DETECTION OF ORGANIC MATTER IN INTERSTELLAR GRAINS

Star formation and the subsequent evolution of planetary systems occurs in dense molecular clouds, which are comprised, in part, of interstellar dust grains gathered from the diffuse interstellar medium (DISM). Radio observations of the interstellar medium reveal the presence of organic molecules in the gas phase and infrared observational studies provide details concerning the solid-state features in dust grains. In particular, a series of absorption bands have been observed near 3.4~2940 cm^–1) towards brightinfrared objects which are seen through large column densities of interstellar dust. Comparisons of organic residues, produced under a variety of laboratory conditions, to the diffuse interstellar medium observations have shown that aliphatic hydrocarbon grains are responsible for the spectral absorption features observed near 3.4 ~2940cm^–1). These hydrocarbons appear to carry the –CH₂– and –CH₃ functional groups in the abundance ratio CH₂/CH₃ ~ 2.5, and theamount of carbon tied up in this component is greater than 4% of the cosmic carbon available. On a galacticscale, the strength of the 3.4 band does notscale linearly with visual extinction, but instead increases more rapidly for objects near the Galactic Center. A similar trend is noted in the strength of the Si–O absorption band near 9.7. The similarbehavior of the C–H and Si–O stretching bands suggests that these two components may be coupled, perhaps in the form of grains with silicate cores and refractory organic mantles. The ubiquity of the hydrocarbon features seen in the near infrared near 3.4throughout our Galaxy and in other galaxies demonstrates the widespread availability of such material for incorporation into the many newly forming planetary systems. The similarity of the 3.4features in any organic material with aliphatic hydrocarbons underscores the need for complete astronomical observational coverage in the 2–30 region, oflines of sight which sample dust in both dense and diffuse interstellar clouds, in order to uniquely specify the composition of interstellar organics. This paper reviews the information available from ground-based observations, although currently the Infrared Satellite Observatory is adding to our body of knowledge on this subject by providing more extensive wavelength coverage. The Murchison carbonaceous meteorite has also been used as an analog to the interstellar observations and has revealed a striking similarity between the light hydrocarbons in the meteorite and the ISM; therefore this review includes comparisons with the meteoritic analog as well as with relevant laboratory residues. Fundamental to the evolution of the biogenic molecules, to the process of planetary system formation, and perhaps to the origin of life, is the connection between the organic material found in the interstellar medium and that incorporated in the most primitive solar system bodies.     

Vesicular-arbuscular mycorrhizae of weedy and colonizer plant species at disturbed sites in Utah

Summary A survey was made of weedy plant species found on distubed sites in Utah. Of the 74 species sampled, 57% were found to contain VA mycorrhizae. Mycorrhizal and nonmycorrhizal species strictly followed taxonomic divisions, regardless of growth habit. Nonmycorrhizal species were members of the Amaranthaceae, Brassicaceae, Capparidaceae, Caryophyllaceae, Chenopodiaceae, Papaveraceae, Polygonaceae, Portulacaceae, Rubiaceae, and Zygophyllaceae.Cover data were obtained for all plant species, including nonweedy species, colonizing seven of the disturbed sites. Flat semiarid sites were dominated by nonmycorrhizal species. The proportion of mycorrhizal plant cover may be related to water availability. Rocky, sloping sites were dominated by mycorrhizal species. Disturbance by fire did not cause a significant change in the mycorrhizal component of the community.This research was supported by U.S. Department of Agriculture Forest Service, Intermountain Forest and Range Experiment Station, Agreement 12-11-204-31, Supplement No. 25     

ECTOPIC PREGNANCY—Early Diagnosis,Clinical Errors and Conservative Operation

This report of eight years'' experience with extrauterine pregnancy by a single gynecologist is an exposition of how the diagnosis was made or why it was missed.Of 26 diagnoses of ectopic pregnancy, five were false (20 per cent); and in three cases (10 per cent) the diagnosis was not made promptly—a total error of 30 per cent.Ectopic pregnancy will be discovered earlier if obstetric patients are always examined shortly after missing the first menstrual period.A palpable adnexal mass was present in 19 of 21 ectopic pregnancies (90 per cent). A mass was palpable in only one of five cases erroneously diagnosed as ectopic pregnancy (20 per cent).Decidual casts were passed by four patients, two of whom did not have ectopic pregnancy.If two gynecologists do not agree on the question of extrauterine pregnancy, a third opinion should be sought or culdoscopy employed.Enucleation of the conceptus and salvage of the oviduct is advocated.     

Regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA levels by L-triiodothyronine

In hypophysectomized rats, hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity, immunoreactive 97-kilodalton (97-kDa) protein, and mRNA were all reduced to undetectable levels. Administration of triiodothyronine (T3) resulted in large increases in all three after a 36-h lag period. HMG-CoA reductase activity, immunoreactive 97-kDa protein levels, and reductase mRNA levels were tightly correlated. Feeding hypophysectomized rats diets containing the bile acid sequestrant colestipol, together with the potent reductase inhibitor mevinolin, resulted in an increase in HMG-CoA reductase activity similar to that seen with T3 but a lesser stimulation of reductase mRNA levels. These results suggest that agents which cause depletion of mevalonate-derived products may share in part with T3 a common mechanism for increasing levels of HMG-CoA reductase activity in order to satisfy cellular needs for these products. Dexamethasone treatment, which is known to prevent the T3-mediated stimulation of reductase activity, caused a marked decrease in 97-kDa immunoreactive material but had little effect on reductase mRNA levels.     

In situ determination of the functional size of hepatic 3-hydroxy-3-methylglutaryl-CoA reductase by radiation inactivation analysis

Radiation inactivation analysis of liver pieces yielded a target size of 210 kDa for hepatic 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase [S)-mevalonate:NADP+ oxidoreductase (CoA-acylating), EC 1.1.1.34) from rats fed a normal diet. Feeding a diet containing mevinolin and colestipol, which causes a marked increase in enzyme activity, resulted in a reduction of the target size to 120 kDa. These results are consistent with those obtained by radiation inactivation and immunoblotting analysis of isolated microsomes and suggest that the increase in HMG-CoA reductase activity caused by these dietary agents is accompanied by a change from a dimer to a monomer form of the enzyme.     

Morphometric and mating compatibility of Dectes texanus texanus (Coleoptera: Cerambycidae) from soybean and sunflower

The cerambycid Dectes texanus texanus LeConte that infests soybean, Glycine max (L.) Merr., is thought to be the same Dectes that damages sunflower, Helianthus annuus L. However, morphometric characteristics and mating compatibility between individuals from soybean and sunflower fields have not been assessed. Eight hundred eighty stalks of soybean and sunflower residues infested with Dectes were collected from Texas and Kansas. Outside stalk diameter of sunflower (22.6 mm) was 3.2 times greater than that of soybean. Diameters of tunnels by Dectes in sunflower and soybean were 7.0 and 3.4 mm, respectively. Widths of head capsules and pronotums were approximately 1.3 times greater for Dectes larvae from sunflower than soybean. Larval, pupal, and adult Dectes from sunflower were approximately 2.5 times heavier and 1.3 times longer than from soybean. Adults reared from residues of soybean and sunflower were paired to evaluate mating compatibility. Although individuals collected and reared from different crop residues differed significantly in size, percentage of mating success by Dectes from the two crops (26.2%) did not differ significantly from that by adults from the same kind of crop (34.9%). Results indicated that Dectes that infest soybean and sunflower are the same species and reconfirmed that farmers should not plant soybean and sunflower in rotation or in adjacent fields.     

Epitope enhancement of a CD4 HIV epitope toward the development of the next generation HIV vaccine

Virus-specific CD4+ T cell help and CD8+ cytotoxic T cell responses are critical for maintenance of effective immunity in chronic viral infections. The importance of CD4+ T cells has been documented in HIV infection. To investigate whether a stronger CD4+ T cell response can be induced by modifications to enhance the T1 epitope, the first CD4+ T cell epitope discovered in HIV-1-gp120, we developed a T1-specific CD4+ T cell line from a healthy volunteer immunized with a canarypox vector expressing gp120 and boosted with recombinant gp120. This T1-specific CD4+ T cell line was restricted to DR13, which is common in U.S. Caucasians and African-Americans and very frequent in Africans. Peptides with certain amino acid substitutions in key positions induced enhanced specific CD4+ T cell proliferative responses at lower peptide concentration than the original epitope. This relatively conserved CD4 epitope improved by the epitope enhancement strategy could be a component of a more effective second generation vaccine construct for HIV infection.     

Isolation and Immunocytochemical Characterization of Three Tachykinin-Related Peptides from the Mosquito,Culex salinarius

Three myotropic peptides belonging to the Arg-amide insect tachykinin family were isolated from whole-body extracts of the mosquito, Culex salinarius. The peptides, APSGFMGMR-NH₂, APYGFTGMR-NH₂ and APSGFFGMR-NH₂ (designated culetachykinin I, II, and III) were isolated and purified on the basis of their ability to stimulate muscle contractions of isolated Leucophaea maderae hindgut. Biologically inactive methionine sulfoxides of two of the three peptides were isolated using an ELISA system based upon antiserum raised against APYGFTGMR-NH₂ and identified with mass spectrometry. Immunocytochemistry localized these peptides in cells in the brain, antennae, subesophageal, thoracic and abdominal ganglion, proventriculus and midgut. Nerve tracts containing these peptides were found in the median nerve of the brain, central body, nervi corpus cardiaci, cervical nerve, antennal lobe and on the surface of the midgut.