Morphology and structural organization of Haller's organ during postembryonic development ofArgas (Persicargas) walkerae (Ixodoidea: Argasidae)

Scanning-electron-microscopic investigations of Haller's organ in larvae, nymphs I, II, III and IV, and male and female adultArgas (Persicargas) walkerae ticks showed that morphology and structural organization change during postembryonic development. Stage-dependent differences existed regarding setal numbers of the anterior pit as well as formation and reticulation of cuticular projections in the capsule cavity. The anterior pit increased in size in the course of postembryonic development. It contained only seven setae in larvae, one conical, setiform and grooved seta each as well as two porose and fine setae. Nymphs I, II, III and IV and adult ticks had equal numbers of setae; however, one additional unilaterally serrate and grooved seta each were present. Setal length increased continuously during postembryonic development and attained maximum values in adult ticks. The capsule consisted of roof and cavity and was located distinctly lateral in larvae, slightly lateral in nymphs I and II, and in all other stages directly on the longitudinal axis of tarsus. The capsule roof showed a reticular structure. The slit-like main aperture was located peripherally and arranged transversally to the longitudinal axis of tarsus I in larvae. Nymphs and adult ticks had a central, circular main aperture. Stage-dependent cuticular projections of varying form protruded into the capsule cavity. Larvae had only single, free-standing projections which ramified slightly and communicated with each other. Projections were more heavily reticulated in nymphs I and II. In nymphs III and IV as well as male and female adult ticks, a long centrally situated tube of reticular appearance was seen, which was supported by a large number of radially organized and interlocking pillars and communicated with the capsule roof. In all tick stages there were always four porose setae present, arranged on the capsule floor.     

A possible pathomechanism of the idiopathic cold contact urticaria.

Urtica is characterized by an erythematous wheal surrounded by a flare and is frequently caused by physical agents (e.g. cold). The exact mechanism and mediators involved in the mechanism of physical urticaria are not known. This study of the role of the neurogenic factors in cold urticaria showed, that local capsaicin treatment (desensitization) of the skin in patients with cold urticaria resulted in the abolition of whealing in response to cold. This result suggests that C-fibers might play an important role in the pathomechanism of idiopathic contact cold urticaria.     

Periodic cleavage of poly(dA) by oligothymidylates covalently linked to the 1,10-phenanthroline-copper complex

1,10-Phenanthroline (OP) was covalently attached to the 3'-terminus of two oligothymidylates via different linkers [abbreviated as T8-(OP) and T6-(OP)]. In the presence of Cu2+ and 3-mercaptopropionic acid (MPA), these reagents induce a hybridization-dependent cleavage of poly(dA) and of a 27 nucleotide long oligodeoxynucleotide containing an A8 sequence. The principal cleavage sites on the 27-mer span four residues located near the 3'-terminal phosphate group of T8-(OP). When poly(dA) was degraded by T6-(OP) and T8-(OP), a series of bands were obtained corresponding to a repeat unit of six and eight nucleotides, respectively. This periodicity reflects the cooperative binding of oligothymidylate-OP to the polynucleotide matrix and the localized nicking sites.     

Quantitative gap junction alterations in mammalian heart cells quickly frozen or chemically fixed after electrical uncoupling

Summary The gap junction morphology was quantified in freeze-fracture replicas prepared from rat auricles that had been either quickly frozen at 6 K or chemically fixed by glutaraldehyde, in a state of normal cell-to-cell conduction or in a state of electrical uncoupling. The general appearance of the gap junctions was similar after both preparative procedures. A quantitative analysis of three gap junctional dimensions provided the following measurements in the quickly frozen conducting auricles (mean±sd): (a) P-face particles' diameter 8.27±0.74 nm (n =5709), (b) P-face particles' center-to-center distance 10.78±2.12 nm (n=4800), and (c) E-face pits' distance 9.99±2.19 nm (n=1600). Corresponding values obtained from chemically fixed tissues were decreased by about 3% for the particle's diameter and about 5% for the particles' and pits' distances. Electrical uncoupling by the action of either 1 mM 2–4-dinitrophenol (DNP), or 3.5 mMn-Heptan-1-ol (heptanol), induced a decrease of the particle's diameter, which amounted to –0.69±0.01 nm (mean ±se) in the quickly frozen preparations and –0.71±0.01 nm in the chemically fixed ones. The particles' distance was decreased by –0.96±0.04 nm in the quickly frozen samples and by –0.90 ±0.03 nm in the chemically fixed ones and the E-face pits' distance was similarly reduced. All differences were statistically significant (P<0.001 for all dimensions). Electrical recoupling after the heptanol effect promoted a return of these gap junctional dimensions towards normal values, which was about 50% complete within 20 min. It is concluded that very similar morphological alterations of the gap junctional structure are induced in the mammalian heart by different treatments promoting electrical uncoupling and that these conformational changes appear independently of the preparative procedure. The suggestion that the observed decrease of the particles' diameter is genuinely related to the closing mechanism of the unit cell-to-cell channel set in thei centers is thus confirmed.     

Immune responses to isolated human cytomegalovirus envelope proteins.

A group of envelope proteins of human cytomegalovirus, gA protein (L. Pereira, M. Hoffman, M. Tatsuno, and D. Dondero, Virology 139:73-86, 1984; L. Pereira, p. 383-404, in B. Roizman, ed., The herpesviruses, vol. 3, 1985), and two protein mixtures (58,000-molecular-weight [58K]-66K and 130K-66K), separated by serial columns prepared with anti-gA immunoglobulin G from sera of immunized guinea pigs, induced neutralizing antibodies and a cellular immune response in the animals. The gA is a disulfide-linked protein complex consisting of high-molecular-weight (greater than 200K), 130K-150K, and 55K-58K proteins.     

The effects of human low and high density lipoproteins on the binding of rat intermediate density lipoproteins to rat liver membranes

Upon incubation with rat liver membranes, radioiodinated rat intermediate density lipoproteins (IDL) interacted with at least two binding sites having a low and a high affinity as demonstrated by the curvilinear Scatchard plots obtained from the specific binding data. The purpose of our work was to identify the nature of these binding sites. Human low density lipoproteins (LDL), contain apolipoprotein B only, and human high density lipoproteins (HDL3), containing neither apolipoprotein B nor E, were both capable of decreasing the specific binding of rat 125I-IDL. The Scatchard analysis clearly revealed that only the low affinity component was affected by the addition of these human lipoproteins. In fact, the low affinity binding component gradually decreased as the amount of human LDL or HDL3 increased in the binding assay. At a 200-fold excess of human LDL or HDL3, the low affinity binding was totally masked, and the Scatchard plot of the specific 125I-IDL binding became linear. Only the high affinity binding component was left, enabling a precise measurement of its binding parameters. In a series of competitive displacement experiments in which the binding assay contained a 200-fold excess of human LDL or HDL3, only unlabeled rat IDL effectively displaced the binding of rat 125I-IDL. We conclude that the low affinity binding of rat IDL to rat liver membranes is due to weak interactions with unspecified lipoprotein binding sites. The camouflage of these sites by human lipoproteins makes possible the study of IDL binding to the high affinity component which likely represents the combined effect of IDL binding to both the remnant and the LDL receptors.     

Stereoscopic back-scattered electron imaging of silver-stained proteins in nucleoli

By using simultaneously the AgNOR silver staining method, back-scattered electron imaging mode and stereo-tilt in scanning electron microscopy (SEM), it is possible to observe the nucleus through the cell surface, the nucleolus, and the tri-dimensional distribution of the AgNOR-associated acidic proteins. In C3H10T1:2 cells and their 7-12-dimethylbenz--anthracene-treated transformants, the staining demonstrates several intranucleolar silver-staining granules (SSG), surrounded by a weakly staining region. The SSG may represent the fibrillar center (FC) and the weakly staining region, the fibrillar dense component (FD). This component can link several SSG together to form a rope-like structure. In cells with no visible nucleolus and inactive nucleolar organizer regions (NORs) the silver-staining granules are less numerous, close together and the presumed fibrillar dense components are not visible. The SSG are located more peripheraly, and the weakly staining region and the rope-like structure are less prominent in control cell nucleoli than in transformed cells with a comparatively high rate of RNA synthesis.     

Specific recognition by the tripeptide lysyl-tryptophyl-alpha-lysine of structural damage induced in DNA by platinum derivatives

The antitumoral derivative cisPt binds to DNA, as do its inactive analogs, trans- and dienPt. Structural damage introduced into DNA after reaction with the Pt derivatives were probed by using the peptide LysTrpLys. This peptide was used for its preferential binding to single-stranded structures (Brun, F., Toulmé, J.J. and Hélène, C. (1975) Biochemistry 14, 558-563). Phosphorescence lifetime measurements show that the Pt-induced heavy atom effects are quite similar in the three peptide-DNA-Pt complexes whatever the nature of the Pt derivative used. In contrast, fluorescence quenching strongly depends on the nature of the Pt derivatives. This quenching was therefore attributed to the stacking interactions engaged by the tryptophan residue with nucleic acid bases. A comparison of fluorescence quenching data for native and modified DNAs demonstrates that modification by dienPt has no effect on stacking interactions and that high levels of modifications by trans Pt are required to observe a change in stacking efficiency. In contrast modification by cis Pt induces the formation of strong stacking sites. The results strongly suggest the existence of locally opened regions in DNA modified by cis Pt.