Estudos sôbre o pneumococo: 4a. nota - Influência do pH do meio sôbre a formação da cápsula pelo pneumococo

One of the features of pneumococcus which has deserved the attention of investigators is the capsule. Since Pasteur, Chamberland and Roux (1881) several functions have been ascribed to it as well as peculiar properties. In the present paper, we take into consideration one only aspect of this problem; it is the relationship which there possibly may be between acidity of the culture medium and the power of capsule formation by pneumococcus. As it is known, this germ requires for its development 7.8 as an optimum pH, but maintains its biological activities down to 5.6. These variations do not take place without large alterations, particularly of the capsule, not only from the morphological but also from the chemical viewpoint. The diameter of the mucous envelopment of the pneumococcus decreases in proportion to the increase of acidity down to its complete extinction. This fact has been regarded by investigators as a biological feature inhe¬ring to the germ itself and as proceeding of self-defense. In an acid medium the existing capsule is destroyed and the germ does not produce it again; consequently, acidity inhibits the formation of the capsule. We tried to check how this phenomenon comes to pass and to elucidated it. As we know, the fundamental compound of the pneumococcus capsule is mucin. In the first place, we experimented the action of acidity on same in the following manner: Mucin extracted from bovine submaxillary gland is precipitated by HC1 at a determined concentration degree; the mucin dissolves again and precipi¬tates in function of this concentration. This property of mucin (solubility in acid medium) modifies a little the interpretation of the mechanism of disappearance of the capsule from the said germ in the culture medium. Indeed: The acidification of the medium consecutive to the growth of pneumococcus reduces the dimensions of the capsule until causing its com¬plete disappearance; but on transferring this strain to new optimum cultiva¬ting conditions the capsule appears again exhuberantly, at times as anteriorly, although with biased virulence. Linking these two facts we draw the following conclusions: Pneumo¬coccus does not lose its capacity of capsule formation in an acid medium; but mucin, whilst being produced, is entirely dissolved in this medium by the aid of acidity; we venture to state that, in spite of medium acidity, the capacity of capsule production is a constant feature of pneumococcus and that the disappearance of the capsule does not depend on the pneumococcus in itself when it produces smooth colonies, but on the chemical properties of mucin, mainly on its solubility in acid medium.

Tacit collusion and capacity withholding in repeated uniform price auctions

This paper contributes to the study of tacit collusion by analyzing infinitely repeated multiunit uniform price auctions in a symmetric oligopoly with capacity constrained firms. Under both the Market Clearing and Maximum Accepted Price rules of determining the uniform price, we show that when each firm sets a price-quantity pair specifying the firm's minimum acceptable price and the maximum quantity the firm is willing to sell at this price, there exists a range of discount factors for which the monopoly outcome with equal sharing is sustainable in the uniform price auction, but not in the corresponding discriminatory auction. Moreover, capacity withholding may be necessary to sustain this out-come. We extend these results to the case where firms may set bids that are arbitrary step functions of price-quantity pairs with any finite number of price steps. Surprisingly, under the Maximum Accepted Price rule, firms need employ no more than two price steps to minimize the value of the discount factor

Forward induction and the excess capacity puzzle: An experimental investigation.

While the theoretical industrial organization literature has long argued that excess capacity can be used to deter entry into markets, there is little empirical evidence that incumbent firms effectively behave in this way. Bagwell and Ramey (1996) propose a game with a specific sequence of moves and partially-recoverable capacity costs in which forward induction provides a theoretical rationalization for firm behavior in the field. We conduct an experiment with a game inspired by their work. In our data the incumbent tends to keep the market, in contrast to what the forward induction argument of Bagwell and Ramey would suggest. The results indicate that players perceive that the first mover has an advantage without having to pre-commit capacity. In our game, evolution and learning do not drive out this perception. We back these claims with data analysis, a theoretical framework for dynamics, and simulation results.

Asymmetries in the capacity-inflation trade-off

This paper analyzes the joint dynamics of two key macroeconomic variables for the conduct of monetary policy: inflation and the aggregate capacity utilization rate. An econometric procedure useful for estimating dynamic rational expectation models with unobserved components is developed and applied in this context. The method combines the flexibility of the unobserved components approach, based on the Kalman recursion, with the power of the general method of moments estimation procedure. A 'hyb id' Phillips curve relating inflation to the capacity utilization gap and incorporating forward and backward looking components is estimated. The results show that such a relationship in non-linear: the slope of the Phillips curve depends significantly on the magnitude of the capacity gap. These findings provide support for studying the implications of asymmetricmonetary policy rules.

Endogenous capacity utilization and the asymmetric effects of monetary policy

This paper investigates the role of variable capacity utilization as a source of asymmetries in the relationship between monetary policy and economic activity within a dynamic stochastic general equilibrium framework. The source of the asymmetry is directly linked to the bottlenecks and stock-outs that emerge from the existence of capacity constraints in the real side of the economy. Money has real effects due to the presence of rigidities in households' portfolio decisions in the form of a Luces-Fuerst 'limited participation' constraint. The model features variable capacity utilization rates across firms due to demand uncertainty. A monopolistic competitive structure provides additional effects through optimal mark-up changes. The overall message of this paper for monetary policy is that the same actions may have different effects depending on the capacity utilization rate of the economy.

Lipschitz harmonic capacity and Bilipschitz images of cantor sets

For bilipschitz images of Cantor sets in Rd we estimate the Lipschitz harmonic capacity and show this capacity is invariant under bilipschitz homeomorphisms.

The retained capacity of Lutzomya longipalpis (Lutz & Neiva) to transmit Leishmania chagasi (Cunha & Chagas) after eight years (64 generations in a closed laboratory colony

A closed Lutzomyia longipalpis colony, from Ceará has been used to transmit Leishmania chagasi isolated from a fox in Pará state. The last time this colony was successfully used in similar transmission experiments was eight years (64 generations) ago indicating that this colony of Lu. longipalpis has fully maintained its vectorial capacity in spite of such a long period of maintainance in the laboratory.

Reduced capacity of peritoneal exudate cells for oxidative killing of Schistosoma mansoni schistosomula

Peritoneal exudate cells from mice infected with Schistosoma mansoni (S-PEC) can kill schistosomula in vitro in the presence of immune serum. S-PEC produce a low level of respiratory burst, and schistosomula mortality in their presence is not reduced when exogenous antioxidants are added, suggesting that with S-PEC, oxidative killing is not important. Hydrogen peroxide (H2O2) and superoxide production by S-PEC, and cells from BCG and thioglycollate (THGL) injected non-infected mice, non-specifically stimulated with opsonized zymosan, were measured. Levels of H2O2 produced by S-PEC were significantly lower than BCG or THGL PEC, and were below the H2O2 threshold for schistosomula killing. This resulted in lower levels of cell-mediated killing of schistosomula in vitro by S-PEC than by BCG or THGL PEC. Superoxide levels, however, were similar between the three cell populations. The efficiency of PEC to kill schistosomules in vitro correlated with H2O2 rather than superoxide levels. The lower tolerance of schistosomula, compared to adult S. mansoni to GSH depleting agents increases their sensitivity to oxidative attack and resulted in higher levels of cell-mediated killing in vitro.

PGE2-Induced IDO1 Inhibits the Capacity of Fully Mature DCs to Elicit an In Vitro Antileukemic Immune Response.

In the last years, dendritic cells (DC) have been evaluated for antitumor vaccination. Although DC-based vaccines have raised great expectations, their clinical translation has been largely disappointing. For these results, several explanations have been proposed. In particular, the concomitant expression by DCs of tolerogenic pathways, such as the immunosuppressive agent indoleamine 2,3-dioxygenase-1 (IDO1), has been demonstrated. The aim of this study is to evaluate both the stimulatory and the tolerogenic feature of monocyte-derived DCs (Mo-DCs) after maturation with PGE2. In particular, the role of IDO1 expression in PGE2-matured Mo-DCs has been addressed. Here we show that PGE2, which is required for full maturation of DCs, is one mediator of DC tolerance by enhancing IDO1. PGE2-mediated expression of IDO1 results in the production of kynurenine, in the generation of Tregs, and in the inhibition of either the allogeneic or the autologous antigen-specific stimulatory capacity of DCs. When pulsed with leukemic lysates and matured with PGE2, DCs are impaired in the induction of IFN-γ secreting CD4(+) and CD8(+) T cells due to IDO1 upregulation. Moreover, the inhibition of IDO1 enhances the antileukemic response. Overall, these results point toward the use of IDO1 inhibitors to enhance the vaccination capacity of DCs, matured with PGE2.

Quasiconformal maps, analytic capacity, and non linear potentials

"Vegeu el resum a l'inici del document del fitxer adjunt."

Traffic forecasts under uncertainty and capacity constraints

Traffic forecasts provide essential input for the appraisal of transport investment projects. However, according to recent empirical evidence, long-term predictions are subject to high levels of uncertainty. This paper quantifies uncertainty in traffic forecasts for the tolled motorway network in Spain. Uncertainty is quantified in the form of a confidence interval for the traffic forecast that includes both model uncertainty and input uncertainty. We apply a stochastic simulation process based on bootstrapping techniques. Furthermore, the paper proposes a new methodology to account for capacity constraints in long-term traffic forecasts. Specifically, we suggest a dynamic model in which the speed of adjustment is related to the ratio between the actual traffic flow and the maximum capacity of the motorway. This methodology is applied to a specific public policy that consists of suppressing the toll on a certain motorway section before the concession expires.

The reproductive capacity of Panstrongylus megistus (Hemiptera: Reduviidae) males treated with precocenes

Reproductive performance including mating, semen transfer, egg production and hatching rate were investigated in pairs of Panstrongylus megistus in wich the male was treated with either precocene II or ethoxyprecocene II, topically applied shortly after imaginal molt. Eighty percent of the males were not able to mate for a period as long as 40 days after treatment. Those males wich did mate (20%) produced small spermatophores; a few (10%) were unable to transfer spermatozoa to female, while the others (10%) exhibited reproductive performance similar to that of non-treated males. The cumulative effects of the precocene on the different stages of reproduction resulted in a drastic reduction of offspring production. The anti-allatal compound precocene seems to inhibit successful reproduction through a corpus allatum inactivation and subsequent lack of secretory activity of the male accessory glands.

Spirura delicata sp. n. (Spiruridae, Spirurinae) from Leontocebus mystax (Callithrichidae) and a check list of other Nematodes of some brazilian primates

Spirura delicata sp. n. from Leontocebus mystax (Six) is proposed and compared to S. guianensis (Ortlepp, 1924) Chitwood, 1938, S. michiganensis Sandground, 1935 and S. nayarani Mirza & Basir, 1938. Their differentiation is based mainly on the size and shape of spicules. Identification of nematode samples recovered from primates along 60 years and presently deposited in the Oswaldo Cruz Helmintological Collection is provided herein through a check list. Some of them are reported in new hsots and/or geographical regions.