The determination of genome size in male and female germ cells of Drosophila melanogaster by DNA-feulgen cytophotometry

Summary The amounts of DNA in haploid and diploid cells of Drosophila melanogaster have been determined by DNA-Feulgen cytophotometry, using Xenopus laevis erythrocyte nuclei as a reference standard. The haploid male genome is estimated to be 0.18 pg DNA and the haploid female genome, 0.20 pg DNA.     

Calcium-dependent slow potassium conductance in rat skeletal myotubes

A prolonged hyperpolarizing afterpotential (amplitude 5–20 mV, half decay time about 400 msec at 25°C) follows the action potential in myotubes and myosacs cultured from rat skeletal muscle. This slow hyperpolarizing afterpotential (hap) is mediated by an increase in membrane K conductance, because its reversal potential follows the Nernst potential for K and is not affected by other ions. The conductance increase measured during the hap (up to four times the resting input conductance) correctly predicts the time course of the slow hap. The slow hap is Ca dependent. Its amplitude decreases when bath [Ca] is lowered, and both amplitude and duration increase when bath [Ca] is raised. The slow hap is blocked by intracellular injection of the calcium chelator, EGTA. It is inhibited by solutions containing 2–4 mM manganese or 1–5 mM barium, but is not blocked by 5–20 mM tetraethylammonium. Myotubes bathed in zero [Na], high [Ca] solutions show calcium action potentials, which are inhibited by 2–10 mM manganese, nickel or cobalt. Myotubes bathed in isotonic Ca salts (or in 2 mM Ca plus 5 mM caffeine) show long-lasting (up to 10 sec) spontaneous hyperpolarizations accompanied by prolonged contractions. These hyperpolarizations are associated with a large increase in input conductance, and they reverse in sign near the K equilibrium potential. They appear to reflect activation of the Ca-sensitive K conductance by Ca released from intracellular stores. The observation that spontaneous hyperpolarizations usually occur with no prior depolarization argues that at least a portion of the slow, Ca-sensitive K conductance system can be activated by internal Ca alone, with no requirement for plasma membrane depolarization. Cultured myotubes also have a faster K conductance system, which is inhibited by 5–20 mM tetraethylammonium or 1–5 mM barium, and is not dependent on Ca for its activation.     

Treatment of hypertonicity in muscles of lip retraction

An EMG biofeedback program was developed for a 56-year-old Parkinsonism patient who exhibited pathological lip hypertonia and retraction. The program was designed to achieve the following goals: (1) to demonstrate a reduction in postural lip hypertonicity and (2) to demonstrate a reduction in lip hypertonicity during a series of increasingly complex speech activities. To achieve the first goal, contrastive tasks of full contraction and relaxation were utilized. Each posture was sustained while voltage measurements were made at specifici intervals. Procedures to modify lip retraction during speech included five tasks in which the patient was to monitor the audio feedback signal. The tasks involved: prolongation of a neutral vowel, consonant-vowel combinations, monosyllabic words, sentences, and a paragraph-reading task. Data collected over six biofeedback sessions are presented. Trend analyses showed consistent muscular reduction within each task. The following explanations for the decrease in the patient's hypertonicity were discussed: (1) reduction of anisometric contraction, (2) reduction of isometric contraction, (3) relearning of agonistic-antagonistic muscle balance.This research was supported in part by the University of Tennessee Neuropathology Services Program.     

The accumulation of superoxide radical during the aerobic action of xanthine oxidase A requiem for H2O4−

The action of xanthine oxidase upon acetaldehyde or xanthine at pH 10.2 has been shown to be accompanied by substantial accumulation of O₂^? during the first few minutes of the reaction. H₂O₂ decreases this accumulation of O₂^? presumably because of the Haber-Weiss reaction ($\text{H}{}_2\text{O}{}_2\text{+}\text{O}{}_2{}^{\mathrm{?}}\text{→}\text{OH}{}^{\mathrm{?}}\text{+}\text{OH}\text{+}\text{O}{}_2$) and very small amounts of superoxide dismutase eliminate it. This accumulation of O₂^? was demonstrated in terms of a burst of reduction of cytochrome $\text{c}$, seen when the latter compound was added after aerobic preincubation of xanthine oxidase with its substrate. The kinetic peculiarities of the luminescence seen in the presence of luminol, which previously led to the proposal of H₂O₄^?, can now be satisfactorily explained entirely on the basis of known radical intermediates.     

Congruency of phylogenies derived from different proteins

Summary This communication examines the question of phylogenetic congruency- i.e., whether or not the branching order of evolutionary trees is independent of the protein studied. It was found that trees constructed for birds on the basis of immunological comparison of their transferrins, albumins, and ovalbumins agree approximately with a published tree based on the amino acid sequences of their lysozymesc. This congruency is especially noteworthy with respect to the phylogenetic position of the chachalaca, a Mexican bird classified on morphological grounds in the family Cracidae of the order Galliformes. At the protein level, this species differs as much from non-cracid galliform birds as does the duck, which belongs to another order. Despite the organismal similarity between cracid and non-cracid galliform birds, the molecular relationship is remote. If this contrast between organismal and molecular results had been based on comparative studies with only lysozyme, one could have ascribed the contrast to the possibility that chachalaca lysozyme was paralogous, rather than orthologous, to the other bird lysozymesc. Examination of several proteins is thus desirable in cases of possible paralogy.This work was supported in part by grants GB-42028X from NSF and GM-21509 from NIH     

Amino acid sequence and immunological properties of chachalaca egg white lysozyme

Summary The amino acid sequence of lysozyme c from chachalaca egg white was determined. Like other bird lysozymes c, that of the chachalaca has 129 amino acid residues. It differs from other avian lysozymes c by 27 to 31 amino acid substitutions as well as by being devoid of phenylalanine. It contains substitutions at 9 positions which are invariant in the other 7 bird lysozymes of known sequence. Although the chachalaca is classified zoologically in the order Galliformes, which includes chickens and other pheasant-like birds, its lysozyme differs more from those of pheasant-like birds than do the lysozymes c of ducks. Phylogenetic analysis of the sequence comparisons confirms that the lineage leading to chachalaca lysozyme c separated from that leading to other galliform lysozymes c before the duck lysozyme c lineage did. This indicates a contrast between protein evolution and evolution at the organismal level. Immunological comparison of chachalacalysozyme c with other lysozymes of known sequence provides further support for the proposal that immunological cross-reactivity is strongly dependent on degree of sequence resemblance among bird lysozymes.103rd communication on lysozymes from the Laboratory of P. Jollès. Supported in part by grants from C.N.R.S. (ER 102), I.N.S.E.R.M. (Groupe de recherche U-116), N.S.F. (GB-42028X), and N.I.H. (GM-21509).