Search PubMed⌕ Search

Biomedical subjects

A Knapp

Publications and source records attributed to A Knapp.

At least 37 records · Page 2Linked to original sources
PubMed1988

[Studies on tryptophan metabolism in calcium oxalate urolithiasis].

In 90 patients with calcium oxalate urolithiasis an oral tryptophan-loading test with 5 g L-tryptophan was performed and the 24-hour urinary excretion of xanthurenic acid and kynurenine was measured. In 10 cases pathological deviations and an excretion pattern of tryptophan metabolites via kynurenine similar as in the hereditary vitamin-B6-dependent xanthurenic aciduria in homozygous or heterozygous from were found. Correlations between the oxalate excretion and the tryptophan metabolism do not exist. A 2-year therapy with 60 mg vitamin B6 was favourable in patients with an excretion of more than 300 mumol XA after a tryptophan load.

Administration, Oral↗
PubMed1987

Serious corneal complications of glaucoma filtering surgery with postoperative 5-fluorouracil.

We studied four patients who, having received postoperative 5-fluorouracil after glaucoma filtering operations, developed serious corneal complications. All four patients had preexisting corneal abnormalities including keratoconjunctivitis sicca, exposure keratopathy, and bullous keratopathy. All of the patients developed epithelial defects in the postoperative period. The complications included bacterial corneal ulceration (two patients), sterile corneal ulceration and corneal perforation (one patient), and a keratinized corneal plaque with underlying sterile stromal infiltrate (one patient). The use of 5-fluorouracil, which is an antimetabolite with considerable corneal epithelial toxicity, after glaucoma filtering surgery frequently causes corneal epithelial defects that may lead to secondary complications. Patients receiving this drug should have their corneal status closely monitored. In patients with corneal epithelial disease, 5-fluorouracil should be used with caution.

Aged↗
PubMed1987

Mycobacterium avium-intracellulare corneal ulcer.

A healthy 28-year-old man developed a slowly progressive corneal ulcer 21 months after an episode of corneal trauma. Acid-fast bacilli were identified in corneal scrapings, and the causative organism was identified as Mycobacterium avium-intracellulare. Medical treatment with topical amikacin and oral rifampin was ineffective, and a therapeutic penetrating keratoplasty was necessary to cure the infection. To the best of our knowledge, this is only the second reported case of a corneal infection caused by a slow-growing nontuberculous mycobacterium (Runyon groups I, II, and III) and the first caused by M. avium-intracellulare. Slowly growing nontuberculous mycobacteria should be considered among those organisms that cause corneal infection, especially in cases characterized by a protracted course and lack of response to conventional antimicrobial therapy.

Adult↗
PubMed1985

Reversion of bovine papillomavirus-induced transformation and immortalization by a xanthate compound.

Bovine papilloma virus-transformed hamster embryo fibroblasts (HEF-BPV) reacted to exposure to tricyclodecan-9-yl-xanthogenate (D609) with immediate reversion to the growth kinetics and the flat morphology of the untransformed parental cells. After six population doublings in the presence of D609, clones which displayed an untransformed morphology in the absence of D609 arose with a high frequency (90%). Such clones had reacquired a limited in vitro lifetime and had lost the ability to induce tumors in athymic nude mice. At the molecular level the revertant clones had lost all extrachromosomal monomeric BPV-1 DNA molecules. Only high molecular weight (HMW) oligomeric BPV-1 DNA that was probably integrated into the cellular genome was still detectable in a methylated transcriptionally inactive state. In contrast to transformed cells, the revertant clones no longer transcribed BPV-1-specific mRNA molecules, but were stimulated by a tumor promoter to transient viral gene expression. This article provides direct evidence for the complete reversibility of the property of "immortality".

Animals↗
PubMed1985

[Urologic complications following radiotherapy of cancers of the corpus uteri].

Patients with endometrial carcinomas who have undergone only radiation therapy represent a negative selection, because of the many concomitant diseases. In the author's group of 134 cases such patients were on average 7 years older than those who had undergone surgery. Even with computer-calculated opposing-field therapy with intracavity packing, radiation damage to the urinary tract must be expected. Of the 134 patients, 75 (55.9%) had pathologic urological findings following radiation therapy. The most commonly affected organ was the bladder (55.2%), followed by the kidneys (21.6%) and the ureter (7.5%). Radiation damage to the urethra could not be verified. The urological complications were hardly affected by the stage of the tumor, but considerably so by the time interval: the rate of urological complications was 68.9% higher after 5 years than after 1 year. Therefore, accurate statements concerning urological complications following primary radiation therapy for endometrial carcinoma cannot be made until 5 years have elapsed.

Female↗
PubMed1984

DNA and RNA virus species are inhibited by xanthates, a class of antiviral compounds with unique properties.

Various DNA and RNA virus species are inhibited by xanthate compounds at concentrations that leave the mitotic activity of uninfected cells unimpaired. The concentration of tricyclodecan -9-yl- xanthogenate that reduces the yield of herpes simplex virus types 1 and 2 by 50% is between 4.5 and 33 microM. The replication of DNA viruses such as simian virus 40 can be blocked at the DNA and RNA level both early and late after infection. The xanthates are not incorporated into nucleic acids. Episomal bovine papilloma virus DNA replication and transcription are also inhibited in transformed cells. The treated cells revert to the normal phenotype by acquisition of contact inhibition and a flat morphology.

Antiviral Agents↗
PubMed1984

On the brain barrier system function and changes of cerebrospinal fluid concentrations of phenylalanine and tyrosine in human phenylketonuria.

In 6 patients with classic phenylketonuria (PKU) the plasma and cerebrospinal fluid (CSF) concentrations of phenylalanine and tyrosine were measured fluorimetrically. The results of the PKU group were compared with data obtained from 17 children without abnormal CSF parameters and free of metabolic or central nervous disorders, in whom a diagnostic lumbal puncture has been performed. The PKU patients showed statistically significant differences in comparison with the controls: plasma and CSF phenylalanine contents were markedly higher (on the average 6.4 and 4.6 times, respectively) in PKU patients. Plasma tyrosine was 1.8 times lower, but CSF tyrosine was about 2.2 times higher in comparison to the controls. In general, the plasma CSF-ratio ( PLR ) of phenylalanine did not change in PKU and could be found in the same range as in the normal controls. In contrast to this, the PLR of tyrosine was found to be significantly lower in PKU patients. The results are discussed with respect to an altered function of the brain barrier systems for the amino acid transport in PKU, and that increased CSF tyrosine contents in PKU may rather reflect disturbances of the intracellular metabolism of the brain cells than changes of the amino acid transport through the brain barrier produced by hyperphenylalaninemia.

Blood-Brain Barrier↗
PubMed1983

Reliability of the Tønnesen technique for the identification of Hunter carriers.

The procedure for the detection of Hunter carriers suggested by Tønnesen et al. (1982) was checked in different mixtures of normal and Hunter cells as well as by examination of five obligate and five potential Hunter carriers. In the presence of fructose 1-phosphate there was a strict correlation between the proportion of mutant cells in the fibroblast culture and sulphate accumulation, both in artificial cell mixtures and in native cell cultures of Hunter carriers. In all obligate heterozygotes studied, sulphate incorporation was increased by a factor of two. The new technique seems to be suitable for carrier diagnosis. Its limitations are discussed.

Biopsy↗
PubMed1983

[Detection of phenylalanine hydroxylase activity in leukocytes and fibroblasts].

Phenylalanine hydroxylase activity measured in leucocytes and fibroblasts by the fluorometric method is nonspecific and can be released by other aromatic hydroxylases. Investigations with the inhibitors p-Cl-phenylalanine, 3-I-tyrosine and 6-F-tryptophan made evident that these results may be caused by the tryptophan hydroxylase and the tyrosine hydroxylase. Phenylalanine hydroxylase activities in leucocytes could also not be measured by radiochemical investigations with [3-14C] phenylalanine (scanner and liquid scintillation technique).

Fibroblasts↗