Search PubMed⌕ Search

Biomedical subjects

J Dekker

Publications and source records attributed to J Dekker.

At least 163 records · Page 9Linked to original sources
PubMed1989

Characterization of lipid-modified immunogenic proteins of Treponema pallidum expressed in Escherichia coli.

This study describes the sequence of the immunodominant Treponema pallidum surface protein TpD and its expression in Escherichia coli. The translated TpD DNA sequence revealed the presence of a putative site for lipid-modification downstream from the signal sequence of this membrane protein. Growth of TpD-expressing E. coli in the presence of radioactive palmitic acid revealed that TpD was lipid-modified. Three other, previously characterized cloned proteins of T. pallidum were also lipid-modified. The N-termini of two of three sequenced T. pallidum proteins contain a tetrapeptide sequence characteristic for lipoproteins in Gram-negative bacteria: Leu-X-Y-Cys. Only TpD differed from this consensus sequence in the substitution of the first residue by Phe. The apparent high incidence of lipoproteins among E. coli recombinants expressing T. pallidum antigens suggest an important role of lipoproteins in the induction of humoral immunity during syphilitic infection.

Amino Acid Sequence↗
PubMed1989

Low antigenicity of HIV-1 rev: rev-specific antibody response of limited value as correlate of rev gene expression and disease progression.

An enzyme immunoassay based on an E. coli-produced HIV-1 rev gene product was used to detect rev-specific antibodies in longitudinally collected serum samples from 196 initially symptom-free men who were seropositive for antibodies to HIV-1 structural proteins and 72 men who seroconverted for such antibodies. In 61% of men no rev-specific antibodies were detected at all, 30% had persistently detectable rev-specific antibodies, and in 9% rev-specific antibodies were only transiently or intermittently detected. When a persistent rev-specific antibody response occurred in subjects who seroconverted to structural proteins, it was always, with one exception, found within 12 months of seroconversion. The rev-specific antibodies were also studied in a transectional sample of sera from the men who remained symptom-free and from those who developed AIDS-related conditions or AIDS, as well as in sera from 31 other men with AIDS-related conditions and in sera from 6 of these men at the time they developed AIDS. The rev-specific antibodies were found in 34% of symptom-free men, in 28% of patients with AIDS-related conditions, and in 16% of patients with AIDS. The low incidence of rev-specific antibodies early after infection may be due to low antigenicity of rev. The lower prevalence of rev-specific antibodies in sera from patients with AIDS, compared with patients with AIDS-related conditions and symptom-free HIV-1-infected individuals, may be explained by a progressive HIV-1-induced immunodeficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1989

Antibody response to a synthetic peptide covering a LAV-1/HTLV-IIIB neutralization epitope and disease progression.

Sequential sera of homosexual men participating in a prospective study on the incidence of HIV-1 infection and risk factors for AIDS were tested for the presence of antibodies to a synthetic 17-mer (Neu21; KSIRIQRGPGRAFVTIG) representing a neutralization epitope as present on the LAV-1/HTLV-IIIB strain of HIV-1. Of 191 at entry, 143 (75%) HIV-1-seropositive men remained anti-Neu21-negative during the follow-up period of 36 months. Thirty-seven (19%) HIV-1-seropositive men were persistently anti-Neu21-positive. Eleven (6%) HIV-1 seropositive men seroconverted for anti-Neu21 during follow-up. Of 75 men developing antibodies to HIV-1, 17 (23%) developed antibodies to Neu21. The incidence of anti-Neu21 seroconversion (calculated as attack rate) after 36 months was significantly lower (P less than 0.00001) among HIV-1-seropositive individuals (8%) than among the 75 HIV-1 seroconverters tested (25%), indicating that seroconversion to this neutralization domain occurs early during infection. AIDS and AIDS-related complex were diagnosed in 17% of the anti-Neu21 negatives and in 11% of the anti-Neu21 positives; this difference was not significant. The presence of HIV-1 antigen (29 versus 28%), the absence of antibodies to core proteins (45 versus 46%) and low CD4+ cell numbers (34 versus 40%) were not seen more frequently among anti-Neu21 negatives than among anti-Neu21 positives. These results argue against a role for antibodies to this LAV-1/HTLV-IIIB neutralization domain in protection against disease progression.

Adult↗
PubMed1989

Antibody response to the viral negative factor (nef) in HIV-1 infection: a correlate of levels of HIV-1 expression.

Antibody responses against the nef gene product of HIV-1 were determined in sequential sera from a longitudinally studied cohort of 194 initially asymptomatic HIV-1-seropositive individuals and 72 individuals who seroconverted for antibodies to HIV-1 structural proteins (gag/env). In the majority of men, nef-specific antibodies, once detected, persisted (67.6%). In some men, nef-specific antibodies were only transiently (6.8%), or intermittently (5.3%), detectable. No nef-specific antibodies were found in the remaining men (20.3%). Nef-specific antibodies were elicited early in infection, but rarely (2/72 men) prior to seroconversion for antibodies to HIV-1 structural proteins. An absent, transient, or intermittent nef-specific antibody response was significantly associated with the absence or disappearance of antibodies to HIV-1 core proteins, with (re)appearance and persistence of HIV-1 core antigen and with the presence of low CD4+ cell numbers, i.e. profiles previously shown to be predictive of rapid disease progression. Although more cases of AIDS and AIDS-related disease (21/86 versus 28/180) occurred in the nef-specific antibody-negative group than in the nef-specific antibody-positive group, this difference did not reach significance.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Metalloendoprotease inhibitors block protein synthesis, intracellular transport, and endocytosis in hepatoma cells.

Fusion of membrane vesicles has been implicated in many intracellular processes including the transport of proteins destined for secretion or storage. Vesicular transport coupled with membrane fusion has been demonstrated for rough endoplasmic reticulum to Golgi and Golgi to plasma membrane transport as well as receptor mediated endocytosis and receptor recycling. Recent studies with inhibitors suggest that metalloendoproteases may mediate a wide variety of intracellular fusion events. Thus, in order to examine the potential role of metalloendoproteases in both transport/secretion and endocytosis/recycling we have used selected dipeptide substrates to probe these processes in human HepG2 cells. Using pulse-chase labeling, immunoprecipitation, and polyacrylamide gel electrophoresis we show that transport and secretion of newly synthesized proteins along the exocytotic route were completely inhibited by substrate dipeptides (e.g. Cbz-Gly-Phe-amide, where Cbz is benzyloxycarbonyl) but not by irrelevant dipeptides (e.g. Cbz-Gly-Gly-amide). The effect was rapid, reversible, and specific. The secretory pathway was blocked between the rough endoplasmic reticulum and Golgi as well as Golgi and plasma membrane as judged by the status of N-glycosylation intermediates. In addition, these inhibitors specifically inhibited protein synthesis without alterations in cellular ATP concentrations. However, cell-free amino acid incorporation was not inhibited. Receptor-mediated uptake of asialoglycoproteins was specifically and reversibly inhibited by dipeptide substrates. This effect appears to be secondary to inhibition of recycling as neither ligand binding nor internalization were affected. Thus the present observations suggest that metalloendoprotease activity may be involved in the regulation of multiple intracellular pathways perhaps at the level of vesicular fusion events.

Biological Transport↗
PubMed1988

Persistent human immunodeficiency virus type 1 antigenemia in children correlates with disease progression.

In a longitudinal study, human immunodeficiency virus type 1 (HIV-1) antigen (HIV-Ag) was measured in serum specimens from 54 children with HIV-1 infection followed for a median duration of 17 months. The persistent detection of free HIV-Ag in a group of 25 children was associated with clinical deterioration in 22 (88%) and a mortality of 52%, whereas the persistent nondetection of free HIV-Ag in a group of 18 children was associated with clinical deterioration in five (28%) and a mortality of 11% during the period of observation. Nine children had transient HIV-1 antigenemia and two children converted from HIV-Ag negative to positive during the study. Free HIV-Ag levels varied inversely with antibody reactivity to viral core proteins p24 and p17 determined by Western immunoblot, suggesting either the formation of immune complexes or a balance between viral expression and the host immune response. Five mother-infant pairs were studied for HIV-Ag expression in the perinatal period. In three of these pairs, both mother and infant were HIV-Ag negative, in one pair the mother had high levels of HIV-Ag and the infant was HIV-Ag negative. In the remaining mother-infant pair, the neonate became HIV-Ag positive but the mother was HIV-Ag negative prepartum and postpartum. These data suggest that HIV-Ag probably does not cross the placenta and that the detection of free HIV-Ag in the offspring of a HIV-1 infected mother most likely indicates viral infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Western↗
PubMed1987

Circadian oscillations in chlorophyll fluorescence in a triazine-resistant chronomutant of Brassica napus.

The objectives of this study were to determine if there was variation in atrazine tolerance, measured by intensity of leaf-disc chlorophyll fluorescence, in triazine-resistant and -susceptible Brassica napus in terms of age of leaf on the plant, time of day, and time of assay after leaf disc removal and immersion in atrazine. In a growth room and field experiment, triazine-susceptible B. napus cv. "Tower" and triazine-resistant B. napus cv. "OAC Triton" were used. Chlorophyll fluorescence intensity measurements were made 15-30 min after disc removal. In both environments, two periods of reduced photosynthetic efficiency occurred in the circadian phase. The times that these periods occurred during the diurnal phase differed between biotypes. A phase shift in leaf chlorophyll fluorescence (LCF) maxima between resistant and susceptible biotypes resulted in two periods, early and late in the light phase, of increased LCF in resistant tissue. This differential pattern in LCF is support for the hypothesis that triazine-resistance chloroplast alterations imply an alteration in the temporal organization of chloroplast physiological function. Atrazine reduced the photosynthetic efficiency of resistant tissue in some instances. This could indicate that triazine resistance is not complete and that some metabolic role may be involved. The results reported here indicate that the most accurate estimation of the physiological state will be obtained from LCF measurements taken soon after leaf disc removal from the plant.

Atrazine↗
PubMed1985

Treatment of sexual dysfunctions in male-only groups: predicting outcome.

Forty men complaining of sexual dysfunctions were treated in male-only groups, using RET, masturbation exercises and social skills training. Sexual functioning improved and social anxiety decreased. Combining these data with previously reported data on 21 men, we tried to predict treatment outcome. Sexual functioning of men with a steady partner and men with varying partners improved; in men without partner(s) no effect could be demonstrated, probably due to a methodological artifact. Inhibited sexual desire was associated with a poor outcome. Several other variables (among them type of dysfunction, social anxiety, age, educational level) did not predict improvement of sexual functioning. This method seems to provide adequate treatment for various complaints of men with quite different backgrounds.

Adult↗
PubMed1983

A long-term follow-up study of couples treated for sexual dysfunctions.

A 5-8 year follow-up was conducted on 140 couples treated for sexual dysfunctions, of whom 88 couples (63%) actually participated. Differences between participant and nonparticipant clients were analyzed. Clients evaluated various aspects of their sexual and nonsexual functioning before and after therapy and in the follow-up period. The correlation between retrospective and original pre- and posttherapeutic data was determined. The effects of treatment for couples not divorced or given additional therapy, couples who separated, and couples given additional therapy were analyzed and compared. The treatments generally led to increased satisfaction about sexual and nonsexual interaction with the partner. The improvement was found to be fairly stable in the follow-up.

Adult↗
PubMed1982

Treatment of homosexual and heterosexual sexual dysfunction in male-only groups of mixed sexual orientation.

Males complaining of erectile and ejaculatory dysfunctions were treated in a structured therapy program. Twenty-one males of heterosexual, homosexual, or bisexual orientation were divided into five groups, with two male therapists for each group. Patients were those usually considered difficult to treat in that 16 had a primary sexual dysfunction with an average duration of 6 years. Extensive evaluations were made before therapy, at the completion of therapy, and at 2-months follow-up. Pre-therapeutic, post-therapeutic, and follow-up measurements indicated that the program was highly successful.

Adult↗