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Biomedical subjects

S Alexander

Publications and source records attributed to S Alexander.

At least 19 recordsLinked to original sources
PubMed1992

Altering the antigenicity of proteins.

To better understand the binding interaction between antigen and antibody we need to distinguish protein residues critical to the binding energy and mechanism from residues merely localized in the interface. By analyzing the binding of monoclonal antibodies to recombinant wild-type and mutant myohemerythrin (MHr) proteins, we were able to test the role of individual critical residues at the highly antigenic site MHr-(79-84), within the context of the folded protein. The results directly show the existence of antigenically critical residues, whose mutations significantly reduce antibody binding to the folded protein, thus verifying peptide-based assignments of these critical residues and demonstrating the ability of buried side chains to influence antigenicity. Taken together, these results (i) distinguish the antigenic surface from the solvent-exposed protein surface before binding, (ii) support a two-stage interaction mechanism allowing inducible changes in protein antigens by antibody binding, and (iii) show that protein antigenicity can be significantly reduced by alteration of single critical residues without destroying biological activity.

Amino Acid Sequence↗
PubMed1992

Chronic neurodegenerative disease associated with HTLV-II infection.

Although human T-cell leukemia virus (HTLV) type I is known to cause a number of diseases, there has been no convincing evidence of pathological changes after infection with the related virus, HTLV-II. We have found an endemic focus of HTLV-II infection among members of an American Indian population in New Mexico, USA. We set out to determine the pathological consequences of HTLV-II infection in this population and identified two sisters (aged 59 and 46 years) with a disease superficially resembling the myeloneuropathy induced by HTLV-I. These women had a syndrome similar to the olivopontocerebellar atrophy variant of multiple system atrophy, and HTLV-II infection was confirmed by western blot and the polymerase chain reaction. Thus, HTLV-II may, like HTLV-I, cause a progressive neurodegenerative disease.

Ataxia↗
PubMed1992

Discoidin proteins of Dictyostelium are necessary for normal cytoskeletal organization and cellular morphology during aggregation.

The onset of aggregation of bacterially-grown Dictyostelium discoideum amoebae is accompanied by the accumulation of the discoidin proteins. An immunofluorescent analysis demonstrates that discoidin is distributed throughout the cytoplasm, but is excluded from vesicles and nucleoli. There is no indication of either extracellular or membrane localization. Translocating amoebae of mutants lacking discoidin form more dispersed pseudopodial regions at the cell periphery, possess an abnormally centered microtubule organizing center, are blunt rather than elongate, and lack the tapered posterior uropod characteristic of translocating wild-type cells. However, in spite of the loss of the normal elongate morphology, discoidinless mutants translocate with instantaneous velocities and directional persistence comparable to wild-type cells, and they respond normally to the rapid addition of cAMP. These results demonstrate that the discoidin proteins are cytoplasmic components essential for the maintenance of the elongate cell morphology, cytoskeletal organization and the ability to align with other cells during aggregation. However, the elongate morphology is not a requisite for rapid and persistent single cell translocation.

Actins↗
PubMed1992

[Immunotherapy of recurrent spontaneous miscarriages (idiopathic abortive disease): preliminary results].

Recurrent spontaneous abortion (greater than or equal to 3 spontaneous miscarriages) represents an entity defined by negative criteria (absence of anatomical, hormonal, autoimmune and chromosomal abnormalities). The immune hypothesis is corroborated by the successes (greater than or equal to 80 %) of specific (paternal leucocytes) or non-specific (intravenous gammaglobulins) immunotherapeutic trials. Studies on the mechanisms of action of those two methods will afford information on the pathogenesis of this condition.

Abortion, Habitual↗
PubMed1992

Neurotoxic effects of platinum compounds in cultured dorsal root ganglion cells.

The neurotoxic cancer chemotherapeutic agent cis-diamminedichloroplatinum (II) (cis-platin) was tested in a model system of cultured embryonic chick dorsal root ganglion cells, in order to investigate cellular mechanisms of toxicity. At 7.5 ug/ml, the drug caused mild toxicity. At doses of 75 ug/ml, cis-platin was toxic to cultures in 6 hours, in both neuronal and non-neuronal cell populations. After 24 hours of incubation with 75 ug/ml cis-platin, there was extensive cell death. The trans isomer of the drug, trans-platin, was less toxic than cis-platin at similar doses, causing less severe damage to the cells as well as less cell death. With both drugs, abnormalities in patterns of nuclear staining were prominent, whereas neuronal cell membrane staining patterns were less affected. Both drugs seemed to affect non-neuronal cells to a greater extent than neurons. Ultrastructural findings with both drugs included nucleolar segregation; mitochondrial changes were nonspecific. In this in vitro system, both cis- and trans-platin are toxic. The toxicity appears to predominantly affect the nucleus, and to preferentially involve non-neuronal cells.

Animals↗
PubMed1991

Synthesis and characterization of a recombinant myohemerythrin protein encoded by a synthetic gene.

The antigenic epitopes of the myohemerythrin (MHr) molecule have been studied extensively. The critical amino acid residues responsible for its immune recognition have been identified by using synthetic peptides and the technique of epitope scanning. To assess the true relevance of these techniques for determining the molecular mechanism of antigenic recognition and immunogenicity, the results obtained with isolated peptides should be tested in the context of the folded protein. To this end, we have designed and constructed a synthetic MHr gene, in modular form, which will allow subsequent alterations of nucleotide sequence encoding epitopes of interest. We have produced the recombinant protein at high level, and have shown by several criteria that it possesses the chemical, physical and immunological properties of the native worm protein. Thus, we have developed a valuable system for detailed immunological studies of the structure and chemistry required for antibody binding to protein.

Amino Acid Sequence↗
PubMed1991

Genetic and molecular characterization of tube, a Drosophila gene maternally required for embryonic dorsoventral polarity.

Loss of maternal function of the tube gene disrupts a signaling pathway required for pattern formation in Drosophila, causing cells throughout the embryo to adopt the fate normally reserved for those at the dorsal surface. Here we demonstrate that tube mutations also have a zygotic effect on pupal morphology and that this phenotype is shared by mutations in Toll and pelle, two genes with apparent intracellular roles in determining dorsoventral polarity. We then describe the isolation of a functionally full-length tube cDNA identified in a phenotypic rescue assay. The tube mRNA is expressed maximally early in embryogenesis and again late in larval development, corresponding to required periods of tube activity as defined by distinct maternal and zygotic loss-of-function phenotypes in tube mutants. Sequence analysis of the cDNA indicates that the tube protein contains five copies of an eight-residue motif and shares no significant sequence similarity with known proteins. These results suggest that tube represents a class of protein active in signal transduction at two stages of development.

Amino Acid Sequence↗
PubMed1991

Indeterminate human immunodeficiency virus type 1 western blots: seroconversion risk, specificity of supplemental tests, and an algorithm for evaluation.

The human immunodeficiency virus type 1 (HIV-1) Western blot is indeterminate in 10%-20% of sera reactive by EIA. Eighty-nine individuals with prior repeatedly reactive EIA and indeterminate Western blots were followed prospectively to study the risk of seroconversion and specificity of supplemental tests. Four high-risk cases seroconverted within 10 months after enrollment (seroconversion risk, 4.5%, 95% confidence interval, 1.2%-11.1%). Among cases with p24 bands initially, 4 (18.2%) of 22 high-risk individuals seroconverted compared with 0 of 33 low-risk cases (P = .03). Specificities of HIV-1 culture, serum p24 antigen, polymerase chain reaction, and recombinant ENV 9 EIA were 100%, 100%, 98.6%, and 94.4%, respectively. An expedited evaluation protocol is proposed. Low-risk individuals with nonreactive EIAs upon repeat testing do not need further follow-up; high-risk individuals should be followed serologically for at least 6 months, especially those with p24 bands on Western blot.

AIDS Serodiagnosis↗
PubMed1991

Translational control of discoidin lectin expression in drsA suppressor mutants of Dictyostelium discoideum.

Genetic analysis in Dictyostelium discoideum has identified regulatory genes which control the developmental expression of the discoidin lectin multigene family. Among these, the drsA mutation is a dominant second-site suppressor of another mutation, disB, which has the discoidinless phenotype. We now demonstrate a novel mechanism by which the drsA allele exerts its suppressive effect on the disB mutation. Interestingly, drsA does not merely bypass the disB mutation and restore the wild-type pattern of lectin expression. Rather, drsA mutant cells have high levels of discoidin lectin synthesis during growth but do not express lectins during aggregation. In contrast, wild-type cells only express lectin protein during the aggregation period of development. Phenocopies of the drsA mutation show a pattern of discoidin expression similar to that seen in the bona fide mutant. These data suggest that there may be a mechanism of negative feedback, resulting from the high levels of discoidin lectin made during growth, which inhibits further discoidin lectin expression during development. Northern (RNA) analysis of developing drsA mutant cells shows that these cells contain high levels of discoidin mRNA, although no discoidin lectin protein is being translated from these messages. Therefore, expression of the discoidin gene family can be controlled at the level of translation as well as transcription.

Blotting, Northern↗
PubMed1991

Modulation of pulmonary permeability in vivo with agents that affect the cytoskeleton.

In vitro studies show that the cytoskeleton of the microvascular barrier moderates polymorphonuclear leukocyte (PMN) diapedesis and the transport of macromolecules. This in vivo study tests indirectly whether the cytoskeleton of the pulmonary microvasculature responds similarly to agents known to reorganize the cytoskeleton to alter diapedesis and permeability in vitro. One of four agents, saline solution, cytochalasin B (which promotes actin microfilament disassembly), leukotriene (LT) B4 (PMN chemoattractant), or phalloidin (which promotes and stabilizes F-actin polymerization) was introduced into the bronchus of the anterior segment of the left lung of anesthetized rats (n = 152) through a tracheostomy and fine-bore cannula. Twenty minutes later, saline solution, cytochalasin B, LTB4, or phalloidin was similarly introduced. PMN accumulations (x 10(4) cells/ml), protein concentration in bronchoalveolar lavage fluid, and lung wet/dry weight ratios were measured 3 hours later. When the initial and secondary treatments were saline solution, PMN accumulations were 3 +/- 1 cells/ml and the protein level was 274 +/- 48 micrograms/ml. Secondary treatment of the saline-treated group with cytochalasin B or LTB4 led to increases in PMN to 18 +/- 2 and 9 +/- 2 cells/ml and protein to 960 +/- 50 and 840 +/- 40 micrograms/ml (p less than 0.05); secondary treatment with phalloidin was similar to that with saline solution. With saline solution used for both treatments, the wet/dry ratio was 3.4 +/- 0.2. Primary saline solution and secondary treatments with either cytochalasin B or LTB4 led to a similar increase in wet/dry ratios to 3.9 +/- 0.1 (p less than 0.05), whereas phalloidin was without effect (3.5 +/- 0.3). Initial cytochalasin B treatment followed by LTB4 led to increased PMN diapedesis (43 +/- 6 cells/ml and wet/dry ratio 4.3 +/- 0.2) (p less than 0.05). Secondary phalloidin treatment attenuated the cytochalasin B effect with counts of 12 +/- 2 PMN/ml, protein levels of 460 +/- 30 micrograms/ml, and a lower wet/dry ratio of 3.7 +/- 0.1 (p less than 0.05). Even more striking, phalloidin as initial treatment further reduced the cytochalasin B effect to 7 +/- 1 PMN/ml, whereas protein level was 490 +/- 60 micrograms/ml and wet/dry ratio was 3.5 +/- 0.1 (p less than 0.05). Further, phalloidin, given initially, attenuated the effect of secondary treatment with LTB4, resulting in fewer cells (4 +/- 2 PMN/ml), a lower wet/dry ratio (3.4 +/- 0.1), and protein level of 650 +/- 20 micrograms/ml (p less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

An Australia-wide epidemic of Pseudomonas pickettii bacteraemia due to contaminated "sterile" water for injection.

Nineteen cases of Pseudomonas pickettii bacteraemia and one case of Pseudomonas cepacia bacteraemia were identified in an Australia-wide outbreak of nosocomial sepsis associated with contaminated water for injection. The contamination was limited to one batch of commercially produced water for injection. Four different organisms were identified (three biotypes of P. pickettii and one of P. cepacia). However, P. pickettii biotype 1 appeared to be relatively more virulent than the other biotypes as it was the only identified organism in blood cultures in nearly all cases of sepsis. The ampoules of "sterile" water were each contaminated with approximately 10(3) organisms per millilitre. The lack of an Australian central reporting system for bacteraemia delayed the recognition of this outbreak.

Adult↗
PubMed1990

Prevalence of antibodies to human immunodeficiency virus and to human T cell leukemia virus type I in transfused sickle cell disease patients.

The prevalence of the human immunodeficiency virus (HIV) antibody and the human T cell leukemia virus type I (HTLV-I) antibody was examined in 116 adults with sickle cell disease. Eighty-eight of them had received a mean of 18.6 transfusions of red blood cells between 1978 and 1985, and none was positive for the HIV antibody. Of 116 patients, 9 (7.8%) tested positive for HTLV-I antibodies. HTLV-I-positive patients were similar to those without HTLV-I antibody with respect to age, number of transfusions, and proportion of patients with greater than 40 transfusions. However, 3 of the 9 HTLV-I-positive patients came from West Africa or from the Caribbean, whereas this proportion was much lower (7/107) in the HTLV-I-negative group (x2, 7.564; P less than .01). Our analysis suggests that the risk of HIV infection in transfused sickle cell disease patients is low. Although HTLV-I antibodies in these patients may not be related to blood transfusions, it seems prudent to screen blood donors for HTLV-I infection.

Adult↗
PubMed1990

Attenuation of acid aspiration edema with phalloidin.

Acid aspiration leads to pulmonary endothelial and epithelial cell (EC/EpC) injury characterized by increased permeability and polymorphonuclear (PMN) leukocyte diapedesis. Actin in the EC/EpC cytoskeleton has been shown to play a significant role in maintenance of the microvascular junction barrier. This study tests indirectly whether the development of permeability and diapedesis following acid aspiration is via disruption of the pulmonary cytoskeleton. Manipulation was achieved by the actin microfilament assembler phalloidin. Anesthetized rats (n = 88) underwent segmental lung installation of 0.1 ml saline or phalloidin (2 x 10(-6) M). Twenty minutes later 0.1 N HCl, saline, or phalloidin was introduced. After 3 h there was an increase in wet-to-dry weight (W/D) ratio of 6.6 and 5.1 in the HCl-injected and noninjected sides, protein concentration, 3,970 and 2,530 micrograms/ml, and accumulation of 93 PMN/ml (x 10(4] in bronchoalveolar lavage (BAL) of the HCl-injected lung. These values were higher than control animals. Local pretreatment with phalloidin attenuated acid-induced localized but not generalized permeability with reduction in W/D ratio, BAL protein concentration, and diapedesis (P less than 0.05). Acid injection into airways also led to elevated thromboxane B2 and leukotriene B4 levels in plasma and BAL (P less than 0.05) and generalized lung leukosequestration, events not affected by phalloidin. Taken together, these data suggest that acid aspiration lung injury is determined largely by loss of integrity of the pulmonary EC/EpC cytoskeleton with resultant loss of barrier function.

Administration, Inhalation↗
PubMed1990

A conserved idiotype and antibodies to retroviral proteins in systemic lupus erythematosus.

22 of 61 systemic lupus erythematosus (SLE) patients produced antibodies to the p24 gag protein of HIV-1 demonstrated by Western blotting. 20 of these 22 patients (91%) also express the 4B4 idiotype (Id 4B4) previously identified on a human anti-Sm monoclonal antibody called 4B4. This represents an enrichment for this Id (seen in only 52% of SLE patients generally). Eight of these 22 SLE patients also have anti-Sm antibody activity. Sm partially inhibits the antibody binding of p24 gag suggesting immunologic cross-reactivity between the retroviral antigen p24 gag and the autoantigen Sm. Anti-Id 4B4 also inhibits p24 gag antibody binding by as much as 40%. Finally the monoclonal antibody 4B4 showed cross-reactivity to Sm and p24 gag. The following points emerge from our studies: (a) SLE patients make antibodies to p24 gag of HIV-1, (b) there is a relationship between immunity to p24 gag and a conserved idiotype, and (c) anti-Sm antibodies can cross-react with p24 gag.

Autoantigens↗
PubMed1989

Routine formal fetal movement counting and risk of antepartum late death in normally formed singletons.

The routine recommendation to women to count fetal movements daily during late pregnancy for the prevention of antepartum late fetal death in normally formed singletons has been evaluated. 68,000 women were randomly allocated within thirty-three pairs of clusters either to a policy of routine counting or to standard care, which might involve selective use of formal counting or informal noting of movements. Antepartum death rates for normally formed singletons were similar in the two groups, regardless of cause of prior risk status. Despite the counting policy, most of these fetuses were dead by the time the mothers received medical attention. The study does not rule out a beneficial effect, but at best, the policy would have to be used by about 1250 women to prevent 1 unexplained antepartum late fetal death, and an adverse effect is just as likely. In addition, formal routine counting would use considerable extra resources.

Belgium↗
PubMed1989

Effects of simvastatin and probucol in hypercholesterolemia (Simvastatin Multicenter Study Group II).

This 12-week, randomized, double-blind, multicenter study compared the efficacy, tolerability and safety of simvastatin (a potent HMG-CoA reductase inhibitor) and probucol. Two doses of simvastatin, 20 or 40 mg once daily, were compared to probucol, 500 mg twice daily. Both simvastatin doses were significantly more effective than probucol in improving the plasma lipid profile. Mean reduction in low density lipoprotein (LDL) cholesterol was 34% with 20-mg simvastatin and 40% with the 40-mg dosage, compared to a mean reduction of 8% with probucol. Simvastatin significantly decreased total cholesterol, triglycerides and apolipo-protein B, and increased high density lipoprotein (HDL) cholesterol and apolipoprotein A-I. Probucol caused some reduction in LDL cholesterol but significantly decreased HDL cholesterol. Both simvastatin and probucol were well tolerated and no serious drug-related events occurred. Simvastatin appears to be a well-tolerated and effective new agent used once-a-day as an adjunct to diet in the management of patients with hypercholesterolemia.

Adult↗