A small deletion and an adjacent base exchange in a potential stem-loop region of the neurofibromatosis 1 gene

Summary A single-strand conformational polymorphism found in the DNA of a patient with neurofibromatosis 1 (NF1) was shown to be caused by a deletion of a CCACC or CACCT sequence and an adjacent transversion, located about 500 base pairs downstream from the region that codes for a functional domain of the NF1 gene product. This mutation could also be detected in the patient and in his affected daughter by heteroduplex analysis. The deletion removes the proximal half of a small potential stem-loop and interrupts the reading frame in exon 1. A severely truncated protein with a grossly altered carboxy terminus lacking one third of its sequence is expected to be formed from the mutant allele.     

Chrysoperla carnea predation on Heliothis virescens larvae parasitized by Microplitis croceipes

Predation by third instar larvae of Chrysoperla (=Chrysopa) carnea (Stephens) (Chrysopidae) did not alter the ratio of unparasitized Heliothis virescens (F.) (Noctuidae) larvae to H. virescens larvae parasitized by Microplitis croceipes (Cresson) (Braconidae) when these second instar larvae were exposed together to the predator on cotton (Gossypium hirsutum L., Malvaceae) in field cages. This indicates that C. carnea larvae did not prefer either parasitized or unparasitized larvae.

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Prédation par Chrysopa carnea des chenilles d'Heliothis virescens parasitées par Microplitis croceipes

Résumé Les prédations de chenilles d'Heliothis virescens, parasitées ou saines, élevées sur coton (Gossypium hirsutum L.), de la variété Stoneville 213, ont été comparées, dans des cages de 10 m² chacune placées dans la nature. Des chenilles du second stade ont été placées sur des pieds de coton dans 10 cages, à raison de 160 chenilles préalablement exposées à M. croceipes pendant leur premier stade et 40 chenilles saines par cage. Des larves du troisième stade de Chrysopa carnea ont été ajoutées dans 6 cages, à raison de 500/cage, et 4 cages ont servi de témoins pour évaluer les autres causes de mortalité. L'expérience a été répétée 2 fois. Les chenilles d'H. virescens ont été retirées au bout d'un jour dans une expérience et au bout de 2 jours dans l'autre. C. carnea n'a fait aucun choix entre chenilles parasitées ou non; la fréquence moyenne de chenilles parasitées n'a pas présenté de différence significative entre les cages avec ou sans C. carnea. Qui qu'il en soit, C. carnea a réduit significativement la survie des chenilles d'H. virescens parasitées ou non.

     

Reflex control of inspiratory duration in newborn infants

We applied graded resistive and elastic loads and total airway occlusions to single inspirations in six full-term healthy infants on days 2-3 of life to investigate the effect on neural and mechanical inspiratory duration (TI). The infants breathed through a face mask and pneumotachograph, and flow, volume, airway pressure, and diaphragm electromyogram (EMG) were recorded. Loads were applied to the inspiratory outlet of a two-way respiratory valve using a manifold system. Application of all loads resulted in inspired volumes decreased from control (P less than 0.001), and changes were progressive with increasing loads. TI measured from the pattern of the diaphragm EMG (TIEMG) was prolonged from control by application of all elastic and resistive loads and by total airway occlusions, resulting in a single curvilinear relationship between inspired volume and TIEMG that was independent of inspired volume trajectory. In contrast, when TI was measured from the pattern of airflow, the effect of loading on the mechanical time constant of the respiratory system resulted in different inspired volume-TI relationships for elastic and resistive loads. Mechanical and neural inspired volume and duration of the following unloaded inspiration were unchanged from control values. These findings indicate that neural inspiratory timing in infants depends on magnitude of phasic volume change during inspiration. They are consistent with the hypothesis that termination of inspiration is accomplished by an "off-switch" mechanism and that inspired volume determines the level of vagally mediated inspiratory inhibition to trigger this mechanism.     

Influence of dilution on the physical state of model bile systems: NMR and quasi-elastic light-scattering investigations

Multinuclear (1H and 31P) nuclear magnetic resonance (NMR) spectroscopy and quasi-elastic light scattering have been used to characterize molecular aggregates formed in dilute sodium taurocholate--egg lecithin solutions. When mixed micelles (1.25 g/dL) are diluted with 150 mM aqueous sodium chloride, light-scattering measurements suggest a transformation from mixed micelles to unilamellar vesicle species. Decreased 1H NMR line widths for bile salt resonances are consistent with predominance of a monomer form. The concurrent appearance of a second phospholipid choline methyl resonance indicates two types of phospholipid environment in slow chemical exchange: this behavior is consistent with small unilamellar vesicles. The appearance of bilayer vesicles in dilute model bile solutions is confirmed by addition of a lanthanide shift reagent (Pr3+), which splits the 1H or 31P head-group peak into two components with distinct chemical shift sensitivities. These mixed micelle and vesicle aggregates are also distinguished by their susceptibility to the lipolytic enzyme phospholipase A2 from cobra venom.     

Effects of nectar concentration on butterfly feeding: measured feeding rates for Thymelicus lineola (Lepidoptera: Hesperiidae) and a general feeding model for adult Lepidoptera

Summary Field observations of the adult European skipper, Thymelicus lineola (Ochs), feeding on concentrated nectars (40–65% sucrose) from a variety of flower species led us to question recent literature stating that butterflies feed primarily, and most effectively, on dilute nectars. Rate of sucrose solution intake, volume consumed and feeding duration were measured for males and females at 25 and 35°C under laboratory conditions. As sucrose concentration increased, the volume of solution ingested per meal first increased and then decreased gradually, while sucrose intake was highest at concentrations 40%. Females fed more than males at all concentrations >10% while temperature had no significant effect on meal size. Feeding duration increased with concentration, was shorter at 35 than at 25°C, and was longer for females than males.The rate of volume intake decreased as concentration incresed, but not nearly as rapidly as predicted by earlier models. Rates did not differ between the sexes but were faster at 35 than 25°C. This increase was contributed to equally by a reduction in viscosity and an increase in power output of the cibarial pump. The form of the relations was similar, with maximum rate of sucrose intake occurring at 40% sucrose.A new mathematical model was developed to describe the rate — concentration relation based on the Hagen-Poiseuille equation for laminar fluid flow through pipes. Our model differs from previous models principally in that the power output of the insect's cibarial pump remains relatively constant while the pressure drop created by the pump to induce suction is highly variable. This change results in a very different feeding rate — sucrose concentration function with the optimal rate of sucrose intake at a concentration of approximately 40%. The model indicates that the same relation should hold for a wide range of proboscis shape and size and type of suction pump, and should therefore be applicable to all other nectar feeders with sucking mouth parts. Independent verifications of the model were carried out by measuring the rate of uptake of sucrose solutions of the adult common armyworm, Pseudaletia unipuncta (Haw.), and of human subjects using a volumetric pipette, both of which gave an excellent fit.Nectar concentrations which correspond to optimal rates of sucrose intake should be highly preferred by insects with high feeding costs, those which are time-limited, or which are very vulnerable while feeding. High transport costs and severe water stress may shift preferences to higher and lower concentrations respectively.     

Construction of a cDNA to the hamster CAD gene and its application toward defining the domain for aspartate transcarbamylase.

cDNA complementary to hamster mRNA encoding the CAD protein, a multifunctional protein which carries the first three enzymes of pyrimidine biosynthesis, was constructed. The longest of these recombinants (pCAD142) covers 82% of the 7.9-kilobase mRNA. Portions of the cDNA were excised and replaced by a lac promoter-operator-initiation codon segment. The resultant plasmids were transfected into an Escherichia coli mutant defective in aspartate transcarbamylase, the second enzyme of the pathway. Complementation of the bacterial defect was observed with as little as 2.2 kilobases of cDNA sequence, corresponding to the 3' region of the mRNA. DNA sequencing in this region of the hamster cDNA reveals stretches which are highly homologous to the E. coli gene for the catalytic subunit of aspartate transcarbamylase; other stretches show no homology. The highly conserved regions probably reflect areas of protein structure critical to catalysis, while the nonconserved regions may reflect differences between the quaternary structures of E. coli and mammalian aspartate transcarbamylases, one such difference being that the bacterial enzyme in its native form is allosterically regulated and the mammalian enzyme is not.     

Cell surface changes in preimplantation mouse embryos during compaction investigated using FITC conjugated lectins after proteolytic enzyme treatment

Summary Fluorescein-conjugated lectins were used to examine the reappearance of glycoproteins on the surface of 8-cell mouse embryos after treatment with proteolytic enzymes. Embryos were decompacted in calcium free medium, treated with various proteases and the process of recompaction monitored. The most effective enzymes in delaying recompaction were subtilopeptidase A and proteinase K at 1 mg/ml; the initiation of recompaction was delayed by about 5 h and 90% recompaction by 14–18 h. Papain and -chymotrypsin were only effective in the absence of calcium. The reappearance of receptors for fluorescein-conjugated Con-A, MPA, RCA-I, FBP, BSL-II and DBA was examined photometrically at 0,8–10 and 17–18 h after proteinase K treatment. There was an increase in binding of MPA, RCA-I, FBP and BSL-II in control embryos during the period of the experiment, between approx. 61 and 80 h post coitum in which embryos passed from the 8-cell stage to the 16–32 cell stage. Con-A binding remained the same and that of DBA decreased. By the time that 50% of enzyme treated embryos had recompacted (8–10 h) binding of Con-A was similar to control embryos. Binding of FBP had almost reached control levels while that of BSL-II, DBA, RCA-I and MPA had reached 60–85% of control levels. When embryos were fully compact (17–18 h) Con-A, FBP and DBA were bound in equal or slightly greater amounts to enzyme treated as to control embryos, and receptors for BSL-II, MPA and RCA-I had recovered almost to control levels. The results clearly show that the recovery of glycoproteins on the surface of 8–16 cell embryos parallels recompaction, providing further evidence for the role of these molecules in compaction.     

Regulation of end-expiratory lung volume during sleep in premature infants

To investigate the regulation of end-expiratory lung volume (EEV) in premature infants, we recorded airflow, tidal volume, diaphragm electromyogram (EMG), and chest wall displacement during sleep. In quiet sleep, EEV during breathing was 10.8 +/- 3.6 (SD) ml greater than the minimum volume reached during unobstructed apneas. In active sleep, no decrease in EEV was observed during 28 of 35 unobstructed apneas. Breaths during quiet sleep had a variable extent of expiratory airflow retardation (braking), and inspiratory interruption occurred at substantial expiratory flow rates. During active sleep, the expiratory flow-volume curve was nearly linear, proceeding nearly to the volume axis at zero flow, and diaphragm EMG activity terminated near the peak of mechanical inspiration. Expiratory duration (TE) and inspiratory duration (TI) were significantly shortened in quiet sleep vs. active sleep although tidal volume was not significantly different. In quiet sleep, diaphragmatic braking activity and shortened TE combined to maintain EEV during breathing substantially above relaxation volume. In active sleep, reduced expiratory braking and prolongation of TE resulted in an EEV that was close to relaxation volume. We conclude that breathing strategy to regulate EEV in premature infants appears to be strongly influenced by sleep state.     

Computer-linked HPLC system for feedback control of fermentation substrates

Summary A data acquisition/control microcomputer system was interfaced to a commercial HPLC data transmission module. Control of substrate (ethanol) levels for four 7.5 L fermenters containing 100 g/L wet weight of the yeastCandida norvegensis was accomplished by employing intermittent, automated HPLC monitoring and a BASIC-encoded proportional integral policy for controlling substrate feed rates. Ethanol levels were maintained at 0.25, 0.50, 0.75 and 1.00% w/v.