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M S Jensen

Publications and source records attributed to M S Jensen.

At least 19 recordsLinked to original sources
PubMed2006

Is smoking a risk factor for decreased semen quality? A cross-sectional analysis.

BACKGROUND: Previous studies suggest a deleterious effect of cigarette smoking on semen quality, but their results have not been consistent. We studied the association between current smoking and semen characteristics and hormonal levels in a large group of healthy men. METHODS: From 1987 to 2004, seven separate occupational or environmental semen quality studies were co-ordinated by our department. A total of 2562 men participated, each providing semen and blood sample and answering a questionnaire about lifestyle and factors related to health. Appropriate semen and smoking data were available for 2542 men. RESULTS: Adjusting for study, age and other covariates, we observed an inverse dose-response relation between smoking and semen volume, total sperm count and percentage motile sperm. Heavy smokers had a 19% lower sperm concentration than non-smokers. We found a positive dose-response relationship between smoking and testosterone, LH and the LH/free testosterone ratios. CONCLUSION: Current smoking in adult life moderately impairs the semen quality. It is well known that semen quality is associated to fecundity. Therefore, it would be sensible to advise men to abstain from smoking to avoid decreased fecundity.

Adult↗
PubMed2005

Fecundability according to male serum inhibin B--a prospective study among first pregnancy planners.

BACKGROUND: New biological markers of male fecundity are needed for use in large-scale epidemiological studies. We studied the association between male inhibin B and fecundability. METHODS: Four hundred and thirty Danish couples without previous reproductive experience were followed from termination of contraception until pregnancy or for a maximum of six menstrual cycles. At enrolment we obtained semen samples (n = 418) and blood samples to measure reproductive hormones, including inhibin B (n = 343). RESULTS: The fecundability odds ratio for an increment of male inhibin B by 1 log pg/ml was 1.428 (95% confidence interval 1.022-1.994), adjusted for factors influencing the crude estimate. Only inhibin B values below 100 pg/ml were strongly related to fecundability. We designed a receiver operating characteristic curve based on the 29 males with serum inhibin B #100 pg/ml. The area under the curve (AUC) for inhibin B was 0.787 and the corresponding AUCs for sperm density and FSH were 0.913 and 0.800, respectively. CONCLUSION: Serum inhibin B may be a reliable marker of male fecundity for epidemiological research and may have some advantages over sperm density. Our findings do not support the replacement of sperm density by male inhibin B when obtaining sperm data is an option.

Adult↗
PubMed2005

Lower sperm counts following prenatal tobacco exposure.

BACKGROUND: Recent findings have indicated that prenatal exposure to tobacco smoke may cause lower sperm concentration in ejaculates of adult men. To extend the research on this hypothesis we investigated the dose-dependency of the association, controlling for other prenatal exposures. METHODS: From 1987 to 1996, four separate occupational semen studies were conducted at three centres in Denmark. A total of 945 men provided semen and blood samples, and information on reproductive and lifestyle factors. In 2004, we collected data on the maternal smoking habits during pregnancy from 522 mothers of the participating men. RESULTS: Adjusting for study subgroup, abstinence time and other factors, we found statistically non-significant differences in mean sperm concentrations: 65.0 x 10(6)/ml [95% confidence interval (CI) 51, 81] among sons of non-smokers; 59.1 x 10(6)/ml (95% CI 46, 75) among sons of mothers who had smoked 1-10 cigarettes/day; and 57.7 x 10(6)/ml (95% CI 40, 81) among those whose mothers had smoked >10 cigarettes/day. The former group had a higher odds ratio (OR) for oligozoospermia (sperm concentration < or =20 x 10(6)/ml) of 1.5 (95% CI 0.9, 2.8), the latter group an OR of 2.6 (95% CI 1.2, 5.8). CONCLUSION: We observed a dose-dependent association between prenatal tobacco exposure, lower sperm concentration and higher risk of oligozoospermia.

Adult↗
PubMed2005

Design and evaluation of a handheld impedance plethysmograph for measuring heart rate variability.

Heart rate variability (HRV) analysis from 10s ECGs has been shown to be reliable. However, the short examination time warrants a user-friendly system that can be used for ad-hoc examinations without normal preparation, unlike ECG. A handheld device has been developed that can measure ultra-short HRV from impedance plethysmographic recordings of the pulse wave in distal superficial arteries. The prototype device was made user-friendly through a compact, pen-like design and the use of integrated metal electrodes that were especially designed for dry operation. The main signal processing was performed by a digital signal processor, where the discrete heart beats were detected using a correlation algorithm that could adapt to individual pulse wave shapes to account for biological variation. The novel device was evaluated in 20 mainly young volunteers, using 10 s time-correlated ECG recordings as the reference method. Agreement between the two methods in measuring heart rate and root mean square of successive differences in the heart beat interval (RMSSD) was analysed using correlation coefficients (Pearson's R2), mean differences with 95% confidence intervals and 95% limits of agreement, and Bland-Altman plots. The correlation between the two methods was R2 = 1.00 and R2 = 0.99 when heart rate and RMSSD were measured, respectively. The Bland-Altman plots showed suitable agreement between the novel device and standard 10 s ECGs, which was substantiated by 95% limits of agreement of the difference of +/- 0.1 beats min(-1) and approximately +/- 10 ms for heart rate and RMSSD, respectively. Therefore the evaluation showed no significant systematic error of the novel device compared with ECG.

Adult↗
PubMed2004

A method to create reference maps for evaluation of ultrasound images of carotid atherosclerotic plaque.

Ten formalin-fixed atherosclerotic carotid plaques removed by endarterectomy were molded into rectangular agar blocks containing fiducial markers on the top surface. Plaque and fiducial markers were imaged with 3-D multiangle ultrasound (US) spatial compounding as well as planar X ray. Subsequently, the blocks were decalcified, sliced, photographed and analyzed histologically. This gave a total of 123 slices. The plaque regions of the photographs were outlined and the outline adjusted to partly compensate for occasional displacement during slicing. Inside this outline, the material constitutions were found by incorporating the histologic information. From this set, slices with 1. too much tissue displacement due to cutting or 2. lack of identification of calcification as found by x ray, were removed. This resulted in 53 reference maps. The material types identified covered soft tissues, fibrous tissue, calcified tissue and unidentified tissues. The 53 reference maps can be used for direct automated quantitative comparison with US images.

Arteriosclerosis↗
PubMed2004

Visual and quantitative evaluation of selected image combination schemes in ultrasound spatial compound scanning.

Multi-angle spatial compound images are normally generated by averaging the recorded single-angle images (SAIs). To exploit possible advantages associated with alternative combination schemes, this paper investigates both the effect of number of angles (Ntheta) as well as operator (mean, median, mean-excluding-maximum (mem), root-mean-square (rms), geometric mean and maximum) on image quality (tissue delineation and artifacts), speckle signal-to-noise ratio (SNRs) and contrast. The evaluation is based on in vitro SAI (+/-21 degrees in steps of delta theta = 7 degrees) of formalin fixed porcine tissue containing adipose, connective and muscular tissue. Image quality increased with number of angles up to +/-14 degrees after which the improvements became debatable. The mem and median operators, which try to render the images more quantitatively correct by suppressing strong echoes from specular reflectors, provide some improvement in this regard. When combining the SAI with the mean operator, the SNR, increases--in general--with Ntheta. For Ntheta = 2, the SNRs increases with delta theta as expected. When Ntheta = 7, the highest SNRs is obtained for the mem, rms, and geometric mean operators, while the lowest SNRs is obtained for the maximum operator. When comparing SNRs for adipose and fibrous tissue, the level is close to 1.91 for adipose tissue but only 1.7 for fibrous tissue which contain relatively few organized scattering structures.

Adipose Tissue↗
PubMed2002

A method to obtain reference images for evaluation of ultrasonic tissue characterization techniques.

A general problem when evaluating ultrasonic methods for tissue characterization is that "a golden standard" is seldom known. This paper describes a manual method to obtain a reference image, with the same geometry as the ultrasound image, indicating spatial location of the different tissue types present in the biological tissue scanned in vitro. A 30 x 10 x 2 mm3 piece of formalin fixed porcine tissue was molded into an agar block, which on the top surface, contained a set of fiducial markers, spaced 2.5 mm. The block was submerged into 20 degrees C water and a set of parallel 7.5 MHz spatial compound ultrasound images of tissue and fiducial markers were recorded each 0.5 mm. Guided by the fiducial markers, the agar block was subsequently cut into slices 2.5 mm thick, photographed and finally analyzed histologically identifying these tissues: collagen rich, collagen poor, micro vessels and muscle fibres. Due to: (1) the cutting procedure, (2) the finite size of the ultrasound beam and (3) the spatial variation in propagation velocity, the macroscopic photographs did not align completely with the ultrasound images. Likewise, the histological image is a geometrically distorted version of the macroscopic photograph, due to the histological preparation process. The histological information was "mapped back" into the format of the ultrasound images the following way: On the macroscopic images, outlines were drawn manually which defined the border of the tissue. These outlines were superimposed on the corresponding ultrasound images (identified via the fiducial markers) and modified to encompass what appeared to be tissue regions on the ultrasound images and subsequently re-applied to the macroscopic image. This modified macroscopic outline was used as guideline when drawing outlines identifying regions of the various tissue types. Specifically, the macroscopic image revealed the borders between the different tissues, while the histological image identified the four tissue types. A set of 12 reference images based on modified macroscopic outlines was created. The overlap between the ultrasound images and the macroscopic images--which are the geometrical basis for the final reference images--was between 77% and 93%. A set of 12 reference images spaced 2.5 mm, identifying spatial location of four different tissue types in porcine muscle has been created. With the reference images, it is possible to quantitatively compare different ultrasound based tissue classification techniques.

Animals↗
PubMed2000

Tetanus-induced asynchronous GABA release in cultured hippocampal neurons.

Asynchronous GABA release was studied in cultured hippocampal neurons using paired whole-cell recordings. Tetanization of the presynaptic GABAergic neuron was accompanied by a train of IPSCs which showed tetanic depression. Asynchronous IPSCs (asIPSCs) also developed during the train and continued for 1.85+/-0.3 s after the stimulation. The threshold frequency for evoking asIPSCs was 10 Hz, while maximal asynchronous activity was achieved at 40 Hz. Perfusion with EGTA-AM blocked asIPSCs. The elevation of [Ca(2+)](i) that accompanies presynaptic action potential firing triggers asynchronous release of GABA vesicles, thereby counteracting tetanic depression of synchronous IPSCs.

2-Amino-5-phosphonovalerate↗
PubMed2000

Release of synaptic zinc is substantially depressed by conventional brain slice preparations.

Research on synaptically-released zinc is frequently done in vitro with acute brain slice preparations. We show here the in vitro hippocampal slice preparation has two major pitfalls for zinc research. First, up to 50% of the synaptic zinc is lost during slice cutting and/or the first 10 min of slice incubation, with the losses being most pronounced on the edges of the slice. Second, the release of the remaining zinc from a slice is substantially depressed (up to 50%) at the low temperatures (32 degrees C) typically used for brain slice studies. In concert, these effects reduce zinc release about 75% in vitro, compared to in vivo. Implications for research on synaptically-released zinc are discussed.

Animals↗
PubMed2000

Zinc-enriched (ZEN) terminals in mouse olfactory bulb.

The present study was designed to localize zinc-enriched (ZEN) terminals in mouse olfactory bulb by means of ZnT3 immunocytochemistry (ICC) and zinc autometallography (AMG). The immunocytochemical staining of ZnT3 was closely correlated with the AMG pattern. ZEN terminals were defined as terminals showing both ZnT3 immunoreactivities and AMG granules. At the light microscopic level, dense staining patterns for ZnT3 immunoreactivity were seen in the granule cell layer and the olfactory glomerular layer. At the ultrastructural level, ZEN terminals were restricted to presynaptic terminals with single or multiple postsynaptic thickenings. The postsynaptic profiles contacting ZEN terminals appeared to be dendrites or somata of granule cells in the granule cell layer and periglomerular cells and mitral/tufted (M/T) cells in the olfactory glomerular layer. This suggests that two main sources of ZEN terminals are present in mouse olfactory bulb: (1) centrifugal fibres making asymmetrical synapses with granule cells and periglomerular cells, and (2) olfactory receptor terminals contacting dendritic profiles of M/T cells or periglomerular cells. The close correlation between ZEN terminals and the glutamatergic system is discussed.

Animals↗
PubMed2000

Histochemically-reactive zinc in amyloid plaques, angiopathy, and degenerating neurons of Alzheimer's diseased brains.

Excess brain zinc has been implicated in Alzheimer's neuropathology. Here we evaluated that hypothesis by searching the brains of Alzheimer's patients for abnormal zinc deposits. Using histochemical methods, we found vivid Zn2+ staining in the amyloid deposits of dense-core (senile) plaques, in the amyloid angiopathy surrounding diseased blood vessels, and in the somata and dendrites of neurons showing the characteristic neurofibrillary tangles (NFT) of Alzheimer's. In contrast, brains from age-matched, non-demented subjects showed only occasional staining for Zn2+ in scattered neurons and possible plaques. A role of abnormal zinc metabolism in Alzheimer's neuropathology is suggested.

Aged↗
PubMed2000

The effect of internal GTPgammaS on GABA-release in cultured hippocampal neurons.

The effects of presynaptic guanosine-5'-O-(3-thio)triphosphate (GTPgammaS) on GABAergic inhibitory postsynaptic currents (IPSCs) were studied in cultured hippocampal neurons using whole-cell recordings. Inclusion of GTPgammaS (0.5-1 mM) in the presynaptic electrode reduced both the amplitude and paired-pulse depression of IPSCs, indicating that the probability of GABA-release had been reduced. Presynaptic GTPgammaS increased the depression of IPSCs by the GABA(B)-receptor-agonist baclofen (10 microM), and the effect of baclofen was poorly reversible after washing. Stimulation of the GABAergic neuron at 80 Hz for 1 s was accompanied by tetanic depression of the IPSCs by 52+/-6% and was followed by post-tetanic potentiation (PTP), reaching a peak value of 71+/-21% and lasting about 100 s. IPSCs evoked after tetanic stimulation were depressed and PTP was absent when tetanic stimulation was applied within 3 min after starting injection of GTPgammaS into the presynaptic neuron. At longer times, basal release underlying a single IPSC was depressed. This affected the ratios recorded in response to tetanic stimulations such that tetanic depression was abolished, while PTP increased to 117+/-34%. In conclusion, GTPgammaS reduces the probability of GABA-release in both a use- and time-dependent manner, most likely through an inhibitory action on presynaptic Ca2+-influx through voltage-gated Ca2+ channels or an interaction with small GTP-binding proteins in the nerve terminals.

Animals↗
PubMed2000

Developmental increase in asynchronous GABA release in cultured hippocampal neurons.

Developmental changes in GABAergic synaptic transmission were examined in cultured hippocampal neurons using patch-clamp recordings and Ca(2+) imaging. In paired recordings, tetanization of the presynaptic GABAergic neuron with 80 pulses at either 40 or 80Hz was accompanied by tetanic depression of inhibitory postsynaptic responses. In neurons that had been cultured for more than two weeks, asynchronous inhibitory postsynaptic currents often appeared during the tetanus and continued for several seconds following stimulation. There was little asynchronous activity in neurons that had been cultured for shorter times. However, no age-related changes were observed in the amplitude of single synchronous inhibitory postsynaptic currents, paired-pulse depression or post-tetanic potentiation of inhibitory postsynaptic currents. Following equimolar replacement of extracellular Ca(2+) with strontium ions (Sr(2+)), single autaptic inhibitory postsynaptic currents were depressed in amplitude and asynchronous inhibitory postsynaptic currents were present on the decaying phase. Sr(2+)-induced asynchronous inhibitory postsynaptic currents showed no dependence on age in culture. Imaging of Ca(2+) in single GABAergic boutons was performed by including Fluo-3 in the patch pipette. During action potential firing induced by stimulating at 80Hz for 1s, intracellular calcium [Ca(2+)](i) increased rapidly in individual boutons. Following the stimulus, [Ca(2+)](i) decayed back to baseline within 10-15s. The half-time of decay increased from 1. 7+/-0.2s at 15days in vitro to 4.0+/-0.2s at 30days in vitro (P<0. 05), with a developmental profile that closely matched the increase in asynchronous inhibitory postsynaptic currents. We propose that the increase in tetanus-induced asynchronous GABA-release during the first month of synapse maturation in vitro is caused by a slowing of the Ca(2+)-clearing mechanisms in the GABAergic boutons. This results in larger and more prolonged elevations of [Ca(2+)](i) during tetanic stimulation, which leads to enhanced asynchronous transmitter release. We propose that the results of this study demonstrate a potentially important aspect of synapse maturation during development, and also imply that GABA release is up-regulated in conditions of decreased Ca(2+) buffering and clearing.

Action Potentials↗
PubMed2000

Various nitric oxide donors protect chick embryonic neurons from cyanide-induced apoptosis.

The discovery of numerous biochemical effects of cyanide not directly related to the inhibition of the respiratory chain, including the involvement of apoptosis, has challenged the basis of traditional antidote treatment, which primarily depends on nitrite-induced conversion of hemoglobin into methemoglobin, releasing the blockade of cytochrome c oxidase by high-affinity binding of cyanide as cyanmethemoglobin. The fact that amyl nitrite has antidotal effects not related to methemoglobin formation has unfolded new mechanism of actions of nitrites including release of nitric oxide (NO). In this study, we characterized the effect of various NO donor compounds on cyanide-induced cell death in cultured chick embryonic neurons. Apoptosis was induced by treating the neuronal cultures with 1 mM NaCN for 1 h, followed by a cyanide-free incubation period of 23 h. Using this treatment protocol, we showed that cyanide-induced apoptosis was blocked in the presence of the different NO donors sodium nitroprusside, S-nitrosoglutathione, S-nitroso-N-acetylpenicillamin, nitroglycerin, 3-morpholinosydnonimine, and diethylamine nitric oxide, indicating independence of the redox-related species of NO released. The effect was confirmed to be mediated by NO, since exhausted NO donors did not afford protection, and the mechanism likely involved chemical modification of thiol groups, since the effect was completely reversed by dithiothreitol. Furthermore, NMDA antagonists protected against cyanide-induced cell death, whereas inhibitors of nitric oxide synthase increased cyanide-induced apoptotic damage, indicating a protective effect of endogenously generated NO, at least in cell cultures.

Animals↗
PubMed1999

Post-tetanic potentiation of GABAergic IPSCs in cultured rat hippocampal neurones.

1. Dual whole-cell patch-clamp recording was used to investigate post-tetanic potentiation (PTP) of GABAergic IPSCs evoked between pairs of cultured rat hippocampal neurones. Tetanization of the presynaptic neurone at frequencies (f) ranging from 5 to 100 Hz resulted in PTP of the IPSCs. Maximum PTP had a magnitude of 51.6 % just after the stimulus train, and lasted up to 1 min. PTP was shown to be dependent on the number of stimuli in the train, but independent of f at frequencies > or =5 Hz. 2. Blocking postsynaptic GABAA receptors with bicuculline during the tetanus did not affect the expression of PTP, showing that it is a presynaptic phenomenon. PTP was strongly affected by changing [Ca2+]o during the tetanus: PTP was reduced by lowering [Ca2+]o, and increased by high [Ca2+]o. 3. PTP was still present after presynaptic injection of BAPTA or EGTA, or following perfusion of the membrane-permeable ester EGTA-tetraacetoxymethyl ester (EGTA AM, 50 microM). On the other hand, EGTA AM blocked spontaneous, asynchronous IPSCs (asIPSCs), which were often associated with tetanic stimulation. 4. Tetanic stimulation in the presence of 4-aminopyridine (4-AP), which promotes presynaptic Ca2+ influx, evoked sustained PTP of IPSCs in half of the neurones tested. 5. The results indicate that PTP at inhibitory GABAergic synapses is related to the magnitude of presynaptic Ca2+ influx during the tetanic stimulation, leading to an enhanced probability of vesicle release in the post-tetanic period. The increase in [Ca2+]i occurs despite the presence of high-affinity exogenous and endogenous intracellular Ca2+ buffers. That PTP of IPSCs depends on the number, and not the frequency, of spikes in the GABAergic neurone is in accordance with a slow clearing of intracellular Ca2+ from the presynaptic terminals.

Animals↗
PubMed1999

Exercise induces recruitment of lymphocytes with an activated phenotype and short telomeres in young and elderly humans.

This study was performed in order to investigate the type of T cells recruited to the blood in response to an acute bout of exercise with regard to mean lengths of telomeric terminal restriction fragments (TRF) and surface activation markers and with special emphasis on age-associated differences. Ten elderly and ten young humans performed maximal bicycle exercise. There was no difference in the number of recruited CD4+ and CD8+ cells between the young and elderly group. In both age groups the immediate increases could be ascribed to recruitment of CD28- cells (CD8+ and CD4+ cells) and memory cells (only CD8+ cells). Furthermore, after exercise mean TRF lengths were significantly reduced in blood mononuclear cells and in CD8+ cells from young subjects and in CD4+ cells from elderly subjects compared with lengths pre-exercise. These findings suggest that the mobilization of T lymphocytes during acute exercise is mainly a redistribution of previously activated cells with an increased replicative story than cells isolated from the blood at rest. Furthermore, elderly humans fulfilling the Senieur protocol have a preserved ability to recruit T lymphocytes in response to acute physical stress.

Adult↗