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At least 73 records · Page 4Linked to original sources
PubMed1988

Human immunodeficiency virus infection of monoblastoid cells: cellular differentiation determines the pattern of virus replication.

Stringent control of human immunodeficiency virus (HIV) replication was observed in the human monoblastoid cell line U937. A low-multiplicity infection of these cells by the LAV1 strain of HIV was productive for 2.5 days; then virus replication became restricted and no further evidence of virion production was observed. The dramatic decrease in HIV production was due in part of reduced accumulation of cytoplasmic viral RNA and occurred in the absence of evident cytopathic effects. In contrast, infected cells induced to differentiate by phorbol ester, vitamin D3, or lymphokine supernatant did not release markers of HIV despite the accumulation of significant levels of cytoplasmic viral RNA. HIV infection altered the pattern of c-myc RNA accumulation in U937 cells. Expression of this gene changes normally in response to the state of cellular differentiation; in infected cells the level of c-myc expression was correlated to the levels of viral RNA accumulation and not to cellular differentiation. These results suggest that restricted replication of HIV in monocytes might be an important mechanism of virus persistence and demonstrate a relationship between HIV replication and monocyte differentiation.

Cell Differentiation↗
PubMed2003

Leptin influences cellular differentiation and progression in prostate cancer.

PURPOSE: Several studies have shown a positive association of dietary fat with prostate cancer. Leptin, a peptide hormone that has a role in the regulation of body weight, currently serves as a more accurate biomarker for total body fat. We designed a study to determine whether leptin influences cellular differentiation and the progression of prostate cancer. MATERIALS AND METHODS: In this study we investigated serum leptin in 21 patients with prostate cancer, 50 with benign prostatic obstruction and 50 healthy individuals matched for sex, body mass index and age. Patients with cancer were stratified into 2 groups by the disease spread, including groups 1--organ confined and 2--advanced disease, and into 3 groups by the differentiation degree, including groups 3--Gleason sum 2 to 4 or well differentiated, 4--Gleason sum 5 to 7 or moderately differentiated and 5--Gleason sum 8 to 10 or poorly differentiated. RESULTS: We noted significant differences in serum leptin in the cancer versus control and cancer versus benign prostatic obstruction groups. In addition, in the prostate cancer group serum leptin correlated with prostate specific antigen and biopsy Gleason score. We also observed significant differences in serum leptin in groups 1 versus 2, 3 versus 5 and 4 versus 5. CONCLUSION: Leptin may have roles in the development of prostate cancer through testosterone and factors related to obesity. It influences cellular differentiation and the progression of prostate cancer.

Adult↗
PubMed2005

[Prognostic value of the grade of cellular differentiation, of mucus presence and the growth pattern of the invasive margin in colorectal adenocarcinomas Dukes B].

BACKGROUND: The unfavorable evolution of approximately 1/3 of the patients with colorectal cancer, classified in the Dukes B stage, shows to be desirable the addition of another approaches morphologic prognostics. The reports of the literature about prognostic significance of cellular differentiation, mucus presence and the pattern of growth of the invasive margin in colorectal cancer were controversial. AIMS: To evaluate the prognostic significance of tumor differentiation, mucus presence and the growth pattern of the invasive margin in patients with colorectal carcinomas classified in Dukes B stage. MATERIALS AND METHOD: A retrospective study of 156 patients who had undergone curative resection for colorectal cancer was made at the Department of Gastroenterology Surgery of the "Hospital do Servidor Público Estadual", in São Paulo, SP, Brazil. Their mean age was 58 (range 28-83) years and consisted of 94 (60.26%) women and 62 (39.74%) men. The cellular differentiation was classified in two degrees: low and high malignancy degree, in agreement with the area of predominant differentiation of the tumor. Tumors with at least 60% of its volume in mucus were called mucinous carcinoma. The growth of the invasive margin was classified as expanding when the tumor showed a well-delineated and circumscribed border pushing the adjacent structures and infiltrating when the tumor advances by a process of seemingly effortless dissection between the normal structures of the bowel wall. RESULTS: There were predominance of tumors of low malignancy (139 (89.10%)), non-mucinous (142 (91.03%)) and with margin of the infiltrating type (123 (78.85%)). Only the growth of the invasive margin influenced the survival of 5 years. Patients with tumor exhibiting margin of the expanding type, presented a favorable outcome than those with margin of the infiltrating type -- 81.82% x 60.98%. CONCLUSION: The type of growth of the invasive tumor margin may help to identify the prognosis of low and high-risk subgroups of patients.

Adenocarcinoma, Mucinous↗
PubMed1993

Biologic markers, cellular differentiation, and metastatic head and neck cancer.

The plateau in survival rates from head and neck cancer as well as the increasing incidence of disease among various populations demands the need for new perspectives in head and neck oncology. In pursuit of that goal, investigators have been developing improved biologic markers for metastatic risk of head and neck cancer. Such markers can be placed into categorical groupings, of which markers for cellular differentiation may be the most relevant. Among the growth factors relevant to head and neck cancer, epidermal growth factor and its receptor have received the most attention. Those tumors with unregulated growth factor control tend towards a more dedifferentiated state. Additionally, the degree of cellular differentiation and resulting risk of metastases may be predetermined in an individual through constitutively expressed susceptibility genes. Polymorphisms of the L-myc oncogene identified within peripheral blood lymphocytes may represent such a marker. Certain polymorphisms of this gene will identify individuals likely to express dedifferentiated head and neck cancer. Finally, the expression of cell-surface differentiation antigens may govern the capacity of cell-mediated host immune systems to control metastatic growth.

Antigens, Differentiation↗
PubMed2000

Murine Delta homologue, mDelta1, expressed on feeder cells controls cellular differentiation.

The Delta/Serrate-Notch pathway is involved in intercellular signaling that controls cell fate during the development of invertebrates and vertebrates. Delta is a prototype of Notch ligands and has been studied extensively in Drosophila. In higher vertebrates, four Delta/Serrate homologues and four Notch homologues have been identified. Recent studies showed that the murine Delta homologue, mDelta1, is essential in early embryogenesis. The biological activity of mammalian Delta and its roles in cellular differentiation, however, have remained unclear. In this study, we first surveyed expression of mDelta1 in the adult mouse and found it to be present in a wide range of tissues. For testing biological activity of mDelta1, we expressed a mDelta1 full-length cDNA in L cells using a eukaryotic expression vector. Effects of mDelta1 on cellular differentiation were examined in two independent systems, featuring C2C12 myogenic differentiation and multipotent murine bone marrow cell differentiation. Inhibition of the former was observed with mDelta1 expression on L cells, associated with suppression of myogenin, a myogenic transcription factor. Expression of mDelta1 in conjunction with GM-CSF promoted differentiation of bone marrow cells to myeloid dendritic cells at the expense of other lineages. Although the effects of mDelta1 on two differentiation systems appeared opposing, as inhibition occurring in one and induction in the other, this can be understood by the unifying concept of generation of diverse cell types from equivalent progenitors. Thus, the present study provided evidence that mammalian Delta participates in intercellular signaling, determining the cell fate in a wide variety of tissues.

Animals↗
PubMed2005

Variable expression of MRP2 (ABCC2) in human placenta: influence of gestational age and cellular differentiation.

MRP2 (ABCC2) is an ATP-binding cassette (ABC)-type membrane protein involved in transport of conjugates of various drugs and endogenous compounds. MRP2 has been localized to the apical membrane of syncytiotrophoblasts and is assumed to be involved in diaplacental transfer of the above substances. It has been shown that both genetic and environmental factors can influence MRP2 expression. We therefore investigated whether gestational age, cellular differentiation, and genetic polymorphisms influence expression and localization of MRP2 in 58 human placenta samples. We detected a significant increase of transporter-mRNA with gestational age by quantitative real-time polymerase chain reaction (MRP2 mRNA/18S rRNA ratio x 1000 +/- S.D.; 0.43 +/- 0.13 in early preterms versus 1.18 +/- 0.44 in late preterms versus 2.1 +/- 0.63 in terms; p < 0.05). MRP2 protein followed the mRNA amount as shown by Western blotting (mean relative band intensity +/- S.D.; 0.56 +/- 0.1 versus 0.7 +/- 0.18 versus 0.92 +/- 0.19; early preterms versus terms p < 0.05). In cultured cytotrophoblasts, MRP2 expression increased with differentiation to syncytiotrophoblasts, with a peak on day 2 (MRP2 mRNA/18S rRNA ratio x 1000 +/- S.D.; 0.06 +/- 0.01 versus 0.88 +/- 0.27 versus 0.24 +/- 0.02 on days 0, 2, and 4). Moreover, we studied the effect of single nucleotide polymorphisms (C-24T; G1249A, and C3972T) in the MRP2 gene on placental expression. One of these polymorphisms (G1249A) resulted in a significantly reduced expression of MRP2 mRNA in preterms. In summary, the expression of MRP2 in human placenta is influenced by gestational age, cellular differentiation, and genetic factors.

Base Sequence↗
PubMed2001

The SMN genes are subject to transcriptional regulation during cellular differentiation.

Proximal spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by degeneration of alpha-motor neurons and muscular atrophy. The causal survival motor neuron (SMN) gene maps to a complex region of chromosome 5q13 harbouring an inverted duplication. Thus, there are two SMN genes, SMN1 and SMN2, but SMN1-deficiency alone causes SMA. In this study we demonstrate, for the first time, down-regulation of SMN promoter activity during cellular differentiation. Specifically, the minimal SMN promoter is four times more active in undifferentiated embryonal carcinoma P19 cells compared to cells treated with retinoic acid (RA) to initiate neuronal differentiation. This effect is mediated by sequences contained within the minimal core promoter that we have confined to the 257 nucleotides upstream of exon 1. We have identified seven regions that are highly conserved between the mouse and human SMN core promoters and this region contains the consensus sequence for a number of transcription factors. Most notably, AhR, HNF-3 and N-Oct3 have already been shown to respond to RA treatment of EC cells, while E47, HNF-3, MAZ, N-Oct3 and Pit-1a have been implicated in embryonic, muscle or neural development. In addition, we have mapped two strong transcription initiation sites upstream of SMN exon 1. The novel -79 site identified in this study is preferentially utilized during human foetal development. Furthermore, analysis of RNA from SMA patients with deletions of the entire SMN1 gene or chimpanzees that lack SMN2 suggests that the level of transcription initiation at these sites may be different for the SMN1 and SMN2 genes. Taken together, this work provides the first demonstration of transcriptional regulation of these genes during cellular differentiation and development. Deciphering the underlying mechanisms responsible for regulating SMN transcription may provide important clues towards enhancing SMN2 gene expression, one target for the treatment of SMA.

Animals↗
PubMed1997

O-Glycosylation and cellular differentiation in a subpopulation of mucin-secreting HT-29 cell line.

Malignant transformation of epithelial cells is associated with abnormal glycosylation of mucins. The aim of this work was to evaluate the changes in the O-glycosylation processes during differentiation of tumor cells by performing in vitro reactions using crude microsomal preparations obtained from a subpopulation of HT-29 cells capable of differentiating into mucin-secreting cells (HT-29 MTX cells). The reactions of O-glycosylation were carried out at different times of culture: before confluence (Day 5), when cells are still undifferentiated, and after confluence (Day 21), when cells display a mucin-secreting phenotype. As acceptor for the UDP-N-acetylgalactosamine:polypeptide Nacetylgalactosaminyltransferase (GalNAc transferase), the peptide motif TTSAPTTS (tandem repeat deduced from MUC5AC human gastric gene, expressed in HT-29 MTX cells) was used. A higher rate of enzyme activity was observed in preconfluent cells, and analysis by capillary electrophoresis and electrospray mass spectrometry showed a different pattern of galactosaminylation in pre- and postconfluent cells. Core 1 UDP-galactose:N-acetyl-alpha-galactosaminyl-R 3-beta-galactosyltransferase (3-beta-galactosyltransferase) activityalso decreased with the differentiation, whereas CMP-neuraminic acid:galactose-beta-1, 3-N-acetyl-alpha-galac- tosaminyl-R 3-alpha-sialyltransferase activity increased. In comparison, the evolving process of mucin biosynthesis was tested by the analysis of purified mucins of HT-29 MTX cells, in amino acid and carbohydrate composition, and immunoreactivity assays using several antibodies and lectins. The results suggested that (i) no mucins were detected at Day 5, while the GalNAc transferase and 3-beta-galactosyltransferase activities were already at high rates; (ii) the mucins purified from postconfluent cells showed a high content of sialic acid in an alpha-2,3-linkage to galactose residues; and (iii) cellular differentiation seemed to be accompanied by more regulated processes of glycosylation. This study of the O-glycosylation in HT-29 MTX cells is thus an interesting approach to analyzing the regulation of mucin biosynthesis during cellular differentiation.

Amino Acid Sequence↗
PubMed2006

Cellular differentiation determines the expression of the hypoxia-inducible protein NDRG1 in pancreatic cancer.

N-myc downstream-regulated gene-1 (NDRG1) is a recently described hypoxia-inducible protein that is upregulated in various human cancers. Pancreatic ductal adenocarcinoma, called pancreatic cancer, is a highly aggressive cancer that is characterised by its avascular structure, which results in a severe hypoxic environment. In this study, we investigated whether NDRG1 is upregulated in these tumours, thus providing a novel marker for malignant cells in the pancreas. By immunohistochemistry, we observed that NDRG1 was highly expressed in well-differentiated cells of pancreatic cancer, whereas the poorly differentiated tumour cells were negative. In addition, hyperplastic islets and ducts of nonquiescent pancreatic tissue were positive. To further explore its selective expression in tumours, two well-established pancreatic cancer cell lines of unequal differentiation status were exposed to 2% oxygen. NDRG1 mRNA and protein were upregulated by hypoxia in the moderately differentiated Capan-1 cells; however, its levels remained unchanged in the poorly differentiated Panc-1 cell line. Taken together, our data suggest that NDRG1 will not serve as a reliable marker of tumour cells in the pancreas, but may serve as a marker of differentiation. Furthermore, we present the novel finding that cellular differentiation may be an important factor that determines the hypoxia-induced regulation of NDRG1.

Biomarkers, Tumor↗
PubMed2005

The activity of the spinal muscular atrophy protein is regulated during development and cellular differentiation.

Spinal muscular atrophy (SMA) is a lethal neuromuscular disease caused by reduced levels of expression of the survival motor neuron (SMN) protein. SMN is part of a macromolecular complex essential for the assembly of the small nuclear ribonucleoproteins (snRNPs) that carry out pre-mRNA splicing. Although the SMN complex has the potential to control the pathway of snRNP biogenesis, it is not known whether SMN function in snRNP assembly is regulated. Here, we analyze SMN interactions and function in mouse tissues and show that, when normalized per cell number, similar levels of the SMN complex are expressed throughout the ontogenesis of the central nervous system (CNS). Strikingly, however, SMN function in snRNP assembly in extracts does not correlate with its expression levels and it varies greatly both among tissues and during development. The highest levels of SMN activity are found during the embryonic and early postnatal development of the CNS and are followed by a sharp decrease to a basal level, which is then maintained throughout life. This downregulation takes place in the spinal cord earlier than in the brain and coincides with the onset of myelination. Using model cell systems and pulse-labeling experiments, we further show that SMN activity and snRNP synthesis are strongly downregulated upon neuronal as well as myogenic differentiation, and linked to the rate of global transcription of postmitotic neurons and myotubes. These results demonstrate that the SMN complex activity in snRNP assembly is regulated and point to a differential requirement for SMN function during development and cellular differentiation.

Animals↗
PubMed1979

Evidence for differential cellular adhesion as the mechanism of sorting-out of various cellular slime mold species.

Various authors have shown previously that if the amoebae of two species of slime molds are mixed they have the ability to sort themselves out. In the work reported here, the sorting-out of cells of several slime mold species was examined in clumps of cells in suspension. Cells of four species, Dictyostelium discoideum (Dd), D. mucoroides (Dm), D. purpureum (Dp), and Polysphondylium violaceum (Pv), were mixed in pairs in suspension and clumps of cells formed. Dd and Pv cells sorted out completely and formed separate clumps, each of single species. Both Dd and Dm, when mixed separately with Dp, formed clumps containing both species. Sorting-out took place in these clumps such that the cells of Dd and Dm partially enveloped the Dp cells. Finally, in the Dd-Dm mixtures, the Dm cells always sorted out such that they surrounded the Dd cells. When mixed in a 1:2 ratio (Dd:Dm) the Dm cells formed a complete shell around a sphere of Dd cells. Sorting-out of cells in clumps in suspension can occur by either of two possible mechanisms: response of cells to a chemotactic gradient or differences in cell surface strengths of adhesion (Steinberg, 1964). Mixing of two species in a clump of cells and observing the process of sorting-out permits one to distinguish between these two mechanisms (Steinberg, 1964). By such an analysis it was found that the sorting-out observed in mixtures of Dd and Dm is consistent with the mechanism of differential cellular adhesion. The major reasons for this are (1) when the adhesive properties of the cells are known to change the Dd cells began to move inside the clumps, (2) the Dd cells coalesced into islands rather than streaming inward independently, and (3) the Dd cells and cell masses did not lie at the center of the clumps but rather lay randomly within the clumps. The partial envelopment observed in the Dd-Dp and Dm-Dp mixtures and the separate clumps formed by the Dd-Pv mixtures are also consistent with differential cellular adhesion. They represent cases in which the interspecific strengths of adhesion are low (Dd-Dp and Dm-Dp) and near zero (Dv-Pv).

Cell Membrane↗
PubMed2001

In vitro models to study cellular differentiation and function in human prostate cancers.

In Vitro Models to Study Cellular Differentiation and Function in Human Prostate Cancers. To augment the currently available models of human prostate cancer in vitro, we have established extended life-span epithelial cultures from biopsies of well-differentiated prostate cancers. The genetic identity of the target cells was assessed by allelotyping, using microsatellites located on chromosome 8p, and microdissection of tissues and primary cell cultures. Cells with an extended life span (PxE6) were derived by recombinant retrovirus infection to introduce the human papilloma virus E6 gene (epithelial cells). Immunophenotyping of the resultant cell strains confirmed retention of differentiated cell functions, and the genotype of the E6-expressing epithelial cells was stable, while SV40-immortalized cultures were more unstable, leading to tetraploidy. All PxE6 cells eventually senesced, but an immortalized epithelial culture, P4E6, was derived from one of the epithelial cultures. The properties of this cell line, which remains close to diploid, are similar to those of early prostate cancer cells, and it retains expression of many prostate-associated antigens, such as prostate-specific antigen (PSA).

Allelic Imbalance↗
PubMed1979

[Hormonal stimulation and in vitro cellular differentiation in the integument of the desert locust Schistocerca gregaria (author's transl)].

Spontaneous cellular differentiation (glandular units appearance with a well-defined duct) is observed in larval integument of Schistocerca cultured in an hormone free medium. Hormonal stimulations modify the expression of this phenomenon, particularly the frequency of new elaborated duct cells belonging to secretory units. The most effective factor is supplied by the prothoracic glands. Complete secretory units can be observed but the glandular cells are in an undifferentiated and unfunctional state. They appear active if the corpora allata act after the prothoracic glands. Corpora allata alone or synthetic juvenile hormones have an inhibitory effect. The addition of alpha-ecdysone permits only cellular divisions, a preliminary and indispensable condition for ulterior differentiation. Between cuticles deposited with beta-ecdysone, new formed ducts take place in the theorical imaginal exuvia. These observations prove that the elaboration and the activity of imaginal glandular units are conditioned by the larval hormonal context: by contrast, sex dimorphism is only a genetic dependant process.

Animals↗
PubMed1991

Loss of intragenomic DNA repair heterogeneity with cellular differentiation.

The influence of terminal differentiation on UV-induced DNA damage and its repair in transcriptionally active and inactive genomic sequences was investigated using the murine 3T3-T proadipocyte cell culture system. Actively cycling 3T3-T cells terminally differentiate into adipocytes after exposure to media containing platelet-depleted human plasma. Suitable DNA fragments were analyzed from four genes: beta-actin, adenosine deaminase, dihydrofolate reductase, and lipoprotein lipase. As a result of 3T3-T cell differentiation, lipoprotein lipase and beta-actin expression was modified, whereas adenosine deaminase and dihydrofolate reductase expression was not affected. A DNA fragment representing the transcriptionally inactive locus 70-38 was also evaluated. UV-induced cyclobutane pyrimidine dimers, detected as UV-specific endonuclease-sensitive sites, in each fragment increased linearly as a function of UV dose (0-20 J/m2) independently of gene expression or differentiation. Sequence-specific repair of dimers was measured in stem and terminally differentiated 3T3-T cells after UV irradiation (10 J/m2). For undifferentiated stem cells, the rate and extent of dimer repair was higher in the actively transcribed adenosine deaminase and dihydrofolate reductase genes than in the inactive lipoprotein lipase or 70-38 fragments, the greater difference being observed in the first 8 h post-UV irradiation. In contrast, similar dimer repair rates were found for each DNA fragment in terminally differentiated 3T3-T cells. These data suggest that cellular differentiation is accompanied by a loss of heterogeneity in intragenomic DNA repair.

3T3 Cells↗
PubMed1977

Composition and synthesis of cellular lipids in Neurospora crassa during cellular differentiation.

The synthesis of cellular lipids of Neurospora crassa was measured during growth on low (2% sucrose)- and high (15% glucose)-carbohydrate supplementation. The amount of lipid per dry weight of cells does not change during the germination and early logarithmic growth periods, but the percentage of phospholipid in the lipid does increase, reaching a maximal value of 90% at 4 to 5 h after inoculation, at which time the phospholipid content of the cells is approximately 60 mumol/g (dry weight). The content of the anionic phospholipids, as a percentage of the lipid fraction, is relatively constant during the growth period, but the contents of the zwitterionic phospholipids phosphatidylcholine and phosphatidylethanolamine change in a reciprocal fashion. During the first 8 h of growth, phosphatidylcholine falls from 53% of the phospholipid to 43%, whereas phosphatidylethanolamine rises from 29 to 38%. The total of these two phospholipids is approximately 83% during the growth period studied. The synthesis of cellular phospholipids, measured either by [32P]H3PO4 or [14C]glucose incorporation, reached maximal levels between 3 and 5 h of growth. The effect of the high-carbohydrate supplement on cellular lipids was minimal. Inclusion of 15% glucose decreased the labeling of phospholipid by [32P]H3PO4, but did not affect lipid composition. This observation is in contrast to the effects of high glucose on mitochondrial phospholipid synthesis.

Cell Differentiation↗
PubMed1999

Cellular differentiation of absorptive cells in the neonatal rat colon: an electron microscopic study.

Cellular differentiation of the absorptive cells in the neonatal-suckling rat colon was investigated using horseradish peroxidase as a macromolecular tracer with a scanning or transmission electron microscope. Numerous villi were lined on oblique folds in an orderly fashion and smaller villi were lined between the folds in the proximal colon in 0- to 12-day-old rats. Three different types of absorptive cells were observed in the epithelium covering their villi: type I cells, type II cells, and type III cells. The type I cells were most numerous, and similar to typical absorptive cells of the adult rat large intestine. The type II cells endocytosed macromolecules into an apical endocytic membrane system without giant lysosome from the large intestinal lumen. The type III cells were characteristic of the well-developed endocytic membrane system, including a large supranuclear giant lysosome specialized for endocytosis, storage, and intracellular digestion as an ileal absorptive cell of the suckling rat. At no time was macromolecular tracer detected in the Golgi apparatus of the absorptive cells or in the intercellular space of the epithelium. These results suggest that the villial absorptive cells of the proximal colon have differentiated to three types at specific neonatal-suckling times. The type II and type III cells were not observed in the epithelium after the disappearance of the villi.

Journal Article↗
PubMed1992

A morphometric study of histological variations during cellular differentiation of normal human colorectal epithelium.

Quantifiable variations existing in the colorectal crypt during cellular differentiation were detected by using simple computer-aided morphometric techniques applied to routinely prepared H&E stained and semithin toluidine blue stained sections of normal colonic mucosa. Generally, most of the morphometric parameters including nuclear volume, nuclear volume weighted mean volume, cytoplasmic volume, cellular volume, nuclear axial ratio (a/b), mean nuclear diameter, nuclear shape factor (NSF) and nuclear maximum angle (Agmax) showed an increasing trend between basal and surface segments. Conversely, the nuclear-cytoplasmic (N/C) ratio, NSF and nuclear circularity index (NCI) decreased between these segments. Epithelial cells in the basal segment had the highest N/C ratio and the lowest cell volume due to their low volumes of cytoplasm. However, substantial increases of cytoplasmic volume occurred in the intermediate segment, thereby expanding the cell volume to 136% of that of the basal segment cell. Data for a/b, NSF, NCI and Agmax suggest that the epithelial nuclei were more ellipsoidal in shape and were aligned more perpendicular to the basement membrane as they reached the surface epithelium. Numerical densities for epithelial cell nuclei were highest in the basal segment, indicating more nuclear profiles at this region per unit area or volume. This also suggested that the basal segment was the active proliferating zone. Such observations agree with previously reported cell kinetic and autoradiographic studies.

Aged↗
PubMed1981

Cellular differentiation and pattern formation in the absence of morphogenesis in the cellular slime mould Polysphondylium pallidum: evidence for a biochemical tip (organizer) in submerged aggregates.

When amoebae of Polysphondylium pallidum WS320 are placed in nonnutrient buffer in roller tube culture they form spherical or ellipsoidal aggregates. At first the aggregates demonstrate a "loose" morphology but by 12 h, with the formation a a cellulose-containing, peripheral sheath, they become "tight" aggregates. At this time stalk differentiation begins. Using various methods for the resolution of prespore (ultrastructure, spore antigen immunofluorescence, periodic acid - Schiff staining) and prestalk (ultrastructure, alkaline phosphatase histochemistry, neutral red staining, Calcofluor fluorescence) cell localization, the pattern of cell differentiation in submerged aggregates was shown to be essentially identical to that of normal pseudoplasmodia. Furthermore, using a cAMP bioassay it was revealed that the submerged aggregates, while devoid of a morphological tip, do possess a biochemical tip which is correlated with sites of neutral red staining and stalk cell differentiation. As a result of these studies, an earlier argument that the tip of the pseudoplasmodium is not essential for the establishment of pattern or in the "organization" of cellular differentiation during slime mould development is contradicted.

Alkaline Phosphatase↗