Changes In Growth Characteristics Research Articles

Long-term cultivation of amphibian melanophores: In vitro ageing and spontaneous transformation to a continuous cell line

Pure melanophore populations isolated from the tail skin of the tadpole, Rana catesbeiana, were mass cultured for a period of 2–3 years. All cell lines of amphibian melanophores studied exhibited growth crisis (in vitro ageing) followed by spontaneous transformation to a continuous cell line, as shown by changes in growth characteristics in mass culture and in clone culture, by the appearance of the cells, and by measurements of cell volumes. Even after becoming a continuous cell line, amphibian melanophores continued to have a diploid chromosome number (2 n=26) in three of four cell lines examined. The chromosome mode in one cell line, however, changed to thirty. Measurement of melanin dispersion after the addition of α-melanocyte-stimulating hormone suggested that the mechanism for melanin dispersion in melanophores changed during in vitro ageing.

Morphometric study of the development of Purkinje cell dendritic trees in the mouse using vertex analysis.

Vertices are the points in an arborescence which interconnect segments and comprise terminal or pendant vertices (Vp), nodal or branching points and the root point. Branching points may be dichotomous (Vd) or trichomtomous (Vt), etc., and are subdivided into distinct two-dimensional topological entities according to the number of terminal vertices they drain, i.e. Vds comprise primary vertices (Va), connecting two Vps; secondary vertices (Vb), connecting one Vp and one Vd or one Vt; and tertiary vertices (Vc), connecting either two Vds, two Vts or one Vt and one Vd. The four types of Vt (Va', Vb', Vc', Vd') similarly connect three, two, one and zero Vps respectively. Each Vt may be transformed into two Vds thus, Va' = Va + Vb; Vb' = Va/3 + 4Vb/3 + Vc/3; Vc' = Vb + Vc and Vd' = 2Vc. Analysis proceeds by transforming mixed trees containing varying proportions of Vds and Vts into entirely dichotomous branching structures. The topology is then defined by the Va/Vb ratio which has a unique value according to the mode of growth and the frequency of Vts. Vertices are ordered by a centrifugal technique. The frequency distribution of vertices of different order allow the changes in growth characteristics and in remodelling to be detected within particular regions of the tree. Metrical parameters are readily incorporated into the analysis since all vertices are interconnected by segments of finite length and are given the same order magnitude as the vertex they drain. The analytical capabilities of the method are exemplified by its application to the study of growth and plasticity in the dendritic trees of Purkinje cells in the mouse. Growth is defined in metrical and topological terms and sites of reorganization within the mature tree are identified.

Niacinamide requirement for growth of Kluyveromyces lactis in minimal medium

Although Kluyveromyces lactis has been used extensively for investigating a variety of metabolic processes, the minimum nutritional requirements for growth of this yeast have not been described. We have determined these minimal requirements and formulated a simple medium which provided growth, as measured turbidometrically, comparable to that obtained with complex media. The medium consisted of the following ingredients per liter: 20 g glucose; 0.41 g MgCl 2; 2.4 g ammonium sulfate; 6.8 g KH 2PO 4; 12.12 g K 2HPO 4; 1200 μg niacinamide; 60 μg biotin; and 6000 μg pantothenic acid. Of the vitamins included, only niacinamide was strictly required to achieve maximum growth. Addition of biotin and pantothenic acid accelerated growth but did not increase the maximum amount of growth which was obtained in the presence of niacinamide alone. Niacin was substituted for niacinamide with no change in growth characteristics. The addition of MnCl 2, ZnCl 2, CaCl 2, and FeCl 2 had no effect on growth but the presence of CuCl 2 at 0.4 m m caused an almost complete inhibition of growth. Mg 2+ ions were required for growth.

Replacement of serum in cell culture by hormones: a study of hormonal regulation of cell growth and specific gene expression.

The hypothesis that the growth of mammalian cells is regulated by hormones is now supported by considerable evidence. Two rat pituitary cell lines, GH3 and GC, a mouse melanoma, M2R (B16), and a human cervical carcinoma cell, HeLa S-3, have been grown indefinitely in serum-free (SF) hormone-supplemented medium. No visible changes of growth characteristics were observed in the cells grown continuously in the SF condition. However, changes in the activity of a plasma membrane enzyme, alkaline phosphatase, and in the relative intensity of surface proteins that are labeled by the [125I] lactoperoxidase technique were found in HeLa cells grown in the SF condition. To study the role of hormones required in the regulation of cell growth, HeLa cells were grown in the absence of one of the required hormones. The following results were obtained. Epidermal growth factor is probably involved in the regulation of the synthesis of macromolecules such as RNA and of the protein content per cell. Transferrin, the accessory factor in the SF condition, supplies iron for cells. The two basic peptides in this SF system, fibroblast growth factor and insulin, are probably involved in the balance of nutrients and energy inside the cell. The replacement of F12 medium with a better-balanced medium, MCDB 105, can mimic the requirements for these two peptides. The steroid hydrocortisone (HC) is probably involved in alteration of the cell surface. This is indicated by the effects of HC on cell morphology, rate of detachment from the dish, and the pattern of [125I] lactoperoxidase labeling of surface proteins. In addition, it is necessary to change the medium more frequently to maintain the culture in the medium without HC. This observation suggests that HC may be involved in the control of homeostatic properties of the cell surface. The production of rat prolactin by GH3 cells was also studied. GH3 cells in the SF condition produce 1.6 microgram prolactin per 10(5) cells in 24 h, while 2.4 microgram is produced in the presence of serum. Prolactin production in the SF condition is enhanced by the presence of thyrotropin-releasing hormone and inhibited by triiodothyronine (T3). T3 is the major growth factor for these cells. Without it cell growth is severely limited, while prolactin production is elevated. This result suggests that the GH3 cell line in the SF condition may be an ideal system for the study of hormonal regulation of cell growth and specific gene expression.

Control of phenotypic expression of cultured melanoma cells by melanocyte stimulating hormones.

STUDIES of the mechanism through which MSH acts in mammals have been restricted to intact animals or to melanomas grown in animals1,2. We describe here a mouse melanoma cell line cultivated in monolayer which when exposed to MSH shows large increases in tyrosinase activity and melanin content, as well as changes in growth characteristics and cellular morphology. In addition, we have found that adenosine 3',5'-monophosphate (cyclic AMP) or its analogue N6,O2'-dibutyryl cyclic AMP (diB cyclic AMP) will substitute for MSH, supporting previous evidence that MSH probably acts through cyclic AMP in mammals1,3.

Transplantation behavior and cytogenetic characteristics of a spontaneous reticulum cell sarcoma in the golden hamster.

AbstractDuring a period of 2 1/2 years, 33 spontaneous reticulum‐cell sarcomas arose in our colony of golden hamsters. One of the tumors, made transplantable in the solid and the ascitic form, is described with regard to behavior in homologous hosts and to cytogenetic characteristics. During four years of transplantation, the tumor changed its pattern of growth and, after an initial phase of localized growth, displayed a leukemialike mode of spread resulting in the death of the hosts on the 6th or 7th day irrespective of site of transplantation. Animals of the same passage reacted differently to tumor implantation: some hamsters developed large tumors without tumor cell spread, others showed very small tumors with heavy tumor cell dissemination. These different modes of growth are assumed to be dependent on host factors.Chromosome analyses were carried out on tumor cells of different transplantation generations. The chromosomes in cells of the 38th generation did not differ from normal hamster cells, except for a higher variation in the number of chromosomes. Within the next 15 passages the karyotype changed considerably, but from then on remained stable with a stemline of 44 chromosomes and six markers. The late replication pattern of sex chromosomes and of most of the autosomes seems to be the same for both normal hamster cells and tumor cells.The DNA content of the tumor cells was found to correspond to the modal chromosome number.No causal relationship between changes in growth characteristics and in karyotype could be established.

Radiation Studies with Sexual Yellow‐Anthered Dallisgrass, Paspalum dilatatum Poir

Dormant seed of an erect, sexual, but highly uniform dallisgrass, Paspalum dilatatum Poir., ecotype were irradiated with gamma rays and neutrons in an effort to induce favorable changes in growth habit. Radiation caused extensive changes in morphology and growth characteristics and also resulted in severe seedling mortality and high sterility. Most of the mutants were inferior to untreated plants, but a few highly fertile, vigorous, decumbent mutants of potential value were recovered in the M2 generation.In general, prominent changes in growth characteristics were accompanied by chromosomal aberrations, reduced viability of male and female gametophytes, and low fertility. Abortion of the female gametophyte corresponded very closely to the reduction in pollen quality. Degeneration of sporogenous tissue was noted at all stages of megasporogenesis and embryo sac development, and there was no evidence of selectivity for a balanced megaspore within the linear tetrad.

Observations on the Biology of the Greentail Prawn, Metapenaeus mastersii (Haswell) (Crustacea Decapoda: Penaeidae)

The ecology, growth, and behaviour of Metapenaeus mastersii from the Brisbane River, Qld., are described. Postlarval stages were found to favour a warm sheltered locality with abundant algal cover and salinity below 20‰. Salinity tolerance range of all stages was from almost fresh to sea-water, and activity was at a minimum when the average temperature fell to 16�C. Carapace length was found to be as reliable a measure of size as overall length or volume. Progression of the modes of length frequency distributions was unsatisfactory for finding growth rate, but showed a steady downstream movement as growth progressed. From the growth rate of captive prawns, age at sexual maturity was estimated as 12-15 months at 16 mm carapace length (males) and 20 mm (females) (76 and 95 mm overall). Males were less tolerant of low salinity than females, but did not migrate as far downstream. Fertilization occurred in the lower reaches of the Brisbane River, but spawning occurred outside. The length-volume relationship of prawns above 10 mm carapace length (48 mm overall) did not conform to the curve: volume = k × (length)³. This deviation was interpreted as due to change of growth characteristics during winter. A reversed respiratory current and other adaptations to burying in the mud, and a possible associated diurnal rhythm are described.

Ein pseudoallel-spezifischer Suppressor bei Salmonella typhimurium

In Salmonella typhimurium, UV-irradiation of the histidine-deficient mutant hi-31 induced a slowly growing reversion to histidine-independence. This formed colonies much smaller than wildtype. By means of transduction the newly created character “small colony” was proved to be heritable. As demonstrated by the following experiments this was due to an independant suppressor-mutation (S-31). After UV-irradiation of hi-31/S-31 a small fraction of cells forming large colonies, revealed growth-characteristics of wildtype. After transduction of small colony type cells by phages raised on wildtype the same large colonies were obtained. Expected to be of genotype hi-31+/S-31, they were used as donor for transduction of hi-31. Both, large colonies (hi-31+/S-31) and small colonies (hi-31/S-31) were isolated, which proved to be stable in further transfers. 26 histidin-requiring mutants, belonging to 4 groups, each of them characterised by the same block in histidine synthesis, were transduced with phage raised on hi-31/S-31. None of them exhibited changes of growth characteristics, resulting from the incorporation of the suppressor-gene. Thus the suppressor S-31 turned out to be pseudoallel-specific. This result is considered as evidence that pseudoalleles of the histidine series in Salmonella typhimurium not only are units of recombination but also of function of genetic material. The differences between levels of functions exhibited by units which have been called pseudoalleles by various investigators are discussed in connection with the gene concept.