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Biomedical subjects

A Walter

Publications and source records attributed to A Walter.

At least 37 records · Page 2Linked to original sources
PubMed2000

Effect of Soil pH on Growth and Cation Deposition in the Root Tip of Zea mays L.

The effects of sandy soil pH on the distribution of growth velocities and on cation concentrations and deposition rates in root growth zones of Zea mays L. seedlings were investigated. The pH values of the rooting medium varied between 4.2 and 8.6 in sand culture (70% saturated) without external supply of nutrients. At all pH values, densities (in µmoles per g fresh weight) of potassium, magnesium, and calcium increased toward the root tip. Lower pH in the medium increased calcium tissue density fivefold and magnesium density 1.7-fold, whereas the density of potassium, the overall elongation rate, and the growth velocity distribution did not show any significant pH dependence. Throughout the growth zone the deposition rates of the divalent cations, as calculated on the basis of the continuity equation, increased with lower pH. The data are consistent with the hypothesis that the effects of pH on the cation deposition rates are due to the increase in the divalent cation concentration of the soil solution at low pH and that the abundant uronic acid residues of the young walls of the meristem provide a reservoir of storage capacity for Ca and Mg under conditions of low nutrient availability.

Journal Article↗
PubMed2000

Percutaneous bone anchor sling using synthetic mesh associated with urethral overcorrection and erosion.

Percutaneous bone anchor bladder neck suspension has been recommended as a less morbid alternative to traditional anti-incontinence procedures. Specifically, it has reported to be associated with shorter duration of hospitalization, catheterization and urinary retention, and equivalent short-term cure rates. Recently, there have been reports of pubic osteomyelitis associated with bone anchor placement, and high incidences of recurrent incontinence. To improve the effectiveness of the procedure the placement of a suburethral synthetic collagen-impregnated mesh without tension was recommended. A specific device is included with the kit (Suture Spacer (Microvasive/Boston Scientific Corp., Natick, MA)) to prevent overcorrection of the urethrovesical junction. We present a case of urethral erosion and complete urinary retention secondary to use of a percutaneous bone anchor sling using a ProteGen mesh (Microvasive/Boston Scientific Corp., Natick, MA). Significant postoperative urethral overcorrection was noted despite intraoperative use of the Suture Spacer.

Aged↗
PubMed2000

Atypical melanocytic proliferation associated with squamous cell carcinoma in situ of the esophagus.

We present the case of a 64-year-old woman who underwent a transhiatal esophagectomy subsequent to the presence of high-grade dysplasia of the esophageal squamous epithelium in repeated biopsies. In the resection specimen chronic esophagitis and multifocal carcinoma in situ of the squamous epithelium were diagnosed, associated with a diffuse intraepithelial proliferation of melanocytic cells. While melanocytic hyperplasia (melanocytosis) has previously been recognized as an occasional reactive lesion that can accompany esophageal inflammation and invasive squamous carcinoma, the present case was unusual because of its cytonuclear and architectural atypia in the melanocytic cell population, resembling features of a melanoma in situ in the absence of manifest invasive malignant melanoma. The disappearance of the melanocytic lesion during follow-up supports its nonneoplastic nature, however. This case illustrates that 'malignant features' in esophageal melanocytosis should be interpreted with caution.

Carcinoma in Situ↗
PubMed2000

Effect of calcium supplements to a maize-soya diet on the bioavailability of minerals and trace elements and the accumulation of heavy metals in growing rats.

Thirty-five (five groups with seven animals each) male albino rats (initial average weight = 44 g) were fed phytate-rich diets (analysed phytic acid concentration = 6.9 g/kg) based on maize and soy bean meal (5 g Ca, 3 g P, 1.2 g Mg, 23 mg Zn, 10 mg Pb, 5 mg Cd/kg diet). Experimental diets were supplemented with 0, 2, 4, 6 and 8 g calcium from CaCO3 per kg. The supplementation of increasing amounts of calcium resulted in a dose-dependent decrease in the apparent absorption of phosphorus. Furthermore, apparent zinc absorption and femur zinc concentration were moderately decreased due to the calcium supplementation. Kidney Cd concentration was significantly lower in rats that were fed the high calcium diets in comparison with the control animals. Femur lead concentration and hepatic delta-aminolevulinic acid dehydratase, which are known to be sensitive parameters of lead accumulation remained unchanged by the different dietary treatments. Magnesium absorption as well as liver and plasma zinc concentration and activity of plasma alkaline phosphatase were also unaffected. Although calcium supplementation may lead to a decrease in the accumulation of certain heavy metals such as cadmium, the carry-over of lead was not affected under the given experimental conditions. Furthermore, calcium-phytate-zinc interactions may adversely affect zinc bioavailability in growing rats.

Alkaline Phosphatase↗
PubMed2000

Leaf development in Ricinus communis during drought stress: dynamics of growth processes, of cellular structure and of sink-source transition.

Dicot leaf growth is characterized by partly transient tip-to-base gradients of growth processes, structure and function. These gradients develop dynamically and interact with dynamically developing stress conditions like drought. In Ricinus communis plants growing under well-watered and drought conditions growth rates peaked during the late night and minimal values occurred in the late afternoon. During this diurnal course the leaf base always showed much higher rates than the leaf tip. The amplitude of this diurnal course decreased when leaves approached maturity and during drought stress without any significant alteration of the diurnal pattern and it increased during the first days after rewatering. Unique relationships between leaf size and cytological structure were observed. This provided the framework for the analysis of changes in assimilation, transpiration and dark respiration, chlorophyll, protein, carbohydrate, and amino acid concentrations, and of activities of sink-source-related enzymes at the leaf tip and base during leaf development in well-watered and drought-stressed plants. Gas exchange was dominated by physiological rather than by anatomical properties (stomatal density). Tip-to-base gradients in carbohydrate concentrations per dry weight and sink-source-related enzymes were absent, whereas significant gradients were found in amino acid concentrations per dry weight. During drought stress, growing leaves developed source function at smaller leaf size, before specific physiological adaptations to drought occurred. The relevance of the developmental status of individual leaves for the drought-stress response and of the structural changes for the biochemical composition changes is discussed.

Amino Acids↗
PubMed2000

CNS involvement in children with newly diagnosed non-Hodgkin's lymphoma.

PURPOSE: To determine the frequency of CNS involvement at diagnosis of non-Hodgkin's lymphoma (NHL), to characterize its pattern of presentation, and to determine its prognostic significance. PATIENTS AND METHODS: We reviewed the records of 445 children (1975 through 1995) diagnosed with NHL (small noncleaved cell NHL/B-cell acute lymphoblastic leukemia [SNCC NHL/B-ALL], 201 patients; lymphoblastic, 113; large cell, 119; other, 12). Tumor burden was estimated by serum lactate dehydrogenase (LDH) measurement and reclassification of disease stage irrespective of CNS involvement (modified stage). RESULTS: Thirty-six of 445 children with newly diagnosed NHL had CNS involvement (lymphoma cells in the CSF [n = 23], cranial nerve palsy [n = 9], both features [n = 4]), representing 13%, 7%, and 1% of small noncleaved cell lymphoma, lymphoblastic lymphoma, and large-cell cases, respectively. By univariate analysis, CNS disease at diagnosis did not significantly impact event-free survival (P =. 095), whereas stage and LDH did; however, children with CNS disease at diagnosis were at 2.0 times greater risk of death than those without CNS disease at diagnosis. In a multivariate analysis, CNS disease was not significantly associated with either overall or event-free survival, whereas both serum LDH and stage influenced both overall and event-free survival. Among cases of SNCC NHL/B-ALL, CNS disease was significantly associated with event-free and overall survival (univariate analysis); however, in multivariate analysis, only LDH had independent prognostic significance. Elevated serum LDH or higher modified stage were associated with a trend toward poorer overall survival among children with CNS disease. CONCLUSION: A greater tumor burden at diagnosis adversely influences the treatment outcome of children with NHL and CNS disease at diagnosis, suggesting a need for ongoing improvement in both systemic and CNS-directed therapy.

Adolescent↗
PubMed2000

Silent lacunar lesions detected by magnetic resonance imaging of children with brain tumors: a late sequela of therapy.

BACKGROUND: Cerebral lacunes, which generally appear on magnetic resonance imaging as foci of white matter loss, usually occur in adults after ischemic infarcts. We report the development of lacunes in children after therapy for brain tumors. PATIENTS AND METHODS: We reviewed the clinical characteristics and radiologic studies of 524 consecutive children with brain tumors treated over a 10-year period. We documented the neuropsychologic findings associated with lacunes and the factors predictive of lacunar development. RESULTS: Lacunes developed in none of the 103 patients observed or treated with surgery alone. Twenty-five of the 421 patients treated with chemotherapy or radiation therapy or both had lacunes. Patients were a median of 4.5 years old at the time of both diagnosis (range, 0.3 to 19.8 years) and radiotherapy (range, 1.5 to 20 years). Fourteen patients were treated with craniospinal irradiation, and 11 were treated with local radiotherapy. The median time from radiotherapy to the appearance of lacunes was 2.01 years (range, 0.26 to 5.7 years). For all patients, lacunes were an incidental finding with no corresponding clinical deficits. The factor most predictive of lacunar development was age less than 5 years at the time of radiotherapy (P =.010). There was no significant difference in estimated decline in intelligence quotient scores between patients with lacunes and age and diagnosis-matched controls. CONCLUSION: Lacunes may be caused by therapy-induced vasculopathy in children with brain tumors, with the most significant predictor being age less than 5 years at the time of radiotherapy.

Adolescent↗
PubMed1999

Diastereoselective Synthesis of C-Glycosylated Amino Acids with Lactams as Peptide Building Blocks.

Readily available by lipase-catalyzed kinetic resolution or from a chiral pool, beta-, gamma-, and delta-lactams can be used as peptide building blocks for the synthesis of C-glycosylated amino acids 1. By reaction with glycosyl dianions, metabolic stable glycosylated amino acids can be prepared diastereoselectively. Ac=acetyl; Bn=benzyl; Boc=tert-butoxycarbonyl; R=Et, Bn; R'=H, alkyl; n=1-3.

Journal Article↗
PubMed1999

Primary nerve-sheath tumours of the trigeminal nerve: clinical and MRI findings.

We reviewed the clinical and MRI findings in primary nerve-sheath tumours of the trigeminal nerve. We retrospectively reviewed the medical records, imaging and histological specimens of 10 patients with 11 primary tumours of the trigeminal nerve. We assessed whether tumour site, size, morphology or signal characteristics were related to symptoms and signs or histological findings. Histological proof was available for 8 of 11 tumours: six schwannomas and two plexiform neurofibromas. The other three tumours were thought to be schwannomas, because they were present in patients with neurofibromatosis type 2 and followed the course of the trigeminal nerve. Uncommon MRI appearances were observed in three schwannomas and included a large intratumoral haemorrhage, a mainly low-signal appearance on T2-weighted images and a rim-enhancing, multicystic appearance. Only four of nine schwannomas caused trigeminal nerve symptoms, including two with large cystic components, one haemorrhagic and one solid tumor. Of the five schwannomas which did not cause any trigeminal nerve symptoms, two were large. Only one of the plexiform neurofibromas caused trigeminal nerve symptoms. Additional neurological symptoms and signs, not related to the trigeminal nerve, could be attributed to the location of the tumour in three patients.

Adolescent↗
PubMed1999

Aicardi-Goutières syndrome: a genetic microangiopathy?

Aicardi-Goutieres syndrome (AGS) (McKusick 225750) is an autosomal recessive disease with onset in the 1st year of life, resulting in progressive microcephaly, calcification of cerebral white matter, thalamus and basal ganglia, generalized cerebral demyelination and a chronic low-grade CSF lymphocytosis, without evidence of infection. We report the autopsy of a patient who died with this disorder at the age of 17 years. Findings were severe microencephaly, diffuse but inhomogeneous cerebral white matter loss with associated astrocytosis, calcific deposits in the white matter, thalami and basal ganglia. Neocortex and cerebellar cortex were affected by wedge-shaped microinfarctions. Small vessels showed calcification in the media, adventitia and perivascular spaces. These findings are similar to some previous publications that in retrospect may have been AGS, but this is the first reported cerebral microangiopathy in which the diagnosis AGS was made during lifetime. This report provides evidence that microangiopathy plays a significant role in the pathogenesis of AGS.

Adolescent↗
PubMed1999

[Development of visual acuity in the early phase after photorefractive keratectomy in myopia].

BACKGROUND: Photorefractive keratectomy (PRK) using the excimer laser is an accepted surgical technique for correction of myopic refraction errors in case of spectacle or contact lens incompatibility. The purpose of this study was to assess the development of uncorrected (UVA) and best-corrected visual acuity (CVA) in the early course following PRK. PATIENTS AND METHODS: 48 eyes of 29 patients that underwent myopic photorefractive keratectomy using 193 nm excimer laser (MEL 60, Aesculap-Meditec) were included in this study. The mean preoperative spherical equivalent was -5.3 +/- 2.4 diopters (D) (range -1.75 to -9.5 D). Pre-, intra- and postoperative treatment was standardized. The median time interval to complete epithelial closure was 2 days. According to their spherical equivalent, patients were divided in two groups: group 1 with myopia < or = 6 D (n = 28), group 2 with myopia more than 6 D (n = 20). Examination of UVA and CVA were performed preoperatively and on days 3, 7 as well as 1 month, 3 and 6 months postoperatively. RESULTS: On day 3 after surgery UVA was 0.43 +/- 0.21 for group 1 with myopia < or = 6 D, and 0.36 +/- 0.14 for group 2 with myopia more than 6 D. The UVA was stable after 3 months (0.92 +/- 0.29 and 0.66 +/- 0.20, respectively), the CVA was stable after 1 month (1.04 +/- 0.18 and 0.86 +/- 0.19, respectively). After surgery, the UVA increased by +0.73 +/- 0.25, whereas the CVA increased by +0.05 +/- 0.10 for the whole group. The difference comparing pre- and postoperative UVA was significantly higher in group 1 (0.81 +/- 0.22) than in group 2 (0.60 +/- 0.26) (p = 0.002). However, postoperative CVA values were not significantly different from preoperative values in both groups after 6 months (p = 0.3). CONCLUSION: Useful uncorrected visual acuity is normally achieved at day 3 after PRK in eyes with mild to moderate myopia. With higher degrees of myopia the uncorrected visual acuity does increase slower towards a lower level. One of the reasons for this phenomenon might be a significant regression of the refractive effects during the first half year after surgery.

Adult↗
PubMed1999

Gli3 is required for Emx gene expression during dorsal telencephalon development.

Dentate gyrus and hippocampus as centers for spatial learning, memory and emotional behaviour have been the focus of much interest in recent years. The molecular information on its development, however, has been relatively poor. To date, only Emx genes were known to be required for dorsal telencephalon development. Here, we report on forebrain development in the extra toes (Xt(J)) mouse mutant which carries a null mutation of the Gli3 gene. This defect leads to a failure to establish the dorsal di-telencephalic junction and finally results in a severe size reduction of the neocortex. In addition, Xt(J)/Xt(J) mice show absence of the hippocampus (Ammon's horn plus dentate gyrus) and the choroid plexus in the lateral ventricle. The medial wall of the telencephalon, which gives rise to these structures, fails to invaginate during embryonic development. On a molecular level, disruption of dorsal telencephalon development in Xt(J)/Xt(J) embryos correlates with a loss of Emx1 and Emx2 expression. Furthermore, the expression of Fgf8 and Bmp4 in the dorsal midline of the telencephalon is altered. However, expression of Shh, which is negatively regulated by Gli3 in the spinal cord, is not affected in the Xt(J)/Xt(J) forebrain. This study therefore implicates Gli3 as a key regulator for the development of the dorsal telencephalon and implies Gli3 to be upstream of Emx genes in a genetic cascade controlling dorsal telencephalic development.

Animals↗
PubMed1999

[Pleiotropic effects of garlic].

Garlic as a herbal remedy reduces a multitude of risk factors which play a decisive role in the genesis and progression of arteriosclerosis: decrease in total and LDL-cholesterol, increase in HDL-cholesterol, reduction of serum triglyceride and fibrinogen concentration, lowering of arterial blood pressure and promotion of organ perfusion, and, finally, enhancement in fibrinolysis, inhibition of platelet aggregation, and diminution of plasma viscosity. In a prospective, 4-year clinical trial with primary endpoint 'arteriosclerotic plaque volume' it was proven not only a 9 to 18% reduction and 3% regression in plaque volume of the total collective under the influence of standardized garlic powder dragees (900 mg/die LI 111), but also of some facets of the phytopharmacologic pleiotropy of this herb: decrease in LDL level by 4%, increase in HDL concentration by 8%, and lowering in blood pressure by 7%. The reduction of arterial blood pressure is due to an additional opening of K(Ca) ion channels in the membrane of vascular smooth muscle cells that effects its hyperpolarization. This membrane hyperpolarization closes about 20% of the L-type Ca2+ channels, consequence of which is vasodilatation. In human coronary arteries, the increase in vascular diameter by 4% is closely associated with an improvement of coronary perfusion by 18%. These pleiotropic effects of garlic result in a reduction of relative cardiovascular risk for infarction and stroke by more than 50%.

Arteriosclerosis↗
PubMed1998

Overexpression of chicken interferon regulatory factor-1 (Ch-IRF-1) induces constitutive expression of MHC class I antigens but does not confer virus resistance to a permanent chicken fibroblast cell line.

The chicken fibroblast cell line C32 has been transfected with the chicken homolog (Ch-IRF-1) of the mammalian transcription factor IRF-1. Stable transfectants were generated, constitutively overexpressing Ch-IRF-1 mRNA and protein. Cells overexpressing Ch-IRF-1 showed enhanced constitutive expression of MHC class I (B-F, beta-microglobulin) antigens. With increasing number of passages cells with normal B-F IV surface antigen expression accumulated. In the revertants, the amount of Ch-IRF-1 mRNA was reduced. Overexpression of Ch-IRF-1 had no effect on the constitutive expression and the induction by chicken interferon type-I and type-II (Ch-IFN) of guanylate-binding protein (GBP). Susceptibility to vesicular stomatitis virus, sindbis virus, Newcastle disease virus and vaccinia virus was not altered by overexpression of Ch-IRF-1. An antiviral state could be induced against all viruses tested by similar amounts of Ch-IFN type I in clone 20-18 expressing Ch-IRF-1 and cells transfected with empty vector.

Animals↗
PubMed1998

Binding of 2-azaanthraquinone derivatives to DNA and their interference with the activity of DNA topoisomerases in vitro.

We have investigated the binding ability to DNA of compounds belonging to the 2-azaanthraquinone-type structure and have examined the effect on the activity of DNA gyrase as well as on mammalian topoisomerases in vitro. Using different biophysical techniques it was found that one of these ligands, 9-((2-dimethylamino)ethyl)amino)-6-hydroxy-7-methoxy-5, 10-dihydroxybenzo[g]isoquinoline-5,10-dione (TPL-I), is an intercalating DNA binding agent, whereas the parent compound tolypocladin (TPL) and a derivative (TPL-II) showed almost no similar affinity to DNA. CD measurements demonstrated a significant and selective binding tendency of TPL-I to alternating purine/pyrimidine sequences with some preference for poly(dA-dT). poly(dA-dT). Tm values were increased of the ligand complex with the alternating AT-containing duplex polymer. The binding to various DNAs was characterized by CD and visible absorption spectral changes. From the latter, different binding constants of 6.2 x 10(5) and 1.5 x 10(5) M-1 were obtained for poly(dA-dT).poly(dA-dT) and poly(dA). poly(dT), respectively. Sedimentation measurements with supercoiled pBR322 plasmid DNA clearly indicated an intercalative binding mechanism associated with an unwinding angle of about 18 degrees. These results suggest that the intercalative binding of TPL-I is promoted by the 2-(dimethylamino)ethylamino group substituted on carbon 9 of the anthraquinone system. The cytotoxic compound TPL-I, but not TPL or TPL-II, effectively inhibited the DNA supercoiling reaction of DNA gyrase and the activity of mammalian topoisomerases I and II as measured by the relaxation assay. TPL-I affects the cleavage reaction of topoisomerases on a single site located in alternating purine-pyrimidine sequence regions. The inhibitory potency of TPL-I can be ascribed to a blocking of cleavage sites on the DNA substrate, which correlates with the sequence preference of the ligand.

Anthraquinones↗
PubMed1998

[Primary orbital implant dislocation. A retrospective study].

BACKGROUND: To compensate the orbital volume deficit after enucleation orbital implants are used. METHOD: Between 1986 and 1996, 449 enucleations were performed. One hundred and fifty-five orbital implants were used: 96 hydroxylapatite-ceramic-silicon (HAK-silicon), 29 hydroxylapatite-ceramic (HAK), 26 Kiel bone chips, 3 Walser and 1 Bangerter implant. RESULTS: Ten orbital implants (6.45%) had to be explanted. Seven of the 96 HAK-silicon implants were explanted: four could be changed, two of them with a smaller and two with a same diameter. We observed a complication rate of 7.29% and a rate of total loss of 3.13%. One luxated HAK-implant could be refixated (3.45%), and one implant (3.85%) of the Kiel bone chip implants was explanted. CONCLUSION: Using different types of orbital implants after enucleation, we observed a complication rate of 7%. However, to avoid the post-enucleation-syndrome and to achieve better motility of the prosthesis, orbital implants should be used.

Adolescent↗