Effect of diisopropylfluorophosphate on muscarinic and gamma-aminobutyric acid receptors in visual cortex of cats.

Administration of diisopropylfluorophosphate (DFP), an organophosphorus (OP) compound, irreversibly inhibits acetylcholinesterase (AChE) and results in cholinergic hyperactivity. This study investigated muscarinic and gamma-aminobutyric acid (GABA) receptor changes in visual cortex of cats following an acute exposure to DFP. A single acute administration of DFP (4 mg/kg) decreased the number of muscarinic receptors at 2, 10, and 20 hours after treatment. GABA receptors were elevated at 2 and 10 hours but returned to within control levels at 20 hours. No significant alteration in muscarinic or GABA receptor affinity was noted. In all cases cortical AChE activity was inhibited 60-90%. These findings show a down regulation of muscarinic receptors after DFP associated with low AChE activity. GABA receptors also are altered, and may be part of a compensatory mechanism to counteract excess cholinergic stimulation.     

Highly regioselective hydrolysis of tricarballylates (“retro-fats”) and citrates by subtilisin

Trimethyl and triethyl esters of tricarballylic acid and citric acid were hydrolysed with porcine liver esterase(PLE) to the isomeric diesters. In all cases the hydrolysis took place with poor regioselectivity (maximum 50% excess). However, the hydrolysis of trimethyl and triethyl esters of tricarballylic acid and of the triethyl ester of citric acid with subtilisin was absolutely regioselective and the symmetric 1,5-diester was obtained.     

Construction of immunogens for synthetic malaria vaccines

The immunogenicity of a peptide consisting of eight repeats of the tetrapeptide sequence NANP (Asn-Ala-Asn-Pro) contained in the circumsporozoite protein of Plasmodium falciparum was investigated in mice under different modes of presentation. This peptide was able to produce biologically active antibodies when administered with adjuvant and linked to a protein carrier. However, a (NANP) peptide polymerized by carbodiimide was found to be immunogenic in the absence of protein carrier in H-2b mice. In contrast, the (NANP)8 peptide polymerized by glutaraldehyde was not immunogenic in the same strain. Furthermore, the efficacy of murabutide in saline, as an immunological adjuvant, was compared to the efficacy of Freund's complete adjuvant.     

Different modes of ligand binding to the hepatic galactose/N-acetylgalactosamine lectin on the surface of rabbit hepatocytes

A study of the binding of three different 125I-labeled, galactose-terminated ligands to the hepatic galactose/N-acetylgalactosamine-specific lectin found on the surface of rabbit hepatocytes revealed that the different ligands manifest different physical parameters of binding. Asialoorosomucoid (125I-ASOR) binding was best described as involving two independent classes of binding sites on rabbit hepatocytes, with 161 000 sites/cell with a dissociation constant of 0.44 nM and 292 000 sites/cell with a Kd of 9.7 nM. Asialotriantennary glycopeptide purified from human alpha-1 protease inhibitor and modified with tyrosine at the N-terminus to permit radioiodination (TRI) [Lee, Y. C., Townsend, R. R., Hardy, M. R., L?nngren, J., Arnarp, J., Haraldsson, M., & L?nn, H. (1983) J. Biol. Chem. 258, 199-202] was also found to bind to two apparent classes of binding sites but with different binding parameters: 292 000 sites/cell of Kd = 1.47 nM and 982 000 sites/cell of Kd = 25.3 nM. A synthetic ligand, alpha,beta-diaspartamide of tris[(beta-lactosyloxy)methyl](6-aminohexanamido)methane (di-tris-lac) containing six nonreducing galactose residues [Lee, R. T., Lin, P., & Lee, Y. C. (1984) Biochemistry 23, 4255-4261], was found to bind to 817 000 sites/cell of Kd = 0.63 nM and 1.23 X 10(6) sites/cell of Kd = 25.3 nM. Thus, there were many more total binding sites for TRI or di-tris-lac on the surface of rabbit hepatocytes than there were for asialoorosomucoid, although the dissociation constants were similar for all three ligands.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterisation of DNA forms associated with cassava latent virus infection.

In addition to the major encapsidated DNA species found in preparations of cassava latent virus (genomic DNAs 1 and 2) there are minor DNA populations of twice (dimeric) and approximately half genome length. Both minor species resemble the genomic DNAs in that they are composed of predominantly circular single-stranded DNA. All of these size groups have a corresponding covalently-closed circular double-stranded DNA form in infected tissue. Infectivity studies using cloned DNAs 1 and 2 show that dimeric DNA routinely appears, suggesting it to be an intermediate in the DNA replicative cycle that can be encapsidated at low efficiency. In contrast, half unit length DNA has not yet been detected after multiple passaging of virus derived from the cloned DNA inoculum. Half unit length DNAs appear to be derived exclusively from DNA 2 and consist of a population of molecules exhibiting a relatively specific deletion. As they have an inhibitory effect on virus multiplication, their encapsidated forms are analogous to defective interfering particles associated with other eukaryotic DNA containing viruses. Small primer molecules associated with the genomic single-stranded DNAs, as reported for another geminivirus, have not been detected in CLV.     

Larvae of Euphausia superba in the Scotia Sea and Bransfield Strait in March 1984 — Development and abundance compared with 1981 larvae

Summary Larvae of Euphausia superba in the Atlantic sector of the Antarctic in March 1984 averaged 580 per 1000 m³ of water. This is 100 times less than we observed in March 1981, but more than the average of 250 larvae per 1000 m³ found in January–February 1981. There was one 1984 high-abundance sample, accounting for 85% of all larvae caught, from the eastern area of confluence of Drake Passage and Weddell Sea waters. Abundances in 1984 near the South Shetland Islands were commonly 5 to 10 larvae per 1000 m³, and younger by 2 to 4 developmental stages than in March 1981. Body lengths of given stages were generally less in 1984 than in 1981. Advanced furcilia stages, particularly, in the 1984 samples tended to be smaller than the same stages in March 1981, indicating relatively poor growth during February 1984. However, the 1984 younger larvae (calyptopes and the developmental forms of furcilia stages 1 and 2) indicated that, in 1984, recent (March) growth had been good — probably better than in February. Dierct observation of the development of calyptopis stage 3 to furcilia stage yielded a development time of 7.7 days, which compares favorably to the 8-day period estimated from field samples. Reduced food availability did not affect the development rate nor give rise to a clearly higher incidence of indirect pathways of development. It is postulated that recruitment was about of month later in 1984 than in 1981 in most of the area studied and was probably going to be less successful.     

A Study of the Chronic Effects of Insecticides in Man

Signs of possible chronic intoxication due to insecticides were sought among 441 apple-growers. A group of 170 persons living in the same environment and 162 other persons having no contact with insecticides were used as controls. It was the first attempt to determine signs of chronic intoxication by organic phosphate and chlorinated hydrocarbon insecticides. The greater incidence of leukopenia and of neurologic manifestations found among the subjects suggest that insecticides may have some chronic effects in man. This assumption is reinforced by the similarities in the findings between the subjects and the environments, and by the parallelism between the duration of exposure to insecticides and the number of affected subjects. The repetition of this study at five-year intervals seems desirable until a sufficient number of apple-growers have been studied who have been exposed to large doses of insecticides for 10, 15 or 20 years.     

Resistance to H-2-restricted but not to allo-H2-specific graft and cytotoxic T lymphocyte responses in lymphoma mutant

The lymphoma mutant RMA-S escaped graft rejection after transplantation over a minor histocompatibility barrier, whereas it was rejected in H-2 allogeneic mice. The parental control line was rejected in both situations. The mutant, which had been selected against MHC class I molecules retained 5 to 10% of the wild-type H-2Db, Kb, and beta 2-microglobulin expression on the cell surface. It remained sensitive to allo-H-2b CTL in vitro, but was completely resistant to minor histocompatibility antigen-specific, H-2b-restricted CTL. It was equally resistant to other H-2b-restricted responses against internally derived Ag, such as tumor-specific CTL or a CTL clone specific for the influenza virus nucleoprotein. The results indicate a target cell defect that selectively abolishes the sensitivity to H-2-restricted CTL directed against internally processed Ag. This appears sufficient to shift the transplantation response over a minor histocompatibility Ag barrier from rejection to acceptance. There are two possible explanations for the results: 1) a block in the MHC class I-directed pathway for internal Ag processing, and 2) subthreshold H-2/Ag ligand density in relation to triggering requirements of restricted CTL. Regardless of the type of defect, the results demonstrate a difference between allo-H-2-specific and H-2-restricted CTL recognition at the level of the target cell.