The cuticle of Caenorhabditis elegans. II. Stage-specific changes in ultrastructure and protein composition during postembryonic development

The cuticle of the free-living nematode Caenorhabditis elegans is a proteinaceous extracellular structure that is replaced at each of four postembryonic molts by the underlying hypodermis. The cuticles of the adult and three juvenile stages (L1, Dauer larva, L4) have been compared ultrastructurally and biochemically. Each cuticle has an annulated surface and comprises two main layers, an inner basal layer and an outer cortical layer. The adult cuticle has an additional clear layer which separates the basal and cortical layers and is traversed by regularly arranged columns of electron-dense material. The fine structure of the cortical layer is similar in cuticles from different stages while that of the basal layer is stage specific. Purified cuticles were obtained by sonication and treatment with sodium dodecyl sulfate (SDS) and their component proteins solubilized with a sulfhydryl reducing agent. The degree of cuticle solubility is stage specific and the insoluble structures for each cuticle were localized by electron microscopy. Analysis of ³⁵S-labeled soluble cuticle proteins by SDS-polyacrylamide gel electrophoresis yields unique banding patterns for each stage. Most proteins are of high molecular weight (100–200 K) and are restricted to particular stages. Sixteen of the nineteen major proteins characterized are specifically degraded by bacterial collagenase. The results indicate that the different molts are not reiterative, but require the integration of both unique and shared gene functions. The potential use of stage-specific cuticle differences to identify and characterize regulatory genes controlling cuticle-type switching during development is discussed.     

Membrane Studies of Streptococcus pyogenes and its L-form growing in hypertonic and physiologically isotonic media. An electron spin resonance spectroscopy approach

Electron spin resonance spectroscopy (ESR) was used to compare the lipid organization, thermal stability and the physical state of the membrane of a human pathogen, Streptococcus pyogenes and its osmotically fragile L-form with this same L-form now adapted to grow under physiologically isotonic conditions (physiological L-form). Comparison of the hyperfine splittings of a derivative of 5-ketostearic acid spin label, I(1 2, 3), after incorporation into the membrane, revealed that the lipid chain rigidity of these membranes is in the order physiological L-form > osmotically fragile L-form > streptococcus. The signal intensity (of the center magnetic field line) versus temperature analysis showed two transitions for these membranes. The first with melting points of 45, 26 and 36 °C and second transition at 70, 63 and 60 °C for the physiological L-form, osmotically fragile L-form and streptococcal membranes, respectively. This same order of membrane lipid chain rigidity was seen from the cooperativities obtained for each of these systems from analysis based on the expression for an $\text{n-}\text{order}$ reaction. The I(12,3) and other probes with the paramagnetic group close to the methyl end of the molecule suggested that this difference in lipid chain rigidity between these organisms resides in the environment closer to the lipid head group region rather than in the hydrophobic lipid core. Another major finding was the binding of I(12, 3) at two or more different sites in each of the membranes examined. This change in lipid chain rigidity now provides an explanation to account for the survival of a previously osmotically fragile L-form in physiologically isotonic media by focusing on changes in the physical nature of its membrane. In so doing, it adds to and reinforces the speculation of the potential survival in vivo and involvement in pathogenesis of osmotically fragile aberrant forms of bacteria.     

The effects of a chitin inhibitor-dimilin- on the production of peritrophic membrane in the locust, Locusta migratoria.

Dimilin, now generally accepted as an inhibitor of chitin production in insects, partially blocks chitin synthesis during the production of the peritrophic membrane. Reduction in chitin leads to reduction in protein in the same proportion. We propose that protein incorporation is affected by the stability of the protein in the matrix such that unbound protein tends to inhibit the addition of further protein.     

Transfer of cell-mediated immunity with cell-free leukocyte extracts: II. Demonstration of antigen-specific and nonspecific components

Transfer of cell-mediated immunity was achieved with dialyzable cell-free extracts from lymphoid cells of mice primed to the contact sensitizing agent, 2,4-dinitrofluorobenzene (DNFB). The biological activity of the extract (Transfer Factor, TF) was analyzed in vivo by the ear thickness assay and in vitro by the macrophage migration inhibition (MMI) test and lymphocyte transformation using the soluble analog, sodium 2,4-dinitrobenzenesulfonate. Consistently positive responses occurred 20 hr following a single intravenous injection of 5 × 10⁷ lymphocyte equivalents per recipient. The most potent source of TF (memory TF) was lymph node cells obtained 30 days after primary exposure to DNFB. By contrast TF prepared at the peak of the response to DNFB was less potent which was shown to be due to the presence in it of a suppressor factor. Memory TF elicited macrophage inhibition factor production in naive lymph node cells whereas positive responses were only obtained in the ear thickness and lymphocyte transformation assays provided recipients had undergone prior subliminal sensitization. Specificity of TF was tested using picryl chloride and oxazolone as control antigens. Results from the MMI and ear thickness assays were consistent with the presence in Transfer Factor of an antigen-specific component. Its effects, however, on the proliferative response to antigen lacked specificity and depended on prior sensitization of recipients, rather than donors, to the inducing antigen. The target of the specific component was considered to be an Ly-1⁺, Ia^?, $\text{Ly}\text{2}\text{3}{}^{\mathrm{?}}$ T cell since MIF production and in vivo delayed hypersensitivity are known to be mediated by a T cell bearing this phenotype. Taken together these findings emphasize the value of using a battery of tests of cell-mediated immune function when studying soluble mediators such as Transfer Factor and suggest that the current system is a valid experimental model for analysis of the Transfer Factor phenomenon.     

Species-specific dissociation into single cells of live sea urchin embryos by fab against membrane components of Paracentrotus lividus and Arbacia lixula

The species and stage specificities of membrane components active in promoting reaggregation of cells dissociated from embryos of the two Mediterranean sea urchin species Paracentrotus lividus and Arbacia lixula have been examined. Membrane proteins extracted with butanol either from purified membranes or from dissociated cells without significant reduction of viability promoted reaggregation of both the homologous and heterologous species. Extracts from plutei and blastulae were equally effective in promoting reaggregation of blastula cells. By contrast, Fab's prepared from IgG raised against these extracts or purified membranes are strictly species specific because they prevent reaggregation of cells and actively dissociate live embryos of only the homologous species. No corresponding stage specificity of the Fab was observed: Fab against extracts from blastula embryos also caused dissociation of plutei. Antigenic analysis of the extracts by the Ouchterlony test revealed the presence of components specific for each species as well as others common to both.     

Quantitative visible spectroscopy at low temperatures: a systematic examination

A systematic study of the enhancement of optical absorption of solutions upon freezing is presented. The enhancement factor, the ratio of absorbance of the frozen solution under given conditions to that of the solution at room temperature, is shown to increase with the optical pathlength of the sample, lower temperatures, and decreasing optical density of the solution. The enhancement factor is only weakly dependent upon wavelength under the defined conditions. This study makes possible a clearer understanding of the factors involved in low-temperature spectroscopy. Also presented are measurements of the relative contributions of the two hemes of cytochrome oxidase to the optical spectrum at ?140°C, as an example of quantitative studies at low temperatures.     

Kinetic resonance Raman spectroscopy of carotenoids: A sensitive kinetic monitor of bacteriorhodopsin mediated membrane potential changes

A rapid (14 – 22 μs) light-induced, bacteriorhodopsin mediated membrane potential has been detected using the technique of kinetic resonance Raman spectroscopy and the model system of β-carotene incorporated into reconstituted vesicles containing bacteriorhodopsin. Our data demonstrate that the kinetic resonance Raman spectrum of β-carotene is an extremely sensitive monitor of kinetic alterations in membrane potential with micron spatial resolution in a highly scattering medium. In addition, our Raman results indicate that the potential sensitivity of β-carotene is an excited state property of the molecule, thus making it an electrochromic monitor of membrane potential. We feel the techniques illustrated in this paper have the advantage of being a native probe of kinetic membrane potential changes and will be applicable to a wide variety of biological systems without the perturbing side-effects which often accompany the use of non-biological, potential-sensitive dyes.     

Location of iron in the Fe2+-bleomycin complex as observed by 13C NMR spectroscopy.

The antineoplastic action of bleomycin is currently thought to arise from the degradation of cellular DNA by the iron-bleomycin complex. Bleomycin A₂ has one iron binding site as revealed by the iron-titrations of bleomycin monitored optically. To probe the structure of the Fe²⁺-bleomycin complex, we studied the paramagnetic effects of its high spin ferrous iron on the nuclear relaxation rates ($\text{1}\text{T}{}_1$) of the natural abundance carbon-13 atoms in the molecule. The presence of Fe²⁺ in bleomycin predominantly enhances the $\text{1}\text{T}{}_1$ of only four protonated carbon atoms in the molecule (C2, C3, C5, and C6). No other protonated carbon atoms are affected significantly. From the magnitudes of the paramagnetic effects of Fe²⁺ on the ¹³C relaxation rates, we obtain distances of 3.6, 4.1, 4.0, and 3.6 Å from the metal to the C2, C3, C5, and C6 carbon atoms, respectively. These results are consistent with the metal ion-chelation of the α-amino group of the terminal diaminopropionic acid residue and the pyrimidine ring but do not implicate any other parts of the bleomycin molecule in binding to iron.     

Photodynamic inactivation and its repair in mycoplasmas

Photodynamic inactivation is the loss in viability observed when organic dye-treated cells are exposed to visible light and molecular oxygen. The photodynamic inactivation of mycoplasmas, the smallest free living cells, has been studied. Depending on the extent of inactivation in Acholeplasma laidlawii, photodynamic induced damage can be repaired if the irradiated cells are incubated in the dark in buffer. Analysis of the DNA of these cells shows that photodynamic inactivation induces single strand breaks which can be repaired during liquid holding. To examine possible damage to the cell membrane, glucose uptake was studied as a permeability measure. Neither acriflavine nor photodynamic inactivation had any measurable effect on membrane permeability.     

Circadian periodicity of tissue glutathione and its relationship with lipid peroxidation in rats

Circadian fluctuations in tissue glutathione (GSH) concentrations and lipid peroxidation in male Sprague-Dawley rats were investigated. Blood and all the organs studied exhibited distinct circadian variation both in GSH concentrations and peroxidation of polyunsaturated fatty acids. There was a great variation among organs in the periodicity and amplitude of the fluctuations in GSH concentrations. Liver displayed the highest variation (approximately 50%) followed by stomach (approximately 37%), heart (approximately 25%) and kidney (approximately 19%). The changes in other organs were significant but of less magnitude. Implications of such variations and caution in interpretation of experimental results in response to the exposure of animals to xenobiotics are discussed.     

Resonance Raman spectroscopy of chemically modified retinals: Assigning the carbon-methyl vibrations in the resonance Raman spectrum of rhodopsin

To assign the observed vibrationsl modes in the resonance Raman spectrum of the retinylidene chromophore of rhodopsin, we have studied chemically modified retinals. The series of analogs investigated are the n-butyl retinals substituted at C₉ and C₁₃. The results obtained for the 11-cis isomer have clearly assigned the CCH₃ vibrational frequencies observed in the spectrum of the retinylidene chromophore. The data show that the C₍₉₎CH₃ stretching vibration can be assigned to the vibrational mode observed in the 1017 cm^?1 region, and the vibration detected at 997 cm^?1 can be assigned to the C₍₁₃CH₃ vibration. The C₍₅₎CH₃ stretching mode does not contribute to the vibrations observed in this region. The splitting in the C_(n)CH₃ (n = 9, 13) vibration is characteristic of the 11-cis conformation. The results on the modified retinals do not support the hypothesis that the splitting arises from equilibrium mixtures of 11-cis, 12-s-cis and 11-cis, 12-s-trans in solution. Thus, this splitting cannot be used to determine whether the chromophore in rhodopsin is in a 12-s-cis or 12-s-trans conformation. However, our results demonstrate that there are other vibrational modes in the spectra which are sensitive to this conformational equilibrium and we use the presence of a strong ~ 1271 cm^?1 mode in bovine and squid rhodopsin spectra as an indication that the chromophore in these pigments is 11-cis, 12-s-trans.     

The uptake of cyclic AMP by human erythrocytes and its effect on membrane phosphorylation.

The effects of time and cyclic AMP concentration on cyclic AMP uptake and membrane phosphorylation were studied using intact human erythrocytes. The rate of uptake of cyclic [³H]AMP was nearly linear with respect to cyclic AMP concentration. The amount taken up was small compared to the extracellular cyclic AMP concentration, but was sufficient to significantly increase the intracellular cyclic AMP concentration. Incubation with cyclic AMP resulted in increased incorporation of ³²P_i into several phosphorylated membrane peptides of the intact erythrocytes. Although cyclic AMP altered the distribution of radioactivity among the membrane components, the total amount of incorporation was not increased. The effect of cyclic AMP on phosphorylation of membrane peptides was observed with extracellular cyclic AMP concentrations as low as 1 μm and was most pronounced in incubations of 1 to 4 h. These results indicate that cyclic AMP can enter erythrocytes in sufficient amounts to alter the activity of cyclic AMP-dependent protein kinases, or to alter the rate of turnover of certain phosphorylated membrane peptides.     

Production of gamma interferon by human T and null cells and its regulation by macrophages

Human mononuclear subpopulations were tested for the capacity to produce interferon after mitogenic stimulation with protein A from Staphylococcus aureus. Mononuclear cells were separated into highly enriched macrophage, T-, B-, and null-cell subpopulations by Sephadex G-10 adherence, anti-human IgG F(ab′) two-column chromatography, and rosetting with sheep erythrocytes. Interferon (IFN) production was observed in both T- and null-cell preparations, but not in macrophage or B-cell preparations. Physicochemical and antigenic characterization of IFN from T- and null-cell preparations showed that both mononuclear subpopulations produced gamma IFN (IFNγ). Regulatory studies showed that IFNγ production was differentially regulated by macrophages. Macrophage addition to T lymphocytes augmented both cellular proliferation and IFNγ production, whereas macrophage addition to null cells suppressed IFNγ production and had no effect on the minimal proliferative response observed for these cells.     

The presence of the milk protein, alpha-lactalbumin and its mRNA in the rat epididymis

alpha-Lactalbumin, a modifier protein that changes the substrate specificity of galactosyltransferase, to promote the synthesis of lactose, is found in the mammary glands of lactating mammals and in milk. Molecules similar to mammary gland alpha-lactalbumin but distinct in their modifier activity have been found in rat epididymal fluid. We report here, using a rat mammary gland alpha-lactalbumin cDNA clone as a hybridization probe, RNA sequences homologous to alpha-lactalbumin mRNA were detected in total RNA from the rat epididymis. This finding suggests that alpha-lactalbumin or similar molecules, in addition to regulating lactose synthesis in the mammary gland, may have other important functions in mammalian reproduction.     

Influence of alkyl ether chain length of acetyl glyceryl ether phosphorylcholine and its ethanolamine analog on biological activity toward rabbit platelets

The preparation of the potent new lipid chemical mediator, 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC), through a facile semisynthetic procedure utilizing the vinyl ether-containing lecithins (plasmalogens) of bovine heart muscle as the starting material results in a derivative with mixed chain alkyl residues. In order to focus more closely on the importance of the various components of AGEPC relative to its biological activity, it was of importance to develop a method for isolation of molecules rich in a specific chain length of the alkyl residue. In the current study it was found that a simple thin-layer chromatographic technique, using a solvent system of methanol water (2:1, $\text{v}\text{v}$), afforded an excellent separation of semisynthetic AGEPC into two species, one containing over 95 mol% 16:0 and the other 95 mol% 18:0 alkyl chain species. The same procedure allowed a comparable separation of the species of 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylethanolamine (AGEPE) prepared from AGEPC by phospholipase D action. On the basis of their effectiveness in releasing serotonin from washed rabbit platelets, the 16:0-rich derivatives of AGEPC and AGEPE exhibited significantly higher specific activities, from three to six-fold, on a molar basis, respectively, than the corresponding 18:0-rich derivatives. These findings are discussed in relation to the importance of the chain length of the alkyl ether group in expression of the biological activity of AGEPC.     

Binding of the carcinogens 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene and its acetate ester to DNA in vitro

Binding of 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene to calf thymus DNA was negligible (1.2 μmole hydrocarbon/mole DNA-P) in the absence of microsomal enzymes whereas in the presence of liver microsomes from unpretreated rats or from rats pretreated with 3-methylcholanthrene binding was greatly enhanced (11.6 and 16.2 μmole hydrocarbon/mole DNA-P respectively). In contrast, the acetate ester of 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene readily bound to DNA non-enzymatically (9.1 μmole hydrocarbon/mole DNA-P). In the presence of a 3′-phosphoadenosine-5′-phosphosulfate (PAPS) generating system, the binding of 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene was independent of sulfate ion. ATP enhanced non-enzymatic binding of 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene to DNA whereas CTP, β,γ-methylene-ATP, and ADP were much less effective suggesting a certain specificity for adenosine in addition to a high energy triphosphate for high binding. These observations suggest that 5-fluoro-7-hydroxymethyl-12-methylbenz(a)anthracene may be converted to a phosphate ester which, like 5-fluoro-7-acetoxymethyl-12-methylbenz(a)anthracene, readily binds to DNA.     

Letter: Unequal contribution to ribosomal assembly of both str alleles in Escherichia coli merodiploids and its relationship to the dominance phenomenon

Two Escherichia coli strains were constructed which are reciprocal diploids for the str locus and isogenic for this region of the chromosome (str^s/′F str^r and str^r/′Fstr³). During exponential growth the steady-state ribosomal pools of both merodiploids are comprised of about 90%, or more, of streptomycin-sensitive ribosomes. Little effect of allele position was found. A similar preponderance of sensitive 30 S subunits over those that are resistant has been found during limited subunit reconstitution when an equimolar mixture of ribosomal proteins from both phenotypes was initially present. The results indicate that the rates of 30 S subunit assembly of both phenotypes are different, and that the sensitive sub-units predominate over the resistant subunits, suggesting that the difference in biosynthetic rate may be the basis for the dominance of this phenotype in vivo. An explanation for some aspects of the physiology of str diploids have been suggested in terms of these findings.     

New procedure of high-voltage electrophoresis in polyacrylamide gel and its application to the sequencing of nucleic acids.

Addition of primary organic amines, such as n-butylamine, to the mobile phase altered the capacity factors and selectivity of benzo[a]pyrene metabolites obtained with reverse-phase high pressure liquid chromatography on an ODS column. Separation of benzo[a]pyrene phenols in particular was improved with 8 of the 10 available metabolites resolved, including those known to be biologically produced. The method offers sufficiently improved resolution or convenience that it should prove useful in comparative studies of metabolism of benzo[a]-pyrene and other polynuclear aromatic hydrocarbons. Applying the method to analysis of benzo[a]pyrene metabolites produced in vitro by hepatic microsomes from the marine fish Stenotomus versicolor indicated the principal phenolic derivatives produced by this fish were 1-hydroxy-, 3-hydroxy-, 7-hydroxy-, and 9-hydroxybenzo[a]pyrene.     

The effect of streptozotocin-induced diabetes on glycogen metabolism in rat kidney and its relationship to the liver system.

The effects in kidney of streptozotocin-induced diabetes and of insulin supplementation to diabetic animals on glycogen-metabolizing enzymes were determined. Kidney glycogen levels were approximately 30-fold higher in diabetic animals than in control or insulintreated diabetic animals. The activities of glycogenolytic enzymes i.e., phosphorylase (both a and b), phosphorylase kinase, and protein kinase were not significantly altered in the diabetic animals. Glycogen synthase (I form) activity decreased in the diabetic animals whereas total glycogen synthase (I + D) activity significantly increased in these animals. The activities were restored to control values after insulin therapy. Diabetic animals also showed a 3-fold increase in glucose 6-phosphate levels. These data suggest that higher accumulation of glycogen in kidneys of diabetic animals is due to increased amounts of total glycogen synthase and its activator glucose 6-phosphate.     

Bacteriophage T4 tail length is controlled by its baseplate

Purified T4 baseplate, when treated with high concentrations of pancreatic RNase, are inactive in $\text{in}\text{vitro}$ complementation assays. Their ability to initiate tail tube assembly is not altered; but the most probably length of the tube-baseplate formed is only 800A, compared to 1000A, the normal tube length, when untreated baseplates are used. Thus, baseplates help to regulate tube length, possibly by a template mechanism. Several minor baseplate proteins which may be involved in determining the length, including gp54, are missing from RNase - treated base-plates. These effects may be due to an unidentified protease contaminant of the RNase, since they are inhibited by phenylmethane sulfonyl fluoride.