Search PubMed⌕ Search

Biomedical subjects

J Beck

Publications and source records attributed to J Beck.

At least 199 records · Page 11Linked to original sources
PubMed1990

The epidemiology of root surface caries.

Although a secular decline is being seen in coronal caries in children in industrialized countries, there appears to be a relatively high prevalence of root caries, with chronologically older adults exhibiting the highest prevalences. This paper reviews the descriptive and analytical epidemiology of root caries as found in recent national, regional, and local studies. A review of the variety of study designs, populations surveyed, and epidemiologic criteria for root caries comprising recent studies is presented as a background for comparison of prevalence rates which range from 7.3% to 69.7% of the population with root decay. In the few incidence studies reported, attack rates range from 1.6 surfaces per 100 surfaces at risk to 6.3 per 1000 surface-months at risk. Risk indicators for root caries are also reviewed with studies applying multivariate techniques implicating age, fluoride, educational level, use of dental services, coronal caries, loss of attachment, and number of teeth as possible risk factors. Although incidence studies have isolated risk factors, the small number of studies result in little agreement. Risk factor models from the Iowa 65+ Oral Health Study and a Risk Indicator model from the Piedmont 65+ Dental Study are presented to illustrate the variety of factors that may be involved in the expression of root surface caries in human populations.

Cohort Studies↗
PubMed1989

Expression of a novel high affinity purine base transport system in mutant mouse S49 cells does not require a functional nucleoside transporter.

A novel type of somatic mutation that causes the expression of a high affinity purine base permease has been inserted into murine S49 lymphoma cells that are deficient in nucleoside transport. Two classes of mutants expressing this nucleobase permease were generated. The first, as exemplified by the AE1HADPAB2 cell line, possesses an augmented capacity to transport low concentrations of the three purine bases, hypoxanthine, guanine, and adenine. The second class of mutants, as typified by the AE1HADPAB5 clone, possesses an augmented capability to translocate low levels of hypoxanthine and guanine, but not adenine. Neither the AE1HADPAB2 nor the AE1HADPAB5 cells can transport nucleosides suggesting that the expression of the high affinity base transporter did not revert the mutation in the nucleoside transport system. Fusion of the AE1HADPAB2 and AE1HADPAB5 cell lines with wild type cells indicated that the expression of the high affinity base transporter behaved in a dominant fashion, while the nucleoside transport deficiency was a recessive trait. These data suggest that the high affinity purine base transporter of mutant cells and the nucleoside transport function of wild type cells are products of different genes and that expression of the former probably requires the unmasking or alteration of a specific genetic locus that is silent or different in wild type cells.

Adenine↗
PubMed1989

New aspects in the treatment of childhood rhabdomyosarcoma: results of the German Cooperative Soft-Tissue Sarcoma Study (CWS-81).

The results of the German Co-operative Soft-Tissue Sarcoma Study (CWS-81) of the treatment of rhabdomyosarcoma are presented. Prior to the introduction of chemotherapy only 10%-20% of the children were successfully treated. Combined multi-agent cytostatic treatment improved the results dramatically. In patients with primary stage III rhabdomyosarcoma, local tumour control by surgery or radiotherapy should be undertaken earlier than week 16, if complete remission has not been achieved by 7-9 weeks. Patients with complete remission or partial tumour regression should be treated with the same combination of chemotherapy, while only partial responders need radiotherapy in addition. Patients with tumours which are primarily resectable without mutilation have a 90% chance of cure; this also applies to patients with primarily unresectable tumours who achieve complete remission after 7-9 weeks of chemotherapy. Total disease-free survival rate for stage III rhabdomyosarcoma patients was 53%. The role of surgery includes primary removal of the tumour or assessment of remission by means of histological spot checks.

Child↗
PubMed1989

Line segregation.

Six experiments investigated the preattentive segregation of line-like patterns composed of discrete elements in a background of distractors. The results indicate that other factors in addition to spatial density influence line segregation. Edge alignment, edge length and principal axis orientation also affect line segregation. Differences in the outputs of Gabor filters fail to account for the perceived segregation of the lines. Possible models of line segregation based on element grouping, feature density and search are briefly discussed.

Contrast Sensitivity↗
PubMed1989

Contrast and spatial variables in texture segregation: testing a simple spatial-frequency channels model.

Observers were shown patterns composed of two textures in which each texture contained two types of elements. The elements were arranged in a striped pattern in the top and bottom regions and in a checked pattern in the center region. Observers rated the degree to which the three regions were seen as distinct. When the elements were squares or lines, perceived segregation resulting from differences in element size could be canceled by differences in element contrast. Minimal perceived segregation occurred when the products of the area and the contrast (areal contrasts) of the elements were equal. This dependence of perceived segregation on the areal contrasts of the elements is consistent with a simple model based on the hypothesis that the perceived segregation of the regions is a function of their differential stimulation of spatial-frequency channels. Two aspects of the data were not consistent with quantitative predictions of the model. First, as the size difference between the large and small elements increased, the ratings at the point of minimum perceived segregation increased. Second, some effects of changing the fundamental frequency of the textures were not predicted by the model. These discrepancies may be explained by a more complex model in which a rectification or similar nonlinearity occurs between two stages of orientation- and spatial-frequency-selective linear filters.

Adult↗
PubMed1989

AIDS in Arkansas. Zidovudine: an overview and rationale for use.

AZT is now the standard of care for all persons with AIDS, ARC or T4 helper cell levels less than 200/mm3. Some authorities are cautiously recommending it with full informed consent for patients who have fewer than 400 mm3 T4 cells or who have sustained a rapid fall in helper cells coupled with new symptoms. The optimum dosage remains to be determined. Although the package insert recommends 200mg p.o. q. 4 hours, b.i.d. and Q6 hour dosage regimes have been reported as being as effective with less toxicity. Folate and B12 levels should be measured and replaced when appropriate to avoid undue hematologic toxicity and therapy should be interrupted for hemoglobin less than 7.5 or neutropenia consisting of fewer than 750 leukocytes/cc. For progressive, less severe marrow toxicity the dose may be decreased to avoid a prolonged nadir. A CBC should be obtained every two weeks for at least the first eight weeks and monthly thereafter if counts are stable. Other toxicities to be monitored include elevated transaminases and co-administration with medications that affect hepatic glucuronidation such as probenecid, NSAID's and acetaminophen. In the eight years since this epidemic appeared on the medical horizon much has been learned about the disease and its treatment. More and more physicians are willing and eager to assume primary care responsibilities for their patients with AIDS and it is hoped AZT and other effective therapies will assist them in this process.

AIDS-Related Complex↗
PubMed1989

Hippocampal rhythmical slow activity during instrumental responses with sexual reinforcement in male rats.

The hippocampal EEG activity was recorded in male rats during the response-contingent reinforcement of a female. The instrumental response was a bar-pressing on a fixed-ratio-10 reinforcement schedule. The frequency of bar-pressing tends to increase during the succeeding copulatory series. The similar phenomenon was observed in the frequency of the hippocampal slow activity (RSA) accompanying the bar-pressing and the pursuit of the female. This tendency was most conspicuously present during the first copulatory series but became less evident during the following ones.

Animals↗
PubMed1989

Chemical pathways of the Maillard reaction.

From reaction mixtures of reducing sugars with primary and secondary amines many heterocyclic and carbocyclic compounds have been separated. From the structures of these substances together with the knowledge about reactive intermediates some degradation pathways can be proposed. Caused by the nature of the sugar (pentose, mono- or disaccharide) and the amine (primary or secondary) differences in the pathways are observed. An attempt is made to present some reactions with emphasis to the Maillard reaction in mammalians.

Chemical Phenomena↗
PubMed1989

A system for on-line detection and resolution of radiolabeled DNA molecules and its application to automated DNA sequence analysis.

We describe a system for the real-time detection of radioactively labeled DNA molecules in gel matrix, and we demonstrate the application of this system to DNA sequence analysis. DNA sequencing reactions prepared by the Sanger chain termination method are resolved by electrophoresis on 8% polyacrylamide gels. During electrophoresis the 32P-labeled DNA fragments are detected by solid state detectors positioned 22 cm from the top surface of the gel. This system is able to resolve a DNA sequence of 300 bases or greater. Optimized protocols that allow sequence information to be obtained from single stranded and double-stranded templates are described. A linear relationship exists between the input dpm and the integrated peak values over a 20-fold range indicating that accurate DNA quantitation is also possible using this system.

Automation↗
PubMed1988

Isolation and sequence analysis of the fatty acid synthetase FAS2 gene from Penicillium patulum.

The fatty acid synthetase complex of Penicillium patulum was isolated and shown to be structurally similar to other known fungal fatty acid synthetases. It is composed of two subunit, alpha and beta, each with a molecular mass of about 200 kDa. P. patulum genomic and cDNA libraries were constructed in lambda gt11 and EMBL3 vectors. From these libraries, the P. patulum FAS2 gene together with its flanking DNA was isolated. The cloned genomic DNA was sequenced over a length of 6357 base pairs. The coding sequence of fatty acid synthetase subunit alpha, being 5571 nucleotides long, was identified within this DNA segment. The FAS2 gene is a mosaic of three exons (514, 4949 and 108 base pairs) and two introns, each of 54 base pairs in length. Both introns were absent in the corresponding cDNA sequences. Like other fungal introns both contain an internal CTAAC sequence, located 10 base pairs upstream of their 3'-exon/intron boundaries. In addition, they have, at their ends, the GTCAAGT and TAG consensus sequences characteristic of all eucaryotic introns. Furthermore, two pairs of direct repeats, of as yet unknown significance, were found in the two P. patulum introns. The P. patulum FAS2 gene encodes a protein of 1857 amino acids and 204.5 kDa molecular mass. It is 90 nucleotides shorter than the corresponding S. cerevisiae gene. In both organisms, the FAS2 genes and their products exhibit a high degree of overall sequence similarity at both the DNA (63%) and protein (68%) levels. Therefore, the fatty acid synthetase alpha subunits of P. patulum and S. cerevisiae obviously contain the same catalytic domains in an identical sequential order.

Amino Acid Sequence↗
PubMed1988

Auditory hair cell innervational patterns in lizards.

The pattern of afferent and efferent innervation of two to four unidirectional (UHC) and two to nine bidirectional (BHC) hair cells of five different types of lizard auditory papillae was determined by reconstruction of serial TEM sections. The species studies were Crotaphytus wislizeni (iguanid), Podarcis (Lacerta) sicula and P. muralis (lacertids), Ameiva ameiva (teiid), Coleonyx variegatus (gekkonid), and Mabuya multifasciata (scincid). The main object was to determine in which species and in which hair cell types the nerve fibers were innervating only one (exclusive innervation), or two or more hair cells (nonexclusive innervation); how many nerve fibers were supplying each hair cell; how many synapses were made by the innervating fibers; and the total number of synapses on each hair cell. In the species studies, efferent innervation was limited to the UHC, and except for the iguanid, C. wislizeni, it was nonexclusive, each fiber supplying two or more hair cells. Afferent innervation varied both with the species and the hair cell types. In Crotaphytus, both the UHC and the BHC were exclusively innervated. In Podarcis and Ameiva, the UHC were innervated exclusively by some fibers but nonexclusively by others (mixed pattern). In Coleonyx, the UHC were exclusively innervated but the BHC were nonexclusively innervated. In Mabuya, both the UHC and BHC were nonexclusively innervated. The number of afferent nerve fibers and the number of afferent synapses were always larger in the UHC than in the BHC. In Ameiva, Podarcis, and Mabuya, groups of bidirectionally oriented hair cells occur in regions of cytologically distinct UHC, and in Ameiva, unidirectionally oriented hair cells occur in cytologically distinct BHC regions.

Afferent Pathways↗
PubMed1988

Malignant peripheral neuroectodermal tumors. A retrospective analysis of 42 patients.

The clinical presentation of the disease and the results of treatment in 42 patients with malignant peripheral neuroectodermal tumors (MPNT) entered into the Cooperative Ewing's, soft tissue, and neuroblastoma trials of the German Society of Pediatric Oncology were retrospectively analyzed. Within the Ewing's sarcoma trial, patients with chest wall lesions were particularly analysed for MPNT features. The period of observation ranged from 15 to 86 months; the median relapse-free time was 24 months. There were 28 male and 14 female patients, the median age of patients was 15 years (range, 9 months-23 years). Thirty-two patients had localized disease (M0), and ten patients presented with primary metastases (M1). The predominant location of the tumors was the thoracopulmonary region, followed by the extremities, the abdominal/pelvic, and head and neck region. Thirty-one of 42 tumors involved the adjacent bone. The disease-free survival according to Kaplan-Meier life-table analysis was 56% +/- 11% for Stage M0 patients at 3 years. Nine of ten patients with M1 disease showed progression of their disease. Most patients had combined modality treatment with surgery, chemotherapy and radiation therapy. Best results were obtained with extensive surgery. Radiation doses ranged from 20 to 60 Gy and could not be correlated with the outcome of the disease. Most recurrences occurred at the site of the primary tumor. In patients with primary chemotherapy after biopsy-proven diagnosis, the responsiveness of this disease to chemotherapy could be demonstrated. Combination chemotherapy containing anthracyclines and high doses of alkylating agents appeared superior.

Actuarial Analysis↗
PubMed1988

Flow cytometry shows recurrent aneuploid clone after remission in megakaryocytic leukemia.

Flow cytometry using a DNA label can quantitate aneuploid clones in malignant tissue. We illustrated the clinical value of this technique in a 71-year-old woman with acute megakaryocytic leukemia, which was diagnosed by staining of the blasts with factor VIII antigen and their morphologic resemblance to megakaryoblasts. Marrow cells were removed from needle biopsies by vortexing in RPMI medium, centrifuged in Ficoll-Hypaque, stained with a propidium-iodide/NP-40 mixture, and analyzed at 488 nm using an argon laser. During 3 weeks of low-dose cytosine arabinoside (ara-c) infusion therapy, hyperdiploid peak A dropped from 35% (day 0) to 2.3% (day 14) to 0% (day 21), with development of marrow hypoplasia. Similarly, hyperdiploid peak B, went from 7.6% to 9.1% to 3.5%. Subsequently, her marrow recovered normal morphology and lost the aneuploid peaks. Her blood counts recovered to near normal. Four months later, she relapsed and had a return of the day-21, incompletely eradicated peak B. There was no evidence of peak A. Repeated treatment with ara-c resulted in temporary suppression of the disease, but she died 3 months later with progressive hepatosplenomegaly. Analysis of cells from her enlarged liver, heavily infiltrated with blasts, showed a large hyperdiploid peak B. In this patient, ara-c therapy induced a remission with permanent eradication of one clone, but incomplete eradication of a second clone, which ultimately led to her relapse and death.

Aged↗
PubMed1988

Increased production of interferon gamma and tumor necrosis factor precedes clinical manifestation in multiple sclerosis: do cytokines trigger off exacerbations?

We have carried out a longitudinal study of interferon (IFN) and tumor necrosis factor (TNF) using a whole-blood mitogen stimulation assay in 20 multiple sclerosis (MS) patients and in a healthy control group. We set up individual profiles and the results were quite constant for each individual, both in healthy donors and in the patients in remission. Before exacerbations, however, we found an increase of IFN-gamma and TNF production preceding clinical symptoms by a maximum of 2 weeks. In benign cases, the increase disappeared rapidly, even before the appearance of symptoms, whereas we found sequelae whenever the increase persisted during weeks. In chronic progressive patients, we frequently found intervening increases. It may be that IFN-gamma and TNF trigger off exacerbations at a very early stage and that these cytokines may also play a role in maintaining disease in chronic progressive and invalidating forms.

Adult↗