Biomedical subjects

R Leiser

Publications and source records attributed to R Leiser.

At least 55 records · Page 3Linked to original sources

PubMed1999

[Computer-based image analysis for experimental and clinical morphology--principles, utilization and marginal limits].

The new computer based image analysis techniques are powerful tools for mophometrical and quantitative image analysis in case of clinical and experimental morphology. Digital image analysis requires a distinction between two phases 1. generation of fundamental data (x,y coordinates and grey values of the pixel) and 2. calculation of parameters from these data. Stereological procedures are very powerful in quantifying morphological phenomenons, but computer based image analysing techniques allow multiple analysis of morphological objects and analysis of statistical distributions. There is great scientific benefit using modern computer based image analysing techniques.

Animals↗

PubMed1999

[Animal experiment models of hypertension in pregnancy--an alternative to clinical studies?].

UNLABELLED: Because of ethical constraints upon research during human pregnancy and of the heterogeneity of preeclampsia a number of experimental animal models were used to study pathophysiology of preeclampsia. We reduced the uteroplacental flow by aortic clip technique in 72 SHR-rats in 4 groups (G 1 not gravid--no clip, G 2 not gravid--aortic clip, G 3 gravid--no clip, G 4 gravid--aortic clip). While gravidity normalised blood pressure in SHR (G 3), reduction of the uteroplacental flow significantly increased maternal blood pressure (G1 240/180 mmHG, G2 238/183 mmHg, G3 148/99 mmHG, G4 200/145 mmHg) and leads to significant higher hematocrit, significant lower plasma renin activity and aldosterone plasma concentration, as it is found in human superimposed preeclampsia. SDS-page electrophoresis proved a significant increase of urinary high density proteins. CONCLUSION: In comparison to chronical inhibition of NO-synthesis or chronical application of ultra-low-doses-endotoxin, reduction of uterine flow by aortic compression is a reliable animal model and leads in SHR to a superimposed preeclampsia-like syndrome with many similarities to human clinical findings. Animal models for preeclampsia are no alternative to clinical studies, but they are furthering our understanding of pathophysiology in many fields.

Aldosterone↗

PubMed1998

Effects of energy and purines in the diet on proliferation, differentiation, and apoptosis in the small intestine of the pig.

The effects of the energy and purine content in the diet on mucosal cell mitosis, function, and apoptosis in the small intestine of pigs were investigated in two experiments. In experiment I, three groups of five pigs were first fed a commercial diet that contained 9.1 MJ metabolizable energy (ME) per kilogram dry matter (DM) and 16.4% crude protein. It was followed by the experimental diets for 5 days each starting with an energy deficit (5.8 MJ ME/kg DM; 7% crude protein) followed by a high-energy diet with low purine content (14.1 MJ ME/kg DM; 13.6% crude protein; 460 mg purines/kg), or alternatively an isocaloric high-purine diet (2,160 mg purines/kg). During experimental periods, blood samples were drawn daily through catheters for insulin-like growth factor-I (IGF-I) determination. The animals were killed at the end of the corresponding feeding period and gut tissue samples were collected. In tissue samples, IGF-I and parameters for the characterization of mitosis (thymidine kinase [TK], proliferating-cell nuclear antigen [PCNA]) and differentiation (RNA content, alkaline phosphatase, sucrase) were measured. The degree of apoptosis was determined histologically. In experiment II, five pigs were fitted with simple T-cannula at the distal jejunum. They were fed the three experimental diets consecutively for 7 days each and sucrase and alkaline phosphatase were measured in digesta (four samples daily). IGF-I in blood but not in tissue clearly responded to the energy content of the diet with a decrease during the deficit and an increase in the two high-energy groups. However, purines had no additional effect on IGF-I. TK, PCNA, and gut weight showed an energy effect on mitosis, which was paralleled by increased peripheral IGF-I. Purines led to a further increase of mitosis, but IGF-I and gut weight were not increased. The degree of mitosis was correlated with higher activities of sucrase and alkaline phosphatase and also with the number of apoptotic cells. The enzyme activity increased from the deficit to the high-energy group and was further elevated due to purines. The results from experiment II also confirm these effects of energy and purines, because the activities of the enzymes in digesta decreased during energy deficit, but increased due to energy and in addition to purines.

Alkaline Phosphatase↗

PubMed1998

3-D confocal laser scanning microscopy used in morphometric analysis of rat Purkinje cell dendritic spines after chronic ethanol consumption.

A confocal laser scanning microscope (with a 543 nm laser) was used for imaging rat Purkinje cell dendritic spines at high 3-D resolution. In a nutritionally controlled study of the rat, 5 months of ethanol consumption was demonstrated to alter the spines of Purkinje cell dendrites in rat cerebellum. Intact spines showed significant elongation after ethanol exposure, whereas this neuromorphological alteration could not be detected in controls. Spine elongation could be regarded as compensative growth of spines in search of new synaptic contacts due to alcohol induced cell loss.

Alcoholism↗

PubMed1997

Term ovine placental vasculature: comparison of sea level and high altitude conditions by corrosion cast and histomorphometry.

The placental vascular architecture differs significantly at high altitude from that at sea level in the human and guinea-pig. Four sheep between 137 and 140 days of gestation, kept near sea level throughout gestation, were used as a normoxic control group for comparison of the placental vasculature with 10 other ewes, kept at high altitude (3820 m above sea level; Barcroft Laboratory, White Mountain Research Station, CA, USA). Placentomes from both groups were prepared for histology and scanning electron microscopy of vascular corrosion casts. Singular perfusion of fetal placentae, as well as combined maternal/fetal injection was performed. The influence of long-term hypoxaemia was determined by qualitative and semi-quantitative evaluation of corrosion casts and histological sections. The fetal vessel casts show a distinct difference in the arrangement of vessels of all sizes in response to long-term hypoxaemia. In the control group, stem arteries and veins are straight and parallel. In contrast, this is much less evident in the hypoxaemic group because arterioles and venules branch off the stem vessels more frequently and in an irregular manner. This leads to a capillary bed that is much more dense due to increased branching and capillary coiling. These observations are confirmed by histomorphometry. In the fetal vessels of high altitude sheep placentomes, we observed a decreased number of vascular cross sections (21.6 +/- 4.7 SEM versus 27.7 +/- 4.0 SEM; P = 0.02). However, the average luminal size per cross section (77.9 +/- 10.5 microns2 SEM versus 59.4 +/- 7.4 microns2 SEM; P = 0.004) was increased at high altitude and the percentage of lumina of the total area (5.7 +/- 0.5 SEM versus 5.3 +/- 0.3 SEM; P = 0.09) indicated a trend towards an increase. In maternal vessels of high altitude placentomes, the number of vessel cross sections (6.5 +/- 0.7 SEM versus 6.0 +/- 0.5 SEM; P = 0.2) remained unchanged, whereas the average luminal size (1108 +/- 122 microns2 SEM versus 844 +/- 77 microns2 SEM; P < 0.001) and the percentage of lumina out of the total area (20.9 +/- 1.8 SEM versus 17.5 +/- 1.7 SEM; P < 0.001) were increased. The interhaemal distance appeared to be slightly but not significantly increased at high altitude. These findings indicate that at high altitude the sheep placenta develops an increased materno-fetal absorptive surface to help guarantee substance exchange.

Altitude↗

PubMed1997

Fetal villosity and microvasculature of the bovine placentome in the second half of gestation.

The architecture of the fetal villous tree and its vasculature in the bovine placentome were studied in the second half of gestation using both conventional histology and histology of ink-filled blood vessels. These were compared with corrosion casts of plastic fillings of the vasculature, prepared for scanning electron microscopy. This combination of morphological methods allows perception of the villous tree throughout gestation from broad-conical to tall-conical form where branch ramification occurs mainly at right angles to the stem. The stem villus typically contains a single central artery and several peripheral veins arranged in parallel. The proximal branches to the stem, the intermediate villi, contain a central arteriole and accompanying venules. The distal branches, the terminal villi, enclose capillary convolutions which consist of an afferent arterial capillary limb, capillary loops and efferent venous capillary limbs. Vascular interconnections exist within the terminal villi, as capillaries or venules between the capillary convolutions, serially bridging them in up to 5 places, and as capillary anastomoses between the capillary loops. Coiling and sinusoidal dilatations of these loops develop near the end of gestation. The intraplacentomal rearrangement of villous trees with progressive gestation and their morphological vascular adaptations are discussed in relation to placental function, including the ever increasing need for transplacental substance exchange. This adaptation allows the blood to traverse the shortest possible arterioarteriolar route to the periphery of the trees where exchange takes place. The need for an increasing blood flow stimulates capillary growth and at the same time optimises the blood flow reaching the placental barrier represented by the vessel cast surface. The capillaries also carry the blood back into the very voluminous system of venules and veins where back diffusion may occur. The total volume of terminal villi of bovine placentome, the 'working part' of villous trees, hence distinctly increases with respect to the stem and intermediate villi, the 'supplying part' of the villous tree. In morphological terms the efficiency of the bovine transplacental diffusional exchange is higher than in the closely related 'co-ruminants' sheep and goats and distinctly higher when compared with the human placenta.

Animals↗

PubMed1997

Ultrastructure of rat Purkinje neurons after chronic ethanol consumption and prolonged abstinence.

In the present study of nutrition control of Wistar white rats, the ultrastructure of cerebellar Purkinje cells was studied after chronic ethanol exposure and a subsequent period of prolonged abstinence: a qualitative investigation of the perikarya of Purkinje cells was performed in age-matched controls (group A) and rats alcohol-fed for 5 months and withdrawn from this diet for 3 months (group B). The results showed massive accumulation of small dense bodies as well as obvious deposition of lipofuscin in the Purkinje cells of group B. Furthermore, ring-shaped Golgi apparatus units, lamellar bodies and degenerative foci dispersed throughout the cytoplasm of the alcohol-treated animals referred to degeneration processes and neuronal cell death, the morphological characteristics and the aetiology of which are discussed.

Alcohol Drinking↗

PubMed1996

Can megadoses of thiamine prevent ethanol-induced damages of rat hippocampal CA1 pyramidal neurones?

The specific aim of this study was to evaluate whether high doses of thiamine can compensate or prevent alcohol-induced damages of rat hippocampus CA1 pyramids. Twenty weeks of ethanol consumption together with a dose of thiamine in the range of 1.19 mg/100 mg food induced significant enlargement (parameters measured were length of the whole spine and diameter of the end-bulb) of dendritic spines. Hypertrophy can be interpreted as a compensation process due to alcohol-induced cell death because viable spines are in search of new synaptic contacts. In contrast, dendritic spines of the alcohol group fed at the same time with a high dose of thiamine (119 mg/ 100 g food = megavitamintherapy) showed normal data concerning these parameters. From these results it may be concluded that a megavitamin therapy supports a neuron's carbohydrate metabolism and therefore could be able to prevent or reduce alcohol-induced damages of hippocampal CA1 pyramidal cells in rat central nervous system.

Alcoholism↗

PubMed1996

Intrauterine growth restriction with absent end-diastolic flow velocity in the umbilical artery is associated with maldevelopment of the placental terminal villous tree.

OBJECTIVE: Our purpose was to evaluate the structure of placental terminal villi and their capillaries in pregnancies complicated by intrauterine growth restriction with absent end-diastolic flow velocity in the umbilical artery. STUDY DESIGN: Glutaraldehyde-perfusion-fixed villous tissue and a plastic cast of the vessels in at least two cotyledons were prepared from 10 cases with intrauterine growth restriction and 9 gestational age-matched control placentas. The structure and dimensions of 20 terminal capillary loops per cast were determined by scanning electron microscopic examination, and their appearances were correlated with the peripheral villi of the perfusion-fixed villous tissue. RESULTS: Capillary loops in the growth-restricted cases were sparse in number and significantly longer than in the control cases (218 microns [72] vs 137 microns [30], mean and SD, p < 0.05). They exhibited fewer branches (4.0 [1.9] per loop vs 6.1 [2.2], p < 0.05) and a majority of loops were uncoiled (79% vs 18%, p < 0.05). The villous tissues from the growth-restricted cases demonstrated elongated villi, consistent with the cast findings. The trophoblast surface was wrinkled and in some areas covered by fibrin plaques. CONCLUSIONS: The terminal villous compartment of the placenta appears to be maldeveloped in preterm intrauterine growth restriction pregnancies where absent end-diastolic flow velocity is demonstrated in the umbilical artery before delivery. These findings are consistent with an increase in fetoplacental vascular impedance at the capillary level and may account for the impaired gas and nutrient transfer in this disorder.

Blood Flow Velocity↗

PubMed1996

Neuroprotective effects of thiamine-megadoses after long-term ethanol application in the rat brain. A structural investigation of hippocampal CA1 pyramidal and cerebellar Purkinje neurons.

Using the Golgi-impregnation technique we could document that twenty weeks of ethanol consumption induce significant elongation of dendritic spines of rat cerebellar Purkinje cells, and as demonstrated for the first time in the present study, of hippocampal pyramidal neurons. Spine hypertrophy might be the result of compensative growth of spines in search of new synaptic contacts due to neuronal cell loss caused by the prolonged ethanol intake. In contrast, this neuromorphological alteration could not be detected in the alcohol group fed at the same time with a high dose of thiamine (119 mg/100 g food) = thiaminemegadose). As thiamine participates in a number of enzymatic reactions primarily concerned with carbohydrate metabolism, it may be concluded that megadoses of thiamine are able to support neuronal energy metabolism, which was initially impaired by ethanol-induced thiamine deficiency. Therefore, a megavitamintherapy in association with chronic alcohol intake could be able to attenuate or prevent ethanol-induced damages in rat central nervous system.

Animals↗

PubMed1994

Initial vascularisation in the pig placenta: I. Demonstration of nonglandular areas by histology and corrosion casts.

The vascular interrelationship of the well-established porcine placenta has previously been described from vascular casts and histology, but not its developmental stages. This study was performed using the same methods on 17 sows of well-known stages of gestation ranging from 9 1/2 to 43 days post coitum (p.c.). At the precontact stage, days 9 1/2 to 12 1/2 p.c., the subepithelial capillaries formed a wide open meshwork of variable diameter, 3-14 microns, without any difference between meso- and antimesometrial side. At the early contact and adhesion stages (days 13 to 18 p.c.), the first increase in vasculature was seen at the mesometrial side close to the embryonic disc of the very long blastocyst at day 15 p.c., 2 days after the first contact between trophoblast and maternal epithelium was seen. At day 18 p.c., the areas with dense capillaries increased markedly at the mesometrial side with the same parallel organization as seen at day 15 p.c., whereas the antimesometrial side still had a relative loose appearance comparable to the previous stages. At the early placental stages (days 20 1/2 to 23 p.c.), the capillary bed formed smooth folds, which in some areas at day 20 1/2 days developed into smaller folds or prerugae. Here the capillaries changed to convoluted forms with slightly bulbous dilations measuring about 30-35 microns in diameter. This developmental progress became more elaborate at day 23: capillaries of the low ridges of prerugae formed irregular dilations up to 50 microns in some areas. At this stage the parallel arrangement of the capillary meshwork characteristic of the previous stage was not longer discernable. By days 32-43 p.c., an increase in microscopic folding was present, and the maternal arterioles could be traced to the top of the ridges, creating the characteristic vascular architecture needed for an efficient exchange of oxygen, carbon dioxide, and nutrients of the basically developed porcine placenta.

Animals↗

PubMed1994

Initial vascularisation in the pig placenta: II. Demonstration of gland and areola-gland subunits by histology and corrosion casts.

Tissues from 10 pregnant pigs between 9 1/2 and 43 days post coitum (p.c.) were prepared for histology and vascular corrosion casts to examine the vascularisation of the gland and areola-gland subunits of the early pig placenta. The endometrial vascular networks shown by casts were equal in both glandular and interglandular fields from days 9 1/2 to 14-15 p.c. This represents a cyclic stage uninfluenced by the early implanting embryo on day 13 p.c. By day 15 p.c., the first areola formation was observed both histologically and on casts. The maternal areolar and glandular capillary network developed into a widely meshed loose type, in contrast to the interareolar type which had a dense and parallel architecture. In some cases extremely large, crooked, and highly anastomosed maternal capillaries developed between these two networks. This specialized transition is thought to form the base for the ring-like seal formation (RSF) of the areolar periphery. A firm materno-fetal anchor therefore "seals" the areola and its glandular secretory contents from its interareolar surroundings. Therefore, the glandular and maternal areolar vasculatures are clearly discernable from that of the fetal areolar vasculature. The former are associated with the known maternao-fetal substance transfer of the porcine areolar-gland subunit. This association, however, seems to remain unspecialized in early placentation, as only the regular roundish areola--not the irregular areola--can be distinctly detected.

Animals↗

PubMed1994

Lectin-histochemical analysis of glycans in ovine and bovine near-term placental binucleate cells.

Chorionic binucleate cells (BNC) occur in several ruminants including cow, deer, goat and sheep. They migrate through the chorionic tight junction to fuse with uterine epithelial cells and discharge their granules into maternal connective tissue. We have compared the BNC of near-term, resin-embedded, ovine and bovine placentae using 15 biotinylated lectins and an avidinperoxidase revealing system. There was pronounced conservation of saccharides between the two species. Several sub-types of N-glycan were present, with highly branched structures being abundant, as shown by Galanthus nivalis, Pisum sativum and Phaseolus vulgaris (leuko) agglutinins. Among the non-reducing terminal saccharides conserved were GalNAc alpha 1,3(Fuc alpha 1,2)-Gal beta 1,4GlcNAc beta 1-, GalNAc alpha 1,6Gal beta 1-, Gal beta 1-, Gal beta 1,4GlcNAc- and Gal beta 1,3GalNAc alpha 1- shown by Dolichos biflorus, Wisteria floribunda, Erythrina cristagalli, and Maclura pomifera agglutinins, respectively. Arachis hypogaea and Glycine max agglutinins tended to bind to bovine BNC at different stages of maturity, while fucosyl residues detectable by Tetragonolobus purpureus and Ulex europaeus-1 agglutinins were not observed in either species. The only major difference related to sialyl residues, with alpha 2,3-linked sialic acid being present in bovine (Maackia amurensis, Limax flavus) and alpha 2,6 sialic acid being present in ovine (Sambucus nigra agglutinin) cells. This conservation of glycan may be related to glycosylation of peptide hormones in the granules, and may thus be important in the targeting of these hormones to their receptors.

Animals↗

PubMed1994

Placental structure: in a comparative aspect.

The outstanding structural diversity of the placenta among mammals, i.e. horse, pig, domestic ruminants, cat. Guinea pig and human, has been studied in a comparative manner using terms of classification such as: type of placental membranes, placental shape, placental maternofetal interdigitation, layers of the placental interhemal barrier, trophoblast invasiveness and decidual cell reaction, formation of syncytiotrophoblast, maternofetal blood flow interrelationships, and placental separation at birth. These terms, originating partly from classical acquirements of knowledge and partly from recent research, are presented and new aspects discussed; thus helping towards a better understanding of the structure and function of the different placental types.

Animals↗

PubMed1993

Development and characteristics of placentation in a carnivore, the domestic cat.

Among the carnivores, development of the fetal membranes and placentation have now been particularly well studied in the domestic cat (Felis catus). Initially, the cat conceptus is bordered by a primitive and a precontact chorion. This becomes part of a temporary choriovitelline placenta which is subsequently supplanted by a chorioallantoic placenta. Following the triphasic process of implantation (which involves apposition, adhesion, and intrusion), the chorioallantoic placenta forms a zonary girdle which separates two paraplacental cupules. These cupules are subdivided from base to tips into 1) extravasate zones with hematomal areas and solid junctional areas containing intermingled fetal and maternal tissue, 2) free polar zones with almost no feto-maternal contact, and 3) interplacental polar zones freely projecting into the uterine lumen or, near the end of pregnancy, facing comparable regions of neighboring fetuses. The placental girdle consists of a lamellar zone characterized by elongate, parallel fetal (chorionic) and maternal (septal) lamellae, a junctional zone where fetal and maternal tissues face each other and intimately intermingle, and a zone of pure endometrial glands. In the lamellar zone the interhemal membrane (placental barrier) is of the endotheliochorial type. As pregnancy progresses, cytotrophoblast in the interhemal barrier contributes to the formation of syncytiotrophoblast and is gradually reduced from being a continuous layer to only scattered cells. The syncytiotrophoblast is usually separated from endothelial cells of the maternal capillaries by a thickened basal lamina (the interstitial membrane) or faces persisting endometrial connective tissue containing some enlarged decidual cells. The efficiency of maternal-fetal physiological exchange depends not only upon the thickness of the interhemal membrane, which in reduced in places to 1.5 microns, but also upon the materno-fetal blood flow interrelationship. This is of the simple crosscurrent type in the cat.

Animals↗

PubMed1993

Microvasculature of regular and irregular areolae of the areola-gland subunit of the porcine placenta: structural and functional aspects.

To examine the vasculature of the areola-gland subunit of advanced pig placenta, tissues from ten animals between 43 and 112 days of gestation were prepared for histology and for scanning electron microscopy of vascular corrosion casts from both maternal and fetal sides. Regular areolae, tributary to one gland only, are round with a wide-meshed and smooth subepithelial capillary network on the maternal side, which is similar to the pre-implantative stage and bordered by an abrupt rim towards the inter-areolar maternal capillary network. On the fetal side, the capillary network follows papillae which protrude into the areolar cavity or converge to form a ring towards the areolar periphery. Irregular areolae, in contrast, have indistinct boundaries and are characterized by two or more gland openings. The maternal capillary network has moderate density and follows the corrugations, whereas the fetal capillary network is basically two-dimensional with some blunt sinusoidal protrusions. Vessel architecture of both areolar types implies facilitated external inflow of blood into the areola on arteriolar as well as on capillary levels, whereas the outflow from the areolar capillaries comprises venules converging into one or two areolar stem veins, and therefore conducts venous blood in a manner different from that of the inter-areolar region. It is suggested that this arrangement could favour vascular control mechanisms in uterus, placenta and fetus. On the basis of these observations and the discussion, it is suggested that these areola-specific vessel systems are important for sustaining the characteristic substance transfers in the areola, the secretion, metabolism and absorption, which according to the literature are not the same in the regular as in the irregular areolar type of the porcine areola-gland subunit of the placenta.

Animals↗

PubMed1990

Alterations of the fetal capillary bed in the guinea pig placenta following long-term hypoxia.

Oxygen supply is an important regulator of the fetal placental capillarization. To determine the effects of long-term hypoxia on the fetal placental vessel arrangement pregnant guinea pigs were kept under hypoxic conditions (12% O2 for 45 days). Vessel casts showed a significant difference in branching and orientation of the vessels between the controls and the hypoxic animals. The hypoxic group had a less orientated capillary bed with increased branching and coiling. By light- and transmission electron microscopical studies, there was a decreased diffusion distance, a decreased diameter of the fetal capillaries, and an increased number of capillary cross-sections. These results are consistent with the hypothesis that chronic hypoxia is responsible for increased branching and coiling of the capillaries resulting in a dense network of short and narrow capillaries in the placenta.

Animals↗

PubMed1990

[Vascular morphology of the bovine testis. Light and scanning electron microscopic studies].

The testicular artery of the bull-testis shows a straight course from the end of the pampiniform plexus to the caudal extremity of testis. There it branches off in Rami tunicales, which lie as stratum arteriosum superficially to the albugineal veins of testis: a multi-layered stratum venosum. Arterial Rami parenchymales centripetales run directly to the mediastinum testis, form coils and then divide in approximately 10 or more thinner Rami parenchymales centrifugales, which extend from the coils into the parenchyma of the gonad. The three-dimensional microvasculature of the bull-testis is strikingly different from that of rodents: The peritubular network of capillaries in the interstitial space is positioned in a more irregular way. Only here and there is discernible a rope-ladder-like or polygonal arrangement of capillaries. A subalbugineal plexus does not exist in the bovine testis. Parenchymal veins drain in albugineal veins and these empty in the venous networks of the pampiniform plexus. Valves are a rare finding in testicular veins. Already low perfusion-pressure easily forces the corrosion-compound to leave the capillary bed and form typical extravasations as bent shovel-like plates, thus filling the clefts of peritubular spaces. Arteries and veins are directly embedded in the parenchyma of testis, surrounded only by a relatively thin margin of perivascular connective tissue. There are no septula testis and therefore a lobular organisation of bovine testis does not exist. The angioarchitecture of the testis plays an important role in thermoregulatory and androgen-transfer mechanisms as well as in the transport of rete-fluid to the epididymis.

Animals↗