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Biomedical subjects

R Mayer

Publications and source records attributed to R Mayer.

At least 217 records · Page 12Linked to original sources
PubMed1987

Localized urethral cancer in women.

The results of treatments for localized carcinoma of the urethra were assessed in 21 consecutive women treated at our institutions over a twenty year period. Only one of the tumors was confined to the distal urethra. Eighty-six percent invaded the periurethral tissues and 24% were known to be associated with regional lymph node metastases. Fifty-seven percent were adenocarcinomas. Five patients refused active therapeutic intervention and expired within one to 30 months following diagnosis. Sixteen patients were treated with extirpative surgery, radiation therapy, or combinations of the two. Four are free of disease at one, four, eleven, and 15 years after treatment. Nine developed pelvic recurrences, two developed pelvic recurrences and distant metastases and one developed distant metastases only from six to 72 months (mean, 19 months) after initial treatment. Eight of these 12 patients died at two to 13 months (mean, 8 months) after secondary treatment, two are alive with residual pelvic tumor, and two are clinically free of disease at 7 and 48 months. Only six patients were known to have distant metastases at the time of death and five of these six had adenocarcinomas. Advanced localized urethral cancer in women is difficult to eradicate and usually fatal.

Adenocarcinoma↗
PubMed1987

Efficacy of antitumor chemotherapy in C3H mice enhanced by the antiangiogenesis steroid, cortisone acetate.

The effect of "antiangiogenesis" therapy using cortisone acetate (CA) with or without heparin on tumor growth as well as in combination with chemotherapy was investigated. C3H mice were implanted intradermally with N-[4-(5-nitro-2-furyl)-thiazolyl]formamide induced undifferentiated transitional cell carcinoma, MBT-2, in the right flank. The treatment was initiated 9 to 10 days after tumor inoculation. Daily injections of CA (250 mg/kg s.c.) suppressed tumor growth significantly in a dose dependent fashion. Administration of heparin (Elkins-Sinn) at the concentration of 200, 400, or 1000 units/ml in drinking water for 3 to 6 days was neither additive nor detrimental to the effect of CA. Chemotherapy was combined with CA; 3 days of administration of 250 mg/kg of CA in tapering doses was used. The chemotherapeutic agent was injected once 24 h before the initial CA. Combinations of chemotherapy (Adriamycin, 2.5-7.5 mg/kg i.v; cisplatin, 3-9 mg/kg i.p.; cyclophosphamide, 50-150 mg/kg i.p.; cis-(diammino)(1,1-cyclobutanedicarboxylate)platinum(II) (JM-8), 60-150 mg/kg i.p.; mitomycin C, 3-4.5 mg/kg i.p.) with CA showed additive suppression of tumor growth. Mice tolerated chemotherapy alone, CA alone, and both in combination. CA combined with JM-8 was not tolerated. Mice tolerated 100 to 150 mg/kg of JM-8, whereas the addition of CA to JM-8 resulted in a 66% (6 of 9) to 89% (8 of 9) mortality rate. CA at a concentration of 5 and 25 micrograms/ml showed no direct cytotoxic activity against MBT-2 cells in vitro. However, 3 days of administration of 250 mg/kg of CA inhibited tumor angiogenesis generated by MBT-2 cells in C3H mice using a dorsal air sac assay. The data suggest that CA alone inhibits tumor angiogenesis in C3H mice and that antiangiogenesis therapy enhances the antitumor efficacy of chemotherapeutic agents without increasing host toxicity (except for JM-8).

Animals↗
PubMed1987

Plasmodium berghei and Plasmodium chabaudi: a neutral endopeptidase in parasite extracts and plasma of infected animals.

By using a sensitive fluorometric method with Val-Leu-Gly-Arg-3-amino-9-ethylcarbazole (VLGR-AEC) as a substrate, two endopeptidase activities were identified in two fractions of Sephacryl S-200 gel filtration from soluble P. berghei and P. chabaudi extracts. Controls with normal mouse erythrocytes, with leukocytes, and with reticulocyte enriched blood and different washing procedures during the preparation of soluble P. berghei extracts showed that the MW greater than 200 kDa fraction was a contaminant from erythrocytes and exhibited an optimal pH activity of 8.2. In contrast, the fraction 130 kDa was related to P. berghei and P. chabaudi and exhibited an optimal pH activity of 7.4. The two enzyme activities were compared with eight different substrates. The parasite endopeptidase showed a strong activity with Val-Leu-Gly-Lys-AEC (VLGK-AEC) and Ser-Gly-Lys-AEC (SGK-AEC) as substrates; in contrast, the mouse host endopeptidase poorly cleaved the VLGK-AEC and did not cleave SGK-AEC. Presence of the hydrophobic benzyl group on serine reduced the hydrolizing properties of P. berghei endopeptidase: the reverse was observed with host endopeptidase. The hydrolysis of the N-polyhydroxyalcanoyl-VLGK-AEC substrate by the parasite neutral endopeptidase strongly increased with the schizogonic stage, as shown with synchronized P. chabaudi in mice. By its physiological pH and specificity the release of this enzyme in mouse plasma during the infection could be of interest in a peptidyl-drug strategy.

Animals↗
PubMed1987

Adenylate cyclase stimulation by VIP in rat and human parotid membranes.

Adenylate cyclase activity was stimulated by vasoactive intestinal peptide (VIP) in rat parotid membranes, in the presence of 100 microM guanosine triphosphate (GTP). The threshold concentration of VIP was 300 nM and the activity doubled at the maximal VIP concentration tested (30 microM). The relative potency of peptides of the VIP family was: VIP greater than peptide histidine isoleucinamide (PHI) greater than secretin. The beta-adrenergic agent isoproterenol was a more efficient activator of rat parotid adenylate cyclase and its stimulatory effect, like that of VIP, depended on the presence of GTP. The effects of VIP and isoproterenol were both potentiated by 10 microM forskolin. By comparison with rat parotid preparations, membranes from a human parotid gland responded similarly to the VIP family of peptides (VIP greater than PHI greater than secretin). In both rat and human parotid membranes, two proteins (Mr 44 kDa and 53 kDa) of the alpha-subunit of Ns (the guanyl nucleotide-binding stimulatory protein) were labelled by ADP-ribosylation, in the presence of cholera toxin. Taken together, these results indicate that VIP receptors, when coupled to Ns, were able to activate the adenylate cyclase system in rat and human parotid membranes.

Adenylyl Cyclases↗
PubMed1987

Effect of syngeneic anti-idiotypic antibody on influenza virus neuraminidase antibody response.

Influenza viruses possess two major surface glycoproteins - hemagglutinin (HA) and neuraminidase (NA). Py203, a monoclonal antibody (Ab) specific for the neuraminidase of the PR8 (H1N1) influenza virus, was used to prepare syngeneic monoclonal anti-idiotypic (anti-Id) Abs. From a BALB/c mouse immunized with Py203 (anti-N1), we obtained RM1, a monoclonal anti-Id Ab. The Py203-Id was detected in a significant fraction of immunoglobulins (Igs) in the primary and secondary responses elicited by PR8 (H1N1) and X31 (H3N2) viruses. In animals injected with minute amounts of RM1 and subsequently boosted with an identical dose of RM1, no detectable anti-NA activity was noted, but a significant increase in Py203-Id-bearing Igs was observed. In the sera of animals injected with minute amounts of RM1 and subsequently boosted with PR8 (H1N1) or X31 (H3N2) viruses, an increase in anti-NA activity and in the level of Py203-Id was noted. Animals injected with large amounts of RM1 and boosted with PR8 and X31 showed a marked suppression of the Py203-Id but no alteration in the anti-NA response. The anti-Id recognizes an idiotope (the Py203 idiotope) shared by antibodies specific for the N1 and N2 neuraminidase variants.

Animals↗
PubMed1987

Melanotic neuroectodermal tumor of infancy with high serum levels of alpha-fetoprotein. Ultrastructural study and immunological evidence of glial fibrillary protein and alpha-fetoprotein.

We report an infant melanotic neuroectodermal tumor in the anterior part of the upper gingiva, which was associated with high urinary excretion of vanilmandelic acid. Serum levels of alpha-fetoprotein were abnormally high (200 ng/ml). They returned to normal after removal of the tumor (10 ng/ml). The tumor was characterized histologically and ultrastructurally by the presence of melanocytic and astrocytic cells containing glial fibrillary protein. Intracellular alpha-fetoprotein was demonstrated by the immunoperoxidase method (PAP) in scattered foci of interstitial cells.

Female↗
PubMed1987

Comparison of unique leucovorin and 5-fluorouracil "escalating" and "maximum" dosage strategies.

In this study (GI 6384), regimens are compared which, in phase II investigations, produced 2-fold increases in the historical rates of objective and minor responses. These regimens were associated with overall survival exceeding 1 year. In arm 1, 5-fluorouracil (FUra) alone, 500 mg/m2 on days 1 through 5 was escalated in 25-mg/m2 increments in monthly courses to produce mild to moderate toxicity. This allows an examination of dose-response relationships and comparisons of therapeutic index. In arm 2, leucovorin (LV), was escalated from 25 to 250 to 500 mg/m2 beginning 1 hour before a bolus FUra (30 mg/kg) every 3 weeks. Arm 3 (not previously tested) employed LV (25 mg/m2) 1 hour before FUra (600 mg/m2) given weekly for 6 weeks. It tested the efficacy of low-dose LV. Arm 4 tested high-dose LV (500 mg/m2) as a 2-hour infusion beginning 1 hour before a bolus FUra (600 mg/m2) weekly for 6 weeks. In a preliminary analysis of this study, findings are statistically consistent with the anticipated high frequencies of objective response. It also finds evidence of biological activity across the wide range of LV dosages and that LV produces an apparent favorable change in FUra side effects from hematological to gastrointestinal toxicities. One or more regimens may favorably change the anticipated prognosis of patients with measurable cancer of the colon and rectum.

Age Factors↗