bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and age‐related change of cerebrovascular noradrenergic (NA) innervation in the Japanese quail
Authors: HAYASHI Kiyonori , FURUSE Mitsuhiro , SOH Tomoki , KUSABA Haruo , IWAMOTO Hisao , ANDŌ Kōichi 
Published: March 2003

ABSTRACTDevelopment of cerebrovascular noradrenergic (NA) innervation was investigated in the Japanese quail, using histofluorescence technique and quantitative analysis. Cerebral perivascular NA nerves arose from the cerebral carotid (CCA), internal ethmoidal (IEA) and vertebral (VA) arteries before hatching, with the first appearance on the CCA and IEA at embryonic day (E) 8 and of the VA at E14. Nerves arising from the IEA were greater in number and spread more rapidly than those from the CCA and VA. On E16, fluorescent fiber bundles lying on the anterior circulation subdivided rapidly into thin fibers. Consequently, the number of NA nerves over the arterial system increased greatly at hatching, particularly along the distal portion of the anterior ramus. At the same developmental stage, all the major arteries of the anterior and posterior circulation were almost entirely covered by NA nerves. The abrupt reorganization of cerebrovascular NA innervation in newborn quails may be related to some specific trophic and vasomotor roles for structural and functional improvement of the cerebral circulation that is required for its brain differentiation at this critical period of development. The supply of NA nerves to the anterior and posterior circulations sequentially increased during development from posthatching day (P) 1–15. Plexuses of NA nerves in each of the major cerebral arteries at P22 and P42–50 were similar in meshwork construction to each other, and to those seen at P15. Likewise, there was no clear statistical difference in the nerve density of the corresponding arteries among the three posthatching ages, except for the caudal basilar artery.
Mechanisms of transjunctional transport of NaCl and water in proximal tubules of mammalian kidneys
Authors: KIIL F. 
Published: March 2003

ABSTRACTTight junctions and the intercellular space of proximal tubules are not accessible to direct measurements of fluid composition and transport rates, but morphological and functional data permit analysis of diffusion and osmosis causing transjunctional NaCl and water transport. In the S2 segment NaCl diffuses through tight junctions along a chloride gradient, but against a sodium gradient. Calculation in terms of modified Nernst–Fick diffusion equation after eliminating electrical terms shows that transport rates (300–500 pmol min–1 mm–1 tubule length) and transepithelial voltage of +2 mV are in agreement with observations. Diffusion coefficients are Dtj=1500 μm2 s–1 in the S1 segment, and Dtj=90–100 μm2 s–1 in the S2 segment where apical intercellular NaCl concentration is 132 mM, 1 mM below complete stop (Dtj=0 and Donnan equilibrium). Tight junctions with gap distance 6 Å are impermeable to mannitol (effective molecular radius 4 Å); reflection coefficients are σ=0.92 for NaHCO3 and σ=0.28 for NaCl, because of difference in anion size. The osmotic force is provided by a difference in effective transjunctional osmolality of 10 mOsm kg–1 in the S1 segment and 30 mOsm kg–1 in the S2 segment, where differences in transjunctional concentration contribute with 21 mOsm kg–1 for NaHCO3 and –4 mOsm kg–1 for NaCl. Transjunctional difference of 30 mOsm kg–1 causes a volume flow of 2 nL min–1 mm–1 tubule length. Luminal mannitol concentration of 30 mM stops all volume flow and diffusive and convective transport of NaCl. In conclusion, transjunctional diffusion and osmosis along gradients generated by transcellular transport of other solutes account for all NaCl transport in proximal tubules.
Sodium/iodide‐symporter: distribution in different mammals and role in entero‐thyroid circulation of iodide
Authors: JOSEFSSON M. , GRUNDITZ T. , OHLSSON T. , EKBLAD E. 
Published: March 2003

ABSTRACTThe sodium (Na+)/iodide (I–)‐symporter (NIS) is abundantly expressed and accumulates iodide in thyroid follicular cells. The NIS is also found in extrathyroidal tissues, particularly gastric mucosa. Controversies exist on the localization of extrathyroidal NIS. We have studied the presence of both NIS peptide and NIS messenger RNA (mRNA) in the digestive tract and thyroid from different mammals. The role of gastric NIS is enigmatic and we aimed to unravel its possible involvement in iodide transport. Methods:  Distribution and expression of NIS were studied using immunocytochemistry and in situ hybridization. Iodide transport in the gastrointestinal tract was measured after oral or intravenous (i.v.) administration of 125I to rats with or without ligation of the pylorus. Results:  All thyroid follicular cells in rat and mouse expressed NIS, whereas a patchy staining was noted in man, pig and guinea‐pig. Gastric mucosa surface epithelium in all species and ductal cells of parotid gland in guinea‐pig, rat and mouse expressed NIS. In parietal cells and in endocrine cells of intestines and pancreas NIS immunoreactivity but no NIS mRNA was found. Studies of 125I uptake showed marked iodide transport from the circulation into the gastric lumen. Conclusions:  The localization of NIS varies slightly among mammals. To establish expression of NIS in a particular cell type the need to correlate the presence of both NIS protein by immunocytochemistry and NIS mRNA by in situ hybridization is emphasized. An entero‐thyroidal circulation of iodide mediated principally by gastric NIS, but possibly also by NIS in salivary glands is suggested.
Collecting duct function in liver cirrhotic rats with early sodium retention
Authors: Jonassen T. E. N. , Heide A. M. , Janjua N. R. , Christensen S. 
Published: March 2003

AbstractLiver cirrhosis is a chronic disease associated with sodium retention due to increased tubular sodium reabsorption. However, the exact tubular site of increased sodium reabsorption in uncertain. We have recently demonstrated selective hypertrophy of the inner stripe of the outer medulla (ISOM) in rats with liver cirrhosis induced by common bile duct ligation (CBL). The present study was designed in order to measure Na–K–ATPase activity in the two major tubular segments located in the ISOM: the thick ascending limb of henles (MTAL) and the collecting ducts (OMCD) in CBL rats. Sham‐operated rats were used as controls. In addition, the natriuretic response to amiloride (0.2 mg kg−1 h−1 i.v) was examined in conscious, chronically instrumented rats during conditions where amiloride‐induced volume losses were replaced continuously using a servo‐controlled i.v. volume replacement system. For 4–5 weeks after CBL, cirrhotic rats showed sodium retention relative to control rats without any sign of ascites. Plasma levels of sodium and aldosterone were normal, but plasma vasopressin was increased. Effective renal plasma flow was significantly increased, whereas glomerular filtration rate (GFR) and renal lithium handling were normal. The CBL rats showed a blunted natriuretic response to amiloride (ΔFENa: 1.17 ± 0.15% vs. 1.65 ± 0.13%; P < 0.05). In rats with CBL, Na–K–ATPase activity per mm tubular length was decreased in the OMCD and unchanged in the TAL segment. These results suggest that increased tubular sodium reabsorption in liver cirrhotic rats with early sodium retention is localized in segments proximal to the collecting ducts.
Localization of a protein inhibitor of carbonic anhydrase in pig tissues
Authors: Ridderstråle Y. , Fierke C. A. , Roush E. D. , Wistrand P. J. 
Published: March 2003

ABSTRACTThe protein inhibitor of carbonic anhydrase (CA), pICA, was localized in pig tissues by an immunohistochemical technique, using rabbit antipICA IgG. Staining for pICA was found in liver sinusoids and kidney glomeruli, where phagocytic cells are located, i.e. Kupffer and mesangial cells, respectively. pICA was not found inside parenchymal cells, or in tissues from striated muscle, heart, eye or lung. It is concluded that the function of pICA is perhaps to bind the carbonic anhydrase isozymes CA I, II, and III, released from erythrocytes into the blood circulation by intravascular haemolysis. The complex of CA‐pICA in plasma may then be transported to the reticuloendothelial system, for degradation and reclamation of CA‐bound zinc. This would be similar to the fate of the haemoglobin–haptoglobin complex for the recycling of iron.
Regulation of Ca2+ channel and phosphatase activities by polyamines in intestinal and vascular smooth muscle – implications for cellular growth and contractility
Authors: Nilsson B.‐O. , Gomez M. F. , Swärd K. , Hellstrand P. 
Published: March 2003

ABSTRACTPolyamines added extracellularly to intestinal and vascular smooth muscle cells cause relaxation through inhibition of Ca2+ channel activity. Intracellularly applied polyamines also affect Ca2+ channel properties. Polyamines do not readily pass over the plasma membrane because of their positive charges but in permeabilized smooth muscle preparations they have free access to the cytoplasm. In this system they increase sensitivity of the contractile machinery to Ca2+ through inhibition of myosin phosphatase activity. The magnitude of Ca2+ channel and phosphatase inhibition depends on the number of positive charges on the polyamine molecule. Polyamines have an obligatory, but yet undefined, role in regulation of cell growth and proliferation. Several groups of protein kinases, such as tyrosine and mitogen activated protein (MAP)‐kinases transmit the growth signal from the plasma membrane to the cell nucleus where mitosis and protein synthesis are initiated. The data reviewed here show that polyamines may affect such signal transmission via inhibition of phosphatase activity.
Modulation of endothelial permeability by 1‐O‐alkylglycerols
Authors: Marigny K. , Pedrono F. , Martin‐Chouly C. A. E. , Youmine H. , Saiag B. , Legrand A. B. 
Published: March 2003

ABSTRACTRegulation of endothelial barrier function often occurs through signalling involving phospholipase C activation which produces diacylglycerol (DAG), a lipidic second messenger activator of protein kinase C (PKC). Therefore, modification of lipidic composition of endothelial cell membranes might modify DAG production and, as a result, alter regulation of endothelial permeability. We investigated the in vitro effects of natural 1‐O‐alkylglycerols on porcine aortic endothelial cell permeability to dye‐labelled albumin. [3H]‐1‐O‐alkylglycerols (10 μm) were substantially incorporated into phosphatidylcholine (6.6%) and phosphatidylethanolamine (4.4%). Stimulation of endothelial cell monolayer with phorbol‐myristate‐acetate or with the calcium ionophore A23187 resulted in a raise in permeability to albumin. Pre‐treatment with 1‐O‐alkylglycerols (10 μm, 24 h) had no effect on basal albumin permeability but totally inhibited the effect of phorbol‐myristate‐acetate, and brought the permeability of A23187‐stimulated endothelial cell monolayers below control. After incubation of cells with [3H]‐1‐O‐alkylglycerols (10 μm, 24 h), we detected the production of the analogue of DAG, and PKC inhibitor, [3H]‐1‐O‐alkyl‐2‐acyl‐glycerol, in resting cells. This production was increased by 58% under A23187 stimulation while phorbol‐myristate‐acetate had no effect. Our data demonstrate that natural 1‐O‐alkylglycerols modify endothelial permeability, and suggest that this effect could be mediated through alteration of lipidic signalling.
Variable frequency trains enhance torque independent of stimulation amplitude
Authors: Slade J. M. , Bickel C. S. , Warren G. L. , Dudley G. A. 
Published: March 2003

Abstract Aim:  Variable frequency trains have been reported to enhance force of fatigued human skeletal muscle. More rapid calcium turnover and/or enhanced stiffness may be responsible for the augmented torque–time integral during surface stimulation at moderate amplitude. In contrast, it has recently been suggested that variable frequency train enhancement occurs only at low forces as a result of preferential stimulation of fast fibres and/or altered motor unit recruitment. If correct, this would limit the practical benefit of variable frequency trains. Accordingly, we tested the hypothesis that torque augmentation by variable frequency trains in fatigued skeletal muscle was independent of stimulation amplitude.Methods:  The m. quadriceps femoris of six males was stimulated with constant frequency trains (six 200‐μs square waves separated by 70 ms) or variable frequency trains (first interpulse interval 5 ms) at an amplitude that initially evoked ∼25 or ∼50% of maximal voluntary isometric torque.Results:  After 180 constant frequency trains (50% duty cycle), isometric peak torque decreased ∼63%. In fatigued muscle, variable frequency trains enhanced the torque–time integral by ∼23% over that for constant frequency trains and this effect was independent of stimulation amplitude. This was due to greater peak torque and less slowing of rise time.Conclusion:  These responses show that the torque–time integral can be enhanced at both moderate and high stimulation amplitudes. As such, it is suggested that neither recruitment nor preferential activation of fast muscle is responsible for the ‘catch‐like’ property that can be demonstrated in fatigued human skeletal muscle.
Effects of normobaric hyperoxia on water content in different organs in rats
Authors: Stuhr L. E. B. , Gjerde E.‐A. B. , Thorsen E. , Reed R. K. 
Published: March 2003

ABSTRACTPulmonary oxygen toxicity is a dose‐dependent effect on alveolar epithelial and endothelial cells resulting in pulmonary oedema. Any concomitant effects on systemic capillary endothelium would be expected to result in capillary leakage and an increase in the tissues' water content. Total tissue water (TTW) in different organs was therefore studied in freely moving rats exposed to 100% O2 at normobaric pressure for 24 or 48 h, and compared to air‐breathing control rats. The TTW for the following tissues was measured: Trachea, left bronchus, left lung, left and right ventricle, left kidney, skin (left paw‐hindlimb), skin (back of the rat), left brain, left eye and thigh muscle left side. There was a significant increase in TTW of the lung accompanied by pleural effusion after 48 h of oxygen exposure as expected in all exposed animals. There was a small increase in TTW of the paw only, and a small decrease or no change in other tissues after 24 and 48 h of exposure. We conclude that there is no evidence of systemic capillary dysfunction as measured by tissue water content after exposure to hyperoxia in a dosage causing pulmonary oedema.
Functional organization of peripheral vasomotor pathways
Authors: Gibbins Ian L. , Jobling Phillip , Morris Judy L. 
Published: March 2003

AbstractAim:  In this article, we review the functional organization of the peripheral autonomic pathways regulating the vasculature.Results:  The final motor neurones in vasomotor pathways tend to be smaller than neurones in other autonomic pathways. This suggests that they have relatively smaller target territories and receive fewer pre‐ganglionic inputs than non‐vasomotor neurones. Nevertheless, single vasomotor neurones project to large areas of the vasculature separated by up to 7 mm. Different functional pools of vasomotor neurones project to specific segments of the vasculature, allowing for the selective neural control of resistance in vessels in proximal or distal regions of the vascular bed. In many cases, each functional pool of vasomotor neurones utilizes a characteristic combination of cotransmitters. The various pools of final motor neurones in vasomotor pathways receive convergent synaptic input from different pools of pre‐ganglionic neurones, many of which also contain neuropeptides which enhance the excitability of the final motor neurones. The excitability of vasomotor neurones regulating gastrointestinal and mesenteric blood flow, also can be increased by the actions of peptides such as substance P that are released from visceral nociceptors.Conclusions:  We propose that autonomic pathways regulating the vasculature are organized into ‘vasomotor units’. Each vasomotor unit consists of a pre‐ganglionic neurone, the final motor neurones it innervates, and the blood vessels that they regulate. The vasomotor units are likely to be grouped into functional pools that can be recruited as necessary to provide highly specific, graded control of blood flow both within and between vascular beds.
Mercury in tigerfish (Hydrocynus vittatus, Castelnau), green happy (Sargochromis codringtonii, Boulenger) and kapenta (Limnothrissa miodon, Boulenger) from Lake Kariba, Zimbabwe
Authors: Mhlanga Wilson 
Published: March 2003

Concentrations of total mercury were determined in Hydrocynus vittatus (Castelnau), Sargochromis codringtonii (Boulenger), and Limnothrissa miodon (Boulenger) from two localities in Lake Kariba, Zimbabwe.The mean concentrations of total mercury in H. vittatus from Basin 5 and Basin 2 were 0.08 mg kg−1 and 0.094 mg kg−1, respectively. In S. codringtonii, mean concentrations were 0.004 mg kg−1 and 0.026 mg kg−1 for Basins 5 and 2, respectively. No mercury was detected in L. miodon from Basin 2 while samples from Basin 5 had a mean concentration of 0.069 mg kg−1 (wet weight). Total mercury concentrations were also determined on a dry weight basis.Within each sampling area, total mercury concentrations were significantly different among species (P < 0.05). For H. vittatus and S. codringtonii, total mercury concentrations (in the same species) were not significantly different between the two localities (P < 0.05).The factors causing the observed differences in total mercury between similar species from different localities and among different species in the same locality (sampling area) are discussed. From the observed low levels of mercury in all three species, it was concluded that the mercury constituted ‘background levels’. These levels are below the maximum concentrations permissible in human fish foods.
Feeding habits of chimpanzees (Pan troglodytes), red‐tail monkeys (Cercopithecus ascanius schmidti) and blue monkeys (Cercopithecus mitis stuhlmanii) on figs in Budongo Forest Reserve, Uganda
Authors: Tweheyo Mnason , Obua Joseph 
Published: March 2003

AbstractFeeding habits of chimpanzees, red‐tail and blue monkeys on figs (Ficus) were studied in compartment N3 of Budongo Forest Reserve, western Uganda, from September 1997 to March 1998. The aim was to examine the spatial and temporal foraging habits of chimpanzees, red‐tail monkeys and blue monkeys on figs in the forest reserve. Both scan and focal sampling methods were used to assess the foraging habits of the primates. It was found that the primates fed on emerging leaves of Ficus mucuso Ficalho, F. varifolia Warb. and F. exasperata Vahl. They also preferred ripe fruits to emerging, young and unripe fruits. The primates spent 78% of the morning eating fruits and leaves and inhabited fig trees with fruits for about 4 h. Fig trees with ripe fruits attracted larger numbers of primate groups. It is concluded that information on the feeding habits of chimpanzees and monkeys is required in order to have a clear understanding of the social behaviour and pattern of movement of the primates and to assist in predicting the likely impacts of poor forest management, forest degradation and loss of food resources on their populations.
The effects of fire and grazing pressure on vegetation cover and small mammal populations in the Maasai Mara National Reserve
Authors: Salvatori V. , Egunyu F. , Skidmore A. K. , De Leeuw J. , Van Gils H. A. M. 
Published: March 2003

AbstractAn extensive study of vegetation changes as a consequence of fire and grazing pressure and their effect on small mammal populations inside the Maasai Mara National Reserve, Kenya, was carried out during May–June 1997. Comparison of vegetation maps from 1979 and 1998 suggested that vegetation in 46% of the Reserve area converted from shrubland to grassland, possibly as a result of fire and grazing pressure. We tested the hypothesis that in areas with high fire and grazing impact the population of small mammals was negatively affected. A low density of rodents was recorded in all habitats except in areas of human activity, where artificial resources are constantly present. Capture efforts were unsuccessful in grasslands. Our results confirm those of Norton‐Griffiths (1979) and Dublin (1995), i.e. that fire and grazing pressure impact the vegetation of the Serengeti–Mara ecosystem and limit the natural regeneration of woodlands. This indirectly affects the small mammal community, which is limited in its long‐term establishment.
GPS telemetry of forest elephants in Central Africa: results of a preliminary study
Authors: Blake S. , Douglas‐Hamilton I. , Karesh W. B. 
Published: March 2003

AbstractFew data exist on the ranging behaviour of forest elephants. A feasibility study on the use of GPS telemetry as a tool to study ranging, seasonal movements and distribution was implemented in the Dzanga‐Sangha and Nouabalé‐Ndoki National Parks Complex of Central African Republic and Congo. The study consisted of two parts – a thorough hand‐held testing of an elephant GPS telemetry collar under tropical forest conditions and the deployment of collars on two elephants. During the feasibility study the system performance was satisfactory; GPS fix acquisition success rate, VHF and UHF collar–researcher communications were adequate. Two elephants, a mature bull and an adult female, were immobilized and fitted with GPS collars in October 1998. After deployment, the female's GPS collar performed well initially, but in less than a month the GPS within the collar stopped acquiring fixes. She was subsequently located using VHF tracking. The male was never relocated strongly suggesting complete failure of the collar. Despite these setbacks, the small amount of data retrieved provide an important first insight into forest elephant ranging and daily activity patterns, with significant conservation implications. When technical difficulties of reliability are overcome, GPS telemetry will provide an exceptionally useful tool in forest elephant research and management.
Hermit crabs, humans and Mozambique mangroves
Authors: Barnes David K. A. 
Published: March 2003

AbstractThere is a complex interrelationship between upper shore hermit crabs (such as Coenobita sp. and Clibanarius sp.), coastal human populations and mangrove forests in Mozambique. The abundance, activity, shell selection and behaviour of three species of hermit crab are related to the level of mangrove cover. With increased density of mangrove trees, the study species of hermit crab changed in abundance, tended to become diurnal, spent more time feeding and were clustered in larger groups when doing so, and selected longer spired shells. All five of the same variables are also linked to the proximity and activity of humans through both direct and indirect actions. Direct effects included a tendency to nocturnal activity with proximity to human activity; indirect effects included increased and more clumped food supplies, and shell middens from intertidal harvesting and deforestation. Mangroves are important to local human populations as well as to hermit crabs, for a wide variety of (similar) reasons. Mangroves provide storm shelter, fisheries and fishery nursery grounds for adjacent human settlements, but they also harbour mosquito populations and their removal provides valuable building materials and fuel. Hermit crabs may be useful (indirectly) to coastal human populations by being a source of food to certain commercial species, and by quickly consuming rotting/discarded food and faeces (thereby reducing disease and pests). They can also cause minor problems to coastal human populations because they use shells of (fisheries) target mollusc species and can be more abundant than the living molluscs, thereby slowing down effective hand collection through confusion over identification. The mixture of positive and negative attributes that the three groups impart to each other in the Quirimba Archipelago, northern Mozambique, is discussed.