Subcellular localization of lethal lysis proteins of bacteriophages lambda and phiX174.

The gene products of the lethal lysis genes S and E of the bacteriophages lambda and phiX174, respectively, were shown to be associated primarily with inner membrane material by isopycnic sucrose gradient centrifugation of lysates of infected cells. A small amount of each polypeptide appeared to be in the outer membrane fraction.     

Autointoxication in residues ofAsparagus officinalis L.

Summary In a greenhouse experiment the growth of asparagus seedlings was retarded by the residue treatments in both vermiculite and sand cultures. In general, the retardation of asparagus root by residues was slightly greater than the retardation of shoot in both cultures. The retardation of the growth of asparagus seedlings by root and stem treatments was usually higher than that by old root litter. Root and stem extracts strongly inhibited the development of asparagus seedlings in the seed bioassay. The inhibition of extracts to the growth of shoot was greater than that to the growth of root. The quantities in the total phenolics and catachol type phenolics from root, stem and old root litter extracts corresponded to the autotoxicity in the seed bioassay. The soil extracts obtained from using acetone, methanol, and XAD-4 extractions strongly inhibited the shoot and root development of asparagus seedlings in the bioassay. The efficiency of phenolics extraction by the XAD-4 method was significantly higher than that by acetone and methanol extractions. The results obtained in the greenhouse experiment and bioassay revealed that phytotoxic substances present in the residues and the soil of asparagus and may be partially responsible for the asparagus replanting problems.     

Resistance of citrus fruit to mass transport of water vapor and other gases

The resistance of oranges (Citrus sinensis L. Osbeck) and grapefruit (Citrus paradisi Macf.) to ethylene, O₂, CO₂, and H₂O mass transport was investigated anatomically with scanning electron microscope and physiologically by gas exchange measurements at steady state. The resistance of untreated fruit to water vapor is far less than to ethylene, CO₂ and O₂. Waxing partially or completely plugs stomatal pores and forms an intermittent cracked layer over the surface of fruit, restricting transport of ethylene, O₂, and CO₂, but not of water; whereas individual sealing of fruit with high density polyethylene films reduces water transport by 90% without substantially inhibiting gas exchange.

Stomata of harvested citrus fruits are essentially closed. However, ethylene, O₂ and CO₂ still diffuse mainly through the residual stomatal opening where the relative transport resistance (approximately 6,000 seconds per centimeter) depends on the relative diffusivity of each gas in air. Water moves preferentially by a different pathway, probably through a liquid aqueous phase in the cuticle where water conductance is 60-fold greater. Other gases are constrained from using this pathway because their diffusivity in liquid water is 10⁴-fold less than in air.

     

Three types of transmitter release from embryonic neurons

Prior to the contact with their target muscle cells in culture, growth cones of many isolated Xenopus embryonic neurons release acetylcholine (ACh) spontaneously. Using patch clamp techniques, this release can be detected by an outside-out patch of muscle membrane placed near the growth cone. Intracellular recording from innervated muscle cells showed spontaneous miniature endplate potentials (MEPPs) of varying amplitudes. Amplitude histograms showed a skewed distribution with multiple peaks, suggesting the existence of subunits in either the quantal packages of ACh released by the nerve terminal or in the postsynaptic muscle response. In addition to the quantal ACh release reflected by MEPPs, nerve terminal also release a large amount of ACh in a non-quantal fashion. This non-quantal ACh release is revealed by the hyperpolarization of the muscle membrane following extracellular application of curare or alpha-bungarotoxin, as well as by denervation of the muscle cell.     

Methylation of type II and type I collagen genes in differentiated and dedifferentiated chondrocytes

The methyl-sensitive restriction endonucleases HpaII and HhaI as well as the methyl-insensitive enzyme MspI were used to examine the methylation status of the pro-alpha 1(II) collagen gene of cartilage. Five different cell types with varying abilities to express type II collagen were studied. Chick embryo chondrocytes express type II collagen, while 5-bromodeoxyuridine-treated chondrocytes, retinoic acid-treated chondrocytes, chick embryo fibroblasts, and erythrocytes do not synthesize type II collagen. Both cDNA and genomic probes for the pro-alpha 1(II) collagen gene were used, covering the complete 3' end of the gene and its flanking sequences. The pro-alpha 1(II) collagen DNA was undermethylated in chondrocytes, compared to either fibroblasts or erythrocytes. However, the methylation of the 5-bromodeoxyuridine-treated and retinoic acid-treated chondrocytes was identical to that of control chondrocytes. The methylation pattern of two regions of the gene of the pro-alpha 2(I) collagen chain was identical in all cell types tested, whether or not the gene was expressed. Our results indicate that genes for these collagen chains differ in their methylation pattern. The type II collagen gene shows reduced methylation in expressing cartilage, but does not acquire an increase in methylation in "dedifferentiated" chondrocytes. The changes in DNA methylation that occur during cell differentiation do not appear to be sufficient to explain gene activation and deactivation.     

Immunochemical Characterization of Pyruvate Dehydrogenase Complex in Rat Brain

Pyruvate dehydrogenase complex (PDHC) in rat brain was studied immunochemically, using antibodies against the bovine kidney PDHC, by immunoblotting, immunoprecipitation, inhibition of enzyme activity, and enzyme-linked immunoabsorbent assay (ELISA). The immunoblots showed that the antibodies bound strongly to the alpha peptide of the pyruvate dehydrogenase (E1) component, and to the dihydrolipoyl transacetylase (E2) and the dihydrolipoyl dehydrogenase (E3) components of PDHC. A similar immunoblotting pattern was observed in all eight brain regions examined. On immunoblotting of the subcellular fractions, these PDHC peptides were observed in mitochondria and synaptosomes but not in the postmitochondrial supernatants. This agrees with other evidence that brain PDHC is localized in the mitochondria. These results, together with those from sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the immunoprecipitin, also showed that the alpha E1, beta E1, and E3 peptides of rat brain PDHC are very similar in sizes to those of the bovine kidney PDHC, being 42, 36, and 58 kD, respectively. The size of the E2 peptide, 66 kD, is different from that of bovine kidney E2, 73 kD. The relative abundance of PDHC protein in nonsynaptic mitochondria was compared by enzyme activity titration and ELISA. Both methods demonstrated that the amount of PDHC antigen in the mitochondria from cerebral cortex is greater than that in the olfactory bulb mitochondria. This is consistent with the results of the activity measurement. The ELISA also showed that the PDHCs in both mitochondrial populations are antigenically similar.(ABSTRACT TRUNCATED AT 250 WORDS)     

Massive scrotal edema as a complication of abdominoplasty

Massive scrotal edema is an unreported complication of abdominoplasty. This patient's postoperative decompensation of medial thigh and scrotal lymphatic return may well have been due to an occult lymphedema tarda or previously compromised lymphatics from the fibrosis of venous stasis disease and obesity.     

The binding of copper(II) and zinc(II) to oxidized glutathione

1H and 13C NMR studies of Zn(II) binding to oxidized glutathione (GSSG) in aqueous solution over the pH range 4-11 show that it forms a complex with a 1:1 Zn:GSSG stoichiometry. At pH values between 6 and 11 the metal ligands are the COO- and NH2 groups of the glutamate residues. Below pH 5 the glycine end of the molecule also binds to the metal ions. EPR and visible absorption spectra of Cu(II) GSSG solutions suggest that similar complexes are formed with Cu(II). The solid products obtained from these solutions are shown by analysis and EPR to be primarily binuclear with Cu2GSSG stoichiometry, although the structures depend on the pH and stoichiometry of the solution from which they were obtained.     

Pharmacological investigation of the mechanisms of platelet-activating factor induced mortality in the mouse

Although the platelets of the mouse are refractory to the direct effects of platelet-activating-factor (PAF), tail vein injection of 10-150 micrograms/kg PAF produces lethal anaphylactic shock. Sensitivity varies with strain and source: Swiss Webster mice show a range of sensitivity and DBA/2 (complement C5-deficient) mice are very resistant. At lethal doses of PAF, animals show labored respiration and general depression; death occurs within 15-45 min. Dexamethasone administered at least 1.5 hr prior consistently protects, whereas the cyclooxygenase inhibitors do not. Antihistamines, adrenergic antagonists, and methysergide have no effect, but cyproheptadine is partially protective at near lethal doses. Calcium entry blockers and calcium chelators, tetracycline and chlortetracycline are partially protective at very high doses consistent with non-specific effects on calcium dependent processes. The arachidonic acid lipoxygenase inhibitors BW755c, phenidone, nordihydroguaiaretic acid and diphenyldisulfide provide nearly complete protection after oral administration of 50-200 mg/kg. Phosphodiesterase inhibitors and dapsone are also effective orally. The leukotriene antagonist FPL55712 administered intraperitoneally (10 mg/kg) 5 min. prior to PAF challenge provides almost complete protection. PAF-induced mortality in the mouse represents a small animal model of systemic anaphylaxis particularly useful for the systemic testing of arachidonic acid lipoxygenase inhibitors and leukotriene antagonists.     

Cilia in the fetal and neonatal canine retina

Cilia in the canine retina were examined at 40, 46 and 50 days of gestation and at birth by scanning electron microscopy, transmission electron microscopy, and by the freeze-fracture technique. Cilia were similar in all age groups examined. Scanning electron micrographs showed them to be smooth-surfaced conical to tubular extensions arising from putative photoreceptor inner segments. Cilia when freeze-fractured contained variable numbers of circumferential rows of 10 nm P-face particles: these constitute the ciliary necklace. Transmission electron micrographs showed the ciliary membrane to contain electron-dense beads which corresponded to the ciliary necklace seen in freeze-fracture replicas. The ciliary necklace identified in the developing canine retina was similar to those found in other types of motile and sensory cilia.