Orientation and withdrawal of pollination drops in Cupressaceae s. l. (Coniferales)

Pollination in the Cupressaceae is studied ex situ, focused on orientation and withdrawal of pollination drops. Orientation of pollination drops is a constant feature in most taxa studied and important for pollen capture. Conspecific pollen causes a withdrawal of pollination drops, varying in time among species from 8 to 24 min, but with little variation within species. Pollination drops of each tested Cupressaceae taxon are also withdrawn when pollinated with foreign, but Cupressaceous pollen. However, they remain unchanged and are not withdrawn immediately when pollinated with pollen of other seed plants. The results clearly indicate that the time for the total withdrawal of pollination drops is strongly influenced by the evolutionary distance of the taxa being involved in the pollination process. Among closely related taxa the withdrawal is much more rapid than in distantly related ones. This points to an effective recognition system regulating the withdrawal of pollination drops, probably controlled by the nucellus. This recognition system can be regarded as an important preadaption for the evolution of a self-incompatibility mechanism. The withdrawal of pollination drops is thus not exclusively a physically induced process as suggested in some earlier studies. Pollination drops of several ovules can fuse to form a large common one, perhaps increasing by this way successful pollen capture.     

Association of CMV-Specific T Cell-Mediated Immunity with CMV DNAemia and Development of CMV Disease in HIV-1–Infected Individuals

Background

Among HIV-1–infected individuals, cytomegalovirus (CMV) reactivation and disease occur in the setting of advanced immunosuppression. The value of a standardized assessment of CMV-specific T-cell mediated immunity by the CMV QuantiFERON assay (CMV-QFT) has not yet been thoroughly investigated in HIV-1–infected subjects.

Methods

Prospective, longitudinal study in 153 HIV-1–infected subjects with a CD4⁺ T cell count < 350/μL who simultaneously underwent CMV-QFT, CMV serology testing and CMV-DNA quantification. Factors associated with CMV-QFT were evaluated. Clinical screening for CMV manifestations was then performed every 3 months.

Results

Among the 141 CMV IgG-seropositive individuals the CMV-QFT assay yielded reactive results in 84% (118/141), negative results in 15% (21/141) and indeterminate (negative mitogen IFN-gamma response) results in 1% (2/141) of subjects. The mean actual CD4⁺ T cell count was significantly higher in CMV-QFT reactive subjects, when compared to CMV-QFT non-reactive individuals (183 ± 102 vs. 126 ± 104 cells/μL, P = 0.015). A significantly lower proportion of CMV-QFT reactive vs. non-reactive patients displayed CMV DNAemia > 100 copies/mL (23% (27/118) vs. 48% (11/23), P = 0.02). Furthermore, a statistically significant inverse association between mitogen IFN-gamma response and CMV-DNAemia > 1000 copies/mL was observed (P < 0.001). During the observational period, 5 CMV end-organ manifestations were observed. In three of the CMV cases the CMV-QFT yielded indeterminate results.

Conclusions

While CMV-QFT reactivity indicates CMV-specific immunity, indeterminate results due to negative mitogen IFN-gamma response might reflect HIV-1-induced immunodeficiency. Thus, dependency upon CD4⁺ T cell count should be considered when interpreting CMV-QFT results.     

Amino acid 324 in the simian immunodeficiency virus SIVmac V3 loop can confer CD4 independence and modulate the interaction with CCR5 and alternative coreceptors

The V3 loop of the simian immunodeficiency virus (SIV) envelope protein (Env) largely determines interactions with viral coreceptors. To define amino acids in V3 that are critical for coreceptor engagement, we functionally characterized Env variants with amino acid substitutions at position 324 in V3, which has previously been shown to impact SIV cell tropism. These changes modulated CCR5 engagement and, in some cases, allowed the efficient usage of CCR5 in the absence of CD4. The tested amino acid substitutions had highly differential effects on viral infectivity. Eleven of sixteen substitutions disrupted entry via CCR5 or the alternative coreceptor GPR15. Nevertheless, most of these variants replicated in the macaque T-cell line 221-89 and some also replicated in rhesus macaque peripheral blood monocytes, suggesting that efficient usage of CCR5 and GPR15 on cell lines is not a prerequisite for SIV replication in primary cells. Four variants showed enhanced entry into the macaque sMagi reporter cell line. However, sMagi cells did not express appreciable amounts of CCR5 and GPR15 mRNA, and entry into these cells was not efficiently blocked by a small-molecule CCR5 antagonist, suggesting that sMagi cells express as-yet-unidentified entry cofactors. In summary, we found that a single amino acid at position 324 in the SIV Env V3 loop can modulate both the efficiency and the types of coreceptors engaged by Env and allow for CD4-independent fusion in some cases.     

Membrane Transport Generated by the Osmotic and Hydrostatic Pressure. Correlation Relation for Parameters L p, σ, and ω

Standard approach to membrane transport generated by osmotic andhydrostatic pressures, developed by Kedem and Katchalsky, is based onprinciples of thermodynamics of irreversible processes. In this paper wepropose an alternative technique. We derive transport equations from fewfairly natural assumptions and a mechanistic interpretation of the flows.In particular we postulate that a sieve-type membrane permeability isdetermined by the pore sizes and these are random within certain range.Assuming that an individual pore is either permeable or impermeable tosolute molecules, the membrane reflection coefficient depends on the ratioof permeable and impermeable pores. Considering flows through permeableand impermeable pores separately, we derive equations for the total volumeflux, solute flux and the solvent flux across the membrane. Comparing themechanistic equations to the Kedem-Katchalsky equations we find the formereasier to interpret physically. Based on the mechanistic equations we alsoderive a correlation relation for the membrane transport parameters L _p,, and . This relation eliminates the need for experimentaldetermination of all three phenomenological parameters, which in somecases met with considerable difficulties.     

Thoracic Rat Spinal Cord Contusion Injury Induces Remote Spinal Gliogenesis but Not Neurogenesis or Gliogenesis in the Brain

After spinal cord injury, transected axons fail to regenerate, yet significant, spontaneous functional improvement can be observed over time. Distinct central nervous system regions retain the capacity to generate new neurons and glia from an endogenous pool of progenitor cells and to compensate neural cell loss following certain lesions. The aim of the present study was to investigate whether endogenous cell replacement (neurogenesis or gliogenesis) in the brain (subventricular zone, SVZ; corpus callosum, CC; hippocampus, HC; and motor cortex, MC) or cervical spinal cord might represent a structural correlate for spontaneous locomotor recovery after a thoracic spinal cord injury. Adult Fischer 344 rats received severe contusion injuries (200 kDyn) of the mid-thoracic spinal cord using an Infinite Horizon Impactor. Uninjured rats served as controls. From 4 to 14 days post-injury, both groups received injections of bromodeoxyuridine (BrdU) to label dividing cells. Over the course of six weeks post-injury, spontaneous recovery of locomotor function occurred. Survival of newly generated cells was unaltered in the SVZ, HC, CC, and the MC. Neurogenesis, as determined by identification and quantification of doublecortin immunoreactive neuroblasts or BrdU/neuronal nuclear antigen double positive newly generated neurons, was not present in non-neurogenic regions (MC, CC, and cervical spinal cord) and unaltered in neurogenic regions (dentate gyrus and SVZ) of the brain. The lack of neuronal replacement in the brain and spinal cord after spinal cord injury precludes any relevance for spontaneous recovery of locomotor function. Gliogenesis was increased in the cervical spinal cord remote from the injury site, however, is unlikely to contribute to functional improvement.     

Semisynthesis of Arg15, Glu15, Met15, and Nle15-aprotinin involving enzymatic peptide bond resynthesis

The semisynthesis of homologues of aprotinin, the bovine pancreatic trypsin inhibitor, is described. The P₁ lysine¹⁵ residue was replaced by two methods. The first procedure, which consisted of two enzymatic steps for the incorporation of other amino acids has previously been described. The second approach consisted of six steps of both enzymatic and chemical nature. The modified inhibitor, in which the lysine¹⁵-alanine¹⁶ peptide bond is hydrolyzed, was used as the starting material. All carboxyl groups of the modified inhibitor were esterified with methanol; the lysine¹⁵ methylester group was then selectively hydrolyzed. Afterward, lysine¹⁵ itself was split off. Arginine, glutamic acid, methionine, andl-2-aminohexanoic acid (norleucine, Nle) were incorporated using water-soluble carbodiimide combined with an acylation catalyst. The methylester group was used to prevent polymerization. The reactive-site peptide bonds were resynthesized using either chymotrypsin or trypsin.     

Integrin-linked kinase controls microtubule dynamics required for plasma membrane targeting of caveolae

Caveolae are specialized compartments of the plasma membrane that are involved in signaling, endocytosis, and cholesterol transport. Their formation requires the transport of caveolin-1 to the plasma membrane, but the molecular mechanisms regulating the transport are largely unknown. Here, we?identify a critical role for adhesion-mediated signaling through β1 integrins and integrin-linked kinase (ILK) in caveolae formation. Mice lacking β1 integrins or ILK in keratinocytes have dramatically reduced numbers of plasma membrane caveolae in?vivo, which is due to impaired transport of caveolin-1-containing vesicles along microtubules (MT) to the plasma membrane. Mechanistically, ILK promotes the recruitment of the F-actin binding protein IQGAP1 to the cell cortex, which, in turn, cooperates with its?effector mDia1 to locally stabilize MTs and to allow?stable insertion of caveolae into the plasma membrane. Our results assign an important role to the integrin/ILK complex for caveolar trafficking to the cell surface.