bluuebunny/crossref_metadata_2025 huggingface dataset:
Perils and pitfalls of lumbar puncture in the emergency department
Authors: Holdgate Anna , Cuthbert Karyn
Published: March 2003

Lumbar Puncture is a procedure commonly performed in the emergency department. It provides important diagnostic information but has a significant number of limitations and complications. This article reviews the role of lumbar puncture in the emergency department based on an extensive review of the current literature, focusing on the recognized contraindications and complications of the procedure and how they can be minimized. The interpretation of diagnostic tests performed on cerebrospinal fluid is also examined, highlighting those tests most commonly ordered from the emergency department.
COSTS OF MOBILE SCREENING FOR DIABETIC RETINOPATHY: A PRACTICAL FRAMEWORK FOR RURAL POPULATIONS
Authors: Lee Sue J. , McCarty Catherine A. , Taylor Hugh R. , Keeffe Jill E.
Published: March 2003

Australia’s rural and remote residents experience considerably higher hospitalisation and death rates due to diabetes than their metropolitan counterparts. There is clearly a need for improved diabetes care services in these areas and interventions that target conditions associated with diabetes will yield beneficial results for the community. All people with diabetes are at risk for diabetic retinopathy, which can cause vision loss and blindness. Although vision loss and blindness due to diabetes is nearly 100% preventable through regular eye examinations, 35% of Victoria’s rural population with diabetes do not have their eyes examined on a regular basis. A pilot, mobile screening program for the early detection of diabetic eye disease was conducted in rural Victoria and proved to be a successful model of adjunct eye care for people with diabetes. Actual costs from the pilot screening were applied to a permanent model for rural eye care. At A$41 per participant, costs for mobile screening were competitive with Medicare rebate costs for eye examinations. The model addresses barriers of accessibility and availability, targets a portion of the rural population with diabetes that is not otherwise having eye examinations, and is cost‐saving to the Government.
Predation on Pacific herring (Clupea pallasi) spawn by birds in Prince William Sound, Alaska
Authors: Bishop Mary A. , Green S. Patrick
Published: March 2003

We examined bird diets in areas with Pacific herring (Clupea pallasi) spawn at northern Montague Island in Prince William Sound, Alaska. Diets of the five most abundant bird species consisted primarily of herring spawn. Using a bioenergetics model, we estimated that in spring 1994 the five‐bird species ate 857.1 metric tons (mt), representing 31% of the estimated spawn deposition. The two most numerous consumers, glaucous‐winged gull (Larus glaucescens) and mew gull (Larus canus) consumed 26% and 3%, respectively, of the estimated spawn deposition. Surf scoters (Melanitta perspicillata), surfbirds (Aphriza virgata), and black turnstone (Arenaria melanocephala) together consumed 2% of the spawn deposition. In years with low spawn biomass, such as 1994, the number of herring larvae produced could be significantly affected by normal rates of avian predation. The high consumption by gulls, shorebirds, and surf scoters underscores the importance of herring spawn in the annual cycle of these species and requires further investigation.
Genetic improvement in the presence of genotype by environment interaction
Authors: LIN Ching Y. , TOGASHI Kenji
Published: March 2003

Although the underlying mechanisms for triggering genotype–environment (GE) interaction are poorly understood, the potential impacts of GE interaction on genetic improvement are well recognized. Genotype–environment interaction may be classified into three levels: breed, individual and gene–environment interactions. Three measures of GE interaction (genetic correlation, interaction correlation, and commonality of individuals selected between environments) are discussed. Three options are currently available to deal with GE interaction: environmental, breeding and marker‐assisted approaches. Three possible selection strategies for improving global net merit were outlined: (i) selection of a specific genotype for each environment; (ii) selection in a single environment alone for overall response across environments; and (iii) global optimum index selection for high stability and average performance across environments. Global optimum index should be the method of choice from the standpoint of global marketing. Because of the complexity of GE interaction, it is impossible to develop a general strategy to deal with different types of GE interaction. Each type of interaction requires its own solution, depending upon a combination of the following six factors: (i) the intensity of GE interaction; (ii) relative economic weights among environments; (iii) the size of environments; (iv) the nature of environments; (v) the nature of GE interaction; and (vi) selection intensity. Profitability is a major concern in animal production. Extra genetic gain does not necessarily mean extra profit. Does additional genetic gain justify the associated costs of dealing with GE interaction? This is a fundamental issue that needs to be considered before a specific breeding strategy for GE interaction is developed.
Relationship between mineral availabilities and dietary phytate in animals
Authors: MATSUI Tohru
Published: March 2003

A large amount of phosphorus (P) in corn and soybean meal is in the form of phytate that is poorly available to monogastric animals. It leads to the presence of large amounts of P in manure, which contributes to the P pollution problem. The fermentation of soybean meal with Aspergillus usamii almost completely degraded phytate and improved P availability in chicks. Although dietary yeast phytase increased P absorption and availability in pigs, its efficacy was less than that of Aspergillus niger phytase. It was suggested that the lesser efficacy of yeast phytase resulted from its lower stability against pepsin. Phytate suppresses zinc availability in monogastric animals. Zinc availability was improved by the substitution of regular soybean meal with fermented soybean meal and by the supplementation with Aspergillus niger phytase in pigs. It has been considered that phytate is easily degraded in the rumen and the availability of phytate P is high in ruminants. However, 20% of phytate in oilseed meals was not degraded in the rumen of sheep. Additionally, heating and formaldehyde treatments with oilseed meals suppressed ruminal degradation of phytate and approximately half of phytate escaped from ruminal degradation in the treated oilseed meals.
Prolactin gene expression in mouse pancreatic islets
Authors: HARIGAYA Toshio , KOMORI Michiko , WATANABE Harumi , WATANABE Satoshi , MATSUI Takuji
Published: March 2003

Mouse prolactin (mPRL) is a single‐chain polypeptide hormone, that is generally secreted from the prolactin cells of the anterior pituitary gland into the blood. However, recent studies have reported the ectopic gene expression of prolactin in several tissues, including the mammary gland, mammary tumors, lymphocytes, brain and decidua. In the present study, PRL gene expression was determined by reverse transcription polymerase chain reaction (RT‐PCR) followed by Southern blot analysis and the nucleotide sequence analysis of the amplified complementary DNA (cDNA) . In situ hybridization was also performed to determine the localization of mPRL mRNA in the pancreas of adult male and female mice during pregnancy and lactation. Total ribonucleic acid (RNA) extracted from the pancreas was reverse transcribed, followed by polymerase chain reaction (PCR) with primers specific for a part of the mPRL cDNA. An amplified product was detected in all samples from the pancreas. This product hybridized specifically to a probe overlapping the entire mPRL cDNA sequence in Southern blot analysis. Nucleotide sequence analysis indicated that the amplified product was completely identical to the pituitary PRL cDNA sequence. Moreover, PRL mRNA was observed in the pancreatic islets by in situ hybridization. These results suggest that PRL mRNA is expressed in mouse pancreatic islets and that PRL may have some autocrine and/or paracrine roles in these tissues.
Flight distance of dairy cows and its relationship to daily routine management procedures and productivity
Authors: UETAKE Katsuji , MORITA Shieru , HOSHIBA Shinji , TANAKA Toshio
Published: March 2003

The objectives of this study were to determine to what extent the flight distance of cows to humans was influenced by sire and management procedures before and after maturity, and whether there was a correlation between the flight distance and productivity on commercial dairy farms. Flight distance of 84 Holstein cows, the stockperson's daily routine management procedures and production performance were recorded repeatedly on eight commercial dairy farms. The management procedures for the animals at the suckling, growing, lactating and dry stages were classified into four categories by degree of tactile interactions between the stockperson and the animal: hand procedures with touch on (category A), nearby (category B) and apart (category C) from the animal, and machinery procedures (category D). There was no apparent sire effect on flight distance (P = 0.08), whereas the flight distance ranged from 1.17 ± 0.86 to 4.47 ± 2.01 m by farm (P < 0.01), and gradually shortened with repetition (P < 0.05). Regression analysis indicated that the length of time of category B at the suckling stage and category B at the dry stage accounted for 37% and 32% of the variation in flight distance, respectively. As for the total time of the four procedure categories, growing stage was the prime predictor of flight distance, which accounted for 36% of the variation. Flight distance tended to correlate with the first calving age (r = 0.66, P = 0.07). These results suggest the importance of non‐producing periods, before maturity and during the dry period, on the subsequent and lifelong advantages of a good relationship between the stockperson and their animals.
Changes in the amount of proteins, glycogen and lipids in porcine oocytes during in vitro meiotic maturation
Authors: NIIMURA Sueo , TAKANO Hiroko , ONISHI Akira , HOSOE Misa
Published: March 2003

Changes in the cytoplasmic inclusions during meiotic maturation were histochemically examined in cultured porcine oocytes. The oocytes contained a small amount of protein and glycogen granules throughout the maturation culture, as well as Sudanophilic lipids composed of small, medium and large droplets. Soon after collection, the amount of Sudanophilic lipid droplets of small and medium size was small and there were 167 ± 11.2 large droplets. After being cultured for 22 h, the number of large lipid droplets decreased remarkably, while the number of small and medium ones increased. There were no differences in the number of Sudanophilic lipid droplets of different sizes between ovulated oocytes and the oocytes cultured for 44 h. The oocytes always contained a large amount of neutral fats and lipoids, but not cholesterols. In the oocytes cultured for 22 h with olomoucine, both the resumption of nuclear maturation and the decrease in the size of the Sudanophilic lipid droplets were inhibited. From the present findings, it appears that the change in the size of the Sudanophilic lipid droplets in the cytoplasm of porcine oocytes is closely related to nuclear maturation.
Molecular cloning, nucleotide sequence and characteristics of a xylanase gene (xynA) from Ruminococcus albus 7
Authors: NAKAMURA Mutsumi , NAGAMINE Takafumi , TAKENAKA Akio , AMINOV Rustem I. , OGATA Koretsugu , TAJIMA Kiyoshi , MATSUI Hiroki , BENNO Yoshimi , ITABASHI Hisao
Published: March 2003

A 2.6‐kb DNA fragment encoding a xylanase gene (xynA) was cloned from the rumen hemicellulolytic bacterium Ruminococcus albus 7. The deduced primary structure of the protein (XynA) was divided into a signal peptide region and 3 domains. Domain A was identified as a family 11 (G) catalytic domain, but one amino acid residue was replaced by another in an active site signature 1 of family 11. Domain B is a stabilizing domain for the catalytic domains of families 10 and 11. Deletion of domain B reduced stability of the xylanase at high temperature and at high and low pH. Domain B may be useful for protein engineering of xylanase. Domain C has sequence similarity to deacetylases and NodB proteins.
Purification and characterization of an angiotensin I‐converting enzyme inhibitory peptide derived from porcine troponin C
Authors: KATAYAMA Kazunori , TOMATSU Makoto , FUCHU Hidetaka , SUGIYAMA Masaaki , KAWAHARA Satoshi , YAMAUCHI Kiyoshi , KAWAMURA Yukio , MUGURUMA Michio
Published: March 2003

To search for a novel angiotensin I‐converting enzyme (ACE) inhibitory peptide, porcine skeletal troponin was hydrolyzed with pepsin. This hydrolysate showed ACE inhibitory activity, and was applied to various kinds of chromatography to separate an active peptide. Analysis using a protein sequencer identified this peptide as RMLGQTPTK (9mer). This sequence was estimated to occur at the 44–52 position of troponin C, and its 50% inhibitory protein concentration (IC50) was 34 µM. RMLGQTP (7mer), a partial peptide of 9mer, showed activity with an IC50 of 503 µM. RP‐HPLC analysis of a reaction mixture of 9mer and ACE showed that 9mer was slowly hydrolyzed by ACE. On the other hand, 7mer was rapidly hydrolyzed by ACE. Activity of 9mer was reduced as its hydrolysis by ACE proceeded. To estimate the resistance of 9mer to digestive proteases after oral administration, it was reacted with pepsin, α‐chymotrypsin, or trypsin. In each of these reaction mixtures, a significant amount of 9mer remained as a substrate after digestion. Remaining ACE inhibitory activity was close to that of 9mer. These results suggest that 9mer might not be digested after oral administration, because of its relatively high resistance to digestive proteases. Therefore, 9mer might be expected to work well in vivo as an ACE inhibitor.
Methane emissions from wetlands and their relationship with vascular plants: an Arctic example
Authors: Joabsson Anna , Christensen Torben Røjle
Published: March 2003

This paper investigates the relationship between vascular plant production and CH4 emissions from an arctic wet tundra ecosystem in north‐east Greenland. Light intensity was manipulated by shading during three consecutive growing seasons (1998–2000). The shading treatment resulted in lower carbon cycling in the ecosystem as mean seasonal net ecosystem exchange (NEE) decreased from −336 to −196 mg CO2 m−2 h−1 and from −476 to −212 mg CO2 m−2 h−1 in 1999 and 2000, respectively, and total ecosystem respiration decreased from 125 to 94 mg CO2 m−2 h−1 in 1999 and from 409 to 306 mg CO2 m−2 h−1 in 2000. Seasonal mean CH4 emissions in controls and shaded plots were, respectively, 6.5 and 4.5 mg CH4 m−2 h−1 in 1999 and 8.3 and 6.2 mg CH4 m−2 h−1 in 2000. We found that CH4 emission was sensitive to NEE and carbon turnover, and it is reasonable to assume that the correlation was due to a combined effect of vegetative CH4 transport and substrate quality coupled to vascular plant production. Total above‐ground biomass was correlated to mean seasonal CH4 emission, but separation into species showed that plant‐mediated CH4 transport was highly species dependent. Potential CH4 production peaked at the same depth as maximum root density (5–15 cm) and treatment differences further suggest that substrate quality was negatively affected by decreased NEE in the shaded plots. The concentration of dissolved CH4 decreased in the control plots as the growing season progressed while it was relatively stable in the shaded plots. This suggests that a progressively better developed root system in the controls increased the capacity to transport CH4 from the soil to the atmosphere. In conclusion, vascular plant photosynthetic rate and subsequent allocation of recently fixed carbon to below‐ground structures seemed to influence both vegetative CH4 transport and substrate quality.
Carbon dynamics within agricultural and native sites in the loess region of western Iowa
Authors: Manies K. L. , Harden J. W. , Kramer L. , Parton W. J.
Published: March 2003

In order to quantify the historical changes in carbon storage that result from agricultural conversion, this study compared the carbon dynamics of two sites in the loess region of Iowa: a native prairie and a cropland. Field data were obtained to determine present‐day carbon storage and its variability within a landscape (a stable ridgetop vs. eroding upper‐midslope vs. depositional lower slope). Models were used to recreate the historical carbon budget of these sites and determine the cropland's potential to be a net CO2 source or sink, relative to the atmosphere.

Regardless of slope position, the cropland site contains approximately half the amount of carbon as prairie. Variability in soil carbon storage within a site as a consequence of slope position is as large or larger (variations of 200–300%) than temporal variation (∼200% at all slope positions). The most extreme difference in soil carbon storage between the cropland and prairie sites is found in the soil at the upper‐midslope, which is the area of greatest erosion. The models estimate that 93–172% of the carbon in the original topsoil has been lost from the cropland's eroding midslope. Much of this carbon is derived from deeper soil horizons. Either a small sink or strong source of carbon to the atmosphere is created, depending on the fate of the eroded sediment and its associated carbon.
Response of wheat canopy CO2 and water gas‐exchange to soil water content under ambient and elevated CO2
Authors: Mitchell Rowan A. C. , Mitchell Valerie J. , Lawlor David W.
Published: March 2003

The nature of the interaction between drought and elevated CO2 partial pressure (pCa) is critically important for the effects of global change on crops. Some crop models assume that the relative responses of transpiration and photosynthesis to soil water deficit are unaltered by elevated pCa, while others predict decreased sensitivity to drought at elevated pCa. These assumptions were tested by measuring canopy photosynthesis and transpiration in spring wheat (cv. Minaret) stands grown in boxes with 100 L rooting volume. Plants were grown under controlled environments with constant light (300 µmol m−2 s−1) at ambient (36 Pa) or elevated (68 Pa) pCa and were well watered throughout growth or had a controlled decline in soil water starting at ear emergence. Drought decreased final aboveground biomass (−15%) and grain yield (−19%) while elevated pCa increased biomass (+24%) and grain yield (+29%) and there was no significant interaction. Elevated pCa increased canopy photosynthesis by 15% on average for both water regimes and increased dark respiration per unit ground area in well‐watered plants, but not drought‐grown ones. Canopy transpiration and photosynthesis were decreased in drought‐grown plants relative to well‐watered plants after about 20–25 days from the start of the drought. Elevated pCa decreased transpiration only slightly during drought, but canopy photosynthesis continued to be stimulated so that net growth per unit water transpired increased by 21%. The effect of drought on canopy photosynthesis was not the consequence of a loss of photosynthetic capacity initially, as photosynthesis continued to be stimulated proportionately by a fixed increase in irradiance. Drought began to decrease canopy transpiration below a relative plant‐available soil water content of 0.6 and canopy photosynthesis and growth below 0.4. The shape of these responses were unaffected by pCa, supporting the simple assumption used in some models that they are independent of pCa.
Soil carbon stocks and land use change: a meta analysis
Authors: Guo L. B. , Gifford R. M.
Published: March 2003

The effects of land use change on soil carbon stocks are of concern in the context of international policy agendas on greenhouse gas emissions mitigation. This paper reviews the literature for the influence of land use changes on soil C stocks and reports the results of a meta analysis of these data from 74 publications. The meta analysis indicates that soil C stocks decline after land use changes from pasture to plantation (−10%), native forest to plantation (−13%), native forest to crop (−42%), and pasture to crop (−59%). Soil C stocks increase after land use changes from native forest to pasture (+ 8%), crop to pasture (+ 19%), crop to plantation (+ 18%), and crop to secondary forest (+ 53%). Wherever one of the land use changes decreased soil C, the reverse process usually increased soil carbon andvice versa. As the quantity of available data is not large and the methodologies used are diverse, the conclusions drawn must be regarded as working hypotheses from which to design future targeted investigations that broaden the database. Within some land use changes there were, however, sufficient examples to explore the role of other factors contributing to the above conclusions. One outcome of the meta analysis, especially worthy of further investigation in the context of carbon sink strategies for greenhouse gas mitigation, is that broadleaf tree plantations placed onto prior native forest or pastures did not affect soil C stocks whereas pine plantations reduced soil C stocks by 12–15%.
Coaction of DNA topoisomerase IIIα and a RecQ homologue during the germ‐line mitosis in Caenorhabditis elegans
Authors: Kim You‐Chan , Lee Min‐Ho , Ryu Sung‐Shin , Kim Ji‐Hoon , Koo Hyeon‐Sook
Published: March 2003

Background: Among the four RecQ homologues predicted from the Caenorhabditis elegans genomic DNA sequence, T04A11.6 is most similar to Bloom syndrome’s protein in humans. To investigate a possible interaction of the protein with topoisomerase IIIα (TOP3α), as observed between TOP3 and RecQ homologues in yeast and human, the top3α gene expression was suppressed by RNA interference (RNAi) in the him‐6(e1104) C. elegans strain which is mutated in T04A11.6 (F. Mueller & C. Wicky, personal communication).

Results: Germ cells in the gonads of the progeny him‐6(e1104);top3α(RNAi) showed severe chromosomal abnormalities and were arrested during mitosis with a subsequent failure in meiotic entry. Most of the aberrant chromosomes were stained by the TUNEL assay but not by the SYTO12 dye, suggesting extensive DNA breaks not associated with apoptosis. The phenotypes in the germ cells of him‐6(e1104);top3α(RNAi) were also observed in the progeny produced by double RNA interference of the top3α and him‐6 gene expression, though at a reduced level. The over‐expressed TOP3α and Him‐6 proteins showed specific physical interaction in vitro, in agreement with the genetic interaction in C. elegans.

Conclusion: In C. elegans, TOP3α and the RecQ homologue (T04A11.6) contribute to genome stability during germ‐line mitosis, probably by acting in a complex.
Protein kinase‐dependent phosphorylation of H,K ATPase‐containing membranes from rat and pig stomachs
Authors: KAYA  , MÅRDH
Published: March 2003

Previously H,K ATPase preparations from pig stomach were shown to contain intrinsic protein kinase activities which phosphorylated specific tyrosine and serine residues in the N‐terminal of the α‐chain of H,K ATPase ( Togawa et al. 1996
). In the present investigation, pig H,K ATPase‐containing membrane preparations were compared with rat preparations. In contrast to results obtained with the α‐subunit of H,K ATPase from pig, phosphorylation was not observed in the rat enzyme. Addition of rat preparations to the pig preparations resulted in decreased phosphorylation in pig preparations. To follow the phosphorylation of membrane proteins in vivo, 32P‐loaded gastric cells prepared from rat were stimulated with several secretagogues. Proteins with molecular weights of about 120 and 80 kDa were markedly phosphorylated upon stimulation, but the α‐subunit of H,K ATPase was not. These results suggest that phosphorylation of tyrosine or serine residues of H,K ATPase found in pig H,K ATPase preparations may not be involved in the acid secretion pathway.
Dilatory responses to acetylcholine, calcitonin gene‐related peptide and substance P in the congestive heart failure rat
Authors: BERGDAHL  , VALDEMARSSON  , NILSSON  , SUN  , HEDNER  , EDVINSSON
Published: March 2003

It was examined to what extent congestive heart failure (CHF) in rats, induced by ligation of the left coronary artery, affects the vascular responses to the vasodilatory substances acetylcholine (ACh), calcitonin gene‐related peptide (CGRP), and substance P (SP). After induction of CHF status, the basilar, mesenteric and renal arteries and the iliac vein were studied in vitro. Dilatory responses were determined in relation to pre‐contraction by the thromboxane mimetic U46619. Sham‐operated animals (Sham) served as controls. U46619 induced stronger contraction in CHF basilar and renal arteries compared with the corresponding segments in Sham. ACh induced concentration‐dependent dilations in all vessels examined with no difference of maximum relaxation or potency between CHF and Sham. SP induced weak dilations in all arteries examined while the response was markedly attenuated in CHF iliac veins compared with Sham (Emax% 12.2 ± 3.4 vs. 32.3 ± 4.8, P = 0.01). The CGRP induced dilation in the CHF basilar artery was weaker (Emax% 18.6 ± 6.5 vs. 66.9 ± 5.0, P < 0.001) and less potent (pEC50: 8.2 ± 0.2 vs. 9.0 ± 0.2, P = 0.01) compared with Sham. Further, CGRP was less potent in the renal artery of CHF rats compared with Sham (pEC50: 8.1 ± 0.2 vs. 9.5 ± 0.3, P < 0.01). In the CHF iliac vein, CGRP was more potent compared with Sham (pEC50: 9.7 ± 0.4 vs. 8.3 ± 0.4, P < 0.05). It can be conculded CHF is accompanied by alterations in the vascular response to the dilatory substances studied. The changes differ between vascular beds and between the different substances.
Relationship between blood pressure and heart‐rate variability during graded head‐up tilt
Authors: YOKOI  , AOKI
Published: March 2003

To investigate the relationship between change in blood pressure and autonomic nerve activity, two types of head‐up tilt experiments were performed. One was a 30°, 45°, 60°, and 90° graded tilt‐up, in which tilt angles were changed at 6‐min intervals and 5 min were spent at each angle. The other was a 10‐min lasting head‐up tilt at 60°. Electrocardiogram (ECG) and blood pressure (Finapres) of 18 healthy non‐smoking subjects (9 men, 9 women) were recorded during the experiments. Heart‐rate variability was examined by general spectral analysis (GSA). The high‐frequency/total‐area ratio (HF/TO) showed a decrease as the tilt angle increased. Compared with the values at the 0° position, these changes were statistically significant (P < 0.05). The low‐frequency/HF ratio (LF/HF) showed a significant (P < 0.05) difference between 0° and 90°, and between 30° and 90°. Some of the subjects could not maintain their blood pressure during either of the head‐up tilt experiments, and they showed only a slight change in HF/TO and LF/HF. This result confirmed that immediate responses to head‐up tilt reflect autonomic nerve activity. Hence, changes in the frequency components were found to be an index of autonomic nerve activity, and they explained the individual differences observed in the ability to control blood pressure during a transition to upright posture.
Diabetic alteration of cardiac vago‐sympathetic modulation assessed with tone–entropy analysis
Authors: OIDA  , KANNAGI  , MORITANI  , YAMORI
Published: March 2003

No clear evidence of diabetic alteration of cardiac sympatho‐vagal balance has been reported to date. We assessed heart rate variability of diabetic patients with the tone–entropy analysis that has been published elsewhere ( Oida et al. 1997
). Tone reflects the cardiac vago‐sympathetic balance and entropy the total autonomic efferent activity. Diabetic influence on tone and entropy was examined in two groups of patients (38–52 years and 60–69 year, total 106) stratified according to the occurrence of impaired glucose tolerance or diabetes mellitus. Ten healthy middle‐aged volunteers were also examined as a reference. Electrocardiographic data were collected at rest for 10 min. Tone increased and entropy decreased significantly with severity of diabetic disorders. The alterations were depicted as a curvi‐linear relation in tone–entropy space, which superimposed adequately on the standard tone‐entropy values obtained in a pharmacological experiment. The results demonstrate that the vago‐sympathetic balance is altered with diabetic disorders: vagal predominance is impaired significantly in proportion to a withdrawal of total autonomic efferent activity.
Blood oxygen partial pressure affects plasma prolactin concentration in humans
Authors: STRÜDER  , HOLLMANN  , WEICKER  , SCHIFFER  , WEBER
Published: March 2003

Responses of plasma prolactin (PRL) concentration to acute and repeated changes in blood oxygen partial pressure (PO2a) at rest were investigated in two studies (A; B), with special reference to possible effects mediated via serotonin (5‐HT) synthesis. In A, nine male subjects inhaled for 105 min gas containing different oxygen fractions for 6 days. Gas concentrations consisted of 14% (A14), 21% (A21), 40% (A40), 60% (A60) and 80% (A80) O2 mixed with N2 as well as 100% O2 (A100). Venous and capillary blood samples were drawn before and every 15 min during gas inhalation for analysis of plasma PRL and PO2a. In B, two groups of subjects (B I; B II) were exposed to 30 min day−1 of gas inhalation over 14 consecutive days. Gas concentration consisted for B I of 14% O2/86% N2 and for B II of 100% O2. During pre‐ and post‐examination a baseline blood sample was drawn, followed by a neuroendocrine test of serotonergic function using a partial 5‐HT1A receptor agonist (60 mg of buspirone hydrochloride). In A, each increase of inhaled oxygen fraction also resulted in higher blood PO2a. In A14, A21 and A40, plasma PRL concentrations did not change from basal level. Increases in plasma PRL concentration were found in A60 after 30 min as well as in A80 and A100 after 15 min. A higher blood PO2a induced a higher plasma PRL secretion but also an earlier decline from peak plasma PRL value despite continued inhalation of the respective oxygen concentration. During post‐examination in B, basal plasma PRL concentrations were increased in B I and decreased in B II. Plasma PRL response to stimulation challenge was not affected by treatments. Thus, chronic adaptations of basal plasma PRL concentrations to decreased/increased blood PO2a were not related to up/down‐regulation, respectively, of central serotonergic receptor function.
Changes in voltage activation of contraction in frog skeletal muscle fibres as a result of sarcoplasmic reticulum Ca2+‐ATPase activity
Authors: Même  , Léoty
Published: March 2003

The effects of cyclopiazonic acid, a specific sarcoplasmic reticulum Ca2+‐ATPase inhibitor, on isometric tension were studied in response to prolonged steady‐state depolarization induced by a rapid change in extracellular potassium concentration (potassium contractures) in frog semitendinosus muscle fibres. Cyclopiazonic acid (1–10 μM) enhanced the amplitude and time‐course of relaxation of 146 m
M potassium contracture. In the presence of cyclopiazonic acid 0.5 μM, the relationship between the amplitude of potassium contractures and the membrane potential shifted to more negative potentials, whereas the steady‐state inactivation curve was unchanged. These observations suggest that cyclopiazonic acid has no effect on voltage sensors. The difference between potassium contractures in the absence and presence of cyclopiazonic acid in skeletal muscle fibres implies that the amplitude and slow relaxation of tension during prolonged steady‐state depolarization may be expected to depend not only on inactivation of the process regulating calcium release from the sarcoplasmic reticulum but also on the ability of the sarcoplasmic reticulum to pump calcium.
Decreased responsiveness of vascular postjunctional α1‐, α2‐adrenoceptors and neuropeptide Y1 receptors in rats with heart failure
Authors: Feng Q. , Sun X. , Lu X. , Edvinsson L. , Hedner T.
Published: March 2003

Heart failure is associated with increased sympathetic nerve activity. We hypothesized that chronic sympathetic stimulation in heart failure resulted in decreased vascular sympathetic responsiveness. A pithed rat model was employed to evaluate peripheral vascular α‐adrenoceptor and neuropeptide Y (NPY) receptor responsiveness. Heart failure was induced in Sprague–Dawley rats by coronary artery ligation. Sham operated rats (Sham) served as controls. Two months after this surgical procedure, both heart failure (n= 30) and Sham (n= 30) rats underwent standard pithing procedure. Pressor responses to preganglionic sympathetic nerve stimulation (PNS) and activation of postjunctional α1‐ and α2‐adrenoceptors as well as Y1 receptors were studied. In response to PNS, cardiac index was similar between heart failure and sham rats (P= n.s.). Mean arterial pressure (MAP) increased in a frequency‐dependent fashion after PNS in heart failure rats as well as in control rats. All the agonists used, i.e. the α1‐adrenoceptor agonist phenylephrine, the α2‐adrenoceptor agonists clonidine and BHT933 as well as NPY, induced dose‐dependent increases in MAP in heart failure and in sham rats. However, in rats with heart failure, the response to all the agonists studied was significantly decreased and the dose response curves were shifted to the right (P < 0.01). We conclude that in vivo vascular response to postjunctional α1‐ and α2‐adrenoceptors as well as Y1 receptors are decreased in rats with heart failure.
No role of interstitial adenosine in insulin‐mediated vasodilation
Authors: Dela  , Stallknecht
Published: March 2003

The mechanisms behind the vasodilatory effect of insulin are not fully understood, but nitric oxide plays an important role. We have investigated the possibility that insulin mediates vasodilatation in the human skeletal muscle via an increase in extracellular adenosine concentrations. In eight healthy subjects (H) and in four subjects with a complete, high (C5–C6/7) spinal cord injury (SCI) a hyperinsulinaemic (480 mU min–1 kg–1), isoglycaemic clamp was performed. SCI subjects were included as it has been proposed that adenosine and adenine nucleotides may be released from nerve endings in the skeletal muscle. Adenosine concentrations in the extracellular fluid (ECF) of skeletal muscle in the thigh were measured by means of the microdialysis technique. Leg blood flow (LBF) was measured by termodilution. In response to insulin infusion, LBF always increased (P < 0.05) (from 228 ± 25 and 318 ± 18 mL min–1 to 451 ± 41 and 530 ± 29 mL min–1, SCI and H, respectively [mean ± SEM]). Concentrations of adenosine in the muscle ECF did not change with infusion of insulin and did not differ between groups (before: 147 ± 55 [SCI] and 207 ± 108 [H] nmol L–1; during: 160 ± 36 [SCI] and 165 ± 74 [H] nmol L–1). No significant correlation between concentrations of adenosine and corresponding LBF rates was achieved (LBF=[–0.0936 ·  Adenosine] + 475. R=–0.092, P=0.22, number of samples=181, number of subjects=12). Conclusion: the mechanism by which insulin mediates an increase in skeletal muscle blood flow is not associated with adenosine in the ECF.
Behavioural responses of γ‐MSH peptides administered into the rat ventral tegmental area
Authors: Klusa  , Svirskis  , Opmane  , Muceniece  , Wikberg
Published: March 2003

The behavioural effects induced by α‐, γ1‐ and γ2‐MSH peptides (0.3 and 3 nmole per rat) injected into the left ventral tegmental area (VTA) of rats were compared. α‐ and γ1‐MSH caused grooming of comparable magnitude, and also additional vertical activity (rearing). By contrast γ2‐MSH caused a moderate but stable catalepsy, and practically no grooming. Moreover, intra‐VTA pre‐treatment with γ2‐MSH, 15 min prior to intra‐VTA γ1‐MSH, markedly attenuated both the γ1‐induced grooming and vertical activities. The differences in the behavioural response of the MSH peptides indicate that they act differentially on MC receptors in the VTA.
Exaggerated volume expansion natriuresis in rats preloaded with hypertonic saline: a paradoxical enhancement by inhibition of prostaglandin synthesis
Authors: Kompanowska‐Jezierska  , Walkowska  , Sadowski
Published: March 2003

In preliminary experiments rats preinfused with hypertonic saline showed exaggerated natriuresis after an additional small volume expansion (SVE). This was systematically studied in anaesthetized Wistar rats prepared for clearance studies of the left kidney and measurements of medullary blood flow (MBF, laser‐Doppler technique) and tissue electrical admittance (Y ), an index of interstitial ion concentration. The rats were preinfused i.v. with 3 mL of 5% NaCl during 90 min. A subsequent injection of isotonic saline, 0.5% of body weight, increased sodium excretion (UNaV ) from 2.1 ± 0.5 to 4.5 ± 1.1 μmol min–1 and urine flow (V ) from 12.0 ± 2.3 to 24.3 ± 5.6 μL min–1 (P < 0.02). The same volume of whole blood increased UNaV from 5.0 ± 1.4 to 8.7 ± 1.7 μmol min–1 and V from 22.3 ± 5.1 to 37.4 ± 5.9 μL min–1 (P < 0.01). The glomerular filtration rate, MBF and Y did not change. In rats preinfused with 0.9% saline no natriuresis was observed after SVE. To examine if prostaglandins (PG) were involved in SVE natriuresis, indomethacin (Indo), 5 mg kg–1 or sodium meclophenamate (Meclo), 7.5 mg kg–1, were added to the injected 0.9% saline. Paradoxically, both PG synthesis inhibitors enhanced natriuresis to SVE. After Indo UNaV increased from 2.0 ± 0.6 to 7.6 ± 1.3 μmol min–1, significantly more than after SVE alone (P < 0.001). At higher baseline UNaV, the increase with Meclo from 4.5 ± 1.2 to 13.5 ± 1.8 μmol min–1 was significantly higher than after whole blood infusion (P < 0.001). MBF decreased and Y increased after both inhibitors. Further studies are required to explain the enhancement of natriuresis after blockade of PG synthesis.
Defective renal dopamine D1‐like receptor signal transduction in obese hypertensive rats
Authors: Lokhandwala  , Hussain
Published: March 2003

It is reported that dopamine promotes renal sodium excretion via activation of D1‐like dopamine receptors located on the proximal tubules. In spontaneously hypertensive rats the natriuretic and diuretic response to exogenously administered and endogenously produced dopamine is reduced, which results from a diminished dopamine‐induced inhibition of the enzyme, Na+,K+‐ATPase. The present study was designed to examine dopamine‐receptor mediated inhibition of Na+,K+‐ATPase and its associated signal transduction pathway in the proximal tubules of Zucker obese and lean control rats. The obese animals were hypertensive, hyperinsulinaemic and hyperglycaemic compared with the lean rats. While dopamine caused inhibition of Na+,K+‐ATPase activity in lean rats, this effect was significantly attenuated in the obese animals. There was significant reduction in D1‐like receptor numbers in the basolateral membranes of obese rats compared with lean rats with no change in the affinity to the ligand [3H]SCH 23390 between the two groups of rats. Dopamine failed to stimulate G proteins as measured by [35S]GTPγS binding in the obese rats. Also, dopamine was unable to cause phospholipase‐C activation in obese rats, but it did activate phospholipase‐C in lean rats. These results show that reduction in D1‐like receptor numbers and a defect in receptor–G protein coupling may account for the inability of dopamine to activate the D1‐like receptor‐coupled signal transduction pathway and cause inhibition of Na+,K+‐ATPase in the obese hypertensive rats.
Oxygen supply to contracting skeletal muscle at the microcirculatory level: diffusion vs. convection
Authors: Pittman R.N.
Published: March 2003

An adequate supply of oxygen is essential for the normal function of all cells. Because skeletal muscle cells have the ability to vary their oxygen demand by over an order of magnitude on going from rest to vigorous contraction, it is important that mechanisms be in place to ensure that the supply of oxygen is maintained at sufficient levels. Microcirculation plays a critical role in this process, as the terminal branches of this intricate network of blood vessels determine the distribution of perfusion, as well as the structural framework for diffusion. The oxygen supply depends on proper functioning of both the convective and diffusive components of the transport system. Convection is responsible for the long‐range, rapid transport of oxygen by bulk flow of the blood and diffusion is the efficient mechanism for transport over the short distances between capillaries and muscle cells. Convective transport is dominated by the movement of red blood cells, as virtually all the oxygen at normal haematocrit is carried inside them, reversibly bound to haemoglobin. Over the years, specialized techniques, many of them video‐based, have been developed for use in intravital microscopy to measure the parameters needed to quantify convection and diffusion in both capillaries and the larger microvessels, arterioles and venules. Most of our knowledge of oxygen transport in the microcirculation of muscle pertains to the resting condition, because one must be able to visualize the structures of interest, such as microvessels and muscle cells, and the large tissue movements that occur during contraction preclude measurements during that time. In resting muscle it has been found that the arterioles are the primary site of the diffusion of oxygen from the circulation, where the oxygen is utilized by nearby muscle cells or diffuses directly to nearby venules or capillaries. Diffusive interactions among neighbouring capillaries have also been observed. In contracting muscles, microvessels observed immediately following the period of stimulation exhibit enhancements of both convective (increased flow of red blood cells) and diffusive (increased perfused capillary surface area) transport. The use of computational models in the interpretation of experimental studies is leading to an increased understanding of the processes that underlie the oxygen transport system in skeletal muscle.
Seasonal changes in heart rate and food intake in reindeer (Rangifer tarandus tarandus)
Authors: Mesteig K. , Tyler N.J.C. , Blix A.S.
Published: March 2003

This study tested the hypothesis that the annual cycle in heart rate (HR) in reindeer is, at least in part, a consequence of seasonal fluctuation in voluntary‐food intake. Heart rate and daily dry matter voluntary‐food intake (DDMVFI) were recorded in two captive female reindeer (Rangifer tarandus tarandus) from April 1995 to August 1996. Heart rate was measured continuously in each animal for 20–24 h for 7 days each month using Polar® Sport Testers (PST); DDMVFI was measured in each animal daily for 17 months. Modal daily heart rate (MDHR) and DDMVFI fluctuated seasonally in close synchrony, both reaching maxima in July and minima in January. The relationship between HR and DDMVFI was investigated experimentally by manipulating the level of feeding in a stepwise manner in May, when appetite was low and in August, when DDMVFI was close to maximum. Heart rate showed stepwise changes in close synchrony with the changes in levels of feeding. These results suggest that the seasonal increase in HR in summer is a consequence of increased food intake and, likewise, decreased HR in winter is a consequence of reduced food intake. The observed relationship between food intake and HR presumably reflects changes in cardiac output and/or the rate of flow of blood to the gastrointestinal tract which are influenced by meal size.
Regulation of K+ transport in the rat distal colon via angiotensin II subtype receptors and K+‐pathways
Authors: Grahnquist L. , Chen M. , Gerasev A. , Aizman R. , Celsi G.
Published: March 2003

The role of angiotensin subtype‐1 (AT1) and ‐2 (AT2) receptors in mediating the effects of angiotensin II (ANG II) on several K+ transporters was studied in rat distal colon using an Ussing chamber. Angiotensin II induced K+ secretion at two different doses. Secretion occurred at 10–8 and 10–4 M, as a result of an increase in serosal‐to‐mucosal flux (Js–m). The ANG II‐induced stimulation of Js–m at a low dose (10–8 M) was abolished by PD123319 while losartan did not alter the low‐dose ANG II‐dependent increase in Js–m. In contrast, the increase in Js–m induced by a high‐dose of ANG II (10–4 M) was blocked by losartan, whereas PD123319 partially reduced the stimulatory effect. In the presence of both blockers, high‐dose ANG II induced an inhibition of basal Js–m. Low‐dose ANG II activated the barium‐sensitive K+ channels, whereas the Na+, K+, 2Cl– cotransporter and the Na+, K+‐ATPase pump were unchanged. At the high dose, ANG II activated the barium‐sensitive K+ channels and the Na+, K+, 2Cl– cotransporter and inhibited the Na+, K+‐ATPase pump. These data indicate that ANG II stimulates serosal‐to‐mucosal K+ flux in the rat distal colon at high and low doses via different receptors and K+ transporters.
Effect of force development on contraction induced glucose transport in fast twitch rat muscle
Authors: Ihlemann J. , Ploug T. , Galbo H.
Published: March 2003

A previous study has shown that in fast twitch frog sartorius muscle contraction stimulated glucose transport depends only on stimulation frequency and not on workload. In contrast, we have recently shown that in rat slow twitch muscle stimulated to contract at constant frequency, glucose transport varies directly with force development and, in turn, metabolism. The present study was carried out to clarify whether the discrepancy between the earlier studies reflected differences in physiological behaviour between fast and slow twitch muscle. We investigated the effect of force development on glucose transport in incubated fast twitch rat flexor digitorum brevis (rich in type 2a fibres) and epitrochlearis (rich in type 2b fibres) muscle. Muscles were electrically stimulated to perform repeated tetanic contractions at 1 Hz for 10 min. Resting length was adjusted to achieve either no force or maximum force. Glucose transport (2‐deoxyglucose uptake) increased when force was produced compared with when it was not (P < 0.05) in both flexor digitorum brevis (19 ± 7 (basal), 163 ± 14 (no force) and 242 ± 17 (max force) nmol × g–1 × 5 min–1) and epitrochlearis (60 ± 4 (basal), 100 ± 7 (no force) and 125 ± 6 (max force) nmol × g–1 × 5 min–1). In both muscles glucose transport increased in parallel with metabolic rate, as reflected by muscle lactate concentrations and 5′ AMP‐activated protein kinase activity, during contractions. In conclusion, as previously shown for rat soleus muscle, at a given stimulation frequency glucose transport varies directly with force development in rat flexor digitorum brevis and epitrochlearis muscle. Accordingly, force development enhances glucose transport in all mammalian muscle fibre types. The influence of force development probably reflects effects of enhanced 5′ AMP‐activated protein kinase activity resulting from reduced intra‐cellular energy status and pH.