Immune deficiency in the X-linked lymphoproliferative syndrome. I. Epstein-Barr virus-specific defects

Eleven males with XLP were evaluated for EBV-specific antibodies during periods of 2 to 7 yr. Variable responses to EBV-specific antigens were found. All 11 patients had subnormal anti-EBNA titers, which probably reflected a T cell deficiency. The patients showed four different patterns in their anti-VCA response: 1) two boys who had experienced malignant lymphoma mounted no antibodies at all; 2) two patients showed intermittent anti-VCA titers; 3) four males had persistently elevated anti-VCA titers; and 4) three patients showed normal anti-VCA titers. ADCC against EBV-infected cells was abnormally low in six patients and was elevated in two patients given gamma-globulin. ADCC titers did not correlate with anti-VCA titers. However, most patients with XLP failed to effect regression of autologous EBV-infected lymphoblastoid cell lines, indicating a deficiency in long-lived T cell-mediated immunity to EBV.     

Molecular Dynamics Simulations of PIP2 and PIP3 in Lipid Bilayers: Determination of Ring Orientation, and the Effects of Surface Roughness on a Poisson-Boltzmann Description

Molecular dynamics (MD) simulations of phosphatidylinositol (4,5)-bisphosphate (PIP₂) and phosphatidylinositol (3,4,5)-trisphosphate (PIP₃) in 1-palmitoyl 2-oleoyl phosphatidylcholine (POPC) bilayers indicate that the inositol rings are tilted ∼40° with respect to the bilayer surface, as compared with 17° for the P-N vector of POPC. Multiple minima were obtained for the ring twist (analogous to roll for an airplane). The phosphates at position 1 of PIP₂ and PIP₃ are within an Ångström of the plane formed by the phosphates of POPC; lipids in the surrounding shell are depressed by 0.5-0.8 Å, but otherwise the phosphoinositides do not substantially perturb the bilayer. Finite size artifacts for ion distributions are apparent for systems of ∼26 waters/lipid, but, based on simulations with a fourfold increase of the aqueous phase, the phosphoinositide positions and orientations do not show significant size effects. Electrostatic potentials evaluated from Poisson-Boltzmann (PB) calculations show a strong dependence of potential height and ring orientation, with the maxima on the −25 mV surfaces (17.1 ± 0.1 Å for PIP₂ and 19.4 ± 0.3 Å for PIP₃) occurring near the most populated orientations from MD. These surfaces are well above the background height of 10 Å estimated for negatively charged cell membranes, as would be expected for lipids involved in cellular signaling. PB calculations on microscopically flat bilayers yield similar maxima as the MD-based (microscopically rough) systems, but show less fine structure and do not clearly indicate the most probable regions. Electrostatic free energies of interaction with pentalysine are also similar for the rough and flat systems. These results support the utility of a rigid/flat bilayer model for PB-based studies of PIP₂ and PIP₃ as long as the orientations are judiciously chosen.     

Possible explanation of the disparity between the in vitro and in vivo measurements of Rubisco activity: a study in loblolly pine grown in elevated pCO2.

Rubisco activity can be measured using gas exchange (in vivo) or using in vitro methods. Commonly in vitro methods yield activities that are less than those obtained in vivo. Rubisco activity was measured both in vivo and in vitro using a spectrophotometric technique in mature Pinus taeda L. (loblolly pine) trees grown using free-air CO2 enrichment in elevated (56 Pa) and current (36 Pa) pCO2. In addition, for studies where both in vivo and in vitro values of Rubisco activity were reported net CO2 uptake rate (A) was modelled based on the in vivo and in vitro values of Rubisco activity reported in the literature. Both the modelling exercise and the experimental data showed that the in vitro values of Rubisco activity were insufficient to account for the observed values of A. A trichloroacetic acid (TCA) precipitation of the protein from samples taken in parallel with those used for activity analysis was co-electrophoresed with the extract used for determining in vitro Rubisco activity. There was significantly more Rubisco present in the TCA precipitated samples, suggesting that the underestimation of Rubisco activity in vitro was attributable to an insufficient extraction of Rubisco protein prior to activity analysis. Correction of in vitro values to account for the under-represented Rubisco yielded mechanistically valid values for Rubisco activity. However, despite the low absolute values for Rubisco activity determined in vitro, the trends reported with CO2 treatment concurred with, and were of equal magnitude to, those observed in Rubisco activity measured in vivo.     

THE ZOOSPORE OF CHLOROKYBUS ATMOPHYTICUS,A CHAROPHYTE WITH SARCINOID GROWTH HABIT

Chlorokybus atmophyticus has a sarcinoid growth habit and produces scale-covered zoospores. Flagella are laterally inserted and attached internally to a multilayered structure characteristic of the Charophyceae. There are two kinds of pyrenoid in each cell, a feature previously observed in only one scaly green flagellate. C. atmophyticus demonstrates that the sarcinoid growth habit arose independently at least twice in the green algae and cannot be used to define taxonomic groups unless combined with other criteria. It is further concluded that C. atmophyticus should be classified in a separate family Chlorokybaceae and a separate order Chloroky bales.     

Inter-monomer electron transfer is too slow to compete with monomeric turnover in bc1 complex

The homodimeric bc₁ complexes are membrane proteins essential in respiration and photosynthesis. The ~ 11 Å distance between the two b_L-hemes of the dimer opens the possibility of electron transfer between them, but contradictory reports make such inter-monomer electron transfer controversial. We have constructed in Rhodobacter sphaeroides a heterodimeric expression system similar to those used before, in which the bc₁ complex can be mutated differentially in the two copies of cyt b to test for inter-monomer electron transfer, but found that genetic recombination by cross-over then occurs to produce wild-type homodimer. Selection pressure under photosynthetic growth always favored the homodimer over heterodimeric variants enforcing inter-monomer electron transfer, showing that the latter are not competitive. These results, together with kinetic analysis of myxothiazol titrations, demonstrate that inter-monomer electron transfer does not occur at rates competitive with monomeric turnover. We examine the results from other groups interpreted as demonstrating rapid inter-monomer electron transfer, conclude that similar mechanisms are likely to be in play, and suggest that such claims might need to be re-examined.     

The role of introns in evolution

What are the roles of 'classical' introns in the evolution of nuclear genes, and what was the origin of these introns? Exon shuffling has been important in the evolution of cell surface and extracellular proteins, but the evidence for it in respect of intracellular proteins is weak. Intron distributions imply that some introns have been removed while others have been inserted in the course of evolution: ancestral patterns of introns may thus have been obscured. Recent evidence on the self-splicing and reverse-splicing abilities of Group II introns supports the hypothesis that these could have been the ancestors of classical introns.     

Skeletal muscle creatine kinase MB alterations in women marathon runners

Total creatine kinase (CK) and CK MB activities were determined in gastrocnemius muscle and serum obtained from 14 female marathon runners. The level of CK MB in muscle increased significantly (p less than 0.05) after chronic exercise training from 5.3% to 10.5% of the total CK activity, but not after acute exercise (post-marathon 8.9%). No significant differences in total CK activities were detected. However, the total CK activity in the muscles were significantly (p less than 0.05) less than those previously reported from the muscle of men runners (1800 U/g, 3000 U/g respectively). No significant correlation existed between fiber type and muscle CK MB activity. Additionally, trace amounts of mitochondrial CK and CK BB were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (597 UL-1) and CK MB (23 UL-1) activities 24 h after the race (r = 0.97, p less than 0.05). These results suggest that gastrocnemius muscle in women adapts to training with increased CK MB activities and imply that skeletal muscle is the major source of elevated serum CK MB activities in women marathon runners.     

Effects of Δ8- and Δ9-Tetrahydrocannabinol on experimentally induced seizures

Effects of Δ⁸- and Δ⁹-tetrahydrocannabinol (Δ⁸- and Δ⁹-THC) on three experimentally induced seizure models, i.e., audiogenic seizure (AS) test, maximal electroshock seizure (MES) test and pentylenetetrazol (PTZ)-induced seizure test were determined in the audiogenic rat. Both tetrahydrocannabinols possess a dose-related anticonvulsant effect against AS, MES and PTZ-induced maximal seizure. Although anticonvulsant potencies do not significantly differ, Δ⁸THC is three times more neurotoxic than Δ⁹THC. In addition, both THC's are without effect on minimal seizure and lethality induced by PTZ. Furthermore, the low protective indexes (TD50/ED50) determined in this study suggest that Δ⁸ and Δ⁹ THC may have poor therapeutic potentials as antiepileptic drugs.