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S Nandi

Publications and source records attributed to S Nandi.

At least 109 records · Page 6Linked to original sources
PubMed1992

Pregnancy-dependent to ovarian-independent progression in mammary tumors delineated in primary culture: changes in signal transduction, growth factor regulation, and matrix interaction.

A model for the evolution of hormone-independent tumors from a pregnancy-dependent precursor is exemplified by the TPDMT-4[pregnancy-dependent (PD)] and T4OI96 [ovarian-independent (OI)] in vivo tumor lines developed in DDD mice. In vivo, the OI tumor grows rapidly in virgin mice and is more anaplastic than the PD tumor which, in virgin mice, grows as a hyperplastic alveolar gland from which tumors arise only during pregnancy. The regulation of the proliferation of these two tumors was compared in primary culture using a three-dimensional, serum-free, collagen gel cell culture system. In medium containing insulin, the growth of cell organoids from PD tumors was stimulated by the same factors that stimulate the growth of normal mammary epithelial cells from virgin or pregnant mice. These factors include progesterone and prolactin (but not estrogen), epidermal growth factor, basic fibroblast growth factor, linoleic acid, cyclic AMP, prostaglandin E2, phosphatidic acid, and lithium. Most of these tumors (about 80%) could not grow in medium with only insulin present; of those that did, growth was slow and was stimulated further by the above agents. PD tumor cells formed stellate colonies in the collagen matrix similar to those of normal cells. These findings show that the growth regulation of PD tumor cells is, in all aspects examined, similar to that of normal cells. In addition, the capacity for growth in the presence of only insulin (more autonomous growth) is not necessarily accompanied by deletions in responses to growth factors or hormones, or in lipid response pathways. In contrast, organoids from OI tumors needed only insulin for growth. The growth of some of these tumors was stimulated further by only basic fibroblast growth factor and phosphatidic acid. Cyclic AMP and agents that elevate intracellular cyclic AMP inhibited growth, the opposite of the response seen in normal or PD cells. OI organoids grew as cell masses rather than as stellate structures. These data show that while PD tumors are remarkably similar to normal cells in the regulation of their proliferation, OI tumors have incurred multiple defects in growth-regulatory pathways possibly including the production of autocrine growth factor(s). In addition, the ability of OI tumor cells to adhere to the collagen gel matrix and undergo normal morphogenesis is reduced. These results may highlight specific events required for the progression from ovarian dependency to ovarian independency related to the hormonal regulation of growth.

Animals↗
PubMed1992

Incidence of c-Ki-ras activation in N-methyl-N-nitrosourea-induced mammary carcinomas in pituitary-isografted mice.

We found previously that mouse mammary epithelial cells cultured in the presence of the mammogenic hormones progesterone and prolactin and treated with the carcinogen N-methyl-N-nitrosourea produced a high frequency of hyperplastic alveolar nodules and carcinomas with squamous metaplasia upon transplantation to syngeneic mice. The majority of these mammary transformants had an activated c-Ki-ras proto-oncogene with a specific point mutation in codon 12 (G35 to A35). To determine whether these in vitro findings parallel mammary carcinogenesis in vivo, virgin female mice were pituitary isografted to increase their circulating levels of progesterone and prolactin. The pituitary isograft results in an increase in proliferation, leading to lobulo-alveolar development and differentiation of the mammary epithelial cells. Five weeks after pituitary isografting, the mice were treated with a single injection of N-methyl-N-nitrosourea (50 micrograms/g body weight). Greater than 90% of the N-methyl-N-nitrosourea-treated mice developed mammary carcinomas between 3 and 7 months after treatment. The majority (75%) of the carcinomas had histopathology identical to that of tumors induced in vitro in the presence of progesterone and prolactin. A number of the mammary cancers (17%) induced in pituitary-isografted mice also had the identical point mutation in the c-Ki-ras proto-oncogene found in the in vitro studies. These results suggest that the hormonal milieu around the time of carcinogen exposure affects not only the incidence and phenotype of the mammary transformants but also the molecular events associated with mammary carcinogenesis.

Animals↗
PubMed1992

Role of endocrine, autocrine, and paracrine interactions in the development of mammary hyperplasia in Wnt-1 transgenic mice.

The Wnt-1 proto-oncogene is transcriptionally activated by mouse mammary tumor virus in mouse mammary tumor virus-induced tumors. Previous studies using transgenic mice showed that Wnt-1 expression in mammary gland causes alveolar hyperplasias which resemble mammary glands of pregnant mice. To understand the role of mammogenic hormones in the genesis of these hyperplasias, we examined the development of these glands before puberty in young transgenic mice and the effects of ovariectomy and adrenalectomy on the growth and morphology of Wnt-1 mammary hyperplasia. Mammary glands of Wnt-1 transgenic females showed hyperplastic morphology as early as 1 week after birth. The normal structure of the uterus of the adult Wnt-1 virgin mouse indicated that the circulating levels of ovarian hormones were not elevated. Ovariectomy and adrenalectomy had no obvious effect on the morphology of these mammary hyperplasias. To assess possible paracrine stimulation of mammary epithelial cells (MEC) by stromal cells, we transplanted MEC from normal BALB/c mice into gland-free fat pads of Wnt-1 transgenic mice and found that normal MEC maintained their normal ductal structure in Wnt-1 fat pads without alveolar development. Further, we did not detect Wnt-1 mRNA expression in the gland-free fat pads of these transgenic mice. When Wnt-1 MEC were transplanted into the fat pads of nude mice and allowed to grow towards existing normal MEC, the morphology of the existing normal MEC remained normal. We concluded that the development of mammary hyperplasia in Wnt-1 transgenic mice is solely dependent on Wnt-1 expression in MEC. We speculate that Wnt-1 may be a growth factor for mammary gland that only acts locally on the cells that produce it.

Adrenalectomy↗
PubMed1992

Depletion of O6-alkylguanine-DNA alkyltransferase by O6-benzylguanine in three-dimensional collagen cultures of normal human breast epithelial cells.

O6-Alkylguanine--DNA alkyltransferase (AGT) is a protein which removes the promutagenic O6-alkylguanine lesion induced in DNA by alkylating agents. Our results demonstrate that freshly isolated organoids from reduction mammoplasty specimens contain significant levels of AGT activity. AGT activity in breast epithelial cells shows interindividual variation. Constitutive levels of AGT activity remain unchanged during short-term serum-free culture of breast epithelial cells inside three-dimensional rat-tail collagen gel matrix. In the present study, we optimized conditions for depleting AGT activity in human breast epithelial cells cultured in three-dimensional collagen gel matrix using O6-methylguanine and O6-benzylguanine which are substrates for AGT. AGT activity was efficiently inactivated by exposure of cells to O6-methylguanine or O6-benzylguanine. Inactivation with O6-benzylguanine was more rapid, of greater magnitude and consistency and occurred at lower concentrations than with O6-methylguanine. Near-complete inactivation (> 99.5%) of AGT activity was reproducibly achieved with 50 microM O6-benzylguanine. In contrast, 500 microM O6-methylguanine was needed to obtain a maximal effect and this reduced AGT activity by only 53-93% of control. Within 30 min of adding the free base, 50 microM O6-benzylguanine depleted 95% of the levels of AGT compared to 30% inhibition with 500 microM O6-methylguanine. The profile for restoration of AGT activity was different following a 24 h incubation and subsequent removal of each of the guanine derivatives. AGT activity levels remained undetectable for at least 2 days after removal of 50 microM O6-benzylguanine from the medium and recovered to only 53% of control values after an additional 3 days. AGT activity levels remained undetectable for at least 2 days after removal of 50 microM O6-benzylguanine from the medium and recovered to only 53% of control values after an additional 3 days. In contrast, following removal of 500 microM O6-methylguanine, the activity was restored from its nadir of 16% of control values reaching pretreatment levels after 5 days. These results suggest that treatment with O6-benzylguanine may be used to modulate the incidence of transforming mutations in cultured human breast epithelial cells treated with chemical carcinogens which give rise to O6-alkylguanine adducts.

Animals↗
PubMed1992

Is hysteria on the wane? A community survey in West Bengal, India.

A field survey was conducted in two villages--Gambhirgachi and Paharpur--in 1972. The survey was repeated after 10 years in the former village and after 15 years in the latter one. The second survey showed very little change in the rate of total mental morbidity. The rate of prevalence of hysteria declined significantly in both villages. In Gambhirgachi the rate of hysteria dropped from 16.9 to 4.6 per 1000 in 10 years, and in Paharpur it dropped from 32.3 to 2.05 per 1000 in 15 years.

Adolescent↗
PubMed1992

Developmental response of adult mammary epithelial cells to various fetal and neonatal mesenchymes.

Adult mouse mammary epithelial cells were isolated and grown in combination with mesenchyme from the following sources: embryonic preputial gland, foot skin, tail skin, genital tubercle skin, mammary gland, and neonatal uterus, vagina and urinary bladder. Following 1 month of in vivo cultivation of the tissue recombinants as grafts underneath the renal capsule of normal female or hyperprolactinaemic (pituitary-grafted) hosts, the specimens were analysed histologically and immunocytochemically for the expression of milk proteins, smooth muscle actin, and cytokeratins. Mesenchymal effects on adult mammary epithelium varied with the source of the mesenchyme and the hormonal status of the host. In normal female hosts preputial gland mesenchyme induced extensive mammary epithelial growth and ductal branching morphogenesis with epithelial differentiation and ductal pattern being comparable to that observed in homotypic recombinants composed of mammary gland mesenchyme plus adult mammary epithelium. Other mesenchymes (from foot, tail, genital tubercle and uterus) preserved ductal morphology and normal epithelial differentiation, but elicited minimal epithelial growth and branching morphogenesis in adult mammary epithelium. In association with urogenital sinus, vaginal or bladder mesenchymes ductal branching morphogenesis of the mammary epithelium was absent or greatly distorted and the epithelium exhibited a stratified cuboidal phenotype even though considerable epithelial growth had occurred. In hyperprolactinaemic hosts (which received a pituitary graft) epithelial growth, alveolar morphogenesis, and synthesis of casein and milk fat globule protein was stimulated in all tissue recombinants although to different extents. Alveolar morphogenesis and milk protein expression were extensive in tissue recombinants prepared with mesenchyme from embryonic mammary gland, preputial gland, tail skin and urinary bladder, but were minimal in tissue recombinants prepared with foot or genital tubercle skin. Few milk-protein-positive alveoli formed in tissue recombinants composed of mammary epithelium combined with urogenital sinus or vaginal mesenchyme, even following growth in pituitary-grafted hosts. These findings demonstrate: (1) that adult mammary epithelial cells are responsive to the growth-promoting influences of heterotypic embryonic and neonatal mesenchymes; (2) that mammary growth and branching morphogenesis are induced to variable extents by different mesenchymes; (3) that fibrous (non-adipose) mesenchymes are effective inducers of mammary epithelial development; and (4) that the ability to form alveoli and produce milk proteins in adult mammary epithelial cells is critically dependent upon the nature of the connective tissue environment.

Animals↗
PubMed1991

Effects of antioxidants and reduced oxygen tension on rat mammary epithelial cells in culture.

Free radical damage has the potential to significantly affect the behavior of cells in culture. In this study the effects of antioxidants (superoxide dismutase, catalase, and vitamin E) and lowered oxygen tension (1% oxygen) on primary culture of rat mammary epithelial cells were examined. Rat mammary epithelial cells were dissociated in collagenase with or without the addition of antioxidants and low oxygen tension, then cultured for 10 d in rat-tail collagen gel matrix and fed with Dulbecco's modified Eagle's F12 medium supplemented with various hormones and growth factors. Growth potential of the mammary cells was enhanced when antioxidants and low oxygen tension were used, alone or in combination, during the cell dissociation period. Using antioxidants and low oxygen tension during the culture period failed to improve growth potential regardless whether cells were dissociated in standard conditions or with antioxidants and low oxygen tension. The use of antioxidants and low oxygen tension during the cell dissociation period also reduced the degree of keratinization of the cells after 10 d of culture. Using antioxidants and low oxygen tension during the cell culture period did not further reduce keratinization if antioxidants and low oxygen tension were used during the dissociation period, but were effective in reducing keratinization if cells were dissociated in standard condition. In this system, antioxidants and low oxygen tension reduced lipid peroxidation during the cell dissociation period. An iron chelator, desferal, can also reduce lipid peroxidation and enhance growth when used during cell dissociation, suggesting the enhanced growth potential by the addition of antioxidants and low oxygen to be due to the reduction of lipid peroxidation.

Animals↗
PubMed1990

Transfection of activated Ha-ras protooncogenes causes mouse mammary hyperplasia.

ras protooncogenes activated by a point mutation have been implicated in the initiation of mammary carcinogenesis. However, the nature of phenotypic alterations induced by activated ras protoonocogenes during initiation has not been well understood. In the present studies, the phenotypic manifestation of activated ras genes was directly analyzed by transfecting them into normal mouse mammary epithelial cells. The ras genes were cotransfected with pSV2neo which expresses the bacterial neomycin resistance gene to partially select for successful transfectants in culture. Transfection of activated Ha-ras protooncogenes, containing a point mutation in codon 12, caused hyperplasia in the mouse mammary gland following transplantation. Hyperplastic phenotype is a prerequisite for neoplastic development. The hyperplasias induced by the activated Ha-ras protooncogenes, however, were not immortal in vivo, another essential characteristic of preneoplastic and neoplastic mouse mammary cells. Control cells transfected only with pSV2neo did not produce any hyperplasia. These results suggest that a functional role of activated ras protooncogenes in the initiation of mouse mammary carcinogenesis may be the induction of a hyperplastic phenotype, a prelude to neoplastic development.

Animals↗