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J Cortés

Publications and source records attributed to J Cortés.

At least 37 records · Page 2Linked to original sources
PubMed2001

Mollusks of Manuel Antonio National Park, Pacific Costa Rica.

The mollusks in Manuel Antonio National Park on the central section of the Pacific coast of Costa Rica were studied along thirty-six transects done perpendicular to the shore, and by random sampling of subtidal environments, beaches and mangrove forest. Seventy-four species of mollusks belonging to three classes and 40 families were found: 63 gastropods, 9 bivalves and 2 chitons, during this study in 1995. Of these, 16 species were found only as empty shells (11) or inhabited by hermit crabs (5). Forty-eight species were found at only one locality. Half the species were found at one site, Puerto Escondido. The most diverse habitat was the low rocky intertidal zone. Nodilittorina modesta was present in 34 transects and Nerita scabricosta in 30. Nodilittorina aspera had the highest density of mollusks in the transects. Only four transects did not clustered into the four main groups. The species composition of one cluster of transects is associated with a boulder substrate, while another cluster of transects associates with site. Two clusters were not associated to any of the factors recorded. Some species were present in previous studies but absent in 1995, while others were absent in the previous studies but found in 1995. For example, Siphonaria gigas was present in 1995 in many transects with a relatively high density, but absent in 1962, probably due to human predation before the establishment of the park. Including this study, a total of 97 species of mollusks in three classes and 45 families have been reported from Manuel Antonio National Park. Sixty-nine species are new reports for the area: 53 gastropods, 14 bivalves and 2 chitons. There are probably more species of mollusks at Manuel Antonio National Park, than the 97 reported here, because some areas have not been adequately sampled (e.g., deep environments) and many micro-mollusks could not be identified.

Animals↗
PubMed2001

[Tectonic survey of the Central Pacific coast of Costa Rica ].

Three fossil coral samples (Pocillopora elegans and Pocillopora damicornis) were collected from a beachrock in Puerto Escondido, central Pacific coast of Costa Rica. The age of the samples ranged from 1272+/-60 to 2010+/-60 years BP. They represent some of the few Holocene fossil corals known from the Pacific coast of the Americas. The uplift rate for the central Pacific coast of Costa Rica was calculated in 0.4 to 2.1 mm year(-1).

Animals↗
PubMed2001

[Corals reef of the Upper Oligocene-Lower Miocene, of Turrialba, Costa Rica].

The outcrops at Jesús Maria (Turrialba, Cartago Province, Costa Rica) present limestone sequences 12 to 30 m thick (packstones: biolithites, biomicrites; and wackstones: biosparites, biomicrosparites), sandstones and conglomerates of Upper Oligocene-Lower Miocene age, correlated to the Punta Pelada Formation. The limestones are characterized by patch reefs with an irregular distribution and a reduced lateral extension (50 m), composed of corals (40%), calcareous algae and foraminiferans (30%), mollusks (20%), and in minor amounts fragments of barnacles, decapods, echinoderms and bryozoans. They consisted of low diversity communities possibly due to diverse geographical, geological and tectonic factors: a narrow continental shelf, very shallow and isolated environments, sea level fluctuations, and exposure to clastic sedimentation associated with intermitent volcanic activity. Equity was also low, with corals making up 40% of all macrofossils, and one species, Antiguastrea cellulosa, as predominant (80% of the corals present). These bioconstructions were developed in an open circulation lagoon environment with transitions, in several occasions, to shallower environments represented by elastic sediments.

Animals↗
PubMed2001

Effects of the 1991-92 El Niño on scleractinian corals of the Costa Rican central Pacific coast.

Coral communities on the central Pacific coast of Costa Rica were affected during the 1991-92 El Niño warming event. More than 57% of all observed colonies at three localities (Parque Nacional Manuel Antonio, Punta Cambutal, and Parque Marino Ballena) were bleached. Mortality during this El Niño was much lower (approximately 9%) than in previous events. Psammocora spp. accounted for approximately 66% of dead corals, while massive (Porites lobota, Pavona spp.) and branching (Pocillopora spp.) for approximately 34%. Our results suggest that the observed bleaching in P. lobata was related to zooxanthellar densities and not to changes in pigment concentrations: only chlorophyll a varied between normally pigmented and bleached colonies at one locality (Ballena). Site differences in zooxanthellar densities or their pigment concentrations, may not be the result of the bleaching event itself, because a percentage of dead corals and zooxanthellar densities of bleached colonies seems to follow a trend with the exposure to tidal regimes and currents at each site. Local oceanographic conditions can be influencing the zooxanthellar densities and their response to the warming, together with intrinsic differences between colonies as well. The impact of this event can be considered serious given the short period of time that elapsed between El Niño related mortalities and the slow reefs recovery, the mode of reproduction of reef building species, and the anthropogenic-originated disturbances which affect the coral communities and reefs of the Costa Rican central Pacific coast.

Animals↗
PubMed2001

Spatial distribution of light and nutrients in some coral reefs of Costa Rica during January 1997.

The proximity of coral reefs to areas of present and future coastal development in Costa Rica highlights the need for assessing environmental conditions important to maintaining healthy corals. In January 1997 a survey of light penetration, inorganic nutrient concentrations, temperature, and salinity was conducted in the patch reefs of Bahía Culebra (Pacific Ocean) and on the Caribbean coast in the fringing reef at Parque Nacional Cahuita and near Limón. Temperature was 28 degrees C at all sites, and salinity ranged from 33 to 36 psu. Light attenuation coefficients ranged from 0.12 to 0.29 m(-1) in reef areas. Seawater nutrient concentrations were within the range of concentrations reported for tropical reef waters; combined NO3- and NO2- and PO4(3-) were each below 1 microM. NH4+ ranged from 0.2 to 7 microM, representing a significant source of nitrogen. The ratio of total dissolved inorganic nitrogen to phosphate averaged 27 for all reef waters. The high nitrate (3.6 microM) and light attenuation (0.95 m(-1)) values from the surface waters of the La Estrella plume (Caribbean coast) show that this river represents a significant source of nitrogen and light attenuation for the neighboring reefs at Cahuita. This survey provides a useful baseline for future studies, which should monitor these important coastal coral reef areas during both wet and dry seasons.

Animals↗
PubMed2001

Biomass, productivity and density of the seagrass Thalassia testudinum at three sites in Cahuita National Park, Costa Rica.

The basic ecology of seagrass beds was investigated by comparing biomass, productivity and density of Thalassia testudinum (turtle grass) at three sites: Puerto Vargas, Punta Cahuita and Rio Perezoso, in Cahuita National Park, Limón, Costa Rica, over a two month period (March-April 1999). Above ground biomass, density, and productivity were highest in the Puerto Vargas site while Punta Cahuita had the least non-green above ground biomass was significantly lower in total biomass than Puerto Vargas. Punta Cahuita was distinguished by the largest grain size, a very hard substrate, and shallower water. Rio Perezoso, on the other hand, had extremely fine sediment and lower salinity, while Puerto Vargas was intermediate both in sediment size and environmental conditions. It appears, therefore, that higher biomass and productivity result from a combination of moderate environmental characteristics and an intermediate sediment size.

Biomass↗
PubMed2001

Requiem for an eastern Pacific seagrass bed.

Few papers concerning seagrasses of the eastern Pacific have been published. This paper presents the first ecological data on the seagrass, Ruppia maritima, from a non-lagoonal setting in the eastern Pacific. A 5000 m2 patch formed by R. maritima, at Playa Iguanita, Bahía Culebra, Pacific coast of Costa Rica was studied. Plant density and leaf length of R. maritima were determined along two transects on different dates. Above and below ground biomass were calculated along one transect. Plant density ranged from 1590 to 8630 individuals m(-2) along the two transects, with means of 5990 +/- 1636 and 6100 +/- 1876 plants m(-2) for transect 1 and 2, respectively. Longest leaf length per plant varied between 0.5 and 23.0 cm. Leaf biomass (LB) ranged from 10 to 97 gm(-2), and root-rhizome biomass (RB) from 31 to 411 gm(-2), resulting in RB:LB ratios of 3.07 to 15.27. Total biomass at Bahía Culebra was lower than at tropical lagoons on the Pacific coast of Mexico, but higher than in the Gulf of Mexico. The below ground: above ground biomass ratio was much higher at Bahía Culebra than at other sites on the Pacific coast of Mexico and the Gulf of Mexico. Another seagrass present at Bahía Culebra was Halophila baillonii, with low densities on the deepest section of the patch. At least 44 invertebrate species associated with the seagrass bed have also been identified. The patch at Playa Iguanita and other sites within Bahía Culebra, as well as their associated organisms, disappeared after a severe storm in June 1996. No seagrasses have been found in the area or in any other location on the Pacific coast of Costa Rica since then.

Alismatales↗
PubMed2001

Planktonic primary production in a tidally influenced mangrove forest on the Pacific coast of Costa Rica.

The seasonal variation of planktonic primary productivity was measured during one year in the main channel in the interior part of the mangrove forest of the Estero de Morales (Estero de Punta Morales), a mangrove system located in the Golfo de Nicoya at the Pacific coast of Costa Rica. Samples were incubated at the surface, 0.5 m and 1.0 m depth and the "light and dark bottle technique" was employed. The annual gross primary productivity (PPg) was 457 and the net primary productivity (PPn) was 278 g C m(-2) a(-1). Daily PPg ranged from 0.29 to 3.88 and PPn from 0.12 to 2.76 g C m(-2) d(-1). The highest rates observed in May and September were due to red tide blooms. The seasonal variation of primary productivity inside the mangrove forest depends closely on the PP in the adjacent area of the upper Golfo de Nicoya. Obviously the PP was light-limited since the compensation depth in the ebb current was found at only 1 m depth. In the flood current it was somewhat deeper. The planktonic primary productivity inside the mangrove forest was completely restricted to the open channels. A simultaneous measurement demonstrated that PPn of the phytoplankton could not take place under the canopy of the mangroves. Additional studies on the time course of the oxygen concentration in the mouth of the main channel over 24 hrs demonstrated a relation between the O2 and the tidal curves. The ebb current had always lower O2 concentrations than the flood current, regardless of the time of the day. The difference to the foregoing high tide, however, was much smaller when the low tide occurred during the day. This indicates that under the canopy the net primary production and hence O2 liberation of the attached macro- and microalgae, together with the high PPn of the phytoplankton in the channels, helped the oxygen concentration not to decrease as far as during the night. Nevertheless it shows that the consumtion of organic material in the submersed part of the mangrove forest exceeds always its production.

Animals↗
PubMed2001

The annual cycle of primary productivity in a tropical estuary: the inner regions of the Golfo de Nicoya, Costa Rica.

A one year cycle of primary productivity (PP) was studied using the "light and dark bottle" technique in the Golfo de Nicoya, located at 10 degrees N and 85 degrees W at the Pacific coast of Costa Rica. Samples were always incubated at 0, 1, 2, 3 and 4 m depth for 5 hrs from 8:30 till 13:30. The measurements were performed twice per month, first around high tide and one week later at low tide to account for tidal influences. This routine study was supplemented by special measurements about regional and short-term variations of primary productivity using the 14C-method, which mainly served to account for the shortcomings of the routinely employed incubation technique. The upper Golfo de Nicoya is an extremely productive, phytoplankton dominated estuarine system with an annual gross PP of 1037, a net PP of 610 and a community respiration of 427 g C m(-2) a(-1). Highest monthly PP values occurred during the dry season and at the beginning of the rainy season. Peaks in primary productivity coincided with massive blooms of red tide forming algae. Internal biological dynamics, estuarine circulation and land run-off are the most important nutrient sources. High water turbidity reduces the euphotic layer to 4-5 m depth, making the underwater light regime the rate limiting factor. On an annual basis, 41% of the organic carbon produced in the system is already consumed in the euphotic layer. Considering the entire water column (mean depth at mean tidal water level is around 7.7 m) 79% is consumed in the pelagial. Taking into account the organic material consumed and stored in the sediments the carbon budget of the upper gulf is probably balanced. Since, however, the system receives a considerable amount of organic material from its terrestrial surroundings (especially from the mangrove forests), a surplus of organic carbon is exported from the upper Golfo de Nicoya, which enhances the overall water productivity of the lower gulf and the adjacent area.

Journal Article↗
PubMed2001

[The mangrove and others vegetation associations in de Gandoca lagoon, Limón, Costa Rica].

Six plant associations were identified at Gandoca Lagoon by photointerpretation and field verification: a) mangroves, b) palm trees swamp, and palm trees with Acrostichum aureum and A. danaefolium, c) mixed palm trees, d) very humid tropical rain forest, and e) tropical beach vegetation. The mangroves cover 12.5 ha surrounding the lagoon and extend 2 km up the Gandoca River. Rhizophora mangle (red mangrove) was the dominant species, with Avicennia germinans (black mangrove), Laguncularia racemosa (white mangrove) and Conocarpus erectus (buttonwood) also present. Moving inland the mangroves grade into a tropical rain forest. Gandoca, the largest and best preserved mangrove of Caribbean Costa Rica, tripled its area from 1976 to 2000. Possible causes include sedimentation and the Limón earthquake, which may have subside the lagoon area.

Costa Rica↗
PubMed2000

Novel octaketide macrolides related to 6-deoxyerythronolide B provide evidence for iterative operation of the erythromycin polyketide synthase.

BACKGROUND: The macrolide antibiotic erythromycin A, like other complex aliphatic polyketides, is synthesised by a bacterial modular polyketide synthase (PKS). Such PKSs, in contrast to other fatty acid and polyketide synthases which work iteratively, contain a separate set or module of enzyme activities for each successive cycle of polyketide chain extension, and the number and type of modules together determine the structure of the polyketide product. Thus, the six extension modules of the erythromycin PKS (DEBS) together catalyse the production of the specific heptaketide 6-deoxyerythronolide B. RESULTS: A mutant strain of the erythromycin producer Saccharopolyspora erythraea, which accumulates the aglycone intermediate erythronolide B, was found unexpectedly to produce two novel octaketides, both 16-membered macrolides. These compounds were detectable in fermentation broths of wild-type S. erythraea, but not in a strain from which the DEBS genes had been specifically deleted. From their structures, both of these octaketides appear to be aberrant products of DEBS in which module 4 has 'stuttered', that is, has catalysed two successive cycles of chain extension. CONCLUSIONS: The isolation of novel DEBS-derived octaketides provides the first evidence that an extension module in a modular PKS has the potential to catalyse iterative rounds of chain elongation like other type I FAS and PKS systems. The factors governing the extent of such 'stuttering' remain to be determined.

Anti-Bacterial Agents↗
PubMed2000

BRCA2 germ-line mutations in Spanish male breast cancer patients.

BACKGROUND: Mutations in the BRCA2 gene account for the majority of the families with male and female breast cancer cases, and a number of BRCA2 mutations have been reported in males with breast cancer. The aim of this study was to characterise BRCA2 germ-line mutations in Spanish male breast cancer patients. PATIENTS AND METHODS: We screened DNA from 11 affected men and 6 women with breast cancer (BC) who had an affected male relative (father or brother). Exons 2-9 and 12-27 were screened by SSCP, and exons 10 and 11 were screened by PTT. PCR products with a variant band were sequenced. RESULTS: Three BRCA2 frameshift mutations were identified (17.6%): the 3374delA in codon 1049 (exon 11), 6857delAA in codon 2010 (exon 11), and 9254delATCAT in codon 3009 (exon 23). These mutations were present in patients with affected first-degree relatives (3 of 9, 33%). The proportion of male patients with a family history of BC in at least one first-degree relative was 53%. CONCLUSIONS: There is an association between BRCA2 mutations and male breast cancer, especially in those with a family history of BC. The high prevalence of BRCA2 mutations among males should be considered when estimating risk for female relatives. All new male cases of BC should be regarded as being possibly inherited and should be fully investigated.

Adult↗
PubMed2000

Changes in left ventricular filling pattern during dobutamine stress Doppler echocardiography.

AIMS: To study the left ventricular filling pattern during stress Doppler echocardiography and its utility in the detection of myocardial ischaemia. METHODS AND RESULTS: Fifty-seven consecutive patients underwent dobutamine stress echocardiography. The left ventricular filling pattern (E-wave velocity; A-wave velocity; E/A ratio; E-wave deceleration time) was analysed at baseline and at maximum heart rate reached. The percentage increase in these parameters from baseline to peak heart rate was also determined. Myocardial ischaemia (regional contractility worsening) was induced in 19 cases (ischaemic group) but not in 38 cases (non-ischaemic group). There were no differences between both groups at baseline. E-wave deceleration time decreased in the non-ischaemic group (197+/-63 vs. 167+/-65 ms, P=0.01) and increased in the ischaemic group (203+/-42 vs. 315+/-135 ms, P<0.0001). A percentage increase in E-wave deceleration time of >30% showed a positive predictive value of 93% and a negative predictive value of 86% for detecting ischaemia, and in the multivariate analysis it was the only Doppler parameter (P<0.0001) that predicted the induction of ischaemia. CONCLUSION: We conclude that myocardial ischaemia provokes an increase in E-wave deceleration time. Analysis of left ventricular filling could help in the identification of those cases which are positive for ischaemia.

Dobutamine↗
PubMed2000

Impairment of adenylate cyclase activity and G-proteins in human uterine leiomyoma.

The mechanisms responsible for the growth of uterine leiomyoma (a frequent cause of infertility in women) are largely unknown. Some data supports that cAMP plays a role in the growth of uterine cells but there are no reports on the status of the cAMP producing system in this human benign neoplasia. In this study, biopsies from leiomyoma and the adjacent myometrium were taken from menstruating women subjected to total hysterectomy for leiomyoma. Adenylate cyclase activity was determined by a protein-binding method, and the expression of alpha(s), alphai1/2, alphai3 and alphai0) G-protein subunits was analysed by immunoblot. The leiomyoma samples exhibited a decreased expression of as and ai1/2 with respect to the adjacent myometrial tissue. No differences were observed in alphai3 and alphaio protein expression. The basal adenylate cyclase activity as well as the efficacy (as assessed by the maximal stimulation levels) of either forskolin or, to a lesser extent, Gpp[NH]p on stimulation the enzyme activity was significantly lower in leiomyoma than in myometrium, whereas the potency (as assessed by the ED50 values) of these two agents did not vary. Present data indicate that the human leiomyoma is associated with low levels of cAMP. It is conceivable that the loss of sensitivity of adenylate cyclase to endogenous regulatory molecules could be related to the pathogenesis of human leiomyomas given that cAMP inhibits the MAP-kinase cascade in uterine tissues.

Adenylyl Cyclase Inhibitors↗
PubMed1999

Application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to the structure determination of medium and large macrocycles formed by palladium(0)-catalyzed allylation of arenesulfonamides, sulfamide, and cyanamide.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry allowed the direct determination of the extent of macrocyclic and linear oligomer formation in the palladium(0)-catalyzed allylation of highly acidic and non-nucleophilic arenesulfonamides, sulfamide, and cyanamide. Palladium-containing 15-membered-ring macrocyclic compounds gave unusual [M - H](+) ions besides [M + Na](+) and [M + K](+) adducts. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1999

BRCA1 mutation analysis in 83 Spanish breast and breast/ovarian cancer families.

A group of 83 Spanish BC/OC families were analysed for BRCA1 germ-line mutations. Analysis of the entire coding sequence was carried out by SSCP and PTT. We identified 5 frameshift mutations: 185delAG (2 times), 189insTGTC, 1241delAC, and 5537delA and 3 missense mutations in BRCA1: 330A > G, 1240C > T, and 5263G > A. The 185delAG mutation was identified in 2 families. One of them was the only Gypsy family participating in our study. All carriers shared the known founder haplotype, although they did not have any Jewish ancestry. Three frameshift mutations were found among the 14 families with 3 or more BC cases and 1 or more OC, which results in a higher percentage (21.4%) of BRCA1 mutations in this group of high risk families. Two missense mutations were found in families with 2 or 3 BC and no OC, indicating a low proportion (4.8%) of mutations in these families. There was no association between bilateral BC and a mutation carrier status. The frequency of BRCA1 involvement is lower than that of any other country hitherto reviewed. Our results highlight the influence of geographical and ethnic origin of the population studied.

Adult↗
PubMed1999

A chain initiation factor common to both modular and aromatic polyketide synthases.

Antibiotic-producing polyketide synthases (PKSs) are enzymes responsible for the biosynthesis in Streptomyces and related filamentous bacteria of a remarkably broad range of bioactive metabolites, including antitumour aromatic compounds such as mithramycin and macrolide antibiotics such as erythromycin. The molecular basis for the selection of the starter unit on aromatic PKSs is unknown. Here we show that a component of aromatic PKS, previously named 'chain-length factor', is a factor required for polyketide chain initiation and that this factor has decarboxylase activity towards malonyl-ACP (acyl carrier protein). We have re-examined the mechanism of initiation on modular PKSs and have identified as a specific initiation factor a domain of previously unknown function named KSQ, which operates like chain-length factor. Both KSQ and chain-length factor are similar to the ketosynthase domains that catalyse polyketide chain extension in modular multifunctional PKSs and in aromatic PKSs, respectively, except that the ketosynthase domain active-site cysteine residue is replaced by a highly conserved glutamine in KSQ and in chain-length factor. The glutamine residue is important both for decarboxylase activity and for polyketide synthesis.

Acyl Carrier Protein↗