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M A Jacobson

Publications and source records attributed to M A Jacobson.

144 records · Page 8Linked to original sources
PubMed1987

Human IgG antibodies to Pseudomonas aeruginosa core lipopolysaccharide determinants are detected in chronic but not acute pseudomonas infection.

Human IgG response to Pseudomonas aeruginosa core lipopolysaccharide determinants was measured after both acute and chronic pseudomonas infection by using lipopolysaccharide purified from PAC605 cells (the most lipopolysaccharide-defective or "roughest" mutant of P. aeruginosa yet described) as a solid phase antigen in ELISA and Western blot immunoassay. The geometric mean IgG anti-PAC605 lipopolysaccharide titer of sera from 18 cystic fibrosis (CF) patients with chronic pseudomonas pulmonary infection was 1808, compared to 171 for convalescent sera of 10 patients with acute pseudomonas bacteremia (p less than 0.001) and 211 for 5 normal human volunteers (p less than 0.001). Western blot immunoassay demonstrated specific IgG anti-core antibodies in 11/18 sera from CF patients but not in the sera of the convalescent bacteremic patients or normal volunteers. IgG anti-Pseudomonas core lipopolysaccharide antibodies appear to be a marker of chronic infection; the possible protective role of these antibodies remains to be established.

Acute Disease↗
PubMed1986

New developments in the treatment of gram-negative bacteremia.

Gram-negative bacteremia is an increasingly important nosocomial infectious problem. Endotoxin, endorphins, leukocyte agglutination and deficient opsonization all appear to be major factors in the pathogenesis of Gram-negative septic shock. Outcome has previously correlated best to underlying disease state. With appropriate double antibiotic therapy and hemodynamic support, however, mortality has decreased even for neutropenic patients. Corticosteroids, naloxone, granulocyte transfusions and immunotherapy are experimental adjunctive modes of therapy that offer hope for even better survival in the future.

Adrenal Cortex Hormones↗
PubMed1984

Isolation and identification of a tyrosyl peptide labeled by 5'-[p-(fluorosulfonyl)benzoyl]-1,N6-ethenoadenosine at a GTP site of glutamate dehydrogenase.

The fluorescent nucleotide analogue 5'-[p-(fluorosulfonyl)benzoyl]-1,N6-ethenoadenosine (5'-FSB epsilon A) was shown previously to react at a GTP inhibitory site on bovine liver glutamate dehydrogenase. The incorporation was limited to 1.28 mol of reagent/mol of subunit and was attributed to 0.95 mol of modified tyrosine/mol of subunit and 0.33 mol of modified lysine/mol of subunit, quantitatively accounting for the total incorporation prior to acid hydrolysis [Jacobson, M. A., & Colman, R. F. (1983) Biochemistry 22, 4247-4257]. The specific tyrosyl peptide modified by 5'-FSB epsilon A has been isolated from a tryptic and chymotryptic digest of modified enzyme by gel filtration and reverse-phase high-performance liquid chromatography and characterized by amino acid and amino-terminal analysis. A unique residue, tyrosine-262, was identified as an essential amino acid within the GTP binding site. The stacked conformation of the fluorescent analogue when enzyme bound suggests that tyrosine-262 may be located in the region of the GTP site which binds the purine ring.

Adenosine↗
PubMed1984

Distance relationships between the catalytic site labeled with 4-(iodoacetamido)salicylic acid and regulatory sites of glutamate dehydrogenase.

The distance between the catalytic site on bovine liver glutamate dehydrogenase labeled with 4-(iodoacetamido)salicylic acid (ISA) and the adenosine 5'-diphosphate (ADP) activatory site occupied by the analogue 2',3'-O-(2,4,6-trinitrocyclohexadienylidene)adenosine 5'-diphosphate (TNP-ADP) was evaluated by energy transfer. Native enzyme and enzyme containing about 1 mol of acetamidosalicylate/mol of subunit bind about 0.5 mol of TNP-ADP/mol of subunit, and TNP-ADP competes for binding with ADP to native and modified enzyme, indicating that the analogue is a satisfactory probe of the ADP site. From the quenching of acetamidosalicylate donor fluorescence upon addition of TNP-ADP, an average distance of 33 A was determined between the catalytic and ADP sites. The fluorescent nucleotide analogue 5'-[p-(fluorosulfonyl)benzoyl]-2-aza-1,N6-ethenoadenosine (5'-FSBa epsilon A) reacts covalently with glutamate dehydrogenase to about 1 mol/peptide chain. As compared to native enzyme, the SBa epsilon A-enzyme exhibits decreased sensitivity to GTP inhibition but retains its catalytic activity as well as its ability to be activated by ADP and inhibited by high concentrations of NADH. Complete protection against decreased sensitivity to GTP inhibition is provided by GTP in the presence of NADH. It is concluded that 5'-FSBa epsilon A modifies a GTP site on glutamate dehydrogenase. The distance of 23 A between the catalytic site labeled with ISA and a GTP site labeled with 5'-FSBa epsilon A was measured from the quenching of salicylate donor fluorescence in the presence of the SBa epsilon A acceptor on a doubly labeled enzyme. The average distance between the ADP and GTP sites was previously measured as 18 A [Jacobson, M. A., & Colman, R. F. (1983) Biochemistry 22, 4247-4257], indicating that the regulatory sites of glutamate dehydrogenase are closer to each other than to the catalytic site.

Adenosine↗
PubMed1984

Evaluation of the intramolecular stacking of the fluorosulfonylbenzoyl derivatives of 1,N6-ethenoadenosine, adenosine, and guanosine.

The differences in conformation in solution of fluorosulfonylbenzoyl nucleosides were analyzed by fluorescence and proton nuclear magnetic resonance spectroscopy. The quantum yield of 5'-p-fluorosulfonylbenzoyl-1,N6-ethenoadenosine (5'-FSB epsilon A) in aqueous solution is low (ø = 0.01) as compared to that of its parent nucleoside, ethenoadenosine (ø = 0.54), and increases approximately 5-fold when measured in a series of solvents of decreasing dielectric constant. The quantum yield of 5'-p-sulfonylbenzoyl-1,N6-ethenoadenosine covalently bound to glutamate dehydrogenase and pyruvate kinase is also 0.01, suggesting that the analogue may exist in the same conformation when enzyme-bound as when free in solution. In D2O, the resonances of the purine ring protons on 5'-FSB epsilon A, 5'-p-fluorosulfonylbenzoyl adenosine (5'-FSBA), and 5'-p-fluorosulfonylbenzoyl guanosine (5'-FSBG) are shifted upfield by about 0.1-0.3 ppm relative to the corresponding protons of their parent nucleosides. The calculated difference in chemical shift (delta delta) decreases as the dielectric constant of the solvent decreases. The delta delta decreases with increasing temperature. These data indicate that 5'-FSB epsilon A, 5'-FSBA, and 5'-FSBG exist in aqueous solution in a conformation in which the purine ring is intramolecularly stacked with the benzoyl moiety. From the magnitude of change in delta delta for 5'-FSB epsilon A, 5'-FSBA, and 5'-FSBG as a function of solvent, it appears that the three analogues differ in their sensitivity to disruption of stacking. The solution conformation of these three fluorosulfonylbenzoyl nucleoside analogues may be an important determinant of their reaction with various enzymes and may explain differences among the analogues in their reaction with a single enzyme.

Adenosine↗
PubMed1983

Resonance energy transfer between the adenosine 5'-diphosphate site of glutamate dehydrogenase and a guanosine 5'-triphosphate site containing a tyrosine labeled with 5'-[p-(fluorosulfonyl)benzoyl]-1,N6-ethenoadenosine.

The fluorescent nucleotide analogue 5'-[p-(fluorosulfonyl)benzoyl]-1,N6-ethenoadenosine (5'-FSB epsilon A) reacts irreversibly with bovine liver glutamate dehydrogenase and modifies one of the natural inhibitory guanosine 5'-triphosphate (GTP) sites [Jacobson, M.A., & Colman, R.F. (1982) Biochemistry 21, 2177-2186]. Enzyme with 1.28 mol of 5'-(p-sulfonylbenzoyl)-1,N6-ethenoadenosine/mol of subunit incorporated and exhibiting maximum change in sensitivity to GTP inhibition is now shown by amino acid analysis to contain 0.95 mol of O-[(4-carboxyphenyl)sulfonyl]tyrosine (CBS-Tyr) and 0.33 mol of N epsilon-[(4-carboxyphenyl)sulfonyl]-lysine (CBS-Lys), quantitatively accounting for the total incorporation prior to acid hydrolysis. As a function of time of incubation with 5'-FSB epsilon A, the amount of CBS-Tyr formed was directly proportional to the change in GTP inhibition. In contrast, an initial formation of CBS-Lys was observed, followed by relatively little additional CBS-Lys although the percent change in GTP inhibition continued to increase. It was concluded that the tyrosine is an essential residue in the GTP binding site of glutamate dehydrogenase, while the lysine modified is not involved in the inhibitory action of GTP. The nucleotide analogue 2'(3')-O-(2,4,6-trinitrophenyl)adenosine 5'-diphosphate (TNP-ADP) was evaluated for its ability to occupy the adenosine 5'-diphosphate (ADP) activator site and to function as an energy acceptor conjointly with 5'-SB epsilon A covalently bound at the GTP site as the energy donor. TNP-ADP activates native enzyme 2-fold and competes kinetically with ADP. As determined by fluorometric titration, the maximum number of TNP-ADP binding sites on native enzyme was 0.5 mol/mol of subunit in the absence and 1 mol/mol of subunit in the presence of reduced coenzyme. The 5'-SB epsilon A-modified enzyme also binds TNP-ADP: 0.5 mol/mol of subunit in the absence or presence of reduced coenzyme. TNP-ADP competes for binding with ADP to native and 5'-SB epsilon A-modified enzyme, indicating that this nucleotide analogue is a satisfactory fluorescent probe of the ADP site of glutamate dehydrogenase. An energy-transfer efficiency of 0.77 was determined from the decrease in donor fluorescence upon addition of TNP-ADP in the absence of reduced coenzyme to modified enzyme containing 1.23 mol of 5'-SB epsilon A/mol of subunit. A value of 18 A was calculated as the average distance between the GTP and ADP regulatory sites. This result indicates that the inhibitory GTP and the activatory ADP sites are close but not identical.

Adenosine↗
PubMedDate not supplied

The uses of computer-aided signal peptide selection and polymerase chain reaction in gene construction and expression of secreted proteins.

The computer program, SIGSEQ2, was used to select heterologous signal peptides from a catalog of published sequences to express the echistatin gene in insect (Sf9) cells. S-values for each amino acid were determined to select empirically the site of cleavage between the signal peptide and mature echistatin. Five gene fragments encoding the signal peptides for human immunoglobulin kappa (Ig kappa), Drosophila 68C glue, antistasin, bovine growth hormone (bGH), and human apolipoprotein E (Apo E) were constructed by the use of long synthetic oligonucleotides or polymerase chain reaction (PCR). Echistatin expression vectors then were constructed using the baculovirus polyhedrin promoter. Following transient transfection, the media were assayed for echistatin activity. The results indicate that the computer program greatly facilitated the selection and design of five different signal peptides and accurately predicted their relative functionality in the expression and secretion of echistatin in insect cell cultures.

Animals↗
PubMedDate not supplied

Treatment of cytomegalovirus retinitis in patients with AIDS.

Retinitis is the commonest clinical manifestation of cytomegalovirus (CMV) infection in patients with AIDS. Untreated patients generally experience progressive involvement of the retina, which may result in blindness. Attempts to treat this condition with vidarabine and interferon-alpha have been uniformly unsuccessful. Therapy with ganciclovir (9[(1,3-dihydroxy-2-propoxy)methyl]guanine) (7.5-15 mg/[kg./d] given intravenously in two or three divided doses) has been shown to halt progression of retinitis and may result in limited healing in some cases; viremia and shedding of virus from other sites (such as the urine) are halted or reduced. However, reactivation of infection and retinitis usually occurs when ganciclovir therapy is discontinued. For that reason, most patients have received continued therapy with the drug, most commonly at a dosage of 5-6 mg/(kg.d) administered as a single intravenous infusion 5-7 days per week. Both retrospective and prospective, randomized trials have shown that maintenance therapy delays (but does not prevent) reactivation of infection. Much more limited studies with foscarnet (trisodium phosphonoformate) suggest that this drug will also be useful for treatment of CMV retinitis in AIDS patients. Further research is needed, however, since existing agents have a low therapeutic ratio and cannot be given orally to patients requiring long-term maintenance therapy.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Presence of macrolide resistance in respiratory flora of HIV-Infected patients receiving either clarithromycin or azithromycin for Mycobacterium avium complex prophylaxis.

Clarithromycin 500 mg po bid or azithromycin 1200 mg po weekly is recommended as first line prophylaxis for Mycobacterium avium complex (MAC) in patients with HIV infection whose CD4 counts are <50 cells/microL. HIV-infected patients with CD4+ T-cell counts <200 cells/microL were randomized to receive either clarithromycin 500 mg po bid or azithromycin 1200 mg po weekly for 12 weeks. Nasopharyngeal swabs for Streptococcus pneumoniae and Haemophilus influenzae plus an anterior nare culture for Staphylococcus aureus were obtained at pretreatment, at 6 weeks, and at 12 weeks. A throat culture for oral flora was obtained for susceptibility testing against erythromycin. Minimum inhibitory concentrations (MICs) for clarithromycin and azithromycin were performed on all S. pneumoniae, H. influenzae, and S. aureus isolates. The study was terminated after respiratory flora, from all participants, revealed macrolide resistance. Because results of recent randomized trials indicate minimal efficacy of continuing MAC prophylaxis in patients who respond to potent combination antiretroviral therapy, the observed high incidence of macrolide-resistant bacterial colonization of the respiratory tract in this trial supports the discontinuation of macrolide prophylaxis in all AIDS patients whose CD4 counts have risen above 100 cells/microL.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

The safety of discontinuation of maintenance therapy for cytomegalovirus (CMV) retinitis and incidence of immune recovery uveitis following potent antiretroviral therapy.

BACKGROUND: Reconstitution of immune function during potent antiretroviral therapy can prompt discontinuation of maintenance cytomegalovirus (CMV) therapy but has also been associated with sight-threatening inflammatory conditions including immune recovery uveitis (IRU). METHOD: Patients with inactive CMV retinitis and a CD4+ cell count above 100/mm3, receiving CMV therapy and stable combination antiretroviral therapy, were assigned to one of two groups based on willingness to discontinue CMV therapy. RESULTS: Thirty-eight participants were enrolled: 28 discontinued anti-CMV therapy (Group 1) and 10 continued CMV treatment (Group 2). Median on-study follow-up was 16 months. One Group 1 participant who experienced an increase in plasma HIV viral load and a decline in CD4+ cell count developed confirmed progression of CMV retinitis. Progression or reactivation CMV retinitis was not observed among Group 2. IRU was present at study entry in 3 participants. Six participants in Group 1 and 3 participants in Group 2 developed IRU on-study. CMV viremia was not detected in any participants, and urinary shedding of CMV was intermittent. CONCLUSION: Recurrence of CMV retinitis following discontinuation of anti-CMV therapy among patients with antiretroviral-induced increases in CD4+ cell count was rare. However, IRU was common in both those who maintained and discontinued anti-CMV therapy.

Adult↗