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H J Kuhn

Publications and source records attributed to H J Kuhn.

At least 19 recordsLinked to original sources
PubMed2004

Expression patterns of erythropoietin and its receptor in the developing midbrain.

The expression patterns of erythropoietin (EPO) and its receptor (EPOR) were investigated in the midbrain and in adjacent parts of the synencephalon and hindbrain of embryonic C57Bl mice. On embryonic (E) day 8 (E8), virtually all neuroepithelial cells expressed EPOR. After neural tube closure, subsets of these cells downregulated EPOR. In contrast, radial glial cells were EPOR-immunolabeled from E11 onwards. Simultaneously, subpopulations of early developing neurons upregulated EPO and expressed HIF-1, known to transcriptionally activate EPO. Three-dimensional reconstructions revealed subpopulations of EPO-expressing neurons: (1) in the trigeminal mesencephalic nucleus (TMN), (2) at the rostral transition of the midbrain and synencephalon, (3) in the basal plate of the midbrain, (4) in the trigeminal motor nucleus, and (5) in the trigeminal principal sensory nucleus. In the rostral midbrain and synencephalon, EPO-immunoreactive neurons were attached to EPOR-expressing radial glial cells. The identity of radial glial cells was proven by their immunoreactivity for antibodies against astrocyte-specific glutamate transporter, brain lipid-binding protein, and nestin. From E12.5 onwards EPOR was downregulated in radial glial cells. Viable neurons of the TMN continued to express EPO and upregulated EPOR. Our findings provide new evidence that components of the EPO system are present in distinct locations of the embryonic brain and, by interactions between neurons and radial glial cells as well as among clustered TMN neurons, may contribute to its morphogenesis. Whether the observed expression patterns of EPO and EPOR may reflect EPO-mediated trophic and/or antiapoptotic effects on neurons is discussed.

Animals↗
PubMed2000

Pattern of calretinin immunoreactivity in the main olfactory system and the vomeronasal system of the tree shrew, Tupaia belangeri.

The distribution of the calcium-binding protein calretinin was studied in peripheral and central parts of the main olfactory system (MOS) and the vomeronasal system (VNS) of adult tree shrew Tupaia belangeri. The calretinin immunoreaction was carried out with a peroxidase-coupled polyclonal antibody. In the VNS, complete labeling of all receptor cells and vomeronasal nerve fibers was observed, whereas only a subset of the somata and dendrites of receptor cells and of the olfactory nerve fibers of the MOS was immunoreactive. From the immunoreactive dendritic clubs of vomeronasal receptor cells, calretinin-labeled structures, presumably clumps of microvilli, arose that terminated within immunopositive portions of the mucus. In the main olfactory bulb, the neuropil of some of the glomeruli was immunoreactive. All periglomerular and many mitral cells were labeled. The external plexiform layer was subdivided into a faintly immunoreactive superficial half and a strongly immunoreactive deep half. Immunoreactive basal dendrites of mitral cells could be followed into either the deep half or the superficial half. In the laminated internal granular layer, a subset of immunopositive granule cells extended dendrites into the external plexiform layer. Mitral cells and granule cells with dendrites ascending to different levels of the external plexiform layer may represent functional subclasses. In the accessory olfactory bulb, all vomeronasal nerve fibers, glomeruli, and mitral/tufted cells were labeled, whereas immunoreactive periglomerular cells and internal granule cells were only scattered. In Tupaia, calretinin immunoreactivity is a more general property of the primary projecting neurons of the VNS than of the MOS and possibly indicates the involvement of calretinin in the perception of certain of the olfactory qualities.

Animals↗
PubMed2000

The patterns of cell death and of macrophages in the developing forebrain of the tree shrew Tupaia belangeri.

The patterns of cell death and of macrophages were investigated in the forebrain and eyes of the tree shrew Tupaia belangeri during five phases of optic cup formation. Seventeen embryos were studied. Three- dimensional reconstructions were made from one embryo of each phase. In phase 1 (V-shaped optic evagination) a midline band of cell death passes through the closing anterior neuroporus. From phases 2 (optic vesicle) to 5 (far-advanced invagination) the midline band of cell death extends in the dorsal wall of the forebrain to its rostral pole and, further, into its ventral wall. At the approximate future position of the optic chiasm this ventral pycnotic area, predicted but so far unidentified by others, is connected to a previously described second band of cell death passing through the optic anlagen. Recently, evidence has been presented that chicken embryos develop holoprosencephaly and cyclopia when ventral forebrain structures are lost secondary to experimentally induced apoptosis. Our findings in Tupaia suggest that, in cases of spontaneous malformations of this kind, such an atypical pycnotic area in the ventral telencephalon might result from the defective regulation of cell death processes during optic cup formation. In the forebrain and eyes of Tupaia, the occurrence of bands of cell death precedes the appearance of the earliest intraepithelial macrophages. From phase 3 (onset of invagination) onwards almost all of them are concentrated along the band of cell death.

Animals↗
PubMed2000

Capillary-contacting horizontal cells in the retina of the tree shrew Tupaia belangeri belong to the mammalian type A.

Previously, ultrastructural evidence has been presented that, in the retina of adult Tupaia belangeri, the perikarya and processes of horizontal cells extensively ensheath the basal lamina of capillary cross sections located between the inner nuclear layer and the outer plexiform layer. The present study tests whether these horizontal cells can be further characterized by applying a polyclonal antibody against glial fibrillary acidic protein (GFAP). GFAP-immunoreactivity was noted in the astrocytic plexus ensheathing retinofugal axons in the nerve fiber layer. The vitreal endfeet and parts of the trunks of M*uller cells were also labelled. Moreover, a large subpopulation of vessel-contacting horizontal cells was strongly GFAP-immunoreactive. Immunoreactivity was found in the perinuclear cytoplasm and in the sturdy primary dendrites of these cells. The somata of GFAP-immunoreactive horizontal cells were unevenly distributed. These cells had three to seven primary dendrites that showed considerable overlap with the dendrites of neighbouring horizontal cells. For these reasons, GFAP-immunoreactive horizontal cells were classified as belonging to the mammalian type A. Whether the simultaneous occurrence of two glial features, viz. extensive ensheathment of retinal capillaries and immunoreactivity for a polyclonal antibody towards GFAP, supports the view that retinal horizontal cells represent a cell type intermediate between neurons and glial cells is discussed.

Animals↗
PubMed1999

FMRFamide immunoreactivity and the invasion of adenohypophyseal cells into the neural lobe in the developing pituitary of the tree shrew Tupaia belangeri.

Ontogenetic development of FMRFamide immunoreactivity in the cells and nerve fibers of the pituitary was studied in the tree shrew Tupaia belangeri. Up to the 26th day of gestation (E26), no FMRFamide immunoreactivity was visible. From E27 onwards it increased continuously until prenatally, on E41, the adult pattern was reached in the adenohypophysis, although at a lower intensity. In the adult Tupaia, as in the other mammals studied so far, a finely stained FMRFamide-immunoreactive fiber network was visible in the neural lobe and the infundibular stalk. As in several other adult mammals including man, endocrine cells in the pars intermedia and numerous scattered cells in the pars distalis were labeled, in contrast to several reports on rats and our studies on Galago, showing no FMRFamide-immunoreactive cells in these locations of the pituitary. With reference to the 'basophil invasion', we found FMRFamide-immunoreactive endocrine cells invading the neural lobe from the pars intermedia during the pituitary development. The distribution pattern of FMRFamide immunoreactivity in Tupaia indicates that the mammalian counterparts of FMRFamide may function as neuromodulators, neurotransmitters or as hormones already in defined prenatal stages.

Aging↗
PubMed1999

Acute and long-term results after transcoronary ablation of septal hypertrophy (TASH). Catheter interventional treatment for hypertrophic obstructive cardiomyopathy.

AIMS: To evaluate acute and long-term symptomatic, haemodynamic (at rest and during exercise) and electrophysiological results of transcoronary ablation of septal hypertrophy (TASH), a catheter interventional treatment for hypertrophic obstructive cardiomyopathy. METHODS AND RESULTS: Sixty-two transcoronary ablations of septal hypertrophy were performed by injection of 4.6+/-2.6 ml 96% ethanol into septal branches in 50 patients with hypertrophic obstructive cardiomyopathy and severe symptoms. Serial left and right heart catheterization, transoesophageal echocardiography and electrophysiological investigations were repeated 2 weeks and 7+/-1 months (n=37) after intervention. Transcoronary ablation of septal hypertrophy led to a reduction in septal thickness, sustained elimination of the outflow obstruction (51+/-41 vs 6+/-10 mmHg at rest, P<0.001; 134+/-48 vs 28+/-32 mmHg, P<0.001, post-extrasystolic), a decrease in left ventricular filling pressures at rest and during exercise and a pronounced clinical improvement. There was no evidence for the creation of an arrhythmogenic substrate as assessed by serial programmed electrical stimulation in 39 patients. However, permanent high-grade atrioventricular block occurred in 17% of the patients. There were two early, but no late deaths during a mean follow-up time of 10. 6+/-5.6 months. CONCLUSION: Transcoronary ablation of septal hypertrophy is a promising new treatment for hypertrophic obstructive cardiomyopathy in patients with severe symptoms. It should now be compared with alternative treatment strategies in prospective randomized studies.

Adult↗
PubMed1999

Lectin binding sites in the vomeronasal organ and the olfactory epithelium of the tree shrew tupaia belangeri.

Lectin binding histochemistry was performed on the peripheral parts of the vomeronasal and olfactory system of Tupaia belangeri to investigate the distribution and density of defined carbohydrate terminals on the cell surface glycoproteins of the specific receptors, nerves and associated glands. Dolichus biflorus lectin staining was identifiable in all cells of the sensory epithelia of both systems, with the exception of the olfactory basal cells. The vomeronasal nerve expressed alpha-N-acetylgalactosamine, the olfactory nerve did not. Differences in the Dolichus biflorus lectin staining pattern were noted in the sensory and the non-sensory epithelium of the vomeronasal organ of pregnant and non-pregnant Tupaia belangeri. Like in other mammals examined so far, the systems were characterized by a moderate to high alpha-fucose density, only the supporting cells of the olfactory epithelium remaining unstained by Ulex europaeus I lectin. Bandeiraea simplicifolia II lectin binding was moderate in the olfactory glands and the brush border. In the vomeronasal organ, sugar residues of alpha- and beta-N-acetyl-D-glucosamine were found selectively in the transition zone between the two vomeronasal epithelia, where regeneration should take place. We tentatively conclude that specific glycoproteins, whose terminal sugars were detected by lectin binding, might be related to the chemoreception and transduction of the olfactory/pheromonal message into a nervous signal or to the histogenesis of the olfactory/vomeronasal system. This study showed that beside the species, pregnancy might play a role in these processes in the vomeronasal organ.

Animals↗
PubMed1998

Pattern of cell death during optic cup formation in the tree shrew Tupaia belangeri.

Developmental cell death during optic cup formation was investigated in the tree shrew Tupaia belangeri. Twenty-six embryos from days 12 to 16 of prenatal ontogenesis were studied by light microscopy. Prior to the optic vesicle stage, a dorsal area of cell death surrounded the lumen of the V-shaped optic evagination (phase 1). A ventral band of dead cells, found in the optic vesicle (phase 2), preceded a dorsal focus of cell death (phase 3) previously described as a characteristic avian feature. During further invagination (phase 4), a peak of cell death was represented by a ventrodorsal band extending from the diencephalon over the complete optic anlage. The main areas of cell death found in phases 2 to 4 were, topographically, segments of this band. Also, the distinct areas of cell death reported in the literature for the vertebrate species studied so far fit well into this ventrodorsal band found in Tupaia. Thus, most probably, a common spatio-temporal sequence of cell death exists in all of them. In Tupaia, dead cells concentrated at the diencephalic insertion of the optic stalk, the suboptic necrotic center (SONC) reported by several authors, were part of the early ventral band of cell death originating from the median floor of the prosencephalon (phase 2). During optic cup formation, the SONC was part of the ventrodorsal band and, thus, was not secondarily formed by the subdivision of a pre-existing distal ventral area of cell death as reported for several other vertebrates.

Animals↗
PubMed1998

The morphogenesis of the arteries of the pelvic extremity. A comparative study of mammals with special reference to the tree shrew Tupaia belangeri (Tupaiidae, Scandentia, Mammalia).

The ontogeny of the arteries of the pelvic extremity of Tupaia belangeri was investigated by light microscopy on the basis of serial sections of 30 embryos, dating from day 17 to day 42 post-copulation. In Tupaia, the gestational period takes approximately 43 days. Additionally, a 3-D reconstruction of the pelvic region and the right leg of a 22-day embryo was prepared. The arteries of an adult Tupaia were studied on the basis of a corrosion cast. The results were compared with the ontogeny of the arterial system of other mammals. In the 17-day embryo, the anlage of the pelvic extremity is penetrated by a capillary plexus. In the 18-day embryo, the a. ischiadica reaches the pelvic limb bud, representing the primary axial artery. On day 19, its r. perforans tarsi extends from the plantar to the dorsal aspect of the foot plate. The a. ischiadica is the main artery of the leg until the stage of the 22-day embryo. Afterwards, the peripheral arteries supplied by it are taken over by the a. iliaca externa and its extension, the a. femoralis. The a. iliaca externa springs from the a. iliaca communis in the 19-day embryo. From day 21 to day 22, the capillary plexus, which is nourished by the a. femoralis, closely approaches the a. ischiadica, and finally, a connecting branch joins the a. ischiadica. The a. ischiadica is then reduced to the a. glutea caudalis, and the aa. femoralis, poplitea profunda (at the cranial aspect of the m. popliteus), and interossea become the main arteries of the pelvic extremity. The a. poplitea superficialis, lying at the caudal aspect of the m. popliteus, and its continuation in the crural region, the a. peronea, develop until the 25-day embryo. The a. peronea gives rise to an r. perforans which penetrates the membrana interossea towards the dorsum of the foot. As a result of a shift of the origin of the a. iliaca externa in the proximal direction, the length of the a. iliaca communis gradually decreases until, on day 24, the a. iliaca externa springs directly from the lateral wall of the aorta. In the 20-day embryo, the a. iliaca externa gives rise to an a. circumflexa ilium profunda towards the lateral pelvic wall, and in 23-day embryos, to the a. profunda femoris. The main branches of the a. profunda femoris develop until day 24. At the same time, the aa. circumflexa femoris lateralis and nutricia ossis femoris arise from the a. femoralis. The a. saphena, which is already recognizable in the 23-day embryo, gives rise to the a. genus descendens, and as an a. plantaris medialis, to four aa. digitales plantares communes (I-IV) at the planta pedis. The development of the a. tibialis cranialis on day 25 takes place independently and without any topographic relation to the a. saphena, which functionally replaces the a. tibialis cranialis in some other mammals. In the 26-day embryo, the aa. peronea and tibialis cranialis extend to the dorsum of the foot where they continue as the aa. dorsales pedis profunda and superficialis. The fourth main artery of the lower leg, the a. caudalis femoris, which is first observed in the 20-day embryo, reaches the lateral aspect of the foot on day 24. Its r. calcaneus runs to the planta pedis. In 30-day embryos, the aa. digitales plantares propriae have differentiated. The corresponding dorsal arteries and the superficial plantar vascular are develop until day 35, so that all important arteries of the pelvic extremity, which are seen in the corrosion cast of the adult, are recognizable. Among the embryos and the adult Tupaia studied, individual variation is minimal. The developmental stage at which the arteries of the leg acquired a secondary vascular wall was ascertained. Only a vessel with a primary vascular wall can dissolve into a capillary plexus later on (e.g., a. interossea). In contrast, the course of an artery which has acquired a secondary vascular wall is determined, because modifications of the course of a vessel often need a capillary plexus as an intermediate st

Animals↗
PubMed1997

Ciliogenesis in photoreceptor cells of the tree shrew retina.

Transmission electron microscopy of the retinal cones from several prenatal, young postnatal and adult tree shrews (Tupaia belangeri) reveals that the centrioles, from which the ciliary precursors of the outer segments grow out, are not transported into a pre-existing inner segment, but are positioned under the apical plasma membrane of cone precursor cells all through the inner segment formation. Ciliogenesis starts before or on embryonic day 20 and thus precedes initial formation of the inner segment by 20 days, which is half the gestation period. Thus, the maturation of the outer segment covers a considerably longer period than has been previously described. Published observations from other mammals can be interpreted as conforming with the situation in Tupaia. In other vertebrates, compared to mammals, marked heterochronies do occur. In Tupaia, the centrioles and the cilium are located close to the central longitudinal axis of the photoreceptor precursor cell from the 20-day-old embryo to the 5-day-old juvenile. In this position the microtubule apparatus originating from the centrioles should be most effective in transporting the mitochondria into the inner segment. In the 12-day-old tree shrew, when transport of the mitochondria into the inner segment has been completed, centrioles and cilium have shifted into an eccentric position and the light-collecting megamitochondria have approached the disks of the outer segment. This eccentric position is maintained in all later developmental stages. In certain of the retinal areas of the adult Tupaia, the connecting cilia of neighbouring cones are always positioned on the same side of the inner segments.

Animals↗
PubMed1997

"Lens mitochondria" in the retinal cones of the tree-shrew Tupaia belangeri.

In all mammals, the mitochondria of the cones of the retina are concentrated in the inner segment. Uniquely in tree-shrews (Tupaia, Scandentia, Mammalia), a "megamitochondrion" exhibiting highly specialized systems of densely packed cristae and a very electron dense matrix, is located apically in the inner segment. The ellipsoid is a solid body containing several megamitochondria and, towards its base, a large number of smaller mitochondria. The refractive index of isolated, but not oriented, inner segments of Tupaia belangeri is higher (XA = 1.405) than in any other mammal studied so far. The consistent geometrical pattern of the multilamellar crista-matrix systems, oriented longitudinally towards the outer segment, suggests an additional optical function of the megamitochondria.

Animals↗
PubMed1996

[Evaluation of the oscillometric blood pressure monitors: Dinamap 1846 and HP M-1008B].

Using the PTB simulator, which emits real signals from patients, we examined the precision of the oscillometric blood pressure measurement with the Dinamap 1846 (Critikon) and the HP M-1008B (Hewlett Packard). For this purpose we simultaneously registered invasive arterial pulsewave, cuff pressure and cuff pressure oscillations of 20 patients from our intensive care unit and stored them in the database of the simulator. The invasive reference blood pressure values were determined following the recommendations given by the Association for the Advancement of Medical Instrumentation. The invasive system showed a cut-off frequency of 35 Hz; the damping constant was 0.21. With 49 record signals from patients we carried out 15 simulated measurements each. From a total of 49 bio-signals from patients the Dinamap 1846 was able to process 41 signals and the HP M-1008B 47 signals. The mean error of the oscillometric blood pressure measurement of the systolic, diastolic and mean arterial pressure amounted to -2.50 mmHg, 3.35 mmHg (P < 0.05) and 1.51 mmHg with the Dinamap 1846 and to -8.5 mmHg (P < 0.001), -5.15 mmHg (P < 0.001) and -5.58 mmHg (P < 0.001) for the HP M-1008B. The 95% confidence limit for the systolic, diastolic and the mean arterial pressure amounts to 56 mmHg, 30 mmHg and 35 mmHg for the Dinamap 1846 and 50 mmHg, 38 mmHg and 35 mmHg for the HP M-1008B. The differences between that two instruments could be caused by the different algorithms for the calculation of blood pressure values and different artefact detection and elimination techniques. The results of the performance tests we achieved with the PTB simulator correspond to the results of other clinical examinations. The American Association for the Advancement of Medical Instrumentation recommends a maximum mean error of 5 +/- 8 mmHg. None of the examined instruments lay within these limits. Due to the systematic and stochastic errors, we think that the Dinamap 1846 (Critikon) and the HP M-1008B (Hewlett Packard) do not achieve performance levels that are adequate for measuring critically ill patients.

Adult↗
PubMed1996

Morphogenesis of megamitochondria in the retinal cone inner segments of Tupaia belangeri (Scandentia).

The morphogenesis of the megamitochondria in the retinal cones of prenatal, young postnatal and adult tree shrews (Tupaia belangeri) was studied by transmission electron microscopy and three-dimensional reconstruction techniques. The initial assembly of the supranuclear cone mitochondria and their subsequent migration towards the developing inner segment conform to the morphogenetic pattern known from other mammals. Within the first postnatal week, however, a marked increase in both the number of the cristae and the matrix density occurs in the inner segment mitochondria of Tupaia. These mitochondria then grow, initially exhibiting a basal-to-apical size-gradient. In the 17-day-old Tupaia, this gradient is superseded by a radial size-gradient that, in addition to the single apical megamitochondrion, is characteristically found in the adult Tupaia. The number of megamitochondria remains almost constant from day 12 of postnatal ontogenesis to the adult stage. Each megamitochondrion consists of an apically located body from which several long processes project towards the base of the inner segment. In the older stages, the number of small mitochondria that most probably have budded off from the megamitochondrial processes clearly increases. We consider that megamitochondria in the cone inner segments of Tupaia arise by the growth of a single mitochondrion and not by the fusion of smaller mitochondria.

Animals↗
PubMed1996

The role of microtubules and microtubule-organising centres during the migration of mitochondria.

The translocation of mitochondria towards the primitive inner segment of the cones in the tree shrew Tupaia belangeri was investigated by transmission electron microscopy. Throughout ontogeny the migrating mitochondria were codistributed with cytoplasmic microtubules which were preserved after the application of conventional preparation techniques for transmission electron microscopy. Both the basal body of the connecting cilium and the second centriole located in the vicinity of the basal body were demonstrated to act as microtubule-organising centres (MTOCs) from which axonemal and cytoplasmic microtubules originated. The megamitochondria in the inner segment of the retinal cones of Tupaia are unique among mammals with respect to their extraordinary size and to their ordered distribution characterised by longitudinal and radial size-gradients within developing and mature cone inner segments. Thus the consistent finding of microtubules and MTOCs in the structurally polarised cones represents an extreme example of the capacity of cells to regulate the transport and distribution of organelles.

Animals↗
PubMed1994

Embryological development of the arterial system of the forelimb in Tupaia.

BACKGROUND: The arterial system of the upper extremities in man shows drastic developmental changes and many individual variations related to interspecific variations in primates. The ontogenetic development in Tupaia was examined from the viewpoint of comparative embryology. METHODS: Histological specimens of 39 embryos were observed and reconstructed in three dimensions using a computer program. Four adult animals were dissected and examined with angiography to ascertain the end stage of development. RESULTS: At the proximal end of the upper arm the deep brachial artery appears first as a concomitant vessel with the radial nerve. It becomes reduced in size and is succeeded by the posterior circumflex humeral artery, which is accompanied initially by the axillary nerve and finally by the radial nerve. The main arterial passageway to the fingers consists of the brachial and interosseous arteries during early development. The superficial brachial artery and median artery are formed later, and their connection becomes the main route of blood supply for the finger arteries up to the adult stage. The ulnar artery is formed at the end of arterial development to form the ulnar end of the superficial palmar arch. The superficial antebrachial arteries are also recognized. CONCLUSIONS: All the arterial elements of the forelimb in Tupaia are observed in a variety of primates, including man, and the characteristics of Tupaia are thought to represent the primitive conditions of the common ancestor of tree shrews and primates.

Angiography↗
PubMed1994

The vomeronasal organ of the New World monkey Saguinus fuscicollis (Callitrichidae). A light and transmission electron microscopic study.

The vomeronasal organ (VNO) of the New World monkey Saguinus fuscicollis (Callitrichidae) is located at the base of the most distal portion of the nasal septum opening into the nasal portion of the ductus nasopalatinus which also communicates with the oral cavity. The lumen of the VNO is limited medially and laterally by a neuroepithelium which is devoid of intraepithelially located blood vessels and composed of receptor, supporting and basal cells. Ultrastructural analysis of the VNO of Saguinus fuscicollis reveals morphological features which lead one to postulate the functional capacity of this organ in these primates. A possible mechanism through which scent marks may be incorporated into the VNO is discussed.

Animals↗
PubMed1994

Postpartum erythrophagocytosis, iron storage and iron secretion in the endometrium of the tree shrew (Tupaia) during pregnancy.

Tree shrews (Tupaia belangeri) develop a bidiscoid endotheliochorial placenta. In addition, histiotrophe secreted by uterine glands is absorbed by the paraplacental trophoblast. Histiotrophe which is rich in iron is necessary for erythropoiesis in the young embryo. This report is part of a study of the accumulation and metabolism of iron in the endometrium of precisely dated pregnant Tupaia belangeri by application of electron spectroscopy and histochemistry. In the endometrium of tree shrews which had been pregnant at least once, iron-laden granules were present in macrophages and secreting cells of uterine glands. Iron accumulated in the endometrium shortly after parturition, when macrophages phagocytosed erythrocytes at small haematomas 0.2-0.5 mm in diameter. These haematomas arose during parturition after bleeding into the uterine stroma when the placental discs were detached. At 24 h after parturition the following structural consequences of the erythrolysosomal breakdown of phagocytosed erythrocytes could be observed: free cytosolic siderin granules, membrane-bound siderosomes, telolysosomes (some of which contained myelin figures or lipid droplets) and mixed telolysosomes (containing membranous stacks and siderin granules). During the lysosomal degradation of phagocytosed erythrocytes, iron was transferred from haemoglobin into a different macromolecular compound. Electron energy loss spectra detected from inside siderosomes indicated an iron-oxygen compound, and high-power bright field electron micrographs of siderosomes demonstrated the ultrastructural pattern characteristic of ferritin. At about d 12 of a new pregnancy, macrophages containing siderosomes closely approached the bases of secreting cells of endometrial glands. This strongly suggests that iron is transferred from the macrophages to the glandular cells. Within the glandular cells, iron-rich histiotrophe was synthesised and released into the glandular lumen. Within the uterine cavity this histiotrophe was absorbed by the omphalopleure. We suggest that among eutherians, postpartum erythrophagocytosis, the transfer of iron from macrophages to uterine glands, and the paraplacental uptake of iron, represent an ancestral mechanism of iron supply to the embryo.

Animals↗