A high incidence of parasitism ofHeliothis SPP. [Lep.: Noctuidae] larvae in cotton in Southeastern Arkansas

During 1981 and 1982, bollworm,Heliothis zea (Boddie), and tobacco budworm,H. virescens (F.), larvae (n=3,666) were collected from 41 cotton fields near Portland, Arkansas (USA) to assess the occurrence of parasitism. Three strategies were employed to controlHeliothis spp. in these fields: (1) release ofTrichogramma pretiosum Riley; (2) insecticidal control; or (3) inaction (check). Insecticide use in nonchemical control fields was reduced, but not eliminated.Heliothis spp. larvae collected in cotton had higher parasitism rates in 1981 (30.9%) and 1982 (50.1%) than had been reported for cotton since the advent of organochlorine insecticide usage. Four species of larval parasites and 1 species of larval-pupal parasite were recorded. The larval parasiteMicroplitis croceipes (Cresson) comprised 90.6% and 94.5% of all parasitic insects reared from field collectedHeliothis spp. in 1981 and 1982, respectively. No difference (P>0.05) in level of parasitism existed betweenH. zea andH. virescens. Differences between treatments occurred only in 1982 whenH. zea larvae were parasitized at a greater (P<0.05) rate in check fields (68.3%) than in insecticidal control fields (44.3%). Higher levels of larval parasitism in cotton fields may be a consequence of reduced insecticide usage and changes in materials applied, particularly the pyrethroids. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Dept. of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.     

Endogenous prostaglandins modulate histamine-induced contraction in canine tracheal smooth muscle

We studied the role of endogenous prostaglandins in modulating the histamine response of canine tracheal smooth muscle (TSM) in vitro. Indomethacin (INDO) (10(-7) - 10(-5) M), a cyclooxygenase and prostaglandin synthesis inhibitor, significantly increased maximum histamine-induced tension (Tmax) and decreased the concentration of histamine required to produce 50% of Tmax (EC50). Acetylsalicylic acid (10(-5) -5 X 10(-4) M), another less potent cyclooxygenase inhibitor, also decreased EC50. Neither the lipoxygenase inhibitor nordihydroguaiaretic acid nor the leukotriene antagonist FPL 55712 had any effect on histamine-induced tension in INDO-pretreated TSM. INDO reduced the standard deviation of EC50 from 0.47 in control TSM (n = 51) to 0.26 in INDO-pretreated TSM (n = 31) (P less than 0.02). High-pressure liquid chromatography established prostacyclin (PGI2), through its degradation product 6-oxo-PGF1 alpha, as the predominant prostaglandin produced by canine TSM. Exogenous PGI2 caused a concentration-dependent relaxation of histamine-contracted TSM. In the tissue bath, spontaneous efflux of 6-oxo-PGF1 alpha from TSM, as measured by radioimmunoassay, averaged 4.7 ng . g muscle-1 . min-1 and increased to 10 ng/g muscle (n = 10, P less than 0.001) with administration of histamine. The isometric tension produced by histamine (10(-4) M) was inversely linearly correlated with the log concentration of endogenous 6-oxo-PGF1 alpha (r = 0.81, P less than 0.01). Our results are consistent with an important role for endogenous bronchodilating prostaglandins, probably prostacyclin, in determining both the histamine sensitivity of canine TSM in vitro and its variability among individual animals.     

Temperature-Sensitive Lethal Mutations on Yeast Chromosome I Appear to Define Only a Small Number of Genes

A method was developed for isolating large numbers of mutations on chromosome I of the yeast Saccharomyces cerevisiae. A strain monosomic for chromosome I (i.e., haploid for chromosome I and diploid for all other chromosomes) was mutagenized with either ethyl methanesulfonate or N-methyl-N'-nitro-N -nitrosoguanidine and screened for temperature-sensitive (Ts^- ) mutants capable of growth on rich, glucose-containing medium at 25° but not at 37°. Recessive mutations induced on chromosome I are expressed, whereas those on the diploid chromosomes are usually not expressed because of the presence of wild-type alleles on the homologous chromosomes. Dominant ts mutations on all chromosomes should also be expressed, but these appeared rarely. — Of the 41 ts mutations analyzed, 32 mapped on chromosome I. These 32 mutations fell into only three complementation groups, which proved to be the previously described genes CDC15, CDC24 and PYK1 (or CDC19). We recovered 16 or 17 independent mutations in CDC15, 12 independent mutations in CDC24 and three independent mutations in PYK1. A fourth gene on chromosome I, MAK16, is known to be capable of giving rise to a ts-lethal allele, but we recovered no mutations in this gene. The remaining nine mutations isolated using the monosomic strain appeared not to map on chromosome I and were apparently expressed in the original mutants because they had become homozygous or hemizygous by mitotic recombination or chromosome loss. — The available information about the size of chromosome I suggests that it should contain approximately 60–100 genes. However, our isolation in the monosomic strain of multiple, independent alleles of just three genes suggests that only a small proportion of the genes on chromosome I is easily mutable to give a Ts^--lethal phenotype. — During these studies, we located CDC24 on chromosome I and determined that it is centromere distal to PYK1 on the left arm of the chromosome.     

Recognition of super-secondary structure in proteins

A procedure to recognize super-secondary structure in protein sequences is described. An idealized template, derived from known super-secondary structures, is used to locate probable sites by matching with secondary structure probability profiles. We applied the method to the identification of βαβ units in β/α type proteins with 75% accuracy. The location of super-secondary structure was then used to refine the original (Garnier et al., 1978) secondary structure prediction resulting in an 8.8% improvement, which correctly assigned 83% of secondary structure elements in 14 proteins. Slight modifications to the Garnier et al. method arc suggested, producing a more accurate identification of protein class and a better prediction for β/α. type proteins. A method for the incorporation of hydrophobic information into the prediction is also described.     

High-cell-density fermentation studies of a recombinantE. coli that expresses atrial natriuretic factor

Summary Studies are presented on the fermentation of recombinantEscherichia coli that express rat atrial natriuretic factor (ANF) as a fusion protein. Our objective was to achieve high cell density while maintaining ANF expression at the same level as observed in shake flasks. Improved fermentation conditions included: maintaining glucose concentrations at 1 g/l, using an enriched medium, adding concentrates of medium throughout the fermentation, and blending oxygen for adequate aeration. Cell densities of 12 g/l (dry weight) were achieved, which represented a 10-fold increase over non-improved conditions, while maintaining ANF levels at 7 mg/g of dry cell mass. When galactose was used as an initial carbon source or as a feed supplement, there was a 2-3-fold increase in the expression of ANF from these high-cell-density fermentations. The recombinant ANF was biologically active.     

High-frequency ventilation of ducks and geese

We studied gas exchange in anesthetized ducks and geese artificially ventilated at normal tidal volumes (VT) and respiratory frequencies (fR) with a Harvard respirator (control ventilation, CV) or at low VT-high fR using an oscillating pump across a bias flow with mean airway opening pressure regulated at 0 cmH2O (high-frequency ventilation, HFV). VT was normalized to anatomic plus instrument dead space (VT/VD) for analysis. Arterial PCO2 was maintained at or below CV levels by HFV with VT/VD less than 0.5 and fR = 9 and 12 s-1 but not at fR = 6 s-1. For 0.4 less than or equal to VT/VD less than or equal to 0.85 and 3 s-1. less than or equal to fR less than or equal to 12 s-1, increased VT/VD was twice as effective as increased fR at decreasing arterial PCO2, consistent with oscillatory dispersion in a branching network being an important gas transport mechanism in birds on HFV. Ventilation of proximal exchange units with fresh gas due to laminar flow is not the necessary mechanism supporting gas exchange in HFV, since exchange could be maintained with VT/VD less than 0.5. Interclavicular and posterior thoracic air sac ventilation measured by helium washout did not change as much as expired minute ventilation during HFV. PCO2 was equal in both air sacs during HFV. These results could be explained by alterations in aerodynamic valving and flow patterns with HFV. Ventilation-perfusion distributions measured by the multiple inert gas elimination technique show increased inhomogeneity with HFV. Elimination of soluble gases was also enhanced in HFV as reported for mammals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prostaglandin synthesis by enterocyte microsomes of rabbit small intestine

We studied the prostaglandin (PG) synthetic capacity of microsomes of a relatively pure population of rabbit enterocytes and determined ideal conditions for product synthesis. The epithelial cells were freed from the basement membrane by a combination of calcium chelation and mechanical vibration, and 100,000 X g microsomes were prepared. These microsomes were found to synthesize PG from exogenously added arachidonic acid. The ideal conditions for the reaction were a microsomal protein concentration of 1.0 mg/ml, an arachidonic acid concentration of 33 uM, a reaction mixture pH of 8.0-9.5 and with epinephrine 1.5 mM added as a cofactor. The product yields increased linearly with time up to 30 min. of incubation and were inhibited by 100 uM indomethacin. Under the above ideal conditions enterocyte microsomes yielded the following products expressed as pmole/mg protein/20 min. incubation: PGF2 alpha 98 +/- 7, PGE2 48 +/- 9, PGD2 28 +/- 7, TxB2 40 +/- 5, 6 Keto PGF1 alpha 15 +/- 6.     

Amino acid sequence of rabbit ventricular myosin light chain-2: Identity with the slow skeletal muscle isoform

Many studies have established a correlation of differences in the activities of various muscle types with differences in the expression of myosin isoforms. In this paper we report the sequence determination of myosin light chain-2 from rabbit slow skeletal (LC2s) and ventricular (LC2v) nmscles. We sequenced tryptic peptides from LC2v which account for all except a few terminal amino acid residues. The major part (87 residues) of the rabbit LC2s sequence, obtained from tryptic and cyanogen bromide (CNBr) peptides, was found to be identical to rabbit LC2v. Our results provide the first sequence information on LC2s from any species, and lend strong support to the hypothesis that LC2s and LC2v are identical. Comparisons of rabbit LC2v and LC2s with rabbit LC2f (from fast skeletal muscle), and also with chicken LC2f and LC2v, show clearly that LC2s and LC2v from mammalian and avian species are more closely related to each other than they are to LC2f isoforms from the same species.     

Oxidation and chemical modification of lung beta-galactoside-specific lectin.

Galaptins are small, soluble, lectins with a specificity for beta-galactose residues. Many galaptins are inactivated by atmospheric oxygen and are protected by disulphide-reducing reagents. We find that each subunit of rat lung galaptin contains one residue of tryptophan and six of cysteine. Oxygen inactivates rat lung galaptin by oxidation of the cysteine residues. During oxidation, the normal dimeric structure is maintained and all disulphide bonds are formed within individual subunits. Exogenous thiols protect against inactivation, but oxidized thiols accelerate inactivation. Human lung fibroblast galaptin is almost completely inactivated within 1 h in tissue culture medium at 37 degrees C. Alkylation of native rat lung galaptin with iodoacetate or ethyleneimine causes substantial loss of activity. The dimeric galaptin structure is maintained. In contrast, alkylation with iodoacetamide yields carboxamidomethyl-galaptin, which is fully active and stable to atmospheric oxygen in the absence of disulphide-reducing reagents. This derivative is very useful for studies of galaptin properties and function.