Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Population Decrease”

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.

At least 37 records · Page 2Linked to original sources
PubMed1999

Halothane, but not the nonimmobilizers perfluoropentane and 1,2-dichlorohexafluorocyclobutane, depresses synaptic transmission in hippocampal CA1 neurons in rats.

UNLABELLED: Volatile anesthetics may decrease synaptic transmission at central neurons by presynaptic and/or postsynaptic actions. Nonimmobilizers are volatile compounds with lipophilicities that suggest that they should (but do not) prevent motor responses to surgical stimuli. However, nonimmobilizers interfere with learning and memory, and, thus, might be predicted to depress synaptic transmission in areas of the brain mediating memory (e.g., hippocampal CA1 neurons). To test this possibility, we stimulated the Schaffer collaterals of rat hippocampal slices and recorded from stratum pyramidale of CA1 neurons. At approximately 0.5 MAC (MAC is the minimum alveolar anesthetic concentration at one standard atmosphere that is required to eliminate movement in response to noxious stimulation in 50% of subjects), halothane decreased population spike amplitude 37% +/- 21% (mean +/- SD), increased latency 15% +/- 9%, and decreased excitatory postsynaptic potentials 16% +/- 10%. In contrast, at concentrations below (0.4 times) predicted MAC, the nonimmobilizer, 1,2 dichlorohexafluorocyclobutane (2N), slightly (not significantly) increased population spike amplitude, decreased population spike latency 9% +/- 4%, and increased excitatory postsynaptic potentials 22% +/- 16%. At concentrations above (2 times) predicted MAC, 2N did not significantly increase population spike, decreased latency 10% +/- 4%, and did not significantly change excitatory postsynaptic potentials. At 0.1 predicted MAC, a second nonimmobilizer, perfluoropentane, tended (P = 0.05) to increase (11% +/- 9%) population spike amplitude, decreased population spike latency 8% +/- 2%, and tended (P = 0.06) to increase excitatory postsynaptic potentials (9% +/- 8%). We conclude that clinically relevant concentrations of halothane depress synaptic transmission at Schaffer collateral-CA1 synapses and that the nonimmobilizers 2N and perfluoropentane have no effect or are excitatory. The Schaffer collateral-CA1 synapse may serve as a useful model for the production of immobility by volatile anesthetics, but is flawed as a model for the capacity of volatile anesthetics to interfere with memory and learning. IMPLICATIONS: Halothane, but not the nonimmobilizers 1,2-dichlorohexafluorocyclobutane and perfluoropentane, inhibits hippocampal synaptic transmission at Schaffer collateral-CA1 synapses.

Action Potentials↗
PubMed1998

Severe experimental uraemia does not decrease the population of rat pituitary somatotrophs.

BACKGROUND: Growth hormone (GH) secretion by the anterior pituitary has been shown to be depressed in severely uraemic rats. Changes in the population of pituitary somatotrophs might be partially responsible for this decrease. METHODS: To analyse the population of pituitary somatotrophs in severe uraemia, immunocytochemical detection and quantification of GH-producing cells were carried out on paraffin sections from young rats either 5/6 nephrectomized, sham-operated fed ad libitum or sham-operated pair-fed with the nephrectomized animals. RESULTS: Nephrectomized rats were severely uraemic and growth retarded. The overall cell density (total pituitary cells/mm2) was higher in 5/6 nephrectomized animals in comparison with the two sham-operated groups. Thus, although the percentage of GH cells was slightly lower in nephrectomized than in control rats, no difference in either the density (cells/mm2) or the cross-sectional area of GH cells was found among groups. CONCLUSIONS: These results suggest that severe experimental uraemia interferes with the maturation process of the pituitary gland and support the contention that differences in either the number or the size of pituitary somatotrophs cannot explain the reduced GH secretion previously reported in severely uraemic rats.

Animals↗
PubMed2005

Effect of combined insecticide sprays and sanitation techniques on population dynamics of Ceratitis capitata (Diptera: Tephritidae) in the central mountains of Israel.

We conducted an environmental manipulation study over a 7-km2 area to examine the effect of different control levels on the population dynamics of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in the central mountains of Israel. Adult male monitoring was carried out from spring to fall during 1988-1991 and year-round from 1994 to 2001. From 1995 to 1997, we manipulated the study area, imposing different levels of control by using a combination of insecticide sprays, tree pruning and removal, and fruit stripping. In the years preceding the manipulation, population dynamics was characterized by a peak summer population size in June-July, followed by a population decrease in August, leading to an early fall peak in September-October. If flies overwinter locally, we expected the intensive control to decrease the early summer population after the control. If flies do not overwinter locally, the control and sanitation activities should not decrease the population level in the following summer. During the entire period discussed, no flies were captured between January and May. The first appearance was recorded in late May or early June, reaching a peak in July. Regardless of control level and extent, the early summer peak remained unchanged during the entire study period, whereas the later fall peak decreased as host density decreased. We suggest that the first peak is the result of a seasonal reinvading population, whereas the later peak is governed by host availability and multiplication of the invading flies. The meaning and possible practical implications of our findings are discussed.

Animals↗
PubMed1985

Serotonin produces a reversible concentration dependent decrease of population spikes in rat hippocampal slices.

Superfusion of slices of rat dorsal hippocampus in vitro with serotonin (5-HT) reversibly decreases the amplitude of the CA1 population spike evoked by stimulation of stratum radiatum. The magnitude of the drug effect is concentration dependent and is greater on submaximal than on maximal population spikes. Concentration-response curves were generated using population spikes 30-60% of maximum by superfusion with increasing concentrations of 5-HT interspersed with perfusion of drug free medium. The EC50 for 5-HT was 3.2 microM. Repeated applications of a maximal dose of 5-HT did not produce tachyphylaxis. The reversibility, reproducibility and concentration dependence of the 5-HT response in the rat hippocampal slice makes this preparation useful for rigorous pharmacological classification of the receptor(s) involved.

Animals↗
PubMed1981

Cellular interactions in immune regulation. Hapten-specific suppression by non-T cells and T cell mediated reversal of suppression.

The ability of lymphoid cells from immunized animals to regulate the response of naive B ceils to the immunizing hapten was studied. Mice were immunized with trinitrophenylated (TNP) bovine gamma globulin (BGG) in complete Freund's adjuvant, and their spleen cells were examined in vivo and in vitro for the presence of specific inhibitory activity. This activity was found to peak 1 wk after immunization, was active against TNP on both T-dependent (BGG) and T-independent (Ficoll and polyacrylamide beads) carriers, and was demonstrable both by mixed cell transfers and mixed cell culture experiments. In in vitro studies, it was shown that the inhibition of the response to TNP- polyacrylamide beads by immune spleen cells was mediated by a non-T cell, possibly a B cell, because the suppressor activity was enriched in a purified B cell preparation. A role for macrophages was not formally ruled out. A specific suppressor factor was produced in vitro by immune spleen cells cultured in the absence of antigen. The suppressor activity was modulated by T .cells because elimination of T cells from the normal spleen cell population decreased suppression; elimination of T cells from the immune spleen cell population did not effect suppression, but elimination of T cells from both the normal and immune spleen cell populations allowed the expression of marked specific suppression. Thus, T cells present in the normal spleen cell population augment the degree of suppression, whereas T cells present in the immune spleen cell population decrease the degree of suppression; that is, T cells present in the immune spleen cell population had the ability to specifically abrogate suppression ("abrosuppression") in a T-independent immune response. It is proposed that the response to a T- independent antigen is regulated by specific suppressor activity generated by a non-T cell and augmented by the interaction of this cell with a T cell. The suppressor activity can be blocked by a specific abrosuppressor T cell. It is suggested that, because suppressor activity appears dominant in the naive state of the immune system, the induction of specific abrosuppressor activity may be essential if an immune response is to take place.

Animals↗
PubMed1984

Age-related changes in the canal of Schlemm.

A quantitative study of semi-thin sections through Schlemm's canal from 44 human eyes was undertaken. It was shown from counts of endothelial nuclei that the cell population decreased with age. The decrease in cell population was estimated from linear regression equations to be in the order of 430 cells per year for the whole canal and 320 cells per year for the canal's inner wall. Evidence was provided which indicated that counts of the giant vacuoles also decreased with age.

Adult↗
PubMed2001

Bacteriological validation of a new apparatus for disinfection of hospital waste at the point of disposal.

OBJECTIVES: To evaluate the ability of a new apparatus (Dipsys 25, Société SGN, Bagnols sur Cèze, France) to disinfect biomedical waste, including both potentially infectious agents and the normal saprophytic flora of the waste. METHODS: Disinfection was assessed using standard methods (reference strains were fixed on reference carriers according to the French AFNOR methods) and nonstandard assays. Assays in conditions of hospital use, evaluations of bacterial survival during storage, sporicidal effect, and spore survival during storage were performed in parallel. Finally, bactericidal effect in extreme conditions (association of high contamination and high bacterial protection conditions) was tested with normal fecal flora. Bacterial counts were performed after treatment by the apparatus and without treatment (controls). All tests were carried out in triplicate. RESULTS: In all treated carriers, a bacterial population decrease of at least 5 log10 was obtained. Assays performed in hospital-use conditions did not show any bacterial growth. Concerning the evaluation of sporicidal effect and spore revival during conservation, a minimum reduction of 5 log10 was observed in all assays performed, without survival. Finally, concerning assays in extreme conditions, the decrease of bacterial population was between 5 log10 and 10 log10 for vegetative anaerobes of normal fecal flora. CONCLUSION: Under our study conditions, the study apparatus reduced the tested microbial populations by a minimal factor of 5 log10. The main advantage of the apparatus is the opportunity to treat contaminated waste inside hospital wards, at the point of initial collection, without pulverization, by nonspecialized staff.

Bacteria, Aerobic↗
PubMed1987

Dietary copper deficiency and autoimmunity in the NZB mouse.

NZB mice were exposed from birth to a diet either adequate or deficient in copper. By age 6 wk the mice exposed to the copper-deficient diet showed symptoms characteristic of copper deficiency (anemia, hypoceruloplasminemia, and achromatrichia). The splenic lymphocytes from the copper-deficient group had reduced numbers of cells expressing the following surface markers: Ly-5, Ly-1, B-220, and sIg. Less than 10% of the splenic lymphocytes in this group were cycling, as determined by flow cytometry analysis. The spontaneous 96-h anti-ss-DNA levels in the copper-deficient group were lower than those in the control group. The exogenous colony-forming units (CFUs) were significantly enhanced in the copper-deficient mice. The decreased splenic lymphoid populations, decreased anti-ss-DNA titers, and increased exogenous CFUs in the copper-deficient mice appear to be due to an increase in erythropoiesis at the expense of lymphopoiesis.

Animals↗
PubMed1982

Alterations of T-cell subsets in primary biliary cirrhosis.

To determine whether abnormalities of immunoregulatory T cells are associated with primary biliary cirrhosis, we characterized peripheral blood mononuclear cells in 16 patients with primary biliary cirrhosis and compared them with 30 normal controls. For this analysis we used monoclonal antibodies to the surface antigens on helper/inducer (T4+) and suppressor (T8+) T cell subsets and to a common T cell antigen (T3+). In contrast to normal persons, patients with primary biliary cirrhosis had reduced percentages of T3+ cells. More importantly, there was a relative decrease in helper/inducer (T4+) cells in 9/16 patients and a decrease in suppressor (T8+) cells in 5/16 patients. Furthermore, clinical studies indicated that patients with a decreased suppressor cell population (increased T4+ : T8+ ratio) had more advanced disease, as reflected by serum bilirubin levels (P less than 0.05) and histological changes in the liver (P less than 0.001), than those patients with a reduced helper T cell population (decreased T4+ : T8+ ratio). These data suggest that abnormalities of immune responsiveness in primary biliary cirrhosis may have a more complex origin than a uniform alteration in one immunoregulatory T-cell subset and that these immunoregulatory cell changes vary according to the severity of the disease.

Adult↗
PubMed1986

Interaction of Clostridium difficile and Escherichia coli with microfloras in continuous-flow cultures and gnotobiotic mice.

We studied the interactions between the entire cecal flora of hamsters and the pathogens Clostridium difficile and Escherichia coli in gnotobiotic mice and in a continuous-flow (CF) culture system in which the growth medium consisted of an extract of fecal pellets from germfree mice. CF cultures and germfree mice were colonized first with C. difficile and E. coli and then with the cecal flora of hamsters. Both in vivo and in vitro hamster flora markedly suppressed the potential pathogens. Contents of CF cultures inoculated with hamster flora were introduced into gnotobiotic mice previously colonized with C. difficile and E. coli. These mice were compared with mice given homogenates of hamster ceca. In both groups, the C. difficile population decreased by a factor of more than 10(6) and the E. coli population decreased by a factor of 10(4) to 10(5). CF culture contents also reduced the size of the dilated germfree mouse cecum to normal. When veal infusion broth was used as a medium, contents of CF cultures colonized with hamster flora failed to eliminate C. difficile from mice. Thus, the extract of fecal pellets appeared to contain a substance important for sustained colonization by important components of the cecal flora. We also studied the ability of collections of isolates to suppress the potential pathogens in both gnotobiotic mice and CF cultures. A total of 150 isolates obtained from predominant hamster flora at the ecologic climax stage (C flora) suppressed C. difficile and E. coli to 10 and 1 to 3%, respectively, of the population sizes attained in monoassociated mice. A total of 67 isolates obtained during ecologic succession combined with a C flora consisting of 100 isolates suppressed the potential pathogens to 0.3 and 0.03% of their original levels, respectively. Similar degrees of suppression occurred in CF cultures, further indicating that anaerobic CF cultures are promising models for investigation of the microbial ecology of C. difficile.

Animals↗
PubMed2002

Thiopurine methyltransferase activity in a Spanish population sample: decrease of enzymatic activity in multiple sclerosis patients.

The present study was performed in order to obtain the thiopurine methyltransferase (TPMT) activity frequency distribution histogram in a Spanish population. A total of 3640 Spanish clinical laboratory samples were evaluated, which included 1249 patients with Crohn's disease, 589 with ulcerative colitis, 348 with multiple sclerosis (MS), 487 with several autoimmune diseases different from the above-mentioned diseases and 967 a donor group. We have measured the TPMT activity in red blood cells (RBCs) by a radiochemical method, using S-adenosyl-L-[methyl-3H]methionine as methyl donor. The different groups present in their entirety a normal distribution histogram and a wide range of TPMT activity from 0 to 41 U/ml RBCs. The differences found between the Spanish population TPMT activity frequency distribution histogram and the pattern previously described in a North American population were not due to azathioprine treatment or gender. The effect of autoimmune diseases on TPMT activity was evaluated: the enzymatic activity was similar in the donor group (19.9 +/- 6.3 U/ml RBCs) and in the patients with Crohn's disease (20.0 +/- 5.8 U/ml RBCs) and ulcerative colitis (19.7 +/- 6.1 U/ml RBCs); however, it decreased significantly (p<0.0001) in MS patients (17.1 +/- 6.1 U/ml RBCs) with respect to the donor group. In conclusion, our results show that the Spanish population TPMT distribution is closer to that of the Jewish population of Israel than to North American populations, and that in MS the enzymatic activity of TPMT decreases significantly. This observation may take into account the usage of azathioprine as therapeutic agent in Spanish MS patients.

Azathioprine↗
PubMed1998

Survival of Escherichia coli O157:H7 after freezing and thawing in ground beef patties.

Survival of Escherichia coli O157:H7 strains QA 326, and ATCC 43889, 43894, and 43895 after freezing (-20 degrees C, 24 h) and thawing (4 degrees C for 12 h, 23 degrees C for 3 h, or microwave heating of 700 W for 120 s) in ground beef patties was determined by reference most probable number (MPN), hydrophobic grid membrane filter SD-39 agar, and sorbitol MacConkey agar (SMA) spread-plating methods. Populations decreased from 0.62 to 2.52 log10 CFU/g, with the extent varying significantly by strain. Strain QA 326 populations almost always decreased the most, up to 1.87 log10 CFU/g more than the least sensitive strain. Microwave heating was the most lethal thawing treatment for strain QA 326, and 4 degrees C thawing was the most lethal treatment for strain ATCC 43894. Thawing treatments varied in relative lethality for the other two strains. For strain QA 326 (4 degrees C and microwave thaw treatments) and strain ATCC 43889 (4 and 23 degrees C thawing), the enumeration method significantly affected a population decrease. The SD-39 agar method best recovered strain QA 326 while the SD-39 agar method and the reference MPN method best recovered strain ATCC 43889 after 4 and 23 degrees C thawing, respectively. The greatest difference in population decrease measured by any two methods was 0.58 log10 CFU/g. Results showed (i) a wide range in freeze-thaw sensitivity among E. coli O157:H7 strains, (ii) no thawing method had consistently and significantly greater lethality, and (iii) the reference MPN, SD-39 agar, and SMA methods differed little in ability to enumerate E. coli O157:H7.

Animals↗
PubMed1987

[Ultrastructure of the median eminence and posterior lobe of the hypophysis in newborn Diocrostonyx torquatus lemmings during a decline in the population count].

Electron microscopically using morphometric analysis, the median eminence and hypophysis posterior lobe have been studied in newborn lemmings (Dicrostonyx torquatus Pallas) at the stage of decreasing population. A comparative characteristics of capillaries in the primary plexus of the portal system and capillaries of the hypophysis posterior lobe is presented. Overtaking developmental rate is demonstrated in the posterior hypophyseal lobe in comparison to that of the median eminence. In the lemmings investigated level of differentiation of the neurohemal areas of the hypothalamus is lower than development of these areas in laboratory mice and rats, according to the literature data. Possible results of weak development of the hypothalamo-hypophyseal connections in newborn lemmings at the stage of decreasing population are discussed.

Animals↗
PubMed2007

Phytoseiulus persimilis response to herbivore-induced plant volatiles as a function of mite-days.

The predatory mite, Phytoseiulus persimilis (Acari: Phytoseiidae), uses plant volatiles (i.e., airborne chemicals) triggered by feeding of their herbivorous prey, Tetranychus urticae (Acari: Tetranychidae), to help locate prey patches. The olfactory response of P. persimilis to prey-infested plants varies in direct relation to the population growth pattern of T. urticae on the plant; P. persimilis responds to plants until the spider mite population feeding on a plant collapses, after which infested plants do not attract predators. It has been suggested that this represents an early enemy-free period for T. urticae before the next generation of females is produced. We hypothesize that the mechanism behind the diminished response of predators is due to extensive leaf damage caused by T. urticae feeding, which reduces the production of volatiles irrespective of the collapse of T. urticae population on the plant. To test this hypothesis we investigated how the response of P. persimilis to prey-infested plants is affected by: 1) initial density of T. urticae, 2) duration of infestation, and 3) corresponding leaf damage due to T. urticae feeding. Specifically, we assessed the response of P. persimilis to plants infested with two T. urticae densities (20 or 40 per plant) after 2, 4, 6, 8, 10, 12 or 14 days. We also measured leaf damage on these plants. We found that predator response to T. urticae-infested plants can be quantified as a function of mite-days, which is a cumulative measure of the standing adult female mite population sampled and summed over time. That is, response to volatiles increased with increasing numbers of T. urticae per plant or with the length of time plant was infested by T. urticae, at least as long at the leaves were green. Predatory mites were significantly attracted to plants that were infested for 2 days with only 20 spider mites. This suggests that the enemy-free period might only provide a limited window of opportunity for T. urticae because relatively low numbers of T. urticae per plant can attract predators. Leaf damage also increased as a function of mite-days until the entire leaf was blanched. T. urticae populations decreased at this time, but predator response to volatiles dropped before the entire leaf was blanched and before the T. urticae population decreased. This result supports our hypothesis that predator response to plant volatiles is linked to and limited by the degree of leaf damage, and that the quantitative response to T. urticae populations occurs only within a range when plant quality has not been severely compromised.

Animals↗
PubMed1984

Novel method for studying the public health significance of macroinvertebrates occurring in potable water.

An experimental procedure was developed to study the association of selected bacteria and macroinvertebrates and their response to free available chlorine disinfection. The organisms selected for study were Escherichia coli ( LacZ545 ), Enterobacter cloacae (ATCC 23355), and the amphipod Hyalella azteca . E. coli was shown to bind tightly (1.6 X 10(4) CFU per amphipod ) to this macroinvertebrate and to resist repeated attempts to wash it off. E. cloacae was shown to bind much less tightly (1.4 X 10(3) CFU per amphipod ) to H. azteca and was less resistant to removal by washing. The extent of association is a function of macroinvertebrate size (surface area), but the procedure produces repeatable results usable for controlled experimentation. This method, together with the dual bacterial identification criteria (morphology and antibiotic resistance), was used to study the response of unassociated and associated E. coli and E. cloacae to disinfection with free available chlorine at 1.0 mg/liter. Unassociated E. coli populations decreased to less than 1% of their zero time controls within 1 min of contact time, whereas more than 2% of the associated E. coli populations remained viable after 60 min of contact at 1.0 mg of free available chlorine per liter. Unassociated E. cloacae populations decreased to less than 1% of their zero time controls within 1 min of contact time, whereas ca. 15% of the associated E. cloacae populations remained viable after 60 min of contact at 1.0 mg of free available chlorine per liter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗
PubMed1997

Apparent decrease in population clearance of theophylline: implications for dosage.

BACKGROUND: Having observed in recent years that the theophylline dose requirements needed to attain peak serum concentrations of 10 to 20 micrograms/ml infrequently reached previously described mean values, we hypothesized that a downward shift in the range of dose requirements had occurred among patients with asthma. STUDY DESIGN: We examined dosage requirements needed to attain peak serum concentrations of 10 to 20 micrograms/ml in all patients with chronic asthma treated with theophylline by the Pediatric Allergy and Pulmonary Clinic at the University of Iowa from 1990 to 1994 (n = 300) and at the Pediatric Pulmonary Clinic at the University of Florida from 1992 to 1995 (n = 93). We then compared these doses to previous dose requirements from 1978 to 1983 determined in the same manner. RESULTS: Despite similar mean peak serum concentrations during both time periods (14 micrograms/ml), mean theophylline dosage requirements during the period of this study were approximately 25% lower among all age groups than those previously observed (p < 0.001). There were no significant differences in mean dosage requirements between the Iowa and Florida patients in any age group examined. CONCLUSIONS: Theophylline dose requirements needed to attain serum concentrations of 10 to 20 micrograms/ml have decreased significantly from those on which current dosing recommendations are based. This suggests a decrease in mean clearance of the population.

Adolescent↗