Plasma progesterone in alpaca (Lama pacos) during pregnancy, parturition and early postpartum

Plasma progesterone concentration during pregnancy and the early postpartum period was measured by radioimmunoassay in five alpacas (Lama pacos), of the Huacaya breed, whose pregnancy length had a mean of 344.8 +/- 4.4 days. Concentration of progesterone increased (P < 0.001) from low premating values (0.11 +/- 0.06 nmol/l) to greater values at 30 days of pregnancy (8.05 +/- 1.13 nmol/l) and remained high up to 2 months of pregnancy. A slight transitory decline was observed between 3 to 7 months. Concentration of plasma progesterone dropped markedly during the 72 h before parturition especially, at the day of parturition.     

The heterochromatin of grasshoppers from the Caledia captiva species complex. I. Sequence evolution and conservation in a highly repeated DNA family

The restriction enzyme TaqI digests 0.2% of the genomic DNA from the grasshopper Caledia captiva to a family of sequences 168 bp in length (length of consensus sequence). The sequence variation of this "Taq family" of repeat units was examined among four races from C. captiva to assay the pattern of evolution within this highly repeated DNA. The Taq-family repeats are located in C-banded heterochromatin on at least one member of each homologous pair of chromosomes; the locations range from centromeric to telomeric. Thirty-nine cloned repeats isolated from two population 1A individuals along with 11 clones from seven populations taken from three of the races demonstrated sequence variation at 72 positions. Pairwise comparisons of the cloned repeats, both within an individual and between different races, indicate that levels of intraspecific divergence, as measured by reproductive incompatibility, do not correlate with sequence divergence among the 168-bp repeats. A number of subsequences within the repeat remain unchanged among all 50 clones; the longest of these is 18 bp. That the same 18-bp subsequence is present in all clones examined is a finding that departs significantly (P less than 0.01) from what would be expected to occur at random. Two other cloned repeats, from a reproductively isolated race of C. captiva, have sequences that show 56% identity with this 18-bp conserved region. An analysis showed that the frequency of occurrence of an RsaI recognition site within the 168- bp repeat in the entire Taq family agreed with that found in the cloned sequences. These data, along with a partial sequence for the entire Taq family obtained by sequencing uncloned repeats, suggest that the consensus sequence from the cloned copies is representative of this highly repeated family and is not a biased sample resulting from the cloning procedure. The 18-bp conserved sequence is part of a 42-bp sequence that possesses dyad symmetry typical of protein-binding sites. We speculate that this may be significant in the evolution of the Taq family of sequences.      

Radiobiological comparison of two radiotherapy treatment techniques for high-risk prostate cancer

Background

To make a radiobiological comparison, for high risk prostate cancer (T3a, PSA > 20 ng/ml or Gleason > 7) of two radiotherapy treatment techniques. One technique consists of a treatment in three phases of the pelvic nodes, vesicles and prostate using a conventional fractionation scheme of 2 Gy/fraction (SIMRT). The other technique consists of a treatment in two phases that gives simultaneously different dose levels in each phase, 2 Gy/fraction, 2.25 Gy/fraction and 2.5 Gy/fraction to the pelvic nodes, vesicles and prostate, respectively (SIBIMRT).

Materials and methods

The equivalent dose at fractionation of 2 Gy (EQD₂), calculated using the linear quadratic model with α/β_prostate = 1.5 Gy, was the same for both treatment strategies. For comparison the parameters employed were D95, mean dose and Tumour Control Probabilities for prostate PTV and D15, D25, D35, D50, mean dose and Normal Tissue Complication Probabilities for the rectum and bladder, with physical doses converted to EQD₂. Parameters were obtained for α/β_prostate = 1.5, 3 and 10 Gy and for α/β_oar = 1, 2, 3, 4, 6 and 8.

Results

For prostate PTV, both treatment strategies are equivalent for α/β_prostate = 1.5 Gy but for higher α/β_prostate, EQD₂ and TCP, decrease for the SIBIMRT technique. For the rectum and bladder when α/β_oar ≤ 2 Gy, EQD₂ and NTCP are lower for the SIMRT technique or equal in both techniques. For α/β_oar ≥ 2–3 Gy, EQD₂ and NTCP increase for the SIMRT treatment.

Conclusions

A comparison between two radiotherapy techniques is presented. The SIBIMRT technique reduces EQD₂ and NTCP for α/β_oar from 2 to 8 Gy.     

Cultured endothelial cells produce heparinlike inhibitor of smooth muscle cell growth

Using cultured cells from bovine and rat aortas, we have examined the possibility that endothelial cells might regulate the growth of vascular smooth muscle cells. Conditioned medium from confluent bovine aortic endothelial cells inhibited the proliferation of growth-arrested smooth muscle cells. Conditioned medium from exponential endothelial cells, and from exponential or confluent smooth muscle cells and fibroblasts, did not inhibit smooth muscle cell growth. Conditioned medium from confluent endothelial cells did not inhibit the growth of endothelial cells or fibroblasts. In addition to the apparent specificity of both the producer and target cell, the inhibitory activity was heat stable and not affected by proteases. It was sensitive flavobacterium heparinase but not to hyaluronidase or chondroitin sulfate ABC lyase. It thus appears to be a heparinlike substance. Two other lines of evidence support this conclusion. First, a crude isolate of glycosaminoglycans (TCA-soluble, ethanol-precipitable material) from endothelial cell-conditioned medium reconstituted in 20 percent serum inhibited smooth muscle cell growth; glycosaminoglycans isolated from unconditioned medium (i.e., 0.4 percent serum) had no effect on smooth muscle cell growth. No inhibition was seen if the glycosaminoglycan preparation was treated with heparinase. Second, exogenous heparin, heparin sulfate, chondroitin sulfate B (dermatan sulfate), chondroitin sulfate ABC, and hyaluronic acid were added to 20 percent serum and tested for their ability to inhibit smooth muscle cell growth. Heparin inhibited growth at concentrations as low as 10 ng/ml. Other glycosaminoglycans had no effect at doses up to 10 μg/ml. Anticoagulant and non- anticoagulant heparin were equally effective at inhibiting smooth muscle cell growth, as they were in vivo following endothelial injury (Clowes and Karnovsk. Nature (Lond.). 265:625-626, 1977; Guyton et al. Circ. Res. 46:625-634, 1980), and in vitro following exposure of smooth muscle cells to platelet extract (Hoover et al. Circ. Res. 47:578-583, 1980). We suggest that vascular endothelial cells may secrete a heparinlike substance in vivo which may regulate the growth of underlying smooth muscle cells.     

Putrescine accumulation in Arabidopsis thaliana transgenic lines enhances tolerance to dehydration and freezing stress

Polyamines have been globally associated to plant responses to abiotic stress. Particularly, putrescine has been related to a better response to cold and dehydration stresses. It is known that this polyamine is involved in cold tolerance, since Arabidopsis thaliana plants mutated in the key enzyme responsible for putrescine synthesis (arginine decarboxilase, ADC; EC 4.1.1.19) are more sensitive than the wild type to this stress. Although it is speculated that the overexpression of ADC genes may confer tolerance, this is hampered by pleiotropic effects arising from the constitutive expression of enzymes from the polyamine metabolism. Here, we present our work using A. thaliana transgenic plants harboring the ADC gene from oat under the control of a stress-inducible promoter (pRD29A) instead of a constitutive promoter. The transgenic lines presented in this work were more resistant to both cold and dehydration stresses, associated with a concomitant increment in endogenous putrescine levels under stress. Furthermore, the increment in putrescine upon cold treatment correlates with the induction of known stress-responsive genes, and suggests that putrescine may be directly or indirectly involved in ABA metabolism and gene expression.Key words: cold acclimation, dehydration, putrescine, polyamines, stress     

Metabotropic γ-aminobutyric acid (GABAB) receptors modulate feeding behavior in the calcisponge Leucandra aspera

Here, we report the presence of the γ-aminobutyric acid (GABA)-ergic system in the calcisponge Leucandra aspera and examine the cellular localization of the components of this system, including GABA-like receptors using immunofluorescence and confocal microscopy. Furthermore, we demonstrate for the first time that GABA plays a functional role as a messenger in regulating sponge-feeding behavior. We found that both GABA(B) R1 and R2 subunits are present in the choanocytes of sponges as well as in the eso- and endopinacocytes. The functional role of GABA in the feeding behavior of this sponge was tested. The involvement of GABA receptors in the endocytic processes in L. aspera was demonstrated with dextran conjugated to Texas Red as a marker for material ingestion and by treating isolated sponge cells with a GABA(B) receptor agonist and an antagonist. The amount of dextran that was ingested increased in dissociated sponge cells when the GABA(B) receptor agonist baclofen was used, and this stimulatory effect was prevented by treatment with the GABA(B) receptor antagonist phaclofen. The baclofen effect on uptake was blocked by treatment with pertussis toxin, thus indicating a role for G proteins in modulating feeding behavior in L. aspera. Moreover, we found evidence that GABA receptors are involved in the consumption of dissolved organic matter by sponge cells. These findings suggest that GABA receptors and their functional role are highly conservative traits in the animal kingdom prenervous system evolution.     

Diffractive corneal inlay for presbyopia

A conceptually new type of corneal inlays for a customized treatment of presbyopia is presented. The diffractive inlay consists on a small aperture disc having an array of micro‐holes distributed inside the open zones of a Fresnel zone plate. In this way, the central hole of the disc lets pass the zero order diffraction and produces an extension of the depth of far focus of the eye, while the diffracted light through the holes in the periphery produce the near focus. Additionally, the micro‐holes in the inlay surface fulfill the essential requirement of allowing the flow of nutrients through it to the cells of the corneal stroma. Theoretical and optical‐bench experimental results for the polychromatic axial Point Spread Function (PSF) were obtained, showing an improved performance compared to the small aperture corneal inlay currently in the market (Kamra). Images of a test object, obtained at several vergences in the surroundings of the far and near foci, are also shown. Picture : Simulation of the appearance of the Diffractive corneal inlay on a real eye.     

A polyamine metabolon involving aminopropyl transferase complexes in Arabidopsis

The conversion of putrescine to spermidine in the biosynthetic pathway of plant polyamines is catalyzed by two closely related spermidine synthases, SPDS1 and SPDS2, in Arabidopsis. In the yeast two-hybrid system, SPDS2 was found to interact with SPDS1 and a novel protein, SPMS (spermine synthase), which is homologous with SPDS2 and SPDS1. SPMS interacts with both SPDS1 and SPDS2 in yeast and in vitro. Unlike SPDS1 and SPDS2, SPMS failed to suppress the speDelta3 deficiency of spermidine synthase in yeast. However, SPMS was able to complement the speDelta4 spermine deficiency in yeast, indicating that SPMS is a novel spermine synthase. The SPDS and SPMS proteins showed no homodimerization but formed heterodimers in vitro. Pairwise coexpression of hemagglutinin- and c-Myc epitope-labeled proteins in Arabidopsis cells confirmed the existence of coimmunoprecipitating SPDS1-SPDS2 and SDPS2-SPMS heterodimers in vivo. The epitope-labeled SPDS and SPMS proteins copurified with protein complexes ranging in size from 650 to 750 kD. Our data demonstrate the existence of a metabolon involving at least the last two steps of polyamine biosynthesis in Arabidopsis.     

The direct activation of MIK,a germinal center kinase (GCK)-like kinase,by MARK,a maize atypical receptor kinase,suggests a new mechanism for signaling through kinase-dead receptors

Signaling by receptor protein kinases (RPKs) involves their dimerization and transphosphorylation. However, atypical RPKs with kinase-defective domains have been described recently. Some of them are essential for proper signaling in animal systems, although the precise mechanism involved is unknown in most cases. Here we describe the cloning and characterization of an atypical plant receptor kinase from maize, MARK, which does not phosphorylate in vitro. A yeast two-hybrid approach has allowed us to identify a new germinal center kinase (GCK)-related protein, MIK, that interacts with MARK. Interestingly, the interaction of the intracellular domain of MARK with the regulator domain of MIK strongly induces MIK kinase activity. As some GCK-related proteins connect cell-surface receptors to the intracellular MAPK cascades, the activation of MIK by direct interaction with MARK could illustrate a new mechanism for signaling through atypical RPKs.