A Comparison of Isozyme and Quantitative Genetic Variation in Pinus Contorta Ssp. Latifolia by F(st)

We employed F-statistics to analyze quantitative and isozyme variation among five populations of Pinus contorta ssp. latifolia, a wind-pollinated outcrossing conifer with wide and continuous distribution in west North America. Estimates of population differentiation (F(ST)) for six quantitative traits were compared with the overall estimate of the differentiation (F*(ST)) from 19 isozymes that tested neutral to examine whether similar evolutionary processes were involved in morphological and isozyme differentiation. While the F(ST) estimates for specific gravity, stem diameter, stem height and branch length were significantly greater than the F*(ST) estimate, as judged from the 95% confidence intervals by bootstrapping, the F(ST) estimates for branch angle and branch diameter were indistinguishable from the F*(ST) estimate. Differentiation in stem height and stem diameter might reflect the inherent adaptation of the populations for rapid growth to escape suppression by neighboring plants during establishment and to regional differences in photoperiod, precipitation and temperature. In contrast, divergences in wood specific gravity and branch length might be correlated responses to population differentiation in stem growth. Possible bias in the estimation of F(ST) due to Hardy-Weinberg disequilibrium (F(IS) & 0), linkage disequilibrium, maternal effects and nonadditive genetic effects was discussed with special reference to P. contorta ssp. latifolia.     

A late role for a subset of neurogenic genes to limit sensory precursor recruitments in Drosophila embryos

Summary In Drosophila, mutations in a class of genes, the neurogenic genes, produce an excess of neurons. This neural hyperplasia has been attributed to the formation of more than the normal number of neuronal precursor cells at the expense of epidermal cells. In order to find out whether the neurogenic genes only act at this intial step of neurogenesis, we studied the replication pattern of the sensory organ precursor cells by monitoring BrdU incorporation in embryos mutant for Notch (N), Delta (Dl), mastermind (mam), almondex (amx), neuralized (neu), big brain (bib) and the Enhancer of split-Complex (E(spl)-C). Using temperature sensitive alleles of two of the neurogenic genes, DI and N, we also induced an acute increase of replicating sensory precursors by shifting briefly to the restricted temperature. We have found that the loss of function of all the seven neurogenic loci that were tested causes an increase in replicating sensory precursor cells, consistent with the model that these neurogenic genes normally participate in the process of restricting the number of neuronal precursors. Whereas the temporal pattern of replication appeared normal in mutants of five of the seven neurogenic loci, in N and mam embryos replicating PNS cells are present beyond the time when they normally undergo replication. Experiments with colchicine suggest that many of these late replicating cells may be newly emerging precursors and probably not additional cell divisions of already recruited precursors. Thus, different neurogenic genes may be required over different periods of time for the specification of sensory precursor cells. Correspondence to: R. Bodmer     

Application of CNDO2 theoretical calculations to interpretation of the chemical reactivity and biological activity of the syn and anti diolepoxides of benzo[a]pyrene

$\text{CNDO}\text{2}$ molecular orbital theoretical calculations performed on the anti and syn diolepoxides (1 and 2) of the potent carcinogen benzo[a]pyrene provide insight into the molecular structure and reactivity of these mutagenic and carcinogenic hydrocarbon metabolites. Hydrogen-bonded interaction between the 7-HO proton and the epoxide oxygen atom of 2 is shown to be absent in the normal semichair conformation of the tetrahydro ring, (H…O bond distance = 2.7 Å), but is energetically favored in a somewhat distorted puckered structure (H…O bond distance = 1.7 Å). Unexpectedly, internal H-bonding alters the relative electron density at C₉ and C₁₀, leading to prediction of the former as the more electrophilic center. Since all reactions of 2 take place exclusively at C₁₀, transannular H-bonding is concluded not to contribute significantly to the structure of 2. Diolepoxide reactions with both weak and strong nucleophiles and with DNA are discussed and the mechanisms interpreted in terms of molecular structure as determined by the theoretical calculations.     

Dynamic light scattering characterization of the detergent-free,delipidated (Ca2+ + Mg2+)-ATPase from sarcoplasmic reticulum

Dynamic light scattering studies have been conducted on the delipidated and detergent-removed (Ca²⁺ + Mg²⁺)-ATPase protein assemblies. Specific characterization of the state of aggregation and the extent of conformation change upon delipidation and detergent removal has been made. The results show that the prominent species are dimers and tetramers of very globular nature, with axial ratios of less than 2 : 1. The hydrodynamic radii of the dimers and the tetramers are, respectively, 57.5 Å and 74.5 Å.The globular nature of these observed entities differ from the delipidated ATPase proteins recently obtained (LeMaire, M., Jorgensen, K.E., Roigaard-Petersen, H. and Moller, J.V. (1976) Biochemistry 15, 5805–5812). Present results suggest that upon the removal of detergents from the lipid-free ATPase protein assembly, only a rather limited degree of aggregation takes place. Such a condition is consistent with models of the membrane protein system which has limited regions of hydrophobic contact. Oligomeric assemblies with aqueous channels is a possible active Ca²⁺ transport model consistent with results of the present data, as well as the data from several other recent studies.     

Chronic instrumentation and longterm investigation in the fetal and maternal baboon: tether system, conditioning procedures and surgical techniques

A tether system, conditioning procedures and surgical techniques were designed to maintain chronic catheters and electrodes in the pregnant baboon and her fetus. The tether system was comprised of a lightweight metal backpack containing catheters and electrodes, couplers, pressure transducers and electrical cabling. The backpack was held snugly in place by shoulder and body straps. A flexible metal tether connected the pack to a ball bearing assembly mounted on the top of the animal's home cage. Attached to the assembly were two infusion pumps, fluid reservoir and slip ring electrical connector. The entire system rotated freely with the movements of the animal; thus, the instrumentation and connectors were secure while access was maintained for continuous physiologic recording and intravascular infusion or intermittent blood sampling with minimal physical restraint. Animals were conditioned to accept the system prior to pregnancy and animals who demonstrated tolerance were bred. An initial group of 10 pregnant animals were sham tethered during pregnancy at 102 +/- 7 days with term gestation estimated at 180 days. Surgical procedures were done at 136 +/- 4 days with placement of catheters in the maternal femoral artery and vein, fetal carotid artery jugular vein and trachea, amniotic fluid cavity, and electrodes for fetal electrocardiogram and electroencephalogram. The mean fetal survival time was 9.3 (range 0 to 29) days. The major complications which led to early delivery were placental abruption and rupture of amniotic membranes. With ultrasonic localization of the placenta and determination of fetal position before surgery, these complications may be avoided.(ABSTRACT TRUNCATED AT 250 WORDS)     

Selection of T cell receptor expression mutants through the functionally linked Ly-6A

Ly-6A is a glycosyl-phosphatidylinositol (GPI)-anchored molecule that participates in murine T cell activation. Activation of T cell hybridomas with anti-Ly-6A monoclonal antibody (mAb) leads to production of interleukin-2 (IL-2), but also to a paradoxical growth inhibition, which was used to select for signaling mutants. Fifteen subclones derived from two independent mutageneses and anti-Ly-6A selection were characterized. Thirteen subclones responded poorly or not at all to soluble anti-Ly-6A mAb. Although the selective pressure was exerted through Ly-6A, only one mutant did not express the Ly-6A antigen. Interestingly, 10 of the 15 subclones expressed either nondetectable or a very low level of T cell receptor/CD3 complex (TCR/CD3). Preferential expansion of TCR/CD3 expression mutants following anti-Ly-6A selection further established functional linkage between Ly-6A and TCR/CD3 complex. The mechanism of the functional coupling was investigated by analyzing the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), one of the early events in T cell activation. We showed that PIP2 was not hydrolyzed in response to anti-Ly-6A in TCR/CD3-negative mutants. Aluminum fluoride, which activates G protein directly, did induce PIP2 hydrolysis in these cells. These data suggest that activation signals originated from Ly-6A must be transmitted first to TCR/CD3 complex, which then couples to the G protein/phospholipase C system. A similar requirement also applies to the Thy-1 protein and lectin receptors. Thus, the TCR/CD3 complex plays a central role in the integration and transmission of activation signals that originated from several T cell surface molecules.     

Hemocyanin–antibody labeling of rhodopsin in mouse retina for a scanning electron microscope study

To reveal the presence of rhodopsin on the surface of the mouse retina, a scanning electron microscope study of the immunolabeling of rhodopsin was attempted. The glutaraldehyde-fixed mouse retina was treated first with rabbit antibodies specific against bovine rhodopsin and then with hemocynin-labeled goat antibodies specific against rabbit antibody. The distribution of hemocyanin label on mouse retina and the technique used for labeling are discussed.     

Hydrophilic gelatin and hyaluronic acid-treated PLGA scaffolds for cartilage tissue engineering

Tissue engineering provides a new strategy for repairing damaged cartilage. Surface and mechanical properties of scaffolds play important roles in inducing cell growth.?Aim: The aim of this study was to fabricate and characterize PLGA and gelatin/hyaluronic acid-treated PLGA (PLGA-GH) sponge scaffolds for articular cartilage tissue engineering. Methods: The PLGA-GH scaffolds were cross-linked with gelatin and hyaluronic acid. Primary chondrocytes isolated from porcine articular cartilages were used to assess cell compatibility. The characteristic PLGA-GH scaffold was higher in water uptake ratio and degradation rate within 42 days than the PLGA scaffold. Results: The mean compressive moduli of PLGA and PLGA-GH scaffolds were 1.72±0.50 MPa and 1.86±0.90 MPa, respectively. The cell attachment ratio, proliferation, and extracellular matrix secretion on PLGA-GH scaffolds are superior to those of PLGA scaffolds. Conclusions: In our study, PLGA-GH scaffolds exhibited improvements in cell biocompatibility, cell proliferation, extracellular matrix synthesis, and appropriate mechanical and structural properties for potential engineering cartilage applications.