The importance of fisheries and aquaculture production for nutrition and food security.

Aquatic food has a significant role to play in global nutrition and food security but is often ignored in that debate. Understanding its potential role is made difficult by the fact that aquatic food covers a large number of species which come from both capture fisheries and aquaculture and the marine and freshwater environments, including finfish, crustacea, molluscs, echinoderms, aquatic plants and other aquatic animals. Further complications arise from the fact that both supply and consumption vary significantly between countries. There are several criteria which need to be considered when discussing nutrition and food security. These include: how much food is produced, whether that production is sustainable, whether the production supports livelihoods, what the nutritional content of the food is and whether that food is safe. The authors conclude that there are many benefits to aquatic food under each of these criteria but there are also some hurdles which need to be overcome. Increased production to feed a growing global population relies on the growth of aquaculture. Challenges to such growth include the supply of raw ingredients for aquafeeds, losses due to disease outbreaks, being able to ensure high standards of food safety and overcoming environmental limitations to expansion. There are also problems with welfare conditions for people working in the supply chain which need to be addressed. Given the challenges to nutrition and food security which the world is currently facing, it is essential that aquatic food is brought into the debate and the significant benefits that aquatic foods provide are acknowledged and exploited.

Les denrées alimentaires d'origine aquatique contribuent de manière significative à la sécurité nutritionnelle et alimentaire mondiale ; or, elles sont souvent ignorées dans les discussions sur le sujet. Il est d'autant plus difficile de se faire une idée exacte de la contribution potentielle des aliments d'origine aquatique que ceuxci recouvrent un grand nombre d'espèces provenant aussi bien des pêches de capture que de l'aquaculture et issues de milieux tant marins que d'eau douce, comme les poissons, les crustacés, les mollusques, les échinodermes, mais aussi la flore aquatique et bien d'autres espèces d'animaux aquatiques. À ces difficultés s'ajoutent celles liées aux variations importantes de l'offre et de la consommation de ces denrées suivant les pays. Un certain nombre de critères sont à examiner lorsqu'on traite des questions de sécurité nutritionnelle et alimentaire. Il convient notamment d'examiner les quantités d'aliments produites, le caractère durable ou non de chaque production, son rôle dans l'économie de subsistance, le contenu nutritionnel des aliments et leur innocuité. Les auteurs concluent que si les aliments d'origine aquatique présentent nombre d'avantages au regard de chacun de ces critères, des obstacles subsistent auxquels il convient de remédier. Les possibilités de produire davantage d'aliments afin de nourrir une population mondiale toujours plus nombreuse sont tributaires de la croissance de l'aquaculture. Cette croissance est limitée par divers facteurs, notamment la disponibilité des matières premières utilisées pour l'alimentation des espèces aquatiques, les pertes dues aux maladies, la nécessité de garantir un niveau élevé de sécurité sanitaire des aliments à travers des normes appropriées et la capacité de résoudre les contraintes environnementales liées à cette expansion. Il faut également apporter une réponse aux problèmes de bien-être professionnel dans la filière. Compte tenu des défis posés par la sécurité nutritionnelle et alimentaire au niveau mondial, il est essentiel d'inscrire les aliments d'origine aquatique à l'ordre du jour des discussions afin que les avantages significatifs de ces productions soient reconnus et exploités.

Aunque revisten importancia para la seguridad nutricional y alimentaria del mundo, los alimentos de origen acuático son a menudo los grandes olvidados de los debates en la materia. La dificultad de aprehender la posible función de estos alimentos estriba en el hecho de que abarcan un gran número de especies procedentes tanto de la pesca de captura como de la acuicultura y de medios tanto marinos como de agua dulce: peces, crustáceos, moluscos, equinodermos y otros animales acuáticos, así como también plantas acuáticas. La cuestión resulta tanto más compleja cuanto que el suministro y el consumo difieren sensiblemente de un país a otro. Existen varios criterios que conviene tener en cuenta al reflexionar sobre cuestiones de seguridad nutricional y alimentaria, entre ellos los siguientes: qué cantidad de alimento se produce; el carácter sostenible o insostenible de la producción; el hecho de que la producción forme parte o no de los medios de subsistencia; el contenido nutricional de los alimentos; o el nivel de inocuidad que estos ofrecen. Los autores llegan a la conclusión de que, a la luz de cada uno de estos criterios, los alimentos acuáticos aportan muchos beneficios, pero también presentan una serie de problemas que es preciso resolver. El logro de una mayor producción destinada a alimentar a la creciente población mundial reposa en el crecimiento de la acuicultura, crecimiento que está sujeto a limitaciones como el aprovisionamiento en ingredientes para los piensos destinados a animales acuáticos, las pérdidas causadas por brotes infecciosos, el cumplimiento de criterios estrictos de inocuidad de los alimentos o la posibilidad, o no, de superar los límites que el medio ambiente impone a la expansión de la actividad. También hay problemas ligados a las condiciones de bienestar de los trabajadores de la cadena de suministro que es preciso abordar. En vista de los problemas de seguridad nutricional y alimentaria a los que ahora mismo hace frente el mundo, es indispensable integrar los alimentos acuáticos en los procesos de debate y reflexión y saber reconocer y aprovechar los importantes beneficios que traen consigo.

Past and future perspectives on mathematical models of tick-borne pathogens.

Ticks are vectors of pathogens which are important both with respect to human health and economically. They have a complex life cycle requiring several blood meals throughout their life. These blood meals take place on different individual hosts and potentially on different host species. Their life cycle is also dependent on environmental conditions such as the temperature and habitat type. Mathematical models have been used for the more than 30 years to help us understand how tick dynamics are dependent on these environmental factors and host availability. In this paper, we review models of tick dynamics and summarize the main results. This summary is split into two parts, one which looks at tick dynamics and one which looks at tick-borne pathogens. In general, the models of tick dynamics are used to determine when the peak in tick densities is likely to occur in the year and how that changes with environmental conditions. The models of tick-borne pathogens focus more on the conditions under which the pathogen can persist and how host population densities might be manipulated to control these pathogens. In the final section of the paper, we identify gaps in the current knowledge and future modelling approaches. These include spatial models linked to environmental information and Geographic Information System maps, and development of new modelling techniques which model tick densities per host more explicitly.

GIS-ODE: linking dynamic population models with GIS to predict pathogen vector abundance across a country under climate change scenarios.

Mechanistic mathematical models such as ordinary differential equations (ODEs) have a long history for their use in describing population dynamics and determining estimates of key parameters that summarize the potential growth or decline of a population over time. More recently, geographic information systems (GIS) have become important tools to provide a visual representation of statistically determined parameters and environmental features over space. Here, we combine these tools to form a 'GIS-ODE' approach to generate spatiotemporal maps predicting how projected changes in thermal climate may affect population densities and, uniquely, population dynamics of Ixodes ricinus, an important tick vector of several human pathogens. Assuming habitat and host densities are not greatly affected by climate warming, the GIS-ODE model predicted that, even under the lowest projected temperature increase, I. ricinus nymph densities could increase by 26-99% in Scotland, depending on the habitat and climate of the location. Our GIS-ODE model provides the vector-borne disease research community with a framework option to produce predictive, spatially explicit risk maps based on a mechanistic understanding of vector and vector-borne disease transmission dynamics.

The impact of increased dispersal in response to disease control in patchy environments.

This paper uses a mathematical framework to investigate the impact of increased movement in response to disturbance caused by disease control strategies. Implementation of invasive disease control strategies such as culling may cause species to disperse beyond their natural range, thus aiding the spread of infection to otherwise infection free areas. Both linear and non-linear dispersal functions are compared with constant per capita dispersal in a coupled two patch SI model. For highly virulent or infrequently transmitted pathogens, it is found that an increase of dispersal due to control requires a higher level of disease control than in the constant dispersal model. Patches which may be sources or reservoirs of infection are investigated and it is found that if dispersal increases in response to control, then all patches, reservoir or not, must be targeted. The single host two patch model is then extended to a two host wildlife/livestock system with one species 'wildlife' free to move between patches and the other 'livestock' confined. In the two host case, control of one species alone will only achieve successful pathogen exclusion if that species is a reservoir for infection.

An alternative to killing? Treatment of reservoir hosts to control a vector and pathogen in a susceptible species.

Parasite-mediated apparent competition occurs when one species affects another through the action of a shared parasite. One way of controlling the parasite in the more susceptible host is to manage the reservoir host. Culling can cause issues in terms of ethics and biodiversity impacts, therefore we ask: can treating, as compared to culling, a wildlife host protect a target species from the shared parasite? We used Susceptible Infected Recovered (SIR) models parameterized for the tick-borne louping ill virus (LIV) system. Deer are the key hosts of the vector (Ixodes ricinus) that transmits LIV to red grouse Lagopus lagopus scoticus, causing high mortality. The model was run under scenarios of varying acaricide efficacy and deer densities. The model predicted that treating deer can increase grouse density through controlling ticks and LIV, if acaricide efficacies are high and deer densities low. Comparing deer treated with 70% acaricide efficacy with a 70% cull rate suggested that treatment may be more effective than culling if initial deer densities are high. Our results will help inform tick control policies, optimize the targeting of control methods and identify conditions where host management is most likely to succeed. Our approach is applicable to other host-vector-pathogen systems.

A model to test how ticks and louping ill virus can be controlled by treating red grouse with acaricide.

Ticks are the most important vectors of disease-causing pathogens in Europe. In the U.K., Ixodes ricinus L. (Ixodida: Ixodidae) transmits louping ill virus (LIV; Flaviviridae), which kills livestock and red grouse, Lagopus lagopus scoticus Lath. (Galliformes: Phasianidae), a valuable game bird. Tick burdens on grouse have been increasing. One novel method to reduce ticks and LIV in grouse may be acaricide treatment. Here, we use a mathematical model parameterized with empirical data to investigate how the acaricide treatment of grouse might theoretically control ticks and LIV in grouse. Assuming a situation in which ticks and LIV impact on the grouse population, the model predicts that grouse density will depend on deer density because deer maintain the tick population. In low deer densities, no acaricide treatment is predicted to be necessary because abundances of grouse will be high. However, at higher deer densities, the model predicts that grouse densities will increase only if high numbers of grouse are treated, and the efficacy of acaricide is high and lasts 20 weeks. The qualitative model predictions may help to guide decisions on whether to treat grouse or cull deer depending on deer densities and how many grouse can be treated. The model is discussed in terms of practical management implications.

Stocking methods and parasite-induced reductions in capture: modelling Argulus foliaceus in trout fisheries.

Argulus foliaceus is a macroparasite which can have a significant impact on yield in recreational trout fisheries, partly by increasing fish mortalities but also by reducing the appetite of infected fish, making them less likely to respond to bait. The aim of this paper is to determine the impact of four commonly used fish stocking methods both on the parasite dynamics, and on fisheries' yields. The wider consequences of the resultant reduction in host feeding are also of interest. To this end four different stocking methods were incorporated into Anderson and May's macroparasite model, which comprises three differential equations representing the host, attached parasite and free-living parasite populations. To each of these a reduction in the fish capture rate, inversely linked to the mean parasite burden, is added and the effects interpreted. Results show that (1) the common practise of increasing the stocking rate as catches drop may be counterproductive; (2) in the absence of any wild population of reservoir hosts, the parasite will be unable to survive if the stocking rate does not exceed the rate of capture; (3) compensatory stocking to account for fish mortalities can have disastrous consequences on yield; and (4) the parasite can, under certain circumstances, maintain the host population by preventing their capture.

Linkage between obesity and a marker near the tumor necrosis factor-alpha locus in Pima Indians.

Because tumor necrosis factor-alpha (TNF-alpha) expression is increased in adipose tissue of both rodent models of obesity and obese humans, it has been considered as a candidate gene for obesity. Pima Indians were scored for genotypes at three polymorphic dinucleotide repeat loci (markers) near the gene TNF-alpha at 6p21.3. In a sib-pair linkage analysis, percent body fat, as measured by hydrostatic weighing, was linked (304 sib-pairs, P = 0.002) to the marker closest (10 kb) to TNF-alpha. The same marker was associated (P = 0.01) by analysis of variance with BMI. To search for possible DNA variants in TNF-alpha that contribute to obesity, single stranded conformational polymorphism analysis was performed from 20 obese and 20 lean subjects. Primer pairs were designed for the entire TNF-alpha protein coding region and part of the promoter. Only a single polymorphism located in the promoter region was detected. No association could be demonstrated between alleles at this polymorphism and percent body fat. We conclude that the linkage of TNF-alpha to obesity might be due to a sequence variant undetected in TNF-alpha or due to a variant in some other closely linked gene.

The effect of seasonal host birth rates on disease persistence.

In this paper, we add seasonality to the birth rate of an SIR model with density dependence in the death rate. We find that disease persistence can be explained by considering the average value of the seasonal term. If the basic reproductive ratio R(0)>1 with this average value then the disease will persist and if R(0)<1 with this average value then the disease will die out. However, if the underlying non-seasonal model displays oscillations towards the equilibrium then the dynamics of the seasonal model can become more complex. In this case, the seasonality can interact with the underlying oscillations, resonate and the population can display a range of complex behaviours including chaos. We discuss these results in terms of two examples, Cowpox in bank voles and Rabbit Haemorrhagic disease in rabbits.

A common variant in PPP1R3 associated with insulin resistance and type 2 diabetes.

Selected candidate genes have been analyzed in the Pima Indians of Arizona based on evidence that insulin resistance and type 2 diabetes have significant genetic determinants. An amino acid substitution at codon 905 of the glycogen-targeting subunit of type 1 protein phosphatase that regulates skeletal muscle glycogenesis was recently reported to be associated with changes in insulin action in Danish subjects. In addition to the variant at 905, we report here a novel substitution at codon 883 and common variant of an "ATTTA" element in the 3'-untranslated region (UTR) of the corresponding gene (PPP1R3). The 3'-UTR variant resembled the mRNA-destabilizing AT(AU)-rich elements (AREs) and resulted in a 10-fold difference in reporter mRNA half-life, was correlated with PPP1R3 transcript and protein concentrations in vivo, and was associated with insulin resistance and type 2 diabetes in the Pimas. The variant is more common in Pimas (0.56) than in Caucasians (0.40). Because of its apparent effect on expression of PPP1R3, it may, in part, contribute to the higher prevalence of type 2 diabetes in this Native American population.

Absence of linkage of obesity and energy metabolism to markers flanking homologues of rodent obesity genes in Pima Indians.

The homologues of single genes that cause obesity in rodents are suggested as candidate genes for modulation of body composition in humans. Among these genes are the four mouse mutations-diabetes (db), obesity (ob), tubby (tub), and yellow agouti (Ay). Variation in the human counterparts to these genes (OB, DB, TUB, and ASP, respectively) may contribute to human obesity, which is thought to have a substantial genetic component. To initially assess the potential contribution of these genes to human obesity, we examined polymorphic DNA markers that, by virtue of syntenic relationships to appropriate regions of the mouse genome, should be closely linked to the human counterparts of these genes. Using combined data from 716 Pima Indians comprising 217 nuclear families, we have tested a number of polymorphic microsatellite markers (three at DB, two at OB, five at TUB, and three at ASP) for sib-pair linkage to BMI, percentage body fat, resting metabolic rate, 24-h energy expenditure, and 24-h respiratory quotient. No significant linkages were found in an analysis of all sibships or in an analysis restricted to discordant sib pairs.

Activity variants of acid phosphatase-3 among chromosome 3 inversions of Drosophila pseudoobscura.

Allozymes of the Ap-3 locus in Drosophila pseudoobscura show very strong associations with chromosome 3 inversions. The 0.98 electrophoretic allele is associated with The TL, SC, CH and PP gene arrangements, while the 1.00 electrophoretic allele is characteristic of the AR and ST gene arrangements. Variation in relative 0.98 and 1.00 AP-3 allozyme activities of chromosome 3 isogenic strains was examined on acrylamide gels in F1 heterozygotes obtained by crossing these strains individually to a reference strain with a slower 0.87 mobility allozyme. F2 analyses demonstrated that the activity variants co-segregate with the Ap-3 locus. Both 0.98 and 1.00 allelic classes are polymorphic for AP-3 activities. In contrast to the virtual monomorphism for an electrophoretic allele, each inversion is polymorphic for AP-3 activities. These results reveal substantially more genetic differentiation among gene arrangements than is evident from electrophoretic allele comparisons. Strains having the PP arrangement are distinct from TL strains in their AP-3 activity expression, and ST strains have a wider range of variation than AR strains. In contrast, no geographical differentiation is evident for strains from the Bogota population of D. pseudoobscura.

Developmental variation in amylase allozyme activity associated with chromosome inversions in Drosophila persimilis.

The amylase locus in Drosophila persimilis is polymorphic for allozymes, two of which show associations with naturally occurring chromosome 3 inversions. Amy1.09 occurs at high frequencies only in Whitney (WT), while the other common arrangements-Standard (ST), Klamath (KL) and Mendocino (MD)-are predominantly Amy 1.00. We have examined numerous strains, representing various electromorphs and inversions, for variation in cis-specific activity expression in both third-instar larvae and adults. Comparisons of these two life stages also allows the survey of developmental variation in amylase activities. The amount of activity variation exceeds electrophoretic variation at this locus. Moreover, this variation is largely nonrandom and reveals more genic divergence among inversions. The 1.00 allozyme of MD is more active than 1.00 KL in larvae and adults and shows a different developmental pattern. The activity of the 1.00 allozyme of KL is greater than 1.00 allozyme of ST in larvae and adults, but these two arrangements have similar developmental patterns. WT 1 with a 1.00 allele is dramatically different from the 1.00 allozymes of other arrangements in its developmental pattern. The 1.09 allozymes has high activity in WT and KL, but these arrangements differ in their developmental pattern of expression, WT being more active in adults. F2 segregational analyses are consistent with the variation being due to either structural enzyme variants or closely linked cis-acting regulatory elements. We argue that the suppression of recombination between arrangements has allowed the divergence in amylase activity among inversions.

Variation in activities of amylase allozymes associated with chromosome inversions in Drosophila pseudoobscura, D. persimilis and D. miranda.

Different electrophoretic alleles of amylase show associations with particular chromosome 3 inversions in D. pseudoobscura and D. persimilis. Relative adult amylase activities were compared in 37, 37 and 10 strains of D. pseudoobscura, D. persimilis and D. miranda, respectively. Strains carrying the same electrophoretic allele were compared by crossing these lines individually to a reference strain carrying a different electrophoretic mobility allele. This procedure allows comparisons among species, inversions, electromorphs and strains for genetic variation in amylase activity. F2 analysis established that the activity variation co-segregates with the structural amylase locus. This type of variation could be due to either structural gene differences or differences in closely linked, cis-acting regulatory regions. Variation has been detected among and within electrophoretic mobility classes. Moreover, this variation is clearly nonrandom and reveals more of the genetic structure associated with the chromosomal inversion phylogeny of D. pseudoobscura and D. persimilis. ----Some of the findings are: (1) Similar electromorphs in D. pseudoobscura and D. persimilis usually show different activities. These species show nearly complete differentiation of amylase alleles, based on activities. (2) D. persimilis has the broadest range of variation in amylase activity, about four-fold between the highest and lowest alleles. D. pseudoobscura and D. miranda are also polymorphic for activity, but have more constrained ranges of variation. D. miranda alleles show on the average about four times the activity of D. pseudoobscura alleles. (3) Some association of electrophoretic mobility and activity has been found. Alleles 1.09 of D. persimilis, as well as 1.43 and 1.55 of D. miranda, have relatively high activity. It may be that these high activity alleles are part of an adaptation to cooler habitats. (4) Within electrophoretic classes, associations of activities with inversions have been found. These are especially strong in D. persimilis. The 1.00 alleles in the ST, KL, MD and WT inversions, the 0.92 allele in the ST and MD inversions and the 1.09 allele in the WT and KL inversions have levels of activities that depend upon the arrangement in which they are located. These results demonstrate that suppression of recombination in inversion heterokaryotypes can result in extensive genic divergence between inversions.

Distinctions among allelic variants associated with chromosome 3 inversions in Drosophila pseudoobscura and Drosophila persimilis.

Efforts were made to discriminate new genetic variants among electrophoretic alleles that are associated with chromosome 3 inversions of Drosophila pseudoobscura and D. persimilis. Apparent genetic similarities for electrophoretic alleles between these two species and among the common inversions they carry were reexamined by altering gel concentration and buffer pH. At the amylase locus, the 1.09 electrophoretic allele could be further separated into two allelic classes that differentiated the WT and KL arrangements. Similarly, the 0.84 electrophoretic allele was divided into two allelic classes, one characteristic of the Santa Cruz phylad arrangements, TL and SC, and the other found in strains of the Standard phylad arrangements and CH. Uncommon amylase alleles proved to be different alleles in the two species. No new allelic variants, however, could be found among strains with the amylase 1.00 allele, the commonest allele in the Standard phylad of both species. No major new allelic variation was detected for acid phosphatase-3 and larval protein-10 that revealed any further differentiation among species or inversions. Variation at all three loci in strains of the Bogota population remained genetically similar to variation in strains of mainland D. pseudoobscura.

Genetic variability of flight metabolism in Drosophila melanogaster. II. Relationship between power output and enzyme activity levels.

The major goal of the studies reported here was to determine the extent to which genetic variation in the activities of the enzymes participating in flight metabolism contributes to variation in the mechanical power output of the flight muscles in Drosophila melanogaster. Isogenic chromosome substitution lines were used to partition the variance of both types of quantitative trait into genetic and environmental components. The mechanical power output was estimated from the wingbeat frequency, wing amplitude and wing morphology of tethered flies by applying the aerodynamic models of Weis-Fogh and Ellington. There were three major results. (1) Chromosomes sampled from natural populations provide a large and repeatable genetic component to the variation in the activities of most of the 15 flight metabolism enzymes investigated and to the variation in the mechanical power output of the flight muscles. (2) The mechanical power output is a sensitive indicator of the rate of flight metabolism (i.e., rate of oxygen consumption during tethered flight). (3) In spite of (1) and (2), no convincing cases of individual enzyme effects on power output were detected, although the number and sign of the significant enzyme-power correlations suggests that such effects are not totally lacking.

Expression of the genes encoding myelin basic protein and proteolipid protein in human malignant gliomas.

Pathological differentiation of oligodendroglioma and mixed oligoastrocytoma from astrocytoma is difficult, relying on morphological characteristics due to the lack of reliable immunohistochemical stains. Oligodendrocytes, the presumed cell of origin of oligodendrogliomas, highly express the genes encoding myelin basic protein (MBP) and proteolipid protein (PLP). We analyzed the expression of these genes to determine whether they might be useful molecular markers of oligodendrocytic tumors. MBP and PLP were highly expressed in all oligodendrogliomas and minimally expressed in glioblastomas multiforme. MBP was highly expressed in mixed oligoastrocytomas, whereas PLP expression was minimal. The association between tumor classification and expression of the MBP and PLP genes was statistically significant. Expression of these genes may serve as a useful molecular marker for some subtypes of human gliomas.

Continuous monitoring of arterial pressure indicates sinoaortic denervated rats are not hypertensive.

The mean arterial pressure (MAP) of nine sinoaortic denervated (SAD) and eight control rats housed in standard-sized metabolic cages was determined continuously via aortic cannulae and computerized data collection over 24 hours. These continuous measurements were compared with direct, mean aortic pressure measurements and indirect, tail-cuff systolic pressure determinations made while these rats were resting in a Lucite restrainer. Denervated rats were studied 1 month after debuffering. Both types of measurements made during restraint indicated that the SAD rats were hypertensive; the MAP averaged 145 +/- 3.4 mm Hg (mean +/- SEM) in SAD rats compared with 119 +/- 2.8 mm Hg in the control group (p less than 0.001), and the tail-cuff pressure in SAD rats was 156 +/- 5.4 vs 121 +/- 2.7 mm Hg in control rats (p less than 0.001). In contrast, continuous monitoring showed that the SAD rats were normotensive; the MAP averaged 119 +/- 4.7 mm Hg in the SAD group and 119 +/- 3.1 mm Hg in the control group. Denervation increased pressure lability; the average 24-hour standard deviation of MAP was 19.0 +/- 1.2 mm Hg in SAD rats vs 8.0 +/- 0.7 mm Hg in control rats (p less than 0.001). Apparently, arterial pressure is elevated during restraint in SAD rats because buffering by the baroreceptor reflex is absent, and pressure measurements made under these conditions give a false indication of hypertension.

Role of the renal nerves in one-kidney, one clip hypertension in rats.

The effects of renal denervation on the onset and maintenance of one-kidney, one clip Goldblatt (1K1C) hypertension were determined. Renal denervation was performed at the time of 1K1C surgery, and was repeated at 3-week intervals to prevent renal nerve regeneration. Denervation delayed the onset of 1K1C hypertension by about 5 weeks, but the final hypertensive state was unaltered. Mean arterial pressure (MAP) averaged 196 +/- 11.4 mm Hg in six rats at 9 weeks after 1K1C surgery and 194 +/- 11.3 mm Hg in eight renal-denervated rats at this time. The delay in the development of 1K1C hypertension following renal denervation could not be explained by interference with renin release. This delay in the development of hypertension could be prevented, however, in renal-denervated 1K1C rats by substituting saline for the drinking water. Two weeks after 1K1C surgery and a high sodium diet, MAP averaged 164 +/- 6.4 mm Hg in eight rats rats with intact renal nerves and 173 +/- 4.8 mm Hg in nine renal-denervated rats. Intact renal nerves are not necessary for the development or maintenance of 1K1C hypertension. Renal denervation delays development of 1K1C hypertension, possibly by delaying the ability of these rats to retain sodium.

Mechanisms of partial renal infarct hypertension.

Contributions of both the renin-angiotensin and immune systems to the aetiology of renal infarct hypertension were examined in Sprague-Dawley rats. Partial renal infarction was produced by ligating and sectioning two out of three branches of the left renal artery. The right kidney remained intact. Renal infarction resulted in rapid development of stable hypertension. One week following infarction, the plasma renin activity (PRA) increased more than threefold. However, PRA returned to control levels 4 weeks after infarction. Chronic immunosuppressive therapy with cyclophosphamide at most only attenuated the development of renal infarct hypertension associated with this transient renin elevation. However, cyclophosphamide prevented the later maintenance phase of the hypertension, and could also completely reverse established infarct hypertension. Activation of the renin-angiotensin system plays a role in the onset of partial renal infarct hypertension, but an intact immune system is required for maintenance of the hypertension. It is hypothesized that immunological reactions against renal tissue maintain renal infarct hypertension.