Orthopedic oncology residency education, how broad and how deep?

Orthopedic residency training has long been an area of active research and discussion, and as the knowledge and concepts in subspecialties evolve, it is crucial to investigate the implications of these advancements in the musculoskeletal oncology field. It is important to note that the acquisition of surgical skills and scientific knowledge from orthopedic texts alone is not sufficient in this area. Orthopedic residents must also acquire multidisciplinary communication and leadership skills, as well as the mental capacity to make sound clinical decisions. Therefore, this commentary highlights the importance of assessing whether the current curriculum provides adequate preparation for residents' future careers, despite the fact that the expansion of subspecialties in orthopedic education has undoubtedly enhanced the depth of knowledge and concepts in the field. In addition, orthopedic residents must adopt an open-minded and scientific approach toward orthopedic oncology, which has unique principles. Moreover, it is crucial that general orthopedic surgeons have the necessary skills to manage patients and know when to refer them. By exploring these issues, we hope to continually contribute to ongoing discussions about how to improve orthopedic residency education.

Gorham-Stout syndrome, the challenge in diagnosis and unique in treatment: a case report

BACKGROUND

Gorham-Stout disease is a rare condition with fewer than 400 reported cases in the literature. The presentation of Gorham-Stout disease varies on the basis of location, extent, fracture, and accompanying symptoms. It lacks a specific histopathological appearance but is characterized by vascular changes and the absence of cellular atypia.

CASE PRESENTATION

This article presents a case study of a 16-year-old Persian boy with an entire femur with Gorham-Stout disease, highlighting the difficulties in managing this condition. The lack of a clear diagnosis resulted in prolonged procedures, delayed medical treatments, and ultimately required total femoral replacement with an endoprosthesis.

CONCLUSION

It is important to note that raising awareness of this disease and its potential complications can facilitate timely and appropriate treatment for patients presenting in the early stages of the disease.

Talus osteohondroma with syndesmosis problem; case report

INTRODUCTION AND IMPORTANCE

Osteochondroma, commonly known as exostosis, is a benign osteocartilaginous mass lesion frequently encountered in orthopaedic clinics. While its benign nature is of little concern, the impact on surrounding tissues can be significant, especially in the case of exostosis located in the distal tibia and fibula, which can damage the syndesmosis.

CASE PRESENTATION

This report presents a rare case of exostosis of the talus that has progressed into the syndesmosis, causing distinct clinical and radiographic symptoms. The patient underwent excision of the lesion through the posterolateral ankle approach, and our main concern was about the approach to the syndesmosis. Ultimately, open reduction and screw fixation were performed for the patient.

CLINICAL DISCUSSION

Exostosis in the talus area is generally uncommon in the literature review, and the presence of the lesion in the posteromedial surface area, as well as its entry and damage to the syndesmosis area, is even less common. Diagnosing the lesion through appropriate methods and a multidisciplinary team approach is crucial for correct diagnosis and treatment. Different approaches to managing syndesmosis have been reported, and suitable treatment for these cases is required.

CONCLUSION

In conclusion, correct diagnosis and excision of the exostosis lesion are essential, but it is also necessary to appropriately identify and manage its adverse effects. The selection of an appropriate treatment strategy for managing these lesions is crucial.

A Comparative Study of Soft Tissue Sarcomas of the Extremities; Brachytherapy versus Radiotherapy

Background: Soft tissue sarcoma (STS) is a wide group of solid tumors with specific features originating from mesenchymal tissue. Radiotherapy (RT) and chemotherapy have been widely applied in the treatment of these tumors to enhance surgical outcomes. This study was performed aiming to compare the results of postoperative brachytherapy (BRT) versus RT in patients who underwent surgical resection of extremity STSs. Methods: In a prospective study from 2011 to 2015, 166 patients with extremity STS who underwent surgical resection were included. All visible tumors, scars, and drain sites, if present during the surgery, were resected. A number of 79 patients received adjuvant RT, and 87 patients underwent BRT after surgical resection. Results: In patients who were treated through RT, the two-year local control was 90% in comparison with 87% for those treated through BRT (P > 0.050). The total radiation dose was 3869 ± 370 and 3048 ± 465 in the patients who underwent RT and in the BRT group (P < 0.001), respectively. The number of radiation sessions in the RT group and BRT group was respectively 27.3 ± 4.5 and 5.8 ± 2.0 (P = 0.001). Conclusion: Not only BRT can lead to similar local control and survival in comparison with the conventional adjuvant RT, but it can also decrease the total dose and number of radiation sessions in patients with STS of the extremity, which is a high grade, in individuals who underwent surgical resection.

Guided growth in the correction of knee deformity in patients with congenital insensitivity to pain

Background

Orthopedic manifestations of congenital insensitivity to pain (CIP) can be devastating if left untreated. Knee deformities are common in patients with CIP and might lead to joint destruction and loss of walking ability. The purpose of the present study was to report the results and complications of guided growth procedures around the knee in patients with CIP.

Methods

In a retrospective review, all patients with CIP who underwent guided growth procedures around the knee from 2009 to 2017 at a tertiary referral hospital were evaluated. Patients with secondary insensitivity to pain (e.g., syringomyelia), as well as patients with incomplete records, were excluded. Demographic data, clinical findings, correction rate, and complications were recorded.

Results

Ten knees in six patients fulfilled the inclusion criteria. The median age was 10 (range, 5–12), with a mean follow-up of 31 months (range, 16–56). Distal femoral tension-band hemiepiphysiodesis was the most common procedure, followed by proximal tibial hemiepiphysiodesis. The mean correction rate was 0.28°/month for femoral deformity. Staples were removed prematurely in one patient due to extrusion. No cases of infection or skin dehiscence were observed. None of the patients needed a reconstructive knee procedure during the study period.

Conclusions

The findings of this study suggest that guided growth procedures might have a role in the correction of knee deformities in patients with CIP. However, the correction rate is lower than that of typically developing children, patients should be closely followed to prevent complications, and stringent patient selection criteria should be followed to ensure success.

Effect of Er:YAG laser irradiation using SWEEPS and PIPS technique on dye penetration depth after root canal preparation

BACKGROUND

This study aimed to investigate the penetration depth of two different dyes after root canal preparation using PIPS and SWEEPS methods.

MATERIALS AND METHODS

A total of 60 single-rooted human teeth which were extracted for periodontal reasons were collected and stored in the sterile saline until using in the study. The crowns of the teeth were cut such that the remaining piece was 12 mm long. The root canals were prepared. Teeth were divided randomly into two initial groups (n = 30): indocyanine green solution (ICG) and methylene blue solution. Then, these teeth were divided into final subgroups (n = 10): Er:YAG laser irradiation with PIPS(photon-induced photoacoustic streaming) technique, Er:YAG laser irradiation with SWEEPS(shock-wave enhanced emission photoacoustic streaming) technique, and no irradiation. The penetration depth measurements were done by the stereo microscope in three zones of each specimen.

RESULTS

The difference between ICG in the control group and PIPS and SWEEPS in the coronal area was not significant. In the middle section the difference between PIPS and the control group was marginally insignificant (P = 0.053). In the methylene blue group, PIPS had significantly higher penetration depth in the apical area compared to the control group (P = 0.004). In the middle section, both PIPS and SWEEPS showed significantly higher penetration than the control group.

CONCLUSION

According to the results of this study, the laser has the potential to increase the penetration of methylene blue. Root canal preparation with the PIPS technique can increase the dye penetration. However, the SWEEPS technique and the conventional method have a similar outcome in terms of dye penetration.

Comparison of Patient-Reported Outcomes between Two Different Techniques of Carpal Tunnel Release: Classical Incision versus Minimal Incision

Background: Carpal tunnel syndrome (CTS) is the most common compression neuropathy in the upper limb which needs surgery in many cases. Two common surgical incisions for carpal tunnel release (CTR) are classical incision and minimal incision. In this survey, the aim is to compare patient-reported outcomes of these two types of incisions. Methods: In this retrospective study, patients with CTS who underwent two different approaches for CTR (classical or minimal) during one year were included. The diagnosis was confirmed clinically and by electrodiagnostic studies. The patients were categorized into two groups regarding the type of surgery. At the 12-month visit, the patients were assessed for functional outcome, level of the pain, and satisfaction with Quick Disability of Arm, Hand and Shoulder score (QuickDASH), the visual analogue score (VAS) scale, and the scar appearance and symptom relief, respectively. Results: 39 patients were entered in this study, 3 of who had bilateral symptoms. The 42 operated hands were divided into two groups: classical incision group (n = 21) and minimal incision group (n = 21). No significant difference was discovered between the two groups considering age and sex. In addition, no significant difference was found in the variables evaluated between the two groups, except for the higher patient satisfaction with the scar appearance in minimal incision group after 12 months. Conclusion: After a one-year period, the minimal incision procedure had no priority to classical incision procedure, except for higher patient satisfaction considering the scar appearance.

Collapsed membranes within pelvic cyst: What is the diagnosis?

Collapsed membranes and daughter cysts are pathognomonic for hydatid cysts on imaging. The comma-shaped lesions, visible within the hydatid cyst in sagittal view of MRI, are collapsed membranes. Although primary hydatid cyst of pelvic cavity is rare, clinicians should remember to include hydatid cysts in differential diagnosis of pelvic cysts.

Interfragmentary motion assessment for three different fixation techniques of femoral neck fractures in young adults

BACKGROUND

Vertical femoral neck fractures in the youth could be happened in high-energy accidents, and because of dominant shearing forces, this fracture is considered as a troublesome injury with a controversy regarding selection of the best fixation method.

OBJECTIVE

The long term goal of this quasi-experimental study was to find the more stable fixation method among cannulated screws (CSs), proximal femoral locking plate (PFLP), and dynamic hip screw with derotational screw (DHS+DS) for this kind of fracture.

METHODS

Twelve fresh-frozen cadaveric femurs were assigned to three groups that were matched for mean bone mineral density and stiffness of intact bone. Vertical fractures were artificially mimicked in the specimens and fixed using three different implants, i.e. CSs, PFLP, and DHS+DS. Then, the samples were tested under incremental, cyclic, and failure loading phases.

RESULTS

The differences in all biomechanical parameters were statistically significant among tested groups (p<0.05). All biomechanical parameters for the DHS+DS method of fixation are significantly different from those corresponding to CSs (p<0.05). There were no significant differences in failure load and failure energy between the PFLP and CSs techniques (p>0.05). Also, there were no significant differences in relative stiffness and femoral head displacement between the PFLP and DHS+DS groups (p>0.05).

CONCLUSIONS

Based on the clinical assumption that restricted weight-bearing regimen is recommended in the postoperative rehabilitation protocol, the results of this study suggest that the priority order of selection for the stable fixation implant of vertical femoral neck fracture in young patients is DHS+DS, then PFLP, and finally CSs.

Communication methods and production techniques in fixed prosthesis fabrication: a UK based survey. Part 1: communication methods

Highlights the importance of dentist-technician communication.

Concludes that dentists must ensure that written prescriptions contain all the necessary information so that the dental technician can fabricate fixed prostheses correctly and without delay.

Recommendations for improved communication are made with the ultimate goal of better patient service.

Statement of the problem The General Dental Council (GDC) states that members of the dental team have to 'communicate clearly and effectively with other team members and colleagues in the interest of patients'. A number of studies from different parts of the world have highlighted problems and confirmed the need for improved communication methods and production techniques between dentists and dental technicians.

Aim The aim of this study was to identify the communication methods and production techniques used by dentists and dental technicians for the fabrication of fixed prostheses within the UK from the dental technicians' perspective. The current publication reports on the communication methods.

Materials and methods Seven hundred and eighty-two online questionnaires were distributed to the Dental Laboratories Association membership and included a broad range of topics. Statistical analysis was undertaken to test the influence of various demographic variables.

Results The number of completed responses totalled 248 (32% response rate). The laboratory prescription and the telephone were the main communication tools used. Statistical analysis of the results showed that a greater number of communication methods were used by large laboratories. Frequently missing items from the laboratory prescription were the shade and the date required. The majority of respondents (73%) stated that a single shade was selected in over half of cases. Sixty-eight percent replied that the dentist allowed sufficient laboratory time. Twenty-six percent of laboratories felt either rarely involved or not involved at all as part of the dental team.

Conclusion This study suggests that there are continuing communication and teamwork issues between dentists and dental laboratories.

Communication methods and production techniques in fixed prosthesis fabrication: a UK based survey. Part 2: production techniques

Highlights that even though clear guidelines are available, there still seems to be a lack of agreement between dentists and laboratories regarding the disinfection and quality of dental impressions.

Despite the promotion of all-ceramic crowns, this survey indicated that metal-ceramic crowns are still the most frequently prescribed for both anterior and posterior restorations.

Aim The aim of this study was to identify the communication methods and production techniques used by dentists and dental technicians for the fabrication of fixed prostheses within the UK from the dental technicians' perspective. This second paper reports on the production techniques utilised.

Materials and methods Seven hundred and eighty-two online questionnaires were distributed to the Dental Laboratories Association membership and included a broad range of topics, such as demographics, impression disinfection and suitability, and various production techniques. Settings were managed in order to ensure anonymity of respondents. Statistical analysis was undertaken to test the influence of various demographic variables such as the source of information, the location, and the size of the dental laboratory.

Results The number of completed responses totalled 248 (32% response rate). Ninety percent of the respondents were based in England and the majority of dental laboratories were categorised as small sized (working with up to 25 dentists). Concerns were raised regarding inadequate disinfection protocols between dentists and dental laboratories and the poor quality of master impressions. Full arch plastic trays were the most popular impression tray used by dentists in the fabrication of crowns (61%) and bridgework (68%). The majority (89%) of jaw registration records were considered inaccurate. Forty-four percent of dental laboratories preferred using semi-adjustable articulators. Axial and occlusal under-preparation of abutment teeth was reported as an issue in about 25% of cases. Base metal alloy was the most (52%) commonly used alloy material. Metal-ceramic crowns were the most popular choice for anterior (69%) and posterior (70%) cases. The various factors considered did not have any statistically significant effect on the answers provided. The only notable exception was the fact that more methods of communicating the size and shape of crowns were utilised for large laboratories.

Conclusion This study suggests that there are continuing issues in the production techniques utilised between dentists and dental laboratories.

Lunate Osteochondral Fracture Treated by Excision: A Case Report and Literature Review

INTRODUCTION

Lunate fracture is a rare injury. Most reports are associated with other wrist injuries such as perilunate dislocation and distal radius fracture. Isolated lunate fracture has been reported even more rarely. The choice of treatment and outcomes are consequently undetermined.

CASE PRESENTATION

In this case report we will describe a lunate avulsion fracture as an isolated injury after a fall from nine meters treated operatively by excision of the comminuted avulsed fragment. After 33 months of follow-up radiographs showed no sign of degenerative joint disorder on simple X-ray, but slight Volar Intercalated Segment Instability (VISI) by a capitolunate angle of 26 degrees was noted. Clinically, the patient was pain free near full wrist and forearm range of motion and could perform his previous vocational and recreational tasks without any limitations.

CONCLUSIONS

Despite apparently good short and mid-term clinical outcome, slight volar intercalated segment instability after 33 months of follow-up revealed that lunotriquetral ligament function was probably lost, which led to static instability. This ligament injury may be missed primarily. Excision of the avulsed osteochondral fragment should be the last option of treatment and most attempts should be tried to fix and/or restore the normal anatomy of ligamentous structure.

Comparison of Three Fixation Methods for Femoral Neck Fracture in Young Adults: Experimental and Numerical Investigations

Femoral neck fractures in young patients are usually caused by a high-energy trauma, which results in a perpendicular fracture. Although efforts are focused on preserving the femoral head in young patients, vertical femoral neck fracture is a problematic orthopedic injury due to the domination of shear forces. Due to controversy regarding which fixation method is the best choice, the purpose of this study was to find the most stable fixation method for this kind of fracture. This study includes experimental testing on cadaveric bone samples and finite element analysis (FEA) for three fracture fixation techniques, namely cannulated screws (CSs), dynamic hip screw with derotational screw (DHS + DS), and proximal femoral locking plate (PFLP). Experimental results of bone-implant stiffness, average femoral head displacement, failure load, failure energy, and relative position of the fractured fragments indicate that DHS + DS offers the strongest structure for stabilizing a vertical femoral neck fracture. Experimental data and FEA results both indicate that under static loading, the DHS + DS method of fixation produces the lowest femoral head displacement and interfragmentary movement, followed by PFLP and then CSs. The results of this research suggest that, based on the clinical assumption that a restricted weight-bearing regimen is recommended in the postoperative rehabilitation protocol, the DHS + DS method of fixation is a better choice compared to CSs and PFLP for a vertical femoral neck fracture fixation in young adults.

Combining Concentrated Autologous Bone Marrow Stem Cells Injection With Core Decompression Improves Outcome for Patients with Early-Stage Osteonecrosis of the Femoral Head: A Comparative Study

The management of early-stage osteonecrosis of the femoral head (ONFH) remains challenging. This study aimed to evaluate the effects of core decompression and concentrated bone marrow implantation on ONFH. The study recruited 28 hips with early ONFH randomly assigned into two groups of core decompression with (group A) and without (group B) bone marrow injection. Patients were evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire, Visual Analogue Scale (VAS) pain index, and MRI. The mean WOMAC and VAS scores in all patients improved significantly (P<0.001). MRI showed a significant improvement in group A (P=0.046) and significant worsening in group B (P<0.001). Bone marrow stem cell injection with core decompression can be effective in early ONFH.

Late sequelae of hip septic arthritis in children

Septic arthritis of the hip in children has multiple sequelae and may result in severe disability. Significant morbidity can be prevented by early recognition and treatment. The authors reviewed 13 children with 14 hips with sequelae of septic arthritis of the hip. All of children had history of hip septic arthritis before age of 4 years. Six were male subjects, and 7 were female subjects. We evaluated the history, clinical findings and radiographs of all children who had been treated at the Imam Khomeini hospital between 1986 and 2001 for septic arthritis of the hip. Final results of operations in patients include range of motion, presence or absence pain, joint stability, limb-length discrepancy were assessed. Three hips had mild pain in usual daily activities and one patient with cerebral palsy experienced hip instability. Most of patients (80%) had flexion contracture about 10-15 degrees .Final results showed average limb length discrepancy was about 2.8 cm. Septic arthritis of the hip in children may result in a spectrum of residual problems and the significant complications can be averted by early detection and treatment. Treatment in younger age cause better outcome.

Turbulencelike behavior of seismic time series

We report on a stochastic analysis of Earth's vertical velocity time series by using methods originally developed for complex hierarchical systems and, in particular, for turbulent flows. Analysis of the fluctuations of the detrended increments of the series reveals a pronounced transition in their probability density function from Gaussian to non-Gaussian. The transition occurs 5-10 hours prior to a moderate or large earthquake, hence representing a new and reliable precursor for detecting such earthquakes.

Comparison of Thymus vulgaris (Thyme), Achillea millefolium (Yarrow) and propolis hydroalcoholic extracts versus systemic glucantime in the treatment of cutaneous leishmaniasis in balb/c mice

BACKGROUND & OBJECTIVES

Leishmaniasis is a parasitic disease transmitted by sand flies. Many investigations are performed to find an effective and safe treatment for leishmaniasis. In this study, we evaluated the efficacy of herbal extracts of Thymus vulgaris (Thyme) and Achillea millefolium (Yarrow), propolis hydroalcoholic extract and systemic glucantime against cutaneous leishmaniasis in Balb/c mice.

METHODS

A total of 45 mice were randomised into five groups each including nine mice. They were treated with pure ethanol 70 degrees, systemic glucantime, Achillea millefolium hydroalcoholic extract, Thymus vulgaris hydroalcoholic extract and propolis hydroalcoholic extract for six weeks. The statistical tests including student t-test were used for analysis. Data were analyzed by SPSS software, ver 13.00.

RESULTS

Mean of ulcer size reduction were -17.66, -22.57, 43.29, 36.09 and 43.77% for the alcohol, glucantime, yarrow, thyme and propolis groups, respectively. The results were suggestive that Thymus vulgaris, Achillea millefolium and propolis hydroalcoholic extracts were significantly more effective in reduction of ulcer size as compared with glucantime (p = 0.006, 0.002 and 0.008, respectively).

INTERPRETATION & CONCLUSION

Our results are suggestive that Thymus vulgaris, Achillea millefolium and propolis extracts are effective for treatment of cutaneous leishmaniasis in mice. Regarding these results, we suggest that efficacy of these extracts alone or in combination are evaluated against human cutaneous leishmaniasis as a randomized clinical trial.

Periosteal osteoblastoma: report of a case with a rare histopathologic presentation and review of the literature

Osteoblastoma is an uncommon benign bone tumor most commonly located in the vertebral column or metaphysis of a long bone. Periosteal location is rare. We report a periosteal-based osteoblastoma, arising from the proximal tibia, in a 20-year-old woman who presented with knee swelling and pain of 2-year duration. Imaging studies showed a metaphyseal surface-based lesion with patchy radiodensities. The cortico-medullary junction was intact. The lesion was totally excised. Histopathologic evaluation disclosed immature bone and osteoid deposition in a vascularized stroma, associated with numerous osteoblasts and osteoclasts rimming the bony trabeculae. Plate-like arrangements of cartilage in the margin of the neoplastic tissue were also identified. At 16 months postoperatively, the patient was well without recurrence. Although extremely unusual, the presence of cartilage does not necessarily exclude the diagnosis of osteoblastoma.

Antiprogestins suppress basal and activin-stimulated follicle-stimulating hormone secretion in an estrogen-dependent manner

Previous studies from our laboratory, demonstrating that suppression of serum FSH by RU486 requires a high estrogen (E) background, suggested that E-inducible progesterone receptors play a role in the regulation of FSH secretion. We demonstrated further that the type II antiprogestin RU486 and the type I antiprogestin ZK98299 both suppressed the elevated serum FSH and FSHbeta messenger RNA levels similarly on the evening of proestrus, but had divergent effects on the morning of estrus, when only RU486, but not ZK98299, lowered the elevated serum FSH level (secondary FSH surge). In the present work we used primary anterior pituitary cell culture to examine whether RU486 caused direct, E-dependent suppression of basal and recombinant human activin A (activin)-induced FSH secretion in the gonadotrope and to compare this direct effect, if any, with that of ZK98299. Primary cell cultures were prepared from anterior pituitaries collected from cycling female rats either on metestrous or proestrous morning and cultured in DMEM, supplemented with charcoal-stripped serum without or with 10 nM estradiol (E2) for 96 h; exposure to test agents occurred during the last 48 h of culture. FSH released into the medium and intracellular FSH content were determined by RIA. In cells from the anterior pituitary of metestrous rats cultured in E2-free medium, neither antiprogestin (10 nM) affected FSH release; in contrast, when cells were cultured in medium to which E2 had been added, both antiprogestins caused profound suppression of both basal and activin (10 ng/ml)-stimulated FSH release. In cell cultures from proestrous rats, both antiprogestins caused a slight, but significant, suppression of basal FSH release even in the absence of added E2; activin-stimulated FSH release, however, was not affected. Upon exposure of the cells from proestrous rats to E2, the antiprogestins potently suppressed both basal and activin-stimulated FSH secretion. Because the foregoing incubations were performed in culture medium devoid of progesterone (P4), the actions of the antiprogestins on FSH secretion were independent of the natural ligand. Addition of P4 (10 nM) to the cell cultures stimulated basal and activin-induced FSH release more in the presence than in the absence of E2. The FSH response to P4 was completely blocked by both antiprogestins in both the absence and presence of E2. Finally, both RU486 and ZK98299 blocked the stimulatory effect of corticosterone (1 microM) on FSH secretion. The observed effects of P4 and antiprogestins were specific for FSH secretion; LH secretion was not similarly suppressed by either antiprogestin, but was, in fact, stimulated by ZK98299 in E2-treated cells. We conclude that 1) E2-inducible progesterone receptors interact with activin-mediated signal transduction to regulate FSH secretion, and 2) unlike on the morning of estrus in vivo, RU486 and ZK98299 affect FSH secretion similarly in the gonadotrope in vitro.

The antiprogestins RU486 and ZK98299 affect follicle-stimulating hormone secretion differentially on estrus, but not on proestrus

Previous in vivo studies from our laboratory indicated that administration of the antiprogestin RU486 on proestrus suppresses both the preovulatory gonadotropin surges and the secondary FSH surge, suggesting a role for the progesterone receptor (PR) in the generation of these surges. The present study was designed to test the effects of another antiprogestin, ZK98299, which has been reported to block the PR through a mechanism different from that of RU486, on gonadotropin secretion in vivo. RU486 and ZK98299 (2 and 6 mg/kg) were administered s.c. at 1230 h on proestrus; uterine intraluminal fluid content, serum gonadotropins, and gonadotropin subunit messenger RNAs (mRNAs) were determined at 1830 h on proestrus and at 0900 h on estrus. At 1830 h on proestrus, both RU486 and ZK98299 at both doses caused equal suppression of the preovulatory FSH surge and FSHbeta mRNA. Both antiprogestins also equally attenuated the preovulatory LH surge at this time, with the higher doses causing greater suppression. In contrast, at 0900 h on estrus, the antiprogestins affected serum FSH differentially; only RU486 suppressed the secondary FSH surge despite the fact that both drugs prevented the release of uterine intraluminal fluid, confirming blockade of progesterone action at the level of the uterus. Neither drug had a significant effect on FSHbeta mRNA at 0900 h on estrus. ZK98299 at the higher dose caused a small, but significant, increase in serum LH. In a subsequent experiment, we compared the effects of RU486 and ZK98299 (6 mg/kg, s.c.), administered at 1230 h on proestrus, on serum FSH raised above the natural secondary FSH surge on the morning of estrus by passive immunization with an antiserum to inhibin-alpha (anti-I) at 1700 h on proestrus. Consistent with the results of the first experiment, both antiprogestins blocked the release of uterine intraluminal fluid, but only RU486 lowered serum FSH in both the normal sheep serum-treated controls and anti-I-treated rats; in contrast, ZK98299 actually increased serum FSH in the normal sheep serum-treated control animals. ZK98299 also increased FSHbeta mRNA in the control group; RU486, on the other hand, reduced FSHbeta mRNA only in the anti-I group. The results demonstrate unequivocally that whereas the effects of the two antiprogestins on serum FSH and FSHbeta mRNA are similar on proestrus, they are divergent on estrus. The data suggest that the functional state of the PR/transcriptional activation complex in the gonadotrope on the morning of estrus is different from that on the evening of proestrus.