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Biomedical subjects

R T Prehn

Publications and source records attributed to R T Prehn.

At least 55 records · Page 3Linked to original sources
PubMed1976

Intralesional BCG in the treatment of metastatic malignant melanoma.

The therapeutic efficacy of intralesional BCG (Bacillus Calmette-Guerin; one immunizing dose every 2 weeks for a minimum of five treatments) was studied in 19 melanoma patients. Of 15 patients evaluable for response, five experienced significant objective improvement (two complete and three partial remissions). Objective improvement was limited to those patients with dermal metastatic disease. In vitro cytotoxicity in the presence of patient's serum bore, on average, a relationship to the clinical disease. In certain individual cases, serum blocking and/or lymphocyte stimulation may have had prognostic significance.

Adolescent↗
PubMed1976

Influence of regenerative capacity and innervation on oncogenesis in the adult frog (Rana pipiens).

Twenty-two sarcomas were induced in 19 adult frogs (Rana pipiens) treated with 3-methylcholanthrene pellets. Thirteen of these tumors arose first in a denervated forelimb, and only 2 arose first in normal or nerve-supplemented control forelimbs (P = 0.004). The remaining tumors developed either as a second tumor in a tumor-bearing frog or in hindlimbs. The critical role of innervation in regenerative capacity suggests that the predilection to tumor formation in the denervated limbs may have resulted from their lessened regenerative capacity.

Animals↗
PubMed1976

Invasion and metastasis of a xenogeneic tumor in nude mice.

When aliquots of a malignant hamster tumor were transplanted to nude mice and to hamsters, the tumor showed 1) more rapid growth in the hamster, 2) local invasion and metastasis in both species, and 3) occasional spontaneous regression in the nude mouse.

Animals↗
PubMed1975

Nongenetic variability in susceptibility to oncogenesis.

Genetically homogeneous mice varied in susceptibility to tumor induction by 3-methylcholanthrene. The early appearance of an induced tumor identified an animal of relatively great susceptibility to tumor induction as compared to other animals of the same genotype.

Animals↗
PubMed1975

Sequential in vitro reactivity of lymphocytes from melanoma patients receiving immunotherapy compared with the reactivity of lymphocytes from healthy donors.

A microcytotoxicity technique was used to determine the sequential in vitro reactivity against melanoma cells of lymphocytes from melanoma patients receiving immunotherapy and from healthy donors. Lymphocytes were collected 2 weeks for 2-3 months and were stored in liquid nitrogen until use. Preliminary studies had indicated that freezing did not effect the reactivity of lymphocytes. Lymphocytes from 10 healthy donors tested against melanoma cells exhibited substantial reactivity which showed no consistent pattern over time. Lymphocytes from 9 melanoma patients exhibited increased reactivity after immunotherapy. Patterns of reactivity against melanoma cells and against bladder carcinoma cells were similar, indicating lack of specificity for melanoma antigens. Correlations with clinical course of the disease were not apparent.

Adult↗
PubMed1975

Relationship of tumor immunogenicity to concentration of the oncogen.

Tumors were induced sc in (BALB/c x DBA/2)F1 female mice by various concentrations of 3-methylcholanthrene (MCA) in paraffin pellets. There was an inverse relationship between MCA concentration and tumor latency (interval between MCA implantation and detection of gross tumor). The tumors were transplanted into syngeneic recipients, and material from this first transplant generation was used to immunize a series of syngeneic mice; any resulting growth was excised. Nonimmunized mice were controls. Immunized and control mice were irradiated and given an sc inoculation of a near-threshold number of tumor cells. Tumor growth from that inoculation was measured weekly in both groups and the antigenicity ratio (mean tumor size in controls/mean tumor size in immunized mice) was calculated. In a series of tumors with similar latencies, the only ones with high antigenicity ratios were those resulting from the high MCA concentration. The results suggested that tumors induced by low levels of oncogen may be good models of spontaneous neoplasia, strengthened the hypothesis that "spontaneous' tumors may actually result from low levels of oncogen, and indicated that neoplastic transformation and the development of immunogenicity are, at least in chemically induced tumors, independent changes that may be produced in the same cell when the concentration of oncogen is sufficient.

Animals↗
PubMed1975

Clinical and immunological significance of human melanoma cytotoxic antibody.

The activity of a complement-dependent cytotoxic antibody in the sera of 21 melanoma patients was investigated using a microcytotoxicity assay. Heat-inactivated sera were caused to react against mechanically dispersed fresh tumor cells in the presence of exogenous blood group AB complement. Cytotoxicity was evaluated relative to pooled normal sera as a control. Sera were cytotoxic against autochthonous tumor cells in 9 of 10 patients with localized or regional melanoma and in 1 of 11 patients with disseminated metastases. Cytotoxicity of sera was unrelated to size of tumor burden. Six of 7 antibody-positive sera (autochthonous system) were noncytotoxic to between 2 and 7 different allogeneic melanoma tumor cell preparations. Immunological reactivity of the cytotoxic antibody-positive and -negative groups was similar with respect to their capacity to be sensitized to dinitrochlorobenzene, produce positive skin tests to microbial antigens, and produce antibodies to typhoid vaccination; serum immunoglobulins were comparable. These results support the reported findings of the presence of cytotoxic antibody in the sera of melanoma patients without disseminated metastases.

Antibodies, Neoplasm↗
PubMed1974

Immunomodulation of tumor growth.

Most and perhaps all neoplasms arouse an immune response in their hosts. Unfortunately, this response is seldom effective in limiting tumor growth. Immunologic surveillance, as originally conceived, probably does not exist. The early weak response to nascent tumors stimulates rather than inhibits their growth. A truly tumor-limiting reaction occurs only in exceptional tumor systems, and then it is relatively late and ineffectual. Immunity may be of great importance in limiting the activity of oncogenic viruses, but is probably seldom the determiner of whether or not an already transformed cell gives rise to a lethal cancer.

Animals↗