Complex interaction between different proteinaceous components within the cell-wall structure ofCandida albicans

We have previously described a monoclonal antibody, MAb DC3:H10, which recognized an epitope preferentially expressed on the surface ofCandida albicans germ tubes. In the present study we examined the MAb-reactive material further. Immunoblot analysis of the material purified partially by Sephadex G-200 and DEAE-Sephacel chromatography reacted with antibodies to theC. albicans C3d receptor (CR2). In an ELISA, MAb DC3:H10 captured antigen that was recognized by both anti-CR2 and anti-mp58 fibrinogen binding mannoprotein polyclonal antibodies. The MAb DC3:H10 failed to compete with either of these antisera in an ELISA. Indirect immunofluo-rescence (IIF) analysis showed differences in surface distribution for the MAb DC3:H10, the CR2, and the mp 58 epitopes. Dual labeling IIF experiments showed MAb DC3:H10 binding to be unaffected by binding of fibrinogen or anti-mp58 antibody. However, the binding patterns of MAb DC3:H10 were modified in the presence of anti-CR2 antibody, suggesting a complex interaction between these cell wall components.     

Structure of Leu5-enkephalin bound to a model membrane as determined by high-resolution NMR

Summary Opioid peptides are thought to interact with the cell membrane in their biological journey to the membrane-bound receptor. Both organic solvents and model membranes have been used previously to determine the stable solution conformations of peptide hormones. Leucine enkephalin has been studied in a number of different environments, but with limited resolution. Here it is shown that leucine enkephalin forms a stable type IV -turn structure in dodecylphosphocholine micelles. We have observed a highly solvent-shielded amide proton with no evidence for a complementary hydrogen bond acceptor. The structural details of the peptide as determined by NMR spectroscopy in solution are described.     

Diacytosis of 125I-asialoorosomucoid by rat hepatocytesa. A non-lysosomal pathway insensitive to inhibition by inhibitors of ligand degradation

Diacytosis of ¹²⁵I-asialoorosomucoid by rat hepatocytes was studied by preincubating the cells with the labelled ligand at 37°C for 30 min or 18°C for 2 h, washing free of cell surface receptor-bound tracer at 4°C and then reincubating at 37°C. The cells preloaded at 37°C released a maximum of 18% of the total intracellular ligand as undegraded molecules after 1 h of incubation with an apparent first-order rate constant of 0.018 min^?1 ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 39}\text{min}$). When the preloaded cells were incubated in the presence of 100 μg/ml unlabelled asialoorosomucoid or 5 mM ethylene glycol bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid, the amount of the released ligand increased to 32 and 37%, respectively, without apparent change in kinetics, indicating that these agents prevented rebinding of the released ligand. In the presence of 5 μM colchicine, 20 μM cytochalasin B, 20 μM chloroquine, 10 mM NH₄Cl, 10 μM monensin or 20 μM leupeptin, degradation of the preloaded ligand was inhibited, whereas the release of the ligand was either slightly increased or unchanged. Similar effects of leupeptin, colchicine and asialoocrosomucoid were observed with cells preloaded at 18°C. These results indicate that diacytosis of ¹²⁵I-asialoorosomucoid occurs from a prelysosomal compartment via a route insensitive to inhibition by the inhibitors of ligand degradation.     

THE PERMISSIVE ROLE OF HYPERTHERMIA IN THE DISAGGREGATION OF BRAIN POLYSOMES BY l-DOPA OR d-AMPHETAMINE1

Abstract— l -DOPA or d -amphetamine administration disaggregates brain polyribosomes in animals maintained in an environment warm enough (26°C) so that the drugs concurrently elevate their body temperatures to above 39°C. The production of equivalent hyperthermia (by keeping control rats at ambient temperatures of 40–44° C) does not cause similar disaggregation of brain polysomes. Hence, the role of hyperthermia in the drug-induced disaggregation is permissive.     

Effects of enkephalins on perfusion pressure in isolated hindlimb preparations

A series of studies were conducted to determine the effects of leucine-(leu-) enkephalin and methionine-(met-) enkephalin on perfusion pressure. These experiments utilized isolated perfused femoral arterial preparations in pentobarbital-anesthetized cats. The enkephalins were administered intraarterially into the femoral artery and changes in perfusion pressure recorded. Leu-enkephalin in doses of 1 μg to 320 μg produced significant dose-dependent decreases in perfusion pressure (4.0 ± 1.3% with 1 μg to 19.1 ± 2.1% with 320 μg). Similar declines in perfusion pressure (5.2 ± 2.4% with 1 μg to 21.7 ± 4.1% with 320 μg) were observed following the administration of met-enkephalin. Pretreatment with naloxone (3 mg/kg) antagonized the effects of both enkephalins. Diphenhydramine (2 mg/kg) effectively antagonized the leu-enkephalin elicited decline in perfusion pressure but blocked the effects of met-enkephalin only at lower agonist doses. Propranolol treatment (4 mg/kg) did not alter the pressure responses to either enkephalin. The results of the study show that intraarterially administered enkephalins exert a vasodilatory effect on vasculature in skeletal muscle which may be direct, indirect or both. The differential antagonism of the effects of the two enkephalins suggest that the two opioids act through different receptors or multiple receptors.     

F plasmid replication and the division cycle of Escherichia coli B/r

A terminal stage in the duplication of many bacterial plasmids involves the transient formation of catenated molecules containing two interlocked monomeric plasmid units. This property of plasmid replication was exploited to examine the relationship between F replication and the division cycle of Escherichia coli B/r cells growing in undisturbed, exponential-phase cultures. Various cultures of F′lac- or FKm^r-containing cells were briefly exposed to [³H]thymidine, and then the transfer of radioactivity into, and out of, a catenated dimer consisting of two closed circular monomers was measured during a chase period. The fraction of plasmid molecules present in this dimer form was determined by separating cellular DNA in alkaline sucrose gradients. In addition, plasmid replication was studied in synchronously growing cultures by measuring both [³H]thymidine incorporation into covalently closed circular DNA and β-galactosidase inducibility. The results suggest that replication of F plasmids can take place throughout the cell division cycle, with the probability of replication increasing toward the end of the cycle. The presence of DNA homologous to the chromosome on the F′lac did not alter the replication pattern of the plasmid during the division cycle.     

The alleles of theH-13 locus

Seven congenic strains differing from C57BL/10Sn at theH-13 locus have been produced which define fourH-13 alleles. Isografting, exchanging of grafts between sublines, F(1) testing, and linkage testing demonstrate the presence of additionalH genes in four of these strains. The medial survival times (MSTs) of skin grafts fromH-13(a) to unimmunizedH-13(b) recipients ranged from 69 to 83 days. Rejection across all other barriers was extremely weak with most MSTs being > 100 days. Preinjection of donor strain thymocytes caused accelerated rejection of skin grafts fromH-13(a) toH-13(b) mice, but had only minimal effect on skin grafts across other barriers. Rejection ofH-13 incompatible grafts was significantly stronger when the donor and host areH-3(a) than when they wereH-3(b).     

Description of the oöcysts of three new species of coccidia (Apicomplexa: Eimeriidae) from lizards in Namibia

Three new species of coccidian were recovered from the intestinal contents and faeces of lizards in Namibia, southwest Africa. Oöcysts of Eimeria barnardi n. sp. are described from Rhoptropus barnardi (Gekkonidae) and are ellipsoidal, 24.3 × 19.9 (21–26.5 × 16–22) m; shape index (length/width) 1.22 (1.12–1.30). A micropyle and oöcyst residuum are absent but a fragmented polar granule is present. Sporocysts are subspherical, 9.2 × 8.3 (8–11 × 7.5–9) m; shape index 1.11 (1.02–1.27). Oöcysts of Eimeria pachybibroni n. sp. were found in Pachydactylus bibroni (Gekkonidae) and are ellipsoidal, 26.2 × 18.2 (21.5–28 × 16–19) m; shape index 1.44 (1.30–1.52). A micropyle and oöcyst residuum are absent but a polar granule is present. Sporocysts are subspherical, 8.9 × 8.0 (8–9.5 × 7–8.5) m; shape index 1.12 (1.03–1.20). Oöcysts of Isospora spilogaster n. sp. are reported from Mabuya spilogaster (Scincidae) and are subspherical, 27.4 × 26.0 (21.5–35 × 21–35) m; shape index 1.05 (1.00–1.13). Micropyle, oöcyst residuum and polar granules are absent. Sporocysts are ellipsoidal, 13.2 × 9.7 (10.5–15 × 9–11) m; shape index 1.36 (1.08–1.50).