateral wedge resection at luteectomy. In each group, luteal ablation was followed by a prompt fall in serum progesterone levels, a premature onset of menses, and the next preovulatory gonadotropin surges 14.7 +/- 1.1 or 15.4 +/- 1.4 days later (mean +/- SE; P greater than 0.25). Although the patterns of circulating estradiol before and after ablation in each group were superimposable, luteectomy in monkeys lacking a contralateral ovary was followed by a large (2- to 4-fold) and prolonged (7--10 days) increase in serum FSH, whereas in monkeys with two ovaries, serum FSH levels exhibited only a small short-lived rise. The findings indicate that 1) prior chronic constraint of ovarian function to a single ovary did not alter the overall time course of new follicle growth culminating in ovulation after luteectomy; 2) the contralateral ovary provided the principal negative feedback regulation of gonadotropin secretion for some time after luteectomy even though it may not have been the exclusive site of new follicle growth; 3) whereas the ability of the luteectomized ovary to regulate tonic gonadotropin secretion was temporarily impaired, its ability to support the customary temporal pattern of follicle growth after luteal ablation was not; 4) some (contralateral) ovarian factor other than estradiol or progesterone apparently made a major contribution to the regulation of FSH secretion after luteectomy; and 5) folliculogenesis culminating in ovulation from a single follicle and the negative feedback regulation of tonic gonadotropin secretion in some circumstances may occur concurrently but separately on opposite ovaries or may occur at different times within the same ovary.

Bioassay of circulating luteinizing hormone in the rhesus monkey: comparison with radioimmunoassay during physiological changes.

The concentration of biologically active LH in rhesus monkey (Macaca mulatta) serum was measured by a highly sensitive bioassay based upon testosterone production by dispersed rat interstitial cells. The sensitivity of the in vitro bioassay was equal to or higher than that of radioimmunoassay, with detection limits of 0.1 mIU of human menopausal gonadotropin (hMG) or 10 ng of a rhesus pituitary gonadotropin preparation (LER-1909-2). Parallel dose-response curves were obtained for hMG and rhesus monkey pituitary gonadotropin. The method permits bioassy of LH in 20-100 micronl of serum from adult male monkeys, and from female monkeys during the follicular and luteal phases of the menstrual cycle. Bioactive LH concentrations could be assayed in 0.25 to 5 micronl of serum from mid-cycle, postmenopausal, and castrated female monkeys. Serum LH was undetectable in two hypophysectomized adult female monkeys and six intact immature animals, and was 13+/-6 (SD) mIU/ml in adult male monkeys. In adult females, follicular phase LH levels ranged from 17 to 169 mIU/ml, with a mean of 76+/-52 mIU/ml. The midcycle LH peak was 1738+/-742 mIU/ml and the luteal phase values ranged from 6-47 mIU/ml, with a mean of 35+/-5 mIU/ml. Serum LH concentrations ranged from 100 to 900 mIU/ml in two menopausal females, and from 590-1480 mIU/ml in castrated females. Treatment of castrated female monkeys with estrogen plus progesterone produced an initial two-fold rise in serum LH within 3 days, followed by a gradual decline to one-fourth to one-tenth of the initial levels after 10 days of treatment. Serum LH was suppressed to undetectable levels during the third week, and remained so for the duration of the 60-day treatment period. Bioactive serum LH levels were comparable to levels determined by radioimmunoassay during the follicular and luteal phases of the menstrual cycle, with increased bio-immunoratio at the midcycle peak. The concentrations of biologically active serum LH in rhesus monkeys were similar to those in the human female during the follicular and luteal phases of the menstrual cycle, and were higher at midcycle and after castration. Serum LH levels measured by the interstitial cell bioassay in the rhesus monkey showed appropriate physiological changes and responses to gonadal steroid administration. Furthermore, the bioassay did not detect the LH-like material measured by heterologous radioimmunoassay in the serum of hypophysectomized, immature and steroid-suppressed monkeys. Thus, the rat interstitial cell assay provides a sensitive and valid procedure for measurement of biologically active LH in the serum of these non-human primates.

Regulation of folliculogenesis in the cycling rhesus monkey: selection of the dominant follicle.

To identify factors regulating the initiation of follicle growth in adult primates, the ovarian cycle of sexually mature rhesus monkeys was interrupted by surgical ablation of the preovulatory follicle or functioning corpus luteum (CL). In 10 of 10 animals, cautery of the largest visible follicle on Day 8-12 of the cycle blocked ovulation, and in all but one abolished the expected midcycle surges of gonadotropin secretion. In 8 monkeys of this group, surges of LH and FSH release occurred 12.4 +/- 0.9 days (d) (mean +/- SE) after cautery, coincident with elevations in serum estrogens, and succeeded by typical luteal phase patterns of circulating progesterone (P). No gonadotropin or estrogen surges were observed during the next 32 days of sampling in the remaining pair, despite visible new vesicular follicles. Removal of the CL in 5 of 5 monkeys 4-6 days after the midcycle LH surge was followed by a reduction in serum P to less than 0.25 ng/ml within 24 h and by the onset of menses within 3-4 days. After luteectomy in 4 of the 5 animals, preoperative levels of LH and FSH were maintained until 12.8 +/- 0.9 days, when typical surges of gonadotropin secretion occurred, followed by a normal luteal phase pattern of P. The fifth luteectomized monkey menstruated again 25 days after ablation without intervening surges of estrogen or gonadotropin release and did not ovulate. Sham follicle cautery did not block ipsilaternal ovulation or impair progesterone secretion by the CL in 2 of 2 monkeys. These observations indicate that, by the middle of the follicular phase, the follicle destined to ovulate had been selected, and that no other follicles were soon competent to mature. That the interval from ablation, at either phase of the cycle, until the next ovulation was the same indicates: a) that the prevailing ovarian steroidal milieu at ablation had no discernible differential effect on the time-course of resumed ovarian activity, and b) that midcycle surges of estrogen or gonadotropin secretion were not required either to initiate or synchronize subsequent follicle growth.

Systemic versus intraovarian progesterone replacement after luteectomy in rhesus monkeys: differential patterns of gonadotropins and follicle growth.

Similar to luteectomy (CLX) alone, systemic replacement of progesterone (P) to maintain circulating midluteal phase levels after CLX, and P withdrawal 10-11 days later were not accompanied by changes in serum FSH or LH levels. The next preovulatory gonadotropin surges, however, were delayed by about 10 days, relative to CLX alone. In contrast, a marked rise in serum FSH was observed after unilateral introvarian P replacement at CLX, even though accompanying patterns of serum estradiol (E2) and P (and the interval to the next LH surge) were not different from those after CLX alone. Our findings indicate that a) P is the principal luteal factor inhibiting new follicle growth, b) P inhibition may be exerted, at least in part, on the ovaries directly, and c) an ovarian factor other than P or E2 may contribute to the regulation of FSH, and perhaps LH, secretion in this primate.

Menstrual cycle characteristics in chronically hemiovariectomized cynomolgus monkeys (Macaca fascicularis).

Circulating levels of LH, FSH, estradiol, and progesterone were measured by RIA in daily serum samples throughout the menstrual cycle in five regularly cycling, chronically hemiovariectomized, adult cynomolgus monkeys. The hormonal patterns, the lengths of the follicular and luteal phases, and the overall cycle length were nearly indistinguishable from those observed in intact cycling monkeys. The findings accord with the notions 1) that in intact monkeys, the contralateral ovary contributes little, if at all, to the regulation of the function or lifespan of the corpus luteum, and 2) that the corpus luteum after spontaneous luteolysis has no local residual effect inimical to new follicle growth.

Corpus luteum--conceptus--follicle relationships during the fertile cycle in rhesus monkeys: pregnancy maintenance despite early luteal removal.

To determine how early in pregnancy cyclic follicle growth is interrupted, 6 pregnant monkeys were luteectomized (CLX) on day 29 or 30 of the cycle (approximately 1 week after implantation) to abbreviate the fertile cycle to approximately the length of nonfertile cycles. Unexpectedly, 3 of 6 monkeys remained pregnant despite early removal of luteal support. In the remainder, which aborted, the next ovulation was delayed beyond the interval typically observed after CLX in nonfertile cycles. Two of 4 other monkeys ovariectomized on day 29 also maintained their pregnancies. Our findings demonstrate that: 1) in 5 of 10 monkeys, the conceptus could survive without luteal support within a week after luteal rescue, and 2) secretion(s) of the conceptus also contribute to an arrest of cyclic follicle growth early in pregnancy.