Consistency in vital statistics.
Explore the source record for details and available documents.
Africa↗
SEARCH · Search PubMed
Results for “Gross Reproduction Rate”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
[Why is the number of births increasing?].
Explore the source record for details and available documents.
Birth Rate↗
The female population of Chile, 1855-1964: a microcomputer balance sheet method.
Explore the source record for details and available documents.
Age Distribution↗
The combined effects of zinc and alga on the life table demography of Anuraeopsis fissa and Brachionus rubens (Rotifera).
In this work the combined effects of zinc and Chlorella on the demography of two co-occurring planktonic rotifers (A. fissa and B. rubens) were evaluated. Chlorella absorbed a significant (about 35%) quantity of zinc from the medium within the 24 h period. The age-specific survivorship curves of A. fissa and B. rubens showed increased mortality rate with increasing zinc concentration in the medium (0 to 0.5 mg L(-1)), at the two Chlorella levels (0.5 x 10(6) and 1.0 x 10(6) cells mL(-1)). In controls, both the rotifer species showed enhanced survival at higher food level (1.0 x 10(6) cells mL(-1)). Low food level (0.5 x 10(6) cells mL(-1)) and higher concentration (0.25 and 0.5 mg L(-1)) of zinc resulted in a steep fall in the survivorship. Regardless of Zn concentration and food level, A. fissa had a shorter average lifespan, lower gross and net reproductive rate, and rate of population increase than B. rubens. The maximum offspring production on a given day in controls for A. fissa was about 2 female(-1), which was reduced to half when exposed to 0.5 mg L(-1) of Zn. At both food levels, A. fissa exposed to Zn at 0.5 mg L(-1) had negative population growth rates. The highest population growth rate (0.94 day(-1)) was observed for B. rubens in controls at 1.0 x 10(6) cell mL(-1) of Chlorella. The present data showed that A. fissa was more sensitive to zinc toxicity than B. rubens. Combination of high vulnerability to metal toxicity and low population growth rate, A. fissa in zinc contaminated waterbodies could be possibly more adversely affected than B. rubens.
Animals↗
Malthusian parameter on the Finnish population in the 20th century.
We were interested in studying a demographic indicator, the Malthusian parameter which had not been investigated earlier in the case of the Finnish population. We computed the Malthusian parameter with a known renewal equation, which is, as usual, approximated on discrete data by using normal distribution, on the Finnish population in the 20th century. The data was collected from the abundant official statistical sources which are known to be accurate and reliable in Finland. In addition to this parameter we computed the gross and net reproduction rates, the total fertility index, and the mean and variance age of females at child-bearing. The Malthusian parameter seems to be a rather good means of characterizing the development of the population. If the parameter is positive for long enough, the population tends to grow. If it is negative, as has been the case in Finland since 1969, the population starts to diminish sooner or later. On the other hand, it cannot take all factors into account. For instance, because of still increasing lifetime and also because of a relatively large quantity of females at the reproductive age the population is not yet decreasing in Finland. In any case, the Malthusian parameter forecasts the future trend of the decreasing population.
Adolescent↗
Effect of salinity stress on the life history variables of Branchipus schaefferi Fisher, 1834 (Crustacea: Anostraca).
BACKGROUND: Freshwater anostracans inhabit ephemeral water bodies in which as the water level decreases due to evaporation the salt concentration increases. Thus, for most anostracans salinity becomes the major stress factor. RESULTS: We tested five concentrations of NaCl (0 to 8 g/l) on the life table demography of Branchipus schaefferi fed Chlorella (alga). Age-specific survivorship curves of male and female B. schaefferi showed nearly a similar pattern in that increased salt concentration resulted in decreased survivorship. The age-specific reproduction (m(x)) of females showed several peaks of cyst production at 0 and 1 g/l salinity while in treatments containing salt at 4 or 8 g/l, there were fewer peaks. Average lifespan, life expectancy at birth, gross and net reproductive rates, generation time and the rate of population increase were all significantly influenced by the salt concentration in the medium. The highest value of net reproductive rate (970 cysts/female) was in treatments containing 0 g/l of salt, while the lowest was 13 cysts/female at 8 g/l. The rate of population increase (r) varied from 0.52 to 0.32 per day depending on the salt concentration in the medium. CONCLUSION: The low survival and offspring production of B. schaefferi at higher salinity levels suggests that this species is unlikely to colonize inland saline water bodies. Therefore, the temporary ponds in which it is found, proper conservative measures must be taken to protect this species.
Journal Article↗
Age-dependent fecundity and fertility life tables of the predator Brontocoris tabidus (Heteroptera: Pentatomidae) under field conditions.
Reproductive potential, longevity, life expectancy, and fertility life tables of Brontocoris tabidus (Signoret) (Heteroptera: Pentatomidae), a predator of lepidopteran defoliators in eucalyptus (Eucalyptus spp.) plantations, were studied in the field. After a 50-d preoviposition period (emergence of adults to the deposition of the first egg mass), ovipositional activity of B. tabidus continued until females died at 160 d. Females laid an average of 4.2 eggs per day and 601.1 eggs in a lifetime. Gross and net reproductive rates were 216.7 and 75.8 females, respectively. Generation time was 146.1 d, the period for doubling the population was 23.4 d, intrinsic rate was 0.03, and finite population increase was 1.03. Number of females per generation increased at 33.4 times. Results from our field studies indicate that B. tabidus has greater potential reproduction, oviposition period, and longevity than was expected from previous laboratory experiments. This suggests that B. tabidus has potential as a biological control agent to limit economically damaging pests in eucalyptus plantations.
Aging↗
Histomorphology, oLH and hCG receptors, and testosterone secretion in vitro in Rambouillet rams from lines in which females had been selected for low or high reproductive rate.
The objective of this study was to determine whether gross or histomorphological components of the testes, capacity and dissociation constants (Kd) of testicular oLH and hCG receptors, and gonadotrophin-stimulated testosterone secretion in vitro differed among Rambouillet rams from lines selected for low or high female reproductive rate and from rams of a random-bred control line. Lines had been selected for approximately 20 years. Data were collected from 22-month-old rams during the late breeding season. Rams among lines did not differ (P > 0.05) in gross testicular characteristics or most histomorphological characteristics. However, the percentage volume of interstitial vascular tissue was greater (P < 0.05) for rams from lines selected for low female reproductive rate than for rams from lines selected for high female reproductive rate. Receptor sites per Leydig cell and binding capacities of oLH and hCG receptors per testis, per gram of parenchyma, and per milligram of membrane protein did not differ (P > 0.05) among lines. The Kd values for oLH and hCG receptors did not differ (P > 0.05) among lines; however, receptor sites per Leydig cell, capacities of testicular parenchyma to bind gonadotrophin and Kd values were higher (P < 0.05) for oLH than for hCG receptors. Total oLH- and hCG-stimulated testosterone secretion in vitro did not differ (P < 0.05) among lines. In conclusion, selection for or against reproductive rate in Rambouillet ewes has not altered gross or most histomorphometric characteristics of the testes of male offspring, with the exception that selection against reproductive rate increased the proportion of testicular volume occupied by vascular tissue within the interstitium.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Deletion of ghrelin impairs neither growth nor appetite.
Pharmacological studies show that ghrelin stimulates growth hormone release, appetite, and fat deposition, but ghrelin's physiological role in energy homeostasis has not been established. Ghrelin was also proposed to regulate leptin and insulin release and to be important for the normal function of stomach, heart, kidney, lung, testis, and placenta. To help determine a definable physiological role for ghrelin, we generated ghrelin-null mice. In contrast to predictions made from the pharmacology of ghrelin, ghrelin-null mice are not anorexic dwarfs; their size, growth rate, food intake, body composition, reproduction, gross behavior, and tissue pathology are indistinguishable from wild-type littermates. Fasting produces identical decreases in serum leptin and insulin in null and wild-type mice. Ghrelin-null mice display normal responses to starvation and diet-induced obesity. As in wild-type mice, the administration of exogenous ghrelin stimulates appetite in null mice. Our data show that ghrelin is not critically required for viability, fertility, growth, appetite, bone density, and fat deposition and not likely to be a direct regulator of leptin and insulin. Therefore, antagonists of ghrelin are unlikely to have broad utility as antiobesity agents.
Animals↗
[Dynamics of Chagas infection transmission in Chile: model and simulation].
Triatoma infestans is the principal vector for Chagas disease in Chile. Although there is enough epidemiological information about human infection, the effect of vector and host (animals and man) populations interrelations over Chagas disease prevalence has not been studied. This work studies a determinist mathematical model for the dynamics of Chagas disease transmission by Triatoma infestans, relating entomological population parameters with infection propagation. The effect of invasion of susceptible animal and human populations by infected triatomine insects and the stability of Chagas disease endemic was simulated. The Ro parameter was estimated. This is a gross appraiser of the infection reproductive rate that relates triatomine insect density, bite rate and mortality. The infected population at equilibrium was estimated. The resulting endemic was highly stable with a great amount of chronic and few acute cases. There is always an acute Chagas epidemic stage after a recent invasion. The need for a threshold triatomine insect population for the genesis of an endemic is proposed.
Animals↗
Marihuana-induced embryotoxicity in the rabbit.
Few teratogenic studies in animals have been performed simulating marihuana smoking in man. An inhalation marihuana teratology study was conducted in albino rabbits utilizing a modified automatic smoking machine originally developed for rats and mice. Appropriate numbers of dams were exposed to 4 puffs (0.14 mg/kg), 8 puffs (0.72 mg/kg), or 16 puffs (1.44 mg/kg) once daily during gestation Days 6 to 18, and sacrificed on Day 28. Control dams were exposed to 12 puffs of placebo cigarettes or sham-treated for a similar duration in the absence of any smoke. Consistency of smoke was monitored by cigarette weights, total particulate matter, concentrations of carbon monoxide (CO), and tetrahydrocannibinol (THC) in smoke, carboxyhemoglobin levels, and plasma THC levels. Except for a transient decrease in dam respiration rates, other gross toxic signs were absent. Reproductive parameters of mothers were generally normal except for a dose-related embryotoxicity predominantly associated with early resorptions. Despite twice the number of embryo/fetal deaths, there were no marihuana soft tissue or skeletal defects. A correlation between dam demises and CO levels among placebo-exposed animals was related to greater quantities of CO being generated during placebo combustion. It has been shown in the rabbit that marihuana is embryotoxic and not a teratogen at plasma THC levels found in human females.
Animals↗
Comparative study on biological parameters of Bemisia tabaci (Genn.) collected on four host plants from Varamin-Iran.
During 2003 biological parameters of sweetpotato whitefly, B. tabaci (Genn.) (Horn. Aleyrodidae) as a major pest of field crops, vegetables and ornamentals were studied. In this study, the infested leaves of cucumber (Cucumis sativus L.) zucchini (Cucurbita pepo L.) eggplant (Solanum melongena L.) and cotton (Gossypium hirsutum L.) with whitefly nymphs and pupae were collected from Varamin-Iran, and were transferred to the laboratory. The newly emerged males and females of each population were released separately into a large cage set on cotton plants. Experiments were carried out in a growth chamber on cotton, (Varamin 76 variety) at 24+/-2 degrees C, 55+/-3% RH and 16:8 h (L: D) photoperiod. The adults of every collected population after emergency were reared in the large cages (40 x 50 x 70) containing pots of cotton plant. The preimaginal developmental time and reproductive parameters of 40 mated females were calculated for each population. The results revealed that the intrinsic rates of increase (r(m)), on cucumber, zucchini, eggplant and cotton were 0.093, 0.068, 0.085 and 0.078 respectively, gross fertility rate, were 67.92, 59.08, 76.13 and 63.14 respectively and mean generation time (T(c)) were 27.4, 27.74, 27.73 and 27.52 days respectively. Other demographic parameters such as intrinsic birth rate (b), intrinsic death rate (d), finite rate of increase (lambda), doubling time (DT), net fecundity rate, net fertility rate , gross fecundity rate, mean age gross fecundity and fertility, mean age net fecundity and fertility, mean age hatch, number of eggs/female/day and daily reproductive rate were also calculated. The results revealed that there were not significant differences between parameters of demography in different populations and the host plant has no significant influence on biological parameters.
Animals↗
Dietary administration of colesevelam hydrochloride does not affect fertility or reproductive performance in rats.
Colesevelam hydrochloride (HCl) (WelChol; Sankyo Pharma) is a novel, highly potent, bile acid-binding polymer used for the treatment of hypercholesterolemia. The primary aim of this study was to determine the effects of dietarily administered colesevelam HCl on fertility and reproductive performance parameters. To assess these effects, sexually mature Sprague-Dawley rats were randomized to one of five treatment groups: feed alone, feed plus control article (SigmaCell), or feed plus colesevelam HCl 200, 1000, or 2000 mg/kg/day. Male and female rats were administered the appropriate group agent for 28 and 15 days, respectively, and were subsequently paired together for cohabitation and mating. Females continued to receive the test agent in their dietary formulation through presumed gestation day (GD) 7. Presumed pregnant females underwent cesarean section on GD 20. Food consumption rate, body weight, gross necropsy, and standard preclinical tests for reproduction and fertility were performed for each test animal. No statistically significant differences were found between control and drug-treated groups for any tested endpoints of reproduction. All animals placed in cohabitation successfully mated. Uterine and litter end points were unaffected by dosages of colesevelam HCl as high as 2000 mg/kg/day. There were no significant differences between treatment group litter averages in the number of corpora lutea, implantation sites, litter size, live fetuses, body weights, early/late resorptions, and the number of dams with viable fetuses. In addition, no external alterations of fetal morphology were attributable to treatment with colesevelam HCl when administered up to the embryo implantation stage. In male animals, no significant differences were found between the colesevelam HCl and control study groups in the average caudal epididymal sperm count or sperm concentration, total number of motile and nonmotile sperm, and the total percentage of motile sperm. Based on these data, colesevelam HCl does not have any significant adverse reproductive or fertility effects in rats, even when administered at doses approximately 30 times greater than the approved clinical dose.
Administration, Oral↗
Developmental toxicology studies of WHI-07, a novel nucleoside analogue-based dual-function microbicide, administered intravaginally to rabbits.
The zidovudine derivative, 5-bromo-6-methoxy-5,6-dihydro-3-azidothymidine-5'-(p-bromophenyl) methoxy alaninyl phosphate (WHI-07), is a dual-function spermicidal and anti-HIV agent with contraceptive and microbicidal activity. In previous subchronic and reproductive toxicity studies and a two-year carcinogenicity study, daily intravaginal application of 0.5 to 2.0% WHI-07 via a gel-microemulsion, was shown to cause no local, systemic and reproductive toxicity or increased carcinogenicity in mice. To evaluate the developmental toxicity potential of WHI-07 in a nonrodent model, subgroups of 20 superovulated NZW rabbits were artificially inseminated and exposed intravaginally to a gel-microemulsion containing 0, 0.5, 1.0, or 2.0% WHI-07 during major organogenesis [gestation days 6-18]. The dose of WHI-07 was equivalent to 1.4x10(6) to 5.7x10(6) times its anti-HIV IC50 and 1400 to 5700 times its spermicidal EC50. Throughout the duration of the experiment (GD 0-29), clinical observations, food consumption, and body weights were recorded. Reproductive and fetal parameters were evaluated following uterotomies on GD 29. Measurements included numbers of corpora lutea, pregnancy, number and distribution of implantations, resorptions, live and dead fetuses, fetal weight, sex ratio, and gross external and skeletal malformations and variations. Maternal food consumption and body weight gain were unaffected by WHI-07 treatment. Hematologic and clinical chemistry determinations on GD 19 and 29 revealed no treatment-related maternal effects. Prior studies of repeated intravaginal administration of WHI-07 gel-microemulsion revealed lack of local toxicity to rabbit vaginal mucosa. In the current study, no drug-related gross lesions were apparent at necropsy. Reproductive indices, ie, pregnancy rate, gravid uterine weights, litter size, number of corpora lutea, implantation sites, pre- and postimplantation losses, viable fetuses, resorptions, fetal body weights, and fetal sex ratio, were not affected by intravaginal exposure to WHI-07. External, and skeletal examinations of fetuses for malformations and variations did not reveal any evidence of teratogenicity in any WHI-07-treated groups. Intravaginal administration of WHI-07 at concentrations as high as 2% did not produce teratogenicity or other developmental toxicity in rabbit conceptus. These findings indicated that WHI-07 shows unique clinical potential to become the active ingredient of a new female-controlled topical microbicidal vaginal contraceptive for women who are at high risk of acquiring HIV/AIDS.
Abnormalities, Drug-Induced↗
Collaborative work to evaluate toxicity on male reproductive organs by repeated dose studies in rats 23). A comparative 2- and 4-week repeated oral dose testicular toxicity study of boric acid in rats.
To assess the validity and limitations of 2-week repeated daily dosing to detect toxic effects on male reproductive organs in rodents, a comparative 2- and 4-week oral repeated dosing study of boric acid, a known testicular toxicant, was given to 6- or 8-week-old Crj:Wistar rats at daily levels of 0, 125, 250 and 500 mg/kg. The ages of the rats were selected so that they were all sacrificed at 10 weeks of age. The testes and epididymides were weighed at necropsy; histopathological specimens were prepared in a routine manner and stained with H&E or PAS-H. In addition, the sperm number and motility rates were evaluated. There were no boric acid-induced effects on reproductive organ weights and on gross behavior/appearance in any groups in either the 2- or 4-week studies. The sperm number and motility rate were not decreased in any group after 2 weeks, while both decreased in the 250 and 500 mg/kg groups after 4 weeks. Histopathologically, as evidence of toxicity at the early stage of boric acid exposure, retention of step 19 spermatids of stages IX-XI was observed in the testes of almost all rats treated with 500 mg/kg after both 2 weeks and 4 weeks. Degenerative/necrotic germ cells and multinucleated giant cell formation were observed in 2 weeks, though to a lesser extent than in 4 weeks. On stage analysis of germinal cells in 2 weeks, spermatogonia and spermatids of stage VII were found to be decreased, and pachytene spermatocytes of stage X were increased. In conclusion, the results indicate that if the selection of doses is appropriate, testicular toxicity of boric acid can be detected even after only 2 weeks of repeated daily oral treatment.
Administration, Oral↗
Financial analysis of pseudorabies control and eradication in swine.
Computerized decision-tree analysis and simulation modeling were used to evaluate control and eradication strategies for pseudorabies virus (PRV) in swine. Three alternative actions were considered for a hypothetical 100-sow, farrow-to-finish operation: (1) depopulation-repopulation, (2) test-and-removal of seropositives (T&R), and (3) vaccination (of the entire herd or of sows only). The expected monetary values for the vaccination and T&R alternatives were similar, which was consistent with the long-standing controversy over the best strategy for dealing with PRV. When the prevalence rate of PRV was less than or equal to 57%, T&R was found to be optimal; otherwise, vaccination of sows only was recommended. Sensitivity analysis was performed to determine how modifications in some of the original assumptions affected the expected monetary values of each strategy. When higher gross margins for the producer were assumed, T&R was preferred at all prevalence rates. Vaccination was preferred when lower gross margins, lower vaccination costs, or better protective effect of PRV vaccines on reproductive performance were assumed. The use of gene-deleted vaccines in conjunction with the T&R strategy was also evaluated. When this option was available, T&R was favored at any prevalence rate (T&R alone when the prevalence was less than or equal to 20%, or combined with gene-deleted vaccination at prevalences greater than 20%). Depopulation-repopulation was not the best option under any circumstance. Once formulated, a decision-tree analysis can be adapted to the prevailing economic or epidemiologic conditions; hence, it is a useful tool in the PRV decision-making process.
Animals↗
Population dynamics and stock assessment for Octopus maya (Cephalopoda: Octopodidae) fishery in the Campeche Bank, Gulf of Mexico.
The octopus (Octopus maya) is one of the most important fish resources in the Mexican Gulf of Mexico with a mean annual yield of 9000 ton, and a reasonable number of jobs created; O. maya represents 80% of the total octopus catch, followed by Octopus vulgaris. There are two artisanal fleets based on Octopus maya and a middle-size fleet that covers both species. Catch-at-length structured data from the artisanal fleets, for the 1994 season (August 1st to December 15th) were used to analyze the O. maya population dynamics and stock and to estimate the current level of exploitation. Von Bertalanffy growth parameters were: L infinity = 252 mm, mantle length; K = 1.4 year-1; oscillation parameters C = 1.0, WP = 0.6; and tz = 0.842 years. A rough estimate of natural mortality was M = 2.2, total mortality from catch curve Z = 8.77, and exploitation rate F/Z = 0.75. This last value suggests an intensive exploitation, even when yield per recruit analysis indicates both fleets may increase the minimum legal size on about 10% to increase yields. The length-based VPA also shows that the stock is being exploited under its maximum acceptable biological limit. These apparently contradictory results are explained by biological and behavioral characteristics of this species. Because most females die after reproduction, a new gross estimation of natural mortality was computed as M = 3.3. The new estimate of exploitation rate was F/Z = 0.57. This new value coincides with results from the length-VPA and the Thompson and Bell methods, the former suggesting that a reduction of 20% in fishing mortality may provide larger yields. This fishery resource is fully exploited and current management measures must be revised to sustain and probably optimize yields.
Animals↗
Comparison of the effects of two lathyrogens on the reproductive system of the laying hen.
The effects of two lathyrogens (beta-aminopropionitrile and semicarbazide) on the reproductive system of the laying hen were compared by measuring the changes in the ovary and oviduct associated with a diminished egg production rate. The laying hens were fed diets containing either beta-aminopropionitrile, the toxic constituent of certain legume seeds in the genus Lathyrus or semicarbazide to induce lathyrogenic effects in which reduced egg production was one of the toxic effects. The gross examination of the reproductive system of the hens revealed that ovarian activity was greatly impaired. The reduced egg production after feeding beta-aminopropionitrile was due to the reduced growth rate of the ovary, and in the case of semicarbazide, to the atresia of large yolky follicles.
Aminopropionitrile↗