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At least 19 recordsLinked to original sources
PubMed1997

Duration and mechanisms of the increased natural cytotoxicity seen after chronic voluntary exercise in rats.

We have recently shown that in vivo natural cytotoxicity is enhanced after chronic exercise in spontaneously hypertensive rats (SHRs). In the present report, we have studied the duration of this augmentation and some possible mechanisms involved. Exercise consisted of voluntary running for 4-5 weeks, with the running distance ranging from 2.7-15.6 km day(-1) during the last week of running. In vivo cytotoxicity was measured as clearance of injected 51Cr-labelled YAC-1 lymphoma cells from the lungs. The in vivo natural cytotoxicity was increased in running SHRs, and also in SHRs that had their running wheel locked for 24 and 48 h prior to the experiment, and was still present after 96 h. The enhancement of in vivo cytotoxicity after 5 weeks of exercise was abolished after an acute injection of the beta-adrenergic receptor antagonist timolol (0.5 mg kg(-1) i.v.), indicating that catecholamines are involved in this augmentation. Interestingly, 24 h after the last exercise bout, the increased natural cytotoxicity could be blocked by timolol. The opioid receptor antagonist naloxone given subcutaneously for 7 days by osmotic pumps (6 mg kg(-1) h(-1)) could not reverse the increased in vivo cytotoxicity seen in the running SHRs, suggesting that opioid receptor mechanisms are not involved, or at least not the naloxone-sensitive mu-receptor. Natural immunity was not influenced by the histamine H2 receptor antagonist ranitidine, either in controls or in runners, indicating that the natural killer cell-regulatory effect of histamine is not present in SHRs and does not seem to be involved in the exercise-induced changes in natural immune function. We conclude that the augmentation of in vivo natural cytotoxicity after voluntary chronic exercise in rats is long-lasting and that the augmentation is partly mediated by beta-adrenergic receptors.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Some factors influencing variations in the rate of natural increase of population in western Maharashtra.

This paper analyzes the impact of various factors on variations in the rate of natural increase of population in Western Maharashtra, India. By using district level data, coefficients of correlation have been calculated between the rate of natural increase, the birth rate and the death rate on the 1 hand and different factors affecting them on the other. The analysis shows that in Western Maharashtra the birth rate is high in response to the high death rate and the high infant mortality rate. It is also revealed that the rate of natural increase of the population declines with an increase in the proportion of working females as well as the proportion of educated males. All this signifies that the region under study is in the 2nd stage of the "demographic transition."

Asia↗
PubMed1988

Increased natural resistance to Listeria monocytogenes in senescent mice correlates with enhanced macrophage bactericidal activity.

Natural resistance to Listeria monocytogenes is increased in aging (18-22-month-old) AB6F1 mice when compared to their younger counterparts. We have investigated several parameters of macrophage function of old AB6F1 mice to establish what macrophage characteristics determine their enhanced resistance to Listeria. Senescent mice had an increased number of macrophages present in unstimulated peritoneal cavity. These macrophages exhibited enhanced bactericidal activity and H2O2 production. Old mice showed a diminished subcutaneous inflammatory response. Kupffer cells obtained from normal uninfected old mice had good levels of listericidal activity, but Kupffer cells obtained from normal young mice could not kill Listeria. The increased natural resistance to Listeria monocytogenes seen in old AB6F1 mice could be the result of enhanced macrophage bactericidal activities in the liver prior to the infection.

Aging↗
PubMed1986

Cocaine increases natural killer cell activity.

The administration of epinephrine to humans increases natural killer (NK) cell activity and numbers. If endogenous catecholamines regulate NK cells, then their activity should be increased by cocaine, an agent that potentiates endogenous catecholamines. We investigated the in vivo effect of cocaine on NK cell activity and on the distribution of lymphocyte subsets, including NK cells. Intravenous cocaine (0.6 mg/kg) produced a three- to fourfold increase in NK cell activity in peripheral blood. The increase was accompanied by a marked and selective increase in circulating NK cells, as identified by the Fc receptor (Leu-11). Normal saline and benzoylecgonine, a major metabolite of cocaine, had little effect on NK cell activity or on levels of Leu-11+ cells. Other lymphocyte subpopulations were not increased by cocaine. The time course of the alterations in NK cell numbers and activity paralleled plasma levels of cocaine. In vitro cocaine did not increase NK cell activity. Our results indicate that cocaine selectively alters the activity and distribution of the NK lymphocyte subset. Because cocaine increases the activity of endogenous catecholamines, these findings suggest that human NK cells are selectively regulated by the sympathetic nervous system.

Adult↗
PubMed1981

Increased natural killer cell activity in experimental American trypanosomiasis.

These studies showed that increased natural killer (NK) cell activity develops during experimental American Trypanosomiasis in mice. Increased cytotoxicity against YAC target cells by peritoneal cavity cells (PEC) was detected as early as 1 day into infection in both C3H/He and C57BL/6 mice. Peak activity occurred 2 days into infection, with significant but variable increases detected in the spleen cells (SC) from these mice. The response subsided in PEC and to a lesser extent in SC by 4 days post-infection. Similar responses were not detected in infected C57BL/6 bgJ/bgJ (beige mutant) mice until the fourth day of infection and peaked at significantly lower levels than the peak on day 2 in beige hybrid mice ([C57BL/6 +/+ X C57BL/6 bgJ/bgJ]F1). The effector cell from infected mice was sensitive to pretreatment with anti-NK 1.2 serum plus complement (C), partially sensitive to anti-Thy 1.2 + C, and insensitive to polyvalent anti-mouse immunoglobulin + C. The cytotoxic activity induced in cells from mice infected for 2 days was recovered in subpopulations nonadherent to plastic or Sephadex G-10. Thus, the anti-YAC effector cell found very early in mice infected with T. cruzi possessed many of the characteristics of natural killer (NK) cells found in normal mice. Other experiments demonstrated that injection of heat-killed preparations of blood-form trypomastigotes (BFT) induced increases in NK activity. The presence of augmented NK activity against YAC tumor cells in both resistant and susceptible strains of mice, together with the presentation of the resistance phenotype in beige mutant mice, which had a lower NK response to infection, is not indicative of a direct role for host protection during infection with T. cruzi by NK cells.

Animals↗
PubMed1995

Regional trends in crude birth, death, and natural increase rates in Russia and the USSR: 1897-1989.

"This paper establishes and discusses briefly regional patterns and trends in crude birth, death, and natural increase rates in Russia and the USSR from the turn of the century to 1989. The study is based on a comparable regional framework and placed in the context of the demographic transition theory. It discusses sources, collection, and quality of data, as well as necessary estimating procedures. An attempt also is made to examine briefly regional age-standardized rates."

Age Factors↗
PubMed1993

Estimation of the intrinsic rate of natural increase and its error by both algebraic and resampling approaches.

The intrinsic rate of natural increase or Malthusian parameter plays a key role fields as diverse as ecology, genetics, demography and evolution. It characterizes the growth of a population in a determinate environment. Since its rigorous statistical estimation requires of intensive calculation, the use of a computer becomes essential. The two main approaches to the calculation of the Malthusian parameter, its error and confidence intervals have been implemented in a program and have been compared by means of an example.

Algorithms↗
PubMedDate not supplied

[Natural increase and migration in the province of Rome: an analysis of 35 years of development (1951-1986)].

Demographic trends in the province of Rome, Italy, are analyzed for the period 1951-1986. Special consideration is given to the effects of natural increase and migration on population growth and structure among municipalities within the province. The author presents "an adaptation of the so-called 'shift and share' analysis to the case of population development; this analysis is usually employed in the study of differences in the regional development of industrial employment. The results...indicate that different evolution patterns exist in the province...studied." (SUMMARY IN ENG AND FRE)

Demography↗
PubMed1982

The factors of urban population growth: net inmigration versus natural increase.

"As a country evolves from a traditional to an advanced society, the part of urban growth that is due to net inmigration follows a simple pattern, which can be described by an inverted U-shaped curve: it first increases, then passes through a maximum, and decreases thereafter. This hypothesis is confirmed by quantitative analysis using time-series and cross-section data. The analysis suggests that in the second half of this century natural increase often provides a slightly higher contribution to urban population growth than net inmigration." (summary in FRE, ITA, JPN, )

Demography↗
PubMed2002

Mistletoe viscotoxins increase natural killer cell-mediated cytotoxicity.

Mistletoe extracts have immunomodulatory activity. We show that nontoxic concentrations of Viscum album extracts increase natural killer (NK) cell-mediated killing of tumor cells but spare nontarget cells from NK lysis. The compounds responsible for this bioactivity were isolated from mistletoe and characterized. They have low molecular mass and are thermostable and protease-resistant. After complete purification by HPLC, they were identified by tandem MS as viscotoxins A1, A2 and A3 (VTA1, VTA2 and VTA3, respectively). Whereas micromolar concentrations of these viscotoxins are cytotoxic to the targets, the bioactivity with respect to NK lysis is within the nanomolar range and differs between viscotoxin isoforms: VTA1 (85 nm), VTA2 (18 nm) and VTA3 (8 nm). Microphysiometry and assays of cell killing indicate that, within such nontoxic concentrations, viscotoxins do not activate NK cells, but act on cell conjugates to increase the resulting lysis.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1993

A middle path: slavery and natural increase in nineteenth-century Minas Gerais.

"This article challenges the conventional notion that all regions of Brazil...were entirely dependent upon the international slave trade for the maintenance or growth of their slave populations.... The arguments will be based on data relating to the nineteenth-century slave population of the province of Minas Gerais.... Despite the size of its slave contingent, Minas Gerais was at best weakly linked to the export sector.... In light of data from the 1830s it will be argued that this economic transformation away from the export sector had a profound impact on slave demography.... New evidence shows that the Mineiro slave population achieved a positive rate of natural increase within a single generation of the termination of the Atlantic slave trade."

Americas↗
PubMed2000

Antibodies to phosphatidylethanolamine and phosphatidylserine are associated with increased natural killer cell activity in non-male factor infertility patients.

Antiphospholipid antibodies (APA) have been identified in patients with recurrent pregnancy loss and IVF failure. Of these, antiphosphatidylethanolamine (aPE) and antiphosphatidylserine (aPS) may have special significance. A link between increased natural killer cell activity (NKa+) and trophoblast cell apoptosis has also been reported. This study was undertaken to determine how the APA profile was associated with peripheral NK cell activity. We evaluated 197 female IVF candidates for APA and NKa. Eighty-nine patients (45%) were APA+ and of these, 51 (57%) were aPE/aPS+. Fifty-four patients (27%) had increased NK cell activity. Some 51% of APA+ and 78% of aPE/aPS+ patients had increased NK cell activity compared with 8% and 13% when APA and aPE/aPS tested negative respectively (P: < 0.0001). Non-male factor infertility patients were APA+ and NKa+ in 57% and 34% of cases respectively, compared with 19% and 13% if a pure male factor was present. Some 88% of aPE/aPS+, non-male factor patients had increased NK cell activity, compared with 12% who tested aPE/aPS negative (P: < 0.0001) and 25% of aPE/aPS+, isolated male factor patients (P: < 0.0001). These findings establish a direct relationship between APA (specifically aPE/aPS) and increased peripheral NK cell activity among non-male factor infertility patients. It is possible that APA do not directly cause reproductive failure but rather function as markers or intermediaries for an underlying, abnormal activation of cellular immunity.

Adult↗
PubMed2001

Increased natural killer-cell activity is associated with infertile women.

PROBLEM: An increase in natural killer (NK)-cell activity has been observed in women with unexplained recurrent miscarriages. Because of the many similarities between infertility and early pregnancy loss patients, we investigated whether infertile women had raised NK-cell activity. METHOD OF STUDY: We tested 94 infertile women who, in spite of treatment, were unable to conceive for 6 or more months. NK-cell activity was measured by using a chromium-51 release cytotoxicity assay. with K562 human myeloid leukemia cells as targets. RESULTS: NK-cell activity of the infertile group (mean +/- SD; 40.2%+/-14.7) was significantly higher than the control group (31.5%+/-11.9, P < 0.0001). The increased NK-cell activity was not associated with age, infertile duration, depression scores, treated hyperprolactinemia, or treated endometriosis. CONCLUSIONS: In certain patients, elevated NK-cell activity may be considered an independent risk factor for infertility.

Abortion, Spontaneous↗
PubMed2002

Dietary counseling to increase natural folate intake: a randomized, placebo-controlled trial in free-living subjects to assess effects on serum folate and plasma total homocysteine.

BACKGROUND: The association between vascular disease and elevated plasma total homocysteine (tHcy) concentrations is caused, in part, by inadequate intakes of dietary folate. Increasing folate intake either through supplements or foods naturally rich in folates has been shown to decrease tHcy concentrations. OBJECTIVE: The aim of this study was to determine whether a similar reduction in tHcy was possible in free-living persons receiving dietary counseling. DESIGN: The study included a 4-wk placebo-controlled dietary intervention trial in which participants consumed either unfortified breakfast cereal (control group) or an extra 350 micro g folate derived from food/d (dietary group). Serum folate and tHcy concentrations in both groups were measured before and after the intervention period, and the concentrations in the dietary group were also measured 17 wk after the intervention period. RESULTS: During the 4-wk intervention, mean dietary folate intake in the dietary group increased from 263 (95% CI: 225, 307) to 618 micro g/d (535, 714), resulting in a mean increase in serum folate of 37% (15%, 63%) and a decrease in tHcy from 12.0 (10.9, 13.3) to 11.3 micro mol/L (10.2, 12.5). A further decrease in tHcy occurred in the dietary group during follow-up, with a final tHcy concentration of 9.7 micro mol/L (8.8, 10.8). CONCLUSIONS: Increasing natural folate intake improved folate status and decreased tHcy concentrations to an extent that may significantly reduce the risk of vascular disease. Dietary modification may have advantages over folic acid fortification because the altered food-consumption patterns lead to increased intakes of several vitamins and minerals and decreased intakes of saturated fatty acids.

Aged↗
PubMed2002

Intravenous fentanyl increases natural killer cell cytotoxicity and circulating CD16(+) lymphocytes in humans.

UNLABELLED: Opioids, including fentanyl, are often administered to patients who may be at risk for the consequences of impaired immune function. We performed a clinical study to test the effects of the synthetic opioid fentanyl on human immune function. Participants received an IV fentanyl initial dose of 3 microg/kg followed by a 2-h IV infusion of 1.2 microg x kg(-1) x h(-1). Peripheral blood was drawn before and after fentanyl administration to test for neutrophil phagocytic function, neutrophil antibody-dependent cell cytotoxicity, natural killer cell cytotoxicity, percentage of lymphocyte populations, T-lymphocyte proliferative response, and in vivo antibody response to a pneumococcal vaccine inoculation given at the end of the fentanyl infusion. Fentanyl exposure under the conditions of this study caused a rapid and significant increase in natural killer cell cytotoxicity, which was coincident with an increase in the percentage of CD16(+) and CD8(+) cells in peripheral blood. Fentanyl did not significantly affect any of the other immune measurements. IMPLICATIONS: Many previous studies have suggested that opioid drugs can impair immune resistance in patients who may be at risk for infection. This study suggests that the opioid fentanyl, when given to healthy humans without coexisting diseases, does not suppress immune resistance. On the basis of these results, the use of fentanyl should not be restricted because of concerns that it may suppress immune function.

Adult↗
PubMed1996

Acute mental stress but not enforced muscle activity transiently increases natural cytotoxicity in spontaneously hypertensive rats.

The influence of acute mental stress and the effect of electrically induced skeletal muscle contractions on natural cytotoxicity in vivo was investigated in spontaneously hypertensive rats Natural cytotoxicity in vivo was measured as the clearance of injected 51Cr-labelled YAC-1 lymphoma cells from the lungs, which are specifically lysed by natural killer cells. The mental stress consisted of an air jet directed towards the animals in their cage for 25 min. During the mental stress there was a significant increase in natural cytotoxicity. Thus, retained radioactivity in the lungs was decreased to 74 +/- 6% of the control levels which was set to 100% (P < 0.01). This augmentation of YAC-1-cell clearance could be blocked with the beta-adrenergic receptor antagonist Timolol. Two hours after termination of the air stress, in vivo cytotoxicity had returned to control levels. In contrast, acute physical stress, consisting of electrically induced muscle contractions for 60 min, had no significant effects on in vivo cytotoxicity, either during the stimulation or 1, 2 or 24 h after the stimulation. Further, significantly increased plasma levels of adrenaline were seen after the air jet stress, but not after muscle stimulation. There were no significant changes in plasma noradrenaline levels either after air stress or muscle stimulation. These results indicate that changes in in vivo cytotoxicity after mild mental stress are dependent on increased plasma catecholamine levels while acute physical stress without changes in catecholamine levels, does not influence in vivo cytotoxicity.

Animals↗
PubMed2002

Elevation of glutathione induced by low-dose gamma rays and its involvement in increased natural killer activity.

We examined the relationship between the induction of an increase in the level of glutathione and the elevation of natural killer (NK) activity in mouse splenocytes by a low dose of gamma rays. The glutathione levels in mouse splenocytes increased significantly between 2 h and 6 h after whole-body gamma irradiation at 0.5 Gy, peaked at 4 h, and then decreased almost to the level before irradiation by 12 h postirradiation. A significant enhancement of NK activity was found in the splenocytes obtained from whole-body-irradiated mice between 4 and 6 h postirradiation. Reduced glutathione (GSH) added exogenously to splenocytes obtained from normal mice enhanced both the total cellular glutathione content and the NK activity in a dose-dependent manner. Other precursors of de novo GSH synthesis, such as cysteine, N-acetylcysteine and oxidized glutathione, also increased the activity. These enhancements were completely blocked by buthionine sulfoximine, an inhibitor of de novo GSH synthesis. We conclude that the induction of endogenous glutathione in living cells immediately after low-dose gamma irradiation is at least partially responsible for the appearance of enhanced NK activity.

Animals↗
PubMed1983

[The natural increase of the Catholic population of Quebec before 1850: historiographic and quantitative perspectives].

"The author presents a critical evaluation of the different estimates of birth, death, and marriage rates in French Canada before 1850. He examines critically the sensitivity of these estimates to changes in the nature of the prevailing conceptual framework. In particular, the impact of the 'natalist' tradition and of the 'demographic transition hypothesis' on these estimates is noted." (summary in ENG)

Americas↗