Retrovirus-mediated immunosuppression. II. FeLV-UV alters in vitro murine T lymphocyte behavior by reversibly impairing lymphokine secretion

Murine splenocytes and cloned murine T cells were used to study the in vitro immunosuppressive effects of UV-inactivated feline leukemia virus (FeLV-UV) on lymphokine secretion. FeLV-UV can significantly depress the accumulation of IL 2 in cultures of Con A-stimulated C57BL/6 splenocytes and in cultures containing the alloreactive helper T cell clone B6D/2-2m plus Con A. Inhibition of lymphokine accumulation in these cultures could not be attributed to absorption or inactivation of IL 2 by the FeLV-UV or to the FeLV-UV-induced production of substances which interfere with the IL 2 bioassay. Thus, FeLV-UV appears to block production and/or secretion of IL 2 by a direct inhibitory effect on IL 2-secreting murine T lymphocytes. Additional studies indicate that FeLV-UV impairs IL 2 production only if added very soon after lymphocyte contact with lymphokine-inducing agents and that IL 2 secretion resumes when FeLV-UV is removed from the culture. FeLV-UV also impairs accumulation of MAF (interferon-gamma?) in cultures of Con A-stimulated C57BL/6 splenocytes and in cultures containing the alloreactive cytotoxic T lymphocyte clone B6D/2-7c plus Con A. The latter observation again suggests that FeLV-UV impairs lymphokine secretion by a direct effect on lymphokine-producing T lymphocytes. Furthermore, it suggests that FeLV-UV does not selectively impair production of IL 2 nor does it have selective inhibitory effects on helper T cells. Rather, FeLV-UV appears to have a general inhibitory effect on lymphokine production by T lymphocytes. Finally, concentrations of FeLV-UV which suppress MAF production by the CTL clone have little influence on the cytolysis mediated by the same cloned T cell population. Thus, the immunosuppressive influence of FeLV-UV is selective for phenomena associated with induction of new T lymphocyte functions, such as lymphokine secretion, and spares other immune functions already expressed by the same cells.     

Systematic Screening of Drosophila Deficiency Mutations for Embryonic Phenotypes and Orphan Receptor Ligands

This paper defines a collection of Drosophila deletion mutations (deficiencies) that can be systematically screened for embryonic phenotypes, orphan receptor ligands, and genes affecting protein localization. It reports the results of deficiency screens we have conducted that have revealed new axon guidance phenotypes in the central nervous system and neuromuscular system and permitted a quantitative assessment of the number of potential genes involved in regulating guidance of specific motor axon branches. Deficiency “kits” that cover the genome with a minimum number of lines have been established to facilitate gene mapping. These kits cannot be systematically analyzed for phenotypes, however, since embryos homozygous for many deficiencies in these kits fail to develop due to the loss of key gene products encoded within the deficiency. To create new kits that can be screened for phenotype, we have examined the development of the nervous system in embryos homozygous for more than 700 distinct deficiency mutations. A kit of ∼400 deficiency lines for which homozygotes have a recognizable nervous system and intact body walls encompasses >80% of the genome. Here we show examples of screens of this kit for orphan receptor ligands and neuronal antigen expression. It can also be used to find genes involved in expression, patterning, and subcellular localization of any protein that can be visualized by antibody staining. A subset kit of 233 deficiency lines, for which homozygotes develop relatively normally to late stage 16, covers ∼50% of the genome. We have screened it for axon guidance phenotypes, and we present examples of new phenotypes we have identified. The subset kit can be used to screen for phenotypes affecting all embryonic organs. In the future, these deficiency kits will allow Drosophila researchers to rapidly and efficiently execute genome-wide anatomical screens that require examination of individual embryos at high magnification.     

Substratum preference of the caddisfly Helicopsyche borealis (Hagen) (Trichoptera: Helicopsychidae)

The position of Helicopsyche borealis (Hagen) (Trichoptera: Helicopsychidae) larvae on the substratum surface is dependent on the current regime but varies with larval size. All size classes of larvae chose significantly different positions on the substratum under high versus low current velocities. All size classes preferred exposed surfaces under low current velocities. Small larvae preferred the upper surfaces of substrata under low current velocities and were physically displaced under high current velocities. Larger larvae also occurred on upper surfaces, but were more evenly dispersed over all surfaces than smaller larvae, and tended to aggregate on down-stream faces of rocks during high flow.     

Sequence analysis and neuronal expression of fasciclin I in grasshopper and Drosophila

The fasciclin I, II, and III glycoproteins are expressed on different subsets of axon bundles (fascicles) in insect embryos and are thus candidates for surface recognition molecules involved in growth cone guidance. Here we present the sequence of grasshopper fasciclin I and the identification and sequence of the Drosophila fasciclin I homolog. In both species, fasciclin I appears to be an extrinsic membrane protein with a signal sequence but no transmembrane region; the protein comprises four homologous domains of approximately 150 amino acids each. Antibodies against Drosophila fasciclin I reveal that it is expressed on the surface of a subset of commissural axon pathways in the embryonic central nervous system and on all sensory axon pathways in the peripheral nervous system. This pattern of expression is similar to that in grasshopper.     

Inhalation anesthesia in adult cattle

An inhalation technique was used for anesthesia during ileal cannulation in five adult cows. Following sedation with intravenous acepromazine, anesthesia was induced intravenously with thiopental sodium in 5% glyceryl guaiacolate solution. Endotracheal intubation was performed and anesthesia maintained with halothane in oxygen via a circle system with a precision vaporizer. In all cases, induction was smooth and no difficulties were experienced during the maintenance of anesthesia. Total anesthesia time was 1.5 to 2.5 hours. Following completion of the surgical procedure, which was performed with the animal in left lateral recumbency, each cow was rolled to a sternal position and supported, if necessary. The endotracheal tube was left in place, with oxygen administration continued, until the animal was able to swallow. Recoveries were rapid and all animals were ambulatory within 30 minutes after completion of the surgery. The only post-operative complication due to anesthesia was transient mouth soreness in two cases, attributed to the use of a mouth speculum during intubation.     

Transposition of an intron in yeast mitochondria requires a protein encoded by that intron

The optional 1143 bp intron in the yeast mitochondrial 21S rRNA gene (omega +) is nearly quantitatively inserted in genetic crosses into 21S rRNA alleles that lack it (omega -). The intron contains an open reading frame that can encode a protein of 235 amino acids, but no function has been ascribed to this sequence. We previously found an in vivo double-strand break in omega - DNA at or close to the intron insertion site only in zygotes of omega + X omega - crosses that appears with the same kinetics as intron insertion. We now show that mutations in the intron open reading frame that would alter the translation product simultaneously inhibit nonreciprocal omega recombination and the in vivo double-strand break in omega - DNA. These results provide evidence that the open reading frame encodes a protein required for intron transposition and support the role of the double-strand break in the process.     

Inorganic and Metal-Organic Growth Requirements of the Genus Bacteroides

The inorganic and metal-organic growth requirements of ruminal and nonruminal Bacteroides species were compared. The heme requirement of many nonruminal Bacteroides species was similar to that of Bacteroides ruminicola subsp. ruminicola and was a general tetrapyrrole requirement. Some nonruminal Bacteroides species utilized succinate or alpha-ketoglutarate, as well as tetrapyrrole-containing compounds, in place of heme. Fe(+) as well as heme was required for maximal yields of some Bacteroides species. The divalent cation requirements of Bacteroides species are complex. Mg(2+) deletion from a medium containing Mg(2+), Ca(2+), Co(2+), and Mn(2+) reduced the yields of all isolates. Ca(2+) deletion from the same medium reduced the growth yields of Bacteroides fragilis, B. fundiliformis, and one strain of B. oralis. The effects of Mg(2+) and Ca(2+) on the growth of Bacteroides isolates was influenced by other divalent cations. Relatively large quantities of Na(+) were obligately required by all of the currently recognized predominant rumen Bacteroides species. Nonruminal Bacteroides species either did not require Na(+) or required only small amounts. The Na(+) requirement of some nonruminal Bacteroides species could be partially replaced by Li(+) or Cs(+). The Na(+) requirement of rumen Bacteroides species was absolute. The inorganic and metal-organic growth requirements of Bacteroides species appear useful as aids in species differentiation.     

Chronology of permethrin resistance in a southern Illinois population of the horn fly (Diptera: Muscidae) during and after selection by pyrethroid use

From 1985 through 1988, horn flies (Haematobia irritans (L)) collected at the Dixon Springs Agricultural Center (DSAC) in southern Illinois were tested in 22 h bioassays for permethrin resistance with residues on cotton cloths. The LC90 for a susceptible field population collected in June 1985 was 0.19 micrograms/cm2. In comparison, flies collected from pyrethroid-tagged cattle in 1985 and 1986 exhibited 25- to 116-fold resistance to permethrin. A 25-fold level of resistance allowed survival on treated cattle 8 wk after pyrethroid tag application. Flies representing the local background population were collected periodically from an untreated herd 2.4 km from the nearest cattle treated with a pyrethroid; these flies exhibited up to 18-fold resistance. Although pyrethroids were not used on DSAC animals after October 1986, all bioassays done in 1987 and 1988 indicated resistance levels of greater than or equal to 7-fold. The 95% confidence intervals for LC90s from all 1987 bioassays overlapped the confidence interval from the corresponding July 1986 estimate for resistant flies collected from pyrethroid-tagged cattle. Although some decline in resistance was evident in 1988, bioassays done at the end of the season produced resistance ratios of 7.4 and 15.3. Survivorship at a diagnostic dose indicated that resistance frequencies remained at 4-8% throughout 1988. Two years' abstinence from pyrethroid use was insufficient to allow an adequate decline in resistance levels.