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Biomedical subjects

R Koch

Publications and source records attributed to R Koch.

At least 163 records · Page 9Linked to original sources
PubMed1993

The North American Collaborative Study of Maternal Phenylketonuria. Status report 1993.

Neonatal screening for phenylketonuria (PKU) has created an unexpected problem as females with PKU are reaching childbearing age. Surveys have revealed that maternal phenylalanine blood concentrations above 1200 mumol/L are associated with microcephaly, mental retardation, congenital heart defects, and intrauterine growth retardation among their offspring. It is estimated that as many as 3000 hyperphenylalaninemic females may be at risk for producing these fetal abnormalities. To examine this problem, the North American Maternal PKU Collaborative Study has been developed to evaluate the efficacy of a phenylalanine-restricted diet in reducing fetal morbidity. Preliminary findings indicate that phenylalanine restriction should begin before conception for females with PKU planning a pregnancy. Dietary control should maintain maternal blood phenylalanine levels between 120 and 360 mumol/L and should provide adequate energy, protein, vitamin, and mineral intake. Pregnant hyperphenylalaninemic females who achieved metabolic control after conception or by the 10th week of pregnancy had a better offspring outcome than anticipated.

Adolescent↗
PubMed1993

Titanium Riechert head ring for MR stereotaxy. Technical note.

Magnetic Resonance has become the preferred neuro-imaging modality. To fully take advantage of the high anatomical resolution the Riechert stereotactic system was adapted for use in Magnetic Resonance Stereotaxy. The head ring which until recently was made of an aluminum alloy has been replaced by an unsegmented head ring of pure titanium without changing the dimensions and fixation mode. No significant misregistration due to eddy currents has been noticed. Minor distortion induced by the titanium head ring can be corrected mathematically. Thus the geometric information is limited only by the pixel resolution of the MR image.

Artifacts↗
PubMed1993

Randomized trial comparing cryopreserved cultured epidermal allografts with tulle-gras in the treatment of split-thickness skin graft donor sites.

Cultured epidermal allografts have been successfully used to treat a wide variety of skin defects ranging from burns to leg ulcers. Their postulated mechanism of action is through release of multiple cytokines that stimulate epithelialization from the wound periphery as well as from remnant epidermal appendages. A randomized, controlled clinical trial was undertaken to compare the efficacy of cryopreserved cultured allograft dressings (CCAD) with tulle-gras dressings in the treatment of split-skin graft donor sites. Five patients were enrolled in the study and in each patient, half of the donor site was allografted and the other half was treated with tulle-gras control. The mean time to complete healing was 6.2 days for CCAD compared with 9.6 days (p = 0.035) for the tulle-gras controls. Patient assessment of pain with dressing changes was also significantly lower at the CCAD-treated sites than at the control sites (p = 0.001). The results indicate that cultured allografts offer greater patient comfort and earlier maturation of regenerated skin.

Adult↗
PubMed1992

DNA markers closely linked to nematode resistance genes in sugar beet (Beta vulgaris L.) mapped using chromosome additions and translocations originating from wild beets of the Procumbentes section.

Genes conferring resistance to the beet cyst nematode (Heterodera schachtii Schm.) have been transferred to sugar beet (Beta vulgaris L.) from three wild species of the Procumbentes section using monosomic addition and translocation lines, because no meiotic recombination occurs between chromosomes of cultured and wild species. In the course of a project to isolate the nematode resistance genes by strategies of reverse genetics, probes were cloned from DNA of a fragmented B. procumbens chromosome carrying a resistance gene, which had been isolated by pulsed-field gel electrophoresis. One probe (pRK643) hybridized with a short dispersed repetitive DNA element, which was found only in wild beets, and thus may be used as a molecular marker for nematode resistance to progeneis of monosomic addition lines segregating resistant and susceptible individuals. Additional probes for the resistance gene region were obtained with a polymerase chain reaction (PCR)-based strategy using repetitive primers to amplify DNA located between repetitive elements. One of these probes established the existence of at least six different chromosomes from wild beet species, each conferring resistance independently of the others. A strict correlation between the length of the wild beet chromatin introduced in fragment addition and translocation lines and the repeat copy number has been used physically to map the region conferring resistance to a chromosome segment of 0.5-3 Mb.

Animals↗
PubMed1992

Prolactin responses to phenylalanine and tyrosine in phenylketonuria.

In normal subjects, ingestion of tyrosine or phenylalanine stimulates prolactin (PRL) secretion. In patients with phenylketonuria (PKU), we found normal PRL responses to phenylalanine, demonstrating that conversion of phenylalanine to tyrosine is not necessary for PRL stimulation. PKU patients also showed greater PRL responses to tyrosine during dietary phenylalanine restriction than when consuming an unrestricted diet; this finding is consistent with inhibition by phenylalanine of tyrosine transport across the blood-brain barrier. Such competitive inhibition of a normal brain function may serve as a model for some of the neurotoxic effects of phenylalanine in PKU.

Adolescent↗
PubMed1992

Maternal phenylketonuria collaborative study, obstetric aspects and outcome: the first 6 years.

OBJECTIVE: The purpose of this study was to evaluate the efficacy of a phenylalanine-restricted diet in reducing fetal morbidity associated with maternal hyperphenylalaninemia in women of childbearing age with blood phenylalanine levels greater than 240 mumol/L (greater than 4 mg/dl) on an unrestricted diet. STUDY DESIGN: Two hundred thirteen pregnant women with hyperphenylalaninemia that resulted in 134 live births have been enrolled in the study. Outcome measures were subject to the chi 2 test, Fisher exact test, analysis of variance, t test, or Wilcoxon nonparametric test for analysis. RESULTS: Optimal fetal outcome appeared to occur when blood phenylalanine levels less than 600 mumol/L (less than 10 mg/dl) were achieved by 8 to 10 weeks' gestation and maintained throughout pregnancy (trimester averages of less than or equal to 360 mumol/L (less than or equal to 6 mg/dl). Initiation of dietary therapy during the third trimester of pregnancy appears to have little beneficial effect on the fetus. CONCLUSIONS: Preconceptual counseling and early entrance into a prenatal care program is essential in achieving optimal fetal outcome in women with hyperphenylalaninemia.

Congenital Abnormalities↗
PubMed1992

Binge eating and weight concerns among young adults. Results from the Zurich cohort study.

In the longitudinal cohort study of young adults from the Canton of Zurich in Switzerland, two groups of eating problems were defined: binge eating and weight concerns. Subjects with these conditions were interviewed at the ages of 27-28 and 29-30 years. The binge eaters, mostly women, differed both from subjects with weight concerns and from controls. They had more severe eating problems and more anxiety and depression. Follow-up as well as retrospective data suggest that eating problems are persistent for the binge eaters, and, to a lesser extent, also for subjects with weight concerns. Even so, professional treatment is rarely sought by subjects with eating problems. These findings encourage long-term studies on eating problems in community samples.

Adult↗
PubMed1992

[Reaction time and temporal serial judgment: corroboration or dissociation?].

Dissociations between a motor response and the subject's verbal report have been reported from various experiments that investigated special experimental effects (e.g., metacontrast or induced motion). To examine whether similar dissociations can also be observed under standard experimental conditions, we compared reaction times (RT) and temporal order judgments (TOJ) to visual and auditory stimuli of three intensity levels. Data were collected from six subjects, each of which served for nine sessions. The results showed a strong, highly significant modality dissociation: While RTs to auditory stimuli were shorter than RTs to visual stimuli, the TOJ data indicated longer processing times for auditory than for visual stimuli. This pattern was found over the whole range of intensities investigated. Light intensity had similar effects on RT and TOJ, while there was a marginally significant tendency of tone intensity to affect RT more strongly than TOJ. It is concluded that modality dissociation is an example of "direct parameter specification", where the pathway from stimulus to response in the simple RT experiment is (at least partially) separate from the pathway that leads to a conscious, reportable representation. Two variants of this notion and alternatives to it are discussed.

Adult↗
PubMed1992

Clinical results with the hydroxyapatite-coated Omnifit hip stem.

A 2-year follow-up from a prospective clinical trial investigation of the hydroxyapatite (HA)-coated Omnifit-HA Hip Stem is presented. Assessment of clinical and functional evaluation parameters demonstrates the excellent results obtained with the femoral stem. Radiographic observations indicate a complete lack of fibrous tissue in the HA-coated regions of the stem, thus promoting direct load transfer between the stem and bone. Comparison with published studies suggests that the clinical results obtained with the HA-coated Omnifit-HA Hip Stem compare favorably with the prior reports.

Adolescent↗
PubMed1992

Inhibitory effects of the antiparkinsonian drugs memantine and amantadine on N-methyl-D-aspartate-evoked acetylcholine release in the rabbit caudate nucleus in vitro.

Slices of the rabbit caudate nucleus were incubated with [3H]choline or [3H]dopamine and then superfused continuously with Mg(++)-free medium. Stimulation with N-methyl-D-aspartate (NMDA), alpha-amino-2,3-dihydro-5-methyl-3-oxo-4-isoxazolepropanoic acid (AMPA), L-glutamate and kainic acid (in that rank order of potencies) caused a concentration-dependent increase in [3H]ACh efflux, which was abolished in the presence of Mg++. This kind of release was Ca(++)-dependent and tetrodotoxin-sensitive. In contrast, NMDA was hardly effective in stimulating [3H]ACh release from hippocampal or cortical slices, as well as [3H]dopamine release from slices of rabbit caudate nucleus. Hence, the presence of cell bodies of stimulated neurons seems to be a prerequisite for the induction of release via NMDA receptors. Dizocilpine [(+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine maleate] at nanomolar concentrations, as well as memantine and amantadine at low micromolar concentrations, inhibited the L-glutamate- and NMDA-evoked [3H]ACh release in a concentration-dependent, noncompetitive and use-dependent manner. Also (+/-)-2-amino-5-phosphopentanoic acid at micromolar concentrations depressed the L-glutamate- and NMDA-induced release, acting, however, in a competitive manner. It is concluded that, by antagonizing NMDA receptor-mediated ACh release, memantine and amantadine may act as functional "anticholinergics" when administered clinically to treat Parkinson's disease.

Acetylcholine↗