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2381. [Article] Role of Peroxisome Proliferator-Activated Receptor Gamma on Prevention/Cure of Mastitis
Mastitis is a major endemic disease in dairy cows resulting in significant economic losses for the dairy industry. The peroxisome proliferator-activated receptor gamma (PPARγ) is a nuclear receptor that ...Citation Citation
- Title:
- Role of Peroxisome Proliferator-Activated Receptor Gamma on Prevention/Cure of Mastitis
- Author:
- Trindade da Rosa, Fernanda
Mastitis is a major endemic disease in dairy cows resulting in significant economic losses for the dairy industry. The peroxisome proliferator-activated receptor gamma (PPARγ) is a nuclear receptor that is able to bind and be activated by natural (e.g., fatty acids) and synthetic (e.g. thiazolidinedione) compounds. PPARγ plays important roles in adipocyte differentiation, inflammation, and re-epithelialization in monogastric. In ruminants, PPARγ may play a role in milk fat synthesis. The aim of this study was to assess the role of PPARγ in host response to mammary infection and milk fat synthesis in ruminants. Our hypothesis is that activation of PPARγ improves the host response to mastitis and increases milk fat yield. By using a synthetic PPARγ agonist in dairy goats in combination with intramammary infection to induce subclinical mastitis, the objectives of the present experiments were to test if activation of PPARγ improves 1) the response to mastitis and 2) milk fat production. To achieve our objectives we performed two in vivo experiments (Experiments 1 and 2). In Experiment 1, 24 Saanen lactating goats with a low body condition score and getting a low-energy diet without vitamin supplementation received a daily intrajugular injection of either 8 mg of 2,4-thiazolidinedione (TZD) per kg of BW or saline (as a control) and, after a week of TZD injection, an intramammary infusion (IMI) of either Streptococcus uberis to induce subclinical mastitis or saline used as a control (6 goats/group). Milk yield and components, body weight, rectal temperature, leukocyte phagocytosis, blood metabolic and inflammation parameters plus insulin, adipocyte size by histology, and expression by RT-qPCR of PPARγ target genes in adipose tissue obtained through biopsy and in mammary epithelial cells (MEC) isolated from milk were assessed. In MEC, expression of CCL2 and IL8 was also measured. Data were analyzed by GLIMMIX of SAS with Mastitis, TZD, and Time and all interactions as main effects and goat as random effect. Statistical significance and tendencies were declared at P < 0.05 and 0.05 ≤ P ≤ 0.10, respectively. The induction of mastitis was successful achieved as indicated by >5-fold increase of milk somatic cells count (SCC) in goats receiving Strep. uberis and by 30% decrease of % polymorphonuclear leukocytes in blood. The SCC in milk were overall lower in TZD-treated goats. Mastitis induction but not TZD decreased milk yield and production of milk fat. Goats receiving Strep. uberis had increased concentrations of glucose, triglycerides, and non-esterified fatty acids (NEFA) in blood after IMI. NEFA was not affected in TZD goats, which did not receive Strep. uberis. Inflammatory markers increased in blood of all goats but the increase of haptoglobin was overall lower in TZD treated goats. Indicators of liver activity, including albumin, paraoxonase, and cholesterol, overall decreased after IMI but cholesterol did not decrease in TZD-treated goats. The bactericidal myeloperoxidase was higher in TZD-treated goats after mastitis. Insulin sensitivity was not affected by TZD or mastitis. Adipocytes size increased over time and was higher in TZD goats not receiving Strep. uberis. Subclinical mastitis increased expression of CCL2 and prevented a decrease in expression of IL8. MEC from TZD-treated goats tended to have higher expression of PPARG, FASN and SCD1 after 3 weeks of TZD treatment. Neither mastitis nor TZD affected the expression of genes in adipose tissue. Overall the data of Experiment 1 indicated that the subclinical mastitis model was successfully achieved. The treatment with TZD decreased somatic cells in milk, improved the response of liver, decreased the severity of inflammation, and increased the killing capacity of neutrophils after IMI. The data suggested a more lipogenic adipose tissue in TZD-treated goats but also some active, although minor, nutrigenomic effect of TZD on MEC that may have counteracted the competition of lipid substrates between mammary and adipose tissue. Blood metabolic data suggested that goats responded to Strep. uberis intramammary infusion similar to dairy cows in negative energy balance. Data obtained from Experiment 1 indicated that TZD aids with mastitis response. TZD had some effect on milk fat synthesis but, overall, had a smaller-than-expected nutrigenomic effect probably also due to the low body condition and low energy in the diet of the goats. Thus, the effect of PPARγ on milk fat synthesis is still unclear. The rationale to perform Experiment 2 stemmed from the possibility that the limited nutrigenomic response observed in Experiment 1 was due to a potential dietary deficiency. Subsequent in vitro work demonstrated that TZD is a strong activator of PPAR but only in the presence of 9-cis-retinoic acid, a metabolite of vitamin A and the activation of PPARγ obligate heterodimer Retinoic-X-Receptor (RXR). Therefore, we hypothesized that continuous activation of PPARγ by TZD in dairy goats supplemented with adequate amount of vitamin A improves the inflammatory response to subclinical mastitis. In order to test this hypothesis we used 12 Saanen multiparous goats in early lactation. Goats received a diet that met the NRC requirements, including vitamin A, and a daily injection of 8 mg TZD per kg of BW (n=6) or saline (n=6; CTRL). Following 14 days of treatment, all goats received an IMI of Strep. uberis to induce subclinical mastitis in the right half of the udder with the left half used as control. Metabolic, inflammation, and oxidative-status profiling in blood including 20 parameters was performed. Milk yield, SCC, rectal temperature and leukocytes phagocytosis were measured. Expression of several PPARγ target genes and genes involved in inflammation was measured in MEC, macrophages isolated from milk, and liver tissue. Data were analyzed by GLIMMIX of SAS with treatment (TRT) and Time and TRTxTime interaction as main effects and goat as random effect. For milk and SCC, mammary half was also included in the main effect (including interactions). Statistical significance and tendencies were declared at P < 0.05 and 0.05 ≤ P ≤ 0.10, respectively. Milk yield decreased after IMI but the decrease was larger in TZD-treated goats. SCC increased after IMI but was not affected by TZD administration. Milk fat decreased after IMI in all halves except in the untreated half of TZD-treated goats. In blood within 2 days from IMI, ceruloplasmin, haptoglobin, and glucose were increased while Zn was decreased. These data confirmed successful induction of sub-clinical mastitis and a status of slight inflammation after IMI. None of the parameters in blood was affected by TZD with the exception of a lower bilirubin concentration and a tendency for higher haptoglobin in TZD vs. CTRL after IMI, indicating a more robust response of the liver to inflammation. The stronger inflammation was also supported by a tendency for higher reactive oxygen metabolites in TZD vs. CTRL group after IMI. We also detected a tendency for a higher globulin in TZD vs. CTRL indicating a better adaptive immune system. Leukocyte phagocytosis was strongly reduced by TZD treatment. None of the genes measured were affected by TZD in liver. In milk macrophages and MEC, expression of inflammatory genes was higher compared to control in halves receiving Strep. uberis, whereas no effect of TZD was observed with the exception of a lower SCD1 in TZD-treated goats compared to CTRL. We conclude that, contrary to our hypothesis, in goats receiving NRC recommended amount of vitamin A, TZD had a minor effect on the response to mastitis with a likely better liver response, but a lower phagocytosis and minor effect on expression of genes. Considering both in vivo experiments, we can conclude that TZD has an important effect on inflammatory response in dairy goats receiving low energy diet without vitamins supplementation but the effect disappears for the most part in goats receiving adequate feeding, including vitamin A. Furthermore, the lack of effects on expression of PPARγ target genes does not support TZD being a strong PPARγ agonist in dairy goats.
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2382. [Article] Security protocols for linear network coding
Network coding, as the next generation of data routing protocols, enables each intermediate node in a network to process and encode its received data before forwarding it to the next nodes. Hence, the ...Citation Citation
- Title:
- Security protocols for linear network coding
- Author:
- Adeli, Majid
Network coding, as the next generation of data routing protocols, enables each intermediate node in a network to process and encode its received data before forwarding it to the next nodes. Hence, the core idea in network coding is to allow a network to encode the data that is being transmitted through it. This revolutionary idea of data routing results in dynamic change in the content of each data packet. That is, in a network coding setting, the original data symbols that are generated at the source nodes evolve hop-by-hop as they travel through the intermediate nodes. This property is clearly in stark contrast with the methods that are used in traditional data routing protocols, where every intermediate node acts as a plain relay. In other words, in the conventional data routing algorithms, every intermediate node solely replicates its incoming data on one or more of its outgoing channels. The criteria and the policies based on which an intermediate node makes decisions about the proper outgoing channels corresponding to each incoming packet depend on the employed routing protocol. Usually, each intermediate node utilizes a set of routing information (such as a routing table) in order to find the most cost effective path or paths to the final destinations. The cost criterion may be defined based on various parameters, but what is fixed is that the general goal is always to find the most optimum route that starts from the node and reaches the final destination at the lowest cost. Upon finding the best output channels, the intermediate node simply copies the pertinent data packet on the optimum channels without inflicting any change in the data payload. This common method of data routing in conventional routing protocols is indeed considered as a very special case in network coding theory. The fact that in network coding every node processes (encodes) its input data to create its outgoing symbols implies that the encoding operation at a given network node can be expressed as a multi-input multi-output function which intakes the node's incoming data symbols as its input arguments and generates the outgoing data symbols departing the node as its outputs. Since each node in the network has its own function, they are called "local encoding function". This way of looking at the network coding operation enables us to simply define linear and nonlinear network coding as the network codes with linear and nonlinear local encoding functions, respectively. Hence, in linear network coding, every node (including the source and the sink nodes) executes a linear function on its incoming data symbols in order to generate its output symbols, while in nonlinear network coding this function is nonlinear. The linearity indicates that every output symbol of a local encoding function can be stated as a unique linear combination of its input symbols. Therefore, in linear network coding, the encoding operations at the intermediate nodes can be stated as matrix multiplications. If linear network coding is applied then each individual network node will have a matrix with known entries and fixed dimensions that represents the network coding operation at that particular node. These matrices will be called "local encoding matrix" in this work, where linear network coding is considered as the employed data routing protocol. The main focus of this thesis is to thoroughly study the security aspects of linear network coding, and propose new ideas and superior solutions for various security challenges that are faced in this class of data routing protocols. In a broad sense, security attacks can be categorized into two major classes: passive attacks and active attacks. In passive attacks (also known as wiretapping or eavesdropping attacks), the attacker threatens the confidentiality aspect of the data; meaning his goal is to obtain illicit access to the content of the data symbols while he is unable or not interested to change (manipulate) the content of the original data symbols. On the other hand, in active attacks (also known as pollution or Byzantine attacks), the attacker threatens the integrity and authenticity of data. That is, while the content of each original data packet is open and visible to everyone (including the attacker), his goal is to change or corrupt the content of data symbols or interrupt the data transmission process by jamming and blocking the flow of data stream in the network. Under assumption of linear network coding being the applied data routing scheme, both of these two attack classes are comprehensively studied in this thesis. Since in linear network coding each and every node in the network mixes up its incoming data to generate its outputs, observing the content of a symbol flowing on a channel usually does not reveal useful information about the original data symbols. This means network coding (and more specifically, linear network coding in our case) offers the network users an inherent and intrinsic level of security which is normally not an option when traditional store-and-forward data routing protocols are employed. In some cases and for some basic applications, this inherent security is enough; however, for many security-aware and sensitive applications that demand tighter security provisions, additional modifications to the base coding scheme are necessary in order to provide higher levels of security. In Chapter 2, six innovative security protocols that are tailored to effectively and efficiently counteract passive attackers in linear network coding are proposed. The solutions proposed in this chapter may be categorized in three main groups. Two protocols (A and B) are designed solely based on the intrinsic security feature of linear network coding. Protocol (A) requires each global encoding vector that is assigned to one of the network channels to have more than one nonzero entry. This stipulation is shown to be satisfied probabilistically with a probability that drastically approaches "1" as the code field, network capacity, or attacker's limitations increase. Protocol (B) is based on re-ordering the original message vector before sending it through the network. The re-ordering process is designed to elaborately scramble the message vector content in such a way that no additional function is required, yet by sending the scrambled message vector, the eavesdropper will not be able to obtain any information about any of the original data symbols. The sink nodes are the only nodes that are able to de-scramble the data and recover the original message vector. Both of these two protocols are extremely light-weight with no throughput reduction. The second group of our security solutions includes two protocols (C and E), each of which utilizes a hash function and a noisy symbol at the source node in order to generate the required random symbols (masking symbols) that are used to conceal the data symbols in the secured message vector. These protocols reduce the data rate by only one unit while they assume very lax conditions on the attacker's ability in accessing the independent network channels. The offered independency between the number of attacked channels and the secure data rate, and also enabling the source node to independently create its own keys and to change them as often as it generates new data packets are two of the remarkable properties of these protocols. The two remaining protocols (D and F) constituting the third group are in fact two variations of the second group protocols. That is, in order to alleviate the computational complexity burden of the algorithms in the second group, the hash functions are substituted by simple light-weight bijective functions in these protocols. Hence, in addition to all the benefits of the algorithms in the second group, these two protocols are also very fast and easy to implement. The fact that in (linear) network coding data symbols are constantly mixed up and intermingled as they travel through the network is indeed a double-edged sword. That is, as mixing and combining the data symbols provides some degree of security against snooping attackers (and this is besides the other advantages of network coding), if a malicious node injects some bogus or invalid data into the main data stream, then the inflicted pollution propagates throughout the network at an enormously great rate and causes the final destination nodes to be unable to recover the original data symbols. This class of attacks in linear network coding (i.e., pollution attacks) is studied in Chapter 3, where we propose a very efficient hierarchical scheme that is able to accurately pinpoint any number of polluting nodes in the network with any locational distribution. Our protocol is also capable of isolating and disconnecting the violating nodes from the rest of the network and therefore fixing the pollution problem in a more fundamental way.
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California's Central Valley agricultural landscapes provide several important wintering regions for Pacific Flyway sandhill crane (Grus canadensis) populations; however, the value of those regions is being ...
Citation Citation
- Title:
- Comparative wintering ecology of two subspecies of sandhill crane : informing conservation planning in the Sacramento-San Joaquin River Delta region of California
- Author:
- Ivey, Gary L.
California's Central Valley agricultural landscapes provide several important wintering regions for Pacific Flyway sandhill crane (Grus canadensis) populations; however, the value of those regions is being compromised by urban expansion, other developments, and conversions to incompatible crop types. Greater (G. c. tabida) and lesser sandhill cranes (G. c. canadensis) both have special conservation status in California; the greater is listed as threatened and the lesser as a bird species of conservation concern by the state. However, basic information about their wintering ecology has been lacking to design biologically sound conservation strategies to maintain their wintering habitats. My study of sandhill cranes focused on one major Central Valley wintering region, the Sacramento-San Joaquin River Delta (Delta). I compared daily movements and winter site fidelity between the two sandhill crane subspecies, evaluated the timing of crane arrival and departure from the region, assessed foraging habitat choices, measured abundance and distribution in the Delta, documented the characteristics of roost sites, and developed habitat conservation models and decision tools for managers to facilitate habitat conservation and management. Both crane subspecies showed strong fidelity to my Delta study area. Foraging flights from roost sites were shorter for greaters than lesser (1.2 ± 0.4 km vs. 3.1 ± 0.1 km, respectively) and consequently, mean size of 95% fixed kernel winter home ranges was an order of magnitude smaller for greaters (1.9 ± 0.4 km² vs.21.9 ± 1.9 km², respectively). The strong site fidelity of greaters to roost complexes within landscapes in the Delta indicates that conservation planning targeted at maintaining and managing for adequate food resources around traditional roost sites can be effective for meeting sandhill crane habitat needs, while the scale of conservation differs by subspecies. I recommend that conservation planning actions consider all habitats within 5 km of a crane roost as a sandhill crane conservation "ecosystem unit." This radius encompasses 95% and 69% of the flights from roosts to foraging location (commuting flights) made by greaters and lessers, respectively. For lessers, a conservation radius of 10 km would encompass 90% of the commuting flights. Management, mitigation, acquisition, easement, planning, and farm subsidy programs intended to benefit cranes will be most effective when applied at these scales. Within these radii, conservation and management of wintering habitats should include creating both new roost and feeding areas to ensure high chances of successful use. Sandhill cranes used major crops and habitat types available in the landscapes surrounding their roost sites and focused most of their foraging in grain crops. They generally avoided dry corn stubble, selected dry rice stubble early in the season, and rarely used dry wild rice stubble. Tilled fields were also usually avoided but were occasionally used shortly after tillage. Mulched corn ranked high in comparison to other corn treatments while mulched rice use was used similarly to dry rice stubble. Both subspecies often highly favored cropland habitats when they were initially flooded. Cranes were attracted to new plantings of pasture and winter wheat. One important difference between the subspecies was that lessers used alfalfa which was generally avoided by greaters. Dry corn stubble was avoided while dry rice stubble was favored early in winter. If wildlife managers want to encourage winter field use by cranes they could provide incentives for favorable practices such as production of grain crops, reduction or delaying tillage and flooding of grain fields, provision of irrigations to some crop types, and increasing the practice of mulching of corn stubble. Of the 69 crane night roosts I identified, 35 were flooded cropland sites and 34 were wetland sites. I found that both larger individual roost sites and larger complexes of roost sites supported larger peak numbers of cranes. Water depth used by roosting cranes averaged 10 cm (range 3-21 cm, mode 7 cm) and was similar between subspecies. Roosting cranes avoided sites that were regularly hunted or had high densities (i.e., > 1 blind/5 ha) of hunting blinds. Roost site design and management should consider providing and maintaining large roost complexes (100 - 1000 ha) ideally in close proximity (< 5 km) to other roost sites, with large individual sites (> 5 ha) of mostly level topography, dominated by shallow water (5-10 cm depths). The fact that cranes readily use undisturbed flooded cropland sites makes this a viable option for creation of roost habitat. Because hunting disturbance can limit crane use of roost sites I suggest these two uses should not be considered compatible. However, if the management objective of an area includes waterfowl hunting, limiting hunting at low blind densities (i.e., < 1 blind/60 ha) and restricting hunting to early morning may be viable options for creating a crane-compatible waterfowl hunt program. Radio-marked sandhill cranes arrived in the Delta beginning 3 October, most arrived in mid-October, and the last radio-marked sandhill crane arrived on 10 December. Departure dates ranged from 15 January to 13 March. Mean arrival and departure dates were similar between subspecies. From mid-December through early-February in 2007-2008, the Delta population ranged from 20,000 to 27,000 sandhill cranes. Abundance varied at the main roost sites during winter, likely because sandhill cranes responded to changes in water and foraging habitat conditions. Sandhill cranes used an area of approximately 1,500 km² for foraging. Estimated peak abundance in the Delta was more than half the total number counted on recent Pacific Flyway midwinter surveys, indicating the Delta region is a key area for efforts in conservation and recovery of wintering sandhill cranes in California. Based on arrival dates, flooding of sandhill crane roost sites should be staggered with some sites flooded in early September and most sites flooded by early October. Maintaining flooding of at least some roost sites through mid-March would provide essential roosting habitat until most birds have departed the Delta region on spring migration. Not all 5-km radius ecosystem units are equal in their value to greater sandhill cranes, and the relative foraging value of a particular parcel within an ecosystem unit depends on the numbers of cranes using the focal roost site, the habitat choices they make, and the probability that they will fly to a particular parcel. Additionally, some ecosystem units overlap, and in these overlap zones, the probability of crane use is higher, because of additive effects. To provide a tool to allow managers to further refine management plans, I developed a model which allows more specific focus of crane conservation, mitigation and habitat management, using what my study revealed about greater sandhill cranes. This model considers the abundance of greaters at individual roost sites and the probability that they would fly to a given location. Sites closer to roosts had a higher probability of crane use. I calculated the probability that greaters would fly to a parcel within concentric 1-km intervals as a product of the proportion of commuting flights of individuals that reached that interval, and the proportion of all commuting flights that reached that interval. Within crane ecosystem units, it is important to protect the existing habitat from further loss and optimize foraging conditions for cranes. I provide a decision matrix to assist with plans to enhance existing crane landscapes, create new crane habitat areas or mitigate habitat losses. This matrix provides a framework for decision-making regarding enhancing sandhill crane foraging and roost site habitats. Wildlife managers could employ a variety of tools to conserve and manage crane habitats, including fee title acquisitions, private conservation easements, and specific cropland management actions to maintain crane-compatible conditions and high food values for cranes (possibly including providing unharvested food plots). My study has demonstrated that most cranes use a relatively small landscape surrounding their traditional roost sites and that they favor certain crops and post-harvest crop management practices for foraging. However, we need a better understanding of the actual carrying capacity for cranes in these crane management zones to ensure that managers can maintain these sites for cranes in the future.