Biomedical subjects

V Dantzer

Publications and source records attributed to V Dantzer.

At least 55 records · Page 3Linked to original sources

PubMed1997

Angiotensin II receptors and renin in the porcine uterus: myometrial AT2 and endometrial AT1 receptors are down-regulated during gestation.

1. The aim of the present study was to characterize the angiotensin II (AngII) receptor subtypes in the porcine uterus and the variation of receptor densities and renin concentrations during gestation. 2. In myometrium from non-pregnant sows, the AngII receptors were almost exclusively AT2 receptors. During gestation, the AngII receptor density was decreased and the AT1 receptor became predominant in the last part of gestation as a result of a down-regulation of the AT2 receptor. 3. In the endometrium, the AT1 receptor was predominant both in non-pregnant sows and throughout gestation. The AngII receptor density was decreased during gestation as a consequence of down-regulation of the AT1 receptor. 4. The renin concentrations in the myometrium and endometrium of pregnant sows did not differ from those in non-pregnant animals. 5. The finding of enzymatically active renin and high densities of AngII receptors in the porcine uterus is in accordance with a functional renin-angiotensin system (RAS), which may be important for an increased vascular permeability and stimulated angiogenesis in early pregnancy and for contraction of the myometrial smooth muscle cells during parturition. The predominance of AT1 receptors in the endometrium of non-pregnant sows differs from an earlier finding in non-pregnant women, where AT2 receptors were predominant in the endometrium. This is in accordance with earlier studies, indicating species differences in the expression and possibly also the physiological roles of the RAS in reproductive tissues.

Angiotensin II↗

PubMed1996

The gyrification of mammalian cerebral cortex: quantitative evidence of anisomorphic surface expansion during phylogenetic and ontogenetic development.

Describing the shapes of 3D objects has proved to be as problematical in biology as in other areas. In an attempt to tackle this problem, established stereological methods (the Cavalieri principle and vertical sectioning) have been used to estimate a 3D shape-dependent quantity which can detect anisomorphic changes and is related to the degree of cortical convolution or gyrification. This isomophy factor is employed to assess phylogenetic and ontogenetic changes in the mammalian cerebral cortex. Gross anatomical differences between cerebral hemispheres of adult domestic mammals (horses, oxen, pigs, goats, dogs, cats and rabbits) were tested by paying attention to species, laterality and sex differences. Human fetal brains were also studied. Mean body weights of domestic mammals varied from 4 kg to 460 kg and brain weights from 10 g to 636 g. Fetuses weighed 39-610 g (crown-rump lengths 85-185 mm) and brain volumes were 4-56 cm3. Isomorphy factors were derived from estimates of hemisphere volumes and cortical surface areas. Hemisphere shape varied between species but no lateral or sex differences were detected. It is concluded that these mammalian brains are, in terms of their gross anatomy, symmetric and not sexually dimorphic. Fetal brains became more convoluted during uterine development. The isomorphy factor offers a convenient measure of gyrification which demonstrates that brains become more convoluted as they enlarge.

Animals↗

PubMed1996

Stereological and allometric studies on mammalian cerebral cortex with implications for medical brain imaging.

Design-based stereological methods (the Cavalieri principle and vertical sectioning) have been used to estimate the volumes, surface areas and thicknesses of the cerebral cortex. Cortices of individual hemispheres were analysed in a selection of 31 adult domestic mammals (horses, oxen, pigs, goats, dogs, cats and rabbits). There were 13 females and 18 males. After correcting for fixation shrinkage effects, results were tested for species, laterality and sex differences using linear regression and analysis of variance. Mean body weights of domestic mammals varied from 4 kg to 460 kg and brain volumes from 11 cm3 to 603 cm3. Hemisphere dimensions varied between species but, except for volume (which exhibited a species x sex interaction effect), no other differences were detected. It is concluded that these mammalian brains are, in terms of their gross anatomy, symmetric and not sexually dimorphic. Apparent cortical thickness (measured directly on slices) proved to be a satisfactory estimate of true thickness (estimated by dividing cortical volume by the mean of outer and inner cortical surfaces). This has implications for medical slice images on which mean cortical thickness can be estimated only from apparent local thicknesses.

Analysis of Variance↗

PubMed1995

Changes in glycan distribution within the porcine interhaemal barrier during gestation.

Changing patterns of glycan distribution are described in porcine placentae at 15, 19, 26, 43, 58, 69 and 109 days gestation, using a carefully selected panel of lectins that allowed partial analysis of saccharide classes and sequences. The lectins used were from Galanthus nivalis, Pisum sativum, Phaseolus vulgaris (leukohaemagglutinin), Triticum vulgaris, Tetragonolobus purpureus, Ulex europaeus-1, Arachis hypogaea, Erythrina cristagalli, Glycine max, Maclura pomifera, Wisteria floribunda, Dolichos biflorus, Maackia amurensis, Sambucus nigra and Limax flavus. During the course of gestation the trophoblast developed from a smooth to a deeply folded membrane, while enlarging fetal and maternal capillaries grew closer to each other. The fetomaternal interface expressed many classes of saccharide, both O- and N-linked, but failed to bind DBA, MAA and SNA. Many granules were present in the maternal epithelium, and a striking feature was the appearance of staining with DBA and UEA-1 by day 43. This stage of pregnancy was also associated with changes in trophoblast glycan expression, with a diminution in staining intensity of AHA, MPA and LTA, but an increased intensity with ECA, SBA and WFA. Changes in lectin binding throughout gestation are correlated with previous ultrastructural findings and their relevance to the immunological and functional aspects of pregnancy is discussed.

Animals↗

PubMed1995

Vascular architecture of the lactating and non-lactating teat of the bitch: a scanning electron- and light microscope study.

Tissues from fourteen mammary glands of eight bitches were prepared for scanning electron microscopy of vascular corrosion casts and for histology to study the vasculature of the lactating and non-lactating teats. The densely-meshed mammary dermal capillary network formed ridges and troughs. The teat ducts were vascularized by a relatively densely-meshed capillary network which drained into veins longitudinally oriented to the ducts. Between eight and fifteen teat duct openings were seen on the tip of the teat, that were sometimes divided by a septum. The inner vascularization of the teat showed that the main papillary arteries divided into undulating secondary papillary arteries which presented numerous semi-constrictions and loops. Their structure may help during erection of the teat. Arteriovenous anastomoses found at different points may participate in blood flow maintenance during suckling, heat regulation and teat erection. Veins freely anastomosed and ran longitudinally to the axis of the teat. They exhibited numerous bicuspid valves. In non-lactating teats, vessels showed the same main architecture and characteristics mentioned above, although these were considerably less marked. The structure of the vascular elements in the teat of the bitch could favor blood flow during suckling and suggest that vessels adapt to the physiological situation.

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↗

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↗

PubMed1993

Immunocytochemical localization of amiloride-sensitive sodium channels in the lower intestine of the hen.

We have used polyclonal antibodies generated against purified bovine renal amiloride-sensitive Na+ channels to localize amiloride-sensitive Na+ channels within the lower intestine (colon and coprodeum) of the hen. These antibodies cross-reacted with two polypeptides exhibiting M(r)'s of 235 and 150 kDa on immunoblots of detergent-solubilized apical membrane fractions from both the colon and coprodeum. The apparent molecular masses of theses polypeptides are in agreement with the M(r)'s of 2 of the subunits of the renal high amiloride-affinity Na+ channel, namely the alpha and the beta (= amiloride binding) subunits. The cellular distribution of Na+ channels was determined by immunoperoxidase and indirect immunofluorescence cytochemical techniques. The apical (luminal) membrane and cytoplasm of villar principal cells in both colon and coprodeum exhibited immunoreactivity, whereas goblet cells were negative. Both principal and goblet cells of the crypts were also negative. We conclude that the amiloride-sensitive Na+ channels are localized to the principal cells of the intestinal villi and that these cells are responsible for intestinal Na+ absorption.

Amiloride↗

PubMed1993

Endocrine correlates of placental permeability during gestation in the pig.

1. Hormone and electrolyte concentrations were determined in amniotic and allantoic fluid collected from sows at 47-112 days of gestation and correlated with placental and fetal membrane electrolyte permeability. 2. Significant differences between the electrolyte and endocrine gestational profiles of amniotic and allantoic fluid were identified. 3. The principal endocrine correlate (r > 0.62; P < 0.01) of gestational changes in the sodium and chloride permeabilities of the porcine placenta and fetal membranes was found to be the concentration of oestrogen in the amniotic fluid.

Allantois↗

PubMed1993

Renin and prorenin in reproductive tissues during gestation in pigs and cattle.

1. High concentrations of prorenin and active renin were previously found in ovarian follicular fluid from cattle but not from pigs. In the present study female reproductive tissues and fluids from cattle and pigs during gestation were investigated to clarify a possible species difference in active renin and prorenin concentrations. 2. Very high concentrations of active renin but no prorenin were found in corpus luteum from both species. 3. Relatively low concentrations of active renin, in the same order as in maternal blood plasma, were found in myometrium, endometrium, placenta and fetal membranes from both species. Prorenin was undetectable in these tissues except for bovine myometrium and porcine endometrium in some animals. 4. The concentrations of active renin and prorenin in amnionic fluid from both species were below the maternal plasma values. In allantoic fluid the concentrations were higher than in amnionic fluid. 5. The plasma concentrations of active renin and prorenin did not change during gestation in pigs. This finding is in contrast to the observations in humans and does not support a systemic effect of prorenin during gestation. 6. The presence of renin in the reproductive tissues, especially the very high concentrations in the corpus luteum, indicates a local function of the renin-angiotensin system during gestation.

Allantois↗

PubMed1993

Purkinje cell complements in mammalian cerebella and the biases incurred by counting nucleoli.

An unbiased stereological counting device (the fractionator) was used to count Purkinje neurons in mammalian cerebella of known weights in order to define the relationship between weight and number. Nucleoli were chosen as the counting unit and numbers were estimated from uniform random samples of wax-embedded tissue sections. For the cerebella of rat, rabbit, cat, dog, goat, sheep, pig, ox, horse and human, there was a significant linear relationship between log number and log weight. The allometric relationship took the form N = 748,500 x W0.627. The relative bias associated with using nucleoli as counting units was assessed separately on disector pairs of sections and amounted to roughly -5% but varied between species. When the brains of females and males were analysed separately (cat, goat, pig, ox, horse, human), there were no significant differences between the regression lines. These results are consistent with earlier findings. They imply that Purkinje neuron packing densities decrease as brain size increases. Moreover, our preliminary findings appear to indicate that, for any given cerebellar weight, females and males have similar numbers of neurons.

Animals↗

PubMed1992

Structural and enzymatic studies on the plasma membrane domains and sodium pump enzymes of absorptive epithelial cells in the avian lower intestine.

The coprodaeum of the domestic hen maintained on a low-NaCl diet adapts by enhanced sodium transport. This study examines the adaptive response at the single cell and whole organ levels. Surface areas of apical (microvillous) and basolateral plasma membranes of columnar absorptive epithelial cells were estimated by use of ultrastructural stereology. The activities of succinic dehydrogenase (a mitochondrial enzyme) and ouabain-sensitive, potassium-dependent paranitrophenyl phosphatase (a sodium pump enzyme) were determined in tissue homogenates. Sodium, potassium-ATPase (pump enzyme) activity in cell membranes was localized by ultrastructural cytochemistry. Apical and basolateral membranes responded differently. In high-NaCl hens, the membrane signature of the average cell was 32 microns 2 (apical), 932 microns 2 (lateral) and 17 microns 2 (basal). Cells from low-NaCl hens had more apical membrane (49 microns 2 per cell) but essentially the same area of basolateral membrane. However, total surfaces per organ were greater for all membranes. Sodium pump enzymes were localized in basolateral membranes. Enzyme activities per unit mitochondrial volume and per unit basolateral membrane surface were higher in low-NaCl birds. These findings are discussed in the context of known mechanisms of transcellular sodium transport via apical ion channels and basolateral pumps.

4-Nitrophenylphosphatase↗

PubMed1992

Measurement and identification of prorenin and renin in ovarian follicular fluid from cattle and pig.

1. In previous studies we have demonstrated and solved several methodological problems in relation to the measurement of prorenin by trypsin activation in rat, bovine, hog and horse plasma. 2. The aim of the present study was to develop a method for the measurement of prorenin in bovine and porcine ovarian follicular fluid. 3. Trypsin activation of follicular fluid generated angiotensin I immunoreactive material (AI IM) in both species. 4. The AI IM interfered with the renin assay, but could be completely removed by a cation exchange resin in a batch-wise technique. 5. The enzymatic activity of trypsin-activated prorenin and pre-existing active renin was completely inhibited by a specific inhibitor of renin. 6. The reactions were optimized and an accurate measurement of prorenin in ovarian follicular fluid was developed. 7. The existence of prorenin and renin in bovine ovarian follicular fluid was established. Prorenin and renin in porcine ovarian follicular fluid was demonstrated for the first time. 8. The ratio between ovarian follicular fluid and plasma was 43 for prorenin and 19 for active renin in cattle. The same ratios in pigs were 1.3 and 0.4, respectively. These findings indicate a species difference with respect to the amount of prorenin or active renin present in ovarian follicular fluid.

Angiotensin II↗

PubMed1992

Quantitative analysis of factors contributing to expansion of microvillous surface area in the coprodaeum of hens transferred to a low NaCl diet.

A stereological study of the lower intestine (coprodaeum) of the domestic hen was undertaken using combined light and electron microscopy. Numbers of columnar absorptive epithelial cells and the dimensions and numbers of microvilli were estimated. The aim was to identify the main factors contributing to an increase in microvillous surface area following transfer of hens from a high to a low NaCl diet on which they were kept for at least 3 wk. The principal contributor to observed changes between organs was cell number. Birds adapted to the low NaCl diet had 57% more cells than high NaCl controls. The average cell had a larger microvillous surface (55%) and this could be explained by the presence of longer (34%) and more densely packed (38%) microvilli. The total number of microvilli per coprodaeum doubled (from 35 x 10(9) on the high NaCl to 71 x 10(9) on the low NaCl diet). The increase in cell number accounted for 67% of the change in surface area and 78% of the change in number of microvilli per organ. These findings emphasise that, when assessing the form and function of a whole organ, it is important to monitor cell populations as well as single cells. This is especially true when studying renewing and expanding (rather than static) populations.

Animals↗

PubMed1991

Gestational changes in electrolyte transport, electrical activity, and permeability of the porcine placenta.

1. The electrolyte transport capacities of the porcine placenta and fetal membranes (amnion, chorion, and allantois) during gestation (47-112 days) were assessed in vitro and in the absence of electrochemical, osmotic, or hydrostatic driving forces. Net transmural transport of 22Na and 36Cl across sections of porcine allantochorion-endometrium (ALCE), amniochorion-endometrium (AMCE), and allantoamnion (AA) mounted in Ussing chambers could not be detected at any stage of gestation. 2. These tissues were characterised throughout gestation by low electrical potential difference (PD; less than 5 mV, fetal side positive with respect to maternal side) and short circuit current (SCC; less than 16 microA.cm-2) which were amiloride and iodoacetate sensitive. 3. A periparturitent reversal in the polarity of PD to fetal side negative and a change in the direction of the SCC was observed in tissues obtained from sows (n = 3) at 111-112 day gestation. These changes were accompanied by a 73% increase in electrical resistance (R) and a 2-10-fold decrease in the permeability of tissues to Na and Cl. 4. Morphological studies revealed a decrease in the thickness of allantoamnion and a decrease in the height of epithelia from ALCE, AMCE, and AA during gestation, indicating a decrease in activity. These morphological changes only partly explained the pre-term electrophysiological changes in these tissues.

Animals↗

PubMed1991

Localization of sodium absorption and chloride secretion in an intestinal epithelium.

Hen coprodeum absorbs sodium electrogenically and, when stimulated by theophylline, secretes chloride. In this study the vibrating microprobe technique was used to localize the transport of these ions to intestinal villi/folds and crypts. With the isolated, stretched epithelium, controlled by light microscopy and scanning electron microscopy, in open circuit, currents were inward, 40 +/- 7 microA/cm2, 50 microns vertically above villi, and outward, 36 +/- 7 microA/cm2 above crypts. The currents decayed exponentially to near zero at 300 microns with the same length constant. A physical model simulating the observed loci of current sources and sinks predicts potential profiles consistent with our data. Extrapolation of the currents gives a surface potential of 45 microV, negative on villi and positive above crypts. Short circuiting increased villus current to 86 +/- 27 microA/cm2 at 50 microns, and amiloride treatment reduced it to -8 microA/cm2; in both cases crypt currents were abolished. The inward currents are compatible with sodium absorption. Induction of chloride secretion after amiloride treatment, resulted in current circuits similar to those induced by sodium absorption, with villus currents of 23 +/- 7 microA/cm2. This is in accord with chloride secretion at the villi. Quantitative estimates of crypt number (860/cm2) and opening diameter (15 microns), in conjunction with isotopic measurements of active and electrical potential-driven ion fluxes demonstrate, however, that only 4% of the potential-driven co-ion transport occurs through the crypts. This indicates that nearly all chloride secretion comes from the sodium-absorbing villar area. Were the chloride secretion to occur solely from the crypts, the current should have been in the opposite direction and 10,000-fold larger.

Amiloride↗

PubMed1991

Avian lower intestine adapts to dietary salt (NaCl) depletion by increasing transepithelial sodium transport and microvillous membrane surface area.

A tissue sampling scheme for tandem assessments of whole-organ physiology and ultrastructure was applied to the lower intestine (coprodaeum) of White Plymouth Rock hens on low- and high-NaCl diets. The objective was to correlate net amiloride-sensitive Na transport determined using the Ussing chamber with the plasma membrane surface areas due to microvilli at the epithelial cell apex. Hens kept on the low-NaCl diet for 3-4 weeks displayed a substantial increase in short-circuit current and in total microvillous membrane surface area. The latter rose from a group mean +/- S.E.M. of about 90 +/- 9.7 cm2 to one of 200 +/- 38 cm2 per organ. An increase in epithelial cell membrane contributed to, but did not fully explain, the increase in microvillous area. No differences in mean cell height or mean cell volume were found but the average cell in the low-NaCl birds was better developed in possessing a greater surface area of microvilli. On the high-NaCl diet, the epithelium was 33 +/- 2.7 microns tall and contained about 270 +/- 15 million cells. Each cell had a volume, on average, of 540 +/- 59 microns 3 and a microvillous surface of 32 +/- 2.6 microns 2. After NaCl depletion, there were 420 +/- 75 million cells and the average microvillous surface was 49 +/- 5.3 microns 2 per cell. The morphological adaptations alone do not explain the increased net Na transport found on the low-NaCl diet. Of cardinal importance is greater density of open Na channels in apical cell membranes.

Adaptation, Physiological↗