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Biomedical subjects

J E Koehler

Publications and source records attributed to J E Koehler.

53 records · Page 3Linked to original sources
PubMed1990

Chlamydia trachomatis RNA polymerase major sigma subunit. Sequence and structural comparison of conserved and unique regions with Escherichia coli sigma 70 and Bacillus subtilis sigma 43.

We identified and sequenced the gene for the Chlamydia trachomatis RNA polymerase major sigma subunit. The gene encodes a 66,141-dalton protein (sigma 66), intermediate in size between the major sigma subunits of Escherichia coli (sigma 70) and Bacillus subtilis (sigma 43). The C. trachomatis sigma 66 subunit had extensive amino acid homology with the sigma 70 and sigma 43. The sigma subunit regions purportedly involved in core enzyme binding and DNA promoter recognition were also highly conserved, despite the lack of a DNA promoter consensus sequence between E. coli and C. trachomatis promoters and the inability of E. coli holoenzyme to specifically transcribe chlamydial genes. Compared with E. coli sigma 70, there were some major differences in the chlamydial sigma 66 sequence, including a gap of 63 amino acids and an additional 16 amino acids at the carboxyl terminus, which may play some role in modifying the sigma-DNA interaction, such that a promoter sequence unique to C. trachomatis is recognized. Monoclonal antibodies specific for E. coli sigma 70 were used to probe for homologous structures between sigma 70 and sigma 66; only one of seven antibodies bound specifically to sigma 66, suggesting minimal conservation of antigenic sites. The chlamydial sigma 66 was present in elementary bodies and was expressed throughout the developmental cycle, which implied that this gene encodes the major vegetative sigma subunit. Because the ability to study the genetics of C. trachomatis is currently limited, this work provides a tool for more detailed study of chlamydial promoter structure and of coordinate gene expression during the developmental cycle.

Bacillus subtilis↗
PubMed1989

Foscarnet therapy for severe acyclovir-resistant herpes simplex virus type-2 infections in patients with the acquired immunodeficiency syndrome (AIDS). An uncontrolled trial.

STUDY OBJECTIVE: To determine whether trisodium phosphonoformate (foscarnet) is efficacious in treating severe mucocutaneous disease due to acyclovir-resistant herpes simplex virus type-2 (HSV-2) infection in patients with the acquired immunodeficiency syndrome (AIDS). DESIGN: Open-labeled drug administration to patients with AIDS and severe ulcerative disease due to acyclovir-resistant HSV-2 infection. SETTING: Medical floors of acute care hospital. PATIENTS: Four patients with AIDS who developed progressive ulcerative mucocutaneous lesions of the genitals, perineum, perianal region, or finger due to acyclovir-resistant, thymidine-kinase (TK)-negative strains of HSV-2. INTERVENTION: Foscarnet, 60 mg/kg body weight intravenously every 8 hours (with reduced dosage for renal impairment), for 12 to 50 days. MEASUREMENT AND MAIN RESULTS: All patients receiving foscarnet had dramatic improvement in their clinical findings with marked clearing of mucocutaneous lesions and eradication of HSV from mucosal surfaces. CONCLUSION: Foscarnet may be an effective treatment for severe mucocutaneous disease due to acyclovir-resistant, TK-negative strains of HSV-2.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Cutaneous vascular lesions and disseminated cat-scratch disease in patients with the acquired immunodeficiency syndrome (AIDS) and AIDS-related complex.

Cutaneous lesions develop frequently in patients infected with human immunodeficiency virus (HIV). We describe the clinical features of four patients with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex who developed angiomatous nodules involving skin and bone, 2 of whom were scratched by a cat. Some of these lesions were clinically indistinguishable from Kaposi sarcoma. When examined with Warthin-Starry staining and electron microscopy, these nodules were noted to contain numerous clumps of a bacterium. Immunoperoxidase staining with an antiserum raised against the cat-scratch disease bacillus stained these organisms in all patients. Cat-scratch disease is usually a self-limited infection, but complicated or prolonged infections have been described in both normal and immunocompromised hosts. In our patients infected with HIV, manifestations of systemic cat-scratch disease included angiomatous nodules, severe systemic symptoms of fever, chills, night sweats and weight loss, elevated erythrocyte sedimentation rate, and decreased hematocrit. Cutaneous lesions involved the face, trunk, and extremities and numbered 2 to greater than 60; osseous lesions involved the fibula, radius, femur, and tibia, and were present in two of four patients. Treatment with x-ray therapy, intralesional vinblastine, penicillin, dicloxacillin, cephradine, and nafcillin had no effect on any lesions; however, treatment with erythromycin, doxycycline, or antimycobacterial antibiotics resulted in complete and rapid resolution of the cutaneous and osseous lesions, and the accompanying signs and symptoms of systemic infection. In patients with AIDS or AIDS-related complex, angiomatous nodules should be carefully evaluated for the presence of this organism, which can be treated and cured with antibiotic agents.

AIDS-Related Complex↗
PubMed1988

Conformational differences between alpha-cyclodextrin in aqueous solution and in crystalline form. A molecular dynamics study.

The computer simulation technique of molecular dynamics is a powerful tool to delineate the conformational differences between a molecule in different environments. As an illustration, the difference between an alpha-cyclodextrin molecule in aqueous solution and in crystalline form is determined. Two molecular dynamics simulations are compared. In one simulation, one alpha-cyclodextrin form in a "truncated octahedron box" containing 611 water molecules is simulated over 90 picoseconds to mimic the solution structure. In the other simulation, the crystalline form is modelled by a molecular dynamics simulation of four unit cells in space group P2(1)2(1)2(1) containing 16 alpha-cyclodextrin molecules and 96 water molecules over a period of 15 picoseconds. The solution structure of alpha-cyclodextrin deviates by about 0.1 nm from that in the crystal and shows twice as much mobility of the atoms. The experimentally observed twist of glucose unit 5 out of alignment with the other five glucose units in the alpha-cyclodextrin torus that is present in the crystal simulation, disappears in the simulation in solution, but the glucosidic torsion angles around the ring remain asymmetric. The hydrogen-bonding patterns in crystal and in solution are rather different. This means that in a crystal structure, the molecule and its (hydration) hydrogen-bonding scheme represent only one static minimum energy picture, whereas the molecular dynamics simulations yield a description of all the many hydrogen-bonding configurations that can occur in solution.

Animals↗
PubMed1988

On the occurrence of three-center hydrogen bonds in cyclodextrins in crystalline form and in aqueous solution: comparison of neutron diffraction and molecular dynamics results.

Three-center (bifurcated) hydrogen bonds may play a role by serving as an intermediate state between different dynamically changing hydrogen bonding patterns. Hydrogen bonding configurations can be studied experimentally by neutron diffraction and theoretically by computer simulation techniques. Here, both methods are used to analyse the occurrence of three-center hydrogen bonds in crystals of cyclodextrins. Almost all experimentally observed three-center hydrogen bonds in the crystal are reproduced in the molecular dynamics (MD) simulations, even as far as the detailed asymmetric geometry is concerned. On the basis of this result a MD simulation of cyclodextrin in aqueous solution is searched for the occurrence of three-center hydrogen bonds. Significant differences are found. In solution more different three-center hydrogen bonds per alpha-cyclodextrin molecule are observed than in the crystal but the population (existence as percent of the simulation period) of each three-center hydrogen bond is lower in solution than in crystal. These may indeed serve as intermediate states in the process of changing one hydrogen bonding pattern into another.

Chemical Phenomena↗
PubMed1987

A molecular dynamics simulation of crystalline alpha-cyclodextrin hexahydrate.

The structure of crystalline alpha-cyclodextrin (alpha-CD) hexahydrate, form I (C36H60O30.6H2O, space group P2(1)2(1)2(1)) is experimentally so well determined by X-ray and by neutron diffraction analyses that the positions of all the hydrogen atoms are available. This provides an opportunity for testing an empirical force field that is currently used in simulations of protein and nucleic acid structures by performing molecular dynamics studies employing the GROMOS program package on a system of 4 unit cells containing 16 alpha-CD molecules and 96 water molecules. A detailed comparison of the simulated and experimentally determined crystal structures shows that the experimental positions of the alpha-CD atoms are reproduced within 0.025 nm, well within the overall experimental accuracy of 0.036 nm; that the water molecules are on average within 0.072 nm from their experimental sites, with two thirds reproduced within experimental accuracy by the calculations; that high correlation is produced between the occurrence of simulated and experimentally observed hydrogen bonds. The good agreement between simulated and experimental results suggests that the tested force field is reliable.

Carbohydrate Conformation↗
PubMed1987

Molecular dynamics simulation of crystalline beta-cyclodextrin dodecahydrate at 293 K and 120 K.

Molecular dynamics (MD) simulations for crystalline beta-cyclodextrin dodecahydrate (beta-CD) at two different temperatures, 293 K and 120 K, have been performed using the GROMOS program package. The calculated structural properties are compared to those obtained from neutron diffraction studies of this system at the quoted temperatures. The simulation was carried out over a period of 20 ps on four unit cells containing 8 beta-CD molecules and 96 water molecules, whereby all atoms were allowed to move. At room temperature, the experimental positions of the (non-hydrogen) glucose atoms are reproduced within 0.034 nm, a value which is smaller than the experimental (0.041 nm) or simulated (0.049 nm) overall root mean square (rms) positional fluctuation. The corresponding numbers for the low temperature study are 0.046 nm, 0.019 nm and 0.022 nm. At both temperatures the experimentally observed degree of anisotropy of the atomic motions is also found in the simulations. The comparison of a variety of structural properties leads to the conclusion that the molecular model and force field used are able to simulate the cyclodextrin system very well. Experimentally observed differences in properties as a function of number of glucose units in the CD molecule (alpha-CD, 6 versus beta-CD, 7) and as a function of temperature are qualitatively reproduced by the simulations.

Carbohydrate Conformation↗
PubMed1987

The failure of routine assessment to detect histories of assault experienced by psychiatric patients.

To test the hypothesis that patients' histories of having been physically or sexually assaulted are often not elicited in routine clinical assessments, the authors reviewed the charts of 100 inpatients for any mention of such experiences. The data were compared with results of earlier research interviews in which the same 100 patients were questioned directly about assault experiences. Comparison of the two sets of data showed that only 9 percent of the assault histories obtained during research interviews were mentioned on the patients' charts. Because of the clinical significance of most major assaults, the authors recommend that clinicians routinely inquire about assault history.

Adult↗
PubMed1983

Attenuation of enkephalin activity in neuroblastoma X glioma NG108-15 hybrid cells by phospholipases.

The role of membrane phospholipids in enkephalin receptor-mediated inhibition of adenylate cyclase (EC 4.6.1.1) activity in neuroblastoma X glioma NG108-15 hybrids was studied by selective hydrolysis of lipids with phospholipases. When NG108-15 cells were treated with phospholipase C from Clostridium welchii at 37 degrees C, an enzyme concentration--dependent decrease in adenylate cyclase activity was observed. The basal and prostaglandin E1 (PGE1)-stimulated adenylate cyclase activities were more sensitive to phospholipase C (EC 3.1.4.3) treatment than were the NaF-5'-guanylylimidodiphosphate (Gpp(NH)p)-sensitive adenylate cyclase activities. Further, Leu5-enkephalin inhibition of basal or PGE1-stimulated adenylate cyclase activity was attenuated by phospholipase C treatment, characterized by a decrease of enkephalin potency and of maximal inhibitory level. [3H]D-Ala2-Met5-enkephalinamide binding revealed a decrease in receptor affinity with no measurable reduction in number of binding sites after phospholipase C treatment. Although opiate receptor was still under the regulation of guanine nucleotide after phospholipase C treatment, adenylate cyclase activity was more sensitive to the stimulation of Gpp(NH)p. Thus, the reduction of opiate agonist affinity was not due to the uncoupling of opiate receptor from N-component. Further, treatment of NG108-15 hybrid cell membrane with phospholipase C at 24 degrees C produced analogous attenuation of enkephalin potency and efficacy without alteration in receptor binding. The reduction in enkephalin potency could be reversed by treating NG108-15 membrane with phosphatidylcholine, but not with phosphatidylserine, phosphatidylinositol, or cerebroside sulfate. The enkephalin activity in NG108-15 cells was not altered by treating the cells with phospholipase A2 o phospholipase C from Bacillus cereus. Hence, apparently, there was a specific lipid dependency in enkephalin inhibition of adenylate cyclase activity.

Adenylyl Cyclases↗
PubMed1982

Potentiation of opiate action in neuroblastoma N18TG2 cells by lipid incorporation.

The effect of cerebroside sulfate, phosphatidylserine, and other phospholipids on opiate receptor function in neuroblastoma N18TG2 cells was studied by incorporation of lipids into the membrane bilayer of viable cells. A concentration- and time-dependent incorporation of sulfatide by N18TG2 cells was observed. The incorporated lipid was not metabolized during the incubation period of up to 48 hr at 37 degrees. Optimal conditions for lipid incorporation were determined to be 4 days after the cell seeding and in 1% fetal calf serum. The incorporated lipid was established to be associated with the plasma membrane fraction of the crude cell homogenate. Furthermore, increases in Vmax but not Km values of the adenylate cyclase for Mg2+, ATP, and prostaglandin E1 were observed in neuroblastoma N18TG2 cells exposed to cerebroside sulfate for 4--6 hr. The incorporation of cerebroside sulfate or phosphatidylserine by N18TG2 cells did not increase the number of opiate binding sites in this cell line as determined by [3H]naloxone, [3H]etorphine, or 3H-labeled D-Ala2-Met5-enkephalinamide binding. Although there was an increase in the affinity of [3H]naloxone binding, linear correlation between the amount of cerebroside sulfate incorporated and the quantity of binding increase was not observed. However, augmentation of both the potencies and the efficacies (maximal inhibitory level) of morphine and enkephalin to regulate adenylate cyclase activity was observed after sulfatide incorporation. At the maximal concentration of cerebroside sulfate used (67 microM) the opiate receptor activity in N18TG2 cells approached that of NG108-15 cells. Identical treatment of N18TG2 cells with cerebroside or psychosine sulfate did not produce any potentiation of the opiate inhibition of adenylate cyclase. Of all of the phospholipids tested--phosphatidylserine, phosphatidylinositol, and phosphatidylcholine--only phosphatidylcholine produced a potentiation of the opiate effect. Both synthetic dipalmitoyl phosphatidylcholine or brain phosphatidylcholine could elicit the potentiation.

Adenylyl Cyclases↗
PubMed1981

Demonstration and characterization of opiate inhibition of the striatal adenylate cyclase.

The conditions in which Leu(5)-enkephalin inhibition of striatal adenylate cyclase was observed were defined. It was determined that enkephalin inhibition was dependent on GTP. The apparent K(m) for GTP in opiate inhibition was determined to be 0.5 and 2 micrometer when 0.1 mM- and 0.5 mM-ATP were used as substrate. ITP, but not CTP or UTP, could substitute for GTP in the reaction. Though the addition of monovalent cations-Na+, K+, Li+, Cs+, and choline+--stimulated striatal adenylate cyclase activity, enkephalin inhibition of striatal adenylate cyclase did not require Na+ when theophylline was used as the phosphodiesterase inhibitor. Under optimal conditions, i.e., 20 micrometer-GTP and 100 mM-Na+, Leu(5)-enkephalin inhibited the strial adenylate cyclase activity by 23-27%. When the enkephalin regulation of the cyclase activity was further characterized, it was observed that Leu(5)-enkephalin inhibited the rate of the enzymatic reaction. Kinetic analysis revealed that the opioid peptide decreases V (max) values but not the K(m) values for the substrates Mg2+ and Mg-ATP. Agents such as MnCl(2), NaF, and guanyl-5'-ylimido-diphosphate, which directly activated the adenylate cyclase, antagonized the opiate inhibition. Levorphanol and (-)naloxone were more potent than dextrorphan and (+) naloxone in inhibiting adenylate cyclase and in reversing the enkephalin inhibition, respectively. There were differences in the potencies of various opiate peptides in their inhibition of striatal adenylate cyclase activity, with Met5- > Leu(5)-enkephalin > beta-endorphin. The opiate receptor through which the enkephalin inhibition was observed is most likely delta in nature, since in the presence of either Na+ or K+, the magnitude of the alkaloid inhibition was reduced, whereas the peptide inhibition was either potentiated or not affected.

Adenylyl Cyclase Inhibitors↗
PubMed1977

Comparative study of antistreptolysin O, antideoxyribonuclease B and multienzyme tests in streptococcal infections.

The results of antistreptolysin O (ASO), antideoxyribonuclease B (ADB), and a multienzyme test, Streptozyme, with 162 sera from a stratified random sample of Wisconsin school children, and specimens routinely submitted for serodiagnosis of Group A streptococcal infections are described. A review of the results of Streptozyme tests of laboratories participating in the State Division of Health Proficiency Testing Program, is also presented. The results of these various tests have revealed both false positive and false negative results with the Streptozyme procedure. Although there was good correlation of the Streptozyme findings with the ASO and ADB tests results with sera from young children, false positive Streptozyme test results increased with age of the study subjects. Our results with the ADB test on sera from apparently normal Wisconsin children and young adults suggest that the upper limits of normal ADB values, suggested by the manufacturers of commercial ADB test kits, may be too low.

Adolescent↗
PubMed1975

Absorbed heterophile and ox-cell hemolysin test in serodiagnosis of infectious mononucleosis.

The accuracy of the absorbed heterophile and the ox-cell hemolysin procedures was compared by testing of 1577 sera routinely submitted to the State Laboratory of Hygiene for serodiagnosis of IM. Results of both tests were in agreement with 1369 (86.8%) sera; additional 122 (7.7%) samples yielded minor disagreements in results. Major discrepancies in results were seen with 86 sera (5.4%). On basis of clinical data peripheral blood smear findings, tests comprising our IM syndrome test battery, and additional serologic tests, we concluded that in most instances of ox-cell hemolysin positive heterophile negative findings, there was evidence to support a diagnosis of IM. Such support was lacking in a majority of cases with heterophile positive, ox-cell negative findings, and in several of these patients infection with agents other than EBV was suggested. On the basis of comparisons of sensitivity, specificity, cost and ease of performance, the ox-cell hemolysin test appears to offer several advantages over the other available IM serodiagnostic procedures for a public health laboratory performing a large number of tests.

Hemolysin Proteins↗
PubMedDate not supplied

Bacillary angiomatosis.

The manifestations of bacillary angiomatosis include diverse cutaneous lesions, visceral parenchymal bacillary peliosis of the spleen and liver, and involvement of single or multiple organ systems. The organisms causing BA are R. henselae and R. quintana, and these organisms have now been cultured from the spleen and cutaneous lesions of BA as well as the blood of patients with visceral and cutaneous BA. The antibiotic regimen of choice for HIV-infected patients is erythromycin 500 mg 4 x a day for 2-4 months, but relapse may necessitate lifelong suppressive therapy. We are maintaining a registry of patients with bacillary angiomatosis and request that we be contacted (415-206-8680, UCSF) if you diagnose a case, preferably before therapy is instituted.

AIDS-Related Opportunistic Infections↗