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Biomedical subjects

J Walter

Publications and source records attributed to J Walter.

At least 19 recordsLinked to original sources
PubMed1992

Local growth of a Burkitt's lymphoma versus disseminated invasive growth of the autologous EBV-immortalized lymphoblastoid cells and their somatic cell hybrids in SCID mice.

Specific host-graft interactions, as well as intrinsic properties of transferred cell, determine tumorigenicity in xenogeneic systems. We compared the growth characteristics of human B-lymphoid cell lines in SCID mice with the well characterized growth pattern in nude mice and observed striking differences in malignancy in the respective hosts. Two cell lines derived from the same individual, the Epstein-Barr-virus(EBV)-positive Burkitt's lymphoma BL 60 (BL) and the autologous EBV-immortalized lymphoblastoid cell line IARC 277 (LCL) were used. In addition, we tested somatic cell hybrids (HYB) of both cell lines, which despite the LCL-like differentiation phenotype show the de-regulated c-myc expression pattern of the parental BL line, assumed to be a critical factor in BL pathogenesis. Subcutaneously (s.c.) injected BL cells produced local progressively growing tumor masses at the injection site without distant metastases in both nude and SCID mice. Although both mouse strains possess the same genetic background (BALB/c) and differ only in the B-cell sub-set, the growth patterns of the LCL and hybrids were completely different. In contrast to the regressive behaviour of LCL and hybrids in nude mice, these lines show invasive and disseminated progressive growth in SCID mice. Peripheral lymph nodes an thymic tissue were preferentially colonized, whereas mucosal-associated lymphoid tissue (Peyer's patches and appendix) and spleen were not infiltrated. The preferential migration of lymphocytes to certain tissues is termed homing in a syngeneic system and mediated by homing receptors and vascular addressins. The "homing" of LCL and hybrids into lymphoid SCID mouse tissue suggests a strong interaction with the endothelial cells of the host. Detailed phenotypic analysis of BL, LCL and 3 different hybrids was performed using an antibody panel against differentiation and adhesion markers. Overall dominance of the LCL phenotype was observed in the hybrids, as indicated by cytology, tumor growth, dissemination and the pattern of surface-marker expression. The c-myc activation in hybrids does not appear to influence growth behavior.

Animals↗
PubMed1992

High plasticity of multispecific DNA methyltransferases in the region carrying DNA target recognizing enzyme modules.

Multispecific cytosine C5 DNA methyltransferases (MTases) methylate more than one specific DNA target. This is due to the presence of several target recognizing domains (TRDs) in these enzymes. Such TRDs form part of a variable centre in the MTase primary sequence, which separates conserved enzyme core sequences responsible for general steps in the methylation reaction. By deleting, rearranging and exchanging several TRDs of multispecific MTases, we demonstrate their modular character; they mediate target recognition independent of a particular TRD or core sequence context. We show also that multispecific MTases can accommodate inert material of non-MTase origin within their variable region without losing their activity. The remarkable plasticity with respect to the material that can be integrated into this region suggests that the enzyme core sequences preceding or following it form separable functional domains. In spite of the documented flexibility multispecific MTases could not be endowed with novel specificities by integration of putative TRDs of monospecific MTases, pointing to differences between multi- and monospecific MTases in the way their core and TRD sequences interact.

Base Sequence↗
PubMed1992

Experimental approaches to guarantee minimal risk of potential virus in purified monoclonal antibodies.

Regarding biological products, increasing awareness of potential side effects have placed great importance not only at protein purity regarding other proteins but on the removal of biologicals such as DNA and especially virus the importance of which may not be known. Monoclonal antibodies (Mab) have come to be an important class of molecules obtained from hybridoma cells, i.e., nonrecombinant cells in culture. It has been noted during the last years, that with rare exceptions hybridoma cell lines contain retrovirus like particles. The infectious nature of the EM-visible particles has been tested for, however, in most cases not been substantiated. In order to bring these valuable biological reagents, Mab's, to good use in man for imaging or therapy, the remaining concern about a potential retroviral infection has to be reduced to an acceptable minimum. We describe experimental approaches for the validation of chromatographic and ultrafiltration steps used in the production of monoclonal antibodies to remove and inactivate murine retrovirus. Present day biotechnological manufacturing processes have been devised incorporating a number of strategic preventive measures that have found wide spread acceptance. They permit to answer the question: how can a potentially harmful infection by an unknown virus be excluded. Knowledge of the efficacy of purification steps to clear infectious model virus is fundamental to devise biotechnological manufacturing processes yielding a purified antibody for use in man.

Animals↗
PubMed1992

Radiographic evidence of disease progression in methotrexate treated and nonmethotrexate disease modifying antirheumatic drug treated rheumatoid arthritis patients: a meta-analysis.

Methotrexate (MTX) has proven to be efficacious in the treatment of rheumatoid (RA), but it remains to be proven whether it can slow disease progression, as determined radiographically, in comparison with other disease modifying antirheumatic drugs (DMARD). We performed a meta-analysis of the available data to answer this question. A literature search, including abstracts, was conducted and inclusion criteria developed (description of patients, accountability of patients, inclusion of a control group of patients, specified radiographic endpoint, and appropriate reading of the radiographs). Publications were scored on a scale of 0 to 5 with a score > or = 3 required for inclusion in the study. For abstracts selected, additional data were obtained directly from the investigators. Data for 353 MTX treated and 205 non-MTX-DMARD treated patients with RA were gathered. Not all publications used the same scoring system, so some assumptions were required to analyze the combined data. Only the erosion score was included since not all publications included a reading of the joint space. All scores were transformed into Sharp scores (Arthritis Rheum 1985;28:1449), including the important contributions of 3 Larsen scored publications. Finally a monthly rate of disease progression was computed. Several comparisons were made. Overall, the rates of disease progression were similar for MTX and non-MTX-DMARD treated patients with RA. The non-MTX-DMARD treated patients with RA were separated into a group treated with gold salts (oral or parenteral) and a group treated with azathioprine with each group compared to the MTX treated patients. MTX had slower rates of disease progression than azathioprine, (rates 0.004 vs 0.012) but not slower rates than gold salts (0.008 vs 0.008). Despite its efficacy, the possible role of MTX in slowing disease progression more than other DMARD, as determined radiographically, appears to be evident only when compared to azathioprine.

Adult↗
PubMed1978

Effect of antidiuretic hormone and indomethacin on intrarenal microsphere distribution.

The purpose of the present study was to reexamine the effect of antidiuretic hormone (ADH) and indomethacin (IM) on intrarenal blood flow distribution by applying the microsphere technique to trained consciuous dogs. ADH and IM were given separately and jointly during maximal water diuresis. ADH in itself caused moderate antidiuresis and marked natriuresis. Although IM by itself had no significant effect on urinary osmotic concentration or solute excretion it greatly enhanced the antidiuretic effect of ADH and abolished its natriuretic effect. Intrarenal blood flow distribution remained unchanged when ADH and IM were given separately but it was shifted toward the inner cortex when the drugs were administered simultaneously. Furthermore, transition from spontaneous antidiuresis to maximal water diuresis did not alter intrarenal blood flow distribution. The results indicate that ADH induced antidiuresis is dissociated from changes in intracortical blood flow distribution. However, the possibility that IM enhancement of ADH mediated antidiuresis is at least in part mediated by intrarenal hemodynamic changes cannot be excluded.

Animals↗
PubMed1978

[Functional effects of micro-oil embolization following lymphography].

Lymphography, if performed correctly, has few clinically relevant complications. Nevertheless, the passage of oily contrast medium into the pulmonary vascular bed along physiological pathways can usually be verified radiographically and functionally. Since that part of the contrast medium filtered in the lungs is of no diagnostic value we think that a total amount of 14--16 ml Lipiodol Ultrafluid should normally suffice for outlining the retroperitoneal lymph passageways from the legs. With smaller amounts one may misinterpret an incomplete filling of the cranial paraaortic lymph nodes as filling defects. We agree with most authors that in patients with abnormal lung function, especially those with restrictive disorders, and in patients with pre-existing right heart strain lymphography should only be considered when truly indicated and only after testing of pulmonary function.

Contrast Media↗
PubMed1978

[Results of screening for risk factors in a rural community (author's transl)].

515 women and 372 men from a rural community of 2862 inhabitants over 14 years volunteered to participate in a screening test for risk factors. We found an exceptionally high percentage of hypertension and hypercholesterolaemia as well as overweight. Women were more frequently affected than men except for smoking, which occurred 3,6 times more often in men than in women. Since the life expectancy of men in this community was clearly lower than that of women, smoking seems to have the most weight as a risk factor for cardiovascular diseases.

Cardiovascular Diseases↗
PubMed1978

Diflunisal compared with naproxen in the treatment of osteoarthrosis of hip or knee: a double-blind trial.

A randomized double-blind trial was carried out in 20 patients with osteoarthrosis of the hip or knee to compare the efficacy and tolerance of treatment with diflunisal or naproxen. During the first 4 weeks, patients received either 250 mg diflunisal or 250 mg naproxen twice daily and this was increased by 250 mg daily in 5 patients on diflunisal and in 3 on naproxen for the second 4 weeks of the trial. The results of subjective assessments made before and at the end of Week 8 showed a trend in favour of diflunisal for improvement of symptoms, except for weight-bearing pain which was improved in only 1 patient in each group. More of the patients receiving diflunisal than naproxen considered treatment to have been satisfactory, and rated their response as equally as good as or better than previous medication. Diflunisal produced significantly high incidence of gastro-intestinal upsets, leading to the withdrawal of 2 patients at Week 4.

Adult↗
PubMed1977

Renal response to vasopressin after inhibition of prostaglandin synthesis.

The renal effects of vasopressin (VP) in water-loaded and hydropenic conscious dogs were examined with and without the previous administration of prostaglandin (PG) synthesis inhibitors (indomethacin and meclophenamate). The parameters studied were: urinary output, sodium and potassium excretion, plasma and urinary osmotic concentration, total renal blood flow, mean arterial pressure, heart rate, and the clearance and extraction ratio of p-aminohippuric acid and inulin. The infusion of VP caused antidiuresis and marked saluresis during water diuresis, whereas it was found to be diuretic and saluretic in hydropenic animals. Inhibition of PG synthesis greatly enhanced the antidiuretic activity of VP and abolished its saluretic and diuretic actions. Changes in renal water and solute excretion and changes in the hemodynamic parameters are uncorrelated. It is concluded that intrarenal PGs may play an important role in modulating the renal action of VP.

Animals↗