Zooplankton as a compound mineralising and synthesizing system: phosphorus excretion

Data on phosphate excretion rates of zooplankton are based on measurements using the pelagic crustacean zooplankton of Lake Vechten and laboratory-cultured Daphnia galeata. In case of Daphnia sp we measured the effects of feeding on P-rich algae and P-poor algae (Scenedesmus) as food on the P-excretion rates at 20°C. The excretion rates of the natural zooplankton community, irrespective of the influence of the factors mentioned, varied by an order of magnitude: 0.025–0.275µg PO₄-Pmg^–1C in zooplankton (C _zp ) h^–1. The temperature accounted for about half the observed variation in excretion rates. The mean excretion rates in the lake, computed for 20°C, varied between 0.141 and 0.260 µg Pmg^–1C _zp h^–1. Based on data of zooplankton biomass in the lake the P-regeneration rates by zooplankton covered between 22 and 239% of the P-demand of phytoplankton during the different months of the study period.In D. galeata, whereas the C/P ratios of the Scenedesmus used as food differed by a factor 5 in the experiments, the excretion rates differed by factor 3 only. Despite the higher P-excretion rates (0.258± 0.022 µg PO₄-P mg^–1 C h^–1) of the daphnids fed with P-rich food than those fed with P-poor food (0.105 ± 0.047 µg PO₄-P mg^–1 C h^p–1), both the categories of the animals were apparently conserving P. A survey of the literature on zooplankton excretion shows that in Daphnia the excretion rates vary by a factor 30, irrespective of the species and size of animals and method of estimation and temperature used.About two-thirds of this variation can be explained by size and temperature. A major problem of comparability of studies on P-regeneration by zooplankton relates to the existing techniques of P determination, which necessitates concentrating the animals several times above the in situ concentration (crowding) and prolonged experimental duration (starving), both of which manifest in marked changes that probably lead to underestimation of the real rates.     

Casein kinase 2 inactivation by Mg2+, Mn2+ and Co2+ ions

In order to elucidate the relationship between hypertension and hypertrophy in the production of heat shock proteins, we studied the induction of the HSP72 synthesis by the heart and gracilis muscles of normo (WKY) and hypertensive (SHR) rats subjected to hyperthermia (42°C±0.5 for 15 min). Two age groups were investigated in each strain: young (2 months, with developing cardiac hypertrophy) and old (18 months, with fully developed chronic cardiac hypertrophy). The gracilis muscle never developed hypertrophy, independently of hypertension or aging. 72 kDa inducible protein was determined by Western blot analysis using a specific monoclonal antibody. We also used a commercial standard, loaded on each blot, to quantitate densitometrically the signal.The heart of young SHR responds to heat shock more than their normotensive age-matched control (298.8±24.7% vs 88.3 ±8.5%, p<0.001). This response is not maintained during aging as we did not find any significant difference between normo-and hypertensive old rats after exposure to hyperthermia (43.6±5.3% vs 65.3±10.4%).Unlike the heart, the gracilis muscle shows a basal spontaneous HSP72 synthesis in both the SHR (71.4±10.8%) and WKY (40.6±11.7%) animals. There was a significant increase in HSP72 synthesis in the gracilis muscle of young SHR with respect to their control (186.2±18.7% vs 115.8±9.9%, p<0.02) which was maintained also during aging (171.9±17.3% vs 95.2±10.5%, p<0.01).In conclusion, these data show that hypertension results in an increased synthesis of HSP72 both in cardiac and gracilis muscle in response to heat shock. This abnormal response is attenuated by aging in the heart but not in the gracilis muscle. Thus, the abnormality seems to be independent from hypertrophy and linked to genetic determination of the disease.     

The invasion-associated type III system of Salmonella typhimurium directs the translocation of Sip proteins into the host cell

The ability of Salmonella typhimurium to interact with host cells is largely dependent on the function of a type III protein-secretion system encoded at centisome 63 of its chromosome. We have shown here that two targets of this protein-secretion system, SipB and SipC, are translocated into cultured intestinal Henle-407 cells. Translocation required the function of the type III secretion apparatus, as an S. typhimurium strain carrying a mutation in invA , which encodes an essential component of this system, failed to translocate the Sip proteins. Null mutations in the genes encoding SipB, SipC or SipD, prevented protein translocation, indicating that these proteins are involved in the translocation process. In contrast, mutations in sipA and sptP , which also encode secreted proteins, did not interfere with the translocation of SipC, indicating that only a subset of targets of the type III secretion system act as translocases. Externally or internally localized bacteria could direct protein translocation into Henle-407 cells as this process occurred in the presence of cytochalasin D at a concentration that prevented bacterial entry, or in the presence of gentamicin added shortly after bacterial internalization at a concentration that killed extracellular Salmonella . These results indicate that protein translocation into host cells may be a universal function of all type III secretion systems.     

Biopolitics: the newest synthesis?

On first impression, the disciplines of genetics and political science would appear to be unrelated. And yet, commencing more than 30 years ago, the interdisciplinary field known as Biopolitics has now taken hold. This essay traces the central thrust of the biopolitical research agenda. It describes, analyzes, and assesses how political scientists have sought to show connections between our species' genetic constitution and our species' political behavior. Important bridges between the two are the neurophysiology of the human brain and the role of evolutionary theory in charting man's adaptational political profile. The parameters of the emerging biopolitical literature raise profound policy questions, some of which are also characterized. This revised version was published online in August 2006 with corrections to the Cover Date.     

Intragenomic distribution and stability of transposable elements in euchromatin and heterochromatin of drosophila melanogaster: non-LTR retrotransposon

The intragenomic location of the elements of the I, G, jockey, F, and Doc transposon families has been studied by the Southern blot analysis, in 12 laboratory Drosophila melanogaster stocks. Elements located in euchromatin, heterochromatin, and on the Y chromosome are identified, and their stability has been assessed by comparing the autoradiographs detected in different stocks and analysis of individual flies. Evidence is shown suggesting that preferential location in euchromatin or heterochromatin and the distribution within heterochromatin are distinctive of transposon families. Elements located in heterochromatin can be unstable. These results are discussed in the context of the relationship between transposable elements and the host genome. Received: 21 August 1996 / Accepted: 24 March 1997     

Identification and Characterization of a New Serotonergic Recognition Site with High Affinity for 5-Carboxamidotryptamine in Mammalian Brain

Abstract: We analyzed the existence of an additional serotonin (5-HT) receptor subtype, sensitive to 5-carboxamidotryptamine, in the mammalian brain. Radioligand binding studies with [³H]5-HT were carried out in rat, guinea pig, and human brain membranes, in the presence of unlabeled drugs to mask the binding to all known 5-HT receptors, with the exception of 5-HT_1E sites. Under these conditions, unlabeled 5-carboxamidotryptamine still showed a biphasic competition curve with a nanomolar affinity component. Saturation studies with 5-[³H]carboxamidotryptamine were carried out in the presence of (±)-8-hydroxy-2-(di- n -propylamino)tetralin, mesulergine, and ergotamine, to mask the binding to all receptors known to be labeled by 5-carboxamidotryptamine. These studies showed the existence in cortex and hippocampus from guinea pig and human brain of a remaining binding site with high affinity ( pK _D = 7.8–8.1) and a unique pharmacological profile. 5-HT and 5-carboxamidotryptamine showed nanomolar affinity, whereas 5-methoxytryptamine recognized this binding site with intermediate affinity. Other drugs exhibited low or very low potency in inhibiting this binding. The addition of 5'-guanylylimidodiphosphate significantly reduced the number of binding sites labeled by 5-[³H]carboxamidotryptamine, in the presence of the masking drugs described above, indicating the interaction with a GTP-binding protein. Preliminary autoradiographic studies in human brain appear to indicate that this 5-HT binding site is present in areas such as the globus pallidus, neocortex, and hippocampus, among others.     

Regulation of L-Type Calcium Channels in GH4 Cells via A1 Adenosine Receptors

Abstract: Identification of A₁ adenosine receptors (A₁Rs) in a tumor cell line derived from rat pituitary (GH₄ cells) was performed by ligand binding and immunological experiments. Subsequently, the involvement of A₁Rs in the regulation of calcium conductance was studied in these cells. The agonist N ⁶-( R )-(2-phenylisopropyl)adenosine ( R -PIA) did not modify the intracellular calcium basal levels, whereas it inhibited the increase produced by 15 m M KCl depolarization. The antagonist 1,3-dipropyl-8-cyclopentylxanthine led to the opening of voltage-dependent cell surface calcium channels in the absence of exogenous KCl. The channels were of the L type because the effect was abolished by calciseptine and by verapamil. These results suggest that endogenous adenosine exerts a tonic inhibitory effect on calcium transport. This was confirmed by the high adenosine concentration found in cell supernatants (up to 1 µ M ) and by the calcium mobilization produced by exogenously added adenosine deaminase. In depolarizing conditions, the calcium peak in the presence of adenosine deaminase was reduced when cells were preincubated with R -PIA, thus suggesting that A₁R activation regulates the intensity of depolarization. These results demonstrate that adenosine is an important regulator of the physiological state of pituitary tumor cells by modulating, in an autocrine manner, the activity of L-type voltage-dependent calcium channels.     

Genetic differentiation and detection of cryptic species in the genus Lepismachilis (Insecta: Microcoryphia) from the Western Mediterranean region

Different species of the bristletail genus Lepismachilis were collected in 14 localities in Italy and Spain and an allozyme electrophoretic survey was carried out to estimate the degree of genetic variability and differentiation at intra- and interspecific levels. Four morphological species were initially identified (L osellai, L. y-signata, L. affinis, L. targionii), but the electrophoretic analysis demonstrated the presence of two additional species among the individuals of L. targionii (Lepismachilis spl and sp2). The validity of these species and their differentiation from L targionii were demonstrated by the fixation of alternative allelic patterns at several loci (7 in Lepismachilis spl and 8 in Lepismachilis sp2), coupled with fixed, previously undetected, morphological differences. In addition, Lepismachilis sp2 was sympatric with L. targionii in three collecting sites, where the fixation of alternative allelic patterns unequivocally demonstrated reproductive isolation. Genetic variability did not seem to be correlated with local ecological factors, and differences between species should rather be explained by different historical factors. Low levels of gene flow, estimated with two different indirect methods, were observed in L. targionii and L. y-signata, and were due to high levels of structuring among populations. Genetic differentiation among conspecific populations was not correlated to their geographical arrangement and the presence of loci fixed for different alleles among them suggested that stochastic factors (such as genetic drift) may have played a role in determining genetic differentiation of geographically isolated populations. Genetic divergence values indicated that the six species are well differentiated and allozyme profiles were diagnostic for all of them. On the other hand, allozyme data did not provide adequate information to resolve evolutionary relationships among the species, nor did they confirm the validity of the two subgenera (Lepismachilis and Berlesilis) in which the genus Lepismachilis is traditionally divided.     

A case of congenital syphilis during the colonial period in Mexico City

Congenital syphilis has been diagnosed very seldom in ancient populations. The case that we examined comes from San Jeronimo's Church (17th and 18th centuries AD; Mexico City). Coffin 43 contained an incomplete skeleton of an approximately 2-year-old infant. The pathological lesions of this skeleton include bilateral osteochondritis, diaphyseal osteomyelitis, and osteitis and/or periostitis on the long bones. The radiographic appearance depicts symmetrical osteomyelitic foci, particularly at the proximal extremity of both tibiae (Wimberger's sign). The skull exhibits hydroceph-aly and periosteal changes on the vault, and the unerupted upper incisors evince dental hypoplasia and other pathological alterations reminiscent of Hutchinson's incisors. All these features strongly suggest a case of early Congenital syphilis. © 1995 Wiley-Liss, Inc.     

Cpn60 is exclusively localized into mitochondria of rat liver and embryonic Drosophila cells

Several reports have claimed that the mitochondrial chaperonin cpn60, or a close homolog, is also present in some other subcellular compartments of the eukaryotic cell. Immunoelectron microscopy studies, using a polyclonal serum against cpn60, revealed that the protein is exclusively localized within the mitochondria of rat liver and embryonic Drosophila cells (SL2). Furthermore, no cpn60 immunoreactive material could be found within the nucleus of SL2 cells subjected to a 1 h 37°C heat-shock treatment. In contrast to these findings, immunoelectron microscopy studies, using a cpn60 monoclonal antibody, revealed mitochondrial and extramitochondrial (plasma membrane, nucleus) immunoreactive material in rat liver cells. Surprisingly, the monoclonal antibody also reacted with fixed proteins of the mature red blood cell. The monoclonal antibody, as well as cpn60 polyclonal sera, only recognize mitochondrial cpn60 in Western blots of liver proteins. Furthermore, none of the cpn60 antibodies used in this study recognized blotted proteins from rat red blood cells. Therefore, we suggest that the reported extramitochondrial localization of cpn60 in metazoan cells may be due to cross-reactivity of some of cpn60 antibodies with conformational epitopes also present in distantly related cpn60 protein homologs that are preserved during fixation procedures of the cells. © 1995 Wiley-Liss, Inc.