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At least 937 records · Page 52Linked to original sources
PubMed2000

A model of the transmission and control of genital herpes.

BACKGROUND: Mathematical modeling of herpes simplex virus type 2 transmission can provide insight into the behavior of the epidemic and the effects of control measures. GOAL: To examine parameter sensitivity and assess control strategies. STUDY DESIGN: The model simulates transmission in a young, sexually active, nonmonogamous population. The population is divided into compartments representing disease status (susceptible, exposed, primary infectious, asymptomatic, recurrent, vaccinated), and flows between compartments are described by differential equations. RESULTS: With a base set of parameter values, the basic reproduction rate (R0) is 1.79, indicating that ultimate prevalence in this population will be 44%. The course of the epidemic is most sensitive to changes in behavioral parameters (time nonmonogamous and partner-change rate) and to the probability of transmission during the asymptomatic stage. CONCLUSION: In the absence of behavior change, efforts to control the epidemic must focus on vaccine development and prevention of transmission during both symptomatic and asymptomatic phases.

Female↗
PubMed1999

Rapid fluorescence assessment of the viability of stressed Lactococcus lactis.

The aim of this study was to establish the use of the fluorescent probes carboxyfluorescein (cF) and propidium iodide (PI) for rapid assessment of viability, using Lactococcus lactis subsp. lactis ML3 exposed to different stress treatments. The cF labeling indicated the reproductive capacity of mixtures of nontreated cells and cells killed at 70 degrees C very well. However, after treatment up to 60 degrees C the fraction of cF-labeled cells remained high, whereas the survival decreased for cells treated at above 50 degrees C and was completely lost for those treated at 60 degrees C. In an extended series of experiments, cell suspensions were exposed to heating, freezing, low pH, or bile salts, after which the colony counts, acidification capacity, glycolytic activity, PI exclusion, cF labeling, and cF efflux were measured and compared. The acidification capacity corresponded with the number of CFU. The glycolytic activity, which is an indicator of vitality, was more sensitive to the stress conditions than the reproduction, acidification, and fluorescence parameters. The cF labeling depended on membrane integrity, as was confirmed by PI exclusion. The fraction of cF-labeled cells was not a general indicator of reproduction or acidification, nor was PI exclusion or cF labeling capacity (the internal cF concentration). When the cells were labeled by cF, a subsequent lactose-energized efflux assay was needed for decisive viability assessment. This novel assay proved to be a good and rapid indicator of the reproduction and acidification capacities of stressed L. lactis and has potential for physiological research and dairy applications related to lactic acid bacteria.

Bile Acids and Salts↗
PubMed1996

Chronic toxicity of fenitrothion to an algae (Nannochloris oculata), a rotifer (Brachionus calyciflorus), and the cladoceran (Daphnia magna).

Chronic toxicity studies were conducted with an algae (Nannochloris oculata), a rotifer (Brachionus calyciflorus), and a cladoceran (Daphnia magna) to determine their relative sensitivities to the organophosphorus insecticide fenitrothion. The cladoceran D. magna was the most sensitive of the three species. The no observed effect concentrations (NOECs) for the study with the algae (1.0 mg/liter) and for the rotifer (1.0 mg/liter) were higher than the NOEC (0.009 microgram/liter) and the LC50 of 24 hr (0.067 microgram/liter) for D. magna. Most of the algal populations were not initially affected by exposure to fenitrothion. Pesticide concentrations higher than 1.0 mg/liter significantly reduced algal densities after 72 hr exposure. The effects of chronic exposure of the rotifer B. calyciflorus to fenitrothion were evaluated using some demographic parameters: intrinsic rate of natural increase (r), generation time, net reproductive rate, and life expectancy. All the parameters studied decreased with increasing toxicant concentrations. The parameters used to determine the effect of the pesticide on D. magna reproduction were mean total young per female, mean brood size, mean time to first reproduction, and r. The r and the rest of the studied parameters were affected at 0.011-microgram/liter and higher fenitrothion concentrations. Growth, as measured by body length, was only depressed significantly at 0.011 microgram/liter pesticide.

Animals↗
PubMed2006

Reproductive, cytological and biochemical toxicity of Yohimbe in male Swiss albino mice.

AIM: To study the effect of Corynanthe Yohimbe (Yohimbe) on germ cells in Swiss albino mice. METHODS: Adult male mice were orally (gavage) treated with different doses (188, 375 and 750 mg/[kg x day]) of aqueous suspension of Yohimbe for 90 days. The following parameters were evaluated: (i) reproductive organ weight, (ii) motility and count of sperm, (iii) study on rate of pregnancy and mean implants, (iv) spermatozoa morphology, (v) cytology of the testes chromosomes, and (vi) biochemical study on estimation of proteins, RNA, DNA, malondialdehyde, nonprotein sulfhydryl (NP-SH) and hormones. RESULTS: The treatment caused significant increase in the weight of seminal vesicles, motility and count of spermatozoa, pre- and post-implants. Male fertility was decreased. These results are confirmed by our data on spermatozoa abnormalities and chromosomal aberrations. The data on biochemical parameters showed increase of malondialdehyde and depletion of NP-SH, proteins, RNA and DNA in the testicular cells. CONCLUSION: Our results elucidated the role of free radical species in cytological and reproductive changes, possibly, under the influence of yohimbine (principal constituent of Yohimbe) on neurotransmitters, including norephinephrine. These data warrant careful use of Yohimbe.

Animals↗
PubMedDate not supplied

Cigarette smoking and semen quality in men of reproductive age.

The effect of cigarette smoking on conventional semen parameters was studied in voluntary men of reproductive age (n = 190). Special attention was focused on sperm motility and its quantitative and qualitative change in vitro during the observation period. The sperm output war normal in both smokers (n = 54) and non-smokers (n = 110), but semen volume was smaller (p less than 0.03) in heavy smokers (greater than 16 cigarettes/day) than non-smokers. In sperm morphology there was no difference between study groups. The only clear difference between men with different smoking habits was in the percentual change in the sperm motility during 24 hours. At the time of first examination, the sperm motility was better (p less than 0.02) in heavy smokers than those who smoked less than 16 cigarettes per day and the motility decreased more rapidly (p less than 0.007) in heavy smokers than non-smokers. The objectively measured initial mean velocities of the whole sperm population and of the progressive spermatozoa were slightly higher in subgroup of smokers than in non-smokers. The rapid decrease in the survival spermatozoa in smokers may be uneconomical and harmful in respect of fertility.

Adult↗
PubMed2006

Application of assisted reproduction for population management in felids: the potential and reality for conservation of small cats.

Assisted reproductive technology (ART), using the primary applied tools of AI, ET, and sperm and embryo cryopreservation, has been promoted over the past decades for its potential to conserve endangered wildlife, including felids. However, if the goal is efficient, consistent production of viable offspring for population management, then the 'potential' of ART has yet to become 'reality' for any non-domestic cat species. For the five small-sized felids (i.e., Brazilian ocelot, fishing cat, Pallas' cat, Arabian sand cat, black-footed cat) managed by Species Survival Plans (SSPs) in North American zoos, achieving this potential may be an absolute necessity if genetically viable captive populations are to be maintained into the next century. Modeling programs suggest that current SSP populations are not sustainable without periodic introduction of new founders and improved demographic parameters, including longer generation intervals and larger population sizes. ART provides the means to address each of these management challenges. In each small cat SSP species, fecal hormone metabolite assays and seminal analysis have proven useful for characterizing basal reproductive parameters, a necessary prerequisite to developing ART. Of the five SSP species, ART has been used to produce living offspring only in the ocelot, including after AI with frozen-thawed spermatozoa and following transfer of frozen-thawed IVF embryos. The true efficacy of these techniques, however, is still unknown. To improve the applicability of ART for population management, priorities for immediate research include further investigation of ovarian stimulation protocols, sperm and embryo cryopreservation methods, embryo culture systems, and fetal and neonatal viability following ART.

Animals↗
PubMed1990

[The reproductive function in experimentally-produced monozygotic twin bulls].

Reproductive functions were evaluated in 12 experimentally derived monozygotic cattle twins (6 pairs). In 4 twin pairs GnRH (20 micrograms Receptal i.m.) was administered in monthly intervals from 6 through 12 months of age. LH-secretion was determined by radioimmunoassay up to 6 hours after the GnRH-challenge in hourly collected peripheral blood samples. In 5 twin pairs (age 14 to 20 months) semen was collected 5 times and processed for cryoconservation. In fresh and in frozen-thawed semen samples sperm motility was determined by means of a computerized system. Twins showed a remarkable uniform response to the GnRH-challenge. One set of twins (HF-breed) had a significantly reduced response compared to the other pairs (DFV-breed). Both individuals of this particular pair had a low percentage of progressively motile spermatozoa. In pairs with physiological sperm motility, variance of this parameter within pairs and between pairs was not different. In contrast, twin uniformity concerning the average velocity of motile spermatozoa was high; differences between set of twins explained most of the total variance. According to this study, reproductive parameters in monozygotic cattle twins are strongly influenced by twin uniformity.

Animals↗
PubMed2003

A simple approximate mathematical model to predict the number of severe acute respiratory syndrome cases and deaths.

BACKGROUND: Severe acute respiratory syndrome (SARS) is currently spreading in many countries. This paper proposes a simple approximate mathematical model for public health practitioners to predict the number of SARS cases and deaths. METHODS: The model is based on four parameters: R(o) (basic reproductive number), F (case-fatality rate), i (incubation period), and d (duration of disease). The calculations can be done by hand or by using a computer spreadsheet. RESULTS: The best parameters to fit Canadian data as of 6 April 2003 (before infection controls took effect) are R(o) = 1.5, F = 30%, i = 5 days, d = 14 days. On 6 April (day 40) there were 74 cases and 7 deaths. If this trend continues, SARS numbers in Canada are predicted to be as follows: 387 cases and 34 deaths by 26 April (day 60), 4432 cases and 394 deaths by 26 May (day 90), and 50 500 cases and 4489 deaths by 25 June (day 120). By comparison, the best parameters to fit Hong Kong data as of 10 April 2003 are R(o) = 2.0, F = 20%, i = 5 days, d = 14 days. CONCLUSIONS: Using the proposed mathematical model, it was estimated that about 1.5 to 2 new infectious cases were produced per infectious case every five days. Also, about 20% to 30% of the cases die within 14 days. The case-fatality may therefore be considerably higher than initially thought. The model indicates that SARS can spread very fast when there are no interventions.

Canada↗
PubMed2004

A deterministic model for the dynamics of furunculosis in chinook salmon Oncorhynchus tshawytscha.

Studies were undertaken to determine the parameters of transmission of Aeromonas salmonicida in chinook salmon Oncorhynchus tshawytscha, and to develop a deterministic model of the dynamics of experimental furunculosis. For determination of disease transmission coefficient (beta), disease-related mortality rate (alpha) and natural mortality rate (gamma), fish in 70 tanks (approximately 42 fish tank(-1)) were each exposed to a single infectious donor fish, 7 tanks were randomly selected daily and all individuals were examined for the presence of A. salmonicida in the kidney. The proportion of susceptible (S), infected (I) and removed (R, dead) individuals were determined daily. The parameters beta, alpha, gamma, reproductive ratio (R0) and threshold density were estimated to be 0.0214 infected ind. d(-1), 0.29 infected ind. d(-1), 0.00015 ind. d(-1), 3.23 and 13.56 ind., respectively. Using these parameters, a deterministic disease model of A. salmonicida infection as a cause of furunculosis was constructed. The net rate at which new individuals became infected (the incidence rate) per unit time was proportional to S x I x beta. The model-produced data for S were significantly associated with experimental data (r2 = 0.92). In brief, a simple SIR (susceptible-infected-removed) model was successfully utilized to simulate observed data

Aeromonas salmonicida↗
PubMed1978

Relationship between epidemiologic and endocrinologic aspects of cervical cancer.

In search of etiologic relevancy of the steroid deviations in urine, we compared the reproductive activities of patients having cervical cancer with those of normal controls. A premenopausal patient experienced the birth of her first child significantly earlier than did the urban control of corresponding age, despite their similarity of age at menarche. However, when the same patient was compared with the premenopausal rural control, this differences was not found. The same parameter also failed to differentiate a postmenopausal patient from the corresponding control of urban origin. The premenopausal patient who was indistinguishable from the rural control by age at first delivery was distinguished from the rural control by reduced excretions of adrenal steroids including 11-deoxy-17 ketosteroids and some corticosteroid metabolites. The spectrum and the degree of deviation of urinary steroids for a patient coincided with the spectrum and the degree of age dependency of the urinary steroids for a normal woman during and after adolescence. These findings indicated that the inability of the reproductive parameter to discriminate a patient was associated with growth retardation in a population, and a maturation deficiency of the adrenal gland (arrest of adrenarche) was implicated in the genesis of cervical cancer.

Adolescent↗
PubMed1995

A diagnostic and prognostic tool for epidemiologic and economic analyses of dairy herd health management.

A computer program framework was established to enable a dairy herd production consultant to perform whole-herd analysis. The diagnostic process was an extensive data analysis 1) to derive key parameters related to production, reproduction, and health and 2) to produce input to a prognostic process. The prognostic process synthesized the obtained information into short- or long-term prognoses for the herd through a complex herd simulation model. Site specificity of parameter estimation and forecasting and explorability of assumptions and results were major characteristics of the approach. A user acceptance problem related to the simulation was addressed through a simultaneous process of development and validation during the introduction of the program framework into veterinary practices. The generally slow adoption of herd simulation models in extension work could be due to lack of credibility of the models. A major barrier to adoption of the current whole-herd approach may be the considerable time required to understand and use the tools properly. An example of a simulation experiment based on data from a New York dairy farm was provided, and the interpretation and practical applications of such simulations were discussed.

Animals↗
PubMed2002

Higher sperm counts in Southern Sweden compared with Denmark.

BACKGROUND: A common aetiology behind time-related deterioration of male reproductive function, including decline of sperm concentration and rising incidence of testicular cancer and cryptorchidism, has been suggested. Accordingly, a high incidence of testicular cancer and low sperm counts have been observed in Denmark, while in Finland opposite figures were found. This may be due to genetic factors. The incidence of testicular cancer is 50% lower in Sweden than in Denmark. Data on sperm counts in a population of Danish military conscripts have been published and we wished therefore to compare them with semen parameters in a corresponding cohort from Southern Sweden, geographically and genetically very closely related to Denmark. METHODS: A total of 305 military conscripts was recruited and investigated in an identical way as those in the Danish study including a questionnaire, physical examination and semen analysis. RESULTS: Men born and raised in Sweden had a 23% higher mean sperm concentration, a 31% higher mean total sperm count and a 14% higher seminal volume compared with their Danish counterparts. CONCLUSIONS: The differences in reproductive parameters between the two genetically very similar populations could not be explained by possible confounders and may be due to unknown environmental or lifestyle-related factors.

Adult↗
PubMed1994

Association of elevated estradiol with remote testicular trauma in young infertile men.

OBJECTIVE: To determine the incidence of remote testicular trauma and of possible related permanent hormonal and seminal changes in infertile men. DESIGN: Retrospective clinical study of hormonal and seminal parameters in a subpopulation of infertile men. SETTING: Andrology Clinic in an academic research environment. PARTICIPANTS: Infertile men, with and without history of remote testicular trauma, and fertile volunteers. MAIN OUTCOME MEASURES: Percentage of infertile men with history of blunt testicular trauma, concentrations of reproductive hormones, and semen parameters. RESULTS: Significant remote blunt testicular trauma was reported by 16.8% of infertile men. This had occurred 2 to 17 years (mean, 16.4 years) before evaluation, mostly with contact sports at adolescent age. Estradiol concentrations after testicular trauma were 19% and 25% higher than in infertile men without history of testicular injury and in fertile controls. Elevated E2 levels did not correlate with T. Infertile men with and without history of testicular trauma showed changes in seminal parameters. CONCLUSION: The incidence of remote blunt testicular trauma in infertile men is unexpectedly high. After injury, FSH-stimulated aromatization of T may increase testicular E2 production, interfere with spermatogenesis, and cause infertility. Consistent use of protective devices in contact sports is recommended.

Adult↗
PubMed2005

[Consequences on women's fecundity and on assisted reproductive technology].

Knowledge of the detrimental role of cigarette smoking on human reproduction is constantly improving. In natural fertility, time to pregnancy is longer, frequency of infertility is increased and fertility rate declines 10% to 20% with a dose-effect relationship. Moreover, women exposed in utero also have lower fertility. Cigarette smoking is also a risk factor for menstrual disorders and for early menopause. In assisted reproductive technology, where many parameters are controlled, the deleterious effects of smoking on fertility have been clearly demonstrated: lower estradiol levels, decreased pregnancy and implantation rates, and poorer oocyte morphology. The two published meta-analyses have concluded that the effects are the same in natural and assisted reproduction. These results are in accordance with biological hypotheses on the local and general effect of tobacco and other cigarettes components. In conclusion, women should be informed about the effect of cigarette smoking on their fertility. Education is very important since in many countries, like France, the percentage of smokers is increasing among women, especially among young women.

Adult↗
PubMed2005

[Levels of bone mineral matrix organization and the mechanisms determining parameters of its formation].

Authors suggest to regard bone mineral matrix as the four-level structure. The first level is represented by an internal structure of a mineral, the second--by mineral morphological structure, the third--by coplanar association of minerals, and the fourth--by macroassociation of minerals in a single complex inside each bone. The most probable mechanisms determining stability of reproduction of mineral matrix parameters on each of these levels are shown. As a result of their functioning, the variants of bone mineral matrix structures are formed that are the programmed reflection of specificity of the given site of organic structures.

Animals↗
PubMedDate not supplied

[Characteristics of the interaction of the influenza and vesicular stomatitis viruses with the splenocytes of inbred mice].

The reproduction activity of many viruses in cells of human and animal immune system has not been studied sufficiently on the body level. It is especially important to determine exactly the sensitivity of the main triad of the immune system cells to a certain virus from the parameters of its intracellular reproduction. Complete elimination of extracellular influenza A/PR8/34 virus from in vivo pre-infected cells of the immune system of mice revealed no reproduction of this virus. Under similar conditions, permanent reproduction of vesicular stomatitis virus has been demonstrated.

Animals↗