Selected contribution: Acute and sustained ventilatory responses to hypoxia in high-altitude natives living at sea level.

High-altitude (HA) natives have blunted ventilatory responses to hypoxia (HVR), but studies differ as to whether this blunting is lost when HA natives migrate to live at sea level (SL), possibly because HVR has been assessed with different durations of hypoxic exposure (acute vs. sustained). To investigate this, 50 HA natives (>3,500 m, for >20 yr) now resident at SL were compared with 50 SL natives as controls. Isocapnic HVR was assessed by using two protocols: protocol 1, progressive stepwise induction of hypoxia over 5-6 min; and protocol 2, sustained (20-min) hypoxia (end-tidal Po(2) = 50 Torr). Acute HVR was assessed from both protocols, and sustained HVR from protocol 2. For HA natives, acute HVR was 79% [95% confidence interval (CI): 52-106%, P = not significant] of SL controls for protocol 1 and 74% (95% CI: 52-96%, P < 0.05) for protocol 2. By contrast, sustained HVR after 20-min hypoxia was only 30% (95% CI: -7-67%, P < 0.001) of SL control values. The persistent blunting of HVR of HA natives resident at SL is substantially less to acute than to sustained hypoxia, when hypoxic ventilatory depression can develop.     

C4 gene polymorphism in primates: evolution,generation, and Chido and Rodgers antigenicity

Eleven new C4d genomic primate sequences of the fourth complement factor (C4) have been obtained. Seven of them belong to five species not yet explored for this gene: Pan paniscus (pygmy chimpanzee), Cercopithecus aethiops (green monkey), Macaca mulatta (rhesus monkey), Macaca fascicularis (cynomolgus), and Saguinus oedipus (cotton top tamarin). The New World monkeys (tamarins, four individuals) sequenced for C4 have a single C4d sequence only, which shows a B isotypic specificity and a Rodgers 3 (Rg3), Chido 1 (Ch1) antigenicity. Rg3 and Ch1 could thus be the oldest Rg/Ch specificity (at least 50 million years old) and Rg1, Rg2, Ch3, and Ch6 could be more recent human-specific antigens. Mechanisms of C4d polymorphism generation were analyzed by compiling all the presently available sequences. Examples of both point mutations and crossing-over events among C4d primate sequences could be detected. The problem of a possible trans-species inheritance of C4d polymorphism was addressed and two apparently contradicting dendrograms were obtained. One of them, constructed by using both exon and intron sequences, does not support trans-species evolution, but supports the proposed theory of extensive homogenization of the C4 genes occurring within each species, because alleles from each primate species cluster together. Another completely different dendrogram, obtained by using exon sequences only, suggests the existence of trans-species evolution for C4d polymorphism, because alleles belonging to different species cluster together in a way similar to that found for HLA class I or II alleles. However, orangutan sequences group together in both kinds of C4d sequence dendrograms and seem to have arisen from an ancestor different from that of chimpanzee, gorilla and man C4d sequences. Finally, further data have been obtained that support trans-species conservation of A-ness and B-ness and the existence of trans-specifically conserved allelic motifs, both in intronic and exonic sequences.     

Proinflammatory gene induction by platelet-activating factor mediated via its cognate nuclear receptor

It has been postulated that intracellular binding sites for platelet-activating factor (PAF) contribute to proinflammatory responses to PAF. Isolated nuclei from porcine cerebral microvascular endothelial cells (PCECs) produced PAF-molecular species in response to H(2)O(2). Using FACS analysis, we demonstrated the expression of PAF receptors on cell and nuclear surfaces of PCECs. Confocal microscopy studies performed on PCECs, Chinese hamster ovary cells stably overexpressing PAF receptors, and isolated nuclei from PCECs also showed a robust nuclear distribution of PAF receptors. Presence of PAF receptors at the cell nucleus was further revealed in brain endothelial cells by radioligand binding experiments, immunoblotting, and in situ in brain by immunoelectron microscopy. Stimulation of nuclei with methylcarbamate-PAF evoked a decrease in cAMP production and a pertussis toxin-sensitive rise in nuclear calcium, unlike observations in plasma membrane, which exhibited a pertussis toxin-insensitive elevation in inositol phosphates. Moreover, on isolated nuclei methylcarbamate-PAF evoked the expression of proinflammatory genes inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) and was associated with augmented extracellular signal-regulated kinase 1/2 phosphorylation and NF-kappaB binding to the DNA consensus sequence. COX-2 expression was prevented by mitogen-activated protein kinase kinase/extracellular signal-regulated kinase 1/2 and NF-kappaB inhibitors. This study describes for the first time the nucleus as a putative organelle capable of generating PAF and expresses its receptor, which upon stimulation induces the expression of the proinflammatory gene COX-2.     

Evolution, systematics, and phylogeography of pleistocene horses in the new world: a molecular perspective

The rich fossil record of horses has made them a classic example of evolutionary processes. However, while the overall picture of equid evolution is well known, the details are surprisingly poorly understood, especially for the later Pliocene and Pleistocene, c. 3 million to 0.01 million years (Ma) ago, and nowhere more so than in the Americas. There is no consensus on the number of equid species or even the number of lineages that existed in these continents. Likewise, the origin of the endemic South American genus Hippidion is unresolved, as is the phylogenetic position of the "stilt-legged" horses of North America. Using ancient DNA sequences, we show that, in contrast to current models based on morphology and a recent genetic study, Hippidion was phylogenetically close to the caballine (true) horses, with origins considerably more recent than the currently accepted date of c. 10 Ma. Furthermore, we show that stilt-legged horses, commonly regarded as Old World migrants related to the hemionid asses of Asia, were in fact an endemic North American lineage. Finally, our data suggest that there were fewer horse species in late Pleistocene North America than have been named on morphological grounds. Both caballine and stilt-legged lineages may each have comprised a single, wide-ranging species.     

Presence of Pathogens and Indicator Microbes at a Non-Point Source Subtropical Recreational Marine Beach

Swimming in ocean water, including ocean water at beaches not impacted by known point sources of pollution, is an increasing health concern. This study was an initial evaluation of the presence of indicator microbes and pathogens and the association among the indicator microbes, pathogens, and environmental conditions at a subtropical, recreational marine beach in south Florida impacted by non-point sources of pollution. Twelve water and eight sand samples were collected during four sampling events at high or low tide under elevated or reduced solar insolation conditions. The analyses performed included analyses of fecal indicator bacteria (FIB) (fecal coliforms, Escherichia coli, enterococci, and Clostridium perfringens), human-associated microbial source tracking (MST) markers (human polyomaviruses [HPyVs] and Enterococcus faecium esp gene), and pathogens (Vibrio vulnificus, Staphylococcus aureus, enterovirus, norovirus, hepatitis A virus, Cryptosporidium spp., and Giardia spp.). The enterococcus concentrations in water and sand determined by quantitative PCR were greater than the concentrations determined by membrane filtration measurement. The FIB concentrations in water were below the recreational water quality standards for three of the four sampling events, when pathogens and MST markers were also generally undetectable. The FIB levels exceeded regulatory guidelines during one event, and this was accompanied by detection of HPyVs and pathogens, including detection of the autochthonous bacterium V. vulnificus in sand and water, detection of the allochthonous protozoans Giardia spp. in water, and detection of Cryptosporidium spp. in sand samples. The elevated microbial levels were detected at high tide and under low-solar-insolation conditions. Additional sampling should be conducted to further explore the relationships between tidal and solar insolation conditions and between indicator microbes and pathogens in subtropical recreational marine waters impacted by non-point source pollution.Global estimates indicate that each year more than 120 million cases of gastrointestinal disease and 50 million cases of severe respiratory diseases are caused by swimming and bathing in wastewater-polluted coastal waters (42). Swimming-related illness is attributed predominantly to exposure to microbial pathogens, which enter the water through point sources, such as sewage outfalls. Water quality at beaches may also be impacted by non-point sources, such as storm water runoff, sand resuspension, animal fecal inputs, and human bather shedding (8, 12, 22, 47, 59).The concentration of indicator microorganisms in a body of recreational water is used to estimate the health risk to bathers. These microbes serve as surrogates for microbial pathogens. Studies show that the U.S. Environmental Protection Agency (EPA)-recommended indicator microbe for marine beaches, enterococci, shows a significant correlation with illness in marine beaches impacted by point source pollution (38, 54). However, a similar correlation has not been identified at beaches impacted by non-point source pollution or subtropical marine beaches (17, 29, 38, 54).The failure to consistently demonstrate an association between enterococci and illness at non-point source beaches calls into question the ability of indicator microbes to predict the presence of pathogens. Studies conducted on the west coast of the United States have shown that indicators are often not correlated with measured pathogens at non-point source beaches (31, 32, 33, 37). Additional studies conducted in a subtropical environment, such as that of South Florida, where this study was conducted, have repeatedly shown the limited accuracy of indicator microbe standards for determining the presence of pathogens (27, 35). This lack of correlation is understandable since an indicator microbe, such as enterococci, may come from relatively low-risk sources of fecal pollution and therefore may not be related to human or other high-risk sources of fecal pollution and pathogens (9). It has also been shown in both subtropical and temperate climates that indicator bacteria can multiply in the environment, resulting in a false impression of increased microbial pollution and pathogen presence (4, 7, 19, 24, 41, 45, 57, 58). Environmental factors, such as tide, rain, and solar insolation, can also have significant and varying effects on the levels of indicator and pathogenic microbes (21, 24, 33).The lack of correlation between pathogens and indicator microbes at non-point source beaches can result in two problematic scenarios. If indicator microbes are absent and pathogens are present (false-negative scenario), regulatory monitoring may fail to identify the potential adverse health effects on bathers due to the pathogens. This problem is likely to occur since indicator bacteria are less resistant to environmental stresses and disinfection at wastewater treatment plants than certain pathogens (6, 15). However, if indicator microbes are present and pathogens are absent (false-positive scenario), there can be unnecessary economic losses due to recreational beach advisories and/or closures. A 4-month closure of Huntington Beach in 1999 due to microbial standard violations resulted in the loss of millions of dollars in tourism income to the business community and almost 2 million dollars in beach closure investigation fees (55; for a review, see reference 27).Given these two possible scenarios, the relationship between indicator microbes and pathogens under different environmental conditions at non-point source beaches representing different geographic and climatic settings should be assessed further. Investigation of this relationship would require a large sample size in order to establish possible significant associations between the various factors and targets. The objective of this study was to conduct a preliminary evaluation of the presence of indicator microbes and pathogens and the possible association between indicator microbes, pathogen measurements, and environmental conditions at a subtropical recreational marine beach in South Florida. Because of cost limitations when multiple targets, including pathogens, are screened, this study was not intended to establish a conclusive relationship between the various factors and targets but was intended to provide insight into both the presence of organisms and possible associations which should be investigated further. Such information would be useful for understanding the potential health risks to bathers from non-point sources of microbes and would also contribute to determining the appropriateness of using indicator microbes to monitor the water quality at non-point source beaches. Although previous studies have assessed the presence of either viral, protozoan, or bacterial pathogens along with indicator microbes in point or non-point source recreational beach waters (27, 33, 37, 47), to our knowledge, this is the first study to assess the presence of all three classes of pathogens (viral, protozoan, and bacterial) as well as indicator microbes at a non-point source recreational beach. This study is also the first study to sample for all these microbes in both water and sand at a non-point source recreational beach. Through analysis of the various microbes under different targeted environmental conditions, this study also included a preliminary evaluation of the sources of microbial contaminants and pathogens and the effectiveness of various analytical methods for microbe detection. The latter part of the study included a comparison of three different methods for enterococcus enumeration, as well as an innovative method for simultaneously concentrating protozoans and viruses from water samples.     

Determinación de la certeza diagnóstica de la gammagrafía tiroidea con tecnecio 99 sestamibi en pacientes con nódulo tiroideo y resultado histopatológico definitivo

Background99mTc sestamibi scanning and aspiration biopsy can predict the histopathological result of a thyroid nodule fairly accurately.ObjectiveTo determine the accuracy of 99mTc sestamibi scanning in detecting malignancy in patients with thyroid nodule confirmed by definitive histopathological report after thyroidectomy.Material and methodsA total of 69 patients with a solitary thyroid nodule were studied. In all patients, fine needle aspiration, total thyroidectomy for suspected thyroid cancer, and histological analysis of the surgical specimen were performed. There were 54 patients with a positive 99mTc sestamibi scan; of these, malignancy was confirmed by histological analysis in 25 and excluded in 29. There were 15 patients with a negative 99mTc sestamibi scan; of these, three had a final diagnosis of cancer and 12 were confirmed as cancer-free.ResultsThe diagnostic accuracy of 99mTc sestamibi scanning in detecting malignancy in thyroid nodules was determined through a statistical analysis. 99mTc sestamibi scan for thyroid cancer had a sensitivity of 89.28% and a specificity of 29.25%. The positive predictive value was 46.29% and the negative predictive value was 80%.ConclusionsWe believe that 99mTc sestamibi scan should be routinely used in all patients with a thyroid nodule and an indeterminate result on fine needle aspiration. This procedure is most useful in excluding malignancy in patients with a negative 99mTc sestamibi scan.     

Signalling and Sexual Conflict: Female Spiders Use Stridulation to Inform Males of Sexual Receptivity

The use of acoustic signals by males during courtship and mating is well known. Nevertheless, their association with female unwillingness to mate is much less studied. In spiders, stridulation during sexual interactions is relatively common in some groups, but mainly restricted to males. In the pholcid spider Holocnemus pluchei, both sexes have stridulatory organs. The aims of the present work were (1) to establish whether female stridulation occurs during intra‐ and inter‐sexual interactions, (2) to determine whether female reproductive status affects the likelihood that she will stridulate and (3) to determine whether female stridulation is influenced by male sexual behaviour. We found that female stridulation usually occurs both during intrasexual interactions and, most frequently, during intersexual interactions. Females with more previous matings stridulated more frequently. Stridulation intensity was higher in females that did not accept new copulations compared with those that copulated. Female stridulation did not vary in elaborated and non‐elaborated courtship. Thus, females use stridulation to communicate levels of sexual receptivity. It is also possible that females use stridulation to indirectly assess male ability to persist and persuade.