Effects of Population Size and Selection Intensity on Responses to Disruptive Selection in DROSOPHILA MELANOGASTER

Disruptive selection for sternopleural bristle number with opportunity for random mating was done in the four treatment combinations of two population sizes (40 pairs and 8 pairs of selected parents) and two selection intensities (1 in 40 and 1 in 2). In each generation, matings among selected parents were observed in a mating chamber, and progeny collected separately from each female parent. In the high number, high selection intensity treatment, divergence between the high and low parts ceased about generation 11. The isolation index increased rapidly to generation 3, but then fluctuated to termination of the population at generation 17. The overall isolation index was significant, indicating a real tendency to assortative mating. The failure of the isolation index to increase after generation 3 was attributed to lower average mating fitness of high males (due to inbreeding) and reduced receptivity of low females (due to a homozygous lethal gene with a large effect on sternopleural bristle number in heterozygotes). In the two low number treatments, isolation indices fluctuated from generation to generation with no obvious trends, and none of the overall isolation indices were significantly different from zero. The high number, low selection intensity treatment showed very little divergence, and one of the replicates showed, in contrast with expectation and the high number, high selection intensity treatment, a significant tendency to disassortative mating. Intense disruptive selection may lead to assortative mating.     

Demonstration of immunoreactive sites on cartilage after in vivo administration of biotinylated anti-type II collagen antibodies

Administration of biotinylated monoclonal antibodies provides the basis of a simple technique for identifying immunoreactive sites in vivo. Biotinylated anti-type II collagen antibodies were injected intraperitoneally into normal DBA/1 mice. The mice were sacrificed after 96 hr and the front paws removed and decalcified to allow tissue sectioning before snap-freezing. Binding of antibodies in vivo was visualized with affinity cytochemical staining using avidin-biotin-peroxidase complexes. Specific binding of antibodies to cartilaginous structures was seen after injection of 20-500 micrograms biotinylated monoclonal or polyclonal anti-type II collagen antibodies, but not after injection of a biotinylated control antibody. This technique should further the detection and localization studies of tissue components involved in the dynamics of physiological and pathological processes.     

Gravitropically-stimulated seedlings show autotropism in weightlessness

In a spaceflight experiment, autotropism by oat ( Avena sativa L.) coleoptiles following gravitropic responses was prominent in weightlessness: counter-reactions led to the straightening of the curved coleoptiles. This was not the case during clinorotation on earth. The autotropic reactions appeared to be related to the stimulus received during the stimulus period, i.e. the greater the response the greater the autotropic counter-reaction. Previous models of the gravitropic system which predicted that coleoptiles would not straighten in weightlessness are disproved. A modification to one of the models is proposed which includes the autotropic response observed in spaceflight. The nature of the counter-reactions in the absence of gravitropic stimulation is discussed.     

ExbB acts as a chaperone-like protein to stabilize TonB in the cytoplasm

The TonB protein is required to transduce energy from the cytoplasmic membrane to outer membrane transport proteins of Gram-negative bacteria. Two accessory proteins, ExbB and ExbD, are required for TonB function and it has been suggested that TonB and ExbBD form a complex in the membrane. In this paper we demonstrate that there are two spatially distinct, functional interactions between ExbBD and TonB. First, there is an interaction between ExbBD and the N-terminal signal-like peptide of TonB, probabiy the formation of a stable complex in the membrane. Second, ExbB interacts with TonB in the cytoplasm. This interaction involves the domain of TonB that is normally periplasmic. Thus, this is a transient interaction which occurs during the synthesis and/or localization of TonB, implying a chaperone-like role for ExbB. The transmembrane topology of ExbB was shown to be consistent with this role.     

Feline Pansteatitis: A Report of Five Cases

Pansteatitis (yellow fat disease, panniculitis, steatitis) is an inflammatory disease of adipose tissue throughout the body (Holzworth 1987). It was first experimentally induced by Mason & Dam in 1946 in cats fed a diet deficient in vita-min E and high in cod liver oil (Mason & Dam 1946). It has since been reported as a clinical condition by several authors (Cordy & Stil-linger 1953, Watson et al 1973, Gaskell et al 1975, Summers et al 1982, Hagiwara et al 1986). Pansteatitis occurs naturally in cats, mink, and pigs as a result of vitamin E deficiency. Vitamin E (α-tocopherol) is a biological antioxidant found in vegetable oils (Holzworth 1987). It serves as a protector of the fats in the diet and in the body. Pansteatitis is caused by a mismatch between intake of unsaturated fatty acids and antioxidants, i.e. vitamin E. The ensu-ing peroxidation of the body fat causes a for-eign body reaction with severe inflammation and cell death. The foremost clinical sign is hy-peraesthesia or severe pain on palpation/han-dling, especially over the back and of the abdo-men. The final diagnosis rests with the histo-logical findings of the above-mentioned lesions in conjunction with acid-fast ceroid pigment (i.e. end-product of lipid peroxidation) in fat cells, in macrophages, in Langhans-type giant cells, and extracellularly (Holzworth 1987).     

Proton nuclear magnetic resonance analysis of anomeric structure of glycosphingolipids. Blood group ABH-active substances.

High resolution nuclear magnetic resonance spectra of permethylated and permethylated-reduced (LiAlH₄) derivatives were recorded in chloroform solution for the following glycosphingolipids with known structure: lactotriaosylceramide, neolactotetraosylceramide (paragloboside), two blood group H-active pentaglycosylceramides (type 1 and type 2 saccharide chains, respectively), a B-active hexaglycosylceramide, an A-active hexaglycosylceramide, and an A-active octaglycosylceramide. Good quality and resolution allow a clear-cut diagnosis of α-anomeric protons of Fuc, Gal, and GalNAc, and in most cases of all β protons. Upon reduction there is a strong deshielding effect on H-1 of Gal of Galβ1 → 3GlcNAc but not on Gal of Galβ1 → 4GlcNAc. It is therefore possible to differentiate type 1 and type 2 chains by this method, a structural difference of importance for serological specificity. Nuclear magnetic resonance spectroscopy may therefore provide conclusive information on the anomeric structure of the immunodeterminant of blood group-active glycolipids using the same derivatives as for sequence analysis by mass spectrometry.     

Isolation and characterization of cells from rat adipose tissue developing into adipocytes.

To identify cells developing into adipocytes by accumulation of triglyceride, rat epididymal fat pad cells from small rats were exposed to (3)H-labeled chylomicron fatty acids in vivo and then liberated with collagenase. Tissue remnants were removed by filtration and mature fat cells by flotation. Aggregating cells were then removed by filtration through a 25- micro m nylon screen. Further purification of cells labeled in vivo was obtained by removing floating cells from those adhering to the bottom of a culture dish. The adhering cells multiplied to a confluent monolayer when cultured in Medium 199 containing serum, glucose, insulin, and a triglyceride emulsion. The cells then gradually enlarged due to granulation of the cytoplasm by a lipid-staining material. After about 2 weeks these granules had coalesced forming mature adipocytes of typical signet-ring appearance. Free adipocytes could then be recovered from the cultures by collagenase treatment. After about 2 weeks of culture these cells had the same size (about 30 micro m) as adipocytes recovered in the original collagenase preparation of the rat epididymal fat pad. They contained triglyceride lipase activity and incorporated glucose into triglycerides to the same extent as cells developed in vivo but had higher lipoprotein lipase activity. In vitro, heparin in a low concentration, prostaglandin E(1), isobutylmethylxanthine, and cholera toxin markedly promoted the development of these cells into adipocytes. This could be shown to occur almost completely indicating that this fraction of cells was homogeneous and consisted of cells with the capacity to form adipocytes. The duplication time was about 2 days and did not change with subculturing. Preadipocytes could be obtained by density gradient centrifugation, isolating triglyceride-containing cells either directly from the pad or after 3 days in culture. All of these cells developed into adipocytes as described above but did not multiply as readily. It was concluded that cells from the epididymal fat pad from small rats can be isolated in a homogenous fraction that develops in culture into cells of identical morphology and function as adipocytes formed in vivo. The differentiation of these cells into adipocytes may be manipulated in vitro.     

Escherichia coli ribonucleotide reductase. Radical susceptibility to hydroxyurea is dependent on the regulatory state of the enzyme.

Ribonucleotide reductase catalyzes the reduction of ribonucleotides to their corresponding deoxyribonucleotides via a radical-mediated mechanism. The enzyme from Escherichia coli consists of the two non-identical proteins, R1 and R2, the latter of which contains the necessary free radical located to a tyrosine residue. The radical scavenger hydroxyurea was found to reduce the tyrosyl radical of R2 in a second-order reaction. The rate constant (0.50 M-1 s-1 at 25 degrees C) for this process was several orders of magnitude lower than the hydroxyurea-dependent reduction of free tyrosyl radicals in solution. This difference probably reflects the fact that the R2 tyrosyl radical is buried in the interior of the protein. Formation of the R1R2 complex changed the susceptibility of the radical to hydroxyurea in a manner that reflects the regulatory state of the holoenzyme. Furthermore, binding of substrate or product to the holoenzyme complex made the R2 radical at least 10 times more susceptible to inactivation by hydroxyurea than it was in the isolated R2 protein. One active site mutation in the R1 protein was shown to affect the sensitivity of the tyrosyl radical of R2 differently than wild type protein R1 does. Our results clearly show that the susceptibility of the tyrosyl radical in R2 to inactivation by hydroxyurea can be used as an efficient probe for the regulatory state of the holoenzyme complex.     

Structure and evolution of the heavy chain from rat immunoglobulin E.

The nucleotide sequence of the rat epsilon-chain mRNA has been determined by sequencing cloned cDNA copies of the mRNA. The established sequence covers the coding region, the 3'-non coding region and most of the 5' non-coding region. A comparison with the nucleotide sequence of the human epsilon-chain constant region reveals that C3 and C4 are the most highly conserved domains. The rat epsilon-chain contains a C-terminal decapeptide which is not present in the human counterpart.