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The interaction between protein-transduction domain (PTD) of the HIV-1 Tat protein and the lipid bilayer labeled with various fluorescence membrane probes is studied by using fluorescence spectroscopy. It is concluded that the membrane fluidity is an important physicochemical parameter, which regulates binding of TAT-PTD to the membrane.

The current hypothesis on the mode of action of the cytolytic delta-endotoxin Cyt 1 A from Bacillus thuringiensis is that the toxin self-assembles into well-defined cation-selective channels or pores, which result in colloidosmotic lysis of the cell. But, a new hypothesis suggests that Cyt 1 A aggregates on the membrane surface and acts in a detergent-like manner, since no change in size or morphology of the vesicles is expected when pores are formed in the osmotically equilibrated membranes.

Standardized extract from the leaves of the Ginkgo biloba tree, labeled EGb761, has been used in clinical trials for its beneficial effects on brain functions, particularly in connection with age-related dementias and Alzheimer's disease (AD). Substantial experimental evidence indicates that EGb761 protects against neuronal damage from a variety of insults, but its cellular and molecular mechanisms remain unknown. Using a neuroblastoma cell line stably expressing an AD-associated double mutation, we report that EGb761 inhibits formation of amyloid-[beta] (A[beta]) fibrils, which are the diagnostic, and possibly causative, feature of AD. The decreased A[beta] fibrillogenesis in the presence of EGb761 was observed both in the conditioned medium of this A[beta]-secreting cell line and in solution in vitro. In the cells, EGb761 significantly attenuated mitochondrion-initiated apoptosis and decreased the activity of caspase 3, a key enzyme in the apoptosis cell-signaling cascade. These results suggest that (i) neuronal damage in AD might be due to two factors: a direct A[beta] toxicity and the apoptosis initiated by the mitochondria; and (ii) multiple cellular and molecular neuroprotective mechanisms, including attenuation of apoptosis and direct inhibition of A[beta] aggregation, underlie the neuroprotective effects of EGb761.

Quantification of the conformation changes in CytA, a cytolytic delta-endotoxin from Bacillus thuringiensis var. israelensis, following its binding with small unilamellar lipid vesicles (SUV) revealed structural changes in CytA upon binding to the membrane. Data show that the trytophan-containing areas of the protein do not penetrate the hydrophobic core of the lipid bilayer. Fourier-transform infrared spectroscopy found that binding results in a loosening of the protein structure without a loss of secondary structure.

The mechanism by which cytolytic delta-endotoxin, CytA, from Bacillus thuringiensis var. israelensis permeabilizes membranes and induces the release of self-quenching fluorescence markers from unilamellar vesicles was determined by measuring its reaction kinetics. The rates of release of fluorescence markers were influenced by the concentration of CytA. CytA exhibited a low association constant to lipid membranes. The results also revealed that binding of a large number of toxin molecules to unilamellar vesicles is essential to maintain the integrity of the latter.

Group B streptococci (GBS) cause sepsis and meningitis in neonates and serious infections in adults with underlying chronic illnesses. Specific antibodies have been shown to be an important factor in protective immunity for neonates, but the role of serum complement is less well defined. To elucidate the function of the complement system in immunity to this pathogen, we have used the approach of gene targeting in embryonic stem cells to generate mice totally deficient in complement component C3. Comparison of C3-deficient mice with mice deficient in complement component C4 demonstrated that the 50% lethal dose for GBS infection was reduced by [nearly equal to] 50-fold and 25-fold, respectively, compared to control mice. GBS were effectively killed in vitro by human blood leukocytes in the presence of specific antibody and C4-deficient serum but not C3-deficient serum. The defective opsonization by C3-deficient serum in vitro was corroborated by in vivo studies in which passive immunization of pregnant dams with specific antibodies conferred protection from GBS challenge to normal and C4-deficient pups but not C3-deficient pups. These results indicate that the alternative pathway is sufficient to mediate effective opsonophagocytosis and protective immunity to GBS in the presence of specific antibody. In contrast, the increased susceptibility to infection of nonimmune mice deficient in either C3 or C4 implies that the classical pathway plays an essential role in host defense against GBS infection in the absence of specific immunity.

The molecular sterol transfer mechanism, involving anionic phospholipids and liver sterol carrier protein-2 (SCP2), induces sterol domain structural modifications and variations in the sterol desorption rate via protein-membrane surface interactions. SCP2 is independent of the protein's ability to facilitate sterol transfer during sterol binding.

The author reviews the publications on cytolytic toxin Cyt1A. The topics of interest include the role of this toxin in mosquitocidal activity, and its potential in synergistic mixtures of Bacillus thuringiensis preparations and in fighting insects' resistance to B. thuringiensis toxins.

It is not easy to test evolution experimentally, mostly due to the near impossibility of controlled experimentation and, consequently, the lack of reproducibility. Thus the evolution theory is not universally [...]

The Division of Cellular, Molecular and Developmental Biology accepted twenty-nine contributions, including nine posters. Amongst the oral presentations, twelve were by graduate and seven by undergraduate students. The unequal distribution [...]