Lewontin and Kojima Meet Fisher: Linkage in a Symmetric Model of Sex Determination

The effect of linkage and epistasis on the evolution of the sex-ratio is studied in a symmetric two-locus model of autosomal sex determination closely related to the symmetric viability model of R. C. Lewontin and K. Kojima. R. A. Fisher's expectation of an even sex ratio for autosomal sex determination by a single gene governs the dynamics when the loci are tightly linked. However, recombination may preclude optimization of the sex ratio just as occurs in viability selection models. Many of the evolutionary phenomena known for the symmetric viability model also occur here. In addition, we exhibit a series of new phenomena related to the presence of surfaces of even sex ratio.     

In vivo binding and clearance of circulating antigen by bispecific heteropolymer-mediated binding to primate erythrocyte complement receptor.

We have used the avidin/biotin system to construct soluble, cross-linked bispecific heteropolymers containing mAb to both the primate E C receptor and the DNP group. These heteropolymers facilitate in vitro binding of DNP-bovine gamma-globulin (DNP-BGG) to both human and squirrel monkey E. Intravenous injection in squirrel monkeys of DNP-BGG followed by heteropolymer leads to E binding and clearance from the circulation of a significant fraction of both heteropolymer and DNP-BGG, without lysis or clearance of the E. This methodology may potentially be used to treat a variety of infectious diseases and other syndromes associated with blood-borne pathogens.     

Genetic and biochemical characterization of a new chymotrypsin isozyme of the house mouse,CTRA-1

Genetic variation of a codominantly inherited pancreas protease, designated CTRA-1, was discovered in the house mouse by isoelectric focusing in polyacrylamide gels. Phenotype CTRA-1A was found in MOLH/Fre and in the majority of common laboratory mouse strains. Phenotype CTRA-1B was found in PWD/Ph. It was characterized by the absence of a corresponding protease band. A third phenotype, CTRA-1C, was observed in IS/Cam and a fourth phenotype, CTRA-1D, was detected in SEG/1. CTRA-1 was found only in the pancreas and may represent the A form of chymotrypsin. The enzyme was shown to be controlled by the presumed structural locus Ctra-1 located on chromosome 8. From two backcross series, including a total of 274 animals, the gene order (Es-1, Es-9)-3.9 +/- 1.7%-Got-2-3.9 +/- 1.7%-(Es-2, Es-7, Es-23)-0.7 +/- 0.5%- Ctra-1-6.3 +/- 2.2%-Prt-2 was established.     

The hydrogen-bonding structure in parallel-stranded duplex DNA is reverse Watson-Crick

Raman spectra of the parallel-stranded duplex formed from the deoxyoligonucleotides 5'-d-[(A)10TAATTTTAAATATTT]-3' (D1) and 5'-d[(T)10ATTAAAATTTATAAA]-3' (D2) in H2O and D2O have been acquired. The spectra of the parallel-stranded DNA are then compared to the spectra of the antiparallel double helix formed from the deoxyoligonucleotides D1 and 5'-d(AAATATTTAAAATTA-(T)10]-3' (D3). The Raman spectra of the antiparallel-stranded (aps) duplex are reminiscent of the spectra of poly[d(A)].poly[d(T)] and a B-form structure similar to that adopted by the homopolymer duplex is assigned to the antiparallel double helix. The spectra of the parallel-stranded (ps) and antiparallel-stranded duplexes differ significantly due to changes in helical organization, i.e., base pairing, base stacking, and backbone conformation. Large changes observed in the carbonyl stretching region (1600-1700 cm-1) implicate the involvement of the C(2) carbonyl of thymine in base pairing. The interaction of adenine with the C(2) carbonyl of thymine is consistent wtih formation of reverse Watson-Crick base pairing in parallel-stranded DNA. Phosphate-furanose vibrations similar to those observed for B-form DNA of heterogenous sequence and high A,T content are observed at 843 and 1092 cm-1 in the spectra of the parallel-stranded duplex. The 843-cm-1 band is due to the presence of a sizable population of furanose rings in the C2'-endo conformation. Significant changes observed in the regions from 1150 to 1250 cm-1 and from 1340 to 1400 cm-1 in the spectra of the parallel-stranded duplex are attributed to variations in backbone torsional and glycosidic angles and base stacking.     

Comparison of Neurologic Responses to the Use of Medetomidine as a Sole Agent or Preanesthetic in Laboratory Beagles

Different dose regimens of medetomidine (a potent α2-adrenergic agonist), adding up to a combined dose of 80 µg/kg, were administered to laboratory beagles to determine physiologic responses including neurologic. The study was intended to determine EEG responses where sufficient sedative and analgesic effects are reached with medetomidine and in contrast its effects when used with ketamine or halothane. Cardiopulmonary responses were very similar in each dose regimen, showing the characteristic properties of single doses of 80 µg/kg of medetomidine. Effective sedative and analgesic duration seemed to be a function of when the largest dose was administered. Adequate additional sedative and analgesic could be gained from injections at doses of half of the initial one. The potent sedative and analgesic effects of medetomidine confirmed by neurologic evaluation supports its potential use as a premedication to general anesthesia in dogs. In this study, 2 different doses of medetomidine were also tested as premedication to both ketamine HCl and halothane anesthesia. Neorologic responses were determined at the same time cardiopulmonary parameters, anesthetic quality, and dose requirements were recorded. Medetomidine was found to have favorable qualities in conjunction with these anesthetics. Cardiopulmonary parameters remained satisfactory in both groups as preanesthetic medication prior to halothane, but no additional benefits could be seen from doses of 40 µg/kg medetomidine compared to 20 µg/kg, except a significant 30% reduction in halothane requirement. The positive chronotropic and inotropic properties of ketamine restored the medeto-midine-induced bradycardia and produced a short anesthetic period of 15 to 30 min depending on the dose of medetomidine. The quality of anesthesia was better when 40 µg/kg medetomidine was used, but recorvery was quicker with 20 µg/kg medetomidine. Medetomidine significantly reduced cerebral activity as demonstrated by recordings of total amplitude and frequency evaluation of the EEG with compressed spectral analysis. This analytical method was effective in confirming clinical signs of sedation, analgesia, and anesthesia in canine subjects.     

DNA Methylation in Eukaryotes: Kinetics of Demethylation and De Novo Methylation during the Life Cycle

We present a model for the kinetics of methylation and demethylation of eukaryotic DNA; the model incorporates values for de novo methylation and the error rate of maintenance methylation. From the equations, an equilibrium is reached such that the proportion of sites which are newly methylated equals the proportion of sites which become demethylated in a cell generation. This equilibrium is empirically determined as the level of maintenance methylation. We then chose reasonable values for the parameters using maize and mice as model species. In general, if the genome is either hypermethylated or hypomethylated it will approach the equilibrium level of maintenance methylation asymptotically over time; events occurring just once per life cycle to suppress methylation can maintain a relatively hypomethylated state. Although the equations developed are used here as framework for evaluating events in the whole genome, they can also be used to evaluate the rates of methylation and demethylation in specific sites over time.     

The binding of palmitoyl-CoA to bovine serum albumin

Bovine serum albumin (BSA) is routinely utilized in vitro to prevent the adverse detergent effects of long-chain acyl-CoA esters (i.e., palmitoyl-CoA) in enzyme assays. Determination of substrate saturation kinetics in the presence of albumin would only be valid if the relationship between bound and free substrate concentrations was known. To elucidate the relationship between bound and free palmitoyl-CoA concentrations in the presence of BSA, several different techniques including equilibrium dialysis, equilibrium partitioning, fluorescence polarization and direct fluorescence enhancement were investigated. Direct fluorescence enhancement using a custom synthesized fluorescent probe, 16-(9-anthroyloxy)palmitoyl-CoA (AP-CoA), was the best approach to this question. Measurement of the relationship between mol of palmitoyl-CoA bound per mol of BSA (nu) versus -log[free palmitoyl-CoA] revealed that the binding of palmitoyl-CoA to BSA, like palmitate was nonlinear, suggesting the presence of more than one class of acyl-CoA binding sites. Computer analyses of the binding data gave a best fit to the 2,4 two-class Scatchard model, suggesting the presence of two high-affinity primary binding sites (k1 = (1.55 +/- 0.46) x 10(-6) M-1) and four lower affinity secondary binding sites (k2 = (1.90 +/- 0.09) x 10(-8) M-1). Further analyses using the six parameter stoichiometric (stepwise) ligand binding model supports the existence of six binding sites with the higher affinities associated with the binding of the first mole of palmitoyl-CoA and weaker binding occurring after the first two sites are occupied. The association constants from this model of multiple binding diminish sequentially (i.e., K1 greater than K2 greater than K3 greater than...greater than or equal to K6), suggesting that each mol of long-chain acyl-CoA binds to BSA with decreasing affinities.     

Epidermal growth factor initiates DNA synthesis after a time-dependent sequence of regulatory events in Swiss 3T3 cells—interactions with hormones and growth factors

Epidermal growth factor (EGF) stimulates the initiation of DNA synthesis in Swiss 3T3 cells after a constant prereplicative period of 14–15 hours. The final rate of initiation follows apparent first-order kinetics and can thus be quantified by a rate constant k. The value of k can be changed by later additions during the prereplicative period: When cells stimulated by a very low concentration of EGF, alone or with insulin, which results in a relatively low value of k, receive a saturating amount of EGF at 15 hours, then k is markedly increased after 4–6 hours. Insulin alone (up to 200 ng/ml) is unable to set the lag phase, but does have a synergistic effect on the value of k given by EGF. When added at 15 hours, insulin also increases k, but after a delay of 4–6 hours. In contrast, both hydrocortisone and prostaglandin E₁ (PGE₁) inhibit the stimulation of DNA synthesis by EGF only during the first 8 hours of the prereplicative period of decreasing the value of k. Prostaglandin F_2α (PGF_2α), which stimulates DNA synthesis in a similar mode as EGF, when added with EGF has a synergistic effect on DNA synthesis. This suggests that EGF and PGF_2α, nevertheless, act through different regulatory events.     

C-methyl phenolics from Qualea species

The trunk wood of Qualea labouriauana contains, besides (2R)-5,7,4′-trihydroxy-3′-methoxy-6,8-dimethylflavanone, (2R)-5,7,4′-trihydroxy-8-methylflavanone, the biosynthetically interesting 2,2′-dihydroxy-4,6,4′,6′-tetramethoxy-3,3′-dimethylbenzophenone. From the trunk wood extract of Q. paraensis the first named flavanone crystallized out directly.     

Dehydrodieugenols from Ocotea cymbarum

The trunk wood of Ocotea cymbarum from the Amazon basin contains α-phellandrene, α-pinene, eugenol, dehydrodieugenol and its monomethyl ether, as well as the previously unknown dehydrodieugenol-B (4,5′-diallyl-2′-hydroxy-2,3′-dimethoxydiphenyl ether).