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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

The origin and early development of the intrinsic innervation in the foetal mouse lung

Tollet, Cecilia Jenny January 2003 (has links)
In this study, the origin and development of the intrinsic innervation in the foetal mouse lung is described and experimental evidence is provided to support the involvement of glial cell line-derived neurotrophic factor (GDNF) in the guidance of nerves and neuronal precursors in the developing lung. Antibodies were used to stain for neuronal precursors, neurones, nerve fibres, primordial epithelium and smooth muscle. These structures were revealed in whole mounts of foetal mouse lungs by immunofluorescence and confocal microscopy, and their spatial and temporal distribution was mapped from the onset of lung development and through the pseudoglandular period. The results showed that neuronal precursors, positive for neural crest cell markers, were present in the vagal tract of the foregut at embryonic day 10 (E10), the time of the evagination of the lung buds. These neural crest-derived cells (NCC) migrated into the lung at E11, along nerve processes directed from the vagus to the smooth musclecovered trachea and emerging lobar bronchi. During E11-E14, a network of nerves and ganglia became established along the dorsal trachea, and large ganglia formed a plexus at the ventral hilum. Nerve trunks issued from these ganglia, travelled along the smooth muscle-covered bronchi, providing a pathway for migrating NCC. To investigate the role of GDNF in the innervation of the lung, an in vitro model of left lung lobes was established. Lung growth and tubule branching was comparable to that in vivo, and neural tissue and smooth muscle continued to grow and thrive. A significant increase in nerve growth occurred when explants were cultured with GDNF compared to controls. Nerves extended, and NCC migrated towards GDNF-impregnated beads suggesting that GDNF may be the molecule guiding nerve fibres and NCC in the lung. The migrating NCC were negative for GDNF-family receptor α1 (GFRα1) during their migration into the lung while the nerves were positive. Since GDNF needs to be associated with its binding receptor, GFRα1, for cellular signalling, GDNF may induce the migration of the NCC if they migrate along the GFRα1-positive nerve fibres. It is concluded that neural tissue and smooth muscle become integral components of the lung shortly after the onset of lung development. The results show that the migration of neural crest-derived cells into the lung and the establishment of the innervation requires coordinated cross-talk between NCC, nerves and smooth muscle throughout development.
42

Functions of Heparan Sulfate During Mouse Development : Studies of Mice with Genetically Altered Heparan Sulfate Biosynthesis

Ringvall, Maria January 2004 (has links)
<p>Heparan sulfate (HS) is a ubiquitous polysaccharide on the cell surface and in the extracellular matrix. HS is an important actor in the regulation of cell signaling, especially in the developing embryo. In combination with cell culture and biochemical experiments, <i>in vivo</i> studies of genetically modified animals have pointed out the sulfation pattern of HS as highly important for binding of ligands, their receptors and other signaling modulators.</p><p>The sulfation pattern of an HS chain is gained by several modifying steps, performed by multiple enzymes during biosynthesis in the Golgi apparatus. By alterations of sulfation pattern, and the amount of sulfate groups, a cell can regulate the binding properties of its HS to different molecules. The most highly sulfated form of HS is called heparin, and can only be found intracellularly in mast cells.</p><p>This thesis describes the phenotypes and the alterations in HS/heparin biosynthesis of two genetically modified mouse strains deficient in N-deacetylase/N-sulfotransferase-1 (NDST1) and -2 (NDST2) respectively. We have found NDST1 to be important for correct sulfation of HS and that NDST2 is crucial in heparin biosynthesis. NDST2 deficient mice completely lack heparin and therefore have a severe mast cell phenotype. NDST1 deficient mice produce undersulfated HS and show several developmental disturbances. Some NDST1 embryos die in utero while the rest die neonatally due to breathing difficulties. Defect brain, eye and skeletal development has also been observed while some organs, such as the liver, appear to be largely unaffected. Several phenotypes are similar to defects seen in other mouse strains with impaired fibroblast growth factor and bone morphogenetic protein signaling, among others. This suggests the phenotypes of NDST1 deficient embryos to be of a multi factorial origin, in complete accordance to the many signaling pathways HS is suggested to modulate.</p>
43

Heparan Sulfate and Development : A Study of NDST Deficient Mice and Embryonic Stem Cells

Holmborn, Katarina January 2006 (has links)
<p>Heparan sulfate (HS) proteoglycans consist of sulfated HS chains covalently bound to core proteins. They are ubiquitously expressed, on the cell surface and in the extracellular matrix, throughout the body. During biosynthesis the HS chain is modified to generate a highly variable pattern of sulfated residues, able to interact with a wide variety of ligands, such as growth factors, morphogens and extracellular matrix molecules. The presence of HS proteoglycans is crucial during various developmental processes as they are involved in generation of morphogen gradients and influence the function of several growth factor pathways essential for tissue assembly and differentiation.</p><p>In this thesis the phenotypes of two mouse strains, deficient in different isoforms of the HS biosynthetic enzyme N-deacetylase/N-sulfotransferase (NDST) have been analyzed. In addition, NDST deficient embryonic stem (ES) cells have been analyzed with regard to HS structure and differentiation capacity. Mice deficient in NDST1 die peri-natally. The embryos display an overall low-sulfated HS and several developmental defects, with a lung phenotype as the predominant cause of death. Mice deficient in NDST2 lack sulfated heparin in connective tissue type mast cells while HS structure is unaltered. These results indicate that NDST1 is the isoform mainly responsible for HS biosynthesis during development. However, NDST1/2 deficient embryos do not survive beyond E5.5 and have a greatly disturbed morphology, suggesting that NDST2 has an essential role during early embryonic development. HS synthesized by NDST1/2 deficient ES cells had a total lack of N-sulfate groups while, interestingly, about half of the 6-O-sulfate groups remained. This result was unexpected since 6-O-sulfotransferases have been thought to be strictly dependent on N-sulfate groups for substrate recognition. Further characterization of the NDST1/2 deficient ES cells during in vitro differentiation demonstrated that the expression pattern of markers for all three germ layers was disturbed. In addition, it was demonstrated that NDST1 is not needed for mast cell development, that lack of NDST2 results in abnormal mast cells and that no mast cells is formed from NDST1/2 deficient ES cells.</p>
44

Functions of Heparan Sulfate During Mouse Development : Studies of Mice with Genetically Altered Heparan Sulfate Biosynthesis

Ringvall, Maria January 2004 (has links)
Heparan sulfate (HS) is a ubiquitous polysaccharide on the cell surface and in the extracellular matrix. HS is an important actor in the regulation of cell signaling, especially in the developing embryo. In combination with cell culture and biochemical experiments, in vivo studies of genetically modified animals have pointed out the sulfation pattern of HS as highly important for binding of ligands, their receptors and other signaling modulators. The sulfation pattern of an HS chain is gained by several modifying steps, performed by multiple enzymes during biosynthesis in the Golgi apparatus. By alterations of sulfation pattern, and the amount of sulfate groups, a cell can regulate the binding properties of its HS to different molecules. The most highly sulfated form of HS is called heparin, and can only be found intracellularly in mast cells. This thesis describes the phenotypes and the alterations in HS/heparin biosynthesis of two genetically modified mouse strains deficient in N-deacetylase/N-sulfotransferase-1 (NDST1) and -2 (NDST2) respectively. We have found NDST1 to be important for correct sulfation of HS and that NDST2 is crucial in heparin biosynthesis. NDST2 deficient mice completely lack heparin and therefore have a severe mast cell phenotype. NDST1 deficient mice produce undersulfated HS and show several developmental disturbances. Some NDST1 embryos die in utero while the rest die neonatally due to breathing difficulties. Defect brain, eye and skeletal development has also been observed while some organs, such as the liver, appear to be largely unaffected. Several phenotypes are similar to defects seen in other mouse strains with impaired fibroblast growth factor and bone morphogenetic protein signaling, among others. This suggests the phenotypes of NDST1 deficient embryos to be of a multi factorial origin, in complete accordance to the many signaling pathways HS is suggested to modulate.
45

Heparan Sulfate and Development : A Study of NDST Deficient Mice and Embryonic Stem Cells

Holmborn, Katarina January 2006 (has links)
Heparan sulfate (HS) proteoglycans consist of sulfated HS chains covalently bound to core proteins. They are ubiquitously expressed, on the cell surface and in the extracellular matrix, throughout the body. During biosynthesis the HS chain is modified to generate a highly variable pattern of sulfated residues, able to interact with a wide variety of ligands, such as growth factors, morphogens and extracellular matrix molecules. The presence of HS proteoglycans is crucial during various developmental processes as they are involved in generation of morphogen gradients and influence the function of several growth factor pathways essential for tissue assembly and differentiation. In this thesis the phenotypes of two mouse strains, deficient in different isoforms of the HS biosynthetic enzyme N-deacetylase/N-sulfotransferase (NDST) have been analyzed. In addition, NDST deficient embryonic stem (ES) cells have been analyzed with regard to HS structure and differentiation capacity. Mice deficient in NDST1 die peri-natally. The embryos display an overall low-sulfated HS and several developmental defects, with a lung phenotype as the predominant cause of death. Mice deficient in NDST2 lack sulfated heparin in connective tissue type mast cells while HS structure is unaltered. These results indicate that NDST1 is the isoform mainly responsible for HS biosynthesis during development. However, NDST1/2 deficient embryos do not survive beyond E5.5 and have a greatly disturbed morphology, suggesting that NDST2 has an essential role during early embryonic development. HS synthesized by NDST1/2 deficient ES cells had a total lack of N-sulfate groups while, interestingly, about half of the 6-O-sulfate groups remained. This result was unexpected since 6-O-sulfotransferases have been thought to be strictly dependent on N-sulfate groups for substrate recognition. Further characterization of the NDST1/2 deficient ES cells during in vitro differentiation demonstrated that the expression pattern of markers for all three germ layers was disturbed. In addition, it was demonstrated that NDST1 is not needed for mast cell development, that lack of NDST2 results in abnormal mast cells and that no mast cells is formed from NDST1/2 deficient ES cells.
46

Apoptosis and caspase-3 activity in isolated fetal rat lung cells, human A549 cells and rat periodontal ligament fibroblasts following exposure to cigarette smoke extract

Ahmed, Asra 26 March 2012 (has links)
Exposure cigarette smoke (CS) during prenatal life is the leading cause of preventable premature death. In this study, we explored the hypothesis that in vitro exposure of fetal lung cells to cigarette smoke extract (CSE) may result in the alteration of apoptosis through activation of caspase-3. Alongside we compared the responses of fetal lung cells with A549 cells and rat periodontal ligament (PDL) fibroblasts exposed to CSE in a dose dependent manner. Caspase-3 activity and inhibition was measured using a fluorometric assay. Cell viability in smoke exposed cells was measured using MTT formazan assay. Caspase-3 expression and cellular localization was detected by western blot analysis and immunofluorescence. Our results indicate that caspase-3 activity was significantly (p < 0.05) elevated and cell viability was significantly inhibited in fetal rat lung cells exposed to 10% or 15 % (v/v) CSE. No significant differences were observed in the caspase-3 activity or cellular viability in A549 cells and rat PDL fibroblasts exposed to 5%, 10% or 15% (v/v) CSE. Activation of caspase-3 in fetal lung connective tissue and alveolar epithelial cells may be one of the reasons for the developmental pulmonary toxicity induced by CSE.
47

Apoptosis and caspase-3 activity in isolated fetal rat lung cells, human A549 cells and rat periodontal ligament fibroblasts following exposure to cigarette smoke extract

Ahmed, Asra 26 March 2012 (has links)
Exposure cigarette smoke (CS) during prenatal life is the leading cause of preventable premature death. In this study, we explored the hypothesis that in vitro exposure of fetal lung cells to cigarette smoke extract (CSE) may result in the alteration of apoptosis through activation of caspase-3. Alongside we compared the responses of fetal lung cells with A549 cells and rat periodontal ligament (PDL) fibroblasts exposed to CSE in a dose dependent manner. Caspase-3 activity and inhibition was measured using a fluorometric assay. Cell viability in smoke exposed cells was measured using MTT formazan assay. Caspase-3 expression and cellular localization was detected by western blot analysis and immunofluorescence. Our results indicate that caspase-3 activity was significantly (p < 0.05) elevated and cell viability was significantly inhibited in fetal rat lung cells exposed to 10% or 15 % (v/v) CSE. No significant differences were observed in the caspase-3 activity or cellular viability in A549 cells and rat PDL fibroblasts exposed to 5%, 10% or 15% (v/v) CSE. Activation of caspase-3 in fetal lung connective tissue and alveolar epithelial cells may be one of the reasons for the developmental pulmonary toxicity induced by CSE.
48

On the isolation, functional characterization and oxygen- induced impairment of resident mesenchymal stromal cells from the human fetal lung.

Möbius, Marius Alexander 07 December 2020 (has links)
Hintergrund: Der medizinische Fortschritt der letzten Jahrzehnte verbessert das Überleben insbesondere extrem kleiner Frühgeborener. Bei diesen stellt die adäquate Oxygenierung über die unreife Lunge den kritischsten Prozess in der klinischen Betreuung dar, an dessen Ende häufig eine Beeinträchtigung der postnatalen Lungenentwicklung und -reifung steht. Klinisch als Bronchopulmonale Dysplasie (BPD) imponierend, stellt diese Erkrankung die häufigste Folge der extremen Frühgeburtlichkeit dar und ist im weiteren Verlauf mit einer bedeutenden Langzeitmortalität und gesundheitsökonomischen Belastung verbunden. Außer der Vermeidung der Frühgeburtlichkeit existiert keine Therapie für BPD. Exogene Mesenchymale Stromazellen (MSC) erwiesen sich jedoch in Tiermodellen der BPD als therapeutisch ausgesprochen wirksam und stellen somit einen vielversprechenden Therapieansatz dar. Dennoch ist wenig über die Mechanismen der exogenen MSC-Wirkung in der frühgeborenen Lunge bekannt; ein Verständnis dieser ist jedoch unabdingbar für eine sichere und effektive Translation von MSC-basierten Therapien in die klinische Anwendung. Hypothese: Lungenresidente MSC sind an der normalen Lungenentwicklung beteiligt, werden durch Bedingungen, welche die zu frühe Geburt simulieren, beeinträchtigt, und tragen so zur Pathogenese der BPD bei. Exogene MSC unterstützen die lungenresidenten MSC in ihrer normalen Funktion und/oder schützen sie vor Schaden. Methoden und Resultate: Um mesenchymale Zellen aus human-fetalem Lungengewebe (FLMSC) zu isolieren, wurde eine Methode zur enzymatischen Gewebedissoziation mit anschließender selektiver Dichtegradientenzentrifugation entwickelt. Der überwiegende Mehrheit der isolierten Lungenmesenchymzellen wurde als MSC identifiziert. Damit ist mit der hier vorliegenden Arbeit erstmals die vollständige Beschreibung von humanen, fetalen Lungen-MSC gelungen. Nabelschnur (UC)MSC wurden durch enzymatischen Verdau der Wharton-Sulze gewonnen. Kultur der FLMSC in einer hypoxischen, den intrauterinen Bedingungen ähnlichen Atmosphäre resultierte in einem das Lungenwachstum stimulierenden Cytokin- und Genexpressionsmuster. Zudem produzierten die FLMSC für Lungenwachstum und -reifung unabdingbare Extrazellulärmatrixproteine. Unter Exposition gegenüber hyperoxischen Kulturbedingungen – welche die zu frühe Geburt mit anschließender Behandlung auf einer Neugeborenenintensivstation simulierten – begannen FLMSC einen Transdifferenzierungsprozess und sezernierten proinflammatorische und antiangiogene Signalmoleküle. Zudem wurde eine Reduktion der Produktion von für die Lungenentwicklung unabdingbaren Matrixproteinen beobachtet. FLMSC sendeten zudem “Danger-Signale” an andere Zellen, sobald sie Hyperoxie ausgesetzt wurden. Exogene UCMSC sezernierten in vitro große Mengen an Proteinen, welche Lungenzellen vor Schaden schützen und Lungenwachstum und -differenzierung unterstützen. Diskussion und Schlussfolgerung: Das Mesenchym der humanen fetalen Lunge am Ende der kanalikulären Entwicklungsphase besteht zum Großteil aus MSC, und nicht Fibroblasten. Das impliziert eine mesenchymale Stamm- und Progenitorzellhierarchie in der fetalen Lunge sowie bislang unbeschriebene zelluläre mesenchymale Transdifferenzierungsprozesse im weiteren intrauterinen Entwicklungsverlauf. In vitro wurde Evidenz für eine Beteiligung der endogenen Lungen-MSC an der normalen Lungenentwicklung generiert; eine Beteiligung an der Koordination von epithelialem und endothelialem Lungenwachstum und -reifung durch die endogenen MSC kann auf Grund der vorliegenden Daten angenommen werden. Nach Exposition gegenüber Hyperoxie entwickelten FLMSC einen die BPD unterstützenden Phänotyp. Exogene UCMSC besitzen das Potential, die in diesem Zustand fehlenden Faktoren bereitzustellen. Endogene pulmonale MSC sind daher potentielles Ziel und potentielle Effektorzellpopulation einer MSC-basierten Therapie für BPD. Dennoch sind weitere in vivo Experimente mit Tiermodellen der extremen Frühgeburtlichkeit unabdingbar, um die Rolle der endogenen MSC in der normalen, und insbesondere gestörten Lungenentwicklung zu verstehen und folgend potente, und vor allem sichere zellbasierte Therapeutika für unsere wohl verletzlichste Patientenpopulation – Frühgeborene – bereitzustellen. / Background: Despite great achievements in neonatal and perinatal medicine over the past decades, the immature lung remains the most critical organ to care for after premature birth. As a consequence, impairment of of postnatal lung development – bronchopulmonary dysplasia or BPD – remains the most common complication of extreme prematurity and a major healthcare burden. There is no therapy for BPD, except prevention of premature birth. Recently, exogenous mesenchymal stromal cells (MSC) have been shown to prevent and rescue impaired lung development in animal models. Understanding the mechanisms behind the beneficial action of these cells is crucial for a successful, safe, and effective clinical translation of these promising MSC-based cell therapies in neonates. Hypothesis: Endogenous lung-resident MSC contribute to normal lung development and become impaired in conditions resembling premature birth, thus playing a part in the pathogenesis of BPD. Exogenous MSC act by supporting and/or preserving the endogenous mesenchymal cell’s function. Methods and Results: Using lung tissue from aborted fetuses, a novel enzyme/density gradient technique was employed to obtain endogenous human fetal lung mesenchymal cells (FLMSC). The vast majority of the so-isolated cells fulfilled all criteria of MSC, making the herein presented work the first complete description of MSC from human fetal lung tissue. Human umbilical cord-derived (UC)MSC were isolated by enzymatic digestion of the Wharton’s jelly. When cultured in hypoxic atmospheres resembling intrauterine conditions, resident FLMSC exerted a gene expression- and cytokine profile supporting epithelial and endothelial lung development, and secreted extracellular matrix components crucial for normal lung growth. After exposure to hyperoxia – thus mimicking premature birth and subsequent treatment on a neonatal intensive care unit – FLMSC showed signs of transdifferentiation, acquired a pro-inflammatory / anti-angiogeneitic secretory profile, diminished production of crucial extracellular matrix components and send out danger signals to other cells. Conversely, UCMSC secreted various paracrine factors protecting lung cells, and proteins contributing to lung growth and alveolarization. Discussion and Conclusions: The human fetal lung’s mesenchyme at the late canalicular stage of development mainly consists of MSC rather than fibroblasts, thus implying a complex mesenchymal stem-/progenitor cell hierarchy and previously undescribed cellular transdifferentiation processes of human endogenous lung mesenchymal progenitors during late pregnancy. Evidence for a contribution of FLMSC to normal lung development was generated in vitro, suggesting a co-ordination of endothelial and epithelial cell fate by human endogenous lung MSC. When challenged with hyperoxia, FLMSC cells acquire a phenotype contributing to the pathogenesis of the BPD. Conversely, UCMSC harbor the potential to provide the factors that these damaged resident MSC lack to produce. The endogenous MSC may therefore represent a potential target of cell-based therapies of BPD. However, in vivo data obtained from premature animals is inevitable to gain further insights into the contribution of endogenous lung MSC to normal and disrupted lung development and to clinically translate potent and safe MSC-based therapeutics for our most vulnerable patient population - premature infants.
49

Rationale for the Study of Fatty Acid Binding Protein 5 in Alveolar Type II Cells

Garrison, Derek S. January 2008 (has links)
No description available.
50

Reproductive strategies of K/t-crossing Theria

Szdzuy, Kirsten 07 June 2006 (has links)
Die Dissertation beschäftigt sich mit den möglichen Gründen für die divergente evolutionäre Entwicklung von Beuteltieren und plazentalen Säugetieren nach der Kreide/Tertiär-Grenze. Eine Erklärung könnten ihre unterschiedlichen Reproduktionsstrategien sein. Während die Beuteltiere sehr embryonale Jungtiere nach einer kurzen Tragzeit gebären, bringen Plazentalier deutlich weiter entwickelte Jungtiere nach einer relativ langen Tragzeit zur Welt. Die Aufrechterhaltung eines stabilen Metabolismus und thermoregulatorische Fähigkeiten der Jungtiere bieten einen großen Vorteil für die Anpassungsfähigkeit an ungünstige Umweltbedingungen, wie sie für die K/T-Grenze vermutet werden. Aus diesem Grund untersucht diese Studie den strukturelle Entwicklungsgrad der Lunge und die metabolischen Fähigkeiten von neonaten Marsupialia und Plazentalia. Histologische, ultrastrukturelle und kalorimetrische Untersuchungen erfolgten in einer integrativen Studie. Basierend auf den Ergebnissen wurde eine Grundplanrekonstruktionen der Neonaten von Marsupialia und Plazentalia durchgeführt. Als Vertreter für nesthockende Plazentalia wurde der Goldhamster (Mesocricetus auratus), die Moschusspitzmaus (Suncus murinus) und das Belangeri Spitzhörnchen (Tupaia belangeri) untersucht. Das Wildmeerschweinchen (Cavia aperea) und die Kurzohr-Elefantenspitzmaus (Macroscelides proboscideus) repräsentieren die nestflüchtenden Plazentalia. Als Marsupialia wurden die Hausspitzmaus-Beutelratte (Monodelphis domestica) und das Tammar-Wallaby (Macropus eugenii) untersucht. Die Ergebnisse bestätigen die starken Unterschiede im Entwicklungsgrad der Neonaten und in der postnatalen Entwicklung zwischen Marsupialia und Plazentalia. Die neonatalen Lungen von M. auratus und S. murinus befinden sich im späten “terminal air sac”-Stadium und weisen viele kleine Atemkammern von 50-80 µm Durchmesser auf. Die Alveolenbildung erfolgt bei M. auratus und S. murinus bereits im Alter von zwei beziehungsweise vier Tagen. Bei T. belangeri, C. aperea und M. proboscideus sind Alveolen bereits zum Zeitpunkt der Geburt vorhanden. Im Gegensatz dazu, befinden sich die Lungen der neonaten Beuteltiere M. domestica und M. eugenii im frühen “terminal air sac”-Stadium mit wenigen großen Atemkammern von 300-400 µm im Durchmesser. Die postnatale Lungenentwicklung erfolgt sehr langsam und die Alveolenbildung startet mit 28 Tagen bei M. domestica und mit 65 Tagen bei M. eugenii. Die Metabolismusmessungen ergaben, daß Marsupialia mit einer niedrigen Metabolismusrate geboren werden und den Adultmetabolismus erst spät in der postnatalen Entwicklung erreichen. Einhergehend mit der weit entwickelten Lungenstruktur weisen die Plazentalia hohe Metabolismusraten zur Geburt auf und erreichen den Adultmetabolismus innerhalb der ersten Lebenswoche. Die Ergebnisse zeigen, dass Jungtiere der Plazentalia, im Vergleich zu jungen Marsupialia, eine höhere Widerstandskraft gegen Umweltschwankungen haben, was als ein evolutiver Vorteil der Reproduktionsstrategie der Plazentalia unter ungünstigen Klimabedingungen interpretiert werden kann. / This project deals with the possible reasons for the evolutionary differentiation between marsupial and placental mammals after the K/T-event. One explanation could be their different reproductive patterns. Marsupialia bear virtually embryonic young after a brief gestation period. In contrast, many eutherians bear anatomically advanced, highly precocious young after a relatively long gestation period. A stable metabolism and thermoregulatory abilities of the young are considered to offer a large adaptive advantage in a changing environment, how it is presumed for the K/T-boundary. Therefore this study determines the developmental stage and the respiratory efficiency of the lungs of marsupial and placental young. Histological, ultrastructural and calorimetric investigations were carried out in an integrated study and from the results morphotype reconstructions of the marsupial and placental neonates were carried out. As representatives for altricial Placentalia, the Golden hamster (Mesocricetus auratus), the Musk shrew (Suncus murinus), and the Belanger’s tree shrew (Tupaia belangeri) were examined. Furthermore the Guinea pig (Cavia aperea) and Short-eared elephant shrew (Macroscelides proboscideus) as typical precocial Placentalia were included. The Marsupialia were represented by the Grey short-tailed opossum (Monodelphis domestica) and the Tammar wallaby (Macropus eugenii). The results confirm clear differences in the developmental degree of the neonates and the postnatal development between marsupial and placental mammals. The newborn lungs of the altricially born placentals M. auratus and S. murinus are at the late terminal air sac stage with numerous small air sacs of 50 - 80 µm in diameter. Alveoli are formed shortly after birth at the age of 2 days in M. auratus and at the age of 4 days in S. murinus. In T. belangeri and in the precocially born C. aperea alveoli are already present at birth. In contrast, the lungs of the newborn marsupials M. domestica and M. eugenii are at the early terminal air sac stage with few large air sacs of 300 – 400 µm in diameter. The postnatal lung development proceeds very slowly in marsupials and alveoli are not present before the age of 28 days in M. domestica and 65 days in M. eugenii. The metabolic investigations demonstrate that Marsupialia have a low metabolism at birth and achieve the adult metabolism late in the postnatal development. All examined Placentalia showed the same pattern of oxygen consumption. Corresponding to their advanced differentiation of the lungs they also exhibit high metabolic abilities at birth and reach the adult metabolism during the first week of life. During this critical period placental young have a higher resistance against certain environmental stresses than marsupial young and this could mean an evolutionary advantage of the placental “reproductive strategy” under suboptimal climatic conditions.

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