The host—parasite relationship of two copepod species and two fish species

A total of 2494 Menidia beryllina and 717 M. peninsulae (Atherinidae) were examined from the Pensacola Bay area for parasitic copepods. M. peninsulae was infested with Bomolochus concinnus (Bomolochidae) and Ergasilus marticatus (Ergasilidae) and had incidences (and intensities) of 12.3% (1.6) and 4.2% (1.3), respectively. Only seven M. peninsulae were infested with both species of parasites. M. beryllina was infested only with E. manicatus and showed different incidences (and intensities) in two areas: Mulatto Bayou, 13.2% (1.9); Catfish Basin, 53.0% (2.3). Fishes with parasites were significantly longer than fishes without parasites and the case of increasing number of parasites with increasing fish length was reinforced. B. concinnus is a warm water parasite on M. peninsulae while E. manicatus acts as a cold water parasite on M. peninsulae and a warm water parasite on M. beryllina . The parasites tended to be overdispersed on their hosts but at the same time showed evidence of negative intraspecific associations within a host. These data suggest intraspecific avoidance by the parasite but active acquisition by the host.     

Lysis of sensitized sheep erythrocytes in human sera deficient in the second component of complement

Analysis of C-dependent lysis of sensitized SRBC by C2-deficient sera (C2D) led to the characterization of a C2 bypass pathway. Lysis in the total hemolytic C assay by C2D sera was Ca2+-dependent and required a high concentration of hemolysin to sensitize E. Selective component depletion indicated a requirement for C1 and C4 of the classical pathway (CP) and proteins B, P, and probably D of the alternative pathway (AP). Total hemolytic C could be restored to normal in these C2D sera by utilizing heavily sensitized E or by the addition of a supranormal concentration of B. This system most closely resembles a pathway described by J. E. May and M. M. Frank which requires antibody, C1, and the AP but not C4 or C2. It differs in its requirement for C4. We hypothesize that this pathway represents vestiges of a more primitive C pathway. It becomes evident and possibly clinically important in the setting of C2 deficiency, by allowing C activation, other than the AP, and perhaps in normal individuals, by damaging microorganisms that have evolved means to inhibit early components of the CP.     

A comparison of calcium-activated potassium channel currents in cell-attached and excised patches

Single channel currents from Ca-activated K channels were recorded from cell-attached patches, which were then excised from 1321N1 human astrocytoma cells. Cells were depolarized with K (110 mM) so that the membrane potential was known in both patch configurations, and the Ca ionophore A23187 or ionomycin (20-100 microM) was used to equilibrate intracellular and extracellular [Ca] (0.3 or 1 microM). Measurements of intracellular [Ca] with the fluorescent Ca indicator quin2 verified that [Ca] equilibration apparently occurred in our experiments. Under these conditions, where both membrane potential and intracellular [Ca] were known, we found that the dependence of the channel percent open time on membrane potential and [Ca] was similar in both the cell-attached and excised patch configuration for several minutes after excision. Current-voltage relations were also similar, and autocorrelation functions constructed from the single channel currents revealed no obvious change in channel gating upon patch excision. These findings suggest that the results of studies that use excised membrane patches can be extrapolated to the K-depolarized cell-attached configuration, and that the relation between [Ca] and channel activity can be used to obtain a quantitative measure of [Ca] near the membrane intracellular surface.     

Control of DNA replication in a transformed lymphoid cell line: coexistence of activator and inhibitor activities

Proliferating lymphocytes contain an intracellular factor, ADR (activator of DNA replication), which can initiate DNA synthesis in isolated quiescent nuclei. Resting lymphocytes lack ADR activity and contain an intracellular inhibitory factor that suppresses DNA synthesis in normal but not transformed nuclei. In this study we describe a MOLT-4 subline that produces both the activator and inhibitory activities which can be separated by ammonium sulfate fractionation. The inhibitor is heat stable and inhibits ADR-mediated DNA replication in a dose-dependent manner. It does not inhibit DNA polymerase alpha activity. The inhibitor must be present at the initiation of DNA replication to be effective, as it loses most of its effectiveness if it is added after replication has begun. The presence of inhibitory activity in proliferating MOLT-4 cells, taken with the previous observation that inhibitor derived from normal resting cells does not affect DNA synthesis by MOLT-4 nuclei, suggests that failure of a down-regulating signal may play an important role in proliferative disorder.     

Effects of chemical composition on nitrogen mineralization from green manures of seven tropical leguminous trees

Green manures from seven tropical leguminous trees were incubated with soil to determine the rates and controls of net nitrogen release. Fresh green manure (leaves and succulent twigs) was mixed with moist soil and incubated in polyethylene bags. Net N mineralization from green manures was estimated by the accumulation of extractable ammonium and nitrate minus the accumulation in soil alone. Patterns of N mineralization were complex, differed among species, and at 12 weeks ranged from 10 to 65 percent of original green-manure N. Cumulative net N mineralization was negatively correlated with initial soluble polyphenol content in the early phases of decomposition (1 through 8 weeks) and with initial lignin content in later phases (4 through 12 weeks). Neither initial percent N nor lignin: N ratio were strongly correlated with N mineralization. The best chemical index of N release was the initial polyphenol: N ratio. This study confirms previous findings that N mineralization from tropical legumes is controlled more by soluble polyphenols than by lignin or N content.     

Antitumor activity of rapamycin in a Phase I trial for patients with recurrent PTEN-deficient glioblastoma

Background

There is much discussion in the cancer drug development community about how to incorporate molecular tools into early-stage clinical trials to assess target modulation, measure anti-tumor activity, and enrich the clinical trial population for patients who are more likely to benefit. Small, molecularly focused clinical studies offer the promise of the early definition of optimal biologic dose and patient population.

Methods and Findings

Based on preclinical evidence that phosphatase and tensin homolog deleted on Chromosome 10 (PTEN) loss sensitizes tumors to the inhibition of mammalian target of rapamycin (mTOR), we conducted a proof-of-concept Phase I neoadjuvant trial of rapamycin in patients with recurrent glioblastoma, whose tumors lacked expression of the tumor suppressor PTEN. We aimed to assess the safety profile of daily rapamycin in patients with glioma, define the dose of rapamycin required for mTOR inhibition in tumor tissue, and evaluate the antiproliferative activity of rapamycin in PTEN-deficient glioblastoma. Although intratumoral rapamycin concentrations that were sufficient to inhibit mTOR in vitro were achieved in all patients, the magnitude of mTOR inhibition in tumor cells (measured by reduced ribosomal S6 protein phosphorylation) varied substantially. Tumor cell proliferation (measured by Ki-67 staining) was dramatically reduced in seven of 14 patients after 1 wk of rapamycin treatment and was associated with the magnitude of mTOR inhibition (p = 0.0047, Fisher exact test) but not the intratumoral rapamycin concentration. Tumor cells harvested from the Ki-67 nonresponders retained sensitivity to rapamycin ex vivo, indicating that clinical resistance to biochemical mTOR inhibition was not cell-intrinsic. Rapamycin treatment led to Akt activation in seven patients, presumably due to loss of negative feedback, and this activation was associated with shorter time-to-progression during post-surgical maintenance rapamycin therapy (p < 0.05, Logrank test).

Conclusions

Rapamycin has anticancer activity in PTEN-deficient glioblastoma and warrants further clinical study alone or in combination with PI3K pathway inhibitors. The short-term treatment endpoints used in this neoadjuvant trial design identified the importance of monitoring target inhibition and negative feedback to guide future clinical development.Trial registration: http://www.ClinicalTrials.gov (#{"type":"clinical-trial","attrs":{"text":"NCT00047073","term_id":"NCT00047073"}}NCT00047073).     

High-performance liquid chromatographic assay of biphenyl metabolism by hepatocytes cultured in an embryo/hepatocyte co-culture medium

A high-performance liquid chromatographic method has been modified for the evaluation of both Phase I and II metabolism of biphenyl by hepatocytes maintained in an embryo/hepatocyte co-culture medium. Extracts of the media, before and after hydrolysis of conjugates, are directly injected onto the HPLC and the major hydroxylated metabolites plus unmetabolized biphenyl are detected by fluorescence after separation under gradient or isocratic conditions. The method is almost free of interferences and is relatively simple and rapid. In the case of the monohydroxylated derivatives, the minimum media concentrations which can be measured are 7 to 20 nM (0.07 to 0.2 pmol on-column). Recoveries from culture medium to which known amounts of biphenyl and metabolites had been added were quantitative (90-103%) and the reproducibility good (interassay CV less than 5%). The assay was applied to cultures of hepatocytes derived from rabbit and from phenobarbital induced and noninduced rat.