Biomedical subjects

Z Roth

Publications and source records attributed to Z Roth.

At least 19 recordsLinked to original sources

PubMed2007

Maternal hyperthermia disrupts developmental competence of follicle-enclosed oocytes: in vivo and ex vivo studies in mice.

Mammalian oocytes are susceptible to thermal stress at various stages of follicular development. We examined whether the ovarian pool of oocytes is susceptible to maternal hyperthermia and if so, whether hyperthermia at the germinal vesicle (GV) stage further affects the developmental competence of preimplantation embryos and offspring quality. Synchronized female mice were exposed to thermal stress (40 degrees C, 65% RH) for 1.5-2h or maintained under normothermal conditions (25 degrees C, 45% RH). Thereafter, mice were paired with stud males. In the first experiment, mated mice were sacrificed 20h post hCG administration, and in vivo-derived zygotes were recovered and cultured in vitro. Maternal hyperthermia decreased the percentage of putative zygotes of apparent normal morphology in the heat-stressed group (81+/-1.3%) as compared to the control group (86+/-1.2%). Developmental competence was also compromised as expressed by the disruption in cleavage timing pattern, resulting in a reduced developmental rate to the blastocyst stage (57+/-2.6% versus 84+/-1.9%). In the second experiment, both groups were left with stud males until litter delivery. Litter size in the first delivery cycle was lower for the heat-stressed group (7.7+/-1.1 pups), followed by a slight increase throughout consecutive cycles as compared to the control group (11.3+/-1.0 pups). Behavioral examinations of 8-week-old pups revealed similar locomotor activity and learning potential between the groups. In summary, the findings indicate that a subpopulation of the ovarian pool of follicles is highly sensitive to thermal stress and that maternal hyperthermia disrupts developmental competence of GV-stage oocytes. Pups that developed from oocytes that survived thermal stress exhibited a developmental potential similar to that of the of control pups.

Animals↗

PubMed2006

Nanofabrication of a space-variant optical transmission filter.

A space-variant optical transmission filter is demonstrated for which a simplified process is used to tailor the spatial response of the filter across the surface of a single wafer. A multilayer stack, of alternating high or low refractive index dielectric materials, was used to produce a narrow transmission notch in the center of a wide stop band. Subsequent patterning and etching of arrays of holes through the volume of the dielectric stack was performed to control the fill factor of the dielectric in the layers. The position of the transmission notch within the reflection spectrum was varied across the device surface by adjusting the hole diameter of the hole arrays. Experimental and numerical simulation were used to confirm the space-variant transmission characteristics of a single-wafer sample with two zones of different hole diameter arrays in the 1550 nm wavelength regime.

Journal Article↗

PubMed2006

Immunological profiles of patients with chronic myeloid leukaemia. I. State before the start of treatment.

In view of the increasing interest in the immunotherapy of CML it seems highly desirable to broaden the present knowledge on the immune reactivity of CML patients. A group of 24 patients and 24 healthy controls were studied for the total of 15 immunological parameters, including the prevalence of antibodies against human herpesviruses and papillomaviruses. To clearly discriminate between changes associated with the disease and those induced by the therapy, all patients were enrolled prior to the start of any anti-leukaemic therapy. Statistically significant differences between patients and controls were found in the levels of IgA, C4 component of complement, CRP and IL-6, the production of Th1 cytokines in stimulated CD3 cells and the E. coli stimulatory index. The analysis of the interrelationship between the results obtained in the individual patients presented some unexpected findings, such as the lack of correlation between the CRP and IL-6 levels. It will be the purpose of a follow-up to determine whether and how the immune status of the patients prior to the treatment correlates with their response to therapy and how the individual immunological profiles change in the course of the disease. These observations will be utilized in the future immunotherapeutic studies to constitute the vaccine- and placebo-treated groups.

Adult↗

PubMed2006

Endocrine alterations associated with extended time interval between estrus and ovulation in high-yield dairy cows.

Short fertile half-lives of the male and female gametes in the female tract necessitate accurate timing of artificial insemination. We examined the possible association between extension of the estrus to ovulation (E-O) interval and alterations in concentrations of estradiol, progesterone, and the preovulatory LH surge before estrus and ovulation. High-yielding Holstein cows (n = 74 from a total of 106) were synchronized and were examined around the time of the subsequent estrus. They were observed continuously for estrual behavior. Blood samples were collected before and after estrus, and ultrasound checks for ovulation were made every 4 h. About three-quarters of the cows exhibited short (but normal) E-O intervals of 22 to 25 h (25%) or normal intervals of 25 to 30 h (47%); 17% of them displayed a long (but normal) E-O interval of 31 to 35 h, and about 10% exhibited a very long E-O interval of 35 to 50 h. Extended E-O interval comprised estrus-to-LH surge and LH surge-to-ovulation intervals that were both longer than normal. Pronounced changes in hormonal concentrations were noted before ovulation in the very long E-O interval group of cows: progesterone and estradiol concentrations were reduced, and the preovulatory LH peak surge was markedly less than in the other 3 groups. Postovulation progesterone concentrations during the midluteal phase were lesser in the very long and the long E-O interval groups compared with those in the short and normal interval groups. Season, parity, milk yield, and body condition did not affect the estrus to LH surge, LH surge to ovulation, and E-O intervals. The results indicate an association between preovulatory-reduced estradiol concentrations and a small preovulatory LH surge, on the one hand, and an extended E-O interval, on the other hand. Delayed ovulation could cause nonoptimal timing of AI, a less than normal preovulatory LH surge that may be associated with suboptimal maturation of the oocyte before ovulation, or reduced progesterone concentrations before and after ovulation. All may be factors associated with poor fertility in cows with a very long E-O interval.

Animals↗

PubMed2005

Disruption of nuclear maturation and rearrangement of cytoskeletal elements in bovine oocytes exposed to heat shock during maturation.

Meiotic maturation in mammalian oocytes is a complex process which involves extensive rearrangement of microtubules, actin filaments and chromosomes. Since cytoskeletal elements are sensitive to disruption by heat shock, a series of experiments were performed to determine whether physiologically relevant heat shock disrupts the progression of the oocyte through meiosis, fertilization and zygote formation. Cumulus-oocyte complexes were cultured at 38.5, 40.0 or 41.0 degrees C for the first 12 h of maturation. Incubation during the last 10 h of maturation and 18 h after fertilization was at 38.5 degrees C and in 5% (v/v) CO2 for both treatments. Examination of the cytoskeleton and the chromosome organization in matured oocytes revealed that oocytes matured at 38.5 degrees C were mostly at metaphase II (MII) stage, while the majority of heat-shocked oocytes were blocked at the first metaphase (MI), first anaphase or first telophase stages. A subset of heat-shocked oocytes possessed misshapen MI spindles with disorganized microtubules and unaligned chromosomes. A higher percentage of TUNEL-positive oocytes was noted for oocytes matured at 41.0 degrees C. Addition of 50 nmol/l sphingosine 1-phosphate to maturation medium blocked the effect of heat shock on progression through meiosis and apoptosis and increased the proportion of oocytes matured at 41.0 degrees C that were at MII. Following insemination, a high percentage of heat-shocked oocytes were unfertilized, while the majority of the control zygotes were fertilized and had two visible pronuclei. In conclusion, heat shock disrupts nuclear maturation and induces apoptosis. These alterations are likely to be involved in the mechanism underlying heat-shock-induced disruption of oocyte capacity for fertilization and subsequent development.

Actin Cytoskeleton↗

PubMed2005

Gene expression for LH receptor, 17 alpha-hydroxylase and StAR in the theca interna of preantral and early antral follicles in the bovine ovary.

The onset of gene expression for three proteins that play pivotal roles in theca interna function, namely the LH receptor (LH-R), cytochrome P450 17 alpha-hydroxylase (17 alpha OH) and the steroidogenic acute regulatory protein (StAR), was determined. Ovaries were obtained on day 9 of the oestrus cycle from mature synchronized dairy cows (n = 5) and gene expression in preantral and antral follicles up to 4 mm in diameter was evaluated by in situ hybridization. LH-R and 17 alpha OH mRNAs were observed first, in the theca interna of large preantral follicles (type 4), concurrent with its morphological differentiation. StAR mRNA appeared later during follicular growth, in follicles >1 mm in diameter (type 6). LH-R and 17 alpha OH mRNAs were found exclusively in the thecal cells, whereas StAR mRNA appeared in thecal cells, granulosa cells of late atretic follicles and oocytes. In early atresia, thecal cells expressed all three mRNAs, and their expression decreased gradually as atresia progressed. Atresia in granulosa cells was characterized by massive apoptosis of periantral, but not peribasal cells, that differentiated into luteal-like cells expressing StAR. In summary, our study suggests that in spite of the presence of 17 alpha OH, a key enzyme in steroidogenesis, the ability to produce steroids by bovine follicles smaller than 1 mm in diameter must be very limited due to the absence of StAR protein. During the early stages of atresia, thecal cells remain morphologically and functionally healthy, and continue to express all three studied mRNAs.

Animals↗

PubMed2004

Sphingosine 1-phosphate protects bovine oocytes from heat shock during maturation.

Sphingosine 1-phosphate (S1P) is a sphingolipid metabolite that can block apoptosis by counteracting the proapoptotic effects of ceramide. Experiments were performed to evaluate whether S1P blocks the disruption in oocyte developmental competence caused by heat shock. Cumulus-oocyte complexes (COCs) were placed in maturation medium and cultured at 38.5 or 41 degrees C for the first 12 h of maturation. Incubation during the last 10 h of maturation, fertilization, and embryonic development were performed at 38.5 degrees C. Heat shock during the first 12 h of maturation reduced cleavage rate, the number of oocytes developing to the blastocyst stage, and the percentage of cleaved embryo that subsequently developed to blastocysts. Addition of 50 nM S1P to maturation medium had no effect on oocytes matured at 38.5 degrees C but blocked effects of thermal stress on cleavage and subsequent development. The blastocysts formed at Day 8 did not differ between S1P and control groups in caspase activity, total cell number, or percentage of cells that were apoptotic. Blocking endogenous generation of S1P by addition of 50 nM N1N-dimethylsphingosine, a sphingosine kinase inhibitor, reduced or tended to reduce cleavage rate and blastocyst development regardless of whether maturation of COCs was at 38.5 or 41 degrees C. Results demonstrate that S1P protects oocytes from a physiologically relevant heat shock and affects oocyte maturation even in the absence of heat shock. The S1P-treated oocytes that survived heat shock and became blastocysts had a normal developmental potential as determined by caspase activity, total cell number, and percentage of apoptotic cells. Thus, modulation of developmental competence of oocytes using S1P may be a useful approach for enhancing fertility in situations where developmental competence of oocytes is compromised.

Animals↗

PubMed2004

Involvement of apoptosis in disruption of developmental competence of bovine oocytes by heat shock during maturation.

Various pathological stimuli such as radiation, environmental toxicants, oxidative stress, and heat shock can initiate apoptosis in mammalian oocytes. Experiments were performed to examine whether apoptosis mediated by group II caspases is the cause for disruption of oocyte function by heat shock applied during maturation in cattle. Bovine cumulus-oocyte complexes (COCs) were cultured at 38.5, 40, or 41 degrees C for the first 12 h of maturation. Incubation during the last 10 h of maturation, fertilization, and embryonic development were at 38.5 degrees C and 5% (v/v) CO2 for all treatments. In the first experiment, exposure of COCs to thermal stress during the first 12 h of maturation reduced cleavage rate and the number of oocytes developing to the blastocyst stage. In the second experiment, a higher percentage of TUNEL-positive oocytes was noted at the end of maturation for oocytes matured at 40 and 41 degrees C than for those at 38.5 degrees C. In addition, the distribution of oocytes classified as having high (>25 intensity units), medium (15-25 intensity units), and low (<15 intensity units) caspase activity was affected by treatment, with a greater proportion of heat-shocked oocytes having medium or high activity. In the third experiment, COCs were placed in maturation medium with vehicle (0.5% [v/v] DMSO) or 200 nM z-DEVD-fmk, an inhibitor of group II caspases. The COCs were matured at 38.5 or 41 degrees C, fertilized and cultured for 8 days. The inhibitor blocked the effect of heat shock on cleavage rate and the percentage of oocytes and cleaved embryos developing to the blastocyst stage. In conclusion, heat shock during oocyte maturation can promote an apoptotic response mediated by group II caspases, which, in turn, leads to disruption of the oocyte's capacity to support early embryonic development following fertilization.

Animals↗

PubMed2004

Social inequality and obesity in Czech school children.

This study uses logistic regressions to consider the effect of social factors, physical activity, meal frequency and BMI of parents on children's body mass index (BMI) values. Three thousand three hundred and sixty-two children aged 7-11 years were examined in 38 schools in the Czech Republic. Six anthropometric characteristics were assessed in 1999-2000. Most important factors influencing children's BMI values were: obesity of both or at least one of the parents, being an only child, residence in small communities, and irregular breakfasts.

Anthropometry↗

PubMed2002

Prediction of acute toxicity of chemicals in mixtures: worms Tubifex tubifex and gas/liquid distribution.

The aim of this contribution is to support our proposal of the procedure for predicting acute toxicity of binary mixtures by QSAR analysis techniques. The changes of a mixture composition are described by molar ratio R and visualized in the R-plot (QCAR--quantitative composition-activity relationships). The approach was inspired by Rault and Dalton's laws, their positive and negative deviations in the behavior of a mixture of real gases, by Loewe and Muischnek isoboles and by the Finney test of additivity. Acute toxicity was determined by the laboratory test with woms Tubifex tubifex. The additivity of the acute toxicity in the binary mixture benzene + nitrobenzene was confirmed and a new interaction is described: "mixed interaction" with the binary mixture aniline + ethanol. The "mixed interaction" means that depending on mixture composition, both potentiation and inhibition can occur. As the first physicochemical descriptor of the changes caused by the changing composition of binary mixtures, the gas/liquid equilibrium was studied and a composition of the gaseous phase was determined by a gas chromatographic method. The method for determination of concentrations in the gaseous phase was described. The gaseous phase composition of benzene + nitrobenzene. benzene + ethanol, benzene + aniline and ethanol + aniline mixtures was analyzed. It was found that if the concentrations of the mixture's components in the gaseous phase behave nonideally (they are not additive), the acute toxicity of the same mixture is not additive as well. Another descriptor to distinguish between potentiation and inhibition will be, however, necessary. The properties, both gaseous phase composition and the acute toxicity, of the benzene + nitrobenzene mixture are additive. In mixtures with the mixed interaction, the R-plot of the composition of the gaseous phase is complex with a large variation of results.

Aniline Compounds↗

PubMed2002

Effect of treatment with follicle-stimulating hormone or bovine somatotropin on the quality of oocytes aspirated in the autumn from previously heat-stressed cows.

Conception in dairy cows during autumn remains low even after summer temperatures decline. This is possibly a residual effect of heat stress on oocyte quality. Lactating Holsteins previously heat-stressed during summer were used in two experiments (n = 8 and 16 cows) in autumn to examine hormonal strategies for improving quality of oocytes. Follicles (3 to 8 mm in diameter) were aspirated by the ovum pick-up procedure on d 4 of two consecutive estrous cycles of treated and control cows. Oocytes were classified morphologically, matured in vitro, chemically activated, and cultured for 8 d. In Experiment 1, FSH (2 x 200 mg, at a 12-h interval) was injected on d 5 and 12 of cycle 1 (treated cycle). Before FSH, the percentage of good quality oocytes (grade I) and the cleavage rate averaged 52 and 24%, respectively, in both groups. During the FSH-treated cycle, more 6- to 9-mm follicles were observed. In the subsequent cycle, rates of grade I oocytes and cleavage were significantly higher in FSH-treated than in control cows (89 vs. 51% and 85 vs. 31%, respectively). In Experiment 2, recombinant bovine somatotropin (bST, 500 mg) was injected on d 4 and 18 of the treated cycle. The bST treatment increased the number of 3- to 5-mm follicles. Before bST, grade I (39%) and cleaved oocytes (40%), were similar across treatment groups. In the subsequent cycle, the percentage of grade I oocytes was significantly higher in treated than in control cows (72 vs. 26%), but cleavage rates were similar. Neither FSH or bST improved blastocyst formation, and regardless of treatment, few blastocysts were formed. Treatment with bST improved oocyte morphology, whereas FSH improved both oocyte morphology and cleavage rates during autumn following summer heat stress.

Animals↗

PubMed2001

IQ and personality traits assessed in childhood as predictors of drinking and smoking behaviour in middle-aged adults: a 24-year follow-up study.

AIMS: The identification of childhood personality predictors of drinking and smoking behaviour in adults. DESIGN: A 24-year follow-up study. SETTING: Prague, the Czech Republic. PARTICIPANTS: Combined cohorts of 220 males and females born of unwanted pregnancies, and 220 control subjects, examined with low attrition rates at ages 9-10, 21-23, 28-31 and 32-35. MEASUREMENTS: In childhood IQ was assessed by the Wechsler Intelligence Scale, Children (WISC), and personality characteristics were rated by teachers, mothers and classmates. In adulthood questionnaires and face-to-face interviews were used to assess drinking and smoking. FINDINGS: Unwanted pregnancy was not related to adult drinking and smoking. The ratings of childhood personality characteristics were condensed into three personality dimensions, i.e. conscientiousness, extroversion and neuroticism, interpreted as three of the Big Five personality dimensions, and found to show some stability into adulthood. Gender, IQ and the three childhood personality traits were used as predictors of adult drinking and smoking behaviour. Adult drinking behaviour was significantly predicted by the block of the three childhood personality traits, low conscientiousness predicting high drinking quantity per occasion (and heavy episodic drinking) whereas extroversion predicted subjects' average daily consumption. Smoking in adulthood was predicted by low IQ and low conscientiousness. CONCLUSIONS: IQ and personality traits in children explain to some degree the drinking and smoking behaviour of adult men and women, but the roles of the different components vary according to the form of substance use.

Adult↗

PubMed2001

Delayed effect of heat stress on steroid production in medium-sized and preovulatory bovine follicles.

During the autumn, the conception rate of dairy cattle in warm countries is low although ambient temperatures have decreased and cows are no longer exposed to summer thermal stress, indicating that there may be a delayed effect of heat stress on cattle fertility. Two experiments were conducted to examine possible delayed effects of heat stress on follicular characteristics and steroid production at two distinct stages of follicular growth: medium-sized and preovulatory follicles, 20 and 26 days after heat exposure, respectively. Lactating cows were subjected to heat stress for 12 h a day in an environmental chamber, during days 2-6 of a synchronized oestrous cycle. In Expt 1, ovaries were collected on day 3 of the subsequent cycle, before selection of the dominant follicle, and medium-sized follicles were classified as atretic or healthy. In Expt 2, on day 7 of the subsequent cycle, PGF(2a) was administered and preovulatory follicles were collected 40 h later. In both experiments, follicular fluid was aspirated, granulosa and thecal cells were incubated, and steroid production was determined. In healthy medium-sized follicles (Expt 1), oestradiol production by granulosa cells and androstenedione production by thecal cells were lower (P < 0.05) and the concentration of progesterone in the follicular fluid was higher in cows that had been previously heat-stressed than in control cows (P < 0.05). In preovulatory follicles (Expt 2), the viability of granulosa cells was lower (P < 0.05) and the concentration of androstenedione in the follicular fluid and its production by thecal cells were lower (P < 0.05) in cows that had been previously heat-stressed than in control cows. In both experiments, the oestradiol concentrations in the follicular fluids were not altered by heat stress. These results demonstrate a delayed effect of heat stress on steroid production and follicular characteristics in both medium-sized and preovulatory follicles; this effect could be related to the low fertility of cattle in the autumn.

Androstenedione↗

PubMed2001

Improvement of quality of oocytes collected in the autumn by enhanced removal of impaired follicles from previously heat-stressed cows.

The fertility of dairy cows decreases during the summer and remains low during the cooler autumn although the animals are no longer under heat stress. The aim of this study was to characterize a delayed effect of summer heat stress on oocyte quality in the autumn and to improve oocyte quality by enhanced removal of follicles damaged during the previous summer. Lactating cows (n = 16) were subjected to heat stress during the summer. In autumn, ovarian follicles (3-7 mm in diameter) were aspirated by an ultrasound-guided procedure during four consecutive oestrous cycles. Follicles were aspirated from control cows on day 4 and from treated cows on days 4, 7, 11 and 15 of each oestrous cycle. All cows received PGF(2alpha) and GnRH injections on days 19 and 21, respectively, and maintained cyclicity, as indicated by plasma progesterone concentrations. On day 4 of each cycle, the oocytes recovered were examined morphologically, matured and activated in vitro, and cultured for 8 days. In cycle 1 (early October) both groups showed low percentages of grade 1 oocytes, cleavage, four- and eight-cell embryos, morulae and parthenogenetic blastocysts. Subsequently, the number of grade 1 oocytes increased earlier (cycle 2) in treated than in control cows (cycle 3; P < 0.05). The cleavage rate in the control group remained relatively low throughout (32-58%), whereas in the treated group it increased from 40% (cycle 1) to 75% (cycles 3 and 4; P < 0.05). The number at each stage of embryo development increased slightly but remained low throughout in the control group, whereas in the treated group significant (P < 0.05) increases of all stages were observed in cycles 3 and 4. The results show a delayed effect of summer heat stress on oocyte quality and embryo development in the autumn. Enhanced removal of the impaired cohort of follicles led to earlier emergence of healthy follicles and high quality oocytes in the autumn.

Animals↗

PubMed2000

Impaired reproduction in heat-stressed cattle: basic and applied aspects.

Summer heat stress (HS) is a major contributing factor in low fertility in lactating dairy cows in hot environments. Although modern cooling systems are used in dairy farms, fertility remains low. This review summarizes the ways in which the functioning of various parts of the reproductive system of cows exposed to HS is impaired. The dominance of the large follicle is suppressed during HS, and the steroidogenic capacity of theca and granulosa cells is compromised. Progesterone secretion by luteal cells is lowered during summer, and in cows subjected to chronic HS, this is also reflected in lower plasma progesterone concentration. HS has been reported to lower plasma concentration of LH and to increase that of FSH; the latter was associated with a drastic reduction in plasma concentration of inhibin. HS impairs oocyte quality and embryo development, and increases embryo mortality. High temperatures compromise endometrial function and alter its secretory activity, which may lead to termination of pregnancy. In addition to the immediate effects, delayed effects of HS have been detected as well. Among them, altered follicular dynamics, suppressed production of follicular steroids, and low quality of oocytes and developed embryos. These may explain the low fertility of cattle during the cool autumn months. Hormonal treatments improve low summer fertility to some extent but not sufficiently for it to equal winter fertility. A limiting factor is the inability of the high-yielding dairy cow to maintain normothermia. A hormonal manipulation protocol, which induces timed insemination, has been found to improve pregnancy rate and to reduce the number of days open during the summer.

Animals↗

PubMed2000

Administration of prostaglandin f(2 alpha) during the early bovine luteal phase does not alter the expression of ET-1 and of its type A receptor: a possible cause for corpus luteum refractoriness.

Luteal regression is initiated by prostaglandin F(2 alpha) (PGF(2 alpha)). In domestic species and primates, demise of the corpus luteum (CL) enables development of a new preovulatory follicle. However, during early stages of the cycle, which are characterized by massive neovascularization, the CL is refractory to PGF(2 alpha). Our previous studies showed that endothelin-1 (ET-1), which is produced by the endothelial cells lining these blood vessels, plays a crucial role during PGF(2 alpha)-induced luteolysis. Therefore, in this study, we compared the effects of PGF(2 alpha) administered at the early and mid luteal phases on ET-1 and its type A receptors (ETA-R) along with plasma ET-1 and progesterone concentrations, and the mRNA levels of PGF(2 alpha) receptors (PGF(2 alpha)-R) and steroidogenic genes. As expected, ET-1 and ETA-R mRNA levels were markedly induced in midcycle CL exposed to luteolytic dose of PGF(2 alpha) analogue (Cloprostenol). In contrast, neither ET-1 mRNA nor its receptors were elevated when the same dose of PGF(2 alpha) analogue was administered on Day 4 of the cycle. In accordance with ET-1 expression within the CL, plasma ET-1 concentrations were significantly elevated 24 h after PGF(2 alpha) injection only on Day 10 of the cycle. The steroidogenic capacity of the CL (plasma progesterone as well as the mRNA levels of steroidogenic acute regulatory protein and cytochrome P450(scc)) was only affected when PGF(2 alpha) was administered during midcycle. Nevertheless, PGF(2 alpha) elicited certain responses in the early CL: progesterone and oxytocin secretion were elevated, and PGF(2 alpha)-R was transiently affected. Such effects probably result from PGF(2 alpha) acting on luteal steroidogenic cells. These findings may suggest, however, that the cell type mediating the luteolytic actions of PGF(2 alpha), possibly the endothelium, could yet be nonresponsive during the early luteal phase.

Animals↗

PubMed2000

Immediate and delayed effects of heat stress on follicular development and its association with plasma FSH and inhibin concentration in cows.

The aim of this study was to characterize the immediate effects of heat stress on plasma FSH and inhibin concentrations, and its involvement in follicular dynamics during a complete oestrous cycle, and to examine a possible delayed effect of heat stress on follicular development. Holstein dairy cows were oestrous synchronized and randomly assigned to either cooled (n = 7) or heat-stressed (n = 6) treatment groups. During a complete oestrous cycle, control cows, which were cooled, maintained normothermia, whereas heat-stressed cows, which were exposed to direct solar radiation, developed hyperthermia. At the end of this oestrous cycle (treated cycle), both groups were cooled and maintained normothermia for the first 10 days of the subsequent oestrous cycle. Throughout this period, follicular development was examined by ultrasonography, and plasma samples were collected. During the second follicular wave of the treated oestrous cycle, a significantly larger cohort of medium sized follicles (6-9 mm) was found in heat-stressed cows than in cooled cows (P < 0.05). The enhanced growth of follicles in this wave in heat-stressed cows was associated with a higher plasma FSH increase which lasted 4 more days (days 8-13 of the oestrous cycle; P < 0.05), and coincided with a decrease in the plasma concentration of immunoreactive inhibin (days 5-18 of the oestrous cycle; P < 0.05). During the follicular phase (days 17-20 of the treated cycle), heat-stressed cows showed an increase in the number of large follicles (>/= 10 mm), and the preovulatory plasma FSH surge was significantly higher in heat-stressed cows than in cooled cows (P < 0.01). The effect of heat stress was also observed during the first follicular wave of the subsequent cycle: the postovulatory plasma FSH concentration was higher (P < 0.01), but fewer medium follicles developed, and the first follicular wave decreased at a slower rate in previously heat-stressed cows than in cooled cows (0.40 and 0.71 follicles per day, respectively). This study shows both immediate and delayed effects of heat stress on follicular dynamics, which were associated with high FSH and low inhibin concentrations in plasma. These alterations may have physiological significance that could be associated with low fertility of cattle during the summer and autumn.

Animals↗

PubMed1999

Acute effects of using a mobile phone on CNS functions.

Twenty volunteers participated in two experiments exploring the acute effects of using the mobile phone Motorola GSM 8700 on the functions of the CNS. When speaking (5 minutes reading a text from daily newspapers) the electromagnetic fields from the mobile apparatus did not affect the visual evoked potentials. Also a 6-min exposure did not reveal any effect of electromagnetic fields on the results in two tests (memory and attention) performed while speaking into the mobile. On the other hand the phone call itself strongly influenced the performance in a secondary task applying a test of switching attention which is a good model for driving a car. The response and decision speed were significantly worse. This is a proof that even a slight psychological stress involved in calling while driving can be a great risk.

Attention↗