Ontogeny and evolution of pelvic diameters in anthropoid primates and in Australopithecus afarensis (AL 288-1)

Pelvic diameters (both anteroposterior [AP] and transverse [TR]) were investigated in a series of anthropoid primates. The ratio of diameters (AP/TR) in each of three pelvic planes (inlet, midpelvis, and outlet) was calculated. In addition to the above, the length of the iliac, pubic, and ischial axes and the angles between these axes were determined. The AP/TR ratio at the pelvic inlet is (reported in millimeters, +/- SD, unless otherwise specified) 1.81 +/- 0.27 in New World monkeys (Cebidae) and Macaca mulatta; 1.53 +/- 0.17 in hylobatids and pongids; 0.87 +/- 0.08 in Homo sapiens; and 0.58 in Australopithecus afarensis (AL 288-1). The AP/TR ratio in the midpelvis is 1.61 +/- 0.23 in nonhominid primates (Cebidae, M. mulatta, hylobatids, and pongids), 1.12 +/- 0.11 in humans, and 0.59 in AL 288-1. In monkeys (Cebidae and M. mulatta), hylobatids, pongids, H. sapiens, and AL 288-1, the ratios of the length of the pubic axis over the ischial axis were 0.84 +/- 0.06, 0.95 +/- 0.07, 1.10 +/- 0.15, and 1.46, respectively; the pubis-ilium angles were 96 +/- 11, 120 +/- 10, 131 +/- 11, and 147 degrees, respectively; and the ischium-pubis angles were 106 +/- 11, 86 +/- 8, 96 +/- 7, and 68 degrees, respectively. In none of these pelvic features was AL 288-1 "intermediate" between pongids and H. sapiens. The anatomical peculiarities of the pelvis in AL 288-1 are explained primarily as the result of early adaptation to erect posture, which resulted in the reduction of the distance between the sacroiliac joint and the hip joint. As a consequence, the sacral promontory moved toward the pubic symphysis, and this resulted in shortening of the AP diameter and widening of the TR diameter at the pelvic inlet.     

Evolution of the sacrum in hominoids

In order to study the formation of the sacrum during the primate evolution, a new way of numbering mammalian vertebrae is presented; this demonstrates that the thoracolumbosacral complex is fixed at 22 vertebrae in 80% and at 22 +/- 1 in 100% of the cases. The shift of a vertebra from one type to another occurs either at the thoracolumbar or at the lumbosacral junction and not at the cervicothoracic junction. Rarely does the shift take place at the sacrococcygeal junction. Data from 318 primates reveal that the seven original lumbar vertebrae of the Old World monkeys are reduced in the great apes by a caudad "thoracization" of one to two lumbar vertebrae and a cephalad sacralization of one to four lumbar vertebrae. In the apes, sacralization is not total and different stages that are intermediate between lumbar and sacral are described. In Homo sapiens there is a total sacralization of the last two original lumbar vertebrae. In addition, development of the sacral wings (alae) is minimal in apes and reaches its maximum in hominids. The tendency of the hominoid sacrum to incorporate the last lumbar vertebrae and to widen markedly provides for an enhanced articulation of the sacrum with the ilium and offers a firm base of support for the trunk during erect posture. This is necessary for the support of the weight of the trunk above the sacrum and for the stabilization of the body during bipedal posture and locomotion. Encephalization did not play any major role in the widening of the sacrum since the former by far preceded the latter.     

Evolution of the lumbosacral angle

The lumbosacral angle (LSA) was studied in 131 children ranging in age from birth to 5 years. This angle increases from an average of 20 degrees at birth to an average of 70 degrees at the age of 5 years; it remains at that level thereafter. This study demonstrates that the formation of the LSA is not related to increasing age, height, or weight. Nor do obstetrical requirements seems to play any major role in the formation of the lumbosacral angle. Rather, it appears that the development of the LSA is related to the progressive acquisition of erect posture and the ontogeny of bipedal locomotion. This angle is almost nil in the nonprimate mammals (who only infrequently stand erect). It is minimal in monkeys who occasionally assume bipedal postures and increases somewhat in living apes who engage in facultative bipedal positional behavior. In the early australopithecines, the LSA is increased over that in apes, and it reaches its maximum in Homo sapiens. Deviations from normal and healthy erect posture in Homo sapiens result in corresponding changes in the lumbosacral angle. Lumbar and sacral angles (both forming the lumbosacral angle) are almost equal in all mammalian species. Since the sacral angle of Australopithecus afarensis is approximately 15 degrees, it can be implied that its lumbosacral angle was small, thus attesting to its "imperfect" erect posture and "primitive" form of bipedal locomotion.     

Orientation of the human sacrum: anthropological perspectives and methodological approaches

Discovering the nature of sacral orientation is of considerable anthropological importance. Therefore, this study aims at presenting a new anthropologically based definition for sacral anatomical orientation (SAO) angle, establishing standards of SAO for human population; examining the relationship between pelvic incidence (PI) and SAO; and associating SAO with demographic parameters. The study population consisted of 424 adult and 14 sub-adult (13-18 years, for SAO only) pelvises. Sacral orientation was measured using two different definitions: a) SAO is the angle created between the intersection of a line running parallel to the superior surface of the sacrum and a line running between the anterior superior iliac spine (ASIS) and the anterior-superior edge of the symphysis pubis; b) PI is the angle created between the perpendicular to the sacral plate at its midpoint and the line connecting this point to the middle of the axis of the acetabulum. SAO was measured using a specially designed mechanical measurement tool and a 3D digitizer. PI was measured via the 3D digitizer. The methods developed by us for measuring SAO and PI in skeletal material are valid and reliable. SAO and PI measures were highly correlated (r = -0.824, P < 0.001). The average SAO was 49.01 degrees (SD = 10.16), and the average PI 54.08 degrees (SD = 12.64). SAO was independent of ethnicity and sex, yet age dependent. This study establishes a methodology for estimating SAO and PI in skeletal material and furnishes the anthropological milieu with base line data regarding these parameters. Future studies in human evolution can greatly benefit from this study.     

The pelvis in the bipedalism of primates

The pelvis in the “Normalstellung” tends in man to tilt backwards. In primates, the pelvis shows a marked tendency to tilt into quadruped posture. In both the bodyweight intensifies those tendencies. Consequently, assuming erect posture and maintaining bipedal balance encounter, in primates, constant resistance from pelvis and bodyweight. In gibbons and ponginae loss of the tail, lengthening of the sacrum and broadening of the ilium combined with a pronounced development of the sacro-tuberous ligament furnish the gluteal muscles with a more powerful reflectory moment on pelvis and body. Moreover, the development of a short head of the femoral bicipital muscle, made the hip-joint to a greater degree independent of the knee-joint. Thus, maintenance of bipedal balance is better developed in gibbons and ponginae than in monkeys. In man broadening of the sacrum altered the position of the acetabulum. Together with ensuing changes of the ilium and the ischium this brought about in the pelvis a balance relationship so that the bodyweight not only causes no resistance to standing upright but even facilitates it. The essence of bipedalism, however, is not only the capacity to rise upright and to stand, but also to walk, that is, to keep the body balanced in the frontal plane on one leg. It is the ventralwards broadening of the ilium, and the sidewards bend of its middle segment, that allow, the strongest part of, the gluteus medius (and minimus) to produce a powerful abducent moment on the pelvis. The lack of a corresponding osteomuscular structure in monkeys as well as in gibbon and ponginae compels these primates to move faster and run straddle-legged, in a more or less forward-bending posture. Lastly it is found that in gibbons and ponginae, not only is the ilium markedly broadened laterally, but also that its sacral part is turned completely sidewards. This indicates that bipedalism in man has developed along quite other lines than in gibbons and ponginae.     

Bipedal behavior and the emergence of erect posture in man

Bipedal behavior is present to some degree in most of the higher primates. Field studies of living pongids have shown that an upright stance and various types and degrees of bipedal progression are not uncommon and are thus presumably advantageous. Bipedal behavior similar to that in living pongids could also have been, and probably was, present in pre-hominids. As the environment of the pre-hominids changed, the increased use of bipedalism was of survival value. That is, it was a behavioral response to environmental circumstances and not just a random event. Once bipedal behavior became habitual, it formed part of a pattern of natural selection which shaped a physical type adapted for erect, bipedal posture.     

Effect of posture and locomotion on energy expenditure

Energy expenditure for human adults and infants and for dogs was measured in resting (supine or lateral) posture, in bipedal posture and locomotion, and in quadrupedal posture and locomotion. Variations in respiratory and heart rate and in body temperature were utilized in this comparative study. Oxygen consumption was also measured in human adults. In human adults, bipedal posture and locomotion were shown to be much less energy-consuming than corresponding quadrupedal posture and locomotion. The opposite was observed in adult dogs, where bipedalism was shown to be much more energy-consuming than quadrupedalism. In addition, this study demonstrated, for human adults in their natural erect posture, an energy expenditure barely higher than in supine or lateral resting posture, while the dogs in their natural quadrupedal stance, the energy expenditure is much higher than in their resting posture. With respect to energy, therefore, humans are more adapted to bipedalism than dogs to quadrupedalism. Human children, at the transitional stage between quadrupedalism and bipedalism, have high and almost equal requirements for all postures and locomotions. This demonstrates, in term of energy, their incomplete adaptation to erect behavior.     

The effects of posture changes on blood pressure and heart rate of anesthetized and reserpinized sloths

1. Tilting sloths anesthetized with chloralose from erect to supine or supine to erect produced little or no effect on heart rate. 2. Tilting anesthetized sloths from erect to supine increased both systolic and diastolic pressures significantly and by about the same amounts. The maximum effect was produced in 20 sec. 3. Pressures stabilized at a higher level than in the erect posture but below the maximum reached in tilting. 4. Tilting these sloths from the supine to the erect posture resulted in a rapid (20 sec) and dramatic fall in pressures to below the initial erect pressure levels. Return to initial erect levels took place slowly. 5. Tilting reserpinized sloths from erect to supine or supine to erect produced little or no effect on heart rate. 6. Tilting reserpinized sloths from erect to supine increased both systolic and diastolic pressures materially and by similar amounts. The maximum effect took 50 sec. 7. Pressures stabilized at higher levels than in the erect posture but less than maximum reached with tilting. 8. Tilting these sloths from supine to erect caused significant falls in pressure to slightly below the initial erect pressure, with maximum effect reached in 30 sec and eventual return to control level. 9. Pressure changes were almost entirely the result of altered venous return. 10. Neither chloralose nor reserpine completely blocked vascular control but reduced it materially.     

CT-based assessment of regional pulmonary microvascular blood flow parameters.

To determine regional pulmonary microvascular mean transit times (MTTs), we used electrocardiogram-gated X-ray computed tomographic imaging to follow bolus radiopaque contrast material through the lungs in anesthetized animals (7 dogs and 1 pig, prone and supine). By deconvolution/reconvolution of regional time-attenuation curves obtained from parenchyma and large lobar arteries, we estimated the microvascular residue function and reconstituted the regional microvascular time-attenuation curves and, thus, regional microvascular MTTs. The mean microvascular MTTs in the supine and prone postures were 3.94 +/- 1.0 and 3.40 +/- 0.84 (mean +/- SD), respectively. The dependent-nondependent vertical gradient of MTT was greater in the supine [slope = 0.25 +/- 0.10 (SD), P < 0.001 by t-test] than in the prone (-0.03 +/- 0.06 in 6 of 8 animals; 2 outliers had positive slopes) posture. In both postures, there was a trend toward faster transit times in the dorsal-basal lung region in six of the eight animals, suggesting gravity-independent higher vascular conductance dorsocaudally. We conclude that deconvolution methods, in association with electrocardiogram-gated high-speed X-ray computed tomography, can provide insights into regional heterogeneity of pulmonary microvascular MTT in vivo.     

Modification of pulmonary gas mixing by postural changes

Mixing for two gases of markedly different gaseous diffusivity, helium (He) (mol wt = 4) and sulfur hexafluoride (SF6) (mol wt = 146) has been studied by a rebreathing method in different postures. In nine normal subjects duplicate measurements were made in the erect (seated), supine, and lateral decubitus posture, at a constant tidal volume (700 ml) and frequency (1 Hz) starting from functional residual capacity (FRC). Additional measurements were made on four of the subjects, rebreathing seated erect at a volume similar to the relaxed FRC supine and supine at a volume similar to the relaxed FRC seated. In the supine posture the mean breath number to reach 99% equilibrium (n99), was not significantly different for the two gases, 8.9 for He and 9.8 for SF6. There was a difference (P less than 0.01) when erect; n99 (He) = 8.2 and n99 (SF6) = 10.9. The greatest He-SF6 difference (P less than 0.001) was in the lateral decubitus position n99 (He) = 10.1 and n99 (SF6) = 15.9. The mean relaxed FRC as percent of seated was 71% supine and 75% in lateral decubitus posture. Rebreathing seated at a lower volume did not abolish the He-SF6 mixing difference nor did rebreathing at a higher volume when supine induce a He-SF6 mixing difference. Thus the effect of posture on gas mixing cannot be due solely to lung volume and must represent a convective and diffusive dependent change in the distribution of ventilation per unit lung volume.     

Reconstruction of the STS 14 (Australopithecus africanus) pelvis

The study reports a reconstruction of the sacrum in STS 14 based on extrapolation from the measurements of the first two sacral vertebrae of STS 14 and of the angle formed by the anterior surfaces of their vertebral bodies. Reconstruction is based on comparisons of, and extrapolation from, sacra of Pan troglodytes, Homo sapiens, and Australopithecus afarensis. The reconstructed sacrum has an anterior sacral curvature of 39°. The two ossa coxae were also completed by mirror imaging of one side by the other. With the pelvis completely reconstructed, the pelvic dimensions for the antero-posterior (AP) diameters of the pelvic inlet, midpelvis, and pelvic outlet are 85, 68, and 69 mm and the corresponding transverse (TR) diameters are 109, 88, and 103 mm, respectively. The posterior sagittal diameters in the three pelvic planes are small compared to the anterior sagittal diameters. This analysis indicates that the STS 14 pelvis is platypelloid in the three pelvic planes; i.e., all the AP diameters are smaller than the corresponding TR diameters. This makes the STS 14 pelvis similar to that to Al 288-1, save for a less pronounced degree of platypelloidy at the inlet in the former. © 1995 Wiley-Liss, Inc.     

Gas exchange in dogs in the prone and supine positions.

To determine the cause of the difference in gas exchange between the prone and supine postures in dogs, gas exchange was assessed by the multiple inert gas elimination technique (MIGET) and distribution of pulmonary blood flow was determined using radioactively labeled microspheres in seven anesthetized paralyzed dogs. Each animal was studied in the prone and supine positions in random order while tidal volume and respiratory frequency were kept constant with mechanical ventilation. Mean arterial PO2 was significantly lower (P less than 0.01) in the supine [96 +/- 10 (SD) Torr] than in the prone (107 +/- 6 Torr) position, whereas arterial PCO2 was constant (38 Torr). The distribution of blood flow (Q) vs. ventilation-to-perfusion ratio obtained from MIGET was significantly wider (P less than 0.01) in the supine [ln SD(Q) = 0.75 +/- 0.26] than in the prone position [ln SD (Q) = 0.34 +/- 0.05]. Right-to-left pulmonary shunting was not significantly altered. The distribution of microspheres was more heterogeneous in the supine than in the prone position. The larger heterogeneity was due in part to dorsal-to-ventral gradients in Q in the supine position that were not present in the prone position (P less than 0.01). The decreased efficiency of oxygenation in the supine posture is caused by an increased ventilation-to-perfusion mismatch that accompanies an increase in the heterogeneity of Q distribution.     

A new reconstruction of Sts 14 pelvis (Australopithecus africanus) from computed tomography and three-dimensional modeling techniques

The purpose of this study is to propose a new reconstruction of the australopithecine Sts 14 pelvis from original fossils. Digital models created from CT images allow us to perform mirroring operations, select valid regions after digital interposition, and reassemble parts. The key-element of the reconstruction is the sacroiliac joint, restored from right and left articular surfaces, which places of the pubic symphysis close to the sagittal plane. The complete pelvis is obtained by 3D model mirroring of hip-bone and sacrum. The present reconstruction of the Sts 14 pelvis is consistent with Schmid's (1983) [Folia Primatol. 40, 283-306, 1983] and Häusler and Schmid's A.L. 288-1 [J. Hum. Evol. 29, 363-383, 1995] pelvic reconstructions by illustrating a relatively platypelloid shape of the pelvic cavity and laterally inclined iliac blades. The pelvic morphology suggests that australopithecines had a less posteriorly tilted sacrum in erect posture than modern humans. As compared with Lovejoy's [Am. J. Phys. Anthropol. Suppl. 50, 460, 1979] A.L. 288-1 pelvic reconstruction, the less transversely flattened shape of the Sts 14 pelvic cavity led to obstetrical mechanics characterized as in humans by ante-ischiatic birth and a curved trajectory. We deduce a human-like movement of rotation and flexion of the fetal skull in the Sts 14 pelvic cavity.     

Rib cage and diaphragm-abdomen compliance in humans: effects of age and posture

The influence of age and posture on compliance of the rib cage (Crc) and diaphragm-abdomen (Cab) compartments of the chest wall was studied in 61 healthy adults (33 men, 28 women) aged 24-75 yr. Chest wall compliance (Cw) was measured by the weighted spirometer technique; Crc and Cab were derived from the slope of the relaxation line of the thoracoabdominal system obtained with two pairs of linearized magnetometers. While Cw was being measured, we monitored electrical activity of the abdominal external oblique muscle with a concentric needle electrode and thoracoabdominal configuration. In 52 subjects, the electromyogram did not show any abdominal muscle activity and the end-expiratory level never departed from the relaxed thoracoabdominal configuration, thus suggesting adequate respiratory muscle relaxation. Aging was associated with significant decreases in Crc and Cab. In the upright posture Crc decreased from 0.164 +/- 0.041 (mean +/- SD) l/cmH2O in the younger subjects (24-39 yr) to 0.114 +/- 0.027 l/cmH2O in the older subjects (55-75 yr). Cab concomitantly fell from 0.032 +/- 0.012 l/cmH2O to 0.020 +/- 0.007 l/cmH2O. These reductions were statistically significant (P less than 0.05-0.01) and were also present in the supine posture. Shifting from the seated to the supine posture did not cause any significant change in Cw but was invariably associated with a decrease in Crc and an increase in Cab.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of posture on shear rates in human brachial and superficial femoral arteries

Shear rate is significantly lower in the superficial femoral compared with the brachial artery in the supine posture. The relative shear rates in these arteries of subjects in the upright posture (seated and/or standing) are unknown. The purpose of this investigation was to test the hypothesis that upright posture (seated and/or standing) would produce greater shear rates in the superficial femoral compared with the brachial artery. To test this hypothesis, Doppler ultrasound was used to measure mean blood velocity (MBV) and diameter in the brachial and superficial femoral arteries of 21 healthy subjects after being in the supine, seated, and standing postures for 10 min. MBV was significantly higher in the brachial compared with the superficial femoral artery during upright postures. Superficial femoral artery diameter was significantly larger than brachial artery diameter. However, posture had no significant effect on either brachial or superficial femoral artery diameter. The calculated shear rate was significantly greater in the brachial (73 +/- 5, 91 +/- 11, and 97 +/- 13 s(-1)) compared with the superficial femoral (53 +/- 4, 39 +/- 77, and 44 +/- 5 s(-1)) artery in the supine, seated, and standing postures, respectively. Contrary to our hypothesis, our current findings indicate that mean shear rate is lower in the superficial femoral compared with the brachial artery in the supine, seated, and standing postures. These findings of lower shear rates in the superficial femoral artery may be one mechanism for the higher propensity for atherosclerosis in the arteries of the leg than of the arm.     

Effect of posture on arterial baroreflex control of heart rate in humans

Altered baroreflex function may contribute to the cardiovascular changes associated with weightlessness. Since central blood volume (CBV) increases during simulated weightlessness we have examined the possibility that acute changes in CBV may modify baroreceptor function. We used graded head-up tilt (HUT) and head-down tilt (HDT) to induce changes in CBV, and neck suction to stimulate carotid baroreceptors, in 6 subjects. The increase in pulse interval induced by a negative pressure of 8.2 kPa (62 mm Hg) imposed for 10 s while supine was compared with the increase while tilted for 8 min at +/- 15 degrees, +/- 30 degrees and +/- 45 degrees. During HDT at 15 degrees the pulse interval over the first 5 cardiac cycles following suction onset was 51 +/- (SEM) 18 ms longer (p less than 0.05), at 30 degrees it was 61 +/- 20 ms longer (p less than 0.05), and at 45 degrees it was 74 +/- 35 ms longer (p less than 0.01), compared with supine. During HUT at 15 degrees the pulse interval was 25 +/- 9 ms shorter (p less than 0.05) than when supine, but was not significantly different at 30 degrees and 45 degrees. These responses occurred independently of changes in brachial blood pressure. Attenuation was also observed after 5 min (56 +/- 17 ms; less than 0.05), and after 40 min (25 +/- 9 ms; p less than 0.05) of 60 degrees HUT compared with supine. We conclude that posture does modify arterial baroreflex control of heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of body orientation on regional lung expansion in dog and sloth

Recent studies (E.A. Hoffman, J. Appl. Physiol. 59: 468-480, 1985) using fast multisliced X-ray computed tomography have demonstrated a ventral-dorsal gradient of fractional lung air content (3.29% air/cm lung height) in supine dogs and an essentially uniform ventral-dorsal air content distribution in the prone dogs [mean = 66 +/- 0.6% (SE) air content]. Since the prone orientation is the dog's normal body posture, we sought to study an animal whose normal body posture was "opposite" to that of the dog. Four two-toed sloths were scanned in the Dynamic Spatial Reconstructor in the prone and supine postures. A supine fractional air content gradient was demonstrated with a regression equation of y = 2.09x + 74.3 (r = 0.92), where y is percent air content and x is vertical height in the lung, and ventral-dorsal air content distribution in the prone posture was uniform with a mean of 85 +/- 0.4% (SE) air content. The low functional residual capacity lung density in the sloth was attributable to unusually large alveoli. The mean heart volume-to-body weight ratio in the dogs was 16.4 +/- 0.6 (SE) ml/kg and that in the sloth was 7.3 +/- 0.4 (SE) ml/kg. Mean lung volume-to-body weight ratios for dogs and sloths were 57 +/- 7 (SE) and 89 +/- 6 ml/kg, respectively. Of particular interest was the fact that large changes in prone vs. supine rib cage and diaphragm geometry previously found in dogs did not occur in sloths, though significant alterations of ventral and dorsal lung geometry prone vs. supine were demonstrated, and lung shape changes in both dog and sloth are attributable to shifts in the intrathoracic position of mediastinal structures.     

Effects of posture on peripheral vascular responses to lower body positive pressure

We tested the hypothesis that peripheral vascular responses (in the lower and upper limbs) to application of lower body positive pressure (LBPP) are dependent on the posture of the subjects. We measured heart rate, stroke volume, mean arterial pressure, leg and forearm blood flow (using the Doppler ultrasound technique), and leg (LVC) and forearm (FVC) vascular conductance in 11 subjects (9 men, 2 women) without and with LBPP (25 and 50 mmHg) in supine and upright postures. Mean arterial pressure increased in proportion to increases in LBPP and was greater in supine than in upright subjects. Heart rate was unchanged when LBPP was applied to supine subjects but was reduced in upright ones. Leg blood flow and LVC were both reduced by LBPP in supine subjects [LVC: 4.8 (SD 4.0), 3.6 (SD 3.5), and 1.4 (SD 1.8) ml.min(-1).mmHg(-1) before LBPP and during 25 and 50 mmHg LBPP, respectively; P < 0.05] but were increased in upright ones [LVC: 2.0 (SD 1.2), 3.4 (SD 3.4), and 3.0 (SD 2.0) ml.min(-1).mmHg(-1), respectively; P < 0.05]. Forearm blood flow and FVC both declined when LBPP was applied to supine subjects [FVC: 1.3 (SD 0.6), 1.0 (SD 0.4), and 0.9 (SD 0.6) ml. min(-1).mmHg(-1), respectively; P < 0.05] but remained unchanged in upright ones [FVC: 0.7 (SD 0.4), 0.7 (SD 0.4), and 0.6 (SD 0.5) ml.min(-1).mmHg(-1), respectively]. Together, these findings indicate that the leg vascular response to application of LBPP is posture dependent and that the response differs in the lower and upper limbs when subjects assume an upright posture.     

Changes in the lumbosacral angle, sacral inclination and the curvature of the lumbar spine during aging.

Measurements of the curvature of the lumbar spine are useful in the investigations of low back pain. It is unclear whether the degree of lumbar lordosis, sacral inclination and lumbosacral angulation are the same for all normal adults. Radiographic studies were carried out on the lumbar spines of subjects aged 9-61 years. Mean and 95% tolerance ranges of the values of lumbar lordosis, lumbosacral angle and sacral inclination for adult age groups up to the sixth decade are given. The results showed that all three parameters varied steadily with age. The pattern of changes differed in males and females. Females had greater angles than males. Sacral inclination appeared to be a more important determinant of the degree of lumbar lordosis. All three parameters showed a tendency to decrease after the sixth decade. The significance of the findings is discussed.     

A radioimmunoassay for plasma dehydroepiandrosterone sulphate incorporating placental steroid sulphatase as a hydrolysing reagent

We describe a method for the measurement of plasma dehydroepiandrosterone sulphate (DHAS) which incorporates a Triton X-100 solubilised preparation of human placental steroid sulphatase as a hydrolysing agent and a direct radioimmunoassay of liberated DHA using a specific antiserum. The hydrolysis procedure is carried out at 50 degrees C for 1 h and an assay run can be completed in 4 h. As determined by the method, plasma concentrations of DHAS in 32 normal adult men (ages 23-58 yr) had a mean value +/- SD of 5.5 +/- 1.89 mumol/l. For 30 normal adult cyclic women (ages 22-35 yr) the mean plasma concentration of DHAS +/- SD was 3.1 +/- 1.35 mumol/l which was significantly lower (P less than 0.01) than found for men. Plasma DHAS concentration were also measured in 50 hirsute female patients. The mean value +/- SD was 5.03 +/- 2.52 mumol/l which was significantly higher (P less than 0.01) than the value for the normal female group. Some 42% of the hirsute patients had DHAS concentrations above the upper 95% probability limit of the normal range for premenopausal women.