The BULT Melanoma: A Spontaneous Transplantable Tumor in Mice

The BULT melanoma originated at Brown University as a spontaneous, small black nodule on the tail of an adult female mouse of the LT/Ch strain. Histological examination of a portion of the tumor indicated that it was intradermal and consisted predominantly of heavily melanized, ovoid to fusiform cells with melanin-laden macrophages scattered among them. The BULT melanoma has been maintained in LT/Ch mice for approximately 5 years by periodic transplantation, at first subcutaneously on the flanks and, more recently, intramuscularly in the hind legs. The shift in transplantation site was made following a marked decline in the growth of subcutaneous grafts. The transplants have retained the uniform deep-black melanization and general histology of the primary melanoma. Numerous melanosomes at all stages of development are found within the melanoma cells. DOPA-positive cytoplasmic vesicles are abundant. Occasional autophagic vacuoles containing clusters of melanosomes are also present. A few metastases from the transplanted melanoma have been observed in lymph nodes and on one occasion in the lungs. When grown in vitro, BULT melanoma cells do not require special growth promoting agents (e.g., TPA; cAMP) in order to proliferate. The BULT melanoma differs in one or more respects from each of the other three transplantable spontaneous mouse melanomas widely used in cancer research. In addition, it arose in a strain of mice characterized by the spontaneous death of melanocytes while the latter are engaged in synthesizing eumelanin within hair follicles. Karyotypic analysis of cultured cells showed a modal chromosome number of 68 with a range of 58–72 chromosomes.     

Responses of Cultured Melanocytes to Defined Growth Factors

To proliferate in vitro, normal melanocytes, unlike normal fibroblasts, require specific growth factors in addition to those supplied in serum. The substances that promote melanocyte proliferation, such as 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and stimulators of cyclic adenosine monophosphate (cAMP), also promote pigmentation. Consequently, cell division and expression of at least some differentiated functions are not mutually exclusive for melanocytes. At present, the only known natural growth factor that can replace TPA in normal human melanocyte cultures is basic fibroblast growth factor (bFGF). Like TPA, bFGF is effective, most of the time, only in the presence of added cAMP. Some preparations of bFGF, however, may have a highly labile, intrinsinc cAMP stimulatory activity. It is thus possible that bFGF can assume two forms, dependent on and independent of cAMP stimulatory activity. Alternatively, a second factor may exist in pituitary glands that co-purifies with bFGF but deteriorates with storage. Abnormal melanocytes in culture, such as those derived from dysplastic nevi and primary melanomas, depend on the specific factors (bFGF and cAMP), whereas melanocytes from metastatic melanomas do not     

Storage Polysaccharide in Coccidial Sporozites after Excystation and Penetration of Cells

SYNOPSIS. Eimeria acervulina, E. necatrix , and E. meleagrimitis sporozoites were examined for carbohydrates by cytochemical methods during dormancy, after excystation, and after penetration of cells. The only carbohydrate found was amylopectin, a homogeneous polymer of glucose. It was distributed in 3 regions: (a) in front of the anterior refractile globule, (b) around the nucleus, and (c) behind the posterior refractile globule. The relative amounts decreased after excystation and penetration of cells until only small amounts remained around the nucleus. The quantity of amylopectin decreased following excystation from 30.0-36.7 to 9.4-13.3 μg glucose/10⁶ oocysts. Over a 6 yr period of storage at 4 C, there was a decrease in the quantity of amylopectin in dormant sporozoites of E. acervulina from 33.3 μg glucose/10⁶ oocysts at 3 mos to 1.5 μg at 6 years. Coincidentally, 3 month- and 1 year-old oocysts of E. acervulina produced patent infections in chicks with a dosage of 5 × 10⁴ oocysts, but only a few of the oocysts that had been stored for 2 years were infective; a dosage of 2 × 10⁶ oocysts was necessary to produce a patent infection. Oocysts which had been stored 6 years did not produce a patent infection.
It was concluded that amylopectin is the energy source for excystation and subsequent penetration of cells. Small amounts of amylopectin are used during dormancy and, when the content in the sporozoite falls below a certain level, the sporozoites lack sufficient energy to infect cells.     

Genetics and Molecular Biology of Mouse Pigmentation

The formation of mouse coat color is a relatively complex developmental process that is affected by a large number of mutations, both naturally occurring and induced. The cloning of the genes in which these mutations occur and the elucidation of the mechanisms by which these mutations disrupt the normal pigmentation pattern is leading to an understanding of the way interactions between gene products lead to a final phenotype.     

A Comparison of Minerals Modified Glutamate Medium with Other Media for the Enumeration of Coliforms in Delicatessen Foods

A comparative assessment has been made of the performance of minerals modified glutamate medium (MMGM), lauryl sulphate tryptose broth (LST), MacConkey broth (MAC) and brilliant green bile broth (BGBB) in the enumeration of coliform organisms present in soft cheese, cooked meat and pâté. The medium MMGM was superior in sensitivity to the other three media and compared favourably with them in specificity; BGBB was inferior to the other media tested.     

An Ultrastructural Investigation of 180°-Rotated Ciliary Meridians in Tetrahymena pyriformis*

SYNOPSIS. An ultrastructural investigation has been carried out on 180°-rotated ciliary meridians (inverted meridians) in Tetrahymena pyriformis temperature-sensitive mutant (mol^b/mol^b), syngen 1, strain B. The longitudinal, transverse and postciliary microtubular bands, the kinetodesmal fiber, and the parasomal sac, are shown to be disposed at a 180° angle to their normal positions or orientations. Other abnormalities are as folows: the first 2 basal bodies of the inverted meridian fail to organize into “couplets” and the inverted meridian intrudes into the anterior pole region; an extra longitudinal microtubular band is found in one of the cell lines.     

Molecular Characterization of the Mouse Tyrosinase Gene:Pigment Cell-Specific Expression in Transgenic Mice

Tyrosinase is the key enzyme in melanin synthesis, and is expressed in the pigment epithelium of the retina, a cell layer derived from the optic cup; and in neural crest-derived melanocytes of skin, hair follicle, choroid, and iris. The tyrosinase gene has been cloned and shown to map to the well-characterized c-locus (albino locus) of the mouse. Subsequent studies demonstrated that a functional tyrosinase minigene was able to rescue the albino phenotype in transgenic mice. The transgene was expressed in a cell type-specific manner in skin and eye. During development of the mouse, the tyrosinase gene is expressed in the pigment epithelium of the retina as early as day 10.5 of gestation. In the hair follicle, tyrosinase gene expression is detected from day 16.5 onwards. This cell-type–specific expression is largely reproduced in transgenic mice. Our results suggest that sequences in the immediate vicinity of the mouse tyrosinase gene are sufficient to provide cell type-specificity and developmental regulation in melanocytes and the pigment epithelium.