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Biomedical subjects

G Schwartsmann

Publications and source records attributed to G Schwartsmann.

At least 19 recordsLinked to original sources
PubMed2006

Impairments of social behavior and memory after neonatal gastrin-releasing peptide receptor blockade in rats: Implications for an animal model of neurodevelopmental disorders.

The gastrin-releasing peptide receptor (GRPR) has been implicated in central nervous system (CNS) diseases, including neurodevelopmental disorders associated with autism. In the present study we examined the effects of GRPR blockade during the neonatal period on behavioral measures relevant to animal models of neurodevelopmental disorders. Male Wistar rats were given an intraperitoneal (i.p.) injection of either saline (SAL) or the GRPR antagonist [D-Tpi(6), Leu(13) psi(CH(2)NH)-Leu(14)] bombesin (6-14) (RC-3095; 1 or 10mg/kg) twice daily for 10days from postnatal days (PN) 1 to 10. Animals treated with RC-3095 showed pronounced deficits in social interaction when tested at PN 30-35 and impaired 24-h retention of memory for both novel object recognition (NOR) and inhibitory avoidance (IA) tasks tested at PN 60-71. Neither short-term memory tested 1.5h posttraining nor open field behavior were affected by neonatal GRPR blockade. The implications of the findings for animal models of neurodevelopmental disorders are discussed.

Age Factors↗
PubMed2006

Molecular mechanisms mediating gastrin-releasing peptide receptor modulation of memory consolidation in the hippocampus.

Although the gastrin-releasing peptide-preferring bombesin receptor (GRPR) has been implicated in memory formation, the underlying molecular events are poorly understood. In the present study, we examined interactions between the GRPR and cellular signaling pathways in influencing memory consolidation in the hippocampus. Male Wistar rats received bilateral infusions of bombesin (BB) into the dorsal hippocampus immediately after inhibitory avoidance (IA) training. Intermediate doses of BB enhanced, whereas a higher dose impaired, 24-h IA memory retention. The BB-induced memory enhancement was prevented by pretraining infusions of a GRPR antagonist or inhibitors of protein kinase C (PKC), mitogen-activated protein kinase (MAPK) kinase and protein kinase A (PKA), but not by a neuromedin B receptor (NMBR) antagonist. We next further investigated the interactions between the GRPR and the PKA pathway. BB-induced enhancement of consolidation was potentiated by coinfusion of activators of the dopamine D1/D5 receptor (D1R)/cAMP/PKA pathway and prevented by a PKA inhibitor. We conclude that memory modulation by hippocampal GRPRs is mediated by the PKC, MAPK, and PKA pathways. Furthermore, pretraining infusion of BB prevented beta-amyloid peptide (25-35)-induced memory impairment, supporting the view that the GRPR is a target for the development of cognitive enhancers for dementia.

Amyloid beta-Peptides↗
PubMed2006

A phase I trial of the bombesin/gastrin-releasing peptide (BN/GRP) antagonist RC3095 in patients with advanced solid malignancies.

Bombesin/gastrin-releasing peptides (BN/GRP) were shown to bind selectively to cell surface receptors, stimulating the growth of various types of malignancies in murine and human models. The novel BN/GRP synthetic receptor antagonist, RC-3095, was able to produce long-lasting tumor regressions in murine and human tumor models in vitro and in vivo. Animal toxicology studies showed no detectable organ toxicity apart from local irritation at the injection site. The purpose of this study was to determine the safety and feasibility of the administration of RC-3095 by daily subcutaneous injections in patients with advanced and refractory solid malignancies. Twenty-five patients received RC-3095 once or twice-daily at doses ranging from 8 to 96 ug/kg. Dose was escalated in groups of 3-5 patients per dose level. The only toxicity observed was local discomfort in the injection site at the highest doses. A single dose administration of RC-3095 at the highest dose level (96 ug/kg) was tested in a clearly hypergastrinemic individual with the Zollingen-Ellison syndrome and produced a decrease in plasma gastrin down to 50% of basal levels in 6 h. There was no objective tumor responses in patients included in the study. A short-lasting minor tumor response was observed in a patient with a GRP-expressing progressive medullary carcinoma of the thyroid. Due to problems with the analytical method, plasma pharmacokinetic data was obtained only from two patients included at the highest dose level. In these patients, RC-3095 reached plasma concentrations >100 ng/mL for about 8 h, which were within therapeutic levels on the basis of prior data obtained in mice and rats. The plasma elimination half-life was between 8.6-10.9 h. Due to the occurrence of local toxicity at the injection site, the dose escalation procedure could not be fully evaluated up to a maximum tolerated dose. Thus, a recommended dose of RC-3095 for Phase II trials could not be clearly established. Considering the novelty of its mechanism of action and impressive preclinical anti-tumor activity, further studies exploiting new formulations of RC-3095 for human use, such as slow-release preparations, and analogues with a more favorable pharmacokinetics are warranted.

Adult↗
PubMed2006

Gastrin-releasing peptide receptor as a molecular target for psychiatric and neurological disorders.

The mammalian bombesin (BB)-like peptide gastrin-releasing peptide (GRP) stimulates cell proliferation, displays a range of neuroendocrine activities, and acts as a growth factor in the pathogenesis of several types of human cancer. Several lines of evidence have indicated that GRP and its receptor (GRPR) might also be involved in the neurochemical alterations associated with psychiatric and neurological disorders. GRP and GRPR are distributed throughout the mammalian central nervous system (CNS). Altered levels of BB-like peptides have been found in the CNS of patients with schizophrenia and Parkinson's disease. Dysfunctions in GRPR-induced cellular calcium signaling have been reported in fibroblasts from patients with Alzheimer's disease. A translocation in the GRPR gene has been associated with autism. Pharmacological and genetic studies in rodents have shown that GRPRs in brain areas such as the dorsal hippocampus and amygdala are importantly involved in regulating synaptic plasticity and aspects of behavior that might be altered in disorders such as anxiety, schizophrenia, depression, autism and dementia. Behaviors modulated by the GRPR in rodents include grooming, food intake, stereotypy, social behavior, and emotionally-motivated learning and memory. Together, these findings support the view that the GRPR should be considered a therapeutic target for a subset of CNS diseases.

Animals↗
PubMed2005

Sentinel lymph node in carcinoma of the anal canal: a review.

AIMS: To review the studies investigating the efficacy of the sentinel lymph node (SLN) procedure in anal canal carcinoma and to evaluate its potential role in guiding a more selective approach for patients with the malignancy. METHODS: A literature search in the PubMed database was preformed using the key words "sentinel lymph node" and "anal cancer". All indexed original articles (except case reports) on the SLN procedure in cancer of the anal canal were analysed. RESULTS: There are five published series to date. Eighty-four patients were studied. Rates of SLN detection and removal ranged from 66 to 100% of patients investigated. Nodal metastases were found in 7.1 to 42% of cases. No serious complications were reported. CONCLUSIONS: The technique has proven to be safe and effective in sampling inguinal SLNs. The detection of occult metastases in clinically unsuspicious nodes represents an important improvement in the process of staging these patients, which has not been possible with any other method of diagnosis. Although SLN procedure is still in an early phase of investigation in this type of cancer, it emerges as an objective method to guide individual therapeutic decisions.

Anus Neoplasms↗
PubMed2005

Screening for antiproliferative activity of six southern Brazilian species of Hypericum.

The crude methanolic extracts of six species of Hypericum growing in southern Brazil (Hypericum caprifoliatum Cham. & Schlecht., H. carinatum Griseb., H. connatum Lam., H. myrianthum Cham. & Schlecht., H. polyanthemum Klotzsch ex Reichardt and H. ternum A. St. Hil.) were screened for their antiproliferative activity against two cell lines (HT-29 human colon carcinoma cells and H-460 non-small cell lung carcinoma). The most active crude extracts were those from H. caprifoliatum, H. myrianthum and, to a lesser extent, from H. connatum. All plants were submitted to fractionation with solvents in increasing polarity and re-assayed for the two cell lines used previously, as well as U-373 human malignant glioma cells. The most active fractions were the hexane fractions obtained from H. caprifoliatum, H. myrianthum and H. ternum.

Antineoplastic Agents, Phytogenic↗
PubMed2003

Epidemiologic correlates of antibody response to human papillomavirus among women at low risk of cervical cancer.

A population at low risk for developing cervical cancer in Southern Brazil was studied to identify the main determinants of serological response to human papillomavirus (HPV). Enzyme-linked immunosorbent assay tests were performed in 976 women to detect serum IgG antibodies against HPV 16 L1 virus-like particles (VLPs) and HPVs 16, 18, 6 and 11 L1 VLPs as a mixture of antigens. Women with four or more sexual partners were more likely to be seropositive than women with one partner (HPV 16 serology odds ratio [OR]=3.06, 95% confidence interval [CI]: 2.0-4.8; HPV 6/11/16/18 serology OR=4.64, 95% CI: 3.0-7.2). HPV DNA and both serological responses were associated. Those positives to HPV 16 serology were twice as likely to have a cytological diagnosis of squamous intraepithelial lesions (SILs) than seronegatives (OR=2.07; 95% CI: 1.0-4.5, and OR=1.73; 95% CI: 0.8-3.8). Seropositivity to HPV 16 and HPV 6/11/16/18 antigens seem to be better markers of past sexual activity than current HPV infection, and humoral response to HPV 16 or HPV 6/11/16/18 may not be a strong indicator of cervical lesions in populations at low risk for cervical lesions.

Adolescent↗
PubMed2002

Anticancer drug discovery and development throughout the world.

This year's American Society of Clinical Oncology International Symposium devoted 2 hours to a lively discussion of various aspects of anticancer drug discovery and development throughout the world. The scientific program started with an overview of efforts directed toward promoting international collaboration in natural product-derived anticancer drug discovery. This was followed by a discussion on the importance of interethnic differences and pharmacogenetics in anticancer drug development. Thereafter, this part of the program was completed by a description of the activities of the newly created Singapore-Hong Kong-Australia Drug Development Consortium and an overview of the contribution of Japan to anticancer drug development. The logistics and regulatory aspects of clinical trials with new anticancer agents in different parts of the world were then presented, with an emphasis on Europe, North America, and Japan. The program was completed with a panel discussion of the efforts to harmonize the exchange of clinical data originating from one region of the globe with other territories, with input from official representatives of the United States Food and Drug Administration and the Medical Devices Evaluation Center of Japan.

Antineoplastic Agents↗
PubMed2002

Potentiation of carbon tetrachloride hepatotoxicity by pentosan polysulfate in rats.

Few data are available in the literature regarding the effect of pentosan polysulfate (PPS) on normal and fibrotic rat livers. In addition, the combination of PPS and carbon tetrachloride (CCl4) has not been studied so far. The objective of this study was to assess the effect of PPS on rat livers treated or not with CCl4 for the induction of liver fibrosis. The study consisted of four stages: 1) hepatic fibrosis induction with CCl4 (N = 36 rats); 2) evaluation of the effect of PPS on CCl4-induced hepatic fibrosis (N = 36 rats); 3) evaluation of the effect of higher doses of PPS in combination with CCl4 (N = 50 rats); 4) evaluation of the presence of an enzymatic inductor effect by PPS (N = 18 rats) using the sodium pentobarbital test which indirectly evaluates hepatic microsomal enzyme activity in vivo. Adult (60 to 70 days) male Wistar rats weighing 180 to 220 g were used. All animals receiving 0.5 ml 8% CCl4 (N = 36) developed hepatic fibrosis, and after 8 weeks they also developed cirrhosis. No delay or prevention of hepatic fibrosis was observed with the administration of 5 mg/kg PPS (N = 8) and 1 mg/kg PPS (N = 8) 1 h after the administration of CCl4, but the increased hepatotoxicity resulting from the combination of the two substances caused massive hepatic necrosis in most rats (N = 45). PPS (40 mg/kg) alone caused hepatic congestion only after 8 weeks, but massive hepatic necrosis was again observed in association with 0.5 ml CCl4 after 1 to 4 weeks of treatment. Unexpectedly, sleeping time increased with time of PPS administration (1, 2, or 3 weeks). This suggests that PPS does not function as an activator of the hepatic microsomal enzymatic system. Further studies are necessary in order to clarify the unexpected increase in hepatotoxicity caused by the combination of CCl4 and high doses of PPS, which results in massive hepatic necrosis.

Animals↗
PubMed2002

Targeting protein kinase C: new therapeutic opportunities against high-grade malignant gliomas?

A large body of evidence suggests that the abnormal phenotype of neoplastic astrocytes, including their excessive proliferation rate and high propensity to invade surrounding tissues, results from mutations in critical genes involved in key cellular events. These genetic alterations can affect cell-surface-associated receptors, elements of signaling pathways, or components of the cell cycle clock, conferring a gain or a loss of relevant metabolic functions of the cells. The understanding of such phenomena may allow the development of more efficacious forms of cancer treatment. Examples are therapies specifically directed against overexpressed epidermal growth factor receptor, hyperactive Ras, excessively stimulated Raf-1, overproduced ornithine decarboxylase, or aberrantly activated cyclin-dependent kinases. The applicability of some of these approaches is now being assessed in patients suffering from primary malignant central nervous system tumors that are not amenable to current therapeutic modalities. Another potentially useful therapeutic strategy against such tumors involves the inhibition of hyperactive or overexpressed protein kinase C (PKC). This strategy is justified by the decrease in cell proliferation and invasion following inhibition of the activity of this enzyme observed in preclinical glioma models. Thus, interference with PKC activity may represent a novel form of experimental cancer treatment that may simultaneously restrain the hyperproliferative state and the invasive capacity of high-grade malignant gliomas without inducing the expected toxicity of classical cytotoxic agents. Of note, the experimental use of PKC-inhibiting agents in patients with refractory high-grade malignant gliomas has indeed led to some clinical responses. The present paper reviews the current status of the biochemistry and molecular biology of PKC, as well as the possibilities for developing novel anti-PKC-based therapies for central nervous system malignancies.

Adolescent↗
PubMed2001

Breast cancer in South America: challenges to improve early detection and medical management of a public health problem.

Breast cancer is a public health issue in South America, with about 70,000 cases and 30,000 deaths expected for the year 2001 according to the World Health Organization database. This is especially the case for the so-called temperate region that includes Argentina, Chile, Uruguay, and Southern Brazil. In these areas, the incidence of breast cancer is in the same range as in most countries in Europe. Notably, Argentina has one of the highest incidences of breast cancer in the world, while in Brazil breast cancer is the second most frequent type of cancer (after skin cancer). The potential risk factors for the higher incidence of this disease in temperate South America are, among others, a high-fat diet, more elevated socioeconomic status, and the low average parity of women. In addition, the influence of European immigration on the genetic background of the population should be considered. Late diagnosis is a major factor affecting the mortality rates, as a significant proportion of patients are still diagnosed at clinical stages II and III. In this article, the available data on the incidence and mortality rates of breast cancer in South America, as well as the published literature on risk factors and the limitations of early detection of the disease, are discussed. The overall management of patients diagnosed at clinical stage IIIA is briefly addressed.

Adult↗
PubMed2001

Multidrug resistance gene expression during the murine ontogeny.

Multidrug resistance (MDR) was described initially for tumor cells which become resistant not only to the specific drug to which they are submitted, but also to a large range of unrelated drugs. The expression of mdr genes, responsible for the phenotype, and their product P glycoprotein (Pgp), is currently under intensive study due to their ample distribution in different organisms and their possible physiological roles which include protection against xenobiotics. In mice, three mdr isoforms expressed in some normal tissues are known. In this work, we analyzed by RT-PCR the expression of mdr1, mdr2 and mdr3 in several organs of BALB/c and C57BL/6 mice during ontogeny. A considerable variation in mdr expression among individuals of the same strain, as well as among different organs in individuals of the same age group and among different age groups, was detected. We also observed a strong tendency for the expression of a greater number of active isoforms in old mice. The large expression range of the mdr isoforms point to an important role as a natural defense system.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2001

Marine organisms as a source of new anticancer agents.

Various active anticancer agents are derived from plants and terrestrial microorganisms. The isolation of C-nucleosides from the Caribbean sponge, Cryptotheca crypta, four decades ago, provided the basis for the synthesis of cytarabine, the first marine-derived anticancer agent to be developed for clinical use. Cytarabine is currently used in the routine treatment of patients with leukaemia and lymphoma. Gemcitabine, one of its fluorinated derivatives, has also been approved for use in patients with pancreatic, breast, bladder, and non-small-cell lung cancer. Over the past decade, several new experimental anticancer agents derived from marine sources have entered preclinical and clinical trials. This field has expanded significantly as a result of improvements in the technology of deep-sea collection, extraction, and large-scale production through aquaculture and synthesis. In this paper, examples of marine-derived experimental agents that are currently undergoing preclinical and early clinical evaluation are briefly discussed. A summary of the available information on the results of phase I and II trials of agents such as aplidine, ecteinascidin-734 (ET-734), dolastatin 10 and bryostatin 1 is also presented.

Animals↗
PubMed2001

Natural products in anticancer therapy.

Many pharmaceutical agents have been discovered by screening natural products from plants, animals, marine organisms and microorganisms. Vincristine, irinotecan, etoposide and paclitaxel are examples of plant-derived compounds that are being employed in cancer treatment, and dactinomycin, bleomycin and doxorubicin are anticancer agents derived from microbial sources. Citarabine is an example of an anticancer agent originating from a marine source. Other agents originating from marine sources are bryostatin-1, aplidine, dolastatin 10 and ET-743, which have recently entered phase I and II clinical trials.

Animals↗