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Biomedical subjects

C Nielsen

Publications and source records attributed to C Nielsen.

At least 91 records · Page 5Linked to original sources
PubMed1996

Development of resistance of zidovudine (ZDV) and didanosine (ddI) in HIV from patients in ZDV, ddI and alternating ZDV/ddI therapy.

OBJECTIVE: To study development of phenotypic and genotypic resistance against zidovudine (ZDV) and didanosine (ddI) during 24 months of mono- and monthly alternating therapy. PATIENTS: Forty-six patients, not previously treated with antiretroviral drugs, were included in the study. METHODS: ZDV and ddI sensitivity were determined in a biological assay based on production of HIV antigen in cultures of CD4+ lymphocytes. The ZDV-associated mutations at codon 41 and 215, and the ddI-associated mutation at codon 74 of the reverse transcriptase (RT) gene were analysed using selective polymerase chain reaction on DNA from peripheral blood mononuclear cells. The biological phenotype [syncytium-inducing (SI)/non-SI(NSI)] of the viral isolates was assessed using a MT2 assay. RESULTS: Of the patients, 82% in ZDV therapy and 73% in alternating therapy developed phenotypic resistant HIV [median inhibitory concentration (IC50) > 0.1 microM]. Patients treated for 1 year with ddI (monotherapy or alternating) had significant higher ddI IC50 values than patients in ZDV monotherapy. During ZDV and alternating therapy, 67 and 75% of the patients, respectively, developed mutations in RT codon 41, whereas 83 and 75%, respectively, developed mutations in codon 215. In patients treated with ddI, 60% developed mutations in codon 74, whereas none of the patients in either alternating ZDV/ddI or ZDV therapy developed this mutation. Forty-six per cent of the patients had SI HIV at start of therapy. Four patients switched from SI to NSI during either ZDV, ddI or alternating therapy. Faster development of resistance was associated with the SI phenotype. CONCLUSIONS: No difference in either phenotypic ZDV or ddI resistance, or genotypic ZDV resistance could be demonstrated during monotherapy or monthly alternating ZDV/ddI therapy, whereas genotypic ddI resistance (mutation in RT codon 74) only were detected in patients in ddI monotherapy. In addition, we found that development of phenotypic and genotypic resistance was faster in patients harbouring SI isolates, and that switches from SI to NSI during therapy was independent of the type of therapy.

Anti-HIV Agents↗
PubMed1996

False negative anti-HIV-1/HIV-2 ELISAs in acute HIV-2 infection.

Since HIV-2 was isolated in 1986, only 1 case of acute HIV-2 infection has been reported. We have identified another patient with primary HIV-2 infection. Follow-up samples were requested from the patient due to discrepant results. The HIV-2 infection was confirmed with HIV-2-specific proviral DNA amplification by PCR. The HIV-2 seroconversion panel obtained was used to evaluate the sensitivity of both combined and specific ELISAs currently in use in Europe, and to investigate the Western-blot patterns on both HIV-1-and HIV-2-specific Western blots. The window period was determined to be less than 37 days with the most sensitive assays. A remarkable difference in sensitivity to HIV-2 antibodies in acute HIV-2 infection was found in combined HIV-1/HIV-2 ELISAs. Three out of the 4 combined sandwich ELISAs appeared to be less sensitive than the indirect ELISAs in HIV-2 seroconversion, leading to a prolonged window period. One HIV-2-specific ELISA was also negative on the first sample, but positive on the second sample. In the HIV-2 Western blot, early reaction with HIV-2-specific env and gag proteins was seen, whereas the HIV-1 Western blot on the first sample revealed gag (p24, p55) reactivity only.

AIDS Serodiagnosis↗
PubMed1996

Risk factors of infantile spasms compared with other seizures in children under 2 years of age.

To analyze the magnitude of the risk factors for infantile spasms, we evaluated the records of 80 children with infantile spasms, 474 children with other types of epilepsy, 2,196 children with febrile seizures, and 262 children with CNS infections. There was a family history of seizures in 13.8% of children with infaNtile spasms, 28.5% of children with other forms of epilepsy, 25.5% of children with febrile seizures, and 5.3% of children with CNS infections. Children with a family history of seizures were 2.82 times more likely to have infantile spasms, 7.05 time more likely to have other epilepsy, and 6.08 time more likely to have febrile seizures than controls (children with CNS infections). However, a family history of seizures increased the risk for infantile spasms only in the cryptogenic group. Children with infantile spasms were significantly more likely to have cerebral palsy, microcephaly, hydrocephaly, CNS malformations, neonatal hypoxia, or neonatal seizures than children with other types of epilepsy, febrile seizures, or CNS infections. There was a modest genetic predisposition to seizures in children with infantile spasms. However, our data suggest a much stronger association with underlying neurologic abnormalities, mainly neonatal seizures, neonatal hypoxia, and CNS malformations.

Age Factors↗
PubMed1996

Synthesis of an AZT-HEPT hybrid and homologous AzddU derivatives.

3'-Azido-2',3'-dideoxyuridines 6 and their corresponding alpha anomers 5 were synthesized by condensation of silylated 6-alkyl and 5,6-dialkyl substituted uracils 2 with methyl 3-azido-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-alpha, beta-D-erythro-pentofuranoside (4). Compounds 5 and 6 were treated with tetrabutylammonium fluoride to obtain the deprotected nucleosides 7 and 8, respectively.

Antiviral Agents↗
PubMed1996

Quantification of HIV-1 RNA during antiretroviral therapy: association with viral phenotype and development of resistance.

The aim of this study was to analyse the interplay between the treatment responses, as assessed by serum HIV-1 RNA levels and CD4 cell counts, virological phenotype and the development of phenotypic and genotypic resistance. A total of 47 late-stage, HIV-1-infected, antiretroviral-naive patients treated with reverse transcriptase inhibitors (zidovudine or didanosine monotherapy or alternating zidovudine and didanosine) as part of a randomized study and remaining on treatment for a minimum of 1 year were included in the study. Baseline serum HIV-1 RNA levels did not differ between the patients harbouring syncytium-inducing (SI) virus and those harbouring non-syncytium-inducing (NSI) virus (P = 0.66), despite the fact that the group of patients with SI virus had a significantly lower median CD4 cell count (P < 0.00005) and a higher proportion of patients diagnosed with AIDS at study entry (11/19 versus 6/25) than did the group with NSI virus. The patients harbouring SI virus had significantly faster clinical progression than that of the patients harbouring NSI virus (P < 0.001). The patients wit

Anti-HIV Agents↗
PubMed1995

Neutralizing antibodies in slowly progressing HIV-1 infection.

Ten asymptomatic individuals who had experienced only limited CD4+ cell loss after prolonged infection with HIV-1 were studied. These individuals had a mean CD4+ cell count of 674 x 10(6) cells/L and a mean duration of infection of 8.5 years. Also included were 10 asymptomatic HIV-1-infected individuals who, over a similar period of infection (7.5 years), had experienced a profound loss of CD4+ cells (mean CD4+ cell count, 54 x 10(6) cells/L). Proviral load was determined using a semiquantitative polymerase chain reaction and was significantly lower in the subjects with slowly progressing infection (SPI) than in subjects with rapidly progressing infection (RPI) (4,000 vs. 40,000 proviral copies/10(6) peripheral blood mononuclear cells; p = 0.0089). Isolation of virus was attempted in all individuals but succeeded only in 6 of 10 individuals with SPI versus all 10 individuals with RPI. Four of six virus isolates obtained from individuals with SPI and 6 of 10 obtained from individuals with RPI were of the syncytia-inducing phenotype. We determined the neutralizing activity of serum against HIVMN, HIVIIIB, and the contemporaneous autologous isolate when available. Serum from individuals with SPI generally neutralized the contemporaneous isolate, whereas serum from individuals with RPI did not [geometric mean antibody titer (GMT), 45 vs. 3; p = 0.0047]. There was no difference in neutralizing ability against HIVMN (GMT,2,593 vs. 2,263; p = 0.74) and only a small difference against HIVIIIB (GMT, 115 vs. 50; p = 0.075). Our results indicate that individuals with SPI are characterized by an ability to neutralize their own HIV strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Synthesis of 4-methylthio analogues of FLT and AZT and their evaluation against HIV.

Silylated 4-methylthiouracil and 4-methylthiothymine were condensed in the presence of TMS triflate with methyl 2,3-dideoxy-3-fluoro-5-O-(4- phenylbenzoyl)-D-erythro-pentofuranoside (3) and methyl 3-azido-5-O- (tert-butyldiphenylsilyl)-2,3-dideoxy-D-erythro-pentofuroside++ + (8), respectively, to give the corresponding nucleosides which were deprotected. The 3'-azido nucleoside was reduced with triphenylphosphine to the corresponding 3'-amino nucleoside. The 3'-amino nucleoside was also obtained by condensation of 4-methylthiothymidine with a 3-phthalimido sugar 14 followed by deprotection. The 4-methylthio analogue 11 of AZT showed moderate activity against HIV.

Antiviral Agents↗
PubMed1995

Receptor function of CD4 structures from African green monkey and pig-tail macaque for simian immunodeficiency virus, SIVsm, SIVagm, and human immunodeficiency virus type-1.

Differences in kinetics of infection, cellular tropism, and cytopathology of SIV and HIV appear to depend on both viral and host factors. We investigated the role of critical CD4 structures from African green monkeys (AGM) a natural SIV host, from pig-tailed macaques (PT) an unnatural SIV host, and from humans, as well as the role of species-specific cellular factors involved in the tropism, kinetics of infection, and cytopathic effects of several SIV and HIV-1. Critical regions of the PT macaque and AGM CD4 genes (V1, V1J1, and V1J1V2J2) were stably expressed as chimeras with the human CD4 gene in human (HeLa and 293) and macaque (CMMT) cell lines. CD4 expressing cell lines were used for infection studies with cell-free SIVsm, SIVmac, SIVsmmPBj, SIVagm, and HIV-1. Results show that both PT CD4 and AGM CD4 supported infection with comparable infection kinetics by all SIV or HIV-1 strains tested. Although structural analysis predicted a major change in secondary structure of AGM CD4/CDR-3, these structural changes did not influence the degree of syncytia formation induced by several SIV and HIV-1. However, the cell line used to express the CD4 gene appeared to be a critical determinant of infection. Thus, SlV strains did not infect human cell lines regardless of the CD4 expressed in these cells. In contrast, HIV-1 did not infect any macaque cell line. This study demonstrates that the differences in CD4 structure among different primate species are clearly not responsible for differences in SIV and HIV infection kinetics, tropism, and cytopathology. However, species-specific factor(s), presumably expressed on the cell surface, markedly influences the ability of SIV or HIV to infect cells expressing CD4.

Amino Acid Sequence↗
PubMed1995

Synthesis of 3'-O-(2-aminoethyl)-2'-deoxyuridines.

Methyl 2-deoxy-3-O-[2-(formylamino)ethyl]-5-O-trityl-D-erythro- pentofuranoside (4) was obtained in a 3-O alkylation reaction by treatment with 2-chloroethylamine in DMF. Compound 4 afforded alpha nucleosides as the main products when condensed with uracils under the Vorbrüggen conditions. The nucleosides were deblocked by treatment with 80% acetic acid and subsequently with sodium methoxide in methanol.

Animals↗
PubMed1995

Calcium in patients on hemodialysis.

Analyzing 415 measurements from 33 patients on chronic maintenance hemodialysis we confirm that 50% of total calcium in the range 1.59 to 3.33 mmol/l gives a valuable approximation to ionized calcium in the range 0.79 to 1.62 mmol/l. However, a small but significant effect of albumin and phosphate on ionized calcium can also be demonstrated. Conventional albumin correction of total calcium using the formula: total calcium + (43 g/l-Albumin g/l).0.017 mmol/g is of poor value in these patients on maintenance hemodialysis.

Calcium↗
PubMed1995

Ultradian variation in serum phosphate concentration in patients on haemodialysis.

To study how much the serum phosphate concentration could vary on the day before scheduled dialysis we obtained 24-37 timed measurements during 24 h in nine patients on maintenance haemodialysis. During the observation there was an increase in serum phosphate concentration of 0.239 +/- 0.022, P < 0.01). Surprisingly six of the nine patients exhibited nine statistically and clinically significant nadirs with decrements of 0.21 +/- 0.04 mmol/l against an intra-assay standard deviation of about 0.05 mmol/l. Five of the nadirs occurred at 11.40-14.50, mean 12.59, and three at 19.00-21.30, mean 20.00. We found no coinciding changes in the serum calcium concentration. These findings indicate that serum phosphate concentrations do not always reflect phosphorus balance or intake.

Activity Cycles↗
PubMed1995

Mineralization defect but no effect on hypercalcemia during clodronate treatment in secondary hyperparathyroidism.

In four patients with severe secondary hyperparathyroidism, treatment with clodronate caused no decrease in serum calcium. In one of the patients treatment for seven months was associated with a severe mineralization defect which was not caused by aluminium. This lesion was reversible upon termination of clodronate treatment. In a single patient without hyperparathyroidism, a precipitous decrease in serum calcium was observed due to clodronate. However, long-term treatment with clodronate did not ameliorate ectopic calcification in this patient. It is concluded that in severe secondary hyperparathyroidism, clodronate does not always decrease serum calcium. Our experience suggest that clodronate like other bisphosphonates may inhibit bone mineralization.

Adult↗
PubMed1995

Prevention and screening in the nursing home.

The primary care physicians must use screening procedures for the elderly that focus on function, with special attention paid to falls, incontinence, malnutrition, and sexuality. Nursing home staff and patients' families can be particularly helpful to the physician.

Aged↗
PubMed1994

[Survival of patients with zidovudine resistant HIV].

The survival of 35 patients with AIDS or advanced HIV infection on zidovudine treatment was related to the viral sensitivity to the drug and to the CD4+ cell count. Fourteen patients died, the survivors were followed up for an average of 804 days. In a univariate Cox model, survival was strongly related to log IC90 (p = 0.0003) and to the CD4+ count (p = 0.0002). In a bivariate model, log IC90 and the CD4+ count contributed to the prediction of survival (p = 0.12 and 0.06, respectively). Large studies of combination or alternation therapy with several anti-HIV-drugs should be given high priority.

Acquired Immunodeficiency Syndrome↗
PubMed1994

S-glucosylated hydantoins as new antiviral agents.

S-Glycosylation took place on reaction of 5-alkylidene- and 5-arylidene-3-aryl-2-thiohydantoins with glycosyl halides under alkaline conditions. Bisglucosylation also took place when N-3 unsubstituted hydantoins were reacted. The bisglucosylated hydantoins produced N-3 glucosylated hydantoins on treatment with ammonia in methanol. In antiviral studies the most active compounds against both HSV-1 and HSV-2 were 5-(2-thienylmethylene)-3-phenyl-2-(2,3,4,6- tetra-O-acetyl-beta-D-glucopyranosyl)-2-thiohydantoin and 5-(2-thienylmethylene)-3-(4-chlorophenyl)-2-(2,3,4,6-tetra-O-acety l-beta-D- glucopyranosyl)-2-thiohydantoin.

Animals↗
PubMed1994

5'-Azido and 5'-fluoro alpha-nucleosides as analogues of AZT and FLT.

5-Azido-2,5-dideoxy-beta-D-erythro-pentofuranosyl nucleosides 10 and their corresponding alpha-anomers 11 have been synthesized by condensation of methyl 3-O-acetyl-5-azido-2,5-dideoxy-beta-D-erythro-pentofuranoside (7) with silylated nucleobases followed by deprotection with methanolic ammonia. Reaction of silylated thymine (19) with methyl 2,3-di-O-benzoyl-5-deoxy-5-fluoro-D-arabino-pentofuranoside (15) and methyl 5-azido-2,3-di-O-benzoyl-5-deoxy-alpha-D-arabino-pentofuranoside (17 alpha) afforded a mixture of the alpha-nucleosides 20 and the acyclo nucleosides 5-fluoro- and 5-azido-2,3-O-dibenzoyl-5-deoxy-1-O-methyl-1-(thymin-1-yl)-D -arabinitol (22). Compounds 20 and 22 were deprotected with methanolic ammonia to give the acyclic nucleosides 21 and 23, respectively. The new nucleosides were inactive against HSV-1 and HIV-1.

Animals↗