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Biomedical subjects

J Jensen

Publications and source records attributed to J Jensen.

At least 55 records · Page 3Linked to original sources

Effects of trout endothelin on the motility of gastrointestinal smooth muscle from the trout and rat.

Trout endothelin (ET), previously isolated from the kidney of the rainbow trout Oncorhynchus mykiss, contains four amino acid substitutions at residues 4-7 compared with rat ET-1. Trout ET produced sustained and concentration-dependent contractions of strips of longitudinal smooth muscle from trout stomach (pD(2) = 7.52 +/- 0.06) and proximal small intestine (pD(2) = 7.80 +/- 0.10) and from rat fundus (pD(2) = 7.78 +/- 0.14). Rat ET-1 was equipotent with trout ET for contraction of rat fundus and 2- to 3-fold more potent for contraction of trout gastrointestinal tissues. In contrast, rat ET-1 was 10- to 20-fold more potent than trout ET in constricting isolated rings of vascular tissue from trout efferent branchial artery and cardinal vein and from rat aorta (Y. Wang et al., 1999, Am. J. Physiol. 277, R1605-R1611). It is known that the contractile effects of ET-1 on rat fundus are mediated through the ET(B) receptor and effects on the rat aorta are mediated through the ET(A) receptor. We propose, therefore, that trout gastrointestinal tissues express an ET(B)-type receptor that differentiates poorly between trout ET and rat ET-1, whereas trout vascular tissues express an ET(A)-type receptor that is preferentially activated by rat ET-1. The rat ET-1-induced contractions of the trout gastrointestinal tissues are in part indirect, involving a serotoninergic neuronal pathway in the intestine and a noncholinergic, nonserotoninergic pathway in the stomach.

Animals↗

The development of balance control in children: comparisons of EMG and kinetic variables and chronological and developmental groupings.

This cross-sectional study examined electromyographic (EMG) and kinetic variables during reactive balance responses in children grouped according to developmental level as compared with chronological age. Purposes were to explore relationships between the two types of variables and the effectiveness of the two grouping methods. Forty-four children between 9 months and 10 years old were tested for reactive balance control on a moveable platform. Surface electrodes measured EMG activity in the gastrocnemius (GA), hamstrings (HA), paraspinals (PS), tibialis anterior (TA), quadriceps (QA), and abdominal (AB) muscles. Timing and distance of center-of-pressure (COP) movements and peak muscle torques at the ankle, knee, and hip were also examined. Significant relationships and group differences were found between postural muscle activity and both the torque generated in the lower limbs and the timing and distance of COP adjustments employed to restabilize balance. As postural muscle activity increased and became more coordinated in timing, peak torque at the ankle and hip also increased, while the distance of and time to complete COP readjustments decreased. Children in younger/developmentally lower groups had smaller-magnitude and less-synergic muscle activity, lower peak torques, longer times to restabilize the COP, and greater COP paths than older/higher developmental groupings. Grouping by developmental level produced more statistical differences than did grouping by age. The correspondence of GA, HA, and PS muscle activity with COP measures and joint peak torques confirms that these muscles are key contributors to the balance synergy correcting for induced forward sway. Additionally, developmental level appears to be a much better predictor of balance improvement than chronological age.

Age Factors↗

Effects of cod bradykinin and its analogs on vascular and intestinal smooth muscle of the Atlantic cod, Gadus morhua.

The effects of [Arg(0),Trp(5),Leu(8)]-BK (cod [Arg(0)]BK) on vascular preparations from branches of the cod celiac artery and on longitudinal smooth muscle preparations from the cod intestine were investigated. Cod [Arg(0)]BK (3 x 10(-8) M) caused a relaxation of the celiac artery precontracted with adrenaline. The relaxation was abolished by the cyclooxygenase inhibitor indomethacin, suggesting that the effect is mediated through the release of prostaglandins, but there was no evidence for the involvement of leukotrienes or nitric oxide in the response. In the intestinal preparations, cod [Arg(0)]BK produced concentration-dependent contractions (pD(2) = 8.28 +/- 0.16). Experiments with N-terminally and C-terminally truncated analogs and with alanine-substituted analogs of cod [Arg(0)]BK demonstrate that the central amino acid Gly(4) and the C-terminal amino acids Leu(8) and Arg(9) are the most important in determining the conformation of the peptide that interacts with the receptor. The results indicate that the ligand binding properties of the cod BK receptor are considerably different from the receptor present in trout tissues and may resemble those of the mammalian B(2) receptor more closely.

Alanine↗

Evolution of vertebrate neuropeptides.

This review describes some of the most typical features in the evolution of neuropeptides. Neuropeptides are synthesized like other polypeptides and proteins, with an amino acid sequence determined by the DNA sequence of the corresponding gene. Mutations of bases in the coding regions of the DNA lead to changes in amino acid sequence, and explain the differences in amino acid sequence of a certain neuropeptide in different animal species. The more distantly related two species are, the more substitutions can be found in one and the same neuropeptide. The biologically active part of the neuropeptide is usually the most conserved part. Neuropeptides also form families of closely related peptides, where several members may occur in one animal species. This is due to gene or exon duplications followed by mutations. Gene splicing and posttranslational processing decides the gene product in a single cell. Difference in sequence may cause difference in function, but more often than not, members of a family appear to produce the same effect. Three neuropeptide families, the tachykinins, the neuropeptide Y family, and the vasoactive intestinal polypeptide/pituitary adenylate cyclase-activating peptide family will be described in more detail.

Amino Acid Sequence↗

Regulatory peptides and control of food intake in non-mammalian vertebrates.

The current view of the control of food intake involves a central feeding system in the hypothalamus receiving input from peripheral systems. The presence of food in the gut stimulates the release of several regulatory peptides that control gut motility and secretion. Some of these peptides also act as feedback satiety signals, responsible for termination of a meal. Among the regulatory peptides suggested as peripheral satiety signals are cholecystokinin and gastrin releasing peptide. A more long-term peripheral regulation of food intake has also been postulated and leptin has been suggested as a regulator of food intake. Several regulatory peptides mediate orexigenic or anorexigenic effects in the central feeding system. Neuropeptide Y and galanin both act centrally and stimulate the intake of food, while corticotropin releasing factor reduces food intake. At present, most information about the regulation of food intake is gained from mammalian studies and these findings are used as a base for a discussion on the current knowledge of how regulatory peptides control appetite in non-mammalian vertebrates.

Animals↗

Schizophrenia--progressive and massive decline in response readiness by episodes.

OBJECTIVE: To relate the pattern of neuropsychological impairments among schizophrenic patients to case history data and disease characteristics in a cross-sectional study of unselected patients, and to integrate these data with two previous longitudinal studies of neuropsychological impairments among schizophrenic patients. METHOD: One hundred consecutive schizophrenic patients were studied with respect to clinical case history and current symptoms, medication and neuropsychological impairment using a comprehensive computerized test battery. RESULTS: The most salient finding was a marked slowing of response readiness, linearly related to the number of previous acute episodes. The resulting deficit was far beyond what has been obtained in any other group of subjects (average -6 SD for >five episode patients). The impairments in many of the other neuropsychological parameters could to some extent be explained with reference to response slowing, with one exception--verbal short-term memory. Adjustment for important confounding factors (age, duration of illness, medication) did not change the strong negative association between response readiness and number of previous episodes. CONCLUSION: These findings, together with findings of our two previous longitudinal studies and a recent replication, prompted us to suggest that each acute schizophrenic episode inflicts damage to a set of hypothetical structures, cognitive pattern generators. We assume that these structures translate intentions to logistic programs. When damaged, delays are introduced into executive functions and corollary discharge processes will run out of phase with intentions. This model implicates new ways of looking at the generative mechanisms of the illness, and on treatment strategies.

Adult↗

Deterioration in peak systolic velocity is closely related to ischaemia during angioplasty: a vectorcardiographic and tissue Doppler imaging study.

We tested the hypothesis that the extent of signs of ischaemia detected by vectorcardiography (VCG) during elective coronary angioplasty (percutaneous transluminal coronary angioplasty; PTCA) is related to systolic and diastolic myocardial velocities, as determined by tissue Doppler echocardiography. A total of 15 patients undergoing PTCA (12 men/three women; age 61+/-9 years), without prior myocardial infarction and with an ejection fraction of >50%, were included. The balloon inflation was repeated three times, with minimum intervals of 2 min between inflations. Tissue Doppler echocardiography was performed, in an apical two- or four-chamber view, before and at the end of each inflation. Peak systolic velocity, time-to-peak systolic velocity (TTP), peak early (E(m)) and late (A(m)) diastolic velocities, the E(m)/A(m) ratio and isovolumic relaxation time were measured in the basal segments of the left ventricle. VCG recordings were carried out during the whole procedure. ST vector magnitude (ST-VM) and ST change vector magnitude (STC-VM) were monitored. The total duration and area of each VCG change during inflation were calculated for each patient. Isovolumic relaxation time, peak E(m) and A(m) values and the E(m)/A(m) ratio did not change significantly during inflation. Peak systolic velocity decreased (6.7+/-2.0 to 5.3+/-1.9 cm/s; P<0.001) and TTP increased (157+/-60 to 192+/-60 ms; P<0.01) during inflation. Both STC-VM time (r=-0.68, P<0.01) and STC-VM area (r=-0.68, P<0.01) were related to peak systolic velocity during inflation. STC-VM time was also related (r=0.55, P<0.05) to the difference in peak systolic velocity during compared with before inflation. ST-VM was less closely related to peak systolic velocity. Thus the duration and degree of ischaemia, as measured by VCG, are related to peak systolic velocity in the basal segments of the left ventricle.

Aged↗

Increased T cell expression of CD154 (CD40-ligand) in multiple sclerosis.

CD154 (CD40-ligand, gp39), expressed on activated T cells, is crucial in T cell-dependent immune responses and may be involved in the pathogenesis of multiple sclerosis (MS). We studied cerebro-spinal fluid and peripheral blood T cell expression of CD154 in MS by flow cytometry. Patients with secondary progressive MS (SPMS) had constitutive CD154 expression on CD4 and CD8 T cells in blood. Constitutive CD154 expression was not observed in patients with relapsing-remitting MS (RRMS) or clinically isolated syndromes (CIS) suggestive of demyelinating disease. After ex vivo activation CD154 was, however, expressed on a higher percentage of T cells from patients with CIS or RRMS than from healthy control subjects. These results suggest involvement of CD154 in the pathogenesis of MS, and the shift from a relapsing-remitting to a secondary progressive disease course may be associated with constitutive, systemic CD154 expression.

Adult↗

Comparison of pain and time of procedures with two first-trimester abortion techniques performed by residents and faculty.

OBJECTIVES: We compared pain perception and procedure time in abortions performed by residents and faculty using a manual vacuum aspirator and electric vacuum curettage devices. STUDY DESIGN: We conducted a randomized trial of 114 women undergoing first-trimester abortions. Patients assessed the level of pain with visual analog scales. RESULTS: The mean procedure times were 5.7 and 6.9 minutes, respectively, with electric vacuum curettage and manual vacuum aspirator. Faculty took less time than residents to perform both procedures. Patients reported a higher pain level with cervical dilatation before resident electric vacuum curettage procedures. Patients undergoing electric vacuum curettage thought that the procedure noise increased their pain. CONCLUSIONS: First-trimester abortion procedures can be performed more quickly by experienced surgeons. The procedure time for the manual vacuum aspirator is greater than that for the electric vacuum curettage. Patient pain perception with aspiration by these two techniques is not different. The level of pain after aspiration did not vary significantly in patients who had abortions performed by residents or faculty.

Abortion, Induced↗

Evaluation of 5' nuclease assay for detection of Actinobacillus pleuropneumoniae.

Sequence detection by the 5' nuclease TaqMan assay uses online detection of internal fluorogenic probes in closed PCR tubes. Primers and probe were chosen from a part of the omlA gene common to all serotypes of Actinobacillus pleuropneumoniae, which gave an amplicon of 92 bp. The test was evaluated with 73 lung isolates and 120 tonsil isolates of A. pleuropneumoniae as well as with a collection of reference strains. By using a C(t) value (cycle number in which the fluorescence exceeds the threshold defined by the software) of 30 as the cutoff limit, the 5' nuclease assay represents a test with 100% sensitivity and 100% specificity. A high degree of reproducibility of the test was demonstrated. If samples with C(t) values of </=30 are considered positive, the detection limit of the assay was 1 CFU/reaction tube, corresponding to a 10-fold higher number of DNA templates. After cycle 30, nonspecific reactions appeared when testing dilutions of DNA templates or pure cultures of A. pleuropneumoniae, as well as when testing tonsil scrapings from specific-pathogen-free herds. The diagnostic sensitivity, as evaluated with 586 tonsil scrapings from animals infected with A. pleuropneumoniae, is the same level as that of a PCR test based on the omlA gene described previously. The 5' nuclease assay represents a fast method for species-specific detection and identification of A. pleuropneumoniae in pure and mixed cultures. The evaluation shows, however, that a C(t) value cutoff limit of </=30 must be chosen in order to obtain reliable results. The investigation emphasizes that a thorough evaluation of the criteria used to define a positive test result is necessary.

Actinobacillus Infections↗

Glucose uptake and metabolic stress in rat muscles stimulated electrically with different protocols.

In the present study, the relationship between the pattern of electrical stimulation and glucose uptake was investigated in slow-twitch muscles (soleus) and fast-twitch muscles (epitrochlearis) from Wistar rats. Muscles were stimulated electrically for 30 min in vitro with either single pulses (frequencies varied between 0.8 and 15 Hz) or with 200-ms trains (0.1-2 Hz). Glucose uptake (measured with tracer amount of 2-[(3)H]deoxyglucose) increased with increasing number of impulses whether delivered as single pulses or as short trains. The highest glucose uptake achieved with short tetanic contractions was similar in soleus and epitrochlearis (10.9 +/- 0.7 and 12.0 +/- 0.8 mmol x kg dry wt(-1) x 30 min(-1), respectively). Single pulses, on the other hand, increased contraction-stimulated glucose uptake less in soleus than in epitrochlearis (7.5 +/- 1.1 and 11.7 +/- 0.5 mmol x kg dry wt(-1) x 30 min(-1), respectively; P < 0.02). Glucose uptake correlated with glycogen breakdown in soleus (r = 0.84, P < 0.0001) and (epitrochlearis: r = 0.91, P < 0.0001). Contraction-stimulated glucose uptake also correlated with breakdown of ATP and PCr and with reduction in force. Our data suggest that metabolic stress mediates contraction-stimulated glucose uptake.

Adenosine Triphosphate↗

Mandibular bone graft material for reconstruction of alveolar cleft defects: long-term results.

OBJECTIVE: To analyze the long-term effect of mandibular bone as donor material in bone grafting of the alveolar process defect in patients with unilateral cleft lip and palate (UCLP), compared with iliac crest cancellous bone. METHOD: During a 7-year period, 101 UCLP patients were bone grafted, 57 cases with iliac crest cancellous bone and 44 with mandibular symphyseal bone. The long-term results with an observation time of more than 4 years were analyzed with respect to marginal bone level and dental and gingival condition in the grafted area. Complications were recorded. RESULTS: The bone level in the grafted area was satisfactory in both groups. Impaction of cleft-side canines was found in 35% of the patients in both groups. Patients with agenesis of the cleft side lateral incisor had significantly more impacted canines, compared with patients with a cleft-side lateral situated in the lesser maxillary segment, probably due to the fact that the lateral incisors help in guiding the canine down through the grafted area. The number of complications was scarce, although both groups demonstrated some gingival retraction with a longer crown length at the cleft side central incisor. CONCLUSION: The findings of this study have changed our strategy in bone grafting. Timing of orthodontic treatment and bone grafting has been more varied depending on the position and presence of teeth in the cleft area. Bone grafting of the alveolar process is not just a local treatment of a bony defect, but in respect to the burden of treatment, bone grafting of the alveolar process has to be planned in accordance with orthodontic treatment and maxillofacial growth.

Alveolar Process↗

Disposition of sulfadimethoxine in camels (Camelus dromedarius) following single intravenous and oral doses.

Single-dose pharmacokinetics of sulfadimethoxine were determined in six adult camels (Camelus dromedarius) following administration of a mean dosage of 17.5 +/- 2.7 mg/kg both i.v. and p.o. Serial blood samples were collected through an indwelling jugular catheter intermittently for 5 days for both routes. Sulfadimethoxine was assayed using high-performance liquid chromatography. Serum drug concentration versus time data for each animal was subjected to linear regression, with the best-fit model selected based on residual analysis. The data fit best into a two-compartment open model, with first-order input for oral administration. For orally administered drug, mean maximum serum concentration of 19.3 +/- 1.7 microg/ml was reached at 11.41 +/- 2.59 hr, with an elimination rate constant of 0.09/hr +/- 0.05/hr and an elimination half-life of 11.7 +/- 3 hr. Mean peak serum concentration following i.v. administration was 223 +/- 48 microg/ml. Mean volume of distribution at steady state was 0.393 +/- 0.049 L/kg. Elimination rate constants differed with i.v. and oral administration, suggesting a flip-flop model. Oral bioavailability was 103% +/- 38%. Comparison of maximum serum concentrations to the microbial breakpoint concentration reported for sulfadimethoxine (512 microg/ml) suggests that the dose used in this study, 17.5 +/- 2.7 mg/kg, is insufficient for achieving therapeutic serum levels.

Administration, Oral↗

Effects of eight polycyclic aromatic compounds on the survival and reproduction of the springtail Folsomia fimetaria L. (Collembola, isotomidae).

The effects of eight polycyclic aromatic compounds on the survival and reproduction of the collembolan Folsomia fimetaria L. were investigated in a well-characterized Danish agricultural soil. With the exception of acridine, polycyclic aromatic hydrocarbons (PAHs) and neutral N-, S-, and O-monosubstituted analogues showed similar toxicities to soil collembolans when the results were expressed in relation to total soil concentrations (mg/kg). The estimated concentrations resulting in a 10% reduction of reproductive output (EC10 values) were based on measured initial concentrations and were for acridine 290 mg/kg, carbazole 10 mg/kg, dibenzofuran 19 mg/kg, dibenzothiophene 7.8 mg/kg, fluoranthene 37 mg/kg, fluorene 7.7 mg/kg, phenantrene 23 mg/kg, and pyrene 10 mg/kg. When the EC10 values were converted to soil pore-water concentrations, they showed a highly significant correlation (r2 = 0.71, p < 0.01) to no-observed-effect concentrations for the freshwater crustacean Daphnia magna, as estimated by a quantitative structure activity relation (QSAR) for baseline toxicity (nonpolar narcosis). Only carbazole and acridine were more than two times more toxic (4.9 and 3.1, respectively) than expected from the Daphnia QSAR data. The latter result indicates that the toxicity of the tested substances is close to that expected for compounds with nonpolar narcosis as the mode of action. However, the relatively large uncertainties in the extrapolation method prevent final conclusions from being drawn.

Animals↗

Effects and risk assessment of linear alkylbenzene sulfonates in agricultural soil. 5. Probabilistic risk assessment of linear alkylbenzene sulfonates in sludge-amended soils.

Linear alkylbenzene sulfonates (LAS) can be found in high concentrations in sewage sludge and, hence, may enter the soil compartment as a result of sludge application. Here, LAS may pose a risk for soil-dwelling organisms. In the present probabilistic risk assessment, statistical extrapolation has been used to assess the risk of LAS to soil ecosystems. By use of a log-normal distribution model, the predicted no-effect concentration (PNEC) was estimated for soil fauna, plants, and a combination of these. Due to the heterogeneous endpoints for microorganisms, including functional as well as structural parameters, the use of sensitivity distributions is not considered to be applicable to this group of organisms, and a direct, expert evaluation of toxicity data was used instead. The soil concentration after sludge application was predicted for a number of scenarios and used as the predicted environmental concentration (PEC) in the risk characterization and calculation of risk quotients (RQ = PEC/PNEC). A LAS concentration of 4.6 mg/kg was used as the current best estimate of PNEC in all RQ calculations. Three levels of LAS contamination (530, 2,600, and 16,100 mg/kg), three half-lives (10, 25, and 40 d), and five different sludge loads (2, 4, 6, 8, and 10 t/ha) were included in the risk scenarios. In Denmark, the initial risk ratio would reach 1.5 in a realistic worst-case consideration. For countries not having similar sludge regulations, the estimated risk ratio may initially be considerably higher. However, even in the most extreme scenarios, the level of LAS is expected to be well beyond the estimated PNEC one year after application. The present risk assessment, therefore, concludes that LAS does not pose a significant risk to fauna, plants, and essential functions of agricultural soils as a result of normal sewage sludge amendment. However, risks have been identified in worst-case scenarios.

Agriculture↗

Improved glucose tolerance and acinar dysmorphogenesis by targeted expression of transcription factor PDX-1 to the exocrine pancreas.

The homeodomain protein PDX-1 is critical for pancreas development and is a key regulator of insulin gene expression. PDX-1 nullizygosity and haploinsufficiency in mice and humans results in pancreatic agenesis and diabetes, respectively. At embryonic day (e) 10.5, PDX-1 is expressed in all pluripotential gut-derived epithelial cells destined to differentiate into the exocrine and endocrine pancreas. At e15, PDX-1 expression is downregulated in exocrine cells, but remains high in endocrine cells. The aim of this study was to determine whether targeted overexpression of PDX-1 to the exocrine compartment of the developing pancreas at e15 would allow for respecification of the exocrine cells. Transgenic (TG) mice were generated in which PDX-1 was expressed in the exocrine pancreas using the exocrine-specific elastase-1 promoter. These mice exhibited a marked dysmorphogenesis of the exocrine pancreas, manifested by increased rates of replication and apoptosis in acinar cells and a progressive fatty infiltration of the exocrine pancreas with age. Interestingly, the TG mice exhibited improved glucose tolerance, but absolute beta-cell mass was not increased. These findings indicate that downregulation of PDX-1 is required for the proper maintenance of the exocrine cell phenotype and that upregulation of PDX-1 in acinar cells affects beta-cell function. The mechanisms underlying these observations remain to be elucidated.

Adipose Tissue↗

Genetic evaluation of dairy cattle using test-day models.

Recently there has been considerable interest in modeling individual test-day records (TDR) for genetic evaluation of dairy cattle as a replacement for the traditional use of estimated accumulated 305-d yields. Some advantages of test-day models (TDM) include the ability to account for environmental effects of each test day, the ability to model the trajectory of the lactation for individual genotypes or groups of animals, and the possibility of genetic evaluations for persistency of production. Also, the use of test-day models avoids the necessity of extending short lactations on culled animals and animals with records in progress. The disadvantages of TDM include computational difficulties associated with analyzing much larger datasets and the need to estimate many more parameters than in a traditional 305-d lactation model. Several different models have been proposed to model the trajectory of the lactation, including so-called "biological functions," various polynomials and character process models. At present, there is not universal agreement on which models to use in routine prediction of breeding values and better methods to compare models are desirable. Obtaining accurate estimates of the dispersion parameters to use in TDM remains a challenge. Methods used include a two-step procedure in which the dispersion parameters are estimated in a series of multivariate models followed by a reduction in order of fit using covariance functions, and a one-step procedure in which the parameters of TDM are estimated using restricted maximum likelihood or Bayesian methods in a random regression model. Further research should focus on including multiple lactation data and accounting for heterogeneity variance.

Algorithms↗

Effects of di(2-ethylhexyl) phthalate and dibutyl phthalate on the collembolan Folsomia fimetaria.

Lethal and sublethal effects of di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) on adult individuals of the collembolan Folsomia fimetaria were investigated in the laboratory by the use of small microcosms. Effects of DEHP and DBP were also tested on newly hatched collembolans in a multidish system. The endpoints were juvenile mortality, growth, and development. When exposed to DEHP, adults and juveniles were unaffected at all test concentrations, that is, up to 5,000 mg/kg. However, DBP caused increased adult mortality at 250 mg/kg and juvenile mortality at 25 mg/kg. For DBP, adult reproduction was a more sensitive endpoint than was survival, with an EC10 and EC50 of 14 and 68 mg/kg, respectively. Juvenile molting frequency seems to be a sensitive parameter, because number of cuticles produced by young springtails was reduced at 1 mg/kg. Toxicity was reduced when soil spiked with DBP was stored at 20 degrees C for a period of up to 28 d before adding the animals. Reduction in toxicity of DBP may be due a combination of degradation, evaporation, and adsorption of DBP to soil material. This was confirmed by chemical analyses, which showed a rapid initial disappearance followed by a much slower disappearance. Our results lead to the overall conclusion that significant adverse effects of phthalates on collembolans are not likely to occur as a result of normal sewage sludge application.

Animals↗