Evidence of macrophage modulation in the mouse pubic symphysis remodeling during the end of first pregnancy and postpartum

In mouse pregnancy, pubic symphysis (PS) remodels into an elastic interpubic ligament (IpL) in a temporally regulated process to provide safe delivery. It restores at postpartum to assure reproductive tract homeostasis. Recently, macrophage localization in the IpL and dynamic changes in the expression of inflammatory mediators observed from the end of pregnancy (D18, D19) to early days postpartum (1dpp, 3dpp) highlighted the necessity of the identification of the key molecules involved in innate immune processes in PS remodeling. Therefore, this study uses morphological and high-sensitivity molecular techniques to identify both macrophage association with extracellular matrix (ECM) remodeling and the immunological processes involved in PS changes from D18 to 3dpp. Results showed macrophage association with active gelatinases and ECM components and 25 differentially expressed genes (DEGs) related to macrophage activities in interpubic tissues from D18 to 3dpp. Additionally, microarray and proteomic analysis showed a significant association of interpubic tissue DEGs with complement system activation and differentially expressed proteins (DEPs) with phagocytosis, highlighting the involvement of macrophage-related activities in mouse PS remodeling. Therefore, the findings suggest that PS ECM remodeling is associated with evidence of macrophage modulation that ensures both IpL relaxation and fast PS recovery postpartum for first labor.

Influence of pubic symphysis stiffness on pelvic load distribution during single leg stance

This study focuses on the influence of the softening and stiffening of pubic symphysis on the load distribution within the bones of the pelvic ring under the physiological loadings of the single leg stance. Muscle forces and joint reaction forces were first determined by inverse dynamics and applied to a linear finite element model of the pelvis. With normal pubic symphysis stiffness, high Von Mises stresses are located on the anterior surface to the sacrum around the sacroiliac joint and on the superior ramus, both on the side of the weight-bearing leg. Softening of the pubic symphysis redirects the load backward, decreases the stresses at the anterior pelvis, and increases them at the posterior pelvis. A stiffening of the pubic symphysis redirects the load forward, increases the load on the posterior pelvis, and decreases them at the anterior pelvis. This investigation highlights the significance of the pubic symphysis on the load distribution of the pelvis and in maintaining the integrity of the structures. Its role should not be neglected when analyzing the pelvis.

Evolution of the human pelvis and obstructed labor: new explanations of an old obstetrical dilemma

Without cesarean delivery, obstructed labor can result in maternal and fetal injuries or even death given a disproportion in size between the fetus and the maternal birth canal. The precise frequency of obstructed labor is difficult to estimate because of the widespread use of cesarean delivery for indications other than proven cephalopelvic disproportion, but it has been estimated that at least 1 million mothers per year are affected by this disorder worldwide. Why is the fit between the fetus and the maternal pelvis so tight? Why did evolution not lead to a greater safety margin, as in other primates? Here we review current research and suggest new hypotheses on the evolution of human childbirth and pelvic morphology. In 1960, Washburn suggested that this obstetrical dilemma arose because the human pelvis is an evolutionary compromise between two functions, bipedal gait and childbirth. However, recent biomechanical and kinematic studies indicate that pelvic width does not considerably affect the efficiency of bipedal gait and thus is unlikely to have constrained the evolution of a wider birth canal. Instead, bipedalism may have primarily constrained the flexibility of the pubic symphysis during pregnancy, which opens much wider in most mammals with large fetuses than in humans. We argue that the birth canal is mainly constrained by the trade-off between 2 pregnancy-related functions: while a narrow pelvis is disadvantageous for childbirth, it offers better support for the weight exerted by the viscera and the large human fetus during the long gestation period. We discuss the implications of this hypothesis for understanding pelvic floor dysfunction. Furthermore, we propose that selection for a narrow pelvis has also acted in males because of the role of pelvic floor musculature in erectile function. Finally, we review the cliff-edge model of obstetric selection to explain why evolution cannot completely eliminate cephalopelvic disproportion. This model also predicts that the regular application of life-saving cesarean delivery has evolutionarily increased rates of cephalopelvic disproportion already. We address how evolutionary models contribute to understanding and decision making in obstetrics and gynecology as well as in devising health care policies.

Quantifying the force transmission through the pelvic joints during total hip arthroplasty: A pilot cadaveric study

BACKGROUND

Total hip arthroplasty is one of the most successful and cost effective procedures in orthopedics. The purpose of this study is to investigate force transmission through the sacroiliac joint as a possible source of post-operative pain after total hip arthroplasty through the following three questions: Does the ipsilateral sacroiliac joint, contralateral sacroiliac joint, or pubic symphysis experience more force during placement? Does the larger mallet used to seat the implant generate a higher force? Does the specimen's bone density or BMI alter force transmission?

METHODS

A solid design acetabular component was impacted into five human cadaver pelves with intact soft tissues. The pressure at both sacroiliac joints and the pubic symphysis was measured during cup placement. This same procedure was replicated using an existing pelvis finite element model to use for comparison.

FINDINGS

The location of the peak force for each hammer strike was found to be specimen specific. The finite model results indicated the ipsilateral sacroiliac joint had the highest pressure and strain followed by the pubic symphysis over the course of the full simulation. The heft of the mallet and bone mineral density did not predict force values or locations. The largest median force was generated in extremely obese specimens.

INTERPRETATION

Contrary to previous ideas, it is highly unlikely that forces experienced at the pelvic joints are large enough to contribute post-operative pain during impaction of an acetabular component. These results indicate more force is conveyed to the pubic symphysis compared to the sacroiliac joints.

Two-leg alternate loading model--a different approach to biomechanical investigations of fixation methods of the injured pelvic ring with focus on the pubic symphysis

The dorsal component of the pelvic ring is considered to be the most essential element for the stability of the pelvic ring. None of the current biomechanical set-ups include the effect of shear stresses by alternating loads that the pelvic ring has to withstand during walking. We hypothesize that a biomechanical test set-up with two-leg alternate loading will lead to stress imitation at the pubic symphysis that are more similar to existing strains than other test set-ups, and would, therefore, be more adequate for biomechanical testing of fixation methods. A new biomechanical two-leg standing test set-up with an alternate pelvic loading was constructed and was validated with six human pelvises from fresh frozen cadavers. Three-dimensional motion tracking was performed. The specimens were subjected to a non-destructive quasi-static test and a non-destructive cyclic test with progressive load amplitude from 170 N to 340 N over 1000 cycles. The initial rotational 'range of motion' and 'mean displacement' around the vertical axis for a pre-load of 170 N was about 0.3° and 0.2°, respectively, increasing by 0.1-0.2° at a load of 340 N. The rotation around the vertical axis and the translation along the frontal horizontal axis confirmed the stability of the pubic symphysis. The rate of ascend of displacements decreased, once the rotation reached 1° or the translation reached 1mm. The current biomechanical test set-up was compared with previous clinical findings, and the method was found valid for measuring inter-segmentary movements at the pubic symphysis.

The mouse pubic symphysis as a remodeling system: morphometrical analysis of proliferation and cell death during pregnancy, partus and postpartum

Marked changes in mice pubic symphysis occur by the end of pregnancy. Tissue remodeling involves a dynamic balance between cell proliferation and programmed cell death as well as changes in the extracellular matrix components. Therefore, it is important to consider both of these cellular behaviors when investigating the mechanism that regulates interpubic tissue remodeling, growth during late pregnancy and partus ensuring involution during the postpartum period. Proliferating and programmed death cells were identified by immunohistochemistry (proliferating cell nuclear antigen and TUNEL detection, respectively) and the rates at which these processes occurred were determined by morphometric analysis. The results demonstrated that cellular proliferation was intense during the period of ligament formation, from D15 to D18, thereafter abruptly declining on D19. From parturition (D19) onwards, an ever-increasing decline in the cellular proliferation levels could be observed. The quantitative analyses of cellular death showed opposite results when compared to cellular proliferation. During early pregnancy the cycle of cellular renovation was clearly proliferative and during late mouse pregnancy the cycle was directed by programmed cellular death. Although the high levels of cellular death during postpartum involution could be shown by the TUNEL-positive cells, we were unable to observed picnotic nucleus at the light microscopy.

Sacral orientation revisited

STUDY DESIGN

A descriptive study of the sacral anatomic orientation (SAO) and its association with pelvic incidence (PI).

OBJECTIVE

To introduce the concept of SAO, establish a method for measuring it, and evaluate its association with pelvic orientation.

SUMMARY OF BACKGROUND DATA

Pelvic orientation (PO) is considered a key factor in spinal shape and balance. Sacral slope (SS), PI, and pelvic tilt (PT) are the most frequently used parameters for evaluating PO. Nevertheless, the association between the anatomic orientation of the sacrum and these parameters has never been established. The aim of the present study is to define the anatomic orientation of the sacrum, to establish a reliable method for measuring it, and to examine its association with PI.

METHODS

SAO was defined as the angle created between the intersection of a line running parallel to the superior endplate surface of the sacrum and a line running between the anterior superior iliac spine (ASIS) and the anterior-superior edge of the symphysis pubis. Methods for measuring SAO and PI on both skeletal populations and living individuals are described. The study was carried out on 424 skeletons (articulated pelves) using a three-dimensional digitizer and on 20 adult individuals using CT three-dimensional images (volume-rendering method). Reliability (intratester and intertester) was assessed using intraclass correlation test. A regression analysis was carried out to evaluate the association between the two measurements.

RESULTS

The mean SAO and PI in the human skeletal population were found to be 48.46 degrees +/- 10.17 degrees and 54.08 degrees +/- 12.64 degrees , respectively and of the living individuals (CT) 52.76 degrees +/- 10.31 degrees and 57.14 degrees +/- 13.08 degrees , respectively. SAO and PI measurements were highly correlated (r = -0.824, and r = -0.828, P < 0.001 for skeletal material and living individuals, respectively). PI can be predicted via SAO, i.e., PI = [-0.971 x SAO] + 101.16 degrees .

CONCLUSIONS

The newly suggested parameter (SAO) may be an important tool in defining the sagittal shape of the spine and understanding its association with spinal diseases.

Effect of pubic symphysiodesis on acetabular rotation and pelvic development in guinea pigs

OBJECTIVE

To evaluate the effect of premature closure of the pubic symphysis on pelvic development.

ANIMALS

18, 21-day-old male guinea pigs.

PROCEDURE

The pubic symphysis was surgically approached in 10 guinea pigs of the symphysiodesis group and in 4 of the sham-operated group; 4 guinea pigs served as unoperated controls. The pubic symphysis was destroyed by use of electrocautery in the 10 guinea pigs of the symphysiodesis group. All guinea pigs were allowed to grow to skeletal maturity and were euthanatized at 33 weeks of age. Body weight was recorded throughout the study and was compared between groups. Histologic examination of the symphyses confirmed premature closure of the pubic symphyseal growth plates in guinea pigs of the symphysiodesis group. Pelvic measurements taken from pretreatment radiographic views and from video images of harvested pelves were compared between groups.

RESULTS

There were no significant differences between groups with regard to pretreatment radiographic variables, rate of weight gain, or body weight at any time. Pubic symphysiodesis resulted in significant narrowing of the caudal aspect of the pelvis, narrowing and shortening of the pubic bones, and outward rotation of the acetabula.

CONCLUSIONS

The pubic symphyseal growth plates contribute significantly to development of the pelvis. Premature closure of these growth plates (pubic symphysiodesis) results in outward rotation of the acetabula, which might be beneficial in some cases of can be hip dysplasia; however, this rotation is accompanied by concomitant narrowing of the caudal aspect of the pelvis.

Chemical synthesis of a Zwitterhormon, insulaxin, and of a relaxin-like bombyxin derivative

The structural motif of insulin and relaxin is frequently seen in molecules of divergent functions and origins. The insect developmental factor bombyxin, the relaxin-like factor from Leydig cells, and the insulin-like factor 4 (INSL4) all are made of two disulfide-linked chains and have one disulfide bond within the A-chain. The polyclonal antibody R6, which was raised against porcine relaxin, reacts with a wide variety of naturally occurring relaxins from primates, marine and terrestrial mammals, and elasmobranchs but does not recognize insulin. The antibody binds mainly to the arginines that occur in the N, N+4 positions in the B-chains of all relaxins which also constitute the receptor-binding site. The receptor-binding haptens were incorporated by total synthesis into human despentapeptide insulin and bombyxin II, a developmental factor from the silk moth Bombyx mori. In the process the insect factor became a perfect antigen for the anti-relaxin antibody, whereas the human insulin was transformed into a bona fide relaxin. The conversion was affected by changing four critical residues so that the insulin activity was retained to the extent of 10% of the original level. This, to the best of our knowledge, is the first designer protein to incorporate two unrelated biological functions in one primary sequence, and we are therefore proposing that, analogous to zwitterion, the generic name "Zwitterhormon" (German spelling) be used for this type of construct.

[Biomechanics of the pubic symphysis. Which forces lead to mobility of the symphysis in physiological conditions?]

For estimation of the loads of fixation devices, physiological movements and acting forces at the symphysis pubis are examined. Experimentally, Walheim determined the movements of the pubic symphysis under physiological conditions (one-leg stance, walking): there is no effective mobility in the horizontal direction. During the one-leg stance he observed symphyseal mobility of up to 2.6 mm (Phi 1.2 mm) in the vertical direction and 1.3 mm (Phi 0.6 mm) in the sagittal direction. During walking he found symphyseal mobility of up to 2.2 mm (Phi 0.9 mm) in the vertical direction and 1.3 mm (Phi 0.6 mm) in the sagittal direction. Until now the forces leading to symphyseal mobility have not been estimated either experimentally or mathematically. In our experimental study we examined ten fresh cadaver anterior pelvic rings by means of a multidirectional force-mobility measurement. Maximal physiological movements, as determined by Walheim, were increasingly induced in ten equal steps, and the forces required were measured for every single step. Out of the resulting force-mobility curves for the ten cadaver specimens the mean force required (with standard deviation) was calculated for each of the ten measure points, separately for the vertical (y-) direction and sagittal (z-) direction. The values were graphically transferred, and a regression curve was created. This curve allows the acting force to be estimated for every movement of the pubic symphysis: During the one-leg stance the mean force to induce mean mobility is 169 N in vertical direction and 148 N in sagittal direction; for maximal mobility a force of 398 N in the vertical direction and 148 N in the sagittal direction is necessary. During walking, the force required to induce mean movement of the symphysis pubis is 120 N in the vertical direction and 68 N in the sagittal direction; for maximal mobility 333 N is required in the vertical direction and 136 N in the sagittal direction. For mobilization of patients with a symphyseal rupture (type Tile B 1) with partial weight-bearing, neutralization of the mean acting forces during the one-leg stance (169 N in the vertical direction, 68 N in the sagittal direction) must be achieved by an adequate fixation device. In cases where full weight bearing is desirable, such as in patients with limited compliance, stability can only be reached by neutralization of the maximal acting forces during walking (333 N in the vertical direction, 136 N in the sagittal direction).

Load transfer across the pelvic bone

Earlier experimental and finite element studies notwithstanding, the load transfer and stress distribution in the pelvic bone and the acetabulum in normal conditions are not well understood. This hampers the development of orthopaedic reconstruction methods. The present study deals with more precise finite element analyses of the pelvic bone, which are used to investigate its basic load transfer and stress distributions under physiological loading conditions. The analyses show that the major part of the load is transferred through the cortical shell. Although the magnitude of the hip joint force varies considerably, its direction during normal walking remains pointed into the anterior/superior quadrant of the acetabulum. Combined with the fact that the principal areas of support for the pelvic bone are the sacro-iliac joint and the pubic symphysis, this caused the primary areas of load transfer to be found in the superior acetabular rim, the incisura ischiadaca region and, to a lesser extent, the pubic bone. Due to the 'sandwich' behavior of the pelvic bone, stresses in the cortical shell are about 50 times higher than in the underlying trabecular bone (15 to 20 MPa vs 0.3-0.4 MPa at one-legged stance). Highest intraarticular pressures are found to occur during one-legged stance and measured about 9 MPa. During the swing phase, these pressures decrease less than linearly with the magnitude of the hip joint force. Muscle forces have a stabilizing effect on the pelvic load transfer. Analysis without muscle forces show that at some locations stresses are actually higher than when muscle forces are included.

The effect of oxytocin receptor blockade on parturition in guinea pigs

The mechanism of the onset of labor is unknown in humans and guinea pigs. Contrary to most other species, progesterone withdrawal appears not to precede the onset of labor. To elucidate the role of oxytocin in the onset and maintenance of labor, guinea pigs were fitted with vascular catheters, an intraabdominal pressure catheter and an array of uterine electromyogram electrodes. An oxytocin antagonist (des-Gly9-[D-Trp2,Thr4,Orn8]dC6-oxytocin, 20 micrograms/kg per h, n = 11) or saline solution (n = 12) was infused starting on day 66 of gestation (term is 69 d). Oxytocin receptor blockade resulted in decreased uterine activity and a prolonged expulsive phase (second stage) of labor. Fetal delivery was delayed and fetal mortality was increased. The onset of the expulsive phase of labor was delayed but maximum uterine activity occurred in time together with a timely change in uterine electromyogram activity from a prepartum to a postpartum pattern following an unaltered progressive increase in baseline uterine activity. This indicates that oxytocin is requisite for the normal progress of the first and second stage of labor, but has no involvement in the mechanism of the onset and the timing of labor.

Diurnal variation of serum progesterone, but not relaxin, prolactin, or estradiol-17 beta in the pregnant bitch

The concentrations of progesterone (P), relaxin (Rlx), estradiol (E2) and PRL were measured by specific RIAs in serum samples collected twice daily at 8:00 am and 3:00 pm at weekly intervals after mating and until whelping in five Labrador Retriever bitches. From weeks 3 to 6 of pregnancy, P exhibited a conspicuous and statistically significant diurnal pattern (P less than 0.05), its serum concentration being approximately twice as high at 8:00 am as at 3:00 pm. A similar but nonsignificant trend was observed weeks 2, 7, and 8, and the overall ratio of the am/pm P concentrations was 2.4 +/- 0.28 (P less than 0.001). Rlx, E2, and PRL did not show a diurnal pattern at any time during pregnancy. The glandular sources and regulation of secretion of Rlx were further investigated. Rlx bioactivity was detected in canine placentas and ovaries, providing supportive evidence that these organs may be a dual source of the hormone in canine pregnancy. Injection of ovine PRL in three pseudopregnant bitches significantly increased serum P concentration as compared with seven untreated pseudopregnant controls, but Rlx was not detectable in serum before, during or after PRL treatment. The data support the view that Rlx and P are independently regulated in the bitch; PRL may be a regulator of P, but not of Rlx secretion. However, as PRL showed no diurnal changes in concentration, it does not appear to be directly responsible for the diurnal pattern exhibited by P.

The pharmacokinetics and pharmacodynamics of a human relaxin in the mouse pubic symphysis bioassay

The effects of dose, route, regimen, and the presence or absence of a repository vehicle [benzopurpurine (BPP)] were determined for a human relaxin (hRlx) in the mouse pubic symphysis bioassay. Administration of 88 micrograms/kg hRlx sc in 1% BPP resulted in delayed, prolonged absorption. Although peak hRlx concentrations were lower, serum concentrations remained elevated longer in the presence of BPP compared to a single sc administration of hRlx in saline at the same dose. The bioavailabilities with and without BPP were similar (109 and 96%, respectively). While the pharmacodynamic effect (i.e. lengthening of the pubic ligament in estrogen-primed mice) was approximately maximum at 88 micrograms/kg hRlx sc with BPP, single sc administration of hRlx without BPP up to 264 micrograms/kg had no effect on pubic ligament length. In the absence of the BPP vehicle, manipulation of the regimen (e.g. multiple sc doses) showed that emulation of the serum concentration-time profile observed for hRlx in the presence of BPP resulted in similar pharmacodynamic effects. It appears that BPP delays the absorption of hRlx after sc administration, resulting in prolonged, elevated hRlx serum concentrations. hRlx has been shown to be effective in this model without BPP if it is administered by a multidose sc schedule. As has been observed with other protein therapeutics, the dosage regimen employed for hRlx delivery appears to be an important determinant of the expression of its pharmacodynamic effects.

Relaxin and the radiolucent fissure in the symphysis pubis during pregnancy: the gas phenomenon

A vertical radiolucent fissure is frequently seen in the symphysis pubis on x-ray pelvimetry studies. This phenomenon is illustrated and discussed. It appears to be a parameter of targeted relaxin softening and stretching of the symphysis.

Mobility of the pubic symphysis. In vivo measurements with an electromechanic method and a roentgen stereophotogrammetric method

Mobility of the pubic symphysis can be measured in vivo by two new methods. One is electromechanic (EM), with steel pins inserted into the bone. The other is roentgen stereophotogrammetric analysis (RSA), with tantalum bone markers implanted into the hip bones. With the first method, movements are directly registered with resistive transducers mounted on the pins. With the second method, movements are deduced with kinematic analysis from roentgen stereophotogrammetric measurements of the positions of the bone markers. Both methods have high precision, about 0.1 mm for translations and 0.1 degrees for rotations. The methods were used in two young volunteers, a man and a woman. In provocative tests with identical loading (alternating, active straight-leg raising in the supine position and standing on alternating left or right leg) there was a good correlation between the two methods. The measured values, i.e., translations of up to 2 mm and rotations of up to 3 degrees, form a basis for more comprehensive studies of normal and pathologic mobility of the pubic symphysis.

Relaxin

The past decade has seen major advances in understanding the chemistry of relaxin. Sensitive radioimmunoassays have allowed description of the secretion patterns of relaxin in several species. It is likely that technical advances in the near future will provide significant quantities of human relaxin as well as monoclonal antibodies to various relaxins. These tools should clarify the physiological roles of relaxin, elucidate its mechanisms of action, and enable testing of human relaxin as a potentially useful pharmacological agent.

Mobility of the pubic symphysis. Measurements by an electromechanical method

Two pins were inserted, one on each side of the symphysis in 15 volunteers and four cadavers. Movements between the pins were registered by two transducers. Symphyseal movements were small. Translations in the transverse and sagittal directions were around or below 1 mm. Rotations in the frontal and sagittal planes were below 1.5 degrees. Movements in the vertical direction were around 2 mm in both sexes. Higher values were observed in multiparous than in nulliparous volunteers.

Relaxin--a review

Relaxin is a polypeptide hormone, similar in structure to insulin and has been found in the female of all species studied. The corpus luteum of pregnancy is the main source of relaxin in many species but in others the decidua is apparently of greater importance. It has also been found in other tissues; e.g. prostatic fluid, testis and ovary. First discovered and extracted from the corpora lutea of pregnant sows in an impure form in 1926, it was found to relax the pubic ligament of the oestrogen primed guinea-pig. It was named after this action, but has since been found to have many other possible roles, including preparation of the endometrium for implantation, inhibition of uterine activity in early pregnancy, remodelling of the uterine stroma during pregnancy, cervical ripening and the initiation of parturition. Relaxin's main cellular action in pregnancy may be to drive collagen biosynthesis in its target organs, thus facilitating the remodelling of the connective tissue. Due to the impurity of relaxin preparations used in clinical trials until the mid-1970's, the role of relaxin in the human has been in doubt. Porcine and rat relaxins have now been highly purified and their detailed structure is known. Human relaxin awaits adequate isolation, purification and characterization, and is not yet available for laboratory and clinical trials. However, the recent preparation of purified porcine relaxin for clinical trials and the availability of specific radioimmunoassays for this relaxin together with the identification of relaxin receptor sites, are rapidly helping to establish the concept that relaxin is indeed an important hormone both in human reproduction and in other physiological processes.

The influence of adrenalectomy on the biomechanical properties of collagenous structures of rats in the post-partum phase

Pregnancy influences the functional properties of both genital and extragenital connective tissues. The sex hormones induce a major part of these changes but also corticosteroids may play a role, as their concentration is elevated during pregnancy and early post-partum. The biomechanical properties of the pubic symphysis, muscle tendon and skin of intact and adrenalectomized rats during the first ten days of the post-partum phase were investigated. For the pubic symphysis and the muscle tendon of the intact animals there was a decrease of the stiffness in the early post-partum phase followed by a restoration. For the adrenalectomized animals there was no such initial decrease, which indicates that relaxation during pregnancy has been less pronounced. However, the strength of muscle tendons from the adrenalectomized animals was markedly decreased during the post-partum phase. The stiffness of the skin from the intact animals was increased in the early post-partum period. The increase was also found in adrenalectomized animals, but here the strength and stiffness were not only restored to the intact level but became further reduced during the post-partum period. It seems therefore that the adrenal glands not only participate in the development of adaptive changes during pregnancy, but also play a role in the stabilization of extragenital connective tissues in the post-partum phase.

[Fine structure of the public symphysis in the mouse]

Classical histological descriptions of the modifications of the mouse pubic symphysis (PS) during pregnancy did not take sufficient account of its structural heterogeneity. Precise morphological study of the PS, in adult male and virgin female mice, was carried out under light and electronic microscopy. Our observations on pregnant females are still imcomplete. Two regions of the PS should be distinguished according to their structure and evolution during pregnancy. The cranial region shows diarthrodial articular characteristics. This region disappears in the female during the first pregnancy and is not reconstituted after parturition. The caudal region comprises two types of cells in the female : typical chondrocytes and a peculiar cell-type whose function has yet to be defined. The latter seems to be responsible for the loose structure of the symphyseal cartilage and to contribute to the development of pseudocavities in the ligament in the final days of pregnancy. It is possible that such cells may be stimulated by relaxin and may secrete a hydrophilic factor such as hyaluronic acid.

[The hip joint arthrodesis. A clinical and experimental study on the effective ankylosis of the hip joint]

It could be demonstrated by clinical, electromyographical, biomechanical and experimental investigations that only a flexed position of 25-30 degrees in medial position between abduction and adduction and in an external rotated position of 5-10 degrees of arthrodesis of the hip the impairment of the periankylotic locomotor centers is minimal.

Changes in the bone and cartilage of the symphysis pubis of the mouse during pregnancy and after parturition, as revealed by metachromatic staining and the periodic acid-Schiff technique

A re-investigation has been made of the histological changes in the tissues of the symphysis pubis of the mouse during the first pregnancy and after parturition, using the techniques of metachromatic staining with toluidine blue, the McManus-Hotchkiss periodic acid-Schiff (p.a.s.) reaction, and basophilic staining with haematoxylin.

During the last week of pregnancy two maj or changes take place: (1) resorption of the anteromedial bony walls of the innominates leading to shortening of the symphysis, and (2) transformation of the symphysial cartilage, manifested by loss of metachromasia and basophilia and ability to react with p.a.s., leading to ultimate disappearance of stainable chondroid matrix and its replacement first by argyrophil and then by collagenous connective tissue. Further resorption of bone from the symphysial walls of the innominates and, probably, retention of fluid in the newly formed connective tissue helps to widen the interpubic gap.

After parturition, the collagenous connective tissue which had replaced the cartilage and resorbed bone reverts to a mesenchyme-like tissue, the cells of which differentiate into osteoblasts or chondroblasts or haemopoietic cells. Cartilage differentiates by deposition of metachromatic chondroid matrix around chondroblasts, the matrix becoming more and more metachromatic, p.a.s.-positive and basophilic. Bone differentiates, first in connective tissue, later by endochondral ossification. Marrow begins to differentiate even before the bone which will confine it is laid down.

The effect of hyaluronidase on metachromasia, basophilia and reaction to p.a.s. of the symphysial tissues is described, and its significance discussed in relation to the pregnancy and post-partum changes.