Delayed Contrast Extravasation MRI for Depicting Tumor and Non-Tumoral Tissues in Primary and Metastatic Brain Tumors

The current standard of care for newly diagnosed glioblastoma multiforme (GBM) is resection followed by radiotherapy with concomitant and adjuvant temozolomide. Recent studies suggest that nearly half of the patients with early radiological deterioration post treatment do not suffer from tumor recurrence but from pseudoprogression. Similarly, a significant number of patients with brain metastases suffer from radiation necrosis following radiation treatments. Conventional MRI is currently unable to differentiate tumor progression from treatment-induced effects. The ability to clearly differentiate tumor from non-tumoral tissues is crucial for appropriate patient management. Ten patients with primary brain tumors and 10 patients with brain metastases were scanned by delayed contrast extravasation MRI prior to surgery. Enhancement subtraction maps calculated from high resolution MR images acquired up to 75 min after contrast administration were used for obtaining stereotactic biopsies. Histological assessment was then compared with the pre-surgical calculated maps. In addition, the application of our maps for prediction of progression was studied in a small cohort of 13 newly diagnosed GBM patients undergoing standard chemoradiation and followed up to 19.7 months post therapy. The maps showed two primary enhancement populations: the slow population where contrast clearance from the tissue was slower than contrast accumulation and the fast population where clearance was faster than accumulation. Comparison with histology confirmed the fast population to consist of morphologically active tumor and the slow population to consist of non-tumoral tissues. Our maps demonstrated significant correlation with perfusion-weighted MR data acquired simultaneously, although contradicting examples were shown. Preliminary results suggest that early changes in the fast volumes may serve as a predictor for time to progression. These preliminary results suggest that our high resolution MRI-based delayed enhancement subtraction maps may be applied for clear depiction of tumor and non-tumoral tissues in patients with primary brain tumors and patients with brain metastases.     

Na+-K+-ATPase in frog esophagus mucociliary cell membranes: inhibition by protein kinase C activation

We examined protein kinase C (PKC)-dependentregulation ofNa⁺-K⁺-ATPasein frog mucociliary cells. Activation of PKC by12-O-tetradecanoylphorbol-13-acetate (TPA) or 1,2-dioctanoyl-sn-glycerol(diC8) either in intact cells or isolated membranes resulted in aspecific inhibition ofNa⁺-K⁺-ATPaseactivity by ~25-45%. The inhibitory effects in membranes exhibited time dependence and dose dependence [half-maximalinhibition concentration (IC₅₀) = 0.5 ± 0.1 nM and 2.4 ± 0.2 µM, respectively, for TPA anddiC8] and were not influenced byCa²⁺. Analysis of the ouabaininhibition pattern revealed the presence of twoNa⁺-K⁺-ATPaseisoforms with IC₅₀ values forcardiac glycoside of 2.6 ± 0.8 nM and 409 ± 65 nM,respectively. Most importantly, the isoform possessing a higheraffinity for ouabain was almost completely inhibited by TPA, whereasits counterpart was hardly sensitive to the PKC activator. The resultssuggest that, in frog mucociliary cells, PKC regulatesNa⁺-K⁺-ATPaseand that this action is related to the specificNa⁺-K⁺-ATPaseisoform.

     

EFFECT OF NITROGEN STARVATION ON OPTICAL PROPERTIES,PIGMENTS, AND ARACHIDONIC ACID CONTENT OF THE UNICELLULAR GREEN ALGA PARIETOCHLORIS INCISA (TREBOUXIOPHYCEAE,CHLOROPHYTA)1

Spectral properties of cell suspensions, individual cells, and extracts of the unicellular green alga Parietochloris incisa (Reisigl) Shin Watan. grown under low light were studied. Long‐term nitrogen (N) deprivation resulted in a decrease of chloroplast volume, appearance of numerous large cytoplasmic oil bodies, and the deposition of triacylglycerols with a high proportion of arachidonic acid. Chlorophylls a and b underwent a synchronous decline, whereas carotenoids (Car) showed a relative increase. Simultaneously, significant qualitative changes in the spectral properties of P. incisa individual cells, cell extracts, and cell suspensions were observed. To a large extent, the spectral changes observed in cell suspension could be attributed to a decrease in overall pigment content, leading to a gradual weakening of the so‐called package effect and accumulation of additional amounts of Car over chl, most probably, in oil bodies. Several optical characteristics of cell suspensions could serve as sensitive indicators of N‐deficiency in P. incisa. Furthermore, the absorption ratios, A₄₇₆/A₆₇₆ and A₆₅₀/A_676, showed close correlations with the Car‐to‐chl ratio and relative arachidonic acid (AA) content, respectively. The latter makes it possible to suggest that the increase in AA percentage in P. incisa proceeds in parallel with a decrease in cell chl content, accounting for the weakening of the package effect. N‐replenishment resulted in complete recovery of cell optical properties. The possible significance of the changes in cell ultrastructure, pigments, lipids, and optical properties is discussed with special reference to the ability of algae to adapt to and survive under conditions of long‐term nutrient deficiency.     

Forces applied by cilia measured on explants from mucociliary tissue

Forces applied by intact mucus-propelling cilia were measured for the first time that we know of using a combined atomic force microscopy (AFM) and electrooptic system. The AFM probe was dipped into a field of beating cilia and its time-dependent deflection was recorded as it was struck by the cilia while the electrooptic system simultaneously and colocally measured the frequency to ensure that no perturbation was induced by the AFM probe. Using cilia from frog esophagus, we measured forces of ~0.21 nN per cilium during the effective stroke. This value, together with the known internal structure of these cilia, leads to the conclusion that most dynein arms along the length of the axoneme contribute to the effective stroke of these cilia.     

Direct involvement of p53 in the base excision repair pathway of the DNA repair machinery

The p53 tumor suppressor that plays a central role in the cellular response to genotoxic stress was suggested to be associated with the DNA repair machinery which mostly involves nucleotide excision repair (NER). In the present study we show for the first time that p53 is also directly involved in base excision repair (BER). These experiments were performed with p53 temperature-sensitive (ts) mutants that were previously studied in in vivo experimental models. We report here that p53 ts mutants can also acquire wild-type activity under in vitro conditions. Using ts mutants of murine and human origin, it was observed that cell extracts overexpressing p53 exhibited an augmented BER activity measured in an in vitro assay. Depletion of p53 from the nuclear extracts abolished this enhanced activity. Together, this suggests that p53 is involved in more than one DNA repair pathway.     

Insulin--a growth hormone

Insulin is a peptide hormone with a high degree of homology with the insulin-like growth factor I (IGF-I). Its biological actions are interlaced with those of GH and IGF-I. The objective of this study is to review the growth promoting actions of insulin. The experimental evidence consists of the use of organ cultures of neonatal mice condilar cartilage insulin which stimulates the cartilage cell differentiation and maturation. Injection of insulin to hypohysectomized rats stimulated tibial growth. Clinical evidence is manifold. Babies with diabetes and hypoinsulinemia are short, whereas babies with hyperinsulinism are big. Children with idiopathic short stature have low insulin whereas obese children with hyperinsulinism are tall. Hypo-insulinized children with diabetes slow their growth until the insulin dose is optimized. It remains to be clarified whether insulin exerts its growth promoting actions via its own receptors, via the IGF-I receptors, or via a hybrid (insulin--IGF-I) receptor.     

Chronic parasite infections cause immune changes that could affect successful vaccination

Several important issues must be considered when performing any vaccination in areas with high prevalence of geohelminths. Immunization of populations infected with geohelminths could be sub-optimal if the immune background is not taken into consideration. Immune modulation and deworming might be essential for effective protective vaccination. In addition, further animal models and clinical studies addressing these issues are required. Underscoring the importance of these issues, a recent report has highlighted several vaccination studies in which nematode-infected mice or pigs failed to mount efficient protective immune responses.     

Unwinding the structure and function of the archaeal MCM helicase

During chromosomal DNA replication, the replicative helicase unwinds the duplex DNA to provide the single-stranded DNA substrate for the polymerase. In archaea, the replicative helicase is the minichromosome maintenance (MCM) complex. The enzyme utilizes the energy of ATP hydrolysis to translocate along one strand of the duplex and unwind the complementary strand. Much progress has been made in elucidating structure and function since the first report on the biochemical properties of an archaeal MCM protein in 1999. We now know the biochemical and structural properties of the enzyme from several archaeal species and some of the mechanisms by which the enzyme is regulated. This review summarizes recent studies on the archaeal MCM protein and discusses the implications for helicase function and DNA replication in archaea.