Effects of Interactions BetweenPasteurella haemolyticaandBordetella parapertussisonin vitroPhagocytosis by Lung Macrophages

The aim of the work was to determine the effect of exposing ovine bronchoalveolar macrophages (BAM)in vivotoPasteurella haemolyticaand/orBordetella parapertussison the subsequent uptake and killing ofP. haemolyticaby these cellsin vitro. Exposurein vivotoP. haemolyticadid not affect the uptake ofP. haemolyticaby BAMin vitrobut reduced (P< 0·05) the intracellular killing of bacteria. Exposurein vivotoB. parapertussishad no significant effect on either the uptake of killing ofP. haemolytica in vitro. However, sequential exposurein vivotoB. parapertussisandP. haemolyticareduced both the ingestion (P< 0·05) and killing (P< 0·001) ofP. haemolytica in vitro. These results indicate that exposure toP. haemolyticacompromised the bacterial killing mechanisms of BAM and that synergy betweenB. parapertussisandP. haemolyticareduced the ability of BAM to ingest bacteria.     

Sensitization of rhabdo-, lenti-, and spumaviruses to human serum by galactosyl(alpha1-3)galactosylation.

Vesicular stomatitis virus, human immunodeficiency virus type 2, and human foamy virus, which were produced by cell lines expressing galactosyl(alpha1-3)galactosyl (alphaGal) sugars, were found to be less stable in human serum than those from alphaGal-negative cells, indicating that galactosyl(alpha1-3)galactosylation sensitizes these viruses as well as mammalian type C oncoviruses (Rother et al., J. Exp. Med. 182:1345-1355, 1995; Takeuchi et al., Nature (London) 379:85-88, 1996) to complement killing via natural anti-alphaGal antibodies. Thus, virus killing mediated by anti-alphaGal antibodies may play a role as a barrier to animal-to-human infection of various enveloped viruses. Virus vectors for human in vivo gene therapy based on the viruses mentioned above should be produced from alphaGal-negative cells.     

Decompression comparison of helium and hydrogen in rats

Lillo, R. S., E. C. Parker, and W. R. Porter.Decompression comparison of helium and hydrogen in rats.J. Appl. Physiol. 82(3): 892-901, 1997.The hypothesis that there are differences in decompression riskbetween He and H₂ wasexamined in 1,607 unanesthetized male albino rats subjected to dives on2% O₂-balance He or 2%O₂-balanceH₂ (depths  50 ATA, bottom times  60 min). The animals were decompressed to 10.8 ATA with profilesvarying from rapid to slow, with up to four decompression stops of up to 60 min each. Maximum likelihood analysis was used to estimate therelative decompression risk on a per unit pressure basis (termed "potency") and the rate of gas uptake and elimination, bothfactors affecting the decompression sickness risk, from a specific dive profile. H₂ potency for causingdecompression sickness was found to be up to 35% greater than that forHe. Uptake rates were unresolvable between the two gases with the timeconstant (TC) estimated at ~2-3 min, leading to saturation inboth cases in <15 min. Washout of both gases was significantly slowerthan uptake, with He washout (TC ~1.5-3 h) substantially slowerthan H₂ washout (TC ~0.5 h). Itis unknown whether the decompression advantage of the faster washout ofH₂ or the disadvantage of itsincreased potency, observed in the rat, would be important for humandiving.

     

Localization of binding site for encephalomyocarditis virus RNA polymerase in the 3'-noncoding region of the viral RNA.

We previously showed that encephalomyocarditis (EMC) virus RNA-dependent RNA polymerase (3Dpol) binds specifically to 3'-terminal segments of EMC virus RNA. This binding, which depends on both the 3'-noncoding region (3'-NCR) and 3'-poly (A) tail [together denoted 3'-NCR(A)], may be an important step in the initiation of virus replication. In this paper, the 3'-NCR and 3'-poly(A) were separately transcribed then mixed, but no complex with 3Dpol was obtained, showing that covalent attachment of the 3'-poly(A) to the 3'-NCR is essential for complex formation. Mutational and deletion analyses localized a critical determinant of 3Dpol binding to a U-rich sequence located 38-49 nucleotides upstream of the 3'-poly(A). Similar analyses led to the identification of a sequence of A residues between positions +10 and +15 of the 3'-poly(A) which are also critical for 3Dpol binding. As U-rich and A-rich regions are important for 3Dpol binding, a speculative model is proposed in which 3Dpol induces and stabilizes the base-pairing of the 3'-poly(A) with the adjacent U-rich sequence to form an unusual pseudoknot structure to which 3Dpol binds with high affinity.     

The structural basis of the multiple forms of human complement component C4

cDNA clones of human complement components C4A and C4B alleles were prepared from mRNA obtained from the liver of a donor heterozygous at both loci. cDNA from one C4A allele was sequenced to give the derived complete amino acid sequence of 1722 amino acid residues of the C4 single chain precursor molecule and the estimated sequences of the three peptide chains of secreted C4. Comparison with partial sequences of a second C4A allele and a C4B allele has led to the tentative identification of some class differences in nucleotide sequences between C4A and C4B and of allelic differences between C4A alleles in this highly polymorphic system.     

Peripheral nerve extract promotes long-term survival and neurite outgrowth in cultured spinal cord neurons

The hypothesis that peripheral, skeletal muscle tissue contains a trophic factor supporting central neurons has recently been investigated in vitro by supplementing the culture medium of spinal cord neurons with muscle extracts and fractions of extract. We extended these studies asking whether or not a trophic factor is present in peripheral nerves, the connecting link between muscle and central neurons via which factors may be translocated from muscle to neurons by the retrograde transport system. Lumbar, 8-day-old chick spinal cords were dissociated into single cells and then cultured in the presence of peripheral nerve extract. Cytosine arabinoside was added to inhibit proliferation of nonneuronal cells. In the presence of nerve extract, spinal cord neurons survived for more than a month, extended numerous neurites, and showed activity of choline acetyltransferase. In the absence of extract, neurons attached and survived for a few days but then died subsequently in less than 10 days. Neurite outgrowth did not occur in the absence of extract. Withdrawal of extract from the medium of established neuronal cultures caused progressive loss of both cells and neurites. Other tissues also contained neuron supporting activity but less than that found in nerve extract. These studies indicate that peripheral nerves contain relatively high levels of spinal cord neuron-directed trophic activity, suggesting translocation of neurotrophic factor from muscle to central target neurons. The neurotrophic factor has long-term (weeks) effects, whereas short-term (days) survival is factor independent.     

Activation of the first component of human complement (C1) by antibody-antigen aggregates.

The activation of subcomponents C1r and C1s in the first component of complement, C1, when bound to antibody-antigen complexes was investigated. Activation was followed both by the splitting of the peptide chains of subcomponents C1r and C1s and by the development of proteolytic activity. For the maximum rate of activation to occur, all components must be present in approximate molar proportions of antibody: C1q:C1r:C1s of 13:1:5:5. For activation of subcomponent C1s, subcomponents C1r or C1r, but not C1r inactivated with iPr2P-F (di-isopropyl phosphorofluorideate), are effective. For activation of subcomponent C1r, subcomponents C1s, C1s or C1s inactivated with iPr2P-F are effective. Subcomponent C1s is activated by C1r, and C1r is activated autocatalytically, probably through the formation of an intermediary C1r. in which the peptide chain is unsplit but a conformational change caused by interaction with the other components has led to the formation of a catalytic site able to split subcomponent C1r to C1r.     

Subcellular localization of alpha-melanocyte-stimulating hormone in the rat hypothalamus.

Homogenates of male rat hypothalami were fractionated by means of differential centrifugation, and α-melanocyte-stimulating hormone (α-MSH) in the various fractions was quantified by radioimmunoassay. Of the total quantity of α-MSH in the homogenate, 36% was recovered in the 11,500 g pellet and 31% sedimented between 11,500 and 105,000 g. α-MSH was not detected in the 105,000 g supernatant fluid. When the 900 g supernatant fluid was fractionated on continuous sucrose density gradients at non-equilibrium conditions, two populations of particles containing α-MSH were observed. When fractionated at equilibrium conditions, the two populations were recovered in a single band. These sedimentation characteristics indicate that the particles that contain α-MSH differ in size but are similar in density. After hypo-osmotic shock, the large particles containing α-MSH were not demonstrable, whereas the small particles appeared to be resistant to such treatment. In their sedimentation, the particles containing α-MSH were indistinguishable from particles containing thyrotropin releasing hormone (TRH) but were separable from those that contained luteinizing hormone releasing hormone (LHRH). It is suggested that the large particles containing α-MSH are synaptosomes.     

The effects of pineal indoles and a crude aqueous pineal extract on ACTH mediated corticosterone release by isolated adrenal cells.

An aqueous extract of bovine pineal tissue contained a principle which caused a potent inhibition of ACTH mediated corticosterone release by isolated adrenal cells, whereas a similar extract of cortical tissue did not have any effect on this process. Two pineal indoles were tested. Melatonin (10^?8 M) did not have any significant effect, whereas 5-methoxytryptophol (10^?8 M) caused a variable but significant additive effect on ACTH mediated corticosterone release. We are uncertain at the present time if this principle is similar to the reported pinealantigonadotropin.