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Biomedical subjects

B Kemp

Publications and source records attributed to B Kemp.

At least 145 records · Page 8Linked to original sources
PubMed1995

Age and gender affect different characteristics of slow waves in the sleep EEG.

Low-frequency EEG was analyzed quantitatively during 2 nights in 40 females and 34 males aged 26 to 101 years. Analyses were based on Rechtschaffen and Kales NREM sleep stages, on absolute low-frequency amplitude (i.e. power in the range of 0.2-2.0 Hz) and on low-frequency continuity. The latter parameter describes how much (0-100%) of the current slow-wave activity is continued in the near-future EEG. Such continuation can occur through closed loops in the underlying neuronal network and cells. These loops are slow, thus corresponding to slow-wave frequencies, and can consist of electrophysiological, chemical and/or other pathways. The continuity percentage then monitors the relative activity of these loops. It does not depend directly on absolute EEG amplitudes. All analyzed parameters, including amplitude-independent continuity, decreased substantially and significantly with increasing age. The amplitudes of low-frequency EEG in females were significantly and substantially (40%) larger than those in males. However, the amplitude-independent continuity percentage did not differ between the genders. These findings support the notion that gender-related anatomical differences have a general effect on EEG amplitude, including during slow-wave sleep. Aging, however, specifically affects the neurophysiological slow-wave-generating mechanism.

Adult↗
PubMed1995

Effects of time of insemination relative to ovulation, as determined by ultrasonography, on fertilization rate and accessory sperm count in sows.

The effects of the timing of insemination relative to ovulation on fertilization rate, accessory sperm count and early embryo development were studied in sows. Oestrus detection was performed at intervals of 8 h. Sows were artificially inseminated once with 3 x 10(9) spermatozoa. Transrectal ultrasonography was performed at intervals of 4 h to determine when ovulation occurred and sows were killed at 120 +/- 6 h after ovulation. For each insemination-ovulation interval of 8 h, fertilization rates were as follows: > 48 h, 35% (n = 1); 48-40 h, 51 +/- 36% (n = 6); 40-32 h, 54 +/- 36% (n = 14); 32-24 h, 79 +/- 32% (n = 19); 24-16 h, 94 +/- 11% (n = 24); 16-8 h, 92 +/- 21% (n = 24); 8-0 h, 95 +/- 22% (n = 21) and for the sows that were inseminated after ovulation: 0 to -8 h, 75 +/- 38% (n = 26); -8 to -16 h, 74 +/- 43% (n = 15) and < -16 h, 0% (n = 1). The median accessory sperm count differed among the groups from 1 (insemination 40-48 h before ovulation) to 126 (insemination 0-8 h after ovulation) (P = 0.0001). Within each 8 h time interval, the normal embryos from sows with less than 90% normal embryos were less developed and had a lower sperm count than did the normal embryos from sows with more than 90% normal embryos (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Effects of a second insemination after ovulation on fertilization rate and accessory sperm count in sows.

Insemination immediately after ovulation causes low fertilization results owing to a low fertilization rate and possibly also owing to polyspermic fertilization. The present experiment was undertaken to study the effects of a second insemination after ovulation on fertilization rate and embryonic development. In multiparous crossbred sows, transrectal ultrasonography was used at intervals of 4 h to determine ovulation. All sows (n = 91) were artificially inseminated with 3 x 10(9) mixed spermatozoa and, in 31 sows, a second insemination took place at 3 +/- 1 (mean +/- SD) h after ovulation. At 119 +/- 5 h after ovulation, the percentage of normal embryos and the accessory sperm count were determined. In the sows that were inseminated once, the percentage of normal embryos decreased when insemination took place more than 24 h before ovulation, from 88 +/- 20% (16-24 h; n = 15) to 63 +/- 40% (24-32 h; n = 10) (P < 0.05). In the sows that were inseminated again after ovulation, the percentage of normal embryos was high, irrespective of the period between first insemination and ovulation. The difference in percentage of normal embryos between the sows that were inseminated once or twice was significant when the first insemination took place between 24 and 32 h before ovulation; 63 +/- 40% (inseminated once, n = 10) and 97 +/- 5% (inseminated twice, n = 8) (P < 0.05). The accessory sperm count of the normal embryos in a litter was positively related to the percentage of normal embryos in a litter, and this relation was not affected by the interval between first insemination and ovulation or by the number of inseminations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Effects of energy source in the diet on reproductive hormones and insulin during lactation and subsequent estrus in multiparous sows.

Two experiments were performed. The first experiment was done to study the effects of dietary energy source on plasma insulin concentration using five gilts in a Latin square design with two diets over two periods. The diets contained either 200 g/kg of cornstarch (Starch) or soybean oil (Fat) as energy sources. Results indicate that insulin response was greater in the Starch-fed than in the Fat-fed gilts. A second experiment was performed in which 18 multiparous sows were fed one of the two experimental diets from farrowing until slaughter at d 35 of subsequent pregnancy. All sows nursed nine pigs. Blood samples were taken from a permanent jugular vein catheter every 12 min during a 12-h period on d 109 +/- 1 of pregnancy, on d 7 +/- 1, 14 +/- 1, and 21 +/- 1 of lactation, and on the day of weaning ( d 22 +/- 1). From 48 h after weaning, blood samples were taken every 4 h until 24 h after ovulation. After that, blood samples were taken at 12-h intervals until d 10 after ovulation. Differences between diets in insulin response were not significant. In Starch-fed sows, LH pulsatility at d 7 of lactation was greater (P < .05), the preovulatory LH surge was greater ( P < .05), and progesterone production was greater (P < .05) from 108 h until 256 h after the LH surge than in the Fat-fed sows. Results indicate that feeding Starch-rich diets to multiparous sows compared with Fat-rich diets, on an isocaloric basis, increases LH pulsatility during early lactation, the preovulatory LH surge, and progesterone production after the LH surge.

Animals↗
PubMed1995

Multi-centre comparison of five eye movement detection algorithms.

Although various investigators have suggested algorithms for the automatic detection of eye movements during sleep, objective comparisons of the proposed methods have previously been difficult due to different recording arrangements of different investigators. In this study the results of five eye movement detection algorithms applied to the same data were compared to visually scored data. The percentages of true and false detections are given for various threshold levels in rapid and slow eye movement detections. The methods gave best results when they were used with the same electrode montage they were designed for but the performance decreased when other montages were used. Subtracting the cross-talk of EEG delta activity improved the correctness of eye movement detections.

Journal Article↗
PubMed1994

Sulfated polyanions prevent HIV infection of lymphocytes by disruption of the CD4-gp120 interaction, but do not inhibit monocyte infection.

Sulfated polyanions (SPs) bind variably to lymphocyte-expressed CD4 and inhibit binding of monoclonal antibodies to the first two domains of CD4. To further define this interaction, soluble recombinant CD4 (sCD4; four extracellular domains), its truncated amino-terminal two-domain derivative, and three linear peptide analogues spanning residues 6-60 (6-24, 20-40, 41-60) in the first domain were investigated for SP binding. Dextran sulfate (DXS) (500 kDa), polyvinyl sulfate, fucoidan, and carrageenan-kappa, each immobilized on carboxymethyl cellulose fibers, bound strongly to both the two-domain and four-domain recombinant CD4 molecules (similar to that observed with native CD4), whereas dextran sulfate (5 kDa), chondroitin 6-sulfate, and pentosan sulfate bound relatively poorly. No peptide binding to SPs was observed. Recombinant gp120 bound poorly (< 10%) to all of the immobilized polyanions, except pentosan sulfate (17%), for which some binding was noted. Binding of radiolabeled V3 loop peptide to SPs was slightly greater, with 20-30% binding to polyvinyl sulfate, dextran sulfate (500 kDa), and pentosan sulfate. Competitive binding studies demonstrated the predominance of sCD4 rather than rgp120 binding to SPs and supported previous data demonstrating a binding site for DXS (500 kDa) on the first domain of CD4 adjacent to the gp120 binding site and recognized by OKT4C and E monoclonal antibodies. Hence disruption of the CD4-gp120 interaction is probably responsible for most of the observed antiviral activity of SPs toward HIV infection of lymphocytes. However, HIV infection and gp120 binding to monocytes was unaffected by SPs, probably because SPs were unable to block the CD4-gp 120 interaction in monocytes.

Amino Acid Sequence↗
PubMed1994

Reproductive characteristics and semen quality in maiden Dutch Warmblood stallions.

The semen characteristics and testicular size of 398 3-year-old maiden Dutch Warmblood stallions were studied during February and March. Mean values (+/- SD) of age (1030 +/- 88 days) and testicular size (9.8 +/- 0.9 cm) of the maiden stallions were determined as well as the following semen characteristics (mean of two ejaculates, taken 1 h apart): volume (65 +/- 26 ml), sperm concentration (2.061 +/- 1.685 x 10(8) ml-1), total number of spermatozoa (1.129 +/- 0.71 x 10(10)), percentage of progressively motile spermatozoa (68 +/- 9%), percentage of live spermatozoa with normal morphology (66 +/- 15%), total number of progressively motile morphologically normal spermatozoa (5.307 +/- 3.833 x 10(9)) and pH (7.5 +/- 0.2). The morphology of the spermatozoa was studied and data on the most common abnormalities are presented. The first and second ejaculates show significant differences (P < 0.05) in volume, motility, number of spermatozoa, sperm morphology, total number of progressively motile morphologically normal spermatozoa and pH. The original breed has been split up into two different lines. There was a significant difference (P < 0.05) in semen characteristics between the types (riding and carriage horses). The semen quality and quantity of semi-siblings were compared and a significant sire effect (P < 0.05) was shown for the following characteristics: volume, motility (%) and sperm concentration. These results indicate that there are differences of heritability of those factors, which makes it possible to select on semen quality.

Animals↗
PubMed1994

Periovulatory profiles of oestradiol, LH and progesterone in relation to oestrus and embryo mortality in multiparous sows using transrectal ultrasonography to detect ovulation.

The timing of oestrus, the concentrations of oestradiol, LH and progesterone, and embryo survival on day 35 of pregnancy in 16 weaned multiparous sows were studied in relation to the moment of ovulation. Ovulation was detected using transrectal ultrasonography. The interval between weaning and ovulation varied between 126 and 214 h (156 +/- 29). The peak oestradiol concentration was 27 +/- 17 pg ml-7; sows with a shorter interval between weaning and ovulation had higher peaks of oestradiol (r = -0.54, P = 0.02). The interval between the peak oestradiol concentration and peak LH concentration was 11 +/- 4 h. The shape, width and height of the LH surge were variable, but did not influence the interval between the peak LH concentration and ovulation, which varied between 26 and 34 h (30 +/- 3). The interval between ovulation and the time when the progesterone concentration rose to more than 1.0 ng ml-1 above basal progesterone concentrations varied from 6 to 19 h (13 +/- 4). Ovulation took place at a more or less constant relative time of the oestrous period (after 72 +/- 8% of the duration of oestrus), irrespective of the duration of oestrus. The timing of the peak concentrations of oestradiol and LH and the rise in progesterone concentrations were closely related to the occurrence of ovulation but not to the onset of oestrus. Embryo survival on day 35 of pregnancy was related to the interval between the peak concentrations of oestradiol and LH (r = -0.68, P = 0.02); shorter intervals resulted in higher embryo survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Gastric protein breakdown and pancreatic enzyme activities in response to two different dietary protein sources in newly weaned pigs.

Seventy pigs were weaned at 25 d of age and fed diets based on either skim-milk powder (SMP) or soybean protein concentrate (SOY). At 0, 3, 6, and 10 d after weaning, pigs were anesthetized, their pancreases were removed, and digesta were collected from different sections of the digestive tract. The ratio between trichloroacetic acid (TCA)-precipitable protein and total (crude) protein (pp:cp) in gastric digesta was higher with SOY feed than with SMP feed. In the jejunum, no difference was found; hence, the degree of protein breakdown in jejunal chyme did not differ between protein sources. Trypsin activities in jejunal chyme and in pancreatic tissue increased (P < .01) after weaning. Chymotrypsin activity in pancreatic tissue tended to decrease after weaning and did not reach "weaning levels" for at least 10 d. Pancreatic trypsin developed more rapidly than chymotrypsin after weaning. Chymotrypsin activities in jejunal digesta were higher (P < .05) for the pigs fed SMP than for those fed SOY. Protease activities in the jejunum at d 6 after weaning were clearly affected (P < .05) by feed intake after weaning. The ratio between trypsin and chymotrypsin activity in jejunal chyme was higher (P < .05) for SOY-fed pigs than for SMP-fed pigs. It was concluded that the stomach plays an important role in the digestion of milk protein and that the development of pancreatic proteases after weaning (synthesis, secretion, breakdown) depends on feed intake and on dietary protein source.

Animals↗
PubMed1994

Digestible lysine requirement of gilts with high genetic potential for lean gain, in relation to the level of energy intake.

One hundred gilts were used to determine the optimal ratio between ileal digestible lysine and digestible energy in the diet, and the effect of energy intake level on this optimal ratio for gilts with high genetic potential for lean gain, between 20 and 45 kg BW. In a 2 x 15 factorial arrangement the pigs were fed either 2.5 or 3.0 times the energy requirements for maintenance. Average daily lysine intake in the treatment period ranged from 6.4 to 18.2 g/d in 15 graduated steps. The first 12 increments were .74 g/d, and the last two increments were 1.48 g/d. Average daily gain (ADG), gain/feed, and protein deposition increased curvilinearly (P < .01) with increasing lysine intake. The ADG was maximized at 606 and 768 g/d, gain/feed was maximized at .564 and .604 kg/kg, and protein deposition was maximized at 108 and 128 g/d at the low- and high-energy levels, respectively. The ratio between lipid and protein deposition decreased curvilinearly with increasing lysine intake (P < .01) and reached a minimum of .53 and .75 at the low- and high-energy levels, respectively. The lysine requirements (ileal digestible lysine/DE, grams/megaJoule), determined with a linear-plateau model, were .57 for ADG and gain/feed, and .62 for protein deposition. These estimated requirements were similar for the two energy levels. Consequently, approximately .60 g of ileal digestible lysine/MJ of DE was required to optimize performance in gilts with high genetic potential for lean gain, irrespective of the feed intake level. In addition, a factorial model to estimate the lysine/energy requirements is proposed.

Animal Feed↗
PubMed1993

[Embryonal mortality in swine: conditions for a low incidence].

Embryonic mortality is an important cause of reproductive losses in the pig. The embryonic mortality rate, 30 per cent on average, will be reduced under optimal management conditions if (1) all sows are inseminated between 10 and 25 hours before ovulation; (2) semen of boars of proven fertility is used; and (3) variation in embryonic development is small. The uterine capacity of sows should also improved to enable the lower mortality rate to be expressed in larger litters.

Animal Husbandry↗
PubMed1993

In synchronized pigs, the duration of ovulation is not affected by insemination and is not a determinant for early embryonic diversity.

The duration of ovulation (i.e., the time interval between the ovulation of the first and the last follicle in a sow during an estrus) is said to be related to embryonic diversity, which in turn is related to embryonic mortality. The relationship between the duration of ovulation and within-litter early embryonic diversity and the influence of insemination on the duration of ovulation were studied. To determine whether ovulation assessment (transrectal ultrasonography) influenced early embryonic development, control sows were not scanned. Multiparous cyclic sows with an exogenously induced estrus were used. Ovulation detection by means of transrectal ultrasonography did not influence fertilization rate, accessory sperm count, early embryonic development or early embryonic diversity, and, therefore, ultrasonography appears to be a worthwhile method for studying the time and duration of ovulation. Insemination did not influence (P>0.05) the duration of ovulation, in sows which ovulated between 39 and 49 hours after hCG injection. The duration of ovulation (mean+/-SD(range)) was 2.4+/-0.7 (1.1 to 4.0) hours in 15 sows which were artificially inseminated at 22 and 30 hours after hCG injection. In 8 noninseminated sows, the duration of ovulation was 2.3+/-0.5 (1.5 to 3.3) hours. The duration of ovulation was not related to embryonic diversity (SD of the number of nuclei or the number of cell cycles of embryos in a litter) at 114 to 121 hours after ovulation. Thus, a difference of up to 3 hours in the duration of ovulation does not seem to be an important determinant of variation in embryonic diversity between sows.

Journal Article↗
PubMed1993

The accessory sperm count is related to early embryonic diversity in pigs.

In pigs, embryonic diversity has been related to embryonic mortality. The relative importance of differences in the duration of ovulation and in the average accessory sperm count (number of sperm cells in the zona pellucida) between sows as a cause of differences in within-litter embryonic diversity was studied. Two experiments were performed in which sows were either ovulating spontaneously (Experiment 1; n=13) or were induced to ovulate with human chorionic gonadotropin (hCG) (Experiment 2; n=15). The sows were slaughtered at 98+/-8 and 118+/-2 h after ovulation, respectively, for observation of embryonic diversity. The duration of ovulation varied between 1 and 4 h and was on average 1.8+/-0.6 and 2.3+/-0.5 h (P>0.10) for Experiment 1 and 2, respectively. Embryonic development in terms of the number of cell cycles tended to differ between Experiment 1 and 2 (3.5+/-0.8 and 5.6+/-0.5, respectively; P<0.10). Within-litter embryonic diversity (SD of number of cell cycles) was 0.83+/-0.35 and 0.60+/-0.27 (P>0.10), respectively. The average per litter accessory sperm count was variable (ranging from 1 to 75) and was affected by experiment (median: 32+/-27 and 12+/-14, respectively; P<0.05). Within-litter embryonic diversity was not related to the duration of ovulation (P>0.10) but was negatively related to the average or median accessory sperm count (P<0.025). The significant relationship between the accessory sperm count and embryonic diversity suggests that the duration of fertilization is a determinant for embryonic diversity.

Journal Article↗
PubMed1993

A proposal for computer-based sleep/wake analysis.

The task group on Signal Analysis within the EC Concerted Action 'Methodology for the analysis of the sleep-wakefulness continuum' has proposed general guidelines for a computer-based sleep analyser that would not suffer from the most conspicuous limitations of manual standard scoring. The proposal specifies a standard format for digitized polygraphic recordings, a basic structure of the analyser, and a graphical output format for the analysis results. These analysis results include all sleep/wake related signal characteristics, an on/off REM sleep/wake process, and a continuous-scale NREM sleep/wake process, all with a time resolution of 1s. Several locally available sleep analysers were made to comply with these specifications and then applied to standardized digital polygraphic sleep recordings that were circulated among the laboratories. Analysis results were distributed, enabling evaluation of the local algorithms.

Journal Article↗
PubMed1992

A simple format for exchange of digitized polygraphic recordings.

A simple digital format supporting the technical aspects of exchange and storage of polygraphic signals has been specified. Implementation of the format is simple and independent of hard- or software environments. It allows for any local montages, transducers, prefiltering, sampling frequencies, etc. At present, 7 laboratories in various countries have used the format for exchanging sleep-wake recordings. These exchanges have made it possible to create a common database of sleep records, to compare the analysis algorithms local to the various laboratories to each other by applying these algorithms to identical signals, and to set up a computer-aided interlaboratory evaluation of manual and automatic analysis methods.

Algorithms↗
PubMed1992

The duration of ovulation in pigs, studied by transrectal ultrasonography, is not related to early embryonic diversity.

The duration of ovulation in pigs was studied by transrectal ultrasonography. The number of preovulatory follicles was counted on both ovaries at 30-minute intervals from 36 hours after the onset of estrus (Group A: naturally ovulating sows that were group-housed and were inseminated and caged during scanning) or 40 hours after treatment with human chorionic gonadotropin (hCG) (Group B: tethered sows that had been induced to ovulate but were not inseminated). The duration of ovulation was (mean+/-SD) 1.8+/-0.6 hours (range 0.75 to 3.25) in Group A (n=13) and 4.6+/-1.7 hours (range 2.0 to 7.0) in Group B (n=8). The difference was significant (P<0.01). In Group A and B sows, respectively, the course of ovulation, expressed as the relation between the relative follicle count (percentage of the maximum follicle count; Y) and the time (percentage of the duration of ovulation; X) was: Y=104.3*e(-0.023*X) (R2=0.95) and Y=98.9*e(-0.018*X) (R2=0.92). The onset of ovulation occurred at approximately two-thirds of the duration of the estrus (Group A: 67+/-6%; Group B: 60+/-10%). Group A sows were artificially inseminated and were slaughtered at 98+/-8 hours (range 77 to 110) after ovulation. The difference between the maximum follicle count and the corpora lutea count was zero or only 1 in 81% (21/26) of the ovaries. Embryonic diversity (within-litter SD of the number of nuclei or of the number of cell cycles) was not related to the duration of ovulation, neither at the level of ovary nor of sow (P>0.05). In conclusion, transrectal ultrasonography was found to be an appropriate nonsurgical method of studying the duration of ovulation in pigs. The duration of ovulation varied both between sows and between groups of sows, and was not related to early embryonic diversity.

Journal Article↗
PubMed1992

Long-term sleep deprivation as a game. The wear and tear of wakefulness.

We report here the first sleep deprivation study done on a group of 5 healthy students (1 female, 4 males, 23-24 years of age) while playing a game (Triviant). In 2 persons an EEG was recorded for 6 consecutive 24 h periods with an ambulatory monitor from the baseline night until 72 h after deprivation. The baseline night showed normal hypnograms. The students were deprived of sleep for 65 h following the baseline night. Sleep deprivation was complete and resulted in bradyphrenia, loss of memory and contact with reality, ataxia, decrease in body temperature and loss of body weight. The main sign of recuperation was a strongly increased slow-wave sleep synchronization during the first recuperation period (day-time sleep) only. There were no signs of REM rebound.

Adult↗